•2w*»K 


MEDICAL 


Gift  of 
John  H.   Chain,   M.D. 


L 


ANATOMY, 


DESCRIPTIVE  AND  SURGICAL 


BY 


HENRY"   GRAY",  F.R.S., 

FELLOW  OF  THE  ROYAL  COLLEGE  OF  SUBGEOSS  ;  LECTTRER  ox  AXATOJCY  AT  ST.  GEORGE'S 
HOSPITAL  MEDICAL  SCHOOL. 


A  NEW  EDITION,  THOROUGHLY  REVISED 


BY 


AUTHORITIES, 


FR"M    THE 


THIRTEENTH  ENGLISH  EDITION 
EDITED  BY  T.  PICKERING  PICK,  F.R.C.S. 

WITH    772    ILLUSTRATIONS,    MANY   OF  WHICH    ARE    NEW. 


LEA   BROTHERS   &  CO., 

PHILADELPHIA  AND  NEW  YORK. 
1897. 


Entered  according  to  Act  of  Congress,  in  the  year  1897,  by 

LEA  BROTHERS  &  CO., 
in  the  office  of  the  Librarian  of  Congress  at  Washington.    All  rights  reserved. 


WESTCOTT  &  THOMSON,  WlLLUM  J.  DORNAN, 

Stereotype™  and  Electrotype™,  Philada.  Printer,  Philada. 


TO 


SIR  BENJAMIN  COLLINS  BRODIE,  BART., 

F.R.S.,   D.C.L., 

SERJEA^TT-SURGEOX   TO  THE  QUZEK, 
COBRESPO>T)LSG    MEMBER  OF  THE  INSTITUTE  OF  FKA2JCE, 

Ubis  TKaork  is  SDeMcateD 

IX  ADMIKATIOS  OF 

HIS   GREAT    TALENTS 

ASD  ES   KEMEMBRAXCK  OP 

MANY   ACTS    OF    KINDNESS    SHOWN    TO   THE   AUTHOE 

FROM  AS 

EARLY  PERIOD  OF  HIS  PROFESSIONAL  CAREER, 


PUBLISHERS'  NOTE  TO  THE  NEW  AMERICAN  EDITION. 


IN  his  masterpiece  HENRY  GRAY  left  undying  evidence  of  his  anatomical 
knowledge  and  of  his  comprehension  of  the  best  method  of  imparting  it  to  other 
minds.  After  forty  years  its  merits  are  only  brightened  by  the  numerous  works 
which  have  endeavored  to  contest  its  supremacy.  During  that  time  it  has  had 
the  benefit  of  the  careful  scrutiny  of  many  leading  anatomists  of  the  English- 
speaking  race.  Anatomy  is  far  from  stationary,  either  in  its  facts  or  in  improve- 
ments in  the  method  of  their  presentation ;  hence  any  work  which  would  faith- 
fully reflect  the  existing  position  of  the  science  must  be  revised  at  comparatively 
frequent  intervals.  Fortunately  for  students  and  practitioners.  Gray's  Anatomy 
enjoys  a  demand  rendering  such  revision  possible. 

An  evidence  of  the  unremitting  attention  bestowed  on  this  book  is  afforded 
in  the  issue  now  presented.  Its  basis  is  found  in  the  revision  of  1896  by  Pro- 
fessor J.  Playfair  McMurrich  and  Dr.  B.  B.  Gallaudet.  The  new  chapters  on 
the  Brain  and  the  Abdominal  Viscera  by  Dr.  Gallaudet  and  Dr.  F.  J.  Brockway, 
respectively,  have  been  retained.  The  section  on  the  Mouth  and  Teeth  has  been 
rewritten  by  Prof.  H.  H.  Burchard,  who  has  taken  account  of  the  latest  advances 
in  the  highly  specialized  department  which  particularly  concerns  students  and 
practitioners  of  Dentistry. 

The  splendid  illustrations  in  Gray  have  long  been  known  as  the  most  effective 
and  intelligible  presentations  of  anatomical  structures  ever  produced.  In  the 
edition  of  1896  this  series  was  increased  by  the  addition  of  one  hundred  and 
thirty-five  new  pictures.  The  total  of  seven  hundred  and  seventy-two  illus- 
trations stands  unchanged  in  the  new  issue,  but  it  includes  a  large  number  of 
new  engravings,  no  expense  having  been  spared  to  effect  improvement  wherever 
possible. 

The  practical  application  of  anatomical  facts  in  medicine  and  surgery  has 
always  been  a  prominent  feature  of  the  work,  and  this  distinctive  character- 
istic has  received  especial  care. 

In  short,  this  edition  is  presented  to  the  medical  public  with  the  con- 
fident expectation  that  it  will  be  found  worthy  in  every  respect  to  main- 
tain the  exalted  position  which  the  work  has  for  so  many  years  enjoyed 
as  the  most  convenient  and  intelligible  exposition  of  its  subject. 


PREFACE  TO  THE  THIRTEENTH  ENGLISH  EDITION. 


WHEN  HENRY  GRAY  published  this  work  in  1858,  he  entitled  it  Anatomy, 
Descriptive  and  Surgical,  and  he  introduced  under  each  subdivision  such 
observations  on  practical  points  of  Surgery  as  show  the  necessity  of  an  accurate 
acquaintance  with  the  anatomy  of  the  part  under  examination.  This  was  the 
first  time  that  such  an  endeavor  had  been  made  by  an  English  Anatomist. 

The    Editor    has    endeavored    to    follow    in    the    lines    originallv  laid  down 

O  «/ 

by  the  Author,  and  has  tried  to  keep  before  himself  the  fact  that  the 
work  is  intended  for  Students  of  Surgery  rather  than  for  the  Scientific 
Anatomist.  Not  that  the  Editor  would  wish  to  disparage,  for  an  instant,  the 
study  of  Philosophical  or  Scientific  Anatomy,  but  that  he  thought  it  right,  con- 
sidering the  class  of  students  for  whom  the  work  is  primarily  intended,  that  he 
should  be  practical  rather  than  abstract  and  theoretical.  Accordingly,  he  has 
not  altered  in  any  way  the  original  plan  of  the  work,  but  has  endeavored  to 
render  it  more  practical,  and  of  more  use  to  the  student,  who  will  hereafter 
have  to  apply  his  knoAvledge  of  Anatomy  to  his  practice  of  Surgery,  by  intro- 
ducing a  considerably  increased  amount  of  Surgical  Anatomy,  and  by  pointing 
out  the  bearings  of  Anatomy  on  the  practice  of  Surgery. 

In  addition  to  this,  the  whole  work  has  undergone  a  careful  revision,  and  in 
some  minor  details  a  rearrangement  has  been  made. 

The  Editor  is  deeply  indebted  to  his  friend  Mr.  Ross  for  much  kind  assist- 
ance in  the  preparation  of  this  edition,  and  also  for  the  help  that  he  has  rendered 
him  in  passing  these  pages  through  the  press. 

To  Dr.  LEONARD  REMFRY  he  is  also  much  indebted  for  his  kindness  in  revis- 
ing the  section  on  the  anatomy  of  the  Female  Organs  of  Generation. 

Several  new  illustrations  have  been  added,  principally  from  dissections  in  the 
Hunterian  Museum  of  the  Royal  College  of  Surgeons.  The  Editor  takes  this 
opportunity  of  thanking  Prosector  PEARSON  for  the  kind  interest  he  has  dis- 
played and  assistance  he  has  rendered  in  the  preparation  of  these  drawings, 
which  were  taken  from  dissections  made  by  this  master  in  the  art  of  dissecting. 


CONTENTS. 


GENERAL  ANATOMY. 


The  Blood 33 

The  Lvmph  and  Chyle 37 

The  Animal  Cell 33 

Epithelium 41 

Connective  Tissue 44 

Pigment    ....        50 

Cartilage 51 

White  Fibro-cartilage 52 

Yellow  or  Reticular,  Elastic  Cartilage  ...  53 

Bone 54 

Development  of  Bone 59 

Muscular  Tissue 64 

Unstriped  Muscle 68 

Nervous  Tissue 69 

The  Brain 73 

The  Nerves 73 

The  Sympathetic  Xerve 75 


PAGE 

Origin  and  Termination  of  Nerves    ....  75 

The  Ganglia 79 

The  Vascular  System 80 

The  Arteries 80 

The  Capillaries 82 

The  Veins 84 

The  Lymphatics 85 

The  Lymphatic  Glands 87 

The  Skin  and  its  Appendages 89 

The  Nails 92 

The  Hair ...  93 

The  Sebaceous  Glands 94 

The  Sudoriferous  Glands 95 

Serous  Membranes 96 

Synovial  Membranes 96 

Mucous  Membranes 97 

Secreting  Glands 98 


DEVELOPMENT. 


Growth  and  Development  of  the  Body  ...  100 

The  Ovum !    ....  100 

Fecundation  of 101 

Segmentation  of 102  j 

Division  of  Blastodermic  Membrane 104 

First  Rudiments  of  the  Embryo 107 

The  Amnion Ill 

The  Chorion 112 

The  Belly-stalk 113 

The  Deci'dua 114  ! 

The  Placenta 115 

Development  of  the  Embrvo  Proper 115 

The  Spiue '. 115 

The  Ribs  and  Sternum 117 

The  Cranium  and  Face 117 

The  Nervous  Centres 120 

The  N«.-rvt-> 122 

The  Eye 122 


The  Ear 124 

The  Nose 125 

The  Skin,  Glands,  and  Soft  Parts  ....  125 

The  Limbs 125 

The  Muscles 126 

The  Blood-vascular  System 126 

Vitelline  Circulation 126 

Placental  Circulation 127 

The  Alimentary  Canal  and  its  Appendages  .    .  132 

The  Respiratory  Organs 134 

The  Urinary  Organs 135 

The  Generative  Organs 137 

Male  Organs 137 

Female  Organs 137 

External  Organs 139 

Chronological  Tables  of  the  Development  of 

the  Foetus  ...  .141 


DESCRIPTIVE   AND   SURGICAL   ANATOMY. 
OSTEOLOGY.— THE  SKELETON. 


The  Skeleton 143  | 

Number  of  the  Bones      143  ' 

Form  of  Bones 143 

THE  SPIXE. 

General  Characters  of  a  Vertebra 144 

Characters  of  the  Cervical  Vertebrae 145 

Atlas 146 

Axis 147 

Vertebra  Prominens 14-s 

Characters  of  the  Dorsal  Vertebrae 149 

Peculiar  Dorsal  Vertebrae 151 

Characters  of  the  Lumbar  Vertebrae 151 

Structure  of  the  Vertebras 152 

Development  of  the  Vertebrae 152 

"      Atlas      153 

Axis 1.34 

Seventh  Cervical    .  .  154 

"      Lumbar  Vertebrae     .    .  154 

Progress  of  Ossification  in  the  Spine 154 

Sacrum 155 

Cocrvx 159 


Of  the  Spine  in  general  .  . 
Surface  Form  of  Spine  . 
Surgical  Anatomy  of  Spine 


THE  SKULL. 


Bones  of  the  Cranium 

Occipital  Bone 

Parietal  Bones 

Frontal  Bone 

Temporal  Bones 

Sphenoid  Bone 

Ethmoid  Bone      

Development  of  the  Cranium 

The  Fontanelles 

Wormian  Bones 

Congenital  Fissures  and  Gaps 

Bones  of  the  Face : 

Nasal  Bones 

Superior  Maxillary  Bones 

Changes  produced  in  Upper  Jaw  by  Age 

Lachrymal  Bones 

Malar  Bones  . 


160 
162 

162 


164 
164 
168 
170 
173 
180 
185 
187 
1  — 


189 
189 
195 
195 
196 


I 


10 


CONTENTS. 


Palate  Bones 197 

Inferior  Turbinated  Bones 200 

Vomer      201 

Lower  Jaw 201 

Changes  produced  in  the  Lower  Jaw  by 

Age 204 

Sutures  of  the  Skull 206 

Vertex  of  the  Skull 208 

Base  of  the  Skull,  Internal  Surface        ....  208 

Anterior  Fossa ...  208 

Middle  Fossa 210 

Posterior  Fossa 211 

Base  of  Skull,  External  Surface 211 

Lateral  Region  of  the  Skull 214 

Temporal  Fossa 215 

Mastoid  Portion 216 

Zygomatic  Fossa 216 

Spheno-maxillary  Fossa 216 

Anterior  Region  of  the  Skull 217 

Orbits 217 

Nasal  Fossae 219 

Surface  Form  of  Skull 222 

Surgical  Anatomy  of  Skull 224 

Os  Hyoides     227 

THE  THORAX. 

The  Sternum 228 

The  Ribs 232 

Peculiar  Ribs 234 

Costal  Cartilages 236 

Surface  Form  of  Chest 236 

Surgical  Anatomy  of  Chest 237 

THE  UPPER  EXTREMITY. 

The  Shoulder  and  Pelvic  Girdles 233 

The  Clavicle 238 

Surface  Form 241 

Surgical  Anatomy 241 

The  Scapula 242 

Surface  Form 247 

Surgical  Anatomy 247 

The  Humerus 248 

Surface  Form 253 

Surgical  Anatomy 253 

The  Forearm 254 

The  Ulna 254 

Surface  Form 259 

The  Radius 259 

Surface  Form 261 

Surgical  Anatomy  of  Bones  of  Forearm  .  261 


The  Hand  ...        262 

The  Carpus 26-? 

Bones  of  the  Upper  Row 262 

Bones  of  the  Lower  Row 266 

The  Metacarpus 267 

Peculiar  Characters  of  the  Metacarpal  Bones  .  268 

Phalanges 270 

Surface  Form  of  Bones  of  Hand  .    .    '.    '.    '.  270 

Surgical  Anatomy  of  Bones  of  Hand     .    .  271 

Development  of  the  Bones  of  the  Hand   .    .    .  271 

THE  LOWER  EXTREMITY. 

The  Hip 272 

Os  Innominatum 272 

Ilium 272 

Ischium 

Os  Pubis 277 

Development  of  the  Os  Innominatum    ....  278 

The  Pelvis 279 

Differences    between    the    Male  and    Female 

Pelvis 282 

Surface  Form  of  Bones  of  Pelvis 283 

Surgical  Anatomy  of  Bones  of  Pelvis    .    .  283 

The  Femur  or  Thigh-Bone 284 

Surface  Form 290 

Surgical  Anatomy 290 

The  Leg 291 

Patella 291 

Surface  Form 292 

Surgical  Anatomy 292 

Tibia 293 

Surface  Form 296 

Fibula 297 

Surface  Form 299 

Surgical  Anatomy  of  Bones  of  Leg    .    -    .  299 

The  Foot 299 

Tarsus 299 

Os  Calcis 299 

Astragalus      393 

Cuboid 303 

Navicular 394 

Cuneiform 395 

Metatarsal  Bones 306 

Phalanges .308 

Development  of  the  Bones  of  the  Foot    .    .    .  308 

Construction  of  the  Foot  as  a  whole  .    .    .  309 

Surface  Form  of  Foot 310 

Surgical  Anatomy  of  Foot 311 

Sesamoid  Bones     .    .       312 


THE  ARTICULATIONS. 


Structures  composing  the  Joints 313 

Articular  Lamella  of  Bone 313 

Ligaments ....  313 

Synovial  Membrane 313 

Bursae 314 

Synovia 314 

Forms  of  Articulation : 

Synarthrosis 314 

Amphiarthrosis 315 

Diarthrosis 315 

Movements  of  Joints 316 

ARTICULATIONS  OF  THE  TRUNK. 

Articulations  of  the  Vertebral  Column  ....  319 

"      Atlas  with  the  Axis  .    .    .  323 

Spine  with  the  Cranium  .  325 
"      Atlas  with    the   Occipital 

Bone 325 

Articulation  of  the  Axis  with  the  Occipital  Bone  3:26 

Surgical  Auatomy  of  Articulations  of  the  Spine.  327 

Temporo-maxillary  Articulation 327 

Surface  Form 330 

Surgical  Anatomy     ...           330 

Articulations  of  the  Ribs  with  the  Vertebra : 

Costo-vertebral 330 

Costo-transverse 331 

Articulations  of  the  Cartilages  of  the  Ribs  with 

the  Sternum  and  Eusiform  Cartilage  .    .    .    .  334 


Interchondral  Articulations 334 

Ligaments  of  the  Sternum        336 

Articulation  of  the  Pelvis  with  the  Spine  .    .    .  336 
Articulations  of  the  Pelvis : 

Articulation  of  the  Sacrum  and  Ilium  .    .  336 

Ligament  between  the  Sacrum  and  Ischium  337 

Articulation  of  the  Sacrum  and  Coccyx    .  339 

Articulation  of  the  Pubes 339 

ARTICULATIONS  OF  THE  UPPER  EXTREMITY. 

Sterno-clavicular 340 

Surface  Form 342 

Surgical  Anatomy 342 

Acromio-clavicular 342 

Surface  Form 344 

Surgical  Anatomy 344 

Proper  Ligaments  of  the  Scapula 344 

Shoulder-joint 345 

Surface  Form 348 

Surgical  Anatomy 348 

Elbow-joint 349 

Surface  Form 352 

Surgical  Anatomy • 352 

Radio-ulnar  Articulations 353 

Surface  Form 356 

Wrist-joint 356 

Surface  Form 357 

Surgical  Anatomy 357 


CONTENTS. 


11 


Articulations  of  the  Carpus 357 

of  the  first  row  of  Carpal  Bones.  357 
of  the  second  row  of  Carpal  Bones  358 
of  the  two  rows  of  Carpal  Bones.  358 

Carpo-metacarpal  Articulations 359 

of  the  Metacarpal  Bone  of  Thumb  and 

Trapezium 359 

of  the  four  inner  Metacarpal  Bones  and 

Carpus .    .    360 

Articulations  of  the  Metacarpal  Bones  ....    361 

Metacarpo-phalangeal  Articulations 361 

Surface  Form 362 

Articulations  of  the  Phalanges 362 

ARTICULATIONS  OF   THE   LOWER  EXTREMITY. 

Hip-joint 362 

Surface  form 366 

Surgical  Anatomy 36(3 

Knee-joint 368 

Surface  Form 374 

Surgical  Anatomy 374 

Articulations  between  the  Tibia  and  Fibula  .  376 


PAGE 

Ankle-joint 377 

Surface  Form 379 

Surgical  Anatomy 379 

Articulations  of  the  Tarsus 380 

of  the  Os  Calcis  and  Astragalus.  330 
of  the  Os  Calcis  and  Cuboid  .  .  381 
of  the  Os  Calcis  and  Xavicular  .  382 

Surgical  Anatomy 382 

of  the  Astragalus  and  Xavicular.  382 
of  the  Xavicular  and  Cuneiform.  ->-3 
of  the  Xavicular  and  Cuboid  . 
of  the  Cuneiform  with  each  other  383 
of  the  External  Cuneiform  and 

.  Cuboid-. 384 

Torso-metatarsal  Articulations 384 

Articulations  of  the  Metatarsal  Bones   ....    385 
Synovial  Membranes  in  Tarsal  and  Metatarsal 

Joints  ....  385 

Metatarso-phalangeal  Articulations 386 

Articulations  of  the  Phalanges 387 

Surface  Form ....    387 


MUSCLES  AND  FASCLE. 


General  Description  of  Muscle 388 

Tendons    

"  Aponeuroses     ....  389 

"  "  Fascia 389 


MUSCLES  AND  FASCI.E  OF  THE  CRANIUM  AND 
FACE. 


Intermaxillary  Region. 

Dissection   .................  401 

Orbicularis  Oris     ..............  401 

Buccinator  .................  402 

Eisorius  ..................  402 

Actions    ..................  402 


Subdivision  into  Groups 

Cranial  Region. 

Dissection 

Occipito-frontalis 

Auricular  Region. 

Dissection 

Attrahens  Aurem 

Attollens  Aurem 

Retrahens  Aurem 

Actions 


Palpebral  Region. 

Dissection 

Orbicularis  Palpebrarum    .... 

Corrugator  Supercilii 

Tensor  Tarsi 

Actions  .          


390 


391 
392 


393 
393 
394 
394 
394 


394 
394 
395 

3S>5 


Temporo- Maxillary  Region. 

Masseteric  Fascia      

Masseter 

Temporal  Fascia 

Dissection 

Temporal 

Ptery go- Maxillary  Region. 

Dissection 

External  Pterygoid 

Internal  Pterygoid 

Actions 

Surface  Form  of  Muscles  of  Head  and  Face 

MUSCLES  AND  FASCI.E  OF  THE  XECK. 
Subdivision  into  Groups 


Orbital  Region. 

Dissection 

Levator  Palpebrse 

Rectus  Superior,  Inferior,  Internal,   and  Ex- 
ternal Recti 

Superior  Oblique 

Inferior  Oblique 

Actions 

Surgical  Anatomy 

Xasal  Region. 

Pyramidalis  Xasi 

Levator  Labii  Superioris  Alseque  Xasi  .... 
Dilatator  Xaris.  Anterior  and  Posterior    .    .    . 

Compressor  Xasi 

Compressor  Xarium  Minor 

Depressor  Alse  Xasi 

Actions 

Superior  Maxillary  Region. 

Levator  Labii  Superioris  (Proprius) 

Levator  Anguli  Oris 

Zygomaticus,  Major  and  Minor 

Actions    . 


3961 
396 

397 
397 
397 
3M 
308 


Superficial  Region. 

Dissection 

Superficial  Cervical  Fascia 

Platysma  Myoides 

Surgical  Anatomy 

Actions 

Deep  Cervical  Fascia 

Sterno-mastoid 

Boundaries  of  the  Triangles  of  the  Neck 

Actions 

Surface  Form 

Surgical  Anatomy 


398 

9  Dissection 

®  Sterno-hyoid 

Z  Sterno-thvroid 

®  Thyro-hyoid 

®  OmVhyoid 

y  Actions 


Infra-hyoid  Region. 


400 
400 
400 
400 


Inferior  Maxillary  Region. 

Dissection 

Levator  Labii  Inferioris 

Depressor  Labii  Inferioris 

Depressor  Anguli  Oris 

Actions 


Supra-hyoid  Region. 
Dissection 
Digastric 
Stylo-hyoid 
Stylo-hyoid  Ligament 
Mylp-hyoid 
Genio-hyoid 
Actions' 


403 
403 
403 
403 
403 


404 
404 
405 
405 
406 


406 


407 
407 
407 
407 
407 
407 
409 
409 
410 
411 
411 


411 
411 
411 


413 
413 


414 


414 
414 


400 
400 

401 
401 
401  I  Dissection 415 


Lingual  Region. 


12 


CONTENTS. 


Genio-liyo-glossus 415 

Hyo-glossus 416 

Chrondro-glossus 41U 

Stylo-glossus 416 

Palato-glossus 416 

Muscular  Substance  of  Tongue 416 

Superior  Lingualis 417 

Transverse  Lingualis 418 

Vertical  Lingualis 418 

Inferior  Lingualis 418 

Surgical  Anatomy 418 

Actions 418 

Pharyngeal  Region. 

Dissection 419 

Inferior  Constrictor 419 

Middle  Constrictor 420 

Superior  Constrictor 420 

Stylo-pharyngeus 420 

Actions 420 

Palatal  Region. 

Dissection 

Levator  Palati 

Tensor  Palati 

Palatine  Aponeurosis 

Azygos  Uvulae 

Palato-glossus 

Palato-pharyngeus 

Salpingo-pharyngeus  .   .   *   ' 

Actions 

Surgical  Anatomy 


421 
421 
422 
422 
422 
422 
422 
423 
423 
423 


Vertebral  Region  (Anterior). 
Rectus  Capitis  Anticus  Major  .... 
Eectus  Capitis  Anticus  Minor  .... 

Rectus  Capitis  Lateralis 

Longus  Colli 

Vertebral  Region  (Lateral). 

Scalenus  Anticus 

Scalenus  Medius 

Scalenus  Posticus 

Actions 

Surface  Form  of  Muscles  of  Neck  .    . 


MUSCLES  AND  FASCIAE  OF  THE  TRUNK. 

Subdivision  into  Groups 

The  Back. 

Subdivision  into  Layers 

First  Layer. 

Dissection    .    .        

Superficial  and  Deep  Fasciae 

Trapezius 

Ligamentum  Nuchae. 

Latissimus  Dorsi 

Second  Layer. 

Dissection 

Levator  Anguli  Scapulae 

Rhomboideus  Minor 

Rhomboideus  Major 

Actions 

Third  Layer. 

Dissection 

Serratus  Posticus  Superior 

Serratus  Posticus  Inferior 

Vertebral  Aponeurosis 

Lumbar  Fascia 

Splenius 

Splenius  Capitis 

Splenius  Colli 

Actions 

Fourth  Layer. 

Dissection 

Erector  Spinse 

Ilio-costalis 

Musculus  Accessorius  ad  Ilio-costalem  .    .    .    , 
Cervicalis  Ascendeus 


424 
424 
425 
425 

425 
425 
426 
426 
427 


427 

427 


428 
428 
428 
430 
430 

431 
431 
431 
431 
432 


432 
432 
432 
433 
433 
433 
433 
433 
434 

434 
434 
434 
436 
436 


[jongissimus  Dorsi 436 

Transversalis  Colli 436 

Trachelo-mastoid     . 436 

pinalis  Dorsi 436 

Spinalis  Colli 436 

Complexus 437 

Biventer  Cervicis 437 

Fifth  Layer. 

Dissection 437 

Semispinalis  Dorsi 437 

Semispinalis  Colli 437 

MultifidusSpinse 4 

Rotatores  Spinae 438 

Supraspinales 43S 

Interspinales 4 

Extensor  Coccygis 438 

Intertransversales 438 

Rectus  Capitis  Posticus  Major 439 

Rectus  Capitis  Posticus  Minor 439 

Obliquus  Capitis  Inferior 439 

Obliquus  Capitis  Superior 439 

Suboccipital  Triangle 439 

Actions 440 

Surface  Form  of  Muscles  of  Back 440 

THE  THORAX. 

Intercostal  Fasciae 441 

Intercostal  Muscles     441 

External  and  Internal  Intercostals 442 

Infracostales  (subcostales) 442 

Triangularis  Sterni 442 

Levatores  Costarum 442 

Actions       443 

Muscles  of  Inspiration  and  Expiration     .    .    .  444 

Diaphragmatic  Region. 

Diaphragm 444 

Actions 446 


The  Abdomen. 

Dissection      

Superficial  Fascia 

External  or  Descending  Oblique     .    .    . 

External  Abdominal  Ring 

The  Intercolumnar  Fibres 

The  Intercolumnar  Fascia 

Poupart's  Ligament 

Gimbernat's  Ligament 

Triangular  Ligament 

Internal  or  Ascending  Oblique    .... 

Cremaster 

Transversalis 

Rectus 

Pyramidalis 

Linea  Alba 

Linese  Semilunares,  Lineae  Transversae 

Actions 

Fascia  Transversalis 

Internal  Abdominal  Ring 

Inguinal  Canal 

The  Deep  Crural  Arch 

Surface  Form  of  Muscles  of  Abdomen  . 

Deep  Muscles  of  the  Abdomen. 

Quadratus  Lumborum 

Actions 


Muscles  of  the  Pelvic  Outlet  and  Perinxnm. 

Corrugator  Cutis  Aui 

External  Sphincter  Ani 

Internal  Sphincter  Ani 

Levator  Ani 

Coccygeus      

Superficial  Perineal  Fascia 

Central  Tendinous  Point 

Transversus  Perinsei  .....-••• 

Accelerator  Urinse 

Erector  Penis 

Triangular  Ligament 

Compressor  Urethrae 


447 
447 
448 
449 
450 
450 
450 
450 
451 
451 
452 
453 
453 
455 
455 
456 
456 
456 
456 
457 
457 
457 


458 
458 


458 
458 
459 
459 
460 
460 
460 
461 
461 
462 
463 
464 


CONTEXTS. 


13 


Muscles  of  the  Perinarum  in  the  Female.     PAGE 

Transversus  Perinan 4»>4 

Sphincter  Vaginae 464 

Erector  Clitoridis 465 

Triangular  Ligament 4i>5 

Compressor  Urethra? ...    465 

MUSCLES  AND  FASCIA  OF  THE  UPPE  : 
EXTREMITY. 

Subdivision  into  Groups 465 

Dissection  of  Pectoral  Region  and  Axilla   .        466 
Fascia?  of  the  Thorax 466 

THE  SHOULDER. 

Anterior  Thoracic  Region. 

Pectoralis  Major .  467 

Costo-coracoid  Membrane 46> 

Pectoralis  Minor 469 

Subclavius 4»>li 

Actions ...  470 

Lateral  Thoracic  Region. 

Serratus  Magnus 470 

Actions ....  471 

Superficial  Fascia 471 

Acromiai  Region. 

Deep  Fascia 471 

Deltoid 471 

Actions 472 

Surgical  Anatomy 472 

Anterior  Scapular  Region. 

Subscapular  Fascia 472 

Subscapularis 472 

Actions 473 

Posterior  Scapular  Region. 

Dissection 473 

Supraspinous  Fascia 473 

Supraspinatus 473 

Infraspinous  Fascia 473 

Infraspiuatus ,    .    .    , 473 

Teres  Minor 474 

Teres  Major 474 

Actions 475 

THE  ARM. 

Anterior  Humeral  Region. 

Dissection 475 

Deep  Fascia  of  Arm 475 

Coraco-brachialis 476 

Biceps .476 

Erachialis  Anticus 477 

Actions 477 

Posterior  Humeral  Region. 

Triceps 477 

Subanconeus 475 

Actions       473 

Surgical  Anatomy 47? 

The  Forearm. 

Dissection 473 

Deep  Fascia  of  Forearm 478 

Anterior  Brachial  Region,  Superficial  Layer. 

Pronator  Eadii  Teres 479 

Flexor  Carpi  Badialis 479 

Palmaris  Longus 430 

Flexor  Carpi  Ulnaris 480 

Flexor  Digitorum  Sublimis 480 

Deep  Layer. 

Dissection 4gj 

Flexor  Profundus  Digitorum  .        .  481 

Flexor  Longus  Pollicis 482 

Pronator  Quadratus *  433 

Actions _.  •  > 


Radial  Region.  PAGE 

Dissection 433 

Supinator  Longus 433 

Extensor  Carpi  Badialis  Longior    .           ...    484 
Extensor  Carpi  Radialis  Brevier 484 

Posterior  Brachtal  Region,  Superficial  Layer. 

Extensor  Communis  Digitorum 485 

Extensor  Minimi  Digiti 435 

Extensor  Carpi  Ulnaris \    486 

Anconeus 486 

Deep  Layer. 

Supinator  Brevis 435 

Extensor  Ossis  Metacarpi  Pollicis 486 

Extensor  Brevis  Pollicis 438 

Extensor  Longus  Pollicis 438 

Extensor  Indicis 433 

Actions 433 

Surgical  Anatomy \  439 

The  Hand. 

Dissection 439 

Anterior  Annular  Ligament 439 

Synovial  Membranes  of  the  Flexor  Tendons 

at  the  Wrist 489 

Posterior  Annular  Ligament 490 

Deep  Palmar  Fascia 490 

Superficial     Transverse     Ligament    of     the 

Fingers 492 

Badial  Group 490 

Abductor  Pollicis 492 

Opponens  Pollicis 492 

Flexor  Brevis  Pollicis 492 

Adductor  Obliquus  Pollicis 493 

Adductor  Transversus  Pollicis 493 

Actions 494 

Ulnar  Group 494 

Palmaris  Brevis 494 

Abductor  Minimi  Digiti 494 

Flexor  Brevis  Minimi  Digiti 494 

Opponens  Minimi  Digiti 495 

Actions 496 

Middle  Palmar  Group 496 

Lumbricales 496 

Interossei  Dorsales 496 

Interossei  Palmares 496 

Actions 497 

Surface  form  of  Muscles  of  Upper  Extremity  .  49? 

Surgical  Anatomy  of  the  Muscles  of  the  Upper 
Extremity. 

Fractures  of  the  Clavicle 499 

Aeromion  Process 499 

Coracoid  Process 500 

Humerus 500 

Olecranon 501 

Radius 501 

Ulna 502 

Radius  and  Ulna 502 

Lower  end  of  Radius  ....    502 

MUSCLES  AND  FASCI.E  OF  THE  LOWER 

EXTREMITY. 
Subdivision  into  Groups 502 

lUac  Region. 

Dissection 503 

Iliac  Fascia 503 

Psoas  Magnus 504 

Psoas  Parvus 594 

Iliacus \    \    \   \  504 

Actions 505 

Surgical  Anatomy 505 

THE  THIGH. 

Anterior  Femoral  Region. 

Dissection 505 

Superficial  Fascia "  506 

Deep  Fascia  (Fascia  Lata) 506 

Saphenous  Opening 507 

Iliac  and  Pubic  portions  of  Fascia  Lata    .    .    .  508 

Tensor  Vaginae  Femoris 593 


14 


CONTENTS. 


PAGE 

Sartorius 508 

Quadriceps  Extensor 509 

Rectus  Femoris 509 

Vastus  Externus 509 

Vastus  Interims  and  Crureus 510 

Subcrureus 510 

Actions 510 

Surgical  Anatomy 511 

Internal  Femoral  Region. 

Dissection 511 

Gracilis 511 

Pectineus 511 

Adductor  Longus 512 

Adductor  Brevis 512 

Adductor  Magnus 513 

Actions 513 

Surgical  Anatomy 513 

THE  HIP. 
Gluteal  Region. 

Dissection 514 

Gluteus  Maximus 514 

Gluteus  Medius 515 

Gluteus  Minimus 516 

Pyriformis 516 

Obturator  Membrane 516 

Obturator  Internus 516 

Gemelli 517 

Gemellus  Superior 517 

Gemellus  Inferior 517 

Quadratus  Femoris 517 

Obturator  Externus 518 

Actions 518 

Posterior  Femoral  Region. 

Dissection 518 

Biceps 518 

Semitendinosus 519 

Semimembranosus 519 

Actions 519 

Surgical  Anatomy  of  Hamstring  Tendons   .    .  520 

The  Leg. 

Dissection  of  Front  of  Leg 520 

Deep  Fascia  of  the  Leg 520 

Anterior  Tibio-fibular  Region. 

Tibialis  Anticus 521 

Extensor  Proprius  Hallucis 521 

Extensor  Longus  Digitorum 521 

Peroneus  Tertius 522 

Actions 522 

Posterior  Tibio-fibular  Region,  Superficial  Layer. 

Dissection 522 

Gastrocuemius 522 


Soleus 523 

Tendo  Achillis 523 

Plantaris 524 

Actions 524 

Deep  Layer. 

Deep  Transverse  Fascia  of  Leg 524 

Popliteus 524 

Flexor  Longus  Hallucis 525 

Flexor  Longus  Digitorum 525 

Tibialis  Posticus 526 

Actions 526 

Fllular  Region. 

Peroneus  Longus 527 

Peroneus  Brevis 527 

Actions 527 

Surgical  Anatomy  of  Tendons  around  Ankle  528 

THE  FOOT. 

Anterior  Annular  Ligament 528 

Internal  Annular  Ligament •.    .    .    .  528 

External  Annular  Ligament 529 

Plantar  Fascia 529 

Dorsal  Region. 
Extensor  Brevis  Digitorum 


530 

Plantar  Region. 

Subdivision  into  Groups 530 

Subdivision  into  Layers 530 

First  Layer 530 

Dissection 530 

Abductor  hallucis 530 

Flexor  brevis  digitorum 530 

Fibrous  Sheatbs  of  Flexor  Tendons   .    .    .  531 

Abductor  Minimi  Digiti 531 

Second  Layer 532 

Flexor  Accessorius 532 

Lumbricales 532 

Third  Layer 532 

Flexor  Brevis  Hallucis 532 

Adductor  Obliquus  Hallucis      533 

Flexor  Brevis  Minimi  Digiti 533 

Adductor  Transversus  Hallucis 533 

Fourth  Layer 534 

Interossei 534 

Surface  Form  of  Muscles  of  Lower  Extremity  535 

Surgical  Anatomy  of  the  Mmdes  of  the  Lower 
Extremity. 

Fracture  of  the  Neck  of  the  Femur 537 

the  Femur  below  Trochauter  Minor  537 

the  Femur  above  the  Condyles     .  538 

the  Patella 538 

the  Tibia 538 

the  Fibula,  with  Dislocation  of  the 

Foot  outward 538 


THE 

General  Anatomy. 
Subdivision  into  Pulmonary  and  Systemic  .    . 

Distribution  of — Where  found 

Mode  of  Division— Anastomoses 

PULMONARY  ARTERY 

THE  AORTA. 


Divisions 

Ascending  Aorta  .... 
Coronary  Arteries    .    .    . 

Arch  of  Aorta 

Peculiarities 

Surgical  Anatomy    .    .    . 

Branches     

Peculiarities  of  Branches 


Arteria  Innominata. 

Relations 545 

Peculiarities 546 

Surgical  Anatomy 546 


ARTERIES. 

Common  Carotid  Arteries. 

539    Course  and  Relations 547 

539    Peculiarities 549 

539  Surface  Marking 549 

540  Surgical  Anatomy 549 

External  Carotid  Artery. 

Course  and  Relations 551 

Surface  Marking 551 

Surgical  Anatomy 551 

Branches 551 

Superior  Thyroid  Artery. 

Course  and  Relations 552 

Branches 552 

Surgical  Anatomy 552 

Lingual  Artery. 

Course  and  Relations 553 

Branches 553 

Surgical  Anatomy 553 


541 
541 
542 
543 
543 
544 
545 
545 


CONTEXTS. 


Facial  Artery.  PAGE 

Course  and  Relations 554 

Branches 555 

Peculiarities 556 

Surgical  Anatomy 556 

Occipital  Artery. 

Course  and  Relations 556 

Branches 557 

Posterior  Auricular  Artery. 

Course  and  Relations 557 

Branches 557 

Ascending  PharyngeaJ  Artery. 

Course  and  Relations 558 

Branches 558 

Surgical  Anatomy 559 

Temporal  Artery. 

Course  and  Relations 559 

Branches 559 

Surgical  Anatomy 559 

Internal  Maxillary  Artery. 

Course  and  Relations      559 

Peculiarities 559 

Branches  from  First  Portion 560 

'•      Second  Portion 561 

"      Third  Portion      562 

SCKGICAL  ANATOMY  OF  THE  TRIANGLES  OF  THE 
NECK. 

Anterior  Triangular  Space. 

Inferior  Carotid  Triangle 563 

Superior  Carotid  Triangle 564 

Submaxillary  Triangle 564 

Posterior  Triangular  Space. 

Occipital  Triangle 565 

Subclavian  Triangle 565 

Internal  Carotid  Artery. 

Cervical  Portion 566 

Petrous  Portion 566 

Cavernous  Portion 566 

Cerebral  Portion 566 

Peculiarities 567 

Surgical  Anatomy 568 

Branches 568 

Ophthalmic  Artery 568 

Cerebral  Branches  of  Internal  Carotid  .    .    .  570 

The  Blood-vessels  of  the  Brain 573 

ARTERIES  OF  UPPER  EXTREMITY. 

Subclavian  Arteries. 

First  Part  of  Right  Subclavian  Artery  ....  577 

First  Part  of  Left  Subclavian  Artery    ....  577 

Second  Part  of  Subclavian  Artery 578 

Third  Part  of  Subclavian  Artery* 578 

Peculiarities 579 

Surface  Marking 579 

Surgical  Anatomy 579 

Branches 5->l 

Vertebral  Artery , 581 

Basilar  Artery 553 

Circle  of  Willis 584 

Thyroid  Axis 584 

Inferior  Thyroid 584 

Suprascapular  Artery 585 

Transversalis  Colli  * 585 

Internal  Mammary 586 

Superior  Intercostal 587 

THE  AXILLA 587 

Surgical  Anatomy  of  the  Axilla 587 

Axillary  Artery. 

First  Portion 589 

Second  Portion 590 

Third  Portion 590 

Peculiarities 90 


Surface  Marking 591 

Surgical  Anatomy 591 

Branches 593 

Brachial  Artery. 

Relations 593 

Bend  of  the  Elbow 593 

Peculiarities  of  Brachial  Artery 594 

Surface  Form 595 

Surgical  Anatomy 595 

Branches 595 

Radial  Artery. 

Relations 597 

Deep  Palmar  Arch 593 

Peculiarities 593 

Surface  Marking 598 

Surgical  Anatomy 598 

Branches 599 

Ulnar  Artery. 

Relations 601 

Peculiarities  of  Ulnar  Artery 601 

Surface  Marking 602 

Surgical  Anatomy 602 

Branches     .    .    .  * 602 

Superficial  Palmar  Arch 604 

ABTEKIES  OF  THE  TRUNK. 
DESCENDING  AORTA 605 

THORACIC  AORTA. 

Course  and  Relations 605 

Surgical  Anatomy 606 

Branches     .    .   .  " 606 

ABDOMINAL  AORTA. 

Course  and  Relations 608 

Surface  Marking 609 

Surgical  Anatomy 609 

Branches 610 

Creliac  Axis 610 

Gastric  Artery 611 

Hepatic  Artery 611 

Splenic  Artery 611 

Superior  Mesenteric  Artery 612 

Inferior  Mesenteric  Artery 614 

Suprarenal  Arteries 615 

Renal  Arteries 616 

Spermatic  Arteries 616 

Ovarian  Arteries .  616 

Phrenic  Arteries 616 

Lumbar  Arteries 617 

Middle  Sacral  Artery 617 

Luschka's  Gland 617 

COMMON  ILIAC  ARTERIES. 

Course  and  Relations 618 

Branches 618 

Peculiarities 618 

Surface  Marking 619 

Surgical  Anatomy 619 

Internal  Iliac  Artery. 

Course  and  Relations 620 

Peculiarities 621 

Surgical  Anatomy 621 

Branches 622 

Vesical  Arteries ' .  622 

Hsernorrhoidal  Arteries 622 

Uterine  Arteries 622 

Vaginal  Arteries 622 

Obturator  Artery 622 

Peculiarities 623 

Internal  Pudic  Artery 623 

In  the  Male 623 

Peculiarities 624 

Surgical  Anatomy 624 

Branches 625 

In  the  Female 625 

Sciatic  Artery 626 

Lumbar  Artery 626 


CONTENTS. 


Lateral  Sacral  Artery 627 

Gluteal  Artery 627 

Surface  Marking  of  Branches  of  Internal  Iliac  .  627 
Surgical   Anatomy   of   Branches  of   Internal 

Iliac 628 

External  Iliac  Artery. 

Course  and  Relations 628 

Surgical  Anatomy 628 

Deep  Epigastric  Artery 629 

Deep  Circumflex  Iliac  Artery 629 

ARTERIES  or  THE  LOWER  EXTREMITY. 
Femoral  Artery. 

Course  and  Relations 630 

Scarpa's  Triangle 630 

Hunter's  Canal 630 

Common  Femoral 631 

Superficial  Femoral 632 

Peculiarities 6 

Surface  Marking € 

Surgical  Anatomy ,    .    .    .  633 

Branches 635 

Deep  Femoral 635 

Branches     ,...,.,..  636 

POPLITEAL  SPACE .   .  637 

Popliteal  Artery. 

Course  and  Relations . 

Peculiarities •  638 


Surface  Marking 638 

Surgical  Anatomy 

branches •    •    639 

Anterior  Tibial  Artery. 

Course  and  Relations 641 

Peculiarities • 642 

Surface  Marking 642 

Surgical  Anatomy 642 

Branches 642 

Dor  sails  Pedis  Artery. 

Course  and  Relations 643 

Peculiarities 643 

Surface  Marking  . 643 

Surgical  Anatomy 643 

Branches 644 

Posterior  Tibial  Artery. 

Course  and  Relations 645 

Peculiarities 645 

Surface  Marking 645 

Surgical  Anatomy 645 

Branches 646 

Peroneal  Artery. 

Course  and  Relations 646 

Peculiarities 646 

Plantar  Arteries 647 

Surface  Marking 648 

Surgical  Anatomy 64b 


THE  VEINS. 


General  Anatomy. 
Subdivision    into   Pulmonary,   Systemic,  and 

Portal 

Anastomoses  of  Veins 

Superficial  Veins 

Deep  Veins,  Venae  Comites 

Sinuses 

PULMONARY  VEINS 

SYSTEMIC  VEINS 

VEINS  OF  THE  HEAD  AND  NECK. 


649 
649 
649 
649 
650 
650 
650 


Frontal  Vein 

Facial  Vein 

Surgical  Anatomy 

Temporal  Vein 

Internal  Maxillary  Vein  .... 
Temporo-maxillary  Vein  .... 
Posterior  Auricular  Vein  .... 
Occipital  Vein 

Veins  of  the  Neck. 

External  Jugular  Vein 

Surgical  Anatomy 

Posterior  External  Jugular  Vein 

Anterior  Jugular  Vein 

Internal  Jugular  Vein 

Surgical  Anatomy 

Lingual  Vein 

Pharyngeal  Vein 

Thyroid  Veins 

Vertebral  Veins  ...... 

Veins  of  the  Diploe    ...... 


Circular  Sinus 

Superior  Petrosal  Sinus < 

Inferior  Petrosal  Sinus < 

Transverse  Sinuses 

Emissary  Veins obi 

VEINS  OF  THE  UPPER  EXTREMITY  AND  THORAX. 

Superficial  Veins ( 

Deep  Veins ' 

Axillary  Vein <™4 

Surgical  Anatomy <™n 

Subclavian  Vein °bo 

Innominate  Veins *»> 

Peculiarities  of 


651 
652 
652 

652  J.    vyw.-« - 

652  Internal  Mammary  Veins 

653  j  Inferior  Thyroid  Veins •    •    ' 

653  j  Superior  Intercostal  Veins 

653  i  Superior  Vena  Cava «"7 

Azygos  Veins °°< 

Bronchial  Veins ' 

Spinal  Veins    .' 6b8 


653 
653 
654 
654 


VEINS  OF  THE  LOWER  EXTREMITY—  ABDOMEN 
AND  PELVIS. 


SSJ  Internal  Saphenous  Vein 

External  Saphenous  Vein WU 


£1  Popliteal  Jein 

654 
655 
655 


Cerebral  Veins. 


Superficial  Cerebral  Veins 
Deep  Cerebral  Veins  .  . 
Cerebellar  Veins  .... 


656 
657 
657 


Sinuses  of  the  Dura  Mater. 

Superior  Longitudinal  Sinus 

Inferior  Longitudinal,  Straight  Sinuses 

Lateral  Sinus     .    ..    

Occipital  Sinuses 

Cavernous  Sinuses 

Surgical  Anatomy 


Femoral  Vein 


671 
672 
672 


Deep  Epigastric  Veins 

Deep  Circumflex  Iliac  Veins »/£ 

Internal  Iliac  Vein . 
Internal  Pudic  Veins 
Common  Iliac  Veins 
Peculiarities 


672 
672 
672 
673 


Inferior  Vena  Cava '•    '    mi 

Peculiarities °{* 

Lumbar  Veins ™* 

Spermatic  Veins    .    . 
Surgical  Anatomy 

Ovarian  Veins 


657 
658 

658    

659  I  Renal  and  Suprarenal  Vems 

659  !  Phrenic  Veins 

659    Hepatic  Veins 


674 
674 
674 
675 
675 
675 


CONTENTS. 


17 


POSTAL  SYSTEM  OF  VEINS.  PAGE 

Superior  Mesenteric  Vein 675 

Splenic  Vein 675 

Inferior  Mesenteric  Vein 675 

Gastric  Veins    .  .    676 


Portal  Vein 677 

CARDIAC  VEINS 677 

Coronary  Sinus 677 


THE   LYMPHATICS. 


Cfeneral  Anatomy. 

Subdivision  into  Deep  and  Superficial 
Lymphatic  or  Conglobate  Glands   .    . 

Thoracic  Duct ' 

Eight  Lymphatic  Duct 


679 
679 
680 
680 


Lymphatics  of  Head,  Face,  and  Xeck. 

Lymphatic  Glands  of  Head 

Lymphatics  of  the  Head 

Superficial  Lymphatics  of  the  Face  .    .    .    . 

Deep  Lymphatics  of  the  Face 

Lymphatics  of  the  Cranium 

Lymphatic  Glands  of  the  Xeck 

Superficial  Cervical  Glands 

Deep  Cervical  Glands 

Superficial  and  Deep  Cervical  Lymphatics  . 
Surgical  Anatomy 


Lumbar  Glands 688 

Superficial  Lymphatics  of  Wall  of  Abdomen  .  689 

of  Gluteal  Region  .    .  689 
of  Scrotum  and  Peri- 

nseum 689 

of  Penis 689 

of    Labia,    Nymphse, 

and  Clitoris     .    .    .  689 

Deep  Lymphatics  of  Pelvis  and  Abdomen  .    .  689 

Lymphatics  of  Bladder 639 

of  Rectum 689 

of  Uterus 689 

of  Testicle 690 

of  Kidney 690 

of  Liver  " 690 

Lymphatic  Glands  of  Stomach 690 


Lymphatics  of  the  Upper  Extremity. 

Superficial  Lymphatic  Glands 

Deep  Lymphatic  Glands 

Axillary  Glands 

Surgical  Anatomy 

Superficial  Lymphatics  of  Upper  Extremity 
Deep  Lymphatics  of  Upper  Extremity  .    .    '. 

Lymphatics  of  the  Lower  Extremity. 

Superficial  Inguinal  Glands 

Surgical  Anatomy 

Deep  Lymphatic  Glands 

Anterior  Tibial  Gland 

Popliteal  Glands 

Deep  Inguinal  Glands 

Gluteal  and  Ischiatic  Glands       

Superficial  Lymphatics  of  Lower  Extremity 

Internal  Group 

External  Group 

Deep  Lymphatics  of  Lower  Extremity    . 

Lymphatic*  of  Pelcis  and  Abdomen. 

Lymphatic  Glands  of  Pelvis 

External  Iliac  Glands 

Internal  Iliac  Glands , 

Sacral  Glands    . 


681 
681 
682 
682 
682 
683 
683 
683! 

684 

gg4  I  Lymphatics  of  Stomach 690 

j  Lymphatic  Glands  of  Spleen 690 

Lymphatics  of  Spleen 690 

684 

gg^  Lymphatic  System  of  the  Intestine. 

6~4    Lymphatic  Glands  of  Small  Intestines  ( Mesen- 

684  teric  Glands ) 691 

685  Lymphatic  Glands  of  Large  Intestine  ....    691 

686  Lymphatics  of  Small  Intestines  (Lactealsi  .    .    691 

of  Large  Intestine 691 


686 
686 
686 
686 
686 
686 
686 
686 
688 
887 
687 


687 
687 


Lymphatics  of  Thorax. 

Lymphatic  Glands  of  Thorax 691 

Intercostal  Glands 691 

Internal  Mammary  Glands 691 

Anterior  Mediastinal  Glands 691 

Posterior  Mediastinal  Glands 691 

Superior  Lymphatics  on  Front  of  Thorax  .    .  691 

Deep  Lymphatics  of  Thorax 691 

Intercostal  Lymphatics 691 

Internal  Mammary  Lymphatics 692 

Lymphatics  of  Diaphragm 692 

Bronchial  Glands 692 

Lymphatics  of  Lung 692 

Cardiac  Lymphatics 692 

Thymic  Lymphatics 692 

Thyroid  Lymphatics 692 

Lymphatics  of  CEsophagus 692 


XERVOUS   SYSTEM. 


General  Anatomy. 


Subdivision  into  Cerebro-spinal  Axis,  Ganglia, 
and  Nerves    ...        

The  Spinal  Cord  and  its  Membranes. 

Dissection 

Membranes  of  the  Cord 

Dura  Mater 

Arachnoid 

Pia  Mater 

Ligamentum  Denticulatum 

Spinal  Cord 

Fissures  of  Cord 

Columns  of  Cord *. 

Structure  of  the  Cord 

Commissure  of  the  Cord 

Minute  Anatomy  of  the  Cord 

Xeuroglia 

White  Substance 

Collateral  Fibres 

Gray  Substance 


693 


693 
693 
693 
694 
695 
695 
695 
696 
697 
697 
697 
698 
698 
698 
700 
701 


The  Brain  and  its  Membranes. 
Membranes  of  the  Brain   . 


Dura  Mater. 

Structure 703 

Arteries,  Veins 703 

Xerves 703 

Glandulse  Pacchioni 703 

Processes  of  the  Dura  Mater 704 

Falx  Cerebri 704 

Tentorium  Cerebelli 704 

Falx  Cerebelli 704 

The  Arachnoid  Membrane. 

Subarachnoid  Space        705 

Cerebro-Spinal  Fluid 705 

The  Pia  Mater 705 

THE  BRAIN. 
Subdivision  into  Cerebrum,  Cerebellum,  Pons 

Varolii,  Medulla  Oblongata 706 

Weight  of  Brain 706 

MEDULLA  OBLONGATA. 

Surface 709 

Pyramids 709 

Olive  or  Olivary  Body 710 


18 


CONTENTS. 


Fuuiculus  Gracilis 714 

Funiculus  Cuneatus 711 

Fuuiculus  of  Eolando 711 

Eestiform  Bodies 712 

External  Arciform  Fibres      712 

Internal  Structure  712 

White  Matter 714 

Funiculus  of  Kolando 714 

Funiculus  Cuneatus 715 

Funiculus  Gracilis 715 

Gray  Matter  of  the  Anterior  and  Lateral  Areas  715 

Gray  Matter  of  the  Posterior  Area 715 

Nuclei 715 

Nuclei  in  Relation  to  Floor  of  the  Fourth  Ven- 
tricle      716 

Nucleus  of  the  Spinal  Accessory  Nerve     .    .    .  716 
Nuclei   of  the   Vagus  and  Glossopharyngeal 

Nerves 716 

Nuclei  of  the  Auditory  Nerve 716 

White  Matter 716 

Pyramid 716 

Olivary  Body 717 

Fibres  in  the  Grooves 717 

Eestiform  Body 717 

Fibres  of  Formatio  Reticularis 718 

Longitudinal  Fibres  of  the  Formatio  Reticu- 
laris   718 

Posterior  Longitudinal  Bundle 718 

Ascending  Root  of  the  Fifth  Nerve 718 

Funiculus  Solitarius 718 

Transverse  and  Dorso-ventral  Fibres    ....  718 

External  Arciform  Fibres 718 

Internal  or  Deep  Arciform  Fibres  .....  719 

Raphe 719 

THE  PONS  VAROLII. 

Ventral  Surface 720 

Dorsal  Surface 720 

Relations  of  the  Cerebellar  Peduncles  to  Each 

Other 720 

Deep  Portion  of  the  Pons 720 

Trapezium 721 

Septum  or  Raphe 721 

Gray  Matter  of  the  Pons 721 

Nuclei  Pontis 721 

Gray  Matter  of  the  Formatio  Reticularis    .    .  721 

Superior  Olivary  Nucleus 722 

Nuclei  of  the  Auditory  Nerve 722 

Nucleus  of  the  Facial  Nerve 722 

Nucleus  of  the  Sixth  Nerve 722 

Nuclei  of  the  Fifth  Nerve 722 

Floor  of  the  Fourth  Ventricle  .  723 


THE  CEREBELLUM. 


Weight  of  the  Cerebellum 

Main  Lobes  of  the  Cerebellum 

Notches  of  the  Cerebellum 

Worm 

Hemispheres 

Lobules  of  Superior  Worm 

Lobules  of  Inferior  Worm 

Structure  of  Each  Lobule 

Lingulaand  Frsenula 

Lobulus  Centralis  and  Alse    ...  .    .    . 

Tuber  Valvulse  and  Postero-inferior  Lobules  . 

Pyramid  and  Digastric  Lobules 

Uvula  and  Amygdalae 

Nodulus  and  Flocculi 

Peduncles  of  the  Cerebellum 

Inferior  Medullary  Velum 

Tent  and  Lateral  Recess 

Superior  Medullary  Velum 

Arbor  Vitse .    .    . 

Fibres  of  the  Peduncles 

Fibrse  Propriaa  of  the  Cerebellum  .    .    .    . 

Fourth  Ventricle 

Boundaries  of  the  Fourth  Ventricle 

Roof  of  Lower  Portion  of  Fourth  Ventricle 

Lateral  Recess ;  Tela  Choroidea  Inferior  . 
Lateral  Recess 


725 
725 
726 
727 
727 
728 
728 
728 
729 
729 
730 
731 
732 
732 
733 
734 
734 
734 
734 
735 
735 
737 
738 

738 
739 


PAGE 

Tela  Choroidea  Inferior 739 

Lingula 740 

Choroid  Plexuses 740 

THE  MID-BRAIN. 

Main  Divisions 741 

Crustse 741 

Fibres  of  the  Crusta 742 

Substantia  Nigra      742 

Tegmentium 742 

Corpora  or  Tubercula  Quadrigemina  ....  743 

Aqueduct  of  Sylvius 744 

Central  Gray  Matter 744 

Superior  Surface  of  Mid-brain     745 

Posterior  Perforated  Lamina 745 

Subthalamic  Region 745 

THE  INTER-BRAIN. 

Optic  Thalamus 746 

Structure  of  the  Optic  Thalamus 747 

Third  Ventricle 748 

Posterior  Commissure 748 

Pineal  Gland 748 

Structure 749 

Epithelial  Roof 749 

Velum  Interpositum 749 

Tela  Choroidea  Superior 750 

Posterior  Perforated  Lamina 750 

Corpora  Albicantia 750 

Tuber  Cinereum       750 

Pituitary  Body 751 

Lamina  Cinerea 751 

Anterior  Boundary 751 

Choroid  Plexuses 751 

Openings 752 

Optic  Tracts 752 

THE  HEMISPHERES. 
General  Considerations  and  Development. 

Frontal  Lobes 753 

Parietal  Lobes 753 

Fornix • 753 

Anterior  Commissure 753 

Corpus  Callosum 753 

Septum  Lucidum 754 

Occipital  Lobe 754 

Temporal  Lobe     754 

The  Lateral  Ventricles,  and  Stntcturfs  in  Connection 
therewith. 

Corpus  Callosum 756 

Central  Cavity  or  Body 757 

Anterior  Cornu 758 

Posterior  Cornu  or  Digital  Cavity 758 

Middle  or  Descending  Cornu 758 

Corpus  Striatum 759 

Internal  Capsule 760 

Tsenia  Semicircularis 760 

Fornix 760 

Anterior  Commissure 762 

Septum  Lucidum 762 

Fifth  Ventricle 763 

Hippocampus  major  or  Cornu  Ammouis   .  763 

Corpus  Fimbriatum 763 

Eminentia  Collaterals  or  Pes  Accessorius  765 

Fascia  Dentata 765 

Choroid  Plexuses 766 

Choroid  Plexus  of  the  Body  of  the  Ventricle  766 

Epithelial  Floor  of  the  Body  of  the  Ventricle  768 

Epithelial  Inner  Wall  of  Descending  Coruu   .  768 

Choroid  Plexus  of  Descending  Cornu     ....  769 

Structure  of  Choroid  Plexus 770 

Transverse  Fissure 770 

Surface  Aspect  of  the  Hemispheres    .    .        .    .  771 

Surface  of  Each  Hemisphere 771 

Gyri  or  Convolutions 773 

Structure  of  the  Convolutions 774 

External  Lobes  and   Fissures  of  the   Hemi- 
sphere    774 

Fissure  of  Sylvius 774 

Fissure  of  Rolando 774 


19 


Parieto-occipital  Fissure    ........ 

Frontal  Lobe  .............. 

Parietal  Lobe     ............. 

Occipital  Lobe  ............ 

Temporal  Lobe  ............. 

Central  Lobe  or  Maud  of  Eeil     ..... 
Mcsial  Lobes  aud  Fissures  of  the  Hemisphere 

Calloso-margiual  Fissure    ....... 

Parieto-occipital  Fissure        ...... 

Calcariue  Fissure  ............ 

Collateral  Fissure     ........... 

Dentate  or  Hippocampal  Fissure  ..... 

Lobes   or   Convolutions  Seen  on   the  In- 
terual  Surface  of  the  Hemisphere  .    .    . 

Gyrus  Foruicatus     ......... 

Marginal  Convolution     ......... 

Quadrate  Lobe  ............. 

Cuneate  or  Occipital  Lobule  ....... 

lufracalcariue    ............. 

Fourth  Temporal  Convolution      ..... 

Hippocampal  Cou  volutiou  ........ 

Unciuate  Gyrus    ............. 

Olfactory  Lobe  ............... 

Anterior  Olfactory  Lobule     ....... 

Posterior   Olfactory   Lobule   or   Anterior 
Perforated  Space  ........... 

Olfactory  Roots     .............. 

Under  Surface  or  "  Base  "  of  the  Eucephalon 

Longitudinal  Fissure  .......... 

luterpeduucular  Space    ........... 

Structure  of  the  Hemisphere    ........ 

Projection  or  Peduncular  Fibres      .... 

Transverse  or  Commissural  Fibres  .    .    . 

iation-fibres  Connecting  Different  Struct- 
ures in  the  Same  Hemisphere  ...... 

Gray  Matter  of  the  Cortex    ...... 

Weight  of  the  Encephalon    ......... 

Cerebral  Localization  and  Topography  .... 

Longitudinal  Fissure  .......    .... 

Fissure  of  Sylvius    ............ 

Fissure  of  Rolando  ............. 

THE  CRANIAL  NERVES. 
Enumeration  ................ 

Olfactory  Nerve    .............. 

Surgical  Anatomy     ........... 

Optic  Nerve    ................ 

Tracts  ................ 

Commissure    .............. 

Surgical  Anatomy     .......... 

Motor  Qcali  Nerve        ....  ...... 

Surgical  Anatomy     .......... 

Pathetic  Nerve  ............... 

Surgical  Anatomy     ........... 

Trifacial  Nerve     .............. 

(Tasserian  Ganglion  ........... 

Ophthalmic  Nerve    ........... 

Lachrymal  and  Frontal  Brandies  .... 

Nasal  Branches      ............ 

Ophthalmic  (Ganglion  .......... 

Superior  Maxillary  Nerve  ........ 

Spheno-palatine  Ganglion  ........ 

Inferior  Maxillary  Nerve  ........ 

An  riculi  (-temporal  Branch      ....... 

Lingual  Branch     ........... 

Inferior  Dental  Branch  ......... 

Otic  Ganglion     ............. 

Submaxillary  Ganglion  ........ 

Surgical  Anatomy  of  Fifth  Nerve  ..... 

Abducens  Nerve    ............. 

Relations  of  the  Orbital  Nerves  ;n  the  Cavern- 
ous Sinus     .............. 

Relations,  etc.  in  the  Sphenoidal  Fissure  .    .    . 
in  the  Orbit  ............ 

Surgical  Anatomy     ........... 

Facial  Nerve  ................ 

Branches  of  Facial  Nerve  ........ 

Surgical  Anatomy    ........... 

Auditory  Nerve    .    .    ............ 

Surgical  Anatomy    ........... 

Glosso-pharyugeal  Nerve       ......... 

2 


PAGE 

774 
775 
776 

777 
777 

77- 
.  77* 

779 
779 
779 
779 

779 
779 
780 
780 
780 
780 
7-1 
7-1 
781 
7--,' 
782 

784 
784 
784 
784 
7-  ! 
785 
785 
786 

786 
789 
789 
790 
790 
790 


790 
792 

793 

793 

793 

793 

794 

794 

795 

796 

796 

796 

797 

797 

798 

798 

799 

801 

803 

805 

806 

~i>7 

-07 

807 

808  < 

809 

810 

810 
810 
810 
811 
811 


Pneumogastric  (Vagus)  Nerve 
Surgical  Anatomy    .    .    .    . 

Spinal  Accessory  Nerve  .    .    .    . 
Surgical  Anatomy    .    .    .    . 

Hypoglossal  Nerve 

Surgical  Anatomy    .    .    .    . 


PAGE 
819 


THE  SPLNAL  NERVES. 

Roots  of  the  Spinal  Nerves 

Origin  of  Anterior  Roots 

of  Posterior  Roots 

Ganglia  of  the  Spinal  Nerves 

Posterior  Divisions  of  the  Spinal  Nerves  .    . 
Anterior  Divisions  of  the  Spinal  Nerves   .    . 

CERVICAL  NERVES. 

Roots  of  the  Cervical  Nerves 

Posterior  Divisions  of  the  Cervical  Nerves   . 
Anterior  Divisions  of  the  Cervical  Nerves    . 

THE  CERVICAL  PLEXUS. 
Superficial  Branches  of  the  Cervical  Plexus 
Deep  Branches  of  the  Cervical  Plexus  ,    .    . 

THE  BRACHIAL  PLEXUS. 
Branches  abort  the  Clnride. 

Posterior  Thoracic 

Suprascapular 


Branches  beloic  the  Claricle. 

Anterior  Thoracic 

Subscapular  Nerves 

Circumflex  Nerve 

Musculo-cutaneous  Nerve 

Internal  Cutaneous  Nerve 

Lesser  Internal  Cutaneous  Nerve    .... 

Median  Nerve 

Ulnar  Nerve  

Musculo-spiral  Nerve 

Radial  Nerve 

PI  interior  Interosseous  Nerve    .... 
Surgical  Anatomy  of  Brachial  Plexus    .    . 

DORSAL  NERVK-. 

Roots  of  the  Dorsal  Nerves 

Posterior  Divisions  of  the  Dorsal  Nerves  . 
Anterior  Divisions  of  the  Dorsal  Nerves  . 

First  Dorsal  Nerve 

Upper  Dorsal  Nerves 

Lower  Dorsal  Nerves  .        

Last  Dorsal  Nerve 

Surgical  Anatomy 


THE  LUMBAR  NERVES. 

Root  of  Lumbar  Nerves 

Posterior  Divisions  of  Lumbar  Nerves  .    .    .    . 
Anterior  Divisions  of  Lumbar  Nerves   .    .    .    . 

THE  LUMBAR  PLEXUS. 

Branches  of  Lumbar  Plexus 

Ilio-hypogastric  Nerve 

Ilio-inguinal  Nerve 

Genito  crural  Nerve 

External  Cutaneous  Nerve 

Obturator  Nerve 

-  >ry  Obturator  Nerve 

Anterior  Crural  Nerve 

Branches  of  Anterior  Crural 

Middle  Cutaneous 

Internal  Cutaneous 

Long  Saphenous 

Muscular  and  Articular  Branches  .... 

THE  SACRAL  AXD  COCCYGEAL  NERVES. 

Roots  of,  origin  of 

Posterior  Divisions  of  Sacral  Nerves 

Coccygeal  Nerve 

Anterior  Divisions  of  Sacral  Nerves 

THE  SACRAL  PLEXUS. 
Superior  Glnteal  Nerve 


815 
816 

.-16    Inferior  Gluteal  Nerve 


823 
823 


825 


826 
M 
826 

827 
827 
BZ7 


an 

928 
830 


831 
B38 


837 
837 


838 
B38 
839 
839 
839 
840 
840 
-41 
842 
844 
844 
844 


845 

846 
846 
846 

848 
848 
B4B 


MB 

849 
850 


850 
B51 

851 

853 
864 

f-.Vi 

966 

855 
855 
856 
856 


857 
857 
858 
858 


861 

m 


20 


CONTENTS. 


PAGE 

Perforating  Cutaneous  Nerve 861 

Pudic  Nerve      861 

Small  Sciatic  Nerve 862 

Great  Sciatic  Nerve 862 

Internal  Popliteal  Nerve 863 

Posterior  Tibial  Nerve 863 

Plantar  Nerves 863 

External  Popliteal  or  Peroneal  Nerve  ....  864 

Anterior  Tibial  Nerve 865 

Musculo-cutaneous  Nerve 865 

Surgical  Anatomy  of  Lumbar  and  Sacral  Plexus  866 

THE  SYMPATHETIC  NEEVE. 

Subdivision  of,  into  Parts 

Branches  of  the  Ganglia,  General  Description 


of 


CERVICAL    PORTION   OF    THE    GANGLIATED 

CORD 

Superior  Cervical  Ganglion 

Carotid  Plexus 

Cavernous  Plexus 

Middle  Cervical  Ganglion 

Inferior  Cervical  Ganglion 

THORACIC  PART  OF  THE  GANGLIATED  CORD  . 

Great  Splanchnic  Nerve 

Lesser  Splanchnic  Nerve 


867 
867 

869 

869 
869 

869 

872 
872 
872 
873 

873i 


Smallest  Splanchnic  Nerve       ,    , 873 

LUMBAR  PORTION  OF  THE  GANGLIATED  CORD  873 

PELVIC  PORTION  OF  THE  GANGLIATED  CORD  874 

THE  GREAT  PLEXUSES  OF  THE  SYMPATHETIC. 

Cardiac  Plexuses 874 

Great  Cardiac  Plexus 874 

Superficial  Cardiac  Plexus 874 

Coronary  Plexuses       874 

Solar  Plexus 875 

Phrenic  Plexus 875 

Suprarenal  Plexus 875 

Renal  Plexus 875 

Spermatic  Plexus 875 

Ovarian  Plexus 876 

Cceliac  Plexus 876 

Superior  Mesenteric  Plexus 877 

Aortic  Plexus 877 

Inferior  Mesenteric  Plexus 877 

Hypogastric  Plexus 877 

Pelvic  Plexus 878 

Inferior  Hsemorrhoidal  Plexus 878 

Vesical  Plexus 878 

Prostatic  Plexus  ...       878 

Vaginal  Plexus 878 

Uterine  Plexus 878 


ORGANS   OF 
TONGUE. 

Structure  of 879 

Papillae  of 880 

Glands  of 882 

Lymphoid  Follicles 882 

Fibrous  Septum  of 882 

Hyo-glossal  Membrane 882 

Arteries  and  Nerves  of 882 

Muscles  of 882 

Nerves  of 883 

Surgical  Anatomy  of 883 


NOSE. 

Cartilages  of 885 

Muscles  of 886 

Skin 886 

Mucous  Membrane 886 

Arteries,  Veins,  and  Nerves 886 

Nasal  Fossse. 

Mucous  Membrane  of 887 

Superior,  Middle,  and  Inferior  Meatuses  .    .    .  887 

Arteries,  Veins,  and  Nerves  of  Nasal  Fossse    .  889 

Surgical  Anatomy  of  Nose  and  Nasal  Fossse   .  889 

EYE. 

Situation,  Form  of 890 

Capsule  of  Tenon 

Tunics  of,  sclerotic 891 

Cornea 892 

Choroid 894 

Ciliary  Processes 895 

Iris 896 

Membrana  Pupillaris 898 

Ciliary  Muscle 898 

Ketina 898 

Structure  of  Retina 898 

Structure  of  Retina  at  Yellow  Spot 902 

Arteria  Centralis  Retinae 902 

Humors  of  the  Eye. 

Aqueous  Humor 903 

Anterior  Chamber 903 

Posterior  Chamber 903 

Vitreous  Body 903 

Crystalline  Lens  and  its  Capsule     ... 

Changes  Produced  in  the  Lens  by  Age  ....  904 


SENSE. 

Appendages  of  the  Eye. 

Eyebrows 907 

Eyelids 907 

Eyelashes 907 

Structure  of  the  Eyelids 907 

Tarsal  Plates 908 

Meibomian  Glands 908 

Conjunctiva       908 

Carunculse  Lachrymales .  909 


Lachrymal  Apparatus. 

Lachrymal  Gland 909 

Canals 910 

Sac 910 

Nasal  Duct 911 

Front  of  Eye .911 

Surgical  Anatomy 911 

EAR. 
External  Ear. 

Pinna,  or  Auricle 912 

Structure  of  Auricle 912 

Ligaments  of  the  Pinna 913 

Muscles  of  the  Pinna 913 

Arteries,  Veins,  and  Nerves  of  the  Pinna    .    .  914 

Auditory  Canal 914 

Surface  Form 915 

Middle  Ear,  or  Tympanum. 

Cavity  of  Tympanum 916 

Eustachian  Tube 917 

Membrani  Tympani 918 

Structure  of 

Ossicles  of  the  Tympanum    .... 

Ligaments  of  the  Ossicula 919 

Muscles  of  the  Tympanum 920 

Mucous  Membrane  of  Tympanum 

Arteries  of  Tympanum 

Veins  and  Nerves  of  Tympanum    .  .    .    920 

Internal  Ear,  or  Labyrinth. 

Vestibule 921 

Semicircular  Canals: 

Superior  Semicircular  Canal     .... 

Posterior  Semicircular  Canal 

External  Semicircular  Canal 922 


Suspensorv  Ligament  of  Lens 905  Cochlea  : 

Canal  of  Petit 905  Central  Axis  of,  or  Modiolus    .... 

Vessels  of  the  Globe  of  the  Eye 905  Spiral  Canal  of      .        .    ...    .    .    .    ... 

Nerves  of  Eyeball 905  Scala  Tympani,   Scala  Vestibuh,   and    bcala 

Surgical  Anatomy  of  Eye 905  Media  . 


21 


The  Organ  of  Cord 

Perilymph 

Membranous  Labyrinth 926 

Utricle  and  Saccule 926 

Membranous  Semicircular  Canals 927 

Endolymph 927 


PAGE 

Otoliths 927 

Vessels  of  the  Labyrinth 927 

Auditory  Nerve,  Vestibular  Nerve 927 

Cochlear  Nerve 928 

Surgical  Anatomy 928 


THE   ORGANS   OF   DIGESTION. 


Subdivisions  of  the  Alimentary  Canal  . 

The  Mouth 

The  Lips 

The  Cheeks 

The  Gums      


THE  TEETH. 

General  Characters  of 

Permanent  Teeth 

Incisors 

Canine * 

Bicuspids 

Molars 

Temporary,  or  Milk  Teeth 

Structure  of  the  Teeth 

Ivory  or  Dentine 

Enamel 

Cortical  Substance 

Development  of  the  Teeth    .    . 

of  the  Permanent  Teeth 
Eruption  of  the  Teeth 


930 
930 
930 
931 
931 


932 
93-2 
932 
933 
933 
933 
935 
935 
935 
937 
938 
938 
942 
942 


!  Parietal  Peritoneum 

Anterior  Wall 

Upper  Wall  .  .  

j  Inferior  Wall 

Visceral  Peritoneum 

Lesser  Sac  or  Bursa  Omentalis 

|  Eecessus  Peritonei  or  Retroperitoneal  Fossa 
'  Duodenal  Fossa- 

Fossa  Intersigmoidea 

i  Pericsecal  Fossae  . 


The  Stomach. 

Form  and  Size 

'.  Position  and  Relations  .... 
l  Relations  in  Detail 

Alterations  in  Position  .... 

Structure     

Mucous  Membrane 

Vessels  and  Nerves  of  Stomach 
,  Surgical  Anatomy 


THE  PALATE. 

Hard  Palate 

Soft  Palate 

Uvula,  Pillars  of  the  Soft  Palate 

Mucous  Membrane,  Aponeurosis,  and  Muscles 
of  Soft  Palate 

The  Tonsils. 

Arteries 

Veins  and  Nerves  of  Tonsils 


THE  SALIVARY  GLAXDS. 
Parotid  Gland. 


Situation  and  Relations 

Stensou's  Duct 

Surface  Form 

Vessels  and  Nerves  of  Parotid  Gland     .    . 

The  Submaxillary  Gland. 

Situation  and  Relations 

Wharton's  Duct 

Vessels  and  Nerves  of  Submaxillary  Gland 

The  SiMingnal  Gland. 

Situation  and  Relations 

Vessels  and  Nerves  of 

Structure  of  Salivary  Glands 

Surface  Form  of  Mouth 


944 
944 
944 

944 


945 
945 


945 
946 
947 
947 


947 
947 
947 


943 
948 

94- 
949 


THE  PHARYXX  AXD  CESOPHAGCS. 
Situation  and  Relations  ...  .... 

Structure  of-  Pharynx 

Surgical  Anatomy 

Relations  of  CEsophagus 

Structure 

Vessels         

Nerves  of 

Surgical  Anatomy .... 


THE  ABDOMEX. 


Boundaries . 
Apertures  of 
Regions  .  . 


Omentum 

itery 

Ligament 


The  Peritoneum. 


951 
951 
952 
952 
953 
953 
954 
954 


957 
959 
959 


986 
986 
986 
986 
988 
993 
994 
994 
996 
997 


999 
1001 
1003 
1004 
1004 
1006 
1007 
1007 


Small  Intestine. 

Duodenum 

Course  of  Adult  Duodenum 

Peritoneal  Relations  of  Duodenum    .    . 

Ligaments  of  Duodenum 

Relations  of  Duodenum 

Jejunum  and  Ilenm 

Structure  of  Small  Intestine 

Mucous  Membrane 

Valvulse  Conuiventes 

Villi 

Structure  of  Villi 

Follicles 

Duodenal  Glands 

Solitary  Glands 

Peyer's  Glands 

Vessels  and  Nerves  of  Small  Intestine  .    .    .    . 

Large  Intestine. 

Structure 

Vessels  and  Nerves 

Csecuni •     .    .    . 

Vermiform  Appendix 

Ileo-colic,  Ileo-csecal    Valve  or  Valvula  Bau- 

hini 

Colon 

Ascending 

Transverse 

Descending 

Sigmoid   ...        .  

Relations  of  Large  Intestine 

Rectum 

Structure  of  Rectum 

Vessels  and  Nerves  of  Rectum 

Relations  of  Rectum 

Surface  Form 

Surgical  Anatomy 


1008 
1009 
1011 
1014 
1014 
1020 
1020 
1021 
1021 
1022 
1023 
1024 
1024 
1025 
1025 
1026 


1028 
1029 
1030 
1032 

1033 
1035 
1035 
1035 
1035 
1036 
1036 
1038 
1040 
1041 
1043 
1045 
1045 


Volume 

Weight 

Surfaces  .    .    .    .    . 

Fissures 

Longitudinal 
Lobes   . 


Liter. 


979 
979 
979 


Right    .    . 

Left  .  .  . 
Quadrate 
Caudate  . 
Spigelian 


1047 
1047 
1049 
1051 
1051 
1052 
1052 
1052 
1052 
1052 
1052 


22 


CONTENTS. 


Ligaments  and  Peritoneal  Relations 1053 

Peritoneal  Lines 1054 

Relations 1055 

Fixation  of  Liver 1056 

Vessels  of  Liver 1057 

Nerves  of  Liver 1058 

Structure  of  Liver 1059 

Microscopic  Appearance  of  Liver 1059 

Hepatic  Cells 1060 

Hepatic  Artery 1060 

Portal  Vein 1060 

Excretory  Apparatus  of  Liver 1063 

Hepatic  Duct 1063 

'  GALL-BLADDER. 

Relations  of  Gall-bladder 1064 

Vessels  and  Nerves  of  Gall-bladder 1064 

Cystic  Duct 1064 

Ductus  Choledochus 1064 

Structure    1065 

Surface  Form  of  Liver 1065 

Surgical  Anatomy  of  Liver 1065 


PANCREAS.  PAGE 

Dissection 1067 

Color 1067 

Volume 1067 

Head 1067 

Body  and  Tail 1069 

Relations  in  Detail 1071 

Vessels  and  Nervus IHT-J 

Surface  Form 107:j 

Surgical  Anatomy    . 1073 


SPLEEN. 

Form  and  Relations 1074 

Fixation  and  Peritoneal  Relations 1076 

Vessels  and  Nerves 1077 

Lymphatic  Vessels 1077 

Structure 1077 

Fibro-elastic  Coat 1078 

Proper  Substance  ......       1078 

Surface  Form  of  Spleen 1081 

Surgical  Anatomy  of  Spleen 1081 


THE   THORAX. 


Cavity  of 1083 

Upper  Opening 1083 

LowerOpening 1083 

THE   PERICARDIUM. 

Structure 1084 

Fibrous  Layer   1084 

Serous  Layer 1085 

Arteries  of  Pericardium     ....  ....  1085 

Nerves  of  Pericardium 1085 

Vestigial  Fold  of  Pericardium 1085 

Surgical  Anatomy 1086 

THE  HEART. 

Position 1086 

Size 1087 

Subdivision  into  Four  Cavities 1087 

Circulation  of  Blood  in  Adult 1087 

Auriculo-ventricular  and  Ventricular  Grooves  1087 

The  Right  Auricle. 

Sinus 1088 

Appendix 1088 

Openings 1088 

Valves 1089 

Relics  of  Foetal  Structure         1089 

Musculi  Pectinati 1089 

The  Right  Ventricle. 
Infimdibuluni   .  .    .  1089 


Openings 1090 

Tricuspid  Valve 1000 

Chordje  Tendinese  and  Columns  Carnese  .    .    .  1090 
Semilunar 1090 

The  Left  Auricle. 

Sinus 1091 

Appendix 1091 

Openings     1091 

Musculi  Pectinati ...  1092 

The  Left  Ventricle. 

Openings     1092 

Mitral  and  Semilunar  Valves 1093 

Endocardium 1094 

Structure  of  Heart. 

Fibrous  Rings 1094 

Muscular  Structure 1094 

Muscular  Structure  of  Auricles 1094 

Muscular  Structure  of  Ventricles 1094 

Vessels  and  Nerves  of  Heart 1095 

Surface  Marking  of  Heart 1096 

Peculiarities  in  Vascular  System  of  Foetus  .    .  1096 

Foramen  Ovale,  Eustachian  Valve 1096 

Ductus  Arteriosus 1097 

Umbilical  or  Hypogastric  Arteries 1097 

Foetal  Circulation 1097 

Changes  in  Vascular  System  at  Birth    ....  1099 


ORGANS   OF   VOICE   AND   RESPIRATION. 


The  Larynx. 

Cartilages  of  the  Larynx 1100 

Thyroid  Cartilage 1100 

Cricoid  Cartilage 1101 

Arytenoid  Cartilages,  Cartilages  of  Santo- 

riui  and  Wrisberg 1102 

Epiglottis 1102 

Ligaments  of  the  Larynx 1102 

Ligaments  Connecting  the  Thyroid  Cartilage 

with  the  Os  Hyoides 1103 

Ligaments  Connecting  the  Thyroid  Cartilage 

with  the  Cricoid .  1103 

Ligaments  Connecting  the  Arytenoid  Carti- 
lages to  the  Cricoid 1103 

Ligaments  of  the  Epiglottis 1103 

Superior  Aperture  of  the  Larynx 1103 

Cavity  of  the  Larynx 1104 


Rima  Glottidis 1104 

False  Vocal  Cords 1105 

True  Vocal  Cords 1105 

Ventricle  of  Larynx,  Sacculus  Laryngis  .    .    .  1105 

Muscles  of  Larynx 1105 

Crico-thyroid 1105 

Crico-arytenoideus  posticus 1  !<>."> 

Crico-arytenoideus  lateralis 1106 

Arytenoideus 1106 

Thyro-arytenoideus 1106 

Muscles  of  the  Epiglottis 1107 

Thyro-epiglottideus 1107 

Aryteno-epiglottideus,  superior 1107 

inferior 1107 

Actions  of  Muscles  of  Larynx 1107 

Mucous  Membrane  of  Larynx  ....'....  1107 
Glands,  Vessels,  and  Nerves  of  Larynx    .    .    .  1108 


CONTENTS. 


23 


PAGE 

The  Trachea. 

Relations .   .  1108 

Bron. -hi 110s 

Structure  of  Trachea 1110 

Cartilages 1110 

Fibrous  Membrane 1111 

Muscular  Fibres 1111 

Mucous  Membrane 1111 

Glands 1111 

Vessels  and  Nerves 1111 

Surface  Form 1111 

Surgical  Anatomy  of  Laryngo-tracheal  Region  1111 

The  Pleura. 

Reflections 1113 

-  and  Nerves 1114 

Surgical  Anatomy 1114 

The  Jlediastina. 

Superior  Mediastinum 1115 

Anterior  Mediastinum 1116 

Middle  Mediastinum 1116 

Posterior  Mediastinum 1116 

The  Lungs. 

Surfaces 1117 

Borders  and  Lobes 1117 


Root  of  Luug 1118 

Weight,  Color,  and  Properties  of  Substance  of 

Lung ins 

Structure  of  Lung 1118 

Serous  Coat  and  Subserous  Areolar  Tissue  .  1118 

Parenchyma  and  Lobules  of  Luug 1118 

Bronchi,  Arrangement  of,  in  Substauce  of 

Luug 1119 

Structure  of  Smaller  Bronchial  Tubes  ....  1119 

The  Air-cells 1119 

Pulmonary  Artery 1119 

Pulmonary  Capillaries  and  Veins 1119 

Bronchial  Arteries  and  Veins  .  1120 

Lymphatics  and  Nerves  of  Lung 1120 

Surface  Form  of  Lungs H20 

Surgical  Anatomy 1122 

The  Wyroid  Gland. 

Surface  and  Relations 1123 

Structure 1123 

Vessels  and  Nerves 1124 

Surgical  Anatomy 1124 

The  Thymiis  Gland. 

Relations 1124 

Structure 1125 

Vessels  and  Nerves 1126 


THE  URINARY  ORGANS. 


The  Kidneys. 

Relations 1127 

Dimensions,  Weight 1127 

General  Structure 1128 

Cortical  Substauce 1129 

Medullary  Substance 1129 

Minute  Structure 1129 

Malpighian  Bodies       1129 

Tufts 1129 

Capsule 1129 

Tubuli  Uriniferi,  Course 1130 

Structure       1132 

Renal  Blood-vessels 1133 

Renal  Veins 1134 

Ven:e  Rectje 1134 

Nerves     1134 

Lymphatics 1135 

Surface  Form 1135 

Surgral  Anatomy 1135 

The  Ureters. 

Situation 1136 

Calices      H3»5 

Course      113*5 

Relations 1136 

Structuiv .  H36 


The  Suprarenal  Capsules. 

Relations 1137 

Structure 1137 

Vessels  and  Nerves 1139 

THE  PELVIS. 

Boundaries 1139 

Contents 1139 

The  Bladder. 

Shape,  Position,  Relations 1139 

Subdivisions 1140 

Urachus 1140 

Ligaments 1142 

Structure    1143 

Interior  of  Bladder 1144 

Vessels  and  Nerves 1144 

Surface  Form 1144 

Surgical  Anatomy 1145 

Male  Urethra. 

Divisions 1146 

Structure 1147 

Surgical  Anatomy 1147 


MALE  GENERATIVE  ORGANS. 


.:e  Gland 1143 

Structure    ...       1149 

—els  and  Nerves 1149 

Surgical  Anatomy 1149 

Cowper's  Glands 1150 

Structure     1150 

THE  PEXIS. 

Boot 1150 

(Hans  Penis 1150 

Body 1150 

Structure  of  Penis       1151 

Corpora  Caveruosa 1151 

Structure     1151 

Arteries  of  the  Penis 1152 

Corpus  Spongiosum 115° 

The  Bulb '  115-? 

Structure  of  Corpus  Spongiosum 1153 

Lyiuphaties.of  the  Penis 1153 

Nerves  of  the  Penis 1153 

Surgical  Anatomy 1153 


THE  TESTES  AND  THEIR  COVERINGS. 

Scrotum 1153 

Coverings  of  the  Testis 1154 

Vessels  and  Nerves  of  the  Coverings  of  the 
Testis 1155 

The  Spermatic  Cord. 

Its  Composition 1155 

Relations  of,  in  Inguinal  Canal 1155 

Arteries  of  the  Cord 1155 

Veins  of  the  Cord 1155 

Lymphatics  and  Nerves  of  the  Cord 1155 

Surgical  Anatomy 1155 

THE  TESTES. 

Form  and  Situation 1156 

Size  and  Weight 1156 

Coverings 1156 

Tunica  Vaginalis 1156 

Tunica  Albuginea 1157 


24 


CONTENTS. 


PAGE 

Mediastinum  Testis 1157 

Tunica  Vasculosa 1157 

Structure  of  the  Testis 1157 

Lobulus  of  the  Testis  .  .  1158 


PAGE 

Vesiculse  fieminales 1160 

Form  and  Size 1160 

Relations 1160 

Structure 1160 

Tubuli  Seminiferi 1158  i  Ejaculatory  Ducts 1160 

Arrangement  in  Lobuli 1158    Structure 1161 

iu  Mediastinum  Testis 1158    Vessels  and  Nerves 1161 

"  in  Epididymis 1158    Surgical  Anatomy 1161 

Vas  Deferens,  Course,  Relations 1159 

Structure 1159  Descent  of  the  Testes. 

Vas  Aberrans 1159    Gubernaculum  Testis 1161 

Surgical  Anatomy 1159    Canal  of  Nuck 1162 


FEMALE  GENERATIVE  ORGANS. 


Mons  Veneris,  Labia  Majora 1163 

"        Labia  Minora 1164 

Clitoris 1164 

Meatus  Urinarius 1165 

Hymen,  Glands  of  Bartholin 1165 

Female  Urethra 1167 

Female  Rectum    ....       1167 

Vagina. 

Relations 1167 

Structure 1167 

Uterus. 

Situation,  Form,  Dimensions 1168 

Fundus,  Body,  and  Cervix 1168 

Ligaments 1170 

Cavity  of  the  Uterus 1171 

Cavity  of  the  Cervix 1171 

Structure 1171  [ 

Vessels  and  Nerves 1173  j 

Its  Form,  Size,  and  Situation  in  the  Foetus  .    .  1173 
at  Puberty 1173 ! 


Its  Form,  Size,  etc.  during  Menstruation  .   .   .  1173 

"        during  Pregnancy      1173 

after  Parturition 1173 

in  Old  Age 1174 

Appendages  of  the  Uterus. 

Fallopian  Tubes 1174 

Structure 1174 

Ovaries 1175 

Structure 1175 

Graafian  Follicles 1176 

Discharge  of  the  Ovum 1177 

Ligament  of  the  Ovary      1177 

Round  Ligaments 1177 

Vessels  and  Nerves  of  Appendages 1178 

Mammary  Glands. 

Situation  and  Size 1178 

Nipple     . 1179 

Structure  of  Mamma 1179 

Vessels  and  Nerves 1279 


SURGICAL  ANATOMY  OF  HERNIA. 

INGUINAL  HERNIA. 


COVERINGS  OF  INGUINAL  HERNIA. 

Dissection 1180 

Superficial  Fascia 1180 

Superficial  Vessels  and  Nerves 1180 

Deep  Layer  of  Superficial  Fascia 1181 

Aponeurosis  of  External  Oblique 1181 

External  Abdominal  Ring 1182 

Pillars  of  the  Ring 1182 

Intercolumnar  Fibres 1182 

Fascia 1182 

Pou part's  Ligament 1183 

Gimbernat's  Ligament 1183 

Triangular  Ligament 1183 

Internal  Oblique  Muscle 1184 

Cremaster 1184 

Transversalis  Muscle 1184 

Spermatic  Canal 1185 

Fascia  Transversalis 1185 

Internal  Abdominal  Ring 1186 


Subperitoneal  Areolar  Tissue 1186 

Deep  Epigastric  Artery 1186 

Peritoneum 1186 

Oblique  Inguinal  Hernia. 
Course  and  Coverings  of  Oblique  Hernia  .    .    .  1187 

Seat  of  Stricture 1188 

Scrotal  Hernia 1189 

;  Bubonocele 1189 

Congenital  Hernia 1189 

Infantile  and  Encysted  Hernia 1189 

Hernia  into  the  Funicular  Process 1189 

Direct  Inguinal  Hernia. 
Course  and  Coverings  of  the  Hernia      .    .    .    .1100 

(  Seat  of  Stricture 1190 

i  Incomplete  Direct  Hernia 1191 

i  Comparative  Frequency  of  Oblique  and  Direct 

Hernia 1191 

;  Division  of  Stricture  in  Inguinal  Hernia      .    .  1191 


FEMORAL  HERNIA. 


Dissection 1191 

Superficial  Fascia 1191 

Cutaneous  Vessels 1191 

Internal  Saphenous  Vein 1191 

Superficial  Inguinal  Glands      1193 

Cutaneous  Nerves 1193 

Deep  Layer  of  Superficial  Fascia 1193 

Cribriform  Fascia 1193 

Fascia  Lata 1193 

Iliac  Portion 1193 

Pubic  Portion 1194 

Saphenous  Opening 1194 


Crural  Arch 1195 

Gimbernat's  Ligament 1196 

Crural  Sheath 1196 

Deep  Crural  Arch 1197 

Crural  Canal 1197 

Femoral  or  Crural  Ring      1198 

Position  of  Parts  around  the  Ring .1 198 

Septum  Crurale 1198 

Descent  of  Femoral  Hernia 1199 

Coverings  of  Femoral  Hernia 1199 

Varieties  of  Femoral  Hernia 1199 

Seat  of  Stricture 1200 


25 


SURGICAL  ANATOMY  OF  PERINEUM  AND  ISCHIO-RECTAL  REGION. 


Ischio-Bectal  Region. 


PAGE   Cowper's  Glands  1205 

.  1201    Dorsal  Vessels  and  Nerves     1205 

.    .  1201    Arterv  of  the  Bulb       1205 

ia     

.    -  1201    Position  of  the  Viscera  at  Outlet  of  Pelvis    .    .  1206 
120°    Prostate  Gland                 1206 

120°    Surgical  Anatomv  of  Lithotomy      1207 

Parts  divided  in  the  Operation    1207 

Male  Perinxum. 
Extent  . 

Parts  to  be  avoided  in  the  Operation      ....  1207 
.  1202     Ahnormal  fYinrsfi  of  Arteries  in  the  Perinaeum    1207 

Dissection  of 
Boundaries  of 
Superficial  Fascia 
Ischio-rectal  Fossa 


Deep  Layer  of  Superficial  Fascia 1203 

Course  taken  bv  the  Urine  in  Rupture  of  the 

Urethra       . 

Muscles  of  the  Perinseum  (Male)     1203  [ 

Deep  Periueal  Fascia      .    .       1204 

Superficial  Layer      1204 

Deep  Layer 1205  . 

Parts  between  the  two  Layers 1205  i 

Compressor  Urethra •    •    •  1205  ' 


Female  Perinseum. 

1203  1  Superficial  Fascia 1207 

Deep  Fascia 1208 

Compressor  Urethrse 1208 

Perineal  Body          1208 

Pelvic  Fascia 1209 

Obturator  Fascia      1209 

Kecto-vesical  Fascia    .       .    .   .  ' 1210 


IN'DEX          1211 


GENERAL  ANATOMY. 


fluids  of  the  body,  which  are  intended  for  its  nutrition,  are  the  lymph, 
_L  the  chyle,  and  the  blood.  There  are  other  fluids  also  which  partially 
subserve  the  same  purpose,  as  the  saliva,  the  gastric  juice,  the  bile,  the  intestinal 
secretion ;  and  others  which  are  purely  excrementitious,  as  the  urine.  But  there 
is  no  need  to  describe  the  rest  in  this  place,  since  they  are  the  secretions  of  special 
organs,  and  are  described,  as  far  as  is  judged  necessary  for  the  purposes  of  this 
work,  in  subsequent  pages.  We  shall  here  speak  first  of  the  blood,  and  next  of 
the  lymph  and  chyle. 

THE   BLOOD. 

The  blood  is  a  thickish,  opaque  fluid,  of  a  bright-red  or  scarlet  color  when  it 
flows  from  the  arteries,  of  a  dark-red  or  purple  color  when  it  flows  from  the  veins. 
It  is  viscid,  and  has  a  somewhat  clammy  feeling ;  it  is  salt  to  the  taste,  and  has  a 
peculiar  faint  odor.  It  has  an  alkaline  reaction.  Its  specific  gravity  at  60°  F.  is 
about  1.0.3.5.  and  its  temperature  is  generally  about  100°  F.,  though  varying 
slightly  in  different  parts  of  the  body. 

General  Composition  of  the  Blood. — When  blood  is  drawn  from  the  body  and 
allowed  to  stand,  it  solidifies  in  the  course  of  a  very  few  minutes  into  a  jelly-like 
mass,  which  has  the  same  appearance  and  volume  as  the  fluid  blood,  and,  like  it, 
looks  quite  uniform.  Soon,  however,  drops  of  a  transparent  yellowish  fluid  begin 
to  ooze  out  from  the  surface  of  this  mass  and  to  collect  around  it.  Coincidently 
with  this  the  clot  begins  to  contract,  so  that,  in  the  course  of  about  twenty-four 
hours,  the  original  mass  of  coagulated  blood  has  become  sepai-ated  into  two  parts 
— a  ;'clot  "  or  "coagulum,"  considerably  smaller  and  firmer  than  the  first-formed 
jelly-like  mass,  and  a  large  quantitv  of  yellowish  fluid,  the  serum, 'in  which  the 
clot  floats. 

The  clot  thus  formed  consists  of  a  solid,  colorless  material,  called  fibrin,  and 
a  large  number  of  minute  cells  or  corpuscles,  called  blood-corpuscles,  which  are 
entangled  and  enclosed  in  the  fibrin.  The  fibrin  is  formed  during  the  act  of  solidi- 
fication. In  the  fluid  blood  in  the  living  body  there  is  a  substance,  named 
fibrinogen,  which  when  acted  upon  by  a  second  material,  also  contained  in  the 
blood,  and  named  a  fibrin-ferment,  forms  a  solid  substance,  fibrin.  This  latter 
in  its  process  of  solidification  encloses  and  entangles  the  blood-corpuscles,  and 
thus  the  clot  is  formed. 

Recent  observations  have  shown  that  the  presence  of  a  trace  of  a  calcium  salt 
is  a  necessary  condition  for  the  transformation  of  fibrinogen  into  fibrin.  The 
fibrin-ferment  does  not  exist  as  such  in  the  blood  contained  in  the  blood-vessels, 
but  seems  to  result  from  the  destruction  of  what  are  known  as  the  white  corpus- 
cles and  the  blood-plaques  to  be  described  later.  These  structures,  more  espe- 
cially the  plaques,  disintegrate  very  rapidly  when  blood  is  drawn  from  the  body, 
liberating  the  ferment,  and  so  producing  coagulation,  and  lesions  of  the  cells 
lining  the  interior  of  the  blood-vessels  seem  also  to  give  rise  to  ferment-produc- 
tion and  the  intra-vascular  formation  of  fibrin. 

3  33 


34  GENERAL   ANATOMY. 

We  may  now  consider  the  constituents  of  the  blood  in  another  way.  If  a  drop 
of  blood  is  placed  in  a  thin  layer  on  a  glass  slide  and  examined  under  the  micro- 
scope, it  will  be  seen  to  consist  of  a  number  of  minute  bodies  or  corpuscles  floating 
in  a  clear  fluid ;  and,  on  more  minute  examination,  it  will  be  found  that  these  cor- 
puscles are  principally  of  two  kinds.  The  one,  greatly  preponderating  over  the 
other  in  point  of  numbers,  is  termed  the  colored  corpuscle ;  the  other,  fewer  in 
number  and  less  conspicuous,  is  termed  the  colorless  corpuscle.  From  this  we 
learn  that  blood  is  a  fluid  holding  a  large  number  of  corpuscles  of  two  varieties  m 
suspension.  The  fluid  is  named  liquor  sanguinis  or  plasma,  and  must  not  be  con- 
fused with  the  serum  spoken  of  above  in  connection  with  the  coagulation  of  the 
blood.  It  is  serum  and  something  more,  for  it  contains  one  at  least  of  the 
elements  or  factors  from  which  fibrin  is  formed.  The  relation  of  these  various 
constituents  of  blood  to  each  other  will  be  easily  understood  by  a  reference  to  the 

subjoined  plan : 

f  Colored  ^ 

Corpuscles    {  Golorless         1 

(  Fibrin  j 
*- Liquor    Sanguinis  < 

(  Serum 

The  blood-corpuscles,  blood-disks,  blood-globules  are,  as  before  stated,  of  two 
kinds :  the  red  or  colored,  and  the  white  or  colorless  corpuscles.  The  relative 
proportion  of  the  one  to  the  other  has  been  variously  estimated  and  no  doubt 
varies  under  different  circumstances.  Thus  venesection,  by  withdrawing  a  large 
proportion  of  the  red  globules,  and  by  favoring  the  absorption  of  lymphatic  fluid 
into  the  blood,  greatly  increases  the  relative  proportion  of  the  white  corpuscles. 
Klein  states  that  in  healthy  human  blood  there  appears  to  be  one  white  corpuscle 
for  600-1200  red  ones.  The  proportion  of  corpuscles,  colored  and  colorless  com- 
bined, to  liquor  sanguinis  is  in  one  hundred  volumes  of  blood  about  thirty-six 
volumes  of  the  former  to  sixty-four  of  the  latter. 

Colored  corpuscles  when  examined  under  the  microscope  are  seen  to  be  circular 
disks,  biconcave  in  profile,  having  a  slight  central  depression,  with  a  raised  bor- 
der (Fig.  1,  b\  When  viewed  with  a  moderate  magnifying  power,  this  central 

depression  looks  darker  than  the  edge.  When  exam- 
ined singly  by  transmitted  light,  their  color  appears  to 
be  of  a  faint  reddish-yellow  when  derived  from  arterial 
blood,  and  greenish-yellow  in  venous  blood.  It  is  to 
their  aggregation  that  blood  owes  its  red  hue.  Their 

size  varies  slightlv  even  in  tne  same  ^r°P  °f  blood,  out 
-it  may  be  stated  that  their  average  diameter  is  about 

rid.  i-Humau  blood-corpus-  WoT  of  an  inch  their  thickness  about  ^ko,  or  nearly 
des.  a.  seen  from  the  surface,  one-quarter  of  their  diameter.  .Besides  these,  especially 
inSeauT^RenVed^phlr1  in  some  anaemic  and  diseased  conditions,  certain  cor- 
^t^-SS81-/.  M<5dSSSS  puscles  are  found  of  a  much  smaller  size,  about  one- 
shrunk  by  evaporation.  third  or  half  the  size  of  the  ordinary  one.  Inese, 

however,  are  very  scarce  in  normal  blood.  The  number  of  red  corpuscles  in  the 
blood  is  enormous;  between  4,000,000  and  5,000,000  are  contained  in  a  cubic 
millimetre.  Power  states  that  the  red  corpuscles  of  an  adult  would  present  an 
aggregate  surface  of  about  3000  square  yards.  Human  blood-disks  present  no 
trace  of  a  nucleus.  They  consist  of  two  parts :  a  colorless  envelope,  or  investing 
membrane,  which  is  composed  largely  of  fatty  material ;  and  a  colored  fluid  con- 
tents, which  is  a  solution  of  a  substance  named  haemoglobin.  Hcemoglobin  is  a 
proteid  compound  of  a  very  complex  constitution,  the  haemoglobin  of  the  horse 
having  the  formula  C712H1130N214S2Fe0245.  It  has  a  great  affinity  for  oxygen,  and 
when  removed  from  the  body  crystallizes  readily  under  certain  circumstances. 
It  is  readily  soluble  in  water,  and  the  addition  of  this  fluid  to  a  drop  of  blood 
speedily  dissolves  out  haemoglobin  from  the  corpuscle. 


THE   BLOOD. 


35 


If  the  web  of  a  frog's  foot  is  spread  out  and  examined  under  the  microscope, 
the  blood  is  seen  to  flow  in  a  continuous  stream  through  the  vessels,  and  the 
corpuscles  show  no  tendency  to  adhere  to  each  other  or  to  the  wall  of  the  vessel. 
Doubtless  the  same  is  the  case  in  the  human  body  ;  but  when  drawn  and  examined 
on  a  slide  without  reagents,  the  blood-globules  often  collect  into  heaps  like 
rouleaux  of  coins  (Fig.  1,  c). 

During  life  the  red  corpuscles  may  be  seen  to  change  their  shape  under  pres- 
sure -  adapt  themselves  to  some  extent  to  the  size  of  the  vessel.  They  are 
also  highly  elastic,  for  they  speedily  recover  their  shape  when  the  pressure  is 
removed.  They  are  soon  influenced  by  the  medium  in  which  they  are  placed, 
and  by  the  specific  gravity  of  the  medmm.  In  water  they  swell  up,  lose  their 
shape,  and  become  globular ;  subsequently  the  haemoglobin  becomes  dissolved  out. 
and  the  envelope  can  be  barely  distinguished  as  a  faint,  circular  outline.  Solu- 
tions of  salt  or  sugar,  denser  than  the  serum,  give  them  a  stellate  or  crenated 
appearance :  and  the  usual  shape  may  be  restored  by  diluting  the  solution  to  the 
proper  point.  The  same  crenated  outline  may  be  produced  as  the  first  effect  of 
the  passage  of  an  electric  shock ;  subsequently,  if  sufficiently  strong,  the  shock 
ruptures  the  envelope.  A  solution  of  salt  or  sugar  of  the  same  specific  gravity  as 
serum  merely  separates  the  blood-globules  mechanically  without  changing  their 
shape. 

The  white  corpuscles  (Fig.  2)  are  rather  larger  than  the  red  in  human  blood, 
measuring  from  about  2innr  to  a^0o  of  an  inch  in  diameter.  They  consist  of  a 
transparent  granular-looking  protoplasm  containing  one,  two,  or  more  nuclei,  and 
presenting  bright  granules,  which  vary  in  different  corpuscles  both  in  quantity 
and  in  their  behavior  to  micro-chemical  reagents.  When  absolutely  at  rest  they 
are  rounded  or  spheroidal,  but  under 


ordinary  circumstances  their  form  is 
very  various,  and  they  have  the  re- 
markable property  of  undergoing 
••  amoeboid  "  changes  (Fig.  3).  That 
is  to  say.  they  have  the  power  of  send- 
ing out  finger-shaped  or  filamentous 
processes  of  their  own  substance,  by 
which  they  move  and  take  up  gran- 
ules from  the  surrounding  substance. 
In  locomotion  the  corpuscle  pushes  out  a  process  of  its  substance — a  pseudopodium, 
as  it  is  called — and  then  shifts  the  rest  of  the  body  into  it.  In  the  same  way, 
when  any  granule  or  particle  comes  in  its  way  it  wraps  a  pseudopodium  round  it, 


FIG.  2.— a.  White  corpuscles  of  human  blood, 
corpuscles.    High  power. 


d.  Red 


FIG.  3.— Human  colorless  blood-corpuscle,  showing  its  successive  changes  of  outline  within  ten 
minutes  when  kept  moist  on  a  warm  stage.    (Schofield.) 

and  then,  withdrawing  it.  lodges  the  particle  in  its  own  substance.  By  means  of 
these  amoeboid  properties  they  have  the  power  of  wandering  or  emigrating  from 
the  blood-vessels  by  penetrating  their  coats,  and  thus  finding  their  way  into  the 
perivascular  spaces. 

The  white  corpuscle  may  be  taken  as  the  type  of  a  true  animal  cell.  It  has 
no  limiting  membrane,  but  consists  of  a  mass  of  transparent  albuminous  substance, 
called  protoplasm,  containing  one  or  more  nuclei.  These  nuclei  may  assume 
varvinc:  shapes,  being  sometimes  spherical,  sometimes  horseshoe-shaped,  some- 
times moniliform.  these  various  shapes  being  transition  stages  between  the  mono- 
nuclear  and  polynuclear  corpuscles. 

The  white  corpuscles  are  very  similar  to,  if  not  identical  with,  the  corpuscles 
of  lymph  and  chyle,  and  they  also  bear  a  strong  resemblance  to  the  cells  found 


36  GENERAL    ANATOMY. 

in  pus.  From  the  fact  that  cells  exactly  like  the  colorless  corpuscles  are  being 
constantly  furnished  to  the  blood  by  the  lymphatic  vessels  and  the  chyle-ducts, 
and  also  from  their  varying  proportions  in  different  parts  of  the  circulation  and 
in  different  pathological  conditions,  the  colorless  corpuscles  have  been  regarded 
— erroneously,  however — as  an  earlier  stage  of  the  colored  blood-disks,  but  the 
evidence  in  favor  of  this  must  be  regarded  as  quite  inconclusive. 

There  can  be  no  doubt  that  during  embryonic  life  the  red  corpuscles  are 
developed  from  mesoblastic  cells  in  the  vascular  area  of  the  blastoderm.  They 
are  at  first  nucleated  and  resemble  white  corpuscles,  except  in  their  color,  and, 
like  them,  are  possessed  of  amoeboid  movements.  They  are  succeeded  by  smaller, 
non-nucleated  corpuscles,  having  all  the  characters  of  adult  colored  corpuscles, 
probably  formed  by  a  conversion  of  the  former  into  the  latter.  So  that  at  birth 
the  nucleated  red  corpuscles  have  disappeared.  In  after  life  an  important  source 
of  the  red  corpuscles  is  the  red  marrow  of  bones,  in  which  certain  cells  found  in 
the  marrow  are  converted  into  colored  blood-corpuscles  by  the  loss  of  their  nuclei, 
and  by  their  protoplasm  becoming  tinged  with  yellow.  It  is  probable,  also,  that 
the  spleen  may  be  a  place  for  the  formation  of  red  corpuscles.  This  theory,  which 
was  formerly  universally  believed,  and  was  then  discarded  for  the  hypothesis  that 
the  spleen  was  concerned  in  the  destruction  of  the  red  corpuscles,  has  lately  been 
revived  by  Bizzozero.  The  question  must  still  be  regarded  as  sub  judice.  The 
proportion  of  white  corpuscles  appears  to  vary  considerably  in  different  parts  of 
the  circulation,  being  much  larger  in  the  blood  of  the  splenic  vein  and  hepatic  vein 
than  in  other  parts  of  the  body,  while  in  the  splenic  artery  they  are  very  scanty. 

In  addition  to  these  corpuscles,  a  third  variety  is  found  in  mammalian  blood, 
and  has  been  specially  studied  and  described  by  Hayem,  Bizzozero,  and  Osier. 
They  are  pale  circular  or  oval  disks,  about  one-quarter  or  one-third  the  size  of  the 
red  blood-corpuscles,  and  apparently  contain  no  nucleus.  They  have  been  named 
blood-plates  or  blood-plaques,  and  are  supposed  by  Bizzozero  to  originate  the  fibrin- 
ferment,  and  to  be  especially  concerned  in  the  coagulation  of  the  blood. 

The  liquor  sanguinis  or  plasma  is  the  fluid  part  of  the  blood,  and  contains  in 
solution  various  organic  substances,  such  as  jibrinogen,  paraglobulin  or  serum 
globulin,  and  serum  albumen,  together  with  certain  salts,  sugar,  fatty  matter,  and 
gases.  Paraglobulin  is  probably  contained  partly  in  solution  in  the  plasma,  and 
partly  in  the  colorless  corpuscles,  and  can  be  obtained  by  diluting  the  liquor  san- 
guinis with  ten  times  its  volume  of  ice-cold  water,  and  then  transmitting  through 
it  a  stream  of  carbon  dioxide.  Fibrinogen  may  be  obtained  in  the  same  way  as 
paraglobulin,  but  the  liquor  sanguinis  must  be  still  further  diluted  and  the  current 
of  carbon  dioxide  must  pass  for  a  much  longer  time.  Fibrin  may  be  obtained 
by  whipping  the  blood,  after  it  has  been  withdrawn  from  the  body,  with  a  bundle 
of  twigs,  to  which  the  fibrin,  as  it  coagulates,  adheres.  Fibrin  may  also  be 
obtained  by  filtering  the  freshly-drawn  blood  of  an  animal  whose  corpuscles  are 
large,  care  being  taken  to  retard  coagulation  as  long  as  possible.  Under  these 
circumstances  the  corpuscles  are  retained  on  the  filter,  and  the  liquor  sanguinis, 
passing  through,  coagulates  and  separates  into  fibrin,  free  from  corpuscles,  and 
serum. 

Fibrin,  thus  obtained,  is  a  white  or  buff-colored  substance,  presenting  a 
stringy  appearance,  and  under  the  microscope  exhibiting  fibrillation.  When 
exposed  to  the  air  for  some  time,  it  becomes  hard,  dry,  brown,  and  brittle.  It  is 
a  proteid  compound,  insoluble  in  hot  or  cold  water,  alcohol  or  ether.  Under  the 
influence  of  dilute  hydrochloric  acid  it  swells  up,  but  does  not  dissolve ;  but  when 
thus  swollen  it  is  easily  dissolved  by  a  solution  of  pepsin.  If  heated  for  a- 
considerable  time  in  a  solution  of  dilute  hydrochloric  acid,  it  gradually 
dissolves. 

Serum  is  the  fluid  liquor  sanguinis  after  the  fibrin  has  been  separated  from  it. 
It  is  a  straw-colored  fluid  having  a  specific  gravity  of  1.027,  with  an  alkaline 
reaction.  Upon  boiling  it  becomes  solid,  on  account  of  the  albumen  which  it 
contains.  It  contains  also  salts,  fatty  matters,  sugar,  and  gases. 


LYMPH  AXD    CHYLE.  37 

Gases  of  the  Blood. — When  blood  is  exposed  to  the  vacuum  of  an  air-pump, 
about  half  its  volume  is  given  off  in  the  form  of  gases.  These  are  carbon  dioxide, 
oxygen,  and  nitrogen.  The  relative  quantities  in  100  volumes  of  arterial  and 
venous  blood,  at  0°  C.  and  1  in.  pressure  of  mercury  are  shown  in  the  accom- 
panying table : 

Oxygen.       Carbon  dioxide.  Nitrogen. 

Arterial  blood,  16  vols.  30  vols.  1  to  2  vols. 

Venous  blood,  6  to  10  vols.        35  vols.  1  to  2  vols. 

Roughly  stated,  they  are  as  follows :  Carbon  dioxide  about  two-thirds  of  the 
whole  quantity  of  gas,  oxygen  rather  less  than  one-third,  nitrogen  below  one- 
tenth  (Huxley).  The  greater  quantity  of  the  oxygen  is  in  loose  chemical  com- 
bination with  the  haemoglobin  of  the  blood-corpuscles,  but  some  part  is  simply 
absorbed,  just  as  it  would  be  by  water.  The  carbon  dioxide  is  in  a  state  of  chem- 
ical combination  with  the  salts  of  the  serum,  especially  the  sodium,  with  which  it  is 
combined  partly  as  a  carbonate  and  partly  as  a  bicarbonate.  The  nitrogen  is 
unimportant.  It  (or  at  least  the  greater  part  of  it)  is  merely  absorbed  from  the 
atmosphere  under  the  pressure  to  which  the  blood  is  exposed,  and  can  therefore  be 
mechanically  removed. 

Blood-crystals. — Haemoglobin,  as  stated  above,  when  separated  from  the  blood- 
corpuscles,  readily  undergoes  crystallization.  These  crystals,  named  hcemoglobin 
crystals,  all  belong.  Avith  the  exception  of  those  obtained  from  the  squirrel,  to  the 
rhombic  system.  In  human  blood  they  are  elongated  prisms  (Fig.  4,  A).  In  the 


FIG.  4. — Blood-crystals.    A.  Hsemoglobin  crystals  from  human  blood.    B.  Hsemin  crystals  from  blood  treated 
with  acetic  acid.    c.'Hamatoidin  crystals  from  an  old  apoplectic  clot. 

squirrel  they  are  hexagonal  plates.  Other  crystals  may  be  obtained  by  mixing 
dried  blood  with  an  equal  quantity  of  common  salt,  and  boiling  it  with  a  few  drops 
of  glacial  acetic  acid.  A  drop  of  the  mixture  placed  on  the  slide  will  show  the 
crystals  on  cooling.  These  are  named  hcemin  crystals,  and  consist  of  small  acic- 
ular  prisms  (Fig.  4.  B).  Occasionally  in  old  blood-clots  a  third  form  of  crystal  is 
found,  the  ha?niatoidin  crystal  (Fig.  4,  c). 

LYMPH  AND  CHYLE. 

Lymph  is  a  transparent,  colorless,  or  slightly  yellow  fluid,  which  is  conveyed 
by  a  system  of  vessels,  named  lymphatics,  into  the  blood.  These  vessels  take 
their  rise  in  nearly  all  parts  of  the  body  from  the  interstices  of  the  connective 
tissue,  and  take  up  the  fluid  contained  in  these  spaces  and  return  it  into  the 
veins  close  to  the  heart,  there  to  be  mixed  with  the  mass  of  the  blood.  The 
greater  number  of  these  lymphatics  empty  themselves  into  one  main  duct,  the 
thoracic  duct,  which  passes  along  the  front  of  the  spine  and  opens  into  one  of  the 
large  veins  at  the  root  of  the  neck.  The  remainder  empty  themselves  into  a 
smaller  duct,  which  terminates  in  the  corresponding  vein  on  the  opposite  side  of 
the  neck. 

Chyle  is  an  opaque,  milky-white  fluid,  absorbed  by  the  villi  of  the  small 
intestines  from  the  food,  and  carried  by  a  set  of  vessels  similar  to  the  lymphatics, 
named  lacteah,  to  the  commencement  of  the  thoracic  duct,  where  it  is  intermingled 


38  GENERAL    ANATOMY. 

with  the  lymph  and  poured  into  the  circulation  through  the  same  channels.  It 
must  be  borne  in  mind  that  these  two  sets  of  vessels,  lymphatics  and  lacteals, 
though  differing  in  name,  are  identical  in  structure,  and  that  the  character  of  the 
fluid  they  convey  is  different  only  while  digestion  is  going  on.  At  other  times  the 
lacteals  convey  a  transparent,  nearly  colorless  fluid  not  to  be  distinguished  from 
lymph.  Both  these  sets  of  vessels,  in  their  passage  to  the  central  duct,  pass 
through  certain  small  glandular  bodies,  termed  lymphatic  glands,  where  their 
contents  perhaps  undergo  elaboration. 

Lymph,  as  its  name  implies,  is  a  watery  fluid.  It  closely  resembles  the  liquor 
sanguinis,  and  contains  about  5  per  cent,  of  albumen  and  1  per  cent,  of  salts. 
When  examined  under  the  microscope,  it  is  found  to  consist  of  a  clear  colorless 
fluid,  in  which  are  floating  a  number  of  corpuscles,  lymph-corpuscles.  These 
bodies  are  identical  in  structure,  and  not  to  be  distinguished  from  the  white  blood- 
corpuscles  previously  described.  They  vary  in  number  in  different  parts  of  the 
lymphatic  vessels,  and  indeed  are  said  by  Kblliker  to  be  absent  in  the  smaller 
ones.  They  are  always  increased  in  number  after  the  passage  of  the  lymph 
through  a  lymphatic  gland,  and  are  said  to  be  increased  in  size  as  the  fluid 
ascends  higher  in  the  course  of  the  circulation. 

Chyle  is  a  milk-white  fluid,  which  exactly  resembles  lymph  in  its  physical  and 
chemical  properties,  except  that  it  has,  in  addition  to  the  other  constituents  of 
lymph,  an  enormous  amount  of  fatty  granules,  "  the  molecular  basis  of  chyle,"  and 
it  is  to  the  presence  of  these  molecules  that  chyle  owes  its  milky  color.  Under 
the  microscope  it  presents  a  number  of  corpuscles,  named  "chyle-corpuscles," 
which  are  indistinguishable  from  lymph-corpuscles  or  white  blood-cells,  and  the 
molecular  basis,  consisting  principally  of  fatty  granules  of  extreme  minuteness 
(Fig.  5,  a),  but  also  of  a  few  small  oil-globules.  Lymph  and  chyle  after  their  pas- 
sage through  their  respective  glands,  if  withdrawn 
from  the  body  and  allowed  to  stand,  separate  more 
or  less  completely  into  a  clear  liquid,  which  is 
identical  with  the  serum  of  the  blood,  and  a  thin 
jelly-like  clot,  consisting  of  a  fibrillated  matrix  in 
which  lymph-corpuscles  or  chyle-corpuscles  and 
fatty  molecules,  as  the  case  may  be,  are  entangled. 
If  the  contents  of  the  thoracic  duct  are  exam- 
ined, especially  after  a  meal,  there  may  be  found 
in  it  corpuscles  with  a  reddish  tinge.  These  have 
been  regarded,  probably  erroneously,  as  immature 
re(^  corpuscles,  or  lymph-  and  chyle-corpuscles 

•^^c;;,         ;:;::;        ;f;^:S      in  process  of  transformation  into  blood-globules. 
FIG.  5.-chyie  from  the  lacteals.  They  frequently  give  to  the  surface  of  clotted 

chyle  and  lymph  a  pinkish  hue.     They  must  not 

be  mistaken  for  mature  blood-globules,  which  are  sometimes  found  in  lymph  and 
chyle,  and  which  are  regarded  by  most  observers  as  accidental — i.  e.  produced  by 
the  manipulations  of  the  dissector. 

THE  ANIMAL  CELL. 

All  the  tissues  and  organs  of  which  the  body  is  composed  were  originally 
developed  from  a  microscopic  body  (the  ovum),  consisting  of  a  soft  gelatinous 
granular  material  enclosed  in  a  membrane,  and  containing  a  vesicle,  or  small 
spherical  body,  inside  which  are  one  or  more  solid  spots  (see  Fig.  73).  This  may 
be  regarded  as  a  perfect  cell.  Moreover,  all  the  solid  tissues  can  be  shown  to  con- 
sist largely  of  similar  bodies,  differing,  it  is  true,  in  external  form,  but  essentially 
similar  to  an  ovum.  These  are  also  cells. 

In  the  higher  organisms  all  such  cells  may  be  defined  as  '.'  nucleated  masses  of 
protoplasm  of  microscopic  size."  The  two  essentials,  therefore,  of  an  animal  cell 
in  the  higher  organisms  are,  the  presence  of  a  soft  gelatinous  granular  material, 


THE  ANIMAL    CELL.  39 

similar  to  that  found  in  the  ovum,  and  which  is  usually  styled  protoplasm ;  and  a 
small  spherical  bodv  imbedded  in  it,  and  termed  a  nucleus;  the  remaining  con- 
stituents of  the  ovum — viz.  its  limiting  membrane  and  the  solid  spot  contained  in 
the  nucleus,  called  the  nucleolus — are  not  considered  essential  to  the  cell,  and  in 
fact  many  cells  exist  without  them. 

Protoplasm  (sarcode,  blastema,  germinal  matter,  or  bioplasm)  is  a  proteid  com- 
pound. It  also  contains  certain  inorganic  substances,  as  phosphorus  and  calcium, 
which  latter  appears  to  be  essential  to  its  life  and  function.  It  is  of  a  semi-fluid, 
vise-id  consistence,  and  appears,  sometimes,  -either  as  a  hyaline  substance,  homo- 
geneous and  clear,  or  as  a  granular  substance,  consisting  of  minute  molecules 
imbedded  in  a  transparent  matrix.  These  molecules  are  regarded  by  some  as 
adventitious  material  taken  in  from  without,  and  often  probably  of  a  fatty  nature, 
since  they  are  frequently  soluble  in  ether.  In  most  cells,  however,  protoplasm 
shows  a  more  definite  structure,  consisting  of  minute  striae  or  fibrils  arranged  in  a 
clear  transparent  matrix,  or  a  honeycombed  reticulum  containing  in  its  interstices 
a  homogeneous  substance.  Protoplasm  is  insoluble  in  water,  coagulates  at  130°  F., 
and  has  a  great  affinity  for  certain  staining  reagents,  as  logwood  or  carmine. 

The  most  striking  characteristics  of  protoplasm  are  its  vital  properties  of 
motion  and  nutrition.  By  motion  is  meant  the  power  which  protoplasm  has  of 
changing  its  shape  and  position  by  some  internal  power  in  itself,  which  enables  it 
to  thrust  out  from  its  main  body  an  irregular  process,  into  which  the  whole  of  the 
protoplasmic  substance  is  gradually  drawn,  so  that  the  mass  comes  to  occupy  a 
new  position.  This,  on  account  of  its  resemblance  to  the  movements  observed  in 
the  Amoeba  or  Proteus  animalcule,  has  been  termed  "amoeboid  movement." 
Ciliary  movement,  or  the  vibration  of  hair-like  processes  from  the  surface  of  any 
structure,  may  also  be  regarded  as  a  variety  of  the  motion  with  which  protoplasm 
is  endowed.  Nutrition  is  the  power  which  protoplasm  has  of  attracting  to  itself 
the  materials  of  growth  from  surrounding  matter.  When  any  foreign  particle 
comes  in  contact  with  the  protoplasmic  substance,  it  becomes  incorporated  in  it 
by  being  enwrapped  by  one  or  more  processes  projected  from  the  parent  mass 
and  enclosed  by  them.  When  thus  taken  up,  it  may  remain  in  the  substance  of 
the  protoplasm  for  some  time  without  change,  or  may  be  assimilated  by  the 
protoplasm. 

The  Nucleus  is  a  minute  body,  imbedded  in  the  protoplasm,  and  usually  of  a 
spherical  or  oval  form,  its  size  having  little  relation  to  the  size  of  the  cell.  It  is 
usually  surrounded  by  a  well-defined  wall,  the  nuclear  membrane,  and  its  contents, 
known  as  the  nuclear  substance,  are  composed  of  a  stroma  or  network  and  an  inter- 
stitial substance,  the  relative  amount  of  the  two  varying  in  different  nuclei.  The 
network  appears  to  be  continuous  through  the  nuclear  membrane  with  the  proto- 
plasmic reticulum,  from  which  it  differs,  however,  in  having  strung  along  it  bands 
of  a  substance  which  stains  readily  with  certain  dyes,  and  is  therefore  named 
chromatin.  The  chromatin  differs  chemically  from  ordinary  protoplasm  in  con- 
taining nuclein,  in  its  power  of  resisting  the  action  of  acids  and  alkalies,  in  its 
imbibing  more  intensely  the  stain  of  carmine,  hsematoxylin,  etc.,  and  in  its 
remaining  unstained  by  some  reagents  which  color  ordinary  protoplasm  ;  as,  for 
example,  nitrate  of  silver. 

The  process  of  reproduction  of  cells  commences  in  the  nucleus,  and  is  usually 
described  as  being  brought  about  by  indirect  or  by  direct  division.  Indirect  division 
or  kari/okinesis  (karyomitosis)  has  been  observed  in  all  the  tissues — generative  cells, 
epithelial  tissue,  connective  tissue,  muscular  tissue,  and  nerve-tissue — and  it  is  the 
typical  method  by  which  the  division  of  cells  takes  place,  although  the  process  of 
reproduction  of  cells  by  direct  division  occurs  not  infrequently,  especially  in  highly 
specialized  cells. 

The  process  of  reproduction  by  indirect  division  commences  in  the  nucleus,  the 
stroma  of  which  undergoes  complex  changes,  leading  to  the  division  of  this  body 
previous  to  the  cleavage  of  the  protoplasm  of  the  cell.  The  changes  consist  briefly 
of  the  following :  (1)  At  the  commencement  of  the  process  the  nuclear  network  is 


40 


GENERAL    ANATOMY. 


well  developed,  but  shows  only  slight  indications  of  activity.  (2)  The  chromatic 
fibrils,  after  rearranging  themselves,  become  thicker,  and  probably  combine  in 
one  long  filament,  which  forms  a  loose  convolution.  This  is  called  the  c/lomerulus 
or  skein  (Fig.  6,  B).  At  the  same  time  a  number  of  protoplasmic  granules  arrange 
themselves  at  two  points  in  the  cell-protoplasm  opposite  each  other ;  these  points 
are  called  the  poles,  and  the  line  midway  between  them,  and  bisecting  at  right 


SIDE 


OR  EQUATORIAL 

VIEW. 


END  OR  POLAR 
VIEW. 

^ 


SIDE  OR  EQUATORIAL 
VIEW. 


A. 


FIG.  6.— Karyokinesis,  or  indirect  cell-division.  Diagram  explaining  the  formation  of  the  chromatic  and 
achromatic  karyokinetic  figures  in  epithelial  cells.  The  radiating  arrangement  of  protoplasmic  granules  is 
also  indicated,  although  it  is  in  the  ova  of  the  lower  animals  that  this  appearance  has  been  more  specially 
studied.  All  the  figures  are  simplified  for  diagrammatic  purposes,  but  represent  stages  which  can  easily  be 
recognized  in  specimens  properly  stained.  The  longitudinal  splitting  of  the  filaments  has  not  been  repre- 
sented. A.  Resting  nucleus,  the  nuclear  network  deeply  stained.  B.  Glomerulus,  convolution  or  skein,  c. 
Rosette  or  wreath.  D.  Aster  or  monaster.  E.  Diaster  or  daughter  star.  F.  Daughter  rosettes.  G.  Daughter 
glomeruli  or  skeins.  H.  Daughter  nuclei.  (By  Dr.  S.  Delepine.) 

angles  a  line  connecting  the  two,  is  called  the  equator.  The  aggregations  of 
protoplasmic  granules  are  termed  the  centrosomes,  and  they  are  surrounded  by 
clear  protoplasmic  areas  known  as  the  archoplasm  spheres.  (3)  The  chromatic 


THE   ANIMAL    CELL.  41 

filament  becomes  arranged  in  more  or  less  distinct  loops  converging  toward 
the  two  poles,  resembling  somewhat  in  appearance  a  rosette  or  wreath  (Fig.  6,  c). 
From  the  poles  to  the  loops,  fine  threads,  not  staining  like  the  others  (achromatic), 
are  seen  bridging  across  the  space  left  between  the  filament  and  the  cell- 
protoplasm.  These  are  known  as  the  nuclear  spindle.  (4)  The  loops  now- 
become  flattened  so  as  to  form  a  festooned  ring  or  star  at  the  equator 
of  the  nucleus.  This  is  known  as  the  single  star,  aster,  monaster.  The  loops 
begin  to  break  transversely  at  the  equator  (Fig.  6,  D*),  having  sometimes 
previously  broken  at  their  polar  ends.  The  nuclear  spindle  or  achromatin  is  very 
distinct,  as  well  as  a  radiating  ari'angement  of  protoplasmic  granules  toward  the 
poles.  It  is  at  this  stage,  or  sometimes  after,  that  a  longitudinal  splitting  of  the 
filaments  occurs,  so  that  they  become  more  numerous  and  more  slender.  (5)  After 
breaking  across  at  the  equator,  the  chromatic  filaments  move  toward  the  poles  as  if 
they  were  guided  by  the  achromatic  threads.  These  threads  bridge  across  between 
the  two  receding  stars,  which  are  known  as  diaster  or  daughter  stars.  The  pro- 
toplasm, with  its  radiating  granules,  begins  to  group  itself  around  the  two  poles 
(Fig.  6,  E).  (6)  The  daughter  stars  have  now  reached  the  poles ;  the  broken  ends 
become  united,  so  that  each  daughter  chromatic  filament  becomes  a  single  festooned 
filament,  forming  a  rosette  or  wreath,  the  daughter  rosettes  or  wreaths.  There 
is  now  distinct  evidence  of  cleavage  in  the  protoplasm  (Fig.  6,  F).  (7)  By  further 
irregular  contraction  the  regular  arrangement  of  the  loops  becomes  lost,  and  the 
filament  presents  a  convoluted  appearance,  constituting  the  daughter  glomeruli  or 
skeins  (Fig.  6,  G).  The  cleavage  of  the  protoplasm  is  now  complete  except  where 
the  achromatic  threads  are  found.  (8)  By  further  convolution  and  contraction 
the  loops  of  the  filament  become  fused  together,  and  form  again  a  network.  The 
nuclear  membrane  which  disappeared  at  the  beginning  of  the  karyokinesis  is 
formed  anew,  and  two  daughter  cells  with  nuclei  are  formed  (Fig.  6,  H).  The 
remains  of  the  achromatic  threads  bridge  across  the  intercellular  substance,  but 
later  usually  disappear  completely. 

In  the  reproduction  of  cells  by  direct  division  the  process  is  brought  about 
either  by  segmentation  or  by  gemmation.  In  reproduction  by  segmentation  or 
n*$ion  the  nucleus  first  splits  by  becoming  constricted  in  its  centre,  and  thus 
assuming  an  hour-glass  shape.  This  leads  to  a  cleavage  or  division  of  the  whole 
protoplasmic  mass  of  the  cell :  and  thus  we  find  that  two  new  cells  have  been 
formed,  consisting  of  the  same  substance  as  the  original  one,  and  each  containing 
a  nucleus.  These  daughter  cells  are  of  course  at  first  smaller  than  the  original 
mother  cell :  but  they  grow,  and  the  process  may  be  repeated  in  them,  so  that 
multiplication  may  rapidly  take  place.  In  reproduction  by  gemmation  a  budding- 
off  or  separation  of  a  portion  of  the  nucleus  and  parent-cell  takes  place,  and, 
becoming  separated,  forms  a  new  organism. 

The  cell-wall,  which  is  not  an  essential  constituent,  and  in  fact  is  often  absent, 
consists  of  a  flexible,  transparent,  structureless  or  finely  striated  membrane,  which 
is  permeable  to  fluids.  As  far  as  is  known,  every  animal  cell  is  derived  from  a 
pre-existing  cell.  The  death  of  cells  is  accomplished  either  by  their  mechanical 
detachment  from  the  surface,  preceded  possibly  by  their  bursting  and  discharg- 
ing their  contents,  or  by  various  forms  of  degeneration — fatty,  pigmentary,  or 
calcareous. 

EPITHELIUM. 

All  the  surfaces  of  the  body — the  external  surface  of  the  skin,  the  internal 
surface  of  the  digestive,  respiratory,  and  genito-urinary  tracts,  the  closed  serous 
cavities,  the  inner  coat  of  the  vessels,  and  the  ducts  of  all  secreting  and  excreting 
glands — are  covered  by  one  or  more  layers  of  simple  cells,  called  epithelium  or 
epithelial  cells.  These  cells  are  also  present  in  the  sensory  and  terminal  parts  of 
the  organs  of  special  sense,  and  in  some  other  organs,  as  the  pituitary  and  thyroid 
bodies.  They  serve  various  purposes,  forming  in  some  cases  a  protective  layer,  in 
others  acting  as  an  agent  in  secretion  and  excretion,  and  again  in  others  being 
concerned  in  the  elaboration  of  the  organs  of  special  sense.  Thus,  in  the  skin, 


42 


GENERAL    ANATOMY. 


the  main  purpose  served  by  the  epithelium  (here  called  the  epidermis)  is  that  of 
protection.  As  the  surface  is  worn  away  by  the  agency  of  friction  or  change  of 
temperature  new  cells  are  supplied,  and  thus  the  surface  of  the  true  skin  and  the 
vessels  and  nerves  which  it  contains  are  defended  from  damage.  In  the  gastro- 
intestinal mucous  membrane  and  in  the  glands  the  epithelial  cells  appear  to  be 
the  principal  agents  in  separating  the  secretion  from  the  blood  or  from  the  aliment- 
ary fluids.  In  other  situations  (as  the  nose,  fauces,  and  respiratory  passages)  the 
chief  office  of  the  epithelial  cells  appears  to  be  to  maintain  an  equable  tempera- 
ture by  the  moisture  with  which  they  keep  the  surface  always  slightly  lubricated. 
In  the  serous  cavities  they  also  keep  the  opposed  layers  moist,  and  thus  facilitate 
their  movements  on  each  other.  Finally,  in  all  internal  parts  they  ensure  a 
perfectly  smooth  surface. 

Of  late  years  there  has  been  a  tendency  on  the  part  of  many  histologists  to- 
divide  these  several  epithelial  linings  into  two  classes :  into  (1)  epithelial  tissue 
proper,  consisting  of  nucleated  protoplasmic  cells,  which  form  continuous  masses- 
on  the  skin  and  mucous  surfaces  and  the  linings  of  the  ducts  and  alveoli  of 
secreting  and  excreting  glands ;  and  (2)  endothelium,  which  is  composed  of  a  single 
layer  of  flattened  transparent  squamous  cells,  joined  edge  to  edge  in  such  a  man- 
ner as  to  form  a  membrane  of  cells.  This  is  found  on  the  free  surfaces  of  the 
serous  membranes,  as  the  lining  membrane  of  the  heart,  blood-vessels,  and  lym- 
phatics ;  on  the  surface  of  the  brain  and  spinal  cord,  and  in  the  anterior  chamber 
of  the  eye.  And,  though  the  separation  must  be  an  artificial  one,  since  every 
gradation  of  transition  between  the  two  classes  may  be  observed,  it  would  seem 
advisable  for  the  purpose  of  description  to  employ  it. 

1.  True  epithelial  tissue  consists  of  one  or  more  layers  of  cells,  united  together 


FIG.  7.— Epithelial  cells  from  the  oral  cavity  of  man.  Magnified  350  times,  a.  Large,  b.  Middle-sized, 
c.  The  same  with  two  nuclei. 

by  an  interstitial  cement-substance,  supported  on  a  basement-membrane,  and  is 
naturally  grouped  into  two  classes,  according  as  there  is  a  single  layer  of  cells  (simple 
epithelium)  or  more  than  one  (stratified  epithelium).  The  various  kinds  of 
epithelium,  whether  arranged  in  a  single  layer  or  in  more  than  one  layer,  are 
usually  spoken  of  as  squamous  or  pavement,  columnar,  spheroidal  or  glandular, 
'  and  ciliated. 

The  pavement  epithelium  (Fig.  7)  is  composed  of  flat  nucleated  scales  of  vari- 
ous shapes,  usually  polygonal,  and  varying  in  size.  These  cells  fit  together  by 
their  edges,  like  the  tiles  of  a  mosaic  pavement.  The  nucleus  is  generally  flat- 
tened, but  may  be  spheroidal.  The  flattening  depends  upon  the  thinness  of  the 
cell.  The  protoplasm  of  the  cell  presents  a  fine  reticulum  or  honeycombed  net- 
work, which  gives  to  the  cell  the  appearance  of  granulation.  This  kind  of  epi- 
thelium is  found  on  the  surface  of  the  skin  (epidermis)  and  on  mucous  surfaces 
which  are  subjected  to  friction.  The  nails,  the  hairs,  and  (in  animals)  the  horns 
are  a  variety  of  this  kind  of  epithelium. 

A  variety  of  squamous  epithelium  which  is  found  in  the  deeper  layers  of 


EPITHELIUM. 


43 


stratified  pavement-epithelium  has  been  termed  prickle  cells.  These  cells  possess 
short  fine  fibrils  which  pass  from  their  margins  to  those  of  neighboring  cells,  serv- 
ing to  connect  them  together.  They  were  first  probably  noticed  by  Max  Schultze 
and  Yirchow,  and  it  was  believed  that  by  them  the  cells  were  dovetailed  together. 
Subsequently  this  was  shown  not  to  be  so  by  Bizzozero,  who  pointed  out  that  the 
prickles  were  attached  to  each  other  by  their  apices  and  formed  minute  bridges 
across  spaces  occurring  between  the  cells  of  the  epithelium. 

The  columnar  or  cylindrical  epithelium  (Fig.  8)  is  formed  of  cylindrical  or 
rod-shaped  cells,  each  containing  a  nucleus,  and  set  together  so  as  to  form  a  com- 


FIG.  8.— Epithelium  of  the  intestinal  villi 
of  the  rabbit.  Magnified  300  times,  a.  Base- 
ment-membrane. 


FIG.  9.— Simple  columnar  epithelium,  from  the  mucous 
membrane  of  the  intestine,  with  goblet-cells  pouring  out 
their  contents.  (Klein  and  Xoble  Smith.) 


plete  membrane.  The  cells  have  a  prismatic  figure,  more  or  less  flattened  from 
mutual  pressure,  and  are  set  upright  on  the  surface  on  which  they  are  supported. 
Their  protoplasm  is  always  more  or  less  longitudinally  striated,  and  they  contain 
a  nucleus  which  is  oval  in  shape  and  contains  an  intranuclear  network. 

This  form  of  epithelium  covers  the  mucous  membrane  of  nearly  the  whole 
gastro-intestinal  tract  and  the  glands  of  that  part,  the  greater  part  of  the  urethra, 
the  vas  deferens.  the  prostate.  Cowper's  glands,  Bartholini's  glands,  and  a  portion 
of  the  uterine  mucous  membrane. 

/  G-oblet-  or  chalice-celis  are  a  modification  of  the  columnar  cell.  They  appear 
to  be  formed  by  an  alteration  in  shape  of  the  columnar  epithelium  (ciliated  or 
otherwise)  consequent  on  the  secretion  into  the  interior  of  the  cell  of  mucin,  the 
chief  organic  constituent  of  mucus,  which  distends  the  upper  part  of  the  cell, 
while  the  nucleus  is  pressed  down  toward  its  deep  part,  until  the  cell  bursts  and 
the  mucus  is  discharged  on  to  the  surface  of  the  mucous  membrane,  as  shown  in 
Fig.  9. 

•        The  spheroidal  or  glandular  epithelium  (Fig.  10)  is  composed  of  circular  or 
polyhedral  cells.     Like  other  forms  of  epithelial  cells,  the  protoplasm  is  a  fine 


FIG.  10. — Spheroidal  epithelium.     Magnified 
250  times. 


Fu;.  11.— Ciliated  epithelium  from  the  human 
trachea.  Magnified  350  times,  a.  Innermost  layers 
of  the  elastic  longitudinal  fibres.  6.  Homogeneous 
innermost  layers  of  the  mucous  membrane,  c. 
Deepest  round  cells,  d.  Middle  elongated  cells,  e. 
Superficial  cells,  bearing  cilia.  . 


reticulum.  which  gives  to  the  cell  the  appearance  of  granulation.  They  are  found 
in  the  terminal  recesses  of  secreting  glands,  and  the  protoplasm  of  the  cells 
usually  contains  the  materials  which  the  cells  secrete. 

Ciliated  epithelium  (Fig.  11)  may  be  of  any  of  the  preceding  forms,  but  usually 


44 


GENERAL    ANATOMY. 


inclines  to  the  columnar  shape.  It  is  distinguished  by  the  presence  of  minute 
processes,  which  are  direct  prolongations  of  the  cell-protoplasm  standing  up  from 
the  free  surface  like  hairs  or  eyelashes  (cilia).  If  the  cells  are  examined  during 
life  or  immediately  on  removal  from  the  living  body  (for  which  in  the  human  sub- 
ject the  removal  of  a  nasal  polypus  offers  a  convenient  opportunity)  in  tepid 
water,  the  cilia  will  be  seen  in  lashing  motion ;  and  if  the  cells  are  separate,  they 
will  often  be  seen  to  be  moved  about  in  the  field  by  that  motion. 

The  situations  in  which  ciliated  epithelium  is  found  in  the  human  body  are : 
the  respiratory  tract  from  the  nose  downward  (except  over  the  lower  portion  of  the 
pharynx  and  the  surface  of  the  vocal  cords)  the  tympanum  and  Eustachian  tube, 
the  Fallopian  tube  and  upper  portion  of  the  uterus,  the  vasa  efferentia,  coni  vas- 
culosi,  and  first  part  of  the  excretory  duct  of  the  testicle,  and  the  ventricles  of  the 
brain  and  central  canal  of  the  spinal  cord. 

Stratified  epithelium  consists  of  several  layers  of  cells  superimposed  one  on  the 
^      top  of  the  other  and  varying  greatly  in  shape.      The  cells  of  the  deepest  layer  are 

for  the  most  part  columnar  in 
form,  and  as  a  rule  form  a  sin- 
gle layer,  placed  vertically  on 
the  supporting  membrane  ;  above 
these  are  several  layers  of  sphe- 
roidal cells,  which  as  they  ap- 
proach the  surface  become  more 
and  more  compressed,  until  the 
superficial  layers  are  found  to 
consist  of  flattened  scales,  the 
margins  of  which  overlap  one 
another,  so  as  to  present  an  im- 
bricated appearance.  Another 
form  of  stratified  epithelium  is 
found  in  what  has  been  termed 
transitional  epithelium,  such  as  / 
exists  in  the  ureters  and  urinary 
bladder.  Here  the  cells  of  the 
most  superficial  layer  are  cubical, 
with  depressions  on  their  under 
surfaces,  which  fit  on  to  the 
rounded  ends  of  the  cells  of  the 
second  layer,  which  are  pear- 
shaped,  the  apices  touching  the 

basement-membrane.  Between  their  tapering  points  is  a  third  variety  of  cells, 
filling  in  the  intervals  between  them,  and  of  smaller  size  than  those  of  the  other 
two  layers. 

2.  Endothelium. — As  before  stated,  endothelial  cells  are  flattened,  transparent, 
squamous  cells,  attached  by  their  margins  by  a  semi-fluid  homogeneous  cement- 
substance,  so  as  to  form  a  continuous  endothelial  membrane.  Though  for  the  most 
part  these  cells  are  squamous,  in  some  places  cells  may  be  found,  either  isolated 
or  occurring  in  patches,  which  are  polyhedral  or  even  columnar.  These  latter 
cells  are  frequently  to  be  found  lining  the  stomata  of  serous  membranes  (Fig.  12). 
As  a  rule,  the  endothelial  cells  are  polygonal  in  outline,  with  sinuous  or  jagged 
margins,  and  are  in  close  apposition,  the  amount  of  cohesive  matter  uniting  them 
being  so  slight  as  not  to  be  apparent.  Their  protoplasmic  substance  appears  to  be 
granular,  but  consists  of  fibrillse  arranged  in  a  network  in  which  the  nucleus  is 
contained,  limited  by  a  membrane  and  having  a  well-developed  reticulum. 

CONNECTIVE    TISSUES. 

By  the  term  connective  tissue  we  mean  a  number  of  tissues  which  possess  this 
feature  in  common — viz.  that  they  serve  the  general  purpose  in  the  animal  economy 


FIG.  12.— Part  of  peritoneal  surface  of  the  central  tendon  of 
diaphragm  of  rabbit,  prepared  with  nitrate  of  silver,  s.  Stomata. 
t.  Lymph-channels,  t.  Tendon-bundles.  The  stomata  are  sur- 
rounded by  cubical  endothelial  cells.  (From  Hand-book  for 
the  Physiological  Laboratory,  Klein.) 


CO  -  v.  Y/ v  -77  VE    TISS  f  *E8. 


45 


of  supporting  and  connecting  the  tissues  of  the  frame.  These  tissues  may  differ 
considerably  from  each  other  in  external  appearance,  but  they  present  neverthe- 
less many  points  of  relationship  with  each  other,  and  are  moreover  developed 
from  the  same  embryonal  elements.  They  are  divided  into  three  great  groups: 
(1)  the  fibrous  connective  tissues,  (2)  cartilage,  and  (3)  bone. 

The  Fibrous  Connective  Tissues. — Three  principal  forms  or  varieties  of  fibrous 
connective  tissue  are  recognized :  (1)  White  fibrous  tissue ;  (2)  Yellow  elastic 
tissue:  (3)  Areolar  tissue.  They  are  all  composed  of  a  matrix  in  which  cells  are 
imbedded,  and  between  the  cells  are  fibres  of  two  kinds,  the  white  and  yellow  or 
elastic.  The  difference  between  the  three  forms  of  tissue  depends  on  the  relative 
proportion  of  the  two  kinds  of  fibre,  in  the  first  variety  enumerated  the  white  fibre 
preponderating ;  in  the  second  variety  the  yellow  elastic  fibres  being  greatly  in 
excess  of  the  white ;  and  the  third  form,  areolar  tissue,  the  two  being  blended  in 
much  more  equal  proportions. 

The  white  fibrous  tissue  (Fig.  13)  is  a  true  connecting  structure,  and  serves 
three  purposes  in  the  animal  economy.  It  serves  to  bind  bones  together  in  the 
form  of  ligaments,  it  serves  to 
connect  muscles  to  bones  or 
other  structures  in  the  form  of 
tendons,  and  it  forms  an  invest- 
ing or  protecting  structure  to 
various  organs  in  the  form  of 
membranes.  Examples  of 
where  it  serves  this  latter  office 
are  to  be  found  in  the  muscular 
fasciae  or  sheaths,  the  perios- 
teum, and  perichondrium ;  the 
investments  of  the  various 
glands,  (such  as  the  tunica 
albuginea  testis.  the  capsule  of 
the  kidney,  etc.).  the  investing  sheath  of  the  nerves  (epineurium).  and  of  various 
organs,  as  the  penis  and  the  eye  (sheath  of  the  corpora  cavernosa  and  corpus 
spongiosum,  and  of  the  sclerotic).  But  in  all  these  parts  the  student  must  bear  in 
mind  that  the  elastic  tissue  enters  in  greater  or  less  proportion.  It  presents  to 
the  naked  eye  the  appearance  of  silvery-white  glistening  fibres,  covered  over  with 
a  quantity  of  loose,  flocculent  tissue  which  binds  the  fibres  together  and  carries 
the  blood-vessels.  It  is  not  possessed  of  any  elasticity,  and  only  the  very 
slightest  extensibility ;  it  is  exceedingly  strong,  so  that  upon  the  application  of 
any  external  violence  the  bone  with  which  it  is  connected  will  fracture  before  the 
fibrous  tissue  will  give  way.  When  examined  under  the  microscope  it  is  found  to 
consist  of  waving  bands  or  bundles  of  minute,  transparent,  homogeneous  filaments 
or  fibrillne,  held  together  by  an  albuminous  semi-fluid  cement-substance  (Fig.  14). 
In  ligaments  and  tendons  these  bundles  run  parallel  with  each  other ;  in  mem- 
branes they  intersect  one  another  in  different  places.  The  bundles  have  a 
tendency  to  split  up  longitudinally  or  send  off  slips  to  join  other  bundles  and 
receive  others  in  return.  The  cells  occurring  in  white  fibrous  tissue  are  often 
called  "tendon  cells."  They  are  situated  on  the  surface  of  groups  of  bundles 
and  are  quadrangular  in  shape,  arranged  in  rows  in  single  file,  each  cell  being 
separated  from  its  neighbors  by  a  narrow  line  of  cement-substance.  The  nucleus 
is  generally  situated  at  one  end  of  the  cell,  the  nucleus  of  the  adjoining  cell  being 
in  close  proximity  to  it  (Fig.  15).  Upon  the  addition  of  acetic  acid  to  white 
fibrous  tissue  it  swells  up  into  a  glassy-looking,  indistinguishable  mass.  When 
boiled  in  water  it  is  converted  almost  completely  into  gelatin. 

Yellow  Elastic  Tissue. — In  certain  parts  of  the  body  a  tissue  is  found  which 
when  viewed  in  mass  is  of  a  yellowish  color,  and  is  possessed  of  great  elasticity,  so 
that  it  is  capable  of  considerable  extension,  and  when  the  extending  force  is  with- 
drawn returns  at  once  to  its  original  condition.  This  is  yellow  elastic  tissue,  in 


FIG.  13.— White  fibrous  tissue.    High  power. 


46 


GENERAL    ANATOMY. 


which  the  elastic  fibres  greatly  preponderate,  to  the  almost  complete  exclusion  of 
the  white  fibrous  element.  It  is  found  in  this  condition  in  the  ligamenta  subflava, 
in  the  vocal  cords,  in  the  longitudinal  coat  of  the  trachea  and  bronchi,  in  the 
inner  coats  of  the  blood-vessels,  especially  the  larger  arteries,  and  to  a  very  con- 


pn 

FIG.  14.— Connective  tissue.  (Klein  and 
Noble  Smith.)  a.  The  white  fibrous  element— 
a  layer  of  more  or  less  sharply-outlined  .paral- 
lel, wavy  bundles  of  connective-tissue  fibrils. 
On  the  surface  of  this  layer  is  b,  a  network  of 
fine  elastic  fibres. 


FIG.  15.— Tendon  of  mouse's  tail,  stained 
with  haematoxylin,  showing  chains  of  cells 
between  the  tendon-bundles.  (From  Quain's 
Anatomy.  E.  A.  Schafer.) 


siderable  extent  in  the  thyro-hyoid,  crico-thyroid,  and  stylo-hyoid  ligaments.  It 
is  also  found  in  the  ligamentum  nuchse  of  the  lower  animals.  When  viewed 
under  the  microscope  (Fig.  16)  it  is  seen  to  consist  of  an  aggregation  of  curling 
fibres,  with  a  well-defined  outline.  They  are  considerably  larger  in  size  than  the 
fibrillse  of  the  white  fibrous  element,  and  vary  much,  being  from  the  -^^o  "o  *°  tne 
•j-oVo  of  an  inch  in  diameter.  The  fibres  form  bold  and  wide  curves,  branch  and 
freely  anastomose  with  each  other.  They  are  homogeneous  in  appearance,  and 
have  a  tendency  to  curl  up,  especially  at  their  broken  ends.  In  some  parts,  where 
the  fibres  are  broad  and  large  and  the  network  close,  the  tissue  presents  the 
appearance  of  a  membrane,  with  gaps  or  perforations  corresponding  to  the  inter- 
vening space.  This  is  to  be  found  in  the  inner  coat  of  the  arteries,  and  to  it  the 
name  of  fenestrated  membrane  has  been  given  by  Henle.  The  yellow  elastic  fibres 
remain  unaltered  by  acetic  acid. 

Areolar  tissue  is  so  called  because  its  meshes  are  easily  distended,  and  thus 
separated  into  areolae  or  spaces,  which  all  open  freely  into  each  other,  and  are 
consequently  easily  blown  up  with  air,  or  permeated  by  fluid  when  injected  into 
any  part  of  the  tissue.  Such  spaces,  however,  do  not  exist  in  the  natural  con- 
dition of  the  body,  but  the  whole  tissue  forms  one  unbroken  membrane  com- 
posed, of  a  number  of  interlacing  fibres,  variously  superimposed.  Hence  the 
term  "the  cellular  membrane  "  is  in  many  parts  of  the  body  more  appropriate 
than  its  more  modern  equivalent.  The  chief  use  of  the  areolar  tissue  is  to  bind 
parts  together,  while  by  the  laxity  of  its  fibres  and  the  permeability  of  its  areolse 
it  allows  them  to  move  on  each  other,  and  affords  a  ready  exit  for  inflammatory 
and  other  effused  fluids.  It  is  one  of  the  most  extensively  distributed  of  all  the 
tissues  in  the  body.  It  is  found  beneath  the  skin  in  a  continuous  layer  all  over 
the  body,  connecting  it  to  the  subjacent  parts.  In  the  same  way  it  is  situated 
beneath  the  mucous  and  serous  membranes.  It  is  also  found  between  muscles, 
vessels,  and  nerves,  forming  investing  sheaths  for  them,  and  connecting  them 
with  surrounding  structures.  In  addition  to  this,  it  is  found  in  the  interior  of 
organs,  binding  together  the  various  lobes  and  lobules  of  the  compound  glands, 


CONNECTIVE    TISSUES. 


47 


the  various  coats  of  the  hollow  viscera,  and  the  fibres  of  muscles,  etc.,  and  thus 
forms  one  of  the  most  important  connecting  media  of  the  various  structures  or 


FIG.  16.— Yellow  elastic  tissue.    High  power. 

organs  of  which  the  body  is  made  up.  In  many  parts  the  areolae  or  interspaces 
of  areolar  tissue  are  occupied  by  fat-cells,  constituting  adipose  tissue,  which  will 
presently  be  described. 

Areolar  tissue  presents  to  the  naked  eye  a  flocculent  appearance,  somewhat 
like  spun  silk.  When  stretched  out,  it  is  seen  to  consist  of  delicate  soft  elastic 
threads  interlacing  with  each  other  in 
every  direction  and  forming  a  network 
of  extreme  delicacy.  When  examined 
under  the  microscope  it  is  found  to  be 
composed  of  white  fibres  and  elastic 
fibres  intercrossing  in  all  directions, 
and  united  together  by  a  homogeneous 
cement  or  ground-substance,  and  filled 
by  cellular  elements,  which  contain  the 
protoplasm  out  of  which  the  whole  is 

developed  and  regenerated 

Ihese    Cell-Spaces    mav  be    brought 
•     ,  i  •          ^i  *  ..-. 

into  view   by  treating  the  tissue  with 

nitrate  of  silver,  and    exposing  it  to 

the  light.     This  will  color  the  fibres  and  ground-substance,  leaving  the  cell-spaces 

unstained. 

The  cells  of  areolar  tissue  (Fig.  IT)  are  of  two  kinds :  1,  flattened  transparent 
cells,  with  an  oblong  nucleus  and  more  or  less  branched,  and  often  united  together 
by  thin-branched  processes ;  and  2.  granular  cells,  some  of  which  are  of  the  size 


17.— Connective-tissue  corpuscles.  (Klein  and 
Noble  Smith.)  m.  Migratory  connective-tissue  cell.  The 
other  two  are  the  ordinary  branched  cells,  each  with  an 
oblong  nucleus. 


48  GENERAL   ANATOMY. 

of  white  blood-corpuscles,  and  like  them  possessed  of  amoeboid  movements  ;  others 
are  of  larger  size,  and  do  not  exhibit  amoeboid  movements  to  any  appreciable 
extent.  They  lie  imbedded  in  the  ground-substance,  and  in  some  situations, 
where  the  areolar  tissue  is  loose  and  the  spaces  large,  so  as  to  contain  several  cells, 
they  form  a  sort  of  lining  for  it.  In  other  situations  where  the  tissue  forms  a 
membranous  layer,  the  flattened  cells,  here  unbranched,  form  an  epithelial-like 
covering  to  its  surface. 

Vessels  and  Nerves  of  Connective  Tissue. — The  blood-vessels  of  connective  tissue 
are  very  few — that  is  to  say,  there  are  few  actually  destined  for  the  tissue  itself, 
although  many  vessels  may  permeate  one  of  its  forms,  the  areolar  tissue,  carrying 
blood  to  other  structures.  In  white  fibrous  tissue  the  blood-vessels  usually  run 
parallel  to  the  longitudinal  bundles  and  between  them,  sending  transverse  com- 
municating branches  across,  and  in  some  forms,  as  the  periosteum  and  dura  mater, 
being  fairly  numerous.  In  the  yellow  elastic  tissue  the  blood-vessels  also  run 
between  the  fibres,  and  do  not  penetrate  them.  Lymphatic  vessels  are  very  numer- 
ous in  most  forms  of  connective  tissue,  especially  in  the  areolar  tissue  beneath  the 
skin  and  the  mucous  and  the  serous  surfaces.  They  are  also  found  in  abundance 
in  the  sheaths  of  tendons,  as  well  as  in  the  tendons  themselves.  Nerves  are  to 
be  found  in  the  white  fibrous  tissue,  where  they  terminate  in  a  special  manner ; 
but  it  is  doubtful  whether  any  nerves  terminate  in  areolar  tissue ;  at  all  events, 
they  have  not  yet  been  demonstrated,  and  the  tissue  is  possessed  of  very  little 
sensibility. 

Development  of  Connective  Tissue. — Fibrous  connective  tissue  is  developed  from 
embryonic  connective-tissue  cells  derived  from  the  mesoblast.  At  an  early  period 
of  development  it  consists  of  nucleated  cells  and  a  muco-albuminous  fluid,  which 
subsequently  becomes  a  pellucid  jelly  and  forms  the  ground-substance.  In  this 
ground-substance  the  two  varieties  of  fibres  become  developed.  As  to  the  manner 
in  which  they  do  so  there  are  two  theories,  some  believing  that  they  are  developed 
from  the  protoplasm  of  the  cells,  others  that  they  are  formed  by  a  deposit  in  the 
ground-substance.  In  the  former  case  the  protoplasm  of  the  cells  is  converted 
wholly  into  elementary  fibres,  the  nucleus  disappearing;  or  else  the  peripheral 
part  of  the  protoplasm  produces  the  fibrous  tissue,  the  original  cell  growing  again 
to  its  original  size,  and  then  throwing  off  a  fresh  portion  to  form  a  new  cell,  and 
itself  persisting  in  contact  with  the  fibres  it  has  formed  as  a  permanent  connective- 
tissue  corpuscle. 

Three  special  forms  of  connective  tissue  must  be  described :  the  mucoid,  the 
lymphoid  or  retiform,  and  basement-membranes. 

1.  The  mucoid  or  gelatinous  connective  tissue  exists  chiefly  in  the  "jelly  of 
Wharton,"  which  forms  the  bulk  of  the  umbilical  cord,  but  is  also  found  in  some 
other  situations  in  the  foetus,  as  in  the  pulp  of  young  teeth,  and  in  certain  stages 
of  the  development  of  connective  tissue  in  various  regions.     In  the  adult  the  vit- 
reous humor  of  the  eye  is  formed  of  the  same  material.     This  tissue  consists  of 
nucleated  cells,  which  branch   and  become  connected  so  as  to  form   trabeculse, 
which  traverse  a  jelly-like  ground  substance,  containing  the  chemical  principle  of 
mucus,  or  mucin,  and  in  smaller  quantities  albumen,  but  no  gelatin.     Sometimes, 
as  in  the  vitreous  humor  of  the  eye,  the  cells  almost  completely  disappear  and  the 
jelly  only  remains. 

2.  Retiform  connective  tissue  (Fig.  18)  is  found  extensively  in  many  parts  of 
the  body,  forming  the  framework  of  some  organs  and  entering  into  the  construc- 
tion of  many  mucous  membranes.     It  is  formed  of  an  interlacement  or  network  of 
very  fine  fibres,  which  closely  resemble  white  fibrous  tissue,  and  in  certain  situ- 
ations may  be  demonstrated  to  be  continuous  with  it.     In  their  behavior  to  certain 
reagents,  however,  they  differ   from   the  ordinary  Avhite  fibres,  and  have  conse- 
quently been  held  to  be  a  third  form  of  connective-tissue  fibres.     In  many  places 
flattened  cells  may  be  seen  connected  with  the  fibres  and  partially  concealing  them, 
presenting  an  appearance  as  if  the  tissue  were  formed  of  a  network  of  branching 
and  anastomosing  cells.     This,  however,  is  not  so,  as  the  cells  can  be  removed  or 


COXXECTIVE    TISS  f  /:>. 


49 


brushed  away,  leaving  the  fibres  intact.     In  many  situations  the  interstices  of  the 

fibres  are  filled  with  rounded  granular  corpuscles,  and  the  tissue  is  then  termed 

lymphoid  or  adenoid  tissue.     The  neuroglia, 

or  fine  gelatinous  connective  tissue  which 

supports    the    nervous    elements    in    the 

cerebro-spinal  axis  and  in  the  retina  has 

been   regarded  as  a  modified  form  of  the 

retiform    connective    tissue.      It    is    now 

known,  however,  to  consist  of  cells  which 

send  off  very  numerous  fine  processes,  and 

develop    from  the  epiblast,  certain  of  the 

cells  forming  the  wall  of  the   medullary 

canal,  becoming  neuroglia  cells,  while  the 

remainder  become  nerve-cells. 

3.  Basement-membranes,  formerly  de- 
scribed as  homogeneous  membranes,  are 
really  a  form  of  connective  tissue.  They 
constitute  the  supporting  membrane,  or 
membrana  propria.  supporting  the  epithe- 
lium of  mucous  membranes  or  secreting 
glands,  and  in  other  situations.  By  means 
of  staining  with  nitrate  of  silver  they  may 

be  shown  to  consist  of  flattened  cells  in  close  apposition,  and  form  therefore  an 
example  of  an  epithelioid  arrangement  of  connective-tissue  cells.  In  some  situ- 
ations the  cells,  instead  of  adhering  by  their  edges,  give  off  branching  processes, 
which  join  with  similar  processes  of  other  cells,  and  so  form  a  network  rather 
than  a  continuous  membrane. 

Adipose  Tissue. — In  almost  all  parts  of  the  body  the  ordinary  areolar  tissue 
contains  a  variable  quantity  of  adipose  or  fatty  tissue.  The  principal  situations 
where  it  is  not  found  are  the  subcutaneous  tissue  of  the  eyelids,  the  penis  and 
urn.  the  nymphfe,  within  the  cavity  of  the  cranium,  and  in  the  lungs, 
except  near  the  roots.  Nevertheless,  its  distribution  is  not  uniform,  in  some  parts 
being  collected  in  great  abundance,  as  in  the  subcutaneous  tissue,  especially  of  the 
abdomen  :  around  the  kidneys ;  on  the  surface  of  the  heart  between  the  furrows ; 
and  in  some  other  situations.  Lastly,  fat  enters  largely  into  the  formation  of  the 


FIG.  18.— Retiform  connective  tissue,  from.  & 
lymphatic  gland :  most  of  the  lymph-corpuscles 
a're  removed.  (From  Klein's  Elements  of  Histology.) 
a.  The  reticulum.  c.  A  capillary  blood-vesseL 


FIG.  19.— Adipose  tissue.    High  power,     a.  Starlike  appearance,  from  crystallization  of  fatty  acids. 

marrow    of  bones.     A    distinction  must,  however,    be  made    between    fat    and 
adipose  tissue ;  the  latter  being  a  distinct  tissue,  the  former  an  oily  matter,  which 


50 


GENERAL    ANATOMY. 


in  addition  to  its  occurrence  in  adipose  tissue  is  also  widely  present  in  the  body, 
as  in  the  fat  of  the  brain  and  liver  and  in  the  blood  and  chyle,  etc. 

Fat-cells  (Fig.  19)  consist  of  a  number  of  vesicles,  varying  in  size,  but  of  about 
the  average  diameter  of  -^-^  of  an  inch.  They  are  formed  of  an  exceedingly 
delicate  protoplasmic  membrane,  filled  with  fatty  matter,  which  is  liquid  during 
life,  but  becomes  solidified  after  death.  They  are  round  or  spherical  where  they 

have  not  been  subjected  to  pressure; 
otherwise  they  assume  a  more  or  less 
angular  outline.  A  nucleus  is  always 
present,  and  can  be  easily  demonstrat- 
ed by  staining  with  hgematoxylin;  in 
the  natural  condition  it  is  so  com- 
pressed by  the  contained  oily  matter 
as  to  be  scarcely  recognizable.  These 
fat-cells  are  contained  in  clusters  in 
the  areolse  of  fine  connective  tissue, 
and  are  held  together  mainly  by  a 
network  of  capillary  blood-vessels, 
which  are  distributed  to  them. 

Fat  is  an  inorganized  substance, 
consisting  of  a  liquid  material  (gly- 
cerin) in  combination  with  certain 
fatty  acids,  stearic,  palmitic,  and 
oleic.  Sometimes  the  acids  separate 
spontaneously  before  the  fat  is  exam- 
ined, and  are  seen  under  the  micro- 
scope in  a  crystalline  form,  as  in  Fig. 

19,  a.     By  boiling  the  tissue  in  ether  or  strong  alcohol  the  fat  may  be  extracted 
from  the  vesicle,  which  is  then  seen  empty  and  shrunken. 

Fat  is  said  to  be  first  detected  in  the  human  embryo  about  the  fourteenth 
week.  The  fat-cells  are  formed  by  the  transformation  of  the  protoplasmic  con- 
nective-tissue corpuscles,  into  which  small  globules  of  fat  find  their  way,  and 
increase  until  they  distend  the  corpuscle  into  the  thin  mantle  of  protoplasm  which 
forms  the  cell-wall,  and  in  which  its  nucleus  is  still  to  be  seen  (Fig.  20). 


FIG.  20.— Development  of  fat.  (Klein  an.l  Noble  Smith.) 
a.  Minute  artery,  v.  Minute  vein.  c.  Capillary  blood- 
vessels in  the  course  of  formation;  they  are  not  yet  com- 
pletely hollowed  out,  there  being  still  left  in  them  proto- 
plasmic septa,  d.  The  ground-substance,  containing 
numerous  nucleated  cells,  some  of  which  are  more  dis- 
tinctly branched  and  flattened  than  others,  and  appear 
therefore  more  spindle-shaped. 


PIGMENT. 

In  various  parts  of  the  body  pigment  is  found ;    most  frequently  in  epithelial 
cells  and  in  the  cells  of  connective  tissue.      Pigmented  epithelial  cells  are  found 
forming  the  external  layer  of  the  retina  (Fig.  21)  and  on  the  posterior  surface  of 
the  iris.     Pigment  is  also  found  in  the  epithelial  cells    of   the 
deeper  layers  of  the  cuticle  in  some  parts  of  the  body — such  as 
the  areola   of  the.  nipple    and  in  colored    patches    of    skin,  and 
especially  in  the  skin  of  the  colored  races,  and  also  in  hair.     It 
is   also  found  in  the  epithelial  cells  of  the  olfactory  region  and 
of  the  membranous  labyrinth  of  the  ear. 

In  the  connective-tissue  cells  pigment  is  frequently  met  with 
in  the  lower  vertebrates.  In  man  it  is  found  in  the  choroid  coat 
of  the  eye,  and  in  the  iris  of  all  but  the  light-blue  eyes  and  the  albino.  It  is 
also  occasionally  met  with  in  the  cells  of  retiform  tissue  and  in  the  pia  mater  of 
the  upper  part  of  the  spinal  cord.  These  cells  are  characterized  by  their  larger 
size  and  branched  processes,  which,  as  well  as  the  body  of  the  cells,  are  filled 
with  granules.  The  pigment  consists  of  dark-brown  or  black  granules  of  very 
small  size,  closely  packed  together  within  the  cells,  but  not  invading  the  nucleus. 
Occasionally  the  pigment  is  yellow,  and  when  occurring  in  the  cells  of  the  cuticle 
constitutes  "freckles." 


FIG.  21.— Pigment- 
cells  of  retina. 


CARTILAGE.  51 

CARTILAGE. 

*r 

Cartilage  is  a  non-vascular  structure  which  is  found  in  various  parts  of  the 
body — in  adult  life  chiefly  in  the  joints,  in  the  parietes  of  the  thorax,  and  in 
various  tubes,  such  as  the  air-passages,  nostrils,  and  ears,  which  are  to  be  kept 
permanently  open.  In  the  foetus  at  an  early  period  the  greater  part  of  the  skele- 
ton is  cartilaginous.  As  this  cartilage  is  afterward  replaced  by  bone,  it  is  called 
temporary*  in  contradistinction  to  that  which  remains  unossified  during  the  whole 
of  life,  and  which  is  called  permanent. 

Cartilage  is  divided,  according  to  its  minute  structure,  into  true  or  hyaline 
cartilage,  fibrous  or  fibro-cartilage.  and  yelloir  or  elastic  or  reticular  cartilage. 
Besides  these  varieties  met  with  in  the  adult  human  subject,  there  is  a  variety 
called  cellular  cartilage*  which  consists  entirely,  or  almost  entirely,  of  cells,  united 
in  some  eases  by  a  network  of  very  fine  fibres,  in  other  cases  apparently  destitute 
of  any  intercellular  substance.  This  is  found  in  the  external  ear  of  rats,  mice, 
and  some  other  animals,  and  is  present  in  the  chorda  dorsalis  of  the  human 
embryo,  but  is  not  found  in  any  other  human  structure.  The  various  cartilages 
in  the  body  are  also  classified,  according  to  their  function  and  position,  into 
articular,  interarticular.  costal,  and  membraniform. 

Hyaline  cartilage,  which  may  be  taken  as  the  type  of  this  tissue,  consists  of  a 
gristly  mass  of  a  firm  consistence,  but  of  considerable  elasticity  and  of  a  pearly- 
bluish  color.  Except  where  it  coats  the  articular  ends  of  bones,  it  is  enveloped 
in  a  fibrous  membrane,  the  perichondrium,  from  the  vessels  of  which  it  imbibes 
its  nutritive  fluids,  being  itself  destitute  of  blood-vessels  :  nor  have  any  nerves 
been  traced  into  it.  Its  intimate 
structure  is  very  simple.  If  a  thin 
slice  is  examined  under  the  micro- 

•e.  it  will  be  found  to  consist  of 
cells  of  a  rounded  or  bluntly  angular 
form,  lying  in  groups  of  two  or  more 
in  a  granular  or  almost  homogeneous 
matrix  (Fig.  22).  The  cells,  when 
arranged  in  groups  of  two  or  more, 
have  generally  a  straight  outline 

-.1  IK..  •*!.— Human  cartilage-cells,  from  the  cricoid  carti- 

wnere  tne\  are  in  contact  \\itn  eacli  iage-  Magnified  sao  times, 
other,  and  in  the  rest  of  their  cir- 
cumference are  rounded.  The  cell-contents  consist  of  clear  translucent  proto- 
plasm containing  minute  granules,  and  imbedded  in  this  are  one  or  two  nuclei, 
having  usually  a  granular  appearance,  but  occasionally  being  clear  and  occupied 
by  one  or  more  nucleoli.  The  cells  are  imbedded  in  cavities  in  the  matrix,  called 
<->irtil,_i<je  l,-i<-uim\  which  are  lined  bv  a  distinct  transparent  membrane  called 
the  capsule.  Each  lacuna  is  genevallv  occupied  by  a  single  cell,  but  during  the 
division  of  the  cells  it  may  contain  two,  four,  or  eight  cartilage-cells.  By 
boiling  the  cartilage  for  some  hours  and  treating  it  with  concentrated  mineral 
acid,  the  capsule  may  be  freed  from  the  matrix,  and  can  then  be  demonstrated  as  a 
distinct  vesicle  containing  the  cells.  By  exposure  to  the  action  of  an  electric  shock 
the  cell  assumes  a  jagged  outline  and  shrinks  away  from  the  interior  of  the 
capsule. 

The  matrix  is  transparent  and  apparently  without  structure,  or  else  presents 
a  dimly  granular  appearance,  like  ground  glass.  Some  observers  have  shown 
that  the  matrix  of  hyaline  cartilage,  and  especially  the  articular  variety,  after 
prolonged  maceration,  can  be  broken  up  into  fine  fibrils.  These  fibrils  are  prob- 
ably of  the  same  nature,  chemically,  as  the  white  fibres  of  connective  tissue.  It 
is  believed  by  some  histologists  that  the  matrix  is  permeated  by  a  number  of 
fine  channels,  which  connect  the  lacunae  with  each  other,  and  that  these  canals 
communicate  with  the  lymphatics  of  the  perichondrium,  and  thus  the  structure  is 
permeated  with  a  current  of  nutritious  fluid. 


52 


GENERAL    ANATOMY. 


The  articular  cartilages,  the  temporary  cartilages,  and  the  costal  cartilages  are 
all  of  the  hyaline  variety.  They  present  minute  differences  in  the  size  and  shape 
of  their  cells  and  in  the  arrangement  of  their  matrix.  In  the  articular  cartilages, 
which  show  no  tendency  to  ossification,  the  matrix  is  finely  granular  under  a  high 
power ;  the  cells  and  nuclei  are  small  and  are  disposed  parallel  to  the  surface  in 
the  superficial  part,  while  nearer  to  the  bone  they  become  vertical.  Articular 
cartilages  have  a  tendency  to  split  in  a  vertical  direction,  probably  from  some 
peculiarity  in  the  intimate  structure  or  arrangement  of  the  component  parts  of 
the  matrix.  In  disease  this  tendency  to  a  fibrous  splitting  becomes  very  manifest. 
Articular  cartilage  is  not  covered  by  perichondrium,  at  least  on  its  free  surface, 
where  it  is  exposed  to  friction,  though  a  layer  of  connective  tissue  can  be  traced 
in  the  adult  over  a  small  part  of  its  circumference  continuous  with  that  of  the 
synovial  membrane,  and  here  the  cartilage-cells  are  more  or  less  branched  and 
pass  insensibly  into  the  branched  connective-tissue  corpuscles  of  the  synovial 
membrane. 

Articular  cartilage  forms  a  thin  incrustation  upon  the  joint-surfaces  of  the 
bones,  and  its  elasticity  enables  it  to  break  the  force  of  any  concussion,  whilst  its 
smoothness  affords  ease  and  freedom  of  movement.  It  varies  in  thickness  accord- 
ing to  the  shape  of  the  bone  on  which  it  lies ;  where  this  is  convex  the  cartilage 
is  thickest  at  the  centre,  where  the  greatest  pressure  is  received ;  and  the  reverse 
is  the  case  on  the  concave  surfaces  of  the  bones.  Articular  cartilage  appears  to 
imbibe  its  nutriment  partly  from  the  vessels  of  the  neighboring  synovial  mem- 
brane, partly  from  those  of  the  bone  upon  which  it  is  implanted.  Mr.  Toynbee 
has  shown  that  the  minute  vessels  of  the  cancellous  tissue  as  they  approach  the 
articular  lamella  dilate  and  form  arches,  and  then  return  into  the  substance  of  the 
bone. 

In  the  costal  cartilages  the  cells  and  nuclei  are  large,  and  the  matrix  has  a 
tendency  to  fibrous  striation,  especially  in  old  age  (Fig.  23).  These  cartilages 

are  also  very  prone  to  ossify.  In  the 
thickest  parts  of  the  costal  cartilages  a 
few  large  vascular  channels  may  be 
detected.  This  appears  at  first  sight  an 
exception  to  the  statement  that  cartilage 
is  a  non-vascular  tissue,  but  is  not  so 
really,  for  the  vessels  give  no  branches  to 
the  cartilage-substance  itself,  and  the 
channels  may  rather  be  looked  upon  as 
involutions  of  the  perichondrium.  The 
ensiform  cartilage  may  be  regarded  as 
one  of  the  costal  cartilages,  and  the 
cartilages  of  the  nose  and  of  the  larynx 
and  trachea  resemble  them  in  microscop- 
ical characters,  except  the  epiglottis  and 
cornicular  laryngis,  which  are  of  the 
reticular  variety. 

The  hyaline  cartilages,  especially  in 
adult  and  advanced  life,  are  prone  to 
calcify — that  is  to  say,  to  have  their 


FIG.  23.— Costal  cartilage  from  a  man  seventy-six 
years  of  age,  showing  the  development  of  fibrous 
structure  in  the  matrix.  In  several  portions  of  the 
specimen  two  or  three  generations  of  cells  are  seen 
enclosed  in  a  parent  cell-wall.  High  power. 


matrix  permeated  by  the  salts  of  lime  without  any  appearance  of  true  bone. 
The  process  of  calcification  occurs  also  and  still  more  frequently,  according  to 
Rollett,  in  such  cartilages  as  those  of  the  trachea,  which  are  prone  afterward  to 
conversion  into  true  bone. 

White  fibro-cartilage  consists  of  a  mixture  of  white  fibrous  tissue  and  cartilag- 
inous tissue  in  various  proportions ;  it  is  to  the  first  of  these  two  constituents 
that  its  flexibility  and  toughness  are  chiefly  owing,  and  to  the  latter  its  elasticity. 
When  examined  under  the  microscope  it  is  found  to  be  made  up  of  fibrous  con- 
nective tissue  arranged  in  bundles,  with  cartilage-cells  between  the  bundles ;  these 


CARTILAGE. 


53 


t«.  a  certain  extent  resemble  tendon-cells,  but  may  be  distinguished  from  them  by 
being  surrounded  by  an  investing  capsule  and  by  their  being  less  flattened  (Fig.  24). 
The  fibro-cartilages  admit  of 
arrangement  into  four  groups 
— interarticular,  connecting, 
circumferential,  and  strati- 
form. 

The  interarticular  fibro-car- 
tilages (msni'st'-i}  are  flattened 


FIG.  24. — White  fibro-cartilage  from  the  semiluuar  disk  of  the 
patella  joint  of  an  ox.    Magnified  100  times. 


nisei)  are 

fibre-cartilaginous  plates,  of  a 
round,  oval,  triangular,  or 
sickle-like  form,  interposed 
between  the  articular  carti- 
lages of  certain  joints.  They 
are  free  on  both  surfaces,  thin- 
ner toward  their  centre  than 
at  their  circumference,  and 
held  in  position  by  their  mar- 
gins and  extremities  being  con- 
nected to  the  surrounding  ligaments.  The  synovial  membrane  of  the  joint  is 
prolonged  over  them  a  short  distance  from  their  attached  margins.  They  are 
found  in  the  temporo-maxillary,  sterno-clavicular,  acromio-clavicular,  wrist  and 
knee-joints.  These  cartilages  are  usually  found  in  those  joints  which  are  most 
exposed  to  violent  concussion  and  subject  to  frequent  movement.  Their  use  is 
— to  maintain  the  apposition  of  the  opposed  surfaces  in  their  various  motions ;  to 
increase  the  depth  of  the  articular  surfaces  and  give  ease  to  the  gliding  movement ; 
to  moderate  the  effects  of  great  pressure  and  deaden  the  intensity  of  the  shocks  to 
which  the  parts  mav  be  subjected.  Humphry  has  pointed  out  that  these  inter- 
articular fibro-cartilages  serve  an  important  purpose  in  increasing  the  variety  of 
movements  in  a  joint.  Thus,  in  the  knee-joint  there  are  two  kinds  of  motion, 
— viz.  angular  movement  and  rotation,  although  it  is  a  hinge  joint,  in  which,  as 
a  rule,  only  one  variety  of  motion  is  permitted ;  the  former  movement  taking 
place  between  the  condyles  of  the  femur  and  the  interarticular  cartilage,  the  latter 
between  the  cartilage  and  the  head  of  the  tibia.  So,  also,  in  the  temporo-maxil- 
lary joint,  the  upward  and  downward  movement  of  opening  and  shutting  the 
mouth  takes  place  between  the  cartilage  and  the  jaw-bone,  the  grinding  move- 
ment between  the  glenoid  cavity  and  the  cartilage,  the  latter  moving  with  the 
jaw-bone. 

The  connecting  fibro-cartilages  are  interposed  between  the  bony  surfaces  of 
those  joints  which  admit  of  only  slight  mobility,  as  between  the  bodies  of  the  ver- 
tebra? and  between  the  pubic  bones.  They  form  disks,  which  adhere  closely  to 
both  of  the  opposed  bones,  and  are  composed  of  concentric  rings  of  fibrous  tissue, 
with  cartilaginous  laminae  interposed,  the  former  tissue  predominating  toward  the 
circumference,  the  latter  toward  the  centre. 

The  circumferential  fibro-cartilages  consist  of  a  rim  of  fibro-cartilage,  which 
surrounds  the  margin  of  some  of  the  articular  cavities,  as  the  cotyloid  cavity  of 
the  hip  and  the  glenoid  cavity  of  the  shoulder ;  they  serve  to  deepen  the  articular 
surface  and  to  protect  the  edges  of  the  bone. 

The  stratiform  fibro-cartilages  are  those  which  form  a  thin  coating  to  osseous 
grooves  through  which  the  tendons  of  certain  muscles  glide.  Small  masses  of 
fibro-cartilage  are  also  developed  in  the  tendons  of  some  muscles,  where  they 
glide  over  bones,  as  in  the  tendons  of  the  peroneus  longus  and  the  tibialis 
posticus. 

Yellow,  or  reticular,  elastic  cartilage  is  found  in  the  human  body  in  the 
auricle  of  the  external  ear,  the  Eustachian  tubes,  the  cornicula  laryngis.  and  the 
epiglottis.  It  consists  of  cartilage-cells  and  a  matrix,  the  latter  being  pervaded 
in  every  direction,  except  immediately  around  each  cell,  by  a  network  of  yellow 


54 


GENERAL    ANATOMY. 


elastic  fibres,  branching  and  anastomosing  in  all  directions  (Fig.  25).  The  fibres 
resemble  those  of  yellow  elastic  tissue,  both  in  appearance  and  in  being  unaffected 
by  acetic  acid ;  and  according  to  Rollett  their  continuity  with  the  elastic  fibres 
of  the  neighboring  tissue  admits  of  being  demonstrated. 

The  distinguishing  feature 
of  cartilage  as  to  its  chemical 
composition  is  that  it  yields 
on  boiling  a  substance  called 
chondrin,  very  similar  to 
gelatin,  but  differing  from  it 
in  not  being  precipitated  by 
tannin.  According  to  Kiihne 
there  is  a  small  amount  of 
gelatin  in  hyaline  cartilage. 
Virchow  believes  that  the 
semilunar  disks  in  the  knee- 
joint  are  wrongly  denomi- 
nated cartilages,  since  they 
yield  no  chondrin  on  boil- 
ing; and  he  appears  to  re- 
gard them  as  a  modification 
with  the  cartilages  in  the 


FIG.  25. — Yellow  cartilage,  ear  of  horse.    High  power. 


agrees 


of  a  tendinous  structure,   which,   however, 
important  particular  of  being  non-vascular. 

Temporary  cartilage  and  the  process  of  its  ossification  will  be  described  with 
Bone. 


/  BONE. 

Structure  and  Physical  Properties  of  Bone. — Bone  is  one  of  the  hardest  struc- 
tures of  the  animal  body ;  it  possesses  also  a  certain  degree  of  toughness  and 
elasticity.  Its  color,  in  a  fresh  state,  is  of  a  pinkish  white  externally,  and  deep 
red  within.  On  examining  a  section  of  any  bone,  it  is  seen  to  be  composed  of  two 
kinds  of  tissue,  one  of  which  is  dense  and  compact  in  texture,  like  ivory ;  the 
other  consists  of  slender  fibres  and  lamellae,  which  join  to  form  a  reticular  struc- 
ture ;  this,  from  its  resemblance  to  lattice- work,  is  called  cancellous.  The  com- 
pact tissue  is  always  placed  on  the  exterior  of  the  bone ;  the  cancellous  is  always 
internal.  The  relative  quantity  of  these  two  kinds  of  tissue  varies  in  different 
bones,  and  in  different  parts  of  the  same  bone,  as  strength  or  lightness  is  requisite. 
Close  examination  of  the  compact  tissue  shows  it  to  be  extremely  porous,  so  that 
the  difference  in  structure  between  it  and  the  cancellous  tissue  depends  merely 
upon  the  different  amount  of  solid  matter,  and  the  size  and  number  of  spaces  in 
each ;  the  cavities  being  small  in  the  compact  tissue  and  the  solid  matter  between 
them  abundant,  whilst  in  the  cancellous  tissue  the  spaces  are  large  and  the  solid 
matter  in  smaller  quantity. 

Bone  during  life  is  permeated  by  vessels  and  is  enclosed  in  a  fibrous  membrane, 
the  periosteum,  by  means  of  which  many  of  these  vessels  reach  the  hard  tissue. 
If  the  periosteum  is  stripped  from  the  surface  of  the  living  bone,  small  bleeding 
points  are  seen,  which  mark  the  entrance  of  the  periosteal  vessels ;  and  on  section 
during  life  every  part  of  the  bone  will  be  seen  to  exude  blood  from  the  minute 
vessels  which  ramify  in  it.  The  interior  of  the  bones  of  the  limbs  presents  a 
cylindrical  cavity  filled  with  marrow  and  lined  by  a  highly  vascular  areolar 
structure,  called  the  medullary  membrane  or  internal  periosteum,  which,  how- 
ever, is  rather  the  areolar  envelope  of  the  cells  of  the  marrow  than  a  definite 
membrane. 

The  periosteum  adheres  to  the  surface  of  the  bones  in  nearly  every  part, 
excepting  at  their  cartilaginous  extremities.  Where  strong  tendons  or  ligaments 


BOXE.  55 

are  attached  to  the  bone,  the  periosteum  is  incorporated  with  them.  It  consists 
of  two  layers  closely  united  together,  the  outer  one  formed  chiefly  of  connective 
tissue,  containing  occasionally  a  few  fat-cells ;  the  inner  one,  of  elastic  fibres  of 
the  finer  kind,  forming  dense  membranous  networks,  which  can  be  again  separated 
into  several  layers.  In  young  bones  the  periosteum  is  thick,  and  very  vascular, 
and  is  intimately  connected  at  either  end  of  the  bone  with  the  epiphysial  cartilage, 
but  less  closely  with  the  shaft,  from  which  it  is  separated  by  a  layer  of  soft  blas- 
tema, containing  a  number  of  granular  corpuscles  or  "  osteoblasts."  in  which 
ossification  proceeds  on  the  exterior  of  the  young  bone.  Later  in  life  the  peri- 
osteum is  thinner,  less  vascular,  and  the  osteoblasts  have  become  converted  into 
an  epithelial  layer,  which  is  separated  from  the  rest  of  the  periosteum  in  many 
places  by  cleft-like  spaces,  which  are  supposed  to  serve  for  the  transmission  of 
lymph.  The  periosteum  serves  as  a  nidus  for  the  ramification  of  the  vessels 
previous  to  their  distribution  in  the  bone ;  hence  the  liability  of  bone  to  exfolia- 
tion or  necrosis,  when  denuded  of  this  membrane  by  injury  or  disease.  Fine 
nerves  and  lymphatics,  which  generally  accompany  the  arteries,  may  also  be 
demonstrated  in  the  periosteum. 

The  marrow  not  only  fills  up  the  cylindrical  cavity  in  the  shafts  of  the  long 
bones,  but  also  occupies  the  spaces  of  the  cancellous  tissue  and  extends  into  the 
larger  bony  canals  (Haversian  canals)  which  contain  the  blood-vessels.  It  differs 
in  composition  in  different  bones.  In  the  shafts  of  adult  long  bones  the  marrow 
is  of  a  yellow  color,  and  contains,  in  100  parts,  96  of  fat,  1  of  areolar  tissue  and 
vessels,  and  3  of  fluid,  with  extractive  matter,  and  consists  of  a  matrix  of  fibrous 
tissue,  supporting  numerous  blood-vessels  and  cells,  most  of  which  are  fat-cells,  but 
some  few  are  "marrow-cells."  In  the  flat  and  short  bones,  in  the  articular  ends 
of  the  long  bones,  in  the  bodies  of  the  vertebrae,  in  the  cranial  diploe,  and  in  the 
sternum  and  ribs,  it  is  of  a  red  color,  and  contains,  in  100  parts,  75  of  water  and 
25  of  solid  matter,  consisting  of  albumen,  fibrin,  extractive  matter,  salts,  and  a 
mere  trace  of  fat.  The  red  marrow  consists  of  a  small  quantity  of  areolar  tissue, 
blood-vessels,  and  numerous  cells,  some  few  of  which  are  fat-cells,  but  the  great 
majority  roundish  nucleated  cells,  the  true  "marrow-cells"  of  Kb'lliker.  These 
marrow-cells  resemble  in  appearance  the  white  corpuscles  of  the  blood,  though 
they  are  larger  and  have  a  relatively  larger  nucleus  and  a  clearer  protoplasm,  but, 
like  them,  possess  amoeboid  movements.  Amongst  them  may  be  seen  smaller 
•cells  (erythroblasts)  which  possess  a  slightly  pinkish  hue  ;  and  it  has  been  held 
by  Neumann  that  they  are  a  transitional  stage  between  marrow-cells  and  red 
blood-corpuscles,  while  others  believe  them  to  be  the  direct  descendants  of  the 
nucleated  embryonic  blood-cells  (see  p.  127),  and  to  be  transformed  into  blood- 
corpuscles  by  the  loss  of  their  nuclei. 

G-iant-cells  (myelo-plaques,  osteoclasts),  large,  multinucleated,  protoplasmic 
masses,  are  also  to  be  found  in  both  sorts  of  adult  marrow,  but  more  particularly 
in  red  marrow.  They  were  believed  by  Kolliker  to  be  concerned  in  the  absorption 
of  bone  matrix,  and  hence  the  name  which  he  gave  to  them — osteoclasts.  They 
excavate  small  shallow  pits  or  cavities,  which  are  named  Howship's  lacunae,  in 
which  they  are  found  lying. 

Vessels  of  Bone. — The  blood-vessels  of  bone  are  very  numerous.  Those  of  the 
compact  tissue  are  derived  from  a  close  and  dense  network  of  vessels  ramifying  in 
the  periosteum.  From  this  membrane  vessels  pass  into  the  minute  orifices  in  the 
compact  tissue,  running  through  the  canals  which  traverse  its  substance.  The 
cancellous  tissue  is  supplied  in  a  similar  way,  but  by  a  less  numerous  set  of  larger 
vessels,  which,  perforating  the  outer  compact  tissue,  are  distributed  to  the  cavities 
of  the  spongy  portion  of  the  bone.  In  the  long  bones  numerous  apertures  may 
be  seen  at  the  ends  near  the  articular  surfaces,  some  of  which  give  passage  to  the 
arteries  of  the  larger  set  of  vessels  referred  to ;  but  the  most  numerous  and  largest 
apertures  are  for  the  veins  of  the  cancellous  tissue,  which  run  separately  from  the 
arteries.  The  medullary  canal  in  the  shafts  of  the  long  bones  is  supplied  by  one 
large  artery  (or  sometimes  more),  which  enters  the  bone  at  the  nutrient  foramen 


56 


GENERAL    ANATOMY. 


(situated  in  most  cases  near  the  centre  of  the  shaft),  and  perforates  obliquely  the 
compact  structure.  The  medullary  or  nutrient  artery,  usually  accompanied  by 
one  or  two  veins,  sends  branches  upward  and  downward  to  supply  the  medullary 
membrane,  which  lines  the  central  cavity  and  the  adjoining  canals.  The  ramifica- 
tions of  this  vessel  anastomose  with  the  arteries  both  of  the  cancellous  and  com- 
pact tissues.  In  most  of  the  flat,  and  in  many  of  the  short  spongy  bones,  one 
or  more  large  apertures  are  observed,  which  transmit,  to  the  central  parts  of  the 
bone,  vessels  corresponding  to  the  medullary  arteries  and  veins.  The  veins  emerge 
from  the  long  bones  in  three  places  (Kb'lliker) :  (1)  by  one  or  two  large  veins, 
which  accompany  the  artery ;  (2)  by  numerous  large  and  small  veins  at  the  artic- 
ular extremities ;  (3)  by  many  small  veins  which  arise  in  the  compact  substance. 
In  the  flat  cranial  bones  the  veins  are  large,  very  numerous,  and  run  in  tortuous 
canals  in  the  diploic  tissue,  the  sides  of  the  canals  being  formed  by  a  thin  lamella 
of  bone,  perforated  here  and  there  for  the  passage  of  branches  from  the  adjacent 
cancelli.  The  same  condition  is  also  found  in  all  cancellous  tissue,  the  veins  being 
enclosed  and  supported  by  osseous  structure  and  having  exceedingly  thin  coats. 
When  the  bony  structure  is  divided,  the  vessels  remain  patulous,  and  do  not  con- 
tract in  the  canals  in  which  they  are  contained.  Hence  the  constant  occurrence 
of  purulent  absorption  after  amputation  in  those  cases  where  the  stump  becomes 
inflamed  and  the  cancellous  tissue  is  infiltrated  and  bathed  in  pus. 

Lymphatic  vessels,  in  addition  to  those  found  in  the  periosteum,  have  been 
traced  by  Cruikshank,  into  the  substance  of  bone,  and  Klein  describes  them  as 
running  in  the  Haversian  canals. 

Nerves  are  distributed  freely  to  the  periosteum,  and  accompany  the  nutrient 
arteries  into  the  interior  of  the  bone.  They  are  said  by  Kb'lliker  to  be  most 

numerous  in  the  articular  extremities 
of  the  long  bones,  in  the  vertebrae  and 
the  larger  flat  bones. 

Minute  Anatomy. — The  intimate 
structure  of  bone,  which  in  all  essential 
particulars  is  identical  in  the  compact 
and  cancellous  tissue,  is  most  easily 
studied  in  a  transverse  section  from  the 
compact  wall  of  one  of  the  long  bones 
after  maceration,  such  as  is  shown  in 
Fig.  26. 

If  this  is  examined  with  a  rather 
low  power  the  bone  will  be  seen  to  be 
mapped  out  into  a  number  of  circular 
districts,  each  one  of  which  consists  of 
a  central  hole,  surrounded  by  a  number 
of  concentric  rings.  These  districts  are 
termed  Haversian  systems ;  the  central 
hole  is  an  Haversian  canal.,  and  the 
rings  around  are  layers  of  bone-tissue 
arranged  concentrically  around  the  cen- 
tral canal,  and  termed  lamella?.  More- 
over, on  closer  examination,  it  will  be  found  that  between  these  lamellae,  and 
therefore  also  arranged  concentrically  around  the  central  canal,  are  a  number  of 
little  dark  specks,  the  lacuna*,  and  that  these  lacunae  are  connected  with  each 
other  and  with  the  central  Haversian  canal  by  a  number  of  fine  dark  lines,  which 
radiate  like  the  spokes  of  a  wheel  and  are  called  canaliculi.  All  these  structures 
— the  concentric  lamellae,  the  lacunae,  and  the  canaliculi — may  be  seen  in  any 
single  Haversian  system,  forming  a  circular  district  round  a  central,  Haversian, 
canal.  Between  these  circular  systems,  filling  in  the  irregular  intervals  which  are 
left  between  them,  are  other  lamellae,  with  their  lacunae  and  canaliculi,  running  in 


FIG  26.— From  a  transverse  section  of  the  shaft  of 
the  humerus.  Magnified  350  times,  a.  Haversian 
canals.  6.  Lacunae,  with  their  canaliculi  in  the  lamellae 
of  these  canals,  c.  Lacunae  of  the  interstitial  lamellae. 
d.  Others  at  the  surface  of  the  Haversian  systems,  with 
canaliculi  given  off  from  one  side. 


BONE. 


57 


various  directions,  but  more  or  less  curved  (Fig.  27).  These  are  termed  interstitial 
lamellae.  Again,  other  lamellae  for  the  most  part  found  on  the  surface  of  the  bone, 
are  arranged  concentrically  to  the  circumference  of  bone,  constituting,  as  it  were, 
a  single  Haversian  system*  of  the  whole  bone,  of  which  the  medullary  cavity  would 
represent  the  Haversian  canal.  These  latter  lamellae  are  termed  circumferential, 
or  by  some  authors  primary  or  fundamental  lamellae,  to  distinguish  them  from  those 
laid  down  around  the  axis  of  the  Haversian  canals,  which  are  then  termed  secondary 
or  special  lamellae. 

The  Haversian  canals,  seen  as  round  holes  in  a  transverse  section  of  bone  at 
or  about  the  centre  of  each  Haversian  system,  may  be  demonstrated  to  be  true 
canals  if  a  longitudinal  section  is  made,  as  in  Fig.  29.  It  will  then  be  seen  that 
these  round  holes  are  tubes  cut  across,  which  run  parallel  with  the  longitudinal 


FIG.  27.— Transverse  section  of  compact  tissue  of  bone.    Magnified  about  150  diameters.    (Sharpey.) 

axis  of  the  bone  for  a  short  distance,  and  then  branch  and  communicate.  They 
vary  considerably  in  size,  some  being  as  large  as  T>^  of  an  inch  in  diameter ;  the 
average  size  being,  however,  about  yl-g-  of  an  inch.  Near  the  medullary  cavity 
the  canals  are  larger  than  those  near  the  surface  of  the  bone.  Each  canal,  as  a 
rule,  contains  two  blood-vessels,  a  small  artery  and  vein ;  the  larger  ones  also  con- 
tain a  small  quantity  of  delicate  connective  tissue,  with  branched  cells,  the  pro- 
cesses of  which  communicate  with  the  branched  processes  of  certain  bone-cells 
in  the  substance  of  the  bone.  Those  canals  near  the  surface  of  the  bone  open 
upon  it  by  minute  orifices,  and  those  near  the  medullary  cavity  open  in  the 
same  way  into  this  space,  so  that  the  whole  of  the  bone  is  permeated  by  a  system 
of  blood-vessels  running  through  the  bony  canals  in  the  centre  of  the  Haversian 
systems. 

The  lamella?  are  thin  plates  of  bone-tissue  encircling  the  central  canal,  and 
might  be  compared,  for  the  sake  of  illustration,  to  a  number  of  sheets  of  paper 
pasted  one  over  another  around  a  central  hollow  cylinder.  After  macerating  a 
piece  of  bone  in  dilute  mineral  acid,  these  lamellae  may  be  stripped  off  in  a  longi- 
tudinal direction  as  thin  films.  If  one  of  these  is  examined  with  a  high  power 
under  the  microscope  it  will  be  found  to  be  composed  of  a  finely  reticular  struc- 
ture, presenting  the  appearance  of  lattice-work  made  up  of  very  slender,  trans- 
parent fibres,  decussating  obliquely,  and  coalescing  at  the  points  of  intersection 
so  as  to  form  an  exceedingly  delicate  network.  In  many  places  the  various 
lamellae  may  be  seen  to  be  held  together  by  tapering  fibres,  which  run  obliquely 
through  them,  pinning  or  bolting  them  together.  These  fibres  were  first  described 
by  Sharpey,  and  were  named  by  him  perforating  fibres. 


58 


GENERAL    ANATOMY. 


FIG.  28. — Nucleated  bone-cells  and  their 
processes,  contained  in  the  bone-lacunee  and 
their  caualiculi  respectively.  From  a  section 
through  the  vertebra  of  an  adult  mouse. 
'(Klein  and  Noble  Smith.) 


The  lacunae  are  situated  between  the  lamellae,  and  consist  of  a  number  of 
oblong  spaces.  In  an  ordinary  microscopic  section,  viewed  by  transmitted  light, 
they  appear  as  dark,  oblong,  opaque  spots,  and  were  formerly  believed  to  be  solid 
cells.  Subsequently,  when  it  was  seen  that  the  Haversian  canals  were  channels 
which  lodge  the  vessels  of  the  part,  and  the  canaliculi  minute  tubes  by  which  the 
plasma  of  the  blood  circulates  through  the  tissue,  it  was  taught  that  the  lacunae 
were  hollow  spaces  filled  during  life  with  the  same  fluid,  and  only  lined  (if  lined 
At  all)  by  a  delicate  membrane.  But  this  view  appears  also  to  be  delusive. 

Examination  of  the  structure  of  bone,  when 
recent,  led  Virchow  to  believe  that  the  lacunae 
are  occupied  during  life  with  a  nucleated  cell, 
the  processes  from  which  pass  down  the  canal- 
iculi— a  view  which  is  now  universally  received 
(Fig.  28).  It  is  by  means  of  these  cells  that 
the  fluids  necessary  for  nutrition  are  brought 
into  contact  with  the  ultimate  tissue  of  bone. 

The  canaliculi  are  exceedingly  minute 
channels,  which  pass  across  the  lamellae  and 
connect  the  lacunae  with  neighboring  lacunae 
and  also  with  the  Haversian  canal.  From  this 
central  canal  a  number  of  the  canaliculi  are 
given  off,  which  radiate  from  it,  and  open  into 
the  first  set  of  lacunae,  arranged  around  the 
Haversian  canal,  between  the  first  and  second 
lamellae.  From  these  lacunae  a  second  set  of 
canaliculi  are  given  off,  which  pass  outward  to 
the  next  series  of  lacunae,  and  so  on  until  they  reach  the  periphery  of  the  Haver- 
sian system ;  here  the  canaliculi  given  off  from  the  last  series  of  lacunae  do  not 
communicate  with  the  lacunae  of  neighboring  Haversian  systems,  but  after  passing 
outward  for  a  short  distance  form  loops  and  return  to  their  own  lacuna.  Thus 
•every  part  of  an  Haversian  system  is  supplied  with  nutrient  fluids  derived 
from  the  vessels  in  the  Haversian  canals  and  traversing  the  canaliculi  and 
lacunae. 

The  bone-cells  are  contained  in  the  lacunae,  which,  however,  they  do  not  com- 
pletely fill.  They  are  flattened  nucleated  cells,  which  Virchow  has  shown  are 
homologous  with  those  of  connective  tissue.  The  cells  are  branched,  and  the 
tranches,  especially  in  young  bones,  pass  into  the  canaliculi  from  the  lacunae. 

If  a  longitudinal  section  is  examined,  as  in  Fig.  29,  the  structure  is  seen  to  be 
the  same.  The  appearance  of  concentric  rings  is  replaced  by  that  of  lamellae  or 
rows  of  lacunae,  parallel  to  the  course  of  the  Haversian  canals,  and  these  canals 
appear  like  half-tubes  instead  of  circular  spaces.  The  tubes  are  seen  to  branch 
and  communicate,  so  that  each  separate  Haversian  canal  runs  only  a  short  distance. 
In  other  respects  the  structure  has  much  the  same  appearance  as  in  transverse 
sections. 

In  sections  of  thin  plates  of  bone  (as  in  the  walls  of  the  cells  which  form  the 
•cancellous  tissue)  the  Haversian  canals  are  absent,  and  the  canaliculi  open  into  the 
spaces  of  the  cancellous  tissue  (medullary  spaces),  which  thus  have  the  same  func- 
tion as  the  Haversian  canals  in  the  more  compact  bone. 

Chemical  Composition. — Bone  consists  of  an  animal  and  an  earthy  part  inti- 
mately combined  together. 

The  animal  part  may  be  obtained  by  immersing  the  bone  for  a  considerable 
time  in  dilute  mineral  acid,  after  which  process  the  bone  comes  out  exactly  the 
same  shape  as  before,  but  perfectly  flexible,  so  that  a  long  bone  (one  of  the  ribs,  for 
•example)  can  easily  be  tied  in  a  knot.  If  now  a  transverse  section  is  made  (Fig. 
30),  the  same  general  arrangement  of  the  Haversian  canals,  lamellae,  lacunae,  and 
canaliculi  is  seen,  though  not  so  plainly,  as  in  the  ordinary  section. 


BOXE. 


59 


The    earthy   part  may  be    obtained    separate  by  calcination,   by  which    the 
animal  matter* is  completely  burned  out.     The  bone  will  still  retain  its  original 

form,   but   it   will  be  white    and  brittle,   will 

a  b          c      b     a     b         have    lost    about    one-third    of    its    original 

weight,  and  will  crumble  down  with  the 
slightest  force.  The  earthy  matter  confers 
on  bone  its  hardness  and  rigidity,  and  the 
animal  matter  its  tenacity. 


FIG.  -2&.— Section  parallel  to  the  surface 
from  the  shaft  of  the  femur.  Magnified  100 
times,  a.  Haversian  canals.  6.  Lacunae  seen 
from  the  side.  c.  Others  seen  from  the  sur- 
face in  lamellae  which  are  cut  horizontally. 


FIG.  30.— Section  of  bone  after  the  removal  of  the  earthy  mat- 
ter by  the  action  of  acids. 

The  animal  base  is  often  called  cartilage, 
but  differs  from  it  in  structure,  in  the  fact  that 
it  is  softer  and  more  flexible,  and  that  when 
boiled  with  a  high  pressure  it  is  almost 
entirely  resolved  into  gelatin. 

The  organic  constituent  of  bone  forms  about 
one-third,  or  33.3  per  cent.;  the  inorganic 
matter,  two-thirds,  or  66. T  per  cent. ;  as  is 
seen  in  the  subjoined  analysis  of  Ber- 
zelius : 


Organic  matter 

Inorganic 

or 
Earthv  matter 


Gelatin  and  blood-vessels 
f  Phosphate  of  lime    . 
I  Carbonate  of  lime    . 
"!  Fluoride  of  calcium 
I  Phosphate  of  magnesia 
t  Soda  and  chloride  of  sodium 


33.30 

51.04 

11.30 

2.00 

1.16 

1.20 

100.00 


Some  chemists  add  to  this  about  1  per  cent,  of  fat. 

Some  difference  exists  in  the  proportion  between  the  two  constituents  of  bone 
at  different  periods  of  life.  In  the  child  the  animal  matter  predominates,  whereas 
in  aged  people  the  bones  contain  a  larger  proportion  of  earthy  matter,  and  the 
animal  matter  i.s  deficient  in  quantity  and  quality.  Hence  in  children  it  is  not 
uncommon  to  find,  after  an  injury  to  the  bones,  that  they  become  bent  or  only 
partially  broken,  whereas  in  old  people  the  bones  are  more  brittle  and  fracture 
takes  place  more  readily.  Some  of  the  diseases,  also,  to  which  bones  are  liable 
mainly  depend  on  the  disproportion  between  the  two  constituents  of  bone.  Thus 
in  the  disease  called  rickets,  so  common  in  the  children  of  the  poor,  the  bones 
become  bent  and  curved,  either  from  the  superincumbent  weight  of  the  body,  or 
under  the  action  of  certain  muscles.  This  depends  upon  some  defect  of  nutrition 
by  which  bone  becomes  deprived  of  its  normal  proportion  of  earthy  matter,  whilst 
the  animal  matter  is  of  unhealthy  quality.  In  the  vertebrae  of  a  rickety  subject 
Dr.  Bostock  found  in  100  parts  79.75  animal  and  20.25  earthy  matter. 

Development  of  Bone. — In  the  foetal  skeleton  some  bones,  such  as  the  long 
bones  of  the  limbs,  are  cartilaginous ;  others,  as  the  cranial  bones,  are  membran- 
ous. Hence  two  kinds  of  ossification  are  described :  the  intracartilaginous  and 
the  intramembranons  ;  and  to  these  a  third  is  sometimes  added,  the  subperiosteal ; 
this,  however,  is  the  same  as  the  second,  only  taking  place  under  different  cir- 
cumstances. 


60 


GENERAL    ANATOMY. 


Intracartilaginous  Ossification. — Just  before  ossification  begins  the  bone  is 
entirely  cartilaginous,  and  in  a  long  bone,  which  may  be  taken  as  an  example, 
the  process  commences  in  the  centre  and  proceeds  toward  the  extremities,  which 
for  some  time  remain  cartilaginous.  Subsequently  a  similar  process  commences 
in  one  or  more  places  in  those  extremities  and  gradually  extends  through  it.  The 

extremity  does  not,  however, 
become  joined  to  the  shaft  of 
the  bone  until  gi*owth  has 
ceased,  but  remains  separated 
by  a  layer  of  cartilaginous 


tissue   termed  epiphysial    carti- 
lage. 

The  first  step  in  the  ossifica- 
tion of  the  cartilage  is  that  the 
cartilage-cells,  at  the  point 
where  ossification  is  commen- 
cing and  which  is  termed  a  cen- 
tre of  ossification,  enlarge  and 
arrange  themselves  in  rows  (Fig. 
31).  The  matrix  in  which  they 
are  imbedded  increases  in  quan- 
tity, so  that  the  cells  become 
further  separated  from  each 
other.  A  deposit  of  calcareous 
material  now  takes  place  in  this 
matrix,  between  the  rows  of 
cells,  so  that  they  become  sepa- 
rated from  each  other  by  longi- 
tudinal columns  of  calcified 
matrix,  presenting  a  granular 
and  opaque  appearance.  Here 
and  there  the  matrix  between 
two  cells  of  the  same  row  also 
becomes  calcified,  and  thus  we 
have  transverse  bars  of  calcified 
substance  stretching  across  from 
calcareous  column  to 


FIG.  3L— Longitudinal  section  through  the  ossifying  portion  of 
a  long  bone  in  the  human  embryo,  o.  Cartilaginous  region.  6. 
Region  of  calcified  matrix. 


one 


another.  Thus  we  have  lon- 
gitudinal groups  of  the  cartilage- 
cells  enclosed  in  oblong  cavities,  the  Avails  of  which  are  formed  of  calcified 
matrix.  These  cavities  are  called  the  primary  areolce  (Sharpey). 

At  the  same  time  that  this  process  is  going  on  in  the  centre  of  the  cartilage  of 
which  the  foetal  bone  consists,  certain  changes  are  taking  place  on  its  surface. 
This  is  covered  by  a  very  vascular  membrane,  the  periosteum,  on  the  inner  surface 
of  which — that  is  to  say,  on  the  surface  in  contact  with  the  cartilage — are  a  number 
of  cells  called  osteoblasts.  By  the  agency  of  these  cells  a  thin  layer  of  bony  tissue 
is  being  formed  between  the  periosteum  and  the  cartilage,  by  the  intramem- 
branous  mode  of  ossification  presently  to  be  described.  We  have  then,  in  this 
first  stage  of  ossification,  two  processes  going  on  simultaneously :  in  the  centre  of 
the  cartilage  the  formation  of  a  number  of  oblong  spaces,  enclosed  by  calcified 
matrix  and  containing  the  cartilage-cells  enlarged  and  arranged  in  groups,  and  on 
the  surface  of  the  cartilage  the  formation  of  a  layer  of  true  membrane-bone.  The 
second  stage  consists  in  the  prolongation  into  the  cartilage  of  processes  of  the 
deeper  or  osteogenetic  layer  of  the  periosteum  (Fig.  32,  ir).  The  processes  consist 
of  blood-vessels  and  cells  (osteoblasts).  They  excavate  passages  through  the  new- 
formed  bony  layer  by  absorption,  and  pass  through  it  into  the  calcified  matrix  (Fig. 
32).  Wherever  these  processes  come  in  contact  with  the  calcified  walls  of  the 


BONE. 


61 


primary  areolae  they  absorb  it,  and  thus  cause  a  fusion  of  the  original  cavities  and 
the  formation  of  larger  spaces,  which  are  termed  the  secondary  areolce  (Sharpey) 


FIG.  32.— Section  of  fcetal  bone  of  cat.  ir.  Irruption  of 
the  subperiosteal  tissue.  ».  Fibrous  layer  of  the  perios- 
teum, o.  Layer  of  osteoblasts.  im.  Subperiosteal  bony 
deposit.  (From  Quain's  Anatomy,  E.  A.  Schafer.) 


FIG.  33.— Part  of  a  longitudinal  section  of 
the  developing  femur  of  a  rabbit,  a.  Flat- 
tened cartilage-cells,  b.  Enlarged  cartilage- 
cells,  c.  d.  Newly-formed  bone.  e.  Osteo- 
blasts. /.  Giant-cells  or  osteoclasts.  g.  h. 
Shrunken  cartilage-cells.  (From  Atlas  of  His- 
tology, Klein  and  Noble  Smith.) 


or  medullary  spaces  (Muller).  In  these  secondary  spaces  the  original  cartilage- 
cells  disappear,  and  their  cavities  become  filled  with  embryonic  marrow,  consisting 
of  osteoblasts  and  vessels,  and  derived,  at  all  events  in  part,  in  the  manner 
described  above,  from  the  osteogenetic  layer  of  the  periosteum  (Fig.  33).  What 
becomes  of  the  cartilage-cells  is  not  finally  determined.  By  most  histologists  they 
are  believed  to  be  converted,  after  division,  into  osteoblasts,  and  so  assist  in  form- 
ing the  embryonic  marrow.  Others,  on  the  other  hand,  believe  that  they  are 
simply  absorbed  and  take  no  part  in  the  formation  of  bone. 

Thus  far,  then,  we  have  got  enlarged  spaces  (secondary  areolae),  the  walls  of 
which  are  still  formed  by  calcified  cartilage-matrix,  containing  an  embryonic 
marrow,  derived  from  the  processes  sent  in  from  the  osteogenetic  layer  of  the  peri- 
osteum, and  consisting  of  blood-vessels  and  round  cells,  osteoblasts  (Fig.  33),  some 
of  which  probably  are  derived  from  the  division  of  the  original  cartilage-cells,  which 
have  disappeared.  The  walls  of  these  secondary  areolae  are  at  this  time  of  only 
inconsiderable  thickness,  but  they  now  become  thickened  by  the  deposition  of  lay- 
ers of  new  bone  on  their  interior.  This  process  takes  place  in  the  following 
manner :  Some  of  the  osteoblasts  of  the  embryonic  marrow,  after  undergoing 
rapid  division,  arrange  themselves  as  an  epithelioid  layer  on  the  surface  of  the 


62 


GENERAL    ANATOMY. 


wall  of  the  space  (Fig.  34).  This  layer  of  osteoblasts  forms  a  bony  stratum, 
and  thus  the  wall  of  the  space  becomes  gradually  covered  with  a  layer  of  true 
osseous  substance.  On  this  a  second 
layer  of  osteoblasts  arrange  them- 
selves, and  in  their  turn  form  an  os- 
seous layer.  By  the  repetition  of  this 
process  the  original  cavity  becomes 
very  much  reduced  in  size,  and  at  last 
only  remains  as  a  small  circular  hole 
in  the  centre,  containing  the  remains 
of  the  embryonic  marrow — that  is,  a 
blood-vessel  and  a  few  osteoblasts. 
This  small  cavity  constitutes  the  Ha- 


FIG.  34.— Transverse  section  from  the  femur  of  a 
human  embryo  about  eleven  weeks  old.  a.  A  med- 
ullary sinus  cut  transversely;  and  b,  another,  long- 
itudinally, c.  Osteoblasts.  a.  Newly-formed  osseous 
substance  of  a  lighter  color,  e.  That  of  greater  age. 
/.  Lacunae  with  their  cells,  g.  A  cell  still  united  to 
an  osteoblast. 


FIG.  35.— Vertical  section  from  the  edge  of  the 
ossifying  portion  of  the  diaphysis  of  a  metatar- 
sal  b'one  from  a  foetal  calf.  (After  Miiller.)  a. 
Ground-mass  of  the  cartilage,  b.  Of  the  bone.  e. 
Newly-formed  bone-cells  in  profile,  more  or  less 
imbedded  in  intercellular  substance,  d.  Medul- 
lary canal  in  process  of  formation,  with  vessels 
and  medullary  cells,  e.  f.  Bone-cells  on  their 
broad  aspect,  g.  Cartilage-capsules  arranged  in 
rows,  and  partly  with  shrunken  cell-bodies. 


versian  canal  of  the  perfectly  ossified  bone.  The  successive  layers  of  osseous 
matter  which  have  been  laid  down  and  which  encircle  this  central  canal,  consti- 
tute the  lamellae  of  which,  as  we  have  seen,  each  Haversian  system  is  made  up. 
As  the  successive  layers  of  osteoblasts  form  osseous  tissue,  certain  of  the  osteo- 
blastic  cells  remain  included  between  the  various  bony  layers.  These  continue 
persistent,  and  remain  as  the  corpuscles  of  the  future  bone,  the  spaces  enclosing 
them  forming  the  lacuna  (Fig.  34).  The  mode  of  the  formation  of  the  canaliculi 
is  not  known. 

Such  are  the  changes  which  may  be  observed  at  one  particular  point,  the  centre 
of  ossification.  While  they  have  been  going  on  here  a  similar  process  has  been 
proceeding  in  the  same  manner  toward  the  end  of  the  shaft,  so  that  in  the  ossify- 
ing bone  all  the  changes  described  above  may  be  seen  in  different  parts,  from  the 
true  bone  in  the  centre  of  the  shaft  to  the  hyaline  cartilage  at  the  extremities. 
The  bone  thus  formed  differs  from  the  bone  of  the  adult  in  being  more  spongy  and 
less  regularly  lamellated. 

Thus  far,  then,  we  have  followed  the  steps  of  a  process  by  which  a  solid  bony 
mass  is  produced,  having  vessels  running  into  it  from  the  periosteum,  Haversian 


BOXE  63 

canals  in  which  those  vessels  run.  medullary  spaces  filled  with  foetal  marrow, 
lacunae  with  their  contained  bone-cells,  and  canaliculi  growing  out  of  these 
lacunae. 

This  process  of  ossification,  however,  is  not  the  origin  of  the  whole  of  the 
skeleton,  for  even  in  those  bones  in  which  the  ossification  proceeds  in  a  great 
measure  from  a  single  centre,  situated  in  the  cartilaginous  shaft  of  a  long  bone,  a 
considerable  part  of  the  original  bone  is  formed  by  intramembranous  ossification 
beneath  the  perichondrium  or  periosteum ;  so  that  the  girth  of  the  bone  is  increased 
by  bony  deposit  from  the  deeper  layer  of  this  membrane.  The  shaft  of  the  bone 
is  at  first  solid,  but  a  tube  is  hollowed  out  in  it  by  absorption  around  the  vessels 
passing  into  it,  which  becomes  the  medullary  canal.  This  absorption  is  supposed 
to  be  brought  about  by  large  "  giant-cells."  which  have  long  been  recognized  as  a 
constituent  of  foetal  marrow,  and  which  are  believed  by  Kolliker  to  have  the  power 
of  absorbing  or  dissolving  bone,  and  he  has  therefore  named  them  "  osteoclasts  " 
(Fig.  33.  /).  They  vary  in  shape  and  size,  and  are  known  by  containing  a  large 
number  of  clear  nuclei,  sometimes  as  many  as  twenty.  The  occurrence  of  similar 
cells  in  some  tumors  of  bones  has  led  to  such  tumors  being  denominated 
"  uiyeloid." 

A-  more  and  more  bone  is  removed  by  this  process  of  absorption  from  the 
interior  of  the  bone  to  form  the  medullary  canal,  so  more  and  more  bone  is 
deposited  on  the  exterior  from  the  periosteum,  until  at  length  the  bone  has  attained 
the  shape  and  size  which  it  is  destined  to  retain  during  adult  life.  As  the  ossifi- 
cation of  the  cartilaginous  shaft  extends  toward  the  articular  ends  it  carries  with 
it.  as  it  were,  a  layer  of  cartilage,  or  the  cartilage  grows  as  it  ossifies,  and  thus  the 
bone  is  increased  in  length.  During  this  period  of  growth  the  articular  end,  or 
epiphysis,  remains  for  some  time  entirely  cartilaginous ;  then  a  bony  centre  appears 
in  it.  and  it  commences  the  same  process  of  intracartilaginous  ossification;  but 
this  process  never  extends  to  any  great  distance.  The  epiphyses  remain  separated 
from  the  shaft  by  a  narrow  cartilaginous  layer  for  a  definite  time.  This  layer 
ultimately  ossifies,  the  distinction  between  shaft  and  epiphysis  is  obliterated,  and ' 
the  bone  assumes  its  completed  form  and  shape.  The  same  remarks  also  apply  to 
the  processes  of  bone  which  are  separately  ossified,  such  as  the  trochanters  of  the 
femur.  The  bones,  having  been  formed,  continue  to  grow  until  the  body  has 
acquired  its  full  stature.  They  increase  in  length  by  ossification  continuing  to 
extend  in  the  epiphysial  cartilage,  which  goes  on  growing  in  advance  of  the  ossi- 
fying process.  They  increase  in  circumference  by  deposition  of  new  bone,  from 
the  deeper  layer  of  the  periosteum,  on  their  external  surface,  and  at  the  same 
time  an  absorption  takes  place  from  within,  by  which  the  medullary  cavity  is 
increased. 

The  medullary  spaces  which  characterize  the  cancellous  tissue  are  produced  by 
the  absorption  of  the  original  foetal  bone  in  the  same  way  as  the  original  medul- 
lary canal  is  formed.  The  distinction  between  the  cancellous  and  compact  tissue 
appears  to  depend  essentially  upon  the  extent  to  which  this  process  of  absorption 
has  been  carried ;  and  we  may  perhaps  remind  the  reader  that  in  morbid  states  of 
the  bone  inflammatory  absorption  produces  exactly  the  same  change,  and  converts 
portions  of  bone  naturally  compact  into  cancellous  tissue. 

Intramembranous  Ossification. — The  intramembranous  ossification  is  that  by 
which  the  bones  of  the  vertex  of  the  skull  are  entirely  formed.  In  the  bones 
which  are  so  developed  no  cartilaginous  mould  precedes  the  appearance  of  the 
bone-tissue.  In  the  membrane  which  occupies  the  place  of  the  future  bone,  a  little 
network  of  bony  spiculae  is  first  noticed,  radiating  from  the  point  of  ossification. 
When  these  rays  of  growing  bone  are  examined  by  the  microscope,  they  are  found 
to  consist  of  a  network  of  fine  clear  fibres  and  granular  cells  with  a  ground- 
substance  between.  The  fibres  are  termed  osteogenic  fibres,  and  soon  become 
dark  and  granular  from  calcification,  and  as  they  calcify  they  are  found  to  enclose 
the  granular  cells  or  u  osteoblasts  "  (Fig.  36).  The  calcification  not  only  involves 
the  osteogenic  fibres,  but  also  the  ground-substance  of  the  tissue  in  which  they 


64 


GENERAL  ANATOMY. 


FIG.  36.— Osteoblasts  from  the  parietal  bone  of  a  human  em- 
bryo thirteen  weeks  old.  (After  Gegenbauer.)  a.  Bony  septa  with 
the  cells  of  the  lacunae.  6.  Layers  of  osteoblasts.  c.  The  latter  in 
transition  to  bone-corpuscles. 


are  contained.     The  cells  at  first  lie  upon  the  osteogenic  fibres,  so  that  they  can 
be  removed  by  brushing   the   specimen   with   a   hair-pencil,  in   order    to   render 

the  fibres  clear ;  but  they  grad- 
ually become  involved  in  the 
ossifying  matrix,  and  form  the 
corpuscles  of  the  future  bone, 
the  spaces  in  which  they  are 
enclosed  constituting  the  la- 
cunae. As  the  tissue  increases 
in  thickness,  vessels  shoot  into 
it,  grooving  for  themselves 
spaces  or  channels,  which  be- 
come the  Haversian  canals. 
Thus,  the  intramembranous 
and  intracartilaginous  processes 
of  ossification  are  similar  in 
their  more  essential  features. 

The  number  of  ossific  cen- 
tres is  different  in  different 
bones.  In  most  of  the  short 
bones  ossification  commences 
by  a  single  point  in  the  centre, 
and  proceeds  toward  the  cir- 
cumference. In  the  long  bones  there  is  a  central  point  of  ossification  for  the 
shaft  or  diaphysis;  and  one  or  more  for  each  extremity,  the  epiphysis.  That 
for  the  shaft  is  the  first  to  appear.  The  union  of  the  epiphyses  with  the  shaft 
takes  place  in  the  reverse  order  to  that  in  which  their  ossification  began,  and 
appears  to  be  regulated  by  the  direction  of  the  nutrient  artery  of  the  bone.  Thus, 
the  nutrient  arteries  of  the  bones  of  the  arm  and  fore-arm  are  directed  toward  the 
elbow,  and  the  epiphyses  of  the  bones  forming  this  joint  become  united  to  the 
shaft  before  those  at  the  opposite  extremity.  In  the  lower  limb,  on  the  other 
hand,  the  nutrient  arteries  pass  in  a  direction  from  the  knee :  that  is,  upward  in 
the  femur,  downward  in  the  tibia  and  fibula ;  and  in  them  it  is  observed  that  the 
upper  epiphysis  of  the  femur,  and  the  lower  epiphysis  of  the  tibia  and  fibula, 
become  first  united  to  the  shaft. 

Where  there  is  only  one  epiphysis,  the  medullary  artery  is  directed  toward 
that  end  of  the  bone  where  there  is  no  additional  centre,  as  toward  the  acromial 
end  of  the  clavicle,  toward  the  distal  end  of  the  metacarpal  bone  of  the  thumb 
and  great  toe,  and  toward  the  proximal  end  of  the  other  metacarpal  and  meta- 
tarsal  bones. 

Besides  these  epiphyses  for  the  articular  ends,  there  are  others  for  projecting 
parts  or  processes,  which  are  formed  separately  from  the  bulk  of  the  bone.  For 
an  account  of  these  the  reader  must  be  referred  to  the  description  of  the  individual 
bones  in  the  sequel. 

A  knowledge  of  the  exact  periods  when  the  epiphyses  become  joined  to  the 
shaft  is  often  of  great  importance  in  medico-legal  inquiries.  It  also  aids  the  sur- 
geon in  the  diagnosis  of  many  of  the  injuries  to  which  the  joints  are  liable;  for  it 
not  infrequently  happens  that,  on  the  application  of  severe  force  to  a  joint,  the 
epiphysis  becomes  separated  from  the  shaft,  and  such  injuries  may  be  mistaken  for 
fracture  or  dislocation. 

MUSCULAR  TISSUE. 

The  muscles  are  formed  of  bundles  of  reddish  fibres,  endowed  with  the  property 
of  contractility.  Two  kinds  of  muscular  tissue  are  found  in  the  animal  body — viz. 
that  of  voluntary  or  animal  life,  and  that  of  involuntary  or  organic  life.  The 
muscles  of  animal  life  (striped  muscles)  are  capable  of  being  put  in  action  and 
controlled  by  the  will.  They  are  composed  of  bundles  of  fibres  enclosed  in  a 


MUSCULAR    TISSUE.  65 

delicate  web  called  the  "  perimysium, "  in  contradistinction  to  the  sheath  of 
areolar  tissue  which  invests  the  entire  muscle,  the  "  epimysium."  The  bundles 
are  termed  "fasciculi;"  they  are  prismatic  in  shape,  of  different  sizes  in 
different  muscles,  and  for  the  most  part  placed  parallel  to  one  another,  though 
they  have  a  tendency  to  converge  toward  their  tendinous  attachments.  Each 
fasciculus  is  made  up  of  a  bundle  of  fibres,  which  also  run  parallel  with  each 
other,  and  which  are  separated  from  one  another  by 
a  delicate  connective  tissue  derived  from  the  peri-  ? 

mysium,  and  termed  cn<l»inii*(iim  (Fig.  37). 

A  muscular  fibre  may  be  said  to  consist  of  a  soft 
contractile  substance  enclosed  in  a  tubular  sheath, 
named  by  Bowman  the  sarculiTiiinn.  The  fibres  are 
cylindrical  or  prismatic  in  shape,  and  are  of  no  great 
length,  not  extending,  it  is  said,  further  than  an  inch 
and  a  half.  They  end  either  by  blending  with  the 
tendon  or  aponeurosis,  or  else  by  becoming  drawn 
out  into  a  tapering  extremity  which  is  connected  to 
the  neighboring  fibre  by  means  of  the  sarcolemma. 
Their  breadth  varies  in  man  from  -^^  to  -g-^-g-  of  an 
inch,  the  average  of  the  majoritv  being  about  -j-i-^. 

,  =  •'     .     •  FIG.  37.— Transverse  section  irom 

As  a  rule,  the  fibres  do  not  divide  or  anastomose:     the  sterno-mastoid  in  man.   Magni- 

V  11  -n-i  J.P-I       fled  50  times,    a.  External  perimys- 

but  occasionally,  especially  m  the  tongue  and  facial     ium.     b.  Fasciculus,     c.  internal 
muscles,  the  fibres  may  be  seen  to  divide  into  several     Perim*8ium-  d-  ^e. 
branches.     The  precise  mode  in  which  the  muscular 

fibre  joins  the  tendon  has  been  variously  described  by  different  observers.  It 
may.  perhaps,  be  sufficient  to  say  that  the  sarcolemma.  or  membranous  investment 
of  the  muscular  fibre,  appears  to  become  blended  with  the  tissue  of  the  tendon, 
and  prolonged  more  or  less  into  the  tendon,  so  that  the  latter  forms  a  kind  of 
sheath  around  the  fibre  for  a  longer  or  shorter  distance.  When  muscular  fibres 
are  attached  to  the  skin  or  mucous  membranes,  their  sarcolemma  probably 
becomes  continuous  with  the  fibres  of  the  areolar  tissue. 

The  sarcolemma,  or  tubular  sheath  of  the  fibre,  is  a  transparent,  elastic,  and 
apparently  homogeneous  membrane  of  considerable  toughness,  so  that  it  will  some- 
times remain  entire  when  the  included  substance  is  ruptured  (see  Fig.  38).  On 
the  internal  surface  of  the  sarcolemma  in  mammalia,  and  also  in  the  substance  of 
the  fibre  in  the  lower  animals,  elongated  nuclei  are  seen  (Fig.  55),  and  in  connec- 
tion with  these  a  row  of  granules,  apparently  fatty,  is  sometimes  observed. 

L  pon  examination  of  a  muscular  fibre  by  transmitted  light  under  a  sufficiently 
high  power,  it  is  found  to  be  apparently  marked  by  alternate  light  and  dark  bands 
or  strise.  which  pass  transversely,  or  somewhat  obliquely,  round  the  fibre  (Fig.  38). 
The  dark  and  light  bands  are  of  nearly  equal  breadth,  and  alternate  with  great  regu- 
larity. Other  striae  pass  longitudinally  over  the  fibres,  though  they  are  less  distinct 
than  the  former.  This  longitudinal  striation  gives  the  fibre  the  appearance  of 
being  made  up  of  a  bundle  of  fibrilla?.  The  muscular  fibre  can  be  broken  up  either 
in  a  longitudinal  or  transverse  direction  (Fig.  39).  If  hardened  in  alcohol,  it  can 
be  broken  up  longitudinally,  and  forms  the  so-called  fibrillae  of  which  some  suppose 
the  fibre  to  be  made  up.  Each  fibril  is  marked  by  transverse  striae,  and  appears 
to  consist  of  a  single  row  of  minute  quadrangular  particles,  named  "  sarcous 
elements  "  by  Bowman.  A  still  further  division,  however,  is  capable  of  being 
made,  and  each  of  these  fibrillse  may  be  divided  into  minute  threads  (Fig.  40,  B,  d). 
consisting  of  an  alternate  dark  and  light  spot.  After  exposure  to  the  action  of 
dilute  hydrochloric  acid,  the  muscular  fibre  can  be  broken  transversely  (Fig.  39, 
B).  It  then  forms  disks  or  plates,  consisting  of  the  same  quadrangular  particles, 
attached  by  their  lateral  surfaces. 

Upon  closer  examination  with  a  very  high  power  the  appearances  become 
more  complicated  and  are  susceptible  of  various  interpretations.  The  transverse 
striation,  which  in  Figs.  38  and  39  appears  as  a  mere  alternation  of  dark  and 


66 


GENERAL    ANATOMY. 


bands,  is  resolved  into  the  appearance  shown  in  Fig.  40,  which  shows  a  series  of 
broad  dark  bands,  separated  by  a  light  band,  which  is  itself  divided  into  two  by  a 
dark  streak.  This  streak  is  termed  Krause' s  membrane  ;  it  is  continuous  at  each 
end  with  the  sarcolemma  investing  the  muscular  fibre.  Thus  it  may  be  said  that 
the  fibre  is  divided  into  a  number  of  transverse  compartments  by  this  membrane, 
each  compartment  containing  in  the  centre  a  dark  plate  with  a  bright  border 
above  and  below ;  that  is  to  say,  between  the  dark  central  part  and  the  membrane 
of  Krause.  A  muscular  fibre  presents,  then,  the  appearance  of  the  following 
layers  in  regular  alternation :  a  dark  layer,  the  transverse  disk ;  a  bright  trans- 
parent layer,  the  lateral  disk  ;  a  dark  line,  the  intermediate  disk  or  membrane  of 
Krause  ;  then  another  lateral  disk,  a  transverse  disk,  and  so  on  (Figs.  40  and  41). 
This  appearance,  following  the  observations  of  Rollett,  is  due  to  the  mode  of  for- 


FIG.  38.— Two  human  muscular  fibres. 
Magnified  350  times.  In  the  one,  the  bundle  of 
flbnllse  (6)  is  torn,  and  the  sarcolemma  (a)  is 
seen  as  an  empty  tube. 


FIG.  39.— Fragments  of  striped  elementary  fibres, 
showing  a  cleavage  in  opposite  directions.  Magnified 
300  diameters.  A.  Longitudinal  cleavage.  The  longi- 
tudinal and  transverse  lines  are  both  seen.  Soma  lon- 
gitudinal lines  are  darker  and  wider  than  the  rest,  and 
are  not  continuous  from  end  to  end.  This  results  from 
partial  separation  of  the  fibrillse.  c.  Fibrillse  separated 
from  one  another  by  violence  at  the  broken  end  of  the 
fibre,  and  marked  by  transverse  lines  equal  in  width  to 
those  on  the  fibre,  c',  c"  represent  two  appearances  com- 
monly presented  by  the  separated  single  fibrillse  (more 
highly  magnified). '  At  c'  the  borders  and  transverse  lines 
are  all  perfectly  rectilinear,  and  the  included  spaces  per- 
fectly rectangular.  At  c"  the  borders  are  scalloped  and 
the  spaces  bead-like.  When  most  distinct  and  definite 
the  fibrilla  presents  the  former  of  these  appearances. 
B.  Transverse  cleavage.  The  longitudinal  lines  are 
scarcely  visible,  a.  Incomplete  fracture  following  the 
opposite  surfaces  of  a  disk,  which  stretches  across  the 
interval,  and  retains  the  two  fragments  in  connection. 
The  edge  and  surfaces  of  this  disk  are  seen  to  be 
minutely  granular,  the  granules  corresponding  in  size 
to  the  thickness  of  the  disk  and  to  the  distance  between 
the  faint  longitudinal  lines.  6.  Another  disk  nearly- 
detached.  6'.  Detached  disk,  more  highly  magnified, 
showing  the  sarcous  elements. 


mation  of  a  muscular  fibre,  which  is  made  up  of  two  principal  parts  :  1,  fibrillge  ; 
and  2,  a  hyaline  or  faintly  granular  substance,  resembling  protoplasm,  and  called 
sarcoplasm.  The  fibrillse  are  arranged  in  bundles  called  muscular  columns  or  sar- 
costyles,  and  these  again  in  larger  groups,  which,  collected  together,  form  the 
fibre.  The  fibrillae  are  surrounded  by  the  sarcoplasm,  which  surrounds  also  the 
columns  and  groups  of  columns,  being  in  these  latter  situations  greater  in  amount 
than  between  the  fibrillse.  So  that  on  transverse  section  a  muscular  fibre  is  seen 
to  be  divided  into  a  number  of  areas,  called  the  areas  of  Cohnheim,  more  or  less 
polyhedral  in  shape,  and  consisting  of  the  columns  of  fibrillre  surrounded  by  trans- 
parent sheaths  of  sarcoplasm.  And  these  areas  are  collected  into  larger  or  smaller 
groups,  which  in  the  same  manner  are  surrounded  by  transparent  sarcoplasm. 
Each  area  of  Cohnheim  presents  a  granular  appearance  due  to  the  cross-section  of  its 
constituent  fibrillge,  surrounded  by  a  small  amount  of  the  hyaline  sarcoplasm.  The 
fibrillae  extend  throughout  the  whole  length  of,  and  are  parallel  to,  the  long  axis  of 
the  muscular  fibre.  They  present  the  following  appearances  in  regular  alternation  : 
(1)  a  dim  prismatic  or  rod-shaped  element,  the  sarcous  element  of  Bowman  ;  (2)  a 
thin  bridge,  which  joins  the  sarcous  element  to  (3)  a  dark  granule.  Then  again 


MUSCULA  R    TIXS  i  /, . 


67 


another  thin  bridge  joining  the  same  granule  to  the  next  sarcous  element,  and  so 
on.  When  these  fibrillse  are  collected  together  into  columns,  and  the  columns  into 
muscular  fibres,  the  appearance  mentioned  above  is  produced.  The  sarcous  ele- 
ments, when  arranged  side  by  side  and  almost  touching  each  other,  with  very 
little  sarcoplasm  between  them,  represent  the  transverse  disk.  The  bridges,  being 
much  thinner  than  the  sarcous  element  or  the  dark  granules,  have  between  each 
other  a  much  larger  amount  of  sarcoplasm.  and  this  gives  to  this  part  the  trans- 
parent appearance  of  the  lateral  disk.  And.  lastly,  the  granules  joined  edge  to 
edge  in  a  row  present  the  appearance  of  a  membrane,  which  represents  the  inter- 
mediate disk. 

On  the  muscular  fibre,  immediately  beneath  the  sarcolemma.  the  sarcoplasm 


FIG.  4'). — Portion  of  a  medium-sized  human  muscular 
fibre.  Magnified  nearly  800  diameters.  B.  Separated  bun- 
dles of  fibrils,  equally  magnified,  a.  a.  Larger,  and  6.  b, 
smaller  collections,  c.  Still  smaller,  d.  d.  The  smallest 
which  could  be  detached. 


FIG.  4L— Part  of  a  striped  muscular  fibre 
of  the  water-beetle,  prepared  with  absolute 
alcohol.  Magnified  300  diameters.  (Klein 
and  Noble  Smith.)  a.  Sarcolemma.  6. 
Membrane  of  Krause :  owing  to  contrac- 
tion during  hardening,  the  sarcolemma 
shows  regular  bulgings.  At  the  side  of 
Krause's  membrane  is  the  transparent  lat- 
eral disk.  Several  nuclei  of  muscle-cor- 
puscles are  shown,  and  in  them  a  minute 
network. 


becomes  here  and  there  collected  into  small,  plate-like  masses.  They  contain  oval 
nuclei,  and  are  termed  ••muscle-corpuscles."'  Finally,  in  the  centre  of  each 
sarcous  element  a  transparent  lighter  band  can  sometimes  be  discerned ;  this  is 
known  as  the  me<li<tn  <li*k  of  Hensen.  and  is  due  to  the  substance  of  the  sarcous 
elements  being  here  thinner. 

This  form  of  muscular  fibre  composes  the  whole  of  the  voluntary  muscles,  all 
the  muscles  of  the  ear.  those  of  the  larnyx,  pharynx,  tongue,  the  upper  half  of  the 
oesophagus,  the  heart,  and  the  walls  of  the  large  veins  at  the  point  where  they 
open  into  it.  The  fibres  of  the  heart,  however,  differ  very  remarkably  from  those 
of  other  striped  muscles.  They  are  smaller  by  one-third,  and  their  transverse 
stria?  are  by  no  means  so  distinct.  The  fibres  are  made  up  of  distinct  quadran- 
gular cells  joined  end  to  end  (Fig.  42).  Each  cell  contains  a  clear  oval  nucleus. 
situated  near  the  centre  of  the  cell.  The  extremities  of  the  cells  have  a  tendency 
to  branch  or  divide,  the  subdivisions  uniting  with  offsets  from  other  cells,  and 
thus  producing  an  anastomosis  of  the  fibres  (Fig.  42).  The  connective  tissue 
between  the  bundles  of  fibres  is  much  less  than  in  ordinary  striped  muscle,  and 
no  sarcolemma  has  been  proved  to  exist. 

The  c<Ti')H<irifs  of  striped  muscle  are  very  abundant,  and  form  a  sort  of  rect- 
angular network,  the  branches  of  which  run  longitudinally  in  the  endomysium 
between  the  muscular  fibres,  and  are  joined  at  short  intervals  by  transverse 
anastomosing  branches.  The  larger  vascular  channels,  arteries  and  veins,  are 


68  GENERAL   ANATOMY. 

found  only  in  the  perimysium,  between  the  muscular  fasciculi.  The  smaller  ves- 
sels present  peculiar  saccular  dilatations,  which  are  supposed  to  act  as  receptacles 

for  the  blood  during  the  contraction  of  the  muscular 
fibres,  when  it  is  pressed  out  from  some  of  the  capil- 
laries. 

Nerves  are  profusely  distributed  to  striped 
muscle.  The  mode  of  their  termination  will  be 
described  on  a  subsequent  page. 

The  existence  of  lymphatic  vessels  in  striped 
muscle  has  not  been  ascertained,  though  they  have 
been  found  in  tendons  and  in  the  sheath  of  the 
muscle. 

The  unstriped  muscle,  or  muscle  of  organic  life,  is 
found  in  the  walls  of  the  hollow  viscera  —  viz.  the 
lower  half  of  the  oesophagus  and  the  whole  of  the 
remainder  of  the  gastro-intestinal  tube  ;  in  the  trachea 
and  bronchi,  and  the  alveoli  and  infundibula  of  the 
lungs ;  in  the  gall-bladder  and  ductus  communis 

-  muscular     chofedochus  ;  in  the  large  ducts  of  the  salivary  and 

fibres  of  the  heart  seen  in  a  longitu-     pancreatic  glands;  in  the  pelvis  and  calices  of  the 

dinal  section.    On  the  right  the  lira-       f.,  ,    c  1111  i  ,1  •          i 

its  of  the  separate  cells  with  their  kidney,  the  ureter,  bladder,  and  urethra ;  m  the 
gruacmmatrfcaeiiyhibil  female  sexual  organs— viz.  the  ovary,  the  Fallopian 

tubes,  the  uterus  (enormously  developed  in  preg- 
nancy), the  vagina,  the  broad  ligaments,  and  the  erectile  tissue  of  the  clitoris ;  in 
the  male  sexual  organs — viz.  the  dartos  scroti,  the  vas  deferens  and  epididymis, 
the  vesiculae  serninales,  the  prostate  gland,  and  the  corpora  cavernosa  and  corpus 
spongiosum ;  in  the  ducts  of  certain  glands,  as  in  Wharton's  duct;  in  the  capsule 
and  trabeculge  of  the  spleen ;  in  the  mucous  membranes,  forming  the  muscularis 
mucosge ;  in  the  skin,  forming  the  arrectores  pilorum,  and  also  in  the  sweat- 
glands  ;  in  the  arteries,  veins,  and  lymphatics ;  in  the  iris  and  the  ciliary  muscle. 

Plain  or  unstriped  muscular  fibre  is  made  up  of  spindle-shaped  cells,  called 
contractile  fibre-cells,  collected  into  bundles  and  held  together  by  a  cement-sub- 
stance, in  which  are  contained  some  connective-tissue  corpuscles  (Fig.  43).  These 
bundles  are  further  aggregated  into  larger  bundles  or  flattened  bands,  and  bound 
together  by  ordinary  connective  tissue. 

The  contractile  fibre-cells  (Fig.  44)  are  elongated,  spindle-shaped,  nucleated 
cells  of  various  lengths,  averaging  from  -$^-$  to  -3-^5-  of  an  inch  in  length,  and  ^3^0" 
to  "s^Vo  of  an  inch  in  breadth.  On  transverse  section  they  are  more  or  less  poly- 
hedral in  shape,  from  mutual  pressure.  They  present  a  faintly  longitudinal  stri- 
ated appearance,  and  consist  of  an  elastic  cell-wall  containing  a  central  bundle  of 
fibrillge,  representing  the  contractile  substance,  and  an  oval  or  rod-like  nucleus, 
which  includes,  Avithin  a  membrane,  a  fine  network  communicating  at  the  poles 
of  the  nucleus  with  the  contractile  fibres  (Klein).  The  adhesive  interstitial  sub- 
stance, which  connects  the  fibre-cells  together,  represents  the  endomysium,  or  del- 
icate connective  tissue  which  binds  the  fibres  of  striped  muscular  tissue  into  fas- 
ciculi ;  while  the  tissue  connecting  the  individual  bundles  together  represents  the 
perimysium.  The  unstriped  muscle,  as  a  rule,  is  not  under  the  control  of  the  will, 
nor  is  the  contraction  rapid  and  involving  the  whole  muscle,  as  is  the  case  with  the 
muscles  of  animal  life.  The  membranes  which  are  composed  of  the  unstriped 
muscle  slowly  contract  in  a  part  of  their  extent,  generally  under  the  influence  of 
a  mechanical  stimulus,  as  that  of  distension  or  of  cold ;  and  then  the  contracted 
part  slowly  relaxes  while  another  portion  of  the  membrane  takes  up  the  contrac- 
tion. This  peculiarity  of  action  is  most  strongly  marked  in  the  intestines,  con- 
stituting their  vermicular  motion. 

Chemical  Composition  of  Muscle. — In  chemical  composition  the  muscular  fibres 
of  both  forms  consist  mainly  of  a  proteid  substance — myosin — which  is  classed 
as  one  of  the  globulins.  It  is  readily  converted  by  the  action  of  dilute  acids 


.YET?  i  -o  us  TISS  UE. 


69 


into  syntonin  or  acid-albumen,  and  by  the  action  of  dilute  alkalies  into  alkali- 
albumen.      Muscle,  which  is  neutral  or  slightly  alkaline  in  reaction  when  at  rest. 


FIG.  43.— Non-striated  elementary  fibres 
from  the  human  colon,  a.  Treated  with 
acetic  acid,  showing  the  corpuscles.  6. 
Fragment  of  a  detached  fibre,  not  touched 
with  acid. 


FIG.  44.— Muscular  fibre-cells  from  human 
arteries.  1.  From  the  popliteal  artery.  A. 
without ;  B.  with  acetic  acid.  2.  From  a 
branch  of  the  anterior  tibial.  a.  Nuclei  of 
the  fibres.  Magnified  350  times. 


is  rendered  acid  by  contraction,  from  the  development  probably  of  sarcolactic 
acid.  After  death  muscle  also  exhibits  an  acid  reaction,  but  this  appears  to  be 
due  to  post-mortem  change. 

NERVOUS    TISSUE. 

The  nervous  tissues  of  the  body  are  comprised  in  two  great  systems — the 
cerebro-.ipinala.ndi  the  sympathetic;  and  each  of  these  systems  consist  of  a  central 
organ,  or  series  of  central  organs,  and  of  nerves. 

The  cerebro-spinal  system  comprises  the  brain  (including  the  medulla  oblongata), 
the  spinal  cord,  the  cranial  nerves,  the  spinal  nerves,  and  the  ganglia  connected 
with  both  these  classes  of  nerves.  The  sympathetic  system  consists  of  a  double 
chain  of  ganglia,  with  the  nerves  which  go  to  and  come  from  them.  It  is  not 
directly  connected  with  the  brain  or  spinal  cord,  though  it  is  so  indirectly  by 
means  of  its  numerous  communications  with  the  cranial  and  spinal  nerves. 

Both  these  nervous  systems  are  composed  of  an  aggregation  of  tissue-elements 
termed  neuron*,  each  of  which  consists  of  a  nucleated  cell  whose  protoplasm  is 
prolonged  into  a  varying  number  of  processes,  one  of  which  is  usually  of  consid- 
erable length  and  forms  the  essential  part  of  a  nerve-fibre.  The  cell-bodies  have 
a  tendency  to  be  associated  together  in  more  or  less  definite  masses,  such  as  the 
spinal  and  sympathetic  ganglia,  the  central  portion  of  the  spinal  cord,  the  floor 
of  the  medulla  oblongata.  the  cortex  of  the  cerebellum  and  of  the  cerebral  hemi- 
spheres, and  the  various  ganglia  distributed  through  the  different  parts  of  the 
brain.  These  masses  present  macroscopically  a  grayish  appearance,  which  con- 
trasts strongly  with  the  pure  Avhite  color  usually  shown  by  the  nerve-fibres,  so 
that  it  is  customary  to  speak  of  the  nervous  system  as  composed  of  two  substances, 
the  gray  matter  and  the  u'hite  or  fibrous  matter.  The  nerve-fibres  of  the  sympa- 
thetic system,  however,  usually  lack  the  constituent  which  gives  the  ordinary 
fibres  their  white  appearance,  and  they  consequently  have  a  grayish  color. 

The  gray  substance  is  distinguished  by  its  dark  reddish-gray  color  and  soft 
consistence.  It  is  found  in  the  brain,  spinal  cord,  and  various  ganglia,  inter- 
mingled with  the  fibrous  nervous  substance,  and  also  in  some  of  the  nerves  of 
special  sense,  and  in  gangliform  enlargements  which  are  found  here  and  there  in 
the  course  of  certain  cerebro-spinal  nerves.  It  is  composed,  as  its  name  implies, 


70 


GENERAL    ANATOMY. 


a 


FIG.  45. — Cell  from  the  anterior  horn  of  the 
gray  matter  of  the  spinal  cord,  a,  Axis-cylinder 
process.  6.  Aggregation  of  pigment-granules. 
(From  Obersteiner.) 


of  cells,  commonly  called  nerve-cells  or  ganglion-corpuscles,  containing  nuclei  and 
nucleoli.  The  cells  together  with  the  blood-vessels  in  the  gray  nerve-substance, 
and  the  nerve-fibres  and  vessels  in  the  white  nerve-substance,  are  imbedded  in  a 
peculiar  ground-substance,  named  by  Virchow  neuroglia,  and  consisting  of  large 
branched  cells  (Fig.  46,  C),  the  branches  passing  in  every  direction  among  the 

nerve-tissue,  thus  holding  it  and  binding  it 
together.  It  is  developed  from  the  epi- 
blast,  and  contains  neither  the  character- 
istic fibres  nor  cells  of  connective  tissue, 
and  therefore  cannot  be  regarded  as  be- 
longing to  the  true  connective  tissues. 
Each  nerve-cell  consists  of  a  finely  gran- 
ular protoplasmic  material,  of  a  reddish  or 
yellowish-brown  color,  which  occasionally 
presents  patches  of  a  deeper  tint,  caused 
by  the  aggregation  of  pigment-granules 
(Fig.  45).  No  distinct  limiting  membrane 
or  cell-wall  has  been  ascertained  to  exist. 
The  nucleus  is,  as  a  rule,  a  large,  well- 
defined,  round,  vesicular  body,  often  pre- 
senting an  intranuclear  network,  and  con- 
taining a  nucleolus  which  is  peculiarly 
clear  and  brilliant.  The  nerve-cells  vary 
in  shape  and  size  ;  some  are  small,  spher- 
ical or  ovoid,  with  generally  an  even  out- 
line, such  as  those  found  in  the  spinal 
ganglia  ;  others,  again,  are  caudate  or  stel- 
late in  shape,  and  are  characterized  by  their  large  size  and  by  their  having  one 
or  more  tail-like  processes  issuing  from  them,  which  occasionally  divide  and  sub- 
divide into  numerous  branches 
(Fig.  46,  A).  These  are  found 
in  greatest  number  in  the  gray 
matter  of  the  spinal  cord.  Still 
others  are  flask-shaped,  as  in 
the  cortex  of  the  cerebellum ;  or 
conical,  as  in  the  cerebral  convo- 
lutions. For  the  most  part  nerve- 
cells  have  one  or  more  processes, 
and  they  are  distinguished  by 
the  number  of  these  processes, 
as  unipolar,  bipolar,  or  multi- 
polar  cells.  These  processes  are 
very  delicate  and  are  direct  con- 
tinuations of  the  protoplasm  of 
the  nerve-cell.  The  majority  of 
the  processes  of  a  multipolar  cell 
are  exceedingly  fine,  and  branch 
dendritically,  spreading  out 
among  the  adjacent  nervous 
elements ;  these  processes  are 
termed  the  protoplasmic  processes 
or  dendrites.  One  of  the  pro- 
cesses, however,  does  not  thus 
branch,  but  gives  off  from  time 
to  time  lateral  branches  termed  collaterals,  and  eventually  form  the  axis-cylinder 
of  a  nerve-fibre ;  this  is  the  axis-cylinder  process. 

The  white  or  fibrous  nerve-substance  or  nerve-fibre  is  found  universally  in  the 


FIG.  46.— Cells  of  nervous  system  impregnated  with  silver 
(Golgi's  method).  A.  Cell  from  the  cortex  of  the  cerebral 
hemispheres  (after  van  Gehuchten).  a.  Protoplasmic  process. 
b.  Axis-cylinder  process,  c.  Collaterals.  B.  T-shaped  cell 
from  spinal  root  ganglion  (after  van  Gehuchten).  C.  Neuroglia- 
cell  from  the  white  substance  of  the  cerebellum  (after  Kol- 
liker). 


NERVOUS    TISSUE. 


71 


nervous  cords,  and  also  constitutes  a  great  part  of  the  brain  and  spinal  cord. 
The  fibres  of  which  it  consists  are  of  two  kinds,  the  medullated  or  white  fibres, 
and  the  non-medullated  or  gray  fibres. 

The  medullated  fibres  form  the  white  part  of  the  brain  and  spinal  cord,  and 
also  the  greater  part  of  the  cerebro-spinal  nerves,  and  give  to  these  structures 
their  opaque,  white  aspect.  When  perfectly  fresh  they  appear  to  be  homo- 
geneous ;  but  soon  after  removal  from  the  body  they  present,  when  exam- 
ined by  transmitted  light,  a  double  outline  or  con- 
tour. as  if  consisting  of  two  parts.  The  central 
portion  is  named  the  axis-cylinder  of  Purkinje  ; 
around  this  is  a  sort  of  sheath  of  fatty  material, 
named  the  white  substance  of  Sch  ivann,  Avhich  gives 
to  the  fibre  its  double  contour,  and  the  whole  is  en- 
closed in  a  delicate  membrane,  the  neurilemma,1 
primitive  sheath,  or  nucleated  sheath  of  Schwann 
(Fig.  47 

The  axis-cylinder  is  the  essential  part  of  the 
nerve-fibre,  and  is  always  present  ;  the  other  parts, 
the  medullary  sheath  and  the  neurilemma.  being 
occasionally  absent,  especially  at  the  origin  and 
termination  of  the  nerve-fibre.  It  undergoes  no 
interruption  from  its  origin  in  the  nerve-centre  to 
its  peripheral  termination,  and  must  be  regarded 
as  a  direct  prolongation  of  a  nerve-cell.  It  con- 
stitutes about  one-half  or  one-third  of  the  nerve- 
fibre,  the  white  substance  being  greater  in  propor- 
tion in  the  nerves  than  in  the  central  organs.  It 
is  perfectly  transparent,  and  is  therefore  indistin- 
guishable in  a  perfectly  fresh  and  natural  state  of 
the  nerve.  When  examined  under  a  high  power  it 
presents  the  appearance  of  longitudinal  striation.  as 
if  composed  of  very  fine,  homogeneous  fibrilla?,  held  together  in  a  faintly  granular 
interstitial  material.  Occasionally  at  its  termination  the  axis-cylinder  of  a  fibre 
may  be  seen  to  break  up  into  exceedingly  fine  fibrillae,  confirming  the  view  of  its 
fibrillar  structure.  These  fibrillse  have  been  termed  the  primitive  fibrillce  of 
Schultze.  The  axis-cylinder  is  said  to  be  enveloped  in  a  very  delicate,  hyaline 
sheath,  which  separates  it  from  the  white  matter  of  Schwann.  The  medullary 
sheath  or  white  matter  of  Schwann  is  regarded  as  being  a  fatty  matter  in  a  fluid 
state,  which  insulates  and  protects  the  essential  part  of  the  nerve  —  the  axis-cylinder. 
The  white  matter  varies  in  thickness  to  a  very  considerable  extent,  in  some  forming 
a  layer  of  extreme  thinness,  so  as  to  be  scarcely  distinguishable,  in  others  forming 
about  one-half  the  nerve-tube.  The  size  of  the  nerve-fibres,  which  varies  from 
TT5T  to  ->  0*0  0  °f  an  incn>  depends  mainly  upon  the  amount  of  the  white  substance. 
though  the  axis-cylinder  also  varies  in  size  Avithin  certain  limits.  The  white  matter 
of  Schwann  does  not  always  form  a  continuous  sheath  to  the  axis-cylinder,  but 
undergoes  interruptions  in  its  continuity  at  regular  intervals,  giving  to  the  fibre 
the  appearance  of  constriction  at  these  points.  These  were  first  described  by  Ran- 
vier.  and  are  known  as  the  nodes 
of  Ranvier  (Fig.  48).  The  por- 
tion of  nerve-fibre  between  two 
nodes  is  called  an  internodal  seg- 

•t.      The  neurilemma  or  prim- 

itivp  ssliparh   i*  tint  intprrnntpfl   at 

1  dr 

the    nodes,  but  passes  over    them 

-r,      i 

as  a  continuous  membrane,   .hacn 

1  In  older  hbtological  works  the  term  "  neurilemma  "  is  used  to  designate  the  fibrous  envelope  of 
the  whole  nerve,  now  called  "  perineuriuru.'' 


FIG.  47.— Human  nerve-fibres.  Mag- 
nified 350  times.  Three  of  them  are  fine, 
one  of  which  is  varicose,  one  of  mid- 
dling thickness,  and  with  a  simple  con- 
tour :  and  three  thick,  two  of  which  are 
double-contoured,  and  one  with  gru- 
mous  contents. 


Fio.48.-A  node  of  Ranvier  of  a  medullated  nerve-fibre, 
viewed  from  above,  magnified  about  750  diameters.  The  medul- 
lary  sheath  is  discontinuous  at  the  node,  whereas  the  axis-cyl- 
inder  passes  from  one  segment  into  the  other.  At  the  node  the 
sheath  of  Schwann  appears  thickened.  (Klein  and  Noble 


72 


GENERAL    ANATOMY. 


internodal  segment  contains  an  oval  nucleus  imbedded  in  the  medullary  sheath, 
and  occasionally  more  than  one  nucleus  may  be  seen  in  the  same  internode. 
Medullated  nerve-fibres  frequently  present  a  beaded  or  varicose  appearance :  this 
is  due  to  manipulation  and  pressure  causing  the  oily  matter  to  collect  into  drops, 
and  in  consequence  of  the  extreme  delicacy  of  the  primitive  sheath  even  slight 
pressure  will  cause  the  transudation  of  the  fatty  matter,  which  collects  as  drops 
of  oil  outside  the  membrane.  This  is,  of  course,  promoted  by  the  action  of  ether 
(Fig.  49). 

The  neurilemma  or  primitive  sheath  (sometimes  called  the  tubular  membrane  or 
sheath  of  Schwann)  presents  the  appearance  of  a  delicate,  structureless  membrane. 
Here  and  there  beneath  it,  and  situated  in  depressions  in  the  white  matter  of 

Schwann,  are  nuclei  surrounded 
by  a  small  amount  of  protoplasm. 
The  nuclei  are  oval  and  somewhat 
flattened,  and  bear  a  definite  rela- 
tion to  the  nodes  of  Ranvier ;  one 
nucleus  generally  lying  in  the 
centre  of  each  node,  though  in 
some  few  instances  two  nuclei 
may  be  found  in  the  same  node. 
The  sheath  of  Schwann,  it  is  to  be 
noted,  does  not  occur  in  the  med- 
ullated fibres  contained  within 
the  spinal  cord  and  brain. 

Non-medullated  Fibres. — Most 
of  the  nerves  of  the  sympathetic 
system,  and  some  of  the  cerebro- 
spinal  (see  especially  the  descrip- 
tion of  the  olfactory  nerve),  con- 
sist of  another  variety  of  nervous 
fibres,  which  are  called  the  gray 
or  gelatinous  nerve-fibres — fibres 
of  Memak  (Fig.  50).  These  con- 
sist of  a  bundle  of  finely  striated 
fibrillge  enclosed  in  a  sheath. 
Nuclei  may  be  detected  at  inter- 
vals in  each  fibre,  situated  between  the  axis-cylinder  and  the  neurilemma.  In 
external  appearance  the  gelatinous  nerves  are  semi-transparent  and  gray  or  yel- 
lowish-gray. The  individual  fibres  vary  in  size,  generally  averaging  about  half 
the  size  of  the  medullated  fibres ;  but,  on  the  one  hand,  the  primitive  fibrillae 
formed  by  the  breaking  up  of  the  cerebro-spinal  fibres,  as  above  mentioned,  are 
of  hardly  appreciable  thickness  ;  while,  on  the  other  hand,  some  of  the  gelatinous 
fibres  (especially  those  on  the  olfactory  bulb)  are  said  to  be  three  or  four  times 
as  thick  as  those  of  the  cerebro-spinal  nerves. 

Chemical  Composition. — The  difference  in  the  chemical  composition  of  the  white 
and  gray  matter  is  indicated  by  the  following  analyses  by  Petrowsky  of  the  brain 
of  the  ox  : 

Gray.  White. 

Water 81.60$  68.30$ 

Solids  (percentage  composition) : 

Proteids 55.37  24.72 

Lecithin 17.24  9.90 

Cholesterin  and  fat 18.68  51.91 

Cerebrin  . 0.53  9.55 

Other  organic  compounds 6.71  3.34 

Salts 1.45  0.57 


FIG.  49.— Magnified  300  diam- 
eters, a.  Nerve-fibre  of  the  com- 
mon eel  in  water.  The  delicate 
line  on  its  exterior  indicates  the 
neurilemma.  The  dark  double- 
edged  inner  one  is  the  white 
matter  of  Schwann,  slight- 
ly wrinkled.  6.  The  same 
in  ether.  Several  oil-globules 
have  coalesced  in  the  interior, 
and  others  have  accumulated 
around  the  exterior  of  the  tube. 
The  white  matter  has  in  part 
disappeared. 


FIG.  50.— A  small  ner- 
vous branch  from  the  sym- 
pathetic of  a  mammal,  a. 
Two  dark-bordered  nerve- 
tubes  among  a  number  of 
Remak's  fibres,  b. 


The  proteids  in  the  above  analysis  practically  represent  the  protoplasm,  which 


TISSUE.  73 

naturally  is  much  greater  in  the  gray  than  in  the  white  matter.  On  the  other 
hand,  the  cholesterin.  fat.  and  cerebrin  (the  latter  ill-defined  nitrogenous  compounds 
belonging  to  the  group  of  glucosides)  are  probably  important  constituents  of  the 
medullary  sheath.  Another  substance  also  occurring  in  the  medullary  sheath, 
though  not  determined  separately  in  the  above  analysis,  is  neurokeratin,  which 
forms  a  fibrous  network  throughout  the  sheath,  and  resembles  keratin  in  its 
marked  resistance  to  reagents.  It  probably  makes  up  the  greater  part  of  the 
unidentified  organic  matter  of  the  white  substance  in  the  above  analysis,  while  in 
the  gray  substance  the  unidentified  matter  is  probably  largely  composed  of 
protagon,  a  phosphorized  compound  closely  resembling  lecithin,  but  differing  from 
it  by  its  insolubility  in  ether. 

The  nervous  structures  are  divided,  as  before  mentioned,  into  two  great  sys- 
tems— viz.  the  cerebro-spinaL  comprising  the  brain  and  spinal  cord,  the  nerves 
connected  with  these  structures,  and  the  ganglia  situated  on  them ;  and  the  sym- 
pathetic, consisting  of  a  double  chain  of  ganglia  and  the  nerves  connected  with 
them.  All  these  structures  require  separate  consideration. 

The  brain  or  encephalon  is  that  part  of  the  cerebro-spinal  system  which  is 
contained  in  the  cavity  of  the  skull.  It  is  divided  into  several  parts,  for  a 
description  of  which  reference  must  be  made  to  the  account  of  the  structure  of 
the  brain  in  a  subsequent  portion  of  this  work.  In  these  parts  the  gray  matter 
is  found  partly  on  the  surface  of  the  brain,  forming  the  cortex  of  the  cerebrum 
and  of  the  cerebellum.  Again,  gray  matter  is  found  in  the  interior  of  the 
brain,  collected  into  large  and  distinct  masses  or  ganglionic  bodies,  such  as  the 
corpus  striatum.  optic  thalamus,  corpora  quadrigemina,  the  olivary  bodies,  and 
the  corpora  dentata  of  the  cerebellum.  Finally,  gray  matter  is  found  intermin- 
gled intimately  with  the  white,  but  without  definite  arrangement,  as  in  tlie 
gray  matter  in  the  pons  Yarolii  and  the  floor  of  the  fourth  ventricle. 

The  white  matter  of  the  brain  is  divisible  into  three  distinct  classes  of  fibres. 
These  are.  in  the  first  place,  projection  fibres,  such  as  the  fibres  which  connect 
the  brain  with  the  spinal  cord ;  that  is  to  say,  those  which  are  usually  traced 
upward  from  the  columns  of  the  spinal  cord,  through  the  medulla  oblongata  into 
the  encephalon.  chiefly  by  means  of  the  anterior  pyramids,  passing  through  the 
pons  Yarolii  and  crura  cerebri  to  the  internal  capsules  of  the  corpora  striata, 
and  thence  to  the  cerebral  cortex,  and  by  means  of  the  restiform  bodies  into  the 
cerebellum.  The  second  class  of  white  fibres  in  the  brain  are  commissural,  con- 
necting opposite  sides  of  the  brain,  as.  for  instance,  the  fibres  of  the  corpus  callo- 
sum  and  the  anterior  commissure  of  the  thalamencephalon.  And  the  third  class 
are  the  association  fibres  which  connect  different  regions  of  the  same  side  of  any 
of  the  portions  of  the  brain.  The  fibres  of  this  last  class  are  more  especially 
developed  in  the  cerebral  hemispheres,  where  they  connect  different  areas  of  the 
cortex,  as.  for  example,  the  cortical  centre  for  sight  in  the  occipital  lobe  with  the 
motor  centre  for  speech  in  the  frontal  lobe. 

The  manner  in  which  the  gray  and  white  matter  are  intermingled  in  the  brain 
and  spinal  cord  is  very  intricate,  and  can  only  be  fully  understood  by  a  careful 
study  of  the  details  of  its  descriptive  anatomy  in  the  sequel.  The  further  consid- 
eration of  this  subject  will  therefore  be  deferred  until  after  the  description  of  the 
various  divisions  of  which  the  cerebro-spinal  system  is  made  up. 

The  nerves  are  round  or  flattened  cords,  formed  of  the  nerve-fibres  already 
described.  They  are  connected  at  one  end  with  the  cerebro-spinal  centre  or  with 
the  ganglia,  and  are  distributed  at  the  other  end  to  the  various  textures  of  the 
body :  they  are  subdivided  into  two  great  classes — the  cerebro-spinal,  which  pro- 
ceed from  the  cerebro-spinal  axis,  and  the  sympathetic  or  ganglionic  nerves,  which 
proceed  from  the  ganglia  of  the  sympathetic.  The  cerebro-spinal  nerves  consist 
of  numerous  nerve-fibres  collected  together  and  enclosed  in  a  membranous  sheath 
(Fig.  51).  A  small  bundle  of  primitive  fibres,  enclosed  in  a  tubular  sheath,  is 
called  a  funicuhis  :  if  the  nerve  is  of  small  size,  it  may  consist  only  of  a  single 
funiculus ;  but  if  large,  the  funiculi  are  collected  together  into  larger  bundles  or 


74 


GENERAL    ANATOMY. 


FIG.  51. — Transverse  section  through  a  microscopic 
nerve,  representing  a  compound  nerve-bundle,  sur- 
rounded by  epineurium.  Magnified  120  diameters. 
The  medullated  fibres  are  seen  as  circles  with  a  cen- 
tral dot — viz.  medullary  sheath  and  axis-cylinder— in 
transverse  section.  They  are  imbedded  in  endoneur- 
ium,  containing  numerous  nuclei,  which  belong  to  the 
connective-tissue  cells  of  the  latter.  (Klein  and  Noble 
Smith.)  p.  Epineurium,  consistingof  laminae  of  fibrous 
connective  tissues,  alternating  with  flattened  nucleated 
connective-tissue  cells.  I.  Lymph-space  between  epi- 
neurium and  surface  of  nerve-bundle. 


fasciculi,  which  are  hound  together  in  a  common  membranous  investment,  and 
constitute  the  nerve. 

In  structure  the  common  mem- 
branous investment,  or  sheath  of  the 
whole  nerve,  which  is  called  the  epi- 
neurium, as  well  as  the  septa  given  off 
from  it,  and  which  separate  the  fas- 
ciculi, consists  of  connective  tissue, 
composed  of  white  and  yellow  elastic 
fibres,  the  latter  existing  in  great 
abundance.  The  tubular  sheath  of 
the  funiculi,  called  the  perineurium, 
consists  of  a  fine,  smooth, 'transparent 
membrane,  which  may  be  easily  sepa- 
rated, in  the  form  of  a  tube,  from  the 
fibres  it  encloses ;  in  structure  it  con- 
sists of  connective  tissue,  which  has  a 
distinctly  lamellar  arrangement,  con- 
sisting of  several  lamellae,  separated 
from  each  other  by  spaces  containing 
lymph.  The  nerve-fibres  are  held 
together  and  supported  within  the 
funiculus  by  delicate  connective  tissue, 
called  the  endoneurium.  It  is  con- 
tinuous with  septa  which  pass  inward 
from  the  innermost  layer  of  the  peri- 
neurium, and  consists  of  a  ground-sub- 
stance in  which  are  imbedded  fine  bun- 
dles of  fibrous  connective  tissue  which 

run  for  the  most  part  longitudinally.  It  serves  to  support  the  capillary  vessels, 
which  are  arranged  so  as  to  form  a  network  with  the  elongated  meshes.  The 
cerebro-spinal  nerves  consist  almost  .exclusively  of  the  medullated  nerve-fibres, 
the  non-medullated  existing  in  very  small  proportions. 

The  blood-vessels  supplying  a  nerve  terminate  in  a  minute  capillary  plexus, 
the  vessels  composing  which  pierce  the  perineurium  and  run,  for  the  most  part, 
parallel  with  the  fibres ;  they  are  connected  together  by  short,  transverse  vessels, 
forming  narrow,  oblong  meshes,  similar  to  the  capillary  system  of  muscle.  Fine 
non-medullated  nerve-fibres  accompany  these  capillary  vessels,  vaso-motor  fibres, 
and  break  up  into  elementary  fibrils,  which  form  a  network  around  the  vessel. 
Horsley  has  also  recently  demonstrated  certain  medullated  fibres  as  running  in 
the  epineurium  and  terminating  in  tactile  corpuscles  or  end-bulbs  of  Krause,  or 
in  small,  but  perfect,  Pacinian  corpuscles.  These  nerve-fibres  are  termed  nervi 
nervorum,  and  have  been  considered  to  have  an  important  bearing  upon  certain 
neuralgic  pains. 

The  nerve-fibres,  as  far  as  is  at  present  known,  do  not  coalesce,  but  pursue  an 
uninterrupted  course  from  the  centre  to  the  periphery.  In  separating  a  nerve, 
however,  into  its  component  funiculi,  it  may  be  seen  that  they  do  not  pursue  a 
perfectly  insulated  course,  but  occasionally  join  at  a  very  acute  angle  with  other 
funiculi  proceeding  in  the  same  direction ;  from  this,  branches  are  given  off,  to 
join  again  in  like  manner  with  other  funiculi.  It  must  be  remembered,  however, 
that  in  these  communications  the  nerve-fibres  do  not  coalesce,  but  merely  pass 
into  the  sheath  of  the  adjacent  nerve,  become  intermixed  with  its  nerve-fibres, 
and  again  pass  on,  to  become  blended  with  the  nerve-fibres  in  some  adjoining 
funiculus. 

Nerves,  in  their  course,  subdivide  into  branches,  and  these  frequently  commu- 
nicate with  branches  of  a  neighboring  nerve.  In  the  subdivision  of  a  nerve  the 
filaments  of  which  it  is  composed  are  continued  from  the  trunk  into  the  branches, 


NERVOUS    TISSUE.  75 

and  at  their  junction  with  the  branches  of  neighboring  nerves  the  filaments  pass 
to  become  intermixed  with  those  of  the  other  nerves  in  their  further  progress ;  in 
no  instance,  however,  have  the  separate  nerve-fibres  been  shown  to  inosculate. 

The  communications  which  take  place  between  two  or  more  nerves  form  what 
is  called  a  plexus.  Sometimes  a  plexus  is  formed  by  the  primary  branches  of  the 
trunks  of  the  nerves — as  the  cervical,  brachial.  lumbar,  and  sacral  plexuses — and 
occasionally  by  the  terminal  funiculi,  as  in  the  plexuses  formed  at  the  periphery 
of  the  body.  In  the  formation  of  a  plexus  the  component  nerves  divide,  then 
join,  and  again  subdivide  in  such  a  complex  manner  that  the  individual  funiculi 
become  interlaced  most  intricately ;  so  that  each  branch  leaving  a  plexus  may 
contain  filaments  from  each  of  the  primary  nervous  trunks  which  form  it.  In  the 
formation  also  of  smaller  plexuses  at  the  periphery  of  the  body  there  is  a  free 
interchange  of  the  funiculi  and  primitive  fibres.  In  each  case,  however,  the 
individual  filaments  remain  separate  and  distinct,  and  do  not  inosculate  with  one 
another. 

It  is  probable  that  through  this  interchange  of  fibres  the  different  branches 
passing  off  from  a  plexus  have  a  more  extensive  connection  with  the  spinal  cord 
than  if  they  each  had  proceeded  to  be  distributed  without  such  connection  with 
other  nerves.  Consequently  the  parts  supplied  by  these  nerves  have  more  extended 
relations  with  the  nervous  centres :  by  this  means,  also,  groups  of  muscles  may  be 
associated  for  combined  action. 

The  sympathetic  nerves  are  constructed  in  the  same  manner  as  the  cerebro- 
spinal  nerves,  but  consist  mainly  of  non-medullated  fibres,  collected  into  funiculi. 
and  enclosed  in  a  sheath  of  connective  tissue.  There  is,  however,  in  these  nerves 
a  certain  admixture  of  medullated  fibres,  and  the  amount  varies  in  different 
nerves.  Those  branches  of  the  sympathetic  which  present  a  well-marked  gray 
color  are  composed  more  especially  of  non-medullated  nerve-fibres,  intermixed 
with  a  few  medullated  fibres ;  whilst  those  of  a  white  color  contain  more  of  the 
latter  fibres  and  a  few  of  the  former.  Occasionally,  the  gray  and  white  cords 
run  together  in  a  single  nerve,  without  any  intermixture,  as  in  the  branches  of 
communication  between  the  sympathetic  ganglia  and  the  spinal  nerves,  or  in  the 
communicating  cords  between  the  ganglia.  These  medullated  fibres  are  derived 
from  the  central  nervous  system  through  the  rami  communicantes,  which  pass  from 
the  cerebro-spinal  nerves  to  the  various  sympathetic  ganglia. 

The  nerve-fibres,  both  of  the  cerebro-spinal  and  sympathetic  system,  convey 
impressions  of  a  twofold  kind.  The  sensory  nerves,  called  also  centripetal  or 
>i.rf'> •/••  -tit  nerve.-,  transmit  to  the  nervous  centres  impressions  made  upon  the 
peripheral  extremities  of  the  nerves,  and  in  this  way  the  mind,  through  the 
medium  of  the  brain,  becomes  conscious  of  external  objects.  The  motor  nerves, 
called  also  centrifugal  or  efferent  nerves,  transmit  impressions  from  the  nervous 
centres  to  the  parts  to  which  the  nerves  are  distributed,  these  impressions  either 
exciting  muscular  contraction,  or  influencing  the  processes  of  nutrition,  growth, 
and  secretion. 

Origin  and  Termination  of  Nerves. — By  the  expression  "  the  termination  of 
nerve-fibres  "  is  signified  their  connection  with  the  nerve-centres,  and  with  the 
parts  they  supply.  The  former  are  sometimes  called  their  origin,  or  central 
termination ;  the  latter  their  peripheral  termination.  The  origin  in  some  cases  is 
single — that  is  to  say.  the  whole  nerve  emerges  from  the  nervous  centre  by  a  single 
root ;  in  other  instances  the  nerve  arises  by  two  or  more  roots,  which  come  off 
from  different  parts  of  the  nerve-centre,  sometimes  widely  apart  from  each  other, 
and  it  often  happens,  when  a  nerve  arises  in  this  way  by  two  roots,  that  the 
functions  of  these  two  roots  are  different ;  as,  for  example,  in  the  spinal  nerves, 
each  of  which  arises  by  two  roots,  the  anterior  of  which  is  motor  and  the  posterior 
sensory.  The  point  where  the  nerve  root  or  roots  emerge  from  the  nervous  centre 
is  named  the  fupcrjicial  or  apparent  origin,  but  the  fibres  of  Avhich  the  nerve 
consists  can  be  traced  for  a  certain  distance  into  the  nervous  centre  to  some  por- 
tion of  the  gray  substance,  which  constitutes  the  deep  or  real  origin  of  the  nerve. 


76  GENERAL    ANATOMY. 

In  the  case  of  motor  or  efferent  nerve-fibres  the  deep  origin  is  in  cells  contained 
within  the  spinal  cord  or  brain,  the  axis-cyliuder  processes  of  these  cells  being 
prolonged  to  form  the  fibres.  In  the  case  of  the  sensory  nerves  the  origin  is 
somewhat  different,  inasmuch  as  they  arise  from  the  cells  of  ganglia  situated 
externally  to  the  central  nervous  system.  The  sensory  fibres  of  a  spinal  nerve 
arise,  for  instance,  from  the  cells  of  the  ganglion  of  the  posterior  root ;  these 
cells  give  off  a  process  which  branches  in  a  T-shaped  manner  (Fig.  46,  B),  one 
of  the  limbs  of  the  T  extending  peripherally,  while  the  other  passes  inwards 
and  penetrates  the  spinal  cord.  In  connection  with  the  sensory  cranial  nerves, 
origins  are  described  imbedded  within  the  substance  of  the  brain  ;  these  are  not, 
however,  the  proper  origins,  but  are  groups  of  cells  around  which  the  fibres, 
growing  inwards  form  the  ganglion-cells,  situated  just  outside  the  brain,  end, 
and  from  which  new  fibres  arise,  which  pass  upwards  in  the  substance  of  the 
brain. 

Peripheral  Terminations  of  Nerves. — The  manner  in  which  nerve-fibres  ter- 
minate peripherally  are  several,  and  may  be  conveniently  studied  in  the  sensory 
and  motor  nerves  respectively.  Sensory  nerves  would  appear  to  terminate  either 
in  minute  primitive  fibrillse  or  networks  of  these  ;  or  else  in  special  terminal  organs, 
which  have  been  termed  peripheral  end-organs,  and  of  which  there  are  three 
principal  varieties — viz.  the  end-bulbs  of  Krause,  the  tactile  corpuscles  of  Wagner, 
and  the  Pacinian  corpuscles. 

Termination  in  Fibrillse. — When  a  medullated  nerve-fibre  approaches  its  termi- 
nation, the  white  matter  of  Schwann  suddenly  disappears,  leaving  only  the  axis- 
cylinder  surrounded  by  the  neurilemma,  and  we  have  now  a  non-medullated 
fibre.  This  undergoes  repeated  division,  and  after  a  time  loses  its  neurilemma, 
and  consists  only  of  an  axis-cylinder,  which  can  be  seen,  in  preparations  stained 
Avith  chloride  of  gold,  to  be  made  up  of  fine  varicose  fibrils.  Finally,  the  axis- 
cylinder  breaks  up  into  its  constituent  primitive  nerve-fibrillse,  which  anastomose 
with  one  another,  thus  forming  a  network,  and  often  present  regular  varicosities. 
This  network  passes  between  the  elements  of  the  tissue  to  which  the  nerves  are 
distributed,  which  is  always  epithelial,  and  the  nerve-fibrils  end  in  the  interstitial 
substance  between  the  epithelial  cells,  or,  as  is  believed  by  some,  actually  ter- 
minate within  the  cells  as  minute  swellings  close  to  the  nucleus.  In  this  \\i\\ 
nerve-fibres  have  been  found  to  terminate  in  the  epithelium  of  the  skin  and 
mucous  membranes,  and  in  the  anterior  epithelium  of  the  cornea. 

The  end-bulbs  of  Krause  (Fig.  52)  are  minute  oblong  or  cylindrical  corpuscles, 
into  the  interior  of  Avhich  the  axis-cylinder  of  the  nerve-fibre  passes,  and  termi- 
nates in  a  coiled,  plexiform  mass  or  in  a  bulbous  extremity.  The  corpuscle  con- 
sists of  a  simple  nucleated  capsule,  containing  a  soft,  homogeneous  core,  in  which 
the  termination  of  the  axis-cylinder  is  contained.  The  white  matter  of  Schwann 
ceases  abruptly  as  the  axis-cylinder  enters  the  corpuscle,  but  the  neurilemma  is 
continued  inward  with  the  axis-cylinder,  and  forms  an  investment  of  the  core, 
lining  the  interior  of  the  capsule.  The  end-bulbs  have  been  described  as  occurring 
in  the  conjunctiva  (where,  in  man,  they  are  spheroidal  in  shape),  in  the  mucous 
membrane  of  the  mouth,  and  in  the  cutis  and  mucous  membrane  of  the  penis, 
clitoris,  and  vagina,  where  they  are  termed  genital  corpuscles.  The  latter  have  a 
mulberry-like  appearance,  from  being  constricted  by  connective-tissue  septa  into 
from  two  to  six  knob-like  masses.  In  the  synovial  membrane  of  certain  joints 
(e.  g.  those  of  the  fingers)  rounded  or  oval  end-bulbs  have  been  found ;  these  are 
designated  articular  end-bulbs. 

The  tactile  corpuscles  (Fig  53),  described  by  Wagner  and  Meissner,  are  oval- 
shaped  bodies,  made  up  of  connective  tissue,  and  consisting  of  a  capsule,  and 
imperfect  membranous  septa,  derived  from  it,  which  penetrate  its  interior.  The 
axis-cylinders,  entering  the  capsule,  pursue  a  convoluted  course,  supported  by  the 
septa,  and  terminate  in  small  globular  or  pyriform  enlargements,  near  the  inner 
surface  of  the  capsule.  These  tactile  corpuscles  have  been  described  as  occurring 
in  the  papillae  of  the  corium  of  the  hand  and  foot,  the  front  of  the  fore-arm,  the 


XER  VO  US    TISS  C  '£. 


77 


skin  of  the  lips,  and  the  mucous  membrane  of  the  tip  of  the  tongue,  the  palpebral 
conjunctiva,  and  the  skin  of  the  nipple      They  are  not  found  in  all  the  papillae; 


FIG.  53.— Tactile  papilla  of  the  hand  treated  with  acetic 
acid.  Magnified  350  times.  A.  Side  view  of  a  papilla  of  the 
FIG.  52.— End-bulb  of  Krause.  a.  Medul-  hand.  a.  Cortical  layer.  6.  Tactile  corpuscle.with  transverse 

lated   nerve-fibre.     b.  Capsule   of  corpuscle.  nuclei,   c.  Small  nerve  of  the  papilla,  with  neurilemma.   d. 

(From  Klein's  Elements  of  Histology.)  Its  two  nervous  fibres  running  with  spiral  coils  around  the 

tactile  corpuscle,  c.  Apparent  termination  of  one  of  these 
fibres.  B.  A  tactile  papilla  seen  from  above,  so  as  to  show 
its  transverse  section,  a.  Cortical  layer,  b.  Nerve-fibre,  c. 
Outer  layer  of  the  tactile  body,  with  nuclei,  d.  Clear 
interior  substance. 

but  from  their  existence  in  those  parts  in  which  the  skin  is  highly  sensitive,  it  is 
probable  that  they  are  specially  concerned  in  the  sense  of  touch,  though  their 
absence  from  the  papillae  of  other  tactile  parts  shows  that  they  are  not  essential  to 
this  sense. 

The  Pacinian  corpuscles !  (Fig.  54)  are  found  in  the  human  subject  chiefly  on 
the  nerves  of  the  palm  of  the  hand  and  sole  of  the  foot  and  in  the  genital  organs 
of  both  sexes,  lying  in  the  subcutaneous  tissue ;  but  they  have  also  been  described 
as  connected  with  the  nerves  of  the  joints,  and  in  some  other  situations,  as  the 
mesentery  of  the  cat  and  along  the  tibia  of  the  rabbit.  Each  of  these  corpuscles 
is  attached  to  and  encloses  the  termination  of  a  single  nerve-fibre.  The  corpuscle, 
which  is  perfectly  visible  to  the  naked  eye  (and  which  can  be  most  easily  demon- 
strated in  the  mesentery  of  a  cat),  consists  of  a  number  of  lamellae  or  capsules, 
arranged  more  or  less  concentrically  around  a  central  clear  space,  in  which  the 
nerve-fibre  is  contained.  Each  lamella  is  composed  of  bundles  of  fine  connective- 
tissue  fibres,  and  is  lined  on  its  inner  surface  by  a  single  layer  of  nucleated  endo- 
thelial  cells.  The  central  clear  space,  which  is  elongated  or  cylindrical  in  shape, 
is  filled  with  a  transparent  material,  in  the  middle  of  which  is  the  single  medullated 
fibre,  which  traverses  the  space  to  near  its  distal  extremity.  Here  it  terminates 
in  a  rounded  knob  or  end,  sometimes  bifurcating  previously,  in  which  case  each 
branch  has  a  similar  arrangement.  Todd  and  Bowman  have  described  minute 
arteries  as  entering  by  the  sides  of  the  nerves  and  forming  capillary  loops  in  the 
intercapsular  spaces,  and  even  penetrating  into  the  central  space.  Other  authors 
describe  the  artery  as  entering  the  corpuscle  at  the  pole  opposite  to  the  nerve- 
fibre. 

Herbst  has  described  a  somewhat  similar  "  nerve-ending  "  to  the  Pacinian  cor- 
puscle, as  being  found  in  the  mucous  membrane  of  the  tongue  of  the  duck  and 
in  some  other  situations.  It  differs,  however,  from  the  Pacinian  corpuscles,  in 
being  smaller,  its  capsules  thinner  and  more  closely  approximated,  and  especially 
in  the  fact  that  the  axis-cylinder  in  the  central  clear  space  is  coated  with  a  con- 
tinuous row  of  nuclei.  These  bodies  are  known  as  the  corpuscles  of  Herbst. 

Tactile  corpuscles  have  been  described  by  Grandry  as  occurring  in  the  papillae 
of  the  beak  and  tongue  of  birds,  and  by  Merkel  as  occurring  in  the  papillae  and 

1  Often  called  in  German  anatomical  works  "  corpuscles  of  Vater." 


78 


GENERAL    ANATOMY. 


epithelium  of  the  skin  of  man  and  animals,  especially  in  those  parts  of  the  skin 
devoid  of  hair.     They  consist  of  a  capsule  composed  of  a  very  delicate,  nucleated 

membrane,  and  contain  two  or  more  granular, 
somewhat  flattened  cells,  between  which  the  med- 
ullated  nerve-fibre,  which  enters  the  capsule  by 
piercing  its  investing  membrane,  is  supposed  to 
terminate. 

The  nerves  supplying  tendons  have  peculiar 
nerve-endings,  and  are  especially  numerous  near 
the  point  where  the  tendon  becomes  muscular. 
In  this  situation  spindle-shaped  bodies  are  found, 
and  are  known  as  the  organs  of  Grolyi.  They  are 
apparently  composed  of  several  tendinous  bundles 
fused  into  one,  into  which  one  or  more  nerve-fibres 
pass,  and,  dividing,  spread  out  between  the  tendon- 
bundles.  Nerve-fibres  occasionally  terminate  in 
tendons  as  end-bulbs  or  as  small  Pacinian  cor- 
puscles. 

In  the  organs  of  special  sense  the  nerves  seem 
to  terminate  in  cells,  which  are  modified  epithe- 
lial cells,  and  have  received  the  name  of  sensory 
or  nerve-epithelium  cells.  In  reality,  however,  the 
nerve-fibre  is  in  these  cases  a  process  of  the  epi- 
thelial cell,  and  if  followed  centrally  will  be  found 
to  end  by  branching  around  a  ganglion-cell.  From 
-this  an  axis-cylinder  continues  the  path  along 
which  the  stimulus  travels  toward  the  brain. 
These  nerve-epithelium  cells  are  to  be  regarded  as 

FIG.  54.—  Pacinian  corpuscle,  with  its  •    n  j-n    j 

system  of  capsules  and  central  cavity.    Specially  modified  neurons. 

Motor  TIPTVP<?    arp    rn    VIP    tv-ipprl   pitlipr    into  nn- 
motor   nerves    dl< 

striped    or    striped    muscular  fibres.      In    the  un- 

.  x  r 

striped   or  involuntary  muscles  the  nerves  are  de- 

•       j      <?  ,1  ,1     ,  •  j  i 

rived    from  the    sympathetic,   and    are    composed 

maJnlv  of    tViP    nrm  mprlnllatprl    fihrp<s        Npar  tlipiv 

maimy  oi    tne  non-mec  i  nores.      iMeartnen 

termination  they  divide  into  a  number  of  branches, 
which  communicate  and  form  an  intimate  plexus. 
At  the  junction  of  the  branches  groups  of  ganglion-cells  are  situated.  From 
these  plexuses  minute  branches  are  given  off,  which  divide  and  break  up  into  the 
ultimate  fibrillseof  which  the  nerve  is  composed.  These  fibrillae  course  between 
the  involuntary  muscle-cells,  and,  according  to  Elischer,  terminate  on  the  surface 
of  the  cell,  opposite  the  nucleus,  in  a  minute  swelling.  Arnold  and  Franken- 
hauser  believed  that  these  ultimate  fibrillre  penetrated  the  muscular  cell  and  ended 
in  the  nucleus.  More  recent  observation  has,  however,  tended  to  disprove  this. 

In  the  striped  or  voluntary  muscle,  the  nerves  supplying  the  muscular  fibres 
are  derived  from  the  cerebro-spinal  nerves,  and  are  composed  mainly  of  medullated 
fibres.  The  nerve,  after  entering  the  sheath  of  the  muscle,  breaks  up  into  fibres, 
or  bundles  of  fibres,  which  form  plexuses,  and  gradually  divide  until,  as  a  rule, 
a  single  nerve-fibre  enters  a  single  muscular  fibre.  Sometimes,  however,  if 
the  muscular  fibre  is  long,  more  than  one  nerve-fibre  enters  it.  Within  the 
muscular  fibre  the  nerve  terminates  in  a  special  expansion,  called  by  Kiihne,  who 
first  accurately  described  them,  motorial  end-plates  (Fig.  55).  *  The  nerve-fibre, 
on  approaching  the  muscular  fibre,  suddenly  loses  its  white  matter  of  Schwann, 
which  abruptly  terminates  ;  the  neurilemma  becomes  continuous  with  the  sarco- 
lemma  of  the  muscle,  and  only  the  axis-cylinder  enters  the  muscular  fibre,  where 
it  immediately  spreads  out,  ramifying  like  the  roots  of  a  tree,  immediately  beneath 

1  They  had,  however,  previously  been  noticed,  though  not  accurately  described,  by  Doyere,  who 
named  them  "  nerve-hillocks." 


. 

a.  Arterial  twig,  ending  in  capillaries, 
which  form  loops  in  some  of  the  inter- 

capsuiar  spaces,  and  one  penetrates  to 

the  central  capsule.    6.  The  fibrous  tissue 

of  the  stalk  prolonged  from  the  perineu- 

rium.    n.  Nerve-tube  advancing  to  the 

central  capsule,  there  losing  its  white 

matter,  and  stretching  along  the  axis  to 

the  opposite  end,  where  it  is  fixed  by  a 
tubercular  enlargement. 


XER  VO  US    TISSUE. 


79 


the  sarcolemma.  and  is  imbedded  in  a  layer  of  granular  matter,  containing  a 
number  of  clear,  oblong  nuclei,  the  whole  constituting  an  end-plate  from  which 
the  contractile  wave  of  the  muscular  fibre  is  said  to  start. 


FIG.  55.— Muscular  fibres  of  Lacerta  viridis  with  the  terminations  of  nerves,  a.  Seen  in  profile.  P.P.  The  nerve 
end-plates,  s.s.  The  base  of  the  plate,  consisting  of  a  granular  mass  with  nuclei,  b.  The  same  as  seen  in  look- 
ing at  a  perfectly  fresh  fibre,  the  nervous  ends  being  probably  still  excitable.  (The  forms  of  the  variously- 
divided  plate  can  hardly  be  represented  in  a  woodcut  by  sufficiently  delicate  and  pale  contours  to  reproduce 
correctly  what  is  seen  i'n  nature.)  c.  The  same  as  seen"  two  hours  after  death  from  poisoning  by  curare. 

The  Ganglia  may  be  regarded  as  separate  and  independent  nervous  centres,  of 
smaller  size  and  les<  complex  structure  than  the  brain,  connected  with  each  other, 
with  the  cerebro-spinal  axis,  and  with  the  nerves  in  various  situations.  They  are 
found  on  the  posterior  root  of  each  of  the  spinal  nerves ;  on  the  posterior  or  sen- 
sory  root  of  the  fifth  cranial  nerve;  on  the  facial  and  auditory  nerves:  and 
on  the  glosso-pharvngeal  and  pneumogastric  nerves.  They  are  also  found  in 
a  connected  series  along  each  side  of 
the  vertebral  column,  forming  the  trunk 
of  the  sympathetic:  and  on  the  branches 
of  that  nerve,  generally  in  the  plexuses 
or  at  the  point  of  junction  of  two  or 
more  nerves  with  each  other  or  with 
branches  of  the  cerebro-spinal  system. 
On  section  they  are  seen  to  consist  of 
a  reddish-gray  substance,  traversed  by 
numerous  white  nerve-fibres  ;  they  vary 
considerably  in  form  and  size;  the 
largest  are  found  in  the  cavity  of  the 
abdomen :  the  smallest,  not  visible  to 
the  naked  eye.  exist  in  considerable 
numbers  upon  the  nerves  distributed 
to  the  different  viscera.  The  ganglia 
are  invested  by  a  smooth  and  firm. 
closely-adhering,  membranous  envelope, 
consisting  of  dense  areolar  tissue ;  this 
sheath  is  continuous  with  the  peri- 
neurium  of  the  nerves,  and  sends  nu- 
merous processes  into  the  interior  of 
the  ganglion,  which  support  the  blood- 
em  supplying  its  substance. 

In  structure  all  ganglia  are  essen- 
tially similar  (Fig.  56),  consisting  of  the 
same   structural   elements  as  the  other 
nervous  centres — viz.  a  collection  of  nerve-cells  and    nerve-fibres.     The  nerve- 
or  ganglion-cells  in  the  ganglia  of  the  spinal  nerves  are   pyriform  in  shape,  the 


FIG.  56. — Section  through  a  microscopic  ganglion. 
Magnified  300  diameters.  (Klein  and  >ioble  Smith.) 
c.  Capsule  of  the  ganglion,  n.  Nerve-fibres  passing  out 
of  the  ganglion.  The  nerve-fibres  which  entered  the 
ganglion  are  not  represented.  The  nerve-fibres  are 
ordinary  medullated  fibres,  but  the  details  of  their 
structure  are  not  shown,  owing  to  the  low  magnifying 
power.  The  ganglion-cells  are  invested  by  special 
capsules,  lined  by  a  few  nuclei,  which  are  here  repre- 
sented as  if  contained  in  the  capsule. 


80 


GENERAL    ANATOMY. 


smaller  end  being  drawn  out  into  a  process  which  bifurcates  at  its  extremity  in  a 
T-like  manner,  the  two  limbs  of  the  T  forming  the  axis-cylinder  of  the  peripheral 
and  central  portions  of  a  sensory  nerve-fibre.  In  the  sympathetic  ganglia  the 
cells  are  multipolar,  and  give  off  a  single  unbranched  axis-cylinder.  Cells  of 
this  type  are  found  in  the  ciliary,  spheno-palatine,  submaxillary,  and  otic  ganglia 
attached  to  certain  of  the  cranial  nerves,  and  these  may  in  consequence  be  con- 
sidered as  the  cranial  portion  of  the  sympathetic  system.  The  ganglion-cells  are 
usually  enclosed  in  a  transparent  capsule  with  nuclei  on  its  inner  surface.  The 
nerve-fibres  on  entering  the  ganglion  lay  aside  their  perineurium,  which  becomes 
continuous  with  the  capsule.  Some  fibres  run  through  the  ganglion  without  being 
connected  with  the  cells. 

THE    VASCULAR   SYSTEM. 

The  Vascular  System,  exclusive  of  its  central  organ,  the  heart,  is  divided  into 
four  classes  of  vessels :  the  arteries,  capillaries,  veins,  and  lymphatics ;  the 
minute  structure  of  which  we  will  now  proceed  briefly  to  describe,  referring  the 

reader  to  the  body  of  the  work  for  all  that 
is  necessary  in  the  details  of  their  ordinary 
anatomy. 

Structure  of  Arteries  (Fig.  57). — The 
arteries  are  composed  of  three  coats :  inter- 
nal or  endothelial  coat  (tunica  intima  of 
Kblliker) ;  middle  muscular  coat  (tunica 
media) ;  and  external  cellular  coat  (tunica 
adventitia). 

The  two  inner  coats  together  are  very 
easily  separated  from  the  external,  as  by 
the  ordinary  operation  of  tying  a  ligature 
on  an  artery.  If  a  fine  string  be  tied  for- 
cibly upon  an  artery  and  then  taken  off, 
the  external  coat  will  be  found  undivided, 
but  the  internal  coats  are  divided  in  the 
track  of  the  ligature  and  can  easily  be  fur- 
ther dissected  from  the  outer  coat.  The 
inner  coat  can  be  separated  from  the  middle 
by  a  little  maceration,  or  it  may  be  stripped 
off  in  small  pieces;  but,  on  account  of  its 
friability,  it  cannot  be  separated  as  a  com- 
plete membrane.  It  is  a  fine,  transparent, 
colorless  structure  which  is  highly  elastic, 
and  is  commonly  corrugated  into  longitudi- 
nal wrinkles.  The  inner  coat  consists  of — 
1.  A  layer  of  pavement-epithelium,  the  cells 
of  which  are  polygonal,  oval,  or  fusiform, 
and  have  very  distinct  round  or  oval  nuclei. 
This  endothelium,  as  it  is  now  generally 
called,  is  brought  into  view  most  distinctly 
by  staining  with  nitrate  of  silver.  2.  A 
subepithelial  layer,  consisting  of  delicate 
connective  tissue  with  branched  cells  lying 
in  the  interspaces  of  the  tissue.  3.  An  elastic  or  fenestrated  layer,  which  con- 
sists of  an  elastic  membrane  containing  a  network  of  elastic  fibres,  having  prin- 
cipally a  longitudinal  direction  and  in  which,  under  the  microscope,  small,  elon- 
gated apertures  or  perforations  may  be  seen,  giving  it  a  fenestrated  appearance. 
It  was  therefore  called  by  Henle  the  fenestrated  membrane.  This  membrane 
forms  the  chief  thickness  of  the  inner  coat,  and  can  be  separated  into  several 
layers,  some  of  which  present  the  appearance  of  a  network  of  longitudinal  elastic 


FIG.  57.— Transverse  section  through  a  small 
artery  and  vein  of  the  mucous  membrane  of  the 
epiglottis  of  a  child.  Magnified  about  350  diame- 
ters. (Klein  and  Noble  Smith.)  A.  Arterv,  show- 
ing the  nucleated  endothelium,  e,  which  lines  it : 
the  vessel  being  contracted,  the  endothelial  cells 
appear  very  thick.  Underneath  the  endothelium 
is  the  wavy  elastic  intima.  The  chief  part  of  the 
wall  of  the  vessel  is  occupied  by  the  circular  mus- 
cle-coat m :  the  staff-shaped  nuclei  of  the  muscle- 
cells  are  well  seen.  Outside  this  is  a,  part  of  the 
adventitia.  This  is  composed  of  bundles  of  con- 
nective-tissue fibres,  shown  in  section,  with  the 
nuclei  of  the  connective-tissue  corpuscles. 
The  adventitia  gradually  merges  into  the  sur- 
rounding connective  tissue,  v.  Vein  showing 
a  thin  endothelial  membrane,  e,  raised  acciden- 
tally from  the  intima,  which  on  account  of  its 
delicacy  is  seen  as  a  mere  line  on  the  media  m. 
This  latter  is  composed  of  a  few  circular  un- 
striped  muscle-cells,  a.  The  adventitia,  simi- 
lar in  structure  to  that  of  an  artery. 


THE 


SYSTEM. 


81 


fibres,  and  others  present  a  more  membranous  character,  marked  by  pale  lines 
having  a  longitudinal  direction.  In  arteries  of  less  than  a  line  in  diameter  the 
subepithelial  layer  consists  of  a  single  layer  of  stellate  cells,  and  the  connective 
tissue  is  only  largely  developed  in  the  large-sized  vessels.  The  fenestrated  mem- 
brane in  microscopic  arteries  is  a  very  thin  layer,  but  in  the  larger  arteries,  and 
especially  in  the  aorta,  it  has  a  very  considerable  thickness. 

The  middle  coat  (tunica  media)  is  distinguished  from  the  inner  by  its  color 
and  by  the  transverse  arrangement  of  its  fibres,  in  contradistinction  to  the  longi- 
tudinal direction  of  those  of  the  inner  coat.  It  consists  of  two  varieties  of  struc- 
ture. t/eUou'  elastic  tissue  and  mnxcular  tissue,  which  are  present  in  varying  quan- 
tities in  different  vessels,  according  to  their  size,  the  former  tissue  preponderating 
in  the  larger  vessels  and  the  latter  in  the  smaller  ones.  In  the  largest 
arteries  this  coat  is  of  great  thickness,  of  a  yellow  color,  and  highly  elastic; 
it  diminishes  in  thickness  and  becomes  redder  in  color  as  the  arteries  become 
smaller,  and  finally  becomes  very  thin  and  disappears.  In  small  arteries  this 
coat  is  purely  muscular,  consisting  of  muscle  fibre-cells  (Fig.  44)  united  to  form 
lamellae  which  vary  in  number  according  to  the  size  of  the  artery ;  the  very  small 
arteries  having  only  a  single  layer,  and  those  not  larger  than  one-tenth  of  a  line 
in  diameter  three  or  four  layers.  In  arteries  of  medium  size  (Fig.  58)  this  coat 
becomes  thicker  in  proportion 

to  the  size  of  the  vessel :  its  Y  v «  <? 

layers  of  muscular  tissue  are 
more  numerous  and  inter- 
mixed with  numerous  fine 
elastic  fibres  which  unite  to 
form  broad-meshed  networks. 
In  the  larger  vessels,  as  the 
femoral,  superior  mesenteric. 
coeliac  axis,  external  iliac, 
brachial  and  popliteal  arte- 
ries, the  elastic  fibres  unite 
to  form  lamellae,  which  alter- 
nate with  the  layers  of  mus- 
cular fibre.  In  the  largest 
arteries  the  muscular  tissue 
is  only  slightly  developed  and 
forms  about  one-third  or  one- 
fourth  of  the  whole  substance 
of  the  middle  coat :  this  is 
especially  the  case  in  the 
aorta  and  trunk  of  the  pul- 
monary artery,  in  which  the 
individual  cells  of  the  mus- 
cular layer  are  imperfectly  formed,  while  in  the  carotid,  axillary,  iliac,  and  sub- 
clavian  arteries  the  muscular  layer  of  the  middle  coat  is  more  developed.  The 
elastic  lamellae  are  well  marked,  may  amount  to  fifty  or  sixty  in  number,  and 
alternate  regularly  with  the  layers  of  muscular  tissue.  They  are  most  distinct 
and  arranged  with  greatest  regularity  in  the  abdominal  aorta,  innominate  artery, 
and  common  carotid.  In  the  larger  arteries  bundles  of  white  connective-tissue 
fibres  have  also  been  found  in  small  quantity  in  the  middle  coat. 

The  i'Xt> •/•//•//  coat  (tunica  adverttitta)  consists  mainly  of  fine  and  closely  felted 
bundles  of  white  connective  tissue,  but  also  contains  elastic  fibres  in  all  but  the 
smallest  arteries.  The  elastic  tissue  is  much  more  abundant  next  the  tunica 
media,  and  it  is  sometimes  described  as  forming  here,  between  the  adventitia  and 
media,  a  special  layer,  the  tunica  elastica  extern  a  of  Henle.  This  layer  is  most 
marked  in  arteries  of  medium  size.  In  the  largest  vessels  the  external  coat  is 
relatively  thin :  but  in  small  arteries  it  is  as  thick  or  thicker  than  the  middle  coat. 


FIG.  58.— An  artery  from  the  mesentery  of  a  child,  .062"',  and  b, 
vein  .067'"  in  diameter,  treated  with  acetic  acid  and  magnified  350 
times,  a.  Tunica  adventitia.  with  elongated  nuclei,  ft.  Nuclei  of 
the  contractile  fibre-cells  of  the  tunica  media,  seen  partly  from  the 
surface,  partly  apparent  in  transverse  section,  y.  Nuclei"  of  the  en- 
dothelial  cells.  6.  Elastic  longitudinal  fibrous  coat. 


GENERAL    ANATOMY. 

In  the  smaller  arteries  it  consists  of  a  single  layer  of  white  connective  tissue  and 
elastic  fibres;  while  in  the  smallest  arteries,  just  above  the  capillaries,  the  elastic 
fibres  are  wanting,  and  the  connective  tissue,  of  Avhich  the  coat  is  composed, 
becomes  more  homogeneous  the  nearer  it  approaches  the  capillaries,  and  is 
gradually  reduced  to  a  thin  membranous  envelope  which  finally  disappears. 

Some  arteries  have  extremely  thin  coats  in  proportion  to  their  size;  this  is 
especially  the  case  in  those  situated  in  the  cavity  of  the  cranium  and  spinal 
canal,  the  diiference  depending  on  the  greater  thinness  of  the  external  and 
middle  coats. 

The  arteries,  in  their  distribution  throughout  the  body,  are  included  in  a  thin 
fibro-areolar  investment,  which  forms  what  is  called  their  sheath.  In  the  limbs 
this  is  usually  formed  by  a  prolongation  of  the  deep  fascia ;  in  the  upper  part 
of  .the  thigh  it  consists  of  a  continuation  downward  of  the  transversalis  and  iliac 
fasciae  of  the  abdomen ;  in  the  neck,  of  a  prolongation  of  the  deep  cervical  fascia. 
The  included  vessel  is  loosely  connected  with  its  sheath  by  a  delicate  areolar  tissue ; 
and  the  sheath  usually  encloses  the  accompanying  veins,  and  sometimes  a  nerve. 
Some  arteries,  as  those  in  the  cranium,  are  not  included  in  sheaths. 

All  the  larger  arteries  are  supplied  with  blood-vessels  like  the  other  organs  of 
the  body ;  they  are  called  the  vasa  vasorum.  These  nutrient  vessels  arise  from  a 
branch  of  the  artery  or  from  a  neighboring  vessel,  at  some  considerable  distance 
from  the  point  at  which  they  are  distributed ;  they  ramify  in  the  loose  areolar 
tissue  connecting  the  artery  with  its  sheath,  and  are  distributed  to  the  external 
coat,  but  do  not,  in  man,  penetrate  the  other  coats ;  though  in  some  of  the  larger 
mammals  some  few  vessels  have  been  traced  into  the  middle  coat.  Minute  veins 
serve  to  return  the  blood  from  these  vessels ;  they  empty  themselves  into  the  venae 
comites  in  connection  with  the  artery.  Lymphatic  vessels  and  lymphatic  spaces 
are  also  present  in  the  outer  coat. 

Arteries  are  also  supplied  with  nerves,  which  are  derived  chiefly  from  the  sym- 
pathetic, but  partly  from  the  cerebro-spinal  system.  They  form  intricate  plexuses 
upon  the  surfaces  of  the  larger  trunks,  and  run  along  the  smaller  branches  as  single 
filaments  or  bundles  of  filaments,  which  twist  around  the  vessel  and  unite  with 
each  other  in  a  plexiform  manner.  The  branches  derived  from  these  plexuses 
penetrate  the  external  coat,  and  are  principally  distributed  to  the  muscular  tissue 
of  the  middle  coat,  and  thus  regulate,  by  causing  the  contraction  and  relaxation 
of  this  tissue,  the  amount  of  blood  sent  to  any  part. 

The  Capillaries. — The  smaller  arterial  branches  (excepting  those  of  the  cavern- 
ous structure  of  the  sexual  organs,  of  the  spleen,  and  in  the  uterine  placenta) 
terminate  in  a  network  of  vessels  which  pervade  nearly  every  tissue  of  the  body. 
These  vessels,  from  their  minute  size,  are  termed  capillaries  (capillus,  a  hair). 
They  are  interposed  between  the  smallest  branches  of  the  arteries  and  the  com- 
mencing veins,  constituting  a  network,  the  branches  of  which  maintain  the  same 
diameter  throughout ;  the  meshes  of  the  network  being  more  uniform  in  shape 
and  'size  than  those  formed  by  the  anastomoses  of  the  small  arteries  and 
veins. 

The  diameter  of  the  capillaries  varies  in  the  different  tissues  of  the  body,  their 
usual  size  being  about  ^jVo  °f  an  incn-  The  smallest  are  those  of  the  brain  and 
the  mucous  membranes  of  the  intestines ;  and  the  largest  those  of  the  skin  and 
the  marrow  of  bone,  where  they  are  stated  to  be  as  large  as  y^V^-  of  an  inch 

The  form  of  the  capillary  net  varies  in  the  different  tissues,  the  meshes  being 
generally  rounded  or  elongated.  The  rounded  form  of  mesh  is  most  common,  and 
prevails  where  there  is  a  dense  network,  as  in  the  lungs,  in  most  glands  and 
mucous  membranes,  and  in  the  cutis ;  here  the  meshes  are  more  or  less  angular, 
sometimes  nearly  quadrangular  or  polygonal ;  more  frequently  irregular. 

Elongated  meshes  are  observed  in  the  bundles  of  fibres  composing  muscles  and 
nerves,  the  meshes  being  usually  of  a  parallelogram  form,  the  long  axis  of  the 
mesh  running  parallel  with  the  long  axis  of  the  nerve  and  fibre.  Sometimes 
the  capillaries  have  a  looped  arrangement ;  a  single  vessel  projecting  from  the 


THE    VASCULAR   SYSTEM. 


83 


common  network  and  returning  after  forming  one  or  more  loops,  as  in  the 
papillae  of  the  tongue  and  skin.  The  number  of  the  capillaries,  and  the  size  of  the 
meshes,  determine  the  degree  of  vascularity  of  a  part.  The  closest  network  and 
the  smallest  interspaces  are  found  in  the  lungs  and  in  the  choroid  coat  of  the  eye. 
In  these  situations  the  interspaces  are  smaller  than  the  capillary  vessels  them- 
selves. In  the  kidney,  in  the  conjunctiva,  and  in  the  cutis  the  interspaces  are 
from  three  to  four  times  as  large  as  the  capillaries  which  form  them ;  and  in  the 
brain  from  eight  to  ten  times  as  large  as  the  capillaries  in  their  long  diameter,  and 
from  four  to  six  times  as  large  in  their  transverse  diameter.  In  the  adventitia 
of  arteries  the  width  of  the  meshes  is  ten  times  that  of  the  capillary  vessels. 
A-  a  general  rule,  the  more  active  the  function  of  the  organ,  the  closer  is  its 
capillary  net  and  the  larger  its  supply  of  blood ;  the  network  being  very  narrow  in 
all  growing  parts,  in  the  glands,  and  in  the  mucous  membranes ;  wider  in  bones 
and  ligaments,  which  are  comparatively  inactive ;  and  nearly  altogether  absent  in 
tendons,  in  which  very  little  organic  change  occurs  after  their  formation. 

Structure. — The  walls  of  the  capillaries  consist  of  a  fine,  transparent,  endothelial 
layer,  composed  of  cells  joined  edge  to  edge  by  an  interstitial  cement-substance, 
and  continuous  with  the  endothelial  cells  which  line  the  arteries  and  veins.  "When 
stained  with  nitrate  of  silver  the  edges  which  bound  the  endothelial  cells  are 
brought  into  view  (Fig.  59).  These  cells  are  of  large  size  and  of  an  irregular  polyg- 
onal or  lanceolate  shape,  each  containing  an  oval  nucleus  which  may  be  brought 
into  view  by  carmine  or  haematoxylin.  Between  their  edges,  at  various  points  of 
their  meeting,  roundish  dark  spots  are  sometimes  seen,  which  have  been  described  as 


FIG.  59.— Capillaries  from  the 
mesentery  of  a  guinea-pig  after  treat- 
ment with  solution  of  nitrate  of  sil- 
ver, a.  Cells.  6.  Their  nuclei. 


FIG.  60.— Finest  vessels  on  the  arterial  side.  From  the  human 
brain.  Magnified  300  times.  1.  Smallest  artery.  2.  Transition 
vessel.  3.  Coarser  capillaries.  4.  Finer  capillaries,  a.  Structure- 
less membrane  still  with  some  nuclei,  representative  of  the 
tunica  adventitia.  b.  Nuclei  of  the  muscular  fibre-cells,  c. 
nuclei  within  the  small  artery,  perhaps  appertaining  to  an 
endothelium.  d.  Nuclei  in  the  transition  vessels. 


stomata,  though  they  are  closed  by  intercellular  substance.  They  have  been 
believed  to  be  the  situation  through  Vhich  the  white  corpuscles  of  the  blood,  when 
migrating  through  the  blood-vessels,  emerge ;  but  this  view,  though  probable,  is 
not  universally  accepted. 

In  many  situations  a  delicate  sheath  or  envelope  of  branched  nucleated  connec- 


84  GENERAL    ANATOMY. 

tive-tissue  cells  is  found  around  the  simple  capillary  tube,  particularly  in  the 
larger  ones,  and  in  places  such  as  the  lymphatic  glands  where  the  capillaries 
are  supported  by  a  retiform  connective  tissue. 

In  the  largest  capillaries  (which  ought,  perhaps,  to  be  described  rather  as  the 
smallest  arteries)  there  is,  outside  the  endothelial  layer,  a  muscular  layer,  consisting 
of  contractile  fibre-cells,  arranged  transversely,  as  in  the  tunica  media  of  the  larger 
arteries  (Fig.  60). 

The  veins,  like  the  arteries,  are  composed  of  three  coats — internal,  middle,  and 
external ;  and  these  coats  are,  with  the  necessary  modifications,  analogous  to  the 
coats  of  the  arteries ;  the  internal  being  the  endothelial,  the  middle  the  muscular, 
and  the  external  the  connective  or  areolar.  The  main  difference  between  the 
veins  and  the  arteries  is  the  comparative  weakness  of  the  middle  coat  of  the 
former,  and  to  this  it  is  due  that  the  veins  do  not  stand  open  when  divided,  as 
the  arteries  do,  and  that  they  are  passive  rather  than  active  organs  of  the 
circulation. 

In  the  veins  immediately  above  the  capillaries  the  three  coats  are  hardly  to  be 
distinguished.  The  endothelium  is  supported  on  an  outer  membrane  separable  into 
two  layers,  the  outer  of  which  is  the  thicker,  and  consists  of  a  delicate,  nucleated 
membrane  (adventitia),  while  the  inner  is  composed  of  a  network  of  longitudinal 
elastic  fibres  (media).  In  the  veins  next  above  these  in  size  (one-fifth  of  a  line, 
according  to  Kolliker)  a  muscular  layer  and  a  layer  of  circular  fibres  can  be  traced, 
forming  the  middle  coat,  while  the  elastic  and  connective  elements  of  the  outer 
coat  become  more  distinctly  perceptible.  In  the  middle-sized  veins  the  typical 
structure  of  these  vessels  becomes  clear.  The  endothelium  is  of  the  same  character 
as  in  the  arteries,  but  its  cells  are  more  oval,  less  fusiform.  It  is  supported  by  a 
connective-tissue  layer,  consisting  of  a  delicate  network  of  branched  cells,  and 
external  to  this  is  a  layer  of  longitudinal  elastic  fibres,  but  seldom  any  appearance 
of  a  fenestrated  membrane.  This  constitutes  the  internal  coat.  The  middle  coat  is 
composed  of  a  thick  layer  of  connective  tissue  writh  elastic  fibres,  intermixed,  in  some 
veins,  with  a  transverse  layer  of  muscular  fibres.  The  white  fibrous  element  is 
in  considerable  excess,  and  the  elastic  fibres  are  in  much  smaller  proportion  in  the 
veins  than  in  the  arteries.  The  outer  coat  consists  of  areolar  tissue,  as  in  the 
arteries,  with  longitudinal  elastic  fibres.  In  the  largest  veins  the  outer  coat  is  from 
two  to  five  times  thicker  than  the  middle  coat,  and  contains  a  large  number  of 
longitudinal  muscular  fibres.  This  is  most  distinct  in  the  inferior  vena  cava,  and 
at  the  termination  of  this  vein  in  the  heart,  in  the  trunks  of  the  hepatic  veins,  in 
all  the  large  trunks  of  the  vena  portae,  in  the  splenic,  superior  mesenteric,  external 
iliac,  renal,  and  azygos  veins.  In  the  renal  and  portal  veins  it  extends  through 
the  whole  thickness  of  the  outer  coat,  but  in  the  other  veins  mentioned  a  layer  of 
connective  and  elastic  tissue  is  found  external  to  the  muscular  fibres.  All  the  large 
veins  Avhich  open  into  the  heart  are  covered  for  a  short  distance  with  u  layer  of 
striped  muscular  tissue  continued  on  to  them  from  the  heart.  Muscular  tissue  is 
wanting  in  the  veins — (1)  of  the  maternal  part  of  the  placenta ;  (2)  in  the  venous 
sinuses  of  the  dura  mater  and  the  veins  of  the  pia  mater  of  the  brain  and  spinal 
cord ;  (3)  in  the  veins  of  the  retina ;  (4)  in  the  veins  of  the  cancellous  tissue  of 
bones  ;  (5)  in  the  venous  spaces  of  the  corpora  cavernosa.  The  veins  of  the  above- 
mentioned  parts  consist  of  an  internal  endothelial  lining  supported  on  one  or  more 
layers  of  areolar  tissue.  The  internal  and  external  jugular  veins  and  the  subclavian 
vein  are  said  to  contain  either  no  muscular  fibres  at  all,  or  at  all  events  only  a 
slight  amount  in  their  middle  coat. 

Most  veins  are  provided  with  valves,  which  serve  to  prevent  the  reflux  of  the 
blood.  They  are  formed  by  a  reduplication  of  the  inner  coat,  strengthened  by 
connective  tissue  and  elastic  fibres,  and  are  covered  on  both  surfaces  with  endo- 
thelium, the  arrangement  of  which  differs  on  the  two  surfaces.  On  the  surface 
of  the  valve  next  the  wall  of  the  vein  the  cells  are  arranged  transversely  ;  whilst 
on  the  other  surface,  over  which  the  current  of  blood  flows,  the  cells  are  arranged 
vertically  in  the  direction  of  the  current.  Their  form  is  semilunar.  They  are 


THE   VASCULAR    SYSTEM. 


85 


attached  by  their  convex  edge  to  the  wall  of  the  vein ;  the  concave  margin  is  free, 
directed  in  the  course  of  the  venous  current,  and  lies  in  close  apposition  with  the 
wall  of  the  vein  as  long  as  the  current  of  blood  takes  its  natural  course ;  if,  how- 
ever, any  regurgitation  takes  place,  the  valves  become  distended,  their  opposed 
edges  are  brought  into  contact,  and  the  current  is  intercepted.  Most  commonly 
two  such  valves  are  found  placed  opposite  one  another,  more  especially  in  the 
smaller  veins  or  in  the  larger  trunks  at  the  point  where  they  are  joined  by  smaller 
branches ;  occasionally  there  are  three  and  sometimes  only  one.  The  wall  of  the 
vein  on  the  cardiac  side  of  the  point  of  attachment  of  each  segment  of  the  valve 
is  expanded  into  a  pouch  or  sinus,  which  gives  to  the  vessel,  when  injected  or  dis- 
tended with  blood,  a  knotted  appearance.  The  valves  are  very  numerous  in  the 
veins  of  the  extremities,  especially  of  the  lower  extremities,  these  vessels  having 
to  conduct  the  blood  against  the  force  of  gravity.  They  are  absent  in  the  very 
small  veins — i.  e.  those  less  than  ^  °f  an  incn  in  diameter ;  also  in  the  venge 
cavse.  the  hepatic  veins,  portal  vein  and  its  branches,  the  renal,  uterine,  and 
ovarian  veins.  A  few  valves  are  found  in  the  spermatic  veins,  and  one  also  at 
their  point  of  junction  with  the  renal  vein  and  inferior  vena  cava  in  both  sexes. 
The  cerebral  and  spinal  veins,  the  veins  of  the  cancellated  tissue  of  bone,  the 
pulmonary  veins,  and  the  umbilical  vein  and  its  branches,  are  also  destitute  of 
valves.  They  are  occasionally  found,  few  in  number, 
in  the  venae  azygos  and  intercostal  veins. 

The  veins  are  supplied  with  nutrient  vessels,  vasa 
vasorutn.  like  the  arteries.  Xerves  also  are  distrib- 
uted to  them  in  the  same  manner  as  to  the  arteries, 
but  in  much  less  abundance. 

The  lymphatic  vessels,  including  in  this  term  the 
lacteal  vessels,  which  are  identical  in  structure  with 
them,  are  composed  of  three  coats.  The  internal  is 
an  endothelial  and  elastic  coat.  It  is  thin,  trans- 
parent, slightly  elastic,  and  ruptures  sooner  than  the 
other  coats.  It  is  composed  of  a  layer  of  elongated 
epithelial  cells  with  serrated  margins,  by  which  the 
adjacent  cells  are  dovetailed  into  one  another.  These 
are  supported  on  a  single  layer  of  longitudinal  elastic 
fibres.  The  middle  coat  is  composed  of  smooth  mus- 
cular and  fine  elastic  fibres,  disposed  in  a  transverse 
direction.  The  external,  or  fibro-areolar,  coat  con- 
sists of  filaments  of  connective  tissue,  intermixed  with 


FIG.  62.— 1.  Endothelium  from  the 
under  surface  of  the  centrum  tendineun 
of  the  rabbit,  a.  Stomata.  2.  Endo- 
t helium  of  the  mediastinum  of  the 
dog.  a.  Stomata.  3.  Section  through 
the  pleura  of  the  same  animal,  b. 
Free  orifices  of  short  lateral  passages 
of  the  lymph-canals.  (Copied  from 
Ludwig,  Schweigger-Seydel,  and  Dyb- 
kowsky.) 


abc      d 

FIG.  61.— Transverse  section  through  the  coats  of  the  thoracic 
duct  of  man.  Magnified  30  times,  a.  Endothelium,  striated  lamellae, 
and  inner  elastic  coat.  b.  Longitudinal  connective  tissue  of  the 
middle  coat.  c.  Transverse  muscles  of  the  same.  d.  Tunica  adven- 
titia.  with  e .  the  longitudinal  muscular  fibres. 


smooth  muscular  fibres,  longitudinally  or  obliquely  disposed.  It  forms  a  protective 
covering  to  the  other  coats,  and  serves  to  connect  the  vessel  with  the  neighboring 
structures.  The  above  description  applies  only  to  the  larger  lymphatics ;  in  the 
smaller  vessels  there  is  no  muscular  or  elastic 'coat,  and  their 'structure  consists 
only  of  a  connective-tissue  coat,  lined  by  endothelium.  The  thoracic  duct  (Fig. 
61)  is  a  somewhat  more  complex  structure  than  the  other  lymphatics;  it  presents 
a  distinct  subepithelial  layer  of  branched  corpuscles,  similar  to  that  found  in  the 
arteries,  and  in  the  middle  coat  is  a  layer  of  connective  tissue  with  its  fibres 


86  GENERAL    ANATOMY. 

arranged  longitudinally.  The  lymphatics  are  supplied  by  nutrient  vessels,  which 
are  distributed  to  their  outer  and  middle  coats ;  but  no  nerves  have  at  present 
been  traced  into  them. 

The  lymphatics  are  very  generally  provided  with  valves,  which  assist  mate- 
rially in  effecting  the  circulation  of  the  fluid  they  contain.  These  valves  are 
formed  of  a  thin  layer  of  fibrous  tissue,  lined  on  both  surfaces  by  endothelium. 
Their  form  is  semilunar;  they  are  attached  by  their  convex  edge  to  the  sides  of 
the  vessel,  the  concave  edge  being  free  and  directed  along  the  course  of  the  con- 
tained current.  Usually  two  such  valves,  of  equal  size,  are  found  opposite  one 
another ;  but  occasionally  exceptions  occur,  especially  at  or  near  the  anastomoses 
of  lymphatic  vessels.  Thus,  one  valve  may  be  of  very  rudimentary  size  and  the 
other  increased  in  proportion. 

The  valves  in  the  lymphatic  vessels  are  placed  at  much  shorter  intervals  than 
in  the  veins.  They  are  most  numerous  near  the  lymphatic  glands,  and  they  are 
found  more  frequently  in  the  lymphatics  of  the  neck  and  upper  extremity  than  in 
the  lower.  The  wall  of  the  lymphatics  immediately  above  the  point  of  attach- 
ment of  each  segment  of  a  valve  is  expanded  into  a  pouch  or  sinus,  which  gives 
to  these  vessels,  when  distended,  the  knotted  or  beaded  appearance  which  they 
present.  Valves  are  wanting  in  the  vessels  composing  the  plexiform  network  in 
which  the  lymphatics  usually  originate  on  the  surface  of  the  body. 

Origin  of  Lymphatics. — The  finest  visible  lymphatic  vessels  (lymphatic  capil- 
laries) form  a  plexiform  network  in  the  tissues  and  organs,  and  they  consist  of  a 
single  layer  of  endothelial  plates,  with  more  or  less  sinuous  margins.  These  ves- 
sels commence  in  an  intercommunicating  system  of  clefts  or  spaces  in  the  connec- 
tive tissue  of  the  different  organs,  which  have  no  complete  endothelial  lining.  They 
have  been  named  the  rootlets  of  the  lymphatics,  and  are  identical  with  the  spaces 
in  which  the  connective-tissue  corpuscles  are  contained.  This  then  is  properly 
regarded  as  one  method  of  their  commencement,  when  the  lymphatic  vessels  are 
apparently  continuous  with  spaces  in  the  connective  tissue,  and  Klein  has  described 
and  figured  a  direct  communication  between  these  spaces  and  the  lymphatic  vessel.1 
But  the  lymphatics  have  also  other  modes  of  origin,  for  the  intestinal  lacteals 
commence  by  closed  extremities,  though  some  observers  believe  that  the  closed 
extremity  is  continuous  with  a  minute  network  contained  in  the  substance  of  the 
villus,  through  which  the  lacteal  is  connected  with  the  epithelial  cells  covering  it. 
Again,  it  seems  now  to  be  conclusively  proved  that  the  serous  membranes  present 
stomata  or  openings  between  the  epithelial  celis  (Fig.  62)  by  which  there  is  an 
open  communication  with  the  lymphatic  system,  and  through  which  the  lymph  is 
thought  to  be  pumped  by  the  ultimate  dilatation  and  contraction  of  the  serous 
surface,  due  to  the  movements  of  respiration  and  circulation,2  so  that  the  serous 
and  synovial  sacs  may  be  regarded,  in  a  certain  sense,  as  large  lymph-cavities  or 
sinuses.  Von  Recklinghausen  was  the  first  to  observe  the  passage  of  milk  and 
other  colored  fluids  through  these  stomata  on  the  peritoneal  surface  of  the 
central  tendon  of  the  diaphragm.  Again,  in  most  glandular  structures  the 
lymphatic  capillaries  have  a  lacunar  origin.  Here  they  begin  in  irregular  clefts  or 
spaces  in  the  tissue  of  the  part ;  occupying  the  penetrating  connective  tissue  and 
surrounding  the  lacunae  or  tubules  of  the  gland,  and  in  many  places  separating  the 
capillary  network  from  the  alveolus  or  tubule,  so  that  the  interchange  between  the 
blood  and  the  secreting  cells  of  the  part  must  be  carried  on  through  this  lymph- 
space  or  lacuna.  Closely  allied  to  this  is  the  mode  of  origin  of  lymphatics  in 
perivascular  and  perineural  spaces.  Sometimes  a  minute  artery  may  be  seen  to  be 
ensheathed  for  a  certain  distance  by  a  lymphatic  capillary  vessel,  which  is 
often  many  times  wider  than  a  blood-capillary.  These  are  known  as  perivascular 
lymphatics. 

1  AtlaK  of  Histology,  pi.  viii.  fig.  xiv. 

2  The  resemblance  between  lymph  and  serum  led  Hewson  long  ago  to  regard  the  serous  cavities 
as  sacs  into  which  the  lymphatics  open.     Recent  microscopic  discoveries  confirm  this  opinion  in  a 
very  interesting  manner. 


THE    VASCULAR    SYSTE^f. 


87 


Terminations  of  Lymphatics. — The  lymphatics,  including  the  lacteals.  discharge 
their  contents  into  the  veins  at  two  points  :  namely,  at  the  angles  of  junction 
of  the  subclavian  and  internal  jugular  veins:  on  the  left  side  by  means  of  the 
thoracic  duct,  and  on  the  right  side  by  the  right  lymphatic  duct.  (See  description 
of  lymphatics  on  a  subsequent  page.) 

Lymphatic  glands  (conglobate  gland*)  are  small  oval  or  bean-shaped  bodies, 
situated  in  the  course  of  lymphatic  and  lacteal  vessels,  so  that  the  lymph  and  chyle 
pass  through  them  on  their  way  to  the  blood.  They  generally  present  on  one 
side  a  slight  depression — the  hilum — through  which  the  blood-vessels  enter  and 
leave  the  interior.  The  efferent  lymphatic  vessel  also  emerges  from  the  gland  at 
this  spot,  while  the  afferent  vessels  enter  the  organ  at  different  parts  of  the 
periphery.  On  section  (Fig.  63),  a  lymphatic  gland  displays  two  different  struc- 
tures: an  external,  of  lighter  color — the  cortical;  and  an  internal,  darker — the 
medullary.  The  cortical  structure  does  not  form  a  complete  investment,  but  is 
deficient  at  the  hilum,  where  the  medullary  portion  reaches  the  surface  of  the 
gland;  so  that  the  efferent  vessel  is  derived  directly  from  the  medullary  structure, 
while  the  afferent  vessels  empty  themselves  into  the  cortical  substance. 

Lymphatic  glands  consist  of  (1)  a  fibrous  envelope,  or  capsule^  from  which  a 
framework  of  processes  (trabecuke)  proceed  inward,  dividing  the  gland  into  open 
spaces  (alveoli)  freelv  communicating  with  each  other ;  (2)  a  quantity  of  adenoid 
tissue  occupying  these  spaces  without  completely  filling  them ;  (3)  a  free  supply 
of  blood-vessels,  which  are  supported  on  the  trabeculse ;  and  (4)  the  afferent  and 
efferent  vessels.  Little  is  known  of  the  nerves,  though  Kb'lliker  describes  some 
fine  nervous  filaments  passing  into  the  hilum. 

The  capsule  is  composed  of  a  layer  of  connective  tissue,  and  from  its  internal 
surface  are  given  off  a  number  of  membranous  septa  or  lamellae,  consisting,  in  man, 
of  connective  tissue,  with  a  small  admixture  of  muscular  fibre-cells ;  but  in  many 
of  the  lower  animals  composed  almost  entirely  of  involuntary  muscular  fibre. 
They  pass  inward,  radiating  toward  the  centre  of  the  gland,  for  a  certain  distance ; 
that  is  to  say,  for  about  one-third  or  one-fourth  of  the  space  between  the  circum- 
ference and  the  centre  of  the  gland. 
They  thus  divide  the  outer  part  of  its 
interior  into  a  number  of  oval  compart- 
ments or  alveoli  (Fig.  63).  This  is  the 
cortical  portion  of  the  gland.  After 
having  penetrated  into  the  gland  for 
some  distance,  these  septa  break  up  into 
a  number  of  smaller  trabeculae,  which 
form  flattened  bands  or  cords,  interlacing 
with  each  other  in  all  directions,  forming 
in  the  central  part  of  the  organ  a  num- 
ber of  intercommunicating  spaces,  also 
called  alveoli.  This  is  the  medullary 
portion  of  the  gland,  and  the  spaces  or 
alveoli  in  it  not  only  freely  communicate 
with  each  other,  but  also  with  the  alveoli 
of  the  cortical  portion.  In  these  alveoli 
or  spaces  (Fig.  64)  is  contained  the 
proper  gland-substance  or  lymphoid 
tissue.  The  gland-pulp  does  not,  how- 
ever, completely  fill  the  alveolar  spaces,  but  leaves,  between  its  outer  margin  and 
the  trabeculne  forming  the  alveoli  a  channel  or  space  of  uniform  width  through- 
out. This  is  termed  the  lymph-path  or  lymph-sinus  (Fig.  66).  Running  across  it 
are  a  number  of  trabeculae  of  retiform  connective  tissue,  the  fibres  of  which  are, 
for  the  most  part,  covered  by  ramified  cells.  This  tissue  appears  to  serve  the 
purpose  of  maintaining  the  gland-pulp  in  the  centre  of  the  space  in  its  proper 
position. 


FIG.  63. — Section  of  small  lymphatic  gland,  half- 
diagrammatioally  given,  witn  the  course  of  the 
Ivmph.  a.  The  envelope.  b.  Septa  between  the  fol- 
licles or  alveoli  of  the  cortical  part.  c.  System  of 
septa  of  the  medullary  portion,  down  to  the  hilum. 
d.  The  follicles,  e.  Lymph-tubes  of  the  medullary 
mass.  /.  Different  lymphatic  streams  which  sur- 
round the  follicles,  and  flow  through  the  interstices 
of  the  medullary  portion,  g.  Confluence  of  these 
passing  through  the  efferent  vessel,  ft,  at  the  hilum. 


88  GENERAL   ANATOMY. 

On  account  of  the  peculiar  arrangement  of  the  framework  of  the  organ,  the 


FIG.  65. — From  the  medullary  substance  of  an 
inguinal  gland  of  the  ox.    (After  His.)    a.  Lymph- 
tube,  with  its  complicated  system  of  vessels,    b. 
Fir,.  64.-Folliclc  from  a  lymphatic  gland  of  the  dog,       Retinacula  stretched  between  the  tube  and  the 
in  vertical  section,    a.  Reticular  sustentacular  substance      |ePta-     c-    Portion   of    another  lymph-tube,     d. 
of  the  more  external  portion,  6,  of  the  more  internal,  and      >.epta. 
c,  of  the  most  external  and  most  finely  webbed  part  on  the 
surface  of  the  follicle,    d.  Origin  of  a  large  lymph-tube. 
e.  Of  a  smaller  one.    /.  Capsule,    g.  Septa,    h.  Vasafferens. 
i.  Investing  space  o'f  the  follicle,  with  its  retinacula.    k. 
One  of  the  divisions  of  the  septa.    1,1.  Attachment  of  the 
lymph-tubes  to  the  septa. 

gland-pulp  in  the  cortical  portion  is  disposed  in  the  form  of  nodules,  and  in  the 

medullary  part  in  the  form  of 
rounded  cords.  It  consists  of 
ordinary  lymphoid  tissue,  be- 
ing made  up  of  a  delicate  re- 
ticulum  of  retiform  tissue, 
which  is  continuous  with  that 
in  the  lymph-paths,  but  mark- 
ed off  from  it  by  a  closer  retic- 
ulation ;  in  its  meshes  are 
closely  packed  lymph-corpus- 
cles, traversed  by  a  dense 
plexus  of  capillary  blood-ves- 
sels. 

The  afferent  vessels,  as 
above  stated,  enter  at  all  parts 
of  the  periphery  of  the  gland, 
and  after  branching  and  form- 
ing a  dense  plexus  in  the  sub- 
stance of  the  capsule,  open 
into  the  lymph-sinuses  of  the  cortical  part.  In  doing  this  they  lose  all  their 
coats  except  their  endothelial  lining,  which  is  continuous  with  a  layer  of  similar 
cells  lining  the  lymph-paths.  In  like  manner  the  efferent  vessel  commences 
from  the  lymph-sinuses  of  the  medullary  portion.  The  stream  of  lymph  carried 
to  the  gland  by  the  afferent  vessel  thus  passes  through  the  plexus  in  the  capsule 
to  the  lymph-paths  of  the  cortical  portion,  where  it  is  exposed  to  the  action  of  the 
gland-pulp ;  flowing  through  these,  it  enters  the  paths  or  sinuses  of  the  medullary 
portion,  and  finally  emerges  from  the  hilum  by  means  of  the  efferent  vessel.  The 
stream  of  lymph  in  its  passage  through  the  lymph-sinuses  is  much  retarded  by 
the  presence  of  the  reticulum.  Hence  morphological  elements,  either  normal  or 


FIG.  66. — Section  of  lymphatic  gland  tissue,  a.  Trabeculee.  b. 
Small  artery  in  substance  of  same.  c.  Lymph-paths,  d.  Lymph- 
corpuscles,  e.  Capillary  plexus. 


THE   SKIN  AND    ITS   APPENDAGES. 


89 


morbid,  are  easily  arrested  and  deposited  in  the  sinuses.  This  is  a  matter  of  con- 
siderable importance  in  connection  with  the  subject  of  poisoned  wounds  and  the 
absorption  of  the  poison  by  the  lymphatic  system,  since  by  this  means  septic 
organisms  carried  along  the  lymphatic  vessels  may  be  arrested  in  the  lymph-sinuses 
of  the  gland  tissue,  and  thus  be  prevented  from  entering  the  general  circulation. 
The  arteries  of  the  gland  enter  at  the  hilum,  and  either  pass  at  once  to  the  gland- 
pulp,  to  break  up  into  a  capillary  plexus,  or  else  run  along  the  trabeculge,  partly 
to  supply  them  and  partly  running  across  the  lymph-paths  to  assist  in  forming  the 
capillary  plexus  of  the  gland-pulp.  This  plexus  traverses  the  lymphoid  tissue, 
but  does  not  pass  into  the  lymph-sinuses.  From  it  the  veins  commence,  and 
emerge  from  the  organ  at  the  same  place  as  that  at  which  the  artery  enters. 

THE  SKIN  AND  ITS  APPENDAGES. 

The  skin  (Fig.  67)  is  the  principal  seat  of  the  sense  of  touch,  and  may  be 
regarded  as  a  covering  for  the  protection  of  the  deeper  tissues ;  it  is  also  an  im- 
portant excretory  and  absorbing  organ.  It  consists  principally  of  a  layer  of  vascular 
connective  tissue,  named  the  derma,  corium,  or  cutis  vercij  and  an  external  covering 
of  epithelium,  termed  the  epidermis  or  cuticle.  On  the  surface  of  the  former  layer 


Superficial 
layers 
Rete 

Xucosum 


Epidermif 

or 
Cuticle 

Derma 


FIG.  67. — A  sectional  view  of  the  skin  (magnified). 

are  the  sensitive  papilla? ;  and  within,  or  imbedded  beneath  it,  are  certain  organs 
with  special  functions — namely,  the  sweat-glands,  hair-follicles^^  sebaceous  glands. 
The  epidermis  or  cuticle  (scarf-skin.  Fig.  68)  is  an  epithelial  structure  belong- 
ing to  the  class  of  stratified  epithelium.  It  is  accurately  moulded  on  the  papillary 
layer  of  the  derma.  It  forms  a  defensive  covering  to  the  surface  of  the  true  skin, 
and  limits  the  evaporation  of  watery  vapor  from  its  free  surface.  It  varies  in 
thickness  in  different  parts.  In  some  situations,  as  in  the  palms  of  the  hands  and 
soles  of  the  feet,  it  is  thick,  hard,  and  horny  in  texture.  This  may  be  partly  due 


90 


GENERAL    ANATOMY. 


to  the  fact  that  these  parts  are  exposed  to  intermittent  pressure,  but  that  this  is 
not  the  only  cause  is  proved  by  the  fact  that  the  condition  exists  to  a  very  consid- 
erable extent  at  birth.  The  more  superficial  layer  of  cells,  called  the  horny  layer 


FIG.  68.— Microscopic  section  of  skin,  showing  the  epidermis  and  derma;  a  hair  in  its  follicle  :  the  erector 
pili  muscle :  sebaceous  and  sudoriferous  glands. 

(stratum  corneuni),  may  be  separated  by  maceration  from  the  deeper  layers,  which 
are  called  the  rete  mucosum,  and  which  consist  of  several  layers  of  differently 
shaped  cells.  The  free  surface  of  the  epidermis  is  marked  by  a  network  of  linear 
furrows  of  variable  size,  marking  out  the  surface  into  a  number  of  spaces  of  polyg- 
onal or  lozenge-shaped  form.  Some  of  these  furrows  are  large,  as  opposite  the 
flexures  of  the  joints,  and  correspond  to  the  folds  in  the  derma  produced  by  their 
movements.  In  other  situations,  as  upon  the  back  of  the  hand,  they  are  exceed- 
ingly fine,  and  intersect  one  another  at  various  angles ;  upon  the  palmar  surface 
of  the  hand  and  fingers  and  upon  the  sole  of  the  foot  these  lines  are  very  distinct 
and  are  disposed  in  curves.  They  depend  upon  the  large  size  and  peculiar  arrange- 
ment of  the  papillae  upon  which  the  epidermis  is  placed.  The  deep  surface  of  the 
epidermis  is  accurately  moulded  upon  the  papillary  layer  of  the  derma,  each  papilla 
being  invested  by  its  epidermic  sheath ;  so  that  when  this  layer  is  removed  by 
maceration,  it  presents  on  its  under  surface  a  number  of  pits  or  depressions  corre- 
sponding to  the  elevations  in  the  papillae,  as  well  as  the  ridges  left  in  the  intervals 
between  them.  Fine  tubular  prolongations  are  continued  from  this  layer  into  the 
ducts  of  the  sudoriferous  and  sebaceous  glands. 

In  structure,  the  epidermis  consists  of  several  layers  of  epithelial  cells  agglu- 
tinated together  and  having  a  laminated  arrangement.  These  several  layers  may 
be  described  as  composed  of  four  different  strata  from  within  outward :  (1)  The 
rete  Malpiyldi,  composed  of  several  layers  of  epithelial  cells,  of  which  the  deepest 
layer  is  elongated  in  figure  and  placed  perpendicularly  on  the  surface  of  the 
corium,  their  lower  ends  being  denticulate,  to  fit  into  corresponding  denticula- 
tions  of  the  true  skin ;  while  the  succeeding  laminae  consist  of  cells  of  a  more 
rounded  or  polyhedral  form,  the  contents  of  which  are  soft,  opaque,  granular,  and 
soluble  in  acetic  acid.  They  are  often  marked  on  their  surfaces  with  ridges  and 
furrows,  and  are  covered  with  numerous  fibrils,  which  connect  the  surfaces  of  the 
cells  :  these  are  known  as  prickle  cells  (see  page  43).  (2)  Immediately  superficial 
co  these  is  a  single  layer  of  flattened,  spindle-shaped  cells,  the  granular  layer,  Avhich 
contain  granules  that  become  deeply  stained  in  haematoxylin,  and  are  composed  of 
a  substance  termed  eleidin.  They  are  supposed  to  be  cells  in  a  transitional 
stage  between  the  protoplasmic  cells  of  the  rete  Malpighii  and  the  horny 
cells  of  the  superficial  layers.  (3)  Above  this  layer  the  cells  become  indis- 
tinct, and  appear,  in  sections,  to  form  a  homogeneous  or  dimly  striated  mem- 
brane composed  of  closely-packed  scales,  in  which  traces  of  a  flattened  nucleus 


THE   8KIN   AND    ITS   APPENDAGE v  91 

may  be  found.  It  is  called  the  stratum  luridnm.  (4)  As  these  cells  suc- 
cessively approach  the  surface  by  the  development  of  fresh  layers  from  beneath, 
they  assume  a  flattened  form  from  the  evaporation  of  their  fluid  contents, 
and  consist  of  many  layers  of  horny  epithelial  scales  in  which  no  nucleus  is 
discernible,  forming  the  stratum  corneum.  These  cells  apparently  become 
changed  in  their  chemical  composition,  as  they  are  now  unaffected  by  acetic  acid. 
The  deepest  layer  of  the  rete  Malpighii  is  separated  from  the  papillae  by  an 
apparently  homogeneous  basement  membrane,  which  is  most  distinctly  brought 
into  view  in  specimens  prepared  with  chloride  of  gold.  This,  according  to  Klein, 
is  merely  the  deepest  portion  of  the  epithelium,  and  is  "  made  up  of  the  basis  of 
the  individual  cells,  which  have  undergone  a  chemical  and  morphological  altera- 
tion." The  black  color  of  the  skin  in  the  negro  and  the  tawny  color  among 
some  of  the  white  races  is  due  to  the  presence  of  pigment  in  the  cells  of  the 
cuticle.  This  pigment  is  more  especially  distinct  in  the  cells  of  the  deeper  layer 
or  rete  mucosum,  and  is  similar  to  that  found  in  the  cells  of  the  pigmentary  layer 
of  the  retina.  As  the  cells  approach  the  surface  and  desiccate,  the  color  becomes 
partially  lost. 

The  derma,  corium,  or  cutis  vera,  is  tough,  flexible,  and  highly  elastic,  in  order 
to  defend  the  parts  beneath  frcm  violence. 

It  varies  in  thickness,  from  a  quarter  of  a  line  to  a  line  and  a  half,  in  differ- 
ent parts  of  the  body.  Thus  it  is  very  thick  in  the  palms  of  the  hands  and  soles 
of  the  feet ;  thicker  on  the  posterior  aspect  of  the  body  than  the  front,  and  on  the 
outer  than  the  inner  side  of  the  limbs.  In  the  eyelids,  scrotum,  and  penis  it  is 
exceedingly  thin  and  delicate.  The  skin  generally  is  thicker  in  the  male  than  in 
the  female,  and  in  the  adult  than  in  the  child. 

The  corium  consists  of  fibrous  connective  tissue,  with  a  large  admixture  of 
elastic  fibres  and  numerous  blood-vessels,  lymphatics,  and  nerves.  The  fibro- 
areolar  tissue  forms  the  framework  of  the  cutis.  and  is  differently  arranged  in 
different  parts,  so  that  it  is  usual  to  describe  it  as  consisting  of  two  layers :  the 
deeper  or  reticular  layer,  and  the  superficial  or  papillary  layer,  t  nstriped 
muscular  fibres  are  found  in  the  superficial  layers  of  the  corium,  wherever  hairs 
are  found ;  and  in  the  subcutaneous  areolar  tissue  of  the  scrotum,  penis,  labia 
majora  of  the  female,  and  the  nipples.  In  the  latter  situation  the  fibres  are 
arranged  in  bands,  closely  reticulated  and  disposed  in  superimposed  laminae. 

The  reticular  layer  consists  of  strong  interlacing  fibrous  bands,  composed 
chiefly  of  the  white  variety  of  fibrous  tissue,  but  containing,  also,  some  fibres  of 
the  yellow  elastic  tissue,  which  vary  in  amount  in  different  parts,  and  connective- 
tissue  corpuscles,  which  are  often  to  be  found  flattened  against  the  white  fibrous 
tissue-bundles.  Toward  the  attached  surface  the  fasciculi  are  large  and  coarse, 
and  the  areolse  which  are  left  by  their  interlacement  are  large,  and  occupied  by 
adipose  tissue  and  sweat-glands.  Below  this  the  elements  of  the  skin  become 
gradually  blended  with  the  subcutaneous  areolar  tissue,  which,  except  in  a  few 
situations,  contains  fat.  Toward  the  free  surface  the  fasciculi  are  much  finer, 
and  their  mode  of  interlacing  close  and  intricate. 

The  papillary  layer  is  situated  upon  the  free  surface  of  the  reticular  layer ;  it  con- 
sists of  numerous  small,  highly  sensitive,  or  vascular  eminences,  the  papilla',  which 
rise  perpendicularly  from  its  surface.  The  papillae  are  conical-shaped  eminences, 
having  a  round  or  blunted  extremity.occasionally  divided  into  two  or  more  parts  and 
connected  by  a  thin  base  with  the  free  surface  of  the  corium.  Their  average  length 
is  about  j-^  of  an  inch,  and  they  measure  at  their  base  -^i-^  of  an  inch  in  diameter. 
On  the  genera]  surface  of  the  body,  more  especially  in  those  parts  which  are  endowed 
with  slight  sensibility,  they  are  few  in  number,  short,  exceedingly  minute,  and 
irregularly  scattered  over  the  surface ;  but  in  some  situations,  as  upon  the  palmar 
surface  of  the  hands  and  fingers,  upon  the  plantar  surface  of  the  feet  and  toes, 
and  around  the  nipple,  they  are  long,  of  large  size,  closely  aggregated  together, 
and  arranged  in  parallel  curved  lines,  forming  the  elevated  ridges  seen  on  the  free 
surface  of  the  epidermis.  In  these  ridges  the  larger  papillae  are  arranged  in  a 


92  GENERAL    ANATOMY. 

double  row,  with  smaller  papillae  between  them ;  and  these  rows  are  subdivided 
into  small  square-shaped  spaces  by  short  transverse  furrows,  regularly  disposed ; 
in  the  centre  of  each  of  these  transverse  furrows  is  the  minute  orifice  of  the  duct 
of  a  sweat-gland.  No  papillae  exist  in  the  grooves  between  the  ridges.  In 
structure  the  papillae  consist  of  very  small  and  closely  interlacing  bundles  of 
finely  fibrillated  tissue,  with  a  few  elastic  fibres.  The  majority  of  the  papillae  con- 
tain loops  of  blood-vessels,  and  these  are  known  as  the  vascular  papillae  in  contra- 
distinction to  others  which  usually  possess  no  blood-vessels,  but  contain  tactile  cor- 
puscles. These  tactile  papillae  are  most  numerous  in  the  derma  of  the  palm  of  the 
hand  and  of  the  sole  of  the  foot,  but  occur  also  in  smaller  numbers  on  the  back 
of  the  hand  and  foot,  on  the  flexor  surface  of  the  forearm,  and  on  the  nipple. 

The  arteries  supplying  the  skin  form  a  network  in  the  subcutaneous  tissue, 
from  which  branches  are  given  off  to  supply  the  sweat-glands,  the  hair-follicles, 
and  the  fat.  Other  branches  are  given  off  which  form  a  plexus  immediately 
beneath  the  corium  ;  from  this  fine  capillary  vessels  pass  into  the  papillae,  forming, 
in  the  smaller  papillae,  a  single  capillary  loop,  but  in  the  larger  a  more  or  less 
convoluted  vessel.  There  are  numerous  lymphatics  supplied  to  the  skin  which 
form  two  networks,  superficial  and  deep,  communicating  with  each  other  and  with 
those  of  the  subcutaneous  tissue  by  oblique  branches.  They  originate  in  the  cell- 
spaces  of  the  tissue. 

The  nerves  of  the  skin  terminate  partly  in  the  epidermis  and  partly  in  the  cutis 
vera.  The  former  form  a  dense  plexus  in  the  superficial  layer  of  the  corium, 
which  extends  horizontally  and  gives  off  numerous  fibrils ;  these  are  prolonged 
into  the  epidermis,  and  terminate  between  the  cells,  either  in  bulbous  extremities 
or  in  a  network  ;  or,  according  to  some  observers,  in  the  deep  epithelial  cells  them- 
selves. The  latter  terminate  in  end-bulbs,  touch-corpuscles,  or  Pacinian  bodies 
in  the  manner  already  described ;  and,  in  addition  to  these,  a  considerable 
number  of  fibrils  are  distributed  to  the  hair-follicles,  which  are  said  to  entwine 
the  follicle  in  a  circular  manner.  Other  nerve-fibres  are  supplied  to  the  plain 
muscular  tissues  of  the  hair-muscles  (arrectores  pili)  and  to  the  muscular  coat  of 
the  blood-vessels.  These  are  probably  non-medullated  fibres. 

The  appendages  of  the  skin  are  the  nails,  the  hairs,  the  sudoriferous  and 
sebaceous  glands,  and  their  ducts. 

The  nails  and  hairs  are  peculiar  modifications  of  the  epidermis,  consisting 
essentially  of  the  same  cellular  structure  as  that  tissue. 

The  nails  are  flattened,  elastic  structures  of  a  horny  texture,  placed  upon  the 
dorsal  surface  of  the  terminal  phalanges  of  the  fingers  and  toes.  Each  nail  is 
convex  on  its  outer  surface,  concave  within,  and  is  implanted  by  a  portion,  called 
the  root,  into  a  groove  in  the  skin  ;  the  exposed  portion  is  called  the  body,  and  the 
anterior  extremity  the  free  edge.  The  nail  has  a  very  firm  adhesion  to  the  cutis, 
being  accurately  moulded  upon  its  surface,  as  the  epidermis  is  in  other  parts.  The 
part  of  the  cutis  beneath  the  body  and  root  of  the  nail  is  called  the  matrix,  because 
it  is  the  part  from  which  the  nail  is  produced.  Corresponding  to  the  body  of  the 
nail,  the  matrix  is  thick,  and  covered  with  large,  highly  vascular  papillae,  arranged 
in  longitudinal  rows,  the  color  of  which  is  seen  through  the  transparent  tissue. 
Behind  this,  near  the  root  of  the  nail,  the  papillae  are  small,  less  vascular,  and 
have  no  regular  arrangement,  and  here  the  tissue  of  the  nail  is  somewhat  more 
opaque ;  hence  this  portion  is  of  a  whiter  color,  and  is  called  the  lunula  on 
account  of  its  shape. 

The  cuticle,  as  it  passes  forward  on  the  dorsal  surface  of  the  finger  or  toe,  is 
attached  to  the  surface  of  the  nail,  a  little  in  advance  of  its  root ;  at  the  extremity 
of  the  finger  it  is  connected  with  the  under  surface  of  the  nail  a  little  behind  its 
free  edge.  The  cuticle  and  horny  substance  of  the  nail  (both  epidermic  structures) 
are  thus  directly  continuous  with  each  other.  The  nails,  in  structure,  consist  of 
cells  having  a  laminated  arrangement,  and  these  are  essentially  similar  to  those 
composing  the  epidermis.  The  deepest  layer  of  cells,  which  lie  in  contact  with 
the  papillae  of  the  matrix,  are  of  elongated  form,  arranged  perpendicularly  to  the 


THE   SKIS   AXD    ITS   APPENDAGES. 


93 


surface ;  those  which  succeed  them  are  of  a  rounded  or  polygonal  form, 
the  more  superficial  ones  becoming  broad,  thin,  and  flattened,  and  so 
closely  compacted  as  to  make  the  limits  of  each  cell  very  indistinct. 
It  is  by  the  successive  growth  of  new  cells  at  the  root  and  under  surface 
of  the  body  of  the  nail  that  it  advances  forward  and  maintains  a  due  thickness, 
whilst,  at  the  same  time,  the  growth  of  the  nail  in  the  proper  direction  is  secured. 
As  these  cells  in  their  turn  become  displaced  by  the  growth  of  new  cells,  they 
assume  a  flattened  form,  their  nuclei  become  indistinct,  and  they  finally  become 
closely  compacted  together  into  a  firm,  dense,  horny  texture.  In  chemical  com- 
position the  nails  resemble  epidermis.  According  to  Mulder,  they  contain  a 
somewhat  larger  proportion  of  carbon  and  sulphur. 

The  hairs  are  peculiar  modifications  of  the  epidermis,  and  consist  essentially 
of  the  same  structure  as  that  membrane.  They  are  found  on  nearly  every  part  of 
the  surface  of  the  body,  excepting  the  palms  of  the  hands,  soles  of  the  feet,  and 
the  penis.  They  vary  much  in  length,  thickness,  and  color  in  different  parts  of 
the  body  and  in  different  races  of  mankind.  In  some  parts,  as  in  the  skin  of  the 
eyelids,  they  are  so  short  as  not  to  project  beyond  the  follicles  containing  them ; 
in  other  parts,  as  upon  the  scalp,  they  are  of  considerable  length :  again,  in  other 
parts,  as  the  eyelashes,  the  hairs  of  the  pubic  region,  and  the  male  whiskers  and 
beard,  they  are  remarkable  for  their  thickness.  The  hairs  generally  present  a 
cylindrical  or  more  or  less  flattened  form  and  a  reniform  outline  upon  transverse 
section. 

A  hair  consists  of  a  root,  the  part  implanted  in  the  skin  ;  the  shaft  or  stem,  the 
portion  projecting  from  its  surface:  and  the  point. 

The  root  of  the  hair  presents  at  its  extremity  a  bulbous  enlargement,  which  is 
whiter  in  color  and  softer  in  texture  than  the  shaft,  and  is  lodged  in  a  follicular 
involution  of  the  epidermis  called  the  hair-follicle.  When  the  hair  is  of  consider- 
able length  the  follicle  extends  into  the  subcutaneous  areolar  tissue.  The  hair- 
follicle  commences  on  the  surface  of  the  skin  with  a  funnel-shaped  opening,  and 
passes  inward  in  an  oblique  direction  to  become  dilated  at  its  deep  extremity,  to 
correspond  with  the  bulbous  condition  of  the  hair  which 
it  contains.  It  has  opening  into  it,  near  its  free  ex- 
tremity, .the  orifices  of  the  ducts  of  one  or  more  seba- 
ceous glands  (Fig.  68).  At  the  bottom  of  each  hair- 
follicle  is  a  small  conical  vascular,  eminence  or  papilla, 
similar  in  every  respect  to  those  found  upon  the  sur- 
face of  the  skin  :  it  is  continuous  with  the  dermic  layer 
of  the  follicle,  is  highly  vascular  and  supplied  with 
nervous  fibrils :  this  is  the  part  through  which  mate- 
rial is  supplied  for  the  production  and  constant  growth 
of  the  hair.  In  structure  the  hair-follicle  consists 
of  two  coats — an  outer  or  dermic,  and  an  inner  or 
epidermic. 

The  outer  or  dermic  coat  is  formed  mainly  of  fibrous 
tissue :  it  is  continuous  with  the  corium,  is  highly 
vascular,  and  supplied  by  numerous  minute  nervous 
filaments.  It  consists  of  three  layers  (Fig.  69).  The 
most  internal,  next  the  cuticular  lining  of  the  follicle, 
consists  of  a  hyaline  basement-membrane,  having  a 
glassy,  transparent  appearance,  which  is  well  marked 
in  the  larger  hair-follicles,  but  is  not  very  distinct  in 
the  follicles  of  minute  hairs.  It  is  continuous  with  the 
basement-membrane  of  the  surface  of  the  corium. 
External  to  this  is  a  layer  of  spindle-shaped  cells, 
arranged  in  a  circular  manner  around  the  follicle  and 
imbedded  in  a  somewhat  fibrous  matrix,  but  reaching  only  as  high  as  the 
entrance  of  the  ducts  of  the  sebaceous  glands.  Externally  is  a  thick  layer  of 


FIG.  69. — Transverse  section 
of  hair-follicle.  1.  Dermic  coat 
of  foUicle.  2.  Epidermic  coat  or 
root-sheath,  a.  Outer  layer  of 
dermic  coat,  with  blood-vessels. 
6,6.  Vessels  cut  across,  c.  Middle 
layer,  d.  Inner  or  hyaline  layer. 
e.  Outer  root-sheath."  /,  g.  Inner 
root-sheath,  h.  Cuticle  of  root- 
sheath,  i.  Hair.  (From  Quain's 
Anatomy,  Biesiadecki.) 


94  GENERAL    ANATOMY. 

connective  tissue,  arranged  in  longitudinal  bundles,  in  which  are  contained  the 
blood-vessels  and  nerves. 

The  inner  or  epidermic  layer  is  closely  adherent  to  the  root  of  the  hair,  so 
that  when  the  hair  is  plucked  from  its  follicle  this  layer  most  commonly  adheres 
to  it  and  forms  what  is  called  the  root-sheath.  It  consists  of  two  strata,  named 
respectively  the  outer  and  inner  root-sheath  ;  the  former  of  these  corresponds  with 
the  Malpighian  layer  of  the  epidermis,  and  resembles  it  in  the  rounded  form  and 
soft  character  of  its  cells ;  at  the  bottom  of  the  hair-follicle  these  cells  become  con- 
tinuous with  those  of  the  root  of  the  hair.  The  inner  root-sheath  consists  of  a 
delicate  cuticle  next  the  hair;  then  of  one  or  two  layers  of  horny,  flattened, 
nucleated  cells,  known  as  Huxley  s  layer ;  and  finally  of  a  single  layer  of  non- 
nucleated,  horny,  flattened  cells,  called  Henle's  layer. 

The  hair-follicle  contains  the  root  of  the  hair,  which  terminates  in  a  bulbous 
extremity,  and  is  excavated  so  as  to  exactly  fit  the  papilla  from  which  it  grows. 
The  bulb  is  composed  of  polyhedral  epithelial  cells,  which  as  they  pass  upward 
into  the  root  of  the  hair  become  elongated  and  spindle-shaped,  except  some  in  the 
centre  which  remain  polyhedral.  Some  of  these  latter  cells  contain  pigment- 
granules,  which  give  rise  to  the  color  of  the  hair.  It  occasionally  happens  that 
these  pigment-granules  completely  fill  the  cells  in  the  centre  of  the  bulb,  which 
gives  rise  to  the  dark  tract  of  pigment  often  found,  of  greater  or  less  length,  in 
the  axis  of  the  hair. 

The  shaft  of  the  hair  consists  of  a  central  pith  or  medulla,  the  fibrous  part  of 
the  hair,  and  the  cortex  externally.  The  medulla  occupies  the  centre  of  the  shaft 
and  ceases  toward  the  point  of  the  hair.  It  is  usually  wanting  in  the  fine  hairs 
covering  the  surface  of  the  body,  and  commonly  in  those  of  the  head.  It  is  more 
opaque  and  deeper  colored  when  viewed  by  transmitted  light  than  the  fibrous  part ; 
but  when  viewed  by  reflected  light  it  is  white.  It  is  composed  of  rows  of  poly- 
hedral cells,  which  contain  air-bubbles.  The  fibrous  portion  of  the  hair  consti- 
tutes the  chief  part  of  the  shaft ;  its  cells  are  elongated  and  unite  to  form  flattened 
fusiform  fibres.  Between  the  fibres  are  found  minute  spaces  which  contain  either 
pigment-granules  in  dark  hair  or  minute  air-bubbles  in  white  hair.  In  addition 
to  this  there  is  also  a  diffused  pigment  contained  in  the  fibres.  The  cells  which 
form  the  cortex  of  the  hair  consist  of  a  single  layer  which  surrounds  those  of 
the  fibrous  part ;  they  are  converted  into  thin,  flat  scales,  having  an  imbricated 
arrangement. 

Connected  with  the  hair-follicles  are  minute  bundles  of  involuntary  muscular 
fibres,  termed  arrectores  pili.  They  arise  from  the  superficial  layer  of  the  corium, 
and  are  inserted  into  the  outer  surface  of  the  hair-follicle,  below  the  entrance  of 
the  duct  of  the  sebaceous  gland.  They  are  placed  on  the  side  toward  which  the 
hair  slopes,  and  by  their  action  elevate  the  hair  (Fig.  68). 

The  sebaceous  glands  are  small,  sacculated,  glandular  organs,  lodged  in  the 
substance  of  the  corium.  They  are  found  in  most  parts  of  the  skin,  but  are  most 
abundant  in  the  scalp  and  face  :  they  are  also  very  numerous  around  the  apertures 
of  the  anus,  nose,  mouth,  and  external  ear ;  but  are  wanting  in  the  palms  of  the 
hands  and  soles  of  the  feet.  Each  gland  consists  of  a  single  duct,  more  or  less 
capacious,  which  terminates  in  a  cluster  of  small  secreting  pouches  or  saccules. 
The  sacculi  connected  with  each  duct  vary,  as  a  rule,  in  numbers  from  two  to  five, 
but,  in  some  instances,  may  be  as  many  as  twenty.  They  are  composed  of  a 
transparent,  colorless  membrane,  enclosing  a  number  of  cells.  Of  these  the  outer 
layer  or  marginal  cells  are  small,  polyhedral,  epithelial  cells,  continuous  with  the 
lining  cells  of  the  duct.  The  remainder  of  the  sac  is  filled  with  larger  cells,  con- 
taining fat,  except  in  the  centre,  where  the  cells  have  become  broken  up,  leaving 
a  cavity  containing  the  ddbris  of  cells  and  a  mass  of  fatty  matter,  which  consti- 
tutes the  sebaceous  secretion.  The  orifices  of  the  ducts  open  most  frequently  into 
the  hair-follicles,  but  occasionally  upon  the  general  surface.  On  the  nose  and  face 
the  glands  are  of  large  size,  distinctly  tabulated,  and  often  become  much  enlarged 


THE   SKIX  AXD    ITS   APPENDAGES. 


95 


from  the  accumulation  of  pent-up  secretion.     The  largest  sebaceous  glands  are 
those  found  in  the  eyelids — the  Meibomian  glands. 

The  sudoriferous  or  sweat  glands  are  the  organs  by  which  a  large  portion  of 
the  aqueous  and  gaseous  materials  are  excreted  by  the  skin.  They  are  found  in 
almost  every  part  of  this  structure,  and  are  situated  in  small  pits  in  the  deep  parts 
of  the  corium,  or,  more  frequently,  in  the  subcutaneous  areolar  tissue,  surrounded 
by  a  quantity  of  adipose  tissue.  They  are  small,  lobular,  reddish  bodies,  consist- 
ing of  a  single  convoluted  tube,  from  which  the  efferent  duct  proceeds  upward 
through  the  corium  and  cuticle,  becomes  somewhat  dilated  at  its  extremity,  and 
opens  on  the  surface  of  the  cuticle  by  an  oblique  valve-like  aperture.  The  efferent 
duct,  as  it  passes  through  the  epidermis,  presents  a  spiral  arrangement,  being 
twisted  like  a  corkscrew,  in  those  parts  where  the  epidermis  is  thick ;  where,  how- 
ever, it  is  thin,  the  spiral  arrangement  does  not  exist.  In  the  superficial  layers 
of  the  corium  the  duct  is  straight,  but  in  the  deeper  layers  it  is  convoluted  or  even 
twisted.  The  spiral  course  of  these  ducts  is  especially  distinct  in  the  thick  cuticle 
of  the  palm  of  the  hand  and  sole  of  the  foot.  The  size  of  the  glands  varies. 
They  are  especially  large  in  those  regions  where  the  amount  of  perspiration  is 
great,  as  in  the  axilla?,  where  they  form  a  thin,  mammillated  layer  of  a  reddish 
color,  which  corresponds  exactly  to  the  situation  of  the  hair  in  this  region ;  they 
are  large  also  in  the  groin.  Their  number  varies.  They  are  most  numerous  on 
the  palm  of  the  hand,  presenting,  according  to  Krause,  2800  orifices  on  a  square 
inch  of  the  integument,  and  are  rather  less  numerous  on  the  sole  of  the  foot.  In 
both  of  these  situations  the  orifices  of  the  ducts  are  exceedingly  regular,  and  cor- 
respond to  the  small  transverse  grooves  which  intersect  the  ridges  of  the  papilla?. 
In  other  situations  they  are  more  irregularly  scattered,  but  in  nearly  equal  num- 
bers, over  parts  including  the  same  extent  of  surface.  In  the  neck  and  back  they 
are  least  numerous,  their  number  amounting  to  417  on  the  square  inch  (Krause). 
Their  total  number  is  estimated  by  the  same  writer  at  2.381.248.  and,  supposing 
the  aperture  of  each  gland  to  represent  a  surface  of  Jg-  of  a  line  in  diameter,  he 
calculates  that  the  whole  of  these  glands  would  present  an  evaporating  surface  of 
about  eight  square  inches.  Each  gland  consists  of  a  single  tube  intricately  con- 
voluted, terminating  at  one  end  by  a  blind  extremity,  and  opening  at  the  other 
end  upon  the  surface  of  the  skin.  In  the  larger  glands  this  single  duct  usually 
divides  and  subdivides  dichotomously  ;  the  smaller  ducts  ultimately  terminating  in 
short  ca?cal  pouches,  rarely  anastomosing.  The  wall  of  the  duct  is  thick,  the 
width  of  the  canal  rarely  exceeding  one-third  of  its  diameter.  The  tube,  both  in 
the  gland  and  where  it  forms  the  excre- 
tory duct,  consists  of  two  layers — an 
outer,  formed  by  fine  areolar  tissue,  and 
an  inner  layer  of  epithelium.  The 
external  or  fibro-cellular  coat  is  thin, 
continuous  with  the  superficial  layer  of 
the  corium.  and  extends  only  as  high 
as  the  surface  of  the  true  skin.  The 
epithelial  lining  in  the  distal  part  of  the 
coiled  tube  of  the  gland  proper  consists 
of  a  single  layer  of  cubical  epithelium, 
supported  on  a  basement  membrane,  and 
beneath  it.  between  the  epithelium  and 
the  fibro-cellular  coat,  there  is  a  layer  of 
what  are  usually  regarded  as  plain  mus- 
cular fibres,  arranged  longitudinally.  In 
the  duct  and  the  proximal  part  of  the 
coiled  tube  of  the  gland  proper  there 
are  two  or  more  layers  of  polyhedral 
cells,  lined  on  their  internal  surface — L  e.  next  the  lumen  of  the  tube — by  a  deli- 
cate membrane  or  cuticle,  and  on  their  outer  surface  by  a  limiting  membrana 


FIG.  70. — Coiled  tube  of  a  sweat-gland  cut  in  vari- 
ous directions,  a.  Longitudinal  section  of  the  proxi- 
mal part  of  the  coiled  tube.  b.  Transverse  section  of 
the  same.  c.  Longitudinal  section  of  the  distal  part  of 
the  coiled  tube.  d.  Transverse  section  of  the  same. 
(From  Klein  and  Noble  Smith's  AUas  of  Histology.) 


96  GENERAL    ANATOMY, 

propria,  but  there  are  no  muscular  fibres.  The  epithelium  is  continuous  with  the 
epidermis  and  with  the  delicate  internal  cuticle,  which  is  all  that  is  present  in  the 
epidermic  portion  of  the  tube.  When  the  cuticle  is  carefully  removed  from  the 
surface  of  the  cutis,  these  convoluted  tubes  of  epithelium  may  be  drawn  out  and 
form  short,  thread-like  processes  on  its  under  surface. 

The  contents  of  the  smaller  sweat-glands  are  quite  fluid ;  but  in  the  larger 
glands  the  contents  are  semi-fluid  and  opaque,  and  contain  a  number  of  colored 
granules  and  cells  which  appear  analogous  to  epithelial  cells. 

SEROUS  MEMBRANES. 

The  serous  membranes  form  shut  sacs  and  may  be  regarded  as  lymph-sacs, 
from  which  lymphatic  vessels  arise  by  stomata  or  openings  between  the  epithelial 
cells  (see  page  86).  The  sac  consists  of  one  portion  which  is  applied  to  the  walls 
of  the  cavity  which  it  lines — the  parietal  portion ;  and  another  reflected  over  the 
surface  of  the  organ  or  organs  contained  in  the  cavity — the  visceral  portion. 
Sometimes  the  sac  is  arranged  quite  simply,  as  the  tunica  vaginalis  testis ;  at  others 
with  numerous  involutions  or  recesses,  as  the  peritoneum,  in  which,  nevertheless, 
the  membrane  can  always  be  traced  continuously  around  the  whole  circumference. 
The  sac  is  completely  closed,  so  that  no  communication  exists  between  the  serous 
cavity  and  the  parts  in  its  neighborhood.  An  apparent  exception  exists  in  the 
peritoneum  of  the  female ;  for  the  Fallopian  tube  opens  freely  into  the  peritoneal 
cavity  in  the  dead  subject,  so  that  a  bristle  can  be  passed  from  the  one  into  the  other. 
But  this  communication  is  closed  during  life,  except  at  the  moment  of  the  passage 
of  the  ovum  out  of  the  ovary  into  the  tube,  as  is  proved  by  the  fact  that  no  inter- 
change of  fluids  ever  takes  place  between  the  two  cavities  in  dropsy  of  the  perito- 
neum or  in  accumulation  of  fluid  in  the  Fallopian  tubes.1  The  serous  membrane 
is  often  supported  by  a  firm,  fibrous  layer,  as  is  the  case  with  the  pericardium,  and 
such  membranes  are  sometimes  spoken  of  as  "fibro-serous." 

The  various  serous  membranes  are  the  peritoneum,  lining  the  cavity  of  the 
abdomen  ;  the  two  pleurae  and  the  pericardium,  lining  the  lungs  and  heart  respec- 
tively ;  and  the  tunicae  vaginales,  surrounding  each  testicle  in  the  scrotum.2 
Serous  membranes  are  thin,  transparent,  glistening  structures,  lined  on  their  inner 
surface  by  a  single  layer  of  polygonal  or  pavement  endothelial  cells,  supported 
on  a  matrix  of  fibrous  connective  tissue,  with  networks  of  fine  elastic  fibres,  in 
which  is  contained  numerous  capillaries  and  lymphatics.  On  the  surface  of  the 
endothelium  between  the  cells  numerous  apertures  or  interruptions  are  to  be  seen. 
Some  of  these  are  stomata,  surrounded  by  a  ring  of  cubical  epithelium  (see  Fig. 
12),  and  communicating  with  a  lymphatic  capillary  (see  p.  86);  others  (pseudosto- 
mata)  are  mere  interruptions  in  the  epithelial  layer,  and  are  occupied  by  pro- 
cesses of  the  branched  connective-tissue  corpuscle  of  the  subjacent  tissue  or  by 
accumulations  of  the  intercellular  cement-substance. 

The  secretion  of  these  membranes  is,  in  most  cases,  only  sufficient  in  quantity 
to  moisten  the  surface,  but  not  to  furnish  any  appreciable  quantity  of  fluid.  When 
a  small  quantity  can  be  collected,  it  appears  to  resemble  in  many  respects  the 
lymph,  and  like  that  fluid  coagulates  spontaneously  ;  but  when  secreted  in  large 
quantities,  as  in  dropsy,  it  is  a  watery  fluid,  which  gives  a  precipitate  of  albumen 
on  boiling. 

SYNOVIAL    MEMBRANES. 

Synovial  membranes,  like  serous  membranes,  are  connective-tissue  membranes 
placed  between  two  movable  tissues,  so  as  to  diminish  friction,  as  between  the  two 
articular  ends  of  the  bones  forming  a  movable  joint ;  between  a  tendon  and  a 

1  The  communication  between  the  uterine  cavity  and  the  peritoneal  sac  is  not  only  apparent  in 
the  dead  subject,  but  is  an  anatomical  fact,  which  is  established  by  the  continuity  of  its  epithelium 
with  that  covering  the  uterus,  Fallopian  tubes,  and  nmbriic. 

2  The  arachnoid  membrane,  lining  the  brain  and  spinal  cord  was  formerly  regarded  as  a  serous 
membrane,  but  is  now  no  longer  classed  with  them,  as  it  differs  from  them  in  structure,  and  does  not 
form  a  shut  sac  as  do  the  other  serous  membranes. 


MUCOUS   MEMBRANE.  97 

bone,  where  the  former  glides  over  the  latter :  and  between  the  skin  and  various 
subcutaneous  bony  prominences. 

The  svnovial  membranes  are  composed  essentially  of  connective  tissue,  con- 
taining numerous  vessels  and  nerves.  It  was  formerly  supposed  that  these  mem- 
branes Avere  analogous  in  structure  to  the  serous  membranes,  and  consisted  of 
a  layer  of  flattened  cells  on  a  basement-membrane.  No  such  cells,  however, 
exist,  and  the  only  ones  found  on  the  surface  are  irregularly  branched 
connective-tissue  corpuscles,  similar  to  those  found  throughout  the  tissue.  Here 
and  there  these  cells  are  collected  in  patches  and  present  the  appearance  of  epi- 
thelium, but  do  not  possess  the  true  characters  of  an  endothelial  layer.  They 
are  surrounded  and  held  together  by  an  albuminous  ground-substance.  A 
further  description  of  the  svnovial  membranes  will  be  found  in  the  descriptive 
anatomy  of  the  joints. 

MUCOUS    MEMBRANE. 

Mucous  membranes  line  all  those  passages  by  which  the  internal  parts  com- 
municate with  the  exterior,  and  are  continuous  with  the  skin  at  the  various  orifices 
of  the  surface  of  the  body.  They  are  soft  and  velvety,  and  very  vascular,  and 
their  surface  is  coated  over  by  their  secretion,  mucus,  which  is  of  a  tenacious  con- 
sistence, and  serves  to  protect  them  from  the  foreign  substances  introduced  into 
the  body  with  which  they  are  brought  in  contact. 

They  are  described  as  lining  the  two  tracts — the  gastro-pulmonary  and  the 
genito-urinary :  and  all,  or  almost  all,  mucous  membranes  may  be  classed  as 
belonging  to  and  continuous  with  the  one  or  the  other  of  these  tracts. 

The  external  surfaces  of  these  membranes  are  attached  to  the  parts  which  they 
line  by  means  of  connective  tissue,  which  is  sometimes  very  abundant,  forming  a 
and  lax  bed.  so  as  to  allow  considerable  movement  of  the  opposed  surfaces 
on  each  other.  It  is  then  termed  the  submucous  tissue.  At  other  times  it  is 
exceedingly  scanty,  and  the  membrane  is  closely  connected  to  the  tissue  beneath ; 
sometimes,  for  example,  to  muscle,  as  in  the  tongue ;  sometimes  to  cartilage,  as 
in  the  larynx :  and  sometimes  to  bone,  as  in  the  nasal  fossae  and  sinuses  of  the 
skull. 

In  structure  a  mucous  membrane  is  composed  of  corium  and  epithelium.  The 
epithelium  is  of  various  forms,  including  the  squamous,  columnar,  and  ciliated, 
and  is  often  arranged  in  several  layers  (see  Fig.  11).  This  epithelial  layer  is 
supported  by  the  corium,  which  is  analogous  to  the  derma  of  the  skin,  and  con- 
sists of  connective  tissue,  either  simply  areolar  or  containing  a  greater  or  less 
quantity  of  lymphoid  tissue.  This  tissue  is  usually  covered  on  its  external  surface 
by  a  transparent  structureless  basement-membrane,  and  internally  merges  into  the 
submucous  areolar  tissue.  It  is  only  in  some  situations  that  the  basement-mem- 
brane can  be  demonstrated.  The  corium  is  an  exceedingly  vascular  membrane, 
containing  a  dense  network  of  capillaries,  which  lie  immediately  beneath  the 
epithelium,  and  are  derived  from  small  arteries  in  the  submucous  tissue. 

The  fibro-vascnlsr  layer  of  the  corium  contains,  besides  the  areolar  tissue  and 
is  unstriped  muscle-cells,  which  form  in  many  situations  a  definite  layer, 
called  the  mus>-uJ<iri*  mu<:-o»(e.  These  are  situated  in  the  deepest  part  of  the  mem- 
brane, and  are  plentifully  supplied  with  nerves.  Other  nerves  pass  to  the  epi- 
thelium and  terminate  between  the  cells.  Lymphatic  vessels  are  found  in  great 
abundance,  commencing  either  by  caecal  extremities  or  in  networks,  and  com- 
municating with  plexuses  in  the  submucous  tissue. 

Imbedded  in  the  mucous  membrane  are  found  numerous  glands,  and  project- 
ing from  it  are  processes  (villi  and  papilla)  analogous  to  the  papillae  of  the  skin. 
These  glands  and  processes,  however,  exist  only  at  certain  parts,  and  it  will  be 
more  convenient  to  defer  their  description  to  the  sequel,  where  the  parts  are 
described  as  thev  occur. 


98 


GENERA L    ANA  TOM  Y. 


SECRETING   GLANDS. 

The  secreting  glands  are  organs  whose  cells  manufacture  a  secretion  of  a  more 
or  less  definite  composition,  the  material  for  the  secretion  being  primarily  selected 
from  the  blood.  The  essential  parts,  therefore,  of  a  secreting  gland  are 
cells,  which  have  the  power  of  extracting  from  the  blood  certain  matters, 
and  in  some  cases  converting  them  into  new  chemical  compounds ;  and  blood- 
vessels, by  which  the  blood  is  brought  into  close  relationship  with  these  cells. 
The  general  arrangement  in  all  secreting  structures — that  is  to  say,  not  only 
in  secreting  glands,  but  also  in  secreting  membranes — is  that  the  cells  are 
arranged  on  one  surface  of  an  extravascular  basement-membrane,  which  supports 
them,  and  a  minute  plexus  of  capillary  vessels  ramifies  on  the  other  surface  of  the 
membrane.  The  cells  then  extract  from  the  blood  certain  constituents  which  pass 
through  the  membrane  into  the  cells,  where  they  are  prepared  and  elaborated. 
The  basement-membrane  does  not,  however,  always  exist,  and  any  free  surface 
would  appear  to  answer  the  same  purpose  in  some  cases. 

By  the  various  modifications  of  this  secreting  surface  the  different  glands  are 
formed.  This  is  generally  effected  by  an  invagination  of  the  membrane  in  different 
ways,  the  object  being  to  increase  the  extent  of  secreting  surface  within  a  given 
bulk. 

In  the  simplest  form  a  single  invagination  takes  place,  constituting  a  simple 
gland ;  this  may  be  either  in  the  form  of  an  open  tube  (Fig.  71,  A),  or  the  walls 


FIG.  71. — Diagrammatic  plan  of  varieties  of  secreting  glands.    A.  Simple  gland.    B.  Sacculated  simple  gland, 
c.  Simple  convoluted  tubular  gland.    D,  E.  Racemose  gland.    F.  Compound  tubular  gland. 

of  the  tube  may  be  dilated  so  as  to  form  a  saccule  (Fig.  71,  B).  These  are  named 
the  simple  tubular  or  saccular  glands.  Or,  instead  of  a  short  tube,  the  invagination 
may  be  lengthened  to  a  considerable  extent,  and  then  coiled  up  to  occupy  less 
space.  This  constitutes  the  simple  convoluted  tubular  gland,  an  example  of  which 
may  be  seen  in  the  sweat-glands  of  the  skin  (Fig.  71,  c). 

If,  instead  of  a  single  invagination,  secondary  invaginations  take  place  from 


SECRETING    GLANDS.  99 

the  primary  one.  as  in  Fig.  71,  D  and  E,  the  gland  is  then  termed  a  compound 
one.  These  secondary  invaginations  may  assume  either  a  saccular  or  tabular  form, 
and  so  constitute  the  two  subdivisions — the  compound  saccularor  racemose  gland, 
and  the  compound  tubular.  The  racemose  gland  in  its  simplest  form  consists  of  a 
primary  invagination  which  forms  a  sort  of  duct,  upon  the  extremity  of  which  are 
found  a  number  of  secondary  imaginations  called  saccules  or  alveoli,  as  in  Brun- 
ner's  glands  (Fig.  71.  D).  But,  again,  in  other  instances,  the  duct,  instead  of  being 
simple,  may  divide  into  branches,  and  these  again  into  other  branches,  and  so  on  ; 
each  ultimate  ramification  terminating  in  a  dilated  cluster  of  saccules,  and  thus  we 
may  have  the  secreting  surface  almost  indefinitely  extended,  as  in  the  salivary 
glands  (Fig.  71,  E).  In  the  compound  tubular  glands  the  division  of  the  pri- 
mary duct  takes  place  in  the  same  way  as  in  the  racemose  glands,  but  the  branches 
retain  their  tubular  form,  and  do  not  terminate  in  saccular  recesses,  but  become 
greatly  lengthened  out  (Fig.  71,  r).  The  best  example  of  this  form  of  gland  is  to 
be  found  in  the  kidney.  All  these  varieties  of  glands  are  produced  by  a  more  or 
less  complicated  invagination  of  a  secreting  membrane,  and  they  are  all  identical 
in  structure ;  that  is  to  say,  the  saccules  or  tubes,  as  the  case  may  be,  are  lined 
with  cells,  generally  spheroidal  or  columnar  in  figure,  and  on  their  outer  surface 
is  an  intimate  plexus  of  capillary  vessels.  The  secretion,  whatever  it  may  be,  is 
eliminated  by  the  cells  from  the  blood,  and  is  poured  into  the  saccule  or  tube,  and 
so  finds  it  way  out  through  the  primary  invagination  on  to  the  free  surface  of  the 
secreting  membrane.  In  addition,  however,  to  these  glands,  which  are  formed  by 
an  invagination  of  the  secreting  membrane,  there  are  some  few  others  which  are 
formed  by  an  evayination  or  protrusion  of  the  same  structure,  as  in  the  vascular 
fringes  of  synovial  membranes.  This  form  of  secreting  structure  is  not  nearly  so 
frequently  met  with. 


ORIGIN  AND  DEVELOPMENT  OF  THE  BODY. 


THE  whole  body  is  developed  out  of  the  ovum  (Fig.  72)  when  fertilized  by  the 
spermatozoon,  the  ovum  being  merely  a  simple  nucleated  cell.  All  the 
complicated  changes  by  which  the  various  intricate  organs  of  the  whole  body  are 
formed  from  one  simple  cell  may  be  reduced  to  two  general  processes — viz.  the 
segmentation  or  cleavage  of  cells,  and  their  differentiation.  The  former  process 
consists  in  the  splitting  of  the  nucleus  and  its  surrounding  protoplasm,  whereby 
the  original  cell  is  represented  by  two.  The  differentiation  of  cells  is  a 
term  used  to  describe  that  unknown  power  or  tendency  impressed  on  cells 
which,  to  all  methods  of  examination  now  known,  seem  absolutely  identical, 
whereby  they  grow  into  different  forms ;  so  that  (to  take  the  first  instance 
which  occurs  in  the  growth  of  the  embryo)  the  indifferent  cells  of  the  vascular  area 
are  differentiated,  some  of  them  into  blood-globules,  others  into  the  solid  tissue 
which  forms  the  blood-vessels.  The  extreme  complexity  of  the  process  of  develop- 


Zona  peUucida. 
Yolk.., 
Germinal  vesicle. 


Germinal  spot. 


Discus  prolig. 


FIG.  72.— Ovum  of  the  sow. 


FIG.  73. — Human   ovum  from  a  mid- 
dle-sized  follicle.     Magnified  350  times. 

a.  Vitelline  membrane  or  zona  peUucida. 

b.  External     border    of    the    yolk   and 
internal   border  of  the    vitelline   mem- 
brane,   c.  Germinal   vesicle   and    germi- 
nal spot. 


ment  renders  it  at  all  times  difficult  to  describe 
it  intelligibly,  and  still  more  so  in  a  work  like 
this,  where  adequate  space  and  illustration  can 
hardly  be  afforded,  having  respect  to  the  main 

purpose  of  the  work.  I  can  only  hope  to  render  the  leading  features  of  the  pro- 
cess tolerably  plain,  and  must  refer  the  reader  who  wishes  to  follow  the  various 
changes  more  minutely  to  the  special  works  on  the  subject,  and  especially  the 
works  of  Minot  and  Hertwig.  Many  of  the  statements  which  are  accepted  in 
human  embryology  are  made  only  on  the  strength  of  observations  on  the  lower 
animals,  many  stages  in  the  development  of  the  human  embryo  being  yet  unknoAvn 
to  us. 

The  ovum  is  a  small  spheroidal  body  situated  in  immature  Graafian  vesicles 
near  their  centre,  but  in  the  mature  ones  in  contact  with  the  membrana  granulosa ' 
at  that  part  of  the  vesicle  which  projects  from  the  surface  of  the  ovary.  The  cells 
of  the  membrana  granulosa  are  accumulated  round  the  ovum  in  greater  number 
than  at  any  other  part  of  the  vesicle,  forming  a  kind  of  granular  zone,  the  discus 
prolic/erus. 

The  human  ovum  (Fig.  73)  is  extremely  minute,  measuring  from  -%^  to  y|-g-  of 
an  inch  in  diameter.  It  is  a  cell  consisting  externally  of  a  transparent  envelope, 
the  zona  peUucida  or  vitelline  membrane.  Within  this,  and  in  close  contact  writh 
it,  is  the  cell-protoplasm  containing  granules  of  yolk  or  vitellus  ;  imbedded  in  the 


100 


1  See  the  description  of  the  ovary  at  a  future  page. 


FERTILIZATION    OF    OVUM.  101 

substance  of  the  yolk  is  a  small  vesicular  body,  the  germinal  vesicle  (vesicle  of  Pur- 
kinje).  the  nucleus  of  the  cell ;  and  this  contains  as  its  nucleolus  a  small  spot,  the 
/  i/t'/'ininatii'a.  or  germinal  spot  of  "NN  agner. 

The  zona  pellucida,  or  vitelline  membrane,  is  a  thick,  colorless,  transparent  mem- 
brane, which  appears  under  the  microscope  as  a  radially  striated  membrane, 
bounded  externally  and  internally  by  a  dark  outline.  The  stride  are  believed  to 
be  minute  pores,  and  are  regarded  as  the  channels  by  which  nutritive  particles 
are  admitted  into  the  interior  of  the  ovum,  and  possibly  the  way  by  which  the 
spermatozoa  gain  access  into  the  interior  of  the  ovum,  after  the  rupture  of  the 
Graafian  follicle.  The  presence  of  these  stride  has  given  to  the  zona  pellucida 
the  name  of  zona  radiata,  or  striated  membrane  of  the  ovum. 

The  yolk  consists  of  granules  or  globules  of  various  sizes  imbedded  in  a  finely 
reticulated  matrix  of  protoplasm.  The  smaller  granules  resemble  pigment;  the 
larger  granules,  which  are  in  the  greatest  number  at  the  periphery,  resemble  fat- 
globules.  In  the  human  ovum  the  number  of  granules  is  comparatively  small. 
Before  and  immediately  after  fertilization  the  cell  protoplasm  shows  distinct 
movements  of  contraction  and  expansion. 

The  germinal  vesicle  consists  of  a  fine,  transparent,  structureless  membrane 
containing  a  clear  matrix,  in  which  are  occasionally  found  a  few  granules.  It  is 
about  T^~Q  of  an  inch  in  diameter,  and  in  immature  ova  lies  nearly  in  the  centre 
of  the  yolk  ;  but  as  the  ovum  becomes  developed  it  approaches  the  surface  and 
enlarges  somewhat. 

The  germinal  spot  occupies  that  part  of  the  periphery  of  the  germinal  vesicle 
which  is  nearest  to  the  periphery  of  the  ovum.  It  is  opaque,  of  a  yellow  color, 
and  finely  granular  in  structure,  measuring  from  ^j7  to  j^T  °^  an  incn- 

The  phenomena  attending  the  discharge  of  the  ova  from  the  Graafian  vesicles, 
since  they  belong  as  much  or  more  to  the  ordinary  function  of  the  ovary  than  to 
the  general  subject  of  the  growth  of  the  body,  are  described  with  the  anatomy  of 
the  ovaries  on  a  subsequent  page. 

Either  before  its  escape  from  the  Graafian  follicle  or  immediately  after,  the 
ovum  undergoes  a  peculiar  change,  which  results  in  the  formation  of  one  or  more 
peculiar  bodies,  the  polar  globules  of  Robin,  and  also  of  another  body,  which 
is  named  the  "female  pronucleus."  The  manner  in  which  these  bodies  are 
developed  from  the  germinal  vesicle  is  briefly  as  follows :  Usually  before  the 
rupture  of  the  Graafian  follicle,  but  after  the  ovum  has  become  mature  or  ripe, 
a  portion  of  the  germinal  vesicle  with  a  small  amount  of  surrounding  protoplasm 
is  protruded  outside  the  yolk,  but  still  remains  within  the  vitelline  membrane ; 
this  forms  a  small  globular  mass  and  constitutes  the  first  polar  globule.  After 
a  time,  generally  not  till  the  ovum  has  entered  the  tube,  a  second  protrusion  of  a 
portion  of  the  germinal  vesicle  takes  place,  and  forms  a  second  polar  globule. 
We  have  thus  about  three-quarters  of  the  germinal  vesicle  extruded  from  the 
yolk  and  about  one-quarter  remaining  behind,  and  at  the  ejection  of  each  of  these 
bodies  a  visible  shrinking  of  the  yolk  takes  place.  The  portion  of  the  germinal 
vesicle  which  remains  behind  recedes  from  the  surface  toward  the  centre  of  the 
yolk  and  assumes  a  spherical  form,  and  is  now  termed  the  i%  female  pronucleus. 
All  these  changes,  it  must  be  understood,  occur  at  each  expulsion  of  an  ovum,  and 
are  quite  independent  of  fecundation. 

The  first  changes  in  the  ovum  which  take  place  at  the  time  of  conception 
appear  to  be  as  follows :  A  spermatozoon  penetrates  the  ovum,  and  comes  into 
contact  with  the  portion  of  the  germinal  vesicle  remaining  in  the  ovum.  It 
seems  as  if  this  normally  occurs  in  the  Fallopian  tube.1  but  it  is  possible  that  it 
sometimes  occurs  before  the  ovum  has  entered  the  tube,  or  after  it  has  passed 
through  the  tube  and  reached  the  cavity  of  the  uterus :  abnormally  it  may  even 

1  Many  physiologists,  as  Bischoff  and  Dr.  M.  Barry,  taught  that  the  ovum  is  fecundated  in  the 
•  i vary,  but  the  reasoning  of  Dr.  Allen  Thomson  appears  very  cogent  in  proving  that  the  usual  spot 
at  which  the  spermatozoa  meet  the  ovum  is  in  the  tube,  down  which  it  slowly  /ravels  to  the  uterus,  in 
its  course  becoming  surrounded  hy  an  albuminous  envelope  derived  from  the  walls  of  the  tube. 


102 


DE  VEL  OPMENT. 


take  place  in  the  peritoneal  cavity.  The  spermatozoon  becomes  buried  in  the 
yolk,  the  tail  disappears,  and  the  head,  which  is  really  the  nucleus  of  the  sperma- 
tozoon, constitutes  the."  male  pronucleus."  This  gradually  approaches  the  female 
pronucleus,  which  by  this  time  is  situated  in  the  centre  of  the  ovum.  As  soon  as 
they  come  into  contact  they  fuse  into  one,  and  thus  fecundation  is  effected 
(Fig.  74).' 


/.  pr.  f.  pr. 


f.pr. 


FIG.  74. — Fertilization  of  the  ovum  of  an  echinoderm.  s.  Spermatozoon,  m.  pr.  Male  pronucleus.  /.  pr.  Fe- 
male pronucleus.  1.  Accession  of  a  spermatozoon  to  the  periphery  of  the  vitellus.  2.  Its  penetration.  3.  Trans- 
formation of  the  head  of  the  spermatozoon  into  the  male  pronucleus.  4,  5.  Blending  of  the  male  and  female 
pronuclei.  (From  Quain's  Anatomy,  Selenka.) 


The  first  result  of  the  fertilization  of  the  ovum  is  its  cleavage  or  multiplica- 
tion, it  being  first  cleft  into  two  masses,  the  germinal  vesicle  having  previously 


FIG.  75. — First  stages  of  segmentation  of  a  mammalian  ovum ;  semi-diagrammatic.  (From  a  drawing  by 
Allen  Thomson.)  z.  p.  Zona  pellucida,  p.  gl.  Polar  globules,  u.  L'pper  cell.  I.  Lower  cell,  a.  Division  into 
two  spheres.  6.  Stage  of  four  spheres,  c.  Eight  spheres,  the  upper  cells  partially  enclosing  the  lower  cells. 
d.  e.  Succeeding  stages  of  segmentation,  showing  the  more  rapid  division  of  the  upper  cells  and  the  enclosure 
of  the  lower  cells  by  them. 


split  up  into  two  nuclei ;  so  that  it  now  consists  of  two  separate  masses  of  proto- 
plasm, each  containing  a  nucleus,  situated  within  the  original  vitelline  membrane, 

1  If  the  student  refers  to  the  development  of  the  generative  organs,  he  will  find  that  the 
ovum  of  the  female  and  the  spermatozoon  of  the  male  are  derived  from  fundamentally  the  same 
structures,  and  therefore  their  fusion  is  the  union  of  two  elements  of  very  similar  morphological 
value. 


SEGMENTATION    OF    OVUM. 


103 


which  takes  no  part  in  this  process  of  division.  Then,  each  of  these  two  daughter 
elements  divides  in  like  manner,  and  thus  four  nucleated  elements  are  formed, 
and  so  on,  until  at  length  a  mulberry-like  agglomeration  of  nucleated  masses  of 
protoplasm  results  (Fig.  To).  These  masses  are  sometimes  termed  segmentation 


The  manner  in  which  segmentation  occurs  is  somewhat  peculiar.  The  two 
spheres  resulting  from  the  first  cleavage  are  of  unequal  size.  One,  which  for  the 
sake  of  distinction  we  will  call  the  upper  cell,  is  larger  than  the  other,  the  lower 
cell.  And  after  they  have  divided  three  or  four  times  the  rate  of  cleavage  in 
the  spheres  derived  from  the  upper  segment  becomes  more  rapid  than  in  those 
derived  from  the  lower  segment.  In  addition  to  this,  the  spheres  derived  from 
the  upper  segment  have  a  tendency  to  spread  over  and  enclose  those  from  the 
lower  segment  :  so  that  by  about  the  ninth  or  tenth  division  there  is  an 
external  layer  of  spheres  derived  from  the  primary  upper  segment  surround- 
ing and  almost  enclosing  a  mass  of  spheres,  which  in  consequence  of  their 
diminished  rate  of  cleavage  are  fewer  in  number  and  larger  in  size,  derived  from 
the  primary  lower  segment  (Fig.  76,  A).  Fluid  collects  between  the  two  sets  of 


FIG.  76. — Ovum  of  the  rabbit  at  the  end  of  the  process  of  segmentation,  oc.  Outer  cells,  ic.  Inner 
cells,  ftp.  Place  where  the  outer  cells  have  not  yet  covered  the  inner  cells.  (From  Balfour,  after  Ed.  van 
Beneden.) 

spheres,  except  at  one  part,  where  they  remain  in  contact,  and  the  ovum  is  con- 
verted into  a  sac.  formed  by  a  layer  of  spheres  derived  from  the  upper  primary 
segment,  and  containing  at  one  part  another  mass  of  spheres  derived  from  the 
lower  primary  segment  (Fig.  76,  B).  The  inner  cells  are  rather  more  granular 
than  the  outer,  beneath  which  they  gradually  spread,  becoming  applied  over  a 
part  of  their  inner  surface  in  a  single  layer :  so  that  the  cavity  is  afterward 
enclosed  more  or  less  completely  in  a  double  layer  of  cells. 

The  ultimate  destination  of  the  outermost  complete  layer  of  spheres  is  at 
present  doubtful.  That  portion  of  it  which  covers  the  inner  cells  is  believed  to  be 
transitory  and  to  gradually  disappear  in  the  course  of  formation  of  the  various 
layers  of  the  blastodermic  vesicle,  while  the  remainder  forms  the  outer  layer 
(epiblast)  of  this  vesicle.  Adopting  this  view,  the  ovum  would  consist  of  a  cavity 
surrounded  by  (1)  a  layer  of  cells  completely  lining  the  interior  of  the  vitelline 
membrane,  and  (2)  by  a  second  layer  internal  to  these  and  partially  lining  the 
interior  of  the  outer  layer,  both  sets  of  cells  derived  from  the  segmentation  of  the 
ovum.  The  sphere  formed  by  this  double  layer  of  cells  is  called  the  4k  blastoder- 
mic vesicle.' 

At  first  the  area  of  the  blastodermic  vesicle,  which  consists  of  both  the 
inner  and  outer  layers  of  cells,  is  a  small  disk,  in  which  the  first  traces  of  the 
embryo  are  seen ;  hence  it  is  called  the  cn'rmhial  disk  or  area  germinativa  (Fig. 


104 


DE  VEL  OPMENT. 


77).  The  first  trace  of  the  embryo  appears  as  a  faint  streak  at  the  posterior 
end  of  the  area  germinativa,  called  the  primitive  trace.  After  the  formation  of 
the  primitive  trace,  but  previous  to  the  appearance  of  the  next  parts  of  the 
embryo,  presently  to  be  described — viz.  the  laminae  dorsales  and  the  notochord 
— the  blastodermic  membrane  consists  of  only  two  layers,  the  epiblast  and  hypo- 
blast,  but  after  the  formation  of  these  structures 
a  third  layer  makes  its  appearance.  This  is  the 
mesoblast,  and  is  situated  between  the  other  two 
(Fig.  78).  The  epiblast  of  the  germinal  disk  is 
formed  of  the  most  superficial  layers  of  the  inner 
cells  which  were  exposed  by  the  disappearance 
of  the  outer  cells,  which  originally  covered  them, 
the  remaining  epiblast  of  the  blastodermic  vesi- 
cle being  probably  the  persistent  outer  cells, 
while  the  hypoblast  is  formed  by  the  rest  of  the 
inner  cells.  In  the  region  of  the  primitive  trace 
the  epiblast  and  hypoblast  fuse  together,  and 
from  the  sides  of  this  line  of  fusion  cells  grow 
out  laterally  into  the  space  between  the  epiblast 
and  hypoblast  to  form  the  mesoblast,  a  further 
formation  of  this  layer  also  taking  place  at  the 
margin  of  the  germinal  disk.  The  blastodermic 
membrane  thus  comes  to  consist  of  three  layers :  The  external,  which  used  to  be 
called  the  serous  layer,  but  is  now  more  commonly  termed  the  epiblast,  or  ecto- 


FIG.  77.— Ovum  with  the  germinal  area, 
seen  in  profile  to  show  the  division  of  the 
blastodermic  membrane.  1.  Vitelline 
membrane.  2.  Blastoderm.  3.  Germinal 
area.  4.  Place  where  the  blastoderm  is 
just  divided  into  its  two  layers. 


FIG.  78.— Section  across  the  anterior  part  of  the  medullary  groove  of  an  early  embryo  of  the  guinea  pig.  (By 
Schafer.  From  Quain's  Anatomy,  1890.)  ep.  Folds  of  epiblast  rising  up  on  either  side  of  the  middle  line,  and 
thus  bounding  the  medullary  groove,  m.g.  Middle  of  medullary  groove,  hy.  Hypoblast,  which  is  in  contact  with 
the  medullary  epiblast  at  the  middle  of  the  groove,  but  is  elsewhere  separated  from  it  by  mesoblast,  m,  which 
has  burrowed  forward  between  the  two  primary  layers.  A  cleft  is  seen  in  the  mesoblast  on  either  side ;  this  is 
the  commencement  of  the  anterior  part  of  the  body-cavity. 

derm :  the  internal,  the  mucous  layer,  the  hypoblast,  or  entoderm  ;  and  the  middle, 
which  is  now  usually  called  the  mesoblast  or  mesoderm,  but  which  was  formerly 
named  the  "  vascular  layer." 

The  epiblast  is  mainly  concerned  in  the  formation  of  the  external  cuticle  and 
the  whole  of  the  nervous  system.  It  consists  of  cells  of  an  epithelial  character ; 
that  is  to  say,  cells  of  an  irregular  columnar  shape,  forming,  for  the  most  part,  a 
single  stratum,  but  becoming  more  numerous  and  flattened  at  the  germinal  disk. 
The  epidermis  of  the  body  and  all  the  involutions  of  the  epidermis  in  the  ducts  of 
superficial  glands,  as  the  mammae,  as  well  as  the  brain,  the  spinal  cord,  the  nerves, 
and  the  portions  of  the  nose,  eye,  and  ear,  which  are  directly  formed  from  the 
brain,  are  developed  from  it.  The  external  layer  of  the  amnion  is  also  formed 
from  the  epiblast,  and  probably  also  a  portion  of  the  chorion. 

The  hypoblast  is  mainly  concerned  in  forming  the  internal  epithelium — viz. 
that  of  the  whole  alimentary  passages  except  the  mouth  and  a  small  portion  of  the 
rectum  near  the  anus  (which  are  formed  by  involutions  of  the  epiblast) ;  that  of 
the  respiratory  tract,  which  is  originally  an  offset  from  the  alimentary  canal ;  and 
the  epithelium  of  all  the  glandular  organs  which  open  into  the  intestinal  tract. 
The  hypoblast  forms  also  the  deeper  layer  of  the  umbilical  vesicle  and  allantois. 


THE  BLASTOD  /•;/,' M. 


105 


Its  cells  are  epithelial,  and  are  at  first  flattened,  but  subsequently  become  columnar 
and  larger  than  those  of  the  epiblast. 


I'l'j.  70.'*— Diagrams  to  show  the  development  of  the  three  layers  of  the  blastoderm  ic  membrane  on  transverse 
section.  A.  Portion  of  the  ovum  with  the  zona  pellucida  and  the  germinal  area.  B  C  D  E  F  G.  Different  stages 
of  development,  o.  I'mbilical  vesicle,  a.  Amnion.  ?.  Intestine,  p.  Peritoneal  cavity,  bounded  by  the 
splanchno-plrural  and  somato-plenral  layers  of  mesoblast.  1.  Vitelline  membrane.  2.  External  blastodermic 
layer.  3.  Middle  layer.  4.  Internal  layer.  ;">.  Medullary  lamina.'  and  groove.  5'.  Medullary  canal.  6.  Epi- 
dermic lamiiue.  7.  Lateral  folds  of  the  amnion.  7'.  The  same  almost  in  contact.  8.  Internal  epithelial 
layer  of  the  amnion.  9.  Epidermis  of  the  embryo.  10.  Chorda  dorsalis.  11.  Vertebral  laminae.  12.  Protover- 
proper.  13.  Muscular  laminse.  14.  Lateral  lamina.  15.  Splanchnopleure.  16.  Somatopleure. 

-lanchnopleure  of  the  umbilical  vesicle.  18.  Muscle  plate.  19.  External  layer  of  the  somatopleure 
20.  Internal  layer  of  the  same.  21.  Mesentery.  22.  Splanchnopleure  of  the  intestine." 


*The  dotted  lines  indicate  the  parts  belonging  to  the  internal  blastodermic  layer:  the  plain  lines,  those 
belonging  to  the  middle:  the  interrupted  lines,  those  belonging  to  the  external.  The  embryo  has  been  repre- 
sented, in  this  and  the  following  diagram,  lying  on  its  back.  '1  lie  natural  position  is  general!]  assumed  to  be 
the  reverse. 


All  the  rest  of  the  embrvo  is  formed  from  the  mesoblast — viz.  all  the  vascular 


106 


DE  VEL  OPMENT. 


and  locomotive  system,  the  cutis,  all  the  connective  tissues,  and  the  genito-urinary 
organs — with  the  exception  of  the  epithelium  of  the  bladder  and  urethra,  which  i's 


151 


FIG.  80.* — Diagrams  to  show  the  development  of  the  three  blastodermic  layers  on  antero-posterior  section.  A 
Portion  of  ovum  with  the  vitelline  membrane  and  germinal  area.  BCD  E'F.  Various  stages  of  development 
G.  Ovum  in  the  uterus  and  formation  of  decidua.  1.  Vitelline  membrane.  2.  External  blastodermic  layer.  2'. 
Vesicula  serosa.  3.  Middle  blastodermic  layer.  4.  Internal  layer.  5.  Vestige  of  the  future  embryo.  0.  Ceph- 
alic flexure  of  the  amnion.  7.  Caudal  flexure.  8.  Spot  where  the  amnion  and  vesicula  serosa  are  continuous. 
8'.  Posterior  umbilicus.  9.  Cardiac  cavitv.  10.  Splanchnopleure  layer  of  the  umbilical  vesicle.  11.  Somato- 
pleure  layer  of  the  amnion.  12.  Internal  layer  or  the  blastoderm  forming  the  intestine.  13,14.  External  layer 
of  the  placenta,  extending  to  the  inner  surface  of  the  vesicula  serosa.  15.  The  same,  now  completely  applied  to 
the  inner  surface  of  the  vesicula  serosa.  16.  Umbilical  cord.  17.  Umbilical  vessels.  IS.  Amnion.  19.  Chorion. 
20.  Foetal  placenta.  21.  Mucous  membrane  of  uterus.  22.  Maternal  placenta.  23.  Decidua  reflexa.  24.  Mus- 
cular wall  of  uterus. 

*The  same  note  applies  to  this  as  to  the  preceding  diagram. 

developed  from  the  hypoblast.     The  vascular  system  of  the  foetus  extends  to  the 
yolk  and  the  maternal  parts  along  the  umbilical  vesicle  and  allantois,  so  that  the 


FIRST  RUDIMEXTS    OF   THE  EMBRYO.  107 

greater  part  of  these  bodies  and  the  outer  layer  of  the  amnion  are  also  formed  out 
of  the  mesoblast.  The  foetal  portion  of  the  placenta,  being  essentially  a  vascular 
structure,  is  also  developed  from  the  mesoblast.  Its  cells  are  irregular  and 
branched  and  surrounded  by  a  considerable  amount  of  intercellular  fluid.  It 
may  therefore  be  regarded  as  resembling  more  closely  embryonic  connective 
tissue. 

First  Rudiments  of  the  Embryo  (Figs.  79  and  80). — The  primitive  trace  alluded 
to  above  as  appearing  in  the  area  germinativa  is  a  very  transitory  structure,  which 
marks  the  direction  of  the  embryonic  axis,  and  is  gradually  lost  sight  of  as 
development  proceeds. 

The  first  real  approach  toward  a  definite  form  in  the  embryo  is  made  (1)  by 
the  development  of  the  central  nervous  system  ;  (2)  by  the  cleavage  of  the  mid- 
dle layer  of  the  blastodermic  membrane  into  a  series  of  segments ;  and  (3)  by 
the  development  of  an  axial  embryonic  skeletal  structure,  the  notochord. 

First,  a  folding  up  of  the  cells  of  the  epiblast  or  outer  layer  takes  place.  This 
commences  in  the  anterior  part  of  the  area  germinativa,  and  extends  in  the  same 
direction  as  the  primitive  trace,  gradually  enclosing  this  latter  until  it  is  lost 
at  the  caudal  extremity  of  the  embryo  (Fig.  81).  This  folding  up  of  the  epi- 
blast gives  rise  to  a  longitudinal  groove  down  its  centre,  in  consequence  of  the 
manner  in  which  the  cells  of  the  epiblast  are  heaped  up  into  two  longitudinal 
ridges,  with  a  furrow  between  them,  so  that  the  sides  and  base  of  the  groove  are 
formed  of  epiblastic  cells  (Fig.  82,  A).  The  mesoblast,  lying  between  the  epiblast 
and  hypoblast.  fills  up  the  space  thus  caused  between  these  two  layers,  so  that 
the  sides  of  the  groove  are  occupied  by  a  longitudinal  thickening  of  mesoblast ;  the 
two  masses  being  separated  at  the  bottom  of  the  groove  by  the  junction  of  the 
epiblast  and  hypoblast  at  the  situation  of  the  primitive  trace.  The  groove  becomes 
deeper  and  deeper  in  consequence  of  the  further  growing  up  of  the  cells  to  form 
the  ridge  on  either  side.  In  this  way  the  ridges  eventually  become  two  plates,  the 
laminie  dorsales  or  medullary  plates,  which  finally  coalesce  and  thus  form  a  closed 
tube,  the  neural  canal,  lined  by  epiblast  and  having  a  covering  of  the  same  mem- 
brane (Fig.  82).  These  membranes  are  at  first  in  contact  with  one  another,  but 
eventually  become  separated,  mesoblastic  structures  growing  up  between  them,  and 
the  line  of  coalescence  becomes  obliterated.  The  coalescence  first  takes  place  in 
the  middle  of  the  embryo,  then  toward  the  cephalic  end,  and  lastly  at  the  caudal 
extremity.  The  lining  of  this  tube  is  developed  into  the  nervous  centres,  the 
covering  into  the  epidermis  of  the  back  and  head.  The  cephalic  extremity  of 
the  neural  canal  is  soon  seen  to  be  more  dilated  than  the  rest,  and  to  present 
constrictions  dividing  it  imperfectly  into  three  chambers :  the  brain  is  developed 
from  this  dilated  portion ;  the  spinal  cord  takes  its  origin  from  the  remainder  of 
the  tube.  Below  the  neural  canal  the  hypoblast  and  epiblast  are  in  contact, 
separating  the  two  longitudinal  thickenings  of  mesoblast  on  either  side  of  the 
canal.  Here  a  thickening  of  the  hypoblast,  commencing  from  the  anterior  end  of 
the  primitive  trace,  takes  place,  and  gradually  separates  itself  off  from  the  hypo- 
blast,  lying  between  this  membrane  and  the  epiblast  below  the  bottom  of  the  neural 
canal.  This  is  known  as  the  notochord  or  chorda  dorsalis.  This  when  fully 
developed,  forms  a  continuous  rod-shaped  body  lying  below  the  primitive  groove 
and  composed  of  clear  epithelium-like  cells.  It  is  essentially  an  embryonic  struc- 
ture, though  traces  of  it  remain  in  the  centre  of  the  intervertebral  disks  through- 
out life.  The  collection  of  mesoblastic  cells,  which  forms  a  thick  longitudinal 
column  on  either  side  of  the  neural  canal,  becomes  separated  from  the  rest  of  the 
mesoblastic  layer.  It  undergoes  a  series  of  transverse  segmentations  and  becomes 
converted  into  a  row  of  well-defined,  dark,  square  segments  or  masses,  separated 
by  clear,  transverse  intervals,  called  the  protovertebrceor  mesoblastic  somites.  They 
first  make  their  appearance  in  the  region  which  afterward  becomes  the  neck,  then 
further  forward  toward  the  head,  and  afterward  extend  along  the  body.  These 
bodies,  as  will  be  explained  hereafter,  are  not  the  same  as  the  permanent  verte- 
brae, but  they  are  differentiated,  partly  into  the  vertebrae  and  partly  into  the 


108 


DE  VELOPMENT. 


muscles  and  true  skin.  On  either  side  of  the  protovertebrse  the  mesoblast  splits 
into  two  layers,  the  upper,  or  that  covered  by  epiblast,  is  called  somatopleure,  and 
the  lower,  lined  by  hypoblast,  the  splanchnopleure  (Fig.  82,  B,  5-5').  From  the 


FIG.  81.— Embryonic  area  of  the  ovum  of  a  rabbit  at  the 
seventh  day.  ay.  Embryonic  area,  o,  o.  Region  of  the 
blastodermic  vesicle  immediately  surrounding  the  embry 
onic  area.  pr.  Primitive  streak,  rf.  Medullary  groove 
(From  Kolliker.) 

former  the  skeleton  muscles  and  true  skin  of  the 
external  parts  of  the  body  are  derived,  from  the  I  at 


FIG.  82.— Transverse  sections 
through  the  embryo-chick  before 
and  some  time  after  the  closure  of 
the  medullary  canal,  to  show  the 
upward  and  downward  inflections 
of  the  blastoderm.  (After  Remak.) 
A.  At  the  end  of  the  first  day.  1. 
Notochord.  2.  Primitive  groove  in 
the  medullary  canal.  3.  Edge  of  the 
dorsal  lamina.  4.  Epiblast.  5.  Meso- 
blast divided  in  its  inner  part.  6. 
Hypoblast.  7.  Section  bfprotoverte- 
bral  plate.  B.  On  the  third  day  in 
the  lumbar  region.  1.  Notochord  in 
its  sheath.  2.  Medullary  canal  now 
closed  in.  3.  Section  of  the  medul- 
lary substance  of  the  spinal  cord. 
4.  Epiblast.  5.  Somatopleure  of 
the  mesoblast.  5'.  Splanchnopleure 
(one  figure  is  placed  in  the  pleuro- 
peritoneal  cavity).  6.  Layers  of  hy- 
poblast in  the  intestines  spreading 
also  over  the  yolk.  4X5.  Part  of  the 
fold  of  the  amnion  formed  by  epi- 
blast and  somatopleure. 


FIG.  83.— Diagrammatic  section  through  the  ovum  of  a  mam- 
mal in  the  long  axis  of  the  embryo,  e.  The  cranio-vertebral  axis 
/,  i.  The  cephalic  and  caudal  portions  of  the  primitive  alimentary 
canal,  a.  The  amnion.  a'.  The  point  of  reflection  into  the  false 
amnion.  v.  Yolk-sac,  communicating  with  the  middle  part  of 
the  intestine  by  v  i,  the  vitello-intestinal  duct.  u.  The  allantois. 
The  ovum  is  surrounded  externally  by  the  villous  chorion. 

aptly  compared  to  a  canoe  turned  over  (Fig.  83). 


ter,  the  muscular  and  other 
mesoblastic  portions  of  the  vis- 
cera. The  space  between  them 
is  the  common  pleuro-peritoneal 
cavity.  Whilst  the  parietes  of 
the  body  are  still  unclosed,  this 
common  pleuro-peritoneal  cav- 
ity is  continuous  with  the  space 
between  the  amnion  and  cho- 
rion, as  seen  in  Fig.  79,  F.  The 
embryo,  which  at  first  seems  to 
be  a  mere  streak,  extends  longi- 
tudinally and  laterally.  As  it 
grows  forward  the  cephalic  end 
becomes  remarkably  curved  on 
itself  (cephalic  flexure),  and 
a  smaller  but  distinct  flexure 
takes  place  at  its  hinder  end 
(caudal  flexure).  At  the  same 
time  the  sides  of  the  embryo 
grow  and  curve  toward  each 
other ;  so  that  the  embryo  is 
In  consequence  of  this  incurv- 


THE    EMBRYO. 


109 


ing  of  the  embryo,  both  in  an  antero-posterior  and  a  lateral  direction,  the  original 
ovum,  with  the  three  layers  derived  from  the  cleavage  of  the  biastodermic  mem- 
brane which  cover  it.  is  converted  into  a  sort  of  hour-glass  shape  with  two  unequal 
globes.  The  smaller  globe  is  formed  by  the  part  of  the  biastodermic  membrane 
(area  germinativa)  which  has  already  undergone  certain  changes  in  the  formation 
of  the  embryo,  and  constitutes  the  part  which  has  been  compared  to  a  canoe.  The 
larger  globe  is  called  the  yolk-sac  or  umbilical  reside,  and  is  formed  by  the  rest  of 
the  biastodermic  membrane — i.  e.  that  part  which  is  not  concerned  in  the  formation 
of  the  area  germinativa.  The  two  freely  communicate  through  the  constriction 
Avhich  is  the  site  of  the  future  umbilicus,  and  through  this  constriction  the  internal 
layer  of  the  biastodermic  membrane  (the  hypoblast)  and  the  innermost  of  the  two 
layers  into  which,  as  has  been  already  stated,  the  mesoblast  divides — viz.  the  splanch- 
nopleure.  pass  out :  the  incurving  having  only  involved  the  somato-pleural  layer  of 
the  mesoblast  and  the  epiblast  (Fig.  84).  The  umbilical  vesicle  is,  therefore,  at 


Hypoblast 

lanchnopleure 


Splanchnopleure 
Somatopleure 
Pleu  ro  -peritoneal 
cavity 


Neural  canal 


FIG.  &!.— Diagrammatic  section  of  embryo,  showing  the  formation  of 
the  umbilical  vesicle. 

first  a  mere  part  of  the  general  cavity  of  the  yolk,  partly  enclosed  by  the  embryo ; 
but  as  the  latter  grows  round  on  all  sides  toward  the  umbilical  aperture,  the 
yolk  becomes  distinguished  into  two  portions.  One  lies  inside  the  embryo,  and 
eventually  forms  a  part  of  the  intestinal  cavity  (out  of  which  also,  as  will  here- 
after be  seen,  the  bladder  is  developed).  The  other  lies  external  to  the  embryo 
and  remains  therefore  for  a  time  a  part  of  what  is.  in  a  more  restricted  sense, 
the  ovum.  The  two  parts  are  almost  separated  from  each  other  by  the  meeting 
of  the  abdominal  walls  of  the  embryo  at  the  umbilicus,  through  which  they 
still  communicate  by  a  passage,  the  omphalo-mesenteric  duct,  the  destination  of 
which  will  be  pointed  out  presently.  The  extra-embryonic  portion  is  of  small 
importance  and  very  temporary  duration  in  the  human  subject.  It  is  for  the 
purpose  of  supplying  nutrition  to  the  embryo  during  the  very  earliest  period, 
before  it  can  obtain  it  from  the  uterine  sinuses  of  the  mother.  In  the  oviparous 
animals,  however,  where  no  supply  of  nutrition  can  be  obtained  from  the 
mother,  since  the  egg  is  entirely  separated  from  her,  the  yolk-sac  is  large  and 
of  great  importance,  as  it  supplies  nutrition  to  the  chick  during  the  whole  of 
fetation.  Vessels  developed  in  the  middle  biastodermic  layer  soon  cover  the 
umbilical  vesicle,  forming  the  i'asciil<~ir  area,  the  chief  vessels  of  which  are  the 
omphalo-rnesenterie.  two  in  number  (Fig.  85).  The  vessels  of  this  area  appear 
to  absorb  the  fluid  of  the  umbilical  vesicle,  which  as  the  fluid  is  absorbed  dries  up 
and  has  no  further  function.  The  activity  of  the  umbilical  vesicle  ceases  about 
the  fifth  or  sixth  week,  at  the  same  time  that  the  allantois,  which  is  the  great  bond 


110 


DE  VEL  OPMENT. 


of  vascular  connection  between  the  embryo  and  the  uterine  tissues,  is  formed.     In 
fact,  the  umbilical  vesicle  provides  for  the  nutrition  of  the  foetus  from  the  ovum 


FIG.  85. — Magnified  view  of  the  human  embryo  of  four  weeks,  with  the  membranes  opened.  (From  Leish- 
mann  after  Coste.)  y.  The  umbilical  vesicle  with  the  omphalo-mesenteric  vessels,  v,  and  its  long  tubular 
attachment  to  the  intestine,  c.  The  yilli  of  the  chorion.  m.  The  amnion  opened,  u.  Cul-de-sac  of  the  allan- 
tois,  and  on  each  side  of  this  the  umbilical  vessels  passing  out  to  the  chorion.  In  the  embryo :  a.  The  eye.  e. 
The  ear-vesicle,  h.  The  heart.  I.  The  liver,  o.  The  upper;  »,  the  lower  limb.  w.  Wolfflan  body,  in  front  of 
which  are  the  mesentery  and  fold  of  intestine.  The  Wolffian  duct  and  tubes  are  not  represented. 

itself,  while  the  allantois  is  the  channel  whereby  it  is  nourished  from  the  uterine 
tissues.  The  umbilical  vesicle,  containing  fluid,  remains  visible,  however,  up  to 
the  fourth  or  fifth  month,  with  its  pedicle  and  the  omphalo-mesenteric  vessels. 
The  latter  vessels  become  atrophied  as  the  functional  activity  of  the  body  with 
which  they  are  connected  ceases. 

So  far  we  have  traced — (1)  the  segmentation  or  cleavage  of  the  yolk  into  a 
number  of  nucleated  cells  or  "  spherules."  (2)  The  accumulation  of  fluid  within 
the  ovum,  and  the  arrangement  of  the  spherules  around  the  fluid  on  the 
internal  surface  of  the  vitelline  membrane,  forming  a  second  membrane,  the 
"  blastodermic  membrane."  (3)  The  separation  of  the  blastodermic  membrane  into 
three  layers,  named,  from  within  outAvard,  the  "hypoblast,"  the  "mesoblast,"  and 
the  "epiblast."  (4)  The  formation  of  an  elongated,  oval-shaped  disk,  called  the 
"  area  germinativa."  (5)  The  appearance  in  the  centre  of  the  area  germinativa  of 
a  delicate  line  or  furrow,  running  longitudinally,  and  called  the  •'  primitive  trace." 
(6)  The  formation  of  a  distinct  groove  in  the  situation  of  this  primitive  trace, 
caused  by  the  growing-up  of  the  cells  on  either  side  of  it,  so  as  to  form  two  longitu- 
dinal ridges,  called  the  "laminae  dorsales."  (7)  The  increase  and  incurvation  of 
these  laminae  dorsales,  until  they  meet  behind,  enclosing  a  canal  lined  by  epiblast. 
The  canal  is  the  neural  canal,  and  from  the  epiblast  which  lines  it  the  nervous 
centres  are  developed.  (8)  The  formation,  in  the  hypoblast  immediately  under  this 
canal,  of  a  continuous  rod-shaped  body,  the  "chorda  dorsalis,"  or  "notochord." 
(9)  The  formation  from  the  mesoblast,  on  either  side  of  the  notochord,  of  a  longi- 


THE   AMNION. 

tudinal  column,  divided  into  a  number  of  square  segments,  the  "  protovertebrae." 
(10)  The  splitting  of  the  mesoblast,  external  to  the  protovertebrae,  into  two  layers — 
the  outer,  called  the  "  somatopleure,"  lined  externally  by  the  epiblast ;  the  inner, 
called  the  "splanchnopleure,"  lined  internally  by  the  hypoblast,  a  space  being  left 
between  the  two  which  forms  the  "  pleuro-peritoneal  cavity."  (11)  The  curving  of 
the  embryo  on  itself,  both  longitudinally  and  laterally,  so  as  to  be  comparable  to  a 
canoe ;  the  walls  being  formed  of  all  three  layers  of  the  blastodermic  membrane 
and  the  well  of  the  canoe — that  is  the  intestinal  cavity  of  the  embryo,  opening 
into  the  cavity  of  the  yolk-sac.  (12)  A  portion  of  the  yolk-sac  lying  in  the  body- 
cavity  of  the  embryo,  and  a  portion  outside  it ;  the  two  communicating  by  a  duct, 
the  "  omphalo-mesenteric  "  duct.  The  portion  of  the  yolk-sac  external  to  the  body- 
cavity  is  termed  the  umbilical  vesicle,  and  provides  nutrition  to  the  embryo  until 
such  time  as  the  placenta  is  formed  ;  vessels,  developed  from  the  middle  blasto- 
dermic layer,  ramifying  over  it,  and  gradually  absorbing  its  contents.1 

The  next  step  toward  a  clear  understanding  of  the  development  of  the  embryo 
is  to  have  a  proper  conception  of  the  manner  in  which  the  membranes  envelop- 
ing the  foetus  are  formed. 

The  membranes  investing  the  foetus  are  the  amnion,  the  chorion,  and  the 
decidua.  The  tAvo  former  are  developed  from  foetal  structures,  and  are  proper  to 
the  foetus ;  the  latter  is  formed  in  the  uterus,  and  is  derived  from  the  maternal 
structures. 

The  Amnion. — The  amnion  is  the  membrane  which  immediately  surrounds  the 
embryo.  It  is  of  small  size  at  first,  but  increases  considerably  toward  the  middle 


False  amnion  or  chorion. 

\ 


FIG.  86.— Diagram  of  a  transverse  section  of  a  mammalian  embryo,  showing  the  mode  of  formation  of  the 
amnion.  The  amniotic  folds  have  nearly  united  in  the  middle  line.  (From  Quain's  Anatomy,  vol.  i.  pt.  1, 1890.) 
Epiblast,  blue ;  mesoblast,  red ;  hypoblast  and  notochord,  black. 

of  pregnancy,  as  the  foetus  acquires  the  power  of  independent  movement.  It  exists 
only  in  reptiles,  birds,  and  mammals,  which  are  hence  called  "  Amniota,"  but  is 
absent  in  amphibia  and  fishes.  It  is  formed  thus :  At  or  near  the  extremities  of 
the  incurved  foetus — that  is  to  say,  at  the  point  of  constriction  of  the  blastodermic 
membrane,  where  the  portion  which  has  undergone  changes  to  form  the  body  of 
the  embryo  joins  the  part  devoted  to  the  formation  of  the  umbilical  vesicle — an 
inflection  of  the  epiblast  and  outer  layer  of  the  mesoblast,  which  have  become 
separated  from  the  inner  layer  of  the  mesoblast  and  hypoblast  by  the  formation  of 
the  pleuro-peritoneal  cavity,  takes  place  (Fig.  79,  D  7).  These  inflections  or  back- 

1  According  to  Professor  John  A.  Ryder,  it  is  "  very  doubtful  if  any  considerable  amount  of 
nutriment  is  supplied  to  the  embryo  from  the  yolk-sac  at  any  time." 


1 1 2  DE  VEL  OPMENT. 

ward  folds  commence  first  at  the  cephalic  extremity,  and  subsequently  at  the  caudal 
end  and  sides,  and  deepen  more  and  more,  in  consequence  of  the  sinking  of  the 
embryo  into  the  blastodermic  vesicle,  until,  gradually  approaching,  they  meet  one 
another  (Fig.  79,  E  7).  After  they  come  in  contact  they  fuse  together,  and  the 
septum  between  them  disappears ;  so  that  the  inner  layer  of  the  cephalic  fold  becomes 
continuous  with  the  inner  layer  of  the  caudal  fold,  and  the  outer  with  the  outer 
(Fig.  79,  F  7').  Thus  we  have  two  membranes,  one  formed  by  the  inner  layer  of  the 
fold — the  true  amnion — which  encloses  a  space  over  the  back  of  the  embryo — the 
amniotic  cavity  (Fig.  79,  F  and  G,  a) — containing  a  clear  fluid,  the  liquor  amnii.1 
The  other,  the  outer  layer  of  the  fold — the  false  amnion — lines  the  internal  surface 
of  the  original  vitelline  membrane.  Between  the  two  is  an  interval,  which  of 
course  communicates  with  the  pleuro-peritoneal  cavity.  This  it  continues  to  do 
until  the  body-walls  of  the  embryo  have  grown  up  and  coalesced  at  the  umbilicus. 
Then  the  amniotic  fold  is  carried  downward,  and  encloses  the  umbilical  cord,  by 
which  the  foetus  is  attached  to  the  placenta.  The  true  amnion — or,  as  it  is 
usually  called,  the  amnion — is  formed  of  two  layers,  derived  respectively  from 
the  epiblast  and  from  the  parietal  layer  of  the  mesoblast. 

The  amnion  is  at  first  in  close  contact  with  the  surface  of  the  body  of  the 
embryo,  but  about  the  fourth  or  fifth  week  fluid  begins  to  accumulate,  and  thus 
separates  the  two.  The  quantity  steadily  increases  up  to  about  the  sixth  month 
of  pregnancy,  after  which  it  diminishes  somewhat.  The  use  of  the  liquor  amnii  is 
believed  to  be  chiefly  to  allow  of  the  movements  of  the  foetus  in  the  later  stages  of 
pregnancy,  though  it  no  doubt  serves  other  purposes  also.  It  contains  about  1 
per  cent,  of  solid  matter,  chiefly  albumen,  with  traces  of  urea,  the  latter  possibly 
derived  from  the  urinary  secretion  of  the  foetus. 

The  Chorion. — We  have  seen  that  in  the  formation  of  the  amnion  we  had 
two  layers  formed  out  of  a  reduplication  of  the  epiblast  and  outer  layer  of 
the  mesoblast :  one — the  true  amnion — which  surrounds  the  embryo  and 
encloses  a  cavity  between  it  and  the  embryo — the  amniotic  cavity  ;  and  secondly, 
the  false  amnion,  which  lies  in  apposition  Avith  the  internal  surface  of  the 
vitelline  membrane,  and  is  continuous  at  its  periphery  with  that  part  of  the 
original  epiblast  and  somatopleural  layer  of  the  mesoblast  which  did  not  enter 
into  the  formation  of  the  area  germinativa ;  and  that  between  these  two  layers 
there  is  a  space  (which  must  not  be  confounded  with  the  amniotic  cavity) 
which  communicates  with  the  pleuro-peritoneal  space,  and,  according  to  Dalton, 
contains  a  semifluid,  gelatinous  material.  The  chorion  is  formed  out  of  the 
vitelline  membrane  with  the  false  amnion  and  its  peripheral  continuation  with 
the  external  layers  of  the  blastoderm  ;  but  the  exact  share  which  the  three  layers 
take  in  its  formation  is  at  present  uncertain.  By  some  embryologists  it  is 
believed  that  the  vitelline  membrane  during  the  rapid  growth  of  the  ovum 
becomes  attenuated,  and  finally  lost ;  by  others  it  is  thought  that  it  combines  with 
the  other  layers  to  form  the  chorion.  But,  whichever  is  true,  at  a  very  early 
period  of  gestation  cellular  processes  or  fringes  groAv  outward  from  the  external 
surface  of  the  chorion,  and  have  been  likened  by  Dalton  to  tufts  of  seaweed. 
They  are  at  first  destitute  of  vessels,  and  are  of  simple  cellular  structure.  These 
fringes,  or  villi,  as  they  subsequently  become,  cover  at  first  the  whole  surface  of 
the  chorion ;  but  as  development  progresses  and  the  placenta,  by  which  the 
extent  of  the  attachment  of  the  ovum  to  the  uterine  walls  is  to  be  limited,  is 
about  to  be  formed,  the  villi  are  not  further  developed  over  the  rest  of  the 
chorion,  but  are  confined  to  that  part  only  which  is  to  form  the  foetal  portion 
of  the  placenta.  They  may,  however,  be  recognized  all  over  the  chorion  as 
abortive  processes  during  the  whole  of  foetal  gestation. 

1  The  student  should  be  careful  not  to  confound  this  cavity  with  that  formed  between  the  true 
and  false  amnion,  which  communicates  with  the  pleuro-peritoneal  cavity  of  the  embryo.  This 
latter  space  ought  with  more  propriety  to  be  called  the  "amniotic  cavity,"  since  it  is  contained 
between  the  layers  of  the  amnion  ;  whereas  the  so-called  amniotic  cavity  is  not  really  between 
the  lavers  of  the  amnion  at  all,  but  between  the  inner  layer  of  the  amnion  and  the  body  of  the 
embryo. 


THE   BELLY  STALK. 


113 


Ann  iotic  fold^ 


The  Belly  Stalk. — During  the  formation  of  the  amnion  the  anterior  end  of 
the  embryo  sinks  down  into  the  blastodermic  vesicle  much  more  rapidly  than  the 
posterior  end,  the  latter,  in 
fact,  remaining  attached  to 
the  surface  of  the  blastoderm 
(Fig.  87.  A).  As  the  forma- 
tion of  the  amnion  proceeds 
the  embryo  becomes  separated 
more  and  more  from  the  sur- 
face of  the  vesicle,  eventually 
being  united  with  it  only  by 
a  short  stalk  arising  from  its 
ventral  surface  (Fig.  87,  B). 
This  is  the  "belly  stalk,"  in 
the  interior  of  which  is  to  be 
found  the  umbilical  vesicle, 
which  has  been  carried  back- 
ward by  the  constriction 
which  produced  the  stalk,  and 
has  been  reduced  to  a  small 
pyriform  vesicle  supported 
upon  a  long  pedicle.  This 
pedicle  is  connected  with  the 
digestive  tract  of  the  embryo, 
and  behind  its  attachment  a 
small  outgrowth  develops  from 
the  ventral  wall  of  the  intes- 
tine, and.  pushing  in  front  of 
it  the  splanchnopleure  which 
forms  the  outer  lining  of  the 
intestine,  extends  out  into  the 
belly  stalk  and  forms  what  is 
known  as  the  aUantois.  In 
some  animals  the  allantois  is 
a  hollow  projection  and  is 
usuallv  styled  the  aUant<jii.t 

*  * 

h  :    but    in    most    mam- 


Amniotic  fold 


AUantois 


3 


FIG.  87. — Diagrams  showing  the  formation  of  the  belly  stalk.  The 
heavy  black  line  represents  the  embryonic  portion  of  the  epiblast, 
the  dotted  portions  and  broken  lines  the  mesoblast,  and  the  inner 

mals.  and  especially  in  man,    continuous  line  the  hypobiast 
the    external    or    mesoblastic 

element  undergoes  great  development,  while  the  internal  or  hypoblastic  element 
undergoes  little  increase  beyond  the  body  of  the  embryo,  so  that  it  is  very 
doubtful  whether  any  cavity  exists  in  the  allantois  beyond  the  limits  of  the 
umbilicus.  A  portion  of  the  allantoic  vesicle  icithin  the  body  cavity  is  eventu- 
ally destined  to  form  the  bladder,  while  the  remainder  forms  an  impervious  cord, 
the  uraeJtits.  stretching  from  the  summit  of  the  bladder  to  the  umbilicus.  The 
belly  stalk  is  at  first  hollow,  its  cavity  being  continuous  with  the  pleuro-peritoneal 
cavity  of  the  embryo  (Fig.  87),  but  it  soon  becomes  solid  by  the  extensive  growth 
of  the  mesoblastic  tissue  which  it  contains.  Over  that  portion  of  the  wall  of  the 
blastodermic  vesicle  with  which  the  outer  end  of  the  belly  stalk  is  connected  the 
chorionic  villi,  already  referred  to,  reach  their  greatest  development,  this  being 
the  region  of  the  placenta.1  In  the  walls  of  the  allantois  vessels  are  formed 
which  extend  their  branches  out  into  the  surrounding  mesoblast  and  into  the 
chorionic  villi.  The  allantois,  accordingly,  though  much  reduced  in  man  in 
comparison  with  the  lower  mammals,  is  still  the  tract  along  which  the  vessels 
extend  which  convey  the  blood  of  the  embryo  to  the  foetal  chorion,  where  it  is 

1  In  some  animals  some  of  the  vessels  of  the  villi  of  the  ohorion  are  derived  from  the  yolk-sac — 
that  is  from  the  omphalo-mesenteric  vessels. 


114 


DE  VEL  OPMENT. 


exposed  to  the  influence  of  the  maternal  blood  circulating  in  the  decidua  or 
uterine  portion  of  the  placenta,  from  which  it  imbibes  the  materials  of  nutrition, 
and  to  which  it  gives  up  effete  material,  the  removal  of  which  is  necessary  for  its 
purification. 

The  Decidua. — The  growth  of  the  chorion  and  placenta  can  only  be  understood 
by  tracing  the  formation  of  the  decidua. 

The  decidua  (Figs.  80  G,  88)  is  formed  from  the  mucous  membrane  of  the 
uterus.  Even  before  the  arrival  of  the  fecundated  ovum  in  the  uterus  the  mucous 

membrane  of  the  latter  is  vascular 
and  tumid,  and  when  the  ovum  has 
reached  the  uterus  it  becomes  im- 
bedded in  the  folds  of  the  mucous 
membrane,  which  grow  up  around  it 
and  finally  completely  encircle  it,  so 
as  to  cover  it  in  entirely  and  exclude 
it  from  the  uterine  cavity.  Thus  two 
portions  of  the  uterine  mucous  mem- 
brane (decidua)  are  formed — viz.  that 
which  coats  the  muscular  wall  of  the 
uterus,  decidua  vera,  and  that  which 
is  in  contact  with  the  ovum,  decidua 
reflexa.  The  decidua  vera  at  the  os 
internum  and  at  the  openings  of  the 
Fallopian  tubes  is  continuous  with 
the  lining  membrane  of  these  canals, 
the  thickening  of  the  original  mucous 
membrane  of  the  uterus  which  con- 
verts it  into  decidua  abruptly  ceasing 
at  these  points.  The  neck  of  the 
uterus  after  conception  is  closed  by 
a  plug  of  mucus.  The  decidua  vera 
is  perforated  by  the  openings  formed 
by  the  enlarged  uterine  glands,  which 
become  much  hypertrophied  and  de- 
veloped into  tortuous  tubes.  It  con- 
tains at  a  later  period  numerous  arte- 
ries and  venous  channels,  continuous 
with  the  uterine  sinuses,  and  it  is 
from  it  that  the  uterine  part  of  the 
placenta  is  developed.  The  portion 
of  the  decidua  vera  which  takes  part 
in  the  formation  of  the  placenta  is 
called  the  decidua  serotina  (Fig. 
88,  /). 

The  decidual  reflexa   is   shaggy 

on  its  outer  aspect,  but  smooth  within.  The  vessels  which  it  contains  at  first 
disappear  after  about  the  third  month.  About  the  fifth  or  sixth  month  the  space 
between  the  two  layers  of  the  decidua  disappears,  and  toward  the  end  of  preg- 
nancy the  decidua  reflexa  is  transformed  into  a  thin  yellowish  membrane,  which 
constitutes  the  external  envelope  of  the  ovum. 

Much  additional  interest  has  been  given  to  the  physiology  of  the  decidua  by 
the  fact,  which  seems  to  be  now  established  by  the  researches  of  Dr.  John 
Williams,  that  every  discharge  of  an  ovum,  whether  impregnated  or  not,  is,  as  a 
rule,  accompanied  by  the  formation  of  a  decidua,  and  that  the  essence  of  men- 
struation consists  in  the  separation  of  a  decidual  layer  of  the  mucous  membrane 
from  the  uterus ;  while  in  the  case  of  pregnancy  there  is  no  exfoliation  of  the 


FIG.  88.— Sectional  plan  of  the  gravid  uterus  in  the 
third  and  fourth  month.  (From  Wagner.)  a.  Plug  of 
mucus  in  the  neck  of  the  uterus.  6.  Fallopian  tube.  e. 
The  decidua  vera.  c2.  The  decidua  vera  passing  into  the 
right  Fallopian  tube  :  the  cavity  of  the  uterus  is  almost 
completely  occupied  by  the  ovum,  e,  e.  Points  of  reflec- 
tion of  the  decidua  reflexa  (in  nature  the  united  decidua 
do  not  stop  here,  but  pass  over  the  whole  uterine  surface 
of  the  placenta),  g.  Supposed  allantois.  h.  Umbilical 
vesicle,  i.  Amnion.  fc.  Chorion,  covered  with  the  decidua 
reflexa.  d.  Cavity  of  the  decidua.  /.  Decidua  serotina, 
or  placental  decidua. 


DEVELOPMENT   OF   THE   EMBRYO   PROPER.  lid 

membrane,  but,  on  the  contrary,  it  undergoes  further  development  in  the  manner 
described  above. 

The  Placenta  is  the  organ  by  which  the  connection  between  the  foetus  and 
mother  is  maintained.  It  therefore  subserves  the  purposes  both  of  circulation 
and  respiration.  It  is  formed  of  two  parts,  as  already  shown — viz.  the  maternal 
portion,  which  is  developed  out  of  the  decidua  vera  (serotina),  and  the  foetal 
portion  formed  out  of  the  villi  of  the  chorion.  Its  shape  in  the  human  subject  is 
that  of  a  disk,  one  surface  of  which  adheres  to  the  uterine  wall,  while  the  other  is 
covered  by  the  amnion.  The  villi  of  the  chorion  gradually  enlarge,  forming 
large  projections — ••  cotyledons  " — which  each  contain  the  ramifications  of  vessels 
communicating  with  the  umbilical  (allantoic)  arteries  and  veins  of  the  foetus. 
These  vascular  tufts  are  covered  with  epithelium,  and  project  into  corresponding 
depressions  in  the  mucous  membrane  (decidua  vera)  of  the  uterine  wall.  The 
maternal  portion  of  the  placenta  consists  of  a  large  number  of  sinuses  formed  by 
an  enlargement  of  the  vessels  of  the  uterine  wall.  These  bring  the  uterine  blood 
into  close  proximity  with  the  villi  of  the  foetal  placenta,  which  dip  into  the 
sinuses.  The  interchange  of  fluids  necessary  for  the  growth  of  the  foetus  and  for 
the  depuration  of  the  blood  takes  place  through  the  walls  of  the  villi.  but  there 
is  no  direct  continuity  between  the  maternal  and  foetal  vessels.  The  foetal  ves- 
sels form  tufts  of  capillaries,  the  blood  from  which  is  returned  by  small  veins, 
which  end  in  tributaries  of  the  umbilical  vein.  The  maternal  arteries  open  into 
spaces  somewhat  after  the  manner  of  the  arteries  of  the  erectile  tissues.  These 
spaces  communicate  with  a  plexus  of  veins  which  anastomose  freely  with  one 
another,  and  give  rise,  at  the  edge  of  the  placenta,  to  a  venous  channel  which  runs 
around  its  whole  circumference — the  placenta!  sinus. 

The  umbilical  cord  is  formed  by  the  gradual  elongation  of  the  belly  stalk.  It 
contains  the  coils  of  two  arteries  (umbilical,  originally  allantoic\  and  a  single  vein, 
united  together  by  a  gelatinous  tissue  (jelly  of  Wharton).  There  are  originally 
two  umbilical  veins,  but  one  of  these  vessels  becomes  obliterated,  as  do  also  the 
two  omphalo-mesenteric  arteries  and  veins  and  the  duct  of  the  umbilical  vesicle, 
all  of  which  are  originally  contained  in  the  belly  stalk.  The  permanent  struc- 
tures of  the  cord  are.  therefore,  furnished  by  the  allantois. 

In  this  manner  the  human  embryo  eventually  becomes  surrounded  by  three 
membranes  :  (1)  the  amnion,  derived  from  the  outer  layer  of  the  mesoblast  and  the 
epiblast:  ('2)  the  ehorion,  formed  from  the  false  amnion  (which  is  derived  from 
the  outer  layer  of  the  mesoblast  and  the  epiblast),  and  (3)  the  decidua,  derived 
from  the  mucous  membrane  of  the  uterus. 

Development  of  the  Embryo  proper. — The  further  development  of  the  embryo 
will,  perhaps,  be  better  understood  if  we  follow  as  briefly  as  possible  the  principal 
facts  relating  to  the  chief  parts  of  which  the  body  consists — viz.  the  spine,  the 
cranium,  the  pharyngeal  cavity,  mouth,  etc.,  the  nervous  centres,  the  organs  of 
the  senses,  the  circulatory  system,  the  alimentary  canal  and  its  appendages,  the 
organs  of  respiration,  and  the  genito-urinary  organs.1  The  reader  is  also 
referred  to  the  chronological  table  of  the  development  of  the  foetus  at  the  end  of 
this  section. 

Development  of  the  Spine. — We  have  already  traced  the  first  steps  in  the 
formation  of  the  spine :  (1)  The  looping  up  of  two  longitudinal  folds  from  the 
cells  of  the  epiblast  on  either  side  of  the  primitive  streak,  so  as  to  form  a  groove, 
and  the  gradual  growing  together  of  these  ridges  (laminae  dorsales)  so  as  to  con- 
vert the  groove  into  a  canal,  which  is  lined  by  epiblast,  and  out  of  which  the 
spinal  cord  is  developed.  (2)  The  formation  in  front  of  this  groove  of  a  con- 
tinuous cellular  cord  enclosed  in  a  structureless  sheath,  the  notochord  or  chorda 
dorsalis  (Fig.  89).  The  notochord  extends  from  the  cephalic  to  the  caudal 

1  The  scope  of  this  work  only  permits  the  briefest  possible  reference  to  these  subjects.  Those 
who  wish  to  study  the  subject  of  embryology  in  more  detail  are  referred  to  Kolliker's  Entwickdunqg- 
y?*-~hichte  ;  to  vol  i.  pt.  1,  of  the  tenth  edition  of  Quain's  Anatomy;  or  to  the  works  of  Professors 
Minot  and  Hertwig. 


116 


DE  VEL  OPMENT. 


extremity  of  the  embryo,  and  lies  in  the  place  which  is  afterward  occupied  by 
the  bodies  of  the  vertebrae.  (3)  On  either  side  of  the  neural  canal  a  portion  of 
the  mesoblastic  layer  is  divided  longitudinally  from  the  rest  of  the  mesoblast, 
so  as  to  form  a  thick  column,  which  extends  from  the  cephalic  to  the  caudal 


FIG.  89.— Transverse  section  through  the  dorsal  region  of  an  embryo  chick,  end  of  third  day.  (From  Foster 
and  Balfour.)  Am.  Amnion.  mp.  Muscle-plate,  cv.  Cardinal  vein.  Ao.  Dorsal  aorta  at  the  point  where  its 
two  roots  begin  to  join.  Ch.  Notochord.  Wd.  Wolffian  duct.  Wb.  Commencement  of  formation  of  Wolffian 
body.  ep.  Epiblast.  so.  Somatopleure.  hy.  Hypoblast.  The  section  passes  through  the  place  where  the  ali- 
mentary canal  (hy)  communicates  with  the  yolk-sac. 

extremity  of  the  embryo  on  either  side  of  the  spinal  canal  and  notochord  (Fig. 
82,  A  7) ;  this  is  the  protovertebral  column.  From  a  part  of  it  is  derived  the 
vertebral  column,  a  considerable  portion  at  the  upper  and  outer  part  being  differ- 
entiated from  it  and  eventually  forming  the  muscles  of  the  back.  (4)  This  column 
undergoes  a  process  of  transverse  segmentation  and  becomes  converted  into  a 
number  of  quadrilateral  blocks,  the  protovertebral  somites.  The  process  of  seg- 
mentation commences  in  the  cervical  region  and  proceeds  successively  through 
the  other  regions  of  the  body  until  a  number  of  segments  are  formed,  which  corre- 
spond very  closely  to  the  number  of  the  permanent  vertebrae.  (5)  From  each  of 
these  protovertebral  somites  masses  of  cells  are  budded  off  towards  the  middle 
line,  the  masses  of  opposite  sides  meeting  around  the  notochord,  which  they 
enclose,  and  extending  dorsally  around  the  spinal  cord,  which  they  also 
enclose.  The  notochord  and  the  spinal  canal  are  thus  surrounded  by  a  cellular 
mass  derived  from  the  mesoblastic  layer,  which  constitutes  the  membranous  matrix 
of  the  vertebras.  (6)  The  next  step  is  the  conversion  of  this  primitive  mem- 
branous matrix  into  cartilage.  This  takes  place  probably  about  the  fourth  or 
fifth  week  in  the  human  embryo  (Kolliker).  At  intervals  along  that  portion  of  the 
membranous  matrix  which  encloses  the  notochord  the  cells  become  pushed  apart 
by  the  formation  between  them  of  a  homogeneous  substance  and  the  tissue 
becomes  converted  into  cartilage.  The  regions  which  are  thus  chondrified  corre- 
spond to  the  intervals  between  the  successive  pairs  of  protovertebral  somites,  and 
form  the  bases  of  the  bodies  of  the  future  vertebrae,  the  segments  of  the  spinal 
column  thus  alternating  in  position  with  the  protovertebrae.  In  the  regions  oppo- 
site each  protovertebral  somite  chondrification  does  not  take  place,  but  the  mem- 
branous matrix  assumes  a  fibrous  structure,  forming  the  intervertebral  disks. 


THE    CRANIUM,  117 

Similar  changes  occur  in  the  portion  of  the  matrix  which  surrounds  the  spinal 
cord.  Opposite  each  vertebral  body  chondrification  takes  place,  producing  the 
cartilaginous  vertebral  arches,  the  intervening  tissue  becoming  transformed  into 
the  ligaments  which  extend  between  the  arches,  chiefly  the  interspinous  liga- 
ments and  the  ligamenta  subflava.  Below  each  subflavan  ligament  an  openino1  is 
left,  through  which  the  spinal  nerves  make  their  exit  from  the  spinal  canal,  the 
nerves,  like  the  provertebne,  alternating  in  position  with  the  vertebral  centra. 
(7)  The  notochord  contained  in  the  centre  of  this  chondrifying  mass  does  not  con- 
tinue to  grow,  but  becomes  in  the  human  subject  relatively  smaller,  so  as,  at  last, 
to  form  a  mere  slender  thread,  except  opposite  the  secondary  segmentations ; 
that  is  to  say,  corresponding  to  the  intervals  between  the  bodies  of  the  perma- 
nent vertebra?.  Here  it  presents  thickenings  and  forms  an  irregular  network, 
the  remains  of  which  are  to  be  found  at  all  periods  of  life  in  the  central  pulp  of 
the  intervertebral  disks. 

Development  of  the  Ribs  and  Sternum. — The  ribs  are  formed  by  extensions  of 
the  blastema  of  the  vertebrae  in  the  mesoblastic  layer  of  the  blastodermic  mem- 
brane. These  speedily  undergo  chondrification,  and  appear  as  cartilaginous  bars, 
and  become  separated  from  the  vertebrae  at  their  posterior  extremities.  At  their 
anterior  ends  the  costal  bars,  which  are  to  form  the  nine  upper  ribs,  turn  upward 
and  fuse  together  so  as  to  form  a  cartilaginous  strip  bounding  a  central  median 
fissure.  The  strips  on  either  side  then  join  in  the  middle  line  from  before  back- 
ward, and  so  give  rise  to  a  longitudinal  piece  of  cartilage,  which  represents  the 
manubrium  and  gladiolus  of  the  sternum.  In  the  process  of  development  the 
sternal  attachment  of  the  eighth  rib  disappears,  while  that  of  the  ninth  sub- 
divides, one  portion  remaining  attached  to  the  inferior  extremity  of  the  cartilag- 
inous sternum  and  becoming  developed  into  the  ensiform  cartilage ;  the  other  por- 
tion receding  from  the  sternum  and  becoming  attached  to  the  rib  above. 

The  further  development  of  the  vertebrae,  ribs,  and  sternum,  and  the  ossifica- 
tion of  their  cartilaginous  structure,  are  described  in  the  body  of  the  work. 

Development  of  the  Cranium  in  general,  and  the  Face. — We  have  seen  that  the 
first  trace  of  the  embryo  consists  in  the  formation  of  a  longitudinal  fold  of  the 
epiblast  on  either  side  of  a  median  groove,  and  that 
these  folds  or  ridges  grow  backward  and  meet  in  the 
median  line,  thus  forming  a  canal.  This  canal,  at  the 
cephalic  extremity  of  the  embryo,  is  dilated  and  forms 
a  bulbous  enlargement.  The  bulbous  enlargement 
soon  expands  into  three  vesicular  dilatations,  which 
are  known  as  the  three  primary  cerebral  vesicles,  from 
which  all  the  different  parts  of  the  encephalon  are 
presently  to  be  developed.  The  most  anterior  of  the 

three    forms    the   thalamencephalon,   whilst   a  hollow  

projection  from  it  forms  the  cerebral  hemispheres ;  the  jj 

middle  one  forms  the  mesencephalon ;    the  posterior         FlG-  90-— Longitudinal  section 

•  •i  ii  iii  i  t     i  mi         °f  tne  head  of  an    embrvo    four 

the  metencepnalon  and  the  myelencepnalon.  The  weeks  old,  seen  from  the  inside 
primary  cerebral  vesicles  are  at' this  time,  of  course,  LSSd  SflAff^JSTZ 
hollow,  and  their  cavities  freelv  communicate  with  i^?rme«dia^'  ^braLn-  •  5-  ,Mi,dJ?le 

11  .  .  _      •  Drain.    t>.   riinoer  Drain.    7.   Alter 

each    other    at  the    points    of    constriction.      As  the   brajn-  &•  Anterior  portion  of  the 

i  ,1  L     i       ,  -11  i  temonum  cerebelli.    9.  Its  lateral 

embrvo  grows,  the  cerebral  vesicles  become  twice  bent    portion  intervening  between  NOS. 
forward  on  their  own  axis  (Figs.   90,  91,   A  and  B).    b^t^J^B£Z^CT?S 
The  upper  or  posterior  curvature  is  called  the  cerebral,    audltory  vesicle. 
the  lower  or  anterior,  the  frontal  protuberance. 

Thus,  we  have  a  triple  cavity  (see  Fig.  91,  A,  where  the  three  cavities  are 
marked  c.  me,  and  mo)  lined  by  epiblast  and  covered  by  the  same  structure. 
Between  these  two  layers  of  epiblast.  a  layer  of  mesoblast,  derived  from  the  pro- 
tovertebral  plates  of  the  trunk,  is  prolonged  and  spreads  over  the  whole  surface 
of  the  cerebral  vesicles.  From  these  structures  the  cranium  and  its  contents  are 
developed.  The  external  layer  of  the  epiblast  forms  the  superficial  epithelium 


118 


DEVEL  OPMENT. 


of  the  scalp.  The  mesoblastic  layer  forms  the  true  skin,  the  blood-vessels,  mus- 
cles, connective  tissue,  bones  of  the  skull,  and  membranes  of  the  brain.  The 
layer  of  epiblast  lining  the  cavity  forms  the  nervous  substance  of  the  encephalon, 
while  the  cavity  itself  constitutes  the  ventricles. 

The  upper  end  of  the  notochord  terminates  at  its  cephalic  end  in  a  pointed 
extremity  which  extends  as  far  forward  as  the  situation  of  the  body  of  the  future 
sphenoid  bone,  and  is  there  imbedded  in  a  mass  of  tissue,  the  "  investing  mass  of 
Rathke."  This  mass,  derived  from  mesoblastic  tissue,  becomes  cartilaginous,  and 


FIG.  91.— Vertical  section  of  the  head  in  early  embryos  of  the  rabbit.  Magnified.  (From  Mihalkovics).  A. 
From  an  embryo  of  five  millimetres  long.  B.  From  an  embryo  of  six  millimetres  long.  c.  Vertical  section  of  the 
anterior  end  of  the  notochord  and  pituitary  body,  etc.  from  an  embryo  sixteen  millimetres  long.  In  A,  the  fau- 
cial  opening  is  still  closed.  In  B,  it  is  formed,  c.  Anterior  cerebral  vesicle,  me.  Mesocerebrum.  mo.  Medulla 
oblongata.  co.  Epiblast.  m.  Wall  of  medullary  canal,  if.  Infundibulum.  am.  Amnion.  spe.  Spheno-ethmoidal. 
be.  Central  (dorsum  sellse),  and  spo,  spheno-occipital  parts  of  the  basis  cranii.  h.  Heart.  /.  Anterior  extremity 
of  primitive  alimentary  canal  and  opening  (later)  of  the  fauces,  i.  Cephalic  portion  of  primitive  intestine. 
tha.  Thalamus.  p'.  Closed  opening  or  the  involuted  part  of  the  pituitary  body  (py).  ch.  Notocnord.  ph.  Pharynx. 

from  it  is  developed  the  basi-occipital  and  basi-sphenoid  bones ;  and  by  lateral 
expansions  from  it  the  occipitals,  the  greater  wings  of  the  sphenoid,  and  the 
periotic  mass  of  cartilage  surrounding  the  primary  auditory  vesicles.  From  the 
front  of  the  investing  mass  of  Rathke,  which  corresponds  in  position  to  the  future 
dorsum  sellae,  two  lateral  bars  are  directed  forward,  enclosing  a  space  which  forms 
the  pituitary  fossa,  in  which  the  pituitary  body  is  eventually  developed.  These 
bars  are  named  the  trabeculce  cranii,  and  extend  as  far  forward  as  the  anterior 
extremity  of  the  head,  where  they  coalesce  with  each  other.  From  them  the  pre- 
sphenoid  and  lateral  masses  of  the  ethmoid  are  developed ;  and  from  their 
coalescence  a  process  is  prolonged  downward  to  form  a  portion  of  the  framework 
of  the  face  hereafter  to  be  described.  From  the  pre-sphenoids,  which  are  developed 
from  these  trabeculae,  a  lateral  expansion  takes  place,  which  forms  the  orbito- 
sphenoid  or  lesser  wings  of  the  sphenoid,  enclosing  the  optic  foramen. 

The  portions  of  the  base  of  the  skull  above  enumerated  are  formed  from  car- 
tilage ;  the  remaining  parts,  comprising  the  vault  of  the  skull,  are  of  membran- 
ous formation. 

The  head  at  first  consists  simply  of  a  cranial  cavity,  the  face  being  subse- 
quently developed  in  the  manner  now  to  be  described  by  a  series  of  arches  with 
clefts  between  them  (Fig.  92).  On  the  outer  surface  of  what  represents  the 
upper  neck  region  of  the  embryo  four  linear  vertical  grooves  make  their  appear- 
ance on  each  side.  Corresponding  grooves  are  also  formed  in  the  Avail  of  the 
intestine,  the  hypoblast  of  the  pharynx  being  thus  brought  into  contact  with  the 
epiblast  of  the  outer  surface  of  the  body  along  the  lines  of  the  grooves.  These 
grooves  represent  the  branchial  or  visceral  clefts,  which  become  actual  perfora- 
tions in  the  lower  vertebrates,  and  place  the  cavity  of  the  pharynx  in  communica- 
tion with  the  exterior.  On  either  side  of  each  groove  a  thickening  of  the  meso- 
derm  occurs,  so  that  five  ridges  are  formed,  the  first  of  which  is  in  front  of  the 


THE   FACE. 


119 


first  groove,  and  the  last  behind  the  last  groove,  while  the  second,  third,  and 
fourth  are  between  successive  grooves.  These  are  the  branchial  arches,  the  first 
of  which  has  its  upper  end  bent  so  as  to  lie  at  an  angle  with  the  lower  end.  each 
half  of  the  arch  being  thus  <-shaped.  The  upper  limb  of  the  <  is  termed  the 
maxillary,  and  the  lower,  the  mandibular  process,  and  between  the  two  there 
lies  a  depression,  the  oral  $inm.  The  outline  of  this  depression  is  pentagonal, 
since  the  ends  of  the  two  maxillary  processes  do  not  unite,  but  have  projecting 
down  between  them  a  broad  plate,  the  fronto-nasal  process.  In  the  mesoblast 
which  occupies  the  axis  of  each  branchial 
arch  a  cartilaginous  bar  develops,  serv- 
ing as  a  support  for  the  arch. 

The  maxillary  processes  unite  with  the 
fronto-nasal  process.  The  latter  consists  of 
three  plates,  a  central  single  one  and  two 
lateral  ones.  The  central  is  called  the 
"  mil-frontal  "  process.  It  is  free  in  front 
and  below,  but  behind  it  is  united  with  the 
coalesced  portion  of  the  trabeculse  cranii, 
which  therefore  probably  assists  in  the  for- 
mation of  the  septum  nasi,  and.  in  addition, 
of  the  prominent  part  of  the  future  nose. 
The  lateral  plates  of  the  fronto-nasal  pro- 
cess are  separated  from  the  central  one  by 
a  depression  or  furrow  on  either  side ; 
these  furrows  form  the  primary  nasal  pits 
or  fossae.  The  lateral  plates  project  down- 
ward parallel  to  the  mid-process  for  a  cer- 
tain distance,  and  then,  curving  inward, 
unite  with  it.  thus  shutting  off  the  nasal 
fossae  from  the  rest  of  the  face.  The 
lateral  masses  of  the  ethmoid  and  lachry- 
mal bones  are  developed  in  the  lateral 
plates,  and  by  their  union  with  the  mid- 
frontal  process  form  the  intermaxillary  bone  and  the  lunula,  or  central  part 
of  the  upper  lip. 

The  maxillary  processes  descend  for  a  short  distance,  forming  the  outer  wall 
of  the  orbit,  in  which  the  malar  bone  is  developed ;  they  then  incline  inward, 
and,  meeting  the  lateral  plate  of  the  fronto-nasal  process,  form  the  floor  of  the 
orbit,  and  shut  it  off  from  the  rest  of  the  face  ;  then,  continuing  their  course 
downward  and  inward,  they  join  the  mid-frontal  process,  and  with  it  complete  the 
alveolar  arch  and  the  superior  maxillary  bone.  Finally,  palatal  processes  are 
formed  by  an  extension  of  the  inner  sides  of  this  arch  ;  these  coalesce  with  each 
other  in  the  median  line,  thus  separating  the  cavity  of  the  mouth  from  the  nasal 

e,  and  completing  the  palate.  In  front,  however,  the  palatal  processes  do  not 
join  with  the  mid-frontal  process,  but  a  cleft  is  left  which  constitutes  the  naso- 
palatine  canal. 

The  maudibular  process  forms  the  lower  jaw  or  mandible,  the  cartilage  which 
it  contains  being  known  as  Meeker  s  cartilage.  This  becomes  ossified,  and  unites 
with  membrane-bones,  developing  in  the  mesoblastic  tissue  around  it,  to  form  the 
mandibular  bone.  Its  upper  end  is  in  contact  with  the  periotic  capsule,  and 
from  it  two  portions  are  separated  and  ossify  to  form  two  of  the  bones  of  the 
middle  ear.  the  malleus  and  incus.  The  second  arch  is  named  the  hyoid  arch ; 
from  it  is  formed  the  styloid  process,  the  stylo-hyoid  ligament,  and  the  lesser 
cornu  of  the  hyoid  bone.  The  third,  or  thyro-hyoid  arch,  gives  origin  to  the  great 
cornu  of  the  hyoid  bone,  while  the  body  of  this  bone  is  formed  between  the 
second  and  third  arches.  The  fourth  and  fifth  arches  do  not  reach  so  great  a 
development  as  the  others,  and  their  cartilages  likewise  only  partially  develop. 


FIG.  92.— Face  of  an  cmbrvo  of  25  to  28  days. 
Magnified  15  times.  1.  Frontal  prominence.  2,3. 
Right  and  left  olfactory  fossa.  4.  Inferior  max- 
illary tubercles,  united  in  the  middle  line.  5. 
Supe'rior  maxillary  tubercles.  6.  Mouth  of  fau- 
ces. 7.  Second  pharyngeal  arch.  8.  Third.  9. 
Fourth.  10.  Primitive  ocular  vesicle.  11.  Prim- 
itive auditory  vesicle. 


120  DEVELOPMENT. 

The  lower  ends  of  their  cartilages  unite  together  to  form  the  thyroid  cartilage  of 
the  larynx. 

Between  the  mandibular  and  maxillary  processes  the  buccal  cavity  or  mouth  is 
formed ;  this  therefore  owes  its  origin  to  the  formation  of  the  processes,  and 
consists  of  mesoblastic  tissue  lined  by  epiblast.  As  has  been  already  stated  (page 
108),  the  cephalic  end  of  the  embryo  becomes  remarkably  curved  on  itself,  the 
fore-  and  mid-brain  bending  downward  over  the  anterior  portion  of  the  original 
blastodermic  membrane,  which  remains  within  the  body  of  the  embryo  and  from 
which  the  fore-gut  is  to  be  developed.  This  fore-gut  terminates  as  a  blind 
extremity  beneath  the  head  (Fig.  91,  A,/).  Another  prominence  forms  on  the 
ventral  surface  of  the  fore-gut,  which  represents  the  rudimentary  heart  (Fig.  91, 
A,  A).  Between  these  two  prominences,  caused  by  the  projection  of  the  fore-brain 
and  the  heart,  an  involution  of  the  epiblast  takes  place,  gradually  deepening 
until  it  comes  in  contact  with  the  upper  part  of  the  alimentary  canal.  This  is 
the  stomodceum  or  mouth,  which  becomes  bounded  by  prominences  constituting 
the  maxillary  and  mandibular  processes.  It  is  at  first  quite  distinct  from  the 
upper  part  of  the  alimentary  canal,  which,  as  we  shall  hereafter  see,  is  formed  by 
the  inner  or  splanchno-pleural  layer  of  the  mesoblast  and  the  hypoblast,  the  two 
cavities  being  separated  by  all  the  layers  of  the  blastodermic  membrane.  A  com- 
munication between  the  two  is,  hoAvever,  gradually  effected  by  the  absorption  of 
these  layers  at  the  anterior  extremity  of  the  primitive  alimentary  cavity  and  the 
hinder  portion  of  the  epiblastic  involution  from  which  the  mouth  is  formed. 

The  branchial  grooves  are  at  first  fully  exposed  on  the  surface  of  the  neck 
region  of  the  body,  but  later  a  fold  of  skin  grows  backward  from  the  lower 
border  of  each  mandibular  process.  This  fuses  below  with  the  side  of  the  body 
and  completely  conceals  the  grooves,  which  disappear,  with  the  exception  of  the 
first.  Both  the  internal  and  external  parts  of  this  persist,  the  former  giving 
rise  to  the  Eustachian  tube  and  the  tympanic  cavity,  Avhile  the  upper  portion  of 
the  latter  forms  the  meatus  auditorius. 

Development  of  the  Nervous  Centres  and  the  Nerves. — The  medullary  groove 
above  described  (page  107)  presents,  about  the  third  week,  three  dilatations  at 
its  upper  end,  separated  by  two  constrictions,  and  at  its  posterior  part  another 

dilatation,  called  the  rhomboidal  sinus.  Soon  after- 
ward the  groove  become  a  closed  canal  (medullary 
canal),  exhibiting  corresponding  dilatations.  This  is 
the  rudiment  of  the  cerebro-spinal  axis.  As  the 
^rasfcjsv  embryo  grows,  its  cephalic  part  becomes  more  curved, 

jtffflgr  ^HH!^  and  the  three  dilatations  at  the  anterior  end  of  the 
primitive  cerebro-spinal  axis  become  vesicles  distinctly 
separate  from  each  other  (Fig.  90).  These  are  the 
cerebral  vesicles — anterior,  middle,  and  posterior.  The 
anterior  cerebral  vesicle  (situated,  at  this  period,  quite 
below  the  middle  vesicle)  is  the  rudiment  of  the  third 
.  ventri^e»  and  °f  tne  Parts  surrounding  it — viz.  the 
a^H  optic  thalami  and  all  the  parts  which  form  the  floor  of 
FIG.  93.— section  of  the  me-  the  third  ventricle.  The  middle  vesicle  represents  the 
aqueduct  of  Sylvius,  with  the  corpora  quadrigemina. 
lp1theiiument3alAnaterior  ^ray  Tne  posterior  vesicle  is  developed  into  the  fourth  ven- 
matter.  4.  Posterior  gray  matter,  tricle,  and  its  walls  form  the  pons  Varolii,  cerebellum, 

5.  Anterior  commissure.    6.  Pos-  ,    „         ,  ,  ,  -in  c  0.1       f        J.-L. 

terior  portion  of  the  canal,  closed     medulla  oblongata,  and  parts  in  the  floor  ot  the  lourtn 

by  the  epithelium  only.    7.  An-      •,,„„+„•    1 
terior  column.  8.  Lateral  column,      ventricle. 

tenor^tl01!!0 poTeriorU^         .  At  an    early  period   in   the    development  of    this 

primitive  brain    a    protrusion    takes    place    from   the 

anterior  vesicle,  which  is  at  first  simple,  but  soon  becomes  divided  into  two  parts 
by  an  antero-posterior  fissure.  These  expand  laterally,  and  the  cerebral  hemi- 
spheres and  corpora  striata  are  developed  from  them.  In  the  roof  of  the  fore- 
part of  the  posterior  cerebral  vesicle  a  thickening  takes  place,  forming  the  rudi- 


THE  NERVOUS    CENTRES.  121 

ment  of  the  cerebellum.  In  consequence  of  these  protrusions  or  outgrowths 
taking  place,  the  three  primary  cerebral  vesicles  are  now  converted  into  six 
permanent  rudiments  of  the  brain  and  medulla  oblongata.  The  anterior  part 
of  the  original  anterior  cerebral  vesicle  (fore-brain,  prosencephalon),  now  divided 
into  two,  constitutes  the  cerebral  hemispheres,  corpus  callosum,  corpora  striata, 
fornix,  lateral  ventricles,  and  olfactory  bulbs.  The  hemispheres  are  at  first  rela- 
tively small  and  do  not  conceal  the  parts  formed  from  the  middle  primary  vesicle 
or  the  optic  thalaini,  which  with  the  optic  nerves,  the  third  ventricle,  and  the 
parts  in  its  floor,  are  furnished  by  the  posterior  portion  of  the  anterior  vesicle 
(inter-brain,  thalamencephalon).  By  the  third  month,  however,  the  hemispheres 
have  risen  above  the  optic  thalami,  and  by  the  sixth  month  above  the  cerebellum. 
Fissures  are  seen  on  the  surface  of  the  hemispheres  at  the  third  month,  but  all 
except  one  disappear.  This  one  persists,  and  forms  the  fissure  of  Sylvius.  The 
permanent  fissures  for  the  convolutions  do  not  form  till  about  the  seventh  or 
eighth  month.  The  middle  cerebral  vesicle  (mid-brain,  mesencephalon)  is  at  first 
situated  at  the  summit  of  the  angle  shown  on  Fig.  90.  Its  smooth  surface  is 
soon  divided,  by  a  median  and  transverse  groove,  into  four  tubercles  (tubercula 
quadrigernina),  which  are  gradually  overlapped  by  the  growth  of  the  cerebral 
hemispheres.  Its  cavity  diminishes  as  its  walls  thicken,  and  contracts  to  form 
the  aqueduct  of  Sylvius.  The  crura  cerebri  are  also  formed  from  this  vesicle. 
The  third  primary  cerebral  vesicle  at  an  early  period  (between  the  ninth  and 
twelfth  week)  consists  of  the  hind-brain  or  metencephalon,  forming  the  cerebel- 
lum, pons  Yarolii.  and  anterior  part  of  the  fourth  ventricle,  and  of  the  after-brain 
or  myelencephalon,  which  forms  the  medulla  oblongata  with  the  rest  of  the  fourth 
ventricle. 

The  development  of  the  pituitary  body  has  of  late  received  much  attention.  It 
is  mainly  formed  by  a  diverticillum  from  the  buccal  involution  of  epiblast.  At  its 
upper  and  front  part  this  involution,  from  which  the  mouth  or  stomodaeum  is 
developed,  forms  a  hollow  saccular  protrusion,  which  extends  into  the  angle  formed 
by  the  bend  of  the  fore -with  the  mid-brain.  Here  it  comes  in  contact  with  a 
median  hollow  protrusion,  Avhich  passes  downward  and  backward  from  the 
posterior  portion  of  the  anterior  cerebral  vesicle  (Fig.  91,  c,  if).  They  become 
intimately  connected,  and  together  form  the  pituitary  body  or  hypophysis. 

When  the  medullary  groove  is  first  closed,  the  foetal  spinal  cord  occupies 
its  whole  length,  and  presents  a  large  central  canal,  which  gradually  contracts  in 
consequence  of  the  thickening  and  rapid  growth  of  the  epiblast  around  it. 
This  increase  in  thickness  takes  place  principally  at  the  sides,  so  that  eventually 
the  central  canal  acquires  on  section  the  appearance  of  a  slit.  The  two  sides  of 
this  slit  eventually  join  in  the  middle,  and  the  original  canal  is  divided  into  two  : 
an  anterior,  which  becomes  the  central  permanent  canal,  which  in  after  life  is  no 
longer  perceptible  to  the  eye,  though  it  is  still  visible  on  microscopic  section  ; 
and  a  posterior,  which  becomes  filled  about  the  ninth  week  with  a  septum  of 
connective  tissue  from  the  pia  mater,  and  forms  the  posterior  fissure  of  the  cord. 
The  anterior  fissure  is  formed  simply  as  a  cleft  left  between  the  lateral  halves 
of  the  cord. 

After  the  fourth  month  the  spinal  column  begins  to  grow  in  length  more 
rapidly  than  the  medulla  spinalis,  so  that  the  latter  no  longer  occupies  the  whole 
canal.  The  cord  is  composed  at  first  entirely  of  uniform-looking  cells,  which  soon 
separate  into  two  layers,  the  inner  of  which  is  composed  of  cells  which  increase 
by  division,  and  develop  outgrowths  which  become  axis-cylinders  of  nerve-fibres. 
These  cells  are  termed  neuroblasts.  The  cells  of  the  outer  layer,  known  as 
tpongioblagte,  scatter  themselves  among  the  neuroblasts,  forming  the  neuroglia 
cells,  some  of  them  migrating  inwards  to  form  the  ependymal  lining  of  the  cavi- 
ties of  the  cord  and  brain. 

The  cerebral  and  spinal  membranes  are,  according  to  Kblliker,  a  production 
from  the  protovertebral  somites,  and  are  recognizable  about  the  sixth  week.  As 
the  fissures  separating  the  segments  of  the  cerebro-spinal  axis  appear,  the  mem- 


122  DEVELOPMENT. 

branes  extend  through  them   and  the  pia  mater  passes  into  the  cerebral  ven- 
tricles. 

The  Nerves. — The  nerves  are  developed,  like  the  rest  of  the  nervous  system, 
from  epiblast.  The  spinal  nerves  are  developed  as  follows :  Close  to  the  point 
of  involution  of  the  epiblast  in  the  median  line — that  is  to  say,  in  the  angle  of 
junction  of  the  neural  and  general  epiblast — a  cellular  swelling  constituting  the 
neural  crest  appears,  and  forms  a  continuous  ridge  on  the  dorsal  aspect  of  the 
neural  canal.  On  this  crest  enlargements  occur,  corresponding  with  the  middle 
of  each  protovertebral  segment.  These  grow  downward  between  the  neural  canal 
and  the  mesoblastic  tissue  forming  the  protovertebne,  and  occupy  a  position  on  the 
lateral  wall  of  the  canal.  These  enlargements  are  the  rudiments  of  the  ganglion 
of  the  posterior  root ;  they  are  at  first  attached  to  the  neural  crest  from  which  they 
spring,  but  subsequently  this  attachment  becomes  lost,  and  they  then  form  isolated 
masses  on  either  side  of  the  neural  canal,  which  now  contains  the  rudimentary 
cord.  They  consist  of  oval  cells,  from  either  end  of  which  a  process  eventually 
springs ;  one,  passing  centrally,  grows  into  the  embryonic  cord  and  constitutes  the 
posterior  root  of  the  nerve  ;  the  other,  growing  peripherally,  joins  the  fibres  of  the 
anterior  root  to  form  the  spinal  nerve. 

The  anterior  root  is,  according  to  the  researches  of  His,  a  direct  outgrowth 
of  certain  cells  which  are  found  in  the  rudimentary  cord,  and  which  are  named 
neuroblasts.  These  cells,  like  those  mentioned  above,  are  oval,  and  have  a  pro- 
longation directed  outward  toward  the  surface  of  the  cord.  These  processes 
pass  out  of  the  cord  in  bundles  and  penetrate  the  mesoblast  and  join  with  fibres 
of  the  posterior  root,  and  from  the  point  of  union  the  nerve  grows  toward  ita 
peripheral  termination. 

Most  of  the  cranial  nerves  are  developed  in  the  same  manner  as  the  posterior 
roots  of  the  spinal  nerves.  That  is  to  say,  the  neural  crest,  developed  from  the 
epiblast,  is  continued  onward,  along  the  dorsal  surface  of  the  cephalic  portion  of 
the  neural  tube,  as  far  as  the  mid-brain.  From  this  a  series  of  swellings  at 
irregular  intervals  form  the  rudimentary  ganglia,  from  the  polar  cells  of  which 
the  nerve  is  formed  and  its  connection  with  the  brain  established.  This  appears 
to  be  the  case  with  the  sensory  portion  of  the  fifth,  the  portion  of  the  facial  con- 
nected with  the  geniculate  ganglion,  the  auditory  and  the  sensory  portions  of 
the  glossopharyngeal  and  pneumogastric.  The  motor  portions  of  the  mixed  nerves 
and  the  third,  fourth,  sixth,  spinal  accessory  and  hypoglossal  arise  like  the 
anterior  roots  of  the  spinal  nerves  from  neuroblasts  in  the  floor  of  the  aqueduct 
of  Sylvius  and  of  the  fourth  ventricle. 

The  olfactory  tract  and  bulb  is  a  protrusion  of  the  antero-ventral  part  of  each 
cerebral  hemisphere.  This  protrusion  comes  in  contact  with  the  thickened  epi- 
blast of  the  olfactory  area  (see  page  125),  from  which  neuroblastic  cells,  which 
are  formed  within  the  area,  pass  out  and  form  a  ganglion  between  the  area  and 
the  olfactory  bulb.  From  this  ganglion  cell-processes  grow  centripetally  to  form 
the  nerve-roots,  and  centrifugally  to  form  the  olfactory  nerves  which  ramify  on  the 
Schneiderian  membrane. 

The  optic  nerve  arises  in  a  manner  somewhat  different  from  any  of  the  other 
cranial  nerves.  It  will  be  considered  in  connection  with  the  development  of 
the  eye. 

The  sympathetic  nerves  are  probably  developed  as  outgrowths  from  the 
ganglia  of  the  spinal  and  cranial  nerves. 

Development  of  the  Eye. — The  nervous  elements  and  non-vascular  parts  of 
the  eye  are  formed  from  the  epiblast,  and  the  vascular  portions  from  the  meso- 
blast ;  but  the  method  of  development  is  somewhat  complicated.  The  essential 
portion  of  the  eye — i.  e.  the  retina  and  the  parts  immediately  connected  with  it 
— is  an  outgrowth  from  the  rudimentary  brain  (primitive  ocular  vesicle),  and  this 
outgrowth  is  met  by  an  ingrowth  from  the  common  epidermic  or  corneous  layer 
of  the  epiblast,  out  of  which  the  lens  and  the  conjunctival  and  cornea!  epithelium 
are  developed. 


THE  EYE. 


123 


The  first  appearance  of  the  eye  consists  in  the  protrusion  or  evagination  from 
the  medullary  wall  of  the  thalamencephalon,  or  inter-brain,  of  a  vesicle,  called  the 
/,/•///<>>/'•••  ocular  This  is  at  first  an  open  cavity  communicating  by  a  hollow 

stalk  with  the  general  cavity  of  the  cerebral  vesicle.  As  the  primitive  ocular  vesi- 
cle is  prolonged  forward,  it  meets  the  epidermic  layer  of  the  epiblast,  which  at  the 
point  of  contact  becomes  thickened,  and  then  forms  a  depression  which  gradually 
encroaches  on  the  most  prominent  part  of  the  primitive  ocular  vesicle,  which  in  its 
turn  appears  to  recede  before  it,  so  as  to  become  at  first  depressed  and  then  inverted 
in  the  manner  indicated  by  the  annexed  figure  (Fig.  94,  A),  so  that  the  cavity  is 
finally  almost  obliterated  by  the  folding  back  of  its  anterior  half,  and  the  original 
sac  converted  into  a  cup-shaped  cavity,  the  ocular  cup,  in  which  the  involuted 
epiblastic  layer,  the  rudiment  of  the  lens,  is  received  (Fig-  94,  B).  This  cup- 
shaped  cavity  consists  therefore  of  two  layers :  one,  the  outer,  originally  the 
posterior  half  of  the  primitive  ocular  vesicle,  is  thin,  and  eventually  forms  the 
pigmental  layer  of  the  retina  : l  the  other  layer,  the  inner,  originally  the  anterior 
or  more  prominent  half,  which  has  become  folded  back,  and  is  much  thicker, 
is  converted  into  the  nervous  layers  of  the  retina.  Between  the  two  are  the 
remains  of  the  cavity  of  the  original  primary  vesicle,  which  finally  becomes 
obliterated  by  the  union  of  its  two  layers.  The  optic  nerve  fibres  originate  from 
the  cells  of  the  ganglionic  layer  of  the  retina,  which  thus  correspond  to  the  cells  ot 
the  posterior  root  ganglia  of  the  spinal  nerves.  From  these  cells  the  fibres  grow 
toward  the  brain,  choosing  the  optic  stalk  as  a  path  along  which  to  grow,  the  stalk 
thus  becoming  gradually  replaced  by  the  optic  nerve.  As  development  proceeds  the 
cup-shaped  cavity  or  ocular  cup  increases  in  size,  and  thus  a  space  is  formed  between 
it  and  the  rudimentary  lens  which  it  contains ;  this  is  the  secondary  ocular  vesicle, 
and  in  it  the  vitreous  humor  is  developed  (Fig.  94,  c).  The  folding  in  of  the  primary 
optic  vesicle  to  produce  the  optic  cup  proceeds  from  above  downward,  and  grad- 
ually surrounds  the  lens,  but  leaves  an  aperture  or  fissure  below,  the  choroidal 
Ussure  or  oculir  cleft,  through  which  vascular  elements,  within  the  vesicle  and 
derived  from  the  mesoblast.  retain  their  con- 
nection with  the  rest  of  the  mesoblast.  This 
gap  or  clefc  is  continued  for  some  distance 


c 

•-/ 

p  /^^^ 


FIG.  9i.— Diagram  of  development  of  the  lens  ABC. 
Different  stages  of  development.  1.  Epidermic  layer.  2. 
Thickening  of  this  layer.  3.  Crystalline  depression.  4. 
Primitive  ocular  vesicle,  its  anterior  part  pushed  back  bv 
the  crystalline  depression.  5.  Posterior  part  of  the  primi- 
tive ocular  vesicle,  forming  the  external  layer  of  the  sec- 
ondary ocular  vesicle.  6.  Point  of  separation  between  the 
lens  and  the  epidermic  layer.  7.  Cavity  of  the  secondary 
ocular  vesicle,  occupied  by  the  vitreous. 


FIG.  95.— Diagrammatic  sketch  of  a  vertical 
longitudinal  section  through  the  eyeball  of  a 
human  foetus  of  four  weeks.  (After  Kolliker). 
Magnified  100  diameters.  The  section  is  a  little  to 
the  side,  so  as  to  avoid  passing  through  the  ocular 
cleft,  c.  The  cuticle,  where  it  becomes  later  the 
cornea.  1.  The  lens.  op.  The  pedicle  of  the 
primary  optic  vesicle,  rp.  Primary  medullary 
cavity  of  the  optic  vesicle,  p.  The  pigment-layer 
of  the  outer  wall.  r.  The  inner  wall  forming  the 
retina.  r#.  Secondary  optic  vesicle,  containing 
the  rudiment  of  the  vitreous  humor. 


into  the  stalk  of  the  optic  vesicle,  and  thus  allows  a  process  of  the  mesoblast  to 
extend  down  the  stalk  to  form  the  arteria  centralis  retinae  and  its  accompanying 
The  lens  is  at  first  a  thickening  of  the  epiblast ;  then  a  depression  or  involu- 


vem. 


tion  takes  place,  thus  forming  an  open  follicle,  the  margins  of  which  gradually 
approach   each  other  and  coalesce,  forming  a  cavity  enclosed  by  epiblastic  cells 

1  This  layer  forms  functionally  part  of  the  choroid,  and  was  formerly  described  as  belonging  to 
this  membrane  ;  it  is  now  described  as  part  of  the  retina,  on  account  of  its  method  of  development. 


124  DEVELOPMENT. 

(Fig.  94).  At  the  point  of  involution  the  external  layer  of  epiblast  separates  from 
the  ball  of  the  lens  and  passes  freely  over  the  surface,  so  that  the  lens  becomes  dis- 
connected from  the  epiblastic  layer  from  which  it  was  developed,  and  recedes  into 
the  ocular  cup,  while  the  cuticular  layer  covering  it  is  developed  into  the  corneal 
epithelium.  The  cells  forming  the  posterior  or  inner  wall  of  the  cavity,  whioh  is  to 
form  the  lens,  rapidly  increase  in  size,  becoming  elongated  and  developed  into 
fibres,  and,  filling  up  the  cavity,  convert  it  into  a  solid  body.  The  cells  on  the 
anterior  wall  undergo  no  change  and  retain  their  cellular  character.  The  secondary 
ocular  vesicle,  or  space  between  the  lens  and  the  hollow  of  the  ocular  cup  (Fig.  94, 
c  7,  and  95),  contains  a  quantity  of  mesoblastic  tissue  continuous  through  the  ocular 
cleft  with  the  rest  of  the  mesoblast,  and  into  this  blood-vessels  project  themselves 
through  the  ocular  cleft.  The  iris  and  ciliary  processes  are  formed  from  this  vas- 
cular tissue,  and  the  choroid  is  developed  in  the  mesoblast  surrounding  the  ocular 
vesicle.  A  portion  of  this  tissue  also  becomes  converted  into  the  vitreous  humor, 
and  surrounds  the  lens  with  a  vascular  membrane — the  vascular  capsule  of  the  lens, 
which  is  connected  with  the  termination  of  the  temporary  artery  (hyaloid)  that 
forms  the  continuation  of  the  central  artery  of  the  retina  through  the  vitreous 
chamber.  This  vascular  capsule  of  the  crystalline  lens  forms  the  membrana 
pupillaris  (described  on  a  subsequent  page),  and  also  attaches  the  borders  of  the 
iris  to  the  capsule  of  the  lens.  It  disappears  about  the  seventh  month. 

The  eyelids  are  formed  at  the  end  of  the  third  month  as  small  cutaneous  folds, 
which  come  together  and  unite  in  front  of  the  globe  and  cornea.  This  union  is 
broken  up  and  the  eyelids  separate  before  the  end  of  foetal  life. 

The  lachrymal  canal  develops  as  a  thickening  of  the  epiblastic  cells  at  the 
bottom  of  the  groove  which  extends  upward  toward  the  eye  between  the  maxillary 
and  the  fronto-nasal  processes.  The  thickening  becomes  hollowed  out  into  a 
canal,  and  the  lips  of  the  groove  meet  over  it,  thus  removing  it  from  the  surface. 

Development  of  the  Ear. — The  first  rudiment  of  the  ear  appears  shortly  after 
that  of  the  eye,  in  the  form  of  a  thickening  of  the  epiblast,  on  the  outside  of  that 
part  of  the  third  Drimary  cerebral  vesicle  which  eventually  forms  the  medulla 
oblongata,  opposite  the  dorsal  end  of  the  second  pharyngeal  arch.  The  thicken- 
ing is  then  followed  by  an  involution  of  the  epiblast,  which  becomes  deeper  and 
deeper,  sinking  toward  the  base  of  the  skull,  and  a  flask-shaped  cavity  is  formed ; 
by  the  narrowing  of  the  external  aperture  the  neck  of  the  flask  constitutes  the 
recessus  labyrinthi.  The  mouth  of  the  flask  then  becomes  closed,  and  thus  a  shut 
sac  is  formed,  the  primitive  auditory  or  otic  vesicle,  which  by  its  sinking  inward 
comes  to  be  placed  between  the  ali-sphenoid  and  basi-occipital  matrices.  From 
it  the  internal  ear  is  formed.  The  middle  ear  and  the  Eustachian  tube  are 
developed  from  the  remains  of  the  first  branchial  cleft,  while  the  pinna  and 
external  meatus  are  developed  from  the  soft  parts  overhanging  the  posterior  mar- 
gin of  the  same  cleft.  The  primary  otic  vesicle  becomes  imbedded  in  a  mass  of 
mesoblastic  tissue,  which  rapidly  undergoes  chondrification  and  ossification.  It, 
as  before  stated,  is  at  first  flask-  or  pear-shaped,  the  neck  of  the  flask,  or  recessus 
labyrinthi,  prolonged  backward,  forms  the  aqugeductus  vestibuli.  From  it  are 
given  off  certain  prolongations  or  diverticula,  from  which  the  various  parts  of  the 
labyrinth  are  formed.  One  from  the  anterior  end  gradually  elongates,  and,  form- 
ing a  tube  bends  on  itself  from  left  to  right  and  becomes  the  cochlea.  Three 
others,  which  appear  on  the  surface  of  the  vesicle,  form  the  semicircular  canals. 
Subsequently,  a  constriction  takes  place  in  the  original  vesicle,  which,  gradually 
increasing,  divides  it  into  two,  and  from  these  are  formed  the  utricle  and 
saccule.  Finally,  the  auditory  nerve,  which  has  been  developed  from  the 
"  neural  crest  "  in  the  manner  above  described  (page  122),  pierces  the  auditory 
capsule  in  two  main  divisions — one  for  the  vestibule,  the  other  for  the  cochlea. 
The  middle  ear  and  Eustachian  tube  are  the  remains  of  the  first  pharyngeal  or 
branchial  cleft  (hyo-mandibular),  and  are,  from  an  early  period, closed  by  the  forma- 
tion of  the  membrana  tympani,  which  consists  of  a  layer  of  epiblast  externally,  a 
layer  of  hypoblast  internally,  and  between  the  two  of  mesoblastic  tissue  consti- 


THE  NOSE.  125 

tuting  its  fibrous  and  vascular  layer.  With  regard  to  the  exact  mode  of  develop- 
ment of  the  ossicles  of  the  middle  ear  there  is  considerable  difference  of  opinion.  The 
malleus  and  incus,  however,  seem  to  be  developed  from  the  proximal  end  of  the 
mandibular  (Meckel's)  cartilage,  while  the  stapes  seems  to  have  a  double  origin, 
its  plate  being  an  ossification  of  the  cartilage  which  fills  the  foramen  ovale  in  the 
embryonic  condition,  while  its  arch  is  an  ossification  of  the  upper  end  of  the 
cartilage  of  the  hyoid  arch. 

The  external  auditory  meatus  is  developed,  like  the  pinna,  from  the  soft  parts 
on  the  posterior  margin  of  the  first  visceral  cleft  by  an  outgrowth  of  the  tissues 
in  this  situation. 

Development  of  the  Nose. — The  olfactory  fossae,  like  the  primary  auditory 
vesicles,  are  formed  in  the  first  instance  by  a  thickening  and  involution  of  the 
epiblast,  which  takes  place  at  a  point  below  and  in  front  of  the  ocular  vesicle 
(Fig.  92,  2,  3).  The  thickening  appears  at  a  very  early  period,  about  the  fourth 
week.  The  borders  of  the  involuted  portion  very  soon  become  prominent,  in  con- 
sequence of  the  development  of  the  mid-frontal  and  lateral  naso-frontal  plates 
above  spoken  of  (page  119),  which  are  formed  on  either  side  of  the  rudimentary 
fossae.  As  these  processes  increase  the  fossae  deepen  and  become  converted  into 
a  deep  channel,  Avhich  eventually  forms  the  upper  part  of  the  nasal  fossae — that 
is,  the  two  superior  meatuses,  the  part  to  which  the  olfactory  nerves  are  dis- 
tributed. At  this  time  they  are  continuous  with  the  buccal  cavity,  a  portion  of 
which  forms  the  lower  part,  or  inferior  meatus  of  the  nasal  fossae.  For  as  the 
palatine  septum  is  formed  the  buccal  cavity  is  divided  into  two  parts,  the  upper 
of  which  forms  the  lower  part  of  the  nasal  fossae,  while  the  remainder  forms  the 
permanent  mouth. 

The  soft  parts  of  the  nose  are  formed  from  the  coverings  of  the  frontal  pro- 
jections and  of  the  olfactory  fossae.  The  nose  is  perceptible  about  the  end  of  the 
second  month.  The  nostrils  are  at  about  the  third  month  closed  by  the  growth 
of  their  epithelium,  but  this  condition  disappears  about  the  fifth  month. 

The  olfactory  nerve,  as  above  pointed  out,  is  formed  from  the  anterior  cerebral 
vesicle  as  a  secondary  vesicle  on  its  under  surface,  and  it  lies  upon  the  involuted 
epiblast.  which  subsequently  forms  the  nasal  fossae. 

Development  of  the  Skin,  Glands,  and  Soft  Parts. — The  epidermis  is  produced 
from  the  external,  the  true  skin  from  the  middle,  blastodermic  layer  (Fig.  79,  19, 
20).  About  the  fifth  week  the  epidermis  presents  two  layers,  the  deeper  one  cor- 
responding to  the  rete  mucosum.  The  subcutaneous  fat  forms  about  the  fourth 
month,  and  the  papillae  of  the  true  skin  about  the  sixth.  A  considerable  desqua- 
mation  of  epidermis  takes  place  during  foetal  life,  and  this  desquamated  epidermis, 
mixed  with  a  sebaceous  secretion,  constitutes  the  vernix  caseosa,  with  which  the 
skin  is  smeared  during  the  last  three  months  of  foetal  life.  The  nails  are  formed 
at  the  third  month,  and  begin  to  project  from  the  epidermis  about  the  sixth.  The 
hairs  appear  between  the  third  and  fourth  months  in  the  form  of  depressions  of 
the  deeper  layer  of  the  epithelium,  which  then  become  inverted  by  a  projection 
from  the  papillary  layer  of  the  skin.  The  papillae  grow  into  the  interior  of  the 
epithelial  layer ;  and  finally,  about  the  fifth  month,  the  foetal  hairs  (lanugo)  appear 
first  on  the  head  and  then  on  the  other  parts.  These  hairs  drop  off  after  birth, 
and  give  place  to  the  permanent  hairs.  The  cellular  structure  of  the  sudorifer- 
ous and  sebaceous  glands  is  formed  from  the  epithelial  layer,  while  the  connective 
tissue  and  blood-vessels  are  derived  from  the  mesoblast  about  the  fifth  or  sixth 
month.  The  mammary  gland  is  also  formed :  partly  from  mesoblast — its  blood- 
vessels and  connective  tissue ;  and  partly  from  epiblast — its  cellular  elements. 
Its  first  rudiment  is  seen  about  the  third  month,  in  the  form  of  a  small  projection 
inward  of  epithelial  elements,  which  invade  the  mesoblast;  from  this  similar 
tracts  of  cellular  elements  radiate ;  these  subsequently  give  rise  to  the  glandular 
follicles  and  ducts.  The  development  of  the  former,  however,  remains  imperfect, 
except  in  the  adult  female. 

Development  of  the  Limbs. — The  upper  and  lower  limbs  begin  to  project,  as 


126  DE  VEL  OPMENT. 

buds,  from  the  anterior  and  posterior  part  of  the  embryo  about  the  fourth  week. 
These  buds  are  formed  by  a  projection  of  the  somatopleure  (i.  e.  the  outer  layer 
of  the  mesoblast  and  the  epiblast),  from  the  point  where  the  mesoblast  splits  into 
its  parietal  and  visceral  layers,  just  external  to  the  vertebral  somites,  of  which 
they  may  be  regarded  as  lateral  extensions.  The  division  of  the  terminal  portion 
of  the  bud  into  fingers  and  toes  is  early  indicated,  and  soon  a  notch  or  constric- 
tion marks  the  future  separation  of  the  hand  or  foot  from  the  forearm  or  leg. 
Next,  a  similar  groove  appears  at  the  site  of  the  elbow  or  knee.  The  indifferent 
tissue  or  blastema,  of  which  the  whole  projection  is  at  first  composed,  is  differen- 
tiated into  muscle  and  cartilage  before  the  appearance  of  any  internal  cleft  for 
the  joints  between  the  chief  bones. 

The  muscles  become  visible  about  the  seventh  or  eighth  week.  They  are 
derived  from  the  protovertebral  somites,  and  are  consequently  at  first  arranged  in 
segments,  a  condition  which  is  retained  by  some  of  the  deeper  muscles  of  the 
back  and  by  the  intercostal  muscles.  Fusion  of  successive  segments  takes  place, 
however,  and  further  differentiation  of  the  muscular  sheet  thus  formed  into  a 
varying  number  of  muscular  bundles  brings  about  the  adult  condition.  The 
muscles  of  the  limbs  are  produced  from  outgrowths  from  the  protovertebral 
somites  in  the  regions  in  which  the  limb  buds  appear. 

Development  of  the  Blood-vascular  System. — There  are  three  distinct  stages 
in  the  development  of  the  circulatory  system  before  it  arrives  at  its  complete  or 
adult  condition,  in  accordance  with  the  manner  in  which  nourishment  is  provided 
for  at  different  periods  of  the  existence  of  the  individual.  In  the  first  stage  there 
is  the  vitelline  circulation,  during  which  nutriment  is  extracted  from  the  yolk  or 
contents  of  the  vitelline  membrane.  In  the  second  stage  there  is  the  placenta! 
circulation,  which  commences  after  the  formation  of  the  placenta,  and  during 
which  nutrition  is  obtained  by  means  of  this  organ  from  the  blood  of  the  mother. 
In  the  third  stage  there  is  the  complete  circulation  of  the  adult,  commencing  at 
birth,  and  during  which  nutrition  is  provided  for  by  the  organs  of  the  individual 
itself. 

1.  The  vitelline  circulation  is  carried  on  partly  within  the  body  of  the  embryo 
and  partly  external  to  it  in  the  vascular  area  of  the  yolk.  It  consists  of  a  median 
tubular  heart,  from  which  two  vessels  (arteries)  project  anteriorly.  These  carry 
the  blood  to  a  plexus  of  capillaries  spread  over  the  area  vasculosa,  and  also,  though 
to  a  less  extent,  in  the  body  of  the  embryo.  From  this  plexus  the  blood  is  returned 
by  two  vessels  (veins)  which  enter  the  heart  posteriorly,  and  thus  a  complete  cir- 
culation is  formed. 

In  these  vessels  and  the  heart  a  fluid  (blood}  is  contained,  in  which  rudimentary 
corpuscles  are  found.  The  mode  of  formation  of  these  elementary  parts  will  have 
first  to  be  considered. 

In  mammalia  the  Heart  is  formed  as  a  longitudinal  fold  of  the  splanchnopleure 
on  either  side  of  the  median  line  in  front  of  the  anterior  extremity  of  the  rudi- 
mentary pharynx,  at  about  the  level  of ^  the  posterior  primary  cerebral  vesicle, 
the  folds  projecting  dorsally  into  the  coslom.  The  walls  of  the  folds  thicken  and 
present  two  distinct  strata  of  cells ;  the  inner  and  thinner  layer  forms  the  endo- 
cardium, the  outer  and  thicker  the  muscular  wall  of  the  heart.  In  its  very  earliest 
and  primitive  condition  the  heart  consists,  therefore,  of  a  pair  of  tubes,  one  on 
either  side  of  the  body.  These,  however,  soon  coalesce  in  the  median  line,  and, 
fusing  together,  form  a  single  central  tube.1  Each  of  the  two  primary  tubes 
receives  posteriorly  a  large  vessel  (a  vein),  and  is  prolonged  anteriorly  into 
a  second  vessel  (an  artery).  So  that  after  fusion  of  the  heart-tubes  has  taken 
place,  there  is,  in  the  primitive  vitelline  circulation,  as  above  mentioned,  a 
single  tubular  heart,  with  two  arteries  proceeding  from  it  and  two  veins  empty- 
ing themselves  into  it.  The  earliest  vessels  are  also  formed  in  the  visceral  layer 
of  the  mesoblast.  They  are  developed  from  that  part  of  the  mesoblast  which  sur- 
rounds the  portion  of  blastoderm  which  is  occupied  by  the  developing  body  of  the 

1  In  most  fishes  and  in  amphibia  the  heart  originates  as  a  single  median  tube. 


THE   BLOOD-VAS<  II.AR    SYSTEM. 


127 


embryo,  and  which  is  known  as  the  "vascular  area."  So  that  the  first  blood- 
vessels are  developed  outside  the  body  of  the  embryo.  Some  of  the  cells  of  which 
the  vascular  area  is  composed  arrange  themselves  in  cords,  the  cords  forming  a 
network.  Fluid  begins  to  collect  in  the  interior  of  the  cords,  forcing  apart  the 
cells  of  Avhich  they  are  composed,  and  converting  them  into  canals,  some  of  the 
cells  collecting  here  and  there  into  groups  adherent  to  the  walls  of  the  canals 
and  projecting  into  their  lumen.  These  are  the  so-called  "blood-islands" 
(Fig.  96.  f).  and  the  cells  which  compose  them  separate  later  on  and  become  the 
embryonic  blood-corpuscles.  The  blood-vessels  early  extend  in  toward  the  em- 
bryo from  the  vascular  area,  the  new  vessels  arising  as  bud-  or  spur-like  out- 
growths from  those  already  existing.  Eventually,  the  vasifactive  process  reaches 
the  embryo  and  the  developing  vessels  come  into  contact  and  communicate  with 
the  heart,  which  by  this  time  has 
been  formed  and  is  already  pul- 
sating before  the  vessels  reach  it. 

The  earliest  embryonic  red 
blood-corpuscles  are  all  nucleated 
and  are  more  properly  termed 
blood-cells,  true  blood-corpuscles, 
wliich  in  all  the  mammalia  are 
non-nucleated,  making  their  ap- 
pearance about  the  second  month 
of  development  and  gradually  re- 
placing the  embryonic  blood-cells. 
The  origin  of  the  corpuscles  is 
somewhat  uncertain ;  some  em- 
bryologists  believe  them  to  be 
formed  from  the  blood-cells  by  the 
extrusion  of  the  nuclei  of  the 
latter,  while  others  maintain  that 
they  are  special  formations  devel- 
oping in  the  protoplasm  of  the  red  blood-cells  and  being  thus  from  the  beginning 
non-nucleated.  In  later  life  the  formation  of  red  corpuscles  seems  to  occur  in 
the  marrow  of  the  bones.  The  white  corpuscles  or  leucocytes  appear  very  early 
in  development,  but  their  exact  origin  is  not  known ;  probably  they  arise  from  the 
mesoblastic  tissue  outside  the  blood-vessels  and  migrate  into  their  interior,  The 
vitelline  circulation  commences  about  the  fifteenth  day  and  lasts  till  the  fifth 
week.  When  fully  established  it  is  carried  on  as  follows :  Proceeding  from 
the  tubular  heart  are  two  arteries,  the  first  aortic  arteries  (Fig.  97),  which 
unite  at  some  distance  from  the  heart  into  a  single  artery.  This  runs  down  in 
front  of  the  primitive  vertebrae  and  behind  the  walls  of  the  intestinal  cavity, 
and  again  divides  into  two  primitive  aortce  or  vertebral  arteries,  and  these  give 
off  five  or  six  omphalo-mesenterie  arteries,  which  ramify  in  that  part  of  the  blas- 
toderm which  surrounds  the  developing  body  of  the  embryo,  and  which  is  known 
as  the  vascular  area.  They  terminate  peripherally  in  a  circular  vessel — the 
terminal  sinus.  This  vessel  surrounds  the  vascular  portion  of  the  germinal  area, 
but  does  not  extend  up  to  the  anterior  end  of  the  embryo.  It  terminates  on 
either  side  in  a  vein  called  the  omphalo-mesenterie.  The  two  omphalo-mesenteric 
veins  open  into  the  opposite  extremity  of  the  heart  to  that  from  which  the  arte- 
ries proceeded. 

2.  The  Placental  Circulation. — As  the  umbilical  vesicle  diminishes,  the  allan- 
tois  and  the  placenta  develop  in  the  manner  already  indicated.  When  the  um- 
bilical vesicle  disappears  the  latter  becomes  the  only  source  of  nutrition  for  the 
embryo.  The  allantois  carries  with  it  to  the  placenta  two  arteries,  derived  from 
branches  of  the  primitive  aorta,  and  two  veins ;  these  vessels  become  much 
enlarged  as  the  placental  circulation  is  established,  but  subsequently  one  of 
the  veins  disappears,  and  in  the  later  stages  of  uterine  life  the  circulation  is 


FIG.  96.— A  portion  of  the  vascular  area  of  a  chick  embryo, 
a.  Blood-vessels  forming  a  network.  6.  Meshes  of  the  net 
work.  c.  Blood-islands.  (From  Kolliker.) 


128 


DE  VEL  OP  MEN  T. 


FIG.  97.— Heart  at  the  fifth  week. 
A.  Opened  from  the  abdominal  aspect. 
1.  Arterial  sinus.  2.  Aortic  arches 
uniting  behind  to  form  the  descending 
aorta.  3.  Auricle.  4.  Auriculo-ven- 
tricular  orifice.  5.  Commencing  septum 
ventriculorum.  6.  Ventricle.  7.  In- 
ferior vena  cava.  B.  Posterior  view  of 
the  same.  1.  Trachea.  2.  Lungs.  3. 
Ventricles.  4,5.  Auricles.  6.  Diaphragm. 
7.  Descending  aorta.  8,  9, 10.  Pneumo- 
gastric  nerves  and  their  branches. 


carried  on  between   the  foetus   and   the  placenta  by  two  arteries  and  one  vein 
(umbilicat). 

During  the  occurrence  of  these  changes  great  alterations  take  place  in  the 

primitive  heart  and  blood-vessels,  above  alluded 
to,  which  will  now  require  description. 

Further  Development  of  the  Heart. — The  sim- 
ple median  tube,  formed  by  the  coalescence  of  the 
pair  of  tubes  of  which  the  primitive  heart  con- 
sists, becomes  elongated  and  bent  on  itself,  so  as 
to  form  an  S-shaped  tube,  the  anterior  part  of  the 
tube  bending  over  to  the  right,  and  the  posterior 
to  the  left.  At  the  same  time  the  middle  portion 
is  protruded  forward  and  arches  transversally  from 
right  to  left  and  at  the  same  time  becomes  twisted 
on  itself,  so  that  the  extremity  from  which  the 
arteries  are  prolonged  is  situated  in  front  and  to 
the  right,  and  that  into  which  the  veins  enter  is 
behind  and  to  the  left.  The  bent  tube  then  be- 
comes divided  by  two  transverse  constrictions 
into  three  parts.  One,  the  posterior,  becomes 
the  auricles,  the  middle  one  forms  the  two  ventricular  cavities,  while  the  anterior 
forms  the  aortic  bulb,  from  which  the  commencement  of  the  aorta  and  pulmonary 
artery  is  developed.  A  division  of  each  of  these  cavities  now  takes  place, 
so  as  to  convert  them  into  right  and  left  ventricle,  right  and  left  auricle, 
and  aorta  and  pulmonary  artery  respectively.  In  the  middle  portion  of  the 
tubular  heart,  the  rudimentary  ventricular  cavities  (Fig.  97,  A,  5),  a  par- 
tition rises  up  from  the  lower  part  of  the  right  wall  of  this  cavity,  and 
gradually  grows  up  until  it  reaches  the  constrictions  which  separate  it  from  the 
other  two,  and  thus  the  interventricular  septum  is  completed.  At  the  same  time 
a  cleft  appears  on  the  outside,  a  little  to  the  right  of  the  most  prominent  point, 
which  ultimately  becomes  the  apex  of  the  heart.  The  cleft  becomes  less  marked 
as  development  progresses,  but  remains  to  some  extent  persistent  throughout  life 
as  the  interventricular  groove. 

The  first  appearance  of  a  division  in  the  posterior  or  auricular  portion  of  the 
tubular  heart  makes  its  appearance,  at  a  very  early  period  of  development,  in 
the  shape  of  two  projecting  pouches,  one  on  either  side ;  these  are  the  rudiments 
of  the  auricular  appendages,  but  the  actual  division  of  the  cavity  by  a  septum 
does  not  occur  until  some  time  later.  This  is  formed  by  the  growth  of  a  partition 
from  the  anterior  wall  of  the  auricular  cavity,  which  grows  backward,  and  par- 
tially separates  the  cavity  into  two.  The  partition,  however,  is  not  completed 
until  after  birth,  a  part  remaining  undeveloped,  and  thus  permitting  of  a  com- 
munication (foramen  ovale)  between  the  two  auricles  during  the  whole  of  foetal 
life.  In  a  like  manner  the  aortic  bulb  is  divided  into  two  by  the  growth  of  a 
septum  downward,  from  the  distal  end  of  the  bulb,  which  divides  the  cavity 
into  the  permanent  aorta  and  the  pulmonary  artery,  and,  uniting  below  with 
the  upper  edge  of  the  interventricular  septum,  places  the  aorta  in  com- 
munication with  the  left,  and  the  pulmonary  artery  with  the  right  ventricle. 
Very  soon  a  superficial  furrow  appears  on  the  external  surface  of  this  portion  of 
the  heart  corresponding  to  the  septum  internally,  and,  becoming  deeper,  the  two 
vessels  are  gradually  separated  from  each  other  through  the  septum,  in  the  imme- 
diate neighborhood  of  the  ventricular  portion  of  the  heart,  whilst  beyond  this  they 
still  remain  joined  together,  and  give  origin  to  the  fourth  and  fifth  aortic  arches, 
presently  to  be  described. 

Further  Development  of  the  Arteries. — In  the  vitelline  circulation  two  arteries 
were  described  as  coming  off  from  the  primitive  heart,  and  running  down  in  front 
of  the  developing  vertebrae.  The  first  change  consists  in  the  fusion  of  these 
arteries  into  one  at  some  distance  from  the  heart,  thus  forming  the  descending 


THE   ARTERIES.  129 

thoracic  and  abdominal  aorta.  In  consequence  of  the  heart  falling  backward  to 
the  lower  part  of  the  neck  and  then  into  the  thorax  as  the  head  is  developed,  the 
tw<>  original  arteries,  proceeding  from  the  heart  to  the  point  effusion  in  the  com- 
mon descending  aorta  become  elongated,  and  assume  an  arched  form,  curving 
backward  on  each  side,  from  the  front  of  the  body  toward  the  vertebral  column 
(Fig.  98,  A).  These  are  the  first  or  primitive  aortic  arches.  As  the  heart  recedes 
into  the  thorax,  and  these  arches,  which  correspond  in  position  to  the  first  pharyn- 
geal  or  mandibular  arch,  become  elongated,  four  pairs  of  arches  are  formed  behind 


— /ii 


FIG.  98.— Diagram  of  the  formation  of  the  aortic  arches  and  the  large  arteries,  i.n.  HI.  iv.  v.  Jr'irst,second,  third, 
fourth,  and  fifth  aortic  arches.  A.  Common  trunk  from  which  the  first  pair  spring:  the  place  where  thesucceed- 
ing  pairs  are  formed  is  indicated  by  dotted  lines.  B.  Common  trunk,  with  four  arches  and  a  trace  of  the  fifth, 
c.  Common  trunk,  with  the  three  last  pairs,  the  first  two  having  been  obliterated.  D.  The  persistent  arteries, 
those  which  have  disappeared  being  indicated  by  dotted  lines.  1.  Common  arterial  trunk.  2.  Thoracic  aorta. 
3.  Right  branch  of  the  common  trunk  which  is  onlv  temporary.  4.  Left  branch,  permanent.  5.  Axillary 
artery.  6.  Vertebral.  7.  s.  Subclavian.  9.  Common  carotid.  10.  External :  and  11,  Internal  carotid.  12.  Aorta. 
13.  Pulmonary  artery.  14, 15.  Right  and  left  pulmonary  arteries. 

them  around  the  pharynx  (Fig.  98).  The  arches,  five  in  number,  remain  per- 
manent in  fishes,  giving  off  from  their  convex  borders  the  branchial  arteries  to 
supply  the  gills.  In  many  animals  the  five  pairs  do  not  exist  together,  for  the 
first  two  have  disappeared  before  the  others  are  formed;  but  this  is  not  so  in  man, 
where  all  five  arches  are  present  and  pervious  during  a  certain  period  of  embryonic 
existence.  Only  some  of  the  arches  in  mammalia  remain  as  permanent  structures ; 
other  arches,  or  portions  of  them,  become  obliterated  or  disappear.  The  first  two 
arches  entirely  disappear.  The  third  remains  as  a  part  of  the  internal  carotid 
artery,  the  remainder  being  formed  by  the  upper  part  of  the  posterior  aortic  root — 
i.  e.  the  descending  part  of  the  original  vessel  which  proceeded  from  the  rudiment- 
ary tubular  heart.  The  common  and  external  carotid  are  formed  from  the  ante- 
rior aortic  root ;  that  is.  the  ascending  portion  of  the  same  primitive  vessel.  The 
fourth  arch  on  the  left  side  becomes  developed  into  the  permanent  arch  of  the 
aorta  in  mammals  :  but  in  birds  it  is  the  fourth  arch  on  the  right  side  which  forms 
the  aortic  arch  :  while  in  reptiles  the  fourth  arch  on  both  sides  persists,  as  there 
is  a  permanent  double  aortic  arch.  The  fourth  arch  on  the  right  side  forms  the 
subclavian  artery,  and  by  the  junction  of  its  commencement  with  the  anterior 
aortic  root,  from  which  the  common  carotid  is  developed,  it  forms  the  innominate 
artery.1  The  fifth  arch  on  the  left  side  forms  the  pulmonary  artery  and  the  duc- 
tus  arteriosus  :  that  on  the  rig;at  side  becomes  atrophied  and  disappears.  The  first 
part  of  the  fifth  left  arch  remains  connected  with  that  part  of  the  bulbous  aorta 
•which  is  separated  as  the  pulmonary  stem,  and  with  it  forms  the  common  pul- 
monary artery.  From  about  the  middle  of  this  arch  two  branches  are  given  off, 
which  form  the  right  and  left  pulmonary  arteries  respectively,  and  the  remaining 
portion — /.  e.  the  part  beyond  the  origin  of  the  branches,  communicating  with  the 
left  fourth  arch,  that  is.  the  descending  part  of  the  arch  of  the  aorta — constitutes 
the  ductus  arteriosMs.  This  rl-ict  remains  pervious  during  the  whole  of  foetal  life, 
and  after  birth  becomes  obliterated. 

The  development  of  the  arteries  in  the  lower  part  of  the  body  is  going  on  dur- 
ing the  same  time.  AA'e  have  seen  that  originally  there  were  two  primitive  arteries 
coming  off  from  the  primary  tubular  heart,  and  that  these  two  vessels,  at  some 

1  This  i*  interesting  in  connection  with  the  position  of  the  recurrent  larvngeal  nerve,  which  is 
ihus  seen  to  hook  round  the  .*ame  primitive  fetal  structure,  which  becomes  on  the  right  side  the  sub- 
clavian artery,  on  the  left  the  arch  of  the  aorta. 

9 


130 


DE  VEL  OP  MEN  T. 


distance  from  the  heart,  became  fused  together  to  form  a  single  median  artery, 
which  coursed  down  in  front  of  the  vertebrae  to  the  bottom  of  the  spinal  column, 
forming  the  permanent  descending  aorta.  From  the  extremity  of  this  the  two 
vitelline  arteries,  which  were  originally  parts  of  the  primitive  main  trunks,  pass 
to  the  area  vasculosa.  As  the  umbilical  vesicle  dwindles  and  the  allantois  grows, 


--vagus  nerve. 

external 

- '  "  carotid. 

^internal 

carotid. 


vertebral. 


right  / 

subclariitii. 


innominate 

artery. 


ascending 
aorta. 


descending  aorta. 


FIG.  99 -Diagram  to  show  the  destination  of  the  arterial  arches  in  man  and  mammals.  (Modified  from 
Rathke.  From  Quain's  Anatomy,  vol  i.  pt.  1, 1890.)  The  truncus  arteriosus  and  the  five  arterial  arches  springing 
from  it  are  represented  in  outline  only ;  the  permanent  vessels  in  colors— those  belonging  to  the  aortic  system 
red,  to  the  pulmonary  system  blue. 

two  large  branches  are  formed  as  lateral  offshoots  of  the  median  aorta.  These  are 
the  two  umbilical  or  hypogastric  arteries,  and  are  concerned  in  the  placental  circu- 
lation. The  portion  of  the  median  aorta  beyond  this  point  becomes  much  dimin- 
ished in  size,  and  eventually  forms  the  sacra  media  artery,  and  thus  the  two 
umbilical  branches  become  in  appearance  bifurcating  branches  of  the  main  aorta. 
The  common  and  internal  iliac  arteries  are  developed  from  the  proximal  end  of 
these  umbilical  arteries ;  the  middle  portion  of  the  vessel,  after  birth,  becomes 
partially  atrophied,  but  in  part  remains  pervious  as  the  superior  vesical  artery  ;  the 
distal  portion  becomes  obliterated,  constituting  part  of  the  superior  ligament  of 
the  bladder.  The  external  iliac  and  femoral  arteries  are  developed  from  a  small 
branch  given  off  from  the  umbilical  arteries  near  their  origin,  and  are  at  first  of 
comparatively  small  size. 

Development  of  the  Veins. — The  formation  of  the  great  veins  of  the  embryo 
may  be  best  considered  under  two  groups,  visceral  and  parietal. 

The  visceral  are  derived  from  the  vitelline  and  umbilical  veins.  In  the  earliest 
period  of  the  circulation  of  the  embryo,  we  have  seen  that  there  were  two  veins 
(vitelline  or  omphalo-mesenteric)  returning  the  blood  from  the  vitelline  membrane. 
These  unite  together  to  form  a  single  channel,  the  sinus  venosus,  which  opens  into 
the  auricular  extremity  of  the  heart.  As  soon  as  the  placenta  begins  to  be  formed 
two  umbilical  veins  appear  and  open  into  the  sinus  venosus,  close  to  the  vitelline 
veins.  The  two  vitelline  veins  enter  the  abdomen  and  run  upward  on  either  side 
of  the  intestinal  canal ;  at  the  upper  part  of  the  abdomen,  in  the  site  of  the  future 
liver,  which  now  begins  to  form  around  them,  transverse  communications  are 
formed,  which  encircle  the  duodenum  and  enclose  it  in  two  vascular  rings.  The 


THE   VEINS. 


131 


portion  of  veins  above  these  vascular  rings  loses  its  connection  with  the  sinus, 
while  the  portion  between  them  breaks  up  into  a  capillary  plexus,  which  ramifies 
in  the  now  partially  developed  liver  together  with  capillary  vessels  from  the  upper 
venous  ring.  Of  these  latter,  some  pass  toward  the  heart  and  join  the  sinus. 
They  have  received  the  name  of  the  vence  kepaticce  revehentes,  and  eventually 
become  the  hepatic  veins ;  others  ramify  in  the  liver,  under  the  name  of  vence 
hepaticce  <i<lrt  /,,  ntes,  and  become  the  branches  of  the  portal  vein.  The  lower 
vascular  rino-  receives  veins  from  the  stomach  and  intestines,  and  becomes  the 

o 

commencement  of  the  portal  vein. 

The  umbilical  veins  at  first  open  into  the  sinus  venosus  near  to  the  vitelline 
veins.     Subsequently  this  communication  becomes  interrupted  by  the  develop- 


FIG.  100.— Diagrams  illustrating  the  development  of  the  great  veins.  The  first  figure  shows  the  cardinal 
veins  emptying  into  the  heart  by  two  lateral  trunks,  "  the  ducts  of  Cuvier."  The  second  figure  shows  the  forma- 
tion of  the  Venae  cavse  and  the  union  of  the  left  iliac  with  the  right  cardinal,  o.  Inferior  vena  cava.  b.  Left  in- 
nominate vein.  The  third  figure  shows  the  cardinal  veins  much  diminished  in  size  and  the  duct  of  Cuvier,  on 
the  left  side,  gradually  diminishing,  c.  Vena  azygos  minor.  The  fourth  figure  shows  the  adult  condition  of  the 
venous  system.  1.  Right  auricle  of  heart.  2.  Vena  cava  superior.  3.  Jugular  veins.  4.  Subclavian  veins. 
5.  Vena  cava  inferior.  6.  Iliac  veins.  7.  Lumbar  veins.  8.  Vena  azygos  major.  9.  Vena  azygos  minor.  10.  Su- 
perior intercostal  vein.  11.  Coronary  sinus,  the  remains  of  the  left  duct  of  Cuvier.  (Modified  from  Dalton.) 

ment  of  a  vascular  network ;  the  vein  on  the  right  side  atrophies  and  disappears, 
while  that  on  the  left  side  greatly  enlarges,  as  the  placenta!  circulation  becomes 
established,  and  communicates  with  the  upper  venous  circle  of  the  vitelline  cir- 
culation. Finally  a  branch  is  formed  between  the  upper  venous  circle  and  the 
right  hepatic  veins,  which  becomes  the  ductus  venosus,  and  by  it  most  of  the  blood 
from  the  umbilical  vein  is  carried  direct  to  the  heart. 

The  Parietal  Veins. — The  first  appearance  of  a  parietal  system  consists  in  the 
appearance  of  two  short  transverse  veins  (the  ducts  of  Cuvier),  which  open  on 
either  side  of  the  auricular  portion  of  the  heart.  Each  of  these  ducts  is  formed 
by  an  ascending  and  descending  vein.  The  ascending  veins  return  the  blood  from 
the  parietes  of  the  trunk  and  the  Wolffian  bodies,  and  are  called  cardinal  veins. 
The  two  descending  ones  return  the  blood  (Fig.  100)  from  the  head,  and  are 
called  primitii.'?  jic/ufar  veins.  The  cardinal  veins  receive  the  blood  returning 
from  the  lower  limb  through  the  iliac  veins.  At  first  the  right  and  left  iliac  veins 
open  into  the  corresponding  cardinals,  but  later  a  connecting  vein  forms  between  the 
lower  portions  of  the  cardinals,  and  through  this  the  blood  of  the  left  iliac  flows  over 
to  join  the  right  cardinal.  At  the  same  time  a  large  venous  trunk,  which  receives 
the  blood  from  the  kidneys,  forms  along  the  middle  line  of  the  posterior  abdom- 
inal wall  and  unites  below  with  the  right  cardinal  and  above  with  the  common 
trunk  of  the  vitelline  and  umbilical  veins  above  the  point  of  entrance  of  the 
venae  revehentes.  This  is  the  inferior  vena  cava.  A  portion  of  the  right  cardi- 


132 


DE  VEL  OP  ME  NT. 


nal,  above  the  point  of  junction  of  the  vena  cava,  becomes  obliterated,  the  upper 
portion,  which  receives  some  of  the  lumbar  and  the  intercostal  veins,  persisting 
as  the  vena  azygos  major ;  while  the  left  cardinal,  separating  below  from  the  left 
iliac,  sends  a  branch  across  the  middle  line  of  the  body  to  form  a  communication 
with  the  azygos  major  and  persists  as  the  azygos  minor. 

The  veins  first  formed  in  the  upper  part  of  the  trunk  are,  as  above  stated,  the 
primitive  jugular  veins.  In  the  greater  part  of  their  extent  they  become  the  internal 
jugular  vein.  Shortly,  two  small  branches  may  be  noticed  opening  into  them  near 
their  termination ;  these  form  the  subclavian  veins.  From  the  point  of  junction  of 
these  veins  on  the  left  side,  a  communicating  branch  makes  its  appearance,  running 
obliquely  across  the  neck  downward  and  to  the  right,  to  open  into  the  primitive 
jugular  vein  of  the  right  side  below  the  point  of  entrance  of  the  subclavian  vein. 
At  the  same  time,  in  consequence  of  the  alteration  in  the  position  of  the  heart, 
and  its  descent  into  the  thorax,  the  direction  of  the  ducts  of  Cuvier  becomes 
altered,  and  they  assume  an  almost  vertical  position.  From  the  portion  of  the 
primitive  jugular  veins,  above  the  branch  of  communication,  the  internal  jugu- 
lars are  formed,  except  that  part  of  the  right  one  which  lies  between  the  point 
of  entrance  of  the  subclavian  of  this  side  and  the  termination  of  the  communi- 
cating branch,  which  becomes  the  right  innominate  vein.  The  communicating 
branch  becomes  the  left  innominate  vein.  The  primitive  jugular  of  the  right 
side,  below  the  communicating  vein,  and  the  right  duct  of  Cuvier,  become  the 
vena  cava  superior,  into  which  the  right  cardinal  (vena  azygos  major)  enters. 
The  lower  part  of  the  left  primitive  jugular  becomes  almost  entirely  oblite- 
rated, except  at  its  lower  end,  where  it  remains  as  a  fibrous  band,  or  sometimes 
a  small  vein,  and  runs  obliquely  over  the  posterior  surface  of  the  left  auricle. 
The  termination  of  the  left  duct  of  Cuvier  remains  persistent,  and  forms  the 
coronary  sinus  (Fig.  100),  the  left  cardinal  separating  from  it  and  emptying  its 
blood  through  the  transverse  connecting  branch  into  the  vena  azygos  major. 
The  fetal  circulation  is  described  at  a  future  page. 

Development  of  the  Alimentary  Canal. — The  development  of  the  intestinal 
cavity  is,  as  shown  above  (page  109),  one  of  the  earliest  phenomena  of  embryonic 
life.  The  original  intestine  consists  of  an  inflection  of  the  hypoblast  extending 
from  one  end  of  the  embryo  to  the  other,  and  is  situated  just  below  the  primitive 
vertebral  column.  At  either  extremity  it  forms  a  closed  tube,  in  consequence  of 
the  cephalic  and  caudal  flexures  (page  109),  and  this  manifestly  divides  it  into  three 
parts ;  a  front  part,  enclosed  in  the  cephalic  fold,  called  the  fore-gut ;  a  posterior 
part,  enclosed  in  the  caudal  fold,  the  hind-gut ;  and  a  central  part  or  mid-gut, 


FIG.  101.— Diagrammatic  outline  of  a  longitudinal  vertical  section  of  the  chick  on  the  fourth  day.  en. 
Epiblast.  srre.  Somatic  mesoblast.  hy.  Hypoblast.  vm.  Visceral  mesoblast.  a/.  Cephalic  fold.  pf.  Caudal  fold 
am.  Cavity  of  true  amnion.  i/.s.  Yolk-sac."  i.  Intestine.  s.  Stomach  and  pharynx,  a.  Future  anus,  still  closed. 
m.  The  mouth,  me.  The  mesentery,  al.  The  allantoic  vesicle,  pp.  Space  between  inner  and  outer  folds  of 
amnion.  (From  Quain's  Anatomy,  Allen  Thomson.) 

which  at  this  time  freely  communicates  with  the  umbilical  vesicle  (Fig.  101). 
The  ends  of  the  fore-  and  hind-gut  do  not  communicate  with  the  surface  of  the 
body,  the  buccal  and  anal  orifices  being  subsequently  formed  by  involutions  of  the 
t,  which  later  on  form  communications  with  the  gut.  From  the  fore-gut 


THE   ALIMENTARY    CAXAL. 


133 


H>2 


103 


FIGS.  102  AND  103.— Early  form  of  the  alimen- 
tary canal.  (From  Kolliker'afterBischoff.)  In  102 
a  front  view,  and  in  103  an  antero-posterior  section 
are  represented,  a.  Four  pharyngeal  or  visceral 
plates.  6.  The  pharynx,  c,  c.  "The  commencing 
lungs,  d.  The  stomach.  /,  /.  The  diverticula 
connected  with  the  formation  of  the  liver,  g. 
The  yolk-sac  into  which  the  middle  intestinal 
groove  opens,  h.  The  post«rior  part  of  the 
intestine. 


are  developed  the  pharynx,  (esophagus,  stomach,  and  duodenum  ;  from  the  hind- 
gut,  a  part  of  the  rectum :  and  from  the 
middle  division,  the  rest  of  the  intestinal 
tube  (Figs.  102  and  103).  The  changes 
which  take  place  in  the  fore-gut  are  as  fol- 
lows :  The  middle  portion  becomes  dilated 
to  form  the  stomach,  and  undergoes  a  ver- 
tical rotation  to  the  right,  so  that  the  pos- 
terior border,  by  which  it  is  attached  to  the 
vertebral  column  by  a  mesenterv,  is  now 
directed  to  the  left,  and  the  anterior  border 
to  the  right.  At  this  time  it  is  straight,  but 
it  soon  undergoes  a  lateral  curve  or  bend  to 
the  right  at  its  upper  end.  It  thus  assumes 
an  oblique  direction,  and  the  left  border 
(originally  the  posterior  or  attached  border) 
becomes  inferior,  and  forms  the  great  cur- 
vature.  The  mesentery  by  which  it  was 
attached  forms  the  great  omentum.  The 
portion  of  the  fore-gut  above  this  dilatation 
remains  straight,  forming  the  pharynx  and 

•-hagus.  while  the  part  below  the  dilated 
stomach  forms  the  duodenum,  and  in  con- 
nection with  this  the  liver  and  pancreas  are 
developed. 

The  hind-gut  is  also  a  closed  tube,  and  from  it  the  middle  third  of  the  rectum 
is  developed,  as  well  as  the  allantois  (page  113),  which  will  be  again  referred  to  in 
connection  with  the  development  of  the  bladder. 

The  mid-yut  is  at  first  an  open  cavity  freely  communicating  with  the  umbilical 
vesicle.  As  the  body-walls  grow,  this  communication  contracts  very  materially, 
though  it  still  exists  to  a  certain  extent,  and  the  open  cavity  becomes  converted 
into  a  straight  tube,  still  open  where  it  communicates  with  the  umbilical  vesicle. 
This  tube  grows  rapidly  in  length,  and  presents  a  primitive  curve  or  loop  down- 
ward and  forward,  and,  in  consequence  of  its  growth  exceeding  that  of  the  walls 
of  the  body-cavity,  a  portion  of  the  loop  protrudes  into  the  stalk  of  the  umbilical 
vesicle.  At  a  subsequent  period,  however,  the  walls  of  the  abdomen  grow  more 
rapidly  than  the  intestine,  which  again  recedes  into  the  body-cavity.  At  a  short 
distance  below  the  most  prominent  point  of  this  loop  a  diverticulum  arises,  which 
marks  the  separation  between  the  large  and  small  intestine.  The  lower  part  of  this 
diverticulum  forms  the  vermiform  appendix :  the  proximal  part,  by  its  continued 
growth,  constitutes  the  ca?curn.  After  this  the  anterior  or  upper  part  of  the  gut, 
corresponding  to  the  small  intestine,  rapidly  increases  in  length,  and  about  the 
eighth  week  becomes  convoluted.  The  lower  or  posterior  part,  corresponding  to  the 
large  intestine,  is  at  first  less  in  calibre  than  the  upper  part,  and  lies  wholly  to  the 
left  side  of  the  convolutions  of  the  small  intestine ;  but  later  on  the  curve  of  the 
large  intestine  begins  to  form,  and  the  first  part  (ascending  colon)  slowly  crosses 
over  to  the  right  side,  first  lying  in  the  middle  line,  just  below  the  liver.  It  is  not 
until  the  sixth  month  that  the  caecum  descends  into  the  right  iliac  fossa,  and  so 
drags  the  ascending  colon  into  its  normal  position  in  the  right  flank. 

The  peritoneal  cavity  is  the  space  left  between  the  visceral  and  parietal  layers 
of  the  mesoblast.  and  the  serous  membrane  is  developed  from  these  structures.  The 
mesenteries  are  formed  from  mesoblastic  tissue  extending  between  the  vertebrae  and 
the  gut  which  develops  the  vascular  and  connective-tissue  elements  of  these  parts. 

The  buccal  cavity  is  formed  by  an  involution  of  the  external  layers  of  the 
blastodermic  membrane,  which  passes  inward  and  meets  the  pharynx,  or  upper 
part  of  the  fore-gut.  The  two  cavities  are,  however,  at  first  completely  separated 
from  each  other  by  all  the  layers  of  the  blastoderm ;  but  at  an  early  period  of 


134  DEVELOPMENT. 

development  a  vertical  slit  appears  between  them  ;  this  gradually  widens  and 
becomes  the  opening  by  which  the  common  cavity  of  the  nose  and  mouth  commu- 
nicates writh  the  pharynx.  The  common  cavity  is  afterward  divided  into  nose 
and  mouth  by  the  development  of  the  palate,  in  the  manner  spoken  of  above. 

The  tongue  appears  about  the  fifth  week  as  a  small  elevation  behind  the 
inferior  maxillary  arch,  to  which  a  pair  of  elevations,  arising  from  the  junction 
of  the  third  and  fourth  pharyngeal  arches,  is  united.  The  line  of  union  of  the 
three  elevations  is  indicated  by  the  V-shaped  groove  in  which  the  circumvallate 
papillae  are  situated.  The  epithelial  layer  is  furnished  by  the  epiblast.  The 
tonsils  appear  about  the  fourth  month. 

The  anus  is  also  formed  by  an  inflection  of  the  epiblast,  which  extends  inward 
to  a  slight  extent,  and  approaches  the  termination  of  the  hind-gut  and  finally  com- 
municates with  it  by  a  solution  of  continuity  in  the  septum  between  the  two.  The 
persistence  of  the  foetal  septum  at  either  the  buccal  or  anal  orifices  constitutes  a 
well-known  deformity — imperforate  oesophagus  or  imperforate  rectum,  as  the  case 
may  be. 

The  liver  appears  after  the  Wolffian  bodies,  about  the  third  week,  in  the  form  of 
a  bifid  process,  projecting  from  the  intestine  at  that  part  which  afterward  forms  the 
duodenum.  This  process  grows  rapidly,  its  terminal  lobes  branching  abundantly 
to  form  a  complicated  tubular  gland.  The  duct  of  the  gland  becomes  the  main 
duct  of  the  liver,  while  the  lobes  become  transformed  into  the  right  and  left 
lobes  of  the  liver  and  surround  the  vitelline  and,  later,  the  umbilical  veins,  which 
break  up  into  a  capillary  plexus  and  ramify  in  their  substance.  About  the  third 
month  the  liver  almost  fills  the  abdominal  cavity.  From  this  period  the  relative 
development  of  the  liver  is  less  active,  more  especially  that  of  the  left  lobe,  which 
now  becomes  smaller  than  the  right ;  but  the  liver  remains  up  to  the  end  of  foetal 
life  relatively  larger  than  in  the  adult. 

The  gall-bladder  appears  about  the  second  month,  as  an  extension  of  the  cavity 
from  which  the  main  duct  of  the  liver  is  developed ;  and  bile  is  detected  in  the 
intestines  by  the  third  month. 

The  pancreas  is  also  an  early  formation,  being  far  advanced  in  the  second 
month.  It,  as  well  as  the  salivary  glands,  which  appear  about  the  same  period, 
originates  in  a  projection  from  the  hypoblastic  canal,  which  afterward  forms  a 
cavity,  and  the  lobules  of  the  gland  are  developed  from  the  ramifications  of  this 
cavity.  The  projection  for  the  pancreas  appears  on  the  dorsal  wall  of  the  intes- 
tine, while  that  for  the  liver  is  on  the  ventral  surface,  and  the  ducts  of  the 
two  glands  are  at  first  usually  separated.  During  development  the  duct  of  the 
pancreas  shifts  its  position  toward  the  ventral  surface  and  finally,  as  a  rule,  joins 
that  from  the  liver. 

The  spleen  is  entirely  of  mesoblastic  origin,  as  it  originates  from  the  mes- 
enteric  fold  which  connects  the  stomach  to  the  vertebral  column  (mesogastrium). 

Development  of  the  Respiratory  Organs. — The  lungs  appear  somewhat  later 
than  the  liver.  They  are  developed  from  a  small  median  cul-de-sac  or  diverticu- 
lum  from  the  upper  part  of  the  fore-gut,  immediately  behind  the  fourth  visceral 
cleft,  as  a  projection  from  the  epithelial  and  fibrous  laminae  of  the  intestines. 
During  the  fourth  week  a  pouch  is  formed  on  either  side  of  the  central  diver- 
ticulum,  and  opens  freely  through  it  into  the  fore-gut  (pharynx).  From  these, 
other  (secondary)  pouches  are  given  oft',  so  that  by  the  eighth  week  the  form  of  the 
lobes  of  the  lungs  may  be  made  out.  The  two  primary  pouches  have  thus  a 
common  pedicle  of  communication  with  the  pharynx.  This  is  developed  into  the 
trachea  (Fig.  97,  B),  the  cartilaginous  rings  of  which  are  perceptible  about  the 
seventh  week.  The  parts  which  afterward  form  the  larynx  are  recognized  as 
early  as  the  sixth  week — viz.  a  projection  on  either  side  of  the  pharyngeal  open- 
ing, which  is  the  rudiment  of  the  arytenoid  cartilage  and  a  transverse  elevation 
from  the  third  pharyngeal  arch,  which  afterward  becomes  the  epiglottis ;  the 
vocal  cords  and  ventricles  of  the  larynx  are  seen  about  the  fourth  month.  Traces 
of  the  diaphragm  appear  in  the  form  of  a  fine  membrane,  separating  the  lungs 


THE   RESPIRATORY  AND    URINARY   ORGANS.  135 

from  the  Wolffian  bodies,  the  stomach,  and  the  liver,  whilst  the  heart  is  still 
near  the  head.  As  the  diaphragm  extends  forward  from  the  vertebral  column  it 
separates  the  common  pleuro-peritoneal  cavity  into  two  parts,  a  thoracic  and 
abdominal. 

Development  of  the  Urinary  Organs.  —  Three  distinct  sets  of  urinary  organs 
occur  in  the  embryo  at  different  periods  of  development,  two  of  them  being  more 
or  less  transitory,  while  the  third  becomes  the  permanent  kidney.  The  first  to 
appear  is  the  pronephros  or  head-kidney  and  it  consists  of  a  small  number  of  some- 
what convoluted  tubules  which  develop  immediately  behind  the  heart  in  the 
mesoblast  of  certain  of  the  protovertebral  somites.  The  tubules  are  segmentally 
arranged,  one  corresponding  to  each  protovertebra,  and  they  communicate  at  one 
extremity  with  the  ccelom  and  at  the  other  with  a  longitudinal  canal  known  as 
the  9egmental  or  Wolffian  duct.  Later  the  second  kidney  appears  below  the 
pronephros,  developing  in  a  similar  manner  and  forming  the  mesonephros  or 
Wolffian  /»/<///.  whose  tubules  are  also  at  first  arranged  segmentally,  though  later 
they  become  more  numerous  than  the  protovertebrce  from  which  they  arise,  by  the 
formation  of  secondary  and  tertiary  tubules  by  budding  from  those  already  pres- 
ent. These  tubules  likewise  communicate  with  the  Wolffian  duct,  and  in  connection 
with  each  of  them  there  is  developed  a  little  knot  of  blood-vessels  which  projects 
into  the  lumen  of  the  tubule,  whose  wall  it  pushes  in  front  of  it,  and  forms  the 
Malpigkian  l>o<h/  or  glomeruhis.  The  third  and  last  kidney  to  appear  is  the  meta- 
nephros  or  permanent  kidney,  which,  together  with  the  ureter,  arises  as  an  out- 
growth from  the  lower  end  of  the  Wolffian  duct, 

The  Wolffian  duct  is  perceptible  about  the  third  week,  forming  an  elongated 
ridge  of  cells  situated  on  either  side  of  the  primitive  vertebra  and  extending  from 
the  heart  to  the  lower  end  of  the  embryo.  It  makes  its  appearance  below  the 
heart  and  behind  the  common  pleuro-peritoneal  cavity,  from  the  mesoblast  at  the 
point  of  separation  of  its  two  layers  into  somatopleure  and  splanchnopleure,  this 
portion  of  the  mesoblast  being  termed  the  "intermediate  cell  mass."  The  ridge 
is  at  first  solid,  but  soon  a  tube  is  hollowed  out  in  it,  and  continuing  to  develop 
posteriorly  it  unites  with  the  proximal  end  of  the  allantois  which  forms  what  is 
termed  the  urogenital  sinus.  Thus  a  communication  is  established  through  the 
Wolffian  tubes  and  ducts  between  the  pleuro-peritoneal  cavity  and  the  cloaca  or 
hinder  part  of  the  alimentary  canal.  The  next  step  is  the  formation  of  a  second 
duct  in  the  neighborhood  of  the  original  duct,  with  which  some  of  the  tubules  of 
the  anterior  part  of  the  segmental  body  (pronephros)  are  connected.  This  is  the 
Miillerian  duct.  The  ureter,  which  is  formed  later,  is,  as  has  been  described,  an 
offshoot  from  the  hinder  part  of  the  Wolffian  duct. 

The  structure  of  the  Wolffian  body  is  in  many  respects  analogous  to  that  of 
the  permanent  kidney  (Fig.  104).  It  is  composed  partly  of  an  excretory  canal 

or  duct,  into  which  open  numerous  "  con- 
duits,"  rectilinear  at  first,  but  afterward 
tortuous,  and  partly  of  a  cellular  or 
glandular  structure,  in  which  Malpig- 
hian  tufts  are  found.  It  is  fixed  to  the 
diaphragm  by  a  superior  ligament,  and 
to  the  spinal  column  by  an  inferior  or 
inguinal  ligament.  Its  office  is  the  same 
as  that  of  the  kidnes  —  viz.  to  secrete 


FIG.  104.  —  Enlarged  view  from  the  front  of  the       flu  if]  pnntaininrr  nrpa     \vnipVi 
left  Wolffian  body  before  the  establishment  of  the       "Ilia  containing  Uiea.  WHICH 

distinction  of  sex.   (From  Farre,  after  Kobeit.)  a,  a,     m  the  bladder.       u  hen   the  permanent 

b,  d.  Tubular  structure   of  the  Wolffian  bodv.     e.       -,  .  •.  c  i      i  c 

Wolffian  duct.  /.  its  upper  extremity.  <j.  its  termi-     kidnevs  are  formed,  the  greater  part  ot 

nation  in  x,  the  urogenital  sinus,    h.  The  duct  of       -i  „  \\*    loc         t    J      J'^  TV^ 

Muiier.   /.  its  upper,  stm  closed,  extremity.   t.  its     the  \\  olthan  body  disappears.      Ine  rest 

lower  end,  terminating  in  the  urogenital  sinus.    /.       tatps  r»nrt  in   thp  formation  nf  thp  nro-an« 
The  mass  of  blastema  for  the  reproductive  organ,       taKes  Part  m  tne  me  OlganS 

ovary  or  testicle.  of  generation. 

The  functional  activity  of  the  Wolf- 
fian bodies  is  very  transitory  ;  they  attain  their  highest  development  by  the  sixth 


136 


DE  VELOPMENT. 


week,  after  which  time  they  begin  to  decrease  in  size  and  have  nearly  disappeared 
by  the  end  of  the  third  month.  The  upper  part  of  the  segmental  body,  the  prone- 
phros,  also  undergoes  atrophy  and  disappears.  In  the  male,  the  Wolffian  duct 
persists,  and  becomes  converted  into  the  vas  deferens,  the  Mullerian  duct  under- 
going atrophy,  a  vestige  of  it,  however,  remaining  as  the  sinus  prostaticus; 
whereas,  on  the  other  hand,  in  the  female,  the  Mullerian  duct  remains  and 
becomes  converted  into  the  whole  length  of  the  genital  passages,  while  the  Wolf- 
fian duct  almost  entirely  disappears  and  remains  only  as  a  vestige.  Prior  to  this, 
however,  the  Wolffian  and  Mullerian  ducts  (together  with  the  ureter  when  formed) 
open  into  the  common  urogenital  sinus  referred  to  above,  and  which  on  its  part 
communicates  with  the  terminal  portion  of  the  intestinal  cavity  which  is  known 
as  the  cloaca  (Fig.  105). 

As  the  allantois  expands  into  the  urinary  bladder  this  common  cavity  is 
divided  into  two  by  a  septum,  and  the  urogenital  sinus  then  communicates  with 
the  anterior  division  and  the  rectum  with  the  posterior.  The  Wolffian  and  Mul- 
lerian ducts  are  soon  connected  by  cellular  substance  into  a  single  mass — the 
genital  cord — in  which  the  Wolffian  ducts  lie  side  by  side  in  front,  and  the  ducts 
of  Muller  behind,  at  first  separate,  but  later  on  uniting  with  each  other. 

It  has  been  stated  that  the  kidney  (metanephros)  is  developed  from  the  lower 
part  of  the  Wolffian  duct.  It  commences  as  a  tubular  diverticulum  from  the 
lower  part  of  the  segmental  duct,  close  to  the  cloaca.  It  extends  upward,  and 
becomes  divided  into  a  number  of  csecal  tubules,  which  represent  the  commence- 
ment of  the  several  divisions  of  the  pelvis  of  the  kidney.  These  tubules  are 
prolonged  into  a  solid  mesoblastic  blastema  situated  near  the  lower  end  of  the 

mesonephros.  The  tubules  then  become  con- 
voluted, and  masses  of  cells  accumulate  on 
their  exterior,  so  as  to  give  to  the  organ  an 
appearance  of  lobulation.  Between  these 
cells  vessels  are  developed,  and  the  vascular 
glomeruli  are  gradually  formed.  The  kid- 
neys at  first,  therefore,  consist  of  cortical 
substance  only,  but  later  on  the  proximal 
ends  of  the  tubes  become  straight  and  ar- 
ranged in  bundles,  and  thus  the  pyramidal 
structure  is  developed.  The  lobulation  of 
the  kidney  is  perceptible  for  some  time  after 
birth. 

The  urinary  bladder,  as  before  stated,  is 
formed  by  a  dilatation  of  the  lower  part  of 
the  stalk  of  the  allantois.  At  the  end  of  the 
second  month  this  forms  a  spindle-shaped 
cavity,  the  bladder,  which  communicates  with 
the  lower  part  of  the  primitive  intestine  by  a 
short  canal,  the  urogenital  sinus,  which  be- 
comes the  first  part  of  the  urethra.  The 
upper  part  of  the  stalk  of  the  allantois,  which 
is  not  dilated,  forms  the  urachus ;  this  extends 
up  into  the  umbilical  cord,  and  at  an  early 
period  of  embryonic  existence  forms  a  tube 
of  communication  with  the  allantois.  It  is 
obliterated  before  the  termination  of  foetal 
life,  but  the  cord  formed  by  its  obliteration  is 
perceptible  throughout  life,  passing  from  the 
upper  part  of  the  bladder  to  the  umbilicus,  and 
it  occasionally  remains  patent  in  the  adult, 
constituting  a  well-known  malformation. 
The  suprarenal  bodies  are  developed  from  two  different  sources.  The  medul- 


FIG.  105. — Diagram  of  the  primitive  uro- 
genital organs  in  the  embryo  previous  to  sex- 
ual distinction.  The  parts  are  shown  chiefly 
in  profile,  but  the  Mullerian  and  Wolffian  ducts 
are  seen  from  the  front.  3.  Ureter.  4.  Urinary 
bladder.  5.  Urachus.  ot.  The  mass  of  blas- 
tema from  which  ovary  or  testicle  is  after- 
ward formed.  W.  Left  Wolffian  body.  x. 
Part  at  the  apex  from  which  the  coni  vascu- 
losi  are  afterward  developed.  w,  w.  Right 
and  left  Wolffian  ducts,  m,  m.  Right  and  left 
Mullerian  ducts  uniting  together  and  with  the 
Wolffian  ducts  in  gc,  the  genital  cord.  ug. 
Sinus  urogenitalis.  i.  Lower  part  of  the  intes 
tine. 


the  labia  majora  or  scrotum  are  formed. 


THE    URINARY  AND    GENERATIVE    ORGANS.  137 

lary  part  of  the  organ  is  of  epiblastic  origin,  and  is  derived  from  the  tissues 
forming  the  sympathetic  ganglia  of  the  abdomen,  while  the  cortical  portion  is  of 
mesoblastic  origin,  and  originates  in  the  mesoblast  just  above  the  kidneys.  The 
two  parts  are  at  first  quite  distinct,  but  become  combined  in  the  process  of  devel- 
opment. The  suprarenal  capsules  are  at  first  larger  than  the  kidney,  but  become 
equal  in  size  about  the  tenth  week,  and  from  that  time  decrease  relatively  to  the 
kidney,  though  they  remain,  throughout  foetal  life,  much  larger  in  proportion 
than  in  the  adult. 

Development  of  the  Generative  Organs. — The  first  appearance  of  the  repro- 
ductive organs  is  essentially  the  same  in  the  two  sexes,  and  consists  in  a 
thickening  at  one  spot  of  the  epithelial  layer  which  lines  the  peritoneal  or 
body  cavity,  with  a  slight  increase  of  the  connective  tissue  beneath  it,  form- 
ing a  low  ridge.  This  is  termed  the  genital  ridge,  and  is  situated  on  the 
mesial  side  of  each  Wolffiaa  body,  and  from  it  the  testicle  in  the  one  sex,  and 
the  ovary  in  the  other,  are  developed.  The  ridge,  as  the  embryo  grows,  grad- 
ually becomes  pinched  off  from  the  Wolffian  body,  with  which  it  is  at  first 
continuous,  though  it  still  remains  connected  to  the  remnant  of  this  body  by  a 
fold  of  peritoneum,  the  mesorchium  or  mesocuriuni.  About  the  seventh  week  the 
distinction  of  sex  begins  to  be  perceptible.  The  epithelium  on  the  genital  ridge, 
which  is  called  "•  germ-epithelium,"  in  the  female  becomes  distinctly  columnar, 
multiplies  rapidly,  and  begins  to  form  primitive  ova,  in  a  manner  presently  to  be 
described ;  whereas  in  the  male,  though  the  germ-epithelium  has  a  tendency  to 
become  columnar,  the  cells  are,  on  the  whole,  flatter  and  smaller  than  in  the 
female. 

Development  of  Male  Organs. — The  tubuli  seminiferi  of  the  testicle  appear  at 
an  early  period.  It  is  believed  that  they  are  formed  by  the  extension  of  epithelial 
cells  on  the  surface  of  the  genital  ridge  into  the  connective  tissue  or  stroma  on 
which  they  rest;  rows  of  cells  are  thus  developed  which  become  the  lining  cells 
of  the  seminal  ducts.  From  the  mesonephros  tubules  grow  toward  the  kidney, 
filtering  into  relation  with  the  seminal  ducts  and  forming  the  tubuli  recti  and 
rete  testis,  through  which  the  semen  escapes  from  the  testis  and  passes  into  the 
tubules  of  the  upper  part  of  the  mesonephros,  which  persist  as  the  epididymis, 
and  thence  make  their  way  to  the  urethra  (urogenital  sinus)  by  the  Wolffian 
duct,  which  becomes  the  vas  deferens  and  ejaculatory  duct  of  the  adult. 

The  Miillerian  ducts  disappear  in  the  male  sex,  with  the  exception  of  their 
lower  ends.  These  unite  in  the  middle  line,  and  open  by  a  common  orifice  into 
the  urogenital  sinus.  This  constitutes  the  uterus  mascuUnua  or  sinus  prostaticus. 
Occasionally,  however,  the  upper  end  of  the  duct  of  Miiller  remains  visible  in 
the  male,  constituting  the  little  pedunculated  body,  called  the  hydatid  of  the 
epididymis,  sometimes  found  in  the  neighborhood  of  the  epididymis,1  between 
the  testes  and  globus  major. 

It  has  been  seen  that  the  upper  portion  of  the  mesonephros  and  the  Wolffian 
ducts  persist.  The  rest  of  the  mesonephros  disappears  almost  entirely,  a  few  of  its 
tubules  forming  the  vas  aberrans  and  a  structure  described  by  Giraldes,  and 
called,  after  him,  "  the  organ  of  Giraldes,"  which  bears  a  good  deal  of  resem- 
blance to  the  organ  of  Rosenmiiller  in  the  other  sex.  It  consists  of  a  number  of 
convoluted  tubules  lying  in  the  cellular  tissue  in  front  of  the  cord,  and  close  to 
the  head  of  the  epididymis. 

The  descent  of  the  testis  and  the  formation  of  the  gubernaculum  are  described 
in  the  body  of  the  work. 

Development  of  Female  Organs. — The  ovary,  as  above  stated,  is  formed  from 
the  genital  ridge,  which  becomes  pinched  off  from  the  remains  of  the  Wolffian 
body,  but  is  still  attached  by  a  mesovarium.  It  consists  of  a  central  part  of  con- 
nective tissue  covered  by  a  layer  of  germ-epithelium,  from  which  the  ova  are 
developed.  This  epithelium  undergoes  repeated  division,  so  that  it  rapidly  increases 

1  Mr.  Osborn,  in  the  St.  Thomas's  Hospital  Reports,  1875,  has  written  an  interesting  paper  point- 
ing out  the  probable  connection  between  this  foetal  structure  and  one  form  of  hydrocele. 


138 


DE  VEL  OPMENT. 


in  thickness  and  forms  several  layers.  Next  certain  of  the  cells  become  enlarged 
and  spherical,  and  form  what  are  called  the  primitive  ova.  Around  these,  other 
epithelial  cells  have  a  tendency  to  arrange  themselves,  so  as  to  enclose  the  ovum 
in  a  follicle.  The  permanent  ova,  enclosed  in  their  Graafian  follicles,  are  thus 
formed. 

The  Fallopian  tube  is  developed  from  that  portion  of  the  duct  of  Miiller  which 
lies  above  the  lumbar  ligament  of  the  Wolffian  body.  This  duct  is  at  first  com- 
pletely closed  at  its  upper  extremity,  and  its  closed  extremity  remains  permanent, 
forming  a  small  cystic  body  attached  to  the  fimbriated  end  of  the  Fallopian  tube, 

and  called  the  "  hydatid  of 
Morgagni."  Below  this  a 
cleft  forms  in  the  duct,  and 
is  developed  into  the  fim- 
briated opening  of  the  Fal- 
lopian tube. 

Below  this  the  duct  of 
Miiller  and  the  ducts  of  the 
Wolffian  bodies  are  united 
together  in  a  structure  called 
"the  genital  cord,"  in  which 
the  two  Miillerian  ducts  ap- 
proach each  other,  lying  side 
by  side,  and  finally  coalesce 
to  form  the  cavity  of  the 


FIG.  106.— Adult  ovary,  parovarium,  and  Fallopian  tube.  (From 
Farre,  after  Kobelt).  a,  a.  Eppophoron  formed  from  the  upper  part 
of  the  Wolffian  body.  b.  Remains  of  the  uppermost  tubes,  sometimes 
forming  hydatids.  c.  Middle  set  of  tubes,  d.  Some  lower  atrophied 
tubes,  e.  Atrophied  remains  of  the  Wolffian  duct.  /.  The  terminal 
bulb  or  hydatid.  h.  The  Fallopian  tube,  originally  the  duct  of  Miiller. 
i.  Hydatid  attached  to  the  extremity.  I.  The  ovary. 


vagina    and 
coalescence 


This 


uterus. 

commences    in 
the   middle    of    the   genital 
cord,  and  corresponds  to  the 
body   of  the    uterus.      The 
upper    parts    of    the    Miil- 
lerian ducts  in  the  genital  cord  constitute  the  cornua  of  the  uterus,  little  devel- 
oped in  the  human  species.     The  only  remains  of  the  Wolffian  body  in  the  com- 


FIG.  107.— Female  genital  organs  of  the  embryo,  with  the  remains  of  the  Wolffian  bodies.  (After  J.  Miiller.) 
A  From  a  foetal  sheep,  a.  The  kidneys.  6.  The  ureters,  c.  The  ovaries,  d.  Remains  of  Wolffian  bodies,  e. 
Fallopian  tubes.  /.  Their  abdominal  openings.  B.  More  advanced,  from  a  foetal  deer  :  a.  Body  of  the  uterus,  b. 
Cornua  c  Tubes,  d.  Ovaries,  e.  Remains  of  Wolffian  bodies,  c.  Still  more  advanced,  from  the  human  foetus 
of  three  months  :  a.  The  body  of  the  uterus.  6.  The  round  ligament,  c.  The  Fallopian  tubes,  d.  The  ovaries. 
e.  Remains  of  the  Wolffian  bodies. 

plete  condition  of  the  female  organs  are  two  rudimentary  or  vestigial  structures, 
which  can  be  found,  on  careful  search,  in  the  broad  ligament  near  the  ovary; 
the  parovarium  or  organ  of  Rosenmilller  and  the  paroophoron  (Fig.  106).  The 


THE    ORGANS    OF    GENERATION. 


139 


organ  of  Rosenmiiller  consists  of  a  number  of  the  tubules  of  the  upper  part  of  the 
Wolffian  body,  and,  consequently,  is  homologous  with  the  epididymis  of  the  male, 
while  the  parob'pboron  is  formed  by  a  few  persistent  tubules  of  the  lower  part  of 
the  body,  corresponding,  therefore,  to  the  organ  of  Giraldes  and  the  vas  aberrans 
of  the  male.  The  lower  portions  of  the  Wolffian  ducts  also  persist  in  the  form  of  a 


10 


FIG.  108.— Development  of  the  external  genital  organs.  Indifferent  type,  i.  n.  in.  Female.  A  and  B.  At  the 
middle  of  the  fifth  month,  c.  At  the  beginning  of  the  sixth.  Male.  A'.  At  the  beginning  of  the  fourth  month. 
B  .  At  the  middle  of  the  fourth  month,  r.'.  At  the  end  of  the  fourth  month.  1.  Cloaca.  2.  Genital  tubercle  3 
Glans  penis  or  clitoridis.  4.  Genital  furrow.  5.  External  genital  folds  (labia  majora  or  scrotum).  6.  Umbilical 
cord.  /.  Anus.  8.  Caudal  extremity  and  coccygeal  tubercle.  9.  Labia  minora.  10.  Urogenital  sinus.  11.  Fraenum 
clitoridis.  12.  Preputium  penis  or  clitoridis.  13.  Opening  of  the  urethra.  14.  Opening  of  the  vagina.  15.  Hvmen. 
16.  Scrotal  raphe. 

pair  of  tube-like  structures,  found  one  on  each  side  in  the  walls  of  the  uterus  and 
termed  the  ducts  of  Gartner.  About  the  fifth  month  an  annular  constriction 
marks  the  position  of  the  neck  of  the  uterus,  and  after  the  sixth  month  the  walls 
of  the  uterus  begin  to  thicken.  The  round  ligament  is  derived  from  the 
inguinal  ligament  of  the  Wolffian  body,  the  peritoneum  constitutes  the  broad 
ligament;  the  superior  ligament  of  the  Wolffian  body  disappears  with  that 
structure  (Fig.  107). 

The  external  organs  of  generation,  like  the  internal,  pass  through  a  stage  in 
which  there   is   no   distinction  of  sex  (Fig.  108,  II,  in).     We  must  therefore 


140  DEVELOPMENT. 

describe  this  stage,  and  then  follow  the  development  of  the  female  and  male 
organs  respectively. 

As  stated  above,  the  anal  depression  at  an  early  period  is  formed  by  an  invo- 
lution of  the  external  epithelium,  and  the  intestine  is  still  closed  at  its  lower  end. 
When  the  septum  between  the  two  opens,  which  is  about  the  fourth  week,  the 
allantois  in  front  and  the  intestine  behind  both  communicate  Avith  the  anal  depres- 
sion. This,  which  is  now  called  the  cloaca,  is  afterward  divided  by  a  vertical 
septum,  whose  lower  edge  thickens  to  form  the  perineum,  and  which  appears  about 
the  second  month.  Two  tubes  are  thus  formed  ;  the  posterior  becomes  the  lower 
part  of  the  rectum,  the  anterior  has  uniting  with  it  the  urogenital  sinus.  In  the 
sixth  week  a  tubercle,  the  genital  tubercle,  is  formed  in  front  of  the  cloaca,  and 
this  is  soon  surrounded  by  two  folds  of  skin,  the  genital  folds.  Toward  the  end 
of  the  second  month  the  tubercle  presents,  on  its  lower  aspect,  a  groove,  the 
genital  furrow,  turned  toward  the  cloaca.  All  these  parts  are  well  developed  by 
the  second  month,  yet  no  distinction  of  sex  is  possible. 

Female  Organs  (Fig.  108,  A,  B,  c). — The  female  organs  are  developed  by  an 
easy  transition  from  the  above.  The  portion  of  the  cloaca  in  front  of  the  septum 
persists  as  the  vestibule  of  the  vagina,  and  forms  a  single  tube  with  the  upper  part 
of  the  vagina,  which,  as  we  have  already  seen,  is  developed  from  the  united 
Miillerian  ducts.  The  genital  tubercle  forms  the  clitoris,  the  genital  folds  the 
labia  majora,  and  the  lips  of  the  genital  furrow  the  labia  minora,  which  remain 
open. 

Male  Organs  (Fig.  108,  A',  B',  c'). — In  the  male  the  changes  are  greater.  The 
genital  tubercle  is  developed  into  the  penis,  the  glans  appearing  in  the  third  month, 
the  prepuce  and  corpora  cavernosa  in  the  fourth.  The  genital  furrow  closes  and 
thus  forms  a  canal,  the  spongy  portion  of  the  urethra.  The  urogenital  sinus 
becomes  elongated  and  forms  the  prostatic  and  membranous  urethra.  The  genital 
folds  unite  in  the  middle  line  to  form  the  scrotum,  at  about  the  same  time  as  the 
genital  furrow  closes — viz.  between  the  third  and  fourth  months. 

The  following  table  is  translated  from  the  work  of  Beaunis  and  Bouchard,  with 
some  alterations,  especially  in  the  earlier  weeks.  It  will  serve  to  present  a  resumS 
of  the  above  facts  in  an  easily  accessible  form.1 

1  It  will  be  noticed  that  the  time  assigned  in  this  table  for  the  appearance  of  the  first  rudiment 
of  some  of  the  bones  varies  in  some  cases  from  that  assigned  in  the  description  of  the  various  bones 
in  the  sequel.  This  is  a  point  on  which  anatomists  differ,  and  which  probably  varies  in  different 
cases. 


CHRONOLOGICAL  TABLE 

OF 

THE  DEVELOPMENT  OF  THE  FCETUS. 

(FROM  BE  AUNTS  AND  BOUCHARD.) 

First  Week. — During  this  period  the  ovum  is  in  the  Fallopian  tube.  Having  been  fertilized  in 
the  upper  part  of  the  tube,  it  slowly  passes  down,  undergoing  segmentation,  aad  reaches 
the  uterus  probably  about  the  end  of  the  first  week.  During  this  time  it  does  not  undergo 
much  increase  in  size. 

Second  Week. — The  ovum  rapidly  increases  in  size  and  becomes  imbedded  in  the  decidua.  so 
that  it  is  completely  enclosed  in  the  decidua  reflexa  by  the  end  of  this  period.  An  ovum 
believed  to  be  of  the  thirteenth  day  after  conception  is  described  by  Reichert.  There  was 
no  appearance  of  any  embryonic  structure.  The  equatorial  margins  of  the  ovum  were  beset 
with  villi.  but  the  surface  in  contact  with  the  uterine  wall  and  the  one  opposite  to  it  were 
bare.  In  another  ovum,  described  by  His,  believed  to  be  of  about  the  fourteenth  day, 
there  was  a  distinct  indication  of  an  embryo.  There  was  a  medullary  groove  bounded  by 
folds.  In  front  of  this  a  slightly  prominent  ridge,  the  rudimentary  heart.  The  amnion 
was  formed  and  the  embryo  was  attached  by  a  stalk,  the  allantois.  to  the  inner  surface  of 
the  chorion.  It  may  be  said,  therefore,  that  these  parts,  the  amnion  and  the  allantois.  and 
the  first  rudiments  of  the  embryo,  the  medullary  groove,  and  the  heart,  are  formed  at  the 
end  of  the  second  week. 

Tliird  Week. — By  the  end  of  the  third  week  the  flexures  of  the  embryo  have  taken  place,  so 
that  it  is  strongly  curved.  The  protovertebral  disks,  which  begin  to  be  formed  early  in  the 
third  week,  present  their  full  complement  In  the  nervous  system  the  primary  divisions 
of  the  brain  are  visible,  and  the  primitive  ocular  and  auditory  vesicles  are  already  formed. 
The  primary  circulation  is  established.  The  alimentary  canal  presents  a  straight  tube  com- 
municating with  the  yolk-sac.  The  pharyngeal  arches  are  formed.  The  limbs  have 
appeared  as  short  buds.  The  Wolffian  bodies  are  visible. 

Fourth  Week. — The  umbilical  vesicle  has  attained  its  full  development.  The  caudal  extremity 
projects.  The  upper  and  the  lower  limbs  and  the  cloaca!  aperture  appear.  The  heart  sep- 
arates into  a  right  and  left  heart.  The  special  ganglia  and  anterior  roots  of  the  spinal 
nerves,  the  olfactory  fossae,  the  lungs  and  the  pancreas  can  be  made  out. 

Fifth  We*k. — The  allantois  is  vascular  in  its  whole  extent.  The  first  traces  of  the  hands  and 
feet  can  be  seen.  The  primitive  aorta  divides  into  aorta  and  pulmonary  artery.  The  duct 
of  Muller  and  genital  gland  are  visible.  The  ossification  of  the  clavicle  and  the  lower  jaw 
commences.  The  cartilage  of  Meckel  occupies  the  first  post-oral  arch. 

Si.rth  Week. — The  activity  of  the  umbilical  vesicle  ceases.  The  pharyngeal  clefts  disappear. 
The  vertebral  column,  primitive  cranium,  and  ribs  assume  the  cartilaginous  condition.  The 
posterior  roots  of  the  nerves,  the  membranes  of  the  nervous  centres,  the  bladder,  kidney, 
tongue,  larynx,  thyroid  body,  the  germs  of  teeth,  and  the  genital  tubercle  and  folds 
are  apparent. 

*h  Week. — The  muscles  begin  to  be  perceptible.     The  points  of  ossification  of  the  ribs, 
scapula,  shaft  of  humerus,  femur,  tibia,  palate,  and  upper  jaw  appear. 

Eighth  Week. — The  distinction  of  arm  and  forearm,  and  of  thigh  and  leg,  is  apparent,  as  well  as 
the  interdigital  clefts.  The  capsule  of  the  lens  and  pupillary  membrane,  the  interventricu- 
lar  and  commencement  of  the  interauricular  septum,  the  salivary  glands,  the  spleen,  and 
suprarenal  capsules  are  distinguishable.  The  larynx  begins  to  become  cartilaginous.  All 
the  vertebral  bodies  are  cartilaginous.  The  points  of  ossification  for  the  ulna,  radius,  fibula, 
and  ilium  make  their  appearance.  The  two  halves  of  the  hard  palate  unite.  The 
sympathetic  nerves  are  now  for  the  first  time  to  be  discerned. 

yiiith  Week. — The  corpus  striatum  and  the  pericardium  are  first  apparent.  The  ovary  and 
testicle  can  be  distinguished  from  each  other.  The  genital  furrow  appears.  The  osseous 
nuclei  of  the  bodies  and  arches  of  the  vertebrae,  of  the  frontal,  vomer,  and  malar  bones  of  the 
shafts  of  the  metacarpal  and  metatarsal  bones,  and  of  the  phalanges  appear.  The  union  of 
the  hard  palate  is  completed.  The  gall-bladder  is  seen. 

Third  Month. — The  formation  of  the  foetal  placenta  advances  rapidly.  The  projection  of  the 
caudal  extremity  disappears.  It  is  possible  to  distinguish  the  male  and  female  organs  from 
each  other.  The  cloacal  aperture  in  divided  into  two  parts.  The  cartilaginous  arches  on  the 
dorsal  region  of  the  spine  close.  The  points  of  ossification  for  the  occipital,  sphenoid, 
lachrymal,  nasal,  squamous  portion  of  temporal  and  ischium  appear,  as  well  as  the  orbital 

141 


142  THE  FCETUS. 

centre  of  the  superior  maxillary.  The  pons  Varolii  and  fissure  of  Sylvius  can  be  made  out. 
The  eyelids,  the  hair,  and  the  nails  begin  to  form.  The  mammary  gland,  the  epiglottis, 
and  prostate  are  beginning  to  develop.  The  union  of  the  testicle  with  the  canals  of  the 
Wolffian  body  takes  place. 

Fourth  Month. — The  closure  of  the  cartilaginous  arches  of  the  spine  is  complete.  Osseous 
points  for  the  first  sacral  vertebra  and  os  pubis  appear.  The  ossification  of  the  malleus  and 
incus  takes  place.  The  corpus  callosum,  the  membrana  lamina  spiralis,  the  cartilage  of 
the  Eustachian  tube,  and  the  tympanic  ring  are  seen.  Fat  is  first  developed  in  the  sub- 
cutaneous cellular  tissue.  The  tonsils  are  seen,  and  the  closure  of  the  genital  furrow  and 
the  formation  of  the  scrotum  and  prepuce  take  place. 

Fifth  Month. — The  two  layers  of  the  decidua  begin  to  coalesce.  Osseous  nuclei  of  the  axis  and 
odontoid  process,  of  the  lateral  points  of  the  first  sacral  vertebra,  of  the  median  points  of 
the  second,  and  of  the  lateral  masses  of  the  ethmoid  make  their  appearance.  Ossification 
of  the  stapes  and  the  petrous  bone  and  ossification  of  the  germs  of  the  teeth  take  place. 
The  germs  of  the  permanent  teeth  and  the  organ  of  Corti  appear.  The  eruption  of  hair  on 
the  head  commences.  The  sudoriferous  glands,  Brunner's  glands,  the  follicles  of  the  tonsil 
and  base  of  the  tongue,  and  the  lymphatic  glands  appear  at  this  period.  The  differentiation 
between  the  uterus  and  vagina  becomes  apparent. 

Sixth  Month. — The  points  of  ossification  for  the  anterior  root  of  the  transverse  process  of  the 
seventh  cervical  vertebra,  the  lateral  points  of  the  second  sacral  vertebra,  the  median  points 
of  the  third,  the  manubrium  sterni  and  the  os  calcis  appear.  The  sacro-vertebral  angle 
forms.  The  cerebral  hemispheres  cover  the  cerebellum.  The  papillae  of  the  skin,  the 
sebaceous  glands,  and  Peyer's  patches  make  their  appearance.  The  free  border  of  the 
nail  projects  from  the  cqrium  of  the  dermis.  The  walls  of  the  uterus  thicken. 

Seventh  Month. — The  additional  points  of  the  first  sacral  vertebra,  the  lateral  points  of  the 
third,  the  median  point  of  the  fourth,  the  first  osseous  point  of  the  body  of  the  sternum, 
and  the  osseous  point  for  the  astragalus  appear.  Meckel's  cartilage  disappears.  The 
cerebral  convolutions,  the  island  of  Reil,  and  the  tubercula  quadrigemina  are  apparent.  The 
pupillary  membrane  atrophies.  The  testicle  passes  into  the  vaginal  process  of  the 
peritoneum. 

Eighth  Month. — Additional  points  for  the  second  sacral  vertebra,  lateral  points  for  the  fourth 
and  median  points  for  the  fifth  sacral  vertebrae,  can  be  seen. 

Ninth  Month. — Additional  points  for  the  third  sacral  vertebra,  lateral  points  for  the  fifth, 
osseous  points  for  the  middle  turbinated  bone,  for  the  body  and  great  cornu  of  the  hyoid. 
for  the  second  and  third  pieces  of  the  body  of  the  sternum,  and  for  the  lower  end  of  the 
femur  appear.  Ossification  of  the  bony  lamina  spiralis  and  axis  of  the  cochlea  takes  place. 
The  eyelids  open,  and  the  testicles  are  in  the  scrotum. 


DESCRIPTIVE  AND  SURGICAL 

ANATOMY. 


OSTEOLOGY-THE  SKELETON. 


T 


HE  entire  skeleton  in  the  adult  consists  of  200  distinct  bones.     These  are — 

The  spine  or  vertebral  column  (sacrum  and  coccyx  included) 26 

Cranium 8 

Face 14 

Os  hyoides,  sternum,  and  ribs 26 

Upper  extremities 64 

Lower  extremities 62 

200 

In  this  enumeration  the  patellae  are  included  as  separate  bones,  but  the  smaller 
sesamoid  bones  and  the  ossicula  auditus  are  not  reckoned.  The  teeth  belong  to 
the  tegumentary  system. 

These  bones  are  divisible  into  four  classes :  Long,  Short.  Flat,  and  Irregular. 

The  Long  Bones  are  found  in  the  limbs,  where  they  form  a  system  of  levers, 
which  have  to  sustain  the  weight  of  the  trunk  and  to  confer  the  p*ower  of  locomo- 
tion. A  long  bone  consists  of  a  shaft  and  two  extremities.  The  shaft  is  a  hollow 
cylinder,  contracted  and  narrowed  to  afford  greater  space  for  the  bellies  of  the 
muscles  :  the  walls  consist  of  dense,  compact  tissue  of  great  thickness  in  the  middle, 
but  becoming  thinner  toward  the  extremities :  the  spongy  tissue  is  scanty,  and 
the  bone  is  hollowed  out  in  its  interior  to  form  the  medullary  canal.  The 
extremities  are  generally  somewhat  expanded  for  greater  convenience  of  mutual 
connection,  for  the  purposes  of  articulation,  and  to  afford  a  broad  surface  for 
muscular  attachment.  Here  the  bone  is  made  up  of  spongy  tissue  with  onlv  a  thin 
coating  of  compact  substance.  The  long  bones  are  not  straight,  but  curved,  the 
curve  generally  taking  place  in  two  directions,  thus  affording  greater  strength  to  the 
bone.  The  bones  belonging  to  this  class  are  the  clavicle,  humerus,  radius,  ulna, 
femur,  tibia,  fibula,  metacarpal  and  metatarsal  bones,  and  the  phalanges. 

Short  Bones. — Where  a  part  of  the  skeleton  is  intended  for  strength  and  com- 
pactness, and  its  motion  is  at  the  same  time  slight  and  limited,  it  is  divided  into  a 
number  of  small  pieces  united  together  by  ligaments,  and  the  separate  bones  are 
short  and  compressed,  such  as  the  bones  of  the  carpm  and  tarsus.  These  bones, 
in  their  structure,  are  spongy  throughout,  excepting  at  their  surface,  where  there 
is  a  thin  crust  of  compact  substance.  The  patella?  also,  together  with  the  other 
sesamoid  bones,  are  by  some  regarded  as  short  bones. 

Flat  Bones. — Where  the  principal  requirement  is  either  extensive  protection 
or  the  provision  of  broad  surfaces  for  muscular  attachment,  we  find  the  osseous 
structure  expanded  into  broad,  flat  plates,  as  is  seen  in  the  bones  of  the  skull  and 
the  shoulder-blade.  These  bones  are  composed  of  two  thin  layers  of  compact  tissue 
enclosing  between  them  a  variable  quantity  of  cancellous  tissue.  In  the  cranial 
bones  these  layers  of  compact  tissue  are  familiarly  known  as  the  tables  of  the 

143 


144  THE   SKELETON. 

skull ;  the  outer  one  is  thick  and  tough ;  the  inner  one  thinner,  denser,  and  more 
brittle,  and  hence  termed  the  vitreous  table.  The  intervening  cancellous  tissue 
is  called  the  diploe.  The  flat  bones  are :  the  occipital,  parietal,  frontal,  nasal, 
lachrymal,  vomer,  scapula,  os  innominatum,  sternum,  ribs,  and  patella. 

The  Irregular  or  Mixed  Bones  are  such  as,  from  their  peculiar  form,  cannot  be 
grouped  under  either  of  the  preceding  heads.  Their  structure  is  similar  to  that 
of  other  bones,  consisting  of  a  layer  of  compact  tissue  externally,  and  of  spongy 
cancellous  tissue  within.  The  irregular  bones  are :  the  vertebrae,  sacrum,  coccyx, 
temporal,  sphenoid,  ethmoid,  malar,  superior  maxillary,  inferior  maxillary,  palate, 
inferior  turbinated,  and  hyoid. 

Surfaces  of  Bones. — If  the  surface  of  any  bone  is  examined,  certain  eminences 
and  depressions  are  seen  to  which  descriptive  anatomists  have  given  the  following 
names. 

These  eminences  and  depressions  are  of  two  kinds  :  articular  and  non-articular. 
Well-marked  examples  of  articular  eminences  are  found  in  the  heads  of  the  humerus 
and  femur  and  of  articular  depressions  in  the  glenoid  cavity  of  the  scapula  and  the 
acetabulum.  Non-articular  eminences  are  designated  according  to  their  form. 
Thus,  a  broad,  rough,  uneven  elevation  is  called  a  tuberosity ;  a  small,  rough 
prominence,  a  tubercle  ;  a  sharp,  slender,  pointed  eminence,  a  spine ;  a  narrow, 
rough  elevation,  running  some  way  along  the  surface,  a  ridge  or  line. 

The  non-articular  depressions  are  also  of  very  variable  form,  and  are  described 
as  fossce,  grooves,  furrows,  fissures,  notches,  etc.  These  non-articular  eminences 
and  depressions  serve  to  increase  the  extent  of  surface  for  the  attachment  of  liga- 
ments and  muscles,  and  are  usually  well  marked  in  proportion  to  the  muscularity 
of  the  subject. 

A  prominent  process  projecting  from  the  surface  of  a  bone,  which  it  has  never 
been  separate  from  or  movable  upon  is  termed  an  apophysis  (from  dno</>um<;,  an 
excrescence) ;  but  if  such  process  is  developed  as  a  separate  piece  from  the  rest  of 
the  bone,  to  which  it  is  afterward  joined,  it  is  termed  an  epiphysis  (from  Ixiipuatz, 
an  accretion).  Diaphysis  means  main  part  of  a  bone  or  shaft  of  a  long  bone. 

THE  SPINE. 

The  Spine  is  a  flexuous  and  flexible  column  formed  of  a  series  of  bones  called 
vertebrce  (from  vertere,  to  turn). 

The  Vertebrae  are  thirty-three  in  number,  exclusive  of  those  which  form  the 
skull,  and  have  received  the  names  cervical,  dorsal,  lumbar,  sacral,  and  coccygeal, 
according  to  the  position  which  they  occupy ;  seven  being  found  in  the  cervical 
region,  twelve  in  the  dorsal,  five  in  the  lumbar,  five  in  the  sacral,  and  four  in  the 
coccygeal. 

This  number  is  sometimes  increased  by  an  additional  vertebra  in  one  region,  or 
the  number  may  be  diminished  in  one  region,  the  deficiency  being  supplied  by 
an  additional  vertebra  in  another.  These  observations  do  not  apply  to  the  cervical 
portion  of  the  spine,  the  number  of  bones  forming  which  is  seldom  increased  or 
diminished. 

The  vertebrae  in  the  upper  three  regions  of  the  spine  are  separate  throughout 
the  whole  of  life ;  but  those  found  in  the  sacral  and  coccygeal  regions  are  in  the 
adult  firmly  united,  so  as  to  form  two  bones — five  entering  into  the  formation 
of  the  upper  bone  or  sacrum,  and  four  into  the  terminal  bone  of  the  spine  or 
coccyx. 

General  Characters  of  a  Vertebra. 

Each  vertebra  consists  of  two  essential  parts — an  anterior  solid  segment  or 
body,  and  a  posterior  segment  or  arch.  The  arch  (neural}  is  formed  of  two  pedi- 
cles and  two  laminae,  supporting  seven  processes — viz.  four  articular,  two  trans- 
verse, and  one  spinous. 

The  bodies  of  the  vertebrae  are  piled  one  upon  the  other,  forming  a  strong 
pillar  for  the  support  of  the  cranium  and  trunk  ;  the  arches  forming  a  hollow 
cylinder  behind  the  bodies  for  the  protection  of  the  spinal  cord.  The  different 


CERVICAL    VERTEBRA.  145 

vertebrae  are  connected  together  by  means  of  the  articular  processes  and  the  inter- 
vertebral  cartilages ;  while  the  transverse  and  spinous  processes  serve  as  levers 
for  the  attachment  of  muscles  which  move  the  different  parts  of  the  spine.  Lastly, 
between  each  pair  of  vertebrae  apertures  exist  through  which  the  spinal  nerves 
pass  from  the  cord.  Each  of  these  constituent  parts  must  now  be  separately 
examined. 

The  Body  or  Centrum  is  the  largest  and  most  solid  part  of  a  vertebra.  Above 
and  below  it  is  flattened ;  its  upper  and  lower  surfaces  are  rough  for  the  attach- 
ment of  the  intervertebral  fibro-cartilages.  and  present  a  rim  around  their  cir- 
cumference. In  front,  it  is  convex  from  side  to  side,  concave  from  above  down- 
ward. Behind,  it  is  flat  from  above  downward  and  slightly  concave  from  side  to 
side.  Its  anterior  surface  is  perforated  by  a  few  small  apertures,  for  the  passage 
of  nutrient  vessels :  whilst  on  the  posterior  surface  is  a  single  large,  irregular 
aperture,  or  occasionally  more  than  one,  for  the  exit  of  veins  from  the  body  of 
the  vertebra — the  ?vmp  basis  vertebrae. 

The  Pedicles  project  backward,  one  on  each  side,  from  the  upper  part  of  the 
body  of  the  vertebra,  at  the  line  of  junction  of  its  posterior  and  lateral  surfaces. 
The  concavities  above  and  below  the  pedicles  are  the  intervertebral  notches  ;  they 
are  four  in  number,  two  on  each  side,  the  inferior  ones  being  generally  the  deeper. 
When  the  vertebra?  are  articulated  the  notches  of  each  contiguous  pair  of  bones 
form  the  intervertebral  foramina,  which  communicate  with  the  spinal  canal  and 
transmit  the  spinal  nerves  and  blood-vessels. 

The  Laminae  are  two  broad  plates  of  bone  which  complete  the  vertebral  arch 
behind,  enclosing  a  foramen,  the  spinal  foramen,  which  serves  for  the  protection 
of  the  spinal  cord ;  they  are  connected  to  the  body  by  means  of  the  pedicles. 
Their  upper  and  lower  borders  are  rough,  for  the  attachment  of  the  ligamenta 
tubflava. 

The  Spinous  Process  projects  backward  from  the  junction  of  the  two  laminae, 
and  serves  for  the  attachment  of  muscles. 

The  Articular  Processes,  four  in  number,  two  on  each  side,  spring  from  the 
junction  of  the  pedicles  with  the  laminae.  The  two  superior  project  upward,  their 
articular  surfaces  being  directed  more  or  less  backward;  the  two  inferior  project 
downward,  their  articular  surfaces  looking  more  or  less  forward.1 

The  Transverse  Processes,  two  in  number,  project  one  at  each  side  from  the 
point  where  the  articular  processes  join  the  pedicle.  They  also  serve  for  the 
attachnienr  of  muscles. 

Character  of  the  Cervical  Vertebrae  (Fig.  109). 

The  Cervical  Vertebrae  are  smaller  than  those  in  any  other  region  of  the  spine, 
and  may  readily  be  distinguished  by  the  foramen  in  the  transverse  process,  which 
<lof>  not  exist  in  the  transverse  process  of  either  the  dorsal  or  lumbar  vertebrae. 

The  Body  is  small,  comparatively  dense,  and  broader  from  side  to  side  than 
fr»ni  before  backward.  The  anterior  and  posterior  surfaces  are  flattened  and  of 
equal  depth :  the  former  is  placed  on  a  lower  level  than  the  latter,  and  its  inferior 
border  is  prolonged  downward,  so  as  to  overlap  the  upper  and  fore  part  of  the 
vertebrae  below.  Its  upper  surface  is  concave  transversely,  and  presents  a  pro- 
jecting lip  on  each  side :  its  lower  surface  is  convex  from  side  to  side,  concave 
from  before  backward,  and  presents  laterally  a  shallow  concavity  which  receives 
the  corresponding  projecting  lip  of  the  adjacent  vertebra.  The  pedicles  are 
directed  obliquely  outward,  and  the  superior  intervertebral  notches  are  deeper. 
but  narrower,  than  the  inferior.  The  lamina1  are  narrow,  long,  thinner  above  than 
below,  and  overlap  each  other,  enclosing  the  spinal  foramen,  which  is  very  large, 
and  of  a  triangular  form.  The  spinous  processes  are  short,  and  bifid  at  the 
extremity  to  afford  greater  extent  of  surface  for  the  attachment  of  muscles,  the 
two  divisions  being  often  of  unequal  size.  They  increase  in  length  from  the 

1  It  may.  perhaps,  be  as  well  to  remind  the  reader  that  the  direction  of  a  surface  is  determined 
by  that  of  a  line  drawn  at  right  angles  to  it. 
10 


146  THE   SKELETON. 

fourth  to  the  seventh.  The  articular  processes  are  oblique :  the  superior  are  of 
an  oval  form,  flattened,  and  directed  backward  and  upward ;  the  inferior  forward 
and  downward.  The  transverse  processes  are  short,  directed  downward,  outward, 
and  forward,  bifid  at  their  extremity,  and  marked  by  a  groove  along  their  upper 
surface,  which  runs  downward  and  outward  from  the  superior  intervertebral 
notch,  and  serves  for  the  transmission  of  one  of  the  cervical  nerves.  They  are 
situated  in  front  of  the  articular  processes  and  on  the  outer  side  of  the  pedicles. 
The  transverse  processes  are  pierced  at  their  base  by  a  foramen,  for  the  transmis- 
sion of  the  vertebral  artery,  vein,  and  plexus  of  nerves.  Each  process  is  formed 
by  two  roots :  the  anterior  root,  sometimes  called  the  costal  process,  arises  from 
the  side  of  the  body,  and  is  the  homologue  of  the  rib  in  the  dorsal  region  of  the 
spine;  the  posterior  root  springs  from  the  junction  of  the  pedicle  with  the  lamina, 
and  corresponds  with  the  transverse  process  in  the  dorsal  region.  It  is  by  the 

Anterior  tubercle  of  trans-- 

verse  process.  |   J  ^  ET^^TV  Transverse  proem. 

Foramen  for  tvrteb 
artery. 

Posterior  tubercle  of 
transverse  process. 

^-Superior  artictdar 

process. 
-Inferior  articular  process. 


?%*     Spinal  Forame 

y 


FIG.  109.— Cervical  vertebra. 

junction  of  the  two  that  the  foramen  for  the  vertebral  vessels  is  formed.  The 
extremity  of  each  of  these  roots  forms  the  anterior  and  posterior  tubercles  of  the 
transverse  processes.1 

The  peculiar  vertebrae  in  the  cervical  region  are  the  first,  or  Atlas  ;  the  second, 
or  Axis  ;  and  the  seventh,  or  Vertebra  prominens.  The  great  modifications  in  the 
form  of  the  atlas  and  axis  are  designed  to  admit  of  the  nodding  and  rotatory 
movements  of  the  head. 

The  Atlas  (Fig.  110)  is  so  named  from  supporting  the  globe  of  the  head.  The 
chief  peculiarities  of  this  bone  are  that  it  has  neither  body  nor  spinous  process. 
The  body  is  detached  from  the  rest  of  the  bone,  and  forms  the  odontoid  process  of 
the  second  vertebra;  while  the  parts  corresponding  to  the  pedicles  join  in  front  to 
form  the  anterior  arch.  The  atlas  consists  of  an  anterior  arch,  a  posterior  arch, 
and  two  lateral  masses.  The  anterior  arch  forms  about  one-fifth  of  the  bone :  its 
anterior  surface  is  convex,  and  presents  about  its  centre  a  tubercle,  for  the  attach- 
ment of  the  Longus  colli  muscle ;  posteriorly  it  is  concave,  and  marked  by  a 
smooth,  oval  or  circular  facet,  for  articulation  with  the  odontoid  process  of  the 
axis.  The  upper  and  lower  borders  give  attachment  to  the  anterior  occipito- 
atlantal  and  the  anterior  atlanto-axial  ligaments,  which  connect  it  with  the  occipital 
bone  above  and  the  axis  below.  The  posterior  arch  forms  about  two-fifths  of  the 
circumference  of  the  bone ;  it  terminates  behind  in  a  tubercle,  which  is  the  rudi- 
ment of  a  spinous  process,  and  g-ives  origin  to  the  Rectus  capitis  posticus  minor. 
The  diminutive  size  of  this  process  prevents  any  interference  in  the  movements 
between  it  and  the  cranium.  The  posterior  part  of  the  arch  presents  above  and 
behind  a  rounded  edge  for  the  attachment  of  the  posterior  occipito-atlantal  liga- 

1  The  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  is  of  large  size, 
and  is  sometimes  known  as  " Chassaignac's "  or  the  "carotid  tubercle."  It  is  in  close  relation  with 
the  carotid  artery,  which  lies  in  front  and  a  little  external  to  il  so  that,  as  was  first  pointed  out  by 
Chassaignac,  the  vessel  can  with  ease  be  compiessed  igainst  it. 


CER  VIC  A  L    VER  TEBR^E. 


147 


ment,  while  in  front,  immediately  behind  each  superior  articular  process,  is  a 
groove,  sometimes  converted  into  a  foramen  by  a  delicate  bony  spiculum  which 
arches  backward  from  the  posterior  extremity  of  the  superior  articular  process. 
These  grooves  represent  the  superior  intervertebral  notches,  and  are  peculiar  from 
being  situated  behind  the  articular  processes,  instead  of  in  front  of  them,  as  in 
the  other  vertebrae.  They  serve  for  the  transmission  of  the  vertebral  artery, 
which,  ascending  through  the  foramen  in  the  transverse  process,  winds  round  the 
lateral  mass  in  a  direction  backward  and  inward.  They  also  transmit  the  suboc- 
cipital  nerve.  On  the  under  surface  of  the  posterior  arch,  in  the  same  situation, 
are  two  other  grooves,  placed  behind  the  lateral  masses,  and  representing  the  infe- 
rior intervertebral  notches  of  other  vertebrae.  They  are  much  less  marked  than 
the  superior.  The  lower  border  also  gives  attachment  to  the  posterior  atlanto- 
axial  ligament,  which  connects  it  with  the  axis.  The  lateral  masses  are  the  most 
bulky  and  solid  parts  of  the  atlas,  in  order  to  support  the  weight  of  the  head ; 
they  present  two  articulating  processes  above,  and  two  below.  The  two  superior 


Tubercle. 


Diagram  of  section  of  odontoid 
process. 

Diagram  of  section  of 
transverse  ligament. 


Foramen  for 
vertebral  artery. 


Groove  for  rertebral  artery 
and  1st  cervical  nerve. 


Rudimentary  spinoits  process.. 

FIG.  110.— First  cervical  vertebra,  or  atlas. 

are  of  large  size,  oval,  concave,  and  approach  each  other  in  front,  but  diverge 
behind ;  they  are  directed  upward,  inward,  and  a  little  backward,  forming  a  kind 
of  cup  for  the  condyles  of  the  occipital  bone,  and  are  admirably  adapted  to  the 
nodding  movements  of  the  head.  Not  unfrequently  they  are  partially  subdivided 
by  a  more  or  less  deep  indentation  which  encroaches  upon  each  lateral  margin. 
The  inferior  articular  processes  are  circular  in  form,  flattened  or  slightly  concave, 
and  directed  downward  and  inward,  articulating  with  the  axis,  and  permitting 
the  rotatory  movements.  Just  below  the  inner  margin  of  each  superior  articular 
surface  is  a  small  tubercle,  for  the  attachment  of  the  transverse  ligament,  which, 
stretching  across  the  ring  of  the  atlas,  divides  it  into  two  unequal  parts ;  the 
anterior  or  smaller  segment  receiving  the  odontoid  process  of  the  axis,  the  posterior 
allowing  the  transmission  of  the  spinal  cord  and  its  membranes.  This  part  of 
the  spinal  canal  is  of  considerable  size,  to  afford  space  for  the  spinal  cord ;  and 
hence  lateral  displacement  of  the  atlas  may  occur  without  compression  of  this 
structure.  The  transverse  processes  are  of  large  size,  project  directly  outward 
from  the  lateral  masses,  and  serve  for  the  attachment  of  special  muscles  which 
T  in  rotating  the  head.  They  are  long,  not  bifid,  and  perforated  at  their  base 
by  a  canal  for  the  vertebral  artery,  which  is  directed  from  below,  upward  and 
backward. 

The  Axis  (Fig.  Ill)  is  so  named  from  forming  the  pivot  upon  which  the  first 
vertebra,  carrying  the  head,  rotates.  The  most  distinctive  character  of  this  bone 
is  the  strong,  prominent  process,  tooth-like  in  form  (hence  the  name  odontoid), 
which  rises  perpendicularly  from  the  upper  surface  of  the  body.  The  body  is  of  a 
triangular  form,  deeper  in  front  than  behind,  and  prolonged  downward  anteriorly 
so  as  to  overlap  the  upper  and  fore  part  of  the  adjacent  vertebra.  It  presents  in 
front  a  median  longitudinal  ridge,  separating  two  lateral  depressions  for  the  attach- 


148 


THE  SKELETON. 


ment  of  the  Longus  colli  muscle  of  either  side.     The  odontoid  process  presents 
two  articulating  surfaces :  one  in  front,  of  an  oval  form,  for  articulation  with  the 


Odontoid  process. 


Rough  surface  for  check  ligaments. 
Articular  surface  for  transverse  ligament 


.Articular  surface  for 
atlas. 


BptooM  process- 


Transverse  process. 


Inferior  articular  process. 
FIG.  111.— Second  cervical  vertebra,  or  axis. 

atlas  ;  another  behind,  for  the  transverse  ligament — the  latter  frequently  encroach- 
ing on  the  sides  of  the  process.  The  apex  is  pointed,  and  gives  attachment  to  one 
fasciculus  of  the  odontoid  ligament  (ligamentum  suspensorium).  Below  the  apex 
the  process  is  somewhat  enlarged,  and  presents  on  either  side  a  rough  impression 
for  the  attachment  of  the  lateral  fasciculi  of  the  odontoid  or  check  ligaments, 
which  connect  it  to  the  occipital  bone  ;  the  base  of  the  process,  where  it  is  attached 
to  the  body,  is  constricted,  so  as  to  prevent  displacement  from  the  transverse 

ligament,  which  binds  it  in  this 

Body.  situation  to  the  anterior  arch  of 

the  atlas.  Sometimes,  however, 
this  process  does  become  dis- 
placed, especially  in  children,  in 
whom  the  ligaments  are  more 
relaxed :  instant  death  is  the 
result  of  this  accident.  The 
pedicles  are  broad  and  strong, 
especially  their  anterior  extrem- 
ities, which  coalesce  with  the 
sides  of  the  body  and  the  root  of 
the  odontoid  process.  The  lam- 
inae are  thick  and  strong,  and  the 
spinal  foramen  large,  but  smaller 
than  that  of  the  atlas.  The  trans- 
verse processes  are  very  small, 
not  bifid,  and  perforated  by  the 
vertebral  foramen,  or  foramen 
for  the  vertebral  artery,  which  is 
directed  obliquely  upward  and 
outward.  The  superior  articular 
surfaces  are  round,  slightly  convex,  directed  upward  and  outward,  and  are 
peculiar  in  being  supported  on  the  body,  pedicles,  and  transverse  processes.  The 
inferior  articular  surfaces  have  the  same  direction  as  those  of  the  other  cervical 
vertebrae.  The  superior  inter  vertebral  notches  are  very  shallow,  and  lie  behind 
the  articular  processes ;  the  inferior  in  front  of  them,  as  in  the  other  cervical 
vertebrae.  The  spinous  process  is  of  large  size,  very  strong,  deeply  channelled  on 
its  under  surface,  and  presents  a  bifid,  tubercular  extremity  for  the  attachment  of 
muscles  which  serve  to  rotate  the  head  upon  the  spine. 

Seventh  Cervical  (Fig.  112). — The  most  distinctive  character  of  this  vertebra  is 


Spinous  process. 
FIG.  112.— Seventh  cervical  vertebra,  or  vertebra  prominens. 


DORSAL    VERTEBRA.  149 

the  existence  of  a  very  long  and  prominent  spinous  process ;  hence  ine  name 
"vertebra  prominens."  This  process  is  thick,  nearly  horizontal  in  direction,  not 
bifurcated,  and  has  attached  to  it  the  ligamentum  nuchae.  The  transverse  process 
is  usually  of  large  size,  especially  its  posterior  root ;  its  upper  surface  has  usually 
a  shallow  groove,  and  it  seldom  presents  more  than  a  trace  of  bifurcation  at  its 
extremity.  The  vertebral  foramen  is  sometimes  as  large  as  in  the  other  cervical 
» ertebrie.  but  is  usually  smaller  on  one  or  both  sides,  and  sometimes  wanting.  On 
the  left  side  it  occasionally  gives  passage  to  the  vertebral  artery ;  more  frequently 
the  vertebral  vein  traverses  it  on  both  sides ;  but  the  usual  arrangement  is  for  both 
artery  and  vein  to  pass  in  front  of  the  transverse  process,  and  not  through  the 
foramen 

Characters  of  the  Dorsal  Vertebrae. 

The  Dorsal  Vertebrae  are  intermediate  in  size  between  those  in  the  cervical  and 
those  in  the  lumbar  region,  and  increase  in  size  from  above  downward,  the  upper 


Superior  articular  process.-  _ 

-—— •  Demi-facet  for  head  of  rib. 


Facet  for  tubercle  of  rib 


Demi-facet  for  head  of  rib. 
Inferior  articular  process. 


FIG.  113.— A  dorsal  vertebra. 


vertebrae  in  this  segment  of  the  spine  being  much  smaller  than  those  in  the  lower 
part  of  the  region.  The  dorsal  vertebrae  may  be  at  once  recognized  by  the  pres- 
ence on  the  sides  of  the  body  of  one  or  more  facets  or  half-facets  for  the  heads  of 
the  ribs. 

The  bodies  of  the  dorsal  vertebrae  resemble  those  in  the  cervical  and  lumbar 
regions  at  the  respective  ends  of  this  portion  of  the  spine ;  but  in  the  middle  of 
the  dorsal  region  their  form  is  very  characteristic,  being  heart-shaped,  and  as 
broad  in  the  antero-posterior  as  in  the  lateral  direction.  They  are  thicker  behind 
than  in  front,  flat  above  and  below,  convex  and  prominent  in  front,  deeply  concave 
behind,  slightly  constricted  in  front  and  at  the  sides,  and  marked  on  each  side, 
near  the  root  of  the  pedicle,  by  two  demi-facets.  one  above,  the  other  below.  These 
are  covered  with  cartilage  in  the  recent  state,  and,  when  articulated  with  the  adjoin- 
ing vertebrae,  form,  with  the  intervening  fibro-cartilage,  oval  surfaces  for  the 
reception  of  the  heads  of  the  corresponding  ribs.  The  pedicles  are  directed  back- 
ward, and  the  inferior  intervertebral  notches  are  of  large  size,  and  deeper  than  in 
any  other  region  of  the  spine.  The  la  mince  are  broad,  thick,  and  imbricated — 
that  is  to  say.  overlapping  one  another  like  tiles  on  a  roof.  The  spinal  foramen  is 
small,  and  of  a  circular  form.  The  spinous  processes  are  long,  triangular  in  form 
(bayonet-shaped),  directed  obliquely  downward,  and  terminate  in  a  tubercular 
extremity.  They  overlap  one  another  from  the  fifth  to  the  eighth,  but  are  less. 


150 


THE  SKELETON. 


oblique  in  direction  above  and  below.     The  articular  processes  are  flat,  nearly 
vertical  in  direction,  and  project  from  the  upper  and  lower  part  of  the  pedicles; 


f  An  entire  facet  above; 
\     a  demi-facet  below. 


~A  demi-facet  above. 


— One  entire  facet. 


(  An  entire  facet. 

\  No  facet  on  transverse 

process,  which  is  ru- 

dimentary. 


An  entire  facet. 

(No facet  on  trans- 
verse process. 
Inferior  articular 
process,  convex 
and  turned  out- 
ward. 


FIG.  114.— Peculiar  dorsal  vertebrae. 

the  superior  being  directed  backward  and  slightly  outward  and  upward,  the  inferior 
forward  and  a  little  inward  and  downward.  The  transverse  processes  arise  from 
the  same  parts  of  the  arch  as  the  posterior  roots  of  the  transverse  processes  in 
the  neck,  and  are  situated  behind  the  articular  processes  and  pedicles ;  they  are 
thick,  strong,  and  of  great  length,  directed  obliquely  backward  and  outward, 
presenting  a  clubbed  extremity,  which  is  tipped  on  its  anterior  part  by  a  small 
concave  surface,  for  articulation  with  the  tubercle  of  a  rib.  Besides  the  articular 
facet  for  the  rib,  three  indistinct  tubercles  may  be  seen  rising  from  the  transverse 
processes,  one  at  the  upper  border,  one  at  the  lower  border,  and  one  externally. 
In  man  they  are  comparatively  of  small  size,  and  serve  only  for  the  attachment 
of  muscles.  But  in  some  animals  they  attain  considerable  magnitude,  either  for 


LUMBAR    VERTEBRA. 


151 


tht-  purpose  of  more  closely  connecting  the  segments  of  this  portion  of  the  spine 
or  for  muscular  and  ligamentous  attachment.  (See  below,  ttcclfth  dorsal  vertebra.) 

The  peculiar  dorsal  vertebrae  are  the  first,  ninth,  tenth,  eleventh,  and  twelfth 
(Fig.  114). 

The  First  Dorsal  Vertebra  presents,  on  each  side  of  the  body,  a  single  entire 
articular  facet  for  the  head  of  the  first  rib  and  a  half  facet  for  the  upper  half  of 
the  second.  The  upper  surface  of  the  body  is  like  that  of  a  cervical  vertebra, 
being  broad  transversely,  concave,  and  lipped  on  each  side.  The  articular  sur- 
fa<'cs  are  oblique,  and  the  spinous  process  thick,  long,  and  almost  horizontal. 

The  Ninth  Dorsal  has  no  demi-facet  beloAv.  In  some  subjects,  however,  the 
ninth  has  two  demi-facets  on  each  side,  then  the  tenth  has  a  demi-facet  at  the  upper 
part :  none  below. 

The  Tenth  Dorsal  has  (except  in  the  cases  just  mentioned)  an  entire  articular 
facet  on  each  side  above,  which  is  partly  placed  on  the  outer  surface  of  the  pedicle. 
It  has  no  demi-facet  below. 

In  the  Eleventh  Dorsal  the  body  approaches  in  its  form  and  size  to  the  lumbar. 
The  articular  facets  for  the  heads  of  the  ribs,  one  on  each  side,  are  of  large  size, 
and  placed  chiefly  on  the  pedicles,  which  are  thicker  and  stronger  in  this  and  the 
next  vertebra  than  in  any  other  part  of  the  dorsal  region.  The  spinous  process  is 
short,  nearly  horizontal  in  direction,  and  presents  a  slight  tendency  to  bifurcation 
at  its  extremity.  The  transverse  processes  are  very  short,  tubercular  at  their 
extremities,  and  have  no  articular  facets  for  the  tubercles  of  the  ribs. 

The  Twelfth  Dorsal  has  the  same  general  characters  as  the  eleventh,  but  may 
be  distinguished  from  it  by  the  inferior  articular  processes  being  convex  and 
turned  outward,  like  those  of  the  lumbar  vertebrae ;  by  the  general  form  of  the 
bn'ly.  laminae,  and  spinous  process,  approaching  to  that  of  the  lumbar  vertebrae; 
and  by  the  transverse  processes  being  shorter,  and  marked  by  three  elevations,  the 
superior,  inferior,  and  external  tubercles,  which  correspond  to  the  mammillary, 
accessory,  and  transverse  processes  of  the  lumbar  vertebrae.  Traces  of  similar 
elevations  are  usually  to  be  found  upon  the  other  dorsal  vertebrae  (vide  ut  supra). 

Characters  of  the  Lumbar  Vertebrae. 

The  Lumbar  Vertebrae  (Fig.  115)  are  the  largest  segments  of  the  vertebral 
column,  and  can  at  once  be  distinguished  bv  the  absence  of  the  foramen  in  the 


Superior  articular  pruce*$ 


FIG.  115. — Lumbar  vertebra. 


transverse  process,  the  characteristic  point  of  the  cervical  vertebrae,  and  by  the 
absence  of  any  articulating  facet  on  the  side  of  the  body,  the  distinguishing  mark 
of  the  dorsal  vertebrae. 

The  body  is  large,  and  has  a  greater  diameter  from  side  to  side  than  from  before 
backward,  slightly  thicker  in  front  than  behind,  flattened  or  slightly  concave  above 
and  below,  concave  behind,  and  deeply  constricted  in  front  and  at  the  sides, 


152  THE  SKELETON. 

presenting  prominent  margins,  which  afford  a  broad  basis  for  the  support  of  the 
superincumbent  weight.  The  pedicles  are  very  strong,  directed  backward  from 
the  upper  part  of  the  bodies ;  consequently,  the  inferior  intervertebral  notches  are 
of  considerable  depth.  The  lamince  are  broad,  short,  and  strong,  and  the  spinal 
foramen  triangular,  larger  than  in  the  dorsal,  smaller  than  in  the  cervical,  region. 
The  spinous  processes  are  thick  arid  broad,  somewhat  quadrilateral,  horizontal  in 
direction,  thicker  below  than  above,  and  terminating  by  a  rough,-  uneven  border. 
The  superior  articular  processes  are  concave,  and  look  backward  and  inward ; 
the  inferior,  convex,  look  forward  and  outward ;  the  former  are  separated  by  a 
much  wider  interval  than  the  latter,  embracing  the  lower  articulating  processes 
of  the  vertebra  above.  The  transverse  processes  are  long,  slender,  directed  trans- 
versely outward  in  the  upper  three  lumbar  vertebrae,  slanting  a  little  upward  in 
the  lower  two.  They  are  situated  in  front  of  the  articular  processes,  instead  of 
behind  them  as  in  the  dorsal  vertebrae,  and  are  homologous  with  the  ribs.  Of  the 
three  tubercles  noticed  in  connection  with  the  transverse  processes  of  the  twelfth 
dorsal  vertebra,  the  superior  ones  become  connected  in  this  region  with  the  back 
part  of  the  superior  articular  processes,  and  have  received  the  name  of  mammttlary 
processes ;  the  inferior  are  represented  by  a  small  process  pointing  downward, 
situated  at  the  back  part  of  the  base  of  the  transverse  process,  and  called  the 
accessory  processes :  these  are  the  true  transverse  processes,  which  are  rudimental 
in  this  region  of  the  spine  ;  the  external  ones  are  the  so-called  transverse  processes, 
the  homologue  of  the  rib,  and  hence  sometimes  called  costal  processes.  Although 
in  man  these  are  comparatively  small,  in  some  animals  they  attain  considerable 
size,  and  serve  to  lock  the  vertebrae  more  closely  together. 

The  Fifth  Lumbar  vertebra  is  characterized  by  having  the  body  much  thicker 
in  front  than  behind,  which  accords  with  the  prominence  of  the  sacro-vertebral 
articulation;  by  the  smaller  size  of  its  spinous  process;  by  the  wide  interval 
between  the  inferior  articulating  processes ;  and  by  the  greater  size  and  thickness 
of  its  transverse  processes. 

Structure  of  the  Vertebrae. — The  structure  of  a  vertebra  differs  in  different 
parts.  The  body  is  composed  of  light,  spongy,  cancellous  tissue,  having  a  thin 
coating  of  compact  tissue  on  its  external  surface  perforated  by  numerous  orifices, 
some  of  large  size,  for  the  passage  of  vessels ;  its  interior  is  traversed  by  one  or 
two  large  canals,  for  the  reception  of  veins,  which  converge  toward  a  single  large, 
irregular  aperture  or  several  small  apertures  at  the  posterior  part  of  the  body  of 
each  bone.  The  arch  and  processes  projecting  from  it  have,  on  the  contrary,  an 
exceedingly  thick  covering  of  compact  tissue. 

Development. — Each  vertebra  is  formed  of  four  primary  cartilaginous  portions 
(Fig.  116),  one  for  each  lamina  and  its  processes,  and  two  for  the  body.  Ossifica- 
tion commences  in  the  laminae  about  the  sixth  week  of  foetal  life,  in  the  situation 
where  the  transverse  processes  afterward  project,  the  ossific  granules  shooting 
backward  to  the  spine,  forward  into  the  pedicles,  and  outward  into  the  transverse 
and  articular  processes.  Ossification  in  the  body  commences  in  the  middle  of  the 
cartilage  about  the  eighth  week  by  two  closely  approximated  centres,  which  speedily 
coalesce  to  form  one  central  ossific  point.  According  to  some  authors,  ossifica- 
tion commences  in  the  laminae  only  in  the  upper  vertebrae — i.  e.  in  the  cervical  and 
upper  dorsal.  The  first  ossific  points  in  the  lower  vertebrae  are  those  which  are  to 
form  the  body,  the  osseous  centres  for  the  laminae  appearing  at  a  subsequent  period. 
At  birth  these  three  pieces  are  perfectly  separate.  During  the  first  year  the  laminae 
become  united  behind  by  a  portion  of  cartilage  in  which  the  spinous  process  is 
ultimately  formed,  and  thus  the  arch  is  completed.  About  the  third  year  the 
body  is  joined  to  the  arch  on  each  side,  in  such  a  manner  that  the  body  is  formed 
from  the  three  original  centres  of  ossification,  the  amount  contributed  by  the  ped- 
icles increasing  in  extent  from  below  upward.  Thus  the  bodies  of  the  sacral 
vertebrae  are  formed  almost  entirely  from  the  central  nuclei ;  the  bodies  of  the 
lumbar  are  formed  laterally  and  behind  by  the  pedicles ;  in  the  dorsal  region  the 
pedicles  advance  as  far  forward  as  the  articular  depressions  for  the  head  of  the 


LUMBAR    VERTEBRA. 


153 


ribs,  forming  these  cavities  of  reception;  and  in  the  neck  the  lateral  portions  of 
the  bodies  are  formed  entirely  by  the  advance  of  the  pedicles.     Before  puberty 


By  4  primary  centres. 


By  4  secondary  centres. 


1  for  each  lamina  ( 6th  week). 
FIG.  116.— Development  of  a  vertebra.' 


By  2  additional  plates. 

J — 1  for  upper  surface  ' 
of  body, 

for  under  surface 

of  body, 
FIG.  117. 


SI  years. 


1  for  each  trans- 
verse process, 
16  years. 


£  (sometimes  1)  for  spinoux  process  (16  years). 
FIG.  118. 


By  3  centres. 


Ifor  anterior  arch  (1st  year), 

not  constant. 


FIG.  119.— Atlas. 


By  6  centres. 


for  odontoid  process 
( 6th  month). 


—  Ifor  each  lateral  mass. 


no  other  changes  occur,  excepting  a  gradual  increase  in  the  growth  of  these 
primary  centres ;  the  upper  and  under  surfaces  of  the  bodies  and  the  ends  of  the 
transverse  and  spinous  processes  being  tipped  with  cartilage,  in  which  ossific 
granules  are  not  as  yet  deposited.  At  sixteen  years  (Fig.  118),  four  secondary 
centres  appear,  one  for  the  tip  of  each  transverse  process,  and  two  (sometimes 
united  into  one)  for  the  end  of  the  spinous  process.  At  twenty-one  years  (Fig. 
117),  a  thin  circular  epiphysial  plate  of  bone  is  formed  in  the  layer  of  cartilage 
situated  on  the  upper  and  under  sur- 
faces of  the  body,  the  former  being 
the  thicker  of  the  two.  All  these 
become  joined,  and  the  bone  is  com- 
pletely formed  between  the  twenty- 
fifth  and  thirtieth  year  of  life. 

Exceptions  to  this  mode  of  de- 
velopment occur  in  the  first,  second, 
and  seventh  cervical,  and  in  the 
vertebrae  of  the  lumbar  region. 

The  Atlas  (Fig.  119).— The  num- 
ber of  centres  of  ossification  of  the 
atlas  is  very  variable.  It  may  be 
developed  from  two,  three,  four,  or 
five  centres.  The  most  frequent  ar- 
rangement is  by  three  centres.  Two 
of  these  are  destined  for  the  two 
lateral  or  neural  musses,  the  ossifica- 
tion of  which  commences  about  the 
seventh  week  near  the  articular  pro- 
s,  and  extend  backward;  these 
portions  of  bone  are  separated  from 
one  another  behind,  at  birth,  by  a 
narrow  interval  filled  in  with  carti- 
lage. Between  the  second  and  third 
years  they  unite  either  directly  or 
through  the  medium  of  a  separate  centre  developed  in  the  cartilage  in  the  middle 
line.  The  anterior  arch,  at  birth,  is  altogether  cartilaginous,  and  in  this  a  sepa- 
rate nucleus  appears  about  the  end  of  the  first  year  after  birth,  and,  extending 
laterally,  joins  the  neural  processes  in  front  of  the  pedicles.  Sometimes  there  are 
two  nuclei  developed  in  the  cartilage,  one  on  either  side  of  the  median  line,  which 
join  to  form  a  single  mass.  And  occasionally  there  is  no  separate  centre,  but  the 


1  for  body  (6th  month  . 
FIG.  120.— Axis. 

8  additional  centres. 


for  tubercles  on  superior  articular  procefs. 
FIG.  121.— Lumbar  vertebra. 


154  THE  SKELETON. 

anterior  arch  is  formed  by  the  gradual  extension  forward  and  ultimate  junction  of 
the  two  neural  processes. 

The  Axis  (Fig.  120)  is  developed  by  six  centres.  The  body  and  arch  of  this 
bone  are  formed  in  the  same  manner  as  the  corresponding  parts  in  the  other  ver- 
tebrge  :  one  centre  (or  two,  which  speedily  coalesce)  for  the  lower  part  of  the  body, 
and  one  for  each  lamina.  The  odontoid  process  consists  originally  of  an  extension 
upward  of  the  cartilaginous  mass  in  which  the  lower  part  of  the  body  is  formed. 
At  about  the  sixth  month  of  foetal  life  two  osseous  nuclei  make  their  appearance 
in  the  base  of  this  process:  they  are  placed  laterally,  and  join  before  birth  to 
form  a  conical  bilobed  mass  deeply  cleft  above ;  the  interval  between  the  cleft  and 
the  summit  of  the  process  is  formed  by  a  wedge-shaped  piece  of  cartilage,  the  base 
of  the  process  being  separated  from  the  body  by  a  cartilaginous  interval,  which 
gradually  becomes  ossified  at  its  circumference,  but  remains  cartilaginous  in  its 
centre  until  advanced  age.1  Finally,  as  Humphry  has  demonstrated,  the  apex  of 
the  odontoid  process  has  a  separate  nucleus,  which  appears  in  the  second  year  and 
joins  about  the  twelfth  year.  In  addition  to  these  there  is  a  secondary  centre  for 
a  thin  epiphysial  plate  on  the  under  surface  of  the  body  of  the  bone. 

The  Seventh  Cervical. — The  anterior  or  costal  part  of  the  transverse  process 
of  the  seventh  cervical  is  developed  from  a  separate  osseous  centre  at  about  the 
sixth  month  of  foetal  life,  and  joins  the  body  and  posterior  division  of  the  trans- 
verse process  between  the  fifth  and  sixth  years.  Sometimes  this  process  continues 
as  a  separate  piece,  and,  becoming  lengthened  outward,  constitutes  what  is  known 
as  a  cervical  rib. 

The  Lumbar  Vertebrae  (Fig.  121)  have  two  additional  centres  (besides  those 
peculiar  to  the  vertebrae  generally)  for  the  mammillary  tubercles,  which  project 
from  the  back  part  of  the  superior  articular  processes.  The  transverse  process  of 
the  first  lumbar  is  sometimes  developed  as  a  separate  piece,  which  may  remain 
permanently  unconnected  with  the  remaining  portion  of  the  bone,  thus  forming  a 
lumbar  rib — a  peculiarity  which  is  rarely  met  with. 

Progress  of  Ossification  in  the  Spine  generally. — Ossification  of  the  laminae  of 
the  vertebrae  commences  at  the  upper  part  of  the  spine,  and  proceeds  gradually 
downward.  Ossification  of  the  bodies,  on  the  other  hand,  commences  a  little 
below  the  centre  of  the  spinal  column  (about  the  ninth  or  tenth  dorsal  vertebra), 
and  extends  both  upward  and  downward.  Although,  however,  the  ossific  nuclei 
make  their  first  appearance  in  the  lower  dorsal  vertebras,  the  lumbar  and  first 
sacral  are  those  in  which  these  nuclei  are  largest  at  birth. 

Attachment  of  Muscles. — To  the  Atlas  are  attached  nine  pairs :  the  Longus 
colli,  Rectus  capitis  anticus  minor,  Rectus  lateralis,  Obliquus  capitis  superior  and 
inferior,  Splenius  colli,  Levator  anguli  scapulae,  First  Intertransverse,  and  Rectus 
capitis  posticus  minor. 

To  the  Axis  are  attached  eleven  pairs :  the  Longus  colli,  Levator  anguli 
scapulae,  Splenius  colli,  Scalenus  medius,  Transversalis  colli,  Intertransversales, 
Obliquus  capitis  inferior,  Rectus  capitis  posticus  major,  Semispinalis  colli,  Mul- 
tifidus  spinae,  Interspinales. 

To  the  remaining  vertebrae,  generally,  are  attached  thirty-five  pairs  and  a  sin- 
gle muscle:  anteriorly,  the  Rectus  capitis  anticus  major,  Longus  colli,  Scalenus 
anticus  medius  and  posticus,  Psoas  magnus  and  parvus,  Quadratus  lumbo- 
rum,  Diaphragm,  Obliquus  abdominis  internus,  and  Transversalis  abdominis — 
posteriorly,  the  Trapezius,  Latissimus  dorsi,  Levator  anguli  scapulae,  Rhomboideus 
major  and  minor,  Serratus  posticus  superior  and  inferior,  Splenius,  Erector  spinae, 
Ilio-costalis,  Longissimus  dorsi,  Spinalis  dorsi,  Cervicalis  ascendens,  Transversalis 
colli,  Trachelo-mastoid,  Complexus,  Biventer  cervicis,  Semispinalis  dorsi  and  colli, 
Multifidus  spinae,  Rotatores  spinae,  Interspinales,  Supraspinales,  Intertransversales, 
Levatores  costarum. 

1  See  Cunningham,  Journ.  Anat.,  vol.  xx.  p.  238. 


SACRAL    AND    COCCYGEAL    VERTEBRA. 


155 


Sacral  and  Coccygeal  Vertebrae. 

The  Sacral  and  Coccygeal  Vertebrae  consist,  at  an  early  period  of  life,  of  nine 
separate  pieces,  which  are  united  in  the  adult  so  as  to  form  two  bones,  five  enter- 
ing into  the  formation  of  the  sacrum,  four  into  that  of  the  coccyx.  Occasionally, 
the  coccyx  consists  of  five  bones.1 

The  Sacrum  (sacer,  sacred)  is  a  large,  triangular  bone  (Fig.  122),  situated  at 
the  lower  part  of  the  vertebral  column,  and  at  the  upper  and  back  part  of  the  pelvic 


FIG.  122. — Sacrum,  anterior  surface. 

cavity,  where  it  is  inserted  like  a  wedge  between  the  two  innominate  bones ;  its 
upper  part  or  base  articulating  with  the  last  lumbar  vertebrae,  its  apex  with  the 
coccyx.  The  sacrum  is  curved  upon  itself,  and  placed  very  obliquely,  its  upper 
extremity  projecting  forward,  and  forming,  with  the  last  lumbar  vertebra,  a  very 
prominent  angle,  called  the  promontory  or  mcro-vertebral  angle  ;  whilst  its  central 
part  is  directed  backward,  so  as  to  give  increased  capacity  to  the  pelvic  cavity. 
It  presents  for  examination  an  anterior  and  posterior  surface,  two  lateral  surfaces, 
a  base,  an  apex,  and  a  central  canal. 

The  Anterior  Surface  is  concave  from  above  downward,  and  slightly  so  from 
side  to  side.  In  the  middle  are  seen  four  transverse  ridges,  indicating  the  original 
division  of  the  bone  into  five  separate  pieces.  The  portions  of  bone  intervening 
between  the  ridges  correspond  to  the  bodies  of  the  vertebrae.  The  body  of  the 
first  segment  is  of  large  size,  and  in  form  resembles  that  of  a  lumbar  vertebra ;  the 
succeeding  ones  diminish  in  size  from  above  downward,  are  flattened  from  before 
backward,  and  curved  so  as  to  accommodate  themselves  to  the  form  of  the  sacrum, 
being  concave  in  front,  convex  behind.  At  each  end  of  the  ridges  above  mentioned 
are  seen  the  anterior  sac-mi.  f<./-<imina,  analogous  to  the  intervertebral  foramina, 

1  Sir  George  Humphry  describes  this  as  the  usual  composition  of  the  coccyx. — On  the  Skeleton, 
p.  456. 


156 


THE   SKELETON. 


four  in  number  on  each  side,  somewhat  rounded  in  form,  diminishing  in  size 

from  above  downward,  and  directed  out- 
ward and  forward ;  they  transmit  the 
anterior  branches  of  the  sacral  nerves. 
External  to  these  foramina  is  the  lateral 
mass,  consisting  at  an  early  period  of 
life  of  separate  segments ;  these  become 
blended,  in  the  adult,  with  the  bodies, 
with  each  other,  and  with  the  posterior 
transverse  processes.  Each  lateral  mass 
is  traversed  by  four  broad,  shallow 
grooves,  which  lodge  the  anterior  sacral 
nerves  as  they  pass  outward,  the  grooves 
being  separated  by  prominent  ridges  of 
bone,  which  give  attachment  to  the  slips 
of  the  Pyriformis  muscle. 

If  a  vertical  section  is  made  through 
the  centre  of  the  bone  (Fig.  123),  the 
bodies  are  seen  to  be  united  at  their  cir- 
cumference by  bone,  a  wide  interval  being 
left  centrally,  which,  in  the  recent  state, 
is  filled  by  intervertebral  substance.  In 
some  bones  this  union  is  more  complete 
between  the  lower  segments  than  between 
the  upper  ones. 

The  Posterior  Surface  (Fig.  124)  is 
convex  and  much  narrower  than  the 
anterior.  In  the  middle  line  are  three 
or  four  tubercles,  which  represent  the 
rudimentary  spinous  processes  of  the  sac- 
ral vertebrae.  Of  these  tubercles,  the 
first  is  usually  prominent,  and  perfectly 
distinct  from  the  rest ;  the  second  and 
third  are  either  separate  or  united  into  a  tubercular  ridge,  which  diminishes  in 
size  from  above  downward  ;  the  fourth  usually,  and  the  fifth  always,  remaining  un- 
developed. External  to  the  spinous  processes  on  each  side  are  the  lamince,  broad 
and  well  marked  in  the  first  three  pieces ;  sometimes  the  fourth,  and  generally 
the  fifth,  being  undeveloped :  in  this  situation  the  lower  end  of  the  sacral  canal 
is  exposed,  and  is  liable  to  be  opened  in  the  sloughing  of  bed-sores.  External  to 
the  laminae  is  a  linear  series  of  indistinct  tubercles  representing  the  articular 
processes  ;  the  upper  pair  are  large,  well  developed,  and  correspond  in  shape  and 
direction  to  the  superior  articulating  processes  of  a  lumbar  vertebra ;  the  second 
and  third  are  small ;  the  fourth  and  fifth  (usually  blended  together)  are  situated 
on  each  side  of  the  sacral  canal :  they  are  called  the  sacral  eornua,  and  articulate 
with  the  cornua  of  the  coccyx.  External  to  the  articular  processes  are  the  four 
posterior  sacral  foramina  ;  they  are  smaller  in  size  and  less  regular  in  form  than 
the  anterior,  and  transmit  the  posterior  branches  of  the  sacral  nerves.  On  the 
outer  side  of  the  posterior  sacral  foramina  is  a  series  of  tubercles,  the  rudiment- 
ary transverse  processes  of  the  sacral  vertebrae.  The  first  pair  of  transverse 
tubercles  are  large,  very  distinct,  and  correspond  with  each  superior  lateral  angle 
of  the  bone ;  the  second,  small  in  size,  enter  into  the  formation  of  the  sacro-iliac 
articulation ;  the  third  give  attachment  to  the  oblique  fasciculi  of  the  posterior 
sacro-iliac  ligaments  ;  and  the  fourth  and  fifth  to  the  great  sacro-sciatic  ligaments. 
The  interspace  between  the  spinous  and  transverse  processes  on  the  back  of  the 
sacrum  presents  a  wide,  shallow  concavity,  called  the  sacral  groove :  it  is 
continuous  above  with  the  vertebral  groove,  and  lodges  the  origin  of  the  Erector 
spinae. 


FIG.  123.— Vertical  section  of  the  sacrum. 


SACRAL    AND    COCCYGEAL     VERTEBRAE. 


157 


The  Lateral  Surface,  broad  above,  becomes  narrowed  into  a  thin  edge  below. 
Its  upper  half  presents  in  front  a  broad,  ear-shaped  surface  for  articulation  with 


Upper  half  of  fifth 
posterior  sacral  foramen. 


FIG.  124. — Sacrum,  posterior  surface. 


the  ilium.  This  is  called  the  auricular  surface,  and  in  the  fresh  state  is  coated 
with  fibro-cartilage.  It  is  bounded  posteriorly  by  deep  and  uneven  impressions, 
for  the  attachment  of  the  posterior  sacro-iliac  ligaments.  The  lower  half  is  thin 
and  sharp,  and  ends  in  a  prominence,  the  inferior  lateral  angle  ;  the  border  gives 
attachment  to  the  greater  and  lesser  sacro-sciatic  ligaments,  and  to  some  fibres 
of  the  Glutens  maximus :  below  the  angle  is  a  deep  notch,  which  is  converted 
into  a  foramen  by  the  transverse  process  of  the  upper  piece  of  the  coccyx,  and 
transmits  the  anterior  division  of  the  fifth  sacral  nerve. 

The  Base  of  the  sacrum,  which  is  broad  and  expanded,  is  directed  upward  and 
forward.  In  the  middle  is  seen  a  large  oval  articular  surface,  which  is  connected 
with  the  under  surface  of  the  body  of  the  last  lumbar  vertebra  by  a  fibre-carti- 
laginous disk.  It  is  bounded  behind  by  the  large,  triangular  orifice  of  the  sacral 
canal.  The  orifice  is  formed  behind  by  the  laminae  and  spinous  process  of  the 
first  sacral  vertebra:  the  superior  articular  processes  project  from  it  on  each  side; 
they  are  oval,  concave,  directed  backward  and  inward,  like  the  superior  articular 
processes  of  a  lumbar  vertebra :  and  in  front  of  each  articular  process  is  an  inter- 
vertebral  notch,  which  forms  the  lower  half  of  the  last  intervertebral  foramen. 
Lastly,  on  each  side  of  the  large  oval  articular  surface  is  a  broad  and  flat  triangular 
surface  of  bone,  which  extends  outward,  supports  the  Psoas  magnus  muscle  and 
lumbo-sacral  cord,  and  is  continuous  on  each  side  with  the  iliac  fossa.  This  is 
called  the  ala  of  the  sacrum,  and  gives  attachment  to  a  few  of  the  fibres  of  the 
Iliacus  muscle. 

The  Apex,  directed  downward  and  forward,  presents  a  small,  oval,  concave 
surface  for  articulation  with  the  coccyx. 

The  Spinal  Canal  runs  throughout  the  greater  part  of  the  bone ;  it  is  large 


158  THE  SKELETON. 

and  triangular  in  form  above,  small  and  flattened,  from  before  backward,  below. 
In  this  situation  its  posterior  wall  is  incomplete,  from  the  non-development  of  the 
laminae  and  spinous  processes.  It  lodges  the  sacral  nerves,  and  is  perforated  by 
the  anterior  and  posterior  sacral  foramina,  through  which  these  pass  out. 

Structure. — It  consists  of  much  loose,  spongy  tissue  within,  invested  externally 
by  a  thin  layer  of  compact  tissue. 

Differences  in  the  Sacrum  of  the  Male  and  Female. — The  sacrum  in  the 
female  is  usually  wider  than  in  the  male  ;  the  lower  half  forms  a  greater  angle  with 
the  upper,  the  upper  half  of  the  bone  being  nearly  straight,  the  lower  half  pre- 
senting the  greatest  amount  of  curvature.  The  bone  is  also  directed  more  obliquely 
backward,  Avhich  increases  the  size  of  the  pelvic  cavity ;  but  the  sacro-vertebral 
angle  projects  less.  In  the  male  the  curvature  is  more  evenly  distributed  over  the 
whole  length  of  the  bone,  and  is  altogether  greater  than  in  the  female. 

Peculiarities  of  the  Sacrum. — This  bone,  in  some  cases,  consists  of  six  pieces ; 
occasionally,  the  number  is  reduced  to  four.  Sometimes  the  bodies  of  the  first 
and  second  segments  are  not  joined  or  the  laminsB  and  spinous  processes  have  not 
coalesced.  Occasionally  the  upper  pair  of  transverse  tubercles  are  not  joined  to 
the  rest  of  the  bone  on  one  or  both  sides  ;  and,  lastly,  the  sacral  canal  may  be  open 
for  nearly  the  lower  half  of  the  bone,  in  consequence  of  the  imperfect  development 
of  the  laminae  and  spinous  processes.  The  sacrum,  also,  varies  considerably  with 
respect  to  its  degree  of  curvature.  From  the  examination  of  a  large  number  of 
skeletons  it  would  appear  that  in  one  set  of  cases  the  anterior  surface  of  this  bone 
was  nearly  straight,  the  curvature,  which  was  very  slight,  affecting  only  its  lower 
end.  In  another  set  of  cases  the  bone  was  curved  throughout  its  whole  length, 
but  especially  toward  its  middle.  In  a  third  set  the  degree  of  curvature  was  less 
marked,  and  affected  especially  the  lower  third  of  the  bone. 

Development  (Fig.  125). — The  sacrum,  formed  by  the  union  of  five  vertebrae,  has 
thirty-five  centres  of  ossification. 

The  bodies  of  the  sacral  vertebras  have  each  three  ossific  centres :  one  for  the 
central  part,  and  one  for  the  epiphysial  plates  on  its  upper  and  under  surface. 
Occasionally  the  primary  centres  for  the  bodies  of  the  first  and  second  piece  of  the 
sacrum  are  double. 

The  arch  of  each  sacral  vertebra  is  developed  by  two  centres,  one  for  each 
lamina.  These  unite  with  each  other  behind,  and  subsequently  join  the  body. 

The  lateral  masses  have  six  additional  centres,  two  for  each  of  the  first  three 
vertebrae.  These  centres  make  their  appearance  above  and  to  the  outer  side  of 
the  anterior  sacral  foramina  (Fig.  125),  and  are  developed  into  separate  segments 


Two  epiphysial  laminse 
for  each  lateral  surface.* 


Additional  centres 
for  the  first  three  pieces.* 


At  birth. 

V2j3«iJ/7 

\'^TV 77—- /*>S       I    I 

At  4%  years. 
FIG.  125.— Development  of  the  sacrum.  FIG.  126.  FIG.  127. 

(Fig.  126) ;  they  are  subsequently  blended  with  each  other,  and  with  the  bodies 
and  transverse  processes  to  form  the  lateral  mass. 

Lastly,  each  lateral  surface  of  the  sacrum  is  developed  by  two  epiphysial  plates 
(Fig.  127) :  one  for  the  auricular  surface,  and  one  for  the  remaining  part  of  the 
thin  lateral  edge  of  the  bone. 


THE    COCCYX. 


159 


of  Development. — At  about  the  eighth  or  ninth  week  of  foetal  life  ossi- 
fication of  the  central  part  of  the  bodies  of  the  first  three  vertebrae  commences, 
and  at  a  somewhat  later  period  that  of  the  last  two.  Between  the  sixth  and 
eighth  months  ossification  of  the  laminae  takes  place;  and  at  about  the  same 
period  the  characteristic  osseous  tubercles  for  the  first  three  sacral  vertebrae  make 
their  appearance.  The  period  at  which  the  arch  becomes  completed  by  the  junction 
of  the  laminae  with  the  bodies  in  front  and  with  each  other  behind  varies  in  different 
segments.  The  junction  between  the  laminae  and  the  bodies  takes  place  first  in 
the  lower  vertebrae  as  early  as  the  second  year,  but  is  not  effected  in  the  upper- 
most until  the  fifth  or  sixth  year.  About  the  sixteenth  year  the  epiphyses  for 
the  upper  and  under  surfaces  of  the  bodies  are  formed,  and  between  the  eighteenth 
and  twentieth  years  those  for  each  lateral  surface  of  the  sacrum  make  their 
appearance.  The  bodies  of  the  sacral  vertebrae  are,  during  early  life,  separated 
from  each  other  by  intervertebral  disks.  But  about  the  eighteenth  year  the  two 
lowest  segments  become  joined  together  by  ossification  extending  through  the 
disk.  This  process  gradually  extends  upward  until  all  the  segments  become 
united,  and  the  bone  is  completely  formed  from  the  twenty-fifth  to  the  thirtieth 
year  of  life. 

Articulations. — With  four  bones:  the  last  lumbar  vertebra,  coccyx,  and  the 
two  ossa  innominata. 

Attachment  of  Muscles. — To  eight  pairs :  in  front,  the  Pyriformis  and  Coccyg- 
eus,  and  a  portion  of  the  Iliacus  to  the  base  of  the  bone ;  behind,  the  Gluteus 
maximus,  Latissirnus  dorsi,  Multifidus  spinae,  and  Erector  spinae.  and  sometimes 
the  Extensor  coccygis. 

The  Coccyx. 

The  Coccyx  (xoxxu£,  cuckoo),  so  called  from  having  been  compared  to  a  cuc- 
koo's beak  (Fig.  128),  is  usually  formed  of  four  small  segments  of  bone,  the  most 
rudimentary  parts  of  the  vertebral  column.  In  each 
of  the  first  three  segments  may  be  traced  a  rudi- 
mentary body,  articular  and  transverse  processes ;  the 
last  piece  (sometimes  the  third)  is  a  mere  nodule  of 
bone,  without  distinct  processes.  All  the  segments  are 
destitute  of  pedicles,  laminae,  and  spinous  processes, 
and,  consequently,  of  intervertebral  foramina  and  spinal 
canal.  The  first  segment  is  the  largest :  it  resembles 
the  lowermost  sacral  vertebra,  and  often  exists  as  a 
separate  piece ;  the  last  three,  diminishing  in  size  from 
above  downward,  are  usually  blended  together  so  as  to 
form  a  single  bone.  The  gradual  diminution  in  the 
size  of  the  pieces  gives  this  bone  a  triangular  form,  the 
base  of  the  triangle  joining  the  end  of  the  sacrum.  It 
presents  for  examination  an  anterior  and  posterior  sur- 
face, two  borders,  a  base,  and  an  apex.  The  anterior 
surface  is  slightly  concave,  and  marked  with  three 
transverse  grooves,  indicating  the  points  of  junction  of 
the  different  pieces.  It  has  attached  to  it  the  anterior 
sacro-coccygeal  ligament  and  Levator  ani  muscle,  and 
supports  the  lower  end  of  the  rectum.  The  posterior 
surface  is  convex,  marked  by  transverse  grooves  similar 
to  those  on  the  anterior  surface ;  and  presents  on  each 
side  a  lineal  row  of  tubercles,  the  rudimentary  articular 
processes  of  the  coccy geal  vertebrae.  Of  these,  the  supe- 
rior pair  are  large,  and  are  called  the  eornua  of  the 
coccyx;  they  project  upward,  and  articulate  with  the 
eornua  of  the  sacrum,  the  junction  between  these  two 
bones  completing  the  fifth  posterior  sacral  foramen  for  the  transmission  of  the  pos- 
terior division  of  the  fifth  sacral  nerve.  The  lateral  borders  are  thin,  and  present  a 


Anterior  surface. 


Posterior  surface. 
FIG.  128.— Coccvx. 


160 


THE  SKELETON. 


FIG.  129.— Lateral  view  of  the  spine. 


series  of  small  eminences,  which  represent 
the  transverse  processes  of  the  coccygeal 
vertebrae.  Of  these,  the  first  on  each  side  is 
the  largest,  flattened  from  before  backward, 
and  often  ascends  to  join  the  lower  part  of 
the  thin  lateral  edge  of  the  sacrum,  thus 
completing  the  fifth  anterior  sacral  foramen 
for  the  transmission  of  the  anterior  division 
of  the  fifth  sacral  nerve ;  the  others  diminish 
in  size  from  above  downward,  and  are  often 
wanting.  The  borders  of  the  coccyx  are 
narrow,  and  give  attachment  on  each  side  to 
the  sacro-sciatic  ligaments,  to  the  Coccygeus 
muscle  in  front  of  the  ligaments,  and  to  the 
Gluteus  maximus  behind  them.  The  base 
presents  an  oval  surface  for  articulation  with 
the  sacrum.  The  apex  is  rounded,  and  has 
attached  to  it  the  tendon  of  the  external 
Sphincter  muscle.  It  is  occasionally  bifid, 
and  sometimes  deflected  to  one  or  other  side. 

Development. — The  coccyx  is  developed 
by  four  centres,  one  for  each  piece.  Occa- 
sionally one  of  the  first  three  pieces  of  this 
bone  is  developed  by  two  centres,  placed  side 
by  side.  The  ossific  nuclei  make  their  ap- 
pearance in  the  following  order :  in  the  first 
segment,  at  birth ;  in  the  second  piece,  at 
from  five  to  ten  years;  in  the  third,  from 
ten  to  fifteen  years ;  in  the  fourth,  from  fif- 
teen to  twenty  years.  As  age  advances  these 
various  segments  become  united  in  the  fol- 
lowing order:  the  first  two  pieces  join;  then 
the  third  and  fourth ;  and,  lastly,  the  bone 
is  completed  by  the  union  of  the  second  and 
third.  At  a  late  period  of  life,  especially  in 
females,  the  coccyx  often  becomes  joined  to 
the  end  of  the  sacrum. 

Articulation. — With  the  sacrum. 

Attachment  of  Muscles. — To  four  pairs 
and  one  single  muscle :  on  either  side,  the 
Coccygeus;  behind,  the  Gluteus  maximus 
and  Extensor  coccygis,  when  present ;  at  the 
apex,  the  Sphincter  ani ;  and  in  front,  the 
Levator  ani. 

The  Spine  in  General. 

The  Spinal  Column,  formed  by  the  junc- 
tion of  the  vertebrae,  is  situated  in  the  median 
line,  at  the  posterior  part  of  the  trunk ;  its 
average  length  is  about  two  feet  two  or  three 
inches,  measuring  along  the  curved  anterior 
surface  of  the  column.  Of  this  length  the 
cervical  part  measures  about  five,  the  dorsal 
about  eleven,  the  lumbar  about  seven  inches, 
and  the  sacrum  and  coccyx  the  remainder. 
The  female  spine  is  about  one  inch  less  than 
the  male. 


THE  SPINE  IN   GENERAL.  161 

Viewed  in  front,  it  presents  two  pyramids  joined  together  at  their  bases,  the 
upper  one  being  formed  by  all  the  vertebrae  from  the  second  cervical  to  the  last 
lumbar,  the  lower  one  by  the  sacrum  and  coccyx.  When  examined  more  closely, 
the  upper  pyramid  is  seen  to  be  formed  of  three  smaller  pyramids.  The  upper- 
most of  these  consists  of  the  six  lower  cervical  vertebrae,  its  apex  being  formed  by 
the  axis  or  second  cervical,  its  base  by  the  first  dorsal.  The  second  pyramid, 
which  is  inverted,  is  formed  by  the  four  upper  dorsal  vertebrae,  the  base  being  at 
the  first  dorsal,  the  smaller  end  at  the  fourth.  The  third  pyramid  commences  at 
the  fourth  dorsal,  and  gradually  increases  in  size  to  the  fifth  lumbar. 

Viewed  laterally  (Fig.  129),  the  spinal  column  presents  several  curves,  which 
correspond  to  the  different  regions  of  the  column,  and  are  called  cervical,  dorsal, 
lumbar,  and  pelvic.  The  cervical  curve  commences  at  the  apex  of  the  odontoid 
process,  and  terminates  at  the  middle  of  the  second  dorsal  vertebra;  it  is  convex 
in  front,  and  is  the  least  marked  of  all  the  curves.  The  dorsal  curve,  which  is 
concave  forward,  commences  at  the  middle  of  the  second,  and  terminates  at  the 
middle  of  the  twelfth  dorsal.  Its  most  prominent  point  behind  corresponds  to 
the  spine  of  the  seventh  dorsal  vertebra.  The  lumbar  curve  commences  at  the 
middle  of  the  last  dorsal  vertebra,  and  terminates  at  the  sacro-vertebral  angle. 
It  is  convex  anteriorly;  the  convexity  of  the  lower  three  vertebrae  being  much 
greater  than  that  of  the  upper  ones.  The  pelvic  curve  commences  at  the  sacro- 
vertebral  articulation  and  terminates  at  the  point  of  the  coccyx.  It  is  concave 
anteriorly.  The  dorsal  and  pelvic  curves  are  the  primary  curves,  and  begin  to 
be  formed  at  an  early  period  of  foetal  life,  and  are  due  to  the  shape  of  the  bodies 
of  the  vertebrae.  The  cervical  and  lumbar  curves  are  compensatory  or  secondary, 
and  are  developed  after  birth  in  order  to  maintain  the  erect  position.  They  are 
due  mainly  to  the  shape  of  the  intervertebral  disks. 

The  spine  has  also  a  slight  lateral  curvature,  the  convexity  of  which  ie 
directed  toward  the  right  side.  This  is  most  probably  produced,  as  Bichat  first 
explained,  chiefly  by  muscular  action,  most  persons  using  the  right  arm  in  prefer- 
ence to  the  left,  especially  in  making  long-continued  efforts,  when  the  body  is 
curved  to  the  right  side.  In  support  of  this  explanation  it  has  been  found  by 
Beclard  that  in  one  or  two  individuals  who  were  left-handed  the  lateral  curvature 
was  directed  to  the  left  side. 

The  spinal  column  presents  for  examination  an  anterior,  a  posterior,  and  two 
lateral  surfaces :  a  base,  summit,  and  spinal  canal. 

The  anterior  surface  presents  the  bodies  of  the  vertebrae  separated  in  the 
recent  state  by  the  intervertebral  disks.  The  bodies  are  broad  in  the  cervical 
region,  narrow  in  the  upper  part  of  the  dorsal,  and  broadest  in  the  lumbar  region. 
The  whole  of  this  surface  is  convex  transversely,  concave  from  above  downward  in 
the  dorsal  region,  and  convex  in  the  same  direction  in  the  cervical  and  lumbar 
regions. 

The  posterior  surface  presents  in  the  median  line  the  spinous  processes.  These 
are  short,  horizontal,  with  bifid  extremities,  in  the  cervical  region.  In  the  dorsal 
region  they  are  directed  obliquely  above,  assume  almost  a  vertical  direction  in  the 
middle,  and  are  horizontal  below,  as  are  also  the  spines  of  the  lumbar  vertebrae. 
They  are  separated  by  considerable  intervals  in  the  loins,  by  narrower  intervals 
in  the  neck,  and  are  closely  approximated  in  the  middle  of  the  dorsal  region. 
Occasionally  one  of  these  processes  deviates  a  little  from  the  median  line — a  fact 
to  be  remembered  in  practice,  as  irregularities  of  this  sort  are  attendant  also  on 
fractures  or  displacements  of  the  spine.  On  either  side  of  the  spinous  processes, 
extending  the  whole  length  of  the  column,  is  the  vertebral  groove  formed  by  the 
laminae  in  the  cervical  and  lumbar  regions,  where  it  is  shallow,  and  by  the  laminae 
and  transverse  processes  in  the  dorsal  region,  where  it  is  deep  and  broad.  In 
the  recent  state  these  grooves  lodge  the  deep  muscles  of  the  back.  External  to 
the  vertebral  grooves  are  the  articular  processes,  and  still  more  externally  the 
transverse  process.  In  the  dorsal  region  the  latter  processes  stand  backward,  on 
11 


162  THE  SKELETON. 

a  plane  considerably  posterior  to  the  same  processes  in  the  cervical  and  lumbar 
regions.  In  the  cervical  region  the  transverse  processes  are  placed  in  front  of  the 
articular  processes,  and  on  the  outer  side  of  the  pedicles,  between  the  interver- 
tebral  foramina.  In  the  dorsal  region  they  are  posterior  to  the  pedicles,  interver- 
tebral  foramina,  and  articular  processes.  In  the  lumbar  they  are  placed  also  in 
front  of  the  articular  processes,  but  behind  the  intervertebral  foramina. 

The  lateral  surfaces  are  separated  from  the  posterior  by  the  articular  processes 
in  the  cervical  and  lumbar  regions,  and  by  the  transverse  processes  in  the  dorsal. 
These  surfaces  present  in  front  the  sides  of  the  bodies  of  the  vertebrae,  marked  in 
the  dorsal  region  by  the  facets  for  articulation  with  the  heads  of  the  ribs.  More 
posteriorly  are  the  intervertebral  foramina,  formed  by  the  juxtaposition  of  the 
intervertebral  notches,  oval  in  shape,  smallest  in  the  cervical  and  upper  part  of 
the  dorsal  regions,  and  gradually  increasing  in  size  to  the  last  lumbar.  They  are 
situated  between  the  transverse  processes  in  the  neck,  and  in  front  of  them  in  the 
back  and  loins,  and  transmit  the  spinal  nerves. 

The  base  of  that  portion  of  the  vertebral  column  formed  by  the  twenty-four 
movable  vertebrae  is  formed  by  the  under  surface  of  the  body  of  the  fifth  lumbar 
vertebra ;  and  the  summit  by  the  upper  surface  of  the  atlas. 

The  vertebral  or  spinal  canal  follows  the  different  curves  of  the  spine ;  it  is 
largest  in  those  regions  in  which  the  spine  enjoys  the  greatest  freedom  of  move- 
ment, as  in  the  neck  and  loins,  where  it  is  wide  and  triangular ;  and  narrow  and 
rounded  in  the  back,  where  motion  is  more  limited. 

Surface  Form. — The  only  part  of  the  vertebral  column  which  lies  closely  under  the  skin, 
and  so  directly  influences  surface  form,  is  the  apices  of  the  spinous  processes.  These  are  always 
distinguishable  at  the  bottom  of  a  median  furrow,  which,  more  or  less  evident,  runs  down  the 
mesial  line  of  the  back  from  the  external  occipital  protuberance  above  to  the  middle  of  the 
sacrum  below.  In  the  neck  the  furrow  is  broad,  and  terminates  below  in  a  conspicuous  projec- 
tion, which  is  caused  by  the  spinous  process  of  the  seventh  cervical  vertebra  (vertebra  prorui- 
nens).  Above  this  the  spinous  process  of  the  sixth  cervical  vertebra  may  sometimes  be  seen; 
the  other  cervical  spines  are  sunken,  and  are  not  visible,  though  the  spine  of  the  axis  can  be 
felt,  and  generally  also  the  spines  of  the  third,  fourth,  and  fifth  cervical  vertebrae.  In  the 
dorsal  region  the  furrow  is  shallow,  and  during  stooping  disappears,  and  then  the  spinous  pro- 
cesses become  more  or  less  visible.  The  markings  produced  by  these  spines  are  small  and  close 
together.  In  the  lumbar  region  the  furrow  is  deep,  and  the  situation  of  the  lumbar  spines  is 
frequently  indicated  by  little  pits  or  depressions,  especially  if  the  muscles  in  the  loins  are  well 
developed  and  the  spine  incurved.  They  are  much  larger  and  farther  apart  than  in  the  dorsal 
region.  In  the  sacral  region  the  furrow  is  shallower,  presenting  a  flattened  area  which  terminates 
below  at  the  most  prominent  part  of  the  posterior  surface  of  the  sacrum,  formed  by  the  spinous 
process  of  the  third  sacral  vertebra.  At  the  bottom  of  the  furrow  may  be  felt  the  irregular 
posterior  surface  of  the  bone.  Below  this,  in  the  deep  groove  leading  to  the  anus,  the  coccyx 
may  be  felt.  The  only  other  portions  of  the  vertebral  column  which  can  be  felt  from  the  surface 
are  the  transverse  processes  of  three  of  the  cervical  vertebrae — viz.  the  first,  the  sixth,  and  the 
seventh.  The  transverse  process  of  the  atlas  can  be  felt  as  a  rounded  nodule  of  bone  just  below 
and  in  front  of  the  apex  of  the  mastoid  process,  along  the  anterior  border  of  the  sterno-mastoid. 
The  transverse  process  of  the  sixth  cervical  vertebra  is  of  surgical  importance.  If  deep  pressure 
be  made  in  the  neck  in  the  course  of  the  carotid  artery,  opposite  the  cricoid  cartilage,  the 
prominent  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  can  be  felt. 
This  has  been  named  Chassaignacs  tubercle,  and  against  it  the  carotid  artery  may  be  most 
conveniently  compressed  by  the  finger.  The  transverse  process  of  the  seventh  cervical  vertebra 
can  also  often  be  felt.  Occasionally  the  anterior  root,  or  costal  process,  is  large  and  segmented 
off,  forming  a  cervical  rib. 

Surgical  Anatomy. — Occasionally  the  coalescence  of  the  laminse  is  not  completed,  and  con- 
sequently a  cleft  is  left  in  the  arches  of  the  vertebrae,  through  which  a  protrusion  of  the  spinal 
membranes  (dura  mater  and  arachnoid),  and  sometimes  of  the  spinal  cord  itself,  takes  place, 
constituting  the  disease  known  SLSspina  bifida.  This  disease  is  most  common  in  the  lumbo-sacral 
region,  on  account  of  the  fact,  previously  stated,  that  the  closure  of  the  arches  takes  place 
gradually  from  above  downward  ;  but  it  may  occur  in  the  dorsal  or  cervical  region,  or  the  arches 
throughout  the  whole  length  of  the  canal  may  remain  unapproximated.  In  some  rare  cases,  in 
consequence  of  the  non-coalescence  of  the  two  primary  centres  from  which  the  body  is  formed, 
a  similar  condition  may  occur  in  front  of  the  canal,  the  bodies  of  the  vertebrae  being  found  cleft 
and  the  tumor  projecting  into  the  thorax,  abdomen,  or  pelvis,  between  the  lateral  halves  of  the 
bodies  affected. 

The  construction  of  the  spinal  column  of  a  number  of  pieces,  securely  connected  together 
and  enjoying  only  a  slight  degree  of  movement  between  any  two  individual  pieces,  though  per- 


THE  SKULL.  163 

mitting  of  a  very  considerable  range  of  movement  as  a  whole,  allows  a  sufficient  degree  of 
mobility  without  any  material  diminution  of  strength.  The  many  joints  of  which  the  spine  is 
composed,  together  with  the  very  varied  movements  to  which  it  is  subjected,  render  it  liable  to 
sprains ;  but  so  closely  are  the  individual  vertebrae  articulated  that  these  sprains  are  rarely  or 
ever  severe,  and  any  amount  of  violence  sufficiently  great  to  produce  tearing  of  the  ligaments 
would  tend  rather  to  cause  a  dislocation  or  fracture.  The  further  safety  of  the  column  and  its 
less  liability  to  injury  is  provided  for  by  its  disposition  in  curves,  instead  of  in  one  straight  line. 
Fur  it  is  an  elastic  column,  and  must  first  bend  before  it  breaks :  under  these  circumstances, 
being  made  up  of  three  curves,  it  represents  three  columns,  and  greater  force  is  required  to  pro- 
'lure  bending  of  a  short  column  than  of  a  longer  one  that  is  equal  to  it  in  breadth  and  material. 
Again,  the  safety  of  the  column  is  provided  for  by  the  interposition  of  the  intervertebral  disk 
bet  ween  the  bodies  of  the  vertebrae,  which  act  as  admirable  buffers  in  counteracting  the  effects  of 
violent  jars  or  shocks.  Fracture-dislocation  of  the  spine  may  be  caused  by  direct  or  indirect 
violence,  or  by  a  combination  of  the  two,  as  when  a  person,  falling  from  a  height,  strikes  against 
some  prominence  and  is  doubled  over  it.  The  fractures  from  indirect  violence  are  the  more  com- 
mon, and  here  the  bodies  of  the  vertebrae  are  compressed,  whilst  the  arches  are  torn  asunder  ; 
whilst  in  fractures  from  direct  violence  the  arches  are  compressed  and  the  bodies  of  the  vertebrae 
M-parated  from  each  other.  It  will  therefore  be  seen  that  in  both  classes  of  injury  the  spinal 
marrow  is  the  part  least  likely  to  be  injured,  and  may  escape  damage  even  where  there  has  been 
considerable  lesion  of  the  bony  framework.  For.  as  Mr.  Jacobson  states,  "being  lodged  in  the 
centre  of  the  column,  it  occupies  neutral  ground  in  respect  to  forces  which  might  cause  fracture. 
For  it  is  a  law  in  mechanics  that  when  a  beam,  as  of  timber,  is  exposed  to  breakage  and  the 
force  does  not  exceed  the  limits  of  the  strength  of  the  material,  one  division  resists  compression, 
another  laceration  of  the  particles,  while  the  third,  between  the  two.  is  in  a  negative  condition."1 
Applying  this  principle  to  the  spine,  it  will  be  seen  that,  whether  the  fracture-dislocation  be  pro- 
duced by  direct  violence  or  indirect,  one  segment,  either  the  anterior  or  posterior,  will  be  exposed 
to  compression,  the  other  to  laceration,  and  the  intermediate  part,  where  the  cord  is  situated, 
will  be  in  a  neutral  state.  When  a  fracture-dislocation  is  produced  by  indirect  violence  the  dis- 
placement is  almost  always  the  same,  the  upper  segment  being  driven  forward  on  the  lower,  so 
that  the  cord  is  compressed  between  the  body  of  the  vertebra  below  and  the  arch  of  the  vertebra 
above. 

The  parts  of  the  spine  most  liable  to  be  injured  are  (1)  the  dorsi-lumbar  region,  for  this  part 
is  near  the  middle  of  the  column,  and  there  is  therefore  a  greater  amount  of  leverage,  and  more- 
over the  portion  above  is  comparatively  fixed,  and  the  vertebrae  which  form  it,  though  much 
smaller,  have  nevertheless  to  bear  almost  as  great  a  weight  as  those  below ;  (2)  the  cervico-dorsal 
region,  because  here  the  flexible  cervical  portion  of  the  spine  joins  the  more  fixed  dorsal  region ; 
an  1  (3|  the  alto-axoid  region,  because  it  enjoys  an  extensive  range  of  movement,  and,  being 
near  the  skull,  is  influenced  by  violence  applied  to  the  head.  In  fracture-dislocation  it  has  been 
proposed  to  trephine  the  spine  and  remove  portions  of  the  laminae  and  spinous  processes.  The 
operation  can  only  be  of  use  when  the  paralysis  is  due  to  the  pressure  of  bone  or  the  effusion  of 
blood,  and  not  to  cases,  which  are  by  far  the  most  common,  where  the  cord  is  crushed  to  a  pulp. 
And  even  in  those  cases  where  the  cord  is  compressed  by  bone  the  portion  of  displaced  bone 
which  presses  on  the  cord  is  generally  the  body  of  the  vertebra  below,  and  is  therefore  inaccess- 
ible to  operation.  The  operative  proceeding  is  one  of  great  severity,  involving  an  extensive  and 
deep  wound  and  great  risk  of  septic  meningitis,  and.  as  the  advantages  to  be  derived  from  it  are 
exceedingly  problematical  and  confined  to  a  very  few  cases,  it  is  not  often  resorted  to.  Trephin- 
ine  has  also  been  resorted  to  in  some  cases  of  paraplegia  due  to  Pott  s  disease  of  the  spine. 
Here  the  paralysis  is  due  to  the  pressure  of  inflammatory  products,  and  where  this  is  new  scar- 
tissue,  formed  by  the  organization  of  granulation  tissue,  its  removal  has  been  attended  with  a 
very  considerable  amount  of  success. 

THE   SKULL. 

The  Skull,  or  superior  expansion  of  the  vertebral  column,  has  been  described 
as  if  composed  of  four  vertebrae,  the  elementary  parts  of  which  are  specially 
modified  in  form  and  size,  and  almost  immovably  connected,  for  the  reception  of 
the  brain  and  special  organs  of  the  senses.  These  vertebrae  are  the  occipital, 
parietal,  frontal,  and  nasal.  Descriptive  anatomists,  however,  divide  the  skull 
into  two  parts,  the  Cranium  and  the  Face.  The  Cranium  (x/>rfvoc,  a  helmet)  is 
composed  of  eight  bones — viz.  the  occipital,  two  parietal,  frontal,  two  temporal, 
KpJn'H'.>(<l.  and  ethmoid.  The  Face  is  composed  of  fourteen  bones — viz.  the  two 
nasal,  two  superior  maxillary,  two  lachrymal,  two  malar,  two  palate,  two  inferior 
turbinated,  corner,  and  inferior  maxillary.  The  ossiculi  audifrus,  the  teeth,  and 
Wonnian  bones  are  not  included  in  this  enumeration. 

1  Holmes's  System  of  Surgery,  vol.  i.  p.  529,  1883. 


164 


THE  SKELETON. 


Skull,  22  bones  < 


Cranium,  8  bones . 


Occipital. 

Two  Parietal. 

Frontal. 

Two  Temporal. 

Sphenoid. 

Ethmoid. 

Two  Nasal. 

Two  Superior  Maxillary. 

Two  Lachrymal. 

Two  Malar. 

Two  Palate. 

Two  Inferior  Turbinated. 

Vomer. 

Inferior  Maxillary. 


THE  CRANIUM. 
The  Occipital  Bone. 
The  Occipital  Bone  (ob,  caput,  against  the  head)  is  situated  at  the  back  part 


Face,  14  bones  .   .  < 


SUPERIOR 
CONSTRICTOR 

>/  Pharynx. 


FIG.  130.— Occipital  bone.    Outer  surface. 

and  base  of  the  cranium,  is  trapezoid  in  form  (Fig.  130),  curved  upon  itself,  and 
presents  for  examination  two  surfaces,  four  borders,  and  four  angles. 

The  external  surface  is  convex.  Midway  between  the  summit  of  the  bone  and 
the  posterior  margin  of  the  foramen  magnum  is  a  prominent  tubercle,  the  external 
occipital  protuberance,  for  the  attachment  of  the  Ligamentum  nuchse ;  and, 
descending  from  it  as  far  as  the  foramen,  a  vertical  ridge,  the  external  occipital 
crest.  This  tubercle  and  crest  vary  in  prominence  in  different  skulls.  Passing 
outward  from  the  occipital  protuberance  is  a  semicircular  ridge  on  each  side,  the 


THE   CRAXIl'M.  165 

•//-,/•  <•(/,•>;  <l  line.  Above  this  line  there  is  often  a  second  less  distinctly  marked 
ridge,  called  the  highest  curved  line  (Unea  supremo] ;  to  it  the  epicranial  aponeurosis 
is  attached.  The  bone  between  these  two  lines  is  smoother  and  denser  than  the 
rest  of  the  surface.  Running  parallel  with  these  from  the  middle  of  the  crest  is 
another  semicircular  ridge  on  each  side,  the  inferior  curved  lines.  The  surface  of 
the  bone  above  the  superior  curved  lines  is  rough  and  porous,  and  in  the  recent 
state  is  covered  by  the  Occipito-frontalis  muscle,  while  the  ridges,  as  well  as  the 
surface  of  the  bone  between  them,  serve  for  the  attachment  of  numerous  muscles. 
The  superior  curved  line  gives  attachment  internally  to  the  Trapezius.  externally 
to  the  muscular  origin  of  the  Occipito-frontalis,  and  to  the  Sterno-cleido-mastoi'd 
to  the  extent  shown  in  Fig.  130 ;  the  depressions  between  the  curved  lines  to  the 
Complexus  internally,  the  Splenius  capitis  and  Obliquus  capitis  superior  exter- 
nally. The  inferior  curved  line  and  the  depressions  below  it  afford  insertion  to 
the  Rectus  capitis  posticus,  major  and  minor. 

The  foramen  magnum  is  a  large,  oval  aperture,  its  long  diameter  extending  from 
before  backward.  It  transmits  the  medulla  oblongata  and  its  membranes,  the 
spinal  accessory  nerves,  the  vertebral  arteries,  the  anterior  and  posterior  spinal 
arteries,  and  the  occipito-axial  ligaments.  Its  back  part  is  wide  for  the  transmis- 
sion of  the  medulla,  and  the  corresponding  margin  rough  for  the  attachment  of  the 
dura  mater  enclosing  it ;  the  fore  part  is  narrower,  being  encroached  upon  by  the 
condyles:  it  has  projecting  toward  it.  from  below,  the  odontoid  process,  and  its 
margins  are  smooth  and  bevelled  internally  to  support  the  medulla  oblongata.  On 
each  side  of  the  foramen  magnum  are  the  condyles,  for  articulation  with  the  atlas ; 
they  are  convex,  oblong,  or  reniform  in  shape,  and  directed  downward  and  out- 
ward :  they  converge  in  front,  and  encroach  slightly  upon  the  anterior  segment  of 
the  foramen.  On  the  inner  border  of  each  condyle  is  a  rough  tubercle  for  the 
attachment  of  the  ligaments  (check}  which  connect  this  bone  with  the  odontoid 
process  of  the  axis ;  whilst  external  to  them  is  a  rough  tubercular  prominence, 
the  ?/v///.v, •,/•*.•  nv  jugular  process  (the  representative  of  the  transverse  process  of  a 
vertebra),  channelled  in  front  by  a  deep  notch,  which  forms  part  of  the  jugular 
foramen  or  foramen  lacerum  posterius.  The  under  surface  of  this  process  presents 
an  eminence  which  represents  the  paranuulotd  process  of  some  mammals.  The 
eminence  is  occasionally  large,  and  extends  as  IOAV  as  the  transverse  process  of  the 
atlas.  This  surface  affords  attachment  to  the  Rectus  capitis  lateralis  muscle  and 
to  the  lateral  occipito-atlantal  ligament ;  its  upper  or  cerebral  surface  presents  a 
deep  groove  which  lodges  part  of  the  lateral  sinus,  whilst  its  external  surface  is 
marked  by  a  quadrilateral  rough  facet,  covered  with  cartilage  in  the  fresh  state,  and 
articulating  with  a  similar  surface  on  the  petrous  portion  of  the  temporal  bone.  On 
the  outer  side  of  each  condyle,  near  its  fore  part,  is  a  foramen,  the  anterior  con~ 
'////"/'/  ;  it  is  directed  downward,  outward,  and  forward,  and  transmits  the  hypo- 

<il  nerve,  and  occasionally  a  meningeal  branch  of  the  ascending  pharvngeal 
artery.  This  foramen  is  sometimes  double.  Behind  each  condyle  is  a  fossa,1  some- 
times perforated  at  the  bottom  by  a  foramen,  the  posterior  condyloid,  for  the  trans- 
mission of  a  vein  to  the  lateral  sinus.  In  front  of  the  foramen  magnum  is  a  strong 
quadrilateral  plate  of  bone,  the  basilar  process,  wider  behind  than  in  front;  its 
under  surface,  which  is  rough,  presenting  in  the  median  line  a  tubercular  ridge, 
the  pharyngeal  ,«/>///«'.  for  the  attachment  of  the  tendinous  raphe  and  Superior 
constrictor  of  the  pharynx  :  and  on  each  side  of  it  rough  depressions  for  the 
attachment  of  the  Rectus  capitis  anticus.  major  and  minor. 

The  Internal  or  Cerebral  Surface  (Fig.  131)  is  deeply  concave.  The  posterior 
or  occipital  part  is  divided  by  a  crucial  ridge  into  four  fossae.  The  two  superior 

e  receive  the  occipital  lobes  of  the  cerebrum,  and  present  slight  eminences 
and  depressions  corresponding  to  their  convolutions.  The  two  inferior,  which 
receive  the  hemispheres  of  the  cerebellum,  are  larger  than  the  former,  and  com- 

1  This  fossa  presents  many  variations  in  size.  It  is  usually  shallow,  and  the  foramen  small ;  occa- 
sionally wanting  on  one  or  both  sides.  Sometimes  both  fossa  and  foramen  are  large,  but  confined  to 
one  side  only ;  more  rarely,  the  fossa  and  foramen  are  very  large  on  both  sides. 


166 


THE   SKELETON. 


paratively  smooth  ;  both  are  marked  by  slight  grooves  for  the  lodgment  of  arteries. 
At  the  point  of  meeting  of  the  four  divisions  of  the  crucial  ridge  is  an  eminence, 
the  internal  occipital  protuberance.  It  nearly  corresponds  to  that  on  the  outer 
surface,  and  is  perforated  by  one  or  more  large  vascular  foramina.  From  this 
eminence  the  superior  division  of  the  crucial  ridge  runs  upward  to  the  superior 
angle  of  the  bone  ;  it  presents  a  deep  groove  for  the  superior  longitudinal  sinus, 
the  margins  of  which  give  attachment  to  the  falx  cerebri.  The  inferior  division, 
the  internal  occipital  crest,  runs  to  the  posterior  margin  of  the  foramen  magnum, 


Superior  angle. 


Inferior  angle. 
FIG.  131.— Occipital  bone.    Inner  surface 

on  the  edge  of  which  it  becomes  gradually  lost ;  this  ridge,  which  is  bifurcated 
below,  serves  for  the  attachment  of  the  falx  cerebelli.  It  is  usually  marked  by  a 
single  groove,  which  commences  at  the  back  part  of  the  foramen  magnum  and 
lodges  the  occipital  sinus.  Occasionally  the  groove  is  double  where  two  sinuses 
exist.  The  transverse  grooves  pass  outward  to  the  lateral  angles ;  they  are  deeply 
channelled,  for  the  lodgment  of  the  lateral  sinuses,  their  prominent  margins  afford- 
ing attachment  to  the  tentorium  cerebelli.1  At  the  point  of  meeting  of  these 
grooves  is  a  depression,  the  torcular  Herophili?  placed  a  little  to  one  or  the  other 
side  of  the  internal  occipital  protuberance.  More  anteriorly  is  the  foramen  mag- 
num, and  on  each  side  of  it,  but  nearer  its  anterior  than  its  posterior  part,  the 

1  Usually  one  of  the  transverse  grooves  is  deeper  and  lm>;ider  than  the  other ;  occasionally,  both 
grooves  are  of  equal  depth  and  breadth,  or  both  equally  indistinct.  The  broader  of  the  two  transverse 
grooves  is  nearly  always  continuous  with  the  vertical  groove  for  the  superior  longitudinal  sinus. 

•    ?  The  columns  of  blood  coming  in  different  directions  were  supposed  to  be  pressed  together  at  this 
point  (torcular,  a  wine-press). 


THE    CRANIUM. 


167 


internal  openings  of  the  anterior  condyloid  foramina  ;  the  internal  openings  of  the 
posterior  condyloid  foramina  are  a  little  external  and  posterior  to  them,  protected 
by  a  small  arch  of  bone.  At  this  part  of  the  internal  surface  there  is  a  very  deep 
groove  in  which  the  posterior  condyloid  foramen,  when  it  exists,  has  its  termina- 
tion. This  groove  is  continuous,  in  the  complete  skull,  with  the  transverse  groove 
on  the  posterior  part  of  the  bone,  and  lodges  the  end  of  the  same  sinus,  the  lateral. 
In  front  of  the  foramen  magnum  is  the  basilar  process,  presenting  a  shallow 
depression,  the  basilar  groove,  which  slopes  from  behind,  upward  and  forward, 
and  supports  the  medulla  oblongata  and  part  of  the  pons  Varolii,  and  on  each  side 
of  the  basilar  process  is  a  narrow  channel,  which,  when  united  with  a  similar 
channel  on  the  petrous  portion  of  the  temporal  bone,  forms  a  groove  which  lodges 
the  inferior  petrosal  sinus. 

Angles. — The  xnnerior  angle  is  received  into  the  interval  between  the  posterior 
superior  angles  of  the  two  parietal  bones  :  it  corresponds  with  that  part  of  the 
skull  in  the  foetus  which  is  called  the  posterior  fontanelle.  The  inferior  angle  is 
represented  by  the  square-shaped  surface  of  the  basilar  process.  At  an  early 
period  of  life  a  layer  of  cartilage  separates  this  part  of  the  bone  from  the  sphenoid, 
but  in  the  adult  the  union  between  them  is  osseous.  The  lateral  angles  corre- 
spond to  the  outer  ends  of  the  transverse  grooves,  and  are  received  into  the  interval 
between  the  posterior  inferior  angles  of  the  parietal  and  the  mastoid  portion  of 
the  temporal. 

Borders. — The  superior  border  extends  on  each  side  from  the  superior  to  the 
lateral  angle,  is  deeply  serrated  for  articulation  with  the  parietal  bone,  and  forms, 
by  this  union,  the  lambdoid  suture.  The  inferior  border  extends  from  the  lateral 
to  the  inferior  angle  :  its  upper  half  is  rough,  and  articulates  with  the  mastoid  por- 
tion of  the  temporal,  forming  the  masto-occipital  suture ;  the  inferior  half  articu- 
lates with  the  petrous  portion  of  the  temporal,  forming  the  petro-occipital  suture ; 
these  two  portions  are  separated  from  one  another  by  the  jugular  process.  In 
front  of  this  process  is  a  deep  notch,  which,  with  a  similar  one  on  the  petrous  por- 
tion of  the  temporal,  forms  the  foramen  lacerum  posterius  or  jugular  foramen. 
This  notch  is  occasionally  subdivided  into  two  parts  by  a  small  process  of  bone, 
and  it  generally  presents  an  aperture  at  its  upper  part,  the  internal  opening  of 
the  posterior  condyloid  foramen. 

Structure. — The  occipital   bone  consists  of  two  compact   laminae,  called  the 
;ui*l  Inner  tables,  having  between  them  the  diploic  tissue;  this  bone  is  espe- 
cially thick  at  the  ridges,  protuberances,  condyles,  and  internal  part  of  the  basilar 
process  :  whilst  at  the  bottom  of  the  fossae,  especially  the  inferior,  it  is  thin,  semi- 
transparent,  and  destitute  of  diploe. 

Development.  (Fig.  132). — At  birth  the  bone  consists  of  four  distinct  parts  :  a 
tabular  or  expanded  portion,  which   lies  behind  the  foramen   magnum  ;   two  con- 
<liflar  parts,  which  form  the  sides  of  the  foramen ;  and  a  basilar  part,  which  lies  in 
front  of  the  foramen.      The  number 
of  nuclei  for   the  tabular  part  vary. 
As  a  rule,  there  are  four,  but  there 
may    be    only  one  (Blandin)    or    as 
many  as  eight  (Meckel).      They  ap- 
pear about  the  eighth  week  of  foetal 
life,  and  soon  unite  to  form  a  single 
piece,  which  is.  however,  fissured  in 
the  direction  indicated  in  the  plate. 
The  basilar  and  two  condyloid  por- 
tions    are    each    developed    from    a 

single  nucleus,  which  appears  a  lit-  ^^ 

tie  later.     The  upper  portion  of  the  »~    ^  1  for  basilar  portion. 

tabular   surface — that  is    to   say,  the      FIG.  132.— Development  of  occipital  bone.    By  seven  centres, 
portion  above  the  transverse  fissure 
— is  developed  from  membrane ;  the  rest  of  the  bone  is  developed  from  cartilage. 


4  for  occipital 


f°r 


I  I 

\  *- 

)  «* 

;j  •*  •* 


separate. 


168 


THE   SKELETON. 


At  about  the  fourth  year  the  tabular  and  the  two  condyloid  pieces  join,  and  about 
the  sixth  year  the  bone  consists  of  a  single  piece.  At  a  later  period,  between  the 
eighteenth  and  twenty-fifth  years,  the  occipital  and  sphenoid  become  united,  form- 
ing a  single  bone. 

Articulations. — With  six  bones :  two  parietal,  two  temporal,  sphenoid,  and 
atlas. 

Attachment  of  Muscles. — To  twelve  pairs  :  to  the  superior  curved  line  are 
attached  the  Occipito-frontalis,  Trapezius,  and  Sterno-cleido-mastoid.  To  the 
space  between  the  curved  lines,  the  Complexus,1  Splenius  capitis,  and  Obliquus 
capitis  superior ;  to  the  inferior  curved  line,  and  the  space  between  it  and  the 
foramen  magnum,  the  Rectus  capitis  posticus,  major  and  minor;  to  the  transverse 
process,  the  Rectus  capitis  lateralis  ;  and  to  the  basilar  process,  the  Rectus  capitis 
anticus,  major  and  minor,  and  Superior  constrictor  of  the  pharynx. 

The  Parietal  Bones. 

The  Parietal  Bones  (paries,  a  wall)  form,  by  their  union,  the  sides  and  roof  of 
the  skull.  Each  bone  is  of  an  irregular  quadrilateral  form,  and  presents  for 
examination  two  surfaces,  four  borders,  and  four  angles. 

Surfaces. — The  external  surf  ace  (Fig.  133)  is  convex,  smooth,  and  marked  about 
its  centre  by  an  eminence  called  the  parietal  eminence,  which  indicates  the  point 


FIG.  133.— Left  parietal  bone.    External  surface. 

where  ossification  commenced.  Crossing  the  middle  of  the  bone  in  an  arched 
direction  are  two  well-marked  curved  lines  or  ridges,  of  which  the  lower  is  the 
more  distinct  and  is  termed  the  temporal  ridge ;  it  marks  the  upper  attachment  of 
the  temporal  muscle  and  follows  a  semicircular  course  across  the  bone.  The  upper 
ridge  is  less  marked,  and  pursues  a  similar  course  across  the  bone,  but  about  two- 

1  To  these  the  Biventer  ''ervicis  should  be  added,  if  it  is  regarded  as  a  separate  muscle. 


THE   PARIETAL    BONES. 


169 


fifths  of  an  inch  above  the  temporal  ridge  ;  it  marks  the  attachment  of  the  temporal 
fascia.  Above  these  ridges  the  surface  of  the  bone  is  rough  and  porous,  and 
covered  by  the  aponeurosis  of  the  Occipito-frontalis ;  between  them  the  bone  is 
smoother  *and  more  polished  than  the  rest ;  below  them  the  bone  forms  part  of 
the  temporal  fossa,  and  affords  attachment  to  the  temporal  muscle.  At  the  back 
part  of  the  superior  border,  close  to  the  sagittal  suture,  is  a  small  foramen,  the 
parietal  foramen,  which  transmits  a  vein  to  the  superior  longitudinal  sinus,  and 
sometimes  a  small  branch  of  the  occipital  artery.  Its  existence  is  not  constant, 
and  its  size  varies  considerably. 

The  internal  surface  (Fig/ 134),  concave,  presents  eminences  and  depressions 
for  lodging  the  convolutions  of  the  cerebrum  and  numerous  furrows  for  the  rami- 
fications of  the  meningeal  arteries;  the  latter  run  upward  and  backward  from  the 


Posterior 

superior 

angle. 


Posterior 

inferior 

angle. 


nterior 
superior 
angle. 


Anterior 
J    inferior 
angle. 


FIG.  134.— Left  parietal  bone.    Internal  surface. 


anterior  inferior  angle  and  from  the  central  and  posterior  part  of  the  lower  border 
of  the  bone.  Along  the  upper  margin  is  part  of  a  shallow  groove,  which,  when 
joined  to  the  opposite  parietal,  forms  a  channel  for  the  superior  longitudinal 
sinus,  the  elevated  edges  of  which  afford  attachment  to  the  falx  cerebri.  Near 
the  groove  are  seen  several  depressions,  especially  in  the  skulls  of  old  persons ; 
they  lodge  the  Pacchionian  bodies.  The  internal  opening  of  the  parietal  foramen 
is  also  seen  when  that  aperture  exists. 

Borders. — The  superior,  the  longest  and  thickest,  is  dentated  to  articulate  with 
its  fellow  of  the  opposite  side,  forming  the  sagittal  suture.  The  inferior  is  divided 
into  three  parts :  of  these,  the  anterior  is  thin  and  pointed,  bevelled  at  the  expense 
of  the  outer  surface,  and  overlapped  by  the  tip  of  the  great  wing  of  the  sphenoid ; 
the  middle  portion  is  arched,  bevelled  at  the  expense  of  the  outer  surface,  and 
overlapped  by  the  squamous  portion  of  the  temporal ;  the  posterior  portion  is  thick 
and  serrated  for  articulation  with  the  mastoid  portion  of  the  temporal.  The 
anterior  border,  deeply  serrated,  is  bevelled  at  the  expense  of  the  outer  surface 
above  and  of  the  inner  below ;  it  articulates  witb^  the  frontal  bone,  forming  the 


170 


THE  SKELETON. 


coronal  suture.  The  posterior  border,  deeply  denticulated,  articulates  with  the 
occipital,  forming  the  lambdoid  suture. 

Angles. — The  anterior  superior  angle,  thin  and  pointed,  corresponds  with  that 
portion  of  the  skull  which  in  the  foetus  is  membranous  and  is  called  the  anterior 
fontanelle.  The  anterior  inferior  angle  is  thin  and  lengthened,  being  received  in 
the  interval  between  the  great  wing  of  the  sphenoid  and  the  frontal.  Its  inner 
surface  is  marked  by  a  deep  groove,  sometimes  a  canal,  for  the  anterior  branch  of 
the  middle  meningeal  artery.  The  posterior  superior  angle  corresponds  with  the 
junction  of  the  sagittal  and  lambdoid  sutures.  In  the  foetus  this  part  of  the  skull 
is  membranous,  and  is  called  the  posterior  fontanelle.  The  posterior  inferior  angle 
articulates  with  the  mastoid  portion  of  the  temporal  bone,  and  generally  presents 
on  its  inner  surface  a  broad,  shallow  groove  for  lodging  part  of  the  lateral  sinus. 

Development. — The  parietal  bone  is  formed  in  membrane,  being  developed  by 
one  centre,  which  corresponds  with  the  parietal  eminence,  and  makes  its  first 
appearance  about  the  seventh  or  eighth  week  of  foetal  life.  Ossification  gradually 
extends  from  the  centre  to  the  circumference  of  the  bone :  the  angles  are  conse- 
quently the  parts  last  formed,  and  it  is  in  their  situation  that  the  fontanelles  exist 
previous  to  the  completion  of  the  growth  of  the  bone. 

Articulations. — With  five  bones :  the  opposite  parietal,  the  occipital,  frontal, 
temporal,  and  sphenoid. 

Attachment  of  Muscles. — One  only,  the  Temporal. 

The  Frontal  Bone. 

The  Frontal  Bone  (from,  the  forehead)  resembles  a  cockle-shell  in  form,  and 
consists  of  two  portions — a  vertical  or  frontal  portion  situated  at  the  anterior  part 


Nasal 
FIG.  135. — Frontal  bone.    Outer  surface. 


of  the  cranium,  forming  the  forehead ;  and  a  horizontal  or  orbito-nasal  portion 
which  enters  into  the  formation  of  the  roof  of  the  orbits  and  nasal  fossae. 


THE  FRONTAL    BONE.  171 

Vertical  Portion. — External  Surface  (Fig.  135). — In  the  median  line,  traversing 
the  bone  from  the  upper  to  the  lower  part,  is  occasionally  seen  a  slightly-elevated 
ridge,  and  in  young  subjects  a  .suture,  which  represents  the  line  of  union  of  the  two 
lateral  halves  of  which  the  bone  consists  at  an  early  period  of  life;  in  the  adult 
this  suture  is  usually  obliterated  and  the  bone  forms  one  piece ;  traces  of  the 
obliterated  suture  are.  however,  generally  perceptible  at  the  lower  part.  On  either 
side  of  this  ridge,  a  little  below  the  centre  of  the  bone,  is  a  rounded  eminence,  the 
frontal  eminence.  These  eminences  vary  in  size  in  different  individuals,  and  are 
occasionally  unsymmetrical  in  the  same  subject.  They  are  especially  prominent 
in  cases  of  well-marked  cerebral  development.  The  whole  surface  of  the  bone 
above  this  part  is  smooth,  and  covered  by  the  aponeurosis  of  the  Occipito-frontalis 
muscle.  Below  the  frontal  eminence,  and  separated  from  it  by  a  slight  groove,  is 
the  superciliary  rilge,  broad  internally,  where  it  is  continuous  with  the  nasal 
eminence,  but  less  distinct  as  it  arches  outward.  These  ridges  are  caused  by  the 
projection  outward  of  the  frontal  sinuses,1  and  give  attachment  to  the  Orbicularis 
palpebrarum  and  Corrugator  supercilii.  Between  the  two  superciliary  ridges  is  a 
smooth  surface,  the  glabella  or  nasal  eminence.  Beneath  the  superciliary  ridge 
is  the  supraorbital  arch,  a  curved  and  prominent  margin,  which  forms  the  upper 
boundary  of  the  orbit,  and  separates  the  vertical  from  the  horizontal  portion  of  the 
bone.  The  outer  part  of  the  arch  is  sharp  and  prominent,  affording  to  the  eye,  in 
that  situation,  considerable  protection  from  injury;  the  inner  part  is  less  promi- 
nent. At  the  junction  of  the  internal  and  middle  third  of  this  arch  is  a  notch, 
sometimes  converted  into  foramen  by  a  bony  process,  and  called  the  supraorbital 
notch  or  foramen.  It  transmits  the  supraorbital  artery,  vein,  and  nerve.  A  small 
aperture  is  seen  in  the  upper  part  of  the  notch,  which  transmits  a  vein  from  the 
diploe  to  join  the  supraorbital  vein.  The  supraorbital  arch  terminates  externally 
in  the  external  angular  process  and  internally  in  the  internal  angular  process. 
The  external  angular  process  is  strong,  prominent,  and  articulates  with  the  malar 
bone ;  running  upward  and  backward  from  it  are  two  well-marked  lines,  which, 
commencing  together  from  the  external  angular  process,  soon  diverge  from  each 
other  and  run  in  a  curved  direction  across  the  bone.  The  lower  one.  the  temporal 
ridg>-.  gives  attachment  to  the  Temporal  muscle,  the  upper  one  to  the  temporal 
fascia.  Beneath  them  is  a  slight  concavity  that  forms  the  anterior  part  of  the 
temporal  fossa  and  gives  origin  to  the  Temporal  muscle.  The  internal  angular 
processes  are  less  marked  than  the  external,  and  articulate  with  the  lachrymal 
bones.  Between  the  internal  angular  processes  is  a  rough,  uneven  interval,  the 
nnx'il  notch,  which  articulates  in  the  middle  line  with  the  nasal  bone,  and  on  either 
side  with  the  nasal  process  of  the  superior  maxillary  bone.  From  the  concavity 
of  this  notch  projects  a  process,  the  nasal  process,  which  extends  beneath  the  nasal 
bones  and  nasal  processes  of  the  superior  maxillary  bones  and  supports  the  bridge  of 
the  nose.  On  the  under  surface  of  this  is  a  long  pointed  process,  the  nasal  spine,  and 
on  either  side  a  small  grooved  surface  enters  into  the  formation  of  the  roof  of  the 
nasal  fossa.  The  nasal  spine  forms  part  of  the  septum  of  the  nose,  articulating  in 
front  with  the  nasal  bones  and  behind  with  the  perpendicular  plate  of  the  ethmoid. 
Internal  Surface  (Fig.  136). — Along  the  middle  line  is  a  vertical  groove,  the 
edges  of  which  unite  below  to  form  a  ridge,  the  frontal  crest;  the  groove  lodges 
the  superior  longitudinal  sinus,  whilst  its  margins  afford  attachment  to  the  falx 
cerebri.  The  crest  terminates  below  at  a  small  notch  which  is  converted  into  a 
foramen  by  articulation  with  the  ethmoid.  It  is  called  the  foramen  ccecum,  and 
varies  in  size  in  different  subjects :  it  is  sometimes  partially  or  completely 
impervious,  lodges  a  process  of  the  falx  cerebri,  and  when  open  transmits  a  vein 

1  Some  confusion  is  occasioned  to  students  commencing  the  study  of  anatomv  by  the  name 
"  sinuses "  having  been  given  to  two  perfectly  different  kinds  of  spaces  connected  with  the  skull. 
It  may  be  as  well,  therefore,  to  state  here,  at  the  outset,  that  the  "sinuses"  in  the  interior  of  the 
cranium  which  produce  the  grooves  on  the  inner  surface  of  the  bones  are  venous  channels  along 
which  the  blood  runs  in  its  passage  back  from  the  brain,  while  the  "sinuses"  external  to  the  cranial 
cavity  the  frontal,  sphenoidal,  ethmoidal,  and  maxillary )  are  hollow  spaces  in  the  bones  themselves 
which  communicate  with  the  nostrils,  and  contain  air. 


172 


THE   SKELETON. 


from  the  lining  membrane  of  the  nose  to  the  superior  longitudinal  sinus.  On 
either  side  of  the  groove  the  bone  is  deeply  concave,  presenting  eminences  and 
depressions  for  the  convolutions  of  the  brain,  and  numerous  small  furrows  for 
lodging  the  ramifications  of  the  anterior  meningeal  arteries.  Several  small, 
irregular  fossae  are  also  seen  on  either  side  of  the  groove,  for  the  reception  of  the 
Pacchionian  bodies. 

Horizontal  Portion. — External  Surface. — This  portion  of  the  bone  consists  of 
two  thin  plates,  which  form  the  vault  of  the  orbit,  separated  from  one  another  by 
the  ethmoidal  notch.  Each  orbital  vault  consists  of  a  smooth,  concave,  triangular 
plate  of  bone,  marked  at  its  anterior  and  external  part  (immediately  beneath  the 


With  superior  maxillary^ 

With  nasal. 
With  perpendicular  plate  of  ethmoid. 

FIG.  136.— Frontal  bone. 


Frontal  sinus. 


\Under  surf  ace  of  nasal  process, 
forming  part  of  roof  of  nose. 

Inner  surface. 


external  angular  process)  by  a  shallow  depression,  the  lachrymal  fossa,  for  lodging 
the  lachrymal  gland ;  and  at  its  anterior  and  internal  part  by  a  depression  (some- 
times a  small  tubercle)  for  the  attachment  of  the  cartilaginous  pulley  of  the 
Superior  oblique  muscle  of  the  eye.  The  ethmoidal  notch  separates  the  two  orbital 
plates ;  it  is  quadrilateral,  and  filled  up,  when  the  bones  are  united,  by  the 
cribriform  plate  of  the  ethmoid.  The  margins  of  this  notch  present  several  half- 
cells,  which,  when  united  with  corresponding  half-cells  on  the  upper  surface  of  the 
ethmoid,  complete  the  ethmoidal  cells ;  two  grooves  are  also  seen  crossing  these 
edges  transversely ;  they  are  converted  into  canals  by  articulation  with  the  ethmoid, 
and  are  called  the  anterior  and  posterior  ethmoidal  canals  :  they  open  on  the  inner 
wall  of  the  orbit.  The  anterior  one  transmits  the  nasal  nerve  and  anterior 
ethmoidal  vessels,  the  posterior  one  the  posterior  ethmoidal  vessels.  In  front  of 
the  ethmoidal  notch,  on  either  side  of  the  nasal  spine,  are  the  openings  of  the 
frontal  sinuses.  These  are  two  irregular  cavities,  which  extend  upward  and 
outward,  a  variable  distance,  between  the  two  tables  of  the  skull,  and  are 
separated  from  one  another  by  a  thin,  bony  septum.  They  give  rise  to  the 


THE    TEMPORAL    BOXES. 


173 


prominences  above  the  supraorbital  arches  called  the  superciliary  ridges.  In  the 
child  they  are  generally  absent,  and  they  become  gradually  developed  as  age 
advances.  These  cavities  vary  in  size  in  different  persons,  are  larger  in  men  than 
in  women,  and  are  frequently  of  unequal  size  on  the  two  sides,  the  right  being 
commonly  the  larger.  They  are  subdivided  by  a  bony  lamina,  which  is  often  dis- 
placed to  one  side.  They  are  lined  by  mucous  membrane,  and  communicate  with 
the  nose  by  the  infundibulum,  and  occasionally  with  each  other  by  apertures  in 
their  septum. 

The  internal  surface  of  the  horizontal  portion  presents  the  convex  upper 
surfaces  of  the  orbital  plates,  separated  from  each  other  in  the  middle  line  by  the 
ethmoidal  notch,  and  marked  by  eminences  and  depressions  for  the  convolutions  of 
the  frontal  lobes  of  the  brain. 

Borders. — The  border  of  the  vertical  portion  is  thick,  strongly  serrated,  bevelled 
at  the  expense  of  the  internal  table  above,  where  it  rests  upon  the  parietal  bones, 
and  at  the  expense  of  the  external  table  at  each  side,  where  it  receives  the  lateral 
pressure  of  those  bones ;  this  border  is  continued  below  into  a  triangular  rough 
surface  which  articulates  with  the  great  wing  of  the  sphenoid.  The  border  of  the 
horizontal  portion  is  thin,  serrated,  and  articulates  with  the  lesser  wing  of  the 
sphenoid. 

Structure. — The  vertical  portion  and  external  angular  processes  are  very  thick, 
consisting  of  diploic  tissue  contained  between  two  compact  laminae.  The  hori- 
zontal portion  is  thin,  translucent,  and  composed  entirely  of  compact  tissue ;  hence 
the  facility  with  which  instruments  can  penetrate  the  cranium  through  this  part  of 
the  orbit. 

Development  (Fig.  137). — The  frontal  bone  is  formed  in  membrane,  being  devel- 
oped by  two  centres,  one  for  each  lateral  half,  which  make  their  appearance  about 
the  seventh  or  eighth  week,  above  the  orbital  arches.  From  this  point  ossification 
extends,  in  a  radiating  manner,  upward  into  the  forehead  and  backward  over  the 
orbit.  At  birth  the  bone  consists  of  two  pieces,  which  afterward  become  united, 
along  the  middle  line,  by  a  suture  which  runs  from  the  vertex  to  the  root  of  the 
nose.  This  suture  usually  becomes  obliterated  within  a  fe\v  years  after  birth  ;  but 
it  occasionally  remains  throughout  life.  Occasionally  secondary  centres  of  ossifica- 
tion appear  for  the  nasal  spine — one  on  either  side  at  the  internal  angular  process 
where  it  articulates  with  the  lachrymal 
bone ;  and  sometimes  there  is  one  on 
either  side  at  the  lower  end  of  the  coronal 
suture.  This  latter  centre  sometimes 
remains  ununited.  and  is  known  as  the 
pterion  ossicle,  or  it  may  join  with  the 
parietal,  sphenoid,  or  temporal  bone. 

Articulations. — With  twelve  bones : 
two  parietal,  the  sphenoid,  the  ethmoid, 
two  nasal,  two  superior  maxillary,  two 
lachrymal,  and  two  malar. 

Attachment  of  Muscles. — To  three 
pairs :  the  Corrugator  supercilii,  Orbicu- 
laris  palpebrarum,  and  Temporal,  on 
each  side. 


FIG.  137.— Frontal  bone  at  birth.    Developed  by 
two  lateral  halves. 


The  Temporal  Bones. 

The  Temporal  Bones  (tempus,  time)  are  situated  at  the  sides  and  base  of  the 
skull,  and  present  for  examination  a  squamous,  mastoid.  and  petrous  portion. 

The  squamous  portion  (squama,  a  scale),  the  anterior  and  upper  part  of  the 
bone,  is  scale-like  in  form,  and  thin  and  translucent  in  texture  (Fig.  138).  Its  outer 
surface  is  smooth,  convex,  and  grooved  at  its  back  part  for  the  deep  temporal 
arteries ;  it  affords  attachment  to  the  Temporal  muscle  and  forms  part  of  the 
temporal  fossa.  At  its  back  part  may  be  seen  a  curved  ridge — part  of  the  temporal 


174 


THE  SKELETON. 


ridge  ;  it  serves  for  the  attachment  of  the  temporal  fascia,  limits  the  origin  of  the 
Temporal  muscle,  and  marks  the  boundary  between  the  squamous  and  mastoid 


process. 
FIG.  138.— Left  temporal  bone.    Outer  surface. 

portions  of  the  bone.  Projecting  from  the  lower  part  of  the  squamous  portion  is  a 
long,  arched  process  of  bone,  the  zygoma  or  zygomatic  process.  This  process  is 
at  first  directed  outward,  its  two  surfaces  looking  upward  and  downward ;  it  then 
appears  as  if  twisted  upon  itself,  and  runs  forward,  its  surfaces  now  looking  in- 
ward and  outward.  The  superior  border  of  the  process  is  long,  thin,  and  sharp, 
and  serves  for  the  attachment  of  the  temporal  fascia.  The  inferior,  short,  thick, 
and  arched,  has  attached  to  it  some  fibres  of  the  Masseter  muscle.  Its  outer  surface 
is  convex  and  subcutaneous  ;  its  inner  is  concave,  and  also  affords  attachment  to  the 
Masseter.  The  extremity,  broad  and  deeply  serrated,  articulates  with  the  malar 
bone.  The  zygomatic  process  is  connected  to  the  temporal  bone  by  three  divisions, 
called  its  roots — an  anterior,  middle,  and  posterior.  The  anterior,  which  is  short, 
but  broad  and  strong,  is  directed  inward,  to  terminate  in  a  rounded  eminence,  the 
eminentia  articularis.  This  eminence  forms  the  front  boundary  of  the  glenoid 
fossa,  and  in  the  recent  state  is  covered  with  cartilage.  The  middle  root  (post- 
glenoid  process)  forms  the  posterior  boundary  of  the  mandibular  portion  of  the 
glenoid  fossa;  while  the  posterior  root,  which  is  strongly  marked,  runs  from  the 
upper  border  of  the  zygoma,  in  an  arched  direction,  upward  and  backward,  form- 
ing the  posterior  part  of  the  temporal  ridge  (supramastoid  crest).  At  the  junction 
of  the  anterior  root  with  the  zygoma  is  a  projection,  called  the  tubercle,  for  the 
attachment  of  the  external  lateral  ligament  of  the  lower  jaw  ;  and  between  the  ante- 
rior and  middle  roots  is  an  oval  depression,  forming  part  (mandibular)  of  the  glenoid 
fossa  (yAjJwp,  a  socket),  for  the  reception  of  the  condyle  of  the  lower  jaw7.  This  fossa 
is  bounded,  in  front,  by  the  eminentia  articularis  ;  behind,  by  the  tympanic  plate  and 
the  auditory  process ;  and  is  divided  into  two  parts  by  a  narrow7  slit,  the  Glaserian 
fissure.  The  anterior  or  mandibular  part,  formed  by  the  squamous  portion  of  the 
bone,  is  smooth,  covered  in  the  recent  state  with  cartilage,  and  articulates  with  the 
condyle  of  the  lower  jaw.  This  part  of  the  glenoid  fossa  is  separated  from  the  audi- 
tory process  by  the  post-glenoid  process,  the  representative  of  a  prominent  tubercle 


175 


which,  in  some  of  the  mammalia,  descends  behind  the  condyle  of  the  jaw.  and 
prevents  it  being  displaced  backward  during  mastication  (Humphry).  The  poste- 
rior part  of  the  glenoid  fossa,  which  lodges  a  portion  of  the  parotid  gland,  is 
formed  chiefly  by  the  tympanic  plate,  a  lamina  of  bone,  which  forms  the  anterior 
wall  of  the  tympanum  and  external  auditory  meatus.  This  plate  of  bone  termi- 
nates externally  in  the  auditory  process,  above  in  the  Glaserian  fissure,  and  below 
forms  a  sharp  edge,  the  vaginal  process,  which  gives  origin  to  some  of  the  fibres  of 
the  Tensor  palati  muscle.  The  Glaserian  fissure,  which  leads  into  the  tympanum, 
lodges  the  processus  gracilis  of  the  malleus,  and  transmits  the  tympanic  branch  of 
the  internal  maxillary  artery.  The  chorda  tympani  nerve  passes  through  a  sepa- 
rate canal,  parallel  to  the  Glaserian  fissure  (canal  of  Huguier),  on  the  outer  side  of 
the  Eustachian  tube,  in  the  retiring  angle  between  the  squamous  and  petrous  por- 
tions of  the  temporal  bone.1 

The  internal  surface  of  the  squamous  portion  (Fig.  139)  is  concave,  presents 


parietal 


Aquseductus  restibuli. 
Depression  for  dura  maier. 
Meat  its  auditorius  interims: 


Eminence  for  superior  semicircular  canal. 
Hiatt'S  Fallopii. 

Opening  for  smaller  petrosal  nercf. 
Depi  ession  for  Gasserian  ganglion. 
Bristle  passed  through  carotid  canal. 


FIG.  139. — Left  temporal  bone.    Inner  surface. 


numerous  eminences  and  depressions  for  the  convolutions  of  the  cerebrum,  and 
two  well-marked  grooves  for  the  branches  of  the  middle  meningeal  artery. 

Borders. — The  superior  border  is  thin,  bevelled  at  the  expense  of  the  internal 
surface,  so  as  to  overlap  the  lower  border  of  the  parietal  bone,  forming  the  squam- 
ous suture.  The  anterior  inferior  border  is  thick,  serrated,  and  bevelled,  alter- 
nately at  the  expense  of  the  inner  and  outer  surfaces,  for  articulation  with  the 
great  wing  of  the  sphenoid. 

The  Mastoid  Portion  (aa<rr6c,  a  nipple  or  teat)  is  situated  at  the  posterior  part  of 
the  bone  :  its  outer  surface  is  rough,  and  gives  attachment  to  the  Occipito-frontalis 
and  Retrahens  aurem  muscles.  It  is  perforated  by  numerous  foramina;  one  of 
these,  of  lai-ge  size,  situated  at  the  posterior  border  of  the  bone,  is  termed  the 
imixtoid  foramen  :  it  transmits  a  vein  to  the  lateral  sinus  and  a  small  artery  from 
the  occipital  to  supply  the  dura  mater.  The  position  and  size  of  this  foramen 

1  This  small  fissure  must  not  be  confounded  with  the  large  canal  which  lies  above  the  Eustachian 
tube  and  transmits  the  Tensor  tympani  muscle. 


176 


THE  SKELETON. 


are  very  variable.  It  is  not  always  present ;  sometimes  it  is  situated  in  the 
occipital  bone  or  in  the  suture  between  the  temporal  and  the  occipital.  The 
mastoid  portion  is  continued  below  into  a  conical  projection,  the  mastoid  process, 
the  size  and  form  of  which  vary  somewhat.  This  process  serves  for  the  attachment 
of  the  Sterno-mastoid,  Splenius  capitis,  and  Trachelo-mastoid  muscles.  On  the 
inner  side  of  the  mastoid  process  is  a  deep  groove,  the  digastric  fossa,  for  the 
attachment  of  the  Digastric  muscle ;  and,  running  parallel  with  it,  but  more  in- 
ternal, the  occipital  groove,  which  lodges  the  occipital  artery.  The  internal  surface 
of  the  mastoid  portion  presents  a  deep,  curved  groove,  the  fossa  sigmoidea,  which 
lodges  part  of  the  lateral  sinus ;  and  into  it  may  be  seen  opening  the  mastoid  fora- 
men. A  section  of  the  mastoid  process  shows  it  to  be  hollowed  out  into  a  number 
of  cellular  spaces,  communicating  with  each  other,  called  the  mastoid  cells  ;  they 
open  by  a  single  or  double  orifice  into  the  back  of  the  tympanum,  are  lined  by  a 
prolongation  of  its  lining  membrane,  and  probably  form  some  secondary  part  of 
the  organ  of  hearing.  The  spaces  at  the  upper  and  front  part  of  the  bone  near 
the  opening  into  the  tympanum  are  large  and  irregular,  and  contain  air.  They 
diminish  in  size  toward  the  lower  part  of  the  bone,  those  situated  at  the  apex  of 
the  mastoid  process  being  quite  small  and  usually  containing  marrow  (Fig.  140). 


TENSOR    TYMPANI. 

'roc.  cochleariformis. 
'Eustachian  tube. 


Carotid  canal. 


Carotid  canal. 
Fenestra  rotunda. 

Pyramid! 


Styloid  process. 
Aquxductus  Fallopii. 

'Harrow  cells. 


FIG.  140. — Section  through  the  petrous  and  mastoid  portions  of  the  temporal  bone,  showing  the  communi- 
cation of  the  cavity  of  the  tympanum  with  the  mastoid  cells. 

The  mastoid  cells,  like  the  other  sinuses  of  the  cranium,  are  not  developed 
until  after  puberty ;  hence  the  prominence  of  this  process  in  the  adult. 

In  consequence  of  the  communication  which  exists  between  the  tympanum  and  mastoid 
cells,  inflammation  of  the  lining  membrane  of  the  former  cavity  may  easily  travel  backward  to 
that  of  the  mastoid  cells,  leading  to  caries  and  necrosis  of  their  walls  and  the  risk  of  transfer- 
ence of  the  inflammation  to  the  lateral  sinus  or  encephalon. 

Borders. — The  superior  border  of  the  mastoid  portion  is  broad  and  rough,  its 
serrated  edge  sloping  outward,  for  articulation  with  the  posterior  inferior  angle  of 
the  parietal  bone.  The  posterior  border,  also  uneven  and  serrated,  articulates 
with  the  inferior  border  of  the  occipital  bone  between  its  lateral  angle  and  jugular 
process. 

The  Petrous  Portion  (TTS^OC,  a  stone),  so  named  from  its  extreme  density  and 
hardness,  is  a  pyramidal  process  of  bone  wedged  in  at  the  base  of  the  skull 
between  the  sphenoid  and  occipital  bones.  Its  direction  from  without  is  inward, 


THE   TEMPORAL   BONES.  177 

forward,  and  a  little  downward.  It  presents  for  examination  a  base,  an  apex, 
three  surfaces,  and  three  borders,  and  contains,  in  its  interior,  the  essential  parts 
of  the  organ  of  hearing.  The  base  is  applied  against  the  internal  surface  of  the 
squamous  and  mastoid  portions,  its  upper  half  being  concealed;  but  its  lower 
half  is  exposed  by  the  divergence  of  those  two  portions  of  the  bone,  which  brings 
into  view  the  oval  expanded  orifice  of  a  canal  leading  into  the  tympanum,  the 
wt'Ktus  auditorim  externus.  This  canal  is  situated  in  front  of  the  mastoid  pro- 

.  and  between  the  posterior  and  middle  roots  of  the  zygoma;  its  upper  mar- 
gin is  smooth  and  rounded,  but  the  greater  part  of  its  circumference  is  surrounded 
by  a  curved  plate  of  bone,  the  auditory  process,  the  free  margin  of  which  is  thick 
and  rough,  for  the  attachment  of  the  cartilage  of  the  external  ear. 

The  apex  of  the  petrous  portion,  rough  and  uneven,  is  received  into  the 
angular  interval  between  the  posterior  border  of  the  greater  wing  of  the  sphenoid 
and  the  basilar  process  of  the  occipital ;  it  presents  the  anterior  or  internal  orifice 
of  the  carotid  canal,  and  forms  the  posterior  and  external  boundary  of  the  foramen 
lacerum  medium. 

The  anterior  surface  of  the  petrous  portion  (Fig.  139)  forms  the  posterior  part 
of  the  middle  fossa  of  the  skull.  This  surface  is  continuous  with  the  squamous 
portion,  to  which  it  is  united  by  a  suture,  the  temporal  or petro-squamous  suture, 
the  remains  of  which  are  distinct  even  at  a  late  period  of  life ;  it  presents  six 
points  for  examination :  1,  an  eminence  near  the  centre,  which  indicates  the  sit- 
uation of  the  superior  semicircular  canal ;  2,  on  the  outer  side  of  this  eminence 
a  depression  indicating  the  position  of  the  tympanum ;  here  the  layer  of  bone 
which  separates  the  tympanum  from  the  cranial  cavity  is  extremely  thin,  and  is 
known  as  the  tegmen  tympani;  3,  a  shallow  groove,  sometimes  double,  leading 
outward  and  backward  to  an  oblique  opening,  the  hiatus  Fallopii,  for  the  passage 
of  the  petrosal  branch  of  the  Yidian  nerve  and  the  petrosal  branch  of  the  middle 
meningeal  artery ;  4.  a  smaller  opening,  occasionally  seen  external  to  the  latter, 
for  the  passage  of  the  smaller  petrosal  nerve ;  5,  near  the  apex  of  the  bone,  the 
termination  of  the  carotid  canal,  the  wall  of  which  in  this  situation  is  deficient  in 
front ;  6,  above  this  canal  a  shallow  depression  for  the  reception  of  the  Gasserian 
ganglion. 

The  posterior  surface  forms  the  front  part  of  the  posterior  fossa  of  the  skull, 
and  is  continuous  with  the  inner  surface  of  the  mastoid  portion  of  the  bone. 
It  presents  three  points  for  examination :  1.  About  its  centre,  a  large  orifice,  the 
niftttis  auditorius  internus.  whose  size  varies  considerably;  its  margins  are  smooth 
and  rounded,  and  it  leads  into  a  short  canal,  about  four  lines  in  length,  which 
runs  directly  outward  and  is  closed  by  a  vertical  plate,  the  lamina  cribrosa, 
which  is  divided  by  a  horizontal  crest,  the  crista  fal'ifonnis.  into  two  unequal 
portions;  the  lower  presenting  three  foramina  or  sets  of  foramina;  one,  just 
below  the  posterior  part  of  the  crest,  consisting  of  a  number  of  small  openings  for 
the  nerves  to  the  saccule ;  a  second,  below  and  posterior  to  this,  for  the  nerve  to 
the  posterior  semicircular  canal :  and  a  third,  in  front  and  below  the  first,  con- 
sisting of  a  number  of  small  openings  which  terminate  in  the  canalis  centralis 
cochleae  and  transmit  the  nerve  to  the  cochlea :  the  upper  portion,  that  above  the 
crista,  presents  behind  a  series  of  small  openings  for  the  passage  of  filaments  to 
the  vestibule  and  superior  and  external  semicircular  canal,  and,  in  front,  one 
large  opening,  the  commencement  of  the  aquaeductus  Fallopii,  for  the  passage  of 
the  facial  nerve.  2.  Behind  the  meatus  auditorius,  a  small  slit,  almost  hidden  by 
a  thin  plate  of  bone,  leading  to  a  canal,  the  aqnceductus  vestibuli,  which  transmits 
a  small  artery  and  vein  and  lodges  a  process  of  the  dura  mater.  3.  In  the  inter- 
val between  these  two  openings,  but  above  them,  an  angular  depression  which 
lodges  a  process  of  the  dura  mater,  and  transmits  a  small  vein  into  the  cancellous 
tissue  of  the  bone. 

The  inferior  or  basilar  surface  (Fig.  141)  is  rough  and  irregular,  and  forms  part 
of  the  base  of  the  skull.  Passing  from  the  apex  to  the  base,  this  surface  presents 
eleven  points  for  examination :  1,  a  rough  surface,  quadrilateral  in  form,  which 

12 


178 


THE  SKELETON. 


serves  partly  for  the  attachment  of  the  Levator  palati  and  Tensor  tympani 
muscles ;  2,  the  large,  circular  aperture  of  the  carotid  canal,  which  ascends  at 
first  vertically,  and  then,  making  a  bend,  runs  horizontally  forward  and  inward; 
it  transmits  the  internal  carotid  artery  and  the  carotid  plexus ;  3,  the  aquceductus 
cochleae,  a  small,  triangular  opening,  lying  on  the  inner  side  of  the  latter,  close  to 
the  posterior  border  of  the  petrous  portion ;  it  transmits  a  vein  from  the  cochlea 
which  joins  the  internal  jugular ;  4,  behind  these  openings  a  deep  depression,  the 
jugular  fossa,  which  varies  in  depth  and  size  in  different  skulls ;  it  lodges  the 
lateral  sinus,  and,  with  a  similar  depression  on  the  margin  of  the  jugular  process 
of  the  occipital  bone,  forms  the  foramen  lacerum  posterius  or  jugular  foramen ; 
5,  a  small  foramen  for  the  passage  of  Jacobson's  nerve  (the  tympanic  branch  of 
the  glosso-pharyngeal) :  this  foramen  is  seen  in  front  of  the  bony  ridge  dividing 


Canals  for  Eustachian  tube  and 

TENSOR  TYMPANI  MUSCLE. 


Bough  quadrilateral  surface. 

Opening  of  carotid  canal. 

Canal  for  Jacobson's  nerve. 

Aquseductus  cochlese. 

Canal  for  Arnold's  nerve. 

Jugular  fossa. 

Vaginal  process. 

Styloid  process. 
Stylo-mastoid  foramen 
Jugular  surface. 
Auricular  fissure. 


STYLO-PHARYNQEUS 


FIG.  141.— Petrous  portion.    Inferior  surface. 


the  carotid  canal  from  the  jugular  fossa ;  6,  a  small  foramen  on  the  outer  wall  of 
the  jugular  fossa,  for  the  entrance  of  the  auricular  branch  of  the  pneumogastric 
(Arnold's)  nerve;  7,  behind  the  jugular  fossa  a  smooth,  square-shaped  facet,  the 
jugular  surface  ;  it  is  covered  with  cartilage  in  the  recent  state,  and  articulates 
with  the  jugular  process  of  the  occipital  bone ;  8,  the  vaginal  process,  a  very 
broad,  sheath-like  plate  of  bone,  which  extends  backward  from  the  carotid  canal 
and  gives  attachment  to  part  of  the  Tensor  palati  muscle :  this  plate  divides 
behind  into  two  laminae,  the  outer  of  which  is  continuous  with  the  auditory  pro- 
cess, the  inner  with  the  jugular  process :  between  these  laminae  is  the  ninth  point 
for  examination,  the  styloid process,  a  long,  sharp  spine,  about  an  inch  in  length: 
it  is  directed  downward,  forward,  and  inward,  varies  in  size  and  shape,  and  some- 
times consists  of  several  pieces,  united  by  cartilage  ;  it  affords  attachment  to  three 
muscles,  the  Stylo-pharyngeus,  Stylo-hyoideus,  and  Stylo-glossus,  and  two  liga- 
ments, the  stylo-hyoid  and  stylo-maxillary  ;  10,  the  stylo-mastoid  foramen,  a  rather 
large  orifice,  placed  between  the  styloid  and  mastoid  processes  :  it  is  the  termina- 


THE    TEMPORAL    BOXES. 


179 


tion  of  the  aquseductus  Fallopii.  and  transmits  the  facial  nerve  and  stylo-mastoid 
artery  :   11.  the  auricular  ri**ure.  situated  between  the  auditory  and  mastoid  pro- 
s,  for  the  exit  of  the  auricular  branch  of  the  pneumogastric  nerve. 

Borders. — The  superior,  the  longest,  is  grooved  for  the  superior  petrosal  sinus, 
ami  has  attached  to  it  the  tentorium  cerebelli ;  at  its  inner  extremity  is  a  semilunar 
notch,  upon  which  the  fifth  nerve  lies.  The  posterior  border  is  intermediate  in 
length  between  the  superior  and  the  anterior.  Its  inner  half  is  marked  by  a  groove, 
which,  when  completed  by  its  articulation  with  the  occipital,  forms  the  channel 
for  the  inferior  petrosal  sinus.  Its  outer  half  presents  a  deep  excavation — the 
jnyular  T\>s*a — which,  with  a  similar  notch  on  the  occipital,  forms  the  foramen 
lacerum  posterius.  A  projecting  eminence  of  bone  occasionally  stands  out  from 
the  centre  of  the  notch,  and  divides  the  foramen  into  two  parts.  The  anterior 
border  i*  divided  into  two  parts — an  outer  joined  to  the  squamous  portion  by  a 
suture,  the  remains  of  which  are  distinct ;  an  inner,  free,  articulating  with  the 
spiuous  process  of  the  sphenoid.  At  the  angle  of  junction  of  the  petrous  and 
squamous  portions  are  seen  two  canals,  separated  from  one  another  by  a  thin  plate 
of  bone,  the  processus  cocJileariformis;  they  both  lead  into  the  tympanum,  the 
upper  one  transmitting  the  Tensor  tympani  muscle,  the  lower  one  the  Eustachian 
tube. 

Structure. — The  squamous  portion  is  like  that  of  the  other  cranial  bones ;  the 
mastoid  portion,  cellular ;  and  the  petrous  portion,  dense  and  hard. 

Development  (Fig.  142). — The  temporal  bone  is  developed  by  ten  centres, 
exclusive  of  those  for  the  internal  ear  and  the  ossicula — viz.  one  for  the  squamous 
portion  including  the  zygoma,  one  for  the  tympanic  plate,  six  for  the  petrous  and 
mastoid  parts,  and  two  for  the  styloid  process.  Just  before  the  close  of  foetal  life 
the  temporal  bone  consists  of  four  parts :  1.  The  squamo-zygomatic,  which  is  ossi- 
fied in  membrane  from  a  single  nucleus,  which  appears  at  its  lower  part  about  the 
second  month.  2.  The  tympanic  plate,  an  imperfect  ring,  which  encloses  the  tym- 
panic membrane.  This  is  also  ossified  from  a  single  centre,  which  appears  rather 
later  than  that  for  the  squamous  portion.  3.  The  petro-mastoid,  which  is  developed 
from  six  centres,  which  appear  about  the  fifth  or  sixth  month.  Four  of  these  are 
for  the  petrous  portion,  and  are  placed  around  the  labyrinth,  and  two  for  the  mas- 
toid (Vrolik).  According  to  Huxley,  the  centres  are  more  numerous,  and  are  dis- 
posed so  as  to  form  three  portions  :  (1)  including  most  of  the  labyrinth,  with  a  part 
of  the  petrous  and  mastoid.  he  has 
named  prootic ;  (2)  the  rest  of  the 
petrous,  the  opisthotic  ;  and  (3)  the 
remainder  of  the  mastoid,  the  epiotic. 
The  petro-mastoid  is  ossified  in  carti- 
lage. 4.  The  styloid  process  is  also 
ossified  in  cartilage  from  two  centres : 
one  for  the  base,  which  appears  before 
birth,  and  is  termed  the  tympano-hyal; 
the  other,  comprising  the  rest  of  the 
process,  is  named  the  stylo-hyal,  and 
does  not  appear  until  after  birth. 
Shortly  before  birth  the  tympanic 
plate  joins  with  the  squamous.  The 
petrous  and  mastoid  join  with  the 
squamous  during  the  first  year,  and 
the  tympano-hyal  portion  of  the  sty- 
loid process  about  the  same  time.  The 
stylo-hyal  does  not  join  the  rest  of  the 
bone  until  after  puberty,  and  in  some 
skulls  never  becomes  united.  The 
subsequent  changes  in  this  bone  are. 
that  the  tympanic  plate  extends  outward,  so 


If  or 
squamous 
portion, 
including 


1  for  tympanic 
plate. 


6  for  petrous 

and  mastoid 

portions. 


g  for  styloid  process. 

FIG.  142. — Development  of  the  temporal  bone, 
ten  centres. 


By 


as  to  form  the  meat  us  auditorius ; 


180 


THE  SKELETON. 


the  glenoid  fossa  becomes  deeper  ;  and  the  mastoid  part,  which  at  an  early  period 
of  life  is  quite  flat,  enlarges  from  the  development  of  the  cellular  cavities  in  its 
interior. 

Articulations. — With  five  bones — occipital,  parietal,  sphenoid,  inferior  maxil- 
lary, and  malar. 

Attachment  of  Muscles. — To  fifteen  :  to  the  squamous  portion,  the  Temporal ; 
to  the  zygoma,  the  Masseter ;  to  the  mastoid  portion,  the  Occipito-frontalis,  Sterno- 
mastoid,  Splenius  capitis,  Trachelo-mastoid,  Digastricus,  and  Retrahens  aurem ; 
to  the  styloid  process,  the  Stylo-pharyngeus,  Stylo-hyoideus,  and  Stylo-glossus ; 
and  to  the  petrous  portion,  the  Levator  palati,  Tensor  tympani,  Tensor  palati,  and 
Stapedius. 

The  Sphenoid  Bone. 

The  Sphenoid  Bone  (a</>qv,  a  wedge)  is  situated  at  the  anterior  part  of  the  base 
of  the  skull,  articulating  with  all  the  other  cranial  bones,  which  it  binds  firmly  and 
solidly  together.  In  its  form  it  somewhat  resembles  a  bat  with  its  wings  extended ; 
and  is  divided  into  a  central  portion  or  body,  two  greater  and  two  lesser  wings 
extending  outward  on  each  side  of  the  body,  and  two  processes — the  pterygoid 
processes — which  project  from  it  below. 

The  body  is  of  large  size,  cuboid  in  form,  and  hollowed  out  in  its  interior  so 
as  to  form  a  mere  shell  of  bone.  It  presents  for  examination  four  surfaces — a 
superior,  an  inferior,  an  anterior,  and  a  posterior. 

The  Superior  Surface  (Fig.  143). — In  front  is  seen  a  prominent  spine,  the 
ethmoidal  spine,  for  articulation  with  the  cribriform  plate  of  the  ethmoid ;  behind 


Middle  dinoid  process 
Posterior  dinoid  process. 


Ethmoidal 
spine. 


Foramen  opticum 
Foramen  lacerum  ante 
rius  or  Sphenoidal 
fissure. 

Foramen  rotundum. 

Foramen  Vesalii: 

Foramen  ovale. 

Foramen  spinosum. 


cs 

FIG.  143.— Sphenoid  bone.    Superior  surface 


this  a  smooth  surface  presenting,  in  the  median  line,  a  slight  longitudinal  eminence, 
with  a  depression  on  each  side  for  lodging  the  olfactory  tracts.  This  surface  is 
bounded  behind  by  a  ridge,  which  forms  the  anterior  border  of  a  narrow,  trans- 
verse groove,  the  optic  groove  ;  it  lodges  the  optic  commissure,  and  terminates  on 
either  side  in  the  optic  foramen,  for  the  passage  of  the  optic  nerve  and  oph- 
thalmic artery.  Behind  the  optic  groove  is  a  small  eminence,  olive-like  in  shape, 
the  olivary  process ;  and  still  more  posteriorly,  a  deep  depression,  the  pituitary 
fossa,  or  sella  turcica,  which  lodges  the  pituitary  body.  This  fossa  is  perforated 
by  numerous  foramina,  for  the  transmission  of  nutrient  vessels  into  the  substance 
of  the  bone.  It  is  bounded  in  front  by  two  small  eminences,  one  on  either  side, 
called  the  middle  dinoid  processes  (xXivq*  a  bed),  which  are  sometimes  connected 
by  a  spiculum  of  bone  to  the  anterior  clinoid  processes,  and  behind  by  a  square- 


THE  SPHENOID   BOXE. 


181 


shaped  plate  of  bone,  the  dor  sum  epliippii  or  dorsum  sella\  terminating  at  each 
superior  angle  in  a  tubercle,  the  posterior  clinoid  processes,  the  size  and  form  of 
which  vary  considerably  in  different  individuals.  These  processes  deepen  the 
pituitary  fo><a.  and  serve  for  the  attachment  of  prolongations  from  the  tentorium 
cerebelli.  The  sides  of  the  dorsum  ephippii  are  notched  for  the  passage  of  the 
sixth  pair  of  nerves,  and  below  present  a  sharp  process,  the  petrosal  process,  which 
is  joined  to  the  apex  of  the  petrous  portion  of  the  temporal  bone,  forming  the  inner 
boundary  of  the  middle  lacerated  foramen.  Behind  this  plate  the  bone  presents 
a  shallow  depression,  which  slopes  obliquely  backward,  and  is  continuous  with  the 
basilar  groove  of  the  occipital  bone  :  it  is  called  the  clivus.  and  supports  the  upper 
part  of  the  pons  Varolii.  On  either  side  of  the  body  is  a  broad  groove,  curved 
something  like  the  italic  letter  /;  it  lodges  the  internal  carotid  artery  and  the 
cavernous  sinus,  and  is  called  the  carotid  or  cavernous  groove.  Along  the  outer 
margin  of  this  groove,  at  its  posterior  part,  is  a  ridge  of  bone  in  the  angle  between 
the  body  and  greater  wing,  called  the  lingula.  The  posterior  surface,  quadrilateral 


Articulates  irith  perpendicular 
Ethmoidal  crest.         plate  of  ethmoi< 


Pterygoid  ridge 


Internal  pterygoid  pla 
Hamidar  process. 

FIG.  144.— Sphenoid  bone.    Anterior  surface.1 

in  form,  is  joined  to  the  basilar  process  of  the  occipital  bone.  During  childhood 
these  bones  are  separated  by  a  layer  of  cartilage  ;  but  in  after-life  (between  the 
eighteenth  and  twenty-fifth  years)  this  becomes  ossified,  ossification  commencing 
above  and  extending  downward :  and  the  two  bones  then  form  one  piece.  The 
anterior  surface  (Fig.  144)  presents,  in  the  middle  line,  a  vertical  ridge  of  bone,  the 
etlimoi-lal  crest,  which  articulates  in  front  with  the  perpendicular  plate  of  the 
ethmoid,  forming  part  of  the  septum  of  the  nose.  On  either  side  of  it  are  irregular 
openings  leading  into  the  sphenoidal  cells  or  sinuses.  These  are  two  large  irregular 
cavities  hollowed  out  of  the  interior  of  the  body  of  the  sphenoid  bone,  and  separated 
from  one  another  by  a  more  or  less  complete  perpendicular  bony  septum.  Their 
form  and  size  vary  considerably:  they  are  seldom  symmetrical,  and  are  often 
partially  subdivided  by  irregular  osseous  laminae.  Occasionally,  they  extend  into 
the  basilar  process  of  the  occipital  nearly  as  far  as  the  foramen  magnum.  The 
septum  is  seldom  quite  vertical,  being  commonly  bent  to  one  or  the  other  side. 
These  sinuses  do  nor  exist  in  children,  but  they  increase  in  size  as  age  advances. 
They  are  partially  closed,  in  front  and  below,  by  two  thin,  curved  plates  of  bone, 
the  sphenoidal  turbinated  bones,  leaving  a  round  opening  at  their  upper  parts,  by 
which  they  communicate  with  the  upper  and  back  part  of  the  nose,  and  occasionally 

1  In  this  figure,  both  the  anterior  and  inferior  surfaces  of  the  body  of  the  sphenoid  bone  are 
shown,  the  bone  being  held  with  the  pterygoid  processes  almost  horizontal. 


182  THE  SKELETON. 

with  the  posterior  ethmoidal  cells  or  sinuses.  The  lateral  margins  of  this  surface 
present  a  serrated  edge,  which  articulates  with  the  os  planum  of  the  ethmoid, 
completing  the  posterior  ethmoidal  cells ;  the  lower  margin,  also  rough  and 
serrated,  articulates  with  the  orbital  process  of  the  palate  bone,  and  the  upper 
margin  with  the  orbital  plate  of  the  frontal  bone.  The  inferior  surface  presents, 
in  the  middle  line,  a  triangular  spine,  the  rostrum,  which  is  continuous  with  the 
ethmoidal  crest  on  the  anterior  surface,  and  is  received  into  a  deep  fissure  between 
the  alge  of  the  vomer.  On  each  side  may  be  seen  a  projecting  lamina  of  bone, 
which  runs  horizontally  inward  from  near  the  base  of  the  pterygoid  process  : 
these  plates,  termed  the  vaginal  processes,  articulate  with  the  edges  of  the  vomer. 
Close  to  the  root  of  the  pterygoid  process  is  a  groove,  formed  into  a  complete  canal 
when  articulated  with  the  sphenoidal  process  of  the  palate  bone ;  it  is  called  the 
ptery go-palatine  canal,  and  transmits  the  pterygo-palatine  vessels  and  pharyngeal 
nerve. 

The  Greater  Wings  are  two  strong  processes  of  bone  which  arise  from  the 
sides  of  the  body,  and  are  curved  in  a  direction  upward,  outward,  and  backward, 
being  prolonged  behind  into  a  sharp-pointed  extremity,  the  spinous  process  of  the 
sphenoid.  Each  wing  presents  three  surfaces  and  a  circumference.  The  superior 
or  cerebral  surface  (Fig.  143)  forms  part  of  the  middle  fossa  of  the  skull ;  it  is 
deeply  concave,  and  presents  eminences  and  depressions  for  the  convolutions  of  the 
brain.  At  its  anterior  and  internal  part  is  seen  a  circular  aperture,  the  foramen 
rotundum,  for  the  transmission  of  the  second  division  of  the  fifth  nerve.  Behind 
and  external  to  this  is  a  large  oval  foramen,  the  foramen  ovale,  for  the  trans- 
mission of  the  third  division  of  the  fifth  nerve,  the  small  meningeal  artery,  and 
sometimes  the  small  petrosal  nerve.1  At  the  inner  side  of  the  foramen  ovale  a 
small  aperture  may  occasionally  be  seen  opposite  the  root  of  the  pterygoid  process ; 
it  is  the  foramen  Vesalii,  transmitting  a  small  vein.  Lastly,  in  the  posterior  angle, 
near  to  the  spine  of  the  sphenoid,  is  a  short  canal,  sometimes  double,  fae  foramen 
spinosum ;  it  transmits  the  middle  meningeal  artery.  The  external  surface 
(Fig.  144)  is  convex,  and  divided  by  a  transverse  ridge,  the  pterygoid  ridge,2  into 
two  portions.  The  superior  or  larger,  convex  from  above  downward,  concave 
from  before  backward,  enters  into  the  formation  of  the  temporal  fossa,  and  gives 
attachment  to  part  of  the  Temporal  muscle.  The  inferior  portion,  smaller  in  size 
and  concave,  enters  into  the  formation  of  the  zygomatic  fossa,  and  affords  attach- 
ment to  the  External  pterygoid  muscle.  It  presents,  at  its  posterior  part,  a 
sharp-pointed  eminence  of  bone,  the  spinous  process,  to  which  are  connected  the 
internal  lateral  ligament  of  the  lower  jaw  and  the  Tensor  palati  muscle.  The 
pterygoid  ridge,  dividing  the  temporal  and  zygomatic  portions,  gives  attachment  to 
part  of  the  External  pterygoid  muscle.  At  its  inner  and  anterior  extremity  is  a 
triangular  spine  of  bone  which  serves  to  increase  the  extent  of  origin  of  this 
muscle.  The  anterior  or  orbital  surface,  smooth  and  quadrilateral  in  form,  assists 
in  forming  the  outer  wall  of  the  orbit.  It  is  bounded  above  by  a  serrated  edge, 
for  articulation  with  the  frontal  bone ;  below,  by  a  rounded  border  which  enters 
into  the  formation  of  the  spheno-maxillary  fissure.  Internally,  it  presents  a  sharp 
border,  which  forms  the  lower  boundary  of  the  sphenoidal  fissure,  and  has  pro- 
jecting from  about  its  centre  a  little  tubercle  of  bone,  which  gives  origin  to  one 
head  of  the  External  rectus  muscle  of  the  eye;  and  at  its  upper  part  is  a  notch 
for  the  transmission  of  a  branch  of  the  lachrymal  artery ;  externally  it  presents  a 
serrated  margin  for  articulation  with  the  malar  bone.  One  or  two  small  foramina 
may  occasionally  be  seen  for  the  passage  of  branches  of  the  deep  temporal 
arteries ;  they  are  called  the  external  orbital  foramina.  Circumference  of  the 
great  wing  (Fig.  143) :  commencing  from  behind,  from  the  body  of  the  sphenoid 
to  the  spine,  the  outer  half  of  this  margin  is  serrated,  for  articulation  with  the 
petrous  portion  of  the  temporal  bone,  whilst  the  inner  half  forms  the  anterior 

1  The  small  petrosal  nerve  sometimes  passes  through  a  special  foramen  between  the  foramen 
ovale  and  foramen  spinosum. 

a  Sometimes  called  infratemporal  crest. 


THE  SPHEXOID    BONE. 


183 


boundary  of  the  foramen  lacerum  medium,  and  presents  the  posterior  aperture  of 
the  Vidian  canal  for  the  passage  of  the  Vidian  nerve  and  artery.  In  front  of  the 
spine  the  circumference  of  the  great  wing  presents  a  serrated  edge,  bevelled  at 
the  expense  of  the  inner  table  below  and  of  the  external  above,  which  articulates 
with  the  squamous  portion  of  the  temporal  bone.  At  the  tip  of  the  great  wing  a 
triangular  portion  is  seen,  bevelled  at  the  expense  of  the  internal  surface,  for 
articulation  with  the  anterior  inferior  angle  of  the  parietal  bone.  Internal  to  this 
is  a  broad  serrated  surface,  for  articulation  with  the  frontal  bone:  this  surface  is 
continuous  internally  with  the  sharp  inner  edge  of  the  orbital  plate,  which  assists 
in  the  formation  of  the  sphenoidal  fissure,  and  externally  with  the  serrated  margin 
for  articulation  with  the  malar  bone. 

The  Lesser  Wings  (processes  of  Ingrassias)  are  two  thin,  triangular  plates  of 
bone  which  arise  from  the  upper  and  lateral  parts  of  the  body  of  the  sphenoid, 
and.  projecting  transversely  outward,  terminate  in  a  sharp  point  (Fig.  143).  The 
superior  surface  of  each  is  smooth,  flat,  broader  internally  than  externally,  and 
supports  part  of  the  frontal  lobe  of  the  brain.  The  inferior  surface  forms  the 
back  part  of  the  roof  of  the  orbit  and  the  upper  boundary  of  the  sphenoidal  fissure 
or  foramen  lacerum  anterius.  This  fissure  is  of  a  triangular  form,  and  leads  from 
the  cavity  of  the  cranium  into  the  orbit :  it  is  bounded  internally  by  the  body  of 
the  sphenoid — above,  by  the  lesser  wing ;  below,  by  the  internal  margin  of  the 
orbital  surface  of  the  great  wing — and  is  converted  into  a  foramen  by  the  articu- 
lation of  this  bone  with  the  frontal.  It  transmits  the  third,  the  fourth,  the  three 
branches  of  the  ophthalmic  division  of  the  fifth,  the  sixth  nerve,  some  filaments 
from  the  cavernous  plexus  of  the  sympathetic,  the  orbital  branch  of  the  middle 
meningeal  artery,  a  recurrent  branch  from  the  lachrymal  artery  to  the  dura 
mater,  and  the  ophthalmic  vein.  The  anterior  border  of  the  lesser  wing  is  ser- 
rated for  articulation  with  the  frontal  bone ;  the  posterior,  smooth  and  rounded,  is 
received  into  the  fissure  of  Sylvius  of  the  brain.  The  inner  extremity  of  this 
border  forms  the  anterior  elinoid  process.  The  lesser  wing  is  connected  to  the 
side  of  the  body  by  two  roots,  the  upper  thin  and  flat,  the  lower  thicker,  obliquely 
directed,  and  presenting  on  its  outer  side,  near  its  junction  with  the  body,  a  small 
tubercle,  for  the  attachment  of  the  common  tendon  of  three  of  the  muscles  of  the 
eye.  Between  the  two  roots  is  the  optic  foramen,  for  the  transmission  of  the  optic 
nerve  and  ophthalmic  artery. 

The  Pterygoid  Processes  (-TSO'J;.  a  wing :  £?ooc,  likeness),  one  on  each  side, 
descend  perpendicularly  from  the  point  where  the  body  and  greater  wing  unite 
(Fig.  145).  Each  process  c  insists  of  an  external  and  an  internal  plate,  separated 
behind  by  an  intervening 
notch — the  pteryyvid  fossa  ; 
but  joined  partially  in  front. 
The  external  pterygoid  plate 
is  broad  and  thin,  turned  a 
little  outward,  and  forms 
part  of  the  inner  wall  of  the 
zyi.r'>matic  fossa.  It  gives 
attachment,  b  v  its  outer  sur- 
face, to  the  External  ptery- 
goid :  its  inner  surface  forms 
part  of  the  pterygoid  f"- 
and  gives  attachment  to  the 
Internal  pterygoid.  The  in- 
ternal ptt- rag-rid  plate  is  much 
narrower  and  longer,  curving 
outward,  at  its  extremity, 
into  a  hook-like  process  of  bone,  the  hamular  process,  around  which  turns  the 
tendon  of  the  Tensor  palati  muscle.  On  the  posterior  surface  of  the  base  of  this 
plate  is  a  small,  oval,  shallow  depression,  the  scaphoid  fossa,  from  which  arises 


FIG.  145. — Sphenoid  bone.    Posterior  surface. 


184 


THE  SKELETON. 


the  Tensor  palati,  and  above  which  is  seen  the  posterior  orifice  of  the  Vidian 
canal.  Below  and  to  the  inner  side  of  the  Vidian  canal,  on  the  posterior  surface 
of  the  base  of  this  plate,  is  a  little  prominence,  which  is  known  by  the  name  of 
the  pterygoid  tubercle.  The  outer  surface  of  this  plate  forms  part  of  the  pterygoid 
fossa,  the  inner  surface  forming  the  outer  boundary  of  the  posterior  aperture  of 
the  nares.  The  Superior  constrictor  of  the  pharynx  is  attached  to  its  posterior 
edge.  The  two  pterygoid  plates  are  separated  below  by  an  angular  interval,  in 
which  the  pterygoid  process,  or  tuberosity,  of  the  palate  bone  is  received.  The 
anterior  surface  of  the  pterygoid  process  is  very  broad  at  its  base,  and  forms  the 
posterior  wall  of  the  spheno-maxillary  fossa.  It  supports  Meckel's  ganglion.  It 
presents,  above,  the  anterior  orifice  of  the  Vidian  canal ;  and  below,  a  rough 
margin,  which  articulates  with  the  perpendicular  plate  of  the  palate  bone. 

The  Sphenoidal  Spongy  Bones  are  two  thin,  curved  plates  of  bones,  which  exist 
as  separate  pieces  until  puberty,  and  occasionally  are  not  joined  to  the  sphenoid 
in  the  adult.  They  are  situated  at  the  anterior  and  inferior  part  of  the  body  of 
the  sphenoid,  an  aperture  of  variable  size  being  left  in  their  anterior  wall,  through 
which  the  sphenoidal  sinuses  open  into  the  nasal  fossae.  They  are  irregular  in 
form  and  taper  to  a  point  behind,  being  broader  and  thinner  in  front.  Their 
upper  surface,  which  looks  toward  the  cavity  of  the  sinus,  is  concave ;  their  under 
surface  convex.  Each  bone  articulates  in  front  with  the  ethmoid,  externally  with 
the  palate ;  its  pointed  posterior  extremity  is  placed  above  the  vomer,  and  is 
received  between  the  root  of  the  pterygoid  process  on  the  outer  side  and  the 
rostrum  of  the  sphenoid  on  the  inner.1 

Development. — Up  to  about  the  eighth  month  of  foetal  life  the  sphenoid  bone 
consists  of  two  distinct  parts :  posterior  or  post-sphenoid  part,  which  comprises 
the  pituitary  fossa,  the  greater  wings,  and  the  pterygoid  processes ;  and  an 
anterior  or  pre-sphenoid  part,  to  which  the  anterior  part  of  the  body  and  lesser 
wings  belong.  It  is  developed  by  fourteen  centres :  eight  for  the  posterior 
sphenoid  division,  and  six  for  the  anterior  sphenoid.  The  eight  centres  for  the 
posterior  sphenoid  are — one  for  each  greater  wing  and  external  pterygoid  plate, 

one  for  each  internal  pterygoid  plate,  two 
for  the  posterior  part  of  the  body,  and  one 
on  each  side  for  the  lingula.  The  six  for 
the  anterior  sphenoid  are  one  for  each 
lesser  wing,  two  for  the  anterior  part  of 
the  body,  and  one  for  each  sphenoidal 
turbinated  bone. 

Post-sphenoid  Division. — The  first 
nuclei  to  appear  are  those  for  the  greater 
wings.  They  make  their  appearance 
between  the  foramen  rotundum  and  fora- 
men ovale  about  the  eighth  week,  and 
from  them  the  external  pterygoid  plates 
are  also  formed.  Soon  after,  the  nuclei 
for  the  posterior  part  of  the  body  appear, 
one  on  either  side  of  the  sella  turcica,  and 
become  blended  together  about  the  middle  of  foetal  life.  About  the  fourth  month 
the  remaining  four  centres  appear,  those  for  the  internal  pterygoid  plates  being 
ossified  in  membrane  and  becoming  joined  to  the  external  pterygoid  plate  about 
the  sixth  month.  The  centres  for  the  lingulse  speedily  become  joined  to  the  rest 
of  the  bone. 

Pre-sphenoid  Division. — The  first  nuclei  to  appear  are  those  for  the  lesser 
wings.  They  make  their  appearance  about  the  ninth  week,  at  the  outer  borders 
of  the  optic  foramina.  A  second  pair  of  nuclei  appear  on  the  inner  side  of  the 

1  A  small  portion  of  the  sphenoidal  turbinated  bone  sometimes  enters  into  the  formation  of  the 
inner  wall  of  the  orbit,  between  the  os  planum  of  the  ethmoid  in  front,  the  orbital  plate  of  the  palate 
below,  and  the  frontal  above. — Cleland,  Roy.  Soc.  Trans.,  1862. 


0-n.e  for  e.ccoTi.        'tv/o  -for- 
Zesser*  icrintf    jtctrf  of  J>ocLy 


FIG.  146. — Plan  of  the  development  of  sphenoid. 
By  fourteen  centres. 


THE  ETHMOID    BOXE. 


185 


foramina  shortly  after,  and.  becoming  united,  form  the  front  part  of  the  body  of 
the  bone.  The  remaining  two  centres  for  the  sphenoidal  turbinated  bones  do  not 
make  their  appearance  until  the  end  of  the  third  year. 

The  pre-sphenoid  is  united  to  the  body  of  the  post-sphenoid  about  the  eighth 
month,  so  that  at  birth  the  bone  consists  of  three  pieces — viz.  the  body  in  the 
centre,  and  on  each  side  the  great  wings  with  the  pterygoid  processes.  The  lesser 
wings  become  joined  to  the  body  at  about  the  time  of  birth.  At  the  first  year 
after  birth  the  greater  wings  and  body  are  united.  From  the  tenth  to  the  twelfth 
year  the  spongy  bones  are  partially  united  to  the  sphenoid,  their  junction  being 
complete  by  the  twentieth  year.  Lastly,  the  sphenoid  joins  the  occipital  from  the 
eighteenth  to  the  twenty-fifth  year. 

Articulations. — The  sphenoid  articulates  with  all  the  bones  of  the  cranium, 
and  five  of  the  face — the  two  malar,  two  palate,  and  vomer :  the  exact  extent  of 
articulation  with  each  bone  is  shown  in  the  accompanying  figures.1 

Attachment  of  Muscles. — To  eleven  pairs  :  the  Temporal.  External  pterygoid, 
Internal  pterygoid.  Superior  constrictor,  Tensor  palati,  Levator  palpebrae,  Ob- 
liqutis  oculi  superior,  Superior  rectus.  Internal  rectus,  Inferior  rectus,  External 
rectos. 

The  Ethmoid  Bone. 

The  Ethmoid  (-/fluo;.  a  sieve)  is  an  exceedingly  light,  spongy  bone,  of  a  cubical 
form,  situated  at  the  anterior  part  of  the  base  of  the  cranium,  between  the  two 
orbits,  at  the  root  of  the  nose,  and  contributing  to  form  each  of  these  cavities. 
It  consists  of  three  parts :  a  horizontal  plate,  which  forms  part  of  the  base  of 
the  cranium ;  a  perpendicular  plate,  which  forms  part  of  the  septum  nasi ;  and 
two  lateral  masses  of  cells. 

The  Horizontal  or  Cribriform  Plate  (Fig.  147)  forms  part  of  the  anterior  fossa 
of  the  base  of  the  skull,  and  is  received  into  the  ethmoid  notch  of  the  frontal 
bone  between  the  two  orbital 
plates.       Projecting     upward 
from  the  middle  line  of  this 
plate  is   a  thick,  smooth,  tri- 
angular process  of  bone,  the 

•  i.  y«UL  so  called  from  its 
resemblance  to  a  cock's  comb. 
Its  base  joins  the  cribriform 
plate.     Its    posterior   border, 
long,  thin.and  slightly  curved, 
serves  for  the  attachment  of 
the  falx  cerebri.     Its  anterior 
border,  short  and  thick,  articu- 
lates  with   the    frontal   bone, 
and  presents  two  small  project- 
ing alae.   which  are   received 
into  corresponding  depressions 
in  the  frontal,  completing  the 
foramen   caecum  behind.     Its 
sides    are    smooth  and    some- 
times bulging ;  in  which  case  it  is  found  to  enclose  a  small  sinus.2     On  each  side 
of  the  crista  galli  the  cribriform  plate  is  narrow  and  deeply  grooved,  to  support 
the  bulb  of  the  olfactory  tract,  and  perforated  by  foramina  for  the  passage  of  the 
olfactory  nerves.     These  foramina  are  arranged  in  three  rows :  the  innermost, 
which  are  the  largest  and  least  numerous,  are  lost  in  grooves  on  the  upper  part 
of  the  septum ;  the  foramina  of  the  outer  row  are  continued  on  to  the  surface  of 

1  It  also  sometimes  articulates  with  the  tuberosity  of  the  superior  maxilla  (see  p.  190). 

*  Sir  George  Humphry  state*  that  the  crista  galli  is  commonly  inclined  to  one  side,  usually  the 
opposite  to  that  toward  which  the  lower  part  of  the  perpendicular  plate  is  bent. — (The  Human  Skde- 

S,  p.  277.) 


With  inferior  turbinated  bone. 


FIG.  147.— Ethmoid  bone.    Outer  surface  of  right  lateral  mass 
(enlarged). 


186 


THE   SKELETON. 


the  upper  spongy  bone.  The  foramina  of  the  middle  row  are  the  smallest ;  they 
perforate  the  bone  and  transmit  nerves  to  the  roof  of  the  nose.  At  the  front  part 
of  the  cribriform  plate,  on  each  side  of  the  crista  galli,  is  a  small  fissure,  which 
transmits  the  nasal  branch  of  the  ophthalmic  nerve ;  and  at  its  posterior  part  a 
a  triangular  notch,  which  receives  the  ethmoidal  spine  of  the  sphenoid. 

The  Perpendicular  Plate  (Fig.  148)  is  a  thin,  flattened  lamella  of  bone,  which 
descends  from  the  under  surface  of  the  cribriform  plate,  and  assists  in  forming 
the  septum  of  the  nose.  It  is  much  thinner  in  the  middle  than  at  the  circum- 
ference, and  is  generally  deflected  a  little  to  one  side.  Its  anterior  border  articu- 
lates with  the  nasal  spine  of  the  frontal  bone  and  crest  of  the  nasal  bones.  Its 
posterior  border,  divided  into  two  parts,  articulates  by  its  upper  half  with  the  eth- 
moidal crest  of  the  sphenoid,  by  its  lower  half  with  the  vomer.  The  inferior 
border  serves  for  the  attachment  of  the  triangular  cartilage  of  the  nose.  On  each 
side  of  the  perpendicular  plate  numerous  grooves  and  canals  are  seen,  leading  from 
foramina  on  the  cribriform  plate  ;  they  lodge  filaments  of  the  olfactory  nerves. 

The  Lateral  Masses  of  the  ethmoid  consist  of  a  number  of  thin-walled  cellular 
cavities,  the  ethm,oidal  cells,  interposed  between  two  vertical  plates  of  bone,  the 
outer  one  of  which  forms  part  of  the  orbit,  and  the  inner  one  part  of  the  nasal  fossa 
of  the  corresponding  side.  In  the  disarticulated  bone  many  of  these  cells  appear 
to  be  broken  ;  but  when  the  bones  are  articulated  they  are  closed  in  at  every  part. 
The  upper  surface  of  each  lateral  mass  presents  a  number  of  apparently  half- 
broken  cellular  spaces ;  these  are  closed  in  when  articulated  by  the  edges  of  the 
ethmoidal  notch  of  the  frontal  bone.  Crossing  this  surface  are  two  grooves  on 
each  side,  converted  into  canals  by  articulation  with  the  frontal ;  they  are  the 
anterior  and  posterior  ethmoidal  foramina,  and  open  on  the  inner  wall  of  the 
orbit.  The  posterior  surface  also  presents  large,  irregular  cellular  cavities,  which 

are  closed  in  by  articula- 
tion with  the  sphenoidal 
tuibinated  bones  and  orbi- 
tal process  of  the  palate. 
The  cells  at  the  anterior 
surface  are  completed  by 
the  lachrymal  bone  and 
nasal  process  of  the  supe- 
rior maxillary,  and  those 
below  also  by  the  superior 
maxillary.  The  outer  sur- 
face of  each  lateral  mass 
is  formed  of  a  thin,  smooth, 
square  plate  of  bone,  called 
the  os  planum ;  it  forms 
part  of  the  inner  wall  of 
the  orbit,  and  articulates, 
above,  with  the  orbital 
plate  of  the  frontal ;  below, 
with  the  superior  maxil- 
lary ;  in  front,  with  the  lachrymal ;  and  behind,  with  the  sphenoid  and  orbital 
process  of  the  palate. 

From  the  inferior  part  of  each  lateral  mass,  immediately  beneath  the  os  planum, 
there  projects  downward  and  backward  an  irregular  lamina  of  bone,  called  the 
unciform  process,  from  its  hook-like  form :  it  serves  to  close  in  the  upper  part  of 
the  orifice  of  the  antrum,  and  articulates  with  the  ethmoidal  process  of  the  inferior 
turbinated  bone.  It  is  often  broken  in  disarticulating  the  bones. 

The  inner  surface  of  each  lateral  mass  forms  part  of  the  outer  wall  of  the  nasal 
fossa  of  the  corresponding  side.  It  is  formed  of  a  thin  lamella  of  bone,  which 
descends  from  the  under  surface  of  the  cribriform  plate,  and  terminates  below  in 
a  free,  convoluted  margin,  the  middle  turbinated  bone.  The  whole  of  this  sur- 


FIG.  148.— Perpendicular  plate  of  ethmoid    (enlarged),  shown  by 
removing  the  right  lateral  mass. 


THE   ETHMOID    BONE.  187 

face  is  rough  and  marked  above  by  numerous  grooves,  which  run  nearly  verti- 
cally downward  from  the  cribriform 
plate :  they  lodge  branches  of  the 
olfactory  nerve,  which  are  distributed 
on  the  mucous  membrane  covering  the 
bone.  The  back  part  of  this  surface 
is  subdivided  by  a  narrow  oblique 
fissure,  the  superior  meatus  of  the 
nose,  bounded  above  by  a  thin,  curved 
plate  of  bone,  the  superior  turbinated 
bone.  By  means  of  an  orifice  at  the 
upper  part  of  this  fissure  the  posterior 
ethmoidal  cells  open  into  the  nose. 
Below,  and  in  front  of  the  superior 
meatus,  is  seen  the  convex  surface  of  u*Sin£!'(3Kf.  ^  Inner  8UrfaCe  °f  right 
the  middle  turbinated  bone.  It  extends 

along  the  whole  length  of  the  inner  surface  of  each  lateral  mass ;  its  lower  mar- 
gin is  free  and  thick,  and  its  concavity,  directed  outward,  assists  in  forming  the 
middle  meatus.  It  is  by  a  large  orifice  at  the  upper  and  front  part  of  the  middle 
meatus  that  the  anterior  ethmoidal  cells,  and  through  them  the  frontal  sinuses, 
communicate  with  the  nose  by  means  of  a  funnel-shaped  canal,  the  infundibulum. 
The  cellular  cavities  of  each  lateral  mass,  thus  walled  in  by  the  os  planum  on  the 
outer  side  and  by  the  other  bones  already  mentioned,  are  divided  by  a  thin  trans- 
verse bony  partition  into  two  sets,  which  do  not  communicate  with  each  other ; 
they  are  termed  the  anterior  and  posterior  ethmoidal  cells  or  sinuses.  The  former, 
more  numerous,  communicate  with  the  frontal  sinuses  above  and  the  middle 
meatus  below  by  means  of  a  long,  flexuous  canal,  the  infundibulum  ;  the  posterior, 
less  numerous,  open  into  the  superior  meatus,  and  communicate  (occasionally) 
with  the  sphenoidal  sinuses. 

Development. — By  three  centres :  one  for  the  perpendicular  lamella,  and  one 
for  each  lateral  mass. 

The  lateral  masses  are  first  developed,  ossific  granules  making  their  appearance 
in  the  os  planum  between  the  fourth  and  fifth  months  of  foetal  life,  and  extending 
into  the  spongy  bones.  At  birth  the  bone  consists  of  the  two  lateral  masses, 
which  are  small  and  ill-developed.  During  the  first  year  after  birth  the  perpen- 
dicular and  horizontal  plates  begin  to  ossify,  from  a  single  nucleus,  and  become 
joined  to  the  lateral  masses  about  the  beginning  of  the  second  year.  The  forma- 
tion of  the  ethmoidal  cells,  which  completes  the  bone,  does  not  commence  until 
about  the  fourth  or  fifth  year. 

Articulations. — With  fifteen  bones :  the  sphenoid,  two  sphenoidal  turbinated, 
the  frontal,  and  eleven  of  the  face — the  two  nasal,  two  superior  maxillary,  two 
lachrymal,  two  palate,  two  inferior  turbinated,  and  the  vomer.  No  muscles  are 
attached  to  this  bone. 

DEVELOPMENT  OF  THE  CRANIUM. 

The  early  stages  of  the  development  of  the  cranium  have  already  been  described  (see  page 
115).  We  have  seen  that  it  is  formed  from  a  layer  of  mesoblast,  derived  from  the  protovertebral 
plates  of  the  trunk,  which  is  spread  over  the  whole  surface  of  the  rudimentary  brain.  That 
portion  of  this  layer  from  which  the  bones  of  the  skull  are  to  be  developed  consists  of  a  thin, 
membranous  capsule. 

Ossification  commences  in  the  roof,  and  is  preceded  by  the  deposition  of  a  membranous 
blastema  upon  the  surface  of  the  cerebral  capsule,  in  which  the  ossifying  process  extends,  the 
primitive  membranous  capsule  becoming  the  internal  periosteum,  and  being  ultimately  blended 
with  the  dura  mater.  Although  the  bones  of  the  vertex  of  the  skull  appear  before  those  at  the 
base,  and  make  considerable  progress  in  their  growth,  at  birth  ossification  is  more  advanced  in 
the  base,  this  portion  of  the  skull  forming  a  solid,  immovable  groundwork. 


188 


THE  SKELETON. 


The  Fontanelles. 

Before  birth  the  bones  at  the  vertex  and  side  of  the  skull  are  separated  from  each  other  by 
membranous  intervals  in  which  bone  is  deficient.  These  intervals  are  principally  found  at  the 
four  angles  of  the  parietal  bones.  Hence  there  are  six  fontanelles.  Their  formation  is  due  to 


FIG.  150.— Skull  at  birth,  showing  the  anterior  FIG.  151.— The  lateral  fontanelles. 

and  posterior  fontanelles. 

the  wave  of  ossification  being  circular  and  the  bones  quadrilateral ;  the  ossific  matter  first  meets 
at  the  margins  of  the  bones,  at  the  points  nearest  to  their  centres  of  ossification,  and  vacuities 
or  spaces  are  left  at  the  angles,  which  are  called  fontanelles,  so  named  from  the  pulsations  of  the 
brain,  which  are  perceptible  at  the  anterior  fontanelle,  and  were  likened  to  the  rising  of  water 
in  a  fountain.  The  anterior  fontanelle  is  the  largest,  and  corresponds  to  the  junction  of  the 
sagittal  and  coronal  sutures;  the  posterior  fontanelle,  of  smaller  size,  is  situated  at  the  junction 
of  the  sagittal  and  lambdoid  sutures ;  the  remaining  ones  are  situated  at  the  inferior  angles  of 
each  parietal  bone.  The  latter  are  closed  soon  after  birth  ;  the  two  at  the  two  superior  angles 
remain  open  longer ;  the  posterior  being  closed  in  a  few  months  after  birth  ;  the  anterior  remain- 
ing open  until  the  first  or  second  year.  These  spaces  are  gradually  filled  in  by  an  extension  of 
the  ossifying  process  or  by  the  development  of  a  Wormian  bone.  Sometimes  the  anterior 
fontanelle  remains  open  beyond  two  years,  and  is  occasionally  persistent  throughout  life. 

Supernumerary  or  Wormian1  Bones. 

In  addition  to  the  constant  centres  of  ossification  of  the  skull,  additional  ones  are  occasion- 
ally found  in  the  course  of  the  sutures.  These  form  irregular,  isolated  bones,  interposed  between 
the  cranial  bones,  and  have  been  termed  Wormian  bones  or  ossa  triquetra.  They  are  most 
frequently  found  in  the  course  of  the  lambdoid  suture,  but  occasionally  also  occupy  the  situation 
of  the  fontanelles,  especially  the  posterior  and,  more  rarely,  the  anterior.  Frequently  one  is 
found  between  the  anterior  inferior  angle  of  the  parietal  bone  and  the  greater  wing  of  the 
sphenoid,  the  pterion  ossicle  (Fig.  151).  They  have  a  great  tendency  to  be  symmetrical  on  the 
two  sides  of  the  skull,  and  they  vary  much  in  size,  being  in  some  cases  not  larger  than  a  pin's 
head,  and  confined  to  the  outer  table ;  in  other  cases  so  large  that  one  pair  of  these  bones  may 
form  the  whole  of  the  occipital  bone  above  the  superior  curved  lines,  as  described  by  Beclard 
and  Ward.  Their  number  is  generally  limited  to  two  or  three,  but  more  than  a  hundred  have 
been  found  in  the  skull  of  an  adult  hydrocephalic  skeleton.  In  their  development,  structure, 
and  mode  of  articulation  they  resemble  the  other  cranial  bones. 

Congenital  Fissures  and  Gaps. 

An  arrest  in  the  ossifying  process  ma}7  give  rise  to  deficiencies  or  gaps ;  or  to  fissures,  which 
are  of  importance  in  a  medico-legal  point  of  view,  as  they  are  liable  to  be  mistaken  for  fractures. 
The  fissures  generally  extend  from  the  margins  toward  the  centre  of  the  bone,  but  the  gaps 
may  be  found  in  the  middle  as  well  as  at  the  edges.  In  course  of  time  they  may  become  covered 
with  a  thin  lamina  of  bone. 

BONES  OF  THE  FACE. 

The  Facial  Bones  are  fourteen  in  number — viz.  the 
Two  Nasal.  Two  Palate. 

•Two  Superior  Maxillary.  Two  Inferior  Turbinated. 

Two  Lachrymal.  Vomer. 

Two  Malar.  Inferior  Maxillary. 

1  Wormius,  a  physician  in  Copenhagen,  is  said  to  have  given  the  first  detailed  description  of 
these  bones. 


THE    NASAL    AND    SUPERIOR    MAXILLARY  BONES. 


189 


"  Of  these,  the  upper  and  lower  jaws  are  the  fundamental  bones  for  mastication, 
and  the  others  are  accessories :  for  the  chief  function  of  the  facial  bones  is  to 
provide  an  apparatus  for  mastication,  while  subsidiary  functions  are  to  provide  for 
the  sense-organs  (eye,  nose,  tongue)  and  a  vestibule  to  the  respiratory  and  vocal 
organs.  Hence  the  variations  in  the  shape  of  the  face  in  man  and  the  lower 
animals  depend  chiefly  on  the  question  of  the  character  of  their  food  and  their  mode 
of  obtaining  it." 

The  Nasal  Bone. 

The  Nasal  (nasus.  the  nose)  are  two  small  oblong  bones,  varying  in  size  and 
form  in  different  individuals :  they  are  placed  side  by  side  at  the  middle  and  upper 
part  of  the  face,  forming,  by  their  junction,  "  the  bridge  "  of  the  nose.  Each  bone 
presents  for  examination  two  surfaces  and  four  borders.  The  outer  surface  is 
concave  from  above  downward,  convex  from  side  to  side;  it  is  covered  by  the 
Pyramidalis  and  Compressor  nasi  muscles,  and  give  attachment  at  its  upper  part 
to  a  few  fibres  of  the  Occipito-frontalis  muscle  (Theile).  It  is  marked  by  numerous 
small  arterial  furrows,  and  perforated  about  its  centre  by  a  foramen,  sometimes 
double,  for  the  transmission  of  a  small  vein.  Sometimes  this  foramen  is  absent  on 
one  or  both  sides,  and  occasionally  the  foramen  caecum  opens  on  this  surface.  The 
inner  surface  is  concave  from  side  to  side,  convex  from  above  downward;  in 
which  direction  it  is  traversed  by  a  longitudinal  groove  (sometimes  a  canal),  for 
the  passage  of  a  branch  of  the  nasal  nerve.  The  superior  border  is  narrow,  thick, 
and  serrated,  for  articulation  with  the  nasal  notch  of  the  frontal  bone.  The  inferior 
border  is  broad,  thin,  sharp,  inclined  obliquely  downward,  outward,  and  back- 
ward, and  serves  for  the  attachment  of  the  lateral  cartilage  of  the  nose.  This 
border  presents,  about  its  middle,  a  notch,  through  which  passes  the  branch  of  the 
nasal  nerve  above  referred  to.  and  is  prolonged  at  its  inner  extremity  into  a  sharp 

spine,  which,  when  articulated 

With  frontal  bone.  with  the  opposite  bone,  forms 

the  nasal  angle.  The  external 
border  is  serrated,  bevelled  at 
the  expense  of  the  internal  sur- 
face above  and  of  the  external 
below,  to  articulate  with  the 
nasal  process  of  the  superior 
maxillary.  The  internal  bor- 
der, thicker  above  than  below, 
articulates  with  its  fellow  of 
the  opposite  side,  and  is  pro- 
longed behind  into  a  vertical 
crest  which  forms  part  of  the 


With 
'opposite  bone. 


Surface. 
FIG.  152.— Right  nasal  bone. 


With 
frontal  spine. 

Crest. 

With 

perpendicular 
plate  of 
ethmoid. 


Groore  for  nasal  nerve. 


Inner  Surface. 
FIG.  153. — Left  nasal  bone. 


septum  of  the  nose  :  this  crest  articulates  with  the  nasal  spine  of  the  frontal  above, 
and  the  perpendicular  plate  of  the  ethmoid  below. 

Development. — By  one  centre  for  each  bone,  which  appears  about  the  same 
period  as  in  the  vertebrae. 

Articulations. — With  four  bones  :  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  opposite  nasal  and  the  superior  maxillary. 

Attachment  of  Muscles. — A  few  fibres  of  the  Occipito-frontalis  muscle. 

The  Superior  Maxillary  Bones. 

The  Superior  Maxillary  (maxilla,  the  jaw-bone)  is  one  of  the  most  important 
bones  of  the  face  from  a  surgical  point  of  view,  on  account  of  the  number  of  diseases 
to  which  some  of  its  parts  are  liable.  Its  careful  examination  becomes,  therefore, 
a  matter  of  considerable  interest.  It  is  the  largest  bone  of  the  face,  excepting  the 
lower  jaw.  and  forms,  by  its  union  with  its  fellow  of  the  opposite  side,  the  whole 

1  W.  W.  Keen,  American  edition,  p.  185. 


190 


THE  SKELETON. 


of  the  upper  jaw.  Each  bone  assists  in  the  formation  of  three  cavities,  the  roof  of 
the  mouth,  the  floor  and  outer  wall  of  the  nasal  fossae,  and  the  floor  of  the 
orbit,  and  also  enters  into  the  formation  of  two  fossae,  the  zygomatic  and  spheno- 
maxillary,  and  two  fissures,  the  spheno-maxillary  and  pterygo-maxillary. 

The  bone  presents  for  examination  a  body  and  four  processes — malar,  nasal, 
alveolar,  and  palate. 

The  body  is  somewhat  cuboid,  and  is  hollowed  out  in  its  interior  to  form  a  large 
cavity,  the  antrum  of  Highmore.  Its  surfaces  are  four — an  external  or  facial,  a 
posterior  or  zygomatic,  a  superior  or  orbital,  and  an  internal. 

The  external  or  facial  surface  (Fig.  154)  is  directed  forward  and  outward. 
Just  above  the  incisor  teeth  is  a  depression,  the  incisive  or  myrtiform  fossa,  which 
gives  origin  to  the  Depressor  alae  nasi ;  and  below  it  to  the  alveolar  border  is 
attached  a  slip  of  the  Orbicularis  oris.  Above  and  a  little  external  to  it  the 
Compressor  nasi  arises.  More  external  is  another  depression,  the  canine  fossa, 

Outer  Surface. 


TENOO    OCULI 


Incisive  fossa. 


Posterior  dental 
canals. 


MaxiUary  tuberosity. 


FIG.  154.— Left  superior  maxillary  bone.    Outer  surface. 

larger  and  deeper  than  the  incisive  fossa,  from  which  it  is  separated  by  a  vertical 
ridge,  the  canine  eminence,  corresponding  to  the  socket  of  the  canine  tooth.  The 
canine  fossa  gives  origin  to  the  Levator  anguli  oris.  Above  the  canine  fossa  is  the 
infraorbital  foramen,  the  termination  of  the  infraorbital  canal ;  it  transmits  the 
infraorbital  vessels  and  nerve.  Above  the  infraorbital  foramen  is  the  margin  of 
the  orbit,  which  affords  partial  attachment  to  the  Levator  labii  superioris  proprius. 
To  the  sharp  margin  of  bone  which  bounds  this  surface  in  front  and  separates  it 
from  the  internal  surface  is  attached  the  Dilator  naris  posterior. 

The  posterior  or  zygomatic  surface  is  convex,  directed  backward  and  outward, 
and  forms  part  of  the  zygomatic  fossa.  It  presents  about  its  centre  several  aper- 
tures leading  to  canals  in  the  substance  of  the  bone ;  they  are  termed  the  posterior 
dental  canals,  and  transmit  the  posterior  dental  vessels  and  nerves.  At  the  lower 
part  of  this  surface  is  a  rounded  eminence,  the  maxillary  tuberosity,  especially 
prominent  after  the  growth  of  the  wisdom-tooth,  rough  on  its  inner  side  for  artic- 
ulation with  the  tuberosity  of  the  palate  bone,  and  sometimes  with  the  external 
pterygoid  plate.  It  gives  attachment  to  a  few  fibres  of  origin  of  the  Internal 


THE   SUPERIOR    MAXILLARY  BONES. 


191 


pterygoid  muscle.  Immediately  above  the  rough  surface  is  a  groove  which,  run- 
nin<*  obliquely  down  on  the  inner  surface  of  the  bone,,  is  converted  into  a  canal 
by  articulation  with  the  palate-bone  forming  the  posterior  palatine  canal. 

The  superior  or  orbital  surface  is  thin,  smooth,  triangular,  and  forms  part  of 
the  floor  of  the  orbit.  It  is  bounded  internally  by  an  irregular  margin  which 
in  front  presents  a  notch,  the  lachrymal  notch,  which  receives  the  lachrymal  bone ; 
in  the  middle  articulates  with  the  os  planum  of  the  ethmoid,  and  behind  with  the 
orbital  process  of  the  palate  bone ;  -bounded  externally  by  a  smooth,  rounded  edge 
which  enters  into  the  formation  of  the  spheno-maxillary  fissure,  and  which  some- 
times articulates  at  its  anterior  extremity  with  the  orbital  plate  of  the  sphenoid ; 
bounded  in  front  by  part  of  the  circumference  of  the  orbit,  which  is  continuous 
on  the  inner  side  with  the  nasal,  on  the  outer  side  with  the  malar,  process.  Along 
the  middle  line  of  the  orbital  surface  is  a  deep  groove,  the  infraorbital,  for  the 
passage  of  the  infraorbital  vessels  and  nerve.  The  groove  commences  at  the  mid- 
dle of  the  outer  border  of  this  surface,  and.  passing  forward,  terminates  in  a  canal, 
which  subdivides  into  two  branches.  One  of  the  canals,  the  infraorbital,  opens 
just  below  the  margin  of  the  orbit;  the  other,  which  is  smaller,  runs  in  the  sub- 
stance of  the  anterior  wall  of  the  antrum :  it  is  called  the  anterior  dental  canal, 
ami  transmits  the  anterior  dental  vessels  and  nerve  to  the  front  teeth  of  the  upper 
jaw.  From  the  back  part  of  the  infraorbital  canal  a  second  small  canal  is  some- 
times given  off",  which  runs  in  the  substance  of  the  bone,  and  conveys  the  middle 
dental  nerve  to  the  bicuspid  teeth.  Occasionally,  this  canal  is  derived  from  the 
anterior  dental.  At  the  inner  and  fore  part  of  the  orbital  surface,  just  external 
to  the  lachrymal  groove  for  the  nasal  duct,  is  a  depression  which  gives  origin  to 
the  Inferior  oblique  muscle  of  the  eye. 

The  internal  surface  (Fig.  loo)  is  unequally  divided  into  two  parts  by  a  hori- 
zontal projection  of  bone,  the  palate  process :  the  portion  above  the  palate  process 


Bone-'  partially  dosing  orifice  of  antrnm 
marked  in  outline. 


Ethmoid.. 

Inferior  turbinated. 
Palate. 


Anterior  nasal  spine. 


Bristle  passed 
through  anterior 
palatine  canal. 


FIG.  155. — Left  superior  maxillary  bone.    Internal  surface. 


forms  part  of  the  outer  wall  of  the  nasal  fossae ;  that  below  it  forms  part  of  the 
cavity  of  the  mouth.  The  superior  division  of  this  surface  presents  a  large,  irreg- 
ular opening  leading  into  the  antrum  <>f  Hiahmore.  At  the  upper  border  of  this 
aperture  are  numerous  broken  cellular  cavities,  which  in  the  articulated  skull  are 
closed  in  by  the  ethmoid  and  lachrymal  bones.  Below  the  aperture  is  a  smooth 


192  THE  SKELETON. 

concavity  which  forms  part  of  the  inferior  meatus  of  the  nasal  fossae,  and  behind 
it  is  a  rough  surface  which  articulates  with  the  perpendicular  plate  of  the  palate 
bone,  traversed  by  a  groove  which,  commencing  near  the  middle  of  the  posterior 
border,  runs  obliquely  downward  and  forward,  and  forms,  when  completed  by  its 
articulation  with  the  palate  bone,  the  posterior  palatine  canal.  In  front  of  the 
opening  of  the  antrum  is  a  deep  groove,  converted  into  a  canal  by  the  lachrymal 
and  inferior  turbinated  bones.  It  is  called  the  lachrymal  groove,  and  lodges  the 
nasal  duct.  More  anteriorly  is  a  well-marked  rough  ridge,  the  inferior  turbinated 
crest,  for  articulation  with  the  inferior  turbinated  bone.  The  concavity  above 
this  ridge  forms  part  of  the  middle  meatus  of  the  nose,  whilst  that  below  it  forms 
part  of  the  inferior  meatus.  The  portion  of  this  surface  below  the  palate  process 
is  concave,  rough  and  uneven,  and  perforated  by  numerous  small  foramina  for  the 
passage  of  nutrient  vessels.  It  enters  into  the  formation  of  the  roof  of  the  mouth. 

The  Antrum  of  Highmore,  or  Maxillary  Sinus,  is  a  large,  pyramidal  cavity 
hollowed  out  of  the  body  of  the  maxillary  bone  :  its  apex,  directed  outward,  is 
formed  by  the  malar  process  ;  its  base,  by  the  outer  wall  of  the  nose.  Its  walls 
are  everywhere  exceedingly  thin,  and  correspond  to  the  orbital,  facial,  and  zygo- 
matic  surfaces  of  the  body  of  the  bone.  Its  inner  wall,  or  base,  presents,  in  the 
disarticulated  bone,  a  large,  irregular  aperture,  which  communicates  with  the 
nasal  fossa.  The  margins  of  this  aperture  are  thin  and  ragged,  and  the  aperture 
itself  is  much  contracted  by  its  articulation  with  the  ethmoid  above,  the  inferior 
turbinated  below,  and  the  palate  bone  behind,1  In  the  articulated  skull  this  cavity 
communicates  with  the  middle  meatus  of  the  nasal  fossae,  generally  by  two  small 
apertures  left  between  the  above-mentioned  bones.  In  the  recent  state  usually 
only  one  small  opening  exists,  near  the  upper  part  of  the  cavity,  sufficiently  large 
to  admit  the  end  of  a  probe,  the  other  being  closed  by  the  lining  membrane  of 
the  sinus. 

Crossing  the  cavity  of  the  antrum  are  often  seen  several  projecting  laminae  of 
bone,  similar  to  those  seen  in  the  sinuses  of  the  cranium ;  and  on  its  posterior  wall 
are  the  posterior  dental  canals,  transmitting  the  posterior  dental  vessels  and  nerves 
to  the  teeth.  Projecting  into  the  floor  are  several  conical  processes,  corresponding 
to  the  roots  of  the  first  and  second  molar  teeth  ;2  in  some  cases  the  floor  is  perfo- 
rated by  the  teeth  in  this  situation. 

It  is  from  the  extreme  thinness  of  the  walls  of  this  cavity  that  we  are  enabled  to  explain 
how  a  tumor  growing  from  the  antrum  encroaches  upon  the  adjacent  parts,  pushing  up  the  floor 
of  the  orbit,  and  displacing  the  eyeball,  projecting  inward  into  the  nose,  protruding  forward  on 
to  the  cheek,  and  making  its  way  backward  into  the  zygomatic  fossa  and  downward  into  the 
mouth. 

The  Malar  Process  is  a  rough,  triangular  eminence,  situated  at  the  angle  of 
separation  of  the  facial  from  the  zygomatic  surface.  In  front  it  is  concave,  form- 
ing part  of  the  facial  surface ;  behind  it  is  also  concave,  and  forms  part  of  the 
zygomatic  fossa ;  above  it  is  rough  and  serrated  for  articulation  with  the  malar 
bone ;  whilst  below  a  prominent  ridge  marks  the  division  between  the  facial  and 
zygomatic  surfaces.  A  small  part  of  the  Masseter  muscle  arises  from  this  process. 

The  Nasal  Process  is  a  thick,  triangular  plate  of  bone,  which  projects  upward, 
inward,  and  backward  by  the  side  of  the  nose,  forming  part  of  its  lateral  boundary. 
Its  external  surface  is  concave,  smooth,  perforated  by  numerous  foramina,  and 
gives  attachment  to  the  Levator  labii  superioris  alaeque  nasi,  the  Orbicularis 
palpebrarum,  and  Tendo  oculi.  Its  internal  surface  forms  part  of  the  outer  wall 
of  the  nose :  at  its  upper  part  it  presents  a  rough,  uneven  surface,  which 
articulates  with  the  ethmoid  bone,  closing  in  the  anterior  ethmoidal  cells ;  below 
this  is  a  transverse  ridge,  the  superior  turbinated  crest,  for  articulation  with  the 

1  In  some  cases,  at  any  rate,  the  lachrymal  bone  encroaches  slightly  on  the  anterior  superior  por- 
tion of  the  opening,  and  assists  in  forming  the  inner  wall  of  the  antrum. 

2  The  number  of  teeth  whose  fangs  are  in  relation  with  the  floor  of  the  antrum  is  variable.     The 
antrum  "  may  extend  so  as  to  be  in  relation  to  all  the  teeth  of  the  true  maxilla,  from  the  canine  to 
the  dens  sapienticE."     (See  Mr.  Salter  on  Abscess  of  the  Antrum,  in  a  System  of  Surgery,  edited  by  T. 
Holmes,  2d  ed.  vol.  iv.  p.  356.) 


THE  SUPERIOR    MAXILLARY  BOXES. 


193 


middle  turbinated  bone  of  the  ethmoid,  bounded  below  by  a  smooth  concavity 
which  forms  part  of  the  middle  meatus  ;  below  this  again  is  the  inferior  turbinated 
crest  (already  described),  where  the  process  joins  the  body  of  the  bone.  Its  upper 
border  articulates  with  the  frontal  bone.  The  anterior  border  of  the  nasal  process 
is  thin,  directed  obliquely  downward  and  forward,  and  presents  a  serrated  edge 
for  articulation  with  the  nasal  bone  :  its  posterior  border  is  thick,  and  hollowed 
into  a  groove,  the  lachrymal  groove,  for  the  nasal  duct :  of  the  two  margins  of  this 
groove,  the  inner  one  articulates  with  the  lachrymal  bone,  the  outer  one  forms 
part  of  the  circumference  of  the  orbit.  Just  where  the  latter  joins  the  orbital 
surface  is  a  small  tubercle,  the  lachrymal  tubercle  :  this  serves  as  a  guide  to  the 
position  of  the  lachrymal  sac  in  the  operation  for  fistula  lachrymalis.  The 
lachrymal  groove  in  the  articulated  skull  is  converted  into  a  canal  by  the  lachrymal 
bone  and  lachrymal  process  of  the  inferior  turbinated ;  it  is  directed  downward, 
and  a  little  backward  and  outward,  is  about  the  diameter  of  a  goose-quill,  slightly 


Anterior  palatine  canal. 


Foramina  of  Stenson. 


Foramen  of  Sear  pa. 


Posterior  palatine  canal. 


Accessory  palatine  foramina. 

FIG.  156.— The  palate  and  alveolar  arch. 

narrower  in  the  middle  than  at  either  extremity,  and  terminates  below  in  the 
inferior  meatus.  It  lodges  the  nasal  duct. 

The  Alveolar  Process  is  the  thickest  and  most  spongy  part  of  the  bone,  broader 
behind  than  in  front,  and  excavated  into  deep  cavities  for  the  reception  of  the  teeth. 
These  cavities  are  eight  in  number,  and  vary  in  size  and  depth  according  to  the 
teeth  they  contain.  That  for  the  canine  tooth  is  the  deepest ;  those  for  the  molars 
are  the  widest,  and  subdivided  into  minor  cavities  ;  those  for  the  incisors  are  single, 
but  deep  and  narrow.  The  Buccinator  muscle  arises  from  the  outer  surface  of  this 
process,  as  far  forward  as  the  first  molar  tooth. 

The  Palate  Process,  thick  and  strong,  projects  horizontally  inward  from  the 
inner  surface  of  the  bone.  It  is  much  thicker  in  front  than  behind,  and  forms  a 
considerable  part  of  the  floor  of  the  nostril  and  the  roof  of  the  mouth. 

Its  inferior  surface  (Fig.  156)  is  concave,  rough  and  uneven,  and  forms  part  of 
the  roof  of  the  mouth.  This  surface  is  perforated  by  numerous  foramina  for  the 
passage  of  the  nutrient  vessels,  channelled  at  the  back  part  of  its  alveolar  border 
by  a  longitudinal  groove,  sometimes  a  canal,  for  the  transmission  of  the  posterior 
palatine  vessels,  and  the  anterior  and  external  palatine  nerves  from  Meckel's  gan- 

13 


THE  SKELETON. 


glion,  and  presents  little  depressions  for  the  lodgment  of  the  palatine  glands.  When 
the  two  superior  maxillary  bones  are  articulated  together,  a  large  orifice  may  be 
seen  in  the  middle  line,  immediately  behind  the  incisor  teeth.  This  is  the  anterior 
palatine  canal  or  fossa.  This  canal,  as  it  passes  through  the  thickness  of  the  palate 
process,  is  divided  into  four  compartments ;  that  is  to  say,  two  canals  branch  off 
laterally  to  the  right  and  left  nasal  fossae,  and  two  canals,  one  in  front  and  one 
behind,  lie  in  the  middle  line.  The  former  pair  of  these  canals  is  named  the 
foramina  of  Stenson,  and  through  them  passes  the  anterior  or  terminal  branch  of 
the  descending  or  posterior  palatine  arteries,  which  ascend  from  the  mouth  to 
the  nasal  fossae.  The  remaining  pair  of  canals  is  termed  the  foramina  of 
Scarpa,  and  transmit  the  naso-palatine  nerves,  the  left  passing  through  the 
anterior,  and  the  right  through  the  posterior,  canal.  On  the  palatal  surface  of 
the  process  a  delicate  linear  suture  may  sometimes  be  seen  extending  from  the 
an:erior  palatine  fossa  to  the  interval  between  the  lateral  incisor  and  the  canine 
tooth.  This  marks  out  the  intermaxillary  or  incisive  bone  which  in  some 
animals  exists  permanently  as  a  separate  piece.  It  includes  the  whole  thickness 
of  the  alveolus,  the  corresponding  part  of  the  floor  of  the  nose,  and  the  anterior 
nasal  spine,  and  contains  the  sockets  of  the  incisor  teeth.  One  or  two  small 
foramina  in  the  alveolar  margin  behind  the  incisor  teeth  are  occasionally  seen  in 
the  adult,  almost  constantly  in  the  young  subject.  They  are  called  the  incisive 
foramina,  and  transmit  vessels  and  nerves  to  the  incisor  teeth.  The  upper  surface 
is  concave  from  side  to  side,  smooth,  and  forms  part  of  the  floor  of  the  nose. 
It  presents  the  upper  orifices  of  the  foramina  of  Stenson  and  Scarpa,  the  former 
being  on  each  side  of  the  middle  line,  the  latter  being  situated  in  the  intermaxil- 
lary suture,  and  therefore  not  visible  unless  the  two  bones  are  placed  in  apposition. 
The  outer  border  of  the  palate  process  is  incorporated  with  the  rest  of  the  bone. 
The  inner  border  is  thicker  in  front  than  behind,  and  is  raised  above  into  a  ridge, 
the  nasal  crest,  which,  with  the  corresponding  ridge  in  the  opposite  bone,  forms  a 
groove  for  the  reception  of  the  vomer.  In  front  this  crest  rises  to  a  considerable 
height,  and  this  portion  is  named  the  incisor  crest.  The  anterior  margin  is 
bounded  by  the  thin,  concave  border  of  the  opening  of  the  nose,  prolonged  forward 

internally  into  a  sharp  process,  forming,  with  a  similar 
process  of  the  opposite  bone,  the  anterior  nasal  spine. 
The  posterior  border  is  serrated  for  articulation  with  the 
horizontal  plate  of  the  palate  bone. 

Development. — This  bone  commences  to  ossify  at 
a  very  early  period,  and  ossification  proceeds  in  it  with 
great  rapidity,  so  that  it  is  difficult  to  ascertain  with 
certainty  its  precise  number  of  centres.  It  appears, 
however,  probable  that  it  is  ossified  by  five  primary  and 
two  secondary  centres.  The  primary  centres  appear 
about  the  seventh  or  eighth  week ;  first,  one  each  for  the 
facial  surface,  the  posterior  part  of  the  alveolus,  and  the 
orbital  plate,  and  a  few  days  later  one  for  the  palate 
process,  and  one  for  the  front  part  of  the  alveolus, 
which  carries  the  incisor  teeth,  and  which  corresponds 
to  the  pre-maxillary  bone  of  the  lower  animals.  All 
these,  except  the  last,  speedily  fuse,  and  the  two 
secondary  centres,  one  for  the  nasal  process  and  the 
other  for  the  malar  process,  appear  and  join  the  rest  of 
the  bone.  By  the  tenth  week  the  bone  consists  of  two 
portions — the  greater  part  of  the  bone  formed  of  six  out 
of  the  seven  centres  and  the  pre-maxillary  portion.  The 
suture  between  these  two  portions  on  the  palate  persists  till  middle  life,  but  is 
not  to  be  seen  on  the  facial  surface.  This  is  believed  by  Callender  to  be  due 
to  the  fact  that  the  front  wall  of  the  sockets  of  the  incisive  teeth  is  not  formed 
by  the  pre-maxillary  bone,  but  by  an  outgrowth  from  the  facial  part  of  the 


Inferior  Surface. 


FIG.  157. — Development  of 
superior  maxillary  bone.  At 
birth. 


THE  LACHRYMAL    BONES.  195 

superior  maxilla.  The  antrum  appears  as  a  shallow  groove  on  the  inner  surface 
of  the  bone  at  an  earlier  period  than  any  of  the  other  nasal  sinuses,  its  develop- 
ment commencing  about  the  fourth  month  of  foetal  life.  The  sockets  for  the 
teeth  are  formed  by  the  growing  downward  of  two  plates  from  the  dental  groove, 
which  subsequently  becomes  divided  by  partitions  jutting  across  from  the  one  to 
the  other. 

Articulations. — With,  nine  bones:  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  seven  of  the  face — viz.  the  nasal,  malar,  lachrymal,  inferior  turbinated,  palate, 
vomer,  and  its  fellow  of  the  opposite  side.'  Sometimes  it  articulates  with  the  orbital 
plate  of  the  sphenoid,  and  sometimes  with  its  external  pterygoid  plate. 

Attachment  of  Muscles. — To  twelve :  the  Orbicularis  palpebrarum,  Obliquus 
oculi  inferior,  Levator  lalm  superioris  alseque  nasi,  Levator  labii  superioris 
proprius.  Levator  anguli  oris.  Compressor  nasi,  Depressor  alse  nasi.  Dilatator 
naris  posterior.  Masseter,  Buccinator,  Internal  pterygoid,  and  Orbicularis  oris. 

CHANGES  PRODUCED  IX  THE  UPPER  JAW  BY  AGE. 

At  birth  and  during  infancy  the  diameter  of  the  bone  is  greater  in  an  antero-posterior 
than  in  a  vertical  direction.  Its  nasal  process  is  long,  its  orbital  surface  large,  and  its  tuberosity 
well  marked.  In  the  adult  the  vertical  diameter  is  the  greater,  owing  to  the  development  of 
the  alveolar  pr-nvss  and  the  increase  in  size  of  the  antrum.  In  old  age  the  bone  approaches 
again  in  character  to  the  infantile  condition  :  its  height  is  diminished,  and  after  the  loss  of  the 
teeth  the  alveolar  process  is  absorbed,  and  the  lower  part  of  the  bone  contracted  and  diminished 
in  thickn.  — 

The  Lachrymal  Bones. 

The  Lachrymal  (laebryma,  a  tear)  are  the  smallest  and  most  fragile  bones  of 
the  face.  They  are  situated  at  the  front  part  of  the  inner  wall  of  the  orbit,  and 
resemble  somewhat  in  form,  thinness,  and  size,  a  finger-nail ;  hence  they  are 
termed  the  o**</  unyuis.  Each  bone  presents  for  examination  two  surfaces  and 
four  borders.  The  external  or  orbital  surface  (Fig.  158)  is  divided  by  a  vertical 
ridge,  the  lachrymal  ••/•> *f.  into  two  parts.  The  portion  of 
bone  in  front  of  this  ridge  presents  a  smooth,  concave. 
longitudinal  groove,  the  free  margin  of  which  unites  with  the 
nasal  process  of  the  superior  maxillary  bone,  completing  the 
lachrymal  groove.  The  upper  part  of  this  groove  lodges  the 
lachrymal  sac :  the  lower  part  lodges  the  nasal  duct.  The 
portion  of  bone  behind  the  ridge  is  smooth,  slightly  concave, 
and  forms  part  of  the  inner  wall  of  the  orbit.  The  ridge, 
with  a  part  of  the  orbital  surface  immediately  behind  it, 
affords  attachment  to  the  Tensor  tarsi :  the  ridge  terminates 
below  in  a  small,  hook-like  projection,  the  hamular  process, 
which  articulares  with  the  lachrymal  tubercle  of  the  superior 
maxillary  bone,  and  completes  the  upper  orifice  of  the  lach- 
rymal groove.  It  sometimes  exists  as  a  separate  piece,  which  rymai  bone.  External 
is  then  called  the  lesser  Minimal  bone.  The  internal  or  nasal  fS^f,'  (Slishtly  en" 
surface  presents  a  depressed  furrow,  corresponding  to  the 
ridge  <>n  irs  outer  surface.  The  surface  of  bone  in  front  of  this  forms  part  of 
the  middle  meatus.  and  that  behind  it  articulates  with  the  ethmoid  bone,  filling  in 
the  anterior  ethmoidal  cells.  Of  the  four  borders,  the  anterior  is  the  longest,  and 
articulates  with  the  nasal  process  of  the  superior  maxillary  bone.  The  posterior. 
thin  and  uneven,  articulates  with  the  os  planum  of  the  ethmoid.  The  superior, 
the  shortest  and  thickest,  articulates  with  the  internal  angular  process  of  the 
frontal  bone.  The  inferior  is  divided  by  the  lower  edge  of  the  vertical  crest  into 
nvo  r-arts :  the  posterior  part  articulates  with  the  orbital  plate  of  the  superior 
maxillary  bone :  the  anterior  portion  is  prolonged  downward  into  a  pointed  pro- 
cess, which  articulates  with  the  lachrymal  process  of  the  inferior  turbinated  bone 
and  assists  in  the  formation  of  the  lachrymal  groove. 


196 


THE   SKELETON. 


Development. — By  a  single  centre,  which  makes  its  appearance  soon  after 
ossification  of  the  vertebrae  has  commenced. 

Articulations. — With  four  bones :  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  superior  maxillary  and  the  inferior  turbinated. 

Attachment  of  Muscles. — To  one  muscle,  the  Tensor  tarsi. 

The  Malar  Bones. 

The  Malar  (mala,  the  cheek)  are  twp  small,  quadrangular  bones,  situated  at 
the  upper  and  outer  part  of  the  face :  they  form  the  prominence  of  the  cheek,  part 
of  the  outer  wall  and  floor  of  the  orbit,  and  part  of  the  temporal  and  zygomatic 
fossae.  Each  bone  presents  for  examination  an  external  and  an  internal  surface ; 
four  processes,  the  frontal,  orbital,  maxillary,  and  zygomatic ;  and  four  borders. 
The  external  surface  (Fig.  159)  is  smooth,  convex,  perforated  near  its  centre  by 
one  or  two  small  apertures,  the  malar  foramina,  for  the  passage  of  nerves  and 
vessels,  covered  by  the  Orbicularis  palpebrarum  muscle,  and  affords  attachment  to 
the  Zygomaticus  major  and  minor  muscles. 

The  internal  surface  (Fig.  160),  directed  backward  and  inward,  is  concave, 
presenting  internally  a  rough,  triangular  surface,  for  articulation  with  the  supe- 


Bristles  passed 

through  temporo- 

malar  canals. 


With  frontal. 


FIG.  159.— Left  malar  bone.     Outer  surface. 


FIG.  160.— Left  malar  bone.    Inner  surface. 


rior  maxillary  bone ;  and  externally,  a  smooth,  concave  surface,  which  above  forms 
the  anterior  boundary  of  the  temporal  fossa,  and  below,  where  it  is  wider,  forms 
part  of  the  zygomatic  fossa.  This  surface  presents,  a  little  above  its  centre,  the 
aperture  of  one  or  two  malar  canals,  and  affords  attachment  to  part  of  two  muscles, 
the  Temporal  above  and  the  Masseter  below.  Of  the  four  processes,  the  frontal 
is  thick  and  serrated,  and  articulates  with  the  external  angular  process  of  the 
frontal  bone.  The  orbital  process  is  a  thick  and  strong  plate,  which  projects 
backward  from  the  orbital  margin  of  the  bone.  Its  supero-internal  surface, 
smooth  and  concave,  forms,  by  its  junction  with  the  orbital  surface  of  the  superior 
maxillary  bone  and  with  the  great  wing  of  the  sphenoid,  part  of  the  floor  and 
outer  wall  of  the  .orbit.  Its  infero-external  surface,  smooth  and  convex,  form* 
part  of  the  zygomatic  and  temporal  fossae.  Its  anterior  margin  is  smooth  and 
rounded,  forming  part  of  the  circumference  of  the  orbit.  Its  superior  margin, 
rough  and  directed  horizontally,  articulates  with  the  frontal  bone  behind  the 
external  angular  process.  Its  posterior  margin  is  rough,  and  serrated  for  articu- 
lation with  the  sphenoid ;  internally  it  is  also  serrated  for  articulation  with  the 
orbital  surface  of  the  superior  maxillary.  At  the  angle  of  junction  of  the  sphe- 
noidal  and  maxillary  portions  a  short,  rounded,  non-articular  margin  is  generally 
seen ;  this  forms  the  anterior  boundary  of  the  spheno-maxillary  fissure :  occasion- 
ally, no  such  non-articular  margin  exists,  the  fissure  being  completed  by  the  direct 
junction  of  the  maxillary  and  sphenoid  bones  or  by  the  interposition  of  a  small 


THE   PALATE   BOXES.  197 

Worinian  bone  in  the  angular  interval  between  them.  On  the  upper  surface  of 
the  orbital  process  are  seen  the  orifices  of  one  or  two  temporo-malar  canals ;  one 
of  these  usually  opens  on  the  posterior  surface,  the  other  (occasionally  two)  on 
the  facial  surface  :  they  transmit  filaments  (temporo-maler)  of  the  orbital  branch 
of  the  superior  maxillary  nerve.  The  maxillary  process  is  a  rough,  triangular 
surface  which  articulates  with  the  superior  maxillary  bone.  The  zygomatic  pro- 
is,  long,  narrow,  and  serrated,  articulates  with  the  zygomatic  process  of  the 
temporal  bone.  Of  the  four  borders,  the  antero-superior  or  orbital  is  smooth, 
arched  and  forms  a  considerable  part  -of  the  circumference  of  the  orbit.  The 
anter<i-iiiT\-i-ior  or  maxillary  border  is  rough,  and  bevelled  at  the  expense  of  its 
inner  table,  to  articulate  with  the  superior  maxillary  bone;  affording  attachment 
by  its  margin  to  the  Levator  labii  superioris  proprius,  just  at  its  point  of  junction 
with  the  superior  maxillary.  The  postero-superior  or  temporal  border,  curved  like 
an  italic  letter  f.  is  continuous  above  with  the  commencement  of  the  temporal 
ridge :  below,  with  the  upper  border  of  the  zygomatic  arch :  it  affords  attachment 
to  the  temporal  fascia.  The  posters-inferior  or  zygomatic  border  is  continuous 
with  the  lower  border  of  the  zygomatic  arch,  affording  attachment  by  its  rough 
edge  to  the  Masseter  muscle. 

Development. — The  malar  bone  ossifies  generally  from  two.  but  occasionally 
from  three,  centres.  One.  which  forms  the  chief  part  of  the  bone,  appears  about 
the  seventh  week,  near  the  orbital  margin.  The  second  appears  somewhat  later, 
along  the  lower  margin.  The  third,  when  it  exists,  is  found  in  the  hinder  border. 
The  bone  is  sometimes,  after  birth,  seen  to  be  divided  by  a  horizontal  suture  into 
an  upper  and  larger  division  and  a  lower  and  smaller.  This  divided  condition  is 
probably  due  to  the  persistent  separation  of  the  two  centres  of  ossification.  In 
some  quadrumana  the  malar  bone  consists  of  two  farts,  an  orbital  and  a  malar, 
which  are  ossified  by  separate  centres. 

Articulations. — With  four  bones :  three  of  the  cranium,  frontal,  sphenoid,  and 
temporal :  and  one  of  the  face,  the  superior  maxillary. 

Attachment  of  Muscles. — To  five :  The  Levator  labii  superioris  proprius, 
Zygomaticus  major  and  minor,  Masseter,  and  Temporal. 

The  Palate  Bones. 

The  Palate  Bones  (palatnm,  the  palate)  are  situated  at  the  back  part  of  the 
nasal  fossae :  they  are  wedged  in  between  the  superior  maxillary  bones  and  the 
pterygoid  processes  of  the  sphenoid.  Each  bone  assists  in  the  formation  of  three 
cavities :  the  floor  and  outer  wall  of  the  nose,  the  roof  of  the  mouth,  and  the  floor 
of  the  orbit,  and  enters  into  the  formation  of  two  fossae,  the  spheno-maxillary  and 
pterygoid :  and  one  fissure,  the  spheno-maxillary.  In  form  the  palate  bone  some- 
what resembles  the  letter  L,  and  may  be  divided  into  an  inferior  or  horizontal 
plate  and  a  superior  or  vertical  plate. 

The  Horizontal  Plate  is  thick,  of  a  quadrilateral  form,  and  presents  two  sur- 
faces and  four  borders.  The  siit>erior  surface,  concave  from  side  to  side,  forms 
the  back  part  of  the  floor  of  the  nostril.  The  inferior  surface,  slightly  concave 
anu  rough,  forms  the  back  part  of  the  hard  palate.  At  its  posterior  part  may  be 
seen  a  transverse  ridge,  more  or  less  marked,  for  the  attachment  of  part  of  the 
apMneurosis  of  the  Tensor  palati  muscle.  At  the  outer  extremity  of  this  ridge  is 
a  deep  groove  converted  into  a  canal  by  its  articulation  with  the  tuberosity  of  the 
superior  maxillary  bone,  and  forming  the  posterior  palatine  canal.  Near  this 
groove  the  orifices  of  one  or  two  small  canals,  accessory  posterior  palatine,  may  be 
seen.  The  anterior  border  is  serrated,  bevelled  at  the  expense  of  its  inferior  sur- 
face, and  articulates  with  the  palate  process  of  the  superior  maxillary  bone.  The 
rior  border  is  concave,  free,  and  serves  for  the  attachment  of  the  soft  palate. 
Its  inner  extremity  is  sharp  and  pointed,  and.  when  united  with  the  opposite  bone, 
forms  a  projecting  process,  the  posterior  nasal  spine,  for  the  attachment  of  the 
Azygos  uvulae.  The  external  border  is  united  with  the  lower  part  of  the  per}  en- 


198 


THE   SKELETON. 


dicular  plate  almost  at  right  angles.  The  internal  border,  the  thickest,  is  serrated 
for  articulation  with  its  fellow  of  the  opposite  side  ;  its  superior  edge  is  raised  into 
a  ridge,  which,  united  with  the  opposite  bone,  forms  a  crest  in  which  the  vomeris 
received. 

The  Vertical  Plate  (Fig.  161)  is  thin,  of  an  oblong  form,  and  directed  upward 
and  a  little  inward.  It  presents  two  surfaces,  an  external  and  an  internal,  and 
four  borders. 

The  internal  surface  presents  at  its  lower  part  a  broad,  shallow  depression, 
which  forms  part  of  the  inferior  meatus  of  the  nose.  Immediately  above  this 

well-marked  horizontal 

Orbital  process. 

Orbital  surface. 


Maxillary  surface. 


Superior  meatus. 
Spheno-palatine  foramen*—^ 


Maxillary 
process. 


Horizontal  Plate. 

FIG.  161. — Left  palate  bone.    Internal  view.    (Enlarged.) 


is    a 

ridge,  the  inferior  turbinated 
crest,  for  articulation  with  the 
inferior  turbinated  bone ; 
above  this,  a  second  broad, 
shallow  depression,  which 
forms  part  of  the  middle  mea- 
tus, surmounted  above  by  a 
horizontal  ridge  less  promi- 
nent than  the  inferior,  the 
superior  turbinated  crest,  for 
articulation  with  the  middle 
turbinated  bone.  Above  the 
superior  turbinated  crest  is  a 
narrow,  horizontal  groove, 
Avhich  forms  part  of  the  su- 
perior meatus. 

The  external  surface  is 
rough  and  irregular  through- 
out the  greater  part  of  its 
extent,  for  articulation  with 
the  inner  surface  of  the  su- 
perior maxillary  bone,  its  upper  and  back  part  being  smooth  where  it  enters  into 
the  formation  of  the  spheno-maxillary  fossa ;  it  is  also  smooth  in  front,  where  it 
covers  the  orifice  of  the  antrum.  Toward  the  back  part  of  this  surface  is  a  deep 
groove,  converted  into  a  canal,  the  posterior 
palatine,  by  its  articulation  with  the  supe- 
rior maxillary  bone.  It  transmits  the  pos- 
terior or  descending  palatine  vessels  and 
one  of  the  descending  palatine  branches 
from  Meckel's  ganglion. 

The  anterior  border  is  thin,  irregular, 
and  presents,  opposite  the  inferior  turbi- 
nated crest,  a  pointed,  projecting  lamina, 
the  maxillary  process,  which  is  directed 
forward,  and  closes  in  the  lower  and  back 
part  of  the  opening  of  the  antrum.  The 
posterior  border  (Fig.  162)  presents  a  deep 
groove,  the  edges  of  which  are  serrated  for 
articulation  with  the  pterygoid  process  of 
the  sphenoid.  At  the  lower  part  of  this 
border  is  seen  a  pyramidal  process  of  bone, 
the  pterygoid  process  or  tuberosity  of  the 
palate,  which  is  received  into  the  angular 
interval  between  the  two  pterygoid  plates 
of  the  sphenoid  at  their  inferior  extremity. 
This  process  presents  at  its  back  part  a 
median  groove  and  two  lateral  surfaces. 


Orbital  process, 
surface. 


•Sphenoidal  palatine 
foramen. 

Sphenoidal  process. 
Articular  portion. 
Non-articular  portion. 


External  Surface. 


Posterior 
nasal  spme. 


AZYQOS  UVUL 

Horizontal 
Plate. 


FIG.  162.— Left  palate  bone.    Posterior  view. 
(Enlarged.) 

The  groove  is  smooth,  and  forms  part 


THE  PALATE   BOXES.  199 

of  the  pterygoid  fossa,  affording  attachment  to  the  Internal  pterygoid  muscle; 
whilst  the  lateral  surfaces  are  rough  and  uneven,  for  articulation  with  the  anterior 
border  of  each  pterygoid  plate.  A  few  fibres  of  the  Superior  constrictor  arise  from 
the  tuberosity  of  the  palate  bone.  The  base  of  this  process,  continuous  with  the 
horizontal  portion  of  the  bone,  presents  the  apertures  of  the  accessory  descending 
palatine  canals,  through  which  pass  the  two  smaller  descending  branches  of 
M-  ••  -kel's  ganglion :  whilst  its  outer  surface  is  rough  for  .articulation  with  the  inner 
surface  of  the  body  of  the  superior  maxillary  bone. 

The  superior  border  of  the  vertical  plate  presents  two  well-marked  processes 
separated  by  an  intervening  notch  or  foramen.  The  anterior,  or  larger,  is  called 
the  <>rhit nl  pro??**  :  the  posterior,  the  sphenoidal. 

The  Orbital  Process,  directed  upward  and  outward,  is  placed  on  a  higher  level 
than  the  sphenoidal.  It  presents  five  surfaces,  which  enclose  a  hollow  cellular 
cavity,  and  is  connected  to  the  perpendicular  plate  by  a  narrow,  constricted  neck. 
Of  these  five  surfaces,  three  are  articular,  two  non-articular  or  free  surfaces.  The 
three  articular  are  the  anterior  or  maxillary  surface,  which  is  directed  forward, 
outward,  and  downward,  is  of  an  oblong  form,  and  rough  for  articulation  with 
the  superior  maxillary  bone.  The  posterior  or  sphenoidal  surface  is  directed 
backward,  upward,  and  inward.  It  ordinarily  presents  a  small,  open  cell,  which 
communicates  with  the  sphenoidal  cells,  and  the  margins  of  which  are  serrated 
for  articulation  with  the  vertical  part  of  the  sphenoidal  turbinated  bone.  The 
internal  or  ethmoidal  surface  is  directed  inward,  upward,  and  forward,  and 
articulates  with  the  lateral  mass  of  the  ethmoid  bone.  In  some  cases  the  cellular 
cavitv  above  mentioned  opens  on  this  surface  of  the  bone;  it  then  communicates 
with  the  posterior  ethmoidal  cells.  More  rarely  it  opens  on  both  surfaces,  and 
then  communicates  both  with  the  posterior  ethmoidal  and  the  sphenoidal  cells. 
The  non-articular  or  free  surfaces  are  the  superior  or  orbital,  directed  upward  and 
outward,  of  triangular  form,  concave,  smooth,  and  forming  the  back  part  of  the 
floor  of  the  orbit :  and  the  external  or  zygomatic  surface,  directed  outward, 
backward,  and  downward,  of  an  oblong  form,  smooth,  lying  in  the  spheno-maxil- 
lary  fossa,  and  looking  into  the  zygomatic  fossa.  The  latter  surface  is  separated 
from  the  orbital  by  a  smooth,  rounded  border,  which  enters  into  the  formation 
of  the  spheno-maxillary  fissure. 

The  Sphenoidal  Process  of  the  palate  bone  is  a  thin,  compressed  plate,  much 
smaller  than  the  orbital,  and  directed  upward  and  inward.  It  presents  three 
surfaces  and  two  borders.  The  superior  surface,  the  smallest  of  the  three, 
articulates  with  the  under  surface  of  the  sphenoidal  turbinated  bone;  it  presents  a 
groove,  which  contributes  to  the  formation  of  the  pterygo-palatine  canal.  The 

•ii.al  surface  is  concave,  and  forms  part  of  the  outer  wall  of  the  nasal  fossa. 
The  external  surface  is  divided  into  an  articular  and  a  non-articular  portion :  the 
former  is  rough,  for  articulation  with  the  inner  surface  of  the  pterygoid  process 
of  the  sphenoid ;  the  latter  is  smooth,  and  forms  part  of  the  spheno-maxillary 
fossa.  The  anteri:ir  border  forms  the  posterior  boundary  of  the  spheno-palatine 
foramen.  The  posterior  border,  serrated  at  the  expense  of  the  outer  table, 
articulates  with  the  inner  surface  of  the  pterygoid  process. 

The  orbital  and  sphenoidal  processes  are  separated  from  one  another  by  a  deep 
notch,  which  is  converted  into  a  foramen,  the  spheno-palatine,  by  articulation 
with  the  sphenoidal  turbinated  bone.  Sometimes  the  two  processes  are  united 
above,  and  form  between  them  a  complete  foramen,  or  the  notch  is  crossed  by  one 
or  more  spiculae  of  bone  so  as  to  form  two  or  more  foramina.  In  the  articulated 
skull  this  foramen  opens  into  the  back  part  of  the  outer  wall  of  the  superior 
meatus.  and  transmits  the  spheno-palatine  vessels  and  the  superior  nasal  and 
-palatine  nerves. 

Development. — From  a  single  centre,  which  makes  its  appearance  about  the 
second  month  at  the  angle  of  junction  of  the  two  plates  of  the  bone.  From  this 
point  ossification  spreads  inward  to  the  horizontal  plate,  downward  into  the 
tuberosity.  and  upward  into  the  vertical  plate.  In  the  foetus  the  horizontal  plate 


200 


THE  SKELETON. 


is  much  longer  than  the  vertical,  and  even  after  it  is  fully  ossified  the  whole  bone 
is  at  first  remarkable  for  its  shortness. 

Articulations. — With  six  bones :  the  sphenoid,  ethmoid,  superior  maxillary, 
inferior  turbinated,  vomer,  and  opposite  palate. 

Attachment  of  Muscles. — To  four :  the  Tensor  palati,  Azygos  uvulae,  Internal 
pterygoid,  and  Superior  constrictor  of  the  pharynx. 

The  Inferior  Turbinated  Bones. 

The  Inferior  Turbinated  Bones  (turbo,  a  whirl)  are  situated  one  on  each  side  of 
the  outer  wall  of  the  nasal  fossae.  Each  consists  of  a  layer  of  thin,  spongy  bone, 
curled  upon  itself  like  a  scroll — hence  its  name  "turbinated  " — and  extends  hori- 
zontally along  the  outer  wall  of  the  nasal  fossa,  immediately  below  the  orifice  of 
the  antrum.  Each  bone  presents  two  surfaces,  two  borders,  and  two  extremities. 

The  internal  surface  (Fig.  163)  is  convex,  perforated  by  numerous  apertures, 
and  traversed  by  longitudinal  grooves  and  canals  for  the  lodgment  of  arteries  and 


FIG.  163.— Right  inferior  turbinated  bone.    Internal 
surface. 


FIG.  164— Right 
External  surface. 


inferior  turbinated    bone. 


veins.  In  the  recent  state  it  is  covered  by  the  lining  membrane  of  the  nose.  The 
external  surface  is  concave  (Fig.  164),  and  forms  part  of  the  inferior  meatus.  Its 
upper  border  is  thin,  irregular,  and  connected  to  various  bones  along  the  outer 
wall  of  the  nose.  It  may  be  divided  into  three  portions  :  of  these,  the  anterior 
articulates  with  the  inferior  turbinated  crest  of  the  superior  maxillary  bone ;  the 
posterior  with  the  inferior  turbinated  crest  of  the  palate  bone  ;  the  middle  portion 
of  the  superior  border  presents  three  well-marked  processes,  which  vary  much  in 
their  size  and  form.  Of  these,  the  anterior  and  smallest  is  situated  at  the  junction 
of  the  anterior  fourth  with  the  posterior  three-fourths  of  the  bone  :  it  is  small  and 
pointed,  and  is  called  the  lachrymal  process ;  it  articulates  by  its  apex  with  the 
anterior  inferior  angle  of  the  lachrymal  bone,  and  by  its  margins  with  the  groove 
on  the  back  of  the  nasal  process  of  the  superior  maxillary,  and  thus  assists  in 
forming  the  canal  for  the  nasal  duct.  At  the  junction  of  the  two  middle  fourths  of 
the  bone,  but  encroaching  on  its  posterior  fourth,  a  broad,  thin  plate,  the  ethmoidal 
process,  ascends  to  join  the  unciform  process  of  the  ethmoid  ;  from  the  lower  border 
of  this  process  a  thin  lamina  of  bone  curves  downward  and  outward,  articulating 
by  its  lower  margin  with  the  lower  edge  of  the  orifice  of  the  antrum :  it  is  called 
the  maxillary  process,  and  fixes  the  bone  firmly  on  to  the  outer  wall  of  the  nasal 
fossa.  The  inferior  border  is  free,  thick,  and  cellular  in  structure,  more  especially 
in  the  middle  of  the  bone.  Both  extremities  are  more  or  less  narrow  and  pointed, 
the  posterior  being  the  more  tapering.  If  the  bone  is  held  so  that  its  outer  con- 
cave surface  is  directed  backward  (i.  e.  toward  the  holder),  and  its  superior  border, 
from  which  the  lachrymal  and  ethmoidal  processes  project,  upward,  the  lachrymal 
process  will  be  directed  to  the  side  to  which  the  bone  belongs.1 

Development. — By  a  single  centre,  which  makes  its  appearance  about  the 
middle  of  foetal  life. 

Articulations. — With  four  bones :  one  of  the  cranium,  the  ethmoid,  and  three 
of  the  face,  the  superior  maxillary,  lachrymal,  and  palate. 

No  muscles  are  attached  to  this  bone. 

1  If  the  lachrymal  process  is  broken  off,  as  is  often  the  case,  the  side  to  which  the  bone  belongs 
may  be  known  by  recollecting  that  the  maxillary  process  is  nearer  the  back  than  the  front  of  the  bone- 


THE    VOMER,    THE    INFERIOR    MAXILLARY   BOXE. 


201 


Ate. 


With  sup.  mar\U.  bones  and  palate. 
FIG.  165.— The  vomer. 


The  Vomer. 

The  Vomer  (vomer,  a  ploughshare)  is  a  single  bone,  situated  vertically  at  the 
back  part  of  the  nasal  fossa?,  forming  part  of  the  septum  of  the  nose.  It  is  thin, 
somewhat  like  a  ploughshare  in  form ;  but  it  varies  in  different  individuals,  being 
frequently  bent  to  one  or  the  other  side ;  it  presents  for  examination  two  surfaces 
and  five  borders.  The  lateral  surfaces  are  smooth,  marked  by  small  furrows  for 
the  lodgment  of  blood-vessels,  and  by  a  groove  on  each  side,  sometimes  a  canal, 
the  n'tso-paJatirc'.  which  runs 
obliquely  downward  and  forward 
to  the  intermaxillary  suture ;  it 
transmits  the  naso-palatine  nerve. 
The  po*t'.  /•"'Superior  border,  the 
thickest,  presents  a  deep  groove. 
bounded  on  each  side  by  a  hori- 
zontal projecting  ala  of  bone ; 
the  groove  receives  the  rostrum 
of  the  sphenoid,  whilst  the  ala? 
are  overlapped  and  retained  by 
lamina?  (the  vaginal  processes)  $* 
which  project  from  the  under 
surface  of  the  body  of  the  sphe- 
noid at  the  base  of  the  pterygoid 
processes.  At  the  front  of  the 
groove  a  fissure  is  left  for  the  transmission  of  blood-vessels  to  the  substance  of 
the  bone.  The  inferior  border,  the  longest,  is  broad  and  uneven  in  front,  where 
it  articulates  with  the  two  superior  maxillary  bones;  thin  and  sharp  behind, 
where  it  j"in>  with  the  palate  bones.  The  upper  half  of  the  antero-superior  bor- 
d  /•  usually  consists  of  two  lamina?  of  bone,  between  which  is  received  the  per- 
pendicular plate  of  the  ethmoid  :  the  lower  half,  also  separated  into  two  lamina?, 
receives  between  them  the  lower  margin  of  the  triangular  cartilage  of  the  nose. 
The  anterior  border  is  short  and  vertical,  and  articulates  with  the  posterior  mar- 
gin of  the  incisor  crest  of  each  superior  maxilla.  The  posterior  border  is  free, 
concave,  and  separates  the  nasal  fossa?  behind.  It  is  thick  and  bifid  above, 
thin  below. 

The  surfaces  of  the  vomer  are  covered  by  mucous  membrane,  which  is  inti- 
mately connected  with  the  periosteum,  with  the  intervention  of  very  little,  if  any, 
subuiucous  connective  tissue. 

Development. — The  vomer  at  an  early  period  consists  of  two  laminae,  separated 
by  a  very  considerable  interval,  and  enclosing  between  them  a  plate  of  cartilage, 
which  is  prolonged  forward  to  form  the  remainder  of  the  septum.  Ossification 
commences  in  it  by  a  single  centre  about  the  eighth  week.  From  this  nucleus  the 
two  laminae  are  formed.  They  begin  to  coalesce  at  the  lower  part,  but  their  union 
is  not  complete  until  after  puberty. 

Articulations. — With  six  bones  :  two  of  the  cranium,  the  sphenoid  and  ethmoid ; 
and  four  of  the  face,  the  two  superior  maxillary  and  the  two  palate  bones ;  and 
with  the  cartilage  of  the  septum. 

The  vomer  has  no  muscles  attached  to  it. 

The  Inferior  Maxillary  Bone. 

The  Inferior  Maxillary  Bone  (the  Mandible),  the  largest  and  strongest  bone 
of  the  face,  serves  for  the  reception  of  the  lower  teeth.  It  consists  of  a  curved, 
horizontal  portion,  the  body,  and  two  perpendicular  portions,  the  rami,  which  join 
the  back  part  of  the  body  nearly  at  right  angles. 

The  Horizontal  Portion  or  Body  (Fig.  166),  is  convex  in  its  general  outline,  and 
curved  somewhat  like  a  horseshoe.  It  presents  for  examination  two  surfaces 
and  two  borders.  The  external  surface  is  convex  from  side  to  side,  concave  from 


202 


THE  SKELETON. 


above  downward.  In  the  .median  line  is  a  vertical  ridge,  the  symphysis,  which 
extends  from  the  upper  to  the  lower  border  of  the  bone,  and  indicates  the  point  of 
junction  of  the  two  pieces  of  which  the  bone  is  composed  at  an  early  period  of  life. 
The  lower  part  of  the  ridge  terminates  in  a  prominent  triangular  eminence,  the 
mental  process.  This  eminence  is  rounded  below,  and  often  presents  a  median 
depression  separating  two  processes,  the  mental  tubercles.  It  forms  the  chin,  a 
feature  peculiar  to  the  human  skull.  On  either  side  of  the  symphysis,  just  below  the 
cavities  for  the  incisor  teeth,  is  a  depression,  the  incisive  fossa,  for  the  attachment 
of  the  Levator  menti  (or  Levator  labii  inferioris) ;  more  externally  is  attached  a 
portion  of  the  Orbicularis  oris  (Accessorii  Orbicularis  inferioris),  and,  still  more 
externally,  a  foramen,  the  mental  foramen,  for  the  passage  of  the  mental  vessels 
and  nerve.  This  foramen  is  placed  just  below  the  interval  between  the  two 
bicuspid  teeth.  Running  outward  from  the  base  of  the  mental  process  on 
each  side  is  a  ridge,  the  external  oblique  line.  The  ridge  is  at  first  nearly 
horizontal,  but  afterward  inclines  upward  and  backward,  and  is  continuous 
with  the  anterior  border  of  the  ramus :  it  affords  attachment  to  the  Depressor 


Coronoid  process. 


Condyle. 


— Angle. 


FIG.  166. — Inferior  maxillary  bone.    Outer  surface.    Side  view. 


labii  inferioris  and   Depressor   anguli  oris ;    below   it   the  Platysma  myoides   is 
attached. 

The  internal  surface  (Fig.  167)  is  concave  from  side  to  side,  convex  from  above 
downward.  In  the  middle  line  is  an  indistinct  linear  depression,  corresponding 
to  the  symphysis  externally ;  on  either  side  of  this  depression,  just  below  its  centre, 
are  four  prominent  tubercles,  placed  in  pairs,  tAvo  above  and  two  below ;  they  are 
called  the  genial  tubercles  or  mental  spines,  and  afford  attachment,  the  upper  to 
the  Genio-hyo-glossi,  the  lower  to  the  Genio-hyoidei  muscles.  Sometimes  the 
tubercles  on  each  side  are  blended  into  one  ;  at  others  they  all  unite  into  an  irregular 
eminence ;  or,  again,  nothing  but  an  irregularity  may  be  seen  on  the  surface  of  the 
bone  at  this  part.  On  either  side  of  the  genial  tubercles  is  an  oval  depression,  the 
sublingual fossa,  for  lodging  the  sublingual  gland;  and  beneath  the  fossa  a  rough 
depression  on  each  side  which  gives  attachment  to  the  anterior  belly  of  the 
Digastric  muscle.  At  the  back  part  of  the  sublingual  fossa  the  internal  oblique 
line  (mylo-Tiyoidean)  commences ;  it  is  at  first  faintly  marked,  but  becomes  more 
distinct  as  it  passes  upward  and  outward,  and  is  especially  prominent  opposite 
the  last  two  molar  teeth ;  it  affords  attachment  throughout  its  whole  extent  to  the 
Mylo-hyoid  muscle ;  the  Superior  constrictor  of  the  pharynx  with  the  pterygo- 
maxillary  ligament  being  attached  above  its  posterior  extremity,  near  the  alveolar 
margin.  The  portion  of  the  bone  above  this  ridge  is  smooth,  and  covered  by  the 


THE   INFERIOR    MAXILLARY  BONE. 


203 


mucous  membrane  of  the  mouth  :  the  portion  below  presents  an  oblong  depression, 
the  svb)ii'.i.rill<.i.r'i  fn**<i.  wider  behind  than  in  front,  for  the  lodgment  of  the  sub- 


GENIO-HYO-GLOSSUS. 


j  E '.    C     --  ;    C  E  _  5 


Mylo-hyoid  ridge. 


Body. 


FIG.  167.— Inferior  maxillary  bone.    Inner  surface.    Side  view. 

maxillary  gland.  The  external  oblique  line  and  the  internal  or  mylo-hyoidean  line 
divide  the  body  of  the  bone  into  a  superior  or  alveolar  and  an  inferior  or  basilar 
portion. 

The  superior  or  alveolar  border  is  wider,  and  its  margins  thicker,  behind  than 
in  front.  It  is  hollowed  into  numerous  cavities,  for  the  reception  of  the  teeth : 
these  cavities  are  sixteen  in  number,  and  vary  in  depth  and  size  according  to  the 
teeth  which  they  contain.  To  its  outer  side,  the  Buccinator  muscle  is  attached  as 
far  forward  as  the  first  molar  tooth.  The  inferior  border  is  rounded,  longer  than 
the  superior,  and  thicker  in  front  than  behind :  it  presents  a  shallow  groove,  just 
where  the  body  joins  the  ramtis.  over  which  the  facial  artery  turns. 

The  Perpendicular  Portions,  or  Kami,  are  of  a  quadrilateral  form.  Each 
presents  for  examination  two  surfaces,  four  borders,  and  two  processes.  The 
ejft?ni<~tl  .•> >i rf •!>•••  is  flat,  marked  with  ridges,  and  gives  attachment  throughout  nearly 
the  whole  of  its  extent  to  the  Masseter  muscle.  The  internal  surface  presents 
about  its  centre  the  oblique  aperture  of  the  inferior  dental  canal,  for  the  passage 
of  the  inferior  dental  vessels  and  nerve.  The  margin  of  this  opening  is  irregular; 
it  presents  in  front  a  prominent  ridge,  surmounted  by  a  sharp  spine,  the  lingula, 
which  gives  attachment  to  the  internal  lateral  ligament  of  the  lower  jaw,  and  at 
its  lower  and  back  part  a  notch  leading  to  a  groove,  the  mylo-hyoidean.  which  runs 
obliquely  downward  to  the  back  part  of  the  submaxillary  fossa,  and  lodges  the 
mylo-hyoid  vessels  and  nerve.  Behind  the  groove  is  a  rough  surface,  for  the 
insertion  of  the  Internal  pterygoid  muscle.  The  inferior  dental  canal  runs  obliquely 
downward  and  forward  in  the  substance  of  the  ramus.  and  then  horizontally 
forward  in  the  body  :  it  is  here  placed  under  the  alveoli,  with  which  it  communi- 
cates by  small  openings.  On  arriving  at  the  incisor  teeth,  it  turns  back  to 
communicate  with  the  mental  foramen,  giving  off  two  small  canals,  which  run 
forward,  to  be  lost  in  the  cancellous  tissue  of  the  bone  beneath  the  incisor  teeth. 
This  canal,  in  the  posterior  two-thirds  of  the  bone,  is  situated  nearer  the  internal 
surface  of  the  jaw :  and  in  the  anterior  third,  nearer  its  external  surface.  Its 
walls  are  composed  of  compact  tissue  at  either  extremity,  and  of  cancellous  in  the 
centre.  It  contains  the  inferior  dental  vessels  and  nerve,  from  which  branches  are 
distributed  to  the  teeth  through  small  apertures  at  the  bases  of  the  alveoli.  The 


204  THE  SKELETON. 

lower  border  of  the  ramus  is  thick,  straight,  and  continuous  with  the  body  of  the 
bone.  At  its  junction  with  the  posterior  border  is  the  angle  of  the  jaw,  which  is 
either  inverted  or  everted,  and  marked  by  rough,  oblique  ridges  on  each  side,  for 
the  attachment  of  the  Masseter  externally,  and  the  Internal  pterygoid  internal Iv  ; 
the  stylo-maxillary  ligament  is  attached  to  the  bone  between  these  muscles.  The 
anterior  border  is  thin  above,  thicker  below,  and  continuous  with  the  external 
oblique  line.  The  posterior  border  is  thick,  smooth,  rounded,  and  covered  by  the 
parotid  gland.  The  upper  border  of  the  ramus  is  thin,  and  presents  two  processes, 
separated  by  a  deep  concavity,  the  sigmoid  notch.  Of  these  processes,  the  anterior 
is  the  coronoid,  the  posterior  the  condyloid. 

The  Coronoid  Process  is  a  thin,  flattened,  triangular  eminence  of  bone,  which 
varies  in  shape  and  size  in  different  subjects,  and  serves  chiefly  for  the  attachment 
of  the  Temporal  muscle.  Its  external  surface  is  smooth,  and  affords  attachment 
to  the  Temporal  muscle.  Its  internal  surface  gives  attachment  to  the  Temporal 
muscle,  and  presents  the  commencement  of  a  longitudinal  ridge,  which  is  continued 
to  the  posterior  part  of  the  alveolar  process.  On  the  outer  side  of  this  ridge  is  a 
deep  groove,  continued  below  on  the  outer  side  of  the  alveolar  process  ;  this  ridge 
and  part  of  the  groove  afford  attachment,  above,  to  the  Temporal ;  below,  to  the 
Buccinator  muscle. 

The  Condyloid  Process,  shorter  but  thicker  than  the  coronoid,  consists  of  two 
portions:  the  condyle^  and  the  constricted  portion  which  supports  the  condyle,  the 
neck.  The  condyle  is  of  an  oblong  form,  its  long  axis  being  transverse,  and  set 
obliquely  on  the  neck  in  such  a  manner  that  its  outer  end  is  a  little  more  forward 
and  a  little  higher  than  its  inner.  It  is  convex  from  before  backward  and  from 
side  to  side,  the  articular  surface  extending  farther  on  the  posterior  than  on  the 
anterior  aspect.  The  neck  of  the  condyle  is  flattened  from  before  backward,  and 
strengthened  by  ridges  which  descend  from  the  fore  part  and  sides  of  the  condyle. 
Its  lateral  margins  are  narrow,  and  present  externally  a  tubercle  for  the  external 
lateral  ligament.  Its  posterior  surface  is  convex  ;  its  anterior  is  hollowed  out 
on  its  inner  side  by  a  depression  (the  pterygoid  fossa),  for  the  attachment  of  the 
External  pterygoid. 

The  Sigmoid  Notch,  separating  the  two  processes,  is  a  deep  semilunar  depres- 
sion, crossed  bv  the  masseteric  vessels  and  nerve. 

Development. — The  lower  jaw  is  developed  principally  from  membrane,  but 
partly  from  cartilage.  The  process  of  ossification  commences  early — before,  indeed, 
any  bone  except  the  clavicle.  Between  the  fifth  and  sixth  week  a  centre  of  ossi- 
fication appears  in  the  membrane  on  the  outer  surface  of  Meckel's  cartilage  (see 
page  118),  from  which  the  greater  part  of  the  bone  is  formed.  A  second  centre 
appears  in  the  membrane  on  the  inner  surface  of  the  tooth-sockets,  from  which  the 
inner  wall  of  the  sockets  of  the  teeth  is  formed  ;  this  terminates  above  in  the  lingula. 
The  anterior  extremity  of  Meckel's  cartilage  becomes  ossified,  forming  the  body 
of  the  bone  on  each  side  of  the  symphysis.  And,  finally,  two  supplemental  patches 
of  cartilage  appear  at  the  condyle  and  at  the  angle,  in  which  centres  of  ossification 
for  these  parts  appear.  At  birth  the  bone  consists  of  two  halves,  united  by  a 
fibrous  symphysis,  in  which  ossification  takes  place  during  the  first  year. 

Articulation. — With  the  glenoid  fossae  of  the  two  temporal  bones. 

Attachment  of  Muscles. — To  fifteen  pairs  :  to  its  external  surface,  commencing 
at  the  symphysis,  and  proceeding  backward:  Levator  menti,  Depressor  labii  infe- 
rioris,  Depressor  anguli  oris,  Platysma  myoides,  Buccinator,  Masseter ;  a  portion 
of  the  Orbicularis  oris  (Accessorii  orbicularis  inferioris)  is  also  attached  to  this 
surface.  To  its  internal  surface,  commencing  at  the  same  point :  Genio-hyo- 
glossus,  Genio-hyoideus,  Mylo-hyoideus,  Digastric,  Superior  constrictor,  Temporal, 
Internal  pterygoid,  External  pterygoid. 

CHANGES  PRODUCED  IN  THE  LOWER  JAW  BY  AGE. 

The  changes  which  the  lower  jaw  undergoes  after  birth  relate  ( 1 )  to  the  alterations  effected 
in  the  body  of  the  bone  by  the  first  and  second  dentitions,  the  loss  of  the  teeth  in  the  aged,  and 


THE  INFERIOR   MAXILLARY  BONE,  205 

SIDE  VIEW  OF  THE  LOWER  JAW  AT  DIFFERENT  PERIODS  OF  LIFE. 


FIG.  168.- At  birth. 


FIG.  171.— In  old  age. 


206  THE  SKELETON. 

the  subsequent  absorption  of  the  alveoli ;  (2)  to  the  size  and  situation  of  the  dental  canal;  and  (3) 
to  the  angle  at  which  the  ranms  joins  with  the  body. 

At  birth  (Fig.  168)  the  bone  consists  of  lateral  halves,  united  by  fibrous  tissue.  The  body 
is  a  mere  shell  of  bone,  containing  the  sockets  of  the  two  incisor,  the  canine,  and  the  two  tem- 
porary molar  teeth,  imperfectly  partitioned  from  one  another.  The  dental  canal  is  of  large  size, 
and  runs  near  the  lower  border  of  the  bone,  the  mental  foramen  opening  beneath  the  socket  of 
the  first  molar.  The  angle  is  obtuse  (175°),  and  the  condyloid  portion  nearly  in  the  same  hori- 
zontal line  with  the  body ;  the  neck  of  the  condyle  is  short,  and  bent  backward.  The  coronoid 
process  is  of  comparatively  large  size,  and  situated  at  right  angles  with  the  rest  of  the  bone. 

After  birth  (Fig.  169)  the  two  segments  of  the  bone  become  joined  at  the  symphysis,  from 
below  upward,  in  the  first  year ;  but  a  trace  of  separation  may  be  visible  in  the  beginning  of  the 
second  year  near  the  alveolar  margin.  The  body  becomes  elongated  in  its  whole  length,  but 
more  especially  behind  the  mental  foramen,  to  provide  space  for  the  three  additional  teeth 
developed  in  this  part.  The  depth  of  the  body  becomes  greater,  owing  to  increased  growth  of 
the  alveolar  part,  to  afford  room  for  the  fangs  of  the  teeth,  and  by  thickening  of  the  subdental 
portion,  which  enables  the  jaw  to  withstand  the  powerful  action  of  the  masticatory  muscles ;  but 
the  alveolar  portion  is  the  deeper  of  the  two,  and,  consequently,  the  chief  part  of  the  body  lies 
above  the  oblique  line.  The  dental  canal  after  the  second  dentition  is  situated  just  above  the 
level  of  the  mylo-hyoid  ridge,  and  the  mental  foramen  occupies  the  position  usual  to  it  in  the 
adult.  The  angle  becomes  less  obtuse,  owing  to  the  separation  of  the  jaws  by  the  teeth. 
(About  the  fourth  year  it  is  140°.) 

In  the  adult  (Fig.  170)  the  alveolar  and  basilar  portions  of  the  body  are  usually  of  equal 
depth.  The  mental  foramen  opens  midway  between  the  upper  and  lower  border  of  the  bone, 
and  the  dental  canal  runs  nearly  parallel  with  the  mylo-hyoid  line.  The  ramus  is  almost  vertical 
in  direction,  and  joins  the  body  nearly  at  right  angles. 

In  old  age  (Fig.  171)  the  bone  becomes  greatly  reduced  in  size;  for  with  the  loss  of  the 
teeth  the  alveolar  process  is  absorbed,  and  the  basilar  part  of  the  bone  alone  remains ;  conse- 
quently, the  chief  part  of  the  bone  is  beloio  the  oblique  line.  The  dental  canal,  with  the  mental 
foramen  opening  from  it,  is  close  to  the  alveolar  border.  The  rami  are  oblique  in  direction,  the 
angle  obtuse,  and  the  neck  of  the  condyle  more  or  less  bent  backward. 

The  Sutures. 

The  bones  of  the  cranium  and  face  are  connected  to  each  other  by  means  of 
Sutures.  That  is,  the  articulating  surfaces  or  edges  of  the  bones  are  more  or  less 
roughened  or  uneven,  and  are  closely  adapted  to  each  other,  a  small  amount  of 
intervening  fibrous  tissue  fastening  them  together.  The  Cranial  Sutures  may  be 
divided  into  three  sets  :  1.  Those  at  the  vertex  of  the  skull.  2.  Those  at  the  side 
of  the  skull.  3.  Those  at  the  base. 

The  sutures  at  the  vertex  of  the  skull  are  three :  the  sagittal,  coronal,  and 
lambdoid. 

The  Sagittal  Suture  (interparietal)  is  formed  by  the  junction  of  the  two  parietal 
bones,  and  extends  from  the  middle  of  the  frontal  bone  backward  to  the  superior 
angle  of  the  occipital.  In  childhood,  and  occasionally  in  the  adult,  when  the  two 
halves  of  the  frontal  bone  are  not  united,  it  is  continued  forward  to  the  root  of 
the  nose.  This  suture  is  sometimes  perforated,  near  its  posterior  extremity,  by 
the  parietal  foramen ;  and  in  front,  where  it  joins  the  coronal  suture,  a  space  is 
occasionally  left  which  encloses  a  large  Wormian  bone. 

The  Coronal  Suture  (fronto-parietafy  extends  transversely  across  the  vertex  of 
the  skull,  and  connects  the  frontal  with  the  parietal  bones.  It  commences  at  the 
extremity  of  the  greater  wing  of  the  sphenoid  on  one  side,  and  terminates  at  the 
same  point  on  the  opposite  side.  The  dentations  of  the  suture  are  more  marked 
at  the  sides  than  at  the  summit,  and  are  so  constructed  that  the  frontal  rests  on 
the  parietal  above,  whilst  laterally  the  frontal  supports  the  parietal. 

The  Lambdoid  Suture  (occipito-parietal],  so  called  from  its  resemblance  to  the 
Greek  letter  A,  connects  the  occipital  with  the  parietal  bones.  It  commences  on 
each  side  at  the  mastoid  portion  of  the  temporal  bone,  and  inclines  upward  to  the 
end  of  the  sagittal  suture.  The  dentations  of  this  suture  are  very  deep  and  dis- 
tinct, and  are  often  interrupted  by  several  small  Wormian  bones. 

The  sutures  at  the  side  of  the  skull  extend  from  the  external  angular  process 
of  the  frontal  bone  to  the  lower  end  of  the  lambdoid  suture  behind.  The  anterior 
portion  is  formed  between  the  lateral  part  of  the  frontal  bone  above  and  the  malar 
and  great  wing  of  the  sphenoid  below,  forming  the  fronto-malar  and  fronto- 


THE   SUTURES.  207 

$l>Jn-ii',i<lnl  sutures.  These  sutures  can  also  be  seen  in  the  orbit,  and  form  part  of 
the  so-called  t/-'i/<s>-'  /•<•  /•/-•/,//  suture.  The  posterior  portion  is  formed  between  the 
parietal  bone  above  and  the  great  wing  of  the  sphenoid,  the  squamous  and  mastoid 
portions  of  the  temporal  bone,  forming  the  spheno-parietaL  squamo-parietal.  and 

>'.'ta?  sutures. 

The  Spheno-parietal  is  very  short :  it  is  formed  by  the  tip  of  the  great  wing  of 
the  sphenoid,  which  overlaps  the  anterior  inferior  angle  of  the  parietal  bone. 

The  Squamo-parietal,  or  Squamous  Suture,  is  arched.  It  is  formed  by  the 
squamous  portion  of  the  temporal  bone  overlapping  the  middle  division  of  the 
lower  border  of  the  parietal. 

The  Masto-parietal  is  a  short  suture,  deeply  dentated.  formed  by  the  posterior 
inferior  angle  of  the  parietal  and  the  superior  border  of  the  mastoid  portion  of  the 
temporal. 

The  sutures  at  the  base  of  the  skull  are  the  basilar  in  the  centre,  and  on  each 
side  the  petro-occipital^  the  imisto-oecipitaL  the  petro-sphenoidal,  and  the  squamo- 
:  il. 

The  Basilar  Suture  is  formed  by  the  junction  of  the  basilar  surface  of  the 
occipital  bone  with  the  posterior  surface  of  the  body  of  the  sphenoid.  At  an  early 
period  of  life  a  thin  plate  of  cartilage  exists  between  these  bones,  but  in  the  adult 
they  become  fused  into  one.  Between  the  outer  extremity  of  the  basilar  suture 
and  the  termination  of  the  lambdoid  an  irregular  suture  exists,  which  is  subdivided 
into  two  portions.  The  inner  portion,  formed  by  the  union  of  the  petrous  part  of 
the  temporal  with  the  occipital  bone,  is  termed  the  petro-occipital.  The  outer 
portion,  formed  by  the  junction  of  the  mastoid  part  of  the  temporal  with  the 
occipital,  is  called  the  masto-occipital.  Between  the  bones  forming  the  petro- 
occipital  suture  a  thin  plate  of  cartilage  exists;  in  the  masto-occipital  is  occa- 
sionally found  the  opening  of  the  mastoid  foramen.  Between  the  outer  extremity 
of  the  basilar  suture  and  the  spheno-parietal  an  irregular  suture  may  be  seen, 
formed  by  the  union  of  the  sphenoid  with  the  temporal  bone.  The  inner  and 
smaller  portion  of  this  suture  is  termed  the  petro-sphenoidal ;  it  is  formed  between 
the  petrous  portion  of  the  temporal  and  the  great  wing  of  the  sphenoid :  the  outer 
portion,  of  greater  length  and  arched,  is  formed  between  the  squamous  portion 
of  the  temporal  and  the  great  wing  of  the  sphenoid ;  it  is  called  the  squamo- 
sphenoidal. 

The  cranial  bones  are  connected  with  those  of  the  face,  and  the  facial  bones 
with  each  other,  by  numerous  sutures,  which,  though  distinctly  marked,  have 
received  no  special  names.  The  only  remaining  suture  deserving  especial  con- 
sideration is  the  transverse.  This  extends  across  the  upper  part  of  the  face,  and 
is  formed  by  the  junction  of  the  frontal  with  the  facial  bones  :  it  extends  from  the 
external  angular  process  <>f  one  side  to  the  same  point  on  the  opposite  side,  and 
connects  the  frontal  with  the  malar,  the  sphenoid,  the  ethmoid,  the  lachrymal,  the 
superior  maxillary,  and  the  nasal  bones  on  each  side. 

The  sutures  remain  separate  for  a  considerable  period  after  the  complete  for- 
mation of  the  skull.  It  is  probable  that  they  serve  the  purpose  of  permitting  the 
growth  of  the  bones  at  their  margins,  while  their  peculiar  formation,  together 
with  the  interposition  of  the  sutural  ligament  between  the  bones  forming  them, 
prevents  the  dispersion  of  blows  or  jars  received  upon  the  skull.  Humphry 
remarks,  "  that,  as  a  general  rule,  the  sutures  are  first  obliterated  at  the  parts  in 
which  the  ossification  of  the  skull  was  last  completed — viz.  in  the  neighborhood 
of  the  fontanelles  :  and  the  cranial  bones  seem  in  this  respect  to  observe  a  similar 
law  to  that  which  regulates  the  union  of  the  epiphyses  to  the  shafts  of  the  long 
bon  The  same  author  remarks  that  the  time  of  their  disappearance  is 

extremely  variable :  they  are  sometimes  found  well  marked  in  skulls  edentulous 

with  age.  while  in  others  which  have  onlv  just  reached  maturitv  thev  can  hardly 

.    j  j 

be  traced. 


208  THE   SKELETON. 

THE  SKULL  AS  A  WHOLE. 

The  Skull,  formed  by  the  union  of  the  several  cranial  and  facial  bones  already 
described,  when  considered  as  a  whole  is  divisible  into  five  regions :  a  superior 
region  or  vertex,  an  inferior  region  or  base,  two  lateral  regions,  and  an  anterior 
region,  the  face. 

The  Vertex  of  the  Skull. 

The  Superior  Region,  or  Vertex,  presents  two  surfaces,  an  external  and  an 
internal. 

The  external  surface  is  bounded,  in  front,  by  the  glabella  and  supraorbital 
ridges ;  behind,  by  the  occipital  protuberance  and  superior  curved  lines  of  the 
occipital  bone ;  laterally,  by  an  imaginary  line  extending  from  the  outer  end  of 
the  superior  curved  line,  along  the  temporal  ridge,  to  the  external  angular  process 
of  the  frontal.  This  surface  includes  the  vertical  portion  of  the  frontal,  the 
greater  part  of  the  parietal,  and  the  superior  third  of  the  occipital  bone ;  it  is 
smooth,  convex,  of  an  elongated  oval  form,  crossed  transversely  by  the  coronal 
suture,  and  from  before  backward,  by  the  sagittal,  which  terminates  behind  in  the 
lambdoid.  The  point  of  junction  of  the  coronal  and  sagittal  sutures  is  named 
the  breffma,  and  is  represented  by  a  line  drawn  vertically  upward  from  the  exter- 
nal auditory  meatus,  the  head  being  in  its  normal  position.  The  point  of  junc- 
tion of  the  sagittal  and  lambdoid  sutures  is  called  the  lambda,  and  is  about  2|- 
inches  above  the  external  occipital  protuberance.  From  before  backward  may  be 
seen  the  frontal  eminences  and  remains  of  the  suture  connecting  the  two  lateral 
halves  of  the  frontal  bone ;  on  each  side  of  the  sagittal  suture  are  the  parietal 
foramen  and  parietal  eminence,  and  still  more  posteriorly  the  convex  surface  of 
the  occipital  bone.  In  the  neighborhood  of  the  parietal  foramen  the  skull  is  often 
flattened,  and  to  this  region  the  name  of  obelion  is  sometimes  -given. 

The  internal  surface  is  concave,  presents  eminences  and  depressions  for  the 
convolutions  of  the  cerebrum,  and  numerous  furrows  for  the  lodgment  of  branches 
of  the  meningeal  arteries.  Along  the  middle  line  of  this  surface  is  a  longitudinal 
groove,  narrow  in  front,  where  it  commences  at  the  frontal  crest,  but  broader 
behind,  where  it  lodges  the  superior  longitudinal  sinus,  and  by  its  margin  affords 
attachment  to  the  falx  cerebri.  On  either  side  of  it  are  several  depressions  for 
the  Pacchionian  bodies,  and  at  its  back  part  the  internal  openings  of  the  parietal 
foramina.  This  surface  is  crossed,  in  front,  by  the  coronal  suture ;  from  before 
backward  by  the  sagittal ;  behind,  by  the  lambdoid. 

The  Base  of  the  Skull. 

The  Inferior  Region,  or  Base  of  the  Skull,  presents  two  surfaces — an  internal 
or  cerebral,  and  an  external  or  basilar. 

The  internal  or  cerebral  surface  (Fig.  172)  presents  three  fossae,  called  the 
anterior,  middle,  and  posterior  fossae  of  the  cranium. 

The  Anterior  Fossa  is  formed  by  the  orbital  plates  of  the  frontal,  the  cribri- 
form plate  of  the  ethmoid,  the  anterior  third  of  the  superior  surface  of  the  body, 
and  the  upper  surface  of  the  lesser  wings  of  the  sphenoid.  It  is  the  most  elevated 
of  the  three  fossae,  convex  externally  where  it  corresponds  to  the  roof  of  the  orbit, 
concave  in  the  median  line  in  the  situation  of  the  cribriform  plate  of  the  ethmoid. 
It  is  traversed  by  three  sutures,  the  ethmo-frontal,  ethmo-sphenoidal,  and  fronto- 
sphenoidal,  and  lodges  the  frontal  lobe  of  the  cerebrum.  It  presents,  in  the 
median  line,  from  before  backward,  the  commencement  of  the  groove  for  the 
superior  longitudinal  sinus  and  the  frontal  crest  for  the  attachment  of  the  falx 
cerebri ;  the  foramen  ccecum,  an  aperture  formed  between  the  frontal  bone  and  the 
crista  galli  of  the  ethmoid,  which,  if  pervious,  transmits  a  small  vein  from  the  nose 
to  the  superior  longitudinal  sinus ;  behind  the  foramen  caecum,  the  crista  galli,  the 
posterior  margin  of  which  affords  attachment  to  the  falx  cerebri ;  on  either  side  of 
the  crista  galli,  the  olfactory  groove,  which  supports  the  bulb  of  the  olfactory 


THE   BASE    OF    THE   SKULL. 


209 


tract,  and  present.-  three  rows  of  foramina  for  its  filaments,  and  in  front  a  slit-like 
opening  for  the  nasal  branch  of  the  ophthalmic  division  of  the  fifth  nerve.     On 


Groove  for  superior  longitudinal  sinus. 

Grooves  for  anterior  meningeal  artery. 

Foramen  ca?c«m. 

Crista  galli. 

Sit  for  nasal  nerve. 

Groove  for  nasal  nerve. 

Anterior  ethmoidal  foramen. 

Orifices  fur  olfactory  nerves. 

Posterior  ethmoidal  foramen. 

Ethmoidal  spine. 


Olfactory  grooves. 

Optic  foramen.. 

Optic  groove. 

Olivary  process. 

Anterior  clinoid  process. 

Middle  clinoid  process. 

Posterior  clinoid  process. 

Groove  for  6th  nerve 

Foramen  lacerum  medium 

Orifice  of  .carotid  canal 

Depression  for  Gasserian  ganglion, 


Meatus  auditorium  interims. 

Slit  for  dura  mater. 

Superior  petrosal  groove. 

Foramen  lacerum  posterius. 

Anterior  condyloid  foramen.' 

Aquzductu*  restibuli. 

Posterior  condyloid  foramen. _ 


Mastoid  foramen. 
Posterior  meningeal  grooves. 


FIG.  172.— Base  of  the  skull.    Inner  or  cerebral  surface. 


the  outer  side  of  each  olfactory  groove  are  the  internal  openings  of  the  anterior  and 
posterior  ethmoidal  foramina  ;  the  former,  situated  about  the  middle  of  the  outer 
margin  of  the  olfactory  groove,  transmits  the  anterior  ethmoidal  vessels  and  the 
nasal  nerve,  which  latter  runs  in  a  depression  along  the  surface  of  the  ethmoid  to 

1  t 


14 


210  THE   SKELETON. 

the  slit-like  opening  above  mentioned ;  whilst  the  posterior  ethmoidal  foramen 
opens  at  the  back  part  of  this  margin  under  cover  of  the  projecting  lamina  of  the 
sphenoid,  and  transmits  the  posterior  ethmoidal  vessels.  Farther  back  in  the 
middle  line  is  the  ethmoidal  spine,  bounded  behind  by  an  elevated  ridge,  sepa- 
rating two  longitudinal  grooves  which  support  the  olfactory  tracts.  Behind  this 
is  a  transverse  sharp  ridge,  running  outward  on  either  side  to  the  anterior  margin 
of  the  optic  foramen,  and  separating  the  anterior  from  the  middle  fossa  of  the 
base  of  the  skull.  The  anterior  fossa  presents,  laterally,  eminences  and  depressions 
for  the  convolutions  of  the  brain  and  grooves  for  the  lodgment  of  the  anterior 
meningeal  arteries. 

The  Middle  Fossa,  somewhat  deeper  than  the  preceding,  is  narrow  in  the 
middle  line,  but  becomes  wider  at  the  side  of  the  skull.  It  is  bounded  in  front  by 
the  posterior  margin  of  the  lesser  wing  of  the  sphenoid,  the  anterior  clinoid  process, 
and  the  ridge  forming  the  anterior  margin  of  the  optic  groove  ;  behind,  by  the 
superior  border  of  the  petrous  portion  of  the  temporal  and  the  dorsum  ephippi ; 
externally  by  the  squamous  portion  of  the  temporal,  anterior  inferior  angle  of  the 
parietal  bone,  and  greater  wing  of  the  sphenoid.  It  is  traversed  by  four  sutures, 
the  squamo-parietal,  spheno-parietal,  squamo-sphenoidal,  and  petro-sphenoidal. 

In  the  middle  line,  from  before  backward,  is  the  optic  groove,  which  supports 
the  optic  commissure,  and  terminates  on  each  side  in  the  optic  foramen,  for 
the  passage  of  the  optic  nerve  and  ophthalmic  artery ;  behind  the  optic  groove 
is  the  olivary  process,  and  laterally  the  anterior  clinoid  2^ocesses,  to  which 
are  attached  processes  of  the  tentorium  cerebelli.  Farther  back  is  the  sella 
turcica,  a  deep  depression  which  lodges  the  pituitary  gland,  bounded  in  front 
by  a  small  eminence  on  either  side,  the  middle  clinoid  process,  and  behind  by  a 
broad  square  plate  of  bone,  the  dorsum  ephippi,  surmounted  at  each  superior 
angle  by  a  tubercle,  the  posterior  clinoid  process  ;  beneath  the  latter  process  is  a 
notch,  for  the  sixth  nerve.  On  each  side  of  the  sella  turcica  is  the  cavernous 
groove :  it  is  broad,  shallow,  and  curved  somewhat  like  the  italic  letter  /;  it 
commences  behind  at  the  foramen  lacerum  medium,  and  terminates  on  the  inner 
side  of  the  anterior  clinoid  process,  and  presents  along  its  outer  margin  a  ridge  of 
bone.  This  groove  lodges  the  cavernous  sinus,  the  internal  carotid  artery,  and 
the  nerves  of  the  orbit.  The  sides  of  the  middle  fossa  are  of  considerable  depth  ; 
they  present  eminences  and  depressions  for  the  convolutions  of  the  brain  and 
grooves  for  the  branches  of  the  middle  meningeal  artery  ;  the  latter  commence 
on  the  outer  side  of  the  foramen  spinosum,  and  consist  of  two  large  branches,  an 
anterior  and  a  posterior ;  the  former  passing  upward  and  forward  to  the  anterior 
inferior  angle  of  the  parietal  bone,  the  latter  passing  upward  and  backward. 
The  following  foramina  may  also  be  seen  from  before  backward :  Most  anteriorly 
is  the  foramen  lacerum  anterius,  or  sphenoidal  fissure,  formed  above  by  the  lesser 
wing  of  the  sphenoid ;  below,  by  the  greater  wing  ;  internally,  by  the  body  of  the 
sphenoid  ;  and  sometimes  completed  externally  by  the  orbital  plate  of  the  frontal 
bone.  It  transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic 
division  of  the  fifth,  the  sixth  nerve,  some  filaments  from  the  cavernous  plexus  of 
the  sympathetic,  the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent 
branch  from  the  lachrymal  artery  to  the  dura  mater,  and  the  ophthalmic  vein. 
Behind  the  inner  extremity  of  the  sphenoidal  fissure  is  the  foramen  rotundum,  for 
the  passage  of  the  second  division  of  the  fifth  or  superior  maxillary  nerve ;  still 
more  posteriorly  is  seen  a  small  orifice,  the  foramen  Vesalii,  an  opening  situated 
between  the  foramen  rotundum  and  ovale,  a  little  internal  to  both  :  it  varies  in  size 
in  different  individuals,  and  is  often  absent ;  when  present,  it  transmits  a  small  vein. 
It  opens  below  into  the  pterygoid  fossa,  just  at  the  outer  side  of  the  scaphoid 
depression.  Behind  and  external  to  the  latter  opening  is  the  foramen  ovale,  which 
transmits  the  third  division  of  the  fifth  or  inferior  maxillary  nerve,  the  small 
meningeal  artery,  and  the  small  petrosal  nerve.1  On  the  outer  side  of  the  foramen 
ovale  is  the  foramen  spinosum,  for  the  passage  of  the  middle  meningeal  artery  ;  and 

1  See  footnote,  p.  182. 


THE   BASE    OF    THE   SKULL.  211 

on  the  inner  side  of  the  foramen  ovale,  the  foramen  lacerum  medium.  This 
aperture  is  filled  up  with  fibrous  tissue  in  the  recent  state.  The  Yidian  nerve 
and  a  meningeal  branch  from  the  ascending  pharyngeal  artery  pierce  this 
cartilage.  On  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone  is 
seen,  from  without  inward,  the  eminence  caused  by  the  projection  of  the  superior 
semicircular  canal :  outside  this  a  depression  corresponding  to  the  roof  of  the 
tympanum :  the  groove  leading  to  the  hiatus  Fallopii,  for  the  transmission  of  the 
petrosal  branch  of  the  Yidian  nerve  and  the  petrosal  branch  of  the  middle 
meningeal  artery ;  beneath  it,  the  smaller  groove,  for  the  passage  of  the  lesser 
petrosal  nerve :  and.  near  the  apex  of  the  bone,  the  depression  for  the  Gasserian 
ganglion  :  and  the  orifice  of  the  carotid  canal,  for  the  passage  of  the  internal  carotid 
arterv  and  carotid  plexus  of  nerves. 

The  Posterior  Fossa,  deeply  concave,  is  the  largest  of  the  three,  and  situated 
on  a  lower  level  than  either  of  the  preceding.  It  is  formed  by  the  posterior  third 
of  the  superior  surface  of  the  body  of  the  sphenoid,  by  the  occipital,  the  petrous 
and  rnastoid  portions  of  the  temporal,  and  the  posterior  inferior  angle  of  the 
parietal  bone  :  it  is  crossed  by  four  sutures,  the  petro-occipital.  the  masto-occipital. 
the  rnasto-parietal.  and  the  basilar :  and  lodges  the  cerebellum,  pons  Yarolii,  and 
medulla  oblongata.  It  is  separated  from  the  middle  fossa  in  the  median  line  by 
the  dorsum  ephippii.  and  on  each  side  by  the  superior  border  of  the  petrous  portion 
of  the  temporal  bone.  This  border  serves  for  the  attachment  of  the  tentorium 
cerebelli.  is  grooved  for  the  superior  petrosal  sinus,  and  at  its  inner  extremity 
presents  a  notch,  upon  which  rests  the  fifth  nerve.  The  circumference  of  the 
fossa  is  bounded  posteriorly  by  the  grooves  for  the  lateral  sinuses.  In  the  centre 
of  this  fossa  is  thefor<i)/i>.-/i  magnum,  bounded  on  either  side  by  a  rough  tubercle, 
which  gives  attachment  to  the  odontoid  or  check  ligaments ;  and  a  little  above 
these  are  seen  the  internal  openings  of  the  anterior  condyloid  foramina,  through 
which  pass  the  hypoglossal  nerve  and  a  meningeal  branch  from  the  ascending 
pharvngeal  artery.  In  front  of  the  foramen  magnum  is  a  grooved  surface,  formed 
by  the  basilar  process  of  the  occipital  bone  and  by  the  posterior  third  of  the  superior 
surface  of  the  body  of  the  sphenoid,  which  supports  the  medulla  oblongata  and 
pons  Yarolii.  and  articulates  on  each  side  with  the  petrous  portion  of  the  temporal 
bone,  forming  the  petro-occipital  suture,  the  anterior  half  of  which  is  grooved  for 
the  inferior  petrosal  sinus,  the  posterior  half  being  encroached  upon  by  fae  foramen 

•im  pott. :•/•/'?/.•*.  or  jugular  foramen.  This  foramen  presents  three  compartments : 
through  the  anterior  passes  the  inferior  petrosal  sinus  :  through  the  posterior,  the 
lateral  sinus  and  some  meningeal  branches  from  the  occipital  and  ascending 
phai-yngeal  arteries :  and  through  the  middle,  the  glosso-pharyngeal,  pneumo- 
gastric,  and  spinal  accessory  nerves.  Above  the  jugular  foramen  is  the  internal 
awl.itorii  in  cat  n*.  for  the  facial  and  auditory  nerves  and  auditory  artery;  behind 
and  external  to  this  is  the  slit-like  opening  leading  into  the  aquaeductus'vestibuli ; 
whilst  between  the  two  latter,  and  near  the  superior  border  of  the  petrous  portion, 

-mall,  triangular  depression  which  lodges  a  process  of  the  dura  mater  and 
occasionally  transmits  a  small  vein  into  the  substance  of  the  bone.  Behind  the 
foramen  magnum  are  the  inferior  occipital  rV/.?.*,/-.  which  lodge  the  hemispheres  of 
the  cerebellum,  separated  from  one  another  by  the  internal  occipital  .crest,  which 
serves  for  the  attachment  of  the  falx  cerebelli  and  lodges  the  occipital  sinus.  The 
3£e  are  surmounted,  above,  by  the  deep  transverse  grooves  for  the 
lodgment  of  the  lateral  sinuses.  These  channels,  in  their  passage  outward, 
groove  the  occipital  bone,  the  posterior  inferior  angle  of  the  parietal,  the  rnastoid 
portion  of  the  temporal,  and  the  jugular  process  of  the  occipital,  and  terminate  at 
the  back  part  of  the  jugular  foramen.  Where  this  sinus  grooves  the  mastoid  portion 
of  the  temporal  bone  the  orifice  of  the  mastoid  foramen  may  be  seen,  and  just 
previous  to  its  termination  it  has  opening  into  it  the  posterior  condyloid  foramen. 
Neither  foramen  is  constant. 

The  External  Surface  of  the  Base  of  the  Skull  (Fig.  173)  is  extremely  irregular. 
It  is  bounded  in  front  by  the  incisor  teeth  in  the  upper  jaws ;   behind  by   the 


212 


THE  SKELETON. 


Anterior  palatine  fossa. 

Transmits  left  naso-palutine  nerve 
Transmits  anterior  palatine  vessel. 
Transmits  right  naso-palatine  nerve 


Accessory  palatine  foramina. 
Posterior  nasal  spine. 

AZYGOS    UVUL/E. 

Hamular  process. 


Sphenoid  process  of  palate 
Pterygo-palatine  canal. 


-TENSOR    TYMPANI. 

Pharyngeal  spine  for 

SUPERIOR    CONSTRICTOR. 

^Situation  of  Eustacliian  tube  anil 
canal  for  TENSOR  TYMPANI. 

TENSOR    PALATI. 

Canal  for  Jacobson'n  nerve. 
^Aquasductus  cochlese. 
Foramen  lacenim  posterius. 
Canal  for  Arnold's  nerve. 
Auricular  fissure. 


FIG.  173.— Base  of  the  skull.    External  surface. 


superior  curved  lines  of  the  occipital  bone;  and  laterally  by  the  alveolar  arch,  the 
lower  border  of  the  malar  bone,  the  zygoma,  and  an  imaginary  line  extending 
from  the  zygoma  to  the  mastoid  process  and  extremity  of  the  superior  curved  line 


THE   BASE    OF    THE   SKULL.  213 

of  the  occiput.  It  is  formed  by  the  palate  processes  of  the  superior  maxillary  and 
palate  bones,  the  vomer,  the  pterygoid  processes,  under  surface  of  the  great  wing, 
spiuous  processes  and  part  of  the  body  of  the  sphenoid,  the  under  surface  of  the 
squamous.  mastoid.  and  petrous  portions  of  the  temporal,  and  the  under  surface 
of  the  occipital  bone.  The  anterior  part  of  the  base  of  the  skull  is  raised  above 
the  level  of  the  rest  of  this  surface  (when  the  skull  is  turned  over  for  the  purpose 
of  examination),  surrounded  by  the  alveolar  process,  which  is  thicker  behind  than 
in  front,  and  excavated  by  sixteen  depressions  for  lodging  the  teeth  of  the  upper 
jaw.  the  cavities  varying  in  depth  and  size  according  to  the  teeth  they  contain. 
Immediately  behind  the  incisor  teeth  is  the  anterior  palatine  fossa.  At  the  bottom 
of  this  fossa  may  usually  be  seen  four  apertures :  two  placed  laterally,  the  foramina 

^''•//.""/i.  which  open  above,  one  in  the  floor  of  each  nostril,  and  transmit  the 
anterior  branch  of  the  posterior  palatine  vessels,  and  two  in  the  median  line  in 
the  intermaxillary  suture,  the  foramina,  of  Searpa,  one  in  front  of  the  other,  the 
anterior  transmitting  the  left,  and  the  posterior  (the  larger)  the  right,  naso-palatine 
nerve.  These  two  latter  canals  are  sometimes  wanting,  or  they  may  join  to  form 
a  single  one,  or  one  of  them  may  open  into  one  of  the  lateral  canals  above  referred 
to.  The  palatine  vault  is  concave,  uneven,  perforated  by  numerous  foramina, 
marked  by  depressions  for  the  palatine  glands,  and  crossed  by  a  crucial  suture, 
formed  by  the  junction  of  the  four  bones  of  which  it  is  composed.  At  the  front 
part  of  this  surface  a  delicate  linear  suture  may  frequently  be  seen,  marking  off 
the  pre-maxillary  portion  of  the  bone.  One  or  two  small  foramina  in  the  alveolar 
margin  behind  the  incisor  teeth,  occasionally  seen  in  the  adult,  almost  constantly  in 
young  subjects,  are  called  the  incisive  foramina  :  they  transmit  nerves  and  vessels 
to  the  incisor  teeth.  At  each  posterior  angle  of  the  hard  palate  is  the  posterior 
palatine  f"i-<i a"  n.  for  the  transmission  of  the  posterior  palatine  vessels  and  large 
descending  palatine  nerve;  and  running  forward  and  inward  from  it  a  groove,  for 
the  same  vessels  and  nerve.  Behind  the  posterior  palatine  foramen  is  the  tuberosity 
of  the  palite  bone,  perforated  by  one  or  more  accessory  posterior  palatine  canals, 
and  marked  by  the  commencement  of  a  ridge,  which  runs  transversely  inward,  and 
serves  for  the  attachment  of  the  tendinous  expansion  of  the  Tensor  palati  muscle. 
Projecting  backward  from  the  centre  of  the  posterior  border  of  the  hard  ]  alate  is 
the  post-  '/  spine,  for  the  attachment  of  the  Azygos  uvulae.  Behind  and 

above  the  hard  palate  is  the  posterior  aperture  of  the  nares,  divided  into  two  parts 
by  the  vomer,  bounded  above  by  the  body  of  the  sphenoid,  below  by  the  horizontal 
plate  of  the  palate  bone,  and  laterally  by  the  pterygoid  processes  of  the  sphenoid. 
Each  aperture  measures  about  an  inch  and  a  quarter  in  the  vertical  and  about 
half  an  inch  in  the  transverse  direction.  At  the  base  of  the  vomer  may  be  seen 
the  expanded  alre  of  this  bone,  receiving  between  them  the  rostrum  of  the  sphenoid. 
Xear  the  lateral  margins  of  the  vomer.  at  the  root  of  the  pterygoid  processes,  are 
the  pterygo-palatine  canals.  The  pterygoid  process,  which  bounds  the  posterior 
nares  on  each  side,  presents  near  its  base  the  pterygoid  or  Vidian  canal,  for  the 
A  idian  nerve  and  artery.  Each  process  consists  of  two  plates,  which  bifurcate  at 
the  extremity  to  receive  the  tuberosity  of  the  ]  alate  bone,  and  are  separated  behind 
by  the  pterygoid  fossa,  which  lodges  the  Internal  pterygoid  muscle.  The  internal 
plate  is  long  and  narrow,  presenting  on  the  outer  side  of  its  base  the  scaphoid  fossa, 
for  the  origin  of  the  Tensor  palati  muscle,  and  at  its  extremity  the  ha  mular  process, 
around  which  the  tendon  of  this  muscle  turns.  The  external  pterygoid  plate  is 
broad,  forms  the  inner  boundary  of  the  zygomatic  fossa,  and  affords  attachment  by 
its  outer  surface  to  the  External  pterygoid  muscle. 

Behind  the  nasal  t<>ss;e  in  the  middle  line  is  the  basilar  surface  of  the  occipital 
bone,  presenting  in  its  centre  the  pharyngeal  spine,  for  the  attachment  of  the 
Superior  constrictor  muscle  of  the  pharynx,  with  depressions  on  each  side  for 
the  insertion  of  the  Rectus  capitis  anticus  major  and  minor.  At  the  base  of  the 
external  pterygoid  plate  is  the  /•>/•<///<••/«  ovale ;  behind  this,  the  foramen  spinosntn 
and  the  prominent  spinous  process  of  the  sphenoid,  which  gives  attachment  to  the 
internal  lateral  ligament  of  the  lower  jaw  and  the  Tensor  palati  muscle.  External 


214  THE  SKELETON. 

to  the  spinous  process  is  the  glenoid  fossa,  divided  into  two  parts  by  the  Glaserian 
fissure  (page  176),  the  anterior  portion  concave,  smooth,  bounded  in  front  by  the 
eminentia  articularis,  and  serving  for  the  articulation  of  the  condyle  of  the  lower 
jaw ;  the  posterior  portion  rough,  bounded  behind  by  the  tympanic  plate,  and 
serving  for  the  reception  of  part  of  the  parotid  gland.  Emerging  from  between  the 
laminae  of  the  vaginal  process  of  the  tympanic  plate  is  the  styloid  process,  and  at 
the  base  of  this  process  is  the  stylo-mastoid  foramen,  for  the  exit  of  the  facial  nerve 
and  entrance  of  the  stylo-mastoid  artery.  External  to  the  stylo-mastoid  foramen  is 
the  auricular  fissure,  for  the  auricular  branch  of  the  pneumogastric,  bounded  behind 
by  the  mastoid  process.  Upon  the  inner  side  of  the  mastoid  process  is  a  deep 
groove,  the  digastric  fossa  ;  and  a  little  more  internally  the  occipital  groove,  for  the 
occipital  artery.  At  the  base  of  the  internal  pterygoid  plate  is  a  large  and  somewhat 
triangular  aperture,  the  foramen  lacerum  medium,  bounded  in  front  by  the  great 
wing  of  the  sphenoid,  behind  by  the  apex  of  the  petrous  portion  of  the  temporal 
bone,  and  internally  by  the  body  of  the  sphenoid  and  basilar  process  of  the 
occipital  bone :  it  presents  in  front  the  posterior  orifice  of  the  Vidian  canal ; 
behind,  the  aperture  of  the  carotid  canal.  The  basilar  surface  of  this  opening 
is  filled  up  in  the  recent  state  by  fibrous  tissue ;  across  its  upper  or  cerebral 
aspect  pass  the  internal  carotid  artery  and  Vidian  nerve.  External  to  this  aperture 
the  petro-sphenoidal  suture  is  observed,  at  the  outer  termination  of  which  is  seen 
the  orifice  of  the  canal  for  the  Eustachian  tube  and  that  for  the  Tensor  tympani 
muscle.  Behind  this  suture  is  seen  the  under  surface  of  the  petrous  portion  of 
the  temporal  bone,  presenting,  from  within  outward  the  quadrilateral,  rough 
surface,  part  of  which  affords  attachment  to  the  Levator  palati  and  Tensor  tympani 
muscles ;  external  to  this  surface  the  orifices  of  the  carotid  canal  and  the  aquse- 
ductus  cochleae,  the  former  transmitting  the  internal  carotid  artery  and  the  ascend- 
ing branches  of  the  superior  cervical  ganglion  of  the  sympathetic,  the  latter  serving 
for  the  passage  of  a  small  artery  and  vein  to  the  cochlea.  Behind  the  carotid 
canal  is  a  large  aperture,  the  jugular  fossa,  formed  in  front  by  the  petrous  portion 
of  the  temporal,  and  behind  by  the  occipital ;  it  is  generally  larger  on  the  right 
than  on  the  left  side,  and  is  divided  into  three  compartments  by  processes  of  dura 
mater.  The  anterior  is  for  the  passage  of  the  inferior  petrosal  sinus  ;  the  posterior, 
for  the  lateral  sinus  and  some  meningeal  branches  from  the  occipital  and  ascending 
pharyngeal  arteries ;  the  central  one,  for  the  glosso-pharyngeal,  pneumogastric, 
and  spinal  accessory  nerves.  On  the  ridge  of  bone  dividing  the  carotid  canal  from 
the  jugular  fossa  is  the  small  foramen  for  the  transmission  of  Jacobson's  nerve; 
and  on  the  outer  wall  of  the  jugular  foramen,  near  the  root  of  the  styloid  process, 
is  the  small  aperture  for  the  transmission  of  Arnold's  nerve.  Behind  the  basilar 
surface  of  the  occipital  bone  is  the  foramen  magnum,  bounded  on  each  side  by  the 
condyles,  rough  internally  for  the  attachment  of  the  cheek  or  odontoid  ligaments, 
and  presenting  externally  a  rough  surface,  the  jugular  process,  which  serves  for 
the  attachment  of  the  Rectus  capitis  lateralis  muscle  and  the  lateral  occipito-atloid 
ligament.  On  either  side  of  each  condyle  anteriorly  is  the  anterior  condyloid  fossa, 
perforated  by  the  anterior  condyloid  foramen,  for  the  passage  of  the  hypoglossal 
nerve  and  a  meningeal  artery.  Behind  each  condyle  is  the  posterior  condyloid 
fossa,  perforated  on  one  or  both  sides  by  the  posterior  condyloid  foramina,  for  the 
transmission  of  a  vein  to  the  lateral  sinus.  Behind  the  foramen  magnum  is  the 
external  occipital  crest,  terminating  above  at  the  external  occipital  protuberance, 
whilst  on  each  side  are  seen  the  superior  and  inferior  curved  lines  ;  these,  as  well 
as  the  surfaces  of  bone  between  them,  are  rough  for  the  attachment  of  the  muscles, 
which  are  enumerated  on  page  168. 

The  Lateral  Region  of  the  Skull. 

The  Lateral  Region  of  the  Skull  is  of  a  somewhat  triangular  form,  the  base  of 
the  triangle  being  formed  by  a  line  extending  from  the  external  angular  process 
of  the  frontal  bone  along  the  temporal  ridge  backward  to  the  outer  extremity  of 


THE    TEMPORAL    FOSSA. 


215 


the  superior  curved  line  of  the  occiput :  and  the  sides  by  two  lines,  the  one  drawn 
downward  and  backward  from  the  external  angular  process  of  the  frontal  bone 
to  the  angle  of  the  lower  jaw,  the  other  from  the  angle  of  the  jaw  upward  and 


Oc( 


d  V 


FIG.  174.— Side  view  of  the  skull. 


backward   to  the  outer  extremity  of  the  superior  curved  line.     This  region  is 
divisible  into  three  portions — temporal  fossa,  mastoid  portion,  and  zygomatic  fossa. 

The  Temporal  Fossa. 

The  Temporal  Fossa  is  bounded  above  and  behind  by  the  temporal  ridge,  which 
extends  from  the  external  angular  process  of  the  frontal  upward  and  backward 
across  the  frontal  and  parietal  bones,  curving  downward  behind  to  terminate  in 
the  posterior  root  of  the  zygomatic  process.  This  ridge  is  generally  double — at  all 
events  in  front,  where  it  is  most  marked.  In  front  it  is  bounded  by  the  frontal, 
malar,  and  great  wing  of  the  sphenoid :  externally  by  the  zygomatic  arch  formed 
conjoin tlv  by  the  malar  and  temporal  bones;  below  it  is  separated  from  the 
made  fossa  by  the  pterygoid  ridge,  seen  on  the  outer  surface  of  the  great 
wing  of  the  sphenoid.  This  fossa  is  formed  by  five  bones,  part  of  the  frontal, 
great  wing  of  the  sphenoid,  parietal,  squamous  portion  of  the  temporal,  and  malar 
bones,  and  is  traversed  by  six  sutures,  part  of  the  transverse  facial,  spheno- 
malpa\  coronal,  spheno-parietal.  squamo-parietal.  and  squamo-sphenoidal.  The 
point  where  the  coronal  suture  crosses  the  temporal  ridge  is  sometimes  named 
the  gtephanion  :  and  the  region  where  the  four  bones,  the  parietal,  the  frontal,  the 
s<iuamous.  and  the  gi-eater  wing  of  the  sphenoid,  meet,  at  the  anterior  inferior  angle 
of  the  parietal  bone,  is  named  the  pterion.  This  point  is  about  on  a  level  with  the 


216  THE  SKELETON. 

external  angular  process  of  the  frontal  bone  and  about  one  and  a  half  inches  behind 
it.  This  fossa  is  deeply  concave  in  front,  convex  behind,  traversed  by  grooves  which 
lodge  branches  of  the  deep  temporal  arteries,  and  filled  by  the  Temporal  muscles. 

The  Mastoid  Portion. 

The  Mastoid  Portion  of  the  side  of  the  skull  is  bounded  in  front  by  the  tubercle 
of  the  zygoma ;  above,  by  a  line  which  runs  from  the  posterior  root  of  the  zygoma 
to  the  end  of  the  masto-parietal  suture ;  behind  and  below  by  the  masto-occipital 
suture.  It  is  formed  by  the  mastoid  and  part  of  the  squamous  and  petrous  por- 
tions of  the  temporal  bone  ;  its  surface  is  convex  and  rough  for  the  attachment  of 
muscles,  and  presents,  from  behind  forward,  the  mastoid  foramen,  the  mastoid 
process,  the  external  auditory  mea^us  surrounded  by  the  auditory  process,  and, 
most  anteriorly,  the  temporo-maxillary  articulation. 

The  Zygomatic  Fossa. 

The  Zygomatic  Fossa  is  an  irregularly  shaped  cavity,  situated  below  and  on  the 
inner  side  of  the  zygoma ;  bounded,  in  front,  by  the  tuberosity  of  the  superior 
maxillary  bone  and  the  ridge  which  descends  from  its  malar  process ;  behind,  by 
the  posterior  border  of  the  pterygoid  process  and  the  eminentia  artlcularis  ;  above, 
by  the  pterygoid  ridge  on  the  outer  surface  of  the  great  wing  of  the  sphenoid  and 
the  under  part  of  the  squamous  portion  of  the  temporal ;  below,  by  the  alveolar 
border  of  the  superior  maxilla ;  internally,  by  the  external  pterygoid  plate ;  and 
externally,  by  the  zygomatic  arch  and  ramus  of  the  lower  jaw.  It  contains  the 
lower  part  of  the  Temporal,  the  External  and  Internal  pterygoid  muscles,  the 
internal  maxillary  artery,  and  inferior  maxillary  nerve  and  their  branches.  At  its 
upper  and  inner  part  may  be  observed  two  fissures,  the  spheno-maxillary  and 
pterygo-maxillary. 

The  Spheno-maxillary  Fissure,  horizontal  in  direction,  opens  into  the  outer  and 
back  part  of  the  orbit.  It  is  formed  above  by  the  lower  border  of  the  orbital  surface 
of  the  great  wing  of  the  sphenoid;  below,  by  the  external  border  of  the  orbital 
surface  of  the  superior  maxilla  and  a  small  part  of  the  palate  bone ;  externally,  by 
a  small  part  of  the  malar  bone:1  internally,  it  joins  at  right  angles  with  the 
pterygo-maxillary  fissure.  This  fissure  opens  a  communication  from  the  orbit  into 
three  fossae — the  temporal,  zygomatic,  and  spheno-maxillary ;  it  transmits  the 
superior  maxillary  nerve  and  its  orbital  branch,  the  infraorbital  vessels,  and 
ascending  branches  from  the  spheno-palatine  or  Meckel's  ganglion. 

The  Pterygo-maxillary  Fissure  is  vertical,  and  descends  at  right  angles  from 
the  inner  extremity  of  the  preceding ;  it  is  a  V-shaped  interval,  formed  by 
the  divergence  of  the  superior  maxillary  bone  from  the  pterygoid  process  of  the 
sphenoid.  It  serves  to  connect  the  spheno-maxillary  fossa  with  the  zygomatic  fossa, 
and  transmits  branches  of  the  internal  maxillary  artery.  It  forms  the  entrance  from 
the  zygomatic  fossa  to  the  spheno-maxillary  fossa. 

The  Spheno-maxillary  Fossa. 

The  Spheno-maxillary  Fossa  is  a  small,  triangular  space  situated  at  the  angle  of 
junction  of  the  spheno-maxillary  and  pterygo-maxillary  fissures,  and  placed  beneath 
the  apex  of  the  orbit.  It  is  formed  above  by  the  under  surface  of  the  body  of 
the  sphenoid  and  by  the  orbital  process  of  the  palate  bone ;  in  front,  by  the  superior 
maxillary  bone ;  behind,  by  the  anterior  surface  of  the  base  of  the  pterygoid 
process  and  lower  part  of  the  anterior  surface  of  the  great  wing  of  the  sphenoid ; 
internally,  by  the  vertical  plate  of  the  palate.  This  fossa  has  three  fissures 
terminating  in  it — the  sphenoidal,  spheno-maxillary,  and  pterygo-maxillary ;  it 
communicates  with  three  fossae,  the  orbital,  nasal,  and  zygomatic,  and  with  the 
cavity  of  the  cranium,  and  has  opening  into  it  five  foramina.  Of  these,  there  are 

1  Occasionally  the  superior  maxillary  bone  and  the  sphenoid  articulate  with  each  other  at  the 
anterior  extremity  of  this  fissure ;  the  malar  is  then  excluded  from  entering  into  its  formation. 


THE   ANTERIOR    REGION   OF    THE   SKULL.  217 

three  on  the  posterior  wall:  the  foramen  rotund  urn  above:  below  and  internal  to 
this,  the  1'idian  :  and  still  more  inferiorly  and  internally,  \hepterygo-palatine.  On 
the  inner  wall  is  the  spheno-palatine  foramen,  by  which  the  spheno-maxillary 
couiniunicates  with  the  nasal  fossa :  and  below  is  the  superior  orifice  of  the 
posterior  palatine  canal,  besides  occasionally  the  orifices  of  the  accessory  posterior 
palatine  canals.  The  fossa  contains  the  superior  maxillary  nerve  and  Meckel's 
ganglion,  and  the  termination  of  the  internal  maxillary  artery. 

The  Anterior  Region  of  the  Skull. 

The  Anterior  Region  of  the  Skull,  which  forms  the  face,  is  of  an  oval  form, 
presents  an  irregular  surface,  and  is  excavated  for  the  reception  of  two  of  the 
organs  of  sense,  the  eye  and  the  nose.  It  is  bounded  above  by  the  glabella  and 
margins  of  the  orbit ;  below,  by  the  prominence  of  the  chin ;  on  each  side  by  the 
malar  bone  and  anrerior  margin  of  the  ramus  of  the  jaw.  In  the  median  line  are 
seen  from  above  downward  the  glabella.  and  diverging  from  it  are  the  superciliary 
ridges,  which  indicate  the  situation  of  the  frontal  sinuses  and  support  the  eyebrows. 
Beneath  the  glabella  is  the  fronto-nasal  suture,  the  mid-point  of  which  is  termed 
the  nasion.  and  below  this  is  the  arch  of  the  nose,  formed  by  the  nasal  bones,  and 
the  nasal  processes  of  the  superior  maxillary.  The  nasal  arch  is  convex  from  side 
to  side,  concave  from  above  downward,  presenting  in  the  median  line  the  inter- 
nasal  suture  formed  between  the  nasal  bones,  laterally  the  naso-maxillary  suture 
formed  between  the  nasal  bone  and  the  nasal  process  of  the  superior  maxillary 
bone.  Below  the  nose  is  seen  the  opening  of  the  anterior  nares,  which  is  heart- 
shaped,  with  the  narrow  end  upward,  and  presents  laterally  the  thin,  sharp 
margins  serving  for  the  attachment  of  the  lateral  cartilages  of  the  nose,  and  in  the 
middle  line  below  a  prominent  process,  the  anterior  nasal  spine,  bounded  by  two 
deep  notches.  Below  this  is  the  intermaxillaru  suture,  and  on  each  side  of  it  the 
incisive  fossa.  Beneath  this  fossa  are  the  alveolar  processes  of  the  upper  and 
lower  jaws,  containing  the  incisor  teeth,  and  at  the  lower  part  of  the  median  line 
the  symphysu  of  the  chin,  the  mental  process,  with  its  two  mental  tubercles, 
separated  by  a  median  groove,  and  the  incisive  fossa  of  the  lower  jaw. 

On  each  side,  proceeding  from  above  downward,  is  the  supraorbital  ridge, 
terminating  externally  in  the  external  angular  process  at  its  junction  with  the 
malar,  and  internally  in  the  internal  angular  process:  toward  the  inner  third  of 
this  ridge  is  the  supraorbital  notch  or  foramen,  for  the  passage  of  the  supraorbital 
Is  and  nerve,  and  at  its  inner  side  a  slight  depression,  for  the  attachment  of 
the  pulley  of  the  Superior  oblique  muscle.  Beneath  the  supraorbital  ridge  is  the 
opening  of  the  orbit,  bounded  externally  by  the  orbital  ridge  of  the  malar  bone ; 
below,  by  the  orbital  ridge  formed  by  the  malar  and  nasal  process  of  superior  max- 
illary :  internally,  by  the  nasal  process  of  the  superior  maxillary  and  the  internal 
angular  process  of  the  frontal  bone.  On  the  outer  side  of  the  orbit  is  the  quadri- 
lareval  anterior  surface  of  the  malar  bone,  perforated  by  one  or  two  small  malar 
foramina.  Below  the  inferior  margin  of  the  orbit  is  the  infraorbital  foramen,  the 
termination  of  the  infraorbital  canal,  and  beneath  this  the  canine  fossa,  which  gives 
attachment  to  the  Levator  anguli  oris ;  bounded  below  by  the  alveolar  processes, 
containing  the  teeth  of  the  upper  and  lower  jaws.  Beneath  the  alveolar  arch  of 
the  lower  jaw  is  the  mental  foramen,  for  the  passage  of  the  mental  vessels  and 
nerve,  the  external  oblique  line,  and  at  the  lower  border  of  the  bone,  at  the  point 
of  junction  of  the  body  with  the  ramus,  a  shallow  groove  for  the  passage  of  the 
facial  artery. 

The  Orbits. 

The  Orbits  (Fig.  175)  are  two  quadrilateral  pyramidal  cavities,  situated  at  the 
upper  and  anterior  part  of  the  face,  their  bases  being  directed  forward  and 
outward,  and  their  apices  backward  and  inward,  so  that  the  axes  of  the  two.  if 
continued  backward,  would  meet  over  the  body  of  the  sphenoid  bone.  Each  orbit 
is  formed  of  seven  bones,  the  frontal,  sphenoid,  ethmoid,  superior  maxillary,  malar. 


218 


THE   SKELETON. 


lachrymal,  and  palate ;  but  three  of  these,  the  frontal,  ethmoid,  and  sphenoid, 
enter  into  the  formation  of  both  orbits,  so  that  the  two  cavities  are  formed  of 
eleven  bones  only.  Each  cavity  presents  for  examination  a  roof,  a  floor,  an  inner 
and  an  outer  wall,  four  angles,  a  circumference  or  base,  and  an  apex.  The  roof 
is  concave,  directed  downward  and  forward,  and  formed  in  front  by  the  orbital 
plate  of  the  frontal ;  behind  by  the  lesser  wing  of  the  sphenoid.  This  surface 
presents  internally  the  depression  for  the  cartilaginous  pulley  of  the  Superior 
oblique  muscle ;  externally,  the  depression  for  the  lachrymal  gland ;  and 
posteriorly,  the  suture  connecting  the  frontal  and  lesser  wing  of  the  sphenoid. 


TENDO  OCUU 


Groove  for 
facial  artery 


FIG.  175.—  Antero-lateral  region  of  the  skull.    (Cryer.) 

The  floor  is  nearly  flat,  and  of  less  extent  than  the  roof;  it  is  formed  chiefly 
by  the  orbital  surface  of  the  superior  maxillary ;  in  front,  to  a  small  extent,  by  the 
orbital  process  of  the  malar,  and  behind,  by  the  superior  surface  of  the  orbital 
process  of  the  palate.  This  surface  presents  at  its  anterior  and  internal  part,  just 
external  to  the  lachrymal  groove,  a  depression  for  the  attachment  of  the  Inferior 
oblique  muscle ;  externally,  the  suture  between  the  malar  and  superior  maxillary 
bones  ;  near  its  middle,  the  infraorbital  groove ;  and  posteriorly,  the  suture  between 
the  maxillary  and  palate  bones. 

The  inner  wall  is  flattened,  and  formed  from  before  backward  by  the  nasal 
process  of  the  superior  maxillary,  the  lachrymal,  os  planum  of  the  ethmoid,  and  a 
small  part  of  the  body  of  the  sphenoid.  This  surface  presents  the  lachrymal 
groove  and  crest  of  the  lachrymal  bone,  and  the  sutures  connecting  the  lachrymal 


THE   AXTERIOR    REGION   OF    THE   SKULL.  219 

with  the  superior  maxillary,  the  ethmoid  with  the  lachrymal  in  front,  and  the 
ethmoid  with  the  sphenoid  behind. 

The  outer  wall  is  formed  in  front  by  the  orbital  process  of  the  malar  bone ; 
behind,  by  the  orbital  surface  of  the  sphenoid.  On  it  are  seen  the  orifices  of  one 
or  two  malar  canals,  and  the  suture  connecting  the  sphenoid  and  malar  bones. 

Angles. — The  superior  external  angle  is  formed  by  the  junction  of  the  upper 
and  outer  walls :  it  presents,  from  before  backward,  the  suture  connecting  the 
frontal  with  the  malar  in  front  and  with  the  great  wing  of  the  sphenoid  behind : 
quite  posteriorly  is  the  foramen  lacerum  anterius,  or  sphenoidal  fissure,  which 
transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic  division  of 
the  fifth,  the  sixth  nerve,  some  filaments  from  the  cavernous  plexus  of  the  sym- 
pathetic, the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent  branch 
from  the  lachrymal  artery  to  the  dura  mater,  and  the  ophthalmic  vein.  The 
•  nt'-rnal  angle  is  formed  by  the  junction  of  the  upper  and  inner  Avail,  and 
presents  the  suture  connecting  the  frontal  bone  with  the  lachrymal  in  front  and 
with  the  ethmoid  behind.  The  point  of  junction  of  these  three  sutures  has  been 
named  the  dacryon.  This  angle  presents  two  foramina,  the  anterior  and  posterior 
ethrnoidal.  the  former  transmitting  the  anterior  ethmoidal  vessels  and  nasal  nerve, 
the  latter  the  posterior  ethmoidal  vessels.  The  inferior  external  angle,  formed 
by  the  junction  of  the  outer  wall  and  floor,  presents  the  spheno-maxillary  fissure, 
which  transmits  the  superior  maxillary  nerve  and  its  orbital  branches,  the  infra- 
orbital  vessels,  and  the  ascending  branches  from  the  spheno-palatine  or  Meek  el's 
ganglion.  The  inferior  internal  <///<//.  is  formed  by  the  union  of  the  lachrymal 
and  os  planum  of  the  ethmoid  with  the  superior  maxillary  and  palate  bones. 
The  '•//•<•</>/'/'/••//••.  or  base,  of  the  orbit,  quadrilateral  in  form,  is  bounded  above 
by  the  supraorbital  ridge ;  below,  by  the  anterior  border  of  the  orbital  plate  of 
the  malar,  superior  maxillary,  and  its  nasal  process ;  externally,  by  the  external 
angular  process  of  the  frontal  and  the  malar  bones ;  internally,  by  the  internal 
angular  process  of  the  frontal  and  the  nasal  process  of  the  superior  maxillarv. 
The  circumference  is  marked  bv  three  sutures,  the  fronto-maxillary  internally, 
the  fronto-malar  externally,  and  the  malo-maxillary  below  :  it  contributes  to  the 
formation  of  the  lachrymal  groove,  and  presents,  above,  the  supraorbital  notch 
(or  foramen),  for  the  passage  of  the  supraorbital  vessels  and  nerve.  The  apex, 
situated  at  the  back  of  the  orbit,  corresponds  to  the  optic  foramen,  a  short,  circular 
canal,  which  transmits  the  optic  nerve  and  ophthalmic  artery.  It  will  thus  be 
seen  that  there  are  nine  openings  communicating  with  each  orbit — viz.  the  optic 
foramen,  foramen  lacerum  anterius.  spheno-maxillary  fissure,  supraorbital  foramen, 
infraorbital  canal,  anterior  and  posterior  ethmoidal  foramina,  malar  foramina,  and 
canal  for  the  nasal  duct. 

The  Nasal  Fossae. 

The  Nasal  Fossae  are  two  large,  irregular  cavities  situated  on  either  side  of  the 
middle  line  of  the  face,  extending  from  the  base  of  the  cranium  to  the  roof  of  the 
mouth,  and  separated  from  each  other  by  a  thin  vertical  septum.  They  communi- 
cate by  two  large  apertures,  the  anterior  nares.  with  the  front  of  the  face,  and  by  the 
two  posterior  nares  with  the  pharynx  behind.  These  fossae  are  much  narrower 
above  than  below,  and  in  the  middle  than  at  the  anterior  or  posterior  openings ; 
their  depth,  which  is  considerable,  is  much  greater  in  the  middle  than  at  either 
extremity.  Each  nasal  fossa  communicates  with  four  sinuses,  the  frontal  above, 
the  sphenoidal  behind,  and  the  maxillary  and  ethmoidal  on  the  outer  wall.  Each 
also  communicates  with  four  cavities:  with  the  orbit  by  the  lachrymal 
groove,  with  the  mouth  by  the  anterior  palatine  canal,  with  the  cranium  by  the 
olfactory  foramina,  and  with  the  spheno-maxillary  fossa  by  the  spheno-palatine 
foramen  :  and  they  occasionally  communicate  with  each  other  by  an  aperture  in 
the  septum.  The  bones  entering  into  their  formation  are  fourteen  in  number : 
three  of  the  cranium,  the  frontal,  sphenoid,  and  ethmoid,  and  all  the  bones  of  the 


220 


THE  SKELETON, 


face,  excepting  the  malar  and  lower  jaw.     Each  cavity  is  bounded  by  a  roof,  a 
floor,  an  inner  and  an  outer  wall. 

The  upper  wall,  or  roof  (Fig.  176),  is  formed  in  front  by  the  nasal  bones  and 
groove  lateral  to  the  nasal  spine  of  the  frontal ;  this  part  is  directed  downward 
and  forward;  in  the  middle,  by  the  cribriform  plate  of  the  ethmoid,  which  is  hori- 
zontal ;  and  behind,  by  the  under  surface  of  the  body  of  the  sphenoid,  sphenoidal 
process  of  the  palate  bone,  and  ala  of  the  vomer,  which  are  directed  downward 
and  backward.  This  surface  presents,  from  before  backward,  the  internal  aspect 
of  the  nasal  bones ;  on  their  outer  side,  the  suture  formed  between  the  nasal  bone 
and  the  nasal  process  of  the  superior  maxillary ;  on  their  inner  side,  the  elevated 
crest  which  receives  the  nasal  spine  of  the  frontal  and  the  perpendicular  plate  of 
the  ethmoid,  and  articulates  with  its  fellow  of  the  opposite  side ;  whilst  the  surface 


Roof. 

Nasal  bone, 

Nasal  spine  of  frontal  bone. 
Horizontal  plate  of  ethmoid. 
Sphenoid. 


Probe  passed  through 
naso-lachrymal  canal. 

-Bristle  passed  through 
infundibulum. 


Outer  Wall. 

-Nasal  proc.  of  sup.  max. 
'Lachrymal, 

'Ethmoid. 

Unciform  process  of  ethmoid. 
Inferior  turbinated. 
Palate. 

Superior  meat  us. 
Middle  meatus. 
Inferior  meatus. 


Floor. 

Anterior  nasal  spine. 
Palate  proc.  of  sup.  max. 
Palate  process  of  palate. 

Posterior  nasal  spins.' 
Anterior  palatine  canal.  - 


FIG.  176.— Roof,  floor,  and  outer  wall  of  left  nasal  fossa. 

of  the  bones  is  perforated  by  a  few  small  vascular  apertures,  and  presents  the 
longitudinal  groove  for  the  nasal  nerve ;  farther  back  is  the  transverse  suture, 
connecting  the  frontal  with  the  nasal  in  front,  and  the  ethmoid  behind,  the 
olfactory  foramina  and  nasal  slit  on  the  under  surface  of  the  cribriform  plate,  and 
the  suture  between  it  and  the  sphenoid  behind :  quite  posteriorly  are  seen  the 
sphenoidal  turbinated  bones,  the  orifices  of  the  sphenoidal  sinuses,  and  the 
articulation  of  the  alse  of  the  vomer  with  the  under  surface  of  the  body  of  the 
sphenoid. 

The  floor  is  flattened  from  before  backward,  concave  from  side  to  side,  and 
wider  in  the  middle  than  at  either  extremity.  It  is  formed  in  front  by  the  palate 
process  of  the  superior  maxillary ;  behind,  by  the  palate  process  of  the  palate  bone. 
This  surface  presents,  from  before  backward,  the  anterior  nasal  spine ;  behind 
this,  the  upper  orifices  of  the  anterior  palatine  canal ;  internally,  the  elevated  crest 
which  articulates  with  the  vomer ;  and  behind,  the  suture  between  the  palate  and 
superior  maxillary  bones,  and  the  posterior  nasal  spine. 

The  inner  wall,  or  septum  (Fig.  177),  is  a  thin  vertical  partition  which  sepa- 
rates the  nasal  fossae  from  one  another ;  it  is  occasionally  perforated,  so  that  the 


THE   ANTERIOR    REGIOX   OF    THE   SKULL. 


221 


foss;\:>  communicate,  and  it  is  often  bent  considerably  to  one  side.1  It  is  formed,  in 
front,  by  tbe  crest  of  tbe  nasal  bones  and  nasal  spine  of  tbe  frontal ;  in  the  middle, 
bv  the  perpendicular  plate  of  the  ethmoid  :  behind,  by  the  vomer,  rostrum  and  eth- 
moidal  crest  of  the  sphenoid;  belo\v.  by  the  crests  of  the  superior  maxillary  and 
palate  bones  It  presents,  in  front,  a  large,  triangular  notch,  which  receives  the  tri- 
angular cartilage  of  the  nose ;  and  behind,  the  guttural  edge  of  the  vomer.  Its 
surface  is  marked  by  numerous  vascular  and  nervous  canals  and  the  groove  for 


Crest  of  nasal  bone. 

Xasal  .opine  of_ 
frontal  bone. 


for  triangular^ 
cartilage  of  septum 


.Crest  of  palate  bone, 
•est  of  superior  maxillary 
bone. 


FIG.  177.— Inner  wall  of  nasal  fossae,  or  septum  of  nose. 


the  naso-palatine  nerve,  and  is  traversed  by  sutures  connecting  the  bones  of  which 
it  is  formed. 

The  outer  wall  (Fig.  176)  is  formed,  in  front,  by  the  nasal,  the  nasal  process 
of  the  superior  maxillary  and  lachrymal,  bones ;  in  the  middle,  by  the  ethmoid 
and  inner  surface  of  the  superior  maxillary  and  inferior  turbinated  bones ;  behind, 
by  the  vertical  plate  of  the  palate  bone  and  the  internal  pterygoid  plate  of  the 
sphenoid.  This  surface  presents  three  irregular  longitudinal  passages,  or  meatuses, 
formed  between  three  plates  of  bone  that  spring  from  it ;  they  are  termed  the 
superior,  middle,  and  inferior  meatuses  of  the  nose.  The  superior  meatus,  the 
smallest  of  the  three,  is  situated  at  the  upper  and  back  part  of  each  nasal  fossa, 
occupying  the  posterior  third  of  the  outer  wall  It  is  situated  between  the  superior 
and  middle  turbinated  bones,  and  has  opening  into  it  two  foramina,  the  spheno- 
pfilatine  at  the  back  of  its  outer  wall,  and  the  posterior  ethmoidal  cells  at  the  front 
part  of  the  outer  wall.  The  opening  of  the  sphenoidal  sinus  is  at  the  upper  and 
back  part  of  the  nasal  fossa  immediately  behind  the  superior  turbinated  bone  and 
into  a  groove,  the  spheno-ethmoMal  recess.  The  middle  meatus  is  situated  between 
the  middle  and  inferior  turbinated  bones,  and  occupies  the  posterior  two-thirds  of 
the  outer  wall  of  the  nasal  fossa.  It  has  two  apertures  :  in  front  that  of  the  inftin- 
dibulum,  by  which  the  meatus  communicates  with  the  anterior  ethmoidal  cells, 
and  through  these  with  the  frontal  sinuses ;  near  the  centre  is  the  orifice  of  the 
ant  mm.  which  varies  somewhat  as  to  its  exact  position  in  different  skulls.  The  infe- 
rior meatus.  the  largest  of  the  three,  is  the  space  between  the  inferior  turbinated 

1  See  footnote,  p.  185. 


222  THE   SKELETON. 

bone  and  the  floor  of  the  nasal  fossa.  It  extends  along  the  entire  length  of  the 
outer  wall  of  the  nose,  is  broader  in  front  than  behind,  and  presents  anteriorly  the 
lower  orifice  of  the  canal  for  the  nasal  duct. 

The  anterior  nares  present  a  heart-shaped  or  pyriform  opening  whose  long 
axis  is  vertical  and  narrow  extremity  upward.  This  opening  in  the  recent  state 
is  much  contracted  by  the  cartilages  of  the  nose.  It  is  bounded  above  by  the 
inferior  border  of  the  nasal  bone ;  laterally  by  the  thin,  sharp  margin  which 
separates  the  facial  from  the  nasal  surface  of  the  superior  maxillary  bone ;  and 
below  by  the  same  border,  where  it  slopes  inward  to  join  its  fellow  of  the  opposite 
side  at  the  anterior  nasal  spine. 

The  posterior  nares  are  the  two  posterior  oval  openings  of  the  nasal  fossae,  by 
which  they  communicate  with  the  upper  part  of  the  pharynx.  They  are  situated 
immediately  in  front  of  the  basilar  process,  and  are  bounded  above  by  the  under 
surface  of  the  body  of  the  sphenoid  ;  below  by  the  posterior  border  of  the  horizontal 
plate  of  the  palate  bone ;  externally,  by  the  internal  surface  of  the  internal  pterygoid 
plate ;  and  internally,  in  the  middle  line,  they  are  separated  from  each  other  by 
the  guttural  border  of  the  vomer. 

Surface  Form. — The  various  bony  prominences  or  landmarks  which  are  to  be  easily  felt  and 
recognized  in  the  head  and  face,  and  which  afford  the  means  of  mapping  out  the  important 
structures  comprised  in  this  region,  are  as  follows : 

1.  Supraorbital  arch.  8.  Parietal  eminences. 

2.  Internal  angular  process.  9.  Temporal  ridge. 

3.  External  angular  process.  10.  Frontal  eminences. 

4.  Zygomatic  arch.  11.  Superciliary  ridges. 

5.  Mastoid  process.  12.  Nasal  bones. 

6.  External  occipital  protuberance.  13.  Lower  margin  of  orbit. 

7.  Superior  curved  line  of  occipital  bone.  14.  Lower  jaw. 

1.  The  supraorbital  arches  are  to  be  felt  throughout  their  entire  extent,  covered  by  the  eye- 
brows. They  form  the  upper  boundary  of  the  circumference  or  base  of  the  orbit,  and  separate 
the  face  from  the  forehead.  They  are  strong  and  arched,  and  terminate  internally  on  each  side 
of  the  root  of  the  nose  in  the  internal  angular  process,  which  articulates  with  the  lachrymal 
bone.  Externally  they  terminate  in  the  external  angular  process,  which  articulates  with  the 
malar  bone.  This  arched  ridge  is  sharper  and  more  defined  in  its  outer  than  in  its  inner  half, 
and  forms  an  overhanging  process  which  protects  and  shields  the  lachrymal  gland.  It  thus  pro- 
tects the  eye  in  its  most  exposed  situation  and  in  the  direction  from  which  blows  are  most  likely 
to  descend.  Tho  supraorbital  arch  varies  in  prominence  in  different  individuals.  It  is  more 
marked  in  the  male  than  in  the  female,  and  in  some  races  of  mankind  than  others.  In  the  less 
civilized  races,  as  the  forehead  recedes  backward,  the  supraorbital  arch  becomes  more  prominent, 
and  approaches  more  to  the  characters  of  the  monkey  tribe,  in  whioh  the  supraorbital  arches  are 
very  largely  developed,  and  acquire  additional  prominence  from  the  oblique  direction  of  the 
frontal  bone.  2.  The  internal  angular  process  is  scarcely  to  be  felt.  Its  position  is  indicated 
by  the  angle  formed  by  the  suprao  ital  arch  with  the  nasal  process  of  the  superior  maxillary 
bone  and  the  lachrymal  bone  at  the  inner  side  of  the  orbit.  Between  the  internal  angular  pro- 
cesses of  the  two  sides  is  a  broad  surface  which  assists  in  forming  the  root  of  the  nose,  and 
immediately  above  this  a  broad,  smooth,  somewhat  triangular  surface,  the  glabella,  situated 
between  the  superciliary  ridges.  3.  The  external  angular  process  is  much  more  strongly  marked 
than  the  internal,  and  is  plainly  to  be  felt.  It  is  formed  by  the  junction  or  confluence  of  the  supra- 
orbital  and  temporal  ridges,  and,  articulating  with  the  malar  bone,  it  serves  to  a  very  consider- 
able extent  to  support  the  bones  of  the  face.  In  carnivorous  animals  the  external  angular  pro- 
cess does  not  articulate  with  the  malar,  and  therefore  this  lateral  support  to  the  bones  of  the  face 
is  not  present.  4.  The  zygomatic  arch  is  plainly  to  be  felt  throughout  its  entire  length,  being 
situated  almost  immediately  under  the  skin.  It  is  formed  by  the  malar  bone  and  the  zygomatic 
process  of  the  temporal  bone.  At  its  anterior  extremity,  where  it  is  formed  by  the  malar  bone, 
it  is  broad  and  forms  the  prominence  of  the  cheek  ;  the  posterior  part  is  narrower,  and  termi- 
nates just  in  front  and  a  little  above  the  tragus  of  the  external  ear.  The  lower  border  is  more 
plainly  to  be  felt  than  the  upper,  in  consequence  of  the  dense  temporal  fascia  being  attached  to 
the  upper  border,  which  somewhat  obscures  its  outline.  Its  shape  differs  very  much  in  individ- 
uals and  in  different  races  of  mankind.  In  the  most  degraded  type  of  skull — as,  for  instance,  in 
the  skull  of  the  negro  of  the  Guinea  Coast — the  malar  bones  project  forward  and  not  outward, 
and  the  zygoma  at  its  posterior  extremity  extends  farther  outward  before  it  is  twisted  on  itself  to 
be  prolonged  forward.  This  makes  the  zygomatic  arch  stand  out  in  bold  relief,  and  affords 
greater  space  for  the  Temporal  muscle.  In  skulls  which  have  a  more  pyramidal  shape,  as  in  the 
Esquimaux  or  Greenlander,  the  malar  bones  do  not  project  forward  and  downward  under  the 
eyes,  as  in  the  preceding  form,  but  take  a  direction  outward,  forming  with  the  zygoma  a  large, 
rounded  sweep  or  segment  of  a  circle.  Thus  it  happens  that  if  two  lines  are  drawn  from  the 


SURFACE  FORM   OF   THE  SKULL.  223 

zygomatic  arches,  touching  the  temporal  ridges,  they  meet  over  the  top  of  the  head,  instead  of 
being  parallel,  or  nearly  so,  as  in  the  European  skull,  in  which  the  zygomatic  arches  are  not 
nearly  so  prominent,  'this  gives  to  the  face  a  more  or  less  oval  type.  5.  Behind  the  ear  is  the 
mastoid  portion  of  the  temporal  bout-,  plainly  to  be  felt,  and  terminating  below  in  a  nipple- 
shaped  process.  Its  anterior  border  can  be  traced  immediately  behind  the  concha,  and  its  apex 
is  on  about  a  level  with  the  lobule  of  the  ear.  It  is  rudimentary  in  infancy,  but  gradually 
develops  in  childhood,  and  is  more  marked  in  the  negro  than  in  the  European.  6.  The  external 
occipital  protuberance  is  always  plainly  to  be  felt  just  at  the  level  where  the  skin  of  the  neck 
joins  that  of  the  head.  At  this  point  the  skull  is  thick  for  the  purposes  of  safety,  while 
radiating  from  it  are  numerous  curved  arches  or  buttresses  of  bone  which  give  to  this  portion  of 
the  skull  further  security.  7.  Running  outward  on  either  side  from  the  external  occipital  protu- 
berance is  an  arched  ridge  of  bone,  which  can  be  more  or  less  plainly  perceived.  This  is  the 
superior  exrrnl  \'u\?  of  the  occipital  bone,  and  gives  attachment  to  some  of  the  muscles  which 
keep  the  head  erect  on  the  spine  ;  accordingly,  we  find  it  more  developed  in  the  negro  tribes,  in 
whom  the  jaws  are  much  more  massive,  and  therefore  require  stronger  muscles  to  prevent  their 
extra  weight  carrying  the  head  forward.  Below  this  line  the  surface  of  bone  at  the  back  of  the 
head  is  obscured  by  the  overlying  muscles.  Above  it,  the  vault  of  the  cranium  is  thinly  covered 
with  soft  structures,  so  that  the  form  of  this  part  of  the  head  is  almost  exactly  that  of  the  upper 
portion  of  the  occipital,  the  parietal,  and  the  frontal  bones  themselves;  and  in  bald  persons 
even  the  lines  of  junction  of  the  bones,  especially  the  junction  of  the  occipital  and  parietal  at 
the  lambdoid  suture,  may  be  defined  as  a  slight  depression,  caused  by  the  thickening  of  the 
borders  of  the  bones  in  this  situation.  8.  In  the  line  of  the  greatest  transverse  diameter  of  the 
head,  on  each  side  of  the  middle  line,  are  generally  to  be  found  the  parietal  eminences,  though 
sometimes  these  eminences  are  not  situated  at  the  point  of  the  greatest  transverse  diameter, 
which  is  at  some  other  prominent  part  of  the  parietal  region.  They  denote  the  point  where 
ossification  of  the  bone  began.  They  are  much  more  prominent  and  well-marked  in  early  life, 
in  consequence  of  the  sharper  curve  of  the  bone  at  this  period,  so  that  it  describes  the  segment 
of  a  smaller  circle.  Later  in  life,  as  the  bone  grows,  the  curve  spreads  out  and  forms  the 
segment  of  a  larger  circle,  so  that  the  eminence  becomes  less  distinguishable.  In  consequence  of 
this  sharp  curve  of  the  bone  in  early  life,  the  whole  of  the  vault  of  the  skull  has  a  squarer  shape 
than  it  has  in  later  life,  and  this  appearance  may  persist  in  some  rickety  skulls.  The  eminence 
is  more  apparent  in  the  negro's  skull  than  in  that  of  the  European.  This  is  due  to  greater  flat- 
tening  of  the  temporal  fossa  in  the  former  skull  to  accommodate  the  larger  Temporal  muscle 
which  exists  in  these  races.  The  parietal  eminence  is  particularly  exposed  to  injury  from  blows 
or  falls  on  the  head,  but  fracture  is  to  a  certain  extent  prevented  by  the  shape  of  the  bone, 
which  forms  an  arch,  so  that  the  force  of  the  blow  is  diffused  over  the  bone  in  every  direction. 
0.  At  the  side  of  the  head  may  be  felt  the  temporal  ridge.  Commencing  at  the  external 
angular  process,  it  may  be  felt  as  a  curved  ridge,  passing  upward  and  then  curving  backward,  on 
the  frontal  bone,  separating  the  forehead  from  the  temporal  fossa.  It  may  then  be  traced,  pass- 
ing backward  in  a  curved  direction,  over  the  parietal  bone,  and,  though  less  marked,  still  gen- 
erally to  be  recognized.  Finally,  the  ridge  curves  downward,  and  terminates  in  the  posterior 
root  of  the  zygoma,  which  separates  the  squamous  from  the  subcutaneous  mastoid  portion  of  the 
temporal  bone.  Mr.  Victor  Horsley  has  recently  shown,  in  an  article  on  the  "Topography  of 
the  Cerebral  Cortex.''  that  the  second  temporal  ridge  (see  page  170)  can  be  made  out  on  the 
living  body.  10.  The  frontal  eminences  vary  a  good  deal  in  different  individuals,  being  con- 
siderably more  prominent  in  some  than  in  others,  and  they  are  often  not  symmetrical  on  the  two 
sides  of  the  body,  the  one  being  much  more  pronounced  than  the  other.  This  is  often  especially 
noticeable  in  the  skull  of  the  young  child  or  infant,  and  becomes  less  marked  as  age  advances. 
The  prominence  of  the  frontal  eminences  depends  more  upon  the  general  shape  of  the  whole 
bone  than  upon  the  size  of  the  protuberances  themselves.  As  the  skull  is  more  highly 
developed  in  consequence  of  increased  intellectual  capacity,  so  the  frontal  bone  becomes  more 
upright  and  the  frontal  eminences  stand  out  in  bolder  relief.  Thus  they  may  be  considered  as 
affording,  to  a  certain  extent,  an  indication  of  the  development  of  the  hemispheres  of  the  brain 
beneath,  and  of  the  mental  powers  of  the  individual.  They  are  not  so  much  exposed  to  injury 
as  the  parietal  eminences.  In  falls  forward  the  upper  extremities  are  involuntarily  thrown  out, 
and  break  the  force  of  the  fall,  and  thus  shield  the  frontal  bone  from  injury.  11.  Below  the 
frontal  eminences  on  the  forehead  are  the  tttpercQiary  ridges,  which  denote  the  position  of  the 
frontal  sinuses,  and  vary  according  to  the  size  of  the  sinuses  in  different  individuals,  being,  as  a 
rule,  small  in  the  female,  absent  in  children,  and  sometimes  unusually  prominent  in  the  male, 
when  the  frontal  sinuses  are  largely  developed.  They  commence  on  either  side  of  the  glabella. 
and  at  first  present  a  rounded  form,  which  gradually  fades  away  at  their  outer  ends.  12.  The 
iinatil  boin'-s  form  the  prominence  of  the  nose.  They  vary  much  in  size  and  shape,  and  to  them 
is  due  the  varieties  in  the  contour  of  this  organ  and  much  of  the  character  of  the  face.  Thus, 
in  the  Mongolian  or  Ethiopian  they  are  flat,  broad  and  thick  at  their  base,  giving  to  these  tribes 
the  flattened  nose  by  which  they  are  characterized,  and  differing  very  "decidedly  from  the 
Caucasian,  in  whom  the  nose,  owing  to  the  shape  of  the  nasal  bones,  is  narrow,  elevated  at  the 
bridge,  and  elongated  downward.  Below,  the  nasal  bones  are  thin  and  connected  with  the  car- 
tilages of  the  nose,  and  the  angle  or  arch  formed  by  their  union  serves  to  throw  out  the  bridge 
of  the  nose,  and  is  much  more  marked  in  some  individuals  than  others.  13.  The  lower  margin 
of  the  orbit,  formed  by  the  superior  maxillary  bone  and  the  malar  bone,  is  plainly  to  be  felt 
throughout  its  entire  length.  It  is  continuous  internally  with  the  nasal  process  of  the  superior 


224  THE  SKELETON. 

maxillary  bone,  which  'forms  the  inner  boundary  of  the  orbit.  At  the  point  of  junction  of  the 
lower  margin  of  the  orbit  with  the  nasal  process  is  to  be  felt  a  little  tubercle  of  bone,  which  can 
be  plainly  perceived  by  running  the  finger  along  the  bone  in  this  situation.  This  tubercle  serves 
as  a  guide  to  the  position  of  the  lachrymal  sac,  which  is  situated  above  and  behind  it.  14.  The 
outline  of  the  lower  jaw  is  to  be  felt  throughout  its  entire  length.  Justin  front  of  the  tragusof 
the  external  ear,  and  below  the  zygomatic  arch,  the  condyle  can  be  made  out.  When  the  mouth 
is  opened  this  prominence  of  bone  can  be  perceived  advancing  out  of  the  glenoid  fossa  on  to  the 
eminentia  articularis,  and  receding  again  when  the  mouth  is  closed.  From  the  condyle  the  pos- 
terior border  of  the  ramus  can  be  felt  extending  down  to  the  angle.  A  line  drawn  from  the  con- 
dyle to  the  angle  would  indicate  the  exact  position  of  this  border.  From  the  angle  to  the 
symphysis  of  the  chin  the  lower,  rounded  border  of  the  body  of  the  bone  is  plainly  to  be  felt. 
At  the  point  of  junction  of  the  two  halves  of  the  bone  is  a  well-marked  triangular  eminence,  the 
mental  process,  which  forms  the  prominence  of  the  chin. 

Surgical  Anatomy. — An  arrest  in  the  ossifying  process  may  give  rise  to  deficiencies  or 
gaps ;  or  to  fissures,  which  are  of  importance  in  a  medico-legal  point  of  view,  as  they  are  liable 
to  De  mistaken  for  fractures.  The  fissures  generally  extend  from  the  margin  toward  the  centre 
of  the  bone,  but  gaps  may  be  found  in  the  middle  as  well  as  at  the  edges.  In  course  of  time 
they  may  become  covered  with  a  thin  lamina  of  bone. 

Occasionally  a  protrusion  of  the  brain  or  its  membranes  may  take  place  through  one  of  these 
gaps  in  an  imperfectly  developed  skull.  When  the  protrusion  consists  of  membranes  only,  and 
is  filled  with  cerebro-spinal  fluid,  it  is  called  a  meningoce  1c ;  when  the  protrusion  consists  of  brain 
as  well  as  membranes,  it  is  termed  an  encephalocele  ;  and  when  the  protruded  brain  is  a  prolonga- 
tion from  one  of  the  ventricles,  and  is  distended  by  a  collection  of  fluid  from  an  accumulation  in 
the  ventricle,  it  is  termed  an  hydrencephnlocele.  This  latter  condition  is  frequently  found  at  the 
root  of  the  nose,  where  a  protrusion  of  the  anterior  horn  of  the  lateral  ventricle  takes  place 
through  a  deficiency  of  the  fronto-nasal  suture.  These  malformations  are  usually  found  in  the 
middle  line,  and  most  frequently  at  the  back  of  the  head,  the  protrusion  taking  place  through 
the  fissures  which  separate  the  four  centres  of  ossification  from  which  the  tabular  portion 
is  originally  developed  (see  page  167).  They  most  frequently  occur  through  the  upper  part  of 
the  vertical  fissure,  which  is  the  last  to  ossify,  but  not  uncommonly  through  the  lower  part,  when 
the  foramen  magnum  may  be  incomplete,  More  rarely  these  protrusions  have  been  met  with  in 
other  situations  than  those  two  above  mentioned,  both  through  normal  fissures,  as  the  sagittal, 
lambdoid,  and  other  sutures,  and  also  through  abnormal  gaps  and  deficiencies  at  the  sides,  and 
even  at  the  base  of  the  skull. 

Fractures  of  the  skull  may  be  divided  into  those  of  the  vault  and  those  of  the  base.  Frac- 
tures of  the  vault  are  usually  produced  by  direct  violence.  This  portion  of  the  skull  varies  in 
thickness  and  strength  in  different  individuals,  but,  as  a  rule,  is  sufficiently  strong  to  resist  a  very 
considerable  amount  of  violence  without  being  fractured.  This  is  due  to  several  causes :  the 
rounded  shape  of  the  head  and  its  construction  of  a  number  of  secondary  elastic  arches,  each 
made  up  of  a  single  bone ;  the  fact  that  it  consists  of  a  number  of  bones,  united,  at  all  events  in 
early  life,  by  a  sutural  ligament,  which  acts  as  a  sort  of  buffer  and  interrupts  the  continuity  of  any 
violence  applied  to  the  skull ;  the  presence  of  arches  or  ridges,  both  on  the  inside  and  outside  of 
the  skull,  which  materially  strengthen  it ;  and  the  mobility  of  the  head  upon  the  spine  which 
further  enables  it  to  withstand  violence.  The  elasticity  of  the  bones  of  the  head  is  especially 
marked  in  the  skull  of  the  child,  and  this  fact,  together  with  the  wide  separation  of  the  indi- 
vidual bones  from  each  other,  and  the  interposition  between  them  of  other  softer  structures 
renders  fracture  of  the  bones  of  the  head  a  very  uncommon  event  in  infants  and  quite  young 
children ;  as  age  advances  and  the  bones  become  joined,  fracture  is  more  common,  though  still 
less  liable  to  occur  than  in  the  adult.  Fractures  of  the  vault  may,  and  generally  do,  involve  the 
whole  thickness  of  the  bone;  but  sometimes  one  table  may  be  fractured  without  any  correspond- 
ing injury  to  the  other.  Thus,  the  outer  table  of  the  skull  may  be  splintered  and  driven  into  the 
diploe,  or  in  the  frontal  or  mastoid  regions  into  the  frontal  or  mastoid  cells,  without  any  injury 
to  the  internal  table.  And  on  the  other  hand,  the  internal  table  has  been  fractured,  and  por- 
tions of  it  depressed  and  driven  inward,  without  any  fracture  of  the  outer  table.  As  a  rule,  in 
fractures  of  the  skull  the  inner  table  is  more  splintered  and  comminuted  than  the  outer, 
and  this  is  due  to  several  causes.  It  is  thinner  and  more  brittle ;  the  force  of  the  violence  as  it 
passes  inward  becomes  broken  up,  and  is  more  diffused  by  the  time  it  reaches  the  inner  table; 
the  bone,  being  in  the  form  of  an  arch,  bends  as  a  whole  and  spreads  out,  and  thus  presses  the 
particles  together  on  the  convex  surface  of  the  arch — i.  e.  the  outer  table — and  forces  them 
asunder  on  the  concave  surface  or  inner  table ;  and,  lastly,  there  is  nothing  firm  under  the  inner 
table  to  support  it  and  oppose  the  force.  Fractures  of  the  vault  may  be  simple  fissures  or  starred 
and  comminuted  fractures,  and  these  may  be  depressed  or  elevated.  These  latter  cases  of 
fracture  with  elevation  of  the  fractured  portion  are  uncommon,  and  can  only  be  produced  by 
direct  wound.  In  comminuted  fracture  a  portion  of  the  skull  is  broken  into  several  pieces, 
the  lines  of  fracture  radiating  from  a  centre  where  the  chief  impact  of  the  blow  was  felt ; 
if  depressed,  a  fissure  circumscribes  the  radiating  line,  enclosing  a  portion  of  skull.  If 
this  area  is  circular,  it  is  termed  a  "pond"  fracture,  and  would  in  all  probability  have  been 
caused  by  a  round  instrument,  as  a  life-preserver  or  hanimer;  if  elliptical  in  shape,  it  is 
termed  a  "  gutter  fracture,"  and  would  owe  its  shape  to  the  instrument  which  had  produced  it, 
as  a  poker. 

Fractures  of  the  base  are  most  frequently  produced  by  the  extension  of  a  fissure  from  the 


SURGICAL    ANATOMY   OF    THE   BONES    OF    THE   FACE.     225 

vault,  as  in  falls  on  the  head,  where  the  fissure  starts  from  the  part  of  the  vault  which  first 
struck  the  ground.  Sometimes,  however,  they  are  caused  by  direct  violence,  when  foreign 
bodies  have  been  forced  through  the  thin  roof  of  the  orbit,  through  the  cribriform  plate  of  the 
ethmoid  from  being  thrust  up  the  nose,  or  through  the  roof  of  the  pharynx.  Other  cases  of 
fracture  of  the  base  occur  from  indirect  violence,  as  in  fracture  of  the  occipital  bone  from  impac- 
tion  of  the  spinal  column  airainst  its  condyles  in  falls  on  the  buttocks,  knees,  or  feet,  or  in  cases 
win-re  the  glenoid  cavity  has  been  fractured  by  the  violent  impact  of  the  condyle  of  the  lower  jaw 
against  it  from  blows  on  the  chin. 

The  most  common  place  for  fracture  of  the  base  to  occur  is  through  the  middle  fossa,  and 
here  the  fissure  usually  takes  a  fairly  definite  course.  Starting  from  the  point  struck,  which  is 
generally  somewhere  in  the  neighborhood  of  the  parietal  eminence,  it  runs  downward  through 
the  parietal  and  squamous  poition  of  the  temporal  bone  and  across  the  petrous  portion  of  this 
bone,  frequently  traversing  and  implicating  the  internal  auditory  meatus.  to  the  middle  lacerated 
foramen.  From  this  it  may  pass  across  the  body  of  the  sphenoid,  through  the  pituitary  fossa  to 
the  middle  lacerated  foramen  of  the  other  side,  and  may  indeed  travel  round  the  whole  cranium, 
so  as  to  completely  separate  the  anterior  from  the  posterior  part.  The  course  of  the  fracture 
should  be  borne  in  mind,  as  it  explains  the  symptoms  to  which  fracture  in  this  region  may  give 
rise .  thus,  if  the  fissure  pass  across  the  internal  auditory  meatus.  injury  to  the  facial  and 
auditory  nerves  may  result,  with  consequent  facial  paralysis  and  deafness;  or  the  tubular  pro- 
longation of  the  arachnoid  around  these  nerves  in  the  meatus  may  be  torn,  and  thus  permit  of 
the  escape  of  the  eerebro-spinal  fluid  should  there  be  a  communication  between  the  internal  ear 
and  the  tympanum  and  the  niembrana  tympani  be  ruptured,  as  is  frequently  the  case ;  again,  if 
the  fissure  passes  across  the  pituitary  fossa  and  the  muco- periosteum  covering  the  under  surface 
of  the  body  of  the  sphenoid  is  torn,  blood  will  find  its  way  into  the  pharynx  and  be  swallowed, 
and  after  a  time  vomiting  of  blood  will  result.  Fractures  of  the  anterior  fossa,  involving  the 
bones  forming  the  roof  of  the  orbit  and  nasal  fossa,  are  generally  the  results  of  blows  on  the  fore- 
head :  but  fracture  of  the  cribriform  plate  of  the  ethmoid  may  be  a  complication  of  fracture  of 
the  nasal  bone.  When  the  fracture  implicates  the  roof  of  the  orbit,  the  blood  finds  its  way 
into  this  cavity,  and.  travelling  forward,  appears  as  a  subconjunctival  ecchymosis.  If  the  roof 
of  the  nasal  fossa  be  fractured,  the  blood  escapes  from  the  nose.  In  rare  cases  there  may 
be  also  escape  of  eerebro-spinal  fluid  from  the  nose  where  the  dura  mater  and  arachnoid  have 
been  torn.  .  In  fractures  of  the  posterior  fossa  extravasation  of  blood  may  appear  at  the  nape  of 
the  neck. 

The  bones  of  the  skull,  being  subcutaneous,  are  frequently  the  seat  of  nodes,  and  not  un- 
coinmonly  necrosis  results  from  this  cause,  as  well  as  from  injury.  Necrosis  may  involve  the  en- 
tire thickness  of  the  skull,  but  is  usually  confined  to  the  external  table.  Necrosis  of  the  internal 
table  alone  is  rarely  met  with.  The  bones  of  the  skull  are  also  frequently  the  seat  of  sarcoma- 
tous  tumor. 

The  skull  in  rickets  is  peculiar:  the  forehead  is  high,  square,  and  projecting,  and  the 
antero-posterior  diameter  of  the  skull  is  long  in  relation  to  the  transverse  diameter.  The  bones 
of  the  face  are  small  and  ill-developed,  and  this  gives  the  appearance  of  a  larger  head  than 
actually  exists.  The  bones  of  the  head  are  often  thick,  especially  in  the  neighborhood  of  the 
sutures,  and  the  anterior  fontanelle  is  late  in  closing,  sometimes  remaining  unclosed  till  the  fourth 
year.  The  condition  of  cram'otabes  has  by  some  been  also  believed  to  be  the  result  of  rickets,  by 
others  is  believed  to  be  due  to  inherited  syphilis.  In  these  cases  the  bone  undergoes  atrophic 
changes  in  patches,  so  that  it  becomes  greatly  thinned  in  places,  generally  where  there  is 
pressure,  as  from  the  pillow  or  nurse's  arm.  It  is,  therefore,  usually  met  with  in  the  parietal 
bone  and  vertical  plate  of  the  occipital  bone. 

In  congenital  syphilis  deposits  of  porous  bone  are  often  found  at  the  angles  of  the  parietal 
bones  and  two  halves  of  the  frontal  bone  which  bound  the  anterior  fontanelle.  These  deposits 
are  separated  by  the  coronal  and  sagittal  sutures,  and  give  to  the  skull  an  appearance  like  a  "hot 
cro>s  bun."  They  are  known  as  Parrot's  nodes,  and  such  a  skull  has  received  the  name  of  nati- 
/'//•///.  from  its  fancied  resemblaooe  to  the  buttocks. 

In  connection  with  the  bones  of  the  face  a  common  malformation  is  cleft  palate,  owing  to 
the  non-union  of  the  palatal  processes  of  the  maxillary  or  pre-oral  arch  (see  page  118).  This 
cleft  may  involve  the  whole  or  only  a  portion  of  the  hard  palate,  and  usually  involves  the  soft 
palate  also.  The  cleft  is  in  the  middle  line,  except  it  involves  the  alveolus  in  front,  when  it  fol- 
low* the  suture  between  the  main  portion  of  the  Done  and  the  pre-rn axillary  bone.  Sometimes 
the  cleft  runs  on  either  side  of  the  pre-maxillary  bone,  so  that  this  bone  is  quite  isolated  from 
the  maxillary  bones  and  hangs  from  the  end  of  the  vomer.  The  malformation  is  usually  asso- 
ciated with  hare-lip,  which,  when  single,  is  almost  always  on  one  side,  corresponding  to  the  posi- 
tion of  the  suture  between  the  lateral  incisor  and  canine  tooth.  Some  few  cases  of  median  hare- 
lip have  been  described.  In  double  hare-lip  there  is  a  cleft  on  each  side  of  the  middle  line. 

The  bones  of  the  face  are  sometimes  fractured  as  the  result  of  direct  violence.  The  two 
most  commonly  broken  are  the  nasal  bone  and  the  inferior  maxilla,  and  of  these  the  latter  is  by 
far  the  most  frequently  fractured  of  all  the  bones  of  the  face.  Fracture  of  the  nasal  bone  is 
for  the  most  part  transverse,  and  takes  place  about  half  an  inch  from  the  free  margin.  The 
broken  portion  may  be  displaced  backward  or  more  generally  to  one  side  by  the  force  which 
produced  the  lesion,  as  there  are  no  muscles  here  which  can  cause  displacement.  The  malar 
bone  is  probably  never  broken  alone ;  that  is  to  say,  unconnected  with  a  fracture  of  the  other 
bones  of  the  face.  The  zygomatic  arch  is  occasionally  fractured,  and  when  this  occurs  from 

15 


226  THE  SKELETON. 

direct  violence,  as  is  usually  the  case,  the  fragments  may  be  displaced  inward.  This  lesion  is 
often  attended  with  great  difficulty  or  even  inability  to  open  and  shut  the  mouth,  and  this  has 
been  stated  to  be  due  to  the  depressed  fragments  perforating  the  temporal  muscle,  but  would 
appear  rather  to  be  caused  by  the  injury  done  to  the  bony  origin  of  the  Masseter  muscle. 
Fractures  of  the  superior  maxilla  may  vary  much  in  degree,  from  the  chipping  off'  of  a  portion 
of  the  alveolar  arch,  a  frequent  accident  when  the  "old  key"  instrument  was  used  for  the 
extraction  of  teeth,  to  an  extensive  comminution  of  the  whole  bone  from  severe  violence,  as  the 
kick  of  a  horse.  The  most  common  situation  for  a  fracture  of  the  inferior  maxillary  bone  is  in 
the  neighborhood  of  the  canine  tooth,  as  at  this  spot  the  jaw  is  weakened  by  the  deep  socket  for 
the  fang  of  this  tooth  ;  it  is  next  most  frequently  fractured  at  the  angle  ;  then  at  the  symphysis, 
and  finally  the  neck  of  the  condyle  or  the  coronoid  process  may  be  broken.  Occasionally  a 
double  fracture  may  occur,  one  in  either  half  of  the  bone.  The  fractures  are  usually  compound, 
from  laceration  of  the  mucous  membrane  covering  the  gums.  The  displacement  is  mainly  the 
result  of  the  same  violence  as  produced  the  injury,  but  may  be  further  increased  by  the  action 
of  the  muscles  passing  from  the  neighborhood  of  the  symphysis  to  the  hyoid  bone. 

The  superior  and  inferior  maxillary  bones  are  both  of  them  frequently  the  seat  of  necrosis, 
though  the  disease  affects  the  lower  much  more  frequently  than  the  upper  jaw,  probably  on 
account  of  the  greater  supply  of  blood  to  the  latter.  It  may  be  the  result  of  periostitis,  from 
tooth  irritation,  injury,  or  the  action  of  some  specific  poison,  as  syphilis,  or  from  salivation  by 
mercury;  it  not  unfrequently  occurs  in  children  after  attacks  of  the  exanthematous  fevers,  and 
a  special  form  occurs  from  the  action  of  the  fumes  of  phosphorus  in  persons  engaged  in  match- 
making. 

Tumors  attack  the  jaw-bones  not  infrequently,  and  these  may  be  either  innocent  or  malig- 
nant: in  the  upper  jaw  cysts  may  occur  in  the  antrum,  constituting  the  so-called  dropsy  of  the 
antrum  ;  or,  again,  cysts  may  form  in  either  jaw  in  connection  with  the  teeth  :  either  cysts  con- 
nected with  the  roots  of  fully-developed  teeth,  the  "dental  cyst;"  or  cysts  connected  with 
imperfectly  developed  teeth,  the  ' '  dentigerous  cyst. ' '  Solid  innocent  tumors  include  the  fibroma, 
the  chondroma,  and  the  osteoma.  Of  malignant  tumors  there  are  two  classes,  the  sarcomata 
and  the  epithelioma.  The  sarcoma  are  of  various  kinds,  the  spindle-celled  and  round-celled,  of 
a  very  malignant  character,  and  the  myeloid  sarcoma,  principally  affecting  the  alveolar  margin  of 
the  bone.  Of  the  epitheliomata  we  find  the  squamous  variety  spreading  to  the  bone  from  the 
palate  or  gum,  and  the  cylindrical  epithelioma  originating  in  the  antrum  or  nasal  fossae. 

Both  superior  and  inferior  maxillary  bones  occasionally  require  removal  for  tumors  and  in 
some  other  conditions.  The  .upper  jaw  is  removed  by  an  incision  from  the  inner  canthus  of  the 
eye,  along  the  side  of  the  nose,  round  the  ala,  and  down  the  middle  line  of  the  upper  lip.  A 
second  incision  is  carried  outward  from  the  inner  canthus  of  the  eye  along  the  lower  margin  of 
the  orbit  as  far  as  the  prominence  of  the  malar  bone.  The  flap  thus  formed  is  reflected  outward 
and  the  surface  of  the  bone  exposed.  The  connections  of  the  bone  to  the  other  bones  of  the 
face  are  then  divided  with  a  narrow  saw.  They  are  (1 )  the  junction  with  the  malar  bone,  pass- 
ing into  the  spheno-maxillary  fissure ;  (2)  the  nasal  process;  a  small  portion  of  its  upper 
extremity,  connected  with  the  nasal  bone  in  front,  the  lachrymal  bone  behind,  and  the  frontal 
bone  above,  being  left;  (3)  the  connection  with  the  bone  on  the  opposite  side  and  the  palate  in 
the  roof  of  the  mouth.  The  bone  is  now  firmly  grasped  with  lion-forceps,  and  by  means  of  a 
rocking  movement  upward  and  downward  the  remaining  attachments  of  the  orbital  plate  with 
the  ethmoid,  and  the  back  of  the  bone  with  the  palate,  broken  through.  The  soft  palate  is  first 
separated  from  the  hard  with  a  scalpel,  and  is  not  removed.  Occasionally  in  removing  the  upper 
jaw  it  will  be  found  that  the  orbital  plate  can  be  spared,  and  this  should  always  be  done  if  possi- 
ble. A  horizontal  saw-cut  is  to  be  made  just  below  the  infraorbital  foramen  and  the  bone  cut 
through  with  a  chisel  and  mallet.  Removal  of  one-half  of  the  lower  jaw  is  sometimes  required. 
If  possible,  the  section  of  the  bone  should  be  made  to  one  side  of  the  symphysis,  so  as  to  save 
the  genial  tubercles  and  the  origin  of  the  genio-hyo-glossus  muscle,  as  otherwise  the  tongue  tends 
to  fall  backward  and  may  produce  suffocation.  Having  extracted  the  central  or  preferably  the 
lateral  incisor  tooth,  a  vertical  incision  is  made  down  to  the  bone,  commencing  at  the  free  margin 
of  the  lip,  and  carried  to  the  lower  border  of  the  bone ;  it  is  then  carried  along  its  lower  border 
to  the  angle  and  up  the  posterior  margin  of  the  ramus  to  a  level  with  the  lobule  of  the  ear. 
The  flap  thus  formed  is  raised  by  separating  all  the  structures  attached  to  the  outer  surface  of 
the  bone.  The  jaw  is  now  sawn  through  at  the  point  where  the  tooth  has  been  extracted,  and 
the  knife  passed  along  the  inner  side  of  the  jaw,  separating  the  structures  attached  to  this  sur- 
face. The  jaw  is  now  grasped  by  the  surgeon  and  strongly  depressed,  so  as  to  bring  down  the 
coronoid  process  and  enable  the  operator  to  sever  the  tendon  of  the  temporal  muscle.  The  jaw 
can  be  now  further  depressed,  care  being  taken  not  to  evert  it  or  rotate  it  outward,  which  would 
endanger  the  internal  maxillary  artery,  and  the  external  pterygoid  torn  through  or  divided.  The 
capsular  ligament  is  now  opened  in  front  and  the  lateral  ligaments  divided,  and  the  jaw  removed 
with  a  few  final  touches  of  the  knife. 

The  antrum  occasionally  requires  tapping  for  suppuration.  This  may  be  done  through  the 
socket  of  a  tooth,  preferably  the  first  molar,  the  fansrs  of  which  are  most  intimately  connected 
with  the  antrum,  or  through  the  facial  aspect  of  the  bone  above  the  alveolar  process.  This  latter 
method  does  not  perhaps  afford  such  efficient  drainage,  but  there  is  less  chance  of  food  finding 
its  way  into  the  cavity.  The  operation  may  be  performed  by  incising  the  mucous  membrane 
above  the  second  molar  tooth,  and  driving  a  trocar  or  any  sharp-pointed  instrument  into  the 
cavity. 


THE   HYOID    BDSE. 


227 


THE  HYOID  BONE. 

The  Hyoid  bone  is  named  from  its  resemblance  to  the  Greek  upsilon ;  it  is 
also  called  the  lingual  bone,  because  it  supports  the  tongue  and  gives  attachment 
to  its  numerous  muscles.  It  is  a  bony  arch,  shaped  like  a  horseshoe,  and 
consisting  of  five  segments,  a 

O 

body,  two  greater  cornua,  and 
two  lesser  cornua.  It  is  sus- 
pended from  the  tip  of  the  sty- 
loid  processes  of  the  temporal 
bone  by  ligamentous  bands,  the 
tfylo-kyoid  ligaments. 

The  Body  (basi-hyaT)  forms 
the  central  part  of  the  bone,  and 
is  of  a  quadrilateral  form ;  its 
anterior  surf  aw  (Fig.  178),  con- 
vex, directed  forward  and  upward. 


THYRO-MYOIO. 
STYLO-HYOIO. 


Body. 


zv; •-• :  : 


MYLO-HYOID. 


QENIO-HYOID. 


STERNO-HYOIO. 


FIG.  178.— Hyoid  bone.    Anterior  surface.    (Enlarged). 


is  divided  into  two  parts  by  a 
vertical  ridge  which  descends 
along  the  median  line,  and  is 
crossed  at  right  angles  by  a  hori- 
zontal ridge,  so  that  this  surface  is  divided  into  four  spaces  or  depressions.  At 
the  point  of  meeting  of  these  two  lines  is  a  prominent  elevation,  the  tubercle. 
The  portion  above  the  horizontal  ridge  is  directed  upward,  and  is  sometimes 
described  as  the  superior  border.  The  anterior  surface  gives  attachment  to  the 
Genio-hyoid  in  the  greater  part  of  its  extent ;  above,  to  the  Genio-hyo-glossus : 
below,  to  the  Mylo-hyoid,  Stylo-hyoid,  and  aponeurosis  of  the  Digastric 
(suprahyoid  aponeurosis) ;  and  between  these  to  part  of  the  Hyo-glossus. 
The  posterior  surface  is  smooth,  concave,  directed  backward  and  downward, 
and  separated  from  the  epiglottis  by  the  thyro-hyoid  membrane  and  by 
a  quantity  of  loose  areolar  tissue.  The  superior  border  is  rounded,  and 
gives  attachment  to  the  thyro-hyoid  membrane,  part  of  the  Genio-hyo-glossi  and 
Chondro-glossi  muscles.  The  inferior  border  gives  attachment,  in  front,  to  the 
Sterno-hyoid :  behind,  to  the  Omo-hyoid  and  to  part  of  the  Thyro-hyoid  at  its 
junction  with  the  great  cornu.  It  also  gives  attachment  to  the  Levator  glandulae 
thyroideae  when  this  muscle  is  present.  The  lateral  surfaces  are  small,  oval,  con- 
vex facets,  covered  with  cartilage  for  articulation  with  the  greater  cornua. 

The  Greater  Cornua  (thyro-hyat)  project  backward  from  the  lateral  surfaces  of 
the  body :  they  are  flattened  from  above  downward,  diminish  in  size  from  before 
backward,  and  terminate  posteriorly  in  a  tubercle  for  the  attachment  of  the  lat- 
eral thyro-hyoid  ligament.  The  outer  surface  gives  attachment  to  the  Hyo-glos- 
sus. their  upper  border  to  the  Middle  constrictor  of  the  pharynx,  their  lower  bor- 
der to  part  of  the  Thyro-hyoid  muscle.  In  youth  the  great  cornua  are  connected 
to  the  body  by  cartilaginous  surfaces  and  held  together  by  ligaments ;  in  middle 
life  they  usually  become  joined. 

The  Lesser  Cornua  (cerato-hyals)  are  two  small,  conical-shaped  eminences 
attached  by  their  bases  to  the  angles  of  junction  between  the  body  and  greater 
cornua.  and  giving  attachment  by  their  apices  to  the  stylo-hyoid  ligaments.1  The 
smaller  cornua  are  connected  to  the  body  of  the  bone  by  a  distinct  diarthrodial 
joint,  which  usually  persists  throughout  life,  but  occasionally  becomes  ankylosed. 

Development. — By  jive  centres :  one  for  the  body,  and  one  for  each   cornu. 
ncation  commences  in  the  body  about  the  eighth  month,  and  in  the  greater 
cornua  toward  the  end  of  foetal  life.     Ossification  of  the  lesser  cornua  commences 
some  months  after  birth. 

Attachment  of  Muscles. — Sterno-hyoid,  Thyro-hyoid,  Omo-hyoid,  aponeurosis 


1  These  ligaments  in  many  animals  are  distinct  bones,  and  in  man  are  occasionally  ossified  to  a 
certain  extent. 


228  THE   SKELETON. 

of  the  Digastric,  Stylo-hyoid,  Mylo-hyoid,  Genio-hyoid,  Genio-hyo-glossus,  Chon- 
dro-glossus,  Hyo-glossus,  Middle  constrictor  of  the  pharynx,  and  occasionally  a  few 
fibres  of  the  Lingualis.  It  also  gives  attachment  to  the  thyro-hyoidean  membrane 
and  the  stylo-hyoid,  thyro-hyoid,  and  hyo-epiglottic  ligaments. 

Surface  Form.— The  hyoid  bone  can  be  felt  in  the  receding  angle  below  the  chin,  and  the 
finger  can  be  carried  along  the  whole  length  of  the  bone  to  the  greater  cornu,  which  is  situated 
just  below  the  angle  of  the  jaw.  This  process  of  bone  is  best  perceived  by  making  pressure  on 
one  cornu,  and  so  pushing  the  bone  over  to  the  opposite  side,  when  the  cornu  of  this  side  will 
be  distinctly  felt  immediately  beneath  the  skin.  This  process  of  bone  is  an  important  landmark 
in  ligature  of  the  lingual  artery. 

Surgical  Anatomy. — The  hyoid  bone  is  occasionally  fractured,  generally  from  direct  vio- 
lence, as  in  the  act  of  garrotting  or  throttling.  The  great  cornu  is  the  part  of  the  bone  most  fre- 
quently broken,  but  sometimes  the  fracture  takes  place  through  the  body  of  the  bone.  In  con- 
sequence of  the  muscles  of  the  tongue  having  important  connections  with  this  bone,  there  is 
great  pain  upon  any  attempt  being  made  to  move  the  tongue,  as  in  speaking  or  swallowing. 

THE  THORAX. 

The  Thorax,  or  Chest,  is  an  osseo-cartilaginous  cage  containing  and  protecting 
the  principal  organs  of  respiration  and  circulation.  It  is  conical  in  shape,  being 
narrow  above  and  broad  below,  flattened  from  before  backward,  and  longer  behind 
than  in  front.  It  is  somewhat  cordiform  on  transverse  section. 

Boundaries. — The  posterior  surface  is  formed  by  the  twelve  dorsal  vertebrae 
and  the  posterior  part  of  the  ribs.  It  is  convex  from  above  downward,  and  pre- 
sents on  each  side  of  the  middle  line  a  deep  groove  inconsequence  of  the  direction 
backward  and  outward  which  the  ribs  take  from  their  vertebral  extremities  to 
their  angles.  The  anterior  surface  is  flattened  or  slightly  convex,  and  inclined 
forward  from  above  downward.  It  is  formed  by  the  sternum  and  costal  cartilages. 
The  lateral  surfaces  are  convex ;  they  are  formed  by  the  ribs,  separated  from  each 
other  by  spaces,  the  intercostal  spaces.  These  are  eleven  in  number,  and  are 
occupied  by  the  intercostal  muscles. 

The  upper  opening  of  the  thorax  is  reniform  in  shape,  being  broader  from  side 
to  side  than  from  before  backward.  It  is  formed  by  the  first  dorsal  vertebra 
behind,  the  upper  margin  of  the  sternum  in  front,  and  the  first  rib  on  each  side. 
It  slopes  downward  and  forward,  so  that  the  anterior  part  of  the  ring  is  on  a 
lower  level  than  the  posterior.  The  antero-posterior  diameter  is  about  two  inches. 
The  lower  opening  is  formed  by  the  twelfth  dorsal  vertebra  behind,  by  the  twelfth 
rib  at  the  sides,  and  in  front  by  the  cartilages  of  the  eleventh,  tenth,  ninth,  eighth, 
and  seventh  ribs,  which  ascend  on  either  side  and  form  an  angle,  the  subcostal 
angle,  from  the  centre  of  which  the  ensiform  cartilage  projects.  It  is  wider  trans- 
versely than  from  before  backward.  It  slopes  obliquely  downward  and  backward, 
so  that  the  cavity  of  the  thorax  is  much  deeper  behind  than  in  front.  The  Dia- 
phragm closes  in  the  opening  forming  the  floor  of  the  thorax. 

In  the  female  the  thorax  differs  as  follows  from  the  male :  1.  Its  general 
capacity  is  less.  2.  The  sternum  is  shorter.  3.  The  upper  margin  of  the  sternum 
is  on  a  level  with  the  lower  part  of  the  body  of  the  third  dorsal  vertebra,  whereas 
in  the  male  it  is  on  a  level  with  the  lower  part  of  the  body  of  the  second  dorsal 
vertebra.  4.  The  upper  ribs  are  more  movable,  and  so  allow  a  greater  enlargement 
of  the  upper  part  of  the  thorax  than  in  the  male. 

The  Sternum. 

The  Sternum  (orsovov,  the  chest)  (Figs.  179,  180)  is  a  flat,  narrow  bone,  sit- 
uated in  the  median  line  of  the  front  of  the  chest,  and  consisting,  in  the  adult,  of 
three  portions.  It  has  been  likened  to  an  ancient  sword;  the  upper  piece,  repre- 
senting the  handle,  is  termed  the  manubrium  ;  the  middle  and  largest  piece,  which 
represents  the  chief  part  of  the  blade,  is  termed  the  gladiolus  ;  and  the  inferior 
piece,  which  is  likened  to  the  point  of  the  sword,  is  termed  the  ensiform  or  xiphoid 
appendix.  In  its  natural  position  its  inclination  is  oblique  from  above  downward 
and  forward.  It  is  flattened  in  front,  concave  behind,  broad  above  becoming 


THE  STERNUM.  229 

narrowed  at  the  point  where  the  first  and  second  pieces  are  connected,  after  which 
it  again  widens  a  little,  and  is  pointed  at  its  extremity.  Its  average  length  in  the 
adult  is  six  inches,  being  rather  longer  in  the  male  than  in  the  female. 

The  First  Piece  of  the  sternum,  or  Manubrium  ( pre-stertium\  is  of  a  somewhat 
triangular  form,  broad  and  thick  above,  narrow  below  at  its  junction  with  the 
middle  piece.  Its  anterior  surface,  convex  from  side  to  side,  concave  from  above 
downward,  is  smooth,  and  affords  attachment  on  each  side  to  the  Pectoralis  major 
and  sternal  origin  of  the  Sterno-cleido-mastoid  muscle.  In  well-marked  bones  the 
ridges  limiting  the  attachment  of  these  muscles  are  very  distinct.  Its  posterior 
surface,  concave  and  smooth,  affords  attachment  on  each  side  to  the  Sterno-hyoid 
and  Sterno-thyroid  muscles.  The  superior  border,  the  thickest,  presents  at  its 
centre  the  pre-sternal  notch  ;  and  on  each  side  an  oval  articular  surface,  directed 
upward,  backward,  and  outward,  for  articulation  with  the  sternal  end  of  the 
clavicle.  The  inferior  border  presents  an  oval,  rough  surface,  covered  in  the  recent 
state  with  a  thin  layer  of  cartilage,  for  articulation  with  the  second  portion  of  the 
bone.  The  lateral  borders  are  marked  above  by  a  depression  for  the  first  costal 
cartilage,  and  below  by  a  small  facet,  which  with  a  similar  facet  on  the  upper 
angle  of  the  middle  portion  of  the  bone,  forms  a  notch  for  the  reception  of  the 
costal  cartilage  of  the  second  rib.  These  articular  surfaces  are  separated  by  a 
narrow,  curved  edge,  which  slopes  from  above  downward  and  inward. 

The  Second  Piece  of  the  sternum,  or  Gladiolus  (rneso-sternuni),  considerably 
longer,  narrower,  and  thinner  than  the  first  piece,  is  broader  below  than  above. 
Its  anten'»r  surface  is  nearly  flat,  directed  upward  and  forward,  and  marked  by 
three  transverse  lines  which  cross  the  bone  opposite  the  third,  fourth,  and  fifth 
articular  depressions.  These  lines  are  produced  by  the  union  of  the  four  separate 
pieces  of  which  this  part  of  the  bone  consists  at  an  early  period  of  life.  At  the 
junction  of  the  third  and  fourth  pieces  is  occasionally  seen  an  orifice,  the  sternal 
foramen  :  it  varies  in  size  and  form  in  different  individuals,  and  pierces  the  bone 
from  before  backward.  This  surface  affords  attachment  on  each  side  to  the 
sternal  origin  of  the  Pectoralis  major.  The  posterior  surface,  slightly  concave,  is 
also  marked  by  three  transverse  lines,  but  they  are  less  distinct  than  those  in 
front :  this  surface  affords  attachment  below,  on  each  side,  to  the  Triangularis 
sterni  muscle,  and  occasionally  presents  the  posterior  opening  of  the  sternal 
foramen.  The  superior  border  presents  an  oval  surface  for  articulation  with  the 
manubrium.  The  inferior  border  is  narrow,  and  articulates  with  the  ensiform 
appendix.  Each  lateral  border  presents,  at  each  superior  angle,  a  small  facet, 
which,  with  a  similar  facet  on  the  manubrium,  forms  a  cavity  for  the  cartilage  of 
the  second  rib ;  the  four  succeeding  angular  depressions  receive  the  cartilages  of 
the  third,  fourth,  fifth,  and  sixth  ribs ;  whilst  each  inferior  angle  presents  a  small 
facet,  which,  with  a  corresponding  one  on  the  ensiform  appendix,  forms  a  notch 
for  the  cartilage  of  the  seventh  rib.  These  articular  depressions  are  separated  by 
a  series  of  curved  interarticular  intervals,  which  diminish  in  length  from  above 
downward,  and  correspond  to  the  intercostal  spaces.  Most  of  the  cartilages 
belonging  to  the  true  ribs,  as  will  be  seen  from  the  foregoing  description,  articulate 
with  the  sternum  at  the  line  of  junction  of  two  of  its  primitive  component  seg- 
lents.  This  is  well  seen  in  many  of  the  lower  animals,  where  the  separate  parts 
of  the  bone  remain  ununited  longer  than  in  man.  In  this  respect  a  striking 
analogy  exists  between  the  mode  of  connection  of  the  ribs  with  the  vertebral 
column  and  the  connection  of  their  cartilages  with  the  sternal  column. 

The  Third  Piece  of  the  sternum,  the  Ensiform  or  Xiphoid  Appendix  (meta- 
sternum),  is  the  smallest  of  the  three;  it  is  thin  and  elongated  in  form,  cartilagi- 
nous in  structure  in  youth,  but  more  or  less  ossified  at  its  upper  part  in  the  adult. 
Its  anterior  surface  affords  attachment  to  the  chondro-xiphoid  ligament;  its 
posterior  surface,  to  some  of  the  fibres  of  the  Diaphragm  and  Triangularis  sterni 
muscles ;  its  lateral  borders,  to  the  aponeurosis  of  the  abdominal  muscles.  Above 
it  articulates  with  the  lower  end  of  the  gladiolus,  and  at  each  superior  angle 
presents  a  facet  for  the  lower  half  of  the  cartilage  of  the  seventh  rib ;  below,  by 


230 


THE   SKELETON. 


STERNO-CLEIDOMASTOID 


FIG.  179.— Sternum  and  costal  cartilages. 


FIG.  180.— Posterior  surface  of  sternum. 


THE   STERNUM. 


231 


its  pointed  extremity  it  gives  attachment  to  the  linea  alba.  This  portion  of  the 
sternum  is  very  various  in  appearance,  being  sometimes  pointed,  broad,  and  thin, 
sometimes  bifid  or  perforated  by  a  round  hole,  occasionally  curved  or  deflected 
Considerably  to  one  or  the  other  side. 

Structure. — The  bone  is  composed  of  delicate  cancellous  structure,  covered  by 
a  thin  layer  of  compact  tissue,  which  is  thickest  in  the  manubrium  between  the 
articular  facets  for  the  clavicles. 

Development. — The  sternum,  including  the  ensifonn  appendix,  is  developed  by 
•jntres :  one  for  the  first  piece  or  manubrium,  four  for  the  second  piece  or 


for  jirst  piece,  two  or  more  centra. 


for  third    ] 

for  fourth  }•  2,  placed  laterally. 


FIG.  181. — Development  of  the  sternum  by  six 
centres.    Time  of  appearance. 


Arrest  of  development 
of  lateral  piece*,  producing 


-Sternal  fissure,  and 
-Sternal  foramen. 


FIG.  182.— Time  of  union  of  sternum. 


gladiolus,  and  one  for  the  ensiform  appendix.     Up  to  the  middle  of  foetal  life  the 
sternum  is  entirely  cartilaginous,  and  when  ossification   takes  place  the  ossific 


I  Barely  unite, 

i    except  in  old  age. 


Between  puberty 
and  the  Soth  year. 

Soon  after  puberty. 


Partly  cartilaginous  to 
advanced  life. 


FIG.   184.— Peculiarities  in  mode 
of  union  of  sternum. 


5     1st  year  after 
birth.' 

1  for  ensiform  }      d  ^  im 

cartilage       J 
FIG.  183.— Peculiarities  in  number  of  centres  of 

sternum. 


granules  are  deposited  in  the  middle  of  the  intervals  between  the  articular  depres- 
-  for  the  costal  cartilages,  in  the  following  order  (Fig.  181):  In  the  first 
piece,  between  the  fifth  and  sixth  months;  in  the  second  and  third,  between  the 
sixth  and  seventh  months;  in  the  fourth  piece,  at  the  ninth  month;  in  the  fifth, 
within  the  first  year  or  between  the  first  and  second  years  after  birth ;  and  in  the 
ensiform  appendix,  between  the  second  and  the  seventeenth  or  eighteenth  years,  by  a 
single  centre  which  makes  its  appearance  at  the  upper  part  and  proceeds  gradually 
downward.  To  these  may  be  added  the  occasional  existence,  as  described  by 
Breschet.  of  two  small  episternal  centres,  which  make  their  appearance  one  on  each 
side  of  the  interclavicular  notch.  They  are  probably  vestiges  of  the  episternal  bone 
of  the  monotremata  and  lizards.  It  occasionally  happens  that  some  of  the  segments 
are  formed  from  more  than  one  centre,  the  number  and  position  of  which  vary 
(Fig.  183).  Thus,  the  first  piece  may  have  two,  three,  or  even  six  centres.  When 


232 


THE  SKELETON. 


\ 


Tuberosity.  two  are  present,  they  are  generally  situated  one 

above  the  other,  the  upper  one  being  the  larger ; 1 
the  second  piece  has  seldom  more  than  one ;  the 
third,  fourth,  and  fifth  pieces  are  often  formed 
from  two  centres  placed  laterally,  the  irregular 
union  of  which  will  serve  to  explain  the  occasional 

,5,  ,  .*c .,  occurrence  of  the  sternal  foramen  (Fig.  184),  or 

%  :  of  the  vertical  fissure  which  occasionally  intersects 

this  part  of  the  bone,  and  which  is  further  ex- 
.  plained  by  the  manner  in  which  the  cartilaginous 
matrix,  in  which  ossification  takes  place,  is  formed 
(see  page  115).  Union  of  the  various  centres  of  the 
gladiolus  commences  about  puberty,  from  below, 
and  proceeds  upward,  so  that  by  the  age  of  twenty- 
five  they  are  all  united,  and  this  portion  of  bone 
consists  of  one  piece  (Fig.  182).  The  ensiform  car- 
tilage becomes  joined  to  the  gladiolus  about  forty. 
The  manubrium  is  occasionally,  but  not  invariably, 
joined  to  the  gladiolus  in  advanced  life  by  bone. 
When  this  union  takes  place,  however,  it  is  gen- 
rally  only  superficial,  a  portion  of  the  centre  of  the 
sutural  cartilage  remaining  unossified. 

Articulations. — AVith  the  clavicles  and  seven 
costal  cartilages  on  each  side. 

Attachment  of  Muscles. — To  nine  pairs  and 
one  single  muscle :  the  Pectoralis  major,  Sterno- 
cleido-mastoid,  Sterno-hyoid,  Sterno-thyroid,  Tri- 
angularis  sterni,  aponeuroses  of  the  Obliquus  ex- 
ternus,  Obliquus  internus,  Transversalis,  Rectus 
muscles,  and  Diaphragm. 

The  Ribs. 

The  Ribs  are  elastic  arches  of  bone,  Avhich 
form  the  chief  part  of  the  thoracic  walls.  They 
are  twelve  in  number  on  each  side ;  but  this 
number  may  be  increased  by  the  development 
of  a  cervical  or  lumbar  rib,  or  may  be  dimin- 
ished to  eleven.  The  first  seven  are  connected 
behind  Avith  the  spine  and  in  front  with  the 
sternum,  through  the  intervention  of  the  costal 
cartilages ;  they  are  called  true  ribs.  The 
remaining  five  are  false  ribs ;  of  these,  the  first 
three  have  their  cartilages  attached  to  the 
cartilage  of  the  rib  above :  the  last  two  are 
free  at  their  anterior  extremities ;  they  are 
termed  floating  ribs.  The  ribs  vary  in  their 
direction,  the  upper  ones  being  less  oblique 
than  those  lowrer  down  and  occupying  the  middle 
of  the  series.  The  extent  of  obliquity  reaches  its 
maximum  at  the  ninth  rib,  and  gradually  de- 
creases from  that  rib  to  the  twelfth.  The  ribs  are 
situated  one  below  the  other  in  such  a  manner 
that  spaces  are  left  between  them,  which  are  called 
FIG.  185.— A  central  rib  of  right  side,  intercostal  spaces.  The  length  of  these  spaces 

corresponds    to    the    length    of    the    ribs;    their 
breadth  is  more  considerable  in  front  than  behind,  and  between  the  upper  than 


Sir  George  Humphry  states  that  this  is  "  probably  the  more  complete  condition." 


THE  RIBS.  233 

betv.-een  the  lower  ribs.  The  ribs  increase  in  length  from  the  first  to  the  seventh, 
when  they  again  diminish  to  the  twelfth.  In  breadth  they  decrease  from  above 
downward ;  in  the  upper  ten  the  greatest  breadth  is  at  the  sternal  extremity. 

Common  Characters  of  the  Ribs  (Fig.  185). — A  rib  from  the  middle  of  the 
series  should  be  taken  in  order  to  study  the  common  characters  of  the  ribs. 

Each  rib  presents  two  extremities,  a  posterior  or  vertebral,  an  anterior  or  ster- 
nal, and  an  intervening  portion — the  body  or  shaft. 

The  posterior  or  vertebral  extremity  presents  for  examination  a  head,  neck, 
and  tuberosity.  The  head  (Fig.  186)  is  marked  by  a  kidney-shaped  articular  sur- 
face, divided  by  a  horizontal  ridge  into  two  facets  for  articulation  with  the  costal 
cavity  formed  by  the  junction  of  the  bodies  of  two  contiguous  dorsal  vertebrae; 
the  upper  facet  is  small,  the  inferior  one  of  larger  size ;  the  ridge  separating  them 
serves  for  the  attachment  of  the  interarticular  ligament.  The  neck  is  that  flat- 
tened portion  of  the  rib  which  extends  outward  from  the  head ;  it  is  about  an 
inch  long,  and  is  placed  in  front  of  the  transverse  process  of  the  lower  of  the  two 
vertebra?  with  which  the  head  articulates.  Its  anterior  surface  is  flat  and  smooth. 
its  posterior  rough  for  the  attachment  of  the  middle  costo-transverse  ligament, 
and  perforated  by  numerous  foramina,  the  direction  of  which  is  less  constant  than 
those  found  on  the  inner  surface  of  the  shaft.  Of  its  two  borders  the  superior 
presents  a  rough  crest  for  the  attachment  of  the  anterior  costo-transverse  ligament ; 
its  inferior  border  is  rounded.  On  the  posterior  surface  of  the  neck,  just  where  it 

For  anterior  costo-transrerse  ligament. 

_^^-A-— — ^^For  posterior  costo-transtersc  ligament. 
Facet  for  body  of  upper  dorsal  rertebra.^ 

Ridge  for  interarticular  ligament.^ 


Facet  for  body  of  loicer  dorsal  vertebra. 

For  transverse  process  of  lower  dorsal  tertebr 


FIG.  186.— Vertebral  extremity  of  a  rib.    External  surface. 

joins  the  shaft,  and  nearer  the  lower  than  the  upper  border,  is  an  eminence — the 
tuberosity,  or  tubercle ;  it  consists  of  an  articular  and  a  non-articular  portion. 
The  articular  portion,  the  more  internal  and  inferior  of  the  two,  presents  a  small. 
oval  surface  for  articulation  with  the  extremity  of  the  transverse  process  of  the 
lower  of  the  two  vertebrae  to  which  the  head  is  connected.  The  non-articular 
portion  is  a  rough  elevation,  which  affords  attachment  to  the  posterior  costo- 
transverse  ligament.  The  tubercle  is  much  more  prominent  in  the  upper  than  in 
the  lower  ribs. 

The  shaft  is  thin  and  flat,  so  as  to  present  two  surfaces,  an  external  and  an 
internal,  and  two  borders,  a  superior  and  an  inferior.  The  external  surface  is 
convex,  smooth  and  marked  at  its  back  part,  a  little  in  front  of  the  tuberosity.  by 
a  prominent  line,  directed  obliquely  from  above  downward  and  outward ;  this 
gives  attachment  to  a  tendon  of  the  Ilio-costalis  muscle  or  of  one  of  its  accessory 
portions,  and  is  called  the  angle.  At  this  point  the  rib  is  bent  in  two  directions. 
If  the  rib  is  laid  upon  its  lower  border,  it  will  be  seen  that  the  portion  of  the  shaft 
in  front  of  the  angle  rests  upon  this  border,  while  the  portion  of  the  shaft  behind 
the  angle  is  bent  inward  and  at  the  same  time  tilted  upward.  The  interval 
between  the  angle  and  the  tuberosity  increases  gradually  from  the  second  to  the 
tenth  rib.  The  portion  of  bone  between  these  two  parts  is  rounded,  rough,  and 
irregular,  and  serves  for  the  attachment  of  the  Longissirnus  dorsi  muscle.  The 
portion  of  bone  between  the  tubercle  and  sternal  extremity  is  also  slightly  twisted 
upon  its  own  axis,  the  external  surface  looking  downward  behind  the  angle,  a  little 
upward  in  front  of  it.  This  surface  presents,  toward  its  sternal  extremity,  an 
oblique  line,  the  anterior  angle.  The  internal  surface  is  concave,  smooth,  directed 
a  little  upward  behind  the  angle,  a  little  downward  in  front  of  it.  This  surface 
is  marked  by  a  ridge  which  commences  at  the  lower  extremity  of  the  head ;  it  is 


234  THE  SKELETON. 

strongly  marked  as  far  as  the  inner  side  of  the  angle,  and  gradually  becomes  lost 
at  the  junction  of  the  anterior  with  the  middle  third  of  the  bone.  The  interval 
between  it  and  the  inferior  border  is  deeply  grooved,  to  lodge  the  intercostal 
vessels  and  nerve.  At  the  back  part  of  the  bone  this  groove  belongs  to  the 
inferior  border,  but  just  in  front  of  the  angle,  where  it  is  deepest  and  broadest,  it 
corresponds  to  the  internal  surface.  The  superior  edge  of  the  groove  is  rounded ;  it 
serves  for  the  attachment  of  the  Internal  intercostal  muscle.  The  inferior  edge 

O 

corresponds  to  the  lower  margin  of  the  rib  and  gives  attachment  to  the  External 
intercostal.  Within  the  groove  are  seen  the  orifices  of  numerous  small  foramina 
which  traverse  the  wall  of  the  shaft  obliquely  from  before  backward.  The 
superior  border,  thick  and  rounded,  is  marked  by  an  external  and  an  internal  lip. 
more  distinct  behind  than  in  front ;  they  serve  for  the  attachment  of  the  External 
and  Internal  intercostal  muscles.  The  inferior  border,  thin  and  sharp,  has  attached 
to  it  the  External  intercostal  muscle.  The  anterior  or  sternal  extremity  is  flat- 
tened, and  presents  a  porous,  oval,  concave  depression,  into  which  the  costal 
cartilage  is  received. 

Peculiar  Ribs. 

The  ribs  which  require  especial  consideration  are  five  in  number — viz.  the  first, 
second,  tenth,  eleventh  and  twelfth. 

The  first  rib  (Fig.  187)  is  one  of  the  shortest  and  the  most  curved  of  all  the  ribs  ; 
it  is  broad  and  flat,  its  surfaces  looking  upward  and  downward,  and  its  borders 
inward  and  outward.  The  head  is  of  small  size,  rounded,  and  presents  only  a 
single  articular  facet  for  articulation  with  the  body  of  the  first  dorsal  vertebra. 
The  neck  is  narrow  and  rounded.  The  tuberosity,  thick  and  prominent,  rests  on 
the  outer  border.  There  is  no  angle,  but  in  this  situation  the  rib  is  slightly  bent, 
with  the  convexity  of  the  bend  upward,  so  that  the  head  of  the  bone  is  directed 
downward.  The  upper  surface  of  the  shaft  is  marked  by  two  shallow  depressions, 
separated  from  one  another  by  a  small  rough  surface  for  the  attachment  of  the 
Scalenus  anticus  muscle — the  groove  in  front  of  it  transmitting  the  subclavian 
vein,  that  behind  it  the  subclavian  artery.  Between  the  groove  for  the  subclavian 
artery  and  the  tuberosity  is  a  rough  surface,  for  the  attachment  of  the  Scalenus 
medius  muscle.  The  under  surface  is  smooth,  and  destitute  of  the  groove  observed 
on  the  other  ribs.  The  outer  border  is  convex,  thick,  and  rounded,  and  at  its 
posterior  part  gives  attachment  to  the  first  serration  of  the  Serratus  magnus ;  the 
inner  is  concave,  thin,  and  sharp,  and  marked  about  its  centre  by  the  commence- 
ment of  the  rough  surface  for  the  Scalenus  anticus.  The  anterior  extremity  is 
larger  and  thicker  than  any  of  the  other  ribs. 

The  second  rib  (Fig.  188)  is  much  longer  than  the  first,  but  bears  a  very  con- 
siderable resemblance  to  it  in  the  direction  of  its  curvature.  The  non-articular 
portion  of  the  tuberosity  is  occasionally  only  slightly  marked.  The  angle  is  slight 
and  situated  close  to  the  tuberosity,  and  the  shaft  is  not  twisted,  so  that  both  ends 
touch  any  plane  surface  upon  which  it  may  be  laid ;  but  there  is  a  similar  though 
slighter  bend,  with  its  convexity  upward,  to  that  found  in  the  first  rib.  The  shaft 
is  not  horizontal,  like  that  of  the  first  rib,  its  outer  surface,  which  is  convex,  look- 
ing upward  and  a  little  outward.  It  presents,  near  the  middle,  a  rough  eminence 
for  the  attachment  of  the  second  and  third  digitations  of  the  Serratus  magnus ; 
behind  and  above  which  is  attached  the  Scalenus  posticus.  The  inner  surface, 
smooth  and  concave,  is  directed  downward  and  a  little  inward ;  it  presents  a  short 
groove  toward  its  posterior  part. 

The  tenth  rib  (Fig.  189)  has  only  a  single  articular  facet  on  its  head. 

The  eleventh  and  twelfth  ribs  (Figs.  190  and  191)  have  each  a  single  articular 
facet  on  the  head,  which  is  of  rather  large  size  ;  they  have  no  neck  or  tuberosity, 
and  are  pointed  at  the  extremity.  The  eleventh  has  a  slight  angle  and  a  shallow 
groove  on  the  lower  border.  The  twelfth  has  neither,  and  is  much  shorter  than 
the  eleventh,  and  the  head  has  a  slight  inclination  downward. 

Structure. — The  ribs  consist  of  cancellous  tissue  enclosed  in  a  thin,  compact  layer. 


PECULIAR    RIBS. 


23o 


Development. — Each  rib,  with  the  exception  of  the  last  two,  is  developed  by 
three  centres  :  one  for  the  shaft,  one  for  the  head,  and  one  for  the  tubercle.  The 
last  tw»»  have  only  two  centres,  that  for  the  tubercle  being  wanting.  Ossification 
commences  in  the  shaft  of  the  ribs  at  a  very  early  period,  before  its  appearance  in 
the  vertebne.  The  epiphysis  of  the  head,  which  is  of  slightly  angular  shape,  and 
that  for  the  tubercle,  of  a  lenticular  form,  make  their  appearance  between  the  six- 


FIG. 


\\gleat-f 


FIG 


Angle 

slightly  marked 

and  close  to 

htberosity. 


FIG.  189. 
Single  articular  facet. 

FIG.  190. 
Fingle  articular  facet ^- 


FlG.  191. 
Single  articular  facet. 


FIGS.  187-191.— Peculiar  ribs. 

teenth  and  twentieth  years,  and  are  not  united  to  the  rest  of  the  bone  until  about 
the  twenty-fifth  year. 

Attachment  of  Muscles. — The  Internal  and  External  intercostals,  Scalenus 
anticus.  Scalenus  medius,  Scalenus  posticus,  Pectoralis  minor,  Serratus  magnus, 
Obliquus  externus,  Obliquus  internus,  Transversalis.  Quadratus  lumborum.  Dia- 
phragm, Latissimus  dorsi,  Serratus  posticus  superior,  Serratus  posticus  inferior, 
Ilio-costalis.  Musculus  accessorius  ad  ilio-costalem.  Longissimus  dorsi.  Cervicalis 
ascendens.  Levatores  costarum,  and  Infracostales. 


236  THE  SKELETON. 

The  Costal  Cartilages. 

The  Costal  Cartilages  (Fig.  179,  p.  230)  are  white,  elastic  structures,  which  serve 
to  prolong  the  ribs  forward  to  the  front  of  the  chest,  and  contribute  very  materially 
to  the  elasticity  of  its  walls.  The  first  seven  are  connected  with  the  sternum,  the 
next  three  with  the  lower  border  of  the  cartilage  of  the  preceding  rib.  The  car- 
tilages of  the  last  two  ribs,  which  have  pointed  extremities,  float  freely  in  the 
walls  of  the  abdomen.  Like  the  ribs,  the  costal  cartilages  vary  in  their  length, 
breadth,  and  direction.  They  increase  in  length  from  the  first  to  the  seventh,  then 
gradually  diminish  to  the  last.  They  diminish  in  breadth,  as  well  as  the  intervals 
between  them,  from  the  first  to  the  last.  They  are  broad  at  their  attachment  to 
the  ribs,  and  taper  toward  their  sternal  extremities,  excepting  the  first  two,  which 
are  of  the  same  breadth  throughout,  and  the  sixth,  seventh  and  eighth,  which  are 
enlarged  where  their  margins  are  in  contact.  In  direction  they  also  vary  :  the  first 
descends  a  little,  the  second  is  horizontal,  the  third  ascends  slightly,  whilst  all  the 
rest  follow  the  course  of  the  ribs  for  a  short  extent,  and  then  ascend  to  the  sternum 
or  preceding  cartilage.  Each  costal  cartilage  presents  two  surfaces,  two  borders, 
and  two  extremities.  The  anterior  surface  is  convex,  and  looks  forward  and 
upward :  that  of  the  first  gives  attachment  to  the  costo-clavicular  ligament  and  the 
•Subclavius  muscle  ;  that  of  the  second,  third,  fourth,  fifth,  and  sixth,  at  their  sternal 
ends,  to  the  Pectoralis  major.1  The  others  are  covered  by,  and  give  partial  attach- 
ment to,  some  of  the  great  flat  muscles  of  the  abdomen.  The  posterior  surface 
is  concave,  and  directed  backward  and  downward,  the  first  giving  attachment  to 
the  Sterno-thyroid,  and  the  six  or  seven  inferior  ones  affording  attachment  to  the 
Transversalis  muscle  and  the  Diaphragm.  Of  the  two  borders,  the  superior  is 
concave,  the  inferior  convex :  they  afford  attachment  to  the  Intercostal  muscles, 
the  upper  border  of  the  sixth  giving  attachment  to  the  Pectoralis  major  muscle. 
The  contiguous  borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the  ninth 
and  tenth,  costal  cartilages  present  small,  smooth,  oblong-shaped  facets  at  the 
points  where  they  articulate.  Of  the  two  extremities,  the  outer  one  is  continuous 
with  the  osseous  tissue  of  the  rib  to  which  it  belongs.  The  inner  extremity  of  the 
first  is  continuous  with  the  sternum ;  the  six  succeeding  ones  have  rounded 
extremities,  which  are  received  into  shallow  concavities  on  the  lateral  margins  of 
the  sternum.  The  inner  extremities  of  the  eighth,  ninth,  and  tenth  costal  cartilages 
are  pointed,  and  are  connected  with  the  cartilage  above.  Those  of  the  eleventh  and 
twelfth  are  free  and  pointed. 

The  costal  cartilages  are  most  elastic  in  youth,  those  of  the  false  ribs  being 
more  so  than  the  true.  In  old  age  they  become  of  a  deep  yellow  color,  and  are 
prone  to  calcify. 

Attachment  of  Muscles. — To  nine :  the  Subclavius,  Sterno-thyroid,  Pectoralis 
major,  Internal  oblique,  Transversalis,  Rectus,  Diaphragm,  Triangularis  sterni,  and 
Internal  intercostals. 

Surface  Form. — The  bones  of  the  chest  are  to  a  very  considerable  extent  covered  by 
muscles,  so  that  in  the  strongly-developed  muscular  subject  they  are  for  the  most  part  con- 
cealed. In  the  emaciated  subject,  on  the  other  hand,  the  ribs,  especially  in  the  lower  and 
lateral  region,  stand  out  as  prominent  ridges  with  the  sunken,  intercostal  spaces  between 
them. 

In  the  middle  line,  in  front,  the  superficial  surface  of  the  sternum  is  to  be  felt  throughout 
its  entire  length,  at  the  bottom  of  a  deep  median  furrow  situated  between  the  two  great  pectoral 
muscles  and  called  the  sternal  furrow.  These  muscles  overlap  the  anterior  surface  somewhat,  so 
that  the  whole  of  the  sternum  in  its  entire  width  is  not  subcutaneous  ;  and  this  overlapping  is 
greater  opposite  the  centre  of  the  bone  than  above  and  below,  so  that  the  furrow  is  wider  at  its 
upper  and  lower  parts,  but  narrower  in  the  middle.  The  centre  of  the  upper  border  of  the  ster- 
num is  visible,  constituting  the  pre-sternal  notch,  but  the  lateral  parts  of  this  border  are  obscured 
by  the  tendinous  origins  of  the  Sterno-mastoid  muscles,  which  present  themselves  as  oblique 
tendinous  cords,  which  narrow  and  deepen  the  notch.  Lower  down  on  the  subcutaneous  surface 
a  well-defined  transverse  ridge  is  always  to  be  felt.  This  denotes  the  line  of  junction  of  the 
manubrium  and  body  of  the  bone,  and  is  a  useful  guide  to  the  second  costal  cartilage,  and  thus 
to  the  identity  of  any  given  rib.  The  second  rib  being  found  through  its  costal  cartilage, 

1  The  first  and  seventh  also,  occasionally, give  origin  to  the  same  muscle. 


THE    COSTAL    CARTILAGES.  237 

it  is  easy  to  count  downward  and  find  any  other  Below  this  point  the  furrow  spreads  out, 
and.  exposing  more  of  the  surface  of  the  body  of  the  sternum,  terminates  below  in  a  sudden 
depression,  the  infmstrntal  rAy»/vW«/<  or  pit  of  the  stomacli  (scrobiculus  cordis),  which  corre- 
sponds to  the  ensiform  cartilage.  This  depression  lies  between  the  cartilages  of  the  seventh  rib. 
and  in  it  the  ensiform  cartilage  may  lie  felt.  The  sternum  in  its  vertical  diameter  presents  a 

feneral  convexity  forward,  the  most  prominent  point  of  which  is  at  the  joint  between  the  rnanu- 
riuru  and  gladiolus. 

On  each  side  of  the  sternum  the  costal  cartilages  and  ribs  on  the  front  of  the  chest  are  par- 
tially obscured  by  the  great  pectoral  muscle:  through  which,  however,  they  are  to  be  felt  as 

s,  with  depressed  intervals  between  them,  corresponding  to  the  intercostal  spaces.    Of  these 
9,  the  one  between  the  second  and  third  ribs  i.s  the  widest,  the  next  two  somewhat  nar- 
rower, and  the  remainder,  with  the  exception  of  the  last  two,  comparatively  narrow. 

The  lower  border  of  the  Pectoralis  major  muscle  corresponds  to  the  fifth  rib,  and  below 
this,  on  the  front  of  the  chest,  the  broad,  flat  outline  of  the  ribs,  as  they  begin  to  ascend, 
and  the  more  rounded  outline  of  the  costal  cartilages,  are  often  visible.  The  lower  boundary 
of  the  front  of  the  thorax,  the  nltdomi no-thoracic,  arcA,  which  is  most  plainly  seen  by 
arching  the  body  backward,  is  formed  by  the  ensiform  cartilage  and  the  cartilages  of  the 
seventh,  eighth,  ninth,  and  tenth  ribs,  and  the  extremities  of  the  eleventh  and  twelfth  ribs  or 
then:  cartii 

On  each  side  of  the  chest,  from  the  axilla  downward,  the  flattened  external  surfaces  of  the 
ribs  may  be  defined  in  the  form  of  oblique  ridges,  separated  by  depressions  corresponding  to  the 
intercostal  spaces.  They  are.  however,  covered  by  muscles,  which  obscure  their  outline  to  a 
certain  extent  in  the  strongly  deve^pedfc^^vertheless.  the  ribs,  with  the  e^BBfea^^^JISL- 
can  generally  be  followed  over  the  f%wJlMU^^^^ij|^^H^lHflBH|^l 
being  almost  completely  covered  by^P^^^W^^RRH^MB^mwify  oe  dlstflfguisnea  ma  small 
portion  of  its  extent.  At  the  back  the  angles  of  the  ribs  form  a  slightly-marked  oblique  line  on 
each  side  of  and  some  distance  from  the  vertebral  spines.  This  line  diverges  somewhat  as  it 
descends,  and  external  to  it  is  a  broad,  convex  surface  caused  by  the  projection  of  the  ribs 
beyond  their  angles.  Over  this  surface,  except  where  covered  by  the  scapula,  the  individual 
ribs  can  be  distinguished. 

Surgical  Anatomy. — Malformations  of  the  sternum  present  nothing  of  surgical  importance 
beyond  the  fact  that  abscesses  of  the  mediastinum  may  sometimes  escape  through  the  sternal 
foramen.  Fractures  of  the  sternum  are  by  no  means  common,  owing,  no  doubt,  to  the  elasticity 
of  the  ribs  and  their  cartilages,  which  support  it  like  so  many  springs.  It  is  frequently  asso- 
ciate'! with  fracture  of  the  spine,  and  may  be  caused  by  forcibly  bending  the  body  either  back- 
ward or  forward  until  the  chin  becomes  impacted  against  the  top  of  the  sternum.  It  may  also 
be  fractured  by  direct  violence  or  by  muscular  action.  The  fracture  usually  occurs  in  the  upper 
half  of  the  body  of  the  bone.  Dislocation  of  the  gladiolus  from  the  manubrium  also  takes  place, 
and  is  sometimes  described  as  a  fracture. 

The  bone,  being  subcutaneous,  is  frequently  the  seat  of  gummatous  tumors,  and  not  uncom- 
monly is  affected  with  caries.  Occasionally  the  bone,  and  especially  its  ensifonn  appendix,  becomes 
altered  in  shape  and  driven  inward  by  the  pressure,  in  workmen,  of  tools  against  their  chest. 

The  ribs  are  frequently  broken,  though  from  their  connections  and  shape  they  are  able  to 
withstand  great  force,  yielding  under  the  injury  and  recovering  themselves  like  a  spring.  The 
middle  of  the  series  are  the  ones  most  liable  to  fracture.  The  first,  and  to  a  less  extent  the 
second,  being  protected  by  the  clavicle,  are  rarely  fractured  ;  and  the  eleventh  and  twelfth,  on 
account  of  their  loose  and  floating  condition,  enjoy  a  like  immunity.  The  fracture  generally 
occurs  from  indirect  violence,  from  forcible  compression  of  the  chest-wall,  and  the  bone  then 

fives  way  at  its  weakest  part — /'.  e.  just  in  front  of  the  angle.  But  the  ribs  may  also  be  broken 
y  direct  violence,  when  the  bone  gives  way  and  is  driven  inward  at  the  point  struck,  or  by  mus- 
cular action.  It  seems  probable,  however,  that  in  these  latter  cases  the  bone  has  undergone 
some  atrophic  changes.  Fracture  of  the  ribs  is  frequently  complicated  with  some  injury  to  the 
viscera  contained  within  the  thorax  or  upper  part  of  the  abdominal  cavity,  and  this  is  most  likely 
to  occur  in  fractures  from  direct  violence. 

Fracture  of  the  costal  cartilages  may  also  take  place,  though  it  is  a  comparatively  rare  injury. 

The  thorax  is  frequently  found  to  be  altered  in  shape  in  certain  diseases. 

The  rickety  thorax  is  caused  chiefly  by  atmospheric  pressure.  The  balance  between  the  air 
on  the  inside  of  the  chest  and  the  outside  during  some  stage  of  respiration  is  not  equal,  the  pre- 
ponderance being  in  favor  of  the  air  outside  ;  and  this,  acting  on  the  softened  ribs,  causes  them 
to  be  forced  in  at  the  junction  of  the  cartilages  with  the  bones,  which  is  the  weakest  part.  In 
consequence  of  this  the  sternum  projects  forward,  with  a  deep  depression  on  either  side  caused 
by  the  sinking  in  of  the  softened  ribs.  The  depression  is  less  on  the  left  side,  on  account  of 
the  ribs  being  supported  by  the  heart.  The  condition  is  known  as  "pigeon-breast."'  The 
lower  ribs,  however,  are  not  involved  in  this  deformity,  as  they  are  prevented  from  falling  in  by 
the  presence  of  the  stomach,  liver,  and  spleen.  And  when  the  liver  and  spleen  are  enlarged, 
as  they  sometimes  are  in  rickets,  the  lower  ribs  may  be  pushed  outward :  this  causes  a  trans- 
verse constriction  just  above  the  costal  arch.  The  anterior  extremities  of  the  ribs  are  usually 
enlarged  in  rickets,  giving  rise  to  what  has  been  termed  the  ''rickety  rosary."  The  phthisical 
chfst  is  often  long  and  narrow,  flattened  from  before  backward,  and  with  great  obliquity  of  the 
ribs  and  projection  of  the  scapulae.  In  pnlmonnry  emphysema  the  chest  is  enlarged  in  all  its 
diameters,  and  presents  on  section  an  almost  circular  outline.  It  has  received  the  name  of  the 


238  THE  SKELETON. 

"  barrel-shaped  chest. "  In  severe  cases  of  lateral  curvature  of  the  spine  the  thorax  becomes 
much  distorted.  In  consequence  of  the  rotation  of  the  bodies  of  the  vertebrae  which  takes 
place  in  this  disease  the  ribs  opposite  the  convexity  of  the  dorsal  curve  become  extremely  con- 
vex behind,  being  thrown  out  and  bulging,  and  at  the  same  time  flattened  in  front,  so  that  the 
two  ends  of  the  same  rib  are  almost  parallel.  Coincident  with  this,  the  ribs  on  the  opposite 
side,  on  the  concavity  of  the  curve,  are  sunk  and  depressed  behind  and  bulging  and  convex  in 
front.  In  addition  to  this  the  ribs  become  occasionally  welded  together  by  bony  material. 

The  ribs  are  frequently  the  seat  of  necrosis  leading  to  abscesses  and  sinuses,  which  may 
burrow  to  a  considerable  extent  over  the  wall  of  the  chest.  The  only  special  anatomical  point 
in  connection  with  these  is  that  care  must  be  taken  in  dealing  with  them  that  the  intercostal 
spaee  is  not  punctured  and  the  pleural  cavity  opened  or  the  intercostal  vessels  wounded. 

In  cases  of  empyema  the  chest  requires  opening  to  evacuate  the  pus.  There  is  consider- 
able difference  of  opinion  as  to  the  best  position  to  do  this.  Probably  the  best  place  in  most 
cases  will  be  found  to  be  between  the  fifth  and  sixth  ribs,  in  or  a  little  in  front  of  the  mid- 
axillary  line.  This  is  the  last  part  of  the  cavity  to  be  closed  by  the  expansion  of  the  lung ;  it 
is  not  thickly  covered  by  soft  parts ;  the  space  between  the  two  ribs  is  sufficiently  great  to  allow 
of  the  introduction  of  a  fair-sized  drainage-tube,  and  the  opening  is  in  a  dependent  position, 
when  the  patient  is  confined  to  bed,  as  he  usually  inclines  toward  the  affected  side,  so  as  to 
allow  the  sound  lung  the  freest  possible  play,  and  so  permits  of  efficient  drainage. 

OF   THE   EXTREMITIES. 

The  extremities,  or  limbs,  are  those  long,  jointed  appendages  of  the  body 
which  are  connected  to  the  trunk  by  one  end  and  free  in  the  rest  of  their  extent. 
They  are  four  in  number :  an  upper  or  thoracic  pair,  connected  with  the  thorax 
through  the  intervention  of  the  shoulder,  and  subservient  mainly  to  prehension ; 
and  a  lower  pair,  connected  with  the  pelvis,  intended  for  support  and  locomotion. 
Both  pairs  of  limbs  are  constructed  after  one  common  type,  so  that  they  present 
numerous  analogies,  while  at  the  same  time  certain  differences  are  observed  in  each, 
dependent  on  the  peculiar  offices  they  have  to  perform. 

The  bones  by  which  the  upper  and  lower  limbs  are  attached  to  the  trunk  are 
named  respectively  the  shoulder  and  pelvic  girdles,  and  they  are  constructed  on  the 
same  general  type,  though  presenting  certain  modifications  relating  to  the  different 
uses  to  which  the  upper  and  lower  limbs  are  respectively  applied.  The  shoulder 
girdle  is  formed  by  the  scapula  and  clavicle,  and  is  imperfect  in  front  and  behind. 
In  front,  however,  the  girdle  is  completed  by  the  upper  end  of  the  sternum,  with 
which  the  inner  extremities  of  the  clavicle  artic.ulate.  Behind,  the  girdle  is  widely 
imperfect  and  the  scapula  is  connected  to  the  trunk  by  muscles  only.  The  pelvic 
girdle  is  formed  by  the  innominate  bones,  and  is  completed  in  front  through  the 
symphysis  pubis,  at  which  the  two  innominate  bones  articulate  with  each  other. 
It  is  imperfect  behind,  but  the  intervening  gap  is  filled  in  by  the  upper  part  of 
the  sacrum.  The  pelvic  girdle,  therefore,  presents,  with  the  sacrum,  a  complete 
ring,  comparatively  fixed,  and  presenting  an  arched  form  which  confers  upon  it  a 
solidity  manifestly  intended  for  the  support  of  the  trunk,  and  in  marked  contrast 
to  the  lightness  and  mobility  of  the  shoulder  girdle. 

With  regard  to  the  morphology  of  these  girdles,  the  blade  of  the  scapula  is 
generally  believed  to  correspond  to  the  ilium ;  but  with  regard  to  the  clavicles 
there  is  some  difference  of  opinion :  formerly  it  was  believed  that  they  corre- 
sponded to  the  ossa  pubis,  meeting  at  the  symphysis,  but  it  is  now  generally  taught 
that  the  clavicle  has  no  homologue  in  the  pelvic  girdle,  and  that  the  os  pubis  and 
ischium  are  represented  by  the  small  coracoid  process  in  man  and  most  mammals. 

THE  UPPER  EXTREMITY. 

The  bones  of  the  upper  extremity  consist  of  those  of  the  shoulder  girdle,  of 
the  arm,  the  forearm,  and  the  hand.  The  shoulder  girdle  consists  of  two  bones, 
the  clavicle  and  the  scapula. 

THE  SHOULDER. 

The  Clavicle. 

The  Clavicle  (clavis,  a  key),  or  collar-bone,  forms  the  anterior  portion  of  the 
shoulder  girdle.  It  is  a  long  bone,  curved  somewhat  like  the  italic  letter  /,  and 


THE    CLAVICLE.  239 

placed  nearly  horizontally  at  the  upper  and  anterior  part  of  the  thorax,  immediately 
above  the  first  rib.  It  articulates  by  its  inner  extremity  with  the  upper  border  of 
the  sternum,  and  by  its  outer  extremity  with  the  acromion  process  of  the  scapula, 
serving  to  sustain  the  upper  extremity  in  the  various  positions  which  it  assumes, 
whilst  at  the  same  time  it  allows  of  great  latitude  of  motion  in  the  arm.1  It 
presents  a  double  curvature  when  looked  at  in  front,  the  convexity  being  forward 
at  the  sternal  end  and  the  concavity  at  the  scapular  end.  Its  outer  third  is  flat- 
tened from  above  downward,  and  extends,  in  the  natural  position  of  the  bone,  from 
a  point  opposite  the  coracoid  process  to  the  acromion.  Its  inner  two-thirds  are  of 
a  cylindrical  form,  and  extend  from  the  sternum  to  a  point  opposite  the  coracoid 
process  of  the  scapula. 

External  or  Flattened  Portion. — The  outer  third  is  flattened  from  above  down- 
ward si  as  to  present  two  surfaces,  an  upper  and  a  lower;  and  two  borders, 
an  anterior  and  a  posterior.  The  upper  surface  is  flattened,  rough,  marked  by 
impressions  for  the  attachment  of  the  Deltoid  in  front  and  the  Trapezius  behind; 
between  these  two  impressions,  externally,  a  small  portion  of  the  bone  is  sub- 
cutaneous. The  under  surface  is  flattened.  At  its  posterior  border,  a  little 
external  to  the  point  where  the  prismatic  joins  with  the  flattened  portion,  is  a  rough 
eminence,  the  conoid  tubercle  ;  this,  in  the  natural  position  of  the  bone,  surmounts 
the  coracoid  process  of  the  scapula  and  gives  attachment  to  the  conoid  ligament. 
From  this  tubercle  an  oblique  line,  occasionally  a  depression,  passes  forward  and 
outward  to  near  the  outer  end  of  the  anterior  border ;  it  is  called  the  oblique  line. 
and  affords  attachment  to  the  trapezoid  ligament.  The  anterior  border  is  concave, 
thin,  and  rough,  and  gives  attachment  to  the  Deltoid ;  it  occasionally  presents,  at 
its  inner  end,  at  the  commencement  of  the  deltoid  impression,  a  tubercle,  the 
deltoid  tubercle,  which  is  sometimes  to  be  felt  in  the  living  subject.  The  posterior 
border  is  convex,  rough,  broader  than  the  anterior,  and  gives  attachment  to  the 
Trapezius. 

Internal  or  Cylindrical  Portion. — The  cylindrical  portion  forms  the  inner  tico- 
tJdrds  of  the  bone.  It  is  curved  so  as  to  be  convex  in  front,  concave  behind,  and 
is  marked  by  three  borders,  separating  three  surfaces.  The  anterior  border  is 
continuous  with  the  anterior  margin  of  the  flat  portion.  At  its  commencement  it 
is  smooth,  and  corresponds  to  the  interval  between  the  attachment  of  the  Pectoralis 
major  and  Deltoid  muscles ;  at  the  inner  half  of  the  clavicle  it  forms  the  lower 
boundary  of  an  elliptical  space  for  the  attachment  of  the  clavicular  portion  of  the 
Pectoralis  major,  and  approaches  the  posterior  border  of  the  bone.  The  superior 
border  is  continuous  with  the  posterior  margin  of  the  flat  portion,  and  separates 
the  anterior  from  the  posterior  surface.  At  its  commencement  it  is  smooth  and 
rounded,  becomes  rough  toward  the  inner  third  for  the  attachment  of  the  Sterno- 
mastoid  muscle,  and  terminates  at  the  upper  angle  of  the  sternal  extremity.  The 
posterior  or  subclavian  border  separates  the  posterior  from  the  inferior  surface,  and 
extends  from  the  conoid  tubercle  to  the  rhomboid  impression.  It  forms  the  pos- 
terior boundary  of  the  groove  for  the  Subclavius  muscle,  and  gives  attachment  to  a 
layer  of  cervical  fascia  covering  the  Omo-hyoid  muscle.  The  anterior  surface  is 
included  between  the  superior  and  anterior  borders.  It  is  directed  forward  and  a 
little  upward  at  the  sternal  end,  outward  and  still  more  upward  at  the  acromial 
extremity,  where  it  becomes  continuous  with  the  upper  surface  of  the  flat  portion. 
Externally,  it  is  smooth,  convex,  nearly  subcutaneous,  being  covered  only  by  the 
Platysma  ;  but,  corresponding  to  the  inner  half  of  the  bone,  it  is  divided  by  a  more 
or  less  prominent  line  into  two  parts :  a  lower  portion,  elliptical  in  form,  rough, 
and  slightly  convex,  for  the  attachment  of  the  Pectoralis  major;  and  an  upper 
part,  which  is  rough,  for  the  attachment  of  the  Sterno-cleido-mastoid..  Between 

1  The  clavicle  acts  especially  as  a  fulcrum  to  enable  the  muscles  to  give  lateral  motion  to  the  arm. 
It  is  accordingly  absent  in  those  animals  whose  fore  limbs  are  used  only  for  progression,  but  is  present 
for  the  most  part  in  those  animals  whose  anterior  extremities  are  clawed  and  used  for  prehension, 
though  in  some  of  them — as,  for  instance,  in  a  large  number  of  the  carnivora — it  is  merely  a  rudi- 
mentary bone  suspended  among  the  muscles,  and  not  articulating  either  with  the  scapula  or 
sternum. 


240 


THE   SKELETON. 


the  two  muscular  impressions  is  a  small  subcutaneous  interval.  The  posterior  or 
cervical  surface  is  smooth,  flat,  and  looks  backward  toward  the  root  of  the  neck. 
It  is  limited,  above,  by  the  superior  border;  below,  by  the  subclavian  border; 
internally,  by  the  margin  of  the  sternal  extremity ;  externally,  it  is  continuous 
with  the  posterior  border  of  the  flat  portion.  It  is  concave  from  within  outward, 
and  is  in  relation,  by  its  lower  part,  with  the  suprascapular  vessels.  This  surface, 
at  about  the  junction  of  the  inner  and  outer  curves,  is  also  in  close  relation  with 
the  brachial  plexus  and  subclavian  vessels.  It  gives  attachment,  near  the  sternal 
extremity,  to  part  of  the  Sterno-hyoid  muscle ;  and  presents,  at  or  near  the  middle, 
a  foramen,  directed  obliquely  outward,  which  transmits  the  chief  nutrient  artery 
of  the  bone.  Sometimes  there  are  two  foramina  on  the  posterior  surface,  or  one 
on  the  posterior,  the  other  on  the  inferior  surface.  The  inferior  or  subclavian 


Acromial  extremity. 


Sternal  extremity. 


FIG.  192.— Left  clavicle.    Superior  surface. 


surface  is  bounded,  in  front,  by  the  anterior  border ;  behind,  by  the  subclavian 
border.     It  is  narrow  internally,  but  gradually  increases  in  width  externally,  and 


FIG.  193.— Left  clavicle.    Inferior  surface. 

is  continuous  with  the  under  surface  of  the  flat  portion.  Commencing  at  the 
sternal  extremity  may  be  seen  a  small  facet  for  articulation  with  the  cartilage  of 
the  first  rib.  This  is  continuous  with  the  articular  surface  at  the  sternal  end  of 
the  bone.  External  to  this  is  a  broad,  rough  impression,  the  rhomboid,  rather 
more  than  an  inch  in  length,  for  the  attachment  of  the  costo-clavicular  (rhomboid) 
ligament.  The  remaining  part  of  this  sin-face  is  occupied  by  a  longitudinal  groove, 
the  subclavian  groove,  broad  and  smooth  externally,  narrow  and  more  uneven 
internally ;  it  gives  attachment  to  the  Subclavius  muscle,  and  by  its  anterior 
margin  to  the  costo-coracoid  membrane.  Not  unfrequently  this  groove  is  sub- 
divided into  two  parts  by  a  longitudinal  line, which  gives  attachment  to  the  inter- 
muscular  septum  of  the  Subclavius  muscle. 

The  internal  or  sternal  extremity  of  the  clavicle  is  triangular  in  form,  directed 
inward  and  a  little  downward  and  forward ;  and  presents  an  articular  facet, 
concave  from  before  backward,  convex  from  above  downward,  which  articulates 
with  the  sternum  through  the  intervention  of  an  interarticular  fibro-cartilage ;  the 
circumference  of  the  articular  surface  is  rough,  for  the  attachment  of  numerous 


THE    CLA  VICLi;.  241 

ligaments.  The  posterior  border  of  this  surface  is  prolonged  backward,  so  as  to 
increase  the  size  of  the  articular  facet ;  the  upper  border  gives  attachment  to  the 
interarticular  fibro-cartilage,  and  the  lower  border  is  continuous  with  the  costal 
facet  on  the  inner  end  of  the  inferior  or  subclavian  surface,  which  articulates  with 
the  cartilage  of  the  first  rib. 

The  outer  or  acromial  extremity,  directed  outward  and  forward,  presents  a 
small,  flattened,  oval  facet,  which  looks  obliquely  downward,  for  articulation  with 
the  acromion  process  of  the  scapula.  The  circumference  of  the  articular  facet  is 
rough,  especially  above,  for  the  attachment  of  the  acromio-clavicular  ligaments. 

Peculiarities  of  the  Bone  in  the  Sexes  and  in  Individuals. — In  the  female  the 
clavicle  is  generally  shorter,  thinner,  less  curved,  and  smoother  than  in  the  male. 
In  those  persons  who  perform  considerable  manual  labor,  which  brings  into  con- 
stant action  the  muscles  connected  with  this  bone,  it  becomes  thicker  and  more 
curved,  its  ridges  for  muscular  attachment  become  prominently  marked,  and  its 
sternal  end  of  a  prismatic  form.  The  right  clavicle  is  generally  longer,  thicker, 
and  rougher  than  the  left. 

Structure. — The  shaft,  as  well  as  the  extremities,  consists  of  cancellous  tissue, 
invested  in  a  compact  layer  much  thicker  in  the  middle  than  at  either  end.  The 
clavicle  is  highly  elastic,  by  reason  of  its  curves.  From  the  experiments  of  Mr. 
Ward  it  has  been  shown  that  it  possesses  sufficient  longitudinal  elastic  force  to 
project  its  own  weight  nearly  two  feet  on  a  level  surface  when  a  smart  blow  is 
struck  on  it ;  and  sufficient  transverse  elastic  force,  opposite  the  centre  of  its 
anterior  convexity,  to  throw  its  own  weight  about  a  foot.  This  extent  of  elastic 
power  must  serve  to  moderate  very  considerably  the  effect  of  concussions  received 
upon  the  point  of  the  shoulder. 

Development. — By  two  centres :  one  for  the  shaft  and  one  for  the  sternal 
extremity.  The  centre  for  the  shaft  appears  very  early,  before  any  other  bone — 
according  to  Beclard,  as  early  as  the  thirtieth  day.  The  centre  for  the  sternal  end 
makes  its  appearance  about  the  eighteenth  or  twentieth  year,  and  unites  with  the 
rest  of  the  bone  about  the  twenty-fifth  \ear. 

Articulations. — With  the  sternum,  scapula,  and  cartilage  of  the  first  rib. 

Attachment  of  Muscles. — To  six  :  the  Sterno-cleido-mastoid,  Trapezius,  Pecto- 
ralis  major,  Deltoid,  Subclavius,  and  Sterno-hyoid. 

Surface  Form. — The  clavicle  can  be  felt  throughout  its  entire  length,  even  in  persons  who 
are  very  fat.  Commencing  at  the  inner  end,  the  enlarged  sternal  extremity,  where  the  bone 
projects  above  the  upper  margin  of  the  sternum,  can  be  felt,  forming  with  the  sternum  and  the 
rounded  tendon  of  the  Sterno-mastoid  a  V-shaped  notch,  the  pre-sternal  notch.  Passing  out- 
ward, the  shaft  of  the  bone  can  be  felt  immediately  under  the  skin,  with  its  convexity  forward 
in  the  inner  two-thirds,  the  surface  partially  obscured  above  and  below  by  the  attachments  of 
the  Sterno-mastoid  and  Pectoralis  major  muscles.  In  the  outer  third  it  forms  a  gentle  curve 
backward,  and  terminates  at  the  outer  end  in  a  somewhat  enlarged  extremity  which  articulates 
with  the  acromial  process  of  the  scapula.  The  direction  of  the  clavicle  is  almost,  if  not  quite, 
horizontal  when  the  arm  is  lying  quietly  by  the  side,  though  in  well-developed  subjects  it  may 
incline  a  little  upward  at  its  outer  end.  Its  direction  is,  however,  very  changeable  with  the 
varying  movements  of  the  shoulder-joint. 

Surgical  Anatomy. — The  clavicle  is  the  most  frequently  broken  of  any  single  bone  in  the 
body.  This  is  due  to  the  fact  that  it  is  much  exposed  to  violence,  and  is  the  only  bony  connec- 
tion between  the  upper  limb  and  the  trunk.  The  bone,  moreover,  is  slender,  and  is  very  super- 
ficial. The  bone  may  be  broken  by  direct  or  indirect  violence  or  by  muscular  action.  The  most 
common  cause  is.  however,  from  indirect  violence,  and  the  bone  then  gives  way  at  the  junction 
of  the  outer  with  the  inner  two-thirds  of  the  bone  ;  that  is  to  say  at  the  junction  of  the  two 
curves,  for  this  is  the  weakest  part  of  the  bone.  The  fracture  is  generally  oblique,  and  the  dis- 
placement of  the  fragments  is  inward,  away  from  the  surface  of  the  body  ;  hence  compound  frac- 
ture of  the  clavicle  is  of  rare  occurrence.  Beneath  the  bone  the  main  vessels  of  the  upper  limb 
and  the  great  nerve-cords  of  the  braehial  plexus  lie  on  the  first  rib,  and  are  liable  to  be  wounded 
in  fracture,  especially  in  fracture  from  direct  violence,  when  the  force  of  the  blow  drives  the 
broken  ends  inward.  Fortunately,  the  Subclavius  muscle  is  interposed  between  these  structures 
and  the  clavicle,  and  this  often  protects  them  from  injury. 

The  clavicle  is  not  uncommonly  the  seat  of  sarcomatous  tumors,  rendering, the  operation 
of  excision  of  the  entire  bone  necessary.  This  is  an  operation  of  considerable  difficulty  and 
danger.  It  is  best  performed  by  exposing  the  bone  freely,  disarticulating  at  the  acromial  end, 
and  turning  it  inward.  The  removal  of  the  outer  part  is  comparatively  easy,  but  resection  of 

16 


242 


THE  SKELETON. 


the  inner  part  is  fraught  with  difficulty,  the  main  danger  being  the  risk  of  wounding  the  great 
veins  which  are  in  relation  with  its  under  surface. 

The  Scapula. 

The  Scapula  (ffxandvy,  a  spade)  forms  the  back  part  of  the  shoulder  girdle.     It 
is  a  large,  flat  bone,  triangular  in  shape,  situated  at  the  posterior  aspect  and  side  of 


FIG.  194.— Left  scapular  anterior  surface,  or  venter. 

the  thorax,  between  the  second  and  seventh,  or  sometimes  the  eighth,  ribs,  its  poste- 
rior border  or  base  being  about  an  inch  from,  and  nearly,  but  not  quite  parallel 
with  the  spinous  processes  of  the  vertebrae,  so  that  it  is  rather  closer  to  them 
above  than  below.  It  presents  for  examination  two  surfaces,  three  borders,  and 
three  angles. 

The  anterior  surface,  or  venter  (Fig.  194),  presents  a  broad  concavity,  the  sub- 
scapular  fossa.  It  is  marked,  in  the  posterior  two-thirds,  by  several  oblique 
ridges,  which  pass  from  behind  obliquely  outward  and  upward ;  the  anterior  third 
is  smooth.  The  oblique  ridges  give  attachment  to  the  tendinous  intersections,  and 
the  surfaces  between  them  to  the  fleshy  fibres,  of  the  Subscapularis  muscle.  The 


THP:  SCAPULA. 


243 


anterior  third  of  the  fossa,  which  is  smooth,  is  covered  by,  but  does  not  afford 
attachment  to.  the  fibres  of  this  muscle.  The  venter  is  separated  from  the 
posterior  border  by  a  smooth,  triangular  margin  at  the  superior  and  inferior 
angles,  and  in  the  interval  between  these  by  a  narrow  edge  which  is  often  deficient. 
This  marginal  surface  affords  attachment  throughout  its  entire  extent  to  the 
Serratus  magnus  muscle.  The  subscapular  fossa  presents  a  transverse  depression 
at  its  upper  part,  where  the  bone  appears  to  be  bent  on  itself,  forming  a  consider- 
able angle,  called  the  subscapular  angle,  thus  giving  greater  strength  to  the  body 
of  the  bone  from  its  arched  form,  while  the  summit  of  the  arch  serves  to  support 
the  spine  and  acromion  process.  It  is  in  this  situation  that  the  fossa  is  deepest, 
so  that  the  thickest  part  of  the  Subscapularis  muscle  lies  in  a  line  perpendicular 


Cora 


Grooce  for  Dorsalis 
Scapulae  Artery. 


FIG.  195. — Left  scapula.    Posterior  surface,  or  dorsum. 

to  the  plane  of  the  glenoid  cavity,  and  must  consequently  operate  most  effectively 
on  the  head  of  the  humerus.  which  is  contained  in  that  cavity. 

The  posterior  surface,  or  dorsum  (Fig.  195),  is  arched  from  above  downward, 
alternately  concave  and  convex  from  side  to  side.     It  is  subdivided  unequally  into 


244  THE  SKELETON. 

two  parts  by  the  spine :  the  portion  above  the  spine  is  called  the  supraspinous 
fossa,  and  that  below  it  the  infraspinous  fossa. 

The  supraspinous  fossa,  the  smaller  of  the  two,  is  concave,  smooth,  and  broader 
at  the  vertebral  than  at  the  humeral  extremity.  It  affords  attachment  by  its  inner 
two-thirds  to  the  Supraspinatus  muscle. 

The  infraspinous  fossa  is  much  larger  than  the  preceding ;  toward  its  vertebral 
margin  a  shallow  concavity  is  seen  at  its  upper  part ;  its  centre  presents  a  promi- 
nent convexity,  whilst  toward  the  axillary  border  is  a  deep  groove  which  runs 
from  the  upper  toward  the  lower  part.  The  inner  two-thirds  of  this  surface 
affords  attachment  to  the  Infraspinatus  muscle ;  the  outer  third  is  only  covered  by 
it,  without  giving  origin  to  its  fibres.  This  surface  is  separated  from  the  axillary 
border  by  an  elevated  ridge,  which  runs  from  the  lower  part  of  the  glenoid  cavity 
downward  and  backward  to  the  posterior  border,  about  an  inch  above  the  inferior 
angle.  The  ridge  serves  for  the  attachment  of  a  strong  aponeurosis  which  sepa- 
rates the  Infraspinatus  from  the  two  Teres  muscles.  The  surface  of  bone  between 
this  line  and  the  axillary  border  is  narrow  in  the  upper  two-thirds  of  its  extent, 
and  traversed  near  its  centre  by  a  groove  for  the  passage  of  the  dorsalis  scapula? 
vessels ;  it  affords  attachment  to  the  Teres  minor.  Its  lower  third  presents  a 
broader,  somewhat  triangular  surface,  which  gives  origin  to  the  Teres  major,  and 
over  which  the  Latissimus  dorsi  glides  ;  sometimes  the  latter  muscle  takes  origin 
by  a  few  fibres  from  this  part.  The  broad  and  narrow  portions  of  bone  above 
alluded  to  are  separated  by  an  oblique  line  which  runs  from  the  axillary  border, 
downward  and  backward,  to  meet  the  elevated  ridge :  to  it  is  attached  the 
aponeurosis  separating  the  two  Teres  muscles  from  each  other. 

The  Spine  is  a  prominent  plate  of  bone  which  crosses  obliquely  the  inner 
four-fifths  of  the  dorsum  of  the  scapula  at  its  upper  part,  and  separates  the  supra- 
from  the  infraspinous  fossa :  it  commences  at  the  vertebral  border  by  a  smooth, 
triangular  surface,  over  which  the  Trapezius  glides,  separated  from  the  bone  by  a 
bursa,  and,  gradually  becoming  more  elevated  as  it  passes  forward,  terminates  in 
the  acrornion  process,  which  overhangs  the  shoulder-joint.  The  spine  is  triangular 
and  flattened  from  above  downward,  its  apex  corresponding  to  the  posterior 
border,  its  base  (which  is  directed  outward)  to  the  neck  of  the  scapula.  It 
presents  two  surfaces  and  three  borders.  Its  superior  surface  is  concave,  assists 
in  forming  the  supraspinous  fossa,  and  affords  attachment  to  part  of  the  Supra- 
spinatus muscle.  Its  inferior  surface  forms  part  of  the  infraspinous  fossa,  gives 
origin  to  part  of  the  Infraspinatus  muscle,  and  presents  near  its  centre  the  orifice 
of  a  nutrient  canal.  Of  the  three  borders,  the  anterior  is  attached  to  the  dorsum 
of  the  bone ;  the  posterior,  or  crest  of  the  spine,  is  broad,  and  presents  two  lips 
and  an  intervening  rough  interval.  To  the  superior  lip  is  attached  the  Trapezius 
to  the  extent  shown  in  the  figure.  A  rough  tubercle  is  generally  seen  occupying 
that  portion  of  the  spine  which  receives  the  insertion  of  the  middle  and  inferior 
fibres  of  this  muscle.  To  the  inferior  lip,  throughout  its  whole  length,  is  attached 
the  Deltoid.  The  interval  between  the  lips  is  also  partly  covered  by  the  fibres  of 
these  muscles.  The  external  border,  or  base,  the  shortest  of  the  three,  is  slightly 
concave,  its  edge  thick  and  round,  continuous  above  with  the  under  surface  of  the 
acromion  process,  below  with  the  neck  of  the  scapula.  The  narrow  portion  of  bone 
external  to  this  border,  and  separating  it  from  the  glenoid  cavity,  is  called  the 
great  scapular  notch,  and  serves  to  connect  the  supra-  and  infraspinous  fossae. 

The  Acromion  Process,  so  called  from  forming  the  summit  of  the  shoulder 
(dxpov,  a  summit ;  cy//oc,  the  shoulder),  is  a  large  and  somewhat  triangular  process, 
flattened  from  behind  forward,  directed  at  first  a  little  outward,  and  then  curving 
forward  and  upward,  so  as  to  overhang  the  glenoid  cavity.  Its  upper  surface, 
directed  upward,  backward,  and  outward,  is  convex,  rough,  and  gives  attachment 
to  some  fibres  of  the  Deltoid,  and  in  the  rest  of  its  extent  it  is  subcutaneous.  Its 
under  surface  is  smooth  and  concave.  Its  outer  border  is  thick  and  irregular,  and 
presents  three  or  four  tubercles  for  the  tendinous  origins  of  the  Deltoid  muscle. 
Its  inner  margin,  shorter  than  the  outer,  is  concave,  gives  attachment  to  a  portion 


THE  SCAPULA.  24-", 

of  the  Trapezius  muscle,  and  presents  about  its  centre  a  small  oval  surface  for 
articulation  with  the  acromial  end  of  the  clavicle.  Its  apex,  which  corresponds 
to  the  point  of  meeting  of  theae  two  borders  in  front,  is  thin,  and  has  attached  to 
it  the  coraco-acromial  ligament. 

Of  the  three  borders  or  costae  of  the  scapula,  the  superior  is  the  shortest  and 
thinnest ;  it  is  concave,  terminating  at  its  inner  extremity  at  the  superior  angle,  at 
its  outer  extremity  at  the  coracoid  process.  At  its  outer  part  is  a  deep,  semicircular 
notch,  the  suprascapular,  formed  partly  by  the  base  of  the  coracoid  process.  This 
notch  is  converted  into  a  foramen  by  the  transverse  ligament,  and  serves  for  the 
passage  of  the  suprascapular  nerve.  The  adjacent  margin  of  the  superior  border 
affords  attachment  to  the  Omo-hyoid  muscle.  The  external,  or  axillary,  border  is 
the  thickest  of  the  three.  It  commences  above  at  the  lower  margin  of  the  glenoid 
cavity,  and  inclines  obliquely  downward  and  backward  to  the  inferior  angle. 
Immediately  below  the  glenoid  cavity  is  a  rough  impression  (the  infraglenoid 
tubercle),  about  an  inch  in  length,  which  affords  attachment  to  the  long  head  of 
the  Triceps  muscle ;  to  this  succeeds  a  longitudinal  groove,  which  extends  as  far 
as  its  lower  third  and  affords  origin  to  part  of  the  Subscapularis  muscle.  The 
inferior  third  of  this  border,  which  is  thin  and  sharp,  serves  for  the  attachment  of 
a  few  fibres  of  the  Teres  major  behind  and  of  the  Subscapularis  in  front.  The 
internal,  or  vertebral,  border,  also  named  the  base,  is  the  longest  of  the  three, 
and  extends  from  the  superior  to  the  inferior  angle  of  the  bone.  It  is  arched, 
intermediate  in  thickness  between  the  superior  and  the  external  borders,  and  the 
portion  of  it  above  the  spine  is  bent  considerably  outward,  so  as  to  form  an 
obtuse  angle  with  the  lower  part.  The  vertebral  border  presents  an  anterior  lip, 
a  posterior  lip,  and  an  intermediate  space.  The  anterior  lip  affords  attachment 
to  the  Serratus  magnus ;  the  posterior  Up,  to  the  Supraspinatus  above  the  spine, 
the  Infraspinatus  below ;  the  interval  between  the  two  lips,  to  the  Levator  anguli 
scapulae  above  the  triangular  surface  at  the  commencement  of  the  spine,  the 
Rhomboideus  minor  to  the  edge  of  that  surface;  the  Rhomboideus  major  being 
attached  by  means  of  a  fibrous  arch  connected  above  to  the  lower  part  of  the 
triangular  surface  at  the  base  of  the  spine,  and  below  to  the  lower  part  of  the 
posterior  border. 

Of  the  three  angles,  the  superior,  formed  by  the  junction  of  the  superior  and 
internal  borders,  is  thin,  smooth,  rounded,  somewhat  inclined  outward,  and  gives 
attachment  to  a  few  fibres  of  the  Levator  anguli  scapulae  muscle.  The  inferior 
angle,  thick  and  rough,  is  formed  by  the  union  of  the  vertebral  and  axillary 
borders,  its  outer  surface  affording  attachment  to  the  Teres  major  and  occasionally 
a  few  fibres  of  the  Latissimus  dorsi.  The  anterior  angle  is  the  thickest  part  of 
the  bone,  and  forms  what  is  called  the  head  of  the  scapula.  The  head  presents  a. 
shallow,  pyriform,  articular  surface,  the  glenoid  cavity  (ytyirtj,  a  socket),  whose 
longest  diameter  is  from  above  downward,  and  its  direction  outward  and  forward. 
It  is  broader  below  than  above;  at  its  apex  is  a  slight  impression  (supraglenoid 
tubercle')  to  which  is  attached  the  long  tendon  of  the  Biceps  muscle.  It  is  covered 
with  cartilage  in  the  recent  state ;  and  its  margins,  slightly  raised,  give  attachment 
to  a  fibro-cartilaginous  structure,  the  glenoid  ligament,  by  which  its  cavity  is 
deepened.  The  neck  of  the  scapula  is  the  slightly  depressed  surface  which  sur- 
rounds the  head ;  it  is  more  distinct  on  the  posterior  than  on  the  anterior  surface, 
and  below  than  above.  In  the  latter  situation  it  has  arising  from  it  a  thick  prom- 
inence, the  coracoid  process. 

The  Coracoid  Process,  so  called  from  its  fancied  resemblance  to  a  crow's  beak 
(xooaz.  a  crow),  is  a  thick,  curved  process  of  bone  which  arises  by  a  broad  base  from 
the  upper  part  of  the  neck  of  the  scapula ;  it  is  directed  at  first  upward  and 
inward,  then,  becoming  smaller,  it  changes  its  direction  and  passes  forward  and 
outward.  The  ascending  portion,  flattened  from  before  backward,  presents  in 
front  a  smooth,  concave  surface  over  which  passes  the  Subscapularis  muscle.  The 
horizontal  portion  is  flattened  from  above  downward,  its  upper  surface  is  convex 
and  irregular,  and  gives  attachment  to  the  Pectoralis  minor ;  its  under  surface  is 


246 


THE   SKELETON. 


smooth;  its  inner  border  is  rough,  and  gives  attachment  to  the  Pectoralis  minor; 
its  outer  border  is  also  rough  for  the  coraco-acromial  ligament,  while  the  apex  is 
embraced  by  the  conjoined  tendon  of  origin  of  the  short  head  of  the  Biceps  and 
of  the  Coraco-brachialis.  At  the  inner  side  of  the  root  of  the  coracoid  process  is 
a  rough  impression  for  the  attachment  of  the  conoid  ligament :  and  running  from 
it  obliquely  forward  and  outward  on  the  upper  surface  of  the  horizontal  portion, 
an  elevated  ridge  for  the  attachment  of  the  trapezoid  ligament. 

Structure. — In  the  head,  processes,  and  all  the  thickened  parts  of  the  bone 
the  scapula  is  composed  of  cancellous  tissue,  while  in  the  rest  of  its  extent  it  is 
composed  of  a  thin  layer  of  dense,  compact  tissue.  The  centre  and  upper  part  of 
the  dorsum,  but  especially  the  former,  are  usually  so  thin  as  to  be  semitransparent ; 


FIG.  196.— Plan  of  the  development  of  the  scapula.  By  seven  centres.  The  epiphyses  (except  one  for  the 
coracoid  process)  appear  from  fifteen  to  seventeen  years,  and  unite  between  twenty-two  and  twenty-five  years 
of  age. 

occasionally  the  bone  is  found  wanting  in  this  situation,  and  the  adjacent  muscles 
come  into  contact. 

Development  (Fig.  196). — By  seven  centres :  one  for  the  body,  two  for  the 
coracoid  process,  two  for  the  acromion,  one  for  the  vertebral  border,  and  one  for 
the  inferior  angle. 

Ossification  of  the  body  of  the  scapula  commences  about  the  second  month  of 
foetal  life  by  the  formation  of  an  irregular  quadrilateral  plate  of  bone  immediately 
behind  the  glenoid  cavity.  This  plate  extends  itself  so  as  to  form  the  chief  part  of 
the  bone,  the  spine  growing  up  from  its  posterior  surface  about  the  third  month. 
At  birth  the  chief  part  of  the  scapula  is  osseous,  only  the  coracoid  and  acromion 
processes,  the  posterior  border,  and  inferior  angle  being  cartilaginous.  About 
the  first  year  after  birth  ossification  takes  place  in  the  middle  of  the  coracoid 
process,  which  usually  becomes  joined  with  the  rest  of  the  bone  at  the  time  when 
the  other  centres  make  their  appearance.  Between  the  fifteenth  and  seventeenth 
years  ossification  of  the  remaining  centres  takes  place  in  quick  succession,  and 


THE  SCAPULA.  247 

in  the  following  order :  first,  near  the  base  of  the  acromion  and  in  the  root  of  the 
coracoid  process,  the  latter  appearing  in  the  form  of  a  broad  scale ;  secondly,  in 
•  the  inferior  angle  and  contiguous  part  of  the  posterior  border  ;  thirdly,  near  the 
extremity  of  the  acromion ;  fourthly,  in  the  posterior  border.  The  acromion 
process,  besides  being  formed  of  two  separate  nuclei,  has  its  base  formed  by  an 
extension  into  it  of  the  centre  of  ossification  which  belongs  to  the  spine,  the 
extent  of  which  varies  in  different  cases.  The  two  separate  nuclei  unite,  and 
then  join  with  the  extension  carried  in  from  the  spine.  These  various  epiphyses 
become  joined  to  the  bone  between  the  ages  of  twenty-two  and  twenty-five  years. 
Sometimes  failure  of  union  between  the  acromion  process  and  spine  occurs,  the 
junction  being  effected  by  fibrous  tissue  or  by  an  imperfect  articulation;  in  some 
cases  of  supposed  fracture  of  the  acromion  with  ligamentous  union  it  is  probable 
that  the  detached  segment  was  never  united  to  the  rest  of  the  bone.  Very  often, 
in  addition  to  these,  a  minute  epiphysis  appears  at  the  margin  of  the  glenoid 
cavity. 

Articulations. — With  the  humerus  and  clavicle. 

Attachment  of  Muscles. — To  seventeen :  to  the  anterior  surface,  the  Subscapu- 
laris :  posterior  surface.  Supraspinatus.  Infraspinatus ;  spine,  Trapezius.  Deltoid ; 
superior  border.  Omo-hyoid;  vertebral  border.  Serratus  magnus,  Levator  anguli 
scapula?.  Rhornboideus  minor  and  major ;  axillary  border,  Triceps,  Teres  minor. 
Teres  major:  glenoid  cavity,  long  head  of  the  Biceps;  coracoid  process,  short 
head  of  the  Biceps.  Coraco-brachialis,  Pectoralis  minor ;  and  to  the  inferior  angle 
occasionally  a  few  fibres  of  the  Latissimus  dorsi. 

Surface  Form. — The  only  parts  of  the  scapula  which  are  truly  subcutaneous  are  the  spine 
and  acrouiion  process,  but.  in  addition  to  these,  the  coracoid  process,  the  internal  or  vertebral 
border  and  inferior  angle,  and.  to  a  less  extent,  the  axillary  border,  may  be  defined.  The  acro- 
mion process  and  spine  of  the  scapula  are  easily  felt  throughout  their  entire  length,  forming, 
with  the  clavicle,  the  arch  of  the  shoulder.  The  acromion  can  be  ascertained  to  be  connected 
to  the  clavicle  at  the  acromio-clavicular  joint  by  running  the  finger  along  it,  its  position  being 
often  indicated  by  an  irregularity  or  bony  outgrowth  from  the  clavicle  close  to  the  joint.  The 
acromion  can  be  felt  forming  the  point  of  the  shoulder,  and  from  this  can  be  traced  backward 
to  join  the  spine  of  the  scapula.  The  place  of  junction  is  usually  denoted  by  a  prominence, 
which  is  sometimes  called  the  angle.  From  here  the  spine  can  be  felt  as  a  prominent  ridge  of 
bone,  marked  on  the  surface  as  an  oblique  depression,  which  becomes  less  and  less  distinct,  and 
terminates  a  little  external  to  the  spinous  processes  of  the  vertebrae.  Its  termination  is  usually 
indicated  by  a  slitrbt  dimple  in  the  skin  on  a  level  with  the  interval  between  the  third  and  fourth 
dorsal  spines.  Below  this  point  the  vertebral  border  of  the  scapula  may  be  traced,  running 
downward  and  outward,  and  thus  diverging  from  the  vertebral  spines,  to  the  inferior  angle  of 
the  bone,  which  can  be  recognized,  although  covered  by  the  Latissimus  dorsi  muscle.  From 
this  angle  the  axillary  border  can  usually  be  traced  through  this  thick  muscular  covering,  form- 
ing, with  the  muscles,  the  posterior  fold  of  the  axilla.  The  coracoid  process  may  be  felt  about 
an  inch  below  the  junction  of  the  middle  and  outer  third  of  the  clavicle.  Its  position  is  indi- 
cated on  the  surface  of  the  body  by  a  slight  depression  which  corresponds  to  the  interval 
between  the  Pectoralis  major  and  Deltoid  muscles.  When  the  arms  are  hanging  by  the  side, 
the  upper  angle  of  the  scapula  corresponds  to  the  upper  border  of  the  second  rib  or  the  interval 
between  the  first  and  second  dorsal  spines,  the  inferior  angle  to  the  upper  border  of  the  eighth 
rib  or  the  interval  between  the  seventh  and  eighth  dorsal  spines. 

Surgical  Anatomy. — Fractures  of  the  body  of  the  scapula  are  rare,  owing  to  the  mobility 
of  the  bone,  the  thick  layer  of  muscles  by  which  it  is  encased  on  both  surfaces,  and  the  elas- 
ticity of  the  ribs  on  which  it  rests.  Fracture  of  the  neck  of  the  bone  is  also  uncommon.  The 
most  frequent  course  of  the  fracture  is  from  the  suprascapular  notch  to  the  infraglenoid 
tubercle,  and  it  derives  its  principal  interest  from  its  simulation  to  a  subglenoid  dislocation  of 
the  humerus.  The  diagnosis  can  be  made  by  noting  the  alteration  in  the  position  of  the 
coracoid  process.  A  fracture  of  the  neck  external  to.  and  not  including,  the  coracoid  process  is 
saiil  to  occur,  but  it  is  exceedingly  doubtful  whether  such  an  accident  ever  takes  place.  The 
acromion  process  is  more  frequently  broken  than  any  other  part  of  the  bone,  and  there  is  some- 
times, in  young  subjects,  a  separation  of  the  epiphysis.  It  is  believed  that  many  of  the  cases 
of  supposed  fracture  of  the  acromion,  with  fibrous  union,  which  have  been  found  on  post-mor- 
tem examination  are  really  cases  of  imperfectly  united  epiphysis.  Sir  Astley  Cooper  believed 
that  most  fractures  of  this  bone  united  by  fibrous  tissue,  and  the  cause  of  this  mode  of  union 
was  the  difficulty  there  was  in  keeping  the  fractured  ends  in  constant  apposition.  The  coracoid 
process  is  occasionally  broken  off,  either  from  direct  violence  or  perhaps,  rarely,  from  muscular 
action. 

Tumors  of  various  kinds  grow  from  the  scapula.  Of  the  innocent  form  of  tumors  prob- 
ably the  osteomata  are  the  most  common.  When  it  grows  from  the  venter  of  the  scapula,  as  it 


248  THE   SKELETON. 

sometimes  does,  it  is  of  the  compact  variety,  such  as  usually  grows  from  membrane-formed 
bones,  as  the  bones  of  the  skull.  This  would  appear  to  afford  evidence  that  this  portion  of  the 
bone  is  formed  from  membrane,  and  not,  like  the  rest  of  the  bone,  from  cartilage.  Sarcomatous 
tumors  sometimes  grow  from  the  scapula,  and  may  necessitate  removal  of  the  bone,  with  or 
without  amputation  of  the  upper  limb.  The  bone  may  be  excised  by  a  T  incision,  and,  the  flaps 
being  reflected,  the  removal  is  commenced  from  the  posterior  or  vertebral  border,  so  that  the 
subscapular  vessels  which  lie  along  the  axillary  border  are  among  the  last  structures  divided,  and 
can  be  at  once  secured. 

THE    ARM. 

The  Humerus. 

The  Humerus  is  the  longest  and  largest  bone  of  the  upper  extremity ;  it  pre- 
sents for  examination  a  shaft  and  two  extremities. 

The  Upper  Extremity  is  the  largest  part  of  the  bone ;  it  presents  a  rounded 
head,  joined  to  the  shaft  by  a  constricted  portion,  called  the  neck,  and  two  other 
eminences,  the  greater  and  lesser  tuberosities  (Fig.  197). 

The  head,  nearly  hemispherical  in  form,1  is  directed  upward,  inward,  and  a 
little  backward,  and  articulates  with  the  glenoid  cavity  of  the  scapula;  its  surface 
is  smooth  and  coated  with  cartilage  in  the  recent  state.  The  circumference  of  its 
articular  surface  is  slightly  constricted,  and  is  termed  the  anatomical  neck,  in  con- 
tradistinction to  the  constriction  which  exists  below  the  tuberosities.  The  latter 
is  called  the  surgical  neck,  from  its  often  being  the  seat  of  fracture.  It  should  be 
remembered,  however,  that  fracture  of  the  anatomical  neck  does  sometimes,  though 
rarely,  occur. 

The  anatomical  neck  is  obliquely  directed,  forming  an  obtuse  angle  with  the 
shaft.  It  is  more  distinctly  marked  in  the  lower  half  of  its  circumference  than  in 
the  upper  half,  where  it  presents  a  narrow  groove,  separating  the  head  from  the 
tuberosities.  Its  circumference  affords  attachment  to  the  capsular  ligament  and 
is  perforated  by  numerous  vascular  foramina. 

The  greater  tuberosity  is  situated  on  the  outer  side  of  the  head  and  lesser 
tuberosity.  Its  upper  surface  is  rounded  and  marked  by  three  flat  facets,  sep- 
arated by  two  slight  ridges :  the  highest  facet  gives  attachment  to  the  tendon 
of  the  Supraspinatus ;  the  middle  one,  to  the  Infraspinatus ;  the  lowest  facet  and 
the  shaft  of  the  bone  below  it,  to  the  Teres  minor.  The  outer  surface  of  the 
great  tuberosity  is  convex,  rough,  and  continuous  with  the  outer  side  of  the  shaft. 

The  lesser  tuberosity  is  more  prominent,  although  smaller  than  the  greater :  it 
is  situated  in  front  of  the  head,  and  is  directed  inward  and  forward.  Its  summit 
presents  a  prominent  facet  for  the  insertion  of  the  tendon  of  the  Subscapularis 
muscle.  The  tuberosities  are  separated  from  one  another  by  a  deep  groove,  the 
bicipital  groove,  so  called  from  its  lodging  the  long  tendon  of  the  Biceps  muscle, 
with  which  runs  a  branch  of  the  anterior  circumflex  artery.  It  commences 
above  between  the  two  tuberosities,  passes  obliquely  downward  and  a  little 
inward,  and  terminates  at  the  junction  of  the  upper  with  the  middle  third  of 
the  bone.  It  is  deep  and  narrow  at  the  commencement,  and  becomes  shallow  and 
a  little  broader  as  it  descends.  Its  borders  are  called,  respectively,  the  external 
and  internal  bicipital  ridges;  to  the  former  of  which  the  name  pectoral  ridge  is, 
also,  often  applied.  In  the  recent  state  this  groove  contains  a  prolongation  of 
the  synovial  membrane  of  the  shoulder-joint,  and  its  floor  receives  that  portion 
of  the  tendon  of  insertion  of  the  Latissimus  dorsi  muscle  which  is  reflected  into 
it  from  the  internal  bicipital  ridge. 

The  Shaft  of  the  humerus  is  almost  cylindrical  in  the  upper  half  of  its  extent, 
prismatic  and  flattened  below,  and  presents  three  borders  and  three  surfaces  for 
examination. 

The  anterior  border  runs  from  the  front  of  the  great  tuberosity  above  to  the 

1  Though  the  head  is  nearly  hemispherical  in  form,  its  margin,  as  Sir  G.  Humphry  has  shown, 
is  by  no  means  a  true  circle.  Its  greatest  measurement  is  from  the  top  of  the  bicipital  groove  in  a 
direction  downward,  inward,  and  backward.  Hence  it  follows  that  the  greatest  elevation  of  the  arm 
can  be  obtained  by  rolling  the  articular  surface  in  this  direction — that  is  to  say,  obliquely  upward, 
outward,  and  forward. 


THE    Hl'MERUS. 


249 


Common  origin  of 

FLEXOR    CARP)    RADIALIS. 
PALMARlS    LONQUS. 
FLEXOR    SUBLlMiS    DIQITOR 
FLEXOR    CARPI     ULNARIS. 


ENSOR   CARPI    RADIAUS 
LONGIOR. 


Common  origin  of 

EXTENSOR    CARPI    RADIALIS  BREVlS, 

••    COMMUNIS  oiarroRUM. 

"      MINIMI    DIOITI. 
"       CARPI    ULNARIS. 
SUPINATOR    BREVlS. 


FIG.  197.— Left  humerus.    Anterior  view. 

coronoid  depression  below,  separating  the  internal  from  the  external  surface.     Its 


250  THE  SKELETON. 

upper  part  is  very  prominent  and  rough,  and  forms  the  outer  lip  of  the  bicipital 
groove.  It  is  here  often  called  the  external  bicipital  ridge,  and  serves  for  the 
attachment  of  the  tendon  of  the  Pectoralis  major.  About  its  centre  it  forms  the 
anterior  boundary  of  the  rough  deltoid  impression  ;  below,  it  is  smooth  and  rounded, 
affording  attachment  to  the  Brachialis  anticus. 

The  external  border  runs  from  the  back  part  of  the  greater  tuberosity  to  the 
external  condyle,  and  separates  the  external  from  the  posterior  surface.  It  is 
rounded  and  indistinctly  marked  in  its  upper  half,  serving  for  the  attachment  of 
the  lower  part  of  the  insertion  of  the  Teres  minor,  and  below  this  of  the  external 
head  of  the  Triceps  muscle ;  its  centre  is  traversed  by  a  broad  but  shallow,  oblique 
depression,  the  musculo-spiral  groove  ;  its  lower  part  is  marked  by  a  prominent, 
rough  margin,  a  little  curved  from  behind  forward,  the  external  supracondylar 
ridge,  which  presents  an  anterior  lip  for  the  attachment  of  the  Supinator  longus 
above  and  Extensor  carpi  radialis  longior  below,  a  posterior  lip  for  the  Triceps, 
and  an  interstice  for  the  attachment  of  the  external  intermuscular  septum. 

The  internal  border  extends  from  the  lesser  tuberosity  to  the  internal  condyle. 
Its  upper  third  is  marked  by  a  prominent  ridge,  forming  the  internal  lip  of  the 
bicipital  groove,  and  gives  attachment  to  the  tendon  of  the  Teres  major.  About 
its  centre  is  a  rough  ridge  for  the  attachment  of  the  Coraco-brachialis,  and  just 
below  this  is  seen  the  entrance  of  the  nutrient  canal,  directed  downward.  Some- 
times there  is  a  second  canal  higher  up,  which  takes  a  similar  direction.  The  infe- 
rior third  of  this  border  is  raised  into  a  slight  ridge,  the  internal  supracondylar 
ridge,  which  becomes  very  prominent  below ;  it  presents  an  anterior  lip  for  the 
attachment  of  the  Brachialis  anticus,  a  posterior  lip  for  the  internal  head  of  the 
Triceps,  and  an  intermediate  space  for  the  internal  intermuscular  septum. 

The  external  surface  is  directed  outward  above,  where  it  is  smooth,  rounded, 
and  covered  by  the  Deltoid  muscle ;  forward  and  outward  below,  where  it  is 
slightly  concave  from  above  downward,  and  gives  origin  to  part  of  the  Brachialis 
anticus  muscle.  About  the  middle  of  this  surface  is  seen  a  rough,  triangular 
impression  for  the  insertion  of  the  Deltoid  muscle  ;  and  below  it  the  musculo-spiral 
groove,  directed  obliquely  from  behind,  forward  and  downward,  and  transmitting 
the  musculo-spiral  nerve  and  superior  profunda  artery. 

The  internal  surface,  less  extensive  than  the  external,  is  directed  inward  above, 
forward  and  inward  below ;  at  its  upper  part  it  is  narrow  and  forms  the  floor  of 
the  bicipital  groove :  to  it  is  attached  the  Latissimus  dorsi.  The  middle  part  of 
this  surface  is  slightly  rough  for  the  attachment  of  some  of  the  fibres  of  the  tendon 
of  insertion  of  the  Coraco-brachialis ;  its  lower  part  is  smooth,  concave,  and  gives 
attachment  to  the  Brachialis  anticus  muscle.1 

The  posterior  surface  (Fig.  198)  appears  somewhat  twisted,  so  that  its  upper 
part  is  directed  a  little  inward,  its  lower  part  backward  and  a  little  outward. 
Nearly  the  whole  of  this  surface  is  covered  by  the  external  and  internal  heads  of 
the  Triceps,  the  former  of  which  is  attached  to  its  upper  and  outer  part,  the  latter 
to  its  inner  and  back  part,  the  two  being  separated  by  the  musculo-spiral  groove. 

The  Lower  Extremity  is  flattened  from  before  backward,  and  curved  slightly 
forward  ;  it  terminates  below  in  a  broad,  articular  surface  which  is  divided  into 
two  parts  by  a  slight  ridge.  Projecting  on  either  side  are  the  external  and  inter 

1  A  small,  hook-shaped  process  of  bone,  varying  from  -fa  to  £  of  an  inch  in  length,  is  not  unfre- 
quently  found  projecting  from  the  inner  surface  of  the  shaft  of  the  humerus  two  inches  above  the 
internal  condyle.  It  is  curved  downward,  forward,  and  inward,  and  its  pointed  extremity  is  connected 
to  the  internal  border,  just  above  the  inner  condyle,  by  a  ligament  or  fibrous  band,  completing  an 
arch  through  which  the  median  nerve  and  brachial  artery  pass  when  these  structures  deviate  from 
their  usual  course.  Sometimes  the  nerve  alone  is  transmitted  through  it,  or  the  nerve  may  be 
accompanied  by  the  ulnar  artery  in  cases  of  high  division  of  the  brachial.  A  well-marked 
groove  is  usually  found  behind  the  process  in  which  the  nerve  and  artery  are  lodged.  This 
space  is  analogous  to  the  supracondyloid  foramen  in  many  animals,  and  probably  serves 
in  them  to  protect  the  nerve  and  artery  from  compression  during  the  contraction  of  the 
muscles  in  this  region.  A  detailed  account  of  this  process  is  given  by  Dr.  Struthers,  in 
his  Anatomical  and  Physiological  Observations,  p.  202.  An  accessory  portion  of  the  Coraco- 
brachialis  muscle  is  frequently  connected  with  this  process,  according  to  Mr.  J.  Wood,  (Journal  of  Anat. 
(ina  Phys.,  No.  1,  Nov.,  1866, 'p.  47). 


THE   HUMERUS. 


251 


nal  condyles.  The  articular  surface  extends  a 
little  lower  than  the  condvles.  and  is  curved 
slightly  forward,  so  as  to  occupy  the  more  ante- 
rior part  of  the  bone ;  its  greatest  breadth  is  in 
the  transverse  diameter,  and  it  is  obliquely  di- 
rected, so  that  its  inner  extremity  occupies  a 
lower  level  than  the  outer.  The  outer  portion  of 
the  articular  surface  presents  a  smooth,  rounded 
eminence,  which  has  received  the  name  of  the 
capitfUuin.  or  /v/</V'//  h'.-'nl  of  the  humerus ;  it 
articulates  with  the  cup-shaped  depression  on 
the  head  of  the  radius,  and  is  limited  to  the 
front  and  lower  part  of  the  bone,  not  extending 
as  far  back  as  the  other  portion  of  the  articular 
surface.  On  the  inner  side  of  this  eminence  is 
a  shallow  groove,  in  which  is  received  the  inner 
margin  of  the  head  of  the  radius.  Above  the 
front  part  of  the  capitellum  is  seen  a  slight  de- 
pression which  receives  the  anterior  border  of  the 
head  of  the  radius  when  the  forearm  is  flexed. 
The  inner  portion  of  the  articular  surface,  the 
trochlea,  presents  a  deep  depression  between 
two  well-marked  borders.  This  surface  is  con- 
vex from  before  backward,  concave  from  side  to 
side,  and  occupies  the  anterior,  lower,  and  pos- 
terior parts  of  the  bone.  The  external  border, 
less  prominent  than  the  internal,  corresponds  to 
the  interval  between  the  radius  and  the  ulna. 
The  internal  border  is  thicker,  more  prominent, 
and  consequently  of  greater  length,  than  the 
external.  The  grooved  portion  of  the  articular 
surface  fits  accurately  within  the  greater  sigmoid 
cavity  of  the  ulna :  it  is  broader  and  deeper  on 
the  posterior  than  on  the  anterior  aspect  of  the 
bone,  and  is  inclined  obliquely  from  behind  for- 
ward and  from  without  inward.  Above  the  front 
part  of  the  trochlear  surface  is  seen  a  smaller 
depression,  the  coronoid fossa,  which  receives  the 
coronoid  process  of  the  ulna  during  flexion  of  the 
forearm.  Above  the  back  part  of  the  trochlear 
surface  is  a  deep,  triangular  depression,  the  olec- 
i'finon  fossa,  in  which  is  received  the  summit  of 
the  olecranon  process  in  extension  of  the  forearm. 
These  fossa?  are  separated  from  one  another  by  a 
thin,  transparent  lamina  of  bone,  which  is  some- 
times perforated,  forming  the  supratrochlear  for- 
aiion  :  their  upper  margins  afford  attachment  to 
the  anterior  and  posterior  ligaments  of  the  elbow- 
joint,  and  they  are  lined,  in  the  recent  state,  by 
the  synovial  membrane  of  this  articulation.  The 
articular  surfaces,  in  the  recent  state,  are  covered 
with  a  thin  layer  of  cartilage.  The  external  con- 
dyle  is  a  small,  tubercular  eminence,  less  promi- 
nent than  the  internal,  curved  a  little  forward, 
and  giving  attachment  to  the  external  lateral  lig- 
ament of  the  elbow-joint,  and  to  a  tendon  common 
to  the  origin  of  some  of  the  extensor  and  supi- 


f  7 

J rocnt 


FIG.  198- —Left  humerus.    Posterior  surface. 


252 


THE   SKELETON. 


Epiphyses  of  head  and  } 
tuberosities  blend   at 
5th  year,  and   unite 
with   shaft    at    20th 
year.  j 


Unites  with  shaft  ) 
at  18th  year.      \  • 


JR 


« 


nator  muscles.  The  internal  condyle,  larger  and  more  prominent  than  the  exter- 
nal, is  directed  a  little  backward :  it  gives  attachment  to  the  internal  lateral  liga- 
ment, to  the  Pronator  radii  teres,  and  to  a 
tendon  common  to  the  origin  of  some  of  the 
flexor  muscles  of  the  forearm.  The  ulnar- 
nerve  runs  in  a  groove  at  the  back  of  the 
internal  condyle,  or  between  it  and  the 
olecranon  process.  These  eminences  are 
directly  continuous  above  with  the  external 
and  internal  borders — i.  e.  the  external  and 
internal  condyloid  ridges.  The  great 
prominence  of  the  inner  one  renders  it 
more  liable  to  fracture. 

Structure. — The  extremities  consist  of 
cancellous  tissue,  covered  with  a  thin,  com- 
pact layer ;  the  shaft  is  composed  of  a 
cylinder  of  compact  tissue,  thicker  at  the 
centre  than  at  the  extremities,  and  hollowed 
out  by  a  large  medullary  canal,  which  ex- 
tends along  its  whole  length. 

Development. — By  seven,  or  occasionally 
eight,  centres  (Fig.  199),  one  for  the  shaft, 
one  for  the  head,  one  for  the  tuberosities, 
one  for  the  radial  head,  one  for  the  troch- 
lear  portion  of  the  articular  surface,  and 
one  for  each  condyle.  The  nucleus  for  the 
shaft  appears  near  the  centre  of  the  bone 
in  the  eighth  week,  and  soon  extends  toward 
the  extremities.  At  birth  the  humerus  is 
ossified  nearly  in  its  whole  length,  the  ex- 
tremities remaining  cartilaginous.  At  the 
beginning  of  the  second  year  ossification 
commences  in  the  head  of  the  bone,  and  during  the  third  year  the  centre  for  the 
tuberosities  makes  its  appearance,  usually  by  a  single  ossific  point,  but  sometimes, 
according  to  Be'clard,  by  one  for  each  tuberosity,  that  for  the  lesser  being  small 
and  not  appearing  until  the  fifth  year.  By  the  sixth  year  the  centres  for  the 
head  and  tuberosities  have  enlarged  and  become  joined,  so  as  to  form  a  single 
large  epiphysis. 

The  lower  end  of  the  humerus  is  developed  in  the  following  manner:  At 
the  end  of  the  second  year  ossification  commences  in  the  radial  portion  of  the 
articular  surface,  and  from  this  point  extends  inward,  so  as  to  form  the  chief  part 
of  the  articular  end  of  the  bone,  the  centre  for  the  inner  part  of  the  articular  surface 
not  appearing  until  about  the  age  of  twelve.  Ossification  commences  in  the  internal 
condyle  about  the  fifth  year,  and  in  the  external  one  not  until  about  the  thirteenth 
or  fourteenth  year.  About  sixteen  or  seventeen  years  the  outer  condyle  and  both 
portions  of  the  articulating  surface  (having  already  joined)  unite  with  the  shaft ; 
at  eighteen  years  the  inner  condyle  becomes  joined;  whilst  the  upper  epiphysis, 
although  the  first  formed,  is  not  united  until  about  the  twentieth  year. 

Articulations. — With  the  glenoid  cavity  of  the  scapula  and  with  the  ulna  and 
radius. 

Attachment  of  Muscles. — To  twenty-four:  to  the  greater  tuberosity,  the 
Supraspinatus,  Infraspinatus,  and  Teres  minor ;  to  the  lesser  tuberosity,  the 
Subscapularis  ;  to  the  external  bicipital  ridge,  the  Pectoralis  major  ;  to  the  internal 
bicipital  ridge,  the  Teres  major;  to  the  bicipital  groove,  the  Latissimus  dorsi ;  to 
the  shaft,  the  Deltoid,  Coraco-brachialis,  Brachialis  anticus,  external  and  internal 
heads  of  the  Triceps ;  to  the  internal  condyle,  the  Pronator  radii  teres,  and  common 
tendon  of  the  Flexor  carpi  radialis,  Palmaris  longus,  Flexor  sublimis  digitorum, 


FIG.  199.— Plan   of  the  development  of  the 
humerus.    By  seven  centres. 


THE  HUMERUS.  253 

and  Flexor  carpi  ulnaris ;  to  the  external  condyloid  ridge,  the  Supinator  longus 
and  Extensor  carpi  radialis  longior ;  to  the  external  condyle,  the  common  tendon 
of  the  Extensor  carpi  radialis  brevior,  Extensor  comnmnis  digitorum.  Extensor 
minimi  digiti,  Extensor  carpi  ulnaris,  and  Supinator  brevis ;  to  the  back  of  the 
external  condyle.  the  Anconeus. 

Surface  Form. — The  humerus  is  almost  entirely  clothed  by  the  muscles  which  surround  it, 
an  1  the  only  parts  of  this  bone  which  are  strictly  subcutaneous  are  small  portions  of  the 
internal  and  external  comlyles.  In  addition  to  these,  the  tuberosities  and  a  part  of  the  head 
of  the  bone  can  be  felt  under  the  skin  and  muscles  by  which  they  are  covered.  Of  these  the 
trreater  tuberosity  forms  the  most  prominent  bony  point  of  the  shoulder,  extending  beyond  the 
aeromion  process  and  covered  by  the  Deltoid  muscle.  It  influences  materially  the  surface  form 
of  the  shoulder.  It  is  best  felt  while  the  arm  is  lying  loosely  by  the  side ;  if  the  arm  be  raised, 
it  rece  lt-s  from  under  the  fintrer.  The  lesser  tuberosity.  directed  forward  and  inward,  is  to  be 
felt  to  the  inner  side  of  the  greater  tuberosity.  just  below  the  acromio-clavicular  joint.  Between 
the  two  tuberosities  lies  the  bicipital  groove.  This  can  be  defined  by  placing  the  finger  and 
making  firm  pressure  just  internal  to  the  greater  tuberosity  ;  then,  by  rotating  the  humerus,  the 
groove  will  be  felt  to  pass  under  the  finger  as  the  bone. is  rotated.  With  the  arm  abducted  from 
the  side,  by  pressing  deeply  in  the  axilla  the  lower  part  of  the  head  of  the  bone  is  to  be  felt. 
On  each  side  of  the  elbow-joint,  and  just  above  it,  the  internal  and  external  condyles  of  the 
boil"  are  to  be  felt.  Of  these  the  internal  is  the  more  prominent,  but  the  ridge  passing  upward 
from  it.  the  internal  condyloid  ridge,  is  much  less  marked  than  the  external,  and,  as  a  rule,  is 
not  to  be  felt.  Occasionally,  however,  we  find  along  this  border  the  hook-shaped  process  men- 
tioned above.  The  external  condyle  is  most  plainly  to  be  seen  during  semiflexion  of  the  fore- 
arm, and  its  position  is  indicated  by  a  depression  between  the  attachment  of  the  adjacent 
mus  -les.  From  it  is  to  be  felt  a  strong  bony  ridge  running  up  the  outer  border  of  the  shaft  of 
the  hone.  This  is  the  external  condyloid  ridge;  it  is  concave  forward,  and  corresponds  with 
the  curved  direction  of  the  lower  extremity  of  the  humerus. 

Surgical  Anatomy. — There  are  several  points  of  surgical  interest  connected  with  the 
humerus.  First,  as  regards  its  development.  The  upper  end,  though  the  first  to  ossify,  is  the 
last  to  join  the  shaft,  and  the  length  of  the  bone  is  mainly  due  to  growth  from  this  upper 
epiphysis.  Hence,  in  cases  of  amputation  of  the  arm  in  young  subjects  the  humerus  continues 
to  urow  considerably,  and  the  end  of  the  bone  which  immediately  after  the  operation  was  cpv- 
eivl  with  a  thick  cushion  of  soft  tissue,  begins  to  project,  thinning  the  soft  parts  and  rendering 
the  stump  conical.  This  may  necessitate  the  removal  of  a  couple  of  inches  or  so  of  the  bone, 
and  even  after  this  operation  a  recurrence  of  the  conical  stump  may  take  place. 

There  are  several  points  of  surgical  interest  in  connection  with  fractures.  First,  as  regard 
their  causation  :  the  bone  may  be  broken  by  direct  or  indirect  violence  like  the  other  long  bones, 
but.  in  addition  to  this,  it  is  probably  more  frequently  fractured  by  muscular  action  than  any 
other  of  this  class  of  bone  in  the  body.  It  is  usually  the  shaft,  just  below  the  insertion  of  the 
Deltoid,  which  is  thus  broken.  I  have  seen  the  accident  happen  from  throwing  a  stone,  and  in 
an  apparently  healthy  adult  from  cutting  a  piece  of  hard  cake  tobacco"  on  a  table.  In  this 
latter  case  there  was  no  disease  of  the  bone  that  could  be  discovered.  Fractures  of  the  upper 
end  may  take  place  through  the  anatomical  neck,  through  the  surgical  neck,  or  separation  of  the 
greater  tuberosity  may  o x-ur.  Fracture  of  the  anatomical  neck  is  a  very  rare  accident;  in  fact. 
it  i-  doubted  by  some  whether  it  ever  occurs.  These  fractures  are  usually  considered  to  be 
intraeapsular.  but  they  are  probably  partly  within  and  partly  without  the  capsule,  as  the  lower 
part  of  the  capsule  is  inserted  some  little  distance  below  the  anatomical  neck,  while  the  upper 
part  is  attached  to  it.  They  may  be  impacted  or  non-impacted.  In  most  cases  there  is  little  or 
no  displacement  on  account  of  the  capsule,  in  whole  or  in  part,  remaining  attached  to  the  lower 
fragment.  But  occasionally  a  very  remarkable  alteration  in  position  takes  place ;  the  upper 
fragment  turns  on  its  own  axis,  so  that  the  cartilaginous  surface  of  the  head  rests  against  the 
upper  end  of  the  lower  fragment.  When  the  fractured  end  is  entirely  separated  from  all  its 
surroundings,  its  vascular  supply  must  be  entirely  cut  off,  and  one  would"  expect  it,  theoretically, 
to  necrose.  But  this  must  be  exceedingly  rare,  for  Gurlt  was  unable  to  find  a  single  authenti- 
cated case  recorded.  Separation  of  the  upper  epiphysis  of  the  humerus  sometimes  occurs  in  the 
young  subject,  and  is  marked  by  a  characteristic  deformity  by  which  the  lesion  may  be  at  once 
recognized.  This  consists  in  the  presence  of  an  abrupt  projection  at  the  front  of  the  joint  some 
short  distance  below  the  coracoid  process,  caused  by  the  upper  end  of  the  lower  fragment.  In 
fractures  of  the  shaft  of  the  humerus  the  lesion  may  take  place  at  any  point,  but  appears  to  be 
more  common  in  the  lower  than  in  the  upper  part  of  the  bone.  The  points  of  interest  in  con- 
nection with  these  fractures  are — ( 1 )  that  the  musculo-spiral  nerve  may  be  injured  as  it  lies  in  the 
groove  on  the  bone,  or  may  become  involved  in  the  callus  which  is  subsequently  thrown  out; 
and  • '!)  the  frequency  of  non-union.  This  is  believed  to  be  more  common  in  the  humerus  than 
in  any  other  bone,  and  various  causes  have  been  assigned  for  it.  It  would  seem  most  probably 
to  be  due  to  the  difficulty  that  there  is  in  fixing  the  shoulder-joint  and  the  upper  fragment,  and 
possibly  also  the  elbow-joint  and  lower  fragment  also.  Other  causes  which  have  been  assigned 
for  the  non-union  are:  (1)  that  in  attempting  passive  motion  of  the  elbow-joint  to  overcome 
any  rigidity  which  may  exist,  the  movement  does  not  take  place  at  the  articulation,  but  at  the 
seat  of  fracture  ;  or  that  the  patient,  in  consequence  of  the  rigidity  of  the  elbow,  in  attempting 


254  THE  SKELETON. 

to  flex  or  extend  the  forearm  moves  the  fragment  and  not  the  joint.  (2)  The  presence  of  small 
portions  of  muscular  tissue  between  the  broken  ends.  (3)  Want  of  support  to  the  elbow,  so 
that  the  weight  of  the  arm  tends  to  drag  the  lower  fragment  away  from  the  upper.  An  import- 
ant distinction  to  make  in  fractures  of  the  lower  end  of  the  humerus  is  between  those  that 
involve  the  joint  and  those  which  do  not ;  the  former  always  serious,  as  they  may  lead  to 
impairment  of  the  utility  of  the  limb.  They  include  the  T-shaped  fracture  and  oblique  frac- 
tures which  involve  the  articular  surface.  The  fractures  which  do  not  involve  the  joint  are  the 
transverse  above  the  condyles  and  detachment  of  one  or  other  condyle. 

Under  the  head  of  separation  of  the  epiphysis  two  separate  injuries  have  been  described. 
One  where  the  whole  of  the  four  ossific  centres  which  form  the  lower  extremity  of  the  bone  are 
separated  from  the  shaft ;  and  secondly,  where  the  articular  portion  is  alone  separated,  the  two 
condyles  remaining  attached  to  the  shaft  of  the  bone.  The  epiphysial  line  between  the  shaft 
and  lower  end  runs  across  the  bone  just  above  the  tips  of  the  condyles,  a  point  to  be  borne  in 
mind  in  performing  the  operation  or  excision. 

Tumors  originating  from  the  humerus  are  of  frequent  occurrence.  A  not  uncommon  place 
for  a  chondroma  to  grow  from  is  the  shaft  of  the  bone  somewhere  in  the  neighborhood  of  the 
insertion  of  the  deltoid.  Sarcomata  frequently  grow  from  this  bone. 

THE  FOEEAEM. 

The  Forearm  is  that  portion  of  the  upper  extremity  which  is  situated  between 
the  elbow  and  the  wrist.  It  is  composed  of  two  bones,  the  ulna  and  radius. 

The  Ulna. 

The  Ulna  (Figs.  200,  201),  so  called  from  its  forming  the  elbow  (wAswj),  is  a 
long  bone,  prismatic  in  form,  placed  at  the  inner  side  of  the  forearm,  parallel  with 
the  radius.  It  is  the  larger  and  longer  of  the  two  bones.  Its  upper  extremity,  of 
great  thickness  and  strength,  forms  a  large  part  of  the  articulation  of  the  elbow- 
joint  ;  it  diminishes  in  size  from  above  downward,  its  lower  extremity  being  very 
small,  and  excluded  from  the  wrist-joint  by  the  interposition  of  an  interarticular 
nbro-cartilage.  It  is  divisible  into  a  shaft  and  two  extremities. 

The  Upper  Extremity,  the  strongest  part  of  the  bone,  presents  for  examination 
two  large,  curved  processes,  the  Olecranon  process  and  the  Coronoid  process ;  and 
two  concave,  articular  cavities,  the  greater  and  lesser  sigmoid  cavities. 

The  Olecranon  Process  (a^ewy,  elbow ;  xpaviov,  head)  is  a  large,  thick,  curved 
eminence  situated  at  the  upper  and  back  part  of  the  ulna.  It  is  curved  forward 
at  the  summit  so  as  to  present  a  prominent  tip,  its  base  being  contracted  where 
it  joins  the  shaft.  This  is  the  narrowest  part  of  the  upper  end  of  the  ulna, 
and,  consequently,  the  most  usual  seat  of  fracture.  The  posterior  surface  of  the 
olecranon,  directed  backward,  is  triangular,  smooth,  subcutaneous,  and  covered 
by  a  bursa.  Its  upper  surface,  directed  upward,  is  of  a  quadrilateral  form,  marked 
behind  by  a  rough  impression  for  the  attachment  of  the  Triceps  muscle ;  and  in 
front,  near  the  margin,  by  a  slight  transverse  groove  for  the  attachment  of  part  of 
the  posterior  ligament  of  the  elbow-joint.  Its  anterior  surface  is  smooth,  concave, 
covered  with  cartilage  in  the  recent  state,  and  forms  the  upper  and  back  part  of 
the  great  sigmoid  cavity.  The  lateral  borders  present  a  continuation  of  the  same 
groove  that  was  seen  on  the  margin  of  the  superior  surface ;  they  serve  for  the 
attachment  of  ligaments ;  viz.  the  back  part  of  the  internal  lateral  ligament 
internally,  the  posterior  ligament  externally.  To  the  inner  border  is  also  attached 
a  part  of  the  Flexor  carpi  ulnaris,  while  to  the  outer  border  is  attached  the 
Anconeus. 

The  Coronoid  Process  (xopwvr],  anything  hooked  like  a  crow's  beak)  is  a  rough, 
triangular  eminence  of  bone  which  projects  horizontally  forward  from  the  upper 
and  front  part  of  the  ulna,  forming  the  lower  part  of  the  great  sigmoid  cavity. 
Its  base  is  continuous  with  the  shaft,  and  of  considerable  strength ;  so  much  so 
that  fracture  of  it  is  an  accident  of  rare  occurrence.  Its  apex  is  pointed,  slightly 
curved  upward,  and  received  into  the  coronoid  depression  of  the  humerus  in 
flexion  of  the  forearm.  Its  upper  surface  is  smooth,  concave,  and  forms  the 
lower  part  of  the  greater  sigmoid  cavity.  The  under  surface  is  concave,  and 
marked  internally  by  a  rough  impression  for  the  insertion  of  the  Brachialis  anticus. 
At  the  junction  of  this  surface  with  the  shaft  is  a  rough  eminence,  the  tubercle  of 


THE    ULXA. 


2o5 


Una. 


?*CXOR   SUBLIUIS 
DIG  TORUM. 


PRONATOR 
RADII    TERES 


Occasional  origin  of 

*LEXOR    LONGUS    POLLICIS 


Radial  oriffin  of  FLEXOR 

SUBUM'S    OIOITOAUU. 


Xtyloid  process. 


8UPINATOH    LONQUS. 

Groove  for  EXTENSOR  O! 

METACARPI    POLLICIS. 

Groove  for  EXTENSOR 

BREVIS    POLLICIS. 


Styloid  process. 
FIG.  200.— Bones  of  the  left  forearm.    Anterior  surfece. 


256  THE  SKELETON. 

the  ulna,  for  the  attachment  of  the  oblique  ligament.  Its  outer  surface  presents  a 
narrow,  oblong,  articular  depression,  the  lesser  sigmoid  cavity.  The  inner  surface, 
by  its  prominent,  free  margin,  serves  for  the  attachment  of  part  of  the  internal 
lateral  ligament.  At  the  front  part  of  this  surface  is  a  small,  rounded  eminence 
for  the  attachment  of  one  head  of  the  Flexor  sublimis  digitorum ;  behind  the 
eminence,  a  depression  for  part  of  the  origin  of  the  Flexor  profundus  digitorum ; 
and,  descending  from  the  eminence,  a  ridge  which  gives  attachment  to  one  head 
of  the  Pronator  radii  teres.  Generally,  the  Flexor  longus  pollicis  has  an  origin 
from  the  lower  part  of  the  coronoid  process  by  a  rounded  bundle  of  muscular  fibres. 

The  Greater  Sigmoid  Cavity,  so  called  from  its  resemblance  to  the  old  shape  of 
the  Greek  letter  2",  is  a  semilunar  depression  of  large  size,  formed  by  the  olecranon 
and  coronoid  processes,  and  serving  for  articulation  with  the  trochlear  surface  of 
the  humerus.  About  the  middle  of  either  lateral  border  of  this  cavity  is  a  notch 
which  contracts  it  somewhat,  and  serves  to  indicate  the  junction  of  the  two 
processes  of  which  it  is  formed.  The  cavity  is  concave  from  above  downward, 
and  divided  into  two  lateral  parts  by  a  smooth,  elevated  ridge  whioiwruns  from  the 
summit  of  the  olecranon  to  the  tip  of  the  coronoid  process.  Of  these  .two  portions, 
the  internal  is  the  larger,  and  is  slightly  concave  transversely;  the  external  por- 
tion is  convex  above,  slightly  con-cave  below.  The  articular  surface,  in  the  recent 
state,  is  covered  with  a  thin  layer  of  cartilage. 

The  Lesser  Sigmoid  Cavity  is  a  narrow,  oblong,  articular  depression,  placed  on 
the  outer  side  of  the  coronoid  process,  and  serving  for  articulation  with  the  head 
of  the  radius.  It  is  concave  from  before  backward,  and  its  extremities,  which 
are  prominent,  serve  for  the  attachment  of  the  orbicular  ligament.  In  the  recent 
state  it  is  covered  with  a  thin  layer  of  cartilage. 

The  Shaft,  at  its  upper  part,  is  prismatic  in  form,  and  curved  from  behind 
forward  and  from  without  inward,  so  as  to  be  convex  behind  and  externally ;  its 
central  part  is  quite  straight ;  its  lower  part  rounded^  smooth,  and  bent  a  little 
outward ;  it  tapers  gradually  from  above  downward,  and  presents  for  examination 
three  borders  and  three  surfaces. 

The  anterior  border  commences  above  at  the  prominent  inner  angle  of  the  coro- 
noid process,  and  terminates  below  in  front  of  the  styloid  process.  It  is  well  marked 
above,  smooth  and  rounded  in  the  middle  of  its  extent,  and  aifords  attachment  to 
the  Flexor  profundus  digitorum :  its  lower  fourth,  marked  off  from  the  rest  of  the 
border  by  the  commencement  of  an  oblique  ridge  on  the  anterior  surface,  serves 
for  the  attachment  of  the  Pronator  quadratus.  It  separates  the  anterior  from  the 
internal  surface. 

The  posterior  border  commences  above  at  the  apex  of  the  triangular  subcuta- 
neous surface  at  the  back  part  of  the  olecranon,  and  terminates  below  at  the  back 
part  of  the  styloid  process ;  it  is  well  marked  in  the  upper  three-fourths,  and 
gives  attachment  to  an  aponeurosis  common  to  the  Flexor  carpi  ulnaris,  the 
Extensor  carpi  ulnaris,  and  the  Flexor  profundus  digitorum  muscles  ;  its  lower 
fourth  is  smooth  and  rounded.  This  border  separates  the  internal  from  the 
posterior  surface. 

The  external  or  interosseous  border  commences  above  by  two  lines,  which  con- 
verge one  from  each  extremity  of  the  lesser  sigmoid  cavity,  enclosing  between  them 
a  triangular  space  for  the  attachment  of  part  of  the  Supinator  brevis,  and  terminates 
beloAv  at  the  middle  of  the  head  of  the  ulna.  Its  two  middle  fourths  are  very  pro- 
minent, its  lower  fourth  is  smooth  and  rounded.  This  border  gives  attachment  to 
the  interosseous  membrane,  except  along  its  upper  fourth,  and  separates  the  anterior 
from  the  posterior  surface. 

The  anterior  surface,  much  broader  above  than  below,  is  concave  in  the  upper 
three-fourths  of  its  extent,  and  affords  attachment  to  the  Flexor  profundus  digi- 
torum ;  its  lower  fourth,  also  concave,  to  the  Pronator  quadratus.  The  lower 
fourth  is  separated  from  the  remaining  portion  of  the  bone  by  a  prominent  ridge, 
directed  obliquely  from  above  downward  and  inward ;  this  ridge  (the  oblique  or 
Pronator  ridge]  marks  the  extent  of  attachment  of  the  Pronator  quadratus  above. 


THE 


257 


Ulna. 


FLEXOR   SUBLIMIS    DlGITORUk 


EXTENSOR   CARPI    ULNARIA 
EXTENSOR    MINIMI    OIOITI. 


EXTENSOR     LONGUS    POLLIClS 


j~        /EXTENSOR     INOICIS 

\  EXTENSOR    COMMUNI 


IS    OIOITORUM. 


FIG.  20L—  Bones  of  the  left  forearm.    Posterior  surface. 


17 


258 


THE   SKELETON. 


At  the  junction  of  the  upper  with  the  middle  third  of  the  bone  is  the  nutrient 
canal  directed  obliquely  upward  and  inward. 

The  posterior  surface,  directed  backward  and  outward,  is  broad  and  concave 
above,  somewhat  narrower  and  convex  in  the  middle  of  its  course,  narrow,  smooth, 
and  rounded  below.  It  presents,  above,  an  oblique  ridge,  which  runs  from  the 
posterior  extremity  of  the  lesser  sigmoid  cavity,  downward  to  the  posterior  border  ; 
the  triangular  surface  above  this  ridge  receives  the  insertion  of  the  Anconeus 
muscle,  whilst  the  ridge  itself  affords  attachment  to  the  Supinator  brevis.  The 
surface  of  bone  below  this  is  subdivided  by  a  longitudinal  ridge,  sometimes  called 
the  perpendicular  line,  into  two  parts :  the  internal  part  is  smooth,  concave,  and 
gives  origin  to  (occasionally  is  merely  covered  by)  the  Extensor  carpi  ulnaris ;  the 
external  portion,  wider  and  rougher,  gives  attachment  from  above  downward  to 
part  of  the  Supinator  brevis,  the  Extensor  ossis  metacarpi  pollicis,  the  Extensor 
longus  pollicis,  and  the  Extensor  indicis  muscles. 

The  internal  surface  is  broad  and  concave  above,  narrow  and  convex  below. 
It  gives  attachment  by  its  upper  three-fourths  to  the  Flexor  profundus  digitorum 
muscle  :  its  lower  fourth  is  subcutaneous. 

The  Lower  Extremity  of  the  ulna  is  of  small  size,  and  excluded  from  the  artic- 
ulation of  the  wrist-joint.  It  presents  for  examination  two  eminences,  the  outer 
and  larger  of  which  is  a  rounded,  articular  eminence,  termed  the  head  of  the  ulna, 
the  inner,  narrower  and  more  projecting,  is  a  non-articular  eminence,  the  styloid 
process.  The  head  presents  an  articular  facet,  part  of  which,  of  an  oval  form,  is 
directed  downward,  and  articulates  with  the  upper  surface  of  the  interarticular 
fibro-cartilage  which  separates  it  from  the  wrist-joint;  the  remaining  portion, 
directed  outward,  is  narrow,  convex,  and  received  into  the  sigmoid  cavity  of  the 
radius.  The  styloid  process  projects  from  the  inner  and  back  part  of  the  bone,  and 
descends  a  little  lower  than  the  head,  terminating  in  a  rounded  summit,  which 
affords  attachment  to  the  internal  lateral  ligament  of  the  wrist.  The  head  is 
separated  from  the  styloid  process,  by  a  depression  for  the  attachment  of  the 

triangular  interarticular  fibro-cartilage  ;  and  behind, 
by  a  shallow  groove  for  the  passage  of  the  tendon  of 
the  Extensor  carpi  ulnaris. 

Structure. — Similar  to  that  of  the  other  long  bones. 
Development. — By  three  centres  :  one  for  the  shaft, 
one  for  the  inferior  extremity,  and  one  for  the  olec- 
ranon (Fig.  202).  Ossification  commences  near  the 
middle  of  the  shaft  about  the  eighth  week,  and  soon 
extends  through  the  greater  part  of  the  bone.  At 
birth  the  ends  are  cartilaginous.  About  the  fourth 
year  a  separate  osseous  nucleus  appears  in  the  middle 
of  the  head,  which  soon  extends  into  the  styloid  pn> 
cess.  About  the  tenth  year  ossific  matter  appears  in 
the  olecranon  near  its  extremity,  the  chief  part  of 
this  process  being  formed  from  an  extension  of  the 
shaft  of  the  bone  into  it.  At  about  the  sixteenth 
year  the  upper  epiphysis  becomes  joined,  and  at 
about  the  twentieth  year  the  lower  one. 

Articulations. — With  the  humerus  and  radius. 
Attachment  of  Muscles. — To  sixteen :  to  the 
olecranon,  the  Triceps,  Anconeus,  and  one  head  of 
the  Flexor  carpi  ulnaris.  To  the  coronoid  process, 
the  Brachialis  anticus,  Pronator  radii  teres,  Flexor 
sublimis  digitorum,  and  Flexor  profundus  digitorum  ; 
generally  also  the  Flexor  longus  pollicis.  To  the 
shaft,  the  Flexor  profundus  digitorum,  Pronator  quad- 
ratus,  Flexor  carpi  ulnaris,  Extensor  carpi  ulnaris,  Anconeus,  Supinator  brevis, 
Extensor  ossis  metacarpi  pollicis,  Extensor  longus  pollicis,  and  Extensor  indicis. 


Olecranon. 

Appears  rt^r^jjfe.j0ins  shaft  at 
10th  year,    j  ,     16th  yeaff 


Appears  at 
4th  year. 


Joins  shaft  at 
20th  year. 


Inferior  extremity. 

FIG.  202.— Plan  of  the  develop- 
ment of  the  ulna.    By  three  centres. 


THE  RADIUS.  259 

Surface  Form. — The  most  prominent  part  of  the  ulna  on  the  surface  of  the  body  is  the 
olecranon  process,  which  can  always  be  felt  at  the  back  of  the  elbow-joint.  When  the  fore- 
arm is  flexed  the  upper  triangular  surface  can  be  felt,  directed  backward ;  during  extension  it 
recedes  into  the  olecranon  fossa,  and  the  contracting  fibres  of  the  triceps  prevent  its  being 
perceived.  At  the  back  of  the  olecranon  is  the  smooth,  triangular,  subcutaneous  surface, 
which  below  is  continuous  with  the  posterior  border  of  the  shaft  of  the  bone;  this  is  to 
be  felt  in  every  position  of  the  joint.  During  extension  the  upper  border  of  the  olecranon  is 
slightly  above  the  level  of  the  internal  condyle,  and  the  process  itself  is  nearer  to  this  condyle 
than  the  outer  one.  Running  down  the  back  of  the  forearm,  from  the  apex  of  the  triangular 
surface  which  forms  the  posterior  surface  of  the  olecranon.  is  a  prominent  ridge  of  bone,  the 
posterior  border  of  the  ulna.  This  is  to  be  felt  throughout  the  entire  length  of  the  shaft  of  the 
bone,  from  the  olecranon  above  to  the  styloid  process  below.  As  it  passes  down  the  forearm  it 
pursues  a  sinuous  course  and  inclines  to  the  inner  side,  so  that,  though  it  is  situated  in  the 
middle  of  the  back  of  the  limb  above,  it  is  on  the  inner  side  of  the  wrist  at  its 'termination.  It 
becomes  rounded  off  in  its  lower  third,  and  may  be  traced  below  to  the  small,  subcutaneous  sur- 
face of  the  styloid  process.  Internal  to  this  border  the  lower  fourth  of  the  internal  surface  is  to 
be  felt.  The  styloid  process  is  to  be  felt  as  a  prominent  tubercle  of  bone,  continuous  above 
with  the  posterior  subcutaneous  border  of  the  ulna,  and  terminating  below  in  a  blunt  apex, 
which  lies  a  little  internal  and  behind,  but  on  a  level  with,  the  wrist-joint.  The  styloid  process 
is  best  felt  when  the  hand  is  in  the  same  line  as  the  bones  of  the  forearm,  and  in  a  position 
midway  between  supination  and  pronation.  If  the  forearm  is  pronated  while  the  finger  is 
placed  on  the  process,  it  will  be  felt  to  recede,  and  another  prominence  of  bone  will  appear  just 
external  and  above  it.  This  is  the  head  of  the  ulna,  which  articulates  with  the  lower  end  of  the 
radius  and  the  triangular  interarticular  fibro-cartilage,  and  now  projects  between  the  tendons  of 
the  Extensor  carpi  ulnaris  and  the  Extensor  minimi  digiti  muscles. 

The  Radius. 

The  Radius  (radius,  a  ray,  or  spoke  of  a  wheel)  is  situated  on  the  outer  side  of 
the  forearm,  lying  side  by  side  with  the  ulna,  which  exceeds  it  in  length  and  size. 
Its  upper  end  is  small,  and  forms  only  a  small  part  of  the  elbow-joint ;  but  its 
lower  end  is  large,  and  forms  the  chief  part  of  the  wrist.  It  is  one  of  the  long 
bones,  prismatic  in  form,  slightly  curved  longitudinally,  and,  like  other  long  bones, 
has  a  shaft  and  two  extremities. 

The  Upper  Extremity  presents  a  head,  neck,  and  tuberosity.  The  head  is  of  a 
cylindrical  form,  depressed  on  its  upper  surface  into  a  shallow  cup  which  articulates 
with  the  capitellum  or  radial  head  of  the  humerus.  In  the  recent  state  it  is  covered 
with  a  layer  of  cartilage  which  is  thinnest  at  its  centre.  Around  the  circumference 
of  the  head  is  a  smooth,  articular  surface,  broad  internally  where  it  articulates  with 
the  lesser  sigmoid  cavity  of  the  ulna  ;  narrow  in  the  rest  of  its  circumference,  where 
it  rotates  within  the  orbicular  ligament.  It  is  coated  with  cartilage  in  the  recent 
state.  The  head  is  supported  on  a  round,  smooth,  and  constricted  portion  of  bone, 
called  the  neck,  which  presents,  behind,  a  slight  ridge,  for  the  attachment  of  part 
of  the  Supinator  brevis.  Beneath  the  neck,  at  the  inner  and  front  aspect  of  the 
bone,  is  a  rough  eminence,  the  bicipital  tuberosity.  Its  surface  is  divided  into  two 
parts  by  a  vertical  line — a  posterior,  rough  portion,  for  the  insertion  of  the  tendon 
of  the  Biceps  muscle :  and  an  anterior,  smooth  portion,  on  which  a  bursa  is 
interposed  between  the  tendon  and  the  bone. 

The  Shaft  of  the  bone  is  prismoid  in  form,  narrower  above  than  below,  and 
slightly  curved,  so  as  to  be  convex  outward.  It  presents  three  surfaces,  separated 
by  three  borders. 

The  anterior  border  extends  from  the  lower  part  of  the  tuberosity  above  to  the 
anterior  part  of  the  base  of  the  styloid  process  below.  It  separates  the  anterior 
from  the  external  surface.  Its  upper  third  is  very  prominent;  and  from  its 
oblique  direction,  downward  and  outward,  has  received  the  name  of  the  oblique 
lt'//>'  of  the  radius.  It  gives  attachment  externally  to  the  Supinator  brevis, 
internally  to  the  Flexor  longus  pollicis,  and  between  these  to  the  Flexor  sublimis 
digitorum.  The  middle  third  of  the  anterior  border  is  indistinct  and  rounded.  Its 
lower  fourth  is  sharp,  prominent,  affords  attachment  to  the  Pronator  quadratus,  and 
terminates  in  a  small  tubercle,  into  which  is  inserted  the  tendon  of  the  Supinator 
longus. 

The  posterior  border  commences  above  at  the  back  part  of  the  neck  of  the 


260  THE  SKELETON. 

radius,  and  terminates  below  at  the  posterior  part  of  the  base  of  the  styloid  process  ; 
it  separates  the  posterior  from  the  external  surface.  It  is  indistinct  above  and  below, 
but  well  marked  in  the  middle  third  of  the  bone. 

The  internal  or  interosseous  border  commences  above  at  the  back  part  of  the 
tuberosity,  where  it  is  rounded  and  indistinct,  becomes  sharp  and  prominent  as 
it  descends,  and  at  its  lower  part  divides  into  two  ridges,  which  descend  to  the 
anterior  and  posterior  margins  of  the  sigmoid  cavity.  This  border  separates  the 
anterior  from  the  posterior  surface,  and  has  the  interosseous  membrane  attached 
to  it  throughout  the  greater  part  of  its  extent. 

The  anterior  surface  is  narrow  and  concave  for  its  upper  three-fourths,  and 
gives  attachment  to  the  Flexor  longus  pollicis  muscle ;  it  is  broad  and  flat  for  its 
lower  fourth,  and  gives  attachment  to  the  Pronator  quadratus.  A  prominent  ridge 
limits  the  attachment  of  the  Pronator  quadratus  below,  and  between  this  and  the 
inferior  border  is  a  triangular  rough  surface  for  the  attachment  of  the  anterior 
ligament  of  the  wrist-joint.  At  the  junction  of  the  upper  and  middle  third  of  this 
surface  is  the  nutrient  foramen,  which  is  directed  obliquely  upward. 

The  posterior  surface  is  rounded,  convex,  and  smooth  in  the  upper  third  of  its 
extent,  and  covered  by  the  Supinator  brevis  muscle.  Its  middle  third  is  broad, 
slightly  concave,  and  gives  attachment  to  the  Extensor  ossis  metacarpi  pollicis 
above,  the  Extensor  brevis  pollicis  below.  Its  lower  third  is  broad,  convex,  and 
covered  by  the  tendons  of  the  muscles,  which  subsequently  run  in  the  grooves  on 
the  lower  end  of  the  bone. 

The  external  surface  is  rounded  and  convex  throughout  its  entire  extent.  Its 
upper  third  gives  attachment  to  the  Supinator  brevis  muscle.  About  its  centre  is 
seen  a  rough  ridge,  for  the  insertion  of  the  Pronator  radii  teres  muscle.  Its  lower 
part  is  narrow,  and  covered  by  the  tendons  of  the  Extensor  ossis  metacarpi  pollicis 
and  Extensor  brevis  pollicis  muscles. 

The  Lower  Extremity  of  the  radius  is  large,  of  quadrilateral  form,  and  provided 
with  two  articular  surfaces — one  at  the  extremity,  for  articulation  with  the  carpus, 
and  one  at  the  inner  side  of  the  bone,  for  articulation  with  the  ulna.  The  carpal 
articular  surface  is  of  triangular  form,  concave,  smooth,  and  divided  by  a  slight 
antero-posterior  ridge  into  two  parts.  Of  these,  the  external  is  large,  of  a  triangular 
form,  and  articulates  with  the  scaphoid  bone ;  the  inner,  smaller  and  quadrilateral, 
articulates  with  the  semilunar.  The  articular  surface  for  the  ulna  is  called  the 
sigmoid  cavity  of  the  radius ;  it  is  narrow,  concave,  smooth,  and  articulates  with 
the  head  of  the  ulna.  The  circumference  of  this  end  of  the  bone  presents  three 
surfaces — an  anterior,  external,  and  posterior.  The  anterior  surface,  rough  and 
irregular,  affords  attachment  to  the  anterior  ligament  of  the  wrist-joint.  The 
external  surface  is  prolonged  obliquely  downward  into  a  strong,  conical  projection, 
the  styloid  process,  which  gives  attachment  by  its  base  to  the  tendon  of  the 
Supinator  longus,  and  by  its  apex  to  the  external  lateral  ligament  of  the  wrist- 
joint.  The  outer  surface  of  this  process  is  marked  by  a  flat  groove,  which  runs 
obliquely  downward  and  forward,  and  gives  passage  to  the  tendons  of  the  Extensor 
ossis  metacarpi  pollicis  and  the  Extensor  brevis  pollicis.  The  posterior  surface  is 
convex,  affords  attachment  to  the  posterior  ligament  of  the  wrist,  and  is  marked  by 
three  grooves.  Proceeding  from  without  inward,  the  first  groove  is  broad  but 
shallow,  and  subdivided  into  two  by  a  slightly  elevated  ridge:  the  outer  of  these 
two  transmits  the  tendon  of  the  Extensor  carpi  radialis  longior,  the  inner  the 
tendon  of  the  Extensor  carpi  radialis  brevior.  The  second,  which  is  near  the 
centre  of  the  bone,  is  a  deep  but  narrow  groove,  bounded  on  its  outer  side  by  a 
sharply-defined  ridge ;  it  is  directed  obliquely  from  above,  downward  and  outward, 
and  transmits  the  tendon  of  the  Extensor  longus  pollicis.  The  third,  lying  most 
internally,  is  a  broad  groove,  for  the  passage  of  the  tendons  of  the  Extensor  indicia 
and  Extensor  communis  digitorum. 

Structure. — Similar  to  that  of  the  other  long  bones. 

Development  (Fig.  203). — By  three  centres :  one  for  the  shaft  and  one  for  each 
extremity.  That  for  the  shaft  makes  its  appearance  near  the  centre  of  the  bone 


THE   RADIUS. 


261 


Head. 

Appears  at  r^^g-^^  Unites  with  shaft 
5th  year.  ~^B^"V     about  puberty. 


Appears  at_ 
•2<l  year. 


Unites  with  shaft 
about  SOth  year. 


Lower  extremity. 

FIG.  203.— Plan  of  the  development  of 
the  radius.    By  three  centres. 


soon  after  the  development  of  the  humerus  commences.     At  birth   the  shaft  is 

ossified,  but  the  ends  of  the  bone  are  cartilaginous.     About  the  end  of  the  second 

year  ossification  commences  in  the  lower  epiph- 

ysis   and  about  the  fifth  year  in  the  upper  one. 

At  the  age  of  seventeenoreighteen  the  upper  epiph- 

ysis  becomes  joined  to  the  shaft,  the  lower  epiph- 

ysis  becoming  united  about  the  twentieth  year. 

Articulation. — With  four  bones :  the  humerus, 
ulna,  scaphoid,  and  semilunar. 

Attachment  of  Muscles. — To  nine :  to  the 
tuberosity.  the  Biceps  ;  to  the  oblique  ridge, 
the  Supinator  brevis,  Flexor  sublimis  digitorum, 
and  Flexor  longus  pollicis ;  to  the  shaft  (its 
anterior  surface),  the  Flexor  longus  pollicis  and 
Pronator  quadratus :  (its  posterior  surface),  the 
Extensor  ossis  metacarpi  pollicis  and  Extensor 
brevis  pollicis;  (its  outer  surface),  the  Pronator 
radii  teres ;  and  to  the  styloid  process,  the 
Supinator  longus. 

Surface  Form. — Just  below  and  a  little  in  front  of 
the  posterior  surface  of  the  external  condyle  a  part  of 
the  head  of  the  radius  maybe  felt,  covered  by  the  orbic- 
ular and  external  lateral  ligaments.  There  is  in  this  situ- 
ation a  little  dimple  in  the  skin,  which  is  most  visible 
when  the  arm  is  extended,  and  which  marks  the  posi- 
tion of  the  head  of  the  bone.  If  the  finger  is  placed  on 
tli is  dimple  and  the  forearm  pronated  and  supinated, 
the  head  of  the  bone  will  be  distinctly  perceived  rotating 
in  the  lesser  sienioid  cavity.  The  upper  half  of  the 
shaft  of  the  radius  cannot  be  felt,  as  it  is  surrounded  by 

the  fleshy  bellies  of  the  muscles  arising  from  the  external  condyle.  The  lower  half  of  the  shaft 
can  be  readily  examined,  though  covered  by  tendons  and  muscles  and  not  strictly  subcutaneous. 
If  traced  downward,  the  shaft  will  be  felt  to  terminate  in  a  lozenge-shaped,  convex  surface  on 
the  outer  side  of  the  base  of  the  styloid  process.  This  is  the  only  subcutaneous  part  of  the  bone, 
and  from  its  lower  extremity  the  apex  of  the  styloid  process  will  be  felt  bending  inward  toward 
the  wrist.  About  the  middle  of  the  posterior  aspect  of  the  lower  extremity  of  the  bone  is  a 
well-marked  ridge,  best  perceived  when  the  hand  is  slightly  flexed  on  the  wrist.  It  bounds  the 
oblique  groove  on  the  posterior  surface  of  the  bone,  through  which  the  tendon  of  the  Rxtensor 
longus  pollicis  runs,  and  serves  to  keep  that  tendon  in  its  place. 

Surgical  Anatomy.— The  two  bones  of  the  forearm  are  more  often  broken  together  than  is 
either  the  radius  or  ulna  separately.  It  is  therefore  convenient  to  consider  the  fractures  of  these 
two  bones  together  in  the  first  instance,  and  subsequently  to  mention  the  principal  fractures 
which  take  place  in  each  bone  individually.  These  fractures  may^be  produced  by  either  direct 
or  indirect  violence,  though  more  commonly  by  direct  violence.  When  indirect  force  is  applied 
to  the  forearm  the  radius  generally  alone  gives  way.  though  both  bones  may  suffer.  The 
fracture  from  indirect  force  generally  takes  place  somewhere  about  the  middle  of  the  bones ; 
fracture  from  direct  violence  may  occur  at  any  part,  more  often,  however,  in  the  lower  half  of 
the  bone.  The  fracture  is  usually  transverse,  but  may  be  more  or  less  oblique.  A  point  of 
interest  in  connection  with  these  fractures  is  the  tendency  that  there  is  for  the  two  bones  to  unite 
across  the  interosseous  membrane;  the  limb  should  therefore  be  put  up  in  a  position  midway 
between  supination  and  pronation,  which  is  not  only  the  most  comfortable  position,  but  also  sep- 
arates the  bones  most  widely  from  each  other,  and  therefore  diminishes  the  risk  of  the  bones 
becoming  united  across  the  interosseous  membrane.  The  splints,  anterior  and  posterior,  which  are 
applied  in  these  cases  should  be  rather  wider  than  the  limb,  so  as  to  prevent  any  lateral  pressure 
on  the  bones.  For  in  these  cases  there  is  a  greater  liability  to  gangrene  from  the  pressure  of  the 
splints  than  in  other  parts  of  the  body.  This  is  no  doubt  due  principally  to  two  causes :  (1) 
the  flexion  of  the  forearm  compressing  to  a  certain  extent  the  brachial  artery  and  retarding  the 
flow  of  blood  to  the  limb :  and  ( 2)  the  superficial  position  of  the  two  main  arteries  of  the  forearm 
in  a  part  of  their  course,  and  their  liability  to  be  compressed  by  the  splints.  The  special 
fractures  of  the  ulna  are — (1 )  Fracture  of  the  olecranon.  This  may  be  caused  by  direct  violence, 
falls  on  the  elbow  with  the  forearm  flexed,  or  by  muscular  action  by  the  sudden  contraction  of 
the  triceps.  The  most  common  place  for  the  fracture  to  occur  is  at  the  constricted  portion 
where  the  olecranon  joins  the  shaft  of  the  bone,  and  the  fracture  may  be  either  transverse  or 
oblique ;  but  any  part  may  be  broken,  even  a  thin  shell  may  be  torn  off.  Fractures  from  direct 
violence  are  occasionally  comminuted.  The  displacement  is  sometimes  very  slight,  owing  to  the 
fibrous  structures  around  the  process  not  being  torn.  (2)  Fracture  of  the  coronoid  process  some- 


262  THE  SKELETON. 

times  occurs  as  a  complication  of  dislocation  backward  of  the  bones  of  the  forearm,  but  it  is 
doubtful  if  it  ever  occurs  as  an  uncomplicated  injury.  (3)  Fractures  of  the  shaft  of  the  ulna 
may  occur  at  any  part,  but  usually  take  place  at  the  middle  of  the  bone  or  a  little  below  it. 
They  are  almost  always  the  result  of  direct  violence.  (4)  The  styloid  process  may  be  knocked 
off  by  direct  violence.  Fractures  of  the  radius  consist  of — (1 )  Fracture  of  the  head  of  the  bone ; 
this  generally  occurs  in  conjunction  with  some  other  lesion,  but  may  occur  as  an  uncomplicated 
injury.  (2)  Fracture  of  the  neck  may  also  take  place,  but  is  generally  complicated  with  other 
injury.  (3)  Fractures  of  the  shaft  of  the  radius  are  very  common,  and  may  take  place  at  any 
part  of  the  bone.  They  may  take  place  from  either  direct  or  indirect  violence.  (4)  The  most 
important  fracture  of  the  radius  is  that  of  the  lower  end  (Colles's  fracture).  The  fracture  is 
transverse,  and  generally  takes  place  about  an  inch  from  the  lower  extremity.  It  is  caused  by 
falls  on  the  palm  of  the  hand,  and  is  an  injury  of  advanced  life,  occurring  more  frequently  in  the 
female  than  the  male.  In  consequence  of  the  manner  in  which  the  fracture  is  caused,  the  upper 
fragment  becomes  driven  into  the  lower,  and  impaction  is  the  result ;  or  else  the  lower  fragment 
becomes  split  up  into  two  or  more  pieces,  so  that  no  fixation  occurs.  Separation  of  the  lower 
epiphysis  of  the  radius  may  take  place  in  the  young.  This  injury  and  Colles's  fracture  may  be 
distinguished  from  other  injuries  in  this  neighborhood — especially  dislocation,  with  which  it  is 
liable  to  be  confounded — by  observing  the  relative  positions  of  the  styloid  processes  of  the  ulna 
and  radius.  In  the  natural  condition  of  parts,  with  the  arm  hanging  by  the  side,  the  styloid  pro- 
cess of  the  radius  is  on  a  lower  level  than  that  of  the  ulna ;  that  is  to  say,  nearer  the  ground. 
After  fracture  or  separation  of  the  epiphysjs  this  process  is  on  the  same  or  higher  level  than  that 
of  the  ulna,  whereas  it  would  be  unaltered  in  position  in  dislocation. 

THE  HAND. 

The  skeleton  of  the  Hand  is  subdivided  into  three  segments — the  Carpus  or 
wrist-bones ;  the  Metacarpus  or  bones  of  the  palm ;  and  the  Phalanges  or  bones 
of  the  fingers. 

The  Carpus. 

The  bones  of  the  Carpus  (xapnoi;,  the  wrist),  eight  in  number,  are  arranged  in 
two  rows.  Those  of  the  upper  row,  enumerated  from  the  radial  to  the  ulnar 
side,  are  the  scaphoid,  semilunar,  cuneiform,  and  pisiform  ;  those  of  the  lower 
row,  enumerated  in  the  same  order,  are  the  trapezium,  trapezoid,  os  magnum,  and 
unciform. 

Common  Characters  of  the  Carpal  Bones. 

Each  bone  (excepting  the  pisiform)  presents  six  surfaces.  Of  these  the  anterior 
or  palmar  and  the  posterior  or  dorsal  are  rough  for  ligamentous  attachment, 
the  dorsal  surface  being  the  broader,  except  in  the  scaphoid  and  semilunar.  The 
superior  or  proximal  and  inferior  or  distal  are  articular,  the  superior  generally 
convex,  the  inferior  concave ;  and  the  internal  and  external  are  also  articular  when 
in  contact  with  contiguous  bones,  otherwise  rough  and  tubercular.  The  structure 
in  all  is  similar,  consisting  of  cancellous  tissue  enclosed  in  a  layer  of  compact  bone. 
Each  bone  is  also  developed  from  a  single  centre  of  ossification. 

Bones  of  the  Upper  Row  (Figs.  204,  205). 

The  Scaphoid  (axdyrj,  a  boat ;  £?<?<?c,  like)  is  the  largest  bone  of  the  first  row. 
It  has  received  its  name  from  its  fancied  resemblance  to  a  boat,  being  broad 
at  one  end,  and  narrowed  like  a  prow  at  the  opposite.  It  is  situated  at  the 
upper  and  outer  part  of  the  carpus,  its  long  axis  being  from  above  downward, 
outward  and  forward.  The  superior  surface  is  convex,  smooth,  of  triangular 
shape,  and  articulates  with  the  lower  end  of  the  radius.  The  inferior  surface, 
directed  downward,  outwrard,  and  backward,  is  smooth,  convex,  also  triangular, 
and  divided  by  a  slight  ridge  into  two  parts,  the  external  of  which  articulates 
with  the  trapezium,  the  inner  with  the  trapezoid.  The  posterior  or  dorsal  surf  ace 
presents  a  narrow,  rough  groove,  which  runs  the  entire  breadth  of  the  bone  and 
serves  for  the  attachment  of  ligaments.  The  anterior  or  palmar  surface  is  concave 
above,  and  elevated  at  its  lower  and  outer  part  into  a  prominent,  rounded  tubercle, 
which  projects  forward  from  the  front  of  the  carpus  and  gives  attachment  to 
the  anterior  annular  ligament  of  the  wrist.  The  external  surface  is  rough  and 
narrow,  and  gives  attachment  to  the  external  lateral  ligament  of  the  wrist.  The 


THE    CARPUS. 


263 


internal  surface  presents   two  articular  facets :  of  these,  the  superior  or  smaller 
one   is   flattened,  of  semilunar   form,  and   articulates  with  the  semilunar;    the 


Carpus. 


EXTENSOR    BREV18 
PO-- 


•MM    LON3U 
POLLICIS. 


EXTENSOR    DIGITORUM 

coMMumsami 

EXTENSOR    INOIC1S 


FIG.  2M.— Bones  of  the  left  hand.    Dorsal  surface. 


inferior  or  larger  is  concave,  forming,  with  the  semilunar  bone,  a  concavity  for  the 
head  of  the  os  magnum. 


264  THE  SKELETON. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  superior  or 
radial  convex,  articular,  surface  upward,  and  the  posterior  surface — i.  e.  the  narrow, 
non-articular,  grooved  surface — toward  you.  The  tubercle  on  the  outer  surface 
points  to  the  side  to  which  the  bone  belongs.1 

Articulations. — With  five  bones :  the  radius  above,  trapezium  and  trapezoid 
below,  os  magnum  and  semilunar  iivternally. 

The  Lunar  or  Semilunar  (semi,  half;  luna,  moon)  bone  may  be  distinguished  by 
its  deep  concavity  and  crescentic  outline.  It  is  situated  in  the  centre  of  the  upper 
row  of  the  carpus,  between  the  scaphoid  and  cuneiform.  The  superior  surface,  con- 
vex, smooth,  and  bounded  by  four  edges,  articulates  with  the  radius.  The  inferior 
surface  is  deeply  concave,  and  of  greater  extent  from  before  backward  than  trans- 
versely :  it  articulates  with  the  head  of  the  os  magnum  and  by  a  long,  narrow 
facet  (separated  by  a  ridge  from  the  general  surface)  with  the  unciform  bone. 
The  anterior  or  palmar  and  posterior  or  dorsal  surfaces  are  rough,  for  the  attach- 
ment of  ligaments,  the  former  being  the  broader  and  of  somewhat  rounded  form. 
The  external  surface  presents  a  narrow,  flattened,  semilunar  facet  for  articulation 
with  the  scaphoid.  The  internal  'surface  is  marked  by  a  smooth,  quadrilateral 
facet,  for  articulation  with  the  cuneiform. 

Hold  it  with  the  convex  articular  surface  for  the  radius  upward,  and  the 
narrowest  non-articular  surface  toward  you.  The  semilunar  facet  for  the  scaphoid 
will  be  on  the  side  to  which  the  bone  belongs. 

Articulations. — With  five  bones :  the  radius  above,  os  magnum  and  unciform 
below,  scaphoid  and  cuneiform  on  either  side. 

The  Cuneiform  (cuneus,  a  wedge ;  forma,  likeness)  may  be  distinguished  by 
its  pyramidal  shape  (os  pyramidale),  and  by  its  having  an  oval,  isolated  facet  for 
articulation  with  the  pisiform  bone.  It  is  situated  at  the  upper  and  inner  side  of 
the  carpus.  The  superior  surface  presents  an  internal,  rough,  non-articular  por- 
tion, and  an  external  or  articular  portion,  which  is  convex,  smooth,  and  articulates 
with  the  triangular  interarticular  fibro-cartilage  of  the  wrist.  The  inferior  sur- 
face, directed  outward,  is  concave,  sinuously  curved,  and  smooth  for  articu- 
lation with  the  unciform.  The  posterior  or  dorsal  surface  is  rough,  for  the  attach- 
ment of  ligaments.  The  anterior  or  palmar  surface  presents,  at  its  inner  side,  an 
oval  facet,  for  articulation  with  the  pisiform  ;  and  is  rough  externally,  for  liga- 
mentous  attachment.  The  external  surface,  the  base  of  the  pyramid,  is  marked 
by  a  flat,  quadrilateral,  smooth  facet,  for  articulation  with  the  semilunar.  The 
internal  surface,  the  summit  of  the  pyramid,  is  pointed  and  roughened,  for  the 
attachment  of  the  internal  lateral  ligament  of  the  wrist. 

Hold  the  bone  with  the  surface  supporting  the  pisiform  facet  away  from 
you,  and  the  concavo-convex  surface  for  the  unciform  downward.  The  base 
of  the  wedge  (i.  e.  the  broad  end  of  the  bone)  will  be  on  the  side  to  which  it 
belongs. 

Articulations. — With  three  bones :  the  semilunar  externally,  the  pisiform  in 
front,  the  unciform  below ;  and  with  the  triangular,  interarticular  fibro-cartilage 
which  separates  it  from  the  lower  end  of  the  ulna. 

The  Pisiform  ( pisum,  a  pea  ;  forma,  likeness)  may  be  known  by  its  small  size 
and  by  its  presenting  a  single  articular  facet.  It  is  situated  at  the  anterior  and 
inner  side  of  the  carpus,  is  nearly  circular  in  form,  and  presents  on  its  posterior 
surface  a  smooth,  oval  facet,  for  articulation  with  the  cuneiform.  This  facet 
approaches  the  superior,  but  not  the  inferior,  border  of  the  bone.  The  anterior 
or  palmar  surface  is  rounded  and  rough,  and  gives  attachment  to  the  anterior 
annular  ligament  and  to  the  Flexor  carpi  ulnaris  and  Abductor  minimi  digit! 
muscles.  The  outer  and  inner  surfaces  are  also  rough,  the  former  being  convex, 
the  latter  usually  concave. 

Hold  the  bone  with  the  posterior  surface — that  which  presents  the  articular 

1  In  these  directions  each  bone  is  supposed  to  be  placed  in  its  natural  position — that  is,  such  a 
position  as  it  would  occupy  when  the  arm  is  hanging  by  the  side,  the  forearm  in  a  position  of  supi- 
nation,  the  thumb  being  directed  outward,  and  the  palm  of  the  hand  looking  forward. 


THE 


265 


facet — toward  YOU.  in  such  a  manner  that  the  faceted  portion  of  the  surface  is 
uppermost.  The  outer,  convex  surface  will  point  to  the  side  to  which  it 
belongs. 

Articulations. — With  one  bone,  the  cuneiform. 


Carpm. 


Groove  for  tendon  of 

FLEXOR    CARPI    RA01ALIS- 

FLEXOR    OSS  S 
METACARPI    POLLICIS. 


EXTENSOR    OSSIS. 
METACARPI    POLLICIS. 


FIG.  205. — Bones  of  the  left  hand.    Palmar  surface. 


Attachment  of  Muscles. — To  two :   the   Flexor    carpi    ulnaris    and  Abductor 
minimi  digiti ;  and  to  the  anterior  annular  ligament. 


266  THE  SKELETON. 

Bones  of  the  Lower  Row  (Figs.  204,  205). 

The  Trapezium  (rpdxe^a,  a  table)  is  of  very  irregular  form.  It  may  be  distin- 
guished by  a  deep  groove,  for  the  tendon  of  the  Flexor  carpi  radialis  muscle. 
It  is  situated  at  the  external  and  inferior  part  of  the  carpus,  between  the  scaphoid 
and  first  metacarpal  bone.  The  superior  surface,  concave  and  smooth,  is  directed 
upward  and  inward,  and  articulates  with  the  scaphoid.  The  inferior  surface, 
directed  downward  and  inward,  is  oval,  concave  from  side  to  side,  convex  from 
before  backward,  so  as  to  form  a  saddle-shaped  surface,  for  articulation  with  the 
base  of  the  first  metacarpal  bone.  The  anterior  or  palmar  surface  is  narrow  and 
rough.  At  its  upper  part  is  a  deep  groove  running  from  above  obliquely  down- 
ward and  inward ;  it  transmits  the  tendon  of  the  Flexor  carpi  radialis,  and  is 
bounded  externally  by  a  prominent  ridge,  the  oblique  ridge  'of  the  trapezium. 
This  surface  gives  attachment  to  the  Abductor  pollicis,  Flexor  ossis  metacarpi 
pollicis,  and  Flexor  brevis  pollicis  muscles,  and  the  anterior  annular  ligament. 
The  posterior  or  dorsal  surface  is  rough.  The  external  surface  is  also  broad  and 
rough,  for  the  attachment  of  ligaments.  The  internal  surface  presents  two 
articular  facets :  the  upper  one,  large  and  concave,  articulates  with  the  trapezoid ; 
the  lower  one,  narrow  and  flattened,  with  the  base  of  the  second  metacarpal 
bone. 

Hold  the  bone  with  the  saddle-shaped  surface  downward  and  the  grooved 
surface  away  from  you.  The  prominent,  rough,  non-articular  surface  points  to 
the  side  to  which  the  bone  belongs. 

Articulations. — With  four  bones  :  the  scaphoid  above,  the  trapezoid  and  second 
metacarpal  bones  internally,  the  first  metacarpal  below. 

Attachment  of  Muscles. — Abductor  pollicis,  Flexor  ossis  metacarpi  pollicis,  and 
part  of  the  Flexor  brevis  pollicis. 

The  Trapezoid  is  the  smallest  bone  in  the  second  row.  It  may  be  known  by 
its  wedge-shaped  form,  the  broad  end  of  the  wedge  forming  the  dorsal,  the  narrow 
end  the  palmar,  surface,  and  by  its  having  four  articular  surfaces  touching  each 
other  and  separated  by  sharp  edges.  The  superior  surface,  quadrilateral  in  form, 
smooth,  and  slightly  concave,  articulates  with  the  scaphoid.  The  inferior  surface 
articulates  with  the  upper  end  of  the  second  metacarpal  bone ;  it  is  convex  from 
side  to  side,  concave  from  before  backward,  and  subdivided  by  an  elevated  ridge 
into  two  unequal  lateral  facets.  The  posterior  or  dorsal  and  anterior  or  palmar 
surfaces  are  rough,  for  the  attachment  of  ligaments,  the  former  being  the  larger 
of  the  two.  The  external  surface,  convex  and  smooth,  articulates  with  the 
trapezium.  The  internal  surface  is  concave  and  smooth  in  front,  for  articulation 
with  the  os  magnum ;  rough  behind,  for  the  attachment  of  an  interosseous 
ligament. 

Hold  the  bone  with  the  larger,  non-articular  surface  toward  you,  and  the 
smooth,  quadrilateral  articular  surface  upward.  The  convex,  articular  surface 
will  point  to  the  side  to  which  the  bone  belongs.1 

Articulations. — With  four  bones  :  the  scaphoid  above,  second  metacarpal  bone 
below,  trapezium  externally,  os  magnum  internally. 

The  Os  Magnum  is  the  largest  bone  of  the  carpus,  and  occupies  the  centre  of 
the  wrist.  It  presents,  above,  a  rounded  portion  or  head,  which  is  received  into 
the  concavity  formed  by  the  scaphoid  and  semilunar  bones  ;  a  constricted  portion 
or  neck ;  and,  below,  the  body.  The  superior  surface  is  rounded,  smooth,  and 
articulates  with  the  semilunar.  The  inferior  surface  is  divided  by  two  ridges  into 
three  facets,  for  articulation  with  the  second,  third,  and  fourth  metacarpal  bones, 
that  for  the  third  (the  middle  facet)  being  the  largest  of  the  three.  The  posterior 
or  dorsal  surface  is  broad  and  rough ;  the  anterior  or  palmar,  narrow,  rounded, 
and  also  rough,  for  the  attachment  of  ligaments.  The  external  surface  articulates 

1  Occasionally  in  a  badly  marked  bone  there  is  some  difficulty  in  ascertaining  to  which  sido  the 
bone  belongs ;  the  following  method  will  sometimes  be  found  useful :  Hold  the  bone  with  its  broader, 
non-articular  surface  upward,  so  that  its  sloping  border  is  directed  toward  you.  The  border  will  slope 
to  the  side  to  which  the  bone  belongs. 


THE  METACARPUS.  267 

with  the  trapezoid  by  a  small  facet  at  its  anterior  inferior  angle,  behind  which  is 
a  rough  depression  for  the  attachment  of  an  interosseous  ligament.  Above  this 
is  a  deep  and  rough  groove,  w,hich  forms  part  of  the  neck  and  serves  for  the 
attachment  of  ligaments,  bounded  superiorly  by  a  smooth,  convex  surface,  for 
articulation  with  the  scaphoid.  The  internal  surface  articulates  with  the  uncifonn 
by  a  smooth,  concave,  oblong  facet  which  occupies  its  posterior  and  superior 
parts,  and  is  rough  in  front,  for  the  attachment  of  an  interosseous  ligament. 

Hold  the  bone  with  the  broader,  non-articular  surface  toward  you,  and  the 
head  upward.  The  small,  articular  facet  at  the  anterior  inferior  angle  of  the 
external  surface  will  point  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  seven  bones :  the  scaphoid  and  semilunar  above ;  the 
second,  third,  and  fourth  metacarpal  below;  the  trapezoid  on  the  radial  side;  and 
the  unciform  on  the  ulnar  side. 

Attachment  of  Muscles. — Part  of  the  Adductor  obliquus  pollicis. 

The  Unciform  (uncus,  a  hook  ;  forma,  likeness)  may  be  readily  distinguished 
by  its  wedge-shaped  form  and  the  hook-like  process  that  projects  from  its  palmar 
surface.  It  is  situated  at  the  inner  and  lower  angle  of  the  carpus,  with  its  base 
downward,  resting  on  the  two  inner  metacarpal  bones,  and  its  apex  directed 
upward  and  outward.  The  superior  surface,  the  apex  of  the  wedge,  is  narrow, 
convex,  smooth,  and  articulates  with  the  semilunar.  The  inferior  surface  articu- 
lates with  the  fourth  and  fifth  metacarpal  bones,  the  concave  surface  for  each 
being  separated  by  a  ridge  which  runs  from  before  backward.  The  posterior  or 
dorsal  surface  is  triangular  and  rough,  for  ligamentous  attachment.  The  anterior 
or  palmar  surface  presents,  at  its  lower  and  inner  side,  a  curved,  hook-like  pro- 
cess of  bone,  the  unciform  process,  directed  from  the  palmar  surface  forward  and 
outward.  It  gives  attachment  by  its  apex  to  the  annular  ligament ;  by  its  inner 
surface  to  the  Flexor  brevis  minimi  digiti  and  the  Flexor  ossis  metacarpi  minimi 
digiti :  and  is  grooved  on  its  outer  side,  for  the  passage  of  the  Flexor  tendons 
into  the  palm  of  the  hand.  This  is  one  of  the  four  eminences  on  the  front  of  the 
carpus  to  which  the  anterior  annular  ligament  is  attached,  the  others  being  the 
pisiform  internally,  the  oblique  ridge  of  the  trapezium  and  the  tuberosity  of  the 
scaphoid  externally.  The  internal  surface  articulates  with  the  cuneiform  by  an 
oblong  facet  cut  obliquely  from  above,  downward  and  inward.  The  external  sur- 
face articulates  with  the  os  magnum  by  its  upper  and  posterior  part,  the  remaining 
portion  being  rough,  for  the  attachment  of  ligaments. 

Hold  the  bone  with  the  hooked  process  away  from  you,  and  the  articular  sur- 
face, divided  into  two  parts,  for  the  metacarpal  bones,  downward.  The  concavity 
of  the  process  will  be  on  the  side  to  which  the  bone  belongs. 

Articulations. — With  five  bones :  the  semilunar  above,  the  fourth  and  fifth 
metacarpal  below,  the  cuneiform  internally,  the  os  magnum  externally. 

Attachment  of  Muscles. — To  three :  the  Flexor  brevis  minimi  digiti,  the  Flexor 

a  metacarpi  minimi  digiti,  the  Flexor  carpi  ulnaris  ;  and  to  the  anterior  annular 
ligament. 

The  Metacarpus. 

The  Metacarpal  Bones  are  five  in  number:  they  are  long,  cylindrical  bones, 
presenting  for  examination  a  shaft  and  two  extremities. 

Common  Characters  of  the  Metacarpal  Bones. 

The  Shaft  is  prismoid  in  form  and  curved  longitudinally,  so  as  to  be  convex  in 
the  longitudinal  direction  behind,  concave  in  front.  It  presents  three  surfaces: 
two  lateral  and  one  posterior.  The  lateral  surfaces  are  concave,  for  the  attach- 
ment of  the  Interossei  muscles,  and  separated  from  one  another  by  a  prominent 
line.  The  posterior  or  dorsal  surface  presents  in  its  distal  half  a  smooth, 
triangular,  flattened  area  which  is  covered,  in  the  recent  state,  by  the  tendons  of 
the  Extensor  muscles.  This  triangular  surface  is  bounded  by  two  lines,  which 
commence  in  small  tubercles  situated  on  the  dorsal  aspect  of  either  side  of  the 


268  THE  SKELETON. 

digital  extremity,  and,  running  backward,  converge  to  meet  together  a  little 
behind  the  centre  of  the  bone  and  form  a  ridge  which  runs  along  the  rest  of  the 
dorsal  surface  to  the  carpal  extremity.  This  ridge  separates  two  lateral,  sloping 
surfaces  for  the  attachment  of  the  Dorsal  interossei  muscles.1  To  the  tubercles 
on  the  digital  extremities  are  attached  the  lateral  ligaments  of  the  metacarpo- 
phalangeal  joints. 

The  carpal  extremity,  or  base,  is  of  a  cuboidal  form,  and  broader  behind  than 
in  front;  it  articulates  above  with  the  carpus,  and  on  each  side  with  the  adjoining 
metacarpal  bones  ;  its  dorsal  and  palmar  surfaces  are  rough,  for  the  attachment  of 
tendons  and  ligaments. 

The  digital  extremity,  or  head,  presents  an  oblong  surface,  flattened  at  each 
side ;  it  articulates  with  the  proximal  phalanx  ;  it  is  broader  and  extends  farther 
forward  in  front  than  behind,  and  is  longer  in  the  antero-posterior  than  in  the 
transverse  diameter.  On  either  side  of  the  head  is  a  tubercle  for  the  attachment 
of  the  lateral  ligament  of  the  metacarpo-phalangeal  joint.  The  posterior  surface, 
broad  and  flat,  supports  the  Extensor  tendons ;  the  anterior  surface  is  grooved  in 
the  middle  line  for  the  passage  of  the  Flexor  tendons,  and  marked  on  each  side  by 
an  articular  eminence  continuous  with  the  terminal  articular  surface. 

Peculiar  Characters  of  the  Metacarpal  Bones. 

The  metacarpal  bone  of  the  thumb  is  shorter  and  wider  than  the  rest,  diverges 
to  a  greater  degree  from  the  carpus,  and  its  palmar  surface  is  directed  inward 
toward  the  palm.  The  shaft  is  flattened  and  broad  on  its  dorsal  aspect,  and 
does  not  present  the  ridge  which  is  found  on  the  other  metacarpal  bones;  it  is 
concave  from  before  backward  on  its  palmar  surface.  The  carpal  extremity, 
or  base,  presents  a  concavo-convex  surface,  for  articulation  with  the  trapezium ; 
it  has  no  lateral  facets.  The  digital  extremity  is  less  convex  than  that  of  the 
other  metacarpal  bones,  broader  from  side  to  side  than  from  before  backward,  and 
terminates  anteriorly  in  a  small  articular,  eminence  on  each  side,  over  which  play 
two  sesamoid  bones. 

The  side  to  which  this  bone  belongs  may  be  known  by  observing  the  little 
prominence  which  is  situated  on  the  outer  or  radial  side  of  its  posterior  surface  just 
above  the  base,  for  the  tendon  of  the  Extensor  ossis  metacarpi  pollicis.  If  the 
bone  is  held  with  the  palmar  surface  upward  and  the  base  toward  the  student, 
the  prominence  will  point  to  the  side  to  which  the  bone  belongs.  Another  means 
by  which  the  side  to  which  the  bone  belongs  may  be  ascertained  is  by  holding  it 
in  the  position  it  occupies  in  the  hand,  with  the  carpal  extremity  upward  and  the 
dorsal  surface  backAvai*d  ;  the  narrower,  radial  border  will  point  to  the  side  to 
which  it  belongs. 

The  metacarpal  bone  of  the  index  finger  is  the  longest  and  its  base  the  largest 
of  the  other  four.  Its  carpal  extremity  is  prolonged  upward  and  inward,  forming 
a  prominent  ridge.  The  dorsal  and  palmar  surfaces  of  this  extremity  are  rough, 
for  the  attachment  of  tendons  and  ligaments.  It  presents  four  articular  facets: 
three  on  the  upper  aspect  of  the  base :  the  middle  one  of  the  three  is  the  largest, 
concave  from  side  to  side,  convex  from  before  backward,  for  articulation  with  the 
trapezoid  ;  the  external  one  is  a  small,  flat,  quadrilateral  facet,  for  articulation  with 
the  trapezium ;  the  internal  one  on  the  summit  of  the  ridge  is  long  and  narrow, 
for  articulation  with  the  os  magnum.  The  fourth  facet  is  on  the  inner  or  ulnar 
side  of  the  extremity  of  the  bone,  and  is  for  articulation  with  the  third  metacarpal 
bone. 

The  side  to  which  this  bone  belongs  is  indicated  by  the  absence  of  the  lateral 
facet  on  the  outer  (radial)  side  of  its  base,  so  that  if  the  bone  is  placed  with  its 
base  toward  the  student  and  the  palmar  surface  upward,  the  side  on  which  there 
is  no  lateral  facet  will  be  that  to  Avhich  it  belongs. 

1  By  these  sloping  surfaces  the  metacarpal  bones  of  the  hand  may  be  at  once  differentiated  from 
those  of  the  ioot. 


THE   METACARPUS. 

The  metacarpal  bone  of  the  middle  finger  is  a  little  smaller  than  the  preceding : 
it  presents  a  pyramidal  eminence  (the  styloid  process)  on  the  radial  side  of  its 
base  (dorsal  aspect)  which  extends  upward  behind  the  os  magnum.  The  carpal, 
articular  facer  is  concave  behind,  flat  in  front,  and  articulates  with  the  os  magnum. 
On  the  radial  side  is  a  smooth,  concave  facet,  for  articulation  with  the  second 
meracarpal  bone,  and  on  the  ulnar  side  two  small,  oval  facets,  for  articulation  with 
the  fourth  metacarpal. 

The  side  to  which  this  bone  belongs  is  easily  recognized  by  the  stvloid  pro- 
on  the  radial  side  of  its  base.  With  the  palmar  surface  uppermost  and  the 
base  toward  the  student,  this  process  points  toward  the  side  to  which  the  bone 
belongs. 

The  metacarpal  bone  of  the  ring  finger  is  shorter  and  smaller  than  the  preced- 
ing, and  its  base  small  and  quadrilateral ;  the  carpal  surface  of  the  base  present- 
ing two  facets,  for  articulation  with  the  unciform  and  os  magnum.  On  the  radial 
side  are  two  oval  facets,  for  articulation  with  the  third  metacarpal  bone ;  and  on 
the  ulnar  side  a  single  concave  facet,  for  the  fifth  metacarpal. 

If  this  bone  is  placed  with  the  base  toward  the  student  and  the  palmar  surface 
upward,  the  radial  side  of  the  base,  which  has  two  facets  for  articulation  with  the 
third  metacarpal  bone,  will  be  on  the  side  to  which  it  belongs.  If,  as  sometimes 
happens  in  badly-marked  bones,  one  of  these  facets  is  indistinguishable,  the  side 
may  be  known  by  selecting  the  surface  on  which  the  larger  articular  facet  is  present. 
This  facet  is  for  the  fifth  metacarpal  bone,  and  would  therefore  be  situated  on  the 
ulnar  side  :  that  is.  the  one  to  which  the  bone  does  not  belong. 

The  metacarpal  bone  of  the  little  finger  presents  on  its  base  one  facet,  which 
is  concavo-convex,  and  which  articulates  with  the  unciform  bone,  and  one  lateral, 
articular  facet,  which  articulates  with  the  fourth  metacarpal  bone.  On  its  ulnar 
side  is  a  prominent  tubercle,  for  the  insertion  of  the  tendon  of  the  Extensor  carpi 
ulnaris.  The  dorsal  surface  of  the  shaft  is  marked  by  an  oblique  ridge  which 
extends  from  near  the  ulnar  side  of  the  upper  extremity  to  the  radial  side  of 
the  lower.  The  outer  division  of  this  surface  serves  for  the  attachment  of  the 
Fourth  dorsal  interosseous  muscle ;  the  inner  division  is  smooth  and  covered  by 
the  Extensor  tendons  of  the  little  finger. 

If  this  bone  is  placed  with  its  base  toward  the  student  and  its  palmar  surface 
upward,  the  side  of  the  head  which  has  a  lateral  facet  will  be  that  to  which  the 
bone  belongs. 

Articulations. — Besides  the  phalangeal  articulations,  the  first  metacarpal  bone 
articulates  with  the  trapezium ;  the  second  with  the  trapezium,  trapezoid,  os 
magnum,  and  third  metacarpal  bones;  the  third  with  the  os  magnum  and  second 
and  fourth  metacarpal  bones :  the  fourth  with  the  os  magnum,  unciform.  and 
third  and  fifth  metacarpal  bones;  and  the  fifth  with  the  unciform  and  fourth 
meracarpal. 

The  1ir*t  has  no  lateral  facets  on  its  carpal  extremity :  the  second  has  no 
lateral  facet  on  its  radial  side,  but  one  on  its  ulnar  side ;  the  third  has  one  on 
its  radial  and  two  on  its  ulnar  side :  the  fourth  has  two  on  its  radial  and  one  on 
its  ulnar  side :  and  the  fifth  has  only  one  on  its  radial  side. 

Attachment  of  Muscles. — To  the  metacarpal  bone  of  the  thumb,  four:  the 
Flexor  r,«sis  metacarpi  pollicis,  Flexor  brevis  pollicis.  Extensor  ossis  metacarpi 
pollicis.  and  First  dorsal  interosseous.  To  the  second  metacarpal  bone,  six: 
the  Flexor  carpi  radialis.  Extensor  carpi  radialis  longior.  Adductor  obliquus 
pollicis.  First  and  Second  dorsal  interosseous.  and  First  palmar  interosseous. 
To  the  third,  six:  the  Extensor  carpi  radialis  brevior.  Flexor  carpi  radialis. 
Adductor  transversus  pollicis.  Adductor  obliquus  pollicis,  and  Second  and  Third 
tl  interosseous.  To  the  fourth,  three:  the  Third  and  Fourth  dorsal  and 
iid  palmar  interosseous.  To  the  fifth,  five:  the  Extensor  carpi  ulnaris, 
Flexor  carpi  ulnaris.  Flexor  ossis  metacarpi  minimi  digiti,  Fourth  dorsal  and 
Third  palmar  interosseous. 


270  THE  SKELETON. 

The  Phalanges. 

The  Phalanges  (internodia)  are  the  bones  of  the  fingers ;  they  are  fourteen  in 
number,  three  for  each  finger,  and  two  for  the  thumb.  They  are  long  bones,  and 
present  for  examination  a  shaft  and  two  extremities.  The  shaft  tapers  from 
above  downward,  is  convex  posteriorly,  concave  in  front  from  above  downward, 
flat  from  side  to  side,  and  marked  laterally  by  rough  ridges,  which  give  attachment 
to  the  fibrous  sheaths  of  the  Flexor  tendons.  The  metacarpal  extremity,  or  base, 
in  the  first  row  presents  an  oval,  concave,  articular  surface,  broader  from  side  to 
side  than  from  before  backward ;  and  the  same  extremity  in  the  other  two  rows, 
a  double  concavity,  separated  by  a  longitudinal  median  ridge,  extending  from  before 
backward.  The  digital  extremities  are  smaller  than  the  others,  and  terminate, 
in  the  first  and  second  rows,  in  two  small,  lateral  condyles,  separated  by  a  slight 
groove ;  the  articular  surface  being  prolonged  farther  forward  on  the  palmar  than 
on  the  dorsal  surface,  especially  in  the  first  row. 

The  Ungual  Phalanges  are  convex  on  their  dorsal-  flat  on  their  palmar,  surfaces; 
they  are  recognized  by  their  small  size  and  by  a  roughened,  elevated  surface  of  a 
horseshoe  form  on  the  palmar  aspect  of  their  lingual  extremity,  which  serves  to 
support  the  sensitive  pulp  of  the  finger. 

Articulations. — The  first  row,  with  the  metacarpal  bones  and  the  second  row 
of  phalanges ;  the  second  row,  with  the  first  and  third ;  the  third,  with  the  second 
row. 

Attachment  of  Muscles. — To  the  base  of  the  first  phalanx  of  the  thumb,  five 
muscles  :  the  Extensor  brevis  pollicis,  Flexor  brevis  pollicis,  Abductor  pollicis, 
Adductor  transversus  and  obliquus  pollicis.  To  the  second  phalanx,  two :  the 
Flexor  longus  pollicis  and  the  Extensor  longus  pollicis.  To  the  base  of  the  first 
phalanx  of  the  index  finger,  the  First  dorsal  and  the  First  palmar  interosseous  ;  to 
that  of  the  middle  finger,  the  Second  and  Third  dorsal  interosseous ;  to  that  of 
the  ring  finger,  the  Fourth  dorsal  and  the  Second  palmar  interosseous ;  and  to  that 
of  the  little  finger,  the  Third  palmar  interosseous,  the  Flexor  brevis  minimi  digiti, 
and  Abductor  minimi  digiti.  To  the  second  phalanges,  the  Flexor  sublimis  digi- 
torum,  Extensor  communis  digitorum,  and,  in  addition,  the  Extensor  indicis  to 
the  index  finger,  the  Extensor  minimi  digiti  to  the  little  finger.  To  the  third 
phalanges,  the  Flexor  profundus  digitorum  and  Extensor  communis  digitorum. 

Surface  Form. — On  the  front  of  the  wrist  are  two  subcutaneous  eminences,  one  on  the 
radial  side,  the  larger  and  flatter,  due  to  the  tuberosity  of  the  scaphoid  and  the  ridge  on  the 
trapezium ;  the  other,  on  the  ulnar  side,  caused  by  the  pisiform  bone.  The  tubercle  of  the 
scaphoid  is  to  be  felt  just  below  and  in  front  of  the  apex  of  the  styloid  process  of  the  radius.  It 
is  best  perceived  by  extending  the  hand  on  the  forearm.  Immediately  below  is  to  be  felt 
another  prominence,  better  marked  than  the  tubercle ;  this  is  the  ridge  on  the  trapezium  which 
gives  attachment  to  some  of  the  short  muscles  of  the  thumb.  On  the  inner  side  of  the  front  of 
the  wrist  the  pisiform  bone  is  to  be  felt,  forming  a  small  but  prominent  projection  in  this  situa- 
tion. It  is  some  distance  below  the  styloid  process  of  the  ulna,  and  may  be  said  to  be  just  below 
the  level  of  the  styloid  process  of  the  radius.  The  rest  of  the  front  of  the  carpus  is  covered  by 
tendons  and  the  annular  ligament,  and  entirely  concealed,  with  the  exception  of  the  hooked  pro- 
cess of  the  unciform,  which  can  only  be  made  out  with  difficulty.  The  back  of  the  carpus  is 
convex  and  covered  by  the  Extensor  tendons,  so  that  none  of  the  posterior  surfaces  of  the  bones 
are  to  be  felt,  with  the  exception  of  the  cuneiform  on  the  inner  side.  Below  the  carpus  the 
dorsal  surfaces  of  the  metacarpal  bones,  except  the  fifth,  are  covered  by  tendons,  and  are  scarcely 
visible  except  in  very  thin  hands.  The  dorsal  surface  of  the  fifth  is,  however,  subcutaneous 
throughout  almost  its  whole  length,  and  is  plainly  to  be  perceived  and  felt.  In  addition  to  this, 
slightly  external  to  the  middle  line  of  the  hand,  is  a  prominence,  frequently  well  marked,  but 
occasionally  indistinct,  formed  by  the  base  of  the  metacarpal  of  the  middle  finger.  The  heads  of 
the  metacarpal  bones  are  plainly  to  be  felt  and  seen,  rounded  in  contour  and  standing  out  in  bold 
relief  under  the  skin,  when  the  fist  is  clenched.  It  should  be  borne  in  mind  that  when  the  fin- 
gers are  flexed  on  the  hand,  the  articular  surfaces  of  the  first  phalanges  glide  off  the  heads  of  the 
metacarpal  bones  on  to  their  anterior  surfaces,  so  that  the  heads  of  these  bones  form  the  prom- 
inence of  the  knuckles  and  receive  the  force  of  any  blow  which  may  be  given.  The  head  of  the 
third  metacarpal  bone  is  the  most  prominent,  and  receives  the  greater  part  of  the  shock  of  the 
blow.  This  bone  articulates  with  the  os  magnum,  so  that  the  concussion  is  carried  through  this 
bone  to  the  scaphoid  and  semilunar,  with  which  the  head  of  the  os  magnum  articulates,  and  by 
these  bones  is  transferred  to  the  radius,  along  which  it  may  be  carried  to  the  capitellum  of  the 
humerus.  The  enlarged  extremities  of  the  phalanges  are  to  be  plainly  felt:  they  form  the 


DEVELOPMENT  OF  THE  BOXES  OF  THE  HAXD. 


271 


joints  of  the  fingers.     When  the  digits  are  bent  the  proximal  phalanges  of  the  joints  form 
prominences,  which  in  the  joint  between  the  first  and  second  phalanges  is  slightly  hollowed,  in 

uui'-e  with  the  irrooved  shape  of  their  articular  surfaces,  whilst  at  the  last  row  the 
prominence  is  flattened  and  square-shaped.  In  the  palm  of  the  hand  the  four  inner  metacarpal 
bones  ar--  n.vered  by  muscles,  tendons,  and  the  palmar  fascia,  and  no  part  of  them  but  their 
heads  is  to  be  distinguished.  With  regard  to  the  thumb,  on  the  dorsal  aspect  the  base  of  the 
metacarpal  bone  forms  a  prominence  below  the  styloid  process  of  the  radius;  the  shaft  is  to  be 
felt,  covered  by  tendons,  terminating  at  its  head  in  a  flattened  prominence,  in  front  of  which  can 
be  felt  the  sesamoid  bones. 

Surgical  Anatomy. — The  carpal  bones  are  little  liable  to  fracture,  except  from  extreme 
violence,  when  the  parts  are  so  comminuted  as  to  necessitate  amputation.  Occasionally  they  are 
the  seat  of  tubercular  disease.  The  metacarpal  bone  and  the  phalanges  are  not  unfrequently 
broken  from  direct  violence.  The  first  metacarpal  bone  is  the  one  most  commonly  fractured ; 
then  the  second,  the  fourth,  and  the  fifth,  the  third  being  the  one  least  frequently  broken. 
There  are  two  diseases  of  the  metacarpal  bones  and  phalanges  which  require  special  mention  on 
account  of  the  frequency  of  their  occurrence.  One  is  tubercular  dactylitis,  consisting  in  a 
deposit  of  tubercular  material  in  the  medullary  canal,  expanding  the  bone,  with  subsequent 

ion  and  resulting  necrosis.  The  other  is  chondroma,  which  is  perhaps  more  frequently 
found  in  connection  with  the  metacarpal  bones  and  phalanges  than  with  any  other  bones. 
They  are  commonly  multiple,  and  may  spring  either  from  the  medullary  canal  or  from  the 
periosteum. 

Development  of  the  Bones  of  the  Hand. 

The  Carpal  Bones  are  each  developed  by  a  single  centre.  At  birth  they  are 
all  cartilaginous.  Ossification  proceeds  in  the  following  order  (Fig.  206) :  In  the 


Carpus. 

One  centre  for  each  bone. 
All  cartilaginous  at  birth 


Metacarpus. 

Tico  centres  for  each  bone  : 
One  for  shaft. 
One  for  digital  extremity, 

except  first. 


Phalanges. 

Tiro  centres  for  each  bone : 
One  for  shaft. 
One  for  metacarpal 
extremity. 


Appears  3rd  year. 

Unite  20th  year. 

Ippears  8th  week. 


•  O<  '- 

/  30th  year. 

Appears  3rd  year. 


Unite  18th-20th  year. 
Appears  8th  week. 


Appear*  Uh-5th  year. 
|  Unite  ISth-SO  year. 
—Appears  8th  vxek. 


FIG.  206.— Plan  of  the  development  of  the  hand. 


os  magnuin  and  unciform  an  ossific  point  appears  during  the  first  year,  the  former 
preceding  the  latter  ;  in  the  cuneiform,  at  the  third  year ;  in  the  trapezium  and 
semilunar.  at  the  fifth  year,  the  former  preceding  the  latter ;  in  the  scaphoid,  at 


272  THE   SKELETON. 

the  sixth  year ;  in  the  trapezoid,  during  the  eighth  year ;  and  in  the  pisiform, 
about  the  twelfth  year. 

The  Metacarpal  Bones  are  each  developed  by  two  centres  :  one  for  the  shaft 
and  one  for  the  digital  extremity  for  the  four  inner  metacarpal  bones ;  one  for  the 
shaft  and  one  for  the  base  for  the  metacarpal  bone  of  the  thumb,  which  in  this 
respect  resembles  the  phalanges.1  Ossification  commences  in  the  centre  of  the 
shaft  about  the  eighth  or  ninth  week,  and  gradually  proceeds  to  either  end  of  the 
bone :  about  the  third  year  the  digital  extremities  of  the  four  inner  metacarpal 
bones  and  the  base  of  the  first  metacarpal  begin  to  ossify,  and  they  unite  about 
the  twentieth  year. 

The  Phalanges  are  each  developed  by  two  centres :  one  for  the  shaft  and  one 
for  the  base.  Ossification  commences  in  the  shaft,  in  all  three  rows,  at  about  the 
eighth  week,  and  gradually  involves  the  whole  of  the  bone  excepting  the  upper 
extremity.  Ossification  of  the  base  commences  in  the  first  row  between  the  third 
and  fourth  years,  and  a  year  later  in  those  of  the  second  and  third  rows.  The  two 
centres  become  united,  in  each  row,  between  the  eighteenth,  and  twentieth  years. 

THE  LOWER  EXTREMITY. 

The  Lower  Extremity  consists  of  three  segments,  the  thigh,  leg,  and  foot,  which 
correspond  to  the  arm,  forearm,  and  hand  in  the  upper  extremity.  It  is  con- 
nected to  the  trunk  through  the  os  innominatum,  or  hip-bone,  which  forms  the 
pelvic  girdle. 

THE  HIP. 
The  Os  Innominatum. 

The  Os  Innominatum  (in,  not ;  nomino,  I  name),  or  nameless  bone,  so  called  from 
bearing  no  resemblance  to  any  known  object,  is  a  large,  irregularly-shaped,  flat  bone, 
constricted  in  the  centre  and  expanded  above  and  below.  With  its  fellow  of  the 
opposite  side  it  forms  the  sides  and  anterior  wall  of  the  pelvic  cavity.  In  young 
subjects  it  consists  of  three  separate  parts,  which  meet  and  form  the  large,  cup-like 
cavity  situated  near  the  middle  of  the  outer  surface  of  the  bone ;  and,  although  in 
the  adult  these  have  become  united,  it  is  usual  to  describe  the  bone  as  divisible 
into  three  portions — the  ilium,  the  ischium,  and  the  os  pubis. 

The  ilium,  so  called  from  its  supporting  the  flank  (ilia),  is  the  superior,  broad 
and  expanded  portion  which  runs  upward  from  the  upper  and  back  part  of  the 
acetabulum  and  forms  the  prominence  of  the  hip. 

The  ischium  (t<T%lou,  the  hip)  is  the  inferior  and  strongest  portion  of  the  bone ; 
it  proceeds  downward  from  the  acetabulum,  expands  into  a  large  tuberosity,  and 
then,  curving  upward,  forms  with  the  descending  ramus  of  the  os  pubis,  a  large 
aperture,  the  obturator  foramen. 

The  os  pubis  is  that  portion  which  runs  horizontally  inward  from  the  inner  side 
of  the  acetabulum  for  about  two  inches,  then  makes  a  sudden  bend,  and  descends 
for  about  one  inch  :  it  forms  the  front  of  the  pelvis,  supports  the  external  organs  of 
generation,  and  has  received  its  name  from  the  skin  over  it  being  covered  with  hair. 

The  Ilium  presents  for  examination  two  surfaces,  an  external  and  an  internal ; 
a  crest,  and  two  borders,  an  anterior  and  a  posterior. 

External  Surface  or  Dorsum  of  the  Ilium  (Fig.  207). — The  back  part  of  this 
surface  is  directed  backward,  downward,  and  outward ;  its  front  part,  forward, 
downward,  and  outward.  It  is  smooth,  convex  in  front,  deeply  concave  behind ; 
bounded  above  by  the  crest,  below  by  the  upper  border  of  the  acetabulum  ;  in  front 
and  behind  by  the  anterior  and  posterior  borders.  This  surface  is  crossed  in  an 
arched  direction  by  three  semicircular  lines — the  superior,  middle,  and  inferior 
gluteal  lines.  The  superior  gluteal  line,  the  shortest  of  the  three,  commences  at 

1  Allan  Thomson  has  demonstrated  the  fact  that  the  first  metacarpal  bone  is  often  developed 
from  three  centres  ;  that  is  to  say,  there  is  a  separate  nucleus  for  the  distal  end,  forming  a  distinct  epiph- 
ysis,  visible  at  the  age  of  seven  or  eight  years.  He  also  states  that  there  are  traces  of  a  proximal 
epiphvsis  in  the  second  metacarpal  bone. — Journal  of  Anatomy,  1869. 


THE 


L\  -\OMIXATUM. 


273 


the  crest,  about  two  inches  in  front  of  its  posterior  extremity  ;  it  is  at  first  distinctly 
marked,  but  as  it  passes  downward  and  outward  to  the  upper  part  of  the  great 
sacn "-sciatic  notch,  where  it  terminates,  it  becomes  less  marked,  and  is  often 
altogether  lost.  Behind  this  line  is  a  narrow  semilunar  surface,  the  upper  part  of 
which  is  rough  and  affords  attachment  to  part  of  the  Gluteus  maximus ;  the  lower 


Crest 


Anterior  superior 
spine. 


Anterior  inferior  spine. 


iEYELLUS    INFERIO 


Hio-pectineal  line 
jor  Gimbemat's  LIGAMENT. 

Spine  of  os  pubisfor 

LIGAMENT. 


Angle  of  os 
pubis. 

RECTUS  ABDOM:I 

PYRAMIDAL  S 


"~*uuinn— -  i  s  c ' 

""i.     Ramus      »/ 

FIG.  207.— Right  os  innominatum.    External  surface. 

part  is  smooth  and  has  no  muscular  fibres  attached  to  it.  The  middle  gluteal  line, 
the  longest  of  the  three,  commences  at  the  crest,  about  an  inch  behind  its  anterior 
extremity,  and,  taking  a  curved  direction  downward  and  backward,  terminates  at 
the  upper  part  of  the  great  sacro-sciatic  notch.  The  base  between  the  superior  and 
middle  curved  lines  and  the  crest  is  concave,  and  affords  attachment  to  the  Gluteus 
medius  muscle.  Near  the  central  part  of  this  line  may  often  be  observed  the  ori- 
fice of  a  nutrient  foramen.  The  inferior  gluteal  line,  the  least  distinct  of  the  three, 
commences  in  front  at  the  upper  part  of  the  anterior  inferior  spinous  process,  and, 
i- 


274 


THE  SKELETON. 


taking  a  curved  direction  backward  and  downward,  terminates  at  the  middle  of 
the  great  sacro-sciatic  notch.  The  surface  of  bone  included  between  the  middle 
and  inferior  curved  lines  is  concave  from  above  downward,  convex  from  before 
backward,  and  affords  attachment  to  the  Gluteus  minimus  muscle.  Beneath  the 
inferior  curved  line,  and  corresponding  to  the  upper  part  of  the  acetabulum,  is  a 
roughened  surface  (sometimes  a  depression),  to  which  is  attached  the  reflected 
tendon  of  the  Rectus  femoris  muscle. 

The  Internal  Surface  (Fig.  208)  of  the  ilium  is  bounded  above  by  the  crest ; 
below  it  is  continuous  with  the  pelvic  surface  of  the  os  pubis  and  ischium,  a  faint 


COMPRESSOR    URETHR/e.  

^^^^  TRANSVERSUS    PEHINEI- 

Crus  penis.        ER\CTOR  PEN1S. 
FIG.  208.— Right  os  innominatum.    Internal  surface. 


line  only  indicating  the  place  of  union ;  and  before  and  behind  it  is  bounded  by 
the  anterior  and  posterior  borders.  It  presents  anteriorly  a  large,  smooth,  concave 
surface,  called  the  internal  iliac  fossa,  or  venter  of  the  ilium,  which  lodges  the 
Iliacus  muscle,  and  presents  at  its  lower  part  the  orifice  of  a  nutrient  canal ;  and 
below  this  a  smooth,  rounded  border  (iliac  portion  of  the  linea  ilio-pectinea\  which 
separates  the  iliac  fossa  from  that  portion  of  the  internal  surface  which  enters  into 


THE    OS  lyyOMISATUM.  275 


the  formation  of  the  true  pelvis,  and  which  gives  attachment  to  part  of  the  Obturator 
internus  muscle.  Behind  the  iliac  fossa  is  a  rough  surface  divided  into  two  por- 
tions. an  anterior  and  a  posterior.  The  anterior  or  auricular  portion,  so  called  from 
its  resemblance  in  shape  to  the  ear,  is  coated  with  cartilage  in  the  recent  state,  and 
articulates  with  a  surface  of  similar  shape  on  the  side  of  the  sacrum.  The  posterior 
portion  is  rough,  for  the  attachment  of  the  posterior  sacro-iliac  ligaments  and  for 
a  part  of  the  origin  of  the  Erector  spinae. 

The  crest  of  the  ilium  is  convex  in  its  general  outline  and  sinuously  curved, 
being  bent  inward  anteriorly,  outward  posteriorly.  It  is  longer  in  the  female 
than  in  the  male,  very  thick  behind,  and  thinner  at  the  centre  than  at  the  extrem- 
ities. It  terminates  at  either  end  in  a  prominent  eminence,  the  anterior  superior 
and  pn!ttt_-r!"'f  sup  ./•/-/•  xpinous  process.  The  surface  of  the  crest  is  broad,  and 
divided  into  an  external  lip,  an  internal  lip,  and  an  intermediate  space.  To  the 
external  lip  is  attached  the  Tensor  vaginae  femoris,  Obliquus  externus  abdominis, 
ami  Latissimus  dorsi,  and  by  its  whole  length  the  fascia  lata  ;  to  the  space  between 
the  lips,  the  Internal  oblique  :  to  the  internal  lip,  the  Transversalis,  Quadratus 
lumborum,  and  Erector  spinte,  the  Iliacus.  and  the  fascia  iliaca. 

The  anterior  border  of  the  ilium  is  concave.  It  presents  two  projections, 
separated  by  a  notch.  Of  these,  the  uppermost,  situated  at  the  junction  of  the 
and  anterior  border,  is  called  the  anterior  superior  spinous  process  of  the  ilium, 
the  outer  border  of  which  gives  attachment  to  the  fascia  lata  and  the  origin  of 
the  Tensor  vaginae  femoris;  its  inner  border,  to  the  Iliacus;  whilst  its  extremity 
affords  attachment  to  Poupart's  ligament  and  the  origin  of  the  Sartorius.  Beneath 
this  eminence  is  a  notch  which  gives  attachment  to  the  Sartorius  muscle,  and 
across  which  passes  the  external  cutaneous  nerve.  Below  the  notch  is  the  anterior 
///r,  /•///•  *].iitt<>,  I*  ],,:„•.  x*.  which  terminates  in  the  upper  lip  of  the  acetabulum  ;  it 
gives  attachment  to  the  straight  tendon  of  the  Rectus  femoris  muscle  and  the 
ilio-femoral  ligament.  On  the  inner  side  of  the  anterior  inferior  spinous  process 
is  a  broad,  shallow  groove,  over  which  passes  the  Iliacus  muscle.  This  groove  is 
bounded  internally  by  an  eminence,  the  ilio-pectineal,  which  marks  the  point  of 
union  of  the  ilium  and  os  pubis. 

The  posterior  border  of  the  ilium,  shorter  than  the  anterior,  also  presents  two 
projections  separated  by  a  notch,  the  posterior  superior  and  the  posterior  inferior 
spinous  pro>->.-**>-*.  The  former  corresponds  with  that  portion  of  the  posterior 
surface  of  the  ilium  which  serves  for  the  attachment  of  the  oblique  portion  of  the 
sacro-iliac  ligaments  and  the  Multifidus  spin*  ;  the  latter  to  the  auricular  portion 
which  articulates  with  the  sacrum.  Below  the  posterior  inferior  spinous  process 
is  a  deep  notch,  the  great  sciatic  or  ih'o-sciatic. 

The  Ischium  forms  the  lower  and  back  part  of  the  os  innominatum.  It  is 
divisible  into  a  thick  and  solid  portion,  the  body  ;  a  large,  rough  eminence,  on  which 
the  body  rests  in  sitting,  the  tuberosity  ;  and  a  thin,  ascending  part,  the  ramus. 

The  body,  somewhat  triangular  in  form,  presents  three  surfaces,  external, 
internal,  and  posterior  ;  and  three  borders,  external,  internal,  and  posterior.  The 
mil  *  ii  rf  •!''••  corresponds  to  that  portion  of  the  acetabulum  formed  by  the 
ischium  :  it  is  smooth  and  concave,  and  forms  a  little  more  than  two-fifths  of 
the  acetabular  cavity  :  its  outer  margin  is  bounded  by  a  prominent  rim  or  lip, 
the  external  border,  to  which  the  cotyloid  fibro-cartilage  is  attached.  Below  the 
acetabulum.  between  it  and  the  tuberosity,  is  a  deep  groove,  along  which  the  tendon 
of  the  Obturator  externus  muscle  runs  as  it  passes  outward  to  be  inserted  into 
the  digital  fossa  of  the  femur.  The  internal  surface  is  smooth,  concave,  and  enters 
into  the  formation  of  the  lateral  boundary  of  the  true  pelvic  cavity.  This  surface 
is  perforated  by  two  or  three  large,  vascular  foramina,  and  affords  attachment  to 
part  of  the  Obturator  internus  muscle.  The  posterior  surface  is  quadrilateral  in 
form,  broad  and  smooth.  Below,  where  it  joins  the  tuberosity,  it  presents  a  groove 
continuous  with  that  on  the  external  surface,  for  the  tendon  of  the  Obturator 
externus  muscle.  The  lower  edge  of  this  groove  is  formed  by  the  tuberosity  of  the 
ischium.  and  affords  attachment  to  the  Gemellus  inferior  muscle.  This  surface  is 


276  THE  SKELETON. 

limited,  in  front,  by  the  margin  of  the  acetabulum  ;  behind,  by  the  posterior  border ; 
it  supports  the  Pyriformis,  the  two  Gemelli,  and  the  Obturator  internus  muscles 
in  their  passage  outward  to  the  great  trochanter.  The  external  border  forms  the 
prominent  rim  of  the  acetabulum,  and  separates  the  posterior  from  the  external 
surface.  To  it  is  attached  the  cotyloid  fibro-cartilage.  The  internal  border  is 
thin,  and  forms  the  outer  circumference  of  the  obturator  foramen.  The  posterior 
border  of  the  body  of  the  ischium  presents,  a  little  below  the  centre.,  a  thin  and 
pointed,  triangular  eminence,  the  spine  of  the  ischium,  more  or  less  elongated  in 
different  subjects ;  its  external  surface  gives  attachment  to  the  Gemellus  superior, 
its  internal  surface  to  the  Coccygeus  and  Levator  ani ;  whilst  to  the  pointed 
extremity  is  connected  the  lesser  sacro-sciatic  ligament.  Above  the  spine  is  a 
notch  of  a  large  size,  the  great  sciatic,  converted  into  a  foramen  by  the  lesser 
sacro-sciatic  ligament ;  it  transmits  the  Pyriformis  muscle,  the  gluteal  vessels 
and  superior  gluteal  nerve  passing  out  of  the  pelvis  above  the  muscles ;  the  sci- 
atic vessels,  the  greater  and  lesser  sciatic  nerves,  the  internal  pudic  vessels  and 
nerve,  and  muscular  branches  from  the  sacral  plexus  below  it.  Below  the  spine 
is  a  smaller  notch,  the  lesser  sciatic  ;  it  is  smooth,  coated  in  the  recent  state  with 
cartilage,  the  surface  of  which  presents  numerous  markings  corresponding  to  the 
subdivisions  of  the  tendon  of  the  Obturator  internus,  Avhich  winds  over  it.  It  is 
converted  into  a  foramen  by  the  sacro-sciatic  ligaments,  and  transmits  the  tendon 
of  the  Obturator  internus,  the  nerve  which  supplies  that  muscle,  and  the  internal 
pudic  vessels  and  nerve. 

The  tuberosity  presents  for  examination  three  surfaces  :  external,  internal,  and 
inferior.  The  external  surface  is  quadrilateral  in  shape,  and  rough  for  the  attach- 
ment of  muscles.  It  is  bounded  above  by  the  groove  for  the  tendon  of  the 
Obturator  externus  ;  in  front  it  is  limited  by  the  posterior  margin  of  the  obturator 
foramen,  and  below  it  is  continuous  with  the  ramus  of  the  bone ;  behind,  it  is 
bounded  by  a  prominent  margin  which  separates  it  from  the  inferior  surface.  In 
front  of  this  margin  the  surface  gives  attachment  to  the  Quadratus  femoris,  and 
anterior  to  this  to  some  of  the  fibres  of  origin  of  the  Obturator  externus.  The 
lower  part  of  the  surface  gives  origin  to  part  of  the  Adductor  magnus.  The 
internal  surface  forms  part  of  the  bony  wall  of  the  true  pelvis.  In  front  it 
is  limited  by  the  posterior  margin  of  the  obturator  foramen.  Behind,  it  is 
bounded  by  a  sharp  ridge,  for  the  attachment  of  a  falciform  prolongation  of  the 
great  sacro-sciatic  ligament ;  it  presents  a  groove  on  the  inner  side  of  this  for  the 
lodgment  of  the  internal  pudic  vessels  and  nerve ;  and,  more  anteriorly,  has 
attached  the  Transversus  perinsei  and  Erector  penis  muscles.  The  inferior  surface 
is  divided  into  two  portions — an  anterior,  rough,  somewhat  triangular  part,  and  a 
posterior,  smooth,  quadrilateral  portion.  The  anterior  surface  is  subdivided  by  _ 
prominent  vertical  ridge,  passing  from  base  to  apex,  into  two  parts ;  the  outer  one 
gives  attachment  to  the  Adductor  magnus ;  the  inner  to  the  great  sacro-sciatic 
ligament.  The  posterior  portion  is  subdivided  into  two  facets  by  an  oblique 
ridge ;  from  the  upper  and  outer  facet  arises  the  Semimembranosus ;  from  the 
lower  and  inner,  the  Biceps  and  Semitendinosus. 

The  ramus,  or  ascending  ramus,  is  the  thin,  flattened  part  of  the  ischium  which 
ascends  from  the  tuberosity  upward  and  inward,  and  joins  the  ramus  of  the  os  pubis, 
their  point  of  junction  being  indicated  in  the  adult  by  a  rough  line.  The  outer 
surface  of  the  ramus  is  rough,  for  the  attachment  of  the  Obturator  externus  muscle, 
and  also  some  fibres  of  the  Adductor  magnus ;  its  inner  surface  forms  part  of  the 
anterior  wall  of  the  pelvis.  Its  inner  border  is  thick,  rough,  slightly  everted,  forms 
part  of  the  outlet  of  the  pelvis,  and  presents  two  ridges  and  an  intervening  space. 
The  ridges  are  continuous  with  similar  ones  on  the  descending  ramus  of  the  os  pubis  : 
to  the  outer  one  is  attached  the  deep  layer  of  the  superficial  perinea!  fascia,  and  to 
the  inner  the  anterior  layer  of  the  triangular  ligament  of  the  perinaeum.  If  these 
two  ridges  are  traced  downward,  they  will  be  found  to  join  with  each  other  just 
behind  the  point  of  origin  of  the  Transversus  perinsei  muscle ;  here  the  two  layers 
of  fascia  are  continuous  behind  the  posterior  border  of  the  muscle.  To  the  inter- 


THE    OS   lyyOMIXATUM.  377 

veiling  space,  just  in  front  of  the  point  of  junction  of  the  ridges,  is  attached  the 
Transversus  perinaei  muscle,  and  in  front  of  this  a  portion  of  the  crus  penis  vel 
clitoridis  and  the  Erector  penis  vel  clitoridis  muscle.  Its  outer  border  is  thin  and 
sharp,  and  forms  part  of  the  inner  margin  of  the  obturator  foramen. 

The  Os  Pubis  forms  the  anterior  part  of  the  os  innominatum,  and,  with  the  bone 
«»f  the  opposite  side,  forms  the  front  boundary  of  the  true  pelvic  cavity.  It  is 
divisible  into  a  body,  a  horizontal  ramus.  and  a  descending  ramus. 

The  body  is  somewhat  quadrilateral  in  shape,  and  presents  for  examination  two 
surfaces  and  four  borders.  The  anterior  surface  is  rough,  directed  forward,  down- 
ward, and  outward.  To  the  upper  and  inner  angle,  immediately  below  the  crest, 
is  attached  the  Adductor  longus :  lower  down,  from  without  inward,  are  attached 
the  Obturator  externus.  the  Adductor  brevis.  and  the  upper  part  of  the  Gracilis. 
The  p<:>*t:-rt"i-  *uf*\i.<~-> .-.  convex  from  above  downward,  concave  from  side  to  side,  is 
smooth,  and  forms  part  of  the  anterior  wall  of  the  pelvis.  It  gives  attachment 
to  the  Levator  ani.  Obturator  internus,  a  few  muscular  fibres  prolonged  from  the 
bladder,  and  the  pubo-prostatic  ligaments.  On  the  outer  end  of  the  upper  border, 
at  about  its  junction  with  the  horizontal  ramus,  there  is  a  prominent  tubercle  called 
the  sp!i/>-  :  to  it  is  attached  the  outer  pillar  of  the  external  abdominal  ring  and 
Poupart's  ligament.  Passing  outward  from  the  spine  is  a  prominent  ridge,  pubic 
portion  <,f  tlie  itto-pcctmeal  ///#•-.  which  marks  the  brim  of  the  true  pelvis:  to  it  is 
attached  a  portion  of  the  conjoined  tendon  of  the  Internal  oblique  and  Transver- 
sal is  muscles.  Gimbernat's  ligament,  and  the  triangular  ligament  of  the  abdomen. 
Internal  to  the  spine  is  the  upper  border  or  crest,  which  extends  to  the  inner  bor- 
der of  the  bone.  It  affords  attachment  anteriorly  to  the  conjoined  tendon  of  the 
Internal  oblique  and  Transversalis,  and  posteriorly  to  the  Rectus  and  Pyramidalis 
muscles.  The  point  of  junction  of  the  crest  with  the  inner  border  of  the  bone  is 
called  the  angle :  to  it.  as  well  as  to  the  symphysis,  is  attached  the  internal  pillar 
of  the  external  abdominal  ring.  The  inner  border,  together  with  that  of  the  bone 
of  the  opposite  side,  forms  the  symphysis  :  it  is  oval,  covered  by  eight  or  nine 
transverse  ridges,  or  a  series  of  nipple-like  processes  arranged  in  rows,  separated 
by  grooves :  they  serve  for  the  attachment  of  a  thin  layer  of  cartilage  placed 
between  it  and  the  central  fibre-cartilage.  The  outer  border  is  sharp  and  forms 
part  of  the  circumference  of  the  obturator  foramen.  The  lower  border  is  united 
to  the  descending  ramus. 

The  horizontal  ramus  extends  from  the  body  to  the  point  of  junction  of  the  os 
pubis  with  the  ilium,  and  forms  the  upper  part  of  the  circumference  of  the  obturator 
foramen.  It  presents  for  examination  a  superior,  inferior,  and  posterior  surface,  and 
an  outer  extremity.  The  *n/»  /•/•</•  ani-fn  •?  presents  a  continuation  of  the  pubic  portion 
of  the  ilio-pectineal  line,  already  mentioned  as  commencing  at  the  spine  of  the  bone. 
In  front  of  this  ridge  the  surface  of  bone  is  triangular  in  form,  wider  externally  than 
internally,  smooth,  and  affords  attachment  to  the  Pectineus  muscle.  The  surface 
is  bounded  externally  by  a  rough  eminence,  the  iUo-pectineal,  which  serves  to 
indicate  the  point  of  junction  of  the  ilium  and  pubes,  and  gives  attachment  to 
the  Psoas  parvus  when  this  muscle  is  present.  The  inferior  surface  forms  the 
upper  boundary  of  the  obturator  foramen,  and  presents  externally  a  broad  and 
deep  oblique  groove,  for  the  passage  of  the  obturator  vessels  and  nerve;  and 
internally  a  sharp  margin  which  forms  part  -f  the  circumference  of  the  obturator 
foramen,  and  to  which  the  obturator  membrane  is  attached.  The  posterior  surface 
forms  part  of  the  anterior  boundary  of  the  true  pelvis.  It  is  smooth,  convex  from 
above  downward,  and  affords  attachment  to  the  upper  fibres  of  the  obturator 
internus.  The  outer  extremity,  the  thickest  part  of  the  ramus,  forms  one-fifth  of 
the  cavity  of  the  acetabulum. 

The  descending  ramus  of  the  os  pubis  is  thin  and  flattened.  It  passes  outward 
and  downward,  becoming  narrower  as  it  descends,  and  joins  with  the  ramus  of  the 
ischium.  Its  <:n~it<-rl»r  .«>irf<ice  is  rough,  for  the  attachment  of  muscles — the  Gracilis 
along  its  inner  border  ;  a  portion  of  the  Obturator  externus  where  it  enters  into 
the  formation  of  the  foramen  of  that  name ;  and  between  these  two  muscles  the 


278  THE   SKELETON. 

Adductores  brevis  and  magnus  from  within  outward.  The  posterior  surface  is 
smooth,  and  gives  attachment  to  the  Obturator  internus  and,  close  to  the  inner 
margin,  to  the  Compressor  urethrse.  The  inner  border  is  thick,  rough,  and  everted, 
especially  in  females.  It  presents  two  ridges,  separated  by  an  intervening  space. 
The  ridges  extend  downward,  and  are  continuous  with  similar  ridges  on  the 
ascending  ramus  of  the  ischium ;  to  the  external  one  is  attached  the  deep  layer  of 
the  superficial  perineal  fascia,  and  to  the  internal  one  the  anterior  layer  of  the 
triangular  ligament  of  the  perinaeum.  The  outer  border  is  thin  and  sharp,  forms 
part  of  the  circumference  of  the  obturator  foramen,  and  gives  attachment  to  the 
obturator  membrane. 

The  cotyloid  cavity,  or  acetabulum,  is  a  deep,  cup-shaped,  hemispherical 
depression,  directed  downward,  outward,  and  forward  ;  formed  internally  by  the 
os  pubis,  above  by  the  ilium,  behind  and  below  by  the  ischium,  a  little  less  than 
two-fifths  being  formed  by  the  ilium,  a  little  more  than  two-fifths  by  the  ischium, 
and  the  remaining  fifth  by  the  pubic  bone.  It  is  bounded  by  a  prominent,  uneven 
rim,  which  is  thick  and  strong  above,  and  serves  for  the  attachment  of  a  fibro- 
cartilaginous  structure  which  contracts  its  orifice  and  deepens  the  surface  for 
articulation.  It  presents,  on  its  inner  side,  a  deep  notch,  the  cotyloid  notch,  which 
is  continuous  with  a  circular  depression,  the  fossa  acetabuli,  at  the  bottom  of  the 
cavity :  this  depression  is  perforated  by  numerous  apertures,  lodges  a  mass  of  fat, 
and  its  margins,  as  well  as  those  of  the  notch,  serve  for  the  attachment  of  the 
ligamentum  teres.  The  notch  is  converted,  in  the  natural  state,  into  a  foramen  by 
a  dense  ligamentous  band  which  passes  across  it.  Through  this  foramen  the 
nutrient  vessels  and  nerves  enter  the  joint. 

The  obturator  or  thyroid  foramen  is  a  large  aperture  situated  between  the 
ischium  and  os  pubis.  In  the  male  it  is  large,  of  an  oval  form,  its  longest  diameter 
being  obliquely  from  above  downward ;  in  the  female  it  is  smaller  and  more 
triangular.  It  is  bounded  by  a  thin,  uneven  margin  to  which  a  strong  membrane 
is  attached ;  and  presents  at  its  upper  and  outer  part  a  deep  groove  which  runs 
from  the  pelvis  obliquely  forward,  inward,  and -downward.  This  groove  is  converted 
into  a  foramen  by  the  obturator  membrane,  and  transmits  the  obturator  vessels 
and  nerve. 

Structure. — This  bone  consists  of  much  cancellous  tissue,  especially  where  it  is 
thick,  enclosed  between  two  layers  of  dense,  compact  tissue.  In  the  thinner  parts 
of  the  bone,  as  at  the  bottom  of  the  acetabulum  and  centre  of  the  iliac  fossa,  it  is 
usually  semitransparent,  and  composed  entirely  of  compact  tissue. 

Development  (Fig.  209). — By  eight  centres  :  three  primary — one  for  the  ilium, 
one  for  the  ischium,  and  one  for  the  os  pubis  ;  and  five  secondary — one  for  the 
crest  of  the  ilium,  one  for  the  anterior  inferior  spinous  process  (said  to  occur  more 
frequently  in  the  male  than  the  female),  one  for  the  tuberosity  of  the  ischium,  one 
for  the  symphysis  pubis  (more  frequent  in  the  female  than  the  male),  and  one  for 
the  Y-shaped  piece  at  the  bottom  of  the  acetabulum.  These  various  centres  appear 
in  the  following  order :  First,  in  the  ilium,  at  the  lower  part  of  the  bone,  imme- 
diately above  the  sciatic  notch,  at  about  the  eighth  or  ninth  week  ;  secondly,  in  the 
body  of  the  ischium,  at  about  the  third  month  of  foetal  life  ;  thirdly,  in  the  body  of 
the  os  pubis,  between  the  fourth  and  fifth  months.  At  birth  the  three  primary 
centres  are  quite  separate,  the  crest,  the  bottom  of  the  acetabulum,  and  the  rami 
of  the  ischium  and  pubes  being  still  cartilaginous.  At  about  the  seventh  or  eighth 
year  the  rami  of  the  os  pubis  and  ischium  are  almost  completely  ossified.  About 
the  thirteenth  or  fourteenth  year  the  three  divisions  of  the  bone  have  extended 
their  growth  into  the  bottom  of  the  acetabulum,  being  separated  from  each  other 
by  a  Y-shaped  portion  of  cartilage,  which  now  presents  traces  of  ossification,  often 
by  two  or  more  centres.  The  ilium  and  ischium  then  become  joined,  and  lastly 
the  os  pubis,  through  the  intervention  of  this  Y-shaped  portion.  At  about  the  age 
of  puberty  ossification  takes  place  in  each  of  the  remaining  portions,  and  they 
become  joined  to  the  rest  of  the  bone  about  the  twenty-fifth  year. 

Articulations. — With  its  fellow  of  the  opposite  side,  the  sacrum,  and  femur. 


THE   PELVIS. 


279 


Attachment  of  Muscles.  —  To  the  ilium,  sixteen.  To  the  outer  lip  of  the  crest, 
the  Tensor  vaginae  femoris,  Obliquus  externus  abdominis,  and  Latissimus  dorsi  ; 
to  the  internal  lip,  the  Iliacus,  Transversalis,  Quadratus  lumborum,  and  Erector 
spinse  ;  to  the  interspace  between  the  lips,  the  Obliquus  internus.  To  the  outer 
surface  of  the  ilium,  the  Gluteus  maximus,  Gluteus  medius,  Gluteus  minimus, 
reflected  tendon  of  the  Rectus  ;  to  the  upper  part  of  the  great  sacro-sciatic  notch,  a 
portion  of  the  Pyriformis  ;  to  the  internal  surface,  the  Iliacus  :  to  that  portion  of 
the  internal  surface  below  the  linea  ilio-pectinea,  the  Obturator  internus,  and  the 
Multifidus  spime  to  the  internal  surface  of  the  posterior  superior  spine  ;  to  the 
anterior  border,  the  Sartorius  and  straight  tendon  of  the  Rectus.  To  the  ischium, 
fourteen.  To  the  outer  surface  of  the  ramus,  the  Obturator  externus  and  Adductor 
magnus  ;  to  the  internal  surface,  the  Obturator  internus  and  Erector  penis.  To  the 
spine,  the  Gemellus  superior,  Levator  ani,  and  Coccygeus.  To  the  tuberosity,  the 
Biceps,  Semitendinosus,  Semimembranosus,  Quadratus  femoris.  Adductor  magnus, 


„      .  ,  .  f  Three  primary  (Ilium,  Ischium,  and  Os  Pubis). 

By  eight  centre*  j  pi^sLndary. 


8.  Symphysis  pubis. 


The  three  primary  centres  unite  through  \-shaped  piece  about  puberty. 
Epiphyses  appear  about  puberty,  and  unite  about  25th  year. 

FIG.  209.— Plan  of  the  development  of  the  os  innoniiimtnm. 

Gemellus  inferior,  Transversus  peringei,  Erector  penis.  To  the  os  pubis.  sixteen: 
Obliquus  externus,  Obliquus  internus,  Transversalis,  Rectus,  Pyramidalis,  Psoas 
parvus,  Pectineus,  Adductor  magnus,  Adductor  longus.  Adductor  brevis,  Gracilis, 
Obturator  externus  and  internus,  Levator  ani,  Compressor  urethrae,  and  occasion- 
ally a  few  fibres  of  the  Accelerator  urinae. 

The  Pelvis  (Figs.  210,  211). 

The  Pelvis,  so  called  from  its  resemblance  to  a  basin  (L.  pelvis),  is  stronger 
and  more  massively  constructed  than  either  the  cranial  or  thoracic  cavity :  it  is  a 
bony  ring,  interposed  between  the  lower  end  of  the  spine,  which  it  supports,  and 
the  lower  extremities,  upon  which  it  rests.  It  is  composed  of  four  bones  :  the  two 
ossa  innominati.  which  bound  it  on  either  side  and  in  front,  and  the  sacrum  and 
coccyx,  which  complete  it  behind. 

The  pelvis  is  divided  by  a  plane  passing  through  the  prominence  of  the  sacrum, 


280 


THE  SKELETON. 


the  linea  ilio-pectinea,  and  the  upper  margin  of  the  symphysis  pubis  into  the  false 
and  true  pelvis. 

The  false   pelvis  is   all   that   expanded   portion  of  the  pelvic  cavity  which  is 
situated  above  this  plane.      It  is  bounded  on  each  side  by  the  ossa  ilii ;   in  front  it 


FIG.  210.— Male  pelvis  (adult). 


is  incomplete,  presenting  a  wide  interval  between  the  spinous  processes  of  the  ilia 
on  either  side,  which  is  filled  up  in  the  recent  state  by  the  parietes  of  the  abdomen  ; 


FIG.  211.— Female  pelvis  (adult). 

behind,  in  the  middle  line,  is  a  deep  notch.  This  broad,  shallow  cavity  is  fitted 
to  support  the  intestines  and  to  transmit  part  of  their  weight  to  the  anterior  wall 
of  the  abdomen,  and  is,  in  fact,  really  a  portion  of  the  abdominal  cavity.  The 
term  false  pelvis  is  incorrect,  and  this  space  ought  more  properly  to  be  regarded  as 
part  of  the  hypogastric  region  of  the  abdomen. 

The  true  pelvis  is  all  that  part  of  the  pelvic  cavity  which  is  situated  beneath 


THE   PELVIS.  281 

the  plane.  It  is  smaller  than  the  false  pelvis,  but  its  walls  are  more  perfect.  For 
convenience  of  description  it  is  divided  into  a  superior  circumference  or  inlet,  an 
inferior  circumference  or  outlet,  and  a  cavity. 

The  superior  circumference  forms  the  margin  or  brim  of  the  pelvis,  the  included 
space  being  called  the  inlet.  It  is  formed  by  the  linea  ilio-pectinea.  completed  in  front 
by  the  crests  of  the  pubic  bones,  and  behind  by  the  anterior  margin  of  the  base  of 
the  sacrum  and  sacro-vertebral  angle.  The  inlet  of  the  pelvis  is  somewhat  heart- 
shaped  obtusely  pointed  in  front,  diverging  on  either  side,  and  encroached  upon 
behind  by  the  projection  forward  of  the  promontory  of  the  sacrum.  It  has  three 
principal  diameters  :  antero-posterior  (sacro-pubic).  transverse,  and  oblique.  The 
antero-posterior  extends  from  the  sacro-vertebral  angle  to  the  symphysis  pubis  ; 
its  average  measurement  is  four  inches  in  the  male,  fojir  and  three-quarters  in  the 
female.  The  transverse  extends  across  the  greatest  width  of  the  inlet,  from  the 
middle  of  the  brim  on  one  side  to  the  same  point  on  the  opposite:  its  average 
measurement  is  four  and  a  half  in  the  male,  five  and  a  quarter  in  the  female. 
The  oblique  extends  from  the  margin  of  the  pelvis,  corresponding  to  the  ilio- 
pectineal  eminence  on  one  side,  to  the  sacro-iliac  symphysis  on  the  opposite 
side:  its  average  measurement  is  four  and  a  quarter  in  the  male,  and  five  in 
the  female. 

The  cavity  of  the  true  pelvis  is  bounded  in  front  by  the  symphysis  pubis  ; 
behind,  by  the  concavity  of  the  sacrum  and  coccyx,  which,  curving  forward  above 
and  below,  contracts  the  inlet  and  outlet  of  the  canal  :  and  laterally  it  is  bounded 
by  a  broad,  smooth,  quadrangular  surface  of  bone,  corresponding  to  the  inner 
surface  of  the  body  of  the  ischium  and  that  part  of  the  ilium  which  is  below 
the  ilio-pectineal  line.  The  cavity  is  shallow  in  front,  measuring  at  the  symphy- 
sis an  inch  and  a  half  in  depth,  three  inches  and  a  half  in  the  middle,  and  four 
inches  and  a  half  posteriorly.  From  this  description  it  will  be  seen  that  the 
cavity  of  the  pelvis  is  a  short,  curved  canal,  considerably  "deeper  on  its  posterior 
than  on  its  anterior  wall,  and  broader  in  the  middle  than  at  either  extremity,  from 
the  projection  forward  of  the  sacro-coccygeal  column  above  and  below.  This 
cavity  contains,  in  the  recent  subject,  the  rectum,  bladder,  and  part  of  the  organs 
of  generation.  The  rectum  is  placed  at  the  back  of  the  pelvis,  and  corresponds  to 
the  curve  of  the  sacro-cocc-ygeal  column  ;  the  bladder  in  front,  behind  the  symphysis 
pubis.  In  the  female  the  uterus'  and  vagina  occupy  the  interval  between  these 
parts. 

The  lower  circumference  of  the  pelvis  is  very  irregular,  and  forms  what  is 
called  the  outlet.  It  is  bounded  by  three  prominent  eminences  :  one  posterior, 
formed  -by  the  point  of  the  coccyx  :  and  one  on  each  side,  the  tuberosities  of  the 
ischia.  These  eminences  are  separated  by  three  notches;  one  in  front,  the  pubic  arch, 
formed  by  the  convergence  of  the  rami  of  the  ischia  and  pubic  bones  on  each  side. 
The  other  notches,  one  on  each  side,  are  formed  by  the  sacrum  and  coccyx  behind, 
the  ischium  in  front,  and  the  ilium  above  :  they  are  called  the  sacro-sciatic  notches  ; 
in  the  natural  state  they  are  converted  into  foramina  by  the  lesser  and  greater 
sacro-sciatic  ligaments.  In  the  recent  state,  when  the  ligaments  are  in  situ,  the 
outlet  of  the  pelvis  is  lozenge-shaped,  bounded  in  front  by  the  subpubic  liga- 
ment and  the  rami  of  the  os  pubis  and  ischium  :  on  each  side  by  the  tuberosities 
of  the  ischia  ;  and  behind  by  the  great  sacro-sciatic  ligaments  and  the  tip  of  the 
coccyx. 

The  diameters  of  the  outlet  of  the  pelvis  are  two,  antero-posterior  and  trans- 
verse. The  antero-potterior  extends  from  the  tip  of  the  coccyx  to  the  lower  part 
of  the  symphysis  pubis  :  its  average  measurement  is  three  and  a  quarter  inches  in 
the  male  and  five  in  the  female.  The  antero-posterior  diameter  varies  with  the 
length  of  the  coccyx,  and  is  capable  of  increase  or  diminution  on  account  of  the 
mobility  of  that  bone.1  The  franzi'i  'fte  extends  from  the  posterior  part  of  one 


1  The  measurements  of  the  pelvis  given  above  are,  I  believe,  fairly  accurate,  but  different  meas- 
urements are  given  by  various  authors,  no  doubt  due  in  a  great  measure  to  differences  in  the  phys- 
ique and  stature  of  the  population  from  whom  the  measurements  have  been  taken.  The  accompany- 


282 


THE   SKELETON. 


ischiatic  tuberosity  to  the  same  point  on  the  opposite  side  :  the  average  measurement 
is  three  and  a  half  inches  in  the  male  and  four  and  three-quarters  in  the  female. 
Position  of  the  Pelvis. — In  the  erect  posture  the  pelvis  is  placed  obliquely 
with  regard  to  the  trunk  of  the  body  :  the  bony  ring,  which  separates  the  true 
from  the  false  pelvis,  and  which  forms  the  essential  part  of  the  pelvis,  is  placed  so 
as  to  form  an  angle  of  about  60°  to  65°  with  the  ground  on  which  we  stand.  The 
pelvic  surface  of  the  symphysis  pubis  looks  upward  and  backward,  the  concavity 
of  the  sacrum  and  coccyx  downward  and  forward,  the  base  of  the  sacrum  in  well- 
formed  female  bodies  being  nearly  four  inches  above  the  upper  border  of  the 
symphysis  pubis,  and  the  apex  of  the  coccyx  a  little  more  than  half  an  inch  above 
its  lower  border.  The  obliquity  is  much  greater  in  the  foetus  and  at  an  early 
period  of  life  than  in  the  adult.  In  consequence  of  this  obliquity  of  the  pelvis 
the  line  of  gravity  of  the  head,  which  passes  through  the  middle  of  the  odontoid 
process  of  the  axis  and  through  the  points  of  junction  of  the  curves  of  the  vertebral 
column  to  the  sacro-vertebral  angle,  descends  toward  the  front  of  the  cavity,  so 
that  it  bisects  a  line  drawn  transversely  through  the  middle  of  the  heads  of  the 
thigh-bones.  And  thus  the  centre  of  gravity  of  the  head  is  placed  immediately 
over  the  heads  of  the  thigh-bones  on  which  the  trunk  is  supported. 

Axes  of  the  Pelvis  (Fig.  212). — The  plane  of  the  inlet  of  the  true  pelvis  will  be 
represented  by  a  line  drawn  from  the  base  of  the  sacrum  to  the  upper  margin  of 
the  symphysis  pubis.  A  line  carried  at  right  angles  with  this  at  its  middle  would 
correspond  at  one  extremity  with  the  umbilicus,  and  at  the  other  with  the  middle 
of  the  coccyx  :  the  axis  of  the  inlet  is  therefore  directed  downward  and  backward. 
The  axis  of  the  outlet,  produced  upward,  would  touch  the  base  of  the  sacrum, 
and  is  therefore  directed  downward  and  forward.  The  axis  of  the  cavity  is 
curved  like  the  cavity  itself:  this  curve  corresponds  to  the  concavity  of  the  sacrum 

and  coccyx,  the  extremities  being  indicated  by 
the  central  points  of  the  inlet  and  outlet.  A 
knowledge  of  the  direction  of  these  axes  serves  to 
explain  the  course  of  the  foetus  in  its  passage 
through  the  pelvis  during  parturition.  It  is  also 
important  to  the  surgeon,  as  indicating  the 
direction  of  the  force  required  in  the  removal  of 
calculi  from  the  bladder,  and  as  determining  the 
direction  in  which  instruments  should  be  used  in 
operations  upon  the  pelvic  viscera. 

Differences  between  the  Male  and  Female 
Pelvis. — The  female  pelvis,  looked  at  as  a  whole, 
is  distinguished  from  the  male  by  the  bones  being 
more  delicate,  by  its  width  being  greater  and  its 
depth  smaller.  The  whole  pelvis  is  less  massive, 
and  its  bones  are  lighter  and  more  slender,  and 
its  muscular  impressions  are  slightly  marked. 
The  iliac  fossae  are  broad  and  expanded,  and  the 
anterior  iliac  spines  widely  separated ;  hence  the 
greater  prominence  of  the  hips.  The  inlet  in 
the  female  is  larger  than  in  the  male ;  it  is  more 
nearly  circular,  and  the  sacro-vertebral  angle 

projects  less  forward.  The  cavity  is  shallower  and  wider ;  the  sacrum  is  shorter 
and  wider,  and  its  lower  half  forms  a  greater  angle  with  its  upper ;  the  obturator 
foramina  are  triangular,  and  smaller  in  size  than  in  the  male.  The  outlet  is 
larger  and  the  coccyx  more  movable.  The  spines  of  the  ischia  project  less  in- 

ing  chart  has  been  formulated  to  show  the  measurements  of  the  pelvis,  which  are  adopted  by  many 

obstetricians. — ED. 

A.  P.          Obi.         Tr. 

Inlet 4  4i  5 

Cavity 4*          4|          4| 

Outlet 5  4J          4" 


plane  o. 


FIG.  212.— Vertical  section  of  the  pel- 
vis, with  lines  indicating  the  axes  of  the 
pelvis. 


THE   PELVIS.  283 

ward.  The  tuberosities  of  the  ischia  and  the  acetabula  are  wider  apart.  The 
pubic  arch  is  wider  and  more  rounded  than  in  the  male,  where  it  is  an  angle 
rather  than  an  arch ;  its  pillars^  are  somewhat  excavated,  and  sloped  from  within 
outward,  so  that  their  inner  surfaces  look  forward.  In  consequence  of  this  the 
width  of  the  fore  part  of  the  pelvic  outlet  is  much  increased  and  the  passage  of  the 
foetal  head  facilitated. 

The  size  of  the  pelvis  varies,  not  only  in  the  two  sexes,  but  also  in  different 
members  of  the  same  sex.  This  does  not  appear  to  be  influenced  in  any  way  by 
the  height  of  the  individual.  Women  of  short  stature,  as  a  rule,  have  broad  pelves. 
Occasionally  the  pelvis  is  equally  contracted  in  all  its  dimensions,  so  much  so  that 
all  its  diameters  measure  an  inch  less  than  the  average,  and  this  even  in  women 
of  average  height  and  otherwise  well  formed.  The  principal  divergences,  however, 
are  found  at  the  inlet,  and  affect  the  relation  of  the  antero-posterior  to  the  transverse 
diameter.  Thus  we  may  have  a  pelvis  the  inlet  of  which  is  elliptical  either  in  a 
transverse  or  antero-posterior  direction  ;  the  transverse  diameter  in  the  former 
and  the  antero-posterior  in  the  latter  greatly  exceeding  the  other  diameters.  Again, 
the  inlet  of  the  pelvis  in  some  instances  is  seen  to  be  almost  circular. 

The  same  differences  are  found  in  various  races.  European  women  are  said  to 
have  the  most  roomy  pelves.  That  of  the  negress  is  smaller,  circular  in  shape,  and  with 
a  narrow  pubic  arch.  The  Hottentots  and  Bushwomen  possess  the  smallest  pelves. 

In  ihefcetus  and  for  several  years  after  birth  the  pelvis  is  small  in  proportion 
to  that  of  the  adult.  The  cavity  is  deep,  and  the  projection  of  the  sacro-vertebral 
angle  less  marked.  The  antero-posterior  and  transverse  diameters  are  nearly 
equal.  About  puberty  the  pelvis  in  both  sexes  presents  the  general  characters  of 
the  adult  male  pelvis ;  but  after  puberty  it  acquires  its  proper  sexual  characters. 

Surface  Form. — The  pelvic  bones  are  so  thickly  covered  with  muscles  that  it  is  only  at  cer- 
tain points  tliat  they  approach  the  surface  and  can  be  felt. through  the  skin.  In  front,  the 
anterior  superior  spinous  process  is  easily  to  be  recognized ;  a  portion  of  it  is  subcutaneous, 
and  in  thin  subjects  may  be  seen  to  stand  out  as  a  prominence  at  the  outer  extremity  of  the  fold 
of  the  groin.  In  fat  subjects  its  position  is  marked  by  an  oblique  depression  amongst  the  sur- 
rounding fat,  at  the  bottom  of  which  the  bony  process  may  be  felt.  Proceeding  upward  and 
outward  from  this  process,  the  crest  of  the  ilium  may  be  traced  throughout  its  whole  length, 
sinuously  curved.  It  is  represented,  in  muscular  subjects,  on  the  surface,  by  a  groove  or  fur- 
row, the  iliac  farrow,  caused  by  the  projection  of  fleshy  fibres  of  the  External  oblique  muscle 
of  the  abdomen.  It  terminates  behind  in  the  posterior  superior  spinous  process,  the  position 
of  which  is  indicated  by  a  slight  depression  on  a  level  with  and  on  each  side  of  the  spinous 
process  of  the  second  sacral  vertebra.  Between  the  two  posterior  superior  spinous  processes, 
but  at  a  lower  level,  is  to  be  felt  the  spinous  process  of  the  third  sacral  vertebra  (see  page  164). 
Another  part  of  the  bony  pelvis  which  is  easiry  accessible  to  the  touch  is  the  tuberosity  of  the 
ischium.  situated  beneath  the  gluteal  fold,  and,  when  the  hip  is  flexed,  easily  to  be  felt,  as  it  is 
then  to  a  great  extent  uncovered  by  muscle.  Finally,  the  spine  of  the  os  pubis  can  always  be 
readily  felt,  and  constitutes  an  important  surgical  guide,  especially  in  connection  with  the  sub- 
ject of  hernia.  It  is  nearly  in  the  same  horizontal  line  with  the  upper  edge  of  the  great  tro- 
chanter.  In  thin  subjects  it  is  very  apparent,  but  in  the  obese  it  is  obscured  by  the  pubic  fat. 
It  can.  however,  be  detected  by  following  up  the  tendon  of  origin  of  the  Adductor  longus 
muscle. 

Surgical  Anatomy. — There  is  arrest  of  development  in  the  bones  of  the  pelvis  in  cases 
of  extroversion  of  the  bladder ;  the  anterior  part  of  the  pelvic  girdle  being  deficient,  the  bodies 
of  the  pubic  bones  imperfectly  developed,  and  the  symphysis  absent.  The  pubic  bones  are 
separated  to  the  extent  of  from  two  to  four  inches,  the  superior  rami  shortened  and  directed 
forward,  and  the  obturator  foramen  diminished  in  size,  nan-owed,  and  turned  outward.  The 
iliac  bones  are  straightened  out  more  than  normal.  The  sacrum  is  very  peculiar.  The  lateral 
curve,  instead  of  being  concave,  is  flattened  out  or  even  convex,  with  the  ilio-sacral  facets 
turned  more  outward  than  normal,  while  the  vertical  curve  is  straightened.1 

Fractures  of  the  pelvis  are  divided  into  fractures  of  the  false  pelvis  and  of  the  true  pelvis. 
Fractures  of  the  false  pelvis  vary  in  extent :  a  small  portion  of  the  crest  may  be  broken  or  one 
of  the  spinous  processes  may  be  torn  off,  and  this  may  be  the  result  of  muscular  action  ;  or  the 
bone  may  be  extensively  comminuted.  This  latter  accident  is  the  result  of  some  crushing  vio- 
lence, and  may  be  complicated  with  fracture  of  the  true  pelvis.  These  cases  may  be  accom- 
panied by  injury  to  the  intestine  as  it  lies  in  the  hollow  of  the  bone,  or  to  the  iliac  vessels  as 
they  course  along  the  margin  of  the  true  pelvis.  Fractures  of  the  true  pelvis  generally  occur 
through  the  horizontal  ramus  of  the  os  pubis  and  the  ascending  ramus  of  the  ischium,  as  this 
is  the  weakest  part  of  the  bony  ring,  and  may  be  caused  either  by  crushing  violence  applied 

1  Wood.     Heath's  Dictionary  of  Practical  Surgery,  i.  426. 


284  THE  SKELETON. 

in  an  antero-posterior  direction,  when  the  fracture  occurs  from  direct  force,  or  by  compression 
laterally,  when  the  acetabula  are  pressed  together,  and  the  bone  gives  way  in  the  same  place 
from  indirect  violence.  Occasionally  the  fracture  may  be  double,  occurring  on  both  sides  of  the 
body.  It  is  in  these  cases  that  injury  to  the  contained  viscera  is  liable  to  take  place  :  the  urethra, 
the  bladder,  the  rectum,  the  vagina  in  the  female,  the  small  intestines,  and  even  the  uterus, 
have  all  been  lacerated  by  a  displaced  fragment.  Fractures  of  the  acetabulum  are  occasionally 
met  with  :  either  a  portion  of  the  rim  may  be  broken  off,  or  a  fracture  may  take  place  through 
the  bottom  of  the  cavity,  and  the  head  of  the  femur  driven  inward  and  project  into  the  pelvic 
cavity.  Separation  of  the  Y-shaped  cartilage  at  the  bottom  of  the  acetabulum  may  also  occur 
in  the  young  subject,  separating  the  bone  into  its  three  anatomical  portions. 

The  sacrum  is  occasionally,  but  rarely,  broken  by  direct  violence — i.  e.  blows,  kicks,  or  falls 
on  the  part.  The  lesion  may  be  complicated  with  injury  to  the  nerves  of  the  sacral  plexus, 
leading  to  paralysis  and  loss  of  sensation  in  the  lower  extremity,  or  to  incontinence  of  faeces 
from  paralysis  of  the  sphincter  ani. 

The  pelvic  bones  often  undergo  important  deformity  in  rickets,  the  effect  of  which  in  the 
adult  woman  may  interfere  seriously  with  childbearing.  In  consequence  of  the  yielding  nature 
of  the  bones,  the  acetabula  become  approximated,  the  symphysis  is  pushed  forward,  and  the 
antero-posterior  diameter  lessened.  In  osteo-malacia  also  great  deformity  may  occur,  the  pelvis 
becoming  beak-shaped.  The  promontory  of  the  sacrum  is  pushed  forward  by  the  weight  of  the 
body,  and  the  sides  of  the  pelvis  are  approximated  by  the  pressure  of  the  two  thigh-bones :  this 
gives  to  the  pelvis  the  peculiar  deformity  which  is  characteristic  of  this  disease. 

THE  THIGH. 
The  Femur,  or  Thigh-Bone. 

The  Femur  (femur,  the  thigh)  is  the  longest,1  largest,  and  strongest  bone  in 
the  skeleton,  and  almost  perfectly  cylindrical  in  the  greater  part  of  its  extent.  In 
the  erect  posture  it  is  not  vertical,  being  separated  from  its  fellow  above  by  a 
considerable  interval,  which  corresponds  to  the  entire  breadth  of  the  pelvis,  but 
inclining  gradually  downward  and  inward,  so  as  to  approach  its  fellow  toward 
its  lower  part,  for  the  purpose  of  bringing  the  knee-joint  near  the  line  of  gravity 
of  the  body.  The  degree  of  this  inclination  varies  in  different  persons,  and  is 
greater  in  the  female  than  the  male,  on  account  of  the  greater  breadth  of  the 
pelvis.  The  femur,  like  other  long  bones,  is  divisible  into  a  shaft  and  two 
extremities. 

The  Upper  Extremity  presents  for  examination  a  head,  a  neck,  and  the  great 
and  lesser  trochanters. 

The  head,  which  is  globular,  and  forms  rather  more  than  a  hemisphere,  is 
directed  upward,  inward,  and  a  little  forward,  the  greater  part  of  its  convexity 
being  above  and  in  front.  Its  surface  is  smooth,  coated  with  cartilage  in  the 
recent  state,  except  at  a  little  behind  and  below  its  centre,  where  is  an  ovoid 
depression,  for  the  attachment  of  the  ligamentum  teres.  The  neck  is  a  flattened 
pyramidal  process  of  bone  which,  connects  the  bead  with  the  shaft.  It  varies  in 
length  and  obliquity  at  various  periods  of  life  and  under  different  circumstances. 
The  angle  is  widest  in  infancy,  and  becomes  lessened  during  growth,  so  that  at 
puberty  it  forms  a  gentle  curve  from  the  axis  of  the  shaft.  In  the  adult  it  forms 
an  angle  of  about  130°  with  the  shaft,  but  varies  in  inverse  proportion  to  the 
development  of  the  pelvis  and  the  stature.  In  consequence  of  the  prominence  of 
the  hips  and  widening  of  the  pelvis  in  the  female,  the  neck  of  the  thigh-bone  forms 
more  nearly  a  right  angle  with  the  shaft  than  it  does  in  man.  It  has  been  stated 
that  the  angle  diminishes  in  old  age  and  the  direction  of  the  neck  becomes 
horizontal,  but  this  statement  is  founded  on  insufficient  evidence.  Sir  George 
Humphry  states  that  the  angle  decreases  during  the  period  of  growth,  but  after 
full  growth  has  been  attained  it  does  not  usually  undergo  any  change,  even  in  old 
age.  He  further  states  that  the  angle  varies  considerably,  in  different  persons  of 
the  same  age.  It  is  smaller  in  short  than  in  long  bones,  and  when  the  pelvis 
is  wide.2  The  neck  is  flattened  from  before  backward,  contracted  in  the  middle, 
and  broader  at  its  outer  extremity,  where  it  is  connected  with  the  shaft,  than  at 
its  summit,  where  it  is  attached  to  the  head.  The  vertical  diameter  of  the  outer 

1  In  a  man  six  feet  high  it  measures  eighteen  inches — one-fourth  of  the  whple  body. 

2  Journal  of  Anatomy  and  Physiology. 


THE    FK.Vrff,    OR    THIGH-BONE. 


285 


OBTURATOR    INTERNUS 

nn  i  GEMCLLI. 

PYRIFCHMI5. 


Fi<;.  J13.— Right  femur.    Anterior  surface. 


half  is  increased  by  the  thicken- 
ing of  the  lower  edge,  which  slopes 
downward  to  join  the  shaft  at  the 
lesser  trochanter,  so  that  the  outer 
half  of  the  neck  is  flattened  from 
before  backward,  and  its  vertical 
diameter  measures  one-third  more 
than  the  antero-posterior.  The  inner  half  is 
smaller  and  of  a  more  circular  shape.  The 
anterior  surface  of  the  neck  is  perforated  by 
numerous  vascular  foramina.  The  posterior 
x/i /-face  is  smooth,  and  is  broader  and  more 
concave  than  the  anterior ;  it  gives  attachment 
to  the  posterior  part  of  the  capsular  ligament 
of  the  hip-joint,  about  half  an  inch  above  the 
posterior  intertrochanteric  line.  The  superior 
border  is  short  and  thick,  and  terminates  exter- 
nally at  the  great  trochanter ;  its  surface  is  per- 
forated by  large  foramina.  The  inferior  border, 
long  and  narrow,  curves  a  little  backward,  to 
terminate  at  the  lesser  trochanter. 

The  Trochanters  (-ooydto.  to  run  or  roll)  are 
prominent  processes  of  bone  which  afford  lever- 
age to  the  muscles  which  rotate  the  thigh  on  its 
axis.  They  are  two  in  number,  the  great  and 
the  lesser. 

The  Great  Trochanter  is  a  large,  irregular, 
quadrilateral  eminence,  situated  at  the  outer 
side  of  the  neck,  at  its  junction  with  the  upper 
part  of  the  shaft.  It  is  directed  a  little  out- 
ward and  backward,  and  in  the  adult  is  about 
three-quarters  of  an  inch  lower  than  the  head. 
It  presents  for  examination  two  surfaces  and 
four  borders.  The  external  surface,  quadri- 
lateral in  form,  is  broad,  rough,  convex,  and 
marked  by  a  prominent  diagonal  line,  which 
extends  from  the  posterior  superior  to  the 
anterior  inferior  angle  ;  this  line  serves  for  the 
attachment  of  the  tendon  of  the  Gluteus  medius. 
Above  the  line  is  a  triangular  surface,  some- 
times rough  for  part  of  the  tendon  of  the  same 
muscle,  sometimes  smooth  for  the  interposition 
of  a  bursa  between  that  tendon  and  the  bone. 
Below  and  behind  the  diagonal  line  is  a  smooth, 
triangular  surface,  over  which  the  tendon  of  the 
Gluteus  maximus  muscle  plays,  a  bursa  being 
interposed.  The  internal  surface  is  of  much 
less  extent  than  the  external,  and  presents  at 
its  base  a  deep  depression,  the  digital  or  tro- 
chanteric  fossa,  for  the  attachment  of  the  tendon 
of  the  Obturator  externus  muscle,  and  in  front 
of  this  an  impression  for  the  attachment  of  the 
Obturator  internus  and  Gemelli.  The  superior 
border  is  free;  it  is  thick  and  irregular,  and 
marked  near  the  centre  by  an  impression  for 
the  attachment  of  the  Pyrifoi  mis.  The  inferior 
border  corresponds  to  the  point  of  junction  of 


286  THE  SKELETON. 

the  base  of  the  trochanter  with  the  outer  surface  of  the  shaft;  it  is  marked  by  a 
rough,  prominent,  slightly  curved  ridge,  which  gives  attachment  to  the  upper 
part  of  the  Vastus  externus  muscle.  The  anterior  border  is  prominent,  somewhat 
irregular,  as  well  as  the  surface  of  bone  immediately  below  it ;  it  affords  attach- 
ment at  its  outer  part  to  the  Gluteus  minimus.  The  posterior  border  is  very 
prominent,  and  appears  as  a  free,  rounded  edge,  which  forms  the  back  part  of  the 
digital  fossa. 

The  Lesser  Trochanter  is  a  conical  eminence  which  varies  in  size  in  different 
subjects ;  it  projects  from  the  lower  and  back  part  of  the  base  of  the  neck.  Its 
base  is  triangular,  and  connected  with  the  adjacent  parts  of  the  bone  by  three 
well-marked  borders :  two  of  these  are  above — the  internal  continuous  with  the 
lower  border  of  the  neck,  the  external  with  the  posterior  intertrochanteric  line — 
while  the  inferior  border  is  continuous  with  the  middle  division  of  the  linea 
aspera,  Its  summit,  which  is  directed  inward  and  backward,  is  rough,  and 
gives  insertion  to  the  tendon  of  the  Psoas  magnus.  The  Iliacus  is  inserted  into 
the  shaft  below  the  lesser  trochanter  between  the  Vastus  internus  in  front  and 
the  Pectineus  behind. 

A  well-marked  prominence  of  variable  size,  which  projects  from  the  upper  and 
front  part  of  the  neck  at  its  junction  with  the  great  trochanter,  is  called  the  tubercle 
of  the  femur  ;  it  is  the  point  of  meeting  of  the  Gluteus  minimus  externally  and  above, 
and  the  Vastus  externus  below.  Running  obliquely  downward  and  inward  from 
the  tubercle  is  the  spiral  line  of  the  femur,  or  anterior  intertrochanteric  line ;  it 
winds  round  the  inner  side  of  the  shaft,  below  the  lesser  trochanter,  and  termi- 
nates in  the  linea  aspera,  about  two  inches  below  this  eminence.  Its  upper  half 
is  rough,  and  affords  attachment  to  the  capsular  ligament  of  the  hip-joint ;  its 
lower  half  is  less  prominent,  and  gives  attachment  to  the  upper  part  of  the  Vastus 
internus.  Running  obliquely  downward  and  inward  from  the  summit  of  the 
great  trochanter  on  the  posterior  surface  of  the  neck  is  a  very  prominent,  well- 
marked  ridge,  the  posterior  intertrochanteric  line.  Its  upper  half  forms  the 
posterior  border  of  the  great  trochanter,  and  its  lower  half  runs  downward  and 
inward  across  the  neck  of  the  bone  to  the  upper  and  back  part  of  the  lesser 
trochanter.  A  slight  ridge  sometimes  commences  about  the  middle  of  the 
posterior  intertrochanteric  line,  and  passes  vertically  downward  for  about  two 
inches  along  the  back  part  of  the  shaft :  it  is  called  the  linea  quadrati,  and  gives 
attachment  to  the  Quadratus  femoris  and  a  few  fibres  of  the  Adductor  magnus 
muscles.1 

The  Shaft,  almost  cylindrical  in  form,  is  a  little  broader  above  than  in  the 
centre,  and  somewhat  flattened  below,  from  before  backward.  It  is  slightly 
arched,  so  as  to  be  convex  in  front  and  concave  behind,  where  it  is  strengthened 
by  a  prominent  longitudinal  ridge,  the  linea  aspera.  It  presents  for  examination 
three  borders,  separating  three  surfaces.  Of  the  three  borders,  one,  the  linea 
aspera,  is  posterior ;  the  other  two  are  placed  laterally. 

The  linea  aspera  (Fig.  214)  is  a  prominent  longitudinal  ridge  or  crest,  on  the 
middle  third  of  the  bone,  presenting  an  external  lip,  an  internal  lip,  and  a  rough 
intermediate  space.  Above,  this  crest  is  prolonged  by  three  ridges.  The  most 
external  one  is  very  rough,  and  is  continued  almost  vertically  upward  to  the  base 
of  the  great  trochanter.  It  is  sometimes  termed  the  gluteal  ridge,  and  gives  attach- 
ment to  part  of  the  Gluteus  maximus  muscle  ;  its  upper  part  is  often  elongated  into 
a  roughened  crest,  on  which  is  a  more  or  less  well-marked,  rounded  tubercle,  a  rudi- 
mental  third  trochanter.  The  middle  ridge,  the  least  distinct,  is  continued  to  the  base 
of  the  trochanter  minor,  and  the  internal  one  is  lost  above  in  the  spiral  line  of  the 
femur.  Below,  the  linea  aspera  is  prolonged  by  two  ridges,  which  enclose  between 
them  a  triangular  space,  the  popliteal  surface.  Of  these  two  ridges,  the  outer  one 
is  the  more  prominent,  and  descends  to  the  summit  of  the  outer  condyle  (external 

1  Generally  there  is  merely  a  slight  thickening  about  the  centre  of  the  intertrochanteric  line, 
marking  the  point  of  attachment  of  the  Quadratus  femoris.  This  is  termed  by  some  anatomists  the 

tubercle  of  the  Quadratus. 


THE   FEMUR,    OR    THIGH-BONE. 


287 


xiil>i'iii-»n<Jifli~n'  line).  The  inner 
one  (internal  supracondylar  line) 
is  less  marked,  especially  at  its 
upper  part,  where  it  is  crossed 
b  the  femoral  arter.  It  ter- 


ATOR   EXTERNUS. 


minates.  below, 
of  the  internal 
small  tubercle, 
l,'.  which 


at  the  summit 
condyle,  in  a 
the  AiJihirf,,/- 
affords  attach- 
ment to  the  tendon  of  the  Ad- 
ductor magnus. 

To  the  inner  lip  of  the  linea 
aspera  and  its  inner  prolongation 
above  and  below  is  attached  the 
Yastus  intern  us,  and  to  the  outer 
lip  and  its  outer  prolongation 
above  is  attached  the  Vastus 
externus.  The  Adductor  magnus 
is  attached  to  the  linea  aspera,  to 
its  outer  prolongation  above  and 
its  inner  prolongation  below. 
Between  the  Vastus  externus  and 
the  Adductor  magnus  are 
attached  two  muscles  —  viz.  the 
Gluteus  maximus  above,  and  the 
short  head  of  the  Biceps  below. 
Between  the  Adductor  magnus 
and  the  Yastus  interims  four 
muscles  are  attached  :  the  Iliacus 
and  Pectineus  above  (the  latter 
to  the  middle  of  the  upper  divis- 
ions) ;  below  these,  the  Adductor 
brevis  and  Adductor  longus.  The 
linea  aspera  is  perforated  a  little 
below  its  centre  by  the  nutrient 
canal,  which  is  directed  obliquely 
upward. 

The  tiro  literal  borders  of  the 
femur  are  only  slightly  marked, 
the  outer  one  extending  from 
the  anterior  inferior  angle  of  the 
great  trochanter  to  the  anterior 
extremity  of  the  external 
condyle  ;  the  inner  one  from  the 
spiral  line,  at  a  point  opposite 
the  trochanter  minor,  to  the  an- 
terior extremity  of  the  internal 
condyle.  The  internal  border 
marks  the  limit  of  attachment 
of  the  Crureus  muscle  internally. 

The  anterior  surface  includes 
that  portion  of  the  shaft  which 
is  situated  between  the  two 
lateral  borders.  It  is  smooth, 
convex,  broader  above  and  below 
than  in  the  centre,  'slightly 
twisted  so  that  its  upper  part  is 


Groove  for  tendon  of 

POPLIT£US. 


FIG.  214.— Right  femur.    Posterior  surface. 


288  THE   SKELETON. 

directed  forward  and  a  little  outward,  its  lower  part  forward,  and  a  little  inward. 
To  the  upper  three-fourths  of  this  surface  the  Crureus  is  attached ;  the  lower 
fourth  is  separated  from  the  muscle  by  the  intervention  of  the  synovia! 
membrane  of  the  knee-joint  and  a  bursa,  and  affords  attachment  to  the 
Subcrureus  to  a  small  extent.  The  external  surface  includes  the  portion 
of  bone  between  the  external  border  and  the  outer  lip  of  the  linea  aspera :  it  is 
continuous  above  with  the  outer  surface  of  the  great  trochanter,  below  with  the 
outer  surface  of  the  external  condyle ;  to  its  upper  three-fourths  is  attached  the 
outer  portion  of  the  Crureus  muscle.  The  internal  surface  includes  the  portion  of 
bone  between  the  internal  border  and  the  inner  lip  of  the  linea  aspera;  it  is 
continuous  above  with  the  lower  border  of  the  neck,  below  with  the  inner  side  of 
the  internal  condyle  :  it  is  covered  by  the  Yastus  internus  muscle. 

The  Lower  Extremity,  larger  than  the  upper,  is  of  a  cuboid  form,  flattened  from 
before  backward,  and  divided  into  two  large  eminences,  the  condyles  (xovoy/oc, 
a  knuckle),  by  an  interval  which  presents  a  smooth  depression  in  front  called  the 
trochlea,  and  a  notch  of  considerable  size  behind — the  inter condyloid  notch.  The 
external  condyle  is  the  more  prominent  anteriorly,  and  is  the  broader  both  in  the 
antero-posterior  and  transverse  diameters.  The  internal  condyle  is  the  narrower, 
longer,  and  more  prominent  inferiorly.  This  difference  in  the  length  of  the  two 
condyles  is  only  observed  when  the  bone  is  perpendicular,  and  depends  upon  the 
obliquity  of  the  thigh-bones,  in  consequence  of  their  separation  above  at  the 
articulation  with  the  pelvis.  If  the  femur  is  held  obliquely,  the  surfaces  of  the 
two  condyles  will  be  seen  to  be  nearly  horizontal.  The  two  condyles  are  directly 
continuous  in  front,  and  form  a  smooth  trochlear  surface,  which  articulates  with 
the  patella.  It  presents  a  median  groove,  which  extends  downward  and  back- 
ward to  the  intercondyloid  notch ;  and  two  lateral  convexities,  of  which  the 
external  is  the  broader,  more  prominent,  and  prolonged  farther  upward  upon  the 
front  of  the  outer  condyle.  The  external  border  is  also  more  prominent,  and  ascends 
higher  than  the  internal  one.  The  intercondyloid  notch  lodges  the  crucial  liga- 
ments ;  it  is  bounded  laterally  by  the  opposed  surfaces  of  the  two  condyles,  and  in 
front  by  the  lower  end  of  the  shaft. 

Outer  Condyle. — The  outer  surface  of  the  external  condyle  presents,  a  little 
behind  its  centre,  an  eminence,  the  outer  tuberosity  ;  it  is  less  prominent  than  the 
inner  tuberosity,  and  gives  attachment  to  the  external  lateral  ligaments  of  the 
knee.  Immediately  beneath  it  is  a  groove  which  commences  at  a  depression  a 
little  behind  the  centre  of  the  lower  border  of  this  surface  :  the  front  part  of  this 
depression  gives  origin  to  the  Popliteus  muscle,  the  tendon  of  which  is  lodged  in 
the  groove  during  flexion  of  the  knee.  The  groove  is  smooth,  lined  with  synovia! 
membrane  in  the  recent  state,  and  runs  to  the  posterior  extremity  of  the  condyle. 
The  inner  surface  of  the  outer  condyle  forms  one  of  the  lateral  boundaries  of  the 
intercondyloid  notch,  and  gives  attachment,  by  its  posterior  part,  to  the  anterior 
crucial  ligament.  The  inferior  surface  is  convex,  smooth,  and  broader  than  that 
of  the  internal  condyle.  The  posterior  extremity  is  convex  and  smooth  :  just 
above  the  articular  surface  is  a  depression  for  the  tendon  of  the  outer  head  of  the 
Gastrocnemius,  above  which  is  the  origin  of  the  Plantaris. 

Inner  Condyle. — The  inner  surface  of  the  inner  condyle  presents  a  convex 
eminence,  the  inner  tuberosity,  rough  for  the  attachment  of  the  internal  lateral 
ligament.  The  outer  side  of  the  inner  condyle  forms  one  of  the  lateral  boundaries 
of  the  intercondyloid  notch,  and  gives  attachment,  somewhat  posteriorly,  to  the 
posterior  crucial  ligament.  Its  inferior  or  articular  surface  is  convex,  and 
presents  a  less  extensive  surface  than  the  external  condyle.  Just  above  the  articular 
surface  of  the  condyle,  behind,  is  a  depression  for  the  tendon  of  origin  of  the  inner 
head  of  the  Gastrocnemius. 

Structure. — The  shaft  of  the  femur  is  a  cylinder  of  compact  tissue,  holloAved 
by  a  large  medullary  canal.  The  cylinder  is  of  great  thickness  and  density  in  the 
middle  third  of  the  shaft,  where  the  bone  is  narrowest  and  the  medullary  canal 
well  formed ;  but  above  and  below  this  the  cylinder  gradually  becomes  thinner, 


THE   FEMUR,    OR    THIGH-BONE. 


289 


owing  to  a  separation  of  the  layers  of  the  bone  into  cancelli.  which  project  into  the 
medullary  canal  and  finally  obliterate  it.  so  that  the  upper  and  lower  ends  of  the 
shaft,  and  the  articular  extremities  more  especially,  consist  of  cancellated  tissue 
invested  by  a  thin,  compact  layer. 

The  arrangement  of  the  cancelli  in  the  ends  of  the  femur  is  remarkable.  In 
the  upper  end  they  are  arranged  in  two  sets.  One,  starting  from  the  top  of  the  head, 
the  upper  surface  of  the  neck,  and  the  great  trochanter,  converge  to  the  inner 
circumference  of  the  shaft  (Fig.  215) ;  these  are  placed  in  the  direction  of  greatest 
pressure,  and  serve  to  support  the  vertical  weight  of  the  body.  The  second  set 
are  planes  of  lamellae  intersecting  the  former  nearly  at  right  angles,  and  are  situ- 
ated in  the  line  of  the  greatest 
tension — that  is  to  say,  along  the 
lines  in  which  the  muscles  and 
ligaments  exert  their  traction. 
In  the  head  of  the  bone  these 


Great  trochatiter. 


_•  Digital  fossa. 


FIG.  215.— Diagram  showing  the  arrange- 
ment of  the  cancelli  of  the  neck  of  the  femur. 


FIG.  216. — Calcar  femorale. 


planes  are  arranged  in  a  curved  form,  in  order  to  strengthen  the  bone  when  exposed 
to  pressure  in  all  directions.  In  the  midst  of  the  cancellous  tissue  of  the  neck  is 
a  vertical  plane  of  compact  bone,  the  femoral  spur  (calcar  femorale)  which  com- 
mences at  the  point  where  the  neck  joins  the  shaft  midway  between  the  lesser 
trochanter  and  the  internal  border  of  the  shaft  of  the  bone,  and  extends  in  the 
direction  of  the  digital  fossa  (Fig.  216).  This  materially  strengthens  this  portion 
of  the  bone.  Another  point  in  connection  with  the  structure  of  the  neck  of  the 
femur  requires  mention,  especially  on  account  of  its  influence  on  the  production  of 
fracture  in  this  situation.  It  will  be  noticed  that  a  considerable  portion  of  the 
great  trochanter  lies  behind  the  level  of  the  posterior  surface  of  the  neck  ;  and  if  a 
section  be  made  through  the  trochanter  at  this  level,  it  will  be  seen  that  the 
posterior  wall  of  the  neck  is  prolonged  into  the  trochanter.  This  prolongation  is 
termed  by  Bigelow  the  "  true  neck."  l  and  forms  a  thin,  dense  plate  of  bone,  which 
passes  beneath  the  posterior  intertrochanteric  ridge  toward  the  outer  surface  of 
the  bone. 

In  the  lower  end  the  cancelli  spring  on  all  sides  from  the  inner  surface  of 
the  cylinder,  and  descend  in  a  perpendicular  direction  to  the  articular  surface,  the 
cancelli  being  strongest  and  having  a  more  accurately  perpendicular  course  above 
the  condyles.  In  addition  to  this,  however,  horizontal  planes  of  cancellous  tissue 


Bigelow  on  the  Hip,  p.  121. 


290 


THE   SKELETON. 


Appears  at    4th 
year;  joins  shaft  •>$ 
about  18th  year.  ^ 


£  Appears  at  end 
>  <?*  of  1st  year  ; 
joins  shaft  about 
18th  year. 


are  to  be  seen,  so  that  the  spongy  tissue  in  this  situation  presents  an  appearance  of 
being  mapped  out  into  a  series  of  rectangular  areas. 

Articulations. — With  three  bones  :  the  os  innominatum,  tibia,  and  patella. 

Development  (Fig.  217). — The  femur  is  developed  by  five  centres  :  one  for  the 

shaft,  one  for  each  extremity,  and  one  for  each  trochanter.     Of  all  the  long  bones, 

except  the  clavicle,  it  is  the  first  to  show  traces  of  ossification :  this  commences  in 

the  shaft,  at  about  the  fifth  week  of  foetal  life,  the  centres  of  ossification  in  the 

epiphyses  appearing  in  the  following 
order:  First,  in  the  lower  end  of 
the  bone,  at  the  ninth  month  of  foetal 
life1  (from  this  the  condyles  and 
tuberosities  are  formed)  ;  in  the  head 
at  the  end  of  the  first  year  after 
Appears  isth-uthyear;  birttl .  in  tte  great  trochanter,  during 

joins  shaft  about  18th         ,        „ '        ,        & 

year.  the  fourth  year ;   and   in  the  lesser 

trochanter,  between  the  thirteenth 
and  fourteenth.  The  order  in  which 
the  epiphyses  are  joined  to  the  shaft 
is  the  reverse  of  that  of  their  appear- 
ance: their  junction  does  not  com- 
mence until  after  puberty,  the  lesser 
trochanter  being  first  joined,  then 
the  great,  then  the  head,  and,  lastly, 
the  inferior  extremity  (the  first  in 
which  ossification  commenced),  which 
is  not  united  until  the  twentieth 
year. 

Attachment  of  Muscles. — To 
twenty-three.  To  the  great  tro- 
chanter :  the  Gluteus  medius,  Gluteus 
minimus,  Pyriformis,  Obturator  inter- 
nus,  Obturator  externus,  Gemellus 
superior,  Gemellus  inferior,  and 
Quadratus  femoris.  To  the  lesser 
trochanter :  the  Psoas  magnus  and 
the  Iliacus  below  it.  To  the  shaft : 

the  Vastus  externus,  Gluteus  maximus,  short  head  of  the  Biceps,  Vastus  internus, 
Adductor  magnus,  Pectineus,  Adductor  brevis,  Adductor  longus,  Crureus,  and 
Subcrureus.  To  the  condyles :  the  Gastrocnemius,  Plantaris,  and  Popliteus. 

Surface  Form. — The  femur  is  covered  with  muscles,  so  that  in  fairly  muscular  subjects  the 
shaft  is  not  to  be  detected  through  its  fleshy  covering,  and  the  only  parts  accessible  to  the  touch 
are  the  outer  surface  of  the  great  trochanter  and  the  lower  expanded  end  of  the  bone.  The 
external  surface  of  the  great  trochanter  is  to  be  felt,  especially  in  certain  positions  of  the  limb.  Its 
position  is  generally  indicated  by  a  depression,  owing  to  the  thickness  of  the  Gluteus  medius  and 
minimus,  which  project  above  it.  When,  however,  the  thigh  is  flexed,  and  especially  if 
crossed  over  the  opposite  one,  the  trochanter  produces  a  blunt  eminence  on  the  surface.  The 
upper  border  is  about  on  a  line  with  the  spine  of  the  os  pubis,  and  its  exact  level  is  indicated  by 
a  line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium,  over  the  outer  side  of  the 
hip,  to  the  most  prominent  point  of  the  tuberosity  of  the  ischium.  This  is  known  as  Nekton's 
line.  The  outer  and  inner  condyles  of  the  lower  extremity  are  easily  to  be  felt.  The  outer  one 
is  more  subcutaneous  than  the  inner  one,  and  readily  felt.  The  tuberosity  on  it  is  comparatively 
little  developed,  but  can  be  more  or  less  easily  recognized.  The  inner  condyle  is  more  thickly 
covered,  and  this  gives  a  general  convex  outline  to  this  part,  especially  when  the  knee  is 
flexed.  The  tuberosity  on  it  is  easily  felt,  and  at  the  upper  part  of  the  condyle  the  sharp 
tubercle  for  the  insertion  of  the  tendon  of  the  Adductor  magnus  can  be  recognized  without 
difficulty.  When  the  knee  is  flexed,  and  the  patella  situated  in  the  interval  between  the  con- 
dyles and  the  upper  end  of  the  tibia,  a  part  of  the  trochlear  surface  of  the  femur  can  be  made 
out  above  the  patella. 

Surgical  Anatomy. — There  are  one  or  two  points  about  the  ossification  of  the  femur 

1  This  is  the  only  epiphysis  in  which  ossification  begins  before  birth. 


Appears  at 
9th  month 
(foetal). 


Joins  shaft  at  20th 
year. 


Lower  extremity. 

FIG.  217.— Plan  of  the  development  of  the  femur, 
five  centres. 


By 


THE   PATELLA. 

bearing  on  practice  to  which  allusion  must  be  made.  It  has  been  stated  above  that  the 
lower  end  of  the  femur  is  the  only  epiphysis  in  which  ossification  has  commenced  at  the  time  of 
birth.  The  presence  of  this  ossific  centre  is,  therefore,  a  proof,  in  newly-born  children  found 
dead,  that  the  child  has  arrived  at  the  full  period  of  utero-gestation,  and  is  always  relied  upon  in 
medico-legal  investigations.  The  position  of  the  epiphysial  line  should  be  carefully  noted.  It 
is  <>n  a  level  with  the  adductor  tubercle,  and  the  epiphysis  does  not,  therefore,  form  the  whole 
of  the  cartilage-clad  portion  of  the  lower  end  of  the  bone.  It  is  essential  to  bear  this  point  in 
mind  in  performing  excision  of  the  knee,  since  growth  in  length  of  the  femur  takes  place  chiefly 
from  the  lower  epiphysis.  and  any  interference  with  the  epiphysial  cartilage  in  a  young  child 
would  involve  suc-h  ultimate  shortening  of  the  limb,  from  want  of  growth,  as  to  render  it 
almost  useless.  Separation  of  the  lower  epiphysis  may  take  place  up  to  the  age  of  twenty,  at 
wlik-h  time  it  becomes  completely  joined  to  the  shaft  of  the  bone  ;  but.  as  a  matter  of  fact,  few 
occur  after  the  age  of  sixteen  or  seventeen.  The  upper  epiphysis  of  the  femur  is  of 
interest  principally  on  account  of  its  being  the  seat  of  origin  of  a  large  number  of  cases  of 
tubercular  disease  of  the  hip-joint.  The  disease  commences  in  the  majority  of  cases  in  the 
highly  vascular  and  growing  tissue  in  the  neighborhood  of  the  epiphysis,  and  from  here  extends 
into  the  joint. 

Fractures  of  the  femur  are  divided,  like  those  of  the  other  long  bones,  into  fractures  of  the 
upper  end ;  of  the  shaft :  and  of  the  lower  end.  The  fractures  of  the  upper  end  may  be 
classified  into  1  »  fracture  of  the  neck  ;  (2)  fracture  at  the  junction  of  the  neck  with  the  great 
trochanter;  (3)  fracture  of  the  great  trochanter;  and  (4)  separation  of  the  epiphysis,  either 
of  the  head  or  of  the  great  trochanter.  The  first  of  these,  fracture  of  the  neck,  is  usually 
termed  intracapsular  fracture,  but  this  is  scarcely  a  correct  designation,  as,  owing  to  the  attach- 
ment of  the  capsular  ligament,  the  fracture  may  be  partly  within  and  partly  without  the  cap- 
sule, when  the  fracture  occurs  at  the  lower  part  of  the  neck.  It  generally  occurs  in  old  people, 
principally  women,  and  usually  from  a  very  slight  degree  of  indirect  violence.  Probably 
the  main  cause  of  the  fracture  taking  place  in  old  people  is  in  consequence  of  the  degenerative 
changes  which  the  bone  has  undergone.  Merkel  believes  that  it  is  mainly  due  to  the  absorp- 
tion of  the  calcar  femorale.  These  fractures  are  occasionally  impacted.  As  a  rule  they  unite  by 
fibrous  tissue,  and  frequently  no  union  takes  place,  and  the  surfaces  of  the  fracture  become 

rh  and  eburnated. 

Fractures  at  the  junction  of  the  neck  with  the  great  trochanter  are  usually  termed  extra- 
capsular.  but  this  designation  is  also  incorrect,  as  the  fracture  is  partly  within  the  capsule, 
owing  to  its  attachment  in  front  to  the  anterior  intertrochanteric  line,  which  is  situated  below 
the  line  of  fracture.  These  fractures  are  produced  by  direct  violence  to  the  great  trochanter.  as 
from  a  blow  or  fall  laterally  on  the  hip.  From  the  manner  in  which  the  accident  is  caused,  the 
neck  of  the  bone  is  driven  into  the  trochanter,  where  it  may  remain  impacted,  or  the  trochanter 
may  be  split  up  into  two  or  more  fragments,  and  thus  no  fixation  takes  place. 

Fractures  of  the  great  trochanter  may  be  either  "oblique  fracture  through  the  trochanter 
major,  without  implicating  the  neck  of  the  bone"  (Astley  Cooper),  or  separation  of  the  great 
troehanter.  Most  of  the  recorded  cases  of  this  latter  injury  occurred  in  young  persons,  and  were 
probably  cases  of  separation  of  the  epiphysis  of  the  great  trochanter.  Separation  of  the  epiphysis 
of  the  head  of  the  femur  has  been  said  to  occur,  but,  as  far  as  I  know,  has  never  been  verified 
by  post-mortem  examination. 

Fractures  of  the  shaft  may  occur  at  any  part,  but  the  most  usual  situation  is  at  or  near  the 
centre  of  the  bone.  They  may  be  caused  by  direct  or  indirect  violence  or  by  muscular  action. 
Fractures  of  the  upper  third  of  the  shaft  are  almost  always  the  result  of  indirect  violence, 
whilst  thu<e  of  the  lower  third  are  the  result,  for  the  most  part,  of  direct  violence.  In  the 
middle  third  fractures  occur  from  both  forms  of  injury  in  about  equal  proportions.  Fractures 
of  the  shaft  are  generally  oblique,  but  thev  may  be  transverse,  longitudinal,  or  spiral.  The 
transverse  fracture  occurs  most  frequently  in  children.  The  fractures  of  the  lower  end  of  the 
femur  include  transverse  fracture  above  the  condyles.  the  most  common  ;  and  this  may  be  com- 
plicated by  a  vertical  fracture  between  the  condyles.  constituting  the  T-shaped  fracture.  In 
these  eases  the  popliteal  artery  is  in  danger  of  being  wounded.  Oblique  fracture,  separating 
either  the  internal  or  external  condyle.  ancf  a  longitudinal  incomplete  fracture  between  the  con- 
dyle>.  may  also  take  place. 

The  femur  as  well  as  the  other  bones  of  the  leg  are  frequently  the  seat  of  acute  necrosis  in 
young  children.  This  is  no  doubt  due  to  their  greater  exposure  to  injury,  which  is  often  the 
exciting  cause  of  this  disease.  Tumors  not  unfrequently  are  found  growing  from  the  femur : 
the  most  common  forms  being  sarcoma,  which  may  grow  either  from  the  periosteum  or  from  the 
medullary  tissue  within  the  interior  of  the  bone ;  and  exostosis.  which  is  commonly  found 
originating  in  the  neighborhood  of  the  epiphysial  cartilage  of  the  lower  end. 

THE  LEG. 

The  skeleton  of  the  Leg  consists  of  three  bones  :  the  Patella,  a  large  sesamoid 
bone,  placed  in  front  of  the  knee  :  the  Tibia  :  and  the  Fibula. 

The  Patella  'Figs.  218,  219.) 
The  Patella  (patella,  a  small  pan)  is  a  flat,  triangular  bone,  situated  at  the 


292 


THE  SKELETON. 


FIG.  218.— Right  patella.    An 
terior  surface. 


FIG.  219.— Right    patella. 
Posterior  surface. 


anterior    part  of    the    knee-joint.     It  is    usually    regarded  as  a  sesamoid  bone, 
developed  in  the  tendon  of  the  Quadriceps  extensor.     It  resembles  these  bones 

(1)  in  its  being  developed  in  a 
tendon  ;  (2)  in  its  centre  of  ossi- 
fication presenting  a  knotty  or 
tuberculated  outline  similar  to 
other  sesamoid  bones ;  (3)  in  its 
structure  being  composed  mainly 
of  dense  cancellous  tissue,  as  in 
the  other  sesamoid  bones.  It 
serves  to  protect  the  front  of 
the  joint,  and  increases  the 
leverage  of  the  Quadriceps  ex- 
tensor by  making  it  act  at  a 
greater  angle.  It  presents  an 
anterior  and  posterior  surface,  three  borders,  and  an  apex. 

The  anterior  surface  is  convex,  perforated  by  small  apertures,  for  the  passage 
of  nutrient  vessels,  and  marked  by  numerous  rough,  longitudinal  striae.  This 
surface  is  covered,  in  the  recent  state,  by  an  expansion  from  the  tendon  of  the 
Quadriceps  extensor,  which  is  continuous  below  Avith  the  superficial  fibres  of  the 
ligamentum  patellae.  Jt  is  separated  from  the  integument  by  a  bursa.  The 
posterior  surface  presents  a  smooth,  oval-shaped,  articular  surface,  covered  with 
cartilage  in  the  recent  state,  and  divided  into  two  facets  by  a  vertical  ridge,  which 
descends  from  the  superior  border  toward  the  inferior  angle  of  the  bone.  The 
ridge  corresponds  to  the  groove  on  the  trochlear  surface  of  the  femur,  and  the  two 
facets  to  the  articular  surfaces  of  the  two  condyles  ;  the  outer  facet,  for  articulation 
with  the  outer  condyle,  being  the  broader  and  deeper.  This  character  serves  to 
indicate  the  side  to  which  the  bone  belongs.  Below  the  articular  surface  is  a 
rough,  convex,  non-articular  depression,  the  lower  half  of  which  gives  attachment 
to  the  ligamentum  patellae,  the  upper  half  being  separated  from  the  head  of  the 
tibia  by  adipose  tissue,  in  which  may  be  found  a  bursa. 

The  superior  border  is  thick,  and  sloped  from  behind,  downward  and  forward : 
it  gives  attachment  to  that  portion  of  the  Quadriceps  extensor  which  is  derived 
from  the  Rectus  and  Crureus  muscles.  The  lateral  borders  are  thinner,  converging 
below.  They  give  attachment  to  that  portion  of  the  Quadriceps  extensor  derived 
from  the  external  and  internal  Vasti  muscles. 

The  apex  is  pointed,  and  gives  attachment  to  the  ligamentum  patellae. 
Structure. — It  consists  of  a  nearly  uniform   dense  cancellous  tissue  covered 
by  a  thin  compact  lamina.     The  cancelli  immediately  beneath  the  anterior  surface 
are  arranged  parallel  with  it.     In  the  rest  of  the  bone  they  radiate  from  the 
posterior  articular  surface    toward  the  other  parts  of  the  bone. 

Development. — By  a  single  centre,  which  makes  its  appearance,  according  to 
Beclard,  about  the  third  year.  In  two  instances  I  have  seen  this  bone  cartilagi- 
nous throughout,  at  a  much  later  period  (six  years).  More  rarely,  the  bone  is 
developed  by  two  centres,  placed  side  by  side.  Ossification  is  completed  about  the 
age  of  puberty. 

Articulations. — With  the  two  condyles  of  the  femur. 

Attachment  of  Muscles. — To  four :  the  Rectus,  Crureus,  Vastus  internus,  and 
Vastus  externus.  These  muscles,  joined  at  their  insertion,  constitute  the  Quadriceps 
extensor  cruris. 

Surface  Form. — The  external  surface  of  the  patella  can  be  seen  and  felt  in  front  of  the 
knee.  In  the  extended  position  of  the  limb  the  internal  border  is  a  little  more  prominent  than 
the  outer,  and  if  the  Quadriceps  extensor  is  relaxed,  the  bone  can  be  moved  from  side  to  side 
and  appears  to  be  loosely  fixed.  If  the  joint  is  flexed,  the  patella  recedes  into  the  hollow 
between  the  condyles  of  the  femur  and  the  upper  end  of  the  tibia,  and  becomes  firmly  fixed 
against  the  femur. 

Surgical  Anatomy. — The  main  surgical  interest  about  the  patella  is  in  connection  with 
fractures ;  which  are  of  common  occurrence.  They  may  be  produced  by  muscular  action  ;  that 


THE   TIBIA.  293 

is  to  say.  by  violent  contraction  of  the  Quadriceps  extensor  while  the  limb  is  in  a  position  of 
semi-flexion,  so  that  the  bone  is  snapped  across  the  condyles;  or  by  direct  violence,  such  as 
falls  on  the  knee.  In  the  former  class  of  cases  the  fracture  is  transverse ;  in  the  latter  it  may 
be  oblique,  longitudinal,  stellate,  or  the  bone  variously  comminuted.  The  principal  interest  in 
these  cases  attache.*  to  their  treatment.  Owing  to  the  wide  separation  of  the  fragments,  and 
the  difficulty  there  is  in  maintaining  them  in  apposition,  union  takes  place  by  fibrous  tissue, 
an  1  this  may  subsequently  stretch,  producing  wide  separation  of  the  fragments  and  permanent 
lameness.  Various  plans,  including  opening  the  joint  and  suturing  the  fragments,  have  been 
advocated  for  overcoming  this  difficulty. 

In  the  larger  number  of  cases  of  fracture  of  the  patella  the  knee-joint  is  involved,  the  car- 
tilatre  which  covers  its  posterior  surface  being  also  torn.  In  some  cases  of  fracture  from  direct 
violence,  however,  this  need  not  necessarily  happen,  the  lesion  involving  only  the  superficial 
part  of  the  bone ;  and,  as  Morris  has  pointed  out.  it  is  an  anatomical  possibility,  in  complete 
fracture,  if  the  lesion  involve  only  the  lower  and  non-articular  part  of  the  bone,  for  it  to  take 
place  without  injury  to  the  synovial  membrane. 

The  Tibia  (Figs.  220,  221). 

The  Tibia  (tibia,  a  flute  or  pipe)  is  situated  at  the  front  and  inner  side  of  the 
leg.  and,  excepting  the  femur,  is  the  longest  and  largest  bone  in  the  skeleton.  It 
is  prismoid  in  form,  expanded  above,  where  it  enters  into  the  knee-joint,  more 
slightly  enlarged  below.  In  the  male  its  direction  is  vertical  and  parallel  with 
the  bone  of  the  opposite  side ;  but  in  the  female  it  has  a  slightly  oblique  direction 
downward  and  outward,  to  compensate  for  the  oblique  direction  of  the  femur 
inward.  It  presents  for  examination  a  shaft  and  two  extremities. 

The  Tipper  Extremity,  or  Head,  is  large,  and  expanded  on  each  side  into  two 
lateral  eminences,  the  tuberosities.  Superiorly,  the  tuberosities  present  two  smooth, 
concave  surfaces,  which  articulate  with  the  condyles  of  the  femur ;  the  internal, 
articular  surface  is  longer,  deeper,  and  narrower  than  the  external,  oval  from 
before  backward,  to  articulate  with  the  internal  condyle ;  the  external  one 
is  broader,  flatter,  and  more  circular,  to  articulate  with  the  external  condyle. 
Between  the  two  articular  surfaces,  and  nearer  the  posterior  than  the  anterior 
aspect  of  the  bone,  is  an  eminence,  the  spinous  process  of  the  tibia,  surmounted 
by  a  prominent  tubercle  on  each  side,  which  gives  attachment  to  the  extremities 
of  the  semilunar  fibro-cartilages ;  in  front  and  behind  the  spinous  process  is  a 
rough  depression  for  the  attachment  of  the  anterior  and  posterior  crucial  ligaments 
and  the  semilunar  fibro-cartilages.  The  anterior  surfaces  of  the  tuberosities  are 
continuous  with  one  another,  forming  a  single  large  surface,  which  is  somewhat 
flattened  :  it  is  triangular,  broad  above,  and  perforated  by  large  vascular  foramina ; 
narrow  below,  where  it  terminates  in  a  prominent  oblong  elevation  of  large  size, 
the  tut',-/-.-},-  of  the  tibia  :  the  lower  half  of  this  tubercle  is  rough,  for  the  attachment 
of  the  ligament  urn  patellie ;  the  upper  half  presents  a  smooth  facet  supporting, 
in  the  recent  state,  a  bursa  which  separates  the  ligament  from  the  bone.  Posteriorly 
the  tuberosities  are  separated  from  each  other  by  a  shallow  depression,  the 
popfit'-'.il  notch,  which  gives  attachment  to  part  of  the  posterior  crucial  ligament 
and  part  of  the  posterior  ligament  of  the  knee-joint.  The  inner  tuberosity  presents 
posteriorly  a  deep  transverse  groove,  for  the  insertion  of  one  of  the  fasciculi  of 
the  tendon  of  the  Semi-membranosus,  Its  lateral  surface  is  convex,  rough,  and 
prominent :  it  gives  attachment  to  the  internal  lateral  ligament.  The  outer  tuber- 
'jxi.tij  presents  posteriorly  a  flat  articular  facet,  nearly  circular  in  form,  directed 
downward,  backward,  and  outward,  for  articulation  with  the  fibula.  Its  lateral 
surface  is  convex  and  rough,  more  prominent  in  front  than  the  internal :  it 
presents  a  prominent  rough  eminence,  situated  on  a  level  with  the  upper  border  of 
the  tubercle  of  the  tibia,  for  the  attachment  of  the  ilio-tibial  band.  Just  below 
this  the  Extensor  longus  digitorum  and  a  slip  from  the  Biceps  are  attached. 

The  Shaft  of  the  tibia  is  of  a  triangular  prismoid  form,  broad  above,  gradually 
decreasing  in  size  to  its  most  slender  part,  at  the  commencement  of  its  lower 
fourth,  where  fracture  most  frequently  occurs ;  it  then  enlarges  again  toward  its 
lower  extremity.  It  presents  for  examination  three  borders  and  three  surfaces. 

The  anterior  border,  the  most  prominent  of  the  three,  is  called  the  crest  of  the 


THE  SKELETON. 


Head. 
Styloid  process. 


EXTERNAL 
LATERAL 

LIGAMENT. 


Fibula. 


Tibia. 


Head.  tibia,  or,  in  popular  language,  the 

shin  ;  it  commences  above  at  the 
tubercle,  and  terminates  below  at 
the  anterior  margin  of  the  inner 
malleolus.  This  border  is  very 
prominent  in  the  upper  two- 
thirds  of  its  extent,  smooth  and 
rounded  below.  It  presents  a 
very  flexuous  course,  being  usually 
curved  outward  above  and  inward 
below  ;  it  gives  attachment  to  the 
deep  fascia  of  the  leg. 

The  internal  border  is  smooth 
and  rounded  above  and  below, 
but  more  prominent  in  the 
centre ;  it  commences  at  the 
back  part  of  the  inner  tuberosity, 
and  terminates  at  the  posterior 
border  of  the  internal  malleolus ; 
its  upper  part  gives  attachment 
to  the  internal  lateral  ligament 
of  .the  knee  to  the  extent  of 
about  two  inches,  and  to  some 
fibres  of  the  Popliteus  muscle ; 
its  middle  third  to  some  fibres 
of  the  Soleus  and  Flexor  longus 
digitorum  muscles. 

The  external  border,  or  in- 
terosseous  ridge,  is  thin  and 
prominent,  especially  its  central 
part,  and  gives  attachment  to 
the  interosseous  membrane ;  it 
commences  above  in  front  of  the 
fibular  articular  facet,  and  bifur- 
cates below,  to  form  the  bounda- 
ries of  a  triangular  rough  surface, 
for  the  attachment  of  the  inter- 
osseous  ligament  connecting  the 
tibia  and  fibula. 

The  internal  surface  is  smooth, 
convex,  and  broader  above  than 
below ;  its  upper  third,  directed 
forward  and  inward,  is  covered 
by  the  aponeurosis  derived  from 
the  tendon  of  the  Sartorius,  and 
by  the  tendons  of  the  'Gracilis 
and  Seinitendinosus,  all  of  which 
are  inserted  nearly  as  far  forward 
as  the  anterior  border ;  in  the  rest 
of  its  extent  it  is  subcutaneous. 

The  external  surface  is  nar- 
rower than  the  internal ;  its  upper 
two-thirds  presents  a  shallow 
groove  for  the  attachment  of  the 
Tibialis  anticus  muscle;  its  lower 
third  is  smooth,  convex,  curves 
gradually  forward  to  the  anterior  part  of  the  bone,  and  is  covered  from  within 


Internal  malleolus. 
External  malleolus. 
FIG.  220.— Bones  of  the  right  leg.    Anterior  surface. 


THE    TIBIA. 


295 


Styloid  process. 


Fibula. 


outward  by  the  tendons  of  the  fol- 
lowing muscles :  Tibialis  anticus, 
Extensor  proprius  hallucis.  Ex- 
tensor longus  digitoruui. 

The  posterior  surface  (Fig.  221) 
presents,  at  its  upper  part,  a  prom- 
inent ridge,  the  oblique  lint'  of  the 
tibia,  which  extends  from  the  back 
part  of  the  articular  facet  for  the 
fibula  obliquely  downward,  to  the 
internal  border,  at  the  junction  of 
its  upper  and  middle  thirds.  It 
marks  the  limit  for  the  insertion 
of  the  Popliteus  muscle,  and  serves 
for  the  attachment  of  the  popliteal 
fascia  and  part  of  the  Soleus, 
Flexor  longus  digitorum,  and  Tib- 
ialis posticus  muscles :  the  tri- 
angular concave  surface,  above  and 
to  the  inner  side  of  this  line,  gives 
attachment  to  the  Popliteus  mus- 
cle. The  middle  third  of  the  pos- 
terior surface  is  divided  by  a 
vertical  ridge  into  two  lateral 
halves  :  the  ridge  is  well  marked 
at  its  commencement  at  the  oblique 
line,  but  becomes  gradually  indis- 
tinct below  :  the  inner  and  broader 
half  gives  attachment  to  the  Flexor 
longus  digitorum,  the  outer  and 
narrower  to  part  of  the  Tibialis 
posticus.  The  remaining  part  of 
the  bone  presents  a  smooth  surface 
covered  by  the  Tibialis  posticus, 
Flexor  longus  digitorum,  and 
Flexor  longus  hallucis  muscles. 
Immediately  below  the  oblique  line 
is  the  medullary  foramen,  which  is 
directed  obliquely  downward. 

The  Lower  Extremity,  much 
smaller  than  the  upper,  presents  five 
surfaces :  it  is  prolonged  downward, 
on  its  inner  side  to  a  strong  pro- 
the  internal.  iiinlh'<;lns.  The 
i)it\  /•/->/•  surface  of  the  bone  is 
quadrilateral,  and  smooth  for  artic- 
ulation with  the  astragalus.  This 
surface  is  concave  from  before  back- 
ward, and  broader  in  front  than  be- 
hind. It  is  traversed  from  before 
backward  by  a  slight  elevation, 
separating  two  lateral  depressions. 
It  is  narrow  internally,  where  the 
articular  surface  becomes  continu- 
ous with  that  on  the  inner  malleolus.  The  anterior  surface  of  the  lower  extrem- 
ity is  smooth  and  rounded  above,  and  covered  by  the  tendons  of  the  Extensor 
muscles  of  the  toes ;  its  lower  margin  presents  a  rough  transverse  depression,  for 


FIG.  221.— Bones  of  the  right  leg.    Posterior  surface. 


296 


THE  SKELETON. 


Upper  extremity. 


Appears  at 
birth. 


.Joins  shaft  about 
20th  year. 


the  attachment  of  the  anterior  ligament  of  the  ankle-joint ;  the  posterior  surface 
presents  a  superficial  groove  directed  obliquely  downward  and  inward,  continuous 
with  a  similar  groove  on  the  posterior  extremity  of  the  astragalus,  and  serving 
for  the  passage  of  the  tendon  of  the  Flexor  longus  hallucis ;  the  external  surface 
presents  a  triangular  rough  depression  for  the  attachment  of  the  inferior  inter- 
osseous  ligament  connecting  it  with  the  fibula ;  the  lower  part  of  this  depression 
is  smooth,  covered  with  cartilage  in  the  recent  state,  and  articulates  with  the 
fibula.  This  surface  is  bounded  by  two  prominent  ridges,  continuous  above  with 
the  interosseous  ridge  ;  they  afford  attachment  to  the  anterior  and  posterior  infe- 
rior tibio-fibular  ligaments.  The  internal  surface  of  the  lower  extremity  is  pro- 
longed downward  to  form  a  strong  pyramidal  process,  flattened  from  without 
inward — the  inner  malleolus.  The  inner  surface  of  this  process  is  convex  and  sub- 
cutaneous ;  its  outer  surface  is  smooth  and  slightly  concave,  and  articulates  with 
the  astragalus ;  its  anterior  border  is  rough,  for  the  attachment  of  the  anterior 
fibres  of  the  Deltoid  ligament ;  its  posterior  border  presents  a  broad  and  deep 
groove,  directed  obliquely  downward  and  inward,  which  is  occasionally  double : 
this  groove  transmits  the  tendons  of  the  Tibialis  posticus  and  Flexor  longus  digi- 
torum  muscles.  The  summit  of  the  internal  malleolus  is  marked  by  a  rough 
depression  behind,  for  the  attachment  of  the  internal  lateral  ligament  of  the 
ankle-joint. 

Structure. — Like  that  of  the  other  long  bones.     At  the  junction  of  the  middle 

and  lower  third,  where  the  bone  is  smallest,  the  wall  .of  the  shaft  is  thicker  than 

in  other  parts,  in  order  to  compensate  for  the  smallness  of  the  calibre  of  the  bone. 

Development. — By  three  centres  (Fig.  222) :  one  for  the  shaft,  and  one  for 

each  extremity.  Ossification  commences 
in  the  centre  of  the  shaft  about  the 
seventh  week,  and  gradually  extends  to- 
ward either  extremity.  The  centre  for 
the  upper  epiphysis  appears  during  the 
first  year;  it  is  flattened  in  form,  and 
has  a  thin,  tongue-shaped  process  in  front 
which  forms  the  tubercle.  That  for  the 
lower  epiphysis  appears  in  the  second 
year.  The  lower  epiphysis  joins  the 
shaft  at  about  the  eighteenth,  and  the 
upper  one  about  the  twentieth,  year. 
Two  additional  centres  occasionally  exist 
— one  for  the  tongue-shaped  process  of 
the  upper  epiphysis,  which  forms  the 
tubercle,  and  one  for  the  inner  malleolus. 
Articulations. — With  three  bones:  the 
femur,  fibula,  and  astragalus. 

Attachment  of  Muscles. — To  twelve: 
to  the  inner  tuberosity,  the  Semimem- 
branosus ;  to  the  outer  tuberosity,  the 
Tibialis  anticus  and  Extensor  longus  digi- 
torum  and  Biceps  ;  to  the  shaft,  its  inter- 
nal surface,  the  Sartorius,  Gracilis,  and 
Semitendinosus  ;  to  its  external  surface, 
the  Tibialis  anticus ;  to  its  posterior  sur- 
face, the  Popliteus,  Soleus,  Flexor  longus  digitorum,  and  Tibialis  posticus  ;  to  the 
tubercle,  the  ligamentum  patellae. 

Surface  Form.— A  considerable  portion  of  the  tibia  is  subcutaneous  and  easily  to  be  felt. 
At  the  upper  extremity  the  tuberosities  are  to  be  recognized  just  below  the  knee.  The  internal 
one  is  broad  and  smooth,  and  merges  into  the  subcutaneous  surface  of  the  shaft  below.  The 
external  one  is  narrower  and  more  prominent,  and  on  it,  about  midway  between  the  apex  of  the 
patella  and  the  head  of  the  fibula,  may  be  felt  a  prominent  tubercle  for  the  insertion  of  the  ilic- 


Appears  at  2nd_ 
year. 


Joins  shaft  about 
18th  year. 


Lower  extremity 


FIG.  222.— Plan  of  the  development  of  the  tibia. 
By  three  centres. 


THE   FIBULA.  297 

tibial  band.  In  front  of  the  upper  end  of  the  bone,  between  the  tuberosities,  is  the  tubercle  of 
the  tibia,  fonnine:  an  oval  eminence,  which  is  continuous  below  with  the  anterior  border  or  crest 
of  the  bone.  This  bonier  can  be  felt,  forming  the  prominence  of  the  shin,  in  the  upper  two- 
thirds  of  its  extent  being  sharp  and  presenting  a  somewhat  flexuous  course,  being  curved  out- 
ward above  and  inward  below.  In  the  lower  third  of  the  leg  the  border  disappears,  and  the 
bone  is  concealed  by  the  tendons  of  the  muscles  on  the  front  of  the  leg.  Internal  to  the  ante- 
rior border  is  to  be  felt  the  broad  internal  surface  of  the  tibja,  slightly  encroached  upon  by  the 
muscles  in  front  and  behind.  It  commences  above  at  the  wide  expanded  inner  tuberosity,  and 
terminates  below  at  the  internal  malleolus.  The  internal  malleolus  is  a  broad  prominence  situ- 
ated on  a  higher  level  and  somewhat  farther  forward  than  the  external  malleolus.  It  overhangs 
the  inner  border  of  the  arch  of  the  foot.  Its  anterior  border  is  nearly  straight;  its  posterior 
border  presents  a  sharp  edge,  which  forms  the  inner  margin  of  the  groove  for  the  tendon  of 
the  Tibialis  posticus  muscle. 

The  Fibula  (Figs.  220,  221). 

The  Fibula  (iibnl<t.  a  clasp)  is  situated  at  the  outer  side  of  the  leg.  It  is  the 
smaller  of  the  two  bones,  and,  in  proportion  to  its  length,  the  most  slender  of  all 
the  long  bones :  it  is  placed  nearly  parallel  but  behind  the  level  of  the  tibia.  Its 
upper  extremity  is  small,  placed  toward  the  back  of  the  head  of  the  tibia  and 
below  the  level  of  the  knee-joint,  and  excluded  from  its  formation ;  the  lower 
extremity  inclines  a  little  forward,  so  as  to  be  on  a  plane  anterior  to  that  of  the 
upper  end,  projects  below  the  tibia,  and  forms  the  outer  ankle.  It  presents  for 
examination  a  shaft  and  two  extremities. 

The  Upper  Extremity,  or  Head,  is  of  an  irregular  quadrate  form,  presenting 
above  a  flattened  articular  facet,  directed  upward,  forward,  and  inward,  for  artic- 
ulation with  a  corresponding  facet  on  the  external  tuberosity  of  the  tibia.  On 
the  outer  side  is  a  thick  and  rough  prominence,  continued  behind  into  a  pointed 
eminence,  the  styloid  process*  which  projects  upward  from  the  posterior  part  of 
the  head.  The  prominence  gives  attachment  to  the  tendon  of  the  Biceps  muscle 
and  to  the  long  external  lateral  ligament  of  the  knee,  the  ligament  dividing  the 
tendon  into  two  parts.  The  summit  of  the  styloid  process  gives  attachment  to  the 
short  external  lateral  ligament.  The  remaining  part  of  the  circumference  of  the 
head  is  rough,  for  the  attachment  of  the  anterior  superior  tibio-fibular  ligament, 
presenting,  in  front,  a  tubercle  for  the  attachment  of  the  upper  and  anterior  part 
of  the  Peroneus  longus ;  and  behind,  another  tubercle  for  the  attachment  of  the 
posterior  superior  tibio-fibular  ligament  and  the  upper  fibres  of  the  Soleus  muscle. 

The  shaft  presents  four  borders — the  antero-external,  the  antero-internal,  the 
postero-external.  and  the  postero-internal  ;  and  four  surfaces — anterior,  posterior, 
internal,  and  external. 

The  antero-external  border  commences  above  in  front  of  the  head,  runs  verti- 
cally downward  to  a  little  below  the  middle  of  the  bone,  and  then,  curving  some- 
what outward,  bifurcates  so  as  to  embrace  the  triangular  subcutaneous  surface 
immediately  above  the  outer  surface  of  the  external  malleolus.  This  border  gives 
attachment  to  an  intermuscular  septum,  which  separates  the  extensor  muscles  on 
the  anterior  surface  of  the  leg  from  the  Peroneus  longus  and  brevis  muscles. 

The  antero-internal  border,  or  interosseous  ridge,  is  situated  close  to  the  inner 
si<le  of  the  preceding,  and  runs  nearly  parallel  with  it  in  the  upper  third  of  its 
extent,  but  diverges  from  it  so  a?  co  include  a  broader  space  in  the  lower  two-thirds. 
It  commences  above  just  beneath  the  head  of  the  bone  (sometimes  it  is  quite 
indistinct  for  about  an  inch  below  the  head),  and  terminates  below*  at  the  apex  of 
a  rough  triangular  surface  immediately  above  the  articular  facet  of  the  external 
malleolus.  It  serves  for  the  attachment  of  the  interosseous  membrane,  and  sepa- 
rates the  extensor  muscles  in  front  from  the  flexor  muscles  behind. 

The  postero-external  border  is  prominent;  it  commences  above  at  the  base 
of  the  styloid  process,  and  terminates  below  in  the  posterior  border  of  the  outer 
malleolus.  It  is  directed  outward  above,  backward  in  the  middle  of  its  course, 
backward  and  a  little  inward  below,  and  gives  attachment  to  an  aponeurosis 
which  separates  the  Peronei  muscles  on  the  outer  surface  of  the  shaft  from  the 
flex  >r  muscles  on  its  posterior  surface. 


298  THE  SKELETON. 

The  postero-internal  border,  sometimes  called  the  oblique  line,  commences  above 
at  the  inner  side  of  the  head,  and  terminates  by  becoming  continuous  with  the 
antero-internal  border  or  interosseous  ridge  at  the  lower  fourth  of  the  bone.  It  is 
well  marked  and  prominent  at  the  upper  and  middle  parts  of  the  bone.  It  gives 
attachment  to  an  aponeurosis  which  separates  the  Tibialis  posticus  from  the  Soleus 
above  and  the  Flexor  longus  hallucis  below. 

The  anterior  surface  is  the  interval  between  the  antero-external  and  antero- 
internal  borders.  It  is  extremely  narrow  and  flat  in  the  upper  third  of  its  extent ; 
broader  and  grooved  longitudinally  in  its  lower  third  ;  it  serves  for  the  attachment 
of  three  muscles,  the  Extensor  longus  digitorum,  Peroneus  tertius,  and  Extensor 
proprius  hallucis. 

The  external  surface  is  the  space  between  the  antero-external  and  postero- 
external  borders.  It  is  much  broader  than  the  preceding,  and  often  deeply  grooved, 
is  directed  outward  in  the  upper  two-thirds  of  its  course,  backward  in  the  lower 
third,  where  it  is  continuous  with  the  posterior  border  of  the  external  malleolus. 
This  surface  is  completely  occupied  by  the  Peroneus  longus  and  brevis  muscles. 

The  internal  surface  is  the  interval  included  between  the  antero-internal  and 
the  postero-internal  borders.  It  is  directed  inward,  and  is  grooved  for  the  attach- 
ment of  the  Tibialis  posticus  muscle. 

The  posterior  surface  is  the  space  included  between  the  postero-external  and 
the  postero-internal  borders ;  it  is  continuous  below  with  the  rough  triangular 
surface  above  the  articular  facet  of  the  outer  malleolus ;  it  is  directed  backward 
above,  backward  and  inward  at  its  middle,  directly  inward  below.  Its  upper 
third  is  rough,  for  the  attachment  of  the  Soleus  muscle  ;  its  lower  part  presents 
a  triangular  rough  surface,  connected  to  the  tibia  by  a  strong  interosseous  ligament, 
and  between  these  two  points  the  entire  surface  is  covered  by  the  fibres  of  origin 
of  the  Flexor  longus  hallucis  muscle.  At  about  the  middle  of  this  surface  is  the 
nutrient  foramen,  which  is  directed  downward. 

The  Lower  Extremity,  or  external  malleolus,  is  of  a  pyramidal  form,  somewhat 
flattened  from  without  inward,  and  is  longer,  and  descends  lower  than  the  internal 
malleolus.  Its  external  surface  is  convex,  subcutaneous,  and  continuous  with  the 
triangular  (also  subcutaneous)  surface  on  the  outer  side  of  the  shaft.  The  internal 
surface  presents  in  front  a  smooth  triangular  facet,  broader  above  than  below,  and 
convex  from  above  downward,  which  articulates  with  a  corresponding  surface  on 
the  outer  side  of  the  astragalus.  Behind  and  beneath  the  articular  surface  is  a 
rough  depression  which  gives  attachment  to  the  posterior  fasciculus  of  the  external 
lateral  ligament  of  the  ankle.  The  anterior  border  is  thick  and  rough,  and  marked 
below  by  a  depression  for  the  attachment  of  the  anterior  fasciculus  of  the  external 
lateral  ligament.  The  posterior  border  is  broad  and  marked  by  a  shallow  groove, 
for  the  passage  of  the  tendons  of  the  Peroneus  longus  and  brevis  muscles.  The 
summit  is  rounded,  and  gives  attachment  to  the  middle  fasciculus  of  the  external 
lateral  ligament. 

In  order  to  distinguish  the  side  to  which  the  bone  belongs,  hold  it  with  the 
lower  extremity  downward  and  the  broad  groove  for  the  Peronei  tendons  back- 
ward— i.  e.  toward  the  holder:  the  triangular  subcutaneous  surface  will  then  be 
directed  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  two  bones :  the  tibia  and  astragalus. 

Development. — By  three  centres  (Fig.  223) :  one  for  the  shaft,  and  one  for 
each  extremity.  Ossification  commences  in  the  shaft  about  the  eighth  week  of 
foetal  life,  a  little  later  than  in  the  tibia,  and  extends  gradually  toward  the 
extremities.  At  birth  both  ends  are  cartilaginous.  Ossification  commences  in 
the  lower  end  in  the  second  year,  and  in  the  upper  one  about  the  fourth  year. 
The  lower  epiphysis,  the  first  in  which  ossification  commences,  becomes  united  to 
the  shaft  about  the  twentieth  year;  the  upper  epiphysis  joins  about  the  twenty- 
fifth  year.  Ossification  appearing  first  in  the  lower  epiphysis  is  contrary  to  the 
rule  which  prevails  with  regard  to  the  commencement  of  ossification  in  epiphyses 
— viz.  that  that  epiphysis  toward  which  the  nutrient  artery  is  directed  commences 


THE    TARSUS:    THE    CALCANEUM. 


299 


Upper  extremity. 


Appears  about ^ 
4th  year. 


Unites  about 
25th  year. 


Appears  at 
2nd.  year. 


Unites  about 
20th  year. 


to  ossifv  last :  but  it  follows  the  rule  which  prevails  with  regard  to  the  union  of 
epiphyses,  by  uniting  first. 

Attachment  of  Muscles. — To  nine  :  to  the  head. 
the  Biceps,  Soleus.  and  Peroneus  longus ;  to  the 
shaft,  its  anterior  surface,  the  Extensor  longus  digi- 
torum,  Peroneus  tertius,  and  Extensor  proprius 
hallticis  ;  to  the  internal  surface,  the  Tibialis  pos- 
ticus  ;  to  the  posterior  surface,  the  Soleus  and  Flexor 
longus  hallucis  ;  to  the  external  surface,  the  Peroneus 
longus  and  brevis. 

Surface  Form. — The  only  parts  of  the  fibula  which  are 
to  be  felt  are  the  head  and  the  lower  part  of  the  external  sur- 
•>f  the  shaft  and  the  external  malleolus.  The  head  is  to 
be  seen  and  felt  behind  and  to  the  outer  side  of  the  outer 
tuberosity  of  the  tibia.  It  presents  a  small,  prominent 
triangular  eminence  slightly  above  the  level  of  the  tubercle 
of  the  tibia.  The  external  malleolus  presents  a  narrow  elon- 
gated prominence,  situated  on  a  plane  posterior  to  the  internal 
malleolus  and  reaching  to  a  lower  level.  From  it  may  be 
traced  the  lower  third  or  half  of  the  external  surface  of  the 
shaft  of  the  bone  in  the  interval  between  the  Peroneus  tertius 
in  front  and  the  other  two  Peronei  tendons  behind. 

Surgical  Anatomy. — In  fractures  of  the  bones  of  the 
letr  both  bones  are  usually  fractured,  but  each  bone  may  be 
broken  separately,  the  fibula  more  frequently  than  the  tibia. 
Fracture  of  both  bones  may  be  caused  either  by  direct  or  indirect 
violence.  When  it  occurs  from  indirect  force,  the  fracture  in 
the  tibia  is  at  the  junction  of  the  middle  and  lower  third  of 
the  bone.  Many  causes  conduce  to  render  this  the  weakest 
part  of  the  bone.  The  fracture  of  the  fibula  is  usually  at 
rather  a  higher  level.  These  fractures  present  great  variety. 
both  as  regards  their  direction  and  condition.  They  may  be 
oblique,  transverse,  longitudinal,  or  spiral.  When  oblique, 

they  are  usually  the  result  of  indirect  violence,  'and  the  direction  of  the  fracture  is  from  behind, 
downward,  forward,  and  inward  in  many  cases,  but  may  be  downward  and  outward  or  downward 
and  backward.  When  transverse,  the  fracture  is  often  at  the  upper  part  of  the  bone,  and  is  the 
result  of  direct  violence.  The  spiral  fracture  usually  commences  as  a  vertical  fissure,  involving 
the  ankle-joint,  and  is  associated  with  fracture  of  the  fibula  higher  up.  It  is  the  result  of  torsion, 
from  twisting  of  the  body  whilst  the  foot  is  fixed. 

Fractures  of  the  tibia  alone  are  almost  always  the  result  of  direct  violence,  except  where  the 
malleolus  is  broken  off  by  twists  of  the  foot.  Fractures  of  the  fibula  alone  may  arise  from 
indirect  or  direct  force,  those  of  the  lower  end  being  usually  the  result  of  the  former,  and  those 
higher  up  being  caused  by  a  direct  blow  on  the  part. 

The  tibia  and  fibula,  like  the  femur,  are  frequently  the  seat  of  acute  necrosis.  Chronic 
abscess  is  more  frequently  met  with  in  the  cancellous  tissue  of  the  head  and  lower  end  of  the 
tibia  than  in  any  other  bone  of  the  body.  The  abscess  is  of  small  size,  very  chronic,  and  the 
result  of  rarefying  osteitis  of  a  localized  portion  of  the  cancellous  tissue. 

The  tibia  is  the  bone  which  is  most  frequently  and  most  extensively  distorted  in  rickets.  It 
gives  way  at  tbe  junction  of  the  middle  and  lower  third,  its  weakest  part,  and  presents  a  curve 
forward  and  outward. 

THE  FOOT  (Figs.    224,    225). 

The  skeleton  of  the  Foot  consists  of  three  divisions :  the  Tarsus,  Metatarsus, 
and  Phalanges. 

The  Tarsus. 

The  bones  of  the  Tarsus  are  seven  in  number :  viz.  the  calcaneum  or  os  calcis, 
astragalus,  cuboid,  navicular.  internal,  middle,  and  external  cuneiform  bones. 


Lover  extremity. 

FIG.  223.— Plan  of  the  develop- 
ment of  the  fibula.  By  three  centres. 


The  Calcaneum. 

The  Calcaneum,  or  Os  Calcis  (<-alx.  the  heel),  is  the  largest  and  strongest  of  the 
tarsal  bones.  It  is  irregularly  cuboidal  in  form,  having  its  long  axis  directed 
forward  and  outward.  It  is  situated  at  the  lower  and  back  part  of  the  foot, 
serving  to  transmit  the  weight  of  the  body  to  the  ground,  and  forming  a  strong 


JOO 


THE   SKELETON. 


Groove  for  PERONEUS  LONQUS 


Groove  for  PERONEUS  BREVIS. 


PERONEUS    TERTIUS. 
PERONEUS    BREVIS. 


Groove  for  tendon  of 

FLEXOR    LONQUS    HALLUOIS. 


Tarsus. 


Metatarsus. 


Innermost  tendon  of 

EXTENSOR    BREVIS    DIQITORUk 


Phalanges. 


EXTENSOR    LONOUS    HALLUCIS. 


FIG.  224.— Bones  of  the  right  foot.    Dorsal  surface. 


THE    TARSUS:     THE    CALCANEUM.  301 

lever  for  the  muscles  of  the  calf.     It  presents  for  examination  six  surfaces: 
superior,  inferior,  external,  internal,  anterior,  and  posterior. 

The  superior  surface  is  formed  behind  by  the  upper  aspect  of  that  part  of  the 
os  calcis  which  projects  backward  to  form  the  heel.  It  varies  in  length  in  differ- 
ent individuals :  is  convex  from  side  to  side,  concave  from  before  backward,  and 
corresponds  above  to  a  mass  of  adipose  substance  placed  in  front  of  the  tendo 
Achillis.  In  the  middle  of  the  superior  surface  are  two  (sometimes  three)  articular 
facets,  separated  bv  a  broad  shallow  groove,  which  is  directed  obliquely  forward 
and  outward,  ana  is  rough  for  the  attachment  of  the  interosseous  ligament 
connecting  the  astragalus  and  os  calcis.  Of  the  two  articular  surfaces,  the  external 
is  the  larger,  and  situated  on  the  body  of  the  bone :  it  is  of  an  oblong  form,  wider 
behind  than  in  front,  and  convex  from  before  backward.  The  internal  articular 
surface  is  supported  on  a  projecting  process  of  bone,  called  the  lesser  process  of 
the  calcaneum  (svMentaculum  taK)  ;  it  is  also  oblong,  concave  longitudinally,  and 
sometimes  subdivided  into  two  parts,  which  differ  in  size  and  shape.  More 
anteriorly  is  seen  the  upper  surface  of  the  greater  process,  marked  by  a  rough 
depression  for  the  attachment  of  numerous  ligaments,  and  a  tubercle  for  the  origin 
of  the  Extensor  brevis  digitorum  muscle. 

The  inferior  surface  is  narrow,  rough,  uneven,  wider  behind  than  in  front 
and  convex  from  side  to  side ;  it  is  bounded  posteriorly  by  two  tubercles  separated 
by  a  rough  depression ;  the  external,  small,  prominent,  and  rounded,  gives  attach- 
ment to  part  of  the  Abductor  minimi  digiti :  the  internal,  broader  and  larger,  for 
the  support  of  the  heel,  gives  attachment,  by  its  prominent  inner  margin,  to  the 
Abductor  hallucis,  and  in  front  to  the  Flexor  brevis  digitorum  muscles ;  the 
depression  between  the  tubercles  gives  attachment  to  the  Abductor  minimi  digiti 
and  plantar  fascia.  The  rough  surface  in  front  of  the  tubercles  gives  attachment 
to  the  long  plantar  ligament  and  to  the  outer  head  of  the  Flexor  accessorius 
muscle :  and  to  a  prominent  tubercle  nearer  the  anterior  part  of  this  surface,  as 
well  as  to  a  transverse  groove  in  front  of  it.  is  attached  the  short  plantar  liga- 
ment. 

The  external  surface  is  broad,  flat,  and  almost  subcutaneous ;  it  presents  near 
its  centre  a  tubercle,  for  the  attachment  of  the  middle  fasciculus  of  the  external 
lateral  ligament.  At  its  upper  and  anterior  part  this  surface  gives  attachment  to 
the  external  calcaneo-astragaloid  ligament ;  and  in  front  of  the  tubercle  it  presents 
a  narrow  surface  marked  by  two  oblique  grooves,  separated  by  an  elevated  ridge 
which  varies  much  in  size  in  different  bones ;  it  is  named  the  peroneal  ridge,  and 
gives  attachment  to  a  fibrous  process  from  the  external  annular  ligament.  The 
xuf'/rior  ciro'jct-  transmits  the  tendon  of  the  Peroneus  brevis  ;  the  inferior,  the 
tendon  of  the  Peroneus  longus. 

The  internal  surface  presents  a  deep  concavity,  directed  obliquely  downward 
and  forward,  for  the  transmission  of  the  plantar  vessels  and  nerves  into  the  sole 
of  the  foot ;  it  affords  attachment  to  part  of  the  Flexor  accessorius  muscle.  This 
surface  presents  an  eminence  of  bone,  the  lesser  process  or  sustentaculum  tali, 
which  projects  horizontally  inward  from  its  upper  and  fore  part,  and  to  which  a 
slip  of  the  tendon  of  the  Tibialis  posticus  is  attached.  This  process  is  concave 
above,  and  supports  the  anterior  articular  surface  of  the  astragalus ;  below,  it  is 
grooved  for  the  tendon  of  the  Flexor  longus  hallucis.  Its  free  margin  is  rough, 
for  the  attachment  of  part  of  the  internal  lateral  ligament  of  the  ankle-joint. 

The  anterior  surface,  of  a  somewhat  triangular  form,  articulates  with  the 
cuboid.  It  is  concave  from  above  downward  and  outward,  and  convex  in  the 
opposite  direction.  Its  inner  border  gives  attachment  to  the  inferior  calcaneo- 
navicular  ligament. 

The  posterior  surface  is  rough,  prominent,  convex,  and  wider  below  than  above. 
Its  lower  part  is  rough,  for  the  attachment  of  the  tendo  Achillis  and  of  the  Plan- 
taris  muscle :  its  upper  part  is  smooth,  and  is  covered  by  a  bursa  which  separates 
the  tendon  from  the  bone. 

Articulations. — With  two  bones :  the  astragalus  and  cuboid. 


302 


THE   SKELETON. 


ABDUCTOR    HALLUCIS. 


OUTER    HEAD    OF    ACCESSORIES 


FLEXOR    BREVIS    HALLUCIS 


Tubercle  of 
navicular. 


TIBIALIS    ANTICUS 


Two 

sesamoid 
bones. 


FLEXOR    BREVIS 

and  ABDUCTOR 

MINIMI    DIGIT1. 


FLEXOR    BREVIS    DIGlTORUM. 


FLEXOR    LONGUS    DIQITORUM. 


FIG.  225.— Bones  of  the  right  foot.    Plantar  surface. 

Attachment  of  Muscles. — To   eight :   part  of  the  Tibialis  posticus,  the  tendo 


THE    TARSUS:    THE   ASTRAGALUS,   THE   CUBOID.  303 

Achillis,  Plantaris,  Abductor  hallucis,  Abductor  minimi  digiti,  Flexor  brevis  digi- 
torum,  Flexor  accessorius,  and  Extensor  brevis  digitorum. 

The  Astragalus. 

The  Astragalus  (d0rpdyaJio<;,  a  die)  is  the  largest  of  the  tarsal  bones,  next  to 
the  os  calcis.  It  occupies  the  middle  and  upper  part  of  the  tarsus,  supporting  the 
tibia  above,  articulating  with  the  malleoli  on  either  side,  resting  below  upon  the 
os  calcis,  and  joined  in  front  to  the  navicular.  This  bone  may  easily  be  recognized 
by  its  large  rounded  head,  by  the  broad  articular  facet  on  its  upper  convex  surface, 
or  by  the  two  articular  facets  separated  by  a  deep  groove  on  its  under  concave 
surface.  It  presents  six  surfaces  for  examination. 

The  superior  surface  presents,  behind,  a  broad  smooth  trochlear  surface  for 
articulation  with  the  tibia.  The  trochlea  is  broader  in  front  than  behind,  convex 
from  before  backward, slightly  concave  from  side  to  side  ;  in  front  of  it  is  the  upper 
surface  of  the  neck  of  the  astragalus,  rough  for  the  attachment  of  ligaments. 
The  inferior  surface  presents  two  articular  facets  separated  by  a  deep  groove. 
The  groove  runs  obliquely  forward  and  outward,  becoming  gradually  broader 
and  deeper  in  front :  it  corresponds  with  a  similar  groove  upon  the  upper  surface 
of  the  os  calcis,  and  forms,  when  articulated  with  that  bone,  a  canal,  fille'd  up  in 
the  recent  state  by  the  interosseous  calcaneo-astragaloid  ligament.  Of  the  two 
articular  facets,  the  posterior  is  the  larger,  of  an  oblong  form  and  deeply  concave 
from  side  to  side  ;  the  anterior,  although  nearly  of  equal  length,  is  narrower,  of  an 
elongated  oval  form,  convex  longitudinally,  and  often  subdivided  into  two  by  an 
elevated  ridge ;  of  these,  the  posterior  articulates  with  the  lesser  process  of  the  os 
calcis  ;  the  anterior,  with  the  upper  surface  of  the  inferior  calcaneo-navicular  liga- 
ment. The  internal  surface  presents  at  its  upper  part  a  pear-shaped  articular  facet 
for  the  inner  malleolus,  continuous  above  with  the  trochlear  surface ;  below  the 
articular  surface  is  a  rough  depression,  for  the  attachment  of  the  deep  portion  of 
the  internal  lateral  ligament.  The  external  surface  presents  a  large  triangular 
facet,  concave  from  above  downward  for  articulation  with  the  external  malleolus ; 
it  is  continuous  above  with  the  trochlear  surface ;  and  in  front  of  it  is  a  rough 
depression  for  the  attachment  of  the  anterior  fasciculus  of  the  external  lateral 
ligament  of  the  ankle-joint.  The  anterior  surface,  convex  and  rounded,  forms 
the  head  of  the  astragalus ;  it  is  smooth,  of  an  oval  form,  and  directed  obliquely 
inward  and  downward;  it  articulates  with  the  navicular.  On  its  under  surface  is 
a  small  facet,  continuous  in  front  with  the  articular  surface  of  the  head,  and 
behind  with  the  smaller  facet  for  the  os  calcis.  This  rests  on  the  inferior  calcaneo- 
navicular  ligament,  being  separated  from  it  by  the  synovial  membrane,  which  is 
prolonged  from  the  anterior  calcaneo-astragaloid  joint  to  the  astragalo-navicular 
joint.  The  head  is  surrounded  by  a  constricted  portion,  the  neck  of  the  astragalus. 
The  posterior  surface  is  narrow,  and  traversed  by  a  groove,  which  runs  obliquely 
downward  and  inward,  and  transmits  the  tendon  of  the  Flexor  longus  hallucis, 
external  to  which  is  a  prominent  tubercle,  to  which  the  posterior  fasciculus  of  the 
external  lateral  ligament  is  attached.  To  the  inner  side  of  the  groove  is  a  second, 
but  less  marked  tubercle. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  broad  articular 
surface  upward,  and  the  rounded  head  forward ;  the  lateral  triangular  articular 
surface  for  the  external  malleolus  will  then  point  to  the  side  to  which  the  bone 
belongs. 

Articulations. — With  four  bones :  tibia,  fibula,  os  calcis,  and  navicular. 

The  Cuboid. 

The  Cuboid  (xyySoc,  a  cube ;  doo^.  like)  bone  is  placed  on  the  outer  side  of 
the  foot,  in  front  of  the  os  calcis,  and  behind  the  fourth  and  fifth  metatarsal  bones. 
It  is  of  a  pyramidal  shape,  its  base  being  directed  upward  and  inward,  its  apex 
downward  and  outward.  It  may  be  distinguished  from  the  other  tarsal  bones  by 


304  THE  SKELETON. 

the  existence  of  a  deep  groove  on  its  under  surface,  for  the  tendon  of  the  Peroneus 
longus  muscle.  It  presents  for  examination  six  surfaces :  three  articular  and 
three  non-articular. 

The  non-articular  surfaces  are  the  superior,  inferior,  and  external.  The 
superior  or  dorsal  surface,  directed  upward  and  outward,  is  rough,  for  the  attach- 
ment of  numerous  ligaments.  The  inferior  or  plantar  surface  presents  in  front  a 
deep  groove,  which  runs  obliquely  from  without,  forward  and  inward  ;  it  lodges 
the  tendon  of  the  Peroneus  longus,  and  is  bounded  behind  by  a  prominent  ridge, 
to  which  is  attached  the  long  calcaneo-cuboid  ligament.  The  ridge  terminates 
externally  in  an  eminence,  the  tuber osity  of  the  cuboid,  the  surface  of  which 
presents  a  convex  facet,  for  articulation  with  the  sesamoid  bone  of  the  tendon 
contained  in  the  groove.  The  surface  of  bone  behind  the  groove  is  rough,  for  the 
attachment  of  the  short  plantar  ligament,  a  few  fibres  of  the  Flexor  brevis  hallucis, 
and  a  fasciculus  from  the  tendon  of  the  Tibialis  posticus.  The  external  surface, 
the  smallest  and  narrowest  of  the  three,  presents  a  deep  notch  formed  by  the 
commencement  of  the  peroneal  groove. 

The  articular  surfaces  are  the  posterior,  anterior,  and  internal.  The  posterior 
surface  is  smooth,  triangular,  and  concavo-convex,  for  articulation  with  the 
anterior  surface  of  the  os  calcis.  The  anterior,  of  smaller  size,  but  also  irregu- 
larly triangular,  is  divided  by  a  vertical  ridge  into  two  facets :  the  inner  one, 
quadrilateral  in  form,  articulates  with  the  fourth  metatarsal  bone ;  the  outer  one, 
larger  and  more  triangular,  articulates  with  the  fifth  metatarsal.  The  internal 
surface  is  broad,  rough,  irregularly  quadrilateral,  presenting  at  its  middle  and 
upper  part  a  smooth  oval  facet,  for  articulation  with  the  external  cuneiform  bone ; 
and  behind  this  (occasionally)  a  smaller  facet,  for  articulation  with  the  navic- 
ular ;  it  is  rough  in  the  rest  of.  its  extent,  for  the  attachment  of  strong  interosseous 
ligaments. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  so  that  its  under  surface, 
marked  by  the  peroneal  groove,  looks  dowrnward,  and  the  large  concavo-convex 
articular  surface  backward  toward  the  holder :  the  narrow  non-articular  surface, 
marked  by  the  commencement  of  the  peroneal  groove,  will  point  to  the  side  to 
which  the  bone  belongs. 

Articulations. — With  four  bones :  the  os  calcis,  external  cuneiform,  and  the 
fourth  and  fifth  metatarsal  bones ;  occasionally  with  the  navicular. 

Attachment  of  Muscles. — Part  of  the  Flexor  brevis  hallucis  and  a  slip  from 
the  tendon  of  the  Tibialis  posticus. 

The  Navicular. 

The  Navicular  or  Scaphoid  bone  is  situated  at  the  inner  side  of  the  tarsus, 
between  the  astragalus  behind  and  the  three  cuneiform  bones  in  front.  It 
may  be  distinguished  by  its  form,  being  concave  behind,,  convex  and  subdivided 
into  three  facets  in  front. 

The  anterior  surface,  of  an  oblong  form,  is  convex  from  side  to  side,  and  sub- 
divided by  two  ridges  into  three  facets,  for  articulation  with  the  three  cuneiform 
bones.  The  posterior  surface  is  oval,  concave,  broader  externally  than  internally, 
and  articulates  with  the  rounded  head  of  the  astragalus.  The  superior  surface  is 
convex  from  side  to  side,  and  rough  for  the  attachment  of  ligaments.  The 
inferior  is  irregular,  and  also  rough  for  the  attachment  of  ligaments.  The  internal 
surface  presents  a  rounded  tubercular  eminence,  the  tuberosity  of  the  navicular, 
the  lower  part  of  which  projects,  and  gives  attachment  to  part  of  the  tendon  of 
the  Tibialis  posticus.  The  external  surface  is  rough  and  irregular,  for  the 
attachment  of  ligamentous  fibres,  and  occasionally  presents  a  small  facet  for 
articulation  with  the  cuboid  bone. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  concave  articular 
surface  backward,  and  the  convex  dorsal  surface  upward ;  the  external  surface — 
i.  e.  the  surface  opposite  the  tubercle — will  point  to  the  side  to  which  the  bone 
belongs. 


THE    CUNEIFORM  BOXES.  305 

Articulations. — With  four  bones :  astragalus  and  three  cuneiform  ;  occasionally 
als<>  with  the  cuboid. 

Attachment  of  Muscles. — Pan  of  the  Tibialis  posticus. 

The  Cuneiform  Bones. 

The  Cuneiform  Bones  have  received  their  name  from  their  wedge-like  shape 

;i  wedge :  /«/•//"/.  likeness).     They  form,   with  the  cuboid,   the  anterior 

m w  of  the  tarsus,  being  placed  between  the  navicular  behind,  the  three  innermost 

metatarsal  bones  in  front,  and  the  cuboid  externally.     They  are  called  the  first^ 

'.  and  third,  counting  from  the  inner  to  the  outer  side  of  the  foot,  and, 

from  their  position.  internal,  inlddb:.  and  external. 

The  Internal  Cuneiform  is  the  largest  of  the  three.  It  is  situated  at  the  inner 
side  of  the  foot,  between  the  navicular  behind  and  the  base  of  the  first  metatarsal 
in  front.  It  may  be  distinguished,  from  the  other  two  by  its  large  size,  and  its 
more  irregular,  wedge-like  form.  Without  the  others,  it  may  be  known  by  the 
large  kidney-shaped  anterior  articulating  surface  and  by  the  prominence  on  the 
inferior  or  plantar  surface  for  the  attachment  of  the  Tibialis  posticus.  It  presents 
f»r  examination  six  surfaces. 

The  internal  surface  is  subcutaneous,  and  forms  part  of  the  inner  border  of  the 

:  it  is  broad,  quadrilateral,  and  presents  at  its  anterior  inferior  angle  a  smooth 
oval  facet,  into  which  the  tendon  of  the  Tibialis  anticus  is  partially  inserted ;  in 
the  rest  of  its  extent  it  is  rough,  for  the  attachment  of  ligaments.  The  external 
•••'•  is  concave,  presenting,  along  its  superior  and  posterior  borders,  a  narrow 
reversed  L-shaped  surface  for  articulation  with  the  middle  cuneiform  behind,  and 
second  metatarsal  bone  in  front;  in  the  rest  of  its  extent  it  is  rough  for  the 
attachment  of  ligaments  and  part  of  the  tendon  of  the  Peroneus  longus.  The 
•/,-,/•  xurf'.t'--' ••:•.  kidney-shaped,  much  larger  than  the  posterior,  articulates  with 
the  metatarsal  bone  of  the  great  toe.  Tbepotterior  surface  is  triangular,  concave* 
and  articulates  with  the  innermost  and  largest  of  the  three  facets  on  the  anterior 
surface  of  the  navicular.  The  inferior  or  plantar  surface  is  rough,  and  presents  a 
prominent  tuberosity  at  its  back  part  for  the  attachment  of  part  of  the  tendon  of 
the  Tibialis  posticus.  It  also  gives  attachment  in  front  to  part  of  the  tendon  of  the 
the  Tibialis  anticus.  The  sup^ri"i-  surface  is  the  narrow-pointed  end  of  the  wedge, 
which  is  directed  upward  and  outward  ;  it  is  rough  for  the  attachment  of  ligaments. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  so  that  its  superior  narrow 
edge  looks  upward,  and  the  long,  kidney-shaped,  articular  surface  forward ;  the 
external  surface,  marked  by  its  vertical  and  horizontal  articular  facets,  will  point 
to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones :  navicular,  middle  cuneiform,  first  and  second 
metatarsal  bones. 

Attachment  of  Muscles. — To  three :  the  Tibialis  anticus  and  posticus.  and 
Peroneus  longus. 

The  Middle  Cuneiform,  the  smallest  of  the  three,  is  of  very  regular  wedge-like 
form,  the  broad  extremity  being  placed  upward,  the  narrow  end  downward.  It 
is  situated  between  the  other  two  bones  of  the  same  name,  and  articulates  with 
the  navicular  behind  and  the  second  metatarsal  in  front.  It  may  be  distinguished 
from  the  external  cuneiform  bone,  which  it  much  resembles  in  general  appearance, 
by  the  articular  facet,  of  angular  form,  which  runs  round  the  upper  and  back  part 
of  its  inner  surface :  and  if  the  two  bones  from  the  same  foot  are  together,  the 
middle  cuneiform  is  much  the  smaller. 

The  anteri'n'  .>-///;f'./o ;•.  triangular  in  form  and  narrower  than  the  posterior, 
articulates  with  the  base  of  the  second  metatarsal  bone.  The  posterior  surface, 
als<>  triangular,  articulates  with  the  navicular.  The  internal  surface  presents  a 
reversed  L-shaped  articular  facet,  running  along  the  superior  and  posterior  borders, 
for  articulation  with  the  internal  cuneiform,  and  is  rough  in  the  rest  of  its  extent 
for  the  attachment  of  ligaments.  The  external  surface  presents  posteriorly  a 
smooth  facet  for  articulation  with  the  external  cuneiform  bone.  The  sup- 

20 


306  THE  SKELETON. 

surface,  forms  the  base  of  the  wedge ;  it  is  quadrilateral,  broader  behind  than  in 
front,  and  rough  for  the  attachment  of  ligaments.  The  inferior  surface,  pointed 
and  tubercular,  is  also  rough  for.  ligamentous  attachment  and  for  the  insertion  of 
a  slip  from  the  tendon  of  the  Tibialis  posticus. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  its  superior  or  dorsal  surface 
upward,  the  broadest  edge  being  toward  the  holder :  the  smooth  facet  (limited 
to  the  posterior  border)  will  then  point  to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones :  navicular,  internal  and  external  cuneiform, 
and  second  metatarsal  bone. 

Attachment  of  Muscles. — A  slip  from  the  tendon  of  the  Tibialis  posticus  is 
attached  to  this  bone. 

The  External  Cuneiform,  intermediate  in  size  between  the  two  preceding,  is 
of  a  very  regular  wedge-like  form,  the  broad  extremity  being  placed  upward,  the 
narrow  end  downward.  It  occupies  the  centre  of  the  front  row  of  the  tarsus 
between  the  middle  cuneiform  internally,  the  cuboid  externally,  the  navicular 
behind,  and  the  third  metatarsal  in  front.  It  is  distinguished  from  the  internal 
cuneiform  bone  by  its  more  regular  wedge-like  shape  and  by  the  absence  of  the 
kidney-shaped  articular  surface  :  from  the  middle  cuneiform,  by  the  absence  of  the 
reversed  L-shaped  facet,  and  by  the  two  articular  facets  which  are  present  on  both 
its  inner  and  outer  surfaces.  It  has  six  surfaces  for  examination. 

The  anterior  surface,  triangular  in  form,  articulates  with  the  third  metatarsal 
bone.  The  posterior  surface  articulates  with  the  most  external  facet  of  the 
navicular,  and  is  rough  below  for  the  attachment  of  ligamentous  fibres.  The 
internal  surface  presents  two  articular  facets,  separated  by  a  rough  depression ; 
the  anterior  one,  sometimes  divided  into  two,  articulates  with  the  outer  side  of  the 
base  of  the  second  metatarsal  bone;  the  posterior  one  skirts  the  posterior  border 
and  articulates  with  the  middle  cuneiform ;  the  rough  depression  between  the  two 
gives  attachment  to  an  interosseous  ligament.  The  external  surface  also  presents 
two  articular  facets,  separated  by  a  rough  non-articular  surface ;  the  anterior  facet, 
situated  at  the  superior  angle  of  the  bone,  is  small,  and  articulates  with  the  inner 
side  of  the  base  of  the  fourth  metatarsal ;  the  posterior  and  larger  one  articulates 
with  the  cuboid ;  the  rough,  non-articular  surface  serves  for  the  attachment  of  an 
interosseous  ligament.  The  three  facets  for  articulation  with  the  three  metatarsal 
foones  are  continuous  with  one  another,  and  covered  by  a  prolongation  of  the  same 
cartilage ;  the  facets  for  articulation  with  the  middle  cuneiform  and  navicular  are 
also  continuous,  but  that  for  articulation  with  the  cuboid  is  usually  separate.  The 
superior  or  dorsal  surface  is  of  an  oblong  square  form,  its  posterior  external  angle 
being  prolonged  backward.  The  inferior  or  plantar  surface  is  an  obtuse  rounded 
margin,  and  serves  for  the  attachment  of  part  of  the  tendon  of  the  Tibialis  posticus, 
part  of  the  Flexor  brevis  hallucis,  and  ligaments. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  broad  dorsal 
surface  upward,  the  prolonged  edge  backward ;  the  separate  articular  facet  for 
the  cuboid  will  point  to  the  proper  side. 

Articulations. — With  six  bones :  the  navicular,  middle  cuneiform,  cuboid,  and 
second,  third,  and  fourth  metatarsal  bones. 

Attachment  of  Muscles. — To  two:  part  of  the  Tibialis  posticus,  and  Flexor 
brevis  hallucis. 

The  Metatarsal  Bones. 

The  Metatarsal  Bones  are  five  in  number ;  they  are  long  bones,  and  present  for 
examination  a  shaft  and  two  extremities. 

Common  Characters. — The  shaft  is  prismoid  in  form,  tapers  gradually  from  the 
tarsal  to  the  phalangeal  extremity,  and  is  slightly  curved  longitudinally,  so  as  to 
be  concave  below,  slightly  convex  above.  The  posterior  extremity,  or  base,  is 
wedge-shaped,  articulating  by  its  terminal  surface  with  the  tarsal  bones,  and  by 
its  lateral  surfaces  with  the  contiguous  metatarsal  bones,  its  dorsal  and  plantar 
surfaces  being  rough  for  the  attachment  of  ligaments.  The  anterior  extremity, 


'    THE   METATARSAL    BOXES.  307 

or  />ead,  presents  a  terminal  rounded  articular  surface,  oblong  from  above 
downward  and  extending  farther  backward  below  than  above.  Its  sides  are 
flattened,  and  present  a  depression,  surmounted  by  a  tubercle,  for  ligamentous 
attachment.  Its  under  surface  is  grooved  in  the  middle  line  for  the  passage  of 
the  Flexor  tendon,  and  marked  on  each  side  by  an  articular  eminence  continuous 
with  the  terminal  articular  surface. 

Peculiar  Characters. — The  First  is  remarkable  for  its  great  thickness,  but  is  the 
shortest  of  all  the  inetatarsal  bones.  The  shaft  is  strong  and  of  well-marked  pris- 
moid  form.  The  posterior  extremity  presents  at  times  a  lateral  articular  facet  for 
the  second  metatarsal :  its  terminal  articular  surface  is  of  large  size,  kidney-shaped; 
its  circumference  is  grooved,  for  the  tarso-metatarsal  ligaments,  and  internally  gives 
attachment  to  part  of  the  tendon  of  the  Tibialis  anticus  :  its  inferior  angle  presents 
a  rough  oval  prominence  for  the  insertion  of  the  tendon  of  the  Peroneus  longus. 
The  head  is  of  large  size:  on  its  plantar  surface  are  two  grooved  facets,  over  which 
glide  sesamoid  bones ;  the  facets  are  separated  by  a  smooth  elevated  ridge. 

This  bone  is  known  by  the  single  kidney-shaped  articular  surface  on  its  base, 
the  deeply  grooved  appearance  of  the  plantar  surface  of  its  head,  and  its  great 
thickness  relatively  to  its  length.  AVhen  it  is  placed  in  its  natural  position,  the 
concave  border  of  the  kidney-shaped  articular  surface  on  its  base  points  to  the  side 
to  which  the  bone  belongs. 

The  Second  is  the  longest  and  largest  of  the  remaining  metatarsal  bones,  being 
prolonged  backward  into  the  recess  formed  between  the  three  cuneiform  bones. 
Its  tar  sal  extremity  is  broad  above,  narrow  and  rough  below.  It  presents  four 
articular  surfaces :  one  behind,  of  a  triangular  form,  for  articulation  with  the 
middle  cuneiform ;  one  at  the  upper  part  of  its  internal  lateral  surface,  for  articu- 
lation with  the  internal  cuneiform :  and  two  on  its  external  lateral  surface,  a 
posterior  and  anterior,  separated  by  a  vertical  ridge.  Each  of  these  external 
articular  surfaces  is  divided  by  a  rough  depression  into  two  parts ;  the  two 
anterior  facets  articulate  with  the  third  metatarsal ;  the  two  posterior  (sometimes 
continuous)  with  the  external  cuneiform.  Occasionally,  in  front  of  and  below 
the  facet  for  the  internal  cuneiform,  is  found  an  indistinct  facet  for  the  first 
metatarsal. 

The  facets  on  the  tarsal  extremity  of  the  second  metatarsal  bone  serve  at  once 
to  distinguish  it  from  the  rest,  and  to  indicate  the  foot  to  which  it  belongs.  The 
fact  that  the  two  posterior  subdivisions  of  the  external  facets  sometimes  run  into 
one  should  not  be  forgotten. 

The  Third  articulates  behind,  by  means  of  a  triangular  smooth  surface,  with 
the  external  cuneiform ;  on  its  inner  side,  by  two  facets,  with  the  second  meta- 
tarsal :  and  on  its  outer  side,  by  a  single  facet,  with  the  fourth  metatarsal.  The 
latter  facet  is  of  circular  form  and  situated  at  the  upper  angle  of  the  base. 

The  third  metatarsal  is  known  by  its  having  at  its  tarsal  end  two  undivided 
facers  on  the  inner  side,  and  a  single  facet  on  the  outer.  This  distinguishes  it  from 
the  second  metatarsal.  in  which  the  two  facets,  found  on  one  side  of  its  tarsal  end, 
are  each  subdivided  into  two.  The  single  facet  (when  the  bone  is  put  in  its  natural 
position)  is  on  the  side  to  which  the  bone  belongs. 

The  Fourth  is  smaller  in  size  than  the  preceding ;  its  tarsal  extremity  presents 
a  terminal  quadrilateral  surface,  for  articulation  with  the  cuboid  ;  a  smooth  facet  on 
the  inner  side,  divided  by  a  ridge  into  an  anterior  portion  for  articulation  with  the 
third  metatarsal,  and  a  posterior  portion  for  articulation  with  the  external  cunei- 
form ;  on  the  outer  side  a  single  facet,  for  articulation  with  the  fifth  metatarsal. 

The  fourth  metatarsal  is  known  by  its  having  a  single  facet  on  either  side  of 
the  tarsal  extremity,  that  on  the  inner  side  being  divided  into  two  parts.  If  this 
subdivision  be  not  recognizable,  the  fact  that  its  tarsal  end  is  bent  somewhat 
outward  will  indicate  the  side  to  which  it  belongs. 

The  Fifth  is  recognized  by  the  tubercular  eminence  on  the  outer  side  of  its 
base.  It  articulates  behind,  by  a  triangular  surface  cut  obliquely  from  without 
inward,  with  the  cuboid,  and  internallv  with  the  fourth  metatarsal. 


308  THE   SKELETON.  , 

The  projection  on  the  outer  side  of  this  bone  at  its  tarsal  end  at  once  distin- 
guishes it  from  the  others,  and  points  to  the  side  to  which  it  belongs. 

Articulations. — Each  bone  articulates  with  the  tarsal  bones  by  one  extremity, 
and  by  the  other  with  the  first  row  of  phalanges.  The  number  of  tarsal  bones 
with  which  each  metatarsal  articulates  is  one  for  the  first,  three  for  the  second,  one 
for  the  third,  two  for  the  fourth,  and  one  for  the  fifth. 

Attachment  of  Muscles. — To  the  first  metatarsal  bone,  three  :  part  of  the 
Tibialis  anticus,  the  Peroneus  longus,  and  First  dorsal  interosseous.  To  the 
second,  four  :  the  Adductor  obliquus  hallucis  and  First  and  Second  dorsal  inter- 
osseous,  and  a  slip  from  the  tendon  of  the  Tibialis  posticus,  and  occasionally  a  slip 
from  the  Peroneus  longus.  To  the  third,  five :  the  Adductor  obliquus  hallucis, 
Second  and  Third  dorsal,  and  First  plantar  interosseous,  and  a  slip  from  the 
tendon  of  the  Tibialis  posticus.  To  the  fourth,  five :  the  Adductor  obliquus  hallucis, 
Third  and  Fourth  dorsal,  and  Second  plantar  interosseous,  and  a  slip  from  the 
tendon  of  the  Tibialis  posticus.  To  the  fifth,  six  :  the  Peroneus  brevis,  Peroneus 
tertius,  Flexor  brevis  minimi  digiti,  Adductor  transversus  hallucis,  Fourth  dorsal, 
and  Third  plantar  interosseous. 

The  Phalanges. 

The  Phalanges  of  the  foot,  both  in  number  and  general  arrangement,  resemble 
those  in  the  hand ;  there  being  two  in  the  great  toe  and  three  in  each  of  the  other 
toes. 

The  phalanges  of  the  first  row  resemble  closely  those  of  the  hand.  The  shaft 
is  compressed  from  side  to  side,  convex  above,  concave  below.  The  posterior 
extremity  is  concave ;  and  the  anterior  extremity  presents  a  trochlear  surface,  for 
articulation  with  the  second  phalanges. 

The  phalanges  of  the  second  row  are  remarkably  small  and  short,  but  rather 
broader  than  those  of  the  first  row. 

The  ungual  phalanges  in  form  resemble  those  of  the  fingers  ;  but  they  are 
smaller,  flattened  from  above  downward,  presenting  a  broad  base  for  articulation 
with  the  second  row,  and  an  expanded  extremity  for  the  support  of  the  nail  and 
end  of  the  toe. 

Articulation. — The  first  row,  with  the  metatarsal  bones  behind  and  second 
phalanges  in  front ;  the  second  row  of  the  four  outer  toes,  with  the  first  and  third 
phalanges ;  of  the  great  toe,  with  the  first  phalanx ;  the  third  row  of  the  four 
outer  toes,  with  the  second  phalanges. 

Attachment  of  Muscles. — To  the  first  phalanges.  Great  toe,  five  muscles : 
innermost  tendon  of  Extensor  brevis  digitorum,  Abductor  hallucis,  Adductor 
obliquus  hallucis,  Flexor  brevis  hallucis,  Adductor  transversus  hallucis.  Second 
toe,  three  muscles :  First  and  Second  dorsal  interosseous  and  First  lumbrical. 
Third  toe,  three  muscles  :  Third  dorsal  and  First  plantar  interosseous  and  Second 
lumbrical.  Fourth  toe,  three  muscles  :  Fourth  dorsal  and  Second  plantar  inter- 
osseous and  Third  lumbrical.  Fifth  toe,  four  muscles  :  Flexor  brevis  minimi 
digiti,  Abductor  minimi  digiti,  and  Third  plantar  interosseous,  and  Fourth 
lumbrical. — Second  phalanges.  Great  toe;  Extensor  longus  hallucis,  Flexor 
longus  hallucis.  Other  toes ;  Flexor  brevis  digitorum,  one  slip  of  the  common 
tendon  of  the  Extensor  longus  and  brevis  digitorum.1 — Third  phalanges  :  two  slips 
from  the  common  tendon  of  the  Extensor  longus  and  Extensor  brevis  digitorum, 
and  the  Flexor  longus  digitorum. 

Development  of  the  Foot  (Fig.  226). 

The  Tarsal  bones  are  each  developed  by  a  single  centre,  excepting  the  os  calcis, 
which  has  an  epiphysis  for  its  posterior  extremity.  The  centres  make  their  appear- 
ance in  the  following  order :  os  calcis,  at  the  sixth  month  of  foetal  life  ;  astragalus, 

1  Except  the  second  phalanx  of  the  fifth  toe,  which  receives  no  slip  from  the  Extensor  brevis 
digitorum. 


OF    THE   FOOT  AS   A    WHOLE. 


309 


about  the  seventh  month  :  cuboid,  at  the  ninth  month  ;  external  cuneiform, 
during  the  first  year  :  internal  cuneiform  in  the  third  year  ;  middle  cuneiform  and 
navicular  in  the  fourth  year.  ,  The  epiphysis  for  the  posterior  tuberosity  of 


ysis. 


Appears  10th  year  ; 

unites  after  puberty. 


Tarsus. 

One  centre  /or  each  bone, 
except  os  colds. 


Metatarsus. 

Tiro  centres  for  each  bone: 
One  for  shaft. 
One  for  digital  extremity 
except  1st. 


Appears  5th  year. 
Unite  18th-20  year. 

Appears  7th  week. 


Appears  7th  week. 

Unite  18th-gOth  year. 
Appears  3rd  year. 

Appears  4^h  year. 
Unite  17-18th  year. 

Phalanges.    Appears  2nd-4th  month.-l 
Two  centres  for  each  bone : 
One  for  shaft, 

One  for  metatarsal      Appears  6th-7th  year, 
extremity.  {-,„•/,,  27th-18th  year.  I 

Appears  2nd- 4th  month. 

Appears  6th  year. 

Unite  17th-18th  year. 

Appears  7th  ireek. 

FIG.  226.— Plan  of  the  development  of  the  foot 

the  os  calcis  appears  at  the  tenth  year,  and  unites  with  the  rest  of  the  bone  soon 
after  puberty. 

The  Metatarsal  bones  are  each  developed  by  two  centres :  one  for  the  shaft 
and  one  for  the  digital  extremity  in  the  four  outer  metatarsal ;  one  for  the  shaft 
and  one  for  the  base  in  the  metatarsal  bone  of  the  great  toe.1  Ossification 
commences  in  the  centre  of  the  shaft  about  the  ninth  week,  and  extends  toward 
either  extremity.  The  centre  in  the  proximal  end  of  the  first  metatarsal  bone 
appears  about  the  third  year,  the  centre  in  the  distal  end  of  the  other  bones 
between  the  fifth  and  eighth  years;  they  become  joined  between  the  eighteenth  and 
twentieth  years. 

The  Phalanges  are  developed  by  tico  centres  for  each  bone :  one  for  the  shaft 
and  one  for  the  metatarsal  extremity. 

Construction  of  the  Foot  as  a  Whole. 

The  foot  is  constructed  on  the  same  principles  as  the  hand,  but  modified  to 
form  a  firm  basis  of  support  for  the  rest  of  the  body  when  in  the  erect  position.  It 

1  As  was  noted  in  the  first  metacarpal  bone,  so  in  the  first  metatarsal,  there  is  often  to  be  observed 
a  tendency  to  the  formation  of  a  second  epiphysis  in  the  distal  extremity.  (See  footnote,  p.  274). 


310  THE  SKELETON. 

is  more  solidly  constructed,  and  its  component  parts  are  less  movable  on  each  other 
than  in  the  hand.  This  is  especially  the  case  with  the  great  toe,  which  has  to 
assist  in  supporting  the  body,  and  is  therefore  constructed  with  greater  solidity ;  it 
lies  parallel  with  the  other  toes,  and  has  a  very  limited  degree  of  mobility,  whereas 
the  thumb,  which  is  occupied  in  numerous  and  varied  movements,  is  constructed 
in  such  a  manner  as  to  permit  of  great  mobility.  Its  metacarpal  bone  is  directed 
away  from  the  others,  so  as  to  form  an  acute  angle  with  the  second,  and  it  enjoys- 
a  considerable  range  of  motion  at  its  articulation  with  the  carpus.  The  foot  is 
placed  at  right  angles  to  the  leg — a  position  which  is  almost  peculiar  to  man,  and 
has  relation  to  the  erect  position  which  he  maintains.  In  order  to  allow  of  its 
supporting  the  weight  of  the  whole  body  in  this  position  with  the  least  expenditure 
of  material,  it  is  constructed  in  the  form  of  an  arch.  This  arch  is  not,  however, 
made  up  of  two  equal  limbs.  The  hinder  one,  which  is  made  up  of  the  os  calcis 
and  the  posterior  part  of  the  astragalus,  is  about  half  the  length  of  the  anterior 
limb,  and  measures  about  three  inches.  The  anterior  limb  consists  of  the  rest  of 
the  tarsal  and  the  metatarsal  bones,  and  measures  about  six  inches.  It  may  be 
said  to  consist  of  two  parts,  an  inner  segment  made  up  of  the  head  of  the  astragalus, 
the  navicular,  the  three  cuneiform,  and  the  three  inner  metatarsal  bones ;  and  an 
outer  segment  composed  of  the  cuboid  and  the  two  outer  metatarsal  bones.  The 
summit  of  the  arch  is  at  the  superior  articular  surface  of  the  astragalus ;  and  its- 
two  extremities — that  is  to  say,  the  two  points  on  which  the  arch  rests  in  standing — 
are  the  tubercles  on  the  under  surface  of  the  os  calcis  posteriorly,  and  the  heads  of 
the  metatarsal  bones  anteriorly.  The  weakest  part  of  the  arch  is  the  joint  between 
the  astragalus  and  scaphoid,  and  here  it  is  more  liable  to  yield  in  those  who  are 
overweighted,  and  in  those  in  whom  the  ligaments  which  complete  and  preserve 
the  arch  are  relaxed.  This  weak  point  in  the  arch  is  braced  on  its  concave  surface 
by  the  inferior  calcaneo-navicular  ligament,  which  is  more  elastic  than  most  other 
ligaments,  and  thus  allows  the  arch  to  yield  from  jars  or  shocks  applied  to  the 
anterior  portion  of  the  foot  and  quickly  restores  it  to  its  pristine  condition.  This 
ligament  is  supported  on  its  under  surface  by  the  tendon  of  the  Tibialis  posticus 
muscle,  which  is  spread  out  into  a  fan-shaped  insertion,  and  prevents  undue 
tension  of  the  ligament  or  such  an  amount  of  stretching  as  would  permanently 
elongate  it. 

In  addition  to  this  longitudinal  arch  the  foot  presents  a  transverse  arch,  at  the 
anterior  part  of  the  tarsus  and  hinder  part  of  the  metatarsus.  This,  however,  can 
scarcely  be  described  as  a  true  arch,  but  presents  more  the  character  of  a  half-dome. 
The  inner  border  of  the  central  portion  of  the  longitudinal  arch  is  elevated  from 
the  ground,  and  from  this  point  the  bones  arch  over  to  the  outer  border,  which  is 
in  contact  with  the  ground,  and,  assisted  by  the  longitudinal  arch,  produce  a  sort  of 
rounded  niche  on  the  inner  side  of  the  foot,  which  gives  the  appearance  of  a 
transverse  as  well  as  a  longitudinal  arch. 

The  arch  of  the  foot,  from  the  point  of  the  heel  to  the  toes,  is  not  quite  straight, 
but  is  directed  a  little  outward,  so  that  the  inner  border  is  a  little  convex  and  the 
outer  border  concave.  This  disposition  of  the  bones  becomes  more  marked  when 
the  longitudinal  arch  of  the  foot  is  lost,  as  in  the  disease  known  under  the  name 
of  "flat-foot." 

Surface  Form. — On  the  dorsum  of  the  foot  the  individual  bones  are  not  to  be  distinguished 
with  the  exception  of  the  head  of  the  astragalus,  which  forms  a  rounded  projection  in  front  of 
the  ankle-joint  when  the  foot  is  forcibly  extended.  The  whole  surface  forms  a  smooth  convex 
outline,  the  summit  of  which  is  the  ridge  formed  by  the  head  of  the  astragalus,  the  navicular, 
the  middle  cuneiform,  and  the  second  metatarsal  bones ;  from  this  it  gradually  inclines  outward 
and  more  rapidly  inward.  On  the  inner  side  of  the  foot,  the  internal  tuberosity  of  the  os  calcis 
and  the  ridge  separating  the  inner  from  the  posterior  surface  of  the  bone  may  be  felt  most  pos- 
teriorly. In  front  of  this,  and  below  the  internal  malleolus,  may  be  felt  the  projection  of  the 
sustentaculum  tali.  Passing  forward  is  the  well-marked  tuberosity  of  the  navicular  bone,  situ- 
ated about  an  inch  or  an  inch  and  a  quarter  in  front  of  the  internal  malleolus.  Further  toward 
the  front,  the  ridge  formed  by  the  base  of  the  first  metatarsal  bone  can  be  obscurely  felt,  and 
from  this  the  shaft  of  the  bone  can  be  traced  to  the  expanded  head  articulating  with  the  base 
of  the  first  phalanx  of  the  great  toe.  Immediately  beneath  the  base  of  this  phalanx,  the 


SURGICAL    ANATOMY   OF   THE  FOOT.  311 

internal  sesamoid  bone  is  to  be  felt.  Lastly,  the  expanded  ends  of  the  bones  forming  the  last 
joint  of  the  great  toe  are  to  be  felt.  On  the  outer  side  of  the  foot  the  most  posterior  bony 
point  is  the  outer  tuberosity  of  the  os  calcis,  with  the  ridge  separating  the  posterior  from  the 
outer  surface  of  the  bone.  *  In  front  of  this  the  greater  part  of  the  external  surface  of  the  os 
calcis  is  subcutaneous ;  on  it,  below  and  in  front  of  the  external  malleolus,  may  be  felt  the  pero- 
neal  ridge,  when  this  process  is  present.  Farther  forward,  the  base  of  the  fifth  metatarsal  bone 
forms  a  prominent  and  well-defined  landmark,  and  in  front  of  this  the  shaft  of  the  bone,  with 
its  expanded  head,  and  the  base  of  the  first  phalanx  may  be  defined.  The  sole  of  the  foot  is 
almost  entirely  covered  by  soft  parts,  so  that  but  few  bony  parts  are  to  be  made  out,  and  these 
somewhat  obscurely.  The  hinder  part  of  the  under  surface  of  the  os  calcis  and  the  heads  of  the 
metatarsal  bones,  with  the  exception  of  the  first,  which  is  concealed  by  the  sesamoid  bones, 
may  be  recognized. 

Surgical  Anatomy.— Considering  the  injuries  to  which  the  foot  is  subjected,  it  is  surpris- 
ing how  seldom  the  tarsal  bones  are  fractured.  This  is  no  doubt  due  to  the  fact  that  the  tarsus 
is  composed  of  a  number  of  bones,  articulated  by  a  considerable  extent  of  surface  and  joined 
together  by  very  strong  ligaments,  which  serve  to  break  the  force  of  violence  applied  to  this 
part  of  the  body.  When  fracture  does  occur,  these  bones,  being  composed  for  the  most  part 
of  a  soft  cancellous  structure,  covered  oaly  bv  a.  thiri  shell  »f  p™nr-g 

-  i     TrjS'  f  *   »-    1    "  -***4   IT1*    • 

the  iractures  are  producea  by 


comminuted,  especially  as  most  of  the  iractures  are  producea  by  afreet "violence.     And  na 
only  a  very  scanty  amount  of  soft  parts  over  them,  the  fractures  are  very  often  compound,  and 
amputation  is  frequently  necessary. 

When  fracture  occurs  in  the  anterior  group  of  tarsal  bones,  it  is  almost  invariably  the  result 
of  direct  violence  ;  but  fractures  of  the  posterior  group,  that  is.  of  the  calcaneum  and  astrag- 
alus, are  most  frequently  produced  by  falls  from  a  height  on  to  the  feet ;  though  fracture  of 
the  os  calcis  may  be  caused  by  direct  violence  or  by  muscular  action.  The  posterior  part  of  the 
bone,  that  is.  the  part  behind  the  articular  surfaces,  is  almost  always  the  seat  of  the  fracture, 
though  some  few  cases  of  fracture  of  the  sustentaculum  tali  and  of  vertical  fracture  between 
the  two  articulating  facets  have  been  recorded.  The  neck  of  the  astragalus,  being  the  weakest 
part  of  the  bone,  is  most  frequently  fractured,  though  fractures  may  occur  in  any  part  and 
almost  in  any  direction,  either  associated  or  not  with  fracture  of  other  bones. 

In  cases  of  club-foot,  especially  in  congenital  cases,  the  bones  of  the  tarsus  become  altered 
in  shape  and  size,  and  displaced  from  their  proper  positions.  This  is  especially  the  case  in  con- 
genital equino-varus.  in  which  the  astragalus,  particularly  about  the  head,  becomes  twisted  and 
atrophied,  and  a  similar  condition  may  be  present  in  the  other  bones,  more  especially  the  navic- 
ular.  The  tarsal  bones  are  peculiarly  liable  to  become  the  seat  of  tubercular  caries  from  com- 
paratively trivial  injuries.  There  are  several  reasons  to  account  for  this.  They  are  composed 
of  a  delicate  cancellated  structure,  surrounded  by  intricate  synovial  membranes.  They  are  situ- 
ated at  the  farthest  point  from  the  central  organ  of  the  circulation  and  exposed  to  vicissitudes 
of  temperature  ;  and,  moreover,  on  their  dorsal  surface  are  thinly  clad  with  soft  parts  which 
have  but  a  scanty  blood-supply.  And  finally,  after  slight  injuries,  they  are  not  maintained  in  a 
condition  of  rest  to  the  same  extent  as  similar  injuries  in  some  other  parts  of  the  body.  Caries 
of  the  calcaneum  and  astragalus  may  remain  limited  to  the  one  bone  fora  long  period,  but  when 
one  of  the  other  bones  is  affected,  the  remainder  frequently  become  involved,  in  consequence  of 
the  disease  spreading  through  the  large  and  complicated  synovial  membrane  which  is  more  or 
less  common  to  these  bones. 

Amputation  of  the  whole  or  a  part  of  the  foot  is  frequently  required  either  for  injury  or 
disease.  The  principal  amputations  areas  follow:  (1)  Syme's:  amputation  at  the  ankle-joint 
by  a  heel-flap,  with  removal  of  the  malleoli  and  sometimes  a  thin  slice  from  the  lower  end  of 
the  tibia.  (2)  Roux's:  amputation  at  the  ankle-joint  by  a  large  internal  flap.  (3)  PirogofFs 
amputation :  removal  of  the  whole  of  the  tarsal  bones,  except  the  posterior  part  of  the  os  calcis 
and  a  thin  slice  from  the  tibia  and  fibula  including  the  two  malleoli.  The  sawn  surface  of  the 
os  calcis  is  then  turned  up  and  united  to  the  similar  surface  of  the  tibia.  (4)  Subastragaloid 
amputation  :  removal  of  the  foot  below  the  astragalus  through  the  joint  between  it  and  the  os 
calcis.  This  operation  has  been  modified  by  Hancock,  who  leaves  the  posterior  third  of  the  os 
calcis  and  turns  it  up  against  the  denuded  surface  of  the  astragalus.  This  latter  operation  is  of 
doubtful  utility  and  is  rarely  performed.  (5)  Chopart's  or  medio-tarsal :  removal  of  the  ante- 
rior part  of  the  foot  with  all  the  tarsal  bones  except  the  os  calcis  and  astragalus ;  disarticula- 
tion  being  effected  through  the  joints  between  the  scaphoid  and  cuboid  in  front,  and  the  astrag- 
alus and  os  calcis  behind.  (6)  Lisfranc's:  amputation  of  the  anterior  part  of  the  foot  through 
the  tarso-metatarsal  joints.  This  has  been  modified  by  Hey,  who  disarticulated  through  the 
joints  of  the  four  outer  metatarsal  bones  with  the  tarsus,  and  sawed  off  the  projecting  internal 
cuneiform ;  and  by  Skey,  who  sawed  off  the  base  of  the  second  metatarsal  bone  and  disarticu- 
lated the  others. 

The  bones  of  the  tarsus  occasionally  require  removal  individually.  This  is  especially  the 
case  with  the  astragalus  and  os  calcis  for  disease  limited  to  the  one  bone,  or  again  the  astragalus 
may  require  excision  in  cases  of  subastragaloid  dislocation,  or,  as  recommended  by  Mr.  Lund, 
in  cases  of  inveterate  talipes.  The  cuboid  has  been  removed  for  the  same  reason  by  Mr.  Solly. 
But  both  these  two  latter  operations  have  fallen  very  much  into  disuse,  and  have  been  super- 
seded by  resection  of  a  wedge-shaped  piece  of  bone  from  the  outer  side  of  the  tarsus.  Finally, 
Mickulicz  and  Watson  have  devised  operations  for  the  removal  of  more  extensive  portions  of 
the  tarsus.  Mickulicz' s  operation  consists  in  the  removal  of  the  os  calcis  and  astragalus,  along 


312  THE   SKELETON. 

with  the  articular  surfaces  of  the  tibia  and  fibula,  and  also  of  the  scaphoid  and  cuboid.  The 
remaining  portion  of  the  tarsus  is  then  brought  into  contact  with  the  sawn  surfaces  of  the  tibia 
and  fibula,  and  fixed  there.  The  result  is  a  position  of  the  shortened  foot  resembling  talipes 
equinus.  Watson's  operation  is  adapted  to  those  cases  where  the  disease  is  confined  to  the 
anterior  tarsal  bones.  By  two  lateral  incisions  he  saws  through  the  bases  of  the  metatarsal 
bones  in  front  and  opens  up  the  joints  between  the  scaphoid  and  astragalus,  and  the  cuboid  and 
os  calcis,  and  removes  the  intervening  bones. 

The  metatarsal  bones  and  phalanges  are  nearly  always  broken  by  direct  violence,  and  in  the 
majority  of  cases  the  injury  is  the  result  of  severe  crushing  accidents,  necessitating  amputation. 
The  metatarsal  bones  and  especially  the  one  of  the  great  toe,  are  frequently  diseased,  either  in 
tubercular  subjects  or  in  perforating  ulcer  of  the  foot. 

Sesamoid  Bones. 

These  are  small  rounded  masses,  cartilaginous  in  early  life,  osseous  in  the  adult, 
which,  are  developed  in  those  tendons  which  exert  a  great  amount  of  pressure  upon 
the  parts  over  which  they  glide.  It  is  said  that  they  are  more  commonly  found  in 
the  male  than  in  the  female,  and  in  persons  of  an  active  muscular  habit  than  in 
those  who  are  weak  and  debilitated.  They  are  invested  throughout  their  whole 
surface  by  the  fibrous  tissue  of  the  tendon  in  which  they  are  found,  excepting  upon 
that  side  which  lies  in  contact  with  the  part  over  which  they  play,  where  they 
present  a  free  articular  facet.  They  may  be  divided  into  two  kinds :  those  which 
glide  over  the  articular  surfaces  of  joints,  and  those  which  play  over  the  cartilag- 
inous facets  found  on  the  surfaces  of  certain  bones. 

The  sesamoid  bones  of  the  joints  in  the  upper  extremity,  are  two  on  the  palmar 
surface  of  the  metacarpo-phalangeal  joint  in  the  thumb,  developed  in  the  tendons 
of  the  Flexor  brevis  pollicis ;  occasionally  one  or  two  opposite  the  metacarpo- 
phalangeal  articulations  of  the  fore  and  little  fingers ;  and,  still  more  rarely,  one 
opposite  the  same  joints  of  the  third  and  fourth  fingers.  In  the  lower  extremity, 
the  patella,  which  is  developed  in  the  tendon  of  the  Quadriceps  extensor ;  two  small 
sesamoid  bones,  found  in  the  tendons  of  the  Flexor  brevis  hallucis,  opposite  the 
metatarso-phalangeal  joint  of  the  great  toe ;  and  occasionally  one  in  the  metatarso- 
phalangeal  joint  of  the  second  toe,  the  little  toe,  and,  still  more  rarely,  the  third 
and  fourth  toes. 

Those  found  in  the  tendons  which  glide  over  certain  bones  occupy  the  following 
situations :  one  sometimes  found  in  the  tendon  of  the  Biceps  cubiti,  opposite  the 
tuberosity  of  the  radius  :  one  in  the  tendon  of  the  Peroneus  longus,  where  it  glides 
through  the  groove  in  the  cuboid  bone ;  one  appears  late  in  life  in  the  tendon  of  the 
Tibialis  anticus,  opposite  the  smooth  facet  of  the  internal  cuneiform  bone ;  one  is 
found  in  the  tendon  of  the  Tibialis  posticus,  opposite  the  inner  side  of  the  head  of  the 
astragalus ;  one  in  the  outer  head  of  the  Gastrocnemius,  behind  the  outer  condyle 
of  the  femur;  and  one  in  the  conjoined  tendon  of  the  Psoas  and  Iliacus,  where  it 
glides  over  the  os  pubis.  Sesamoid  bones  are  found  occasionally  in  the  tendon  of 
the  Gluteus  maximus,  as  it  passes  over  the  great  trochanter,  and  in  the  tendons 
which  wind  round  the  inner  and  outer  malleoli. 


THE  ARTICULATIONS. 


fTlHE  various  bones  of  which  the  Skeleton  consists  are  connected  together  at 
J_  different  parts  of  their  surfaces,  and  such  a  connection  is  designated  by  the 
name  of  Joint  or  Articulation.  If  the  joint  is  immovable,  as  between  the  cranial  and 
most  of  the  facial  bones,  the  adjacent  margins  of  the  bones  are  applied  in  almost 
close  contact,  a  thin  layer  of  fibrous  membrane,  the  sutural  ligament,  and,  at  the 
base  of  the  skull,  in  certain  situations,  a  thin  layer  of  cartilage,  being  interposed. 
Where  slight  movement  is  required,  combined  with  great  strength,  the  osseous  sur- 
faces are  united  by  tough  and  elastic  fibro-cartilages,  as  in  the  joints  between  the 
bodies  of  the  vertebrae  and  interpubic  articulations ;  but  in  the  movable  joints  the 
bones  forming  the  articulation  are  generally  expanded  at  the  ends  for  greater  con- 
venience of  mutual  connection,  covered  by  cartilage,  held  together  by  strong  bands 
or  capsules  of  fibrous  tissue  called  ligaments,  and  partially  lined  by  a  membrane, 
the  synovia!,  membrane,  which  secretes  a  fluid  to  lubricate  the  various  parts  of 
which  the  joint  is  formed;  so  that  the  structures  which  enter  into  the  formation 
of  a  joint  are  bone,  cartilage,  fibro-cartilage,  ligament,  and  synovia!  membrane. 

Bone  constitutes  the  fundamental  element  of  all  the  joints.  In  the  long  bones 
the  extremities  are  the  parts  which  form  the  articulations ;  they  are  generally 
somewhat  enlarged,  consisting  of  spongy  cancellous  tissue,  with  a  thin  coating  of 
compact  substance.  In  the  flat  bones  the  articulations  usually  take  place  at  the 
edges,  and,  in  the  short  bones  at  various  parts  of  their  surface.  The  layer  of 
compact  bone  which  forms  the  articular  surface,  and  to  which  the  cartilage  is 
attached,  is  called  the  articular  lamella.  It  is  of  a  white  color,  extremely  dense, 
and  varies  in  thickness.  Its  structure  differs  from  ordinary  bone-tissue  in  this 
respect,  that  it  contains  no  Haversian  canals,  and  its  lacunae  are  much  larger  than 
in  ordinary  bone  and  have  no  canaliculi.  The  vessels  of  the  cancellous  tissue,  as 
they  approach  the  articular  lamella,  turn  back  in  loops,  and  do  not  perforate  it ; 
this  layer  is  consequently  more  dense  and  firmer  than  ordinary  bone,  and  is  evi- 
dently designed  to  form  a  firm  and  unyielding  support  for  the  articular  cartilage. 

The  cartilage,  which  covers  the  articular  surfaces  of  bone,  and  is  called  the 
articular,  will  be  found  described,  with  the  other  varieties  of  cartilage,  in  the  section 
on  General  Anatomy  (page  51). 

Ligaments  consist  of  bands  of  various  forms,  serving  to  connect  together  the 
articular  extremities  of  bones,  and  composed  mainly  of  bundles  of  white  fibrous 
tissue  placed  parallel  with,  or  closely  interlaced  with,  one  another,  and  presenting 
a  white,  shining,  silvery  aspect.  A  ligament  is  pliant  and  flexible,  so  as  to  allow 
of  the  most  perfect  freedom  of  movement,  but  strong,  tough,  and  inextensile,  so 
as  not  readily  to  yield  under  the  most  severely  applied  force ;  it  is  consequently 
well  adapted  to  serve  as  the  connecting  medium  between  the  bones.  Some  liga- 
ments consist  entirely  of  yellow  elastic  tissue,  as  the  ligamenta  subflava,  which 
connect  together  the  adjacent  arches  of  the  vertebrae  and  the  ligamentum  nuchae 
in  the  lower  animals.  In  these  cases  it  will  be  observed  that  the  elasticity  of  the 
ligament  is  intended  to  act  as  a  substitute  for  muscular  power. 

Synovial  membrane  is  a  thin,  delicate  membrane  of  connective  tissue,  with 
branched  connective-tissue  corpuscles.  Its  secretion  is  thick,  viscid,  and  glairy, 
like  the  white  of  egg,  and  is  hence  termed  synovia.  The  synovial  membranes 
found  in  the  body  admit  of  subdivision  into  three  kinds — articular,  bursal,  and 
vaginal. 

The  articular  synovial  membranes  are  found  in  all  the  freely  movable  joints. 
In  the  foetus  this  membrane  is  said,  by  Toynbee,  to  be  continued  over  the  surface 

313 


314  THE   ARTICULATIONS. 

of  the  cartilages ;  but  in  the  adult  it  is  wanting,  excepting  at  their  circumference, 
upon  which  it  encroaches  for  a  short  distance,  and  to  which  it  is  firmly  attached ; 
it  then  invests  the  inner  surface  of  the  capsular  or  other  ligaments  enclosing  the 
joint,  and  is  reflected  over  the  surface  of  any  tendons  passing  through  its  cavity,  as 
the  tendon  of  the  Popliteus  in  the  knee  and  the  tendon  of  the  Biceps  in  the 
shoulder.  Hence  the  articular  synovial  membrane  may  be  regarded  as  a  short 
wide  tube,  attached  by  its  open  ends  to  the  margins  of  the  articular  cartilages,  and 
covering  the  inner  surface  of  the  various  ligaments  which  connect  the  articular 
surfaces,  so  that  along  with  the  cartilages  it  completely  encloses  the  joint-cavity. 
In  some  of  the  joints  the  synovial  membrane  is  thrown  into  folds,  which  pass 
across  the  cavity.  They  are  called  synovial  ligaments,  and  are  especially  distinct 
in  the  knee.  In  other  joints  there  are  flattened  folds,  subdivided  at  their  margins- 
into  fringe-like  processes,  the  vessels  of  which  have  a  convoluted  arrangement. 
These  latter  generally  project  from  the  synovial  membrane  near  the  margin  of  the 
cartilage  and  lie  flat  upon  its  surface.  They  consist  of  connective  tissue  covered 
with  endothelium,  and  contain  fat-cells  in  variable  quantities,  and,  more  rarely, 
isolated  cartilage-cells.  The  larger  folds  often  contain  considerable  quantities  of 
fat.  They  were  described  by  Clopton  Havers  as  mucilaginous  glands,  and  as  the 
source  of  the  synovial  secretion.  Under  certain  diseased  conditions  similar  pro- 
cesses are  found  covering  the  entire  surface  of  the  synovial  membrane,  forming  a 
mass  of  pedunculated  fibro-fatty  growths  which  project  into  the  joint.  Similar 
structures  are  also  found  in  some  of  the  bursal  and  vaginal  synovial  membranes. 

The  bursal  synovial  membranes  are  found  interposed  between  surfaces  which 
move  upon  each  other,  producing  friction,  as  in  the  gliding  of  a  tendon  or  of  the 
integument  over  projecting  bony  surfaces.  They  admit  of  subdivision  into  two 
kinds,  the  bursce  mucosce  and  the  bursce  synovice.  The  bursce  mucosce  are  large, 
simple,  or  irregular  cavities  in  the  subcutaneous  areolar  tissue,  enclosing  a  clear 
viscid  fluid.  They  are  found  in  various  situations,  as  between  the  integument  and 
the  front  of  the  patella,  over  the  olecranon,  themalleoli,  and  other  prominent  parts. 
The  bursce  synovice  are  found  interposed  between  muscles  or  tendons  as  they  play 
over  projecting  bony  surfaces,  as  between  the  Glutei  muscles  and  the  surface  of 
the  great  trochanter.  They  consist  of  a  thin  wall  of  connective  tissue,  partially 
covered  by  patches  of  cells,  and  contain  a  viscid  fluid.  Where  one  of  these  exists 
in  the  neighborhood  of  a  joint,  it  usually  communicates  with  its  cavity,  as  is  gen- 
erally the  case  with  the  bursa  between  the  tendon  of  the  Psoas  and  Iliacus  and 
the  capsular  ligament  of  the  hip,  or  the  one  interposed  between  the  under  surface 
of  the  Subscapularis  and  the  neck  of  the  scapula. 

The  vaginal  synovial  membranes  (synovial  sheaths)  serve  to  facilitate  the  gliding 
of  tendons  in  the  osseo-fibrous  canals  through  which  they  pass.  The  membrane  is 
here  arranged  in  the  form  of  a  sheath,  one  layer  of  which  adheres  to  the  wall  of 
the  canal,  and  the  other  is  reflected  upon  the  surface  of  the  contained  tendon,  the 
space  between  the  two  free  surfaces  of  the  membrane  being  partially  filled  with 
synovia.  These  sheaths  are  chiefly  found  surrounding  the  tendons  of  the  flexor 
and  extensor  muscles  of  the  fingers  and  toes  as  they  pass  through  the  osseo-fibrous 
canals  in  the  hand  or  foot. 

Synovia  is  a  transparent,  yellowish-white  or'  slightly  reddish  fluid,  viscid  like 
the  white  of  egg,  having  an  alkaline  reaction  and  slightly  saline  taste.  It  consists, 
according  to  Frerichs,  in  the  ox,  of  94.85  water,  0.56  mucus  and  epithelium,  0.07 
fat,  3.51  albumen  and  extractive  matter,  and  0.99  salts. 

The  articulations  are  divided  into  three  classes :  Synarthrosis,  or  immovable  ; 
amphiarthrosis,  or  mixed;  and  diarthrosis,  or  movable  joints. 

1.  Synarthrosis.    Immovable  Articulations. 

Synarthrosis  includes  all  those  articulations  in  which  the  surfaces  of  the  bones 
are  in  almost  direct  contact,  fastened  together  by  an  intervening  mass  of  connective 
tissue,  and  in  which  there  is  no  appreciable  motion,  as  the  joints  between  the  bones 


CLASSIFICATION  OF  JOINTS.  315 

of  the  cranium  and  face,  excepting  those  of  the  lower  jaw.  The  varieties  of  synar- 
throsis  are  four  in  number  :  Sutura.  Schindylesis,  Gomphosis,  and  Synchondrosis. 

Sutura  (a  seam)  is  that  form  of  articulation  where  the  contiguous  margins  of 
flat  bones  are  united  by  a  thin  layer  of  fibrous  tissue.  It  is  met  with  only  in  the 
skull.  Where  the  articulating  surfaces  are  connected  by  a  series  of  processes  and 
indentations  interlocked  together,  it  is  termed  sutura  vera,  of  which  there  are 
three  varieties :  sutura  dentata.  serrata,  and  limbosa.  The  surfaces  of  the  bones 
are  not  in  direct  contact,  being  separated  by  a  layer  of  membrane  continuous 
externally  with  the  pericranium,  internally  with  the  dura  mater.  The  sutura 
dentata  (dens,  a  tooth)  is  so  called  from  the  tooth-like  form  of  the  projecting 
articular  processes,  as  in  the  suture  between  the  parietal  bones.  In  the  sutura 
serratu  (*</VY/.  a  saw)  the  edges  of  the  two  bones  forming  the  articulation  are 
serrated  like  the  teeth  of  a  fine  saw,  as  between  the  two  portions  of  the  frontal 
bone.  In  the  sutura  limbosa  (limbus,  a  selvage),  besides  the  dentated  processes, 
there  is  a  certain  degree  of  bevelling  of  the  articular  surfaces,  so  that  the  bones 
overlap  one  another,  as  in  the  suture  between  the  parietal  and  frontal  bones. 
When  the  articulation  is  formed  by  roughened  surfaces  placed  in  apposition  with 
one  another,  it  is  termed  the  false  suture  (sutura  notha),  of  which  there  are  two 
kinds :  the  sutura  squamosa  {fqmamd^  a  scale),  formed  by  the  overlapping  of  two 
contiguous  bones  by  broad  bevelled  margins,  as  in  the  squamo-parietal  (squamous) 
suture;  and  the  sutura  Jiariiif/nia  (appovia,  a  joining  together),  where  there  is 
simple  apposition  of  two  contiguous  rough  bony  surfaces,  as  in  the  articulation 
between  the  two  superior  maxillary  bones  or  of  the  horizontal  plates  of  the  palate 
bones. 

Schindylesis  (ay^d-j/^a^.  a  fissure)  is  that  form  of  articulation  in  which  a  thin 
plate  of  bone  is  received  into  a  cleft  or  fissure  formed  by  the  separation  of  two 
laminae  in  another  bone,  as  in  the  articulation  of  the  rostrum  of  the  sphenoid  and 
perpendicular  plate  of  the  ethmoid  with  the  vomer,  or  in  the  reception  of  the  latter 
in  the  fissure  between  the  superior  maxillary  and  palate  bones. 

Gomphosis  (yo/tfoc,  a  nail)  is  an  articulation  formed  by  the  insertion  of  a 
conical  process  into  a  socket,  as  a  nail  is  driven  into  a  board ;  this  is  not  illustrated 
by  any  articulation  between  bones,  properly  so  called,  but  is  seen  in  the  articulation 
of  the  teeth  with  the  alveoli  of  the  maxillary  bones. 

Synchondrosis. — Where  the  connecting  medium  is  cartilage  the  joint  is  termed 
a  Synchondrosis.  This  is  a  temporary  form  of  joint,  for  the  cartilage  becomes  con- 
verted into  bone  before  adult  life  (synostosis).  Such  a  joint  is  found  between  the 
epiphyses  and  shafts  of  long  bones. 

2.  Amphiarthrosis.    Mixed  Articulations. 

In  this  form  of  articulation  the  contiguous  osseous  surfaces  are  connected 
together  by  broad  flattened  disks  of  fibro-cartilage,  of  a  more  or  less  com- 
plex structure,  which  adhere  to  the  end  of  each  bone,  as  in  the  articulation  be- 
tween the  bodies  of  the  vertebrae  and  the  pubic  symphyses.  This  is  termed 
Symphysis.  Or,  secondly,  the  bony  surfaces  are  united  by  an  interosseous  liga- 
ment, as  in  the  inferior  tibio-fibular  articulation.  To  this  the  term  Syndesmosis. 
is  applied. 

3.  Diarthrosis.    Movable  Articulations. 

This  form  of  articulation  includes  the  greater  number  of  the  joints  in  the  bodyr 
mobility  being  their  distinguishing  character.  They  are  formed  by  the  approxi- 
mation of  two  contiguous  bony  surfaces  covered  with  cartilage,  connected  by 
ligaments  and  lined  by  synovial  membrane.  The  varieties  of  joints  in  this  class 
have  been  determined  by  the  kind  of  motion  permitted  in  each.  There  are  two 
varieties  in  which  the  movement  is  uniaxial :  that  is  to  say,  all  movements  take 
place  around  one  axis.  In  one  form,  the  Ginglymus.  this  axis  is,  practically 
speaking,  transverse ;  in  the  other,  the  trochoid  or  pivot-joint,  it  is  longitudinal. 
There  are  two  varieties  where  the  movement  is  biaxial,  or  around  two  horizontal 


316  THE   ARTICULATIONS. 

axes  at  right  angles  to  each  other  or  at  any  intervening  axis  between  the  two. 
These  are  the  condyloid  and  saddle-joint.  There  is  one  form  of  joint  where  the 
movement  is  polyaxial,  the  enarthrosis  or  ball-and-socket  joint.  And  finally  there 
are  the  Arthrodia  or  Gliding  joints. 

Ginglymus  or  Hinge-joint  (yr'yyAu/zoc,  a  hinge). — In  this  form  of  joint  the 
articular  surfaces  are  moulded  to  each  other  in  such  a  manner  as  to  permit  motion 
only  in  one  plane,  forward  and  backward ;  the  extent  of  motion  at  the  same  time 
being  considerable.  The  direction  which  the  distal  bone  takes  in  this  motion  is 
never  in  the  same  plane  as  that  of  the  axis  of  the  proximal  bone,  but  there  is 
always  a  certain  amount  of  alteration  from  the  straight  line  during  flexion.  The 
articular  surfaces  are  connected  together  by  strong  lateral  ligaments,  which  form 
their  chief  bond  of  union.  The  most  perfect  forms  of  ginglymus  are  the  inter- 
phalangeal  joints  and  the  joint  between  the  humerus  and  ulna ;  the  knee  and  ankle 
are  less  perfect,  as  they  allow  a  slight  degree  of  rotation  or  lateral  movement  in 
certain  positions  of  the  limb. 

Trochoides  (pivot-joint). — Where  the  movement  is  limited  to  rotation,  the  joint 
is  formed  by  a  pivot-like  process  turning  within  a  ring,  or  the  ring  on  the  pivot,  the 
ring  being  formed  partly  of  bone,  partly  of  ligament.  In  the  superior  radio-ulnar 
articulation  the  ring  is  formed  partly  by  the  lesser  sigmoid  cavity  of  the  ulna ;  in 
the  rest  of  its  extent,  by  the  orbicular  ligament ;  here  the  head  of  the  radius 
rotates  within  the  ring.  In  the  articulation  of  the  odontoid  process  of  the  axis 
with  the  atlas  the  ring  is  formed  in  front  by  the  anterior  arch  of  the  atlas ;  behind, 
by  the  transverse  ligament ;  here  the  ring  rotates  round  the  odontoid  process. 

Condyloid  Articulations. — In  this  form  of  joint  an  ovoid  articular  head,  or 
•condyle,  is  received  into  an  elliptical  cavity  in  such  a  manner  as  to  permit  of 
flexion  and  extension,  adduction  and  abduction  and  circumduction,  but  no  axial 
rotation.  The  articular  surfaces  are  connected  together  by  anterior,  posterior,  and 
lateral  ligaments.  An  example  of  this  form  of  joint  is  found  in  the  wrist. 

Articulations  by  Reciprocal  Eeception  (saddle-joint). — In  this  variety  the 
articular  surfaces  are  concavo-convex  ;  that  is  to  say,  they  are  inversely  convex  in 
one  direction  and  concave  in  the  other.  The  movements  are  the  same  as  in  the 
preceding  form ;  that  is  to  say,  there  is  flexion,  extension,  adduction,  abduction, 
and  circumduction,  but  no  axial  rotation.  The  articular  surfaces  are  connected  by 
a  capsular  ligament.  The  best  example  of  this  form  of  joint  is  the  carpo-meta- 
carpal  joint  of  the  thumb. 

Enarthrosis  is  that  form  of  joint  in  which  the  distal  bone  is  capable  of  motion 
around  an  indefinite  number  of  axes  which  have  one  common  centre.  It  is  formed 
by  the  reception  of  a  globular  head  into  a  deep  cup-like  cavity  (hence  the  name 
"  ball-and-socket "),  the  parts  being  kept  in  apposition  by  a  capsular  ligament 
strengthened  by  accessory  ligamentous  bands.  Examples  of  this  form  of  articulation 
are  found  in  the  hip  and  shoulder. 

Arthrodia  is  that  form  of  joint  which  admits  of  a  gliding  movement ;  it  is 
formed  by  the  approximation  of  plane  surfaces  or  one  slightly  concave,  the  other 
slightly  convex,  the  amount  of  motion  between  them  being  limited  by  the 
ligaments,  or  osseous  processes,  surrounding  the  articulation ;  as  in  the  articular 
processes  of  the  vertebrae,  the  carpal  joints,  except  that  of  the  os  magnum  with  the 
scaphoid  and  semilunar  bones,  and  the  tarsal  joints  with  the  exception  of  the  joint 
between  the  astragalus  and  the  navicular. 

On  the  next  page,  in  a  tabular  form,  are  the  names,  distinctive  characters,  and 
examples  of  the  different  kinds  of  articulations. 

The  Kinds  of  Movement  admitted  in  Joints. 

The  movements  admissible  in  joints  may  be  divided  into  four  kinds  :  gliding, 
angular  movement,  circumduction,  and  rotation.  These  movements  are  often, 
however,  more  or  less  combined  in  the  various  joints,  so  as  to  produce  an  infinite 
variety,  and  it  is  seldom  that  we  find  only  one  kind  of  motion  in  any  particular  joint. 


CLASSIFICATION   OF  JOISTS. 


317 


Immovable  Joint. 
Surfaces  separated 
by  fibrous  mem- 
brane or  by  line 
of  cartilage,  with- 
out any  interven- 
ing  synovial 
cavity,  and  im- 
movably o-on- 
nected  with  each 
other. 

As  in  joints  of 
cranium  and  face 
(except  lower 
jaw). 


Amphiarthrosis. 
Mixed  Articula- 
tion. 


Diarthrosis, 
Movable   Joint. 


Sutura.  Ar- 
ticulation by 
processes  and 
inden  t  a  t  i  o  n  s 
interlocked  to- 
gether. 


Sutura  vera 
(true),  articulate 
by  indented  bor- 
ders. 


Sutura      notha 

(false),     articulate 
by  rough  surfaces. 


Dentata,  having 
tooth-like  proces- 

As  in  interparietal 
suture. 

Serrata,  having  ser- 
rated edges  like  the 
teeth  of  a  saw. 

As  in  interfrontal 
suture. 

Limbosa,  having 
bevelled  margins  and 
dentated  processes. 

As  in  fronto-parie- 
tal  suture. 

Squamosa,  formed 
by  thin  bevelled  mar- 
gins, overlapping  each 
other. 

As  in  squamo-parie- 
tal  suture. 

ffarmonia.formedbj 
the  apposition  of  con- 
tiguous rough  surfaces. 
As    in    intermaxil- 
v  lary  suture. 

Schindylesis. — Articulation  formed  by  the  reception  of  a 
thin  plate  of  one  bone  into  a  fissure  of  another. 

As  in  articulation  of  rostrum  of  sphenoid  with  vomer. 
Gromphosis. — Articulation   formed  by  the  insertion  of  a 
conical  process  into  a  socket :  the  teeth. 
Synchondrosis. — Epiphysial  lines. 

Symphysis. — Surfaces  connected  by  fibro-cartilage,  not 
separated  by  synovial  membrane,  and  having  limited  motion. 
As  in  joints  between  bodies  of  vertebra. 

Syndesmosis. — Surfaces  united  by  an  interosseous  ligament. 
As  in  the  inferior  tibio-fibular  articulation. 

Gringlymus. — Hinge-joint;  motion  limited  to  two  directions, 

forward  and  backward.     Articular  surfaces  fitted  together 

-  to  permit  of  movement  in  one  plane.     As  in  the  inter- 

phalangeal  joints  and  the  joint  between  the  humerus  and  the 

ulna. 

TrocJtoides.  or  Pivot-joint. — Articulation  by  a  pivot  process 
turning  within  a  ring  or  ring  around  a  pivot.  As  in  superior 
radio-ulnar  articulation  and  atlanto-axial  joint. 

Condyloid. — Ovoid  head  received  into  elliptical  cavity. 
Movements  in  every  direction  except  axial  rotation.  As  the 
wrist-joint. 

Reciprocal  Reception  (saddle-joint). — Articular  surfaces 
inversely  convex  in  one  direction  and  concave  in  the  other. 
Movement  in  every  direction  except  axial  rotation.  As  in  the 
carpo-metacarpal  joint  of  the  thumb. 

Enarthrosts. — Ball-and-socket  joint ;  capable  of  motion  in 
all  directions.  Articulations  by  a  globular  head  received  into 
a  cup-like  cavity.  A?  in  hip-  and  shoulder-joints. 

Arthmdia. — Gliding  joint ;  articulations  by  plane  surfaces, 
which  glide  upon  each  other.  As  in  carpal  and  tarsal  articu- 
lations. 


318  THE   ARTICULATIONS 

Grliding  movement  is  the  most  simple  kind  of  motion  that  can  take  place  in  a 
joint,  one  surface  gliding  or  moving  over  another  without  any  angular  or  rotatory 
movement.  It  is  common  to  all  movable  joints,  but  in  some,  as  in  the  articu- 
lations of  the  carpus  and  tarsus,  it  is  the  only  motion  permitted.  This  movement 
is  not  confined  to  plane  surfaces,  but  may  exist  between  any  two  contiguous 
surfaces,  of  whatever  form,  limited  by  the  ligaments  which  enclose  the  articu- 
lation. 

Angular  movement  occurs  only  between  the  long  bones,  and  by  it  the  angle 
between  the  two  bones  is  increased  or  diminished.  It  may  take  place  in  four 
directions :  forward  and  backward,  constituting  flexion  and  extension,  or  inward 
and  outward,  from  the  mesial  line  of  the  body  (or  in  the  fingers  and  toes  from 
the  middle  line  of  the  hand  or  foot),  constituting  adduction  and  abduction.  The 
strictly  ginglymoid  or  hinge-joints  admit  of  flexion  and  extension  only.  Abduction 
and  adduction,  combined  with  flexion  and  extension,  are  met  with  in  the  more 
movable  joints;  as  in  the  hip,  shoulder,  and  metacarpal  joint  of  the  thumb,  and 
partially  in  the  wrist. 

Circumduction  is  that  limited  degree  of  motion  which  takes  place  between  the 
head  of  a  bone  and  its  articular  cavity,  whilst  the  extremity  and  sides  of  the  limb 
are  made  to  circumscribe  a  conical  space,  the  base  of  which  corresponds  with  the 
inferior  extremity  of  the  limb,  the  apex  with  the  articular  cavity ;  this  kind  of 
motion  is  best  seen  in  the  shoulder-  and  hip-joints. 

Rotation  is  the  movement  of  a  bone  upon  an  axis,  which  is  the  axis  of  the  pivot 
on  which  the  bone  turns,  as  in  the  articulation  between  the  atlas  and  axis,  when 
the  odontoid  process  serves  as  a  pivot  around  which  the  atlas  turns ;  or  else  is  the 
axis  of  a  pivot-like  process  which  turns  within  a  ring,  as  in  the  rotation  of  the 
radius  upon  the  humerus. 

Ligamentous  Action  of  Muscles. — The  movements  of  the  different  joints  of  a  limb 
are  combined  by  means  of  the  long  muscles  which  pass  over  more  than  one  joint, 
and  which,  when  relaxed  and  stretched  to  their  greatest  extent,  act  to  a  certain 
extent  as  elastic  ligaments  in  restraining  certain  movements  of  one  joint,  except  when 
combined  with  corresponding  movements  of  the  other,  these  latter  movements 
being  usually  in  the  opposite  direction.  Thus  the  shortness  of  the  hamstring 
muscles  prevents  complete  flexion  of  the  hip,  unless  the  knee-joint  be  also  flexed, 
so  as  to  bring  their  attachments  nearer  together.  The  uses  of  this  arrangement 
are  threefold :  1.  It  co-ordinates  the  kinds  of  movement  which  are  the  most 
habitual  and  necessary,  and  enables  them  to  be  performed  with  the  least  expendi- 
ture of  power.  "  Thus  in  the  usual  gesture  of  the  arms,  whether  in  grasping  or 
rejecting,  the  shoulder  and  the  elbow  are  flexed  simultaneously,  and  simultaneously 
extended,"  in  consequence  of  the  passage  of  the  Biceps  and  Triceps  cubiti  over  both 
joints.  2.  It  enables  the  short  muscles  which  pass  over  only  one  joint  to  act  upon 
more  than  one.  "  Thus,  if  the  Rectus  femoris  remain  tonically  of  such  length 
that,  when  stretched  over  the  extended  hip,  it  compels  extension  of  the  knee,  then 
the  Gluteus  maximus  becomes  not  only  an  extensor  of  the  hip,  but  an  extensor 
of  the  knee  as  well."  3.  It  provides  the  joints  with  ligaments  Avhich,  while  they 
are  of  very  great  power  in  resisting  movements  to  an  extent  incompatible  with  the 
mechanism  of  the  joint,  at  the  same  time  spontaneously  yield  when  necessary. 
"  Taxed  beyond  its  strength,  a  ligament  will  be  ruptured,  whereas  a  contracted 
muscle  is  easily  relaxed;  also,  if  neighboring  joints  be  united  by  ligaments,  the 
amount  of  flexion  or  extension  of  each  must  remain  in  constant  proportion  to  that 
of  the  other ;  while,  if  the  union  be  by  muscles,  the  separation  of  the  points  of  attach- 
ment of  those  muscles  may  vary  considerably  in  different  varieties  of  movement, 
the  muscles  adapting  themselves  tonically  to  the  length  required."  The  quotations 
are  from  a  very  interesting  paper  by  Dr.  Cleland  in  the  Journal  of  Anatomy  and 
Physiology,  No.  1,  1866,  p.  85 ;  by  whom  I  believe  this  important  fact  in  the 
mechanism  of  joints  was  first  clearly  pointed  out,  though  it  has  been  independently 
observed  afterward  by  other  anatomists.  Dr.  W.  W.  Keen  points  out  how 
important  it  is  "  that  the  surgeon  should  remember  this  ligamentous  action  of 


OF   THE    VERTEBRAL    COLUMN.  319 

muscles  in  making  passive  motion — for  instance,  at  the  wrist  after  Colles's  fracture. 
If  the  fingers  be  extended,  the  wrist  can  be  flexed  to  a  right  angle.  If,  however, 
they  be  first  flexed,  as  in  "  making  a  fist,"  flexion  at  the  wrist  is  quickly  limited  to 
from  forty  to  fifty  degrees  in  different  persons,  and  is  very  painful  beyond  that 
point.  Hence  passive  motion  here  should  be  made  with  the  fingers  extended. 
In  the  leg,  when  flexing  the  hip,  the  knee  should  be  flexed."  Dr.  Keen  further 
points  out  that  kt  a  beautiful  illustration  of  this  is  seen  in  the  perching  of  birds, 
whose  toes  are  forced  to  clasp  the  perch  by  just  such  a  passive  ligamentous 
action  so  soon  as  they  stoop.  Hence  they  can  go  to  sleep  and  not  fall  off  the 
perch." 

The  articulations  may  be  arranged  into  those  of  the  trunk,  those  of  the  upper 
extremity,  and  those  of  the  lower  extremity. 

ARTICULATIONS  OF  THE  TRUNK. 

These  may  be  divided  into  the  following  groups,  viz. : 


I.  Of  the  vertebral  column. 

II.  Of  the  atlas  with  the  axis. 

III.  Of  the  atlas  Avith  the  occipital  bone. 

IV.  Of  the  axis  with  the  occipital  bone. 
V.  Of  the  lower  jaw. 

VI.  Of  the  ribs  with  the  vertebrae. 


VII.  Of  the  cartilages  of  the  ribs  with 
the  sternum  and  with  each  other. 
VIII.  Of  the  sternum. 
IX.  Of  the  vertebral  column  with  the 

pelvis. 
X.  Of  the  pelvis. 


I.    Articulations  of  the  Vertebral  Column. 

The  different  segments  of  the  spine  are  connected  together  by  ligaments,  which 
admit  of  the  same  arrangement  as  the  vertebras.  They  may  be  divided  into  five 
sets:  1.  Those  connecting  the  bodies  of  the  vertebrae.  2.  Those  connecting  the 
lamuice.  3.  Those  connecting  the  articular  processes.  4.  Those  connecting  the 
spinous  processes.  5.  Those  of  the  transverse  processes. 

The  articulations  of  the  bodies  of  the  vertebrae  with  each  other  form  a  series 
of  amphiarthrodial  joints  (symphyses]  ;  those  between  the  articular  processes  form 
a  series  of  arthrodial  joints. 

1.    THE  LIGAMENTS  OF  THE  BODIES. 

Anterior  Common  Ligament.  Posterior  Common  Ligament. 

Intervertebral  Substance. 

The  Anterior  Common  Ligament  (Figs.  227,  228,  235,  239)  is  a  broad  and 
strong  band  of  ligamentous  fibres  which  extends  along  the  front  surface  of  the 
bodies  of  the  vertebrae  from  the  axis  to  the  sacrum.  It  is  broader  below  than 
above,  thicker  in  the  dorsal  than  in  the  cervical  or  lumbar  regions,  and  somewhat 
thicker  opposite  the  front  of  the  body  of  each  vertebra  than  opposite  the  inter- 
vertebral  substance.  It  is  attached,  above,  to  the  body  of  the  axis  by  a  pointed 
process,  where  it  is  continuous  with  the  anterior  atlanto-axial  ligament,  and  is 
connected  with  the  tendon  of  insertion  of  the  Longus  colli  muscle,  and  extends 
down  as  far  as  the  upper  bone  of  the  sacrum.  It  consists  of  dense  longitudinal 
fibres,  which  are  intimately  adherent  to  the  intervertebral  substance  and  the 
prominent  margins  of  the  vertebrae,  but  less  closely  to  the  middle  of  the  bodies. 
In  the  latter  situation  the  fibres  are  exceedingly  thick,  and  serve  to  fill  up  the 
concavities  on  their  front  surface  and  to  make  the  anterior  surface  of  the  spine 
more  even.  This  ligament  is  composed  of  several  layers  of  fibres,  which  vary  in 
length,  but  are  closely  interlaced  with  each  other.  The  most  superficial  or  longest 
fibres  extend  between  four  or  five  vertebrae.  A  second  subjacent  set  extend 
between  two  or  three  vertebrae,  whilst  a  third  set,  the  shortest  and  deepest,  extend 
from  one  vertebra  to  the  next.  At  the  side  of  the  bodies  the  ligament  consists  of 
a  few  short  fibres,  which  pass  from  one  vertebra"  to  the  next,  separated  from  the 
median  portion  by  large  oval  apertures  for  the  passage  of  vessels. 

The  Posterior  Common  Ligament  (Figs.  227,  231)  is  situated  within  the  spinal 


320 


THE  ARTICULATIONS 


canal,  and  extends  along  the  posterior  surface  of  the  bodies  of  the  vertebrae  from 
the  body  of  the  axis  above,  where  it  is  continuous  with  the  occipito-axial  ligament, 
to  the  sacrum  below.  It  is  broader  above  than  below,  and  thicker  in  the  dorsal 
than  in  the  cervical  or  lumbar  regions.  In  the  situation  of  the  intervertebral 
substance  and  contiguous  margins  of  the  vertebrae,  where  the  ligament  is  more 
intimately  adherent,  it  is  broad,  and  presents  a  series  of  dentations  with  inter- 
vening concave  margins ;  but  it  is  narrow  and  thick  over  the  centre  of  the  bodies, 
from  which  it  is  separated  by  the  vence  basis  vertebrae.  This  ligament  is  composed 
of  smooth,  shining,  longitudinal  fibres,  denser  and  more  compact  than  those  of  the 
anterior  ligament,  and  composed  of  a  superficial  layer  occupying  the  interval 
between  three  or  four  vertebrae,  and  of  a  deeper  layer  which  extends  between 
one  vertebra  and  the  next  adjacent  to  it.  It  is  separated  from  the  dura  mater  of 


ANTERIOR    COMMON 


POSTERIOR 
COMMON 
LIGAMENT. 


FIG.  227.— Vertical  section  of  two  vertebree  and  their  ligaments,  from  the  lumbar  region. 

the  spinal  cord  by  some  loose  connective  tissue  which  is  very  liable  to  serous 
infiltration. 

The  Intervertebral  Substance  (Figs.  227,  236)  is  a  lenticular  disk  of  composite 
structure  interposed  between  the  adjacent  surfaces  of  the  bodies  of  the  vertebrae 
from  the  axis  to  the  sacrum,  and  forming  the  chief  bond  of  connection  between 
those  bones.  These  disks  vary  in  shape,  size,  and  thickness  in  different  parts  of 
the  spine.  In  shape  they  accurately  correspond  with  the  surfaces  of  the  bodies 
between  which  they  are  placed,  being  oval  in  the  cervical  and  lumbar  regions,  and 
circular  in  the  dorsal.  Their  size  is  greatest  in  the  lumbar  region.  In  thickness 
they  vary  not  only  in  the  different  regions  of  the  spine,  but  in  different  parts  of 
the  same  disk :  thus,  they  are  much  thicker  in  front  than  behind  in  the  cervical 
and  lumbar  regions,  while  they  are  uniformly  thick  in  the  dorsal  region.  The 
intervertebral  disks  form  about  one-fourth  of  the  spinal  column,  exclusive  of  the 
first  two  vertebrae ;  they  are  not  equally  distributed,  however,  between  the  various 
bones ;  the  dorsal  portion  of  the  spine  having,  in  proportion  to  its  length,  a  much 
smaller  quantity  than  in  the  cervical  and  lumbar  regions,  which  necessarily  gives 
to  the  latter  parts  greater  pliancy  and  freedom  of  movement.  The  intervertebral 
disks  are  adherent,  by  their  surfaces,  to  a  thin  layer  of  hyaline  cartilage  which 
covers  the  upper  and  under  surfaces  of  the  bodies  of  the  vertebrae,  and  in  which  the 
epiphysial  plate  develops,  and  by  their  circumference  are  closely  connected  in. 


OF    THE    VERTEBRAL    COLUMX.  321 

front  to  the  anterior,  and  behind  to  the  posterior  common  ligament ;  whilst  in  the 
dorsal  region  they  are  connected  laterally,  by  means  of  the  interarticular  ligament, 
to  the  heads  of  those  ribs  which  articulate  with  two  vertebrae  ;  they,  consequently, 
form  part  of  the  articular  cavities  in  which  the  heads  of  these  bones  are  received. 
Structure  of  the  Intervertebral  Substance. — The  intervertebral  substance  is 
composed,  at  its  circumference,  of  laminre  of  fibrous  tissue  and  fibro-cartilage ; 
and.  at  its  centre,  of  a  soft,  pulpy,  highly  elastic  substance,  of  a  yellowish  color, 
which  rises  up  considerably  above  the  surrounding  level  when  the  disk  is  divided 
horizontally.  This  pulpy  substance,  which  is  especially  well  developed  in  the 
lumbar  region,  is  the  remains  of  the  chorda  dorsalis,  and,  according  to  Luschka, 
contains  a  small  synovial  cavity  in  its  centre.  The  laminae  are  arranged  concen- 
trically one  within  the  other,  the  outermost  consisting  of  ordinary  fibrous  tissue, 
but  the  others  and  more  numerous  consisting  of  white  fibro-cartilage.  These 
plates  are  not  quite  vertical  in  their  direction,  those  near  the  circumference  being 
curved  outward  and  closely  approximated ;  whilst  those  nearest  the  centre  curve 
in  the  opposite  direction,  and  are  somewhat  more  widely  separated.  The  fibres  of 
which  each  plate  is  composed  are  directed,  for  the  most  part,  obliquely  from  above 
downward,  the  fibres  of  adjacent  plates  passing  in  opposite  directions  and  varying 
in  every  layer  :  so  that  the  fibres  of  one  layer  are  directed  across  those  of  another, 
like  the  limbs  of  the  letter  X.  This  laminar  arrangement  belongs  to  about  the 
outer  half  of  each  disk.  The  pulpy  substance  presents  no  concentric  arrangement, 
and  consists  of  a  fine  fibrous  matrix,  containing  angular  cells,  united  to  form  a 
reticular  structure. 

'2.  LIGAMENTS  CONNECTING  THE  LAMINJE. 
Ligamenta  Subflava. 

The  Ligamenta  Subflava  (Fig.  227)  are  interposed  between  the  laminae  of  the 
vertebrae,  from  the  axis  to  the  sacrum.  They  are  most  distinct  when  seen  from 
the  interior  of  the  spinal  canal :  when  viewed  from  the  outer  surface  they  appear 
short,  being  overlapped  by  the  lamina.  Each  ligament  consists  of  two  lateral 
portions,  which  commence  on  each  side  at  the  root  of  either  articular  process,  and 
pass  backward  to  the  point  where  the  laminae  converge  to  form  the  spinous 
process,  where  their  margins  are  in  contact  and  to  a  certain  extent  united ;  slight 
intervals  being  left  for  the  passage  of  small  vessels.  These  ligaments  consist  of 
yellow  elastic  tissue,  the  fibres  of  which,  almost  perpendicular  in  direction,  are 
attached  to  the  anterior  surface  of  the  laminae  above,  some  distance  from  its 
inferior  margin,  and  to  the  posterior  surface,  as  well  as  to  the  margin  of  the 
lamina  below.  In  the  cervical  region  they  are  thin  in  texture,  but  very  broad  and 
long  :  they  become  thicker  in  the  dorsal  region,  and  in  the  lumbar  acquire  very 
derable  thickness.  Their  highly  elastic  property  serves  to  preserve  the 
upright  posture  and  to  assist  in  resuming  it  after  the  spine  has  been  flexed. 
These  ligaments  do  not  exist  between  the  occiput  and  atlas  or  between  the  atlas 
and  axis. 

3.  LIGAMENTS  CONNECTING  THE  ARTICULAR  PROCESSES. 
Capsular. 

The  Capsular  Ligaments  (Fig.  229)  are  thin  and  loose  ligamentous  sacs,  attached 
to  the  contiguous  margins  of  the  articulating  processes  of  each  vertebra  through 
the  greater  part  of  their  circumference,  and  completed  internally  by  the  ligamenta 
subflava.  They  are  longer  and  looser  in  the  cervical  than  in  the  dorsal  or  lumbar 
regions.  The  capsular  ligaments  are  lined  on  their  inner  surface  by  synovial 
membrane. 

4.  LIGAMENTS  CONNECTING  THE  SPINOUS  PROCESSES. 
Supraspinous.  Interspinous. 

The  Supraspinous  Ligament  (Fig.  227)  is  a  strong  fibrous  cord,  which  connects 
21 


322  THE   ARTICULATIONS 

together  the  apices  of  the  spinous  processes  from  the  seventh  cervical  to  the  spinous 
processes  of  the  sacrum.  It  is  thicker  and  broader  in  the  lumbar  than  in  the  dorsal 
region,  and  intimately  blended,  in  both  situations,  with  the  neighboring  aponeu- 
rosis.  The  most  superficial  fibres  of  this  ligament  connect  three  or  four  vertebrae  ; 
those  deeper-seated  pass  between  two  or  three  vertebrae  ;  whilst  the  deepest  connect 
the  contiguous  extremities  of  neighboring  vertebrae.  It  is  continued  upward  to 
the  external  occipital  protuberance,  as  the  posterior  margin  of  the  ligamentum 
nuchaa,  which,  in  the  human  subject,  is  comparatively  thin  and  forms  an  inter- 
muscular  septum. 

The  Interspinous  Ligaments  (Fig.  227),  thin  and  membranous,  are  interposed 
between  the  spinous  processes.  Each  ligament  extends  from  the  root  to  the 
summit  of  each  spinous  process  and  connects  together  their  adjacent  margins. 
They  are  narrow  and  elongated  in  the  dorsal  region ;  broader,  quadrilateral  in 
form,  and  thicker  in  the  lumbar  region  ;  and  only  slightly  developed  in  the  neck. 

5.  LIGAMENTS  CONNECTING   THE  TRANSVERSE  PROCESSES. 
Intertransverse. 

The  Intertransverse  Ligaments  consist  of  bundles  of  fibres  interposed 
between  the  transverse  processes.  In  the  cervical  region  they  consist  of  a  few 
irregular,  scattered  fibres  ;  in  the  dorsal,  they  are  rounded  cords  intimately  con- 
nected with  the  deep  muscles  of  the  back  ;  in  the  lumbar  region  they  are  thin  and 
membranous. 

Actions. — The  movements  permitted  in  the  spinal  column  are,  Flexion,  Exten- 
sion, Lateral  Movement,  Circumduction,  and  Rotation. 

In  Flexion,  or  movement  of  the  spine  forward,  the  anterior  common  ligament 
is  relaxed,  and  the  intervertebral  substances  are  compressed  in  front,  while  the 
posterior  common  ligament,  the  ligamenta  subflava,  and  the  inter-  and  supra- 
spinous  ligaments  are  stretched,  as  well  as  the  posterior  fibres  of  the  intervertebral 
disks.  The  interspaces  between  the  laminae  are  widened,  and  the  inferior  articular 
processes  of  the  vertebrae  above  glide  upward  upon  the  articular  processes  of  the 
vertebrae  below.  Flexion  is  the  most  extensive  of  all  the  movements  of  the  spine. 

In  Extension,  or  movement  of  the  spine  backward,  an  exactly  opposite  dis- 
position of  the  parts  takes  place.  This  movement  is  not  extensive,  being  limited  by 
the  anterior  common  ligament  and  by  the  approximation  of  the  spinous  processes. 

Flexion  and  extension  are  most  free  in  the  lower  part  of  the  lumbar  region 
between  the  third  and  fourth  and  fourth  and  fifth  lumbar  vertebrae ;  above  the 
third  they  are  much  diminished,  and  reach  their  minimum  in  the  middle  and 
upper  part  of  the  back.  They  increase  again  in  the  neck,  the  capability  of  motion 
backward  from  the  upright  position  being  in  this  region  greater  than  that  of  the 
motion  forward,  whereas  in  the  lumbar  region  the  reverse  is  the  case. 

In  Lateral  Movement,  the  sides  of  the  intervertebral  disks  are  compressed,  the 
extent  of  motion  being  limited  by  the  resistance  offered  by  the  surrounding  liga- 
ments and  by  the  approximation  of  the  transverse  processes.  This  movement  may 
take  place  in  any  part  of  the  spine,  but  is  most  free  in  the  neck  and  loins. 

Circum.duction  is  very  limited,  and  is  produced  merely  by  a  succession  of  the 
preceding  movements. 

Rotation  is  produced  by  the  twisting  of  the  intervertebral  substances  ;  this, 
although  only  slight  between  any  two  vertebrae,  produces  a  great  extent  of  move- 
ment when  it  takes  place  in  the  whole  length  of  the  spine,  the  front  of  the 
column  being  turned  to  one  or  the  other  side.  This  movement  takes  place  only  to 
a  slight  extent  in  the  neck,  but  is  freer  in  the  upper  part  of  the  dorsal  region,  and 
is  altogether  absent  in  the  lumbar  region. 

It  is  thus  seen  that  the  cervical  region  enjoys  the  greatest  extent  of  each 
variety  of  movement,  flexion  and  extension  especially  being  very  free.  In  the 
dorsal  region  the  three  movements  of  flexion,  extension,  and  circumduction  are 
only  permitted  to  a  slight  extent,  while  rotation  is  very  free  in  the  upper  part  and 


OF    THE   ATLAS    WITH    THE   AXIS.  323 

ceases  below.  In  the  lumbar  region  there  is  free  flexion,  extension,  and  lateral 
movement,  but  no  rotation. 

As  Sir  George  Humphry  has  pointed  out,  the  movements  permitted  are  mainly 
due  to  the  shape  and  position  of  the  articulating  processes.  In  the  loins  the 
inferior  articulating  processes  are  turned  outward  and  embraced  by  the  superior ; 
this  renders  rotation  in  this  region  of  the  spine  impossible,  while  there  is  nothing 
to  prevent  a  sliding  upward  and  downward  of  the  surfaces  on  each  other,  so  as  to 
allow  of  flexion  and  extension.  In  the  dorsal  region,  on  the  other  hand,  the 
articulating  processes,  by  their  direction  and  mutual  adaptation,  especially  at  the 
upper  part  of  the  series,  permit  of  rotation,  but  prevent  extension  and  flexion, 
•while  in  the  cervical  region  the  greater  obliquity  and  lateral  slant  of  the  articular 
processes  allow  not  only  flexion  and  extension,  but  also  rotation. 

The  principal  muscles  which  produce  flexion  are  the  Sterno-mastoid,  Rectus 
capitis  anticus  major,  and  Longus  colli ;  the  Scaleni ;  the  abdominal  muscles  and 
the  Psoas  magnus.  Extension  is  produced  by  the  fourth  layer  of  the  muscles  of 
the  back,  assisted  in  the  neck  by  the  Splenius,  Semispinalis  dorsi  et  colli,  and 
the  Multifidus  spinae.  Lateral  motion  is  produced  by  the  fourth  layer  of  the 
muscles  of  the  back,  by  the  Splenius  and  the  Scaleni,  the  muscles  of  one  side  only 
acting;  and  rotation  by  the  action  of  the  following  muscles  of  one  side  only — viz. 
the  Sterno-mastoid.  the  Rectus  capitis  anticus  major,  the  Scaleni,  the  Multifidus 
spinse,  the  Complexus,  and  the  abdominal  muscles. 

II.  Articulation  of  the  Atlas  with  the  Axis. 

The  articulation  of  the  Atlas  with  the  Axis  is  of  a  complicated  nature,  comprising 
no  fewer  than  four  distinct  joints.  There  is  a  pivot  articulation  between  the  odontoid 
process  of  the  axis  and  the  ring  formed  between  the  anterior  arch  of  the  atlas  and 
the  transverse  ligament  (see  Fig.  230).  Here  there  are  two  joints :  one  in  front 
between  the  posterior  surface  of  the  anterior  arch  of  the  atlas  and  the  front  of  the 
odontoid  process  (the  atlo-odontoid  joint  of  Oruveilhier) ;  the  other  between  the 
anterior  surface  of  the  transverse  ligament  and  the  back  of  the  process  (the 
si/ndesmo-odontoid  joint}.  Between  the  articular  processes  pf  the  two  bones 
there  is  a  double  arthrodia  or  gliding  joint.  The  ligaments  which  connect  these 
bones  are  the 

Two  Anterior  Atlanto-axial.  Transverse. 

Posterior  Atlanto-axial.  Two  Capsular. 

Of  the  Two  Anterior  Atlanto-axial  Ligaments  (Fig.  228),  the  more  superficial  is 
a  rounded  cord,  situated  in  the  middle  line ;  it  is  attached,  above,  to  the  tubercle 
on  the  anterior  arch  of  the  atlas  ;  below,  to  the  base  of  the  odontoid  process  and  to 
the  front  of  .the  body  of  the  axis.  The  deeper  ligament  is  a  membranous  layer, 
attached,  above,  to  the  lower  border  of  the  anterior  arch  of  the  atlas ;  below,  to 
the  base  of  the  odontoid  process  and  front  of  the  body  of  the  axis.  These  ligaments 
are  in  relation,  in  front,  with  the  Recti  antici  majores. 

The  Posterior  Atlanto-axial  Ligament  (Fig.  229)  is  a  broad  and  thin  membranous 
laver,  attached,  above,  to  the  lower  border  of  the  posterior  arch  of  the  atlas; 
below,  to  the  upper  edge  of  the  laminae  of  the  axis.  This  ligament  supplies 
the  place  of  the  ligamenta  subflava,  and  is  in  relation,  behind,  with  the  Inferior 
oblique  muscles. 

The  Transverse  Ligament l  (Figs.  230,  231)  is  a  thick  and  strong  ligamentous 
band,  which  arches  across  the  ring  of  the  atlas,  and  serves  to  retain  the  odontoid 
process  in  firm  connection  with  its  anterior  arch.  This  ligament  is  flattened  from 
before  backward,  broader  and  thicker  in  the  middle  than  at  either  extremity,  and 

1  It  has  been  found  necessary  to  describe  the  transverse  lisament  with  those  of  the  atlas  and 
axis  ;  but  the  student  must  remember  that  it  is  really  a  portion  of  the  mechanism  by  which  the 
movements  of  the  head  on  the  spine  are  regulated  :  so  that  the  connections  between  the  atlas  and 
axis  ought  always  to  be  studied  together  with  those  between  the  latter  bones  and  the  skull. 


324 


THE   ARTICULATIONS 


firmly  attached  on  each  side  to  a  small  tubercle  on  the  inner  surface  of  the  lateral 
mass  of  the  atlas.  As  it  crosses  the  odontoid  process,  a  small  fasciculus  is  derived 
from  its  upper  and  lower  borders ;  the  former  passing  upward,  to  be  inserted  into 
the  basilar  process  of  the  occipital  bone  ;  the  latter,  downward,  to  be  attached  to 
the  posterior  surface  of  the  body  of  the  axis ;  hence,  the  whole  ligament  has 
received  the  name  of  cruciform.  The  transverse  ligament  divides  the  ring  of  the 
atlas  into  two  unequal  parts :  of  these,  the  posterior  and  larger  serves  for  the 
transmission  of  the  cord  and  its  membranes  and  the  spinal  accessory  nerves ; 
the  anterior  and  smaller  contains  the  odontoid  process.  Since  the  space  between 
the  anterior  arch  of  the  atlas  and  the  transverse  ligament  is  smaller  at  the  lower 


|     CAPSULAR    LIGA- 
MENT and 
synovial  mem- 
brane. 


APSULAR    LIGAMENT 

and  synovial 
membrane. 


FIG.  228.— Occipito-atloid  and  atlo-axoid  ligaments.    Front  view. 

part  than  the  upper  (because  the  transverse  ligament  embraces  firmly  the  narrow 
neck  of  the  odontoid  process),  this  process  is  retained  in  firm  connection  with 
the  atlas  after  all  the  other  ligaments  have  been  divided. 

The  Capsular  Ligaments  connect  the  articular  processes  of  the  atlas  and  axis,  the 
fibres  being  strongest  on  the  posterior  and  internal  part  of  the  articulation,  access- 
ory ligaments  ;  these  latter  extend  downward  and  inward  to  the  body  of  the  axis. 

There  are  four  Synovial  Membranes  in  this  articulation :  one  lining  the  inner 
surface  of  each  of  the  capsular  ligaments ;  one  between  the  anterior  surface  of  the 
odontoid  process  and  the  anterior  arch  of  the  atlas,  the  ado-odontoid  joint; 
and  one  between  the  posterior  surface  of  the  odontoid  process  and  the  transverse 
ligament,  the  syndesmo-odontoid  joint.  The  latter  often  communicates  with 
those  between  the  condyles  of  the  occipital  bone  and  the  articular  surfaces  of  the 
atlas. 

Actions. — This  joint  allows  the  rotation  of  the  atlas  (and,  with  it,  of  the  cra- 
nium) upon  the  axis,  the  extent  of  rotation  being  limited  by  the  odontoid  liga- 
ments. 

The  principal  muscles  by  which  this  action  is  produced  are  the  Sterno-mastoid 
and  Complexus  of  one  side,  acting  with  the  Rectus  capitis  anticus  major,  Splenius, 
Trachelo-mastoid,  Rectus  capitis  posticus  major,  and  Inferior  oblique  of  the  other 
side. 


OF    THE  ATLAS    WITH    THE    OCCIPITAL    BONE. 


325 


ARTICULATIONS  OF  THE  SPINE  WITH  THE  CRANIUM. 

The  ligaments  connecting  the  spine  with  the  cranium  may  be  divided  into  two 
sets — those  connecting  the  occipital  bone  with  the  atlas,  and  those  connecting  the 
occipital  bone  with  the  axis. 

III.  Articulation  of  the  Atlas  with  the  Occipital  Bone. 

This  articulation  is  a  double  condyloid  joint.     Its  ligaments  are  the 

Two  Anterior  Occipito-atlantal.  Two  Lateral  Occipito-atlantal. 

Posterior  Occipito-atlantal.  Two  Capsular. 

Of  the  Two.  Anterior  Occipito-atlantal  Ligaments  (Fig.  228),  the  superficial  is 
a  strong,  narrow,  rounded  cord,  attached,  above,  to  the  basilar  process  of  the 


Arch  for  passage  of 
vertebral  artery 
and  1st  cervical 


FIG.  229. — Occipito-atloid  and  atlo-axoid  ligaments.    Posterior  view. 

occiput ;  below,  to  the  tubercle  on  the  anterior  arch  of  the  atlas :  the  deeper  liga- 
ment is  a  broad  and  thin  membranous  layer  which  passes  between  the  anterior 
margin  of  the  foramen  magnum  above,  and  the  whole  length  of  the  upper  border 
of  the  anterior  arch  of  the  atlas  below.  This  ligament  is  in  relation,  in  front,  with 
the  Recti  antici  minores ;  behind,  with  the  odontoid  ligaments. 

The  Posterior  Occipito-atlantal  Ligament  (Fig.  229)  is  a  very  broad  but  thin 
membranous  lamina  intimately  blended  with  the  dura  mater.  It  is  connected, 
above,  to  the  posterior  margin  of  the  foramen  magnum  ;  below,  to  the  upper  border 
of  the  posterior  arch  of  the  atlas.  This  ligament  is  incomplete  at  each  side,  and 
forms,  with  the  superior  intervertebral  notch,  an  opening  for  the  passage  of  the 
vertebral  artery  and  suboccipital  nerve.  It  is  in  relation,  behind,  with  the  Recti 
postici  minores  and  Obliqui  superiores  ;  in  front,  with  the  dura  mater  of  the  spinal 
canal,  to  which  it  is  intimately  adherent. 

The  Lateral  Ligaments  are  strong  fibrous  bands,  directed  obliquely  upward 
and  inward,  attached  above  to  the  jugular  process  of  the  occipital  bone  ;  below,  to 
the  base  of  the  transverse  process  of  the  atlas. 

The  Capsular  Ligaments  surround  the  condyles  of  the  occipital  bone,  and  con- 


326 


THE   ARTICULATIONS. 


nect  them  with  the  articular  processes  of  the  atlas ;  they  consist  of  thin  and  loose 
capsules,  which  enclose  the  synovial  membrane  of  the  articulation. 

Synovial  Membranes. — There  are  two  synovial  membranes  in  this  articulation, 
one  lining  the  inner  surface  of  each  of  the  capsular  ligaments.  These  occasionally 
communicate  with  that  between  the  posterior  surface  of  the  odontoid  process  and 
the  transverse  ligament. 

Actions. — The  movements  permitted  in  this  joint  are  flexion  and  extension, 
which  give  rise  to  the  ordinary  forward  and  baclovard  nodding  of  the  head,  besides 


FIG.  230.— Articulation  between  odontoid  process  and  atlas. 

slight  lateral  motion  to  one  or  the  other  side.  When  either  of  these  actions  is 
carried  beyond  a  slight  extent,  the  whole  of  the  cervical  portion  of  the  spine  assists 
in  its  production.  Flexion  is  mainly  produced  by  the  action  of  the  Rectus  capitis 
anticus  major  et  minor  and  the  Sterno-mastoid-  muscles  ;  extension  by  the  Rectus 
capitis  posticus  major  et  minor,  the  Superior  oblique,  the  Complexus,  Splenius, 
and  upper  fibres  of  the  Trapezius.  The  Recti  laterales  are  concerned  in  the  lat- 
eral movement,  assisted  by  the  Trapezius,  Splenius,  Complexus,  Sterno-mastoid, 
and  the  Recti  laterales  of  the  same  side,  all  acting  together.  According  to  Cru- 
veilhier,  there  is  a  slight  motion  of  rotation  in  this  joint. 

IV.  Articulation  of  the  Axis  with  the  Occipital  Bone. 

Occipito-axial.  Three  Odontoid. 

To  expose  these  ligaments  the  spinal  canal  should  be  laid  open  by  removing 
the  posterior  arch  of  the  atlas,  the  laminge  and  spinous  process  of  the  axis,  and 
the  portion  of  the  occipital  bone  behind  the  foramen  magnum,  as  seen  in  Fig.  231. 

The  Occipito-axial  Ligament  (apparatus  ligamentosus  colli)  is  situated  within 
the  spinal  canal.  It  is  a  broad  and  strong  ligamentous  band,  which  covers  the 
odontoid  process  and  its  ligaments,  and  appears  to  be  a  prolongation  upward  of 
the  posterior  common  ligament  of  the  spine.  It  is  attached,  below,  to  the  posterior 
surface  of  the  body  of  the  axis,  and,  becoming  expanded  as  it  ascends,  is  inserted 
into  the  basilar  groove  of  the  occipital  bone,  in  front  of  the  foramen  magnum,  where 
it  becomes  blended  with  the  dura  mater  of  the  skull. 

Relations. — By  its  anterior  surface  with  the  transverse  ligament,  by  its  posterior 
surface  with  the  dura  mater. 

The  Lateral  Odontoid  or  Check  Ligaments  (alar  ligaments)  are  strong,  fibrous 
cords,  which  arise  one  on  either  side  of  the  upper  part  of  the  odontoid  process, 
and,  passing  obliquely  upward  and  outward,  are  inserted  into  the  rough 
depressions  on  the  inner  side  of  the  condyles  of  the  occipital  bone.  In  the 
triangular  interval  between  these  ligaments  another  strong  fibrous  cord  (liga- 
mentum  suspensorium  or  middle  odontoid  ligament)  may  be  seen,  which  passes 
almost  perpendicularly  from  the  apex  of  the  odontoid  process  to  the  anterior 
margin  of  the  foramen,  being  intimately  blended  with  the  deep  portion  of  the 


TEMPORO-MAXILLAR Y  ARTICULA TION. 


327 


anterior  occipito-atloid  ligament  and  upper  fasciculus  of  the  transverse  ligament 
of  the  atlas. 

Actions. — The  odontoid  ligaments  serve  to  limit  the  extent  to  which  rotation 


The  vertical  portion  of 

ODONTOID    LIGAMENTS. 


fCAPSULAR    LIGAMENT 

'  <       and  synovial 
(        membrane. 


CAPSULAR    LIGAMENT 

and  synovial 
membrane. 


FIG.  231.—  Occipito-axoid  and  atlo-axoid  ligaments.    Posterior  view,  obtained  by  removing  the  arches  of  the 
vertebrae  and  the  posterior  part  of  the  skull. 

of  the  cranium  may  be  carried  ;  hence  they    have    received  the  name  of  check 
ligaments. 

In  addition  to  these  ligaments,  which  connect  the  atlas  and  axis  to  the  skull, 
the  ligamentum  nuchae  must  be  regarded  as  one  of  the  ligaments  by  which  the 
spine  is  connected  with  the  cranium.  It  is  described  on  a  subsequent  page. 

Surgical  Anatomy.  —  The  ligaments  which  unite  the  component  parts  of  the  vertebrae 
together  are  so  strong,  and  these  bones  are  so  interlocked  by  the  arrangement  of  their 
articulating  processes,  that  dislocation  is  very  uncommon,  and,  indeed,  unless  accompanied  by 
fracture,  rarely  occurs,  except  in  the  upper  part  of  the  neck.  Dislocation  of  the  occiput  from 
the  atlas  has  only  been  recorded  in  one  or  two  cases  ;  but  dislocation  of  the  atlas  from  the  axis, 
with  rupture  of  the  transverse  ligament,  is  much  more  common  :  it  is  tbe  mode  in  which 
death  is  produced  in  many  cases  of  execution  by  hanging.  In  the  lower  part  of  the  neck  — 
tbat  is,  below  the  third  cervical  vertebra—  dislocation  unattended  by  fracture  occasionally  takes 
place. 

V.    Temporo-maxillary  Articulation. 

This  is  a  double  or  bilateral  condyloid  joint:  the  parts  entering  into  its 
formation  on  each  side  are,  above,  the  anterior  part  of  the  glenoid  cavity  of  the 
temporal  bone  and  the  eminentia  articularis  ;  and,  below,  the  condyle  of  the  lower 
jaw.  The  ligaments  are  the  following: 


External  Lateral. 
Internal  Lateral. 

Interarticular 


Stylo-maxillary. 
Capsular. 
Fibro-cartilae. 


The  External  Lateral  Ligament  (Fig.  232)  is  a  short,  thin,  and  narrow 
fasciculus,  attached,  above,  to  the  outer  surface  of  the  zygoma  and  to  the  rough 
tubercle  on  its  lower  border  ;  below,  to  the  outer  surface  and  posterior  border  of 
the  neck  of  the  lower  jaw.  It  is  broader  above  than  below  ;  its  fibres  are  placed 


328 


THE   ARTICULATIONS. 


parallel  with  one  another,  and  directed  obliquely  downward  and  backward.      Ex- 
ternally, it  is  covered  by  the  parotid  gland  and  by  the  integument.     Internally, 


FIG.  232.— Temporo-maxillary  articulation.    External  view. 

it  is  in  relation  with  the  capsular  ligament,  of  which  it  is  an  accessory  band,  and 
not  separable  from  it. 

The  Internal  Lateral  Ligament 
(Fig.   233)  is  a  specialized  band 


x  "-1  ">  *  5t^*  *^^^i^  ^^^••••Mi     •!*'  «  ""•   **'  -:.  c.  - 


above  to  the  spinous  process  of  the 
sphenoid  bone,  and,  becoming 
broader  as  it  descends,  is  inserted 
into  the  lingula  and  margin  of  the 
dental  foramen.  Its  outer  surface 
is  in  relation,  above,  with  the  Ex- 
ternal pterygoid  muscle ;  lower 
down,  it  is  separated  from  the 
neck  of  the  condyle  by  the  internal 
maxillary  artery ;  and  still  more 
interiorly,  the  inferior  dental  ves- 
sels and  nerve  separate  it  from  the 
ramus  of  the  jaw.  The  inner  sur- 
face is  in  relation  with  the  Inter- 
nal pterygoid. 

The  Stylo -maxillary   Ligament 
is  also  a  specialized  band  of  the 
_  cervical  fascia,  which  extends  from 

FIG.  233.-Temporo-maxillary  articulation.  Internal  view,    near   the   apex  of  the   Styloid  pro- 

cess  of  the  temporal  bone  to  the 
angle  and  posterior  border  of  the  ramus  of  the  lower  jaw,  between  the  Masseter 
and  Internal  pterygoid  muscles.  This  ligament  separates  the  parotid  from  the 
submaxillary  gland,  and  has  attached  to  its  inner  side  part  of  the  fibres  of  origin 
of  the  Stylo-glossus  muscle.  Although  usually  classed  among  the  ligaments  of 
the  jaw,  it  can  only  be  considered  as  an  accessory  in  the  articulation. 


TEMPOR 0-MA XILLA RY  AR TICULA TIOX. 


329 


—Vertical  section  of  temporo-maxillary  ar- 


The  Capsular  Ligament  forms  a  thin  and  loose  ligamentous  capsule,  attached 
above  to  the  circumference  of  the  glenoid  cavity  and  the  articular  surface  im- 
mediately in  front ;  below,  to  the  neck  of  the  condyle  of  the  lower  jaw.  It  consists 
of  a  few  thin  scattered  fibres,  and  can  hardly  be  considered  as  a  distinct  ligament ; 
it  is  thickest  at  the  back  part  of  the  articulation.1 

The  Interarticular  Fibro-cartilage  (Fig.  234)  is  a  thin  plate  of  an  oval  form, 
placed  horizontally  between  the  condyle  of  the  jaw  and  the  glenoid  cavity.  Its 
upper  surface  is  concavo-convex  from 
before  backward,  and  a  little  convex 
transversely,  to  accommodate  itself 
to  the  form  of  the  glenoid  cavity. 
Its  under  surface,  where  it  is  in  con- 
tact with  the  condyle.  is  concave. 
Its  circumference  is  connected  to  the 
capsular  ligament,  and  in  front  to  the 
tendon  of  the  External  pterygoid 
muscle.  It  is  thicker  at  its  circum- 
ference, especially  behind,  than  at 
its  centre,  where,  at  times,  it  is  per- 
forated. The  fibres  of  which  it  is 
composed  have  a  concentric  arrange- 
ment, more  apparent  at  the  circum- 
ference than  at  the  centre.  Its 
surfaces  are  smooth.  It  divides  the  joint  into  two  cavities,  each  of  which  is  fur- 
nished with  a  separate  synovial  membrane. 

The  Synovial  Membranes,  two  in  number,  are  placed,  one  above,  and  the  other 
below,  the  fibro-cartilage.  The  upper  one.  the  larger  and  looser  of  the  two,  is 
continued  from  the  margin  of  the  cartilage  covering  the  glenoid  cavity  and 
eminentia  articularis  on  to  the  upper  surface  of  the  fibro-cartilage.  The  lower  one 
s  from  the  under  surface  of  the  fibro-cartilage  to  the  neck  of  the  condyle  of 
the  jaw.  being  prolonged  downward  a  little  farther  behind  than  in  front. 

The  H'-ri'es  of  this  joint  are  derived  from  the  auriculo-temporal  and  masseteric 
branches  of  the  inferior  maxillary.  The  arteries  are  derived  from  the  temporal 
branch  of  the  external  carotid. 

Actions. — The  movements  permitted  in  this  articulation  are  very  extensive. 
Thus,  the  jaw  may  be  depressed  or  elevated,  or  it  may  be  carried  forward  or 
backward  or  from  side  to  side.  It  is  by  the  alternation  of  these  movements, 
performed  in  succession,  that  a  kind  of  rotatory  motion  of  the  lower  jaw  upon  the 
upper  takes  place,  which  materially  assists  in  the  mastication  of  the  food. 

If  the  movement  of  depression  is  carried  only  to  a  slight  extent,  the  condyles 
remain  in  the  glenoid  cavities,  rotating  on  a  transverse  axis  against  the  inter- 
articular  fibro-cartilage ;  but  if  the  depression  is  considerable,  the  condyles  glide 
from  the  glenoid  fossae  on  to  the  articular  eminences,  carrying  with  them  the 
interarticular  fibro-cartilages.  so  that  in  opening  the  mouth  widely  the  two  move- 
ments are  combined — i.  e.  the  condyle  rotates  on  a  transverse  axis  against  the 
fibro-cartilage.  and  at  the  same  time  glides  forward,  carrying  the  fibro-cartilage 
with  it.  When  the  jaw  is  elevated  after  forced  depression,  the  condyles  and 
fibro-cartilages  return  to  their  original  position.  When  the  jaw  is  carried  for- 
ward and  backward  or  from  side  to  side,  an  oblique  gliding  movement  of  the 
fibro-cartilages  and  condyles  upon  the  glenoid  cavities  takes  place  in  the  cor- 
responding direction. 

The  lower  jaw  is  depressed  by  its  own  weight,  assisted  by  the  Platysma,  the 
Digastric,  the  Mylo-hyoid.  and  the  Genio-hyoid.  It  is  elevated  by  the  anterior 
part  of  the  Temporal.  Masseter.  and  Internal  pterygoid.  It  is  drawn  forward  by 

1  Sir  G.  Humphry  describes  the  internal  portion  of  the  capsular  ligament  separately,  as  the  short 
internal  lateral  ligament ;  and  it  certainly  seem?  as  deserving  of  a  separate  description  as  the  external 
lateral  ligament  is. 


330  THE   ARTICULATIONS 

the  simultaneous  action  of  the  External  pterygoid  and  the  superficial  fibres  of 
the  Masseter ;  and  it  is  drawn  backward  by  the  deep  fibres  of  the  Masseter  and 
the  posterior  fibres  of  the  Temporal  muscle.  The  grinding  movement  is  caused 
by  the  alternate  action  of  the  two  External  pterygoids. 

Surface  Form. — The  temporo-maxillary  articulation  is  quite  superficial,  situated  below  the 
base  of  the  zygoma,  in  front  of  the  tragus  and  external  auditory  meatus,  and  behind  the  posterior 
border  of  the  upper  part  of  the  Masseter  muscle.  Its  exact  position  can  be  at  once  ascer- 
tained by  feeling  for  the  condyle  of  the  jaw,  the  working  of  which  can  be  distinctly  felt  in  the 
movements  of  the  lower  jaw  either  vertically  or  from  side  to  side.  When  the  mouth  is  opened 
wide,  the  condyle  advances  out  of  the  glenoid  fossa  on  to  the  eminentia  articularis  and  a  depres- 
sion is  felt  in  the  situation  of  the  joint. 

Surgical  Anatomy. — The  lower  jaw  is  dislocated  only  in  one  direction — viz.  forward.  The 
accident  is  caused  by  violence  or  muscular  action.  When  the  mouth  is  open,  the  condyle  is 
situated  on  the  eminentia  articularis,  and  any  sudden  violence,  or  even  a  sudden  muscular  spasm, 
as  during  a  convulsive  yawn,  may  displace  the  condyle  forward  into  the  zygomatic  fossa.  The 
displacement  may  be  unilateral  or  bilateral,  according  as  one  or  both  of  the  condyles  are  dis- 
placed. The  latter  of  the  two  is  the  more  common. 

Sir  Astley  Cooper  described  a  condition  which  he  termed  "  subluxation. "  It  occurs 
principally  in  delicate  women,  and  is  believed  by  some  to  be  due  to  the  relaxation  of  the  liga- 
ments, permitting  too  free  movement  of  the  bone,  and  possibly  some  displacement  of  the  fibro- 
cartilage.  Others  have  believed  that  it  is  due  to  gouty  or  rheumatic  changes  in  the  joint.  In 
close  relation  to  the  condyle  of  the  jaw  is  the  external  auditory  meatus  and  the  tympanum  ;  any 
force,  therefore,  applied  to  the  bone  is  liable  to  be  attended  with  damage  to  these  parts,  or 
inflammation  in  the  joint  may  extend  to  the  ear,  or  on  the  other  hand  inflammation  of  the  middle 
ear  may  involve  the  articulation  and  cause  its  destruction,  thus  leading  to  ankylosis  of  the  joint. 
In  children,  arthritis  of  this  joint  may  also  follow  the  exanthemata,  and  in  adults  occurs  as  the 
result  of  some  constitutional  conditions,  as  rheumatism  or  gout.  The  temporo-maxillary  joint  is 
also  frequently  the  seat  of  osteo-arthritis,  leading  to  great  suffering  during  efforts  of  mastication. 
A  peculiar  affection  sometimes  attacks  the  neck  and  condyle  of  the  lower  jaw,  consisting  in 
hypertrophy  and  elongation  of  these  parts  and  consequent  protrusion  of  the  chin  to  the  oppo- 
site side. 

VI.    Articulations  of  the  Ribs  with  the  Vertebrae. 

The  articulations  of  the  ribs  with  the  vertebral  column  may  be  divided  into 
two  sets :  1.  Those  which  connect  the  heads  of  the  ribs  with  the  bodies  of  the 
vertebrae,  costo-central.  2.  Those  which  connect  the  necks  and  tubercles  of  the 
ribs  with  the  transverse  processes,  costo-transverse. 

1.    ARTICULATIONS  BETWEEN  THE  HEADS  OF  THE  RIBS  AND  THE  BODIES 
OF  THE  VERTEBRAE  (Fig.  235). 

These  constitute  a  series  of  arthrodial  joints,  formed  by  the  articulation  of  the 
heads  of  the  ribs  with  the  cavities  on  the  contiguous  margins  of  the  bodies  of  the 
dorsal  vertebrae,  connected  together  by  the  following  ligaments : 

Anterior  Costo-central  or  Stellate. 
Capsular.  Interarticular. 

The  Anterior  Costo-vertebral  or  Stellate  Ligament  connects  the  anterior  part  of 
the  head  of  each  rib  with  the  sides  of  the  bodies  of  two  vertebrae  and  the  inter- 
vertebral  disk  between  them.  It  consists  of  three  flat  bundles  of  ligamentous 
fibres,  which  radiate  from  the  anterior  part  of  the  head  of  the  rib.  The  superior 
fasciculus  passes  upward  to  be  connected  with  the  body  of  the  vertebra  above ; 
the  inferior  one  descends  to  the  body  of  the  vertebra  below ;  and  the  middle  one, 
the  smallest  and  least  distinct,  passes  horizontally  inward,  to  be  attached  to  the 
intervertebral  substance. 

Relations. — In  front,  with  the  thoracic  ganglia  of  the  sympathetic,  the  pleura, 
and,  on  the  right  side,  with  the  vena  azygos  major;  behind,  with  the  interarticular 
ligament  and  synovial  membranes. 

In  the  first  rib,  which  articulates  with  a  single  vertebra  only,  this  ligament 
does  not  present  a  distinct  division  into  three  fasciculi ;  its  fibres,  however,  radiate, 
and  are  attached  to  the  body  of  the  last  cervical  vertebra,  as  well  as  to  the  body  of 
the  vertebra  with  which  the  rib  articulates.  In  the  tenth,  eleventh,  and  twelfth 
ribs  also,  which  likewise  articulate  with  a  single  vertebra,  the  division  does  not 


OF    THE   RIBS    WITH   THE    VERTEBRA. 


331 


INTERARTICULAR    LIQAME 

Loirer  synovia!  carity. 

FIG.  235.— Costo-vertebral  and  costo-transveree  articulations.    Ante- 
rior view. 


exist :  but  the  fibres  of  the  ligament  in  each  case  radiate  and  are  connected  with 
the  vertebra  above,  as  \vell  as  that  with  which  the  ribs  articulate. 

The  Capsular  Ligament  is  a  thin  and  loose  ligamentous  bag.  which  surrounds 
the  joint  between  the  head  of  the  rib  and  the  articular  cavity  formed  by  the 
inrervertebral  disk  and  the 
adjacent  vertebra.  It  is 
very  thin,  firmly  connected 
with  the  anterior  ligament, 
and  most  distinct  at  the 
upper  and  lower  parts  of 
the  articulation.  Behind, 
some  of  its  fibres  pass 
through  the  intervertebral 
f«rarnen  to  the  back  of  the 
intervertebral  disk.  This 
is  the  analogue  of  the  Hga- 
mentum  conjugate  of  some 
mammals,  which  unites  the 
heads  of  opposite  ribs  a 
the  back  of  the  interverte- 
bral disk. 

The  Interarticular  Liga- 
ment is  situated  in  the 
interior  of  the  joint.  It 
consists  of  a  short  band  of 
fibres,  flattened  from  above 
downward,  attached  by  one 
extremity  to  the  sharp 
crest  on  the  head  of  the 
rib,  and  by  the  other  to  the  intervertebral  disk.  It  divides  the  joint  into  two  cavities, 
which  have  no  communication  with  each  other.  In  the  first,  tenth,  eleventh,  and 
twelfth  ribs  the  interarticular  ligament  does  not  exist ;  consequently,  there  is  but 
one  synovial  membrane.  , 

The  Synovial  Membrane. — There  are  two  synovial  membranes  in  each  of  the 
articulations  in  which  there  is  an  interarticular  ligament,  one  on  each  side  of  this 
structure. 

•2.  ARTICULATIONS  OF  THE  XECKS  AND  TUBERCLES  OF  THE  RIBS  WITH 

THE  TRANSVERSE  PROCESSES  (Fig.  236). 

The  articular  portion  of  the  tubercle  of  the  rib  and  adjacent  transverse  process 
form  an  arthrodial  joint. 

In  the  eleventh  and  twelfth  ribs  this  articulation  is  wanting. 
The  ligaments  connecting  these  parts  are  the — 

Superior  Costo-transverse. 

Middle  Costo-transverse  (Interosseous). 

Posterior  Costo-transverse. 

Capsular. 

The  Superior  Costo-transverse  Ligament  has  two  sets  of  fibres  :  the  one  (anterior 
costo-transi'erse  liyam>-nt)  is  attached  to  the  crest  on  the  upper  border  of  the  neck 
of  each  rib.  and  passes  obliquely  upward  and  outward  to  the  lower  border  of  the 
transverse  process  immediately  above ;  the  other  (posterior  costo-transverse  liga- 
ment] is  attached  to  the  neck  of  the  rib,  and  passes  upward  and  inward  to  the  base 
of  the  transverse  process  and  border  of  the  lower  articular  process  of  the  vertebra 
above.  This  ligament  is  in  relation,  in  front,  with  the  intercostal  vessels  and 
nerves;  behind,  with  the  Longissimus  dorsi.  Its  internal  border  completes  an 
aperture  formed  between  it  and  the  articular  processes,  through  which  pass  the 


332  THE  ARTICULATIONS. 

posterior  branches  of  the  intercostal  vessels  and  nerves.  Its  external  border  is 
continuous  with  a  thin  aponeurosis  which  covers  the  External  intercostal  muscle. 

The  first  rib  has  no  anterior  costo-transverse  ligament. 

The  Middle  Costo-transverse  or  Interosseous  Ligament  consists  of  short  but 
strong  fibres  which  pass  between  the  rough  surface  on  the  posterior  part  of  the 
neck  of  each  rib  and  the  anterior  surface  of  the  adjacent  transverse  process.  In 


ANTERIOR    COSTO-TRANSVERSE 

LIGAMENT    DIVIDED. 


or  INTEHOSSEOUS 

POSTERIOR    COSTO- 
TRANSVERSE    LIGAMENT 


FIG.  236.— Costo-transverse  articulation.    Seen  from  above. 

order  fully  to  expose  this  ligament,  a  horizontal  section  should  be  made  across  the 
transverse  process  and  corresponding  part  of  the  rib  ;  or  the  rib  may  be  forcibly 
separated  from  the  transverse  process  and  its  fibres  put  on  the  stretch. 

In  the  eleventh  and  twelfth  ribs  this  ligament  is  quite  rudimentary  or 
wanting. 

The  Posterior  Costo-transverse  Ligament  is  a  short  but  thick  and  strong  fascic- 
ulus which  passes  obliquely  from  the  summit  of  the  transverse  process  to  the 
rough  non-articular  portion  of  the  tubercle  of  the  rib.  This  ligament  is  shorter 
and  more  oblique  in  the  upper  than  in  the  lower  ribs.  Those  corresponding  to 
the  superior  ribs  ascend,  while  those  of  the  inferior  ribs  descend  slightly. 

In  the  eleventh  and  twelfth  ribs  this  ligament  is  wanting. 

The  Capsular  Ligament  is  a  thin,  membranous  sac  attached  to  the  circumference 
of  the  articular  surfaces,  and  enclosing  a  small  synovial  membrane. 

In  the  eleventh  and  twelfth  ribs  this  ligament  is  absent. 

Actions. — The  heads,  necks,  and  tubercles  of  the  ribs  are  so  closely  connected 
to  the  bodies  and  transverse  processes  of  the  vertebrae  that  only  a  slight  gliding 
movement  of  the  articular  surfaces  on  each  other  can  take  place  in  these  articu- 
lations. The  result  of  this  gliding  movement  is  for  the  upper  six  ribs  an  ele- 
vation of  the  front  and  middle  portion  of  the  rib,  the  hinder  part  being  pre- 
vented from  performing  any  upward  movement  by  its  close  connection  with  the 
spine.  In  this  gliding  movement  the  rib  rotates  on  an  axis  corresponding  with 
a  line  drawn  through  the  two  articulations,  Costo-central  and  Costo-transverse, 
which  the  rib  forms  with  the  spine.  Of  the  four  succeeding  ribs,  each  one, 
besides  rotating  on  the  above-mentioned  axis,  also  rotates  on  an  axis  corre- 
sponding with  a  line  drawn  from  the  head  of  the  rib  to  the  sternum.  In  other 
words,  an  upivard  and  backward  gliding  is  permitted  between  tubercle  and  trans- 
verse process,  owing  to  the  especial  degree  of  obliquity  existing  between  the  corre- 


OF    THE  RIBS    WITH   THE    VERTEBRA. 


333 


spending  facets.  By  the  first  movement  an  elevation  of  the  anterior  part  of  the 
rib  takes  place,  and  a  consequent  enlargement  of  the  antero-posterior  diameter  of 
the  chest.  None  of  the  ribs  lie  in 
a  truly  horizontal  plane ;  they  are 
all  directed  more  or  less  obliquely, 
so  that  their  anterior  extremities 
lie  on  a  lower  level  than  their  pos- 
terior, and  this  obliquity  increases 
from  the  first  to  the  seventh,  and 
then  again  decreases.  If  we  ex- 
amine any  one  rib — say.  that  in 
which  there  is  the  greatest  obliq- 
uity— we  shall  see  that  it  is  ob- 
vious that  as  its  sternal  extremity 
is  carried  upward,  it  must  also  be 
thrown  forward ;  so  that  the  rib 
may  be  regarded  as  a  radius  mov- 
ing on  the  vertebral  joint  as  a  cen- 
tre, and  causing  the  sternal  attach- 
ment to  describe  an  arc  of  a  circle 
in  the  vertical  plane  of  the  body. 
Since  all  the  ribs  are  oblique  and 
connected  in  front  to  the  sternum 
by  the  elastic  costal  cartilages,  they 
must  have  a  tendency  to  thrust  the 
sternum  forward,  and  so  increase 
the  antero-posterior  diameter  of 
the  chest.  By  the  second  move- 
ment— that  of  the  rotation  of  the 
rib  on  an  axis  corresponding  with 
a  line  drawn  from  the  head  of  the 
rib  to  the  sternum — an  elevation 
of  the  middle  portion  of  the  rib 
takes  place,  and  consequently  an 
increase  in  the  transverse  diameter 
of  the  chest.  This  elevation  of 
the  3d.  4th,  5th,  and  6th  ribs  is 
due  entirely  to  the  shapes  of  the 
ribs — i.  e.  each  rib  being  bent  or 

twisted  around  three  axes — and  not  to  this  movement  (see  above).  For 
the  7th,  8th,  9th,  and  10th  ribs  this  elevation  is  due  both  to  their  shapes 
and  to  this  movement.  The  last  two  ribs  move  chiefly  backward  and  for-' 
ward,  and  with  very  little  "  elevation "  of  their  middle  portions  (see  Fig. 
237).  The  mobility  of  the  different  ribs  varies  very  much.  The  first  rib  is 
more  fixed  than  the  others,  on  account  of  the  weight  of  the  upper  extremity 
and  the  strain  of  the  ribs  beneath  ;  but  on  the  freshly  dissected  thorax  it  moves  as 
freely  as  the  others.  From  the  same  causes  the  movement  of  the  second  rib  is 
also  not  very  extensive.  In  the  other  ribs  this  mobility  increases  successively 
doAvn  to  the  last  two,  which  are  very  movable.  The  ribs  are  generally  more 
movable  in  the  female  than  in  the  male. 

VII.  Articulation  of  the  Cartilages  of  the  Ribs  with  the  Sternum, 

etc.  (Fip.  238). 

The  articulations  of  the  cartilages  of  the  true  ribs  with  the  sternum  are  artb.ro- 
dial  joints,  with  the  exception  of  the  first,  in  which  the  cartilage  is  almost  always 
directly  united  writh  the  sternum,  and  which  must  therefore  be  regarded  as  a 
synarthrodial  articulation.  The  ligaments  connecting  them  are — 


FIG.  237. — Diagrams  showing  the  axis  of  rotation  of  the 
ribs  in  the  movements  of  respiration.  The  one  axis  of  rota- 
tion corresponds  with  a  line  drawn  through  the  two  articu- 
lations which  the  rib  forms  with  the  spine  (a,  b),  and  the 
other  with  a  line  drawn  from  the  head  of  the  rib  to  the 
sternum  (A,  B).  (From  Kirke's  Handbook  of  Physioloyy.) 


334  THE  ARTICULATIONS 

Anterior  Chondro-sternal.  Interarticular  Chondro-sternal. 

Posterior  Chondro-sternal.  Anterior  Chondro-xiphoid. 

Capsular.  Posterior  Chondro-xiphoid. 

The  Anterior  Chondro-sternal  Ligament  is  a  broad  and  thin  membranous  band 
that  radiates  from  the  front  of  the  inner  extremity  of  the  cartilages  of  the  true 
ribs  to  the  anterior  surface  of  the  sternum.  It  is  composed  of  fasciculi  which  pass 
in  different  directions.  The  superior  fasciculi  ascend  obliquely,  the  inferior  pass 
obliquely  downward,  and  the  middle  fasciculi  horizontally.  The  superficial  fibres 
of  this  ligament  are  the  longest :  they  intermingle  with  the  fibres  of  the  ligaments 
above  and  below  them,  with  those  of  the  opposite  side,  and  with  the  tendinous 
fibres  of  origin  of  the  Pectoralis  major,  forming  a  thick  fibrous  membrane  which 
covers  the  surface  of  the  sternum.  This  is  more  distinct  at  the  lower  than  at  the 
upper  part. 

The  Posterior  Chondro-sternal  Ligament,  less  thick  and  distinct  than  the 
anterior,  is  composed  of  fibres  which  radiate  from  the  posterior  surface  of  the 
sternal  end  of  the  cartilages  of  the  true  ribs  to  the  posterior  surface  of  the  sternum, 
becoming  blended  with  the  periosteum. 

The  Capsular  Ligament  surrounds  the  joints  formed  between  the  cartilages 
of  the  true  ribs  and  the  sternum.  It  is  very  thin,  intimately  blended  with  the 
anterior  and  posterior  ligaments,  and  strengthened  at  the  upper  and  lower  part  of 
the  articulation  by  a  few  fibres  which  pass  from  the  cartilage  to  the  side  of  the 
sternum.  These  ligaments  protect  the  synovial  membranes. 

The  Interarticular  Chondro-sternal  Ligaments. — These  are  only  found  between 
the  second  and  third  costal  cartilages  and  the  sternum.  The  cartilage  of  the 
second  rib  is  connected  with  the  sternum  by  means  of  an  interarticular  ligament 
attached  by  one  extremity  to  the  cartilage  of  the  second  rib,  and  by  the  other 
extremity  to  the  cartilage  which  unites  the  first  and  second  pieces  of  the  sternum. 
This  articulation  is  provided  with  two  synovial  membranes.  The  cartilage  of  the 
third  rib  is  connected  with  the  sternum  by  means  of  an  interarticular  ligament 
which  is  attached  by  one  extremity  to  the  cartilage  of  the  third  rib,  and  by  the 
other  extremity  to  the  point  of  junction  of  the  second  and  third  pieces  of  the 
sternum.  This  articulation  is  provided  with  two  synovial  membranes. 

The  Anterior  Chondro-xiphoid. — This  is  a  band  of  ligamentous  fibres  which 
connects  the  anterior  surface  of  the  seventh  costal  cartilage,  and  occasionally  also 
that  of  the  sixth,  to  the  anterior  surface  of  the  ensiform  appendix.  It  varies  in 
length  and  breadth  in  different  subjects. 

The  Posterior  Chondro-xiphoid  is  a  similar  band  of  fibres  on  the  internal  or 
posterior  surface,  though  less  thick  and  distinct. 

Synovial  Membranes. — There  is  no  synovial  membrane  between  the  first  costal 
cartilage  and  the  sternum,  as  this  cartilage  is  directly  continuous  with  the  sternum. 
There  are  two  synovial  membranes,  both  in  the  articulation  of  the  second  and  third 
costal  cartilages  to  the  sternum.  There  is  generally  one  synovial  membrane  in  each 
of  the  joints  between  the  fourth,  fifth,  sixth,  and  seventh  costal  cartilages  to  the 
sternum;  but  it  is  sometimes  absent  in  the  sixth  and  seventh  chondro-sternal 
joints.  Thus  there  are  eight  synovial  cavities  on  each  side  in  the  articulations 
between  the  costal  cartilages  of  the  true  ribs  and  the  sternum.  After  middle  life 
the  articular  surfaces  lose  their  polish,  become  roughened,  and  the  synovial 
membranes  appear  to  be  wanting.  In  old  age  the  articulations  do  not  exist,  the 
cartilages  of  most  of  the  ribs  becoming  continuous  with  the  sternum. 

Actions. — The  movements  which  are  permitted  in  the  chondro-sternal  articu- 
lations are  limited  to  elevation  and  depression,  and  these  only  to  a  slight  extent. 

Articulations  of  the  Cartilages  of  the  Ribs  with  each  other 
(Interchondral)  (Fig.   238). 

The  contiguous  borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the 
ninth  and  tenth,  costal  cartilages  articulate  with  each  other  by  small,  smooth, 


OF    THE   RIBS    WITH    THEIR    CARTILAGES. 


335 


oblong-shaped  facets.  Each  articulation  is  enclosed  in  a  thin  capsular  ligament 
lined  by  ftynovial  membrane,  and  strengthened  externally  and  internally  by  liga- 
mentous  fibres  (interchondral  ligaments)  which  pass  from  one  cartilage  to  the 
other.  Sometimes  the  fifth  costal  cartilage,  more  rarely  that  of  the  ninth,  articu- 
lates, by  its  lower  border,  with  the  adjoining  cartilage  by  a  small  oval  facet ;  more 

The  synovial  cavities  exposed  by 
a  vertical  section  of  the  sternum  and  curtilages. 

Cartilage  continous  with 
sternum. 


ana 
two  synovial  membranes. 


Single  synovial 
membrane. 


FIG.  238.— Chondro-sternal,  chondro-xiphoid.  and  interchondral  articulations.    Anterior  view. 

frequently  they  are  connected  together  by  a  few  ligamentous  fibres.     Occasionally 
the  articular  surfaces  above  mentioned  are  wanting. 

Articulations  of  the  Ribs  with  their  Cartilages  (Costo-chondral) 

(Fig.  238). 

The  outer  extremity  of  each  costal  cartilage  is  received  into  a  depression  in  the 
sternal  end  of  the  ribs,  and  the  two  are  held  together  by  the  periosteum. 


336 

VIII.  Ligaments  of  the  Sternum. 

The  first  piece  of  the  sternum  is  united  to  the  second  either  by  an  amphi- 
arthrodial  joint — a  single  piece  of  true  fibro-cartilage  uniting  the  segments — or 
by  a  diarthrodial  joint,  in  which  each  bone  is  clothed  with  a  distinct  lamina  of 
cartilage,  adherent  on  one  side,  free  and  lined  with  synovia!  membrane  on  the 
other.  In  the  latter  case  the  cartilage  covering  the  gladiolus  is  continued  without 
interruption  on  to  the  cartilages  of  the  second  ribs.  Mr.  Rivington  has  found  the 
diarthrodial  form  of  joint  in  about  one-third  of  the  specimens  examined  by  him  ; 
Mr.  Maisonneuve  more  frequently.  It  appears  to  be  rare  in  childhood,  and  is 
formed,  in  Mr.  Rivington's  opinion,  from  the  amphiarthrodial  form  by  absorption. 
The  diarthrodial  joint  seems  to  have  no  tendency  to  ossify  at  any  age,  while  the 
amphiarthrodial  is  more  liable  to  do  so,  and  has  been  found  ossified  as  early  as 
thirty-four  years  of  age.  The  two  segments  are  further  connected  by  an 

Anterior  Intersternal  Ligament  and  a 
Posterior  Intersternal  Ligament. 

The  Anterior  Intersternal  Ligament  consists  of  a  layer  of  fibres,  having  a 
longitudinal  direction ;  it  blends  with  the  fibres  of  the  anterior  chondro-sternal 
ligaments  on  both  sides,  and  with  the  tendinous  fibres  of  origin  of  the  Pectoralis 
major.  This  ligament  is  rough,  irregular,  and  much  thicker  below  than  above. 

The  Posterior  Intersternal  Ligament  is  disposed  in  a  somewhat  similar 
manner  on  the  posterior  surface  of  the  articulation. 

IX.  Articulation  of  the  Pelvis  with  the  Spine. 

The  ligaments  connecting  the  last  lumbar  vertebra  with  the  sacrum  are  similar 
to  those  which  connect  the  segments  of  the  spine  with  each  other — viz  :  1.  The 
continuation  downward  of  the  anterior  and  posterior  common  ligaments.  2.  The 
intervertebral  substance  connecting  the  flattened  oval  surfaces  of  the  two  bones 
and  forming  an  amphiarthrodial  joint.  3.  Ligamenta  subflava,  connecting  the 
arch  of  the  last  lumbar  vertebra  with  the  posterior  border  of  the  sacral  canal. 
4.  Capsular  ligaments  connecting  the  articulating  processes  and  forming  a  double 
arthrodia.  5.  Inter-  and  supraspinous  ligaments. 

The  two  proper  ligaments  connecting  the  pelvis  with  the  spine  are  the  lumbo- 
sacral  and  ilio-lumbar. 

The  Lumbo-sacral  Ligament  (Fig.  239)  is  a  short,  thick,  triangular  fasciculus, 
which  is  connected  above  to  the  lower  and  front  part  of  the  transverse  process 
of  the  last  lumbar  vertebra,  passes  obliquely  outward,  and  is  attached  below  to 
the  lateral  surface  of  the  base  of  the  sacrum,  becoming  blended  with  the  anterior 
sacro-iliac  ligament.  This  ligament  is  in  relation,  in  front,  with  the  Psoas 
muscle,  and  represents  the  anterior  costo-transverse  ligament. 

The  Ilio-lumbar  Ligament  (Fig.  239)  passes  horizontally  outward  from  the 
apex  of  the  transverse  process  of  the  last  lumbar  vertebra  to  the  crest  of  the  ilium 
immediately  in  front  of  the  sacro-iliac  articulation.  It  is  of  a  triangular  form, 
thick  and  narrow  internally,  broad  and  thinner  externally.  It  is  in  relation,  in 
front,  with  the  Psoas  muscle  ;  behind,  with  the  muscles  occupying  the  vertebral 
groove ;  above,  with  the  Quadratus  lumborum. 

X.  Articulations  of  the  Pelvis. 

The  ligaments  connecting  the  bones  of  the  pelvis  with  each  other  may  be 
divided  into  four  groups :  1.  Those  connecting  the  sacrum  and  ilium.  2.  Those 
passing  between  the  sacrum  and  ischium.  3.  Those  connecting  the  sacrum  and 
coccyx.  4.  Those  between  the  two  pubic  bones. 

1.    ARTICULATIONS  OF  THE  SACRUM  AND  ILIUM. 

The  sacro-iliac  articulation  is  formed  between  the  lateral  surfaces  of  the 
sacrum  and  ilium.  The  anterior  or  auricular  portion  of  each  articular  surface 


OF   THE  PELVIS. 


337 


is  covered  with  a  thin  plate  of  cartilage,  thicker  on  the  sacrum  than  on  the 
ilium.  The  surfaces  of  these  cartilages  are  usually  in  close  contact,  but  not 
united.  Sometimes  fine  fibres  are  found  running  between  portions  of  these  sur- 
faces, which  in  other  cases  may  be,  in  the  adult,  rough  and  irregular,  and  sepa- 
rated from  one  another  by  spaces  containing  synovial-like  fluid.  The  ligaments 
connecting  these  surfaces  are  the  anterior  and  posterior  sacro-iliac. 

The   Anterior   Sacro-iliac   Ligament   (Fig.    239)    consists   of    numerous   thin 
ligamentous  bands  which  connect  the  anterior  surfaces  of  the  sacrum  and  ilium. 


Aperture  of  communication 
with 

PSOAS  and  ILIACUS. 


Femur.  \ 

FIG.  239.—  Articulations  of  pel  vis  and  hip.    Anterior  view. 

The  Posterior  Sacro-iliac  (Fig.  240)  is  a  strong  interosseous  ligament,  situated 
in  a  deep  depression  between  the  sacrum  and  ilium  behind,  and  forming  the  chief 
bond  of  connection  between  those  bones.  It  consists  of  numerous  strong  fasciculi 
which  pass  between  the  bones  in  various  directions.  Three  of  these  are  of  large 
size  :  the  two  superior,  nearly  horizontal  in  direction,  arise  from  the  first  and 
second  transverse  tubercles  on  the  posterior  surface  of  the  sacrum,  and  are  inserted 
into  the  rough,  uneven  surface  at  the  posterior  part  of  the  inner  surface  of  the 
ilium.  The  third  fasciculus,  oblique  in  direction,  is  attached  by  one  extremity  to 
the  third  transverse  tubercle  on  the  posterior  surface  of  the  sacrum,  and  by  the 
other  to  the  posterior  superior  spine  of  the  ilium  ;  it  is  sometimes  called  the 
sacro-iliac  ligament. 


The  position  of  the  sacro-iliac  joint  is  indicated  by  the  posterior  superior  spine  of  the  ilium. 
This  process  is  immediately  behind  the  centre  of  the  articulation. 

2.  LIGAMENTS  PASSING  BETWEEN  THE  SACRUM  AND  ISCHIUM  (Fig.  240). 

The  Great  Sacro-sciatic  (Posterior). 
The  Lesser  Sacro-sciatic  (Anterior). 

The  Great  or  Posterior  Sacro-sciatic  Ligament  is  situated  at  the  lower  and 
back  part  of  the  pelvis.     It  is  thin,  flat,  and  triangular  in  form  ;  narrower  in  the 
22 


338 


THE  ARTICULATIONS 


middle  than  at  the  extremities ;  attached  by  its  broad  base  to  the  posterior  inferior 
spine  of  the  ilium,  to  the  fourth  and  fifth  transverse  tubercles  of  the  sacrum,  and 
to  the  lower  part  of  the  lateral  margin  of  that  bone  and  the  coccyx.  Passing 
obliquely  downward,  outward,  and  forward,  it  becomes  narrow  and  thick,  and 
at  its  insertion  into  the  inner  margin  of  the  tuberosity  of  the  ischium  it  increases 
in  breadth,  and  is  prolonged  forward  along  the  inner  margin  of  the  ramus,  forming 
what  is  known  as  the  falciform  ligament.  The  free  concave  edge  of  this  prolonga- 
tion has  attached  to  it  the  obturator  fascia,  with  which  it  forms  a  kind  of  groove, 
protecting  the  internal  pudic  vessels  and  nerve.  One  of  its  surfaces  is  turned 
toward  the  perinseum,  the  other  toward  the  Obturator  internus  muscle. 

The  posterior  surface  of  this  ligament  gives  origin,  by  its  whole  extent,  to  fibres 
of  the  Gluteus  maximus.     Its  anterior  surface   is  united  to  the  lesser  sacro-sciatic 


ANTERIOR  Or  LESSER 

SACRO-SCIATIC 

LIGAMENT. 


femur.1 

FIG.  240. — Articulations  of  pelvis  and  hip.    Posterior  view. 

ligament.  Its  external  border  forms,  above,  the  posterior  boundary  of  the  great 
sacro-sciatic  foramen,  and,  below,  the  lower  boundary  of  the  lesser  sacro-sciatic 
foramen.  Its  lower  border  forms  part  of  the  boundary  of  the  perinaeum.  It  is 
pierced  by  the  coccygeal  branch  of  the  sciatic  artery  and  coccygeal  nerve. 

The  Lesser  or  Anterior  Sacro-sciatic  Ligament,  much  shorter  and  smaller 
than  the  preceding,  is  thin,  triangular  in  form,  attached  by  its  apex  to  the  spine 
of  the  ischium,  and  internally,  by  its  broad  base,  to  the  lateral  margin  of  the 
sacrum  and  coccyx,  anterior  to  the  attachment  of  the  great  sacro-sciatic  ligament, 
with  which  its  fibres  are  intermingled. 

It  is  in  relation,  anteriorly,  with  the  Coccygeus  muscle ;  posteriorly,  it  is  covered 
by  the  great  sacro-sciatic  ligament  and  crossed  by  the  internal  pudic  vessels  and 
nerve.  Its  superior  border  forms  the  lower  boundary  of  the  great  sacro-sciatic 
foramen ;  its  inferior  border,  part  of  the  lesser  sacro-sciatic  foramen. 

These  two  ligaments  convert  the  sacro-sciatic  notches  into  foramina.  The 
superior  or  great  sacro-sciatic  foramen  is  bounded,  in  front  and  above,  by  the 


OF   THE   PELVIS.  339 

posterior  border  of  the  os  innominatum  ;  behind,  by  the  great  sacro-sciatic  ligament ; 
and  below,  by  the  lesser  sacro-sciatic  ligament.  It  is  partially  filled  up,  in  the 
recent  state,  by  the  Pyriformis  muscle,  which  passes  through  it.  Above  this  muscle 
the  gluteal  vessels  and  superior  gluteal  nerve  emerge  from  the  pelvis,  and,  below 
it.  the  sciatic  vessels  and  nerves,  the  internal  pudic  vessels  and  nerve,  and  muscular 
branches  from  the  sacral  plexus.  The  inferior  or  lesser  sacro-sciatic  foramen  is 
bounded,  in  front,  by  the  tuber  ischii ;  above,  by  the  spine  and  lesser  sacro-sciatic 
ligament ;  behind,  by  the  greater  sacro-sciatic  ligament.  It  transmits  the  tendon 
of  the  Obturator  internus  muscle,  its  nerve,  and  the  internal  pudic  vessels  and 
nerve. 

3.  ARTICULATION  OF  THE  SACRUM  AND  COCCYX. 

This  articulation  is  an  arthrodial  joint,  and  is  formed  between  the  oval  sur- 
face at  the  apex  of  the  sacrum  and  the  base  of  the  coccyx.  It  is  connected  by 
the  following  ligaments : 

Interarticular. 

Anterior  Sacro-coccygeal.  Lateral  Sacro-coccygeal. 

Posterior  Sacro-coccygeal.  Interposed  Fibro-cartilage. 

The  Interarticular  Ligaments  connect  the  cornua  of  the  two  bones. 

The  Anterior  Sacro-coccygeal  Ligament  consists  of  a  few  irregular  fibres  which 
descend  from  the  anterior  surface  of  the  sacrum  to  the  front  of  the  coccyx,  becom- 
ing blended  with  the  periosteum. 

The  Posterior  Sacro-coccygeal  Ligaments  are  the  superficial  and  the  deep.  The 
superficial  is  a  flat  band  of  ligamentous  fibres,  of  a  pearly  tint,  which  arises  from 
the  margin  of  the  lower  orifice  of  the  sacral  canal  and  descends  to  be  inserted 
into  the  posterior  surface  of  the  coccyx.  This  ligament  completes  the  lower  and 
back  part  of  the  sacral  canal.  The  deep  consists  of  a  few  fibres,  which  descend 
to  the  coccyx  from  that  part  of  the  sacrum  which  forms  the  anterior  wall  of  the 
lower  part  of  the  sacral  canal.  Its  lower  end  blends  with  the  preceding. 

The  Lateral  Sacro-coccygeal  Ligaments  are  ligamentous  bands,  each  of  which 
passes  from  the  inferior  lateral  angle  of  the  sacrum  to  the  transverse  process  of 
the  first  piece  of  the  coccyx. 

A  Fibro-cartilage  is  interposed  between  the  contiguous  surfaces  of  the  sacrum 
and  coccyx.  It  is  somewhat  thicker  in  front  and  behind  than  at  the  sides.  Occa- 
sionally, a  synovial  membrane  is  found  when  the  coccyx  is  freely  movable,  which 
is  more  especially  the  case  during  pregnancy. 

The  different  segments  of  the  coccyx  are  connected  together  by  an  extension 
downward  of  the  anterior  and  posterior  sacro-coccygeal  ligaments,  a  thin  annular 
disk  of  fibro-cartilage  being  interposed  between  each  of  the  bones.  In  the  adult 
male  all  the  pieces  become  ossified,  but  in  the  female  this  does  not  commonly 
occur  until  a  later  period  of  life.  The  separate  segments  of  the  coccyx  are  first 
united,  and  at  a  more  advanced  age  the  joint  between  the  sacrum  and  coccyx  is 
obliterated. 

Actions. — The  movements  Avhich  take  place  between  the  sacrum  and  coccyx, 
and  between  the  different  pieces  of  the  latter  bone,  are  slightly  forward  and 
backward ;  they  are  very  limited.  Their  extent  increases  during  pregnancy. 

4.  ARTICULATION  OF  THE  OSSA  PUBIS  (Fig.  241). 

The  articulation  between  the  pubic  bones  is  an  amphiarthrodial  joint,  formed 
by  the  junction  of  the  two  oval  articular  surfaces  of  the  ossa  pubis.  The  articular 
surface  has  been  described  on  a  former  page  under  the  name  of  symphysis,  and  the 
same  name  is  given  to  the  joint.  The  ligaments  of  this  articulation  are  the 

Anterior  Pubic.  Posterior  Pubic. 

Superior  Pubic.  Subpubic. 

Interpubic  disk. 


340 


THE   ARTICULATIONS. 


Hyaline  carrilage  covering  bone. 
Intermediate  fibro-cartilage. 

Cavity  at  upper  and  back 


FIG.  241.— Vertical  section  of  the  symphysis  pubis. 
Made  near  its  posterior  surface. 


The  Anterior  Pubic  Ligament  consists  of  several  superimposed  layers  which 
pass  across  the  front  of  the  articulation.  The  superficial  fibres  pass  obliquely 

from  one  bone  to  the  other,  decussating 
and  forming  an  interlacement  with  the 
fibres  of  the  aponeurosis  of  the  Ex- 
ternal oblique  and  the  tendon  of  the 
Rectus  muscles.  The  deep  fibres  pass 
transversely  across  the  symphysis,  and 
are  blended  with  the  fibro-cartilage. 

The  Posterior  Pubic  Ligament  con- 
sists of  a  few  thin,  scattered  fibres 
which  unite  the  two  pubic  bones  pos- 
teriorly. 

The  Superior  Pubic  Ligament  is  a 
band  of  fibres  which  connects  together 
the  two  pubic  bones  superiorly. 

The  Subpubic  Ligament  is  a  thick, 
triangular  arch  of  ligamentous  fibres, 
connecting  together  the  two  pubic 
bones  below  and  forming  the  upper 
boundary  of  the  pubic  arch.  Above, 
it  is  blended  with  the  interarticular 

fibro-cartilage ;  laterally  it  is  united  with  the  rami  of  the  os  pubis.     Its  fibres  are 
closely  connected  and  have  an  arched  direction. 

The  Interpubic  Disk  consists  of  a  disk  of  cartilage  and  fibro-cartilage  con- 
necting the  surfaces  of  the  pubic  bones  in  front.  Each  pubic  symphysis  is  covered 
by  a  thin  layer  of  hyaline  cartilage  which  is  firmly  connected  to  the  bone  by 
a  series  of  nipple-like  processes  which  accurately  fit  Avithin  corresponding  depres- 
sions on  the  osseous  surfaces.  These  opposed  cartilaginous  surfaces  are  connected 
together  by  an  intermediate  stratum  of  fibrous  tissue  and  fibro-cartilage  which 
varies  in  thickness  in  different  subjects.  It  often  contains  a  cavity  in  its  centre, 
probably  formed  by  the  softening  and  absorption  of  the  fibro-cartilage,  since  it 
rarely  appears  before  the  tenth  year  of  life,  and  is  not  lined  by  synovia!  membrane. 
It  is  larger  in  the  female  than  in  the  male,  but  it  is  very  questionable  whether  it 
enlarges,  as  was  formerly  supposed,  during  pregnancy.  It  is  most  frequently 
limited  to  the  upper  and  back  part  of  the  joint,  but  it  occasionally  reaches  to  the 
front,  and  may  extend  the  entire  length  of  the  cartilage.  This  cavity  may  be 
easily  demonstrated  by  making  a  vertical  section  of  the  symphysis  pubis  near  its 
posterior  surface. 

The  Obturator  Ligament  is  more  properly  regarded  as  analogous  to  the 
muscular  fasciae,  with  which  it  will  be  described. 

ARTICULATIONS  OF  THE  UPPER  EXTREMITY. 

The  articulations  of  the  upper  extremity  may  be  arranged  in  the  following 
groups :  I.  Sterno-clavicular  articulation.  II.  Acromio-clavicular  articulation. 
III.  Ligaments  of  the  Scapula.  IV.  Shoulder-joint.  V.  Elbow-joint.  VI. 
Radio-ulnar  articulations.  VII.  Wrist-joint.  VIII.  Articulations  of  the  Carpal 
Bones.  IX.  Carpo-metacarpal  articulations.  X.  Metacarpo-phalangeal  articula- 
tions. XI.  Articulations  of  the  Phalanges. 

/-  I.  Sterno-clavicular  Articulation  (Fig.  242). 

The  Sterno-clavicular  is  regarded  by  most  anatomists  as  an  arthrodial  joint, 
but  Cruveilhier  considers  it  to  be  an  articulation  by  reciprocal  reception.  Probably 
the  former  opinion  is  the  correct  one,  the  varied  movement  which  the  joint 
enjoys  being  due  to  the  interposition  of  an  interarticular  fibro-cartilage  between 
the  joint  surfaces.  The  parts  entering  into  its  formation  are  the  sternal  end  of  the 


STERNO- CLA  VICULAR   AR TICULA  TION. 


341 


clavicle,  the  upper  and  lateral  part  of  the  first  piece  of  the  sternum,  and  the 
cartilage  of  the  first  rib.     The  articular  surface  of  the  clavicle  is  much  larger  than 


FIG.  242.— Sterno-clavicular  articulation.    Anterior  view. 

that  of  the  sternum,  and  invested  with  a  layer  of  cartilage  l  which  is  considerably 
thicker  than  that  on  the  latter  bone.     The  ligaments  of  this  joint  are  the 

Anterior  Sterno-clavicular.  Interclavicular. 

Posterior  Sterno-clavicular.  Costo-clavicular  (rhomboid). 

Interarticular  Fibro-cartilage. 

The  Anterior  Sterno-clavicular  Ligament  is  a  broad  band  of  fibres  which 
covers  the  anterior  surface  of  the  articulation,  being  attached,  above,  to  the  upper 
and  front  part  of  the  inner  extremity  of  the  clavicle,  and,  passing  obliquely 
downward  and  inward,  is  attached,  below,  to  the  upper  and  front  part  of  the  first 
piece  of  the  sternum.  This  ligament  is  covered,  in  front,  by  the  sternal  portion  of 
the  Sterno-cleido-mastoid  and  the  integument ;  behind,  it  is  in  relation  with  the 
interarticular  fibro-cartilage  and  the  two  synovial  membranes. 

The  Posterior  Sterno-clavicular  Ligament  is  a  similar  band  of  fibres  which 
covers  the  posterior  surface  of  the  articulation,  being  attached,  above,  to  the  upper 
and  back  part  of  the  inner  extremity  of  the  clavicle,  and,  passing  obliquely 
downward  and  inward,  is  attached,  below,  to  the  upper  and  back  part  of  the  first 
piece  of  the  sternum.  It  is  in  relation,  in  front,  with  the  interarticular  fibro- 
cartilage  and  synovial  membranes ;  behind,  with  the  Sterno-hyoid  and  Sterno- 
thyroid  muscles. 

The  Interclavicular  Ligament  is  a  flattened  band  which  varies  considerably 
in  form  and  size  in  different  individuals ;  it  passes  in  a  curved  direction  from  the 
upper  part  of  the  inner  extremity  of  one  clavicle  to  the  other,  and  is  closely 
attached  to  the  upper  margin  of  the  sternum.  It  is  in  relation,  in  front,  with  the 
integument :  behind,  with  the  Sterno-thyroid  muscles. 

The  Costo-clavicular  Ligament  (rhomboid)  is  short,  flat,  and  strong :  it  is  of 
a  rhomboid  form,  attached,  below,  to  the  upper  and  inner  part  of  the  cartilage  of 
the  first  rib :  it  ascends  obliquely  backward  and  outward,  and  is  attached,  above, 
to  the  rhomboid  depression  on  the  under  surface  of  the  clavicle.  It  is  in  relation, 
in  front,  with  the  tendon  of  origin  of  the  Subclavius ;  behind,  with  the  subclavian 
vein. 

The  Interarticular  Fibro-cartilage  is  a  flat  and  nearly  circular  disk,  interposed 
between  the  articulating  surfaces  of  the  sternum  and  clavicle.  It  is  attached, 

1  According  to  Bruch,  the  sternal  end  of  the  clavicle  is  covered  by  a  tissue  which  is  rather 
fibrous  than  cartilaginous  in  structure. 


342  THE   ARTICULATIONS. 

above,  to  the  upper  and  posterior  border  of  the  articular  surface  of  the  clavicle  ; 
below,  to  the  cartilage  of  the  first  rib,  at  its  junction  with  the  sternum ;  and  by 
its  circumference,  to  the  anterior  and  posterior  sterno-clavicular  and  interclavicular 
ligaments.  It  is  thicker  at  the  circumference,  especially  its  upper  and  back  part, 
than  at  it's  centre  or  below.  It  divides  the  joint  into  two  cavities,  each  of  which  is 
furnished  with  a  separate  synovial  membrane. 

Of  the  two  Synovial  Membranes  found  in  this  articulation,  one  is  reflected 
from  the  sternal  end  of  the  clavicle  over  the  adjacent  surface  of  the  fibro-cartilage 
and  cartilage  of  the  first  rib  ;  the  other  is  placed  between  the  articular  surface  of 
the  sternum  and  adjacent  surface  of  the  fibro-cartilage  ;  the  latter  is  the  larger  of 
the  two.  They  seldom  contain  much  synovia. 

Actions. — This  articulation  is  the  centre  of  the  movements  of  the  shoulder,  and 
admits  of  a  limited  amount  of  motion  in  nearly  every  direction — upward,  down- 
ward, backward,  forward — as  well  as  circumduction.  When  these  movements 
take  place  in  the  joint,  the  clavicle  in  its  motion  carries  the  scapula  with  it,  this 
bone  gliding  on  the  outer  surface  of  the  chest.  This  joint  therefore  forms  the 
centre  from  which  all  movements  of  the  supporting  arch  of  the  shoulder  originate, 
and  is  the  only  point  of  articulation  of  this  part  of  the  skeleton  with  the  trunk. 
"  The  movements  attendant  on  elevation  and  depression  of  the  shoulder  take  place 
between  the  clavicle  and  the  interarticular  fibro-cartilage,  the  bone  rotating  upon 
the  ligament  on  an  axis  drawn  from  before  backward  through  its  own  articular 
facet.  When  the  shoulder  is  moved  forward  and  backward,  the  clavicle,  with 
the  interarticular  fibro-cartilage,  rolls  to  and  fro  on  the  articular  surface  of  the 
sternum,  revolving,  with  a  sliding  movement,  round  an  axis  drawn  nearly  vertically 
through  the  sternum.  In  the  circumduction  of  the  shoulder,  which  is  compounded 
of  these  two  movements,  the  clavicle  revolves  upon  the  interarticular  fibro-cartilage, 
and  the  latter,  with  the  clavicle,  rolls  upon  the  sternum."  l  Elevation  of  the  clavicle 
is  principally  limited  by  the  costo-clavicular  ligament ;  depression,  by  the  inter- 
clavicular.  The  muscles  which  raise  the  clavicle,  as  in  shrugging  the  shoulders, 
are  the  upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapulae,  the  clavicular 
head  of  the  Sterno-mastoid,  assisted  to  a  certain  extent  by  the  two  Rhomboids, 
which  pull  the  inferior  angle  of  the  Scapula  backward  and  upward,  and  so  raise 
the  clavicle.  The  depression  of  the  clavicle  is  principally  effected  by  gravity, 
assisted  by  the  Subclavius,  Pectoralis  minor,  and  lower  fibres  of  the  Trapezius. 
It  is  drawn  backward  by  the  Rhomboids  and  the  middle  and  lower  fibres  of  the 
Trapezius,  and  forward  by  the  Serratus  magnus  and  Pectoralis  minor. 

Surface  Form. — The  position  of  the  sterno-clavicular  joint  may  be  easily  ascertained  by  feel- 
ing the  enlarged  sternal  end  of  the  collar-bone  just  external  to  the  long,  cord-like,  sternal  origin 
of  the  Sterno-mastoid  muscle.  If  this  muscle  is  relaxed  by  bending  the  head  forward,  a  depres- 
sion just  internal  to  the  end  of  the  clavicle,  and  between  it  and  the  sternum,  can  be  felt,  indica- 
ting the  exact  position  of  the  joint,  which  is  subcutaneous.  When  the  arm  hangs  by  the  side, 
the  cavity  of  the  joint  is  V-shaped.  If  the  arm  is  raised,  the  bones  become  more  closely  approx- 
imated, and  the  cavity  becomes  a  mere  slit. 

Surgical  Anatomy. — The  strength  of  this  joint  mainly  depends  upon  its  ligaments,  and 
it  is  to  this,  and  to  the  fact  that  the  force  of  the  blow  is  generally  transmitted  along  the 
long  axis  of  the  clavicle,  that  dislocation  rarely  occurs,  and  that  the  bone  is  generally  broken 
rather  than  displaced.  When  dislocation  does  occur,  the  course  which  the  displaced  bone  takes 
depends  more  upon  the  direction  in  which  the  violence  is  applied  than  upon  the  anatomical 
construction  of  the  joint;  it  may  be  either  forward,  backward,  or  upward.  The  chief  point 
worthy  of  note,  as  regards  the  construction  of  the  joint,  in  regard  to  dislocations,  is  the  fact 
that,  owing  to  the  shape  of  the  articular  surfaces  being  so  little  adapted  to  each  other,  and 
that  the  strength  of  the  joint  mainly  depends  upon  the  ligaments,  the  displacement  when 
reduced  is  very  liable  to  recur,  and  hence  it  is  extremely  difficult  to  keep  the  end  of  the  bone  in  its 
proper  place. 

II.  Acromio-clavicular  Articulation  (Fig.  243). 

The  Acromio-clavicular  is  an  arthrodial  joint  formed  between  the  outer 
extremity  of  the  clavicle  and  the  upper  edge  of  the  acromion  process  of  the 
scapula.  Its  ligaments  are  the 

1  Humphry,  On  the  Human  Skeleton,  p.  402. 


A  CROXIO- CLA  VICULAR   ARTICULA  TION. 


343 


Superior  Acromio-clavicular. 
Inferior  Acromio-clavicular. 
Interarticular  Fibro-cartilage. 


(  Trapezoid 

Coraco-clavicular  <        and 
Conoid. 


The  Superior  Acromio-clavicular  Ligament  is  a  broad  band,  of  a  quadrilateral 
form,  which  covers  the  superior  part  of  the  articulation,  extending  between  the 
upper  part  of  the  outer  end  of  the  clavicle  and  the  adjoining  part  of  the  upper 
surface  of  the  acromion.  It  is  composed  of  parallel  fibres  which  interlace  with 
the  aponeurosis  of  the  Trapezius  and  Deltoid  muscles ;  below,  it  is  in  contact  with 
the  interarticular  fibro-cartilage  (when  it  exists)  and  the  synovial  membranes. 

The  Inferior  Acromio-clavicular  Ligament,  somewhat  thinner  than  the  pre- 
ceding, covers  the  under  part  of  the  articulation,  and  is  attached  to  the  adjoining 
surfaces  of  the  two  bones.  It  is  in  relation,  above,  with  the  synovial  membranes, 
and  in  rare  cases  with  the  interarticular  fibro-cartilage ;  below,  with  the  tendon 


FIG.  243.— The  left  shoulder-joint,  scapulo-clavicular  articulations,  and  proper  ligaments  of  scapula. 

of  the  Supraspinatus.  These  two  ligaments  are  continuous  with  each  other  in 
front  and  behind,  and  form  a  complete  capsule  round  the  joint. 

The  Interarticular  Fibro-cartilage  is  frequently  absent  in  this  articulation. 
^  hen  it  exists  it  generally  only  partially  separates  the  articular  surfaces,  and 
occupies  the  upper  part  of  the  articulation.  More  rarely  it  completely  separates 
the  joint  into  two  cavities. 

The  Synovial  Membrane. — There  is  usually  only  one  synovial  membrane  in 
this  articulation,  but  when  a  complete  interarticular  fibro-cartilage  exists  there  are 
two  synovial  membranes. 

The  Coraco-clavicular  Ligament  serves  to  connect  the  clavicle  with  the  coracoid 
process  of  the  scapula.  It  does  not  properly  belong  to  this  articulation,  but  as  it 
forms  a  most  efficient  means  in  retaining-  the  clavicle  in  contact  with  the  acromial 


344  THE  ARTICULATIONS. 

process,  it  is  usually  described  with  it.  It  consists  of  two  fasciculi,  called  the 
trapezoid  and  conoid  ligaments. 

The  Trapezoid  Ligament,  the  anterior  and  external  fasciculus,  is  broad,  thin, 
and  quadrilateral ;  it  is  placed  obliquely  between  the  coracoid  process  and  the 
clavicle.  It  is  attached,  below,  to  the  upper  surface  of  the  coracoid  process ; 
above,  to  the  oblique  line  on  the  under  surface  of  the  clavicle.  Its  anterior  border 
is  free;  its  posterior  border  is  joined  with  the  conoid  ligament,  the  two  forming 
by  their  junction  a  projecting  angle. 

The  Conoid  Ligament,  the  posterior  and  internal  fasciculus,  is  a  dense  band  of 
fibres,  conical  in  form,  the  base  being  turned  upward,  the  summit  downward.  It 
is  attached  by  its  apex  to  a  rough  impression  at  the  base  of  the  coracoid  process, 
internal  to  the  preceding;  above,  by  its  expanded  base,  to  the  conoid  tubercle  on 
the  under  surface  of  the  clavicle,  and  to  a  line  proceeding  internally  from  it  for 
half  an  inch.  These  ligaments  are  in  relation,  in  front,  with  the  Subclavius  and 
Deltoid ;  behind,  with  the  Trapezius.  They  serve  to  limit  rotation  of  the  scapula, 
the  Trapezoid  limiting  rotation  forward,  and  the  Conoid  backward. 

Actions. — The  movements  of  this  articulation  are  of  two  kinds  :  1.  A  gliding 
motion  of  the  articular  end  of  the  clavicle  on  the  acromion.  2.  Rotation  of  the 
scapula  forward  and  backward  upon  the  clavicle,  the  extent  of  this  rotation  being 
limited  by  the  two  portions  of  the  coraco-clavicular  ligament. 

The  acromio-clavicular  joint  has  important  functions  in  the  movements  of  the 
upper  extremity.  It  has  been  well  pointed  out  by  Sir  George  Humphry  that  if  there 
had  been  no  joint  between  the  clavicle  and  scapula  the  circular  movement  of  the 
scapula  on  the  ribs  (as  in  throwing  both  shoulders  backward  or  forward)  would 
have  been  attended  with  a  greater  alteration  in  the  direction  of  the  shoulder  than  is 
consistent  with  the  free  use  of  the  arm  in  such  position,  and  it  would  have  been 
impossible  to  give  a  blow  straight  forward  with  the  full  force  of  the  arm  ;  that  is  to 
say,  with  the  combined  force  of  the  scapula,  arm,  and  forearm.  "  This  joint,"  as 
he  happily  says,  "is  so  adjusted  as  to  enable  either  bone  to  turn  in  a  hinge-like 
manner  upon  a  vertical  axis  drawn  through  the  other,  and  it  permits  the  surfaces 
of  the  scapula,  like  the  baskets  in  a  roundabout  swing,  to  look  the  same  way  in 
every  position  or  nearly  so."  Again,  when  the  whole  arch  formed  by  the  clavicle 
and  scapula  rises  and  falls  (in  elevation  or  depression  of  the  shoulders),  the  joint 
between  these  two  bones  enables  the  scapula  still  to  maintain  its  lower  part  in 
contact  with  the  ribs. 

Surface  Form. — The  position  of  the  acromio-clavicular  joint  can  generally  be  ascertained  by 
the  slightly  enlarged  extremity  of  the  outer  end  of  the  clavicle,  which  causes  it  to  project  above 
the  level  of  the  acromion  process  of  the  scapula.  Sometimes  this  enlargement  is  so  considerable 
as  to  form  a  rounded  eminence,  which  is  easily  to  be  felt.  The  joint  lies  in  the  plane  of  a  ver- 
tical line  passing  up  the  middle  of  the  front  of  the  arm. 

Surgical  Anatomy. — Owing  to  the  slanting  shape  of  the  articular  surfaces  of  this  joint, 
dislocation  generally  occurs  downward ;  that  is  to  say,  the  acromion  process  of  the  scapula  is 
dislocated  Bunder  the  outer  end  of  the  clavicle ;  but  dislocations  in  the  opposite  direction  have 
been  described.  The  displacement  is  often  incomplete;  on  account  of  the  strong  coraco-claviculai 
ligaments,  which  remain  untorn.  The  same  difficulty  exists,  as  in  the  sterno-clavicular  disloca- 
tion, in  maintaining  the  ends  of  the  bone  in  position  after  reduction. 

III.  Proper  Ligaments  of  the  Scapula  (Fig.  243). 
The  proper  ligaments  of  the  scapula  are  the 

Coraco-acromial.  Transverse. 

The  Coraco-acromial  Ligament  is  a  broad,  thin,  flat  band,  of  a  triangular  shape, 
extended  transversely  above  the  upper  part  of  the  shoulder-joint,  between  the 
coracoid  and  acromial  processes.  It  is  attached,  by  its  apex,  to  the  summit  of  the 
acromion  just  in  front  of  the  articular  surface  for  the  clavicle,  and  by  its  broad 
base  to  the  whole  length  of  the  outer  border  of  the  coracoid  process.  Its  posterior 
fibres  are  directed  obliquely  backward  and  inward,  its  anterior  fibres  transversely 
inward.  This  ligament  completes  the  vault  formed  by  the  coracoid  and  acromion 


THE  SHOULDER-JOINT. 


345 


processes  for  the  protection  of  the  head  of  the  humerus.  It  is  in  relation,  above, 
with  the  clavicle  and  under  surface  of  the  Deltoid  ;  below,  with  the  tendon  of  the 
Supraspinatus  muscle,  a  bursa  being  interposed.  Its  anterior  border  is  continuous 
with  a  dense  cellular  lamina  that  passes  beneath  the  Deltoid  upon  the  tendons  of 
the  Supra-  and  Infraspinatus  muscles.  This  ligament  is  sometimes  described  as 
consisting  of  two  marginal  bands  and  a  thinner  intervening  portion,  the  two 
bands  being  attached  respectively  to  the  apex  and  base  of  the  coracoid  process, 
and  joining  together  at  their  attachment  into  the  acromion  process.  When  the 
Pectoralis  minor  is  inserted,  as  sometimes  is  the  case,  into  the  capsule  of  the 
shoulder-joint,  instead  of  into  the  coracoid  process,  it  passes  between  these  two 
bands,  and  the  intervening  portion  is  then  deficient. 

The  Transverse  or  Coracoid  (stiprascapular]  Ligament  converts  the  suprascapu- 
lar  notch  into  a  foramen.  It  is  a  thin  and  flat  fasciculus,  narrower  at  the  mid- 
dle than  at  the  extremities,  attached  by  one  end  to  the  base  of  the  coracoid 
process,  and  by  the  other  to  the  inner  extremity  of  the  scapular  notch.  The 
suprascapular  nerve  passes  through  the  foramen ;  the  suprascapular  vessels  pass 
over  the  ligament. 

Movements  of  Scapula. — The  scapula  is  capable  of  being  moved  upward  and 
downward,  forward  and  backward,  or,  by  a  combination  of  these  movements,  cir- 
cumducted  on  the  wall  of  the  chest.  The  muscles  which  raise  the  scapula  are  the 
upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapulae,  and  the  two  Rhom- 
boids ;  those  which  depress  it  are  the  lower  fibres  of  the  Trapezius,  the  Pectoralis 
minor,  and,  through  the  clavicle,  the  Subclavius.  The  scapula  is  drawn  backward 
by  the  Rhomboids  and  the  middle  and  lower  fibres  of  the  Trapezius,  and  forward 
by  the  Serratus  magnus  and  Pectoralis  minor,  assisted,  when  the  arm  is  fixed,  by 
the  Pectoralis  major.  The  mobility  of  the  scapula  is  very  considerable?  and 
greatly  assists  the  movements  of  the  arm  at  the  shoulder-joint.  Thus,  in  raising 
the  arm  from  the  side  the  Deltoid  and  Supraspinatus  can  only  lift  it  to  a  right 
angle  with  the  trunk,  the  further  elevation  of  the  limb  being  effected  by  the 
Trapezius  moving  the  scapula  on  the  wall  of  the  chest.  This  mobility  is  of  special 
importance  in  ankylosis  of  the  shoulder-joint,  the  movements  of  this  bone  com- 
pensating to  a  very  great  extent  for  the  immobility  of  the  joint. 

^  IV.  Shoulder-Joint  (Fig.  243). 

The  Shoulder  is  an  enarthrodial  or  ball-and-socket  joint.  The  bones  entering 
into  its  formation  are  the  large  globular  head  of  the  humerus,  which  is  received 


BICEPS. 
CORACO    ACROMIAL  ',    GLENOID    LIGAMENT. 

LIGAMENT.  ',         / 

DELTOID  _!_ 

SUPRA 
SPINATUS. 


DELTOID.  SUPRA    SPINATUS. 


•^SUB- 
SCAPULA  mS. 


Y    ^i 

/        i 

TERES  MAJOR.     Circumflex  vessels. 


BSCAPULARIS. 


CircumHejc  ressds. 


FIG.  244.— Vertical  sections  through  the  shoulder  joint,  the  arm  being  vertical  and  horizontal.    (After 

into  the  shallow  glenoid  cavity  of  the  scapula — an  arrangement  which  permits  of 
very  considerable  movement,  whilst  the  joint  itself  is  protected  against  displacement 


346  THE  ARTICULATIONS. 

by  the  tendons  which  surround  it  and  by  atmospheric  pressure.  The  ligaments  do 
not  maintain  the  joint  surfaces  in  apposition,  because  when  they  alone  remain  the 
humerus  can  be  separated  to  a  considerable  extent  from  the  glenoid  cavity  ;  their 
use,  therefore,  is  to  limit  the  amount  of  movement.  Above,  the  joint  is  protected 
by  an  arched  vault,  formed  by  the  under  surface  of  the  coracoid  and  acromion 
processes,  and  the  coraco-acromial  ligament.  The  articular  surfaces  are  covered  by 
a  layer  of  cartilage  :  that  on  the  head  of  the  humerus  is  thicker  at  the  centre  than 
at  the  circumference,  the  reverse  being  the  case  in  the  glenoid  cavity.  The  liga- 
ments of  the  shoulder  are  the 

Capsular.  Coraco-humeral. 

Glenoid.1  Transverse  humeral. 

The  Capsular  Ligament  completely  encircles  the  articulation,  being  attached, 
above,  to  the  circumference  of  the  glenoid  cavity  beyond  the  glenoid  ligament ; 
below,  to  the  anatomical  neck  of  the  humerus,  approaching  nearer  to  the  articular 
cartilage  above  than  in  the  rest  of  its  extent.  It  is  thicker  above  and  below  than 
elsewhere,  and  is  remarkably  loose  and  lax,  and  much  larger  and  longer  than  is 
necessary  to  keep  the  bones  in  contact,  allowing  them  to  be  separated  from  each 
other  more  than  an  inch — an  evident  provision  for  that  extreme  freedom  of  move- 
ment which  is  peculiar  to  this  articulation.  Its  superficial  surface  is  strengthened, 
above,  by  the  Supraspinatus  ;  below,  by  the  long  head  of  the  Triceps  ;  posteriorly, 
by  the  tendons  of  the  Infraspinatus  and  Teres  minor ;  and  anteriorly,  by  the  ten- 
don of  the  Subscapularis.  The  capsular  ligament  usually  presents  three  open- 
ings ;  one  anteriorly,  below  the  coracoid  process,  establishes  a  communication 
between  the  synovial  membrane  of  the  joint  and  a  bursa  beneath  the  tendon 
of  the  Subscapularis.  The  second,  which  is  not  constant,  exists  between  the 
joint  and  a  bursal  sac  belonging  to  the  Infraspinatus  muscle.  ,The  third  is 
seen  between  the  two  tuberosities,  for  the  passage  of  the  long  tendon  of  the 
Biceps  muscle. 

The  Coraco-humeral  is  a  broad  band  which  strengthens  the  upper  part  of  the 
capsular  ligament.  It  arises  from  the  outer  border  of  the  coracoid  process,  and 
passes  obliquely  downward  and  outward  to  the  front  of  the  great  tuberosity 
of  the  humerus,  being  blended  with  the  tendon  of  the  Supraspinatus  muscle. 
This  ligament  is  intimately  united  to  the  capsular  in  the  greater  part  of  its 
extent. 

The  Transverse  Humeral  Ligament. — This  is  a  broad  band  of  fibrous  tissue  pass- 
ing from  the  lesser  to  the  greater  tuberosity  of  the  humerus,  and  always  limited  to 
that  portion  of  the  bone  Avhich  lies  above  the  epiphysial  line.  It  converts  the 
bicipital  groove  into  an  osseo-aponeurotic  canal,  and  is  the  analogue  of  the 
strong  process  of  bone  which  connects  the  summits  of  the  two  tuberosities  in  the 
musk  ox. 

Supplemental  Bands  of  the  Capsular  Ligament. — In  addition  to  the  coraco- 
humeral,  the  capsular  ligament  is  strengthened  by  supplemental  bands  in  the 
interior  of  the  joint.  These  bands  (gleno-humeral  ligaments)  are  situated  on 
the  fore  part  of  the  capsule,  and.  the  superior  passes  from  the  upper  part  of 
the  anterior  margin  of  the  glenoid  cavity  to  the  upper  end  of  the  bicipital 
groove.  This  is  sometimes  known  as  Flood's  ligament,  and  is  supposed  to 
correspond  with  the  ligamentum  teres  of  the  hip-joint.  The  middle  one,  from 
the  same  origin,'  passes  downward  and  outward  to  the  lower  part  of  the  lesser 
tuberosity.  Between  these  two  is  the  orifice  of  the  subscapular  bursa.  The 
inferior  band  passes  from  the  middle  of  the  anterior  edge  of  the  glenoid  cavity 
to  the  under  part  of  the  neck  of  the  humerus.  The  two  latter  are  known  as 
Schlemm's  ligaments. 

The  Grlenoid  Ligament  is  a  fibrous  rim  attached  round  the  margin  of  the 

1  The  long  tendon  of  origin  of  the  Biceps  muscle  also  acts  as  one  of  the  ligaments  of  this 
joint.  See  the  observations  on  p.  318  on  the  function  of  the  muscles  passing  over  more  than  ont> 
joint. 


THE  SHOULDER-JOIXT.  347 

glenoid  cavity.  It  is  continuous  above  with  the  long  tendon  of  the  Biceps, 
which  bifurcates  at  that  point. 

The  Synovial  Membrane  is  reflected  from  the  margin  of  the  glenoid  cavity  over 
the  fibro-cartilaginous  rim  surrounding  it :  it  is  then  reflected  over  the  internal 
surface  of  the  capsular  ligament,  covers  the  lower  part  and  sides  of  the  neck  of  the 
burner  us.  and  is  continued  a  short  distance  over  the  cartilage  covering  the  head 
of  the  bone.  The  long  tendon  of  the  Biceps  muscle  which  passes  through  the 
capsular  ligament  is  enclosed  in  a  tubular  sheath  of  synovial  membrane,  which  is 
reflected  upon  it  at  the  point  where  it  perforates  the  capsule,  and  is  continued 
around  it  as  far  as  the  summit  of  the  glenoid  cavity.  The  tendon  of  the  Biceps  is 
thus  enabled  to  traverse  the  articulation,  but  it  is  not  contained  in  the  interior  of 
the  synovial  cavity.  The  synovial  membrane  communicates  with  a  large  bursal 
sac  beneath  the  tendon  of  the  Subscapularis,  by  an  opening  on  the  anterior 
side  of  the  capsular  ligament ;  it  also  occasionally  communicates  with  another 
bursal  sac.  beneath  the  tendon  of  the  Infraspinatus,  through  an  orifice  at  its 
posterior  part.  A  third  bursal  sac,  which  does  not  communicate  with  the  joint, 
is  placed  between  the  under  surface  of  the  Deltoid  and  the  outer  surface  of  the 
capsule. 

The  Muscles  in  relation  with  the  joint  are,  above,  the  Supraspinatus ;  below, 
the  long  head  of  the  Triceps :  internally,  the  Subscapularis ;  externally,  the  Infra- 
spinatus and  Teres  minor  ;  within,  the  long  tendon  of  the  Biceps.  The  Deltoid  is 
placed  most  externally,  and  covers  the  articulation  on  its  outer  side,  as  well  as  in 
front  and  behind. 

The  Arteries  supplying  the  joint  are  articular  branches  of  the  anterior  and 
posterior  circumflex,  and  suprascapular. 

The  Xffi-f  •>•  are  derived  from  the  circumflex  and  suprascapular. 

Actions. — The  shoulder-joint  is  capable  of  movement  in  every  direction,  forward, 
backward,  abduction,  adduction,  circumduction,  and  rotation.  The  humerus  is 
drawn  fnru'ard  by  the  Pectoralis  major,  anterior  fibres  of  the  Deltoid.  Coraco- 
brachialis,  and  by  the  Biceps  when  the  forearm  is  flexed ;  backward,  by  the  Latis- 
simus  dorsi.  Teres  major.-  posterior  fibres  of  the  Deltoid,  and  by  the  Triceps  when 
the  forearm  is  extended  :  it  is  abducted  (elevated)  by  the  Deltoid  and  Supraspinatus ; 
it  i*  adducted  (depressed)  by  the  Subscapularis,  Pectoralis  major,  Latissimus  dorsi, 
and  Teres  major  ;  it  is  rotated  outward  by  the  Infraspinatus  and  Teres  minor; 
and  it  is  rotated  imvard  by  the  Subscapularis,  Latissimus  dorsi,  Teres  major,  and 
Pectoralis  major. 

The  most  striking  peculiarities  in  this  joint  are :  1.  The  large  size  of  the  head 
of  the  humerus  in  comparison  with  the  depth  of  the  glenoid  cavity,  even  when 
supplemented  by  the  glenoid  ligament.  2.  The  looseness  of  the  capsule  of  the 
joint.  3.  The  intimate  connection  of  the  capsule  with  the  muscles  attached  to  the 
head  of  the  humerus.  4.  The  peculiar  relation  of  the  biceps  tendon  to  the  joint. 

It  is  in  consequence  of  the  relative  size  of  the  two  articular  surfaces  that  the 
joint  enjoys  such  free  movement  in  every  possible  direction.  When  these  movements 
of  the  arm  are  arrested  in  the  shoulder-joint  by  the  contact  of  the  bony  surfaces 
and  by  the  tension  of  the  corresponding  fibres  of  the  capsule,  together  with  that  of 
the  muscles  acting  as  accessory  ligaments,  they  can  be  carried  considerably  farther 
by  the  movements  of  the  scapula,  involving,  of  course,  motion  at  the  acroniio-  and 
sterno-clavicular  joints.  These  joints  are  therefore  to  be  regarded  as  accessory 
structures  to  the  shoulder-joint.1  The  extent  of  these  movements  of  the  scapula  is 
very  considerable,  especially  in  extreme  elevation  of  the  arm,  which  movement  is 
best  accomplished  when  the  arm  is  thrown  somewhat  forward,  since  the  articular 
surface  of  the  humerus  is  broader  in  the  middle  than  at  either  end,  especially  the 
lower,  so  that  the  range  of  elevation  directly  forward  is  less,  and  that  directly 
backward  still  more  restricted.  The  great  width  of  the  central  portion  of  the 
humeral  head  also  allows  of  very  free  horizontal  movement  when  the  arm  is 
raised  to  a  right  angle,  in  which  movement  the  arch  formed  by  the  acromion,  the 

1  See  p.  344. 


348  THE  ARTICULATIONS. 

coracoid  process,  and  the  coraco-acromial  ligament  constitutes  a  sort  of  supple- 
mental articular  cavity  for  the  head  of  the  bone. 

The  looseness  of  the  capsule  is  so  great  that  the  arm  will  fall  about  an  inch 
from  the  scapula  when  the  muscles  are  dissected  from  the  capsular  ligament  and 
an  opening  made  in  it  to  remove  the  atmospheric  pressure.  The  movements  of 
the  joint,  therefore,  are  not  regulated  by  the  capsule  so  much  as  by  the  surrounding 
muscles  and  by  the  pressure  of  the  atmosphere — an  arrangement  which  "  renders 
the  movements  of  the  joint  much  more  easy  than  they  would  otherwise  have  been, 
and  permits  a  swinging,  pendulum-like  vibration  of  the  limb  when  the  muscles 
are  at  rest"  (Humphry).  The  fact,  also,  that  in  all  ordinary  positions  of  the  joint 
the  capsule  is  not  put  on  the  stretch  enables  the  arm  to  move  freely  in  all  direc- 
tions. Extreme  movements  are  checked  by  the  tension  of  appropriate  portions  of 
the  capsule,  as  well  as  by  the  interlocking  of  the  bones.  Thus  it  is  said  that 
"  abduction  is  checked  by  the  contact  of  the  great  tuberosity  with  the  upper  edge  of 
the  glenoid  cavity,  adduction  by  the  tension  of  the  coraco-humeral  ligament " 
(Beaunis  et  Bouchard). 

The  intimate  union  of  the  tendons  of  the  four  short  muscles  with  the  capsule 
converts  these  muscles  into  elastic  and  spontaneously  acting  ligaments  of  the  joint, 
and  it  is  regarded  as  being  also  intended  to  prevent  the  folds  into  which  all  portions 
of  the  capsule  would  alternately  fall  in  the  varying  positions  of  the  joint  from  being 
driven  between  the  bones  by  the  pressure  of  the  atmosphere. 

The  peculiar  relations  of  the  Biceps  tendon  to  the  shoulder-joint  appear  to  sub- 
serve various  purposes.  In  the  first  place,  by  its  connection  with  both  the  shoulder 
and  elbow  the  muscle  harmonizes  the  action  of  the  two  joints,  and  acts  as  an 
elastic  ligament  in  all  positions,  in  the  manner  previously  adverted  to.1  Next,  it 
strengthens  the  upper  part  of  the  articular  cavity,  and  prevents  the  head  of  the 
humerus  from  being  pressed  up  against  the  acromion  process,  when  the  Deltoid 
contracts,  instead  of  forming  the  centre  of  motion  in  the  glenoid  cavity.  By  its 
passage  along  the  bicipital  groove  it  assists  in  rendering  the  head  of  the  humerus 
steady  in  the  various  movements  of  the  arm.  When  the  arm  is  raised  from  the 
side  it  assists  the  Supra-  and  Infraspinatus  in  rotating  the  head  of  the  humerus  in 
the  glenoid  cavity.  It  also  holds  the  head  of  the  bone  firmly  in  contact  with  the 
glenoid  cavity,  and  prevents  its  slipping  over  its  lower  edge,  or  being  displaced  by 
the  action  of  the  Latissimus  dorsi  and  Pectoralis  major,  as  in  climbing  and  many 
other  movements. 

Surface  Form. — The  direction  and  position  of  the  shoulder-joint  may  be  indicated  by  a  line 
drawn  from  the  middle  of  the  coraco-acromial  ligament,  in  a  curved  direction,  with  its  con- 
vexity inward,  to  the  innermost  part  of  that  portion  of  the  head  of  the  humerus  which  can  be 
felt  in  the  axilla  when  the  arm  is  forcibly  abducted  from  the  side.  When  the  arm  hangs  by  the 
side,  not  more  than  one-third  of  the  head  of  the  bone  is  in  contact  with  the  glenoid  cavity,  and 
three-quarters  of  its  circumference  is  in  front  of  a  vertical  line  drawn  from  the  anterior  border  of 
the  acromion  process. 

Surgical  Anatomy. — Owing  to  the  construction  of  the  shoulder-joint  and  the  freedom  of 
movement  which  it  enjoys,  as  well  as  in  consequence  of  its  exposed  situation,  it  is  more  frequently 
dislocated  than  any  other  joint  in  the  body.  Dislocation  occurs  when  the  arm  is  abducted,  and 
when,  therefore,  the  head  of  the  humerus  presses  against  the  lower  and  front  part  of  the  cap- 
sule, which  is  the  thinnest  and  least  supported  part  of  the  ligament.  The  rent  in  the  capsule 
almost  invariably  takes  place  in  this  situation,  and  through  it  the  head  of  the  bone  escapes,  so 
that  the  dislocation  in  most  instances  is  primarily  subglenoid.  The  head  of  the  bone  does  not 
usually  remain  in  this  situation,  but  generally  assumes  some  other  position,  which  varies  accord- 
ing to  the  direction  and  amount  of  force  producing  the  dislocation  and  the  relative  strength  of 
the  muscles  in  front  and  behind  the  joint.  In  consequence  of  the  muscles  at  the  back  being 
stronger  than  those  in  front,  and  especially  on  account  of  the  long  head  of  the  Triceps  pre- 
venting the  bone  passing  backward,  dislocation  forward  is  much  more  common  than  back- 
ward. The  most  frequent  position  which  the  head  of  the  humerus  ultimately  assumes  is  on  the 
front  of  the  neck  of  the  scapula,  beneath  the  coracoid  process,  and  hence  named  subcora- 
coid.  Occasionally,  in  consequence  probably  of  a  greater  amount  of  force  being  brought  to 
bear  on  the  limb,  the  head  is  driven  farther  inward,  and  rests  on  the  upper  part  of  the  front 
of  the  chest,  beneath  the  clavicle  (subclavicular).  Sometimes  it  remains  in  the  position 
in  which  it  was  primarily  displaced,  resting  on  the  axillary  border  of  the  scapula  (subglenoid), 

1  See  p.  318. 


THE  ELBOW-JOINT.  349 

and  rarely  it  passes  backward  and  remains  in  the  infraspinatous  fossa,  beneath  the  spine  (sub- 
spinous). 

The  shoulder-joint  is  sometimes  the  seat  of  all  those  inflammatory  affections,  both  acute  and 
chronic,  which  attack  joints,  though  perhaps  less  frequently  than  some  other  joints  of  equal  size 
and  importance.  Acute  synovitis  may  result  from  injury,  rheumatism,  or  pyaemia,  or  may  fol- 
low secondarily  on  the  so-called  acute  epiphysitis  of  infants.  It  is  attended  with  effusion  into 
the  joint,  and  when  this  occurs  the  capsule  is  evenly  distended  and  the  contour  of  the  joint 
rounded.  Special  projections  may  occur  at  the  site  of  the  openings  in  the  capsular  ligament. 
Thus  a  swelling  may  appear  just  in  front  of  the  joint,  internal  to  the  lesser  tuberosity,  from  effu- 
sion into  the  bursa  beneath  the  Subscapularis  muscle ;  or,  again,  a  swelling  which  is  sometimes 
bilobed  may  be  seen  in  the  interval  between  the  Deltoid  and  Pectoralis  major  muscles,  from  effu- 
sion into  the  diverticulum,  which  runs  down  the  bicipital  groove  with  the  tendon  of  the  biceps. 
The  effusion  into  the  synovial  membrane  can  be  best  ascertained  by  examination  from  the  axilla, 
where  a  soft,  elastic,  fluctuating  swelling  can  usually  be  felt. 

Tubercular  arthritis  not  unfrequently  attacks  the  shoulder-joint,  and  may  lead  to  total  de- 
struction of  the  articulation,  when  ankylosis  may  result  or  long-protracted  suppuration  may 
necessitate  excision.  This  joint  is  also  one  of  those  which  is  most  liable  to  be  the  seat  of  osteo- 
arthritis.  and  may  also  be  affected  in  gout  and  rheumatism ;  or  in  locomotor  ataxy,  when  it 
becomes  the  seat  of  Charcot's  disease. 

Excision  of  the  shoulder-joint  may  be  required  in  cases  of  arthritis  (especially  the  tuber- 
cular form )  which  have  gone  on  to  destruction  of  the  articulation :  in  compound  dislocations  and 
fractures,  particularly  those  arising  from  gunshot  injuries,  in  which  there  has  been  extensive 
injury  to  the  head  of  the  bone ;  in  some  cases  of  old  unreduced  dislocation,  where  there  is  much 
pain  ;  and  possibly  in  some  few  cases  of  growth  connected  with  the  upper  end  of  the  bone.  The 
operation  is  best  performed  by  making  an  incision  from  the  middle  of  the  coraco-acromial  liga- 
ment down  the  arm  for  about  three  inches :  this  will  expose  the  bicipital  groove  and  the  tendon 
of  the  Biceps,  which  may  be  either  divided  or  hooked  out  of  the  way,  according  as  to  whether  it 
is  implicated  in  the  disease  or  not.  The  capsule  is  then  freely  opened,  and  the  muscles  attached 
to  the  greater  and  lesser  tuberosities  of  the  humerus  divided.  The  head  of  the  bone  can 
then  be  thrust  out  of  the  wound  and  sawn  off,  or  divided  with  a  narrow  saw  in  situ  and 
subsequently  removed.  The  section  should  be  made,  if  possible,  just  below  the  articular  surface, 
so  as  to  leave  the  bone  as  long  as  possible.  The  glenoid  cavity  must  then  be  examined,  and 
gouged  if  carious. 

V.  Elbow-Joint. 

The  Elbow  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  forma- 
tion are  the  trochlear  surface  of  the  humerus,  which  is  received  into  the  greater 
sigmoid  cavity  of  the  ulna,  and  admits  of  the  movements  peculiar  to  this  joint — viz. 
flexion  and  extension  ;  whilst  the  lesser,  or  radial,  head  of  the  humerus  articulates 
with  the  cup-shaped  depression  on  the  head  of  the  radius ;  the  circumference  of  the 
head  of  the  radius  articulates  with  the  lesser  sigmoid  cavity  of  the  ulna,  allowing  of 
the  movement  of  rotation  of  the  radius  on  the  ulna,  the  chief  action  of  the  supe- 
rior radio-ulnar  articulation.  The  articular  surfaces  are  covered  with  a  thin  layer 
of  cartilage,  and  connected  together  by  a  capsular  ligament  of  unequal  thickness, 
being  especially  thickened  on  its  two  sides  and,  to  a  less  extent,  in  front  and 
behind.  These  thickened  portions  are  usually  described  as  distinct  ligaments 
under  the  following  names: 

Anterior.  Internal  Lateral. 

Posterior.  External  Lateral. 

The  orbicular  ligament  of  the  upper  radio-ulnar  articulation  must  also  be 
reckoned  among  the  ligaments  of  the  elbow. 

The  Anterior  Ligament  (Fig.  245)  is  a  broad  and  thin  fibrous  layer  which 
covers  the  anterior  surface  of  the  joint.  It  is  attached  to  the  front  of  the  internal 
condyle  and  to  the  front  of  the  humerus  immediately  above  the  coronoid  fossa ; 
below,  to  the  anterior  surface  of  the  coronoid  process  of  the  ulna  and  orbicular 
ligament,  being  continuous  on  each  side  with  the  lateral  ligaments.  Its  superficial 
fibres  pass  obliquely  from  the  inner  condyle  of  the  humerus  outward  to  the 
orbicular  ligament.  The  middle  fibres,  vertical  in  direction,  pass  from  the  upper 
part  of  the  coronoid  depression  and  become  partly  blended  with  the  preceding,  but 
mainly  inserted  into  the  anterior  surface  of  the  coronoid  process.  The  deep  or 
transverse  set  intersects  these  at  right  angles.  This  ligament  is  in  relation,  in 
front.  Avith  the  Brachialis  anticus,  except  at  its  outermost  part ;  behind,  with  the 
svnovial  membrane. 


350 


THE   ARTICULATIONS. 


The  Posterior  Ligament  (Fig.  246)  is  a  thin  and  loose  membranous  fold,  attached, 
above,  to  the  lower  end  of  the  humerus,  on  a  level  with  the  upper  part  of  the 
olecranon  fossa  ;  below,  to  the  margin  of  the  olecranon.  The  superficial  or  trans- 
fibres pass  between  the  adjacent  margins  of  the  olecranon  fossa.  The 


verse 


deeper  portion  consists  of  vertical  fibres,  which  pass  from  the  upper  part  of  the 
olecranon  fossa  to  the  margin  of  the  olecranon.      This  ligament  is  in  relation, 

behind,  with  the  tendon  of  the  Tri- 
ceps  and  the  Anconeus  ;  in  front, 
with  the  synovial  membrane. 


FIG.  245. — Left  elbow-joint,  showing  anterior 
and  internal  ligaments. 


FIG.    '246.— Left     elbow-joint,    showing 
posterior  and  external  ligaments. 


The  Internal  Lateral  Ligament  (Fig.  245)  is  a  thick  triangular  band  consisting 
of  two  portions,  an  anterior  and  posterior,  united  by  a  thinner  intermediate  por- 
tion. The  anterior  portion,  directed  obliquely  forward,  is  attached,  above,  by  its 
apex,  to  the  front  part  of  the  internal  condyle  of  the  humerus ;  and,  below,  by  its 
broad  base,  to  the  inner  margin  of  the  coronoid  process.  The  posterior  portion, 
also  of  triangular  form,  is  attached,  above,  by  its  apex,  to  the  lower  and  back 
part  of  the  internal  condyle ;  below,  to  the  inner  margin  of  the  olecranon. 
Between  these  two  bands  a  few  intermediate  fibres  descend  from  the  internal  con- 
dyle to  blend  with  a  transverse  band  of  ligamentous  tissue  which  bridges  across 
the  notch  between  the  olecranon  and  coronoid  processes.  This  ligament  is  in 
relation,  internally,  with  the  Triceps  and  Flexor  carpi  ulnaris  muscles  and  the- 
ulnar  nerve,  and  gives  origin  to  part  of  the  Flexor  sublimis  digitorum. 

The  External  Lateral  Ligament  (Fig.  246)  is  a  short  and  narrow  fibrous  band, 
less  distinct  than  the  internal,  attached,  above,  to  a  depression  below  the  external 
condyle  of  the  humerus ;  below,  to  the  orbicular  ligament,  some  of  its  most  pos- 
terior fibres  passing  over  that  ligament,  to  be  inserted  into  the  outer  margin  of  the 


THE   ELBOW-JOINT. 


351 


ulna.  This  ligament  is  intimately  blended  with  the  tendon  of  origin  of  the 
Supinator  brevis  muscle. 

The  Synovial  Membrane  is  very  extensive.  It  covers  the  margin  of  the 
articular  surface  of  the  humerus.  and  lines  the  coronoid  and  olecranon  fossae  on 
that  bone ;  from  these  points  it  is  reflected  over  the  anterior,  posterior,  and 
lateral  ligaments,  and  forms  a  pouch  between  the  lesser  sigmoid  cavity,  the 
internal  surface  of  the  orbicular  ligament,  and  the  circumference  of  the  head  of 
the  radius. 

Between  the  capsular  ligament  and  the  synovial  membrane  are  three  masses 
of  fat ;  one.  the  largest,  above  the  olecranon  fossa,  which  is  pressed  into  the  fossa  by 
the  triceps  during  flexion ;  a  second,  over  the  coronoid  fossa ;  and  a  third,  over 
the  radial  fossa.  These  are  pressed  into  their  respective  fossae  during  extension. 

The  JIuseles  in  relation  with  the  joint  are,  in  front,  the  Brachialis  anticus; 
behind,  the  Triceps  and  Anconeus;  externally,  the  Supinator  brevis  and  the 
common  tendon  of  origin  of  the  Extensor  muscles ;  internally,  the  common 
tendon  of  origin  of  the  Flexor  muscles,  and  the  Flexor  carpi  ulnaris,  with  the 
ulnar  nerve. 

The  Arteries  supplying  the  joint  are  derived  from  the  communicating  branches 
between  the  superior  profunda,  inferior  profunda,  and  anastomotica  magna  arteries, 
branches  of  the  brachial,  with  the  anterior,  posterior,  and  interosseous  recurrent 
branches  of  the  ulnar  and  the  recurrent  branch  of  the  radial.  These  vessels  form 
a  complete  chain  of  inosculation  around  the  joint. 

The  Serves  are  derived  from  the  ulnar  as  it  passes  between  the  internal  con- 
dyle  and  the  olecranon ;  a  filament  from  the  musculo-cutaneous  (Rudinger),  and 
two  from  the  median  (Macalister). 

Actions. — The  elbow-joint  comprises  three  different  portions — viz,  the  joint 
between  the  ulna  and  humerus,  that  between 
the  head  of  the  radius  and  the  humerus.  and 
the  superior  radio-ulnar  articulation,  described 
below.  All  these  articular  surfaces  are  in- 
vested by  a  common  synovial  membrane,  and 
the  movements  of  the  whole  joint  should  be 
studied  together.  The  combination  of  the 
movements  of  flexion  and  extension  of  the 
forearm  with  those  of  pronation  and  supina- 
tion  of  the  hand,  which  is  ensured  by  the  two 
being  performed  at  the  same  joint,  is  essen- 
tial to  the  accuracy  of  the  various  minute 
movements  of  the  hand. 

The  portion  of  the  joint  between  the  ulna 
and  humerus  is  a  simple  hinge-joint,  and 
allows  of  movements  of  flexion  and  extension 
only.  Owing  to  the  obliquity  of  the  trochlear 
surface  of  the  humerus.  this  movement  does 
not  take  place  in  a  straight  line ;  so  that 
when  the  forearm  is  extended  and  supinated 
the  axis  of  the  arm  and  forearm  is  not  in 
the  same  line,  but  the  one  portion  of  the  limb 
forms  an  angle  with  the  others,  and  the  hand, 
with  the  forearm,  is  directed  outward.  Dur- 
ing flexion,  on  the  other  hand,  the  forearm 
and  the  hand  tend  to  approach  the  middle 
line  of  the  body,  and  thus  enable  the  hand  to 
be  easily  carried  to  the  face.  The  shape  of 

the  articular  surface  of  the  humerus,  with  its  prominences  and  depressions 
accurately  adapted  to  the  opposing  surfaces  of  the  olecranon,  prevents  any  lateral 
movement.  Flexion  is  produced  by  the  action  of  the  Biceps  and  Brachialis 


FIG.  247.— Sagittal  section  of  the  right 
elbow-joint,  taken  somewhat  obliquely 
and  seen  from  the  radial  aspect.  (After 
Braune.) 


352  THE  ARTICULATIONS. 

anticus,  assisted  by  the  muscles  arising  from  the  internal  condyle  of  the  humerus 
and  the  Supinator  longus ;  extension,  by  the  Triceps  and  Anconeus,  assisted  by 
the  extensors  of  the  wrist  and  by  the  Extensor  communis  digitorum  and  Extensor 
minimi  digiti. 

The  joint  between  the  head  of  the  radius  and  the  capitellum  or  radial  head  of 
the  humerus  is  an  arthrodial  joint.  The  bony  surfaces  would  of  themselves  con- 
stitute an  enarthrosis,  and  allow  of  movement  in  all  directions  were  it  not  for  the 
orbicular  ligament  by  which  the  head  of  the  radius  is  bound  down  firmly  to  the 
sigmoid  cavity  of  the  ulna,  and  which  prevents  any  separation  of  the  two  bones 
laterally.  It  is  to  the  same  ligament  that  the  head  of  the  radius  owes  its  security 
from  dislocation,  which  would  otherwise  constantly  occur  as  a  consequence  of  the 
shallowness  of  the  cup-like  surface  on  the  head  of  the  radius.  In  fact,  but  for 
this  ligament  the  tendon  of  the  biceps  would  be  liable  to  pull  the  head  of  the 
radius  out  of  the  joint.1  In  complete  extension  the  head  of  the  radius  glides  so 
far  back  on  the  outer  condyle  that  its  edge  is  plainly  felt  at  the  back  of  the 
articulation.  Flexion  and  extension  of  the  elbow-joint  are  limited  by  the 
tension  of  the  structures  on  the  front  and  back  of  the  joint,  the  limitation  of 
flexion  being  also  aided  by  the  soft  structures  of  the  arm  and  forearm  coming  in 
contact. 

In  combination  with  any  position  of  flexion  or  extension  the  head  of  the  radius 
can  be  rotated  in  the  upper  radio-ulnar  joint,  carrying  the  hand  with  it.  The 
hand  is  articulated  to  the  lower  surface  of  the  radius  only,  and  the  concave  or 
sigmoid  surface  on  the  lower  end  of  the  radius  travels  round  the  lower  end  of 
the  ulna.  The  latter  bone  is  excluded  from  the  wrist-joint  (as  will  be  seen  in  the 
sequel)  by  the  interarticular  fibre-cartilage.  Thus,  rotation  of  the  head  of  the 
radius  round  an  axis  which  passes  through  the  centre  of  the  radial  head  of  the 
humerus  imparts  circular  movement  to  the  hand  through  a  very  considerable  arc. 

Surface  Form. — If  the  forearm  be  slightly  flexed  on  the  arm,  a  curved  crease  or  fold  with 
its  convexity  downward  may  be  seen  running  across  the  front  of  the  elbow,  extending  from  one 
condyle  to  the  other.  The  centre  of  this  fold  is  some  slight  distance  above  the  line  of  the  joint. 
The  position  of  the  radio-humeral  portion  of  the  ioint  can  be  at  once  ascertained  by  feeling  for  a 
slight  groove  or  depression  between  the  head  of  the  radius  and  the  capitellum  of  the  humerus  at 
the  back  of  the  articulation. 

Surgical  Anatomy. — From  the  great  breadth  of  the  joint,  and  the  manner  in  which  the 
articular  surfaces  are  interlocked,  and  also  on  account  of  the  strong  lateral  ligaments  and  the 
support  which  the  joint  derives  from  the  mass  of  muscles  attached  to  each  condyle  of  the 
humerus,  lateral  displacement  of  the  bones  is  very  uncommon,  whereas  antero-posterior  disloca- 
tion, on  account  of  the  shortness  of  the  antero-posterior  diameter,  the  weakness  of  the  anterior 
and  posterior  ligaments,  and  the  want  of  support  of  muscles,  much  more  frequently  takes  place, 
dislocation  backward  taking  place  when  the  forearm  is  in  a  position  of  extension,  and  forward 
when  in  a  position  of  flexion.  For,  in  the  former  position,  that  of  extension,  the  coronoid  pro- 
cess is  not  interlocked  into  the  coronoid  fossa,  and  loses  its  grip  to  a  certain  extent,  whereas  the 
olecranon  process  is  in  the  plecranon  fossa,  and  entirely  prevents  displacement  forward.  On 
the  other  hand,  during  flexion,  the  coronoid  process  is  in  the  coronoid  fossa,  and  prevents 
dislocation  backward,  while  the  olecranon  loses  its  grip  and  is  not  so  efficient,  as  during  exten- 
sion, in  preventing  a  forward  displacement.  When  lateral  dislocation  does  take  place,  it  is  gen- 
erally incomplete. 

Dislocation  of  the  elbow-joint  is  of  common  occurrence  in  children,  far  more  common 
than  dislocation  of  any  other  articulation,  for,  as  a  rule,  fracture  of  a  bone  more  frequently 
takes  place,  under  the  application  of  any  severe  violence,  in  young  persons  than  dislocation.  In 
lesions  of  this  joint  there  is  often  very  great  difficulty  in  ascertaining  the  exact  nature  of  the 
injury. 

The  elbow-joint  is  occasionally  the  seat  of  acute  synovitis.  The  synovial  membrane  then 
becomes  distended  with  fluid,  the  bulging  showing  itself  principally  around  the  olecranon  pro- 
cess ;  that  is  to  say,  on  its  inner  and  outer  sides  and  above,  in  consequence  of  the  laxness  of  the 
posterior  ligament.  Occasionally  a  well-marked,  triangular  projection  may  be  seen  on  the  outer 
side  of  the  olecranon,  from  bulging  of  the  synovial  membrane  beneath  the  Anconeus  muscle. 
Again,  there  is  often  some  swelling  just  above  the  head  of  the  radius,  in  the  line  of  the  radio- 
humeral  joint.  There  is  generally  not  much  swelling  at  the  front  of  the  joint,  though  sometimes 
deep-seated  fulness  beneath  the  Brachialis  anticus  may  be  noted.  AVhen  suppuration  occurs  the 
abscess  usually  points  at  one  or  other  border  of  the  Triceps  muscle ;  occasionally  the  pus 
diseharges  itself  in  front,  near  the  insertion  of  the  Brachialis  anticus  muscle.  Chronic  synovitis, 

1  Humphry,  op.  cit.,  p.  419. 


THE   RADIO-ULNAR    ARTICULATIONS.  353 

usuall.v  of  tubercular  origin,  is  of  common  occurrence  in  the  elbow-joint :  under  these  circum- 
stances the  forearm  tends  to  assume  the  position  of  semi-flexion,  which  is  that  of  greatest  ease 
and  relaxation  of  ligaments.  It  should  be  borne  in  mind,  that  should  ankylosis  occur  in  this  or 
the  extended  position,  the  limb  will  not  be  nearly  so  useful  as  if  ankylosed  in  a  position  of  rather 
less  than  a  right  angle.  Loose  cartilages  are  sometimes  met  with  in  the  elbow-joint,  not  so 
commonly,  however,  as  in  the  knee ;  nor  do  they,  as  a  rule,  give  rise  to  such  urgent  symptoms 
as  in  this  articulation,  and  rarely  require  operative  interference.  The  elbow-joint  is  also  some- 
times affected  with  osteo-arthritis.  but  this  affection  is  less  common  in  this  articulation  than  in 
some  other  of  the  larger  joints. 

Excision  of  the  elbow  is  principally  required  for  three  conditions :  viz.  tubercular  arthritis, 
injury  and  its  results,  and  faulty  ankylosis ;  but  may  be  necessary  for  some  other  rarer  condi- 
tions, such  as  disorganizing  arthritis  after  pyaemia,  unreduced  dislocations,  and  osteo-arthritis. 
The  results  of  the  operation  are.  as  a  rule,  more  favorable  than  those  of  excision  of  any  other 
joint,  and  it  is  one.  therefore,  that  the  surgeon  should  never  hesitate  to  perform,  especially  in 
the  first  three  of  the  conditions  mentioned  above.  The  operation  is  best  performed  by  a  single 
vertical  incision  down  the  back  of  the  joint,  a  transverse  incision,  over  the  outer  condyle,  being 
added  if  the  parts  are  much  thickened  and  fixed.  A  straight  incision  is  made  about  four 
inches  long,  the  mid- point  of  which  is  on  a  level  with  and  a  little  to  the  inner  side  of  the  tip  of 
the  olecranon.  This  incision  is  made  down  to  the  bone,  through  the  substance  of  the  Triceps 
mus  -le.  The  operator  with  the  point  of  his  knife,  and  guarding  the  soft  parts  with  his  thumb- 
nail, separates  them  from  the  bone.  In  doing  this  there  are  two  structures  which  he  should 
carefully  avoid :  the  ulnar  nerve,  which  lies  parallel  to  his  incision,  but  a  little  internal,  as 
it  courses  down  between  the  internal  condyle  and  the  olecranon  process,  and  the  prolongation  of 
the  Triceps  into  the  deep  fascia  of  the  forearm  over  the  Anconeus  muscle.  Having  cleared  the 
bones  and  divided  the  lateral  and  posterior  ligaments,  the  forearm  is  strongly  flexed  and  the 
ends  of  the  bone  turned  out  and  sawn  off.  The  section  of  the  humerus  should  be  through 
the  base  of  the  condyles.  that  of  the  ulna  and  radius  should  be  just  below  the  level  of  the 
les<t r  sigmoid  cavity  of  the  ulna  and  the  neck  of  the  radius.  In  this  operation  the  object  is 
to  obtain  such  union  as  shall  allow  free  motion  of  the  bones  of  the  forearm ;  and,  therefore, 
passive  motion  must  be  commenced  early,  that  is  to  say,  about  the  tenth  day. 

VI.  Radio-ulnar  Articulations. 

The  articulation  of  the  radius  with  the  ulna  is  effected  by  ligaments  which 
connect  together  both  extremities  as  well  as  the  shafts  of  these  bones.  They  may, 
consequently,  be  subdivided  into  three  sets :  1,  the  superior  radio-ulnar,  which  is 
a  portion  of  the  elbow-joint;  2,  the  middle  radio-ulnar;  and,  3,  the  inferior  radio- 
ulnar  articulations. 

1.  SUPERIOR  RADIO-ULNAR  ARTICULATION. 

This  articulation  is  a  trochoid  or  pivot-joint.  The  bones  entering  into  its 
formation  are  the  inner  side  of  the  circumference  of  the  head  of  the  radius  rotating 
within  the  lesser  sigmoid  cavity  of  the  ulna.  Its  only  ligament  is  the  annular  or 
orbicular, 

The  Orbicular  Ligament  (Fig.  246)  is  a  strong,  flat  band  of  ligamentous  fibres, 
which  surrounds  the  head  of  the  radius,  and  retains  it  in  firm  connection  with  the 
k-.-M.-r  sigmoid  cavity  of  the  ulna.  It  forms  about  four-fifths  of  a  fibrous  ring, 
attached  by  each  end  to  the  extremities  of  the  lesser  sigmoid  cavity,  and  is  smaller 
at  the  lower  part  of  its  circumference  than  above,  by  which  means  the  head  of  the 
radius  is  more  securely  held  in  its  position.  Its  outer  surface,  is  strengthened 
by  the  external  lateral  ligament  of  the  elbow,  and  affords  origin  to  part  of  the 
Supinator  brevis  muscle.  Its  inner  surface  is  smooth,  and  lined  by  synovial 
membrane.  The  synovial  membrane  is  continuous  with  that  which  lines  the 
elbow-joint. 

Actions. — The  movement  which  takes  place  in  this  articulation  is  limited  to 
rotation  of  the  head  of  the  radius  within  the  orbicular  ligament,  and  upon  the 
lesser  sigmoid  cavity  of  the  ulna,  rotation  forward  being  called pronation;  rotation 
backward,  xii^'mat'inn.  Supination  is  performed  by  the  Biceps  and  Supinator 
brevis.  assisted  to  a  slight  extent  by  the  Extensor  muscles  of  the  thumb  and,  in 
certain  positions,  by  the  Supinator  longus.  Pronation  is  performed  by  the  Pro- 
nator  radii  teres  and  the  Pronator  quadratus,  assisted,  in  some  positions,  by  the 
Flexor  carpi  radialis. 

Surface  Form. — The  position  of  the  superior  radio-ulnar  joint  is  marked  on  the  surface  of 

23 


354 


THE   ARTICULATIONS. 


the  body  by  the  little  dimple  on  the  back  of  the  forearm  which  indicates  the  position  of  the  head 
of  the  radius. 

Surgical  Anatomy. — Dislocation  of  the  head  of  the  radius  alone  is  not  an  uncommon 
accident,  and  occurs  most  frequently  in  young  persons  from  falls  on  the  hand  when  the  forearm 
is  extended  and  supinated,  the  head  of  the  bone  being  displaced  forward.  It  is  attended  by 
rupture  of  the  orbicular  ligament. 

2.  MIDDLE  RADIO-ULNAR  ARTICULATION. 

The  interval  between  the  shafts  of  the  radius  and  ulna  is  occupied  by  two 
ligaments. 

Oblique.  Interosseous. 

The  Oblique  or  Round  Ligament  (Fig.  245)  is  a  small,  flattened  fibrous  band 
which  extends  obliquely  downward  and  outward  from  the  tubercle  of  the  ulna  at 
the  base  of  the  coronoid  process  to  the  radius  a  little  below  the  bicipital  tuberosity. 
Its  fibres  run  in  the  opposite  direction  to  those  of  the  interosseous  ligament,  and 
it  appears  to  be  placed  as  a  substitute  for  it  in  the  upper  part  of  the  interosseous 
interval.  This  ligament  is  sometimes  wanting. 

The  Interosseous  Membrane  is  a  broad  and  thin  plane  of  fibrous  tissue  descending 
obliquely  downward  and  inward,  from  the  interosseous  ridge  on  the  radius  to  that 


Inferior  radio-ulnar 
articulation. 


Wrist-joint. 


Carpal  articulations. 


•po-metacarpal 
articulations. 


FIG.  248.— Ligaments  of  wrist  and  hand.    Anterior  view. 

on  the  ulna.  It  is  deficient  above,  commencing  about  an  inch  beneath  the  tubercle 
of  the  radius ;  is  broader  in  the  middle  than  at  either  extremity ;  and  presents  an 
oval  aperture  just  above  its  lower  margin  for  the  passage  of  the  anterior  inter- 
osseous vessels  to  the  back  of  the  forearm.  This  ligament  serves  to  connect  the 
bones  and  to  increase  the  extent  of  surface  for  the  attachment  of  the  deep  muscles. 
Between  its  upper  border  and  the  oblique  ligament  an  interval  exists  through 
which  the  posterior  interosseous  vessels  pass.  Two  or  three  fibrous  bands  are 
occasionally  found  on  the  posterior  surface  of  this  membrane  which  descend 
obliquely  from  the  ulna  toward  the  radius,  and  which  have  consequently  a  direc- 
tion contrary  to  that  of  the  other  fibres.  It  is  in  relation,  in  front,  by  its  upper 
three-fourths  with  the  Flexor  longus  pollicis  on  the  outer  side,  and  with  the 
Flexor  profundus  digitorum  on  the  inner,  lying  upon  the  interval  between  which 
are  the  anterior  interosseous  vessels  and  nerve  ;  by  its  lower  fourth,  with  the 
Pronator  quadratus ;  behind,  with  the  Supinator  brevis,  Extensor  ossis  metacarpi 


RADIO-ULNAR    ARTICULATIONS. 


355 


pollicis.  Extensor  brevis  pollicis,  Extensor  longus  pollicis,  Extensor  indicis ;  and, 
near  the  wrist,  with  the  anterior  interosseous  artery  and  posterior  interosseous 
nerve. 

3.  INFERIOR  RADIO-ULNAR  ARTICULATION. 

This  is  a  pivot-joint,  formed  by  the  head  of  the  ulna  received  into  the  sigmoid 
cavity  at  the  inner  side  of  the  lower  end  of  the  radius.  The  articular  surfaces  are 
covered  by  a  thin  layer  of  cartilage,  and  connected  together  by  the  following  lig- 
aments : 

Anterior  Radio-ulnar.  Posterior  Radio-ulnar. 

Interarticular  Fibro-cartilage. 

The  Anterior  Radio-ulnar  Ligament  (Fig.  248)  is  a  narrow  band  of  fibres 
extending  from  the  anterior  margin  of  the  sigmoid  cavity  of  the  radius  to  the 
anterior  surface  of  the  head  of  the  ulna. 

The  Posterior  Radio-ulnar  Ligament  (Fig.  249)  extends  between  similar  points 
on  the  posterior  surface  of  the  articulation. 


Inferior  radio-ulnar 

articulation 


Wrist- joint 


Cafpal  articulations. 


Carpo-metacarpal 

articulation 


FIG.  249.—  Ligaments  of  wrist  and  hand.    Posterior  view. 


The  Interarticular  Fibro-cartilage  (Fig.  251)  is  triangular  in  shape,  and  is 
placed  transversely  beneath  the  head  of  the  ulna,  binding  the  lower  end  of  this 
bone  and  the  radius  firmly  together.  Its  circumference  is  thicker  than  its  centre, 
which  is  thin  and  occasionally  perforated.  It  is  attached  by  its  apex  to  a  depression 
which  separates  the  styloid  process  of  the  ulna  from  the  head  of  that  bone;  and 
by  its  base,  which  is  thin,  to  the  prominent  edge  of  the  radius,  which  separates  the 
sigmoid  cavity  from  the  carpal  articulating  surface.  Its  margins  are  united  to  the 
ligaments  of  the  wrist-joint.  Its  tipper  surface,  smooth  and  concave,  articulates 
with  the  head  of  the  ulna,  forming  an  arthrodial  joint  ;  its  under  surface,  also 
concave  and  smooth,  forms  part  of  the  wrist-joint  and  articulates  with  the  cuneiform 
bone.  Both  surfaces  are  lined  by  a  synovial  membrane  —  the  upper  surface,  by 
one  peculiar  to  the  radio-ulnar  articulation  ;  the  under  surface,  by  the  synovial 
membrane  of  the  wrist. 

The  Synovial  Membrane  (Fig.  251)  of  this  articulation  has  been  called,  from 
its  extreme  looseness,  the  membrana  saccifonnis  ;  it  extends  horizontally  inward 
between  the  head  of  the  ulna  and  the  interarticular  fibro-cartilage,  and  upward 
between  the  radius  and  the  ulna,  forming  here  a  very  loose  cul-de-sac.  The  quan- 
tity of  synovia  which  it  contains  is  usually  considerable. 

Actions.  —  The  movement  in  the  inferior  radio-ulnar  articulation  is  just  the 
reverse  of  that  between  the  two  bones  above.  It  consists  of  a  movement  of  rota- 


356 


THE   ARTICULATIONS 


tion  of  the  lower  end  of  the  radius  round  an  axis  which  corresponds  to  the  centre 
of  the  head  of  the  ulna.  When  the  radius  rotates  forward,  pronation  of  the  fore- 
arm and  hand  is  the  result ;  and  when  backward,  supination.  It  will  thus  be  seen 
that  in  pronation  and  supination  of  the  forearm  and  hand  the  radius  describes  a 
segment  of  a  cone,  the  axis  of  which  extends  from  the  centre  of  the  head  of  the 
radius  to  the  middle  of  the  head  of  the  ulna.  In  this  movement,  however,  the 
ulna  is  not  quite  stationary,  but  is  circumducted  a  little  in  the  opposite  direction. 
So  that  it  also  describes  the  segment  of  a  cone,  though  of  smaller  size  than  that 
described  by  the  radius.  The  movement  which  causes  this  alteration  in  the  posi- 
tion of  the  head  of  the  ulna  takes  place  principally  at  the  shoulder-joint  by  a  rota- 
tion of  the  humerus,  but  possibly  also  to  a  slight  extent  at  the  elbow-joint.1 

Surface  Form. — The  position  of  the  inferior  radio-ulnar  joint  may  be  ascertained  by 
feeling  for  a  slight  groove  at  the  back  of  the  wrist,  between  the  prominent  head  of  the 
ulna  and  the  lower  end  of  the  radius,  when  the  forearm  is  in  a  state  of  almost  complete  prona- 
tion. 

VII.  Radio-carpal  or  Wrist-joint. 

The  Wrist  is  a  condyloid  articulation.     The  parts  entering  into  its  formation 

are  the  lower  end  of  the  radius  and  under  surface 
of  the  interarticular  fibro-cartilage,  which  form 
together  the  receiving  cavity,  and  the  scaphoid, 
semilunar,  and  cuneiform  bones,  which  form  the 
condyle.  The  articular  surface  of  the  radius  and 
the  under  surface  of  the  inter-articular  fibro-car- 
tilage are  the  receiving  cavity,  forming  together 
a  transversely  elliptical  concave  surface.  The 
articular  surfaces  of  the  scaphoid,  semilunar,  and 
cuneiform  bones  form  together  a  smooth,  convex 
surface,  the  condyle,  which  is  received  into  the 
concavity  above  mentioned.  All  the  bony  sur- 
faces of  the  articulation  are  covered  with  cartilage, 
and  connected  together  by  a  capsule,  which  is 
divided  into  the  following  ligaments : 

External  Lateral.  Anterior. 

Internal  Lateral.  Posterior. 


qnum 


EXTENSOR  SEC. 
INTERN. POLL. 


The  External  Lateral  Ligament  (radio-carpal) 
(Fig.  248)  extends  from  the  summit  of  the  styloid 
process  of  the  radius  to  the  outer  side  of  the 
scaphoid,  some  of  its  fibres  being  prolonged  to  the 
trapezium  and  annular  ligament. 

The  Internal  Lateral  Ligament  (ulno-carpat)  is 
a  rounded  cord,  attached,  above,  to  the  extremity 
of  the  styloid  process  of  the  ulna,  and  dividing 
below  into  two  fasciculi,  which  are  attached,  one 
to  the  inner  side  of  the  cuneiform  bone,  the  other 
to  the  pisiform  bone  and  annular  ligament. 

The  Anterior  Ligament  is  a  broad  membranous 
band,  attached,  above,  to  the  anterior  margin  of 
the  lower  end  of  the  radius,  its  styloid  process  and 
the  ulna :  its  fibres  pass  downward  arid  inward  to 
be  inserted  into  the  palmar  surface  of  the  scaphoid, 
semilunar,  and  cuneiform  bones,  some  of  the  fibres 
being  continued  to  the  os  magnum.  In  addition 
to  this  broad  membrane,  there  is  a  distinct 
rounded  fasciculus,  superficial  to  the  rest,  which  passes  from  the  base  of  the  styloid 
process  of  the  ulna  to  the  semilunar  and  cuneiform  bones.  This  ligament  is  per- 
1  See  Journ.  of  Anat.  and  Pkys.,  vol.  xix.,  parts  ii.,  iii.,  and  iv. 


FIG.  250. — Longitudinal  section  of  the 
right  forearm,  hand,  and  third  finger, 
viewed  from  the  ulnar  aspect.  (After 
Braune.) 


OF   THE    CARPUS.  357 

forated  by  numerous  apertures  for  the  passage  of  vessels,  and  is  in  relation,  in 
front,  with  the  tendons  of  the  Flexor  profundus  digitorum  and  Flexor  longus  pol- 
licis  :  behind,  with  the  synovial  membrane  of  the  wrist-joint. 

The  Posterior  Ligament  (Fig.  249),  less  thick  and  strong  than  the  anterior,  is 
attache'!,  above,  to  the  posterior  border  of  the  lower  end  of  the  radius  ;  its  fibres 
obliquely  downward  and  inward,  to  be  attached  to  the  dorsal  surface  of  the 
scaphoid,  semilunar,  and  cuneiform  bones,  being  continuous  with  those  of  the 
dorsal  carpal  ligaments.  This  ligament  is  in  relation,  behind,  with  the  extensor 
tendons  of  the  fingers ;  in  front,  with  the  synovial  membrane  of  the  wrist. 

The  Synovial  Membrane  (Fig.  251)  lines  the  inner  surface  of  the  ligaments 
above  described,  extending  from  the  lower  end  of  the  radius  and  interarticular 
fibro-cartilage  above  to  the  articular  surfaces  of  the  carpal  bones  below.  It  is 
and  lax.  and  presents  numerous  folds,  especially  behind. 

Relations. — The  wrist-joint  is  covered  in  front  by  the  flexor  and  behind  by  the 
extensor  tendons  ;  it  is  also  in  relation  with  the  radial  and  ulnar  arteries. 

The  Arii- 1- i  i' .*  supplying  the  joint  are  the  anterior  and  posterior  carpal  branches 
of  the  radial  and  ulriar,  the  anterior  and  posterior  interosseous.  and  some  ascending 
branches  from  the  deep  palmar  arch. 

The  X>  /•' ••  •.-•    are  derived  from  the  ulnar  and  posterior  interosseous. 

Actions. — The  movements  permitted  in  this  joint  are  flexion,  extension,  abduc- 
tion, adduction,  and  circumduction.  Its  actions  will  be  further  studied  with  those 
of  the  carpus,  with  which  they  are  combined. 

Surface  Form. — The  line  of  the  radio-carpal  joint  is  on  a  level  with  the  apex  of  the  styloid 
the  ulna. 

Surgical  Anatomy .-j-The  wrist-joint  is  rarely  dislocated,  its  strength  depending  mainly 
upon  the  numerous  strong  tendons  which  surround  the  articulation.  Its  security  is  further  pro- 
vided for  by  the  number  of  small  bones  of  which  the  carpus  is  made  up,  and  which  are  united 
by  very  strung  ligaments.  The  slight  movement  which  takes  place  between  the  several  bones 

-  tu  break  the  jars  that  result  from  falls  or  blows  on  the  hand.  Dislocation  backward, 
which  is  the  more  common,  simulates  to  a  considerable  extent  Colles'  fracture  of  the  radius,  and 
is  liable  to  be  mistaken  i'or  it.  The  diagnosis  can  be  easily  made  out  by  observing  the 
relative  position  of  the  styloid  processes  of  the  radius  and  the  ulna.  In  the  natural  condition  the 
styloid  prix-oss  of  the  radius  is  on  a  lower  level — f.  e.  nearer  the  ground — when  the  arm  hangs  by 
the  >ide.  than  that  of  the  ulna,  and  the  same  would  be  the  case  in  dislocation.  In  Colles'  frac- 
ture, on  the  other  hand,  the  styloid  process  of  the  radius  is  on  the  same,  or  even  a  higher  level 
than  that  of  the  ulna. 

The  wrist -joint  is  occasionally  the  seat  of  acute  synovitis,  the  result  of  traumatism  or  arising 
in  the  rheumatic  or  pya?mic  state.  When  the  synovial  sac  is  distended  with  fluid,  the  swelling 
(test  on  the  dorsal  aspect  of  the  wrist,  showing  a  general  fulness,  with  some  bulging  between 
the  tendons.  The  inflammation  is  prone  to  extend  to  the  intercarpal  joints  and  to  attack  also 
the  sheaths  of  the  tendons  in  the  neighborhood.  Chronic  inflammation  of  the  wrist  is  generally 
tubercular,  and  often  leads  to  similar  disease  in  the  synovial  sheaths  of  adjacent  tendons  and  of  ' 
the  intercarpal  joints.  The  disease,  therefore,  when  progressive,  often  leads  to  necrosis  of  the 
carpal  bones,  and  the  result  is  often  unsatisfactory. 

VIII.  Articulations  of  the  Carpus. 
These  articulations  may  be  subdivided  into  three  sets: 

1.  The  Articulations  of  the  First  Row  of  Carpal  Bones. 

2.  The  Articulations  of  the  Second  Row  of  Carpal  Bones. 

3.  The  Articulations  of  the  Two  Rows  with  each  other. 

1.  ARTICULATIONS  OF  THE  FIRST  Row  OF  CARPAL  BOXES. 

These  are  arthrodial  joints.  The  ligaments  connecting  the  scaphoid,  semilunar, 
and  cuneiform  bones  are — 

Dorsal.  Palmar. 

Two  Interosseous. 

The  Dorsal  Ligaments   are  placed   transversely  behind   the  bones  of  the  first 

row  ;  they  connect  the  scaphoid  and  semilunar  and  the  semilunar  and  cuneiform. 

The  Palmar  Ligaments  connect  the  sea]  hoid  and  semilunar  and  the  semilunar 


358  THE  ARTICULATIONS. 

and  cuneiform  bones ;  they  are  less  strong  than  the  dorsal,  and  placed  very  deeply 
under  the  anterior  ligament  of  the  wrist. 

The  Interosseous  Ligaments  (Fig.  251)  are  two  narrow  bundles  of  fibrous 
tissue  connecting  the  semilunar  bone  on  one  side  with  the  scaphoid,  and  on  the 
other  with  the  cuneiform.  They  are  on  a  level  with  the  superior  surfaces  of  these 
bones,  and  close  the  upper  part  of  the  spaces  betAveen  them.  Their  upper  surfaces 
are  smooth,  and  form  with  the  bones  the  convex  articular  surfaces  of  the  wrist- 
joint. 

The  ligaments  connecting  the  pisiform  bone  are — 

Capsular.  Two  Palmar  ligaments. 

The  Capsular  Ligament  is  a  thin  membrane  which  connects  the  pisiform  bone 
to  the  cuneiform.  It  is  lined  with  a  separate  synovia!  membrane. 

The  two  Palmar  Ligaments  are  two  strong  fibrous  bands  which  connect  the 
pisiform  to  the  unciform,  the  piso-uncinate,  and  to  the  base  of  the  fifth  metacarpal 
bone,  the  piso-metacarpal  ligament  (Fig.  248). 

2.  ARTICULATIONS  OF  THE  SECOND  Row  OF  CARPAL  BONES. 

These  are  also  arthrodial  joints.  The  articular  surfaces  are  covered  with  carti- 
lage, and  connected  by  the  following  ligaments : 

Dorsal.  Palmar. 

Three  Interosseous. 

The  Dorsal  Ligaments  extend  transversely  from  one  bone  to  another  on  the 
dorsal  surface,  connecting  the  trapezium  with  the  trapezoid,  the  trapezoid  with 
the  os  magnum,  and  the  os  magnum  with  the  unciform. 

The  Palmar  Ligaments  have  a  similar  arrangement  on  the  palmar  surface. 

The  three  Interosseous  Ligaments,  much  thicker  than  those  of  the  first  row, 
are  placed  one  between  the  os  magnum  and  the  unciform,  a  second  between  the 
os  magnum  and  the  trapezoid,  and  a  third  between  the  trapezium  and  trapezoid. 
The  first  of  these  is  much  the  strongest,  and  the  third  is  sometimes  wanting. 
Sometimes  a  slender  interosseous  band  connects  the  os  magnum  and  the  scaphoid. 

3.    A.RTICULATIONS  OF  THE  TWO  ROWS  OF  CARPAL  BONES  WITH  EACH   OTHER. 

The  joint  between  the  scaphoid,  semilunar,  and  cuneiform,  and  the  second  row 
of  the  carpus,  or  the  mid-carpal  joint,  is  made  up  of  three  distinct  portions ;  in  the 
centre  the  head  of  the  os  magnum  and  the  superior  margin  of  the  unciform 
articulate  with  the  deep,  cup-shaped  cavity  formed  by  the  scaphoid  and  semilunar 
bones,  and  constitute  a  sort  of  ball-and-socket  joint.  On  the  outer  side  the 
trapezium  and  trapezoid  articulate  with  the  scaphoid,  and  on  the  inner  side  the 
unciform  articulates  with  the  cuneiform,  forming  gliding  joints. 

The  ligaments  are — 

Anterior  or  Palmar.  External  Lateral. 

Posterior  or  Dorsal.  Internal  Lateral. 

The  Anterior  or  Palmar  Ligaments  consist  of  short  fibres,  which  pass,  for  the 
most  part,  from  the  palmar  surface  of  the  bones  of  the  first  row  to  the  front  of  the 
os  magnum. 

The  Posterior  or  Dorsal  Ligaments  consist  of  short,  irregular  bundles  of  fibres 
passing  between  the  bones  of  the  first  and  second  row  on  the  dorsal  surface  of  the 
carpus. 

The  Lateral  Ligaments  are  very  short :  they  are  placed,  one  on  the  radial,  the 
other  on  the  ulnar  side  of  the  carpus ;  the  former,  the  stronger  and  more  distinct, 
connecting  the  scaphoid  and  trapezium  bones,  the  latter  the  cuneiform  and  unciform  ; 
they  are  continuous  with  the  lateral  ligaments  of  the  wrist-joint. 

The  Synovial  Membrane  of  the  Carpus  is  very  extensive :  it  passes  from  the 


CARPO-METACARPAL    ARTICULATIONS.  359 

under  surface  of  the  scaphoid,  semilunar.  and  cuneiform  bones  to  the  upper  surface 
of  the  bones  of  the  second  row.  sending  upward  two  prolongations — between  the 
scaphoid  and  semilunar  and  the  semilunar  and  cuneiform  ;  sending  downward 
three  prolongations  between  the  four  bones  of  the  second  row,  which  are  further 
continued  onward  into  the  carpo-metacarpal  joints  of  the  four  inner  metacarpal 
bones,  and  also  for  a  short  distance  between  the  metacarpal  bones.  There  is  a 
separate  synovial  membrane  between  the  pisiform  and  cuneiform  bones. 

Actions. — The  articulation  of  the  hand  and  wrist,  considered  as  a  whole,  is 
divided  into  three  parts:  (1)  the  radius  and  the  interarticular  fibro-cartilage ; 
(-)  the  meniscus,  formed  by  the  scaphoid,  semilunar,  and  cuneiform,  the  pisiform 
bone  having  no  essential  part  in  the  movements  of  the  hand ;  (3)  the  hand  proper, 
the  metacarpal  bones  with  the  four  carpal  bones  on  which  they  are  supported — viz. 
the  trapezium,  trapezoid,  os  magnum,  and  unciform.  These  three  elements  form 
two  joints  :  (1)  the  superior  (wrist-joint  proper),  between  the  meniscus  and  bones 
of  the  forearm :  (2)  the  inferior,  between  the  hand  and  meniscus  (transverse  or 
mid-carpal  joint). 

(1)  The  articulation  between  the  forearm  and  carpus  is  a  true  condyloid  artic- 
ulation, and  therefore  all  movements  but  rotation  are  permitted.  Flexion  and 
extension  are  the  most  free,  and  of  these  a  greater  amount  of  extension  than  flexion 
is  permitted  on  account  of  the  articulating  surfaces  extending  farther  on  the  dorsal 
than  on  the  palmar  aspect  of  the  carpal  bones.  In  this  movement  the  carpal 
bones  rotate  on  a  transverse  axis  drawn  between  the  tips  of  the  styloid  processes 
of  the  radius  and  ulna.  A  certain  amount  of  adduction  (or  ulnar  flexion)  and 
abduction  (or  radial  flexion)  is  also  permitted.  Of  these  the  former  is  considerably 
greater  in  extent  than  the  latter.  In  this  movement  the  carpus  revolves  upon  an 
uttero-posterior  axis  drawn  through  the  centre  of  the  wrist.  Finally,  circumduction 
is  permitted  by  the  consecutive  movements  of  adduction,  extension,  abduction,  and 
flexion,  with  intermediate  movements  between  them.  There  is  no  rotation,  but 
this  is  provided  for  by  the  supination  and  pronation  of  the  radius  on  the  ulna. 
The  movement  of  flexion  is  performed  by  the  Flexor  carpi  radialis,  the  Flexor 
carpi  ulnaris.  and  the  Palmaris  longus ;  extension,  by  the  Extensor  carpi  radialis 
longior  et  brevior  and  the  Extensor  carpi  ulnaris  ;  adduction  (ulnar  flexion),  by  the 
Flexor  carpi  ulnaris  and  the  Extensor  carpi  ulnaris  ;  and  abduction  (radial  flexion), 
by  the  Extensors  of  the  thumb  and  the  Extensor  carpi  radialis  longior  et  brevior 
and  the  Flexor  carpi  radialis. 

(-)  The  chief  movements  permitted  in  the  transverse  or  mid-carpal  joint  are 
flexion  and  extension  and  a  slight  amount  of  rotation.  In  flexion  and  extension, 
which  is  the  movement  most  freely  enjoyed,  the  trapezium  and  trapezoid  on  the 
radial  side  and  the  unciform  on  the  ulnar  side  glide  forward  and  backward  on  the 
scaphoid  and  cuneiform  respectively,  while  the  head  of  the  os  magnum  and  the 
superior  surface  of  the  unciform  rotate  in  the  cup-shaped  cavity  of  the  scaphoid 
and  semilunar.  Flexion  at  this  joint  is  freer  than  extension.  A  very  trifling 
amount  of  rotation  is  also  permitted,  the  head  of  the  os  magnum  rotating  round  a 
vertical  axis  drawn  through  its  own  centre,  while  at  the  same  time  a  slight  gliding 
movement  takes  place  in  the  lateral  portions  of  the  joint. 

IX.  Carpo-metacarpal  Articulations. 

1.  ARTICULATION  OF  THE  METACARPAL  BOXE  OF  THE  THUMB  WITH  THE 

TRAPEZIUM. 

This  is  a  joint  of  reciprocal  reception,  and  enjoys  great  freedom  of  movement, 
on  account  of  the  configuration  of  its  articular  surfaces,  which  are  saddle-shaped, 
so  that,  on  section,  each  bone  appears  to  be  received  into  a  cavity  in  the  other, 
according  to  the  direction  in  which  they  are  cut.  Its  ligaments  are  a  capsular 
ligament  and  a  synovial  membrane. 

The  Capsular  Ligament  is  a  thick  but  loose  capsule  which  passes  from  the 
circumference  of  the  upper  extremity  of  the  metacarpal  bone  to  the  rough  edge 


360 


THE   ARTICULATIONS. 


bounding  the  articular  surface  of  the  trapezium ;  it  is  thickest  externally  and 
behind,  and  lined  by  a  separate  synovial  membrane. 

Movements. — In  the  articulation  of  the  metacarpal  bone  of  the  thumb  with  the 
trapezium  the  movements  permitted  are  flexion,  extension,  adduction,  abduction, 
and  circumduction.  When  the  joint  is  flexed  the  metacarpal  bone  is  brought  in 
front  of  the  palm  and  the  thumb  is  gradually  turned  to  the  fingers.  It  is  bv  this 
peculiar  movement  that  the  tip  of  the  thumb  is  opposed  to  the  other  digits ;  for 
by  slightly  flexing  the  fingei'S  the  palmar  surface  of  the  thumb  can  be  brought  in 
contact  with  their  palmar  surfaces  one  after  another. 

2.  ARTICULATIONS  or  THE  METACARPAL  BONES  OF  THE  FOUR  INNER 
FINGERS  WITH  THE  CARPUS. 

The  joints  formed  between  the  carpus  and  four  inner  metacarpal  bones  are 
arthrodial  joints.  The  ligaments  are — 


Dorsal. 


Palmar. 


Interosseous. 


The  Dorsal  Ligaments,  the  strongest  and  most  distinct,  connect  the  carpal  and 
metacarpal  bones  on  their  dorsal  surface.  The  second  metacarpal  bone  receives 
two  fasciculi — one  from  the  trapezium,  the  other  from  the  trapezoid ;  the  third 
metacarpal  receives  two — one  from  the  trapezoid  and  one  from  the  os  magnum ; 

the  fourth  two — one  from  the  os 
magnum  and  one  from  the  unciform  ; 
the  fifth  receives  a  single  fasciculus 
from  the  unciform  bone,  which  is 
continuous  with  a  similar  ligament 
on  the  palmar  surface,  forming  an 
incomplete  capsule. 

The  Palmar  Ligaments  have  a 
somewhat  similar  arrangement  on  the 
palmar  surface,  with  the  exception 
of  the  third  metacarpal,  which  has 
three  ligaments — an  external  one 
from  the  trapezium,  situated  above 
the  sheath  of  the  tendon  of  the 
Flexor  carpi  radialis ;  a  middle  one, 
from  the  os  magnum  ;  and  an  inter- 
nal one,  from  the  unciform. 

The  Interosseous  Ligaments  con- 
sist of  short,  thick  fibres,  Avhich  are 
limited  to  one  part  of  the  earpo- 
metacarpal  articulation ;  they  con- 
nect the  contiguous  inferior  angles 
of  the  os  magnum  and  unciform  with 
the  adjacent  surfaces  of  the  third 
and  fourth  metacarpal  bones. 

The  Synovial  Membrane  is  a  con- 
tinuation of  that  between  the  two 

rows  of  carpal  bones.     Occasionally,  the  articulation  of  the  unciform  with  the 
fourth  and  fifth  metacarpal  bones  has  a  separate  synovial  membrane. 

The  synovial  membranes  of  the  wrist  and  carpus  (Fig.  251)  are  thus  seen  to 
be  five  in  number.  The  first,  the  membrana  sacciformis,  passes  from  the  lower 
end  of  the  ulna  to  the  sigmoid  cavity  of  the  radius,  and  lines  the  upper  surface 
of  the  interarticular  fibro-cartilage.  The  second  passes  from  the  lower  end  of 
the  radius  and  interarticular  fibro-cartilage  above  to  the  bones  of  the  first  row- 
below.  The  third,  the  most  extensive,  passes  between  the  contiguous  margins  of 
the  two  rows  of  carpal  bones — between  the  bones  of  the  second  row  to  the  carpal 


FIG.  251.— Vertical  section  through  the  articulations  at 
the  wrist,  showing  the  five  synovial  membranes. 


META C'ARPO-PHALAXGEAL    ARTICULA TIONS. 


361 


extremities  of  the  four  inner  metacarpal  bones.  The  fourth,  from  the  margin  of 
the  trapezium  to  the  metacarpal  bone  of  the  thumb.  The  fifth,  between  the 
adjacent  margins  of  the  cuneiform  and  pisiform  bones. 

Actions. — The  movement  permitted  in  the  carpo-metacarpal  articulations  of  the 
four  inner  fingers  is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  each 
other,  the  extent  of  which  varies  in  the  different  joints.  Thus  the  articulation  of 
the  metacarpal  bone  of  the  little  finger  is  most  movable,  then  that  of  the  ring 
finger.  The  metacarpal  bones  of  the  index  and  middle  fingers  are  almost 
immovable. 


Jletacarpo-phalangeal 
articulation. 


3.    ARTICULATION'S    OF    THE    METACARPAL    BOXES    WITH    EACH    OTHER. 

The  carpal  extremities  of  the  four  inner  metacarpal  bones  articulate  with 
one  another  at  each  side  by  small  surfaces  covered  with  cartilages,  and  connected 
together  by  dorsal,  palmar,  and  interosseous  ligaments. 

The  Dorsal  and  Palmar  Ligaments  pass  transversely  from  one  bone  to  another 
on  the  dorsal  and  palmar  surfaces.  The  Interosseous  Ligaments  pass  between 
their  contiguous  surfaces,  just  beneath  their  lateral  articular  facets. 

The  Synovial  Membrane  between  the  lateral  facets  is  a  reflection  from  that 
between  the  two  rows  of  carpal  bones. 

The  Transverse  Metacarpal  Ligaments  (Fig.  252)  is  a  narrow  fibrous  band  which 
passes  transversely  across  the  anterior  surfaces  of  the  digital  extremities  of  the  four 
inner  metacarpal  bones,  connecting 
them  together.  It  is  blended  an- 
teriorly with  the  anterior  (glenoid) 
ligament  of  the  metacar^al-phalan- 
geal  articulations.  To  its  posterior 
border  is  connected  the  fascia  which 
covers  the  Interossei  muscles.  Its 
superficial  surface  is  concave  where 
the  flexor  tendons  pass  over  it.  Be- 
neath it  the  tendons  of  the  Inter- 
muscles  pass  to  their  insertion. 

X.  Metacarpo-phalangeal  Articu- 
lations (Fig.  252). 

These   articulations    are  of    the 
condyloid  kind,  formed  by  the  re- 
ception of  the  rounded  head  of  the 
metacarpal   bone   into   a   superficial 
cavity  in  the  extremity  of  the  first 
phalanx.      The  ligaments  are — 
Anterior. 
Two  Lateral. 

The  Anterior  Ligaments  (Gl  * 
Ligaments  of  Cruveilhier)  are  thick, 
dense,  fibrous  structures,  placed  on 
the  palmar  surface  of  the  joints  in 
the  intervals  between  the  lateral 
ligaments,  to  which  they  are  con- 
nected :  they  are  loosely  united  to 
the  metacarpal  bone,  but  very  firmly 
to  the  base  of  the  first  phalanges. 
Their  palmar  surface  is  intimately 
blended  with  the  transverse  metacar- 
pal ligament,  and  presents  a  groove  for 
the  passage  of  the  flexor  tendons,  the 


Phalangeal 
articulations. 


FIG.  252.— Articulations  of  the  phalanges. 


362  THE  ARTICULATIONS. 

sheath  surrounding  which  is  connected  to  each  side  of  the  groove.  By  their  deep 
surface  they  form  part  of  the  articular  surface  for  the  head  of  the  metacarpal  bone, 
and  are  lined  by  a  synovial  membrane. 

The  Lateral  Ligaments  are  strong,  rounded  cords  placed  one  on  each  side  of 
the  joint,  each  being  attached  by  one  extremity  to  the  posterior  tubercle  on  the 
side  of  the  head  of  the  metacarpal  bone,  and  by  the  other  to  the  contiguous 
extremity  of  the  phalanx. 

Actions. — The  movements  which  occur  in  these  joints  are  flexion,  extension, 
adduction,  abduction,  and  circumduction  ;  the  lateral  movements  are  very  limited. 

Surface  Form. — The  prominences  of  the  knuckles  do  not  correspond  to  the  position  of  the 
joints  either  of  the  metacarpo-phalangeal  or  interphalangeal  articulations.  These  prominences 
are  invariably  formed  by  the  distal  ends  of  the  proximal  bone  of  each  joint,  and  the  line  indi- 
cating the  position  of  the  joint  must  be  sought  considerably  in  front  of  the  middle  of  the  knuckle. 
The  usual  rule  for  finding  these  joints  is  to  flex  the  distal  phalanx  on  the  proximal  one  to  a  right 
angle  ;  the  position  of  the  joint  is  then  indicated  by  an  imaginary  line  drawn  along  th'e  middle  of 
the  lateral  aspect  of  the  proximal  phalanx. 

XI.  Articulations  of  the  Phalanges. 
These  are  ginglymus  joints.     The  ligaments  are — 

Anterior.  Two  Lateral. 

The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metacarpo- 
phalangeal  articulations ;  the  extensor  tendon  supplies  the  place  of  a  posterior 
ligament. 

Actions. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion 
and  extension  ;  these  movements  are  more  extensive  between  the  first  and  second 
phalanges  than  between  the  second  and  third.  The  movement  of  flexion  is  very 
considerable,  but  extension  is  limited  by  the  anterior  and  lateral  ligaments. 

ARTICULATIONS  OF   THE  LOWER  EXTREMITY. 

The  articulations  of  the  Lower  Extremity  comprise  the  following  groups  : 
I.  The  hip-joint.  II.  The  knee-joint.  III.  The  articulations  between  the  tibia 
and  fibula.  IV.  The  ankle-joint.  V.  The  articulations  of  the  tarsus.  VI.  The 
tarso-metatarsal  articulations.  VII.  The  rnetatarso-phalangeal  articulations. 
VIII.  The  articulations  of  the  phalanges. 

I.  Hip-joint  (Fig.  253). 

This  articulation  is  an  enarthrodial  or  ball-and-socket  joint,  formed  by  the 
reception  of  the  head  of  the  femur  into  the  cup-shaped  cavity  of  the  acetabulum. 
The  articulating  surfaces  are  covered  with  cartilage,  that  on  the  head  of  the  femur 
being  thicker  at  the  centre  than  at  the  circumference,  and  covering  the  entire 
surface,  with  the  exception  of  a  depression  just  below  its  centre  for  the  ligamentum 
teres ;  that  covering  the  acetabulum  is  much  thinner  at  the  centre  than  at  the 
circumference.  It  forms  an  incomplete  cartilaginous  ring  of  a  horseshoe  shape, 
deficient  below  and  in  front,  and  having  in  its  centre  a  circular  depression,  which 
is  occupied  in  the  recent  state  by  a  mass  of  fat  covered  by  synovial  membrane. 
The  ligaments  of  the  joints  are  the 

Capsular.  Teres. 

Ilio-femoral.  Cotyloid. 

Transverse. 

The  Capsular  Ligament  is  a  strong,  dense,  ligamentous  capsule,  embracing  the 
margin  of  the  acetabulum  above  and  surrounding  the  neck  of  the  femur  below. 
Its  upper  circumference  is  attached  to  the  acetabulum,  above  and  behind,  two  or 
three  lines  external  to  the  cotyloid  ligament ;  but  in  front  it  is  attached  to  the 
outer  margin  of  this  ligament,  and  opposite  to  the  notch  where  the  margin  of  this 
cavity  is  deficient,  it  is  connected  to  the  transverse  ligament,  and  by  a  few  fibres 


THE  HIP-JOINT.  363 

to  the  edge  of  the  obturator  foramen.  Its  lower  circumference  surrounds  the  neck 
of  the  femur,  being  attached,  in  front,  to  the  spiral  or  anterior  intertrochanteric 
line  ;  above,  to  the  base  of  the  neck ;  behind,  to  the  neck  of  the  bone,  about  half 
an  inch  above  the  posterior  intertrochanteric  line.  From  this  insertion  the  fibres 
are  reflected  upward  over  the  neck  of  the  femur,  forming  a  sort  of  tubular  sheath 
(the  cervical  reflection],  which  blends  with  the  periosteum  and  can  be  traced  as  far 
as  the  articular  cartilage.  It  is  much  thicker  ait  the  upper  and  fore  part  of  the 
joint,  where  the  greatest  amount  of  resistance  is  required,  than  below  and  internally, 
where  it  is  thin,  loose,  and  longer  than  in  any  other  part.  It  consists  of  two  sets 
of  fibres,  circular  and  longitudinal.  The  circular  fibres  are  most  abundant  at  the 
lawer  and  back  part  of  the  capsule,  while  the  longitudinal  fibres  are  greatest  in 


FIG.  253. — Left  hip-joint  laid  open. 

amount  at  the  upper  and  front  part  of  the  capsule,  where  they  form  distinct  bands 
or  accessory  ligaments,  of  which  the  most  important  is  the  ilio-femoral.  The 
other  accessory  bands  are  known  as  the  pubo-femoral,  passing  from  the  ilio- 
pectineal  eminence  to  the  front  of  the  capsule  ;  ilio-trochanteric,  from  the  anterior 
inferior  spine  of  the  ilium  to  the  front  of  the  great  trochanter  ;  and  ischio-capsular, 
passing  from  the  ischium.  just  below  the  acetabulum,  to  blend  with  the  circular 
fibres  at  the  lower  part  of  the  joint.  The  external  surface  (Fig.  239,  page  337)  is 
rough,  covered  by  numerous  muscles,  and  separated  in  front  from  the  Psoas  and 
Iliacus  by  a  synovial  bursa,  which  not  unfrequently  communicates,  by  a  circular 
aperture,  with  the  cavity  of  the  joint.  It  differs  from  the  capsular  ligament  of  the 
shoulder  in  being  much  less  loose  and  lax,  and  in  not  being  perforated  for  the 
pa-sage  of  a  tendon. 

The  Ilio-femoral  Ligament  (Figs.  239  and  254)  is  an  accessory  band  of  fibres 
extending  obliquely  across  the  front  of  the  joint;  it  is  intimately  connected  with 
the  capsular  ligament,  and  serves  to  strengthen  it  in  this  situation.  It  is  attached, 
above,  to  the  lower  part  of  the  anterior  inferior  spine  of  the  ilium  ;  and,  diverging 
below,  forms  two  bands,  of  which  one  passes  downward  to  be  inserted  into  the 


364 


THE   ARTICULATIONS. 


lower  part  of  the  anterior  intertrochanteric  line  ;  the  other  passes  downward 
and  outward  to  be  inserted  into  the  upper  part  of  the  same  line  and  adjacent 
part  of  the  neck  of  the  femur.  Between  the  two  bands  is  a  thinner  part  of  the 
capsule.  Sometimes  there  is  no  division,  but  the  ligament  spreads  out  into  a  flat, 
triangular  band,  which  is  attached  below  into  the  whole  length  of  the  anterior  inter- 
trochanteric line.  This  ligament  is  frequently  called  the  Y-shaped  ligament  of 
Bigelow.  Its  upper  band  is  the  ilio-trochanteric  ligament. 

The  Ligamentum  Teres  is  a  triangular  band  implanted  by  its  apex  into  the 
depression  a  little  behind  and  below  the  centre  of  the  head  of  the  femur,  and 
by  its  broad  base  into  the  margins  of  the  cotyloid  notch,  becoming  blended  with 
the  transverse  ligament.  It  is  formed  of  connective  tissue,  surrounded  by  a  tubular 
sheath  of  synovial  membrane.  Sometimes  only  the  synovial  fold  exists,  or  the 
ligament  may  be  altogether  absent.  The  ligament  is  made  tense  when  the  hip  is 

semiflexed,  and  the  limb  then  adducted  and 

^__^  rotated  outward ;    it  is,  on   the   other  hand, 

relaxed  when  the  limb  is  abducted..  It  has, 
however,  but  little  influence  as  a  ligament, 
though  it  may  to  a  certain  extent  limit  move- 
ment, and  would  appear  to  be  merely  a  modi- 
fication of  the  folds  which  in  other  joints 


OBTURATOR 
'"  MEMBRANE. 


FIG.  254.— Hip-joint,  showing  the  ilio-femoral 
ligament.    (After  Bigelow.) 


FIG.  255.— Vertical  section  through  hip-joint.    (Henle.) 


fringe  the  margins  of  reflection  of  synovial  membranes  (see  page  314). 

The  Cotyloid  Ligament  is  a  fibre-cartilaginous  rim  attached  to  the  margin  of 
the  acetabulum,  the  cavity  of  which  deepens ;  at  the  same  time  it  protects  the 
edges  of  the  bone  and  fills  up  the  inequalities  on  its  surface.  It  bridges  over  the 
notch  as  the  transverse  ligament,  and  thus  forms  a  complete  circle,  which  closely 
surrounds  the  head  of  the  femur,  and  assists  in  holding  it  in  its  place,  acting  as  a 
sort  of  valve.  It  is  prismoid  in  form,  its  base  being  attached  to  the  margin  of  the 
acetabulum,  and  its  opposite  edge  being  free  and  sharp ;  whilst  its  two  surfaces 
are  invested  by  synovial  membrane,  the  external  one  being  in  contact  with  the 
capsular  ligament,  the  internal  one  being  inclined  inward,  so  as  to  narrow  the 
acetabulum  and  embrace  the  cartilaginous  surface  of  the  head  of  the  femur.  It 
is  much  thicker  above  and  behind  than  below  and  in  front,  and  consists  of  close, 
compact  fibres,  which  arise  from  different  points  of  the  circumference  of  the 
acetabulum  and  interlace  with  each  other  at  very  acute  angles. 

The  Transverse  Ligament  is  in  reality  a  portion   of  the  cotyloid  ligament, 


THE   HIP-JOINT. 


365 


though  differing  from  it  in  having  no  nests  of  cartilage-cells  amongst  its  fibres. 
It  consists  of  strong,  flattened  fibres,  which  cross  the  notch  at  the  lower  part  of  the 
acetabulum  and  convert  it  into  a  foramen.  Thus  an  interval  is  left  beneath  the 
ligament  for  the  passage  of  nutrient  vessels  to  the  joint. 

The  Synovial  Membrane  is  very  extensive.  Commencing  at  the  margin  of  the 
cartilaginous  surface  of  the  head  of  the  femur,  it  covers  all  that  portion  of  the 
neck  which  is  contained  within  the  joint;  from  the  neck  it  is  reflected  on  the 
internal  surface  of  the  capsular  ligament,  covers  both  surfaces  of  the  cotyloid  liga- 
ment and  the  mass  of  fat  contained  in  the  depression  at  the  bottom  of  the  acetab- 


ligament 


RECT.    FEM. 


Ileo-fem.  ligament 


Pub.  fern,  ligament 


FIG.  256. — Relation  of  muscles  to  hip-joint.    (Henle.) 

ulum.  and  is  prolonged  in  the  form  of  a  tubular  sheath  around  the  ligamentum 
teres  as  far  as  the  head  of  the  femur. 

The  muscles  in  relation  with  the  joint  are,  in  front,  the  Psoas  and  Hiacus, 
separated  from  the  capsular  ligament  by  a  synovial  bursa;  above,  the  reflected 
head  of  the  Rectus  and  Glutens  minimus,  the  latter  being  closely  adherent  to  the 
capsule  :  internally,  the  Obturator  externus  and  Pectineus ;  behind,  the  Pyriformis, 
Gemellus  superior.  Obturator  internus,  Gemellus  inferior,  Obturator  externus,  and 
Qnadratus  femoris  (Fig.  256). 

The  arteries  supplying  the  joint  are  derived  from  the  obturator,  sciatic,  internal 

umflex.  and  gluteal. 

The  nerves  are  articular  branches  from  the  sacral  plexus,  great  sciatic,  obtu- 
rator, accessory  obturator,  and  a  filament  from  the  branch  of  the  anterior  crural 
supplying  the  Rectus. 

Actions. — The  movements  of  the  hip,  like  those  of  all  enarthrodial  joints,  are 
very  extensive  ;  they  are  flexion,  extension,  adduction,  abduction,  circumduction, 
and  rotation. 

The  hip-joint  presents  a  very  striking  contrast  to  the  other  great  enarthrodial 
joint — the  shoulder — in  the  much  more  complete  mechanical  arrangements  for  its 
security  and  for  the  limitation  of  its  movements.  In  the  shoulder,  as  we  have  seen, 
the  head  of  the  humerus  is  not  adapted  at  all  in  shape  to  the  glenoid  cavity,  and  is 


THE   ARTICULATIONS. 

hardly  restrained  in  any  of  its  ordinary  movements  by  the  eapsular  ligament.  In 
the  hip-joint,  on  the  contrary,  the  head  of  the  femur  is  closely  fitted  to  the  acetab- 
ulum  for  a  distance  extending  over  nearly  half  a  sphere,  and  at  the  margin  of 
the  bony  cup  it  is  still  more  closely  embraced  by  the  ligamentous  ring  of  the 
cotyloid  ligament,  so  that  the  head  of  the  femur  is  held  in  its  place  by  that 
ligament  even  when  the  fibres  of  the  capsule  have  been  quite  divided  (Humphry). 
The  anterior  portion  of  the  capsule,  described  as  the  ilio-femoral  or  accessory 
ligament,  is  the  strongest  of  all  the  ligaments  in  the  body,  and  is  put  on  the  stretch 
by  any  attempt  to  extend  the  femur  beyond  a  straight  line  with  the  trunk.  That 
is  to  say,  this  ligament  is  the  chief  agent  in  maintaining  the  erect  position  without 
muscular  fatigue,  the  action  of  the  extensor  muscles  of  the  buttock  being  balanced 
by  the  tension  of  the  ilio-femoral  and  eapsular  ligaments.  The  security  of  the 
joint  may  be  also  provided  for  by  the  two  bones  being  directly  united  through 
the  ligamentum  teres ;  but  it  is  doubtful  whether  this  so-called  ligament  can 
have  much  influence  upon  the  mechanism  of  the  joint.  Flexion  of  the  hip-joint 
is  arrested  by  the  soft  parts  of  the  thigh  and  abdomen  being  brought  into 
contact ; 1  extension,  by  the  tension  of  the  ilio-femoral  ligament  and  front  of  the 
capsule ;  adduction,  by  the  thighs  coming  into  contact ;  adduction,  with  flexion  by 
the  outer  band  of  the  ilio-femoral  ligament,  the  ilio-trochanteric  ligament,  the 
outer  part  of  the  eapsular  ligament ;  abduction,  by  the  inner  band  of  the  ilio-femoral 
ligament  and  the  pubo-femoral  band ;  rotation  outward,  by  the  outer  band  of  the 
ilio-femoral  ligament ;  and  rotation  inward,  by  the  ischio-capsular  ligament  and 
the  hinder  part  of  the  capsule.  The  muscles  which  flex  the  femur  on  the  pelvis 
are  the  Psoas,  Iliacus,  Rectus,  Sartorius,  Pectineus,  Adductor  longus  and  brevis, 
and  the  anterior  fibres  of  the  Gluteus  medius  and  minimus.  Extension  is  mainly 
performed  by  the  Gluteus  maximus,  assisted  by  the  hamstring  muscles.  The 
thigh  is  adducted  by  the"  Adductor  magnus,  longus  and  brevis,  the  Pectineus, 
and  Gracilis,  and  abducted  by  the  Gluteus  maximus,  medius,  arid  minimus.  The 
muscles  which  rotate  the  thigh  inward  are  the  anterior  fibres  of  the  Gluteus 
medius,  the  Gluteus  minimus,  and  the  Tensor  vaginae  femoris ;  while  those  which 
rotate  it  outward  are  the  posterior  fibres  of  the  Gluteus  medius,  the  Pyriformis, 
Obturator  externus  and  internus,  Gemellus  superior  and  inferior,  Quadratus  femoris, 
Psoas,  Iliacus,  Gluteus  maximus,  the  three  Adductors,  the  Pectineus,  and  the 
Sartorius. 

Surface  Form. — A  line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium  to 
the  most  prominent  part  of  the  tuberosity  of  the  ischium  (Nekton's  line)  runs  through  the 
centre  of  the  acetabulum,  and  would,  therefore,  indicate  the  level  of  the  hip-joint;  or,  in  other 
words,  the  upper  border  of  the  great  trochanter,  which  lies  on  Nekton's  line,  is  on  a  level  with 
the  centre  of  the  hip-joint. 

Surgical  Anatomy. — In  dislocation  of  the  hip  "  the  head  of  the  thigh-bone  ma}'  rest  at 
any  point  around  its  socket"  (Bryant) ;  but  whatever  position  the  head  ultimately  assumes,  the 
primary  displacement  is  generally  downward  and  inward,  the  capsule  giving  way  at  its  weakest — 
that  is,  its  lower  and  inner — part.  The  situation  that  the  head  of  the  bone  subsequently  assumes 
is  determined  by  the  degree  of  flexion  or  extension,  and  of  outward  or  inward  rotation  of 
the  thigh  at  the  moment  of  luxation,  influenced,  no  doubt,  by  the  ilio-femoral  ligament,  which 
is  not  easily  ruptured.  When,  for  instance,  the  head  is  forced  backward,  this  ligament  forms  a 
fixed  axis,  round  which  the  head  of  the  bone  rotates,  and  is  thus  driven  on  to  the  dorsum  of  the 
ilium.  The  ilio-femoral  ligament  also  influences  the  position  of  the  thigh  in  the  various  disloca- 
tions :  in  the  dislocations  backward  it  is  tense,  and  produces  inversion  of  the  limb ;  in  the 
dislocation  on  to  the  pubes  it  is  rekxed,  and  therefore  allows  the  external  rotators  to  evert  the 
thigh  ;  while  in  the  thyroid  dislocation  it  is  tense  and  produces  flexion.  The  muscles  inserted 
into  the  upper  part  of  the  femur,  with  the  exception  of  the  Obturator  internus,  have  very  little 
direct  influence  in  determining  the  position  of  the  bone.  But  Bigelow  has  endeavored  to  show 
that  the  Obturator  internus  is  the  principal  agent  in  determining  whether,  in  the  backward 
dislocations,  the  head  of  the  bone  shall  be  ultimately  lodged  on  the  dorsum  of  the  ilium  or  in 
or  near  the  sciatic  notch.  In  both  dislocations  the  head  passes,  in  the  first  instance,  in  the 
same  direction;  but,  as  Bigelow  asserts,  in  the  displacement  on  to  the  dorsum,  the  head  of  the 
bone  travels  up  behind  the  acetabulum,  between  the  muscle  and  the  pelvis ;  while  in  the  disloca- 

1  The  hip-joint  cannot  be  completely  flexed,  in  most  persons,  without  at  the  same  time  flexing 
the  knee,  on  account  of  the  shortness  of  the  hamstring  muscles. — Cleland,  Journ.  of  Anat.  and  Phys., 
No.  1,  Old  Series,  p.  87. 


THE  HIP-JOIXT.  367 

tion  into  the  sciatic  notch,  the  head  passes  behind  the  muscle,  and  is  therefore- prevented  from 
reaching  the  dorsum,  in  consequence  of  the  tendon  of  the  muscle  arching  over  the  neck  of  the 
bone,  and  so  remains  in  the  neighborhood  of  the  sciatic  notch.  Bigelow.  therefore,  distinguishes 
these  two  forms  of  dislocation  by  describing  them  as  dislocations  backward,  "  above  and  below," 
the  Obturator  iutemus. 

The  ilio-femoral  ligament  is  rarely  torn  in  dislocations  of  the  hip,  and  this  fact  is  taken 
advantage  of  by  the  surgeon  in  reducing  these  dislocations  by  manipulation.  It  is  made  to  act 
as  a  fulcrum  to  a  lever,  of  which  the  long  arm  is  the  shaft  of  the  femur,  and  the  short  arm  the 
neck  of  the  bone. 

The  hip-joint  is  rarely  the  seat  of  acute  synovitis  from  injury,  on  account  of  its  deep 
position  and  its  thick  covering  of  soft  parts.  Acute  inflammation  may,  and  does,  frequently 
occur  as  the  result  of  constitutional  conditions,  as  rheumatism,  pyaemia,  etc.  When,  in  these 
cases,  effusion  takes  place,  and  the  joint  becomes  distended  with  fluid,  the  swelling  is  not  very 
easy  to  detect  on  account  of  the  thickness  of  the  capsule  and  the  depth  of  the  articulation.  It 
is  principally  to  be  found  on  the  front  of  the  joint,  just  internal  to  the  ilio-femoral  ligament; 
or  behind,  at  the  lower  and  back  part.  In  these  two  places  the  capsule  is  thinner  than 
elsewhere.  Disease  of  the  hip-joint  is  much  more  frequently  of  a  chronic  character  and  is 
usually  i.if  a  tubercular  origin.  It  begins  either  in  the  bones  or  in  the  synovia!  membrane, 
more  frequently  in  the  former,  and  probably,  in  most  cases,  at  the  growing,  highly  vascular 
in  the  neighborhood  of  the  epiphysial  cartilage.  In  this  respect  it  differs  very  materially 
from  tubercular  arthritis  of  the  knee,  where  the  disease  usually  commences  in  the  synovial 
membrane.  The  reasons  for  this  are  twofold :  first,  this  part  being  the  centre  of  rapid  growth, 
its  nutrition  is  unstable  and  apt  to  pass  into  inflammatory  action;  and,  secondly,  great 
strain  is  thrown  upon  it.  from  the  frequency  of  falls  and  blows  upon  the  hip,  which  causes 
crushing  of  the  epiphysial  eartilase  or  the  cancellous  tissue  in  its  neighborhood,  with  the  results 
likely  to  follow  such  an  injury,  fn  addition  to  these,  the  depth  of  the  joint  protects  it  from  the 
causes  of  synovitis. 

In  chronic  hip-disease  the  affected  limb  assumes  an  altered  position,  the  cause  of  which  it 
is  important  to  understand.  In  the  early  stage  of  a  typical  case  the  limb  is  flexed,  abducted, 
and  rotated  outward.  In  this  position  all [the  ligaments  of  the  joint  are  relaxed  :  the  front  of 
the  capsule  by  flexion :  the  outer  band  of  the  ilio-femoral  ligament  by  abduction ;  and  the 
inner  band  of  this  ligament  and  the  back  of  the  capsule  by  rotation  outward.  It  is,  therefore, 
the  position  of  the  greatest  ease.  The  condition  is  not  quite  obvious  at  first  upon  examining  a 
patient.  If  the  patient  is  laid  in  the  supine  position,  the  affected  limb  will  be  found  to  be 
extended  and  parallel  with  the  other.  But  it  will  be  found  that  the  pelvis  is  tilted  downward 
on  the  diseased  side  and  the  limb  apparently  longer  than  its  fellow,  and  that  the  lumbar 
spine  is  arched  forward  (lordosis).  If  now  the  thigh  is  abducted  and  flexed,  the  tilting  down- 
wan!  and  the  arching  forward  of  the  pelvis  disappears.  The  condition  is  thus  explained.  A 
limb  which  is  flexed  and  abducted  is  obviously  useless  for  progression,  and.  in  order  to  over- 
come the  difficulty,  the  patient  depresses  the  affected  side  of  his  pelvis  in  order  to  produce 
parallelism  of  his  limbs,  and  at  the  same  time  rotates  his  pelvis  on  its  transverse  horizontal  axis, 
so  as  to  direct  the  limb  downward  instead  of  forward.  In  the  latter  stages  of  the  disease  the 
limb  becomes  flexed  and  abducted  and  inverted.  This  position  probably  depends  upon  muscular 
action,  at  all  events  as  regards  the  adduction.  The  Adductor  muscles  are  supplied  by  the 
obturator  nerve,  which  also  largely  supplies  the  joint.  These  muscles  are  therefore  thrown  into 
reflex  action  by  the  irritation  of  the  peripheral  terminations  of  this  nerve  in  the  inflamed  artic- 
ulation. Osteo-arthritis  is  not  uncommon  in  the  hip-joint,  and  it  is  said  to  be  more  common  in 
the  male  than  in  the  female,  in  whom  the  knee-joint  is  more  frequently  affected.  It  is  a  disease 
of  middle  age  or  more  advanced  period  of  life. 

Congenital  dislocation  is  more  commonly  met  with  in  the  hip-joint  than  in  any  other  articula- 
tion. The  displacement  usually  takes  place  on  to  the  dorsum  ilii.  It  gives  rise  to  extreme 
lordosis.  and  a  waddling  gait  is  noticed  as  soon  as  the  child  commences  to  walk. 

Excision  of  the  hip  may  be  required  for  disease  or  for  injury,  especially  gunshot.  It  may 
be  performed  either  by  an  anterior  incision  or  a  posterior  one.  The  former  one  entails  less 
interference  with  important  structures,  especially  muscles,  than  the  posterior  one,  but  permits 
of  less  efficient  drainage.  In  these  days,  however,  when  the  surgeon  aims  at  securing 
healing  of  his  wound  without  suppuration,  this  second  desideratum  is  not  of  so  much  import- 
ance. In  the  operation  in  front  the  surgeon  makes  an  incision  three  to  four  inches  in  length, 
starting  immediately  below  and  external  to  the  anterior  superior  spinous  process  of  the  ilium, 
downward  and  inward  between  the  Sartorius  and  Tensor  vaginae  femoris.  to  the  neck  of  the 
bone,  dividing  the  capsule  at  its  upper  part.  A  narrow-bladed  saw  now  divides  the  neck  of  the 
femur,  and  the  head  of  the  bone  is  extracted  with  sequestrum  forceps.  All  diseased  tissue  is 
carefully  removed  with  a  sharp  spoon  or  scissors,  and  the  cavity  thoroughly  flushed  out  with  a 
hot  antiseptic  fluid. 

The  posterior  method  consists  in  making  an  incision  three  or  four  inches  long,  commencing 
midway  between  the  top  of  the  .great  trochanter  and  the  anterior  superior  spine,  and  ending 
over  the  shaft,  just  below  the  trochanter.  The  muscles  are  detached  from  the  great  trochanter, 
and  the  capsule  opened  freely.  The  head  and  neck  are  freed  from  the  soft  parts  and  the  bone 
sawn  through  just  below  the  top  of  the  trochanter  with  a  narrow  saw.  The  head  of  the  bone  is 
then  levered  out  of  the  acetabulum.  In  both  operations,  if  the  acetabulum  is  eroded,  it  must  be 
freely  gouged. 


368  THE  ARTICULATIONS. 

II.    Knee-joint. 

The  knee-joint  was  formerly  described  as  a  ginglymus  or  hinge-joint,  but  is 
really  of  a  much  more  complicated  character.  It  must  be  regarded  as  consisting 
of  three  articulations  together :  one  between  each  condyle  of  the  femur  and  the 
corresponding  tuberosity  of  the  tibia,  which  are  condyloid  joints,  and  one  between 
the  patella  and  the  femur,  which  is  partly  arthrodial,  but  not  completely  so,  since 
the  articular  surfaces  are  not  mutually  adapted  to  each  other,  so  that  the  movement 
is  not  a  simple  gliding  one.  This  view  of  the  construction  of  the  knee-joint  receives 
confirmation  from  the  study  of  the  articulation  in  some  of  the  lower  mammals, 
where  three  synovial  membranes  are  sometimes  found,  corresponding  to  these  three 
subdivisions,  either  entirely  distinct  or  only  connected  together  by  small  communi- 
cations. This  view  is  further  rendered  probable  by  the  existence  of  the  two  crucial 
ligaments  within  the  joint,  which  must  be  regarded  as  the  external  and  internal 
lateral  ligaments  of  the  inner  and  outer  joints  respectively.  The  existence  of 
the  ligamentum  mucosum  would  further  indicate  a  tendency  to  separation  of  the 
synovial  cavity  into  two  minor  sacs,  one  corresponding  to  each  joint. 

The  bones  entering  into  the  formation  of  the  knee-joint  are  the  condyles  of  the 
femur  above,  the  head  of  the  tibia  below,  and  the  patella  in  front.  The  bones  are 
connected  together  by  ligaments,  some  of  which  are  placed  on  the  exterior  of  the 
joint,  while  others  occupy  its  interior. 

External  Ligaments.  Interior  Ligaments. 

Anterior,     or     Ligamentum  Pa-           Anterior,  or  External  Crucial. 

tellae.  Posterior,  or  Internal  Crucial. 

Posterior,    or   Ligamentum  Pos-           Two  Semilunar  Fibro-cartilages. 

ticum  Winslowii.  Transverse. 

Internal  Lateral.  Coronary. 

Two  External  Lateral.  Ligamentum  mucosum. 

Capsular.  Ligamenta  alaria. 

The  Anterior  Ligament,  or  Ligamentum  Patellae  (Fig.  257),  is  the  central 
portion  of  the  common  tendon  of  the  Extensor  muscles  of  the  thigh  which  is 
continued  from  the  patella  to  the  tubercle  of  the  tibia,  supplying  the  place  of  an 
anterior  ligament.  It  is  a  strong,  flat,  ligamentous  band  about  three  inches  in 
length,  attached,  above,  to  the  apex  of  the  patella  and  the  rough  depression  on  its 
posterior  surface ;  below,  to  the  lower  part  of  the  tubercle  of  the  tibia,  its  superficial 
fibres  being  continuous  over  the  front  of  the  patella  with  those  of  the  tendon  of  the 
Quadriceps  extensor.  The  lateral  portions  of  the  tendon  of  the  Extensor  muscles 
pass  down  on  either  side  of  the  patella,  attached  to  the  borders  of  this  bone  and  its 
ligament,  to  be  inserted  into  the  upper  extremity  of  the  tibia  on  each  side  of  the 
tubercle ;  externally,  these  portions  merge  into  the  capsular  ligament.  They  are 
termed  lateral  patellar  ligaments.  The  posterior  surface  of  the  ligamentum  patellae 
can  usually  be  easily  separated  from  the  front  of  the  capsular  ligament. 

The  Posterior  Ligament  (Ligamentum  Posticum  Winslowii)  (Fig.  258)  is  a 
broad,  flat,  fibrous  band  formed  of  fasciculi,  obliquely  directed,  and  separated  from 
one  another  by  apertures  for  the  passage  of  vessels  and  nerves.  The  strongest  of 
these  fasciculi  is  derived  from  the  tendon  of  the  Semimembranosus,  and  passes  from 
the  back  part  of  the  inner  tuberosity  of  the  tibia  obliquely  upward  and  outward  to 
the  back  part  of  the  outer  condyle  of  the  femur,  within  the  intercondyloid  notch. 
The  posterior  ligament  forms  part  of  the  floor  of  the  popliteal  space. 

The  Internal  Lateral  Ligament  is  a  broad,  flat,  membranous  band,  thicker 
behind  than  in  front,  and  situated  nearer  to  the  back  than  the  front  of  the  joint. 
It  is  attached,  above,  to  the  inner  tuberosity  of  the  femur ;  below,  to  the  inner 
tuberosity  and  inner  surface  of  the  shaft  of  the  tibia  to  the  extent  of  about  two 
inches.  It  is  crossed,  at  its  lower  part,  by  the  tendons  of  the  Sartorius,  Gracilis, 
and  Semitendinosus  muscles,  a  synovial  bursa  being  interposed.  Its  deep  surface 
covers  the  anterior  portion  of  the  tendon  of  the  Semimembranosus,  the  synovial 


THE 


369 


membrane  of  the  joint,  and  the  inferior  internal  articular  vessels  and  nerve;  it  is 
intimately  adherent  to  the  internal  semilunar  fibro-cartilage. 


FIG.  257.— Right  knee-joint.    Anterior  view. 


FIG.  258.— Right  knee-joint.    Posterior  view. 


The  Long  External  Lateral  Ligament  is  a  strong,  rounded,  fibrous  cord  situated 
nearer  to  the  back  than  the  front  of  the  joint.  It  is  attached,  above,  to  the  back 
part  of  the  outer  tuberosity  of  the  femur ;  below,  to  the  outer  part  of  the  head  of 
the  fibula.  Its  nnt>-r  surface  is  covered  by  the  tendon  of  the  Biceps,  which  divides 
at  its  insertion  into  two  parts,  separated  by  the  ligament.  The  ligament  has, 
passing  beneath  it.  the  tendon  of  the  Popliteus  muscle  and  the  inferior  external 
articular  vessels  and  nerve. 

The  Short  External  Lateral  Ligament  is  a  bundle  of  fibres  placed  behind  the 
preceding,  attached,  above,  together  with  the  outer  head  of  the  Gastrocnemius. 
to  the  outer  condyle  of  the  femur ;  below,  to  the  summit  of  the  styloid  process 
of  the  fibula.  This  ligament  is  intimately  connected  with  the  capsular  liga- 
ment, and  has.  passing  beneath  it,  the  tendon  of  the  Popliteus  muscle  and  the 
inferior  external  articular  vessels  and  nerve. 

The  Capsular  Ligament  consists  of  an  exceedingly  thin  but  strong,  fibrous 
membrane  which  fills  in  the  intervals  left  between  the  stronger  bands  above 
described,  and  is  inseparably  connected  with  them.  In  front  it  blends  with  the 
lateral  patellar  ligaments  and  fills  in  the  interval  between  the  anterior  and 
lateral  ligaments  of  the  joint,  with  which  latter  structures  it  is  closely  connected. 
Behind,  it  is  strong,  and  formed  chiefly  of  vertical  fibres,  which  arise  above  from 
the  condyles  and  intercondyloid  notch  of  the  femur,  and  is  connected  below  with 
the  back  part  of  the  head  of  the  tibia,  being  closely  united  with  the  origins  of 
the  Gastrocnemius.  Plantaris.  and  Popliteus  muscles.  It  passes  in  front  of,  but  is 
inseparably  connected  with,  the  posterior  ligament. 

The  Crucial  are  two  interosseous  ligaments  of  considerable  strength  situated 

84 


370 


THE   ARTICULATIONS. 


Femur. 


in  the  interior  of  the  joint,  nearer  its  posterior  than  its  anterior  part.     They  are 
called  crucial  because  they  cross  each  other  somewhat  like  the  lines  of  the  letter 

X  ;  and  have  received  the  names  anterior 
and  posterior,  from  the  position  of  their 
attachment  to  the  tibia. 

The  Anterior,  or  External  Crucial  Liga- 
ment (Fig.  259),  is  attached  to  the  depres- 
sion in  front  of  the  spine  of  the  tibia,  being 
blended  with  the  anterior  extremity  of  the 
external  semilunar  fibro-cartilage,  and,  pass- 
ing obliquely  upward,  backward,  and  out- 
ward, is  inserted  into  the  inner  and  back 
part  of  the  outer  condyle  of  the  femur.  Its 
direction  is  upward,  backward,  and  outward. 
The  Posterior,  or  Internal  Crucial  Lig- 
ament, is  stronger,  but  shorter  and  less  ob- 
lique in  its  direction,  than  the  anterior.  It 
is  attached  to  the  back  part  of  the  depres- 
sion behind  the  spine  of  the  tibia,  to  the 
popliteal  notch,  and  to  the  posterior  extrem- 
ity of  the  external  semilunar  fibro-cartilage ; 
and  passes  upward,  and  somewhat  forward, 
and  inward,  to  be  inserted  into  the  outer  part 
of  the  inner  condyle  of  the  femur.  As  it 
crosses  the  anterior  crucial  ligament  a  fas- 
ciculus is  given  off  from  it,  which  blends  with 
the  posterior  part  of  that  ligament.  It  is 
in  relation,  in  front,  with  the  anterior 
crucial  ligament;  behind,  with  the  capsular 
ligament. 

The  Semilunar  Fibro-cartilages  (Fig.  260) 
are  two  crescentic  lamellae  which  serve  to 
deepen  the  surface  of  the  head  of  the  tibia,  for  articulation  with  the  condyles  of 
the  femur.  The  circumference  of  each  cartilage  is  thick,  convex,  and  attached  to 
the  inside  of  the  capsule  of  the  knee  ;  the  inner  border  is  thin,  concave  and 

free.  Their  upper  surfaces 
are  concave,  and  in  relation 
with  the  condyles  of  the 
femur ;  their  lower  surfaces 
are  flat,  and  rest  upon  the 
head  of  the  tibia.  Each  car- 
tilage covers  nearly  the  outer 
tAvo-thirds  of  the  correspond- 
ing articular  surface  of  the 
tibia,  leaving  the  inner  third 
uncovered  ;  both  surfaces  are 
smooth  and  invested  by  syno- 
vial  membrane. 

The    Internal    Semilunar 
Fibro-cartilage  is  nearly  sem- 

Fio.260.— Head  of  tibia,  with  semilunar  cartilages,  etc.    Seen  from       i  circular     in     form      a     little 
above.    Right  side.  '          ,       . 

elongated  irom  betore  back- 
ward, and  broader  behind  than  in  front ;  its  anterior  extremity,  thin  and  pointed, 
is  attached  to  a  depression  on  the  anterior  margin  of  the  head  of  the  tibia,  in 
front  of  the  anterior  crucial  ligament ;  its  posterior  extremity  is  attached  to  the 
depression  behind  the  spine,  between  the  attachments  of  the  external  semilunar 
fibro-cartilage  and  the  posterior  crucial  ligaments. 


FIG.  259.— Right  knee-joint.    Showing  inter 
nal  ligaments. 


THE   KXEE-JOIXT. 


371 


The  External  Semilunar  Fibro-cartilage  forms  nearly  an  entire  circle,  covering 
a  larger  portion  of  the  articular  surface  than  the  internal  one.  It  is  grooved  on 
its  outer  side  for  the  tendon 
of  the  Popliteus  muscle.  Its 
extremities,  at  their  insertion, 
are  interposed  between  the 
two  extremities  of  the  inter- 
nal semilunar  fibro-cartilage ; 
the  anterior  extremity  being 
attached  in  front  of  the  spine 
of  the  tibia  to  the  outer  side 
of,  and  behind,  the  anterior 
crucial  ligament,  with  which 
it  blends :  the  posterior  ex- 
tremity being  attached  behind 
the  spine  of  the  tibia,  in  front 
of  the  posterior  extremity  of 
the  internal  semilunar  fibro- 
cartilage.  Just  before  its  in- 
sertion posteriorly  it  gives  off 
a  strong  fasciculus,  which 
passes  obliquely  upward  and 
inward,  to  be  inserted  into 
the  inner  condyle  of  the 
femur,  close  to  the  attach- 
ment of  the  posterior  crucial 
ligament.  Occasionally  a 
small  fasciculus  is  given  off 
which  passes  forward  to  be 
inserted  into  the  back  part 
of  the  anterior  crucial  lig- 
ament. The  external  semi- 
lunar  fibro-cartilage  gives  off 
from  its  anterior  convex  mar- 
gin a  fasciculus  which  forms 
the  transverse  ligament. 

The  Transverse  Ligament 
is  a  band  of  fibres  which 
passes  transversely  from  the 
anterior  convex  margin  of  the  external  semilunar  fibro-cartilage  to  the  anterior 
convex  margin  of  the  internal  semilunar  fibro-cartilage ;  its  thickness  varies 
considerably  in  different  subjects,  and  it  is  sometimes  absent  altogether. 

The  Coronary  Ligaments  are  merely  portions  of  the  capsular  ligament,  which 
connect  the  circumference  of  each  of  the  semilunar  fibro-cartilages  with  the 
margin  of  the  head  of  the  tibia. 

The  Synovial  Membrane  of  the  knee-joint  is  the  largest  and  most  extensive  in 
the  body.  Commencing  at  the  upper  border  of  the  patella,  it  forms  a  short  cul-de- 
8>ir  beneath  the  Quadriceps  extensor  tendon  of  the  thigh,  on  the  lower  part  of  the 
front  of  the  shaft  of  the  femur :  this  communicates  with  a  synovial  bursa  inter- 
posed between  the  tendon  and  the  front  of  the  femur  by  an  orifice  of  variable  size. 
On  each  side  of  the  patella  the  synovial  membrane  extends  beneath  the  aponeurosis 
of  the  Vasti  muscles,  and  more  especially  beneath  that  of  the  Vastus  internus. 
Below  the  patella  it  is  separated  from  the  anterior  ligament  by  the  anterior  part 
of  the  capsule  and  a  considerable  quantity  of  adipose -tissue.  In  this  situation  it 
sends  off  a  triangular  prolongation,  containing  a  few  ligamentous  fibres,  which 
extends  from  the  anterior  part  of  the  joint  below  the  patella  to  the  front  of  the 
intercondyloid  notch.  This  fold  has  been  termed  the  ligamentum  mucosum.  It 


FIG.  261.— Longitudinal  section  through  the  middle  of  the  right 
knee-joint.    (After  Braune.) 


372  THE  ARTICULATIONS. 

also  sends  off  two  fringe-like  folds,  called  the  ligamenta  alaria,  which  extend  from 
the  sides  of  the  ligamentum  mucosum,  upward  and  laterally  between  the  patella 
and  femur.  On  either  side  of  the  joint  it  passes  downward  from  the  femur,  lining 
the  capsule  to  its  point  of  attachment  to  the  semiluriar  cartilages  ;  it  may  then  be 
traced  over  the  upper  surfaces  of  these  cartilages  to  their  free  borders,  and  from 
thence  along  their  under  surfaces  to  the  tibia.  At  the  back  part  of  the  external 
one  it  forms  a  cul-de-sac  between  the  groove  on  its  surface  and  the  tendon  of  the 
Popliteus ;  it  surrounds  the  crucial  ligaments  and  lines  the  inner  surface  of  the 
ligaments  which  enclose  the  joints.  The  pouch  of  synovial  membrane  between 
the  Extensor  tendon  and  front  of  the  femur  is  supported,  during  the  movements 
of  the  knee,  by  a  small  muscle,  the  Subcrureus,  which  is  inserted  into  the  upper 
part  of  the  capsular  ligament. 

The  folds  of  synovial  membrane  and  the  fatty  processes  contained  in  them  act, 
as  it  seems,  mainly  as  padding  to  fill  up  interspaces  and  obviate  concussions. 
Sometimes  the  bursa  beneath  the  Quadriceps  extensor  is  completely  shut  off  from 
the  rest  of  the  synovial  cavity,  thus  forming  a  closed  sac  between  the  Quadriceps 
and  the  lower  part  of  the  front  of  the  femur,  or  it  may  communicate  with  the 
synovial  cavity  by  a  minute  aperture. 

The  bursse  about  the  knee-joint  are  the  following : 

In  front  there  are  three  bursse :  one  is  interposed  between  the  patella  and  the 
skin ;  another,  of  small  size,  between  the  upper  part  of  the  tuberosity  of  the  tibia 
and  the  ligamentum  patellae  ;  and  a  third  between  the  lower  part  of  the  tuberosity 
of  the  tibia  and  the  skin.  On  the  outer  side  there  are  four  bursse  :  (1)  one  beneath 
the  outer  head  of  the  Gastrocnemius  (which  sometimes  communicates  with  the 
joint);  (2)  one  above  the  external  lateral  ligament  between  it  and  the  tendon  of 
the  Biceps ;  (3)  one  beneath  the  external  lateral  ligament  between  it  and  the  ten- 
don of  the  Popliteus  (this  is  sometimes  only  an  expansion  from  the  next  bursa) ; 
(4)  one  beneath  the  tendon  of  the  Popliteus  between  it  and  the  condyle  of  the  femur, 
which  is  almost  always  an  extension  from  the  synovial  membrane. 

On  the  inner  side  there  are  five  bursse  :  (1)  one  beneath  the  inner  head  of  the 
Gastrocnemius,  which  sends  a  prolongation  between  the  tendons  of  the  Gastro- 
cnemius and  Semimembranosus :  this  bursa  often  communicates  with  the  joint; 
(2)  one  above  the  internal  lateral  ligament  between  it  and  the  tendons  of  the 
Sartorius,  Gracilis,  and  Semitendinosus ;  (3)  one  beneath  the  internal  lateral 
ligament  between  it  and  the  tendon  of  the  Semimembranosus :  this  is  sometimes 
only  an  expansion  from  the  next  bursa ;  (4)  one  beneath  the  tendon  of  the  Semi- 
membranosus, between  it  and  the  head  of  the  tibia ;  (5)  sometimes  there  is  a  bursa 
between  the  tendons  of  the  Semimembranosus  and  of  the  Semitendinosus. 

Structures  around  the  Joint. — In  front  and  at  the  sides,  the  Quadriceps  exten- 
sor ;  on  the  outer  side,  the  tendons  of  the  Biceps  and  the  Popliteus  and  the 
external  popliteal  nerve ;  on  the  inner  side,  the  Sartorius,  Graxnlis,  Semitendinosus, 
and  Semimembranosus  ;  behind,  an  expansion  from  the  tendon  of  the  Semimembra- 
nosus, the  popliteal  vessels,  and  the  internal  popliteal  nerve,  Popliteus,  Plantaris, 
and  inner  and  outer  heads  of  the  Gastrocnemius,  some  lymphatic  glands,  and 
fat. 

The  Arteries  supplying  the  joint  are  derived  from  the  anastomotica  magna 
branch  of  the  femoral,  articular  branches  of  the  popliteal,  anterior  and  posterior 
recurrent  branches  of  the  anterior  tibial,  and  descending  branch  from  the  external 
circumflex  of  the  Profunda. 

The  Nerves  are  derived  from  the  obturator,  anterior  crural,  and  external  and 
internal  popliteal. 

Actions. — The  knee-joint  permits  of  movements  of  flexion  and  extension,  and, 
in  certain  positions,  of  slight  rotation  inward  and  outward.  The  movement  of 
flexion  and  extension  does  not,  however,  take  place  in  a  simple,  hinge-like  man- 
ner, as  in  other  joints,  but  is  a  complicated  movement,  consisting  of  a  certain 
amount  of  gliding  and  rotation  ;  so  that  the  same  part  of  one  articular  surface  is 
not  always  applied  to  the  same  part  of  the  other  articular  surface,  and  the  axis 


THE   KNEE-JOIXT.  373- 

~ 

of  motion  is  not  a  fixed  one.     If  the  joint  is  examined  while  in  a  condition  of 

extreme  flexion,  the  posterior  part  of  the  articular  surfaces 

of  the  tibia  will  be  found  to  be  in.  contact  with  the  posterior 

rounded  extremities  of  the  condyles  of  the  femur ;  and  if 

a    simple   hinge-like  movement    were  to  take  place,   the 

axis,  round  which   the   revolving  movement   of  the   tibia 

occurs,  would  be  in  the  back  part  of  the  condyle.     If  the 

leg  is  now  brought  forward  into  a  position  of  semiflexion, 

the  upper  surface  of  the  tibia  will  be  seen  to  glide  over 

the  condyles  of  the  femur,  so  that  the  middle  part  of  the 

articular  facers  are  in  contact,  and  the  axis  of  rotation 

must  therefore  have  shifted  forward  to  nearer  the  centre          FlG    y>2_ View   of  t] 

of  the  condvles.     If  the  leg   is   now  brought   into   the     posterior  surface  of  the  pa- 

,,         •..  -ii/»-i  TT  i  i  -i       tella,  showing    diagrammat- 

extended  position,  a  still  further  gliding  takes  place  and     icaiiy  the  areas  of  contact 
a  further  shifting  forward  of  the  axis  of  rotation.     This     ^jtions  of  ttie'kjnee'^5 
is  not.  however,  a  simple  movement,  but  is  accompanied 

by  a  certain  amount  of  rotation  outward  round  a  vertical  axis  drawn  through  the 
centre  of  the  head  of  the  tibia.  This  rotation  is  due  to  the  greater  length  of  the 
internal  condyle,  and  to  the  fact  that  the  anterior  portion  of  its  articular  surface 
is  inclined  obliquely  outward.  In  consequence  of  this  it  will  be  seen  that  toward 
the  close  of  the  movement  of  extension — that  is  to  say.  just  before  complete 
extension  is  effected — the  tibia  glides  obliquely  upward  and  outward  over  this 
oblique  surface  of  the  inner  condyle,  and  the  leg  is  therefore  necessarily  rotated 
outward.  In  flexion  of  the  joint  the  converse  of  these  movements  takes  place: 
the  tibia  glides  backward  round  the  end  of  the  femur,  and  at  the  commencement 
of  the  movement  the  tibia  is  directed  downward  and  inward  along  the  oblique 
curve  of  the  inner  condyle,  thus  causing  an  inward  rotation  to  the  leg. 

During  flexion  and  extension  the  patella  moves  on  the  lower  end  of  the  femur, 
but  this  movement  is  not  a  simple  gliding  one ;  for  if  the  articular  surface  of  this 
bone  is  examined,  it  will  be  found  to  present  on  each  side  of  the  central  vertical 
ridge  two  less  marked  transverse  ridges,  which  divide  the  surface,  except  a  small 
portion  along  the  inner  border,  which  is  cut  off  by  a  slight  vertical  ridge  into 
six  facets  (see  Fig.  262),  and  therefore  does  not  present  a  uniform  curved  sur- 
face, a*  would  be  the  case  if  a  simple  gliding  movement  took  place.  These  six 
facets — three  on  each  side  of  the  median  vertical  ridge — correspond  to  and  denote 
the  parts  of  the  bone  respectively  in  contact  with  the  condyles  of  the  femur  during 
flexion,  semiflexion.  and  extension.  In  flexion  only  the  upper  facets  on  the  patella 
are  in  contact  with  the  condyles  of  the  femur ;  the  lower  two-thirds  of  the  bone 
rests  upon  the  mass  of  fat  which  occupies  the  space  between  the  femur  and  tibia. 
In  the  semiflexed  position  of  the  joint  the  middle  facets  on  the  patella  rest  upon 
the  uv>st  prominent  portion  of  the  condyles.  and  thus  afford  greater  leverage  to 
the  Quadriceps  by  increasing  its  distance  from  the  centre  of  motion.  In  complete 
extension  the  patella  is  drawn  up,  so  that  only  the  lower  facets  are  in  contact  with 
the  articular  surfaces  of  the  condyles.  The  narrow  strip  along  the  inner  border 
is  an  exception  to  this,  and  would  appear  to  be  in  contact  with  the  internal  condyle 
throughout  its  whole  extent  in  every  position  of  the  joint.  As  in  the  elbow,  so  it 
is  in  the  knee — the  axis  of  rotation  in  flexion  and  extension  is  not  precisely  at 
right  angles  to  the  axis  of  the  bone,  but  during  flexion  there  is  a  certain  amount 
of  alteration  of  plane ;  so  that,  whereas  in  flexion  the  femur  and  tibia  are  in  the 
same  plane,  in  extension  the  one  bone  forms  an  angle  of  about  ten  degrees  with 
the  other.  There  is,  however,  this  difference  between  the  two  extremities :  that 
in  the  upper,  during  extension,  the  humeri  are  parallel  and  the  bones  of  the 
forearm  diverge;  in  the  lower,  the  femora  converge  below  and  the  tibia  are 
parallel. 

In  addition  to  the  slight  rotation  during  flexion  and  extension,  the  tibia  enjoys 
an  independent  rotation  on  the  condyles  of  the  femur  in  certain  positions  of  the 
joint.  This  movement  takes  place  between  the  interarticular  fibro-cartilages  and 


374  THE  ARTICULATIONS. 

the  tibia,  whereas  the  movement  of  flexion  and  extension  takes  place  between  the 
interarticular  fibro-cartilages  and  the  femur.  So  that  the  knee  may  be  said  to 
consist  of  two  joints,  separated  by  the  fibro-cartilages  :  an  upper  (menisco-femoral), 
in  which  flexion  and  extension  take  place ;  and  a  lower  (menisco-tibial),  allowing 
of  a  certain  amount  of  rotation.  This  latter  movement  can  only  take  place  in  the 
semiflexed  position  of  the  limb,  when  all  the  ligaments  are  relaxed. 

During  flexion  the  ligamentum  patellae  is  put  upon  the  stretch,  as  is  also 
the  posterior  crucial  ligament  in  extreme  flexion.  The  other  ligaments  are  all 
relaxed  by  flexion  of  the  joint,  though  the  relaxation  of  the  anterior  crucial  ligament 
is  very  trifling.  Flexion  is  only  checked  during  life  by  the  contact  of  the  leg  with 
the  thigh.  In  extension  the  ligamentum  patellae  becomes  relaxed,  and,  in  extreme 
extension  completely  so,  so  as  to  allow  free  lateral  movement  to  the  patella,  which 
then  rests  on  the  front  of  the  lower  end  of  the  femur.  The  other  ligaments,  with 
the  exception  of  the  posterior  crucial,  which  is  partly  relaxed,  are  all  on  the  stretch. 
When  the  limb  has  been  brought  into  a  straight  line,  extension  is  checked  mainly 
by  the  tension  of  all  the  ligaments  except  the  posterior  crucial  and  ligamentum 
patellae.  The  movements  of  rotation,  of  which  the  knee  is  capable,  are  permitted 
in  the  semiflexed  condition  by  the  partial  relaxation  of  both  crucial  ligaments,  as 
well  as  the  lateral  ligaments.  Rotation  inward  appears  to  be  limited  by  the 
tension  of  the  anterior  crucial  ligament,  and  by  the  interlocking  of  the  two  liga- 
ments ;  but  rotation  outward  does  not  appear  to  be  checked  by  either  crucial 
ligament,  since  they  uncross  during  the  execution  of  this  movement,  but  by  the 
lateral  ligaments,  especially  the  internal.  The  main  function  of  the  crucial  liga- 
ments is  to  act  as  a  direct  bond  of  union  between  the  tibia  and  femur,  preventing 
the  former  bone  from  being  carried  too  far  backward  or  forward.  Thus  the 
anterior  crucial  ligament  prevents  the  tibia  being  carried  too  far  forward  by  the 
extensor  tendons,  and  the  posterior  crucial  checks  too  great  movement  backward 
by  the  flexors.  They  also  assist  the  lateral  ligaments  in  resisting  any  lateral 
bending  of  the  joint.  The  interarticular  cartilages  are  intended,  as  it  seems, 
to  adapt  the  surface  of  the  tibia  to  the  shape  of  the  femur  to  a  certain  extent, 
so  as  to  fill  up  the  intervals  which  would  otherwise  be  left  in  the  varying 
positions  of  the  joint,  and  to  interrupt  the  jars  which  would  be  so  frequently 
transmitted  up  the  limb  in  jumping  or  falls  on  the  feet;  also  to  permit  of  the 
two  varieties  of  motion,  flexion  and  extension,  and  rotation,  as  explained  above. 
The  patella  is  a  great  defence  to  the  knee-joint  from  any  injury  inflicted  in  front, 
and  it  distributes  upon  a  large  and  tolerably  even  surface  during  kneeling  the 
pressure  which  would  otherwise  fall  upon  the  prominent  ridges  of  the  condyles ;  it 
also  affords  leverage  to  the  Quadriceps  extensor  muscle  to  act  upon  the  tibia ;  and 
Mr.  Ward  has  pointed  out ]  how  this  leverage  varies  in  the  various  positions  of  the 
joint,  so  that  the  action  of  the  muscles  produces  velocity  at  the  expense  of  force  in 
the  commencement  of  extension,  and,  on  the  contrary,  at  the  close  of  extension 
tends  to  diminish  velocity,  and  therefore  the  shock  to  the  ligaments ;  whilst  in  the 
standing  position  it  draws  the  tibia  powerfully  forward,  and  thus  maintains  it  in 
its  place. 

Extension  of  the  leg  on  the  thigh  is  performed  by  the  Quadriceps  extensor ; 
flexion  by  the  hamstring  muscles,  assisted  by  the  Gracilis  and  Sartorius,  and, 
indirectly,  by  the  Gastrocnemius,  Popliteus,  and  Plantaris ;  rotation  outward,  by 
the  Biceps ;  and  rotation  inward  by  the  Popliteus,  Semitendinosus,  and,  to  a 
slight  extent,  the  Semimembranosus,  the  Sartorius,  and  the  Gracilis. 

Surface  Form. — The  interval  between  the  two  bones  entering  into  the  formation  of  the 
knee-joint  can  always  easily  be  felt.  If  the  limb  is  extended,  it  is  situated  on  a  slightly  higher  level 
than  the  apex  of  the  patella;  but  if  the  limb  is  slightly  flexed,  a  knife  carried  horizontally  back- 
ward immediately  below  the  apex  of  the  patella  would  pass  directly  into  the  joint.  When  the 
knee-joint  is  distended  with  fluid,  the  outline  of  the  synovial  membrane  at  the  front  of  the  knee 
may  be  fairly  well  mapped  out. 

Surgical  Anatomy. — From  a  consideration  of  the  construction  of  the  knee-joint  it  would 
at  first  sight  appear  to  be  one  of  the  least  secure  of  any  of  the  joints  in  the  body.  It  is  formed 

1  Human  Osteology,  p.  405. 


THE  KNEE-JOINT.  375 

between  the  two  longest  bones,  and  therefore  the  amount  of  leverage  which  can  be  brought  to 
bear  upon  it  is  very  considerable  ;  the  articular  surfaces  are  but  ill  adapted  to  each  other,  and 
the  range  and  variety  of  motion  which  it  enjoys  is  great.  All  these  circumstances  tend  to  render 
the  articulation  very  insecure ;  but,  nevertheless,  on  account  of  the  very  powerful  ligaments 
which  bind  the  bones  together,  the  joint  is  one  of  the  strongest  in  the  body,  and  dislocation 
from  traumatism  is  of  very  rare  occurrence.  When,  on  the  other  hand,  the  ligaments  have 
been  softened  or  destroyed  by  disease,  partial  displacement  is  very  liable  to  occur,  and  is 
frequently  brought  about  by  the  mere  action  of  the  muscles  displacing  the  articular  surfaces 
from  each  other.  The  tibia  may  be  dislocated  in  any  direction  from  the  femur — forward,  back- 
ward, inward,  or  outward  ;  or  a  combination  of  two  of  these  dislocations  may  occur — that  is,  the 
tibia  may  be  dislocated  forward  and  laterally,  or  backward  and  laterally;  and  any  of  these  dis- 
locations may  be  complete  or  incomplete.  As  a  rule,  however,  the  antero-posterior  dislocations 
are  complete,  the  lateral  ones  incomplete. 

One  or  other  of  the  semilunar  cartilages  may  become  displaced  and  nipped  between  the 
femur  and  tibia..  The  accident  is  produced  by  a  twist  of  the  leg  when  the  knee  is  flexed,  and  is 
accompanied  by  a  sudden  pain  and  fixation  of  the  knee  in  a  flexed  position.  The  cartilage  may 
be  displaced  either  inward  or  outward  :  that  is  to  say,  either  inward  toward  the  tibial  spine,  so 
that  the  cartilage  becomes  lodged  in  the  intercondyloid  notch  ;  or  outward,  so  that  the  cartilage 
projects  beyond  the  margin  of  the  two  articulating  bones.  Acute  synovitis,  the  result  of 
traumatism  or  exposure  to  cold,  is  very  common  in  the  knee,  on  account  of  its  superficial  posi- 
tion. When  distended  with  fluid,  the  swelling  shows  itself  above  and  at  the  sides  of  the  patella, 
reaching  about  an  inch  or  more  above  the  trochlear  surface  of  the  femur,  and  extending  a  little 
higher  under  the  Vastus  internus  than  the  Vastus  externus.  Occasionally  the  swelling  may 
extend  two  inches  or  more.  At  the  sides  of  the  patella  the  swelling  extends  lower  at  the  inner 
side  than  it  does  on  the  outer  side.  The  lower  level  of  the  synovia!  membrane  is  just  above  the 
level  of  the  upper  part  of  the  head  of  the  fibula.  In  the  middle  line  it  covers  the  upper  third 
of  the  ligamentum  patellae,  being  separated  from  it,  however,  by  the  capsule  and  a  little  fat. 
Chronic  synovitis  principally  shows  itself  in  the  form  of  pulpy  degeneration  of  the  synovial 
membrane,  leading  to  tubercular  arthritis.  The  reasons  why  tubercular  disease  of  the  knee 
usually  commences  in  the  synovial  membrane  appear  to  be  the  complex  and  extensive  nature  of 
this  sac;  the  extensive  vascular  supply  to  it ;  .and  the  fact  that  injuries  are  generally  diffused 
and  applied  to  the  front  of  the  joint  rather  than  to  the  ends  of  the  bones.  Syphilitic  disease 
not  nnfrequently  attacks  the  knee-joint.  In  the  hereditary  form  of  the  disease  it  is  usually 
symmetrical,  attacking  both  joints,  which  become  filled  with  synovial  effusion,  and  is  very 
intractable  and  difficult  of  cure.  In  the  tertiary  form  of  the  disease  gummatous  infiltration  of 
the  synovial  membrane  may  take  place.  The  knee  is  one  of  the  joints  most  commonly  affected 
with  osteo-arthritis.  and  is  said  to  be  more  frequently  the  seat  of  this  disease  in  women  than  in 
men.  The  occurrence  of  the  so-called  loose  cartilage  is  almost  confined  to  the  knee,  though  they 
are  occasionally  met  with  in  the  elbow,  and,  rarely,  in. some  other  joints.  Many  of  them  occur 
in  cases  of  osteo-arthritis,  in  which  calcareous  or  cartilaginous  material  is  formed  in  one  of  the 
synovial  fringes  and  constitutes  the  foreign  body,  and  may  or  may  not  become  detached,  in  the 
former  case  only  meriting  the  usual  term,  "loose"  cartilage.  In  other  cases  they  have  their 
origin  in  the  exudation  of  inflammatory  lymph,  and  possibly,  in  some  rare  instances,  a  portion 
of  the  articular  cartilage  or  one  of  the  semilunar  cartilages  becomes  detached  and  constitutes  the 
foreign  body. 

Genu  valgum,  or  knock-knee,  is  a  common  deformity  of  childhood,  in  which,  owing  to 
changes  in  and  about  the  joint,  the  angle  between  the  outer  border  of  the  tibia  and  femur  is 
diminished,  so  that -as  the  patient  stands  the  two  internal  condyles  of  the  femora  are  in  contact, 
but  the  two  internal  malleoli  of  the  tibiae  are  more  or  less  widely  separated  from  each  other. 
When,  however,  the  knees  are  flexed  to  a  right  angle,  the  two  legs  are  practically  parallel  with 
each  other.  At  the  commencement  of  the  disease  there  is  a  yielding  of  the  internal  lateral  liga- 
ment and  other  fibrous  structures  on  the  inner  side  of  the  joint ;  as  a  result  of  this  there  is  a' 
constant  undue  pressure  of  the  outer  tuberosity  of  the  tibia  against  the  outer  condyle  of  the 
femur.  This  extra  pressure  causes  arrest  of  growth  and,  possibly,  wasting  of  the  outer  con- 
dyle, and  a  consequent  tendency  for  the  tibia  to  become  separated  from  the  internal  condyle. 
To  prevent  this  the  internal  condyle  becomes  depressed ;  probably,  as  was  first  pointed  out  by 
Mikulicz,  by  an  increased  growth  of  the  lower  end  of  the  diaphysis  on  its  inner  side,  so  that  the 
line  of  the  epiphysis  becomes  oblique  instead  of  transverse  to  the  axis  of  the  bone,  with  a  direc- 
tion downward  and  inward. 

Excision  of  the  knee-joint  is  most  frequently  required  for  tubercular  disease  of  this  articula- 
tion, but  is  also  practised  in  cases  of  disorganization  of  the  knee  after  rheumatic  fever,  pyaemia, 
etc. ,  in  osteo-arthritis.  and  in  ankylosis.  It  is  also  occasionally  called  for  in  cases  of  injury,  gun- 
shot or  otherwise.  The  operation  is  best  performed  either  by  a  horseshoe  incision,  starting  from 
one  condyle,  descending  as  low  as  the  tubercle  of  the  tibia,  where  it  crosses  the  leg,  and  is  then 
carried  upward  to  the  other  condyle ;  or  by  a  transverse  incision  across  the  patella.  In  this 
latter  incision  the  patella  is  either  removed  or  sawn  across,  and  the  halves  subsequently  sutured 
together.  The  bones  having  been  cleared,  and  in  those  cases  where  the  operation  is  performed 
for  tubercular  disease  all  pulpy  tissue  having  been  carefully  removed,  the  section  of  the  femur 
is  first  made.  This  should  never  include,  in  children,  more  than,  at  the  most,  two-thirds 
of  the  articular  surface,  otherwise  the  epiphysis  will  be  included,  with  disastrous  results  as  far 
as  regards  the  growth  of  the  limb.  Afterward  a  thin  slice  should  be  removed  from  the  upper 


376  THE  ARTICULATIONS. 

end  of  the  tibia,  not  more  than  half  an  inch.  If  any  diseased  tissue  still  appears  to  be  left  in 
the  bones,  it  should  be  removed  with  the  gouge  rather  than  that  a  further  section  of  the  bones 
should  be  made. 

III.  Articulations  between  the  Tibia  and  Fibula. 

The  articulations  between  the  tibia  and  fibula  are  effected  by  ligaments  which 
connect  both  extremities,  as  well  as  the  shafts  of  the  bones.  They  may,  con- 
sequently, be  subdivided  into  three  sets :  1.  The  Superior  Tibio-fibular  articula- 
tion. 2.  The  Middle  Tibio-fibular  ligament  or  interosseous  membrane.  3.  The 
Inferior  Tibio-fibular  articulation. 

1.  SUPERIOR  TIBIO-FIBULAR  ARTICULATION. 

This  articulation  is  an  arthrodial  joint.  The  contiguous  surfaces  of  the  bones 
present  two  flat,  oval  facets  covered  with  cartilage,  and  connected  together  by  the 
following  ligaments: 

Anterior  Superior  Tibio-fibular. 
Posterior  Superior  Tibio-fibular. 

The  Anterior  Superior  Ligament  (Fig.  259)  consists  of  two  or  three  broad  and 
flat  bands  which  pass  obliquely  upward  and  inward  from  the  front  of  the  head  of 
the  fibula  to  the  front  of  the  outer  tuberosity  of  the  tibia. 

The  Posterior  Superior  Ligament  (Fig.  258)  is  a  single  thick  and  broad  band 
which  passes  upward  and  inward  from  the  back  part  of  the  head  of  the  fibula  to 
the  back  part  of  the  outer  tuberosity  of  the  tibia.  It  is  covered  by  the  tendon  of 
the  Popliteus  muscle. 

A  Synovial  Membrane  lines  this  articulation,  which  at  its  upper  and  back  part 
is  occasionally  continuous  with  that  of  the  knee-joint. 

2.    MIDDLE  TIBIO-FIBULAR  LIGAMENT  OR  INTEROSSEOUS  MEMBRANE. 

An  interosseous  membrane  extends  between  the  contiguous  margins  of  the 
tibia  and  fibula,  and  separates  the  muscles  on  the  front  from  those  on  the  back  of 
the  leg.  It  consists  of  a  thin,  aponeurotic  lamina  composed  of  oblique  fibres 
which  pass  downward  and  outward  between  the  interosseous  ridges  on  the  two 
bones.  It  is  broader  above  than  below.  Above  its  upper  border  is  a  large,  oval 
aperture  for  the  passage  of  the  anterior  tibial  vessels  forward  to  the  anterior  aspect 
of  the  leg ;  and  at  its  lower  part  an  opening  for  the  passage  of  the  anterior  pero- 
neal  vessels.  It  is  continuous  below  with  the  inferior  interosseous  ligament,  and 
is  perforated  in  numerous  parts  for  the  passage  of  small  vessels.  It  is  in  relation, 
in  front,  with  the  Tibialis  anticus,  Extensor  longus  digitorum,  Extensor  proprius 
hallucis,  Peroneus  tertius,  and  the  anterior  tibial  vessels  and  nerve ;  behind,  with 
'the  Tibialis  posticus  and  Flexor  longus  hallucis. 

3.  INFERIOR  TIBIO-FIBULAR  ARTICULATION. 

This  articulation  is  formed  by  the  rough,  convex  surface  of  the  inner  side  of 
the  lower  end  of  the  fibula,  connected  with  a  concave  rough  surface  on  the  outer 
side  of  the  tibia.  Below,  to  the  extent  of  about  two  lines,  these  surfaces  are 
smooth,  and  covered  writh  cartilage,  which  is  continuous  with  that  of  the  ankle- 
joint.  The  ligaments  of  this  joint  are — 

Anterior  Inferior  Tibio-fibular.  Transverse. 

Posterior  Inferior  Tibio-fibular.  Inferior  Interosseous. 

The  Anterior  Inferior  Ligament  (Fig.  264)  is  a  flat,  triangular  band  of  fibres, 
broader  below  than  above,  which  extends  obliquely  downward  and  outward 
between  the  adjacent  margins  of  the  tibia  and  fibula,  on  the  front  aspect  of  the 
articulation.  It  is  in  relation,  in  front,  with  the  Peroneus  tertius,  the  aponeurosis 


THE  ANKLE-JOINT.  377 

of  the  leg,  and  the  integument ;  behind,  with  the  inferior  inter-osseous  ligament ; 
and  lies  in  contact  with  the  cartilage  covering  the  astragalus. 

The  Posterior  Inferior  Ligament,  smaller  than  the  preceding,  is  disposed  in  a 
similar  manner  on  the  posterior  surface  of  the  articulation. 

The  Transverse  Ligament  is  a  long,  narrow  band,  continuous  with  the  preceding, 
passing  transversely  across  the  back  of  the  joint,  from  the  external  malleolus  to 
the  posterior  border  of  the  articular  surface  of  the  tibia,  almost  as  far  as  its  mal- 
leolar  process.  This  ligament  projects  below  the  margin  of  the  bones,  and  forms 
part  of  the  articulating  surface  for  the  astragalus. 

The  Inferior  Interosseous  Ligament  consists  of  numerous  short,  strong,  fibrous 
bands  which  pass  between  the  contiguous  rough  surfaces  of  the  tibia  and  fibula, 
and  constitute  the  chief  bond  of  union  between  the  bones.  This  ligament  is  con- 
tinuous above  with  the  interosseous  membrane. 

The  Synovial  Membrane  lining  the  articular  surface  is  derived  from  that  of  the 
ankle-joint. 

Actions. — The  movement  permitted  in  these  articulations  is  limited  to  a  very 
slight  gliding  of  the  articular  surfaces  one  upon  another. 

IV.  Ankle-joint. 

The  Ankle  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  forma- 
tion are  the  lower  extremity  of  the  tibia  and  its  malleolus  and  the  external  mal- 
leolus of  the  fibula.  These  bones  are  united  above,  and  form  a  mortise  to  receive 
the  upper  convex  surface  of  the  astragalus  and  its  two  lateral  facets.  The  bony 
surfaces  are  covered  with  cartilage,  and  connected  together  by  a  capsule,  which  in 
places  forms  thickened  bands  constituting  the  following  ligaments : 

Anterior.  Internal  Lateral. 

Posterior.  External  Lateral. 

The  Anterior  Tibio-tarsal  Ligament  (Fig.  263)  is  a  broad,  thin,  membranous 
layer,  attached,  above,  to  the  margin  of  the  articular  surface  of  the  tibia ;  below, 


Tarso-  metata  rsal 
articulations. 


— ^^B^' 

FIG.  263.— Ankle-joint :  tarsal  and  tarso-metatarsal  articulations.    Internal  view.    Right  side. 


to  the  margin  of  the  astragalus,  in  front  of  its  articular  surface.     It  is  in  relation, 
in  front,  with  the  Extensor  tendons  of  the  toes,  with  the  tendons  of  the  Tibialis 


378 


THE  ARTICULATIONS. 


anticus  and  Peroneus  tertius,  and  the  anterior  tibial  vessels  and  nerve  ;  behind,  it 
lies  in  contact  with  the  synovial  membrane. 

The  Posterior  Tibio-tarsal  Ligament  is  very  thin,  and  consists  principally  of 
transverse  fibres.  It  is  attached,  above,  to  the  margin  of  the  articular  surface  of  the 
tibia,  blending  with  the  transverse  tibio-fibular  ligament ;  below,  to  the  astragalus, 
behind  its  superior  articular  facet.  Externally  it  is  thicker  than  internally,  where 
a  somewhat  thickened  band  of  transverse  fibres  is  attached  to  the  hollow  on  the 
inner  surface  of  the  external  malleolus. 

The  Internal  Lateral  or  Deltoid  Ligament  is  a  strong,  flat,  triangular  band, 
attached,  above,  to  the  apex  and  anterior  and  posterior  borders  of  the  inner  mal- 
leolus. The  most  anterior  fibres  pa.ss  forward  to  be  inserted  into  the  navicular 
bone  and  the  inferior  calcaneo-navicular  ligament ;  the  middle  descend  almost 
perpendicularly  to  be  inserted  into  the  sustentaculum  tali  of  the  os  calcis  ;  and  the 
posterior  fibres  pass  backward  and  outward  to  be  attached  to  the  inner  side  of  the 
astragalus.  This  ligament  is  covered  by  the  tendons  of  the  Tibialis  posticus  and 
Flexor  longus  digitorum  muscles. 


Inferior  tibio-fibular  articulation. 

Ankle-joint. 

Tarsal  articulations. 

Tarso-metatarsal 

articulations. 


FIG.  264.— Ankle-joint :  tarsal  and  tarso-metatarsal  articulations.    External  view.    Right  side. 


The  External  Lateral  Ligament  (Fig.  264)  consists  of  three  distinctly  special- 
ized fasciculi  of  the  capsule,  taking  different  directions  and  separated  by  distinct 
intervals ;  for  which  reason  it  is  described  by  some  anatomists  as  three  distinct 
ligaments.1 

The  anterior  fasciculus  (anterior  astragalo-fibular),  the  shortest  of  the  three, 
passes  from  the  anterior  margin  of  the  summit  of  the  external  malleolus,  downward 
and  forward,  to  the  astragalus,  in  front  of  its  external  articular  facet. 

The  posterior  fasciculus  (posterior  astragalo-fibular),  the  most  deeply  seated, 
passes  from  the  depression  at  the  inner  and  back  part  of  the  external  malleolus 
to  a  prominent  tubercle  on  the  posterior  surface  of  the  astragalus.  Its  fibres  are 
almost  horizontal  in  direction. 

The  middle  fasciculus  (calcaneo-fibular),  the  longest  of  the  three,  is  a  narrow, 
rounded  cord  passing  from  the  apex  of  the  external  malleolus  downward  and 
slightly  backward  to  a  tubercle  on  the  outer  surface  of  the  os  calcis.  It  is  covered 
by  the  tendons  of  the  Peroneus  longus  and  brevis. 

1  Humphry,  On  the  Skeleton,  p.  559. 


THE   AXKLE-JOIXT.  379 

The  Synovial  Membrane  invests  the  inner  surface  of  the  ligaments,  and  sends 
a  duplicature  upward  between  the  lower  extremities  of  the  tibia  and  fibula  for  a 
short  distance. 

Relations. — The  tendons,  vessels,  and  nerves  in  connection  with  the  joint  are, 
in  front,  from  within  outward,  the  Tibialis  anticus,  Extensor  proprius  hallucis, 
anterior  tibial  vessels,  anterior  tibial  nerve.  Extensor  communis  digitorum,  and 
Peroneus  tertius  :  behind,  from  within  outward,  the  Tibialis  posticus,  Flexor  longus 
digitorum.  posterior  tibial  vessels,  posterior  tibial  nerve,  Flexor  longus  hallucis ; 
and.  in  the  groove  behind  the  external  malleolus,  the  tendons  of  the  Peroneus 

C  * 

longus  and  brevis. 

The  Arteries  supplying  the  joint  are  derived  from  the  malleolar  branches  of  the 
anterior  tibial  and  the  peroneal. 

The  Serves  are  derived  from  the  anterior  and  posterior  tibial. 

Actions. — The  movements  of  the  joint  are  those  of  flexion  and  extension. 
The  malleoli  tightly  embrace  the  astragalus  in  all  positions  of  the  joint,  so  that  any 
slight  degree  of  lateral  movement  which  may  exist  is  simply  due  to  stretching 
of  the  inferior  tibio-fibular  ligaments  and  slight  bending  of  the  shaft  of  the 
fibula.  Of  the  ligaments,  the  internal,  or  deltoid,  is  of  very  great  power — so 
much  so  that  it  usually  resists  a  force  which  fractures  the  process  of  bone  to  which 
it  is  attached.  Its  middle  portion,  together  with  the  middle  fasciculus  of  the 
external  lateral  ligament,  binds  the  bones  of  the  leg  firmly  to  the  foot  and  resists 
displacement  in  every  direction.  Its  anterior  and  posterior  fibres  limit  extension 
and  flexion  of  the  foot  respectively,  and  the  anterior  fibres  also  limit  abduction. 
The  posterior  portion  of  the  external  lateral  ligament  assists  the  middle  portion  in 
resisting  the  displacement  of  the  foot  backward,  and  deepens  the  cavity  for  the 
reception  of  the  astragalus.  The  anterior  fasciculus  is  a  security  against  the  dis- 
placement of  the  foot  forward,  and  limits  extension  of  the  joint.  The  movements 
of  abduction  and  adduction  of  the  foot,  together  with  the  minute  changes  in  form 
by  which  it  is  applied  to  the  ground  or  takes  hold  of  an  object  in  climbing,  etc.,  are 
mainly  effected  in  the  tarsal  joints,  the  one  which  enjoys  the  greatest  amount  of 
motion  being  that  between  the  astragalus  and  os  calcis  behind  and  the  navicular 
and  cuboid  in  front.  This  is  often  called  the  transverse  or  medio-tarsal  joint .  and 
it  can.  with  the  subordinate  joints  of  the  tarsus,  replace  the  ankle-joint  in  a  great 
measure  when  the  latter  has  become  ankylosed. 

Extension  of  the  tarsal  bones  upon  the  tibia  and  fibula  is  produced  by  the 
Gastrocnemius,  Soleus,  Plantaris,  Tibialis  posticus,  Peroneus  longus  and  brevis, 
Flexor  longus  digitorum,  and  Flexor  longus  hallucis ;  flexion,  by  the  Tibialis  anti- 
ens.  Peroneus  tertius.  Extensor  longus  digitorum.  and  Extensor  proprius  hallucis  ;* 
adduction,  in  the  extended  position,  is  produced  by  the  Tibialis  anticus  and  posti- 
cus :  and  abduction  by  the  Peronei. 

Surface  Form. — The  line  of  the  ankle-joint  may  be  indicated  by  a  transverse  line  drawn 

s  the  front  of  the  lower  part  of  the  leg,  about  half  an  inch  above  the  level  of  the  tip  of  the 
internal  malleolus. 

Surgical  Anatomy. — Displacement  of  the  trochlear  surface  of  the  astragalus  from  the 
tibio-fibular  mortise  is  not  of  common  occurrence,  as  the  ankle-joint  is  a  very  strong  and  powerful 
articulation,  and  great  force  is  required  to  produce  it.  Nevertheless,  dislocation  does  occasionally 
occur,  both  in  an  an tero- posterior  and  a  lateral  direction.  In  the  latter,  which  is  the  most  com- 
mon, fracture  is  a  necessary  accompaniment  of  the  injury.  The  dislocation  in  these  cases  is 
somewhat  peculiar,  and  is  not  a  displacement  in  a  horizontally  lateral  direction,  such  as  usually 
occurs  in  lateral  dislocations  of  ginglymoid  joints,  but  the  astragalus  undergoes  a  partial  rotation 
round  an  antero-posterior  axis  drawn  through  its  own  centre,  so  that  the  superior  surface,  instead 
of  being  directed  upward,  is  inclined  more  or  less  inward  or  outward  according  to  the  variety  of 
the  displacement. 

The  ankle-joint  is  more  frequently  sprained  than  any  joint  in  the  body,  and  this  may  lead 
to  acute  svnoyitis.  In  these  cases,  when  the  synovial  sac  is  distended  with  fluid,  the  bulging 
appears  principally  in  the  front  of  the  joint,  beneath  the  anterior  tendons,  and  on  either  side, 
between  the  Tibialis  anticus  and  the  internal  lateral  ligament  on  the  inner  side,  and  between  the 

1  The  student  must  bear  in  mind  that  the  Extensor  longus  digitorum  and  Extensor  proprius  hal- 
lucis are  extensors  of  the  toes,  but  flexors  of  the  ankle,  and  that  the  Flexor  longus  digitorum  and  Flexor 
longus  hallucis  are  flexors  of  the  toes,  but  ejcfen-sors  of  the  ankle. 


380 


THE   ARTICULATIONS 


Peroneus  tertius  and  the  external  lateral  ligament  on  the  outer  side.  In  addition  to  this,  bulging 
frequently  occurs  posteriorly,  and  a  fluctuating  swelling  may  be  detected  on  either  side  of  the 
tendo  Achillis. 

Chronic  synovitis  may  result  from  frequent  sprains,  and  when  once  this  joint  has  been 
sprained  it  is  more  liable  to  a  recurrence  of  the  injury  than  it  was  before  ;  or  it  may  be  tuber- 


FIG.  265.— Section  of  the  right  foot  near  its  inner  border,  dividing  the  tibia,  astragalus,  navicular,  internal 
cuneiform,  and  first  metatarsal  bone,  and  the  first  phalanx  of  the  great  toe.    (After  Braune.) 

cular  in  its  origin,  the  disease  usually  commencing  in  the  astragalus  and  extending  to  the  joint, 
though  it  may  commence  as  a  tubercular  synovitis  the  result  probably  of  some  slight  strain  in  a 
tubercular  subject. 

Excision  of  the  ankle-joint  is  not  often  performed  for  two  reasons.  In  the  first  place, 
disease  of  the  articulation  for  which  this  operation  is  indicated  is  frequently  associated  with 
disease  of  the  tarsal  bones,  which  prevents  its  performance;  and,  secondly,  the  foot  after 
excision  is  frequently  of  very  little  use  ;  far  less,  in  fact,  than  after  a  Symes's  amputation,  which 
is  often,  therefore,  a  preferable  operation  in  these  cases.  P]xcision  may,  however,  be  attempted 
in  cases  of  tubercular  arthritis,  in  a  young  and  otherwise  healthy  subject,  where  the  disease  is 
limited  to  the  bones  forming  the  joint.  It  may  also  be  required  after  injury  where  the  vessels 
and  nerves  have  not  been  damaged  and  the  patient  is  young  and  free  from  visceral  disease. 
The  excision  is  best  performed  by  two  lateral  incisions.  One  commencing  two  and  a  half  inches 
above  the  external  malleolus,  carried  down  the  posterior  border  of  the  fibula,  round  the  end  of 
the  bone,  and  then  forward  and  downward  as  far  as  the  calcaneo-cuboid  joint,  midway  between 
the  tip  of  the  external  malleolus  and  the  tuberosity  on  the  fifth  metatarsal  bone.  Through  this 
incision  the  fibula  is  cleared,  the  external  lateral  ligament  is  divided,  and  the  bone  sawn  through 
at  the  upper  end  of  the  incision  and  removed.  A  similar  curved  incision  is  now  made  on  the 
inner  side  of  the  foot,  commencing  two  and  a  half  inches  above  the  lower  end  of  the  tibia, 
carried  down  the  posterior  border  of  the  bone,  round  the  internal  malleolus,  and  forward  and 
downward  to  the  tuberosity  of  the  navicular  bone.  Through  this  incision  the  tibia  is  cleared  in 
front  and  behind,  the  internal  lateral,  the  anterior  and  posterior  ligaments  divided,  and  the  end 
of  the  tibia  protruded  through  the  wound  by  displacing  the  foot  outward,  and  sawn  off  sufficiently 
high  to  secure  a  healthy  section  of  bone.  The  articular  surface  of  the  astragalus  is  now  to  be 
sawn  off  or  the  whole  bone  removed.  In  cases  where  the  operation  is  performed  for  tubercular 
arthritis  the  latter  course  is  probably  preferable,  as  the  injury  done  by  the  saw  is  frequently  the 
starting  point  of  fresh  caries;  and  after  removal  of  the  whole  bone  the  shortening  is  not  appreci- 
ably increased,  and  the  result  as  regards  union  appears  to  be  as  good  as  when  two  sawn  surfaces 
of  bone  are  brought  into  apposition. 

V.  Articulations  of  the  Tarsus. 

1.   ARTICULATIONS  OF  THE  Os  CALCIS  AND  ASTRAGALUS. 

The  articulations  between  the  os  calcis  and  astragalus  are  two  in  number — 
anterior  and  posterior.  They  are  arthrodial  joints.  The  bones  are  connected 
together  by  four  ligaments  : 


External  Calcaneo-astragaloid. 
Internal  Calcaneo-astragaloid. 


Posterior  Calcaneo-astragaloid. 
Interosseous. 


OF   THE   TARSUS.  381 

The  External  Calcaneo-astragaloid  Ligament  (Fig.  264)  is  a  short,  strong, 
fasciculus  passing  from  the  outer  surface  of  the  astragalus,  immediately  beneath 
its  external  malleolar  facet,  to  the  outer  surface  of  the  os  calcis.  It  is  placed  in 
front  of  the  middle  fasciculus  of  the  external  lateral  ligament  of  the  ankle-joint, 
with  the  fibres  of  which  it  is  parallel. 

The  Internal  Calcaneo-astragaloid  Ligament  is  a  band  of  fibres  connecting  the 
internal  tubercle  of  the  back  of  the  astragalus  with  the  back  of  the  sustentaculum 
tali.  Its  fibres  blend  with  those  of  the  inferior  calcaneo-navicular  ligament. 

The  Posterior  Calcaneo-astragaloid  Ligament  (Fig.  263)  connects  the  posterior 
external  tubercle  of  the  astragalus  with  the  upper  and  inner  part  of  the  os  calcis ; 
it  is  a  short,  narrow  band,  the  fibres  of  Avhich  radiate  from  their  narrow  attach- 
ment to  the  astragalus; 

The  Interosseous  Ligament  forms  the  chief  bond  of  union  between  the  bones. 
It  consists  of  numerous  vertical  and  oblique  fibres  attached  by  one  extremity  to  the 
groove  between  the  articulating  facets  on  the  under  surface  of  the  astragalus ;  by 
the  other  to  a  corresponding  depression  on  the  upper  surface  of  the  os  calcis.  It 
is  very  thick  and  strong,  being  at  least  an  inch  in  breadth  from  side  to  side,  and 
serves  to  unite  the  os  calcis  and  astragalus  solidly  together. 

The  Synovial  Membranes  (Fig.  267)  are  two  in  number :  one  for  the  posterior 
calcaneo-astragaloid  articulation ;  a  second  for  the  anterior  calcaneo-astragaloid 
joint.  The  latter  synovial  membrane  is  continued  forward  between  the  contiguous 
surfaces  of  the  astragalus  and  navicular  bones. 

Actions. — The  movements  permitted  between  the  astragalus  and  os  calcis  are 
limited  to  a  gliding  of  the  one  bone  on  the  other  in  a  direction  from  before  back- 
ward, and  from  side  to  side. 

2.  ARTICULATIONS  OF  THE  Os  CALCIS  WITH  THE  CUBOID. 
The  ligaments  connecting  the  os  calcis  with  the  cuboid  are  four  in  number: 

pv        -,  (  Superior  Calcaneo-cuboid. 

\  Internal  Calcaneo-cuboid  (Interosseous). 
pi     t  (  Long  Calcaneo-cuboid. 

\  Short  Calcaneo-cuboid. 

The  Superior  Calcaneo-cuboid  Ligament  (Fig.  264)  is  a  thin  and  narrow  fasciculus 
which  passes  between  the  contiguous  surfaces  of  the  os  calcis  and  cuboid  on  the 
dorsal  surface  of  the  joint. 

The  Internal  Calcaneo-cuboid  (Interosseous)  Ligament  (Fig.  264)  is  a  short 
but  thick  and  strong  band  of  fibres  arising  from  the  os  calcis,  in  the  deep  hollow 
which  intervenes  between  it  and  the  astragalus,  and  closely  blended,  at  its  origin, 
with  the  superior  calcaneo-navicular  ligament.  It  is  inserted  into  the  inner  side  of 
the  cuboid  bone.  This  ligament  forms  one  of  the  chief  bonds  of  union  between 
the  first  and  second  rows  of  the  tarsus. 

The  Long  Calcaneo-cuboid  (Long  Plantar)  Ligament  (Fig.  266),  the  more  super- 
ficial of  the  two  plantar  ligaments,  is  the  longest  of  all  the  ligaments  of  the  tarsus  : 
it  is  attached  to  the  under  surface  of  the  os  calcis,  from  near  the  tuberosities,  as  far 
forward  as  the  anterior  tubercle ;  its  fibres  pass  forward  to  be  attached  to  the 
ridge  on  the  under  surface  of  the  cuboid  bone,  the  more  superficial  fibres  being 
continued  onward  to  the  bases  of  the  second,  third,  and  fourth  metatarsal  bones. 
This  ligament  crosses  the  groove  on  the  under  surface  of  the  cuboid  bone,  convert- 
ing it  into  a  canal  for  the  passage  of  the  tendon  of  the  Peroneus  longus. 

The  Short  Calcaneo-cuboid  (Short  Plantar)  Ligament  lies  nearer  to  the  bones 
than  the  preceding,  from  which  it  is  separated  by  a  little  adipose  tissue.  It  is 
exceedingly  broad,  about  an  inch  in  length,  and  extends  from  the  tubercle  and  the 
depression  in  front  of  it,  on  the  fore  part  of  the  under  surface  of  the  os  calcis,  to 
the  inferior  surface  of  the  cuboid  bone  behind  the  peroneal  groove. 


382 


THE   ARTICULATIONS 


Synovial  Membrane. — The  synovial  membrane  in  this  joint  is  distinct.  It 
lines  the  inner  surface  of  the  ligaments. 

Actions. — The  movements  permitted  between  the  os  calcis  and  cuboid  are 
limited  to  a  slight  gliding  upon  each  other. 

3.  THE  LIGAMENTS  CONNECTING  THE  Os  CALCIS  AND  NAVICULAR. 

Though  these  two  bones  do  not  directly  articulate,  they  are  connected  together 
by  two  ligaments  : 

Superior  or  External  Calcaneo-navicular. 
Inferior  or  Internal  Calcaneo-navicular. 

The  Superior  or  External  Calcaneo-navicular  (Fig.  264)  arises,  as  already 
mentioned,  with  the  internal  calcaneo-cuboid  in  the  deep  hollow  between  the 
astragalus  and  os  calcis ;  it  passes  forward  from  the  inner  side  of  the  anterior  ex- 
tremity of  the  os  calcis  to  the  outer  side  of  the  navicular  bone.  These  two  liga- 
ments resemble  the  letter  Y,  being  blended  together  behind,  but  separated  in  front. 
The  Inferior  or  Internal  Calcaneo-navicular  (Fig.  266)  is  by  far  the  larger 

and  stronger  of  the  two  ligaments  between 
these  bones ;  it  is  a  broad  and  thick  band  of 
fibres,  which  passes  forward  and  inward  from 
the  anterior  margin  of  the  sustentaculum  tali 
of  the  os  calcis  to  the  under  surface  of  the 
navicular  bone.  This  ligament  not  only 
serves  to  connect  the  os  calcis  and  navicular, 
but  supports  the  head  of  the  astragalus,  form- 
ing part  of  the  articular  cavity  in  which  it  is 
received.  The  upper  surface  presents  a  fibro- 
cartilaginous  facet,  lined  by  the  synovial 
membrane  continued  from  the  anterior  cal- 
caneo-astragaloid  articulation,  upon  which 
the  head  of  the  astragalus  rests.  Its  under 
surface  is  in  contact  with  the  tendon  of  the 
Tibialis  posticus  muscle  ; l  its  inner  border  is 
blended  with  the  fore  part  of  the  Deltoid 
ligament,  thus  completing  the  socket  for  the 
head  of  the  astragalus. 

Surgical  Anatomy. — The  inferior  caleaneo-nav- 
icular  ligament,  by  supporting  the  head  of  the  astrag- 
alus, is  principally  concerned  in  maintaining  the 
arch  of  the  foot,  and  when  it  yields  the  head  of 
the  astragalus  is  pressed  downward,  inward,  and  for- 
ward by  the  weight  of  the  body,  and  the  foot  becomes 
flattened,  expanded,  and  turned  outward,  constituting 
the  disease  known  as  flat-foot.  This  ligament  con- 
tains a  considerable  amount  of  elastic  fibre,  so  as  to 
give  elasticity  to  the  arch  and  spring  to  the  foot; 
hence  it  is  sometimes  called  the  "spring"  ligament. 
It  is  supported,  on  its  under  surface,  by  the  tendon 
of  the  Tibialis  posticus,  which  spreads  out  at  its 
insertion  into  a  number  of  fasciculi  which  are  attached 

Fio.  266.-Ligaments'  of  the  plantar  surface  to  most  of  the  tarsal  and  metatarsal  bones  ;  this  pre- 
of  the  foot.  vents  undue  stretching  of  the  ligament  and  is  a  pro- 

tection against  the  occurrence  of  flat-foot. 

4.  ARTICULATION  OF  THE  ASTRAGALUS  WITH  THE  NAVICULAR  BONE. 
The  articulation  between  the  astragalus  and  navicular  is  an  arthrodial  joint : 

the  rounded  head  of  the  astragalus  being  received  into  the  concavity  formed  by 
1  Mr.  Hancock  describes  an  extension  of  this  ligament  upward  on  the  inner  side  of  the  foot, 
which  completes  the  socket  of  the  joint  in  that  direction  (Lancet,  llibb,  vol.  i.  p.  o 


OF   THE    TARSUS.  383 

the  posterior  surface  of  the  navicular,  the  anterior  articulating  surface  of  the 
calcaneum,  and  the  upper  surface  of  the  inferior  calcaneo-navicular  ligament, 
which  fills  up  the  triangular  interval  between  those  bones.  The  only  ligament  of 
this  joint  is  the  superior  astragalo-navicular.  It  is  a  broad  band,  which  passes 
obliquely  forward  from  the  neck  of  the  astragalus  to  the  superior  surface  of  the 
navicular  bone.  It  is  thin,  and  weak  in  texture,  and  covered  by  the  Extensor  ten- 
dons. The  inferior  calcaneo-navicular  supplies  the  place  of  an  inferior  ligament. 

The  Synovial  Membrane  which  lines  the  joint  is  continued  forward  from  the 
anterior  calcaneo-astragaloid  articulation. 

Actions. — This  articulation  permits  of  considerable  mobility,  but  its  feebleness 
is  such  as  to  allow  occasionally  of  dislocation  of  the  other  bones  of  the  tarsus 
from  the  astragalus. 

The  transverse  tarsal  or  medio-tar sal  joint  is  formed  by  the  articulation  of  the 
os  calcis  with  the  cuboid,  and  by  the  articulation  of  the  astragalus  with  the  nav- 
icular. The  movement  which  takes  place  in  this  joint  is  more  extensive  than  that 
in  the  other  tarsal  joints,  and  consists  of  a  sort  of  rotation  by  means  of  which  the 
sole  of  the  foot  may  be  slightly  flexed  and  extended  or  carried  inward  and  outward. 

5.  THE  ARTICULATION  OF  THE  NAVICULAR  WITH  THE  CUNEIFORM  BONES. 
The  navicular  is  connected  to  the  three  cuneiform  bones  by 
Dorsal  and  Plantar  ligaments. 

The  Dorsal  Ligaments  are  small,  longitudinal  bands  of  fibrous  tissue  arranged 
as  three  bundles,  one  to  each  of  the  cuneiform  bones.  That  bundle  of  fibres 
which  connects  the  navicular  with  the  internal  cuneiform  is  continued  round  the 
inner  side  of  the  articulation  to  be  continuous  with  the  plantar  ligament  which 
connects  these  two  bones. 

The  Plantar  Ligaments  have  a  similar  arrangement  to  those  on  the  dorsum. 
They  are  strengthened  by  processes  given  off  from  the  tendon  of  the  Tibialis  posticus. 

Actions. — The  movements  permitted  between  the  navicular  and  cuneiform 
bones  are  limited  to  a  slight  gliding  upon  each  other. 

The  Synovial  Membrane  of  these  joints  is  part  of  the  great  tarsal  synovial 
membrane. 

6.  THE  ARTICULATION  OF  THE  NAVICULAR   WITH  THE  CUBOID. 

The  navicular  bone  is  connected  with  the  cuboid  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligament  consists  of  a  band  of  fibrous  tissue  which  passes  obliquely 
forward  and  outward  from  the  navicular  to  the  cuboid  bone. 

The  Plantar  Ligament  consists  of  a  band  of  fibrous  tissue  which  passes  nearly 
transversely  between  these  two  bones. 

The  Interosseous  Ligament  consists  of  strong  transverse  fibres  which  pass 
between  the  rough  non-articular  portions  of  the  lateral  surfaces  of  these  two 
bones. 

Actions. — The  movements  permitted  between  the  navicular  and  cuboid  bones 
are  limited  to  a  slight  gliding  upon  each  other. 

The  Synovial  Membrane  of  this  joint  is  part  of  the  great  tarsal  synovial 
membrane. 

7.  THE  ARTICULATION  OF  THE  CUNEIFORM  BONES  WITH  EACH  OTHER. 

These  bones  are  connected  together  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligaments  consist  of  two  bands  of  fibrous  tissue  which  pass  trans- 
versely, one  connecting  the  internal  with  the  middle  cuneiform,  and  the  other 
connecting  the  middle  with  the  external  cuneiform. 

The  Plantar  Ligaments  have  a  similar  arrangement  to  those  on  the  dorsum. 


384  THE  ARTICULATIONS. 

They  are  strengthened  by  the  processes  given  off  from  the  tendon  of  the  Tibialis 
posticus. 

The  Interosseous  Ligaments  consist  of  strong  transverse  fibres  which  pass 
between  the  rough  non-articular  portions  of  the  lateral  surfaces  of  the  adjacent 
cuneiform  bones. 

The  Synovial  Membrane  of  these  joints  is  part  of  the  great  tarsal  synovial 
membrane. 

Actions. — The  movements  permitted  between  the  cuneiform  bones  are  limited 
to  a  slight  gliding  upon  each  other. 

8.  THE  ARTICULATION  OF  THE  EXTERNAL  CUNEIFORM  BONE  WITH  THE  CUBOID. 

These  bones  are  connected  together  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligament  consists  of  a  band  of  fibrous  tissue  which  passes  trans- 
versely between  these  two  bones. 

The  Plantar  Ligament  has  a  similar  arrangement.  It  is  strengthened  by  a 
process  given  off  from  the  tendon  of  the  Tibialis  posticus. 

The  Interosseous  Ligament  consists  of  strong  transverse  fibres  which  pass 
between  the  rough  non-articular  portions  of  the  lateral  surfaces  of  the  adjacent 
sides  of  these  two  bones. 

The  Synovial  Membrane  of  this  joint  is  part  of  the  great  tarsal  synovial 
membrane. 

Actions. — The  movements  permitted  between  the  external  cuneiform  and  cuboid 
are  limited  to  a  slight  gliding  upon  each  other. 

Nerve-supply. — All  the  joints  of  the  tarsus  are  supplied  by  the  anterior  tibial 
nerve. 

Surgical  Anatomy. — In  spite  of  the  great  strength  of  the  ligaments  which  connect  the 
tarsal  bones  together,  dislocation  at  some  of  the  tarsal  joints  does  occasionally  occur;  though,  on 
account  of  the  spongy  character  of  the  bones,  they  are  more  frequently  broken  than  dislocated, 
as  the  result  of  violence.  When  dislocation  does  occur,  it  is  most  commonly  in  connection  with 
the  astragalus ;  for  not  only  may  this  bone  be  dislocated  from  the  tibia  and  fibula  at  the  ankle- 
joint,  but  the  other  bones  may  be  dislocated  from  it,  the  trochlear  surface  of  the  bone  remaining 
in,  situ  in  the  tibio-fibular  mortise.  This  constitutes  what  is  known  as  the  subastragaloid 
dislocation.  Or,  again,  the  astragalus  may  be  dislocated  from  all  its  connections — from  the 
tibia  and  fibula  above,  the  os  calcis  below,  and  the  navicular  in  front — and  may  even  undergo  a 
rotation,  either  on  a  vertical  or  horizontal  axis.  In  the  former  case  the  long  axis  of  the  bone 
becoming  directed  across  the  joint,  so  that  the  head  faces  the  articular  surface  on  one  or 
other  malleolus ;  or,  in  the  latter,  the  lateral  surfaces  becoming  directed  upward  and  down- 
ward, so  that  the  trochlear  surface  faces  to  one  or  the  other  side.  Finally,  dislocation  may 
occur  at  the  medio-tarsal  joint,  the  anterior  tarsal  bones  being  luxated  from  the  astragalus  and 
calcaneum.  The  other  tarsal  bones  are  also,  occasionally,  though  rarely,  dislocated  from  their 
connections. 

VI.   Tarso-metatarsal  Articulations. 

These  are  arthrodial  joints.  The  bones  entering  into  their  formation  are  four 
tarsal  bones — viz.  the  internal,  middle,  and  external  cuneiform  and  the  cuboid — 
which  articulate  with  the  metatarsal  bones  of  the  five  toes.  The  metatarsal  bone 
of  the  great  toe  articulates  with  the  internal  cuneiform  ;  that  of  the  second  is 
deeply  wedged  in  between  the  internal  and  external  cuneiform,  resting  against  the 
middle  cuneiform,  and  being  the  most  strongly  articulated  of  all  the  metatarsal 
bones ;  the  third  metatarsal  articulates  with  the  extremity  of  the  external  cunei- 
form ;  the  fourth  with  the  cuboid  and  external  cuneiform  ;  and  the  fifth,  with  the 
cuboid.  The  articular  surfaces  are  covered  with  cartilage,  lined  by  synovial 
membrane,  and  connected  together  by  the  following  ligaments : 

Dorsal.  Plantar.  Interosseous. 

The  Dorsal  Ligaments  consist  of  strong,  flat,  fibrous  bands,  which  connect  the 
tarsal  with  the  metatarsal  bones.  The  first  metatarsal  is  connected  to  the  internal 
cuneiform  by  a  single  broad,  thin,  fibrous  band;  the  second  has  three  dorsal 


714  RSO-META  TA RSA L    AR TICULA  TIONS.  385 

ligaments,  one  from  each  cuneiform  bone;  the  third  has  one  from  the  external 
cuneiform ;  the  fourth  has  two,  one  from  the  external  cuneiform  and  one  from  the 
cuboid ;  and  the  fifth,  one  from  the  cuboid. 

The  Plantar  Ligaments  consist  of  longitudinal  and  oblique  fibrous  bands 
connecting  the  tarsal  and  metatarsal  bones,  but  disposed  with  less  regularity 
than  on  the  dorsal  surface.  Those  for  the  first  and  second  metatarsal  are  the  most 
strongly  marked ;  the  second  and  third  metatarsal  receive  strong  fibrous  bands 
which  pass  obliquely  across  from  the  internal  cuneiform;  the  plantar  ligaments 
of  the  fourth  and  fifth  metatarsal'  consist  of  a  few  scanty  fibres  derived  from  the 
cuboid. 

The  Interosseous  Ligaments  are  three  in  number — internal,  middle,  and  external. 
The  internal  one  passes  from  the  outer  extremity  of  the  internal  cuneiform  to  the 
adjacent  angle  of  the  second  metatarsal.  The  middle  one,  less  strong  than  the 
preceding,  connects  the  external  cuneiform  with  the  adjacent  angle  of  the  second 
metatarsal.  The  external  interosseous  ligament  connects  the  outer  angle  of  the 
external  cuneiform  with  the  adjacent  side  of  the  third  metatarsal. 

The  Synovial  Membrane  between  the  internal  cuneiform  bone  and  the  first 
metatarsal  bone  is  a  distinct  sac.  The  synovial  membrane  between  the  middle  and 
external  cuneiform  behind,  and  the  second  and  third  metatarsal  bones  in  front,  is 
part  of  the  great  tarsal  synovial  membrane.  Two  prolongations  are  sent  forward 
from  it — one  between  the  adjacent  sides  of  the  second  and  third  metatarsal  bones, 
and  one  between  the  third  and  fourth  metatarsal  bones.  The  synovial  membrane 
between  the  cuboid  and  the  fourth  and  fifth  metatarsal  bones  is  a  distinct  sac.  From 
it  a  prolongation  is  sent  forward  between  the  fourth  and  fifth  metatarsal  bones. 

Actions. — The  movements  permitted  between  the  tarsal  and  metatarsal  bones 
are  limited  to  a  slight  gliding  upon  each  other. 

ARTICULATIONS  OF  THE  METATARSAL  BONES  WITH  EACH  OTHER. 

The  base  of  the  first  metatarsal  bone  is  not  connected  with  the  second  meta- 
tarsal bone  by  any  ligaments ;  but  there  may  be  a  bursa  between  the  "occa- 
sional "  facets  (see  page  307). 

The  bases  of  the  four  outer  metatarsal  bones  are  connected  together  bv  dorsal, 
plantar,  and  interosseous  ligaments. 

The  Dorsal  Ligaments  consist  of  bands  of  fibrous  tissue  which  pass  transversely 
between  the  adjacent  metatarsal  bones. 

The  Plantar  Ligaments  have  a  similar  arrangement  to  those  on  the  dorsum. 

The  Interosseous  Ligaments  consist  of  strong  transverse  fibres  which  pass  between 
the  rough  non-articular  portions  of  the  lateral  surfaces. 

The  Synovial  Membrane  between  the  second  and  third  and  the  third  and  fourth 
metatarsal  bones  is  part  of  the  great  tarsal  synovial  membrane. 

The  synovial  membrane  between  the  fourth  and  fifth  metatarsal  bones  is  a 
prolongation  of  the  synovial  membrane  of  the  cubo-metatarsal  joint. 

Actions. — The  movement  permitted  in  the  tarsal  ends  of  the  metatarsal  bones 
is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  one  another. 

THE  SYNOVIAL  MEMBRANES  IN  THE  TARSAL  AND  METATARSAL  JOINTS. 

The  Synovial  Membranes  (Fig.  267)  found  in  the  articulations  of  the  tarsus 
and  metatarsus  are  six  in  number :  one  for  the  posterior  calcaneo-astragaloid 
articulation;  a  second  for  the  anterior  calcaneo-astragaloid  and  astragalo-navicular 
articulations ;  a  third  for  the  calcaneo-cuboid  articulation  ;  and  a  fourth  for  the 
articulations  of  the  navicular  with  the  three  cuneiform,  the  three  cuneiform  with 
each  other,  the  external  cuneiform  with  the  cuboid,  and  the  middle  and  external 
cuneiform  with  the  bases  of  the  second  and  third  metatarsal  bones,  and  the  lateral 
surfaces  of  the  second,  third,  and  fourth  metatarsal  bones  with  each  other  ;  a  fifth 
for  the  internal  cuneiform  with  the  metatarsal  bone  of  the  great  toe ;  and  a  sixth 
for  the  articulation  of  the  cuboid  with  the  fourth  and  fifth  metatarsal  bones.  A 

25 


386 


THE   ARTICULATIONS 


small  synovial  membrane  is  sometimes  found  between  the  contiguous  surfaces  of  the 
navicular  and  cuboid  bones. 

Nerve-supply. — The  nerves  supplying  the  tarso-metatarsal  joints  are  derived 
from  the  anterior  tibial. 

The  digital  extremities  of  all  the  metatarsal  bones  are  connected  together  by 
the  transverse  metatarsal  ligament. 

The  Transverse  Metatarsal  Ligament  is  a  narrow  fibrous  band  which  passes 
transverselv  across  the  anterior  extremities  of  all  the  metatarsal  bones,  connecting 


FIG.  267.— Oblique  section  of  the  articulations  of  the  tarsus  and  metatarsus.    Showing  the  six  synovial 
membranes. 

them  together.  It  is  blended  anteriorly  with  the  plantar  (glenoid)  ligament  of 
the  metatarso-phalangeal  articulations.  To  its  posterior  border  is  connected  the 
fascia  covering  the  Interossei  muscles.  Its  superficial  surface  is  concave  where 
the  Flexor  tendons  pass  over  it.  Beneath  it  the  tendons  of  the  Interossei  muscles 
pass  to  their  insertion.  It  differs  from  the  transverse  metacarpal  ligament  in  that 
it  connects  the  metatarsal  bone  of  the  great  toe  with  the  rest  of  the  metatarsal 
bones. 

VII.  Metatarso-phalangeal  Articulations. 

The  metatarso-phalangeal  articulations  are  of  the  condyloid  kind,  formed  by  the 
reception  of  the  rounded  head  of  the  metatarsal  bone  into  a  superficial  cavity  in  the 
extremity  of  the  first  phalanx. 

The  ligaments  are — 

Plantar.  Two  Lateral. 

The  Plantar  Ligaments  (Glenoid  ligaments  of  Cruveilhier)  are  thick,  dense, 
fibrous  structures.  Each  is  placed  on  the  plantar  surface  of  the  joint  in  the 
interval  between  the  lateral  ligaments,  to  which  they  are  connected ;  they  are 
loosely  united  to  the  metatarsal  bone,  but  very  firmly  to  the  base  of  the  first 
phalanges.  Their  plantar  surface  is  intimately  blended  with  the  transverse  meta- 
tarsal ligament,  and  presents  a  groove  for  the  passage  of  the  Flexor  tendons,  the 
sheath  surrounding  which  is  connected  to  each  side  of  the  groove.  By  their  deep 
surface  they  form  part  of  the  articular  surface  for  the  head  of  the  metatarsal  bone, 
and  are  lined  by  a  synovial  membrane. 

The  Lateral  Ligaments  are  strong,  rounded  cords,  placed  one  on  each  side  of  the 
joint,  each  being  attached,  by  one  extremity,  to  the  posterior  tubercle  on  the  side  of 
the  head  of  the  metatarsal  bone  ;  and,  by  the  other,  to  the  contiguous  extremity  of 
the  phalanx. 

The  Posterior  Ligament  is  supplied  by  the  extensor  tendon  placed  over  the  back 
of  the  joint. 

Actions. — The  movements  permitted  in  the  metatarso-phalangeal  articulations 
are  flexion,  extension,  abduction,  and  adduction. 


OF   THE   PHALANGES.  387 

VIII.  Articulations  of  the  Phalanges. 

The  articulations  of  the  phalanges  are  ginglymus  joints. 

The  ligaments  are — 

Plantar.  Two  Lateral. 

The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metatarso- 
phalangeal  articulations ;  the  extensor  tendon  supplies  the  place  of  a  posterior 
ligament. 

Actions. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion 
and  extension :  these  movements  are  more  extensive  between  the  first  and  second 
phalanges  than  between  the  second  and  third.  The  movement  of  flexion  is  very 
considerable,  but  extension  is  limited  by  the  anterior  and  lateral  ligaments. 

Surface  Form. — The  principal  joints  which  it  is  necessary  to  distinguish,  with  regard  to  the 
surgery  of  the  foot,  are  the  medio-tarsal  and  the  tarso-metatarsal  joints.  The  joint  between  the 
astragalus  and  the  navicular  is  best  found  by  means  of  the  tubercle  of  the  navicular  bone,  for 
the  line  of  the  joint  is  immediately  behind  this  process.  If  the  foot  is  grasped  and  forcibly 
extended,  a  rounded  prominence,  the  head  of  the  astragalus,  will  appear  on  the  inner  side  of 
the  dorsum  in  front  of  the  ankle-joint,  and  if  a  knife  is  carried  downward,  just  in  front  of  this 
prominence  and  behind  the  line  of  the  navicular  tubercle,  it  will  enter  the  astragalo-navicular 
joint.  The  calcaneo-cuboid  joint  is  situated  midway  between  the  external  malleolus  and  the 
prominent  end  of  the  fifth  metatarsal  bone.  The  plane  of  the  joint  is  in  the  same  line  as  that 
of  the  astragalo-navicular.  The  position  of  the  joint  between  the  fifth  metatarsal  bone  and  the 
cuboid  is  easily  found  by  tbe  projection  of  tbe  fifth  metatarsal  bone,  which  is  the  guide  to  it. 
The  direction  of  the  line  of  tbe  joint  is  very  oblique,  so  that,  if  continued  onward,  it  would 
pass  through  the  head  of  the  first  metatarsal  bone.  The  joint  between  the  fourth  metatarsal 
bone  and  the  cuboid  and  external  cuneiform  is  the  direct  continuation  inward  of  the  previous 
joint,  but  its  plane  is  less  oblique  ;  it  would  be  represented  by  a  line  drawn  from  the  outer  side 
of  the  articulation  to  the  middle  of  the  first  metatarsal  bone.  The  plane  of  the  joint  between 
the  third  metatarsal  bone  and  the  external  cuneiform  is  almost  transverse.  It  would  be  repre- 
sented by  a  line  drawn  from  the  outer  side  of  tbe  joint  to  the  base  of  the  first  metatarsal  bone. 
The  tarso-metatarsal  articulation  of  tbe  great  toe  corresponds  to  a  groove  which  can  be  felt  by 
making  firm  pressure  on  the  inner  side  of  the  foot  one  inch  in  front  of  the  tubercle  on  the 
navicular  bone ;  and  the  joint  between  the  second  metatarsal  bone  and  the  middle  cuneiform  is 
to  be  found  on  the  dorsum  of  tbe  foot,  half  an  inch  behind  the  level  of  tbe  tarso-metatarsal 
joint  of  the  great  toe.  Tbe  line  of  the  joints  between  the  metatarsal  bones  and  the  first 
phalanges  is  alxmt  an  inch  behind  the  webs  of  the  corresponding  toes. 


THE  MUSCLES  AND  FASCIJ1.1 


THE  Muscles  are  connected  with  the  bones,  cartilages,  ligaments,  and  skin, 
either  directly  or  through  the  intervention  of  fibrous  structures  called  tendons 
or  aponeuroses.  Where  a  muscle  is  attached  to  bone  or  cartilage,  the  fibres  ter- 
minate in  blunt  extremities  upon  the  periosteum  or  perichondriurn,  and  do  not 
come  into  direct  relation  with  the  osseous  or  cartilaginous  tissue.  Where  muscles 
are  connected  with  the  skin,  they  either  lie  as  a  flattened  layer  beneath  it,  or  are 
connected  with  its  areolar  tissue  by  larger  or  smaller  bundles  of  fibres,  as  in  the 
muscles  of  the  face. 

The  muscles  vary  extremely  in  their  form.  In  the  limbs,  they  are  of  consid- 
erable length,  especially  the  more  superficial  ones,  the  deep  ones  being  generally 
broad  ;  they  surround  the  bones  and  form  an  important  protection  to  the  various 
joints.  In  the  trunk  they  are  broad,  flattened,  and  expanded,  forming  the  parietes 
of  the  cavities  which  they  enclose ;  hence  the  reason  of  the  terms,  long,  broad, 
short,  etc.,  used  in  the  description  of  a  muscle. 

There  is  a  considerable  variation  in  the  arrangement  of  the  fibres  of  certain 
muscles  with  reference  to  the  tendons  to  which  they  are  attached.  In  some,  the 
fibres  are  parallel  and  run  directly  from  their  origin  to  their  insertion  ;  these  are 
quadrilateral  muscles,  such  as  the  Thyro-hyoid.  A  modification  of  these  is  found 
in  the  fusiform  muscles,  in  which  the  fibres  are  not  quite  parallel,  but  slightly 
curved,  so  that  the  muscle  tapers  at  each  end ;  in  their  action,  however,  they 
resemble  the  quadrilateral  muscles.  Secondly,  in  other  muscles  the  fibres  are 
convergent ;  arising  by  a  broad  origin,  they  converge  to  a  narrow  or  pointed 
insertion.  This  arrangement  of  fibres  is  found  in  the  triangular  muscles — e.  g.  the 
Temporal.  In  some  muscles,  which  otherwise  would  belong  to  the  quadrilateral 
or  triangular  type,  the  origin  and  insertion  are  not  in  the  same  plane,  but  the  plane 
of  the  line  of  origin  intersects  that  of  their  insertion  ;  such  is  the  case  in  the 
Pectineus  muscle.  Thirdly,  in  some  muscles  the  fibres  are  oblique  and  converge, 
like  the  plumes  of  a  pen,  to  one  side  of  a  tendon,  which  runs  the  entire  length  of 
the  muscle.  Such  a  muscle  is  rhomboidal  or  pennifonn,  as  the  Peronei.  A 
modification  of  these  rhomboidal  muscles  is  found  in  those  cases  where  oblique  fibres 
converge  to  both  sides  of  a  central  tendon  which  runs  down  the  middle  of  the 
muscle  ;  these  are  called  bipenniform,  and  an  example  is  afforded  in  the  Rectus 
femoris.  Finally,  we  have  muscles  in  which  the  fibres  are  arranged  in  curved 
bundles  in  one  or  more  planes,  as  in  the  Sphincter  muscles.  The  arrangement  of 
the  muscular  fibres  is  of  considerable  importance  in  respect  to  their  relative 
strength  and  range  of  movement.  Those  muscles  where  the  fibres  are  long  and 
few  in  number  have  great  range,  but  diminished  strength  ;  where,  on  the  other 
hand,  the  fibres  are  short  and  more  numerous,  there  is  great  power,  but  lessened 
range. 

Muscles  differ  much  in  size :  the  Gastrocnemius  forms  the  chief  bulk  of  the 
back  of  the  leg,  and  the  fibres  of  the  Sartorius  are  nearly  two  feet  in  length,  whilst 

1  The  Muscles  and  Fasciae  are  described  conjointly,  in  order  that  the  student  may  consider  the 
arrangement  of  the  latter  in  his  dissection  of  the  former.  It  is  rare  for  the  student  of  anatomy  in  this 
country  to  have  the  opportunity  of  dissecting  the  fascine  separately ;  and  it  is  for  this  reason,  as  well 
as  from  the  close  connection  that  exists  between  the  muscles  and  their  investing  sheaths,  that  they  are 
considered  together.  Some  general  observations  are  first  made  on  the  anatomy  of  the  muscles  and 
fascire,  the  special  description  being  given  in  connection  with  the  different  regions. 
388 


GENERAL    ANATOMY.  389 

the  Stapedius.  a  small  muscle  of  the  internal  ear,  weighs  about  a  grain,  and  its 
fibres  are  not  more  than  two  lines  in  length. 

The  names  applied  to  the  various  muscles  have  been  derived — 1,  from  their 
situation,  as  the  Tibialis.  Radialis.  Ulnaris.  Peroneus;  2,  from  their  direction,  as 
the  Rectus  abdominis,  Obliqui  capitis,  Transversalis  :  3,  from  their  uses,  as  Flexors, 
Extensors.  Abductors,  etc. :  4.  from  their  shape,  as  the  Deltoid,  Trapezius,  Rhom- 
boideus :  o.  from  the  number  of  their  divisions,  as  the  Biceps,  the  Triceps ;  6, 
from  their  points  of  attachment,  as  the  Sterno-cleido-mastoid,  Sterno-hyoid, 
Sterno-thyroid. 

In  the  description  of  a  muscle  the  term  origin  is  meant  to  imply  its  more  fixed 
or  central  attachment,  and  the  term  insertion,  the  movable  point  to  which  the 
force  of  the  muscle  is  directed ;  but  the  origin  is  absolutely  fixed  in  only  a  very 
small  number  of  muscles,  such  as  those  of  the  face,  which  are  attached  by  one 
extremity  to  the  bone  and  by  the  other  to  the  movable  integument;  in  the  greater 
number  the  muscle  can  be  made  to  act  from  either  extremity. 

In  the  dissection  of  the  muscles  the  student  should  pay  especial  attention  to 
the  exact  origin,  insertion,  and  actions  of  each,  and  its  more  important  relations 
with  surrounding  parts.  An  accurate  knowledge  of  the  points  of  attachment  of 
the  muscles  is  of  great  importance  in  the  determination  of  their  action.  By  a 
knowledge  of  the  action  of  the  muscles  the  surgeon  is  able  to  explain  the  causes 
of  displacement  in  various  forms  of  fracture  and  the  causes  which  produce 
distortion  in  various  deformities,  and,  consequently,  to  adopt  appropriate  treat- 
ment in  each  case.  The  relations,  also,  of  some  of  the  muscles,  especially  those  in 
immediate  apposition  with  the  larger  blood-vessels,  and  the  surface-markings  they 
produce,  should  be  especially  remembered,  as  they  form  useful  guides  in  the 
application  of  a  ligature  to  those  vessels. 

Tendons  are  white,  glistening,  fibrous  cords,  varying  in  length  and  thickness, 
sometimes  round,  sometimes  flattened,  of  considerable  strength,  and  devoid  of 
elasticity.  They  consist  almost  entirely  of  white  fibrous  tissue,  the  fibrils  of 
which  have  an  undulating  course  parallel  with  each  other  and  are  firmly  united 
together.  They  are  very  sparingly  supplied  with  blood-vessels,  the  smaller 
tendons  presenting  in  their  interior  not  a  trace  of  them.  Nerves  also  are  not 
present  in  the  smaller  tendons,  but  the  larger  ones,  as  the  tendo  Achillis,  receive 
nerves  which  accompany  the  nutrient  vessels.  The  tendons  consist  principally  of 
a  substance  which  yields  gelatin. 

Aponeuroses  are  flattened  or  ribbon-shaped  tendons,  of  a  pearly-white  color, 
iridescent,  glistening,  and  similar  in  structure  to  the  tendons.  They  are  destitute 
of  nerves,  and  the  thicker  ones  only  sparingly  supplied  with  blood-vessels. 

The  tendons  and  aponeuroses  are  connected,  on  the  one  hand,  with  the  muscles, 
and.  on  the  other  hand,  with  the  movable  structures,  as  the  bones,  cartilages, 
ligaments,  fibrous  membranes  (for  instance,  the  sclerotic),  and  the  synovial  mem- 
branes (subcrureus).  Where  the  muscular  fibres  are  in  a  direct  line  with  those 
of  the  tendon  or  aponeurosis,  the  two  are  directly  continuous,  the  muscular  fibre 
being  distinguishable  from  that  of  the  tendon  only  by  its  striation.  But  where 
the  muscular  fibre  joins  the  tendon  or  aponeurosis  at  an  oblique  angle  the  former 
terminates,  according  to  Kolliker.  in  rounded  extremities,  which  are  received 
into  corresponding  depressions  on  the  surface  of  the  latter,  the  connective  tissue 
between  the  fibres  being  continuous  with  that  of  the  tendon.  The  latter  mode 
of  attachment  occurs  in  all  the  penniform  and  bipenniform  muscles,  and  in 
those  muscles  the  tendons  of  which  commence  in  a  membranous  form,  as  the 
Gastrocnomius  and  Soleus. 

The  fascia?  (fascia,  a  bandage)  are  fibro-areolar  or  aponeurotic  laminae  of 
variable  thickness  and  strength,  found  in  all  regions  of  the  body,  investing  the 
softer  and  more  delicate  organs.  The  fasciae  have  been  subdivided,  from  the 
situation  in  which  they  are  found,  into  two  groups,  superficial  and  deep. 

The  superficial  fatcia  is  found  immediately  beneath  the  integument  over  almost 
the  entire  surface  of  the  body.  It  connects  the  skin  with  the  deep  or  aponeurotic 


390  THE  MUSCLES   AND    FASCIA. 

fascia,  and  consists  of  fibro-areolar  tissue,  containing  in  its  meshes  pellicles  of  fat 
in  varying  quantity.  In  the  eyelids  and  scrotum,  where  adipose  tissue  is  rarely 
deposited,  this  tissue  is  very  liable  to  serous  infiltration.  The  superficial  fascia 
varies  in  thickness  in  different  parts  of  the  body :  in  the  groin  it  is  so  thick  as  to 
be  capable  of  being  subdivided  in  several  laminge,  but  in  the  palm  of  the  hand  it 
is  of  extreme  thinness  and  intimately  adherent  to  the  integument.  The  superficial 
fascia  is  capable  of  separation  into  two  or  more  layers,  between  which  are  found  the 
superficial  vessels  and  nerves,  as  the  superficial  epigastric  vessels  in  the  abdominal 
region,  the  radial  and  ulnar  veins  in  the  forearm,  the  saphenous  veins  in  the  leg 
and  thigh,  and  the  superficial  lymphatic  glands  ;  certain  cutaneous  muscles  also  are 
situated  in  the  superficial  fascia,  as  the  Platysma  myoides  in  the  neck,  and  the 
Orbicularis  palpebrarum  around  the  eyelids.  This  fascia  is  most  distinct  at  the 
lower  part  of  the  abdomen,  the  scrotum,  perinseum,  and  extremities ;  is  very  thin 
in  those  regions  where  muscular  fibres  are  inserted  into  the  integument,  as  on  the 
side  of  the  neck,  the  face,  and  around  the  margin  of  the  anus.  It  is  very  dense 
in  the  scalp,  in  the  palms  of  the  hands,  and  soles  of  the  feet,  forming  a  fibro-fatty 
layer  which  binds  the  integument  firmly  to  the  subjacent  structure. 

The  superficial  fascia  connects  the  skin  to  the  subjacent  parts,  facilitates  the 
movement  of  the  skin,  serves  as  a  soft  medium  for  the  passage  of  vessels  and  nerves 
to  the  integument,  and  retains  the  warmth  of  the  body,  since  the  fat  contained  in 
its  areolse  is  a  bad  conductor  of  heat. 

The  deep  fascia  is  a  dense,  inelastic,  unyielding  fibrous  membrane,  forming 
sheaths  for  the  muscles  and  affording  them  broad  surfaces  for  attachment.  It 
consists  of  shining  tendinous  fibres,  placed  parallel  with  one  another,  and  connected 
together  by  other  fibres  disposed  in  a  rectilinear  manner.  It  is  usually  exposed  on 
the  removal  of  the  superficial  fascia,  forming  a  strong  investment,  which  not  only 
binds  down  collectively  the  muscles  in  each  region,  but  gives  a  separate  sheath  to 
each,  as  well  as  to  the  vessels  and  nerves.  The  fasciae  are  thick  in  unprotected 
situations,  as  on  the  outer  side  of  a  limb,  and  thinner  on  the  inner  side.  The  deep 
fasciae  assist  the  muscles  in  their  action  by  the  degree  of  tension  and  pressure  they 
make  upon  their  surface ;  and  in  certain  situations  this  is  increased  and  regulated 
by  muscular  action ;  as,  for  instance,  by  the  Tensor  vaginas  femoris  and  Gluteus 
maximus  in  the  thigh,  by  the  Biceps  in  the  upper  and  lower  extremities,  and 
Palmaris  longus  in  the  hand.  In  the  limbs  the  fasciae  not  only  invest  the  entire 
limb,  but  give  off  septa  which  separate  the  various  muscles,  and  are  attached 
beneath  to  the  periosteum :  these  prolongations  of  fasciae  are  usually  spoken  of  as 
intermuscular  septa. 

The  Muscles  and  Fasciae  may  be  arranged,  according  to  the  general  division 
of  the  body,  into  those  of  the  cranium,  face,  and  neck  ;  those  of  the  trunk  ;  those  of 
the  upper  extremity ;  and  those  of  the  lower  extremity. 

MUSCLES  AND  FASCLffi   OF  THE   CRANIUM  AND  FACE. 

The  muscles  of  the  Cranium  and  Face  consist  of  ten  groups,  arranged  according 
to  the  region  in  which  they  are  situated : 

1.  Cranial  Region.  6.  Superior  Maxillary  Region. 

2.  Auricular  Region.  7.  Inferior  Maxillary  Region. 

3.  Palpebral  Region.  8.  Intermaxillary  Region. 

4.  Orbital  Region.  9.  Temporo-maxillary  Region. 

5.  Nasal  Region.  10.  Pterygo-maxillary  Region. 

The  muscles  contained  in  each  of  these  groups  are  the  following : 

1.    Cranial  Region.  2.  Auricular  Region. 

Occipito-frontalis.  Attollens  aurem. 

Attrahens  aurem. 
Retrahens  aurem. 


CRANIAL    REGION. 


391 


3.  Palpebral  Region. 

Orbicularis  palpebrarum. 
Corrugator  supercilii. 
Tensor  tarsi. 

4.  Orbital  Region. 

Levator  palpebrae. 
Rectus  superior. 
Rectus  inferior. 
Rectus  internus. 
Rectus  externus. 
Obliquus  superior. 
Obliquus  inferior. 

5.  Nasal  Region. 

Pyrarnidalis  nasi. 

Levator  labii  superioris  alaeque  nasi. 

Dilatator  naris  posterior. 

Dilatator  naris  anterior. 

Compressor  nasi.    . 

Compressor  nai'ium  minor. 

Depressor  alse  nasi. 


6.  Superior  Maxillary  Region. 

Levator  labii  superioris. 
Levator  anguli  oris. 
Zygomaticus  major. 
Zygomaticus  minor. 

7.  Inferior  Maxillary  Region. 

Levator  labii  inferioris. 
Depressor  labii  inferioris. 
Depressor  anguli  oris. 

8.  Intermaxillary  Region. 

Buccinator. 
Risorius. 
Orbicularis  oris. 

9.  Temporo-maxillary  Region. 

Masseter. 
Temporal. 

10.  Ptery go-maxillary  Region. 

Pterygoideus  externus. 
Pterygoideus  internus. 


1.  Cranial  Region— Occipito-frontalis. 

Dissection  (Fig.  268). — The  head  being  shaved,  and  a  block  placed  beneath  the  back  of 
the  neck,  make  a  vertical  incision  through  the  skin  from  before  backward,  commencing 
at  the  root  of  the  nose  in  front,  and  terminating  behind  at  the  occipital  protuberance ;  make 


1.  Dissection  of  scalp. 


2,  3,  of  auricular  region. 


4,  5,  6,  of  face. 


7,  8,  of  neck. 


FIG.  268.— Dissection  of  the  head,  face,  and  neck. 

a  second  incision  in  a  horizontal  direction  along  the  forehead  and  round  the  side  of  the 
head,  from  the  anterior  to  the  posterior  extremity  of  the  preceding.  Raise  the  skin  in  front, 
from  the  subjacent  muscle,  from  below  upward ;  this  must  be  done  with  extreme  care, 
removing  the  integument  from  the  outer  surface  of  the  vessels  and  the  nerves  which  lie 
between  the  two. 

The  Skin  of  the  Scalp. — This  is  thicker  than  in  any  other  part  of  the  body.    It 
is  intimately  adherent  to  the  superficial  fascia.     The  hair-follicles  are  very  closely 


392 


THE   MUSCLES   AND    FASCIA. 


set  together,  and  extend  throughout  the  whole  thickness  of  the  skin.      It  also  con- 
tains a  number  of  sebaceous  glands. 

The  superficial  fascia  in  the  cranial  region  is  a  firm,  dense,  fibro-fatty  layer, 
intimately  adherent  to  the  integument,  and  to  the  Occipito-frontalis  and  its  tendi- 


CORRUQATOR 


DILATATOR    NARIS    POSTERIOR 

COMPRESSOR     MARIUM     MINOR 

DEPRESSOR    ALXE    NASI. 


LEVATOR    MENTI. 


FIG.  269.— Muscles  of  the  head,  face,  and  neck. 

nous  aponeurosis ;  it  is  continuous,  behind,  with  the  superficial  fascia  at  the  back 
part  of  the  neck  ;  and,  laterally,  is  continued  over  the  temporal  fascia.  It  con- 
tains between  its  layers  the  superficial  vessels  and  nerves  and  much  granular  fat. 
The  Occipito-frontalis  (Fig.  269)  is  a  broad  musculo-fibrous  layer,  which  covers 
the  whole  of  one  side  of  the  vertex  of  the  skull,  from  the  occiput  to  the  eyebrow. 
It  consists  of  two  muscular  slips,  separated  by  an  intervening  tendinous  aponeurosis. 
The  occipital  portion,  thin,  quadrilateral  in  form,  and  about  an  inch  and  a  half  in 
length,  arises  from  the  outer  two-thirds  of  the  superior  curved  line  of  the  occipital 
bone,  and  from  the  mastoid  portion  of  the  temporal.  Its  fibres  of  origin  are 
tendinous,  but  they  soon  become  muscular,  and  ascend  in  a  parallel  direction  to 


THE   Al~i;i<  TLAR    REGION.  393 

terminate  in  a  tendinous  aponeurosis.  The  frontal  portion  is  thin,  of  a  quadri- 
lateral form,  and  intimately  adherent  to  the  superficial  fascia.  It  is  broader,  its 
fibres  are  longer,  and  their  structure  paler  than  the  occipital  portion.  Its  internal 
fibres  are  continuous  with  those  of  the  Pyramidalis  nasi.  Its  middle  fibres  become 
blended  with  the  Corrugator  supercilii  and  Orbicularis  palpebrarum ;  and  the 
outer  fibres  are  also  blended  with  the  latter  muscle  over  the  external  angular  pro- 
cess. According  to  Theile.  the  innermost  fibres  are  attached  to  the  nasal  bones, 
the  outer  to  the  external  angular  process  of  the  frontal  bone.  From  these 
attachments  the  fibres  are  directed  upward,  and  join  the  aponeurosis  below  the 
coronal  suture.  The  inner  margins  of  the  frontal  portions  of  the  two  muscles  are 
joined  together  for  some  distance  above  the  root  of  the  nose ;  but  between  the 
occipital  portions  there  is  a  considerable,  though  variable,  interval,  which  is  occupied 
by  the  aponeuru.<is. 

The  aponeurosis  covers  the  upper  part  of  the  vertex  of  the  skull,  being 
continuous  across  the  middle  line  with  the  aponeurosis  of  the  opposite  muscle. 
Behind,  it  is  attached,  in  the  interval  between  the  occipital  origins,  to  the  occipital 
protuberance  and  superior  curved  lines  above  the  attachment  of  the  Trapezius  ;  in 
front,  it  forms  a  short  and  narrow  prolongation  between  the  frontal  portions ;  and 
on  each  side  it  has  connected  with  it  the  Attollens  and  Attrahens  aurem  muscles  ; 
in  this  situation  it  loses  its  aponeurotic  character,  and  is  continued  over  the 
temporal  fascia  to  the  zygoma  as  a  layer  of  laminated  areolar  tissue.  This 
aponeurosis  is  closely  connected  to  the  integument  by  the  firm,  dense,  fibro- 
fatty  layer,  which  forms  the  superficial  fascia  ;  it  is  connected  with  the  pericranium 
by  "loose  cellular  tissue,  which  allows  of  a  considerable  degree  of  movement  of  the 
integument. 

Nerves. — The  frontal  portion  of  the  Occipito-frontalis  is  supplied  by  the  facial 
nerve :  its  occipital  portion  by  the  posterior  auricular  branch  of  the  facial,  and 
sometimes  by  the  occipitalis  minor. 

Actions. — The  frontal  portion  of  the  muscle  raises  the  eyebrows  and  the  skin 
over  the  root  of  the  nose,  and  at  the  same  time  draws  the  scalp  forward,  throwing 
the  integument  of  the  forehead  into  transverse  wrinkles.  The  posterior  portion 
draws  the  scalp  backward.  By  bringing  alternately  into  action  the  frontal  and 
occipital  portions  the  entire  scalp  may  be  moved  forward  and  backward.  In  the 
ordinary  action  of  the  muscles,  the  eyebrows  are  elevated,  and  at  the  same  time 
the  aponeurosis  is  fixed  by  the  posterior  portion,  thus  giving  to  the  face  the 
expression  of  surprise :  if  the  action  is  more  exaggerated,  the  eyebrows  are  still 
further  raised,  and  the  skin  of  the  forehead  thrown  into  transverse  wrinkles,  as  in 
the  expression  of  fright  or  horror. 

2.  Auricular  Region  (Fig.  269). 
Attrahens  aurem.  Attollens  aurem. 

Retrahens  aurem. 

These  three  small  muscles  are  placed  immediately  beneath  the  skin  around  the 
external  ear.  In  man,  in  whom  the  external  ear  is  almost  immovable,  they  are 
rudimentary.  They  are  the  analogues  of  large  and  important  muscles  in  some  of 
the  mammalia. 

Dissection. — This  requires  considerable  care,  and  should  be  performed  in  the  following 
manner:  To  expose  the  Attollens  aurem.  draw  the  pinna  or  broad  part  of  the  ear  downward, 
when  a  tense  band  will  be  felt  beneath  the  skin,  passing  from  the  side  of  the  head  to  the 
upper  part  of  the  concha :  by  dividing  the  skin  over  this  band,  in  a  direction  from  below 
upward,  and  then  reflecting  it  on  each  side,  the  muscle  is  exposed.  To  bring  into  view  the 
Attrahens  aurem.  draw  the  helix  backward  by  means  of  a  hook,  when  the  muscle  will  be  made 
tense,  and  may  be  exposed  in  a  similar  manner  to  the  preceding.  To  expose  the  Retrahens 
aurem,  draw  the  pinna  forward,  when  the  muscle,  being  made  tense,  may  be  felt  beneath  the 
skin  at  its  insertion  into  the  back  part  of  the  concha,  and  may  be  exposed  in  the  same  manner 
a.s  the  other  mu~ 

The  Attrahens  aurem  (Anricularis  anterior),  the  smallest  of  the  three,  is  thin, 
fan-shaped,  and  its  fibres  pale  and  indistinct ;  they  arise  from  the  lateral  edge  of 


394  THE   MUSCLES   AND    FASCIAE. 

the  aponeurosis  of  the  Occipito-frontalis,  and  converge  to  be  inserted  into  a 
projection  on  the  front  of  the  helix. 

Relations. — Superficially,  with  the  skin ;  deeply,  with  the  areolar  tissue  derived 
from  the  aponeurosis  of  the  Occipito-frontalis,  beneath  which  are  the  temporal 
artery  and  vein  and  the  temporal  fascia. 

The  Attollens  aurem  (Auricularis  superior),  the  largest  of  the  three,  is  thin 
and  fan-shaped :  its  fibres  arise  from  the  aponeurosis  of  the  Occipito-frontalis  and 
converge  to  be  inserted  by  a  thin,  flattened  tendon  into  the  upper  part  of  the 
cranial  surface  of  the  pinna. 

Eelations. — Superficially,  with  the  integument ;  deeply,  with  the  areolar  tissue 
derived  from  the  aponeurosis  of  the  Occipito-frontalis,  beneath  which  is  the  temporal 
fascia. 

The  Retrahens  aurem  (Auricularis  posterior)  consists  of  two  or  three  fleshy 
fasciculi,  which  arise  from  the  mastoid  portion  of  the  temporal  bone  by  short 
aponeurotic  fibres.  They  are  inserted  into  the  lower  part  of  the  cranial  surface 
of  the  concha. 

Relations. — Superficially,  with  the  integument ;  deeply,  with  the  mastoid  portion 
of  the  temporal  bone. 

Nerves. — The  Attrahens  and  Attollens  aurem  are  supplied  by  the  temporal 
branch  of  the  facial ;  the  Retrahens  aurem  is  supplied  by  the  posterior  auricular 
branch  of  the  same  nerve. 

Actions. — In  man,  these  muscles  possess  very  little  action  :  the  Attrahens  aurem 
draws  the  ear  forward  and  upward ;  the  Attollens  aurem  slightly  raises  it ;  and  the 
Retrahens  aurem  draws  it  backward. 

3.  Palpebral  Region  (Fig.  269). 

Orbicularis  palpebrarum.  Levator  palpebrae. 

Corrugator  supercilii.  Tensor  tarsi. 

Dissection  (Fig.  256). — In  order  to  expose  the  muscles  of  the  face,  continue  the  longi- 
tudinal incision  made  in  the  dissection  of  the  Occipito-frontalis  down  the  median  line  of  the 
face  to  the  tip  of  the  nose,  and  from  this  point  onward  to  the  upper  lip ;  and  carry  another 
incision  along  the  margin  of  the  lip  to  the  angle  of  the  mouth,  and  transversely  across  the  face 
to  the  angle  of  the  jaw.  Then  make  an  incision  in  front  of  the  external  ear,  from  the  angle  of 
the  jaw  upward,  to  join  the  transverse  incision  made  in  exposing  the  Occipito-frontalis. 
These  incisions  include  a  square-shaped  flap,  which  should  be  removed  in  the  direction  marked 
in  the  figure,  with  care,  as  the  muscles  at  some  points  are  intimately  adherent  to  the 
integument. 

The  Orbicularis  palpebrarum  is  a  sphincter  muscle,  which  surrounds  the  cir- 
cumference of  the  orbit  and  eyelids.  It  arises  from  the  internal  angular  process 
of  the  frontal  bone,  from  the  nasal  process  of  the  superior  maxillary  in  front  of  the 
lachrymal  groove  for  the  nasal  duct,  and  from  the  anterior  surface  and  borders  of  a 
short  tendon,  the  tendo palpebrarum,  placed  at  the  inner  angle  of  the  orbit.  From 
this  origin  the  fibres  are  directed  outward,  forming  a  broad,  thin,  and  flat  layer, 
which  covers  the  eyelids,  surrounds  the  circumference  of  the  orbit,  and  spreads  out 
over  the  temple  and  downward  on  the  cheek.  The  palpebral  portion  (ciliaris)  of  the 
Orbicularis  is  thin  and  pale  ;  it  arises  from  the  bifurcation  of  the  tendo  palpebrarum, 
and  forms  a  series  of  concentric  curves,  which  are  united  on  the  outer  side  of  the  eye- 
lids at  an  acute  angle  by  a  cellular  raphe,  some  being  inserted  into  the  external  tarsal 
ligament  and  malar  bone.  The  orbicular  portion  (orbicularis  latus)  is  thicker  and 
of  a  reddish  color  :  its  fibres  are  well  developed,  and  form  complete  ellipses.  The 
upper  fibres  of  this  portion  blend  with  the  Occipito-frontalis  and  Corrugator 
supercilii. 

Relations. — By  its  superficial  surface,  with  the  integument.  By  its  deep 
surface,  above,  with  the  Occipito-frontalis  and  Corrugator  supercilii,  with  which 
it  is  intimately  blended,  and  with  the  supra-orbital  vessels  and  nerve  ;  below,  it 
covers  the  lachrymal  sac,  and  the  origin  of  the  Levator  labii  superioris  algeque 
nasi,  the  Levator  labii  superioris,  and  the  Zygomaticus  minor  muscles.  Inter- 


THE   PALPEBRAL    REGION. 


395 


nally,  it  is  occasionally  blended  with  the  Pyramidalis  nasi.  Externally,  it  lies 
on  the  temporal  fascia.  On  the  eyelids  it  is  separated  from  the  conjunctiva  by 
the  Levator  palpebrge,  the  tarsal  ligaments,  the  tarsal  plates,  and  the  Meibomian 
glands. 

The  tendo  palpebrarum  (tendo  oculi)  is  a  short  tendon,  about  two  lines  in  length 
and  one  in  breadth,  attached  to  the  nasal  process  of  the  superior  maxillary  bone 
in  front  of  the  lachrymal  groove  for  the  nasal  duct.  Crossing  the  lachrymal  sac, 
it  divides  into  two  parts,  each  division  being  attached  to  the  inner  extremity  of  the 
corresponding  tarsal  plate.  As  the  tendon  crosses  the  lachrymal  sac.  a  strong 
aponeurotic  lamina  is  given  off  from  the  posterior  surface,  which  expands  over 
the  sac,  and  is  attached  to  the  ridge  on  the  lachrymal  bone.  This  is  the  reflected 
aponeurosis  of  the  tendo  palpebrarum. 

Use  of  Tendo  oculi. — Besides  giving  attachment  to  part  of  the  Orbicularis 
palpebrarum.  and  to  the  tarsal  plates,  it  serves  to  suck  the  tears  into  the  lachrymal 
sac,  by  its  attachment  to  the  sac.  Thus,  each  time  the  eyelids  are  closed,  the  tendo 
oculi  becomes  tightened,  and  draws  the  wall  of  the  lachrymal  sac  outward  and 
forward,  so  that  a  vacuum  is  made  in  the  sac,  and  the  tears  are  sucked  along  the 
lachrymal  canals  into  it. 

The  Corrugator  supercilii  is  a  small,  narrow,  pyramidal  muscle,  placed  at  the 
inner  extremity  of  the  eyebrow,  be- 
neath the  Occipito-frontalis  and 
Orbicularis  palpebrarum  muscles. 
It  arises  from  the  inner  extremity 
of  the  superciliary  ridge;  from 
whence  its  fibres  pass  upward  and 
outward,  to  be  inserted  into  the 
under  surface  of  the  orbiculai'is,  op- 
posite the  middle  of  the  orbital  arch. 

Relations. — By  its  anterior  sur- 
face with  the  Occipito-frontalis  and 
Orbicularis  palpebrarum  muscles ; 
by  its  posterior  surface,  with  the 
frontal  bone  and  supratrochlear  - 
nerve. 

The  Levator  palpebrae  will  be 
described  with  the  muscles  of  the 
orbital  region. 

The  Tensor  tarsi  (Homer's 
muscle)  (Fig.  270)  is  a  small  thin 
muscle  about  three  lines  in  breadth 
and  six  in  length,  situated  at  the 
inner  side  of  the  orbit,  behind  the 
tendo  oculi.  It  arises  from  the  crest 
and  adjacent  part  of  the  orbital  sur- 
face of  the  lachrymal  bone,  and,  pass- 
ing across  the  'lachrymal  sac,  divides  into  two  slips,  which  cover  the  lachrymal 
canals,  and  are  inserted  into  the  tarsal  plates  internal  to  the  puncta  lachrymalia. 
Its  fibres  appear  to  be  continuous  with  those  of  the  palpebral  portion  of  the 
Orbicularis  palpebrarum ;  it  is  occasionally  very  indistinct. 

Neives. — The  Orbicularis  palpebrarum,  Corrugator  supercilii,  and  Tensor  tarsi 
are  supplied  by  the  facial  nerve. 

Actions. — The  Orbicularis  palpebrarum  is  the  sphincter  muscle  of  the  eyelids. 
The  palpebral  portion  acts  involuntarily,  closing  the  lids  gently,  as  in  sleep  or  in 
blinking;  the  orbicular  portion  is  subject  to  the  will.  When  the  entire  muscle  is 
brought  into  action,  the  skin  of  the  forehead,  temple,  and  cheek  is  drawn  inward 
toward  the  inner  angle  of  the  orbit,  and  the  eyelids  are  firmly  closed  as  in  photophobia. 
When  the  skin  of  the  forehead,  temple,  and  cheek  is  thus  drawn  inward  by  the 


Orbicular 
portion 


FIG.  270.— Inner  part  of  orbicularis  palpebrarum,  seen 
from  behind.    (Henle.) 


396 


THE   MUSCLES  AND    FASCIA. 


action  of  the  muscle  it  is  thrown  into  folds,  especially  radiating  from  the  outer 
angle  of  the  eyelids,  which  give  rise  in  old  age  to  the  so-called  "  crow's  feet."  The 

O  «/  O  O 

Levator  palpebrse  is  the  direct  antagonist  of  this  muscle ;  it  raises  the  upper  eyelid 
and  exposes  the  globe.  The  Corrugator  supercilii  draws  the  eyebrow  downward 
and  inward,  producing  the  vertical  wrinkles  of  the  forehead.  It  is  the  "  frowning  " 
muscle,  and  may  be  regarded  as  the  principal  agent  in  the  expression  of  suffering. 
The  Tensor  tarsi  draws  the  eyelids  and  the  extremities  of  the  lachrymal  canals 
inward  and  compresses  them  against  the  surface  of  the  globe  of  the  eye ;  thus 
placing  them  in  the  most  favorable  situation  for  receiving  the  tears.  It  serves, 
also,  to  compress  the  lachrymal  sac. 

4.  Orbital  Region  (Fig.  271). 

Levator  palpebrae  superioris.  Rectus  internus. 

Rectus  superior.  Rectus  externus. 

Rectus  inferior.  Obliquus  oculi  superior. 

Obliquus  oculi  inferior. 

Dissection. — To  open  the  cavity  of  the  orbit,  remove  the  skull-cap  and  brain ;  then  saw 
through  the  frontal  bone  at  the  inner  extremity  of  the  supraorbital  ridge,  and   externally  at  its 


FIG.  271.— Muscles  of  the  right  orbit. 

junction  with  the  malar.  Break  in  pieces  the  thin  roof  of  the  orbit  by  a  few  slight  blows 
of  the  hammer,  and  take  it  away;  drive  forward  the  superciliary  portion  of  the  frontal  bone  by 
a  smart  stroke,  but  do  not  remove  it,  as  that  would  destroy  the  pulley  of  the  Obliquus 
superior.  When  the  fragments  are  cleared  away,  the  periosteum  of  the  orbit  will  be  exposed  ; 
this  being  removed,  together  with  the  fat  which  fills  the  cavity  of  the  orbit,  the  several  muscles 
of  this  region  can  be  examined.  The  dissection  will  be  facilitated  by  distending  the  globe 
of  the  eye.  In  order  to  effect  this,  puncture  the  optic  nerve  near  the  eyeball  with  a  curved 
needle,  and  push  the  needle  onward  into  the  globe ;  insert  the  point  of  a  blowpipe  through 
this  aperture,  and  force  a  little  air  into  the  cavity  of  the  eyeball ;  then  apply  a  ligature  round 
the  nerve  so  as  to  prevent  the  air  escaping.  The  globe  being  now  drawn  forward,  the  muscles 
will  be  put  upon  the  stretch. 

The  Levator  palpebrae  superioris  is  thin,  flat,  and  triangular  in  shape.  It 
arises  from  the  under  surface  of  the  lesser  wing  of  the  sphenoid,  above  and  in 
front  of  the  optic  foramen,  from  which  it  is  separated  by  the  origin  of  the  Superior 
rectus,  and  is  inserted,  by  a  broad  aponeurosis,  into  the  anterior  surface  of  the 
superior  tarsal  plate.  From  this  aponeurosis  a  thin  expansion  is  continued 
onward,  passing  between  the  fibres  of  the  Orbicularis  to  be  inserted  into  the  skin 
of  the  lid.  At  its  origin  it  is  narrow  and  tendinous,  but  soon  becomes  broad  and 
fleshy,  and  finally  terminates  in  a  broad  aponeurosis. 

Relations. — By  its  upper  surface,   with   the  frontal    nerve   and   supraorbital 


THE    ORBITAL    REGION.  397 

artery,  the  periosteum  of  the  orbit,  and,  in  the  lid,  with  the  inner  surface  of 
the  tarsal  ligament ;  by  its  under  surface,  with  the  Superior  rectus,  and,  in  the 
lid,  with  the  conjunctiva.  A  small  branch  of  the  third  nerve  enters  its  under 
surface. 

The  Superior  rectus,  the  thinnest  and  narrowest  of  the  four  Recti.  arises  from 
the  upper  margin  of  the  optic  foramen  beneath  the  Levator  palpebrge  and  Superior 
oblique,  and  from  the  fibrous  sheath  of  the  optic  nerve,  and  is  inserted  by  a 
tendinous  expansion  into  the  sclerotic  coat,  about  three  or  four  lines  from  the 
margin  of  the  cornea. 

Relations. — By  its  upper  surface,  with  the  Levator  palpebrae  ;  by  its  under  sur- 
fii'-t\  with  the  optic  nerve,  the  ophthalmic  artery,  the  nasal  nerve,  and  the  branch 
of  the  third  nerve  which  supplies  it ;  and,  in  front,  with  the  tendon  of  the  Superior 
oblique  and  the  globe  of  the  eye. 

The  Inferior  and  Internal  Recti  arise  by  a  common  tendon  (the  ligament  of 
Zinn),1  which  is  attached  round  the  circumference  of  the  optic  foramen,  except  at 
its  upper  and  outer  part.  The  External  rectus  has  two  heads :  the  upper  one 
arises  from  the  outer  margin  of  the  optic  foramen  immediately  beneath  the  Superior 
rectus ;  the  lower  head,  partly  from  the  ligament  of  Zinn  and  partly  from  a  small 
pointed  process  of  bone  on  the  lower  margin  of 
the  sphenoidal  fissure.  Each  muscle  passes  Rectus  superior. 

forward  in  the  position  implied  by  its  name,  to  Levator 

be  inserted  by  a  tendinous  expansion  (the  paipebrce  superior, 
tunica  albugined]  into  the  sclerotic  coat,  about  Obiiquu* superior. : 
three  or  four  lines  from  the  margin  of  the  T.««S5 

cornea.  Between  the  two  heads  of  the  Ex- 
ternal rectus  is  a  narrow  interval,  through 
which  passes  the  third,  the  nasal  branch  of  the 
ophthalmic  division  of  the  fifth  and  sixth 
nerves,  and  the  ophthalmic  vein.  Although 

1  IT        c    j.1.  1  Keclus  inferior. 

nearly  all  ot  these  muscles  present  a  common 

orio-in  and  arp  insprtpd  in  •  similar  manner  FIG.  272.— The  relative  position  and  attach- 
)nelrl  ment  of  the  muscles  of  the  left  eyeball. 

into  the  sclerotic  coat,  there  are  certain  differ- 
ences to  be  observed  in  them  as  regards  their  length  and  breadth.     The  Internal 
rectus  is  the  broadest,  the  External  is  the  longest,  and  the  Superior  is  the  thinnest 
and  narrowest. 

The  Superior  oblique  is  a  fusiform  muscle  placed  at  the  upper  and  inner  side  of 
the  orbit,  internal  to  the  Levator  palpebrge.  It  arises  about  a  line  above  the  inner 
margin  of  the  optic  foramen,  and,  passing  forward  to  the  inner  angle  of  the  orbit, 
terminates  in  a  rounded  tendon,  which  plays  in  a  ring  or  pulley  (trochled)  formed  by 
fibro-cartilaginous  tissue  attached  to  a  depression  beneath  the  internal  angular  pro- 
cess of  the  frontal  bone,  the  contiguous  surfaces  of  the  tendon  and  ring  being  lined 
by  a  delicate  synovial  membrane  and  enclosed  in  a  thin  fibrous  investment.  The 
tendon  is  reflected  backward,  outward,  and  downward  beneath  the  Superior  rectus 
to  the  outer  part  of  the  globe  of  the  eye,  and  is  inserted  into  the  sclerotic  coat, 
midway  between  the  cornea  and  entrance  of  the  optic  nerve,  the  insertion  of  the 
muscle  lying  between  the  Superior  and  External  recti. 

Relations. — By  its  upper  surface,  with  the  periosteum  covering  the  roof  of  the 
orbit  and  the  fourth  nerve :  the  tendon,  where  it  lies  on  the  globe  of  the  eye  is 
covered  by  the  Superior  rectus;  by  its  undi-r  surface,  with  the  nasal  nerve  and 
the  upper  border  of  the  internal  rectus. 

The  Inferior  oblique  is  a  thin,  narrow  muscle  placed  near  the  anterior  margin 
of  the  orbit.  It  arises  from  a  depression  on  the  orbital  plate  of  the  superior 

1  The  ligament  of  Zinn  ought,  perhaps  more  appropriately,  to  be  termed  the  aponeurosis  or  tendon 
of  Zinn.  Mr.  C.  B.  Lockwood  has  described  a  somewhat  similar  structure  on  the  under  surface  of  the 
Superior  rectus  muscle,  which  is  attached  to  the  lesser  wing  of  the  sphenoid,  forming  the  upper  and 
outer  margin  of  the  optic  foramen.  This  superior  tendon  gives  origin  to  the  Superior  rectus,  the 
superior  head  of  the  External  rectus,  and  the  upper  part  of  the  Internal  rectus.  (Journal  of  Anatomy 
and  Physiology,  vol.  xx.  part  i.  p.  1.) 


398  THE  MUSCLES  AND    FASCIA. 

maxillary  bone,  external  to  the  lachrymal  groove  for  the  nasal  duct.  Passing  out- 
ward, backward,  and  upward  beneath  the  Inferior  rectus,  and  then  between  the 
eyeball  and  the  External  rectus,  it  is  inserted  into  the  outer  part  of  the  sclerotic 
coat  between  the  Superior  and  External  recti,  near  to,  but  somewhat  behind,  the 
tendon  of  insertion  of  the  Superior  oblique. 

Relations. — By  its  ocular  surface,  with  the  globe  of  the  eye  and  with  the  Inferior 
rectus ;  by  its  orbital  surface,  with  the  periosteum  covering  the  floor  of  the  orbit, 
and  with  the  External  rectus.  Its  borders  look  forward  and  backward ;  the 
posterior  one  receives  a  branch  of  the  third  nerve. 

Nerves. — The  Levator  palpebrae,  Inferior  oblique,  and  all  the  Recti  excepting 
the  External,  are  supplied  by  the  third  nerve  ;  the  Superior  oblique,  by  the  fourth  ; 
the  External  rectus,  by  the  sixth. 

Actions. — The  Levator  palpebrge  raises  the  upper  eyelid,  and  is  the  direct 
antagonist  of  the  Orbicularis  palpebrarum.  The  four  Recti  muscles  are  attached 
in  such  a  manner  to  the  globe  of  the  eye  that,  acting  singly,  they  will  turn  it 
either  upward,  downward,  inward,  or  outward,  as  expressed  by  their  names. 
The  movement  produced  by  the  Superior  or  Inferior  rectus  is  not  quite  a  simple 
one,  for,  inasmuch  as  they  pass  obliquely  outward  and  forward  to  the  eyeball,  the 
elevation  or  depression  of  the  cornea  must  be  accompanied  by  a  certain  deviation 
inward,  with  a  slight  amount  of  rotation,  which,  however,  is  corrected  by  the 
Oblique  muscles,  the  Inferior  oblique  correcting  the  deviation  inward  of  the 
Superior  rectus,  and  the  Superior  oblique  that  of  the  Inferior  rectus.  The  con- 
traction of  the  External  and  Internal  recti,  on  the  other  hand,  produces  a  purely 
horizontal  movement.  If  any  two  contiguous  recti  of  one  eye  act  together,  thev 
carry  the  globe  of  the  eye  in  the  diagonal  of  these  directions — viz.  upward  and 
inward,  upward  and  outward,  downward  and  inward,  or  downward  and  outward. 
The  movement  of  circumduction,  as  in  looking  round  a  room,  is  performed  by 
the  alternate  action  of  the  four  Recti.  The  Oblique  muscles  rotate  the  eyeball 
on  its  antero-posterior  axis,  this  kind  of  movement  being  required  for  the  correct 
viewing  of  an  object  when  the  head  is  moved  laterally,  as  from  shoulder  to 
shoulder,  in  order  that  the  picture  may  fall  in  all  respects  on  the  same  part  of  the 
retina  of  each  eye.1 

Surgical  Anatomy. — The  position  and  exact  point  of  insertion  of  the  tendons  of  the 
Internal  and  External  recti  muscles  into  the  globe  should  be  carefully  examined  from  the  front  of 
the  eyeball,  as  the  surgeon  is  often  required  to  divide  the  one  or  the  other  muscle  for  the  cure 
of  strabismus.  In  convergent  strabismus,  which  is  the  more  common  form  of  the  disease,  the 
eye  is  turned  inward,  requiring  the  division  of  the  Internal  rectus.  In  the  divergent  form, 
which  is  more  rare,  the  eye  is  turned  outward,  the  External  rectus  being  especially  implicated. 
The  deformity  produced  in  either  case  is  to  be  remedied  by  division  of  one  or  the  other  muscle. 
The  operation  is  thus  performed :  The  lids  are  to  be  well  separated  ;  the  eyeball  being  rotated 
outward  or  inward,  the  conjunctiva  should  be  raised  by  a  pair  of  forceps  and  divided  immediately 
beneath  the  lower  border  of  the  tendon  of  the  muscle  to  be  divided,  a  little  behind  its  insertion 
into  the  sclerotic ;  the  submucous  areolar  tissue  is  then  divided,  and  into  the  small  aperture 
thus  made  a  blunt  hook  is  passed  upward  between  the  muscle  and  the  globe,  and  the  tendon  of 
the  muscle  and  conjunctiva  covering  it  divided  by  a  pair  of  blunt-pointed  scissors.  Or  the 
tendon  may  be  divided  by  a  subconjunctival  incision,  one  blade  of  the  scissors  being  passed 
upward  between  the  tendon  and  the  conjunctiva,  and  the  other  between  the  tendon  and  the 
sclerotic.  The  student,  when  dissecting  these  muscles,  should  remove  on  one  side  of  the  subject 
the  conjunctiva  from  the  front  of  the  eye,  in  order  to  see  more  accurately  the  position  of  the 
tendons,  while  on  the  opposite  side  the  operation  may  be  performed. 

5.  Nasal  Region  (Fig.  269). 

Pyramidalis  nasi.  t    Dilatator  naris  anterior. 

y  Levator  labii  superioris  algeque  nasi.  f    Compressor  nasi. 

j  Dilatator  naris  posterior.  ^  Compressor  narium  minor. 

v'  Depressor  alge  nasi. 

1  "  On  the  Oblique  Muscles  of  the  Eye  in  Man  and  Vertebrate  Animals,"  by  John  Struthers,  M.  D., 
in  Anatomwal  and  Physiological  Observations.  For  a  fuller  account  of  the  various  co-ordinate  actions 
of  the  muscles  of  a  single  eye  and  of  both  eyes  than  our  space  allows,  the  reader  may  be  referred  to 
Dr.  M.  Foster's  Teal-book  of  Physiology. 


THE   NASAL    REGION.  399 

The  Pyramidalis  nasi  is  a  small  pyramidal  slip  prolonged  downward  from  the 
Occipito-frontalis  upon  the  side  of  the  nose,  where  it  becomes  tendinous  and 
blends  with  the  Compressor  nasi.  As  the  two  muscles  descend  they  diverge, 
leaving  an  angular  interval  between  them. 

Relations. — By  its  upper  surface,  with  the  skin  ;  by  its  under  surface,  with  the 
frontal  and  nasal  bones. 

The  Levator  labii  superioris  alaeque  nasi  is  a  thin  triangular  muscle  placed 
by  the  side  of  the  nose,  and  extending  between  the  inner  margin  of  the  orbit  and 
upper  lip.  It  arises  by  a  pointed  extremity  from  the  upper  part  of  the  nasal 
process  of  the  superior  maxillary  bone,  and,  passing  obliquely  downward  and 
outward,  divides  into  two  slips,  one  of  which  is  inserted  into  the  cartilage  of  the 
ala  of  the  nose ;  the  other  is  prolonged  into  the  upper  lip,  becoming  blended  with 
the  Orbicularis  oris  and  Levator  labii  superioris  proprius. 

Relations. — In  front,  with  the  integument,  and  with  a  small  part  of  the 
Orbicularis  palpebrarum  above. 

The  Dilatator  naris  posterior  is  a  small  muscle  which  is  placed  partly  beneath 
the  elevator  of  the  nose  and  lip.  It  arises  from  the  margin  of  the  nasal  notch  of 
the  superior  maxilla  and  from  the  sesamoid  cartilages,  and  is  inserted  into  the 
skin  near  the  margin  of  the  nostril. 

The  Dilatator  naris  anterior  is  a  thin  delicate  fasciculus  passing  from  the 
cartilage  of  the  ala  of  the  nose  to  the  integument  near  its  margin.  This  muscle  is 
situated  in  front  of  the  preceding. 

The  Compressor  nasi  is  a  small,  thin,  triangular  muscle  arising  by  its  apex 
from  the  superior  maxillary  bone,  above  and  a  little  external  to  the  incisive  fossa ; 
its  fibres  proceed  upward  and  inward,  expanding  into  a  thin  aponeurosis  which 
is  attached  to  the  fibro-cartilage  of  the  nose  and  is  continuous  on  the  bridge  of 
the  nose  with  that  of  the  muscle  of  the  opposite  side  and  with  the  aponeurosis  of 
the  Pyramidalis  nasi. 

The  Compressor  narium  minor  is  a  small  muscle  attached  by  one  end  to  the  alar 
cartilage,  and  by  the  other  to  the  integument  at  the  end  of  the  nose. 

The  Depressor  alae  nasi  is  a  short  radiated  muscle  arising  from  the  incisive 
fossa  of  the  superior  maxilla ;  its  fibres  ascend  to  be  inserted  into  the  septum  and 
back  part  of  the  ala  of  the  nose.  This  muscle  lies  between  the  mucous  membrane 
and  muscular  structure  of  the  lip. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  facial  nerve. 

Actions. — The  Pyramidalis  nasi  draws  down  the  inner  angle  of  the  eyebrows 
and  produces  transverse  wrinkles  over  the  bridge  of  the  nose  ;  by  some  anatomists 
it  is  also  considered  as  an  elevator  of  the  ala,  and,  consequently,  a  dilator  _>f  the 
nose.1  The  Levator  labii  superioris  alaeque  nasi  draws  upward  the  upper  lip  and 
ala  of  the  nose  :  its  most  important  action  is  upon  the  nose,  which  it  dilates  to  a 
considerable  extent.  The  action  of  this  muscle  produces  a  marked  influence  over 
the  countenance,  and  it  is  the  principal  agent  in  the  expression  of  contempt  and 
disdain.  The  two  Dilatatores  nasi  enlarge  the  aperture  of  the  nose.  Their  action 
in  ordinary  breathing  is  to  resist  the  tendency  of  the  nostrils  to  close  from 
atmospheric  pressure,  but  in  difficult  breathing  they  may  be  noticed  to  be  in 
violent  action,  as  well  as  in  some  emotions,  as  anger.  The  Depressor  alae  nasi  is 
a  direct  antagonist  of  the  other  muscles  of  the  nose,  drawing  the  ala  of  the 
nose  downward,  and  thereby  constricting  the  aperture  of  the  nares.  The  Com- 
pressor nasi  depresses  the  cartilaginous  part  of  the  nose  and  compresses  the  alae 
together. 

1  Although  this  muscle  anatomically  seems  to  be  a  continuation  of  the  Occipito-frontalis  down- 
ward, it  is  really  the  reverse.  Its  origin  is  from  the  nose  below,  and  its  insertion  into  the  Occipito- 
frontalis  and  skin.  If  one  pole  of  a  battery  be  placed  in  front  of  the  lobe  of  the  ear,  and  the  other 
(a  small  pointed  one)  be  carried  up  and  down  over  the  nose  and  forehead  in  the  middle  line,  it  is  easy 
to  find  a  nodal  point  of  indifference  above  which  the  Occipito-frontal  draws  the  parts  upward,  and 
below  which  the  Pyramidalis  draws  them  downward  ( W.  W.  Keen,  M.  D.,  American  edition). 


400  THE   MUSCLES  AND    FASCIA. 

6.  Superior  Maxillary  Region  (Fig.  269). 

\     Levator  labii  superioris.  •/   Zygomaticus  major. 

/  Levator  anguli  oris.  y  Zygomaticus  minor. 

The  Levator  labii  superioris  (proprius)  is  a  thin  muscle  of  a  quadrilateral  form. 
It  arises  from  the  lower  margin  of  the  orbit  immediately  above  the  infraorbital 
foramen,  some  of  its  fibres  being  attached  to  the  superior  maxilla,  others  to  the 
malar  bone ;  its  fibres  converge  to  be  inserted  into  the  muscular  substance  of  the 
upper  lip. 

Relations. — By  its  superficial  surface  above,  with  the  lower  segment  of  the 
Orbicularis  palpebrarum ;  below,  it  is  subcutaneous.  By  its  deep  surface  it 
conceals  the  origin  of  the  Compressor  nasi  and  Levator  anguli  oris  muscles, 
and  the  infraorbital  vessels  and  nerve,  as  they  escape  from  the  infraorbital 
foramen. 

The  Levator  anguli  oris  arises  from  the  canine  fossa  immediately  below  the 
infraorbital  foramen  ;  its  fibres  incline  downward  and  a  little  outward,  to  be 
inserted  into  the  angle  of  the  mouth,  intermingling  with  those  of  the  Zygomaticus 
major,  the  Depressor  anguli  oris,  and  the  Orbicularis. 

Relations. — By  its  superficial  surface,  with  the  Levator  labii  superioris  and 
->  the  infraorbital  vessels  and  nerves ;  by  its  deep  surface,  with  the  superior  maxilla, 
the  Buccinator,  and  the  mucous  membrane. 

The  Zygomaticus  major  is  a  slender  fasciculus  which  arises  from  the  malar 
bone,  in  front  of  the  zygomatic  suture,  and,  descending  obliquely  downward  and 
inward,  is  inserted  into  the  angle  of  the  mouth,  where  it  blends  with  the  fibres  of 
the  Levator  anguli  oris,  the  Orbicularis  oris,  and  the  Depressor  anguli  oris. 

Relations. — By  its  superficial  surface,  with  the  subcutaneous  adipose  tissue; 
by  its  deep  surface,  with  the  malar  bone  and  the  Masseter  and  Buccinator 
muscles. 

The  Zygomaticus  minor  arises  from  the  malar  bone  immediately  behind  the 
maxillary  suture,  and,  passing  downward  and  inward,  is  continuous  with  the 
Orbicularis  oris  at  the  outer  margin  of  the  Levator  labii  superioris.  It  lies  in  front 
of  the  preceding. 

Relations. — By  its  superficial  surface,  with  the  integument  and  the  Orbicularis 
palpebrarum  above;  by  its  deep  surface,  with  the  Masseter,  Buccinator,  and 
Levator  anguli  oris. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Levator  labii  superioris  is  the  proper  elevator  of  the  upper  lip, 
carrying  it  at  the  same  time  a  little  forward.  It  assists  in  forming  the  naso-labial 
ridge,  which  passes  from  the  side  of  the  nose  to  the  upper  lip  and  gives  to  the  face 
an  expression  of  sadness.  The  Levator  anguli  oris  raises  the  angle  of  the  mouth, 
and  assists  the  Levator  labii  superioris  in  producing  the  naso-labial  ridge.  The 
Zygomaticus  major  draws  the  angle  of  the  mouth  backward  and  upward,  as  in 
laughing ;  whilst  the  Zygomaticus  minor,  being  inserted  into  the  outer  part  of  the 
upper  lip  and  not  into  the  angle  of  the  mouth,  draws  it  backward,  upward,  and 
outward,  and  thus  gives  to  the  face  an  expression  of  sadness. 


1 


7.  Inferior  Maxillary  Region  (Fig.  269). 

Levator  labii  inferioris  (Levator  menti). 
j  Depressor  labii  inferioris  (Quadratus  menti). 
j  Depressor  anguli  oris  (Triangularis  menti). 


Dissection. — The  muscles  in  this  region  may  be  dissected  by  making  a  vertical  incision 
through  the  integument  from  the  margin  of  the  lower  lip  to  the  chin  :  a  second  incision  should 
then  be  carried  along  the  margin  of  the  lower  jaw  as  far  as  the  angle,  and  the  integument  care- 
fully removed  in  the  direction  shown  in  Fig.  268. 

The  Levator  labii  inferioris  (Levator  menti)  is  to  be  dissected  by  everting  the 
lower  lip  and  raising  the  mucous  membrane.  It  is  a  small  conical  fasciculus  placed 
on  the  side  of  the  frsenum  of  the  lower  lip.  It  arises  from  the  incisive  fossa, 


INFERIOR  MAXILLARY  AND  INTERMAXILLARY  REGIONS.   401 

external  to  the  symphysis  of  the  lower  jaw;  its  fibres  descend  to  be  inserted  into 
the  integument  of  the  chin. 

Relation. — On  its  inner  surface,  with  the  mucous  membrane ;  in  the  median 
line,  it  is  blended  with  the  muscle  of  the  opposite  side;  and  on  its  outer  side,  with 
the  Depressor  labii  inferioris. 

The  Depressor  labii  inferioris  (Quadratus  menti)  is  a  small  quadrilateral 
muscle.  It  arises  from  the  external  oblique  line  of  the  lower  jaw,  between  the 
symphysis  and  mental  foramen,  and  passes  obliquely  upward  and  inward,  to  be 
inserted  into  the  integument  of  the  lower  lip,  its  fibres  blending  with  the  Orbicularis 
oris  and  with  those  of  its  fellow  of  the  opposite  side.  It  is  continuous  with  the 
fibres  of  the  Platysma  at  its  origin.  This  muscle  contains  much  yellow  fat  inter- 
mingled with  its  fibres. 

Relations. — By  its  superficial  surface,  with  part  of  the  Depressor  anguli  oris 
and  Avith  the  integument,  to  which  it  is  closely  connected ;  by  its  deep  surface, 
with  the  mental  vessels  and  nerves,  the  mucous  membrane  of  the  lower  lip,  the 
labial  glands,  and  the  Levator  menti,  Avith  which  it  is  intimately  united. 

The  Depressor  anguli  oris  (Triangularis  menti)  is  triangular  in  shape,  arising, 
by  its  broad  base,  from  the  external  oblique  line  of  the  lower  jaw,  from  whence  its 
fibres  pass  upward,  to  be  inserted,  by  a  narroAv  fasciculus,  into  the  angle  of  the 
mouth.  It  is  continuous  Avith  the  Platysma  at  its  origin  and  Avith  the  Orbicu- 
laris oris  and  Risorius  at  its  insertion,  and  some  of  its  fibres  are  directly  continuous 
Avith  those  of  the  Levator  anguli  oris. 

Relations. — By  its  superficial  surface,  with  the  integument ;  by  its  deep  surface, 
with  the  Depressor  labii  inferioris  and  Buccinator. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Levator  labii  inferioris  raises  the  lower  lip  and  protrudes  it 
forward,  and  at  the  same  time  Avrinkles  the  integument  of  the  chin,  expressing 
doubt  or  disdain.  The  Depressor  labii  inferioris  draAvs  the  loAver  lip  directlv 
doAvmvard  and  a  little  outAvard,  as  in  the  expression  of  irony.  The  Depressor 
anguli  oris  depresses  the  angle  of  the  mouth,  being  the  antagonist  to  the  Levator 
anguli  oris  and  Zygomaticus  major;  acting  with  these  muscles,  it  will  draAv  the 
angle  of  the  mouth  directly  backward. 

8.  Intermaxillary  Region. 
Orbicularis  oris.  J  Buccinator.  Risorius. 

Dissection. — The  dissection  of  these  muscles  may  be  considerably  facilitated  by  filling  the 
cavity  of  the  mouth  with  tow,  so  as  to  distend  the  cheeks  and  lips ;  the  mouth  should  then  be 
closed  by  a  few  stitches  and  the  integument  carefully  remoA'ed  from  the  surface. 

The  Orbicularis  oris  (Fig.  269)  is  not  a  sphincter  muscle,  like  the  Orbicularis 
palpebrarum,  but  consists  of  numerous  strata  of  muscular  fibres,  having  different 
directions.  Avhich  surround  the  orifice  of  the  mouth.  These  fibres  are  partially 
derived  from  the  other  facial  muscles  Avhich  are  inserted  into  the  lips,  and  are 
partly  fibres  proper  to  the  lips  themselves.  Of  the  former,  a  considerable  number 
are  derived  from  the  Buccinator  and  form  the  deeper  stratum  .of  the  Orbicularis. 
Some  of  them — namely,  those  near  the  middle  of  the  muscle — decussate  at  the  angle 
of  the  mouth,  those  arising  from  the  upper  jaw  passing  to  the  lower  lip,  and  those 
from  the  loAver  jaAV  to  the  upper  lip.  Other  fibres  of  the  muscle,  situated  at  its 
upper  and  loAver  part,  pass  across  the  lips  from  side  to  side  without  interruption. 
Superficial  to  this  stratum  is  a  second,  formed  by  the  LeA'ator  and  Depressor 
anguli  oris,  Avhich  cross  each  other  at  the  angle  of  the  mouth,  those  from  the 
Depressor  passing  to  the  upper  lip,  and  those  from  the  LeA'ator  to  the  lower  lip, 
along  Avhich  they  run  to  be  inserted  into  the  skin  near  the  median  line.  In 
addition  to  these  there  are  fibres  from  the  other  muscles  inserted  into  the  lips — the 
Levator  labii  superioris,  the  Levator  labii  superioris  alaeque  nasi,  the  Zygornatici, 
and  the  Depressor  labii  inferioris :  these  intermingle  Avith  the  transverse  fibres 
above  described,  and  haA'e  principally  an  oblique  direction.  The  proper  fibres  of 


402  THE  MUSCLES  AND   FASCIJB. 

the  lips  are  oblique,  and  pass  from  the  under  surface  of  the  skin  to  the  mucous 
membrane  through  the  thickness  of  the  lip.  And  in  addition  to  these  are  fibres 
by  which  the  muscle  is  connected  directly  with  the  maxillary  bones  and  the  septum 
of  the  nose.  These  consist,  in  the  upper  lip,  of  four  bands,  two  of  which  (Accessorii 
orbicularis  superioris)  arise  from  the  alveolar  border  of  the  superior  maxilla, 
opposite  the  lateral  incisor  tooth,  and,  arching  outward  on  each  side,  are  continuous 
at  the  angles  of  the  mouth  with  the  other  muscles  inserted  into  this  part.  The 
two  remaining  muscular  slips,  called  the  Naso-labialis,  connect  the  upper  lip  to  the 
back  of  the  septum  of  the  nose :  as  they  descend  from  the  septum  an  interval  is 
left  between  them.  It  is  this  interval  which  forms  the  depression  (philtrum)  seen  on 
the  surface  of  the  skin  beneath  the  septum  of  the  nose.  The  additional  fibres  for 
the  lower  segment  (Accessorii  orbicularis  inferioris)  arise  from  the  inferior  maxilla, 
externally  to  the  Levator  labii  inferioris,  and  arch  outward  to  the  angles  of  the 
mouth,  to  join  the  Buccinator  and  the  other  muscles  attached  to  this  part. 

Relations. — By  its  superficial  surface,  with  the  integument,  to  which  it  is 
closely  connected ;  by  its  deep  surface,  with  the  buccal  mucous  membrane,  the 
labial  glands,  and  coronary  vessels ;  by  its  outer  circumference  it  is  blended  with 
the  numerous  muscles  which  converge  to  the  mouth  from  various  parts  of  the  face. 
Its  inner  circumference  is  free,  and  covered  by  the  mucous  membrane. 

The  Bucciiiator  (Fig.  282)  is  a  broad,  thin  muscle,  quadrilateral  in  form, 
which  occupies  the  interval  between  the  jaws  at  the  side  of  the  face.  It  arises 
from  the  outer  surface  of  the  alveolar  processes  of  the  upper  and  lower  jaws, 
corresponding  to  the  three  molar  teeth,  and,  behind,  from  the  anterior  border  of 
the  pterygo-maxillary  ligament.  The  fibres  converge  toward  the  angle  of  the 
mouth,  where  the  central  fibres  intersect  each  other,  those  from  below  being 
continuous  with  the  upper  segment  of  the  Orbicularis  oris,  and  those  from  above 
with  the  inferior  segment;  the  highest  and  lowest  fibres  continue  forward  uninter- 
ruptedly into  the  corresponding  segment  of  the  lip,  without  decussation. 

Relations. — By  its  superficial  surface,  behind,  with  a  large  mass  of  fat,  which 
separates  it  from  the  ramus  of  the  lower  jaw,  the  Masseter,  and  a  small  portion  of 
the  Temporal  muscle ;  anteriorly,  with  the  Zygomatici,  Risorius,  Levator  anguli 
oris,  Depressor  anguli  oris,  and  Stenson's  duct,  which  pierces  it  opposite  the 
second  molar  tooth  of  the  upper  jaw  ;  the  facial  artery  and  vein  cross  it  from  below 
upward ;  it  is  also  crossed  by  the  branches  of  the  facial  and  buccal  nerves ;  by 
its  internal  surface,  with  the  buccal  glands  and  mucous  membrane  of  the  mouth. 

The  pterygo-maxillary  ligament  separates  the  Buccinator  muscle  from  the 
Superior  constrictor  of  the  pharynx.  It  is  a  tendinous  band,  attached  by  one 
extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other  to  the 
posterior  extremity  of  the  internal  oblique  Mne  of  the  lower  jaw.  Its  inner  surface 
corresponds  to  the  cavity  of  the  mouth,  and  is  lined  by  mucous  membrane.  Its 
outer  surface  is  separated  from  the  ramus  of  the  jaw  by  a  quantity  of  adipose 
tissue.  Its  posterior  border  gives  attachment  to  the  Superior  constrictor  of  the 
pharynx ;  its  anterior  border,  to  the  fibres  of  the  Buccinator  (see  Fig.  282). 

The  Risorius  (Santorini)  (Fig,  269)  consists  of  a  narrow  bundle  of  fibres  which 
arises  in  the  fascia  over  the  Masseter  muscle,  and,  passing  horizontally  forward, 
is  inserted  into  the  skin  at  the  angle  of  the  mouth.  It  is  placed  superficial  to  the 
Platysma,  and  is  broadest  at  its  posterior  extremity.  This  muscle  varies  nmchin 
its  size  and  form. 

Nerves. — The  Orbicularis  oris  and  the  Risorius  are  supplied  by  the  facial,  the 
Buccinator  by  the  facial  and  by  the  buccal  branch  of  the  inferior  maxillary  nerve ; 
which  latter,  however,  is  by  many  anatomists  regarded  as  a  sensory  nerve  only. 

Actions. — The  Orbicularis  oris  in  its  ordinary  action  produces  the  direct  closure 
of  the  lips ;  by  its  deep  fibres,  assisted  by  the  oblique  ones,  it  closely  applies  the 
lips  to  the  alveolar  arch.  The  superficial  part,  consisting  principally  of  the 
decussating  fibres,  brings  the  lips  together  and  also  protrudes  them  forward.  The 
Buccinators  contract  and  compress  the  cheeks,  so  that,  during  the  process  of 
mastication,  the  food  is  kept  under  the  immediate  pressure  of  the  teeth.  When 


THE  TEMPORO-MAXILLARY  REGION.  403 

the  cheeks  have  been  previously  distended  with  air,  the  Buccinator  muscles  expel 
it  from  between  the  lips,  as  in  blowing  a  trumpet.  Hence  the  name  (buccina,  a 
trumpet).  The  Risorius  retracts  the  angles  of  the  mouth,  and  is  therefore  regarded 
as  the  "smiling"  muscle. 

9.  Temporo -maxillary  Region. 
*  Masseter.  J  Temporal. 

Masseteric  Fascia. — Covering  the  Masseter  muscle,  and  firmly  connected  with 
it,  is  a  strong  layer  of  fascia  derived  from  the  deep  cervical  fascia.  Above,  this 
fascia  is  attached  to  the  lower  border  of  the  zygoma,  and,  behind,  it  covers  the 
parotid  gland,  constituting  the  parotid  fascia. 

The  Masseter  is  exposed  by  the  removal  of  this  fascia  (Fig.  269) ;  it  is  a  short, 
thick  muscle,  somewhat  quadrilateral  in  form,  consisting  of  two  portions,  super- 
ficial and  deep.  The  superficial  portion,  the  larger,  arises  by  a  thick,  tendinous 
aponeurosis  from  the  malar  process  of  the  superior  maxilla,  and  from  the  anterior 
two-thirds  of  the  lower  border  of  the  zygomatic  arch :  its  fibres  pass  downward 
and  backward,  to  be  inserted  into  the  angle  and  lower  half  of  the  outer  surface 
of  the  ramus  of  the  jaw.  The  deep  portion  is  much  smaller  and  more  muscular 
in  texture ;  it  arises  from  the  posterior  third  of  the  lower  border  and  the  whole  of 
the  inner  surface  of  the  zygomatic  arch ;  its  fibres  pass  downward  and  forward, 
to  be  inserted  into  the  upper  half  of  the  ramus  and  outer  surface  of  the  coronoid 
process  of  the  jaw.  The  deep  portion  of  the  muscle  is  partly  concealed,  in  front 
by  the  superficial  portion ;  behind,  it  is  covered  by  the  parotid  gland.  The  fibres 
of  the  two  portions  are  united  at  their  insertion. 

Relations. — By  its  superficial  surface,  with  the  Zygomatici,  the  Socia  parotidis, 
and  Stenson's  duct ;  the  branches  of  the  facial  nerve  and  the  transverse  facial 
vessels,  which  cross  it ;  the  masseteric  fascia;  the  Risorius,  SSjrtgri&i,  Platysma 
myoides,  and  the  integument ;  by  its  deep  surface,  with  the  Temporal  muscle  at 
its  insertion,  the  ramus  of  the  jaw,  and  the  Buccinator,  from  which  it  is  separated 
by  a  mass  of  fat.  The  masseteric  nerve  and  artery  enter  it  on  its  deep  surface. 
Its  posterior  margin  is  overlapped  by  the  parotid  gland.  Its  anterior  margin 
projects  over  the  Buccinator  muscle,  and  the  facial  vein  lies  on  it  below. 

The  temporal  fascia  is  seen,  at  this  stage  of  the  dissection  covering  in  the 
Temporal  muscle.  It  is  a  strong,  fibrous  investment,  covered,  on  its  outer  surface, 
by  the  Attrahens  and  Attollens  aurem  muscles,  the  aponeurosis  of  the  Occipito- 
frontalis.  and  by  part  of  the  Orbicularis  palpebrarum.  The  temporal  vessels  and 
the  auriculo-temporal  nerve  cross  it  from  below  upward.  Above,  it  is  a  single 
layer,  attached  to  the  entire  extent  of  the  upper  temporal  ridge ;  but  below,  where 
it  is  attached  to  the  zygoma,  it  consists  of  two  layers,  one  of  which  is  inserted  into 
the  outer,  and  the  other  into  the  inner,  border  of  the  zygomatic  arch.  A  small 
quantity  of  fat,  the  orbital  branch  of  the  temporal  artery,  and  a  filament  from  the 
orbital,  or  temporo-malar,  branch  of  the  superior  maxillary  nerve,  are  contained 
between  these  two  layers.  It  affords  attachment  by  its  inner  surface  to  the 
superficial  fibres  of  the  Temporal  muscle.  , 

Dissection. — In  order  to  expose  the  Temporal  muscle,  remove  the  temporal  fascia,  which 
may  be  effected  by  separating  it  at  its  attachment  along  the  upper  border  of  the  zygoma,  and 
dissecting  it  upward  from  the  surface  of  the  muscle.  The  zygomatic  arch  should  then 
be  divided  in  front  at  its  junction  with  the  malar  bone,  and  behind  near  the  external  auditory 
meatu.s.  and  drawn  downward  with  the  Masseter,  which  should  be  detached  from  its  inser- 
tion into  the  ramus  and  angle  of  the  jaw.  The  whole  extent  of  the  Temporal  muscle  is  then 
exposed. 

The  Temporal  (Fig.  273)  is  a  broad,  radiating  muscle  situated  at  the  side  of  the 
head  and  occupying  the  entire  extent  of  the  temporal  fossa.  It  arises  from  the 
whole  of  the  temporal  fossa  except  that  portion  of  it  that  is  formed  by  the  malar 
bone.  Its  attachment  extends  from  the  external  angular  process  of  the  frontal  in 
front  to  the  mastoid  portion  of  the  temporal  behind,  and  from  the  curved  line  on 
the  frontal  and  parietal  bones  above  to  the  pterygoid  ridge  on  the  great  wing  of 


404  THE  MUSCLES  AND   FASCIA. 

the  sphenoid  below.     It  is  also  attached  to  the  inner  surface  of  the  temporal  fascia. 
Its  fibres  converge  as  they  descend,  and  terminate  in  an  aponeurosis,  the  fibres  of 


FIG.  273.— The  Temporal  muscle,  the  zygoma  and  Masseter  having  been  removed. 

which,  radiated  at  its  commencement,  converge  into  a  thick  and  flat  tendon,  which 
is  inserted  into  the  inner  surface,  apex,  and  anterior  border  of  the  coronoid  process 
of  the  jaw,  nearly  as  far  forward  as  the  last  molar  tooth. 

Relations. — By  its  superficial  surface,  with  the  integument,  the  Attrahens  and 
Attollens  aurem  muscles,  the  temporal  vessels  and  nerves,  the  aponeurosis  of  the 
Occipito-frontalis,  the  temporal  fascia,  the  zygoma,  and  Masseter  ;  by  its  deep 
surface,  with  the  temporal  fossa,  the  External  pterygoid  and  part  of  the  Buccinator 
muscles,  the  internal  maxillary  artery,  its  deep  temporal  branches,  and  the  deep 
temporal  nerves.  Behind  the  tendon  are  the  masseteric  vessels  and  nerve,  and  in 
front  of  it  the  buccal  vessels  and  nerve.  Its  anterior  border  is  separated  from  the 
malar  bone  by  a  mass  of  fat. 

Nerves. — Both  muscles  are  supplied  by  the  inferior  maxillary  nerve. 

10.  Pterygo-maxillary  Region  (Fig.  274). 
4  External  Pterygoid.  )   Internal  Pterygoid. 

Dissection. — The  Temporal  muscle  having  been  examined,  saw  through  the  base  of  the 
coronoid  process,  and  draw  it  upward,  together  with  the  Temporal  muscle,  which  should  be 
detached  from  the  surface  of  the  temporal  fossa.  Divide  the  ramus  of  the  jaw  just  below  the 
condyle.  and  also,  by  a  transverse  incision  extending  across  the  middle,  just  above  the  dental 
foramen ;  remove  the  fragment,  and  the  Pterygoid  muscles  will  be  exposed. 

The  External  Pterygoid  is  a  short,  thick  muscle,  somewhat  conical  in  form, 
which  extends  almost  horizontally  between  the  zygomatic  fossa  and  the  condyle  of 
the  jaw.  It  arises  from  the  pterygoid  ridge  on  the  great  wing  of  the  sphenoid  and 
the  portion  of  bone  included  between  it  and  the  base  of  the  pterygoid  process, 
and  from  the  outer  surface  of  the  external  pterygoid  plate.  Its  fibres  pass 
horizontally  backward  and  outward,  to  be  inserted  into  a  depression  in  front  of 
the  neck  of  the  condyle  of  the  lower  jaw  and  into  the  corresponding  part  of  the 
interarticular  fibro-cartilage.  This  muscle,  at  its  origin,  appears  to  consist  of  two 
portions  separated  by  a  slight  interval ;  hence  the  terms  upper  and  lower  head 
sometimes  used  in  the  description  of  the  muscle. 

Relations. — By  its   external  surface,  with  the  ramus  of   the  lower  jaw,   the 


THE   PTERYGO-MAXILLARY  REGION. 


405 


internal  maxillary  artery,  which  crosses  it,1  the  tendon  of  the  Temporal  muscle, 
and  the  Masseter :  by  its  internal  surface  it  rests  against  the  upper  part  of  the 
Internal  pterygoid.  the  internal  lateral  ligament,  the  middle  meningeal  artery, 


FIG.  274.— The  Pterygoid  muscles,  the  zygomatic  arch  and  a  portion  of  the  ramns  of  the  jaw  having  been 
removed. 

and  inferior  maxillary  nerve  :  by  its  upper  border  it  is  in  relation  with  the  temporal 
and  masseteric  branches  of  the  inferior  maxillary  nerve ;  by  its  lower  border  it  is 
in  relation  with  the  inferior  dental  and  gustatory  nerves,  and  it  is  pierced  by^the 
buccal  nerve.  In  the  interval  between  the  two  portions  of  the  muscle  the  internal 
maxillary  artery  passes,  when  this  vessel  lies  on  the  muscle  (see  Fig.  274). 

The  Internal  Pterygoid  is  a  thick,  quadrilateral  muscle,  and  resembles  the 
Masseter  in  form.  It  arises  from  the  pterygoid  fossa,  being  attached  to  the  inner 
surface  of  the  external  pterygoid  plate  and  to  the  grooved  surface  of  the  tuberosity 
of  the  palate  bone,  and  by  a  second  slip  from  the  outer  surface  of  the  tuberosity 
of  the  palate  bone  and  from  the  tuberosity  of  the  superior  maxillary  bone ;  its  fibres 
pass  downward,  outward,  and  backward,  to  be  inserted,  by  a  strong,  tendinous 
lamina,  into  the  lower  and  back  part  of  the  inner  side  of  the  ramus  and  angle  of 
the  lower  jaw.  as  high  as  the  dental  foramen. 

Eelations. — By  its  external  surface,  with  the  ramus  of  the  lower  jaw,  from 
which  it  is  separated,  at  its  upper  part,  by  the  External  pterygoid,  the  internal 
lateral  ligament,  the  internal  maxillary  artery,  the  dental  vessels  and  nerves,  and 
the  lingual  nerve :  by  its  internal  nor/ace^  with  the  Tensor  palati,  being  separated 
from  the  Superior  constrictor  of  the  pharynx  by  a  cellular  interval. 

Nerves. — These  muscles  are  supplied  by  the  inferior  maxillary  nerve. 

Actions. — The  Temporal  and  Masseter  and  Internal  pterygoid  raise  the  lower 
jaw  against  the  upper  with  great  force.  The  superficial  portion  of  the  Masseter 
assists  the  External  pterygoid  in  drawing  the  lower  jaw  forward  upon  the  upper, 
the  jaw  being  drawn  back  again  by  the  deep  fibres  of  the  Masseter  and  posterior 
fibres  of  the  Temporal.  The  External  pterygoid  muscles  are  the  direct  agents  in 
the  trituration  of  the  food,  drawing  the  lower  jaw  directly  forward,  so  as  to  make 
the  lower  teeth  project  beyond  the  upper.  If  the  muscle  of  one  side  acts,  the 
corresponding  side  of  the  jaw  is  drawn  forward,  and,  the  other  condyle  remaining 
fixed,  the  symphysis  deviates  to  the  opposite  side.  The  alternation  of  these 
movements  on  the  two  sides  produces  trituration. 

1  This  is  the  usual  relation,  but  in  many  cases  the  artery  will  be  found  below  the  muscle 


406  THE  MUSCLES  AND   FASCIA. 

Surface  Form. — The  outline  of  the  muscles  of  the  head  and  face  cannot  be  traced  on  the 
surface  of  the  body,  except  in  the  case  of  two  of  the  masticatory  muscles.  Those  of  the  head 
are  thin,  so  that  the  outline  of  the  bone  is  perceptible  beneath  them.  Those  in  the  face  are 
small,  covered  by  soft  skin,  and  often  by  a  considerable  layer  of  fat,  so  that  their  outline  is  con- 
cealed, but  they  serve  to  round  off  and  smooth  prominent  borders  and  to  fill  up  what  would  be 
otherwise  unsightly  angular  depressions.  Thus,  the  Orbicularis  palpebrarum  rounds  off  the 
prominent  margin  of  the  orbit,  and  the  Pyramidalis  nasi  fills  in  the  sharp  depression  beneath 
the  glabella,  and  thus  softens  and  tones  down  the  abrupt  depression  which  is  seen  on  the 
unclothed  bone.  In  like  manner,  the  labial  muscles,  converging  to  the  lips  and  assisted  by  the 
superimposed  fat,  fill  in  the  sunken  hollow  of  the  lower  part  of  the  face.  Although  the  muscles 
of  the  face  are  usually  described  as  arising  from  the  bones  and  inserted  into  the  nose,  lips,  and 
corners  of  the  mouth,  they  have  fibres  inserted  into  the  skin  of  the  face  along  their  whole 
extent,  so  that  almost  every  point  of  the  skin  of  the  face  has  its  muscular  fibre  to  move  it ; 
hence  it  is  that  when  in  action  the  facial  muscles  produce  alterations  in  the  skin-surface, 
giving  rise  to  the  formation  of  various  folds  or  wrinkles,  or  otherwise  altering  the  relative 
position  of  parts,  so  as  to  produce  the  varied  expressions  with  which  the  face  is  endowed ; 
hence  these  muscles  are  termed  the  "muscles  of  expression."  The  only  two  muscles  in  this 
region  which  greatly  influence  surface  form  are  the  Masseter  and  the  Temporal.  The  Masseter 
is  a  quadrilateral  muscle,  which  imparts  fulness  to  the  hinder  part  of  the  cheek.  When  the 
muscle  is  firmly  contracted,  as  when  the  teeth  are  clenched,  its  outline  is  plainly  visible; 
the  anterior  border  forms  a  prominent  vertical  ridge,  behind  which  is  a  considerable  fulness, 
especially  marked  at  the  lower  part  of  the  muscle ;  this  fulness  is  entirely  lost  when  the 
mouth  is  opened  and  the  muscle  no  longer  in  a  state  of  contraction.  The  Temporal  muscle 
is  fan-shaped,  and  fills  the  Temporal  fossa,  substituting  for  it  a  somewhat  convex  form, 
the  anterior  part  of  which,  on  account  of  the  absence  of  hair  over  the  temple,  is  more 
marked  than  the  posterior,  and  stands  out  in  strong  relief  when  the  muscle  is  in  a  state  of  con- 
traction. 

MUSCLES  AND  FASCLE  OF  THE  NECK. 

The  muscles  of  the  neck  may  be  arranged  into  groups  corresponding  with  the 
region  in  which  they  are  situated. 

These  groups  are  nine  in  number : 

1.  Superficial  cervical  region.  5.  Muscles  of  the  Pharynx. 

2.  Depressors  of  the  Os  Hyoides  6.  Muscles  of  the  Soft  Palate. 

and  Larynx.  7.  Muscles  of  the  Anterior  Ver- 

3.  Elevators  of  the  Os  Hyoides  tebral  Region. 

and  Larynx.  8.  Muscles  of  the  Lateral  Ver- 

4.  Muscles  of  the  Tongue.  tebral  Region. 

9.  Muscles  of  the  Larynx. 

The  muscles  contained  in  each  of  these  groups  are  the  following : 
1.  Superficial  Region.  Lingual  Region. 

Platysma  myoides.  4.  Muscles  of  the  Tongue. 

Sterno-cleido-mastoid.  Genio-hyo-glossus. 

Hyo-glossus. 

Infra-Jiyoid  Region.  Lingualis. 

2.  Depressors  of  the  Os  hyoides  and  Stylo-glossus. 

Larynx.  Palato-glossus. 

Sterno-hyoid.  5.  Muscles  of  the  Pharynx. 

Sterno-thyroid.  Constrictor  inferior. 

Thyro-hyoid.  Constrictor  medius. 

Omo-hyoid.  Constrictor  superior. 

Stylo-pharyngeus. 
Supra-hyoid  Region.  Palato-pharyngeus. 

3.  Elevators  of  the  Os  hyoides  and  g.  Muscles  of  the  Soft  Palate. 

Larynx.  Levator  palati. 

Digastric.  Tensor  palati. 

Stylo-hyoid.  Azygos  uvulae. 

Mylo-hyoid.  Palato-glossus. 

Genio-hyoid.  Palato-pharyngeus. 


THE   SUPERFICIAL    CERVICAL    REGION.  407 

7.  Muscles  of  the  Anterior  Vertebral       8.  Muscles  of  the  Lateral  Vertebral 

Region.  Region. 

Rectus  eapitis  anticus  major.  Scalenus  anticus. 

Rectus  eapitis  anticus  minor.  Scalenus  medms. 

Rectus  lateralis.  Scalenus  posticus. 

Longus  colli.  9.   Muscles  of  the  Larynx. 

Included  in  the  description  of 
the  Larynx. 

1.  Superficial  Cervical  Region. 
/Platysma  myoides.  J  Sterno-cleido-mastoid. 

Dissection. — A  block  having  been  placed  at  the  back  of  the  neck,  and  the  face  turned  to 
the  side  opposite  that  to  be  dissected,  so  as  to  place  the  parts  upon  the  stretch,  make  two  trans- 
verse incisions :  one  from  the  chin,  along  the  margin  of  the  lower  jaw,  to  the  mastoid  process, 
and  the  other  along  the  upper  border  of  the  clavicle.  Connect  these  by  an  oblique  incision 
made  in  the  course  of  the  Sterno-mastoid  muscle,  from  the  mastoid  process  to  the  sternum ;  the 
two  flaps  of  integument  having  been  removed  in  the  direction  shown  in  Fig.  268,  the  superficial 
fascia  will  be  exposed. 

The  Superficial  Cervical  Fascia  is  a  thin,  aponeurotic  lamina  which  is  hardly 
demonstrable  as  a  separate  membrane.  Beneath  it  is  found  the  Platysma  myoides 
muscle. 

The  Platysma  myoides  (Fig.  269)  is  a  broad,  thin  plane  of  muscular  fibres 
placed  immediately  beneath  the  superficial  fascia  on  each  side  of  the  neck.  It 
arises  by  thin,  fibrous  bands  from  the  fascia  covering  the  upper  part  of  the  Pectoral 
and  Deltoid  muscles :  its  fibres  proceed  obliquely  upward  and  inward  along  the 
side  of  the  neck.  The  anterior  fibres  interlace,  in  front  of  the  jaw.  with  the  fibres 
of  the  muscle  of  the  opposite  side  ;  the  posterior  fibres  pass  over  the  lower  jaw.  a 
few  of  them  being  attached  to  the  bone  below  the  external  oblique  line,  the  greater 
number  passing  on  to  be  inserted  into  the  skin  and  subcutaneous  tissue  of  the  lower 
part  of  the  face,  many  of  these  fibres  blending  with  the  muscles  about  the  angle 
and  lower  part  of  the  mouth.  Sometimes  fibres  can  be  traced  to  the  Zygomatic 
muscles  or  to  the  margin  of  the  Orbicularis  palpebrarum.  Beneath  the  Platysma 
the  external  jugular  vein  may  be  seen  descending  from  the  angle  of  the  jaw  to  the 
clavicle. 

Surgical  Anatomy. — It  is  essential  to  remember  the  direction  of  the  fibres  of  the 
Platysma  in  connection  with  the  operation  of  bleeding  from  the  external  jugular  vein ;  for  if  the 
point  of  the  lancet  is  introduced  in  the  direction  of  the  muscular  fibres,  the  orifice  made  will  be 
filled  up  by  the  contraction  of  the  muscle,  and  blood  will  not  flow;  but  if  the  incision  is  made 
across  the  course  of  the  fibres,  they  will  retract  and  expose  the  orifice  in  the  vein,  and  so  allow 
the  flow  of  blood. 

Relations. — By  its  external  surface,  with  the  integument,  to  which  it  is  united 
more  closely  below  than  above ;  by  its  internal  surface,  with  the  Pectoralis 
major.  Deltoid,  and  Trapezius,  and  with  the  clavicle;  in  the  neck,  with  the 
external  and  anterior  jugular  veins,  the  deep  cervical  fascia,  the  superficial 
branches  of  the  cervical  plexus,  the  Sterno-mastoid,  Sterno-hyoid,  Omo-hyoid, 
and  Digastric  muscles ;  behind  the  Sterno-mastoid  muscle  it  covers  the  Scaleni 
muscles  and  the  nerves  of  the  brachial  plexus ;  on  the  face  it  is  in  relation 
with  the  parotid  gland,  the  facial  artery  and  vein,  and  the  Masseter  and  Buccinator 
muscles. 

Action. — The  Platysma  myoides  produces  a  slight  wrinkling  of  the  surface  of 
the  skin  of  the  neck,  in  an  oblique  direction,  when  the  entire  muscle  is  brought 
into  action.  Its  anterior  portion,  the  thickest  part  of  the  muscle,  depresses  the 
lower  jaw  ;  it  also  serves  to  draw  down  the  lower  lip  and  angle  of  the  mouth  on 
each  side,  being  one  of  the  chief  agents  in  the  expression  of  melancholy. 

The  Deep  Cervical  Fascia  (Fig.  275)  is  a  strong,  fibrous  layer  which  invests  the 
muscles  of  the  neck  and  encloses  the  vessels  and  nerves.  It  commences,  as  an 
extremely  thin  layer,  at  the  back  part  of  the  neck,  where  it  is  attached  to  the 


408 


THE   MUSCLES  AND    FASCIA. 


ligamentum  nuchae  and  to  the  spinous  process  of  the  seventh  cervical  vertebrae, 
and,  passing  forward,  invests  the  Trapezius  muscle ;  from  the  anterior  border  of 


OMO-HYOID. 

Thyroid  body. 


Common  carotid  artery. 
Internal  jugular  vein. 

STERNO-MASTOID-v 


Pneumogas- j 
trie  nerve,  j  '"--- 


External  ] 
jugular   \— 
vein.     ) 


-  Anterior  jugular  vein. 

,.    STERNO-HYOID. 
—  STER  NO-THYROID. 

Trachea. 


-  (Esophagus. 

...LONGUS    COLLI. 

— 6th  cervical. 
—Vertebral  vessels. 


--SEMI-SPINALIS   COLLI. 


TRAPEZIUS. 


COMPLEXUS. 
-SPLENIUS    CAPITIS. 


FIG.  275.— Section  of  the  neck  at  about  the  level  of  the  sixth  cervical  vertebra,  showing  the  arrangement  of 
the  deep  cervical  fascia. 

this  muscle  it  forms  a  layer  which  covers  in  the  posterior  triangle  of  the  neck ; 
and,  passing  forward  to  the  posterior  border  of  the  Sterno-mastoid  muscle,  divides 
into  two  layers,  one  of  which  passes  over,  and  the  other  under,  that  muscle. 
The  layer  which  passes  over  the  muscle  is  continued  forward  to  the  front  of 
the  neck,  and  blends  with  the  fascia  of  the  opposite  side,  covering  the  anterior 
triangle.  It  is  joined  on  its  under  surface,  except  for  about  an  inch  below,  by  a 
lamella  derived  from  the  layer  covering  the  deep  surface  of  the  Sterno-mastoid 
muscle.  Where  these  two  layers  do  not  meet  a  little  space  is  left  between  them,  as 
they  both  pass  inward  .to  the  middle  line  of  the  neck.  This  is  Burns 's  space,  and 
contains  a  little  areolar  tissue  and  fat,  ;i,nd  occasionally  a  small  lymphatic  gland. 
If  traced  upward,  the  anterior  layer  of  the  cervical  fascia  is  found  to  pass  across 
the  parotid  gland  and  Masseter  muscle,  forming  the  parotid  and  masseteric  fascice, 
and  is  attached  to  the  lower  border  of  the  zygoma,  and,  more  anteriorly,  to  the  lower 
border  of  the  body  of  the  jaw  ;  if  traced  downward,  it  is  seen  to  pass  to  the  upper 
border  of  the  clavicle  and  sternum,  being  pierced  just  above  the  former  bone  by  the 
external  jugular  vein.  In  the  middle  line  of  the  neck  the  fascia  is  connected  to  the 


THE  SUPERFICIAL    CERVICAL    REGION.  409 

symphysis  of  the  inferior  maxilla,  and,  lower  down,  to  the  hyoid  bone,  between 
which  points  it  is  thin  ;  below  the  hyoid  bone  it  becomes  thicker,  and  is  attached 
below  to  the  anterior  margin  of  the  upper  border  of  the  sternum.  The  layer 
of  the  deep  cervical  fascia  which  passes  under  the  Sterno-mastoid  covers  the 
anterior  surface  of  the  Scalenus  anticus  muscle.  At  the  outer  side  of  the 
carotid  vessels  it  divides  into  two,  one  layer  passing  in  front  of  the  vessels,  the 
other  behind  them.  The  layer  which  passes  in  front  of  the  vessels  again  divides 
into  three  lamella*.  Of  these,  the  anterior  lamella,  except  for  an  inch  below 
where  it  forms  the  posterior  boundary  of  Burns's  space,  joins  the  layer  of  cervical 
fascia  passing  over  the  Sterno-mastoid,  and  with  it  passes  to  the  middle  line 
covering  the  anterior  surface  of  the  Depressor  muscles  of  the  hyoid  bone.  The 
portion  of  this  lamella  which  invests  the  Omo-hyoid  is  continued  downward  as  a 
distinct  process,  which  descends  to  be  inserted  into  the  sternum  and  cartilage  of 
the  first  rib.  and  becomes  connected  with  the  Costo-coracoid  membrane.  The 
middle  lamella  passes  behind  the  depressors  of  the  hyoid  bone  and  in  front  of  the 
thyroid  body  to  meet  its  fellow  of  the  opposite  side,  in  front  of  the  trachea.  At 
the  root  of  the  neck  this  middle  lamella  can  be  traced  downward  into  the  thorax 
to  become  continuous  with  the  fibrous  layer  of  the-  pericardium.  The  posterior 
lamella  passes  over  to  the  inner  side  of  the  carotid  vessels,  and  joins  the  layer 
passing  behind  them,  thus  enclosing  them  in  a  sheath.  The  layer  of  cervical 
fascia  which  passes  behind  the  carotid  vessels,  having  been  joined  by  the  posterior 
of  the  three  lamellae  from  the  layer  of  fascia  passing  in  front  of  the  vessels,  is 
prolonged  inward,  behind  the  pharynx  and  oesophagus,  forming  a  sheath  for  the 
Prevertebral  muscles,  the  prevertebral  fascia.  The  layer  of  the  deep  cervical 
fascia,  which  passes  behind  the  Sterno-mastoid,  gives  off  another  lamella,  which 
passes  downward  and  outward  over  the  brachial  plexus  and  subclavian  vessels,  to 
assist  in  forming  the  axillary  sheath.  The  two  layers  of  the  deep  cervical  fascia, 
where  they  unite  opposite  the  angle  of  the  lower  jaw,  bind  the  Sterno-mastoid 
muscle  to  this  part  of  the  bone.  From  that  portion  of  the  cervical  fascia  which 
is  attached  to  the  angle  of  the  jaw  a  process  of  extreme  density  is  found  passing 
behind  to  the  inner  side  of  the  parotid  gland,  to  be  attached  to  the  apex  of  the 
styloid  process  of  the  temporal  bone  ;  this  is  termed  the  Stylo-maxillary  liga- 
ment. 

The  Sterno-mastoid  or  Sterno-cleido-mastoid  <  Fig.  276)  is  a  large,  thick  muscle, 
which  passes  obliquely  across  the  side  of  the  neck,  being  enclosed  between  the  two 
layers  of  the  deep  cervical  fascia.  It  is  thick  and  narrow  at  its  central  part,  but  is 
broader  and  thinner  at  each  extremity.  It  arises,  by  two  heads,  from  the  sternum 
and  clavicle.  The  sternal  portion  is  a  rounded  fasciculus,  tendinous  in  front,  fleshy 
behind,  which  arises  from  the  upper  and  anterior  part  of  the  first  piece  of 
the  sternum,  and  is  directed  upward,  outward,  and  backward.  The  clavicular 
portion  arises  from  the  inner  third  of  the  superior  border  of  the  clavicle,  being 
composed  of  fleshy  and  aponeurotic  fibres  :  it  is  directed  almost  vertically  upward. 
These  two  portions  are  separated  from  one  another,  at  their  origin,  by  a  triangular 
cellular  interval,  but  become  gradually  blended,  below  the  middle  of  the  neck, 
into  a  thick,  rounded  muscle,  which  is  inserted,  by  a  strong  tendon,  into  the  outer 
surface  of  the  mastoid  process,  from  its  apex  to  its  superior  border,  and  by  a  thin 
aponeurosis  into  the  outer  two-thirds  of  the  superior  curved  line  of  the  occipital 
bone.  The  Sterno-mastoid  varies  much  in  its  extent  of  attachment  to  the  clavicle  : 
in  one  case  the  clavicular  may  be  as  narrow  as  the  sternal  portion  ;  in  another,  - 
as  much  as  three  inches  in  breadth.  When  the  clavicular  origin  is  broad  it  is  - 
occasionally  subdivided  into  numerous  slips  separated  by  narrow  intervals.  More 
rarely,  the  corresponding  margins  of  the  Sterno-mastoid  and  Trapezius  have  been 
found  in  contact.  In  the  application  of  a  ligature  to  the  third  part  of  the  sub- 
clavian artery  it  will  be  necessary,  where  the  muscles  come  close  together,  to 
divide  a  portion  of  one  or  of  both. 

This  muscle  divides  the  quadrilateral  space  at  the  side  of  the  neck  into  two 
triangles,  an  anterior  and  a  posterior.   *The  boundaries  of  the  anterior   triangle 


410 


THE  MUSCLES  AND   FASCIA. 


are,  in  front,  the  median  line  of  the  neck  ;  above,  the  lower  border  of  the  body  of 
the  jaw,  and  an  imaginary  line  drawn  from  the  angle  of  the  jaw  to  the  mastoid 


FIG.  276.— Muscles  of  the  neck  and  boundaries  of  the  triangles. 

process ;  behind,  the  anterior  border  of  the  Sterno-mastoid  muscle.  The  boundaries 
of  the  posterior  triangle  are,  in  front,  the  posterior  border  of  the  Sterno-mastoid ; 
below,  the  upper  border  of  the  clavicle;  behind,  the  anterior  margin  of  the 
Trapezius.1 

Relations. — By  its  superficial  surface,  with  the  integument  and  Platysma, 
from  which  it  is  separated  by  the  external  jugular  vein,  the  superficial  branches 
of  the  cervical  plexus,  and  the  anterior  layer  of  the  deep  cervical  fascia.  By  its 
deep  surface  it  is  in  relation  with  the  Sterno-clavicular  articulation ;  a  process  of 
the  deep  cervical  fascia ;  the  Sterno-hyoid,  Sterno-thyroid,  Omo-hyoid,  posterior 
belly  of  the  Digastric,  Levator  anguli  scapulae,  Splenius  and  Scaleni  muscles  ; 
common  carotid  artery,  internal  jugular  vein,  commencement  of  the  internal  and 
external  carotid  arteries,  the  occipital,  subclavian,  transversalis  colli,  and  supra- 
scapular  arteries  and  veins ;  the  pneumogastric,  hypoglossal,  descendens  and 
communicans  hypoglossi  nerves,  and  the  spinal  accessory  nerve,  which  pierces 
its  upper  third ;  the  cervical  plexus,  part  of  the  parotid  gland  and  deep  lymphatic 
glands. 

Nerves. — The  Platysma  myoides  is  supplied  by  the  facial  and  superficial 
branches  of  the  cervical  plexus ;  the  Sterno-cleido-mastoid,  by  the  spinal  accessory 
and  deep  branches  of  the  cervical  plexus. 

Actions. — When  only  one  Sterno-mastoid  muscle  acts,  it  flexes  the  head  and 
draws  it  toward  the  shoulder  of  the  same  side,  assisted  by  the  Splenius  and  the 
Obliquus  capitis  inferior  of  the  opposite  side.  At  the  same  time  it  rotates  the  head 
so  as  to  carry  the  face  toward  the  opposite  side.  When  both  muscles  are  brought 

1  The  anatomy  of  these  triangles  will  be  more  exactly  described  with  that  of  the  vessels  of  the 
neck. 


THE   IXFRA-HYOID    REGION.  411 

into  action  they  serve  to  depress  the  head  upon  the  neck  and  the  neck  upon  the 
chest.     If  the  head  is  fixed,  they  assist  in  elevating  the  thorax  in  forced  inspiration. 

Surface  Form. — The  anterior  edge  of  the  muscle  forms  a  very  prominent  ridge  beneath 
the  skin,  which  it  is  important  to  notice,  as  it  forms  a  guide  to  the  surgeon  in  making  the  neces- 
sary incisions  for  ligature  of  the  common  carotid  artery  and  for  oesophagotomy. 

Surgical  Anatomy. — The  relations  of  the  sternal  and  clavicular  parts  of  the  Sterno-mastoid 
should  be  carefully  examined,  as  the  surgeon  is  sometimes  required  to  divide  one  or  both  por- 
tions of  the  muscles  in  u:ni-ueclc.  One  variety  of  this  distortion  is  produced  by  spasmodic  con- 
traction or  rigidity  of  the  Sterno-mastoid  :  the  head  being  carried  down  toward  the  shoulder  of 
the  same  s'ule.  and  the  face  turned  to  the  opposite  side  and  fixed  in  that  position.  When  there 
is  permanent  shortening  subcutaneous  division  of  the  muscle  is  resorted  to.  This  is  performed 
by  introducing  a  tenotomy  knife  beneath  it,  close  to  its  origin,  and  dividing  it  from  behind  for- 
ward whilst  the  muscle  is  put  well  upon  the  stretch.  There  is  seldom  any  difficulty  in  dividing 
the  sternal  portion,  by  making  a  puncture  on  the  inner  side  of  the  tendon,  and  then  pushing  a 
blunt  tenotome  behind  it.  and  cutting  forward.  In  dividing  the  clavicular  portion  care  must  be 
taken  to  avoid  wounding  the  external  jugular  vein,  which  runs  parallel  with  the  posterior  border 
of  the  muscle  in  this  situation,  or  the  anterior  jugular  vein,  which  crosses  beneath  it.  If  the 
external  jugular  vein  lies  near  the  muscle,  it  is  safer  to  make  the  first  puncture  at  the  outer  side 
of  the  tendon,  and  introduce  a  blunt  tenotome  from  without  inward.  Some  of  the  fibres  of  the 
Sterno-mastoid  muscle  are  occasionally  torn  during  birth,  especially  in  breech  presentations ;  this 
is  accompanied  by  haemorrhage  and  formation  of  a  swelling  within  the  substance  of  the  muscle. 
This  by  some  is  believed  to  be  one  of  the  causes  of  wry-neck. 

2.  Infra-hyoid  Region  (Figs.  276,  277). 
DEPRESSORS  OF  THE  Os  HYOIDES  AND  LARYNX. 

/  Sterno-hyoid.  .  Thyro-hyoid. 

Sterno-thyroid.  Omo-hyoid. 

Dissection. — The  muscles  in  this  region  may  be  exposed  by  removing  the  deep  fascia  from 
the  front  of  the  neck.  In  order  to  see  the  entire  extent  of  the  Omo-hyoid  it  is  necessary  to 
divide  the  Sterno-mastoid  at  its  centre,  and  turn  its  ends  aside,  and  to  detach  the  Trapezius 
from  the  clavicle  and  scapula.  This,  however,  should  not  be  done  until  the  Trapezius  has  been 
dissected. 

The  Sterno-hyoid  is  a  thin,  narrow,  ribbon-like  muscle,  which  arises  from  the 
inner  extremity  of  the  clavicle  and  the  upper  and  posterior  part  of  the  first  piece 
of  the  sternum  ;  passing  upward  and  inward,  it  is  inserted,  by  short,  tendinous 
fibres,  into  the  lower  border  of  the  body  of  the  os  hyoides.-  This  muscle  is  separated, 
below,  from  its  fellow  by  a  considerable  interval ;  but  they  approach  one  another 
in  the  middle  of  their  course,  and  again  diverge  as  they  ascend.  It  sometimes 
presents,  immediately  above  its  origin,  a  transverse  tendinous  intersection,  like 
those  in  the  Rectus  abdominis. 

Relations. — By  its  superficial  surface,  below,  with  the  sternum,  the  sternal  end 
of  the  clavicle,  and  the  Sterno-mastoid ;  and  above,  with  the  Platysma  and  deep 
cervical  fascia  :  by  its  deep  surface,  with  the  Sterno-thyroid,  Crico-thyroid,  and 
Thyro-hyoid  muscles,  the  thyroid  gland,  the  superior  thyroid  vessels,  the  thyroid 
cartilage,  the  crico-thyroid  and  thyro-hyoid  membranes. 

The  Sterno-thyroid  is  situated  beneath  the  preceding  muscle,  but  is  shorter  and 
wider  than  it.  It  arises  from  the  posterior  surface  of  the  first  bone  of  the  sternum, 
below  the  origin  of  the  Sterno-hyoid,  and  from  the  edge  of  the  cartilage  of  the 
first  rib.  and  is  inserted  into  the  oblique  line  on  the  side  of  the  ala  of  the  thyroid 
cartilage.  This  muscle  is  in  close  contact  with  its  fellow  at  the  lower  part  of  the 
neck,  and  is  occasionally  traversed  by  a  transverse  or  oblique  tendinous  intersection, 
like  those  in  the  Rectus  abdominis. 

Relations. — By  its  anterior  surface,  with  the  Sterno-hyoid,  Omo-hyoid,  and 
Sterno-mastoid ;  by  its  p^sterinr  surface,  from  below  upward,  with  the  trachea, 
vena  innominata.  common  carotid  (and  on  the  right  side  the  arteria  innominata), 
the  thyroid  gland  and  its  vessels,  and  the  lower  part  of  the  larynx.  The  middle 
thyroid  vein  lies  along  its  inner  border,  a  relation  which  it  is  important  to 
remember  in  the  operation  of  tracheotomy. 

The  Thyro-hyoid  is  a  small,  quadrilateral  muscle  appearing  like  a  continuation 


THE  MUSCLES   AND    FASCIAE. 

of  the  Sterno-thyroid.  It  arises  from  the  oblique  line  on  the  side  of  the  thyroid 
cartilage,  and  passes  vertically  upward  to  be  inserted  into  the  lower  border  of  the 
body  and  greater  cornu  of  the  hyoid  bone. 

Relations. — By  its  external  surface,  with  the  Sterno-hyoid  and  Omo-hyoid 
muscles  ;  by  its  internal  surface,  with  the  thyroid  cartilage,  the  thyro-hyoid 
membrane,  and  the  superior  laryngeal  vessels  and  nerve. 

The  Omo-hyoid  passes  across  the  side  of  the  neck,  from  the  scapula  to  the 

Symphysis 
of  jaw. 


Sternum. 
FIG.  277. — Muscles  of  the  neck.    Anterior  view. 

hyoid  bone.  It  consists  of  two  fleshy  bellies,  united  by  a  central  tendon.  It 
arises  from  the  upper  border  of  the  scapula  close  to,  and  occasionally  from  the 
transverse  ligament  which  crosses,  the  suprascapular  notch  ;  its  extent  of  attach- 
ment varying  from  a  few  lines  to  an  inch.  From  this  origin  the  posterior  belly 
forms  a  flat,  narrow  fasciculus,  which  inclines  forward  and  slightly  upward 
across  the  lower  part  of  the  neck,  behind  the  Sterno-mastoid  muscle,  where  it 
becomes  tendinous ;  it  then  changes  its  direction,  forming  an  obtuse  angle,  and 
terminates  in  the  anterior  belly,  which  passes  almost  vertically  upward,  close  to 
the  outer  border  of  the  Sterno-hyoid,  to  be  inserted  into  the  lower  border  of  the 
body  of  the  os  hyoides,  just  external  to  the  insertion  of  the  Sterno-hyoid.  The  central 
tendon  of  this  muscle,  which  varies  much  in  length  and  form,  is  held  in  position 
by  a  process  of  the  deep  cervical  fascia,  which  includes  it  in  a  sheath.  This 
process  is  prolonged  down,  to  be  attached  to  the  cartilage  of  the  first  rib*  and  the 
sternum.  It  is  by  this  means  that  the  angular  form  of  the  muscle  is  main- 
tained. 

This  muscle  subdivides  each  of  the  two  large  triangles  at  the  side  of  the  neck 
into  two  smaller  triangles ;  the  two  posterior  ones  being  the  posterior  superior  or 
occipital,  and  the  posterior  inferior  or  subclavian  ;  the  two  anterior,  the  anterior 
superior  or  superior  carotid,  and  the  anterior  inferior  or  inferior  carotid  triangle. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  the  Sterno-mastoid, 
deep  cervical  fascia,  Platysma,  and  integument ;  by  its  deep  surface,  with  the 
Scaleni  muscles,  phrenic  nerve,  lower  cervical  nerves,  Avhich  go  to  form  the  brachial 


THE   SUPRA-HYOID    REGION.  413 

plexus,  the  suprascapular  vessels  and  nerve,  sheath  of  the  common  carotid  artery 
and  internal  jugular  vein,  the  Sterno-thyroid  and  Thyro-hyoid  muscles. 

Nerves. — The  Thyro-hyoid  is  supplied  by  the  hypoglossal ;  the  other  muscles 
of  this  group  by  branches  from  the  loop  of  communication  between  the  descendens 
and  comruunicans  hypoglossi. 

Actions. — These  muscles  depress  the  larynx  and  hyoid  bone,  after  they  have 
been  drawn  up  with  the  pharynx  in  the  act  of  deglutition.  The  Omo-hyoid 
muscles  not  only  depress  the  hyoid  bone,  but  carry  it  backward  and  to  one  or  the 
other  side.  It  is  concerned  especially  in  the  act  of  sucking,  and  is  also  a  tensor 
of  the  cervical  fascia.  The  Thyro-hyoid  may  act  as  an  elevator  of  the  thyroid 
cartilage  when  the  hyoid  bone  ascends,  drawing  upward  the  thyroid  cartilage, 
behind  the  os  hyoides.1  The  Sterno-thyroid  acts  as  a  depressor  of  the  thyroid 
cartilage. 

3.  Supra-hyoid  Region  (Figs.  276.  277). 
ELEVATORS  OF  THE  Os  HYOIDES — DEPRESSORS  OF  THE  LOWER  JAW. 

/  Digastric.  Mylo-hyoid. 

Stylo-hyoid.  <  renio-hyoid. 

Dissection. — To  dissect  these  muscles  a  Jalock  should  be  placed  beneath  the  back  of  the 
neck,  and  the  head  drawn  backward  and  retained  in  that  position.  On  the  removal  of  the  deep 
fascia  the  muscles  are  at  once  exposed. 

The  Digastric  consists  of  two  fleshy  bellies  united  by  an  intermediate,  rounded 
tendon.  It  is  a  small  muscle,  situated  below  the  side  of  the  body  of  the  lower 
jaw,  and  extending,  in  a  curved  form,  from  the  side  of  the  head  to  the  syrnphysis 
of  the  jaw.  The  posterior  belly,  longer  than  the  anterior,  arises  from  the  digastric 
groove  on  the  inner  side  of  the  mastoid  process  of  the  temporal  bone,  and  passes 
downward,  forward,  and  inward.  The  anterior  belli/  arises  from  a  depression 
on  the  inner  side  of  the  lower  border  of  the  jaw,  close  to  the  symphysis,  and 
-  downward  and  backward.  The  two  bellies  terminate  in  the  central 
tendon  which  perforates  the  Stylo-hyoid,  and  is  held  in  connection  with  the  side 
of  the  body  and  the  greater  cornu  of  the  hyoid  bone  by  a  fibrous  loop,  lined  by  a 
synovial  membrane.  A  broad  aponeurotic  layer  is  given  off  from  the  tendon  of 
the  Digastric  on  each  side,  which  is  attached  to  the  body  and  great  cornu  of  the 
hyoid  bone :  this  is  termed  the  supra-hyoid  aponeurosis.  It  forms  a  strong  layer 
of  fascia  between  the  anterior  portion  of  the  two  muscles,  and  a  firm  investment 
for  the  other  muscles  of  the  supra-hvoid  region  which  lie  deeper. 

The  Digastric  muscle  divides  the  anterior  superior  triangle  of  the  neck  into 
two  smaller  triangles :  the  upper,  or  submaxillary.  being  bounded,  above,  by  the 
lower  border  of  the  body  of  the  jaw,  and  a  line  drawn  from  its  angle  to  the 
mastoid  process ;  below,  by  the  posterior  belly  of  the  Digastric  and  the  Stylo- 
hyoid  muscles :  in  front,  by  the  anterior  belly  of  the  Digastric,  the  lower  or 
superior  <:<ir<Ai<l  //•/<///</?£  being  bounded  above  by  the  posterior  belly  of  the  Digas- 
tric, behind  by  the  Sterno-mastoid,  below  by  the  Omo-hyoid. 

Relations. — By  it-  •/'<//  surface,  with  the  Platysma,  Sterno-mastoid.  part 

of  the  Splenius.  Trachelo-mastoid,  and  Stylo-hyoid  muscles,  and  the  parotid  gland. 
By  its  d>:->  /'  turfa^e.  the  anterior  belly  lies  on  the  Mylo-hyoid :  the  posterior  belly 
on  the  Stylo-glossus.  Stylo-pharyngeus,  and  Hvo-glossus  muscles,  the  external 
carotid  artery  and  its  lingual  and  facial  branches,  the  internal  carotid  artery, 
internal  jugular  vein,  and  hypoglossal  nerve. 

The  Stylo-hyoid  is  a  small,  slender  muscle,  lying  in  front  of,  and  above,  the 
posterior  belly  of  the  Digastric.  It  arises  from  the  back  and  outer  surface  of  the 
styloid  process,  near  the  base;  and.  passing  downward  and  forward,  is  inserted 
into  the  body  of  the  hyoid  bone,  just  at  its  junction  with  the  greater  cornu.  and 

1  It  is  this  action  of  the  Thyro-hyoid  muscle  which,  as  Dr.  Buchanan  has  pointed  out,  "  causes  or 
permits  the  folding  back  of  the  epiglottis  over  the  upper  orifice  of  the  larynx."  (Joui-n.  of  Anat.  and 
Physs.  2d  series,  No.  III.  p.  255;. 


414  THE   MUSCLES   AND    FASCIAE. 

immediately  above  the  Omo-hyoid.  This  muscle  is  perforated,  near  its  insertion,  by 
the  tendon  of  the  Digastric. 

Relations. — The  relations  are  the  same  as  those  of  the  posterior  belly  of  the 
Digastric. 

The  Stylo-hyoid  Ligament. — In  connection  with  the  Stylo-hyoid  muscle  may  be 
described  a  ligamentous  band,  the  Stylo-hyoid  ligament.  It  is  a  fibrous  cord,  often 
containing  a  little  cartilage  in  its  centre,  which  continues  the  styloid  process  down 
to  the  hyoid  bone,  being  attached  to  the  tip  of  the  former  and  the  small  cornu  of 
the  latter.  It  is  often  more  or  less  ossified. 

The  Digastric  and  Stylo-hyoid  should  be  removed,  in  order  to  expose  the  next  muscle. 

The  Mylo-hyoid  is  a  flat,  triangular  muscle,  situated  immediately  beneath  the 
anterior  belly  of  the  Digastric,  and  forming,  with  its  fellow  of  the  opposite  side,  a 
muscular  floor  for  the  cavity  of  the  mouth.  It  arises  from  the  whole  length  of 
the  mylo-hyoid  ridge,  extending  from  the  symphysis  in  front  to  the  last  molar 
tooth  behind.  The  posterior  fibres  pass  obliquely  forward,  to  be  inserted  into  the 
body  of  the  os  hyoides.  The  middle  and  anterior  fibres  are  inserted  into  a  median 
fibrous  raphe,  extending  from  the  symphysis  of  the  lower  jaw  to  the  hyoid  bone, 
where  they  join  at  an  angle  with  the  fibres  of  the  opposite  muscle.  This  median 
raphe  is  sometimes  wanting ;  the  muscular  fibres  of  the  two  sides  are  then  directly 
continuous  with  one  another. 

Relations. — By  its  cutaneous  surface,  with  the  Platysma,  the  anterior  belly  of 
the  Digastric,  the  supra-hyoid  aponeurosis,  the  submaxillary  gland,  submental 
vessels,  and  mylo-hyoid  vessels  and  nerve ;  by  its  deep  or  superior  surface,  with 
the  Genio-hyoid,  part  of  the  Hyo-glossus,  and  Stylo-glossus,  muscles,  the  hypo- 
glossal  and  lingual  nerves,  the  submaxillary  ganglion,  the  sublingual  gland,  the 
deep  portion  of  the  submaxillary  gland  and  Wharton's  duct ;  the  sublingual  and 
ranine  vessels,  and  the  buccal  mucous  membrane. 

Dissection. — The  Mylo-hyoid  should  now  be  removed,  in  order  to  expose  the  muscles  which 
lie  beneath :  this  is  effected  by  detaching  it  from  its  attachments  to  the  hyoid  bone  and  jaw,  and 
separating  it  by  a  vertical  incision  from  its  fellow  of  the  opposite  side. 

The  Genio-hyoid  is  a  narrow,  slender  muscle,  situated  immediately  beneath  * 
the  inner  border  of  the  preceding.  It  arises  from  the  inferior  genial  tubercle  on 
the  inner  side  of  the  symphysis  of  the  jaw,  and  passes  downward  and  backward, 
to  be  inserted  into  the  anterior  surface  of  the  body  of  the  os  hyoides.  This  muscle 
lies  in  close  contact  with  its  fellow  of  the  opposite  side,  and  increases  slightly  in 
breadth  as  it  descends. 

Relations. — It  is  covered  by  the  Mylo-hyoid,  and  lies  on  the  Genio-hyo- 
glossus. 

Nerves. — The  Digastric  is  supplied :  its  anterior  belly,  by  the  mylo-hyoid  branch 
of  the  inferior  dental ;  its  posterior  belly,  by  the  facial ;  the  Stylo-hyoid,  by  the 
facial ;  the  Mylo-hyoid,  by  the  mylo-hyoid  branch  of  the  inferior  dental ;  the  Genio- 
hyoid,  by  the  hypoglossal. 

Actions. — This  group  of  muscles  performs  two  very  important  actions.  They 
raise  the  hyoid  bone,  and  with  it  the  base  of  the  tongue,  during  the  act  of  degluti- 
tion;  or,  when  the  hyoid  bone  is  fixed  by  its  depressors  and  those  of  the  larynx, 
they  depress  the  lower  jaw.  During  the  first  act  of  deglutition,  when  the  mass 
is  being  driven  fromthe  mouth  into  the  pharynx,  the  hyoid  bone,  and  with  it  the 
tongue,  is  carried  upward  and  forward  by  the  anterior  belly  of  the  Digastric,  the 
Mylo-hyoid,  and  Genio-hyoid  muscles.  In  the  second  act,  when  the  mass  is  pass- 
ing through  the  pharynx, ^the  direct  elevation  of  the  hyoid  bone  takes  place  by 
the  combined  action  of  all  the  muscles ;  and  after  the  food  has  passed  the  hyoid 
bone  is  carried  upward  and  backward  by  the  posterior  belly  of  the  Digastric  and 
Stylo-hyoid  muscles,  which  assist  in  preventing  the  return  of  the  morsel  into  the 
mouth. 

1  This  refers  to  the  depth  of  the  muscles  from  the  skin  in  the  order  of  dissection.  In  the  erect 
position  of  the  body  each  of  these  muscles  lies  above  the  preceding. 


THE   LINGUAL    REGION. 


415 


4.  Lingual  Region. 

Genio-hyo-glossus.  Stylo-glossus. 

Hyo-glossus.  Palato-glossus. 

Chondro-glossus. 

Dissection.— After  completing  the  dissection  of  the  preceding  muscles,  saw  through  the 
lower  jaw  just  external  to  the  symphysis.  Then  draw  the  tongue  forward,  and  attach  it,  by  a 
stitch,  to  the  nose ;  when  its  muscles,  which  are  thus  put  on  the  stretch,  may  be  examined. 

The  Genio-hyo-glossus  has  received  its  name  from  its  triple  attachment  to  the 
jaw.  hyoid  bone,  and  tongue,  but  it  would  be  better  named  the  Grenio-glossu*, 


FIG.  278.— Muscles  of  the  tongues  Left  side. 

since  its  attachment  to  the  hyoid  bone  is  verj,slight  or  altogether  absenf.  It  is  a 
flat,  triangular  muscle,  placed  vertically  on 'either  side  of  the  middle  line,  its  apex 
corresponding  with  its  point  of  attachment  to  the  lower  jaw,  its  base  with  its 
insertion  into  the  tongue  and  hyoid  bone.  It  arises  by  a  short  tendon  from  the 
superior  genial  tubercle  on  the  inner  side  of  the  symphysis  of  the  jaw,  immediately 
above  the  Genio-hyoid  ;  from  this  point  the  muscle  spreads  out  in  a  fan-like  form, 
a  few  of  the  inferior  fibres  passing  downward,  to  be  attached  by  a  thin  aponeurosis 
into  the  upper  part  of  the  body  of  the  hyoid  bone  ;  the  middle  fibres  passing  back- 
ward, and  the  superior  ones  upward  and  forward,  to  enter  the  whole  length  of  the 
under  surface  of  the  tongue,  from  the  base  to  the  apex.  The  two  muscles  lie  on 
either  side  of  the  median  plane ;  behind,  thev  are  quite  distinct  from  ea.ch  other, 
and  are  separated  at  their  insertion  into  the  under  surface  of  the  tongue  oy  a  ten- 
dinous raphe,  which  extends  through  the  middle  of  the  organ ;  in  front,  the  two 
muscles  are  more  or  less  blended  :  distinct  fasciculi  are  to  be  seen  passing  off  from 
one  muscle,  crossing  the  middle  line,  and  intersecting  with  bundles  of  fibres 
derived  from  the  muscle  on  the  other  side  (Fig.  279). 

Relations. — By  its  internal  surface  it  is  in  contact  with  its  fellow  of  the  opposite 


416 


THE  MUSCLES  AND    FASCIA. 


side;  by  its  external  surf  ace,  with  the  Inferior  lingualis,  the  Hyo-glossus,  the  lin- 
gual artery  and  hypoglossal   nerve,  the  lingual  nerve,  and  sublingual  gland ;  by 

its  upper  border,  with  the  mucous  membrane  of 
the  floor  of  the  mouth  (frsenum  linguse) ;  by  its 
lower  border,  with  the  Genio-hyoid. 

The  Hyo-glossus  is  a  thin,  flat,  quadrilateral 
muscle  which  arises  from  the  side  of  the  body 
and  whole  length  of  the  greater  cornu  of  the  hy- 
oid  bone,  and  passes  almost  vertically  upward  to 
enter  the  side  of  the  tongue,  between  the  Stylo- 
glossus  and  Lingualis.  Those  fibres  of  this  mus- 
cle which  arise  from  the  body  (basio-glossus)  are 
directed  upward  and  backward,  overlapping 
those  arising  from  the  greater  cornu  (kerato- 
glossus),  which  are  directed  upward  and  forward. 
Relations. — By  its  external  surface,  with  the 
Digastric,  the  Stylo-hyoid,  Stylo-glossus,  and 
Mylo-hyoid  muscles,  the  submaxillary  ganglion, 
the  lingual  and  hypoglossal  nerves,  Wharton's 
duct,  and  the  deep  portion  of  the  submaxillary 
gland  ;  by  its  deep  surface,  with  the  Stylo-hyoid 
ligament,  the  Genio-hyo-glossus,  Lingualis,  and 
Middle  constrictor,  the  lingual  vessels,  and  the 
glosso-pharyngeal  nerve. 

The  Chondro-glossus  is  a  distinct  muscular 
slip,  about  three-quarters  to  an  inch  in  length, 
which  arises  from  the  inner  side  and  base  of  the 
lesser  cornu  of  the  hyoid  bone  and  contiguous 
portion  of  the  body  of  the  bone,  and  passes 
directly  upward  to  blend  with  the  intrinsic  mus- 
cular fibres  of  the  tongue,  between  the  Hyo- 
glossus  and  Genio-hyo-glossus.  A  small  slip  of 
muscular  fibre  is  occasionally  found,  arising  from  the  cartilage  triticea  in  the 
thyro-hyoid  ligament,  and  passing  upward  and  forward  to  enter  the  tongue  with 
the  hindermost  fibres  of  the  Hyo-glossus. 

The  Stylo-glossus,  the  shortest  and  smallest  of  the  three  styloid  muscles,  arises 
from  the  anterior  and  outer  side  of  the  styloid  process,  near  its  apex,  and  from  the 
stylo-maxillary  ligament,  to  which  its  fibres,  in  most  cases,  are  attached  by  a  thin 
aponeurosis.  Passing  downward  and  forward  between  the  internal  and  external 
carotid  arteries,  and  becoming  nearly  horizontal  in  its  direction,  it  divides  upon 
the  side  of  the  tongue  into  two  portions  :  one  longitudinal,  which  enters  the  side 
of  the  tongue  near  its  dorsal  surface,  blending  with  the  fibres  of  the  Lingualis  in 
front  of  the  Hyo-glossus ;  the  other  oblique,  which  overlaps  the  Hyo-glossus 
muscle  and  decussates  with  its  fibres. 

Relations. — By  its  external  surface,  from  above  downward,  with  the  parotid 
gland,  the  Internal  pterygoid  muscle,  the  lingual  nerve,  and  the  mucous  membrane 
of  the  mouth ;  by  its  internal  surface,  with  the  tonsil,  the  Superior  constrictor, 
and  the  Hyo-glossus  muscle. 

The  Palato-glossus,  or  Constrictor  isthmi  faucium,  although  it  is  one  of  the 
muscles  of  the  tongue,  serving  to  draw  its  base  upward  during  the  act  of  degluti- 
tion, is  more  nearly  associated  with  the  soft  palate,  both  in  its  situation  and  func- 
tion ;  it  will  consequently  be  described  with  that  group  of  muscles. 

Nerves. — The  Palato-glossus  is  probably  innervated  by  the  spinal  accessory  nerve, 
through  the  pharyngeal  plexus ;  the  Inferior  lingualis,  according  to  some  authors, 
by  the  chorda  tympani ;  the  remaining  muscles  of  this  group,  by  the  hypoglossal. 
Muscular  Substance  of  Tongue. — The  muscular  fibres  of  the  tongue  run  in  vari- 
ous directions.     These  fibres  are  divided  into  two  sets — Extrinsic  and  Intrinsic. 


CHONDRO-GLOSSUS. 


FIG.  279.— Muscles  of  the  tongue  from  be- 
low. (From  a  preparation  in  the  Museum  of 
the  Royal  College  of  Surgeons  of  England.) 


THE   LINGUAL   REGION. 


417 


The  extrinsic  muscles  of  the  tongue  are  those  which  have  their  origin  external, 
and  only  their  terminal  fibres  contained  in  the  substance  of  the  organ.  They  are : 
the  Stylo-glossus,  the  Hyo-glossus,  the  Palato-glossus,  the  Genio-hyo-glossus,  and 
part  of  the  Superior  constrictor  of  the  pharynx  (Pharyngeo-glossus).  The  intrinsic 
are  those  which  are  contained  entirely  within  the  tongue,  and  form  the  greater 
part  of  its  muscular  structure. 

The  tongue  consists  of  symmetrical  halves  separated  from  each  other  in  the 
middle  line  by  a  fibrous  septum.  Each  half  is  composed  of  muscular  fibres 
arranged  in  various  directions,  containing  much  interposed  fat  and  supplied  by 
vessels  and  nerves. 

To  demonstrate  the  various  fibres  of  the  tongue,  the  organ  should  be  sub- 
jected to  prolonged  boiling,  in  order  to  soften  the  connective  tissue;  the  dis- 
section may  then  be  commenced  from  the  dorsum  (Fig.  280).  Immediately 
beneath  the  mucous  membrane  is  a  submucous,  fibrous  layer,  into  which  the 
muscular  fibres  which  terminate  on  the  surface  of  the  tongue  are  inserted. 

Upon  removing  this,  with  the  mucous  mem- 
brane, the  first  stratum  of  muscular  fibres  is 
exposed.  This  belongs  to  the  group  of  intrin- 
sic muscles,  and  has  been  named  the  Superior 
lingualis.  It  consists  of  a  thin  layer  of 


Cut  edge  of  Superficial  lingualis. 

FIG.  280.— Muscles  on  the  dorsum  of  the 
tongue. 


FIG.  281.— Coronal  section  of  tongue.  Showing  intrinsic 
muscles.  (Altered  from  Krause.)  a,  lingual  artery :  b,  Inferior 
lingualis,  cut  through ;  c,  fibres  of  Hyo-glossus ;  d,  oblique  fibres 
of  stylo-glossus;  e,  insertion  of  Transverse  lingualis;  /,  Supe- 
rior lingualis ;  g,  papillae  to  tongue  ;  h,  vertical  fibres  of  Gemo- 
hyo-glossus  intersecting  Transverse  lingualis  ;  i,  septum. 


oblique  and  longitudinal  fibres  which  arise  from  the  submucous  fibrous  layer,  close 
to  the  Epiglottis,  and  from  the  fibrous  septum,  and  pass  forward  and  outward  to 
the  edges  of  the  tongue.  Between  its  fibres  pass  some  vertical  fibres  derived  from 
the  Genio-hyo-glossus  and  from  the  vertical  intrinsic  muscle,  which  will  be  described 
later  on.  Beneath  this  layer  is  the  second  stratum  of  muscular  fibres,  derived  prin- 
cipally from  the  extrinsic  muscles.  In  front  it  is  formed  by  the  fibres  derived  from 
the  Stylo-glossus,  running  along  the  side  of  the  tongue,  and  sending  one  set  of  fibres 
over  the  dorsum  which  runs  obliquely  forward  and  inward  to  the  middle  line,  and 
another  set  of  fibres,  seen  at  a  later  period  of  the  dissection,  on  to  the  under  surface 
of  the  sides  of  the  anterior  part  of  the  tongue,  which  run  forward  and  inward, 
between  the  fibres  of  the  Hyo-glossus,  to  the  middle  line.  Behind  this  layer  of 
fibres,  derived  from  the  Stylo-glossus,  are  fibres  derived  from  the  Hyo-glossus, 
assisted  by  some  few  fibres  of  the  Palato-glossus.  The  Hyo-glossus,  entering  the 
side  of  the  under  surface  of  the  tongue,  between  the  Stylo-glossus  and  Inferior  lin- 

27 


418  THE  MUSCLES  AND   FASCIA. 

gualis,  passes  round  its  margin  and  spreads  out  into  a  laye-r  on  the  dorsum,  which 
occupies  the  middle  third  of  the  organ,  and  runs  almost  transversely  inward  to  the 
septum.  It  is  reinforced  by  some  fibres  from  the  Palato-glossus ;  other  fibres  of  this 
muscle  pass  more  deeply  and  intermingle  with  the  next  layer.  The  posterior  part 
of  the  second  layer  of  the  muscular  fibres  of  the  tongue  is  derived  from  those 
fibres  of  the  Hyo-glossus  which  arise  from  the  lesser  cornu  of  the  hyoid  bone,  and 
are  here  described  as  a  separate  muscle — the  Chondro-glossus.  The  fibres  of  this 
muscle  are  arranged  in  a  fan-shaped  manner,  and  spread  out  over  the  posterior 
third  of  the  tongue.  Beneath  this  layer  is  the  great  mass  of  the  intrinsic  muscles 
of  the  tongue,  intersected  at  right  angles  by  the  terminal  fibres  of  one  of  the 
extrinsic  muscles — the  Genio-hyo-glossus.  This  portion  of  the  tongue  is  paler 
in  color  and  softer  in  texture  than  that  already  described,  and  is  sometimes 
designated  the  medullary  portion  in  contradistinction  to  the  firmer  superficial  part, 
which  is  termed  the  cortical  portion.  It  consists  largely  of  transverse  fibres,  the 
Transverse  lingualis,  and  of  vertical  fibres,  the  Vertical  lingualis.  The  Transverse 
lingualis  forms  the  largest  portion  of  the  third  layer  of  muscular  fibres  of  the 
tongue.  The  fibres  arise  from  the  median  septum,  and  pass  outward  to  be  inserted 
into  the  submucous  fibrous  layer  at  the  sides  of  the  tongue.  Intermingled  with 
these  transverse  intrinsic  fibres  are  transverse  extrinsic  fibres  derived  from  the 
Palato-glossus  and  the  Superior  constrictor  of  the  pharynx.  These  transverse 
extrinsic  fibres,  however,  run  in  the  opposite  direction,  passing  inward,  toward 
the  septum.  Intersecting  the  transverse  fibres  are  a  large  number  of  vertical  fibres 
derived  partly  from  the  Genio-hyo-glossus  and  partly  from  vertical  intrinsic  fibres, 
the  Vertical  lingualis.  The  fibres  derived  from  the  Genio-hyo-glossus  enter  the 
under  surface  of  the  tongue  on  each  side  of  the  median  septum  from  base  to  apex. 
They  ascend  in  a  radiating  manner  to  the  dorsum,  being  inserted  into  the  sub- 
mucous  fibrous  layer  covering  the  tongue  on  each  side  of  the  middle  line.  The 
Vertical  lingualis  is  found  only  at  the  borders  of  the  fore  part  of  the  tongue, 
external  to  the  fibres  of  the  Genio-hyo-glossus.  Its  fibres  extend  from  the  upper 
to  the  under  surface  of  the  tongue,  decussating  Avith  the  fibres  of  the  other  muscles, 
and  especially  with  the  Transverse  lingualis.  The  fourth  layer  of  muscular  fibres 
of  the  tongue  consists  partly  of  extrinsic  fibres  derived  from  the  Stylo-glossus,  and 
partly  of  intrinsic  fibres,  the  Inferior  lingualis.  At  the  sides  of  the  under  surface  of 
the  tongue  are  some  fibres  derived  from  the  Stylo-glossus,  which,  as  it  runs  forward 
at  the  side  of  the  tongue,  gives  off  fibres  which,  passing  forward  and  inward  between 
the  fibres  of  the  Hyo-glossus,  form  an  inferior  oblique  stratum  Avhich  joins  in  front 
with  the  anterior  fibres  of  the  Inferior  lingualis.  The  Inferior  lingualis  is  a  longi- 
tudinal band,  situated  on  the  under  surface  of  the  tongue,  lying  in  the  interval 
between  the  Stylo-glossus,  in  front  of  the  Hyo-glossus,  and  the  Genio-hyo-glossus, 
and  extending  from  the  base  to  the  apex  of  the  organ.  Posteriorly,  some  of  the 
fibres  are  lost  in  the  base  of  the  tongue,  and  others  are  occasionally  attached  to 
the  hyoid  bone.  It  blends  with  the  fibres  of  the  Hyo-glossus,  and  is  continued 
forward  as  far  as  the  apex  of  the  tongue.  It  is  in  relation  by  its  under  surface 
with  the  ranine  artery. 

Surgical  Anatomy. — The  fibrous  septum  which  exists  between  the  two  halves  of  the 
tongue  is  very  complete,  so  that  the  anastomosis  between  the  two  lingual  arteries  is  not  very 
free,  a  fact  often  illustrated  by  injecting  one-half  of  the  tongue  with  colored  size,  while  the  other 
half  is  left  uninjected  or  is  injected  with  size  of  a  different  color. 

This  is  a  point  of  considerable  importance  in  connection  with  removal  of  one-half  of  the 
tongue  for  cancer,  an  operation  which  is  now  frequently  resorted  to  when  the  disease  is  strictly 
confined  to  one  side  of  the  tongue.  If  the  mucous  membrane  is  divided  longitudinally  exactly 
in  the  middle  line,  the  tongue  can  be  split  into  halves  along  the  median  raphe  without  any 
appreciable  haemorrhage,  and  the  diseased  half  can  then  be  removed. 

Actions. — The  movements  of  the  tongue,  although  numerous  and  complicated, 
may  be  understood  by  carefully  considering  the  direction  of  the  fibres  of  its 
muscles.  The  G-enio-hyo-glossi  muscles,  by  means  of  their  posterior  fibres,  draw 
the  base  of  the  tongue  forward,  so  as  to  protrude  the  apex  from  the  mouth.  The 
anterior  fibres  draw  the  tongue  back  into  the  mouth.  The  whole  length  of  these 


THE  PHARYNGEAL    REGION. 


419 


two  muscles,  acting  along  the  middle  line  of  the  tongue,  draw  it  downward,  so  as  to 
make  it  concave  from  side  to  side,  forming  a  channel  along  which  fluids  may  pass 
toward  the  pharynx,  as  in  sucking.  The  Hyo-glo9*i  muscles  depress  the  tongue 
and  draw  down  its  sides,  so  «s  to  render  it  convex  from  side  to  side.  The  Stylo- 
</  muscles  draw  the  tongue  upward  and  backward.  The  Palato-glossi  muscles 
draw  the  base  of  the  tongue  upward.  With  regard  to  the  intrinsic  muscles,  both 
the  Superior  and  Inferior  linguales  tend  to  shorten  the  tongue,  but  the  former,  in 
addition,  turn  the  tip  and  sides  upward  so  as  to  render  the  dorsum  concave,  while 
the  latter  pull  the  tip  downward  and  cause  the  dorsum  to  become  convex.  The 
Transverse  lingualis  narrows  and  elongates  the  tongue,  and  the  Vertical  lingualis 
flattens  and  broadens  it.  The  complex  arrangement  of  the  muscular  fibres  of 
the  tongue,  and  the  various  directions  in  which  they  run,  give  to  this  organ  the 
power  of  assuming  the  various  forms  necessary  for  the  enunciation  of  the  different 
consonantal  sounds ;  and  Dr.  Macalister  states  that  "  there  is  reason  to  believe 
that  the  musculature  of  the  tongue  varies  in  different  races  owing  to  the  hereditary 
practice  and  habitual  use  of  certain  motions  required  for  enunciating  the  several 
vernacular  languages." 

5.  Pharyngeal  Region. 


Inferior  constrictor. 

Middle  constrictor. 

Palato-pharyngeus.      1 
Salpingo-pharyngeus.  J 


Superior  constrictor. 
Stylo-pharyngeus. 

(See  next  section.) 


Dissection  Fisr.  2^2  . — In  order  to  examine  the  muscles  of  the  pharynx,  cut  through  the 
trachea  and  oesophagus  just  above  the  sternum,  and  draw  them  upward  by  dividing  the  loose 
areolar  tissue  connecting  the  pharynx  with  the 
front  of  the  vertebral  column.  The  parts 
being  drawn  well  forward,  apply  the  edge  of 
the  saw  immediately  behind  the  styloid  pro- 
and  saw  the  base  of  the  skull  through 
from  below  upward.  The  pharynx  and  mouth 
should  then  be  stuffed  with  tow.  in  order  to 
distend  its  cavity  and  render  the  muscles  tense 
and  easier  of  dissection. 

The  Inferior  constrictor,  the  most 
superficial  and  thickest  of  the  three 
constrictors,  arises  from  the  sides  of  the 
cricoid  and  thyroid  cartilages.  To  the 
cricoid  cartilage  it  is  attached  in  the 
interval  between  the  Crico-thyroid  mus- 
cle in  front  and  the  articular  facet  for 
the  thyroid  cartilage  behind.  To  the 
thyroid  cartilage  it  is  attached  to  the 
oblique  line  on  the  side  of  tLe  great  ala. 
the  cartilaginous  surface  behind  it.  near- 
ly as  far  as  its  posterior  border,  and  to 
the  inferior  cornu.  From  these  attach- 
ments the  fibres  spread  backward  and 
inward,  to  be  inserted  into  the  fibrous 
raphe  in  the  posterior  median  line  of 
the  pharynx.  The  inferior  fibres  are 
horizontal,  and  continuous  with  the 
fibres  of  the  oesophagus :  the  rest  as- 
cend, increasing  in  obliquity,  and  over- 
lap the  Middle  constrictor.  The  supe- 
rior laryngeal  nerve  and  artery  pass 
near  the  upper  border,  and  the  inferior,  or  recurrent  laryngeal,  beneath  the  lower 
border  of  this  muscle,  previous  to  their  entering  the  larynx. 

Relations. — It  is  covered  by  a  dense  cellular  membrane  which  surrounds  the 


FIG.  382.— Muscles  of  the  pharynx.   External  view. 


420  THE  MUSCLES  AND   FASCIAE. 

entire  pharynx.  Behind,  it  is  in  relation  with  the  vertebral  column  and  the 
Longus  colli  muscle ;  laterally,  with  the  thyroid  gland,  the  common  carotid  artery, 
and  the  Sterno-thyroid  muscle ;  by  its  internal  surf  ace,  with  the  Middle  constrictor, 
the  Stylo-pharyngeus,  Palato-pharyngeus,  the  fibrous  coat  and  mucous  membrane 
of  the  pharynx. 

The  Middle  constrictor  is  a  flattened,  fan-shaped  muscle,  smaller  than  the  pre- 
ceding. It  arises  from  the  whole  length  of  the  upper  surface  of  the  greater  cornu 
of  the  hyoid  bone,  from  the  lesser  cornu,  and  from  the  stylo-hyoid  ligament.  The 
fibres  diverge  from  their  origin,  the  lower  ones  descending  beneath  the  Infe- 
rior constrictor,  the  middle  fibres  passing  transversely,  and  the  upper  fibres 
ascending  and  overlapping  the  Superior  constrictor.  The  muscle  is  inserted  into 
the  posterior  median  fibrous  raphe,  blending  in  the  middle  line  with  the  one  of  the 
opposite  side. 

Relations. — This  muscle  is  separated  from  the  Superior  constrictor  by  the 
glosso-pharyngeal  nerve  and  the  Stylo-pharyngeus  muscle,  and  from  the  Inferior 
constrictor  by  the  superior  laryngeal  nerve.  Behind,  it  lies  on  the  vertebral 
column,  the  Longus  colli,  and  the  Rectus  capitis  anticus  major.  On  each  side  it 
is  in  relation  with  the  carotid  vessels,  the  pharyngeal  plexus,  and  some  lymphatic 
glands.  Near  its  origin  it  is  covered  by  the  Hyo-glossus,  from  which  it  is  separated 
by  the  lingual  vessels.  It  lies  upon  the  Superior  constrictor,  the  Stylo-pharyngeus, 
the  Palato-pharyngeus,  the  fibrous  coat,  and  the  mucous  membrane  of  the 
phai'ynx. 

The  Superior  Constrictor  is  a  quadrilateral  muscle,  thinner  and  paler  than  the 
other  constrictors,  and  situated  at  the  upper  part  of  the  pharynx.  It  arises  from 
the  lower  third  of  the  posterior  margin  of  the  internal  pterygoid  plate  and  its 
hamular  process,  from  the  contiguous  portion  of  the  palate  bone  and  the  reflected 
tendon  of  the  Tensor  palati  muscle,  from  the  pterygo-maxillary  ligament,  from  the 
alveolar  process  above  the  posterior  extremity  of  the  mylo-hyoid  ridge,  and  by  a 
few  fibres  from  the  side  of  the  tongue.  From  these  points  the  fibres  curve  back- 
ward, to  be  inserted  into  the  median  raphe,  being  also  prolonged  by  means  of  a 
fibrous  aponeurosis  to  the  pharyngeal  spine  on  the  basilar  process  of  the  occipital 
bone.  The  superior  fibres  arch  beneath  the  Levator  palati  and  the  Eustachian 
tube,  the  interval  between  the  upper  border  of  the  muscle  and  the  basilar  process 
being  deficient  in  muscular  fibres  and  closed  by  fibrous  membrane.  This  interval 
is  known  as  the  sinus  of  Morgagni. 

Relations. — By  its  outer  surface,  with  the  vertebral  column,  the  internal  carotid 
artery,  the  internal  jugular  vein,  the  glosso-pharyngeal,  pneumogastric,  spinal 
accessory,  hypoglossal,  and  sympathetic  nerves,  the  Middle  constrictor,  which 
overlaps  it,  and  the  Stylo-pharyngeus ;  by  its  internal  surface,  with  the  Palato- 
pharyngeus,  the  tonsil,  the  fibrous  coat  and  mucous  membrane  of  the  pharynx. 

The  Stylo-pharyngeus  is  a  long,  slender  muscle,  round  above,  broad  and  thin 
below.  It  arises  from  the  inner  side  of  the  base  of  the  styloid  process,  passes 
downward  along  the  side  of  the  pharynx  between  the  Superior  and  Middle 
constrictors,  and  spreads  out  beneath  the  mucous  membrane,  where  some  of  its 
fibres  are  lost  in  the  Constrictor  muscles ;  and  others,  joining  with  the  Palato- 
pharyngeus,  are  inserted  into  the  posterior  border  of  the  thyroid  cartilage.  The 
glosso-pharyngeal  nerve  runs  on  the  outer  side  of  this  muscle,  and  crosses  over  it 
in  passing  forward  to  the  tongue. 

Relations. — Externally,  with  the  Stylo-glossus  muscle,  the  parotid  gland,  the 
external  carotid  artery,  and  the  Middle  constrictor ;  internally,  with  the  internal 
carotid,  the  internal  jugular  vein,  the  Superior  constrictor,  Palato-pharyngeus,  and 
mucous  membrane. 

Nerves. — The  Constrictors  are  supplied  by  branches  from  the  pharyngeal 
plexus,  the  Stylo-pharyngeus  by  the  glosso-pharyngeal  nerve,  and  the  Inferior 
constrictor  by  an  additional  branch  from  the  external  laryngeal  nerve  and  by  the 
recurrent  laryngeal. 

Actions. — When  deglutition  is  about  to  be  performed,  the  pharynx  is  drawn 


THE  PALATAL    REGIOX. 


421 


upward  and  dilated  in  different  directions,  to  receive  the  morsel  propelled  into  it 
from  the  mouth.  The  Stylo-pharyngei,  which  are  much  farther  removed  from 
one  another  at  their  origin  than  at  their  insertion,  draw  the  sides  of  the  pharynx 
upward  and  outward,  and  so  increase  its  transverse  diameter,  its  breadth  in  the 
antero-posterior  direction  being  increased  by  the  larynx  and  tongue  being  carried 
forward  in  their  ascent.  As  soon  as  the  morsel  is  received  in  the  pharynx,  the 
Elevator  muscles  relax,  the  bag  descends,  and  the  Constrictors  contract  upon 
the  morsel,  and  convey  it  gradually  downward  into  the  oesophagus.  Besides 
its  action  in  deglutition,  the  pharynx  also  exerts  an  important  influence  in  the 
modulation  of  the  voice,  especially  in  the  production  .of  the  higher  tones. 

6.  Palatal  Region. 

Levator  palati.  Palato-glossus. 

Tensor  palati.  Palato-pharyngeus. 

Azygos  uvulae.  Salpingo-pharyngeus. 

Dissection  (Fiir.  283). — Lay  open  the  pharynx  from  behind  by  a  vertical  incision  extending 
from  its  upper  to  its  lower  part,  and  partially  divide  the  occipital  attachment  by  a  transverse 
incision  on  each  side  of  the  vertical  one  ;  the  posterior  surface  of  the  soft  palate  is  then  exposed. 
Having  fixed  the  uvula  so  as  to  make  it  tense,  the  mucous  membrane  and  glands  should  be  care- 
fully removed  from  the  posterior  surface  of  the  soft  palate,  and  the  muscles  of  this  part  are  at 
once  exposed. 

The  Levator  palati  is  a  long,  thick,  rounded  muscle,  placed  on  the  outer  side 


FIG.  283.— Muscles  of  the  soft  palate,  the  pharynx  being  laid  open  from  behind. 


of  the  posterior  nares.  It  arises  from  the  under  surface  of  the  apex  of  the  petrous 
portion  of  the  temporal  bone,  and  from  the  adjoining  cartilaginous  portion  of  the 
Eustachian  tube ;  after  passing  into  the  pharynx,  above  the  upper  concave  margin 


422  THE  MUSCLES  AND   FASCIJE. 

of  the  Superior  constrictor,  it  passes  obliquely  downward  and  inward,  its  fibres 
spreading  out  in  the  soft  palate  as  far  as  the  middle  line,  where  they  blend  with 
those  of  the  opposite  side. 

Relations. — Externally,  with  the  Tensor  palati  and  Superior  constrictor; 
internally,  with  the  mucous  membrane  of  the  pharynx ;  posteriorly,  with  the 
posterior  fasciculus  of  the  Palato-pharyngeus,  the  Azygos  uvulae,  and  the  mucous 
lining  of  the  soft  palate. 

The  Circumflexus  or  Tensor  palati  is  a  broad,  thin,  ribbon-like  muscle,  placed 
on  the  outer  side  of  the  Levator  palati,  and  consisting  of  a  vertical  and  a  horizontal 
portion.  The  vertical  portion  arises  by  a  broad,  thin,  and  flat  lamella  from  the 
scaphoid  fossa  at  the  base  of  the  internal  pterygoid  plate  ;  from  the  spine  of  the 
sphenoid ;  the  vaginal  process  of  the  temporal  bone  and  the  anterior  aspect  of 
the  cartilaginous  portion  of  the  Eustachian  tube  :  descending  vertically  between 
the  internal  pterygoid  plate  and  the  inner  surface  of  the  Internal  pterygoid 
muscle,  it  terminates  in  a  tendon,  which  winds  round  the  hamular  process,  being 
retained  in  this  situation  by  some  of  the  fibres  of  origin  of  the  Internal  pterygoid 
muscle,  and  lubricated  by  a  bursa.  The  tendon  or  horizontal  portion  then  passes 
horizontally  inward,  and  is  inserted  into  a  broad  aponeurosis,  the  palatine 
aponeurosis,  and  into  the  transverse  ridge  on  the  horizontal  portion  of  the  palate 
bone. 

Relations. — Externally,  with  the  Internal  pterygoid;  internally,  with  the 
Levator  palati,  from  which  it  is  separated  by  the  Superior  constrictor,  and  with 
the  internal  pterygoid  plate.  In  the  soft  palate  its  tendon  and  the  palatine 
aponeurosis  is  anterior  to  that  of  the  Levator  palati,  being  covered  by  the  Palato- 
glossus  and  the  mucous  membrane. 

Palatine  Aponeurosis. — Attached  to  the  posterior  border  of  the  hard  palate  is 
a  thin,  firm,  fibrous  lamella  which  supports  the  muscles  and  gives  strength  to  the 
soft  palate.  It  is  thicker  above  than  below,  where  it  becomes  very  thin  and 
difficult  to  define.  Laterally,  it  is  continuous  with  the  pharyngeal  aponeurosis. 

The  Azygos  uvulae  is  not  a  single  muscle,  as  would  be  inferred  from  its  name, 
but  a  pair  of  narrow  cylindrical  fleshy  fasciculi  placed  side  by  side  in  the  median 
line  of  the  soft  palate.  Each  muscle  arises  from  the  posterior  nasal  spine  of  the 
palate  bone  and  from  the  contiguous  tendinous  aponeurosis  of  the  soft  palate,  and 
descends  to  be  inserted  into  the  uvula. 

Relations. — Anteriorly,  with  the  tendinous  expansion  of  the  Levatores  palati ; 
behind,  with  the  posterior  fasciculus  of  the  Palato-pharyngeus  and  the  mucous 
membrane. 

The  two  next  muscles  are  exposed  by  removing  the  mucous  membrane  from  the  pillars  of 
the  soft  palate  throughout  nearly  their  whole  extent. 

The  Palato-glossus  (Constrictor  isthmi  faucium)  is  a  small  fleshy  fasciculus, 
narrower  in  the  middle  than  at  either  extremity,  forming,  with  the  mucous 
membrane  covering  its  surface,  the  anterior  pillar  of  the  soft  palate.  It  arises 
from  the  anterior  surface  of  the  soft  palate  on  each  side  of  the  uvula,  and,  passing 
downward,  forward,  and  outward  in  front  of  the  tonsil,  is  inserted  into  the  side 
of  the  tongue,  some  of  its  fibres  spreading  over  the  dorsum,  and  others  passing 
deeply  into  the  substance  of  the  organ  to  intermingle  with  the  Transversus  linguae. 
In  the  soft  palate  the  fibres  of  this  muscle  are  continuous  with  those  of  the  muscle 
of  the  opposite  side. 

The  Palato-pharyngeus  is  a  long,  fleshy  fasciculus,  narrower  in  the  middle  than 
at  either  extremity,  forming,  with  the  mucous  membrane  covering  its  surface,  the 
posterior  pillar  of  the  soft  palate.  It  is  separated  from  the  Palato-glossus  by  an 
angular  interval,  in  which  the  tonsil  is  lodged.  It  arises  from  the  soft  palate  by 
an  expanded  fasciculus,  which  is  divided  into  two  parts  by  the  Levator  palati  and 
Azygos  uvulae.  The  posterior  fasciculus  lies  in  contact  with  the  mucous  membrane, 
and  also  joins  with  the  corresponding  muscle  in  the  middle  line ;  the  anterior 
fasciculus,  the  thicker,  lies  in  the  soft  palate  between  the  Levator  and  Tensor,  and 


THE  PALATAL   REGION.  423 

joins  in  the  middle  line  the  corresponding  part  of  the  opposite  muscle.  Passing 
outward  and  downward  behind  the  tonsil,  the  Palato-pharyngeus  joins  the  Stylo- 
pharyngeus,  and  is  inserted  with  that  muscle  into  the  posterior  border  of  the 
thyroid  cartilage,  some  of  its  fibres  being  lost  on  the  side  of  the  pharynx,  and 
others  passing  across  the  middle  line  posteriorly  to  decussate  with  the  muscle  of 
the  opposite  side. 

The  Salpingo-pharyngeus. — This  muscle  arises  from  the  inferior  part  of  the 
Eustachian  tube  near  its  orifice ;  it  passes  downward  and  blends  with  the  posterior 
fasciculus  of  the  Palato-pharyngeus. 

Relations. — In  the  soft  palate  its  posterior  surface  is  covered  by  mucous 
membrane,  from  which  it  is  separated  by  a  layer  of  palatine  glands.  By  its 
anterior  surface  it  is  in  relation  with  the  Tensor  palati.  Where  it  forms  the 
posterior  pillar  of  the  fauces  it  is  covered  by  mucous  membrane,  excepting  on  its 
outer  surface.  In  the  pharynx  it  lies  between  the  mucous  membrane  and  the 
Constrictor  muscles. 

In  a  dissection  of  the  soft  palate  from  its  posterior  or  nasal  surface  to  its  anterior 
or  oral  surface,  the  muscles  would  be  exposed  in  the  following  order :  viz.  the 
posterior  fasciculus  of  the  Palato-pharyngeus,  covered  over  by  the  mucous  membrane 
reflected  from  the  floor  of  the  nasal  fossse  ;  the  Azygos  uvulae ;  the  Levator  palati ; 
the  anterior  fasciculus  of  the  Palato-pharyngeus ;  the  aponeurosis  of  the  Tensor 
palati.  and  the  Palato-glossus  covered  over  by  a  reflection  from  the  oral  mucous 
membrane. 

Nerves. — The  Tensor  palati  is  supplied  by  a  branch  from  the  otic  ganglion ; 
the  remaining  muscles  of  this  group  are  in  all  probability  supplied  by  the  internal 
branch  of  the  spinal  accessory,  whose  fibres  are  distributed  along  with  certain 
branches  of  the  pneumogastric  through  the  pharyngeal  plexus.1 

Actions. — During  the  first  stage  of  deglutition  the  morsel  of  food  is  driven  back 
into  the  fauces  by  the  pressure  of  the  tongue  against  the  hard  palate,  the  base  of 
the  tongue  being,  at  the  same  time,  retracted,  and  the  larynx  raised  with  the 
pharynx,  and  carried  forward  under  it.  During  the  second  stage  the  epiglottis  is 
pressed  over  the  superior  aperture  of  the  larynx,  and  the  morsel  glides  past  it ; 
then  the  Palato-glossi  muscles,  the  constrictors  of  the  fauces,  contract  behind  the 
food  ;  the  soft  palate  is  slightly  raised  by  the  Levator  palati.  and  made  tense  by 
the  Tensor  palati ;  and  the  Palato-pharyngei,  by  their  contraction,  pull  the  pharynx 
upward  over  the  morsel  of  food,  and  at  the  same  time  come  nearly  together,  the 
uvula  filling  up  the  slight  interval  between  them.  By  these  means  the  food  is 
prevented  passing  into  the  upper  part  of  the  pharynx  or  the  posterior  nares ;  at 
the  same  time  the  latter  muscles  form  an  inclined  plane,  directed  obliquely  down- 
ward and  backward,  along  the  under  surface  of  which  the  morsel  descends  into 
the  lower  part  of  the  pharynx.  The  Salpingo-pharyngeus  raises  the  upper  and 
lateral  part  of  the  pharynx — i.  e.  that  part  which  is  above  the  point  where  the 
Stylo-pharyngeus  is  attached  to  the  pharynx. 

Surgical  Anatomy. — The  muscles  of  the  soft  palate  should  be  carefully  dissected,  the  rela- 
tions they  bear  to  the  surrounding  parts  especially  examined,  and  their  action  attentively  studied 
upon  the  dead  subject,  as  the  surgeon  is  required  to  divide  one  or  more  of  these  muscles  in  the 
operation  of  staphylorraphy.  Sir  W.  Fergusson  was  the  first  to  show  that  in  the  congenital 
deficiency  called  cleft  palate  the  edges  of  the  fissure  are  forcibly  separated  by  the  action  of  the 
Levatores  palati  and  Palato-pharyngei  muscles,  producing  very  considerable  impediment  to  the 
healing  process  after  the  performance  of  the  operation  for  uniting  their  margins  by  adhesion  ;  he, 
consequently,  recommended  the  division  of  these  muscles  as  one  of  the  most  important  steps  in 
the  operation.  This  he  effected  by  an  incision  made  with  a  curved  knife  introduced  behind  the 
soft  palate.  The  incision  is  to  be  halfway  between  the  hamular  process  and  Eustachian  tube, 
and  perpendicular  to  a  line  drawn  between  them.  This  incision  perfectly  accomplishes  the 
division  of  the  Levator  palati.  The  Palato-pharyngeus  may  be  divided  by  cutting  across  the 
posterior  pillar  of  the  soft  palate,  just  below  the  tonsil,  with  a  pair  of  blunt-pointed  curved 
scissors :  and  the  anterior  pillar  may  be  divided  also.  To  divide  the  Levator  palati  the  plan 
recommended  by  Mr.  Pollock  is  to  be  greatly  preferred.  The  soft  palate  being  put  upon  the 
stretch,  a  double-edged  knife  is  passed  through  it  just  on  the  inner  side  of  the  hamular  process 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxiii.  p.  523. 


424 


THE  MUSCLES  AND    FASCIAE. 


and  above  the  line  of  the  Levator  palati.  The  handle  being  now  alternately  raised  and 
depressed,  a  sweeping  cut  is  made  along  the  posterior  surface  of  the  soft  palate,  and  the  knife 
withdrawn,  leaving  only  a  small  opening  in  the  mucous  membrane  on  the  anterior  surface.  If 
this  operation  is  performed  on  the  dead  body  and  the  parts  afterward  dissected,  the  Levator 
palati  will  be  found  completely  divided.  In  the  present  day,  however,  this  division  of  the 
muscles,  as  part  of  the  operation  of  staphylorraphy,  is  not  so  much  insisted  upon.  All  tension 
is  prevented  by  making  longitudinal  incisions  on  either  side,  parallel  to  the  cleft  and  just 
internal  to  the  hamular  process,  in  such  a  position  as  to  avoid  the  posterior  palatine  artery. 

7.  Anterior  Vertebral  Region. 

Rectus  capitis  anticus  major.  Rectus  capitis  lateralis. 

Rectus  capitis  anticus  minor.  Longus  colli. 

The  Rectus  capitis  anticus  major  (Fig.  284),  broad   and  thick  above,  narrow 
below,  appears  like  a  continuation  upward  of  the  Scalenus  anticus.     It  arises  by 


FIG.  284.— The  prevertebral  muscles. 

four  tendinous  slips  from  the  anterior  tubercles  of  the  transverse  processes  of  the 
third,  fourth,  fifth,  and  sixth  cervical  vertebrae,  and  ascends,  converging  toward 
its  fellow  of  the  opposite  side,  to  be  inserted  into  the  basilar  process  of  the  occip- 
ital bone. 

Relations. — By  its  anterior  surface,  with  the  pharynx,  the  sympathetic  nerve, 
and  the  sheath  enclosing  the  internal  and  common  carotid  artery,  internal  jugular 
vein,  and  pneumogastric  nerve ;  by  its  posterior  surface,  with  the  Longus  colli,  the 
Rectus  capitis  anticus  minor,  and  the  upper  cervical  vertebrae. 

The  Rectus  capitis  anticus  minor  is  a  short,  flat  muscle,  situated  immediately 
behind  the  upper  part  of  the  preceding.  It  arises  from  the  anterior  surface  of  the 
lateral  mass  of  the  atlas  and  from  the  root  of  its  transverse  process,  and,  passing 


THE  LATERAL    VERTEBRAL   REGION.  425 

obliquely  upward  and  inward,  is  inserted  into  the  basilar  process  immediately 
behind  the  preceding  muscle. 

Relations. — By  its  anterior  surface,  with  the  Rectus  capitis  anticus  major;  by 
its  posterior  surface,  with  the  front  of  the  occipito-atlantal  articulation. 

The  Rectus  capitis  lateralis  is  a  short,  flat  muscle,  which  arises  from  the  upper 
surface  of  the  transverse  process  of  the  atlas,  and  is  inserted  into  the  under  surface 
of  the  jugular  process  of  the  occipital  bone. 

Relations. — By  its  anterior  surface,  with  the  internal  jugular  vein  ;  by  its  pos- 
terior surface,  with  the  vertebral  artery.  On  its  outer  side  lies  the  occipital  artery ; 
on  its  inner  side,  the  suboccipital  nerve. 

The  Longus  colli  is  a  long,  flat  muscle,  situated  on  the  anterior  surface  of  the 
spine,  between  the  atlas  and  the  third  dorsal  vertebra.  It  is  broad  in  the  middle, 
narrow  and  pointed  at  each  extremity,  and  consists  of  three  portions :  a  superior, 
oblique,  an  inferior  oblique,  and  a  vertical  portion.  The  superior  oblique  portion 
arises  from  the  anterior  tubercles  of  the  transverse  processes  of  the  third,  fourth, 
and  fifth  cervical  vertebrae,  and,  ascending  obliquely  inward,  is  inserted  by  a  nar- 
row tendon  into  the  tubercle  on  the  anterior  arch  of  the  atlas.  The  inferior 
oblique  portion,  the  smallest  part  of  the  muscle,  arises  from  the  front  of  the  bodies 
of  the  first  two  or  three  dorsal  vertebrae,  and,  ascending  obliquely  outward,  is 
inserted  into  the  anterior  tubercles  of  the  transverse  processes  of  the  fifth  and 
sixth  cervical  vertebrae.  The  vertical  portion  lies  directly  on  the  front  of  the  spine ; 
it  arises,  below,  from  the  front  of  the  bodies  of  the  upper  three  dorsal  and  lower 
three  cervical  vertebrae,  and  is  inserted  above  into  the  front  of  the  bodies  of  the 
second,  third,  and  fourth  cervical  vertebrae  above. 

Relations. — By  its  anterior  surface,  with  the  pharynx,  the  oesophagus,  sympa- 
thetic nerve,  the  sheath  of  the  great  vessels  of  the  neck,  the  inferior  thyroid  artery, 
and  recurrent  laryngeal  nerve ;  by  its  posterior  surface,  with  the  cervical  and  dorsal 
portions  of  the  spine.  Its  inner  border  is  separated  from  the  opposite  muscle  by 
a  considerable  interval  below,  but  they  approach  each  other  above. 

8.  Lateral  Vertebral  Region. 

Scalenus  anticus.  Scalenus  medius. 

Scalenus  posticus. 

The  Scalenus  anticus  is  a  conical-shaped  muscle,  situated  deeply  at  the  side  of 
the  neck,  behind  the  Sterno-mastoid.  It  arises  from  the  anterior  tubercles  of  the 
transverse  processes  of  the  third,  fourth,  fifth,  and  sixth  cervical  vertebrae,  and, 
descending  almost  vertically,  is  inserted  by  a  narrow,  flat  tendon  into  the  impression 
on  the  inner  border  and  upper  surface  of  the  first  rib.  The  lower  part  of  this 
muscle  separates  the  subclavian  artery  and  vein,  the  latter  being  in  front,  and  the 
former,  with  the  brachial  plexus,  behind. 

Relations. — In  front,  with  the  clavicle,  the  Subclavius,  Sterno-mastoid,  and 
Omo-hyoid  muscles,  the  transversalis  colli,  the  suprascapular  and  ascending  cer- 
vical arteries,  the  subclavian  vein,  and  the  phrenic  nerve  ;  by  its  posterior  surface, 
with  the  Scalenus  medius,  pleura,  the  subclavian  artery,  and  brachial  plexus  of 
nerves.  It  is  separated  from  the  Longus  colli,  on  the  inner  side,  by  the  vertebral 
artery.  On  the  anterior  tubercles  of  the  transverse  processes  of  the  cervical  ver- 
tebrae, between  the  attachments  of  the  Scalenus  anticus  and  Longus  colli,  lies  the 
ascending  cervical  branch  of  the  inferior  thyroid  artery. 

The  Scalenus  medius,  the  largest  and  longest  of  the  three  Scaleni,  arises  from 
the  posterior  tubercles  of  the  transverse  processes  of  the  lower  six  cervical  vertebrae, 
and.  descending  along  the  side  of  the  vertebral  column,  is  inserted  by  a  broad 
attachment  into  the  upper  surface  of  the  first  rib,  behind  the  groove  for  the  sub- 
clavian artery,  as  far  back  as  the  tubercle.  It  is  separated  from  the  Scalenus 
anticus  by  a  subclavian  artery  below  and  the  cervical  nerves  above.  The  pos- 
terior thoracic,  or  nerve  of  Bell,  is  formed  in  the  substance  of  the  Scalenus  medius 
and  emerges  from  it. 


426 


THE  MUSCLES  AND    FASCIA 


Relations. — By  its  anterior  surface,  with  the  Sterno-mastoid ;  it  is  crossed  by 
the  clavicle,  the  Omo-hyoid  muscle,  subclavian  artery,  and  the  cervical  nerves.  To 
its  outer  side  is  the  Levator  anguli  scapulae  and  the  Scalenus  posticus  muscle. 

The  Scalenus  posticus,  the  smallest  of  the  three  Scaleni,  arises,  by  two  or  three 
separate  tendons,  from  the  posterior  tubercles  of  the  transverse  processes  of  the 
lower  two  or  three  cervical  vertebrae,  and,  diminishing  as  it  descends,  is  inserted 
by  a  thin  tendon  into  the  outer  surface  of  the  second  rib,  behind  the  attachment  of 
the  Serratus  magnus.  This  is  the  most  deeply  placed  of  the  three  Scaleni,  and  is 
occasionally  blended  with  the  Scalenus  medius. 

Nerves. — The  Rectus  capitis  anticus  major  and  minor  and  the  Rectus  lateralis 
-are  supplied  by  the  first  cervical  nerve,  and  from  the  loop  formed  between  it  and 


SUPERIOR 


FIG.  2&5.— Muscles  of  the  neck.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of 
England.) 

the  second  ;  the  Longus  colli  and  Scaleni,  by  branches  from  the  anterior  divisions 
of  the  lower  cervical  nerves  (fifth,  sixth,  seventh,  and  eighth)  before  they  form  the 
brachial  plexus.  The  Scalenus  medius  also  receives  a  filament  from  the  deep 
•external  branches  of  the  cervical  plexus. 

Actions. — The  Rectus  anticus  major  and  minor  are  the  direct  antagonists  of  the 
muscles  at  the  back  of  the  neck,  serving  to  restore  the  head  to  its  natural  position 
after  it  has  been  drawn  backward.  These  muscles  also  serve  to  flex  the  head,  and, 


OF   THE    TRUXK.  427 

from  their  obliquity,  rotate  it,  so  as  to  turn  the  face  to  one  or  the  other  side.  The 
Longus  colli  flexes  and  slightly  rotates  the  cervical  portion  of  the  spine.  The 
Scaleni  muscles,  when  they  take  their  fixed  point  from  above,  elevate  the  first  and 
second  ribs,  and  are,  therefore,  inspiratory  muscles.  When  they  take  their  fixed 
point  from  below,  they  bend  the  spinal  column  to  one  or  the  other  side.  If  the 
muscles  of  both  sides  act,  lateral  movement  is  prevented,  but  the  spine  is  slightly 
flexed.  The  Rectus  lateralis,  acting  on  one  side,  bends  the  head  laterally. 

Surface  Form. — The  muscles  in  the  neck,  with  the  exception  of  the  Platysma  myoides,  are 
invested  by  the  deep  cervical  fascia,  which  softens  down  their  form,  and  is  of  considerable 
importance  in  connection  with  deep  cervical  abscesses  and  tumors,  modifying  the  direction  of 
their  growth  and  causing  them  to  extend  laterally  instead  of  toward  the  surface.  The  Platysma 
myoides  does  not  influence  surface  form  except  it  is  in  action,  when  it  produces  wrinkling  of  the 
skin  of  the  neck,  which  is  thrown  into  oblique  ridges  parallel  with  the  fasciculi  of  the  muscle. 
Sometimes  this  contraction  takes  place  suddenly  and  repeatedly  as  a  sort  of  spasmodic  twitching, 
the  result  of  a  nervous  habit.  The  Sterno-deido-mastoid  is  the  most  important  muscle  of  the 
neck  as  regards  its  surface  form.  If  the  muscle  is  put  into  action  by  drawing  the  chin  down- 
ward and  to  the  opposite  shoulder,  its  surface  form  will  be  plainly  outlined.  The  sternal  origin 
will  stand  out  as  a  sharply-defined  ridge,  while  the  clavicular  origin  will  present  a  flatter  and  not 
so  prominent  an  outline.  The  fleshy  middle  portion  will  appear  as  an  oblique  roll  or  elevation, 
with  a  thick  rounded  anterior  border  gradually  becoming  less  marked  above.  On  the  opposite 
side — i.  e.  on  the  side  to  which  the  head  is  turned — the  outline  is  lost,  its  place  being  occupied 
by  an  oblique  groove  in  the  integument.  When  the  muscle  is  at  rest  its  anterior  border  is  still 
visible,  forming  an  oblique  rounded  ridge,  terminating  below  in  the  sharp  outline  of  the  sternal 
head.  The  posterior  border  of  the  muscle  does  not  show  above  the  clavicular  head.  The 
anterior  border  is  defined  by  drawing  a  line  from  the  tip  of  the  mastoid  process  to  the  sterno- 
clavicular  joint.  It  is  an  important  surface-marking  in  the  operation  of  ligature  of  the  common 
carotid  artery  and  some  other  operations.  Between  the  sternal  and  clavicular  heads  is  a  slight 
depression,  most  marked  when  the  muscle  is  in  action.  This  is  bounded  below  by  the  prominent 
sternal  extremity  of  the  clavicle.  Between  the  sternal  origins  of  the  two  muscles  is  a  V-shaped 
space,  the  siiprasternal  notch,  more  pronounced  below,  and  becoming  toned  down  above,  where 
the  Sterno-hyoid  and  Sterno-thyroid  muscles,  lying  upon  the  trachea,  become  more  prominent. 
Above  the  hyoid  bone,  in  the  middle  line,  the  anterior  belly  of  the  Digastric  to  a  certain  extent 
influences  surface  form.  It  corresponds  to  a  line  drawn  from  the  syrnphysis  of  the  lower  jaw  to 
the  side  of  the  body  of  the  hyoid  bone,  and  renders  this  part  of  the  hyo-mental  region  convex. 
In  the  posterior  triangle  of  the  neck,  the  posterior  belly  of  the  Omo-hyoid.  when  in  action,  forms 
a  conspicuous  object,  especially  in  thin  necks,  presenting  a  cord-like  form  running  across  this 
region,  almost  parallel  with,  and  a  little  above,  the  clavicle. 

MUSCLES  AND  FASCLE  OF  THE  TRUNK. 

The  muscles  of  the  Trunk  may  be  arranged  in  four  groups  :  the  muscles  of  the 
Back,  of  the  Thorax,  of  the  Abdomen,  and  of  the  Perinaeum. 

THE  BACK. 

The  muscles  of  the  Back  are  very  numerous,  and  may  be  subdivided  into  five 
layers. 

FIRST  LAYER.  FOURTH  LAYER. 

Trapezius.  Sacral  and  Lumbar  Regions. 

Latissimus  dorsi.  -r, 

Erector  spmae. 

SECOND  LAYER. 

T  ..  Dorsal  Region. 

Levator  anguii  scapulae. 

Rhomboideus  minor.  Iho-costalis. 

Rhomboideus  major.  Musculus  accessonus  ad  ilio-costalem. 

Longissimus  dorsi. 

THIRD  LAYER.  S-pinalis  dorsi' 

Serratus  posticus  superior.  c 

Serratus  posticus  inferior. 

Splenius  capitis.  Cervicalis  ascendens. 

Splenius  colli.  Transversalis  colli. 


428 


THE   MUSCLES  AND    FASCIAE 


Trachelo-mastoid. 
Complexus. 
Biventer  cervicis. 
Spinalis  colli. 

FIFTH  LAYER. 

Semispinalis  dorsi. 
Semispinalis  colli. 
Multifidus  spinse. 


Rotatores  spinae. 

Supraspinales. 

Interspinales. 

Extensor  coccygis. 

Intertransversales. 

Rectus  capitis  posticus  major. 

Rectus  capitis  posticus  minor. 

Obliquus  capitis  superior. 

Obliquus  capitis  inferior. 


First  Layer. 

Trapezius.  j    Latissimus  dorsi. 

Dissection  (Fig.    286). — Place  the  body  in   a  prone   position,  with  the  arms  extended 
over  the  sides  of  the  table,  and  the  chest  and  abdomen  supported  by  several  blocks,  so  as 

to  render  the  muscles  tense.  Then  make  an  incision 
along  the  middle  line  of  the  back  from  the  occipital 
protuberance  to  the  coccyx.  Make  a  transverse  incision 
from  the  upper  end  of  this  to  the  mastoid  process,  and 
a  third  incision  from  its  lower  end,  along  the  crest  of 
the  ilium  to  about  its  middle.  This  large  intervening 
space  should,  for  convenience  of  dissection,  be  sub- 
divided by  a  fourth  incision,  extending  obliquely  from 
the  spinous  process  of  the  last  dorsal  vertebra,  upward 
and  outward,  to  the  acromion  process.  This  incision 
corresponds  with  the  lower  border  of  the  Trapezius 
muscle.  The  flaps  of  integument  are  then  to  be  re- 
moved in  the  direction  shown  in  the  figure. 

The  superficial  fascia  is  exposed  upon  re- 
moving the  skin  from  the  back.  It  forms  a 
layer  of  considerable  thickness  and  strength, 
in  Avhich  a  quantity  of  granular  pinkish  fat  is 
contained.  It  is  continuous  with  the  super- 
ficial fascia  in  other  parts  of  the  body.  The 
deep  fascia  is  a  dense  fibrous  layer  attached  to 
the  occipital  bone,  the  spines  of  the  vertebrae, 
the  crest  of  the  ilium,  and  the  spine  of  the 
scapula.  It  covers  over  the  superficial  muscles, 
forming  sheaths  for  them,  and  is  continuous, 
in  the  neck  at  the  anterior  border  of  the  Tra- 
pezius, with  the  deep  cervical  fascia ;  on  the 
thorax,  with  the  deep  fascia  of  the  axilla  and 
chest,  and  on  the  abdomen  with  the  fascia 
covering  the  abdominal  muscles. 

The  Trapezius  (Fig.  287)  is  a  broad,  flat, 
triangular  muscle,  placed  immediately  be- 
neath the  skin  and  fascia,  and  covering  the  upper  and  back  part  of  the  neck  and 
shoulders.  It  arises  from  the  inner  third  of  the  superior  curved  line  of  the  occipital 
bone ;  from  the  ligamentum  nuchse,  the  spinous  process  of  the  seventh  cervical, 
and  those  of  all  the  dorsal  vertebras ;  and  fr am  the  corresponding  portion  of  the 
supraspinous  ligament.  From  this  origin  the  superior  fibres  proceed  downward 
and  outward,  the  inferior  ones  upward  and  outward,  and  the  middle  fibres 
horizontally,  and  are  inserted,  the  superior  ones  into  the  outer  third  of  the 
posterior  border  of  the  clavicle ;  the  middle  fibres  into  the  inner  margin  of  the 
acromion  process,  and  into  the  superior  lip. of  the  posterior  border  or  crest  of  the 
spine  of  the  scapula ;  the  inferior  fibres  converge  near  the  scapula,  and  terminate 
in  a  triangular  aponeurosis,  which  glides  over  a  smooth  surface  at  the  inner  extremity 
of  the  spine,  to  be  inserted  into  a  tubercle  at  the  outer  part  of  this  smooth  surface. 
The  Trapezius  is  fleshy  in  the  greater  part  of  its  extent,  but  tendinous  at  its  origin 


FIG.  286.— Dissection  of  the  muscles  of  the 
back. 


OF   THE   BACK. 


429 


FIG.  287.— Muscles  of  the  back.    On  the  left  side  is  exposed  the  first  layer ;  on  the  right  side,  the  second  layer 
and  part  of  the  third. 

and  insertion.    At  its  occipital  origin  it  is  connected  to  the  bone  by  a  thin  fibrous 
lamina,  firmly  adherent  to  the  skin,  and  wanting  the  lustrous,  shining  appearance 


430  THE  MUSCLES  AND   FASCIAE 

of  aponeuroses.  At  its  origin  from  the  spines  of  the  vertebrae  it  is  connected  to 
the  bones  by  means  of  a  broad  semi-elliptical  aponeurosis,  which  occupies  the 
space  between  the  sixth  cervical  and  the  third  dorsal  vertebrae,  and  forms,  with 
the  aponeurosis  of  the  opposite  muscle,  a  tendinous  ellipse.  The  rest  of  the  muscle 
arises  by  numerous  short  tendinous  fibres.  If  the  Trapezius  is  dissected  on  both 
sides,  the  two  muscles  resemble  a  trapezium  or  diamond-shaped  quadrangle ;  two 
angles  corresponding  to  the  shoulders ;  a  third  to  the  occipital  protuberance ; 
and  the  fourth  to  the  spinous  process  of  the  last  dorsal  vertebra. 

The  clavicular  insertion  of  this  muscle  varies  as  to  the  extent  of  its  attach- 
ment ;  it  sometimes  advances  as  far  as  the  middle  of  the  clavicle,  and  may  even 
become  blended  with  the  posterior  edge  of  the  Sterno-mastoid  or  overlap  it.  This 
should  be  borne  in  mind  in  the  operation  for  tying  the  third  part  of  the  subclavian 
artery. 

Relations. — By  its  superficial  surface,  with  the  integument;  by  its  deep 
surface,  in  the  neck,  with  the  Complexus,  Splenius,  Levator  anguli  scapulas,  and 
Rhomboideus  minor ;  in  the  back,  with  the  Rhomboideus  major,  Supraspinatus, 
Infraspinatus,  and  Vertebral  aponeurosis  (which  separates  it  from  the  prolongations- 
of  the  Erector  spinae),  and  the  Latissimus  dorsi.  The  spinal  accessory  nerve  and 
the  superficial  cervical  artery  pass  beneath  the  anterior  border  of  this  muscle, 
near  the  clavicle.  The  anterior  margin  of  its  cervical  portion  forms  the  posterior 
boundary  of  the  posterior  triangle  of  the  neck,  the  other  boundaries  being  the  Sterno- 
mastoid  in  front  and  the  clavicle  below. 

The  Ligamentum  nuchae  (Fig.  287)  is  a  thin  band  of  condensed  cellulo-fibrous- 
membrane  placed  in  the  line  of  union  between  the  two  Trapezii  in  the  neck.  It 
extends  from  the  external  occipital  protuberance  to  the  spinous  process  of  the 
seventh  cervical  vertebra,  where  it  is  continuous  with  the  supraspinous  ligament. 
From  its  anterior  surface  a  fibrous  lamina  is  given  off,  which  is  attached  to  the 
spinous  process  of  each  of  the  cervical  vertebrae,  excepting  the  atlas,  so  as  to  form 
a  septum  between  the  muscles  on  each  side  of  the  neck.  In  man  it  is  merely  the 
rudiment  of  an  important  elastic  ligament  which,  in  some  of  the  lower  animals, 
serves  to  sustain  the  weight  of  the  head. 

The  Latissimus  dorsi  is  a  broad  flat  muscle  which  covers  the  lumbar  and 
the  lower  half  of  the  dorsal  regions,  and  is  gradually  contracted  into  a  narrow 
fasciculus  at  its  insertion  into  the  humerus.  It  arises  by  an  aponeurosis  from  the 
spinous  processes  of  the  six  inferior  dorsal,  from  those  of  the  lumbar  and  sacral 
vertebrae,  and  from  the  supraspinous  ligament.  Over  the  sacrum  the  aponeurosis 
of  this  muscle  blends  with  the  posterior  layer  of  the  lumbar  fascia.  It  also  arises 
from  the  external  lip  of  the  crest  of  the  ilium,  behind  the  origin  of  the  External 
oblique,  and  by  fleshy  digitations  from  the  three  or  four  lower  ribs,  which  are 
interposed  between  similar  processes  of  the  External  oblique  muscle  (Fig.  292, 
page  449).  From  this  extensive  origin  the  fibres  pass  in  different  directions,  the 
upper  ones  horizontally,  the  middle  obliquely  upward,  and  the  lower  vertically 
upward,  so  as  to  converge  and  form  a  thick  fasciculus,  which  crosses  the  inferior 
angle  of  the  scapula,  and  occasionally  receives  a  few  fibres  from  it.  The  muscle 
then  curves  around  the  lower  border  of  the  Teres  major,  and  is  twisted  upon  itself, 
so  that  the  superior  fibres  become  at  first  posterior  and  then  inferior,  and  the 
vertical  fibres  at  first  anterior  and  then  superior.  It  then  terminates  in  a  short 
quadrilateral  tendon,  about  three  inches  in  length,  which,  passing  in  front  of  the 
tendon  of  the  Teres  major,  is  inserted  into  the  bottom  of  the  bicipital  groove  of 
the  humerus,  its  insertion  extending  higher  on  the  humerus  than  that  of  the 
tendon  of  the  Pectoralis  major.  The  lower  border  of  the  tendon  of  this  muscle  is 
united  with  that  of  the  Teres  major,  the  surfaces  of  the  two  being  separated  by  a 
bursa ;  another  bursa  is  sometimes  interposed  between  the  muscle  and  the  inferior 
angle  of  the  scapula.  This  muscle  at  its  insertion  gives  off  an  expansion  to  the 
deep  fascia  of  the  arm. 

A  muscular  slip,  varying  from  3  to  4  inches  in  length,  and  from  \  to  £  of  an  inch  in  breadth, 
occasionally  arises  from  the  upper  edge  of  the  Latissimus  dorsi  about  the  middle  of  the  posterior 


OF   THE  BACK.  431 

fold  of  the  axilla,  and  crosses  the  axilla  in  front  of  the  axillary  vessels  and  nerves,  to  join  the 
under  surface  of  the  tendon  of  the  Pectoralis  major,  the  Cpraco-brachialis,  or  the  fascia  over  the 
Biceps.  The  position  of  this  abnormal  slip  is  a  point  of  interest  in  its  relation  to  the  axillary 
artery,  as  it  crosses  the  vessel  just  above  the  spot  usually  selected  for  the  application  of  a  ligature, 
and  may  mislead  the  surgeon  during  the  operation.  It  may  be  easily  recognized  by  the  transverse 
direction  of  its  fibres.  Dr.  Struther  found  it,  in  8  out  of  105  subjects,  occurring  seven  times  on 
both  sides. 

Relations. — Its  superficial  surface  is  subcutaneous,  excepting  at  its  upper  part, 
where  it  is  covered  by  the  Trapezius,  and  at  its  insertion,  where  its  tendon  is 
crossed  by  the  axillary  vessels  and  the  brachial  plexus  of  nerves.  By  its  deep 
surface  it  is  in  relation  with  the  Lumbar  fascia,  the  Serratus  posticus  inferior,  the 
lower  external  intercostal  muscles  and  ribs,  inferior  angle  of  the  scapula,  Rhom- 
boideus  major,  Infraspinatus,  and  Teres  major.  Its  outer  margin  is  separated 
below  from  the  External  oblique  by  a  small  triangular  interval ;  and  another 
triangular  interval  exists  between  its  upper  border  and  the  margin  of  the  Trapezius, 
in  which  the  Rhomboideus  major  muscle  is  exposed. 

Nerves. — The  Trapezius  is  supplied  by  the  spinal  accessory,  and  by  branches 
from  the  anterior  divisions  of  the  third  and  fourth  cervical  nerves :  the  Latissimus 
dorsi,  by  the  middle  or  long  subscapular  nerve. 

Second  Layer. 

Levator  anguli  scapulae.  Rhomboideus  minor. 

Rhomboideus  major. 

Dissection. — The  Trapezius  must  be  removed,  in  order  to  expose  the  next  layer ;  to  effect 
this,  detach  the  muscle  from  its  attachment  to  the  clavicle  and  spine  of  the  scapula,  and  turn 
it  back  toward  the  spine. 

The  Levator  anguli  scapulae  is  situated  at  the  back  part  and  side  of  the  neck. 
It  arises  by  tendinous  slips  from  the  posterior  tubercles  of  the  transverse  processes 
of  the  four  upper  cervical  vertebrae ;  these,  becoming  fleshy,  are  united  so  as  to 
form  a  flat  muscle,  which,  passing  downward  and  backward,  is  inserted  into  the 
posterior  border  of  the  scapula,  betAveen  the  superior  angle  and  the  triangular 
smooth  surface  at  the  root  of  the  spine. 

Relations. — By  its  superficial  surface,  with  the  integument,  Trapezius,  and 
Sterno-mastoid ;  by  its  deep  surface,  with  the  Splenius  colli,  Transversalis  colli, 
Cervicalis  ascendens,  and  Serratus  posticus  superior  muscles,  and  with  the  trans- 
versalis  colli  and  posterior  scapular  arteries. 

The  Rhomboideus  minor  arises  from  the  ligamentum  nuchae  and  spinous 
processes  of  the  seventh  cervical  and  first  dorsal  vertebrae.  Passing  downward 
and  outward,  it  is  inserted  into  the  margin  of  the  triangular  smooth  surface  at  the 
root  of  the  spine  of  the  scapula.  This  small  muscle  is  usually  separated  from  the 
Rhomboideus  major  by  a  slight  cellular  interval. 

Relations. — By  its  superficial  (posterior)  surface,  with  the  Trapezius ;  by  its 
deep  surface,  with  the  same  structures  as  the  Rhomboideus  major. 

The  Rhomboideus  major  is  situated  immediately  below  the  preceding,  the 
adjacent  margins  of  the  two  being  occasionally  united.  It  arises  by  tendinous 
fibres  from  the  spinous  processes  of  the  four  or  five  upper  dorsal  vertebrae  and  the 
supraspinous  ligament,  and  is  inserted  into  a  narrow  tendinous  arcb  attached 
above  to  the  lower  part  of  the  triangular  surface  at  the  root  of  the  spine ;  below, 
to  the  inferior  angle,  the  arch  being  connected  to  the  border  of  the  scapula  by  a 
thin  membrane.  When  the  arch  extends,  as  it  occasionally  does,  but  a  short 
distance,  the  muscular  fibres  are  inserted  into  the  scapula  itself. 

Relations. — By  its  superficial  (posterior)  surface,  witb  the  Latissimus  dorsi ;  by 
its  deep  (anterior)  surface,  with  the  Serratus  posticus  superior,  posterior  scapular 
artery,  the  vertebral  aponeurosis  which  separates  it  from  the  prolongations  from 
the  Erector  spinae,  the  Intercostal  muscles,  and  ribs. 

Nerves. — The  Rhomboid  muscles  are  supplied  by  branches  from  the  anterior- 


432  THE  MUSCLES  AND   FASCIA 

division  of  the  fifth  cervical  nerve ;  the  Levator  anguli  scapulae,  by  the  anterior 
division  of  the  third  and  fourth  cervical  nerves. 

Actions. — The  movements  effected  by  the  preceding  muscles  are  numerous,  as 
may  be  conceived  from  their  extensive  attachment.  The  whole  of  the  Trapezius 
when  in  action  retracts  the  scapula  and  rotates  it  on  a  sagittal  axis  ;  if  the  head  is 
fixed,  the  upper  part  of  the  Trapezius  will  elevate  the  point  of  the  shoulder,  as  in 
supporting  weights ;  when  the  lower  fibres  are  brought  into  action,  they. assist  in 
depressing  the  bone.  If  the  scapula  is  prevented  from  gliding  on  the  chest,  the 
middle  and  lower  fibres  of  the  muscle  cause  it  to  rotate,  so  that  the  acromion  is 
raised.  If  the  shoulders  are  fixed,  both  Trapezii,  acting  together,  will  draw  the 
head  directly  backward ;  or  if  only  one  acts,  the  head  is  drawn  to  the  corresponding 
side. 

The  Latissimus  dorsi,  when  it  acts  upon  the  humerus,  draws  it  backward, 
adducts,  and  at  the  same  time  rotates  it  inward.  It  is  the  muscle  which  is 
principally  employed  in  giving  a  downward  blow,  as  in  felling  a  tree  or  in  sabre 
practice.  If  the  arm  is  fixed,  the  muscle  may  act  in  various  ways  upon  the  trunk  ; 
thus,  it  may  raise  the  lower  ribs  and  assist  in  forcible  inspiration  ;  or,  if  both  arms 
are  fixed,  the  two  muscles  may  assist  the  Abdominal  and  great  Pectoral  muscles  in 
suspending  and  drawing  the  whole  trunk  forward,  as  in  climbing  or  walking  on 
crutches. 

The  Levator  anguli  scapulce  raises  the  superior  angle  of  the  scapula,  assisting 
the  Trapezius  in  bearing  weights  or  in  shrugging  the  shoulders.  If  the  shoulder 
be  fixed,  the  Levator  anguli  scapulae  inclines  the  neck  to  the  corresponding  side 
and  rotates  it  in  the  same  direction.  The  Rhomboid  muscles  carry  the  inferior 
angle  backward  and  upward,  thus  producing  a  slight  rotation  of  the  scapula  upon 
the  side  of  the  chest,  the  Rhomboideus  major  acting  especially  on  the  lower  angle 
of  the  scapula  through  the  tendinous  arch  by  which  it  is  inserted.  The  Rhomboid 
muscles,  acting  together  with  the  middle  and  inferior  fibres  of  the  Trapezius,  will 
draw  the  scapula  directly  backward  toward  the  spine. 

Third  Layer. 

Scrratus  posticus  superior.  Serratus  posticus  inferior. 

01-      f  Splenius  capitis. 
Splenms^  0^1 

[  feplenms  coin. 

Dissection. — To  bring  into  view  the  third  layer  of  muscles,  remove  the  whole  of  the  second, 
together  with  the  Latissimus  dorsi,  by  cutting  through  the  Levator  anguli  scapulae  and  Rhom- 
boid muscles  near  their  insertion,  and  reflecting  them  upward,  and  by  dividing  the  Latissimus 
dorsi  in  the  middle  by  a  vertical  incision  carried  from  its  upper  to  its  lower  part,  and  reflecting 
the  two  halves  of  the  muscle. 

The  Serratus  posticus  superior  is  a  thin,  flat,  quadrilateral  muscle  situated  at 
the  upper  and  back  part  of  the  thorax.  It  arises  by  a  thin  and  broad  aponeurosis 
from  the  ligamentum  nuchae,  and  from  the  spinous  processes  of  the  last  cervical 
and  two  or  three  upper  dorsal  vertebrae  and  from  the  supraspinous  ligament. 
Inclining  downward  and  outward,  it  becomes  muscular,  and  is  inserted,  by  four 
fleshy  digitations  into  the  upper  borders  of  the  second,  third,  fourth,  and  fifth  ribs, 
a  little  beyond  their  angles. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  Rhomboidei,  and 
Levator  anguli  scapulae ;  by  its  deep  surface,  with  the  Splenius  and  the  vertebral 
aponeurosis,  which  separates  it  from  the  prolongations  of  the  Erector  spinae, 
and  with  the  Intercostal  muscles  and  ribs. 

The  Serratus  posticus  inferior  is  situated  at  the  junction  of  the  dorsal  and  lumbar 
regions ;  it  is  of  an  irregularly  quadrilateral  form,  broader  than  the  preceding, 
and  separated  from  it  by  a  considerable  interval.  It  arises  by  a  thin  aponeurosis 
from  the  spinous  processes  of  the  last  two  dorsal  and  two  or  three  upper  lumbar 
vertebrae,  and  from  the  supraspinous  ligaments.  Passing  obliquely  upward 
and  outward,  it  becomes  fleshy,  and  divides  into  four  flat  digitations,  which  are 
inserted  into  the  lower  borders  of  the  four  lower  ribs,  a  little  beyond  their  angles. 


OF  THE  BACK.  433 

The  thin  aponeurosis  of  origin  is  intimately  blended  with  the  tendon  of  origin  of 
the  Latissimus  dorsi  muscle  and  with  the  lumbar  fascia  (posterior  layer). 

Relations. — By   its   snpern<-ial  surface,    Avith  the  Latissimus   dorsi,  with   the 
aponeurosis  of  which  its  own  aponeurotic   origin  is  inseparably  blended ;  by  its 
surface,  the  Erector  spinoe,  ribs,  and  Intercostal  muscles.     Its  upper  margin 
is  continuous  with  the  vertebral  aponeurosis. 

The  }\'rt>'lrai  apont'iiroxis  is  a  thin,  fibrous  lamina  extending  along  the  whole 
length  of  the  back  part  of  the  thoracic  region,  serving  to  bind  down  the  long 
extensor  muscles  of  the  back  which  support  the  spine  and  head,  and  separate 
them  from  those  muscles  which  connect  the  spine  to  the  upper  extremity.  It  con- 
sists of  longitudinal  and  transverse  fibres  blended  together,  forming  a  thin  lamella, 
which  is  attached  in  the  median  line  to  the  spinous  processes  of  the  dorsal  vertebra; 
externally,  to  the  angles  of  the  ribs ;  and  below,  to  the  aponeurosis  of  the  Serratus 
posticus  inferior  and  tendon  of  origin  of  the  Latissimus  dorsi,  with  both  of  which 
it  is  continuous ;  above,  it  passes  beneath  the  Serratus  posticus  superior,  and 
blends  with  the  deep  fascia  of  the  neck. 

The  Lumbar  fascia  (Figs.  287  and  295)  occupies  the  interval  between  the  last 
rib  and  crest  of  the  ilium.  It  is  attached  internally  to  the  spinous  process  of  the  . 
lumbar  and  sacral  vertebrae ;  above,  to  the  last  rib  and  to  the  cartilage  of  the 
eleventh  rib  ;  below,  to  the  posterior  third  of  the  crest  of  the  ilium.  The  posterior 
layer  of  this  fascia  blends  with,  and  is  practically  the  same  thing  as,  the  aponeu- 
rosis of  the  Latissimus  dorsi  and  Serratus  posticus  inferior.  It  gives  attachment 
to  the  Internal  oblique  muscle  of  the  abdomen.  The  anterior  or  deep  surface 
gives  off  two  layers  :  one  lies  between  the  Erector  spinse  and  Quadratus  lumborum, 
and  is  attached  to  the  tips  of  the  transverse  processes  of  the  lumbar  vertebrae 
(posterior  aponeurosis  of  the  Transversalis  muscle);  the  other  lies  on  the  anterior 
or  internal  surface  of  the  Quadratus  lumborum,  and  is  attached  to  the  front  part 
of  the  same  transverse  processes  (transversalis  fascia).  The  upper  portion  of  this 
layer,  which  extends  from  the  transverse  process  of  the  first  lumbar  vertebra  to 
the  apex  and  lower  border  of  the  last  rib,  constitutes  the  ligamentum  arcuatum 
externum.  Therefore  these  three  layers  of  the  lumbar  fascia  form  two  spaces : 
between  the  posterior  and  middle  layer  is  situated  the  Erector  spinae  and  the 
Multifidus  spinse  ;  between  the  middle  and  anterior  layers  is  situated  the  Quad- 
ratus lumborum. 

Now  detach  the  Serratus  posticus  superior  from  its  origin,  and  turn  it  outward,  when  the 
Splenius  muscle  will  be  brought  into  view. 

The  Splenius  is  situated  at  the  back  of  the  neck  and  upper  part  of  the  dorsal 
region.  At  its  origin  it  is  a  single  muscle,  narrow,  and  pointed  in  form  ;  but  it 
soon  becomes  broader,  and  divides  into  two  portions,  which  have  separate  inser- 
tions. It  arises,  by  tendinous  fibres,  from  the  lower  half  of  the  ligamentum  nuchae, 
from  the  spinous  processes  of  the  last  cervical  and  of  the  six  upper  dorsal  vertebrae, 
and  from  the  supraspinous  ligament.  From  this  origin  the  fleshy  fibres  proceed 
obliquely  upward  and  outward,  forming  a  broad  flat  muscle,  which  divides  as  it 
ascends  into  two  portions,  the  Splenius  capitis  and  Splenius  colli. 

The  Splenius  capitis  is  inserted  into  the  mastoid  process  of  the  temporal  bone, 
and  into  the  rough  surface  on  the  occipital  bone  just  beneath  the  superior  curved 
line. 

The  Splenius  colli  is  inserted,  by  tendinous  fasciculi,  into  the  posterior  tubercles 
of  the  transverse  processes  of  the  two  or  three  upper  cervical  vertebrae. 

The  Splenius  is  separated  from  its  fellow  of  the  opposite  side  by  a  triangular 
interval,  in  which  is  seen  the  Complexus. 

Relations. — By  its  superficial  s;trface,  with  the  Trapezius,  from  which  it  is 
separated  below  by  the  Rhomboidei  and  the  Serratus  posticus  superior.  It  is 
covered  at  its  insertion  by  the  Sterno-mastoid,  and  at  the  lower  and  back  part  of 
the  neck  by  the  Levator  anguli  scapulae :  by  its  deep  surface,  with  the  Spinalis 
dorsi,  Longissimus  dorsi,  Semispinalis  colli,  Complexus,  Trachelo-mastoid,  and 
Transversalis  colli. 

28 


434  THE  MUSCLES   AND   FASCIAE 

Nerves. — The  Splenius  is  supplied  from  the  external  branches  of  the  posterior 
divisions  of  the  cervical  nerves ;  the  Serratus  posticus  superior  is  supplied  by  the 
external  branches  of  the  posterior  divisions  of  the  upper  dorsal  nerves  ;  the  Serratus 
posticus  inferior  by  the  external  branches  of  the  posterior  divisions  of  the  lower 
dorsal  nerves. 

Actions. — The  Serrati  are  respiratory  muscles.  The  Serratus  posticus  supe- 
rior elevates  the  ribs ;  it  is  therefore  an  inspiratory  muscle ;  while  the  Serratus 
inferior  draws  the  lower  ribs  downward  and  backward,  and  thus  elongates  the 
thorax.  It  also  fixes  the  lower  ribs,  thus  aiding  the  downward  action  of  the 
diaphragm  and  resisting  the  tendency  which  it  has  to  draw  the  lower  ribs  upward 
and  forward.  It  must  therefore  be  regarded  as  a  muscle  of  inspiration.  This  muscle 
is  also  probably  a  tensor  of  the  vertebral  aponeurosis.  The  Splenii  muscles  of  the 
two  sides,  acting  together,  draw  the  head  directly  backward,  assisting  the  Trapezius 
and  Complexus  ;  acting  separately,  they  draw  the  head  to  one  or  the  other  side,  and 
slightly  rotate  it,  turning  the  face  to  the  same  side.  They  also  assist  in  supporting 
the  head  in  the  erect  position. 

Fourth  Layer. 

Sacral  and  Lumbar  Regions.  Cervical  Region. 

Erector  spinse.  Cervicalis  ascendens. 

Dorsal  Region.  Transversalis  colli. 

Ilio-costalis.  Trachelo-mastoid. 

Musculus  accessorius  ad  ilio-costalem.  Complexus. 

Longissimus  dorsi.  Biventer  cervicis. 

Spinalis  dorsi.  Spinalis  colli. 

Dissection. — To  expose  the  muscles  of  the  fourth  layer,  remove  entirely  the  Serrati  and  the 
vertebral  and  lumbar  fasciae.  Then  detach  the  Splenius  by  separating  its  attachment  to  the 
spinous  processes  and  reflecting  it  outward. 

The  Erector  spinae  (Fig.  288)  and  its  prolongations  in  the  dorsal  and  cervical 
regions  fill  up  the  vertebral  groove  on  each  side  of  the  spine.  It  is  covered  in 
the  lumbar  region  by  the  lumbar  fascia ;  in  the  dorsal  region,  by  the  Serrati 
muscles  and  the  vertebral  aponeurosis ;  and  in  the  cervical  region,  by  a  layer  of 
cervical  fascia  continued  beneath  the  Trapezius  and  the  Splenius.  This  large 
muscular  and  tendinous  mass  varies  in  size  and  structure  at  different  parts  of  the 
spine.  In  the  sacral  region  the  Erector  spinse  is  narrow  and  pointed,  and  its  origin 
chiefly  tendinous  in  structure.  In  the  lumbar  region  the  muscle  becomes  enlarged, 
and  forms  a  large  fleshy  mass.  In  the  dorsal  region  it  subdivides  into  two  parts, 
which  gradually  diminish  in  size  as  they  ascend  to  be  inserted  into  the  vertebrae 
and  ribs.  In  the  cervical  region  it  is  gradually  lost,  where  a  number  of  small  muscles 
are  continued  upward  to  the  head  to  support  it  upon  the  spine. 

The  Erector  spinae  arises  from  the  sacro-iliac  groove,  and  from  the  anterior 
surface  of  a  very  broad  and  thick  tendon,  which  is  attached,  internally,  to  the 
spines  of  the  sacrum,  to  the  spinous  processes  of  the  lumbar  vertebrae,  and  the 
supraspinous  ligament ;  externally,  to  the  back  part  of  the  inner  lip  of  the  crest  of 
the  ilium,  and  to  the  series  of  eminences  on  the  posterior  part  of  the  sacrum, 
which  represents  the  transverse  processes,  where  it  blends  with  the  great  sacro- 
sciatic  ligament.  The  muscular  fibres  form  a  single  large  fleshy  mass,  bounded  in 
front  by  the  transverse  processes  of  the  lumbar  vertebrae  and  by  the  middle  lamella 
of  the  lumbar  fascia.  Opposite  the  last  rib  it  divides  into  two  parts,  the  Ilio- 
costalis  and  the  Longissimus  dorsi. 

The  Ilio-costalis  (Sacro-lumbalis),  the  external  and  smaller  portion  of  the 
Erector  spinae,  is  inserted,  generally,  by  six  or  seven  flattened  tendons  into  the 
angles  of  the  six  or  seven  lower  ribs.  The  number  of  the  tendons  of  this  muscle 
is,  however,  very  variable,  and  therefore  the  number  of  ribs  into  which  it  is 
inserted.  Frequently  it  is  found  to  possess  nine  or  ten  tendons,  and  sometimes  as 
many  tendons  as  there  are  ribs,  and  is  then  inserted  into  the  angles  of  all  the  ribs. 


OF   THE  BACK. 

Occipital  bone. 


435 


MULT1FIDUS    SPIN 


First  dorsal  vertebra 


First  lumbar  vertebra. 


First  sacral  vertebra 


FIG.  288.— Muscles  of  the  back.    Deep  layers. 

If  this  muscle  is  reflected  outward,  it  will  be  seen  to  be  reinforced  by  a  series  of 
muscular  slips  which  arise  from  the  angles  of  the  ribs ;  by  means  of  these  the  Ilio- 


433  THE   MUSCLES  AND   FASCIA 

costalis  is  continued  upward  to  the  upper  ribs  and  cervical  portion  of  the  spine. 
The  accessory  portions  form  two  additional  muscles,  the  Musculus  accessorius  and 
the  Cervicalis  ascendens. 

The  Musculus  accessorius  ad  ilio-costalem  arises,  by  separate  flattened  tendons, 
from  the  angles  of  the  six  lower  ribs ;  these  become  muscular,  and  are  finally 
inserted,  by  separate  tendons,  into  the  angles  of  the  six  upper  ribs. 

The  Cervicalis  ascendens1  is  the  continuation  of  the  Accessorius  upward  into 
the  neck  ;  it  is  situated  on  the  inner  side  of  the  tendons  of  the  Accessorius,  arising 
from  the  angles  of  the  four  or  five  upper  ribs,  and  is  inserted  by  a  series  of  slender 
tendons  into  the  posterior  tubercles  of  the  transverse  processes  of  the  fourth,  fifth, 
and  sixth  cervical  vertebrae. 

The  Longissimus  dorsi  is  the  inner  and  larger  portion  of  the  Erector  spinae. 
In  the  lumbar  region,  where  it  is  as  yet  blended  with  the  Ilio-costalis,  some  of  the 
fibres  are  attached  to  the  whole  length  of  the  posterior  surface  of  the  transverse 
processes  of  the  lumbar  vertebrae,  to  the  tubercles  at  the  back  of  the  articular 
processes,  and  to  the  middle  layer  of  the  lumbar  fascia.  In  the  dorsal  region  the 
Longissimus  dorsi  is  inserted,  by  long  thin  tendons,  into  the  tips  of  the  transverse 
processes  of  all  the  dorsal  vertebrae,  and  into  from  seven  to  eleven  of  the  lower 
ribs  between  their  tubercles  and  angles.  This  muscle  is  continued  upward,  to  the 
cranium  and  cervical  portion  of  the  spine  by  means  of  two  additional  muscles,  the 
Transversalis  colli  and  Trachelo-mastoid. 

The  Transversalis  colli  (or  cervicis),  placed  on  the  inner  side  of  the  Longis- 
simus dorsi,  arises  by  long  thin  tendons  from  the  summits  of  the 'transverse  pro- 
cesses of  the  six  upper  dorsal  vertebrae,  and  is  inserted  by  similar  tendons  into 
the  posterior  tubercles  of  the  transverse  processes  of  the  cervical  vertebrae  from 
the  second  to  the  sixth. 

The  Trachelo-mastoid  lies  on  the  inner  side  of  the  preceding,  between  it  and  the 
Complexus  muscle.  It  arises,  by  four  tendons,  from  the  transverse  processes  of 
the  third,  fourth,  fifth,  and  sixth  dorsal  vertebrae,  and  by  additional  separate 
tendons  from  the  articular  processes  of  the  three  or  four  lower  cervical.  The  fibres 
form  a  small  muscle,  which  ascends  to  be  inserted  into  the  posterior  margin  of 
the  mastoid  process,  beneath  the  Splenius  and  Sterno-mastoid  muscles.  This 
small  muscle  is  almost  always  crossed  by  a  tendinous  intersection  near  its  insertion 
into  the  mastoid  process.2 

Relations. — The  Erector  spinae  and  its  prolongations  are  bound  down  to  the 
vertebrae  and  ribs  in  the  lumbar  and  dorsal  regions  by  the  lumbar  fascia  and  the 
vertebral  aponeurosis.  The  inner  part  of  these  muscles  covers  the  muscles  of  the 
fifth  layer.  In  the  neck  they  are  in  relation,  by  their  superficial  surface,  with  the 
Trapezius  and  Splenius ;  by  their  deep  surface,  with  the  Semispinalis  dorsi  et  colli 
and  the  Recti  and  Obliqui. 

The  Spinalis  dorsi  connects  the  spinous  processes  of  the  upper  lumbar  and  the 
dorsal  vertebrae  together  by  a  series  of  muscular  and  tendinous  slips  which  are 
intimately  blended  with  the  Longissimus  dorsi.  It  is  situated  at  the  inner  side  of 
the  Longissimus  dorsi,  arising,  by  three  or  four  tendons,  from  the  spinous  pro- 
cesses of  the  first  two  lumbar  and  the  last  two  dorsal  vertebrae :  these,  uniting, 
form  a  small  muscle,  which  is  inserted,  by  separate  tendons,  into  the  spinous  pro- 
cesses of  the  dorsal  vertebrae,  the  number  varying  from  four  to  eight.  It  is ' 
intimately  united  with  the  Semispinalis  dorsi,  which  lies  beneath  it. 

The  Spinalis  colli  is  a  small  muscle,  connecting  together  the  spinous  processes 
of  the  cervical  vertebrae,  and  analogous  to  the  Spinalis  dorsi  in  the  dorsal  region. 
It  varies  considerably  in  its  size  and  in  its  extent  of  attachment  to  the  vertebrae, 
not  only  in  different  bodies,  but  on  the  two  sides  of  the  same  body.  It  usually 
arises  by  fleshy  or  tendinous  slips,  varying  from  two  to  four  in  number,  from  the 

1  This  muscle  is  sometimes  called   "  Cervicaiis  uescendens."     The   student   should    remember 
that  these  long  muscles  take  their  fixed  point  from  above  or  from  below  according  to  circumstances. 

2  These  two  muscles  are  sometimes  described  as  one,  having  a  common  origin,  but  dividing  above 
at  their  insertion.     The  Trachelo-mastoid  is  then  termed  the  Transversalis  capitis. 


OF    THE  BACK.  437 

spinous  processes  of  the  fifth,  sixth,  and  seventh  cervical  vertebrae,  and  occasionally 
from  the  first  and  second  dorsal,  and  is  inserted  into  the  spinous  process  of  the 
axis,  and  occasionally  into  the  spinous  processes  of  the  two  vertebrae  below  it. 
This  muscle  was  found  absent  in  five  cases  out  of  twenty-four. 

The  Complexus  is  a  broad  thick  muscle,  situated  at  the  upper  and  back  part  of 
the  neck,  beneath  the  Splenius,  and  internal  to  the  Transversalis  colli  and  Trachelo- 
mastoid.  It  arises,  by  a  series  of  tendons,  about  seven  in  number,  from  the  tips 
of  the  transverse  processes  of  the  upper  three  dorsal  and  seventh  cervical  vertebrae, 
and  from  the  articular  processes  of  the  three  cervical  above  this.  The  tendons, 
uniting,  form  a  broad  muscle,  which  passes  obliquely  upward  and  inward,  and 
is  inserted  into  the  innermost  depression  between  the  two  curved  lines  of  the 
occipital  bone.  This  muscle,  about  its  middle,  is  traversed  by  a  transverse  tendi- 
nous intersection. 

The  Biventer  cervicis  is  a  small  fasciculus,  situated  on  the  inner  side  of  the 
preceding,  and  in  the  majority  of  cases  blended  with  it  ;  it  has  received  its  name 
from  having  a  tendon  intervening  between  two  fleshy  bellies.  It  is  sometimes 
described  as  a  separate  muscle,  arising,  by  from  two  to  four  tendinous  slips,  from 
the  transverse  processes  of  as  many  of  the  upper  dorsal  vertebrae,  and  inserted, 
on  the  inner  side  of  the  Complexus,  into  the  superior  curved  line  of  the  occipital 
bone. 

Relations.  —  The  Complexus  is  covered  by  the  Splenius  and  the  Trapezius.  It 
lies  on  the  Rectus  capitis  posticus  major  and  minor,  the  Obliquus  capitis  superior 
and  inferior,  and  on  the  Semispinalis  colli,  from  which  it  is  separated  by  the  pro- 
funda  cervicis  artery,  the  princeps  cervicis  artery,  and  branches  of  the  posterior 
cervical  plexus  of  nerves.  The  Biventer  cervicis  is  separated  from  its  fellow  of 
the  opposite  side  by  the  ligamentum  nuchae. 

Nerves.  —  The  Erector  spinae  and  its  subdivisions  in  the  dorsal  region  are 
supplied  by  the  external  branches  of  the  posterior  divisions  of  the  lumbar  and 
dorsal  nerves,  while  its  subdivisions  in  the  cervical  region,  the  Transversalis  colli 
and  Trachelo-mastoid,  are  supplied  by  the  external  branches  of  the  posterior 
divisions  of  the  cervical  nerves  ;  the  Complexus,  by  the  internal  branches  of  the 
posterior  divisions  of  the  cervical  nerves,  the  suboccipital  and  great  occipital. 
The  Spinalis  colli  is  supplied  by  the  internal  branches  of  the  posterior  divisions 
of  the  cervical  nerves  ;  and  the  Spinalis  dorsi,  by  the  internal  branches  of  the  pos- 
terior divisions  of  the  dorsal  nerves. 

Fifth  Layer. 

Semispinalis  dorsi.  Extensor  coccygis. 

Semispinalis  colli.  Intertransversales. 

Multifidus  spinae.  Rectus  capitis  posticus  major. 

Rotatores  spinae.  Rectus  capitis  posticus  minor. 

Supraspinales.  Obliquus  capitis  superior. 

Interspinales.  Obliquus  capitis  inferior. 

Dissection.  —  Remove  the  muscles  of  the  preceding  layer  by  dividing  and  turning  aside  the 
Complexus  ;  then  detach  the  Spinalis  and  Longissimus  dorsi  from  their  attachments,  divide  the 
Erector  spinae  at  its  connection  below  to  the  sacral  and  lumbar  spines,  and  turn  it  outward. 
The  muscles  filling  up  the  interval  between  the  spinous  and  transverse  processes  are  then 


The  Semispinalis  dorsi  (Fig.  288)  consists  of  thin,  narrow,  fleshy  fasciculi 
interposed  between  tendons  of  considerable  length.  It  arises  by  a  series  of  small 
tendons  from  the  transverse  processes  of  the  lower  dorsal  vertebrae,  from  the 
tenth  or  eleventh  to  the  fifth  or  sixth  ;  and  is  inserted,  by  five  or  six  tendons, 
into  the  spinous  processes  of  the  upper  four  dorsal  and  lower  two  cervical  vertebrae. 

The  Semispinalis  colli,  thicker  than  the  preceding,  arises  by  a  series  of  tendinous 
and  fleshy  fibres  from  the  transverse  processes  of  the  upper  four  dorsal  vertebrae 
and  from  the  articular  processes  of  the  lower  four  cervical  vertebrae  ;  and  is 
inserted  into  the  spinous  processes  of  four  cervical  vertebrae,  from  the  axis  to  the 


438  THE  MUSCLES  AND   FASCIA 

fifth  cervical.  The  fasciculus  connected  with  the  axis  is  the  largest,  and  chiefly 
muscular  in  structure. 

Relations. — By  their  superficial  surface,  from  below  upward,  with  the  Spinalis 
dorsi,  Longissimus  dorsi,  Splenius,  Complexus,  the  profunda  cervicis  artery,  the 
princeps  cervicis  artery,  and  the  internal  branches  of  the  posterior  divisions  of 
the  first,  second,  and  third  cervical  nerves  ;  by  their  deep  surface,  with  the  Mul- 
tifidus  spinae. 

The  Multifidus  spinse  consists  of  a  number  of  fleshy  and  tendinous  fasciculi 
which  fill  up  the  groove  on  either  side  of  the  spinous  processes  of  the  vertebrae, 
from  the  sacrum  to  the  axis.  In  the  sacral  region  these  fasciculi  arise  from  the 
back  of  the  sacrum,  as  low  as  the  fourth  sacral  foramen,  and  from  the  aponeurosis 
of  origin  of  the  Erector  spinae ;  in  the  iliac  region,  from  the  inner  surface  of  the 
posterior  superior  spine  of  the  ilium  and  posterior  sacro-iliac  ligaments  ;  in  the  lum- 
bar regions,  from  the  articular  processes ;  in  the  dorsal  region,  from  the  trans- 
verse processes  ;  and  in  the  cervical  region,  from  the  articular  processes.  Each 
fasciculus,  passing  obliquely  upward  and  inward,  is  inserted  into  the  lamina  and 
whole  length  of  the  spinous  process  of  one  of  the  vertebrae  above.  These  fasciculi 
vary  in  length  :  the  most  superficial,  the  longest,  pass  from  one  vertebra  to  the 
third  or  fourth  above  ;  those  next  in  order  pass  from  one  vertebra  to  the  second  or 
third  above ;  whilst  the  deepest  connect  two  contiguous  vertebras. 

Relations. — By  its  superficial  surface,  with  the  Longissimus  dorsi,  Spinalis 
dorsi,  Semispinalis  dorsi,  and  Semispinalis  colli ;  by  its  deep  surface,  with  the 
laminae  and  spinous  processes  of  the  vertebrae,  and  with  the  Rotatores  spinae  in 
the  dorsal  region. 

The  Rotatores  spinse  are  found  only  in  the  dorsal  region  of  the  spine,  beneath 
the  Multifidus  spinae ;  they  are  eleven  in  number  on  each  side.  Each  muscle 
is  small  and  somewhat  quadrilateral  in  form ;  it  arises  from  the  upper  and  back 
part  of  the  transverse  process,  and  is  inserted  into  the  lower  border  and  outer 
surface  of  the  lamina  of  the  vertebra  above,  the  fibres  extending  as  far  inward  as 
the  root  of  the  spinous  process.  The  first  is  found  between  the  first  and  second 
dorsal ;  the  last,  between  the  eleventh  and  twelfth.  Sometimes  the  number  of 
these  muscles  is  diminished  by  the  absence  of  one  or  more  from  the  upper  or  lower 
end. 

The  Supraspinales  consist  of  a  series  of  fleshy  bands  which  lie  on  the  spinous 
processes  in  the  cervical  region  of  the  spine. 

The  Interspinales  are  short  muscular  fasciculi,  placed  in  pairs  between  the 
spinous  processes  of  the  contiguous  vertebrae,  one  on  each  side  of  the  interspinous 
ligament.  In  the  cervical  region  they  are  most  distinct,  and  consist  of  six  pairs, 
the  first  being  situated  between  the  axis  and  third  vertebra,  and  the  last  between 
the  last  cervical  and  the  first  dorsal.  They  are  small  narrow  bundles,  attached, 
above  and  'below,  to  the  apices  of  the  spinous  processes.  In  the  dorsal  region 
they  are  found  between  the  first  and  second  vertebrae,  and  occasionally  between 
the  second  and  third ;  and  below,  between  the  eleventh  and  twelfth.  In  the 
lumbar  region  there  are  four  pairs  of  these  muscles  in  the  intervals  between  the 
five  lumbar  vertebrae.  There  is  also  occasionally  one  in  the  interspinous  space, 
between  the  last  dorsal  and  first  lumbar,  and  between  the  fifth  lumbar  and  the 
sacrum. 

The  Extensor  coccygis  is  a  slender  muscular  fasciculus,  occasionally  present, 
which  extends  over  the  lower  part  of  the  posterior  surface  of  the  sacrum  and 
coccyx.  It  arises  by  tendinous  fibres  from  "the  last  bone  of  the  sacrum  or  first 
piece  of  the  coccyx,  and  passes  downward  to  be  inserted  into  the  lower  part  of 
the  coccyx.  It  is  a  rudiment  of  the  Extensor  muscle  of  the  caudal  vertebrae 
which  exists  in  some  animals. 

The  Intertransversales  are  small  muscles  placed  between  the  transverse  pro- 
cesses of  the  vertebrae.  In  the  cervical  region  they  are  most  developed,  consisting 
of  rounded  muscular  and  tendinous  fasciculi,  which  are  placed  in  pairs,  passing 
between  the  two  anterior  and  the  two  posterior  tubercles  of  the  transverse  processes 


OF    THE    BAfK.  439 

of  two  contiguous  vertebrae,  separated  from  one  another  by  the  anterior  division  of 
the  cervical  nerve,  which  lies  in  the  groove  between  them.  In  this  region  there 
are  seven  pairs  of  these  muscles,  the  first  pair  being  between  the  atlas  and  axis, 
and  the  last  pair  between  the  seventh  cervical  and  first  dorsal  vertebrae.  In  the 
il  f>-'/io/i  they  are  least  developed,  consisting  chiefly  of  rounded  tendinous 
cords  in  the  intertransverse  spaces  of  the  upper  dorsal  vertebrae ;  but  between  the 
transverse  processes  of  the  lower  three  dorsal  vertebrae,  and  between  the  transverse 
processes  of  the  last  dorsal  and  the  first  lumbar,  they  are  muscular  in  structure. 
In  the  lumbar  region  they  are  four  in  number,  and  consist  of  a  single  muscular 
layer,  which  occupies  the  entire  interspace  between  the  transverse  processes  of  the 
lower  lumbar  vertebrae,  whilst  those  between  the  transverse  processes  of  the  upper 
lumbar  are  not  attached  to  more  than  half  the  breadth  of  the  process. 

The  Rectus  capitis  posticus  major  arises  by  a  pointed  tendinous  origin  from  the 
spinous  process  of  the  axis,  and,  becoming  broader  as  it  ascends,  is  inserted  into 
the  inferior  curved  line  of  the  occipital  bone  and  the  surface  of  bone  immediately 
below  it.  As  the  muscles  of  the  two  sides  pass  upward  and  outward,  they  leave 
between  them  a  triangular  space,  in  which  are  seen  the  Recti  capitis  postici 
min ores  muscles. 

Relations — By  its  superficial  surface,  with  the  Complexus.  and,  at  its  inser- 
tion, with  the  Superior  oblique  :  by  its  deep  surface,  with  part  of  the  Rectus  capitis 
p«>stictis  minor,  the  posterior  arch  of  the  atlas,  the  posterior  occipito-atlantal  liga- 
ment, and  part  of  the  occipital  bone. 

The  Rectus  capitis  posticus  minor,  the  smallest  of  the  four  muscles  in  this 
region,  is  of  a  triangular  shape  :  it  arises  by  a  narrow  pointed  tendon  from  the 
tubercle  on  the  posterior  arch  of  the  atlas,  and,  becoming  broader  as  it  ascends,  is 
inserted  into  the  rough  surface  beneath  the  inferior  curved  line,  nearly  as  far  as 
the  foramen  magnum,  nearer  to  the  middle  line  than  the  preceding. 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  the  Rectus 
capitis  posticus  major;  b\  its  deep  surface,  with  the  posterior  occipito-atlantal 
ligament. 

The  Obliquus  capitis  inferior,  the  larger  of  the  two  Oblique  muscles,  arises 
from  the  apex  of  the  spinous  process  of  the  axis,  and  passes  almost  horizontally 
outward,  to  be  inserted  into  the  lower  and  back  part  of  the  transverse  process  of 
the  atlas. 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  with  the  pos- 
terior division  of  the  second  cervical  nerve,  which  crosses  it ;  by  its  deep  surface, 
with  the  vertebral  arterv  and  posterior  atlanto-axial  ligament. 

The  Obliquus  capitis  superior,  narrow  below,  wide  and  expanded  above,  arises 
by  tendinous  fibres  from  the  upper  surface  of  the  transverse  process  of  the  atlas, 
joining  with  the  insertion  of  the  preceding,  and.  passing  obliquely  upward  and 
inward,  is  inserted  into  the  occipital  bone,  between  the  two  curved  lines,  external 
to  the  Complexus. 

Relations. — By  its  superficial  surface,  with  the  Com  plexus  and  Trachelo-mastoid. 
By  its  deep  surface,  with  the  posterior  occipito-atlantal  ligament. 

The  Suboccipital  Triangle. — Between  the  two  oblique  muscles  and  the  Rectus 
capitis  posticus  major  a  triangular  interval  exists,  the  suboccipital  triangle.  This 
triangle  is  bounded,  above  and  internally,  by  the  Rectus  capitis  posticus  major; 
above  and  externally,  by  the  Obliquus  capitis  superior ;  below  and  externally,  by  the 
Obliquus  capitis  inferior.  It  is  covered  in  by  a  layer  of  dense  fibro-fatty  tissue, 
situated  beneath  the  Complexus  muscle.  The  floor  is  formed  by  the  posterior 
occipito-atlantal  ligament,  the  posterior  arch  of  the  atlas,  and  the  posterior  atlanto- 
axial  ligament.  It  contains  the  vertebral  artery,  as  it  runs  in  a  deep  groove  on  the 
upper  surface  of  the  posterior  arch  of  the  atlas,  and  the  posterior  division  of  the 
suboccipital  nerve. 

Nerves. — The  Semispinalis  dorsi  and  Rotatores  spinae  are  supplied  by  the 
internal  branches  of  the  posterior  divisions  of  the  dorsal  nerves ;  the  Semispinalis 
colli,  by  the  internal  branches  of  the  posterior  divisions  of  the  cervical  nerves :  the 


440  THE   MUSCLES  AND    FASCIA. 

Supraspinalesandlnterspinales  are  supplied  by  the  internal  branches  of  the  posterior 
divisions  of  the  cervical,  dorsal,  and  lumbar  nerves  in  the  respective  regions ;  the 
Intertransversales,  by  the  internal  branches  of  the  posterior  divisions  of  the  cervical, 
dorsal,  and  lumbar  nerves ;  the  Multifidus  spinge,  by  the  same,  with  the  addition 
of  the  internal  branches  of  the  posterior  divisions  of  the  sacral  nerves.  The  Recti 
and  Obliqui  muscles  are  all  supplied  by  the  suboccipital  nerve  ;  the  Inferior  oblique 
is  also  supplied  by  the  great  occipital  nerve. 

Actions. — When  both  the  Spinales  dorsi  contract,  they  extend  the  dorsal 
region  of  the  spine ;  Avhen  only  one  muscle  contracts,  it  helps  to  bend  the  dorsal 
portion  of  the  spine  to  one  side.  The  Erector  spinge,  comprising  the  Ilio-costalis 
and  the  Longissimus  dorsi  with  their  accessory  muscles,  serves,  as  its  name  implies, 
to  maintain  the  spine  in  the  erect  posture ;  it  also  serves  to  bend  the  trunk  back- 
ward when  it  is  required  to  counterbalance  the  influence  of  any  weight  at  the 
front  of  the  body,  as,  for  instance,  when  a  heavy  weight  is  suspended  from  the 
neck,  or  when  there  is  any  great  abdominal  distension,  as  in  pregnancy  or  dropsy  ; 
the  peculiar  gait  under  such  circumstances  depends  upon  the  spine  being  drawn 
backward  by  the  counterbalancing  action  of  the  Erector  spinge  muscles.  The 
muscles  which  form  the  continuation  of  the  Erector  spinge  upward  steady  the 
head  and  neck,  and  fix  them  in  the  upright  position.  If  the  Ilio-costalis  and 
Longissimus  dorsi  of  one  side  act,  they  serve  to  draw  down  the  chest  and  spine  to 
the  corresponding  side.  The  Cervicales  ascendens,  taking  their  fixed  points  from 
the  cervical  vertebras,  elevate  those  ribs  to  which  they  are  attached ;  taking  their  fixed 
points  from  the  ribs,  both  muscles  help  to  extend  the  neck  ;  while  one  muscle 
bends  the  neck  to  its  own  side.  The  Transversalis  colli,.  when  both  muscles  act, 
taking  their  fixed  point  from  below,  bend  the  neck  backward.  The  Trachelo- 
mastoid,  when  both  muscles  act,  taking  their  fixed  point  from  below,  bend  the  head 
backward ;  while,  if  only  one  muscle  acts,  the  face  is  turned  to  the  side  on  which 
the  muscle  is  acting,  and  then  the  head  is  bent  to  the  shoulder.  The  two  Recti 
muscles  draw  the  head  backward.  The  Rectus  capitis  posticus  major,  owing  to 
its  obliquity,  rotates  the  cranium,  with  the  atlas,  round  the  odontoid  process, 
turning  the  face  to  the  same  side.  The  Multifidus  spinge  acts  successively  upon  the 
different  parts  of  the  spine ;  thus,  the  sacrum  furnishes  a  fixed  point  from  which 
the  fasciculi  of  this  muscle  act  upon  the  lumbar  region ;  these  then  become  the 
fixed  points  for  the  fasciculi  moving  the  dorsal  region,  and  so  on  throughout  the 
entire  length  of  the  spine;  it  is  by  the  successive  contraction  and  relaxation  of 
the  separate  fasciculi  of  this  and  other  muscles  that  the  spine  preserves  the  erect 
posture  without  the  fatigue  that  would  necessarily  have  been  produced  had  this 
position  been  maintained  by  the  action  of  a  single  muscle.  The  Multifidus  spinge, 
besides  preserving  the  erect  position  of  the  spine,  serves  to  rotate  it,  so  that  the 
front  of  the  trunk  is  turned  to  the  side  opposite  to  that  from  which  the  muscle 
acts,  this  muscle  being  assisted  in  its  action  by  the  Obliquus  externus  abdominis. 
The  Complexi  draw  the  head  directly  backward  :  if  one  muscle  acts,  it  draws 
the  head  to  one  side,  and  rotates  it  so  that  the  face  is  turned  to  the  opposite 
side.  The  Superior  oblique  draws  the  head  backward,  and,  from  the  obliquity 
in  the  direction  of  its  fibres,  will  slightly  rotate  the  cranium,  turning  the  face  to 
the  opposite  side.  The  Obliquus  capitis  inferior  rotates  the  atlas,  and  with  it  the 
cranium,  round  the  odontoid  process,  turning  the  face  to  the  same  side.  The 
Semispinales,  when  the  muscles  of  the  two  sides  act  together,  help  to  extend  the 
spine  ;  when  the  muscles  of  one  side  only  act,  they  rotate  the  dorsal  and  cervical 
parts  of  the  spine,  turning  the  body  to  the  opposite  side.  The  Supraspinales  and 
Interspinales  by  approximating  the  spinous  processes  help  to  extend  the  spine. 
The  Intertransversales  approximate  the  transverse  processes,  and  help  to  bend  the 
spine  to  one  side.  The  Rotatores  spinge  assist  the  Multifidus  spinge  to  rotate  the 
spine,  so  that  the  front  of  the  trunk  is  turned  to  the  side  opposite  to  that  from 
which  the  muscle  acts. 

Surface  Forms. — The  surface  forms  produced  by  the  muscles  of  the  back  are  numerous  and 
difficult  to  analyze  unless  they  are  considered  in  systematic  order.  The  most  superficial  layer, 


OF    THE    THORAX.  441 

consisting  of  large  strata  of  muscular  substance,  influences  to  a  certain  extent  the  surface  form, 
and  at  the  same  time  reveals  the  forms  of  the  layers  beneath.  The  Trapezius  at  the  upper  part 
of  the  back,  and  in  the  neck,  covers  over  and  softens  down  the  outline  of  the  underlying  muscles. 
Its  anterior  border  forms  the  posterior  boundary  of  the  posterior  triangle  of  the  neck.  It  forms 
a  slight  undulating  ridge  which  passes  downward  and  forward  from  the  occiput  to  the  junction 
of  the  middle  and  outer  third  <jf  the  clavicle.  The  tendinous  ellipse  formed  by  a  part  of  the 
origin  of  the  two  muscles  at  the  back  of  the  neck  is  always  to  be  seen  as  an  oval  depression, 
more  marked  when  the  muscle  is  in  action.  A  slight  dimple  on  the  skin  opposite  the  interval 
between  the  spinous  processes  of  the  third  and  fourth  dorsal  vertebrae  marks  the  triangular 
aponeurosis  by  which  the  inferior  fibres  are  inserted  into  the  root  of  the  spine  of  the  scapula. 
From  this  point  the  inferior  border  of  the  muscle  may  be  traced  as  an  undulating  ridge  to  the 
spinous  pro -ess  of  the  twelfth  dorsal  vertebra.  In  like  manner,  the  Latissimus  dorsi  softens 
down  and  modulates  the  underlying  structures  at  the  lower  part  of  the  back  and  lower  part  of 
the  side  of  the  chest.  In  this  way  it  modulates  the  outline  of  the  Erector  spinse ;  of  the  Serratus 
posticus  inferior,  which  is  sometimes  to  be  discerned  through  it,  and  is  sometimes  entirely 
obscured  by  it :  of  part  of  the  Serratus  magnus  and  Superior  oblique,  which  it  covers  ;  and  of 
the  convex  oblique  ridges  formed  by  the  ribs  with  the  intervening  intercostal  spaces.  The 
anterior  border  of  the  muscle  is  the  only  part  which  gives  a  distinct  surface  form.  This  border 
may  be  traced,  when  the  muscle  is  in  action,  as  a  rounded  edge,  starting  from  the  crest  of  the 
ilium,  and  passing  obliquely  forward  and  upward  to  the  posterior  border  of  the  axilla,  where  it 
combines  with  the  Teres  major  in  forming  a  thick  rounded  fold,  the  posterior  boundary  of  the 
axillary  space.  The  muscles  in  the  second  layer  influence  to  a  very  considerable  extent  the  surface 
form  of  the  back  of  the  neck  and  upper  part  of  the  trunk.  The  Levator  anguli  scapulae  reveals 
itself  as  a  prominent  divergent  line,  running  downward  and  outward,  from  the  transverse  pro- 
cesses of  the  upper  cervical  vertebrae  to  the  angle  of  the  scapula,  covered  over  and  toned  down 
by  the  overlying  Trapezius.  The  RkamboAIa,  produce,  when  in  action,  a  vertical  eminence 
between  the  internal  border  of  the  scapula  and  the  spinal  furrow,  varying  in  intensity  according 
to  the  condition  of  contraction  or  relaxation  of  the  Trapezius  muscle,  by  which  they  are  for  the 
most  part  covered.  The  lowermost  part  of  the  Rhomboideus  major  is  uncovered  by  the  Trapezius, 
and  forms  on  the  surface  an  oblique  ridge  running  upward  and  inward  from  the  inferior  angle 
of  the  scapula.  Of  the  muscles  of  the  third  layer  of  the  back,  the  Serratus  posticus  superior 
does  not  in  any  way  influence  surface  form.  The  Serratus  posticus  inferior,  when  in  strong 
action,  may  occasionally  be  revealed  as  an  elevation  beneath  the  Latissimus  dorsi.  The  Splenii 
by  their  divergence  serve  to  broaden  out  the  upper  part  of  the  back  of  the  neck  and  produce  a 
local  fulness  in  this  situation,  but  do  not  otherwise  influence  surface  form.  Beneath  all  these 
muscles  those  of  the  fourth  layer — the  Erector  *r>!i<ff  and  its  continuations — influence  the  surface 
form  in  a  decided  manner.  In  the  loins,  the  Erector  spinae,  bound  down  by  the  lumbar  fascia, 
forms  a  rounded  vertical  eminence,  which  determines  the  depth  of  the  spinal  furrow,  and  which 
below  tapers  to  a  point  on  the  posterior  surface  of  the  sacrum  and  becomes  lost  there.  In  the 
back  it  forms  a  flattened  plane  which  gradually  becomes  lost.  In  the  neck  the  only  part  of  this 
group  of  muscles  which  influences  surface  form  is  the  TracheJo-mastofd,  which  produces  a  short 
convergent  line  across  the  upper  part  of  the  posterior  triangle  of  the  neck,  appearing  from 
under  cover  of  the  posterior  border  of  the  Sterno-mastoid  and  being  lost  below  beneath  the 
Trapezius. 

THE  THORAX. 

The  Muscles  exclusively  connected  with  the  bones  in  this  region  are  few  in 
number.  They  are  the 

\     Intercostales  externi.  Infracostales. 

Intercostales  interni.  Triaugularis  sterni. 

Levatores  costarum. 

Intercostal  Fasciae. — A  thin  but  firm  layer  of  fascia  covers  the  outer  surface  of 
the  External  intercostal  and  the  inner  surface  of  the  Internal  intercostal  muscles ; 
and  a  third  layer,  the  middle  intercostal  fascia,  more  delicate,  is  interposed  between 
the  two  planes  of  muscular  fibres.  These  are  the  intercostal  fasciae  ;  they  archest 
marked  in  those  situations  where  the  muscular  fibres  are  deficient,  as  between  the 
External  intercostal  muscles  and  sternum,  in  front,  and  between  the  Internal 
intercostals  and  spine,  behind. 

The  Intercostal  muscles  (Fig.  299)  are  two  thin  planes  of  muscular  and  tendinous 
fibres,  placed  one  over  the  other,  filling  up  the  intercostal  spaces,  and  being  directed 
obliquely  between  the  margins  of  the  adjacent  ribs.  They  have  received  the  name 
'•  external  "  and  i- internal  "  from  the  position  they  bear  to  one  another.  The 
tendinous  fibres  are  longer  and  more  numerous  than  the  muscular ;  hence  the  walls 
of  the  intercostal  spaces  possess  very  considerable  strength,  to  which  the  crossing  of 
the  muscular  fibres  materially  contributes. 


442  THE  MUSCLES  AND    FASCIA 

The  External  Intercostals  are  eleven  in  number  on  each  side.  They  extend 
from  the  tubercles  of  the  ribs,  behind,  to  the  commencement  of  the  cartilages  of 
the  ribs,  in  front,  where  they  terminate  in  a  thin  membranous  aponeurosis,  which 
is  continued  forward  to  the  sternum.  They  arise  from  the  lower  border  of  each 
rib,  and  are  inserted  into  the  upper  border  of  the  rib  below.  In  the  two  lowest 
spaces  they  extend  to  the  end  of  the  cartilages.  Their  fibres  are  directed  obliquely 
downward  and  forward,  in  a  similar  direction  with  those  of  the  External  oblique 
muscle  of  the  abdomen.  They  are  thicker  than  the  Internal  intercostals. 

Relations. — By  their  outer  surface,  with  the  muscles  which  immediately  invest 
the  chest — viz.  the  Pectoralis  major  and  minor,  Serratus  magnus,  and  Rhomboideus 
major,  Serratus  posticus  superior  and  inferior,  Scalenus  posticus,  Ilio-costalis, 
Longissimus  dorsi,  Cervicalis  ascendens,  Transversalis  colli,  Levatores  costarum, 
and  the  Obliquus  externus  abdominis ;  by  their  internal  surface,  with  the  middle 
intercostal  fascia,  which  separates  them  from  the  intercostal  vessels  and  nerve,  and 
the  Internal  intercostal  muscles,  and,  behind,  from  the  pleura. 

The  Internal  intercostals  are  also  eleven  in  number  on  each  side.  They 
commence  anteriorly  at  the  stei'num,  in  the  interspaces  between  the  cartilages  of 
the  true  ribs,  and  from  the  anterior  extremities  of  the  cartilages  of  the  false  ribs, 
and  extend  backward  as  far  as  the  angles  of  the  ribs,  whence  they  are  continued 
to  the  vertebral  column  by  a  thin  aponeurosis.  They  arise  from  the  ridge  on  the 
inner  surface  of  each  rib,  as  well  as  from  the  corresponding  costal  cartilage,  and 
are  inserted  into  the  upper  border  of  the  rib  below.  Their  fibres  are  directed 
obliquely  downward  and  backward,  passing  in  the  opposite  direction  to  the  fibres 
of  the  External  intercostal  muscle. 

Relations. — By  their  external  surface,  with  the  intercostal  vessels  and  nerves, 
and  the  middle  intercostal  fascia,  which  separates  them  from  the  External  inter- 
costal muscles  ;  by  their  internal  surface,  with  the  internal  intercostal  fascia, 
which  separates  them  from  the  pleura  costalis,  Triangularis  sterni,  and  Diaphragm. 

The  Infracostales  (subcostales)  consist  of  muscular  and  aponeurotic  fasciculi, 
which  vary  in  number  and  length  :  they  are  placed  on  the  inner  surface  of  the  ribs, 
where  the  Internal  intercostal  muscles  cease ;  they  arise  from  the  inner  surface  of 
one  rib,  and  are  inserted  into  the  inner  surface  of  the  first,  second,  or  third  rib 
below.  Their  direction  is  most  usually  oblique,  like  the  Internal  intercostals. 
They  are  most  frequent  between  the  lower  ribs. 

The  Triangularis  sterni  is  a  thin  plane  of  muscular  and  tendinous  fibres, 
situated  upon  the  inner  wall  of  the  front  of  the  chest.  It  arises  from  the  lower 
part  of  the  side  of  the  sternum,  from  the  inner  surface  of  the  ensiform  cartilage, 
and  from  the  sternal  ends  of  the  costal  cartilages  of  the  three  or  four  lower  true 
ribs.  Its  fibres  diverge  upward  and  outward,  to  be  inserted  by  fleshy  digitations 
into  the  lower  border  and  inner  surfaces  of  the  costal  cartilages  of  the  second, 
third,  fourth,  and  fifth  ribs.  The  lowest  fibres  of  this  muscle  are  horizontal  in 
their  direction,  and  are  continuous  with  those  of  the  Transversalis  ;  those  which 
succeed  are  oblique,  whilst  the  superior  fibres  are  almost  vertical.  This  muscle 
varies  much  in  its  attachment,  not  only  in  different  bodies,  but  on  opposite  sides 
of  the  same  body. 

Relations. — In  front,  with  the  sternum,  ensiform  cartilage,  costal  cartilages, 
Internal  intercostal  muscles,  and  internal  mammary  vessels ;  behind,  with  the 
pleura,  pericardium,  and  anterior  mediastinum. 

The  Levatores  Costarum  (Fig.  288),  twelve  in  number  on  each  side,  are  small 
tendinous  and  fleshy  bundles,  which  arise  from  the  extremities  of  the  transverse 
processes  of  the  seventh  cervical  and  eleven  upper  dorsal  vertebrae,  and,  passing 
obliquely  downward  and  outward,  are  inserted  into  the  upper  border  of  the  rib 
below  them,  between  the  tubercle  and  the  angle.  That  for  the  first  rib  arises 
from  the  transverse  process  of  the  last  cervical  vertebra,  and  that  for  the  last  from 
the  eleventh  dorsal.  The  Inferior  levatores  divide  into  two  fasciculi,  one  of  which 
is  inserted  as  above  described ;  the  other  fasciculus  passes  down  to  the  second  rib 


OF    THE    THORAX. 


443 


below  its  origin  ;  thus,  each  of  the  lower  ribs  receives  fibres  from  the  transverse 
processes  of  two  vertebra. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  intercostal  nerves. 

Actions. — The  Intercostals   are  the  chief  agents  in  the  movement  of  the  ribs 


STERNO-MASTOID. 


SCALENUS    MEDIUS. 
SCALENUS    ANTICUS. 


FIG.  289.— Posterior  surface  of  sternum  and  costal  cartilages,  showing  Triangularis  sterni  muscle.    (From  a 
preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

in  ordinary  respiration.  When  the  first  rib  is  elevated  and  fixed  by  the  Scaleiii,  the 
External  intercostals  raise  the  other  ribs,  especially  their  fore  part,  and  so  increase 
the  capacity  of  the  chest  from  before  backward  :  at  the  same  time  they  evert  their 
lower  borders,  and  so  enlarge  the  thoracic  cavity  transversely.  The  Internal 
intercostals.  at  the  side  of  the  thorax,  depress  the  ribs  and  invert  their  lower 
borders,  and  so  diminish  the  thoracic  cavity  ;  but  at  the  fore  part  of  the  chest  these 
muscles  assist  the  External  intercostals  in  raising  the  cartilages.1  The  Levatores 

1  The  view  of  the  action  of  the  Intercostal  muscles  given  in  the  text  is  that  which  is  taught  by 
Hutchinson  (Cyd.  of  Anat.  and  Phys.,  art.  "Thorax"),  and  is  usually  adopted  in  our  schools.  It  is, 
however,  much  disputed.  Hamberger  believed  that  the  External  intercostals  act  as  elevators  of  the 
ribs,  or  muscles  of  inspiration,  while  the  Internal  act  in  expiration.  Haller  taught  that  both  sets  of 
muscles  act  in  common — viz.  as  muscles  of  inspiration — and  this  view  is  adopted  by  many  of  the  best 
anatomists  of  the  Continent,  and  appears  supported  by  many  observations  made  on  the  human  subject 
under  various  conditions  of  disease,  and  on  living  animals  after  the  muscles  have  been  exposed  under 
chloroform.  The  reader  may  consult  an  interesting  paper  by  Dr.  Cleland  in  the  Journal  of  Anat.  and 
Phys.  No.  II..  May,  1867,  p."  209,  "On the  Hutchinsonian  theory  of  the  Action  of  the  Intercostal 
Muscles,"  who  refers  also  to  Henle,  Luschka,  Budge,  and  Baumier,  Obsermtions  on  (he  Action  of  the 
Intfrco.<tal  Mu^le*.  Erlangen.  1860.  (In  NewSyd.  Soc.'gYear-Bookfor  1861,  p.  69.)  Dr.  W.  W.  Keen  has 
come  to  the  conclusion,  from  experiments  made  upon  a  criminal  executed  by  hanging,  that  the  Exter- 


444  THE  MUSCLES  AND    FASCIA. 

costarum  assist  the  External  intercostals  in  raising  the  ribs.  The  Triangularis 
sterni  draws  down  the  costal  cartilages ;  it  is  therefore  an  expiratory  muscle. 

Muscles  of  Inspiration  and  Expiration. — The  muscles  which  assist  the  action 
of  the  Diaphragm  in  ordinary  tranquil  inspiration  are  the  Intercostals  and  the 
Levatores  costarum,  as  above  stated,  and  the  Scaleni.  When  the  need  for  more 
forcible  action  exists,  the  shoulders  and  the  base  of  the  scapula  are  fixed,  and  then 
the  powerful  muscles  of  forced  inspiration  come  into  play ;  the  chief  of  these  are 
the  Trapezius,  the  Pectoralis  minor,  the  Serratus  posticus  superior  and  inferior, 
and  the  Rhomboidei.  The  lower  fibres  of  the  Serratus  magnus  may  possibly  assist 
slightly  in  dilating  the  chest  by  raising  and  everting  the  ribs.  The  Sterno- 
mastoid  also,  when  the  head  is  fixed,  assists  in  forced  inspiration  by  drawing  up 
the  sternum  and  by  fixing  the  clavicle,  and  thus  affording  a  fixed  point  for  the 
action  of  the  muscles  of  the  chest.  The  Ilio-costalis  and  Quadratus  lumborurn 
assist  in  forced  inspiration  by  fixing  the  last  rib  (see  page  458). 

The  ordinary  action  of  expiration  is  hardly  effected  by  muscular  force,  but 
results  from  a  return  of  the  walls  of  the  thorax  to  a  condition  of  rest,  owing  to 
their  own  elasticity  and  to  that  of  the  lungs.  Forced  expiratory  actions  are 
performed  mainly  by  the  flat  muscles  (Obliqui  and  Transversalis)  of  the  abdomen, 
assisted  also  by  the  Rectus.  Other  muscles  of  forced  expiration  are  possibly  the 
Internal  intercostals  and  Triangularis  sterni  (as  above  mentioned),  and  the  Ilio- 
costalis. 

THE  DIAPHRAGMATIC  REGION. 

Diaphragm. 

The  Diaphragm  (did(ppa-yfj.a,  a  partition  wall )  (Fig.  290)  is  a  thin  musculo- 
fibrous  septum,  placed  obliquely  at  the  junction  of  the  upper  with  the  middle  third 
of  the  trunk,  and  separating  the  thorax  from  the  abdomen,  forming  the  floor  of  the 
former  cavity  and  the  roof  of  the  latter.  It  is  elliptical,  its  longest  diameter  being 
from  side  to  side,  somewhat  fan-shaped,  the  broad  elliptical  portion  being  hori- 
zontal, the  narrow  part,  which  represents  the  handle  of  the  fan,  vertical,  and 
joined  at  right  angles  to  the  former.  It  is  from  this  circumstance  that  some 
anatomists  describe  it  as  consisting  of  two  portions,  the  upper  or  great  muscle  of 
the  Diaphragm,  and  the  lower  or  lesser  muscle.  It  arises  from  the  whole  of  the 
internal  circumference  of  the  thorax ;  being  attached,  in  front,  by  fleshy  fibres  to 
the  ensiform  cartilage ;  on  either  side,  to  the  inner  surface  of  the  cartilages  and 
bony  portions  of  the  six  or  seven  inferior  ribs,  interdigitating  with  the  Transver- 
salis ;  and  behind,  to  two  aponeurotic  arches,  named  the  ligamentum  arcuatum 
externum  et  internum,  and  to  the  lumbar  vertebne.  The  fibres  from  these  sources 
vary  in  length ;  those  arising  from  the  ensiform  appendix  are  very  short  and 
occasionally  aponeurotic ;  those  from  the  ligamenta  arcuata,  and  more  especially 
those  from  the  cartilages  of  the  ribs  at  the  side  of  the  chest,  are  longer,  describe 
well-marked  curves  as  they  ascend,  and  finally  converge  to  be  inserted  into  the 
circumference  of  the  central  tendon.  Between  the  sides  of  the  muscular  slip  from 
the  ensiform  appendix  and  the  cartilages  of  the  adjoining  ribs  the  fibres  of  the 
Diaphragm  are  deficient,  the  interval  being  filled  by  areolar  tissue,  covered  on  the 
thoracic  side  by  the  pleurae ;  on  the  abdominal,  by  the  peritoneum.  This  is, 
consequently,  a  weak  point,  and  a  portion  of  the  contents  of  the  abdomen  may 
protrude  into  the  chest,  forming  phrenic  or  diaphragmatic  hernia,  or  a  collection 
of  pus  in  the  mediastinum  may  descend  through  it,  so  as  to  point  at  the 
epigastrium. 

The  ligamentum  arcuatum  internum  is  a  tendinous  arch,  thrown  across  the 
upper  part  of  the  Psoas  magnus  muscle,  on  each  side  of  the  spine.  It  is  connected, 
by  one  end,  to  the  outer  side  of  the  body  of  the  first  lumbar  vertebra,  being 
continuous  with  the  outer  side  of  the  tendon  of  the  corresponding  crus ;  and,  by 

nal  intercostals  are  muscles  of  expiration,  as  they  pulled  the  ribs  down,  while  the  Internal  intercostals 
pulled  the  ribs  up  and  are  muscles  of  inspiration  ( Trans.  CM.  Phys.  Philadelphia,  Third  Series,  vol.  i., 
1875,  p.  97). 


THE   DIAPHRAGMATIC  REGION. 


445 


the  other  end.  to  the  front  of  the  transverse  process  of  the  first,  and  sometimes 
also  to  that  of  the  second,  lumbar  vertebra. 

The  U'!<iin> •ittiini  <ir<-ii<itiiii(  externum  is  the  thickened  upper  margin  of  the  ante- 
rior lamella  of  the  lumbar  fascia  :  it  arches  across  the  upper  part  of  the  Quadratus 
lumborum,  being  attached,  by  one  extremity,  to  the  front  of  the  transverse  process 
of  the  first,  sometimes  also  of  the  second,  lumbar  vertebra,  and,  by  the  other,  to 
the  apex  and  lower  margin  of  the  last  rib. 

The  Crura  — The  Diaphragm  is  connected  to  the  spine  by  two  crura  or  pillars, 
which  are  situated  on  the  bodies  of  the  lumbar  vertebrae,  on  each  side  of  the  aorta. 
The  crura.  at  their  origin,  are  tendinous  in  structure ;  the  right  crus,  larger  and 
longer  than  the  left,  arising  from  the  anterior  surface  of  the  bodies  and  inter- 
vertebral  substances  of  the  three  or  four  upper  lumbar  vertebras ;  the  left,  from 


FIG.  290.— The  Diaphragm.    Under  surface. 

the  two  upper :  both  blending  with  the  anterior  common  ligament  of  the  spine. 
These  tendinous  portions  of  the  crura  pass  forward  and  inward,  and  gradually 
converge  to  meet  in  the  middle  line,  forming  an  arch,  beneath  which  passes  the 
aorta,  vena  azygos  major,  and  thoracic  duct.  From  this  tendinous  arch  muscular 
fibres  arise,  which  diverge,  the  outermost  portion  being  directed  upward  and 
outward  to  the  central  tendon :  the  innermost  decussating  in  front  of  the  aorta, 
and  then  diverging,  so  as  to  surround  the  oesophagus  before  ending  in  the  central 
tendon.  The  fibres  derived  from  the  right  crus  are  the  most  numerous  and  pass 
in  front  of  those  derived  from  the  left. 

The  Central  or  Cordif»rtn  7'<  /,,/<>»  of  the  Diaphragm  is  a  thin  but  strong 
tendinous  aponeurosis,  situated  at  the  centre  of  the  vault  formed  by  the  muscle, 
immediately  below  the  pericardium,  with  which  its  upper  surface  is  blended.  It 
is  shaped  somewhat  like  a  trefoil  leaf,  consisting  of  three  divisions,  or  leaflets, 


446  THE  MUSCLES  AND   FASCIA. 

separated  from  one  another  by  slight  indentations.  The  right  leaflet  is  the  largest : 
the  middle  one,  directed  toward  the  ensiform  cartilage,  the  next  in  size ;  and  the 
left,  the  smallest.  In  structure,  the  tendon  is  composed  of  several  planes  of  fibres, 
which  intersect  one  another  at  various  angles,  and  unite  into  straight  or  curved 
bundles — an  arrangement  which  affords  it  additional  strength. 

The  Openings  connected  with  the  Diaphragm  are  three  large  and  several 
smaller  apertures.  The  former  are  the  aortic,  the  oesophageal,  and  the  opening 
for  the  vena  cava. 

The  aortic  opening  is  the  lowest  and  the  most  posterior  of  the  three  large  aper- 
tures connected  with  this  muscle.  It  is  situated  in  the  middle  line,  immediately 
in  front  of  the  bodies  of  the  vertebrae ;  and  is,  therefore,  behind  the  Diaphragm, 
not  in  it.  It  is  an  osseo-aponeurotic  aperture,  formed  by  a  tendinous  arch  thrown 
across  the  front  of  the  bodies  of  the  vertebrae,  from  the  crus  on  one  side  to  that 
on  the  other,  and  transmits  the  aorta,  vena  azygos  major,  thoracic  duct,  and 
sometimes  the  left  sympathetic  nerve.  Occasionally  some  tendinous  fibres  are 
prolonged  across  the  bodies  of  the  vertebrae  from  the  inner  part  of  the  lower  end 
of  the  crura,  passing  behind  the  aorta,  and  thus  converting  the  opening  into  a 
fibrous  ring. 

The  oesophageal  opening,  elliptical  in  form,  muscular  in  structure,  and  formed 
by  the  two  crura,  is  placed  above,  and,  at  the  same  time,  anterior,  and  a  little  to 
the  left  of,  the  preceding.  It  transmits  the  oesophagus  and  pneumogastric  nerves. 
The  anterior  margin  of  this  aperture  is  occasionally  tendinous,  being  formed  by  the 
margin  of  the  central  tendon. 

The  opening  for  the  vena  cava  (foramen  quadraturti)  is  the  highest;  it  is  quad- 
rilateral in  form,  tendinous  in  structure,  and  placed  at  the  junction  of  the  right 
and  middle  leaflets  of  the  central  tendon,  its  margins  being  bounded  by  four 
bundles  of  tendinous  fibres,  which  meet  at  right  angles. 

The  right  crus  transmits  the  sympathetic  and  the  greater  and  lesser  splanchnic 
nerves  of  the  right  side ;  the  left  crus,  the  greater  and  lesser  splanchnic  nerves  of 
the  left  side  and  the  vena  azygos  minor. 

The  Serous  Membranes  in  relation  with  the  Diaphragm  are  four  in  number: 
three  lining  its  upper  or  thoracic  surface ;  one,  its  abdominal.  The  three  serous 
membranes  on  its  upper  surface  are  the  pleura  on  either  side  and  the  serous  layer 
of  the  pericardium,  which  covers  the  middle  portion  of  the  tendinous  centre.  The 
serous  membrane  covering  its  under  surface  is  a  portion  of  the  general  peritoneal 
membrane  of  the  abdominal  cavity. 

The  Diaphragm  is  arched,  being  convex  toward  the  chest  and  concave  to  the 
abdomen.  The  right  portion  forms  a  complete  arch  from  before  backward,  being 
accurately  moulded  over  the  convex  surface  of  the  liver,  and  having  resting  upon 
it  the  concave  base  of  the  right  lung.  The  left  portion  is  arched  from  before  back- 
ward in  a  similar  manner ;  but  the  arch  is  narrower  in  front,  being  encroached  upon 
by  the  pericardium,  and  lower  than  the  right,  at  its  summit,  by  about  three-quarters 
of  an  inch.  It  supports  the  base  of  the  left  lung,  and  covers  the  great  end  of  the 
stomach,  the  spleen,  and  left  kidney.  At  its  circumference  the  Diaphragm  is 
higher  in  the  mesial  line  of  the  body  than  at  either  side ;  but  in  the  middle  of  the 
thorax  the  central  portion,  which  supports  the  heart,  is  on  a  lower  level  than  the 
two  lateral  portions. 

Nerves. — The  Diaphragm  is  supplied  by  the  phrenic  nerves  and  phrenic  plexus 
of  the  sympathetic. 

Actions. — The  Diaphragm  is  the  principal  muscle  of  inspiration.  When  in  a 
condition  of  rest  the  muscle  presents  a  domed  surface,  concave  toward  the  abdo- 
men ;  and  consists  of  a  circumferential  muscular  and  a  central  tendinous  part. 
When  the  muscular  fibres  contract,  they  become  less  arched,  or  nearly  straight, 
and  thus  cause  the  central  tendon  to  descend,  and  in  consequence  the  level  of  the 
chest-wall  is  lowered,  the  vertical  diameter  of  the  chest  being  proportionally 
increased.  In  this  descent  the  different  parts  of  the  tendon  move  unequally. 
The  left  leaflet  descends  to  the  greatest  extent;  the  right  to  a  less  extent,  on 


OF    THE   A  B DOMEX. 


447 


account  of  the  liver ;  and  the  central  leaflet  the  least,  because  of  its  connection  to 
the  pericardium.  In  descending  the  diaphragm  presses  on  the  abdominal  viscera, 
and  so  to  a  certain  extent  causes  a  projection  of  the  abdominal  wall ;  but  in  conse- 
quence of  these  viscera  not  yjelding  completely,  the  central  tendon  becomes  a  fixed 
point,  and  enables  the  circumferential  muscular  fibres  to  act /row  it,  and  so  elevate 
the  lower  ribs  and  expand  the  lower  part  of  the  thoracic  cavity ;  and  Duchenne 
has  shown  that  the  Diaphragm  has  the  power  of  elevating  the  ribs,  to  which  it 
is  attached,  by  its  contraction,  if  the  abdominal  viscera  are  in  situ,  but  that  if  these 
organs  are  removed,  this  power  is  lost.  When  at  the  end  of  inspiration  the  Dia- 
phragm relaxes,  the  thoracic  walls  return  to  their  natural  position  in  consequence 
of  their  elastic  reaction  and  of  the  elasticity  and  weight  of  the  displaced  viscera.1 

In  all  expulsive  acts  the  Diaphragm  is  called  into  action,  to  give  additional 
power  to  each  expulsive  effort.  Thus,  before  sneezing,  coughing,  laughing,  and 
crying,  before  vomiting,  previous  to  the  expulsion  of  the  urine  and  faeces,  or  of 
the  foetus  from  the  womb,  a  deep  inspiration  takes  place. 

The  height  of  the  Diaphragm  is  constantly  varying  during  respiration,  the 
muscle  being  carried  upward  or  downward  from  the  average  level ;  its  height  also 
varies  according  to  the  degree  of  distension  of  the  stomach  and  intestines,  and  the 
size  of  the  liver.  After  a  forced  expiration,  the  right  arch  is  on  a  level,  in  front, 
with  the  fourth  costal  cartilage  :  at  the  side,  with  the  fifth,  sixth,  and  seventh 
ribs  ;  and  behind,  with  the  eighth  rib,  the  left  arch  being  usually  from  one  to  two 
ribs'  breadth  below  the  level  of  the  right  one.  In  a  forced  inspiration,  it  descends 
from  one  to  two  inches ;  its  slope  would  then  be  represented  by  a  line  drawn  from 
the  ensiform  cartilage  toward  the  tenth  rib. 

THE  ABDOMEN. 
Superficial  Muscles. 


J  Transversalis. 
.   Rectus. 


The  Muscles  in  this  region  are,  the 
'    Obliquus  Externus. 
N  Obliquus  Internus. 

Pyramidalis. 

Dissection  i'Fig.  291).— To  dissect  the  abdominal 
muscles,  make  a  vertical  incision  from  the  ensiform  car- 
tilage to  the  pubes;  a  second  incision  from  the  umbilicus 
obliquely  upward  and  outward  to  the  outer  surface  of  the 
chest,  as  high  as  the  lower  border  of  the  fifth  or  sixth  rib : 
and  a  third,  commencing  midway  between  the  umbilicus 
and  pubes.  transversely  outward  to  the  anterior  superior 
iliac  spine,  and  along  the  crest  of  the  ilium  as  far  as  its 
posterior  third.  Then  reflect  the  three  flaps  included  be- 
tween these  incisions  from  within  outward,  in  the  lines  of 
direction  of  the  muscular  fibres.  If  necessary,  the  abdom- 
inal muscles  may  be  made  tense  by  inflating  the  peritoneal 
cavity  through  the  umbilicus. 

The  Superficial  fascia  of  the  abdomen  consists 
over  the  greater  part  of  the  abdominal  wall  of  a 
single  layer  of  fascia,  which  contains  a  variable 
amount  of  fat ;  but  as  this  layer  approaches  the 
groin  it  is  easily  divisible  into  two  layers,  be- 
tween which  are  found  the  superficial  vessels  and 
nerves  and  the  superficial  inguinal  lymphatic 
glands.  The  superficial  layer  is  thick,  areolar  in 
texture,  containing  adipose  tissue  in  its  meshes, 
the  quantity  of  which  varies  in  different  subjects. 
Below  it  passes  over  Poupart's  ligament,  and  is 
continuous  with  the  outer  layer  of  the  superficial 
fascia  of  the  thigh.  In  the  male  this  fascia  is  continued  over  the  penis  and  outer 

1  For  a  detailed  description  of  the  general  relations  of  the  Diaphragm,  and  its  action,  refer  to 
Dr.  Sibson's  Medical  Anatomy. 


S.  Dis- 
section of 

inguinal 
hernia. 


FIG.  291.— Dissection  of  abdomen. 


448  THE  MUSCLES  AND    FASCIA 

surface  of  the  cord  to  the  scrotum,  where  it  helps  to  form  the  dartos.  As  it  passes 
to  the  scrotum  it  changes  its  character,  becoming  thin,  destitute  of  adipose  tissue 
and  of  a  pale  reddish  color,  and  in  the  scrotum  it  acquires  some  involuntary  mus- 
cular fibres.  From  the  scrotum  it  may  be  traced  backward  to  be  continuous  with 
the  superficial  fascia  of  the  perinseum.  In  the  female  this  fascia  is  continued  into 
the  labia  majora.  The  deeper  layer  (fascia  of  Scarpa)  is  thinner  and  more  mem- 
branous in  character  than  the  superficial  layer.  In  the  middle  line  it  is  intimately 
adherent  to  the  linea  alba ;  above,  it  is  continuous  with  the  superficial  fascia  over 
the  rest  of  the  trunk  ;  below,  it  blends  with  the  fascia  lata  of  the  thigh  a  little 
below  Poupart's  ligament ;  and  below  and  internally  it  is  continued  over  the  penis 
and  spermatic  cord  to  the  scrotum,  where  it  helps  to  form  the  dartos.  From  the 
scrotum  it  may  be  traced  backward  to  be  continuous  with  the  deep  layer  of  the 
superficial  fascia  of  the  perinseum.  In  the  female  it  is  continued  into  the  labia 
majora. 

The  External  or  Descending  Oblique  muscle  (Fig.  292)  is  situated  on  the  side 
and  fore  part  of  the  abdomen  ;  being  the  largest  and  the  most  superficial  of  the 
three  flat  muscles  in  this  region.  It  is  broad,  thin,  and  irregularly  quadrilateral, 
its  muscular  portion  occupying  the  side,  its  aponeurosis  the  anterior  wall,  of  the 
abdomen.  It  arises,  by  eight  fleshy  digitations,  from  the  external  surface  and 
lower  borders  of  the  eight  inferior  ribs ;  these  digitations  are  arranged  in  an 
oblique  line  running  downward  and  backward ;  the  upper  ones  being  attached 
close  to  the  cartilages  of  the  corresponding  ribs  ;  the  lowest,  to  the  apex  of  the 
cartilage  of  the  last  rib ;  the  intermediate  ones,  to  the  ribs  at  some  distance  from 
their  cartilages.  The  five  superior  serrations  increase  in  size  from  above  down- 
ward, and  are  received  between  corresponding  processes  of  the  Serratus  magnus ; 
the  three  lower  ones  diminish  in  size  from  above  downward,  receiving  between 
them  corresponding  processes  from  the  Latissimus  dorsi.  From  these  attachments, 
the  fleshy  fibres  proceed  in  various  directions.  Those  from  the  lowest  ribs  pass 
nearly  vertically  downward,  to  be  inserted  into  the  anterior  half  of  the  outer  lip 
of  the  crest  of  the  ilium  ;  the  middle  and'upper  fibres,  directed  downward  and  for- 
ward, terminate  in  tendinous  fibres,  opposite  a  line  drawn  from  the  prominence 
of  the  ninth  costal  cartilage  to  the  anterior  superior  spinous  process  of  the  ilium, 
which  then  spread  out  into  a  broad  aponeurosis. 

The  Aponeurosis  of  the  External  Oblique  is  a  thin,  but  strong  membranous 
aponeurosis,  the  fibres  of  which  are  directed  obliquely  downward  and  inward.  It 
is  joined  with  that  of  the  opposite  muscle  along  the  median  line,  covers  the 
whole  of  the  front  of  the  abdomen ;  above,  it  is  connected  with  the  lower  border 
of  the  Pectoralis  major ;  below,  its  fibres  are  closely  aggregated  together,  and 
extend  obliquely  across  from  the  anterior  superior  spine  of  the  ilium  to  the  spine 
of  the  os  pubis  and  the  linea  ilio-pectinea.  In  the  median  line  it  interlaces  with 
the  aponeurosis  of  the  opposite  muscle,  forming  the  linea  alba,  which  extends  from 
the  ensiform  cartilage  to  the  symphysis  pubis. 

That  portion  of  the  aponeurosis  which  extends  between  the  anterior  superior 
spine  of  the  ilium  and  the  spine  of  the  os  pubis  is  a  broad  band,  folded  inward, 
and  continuous  below  with  the  fascia  lata ;  it  is  called  Poupart's  ligament.  The 
portion  which  is  reflected  from  Poupart's  ligament  at  the  spine  of  the  os  pubis 
along  the  pectineal  line  is  called  Grimbernat's  ligament.  From  the  point  of  attach- 
ment of  the  latter  to  the  pectineal  line,  a  few  fibres  pass  upward  and  inward, 
behind  the  inner  pillar  of  the  ring,  to  the  linea  alba.  They  diverge  as  they  ascend, 
and  form  a  thin,  triangular,  fibrous  band,  which  is  called  the  triangular  ligament 
of  the  abdomen. 

In  the  aponeurosis  of  the  External  oblique,  immediately  above  the  crest  of  the 
os  pubis,  is  a  triangular  opening,  the  external  abdominal  ring,  formed  by  a  separa- 
tion of  the  fibres  of  the  aponeurosis  in  this  situation. 

Relations. — By  its  external  surface,  with  the  superficial  fascia,  superficial 
epigastric  and  circumflex  iliac  vessels,  and  some  cutaneous  nerves ;  by  its  internal 
surface,  with  the  Internal  oblique,  the  lower  part  of  the  eight  inferior  ribs,  and 


OF    THE   ABDOMEX. 

Intercostal  muscles,  the  Cremaster.  the  spermatic  cord  in  the  male,  and  round  liga- 
ment in  the  female.  Its  posterior  border,  extending  from  the  last  rib  to  the  crest 
of  the  ilium,  is  fleshy  throughout  and  free ;  it  is  occasionally  overlapped  by  the 
Latissiinus  dorsi.  though  generally  a  triangular  interval  exists  between  the  two 
muscles  near  the  crest  of  the  ilium,  in  which  is  seen  a  portion  of  the  internal 
oblige.  This  triangle.  Pitt's  triangle,  is  therefore  bounded  in  front  by  the 


External  abdo- 
minal ring. 
Gimbfrnafs--. 
ligament.      I 


^ 
r  Put**. 

FIG.  292.— The  External  oblique  muscle. 


External  oblique,  behind  by  the  Latissimus  dorsi.  below  by  the  crest  of  the  ilium, 
while  its  flooj:  is  formed  by  the  Internal  oblique  (Fig.  287). 

The  following  parts  of  the  aponeurosis  of  the  External  oblique  muscle  require 
to  be  further  described  :  viz.  the  external  abdominal  ring,  the  intercolumnar  fibres 
and  fascia.  Poupart's  ligament,  Gimbernat's  ligament,  and  the  triangular  ligament 
of  the  abdomen. 

The  External  Abdominal  Ring. — Just  above,  and  to  the  outer  side  of  the  crest 
of  the  os  pubis,  an  interval  is  seen  in  the  aponeurosis  of  the  External  oblique, 
called  the  External  abdominal  ring.  The  aperture  is  oblique  in  direction,  some- 


450  THE   MUSCLES   AND    FASCIA 

what  triangular  in  form,  and  corresponds  with  the  course  of  the  fibres  of  the 
aponeurosis.  It  usually  measures  from  base  to  apex  about  an  inch,  and 
transversely  about  half  an  inch.  It  is  bounded  below  by  the  crest  of  the  os 
pubis ;  above,  by  a  series  of  curved  fibres,  the  inter  columnar,  which  pass  across 
the  upper  angle  of  the  ring,  so  as  to  increase  its  strength ;  and  on  each  side,  by 
the  margins  of  the  opening  in  the  aponeurosis,  which  are  called  the  columns  or 
pillars  of  the  ring. 

The  external  pillar,  which  is  at  the  same  time  inferior  from  the  obliquity  of  its 
direction,  is  the  stronger :  it  is  formed  by  that  portion  of  Poupart's  ligament 
which  is  inserted  into  the  spine  of  the  os  pubis ;  it  is  curved  so  as  to  form  a  kind 
of  groove,  upon  which  the  spermatic  cord  rests.  The  internal  or  superior  pillar 
is  a  broad,  thin,  flat  band  which  is  attached  to  the  front  of  the  symphysis  pubis, 
interlacing  with  its  fellow  of  the  opposite  side,  that  of  the  right  side  being  super- 
ficial. 

The  external  abdominal  ring  gives  passage  to  the  spermatic  cord  in  the  male, 
and  round  ligament  in  the  female :  it  is  much  larger  in  men  than  in  women,  on 
account  of  the  large  size  of  the  spermatic  cord,  and  hence  the  greater  frequency 
of  inguinal  hernia  in  men. 

The  intercolumnar  fibres  are  a  series  of  curved  tendinous  fibres,  which  arch 
across  the  lower  part  of  the  aponeurosis  df  the  External  oblique.  They  have 
received  their  name  from  stretching  across  between  the  two  pillars  of  the  external 
ring,  describing  a  curve  Avith  the  convexity  downward.  They  are  much  thicker 
and  stronger  at  the  outer  margin  of  the  external  ring,  where  they  are  connected 
to  the  outer  third  of  Poupart's  ligament,  than  internally,  where  they  are  inserted 
into  the  linea  alba.  They  are  more  strongly  developed  in  the  male  than  in  the 
female.  The  intercolumnar  fibres  increase  the  strength  of  the  lower  part  of  the 
aponeurosis,  and  prevent  the  divergence  of  the  pillars  from  one  another. 

These  intercolumnar  fibres  as  they  pass  across  the  external  abdominal  ring  are 
themselves  connected  together  by  delicate  fibrous  tissue,  thus  forming  a  fascia, 
which^as  it  is  attached  to  the  pillars  of  the  ring  Covers  it  in,  and^is  called  the 
intercolumnar  fascia.  This  intercolumnar  fascia  is  continued  down  as  a  tubular 
prolongation  around  the  outer  surface  of  the  cord  and  testis,  and  encloses  them  in 
a  distinct  sheath ;  hence  it  is  also  called  the  external  spermatic  fascia. 

The  sac  of  an  inguinal  hernia,  in  passing  through  the  external  abdominal  ring,  receives  an 
investment  from  the  intercolumnar  fascia. 

If  the  finger  is  introduced  a  short  distance  into  the  external  abdominal  ring 
and  the  limb  is  then  extended  and  rotated  outward,  the  aponeurosis  of  the 
External  oblique,  together  with  the  iliac  portion  of  the  fascia  lata,  will  be  felt  to 
become  tense,  and  the  external  ring  much  contracted ;  if  the  limb  is  on  the  con- 
trary flexed  upon  the  pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax 
and  the  external  abdominal  ring  sufficiently  enlarged  to  admit  the  finger  with 
comparative  ease :  hence  the  patient  should  always  be  put  in  the  latter  position 
when  the  taxis  is  applied  for  the  reduction  of  an  inguinal  hernia  in  order  that  the 
abdominal  walls  may  be  relaxed  as  much  as  possible. 

Poupart's  ligament,  or  the  crural  arch,  is  the  lower  border  of  the  aponeurosis  of 
the  External  oblique  muscle,  and  extends  from  the  anterior  superior  spine  of 
the  ilium  to  the  pubic  spine.  From  this  latter  point  it  is  reflected  outward  to  be 
attached  to  the  pectineal  line  for  about  half  an  inch,  forming  Gimbernat's  liga- 
ment. Its  general  direction  is  curved  downward  toward  the  thigh,  where  it  is 
continuous  with  the  fascia  lata.  Its  outer  half  is  rounded  and  oblique  in  direction. 
Its  inner  half  gradually  widens  at  its  attachment  to  the  os  pubis,  is  more  horizontal 
in  direction,  and  lies  beneath  the  spermatic  cord. 

Nearly  the  whole  of  the  space  included  betAveen  the  crural  arch  and  the 
innominate  bone  is  filled  in  by  the  parts  which  descend  from  the  abdomen  into  the 
thigh.  These  will  be  referred  to  again  on  a  subsequent  page. 

Gimbernat's  ligament  is  that  part  of  the  aponeurosis  of  the  External  oblique 


OF    THE   ABDOMEN. 


451 


muscle  which  is  reflected  downward  and  outward  from  the  spine  of  the  os  pubis 
to  be  inserted  into  the  pectineal  line.  It  is  about  half  an  inch  in  length,  larger 
in  the  male  than  in  the  female,  almost  horizontal  in  direction  in  the  erect 
posture,  and  of  a  triangular  form  with  the  base  directed  outward.  Its  base, 
or  outer  margin,  is  concave,  thin,  and  sharp,  and  lies  in  contact  with  the  crural 
sheath.  Its  apex  corresponds  to  the  spine  of  the  os  pubis.  Its  posterior  margin 
is  attached  to  the  pectineal  line,  and  is  continuous  with  the  pubic  portion  of  the 
fascia  lata.  Its  anterior  margin  is  continuous  with  Poupart's  ligament. 

The  triangular  ligament  of  the  abdomen  is  a  band  of  tendinous  fibres  of  a 
triangular  shape,  which  is  attached  by  its  apex  to  the  pectineal  line,  where  it  is 
continuous  with  Gimbernat's  ligament.  It  passes  inward  beneath  the  spermatic 
cord,  and  expands  into  a  somewhat  fan-shaped  fascia,  lying  behind  the  inner  pillar 
of  the  external  abdominal  ring,  and  in  front  of  the  conjoined  tendon,  and  interlaces 
with  the  ligament  of  the  other  side  at  the  linea  alba. 

Dissection. — Detach  the  External  oblique  by  dividing  it  across,  just  in  front  of  its  attach- 
ment to  the  ribs,  as  far  as  its  posterior  border,  and  separate  it  below  from  the  crest  of  the  ilium 
as  far  as  the  anterior  superior  spine ;  then  separate  the  muscle  carefully  from  the  Internal  oblique, 
which  lies  beneath,  and  turn  it  toward  the  opposite  side. 

The  Internal  or  Ascending  oblique  muscle  (Fig.  29£),  thinner  and  smaller 
than  the  preceding,  beneath  which  it  lies,  is  of  an  irregularly  quadrilateral  form, 


Conjoined  tendon. 
CREMASTER. 


FIG.  293.— The  internal  oblique  muscle. 


and  situated  at  the  side  and  fore  part  of  the  abdomen.     It  arises,  by  fleshy  fibres, 
from   the  outer  half  of  Poupart's  ligament,  being  attached  to  the  groove  on  its 


452  THE  MUSCLES  AND   FASCIAE 

upper  surface ;  from  the  anterior  two-thirds  of  the  middle  lip  of  the  crest  of  the 
ilium,  and  from  the  posterior  lamella  of  the  lumbar  fascia.  From  this  origin  the 
fibres  diverge :  those  from  Poupart's  ligament,  few  in  number  and  paler  in  color 
than  the  rest,  arch  downward  and  inward  across  the  spermatic  cord,  and,  becoming 
tendinous,  are  inserted,  conjointly  with  those  of  the  Transversalis,  into  the  crest 
of  the  os  pubis  and  pectineal  line,  to  the  extent  of  half  an  inch,  forming  what  is 
known  as  the  conjoined  tendon  of  the  Internal  oblique  and  Transversalis ;  those 
from  the  anterior  third  of  the  iliac  origin  are  horizontal  in  their  direction,  and, 
becoming  tendinous  along  the  lower  fourth  of  the  linea  semilunaris,  pass  in  front  of 
the  Rectus  muscle  to  be  inserted  into  the  linea  alba ;  those  which  arise  from  the 
middle  third  of  the  origin  from  the  crest  of  the  ilium  pass  obliquely  upward  and 
inward,  and  terminate  in  an  aponeurosis,  which  divides  opposite  the  linea  semilunaris 
into  two  lamellae,  which  are  continued  forward,  in  front  and  behind  the  Rectus 
muscle,  to  the  linea  alba,  the  posterior  lamella  being  also  connected  to  the  cartilages 
of  the  seventh,  eighth,  and  ninth  ribs  ;  the  most  posterior  fibres  pass  almost 
vertically  upward,  to  be  inserted  into  the  lower  borders  of  the  cartilages  of  the 
three  lower  ribs,  being  continuous  with  the  Internal  intercostal  muscles. 

The  conjoined  tendon  of  the  Internal  oblique  and  Transversalis  is  inserted  into 
the  crest  of  the  os  pubis  and  pectineal  line,  immediately  behind  the  external 
abdominal  ring,  serving  to  protect  what  would  otherwise  be  a  weak  point  in  the 
abdominal  wall.  Sometimes  this  tendon  is  insufficient  to  resist  the  pressure 
from  within,  and  is  carried  forward  in  front  of  the  protrusion  through  the  external 
ring,  forming  one  of  the  coverings  of  direct  inguinal  hernia ;  or  the  hernia  forces 
its  way  through  the  fibres  of  the  conjoined  tendon. 

The  aponeurosis  of  the  Internal  oblique  is  continued  forward  to  the  middle  line 
of  the  abdomen,  where  it  joins  with  the  aponeurosis  of  the  opposite  muscle  at  the 
linea  alba,  and  extends  from  the  margin  of  the  thorax  to  the  os  pubis.  At  the  outer 
margin  of  the  Rectus  muscle,  this  aponeurosis,  for  the  upper  three-fourths  of  its 
extent,  divides  into  two  lamellae,  which  pass,  one  in  front  and  the  other  behind 
the  muscle,  enclosing  it  in  a  kind  of  sheath,  and  reuniting  on  its  inner  border  at 
the  linea  alba ;  the  anterior  layer  is  blended  with  the  aponeurosis  of  the  External 
oblique  muscle ;  the  posterior  layer  with  that  of  the  Transversalis.  Along  the 
lower  fourth  the  aponeurosis  passes  altogether  in  front  of  the  Rectus  without  any 
separation. 

Relations. — By  its  external  surface,  with  the  External  oblique,  Latissimus 
dorsi,  spermatic  cord,  and  external  ring ;  by  its  internal  surface,  with  the  Trans- 
versalis muscle,  the  lower  intercostal  vessels  and  nerves,  the  ilio-hypogastric  and 
the  ilio-inguinal  nerves.  Near  Poupart's  ligament  it  lies  on  the  fascia  transversalis, 
internal  ring,  and  spermatic  cord.  Its  lower  border  forms  the  upper  boundary  of 
the  spermatic  canal. 

The  Cremaster  muscle  is  a  thin  muscular  layer,  composed  of  a  number  of 
fasciculi  which  arise  from  the  middle  of  Poupart's  ligament  at  the  inner  side  of 
the  Internal  oblique,  being  connected  Avith  that  muscle,  and  also  occasionally  with 
the  Transversalis.  It  passes  along  the  outer  side  of  the  spermatic  cord,  descends 
with  it  through  the  external  abdominal  ring  upon  the  front  and  sides  of  the  cord, 
and  forms  a  series  of  loops  which  differ  in  thickness  and  length  in  different  subjects. 
Those  at  the  upper  part  of  the  cord  are  exceedingly  short,  but  they  become  in 
succession  longer  and  longer,  the  longest  reaching  down  as  low  as  the  testicle, 
where  a  few  are  inserted  into  the  tunica  vaginalis.  These  loops  are  united 
together  by  areolar  tissue,  and  form  a  thin  covering  over  the  cord  and  testis,  the 
fascia  cremasterica.  The  fibres  ascend  along  the  inner  side  of  the  cord,  and  are 
inserted  by  a  small  pointed  tendon  into  the  crest  of  the  os  pubis  and  front  of  the 
sheath  of  the  Rectus  muscle. 

It  will  be  observed  that  the  origin  and  insertion  of  the  Cremaster  is  precisely 
similar  to  that  of  the  lower  fibres  of  the  Internal  oblique.  This  fact  affords  an  easy 
explanation  of  the  manner  in  which  the  testicle  and  cord  are  invested  by  this 
muscle.  At  an  early  period  of  foetal  life  the  testis  is  placed  at  the  lower  and  back 


OF    THE   ABDOMEN.  453 

part  of  the  abdominal  cavity,  but  during  its  descent  toward  the  scrotum,  which 
takes  place  before  birth,  it  passes  beneath  the  arched  fibres  of  the  Internal  oblique. 
In  its  passage  beneath  this  muscle  some  fibres  are  derived  from  its  lower  part 
which  accompany  the  testicle  and  cord  into  the  scrotum.  It  occasionally  happens 
that  the  loops  of  the  Cremaster  surround  the  cord,  some  lying  behind  as  well  as  in 
front.  It  is  probable  that  under  these  circumstances  the  testis,  in  its  descent, 
passed  through  instead  of  beneath  the  fibres  of  the  Internal  oblique. 

In  the  descent  of  an  oblique  inguinal  hernia,  which  takes  the  same  course  as 
the  spermatic  cord,  the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle 
becomes  largely  developed  in  cases  of  hydrocele  and  large  old  scrotal  hernia.  No 
such  muscles  exist  in  the  female,  but  an  analogous  structure  is  developed  in  those 
cases  where  an  oblique  inguinal  hernia  descends  beneath  the  margin  of  the  Internal 
oblique. 

Dissection. — Detach  the  Internal  oblique  in  order  to  expose  the  Transversalis  beneath.  This 
may  be  effected  by  dividing  the  muscle,  above,  at  its  attachment  to  the  ribs ;  below,  at  its  con- 
nection with  Poupart  s  ligament  and  the  crest  of  the  ilium ;  and  behind,  by  a  vertical  incision 
extending  from  the  last  rib  to  the  crest  of  the  ilium.  The  muscle  should  previously  be  made 
tense  by  drawing  upon  it  with  the  fingers  of  the  left  hand,  and  if  its  division  is  carefully  effected, 
the  cellular  interval  between  it  and  the  Transversalis,  as  well  as  the  direction  of  the  fibres  of  the 
latter  muscle,  will  afford  a  clear  guide  to  their  separation  ;  along  the  crest  of  the  ilium  the  cir- 
cumflex iliac  vessels  are  interposed  between  them,  and  form  an  important  guide  in  separating 
them.  The  muscle  should  then  be  thrown  forward  toward  the  linea  alba. 

The  Transversalis  muscle  (Fig.  294),  so  called  from  the  direction  of  its  fibres,  is 
the  most  internal  flat  muscle  of  the  abdomen,  being  placed  immediately  beneath 
the  Internal  oblique.  It  arises  by  fleshy  fibres  from  the  outer  third  of  Poupart's 
ligament ;  from  the  inner  lip  of  the  crest  of  the  ilium  for  its  anterior  three- 
fourths  ;  from  the  inner  surface  of  the  cartilages  of  the  six  lower  ribs,  interdigitating 
with  the  Diaphragm  ;  and  by  the  middle  layer  of  the  lumbar  fascia  (posterior  apon- 
i-u'rosis  of  the  muscle  itself)  from  the  tips  of  the  transvere  processes  of  the  lumbar 
vertebrae.  The  muscle  terminates  in  front  in  a  broad  aponeurosis,  the  lower  fibres 
of  which  curve  downward  and  inward,  and  are  inserted,  together  with  those  of 
the  Internal  oblique,  into  the  lower  part  of  the  linea  alba,  the  crest  of  the  os 
pubis  and  pectineal  line,  forming  Avhat  is  known  as  the  conjoined  tendon  of  the 
Internal  oblique  and  Transversalis.  Throughout  the  rest  of  its  extent  the  apon- 
eurosis passes  horizontally  inward,  and  is  inserted  into  the  linea  alba ;  its  upper 
three-fourths  passing  behind  the  Rectus  muscle,  blending  with  the  posterior  lamella 
of  the  Internal  oblique ;  its  lower  fourth  passing  in  front  of  the  Rectus. 

Relations. — By  its  external  surface,  with  the  Internal  oblique,  and  the  inner 
surface  of  the  cartilages  of  the  lower  ribs ;  by  its  internal  surface,  with  the  fascia 
transversalis,  which  separates  it  from  the  peritoneum.  Its  lower  border  forms  the 
upper  boundary  of  the  spermatic  canal. 

Dissection. — To  expose  the  Rectus  muscle,  open  its  sheath  by  a  vertical  incision  extending 
from  the  margin  of  the  thorax  to  the  os  pubis.  and  then  reflect  the  two  portions  from  the  surface 
of  the  muscle,  which  is  easily  done,  excepting  at  the  lineae  transversae,  where  so  close  an 
adhesion  exists  that  the  greatest  care  is  requisite  in  separating  them.  Now  raise  the  outer  edge 
of  the  muscle,  in  order  to  examine  the  posterior  layer  of  the  sheath.  By  dividing  the  muscle  in 
the  centre,  and  turning  its  lower  part  downward,  the  point  where  the  posterior  wall  of  the 
sheath  terminates  in  a  thin  curved  margin  will  be  seen. 

The  Rectus  abdominis  is  a  long  flat  muscle,  which  extends  along  the  whole 
length  of  the  front  of  the  abdomen,  being  separated  from  its  fellow  of  the  opposite 
side  by  the  linea  alba.  It  is  much  broader,  but  thinner,  above  than  below,  and 
arises  by  two  tendons,  the  external  or  larger  being  attached  to  the  crest  of  the  os 
pubis,  the  internal,  smaller  portion  interlacing  with  its  fellow  of  the  opposite  side, 
and  being  connected  with  the  ligaments  covering  the  front  of  the  symphysis  pubis. 
The  fibres  ascend,  and  the  muscle  is  inserted  by  three  portions  of  unequal  size 
into  the  cartilages  of  the  fifth,  sixth,  and  seventh  ribs.  Some  fibres  are  occasion- 
ally connected  with  the  costo-xiphoid  ligaments  and  side  of  the  ensiform  cartilage. 

The  Rectus  muscle  is  traversed  bv  tendinous  intersections,  three  in  number. 


454 


THE  MUSCLES  AND    FASCIA 


which  have  received  the  name  of  linece  transversce.  One  of  these  is  usually 
situated  opposite  the  umbilicus,  and  two  above  that  point ;  of  the  latter,  one 
corresponds  to  the  extremity  of  the  ensiform  cartilage,  and  the  other  to  the 
interval  between  the  ensiform  cartilage  and  the  umbilicus,  These  intersections 
pass  transversely  or  obliquely  across  the  muscle  in  a  zigzag  course ;  they  rarely 
extend  completely  through  its  substance,  sometimes  pass  only  halfway  across 


Linea 


"t~iG.  294.— The  Transversalis,  Rectus,  and  Pyramidalis  muscles. 

it,  and  are  intimately  adherent  in  front  to  the  sheath  in  which  the  muscle  is 
enclosed. 

The  Rectus  is  enclosed  in  a  sheath  (Fig.  295)  formed  by  the  aponeuroses  of  the 
Oblique  and  Transversalis  muscles,  which  are  arranged  in  the  following  manner. 
When  the  aponeurosis  of  the  Internal  oblique  arrives  at  the  outer  margin  of  the 
Rectus,  it  divides  into  two  lamellae,  one  of  which  passes  in  front  of  the  Rectus, 
blending  with  the  aponeurosis  of  the  External  oblique ;  the  other,  behind  it, 
blending  with  the  aponeurosis  of  the  Transversalis ;  and  these,  joining  again  at  its 


OF   THE   ABDOMEN. 


455 


inner  border,  are  inserted  into  the  linea  alba.  This  arrangement  of  the  aponeuroses 
exists  along  the  upper  three-fourths  of  the  muscle :  at  the  commencement  of  the 
lower  fourth,  the  posterior  wall  of  the  sheath  terminates  in  a  thin  curved  margin, 
the  semilunar  fold  of  Douglas,  the  concavity  of  which  looks  downward  toward 
the  pubes ;  the  aponeuroses  of  all  three  muscles  passing  in  front  of  the  Rectus 
without  any  separation.  The  extremities  of  the  fold  of  Douglas  descend  as  pillars 
to  the  os  pubis.  The  inner  pillar  is  attached  to  the  symphysis  pubis ;  the  outer 
pillar,  which  is  named  by  Braune  the  ligament  of  Hesselbach,  divides  below  to 
enclose  the  internal  abdominal  ring;  the  internal  fibres  are  attached  to  the 
horizontal  ramus  of  the  os  pubis  and  the  pectineal  fascia ;  the  external  ones  pass 
to  the  Psoas  fascia  and  to  the  Transversalis  where  it  arises  from  Poupart's 
ligament  on  the  outer  side  of  the  ring.  The  Rectus  muscle,  in  the  situation 


FIG.  203.— A  Transverse  section  of  the  abdomen  in  the  lumbar  region. 

where  its  sheath  is  deficient,  is  separated  from  the  peritoneum  by  the  transversalis 
fascia. 

The  Pyramidalis  is  a  small  muscle,  triangular  in  shape,  placed  at  the  lower 
part  of  the  abdomen,  in  front  of  the  Rectus.  and  contained  in  the  same  sheath 
with  that  muscle.  It  arises  by  tendinous  fibres  from  the  front  of  the  os  "pubis 
and  the  anterior  pubic  ligament ;  the  fleshy  portion  of  the  muscle  passes  upward, 
diminishing  in  size  as  it  ascends,  and  terminates  by  a  pointed  extremity,  which  is 
inserted  into  the  linea  alba,  midway  between  the  umbilicus  and  the  os  pubis.  This 
muscle  is  sometimes  found  wanting  on  one  or  both  sides ;  the  lower  end  of  the 
Rectus  then  becomes  proportionately  increased  in  size.  Occasionally  it  has  been 
found  double  on  one  side,  or  the  muscles  of  the  two  sides  are  of  unequal  size. 
Sometimes  its  length  exceeds  what  is  stated  above. 

Eelations. — Its  anterior  surface  is  covered  by  the  sheath  of  the  Rectus.  Its 
jiotten'or  surface  rests  against  the  Rectus  itself.  To  expose  the  Pyramidalis, 
make,  through  the  sheath  of  the  Rectus.  a  vertical  incision  the  lower  end  of 
which  should  begin  just  a  little  to  one  side  of.  and  on  a  level  with,  the  symphysis 
pubi*. 

Nerves. — The  abdominal  muscles  are  supplied  by  the  lower  intercostal  nerves. 
The  Internal  oblique  also  receives  a  filament  from  the  ilio-inguinal  nerve.  The 
Cremaster  is  supplied  by  the  genital  branch  of  the  Genito-crural. 

In  the  description  of  the  abdominal  muscles  mention  has  frequently  been  made 
of  the  linea  alba,  lineae  semilunares,  and  linere  transversae  ;  when  the  dissection  of 
the  muscles  is  completed  these  structures  should  be  examined. 

The  linea  alba  is  a  tendinous  raphe  seen  along  the  middle  line  of  the  abdomen, 
extending  from  the  ensiform  cartilage  to  the  symphysis  pubis,  to  which  it  is 


456  THE  MUSCLES  AND    FASCIAE 

attached.  It  is  placed  between  the  inner  borders  of  the  Recti  muscles,  and  is 
formed  by  the  blending  of  the  aponeuroses  of  the  Obliqui  and  Transversales  muscles. 
It  is  narrow  below,  corresponding  to  the  narrow  interval  existing  between  the 
Recti ;  but  broader  above,  as  these  muscles  diverge  from  one  another  in  their 
ascent,  becoming  of  considerable  breadth  after  great  distension  of  the  abdomen  from 
pregnancy  or  ascites.  It  presents  numerous  apertures  for  the  passage  of  vessels 
and  nerves  :  the  largest  of  these  is  the  umbilicus,  which  in  the  foetus  transmits  the 
umbilical  vessels,  but  in  the  adult  is  obliterated,  the  cicatrix  being  stronger  than 
the  neighboring  parts ;  hence  umbilical  hernia  occurs  in  the  adult  near  the 
umbilicus,  whilst  in  the  foetus  it  occurs  at  the  umbilicus.  The  linea  alba  is  in 
relation,  in  front,  with  the  integument,  to  which  it  is  adherent,  especially  at  the 
umbilicus ;  behind,  it  is  separated  from  the  peritoneum  by  the  transversalis  fascia  ; 
and  below,  by  the  urachus,  and  the  bladder  when  that  organ  is  distended. 

The  lineae  semilunares  are  two  curved  tendinous  lines  placed  one  on  each  side 
of  the  linea  alba.  Each  corresponds  with  the  outer  border  of  the  Rectus  muscle, 
extends  from  the  cartilage  of  the  ninth  rib  to  the  pubic  spine,  and  is  formed  by 
the  aponeurosis  of  the  Internal  oblique  at  its  point  of  division  to  enclose  the 
Rectus,  where  it  is  reinforced  in  front  by  the  External  oblique  and  behind  by  the 
Transversalis. 

The  lineae  transversae  are  three  narrow  transverse  lines  which  intersect  the 
Recti  muscles,  as  already  mentioned  ;  they  connect  the  lineae  semilunares  with  the 
linea  alba. 

Actions. — The  abdominal  muscles  perform  a  threefold  action : 

When  the  pelvis  and  thorax  are  fixed,  they  compress  the  abdominal  viscera,  by 
constricting  the  cavity  of  the  abdomen,  in  which  action  they  are  materially  assisted 
by  the  descent  of  the  diaphragm.  By  these  means  the  foetus  is  expelled  from  the 
uterus,  the  faeces  from  the  rectum,  the  urine  from  the  bladder,  and  the  contents  of 
the  stomach  in  vomiting. 

If  the  pelvis  and  spine  are  fixed,  these  muscles  compress  the  lower  part  of  the 
thorax,  materially  assisting  expiration.  If  the  pelvis  alone  is  fixed,  the  thorax  is 
bent  directly  forward  when  the  muscles  of  both  sides  act,  or  to  either  side  when 
those  of  the  two  sides  act  alternately,  rotation  of  the  trunk  at  the  same  time  taking 
place  to  the  opposite  side. 

If  the  thorax  is  fixed,  these  muscles,  acting  together,  draw  the  pelvis  upward, 
as  in  climbing ;  or,  acting  singly,  they  draw  the  pelvis  upward,  and  rotate  the 
vertebral  column  to  one  side  or  the  other.  The  Recti  muscles,  acting  from  below, 
depress  the  thorax,  and  consequently  flex  the  vertebral  column  ;  when  acting  from 
above,  they  flex  the  pelvis  upon  the  vertebral  column.  The  Pyramidales  are 
tensors  of  the  linea  alba. 

The  fascia  transversalis  is  a  thin  aponeurotic  membrane  which  lies  between 
the  inner  surface  of  the  Transversalis  muscle  and  the  peritoneum.  It  forms  part 
of  the  general  layer  of  fascia  which  lines  the  interior  of  the  abdominal  and  pelvic 
cavities,  and  is  directly  continuous  with  the  iliac  and  pelvic  fasciae.  In  the  inguinal 
region  the  transversalis  fascia  is  thick  and  dense  in  structure,  and  joined  by  fibres 
from  the  aponeurosis  of  the  Transversalis  muscle,  but  it  becomes  thin  and  cellular 
as  it  ascends  to  the  diaphragm.  Below,  it  has  the  following  attachments  :  external 
to  the  femoral  vessels  it  is  connected  to  the  posterior  margin  of  Poupart's  ligament, 
and  is  there  continuous  with  the  iliac  fascia.  Internal  to  the  femoral  vessels  it  is 
thin  and  attached  to  the  os  pubis  and  pectineal  line,  behind  the  conjoined  tendon, 
with  which  it  is  united;  and,  corresponding  to  the  point  where  the  femoral  vessels 
pass  into  the  thigh,  this  fascia  descends  in  front  of  them,  forming  the  anterior 
wall  of  the  crural  sheath.  The  spermatic  cord  in  the  male  and  the  round  ligamerft 
in  the  female  pass  through  this  fascia :  the  point  where  they  pass  through  is  called 
the  internal  abdominal  ring.  This  opening  is  not  visible  externally,  owing  to  a 
prolongation  of  the  transversalis  fascia  on  the  structures,  forming  the  infundib- 
uliform  process. 

The  internal  or  deep   abdominal  ring  is  situated  in  the  transversalis  fascia, 


OF   THE  ABDOMEN.  457 

midway  between  the  anterior  superior  spine  of  the  ilium  and  the  spine  of  the  os 
pubis,  and  about  half  an  inch  above  Poupart's  ligament.  It  is  of  an  oval  form, 
the  extremities  of  the  oval  directed  upward  and  downward,  varies  in  size  in  different 
subjects,  and  is  much  larger  in  the  male  than  in  the  female.  It  is  bounded,  above 
and  externally,  by  the  arched  fibres  of  the  Trans versalis  ;  below  and  internally,  by 
the  deep  epigastric  vessels.  It  transmits  the  spermatic  cord  in  the  male  and  the 
round  ligament  in  the  female.  From  its  circumference  a  thin  funnel-shaped 
membrane,  the  infundibuliform  fascia,  is  continued  round  the  cord  and  testis, 
enclosing  them  in  a  distinct  pouch. 

When  the  sac  of  an  oblique  inguinal  hernia  passes  through  the  internal  or  deep  abdominal 
ring,  the  infundibuliform  process  of  the  transversalis  fascia  forms  one  of  its  coverings. 

The  inguinal  or  spermatic  canal  contains  the  spermatic  cord  in  the  male  and 
the  round  ligament  in  the  female.  It  is  an  oblique  canal  about  an  inch  and  a  half 
in  length,  directed  downward  and  inward,  and  placed  parallel  to  and  a  little  above 
Poupart's  ligament.  It  commences  above  at  the  internal  or  deep  abdominal  ring, 
which  is  the  point  where  the  cord  enters  the  spermatic  canal,  and  terminates  below 
at  the  external  ring.  It  is  bounded  in  front  by  the  integument  and  superficial 
fascia,  by  the  aponeurosis  of  the  External  oblique  throughout  its  whole  length,  and 
by  the  Internal  oblique  for  its  outer  third ;  behind,  by  the  triangular  ligament,  the 
conjoined  tendon  of  the  Internal  oblique  and  Transversalis,  transversalis  fascia, 
and  the  subperitoneal  fat  and  peritoneum ;  above,  by  the  arched  fibres  of  the 
Internal  oblique  and  Transversalis  ;  below,  by  the  union  of  the  fascia  transversalis 
with  Poupart's  ligament. 

That  form  of  protrusion  in  which  the  intestine  follows  the  course  of  the  spermatic  cord 
along  the  spermatic  canal  is  called  oblique  inguinal  hernia. 

The  Deep  Crural  Arch. — Passing  across  the  front  of  the  crural  arch,  on  the 
abdominal  side  of  Poupart's  ligament  and  closely  connected  with  it,  is  a  thickened 
band  of  fibres  called  the  deep  crural  arch.  It  is  apparently  a  thickening  of  the 
fascia  transversalis,  joining  externally  to  the  centre  of  Poupart's  ligament,  and 
arching  across  the  front  of  the  crural  sheath  to  be  inserted  by  a  broad  attachment 
into  the  pectineal  line,  behind  the  conjoined  tendons.  In  some  subjects  this 
structure  is  not  very  prominently  marked,  and  not  unfrequently  it  is  altogether 
wanting. 

Surface  Form. — The  only  two  muscles  of  this  group  which  have  any  considerable  influ- 
ence on  surface  form  are  the  External  oblique  and  Rectus  muscles  of  the  abdomen.  With 
regard  to  the  External  oblique,  the  upper  digitations  of  its  origin  from  the  ribs  are  well  marked, 
intermingled  with  the  serrations  of  the  Serratus  magnus;  the  lower  digitations  are  not  visible, 
being  covered  by  the  thick  border  of  the  Latissimus  dorsi.  Its  attachment  to  the  crest  of  the 
ilium,  in  conjunction  with  the  Internal  oblique,  forms  a  thick  oblique  roll,  which  determines  the 
iliac  furrow.  Sometimes  on  the  front  of  the  lateral  region  of  the  abdomen  an  undulating  out- 
line marks  the  spot  where  the  muscular  fibres  terminate  and  the  aponeurosis  commences.  The 
outer  border  of  the  Rectus  is  defined  by  the  Hnea  semilunaris,  which  may  be  exactly  defined  by 
putting  the  muscle  into  action.  It  corresponds  with  a  curved  line,  with  its  convexity  outward, 
drawn  from  the  lowest  part  of  the  cartilage  of  the  seventh  rib  to  the  spine  of  the  os  pubis,  so  • 
that  the  centre  of  the  line,  at  or  near  the  umbilicus,  is  three  inches  from  the  median  line.  The 
inner  border  of  the  Rectus  corresponds  to  the  linea  alba,  marked  on  the  surface  of  the  body  by 
a  groove,  the  abdominal  furrow,  which  extends  from  the  infrasternal  fossa  to,  or  to  a  little  below, 
the  umbilicus,  where  it  gradually  becomes  lost.  The  surface  of  the  Rectus  presents  three  trans- 
verse furrows,  the  linece  transversce.  The  upper  two  of  these,  one  opposite  or  a  little  below  the 
tip  of  the  ensiform  cartilage,  and  another,  midway  between  this  point  and  the  umbilicus,  are 
usually  well  marked  ;  the  third,  opposite  the  umbilicus,  is  not  so  distinct.  The  umbilicus,  situ- 
ated in  the  linea  alba,  varies  very  much  in  position  as  regards  its  height.  It  is  always  situated 
above  a  zone  drawn  round  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium,  gene- 
rally being  about  three-quarters  of  an  inch  to  an  inch  above  this  line.  It  generally  corresponds, 
therefore,  to  the  fibro-cartilage  between  the  third  and  fourth  lumbar  vertebra?. 

Deep  Muscles  of  the  Abdomen. 

Psoas  parvus.  Iliacus.r 

Psoas  magnus.  Quadratus  lumborum. 


458  THE  MUSCLES  AND   FASCIA 

The  Psoas  magnus,  the  Psoas  parvus,  and  the  Iliacus  muscles,  with  the  fascia 
covering  them,  will  be  described  with  the  Muscles  of  the  Lower  Extremity  (see 
page  504). 

The  Fascia  covering  the  Quadratus  Lumborum. — This  is  the  most  anterior  of  the 
two  layers  of  fascia  which  are  given  off  from  the  anterior  or  deep  surface  of  the  lum- 
bar fascia  (see  page  433).  It  is  a  thin  layer  of  fascia  (part  of  transversalis  fascia?), 
which,  passing  over  the  anterior  surface  of  the  Quadratus  lumborum,  is  attached, 
internally,  to  the  anterior  surface  of  the  transverse  processes  of  the  lumbar  verte- 
brae ;  below  to  the  ilio-lumbar  ligament ;  and  above,  to  the  apex  and  lower  border 
of  the  last  rib. 

The  portion  of  this  fascia  which  extends  from  the  transverse  process  of  the 
first  lumbar  vertebra  to  the  apex  and  lower  border  of  the  last  rib  constitutes  the 
ligamentum  arcuatum  externum. 

The  Quadratus  lumborum  (Fig.  288,  page  435)  is  situated  in  the  lumbar  region. 
It  is  irregularly  quadrilateral  in  shape,  and  broader  below  than  above.  It  arises  by 
aponeurotic  fibres  from  the  ilio-lumbar  ligament  and  the  adjacent  portion  of  the 
crest  of  the  ilium  for  about  two  inches,  and  is  inserted  into  the  lower  border  of  the 
last  rib  for  about  half  its  length  and  by  four  small  tendons,  into  the  apices  of 
the  transverse  processes  of  the  four  upper  lumbar  vertebrae.  Occasionally  a  second 
portion  of  this  muscle  is  found  situated  in  front  of  the  preceding.  This  arises  from 
the  upper  borders  of  the  transverse  processes  of  the  lumbar  vertebras,  and  is  inserted 
into  the  lower  margin  of  the  last  rib.  The  Quadratus  lumborum  is  contained  in  a 
sheath  formed  by  the  anterior  and  middle  lamellae  of  the  lumbar  fasciae. 

Relations. — Its  anterior  surface  (or  rather  the  fascia  Avhich  covers  its  anterior 
surface)  is  in  relation  with  the  colon  and  the  kidney.  Its  posterior  surface  is  in 
relation  with  the  middle  lamella  (posterior  aponeurosis  of  the  Transversalis  muscle) 
of  the  lumbar  fascia,  which  separates  it  from  the  Erector  spinae.  The  Quadratus 
lumborum  extends,  however,  beyond  the  outer  border  of  the  Erector  spinae. 

Nerve-supply. — The  anterior  branches  of  the  lumbar  nerves. 

Actions. — The  Quadratus  lumborum  draws  down  the  last  rib,  and  acts  as  a 
muscle  of  inspiration ;  and,  at  the  same  time,  by  fixing  the  last  rib,  it  opposes 
the  tendency  of  the  Diaphragm  to  draw  it  upward,  and  thus  it  becomes  an  assist- 
ant to  inspiration.  If  the  thorax  and  spine  are  fixed,  it  may  act  upon  the  pelvis, 
raising  it  toward  its  own  side  when  only  one  muscle  is  put  in  action  ;  and  when 
both  muscles  act  together,  either  from  below  or  above,  they  flex  the  trunk. 

Muscles  of  the  Pelvic  Outlet  or  of  the  Ischio-rectal  Region  and  Perinaeum. 

Corrugator  cutis  ani.  Internal  sphincter  ani. 

External  sphincter  ani.  Levator  ani. 

Coccygeus. 
fTransversus  perinaei.  TTransversus  perinasi. 

r    n/r  i         Accelerator  urinae.  r    -n       i       \  Sphincter  vaginas. 

In  Male.  <  -,-,  .  In  Female.    <  «*  v,    6.  -,. 

Erector  penis.  |  Erector  clitoridis. 

^Compressor  urethrae.  ^Compressor  urethrae. 

The  Corrugator  Cutis  Ani. — Around  the  anus  is  a  thin  stratum  of  involuntary 
muscular  fibre,  which  surrounds  it  in  a  radiating  manner.  Internally,  the  fibres 
fade  off  into  the  submucous  tissue,  whilst  externally  they  blend  with  the  true  skin. 
By  its  contraction  it  raises  the  skin  into  ridges  radiating  from  the  margin  of  the  anus. 

The  External  sphincter  ani  is  a  thin,  flat  plane  of  muscular  fibres,  elliptical  in 
shape  and  intimately  adherent  to  the  integument  surrounding  the  margin  of  the 
anus.  It  measures  about  three  or  four  inches  in  length  from  its  anterior  to  its 
posterior  extremity,  being  about  an  inch  in  breadth  opposite  the  anus.  It  arises 
from  the  tip  of  the  coccyx  by  a  narrow  tendinous  band,  and  from  the  superficial 
fascia  in  front  of  that  bone  ;  and  is  inserted  into  the  central  tendinous  point  of  the 
perinaeum,  joining  with  the  Transversus  perinaei,  the  Levator  ani,  and  the  Accelera- 
tor urinae.  Like  other  sphincter  muscles,  it  consists  of  two  planes  of  muscular 


OF    THE   PERINEUM  AXD    PELVIC   OUTLET. 


459 


fibre,  which  surround  the  margin  of  the  anus,  and  join  in  a  commissure  in  front 
and  behind. 

Nerve-supply. — A  branch  from  the  anterior  division  of  the  fourth  sacral  and 
the  inferior  haemorrhoidal  branch  of  the  internal  pudic. 

Actions. — The  action  of  this  muscle  is  peculiar :  1.  It  is,  like  other  muscles, 
always  in  a  state  of  tonic  contraction,  and  having  no  antagonistic  muscle  it  keeps 
the  anal  orifice  closed.  2.  It  can  be  put  into  a  condition  of  greater  contraction 
under  the  influence  of  the  will,  so  as  to  more  firmly  occlude  the  anal  aperture. 
3.  Taking  its  fixed  point  at  the  coccyx,  it  helps  to  fix  the  central  point  of  the 
perinaeum,  so  that  the  Accelerator  may  act  from  this  fixed  point. 

The  Internal  sphincter  is  a  muscular  ring  which  surrounds  the  lower  extremity 
of  the  rectum  for  about  an  inch,  its  inferior  border  being  contiguous  to,  but  quite 
separate  from,  the  External  sphincter.  This  muscle  is  about  two  lines  in  thickness, 
and  is  formed  by  an  aggregation  of  the  involuntary  circular  fibres  of  the  intestine. 
It  is  paler  in  color  and  less  coarse  in  texture  than  the  External  sphincter. 

Actions. — Its  action  is  entirely  involuntary.  It  helps  the  External  sphincter 
to  occlude  the  anal  aperture. 

The  Levator  ani  (Fig.  296)  is  a  broad,  thin  muscle,  situated  on  each  side  of  the 
pelvis.  It  is  attached  to  the  inner  surface  of  the  sides  of  the  true  pelvis,  and 


Ureter 


Eecto-tesical 
fascia, 


Peltic  fasci 


Veins  of 
prostatic  plexu* 

Trans,  perinfi 
muscle 


FIG.  2%.— Pelvis  seen  from  behind,  showi 


ani.    (Henlej 


descending  unites  with  its  fellow  of  the  opposite  side  to  form  the  floor  of  the  pelvic 
cavity.  It  supports  the  viscera  in  this  cavity  and  surrounds  the  various  structures 
which  pass  through  it.  It  arises,  in  front,  from  the  posterior  surface  of  the  body 
and  ramus  of  the  os  pubis  on  the  outer  side  of  the  symphysis ;  posteriorly,  from 
the  inner  surface  of  the  spine  of  the  ischium ;  and  between  these  two  points  from 
the  angle  of  division  between  the  obturator  and  recto-vesical  layers  of  the  pelvic 
fascia  at  their  under  part.  The  fibres  pass  downward  to  the  middle  line  of  the  floor 
of  the  pelvis,  and  are  inserted,  the  most  posterior  into  the  sides  of  the  apex 
of  the  coccyx  ;  those  placed  more  anteriorly  unite  with  the  muscles  of  the  opposite 
side,  in  a  median  fibrous  raphe,  which  extends  between  the  coccyx  and  the  margin 
of  the  anus.  The  middle  fibres,  which  form  the  larger  portion  of  the  muscle,  are 


460  THE   MUSCLES  AND   FASCIA 

inserted  into  the  side  of  the  rectum,  blending  with  the  fibres  of  the  Sphincter 
muscles ;  lastly,  the  anterior  fibres,  the  longest,  descend  upon  the  side  of  the 
prostate  gland  to  unite  beneath  it  with  the  muscle  of  the  opposite  side,  blending 
with  the  fibres  of  the  External  sphincter  and  Transversus  perinaei  muscles  at  the 
central  tendinous  point  of  the  perinaeum. 

The  anterior  portion  is  occasionally  separated  from  the  rest  of  the  muscle  by 
connective  tissue.  From  this  circumstance,  as  well  as  from  its  peculiar  relation 
with  the  prostate  gland,  descending  by  its  side,  and  surrounding  it  as  in  a  sling, 
it  has  been  described  by  Santorini  and  others  as  a  distinct  muscle,  under  the  name 
of  Levator  prostates.  In  the  female,  the  anterior  fibres  of  the  Levator  ani  descend 
upon  the  side  of  the  vagina. 

Relations. — By  its  inner  or  pelvic  surface,  with  the  recto-vesical  fascia,  which 
separates  it  from  the  viscera  of  the  pelvis  and  from  the  peritoneum.  By  its  outer 
or  perineal  surface,  it  forms  the  inner  boundary  of  the  ischio-rectal  fossa,  and  is 
covered  by  a  thin  layer  of  fascia,  the  ischio-rectal  or  anal  fascia,  given  off  from  the 
obturator  fascia.  Its  posterior  border  is  continuous  with  the  Coccygeus  muscle. 
Its  anterior  border  is  separated  from  the  muscle  of  the  opposite  side  by  a  triangular 
space,  through  which  the  urethra,  and  in  the  female  the  vagina,  passes  from  the 
pelvis. 

Nerve-supply. — A  branch  from  the  anterior  division  of  the  fourth  sacral  nerve. 

Actions. — This  muscle  supports  the  lower  end  of  the  rectum  and  vagina,  and 
also  the  bladder  during  the  efforts  of  expulsion.  It  elevates  and  inverts  the  lower 
end  of  the  rectum  after  it  has  been  protruded  and  everted  during  the  expulsion  of 
the  faeces.  It  is  also  a  muscle  of  forced  expiration. 

The  Coccygeus  is  situated  behind  and  parallel  with  the  preceding.  It  is  a  tri- 
angular plane  of  muscular  and  tendinous  fibres,  arising,  by  its  apex,  from  the 
spine  of  the  ischium  and  lesser  sacro-sciatic  ligament,  and  inserted,  by  its  base, 
into  the  margin  of  the  coccyx  and  into  the  side  of  the  lower  piece  of  the  sacrum. 
This  muscle  is  continuous  with  the  posterior  border  of  the  Levator  ani,  and  closes 
in  the  back  part  of  the  outlet  of  the  pelvis. 

Relations. — By  its  inner  or  pelvic  surface,  with  the  rectum ;  by  its  external 
surface,  with  the  lesser  sacro-sciatic  ligament ;  by  its  posterior  border,  with  the 
Pyriformis. 

Nerve-supply. — A  branch  from  the  fourth  and  fifth  sacral  nerves. 

Action. — The  Coccygei  muscles  raise  and  support  the  coccyx  after  it  has  been 
pressed  backward  during  defecation  or  parturition. 

Superficial  Fascia. — The  superficial  fascia  of  the  perinaeum  consists  of  two 
layers,  superficial  and  deep,  as  in  other  regions  of  the  body. 

The  superficial  layer  is  thick,  loose,  areolar  in  texture,  and  contains  much 
adipose  tissue  in  its  meshes,  the  amount  of  which  varies  in  different  subjects.  In 
front,  it  is  continuous  with  the  dartos  of  the  scrotum ;  behind,  it  is  continuous 
with  the  subcutaneous  areolar  tissue  surrounding  the  anus  ;  and,  on  either  side, 
with  the  same  fascia  on  the  inner  side  of  the  thighs.  This  layer  should  be  care- 
fully removed  after  it  has  been  examined,  when  the  deep  layer  will  be  exposed. 

The  deep  layer  of  superficial  fascia  (Fascia  of  Colles)  is  thin,  aponeurotic  in 
structure,  and  of  considerable  strength,  serving  to  bind  down  the  muscles  of  the 
root  of  the  penis.  It  is  continuous,  in  front,  with  the  dartos  of  the  scrotum ;  on 
either  side  it  is  firmly  attached  to  the  margins  of  the  rami  of  the  os  pubis  arid 
ischium,  external  to  the  crus  penis,  and  as  far  back  as  the  tuberosity  of  the  isch- 
ium;  posteriorly,  it  curves  down  behind  the  Transversus  perinaei  muscles  to  join 
the  lower  margin  of  the  deep  perineal  fascia.  This  fascia  not  only  covers  the 
muscles  in  this  region,  but  sends  down  a  vertical  septum  from  its  under  surface,  which 
separates  the  back  part  of  the  subjacent  space  into  two,  being  incomplete  in  front. 

The  Central  Tendinous  Point  of  the  Perinseum. — This  is  a  fibrous  point  in  the 
middle  line  of  the  perinaeum,  between  the  urethra  and  the  rectum,  being  about 
half  an  inch  in  front  of  the  anus.  At  this  point  four  muscles  converge  and  are 
attached  :  viz.  the  External  sphincter  ani,  the  Accelerator  urinae,  and  the  two 


OF   THE   FERINE  I'M. 


461 


Transversus  perinaei ;  so  that  by  the  contraction  of  these  muscles,  which  extend  in 
opposite  directions,  it  serves  as  a  fixed  point  of  support. 

The  Transversus  perinaei  is  a  narrow  muscular  slip,  which  passes  more  or  less 
transversely  across  the  back  part  of  the  perineal  space.  It  arises  by  a  small  tendon 
from  the  inner  and  fore  part  of  the  tuberosity  of  the  ischium.  and,  passing  inward, 
is  inserted  into  the  central  tendinous  point  of  the  perinaeum,  joining  in  this  situation 


FIG.  297.— The  perinaeum.    The  integument  and  superficial  layer  of  superficial  fascia  reflected. 

with  the  muscle  of  the  opposite  side,  the  External  sphincter  ani  behind,  and  the 
Accelerator  urinae  in  front. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their  contraction  they  serve  to  fix  the  central  tendinous  point  of 
the  perinaeum. 

The  Accelerator  urinae  (Ejaculator  seminis,  or  Bulbo-cavernosus)  is  placed  in 
the  middle  line  of  the  perinaeum.  immediately  in  front  of  the  anus.  It  consists  of 
two  symmetrical  halves,  united  along  the  median  line  by  a  tendinous  raphe.  It 
arises  from  the  central  tendon  of  the  perinaeum.  and  from  the  median  raphe  in 
front.  From  this  point  its  fibres  diverge  like  the  plumes  of  a  pen ;  the  most 
posterior  form  a  thin  layer,  which  are  lost  on  the  anterior  surface  of  the  triangular 
ligament ;  the  middle  fibres  encircle  the  bulb  and  adjacent  parts  of  the  corpus 
spongiosum.  and  join  with  the  fibres  of  the  opposite  side,  on  the  upper  part  of  the 
corpus  spongiosum.  in  a  strong  aponeurosis :  the  anterior  fibres,  the  longest  and 
most  distinct,  spread  out  over  the  sides  of  the  corpus  cavernosum,  to  be  inserted 
partly  into  that  body,  anterior  to  the  Erector  penis,  occasionally  extending  to  the 
os  pubis ;  partly  terminating  in  a  tendinous  expansion,  which  covers  the  dorsal 
vessels  of  the  penis.  The  latter  fibres  are  best  seen  by  dividing  the  muscle 
longitudinally,  and  dissecting  it  outward  from  the  surface  of  the  urethra. 

Action. — This  muscle  serves  to  empty  the  canal  of  the  urethra,  after  the 
bladder  has  expelled  its  contents ;  during  the  greater  part  of  the  act  of  micturition 
its  fibres  are  relaxed,  and  it  only  comes  into  action  at  the  end  of  the  process.  The 
middle  fibres  are  supposed,  by  Krause.  to  assist  in  the  erection  of  the  corpus 


462 


THE  MUSCLES  AND    FASCIA 


spongiosum,  by  compressing  the  erectile  tissue  of  the  bulb.  The  anterior  fibres, 
according  to  Tyrrel,  also  contribute  to  the  erection  of  the  penis,  as  they  are  inserted 
into,  and  continuous  with,  the  fascia  of  the  penis,  compressing  the  dorsal  vein 
during  the  contraction  of  the  muscle. 

The  Erector  penis  (Ischio-cavernous)  covers  part  of  the  crus  penis.  It  is  an 
elongated  muscle,  broader  in  the  middle  than  at  either  extremity,  and  situated  on 
either  side  of  the  lateral  boundary  of  the  peringeum.  It  arises  by  tendinous  and 


FIG.  298.— The  muscles  attached  to  the  front  of  the  pelvis.    (From  a  preparation  in  the  Museum  of  the  Royal 
College  of  Surgeons  of  England.) 

fleshy  fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium,  behind  the 
crus  penis,  from  the  surface  of  the  crus,  and  from  the  adjacent  portion  of  the 
ramus  of  the  ischium.  From  these  points  fleshy  fibres  succeed,  which  end  in  an 
aponeurosis  which  is  inserted  into  the  sides  and  under  surface  of  the  crus  penis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  compresses  the  crus  penis  and  retards  the  return  of  the  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

Between  the  muscles  just  examined  a  triangular  space  exists,  bounded 
internally  by  the  Accelerator  urinae,  externally  by  the  Erector  penis,  and  behind 


OF   THE   PERINJEUM. 


463 


by  the  Transversus  perinsei.  The  floor  of  this  space  is  formed  by  the  triangular 
ligament  of  the  urethra  (deep  perineal  fascia),  and  running  from  behind  forward 
in  it  are  the  superficial  perineal  vessels  and  nerve,  and  the  transverse  perineal 
artery  coursing  along  the  posterior  boundary  of  the  space  on  the  Transversus 
perinsei  muscle. 

The  Triangular  Ligament  (Deep  perineal  fascia)  is  a  dense  membranous  lamina, 
which  closes  the  front  part  of  the  outlet  of  the  pelvis.  It  is  triangular  in  shape, 
about  an  inch  and  a  half  in  depth,  attached  above,  by  its  apex,  to  the  under 
surface  of  the  symphysis  pubis  and  subpubic  ligament ;  and  on  each  side  to  the 
rami  of  the  ischium  and  pubes,  beneath  the  crura  penis.  Its  inferior  margin,  or 
base,  is  directed  toward  the  rectum,  and  connected  to  the  central  tendinous  point 
of  the  perinseum.  It  is  continuous  with  the  deep  layer  of  the  superficial  fascia 
behind  the  Transversus  perinaei  muscle,  and  with  a  thin  fascia  which  covers  the 
cutaneous  surface  of  the  Levator  ani  muscle  (anal  or  ischio-rectal  fascia). 


GREAT  SACRO- 
SCIATIC    LIGAMENT 


Superficial  perineal  artery. 
Superficial  perineal  nerre. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


FIG.  299.— The  superficial  muscles  and  vessels  of  the  perinaeum. 


The  Triangular  ligament  is  perforated  by  the  urethra,  about  an  inch  below  the 
symphysis  pubis.  The  aperture  is  circular  in  form,  and  about  three  or  four  lines 
in  diameter.  Above  this  is  the  aperture  for  the  dorsal  vein  of  the  penis ;  and, 
outside  the  latter,  branches  of  the  pudic  nerve  and  artery  pierce  it. 

The  triangular  ligament  consists  of  two  layers,  superficial  or  inferior,  and  deep 
or  superior ;  these  are  separated  in  front,  but  united  behind. 

The  superficial  layer  on  its  inferior  surface  is  intimately  connected  with,  and 
sends  an  expansion  to,  the  bulb.  It  is  pierced  by  the  duct  of  Cowper  s  gland  and 
by  the  membranous  urethra ;  as  is  also  the  following  layer. 

The  deep  layer  is  derived  laterally  from  the  obturator  fascia ; 1  superiorly 
expansions  from  it  are  given  off  into  the  sheath  of  the  prostate  gland,  this  sheath. 
in  its  turn,  being  formed  from  the  recto-vesical  fascia. 

Structures  between  the  Two  Layers  of  the  Triangular  Ligament. — If  the 
superficial  layer  of  this  fascia  is  detached  on  either  side,  the  following  structures 

1  "On  the  Anatomy  of  the  Posterior  Layer  of  the  Triangular  Ligament,"  see  a  paper  by  Mr 
Carrington,  Guy's  Hospital  Reports. 


464 


THE   MUSCLES  AND    FASCIAE 


will  be  seen  between  it  and  the  deep  layer :  the  subpubic  ligament  above,  close  to 
the  pubes ;  the  dorsal  vein  of  the  penis ;  the  membranous  portion  of  the  urethra, 
and  the  Compressor  urethras  muscle ;  Cowper's  glands  and  their  ducts ;  the  pudic 
vessels  and  nerve ;  the  artery  and  nerve  of  the  bulb,  and  a  plexus  of  veins. 

The  Compressor  urethras  (Constrictor  urethrce)  surrounds  the  whole  length  of 
the  membranous  portion  of  the  urethra,  and  is  contained  between  the  two  layers 


Anterior  layer  of 

deep  perineal  fascia  removed, 

showing 

COMPRESSOR    URETHRA. 

Internal  pudic  artery. 
Artery  of  the  bulb. 
Cowper's  gland. 


^"^-  1^ —  ^-fc  , ,  ^futf^^ 

FIG.  300.— Triangular  ligament  or  deep  perineal  fascia.    On  the  left  side  the  superficial  layer  has  heen 
removed. 


of  the  triangular  ligament.  It  arises,  by  aponeurotic  fibres,  from  the  upper  part 
of  the  ramus  of  the  os  pubis  on  each  side,  to  the  extent  of  half  or  three-quarters 
of  an  inch  :  each  segment  of  the  muscle  passes  inward,  and  divides  into  two 
fasciculi,  which  surround  the  urethra  from  the  prostate  gland  behind  to  the 
bulbous  portion  of  the  urethra  in  front ;  and  unite,  at  the  upper  and  lower 
surfaces  of  this  tube,  with  the  muscle  of  the  opposite  side,  by  means  of  a  tendinous 
raphe. 

Actions. — The  muscles  of  both  sides  act  together  as  a  sphincter,  compressing 
the  membranous  portion  of  the  urethra.  During  the  transmission  of  fluids  they, 
like  the  Acceleratores  urinae,  are  relaxed,  and  only  come  into  action  at  the  end  of 
the  process  to  eject  the  last  of  the  fluid. 

Muscles  of  the  Perinaeum  in  the  Female. 

The  Transversus  perinsei  in  the  female  is  a  narrow  muscular  slip,  which  passes 
more  or  less  transversely  across  the  back  part  of  the  perineal  space.  It  arises  by 
a  small  tendon  from  the  inner  and  fore  part  of  the  tuberosity  of  the  ischium,  and, 
passing  inward,  is  inserted  into  the  central  line  of  the  peringeum,  joining  in  this 
situation  with  the  muscle  of  the  opposite  side,  the  External  sphincter  ani  behind, 
and  the  Sphincter  vaginas  in  front. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their  contraction  they  serve  to  fix  the  central  tendinous  point  of 
the  perinfeum. 

The  Sphincter  vaginae  surrounds  the  orifice  of  the  vagina,  and  is  analogous 
to  the  Accelerator  urinse  in  the  male.  It  is  attached  posteriorly  to  the  central 


OF   THE    UPPER    EXTREMITY.  465 

tendinous  point  of  the  perinaeum,  where  it  blends  with  the  External  sphincter  ani. 
Its  fibres  pass  forward  on  each  side  of  the  vagina,  to  be  inserted  into  the  corpora 
cavernosa  of  the  clitoris,  a  fasciculus  crossing  over  the  body  of  the  organ  so  as  to 
compress  the  dorsal  vein. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  diminishes  the  orifice  of  the  vagina.  The  anterior  fibres  contribute 
to  the  erection  of  the  clitoris,  as  they  are  inserted  into  and  are  continuous  with  the 
fascia  of  the  clitoris ;  compressing  the  dorsal  vein  during  the  contraction  of  the 
muscle. 

The  Erector  clitoridis  resembles  the  Erector  penis  in  the  male,  but  is  smaller  than 
it.  It  covers  the  unattached  part  of  the  crus  clitoridis.  It  is  an  elongated  muscle, 
broader  at  the  middle  than  at  either  extremity,  and  situated  on  either  side  of  the 
lateral  boundary  of  the  perinaeum.  It  arises  by  tendinous  and  fleshy  fibres  from 
the  inner  surface  of  the  tuberosity  of  the  ischium,  behind  the  crus  clitoridis  from 
the  surface  of  the  crus,  and  from  the  adjacent  portion  of  the  ramus  of  the  ischium. 
From  these  points  fleshy  fibres  succeed,  which  end  in  an  aponeurosis,  which  is 
inserted  into  the  sides  and  under  surface  of  the  crus  clitoridis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  compresses  the  crus  clitoridis  and  retards  the  return  of  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

The  triangular  ligament  (deep  perineal  fascia)  in  the  female  is  not  so  strong  as 
in  the  male.  It  is  attached  to  the  pubic  arch,  its  apex  being  connected  with  the  sym- 
physis  pubis.  It  is  divided  in  the  middle  line  by  the  aperture  of  the  vagina,  with 
the  external  coat  of  which  it  becomes  blended,  and  in  front  of  this  is  perforated 
by  the  urethra.  Its  posterior  border  is  continuous,  as  in  the  male,  with  the  deep 
layer  of  the  superficial  fascia  around  the  Transversus  perinaei  muscle. 

Structures  between  the  Two  Layers  of  the  Triangular  Ligament. — The  subpubie 
ligament  above,  the  dorsal  vein  of  the  clitoris,  the  urethra  and  the  Compressor 
urethrje  muscle,  the  glands  of  Bartholin  and  their  ducts ;  the  pudic  vessels  and 
the  dorsal  nerve  of  the  clitoris ;  the  artery  of  the  bulbi  vestibuli,  and  a  plexus 
of  veins. 

The  Compressor  urethrae  (eonttrietor  urethra;  or  deep  transversus  perincei)  arises, 
on  each  side  from  the  margin  of  the  descending  ramus  of  the  os  pubis.  The  fibres,, 
passing  inward,  divide  into  two  sets  ;  those  of  the  fore  part  of  the  muscle  are 
directed  across  the  subpubie  arch  in  front  of  the  urethra  to  blend  with  the  mus- 
cular fibres  of  the  opposite  side ;  while  those  of  the  hinder  and  larger  part  pass 
inward  to  blend  with  the  wall  of  the  vagina  behind  the  urethra. 

MUSCLES  AND  FASCLE  OF  THE  UPPER  EXTREMITY. 

The  Muscles  of  the  Upper  Extremity  are  divisible  into  groups,  corresponding 
with  the  different  regions  of  the  limb. 

OF  THE  SHOULDER.  OF  THE  ARM. 

Anterior  Thoracic  Region.  Anterior  Humeral  Region. 

Pectoralis  major.     Pectoralis  minor.  Coraco-brachialis.                Biceps. 

Subclavius.  Brachialis  anticus. 

ral  Thoracic  Region.  Posterior  Numeral  Region. 

Serratus  magnus.  Triceps.                    Subanconeus. 
Acromial  Region. 

Deltoid.  OF  THE  FOREARM. 

Anterior  Scapular  Region.  Anterior  Radio-ulnar  Region. 

Subscapularis.    '  "3        r^onator  radii  teres. 

'  •„  •-    \  r  lexor  carpi  radians. 

Posterior  Scapular  Region.  ^  ^ }  palmaris  longus. 

Supraspinatus.          Teres  minor.  £-Ji      Flexor  carpi  ulnaris. 

Infraspinatus.           Teres  major.  ~7.        ^Flexor  sublimis  digitorum. 


466 


THE   MUSCLES  AND    FASCIA. 


d,  ^    (  Flexor  profundus  digitorum. 
%  >->  •{  Flexor  longus  pollicis. 
^  >_}    (^Pronator  quadratus. 

Radial  Region. 

Supinator  longus. 

Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevior. 

Posterior  Radio-ulnar  Region. 

li        f  Extensor  communis   digitorum. 
£  £  J  Extensor  minimi  digiti. 
£*  J  Extensor  carpi  ulnaris. 
(^Anconeus. 
^  Supinator  brevis. 

^      Extensor  ossis  metacarpi  pollicis. 
Extensor  brevis  pollicis. 

*      — 


OF  THE  HAND. 
Radial  Region. 
Abductor  pollicis. 
Flexor  ossis  metacarpi  pollicis  (Opponens 

pollicis). 

Flexor  brevis  pollicis. 
Adductor  pollicis. 

Ulnar  Region. 
Palmaris  brevis. 
Abductor  minimi  digiti. 
Flexor  brevis  minimi  digiti. 
Flexor    ossis    metacarpi    minimi    digiti 
(Opponens  minimi  digiti). 

Palmar  Region. 

Lumbricales. 

Extensor  longus  pollicis.  Interossei  palmares. 

•Extensor  indicis.  Interossei  dorsales. 

Dissection  of  Pectoral  Region  and  Axilla  (Fig.  301 ). — The  arm  being  drawn  away  from  the 
side  nearly  at  right  angles  with  the  trunk,  and  rotated  outward,  make  a  vertical  incision  through 

the  integument  in  the  median  line  of  the 
chest,  from  the  upper  to  the  lower  part  of 
the  sternum ;  a  second  incision  along  the 
lower  border  of  the  Pectoral  muscle,  from 
the  ensiform  cartilage  to  the  inner  side  of 
the  axilla;  a  third,  from  the  sternum 
along  the  clavicle,  as  far  as  its  centre ; 
and  a  fourth,  from  the  middle  of  the 
clavicle  obliquely  downward,  along  the 
interspace  between  the  Pectoral  and  Del- 
toid muscles,  as  low  as  the  fold  of  the 
armpit.  The  flap  of  integument  is  then 
to  be  dissected  off  in  the  direction  indi- 
cated in  the  figure,  but  not  entirely 
removed,  as  it  should  be  replaced  on  com- 
pleting the  dissection.  If  a  transverse 
incision  is  now  made  from  the  lower  end 
of  the  sternum  to  the  side  of  the  chest, 
as  far  as  the  posterior  fold  of  the  armpit, 
and  the  integument  reflected  outward, 
the  axillary  space  will  be  more  completely 
exposed. 

Fasciae  of  the  Thorax. 
The  superficial  fascia  of  the 
thoracic  region  is  a  loose  cellulo- 
fibrous  layer  enclosing  masses  of 
fat  in  its  spaces.  It  is  continu- 
ous with  the  superficial  fascia  of 
the  neck  and  upper  extremity 
above,  and  of  the  abdomen  below. 
Opposite  the  mamma,  it  divides  into 
two  layers,  one  of  which  passes  in 


3.  Dissection  of 
Shoulder  and  Arm. 


1.  Dissection  of 
Pectoral  Region 
and  Axilla. 


2.  Bend  of  Elbow. 


4-  Forearm. 


Palm  of  Hand. 


FIG.  301.— Dissection  of  upper  extremity. 


front,  the  other  behind  that  gland ;  and  from  both  of  these  layers  numerous  septa 
pass  into  its  substance,  supporting  its  various  lobes  :  from  the  anterior  layer  fibrous 
processes  pass  forward  to  the  integument  and  nipple.  These  processes  were  called 
by  Sir  A.  Cooper  the  ligamenta  suspensoria,  from  the  support  they  afford  to  the 
gland  in  this  situation. 

The  deep  fascia  of  tbe  thoracic  region  is  a  thin  aponeurotic  lamina,  covering 
the  surface  of  the  great  Pectoral  muscle,  and  sending  numerous  prolongations 


THE  SHOULDER.  467 

between  its  fasciculi :  it  is  attached,  in  the  middle  line,  to  the  front  of  the 
sternum;  and,  above,  to  the  clavicle.  It  is  very  thin  over  the  upper  part  of  the 
muscle,  thicker  in  the  interval  between  the  Pectoralis  major  and  Latissimus  dorsi, 
where  it  closes  in  the  axillary  space,  and  divides  at  the  outer  margin  of  the  latter 
muscle  into  two  layers,  one  of  which  passes  in  front,  and  the  other  behind  it ; 
these  proceed  as  far  as  the  spinous  processes  of  the  dorsal  vertebrae,  to  Avhich 
they  are  attached.  At  the  lower  part  of  the  thoracic  region  this  fascia  is  well 
developed,  and  is  continuous  with  the  fibrous  sheath  of  the  Recti  muscles. 

THE  SHOULDER. 
Anterior  Thoracic  Region. 

Pectoralis  major.  Pectoralis  minor. 

Subclavius. 

The  Pectoralis  major  (Fig.  302)  is  a  broad,  thick,  triangular  muscle,  situated 
at  the  upper  and  fore  part  of  the  chest,  in  front  of  the  axilla.  It  arises  from  the 
anterior  surface  of  the  sternal  half  of  the  clavicle ;  from  half  the  breadth  of  the 
anterior  surface  of  the  sternum,  as  low  down  as  the  attachment  of  the  cartilage 
of  the  sixth  or  seventh  rib ;  this  portion  of  its  origin  consists  of  aponeurotic 
fibres,  which  intersect  with  those  of  the  opposite  muscle ;  it  also  arises  from  the 
cartilages  of  all  the  true  ribs,  with  the  exception,  frequently,  of  the  first  or  of  the 
seventh,  or  both  ;  and  from  the  aponeurosis  of  the  External  oblique  muscle  of  the 
abdomen.  The  fibres  from  this  extensive  origin  converge  toward  its  insertion, 
giving  to  the  muscle  a  radiated  appearance.  Those  fibres  which  arise  from  the 
clavicle  pass  obliquely  outward  and  downward,  and  are  usually  separated  from  the 
rest  by  a  cellular  interval :  those  from  the  lower  part  of  the  sternum,  and  the 
cartilages  of  the  lower  true  libs,  pass  upward  and  outward,  whilst  the  middle 
fibres  pass  horizontally.  They  all  terminate  in  a  flat  tendon,  about  two  inches 
broad,  which  is  inserted  into  the  anterior  bicipital  ridge  of  the  humerus.  This 
tendon  consists  of  two  lamin-ae,  placed  one  in  front  of  the  other,  and  usually 
blended  together  below.  The  anterior,  the  thicker,  receives  the  clavicular  and 
upper  half  of  the  sternal  portion  of  the  muscle  ;  and  its  fibres  are  inserted  in  the 
same  order  as  that  in  which  they  arise ;  that  is  to  say,  the  outermost  fibres  of 
origin  from  the  clavicle  are  inserted  at  the  uppermost  part  of  the  tendon  ;  the 
upper  fibres  of  origin  from  the  sternum  pass  down  to  the  lowermost  part  of  this 
anterior  lamina  of  the  tendon  and  extend  as  low  as  the  tendon  of  the  Deltoid  and 
join  with  it.  The  posterior  lamina  of  the  tendon  receives  the  attachment  of  the 
lower  half  of  the  sternal  portion  and  the  deeper  part  of  the  muscle  from  the  costal 
cartilages.  These  deep  fibres,  and  particularly  those  from  the  lower  costal  carti- 
lages, ascend  the  higher,  turning  backward  successively  behind  the  superficial  and 
upper  ones,  so  that  the  tendon  appears  to  be  twisted.  The  posterior  lamina 
reaches  higher  on  the  humerus  than  the  anterior  one,  and  from  it  an  expansion  is 
given  off  which  covers  the  bicipital  groove  and  blends  with  the  capsule  of  the 
shoulder-joint.  Another  expansion  passes  downward  to  the  fascia  of  the  arm. 

Relations. — By  its  anterior  surface,  with  the  integument,  the  superficial  fascia, 
the  Platysma,  the  mammary  gland,  and  the  deep  fascia  ;  by  its  posterior  surface  : 
its  thoracic  portion,  with  the  sternum,  the  ribs  and  costal  cartilages,  the  costo- 
coracoid  membrane,  the  Subclavius,  Pectoralis  minor,  Serratus  magnus,  and  the 
Intercostals ;  its  axillary  portion  forms  the  anterior  watl  of  the  axillary  space,  and 
covers  the  axillary  vessels  and  nerves,  the  Biceps  and  Coraco-brachialis  muscles. 
Its  tipper  border  lies  parallel  with  the  Deltoid,  from  which  it  is  separated  by  a 
slight  interspace  in  which  lie  the  cephalic  vein  and  descending  branch  of  the 
acromial  thoracic  artery.  Its  lower  border  forms  the  anterior  margin  of  the  axilla, 
being  at  first  separated  from  the  Latissimus  dorsi  by  a  considerable  interval ;  but 
both  muscles  gradually  converge  toward  the  outer  part  of  the  space. 

Dissection. — Detach  the  Pectoralis  major  by  dividing  the  muscle  along  its  attachment  to  the 
clavicle,  and  by  making  a  vertical  incision  through  its  substance  a  little  external  to  its  line  of 


468 


THE  MUSCLES  AND   FASCIA. 


attachment  to  the  sternum  and  costal  cartilages.  The  muscle  should  then  be  reflected  outward, 
and  its  tendon  carefully  examined.  The  Pectoralis  minor  is  now  exposed,  and  immediately 
above  it,  in  the  interval  between  its  upper  border  and  the  clavicle,  a  strong  fascia,  the  costo- 
coracoid  membrane. 

The  costo-coracoid  membrane  is  a  strong  fascia  placed  between   the  clavicle 
and  the  upper  border  of  the  Pectoralis  minor  muscle,  which  protects  the  axillary 


FIG.  302.— Muscles  of  the  chest  and  front  of  the  arm.    Superficial  view. 

vessels  and  nerves.  Above,  it  is  attached  to  the  anterior  margin  of  the  Subclavian 
groove  on  the  under  surface  of  the  clavicle,  and  is  connected  with  a  layer  of 
cervical  fascia  which  overlies  the  Omo-hyoid  muscle,  and  forms  the  posterior  layer 
of  the  sheath  of  the  Subclavius  muscle.  Internally,  it  is  attached  to  the  first  rib 
internal  to  the  origin  of  the  Subclavius  muscle.  Externally  it  is  very  thick  and 
dense,  and  is  attached  to  the  coracoid  process.  The  portion  extending  from  its 
attachment  to  the  first  rib  to  the  coracoid  process  is  often  whiter  and  denser  than 
the  rest ;  this  is  sometimes  called  the  costo-coracoid  ligament.  Below,  it  is  thin, 
and  at  the  upper  border  of  the  Pectoralis  minor  it  splits  into  two  layers  to  invest 
the  muscle ;  from  the  lower  border  of  the  Pectoralis  minor  it  is  continued  down- 


THE   ANTERIOR    THORACIC  REGION. 


469 


ward  to  join  the  axillary  fascia,  and  outward  to  join  the  fascia  over  the  short 
head  of  the  Biceps.  The  costo-coracoid  membrane  is  pierced  by  the  cephalic  vein, 
the  acromial  thoracic  artery  and  vein,  superior  thoracic  artery,  and  anterior 
thoracic  nerves. 

The  Pectoralis  minor  (Fig.  303)  is  a  thin,  flat,  triangular  muscle,  situated  at 
the  upper  part  of  the  thorax,  beneath  the  Pectoralis  major.     It  arises  by  three 


FIG.  303. — Muscles  of  the  chest  and  front  of  the  arm,  with  the  boundaries  of  the  axilla. 

tendinous  digitations  from  the  upper  margin  and  outer  surface  of  the  third, 
fourth,  and  fifth  ribs,  near  their  cartilages,  and  from  the  aponeurosis  covering  the 
Intercostal  muscles  ;  the  fibres  pass  upward  and  outward,  and  converge  to  form  a 
flat  tendon,  which  is  inserted  into  the  inner  border  and  upper  surface  of  the  cora- 
coid  process  of  the  scapula. 

Relations. — By  its  anterior  surface,  with  the  Pectoralis  major  and  the  superior 
thoracic  vessels  and  nerves ;  by  its  posterior  surface,  with  the  ribs,  Intercostal 
muscles,  Serratus  magnus.  the  axillary  space,  and  the  axillary  vessels  and  nerves. 
Its  upper  border  is  separated  from  the  clavicle  by  a  triangular  interval,  broad 
internally,  narrow  externally,  bounded  in  front  by  the  costo-coracoid  membrane, 
and  internally  by  the  ribs.  In  this  space  are  the  first  part  of  the  axillary  vessels 
and  nerves. 

The  costo-coracoid  membrane  should  now  be  removed,  when  the  Subclavius  muscle  will  be 

seen. 

The  Subclavius  is  a  long,  thin,  spindle-shaped  muscle,  placed  in  the  interval 
between  the  clavicle  and  the  first  rib.  It  arises  by  a  short,  thick  tendon  from  the 
first  rib  and  its  cartilage  at  their  junction,  in  front  of  the  rhomboid  ligament;  the 


470 


THE   MUSCLES  AND   FASCIA. 


Nerves.- 

Slip  of  SERRATUS  MAGNUS  to  1st  rib. 

Spine  of  scapula. 


fleshy  fibres  proceed  obliquely  upward  and  outward,  to  be  inserted  into  a  deep 
groove  on  the  under  surface  of  the  middle  third  of  the  clavicle. 

Relations. — By  its  upper  surface,  with  the  clavicle.  By  its  under  surface  it  is 
separated  from  the  first  rib  by  the  subclavian  vessels  and  brachial  plexus  of  nerves. 
Its  anterior  surface  is  separated  from  the  Pectoralis  major  by  the  costo-coracoid 
membrane,  which,  with  the  clavicle,  forms  an  osseo-fibrous  sheath  in  which  the 
muscle  is  enclosed. 

If  the  costal  attachment  of  the  Pectoralis  minor  is  divided  across,  and  the  muscle  reflected 
outward,  the  axillary  vessels  and  nerves  are  brought  fully  into  view,  and  should  be  examined. 

The  Pectoral  muscles  are  supplied  by  the  anterior  thoracic  nerves ; 
the  Subclavius,  by  a  filament  from  the  cord 
formed  by  the  union  of  the  fifth  and  sixth 
cervical  nerves. 

Actions. — If  the  arm  has  been  raised  by 
the  Deltoid,  the  Pectoralis  major  will,  con- 
jointly with  the  Latissimus  dorsi  and  Teres 
major,  depress  it  to  the  side  of  the  chest. 
If  acting  alone,  it  adducts  and  draws  for- 
ward the  arm,  bringing  it  across  the  front 
of  the  chest,  and  at  the  same  time  rotates 
it  inward.  The  Pectoralis  minor  depresses 
the  point  of  the  shoulder,  drawing  the  scapula 
downward  and  inward  to  the  thorax,  and 
throwing  the  inferior  angle  backward.  The 
Subclavius  depresses  the  shoulder,  drawing 
the  clavicle  downward  and  forward.  When 
the  arms  are  fixed,  all  three  muscles  act  upon 
the  ribs,  drawing  them  upward  and  expand- 
ing the  chest,  and  thus  becoming  very 
important  agents  in  forced  inspiration. 
Asthmatic  patients  always  assume  an  atti- 
tude which  fixes  the  shoulders,  so  that  all 
these  muscles  may  be  brought  into  action  to 
assist  in  dilating  the  cavity  of  the  chest. 

Lateral  Thoracic  Region. 

Serratus  magnus. 

The  Serratus  magnus  (Fig.  304)  is  a 
broad,  thin,  and  irregularly  quadrilateral 
muscle,  situated  at  the  upper  part  and 
side  of  the  chest.  It  consists  of  two  tri- 
angular or  fan-shaped  portions ;  the  upper 
one  having  the  apex  of  the  triangle  at- 
FIG.  304  -Serratus  magnus.  (From  a  prep-  tached  to  the  first  and  second  ribs,  and  the 

aration  in  the  Museum  of  the  Royal  College  of     i  , ,  -,  j          .    t      i  i_      j 

Surgeons  of  England.)  base  to  the  upper  angle  and  vertebral  border 

of  the  scapula ;    the    lower  with    its    apex 

behind  attached  to  the  inferior  angle  of  the  scapula,  and  its  base  in  front  con- 
nected with  the  ribs  from  the  second  to  the  eighth.  It  arises  by  nine  fleshy 
digitations  from  the  outer  surface  and  upper  border  of  the  eight  upper  ribs  (the 
second  rib  having  two),  and  from  the  aponeurosis  covering  the  upper  intercostal 
muscles,  and  is  inserted  into  the  whole  length  of  the  anterior  aspect  of  the  poste- 
rior border  of  the  scapula.  The  upper  fan-shaped  portion  is  attached  to  the  fore 
part  of  the  outer  surfaces  of  the  first  and  second  ribs  ;  its  fibres  spread  out,  the 
upper  ones  forming  a  thick  fasciculus,  which  passes  upward  and  backward,  and 
is  attached  to  the  triangular  smooth  surface  on  the  anterior  aspect  of  the  superior 
angle  of  the  scapula ;  the  remaining  fibres  proceed  backward  and  downward  to 


IEXTKHNU*  OBLIQUUS. 


8th  rib. 


THE   ACRO^fIAL    REGION.  471 

be  attached  to  the  posterior  border  of  the  scapula  between  the  superior  and  inferior 
angles.  The  lower  fan-shaped  portion  is  attached  posteriorly  by  its  apex  to  the 
anterior  surface  of  the  inferior  angle  of  the  scapula,  partly  by  muscular,  partly 
bv  tendinous  fibres ;  it  spreads  out  like  a  fan,  the  upper  fibres  passing  forward 
and  upward,  the  lower  horizontally  forward  to  be  inserted  into  the  outer  surface 
of  the  fore  part  of  the  ribs  from  the  second  to  the  eighth,  by  a  series  of  muscular 
digitations.  In  the  intervals  between  the  four  lower  of  these  are  received  cor- 
responding processes  of  the  External  oblique. 

Relations. — This  muscle  is  covered,  in  front,  by  the  Pectoral  muscle ;  behind 
by  the  Snbscapularis ;  above,  by  the  axillary  vessels  and  nerves.  Its  deep  surface 
rests  upon  the  ribs  and  Intercostal  muscles. 

Nerves. — The  Serratus  rnagnus  is  supplied  by  the  posterior  thoracic  nerve. 

Actions. — The  Serratus  magnus,  as  a  whole,  carries  the  scapula  forward,  and 
at  the  same  time  raises  the  vertebral  border  of  the  bone.  It  is  therefore  concerned 
in  the  action  of  pushing.  Its  lower  and  stronger  fibres  move  forward  the  lower 
angle  and  assist  the  Trapezius  in  rotating  the  bone  round  an  axis  through  its  centre, 
and  thus  assists  this  muscle  in  raising  the  acromion  and  supporting  weights  upon 
the  shoulder.  It  is  possible  that  when  the  shoulders  are  fixed  the  lower  fibres 
may  assist  in  raising  and  everting  the  ribs ;  but  it  is  not  the  important  inspiratory 
muscle  which  it  was  formerly  believed  to  be. 

Surgical  Anatomy. — -When  the  muscle  is  paralyzed  the  vertebral  border,  and  especially 
the  lower  angle,  leave  the  ribs  and  stand  out  prominently  on  the  surface,  giving  a  peculiar 
"winged  appearance  to  the  back.  The  patient  is  unable  to  raise  the  arm  above  a  right  angle, 
and  an  attempt  to  do  so  is  followed  by  a  revolution  of  the  scapula,  instead  of  by  the  elevation 
of  the  arm. 

Dissection. — After  completing  the  dissection  of  the  axilla,  if  the  muscles  of  the  back  have 
been  dissected,  the  upper  extremity  should  be  separated  from  the  trunk.  Saw  through  the 
clavicle  at  its  centre,  and  then  cut  through  the  muscles  which  connect  the  scapula  and  arm  with 
the  trunk,  viz.  :  the  Pectoralis  minor  in  front,  Serratus  magnus  at  the  side,  and  the  Levator 
anguli  scapulae,  the  Rhomboids.  Trapezius.  and  Latissimus  dorsi  behind.  These  muscles  should 
be  cleaned  and  traced  to  their  respective  insertions.  Then  make  an  incision  through  the  integu- 
ment, commencing  at  the  outer  third  of  the  clavicle,  and  extending  along  the  margin  of  that 
bone,  the  acromion  process,  and  spine  of  the  scapula ;  the  integument  should  be  dissected  from 
above  downward  and  outward,  when  the  fascia  covering  the  Deltoid  is  exposed  (Fig.  301,  No.  3). 

The  superficial  fascia  of  the  upper  extremity  is  a  thin  cellulo-fibrous  layer, 
containing  the  superficial  veins  and  lymphatics,  and  the  cutaneous  nerves.  It  is 
most  distinct  in  front  of  the  elbow,  and  contains  very  large  superficial  veins  and 
nerves :  in  the  hand  it  is  hardly  demonstrable,  the  integument  being  closely 
adherent  to  the  deep  fascia  by  dense  fibrous  bands.  Small  subcutaneous  bursae  are 
found  in  this  fascia  over  the  acromion,  the  olecranon,  and  the  knuckles.  The 
deep  fascia  of  the  upper  extremity  comprises  the  aponeurosis  of  the  shoulder, 
arm.  and  forearm,  the  anterior  and  posterior  annular  ligaments  of  the  carpus,  and 
the  palmar  fascia.  These  will  be  considered  in  the  description  of  the  muscles  of 
the  several  regions. 

Acromial  Region. 
Deltoid. 

The  deep  fascia  covering  the  Deltoid  (deltoid  aponeurosis)  is  a  fibrous  layer 
which  covers  the  outer  surface  of  the  muscle,  thick  and  strong  behind,  where  it 
is  continuous  with  the  infraspinatus  fascia,  thinner  over  the  rest  of  its  extent. 
It  sends  down  numerous  prolongations  between  the  fasciculi  of  the  muscle. 
In  front,  it  is  continuous  with  the  fascia  covering  the  great  Pectoral  muscle ; 
behind,  with  that  covering  the  Infraspinatus ;  above,  it  is  attached  to  the  clavicle, 
the  acromion,  and  spine  of  the  scapula  ;  below,  it  is  continuous  with  the  deep  fascia 
of  the  arm. 

The  Deltoid  (Fig.  302)  is  a  large,  thick,  triangular  muscle,  which  gives  the 
rounded  outline  to  the  shoulder,  and  has  received  its  name  from  its  resemblance  to 
the  Greek  letter  /\  reversed.  It  surrounds  the  shoulder-joint  in  the  greater  part 
of  its  extent,  covering  it  on  its  outer  side,  and  in  front  and  behind.  It  arises  from 


472  THE  MUSCLES  AND   FASCIA 

the  outer  third  of  the  anterior  border  and  upper  surface  of  the  clavicle ;  from  the 
outer  margin  and  upper  surface  of  the  acromion  process,  and  from  the  lower  lip  of 
the  posterior  border  of  the  spine  of  the  scapula,  as  far  back  as  the  triangular 
surface  at  its  inner  end.  From  this  extensive  origin  the  fibres  converge  toward 
their  insertion,  the  middle  passing  vertically,  the  anterior  obliquely  backward,  the 
posterior  obliquely  forward ;  they  unite  to  form  a  thick  tendon,  which  is  inserted 
into  a  rough  prominence  on  the  middle  of  the  outer  side  of  the  shaft  of  the 
humerus.  At  its  insertion  the  muscle  gives  off  an  expansion  to  the  deep  fascia  of 
the  arm.  This  muscle  is  remarkably  coarse  in  texture,  and  the  arrangement  of 
its  muscular  fibres  is  somewhat  peculiar ;  the  central  portion  of  the  muscle — that 
is  to  say,  the  part  arising  from  the  acromion  process — consists  of  oblique  fibres, 
which  arise  in  a  bipenniform  manner  from  the  sides  of  tendinous  intersections, 
generally  four  in  number,  which  are  attached  above  to  the  acromion  process  and 
pass  downward  parallel  to  one  another  in  the  substance  of  the  muscle.  The 
oblique  muscular  fibres  thus  formed  are  inserted  into  similar  tendinous  intersec- 
tions, generally  three  in  number,  which  pass  upward  from  the  insertion  of  the 
muscle  into  the  humerus  and  alternate  with  the  descending  septa.  The  lateral 
portions  of  the  muscle — that  is  to  say,  the  fibres  arising  from  the  clavicle  and 
spine  of  the  scapula — are  not  arranged  in  this  manner,  but  consist  of  parallel 
fasciculi  passing  from  their  origin  above,  to  be  inserted  into  the  margins  of  the 
inferior  tendon. 

Relations. — By  its  superficial  surface,  with  the  integument,  the  superficial 
fascia,  Platysma,  and  supra-acromial  nerves.  Its  deep  surface  is  separated  from 
the  head  of  the  humerus  by  a  large  sacculated  synovial  bursa,  and  covers  the 
coracoid  process,  coraco-acromial  ligament,  Pectoralis  minor,  Coraco-brachialis, 
both  heads  of  the  Biceps,  the  tendon  of  the  Pectoralis  major,  the  insertions 
of  the  Supraspinatus,  Infraspinatus,  and  Teres  minor,  the  scapular  and 
external  heads  of  the  Triceps,  the  circumflex  vessels  and  nerve,  and  the  humerus. 
Its  anterior  border  is  separated  at  its  upper  part  from  the  Pectoralis  major  by 
a  cellular  interspace,  which  lodges  the  cephalic  vein  and  descending  branch  of  the 
acromial  thoracic  artery :  lower  down  the  two  muscles  are  in  close  contact.  Its 
posterior  border  rests  on  the  Infraspinatus  and  Triceps  muscles 
Nerves. — The  Deltoid  is  supplied  by  the  circumflex  nerve- 
Actions. — The  Deltoid  raises  the  arm  directly  from  the  side,  so  as  to  bring  it 
at  right  angles  with  the  trunk.  Its  anterior  fibres,  assisted  by  the  Pectoralis 
major,  draw  the  arm  forward;  and  its  posterior  fibres,  aided  by  the  Teres  major 
and  Latissimus  dorsi,  draw  it  backward. 

Surgical  Anatomy. — The  Deltoid  is  very  liable  to  atrophy,  and  when  in  this  condition 
simulates  dislocation  of  the  shoulder-joint,  as  there  is  flattening  of  the  shoulder  and  apparent 
prominence  of  the  acromion  process ;  upon  examination,  however,  it  will  be  found  that  the 
relative  position  of  the  great  tuberosity  of  the  humerus  to  the  acromion  and  coracoid  process  is 
unchanged.  Atrophy  of  the  Deltoid  may  be  due  to  disuse  or  loss  of  trophic  influence,  either 
from  injury  to  the  circumflex  nerve  or  cord  lesions,  as  in  infantile  paralysis. 

Dissection. — Divide  the  Deltoid  across,  near  its  upper  part,  by  an  incision  carried  along  the 
margin  of  the  clavicle,  the  acromion  process,  and  spine  of  the  scapula,  and  reflect  it  downward : 
the  bursa  will  be  seen  on  its  under  surface,  as  well  as  the  circumflex  vessels  and  nerve. 

Anterior  Scapular  Region. 

Subscapularis. 

The  subscapular  fascia  is  a  thin  membrane  attached  to  the  entire  circumference 
of  the  subscapular  fossa,  and  affording  attachment  by  its  inner  surface  to  some  of 
the  fibres  of  the  Subscapularis  muscle :  when  this  is  removed,  the  Subscapularis 
muscle  is  exposed. 

The  Subscapularis  (Fig.  303)  is  a  large  triangular  muscle  which  fills  up  the 
subscapular  fossa,  arising  from  its  internal  two-thirds,  with  the  exception  of  a 
narrow  margin  along  the  posterior  border,  and  the  surfaces  at  the  superior  and 
inferior  angles  which  afford  attachment  to  the  Serratus  magnus.  Some  fibres 


THE  POSTERIOR   SCAPULAR   REGION.  473 

arise  from  tendinous  laminae,  which  intersect  the  muscle,  and  are  attached  to 
ridges  on  the  bone ;  and  others  from  an  aponeurosis,  which  separates  the  muscle 
from  the  Teres  major  and  the  long  head  of  the  Triceps.  The  fibres  pass 
outward,  and  gradually  converging,  terminate  in  a  tendon,  which  is  inserted 
into  the  lesser  tuberosity  of  the  humerus.  Those  fibres  which  arise  from  the 
axillary  border  of  the  scapula  are  inserted  into  the  neck  of  the  humerus  to 
the  extent  of  an  inch  below  the  tuberosity.  The  tendon  of  the  muscle  is  in 
close  contact  with  the  capsular  ligament  of  the  shoulder-joint,  and  glides  over 
a  large  bursa,  which  separates  it  from  the  base  of  the  coracoid  process.  This 
bursa  communicates  with  the  cavity  of  the  joint  by  an  aperture  in  the  capsular 
ligament. 

Relations. — By  its  anterior  surface,  with  the  Serratus  magnus,  Coraco- 
brachialis.  and  Biceps,  the  axillary  vessels  and  nerves,  and  the  subscapular  vessels 
and  nerves :  by  its  posterior  surface,  with  the  scapula  and  the  capsular  ligament 
of  the  shouldev-joint.  Its  lower  border  is  contiguous  with  the  Teres  major  and 
Latissimus  dorsi. 

Nerves. — It  is  supplied  by  the  upper  and  lower  subscapular  nerves. 

Actions. — The  Subscapularis  rotates  the  head  of  the  humerus  inward  ;  when 
the  arm  is  raised,  it  draws  the  humerus  downward.  Together  with  the  following 
muscles  it  is  a  defence  to  the  shoulder-joint,  as,  by  their  tension,  they  all  prevent 
displacement  of  the  head  of  the  bone. 

Posterior  Scapular  Region  (Fig.  305). 

Supraspinatus.  Teres  minor. 

Infraspinatus.  Teres  major. 

Dissection. — To  expose  these  muscles,  and  to  examine  their  mode  of  insertion  into  the 
humerus.  detach  the  Deltoid  and  Trapezius  from  their  attachment  to  the  spine  of  the  scapula 
and  acromion  process.  Remove  the  clavicle  by  dividing  the  ligaments  connecting  it  with  the 
coracoid  process,  and  separate  it  at  its  articulation  with  the  scapula :  divide  the  aeromion  process 
near  its  root  with  a  saw.  The  fragments  being  removed,  the  tendons  of  the  posterior  Scapular 
muscles  will  be  fully  exposed,  and  can  be  examined.  A  block  should  be  placed  beneath  the 
shoulder-joint,  so  as  to  make  the  muscles  tense. 

The  Supraspinous  fascia  is  a  thick  and  dense  membranous  layer,  which  com- 
pletes the  osseo-fibrous  case  in  which  the  Supraspinatus  muscle  is  contained, 
affording  attachment,  by  its  inner  surface,  to  some  of  the  fibres  of  the  muscle.  It 
is  thick  internally,  but  thinner  externally  under  the  coraco-acromial  ligament. 
"W  hen  this  fascia  is  removed,  the  Supraspinatus  muscle  is  exposed. 

The  Supraspinatus  muscle  occupies  the  whole  of  the  supraspinous  fossa,  arising 
from  its  internal  two-thirds  and  from  the  strong  fascia  which  covers  its  sur- 
face. The  muscular  fibres  converge  to  a  tendon  which  passes  across  the  capsular 
ligament  of  the  shoulder-joint,  to  which  it  is  intimately  adherent,  and  is  inserted 
into  the  highest  of  the  three  facets  on  the  great  tuberosity  of  the  humerus. 

Relations. — By  its  upper  surface,  with  the  Trapezius,  the  clavicle,  the  aeromion, 
the  coraco-acromial  ligament,  and  the  Deltoid ;  by  its  under  surface,  with  the 
scapula  the  suprascapular  vessels  and  nerve,  and  upper  part  of  the  shoulder-joint. 

The  Infraspinous  fascia  is  a  dense  fibrous  membrane,  covering  in  the  Infra- 
spinatus muscle  and  attached  to  the  circumference  of  the  infraspinous  fossa;  it 
affords  attachment,  by  its  inner  surface,  to  some  fibres  of  that  muscle.  At  the  point 
where  the  Infraspinatus  commences  to  be  covered  by  the  Deltoid,  this  fascia  divides 
into  two  layers :  one  layer  passes  over  the  Deltoid  muscle,  helping  to  form  the 
Deltoid  fascia  already  described  ;  the  other  passes  beneath  the  Deltoid  to  the 
shoulder-joint. 

The  Infraspinatus  is  a  thick,  triangular  muscle,  which  occupies  the  chief  part 
of  the  infraspinous  fossa,  arising  by  fleshy  fibres  from  its  internal  two-thirds,  and 
by  tendinous  fibres  from  the  ridges  on  its  surface :  it  also  arises  from  a  strong 
fascia  which  covers  it  externally,  and  separates  it  from  the  Teres  major  and  minor. 
The  fibres  converge  to  a  tendon  which  glides  over  the  external  border  of  the 
spine  of  the  scapula,  and,  passing  across  the  capsular  ligament  of  the  shoulder- 


474 


THE  MUSCLES  AND   FASCIA. 


joint,  is  inserted  into  the  middle  facet  on  the  great  tuberosity  of  the  humerus. 
The  tendon  of  this  muscle  is  occasionally  separated  from  the  spine  of  the  scapula 
by  a  synovial  bursa  which  communicates  with  the  synovial  cavity  of  the  shoulder- 
joint. 

Relations. — By  its  posterior  surface,  with  the  Deltoid,  the  Trapezius,  Latissimus 
dorsi,  and  the  integument ;  by  its  anterior  surface,  with  the  scapula,  from  which 


FIG.  305.— Muscles  on  the  dorsum  of  the  Scapula  and  the  Triceps. 

it  is  separated  by  the  suprascapular  and  dorsalis  scapulae  vessels,  and  with  the 
capsular  ligament  of  the  shoulder-joint.  Its  loiver  border  is  in  contact  with  the 
Teres  minor,  occasionally  united  with  it,  and  with  the  Teres  major. 

The  Teres  minor  is  a  narrow,  elongated  muscle,  which  lies  along  the  inferior 
border  of  the  scapula.  It  arises  from  the  dorsal  surface  of  the  axillary  border  of 
the  scapula  for  the  upper  two-thirds  of  its  extent,  and  from  two  aponeurotic 
laminae,  one  of  which  separates  this  muscle  from  the  Infraspinatus,  the  other  from 
the  Teres  major;  its  fibres  pass  obliquely  upward  and  outward,  and  terminate 
in  a  tendon  which  is  inserted  into  the  lowest  of  the  three  facets  on  the  great 
tuberosity  of  the  humerus,  and,  by  fleshy  fibres,  into  the  humerus  immediately 
below  it.  The  tendon  of  this  muscle  passes  across  the  capsular  ligament  of  the 
shoulder-joint. 

Relations. — By  its  posterior  surface,  with  the  Deltoid,  and  the  integument ; 
by  its  anterior  surface,  with  the  scapula,  and  dorsal  branch  of  the  subscapular 
artery,  the  long  head  of  the  Triceps,  and  the  shoulder-joint ;  by  its  upper  border, 
with  the  Infraspinatus;  by  its  lower  border,  with  the  Teres  major,  from  which  it 
is  separated  anteriorly  by  the  long  head  of  the  Triceps. 

The  Teres  major  is  a  broad  and  somewhat  flattened  muscle,  which  arises  from 
the  dorsal  aspect  of  the  inferior  angle  of  the  scapula,  and  from  the  fibrous  septa 
interposed  between  it  and  the  Teres  minor  and  Infraspinatus ;  the  fibres  are 


THE  A  I? If.  475 

directed  upward  and  outward,  and  terminate  in  a  flat  tendon,  about  two  inches 
in  length,  which  is  inserted  into  the  internal  bicipital  ridge  of  the  humerus.  The 
tendon  of  this  muscle,  at  its  insertion  into  the  humerus,  lies  behind  that  of  the 
Latissimus  dorsi,  from  which  it  is  separated  by  a  synovia!  bursa.  the  two  tendons 
being,  however,  united  along  their  lower  borders  for  a  short  distance. 

Relations. — By  its  posterior  surface,  with  the  integument,  from  which  it  is 
separated,  internally,  by  the  Latissimus  dorsi;  and  externally,  by  the  long  head 
of  the  Triceps ;  by  its  anterior  surface,  with  the  Subscapularis,  Latissimus  dorsi, 
Coraco-brachialis,  short  head  of  the  Biceps,  the  axillary  vessels,  and  brachial 
plexus  of  nerves.  Its  upper  border  is  at  first  in  relation  with  the  Teres  minor, 
from  which  it  is  afterward  separated  by  the  long  head  of  the  Triceps.  Its  lower 
border  forms,  in  conjunction  with  the  Latissimus  dorsi,  part  of  the  posterior 
boundary  of  the  axilla. 

Nerves. — The  Supra-  and  Infraspinatus  muscles  are  supplied  by  the  suprascap- 
ular  nerve ;  the  Teres  minor,  by  the  circumflex ;  and  the  Teres  major,  by  the 
lower  subscapular. 

Actions. — The  Supraspinatus  assists  the  Deltoid  in  raising  the  arm  from  the 
side,  and  fixes  the  head  of  the  humerus  in  its  socket.  The  Infraspinatus  and 
Teres  minor  rotate  the  head  of  the  humerus  outward  :  when  the  arm  is  raised,  they 
assist  in  retaining  it  in  that  position  and  carrying  it  backward.  One  of  the  most 
important  uses  of  these  three  muscles  is  the  great  protection  they  afford  to  the 
shoulder-joint,  the  Supraspinatus  supporting  it  above,  and  preventing  displacement 
of  the  head  of  the  humerus  downward,  while  the  Infraspinatus  and  Teres  minor 
protect  it  behind,  and  prevent  dislocation  forward.  The  Teres  major  assists 
the  Latissimus  dorsi  in  drawing  the  humerus  downward  and  backward,  when  pre- 
viouslv  raised,  and  rotating  it  inward;  when  the  arm  is  fixed,  it  mav  assist  the 

,  •/ 

Pectoral  and  Latissimus  dorsi  muscles  in  drawing  the  trunk  forward. 

THE  AEM. 

Anterior  Humeral  Region  (Fig.  303). 
Coraco-brachialis.  Biceps.  Brachialis  anticus. 

Dissection. — The  arm  being  placed  on  the  table,  with  the  front  surface  uppermost,  make 
a  vertical  incision  through  the  integument  along  the  middle  line,  from  the  outer  extremity  of 
the  anterior  fold  of  the  axilla,  to  about  two  inches  below  the  elbow-joint,  where  it  should  be 
joined  by  a  transverse  incision,  extending  from  the  inner  to  the  outer  side  of  the  forearm ;  the 
two  flaps  being  reflected  on  either  side,  the  fascia  should  be  examined  (Fig.  301 ). 

The  deep  fascia  of  the  arm  is  continuous  with  that  covering  the  shoulder  and 
front  of  the  great  Pectoral  muscle,  by  means  of  which  it  is  attached,  above,  to  the 
clavicle,  acromion,  and  spine  of  the  scapula ;  it  forms  a  thin,  loose,  membranous 
sheath  investing  the  muscles  of  the  arm,  sending  down  septa  between  them,  and 
composed  of  fibres  disposed  in  a  circular  or  spiral  direction,  and  connected  together 
by  vertical  and  oblique  fibres.  It  differs  in  thickness  at  different  parts,  being  thin 
over  the  Biceps,  but  thicker  where  it  covers  the  Triceps,  and  over  the  condyles  of 
the  humerus  :  it  is  strengthened  by  fibrous  aponeuroses,  derived  from  the  Pectoralis 
major  and  Latissimus  dorsi  on  the  inner  side,  and  from  the  Deltoid  externally. 
On  either  side  it  gives  off  a  strong  intermuscular  septum^  which  is  attached  to  the 
condyloid  ridge  and  condyle  of  the  humerus.  These  septa  serve  to  separate  the 
muscles  of  the  anterior  from  those  of  the  posterior  brachial  region.  The  external 
intermuscular  septum  extends  from  the  lower  part  of  the  external  bicipital  ridge, 
along  the  external  condyloid  ridge,  to  the  outer  condyle  ;  it  is  blended  with  the 
tendon  of  the  Deltoid,  gives  attachment  to  the  Triceps  behind,  to  the  Brachialis 
anticus,  Supinator  longus,  and  Extensor  carpi  radialis  longior,  in  front ;  and  is 
perforated  by  the  musculo-spiral  nerve  and  superior  profunda  artery.  The  internal 
intermuscular  septum,  thicker  than  the  preceding,  extends  from  the  lower  part  of 
the  internal  lip  of  the  bicipital  groove  below  the  Teres  major,  along  the  internal 
condyloid  ridge  to  the  inner  condyle ;  it  is  blended  with  the  tendon  of  the  Coracc- 
brachialis.  and  affords  attachment  to  the  Triceps  behind,  and  the  Brachialis  anticus 


476  THE   MUSCLES  AND    FASCIA. 

in  front.  It  is  perforated  by  the  ulnar  nerve  and  the  inferior  profunda  and  anasto- 
motic  arteries.  At  the  elbow  the  deep  fascia  is  attached  to  all  the  prominent 
points  round  the  joint — viz.  the  condyles  of  the  hurnerus  and  the  olecranon  process 
of  the  ulna — and  is  continuous  with  the  deep  fascia  of  the  forearm.  Just  below  the 
middle  of  the  arm,  on  its  inner  side,  in  front  of  the  internal  intermuscular  septum, 
is  an  oval  opening  in  the  deep  fascia  which  transmits  the  basilic  vein  and  some 
lymphatic  vessels.  On  the  removal  of  this  fascia  the  muscles,  vessels,  and  nerves 
of  the  anterior  humeral  region  are  exposed. 

The  Coraco-brachialis,  the  smallest  of  the  three  muscles  in  this  region,  is  sit- 
uated at  the  upper  and  inner  part  of  the  arm.  It  arises  by  fleshy  fibres  from 
the  apex  of  the  coracoid  process,  in  common  with  the  short  head  of  the  Biceps, 
and  from  the  intermuscular  septum  between  the  two  muscles ;  the  fibres  pass 
downward,  backward,  and  a  little  outward,  to  be  inserted  by  means  of  a  flat  ten- 
don into  a  rough  ridge  at  the  middle  of  the  inner  surface  and  internal  border  of 
the  shaft  of  the  humerus  between  the  origins  of  the  Triceps  and  Brachialis  anticus. 
It  is  perforated  by  the  musculo-cutaneous  nerve.  The  inner  border  of  the  muscle 
forms  a  guide  to  the  position  of  the  brachial  artery  in  tying  the  vessel  in  the  upper 
part  of  its  course. 

Relations. — By  its  anterior  surface,  with  the  Pectoralis  major  above,  and  at 
its  insertion  with  the  brachial  vessels  and  median  nerve  which  cross  it;  by  its 
posterior  surface,  with  the  tendons  of  the  Subscapularis,  Latissimus  dorsi,  and 
Teres  major,  the  inner  head  of  the  Triceps,  the  humerus,  and  the  anterior  circum- 
flex vessels ;  by  its  inner  border,  with  the  brachial  artery,  and  the  median  and 
musculo-cutaneous  nerves ;  by  its  outer  border,  with  the  short  head  of  the  Biceps 
and  Brachialis  anticus. 

The  Biceps  (Biceps  flexor  cubiti)  is  a  long  fusiform  muscle,  occuping  the  whole 
of  the  anterior  surface  of  the  arm,  and  divided  above  into  two  portions  or  heads, 
from  which  circumstance  it  has  received  its  name.  The  short  head  arises  by  a 
thick  flattened  tendon  from  the  apex  of  the  coracoid  process,  in  common  Avith  the 
Coraco-brachialis.  The  long  head  arises  from  the  supraglenoid  tubercle  on  the 
upper  margin  of  the  glenoid  cavity,  by  a  long  rounded  tendon,  which  is  continuous 
with  the  glenoid  ligament.  This  tendon  arches  over  the  head  of  the  humerus, 
being  enclosed  in  a  special  sheath  of  the  synovial  membrane  of  the  shoulder-joint ; 
it  then  passes  through  an  opening  in  the  capsular  ligament  at  its  attachment  to  the 
humerus,  and  descends  in  the  bicipital  groove,  in  which  it  is  retained  by  a  fibrous 
prolongation  from  the  tendon  of  the  Pectoralis  major.  The  fibres  from  this  tendon 
form  a  rounded  belly,  and,  about  the  middle  of  the  arm,  join  Avith  the  portion  of 
the  muscle  derived  from  the  short  head.  The  belly  of  the  muscle,  narrow  and 
somewhat  flattened,  terminates  above  the  elboAv  in  a  flattened  tendon,  Avhich  is 
inserted  into  the  back  part  of  the  tuberosity  of  the  radius,  a  synovial  bursa  being 
interposed  between  the  tendon  and  the  front  of  the  tuberosity.  The  tendon  of  the 
muscle  is  thin  and  broad  ;  as  it  approaches  the  radius  it  becomes  narrow  and  tAvisted 
upon  itself,  so  that  its  external  border  becomes  anterior,  arid  its  posterior  flat  sur- 
face is  applied  to  the  back  of  the  tuberosity :  opposite  the  bend  of  the  elbow  the 
tendon  gives  off,  from  its  inner  side,  a  broad  aponeurosis,  the  bicipital  fascia  (semi- 
lunar  fascia),  which  passes  obliquely  doAvnAvard  and  inAvard  across  the  brachial 
artery,  and  is  continuous  with  the  deep  fascia  of  the  forearm  (Fig.  302).  The 
inner  border  of  this  muscle  forms  a  guide  to  the  position  of  the  vessel  in  tying  the 
brachial  artery  in  the  middle  of  the  arm.1 

Relations. — Its  anterior  surface  is  overlapped  above  by  the  Pectoralis  major 
and  Deltoid ;  in  the  rest  of  its  extent  it  is  covered  by  the  superficial  and  deep 
fasciae  and  the  integument.  Its  posterior  surface  rests  on  the  shoulder-joint  and 

1 A  third  head  to  the  Biceps  is  occasionally  found  (Theile  says  as  often  as  once  in  eight  or  nine 
subjects),  arising  at  the  upper  and  inner  part  of  the  Brachialis  anticus,  with  the  fibres  of  which  it 
is  continuous,  and  inserted  into  the  bicipital  fascia  and  inner  side  of  the  tendon  of  the  Biceps.  In 
most  cases  this  additional  slip  passes  behind  the  brachial  artery  in  its  course  down  the  arm.  Occa- 
sionally the  third  head  consists  of  two  slips  which  pass  down,  one  in  front,  the  other  behind  the  artery, 
concealing  the  vessel  in  the  lower  half  of  the  arm. 


THE  POSTERIOR   HUMERAL    REGION.  477 

humerus.  from  which  it  is  separated  by  the  Subscapularis,  Teres  major,  Latissimus 
dorsi,  Brachialis  anticus.  and  the  musculo-cutaneous  nerve.  Its  inner  border  is 
in  relation  with  the  Coraco-brachialis.  the  brachial  vessels,  and  median  nerve  ;  its 
outer  border,  with  the  Deltoid  and  Supinator  longus. 

The  Brachialis  anticus  is  a  broad  muscle,  which  covers  the  elbow-joint  and 
the  lower  half  of  the  front  of  the  humerus.  It  is  somewhat  compressed  from 
before  backward,  and  is  broader  in  the  middle  than  at  either  extremity.  It  arises 
from  the  lower  half  of  the  outer  and  inner  surfaces  of  the  shaft  of  the  humerus, 
and  commences  above  at  the  insertion  of  the  Deltoid,  which  it  embraces  by  two 
angular  processes.  Its  origin  extends  below,  to  within  an  inch  of  the  margin  of 
the  articular  surface,  and  is  limited  on  each  side  by  the  external  and  internal 
borders  of  the  shaft  of  the  humerus.  It  also  arises  from  the  intermuscular  septa 
on  each  side,  but  more  extensively  from  the  inner  than  the  outer,  from  which  it  is 
separated  below  by  the  Supinator  longus  and  Extensor  carpi  radialis  longior.  Its 
fibres  converge  to  a  thick  tendon,  which  is  inserted  into  a  rough  depression  on  the 
inferior  surface  of  the  coronoid  process  of  the  ulna,  being  received  into  an  interval 
between  two  fleshy  slips  of  the  Flexor  digitorum  profundus. 

Eelations. — By  its  anterior  surface*  with  the  Biceps,  the  brachial  vessels, 
musculo-cutaneous,  and  median  nerves ;  by  its  posterior  surface,  with  the 
humerus  and  front  of  the  elbow-joint ;  by  its  inner  border,  with  the  Triceps,  ulnar 
nerve,  and  Pronator  radii  teres,  from  which  it  is  separated  by  the  intermuscular 
septum  :  by  its  outer  border,  with  the  musculo-spiral  nerve,  radial  recurrent 
artery,  the  Supinator  longus.  and  Extensor  carpi  radialis  longior. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  musculo-cutaneous 
nerve,  but  the  nerve  to  the  Coraco-brachialis  is  often  an  independent  branch  of 
the  outer  cord  of  the  Brachial  plexus.  The  Brachialis  anticus  usually  receives 
an  additional  filament  from  the  musculo-spiral. 

Actions. — The  Coraco-brachialis  draws  the  humerus  forward  and  inward,  and 

ita  in  elevating  it.  The  Biceps  is  a  flexor  of  the  forearm  :  it  is  also  a  supinator, 
and  makes  tense  the  deep  fascia  of  the  forearm  by  means  of  the  bicipital  fascia. 
The  Brachialis  anticus  is  a  flexor  of  the  forearm,  and  protects  the  elbow-joint. 
When  the  forearm  is  fixed,  the  Biceps  and  Brachialis  anticus  flex  the  arm,  as  is 
seen  in  efforts  of  climbing. 

Posterior  Humeral  Region. 
Triceps.  Subanconeus. 

The  Triceps  ( Triceps  extemor  cubiti)  (Fig.  305)  is  situated  on  the  back  of  the 
arm.  extending  the  entire  length  of  the  posterior  surface  of  the  humerus.  It  is  of 
large  size,  and  divided  above  into  three  parts;  hence  its  name.  These  three 
portions  have  been  named  (1)  the  middle,  scapular,  or  long  head ;  (2)  the  external, 
or  long  humeral ;  and  (3)  the  internal,  or  short  humeral  head. 

The  middle  or  scapular  head  arises,  by  a  flattened  tendon,  from  a  rough 
triangular  depression  immediately  below  the  glenoid  cavity,  being  blended  at  its 
upper  part  with  the  capsular  ligament :  the  muscular  fibres  pass  downward 
between  the  two  other  portions  of  the  muscle,  and  join  with  them  in  the  common 
tendon  of  insertion. 

The  external  head  arises  from  the  posterior  surface  of  the  shaft  of  the  humerus, 
between  the  insertion  of  the  Teres  minor  and  the  upper  part  of  the  musculo-spiral 
groove;  from  the  external  border  of  the  humerus  and  the  external  intermuscular 
septum :  the  fibres  from  this  origin  converge  toward  the  common  tendon  of 
insertion. 

The  internal  head  arises  from  the  posterior  surface  of  the  shaft  of  the  humerus, 
below  the  groove  for  the  musculo-spiral  nerve ;  commencing  above,  narrow  and 
pointed,  below  the  insertion  of  the  Teres  major,  and  extending  to  within  an  inch 
of  the  trochlear  surface :  it  also  arises  from  the  internal  border  of  the  humerus 
and  internal  intermuscular  septum.  The  fibres  of  this  portion  of  the  muscle  are 


478  THE  MUSCLES   AND    FASCIAE. 

directed,  some  downward  to  the  olecranon,  whilst  others  converge  to  the  common 
tendon  of  insertion. 

The  common  tendon  of  the  Triceps  commences  about  the  middle  of  the  back  part 
of  the  muscle :  it  consists  of  two  aponeurotic  laminae,  one  of  which  is  subcutaneous 
and  covers  the  posterior  surface  of  the  muscle  for  the  lower  half  of  its  extent ;  the 
other  is  more  deeply  seated  in  the  substance  of  the  muscle  :  after  receiving  the 
attachment  of  the  muscular  fibres,  they  join  together  above  the  elbow,  and  are 
inserted,  for  the  most  part,  into  the  back  part  of  the  upper  surface  of  the  olecranon 
process  ;  a  band  of  fibres  is,  however,  continued  downward,  on  the  outer  side, 
over  the  Anconeus,  to  blend  with  the  deep  fascia  of  the  forearm.  A  small  bursa, 
occasionally  multilocular,  is  situated  on  the  front  part  of  this  surface,  beneath  the 
tendon. 

The  long  head  of  the  Triceps  descends  between  the  Teres  minor  and  Teres 
major,  dividing  the  triangular  space  between  these  two  muscles  and  the  humerus 
into  two  smaller  spaces,  one  triangular,  the  other  quadrangular  (Fig.  305).  The 
triangular  space  contains  the  dorsalis  scapulae  vessels ;  it  is  bounded  by  the  Teres 
minor  above,  the  Teres  major  below,  and  the  scapular  head  of  the  Triceps 
externally :  the  quadrangular  space  transmits  the  posterior  circumflex  vessels 
and  the  circumflex  nerve ;  it  is  bounded  by  the  Teres  minor  above,  the  Teres 
major  below,  the  scapular  head  of  the  Triceps  internally,  and  the  humerus  exter- 
nally. 

Relations. — By  its  posterior  surface,  with  the  Deltoid  above :  in  the  rest  of  its 
extent  it  is  subcutaneous ;  by  its  anterior  surface,  with  the  humerus,  musculo- 
spiral  nerve,  superior  profunda  vessels,  and  back  part  of  the  elbow-joint.  Its 
middle  or  long  head  is  in  relation,  behind,  with  the  Deltoid  and  Teres  minor ;  in 
front,  with  the  Subscapularis,  Latissimus  dorsi,  and  Teres  major. 

The  Subanconeus  is  a  name  given  to  a  few  fibres  from  the  lower  part  of  the 
Triceps  muscle,  which  are  inserted  into  the  posterior  ligament  of  the  elbow-joint. 
By  some  authors  it  is  regarded  as  the  analogue  of  the  Subcrureus  in  the  lower 

*/  O  O 

limb,  but  it  is  not  a  separate  muscle. 

Nerves. — :The  Triceps  is  supplied  by  the  musculo-spiral  nerve. 

Actions. — The  Triceps  is  the  great  extensor  muscle  of  the  forearm,  serving, 
when  the  forearm  is  flexed,  to  extend  the  elbow-joint.  It  is  the  direct  antagonist 
of  the  Biceps  and  Brachialis  anticus.  When  the  arm  is  extended  the  long  head 
of  the  muscle  may  assist  the  Teres  major  and  Latissimus  dorsi  in  drawing  the 
humerus  backward  and  in  adducting  it  to  the  thorax.  The  long  head  of  the 
Triceps  protects  the  under  part  of  the  shoulder-joint,  and  prevents  displacement 
of  the  head  of  the  humerus  downward  and  backward.  The  Subanconeus  draws 
up  the  posterior  ligament  during  extension  of  the  forearm. 

Surgical  Anatomy.— The  existence  of  the  band  of  fibres  from  the  Triceps  to  the  fascia  of 
the  forearm  is  of  importance  in  excision  of  the  elbow,  and  should  always  be  carefully  preserved 
from  injury  by  the  operator,  as  by  means  of  these  fibres  the  patient  is  enabled  to  extend  the 
forearm,  a  movement  which  would  otherwise  mainly  be  accomplished  by  gravity ;  that  is  to  say, 
allowing  the  forearm  to  drop  from  its  own  weight. 

THE  FOREARM. 

Dissection. — To  dissect  the  forearm,  place  the  limb  in  the  position  indicated  in  Fig.  301 ; 
make  a  vertical  incision  along  the  middle  line  from  the  elbow  to  the  wrist,  and  a  transverse 
incision  at  the  extremity  of  this ;  the  superficial  structures  being  removed,  the  deep  fascia  of 
the  forearm  is  exposed. 

The  deep  fascia  of  the  forearm,  continuous  above  with  that  enclosing  the  arm, 
is  a  dense,  highly  glistening  aponeurotic  investment,  which  forms  a  general  sheath 
enclosing  the  muscles  in  this  region  ;  it  is  attached,  behind,  to  the  olecranon  and 
posterior  border  of  the  ulna,  and  gives  oif  from  its  inner  surface  numerous  inter- 
muscular  septa,  which  enclose  each  muscle  separately.  Below,  it  is  continuous  in 
front  with  the  anterior  annular  ligament,  and  forms  a  sheath  for  the  tendon  of  the 
Palmaris  longus  muscle,  which  passes  over  the  annular  ligament  to  be  inserted 
into  the  palmar  fascia.  Behind,  near  the  wrist-joint,  it  becomes  much  thickened 


THE   FOREARM.  479 

by  the  addition  of  many  transverse  fibres,  and  forms  the  posterior  annular  liga- 
ment. It  consists  of  circular  and  oblique  fibres,  connected  together  by  numerous 
vertical  fibres.  It  is  much  thicker  on  the  dorsal  than  on  the  palmar  surface,  and 
at  the  lower  than  at  the  upper  part  of  the  forearm,  and  is  strengthened  by 
tendinous  fibres  derived  from  the  Brachialis  anticus  and  Biceps  in  front,  and  from 
the  Triceps  behind.  Its  inner  surface  gives  origin  to  muscular  fibres,  especially 
at  the  upper  part  of  the  inner  and  outer  sides  of  the  forearm,  and  forms  the 
boundaries  of  a  series  of  conical-shaped  cavities,  in  which  the  muscles  are 
contained.  Besides  the  vertical  septa  separating  each  muscle,  transverse  septa  are 
given  off  both  on  the  anterior  and  posterior  surfaces  of  the  forearm,  separating  the 
deep  from  the  superficial  layer  of  muscles.  Numerous  apertures  exist  in  the  fascia 
for  the  passage  of  vessels  and  nerves ;  one  of  these,  of  large  size,  situated  at  the 
front  of  the  elbow,  serves  for  the  passage  of  a  communicating  branch  between  the 
superficial  and  deep  veins. 

The  muscles  of  the  forearm  may  be  subdivided  into  groups  corresponding  to 
the  region  they  occupy.  One  group  occupies  the  inner  and  anterior  aspect  of  the 
forearm,  and  comprises  the  Flexor  and  Pronator  muscles.  Another  group  occupies 
its  outer  side,  and  a  third  its  posterior  aspect.  The  two  latter  groups  include  all 
the  Extensor  and  Supinator  muscles. 

Anterior  Radio -Ulnar  Region. 

Superficial  Layer. 

Pronator  radii  teres.  Flexor  carpi  ulnaris. 

Flexor  carpi  radialis.  Flexor  sublimis  digitorum. 

Palmaris  longus. 

These  muscles  take  origin  from  the  internal  condyle  of  the  humerus  by  a 
common  tendon. 

The  Pronator  radii  teres  arises  by  two  heads.  One,  the  larger  and  more 
superficial,  arises  from  the  humerus,  immediately  above  the  internal  condyle,  and 
from  the  tendon  common  to  the  origin  of  the  other  muscles  ;  also  from  the  fascia 
of  the  forearm  and  intermuscular  septum  between  it  and  the  Flexor  carpi  radialis. 
The  other  head  is  a  thin  fasciculus  which  arises  from  the  inner  side  of  the 
coronoid  process  of  the  ulna,  joining  the  preceding  at  an  acute  angle.  Between 
the  two  heads  passes  the  median  nerve.  The  muscle  passes  obliquely  across  the 
forearm  from  the  inner  to  the  outer  side,  and  terminates  in  a  flat  tendon,  which 
turns  over  the  outer  margin  of  the  radius,  and  is  inserted  into  a  rough  impression 
at  the  middle  of  the  outer  surface  of  the  shaft  of  that  bone. 

Relations. — By  its  anterior  surface,  with  the  deep  fascia,  the  Supinator  longus, 
and  the  radial  vessels  and  nerve ;  by  its  posterior  surface,  with  the  Brachialis 
anticus,  Flexor  sublimis  digitorum,  the  median  nerve,  and  ulnar  artery,  the  small 
or  deep  head  being  interposed  between  the  two  latter  structures.  Its  outer  border 
forms  the  inner  boundary  of  a  triangular  space  (cubital  fossa)  in  which  is  placed 
the  brachial  artery,  median  nerve,  and  tendon  of  the  Biceps  muscle.  Its  inner 
border  is  in  contact  with  the  Flexor  carpi  radialis. 

Surgical  Anatomy. — This  muscle,  when  suddenly  brought  into  very  active  use,  as  in  the 
game  of  lawn  tennis,  is  apt  to  be  strained,  producing  slight  swelling,  tenderness,  and  pain  on 
putting  the  muscle  into  action.  This  is  known  as  "lawn-tennis  arm." 

The  Flexor  carpi  radialis  lies  on  the  inner  side  of  the  preceding  muscle.  It 
arises  from  the  internal  condyle  by  the  common  tendon,  from  the  fascia  of  the  fore- 
arm, and  from  the  intermuscular  septa  between  it  and  the  Pronator  radii  teres,  on 
the  outside,  the  Palmaris  longus  internally,  and  the  Flexor  sublimis  digitorum 
beneath.  Slender  and  aponeurotic  in  structure  at  its  commencement,  it  increases 
in  size,  and  terminates  in  a  tendon  which  forms  the  lower  two-thirds  of  its  length. 
This  tendon  passes  through  a  canal  on  the  outer  side  of  the  annular  ligament, 
runs  through  a  groove  in  the  os  trapezium  (which  is  converted  into  a  canal  by  a 
fibrous  sheath,  and  lined  by  a  synovial  membrane),  and  is  inserted  into  the  base 


480 


THE  MUSCLES  AND   FASCIAE. 


of  the  metacarpal  bone  of  the  index  finger,  and  by  a  slip  into  the  base  of  the 

metacarpal  bone  of  the  middle  finger.     The  radial  artery  lies  between  the  tendon 

of  this  muscle  and  the  Supinator  longus,  and  may  easily  be  tied  in  this  situation. 

Relations. — By  its  superficial  surf  ace,  with  the  deep  fascia  and  the  integument; 

by  its  deep  surface,  with  the  Flexor  subliniis  digitorum,  Flexor  longus  pollicis,  and 

wrist-joint ;  by  its  outer  border,  with  the  Pronator  radii  teres  and  the  radial  vessels  ; 

by  its  inner  border,  with  the  Palmaris  longus  above  and  the  median  nerve  below. 

The  Palmaris  longus  is  a  slender,  fusiform  muscle  lying  on  the  inner  side  of 

the  preceding.  It  arises  from  the  inner  condyle  of 
the  humerus  by  the  common  tendon,  from  the  deep 
fascia,  and  the  intermuscular  septa  between  it  and 
the  adjacent  muscles.  It  terminates  in  a  slender, 
flattened  tendon  which  passes  over  the  annular 
ligament  to  end  in  the  palmar  fascia,  frequently 
sending  a  tendinous  slip  to  the  short  muscles  of 
the  thumb.  This  muscle  is  often  absent ;  or  it 
may  be  tendinous  above  and  muscular  below  ;  or 
muscular  at  both  extremities  of  a  middle  tendon. 

Eelations. — By  its  deep  surface,  Avith  the  Flexor 
sublimis  digitorum ;  internally,  Avith  the  Flexor  carpi 
ulnaris ;  externally,  with  the  Flexor  carpi  radialis. 
The  median  nerve  lies  close  to  the  tendon,  just 
above  the  wrist,  on  its  inner  and  posterior  side. 
The  Flexor  carpi  ulnaris  lies  along  the  ulnar 
side  of  the  forearm.  It  arises  by  two  heads  con- 
nected by  a  tendinous  arch,  beneath  which  pass 
the  ulnar  nerve  and  posterior  ulnar  recurrent 
artery.  One  head  arises  from  the  inner  condyle 
of  the  humerus  by  the  common  tendon ;  the  other, 
from  the  inner  margin  of  the  olecranon  by  an 
aponeurosis  which  arises  also  from  the  upper  two- 
thirds  of  the  posterior  border  of  the  ulna,  in  com- 
mon with  the  Extensor  carpi  ulnaris  and  the  Flexor 
profundus  digitorum ;  other  fibres  spring  from  the 
septum  between  it  and  the  Flexor  subliniis  digito- 
rum. The  fibres  terminate  in  a  tendon  which  occu- 
pies the  anterior  part  of  the  lower  half  of  the 
muscle,  and  is  inserted  into  the  pisiform  bone,  and 
is  prolonged  from  this  to  the  fifth  metacarpal  and 
unciform  bones  by  the  piso-metacarpal  and  piso- 
uncinate  ligaments  and  to  the  annular  ligament. 
The  ulnar  artery  lies  on  the  outer  side  of  the 
tendon  of  this  muscle,  in  the  lower  two-thirds  of 
the  forearm,  the  tendon  forming  a  guide  in  tying 
the  vessel  in  this  situation. 

Relations. — By  its  superficial  surface,  with  the 
deep  fascia,  with  which  it  is  intimately  connected 
for  a  considerable  extent ;  by  its  deep  surface, 
with  the  Flexor  sublimis  digitorum,  the  Flexor 
profundus  digitorum,  the  Pronator  quadratus,  and 
the  ulnar  vessels  and  nerve  ;  by  its  outer  or  radial 
border,  with  the  Palmaris  longus  above,  and  the 
ulnar  vessels  and  nerve  below. 

The  Flexor  sublimis  digitorum  (perforatus)  is 
placed  beneath  the  preceding  muscles,  which  therefore  must  be  removed  in  order 
to  bring  its  attachment  into  view.  It  is  the  largest  of  the  muscles  of  the  super- 
ficial layer,  and  arises  by  three  heads.  One  head  arises  from  the  internal  condyle 


FIG.  306.— Front  of  the  left  forearm. 
Superficial  muscles. 


THE  ANTERIOR   BRACHIAL    REGION.  481 

of  the  humerus  by  the  common  tendon,  from  the  internal  lateral  ligament  of  the 
elbow-joint,  and  from  the  intermuscular  septum  common  to  it  and  the  pre- 
ceding muscles.  The  second  head  arises  from  the  inner  side  of  the  coronoid 
process  of  the  ulna,  above  the  ulnar  origin  of  the  Pronator  radii  teres  (Fig.  200, 
p.  255).  The  third  head  arises  from  the  oblique  line  and  from  a  portion  of 
the  anterior  border  of  the  radius,  extending  to  just  below  the  insertion  of 
the  Pronator  radii  teres.  The  fibres  pass  vertically  downward,  forming 
a  broad  and  thick  muscle,  which  divides  into  four  tendons  about  the 
middle  of  the  forearm ;  as  these  tendons  pass  beneath  the  annular  ligament 
into  the  palm  of  the  hand  they  are  arranged  in  pairs,  the  anterior  pair  corre- 
sponding to  the  middle  and  ring  fingers,  the  posterior  pair  to  the  index  and 
little  fingers.  The  tendons  diverge  from  one  another  as  they  pass  onward. 
Opposite  the  base  of  the  first  phalanges  each  tendon  divides  into  two  slips,  to 
allow  of  the  passage  of  the  corresponding  tendons  of  the  Flexor  profundus 
digitorum :  the  two  portions  of  the  tendon  then  unite  and  form  a  grooved  channel 
for  the  reception  of  the  accompanying  deep  flexor  tendon.  Finally  they  subdivide 
a  second  time,  to  be  inserted  into  the  sides  of  the  second  phalanges  about  their 
middle.  After  leaving  the  palm  these  tendons,  accompanied  bv  the  deep  flexor 
tendons,  lie  in  osseo-aponeurotic  canals  formed  by  the  fibrous  sheath  of  the  tendons 
and  the  bones  (Fig.  316). 

Relations. — In  the  forearm,  by  its  superficial  surface,  with  the  deep  fascia  and 
all  the  preceding  superficial  muscles  ;  by  its  deep  surface,  with  the  Flexor  profundus 
digitorum.  Flexor  longus  pollicis,  the  ulnar  vessels  and  nerve,  and  the  median 
nerve.  In  the  hand  its  tendons  are  in  relation,  in  front,  with  the  palmar  fascia, 
superficial  palmar  arch,  and  the  branches  of  the  median  nerve ;  behind,  with  the 
tendons  of  the  deep  Flexor  and  the  Lumbricales. 

Fibrous  Sheath  of  the  Flexor  Tendons. — The  flexor  tendons  of  the  fingers  as 
they  run  along  the  phalanges  are  retained  against  the  bones  by  a  fibrous  sheath, 
forming  osseo-aponeurotic  canals.  These  sheaths  are  formed*  by  strong  fibrous 
bands  which  arch  across  the  tendons  and  are  attached  on  each  side  to  the  margins, 
of  the  phalanges.  Opposite  the  middle  of  the  proximal  and  second  phalanges  the 
sheath  is  very  strong,  and  the  fibres  pass  transversely;  but  opposite  the  joints  it  is 
much  thinner,  and  the  fibres  pass  obliquely.  Each  sheath  is  lined  by  a  synovia! 
membrane,  which  is  reflected  on  the  contained  tendon. 

Deep  Layer. 

Flexor  profundus  digitorum.  Flexor  longus  pollicis. 

Pronator  quadratus. 

Dissection. — Divide  each  of  the  supewcial  muscles  at  its  centre,  and  turn  either  end  aside ; 
the  deep  layer  of  muscles,  together  -^itb.  the  median  nerve  and  ulnar  vessels,  will  then  be 
exposed.  jr 

The  Flexor  profundus  digrcorum  (perfbrans)  (Fig.  307)  is  situated  on  the 
ulnar  side  of  the  forearm,  immediately  beneath  the  superficial  Flexors.  It  arises 
from  the  upper  three-fourths  of  the  anterior  and  inner  surfaces  of  the  shaft  of  the 
ulna,  embracing  the  insertion  of  the  Brachialis  anticus  above,  and  extending, 
below,  to  within  a  short  distance  of  the  Pronator  quadratus.  It  also  arises  from  a 
depression  on  the  inner  side  of  the  coronoid  process ;  bv  an  aponeurosis  from  the 
upper  three-fourths  of  the  posterior  border  of  the  ulna,  in  common  with  the  Flexor 
and  Extensor  carpi  ulnaris  :  and  from  the  ulnar  half  of  the  interosseous  membrane. 
The  fibres  form  a  fleshy  belly  of  considerable  size,  which  divides  into  four  tendons  : 
these  pass  under  the  annular  ligament  beneath  the  tendons  of  the  Flexor  sublimis 
digitorum.  Opposite  the  first  phalanges  the  tendons  pass  between  the  two  slips  of 
the  tendons  of  the  Flexor  sublimis  digitorum,  and  are  finally  inserted  into  the 

-  of  the  last  phalanges.  The  tendon  of  the  index  finger  is  distinct ;  the  rest 
are  connected  together  by  cellular  tissue  and  tendinous  slips  as  far  as  the  palm  of 
the  hand.  The  tendons  of  this  and  those  of  the  Flexor  sublimis  digitorum,  whilst 
contained  in  the  osseo-aponeurotic  canals  of  the  fingers,  are  invested  in  a  synovial 

31 


482 


THE  MUSCLES  AND    FASCIA. 


FIG.  307.— Front  of  the  left  forearm.    Deep  muscles. 


sheath,  and  are  connected  to  each 
other  and  to  the  phalanges  by  slender 
tendinous  filaments,  called  vincula 
accessoria  tendinum.  One  of  these  con- 
nects the  deep  tendon  to  the  bone  be- 
fore it  passes  through  the  superficial 
tendon ;  a  second  connects  the  two 
tendons  together,  after  the  deep  ten- 
dons have  passed  through ;  and  a 
third  connects  the  deep  tendon  to  the 
head  of  the  second  phalanx.  This  last 
consists  largely  of  yellow  elastic  tissue, 
and  may  assist  in  drawing  down  the 
tendon  after  flexion  of  the  finger.1 

Four  small  muscles,  the  Lum- 
bricales,  are  connected  with  the  ten- 
dons of  the  Flexor  profundus  in  the 
palm.  They  will  be  described  with 
the  muscles  in  that  region. 

Relations. — By  its  superficial  sur- 
face, in  the  forearm,  with  the  Flexor 
sublimis  digitorum,  the  Flexor  carpi 
ulnaris,  the  ulnar  vessels  and  nerve, 
and  the  median  nerve ;  and  in  the 
hand,  with  the  tendons  of  the  super- 
ficial Flexor ;  by  its  deep  surface,  in 
the  forearm,  with  the  ulna,  the  in- 
terosseous  membrane,  the  Pronator 
quadratus ;  and  in  the  hand,  Avith  the 
interossei,  Adductor  pollicis,  and  deep 
palmar  arch  ;  by  its  ulnar  border,  with 
the  Flexor  carpi  ulnaris  ;  by  its  radial 
border,  with  the  Flexor  longus  pollicis, 
the  anterior  interosseous  vessels  and 
nerve  being  interposed. 

The  Flexor  longus  pollicis  is  situ- 
ated on  the  radial  side  of  the  forearm, 
lying  on  the  same  plane  as  the  pre- 
ceding. It  arises  from  the  grooved 
anterior  surface  of  the  shaft  of  the 
radius,  commencing  above,  imme- 
diately below  the  tuberosity  and  ob- 
lique line,  and  extending  below  to 
within  a  short  distance  of  the  Pro- 
nator quadratus.  It  also  arises  from 
the  adjacent  part  of  the  interosseous 
membrane,  and  generally  by  a  fleshy 
slip  from  the  base  of  the  coronoid 
process.  The  fibres  pass  downward. 
and  terminate  in  a  flattened  tendon 
which  passes  beneath  the  annular 
ligament,  is  then  lodged  in  the  in- 
terspace between  the  outer  head  of 
the  Flexor  brevis  pollicis  and  the 
Adductor  obliquus  pollicis,  and  en- 
tering an  osseo-aponeurotlc  canal 


Marshall,  Brit,  and  For.  Med.-Chir.  Rev.,  1853. 


THE  RADIAL   REGION.  483 

similar  to  those  for  the  other  flexor  tendons,  is  inserted  into  the  base  of  the 
last  phalanx  of  the  thumb. 

Relations. — By  its  superficial  surface,  with  the  Flexor  sublimis  digitorum, 
Flexor  carpi  radialis,  Supinator  longus,  and  radial  vessels  ;  by  its  deep  surface, 
with  the  radius,  interosseous  membrane,  and  Pronator  quadratus ;  by  its  ulnar 
IxH-'b-i'.  with  the  Flexor  profundus  digitorum,  from  which  it  is  separated  by  the 
anterior  interosseous  vessels  and  nerve. 

The  Pronator  quadratus  is  a  small,  flat,  quadrilateral  muscle,  extending  trans- 
versely across  the  front  of  the  radius  and  ulna,  above  their  carpal  extremities.  It 
arises  from  the  oblique  or  pronator  ridge  on  the  lower  part  of  the  anterior  surface 
of  the  shaft  of  the  ulna ;  from  the  lower  fourth  of  the  anterior  surface  and  the 
anterior  border  of  the  ulna ;  and  from  a  strong  aponeurosis  which  covers  the  inner 
third  of  the  muscle.  The  'fibres  pass  horizontally  outward,  to  be  inserted  into 
the  lower  fourth  of  the  anterior  surface  anxl  anterior  border  of  the  shaft  of  the 
radius. 

Relations. — By  its  superficial  surface,  with  the  Flexor  profundus  digitorum,  the 
Flexor  longus  pollicis.  Flexor  carpi  radialis,  and  the  radial  vessels ;  by  its  deep 
9urfaee4  with  the  radius,  ulna,  and  interosseous  membrane. 

Nerves. — All  the  muscles  of  the  superficial  layer  are  supplied  by  the  median 
nerve,  excepting  the  Flexor  carpi  ulnaris,  which  is  supplied  by  the  ulnar.  Of  the 
deep  layer,  the  Flexor  profundus  digitorum  is  supplied  conjointly  by  the  ulnar  and 
by  the  median  through  its  branch,  the  anterior  interosseous  nerve,  which  also  sup- 
plies the  Flexor  longus  pollicis  and  Pronator  quadratus. 

Actions. — These  muscles  act  upon  the  forearm,  the  wrist,  and  hand.  The 
Pronator  radii  teres  helps  to  rotate  the  radius  upon  the  ulna,  rendering  the  hand 
prone :  when  the  radius  is  fixed  it  assists  the  other  muscles  in  flexing  the 
forearm.  The  Flexor  carpi  radialis  is  one  of  the  flexors  of  the  wrist ;  when 
acting  alone  it  flexes  the  wrist,  inclining  it  to  the  radial  side.  It  can  also 
r  in  pronating  the  forearm  and  hand,  and,  by  continuing  its  action,  to  bend 
the  elbow.  The  Flexor  carpi  ulnaris  is  one  of  the  flexors  of  the  wrist :  when 
acting  alone  it  flexes  the  wrist,  inclining  it  to  the  ulnar  side,  and,  by  continuing 
to  contract,  to  bend  the  elbow.  The  Palmaris  longus  is  a  tensor  of  the  palmar 
fascia.  It  also  assists  in  flexing  the  wrist  and  elbow.  The  Flexor  sublimis 
digitorum  flexes  the  second  phalanges.  It  assists  in  flexing  the  wrist  and  elbow. 
The  Flexor  profundus  digitorum  flexes  the  terminal  phalanges  (see  page  497). 
After  the  Flexor  sublimis  has  bent  the  second  phalanx,  the  Flexor  profundus 
flexes  the  terminal  one,  but  it  cannot  do  so  until  after  the  contraction  of  the  super- 
ficial muscle.  It  also  assists  in  flexing  the  wrist.  The  Flexor  longus  pollicis  is  a 
flexor  of  the  phalanges  of  the  thumb.  When  the  thumb  is  fixed  it  also  assists  in 
flexing  the  wrist.  The  Pronator  quadratus  helps  to  rotate  the  radius  upon  the 
ulna,  rendering  the  hand  prone. 

Radial  Region  (Fig.  308). 

Supinator  longus.  Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevier. 

Dissection. — Divide  the  integument  in  the  same  manner  as  in  the  dissection  of  the  anterior 
brachial  region,  and.  after  having  examined  the  cutaneous  vessels  and  nerves  and  deep  fascia, 
remove  all  thuse  structures.  The  muscles  will  then  be  exposed.  The  removal  of  the  fascia  will 
be  considerably  facilitated  by  detaching  it  from  below  upward.  Great  care  should  be  taken  to 
avoid  cutting  across  the  tendons  of  the  muscles  of  the  thumb,  which  cross  obliquely  the  larger 
tendons  running  down  the  back  of  the  radius. 

The  Supinator  longus  is  the  most  superficial  muscle  on  the  radial  side  of  the 
forearm :  it  is  fleshy  for  the  upper  two-thirds  of  its  extent,  tendinous  below.  It 
arises  from  the  upper  two-thirds  of  the  external  condyloid  ridge  of  the  humerus, 
and  from  the  external  intermuscular  septum,  being  limited  above  by  the 


484 


THE   MUSCLES  AND   FASCIA. 


FIG.  308.—  Posterior  surface  of  the  forearm. 
flcial  muscles. 


Super- 


musculo-spiral  groove.  The  fibres 
terminate  above  the  middle  of  the  fore- 
arm in  a  flat  tendon  which  is  inserted 
into  the  outer  side  of  the  base  of 
the  styloid  process  of  the  radius. 

Relations. — By  its  superficial  sur- 
face, with  the  integument  and  fascia 
for  the  greater  part  of  its  extent ; 
near  its  insertion  it  is  crossed  by  the 
Extensor  ossis  metacarpi  pollicis  and 
the  Extensor  brevis  pollicis ;  by  its 
deep  surface,  with  the  humerus,  the 
Extensor  '  carpi  radialis  longior  and 
brevior,  the  insertion  of  the  Pronator 
radii  teres,  and  the  Supinator  brevis; 
bv  its  inner  border,  above  the  elbow, 
w'ith  the  Brachialis  anticus,  the 
musculo-spiral  nerve,  and  radial  re- 
current artery  ;  and  in  the  forearm 
with  the  radial  vessels  and  nerve. 

The  Extensor  carpi  radialis  longior 
is  placed  partly  beneath  the  pre- 
ceding muscle.  It  arises  from  the 
lower  third  of  the  external  condyloid 
ridge  of  the  humerus,  and  from  the 
external  intermuscular  septum.  The 
fibres  terminate  at  the  upper  third  of 
the  forearm  in  a  flat  tendon,  which 
runs  along  the  outer  border  of  the 
radius,  beneath  the  extensor  tendons 
of  the  thumb ;  it  then  passes  through 
a  groove  common  to  it  and  the  Ex- 
tensor carpi  radialis  brevior,  imme- 
diately behind  the  styloid  process,  and 
is  inserted  into  the  base  of  the  meta- 
carpal  bone  of  the  index  finger,  on  its 
radial  side. 

Relations. — By  its  superficial  sur- 
face, with  the  Supinator  longus,  and 
fascia  of  the  forearm;  its  outer  side-is 
crossed  obliquely  by  the  extensor  ten- 
dons of  the  thumb  ;  by  its  deep  surface, 
with  the  elbow-joint,  the  Extensor 
carpi  radialis  brevior,  and  back  part 
of  the  wrist. 

The  Extensor  carpi  radialis  brevior 
is  shorter,  as  its  name  implies,  and 
thicker  than  the  preceding  muscle,  be- 
neath which  it  is  placed.  It  arises 
from  the  external  condyle  of  the 
humerus  by  a  tendon  common  to  it 
and  the  three  following  muscles ;  from 
the  external  lateral  ligament  of  the 
elbow-joint,  from  a  strong  aponeurosis 
which  covers  its  surface,  and  from 
the  intermuscular  septa  between  it  and 
the  adjacent  muscles.  The  fibres  ter- 


THE   POSTERIOR    BRACHIAL    REGION.  485 

minate  about  the  middle  of  the  forearm  in  a  flat  tendon  which  is  closely  connected 
with  that  of  the  preceding  muscle,  and  accompanies  it  to  the  wrist,  lying  in  the 
same  groove  on  the  posterior  surface  of  the  radius ;  it  passes  beneath  the  extensor 
tendons  of  the  thumb,  then  -beneath  the  annular  ligament,  and,  diverging  some- 
what from  its  fellow,  is  inserted  into  the  base  of  the  metacarpal  bone  of  the  middle 
finger,  on  its  radial  side. 

The  tendons  of  the  two  preceding  muscles  pass  through  the  same  compartment 
of  the  annular  ligament,  and  are  lubricated  by  a  single  synovial  membrane,  but  are 
separated  from  each  other  by  a  small  vertical  ridge  of  bone  as  they  lie  in  the 
groove  at  the  back  of  the  radius. 

Relations. — By  its  superficial  surface,  with  the  Extensor  carpi  radialis  longior, 
and  with  the  Extensor  muscles  of  the  thumb  which  cross  it ;  by  its  deep  surface, 
with  the  Supinator  brevis.  tendon  of  the  Pronator  radii  teres,  radius,  and  wrist- 
joint  ;  by  its  ulnar  border,  with  the  Extensor  communis  digitorum. 

Posterior  Radio-Ulnar  Region  (Fig.  308). 

Superficial  Layer. 

Extensor  communis  digitorum.  Extensor  carpi  ulnaris. 

Extensor  minimi  digiti.  Anconeus. 

The  Extensor  communis  digitorum  is  situated  at  the  back  part  of  the  forearm. 
It  arises  from  the  external  condyle  of  the  humerus  by  the  common  tendon,  from 
the  deep  fascia,  and  the  intermuscular  septa  between  it  and  the  adjacent  muscles. 
Just  below  the  middle  of  the  forearm  it  divides  into  three  tendons,  which  pass, 
together  with  the  Extensor  indicis,  through  a  separate  compartment  of  the  annular 
ligament,  lubricated  by  a  synovial  membrane.  The  tendons  then  diverge,  the 
innermost  one  dividing  into  two ;  and  all,  after  passing  across  the  back  of  the 
hand,  are  inserted  into  the  second  and  third  phalanges  of  the  fingers  in  the 
following  manner :  Each  tendon  becomes  narrow  and  thickened  opposite  the  meta- 
carpo-phalaugeal  articulation,  and  gives  off  a  thin  fasciculus  upon  each  side  of  the 
joint,  which  blends  with  the  lateral  ligaments  and  serves  as  the  posterior  ligament ; 
after  having  passed  the  joint  it  spreads  out  into  a  broad  aponeurosis,  which  covers 
the  whole  of  the  dorsal  surface  of  the  first  phalanx,  being  reinforced,  in  this 
situation,  by  the  tendons  of  the  Interossei  and  Lumbricales.  Opposite  the  first 
phalanges!  joint  this  aponeurosis  divides  into  three  slips,  a  middle  and  two  lateral : 
the  former  is  inserted  into  the  base  of  the  second  phalanx  ;  and  the  two  lateral, 
which  are  continued  onward  along  the  sides  of  the  second  phalanx,  unite  by 
their  contiguous  margins,  and  are  inserted  into  the  dorsal  surface  of  the  last 
phalanx.  As  the  tendons  cross  the  phalangeal  joints  they  furnish  them  with 
posterior  ligaments.  The  tendons  of  the  middle,  ring,  and  little  fingers  are 
connected  together,  as  they  cross  the  hand,  by  small,  oblique,  tendinous  slips,  or 
'  fa  :  those  on  each  side  of  the  ring  finger  are  strong,  and  bind  the  tendon  of 
this  finger  closely  to  those  of  the  middle  and  little  finger,  so  that  it  cannot,  in 
general,  be  freely  extended  without  moving  the  other  two.  Sometimes  there  is 
also  a  thin  slip  between  the  tendons  of  the  index  and  middle  fingers.  The  tendons 
of  the  index  and  little  fingers  also  receive,  before  their  division,  the  special  extensor 
tendons  belonging  to  them. 

Relations. — By  its  *»/» '-rticial  surface,  with  the  fascia  of  the  forearm  and  hand, 
the  posterior  annular  ligament,  and  integument;  by  its  deep  surface,  with  the 
Supinator  T)revis,  the  Extensor  muscles  of  the  thumb  and  index  finger,  the 
posterior  interosseous  vessels  and  nerve,  the  wrist-joint,  carpus,  metacarpus,  and 
phalanges  ;  by  its  radial  border,  with  the  Extensor  carpi  radialis  brevior ;  by  its 
ulnar  border,  with  the  Extensor  minimi  digiti  and  Extensor  carpi  ulnaris. 

The  Extensor  minimi  digiti  is  a  slender  muscle  placed  on  the  inner  side  of 
the  Extensor  communis,  with  which  it  is  generally  connected.  It  arises  from  the 
common  tendon  by  a  thin,  tendinous  slip,  and  from  the  intermuscular  septa 
between  it  and  the  adjacent  muscles.  Its  tendon  runs  through  a  separate 


486  THE  MUSCLES  AND   FASCIA. 

compartment  in  the  annular  ligament  behind  the  inferior  radio-ulnar  joint,  then 
divides  into  two  as  it  crosses  the  hand,  one  slip  being  united  to  the  common 
extensor  by  a  cross-piece  at  the  metacarpo-phalangeal  articulation.  Both  finally 
spread  into  a  broad  aponeurosis  which  blends  with  the  common  extensor  to  the 
finger,  and  is  inserted  into  the  second  and  third  phalanges.  The  tendon  is 
situated  on  the  ulnar  side  of,  and  somewhat  more  superficial  than,  the  common 
extensor. 

The  Extensor  carpi  ulnaris  is  the  most  superficial  muscle  on  the  ulnar  side  of 
the  forearm.  It  arises  from  the  external  condyle  of  the  humerus  by  the  common 
tendon ;  from  the  middle  third  of  the  posterior  surface  of  the  ulna,  below  the 
Anconeus,  and  by  an  aponeurosis  from  the  posterior  border  of  the  ulna  in  common 
with  the  Flexor  carpi  ulnaris  and  the  Flexor  profundus  digitorum ;  and  from  the 
deep  fascia  of  the  forearm.  This  muscle  terminates  in  a  tendon  which  runs  through 
a  groove  behind  the  styloid  process  of  the  ulna,  passes  through  a  separate  compart- 
ment in  the  annular  ligament,  and  is  inserted  into  the  prominent  tubercle  on  the 
ulnar  side  of  the  base  of  the  metacarpal  bone  of  the  little  finger. 

Relations. — By  its  superficial  surface,  with  the  deep  fascia  of  the  forearm  ;  by 
its  deep  surface,  with  the  ulna  and  the  muscles  of  the  deep  layer. 

The  Anconeus  is  a  small  triangular  muscle  placed  behind  and  below  the  elbow- 
joint,  and  appears  to  be  a  continuation  of  the  external  portion  of  the  Triceps.  It 
arises  by  a  separate  tendon  from  the  back  part  of  the  outer  condyle  of  the  humerus, 
and  is  inserted  into  the  side  of  the  olecranon  and  upper  fourth  of  the  posterior 
surface  of  the  shaft  of  the  ulna ;  its  fibres  diverge  from  their  origin,  the  upper 
ones  being  directed  transversely,  the  lower  obliquely  inward. 

Relations. — By  its  superficial  surface,  with  a  strong  fascia  derived  from  the 
Triceps  ;  by  its  deep  surface,  with  the  elbow-joint,  the  orbicular  ligament,  the 
ulna,  and  a  small  portion  of  the  Supinator  brevis. 

Deep  Layer  (Fig.  310). 

Supinator  brevis.  Extensor  brevis  pollicis. 

Extensor  ossis  metacarpi  pollicis.  Extensor  longus  pollicis. 

Extensor  indicis. 

The  Supinator  brevis  is  a  broad  muscle,  of  a  hollow  cylindrical  form,  curved 
round  the  upper  third  of  the  radius.  It  consists  of  two  distinct  planes  of  muscular 
fibres,  between  which  lies  the  posterior  interosseous  nerve.  The  two  planes  arise 
in  common :  the  superficial  one  by  tendinous,  and  the  deeper  by  muscular  fibres 
from  the  external  condyle  of  the  humerus  ;  from  the  external  lateral  ligament  of  the 
elbow-joint  and  the  orbicular  ligament  of  the  radius ;  from  the  ridge  on  the  ulna, 
which  runs  obliquely  downward  from  the  posterior  extremity  of  the  lesser  sigmoid 
cavity  ;  from  the  triangular  depression  in  front  of  this  ridge ;  and  from  a  tendinous 
expansion  which  covers  the  surface  of  the  muscle.  The  superficial  fibres  surround 
the  upper  part  of  the  radius,  and  are  inserted  into  the  outer  edge  of  the  bicipital 
tuberosity  and  to  the  oblique  line  of  the  radius,  as  low  down  as  the  insertion  of  the 
Pronator  radii  teres.  The  upper  fibres  of  the  deeper  plane  form  a  sling-like 
fasciculus,  which  encircles  the  neck  of  the  radius  above  the  tuberosity  and  is 
attached  to  the  back  part  of  its  inner  surface :  the  greater  part  of  this  portion  of 
the  muscle  is  inserted  into  the  posterior  and  external  surface  of  the  shaft,  midway 
between  the  oblique  line  and  the  head  of  the  bone.  Between  the  insertion  of  the 
two  planes  the  posterior  interosseous  nerve  lies  on  the  shaft  of  the  bone. 

Relations. — By  its  superficial  surface,  with  the  superficial  Extensor  and 
Supinator  muscles,  and  the  radial  vessels  and  nerve ;  by  its  deep  surface,  with  the 
elbow-joint,  the  interosseous  membrane,  and  the  radius. 

The  Extensor  ossis  metacarpi  pollicis  is  the  most  external  and  the  largest  of 
the  deep  extensor  muscles :  it  lies  immediately  below  the  Supinator  brevis,  with 
which  it  is  sometimes  united.  It  arises  from  the  posterior  surface  of  the  shaft  of 
the  ulna  below  the  insertion  of  the  Anconeus,  from  the  interosseous  membrane, 


THE  POSTERIOR   BRACHIAL   REGION. 


487 


and  from  the  middle  third  of  the  posterior  surface  of  the  shaft  of  the  radius. 

-ing  obliquely  downward  and  outward,  it  terminates  in  a  tendon  which  runs 
through  a  groove  on  the  outer  side 
of  the  styloid  process  of  the  ,radius, 
accompanied  by  the  tendon  of  the 
Extensor  brevis  pollicis.  and  is  in- 
serted  into  the  base  of  the  rneta- 
carpal  bone  of  the  thumb.  It  occa- 
sionally gives  off  two  slips,  near  its 
insertion — one  to  the  Trapezium, 
and  the  other  to  blend  with  the 
origin  of  the  Abductor  pollicis. 

Relations. — By  irs  superficial 
surf'!'--',  with  the  Extensor  com- 
munis  digitorum.  Extensor  minimi 
digiti,  and  fascia  of  the  forearm, 
and  with  the  branches  of  the  pos- 
terior interosseous  artery  and  nerve 
which  cross  it ;  by  its  deep  surface, 


Internal 
condyle. 


External 
condyle. 


CAPSULAR 
LIGAMENT. 


B«|NM, 


FIG.  309.— Supinator  brevis.  (From  a  prepara- 
tion in  the  Museum  of  the  Royal  College  of 
Surgeons  of  England). 


EXTENSOR 
CARPI  ULNARIS. 


FIG.  310.— Posterior  surface  of  the  forearm.    Deep  muscles. 


with  the  ulna,  interosseous  membrane,  radius,  the  tendons  of  the  Extensor  carpi 
radialis  longior  and  brevior,  which  it  crosses  obliquely,  and,  at  the  outer  side  of 
the  wrist,  with  the  radial  vessels  :  by  its  upper  border,  with  the  Supinator  brevis ; 
by  its  luwer  border,  with  the  Extensor  brevis  pollicis. 


488  THE   MUSCLES  AND    FASCIAE. 

The  Extensor  brevis  pollicis  (Extensor  primi  internodii  pollicis),  the  smallest 
muscle  of  this  group,  lies  on  the  inner  side  of  the  preceding.  It  arises  from  the  pos- 
terior surface  of  the  shaft  of  the  radius,  below  the  Extensor  ossis  metacarpi  pollicis, 
and  from  the  interosseous  membrane.  Its  direction  is  similar  to  thai  of  the 
Extensor  ossis  metacarpi  pollicis,  its  tendon  passing  through  the  same  groove  on 
the  outer  side  of  the  styloid  process,  to  be  inserted  into  the  base  of  the  first  phalanx 
of  the  thumb. 

Relations. — The  same  as  those  of  the  Extensor  ossis  metacarpi  pollicis. 

The  Extensor  longus  pollicis  (Extensor  secundi  internodii  pollicis)  is  much  larger 
than  the  preceding  muscle,  the  origin  of  which  it  partly  covers  in.  It  arises  from 
the  posterior  surface  of  the  shaft  of  the  ulna,  below  the  origin  of  the  Extensor 
ossis  metacarpi  pollicis,  and  from  the  interosseous  membrane.  It  terminates  in  a 
tendon  which  passes  through  a  separate  compartment  in  the  annular  ligament, 
lying  in  a  narrow,  oblique  groove  at  the  back  part  of  the  lower  end  of  the  radius. 
It  then  crosses  obliquely  the  tendons  of  the  Extensor  carpi  radialis  longior  and 
brevior,  being  separated  from  the  other  extensor  tendons  of  the  thumb  by  a 
triangular  interval,  in  which  the  radial  artery  is  found,  and  is  finally  inserted  into 
the  base  of  the  last  phalanx  of  the  thumb. 

Relations. — By  its  superficial  surface,  with  the  same  parts  as  the  Extensor  ossis 
metacarpi  pollicis ;  by  its  deep  surface,  Avith  the  ulna,  interosseous  membrane,  the 
posterior  interosseous  nerve,  radius,  the  wrist,  the  radial  vessels,  and  metacarpal 
bone  of  the  thumb. 

The  Extensor  indicis  is  a  narrow,  elongated  muscle  placed  on  the  inner  side  of, 
and  parallel  with,  the  preceding.  It  arises  from  the  posterior  surface  of  the  shaft 
of  the  ulna,  below  the  origin  of  the  Extensor  longus  pollicis  and  from  the  inter- 
osseous membrane.  Its  tendon  passes  with  the  Extensor  communis  digitorum 
through  the  same  canal  in  the  annular  ligament,  and  subsequently  joins  the  tendon 
of  the  Extensor  communis  which  belongs  to  the  index  finger,  opposite  the  lower 
end  of  the  corresponding  metacarpal  bone,  lying  to  the  ulnar  side  of  the  tendon 
from  the  .common  Extensor. 

Relations. — The  relations  are  similar  to  those  of  the  preceding  muscles. 

Nerves. — The  Supinator  longus,  Extensor  carpi  radialis  longior,  and  Anconeus 
are  supplied  by  branches  from  the  musculo-spiral  nerve ;  the  remaining  muscles 
of  the  radial  and  posterior  brachial  regions,  by  the  posterior  interosseous  nerve. 

Actions. — The  muscles  of  the  radial  and  posterior  brachial  regions,  which 
comprise  all  the  extensor  and  supinator  muscles,  act  upon  the  forearm,  wrist,  and 
hand ;  they  are  the  direct  antagonists  of  the  pronator  and  flexor  muscles.  The 
Anconeus  assists  the  Triceps  in  extending  the  forearm.  The  chief  action  of  the 
Supinator  longus  is  that  of  a  flexor  of  the  elbow-joint,  but  in  addition  to  this  it 
may  act  both  as  a  supinator  or  a  pronator ;  that  is  to  say,  if  the  forearm  is  forcibly 
pronated  it  will  act  as  a  supinator,  and  bring  the  bones  into  a  position  midway 
between  supination  and  pronation  ;  and,  vice  versd,  if  the  arm  is  forcibly  supinated, 
it  will  act  as  a  pronator,  and  bring  the  bones  into  the  same  position,  midway 
between  supination  and  pronation.  The  action  of  the  muscle  is  therefore  to  throw 
the  forearm  and  hand  into  the  position  they  naturally  occupy  when  placed  across 
the  chest.  The  Supinator  brevis  is  a  supinator  ;  that  is  to  say,  when  the  radius 
has  been  carried  across  the  ulna  in  pronation  and  the  back  of  the  hand  is  directed 
forward,  this  muscle  carries  the  radius  back  again  to  its  normal  position  on  the 
outer  side  of  the  ulna,  and  the  palm  of  the  hand  is  again  directed  forward.  The 
Extensor  carpi  radialis  longior  extends  the  wrist  and  abducts  the  hand.  It  may 
also  assist  in  bending  the  elbow-joint;  at  all  events,  it  serves  to  fix  or  steady  this 
articulation.  The  Extensor  carpi  radialis  brevior  assists  the  Extensor  carpi  radi- 
alis longior  in  extending  the  wrist,  and  may  also  act  slightly  as  an  abductor  of  the 
hand.  The  Extensor  carpi  ulnaris  helps  to  extend  the  hand,  but  when  acting 
alone  inclines  it  toward  the  ulnar  side ;  by  its  continued  action  it  extends  the 
'  elbow-joint.  The  Extensor  communis  digitorum  extends  the  phalanges,  then  the 
wrist,  and  finally  the  elbow.  It  acts  principally  on  the  proximal  phalanges,  the 


THE   HAXD 


489 


.ONO.     FLE 


middle  and  terminal  phalanges  being  extended  by  the  Interossei  and  Lumbri- 
cales.  It  has  also  a  tendency  to  separate  the  fingers  as  it  extends  them.  The 
Extensor  minimi  digiti  extends  similarly  the  little  finger,  and  by  its  continued 
action  it  assists  in  extending  the  wrist.  It  is  owing  to  this  muscle  that  the  little 
finger  can  be  extended  or  pointed  whilst  the  others  are  flexed.  The  chief  action  of 
the  Extensor  ossis  metacarpi  pollicis  is  to  carry  the  thumb  outward  and  backward 
from  the  palm  of  the  hand,  and  hence  it  has  been  called  the  abductor  longus 
poUicis.  By  its  continued  action  it  helps  to  extend  and  abduct  the  wrist.  The 
Extensor  brevis  pollicis  extends  the  proximal  phalanx  of  the  thumb.  By  its 
continued  action  it  helps  to  extend  and  abduct  the  wrist.  The  Extensor  longus 
pollicis  extends  the  terminal  phalanx  of  the  thumb.  By  its  continued  action  it 
helps  to  extend  and  abduct  the  wrist.  The  Extensor  mdicis  extends  the  first 
phalanx  of  the  index  finger,  and  by  its  continued  action  assists  in  extending  the 
wrist.  It  is  owing  to  this  muscle  that  the  index  finger  can  be  extended  or  pointed 
while  the  others  are  flexed. 

Surgical  Anatomy. — The  tendons  of  the  Extensor  muscles  of  the  thumb  are  liable  to 
become  strained  and  their  sheaths  inflamed  after  excessive  exercise,  producing  a  sausage-shaped 
swelling  along  the  course  of  the  tendon,  and  giving  a  peculiar  creaking  sensation  to  the  finger 
when  the  muscle  acts.  In  consequence  of  its  often  being  caused  by  such  movements  as  wringing 
clothes,  it  is  known  as  ''washerwoman's  sprain." 

THE  HAND. 

Dissection  (Fig.  301). — Make  a  transverse  incision  across  the  front  of  the  wrist,  and  a 
second  across  the  he&ds  of  the  metacarpal  bones  :  connect  the  two  by  a  vertical  incision  in  the 
middle  line,  and  continue  it  through  the  cen- 
tre of  the  middle  finger.  The  anterior  and 
posterior  annular  ligaments  and  the  palmar 
fascia  should  then  be  dissected. 

The  Anterior  Annular  Ligament  is 
a  strong,  fibrous  band  which  arches 
over  the  carpus,  converting  the  deep 
groove  on  the  front  of  the  carpal 
bones  into  a  canal,  beneath  which 
the  flexor  tendons  of  the 
fingers.  It  is  attached,  internally,  to 
the  pisiform  bone  and  unciform  pro- 
•f  the  unciform  bone,  and  ex- 
ternally to  the  tuberosity  of  the 
scaphoid  and  to  the  inner  part  of  the 
anterior  surface  and  the  ridge  on  the 
trapezium.  It  is  continuous,  above, 
with  the  deep  fascia  of  the  forearm,  of  which  it  may  be  regarded  as  a  thickened 
portion,  and.  below,  with  the  palmar  fascia.  It  is  crossed  by  the  ulnar  vessels 
and  nerve  and  the  cutaneous  branches  of  the  median  and  ulnar  nerves.  At  its 
outer  extremity  is  the  tendon  of  the  Flexor  carpi  radialis,  which  lies  in  the  groove 
on  the  trapezium  between  the  attachments  of  the  annular  ligament  to  the  bone. 
It  has  inserted  into  its  anterior  surface  the  tendon  of  the  Palmaris  longus  and 
part  of  the  tendon  of  the  Flexor  carpi  ulnaris,  and  has  arising  from  it,  below,  the 
small  muscles  of  the  thumb  and  little  finger.  Beneath  it  pass  the  tendons  of  the 
Flexor  sublimis  and  profundus  digitorum,  the  Flexor  longus  pollicis,  and  the 
median  nerve. 

The  Synovial  Membranes  of  the  Flexor  Tendons  at  the  Wrist. — There  are  two 
synovial  membranes  which  enclose  all  the  tendons  as  they  pass  beneath  this  lig- 
ament— one  for  the  Flexor  sublimis  and  profundus  digitorum,  the  other  for  the 
Flexor  longus  pollicis.  They  extend  up  into  the  forearm  for  about  an  inch  above 
the  annular  ligament,  and  downward  about  halfway  along  the  metacarpal  bone, 
where  they  terminate  in  a  blind  diverticulum  around  each  pair  of  tendons,  with 
the  exception  of  the  thumb  and  sometimes  the  little  finger — in  these  two  fingers 


FIG.  311.— Transverse  section  through  the  wrist,  show- 
ing the  annular  ligaments  and  the  canals  for  the  passage 
of  the  tendons. 


490 


THE  MUSCLES  AND   FASCIA. 


the  diverticulum  is  continued  on,  and  communicates  with  the  synovial  sheath  of  the 
tendons.  In  the  other  three  fingers  the  synovial  sheath  of  the  tendons  in  the  fingers 
begins  as  a  blind  pouch  without  communication  with  the  large  synovial  sac  (Fig.  313). 


Surgical  Anatomy. — This  arrangement  of  the  synovial  sheaths  explains  the  fact  that  thecal 
abscess  in  the  thuinb  and  little  finger  is  liable  to  be  followed  by  abscesses  in  the  forearm,  from  exten- 
sion of  the  inflammation 

ANNULAR    LIGAMENT. 

FLEXOR  LONGUS  pOLLicis.  I  Median  nerve. 

FLEXOR    CARPI    RADIAL1S.  \  I  /          JJlndT  VCSS 

MUSCLES    OF  THUMB,  \  \  III  /PALMARIS    BREV1S. 


1st  Metacarpal. 


EXT.    PRIM 

INTERNOD. 

POLL. 

EXT.    SEC 
INTERNOD. 

POLL. 

Trapezium! 

Radial  vessels. 

EXT.    CARP.    RAD.    LONG. 

Trapezoid. 

EXTENSOR    CARPI     RADIALIS 
BREVIOR. 


MUSCLES    OF 
LITTLE 
FINGER. 


EXT.    CPRPI 
ULNARIS. 


EXTENSOR 
•MINIMI 
DIGIT). 

EXTENSOR 

COMMUNIS 

DIGITORUM. 


along  the  continuous 
synovial  sheaths.  Gan- 
glion is  apt  to  occur  in 
this  situation,  constitu- 
ting "compound  palmar 
ganglion  " :  it  presents 
an  hour-glass  outline, 
with  a  swelling  in  front 
of  the  wrist  and  in  the 
palm  of  the  hand,  and  a 
constriction  correspond- 
ing to  the  annular  liga- 
ment between  the  two. 
The  fluid  can  be  forced 
from  the  one  swelling  to 
the  other  under  the  liga- 
ment. 

EXTENSOR    INDICIS. 

Os  magnum.  The  Posterior  An- 

PIG.  312.— Transverse  section  through  the  carpus,  showing  the  relative  posi-  nular    Ligament   IS    a 
tions  of  the  tendons,  vessels,  and  nerves.    (Henle.)  strong;    fibrous    band 

extending  transversely  across  the  back  of  the  wrist,  and  consisting  of  the  deep 
fascia  of  the  back  of  the  forearm,  strengthened  by  the  addition  of  some  transverse 
fibres.  It  forms  a  sheath  for  the  extensor  tendons  in  their  passage  to  the  fingers, 

being  attached,  internally,  to  the  styloid 
process  of  the  ulna,  the  cuneiform  and 
pisiform  bones ;  externally,  to  the  margin 
of  the  radius ;  and,  in  its  passage  across 
the  wrist,  to  the  elevated  ridges  on  the 
posterior  surface  of  the  radius.  It  pre- 
sents six  compartments  for  the  passage 
of  tendons,  each  of  which  is  lined  by  a 
separate  synovial  membrane.  These  are, 
from  without  inward — 1.  On  the  Outer 
side  of  the  styloid  process,  for  the  ten- 
dons of  the  Extensor  ossis  metacarpi 
and  Extensor  brevis  pollicis  ;  2.  Behind 
the  styloid  process,  for  the  tendons  of 
the  Extensor  carpi  radialis  longior  and 
brevior;  3.  About  the  middle  of  the 
posterior  surface  of  the  radius,  for  the 
tendon  of  the  Extensor  longus  pollicis ; 
4.  To  the  inner  side  of  the  latter,  for  the 
tendons  of  the  Extensor  communis  digi- 
torum  and  Extensor  indicis;  5.  Oppo- 
site the  interval  between  the  radius  and 
ulna,  for  the  Extensor  minimi  digiti ; 

FIG.  313.— Diagram  showing  the  arrangement  of  the    6.   Grooving  the  back  of  the  ulna,  for  the 

tendon  of  the  Extensor  carpi  ulnaris. 
The  synovial  membranes  lining  these  sheaths  are  usually  very  extensive,  reach- 
ing from  above  the  annular  ligament,  down  upon  the  tendons  for  a  variable 
distance  on  the  back  of  the  hand. 

The  deep  palmar  fascia  (Fig.  314)  forms  a  common  sheath  which  invests  the 
muscles  of  the  hand.  It  consists  of  a  central  and  two  lateral  portions. 

The  central  portion  occupies  the  middle  of  the  palm,  is  triangular  in  shape,  of 


THE   HAND. 


491 


great  strength  and  thickness,  and  binds  down  the  tendons  in  this  situation.  It  is 
narrow  above,  being  attached  to  the  lower  margin  of  the  annular  ligament,  and 
receives  the  expanded  tendon  of  the  Palmaris  longus  muscle.  Below,  it  is  broad 
and  expanded,  and  divides  into  four  slips,  for  the  four  fingers.  Each  slip  gives  off 
superficial  fibres,  which  are  inserted  into  the  skin  of  the  palm  and  finger,  those  to 
the  palin  joining  the  skin  at  the  furrow  corresponding  to  the  metacarpo-phalangeal 
articulation,  and  those  to  the  fingers  passing  into  the  skin  at  the  transverse  fold 
at  the  base  of  the  fingers.  The  deeper  part  of  each  slip  subdivides  into  two  pro- 
cesses, which  are  inserted  into  the  lateral  margins  of  the  anterior  (glenoid)  liga- 
ment of  the  metacarpo-phalangeal  joint.  From  the  sides  of  these  processes 


Digital  artery. 
Digital  nerce. 


...EXTENSOR    METACARPI    AND 
EXTENSOR    BREVIS    POLLICIS. 


FLEXOR    LONGUS    POLLICIS. 


FIG.  314.— Palmar  fascia. 
England.) 


(Altered  from  a  dissection  in  the  Museum  of  the  Royal  College  of  Surgeons  of 


offsets  are  sent  backward,  to  be  attached  to  the  borders  of  the  lateral  surfaces  of 
the  metacarpal  bones  at  their  distal  extremities.  By  this  arrangement  short 
channels  are  formed  on  the  front  of  the  lower  ends  of  the  metacarpal  bones, 
through  which  the  flexor  tendons  pass.  Dr.  W.  W.  Keen  describes  a  fifth  slip  as 
frequently  found  passing  to  the  thumb.  The  intervals  left  in  the  fascia  between 
the  four  fibrous  slips  transmit  the  digital  vessels  and  nerves  and  the  tendons  of 
the  Lumbricales.  At  the  points  of  division  of  the  palmar  fascia  into  the  slips 
above  mentioned  numerous  strong,  transverse  fibres  bind  the  separate  processes 
together.  The  palmar  fascia  is  intimately  adherent  to  the  integument  by  dense 
fibro-areolar  tissue,  forming  the  superficial  palmar  fascia,  and  gives  origin  by  its 
inner  margin  to  the  Palmaris  brevis :  it  covers  the  superficial  palmar  arch,  the 


492  THE   MUSCLES  AND    FASCIA. 

tendons  of  the  flexor  muscles,  and  the  branches  of  the  median  and  ulnar  nerves, 
and  on  each  side  it  gives  off  a  vertical  septum,  which  is  continuous  with  the 
interosseous  aponeurosis  and  separates  the  lateral  from  the  middle  palmar  group 
of  muscles. 

The  lateral  portions  of  the  palmar  fascia  are  thin,  fibrous  layers,  which  cover, 
on  the  radial  side,  the  muscles  of  the  ball  of  the  thumb,  and,  on  the  ulnar  side,  the 
muscles  of  the  little  finger ;  they  are  continuous  with  the  dorsal  fascia,  and  in  the 
palm  with  the  central  portion  of  the  palmar  fascia. 

The  Superficial  Transverse  Ligament  of  the  Fingers  is  a  thin,  fibrous  band 
which  stretches  across  the  roots  of  the  four  fingers,  and  is  closely  attached  to  the 
skin  of  the  clefts,  and  internally  to  the  fifth  metacarpal  bone,  forming  a  sort  of 
rudimentary  web.  Beneath  it  the  digital  vessels  and  nerves  pass  onward  to  their 
destination. 

Surgical  Anatomy. — The  palmar  fascia  is  liable  to  undergo  contraction,  producing  a  very 
inconvenient  deformity  known  as  "Dupuytren's  contraction."  The  ring  and  little  fingers  are 
most  frequently  implicated,  but  the  middle,  the  index,  and  the  thumb  may  be  involved.  The 
proximal  phalanx  is  drawn  down  and  cannot  be  straightened,  and  the  two  distal  phalanges 
become  similarly  flexed  as  the  disease  advances. 

The  Muscles  of  the  Hand  are  subdivided  into  three  groups :  1.  Those  of  the 
thumb,  which  occupy  the  radial  side ;  2.  Those  of  the  little  finger,  which  occupy 
the  ulnar  side ;  3.  Those  in  the  middle  of  the  palm  and  between  the  interosseous 
spaces. 

Radial  Region  (Figs.  315,  316). 
Muscles  of  the  Thumb. 

Abductor  pollicis.  Flexor  brevis  pollicis. 

Opponens  (Flexor  ossis  metacarpi)  pollicis.     Adductor  obliquus  pollicis. 
Adductor  transversus  pollicis. 

The  Abductor  pollicis  is  a  thin,  flat  muscle  placed  immediately  beneath  the 
integument.  It  arises  from  the  ridge  of  the  os  trapezium  and  annular  ligament, 
and,  passing  outward  and  downward,  is  inserted  by  a  thin,  flat  tendon  into  the 
radial  side  of  the  base  of  the  first  phalanx  of  the  thumb,  sending  a  slip  to  join  the 
tendon  of  the  Extensor  longus  pollicis. 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia ;  by  its  deep 
surface,  with  the  Opponens  pollicis,  from  which  it  is  separated  by  a  thin  apo- 
neurosis. Its  inner  border  is  separated  from  the  Flexor  brevis  pollicis  by  a  narrow 
cellular  interval. 

The  Opponens  pollicis  is  a  small,  triangular  muscle  placed  beneath  the 
preceding.  It  arises  from  the  palmar  surface  of  the  trapezium  and  annular 
ligament,  passes  downward  and  outward,  and  is  inserted  into  the  whole  length  of 
the  metacarpal  bone  of  the  thumb  on  its  radial  side. 

Relations. — By  its  superficial  surface,  with  the  Abductor  pollicis ;  by  its  deep 
surface,  with  the  trapezio-metacarpal  articulation ;  by  its  inner  border,  with  the 
Flexor  brevis  pollicis. 

The  Flexor  brevis  pollicis  is  much  larger  than  either  of  the  two  preceding 
muscles,  beneath  which  it  is  placed.  It  consists  of  two  portions,  outer  and  inner. 
The  outer  and  more  superficial  portion  arises  from  the  trapezium  and  outer  two- 
thirds  of  the  annular  ligament,  and  passes  along  the  outer  side  of  the  tendon  of 
the  Flexor  longus  pollicis,  and,  becoming  tendinous,  has  a  sesamoid  bone  developed 
in  its  tendon,  and  is  inserted  into  the  outer  side  of  the  base  of  the  first  phalanx  of 
the  thumb.  The  inner  and  deeper  portion  of  the  muscle  is  very  small,  and  arises 
from  the  ulnar  side  of  the  first  metacarpal  bone,  and  is  inserted  into  the  inner  side 
of  the  base  of  the  first  phalanx  with  the  Adductor  obliquus  pollicis.  A  sesamoid 
bone  is  developed  in  the  common  tendon  of  insertion. 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia ;  by  its  deep  sur- 


THE   RADIAL    REGION.  493 

face,  with  the  tendon  of  the  Flexor  carpi  radialis  :  by  its  external  surface,  with  the 
Opponens  pollicis:  by  its  internal  *i.irfa<-<-.  with  the  Adductor  obliquus  pollicis. 

The  Adductor  obliquus  poliicis  arises  by  several  slips  from  the  os  magnum,  the 
bases  of  the  second  and  third  metacarpal  bones,  the  anterior  annular  ligament,  and 
the  sheath  of  the  tendon  of  the  Flexor  carpi  radialis.  From  this  origin  the  greater 
number  of  fibres  pass  obliquely  downward  and  converge  to  a  tendon,  which, 
uniting  with  the  tendons  of  the  deeper  portion  of  the  Flexor  brevis  pollicis  and 
the  Adductor  transversus,  is  inserted  into  the  inner  side  of  the  base  of  the  first 
phalanx  of  the  thumb,  a  sesamoid  bone  being  developed  in  the  tendon  of  insertion. 
A  considerable  fasciculus,  however,  passes  more  obliquely  outward  beneath  the 


3d  Metacarpal  bone. 


FLEXOR    BREVIS    POLLICIS.  • 


/ 

ABDUCTOR    POLLICIS. 

FIG.  315.— Muscles  of  thumb.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of 
England.! 

tendon  of  the  long  flexor  to  join  the  superficial  portion  of  the  short  flexor  and  the 
Abductor  pollicis.1 

Eelations. — By  its  superiii'-tal  surface,  with  the  Flexor  longus  pollicis  and  the 
outer  head  of  the  Flexor  brevis  pollicis.      Its  deep  surface  covers  the  Adductor 
transversus  pollicis.  and  is  in  relation  with  the  deep  palmar  arch,  which  p.: 
between  the  two  adductors. 

The  Adductor  transversus  pollicis  (Fig.  315)  is  the  most  deeply  seated  of  this 
group  of  muscles.  It  is  of  a  triangular  form,  arising,  by  its  broad  base,  from  the 
lower  two-thirds  of  the  metacarpal  bone  of  the  middle  finger  on  its  palmar  surface  : 
the  fibres,  proceeding  outward,  converge,  to  be  inserted,  with  the  inner  tendon  of 
the  Flexor  brevis  pollicis.  and  the  Adductor  obliquus  pollicis,  into  the  ulnar  side  of 
the  base  of  the  first  phalanx  of  the  thumb.  From  the  common  tendon  of  insertion 
a  slip  is  prolonged  to  the  Extensor  longus  pollicis. 

Eelations. — By  its  *ni>erii'-!'il  *-u.rface.  with  the  Adductor  obliquus  pollicis. 
the  tendons  of  the  Flexor  profundus.  and  the  Lumbricales.  Its  deep  surface 
covers  the  first  two  interosseous  spaces,  from  which  it  is  separated  by  a  strong 
aponeuri--  & 

Three  of  these  muscles  of  the  thumb,  the  Abductor,  the  Adductor  transversus, 

1  This  muscle  was  formerij  described  as  the  deep  portion  of  the  Flexor  brevis  pollicis. 


494  THE  MUSCLES  AND    FASCIA. 

and  the  Flexor  brevis  pollicis,  at  their  insertions  give  off  fibrous  expansions  which 
join  the  tendon  of  the  Extensor  longus  pollicis.  This  permits  of  flexion  of  the 
proximal  phalanx  and  extension  of  the  terminal  phalanx  at  the  same  time.  These 
expansions,  originally  figured  by  Albinus,  have  been  more  recently  described  by 
M.  Duchenne  (Physiologie  des  Mouvements,  page  29*9). 

Nerves. — The  Abductor,  Opponens,  and  outer  head  of  the  Flexor  brevis  pollicis 
are  supplied  by  the  median  nerve  ;  the  inner  head  of  the  Flexor  brevis,  and  the 
Adductors,  by  the  ulnar  nerve. 

Actions. — The  actions  of  the  muscles  of  the  thumb  are  almost  sufficiently  indi- 
cated by  their  names.  This  segment  of  the  hand  is  provided  with  three  extensors 
— an  extensor  of  the  metacarpal  bone,  an  extensor  of  the  first,  and  an  extensor  of 
the  second  phalanx ;  these  occupy  the  dorsal  surface  of  the  forearm  and  hand. 
There  are  also  three  flexors  on  the  palmar  surface — a  flexor  of  the  metacarpal 
bone,  a  flexor  of  the  proximal,  and  a  flexor  of  the  terminal  phalanx ;  there  is  also 
an  Abductor  and  two  Adductors.  The  Abductor  pollicis  moves  the  metacarpal 
bone  of  the  thumb  outward ;  that  is,  away  from  the  index  finger.  The  Flexor 
ossis  rnetacarpi  pollicis  flexes  the  metacarpal  bone — -that  is,  draws  it  inward  over 
the  palm — and  at  the  same  time  rotates  the  bone,  so  as  to  turn  the  ball  of  the 
thumb  toward  the  fingers,  thus  producing  the  movement  of  opposition.  The 
Flexor  brevis  pollicis  flexes  the  proximal  phalanx  of  the  thumb.  The  Adductores 
pollicis  move  the  metacarpal  bone  of  the  thumb  inward;  that  is,  toward  the 
index  finger.  These  muscles  give  to  the  thumb  its  extensive  range  of  motion. 
It  Avill  be  noticed,  however,  that  in  consequence  of  the  position  of  the  first  meta- 
carpal bone  these  movements  differ  from  the  corresponding  movements  of  the 
metacarpal  bones  of  the  other  fingers.  Thus  extension  of  the  thumb  more  nearly 
corresponds  to  the  motion  of  abduction  in  the  other  fingers,  and  flexion  to 
adduction. 

Ulnar  Region  (Fig.  316). 

Palmaris  brevis. 
Muscles  of  the  Little  Finger. 

Abductor  minimi  digiti.  Flexor  brevis  minimi  digiti. 

Opponens  (Flexor  ossis  metacarpi)  minimi  digiti. 

The  Palmaris  brevis  is  a  thin  quadrilateral  muscle  placed  beneath  the  integu- 
ment on  the  ulnar  side  of  the  hand.  It  arises  by  tendinous  fasciculi  from  the 
annular  ligament  and  palmar  fascia ;  the  fleshy  fibres  pass  inward,  to  be  inserted 
into  the  skin  on  the  inner  border  of  the  palm  of  the  hand. 

Relations. — By  its  superficial  surface,  with  the  integument,  to  which  it  is 
intimately  adherent,  especially  by  its  inner  extremity ;  by  its  deep  surface,  with 
the  inner  portion  of  the  palmar  fascia,  which  separates  it  from  the  ulnar  vessels 
and  nerve,  and  from  the  muscles  of  the  ulnar  side  of  the  hand. 

The  Abductor  minimi  digiti  is  situated  on  the  ulnar  border  of  the  palm  of  the 
hand.  It  arises  from  the  pisiform  bone,  and  terminates  in  a  flat  tendon  which 
divides  into  two  slips :  one  passes  under  the  lateral  expansion  of  the  extensor 
tendon,  opposite  the  metacarpo-phalangeal  articulation,  and  is  inserted  into  the 
ulnar  side  of  the  base  of  the  first  phalanx  of  the  little  finger.  The  other  slip 
passes  over  the  expansion,  and  is  inserted  into  the  ulnar  border  of  the  shaft  of  the 
same  phalanx. 

Relations. — By  its  superficial  surface,  with  the  inner  portion  of  the  palmar 
fascia,  and  the  Palmaris  brevis ;  by  its  deep  surface,  with  the  Flexor  ossis  meta- 
carpi minimi  digiti ;  by  its  outer  border,  with  the  Flexor  brevis  minimi  digiti. 

The  Flexor  brevis  minimi  digiti  lies  on  the  same  plane  as  the  preceding  muscle, 
on  its  radial  side.  It  arises  from  the  tip  of  the  unciform  process  of  the  unciform 
bone  and  anterior  surface  of  the  annular  ligament,  and  is  inserted  into  the  base 
of  the  first  phalanx  of  the  little  finger.  It  is  separated  from  the  Abductor  at  its 
origin  by  the  deep  branches  of  the  ulnar  artery  and  nerve.  This  muscle  is  some- 
times wanting ;  the  Abductor  is  then,  usually,  of  large  size. 


THE    ULXAR    REGION. 


495 


Relations. — By  its  superficial  surface,  with  the  internal  portion  of  the  palmar 
fascia,  and  the  Palmaris  brevis ;  by  its  deep  surface,  with  the  Opponens. 

The  Opponens  minimi  digiti  (Fig.  307)  is  of  a  triangular  form,  and  placed 
immediately  beneath  the  preceding  muscles.  It  arises  from  the  unciform  process 


FIG.  316.— Muscles  of  the  left  hand.    Palmar  surface. 


of  the  unciform  bone  and  contiguous  portion  of  the  annular  ligament ;  its  fibres 
pass  downward  and  inward,  to  be  inserted  into  the  whole  length  of  the  meta- 
carpal  bone  of  the  little  finger,  along  its  ulnar  margin. 

Relations. — By  its  mpcrjicial  surface,  with  the  Flexor  brevis  and  Abductor 
minimi    digiti :   by   its   deep  surface,   with  the  Interossei  muscles  in  the  fourth 


496  THE  MUSCLES  AND   FASCIA. 

metacarpal  space,  the  metacarpal  bone,  and  the  Flexor  tendons  of  the  little 
finger. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  ulnar  nerve. 

Actions. — The  Abductor  minimi  digiti  abducts  the  little  finger  from  the  middle 
line  of  the  hand.  It  corresponds  to  a  dorsal  interosseous  muscle.  It  also  assists 
in  flexing  the  proximal  phalanx.  The  Flexor  brevis  minimi  digiti  abducts  the 
little  finger  from  the  middle  line  of  the  hand.  It  also  assists  in  flexing  the 
proximal  phalanx.  The  Opponens  minimi  digiti  draws  forward  the  fifth  meta- 
carpal bone,  so  as  to  deepen  the  hollow  of  the  palm.  The  Palmaris  brevis  corrugates 
the  skin  on  the  inner  side  of  the  palm  of  the  hand. 

Middle  Palmar  Region. 

Lumbricales.  Interossei  palmares. 

Interossei  dorsales. 

The  Lumbricales  (Fig.  316)  are  four  small  fleshy  fasciculi,  accessories  to  the 
deep  Flexor  muscle.  They  arise  by  fleshy  fibres  from  the  tendons  of  the  deep 
Flexor :  the  first  and  second,  from  the  radial  side  and  palmar  surface  of  the  tendons 
of  the  index  and  middle  fingers ;  the  third,  from  the  contiguous  sides  of  the  ten- 
dons of  the  middle  and  ring  fingers ;  and  the  fourth,  from  the  contiguous  sides  of 
the  tendons  of  the  ring  and  little  fingers.  They  pass  to  the  radial  side  of  the 
corresponding  fingers,  and  opposite  the  metacarpo-phalangeal  articulation  each 
tendon  terminates  in  a  broad  aponeurosis  which  is  inserted  into  the  tendinous 
expansion  from  the  Extensor  communis  digitorum,  covering  the  dorsal  aspect  of 
each  finger. 

The  Interossei  muscles  are  so  named  from  occupying  the  intervals  between 
the  metacarpal  bones.  They  are  divided  into  two  sets,  a  dorsal  and  palmar ;  the 
former  are  four  in  number,  one  in  each  metacarpal  space ;  the  latter,  three  in 
number,  lie  upon  the  metacarpal  bones. 

The  Dorsal  interossei  are  four  in  number,  larger  than  the  palmar,  and  occupy 
the  intervals  between  the  metacarpal  bones.  They  are  bipenniform  muscles, 
arising  by  two  heads  from  the  adjacent  sides  of  the  metacarpal  bones,  but  more 
extensively  from  that  side  of  the  metacarpal  bone  which  corresponds  to  the  side 
of  the  finger  in  which  the  muscle  is  inserted.  They  are  inserted  into  the  bases 
of  the  first  phalanges  and  into  the  aponeurosis  of  the  common  extensor  tendon. 
Between  the  double  origin  of  each  of  these  muscles  is  a  narrow  triangular  interval, 
through  the  first  of  which  passes  the  radial  artery  ;  through  the  other  three  passes 
a  perforating  branch  from  the  deep  palmar  arch. 

The  First  dorsal  interosseous  muscle,  or  Abductor  indicis,  is  larger  than  the 
others.  It  is  flat,  triangular  in  form,  and  arises  by  two  heads,  separated  by  a 
fibrous  arch,  for  the  passage  of  the  radial  artery  from  the  dorsum  to  the  palm  of 
the  hand.  The  outer  head  arises  from  the  upper  half  of  the  ulnar  border  of  the 
first  metacarpal  bone ;  the  inner  head,  from  almost  the  entire  length  of  the  radial 
border  of  the  second  metacarpal  bone ;  the  tendon  is  inserted  into  the  radial  side 
of  the  index  finger.  The  second  and  third  dorsal  interossei  are  inserted  into  the 
middle  finger,  the  former  into  its  radial,  the  latter  into  its  ulnar  side.  The  fourth 
is  inserted  into  the  ulnar  side  of  the  ring  finger. 

The  Palmar  interossei,  three  in  number,  are  smaller  than  the  Dorsal,  and  placed 
upon  the  palmar  surface  of  the  metacarpal  bones,  rather  than  between  them. 
They  arise  from  the  entire  length  of  the  metacarpal  bone  of  one  finger,  and  are 
inserted  into  the  side  of  the  base  of  the  first  phalanx  and  aponeurotic  expansion 
of  the  common  extensor  tendon  of  the  same  finger. 

The  first  arises  from  the  ulnar  side  of  the  second  metacarpal  bone,  and  is 
inserted  into  the  same  side  of  the  index  finger.  The  second  arises  from  the  radial 
side  of  the  fourth  metacaVpal  bone,  and  is  inserted  into  the  same  side  of  the  ring 
finger.  The  third  arises*"  *rom  the  radial  side  of  the  fifth  metacarpal  bone,  and  is 
inserted  into  the  same  side  of  the  little  finger.  From  this  account  it  may  be  seen 


THE   MIDDLE   PALMAR    REGION. 


497 


that  each  finger  is  provided  with  two  Interossei  muscles,  with  the  exception  of 
the  little  finger,  in  which  the  Abductor  muscle  takes  the  place  of  one  of  the  pair. 

Nerves. — The  two  outer  Lumbricales  are  supplied  by  the  median  nerve  ;  the 
rest  of  the  muscles  of  this  group,  by  the  ulnar.  All  the  Interossei  are  supplied  by 
the  ulnar. 

Actions. — The  Palmar  interossei  muscles  adduct  the  fingers  to  an  imaginary 
line  drawn  longitudinally  through  the  centre  of  the  middle  finger;  and  the  Dorsal 
interossei  abduct  the  fingers  from  that  line.  In  addition  to  this,  the  Interossei,  in 


FIG.  317.— The  Dorsal  interossei  of  left  hand. 


FIG.  318.— The  Palmar  interossei  of  left  hand. 


conjunction  with  the  Lumbricales,  flex  the  first  phalanges  at.  the  metacarpo-phalan- 
geal  joints.  and  extend  the  second  and  third  phalanges  in  consequence  of  their 
insertion  into  the  expansion  of  the  extensor  tendons.  The  Extensor  communis 
digitorum  is  believed  to  act  almost  entirely  on  the  first  phalanges. 

SURFACE  FORM  OF  THE  UPPER  EXTREMITY. 


The  Pi-cfornJifi  major  largely  influences  surface  form  and  conceals  a  considerable  part  of  the 
thoracic  wall  in  front.  Its  sternal  origin  presents  a  festooned  border  which  bounds  and  deter- 
mines the  width  of  the  sternal  furrow.  Its  clavicular  origin  is  somewhat  depressed  and  flattened, 
and  between  the  two  portions  of  the  muscle  is  often  an  oblique  depression  which  differentiates 
the  one  from  the  other.  The  outer  margin  of  the  muscle  is  generally  well  marked  above,  and 
bounds  the  infraclavicular  fossa,  a  triangular  interval  which  separates  the  Pectoralis  major  from 
the  Deltoid.  It  gradually  becomes  less  marked  as  it  approaches  the  tendon  of  insertion,  and 
becomes  more  closely  blended  with  the  Deltoid  muscle.  The  lower  border  of  the  Pectoralis 
major  forms  the  rounded  anterior  axillary  fold,  and  corresponds  with  the  direction  of  the  fifth 
rib.  The  Pi-ftoi-fili.t  utinn,-  influences  surface  form.  When  the  arm  is  raised  its  lowest  slip  of 
origin  produces  a  local  fulness  just  below  the  border  of  the  anterior  fold  of  the  axilla,  and  so 
serves  to  break  the  sharp  line  of  the  lower  border  of  the  Pectoralis  major  muscle,  which  is 
produced  when  the  arm  is  in  this  position.  The  origin  of  the  Serratus  niagnus  produces  a  very 
characteristic  surface  marking.  When  the  arm  is  raised  from  the  side  in  a  well-developed 
subject,  the  five  or  six  lower  serrations  are  plainly  discernible,  forming  a  zigzag  line,  caused  by 
the  series  of  digitations.  which  diminish  in  size  from  above  downward,  and  have  their  apices 
arranged  in  the  form  of  a  curve.  When  the  arm  is  lying  by  the  side,  the  first  serration  to 
appear,  at  the  lower  margin  of  the  Pectoralis  major,  is  the  one  attached  to  the  fifth  rib.  The 
Deltoid,  with  the  prominence  of  the  upper  extremit\T  of  the  humerus,  produces  the  rounded 
outline  of  the  shoulder.  It  is  rounder  and  fuller  in  front  thaigfcf»ehind.  where  it  presents  a 
somewhat  flattened  form.  Its  anterior  border,  above,  present  a  rounded,  slightly  curved 
eminence,  which  bounds  externally  the  infraclavicular  fossa  ;  below,  it  is  closely  united  with  the 


498  THE  MUSCLES  AND   FASCIA. 

Pectoralis  major.  Its  posterior  border  is  thin,  flattened,  and  scarcely  marked  above  ;  below,  it 
is  thicker  and  more  prominent.  When  the  muscle  is  in  action,  the  middle  portion  becomes 
irregular,  presenting  alternate  longitudinal  elevations  and  depressions,  the  elevations  correspond- 
ing to  the  flesh\?  portions,  the  depressions  to  the  tendinous  intersections  of  the  muscle.  The 
insertion  of  the  Deltoid  is  marked  by  a  depression  on  the  outer  side  of  the  middle  of  the  arm. 
Of  the  scapular  muscles,  the  only  one  which  materially  influences  surface  form  is  the  Teres 
major,  which  assists  the  Latissimus  dorsi  in  forming  the  thick,  rounded  fold  of  the  posterior 
boundary  of  the  axilla.  When  the  arm  is  raised,  the  Coraco-brachialis  reveals  itself  as  a  long, 
narrow  elevation  which  emerges  from  under  cover  of  the  anterior  fold  of  the  axilla  and  runs 
downward,  internal  to  the  shaft  of  the  hunierus.  When  the  arm  is  hanging  by  the  side,  its 
front  and  inner  part  presents  the  prominence  of  the  Biceps,  bounded  on  either  side  by  an  inter- 
muscular  depression.  This  muscle  determines  the  contour  of  the  front  of  the  arm,  and  extends 
from  the  anterior  margin  of  the  axilla  to  the  bend  of  the  elbow.  Its  upper  tendons  are  con- 
cealed by  the  Pectoralis  major  and  the  Deltoid,  and  its  lower  tendon  sinks  into  the  space  at  the 
bend  of  the  elbow.  When  the  muscle  is  in  a  state  of  complete  contraction — that  is  to  say, 
when  the  forearm  has  been  flexed  and  supinated — it  presents  a  rounded  convex  form,  bulged 
out  laterally,  and  its  length  is  diminished.  On  each  side  of  the  Biceps,  at  the  lower  part  of 
the  arm,  the  BracMalis  anticus  is  discernible.  On  the  outer  side  it  forms  a  narrow  eminence 
which  extends  some  distance  up  the  arm  along  the  border  of  the  Biceps.  On  the  inner  side  it 
shows  itself  only  as  a  little  fulness  just  above  the  elbow.  On  the  back  of  the  arm  the  long  head 
of  the  Triceps  may  be  seen  as  a  longitudinal  eminence  emerging  from  under  cover  of  the  Deltoid, 
and  gradually  merging  into  the  longitudinal  flattened  plane  of  the  muscle  on  the  lower  part  of 
the  back  of  the  arm.  On  the  anterior  aspect  of  the  elbow  are  to  be  seen  two  muscular  eleva- 
tions, one  on  each  side,  separated  above  and  converging  below  so  as  to  form  a  triangular  space. 
Of  these,  the  inner  elevation,  consisting  of  the  flexors  and  pronator,  forms  the  prominence 
along  the  inner  side  and  front  of  the  forearm.  It  is  a  fusiform  mass,  pointed  above  at  the 
internal  condyle  and  gradually  tapering  off  below.  The  Pronator  radii  tercs,  the  innermost 
muscle  of  the  group,  forms  the  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It 
is  shorter,  less  prominent,  and  more  oblique  than  the  outer  boundary.  The  most  prominent 
part  of  the  eminence  is  produced  by  the  Flexor  carpi  radialis,  the  muscle  next  in  order  on  the 
inner  side  of  the  preceding  one.  It  forms  a  rounded  prominence  above,  and  can  be  traced 
downward  to  its  tendon,  which  can  be  felt  lying  on  the  front  of  the  wrist,  nearer  to  the  radial 
than  to  the  ulnar  border,  and  to  the  inner  side  of  the  radial  artery.  The  Palmaris  longus 
presents  no  surface  marking  above,  but  below  is  the  most  prominent  tendon  on  the  front  of  the 
wrist,  standing  out,  when  the  muscle  is  in  action,  as  a  sharp,  tense  cord  beneath  the  skin.  The 
Flexor  sublimis  digitorum  does  not  directly  influence  surface  form.  The  position  of  its  four 
tendons  on  the  front  of  the  lower  part  of  the  forearm  is  indicated  by  an  elongated  depression 
between  the  tendons  of  the  Palmaris  longus  and  the  Flexor  carpi  ulnaris.  The  Flexor  carpi 
ulnaris  occupies  a  small  part  of  the  posterior  surface  of  the  forearm,  and  is  separated  from  the 
extensor  and  supinator  group,  which  occupies  the  greater  part  of  this  surface,  by  the  ulnar 
furrow,  produced  by  the  subcutaneous  posterior  border  of  the  ulna.  Its  tendon  can  be  perceived 
along  the  ulnar  border  of  the  front  of  the  forearm,  and  is  most  marked  when  the  hand  is  flexed 
and  adducted.  The  deep  muscles  of  the  front  of  the  forearm  have  no  direct  influence  on  surface 
form.  The  external  group  of  muscles  of  the  forearm,  consisting  of  the  extensors  and  supi- 
nators,  occupy  the  outer  and  a  considerable  portion  of  the  posterior  surface  of  this  region.  They 
form  a  fusiform  mass,  which  is  altogether  on  a  higher  level  than  the  pronato-flexor  group.  Its 
apex  emerges  from  between  the  Triceps  and  Brachialis  anticus  muscles  some  distance  above  the 
elbow-joint,  and  acquires  its  greatest  breadth  opposite  the  external  condyle,  and  thence  gradually 
shades  off  into  a  flattened  surface.  About  the  middle  of  the  forearm  it  divides  into  two  longi- 
tudinal eminences  which  diverge  from  each  other,  leaving  a  triangular  interval  between  them. 
The  outer  of  these  two  groups  of  muscles  consists  of  the  Supinator  longus  and  the  Extensor 
carpi  radialis  longior  et  brevior,  which  form  a  longitudinal  eminence  descending  from  the  exter- 
nal condyloid  ridge  in  the  direction  of  the  styloid  process  of  the  radius.  The  other  and  more 
posterior  group  consists  of  the  Extensor  communis  digitorum.  the  Extensor  minimi  digit! .  and 
the  Extensor  carpi  ulnaris.  It  commences  above  as  a  tapering  form  at  the  external  condyle  of 
the  humerus,  and  is  separated  behind  at  its  upper  part  from  the  Anconeus  by  a  well-marked 
furrow,  and  below,  from  the  pronato-flexor  mass,  by  the  ulnar  furrow.  In  the  triangular  inter- 
val left  between  these  two  groups  the  extensors  of  the  thumb  and  index  finger  are  seen.  The 
only  two  muscles  of  this  region  which  require  special  mention  as  independently  influencing 
surface  form  are  the  Supinator  longus  and  the  Anconeus.  The  inner  border  of  the  Supinator 
longus  forms  the  outer  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It  com- 
mences as  a  rounded  border  above  the  condyle,  and  is  longer,  less  oblique,  and  more  prominent 
than  the  inner  boundary.  Lower  down,  the  muscle  forms  a  full  fleshy  mass  on  the  outer  side  of 
the  upper  part  of  the  forearm,  and  below  tapers  into  a  tendon,  which  may  be  traced  down  to 
the  styloid  process  of  the  radius.  The  Anconeus  presents  a  well-marked  and  characteristic 
surface  form  in  the  shape  of  a  triangular,  slightly  elevated  surface,  immediately  external  to  the 
subcutaneous  posterior  surface  of  the  olecranon,  and  differentiated  from  the  common  extensor 
group  by  a  well-marked  oblique  longitudinal  depression.  The  upper  angle  of  the  triangle  corre- 
sponds to  the  external  condyle,  and  is  marked  by  a  depression  or  dimple  in  this  situation.  In 
the  triangular  interval  caused  by  the  divergence  from  each  other  of  the  two  groups  of  muscles 
into  which  the  extensor  and  supinator  group  is  divided  at  the  lower  part  of  the  forearm  an 


SURGICAL    ANATOMY   OF   THE    UPPER   EXTREMITY.        499 

oblique  elongated  eminence  is  seen,  caused  by  the  emergence  of  two  of  the  extensors  of  the 
thumb  from  their  deep  origin  at  the  back  of  the  forearm.  This  eminence,  full  above  and  be- 
coming flattened  out  and  partially  subdivided  below,  runs  downward  and  outward  over  the  back 
and  outer  surface  of  the  radius  to  the  outer  side  of  the  wrist-joint,  where  it  forms  a  ridge, 
especially  marked  when  the  thumb  is  extended,  which  passes  onward  to  the  posterior  aspect  of 
the  thumb.  The  tendons  of  most  of  the  extensor  muscles  are  to  be  seen  and  felt  at  the  level 
of  the  wrist-joint.  Most  externally  are  the  tendons  of  the  Extensor  ossis  metacarpi  pollicis  and 
the  Extensor  brevis  pollicis.  forming  a  vertical  ridge  over  the  outer  side  of  the  joint  from  the 
styloid  process  of  the  radius  to  the  thumb.  Internal  to  this  is  the  oblique  ridge  produced  by 
the  tendon  of  the  Extensor  longus  pollicis,  very  noticeable  when  the  muscle  is  in  action.  The 
Extensor  carpi  radialis  longior  is  scarcely  to  be  felt,  but  the  Extensor  carpi  radialis  brevior  can 
be  distinctly  perceived  as  a  vertical  ridge  emerging  from  under  the  inner  border  of  the  tendon 
of  the  Extensor  longus  pollicis.  when  the  hand  is  forcibly  extended  at  the  wrist.  Internal  to 
this,  again,  can  be  felt  the  tendons  of  the  Extensor  indicis,  Extensor  communis  digitorum,  and 
Extensor  minimi  digiti :  the  latter  tendon  being  separated  from  those  of  the  common  extensor 
by  a  slight  furrow.  The  muscles  of  the  hand  are  princjpally  concerned,  as  far  as  regards  sur- 
face-form, in  producing  the  thenar  and  hypothenar  eminences,  and  individually  are  not  to  be 
distinguished,  on  the  surface,  from  each  other.  The  Adductor  transversus  pollicis  is.  however, 
an  exception  to  this  :  its  anterior  border  gives  rise  to  a  ridge  across  the  web  of  skin  connecting 
the  thumb  to  the  rest  of  the  hand.  The  thenar  eminence  is  much  larger  and  rounder  than  the 
hypothenar  one.  which  presents  a  longer  and  narrower  eminence  along  the  ulnar  side  of  the 
hand.  When  the  Palmar!.*  ///•«/>  is  in  action  it  produces  a  wrinkling  of  the  skin  over  the  hypo- 
thenar eminence,  and  a  deep  dimple  on  the  ulnar  border  of  the  hand.  The  anterior  extremities 
of  the  Lumliric'tl  //(//.W-.*  help  to  produce  the  soft  eminences  just  behind  the  clefts  of  the  fingers, 
separated  from  each  other  by  depressions  corresponding  to  the  flexor  tendons  in  their  sheaths. 
Between  the  thenar  and  hypothenar  eminences,  at  the  wrist -joint,  is  a  slight  groove  or  depression, 
widening  out  as  it  approaches  the  fingers;  beneath  this  we  have  the  strong  central  part  of  the 
palmar  fascia.  Here  we  have  some  fiirrows,  which  are  pretty  constant  in  their  arrangement, 
and  bear  some  resemblance  to  the  letter  M.  One  of  these  furrows  passes  obliquely  outward 
from  the  groove  between  the  thenar  and  hypothenar  regions  to  the  head  of  the  metacarpal  bone 
of  the  index  finger.  A  second  passes  inward,  with  a  slight  inclination  upward,  from  the  termi- 
nation of  the  first  to  the  ulnar  side  of  the  hand.  A  third  runs  parallel  with  the  second  and 
about  three-quarters  of  an  inch  below  it  Lastly,  crossing  these  two  latter  furrows,  is  an  oblique 
furrow  parallel  with  the  first.  The  skin  of  the  palm  of  the  hand  differs  considerably  from  that 
of  the  forearm.  At  the  wrist  it  suddenly  becomes  hard  and  dense,  and  covered  with  a  thick 
layer  of  cuticle.  The  skin  in  the  thenar  region  presents  these  characteristics  less  than  elsewhere. 
In  spite  of  this  hardness  and  density,  the  skin  of  the  palm  is  exceedingly  sensitive  and  very 
vax-ular.  It  is  destitute  of  hair,  and  no  sebaceous  follicles  have  been  found  in  this  region. 
Over  the  fingers  the  skin  again  becomes  thinner,  especially  at  the  flexures  of  the  joints,  and 
over  the  terminal  phalantres  it  is  thrown  into  numerous  parallel  ridges  in  consequence  of  the 
arrangement  of  the  papillae  in  it.  The  superficial  fascia  in  the  palm  is  made  up  of  dense  fibro- 
fatty  tissue.  This  tissue  binds  down  the  skin  so  firmly  to  the  deep  palmar  fascia  that  very  little 
movement  is  permitted  between  the  two.  On  the  back  of  the  hand  the  Dorsal  interossei  pro- 
duce elongate'!  swellings  between  the  metacarpal  bones.  The  first  dorsal  interosseous  (Abductor 
indicis i.  when  the  thumb  is  closely  adducted  to  the  hand,  forms  a  prominent  fusiform  bulging; 
the  other  interossei  are  not  so  marked. 

SURGICAL  ANATOMY  OF  THE  UPPER  EXTREMITY. 

The  student,  having  completed  the  dissection  of  the  muscles  of  the  upper  extremity,  should 
consider  the  effects  likely  to  be  produced  by  the  action  of  the  various  muscles  in  fracture  of  the 
bones. 

In  considering  the  actions  of  the  various  muscles  upon  fractures  of  the  upper  extremity,  I 
have  selected  the  most  common  forms  of  injury,  both  for  illustration  and  description. 

Fracture  of  the  middle  of  the  clavicle  (Fig.  319)  is  always  attended  with  considerable  dis- 
placement :  the  inner  end  of  the  outer  fragment  is  displaced  inward  and  backward,  while  the 
outer  end  of  the  same  fragment  is  rotated  forward,  owing  to  the  displacement  backward  of  its 
inner  end.  The  whole  outer  fragment  is  somewhat  depressed. 

The  displacement  is  produced  as  follows:  inward,  by  the  muscles  passing  from  the  chest  to 
the  outer  fragment  of  the  clavicle,  to  the  scapula,  and  to  the  humerus — viz.  the  Subclavius,  the 
Pectoralis  minor  and  major,  and  the  Latissimus  dorsi ;  backward,  with  consequent  rotation  of 
the  outer  end  of  the  outer  frainnent  forward  by  the  Pectoral  muscles.  The  depression  of  the 
whole  outer  fragment  is  produced  by  the  weight  of  the  arm  and  by  the  contraction  of  the  Deltoid. 
The  outer  end  of  the  inner  fragment  appears  to  be  elevated,  the  skin  being  drawn  tensely  over 
it :  this  is  owing  to  the  depression  of  the  outer  fragment,  as  the  inner  fragment  is  usually  kept 
fixed  by  the  costo-clavicular  ligament  and  by  the  antagonism  between  the  Sterno-mastoid  and 
Pectoralis  major  muscles.  But  it  may  be  raised  by  an  unusually  strong  Sterno-mastoid,  or  by 
the  inner  end  of  the  outer  fragment  getting  below  and  behind  it.  The  causes  of  displacement 
having  been  ascertained,  it  is  easy  to  apply  the  appropriate  treatment.  The  outer  fragment  is 
to  be  drawn  outward,  and.  together  with  the  scapula,  raised  upward  to  a  level  with  the  inner 
fragment,  and  retained  in  that  position. 


500 


THE   MUSCLES  AND   FASCIAE. 


FIG.  319.— Fracture  of  the  middle  of  the 
clavicle. 


In  fracture  of  the  acromial  end  of  the  clavicle,  between  the  conoid  and  trapezoid  ligaments, 
only  slight  displacement  occurs,  as  these  ligaments,  from  their  oblique  insertion,  serve  to  hold 

both  portions  of  the  bone  in  apposition.  Fracture,  also, 
of  the  sternal  end,  internal  to  the  costo-clavicular  liga- 
ment, is  attended  with  only  slight  displacement,  this 
ligament  serving  to  retain  the  fragments  in  close  appo- 
sition. 

Fracture  of  the  acromion  process  usually  arises  from 
violence  applied  to  the  upper  and  outer  part  of  the 
shoulder ;  it  is  generally  known  by  the  rotundity  of  the 
shoulder  being  lost,  from  the  Deltoid  drawing  the  frac- 
tured portion  downward  and  forward  ;  and  the  displace- 
ment may  easily  be  discovered  by  tracing  the  margin  of 
the  clavicle  outward,  when  the  fragment  will  be  found 
resting  on  the  front  and  upper  part  of  the  head  of  the 
humerus.  In  order  to  relax  the  anterior  and  outer 
fibres  of  the  Deltoid  (the  opposing  muscle),  the  arm 
should  be  drawn  forward  across  the  chest  and  the  elbow 
well  raised,  so  that  the  head  of  the  bone  may  press  the 
acromion  process  upward  and  retain  it  in  its  position. 

Fracture  of  the  coracoid  process  is  an  extremely  rare 
accident,  and  is  usually  caused  by  a  sharp  blow  on  the 
point  of  the  shoulder.  Displacement  is  here  produced 
by  the  combined  actions  of  the  Pectoralis  minor,  short 
head  of  the  Biceps,  and  Coraco-brachialis,  the  former 
muscle  drawing  the  fragment  inward,  and  the  latter 
directly  downward,  the  amount  of  displacement  being 
limited  by  the  connection  of  this  process  to  the  acromion 
by  means  of  the  coraco-acromial  ligament.  In  order  to 
relax  these  muscles  and  replace  the  fragments  in  close 
apposition,  the  forearm  should  be  flexed  so  as  to  relax 
the  Biceps,  and  the  arm  drawn  forward  and  inward  across  the  chest,  so  as  to  relax  the  Coraco- 
brachialis  ;  the  humerus  should  then  be  pushed  upward  against  the  coraco-acromial  ligament, 
and  the  arm  retained  in  that  position. 

Fracture  of  the  surgical  neck  of  the  humerus  (Fig.  320)  is  very  common,  is  attended  with 
considerable  displacement,  and  its  appearances  correspond  somewhat  with  those  of  dislocation 
of  the  head  of  the  humerus  into  the  axilla.  The  upper  fragment  is  slightly  elevated  under  the 
coraco-acromial  ligament  by  the  muscles  attached  to  the  greater  and  lesser  tuberosities ;  the 
lower  fragment  is  drawn  inward  by  the  Pectoralis  major,  Latissimus  dorsi,  and  Teres  major ;  and 
the  humerus  is  thrown  obliquely  outward  from  the  side  by  the  Deltoid,  and  occasionally  elevated 
so  as  to  project  beneath  and  in  front  of  the  coracoid  process.  The  deformity  is  reduced  by 

fixing  the  shoulder  and  drawing  the  arm  outward  and  down- 
ward. To  counteract  the  opposing  muscles,  and  to  keep  the 
fragments  in  position,  the  arm  should  be  drawn  from  the  side 
and  pasteboard  splints  applied  on  its  four  sides ;  a  large  conical- 
shaped  pad  should  be  placed  in  the  axilla,  with  the  base  turned 
upward  and  the  elbow  approximated  to  the  side,  and  retained 
there  by  a  broad  roller  passed  round  the  chest ;  the  forearm 
should  then  be  flexed,  and  the  hand  supported  in  a  sling,  care 
being  taken  not  to  raise  the  elbow,  otherwise  the  lower  frag- 
ment may  be  displaced  upward. 

In  fracture  of  the  shaft  of  the  humerus  below  the  inser- 
tion of  the  Pectoralis  major,  Latissimus  dorsi,  and  Teres  major, 
and  above  the  insertion  of  the  Deltoid,  there  is  also  consider- 
able deformity,  the  upper  fragment  being  drawn  inward  by  the 
first-mentioned  muscles,  and  the  lower  fragment  upward  and 
outward  by  the  Deltoid,  producing  shortening  of  the  limb  and 
a  considerable  prominence  at  the  seat  of  fracture,  from  the 
fractured  ends  of  the  bone  riding  over  one  another,  especially 
if  the  fracture  takes  place  in  an  oblique  direction.  The  frag- 
ments may  be  brought  into  apposition  b}7  extension  from  the 
elbow,  and  retained  in  that  position  by  adopting  the  same 
means  as  in  the  preceding  injury. 

In  fractures  of  the  shaft  of  the  humerus  immediately  below 
the  insertion  of  the  Deltoid,  the  amount  of  deformity  depends  greatly  upon  the  direction  of  the 
fracture.  If  it  occurs  in  a  transverse  direction,  only  slight  displacement  takes  place,  the  upper 
fragment  being  drawn  a  little  forward ;  but  in  oblique  fracture  the  conibined  actions  of  the 
Biceps  and  Brachialis  anticus  muscles  in  front  and  the  Triceps  behind  draw  upward  the 
lower  fragment,  causing  it  to  glide  over  the  upper  fragment,  either  backward  or  forward, 
according  to  the  direction  of  the  fracture.  Simple  extension  reduces  the  deformity,  and 
the  application  of  splints  on  the  four  sides  of  the  arm  will  retain  the  fragments  in  apposition. 


FIG.  320.— Fracture  of  the  surgical 
neck  of  the  humerus. 


SURGICAL    ANATOMY   OF    THE    UPPER    EXTREMITY.        501 


FIG.  321.— Fracture  of  the  humerus 
above  the  condyles. 


Care  should  be  taken  not  to  raise  the  elbow,  but  the  forearm  and  hand  may  be  supported 
in  a  sling. 

Fracture  of  the  humerus  (Fig.  321)  immediately  above  the  condyles  deserves  very  attentive 
consideration,  as  the  general  appearances  correspond  somewhat  with  those  produced  by  sep- 
aration of  the  epiphysis  of  the  humerus,  and  with  those 
of  dislocation  of  the  radius  and  ulna  backward.  If  the 
direction  of  the  fracture  is  oblique  from  above,  downward 
and  forward,  the  lower  fragment  is  drawn  upward  and 
backward  by  the  Brachialis  anticus  and  Biceps  in  front  and 
the  Triceps  behind.  This  injury  may  be  diagnosed  from  dis- 
location by  the  increased  mobility  in  fracture,  the  existence 
of  crepitus,  and  the  fact  of  the  deformity  being  remedied  by 
extension,  on  the  discontinuance  of  which  it  is  reproduced. 
The  age  of  the  patient  is  of  importance  in  distinguishing  this 
form  of  injury  from  separation  of  the  epiphysis.  If  frac- 
ture occurs  in  the  opposite  direction  to  that  shown  in  the 
accompanying  figure,  the  lower  fragment  is  drawn  upward 
and  forward,  causing  a  considerable  prominence  in  front,  and 
the  upper  fragment  projects  backward  beneath  the  tendon 
of  the  Triceps  muscle. 

Fracture  of  the  olecranon  process  (Fig.  322)  is  a  frequent 
accident.  The  detached  fragment  is  displaced  upward,  by 
the  action  of  the  Triceps  muscle,  from  half  an  inch  to  two 
inches ;  the  prominence  of  the  elbow  is  consequently  lost, 
ami  a  deep  hollow  is  felt  at  the  back  part  of  the  joint, 
which  is  much  increased  on  flexing  the  limb.  The  patient 
at  the  same  time  loses,  more  or  less,  the  power  of  extending 
the  forearm.  The  treatment  consists  in  relaxing  the  Triceps 
by  extending  the  limb,  and  retaining  it  in  the  extended  posi- 
tion by  means  of  a  long  straight  splint  applied  to  the  front 
of  the  arm  ;  the  fragments  are  thus  brought  into  close  apposition,  and  may  be  further  approxi- 
mated by  drawing  down  the  upper  fragment.  Union  is  generally  ligamentous. 

Fracture  of  the  neck  of  the  radius  is  an  exceedingly  rare  accident,  and  is  generally  caused 
by  direct  violence.  Its  diagnosis  is  somewhat  obscure,  on  account  of  the  slight  deformity  visible, 
the  injured  part  being  surrounded  by  a  large  number  of  muscles ;  but  the  movements  of  prona- 
tion anil  supination  are  entirely  lost,  The  upper  fragment  is  drawn  outward  by  the  Supinator 
brevis.  its  extent  of  displacement  being  limited  by  the  attachment  of  the  orbicular  ligament. 
The  lower  fragment  is  drawn  forward  and  slightly 
upward  by  the  Biceps,  and  inward  by  the  Pro- 
nator  radii  teres,  its  displacement  forward  and 
upward  being  counteracted  in  some  degree  by 
the  Supinator  brevis.  The  treatment  essentially 
consists  in  relaxing  the  Biceps,  Supinator  brevis, 
and  Pronator  radii  teres  muscles  by  flexing  the 
forearm,  and  placing  it  in  a  position  midway 
between  pronation  and  supination,  extension 
having  been  previously  made  so  as  to  bring  the 
parts  in  apposition. 

In  fracture  of  the  radius  (Fig.  323)  near 
its  centre,  the  upper  fragment  is  drawn  upward 
by  the  Biceps  and  inward  by  the  Pronator  radii 
teres.  holding  a  position  midway  between  pro- 
nation  and  supination,  and  a  degree  of  fulness 
in  the  upper  half  of  the  forearm  is  thus  pro- 
duced :  the  lower  fragment  is  drawn  downward 
and  inward  toward  the  ulna  by  the  Pronator 
quadratus.  and  thrown  into  a  state  of  pronation  FIG.  322.— Fracture  of  the  olecranon. 

by  the  same  muscle :  at  the  same  time,  the  Su- 
pinator longus,  by  elevating  the  styloid  process,  into  which  it  is  inserted,  will  serve  to  depress 
the  upper  end  of  the  lower  fragment  still  more  toward  the  ulna.  In  order  to  relax  the  opposing 
muscles  the  forearm  should  be  bent,  and  the  limb  placed  in  a  position  midway  between  prona- 
tion and  supination ;  the  fracture  is  then  easily  reduced  by  extension  from  the  wrist  and  elbow : 
well-padded  splints  should  be  applied  on  both  sides  of  the  forearm  from  the  elbow  to  the  wrist ; 
the  hand  being  allowed  to  fall,  will,  by  its  own  weight,  counteract  the  action  of  the  Pronator 
quadratus  and  Supinator  longus.  and  elevate  the  lower  fragment  to  the  level  of  the  upper  one. 

In  fracture  of  the  shaft  of  the  ulna  the  upper  fragment  retains  its  usual  position,  but  the  lower 
fragment  is  drawn  outward  toward  the  radius  by  the  Pronator  quadratus,  producing  a  well-marked 
depression  at  the  seat  of  fracture  and  some  fulness  on  the  dorsal  and  palmar  surfaces  of  the 
forearm.  The  fracture  is  easily  reduced  by  extension  from  the  wrist  and  forearm.  The  fore- 
arm should  be  flexed,  and  placed  in  a  position  midway  between  pronation  and  supination,  and 
well-padded  splints  applied  from  the  elbow  to  the  ends  of  the  fingers. 


502 


THE  MUSCLES  AND    FASCIA. 


In  fracture  of  the  shafts  of  the  radius  and  ulna  together  the  lower  fragments  are  drawn 
upward,  sometimes  forward,  sometimes  backward,  according  to  the  direction  of  the  fracture, 
by  the  combined  actions  of  the  Flexor  and  Extensor  muscles,  producing  a  degree  of  fulness  on 

the  dorsal  or  palmar  surface  of  the  forearm ;  at 
the  same  time  the  two  fragments  are  drawn  into 
contact  by  the  Pronator  quadratus,  the  radius 
being  in  a  state  of  pronation  :  the  upper  frag- 
ment of  the  radius  is  drawn  upward  and  inward 
by  the  Biceps  and  Pronator  radii  teres  to  a  higher 
level  than  the  ulna;  the  upper  portion  of  the 
ulna  is  slightly  elevated  by  the  Brachialis  anticus. 
The  fracture  may  be  reduced  by  extension  from 
the  wrist  and  elbow,  and  the  forearm  should  be 
placed  in  the  same  position  as  in  fracture  of  the 
ulna. 

In  fracture  of  the  lower  end  of  the  radius 
(Fig.  324)  the  displacement  which  is  produced 

is  very  considerable,  and  bears  some  resemblance  to  dislocation  of  the  carpus  backward,  from 
which  it  should  be  carefully  distinguished.  The  lower  fragment  is  drawn  upward  and  backward 
behind  the  upper  fragment  by  the  combined  actions  of  the  Supinator  longus  and  the  flexors  and 
the  extensors  of  the  thumb  and  carpus,  producing  a  well-marked  prominence  on  the  back  of  the 
wrist,  with  a  deep  depression  above  it.  The  upper  fragment  projects  forward,  often  lacerating 
the  substance  of  the  Pronator  quadratus,  and  is  drawn  by  this  muscle  into  close  contact  with  the 
lower  end  of  the  ulna,  causing  a  projection  on  the  anterior  surface  of  the  forearm,  immediately 


FIG.  323.— Fracture  of  the  shaft  of  the  radius. 


FIG.  324.— Fracture  of  the  lower  end  of  the  radius. 

above  the  carpus,  from  the  flexor  tendons  being  thrust  forward.  This  fracture  may  be  distin- 
guished from  dislocation  by  the  deformity  being  removed  on  making  sufficient  extension,  when 
crepitus  may  be  occasionally  detected ;  at  the  same  time,  on  extension  being  discontinued,  the 
parts  immediately  resume  their  deformed  appearance  (see  also  page  232).  The  age  of  the 
patient  will  also  assist  in  determining  whether  the  injury  is  fracture  or  separation  of  the  epiph- 
ysis.  The  treatment  consists  in  flexing  the  forearm,  and  making  powerful  extension  from  the 
wrist  and  elbow,  depressing  at  the  same  time  the  radial  side  of  the  hand,  and  retaining  the  parts 
in  that  position  by  well-padded  pistol-shaped  splints. 

MUSCLES  AND  FASCLE  OF  THE  LOWER  EXTREMITY. 

The  Muscles  of  the  Lower  Extremity  are  subdivided  into  groups,  corresponding 
with  the  different  regions  of  the  limb. 

ILIAC  REGION. 
Psoas  magnus. 
Psoas  parvus. 
Iliacus. 

THIGH. 

Anterior  Femoral  Region. 

Tensor  vaginae  femoris. 

Sartorius. 

Rectus. 

Vastus  externus. 

Vastus  internus. 

Crureus. 


Internal  Femoral  Region. 

Gracilis. 
Pectineus. 
Adductor  longus. 
Adductor  brevis. 
Adductor  magnus. 


Subcrureus. 


HIP. 
G-luteal  Region. 

Gluteus  maximus. 
Gluteus  medius. 
Gluteus  minimus. 
Pyriformis. 


THE   ILIAC 


Gemellus  superior. 
Obturator  interims. 
Geniellus  inferior. 
Obturator  externus.  - 
Quadratus  femoris. 

Posterior  Femoral  Region. 
Biceps. 

Seuiitendinosus. 
Semimembranosus. 

LEG. 

Anterior  Tibio-nbular  Region 
Tibialis  anticus. 
E.vcnsor  longus  digitorum. 
Extensor  proprius  hallucis. 
Peroneus  tertius. 

Posterior  Tibio-fibular  Region. 

Superficial  Layer. 
Gastrocnemius. 
Plantaris. 
Soleus. 

Deep  layer. 
Popliteus. 

Flexor  longus  hallucis. 
Flexor  longus  digitorum. 
Tibialis  posticus. 


Fibular  Region. 

Peroneus  longus. 
Peroneus  brevis. 

FOOT. 

Dorsal  Region. 
Extensor  brevis  digitorum. 

Plantar  Region. 

First  Layer. 
Abductor  hallucis. 
Flexor  brevis  digitorum. 
Abductor  minimi  digiti. 

Second  Layer. 
Flexor  accessorius. 
Lumbricales. 

Third  Layer. 

Flexor  brevis  hallucis. 
Adductor  obliquus  hallucis. 
Flexor  brevis  minimi  digiti. 
Adductor  transversus  pedis. 


Fourth  Layer. 
The  Interossei. 


Psoas  niagnus. 


ILIAC   REGION. 
Psoas  parvus. 


Iliacus. 


Dissection. — Xo  detailed  description  is  required  for  the  dissection  of  these  muscles.  On 
the  removal  of  the  viscera  from  the  abdomen  they  are  exposed,  covered  by  the  peritoneum  and 
a  thin  layer  of  fascia,  the  iliac  fascia. 

The  iliac  lascia1  is  the  aponeurotic  layer  which  lines  the  back  part  of  the 
abdominal  cavity,  and  covers  the  Psoas  and  Iliacus  muscles  throughout  their  whole 
extent.  It  is  thin  above,  and  becomes  gradually  thicker  below  as  it  approaches 
the  crural  arch.  It  is  a  part  of  the  general  ffi#ci>.i  transversals. 

The  portion  covering  the  Psoas  is  attached,  above,  to  the  ligamentum  arcuatum 
internum  :  internally,  by  a  series  of  arched  processes  to  the  intervertebral  substances 
and  prominent  margins  of  the  bodies  of  the  vertebrae,  and  to  the  upper  part  of  the 
sacrum,  the  intervals  so  left,  opposite  the  constricted  portions  of  the  bodies, 
transmitting  the  lumbar  arteries  and  filaments  of  the  sympathetic  nerve.  Ex- 
ternally, above  the  crest  of  the  ilium,  this  portion  of  the  iliac  fascia  is  continuous 
with  the  anterior  lamella  of  the  lumbar  fascia  (see  page  433),  but  below  the  crest 
of  the  ilium  it  is  continuous  with  the  fascia  covering  the  Iliacus. 

The  portion  investing  the  Iliacus  is  connected  externally  to  the  whole  length 
of  the  inner  border  of  the  crest  of  the  ilium,  and  internally  to  the  brim  of  the 
true  pelvis  or  iliac  pfirtion  of  the  ilio-pectineal  line,  and  at  the  ilio-pectineal  emi- 
nence it  receives  the  tendon  of  insertion  of  the  Psoas  parvus.  when  that  muscle 
exists.  External  to  the  femoral  vessels,  this  fascia  is  intimately  connected  to  the 
posterior  margin  of  Poupart's  ligament,  and  is  continuous  with  the  fascia  traiis- 
versalis.  Internal  to  the  vessels  it  is  attached  to  the  ilio-pectineal  line  behind  the 
conjoined  tendon,  where  it  is  again  continuous  with  the  transversalis  fascia ;  and, 

1  The  student  must  not  confound  this  fascia  with  the  iliac  portion  of  the  fascia  lota  (see  p.  508). 


504  THE  MUSCLES   AND   FASCIA. 

corresponding  to  the  point  where  the  femoral  vessels  pass  into  the  thigh,  this  fascia 
descends  behind  them,  forming  the  posterior  Avail  of  the  crural  sheath.  This 
portion  of  the  iliac  fascia  which  passes  behind  the  femoral  vessels  is  also  attached 
to  the  ilio-pectineal  line  beyond  the  limits  of  the  attachment  of  the  conjoined 
tendon  ;  at  this  part  it  is  continuous  with  the  pubic  portion  of  the  fascia  lata  of 
the  thigh.  The  external  iliac  vessels  lie  in  front  of  the  iliac  fascia,  but  all  the 
branches  of  the  lumbar  plexus  behind  it ;  it  is  separated  from  the  peritoneum  by  a 
quantity  of  loose  areolar  tissue. 

The  Psoas  magnus  (Fig.  326)  is  a  long  fusiform  muscle  placed  on  the  side  of 
the  lumbar  region  of  the  spine  and  margin  of  the  pelvis.  It  arises  from  the  front 
of  the  bases  and  lower  borders  of  the  transverse  processes  of  the  lumbar  vertebrae 
by  five  fleshy  slips ;  also  from  the  sides  of  the  bodies  and  the  corresponding 
intervertebral  substances  of  the  last  dorsal  and  all  the  lumbar  vertebrae.  The 
muscle  is  connected  to  the  bodies  of  the  vertebrae  by  five  slips  ;  each  slip  is  attached 
to  the  upper  and  lower  margins  of  two  vertebrae,  and  to  the  intervertebral  substance 
between  them,  the  slips  themselves  being  connected  by  the  tendinous  arches  which 
extend  across  the  constricted  part  of  the  bodies,  and  beneath  which  pass  the  lumbar 
arteries  and  sympathetic  nerves.  These  tendinous  arches  also  give  origin  to 
muscular  fibres,  and  protect  the  blood-vessels  and  nerves  from  pressure  during  the 
action  of  the  muscle.  The  first  slip  is  attached  to  the  contiguous  margins  of  the 
last  dorsal  and  first  lumbar  vertebrae ;  the  last  to  the  contiguous  margins  of  the 
fourth  and  fifth  lumbar,  and  to  the  intervertebral  substance.  From  these  points 
the  muscle  passes  down  across  the  brim  of  the  pelvis,  and,  diminishing  gradually 
in  size,  passes  beneath  Poupart's  ligament,  and  terminates  in  a  tendon  which, 
after  receiving  the  fibres  of  the  Iliacus,  is  inserted  into  the  lesser  trochanter  of 
the  femur. 

Relations. — In  the  lumbar  region  :  by  its  anterior  surface,  which  is  placed 
behind  the  peritoneum,  with  the  iliac  fascia,  the  ligamentum  arcuatum  internum, 
the  kidney,  Psoas  parvus,  renal  vessels,  ureter,  spermatic  vessels,  genito-crural 
nerve,  and  the  colon ;  by  its  posterior  surface,  with  the  transverse  processes  of  the 
lumbar  vertebrae  and  the  Quadratus  lumborum,  from  which  it  is  separated  by  the 
anterior  lamella  of  the  lumbar  fascia.  The  anterior  crural  nerve  is  at  first 
situated  in  the  substance  of  the  muscle,  and  emerges  from  its  outer  border  at  the 
lower  part.  The  lumbar  plexus  is  situated  in  the  posterior  part  of  the  substance 
of  the  muscle.  By  its  inner  side  the  muscle  is  in  relation  with  the  bodies  of  the 
lumbar  vertebras,  the  lumbar  arteries,  the  ganglia  of  the  sympathetic  nerve,  and 
their  branches  of  communication  with  the  spinal  nerves ;  the  lumbar  glands ;  the 
vena  cava  inferior  on  the  right  and  the  aorta  on  the  left  side,  and  along  the  brim 
of  the  pelvis  with  the  external  iliac  artery.  In  the  thigh  it  is  in  relation,  in  front, 
with  the  fascia  lata ;  behind,  with  the  capsular  ligament  of  the  hip,  from  which  it 
is  separated  by  a  synovial  bursa,  which  frequently  communicates  with  the  cavity 
of  the  joint  through  an  opening  of  variable  size;  by  its  inner  border,  with  the 
Pectineus  and  the  femoral  artery,  which  slightly  overlaps  it :  by  its  outer  border, 
with  the  anterior  crural  nerve  and  Iliacus  muscle. 

The  Psoas  parvus  is  a  long  slender  muscle  placed  in  front  of  the  Psoas  magnus. 
It  arises  from  the  sides  of  the  bodies  of  the  last  dorsal  and  first  lumbar  vertebrae 
and  from  the  intervertebral  substance  between  them.  It  forms  a  small  flat  muscular 
bundle,  which  terminates  in  a  long  flat  tendon  inserted  into  the  ilio-pectineal 
eminence,  and,  by  its  outerfborder,  into  the  iliac  fascia.  This  muscle  is  often 
absent,  and,  according  to  Cruveilhier,  sometimes  double. 

Relations. — It  is  covered  by  the  peritoneum,  and,  at  its  origin,  by  the  ligamentum 
arcuatum  internum ;  it  rests  on  the  Psoas  magnus. 

The  Iliacus  is  a  flat,  triangular  muscle  which  fills  up  the  whole  of  the  iliac 
fossa.  It  arises  from  the  upper  two-thirds  of  this  fossa  and  from  the  inner  margin 
of  the  crest  of  the  ilium ;  behind,  from  the  ilio-lumbar  ligament  and  base  of  the 
sacrum  ;  in  front,  from  the  anterior  superior  and  anterior  inferior  spinous  processes 
of  the  ilium,  from  the  notch  between  them,  and  by  a  few  fibres  from  the  capsule 


THE    THIGH.  505 

of  the  hip-joint.  The  fibres  converge  to  be  inserted  into  the  outer  side  of  the 
tendon  of  the  Psoas,  some  of  them  being  prolonged  into  the  oblique  line  which 
extends  from  the  lesser  trochanter  to  the  linea  aspera.1 

Relations. —  Within  the  pelvis :  by  its  anterior  surface,  with  the  iliac  fascia, 
which  separates  the  muscle  from  the  peritoneum,  and  with  the  external  cutaneous 
nerve ;  on  the  right  side,  with  the  caecum ;  on  the  left  side,  with  the  sigmoid 
flexure  of  the  colon ;  by  its  posterior  surface,  with  the  iliac  fossa ;  by  its  inner 
border,  with  the  Psoas  magnus  and  .anterior  crural  nerve.  In  the  thigh,  it  is  in 
relation,  by  its  anterior  surface,  with  the  fascia  lata.  Rectus.  and  Sartorius; 
behind,  with  the  capsule  of  the  hip-joint,  a  synovial  bursa  common  to  it  and  the 
Psoas  magnus  being  interposed. 

Nerves. — The  Psoas  magnus,  and  the  Psoas  parvus  when  it  exists,  are  supplied 
by  the  anterior  branches  of  the  lumbar  nerves ;  the  Iliacus  by  the  anterior  crural. 

Actions. — The  Psoas  and  Iliacus  muscles,  acting  from  above,  flex  the  thigh 
upon  the  pelvis,  and.  at  the  same  time,  rotate  the  femur  outward,  from  the 
obliquity  of  their  insertion  into  the  inner  and  back  part  of  that  bone.  Acting 
from  below,  the  femur  being  fixed,  the  muscles  of  both  sides  bend  the  lumbar 
portion  of  the  spine  and  pelvis  forward.  They  also  serve  to  maintain  the  erect 
position,  by  supporting  the  spine  and  pelvis  upon  the  femur,  and  assist  in  raising 
the  trunk  when  the  body  is  in  the  recumbent  posture. 

The  Psoas  parvus  is  a  tensor  of  the  iliac  fascia. 

Surgical  Anatomy. — In  the  iliac  fascia  there  is  no  definite  septum  between  the  portions  of 
fascia  covering  the  Psoas  and  Iliacus  respectively,  and  the  fascia  is  only  connected  to  the  subja- 
cent muscles  by  a  quantity  of  loose  connective  tissue.  When  abscess  forms  beneath  this  fascia, 
as  it  is  very  apt  to  do.  the  matter  is  contained  in  an  osseo-fibrous  cavity  which  is  closed  on  all 
sides  within  the  abdomen,  and  is  open  only  at  its  lower  part,  where  the  fascia  is  prolonged  over 
the  muscle  into  the  thigh. 

-s  within  the  sheath  of  the  Psoas  muscle  (Psocts  abscess)  is  generally  due  to  tubercular 
caries  of  the  bodies  of  the  lower  dorsal  and  lumbar  vertebrae.  When  the  disease  is  in  the  dorsal 
region,  the  matter  tracts  down  the  posterior  mediastinum,  in  front  of  the  bodies  of  the  vertebrae, 
and.  passing  beneath  the  ligamentum  arcuatuni  internum,  enters  the  sheath  of  the  Psoas  muscle, 
down  which  it  passes  as  far  as  the  pelvic  brim ;  it  then  gets  beneath  the  iliac  portion  of  the  fascia 
and  fills  up  the  iliac  fossa.  In  consequence  of  the  attachment  of  the  fascia  to  the  pelvic  brim,  it 
rarely  finds  its  way  into  the  pelvis,  but  passes  by  a  narrow  opening  under  Poupart's  ligament 
into  the  thigh,  to  the  outer  side  of  the  femoral  vessels.  It  thus  follows  that  a  Psoas  abscess  may 
be  described  as  consisting  of  four  parts:  (1)  a  somewhat  narrow  channel  at  its  upper  part,  in  the 

-  sheath  :  i2'  a  dilated  sac  in  the  iliac  fossa  ;  (3)  a  constricted  neck  under  Poupart's  liga- 
ment :  and  4  a  dilated  sac  in  the  upper  part  of  the  thigh.  When  the  lumbar  vertebrae  are 
the  seat  of  the  disease,  the  matter  finds  its  way  directly  into  the  substance  of  the  muscle.  The 
muscular  fibres  are  destroyed,  and  the  nervous  cords  contained  in  the  abscess  are  isolated  and 
exposed  in  its  interior :  the  femoral  vessels  which  lie  in  front  of  the  fascia  remain  intact,  and  the 
peritoneum  seldom  becomes  implicated.  All  Psoas  abscesses  do  not,  however,  pursue  this 
course  :  the  matter  may  leave  the  muscle  above  the  crest  of  the  ilium,  and,  tracking  backward, 
may  point  in  the  loin  nonpar  abscess) ;  or  it  may  point  above  Poupart's  ligament  in  the  inguinal 
region ;  or  it  may  follow  the  course  of  the  iliac  vessels  into  the  pelvis,  and,  passing  through  the 
great  saero-sciatic  notch,  discharge  itself  on  the  back  of  the  thigh ;  or  it  may  open  into  the 
bladder  or  find  its  way  into  the  perinasum. 

THE  THIGH. 
Anterior  Femoral  Region. 

Tensor  vaginae  femoris.  Vastus  externus. 

Sartorius.  Vastus  internus. 

Rectus.  Crureus. 
Subcrureus. 

Dissection.— To  expose  the  muscles  and  fasciae  in  this  region,  make  an  incision  along 
Poupart's  ligament,  from  the  anterior  superior  spine  of  the  ilium  to  the  spine  of  the  os  pubis; 
a  vertical  incision  from  the  centre  of  this,  along  the  middle  of  the  thigh  to  below  the  knee-joint; 
and  a  transverse  incision  from  the  inner  to  the  outer  side  of  the  leg,  at  the  lower  end  of  the  ver- 
tical incision.  The  flaps  of  integument  having  been  removed,  the  superficial  and  deep  fasciae 

1  The  Psoas  and  Iliacus  are  sometimes  regarded  as  a  single  muscle,  the  Hio-psoag,  having  two 
heads  of  origin  and  a  single  insertion. 


506 


THE  MUSCLES  AND    FASCIAE. 


should  be  examined.  The  more  advanced  student  should  commence  the  study  of  this  region  by 
an  examination  of  the  anatomy  of  femoral  hernia  and  Scar  pa's  triangle,  the  incisions  for  the 
dissection  of  which  are  marked  out  in  the  figure  below, 

The  superficial  fascia  forms  a  continuous  layer  over  the  whole  of  the  thigh, 
consisting  of  areolar  tissue,  containing  in  its  meshes  much  fat,  and  capable  of 
being  separated  into  two  or  more  layers,  between  which  are  found  the  superficial 
vessels  and  nerves.  It  varies  in  thickness  in  different  parts  of  the  limb :  in  the 
groin  it  is  thick,  and  the  two  layers  are  separated  from  one  another  by  the  super- 
ficial inguinal  lymphatic  glands,  the  internal  saphenous  vein,  and  several  smaller 
vessels.  One  of  these  two  layers,  the  superficial,  is  continuous  above  with  the 
superficial  fascia  of  the  abdomen.  The  deep  layer  of  the  superficial  fascia  is  a 
very  thin,  fibrous  layer,  best  marked  on  the  inner  side  of  the  long  'saphenous  vein 
and  below  Poupart's  ligament.  It  is  placed  beneath  the  subcutaneous  vessels  and 
nerves  and  upon  the  surface  of  the  fascia  lata.  It  is  intimately  adherent  to  the 
fascia  lata  a  little  below  Poupart's  ligament.  It  covers  the  saphenous  opening  in 
the  fascia  lata,  being  closely  united  to  its  circumference,  and  is  connected  to  the 
sheath  of  the  femoral  vessels,  corresponding  to  its  under  surface.  The  portion  of 
fascia  covering  this  aperture  is  perforated  by  the  internal  saphenous  vein  and  by 
numerous  blood-  and  lymphatic  vessels  ;  hence  it  has  been  termed  the  cribriform 

fascia,  the  openings  for  these  vessels  having 
been  likened  to  the  holes  in  a  sieve.  The 
cribriform  fascia  adheres  closely  both  to  the 
superficial  fascia  and  to  the  fascia  lata,  so  that 
it  is  described  by  some  anatomists  as  part  of  the 
fascia  lata,  but  is  usually  considered  (as  in  this 
work)  as  belonging  to  the  superficial  fascia.  It 
is  not  until  the  cribriform  fascia  has  been  cleared 
away  that  the  saphenous  opening  is  seen,  so  that 
this  opening  does  not  in  ordinary  cases  exist 
naturally,  but  is  the  result  of  dissection.  Mr. 
Callender,  however,  speaks  of  cases  in  which, 
probably  as  the  result  of  pressure  from  enlarged 
inguinal  lymphatic  glands,  the  fascia  has  become 
atrophied,  and  a  sapbenous  opening  exists  inde- 
pendent of  dissection.  A  femoral  hernia  in  pass- 
ing through  the  saphenous  opening  receives  the 
cribriform  fascia  as  one  of  its  coverings.  A  large 
subcutaneous  bursa  is  found  in  the  superficial 
fascia  over  the  patella. 

The  deep  fascia  of  the  thigh  is  exposed  on  the 
removal  of  the  superficial  fascia,  and  is  named, 
from  its  great  extent,  the  fascia  lata ;  it  forms  a 
uniform  investment  for  the  whole  of  this  region 
of  the  limb,  but  varies  in  thickness  in  different 
parts  ;  thus,  it  is  thicker  in  the  upper  and  outer 
part  of  the  thigh,  where  it  receives  a  fibrous 
expansion  from  the  Gluteus  maximus  muscle,  and 
the  Tensor  vaginas  femoris  is  inserted  between  its 
layers :  it  is  very  thin  behind,  and  at  the  upper 
and  inner  part  where  it  covers  the  Adductor 
muscles,  and  again  becomes  stronger  around  the 
knee,  receiving  fibrous  expansions  from  the 

FIG.  325.— Dissection  of  lower  extremity,    tendon  of  the   Biceps  externally,  and  from  the 

Sartorius  internally,  and  Quadriceps  extensor 
cruris  in  front.  The  fascia  lata  is  attached,  above  and  behind,  to  the  back  of  the 
sacrum  and  coccyx  ;  externally,  to  the  crest  of  the  ilium ;  in  front,  to  Poupart's 
ligament  and  to  the  body  of  the  os  pubis ;  and  internally,  to  the  descending  ramus 


1.  Dissection  of 
femoral  hernia, 

I  and  Scarpa's 
triangle. 


2.  Front  of  thigh. 


3.  Front  of  leg. 


4-  Dorsum  of  foot. 


Front  view. 


THE   ANTERIOR    FEMORAL    REGION. 


507 


of  the  os  pubis,  to  the  ascending  ramus  and 
tuberosity  of  the  ischium,  and  to  the  lower 
border  of  the  great  sacro-sciatic  ligament. 
From  its  attachment  to  the  crest  of  the  ilium 
it  passes  down  over  the  Gluteus  medius  muscle 
to  the  upper  border  of  the  Gluteus  maximus, 
where  it  splits  into  two  layers,  one  passing 
superficial  to  and  the  other  beneath  this  muscle. 
At  the  lower  border  of  the  muscle  the  two 
layers  unite.  Externally,  just  below  the  great 
trochanter.  the  fascia  lata  receives  the  greater 
part  of  the  tendon  of  insertion  of  the  Gluteus 
maximus,  and  becomes  proportionately  thick- 
ened. The  portion  of  the  fascia  lata  arising 
from  the  front  part  of  the  crest  of  the  ilium, 
corresponding  to  the  origin  of  the  Tensor 
vaginae  femoris,  passes  down  the  outer  side 
of  the  thigh  as  two  layers,  one  superficial 
and  the  other  beneath  this  muscle ;  these  at 
its  lower  end  become  blended  together  into 
a  thick  and  strong  band,  having  first  received 
the  insertion  of  the  muscle.  This  band  is 
continued  dowmvard,  under  the  name  of  the 
ttio-tibial  band,  to  be  inserted  into  the  external 
tuberosity  of  the  tibia.  Below,  the  fascia 
lata  is  attached  to  all  the  prominent  points 
around  the  knee-joint — viz.  the  condyles  of 
the  femur,  tuberosities  of  the  tibia,  and  head 
of  the  fibula.  On  each  side  of  the  patella  it  is 
strengthened  by  transverse  fibres  given  off 
from  the  lower  part  of  the  Vasti  muscles, 
which  are  attached  to  and  support  this  bone. 
Of  these  the  outer  is  the  stronger,  and  is  con- 
tinuous with  the  ilio-tibial  band.  From  the 
inner  surface  of  the  fascia  lata  are  given  off 
two  strong  intermuscular  septa,  which  are 
attached  to  the  whole  length  of  the  linea 
aspera  and  its  prolongations  above  and  below : 
the  external  and  stronger  one,  which  extends 
from  the  insertion  of  the  Glutens  maximus  to 
the  outer  condyle,  separates  the  Yastus  ex- 
ternus  in  front  from  the  short  head  of  the 
Biceps  behind,  and  gives  partial  origin  to  these 
muscles;  the  inner  one,  the  thinner  of  the 
two,  separates  the  Vastus  internus  from  the 
Adductor  and  Pectineus  muscles.  Besides 
these  there  are  numerous  smaller  septa,  sepa- 
rating the  individual  muscles  and  enclosing 
each  in  a  distinct  sheath.  At  the  upper  and 
inner  part  of  the  thigh,  a  little  below  Poupart's 
ligament,  a  large  oval-shaped  aperture  is 
observed  after  the  superficial  fascia  has  been 
cleared  off :  it  transmits  the  internal  saphenous 
vein  and  other  smaller  vessels,  and  is  termed 
the  saphenous  opening.  In  order  more  correctly 
to  consider  the  mode  of  formation  of  this 
aperture,  the  fascia  lata  in  this  part  of  the 


FIG.  326.— Muscles  of  the  iliac  and  anterior 
femoral  regions. 


508  THE  MUSCLES  AND   FASCIA 

thigh  is  described  as  consisting  of  two  portions — an  iliac  portion  and  a  pubic 
portion. 

The  iliac  portion  is  all  that  part  of  the  fascia  lata  on  the  outer  side  of  the 
saphenous  opening.  It  is  attached,  externally,  to  the  crest  of  the  ilium  and 
its  anterior  superior  spine,  to  the  whole  length  of  Poupart's  ligament  as  far 
internally  as  the  spine  of  the  os  pubis,  and  to  the  pectineal  line  in  conjunction 
with  Gimbernat's  ligament.  From  the  spine  of  the  os  pubis  it  is  reflected  down- 
ward and  outward,  forming  an  arched  margin,  the  boundary  or  falciform  process 
(superior  cornu)  of  the  saphenous  opening ;  this  margin  overlies  and  is  adherent 
to  the  anterior  layer  of  the  sheath  of  the  femoral  vessels :  to  its  edge  is  attached 
the  cribriform  fascia ;  and,  below,  it  is  continuous  with  the  pubic  portion  of  the 
fascia  lata. 

The  pubic  portion  is  situated  at  the  inner  side  of  the  saphenous  opening :  at 
the  lower  margin  of  this  aperture  it  is  continuous  with  the  iliac  portion ;  traced 
upward,  it  covers  the  surface  of  the  Pectineus,  Adductor  longus,  and  Gracilis 
muscles,  and,  passing  behind  the  sheath  of  the  femoral  vessels,  to  which  it  is 
closely  united,  is  continuous  with  the  sheath  of  the  Psoas  and  Iliacus  muscles, 
and  is  attached  above  to  the  ilio-pectineal  line,  where  it  becomes  continuous  with 
the  iliac  fascia.  From  this  description  it  may  be  observed  that  the  iliac  portion 
of  the  fascia  lata  passes  in  front  of  the  femoral  vessels,  and  the  pubic  portion 
behind  them,  so  that  an  apparent  aperture  exists  between  the  two,  through  which 
the  internal  saphenous  joins  the  femoral  vein.1 

The  fascia  should  now  be  removed  from  the  surface  of  the  muscles.  This  may  be  effected 
by  pinching  it  up  between  the  forceps,  dividing  it,  and  separating  it  from  each  muscle  in  the 
course  of  its  fibres. 

The  Tensor  vaginse  femoris  arises  from  the  anterior  part  of  the  outer  lip  of 
the  crest  of  the  ilium,  and  from  the  outer  surface  of  the  anterior  superior  spinous 
process,  between  the  Gluteus  medius  and  Sartorius.  It  is  inserted  into  the  fascia 
lata  about  one-fourth  down  the  outer  side  of  the  thigh.  From  the  point  of  inser- 
tion the  fascia  is  continued  downward  to  the  head  of  the  tibia  as  a  thickened  band, 
the  ilio-tibial  band. 

Relations. — By  its  superficial  surface,  with  the  fascia  lata  and  the  integument ; 
by  its  deep  surface,  with  the  Gluteus  medius,  Rectus  femoris,  Vastus  externus, 
and  the  ascending  branches  of  the  external  circumflex  artery;  by  its  anterior 
border,  with  the  Sartorius,  from  which  it  is  separated  below  by  a  triangular  space, 
in  which  is  seen  the  Rectus  femoris ;  by  its  posterior  border,  with  the  Gluteus 
medius. 

The  Sartorius,  the  longest  muscle  in  the  body,  is  flat,  narrow,  and  ribbon-like ; 
it  arises  by  tendinous  fibres  from  the  anterior  superior  spinous  process  of  the 
ilium  and  the  upper  half  of  the  notch  below  it,  passes  obliquely  across  the  upper 
and  anterior  part  of  the  thigh,  from  the  outer  to  the  inner  side  of  the  limb,  then 
descends  vertically,  as  far  as  the  inner  side  of  the  knee,  passing  behind  the  inner 
condyle  of  the  femur,  and  terminates  in  a  tendon  which,  curving  obliquely 
forward,  expands  into  a  broad  aponeurosis  inserted  into  the  upper  part  of  the 
inner  surface  of  the  shaft  of  the  tibia,  nearly  as  far  forward  as  the  crest.  This 
expansion  is  inserted  into  the  bone  by  an  inverted  U-shaped  aponeurosis:  part 
of  it  is  inserted  behind  the  attachment  of  the  Gracilis  and  Semitendinosus,  and 
another  part,  arching  over  the  upper  border  of  the  tendon  of  the  Gracilis,  is  inserted 
into  the  tibia  in  front  of  these  muscles.  An  oifset  is  derived  from  the  upper  margin 
of  this  aponeurosis,  which  blends  with  the  fibrous  capsule  of  the  knee-joint,  and 
another,  given  off  from  its  lower  border,  blends  with  the  fascia  on  the  inner  side 
of  the  leg. 

The  relations  of  this  muscle  to  the  femoral  artery  should  be  carefully  examined, 
as  it  constitutes  the  chief  guide  in  tying  the  artery.  In  the  upper  third  of  the 
thigh  it  forms  the  outer  side  of  a  triangular  space,  Scarpas  triangle,  the  inner 

1  These  parts  will  be  again  more  particularly  described  with  the  anatomy  of  Hernia. 


THE  ANTERIOR   FEMORAL   REGION.  509 

side  of  which  is  formed  by  the  Adductor  longus,  and  the  base,  turned  upward, 
by  Poupart's  ligament ;  the  femoral  artery  passes  perpendicularly  through  the 
middle  of  this  space  from  its  base  to  its  apex.  In  the  middle  third  of  the 
thigh  the  femoral  artery  lie&  first  along  the  inner  border,  and  then  behind  the 
Sartorius. 

Relations. — By  its  superficial  surface,  with  the  fascia  lata  and  integument; 
by  its  deep  surface,  with  the  Rectus,  Iliacus,  Psoas,  Vastus  internus,  anterior 
crural  nerve,  sheath  of  the  femoral  vessels,  Adductor  longus,  Adductor  magnus, 
Gracilis,  Semitendinosus,  long  saphenous  nerve,  and  internal  lateral  ligament  of 
the  knee-joint. 

The  Quadriceps  extensor  includes  the  four  remaining  muscles  on  the  front  of 
the  thigh.  It  is  the  great  Extensor  muscle  of  the  leg,  forming  a  large  fleshy 
mass  which  covers  the  front  and  sides  of  the  femur,  being  united  below  into  a 
single  tendon,  attached  to  the  patella,  and  above  subdivided  into  separate  por- 
tions, which  have  received  distinct  names.  Of  these,  one  occupying  the  middle 
of  the  thigh,  connected  above  with  the  ilium,  is  called  the  Rectus  femoris,  from  its 
straight  course.  The  other  divisions  lie  in  immediate  connection  with  the  shaft 
of  the  femur,  which  they  cover  from  the  trochanters  to  the  condyles.  The  portion 
on  the  outer  side  of  the  femur  is  termed  the  Vastus  externus  ;  that  covering  the 
inner  side,  the  Vastus  internus ;  and  that  covering  the  front  of  the  femur,  the 
<  'n/reus.  The  two  latter  portions  are,  however,  so  intimately  blended  as  to  form 
but  one  muscle. 

The  Rectus  femoris  is  situated  in  the  middle  of  the  anterior  region  of  the 
thigh  :  it  is  fusiform  in  shape,  and  its  superficial  fibres  are  arranged  in  a  bipenni- 
form  manner,  the  deep  fibres  running  straight  down  to  the  deep  aponeurosis.  It 
arises  by  two  tendons :  one  the  straight  tendon,  or  short  head,  from  the  anterior 
inferior  spinous  process  of  the  ilium ;  the  other  is  flattened,  and  curves  outward, 
to  be  attached  to  a  groove  above  the  brim  of  the  acetabulum ;  this  is  the  reflected 
tendon,  or  long  head,  of  the  Rectus ;  it  unites  with  the  straight  tendon  at  an 
acute  angle,  and  then  spreads  into  an  aponeurosis,  from  which  the  muscular 
fibres  arise.1  The  muscle  terminates  in  a  broad  and  thick  aponeurosis  which 
occupies  the  lower  two-thirds  of  its  posterior  surface,  and,  gradually  becoming 
narrowed  into  a  flattened  tendon,  is  inserted  into  the  patella  in  common  with  the 
Vasti  and  Crureus. 

Relations. — By  its  superficial  surface,  with  the  anterior  fibres  of  the  Gluteus 
minimus,  the  Tensor  vaginge  femoris,  the  Sartorius,  and  the  Psoas  and  Iliacus ;  by 
its  lower  three-fourths,  with  the  fascia  lata;  by  its  posterior  surface,  with  the 
hip-joint,  the  external  circumflex  vessels,  and  the  Crureus  and  Vasti  muscles. 

The  three  remaining  muscles  have  been  described  collectively  by  some  anat- 
omists, separate  from  the  Rectus,  under  the  name  of  the  Triceps  extensor  cruris. 

The  Vastus  externus  is  the  largest  part  of  the  Quadriceps  extensor.  It  arises 
by  a  broad  aponeurosis,  which  is  attached  to  the  tubercle  of  the  femur,  to  the 
anterior  and  inferior  borders  of  the  great  trochanter,  to  a  rough  line  leading  from 
the  trochanter  major  to  the  linea  aspera,  and  to  the  outer  lip  of  the  linea  aspera: 
this  aponeurosis  covers  the  upper  three-fourths  of  the  muscle,  and  from  its  inner 
surface  many  fibres  arise.  A  few  additional  fibres  arise  from  the  tendon  of  the 
Gluteus  maximus  and  from  the  external  intermuscular  septum  between  the  Vastus 
externus  and  short  head  of  the  Biceps.  The  fibres  form  a  large  fleshy  mass  which 
is  attached  to  a  strong  aponeurosis,  placed  on  the  under  surface  of  the  muscle  at 
its  lower  part :  this  becomes  contracted  and  thickened  into  a  flat  tendon,  which  is 
inserted  into  the  outer  border  of  the  patella,  blending  with  the  great  extensor 
tendon. 

1  Mr.  W.  R.  Williams,  in  an  interesting  paper  in  the  Journ.  of  Anat.  and  Phys.,  vol.  xiii.  p.  204, 
points  out  that  the  reflected  tendon  is  the  real  origin  of  the  muscle,  and  is  alone  present 
in  early  foetal  life.  The  direct  tendon  is  merely  an  accessory  band  of  condensed  fascia.  The 
paper  will  well  repay  perusal,  though  in  some  particulars  I  think  the  description  in  the  text 
more  generally  accurate. — ED. 


510  THE  MUSCLES  AND    FASCIAE. 

Relations. — By  its  superficial  surface,  with  the  Rectus,  the  Tensor  vaginae 
femoris,  the  fascia  lata,  and  the  Gluteus  maximus,  from  which  it  is  separated  by 
a  synovial  bursa ;  by  its  deep  surface,  with  the  Crureus,  some  large  branches  of 
the  external  circumflex  artery  and  anterior  crural  nerve  being  interposed. 

The  Vastus  internus  and  Crureus  are  so  inseparably  connected  together  as  to 
form  but  one  muscle,  as  which  it  will  be  accordingly  described.  It  is  the  smallest 
portion  of  the  Quadriceps  extensor.  The  anterior  portion  of  it,  covered  by  the 
Rectus,  is  called  the  Crureus ;  the  internal  portion,  which  lies  immediately 
beneath  the  fascia  lata,  the  Vastus  internus.  It  arises  by  an  aponeurosis,  which 
is  attached  to  the  lower  part  of  the  line  that  extends  from  the  inner  side  of  the 
neck  of  the  femur  to  the  linea  aspera,  from  the  inner  lip  of  the  linea  aspera, 
from  the  ridge  leading  from  the  linea  aspera  to  the  internal  condyle  and  internal 
intermuscular  septum.  It  also  arises  from  nearly  the  Avhole  of  the  internal, 
anterior,  and  external  surfaces  of  the  shaft  of  the  femur,  limited,  above,  by  the  line 
between  the  two  trochanters,  and  extending,  below,  to  within  the  lower  fourth  of 
the  bone.  From  these  different  origins  the  fibres  converge  to  a  broad  aponeurosis 
which  covers  the  anterior  surface  of  the  middle  portion  of  the  muscle  (the  Crureus) 
and  the  deep  surface  of  the  inner  division  of  the  muscle  (the  Vastus  internus),  and 
which  gradually  narrows  down  to  its  insertion  into  the  patella,  where  it  blends  with 
the  other  portions  of  the  Quadriceps  extensor.  The  muscular  fibres  of  the  Vastus 
internus  extend  lower  down  than  those  of  the  Vastus  externus,  so  that  the  capsule 
of  the  joint  is  less  covered  with  muscular  fibres  on  the  outer  than  on  the  inner 
side. 

Relations. — By  its  superficial  surface,  with  the  Psoas  and  Iliacus,  the  Rectus, 
Sartorius,  Pectineus,  Adductors,  and  fascia  lata,  femoral  vessels,  and  saphenous 
nerve ;  by  its  deep  surface,  with  the  femur,  Subcrureus,  and  synovial  membrane 
of  the  knee-joint. 

The  student  will  observe  the  striking  analogy  that  exists  between  the  Quadri- 
ceps extensor  and  the  Triceps  muscle  in  the  upper  extremity.  So  close  is  this 
similarity  that  M.  Cruveilhier  has  described  it  under  the  name  of  the  Triceps 
femoralis.  Like  the  Triceps  extensor  cubiti,  it  consists  of  three  distinct  divisions, 
or  heads :  a  middle  or  long  head,  the  Rectus,  analogous  to  the  long  head  of  the 
Triceps,  attached  to  the  ilium,  and  two  other  portions,  which  may  be  called  the 
external  and  internal  heads  of  the  Triceps  femoralis.  These,  it  will  be  noticed, 
are  strictly  analogous  to  the  outer  and  inner  heads  of  the  Triceps  in  the  arm. 

The  tendons  of  the  different  portions  of  the  Quadriceps  extensor  unite  at  the 
lower  part  of  the  thigh,  so  as  to  form  a  single  strong  tendon  which  is  inserted 
into  the  upper  part  of  the  patella.  More  properly,  the  patella  may  be  regarded  as 
a  sesamoid  bone,  developed  in  the  tendon  of  the  Quadriceps,  and  the  ligamentum 
patellae,  which  is  continued  from  the  lower  part  of  the  patella  to  the  tuberosity  of 
the  tibia,  as  the  proper  tendon  of  insertion  of  the  muscle.  A  synovial  bursa,  the 
post-patellar  bursa,  is  interposed  between  the  tendon  and  the  upper  part  of  the 
tuberosity  of  the  tibia  ;  and  another,  the  prepatellar  bursa,  is  placed  over  the 
patella  itself.  This  latter  bursa  often  becomes  enlarged,  constituting  "  housemaid's 
knee." 

The  Subcrureus  is  a  small  muscle,  usually  distinct  from  the  Crureus,  but  occa- 
sionally blended  with  it,  which  arises  from  the  anterior  surface  of  the  lower  part 
of  the  shaft  of  the  femur,  and  is  inserted  into  the  upper  part  of  the  cul-de-sac  of 
the  capsular  ligament  which  projects  upward  beneath  the  Quadriceps  for  a  variable 
distance.  It  sometimes  consists  of  two  separate  muscular  bundles. 

Nerves. — The  Tensor  vaginae  femoris  is  supplied  by  the  superior  gluteal  nerve  ; 
the  other  muscles  of  this  region  by  branches  from  the  anterior  crural. 

Actions. — The  Tensor  vaginae  femoris  is  a  tensor  of  the  fascia  lata ;  continuing 
its  action,  the  oblique  direction  of  its  fibres  enables  it  to  abduct  and  to  rotate  the 
thigh  inward.  In  the  erect  posture,  acting  from  below,  it  will  serve  to  steady  the 
pelvis  upon  the  head  of  the  femur,  and  by  means  of  the  ilio-tibial  band  it  steadies 
the  condyles  of  the  femur  on  the  articular  surfaces  of  the  tibia,  and  assists  the 


THE    INTERNAL    FEMORAL    REGION.  511 

Gluteus  maximus  in  f  apporting  the  knee  in  the  extended  position.  TheSartorius 
flexes  the  leg  upon  ihe  thigh,  and.  continuing  to  act,  flexes  the  thigh  upon  the 
pelvis  :  it  next  rotates  the  thigh  outward.  It  was  formerly  supposed  to  adduct  the 
thigh,  so  as  to  cross  one  leg  over  the  other,  and  hence  received  its  name  of  Sartorius. 
or  tailor's  muscle  (sartor,  a  tailor),  because  it  was  supposed  to  assist  in  crossing  the 
k'^s  in  the  squatting  position.  When  the  knee  is  bent  the  Sartorius  assists  the 
Semitendinosus,  Semimembranosus,  and  Popliteus  in  rotating  the  tibia  inward. 
Taking  its  fixed  point  from  the  leg,  it  flexes  the  pelvis  upon  the  thigh,  and,  if  one 
muscle  acts,  assists  in  rotating  the  pelvis.  The  Quadriceps  extensor  extends  the 
leg  upon  the  thigh.  Taking  its  fixed  point  from  the  leg,  as  in  standing,  this  muscle 
will  act  upon  the  femur,  supporting  it  perpendicularly  upon  the  head  of  the  tibia, 
and  thus  maintaining  the  entire  weight  of  the  body,  or  in  the  stooping  position  it 
will  straighten  the  knee,  and  therefore  assist  the  trunk  in  rising  into  the  erect 
position.  The  Rectus  muscle  assists  the  Psoas  and  Iliacus  in  supporting  the  pel- 
vis and  trunk  upon  the  femur  or  in  bending  it  forward. 

Surgical  Anatomy. — A  few  fibres  of  the  Rectus  muscle  are  liable  to  be  ruptured  from 
severe  strain.  This  accident  is  especially  liable  to  occur  during  the  games  of  football  and  cricket, 
and  is  sometimes  known  as  "cricket  thigh.  "  The  patient  experiences  a  sudden  pain  in  the  part, 
as  if  he  had  been  struck,  and  the  Rectus  muscle  stands  out  and  is  felt  to  be  tense  and  rigid.  The 
accident  is  often  followed  by  considerable  swelling  from  inflammatory  effusion.  Occasionally  the 
Quadriceps  extensor  may  be  torn  away  from  its  insertion  into  the  patella,  or  the  tendon  of  the 
patella  may  be  ruptured  about  an  inch  above  the  bone.  This  accident  is  caused  in  the  same 
manner  as  fracture  of  the  patella  by  muscular  action  is  produced — viz.  by  a  violent  muscular 
effort  to  prevent  falling  whilst  the  knee  is  in  a  position  of  semiflexion.  A  distinct  gap  can  be 
felt  above  the  patella,  and,  owing  to  the  retraction  of  the  muscular  fibres,  union  may  fail  to  take 
place. 

Internal  Femoral  Region. 

Gracilis.  Adductor  longus. 

Pectineus.  Adductor  brevis. 

Adductor  magnus. 

Dissection. — These  muscles  are  at  once  exposed  by  removing  the  fascia  from  the  fore  part 
and  inner  side  of  the  thigh.  The  limb  should  be  abducted,  so  as  to  render  the  muscles  tense 
and  easier  of  dissection. 

The  Gracilis  (Figs.  326.  329)  is  the  most  superficial  muscle  on  the  inner  side 
of  the  thigh.  It  is  thin  and  flattened,  broad  above,  narrow  and  tapering  below. 
It  arises  by  a  thin  aponeurosis,  between  two  and  three  inches  in  breadth,  from  the 
lower  half  of  the  margin  of  the  syinphysis  and  the  inner  margin  of  the  descending 
ramus  of  the  os  pubis.  The  fibres  pass  vertically  downward,  and  terminate  in  a 
rounded  tendon  which  passes  behind  the  internal  condyle  of  the  femur,  and, 
curving  round  the  inner  tuberosity  o£  the  tibia,  becomes  flattened,  and  is  inserted 
into  the  upper  part  of  the  inner  surface  of  the  shaft  of  the  tibia,  below  the  tuber- 
osity. The  tendon  of  this  muscle  is  situated  immediately  above  that  of  the 
Semitendinosus.  and  is  surrounded  by  the  tendon  of  the  Sartorius,  with  which  it  is 
in  part  blended.  As  it  passes  across  the  internal  lateral  ligament  of  the  knee-joint 
it  is  separated  from  it  by  a  synovial  bursa  common  to  it  and  the  Semitendinosus 
muscle. 

Relations.— By  its  superficial  surface,  with  the  fascia  lata  and  the  Sartorius 
below  :  the  internal  saphenous  vein  crosses  it  obliquely  near  its  lower  part,  lying 
superficial  to  the  fascia  lata ;  the  internal  saphenous  nerve  emerges  between  its 
tendon  and  that  of  the  Sartorius  ;  by  its  deep  surface,  with  the  Adductor  brevis  and 
the  Adductor  magnus  and  the  internal  lateral  ligament  of  the  knee-joint. 

The  Pectineus  (Fig.  326 )  is  a  flat,  quadrangular  muscle  situated  at  the  anterior 
part  of  the  upper  and  inner  aspect  of  the  thigh.  It  arises  from  the  linea  ilio- 
pectinea.  from  the  surface  of  the  bone  in  front  of  it  between  the  pectineal  eminence 
and  spine  of  the  os  pubis,  and  from  the  fascia  covering  the  anterior  surface  of  the 
muscle  :  the  fibres  pass  downward,  backward,  and  outward,  to  be  inserted  into  a 
rough  line  leading  from  the  lesser  trochanter  to  the  linea  aspera. 

Relations. — By  it.-  >mi.  ,-ior  surface,  with  the  pubic   portion  of  the  fascia  lata. 


512 


THE  MUSCLES  AND    FASCIA. 


which  separates  it  from  the  femoral  vessels   and  internal  saphenous  vein ;   by  its 
posterior  surface,  with  the  capsular  ligament  of  the  hip-joint,  the  Adductor  brevis 

and  Obturator  externus  muscles,  the  obtura- 
tor vessels  and  nerve  being  interposed  ;  by 
its  outer  border,  with  the  Psoas,  a  cellular 
interval  separating  them,  through  which 
passes  the  internal  circumflex  vessels ;  by 
its  inner  border,  with  the  margin  of  the 
Adductor  longus. 

The  Adductor  longus,  the  most  super- 
ficial of  the  three  Adductors,  is  a  flat  tri- 
angular muscle  lying  on  the  same  plane  as 
the  Pectineus.  It  arises,  by  a  flat  narrow 
tendon,  from  the  front  of  the  os  pubis,  at 
the  angle  of  junction  of  the  crest  with  the 
symphysis ;  and  soon  expands  into  a  broad 
fleshy  belly,  which,  passing  downward,  back- 
ward, and  outward,  is  inserted,  by  an  apo- 
neurosis,  into  the  linea  aspera,  between  the 
Vastus  internus  and  the  Adductor  magnus, 
with  which  it  is  usually  blended. 

Relations. — By  its  anterior  surface,  with 
the  fascia  lata,  the  Sartorius,  and,  near  its 
insertion,  with  the  femoral  artery  and 
vein ;  by  its  posterior  surface,  with  the 
Adductor  brevis  and  magnus,  the  anterior 
branches  of  the  obturator  nerve,  and  with 
the  profunda  artery  and  vein  near  its  inser- 
tion ;  by  its  outer  border,  with  the  Pecti- 
neus ;  by  its  inner  border,  with  the  Gracilis. 

The  Pectineus  and  Adductor  longus  should 
now  be  divided  near  their  origin,  and  turned  down- 
ward, when  the  Adductor  brevis  and  Obturator  ex- 
ternus will  be  exposed. 

The  Adductor  brevis  is  situated  im- 
mediately behind  the  two  preceding  mus- 
cles. It  is  somewhat  triangular  in  form, 
and  afises  by  a  narrow  origin  from  the 
outer  surface  of  the  body  and  descending 
ramus  of  the  os  pubis,  between  the  Gracilis 
and  Obturator  externus.  Its  fibres,  passing 
backward,  outward,  and  downward,  are  in- 
serted, by  an  aponeurosis,  into  the  lower 
part  of  the  line  leading  from  the  lesser 
trochanter  to  the  linea  aspera  and  the  upper 
part  of  the  linea  aspera,  immediately  behind 
the  Pectineus  and  upper  part  of  the  Adduc- 
tor longus. 

Relations. — By  its  anterior  surface,  with 
the  Pectineus,  Adductor  longus,  profunda 
femoris  artery,  and  anterior  branches  of 
the  obturator  nerve ;  by  its  posterior  sur- 

Fio.327.-Deep  muscles  of  the  internal  femoral    face,      with      the      Adductor      magnus       and 
region.  '    . 

posterior    branch   of    the   obturator    nerve ; 

by  its  outer  border,  with  the  Obturator  externus  and  conjoined  tendon  of  the 
Psoas  and  Iliacus ;  by  its  inner  border,  with  the  Gracilis  and  Adductor  magnus. 


THE   INTERNAL    FEMORAL    REGION.  513 

This  muscle  is  pierced,  near  its  insertion,  by  the  middle  perforating  branch  of 
the  profunda  femoris  artery. 

The  Adductor  brevis  should  now  be  cut  away  sear  its  origin,  and  turned  outward,  when 
the  entire  extent  of  the  Adductor -inagnus  will  be  exposed. 

The  Adductor  magnus  is  a  large  triangular  muscle  forming  a  septum  between 
the  muscles  on  the  inner  and  those  on  the  back  of  the  thigh.  It  arises  from  a 
small  part  of  the  descending  ramus  of  the  os  pubis,  from  the  ascending  ramus 
of  the  ischium,  and  from  the  outer  margin  and  under  surface  of  the  tuberosity 
of  the  ischium.  Those  fibres  which  arise  from  the  ramus  of  the  os  pubis 
are  very  short,  horizontal  in  direction,  and  are  inserted  into  the  rough  line 
leading  from  the  great  trochanter  to  the  linea  aspera,  internal  to  the  Gluteus 
maximus;  those  from  the  ramus  of  the  ischium  are  directed  downward  and 
outward  with  different  degrees  of  obliquity,  to  be  inserted,  by  means  of  a  broad 
aponeurosis.  into  the  linea  aspera  and  the  upper  part  of  its  internal  prolonga- 
tion below.  The  internal  portion  of  the  muscle,  consisting  principally  of  those 
fibres  which  arise  from  the  tuberositv  of  the  ischium,  forms  a  thick  fleshy  mass 
consisting  of  coarse  bundles  which  descend  almost  vertically,  and  terminate  about 
the  lower  third  of  the  thigh  in  a  rounded  tendon,  which  is  inserted  into  the 
Adductor  tubercle  on  the  inner  condyle  of  the  femur,  being  connected  by  a  fibrous 
expansion  to  the  line  leading  upward  from  the  tubercle  to  the  linea  aspera. 
Between  the  two  portions  of  the  muscle  an  interval  is  left,  tendinous  in  front, 
fleshy  behind,  for  the  passage  of  the  femoral  vessels  into  the  popliteal  space.  The 
external  portion  of  the  muscle  at  its  attachment  to  the  femur  presents  three  or  four 
osseo-aponeurotic  openings,  formed  by  tendinous  arches  attached  to  the  bone,  from 
which  muscular  fibres  arise.  The  three  superior  of  these  apertures  are  for  the 
three  perforating  arteries,  and  the  fourth,  when  it  exists,  for  the  terminal  branch 
of  the  profunda. 

Relations. — By  its  anterior  surface,  with  the  Pectineus.  Adductor  brevis. 
Adductor  longus,  and  the  femoral  and  profunda  vessels  and  obturator  nerve ;  by 
its  posterior  surface,  with  the  great  sciatic  nerve,  the  Gluteus  maximus.  Biceps, 
Semitendinosus,  and  Semimembranosus.  By  its  superior  or  shortest  border  it  lies 
parallel  with  the  Quadratus  femoris,  the  internal  circumflex  artery  passing  between 
them  :  by  its  internal  or  longest  border,  with  the  Gracilis,  Sartorius,  and  fascia 
lata  :  by  its  external  or  attache-:1  border  it  is  inserted  into  the  femur  behind  the 
Adductor  brevis  and  Adductor  longus,  which  separate  it  from  the  Vastus  internus, 
and  in  front  of  the  Gluteus  maximus  and  short  head  of  the  Biceps,  which  separate 
it  from  the  A  astus  externus. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  obturator  nerve. 
The  Pectineus  receives  additional  branches  from  the  accessory  obturator  and  ante- 
rior crural,  and  the  Adductor  magnus  an  additional  branch  from  the  great  sciatic. 

Actions. — The  Pectineus  and  three  Adductors  adduct  the  thigh  powerfully : 
they  are  especially  used  in  horse  exercise,  the  flanks  of  the  horse  being  grasped 
between  the  knees  by  the  actions  of  these  muscles.  In  consequence  of  the  obliquity 
of  their  insertion  into  the  linea  aspera  they  rotate  the  thigh  outward,  assisting 
the  external  Rotators,  and  when  the  limb  has  been  abducted  they  draw  it  inward, 
carrying  the  thigh  across  that  of  the  opposite  side.  The  Pectineus  and  Adductor 
brevis  and  longus  assist  the  Psoas  and  Iliacus  in  flexing  the  thigh  upon  the  pelvis. 
In  progression,  also,  all  these  muscles  assist  in  drawing  forward  the  hinder  limb. 
The  Gracilis  assists  the  Sartorius  in  flexing  the  leg  and  rotating  it  inward ;  it  is 
also  an  adductor  of  the  thigh.  If  the  lower  extremities  are  fixed,  these  muscles 
may  take  their  fixed  point  from  below  and  act  upon  the  pelvis,  serving  to  maintain 
the  body  in  an  erect  posture,  or,  if  their  action  is  continued,  to  flex  the  pelvis 
forward  upon  the  femur. 

Surgical  Anatomy. — The  Adductor  longus  is  liable  to  be  severely  strained  in  those 
who  ride  much  on  horseback,  or  its  tendon  to  be  ruptured  by  suddenly  gripping  the  saddle. 
And.  occasionally,  especially  in  cavalry  soldiers,  the  tendon  may  become  ossified,  constituting  the 
"rider's  bone/' 

33 


514 


THE   MUSCLES   AND    FASCIAE. 


1.  Dissection  of 
gluteal  region. 


THE  HIP. 
Gluteal  Region. 

Gluteus  maximus.  Gemellus  superior. 

Gluteus  medius.  Obturator  internus. 

Gluteus  minimus.  Gemellus  inferior. 

Pyriformis.  Obturator  externus. 

Quadratus  femoris. 

Dissection  (Fig.  328). — The  subject  should  be  turned  on  its  face,  a  block  placed  beneath 
the  pelvis  to  make  the  buttocks  tense,  and  the  limbs  allowed  to  hang  over  the  end  of  the  table, 
with  the  foot  inverted  and  the  thigh  abducted.  Make  an  incision  through  the  integument  along 
the  crest  of  the  ilium  to  the  middle  of  the  sacrum,  and  thence  downward  to  the  tip  of  the  coccyx, 
and  carry  a  second  incision  from  that  point  obliquely  downward  and  outward  to  the  outer  side 
of  the  thigh,  four  inches  below  the  great  trochanter.  The  portion  of  integument  included 
between  these  incisions  is  to  be  removed  in  the  direction  shown  in  the  figure. 

The  Gluteus  maximus  (Fig.  329),  the  most  superficial  muscle  in  the  gluteal 
region,  is  a  very  broad  and  thick,  fleshy  mass  of  a  quadrilateral  shape,  which 
forms  the  prominence  of  the  nates.  Its  large  size  is  one  of  the  most  characteristic 
points  in  the  muscular  system  in  man,  connected  as  it  is  with  the  power  he  has  of 
maintaining  the  trunk  in  the  erect  posture.  In  structure  the  muscle  is  remarkably 
coarse,  being  made  up  of  muscular  fasciculi  lying  parallel  with  one  another,  and 

collected  together  into  large  bundles,  separated 
by  deep  cellular  intervals.  It  arises  from  the 
superior  gluteal  line  of  the  ilium  and  the  por- 
tion of  bone,  including  the  crest,  immediately 
behind  it ;  from  the  posterior  surface  of  the  lower 
part  of  the  sacrum,  the  side  of  the  coccyx,  the 
aponeurosis  of  the  Erector  spinae  muscle,  and 
the  great  sacro-sciatic  ligament.  The  fibres 
are  directed  obliquely  downward  and  outward ; 
those  forming  the  upper  together  with  the 
superficial  fibres  of  the  lower  portion  termi- 
nate in  a  thick  tendinous  lamina,  which  passes 
across  the  great  trochanter,  and  is  inserted  into 
the  fascia  lata  covering  the  outer  side  of  the 
thigh,  the  deep  fibres  of  the  lower  portion  be- 
ing inserted  by  a  tendon  into  the  rough  line 
leading  from  the  great  trochanter  to  the  linea 
aspera  between  the  Vastus  externus  and  Ad- 
ductor magnus. 

Three  synovial  bursce  are  usually  found  in 
relation  with  this  muscle.  One  of  these,  of 
large  size,  and  generally  multilocular,  separates 
it  from  the  great  trochanter.  A  second,  often 
wanting,  is  situated  on  the  tuberosity  of  the 
ischium.  A  third  is  found  between  the  tendon 
of  this  muscle  and  the  Vastus  externus. 

Relations. — By  its  superficial  surface,  Avith 
a  thin  fascia,  which  separates  it  from  the  sub- 
cutaneous tissue ;  by  its  deep  surface,  from 
above  downward,  with  the  ilium,  sacrum,  coccyx, 
and  great  sacro-sciatic  ligament,  part  of  the 
Gluteus  medius,  Pyriformis,  Gemelli,  Obturator 
internus,  Quadratus  femoris,  the  tuberosity  of 
poStFerior^i7w.i88ecti°n  °f  lower  extremity"  the  ischium,  great  trochanter,  the  origin  of  the 

Biceps,     Semitendinosus,      Semimembranosus, 

and  Adductor  magnus  muscles.     The  gluteal  vessels  and  superior  gluteal  nerve 
are  seen  issuing  from  the  pelvis  above  the  Pyriformis  muscle,  the  sciatic  and 


<3     /  3.  Back  of  thigh. 


2.  Popliteal  space 


4-  Back  of  leg. 


5.  Sole  of  foot. 


THE    GLUTEAL    REGION. 


515 


internal  pudic  vesels  and  nerves, 
and  muscular  branches  from  the 
sacral  plexus  below  it.  Its  up- 
per border  is  connected  with, the 
Gluteus  medius  by  the  fascia 
lata  :  its  lower  border  is  free  and 
prominent. 

Dissection. — Now  divide  the  Glu- 
teus maximus  near  its  origin  by  a  ver- 
tical incision  carried  from  its  upper  to 
its  lower  border:  a  cellular  interval 
will  be  exposed,  separating  it  from 
the  Glutens  medius  and  External 
rotator  muscles  beneath.  The  upper 
portion  of  the  muscle  is  to  be  alto- 
gether detached,  and  the  lower  portion 
turned  outward :  the  loose  areolar 
filling  up  the  interspace  be- 
tween the  trochanter  major  and  tuber- 
osity  of  the  ischium  being  removed, 
the  parts  already  enumerated  as  ex- 
posed by  the  removal  of  this  muscle 
will  be  seen. 

The  Gluteus  medius  is  a 
broad,  thick,  radiated  muscle, 
situated  on  the  outer  surface  of 
the  pelvis.  Its  posterior  third  is 
covered  by  the  Gluteus  maximus ; 
its  anterior  two-thirds  by  the 
fascia  lata.  which  separates  it 
from  the  integument.  It  arises 
from  the  outer  surface  of  the 
ilium,  between  the  superior  and 
middle  gluteal  lines,  and  from 
the  outer  lip  of  that  portion  of 
the  crest  which  is  between  them ; 
it  also  arises  from  the  dense 
fascia  ( Gluteal  aponeurosis)  cover- 
ing its  outer  surface.  The  fibres 
converge  to  a  strong  flattened 
tendon  which  is  inserted  into  the 
oblique  line  which  traverses  the 
outer  surface  of  the  great  tro- 
chanter. A  synovial  bursa  sepa- 
rates the  tendon  of  the  muscle 
from  the  surface  of  the  trochanter 
in  front  of  its  insertion. 

Relations. — By  its  superficial 
surface,  with  the  Gluteus  maxi- 
mus behind,  the  Tensor  vaginse 
femoris  and  deep  fascia  in.  front ; 
by  its  deep  surf-'i •:•>'-.  with  the 
Gluteus  minimus  and  the  gluteal 
vessels  and  superior  gluteal  nerve. 
<ttf-rior  border  is  blended 
with  the  Gluteus  minimus.  Its 
/<//•  border  lies  parallel  with 
the  Pyriformis.  the  gluteal  ves- 
sels intervening. 


FIG.  329.— Muscles  of  the  hip  and  thigh. 


516  THE  MUSCLES  AND   FASCIA. 

This  muscle  should  now  be  divided  near  its  insertion  and  turned  upward,  when  the  Gluteus 
minimus  will  be  exposed. 

The  G-luteus  minimus,  the  smallest  of  the  three  Glutei,  is  placed  immediately 
beneath  the  preceding.  It  is  fan-shaped,  arising  from  the  outer  surface  of  the 
ilium,  between  the  middle  and  inferior  gluteal  lines,  and  behind,  from  the  margin 
of  the  great  sacro-sciatic  notch ;  the  fibres  converge  to  the  deep  surface  of  a 
radiated  aponeurosis,  which,  terminating  in  a  tendon,  is  inserted  into  an  impres- 
sion on  the  anterior  border  of  the  great  trochanter.  A  synovial  bursa  is  inter- 
posed between  the  tendon  and  the  great  trochanter. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  medius,  and  the  gluteal 
vessels  and  superior  gluteal  nerve  ;  by  its  deep  surface,  with  the  ilium,  the  reflected 
tendon  of  the  Rectus  femoris,  and  capsular  ligament  of  the  hip-joint.  Its  anterior 
margin  is  blended  with  the  Gluteus  medius;  its  posterior  margin  is  often  joined 
with  the  tendon  of  the  Pyriformis. 

The  Pyriformis  is  a  flat  muscle,  pyramidal  in  shape,  lying  almost  parallel  with 
the  posterior  margin  of  the  Gluteus  medius.  It  is  situated  partly  within  the  pelvis 
at  its  posterior  part  and  partly  at  the  back  of  the  hip-joint.  It  arises  from  the 
front  of  the  sacrum  by  three  fleshy  digitations  attached  to  the  portions  of  bone 
between  the  first,  second,  third,  and  fourth  anterior  sacral  foramina,  and  also  from 
the  groove  leading  from  the  foramina :  a  few  fibres  also  arise  from  the  margin  of 
the  great  sacro-sciatic  foramen  and  from  the  anterior  surface  of  the  great  sacro- 
sciatic  ligament.  The  muscle  passes  out  of  the  pelvis  through  the  great  sacro- 
sciatic  foramen,  the  upper  part  of  which  it  fills,  and  is  inserted  by  a  rounded 
tendon  into  the  upper  border  of  the  great  trochanter,  behind,  but  often  blended 
with,  the  tendon  of  the  Obturator  internus  and  Gemelli  muscles. 

Relations. — By  its  anterior  surface,  within  the  pelvis,  with  the  Rectum  (espe- 
cially on  the  left  side),  the  sacral  plexus  of  nerves,  and  the  branches  of  the  internal 
iliac  vessels  ;  external  to  the  pelvis,  with  the  os  innoniinatum  and  capsular  liga- 
ment of  the  hip-joint;  by  its  posterior  surface,  within  the  pelvis,  with  the  sacrum, 
and  external  to  it,  with  the  Gluteus  maximus;  by  its  upper  border,  with  the 
Gluteus  medius,  from  which  it  is  separated  by  the  gluteal  vessels  and  superior 
gluteal  nerve ;  by  its  lower  border,  with  the  Gemellus  superior  and  Coccygeus, 
the  sciatic  vessels  and  nerves,  the  internal  pudic  vessels  and  nerve,  and  muscular 
branches  from  the  sacral  plexus,  passing  from  the  pelvis  in  the  interval  between  the 
two  muscles. 

The  Obturator  membrane  is  a  thin  layer  of  interlacing  fibres  which  closes  the 
obturator  foramen.  It  is  attached,  externally,  to  the  margin  of  the  foramen ; 
internally,  to  the  posterior  surface  of  the  ischio-pubic  ramus,  internal  to  the  inner 
margin  of  the  foramen.  It  is  occasionally  incomplete,  and  presents  at  its  upper 
and  outer  part  a  small  canal,  which  is  bounded  below  by  a  thickened  band  of  fibres, 
for  the  passage  of  the  obturator  vessels  and  nerve.  Each  obturator  muscle  is 
connected  with  this  membrane. 

Dissection. — The  next  muscle,  as  well  as  the  origin  of  the  Pyriformis,  can  only  be  seen 
when  the  pelvis  is  divided  and  the  viscera  removed. 

The  Obturator  internus,  like  the  preceding  muscle,  is  situated  partly  within 
the  cavity  of  the  pelvis  and  partly  at  the  back  of  the  hip-joint.  It  arises  from  the 
inner  surface  of  the  anterior  and  external  wall  of  the  pelvis,  around  the  inner  side 
of  the  obturator  foramen,  being  attached  to  the  descending  ramus  of  the  os  pubis 
and  the  ascending  ramus  of  the  ischium,  and  at  the  side  to  the  inner  surface  of 
the  body  of  the  ischium,  between  the  margin  of  the  obturator  foramen  in  front 
and  the  great  sacro-sciatic  notch  behind,  and  to  the  inner  surface  of  the  ilium 
below  the  brim  of  the  true  pelvis.  It  also  arises  from  the  inner  surface  of  the 
obturator  membrane,  except  at  its  lower  part,  and  from  the  tendinous  arch  which 
completes  the  canal  for  the  passage  of  the  obturator  vessels  and  nerve.  The  fibres 
are  directed  backward  and  downward,  and  terminate  in  four  or  five  tendinous 
bands  which  are  found  on  its  deep  surface :  these  bands  are  reflected  at  a  right 


THE    GLUTEAL   REGION.  517 

angle  over  the  inner  surface  of  the  tuberosity  of  the  ischium,  which  is  grooved  for 
their  reception  :  the  groove  is  covered  with  cartilage  and  lined  with  a  synovial 
bursa.  The  muscle  leaves  the  pelvis  by  the  lesser  sacro-sciatic  notch,  and  the 
tendinous  bands  unite  into  a  single  flattened  tendon,  which  passes  horizontally 
outward,  and,  after  receiving  the  attachment  of  the  Gemelli,  is  inserted  into  the 
inner  surface  of  the  great  trochanter  in  front  of  the  Obturator  externus.  A 
synovial  bursa.  narrow  and  elongated  in  form,  is  usually  found  between  the  tendon 
of  this  muscle  and  the  capsular  ligament  of  the  hip  :  it  occasionally  communicates 
with  the  bursa  between  the  tendon  and  the  tuberosity  of  the  ischium,  the  two 
forming  a  single  sac. 

In  order  to  display  the  peculiar  appearances  presented  by  the  tendon  of  this  muscle,  it  must 
be  divided  near  its  insertion  and  reflected  outward. 

Relations. —  Within  the  pelvis  this  muscle  is  in  relation,  by  its  anterior  surface, 
with  the  obturator  membrane  and  inner  surface  of  the  anterior  wall  of  the  pelvis; 
by  its  posterior  surface*  with  the  pelvic  and  obturator  fasciae,  which  separate  it  from 
the  Levator  ani ;  and  it  is  crossed  by  the  internal  pudic  vessels  and  nerve.  This 
surface  forms  the  outer  boundary  of  the  ischio-rectal  fossa.  External  to  the  pelvis 
it  is  covered  by  the  great  sciatic  nerve  and  Gluteus  maximus,  and  rests  on  the  back 
part  of  the  hip-joint. 

The  Gemelli  are  two  small  muscular  fasciculi,  accessories  to  the  tendon  of  the 
Obturator  internus,  which  is  received  into  a  groove  between  them.  They  are  called 
superior  and  inferior. 

The  Gemellus  superior,  the  smaller  of  the  two,  arises  from  the  outer  surface 
of  the  spine  of  the  ischium,  and.  passing  horizontally  outward,  becomes  blended 
with  the  upper  part  of  the  tendon  of  the  Obturator  internus,  and  is  inserted  with 
it  into  the  inner  surface  of  the  great  trochanter.  This  muscle  is  sometimes 
wanting. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the 
sciatic  vessels  and  nerves ;  by  its  deep  surface,  with  the  capsule  of  the  hip-joint ; 
by  its  )ipp>  r  }'»r<l>:r.  with  the  lower  margin  of  the  Pyriformis  ;  by  its  lower  border, 
with  the  tendon  of  the  Obturator  internus. 

The  Gemellus  inferior  arises  from  the  upper  part  of  the  tuberosity  of  the 
ischium.  where  it  forms  the  lower  edge  of  the  groove  for  the  Obturator  internus 
tendon,  and,  passing  horizontally  outward,  is  blended  with  the  lower  part  of  the 
tendon  of  the  Obturator  internus,  and  is  inserted  with  it  into  the  inner  surface  of 
the  great  trochanter. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the 
sciatic  vessels  and  nerves ;  by  its  deep  surface,  with  the  capsular  ligament  of  the 
hip-joint :  by  its  upper  border,  with  the  tendon  of  the  Obturator  internus ;  by  its 
lower  border,  with  the  tendon  of  the  Obturator  externus  and  Quadratus  femoris. 

The  Quadratus  femoris  is  a  short,  flat  muscle,  quadrilateral  in  shape  (hence 
its  name),  situated  between  the  Gemellus  inferior  and  the  upper  margin  of  the 
Adductor  magnus.  It  arises  from  the  external  lip  of  the  tuberosity  of  the  ischium, 
and.  proceeding  horizontally  outward,  is  inserted  into  the  upper  part  of  the  linea 
quadrati :  that  is.  the  line  which  crosses  the  posterior  intertrochanteric  line.  A 
synovial  bursa  is  often  found  between  the  under  surface  of  this  muscle  and  the 
lesser  trochanter.  to  which  it  extends. 

Relations. — By  its  posterior  surface,  with  the  Gluteus  maximus  and  the  sciatic 
vessels  and  nerves ;  by  its  anterior  surface,  with  the  tendon  of  the  Obturator 
externus  and  trochanter  minor  and  with  the  capsule  of  the  hip-joint ;  by  its 
upper  border,  with  the  Gemellus  inferior.  Its  lower  border  is  separated  from  the 
Adductor  magnus  by  the  terminal  branches  of  the  internal  circumflex  vessels. 

Dissection. — In  order  to  expose  the  next  muscle  (the  Obturator  externus),  it  is  necessary 
to  remove  the  Psoas.  Iliacus,  Pectineus,  and  Adductor  brevis  and  longus  muscles  from  the  front 
and  inner  side  of  the  thigh,  and  the  Gluteus  maximus  and  Quadratus  femoris  from  the  back 
part.  Its  dissection  should,  consequently,  be  postponed  until  the  muscles  of  the  anterior  and 
internal  femoral  regions  have  been  explained. 


518  THE  MUSCLES  AND   FASCIAE. 

The  Obturator  externus  (Fig.  327)  is  a  flat,  triangular  muscle  which  covers  the 
outer  surface  of  the  anterior  wall  of  the  pelvis.  It  arises  from  the  margin  of  bone 
which  forms  the  inner  boundary  of  the  obturator  foramen — viz.  from  the  body  and 
descending  ramus  of  the  os  pubis  and  the  ramus  of  the  ischium  ;  it  also  arises  from 
the  inner  two-thirds  of  the  outer  surface  of  the  obturator  membrane,  and  from  the 
tendinous  arch  which  completes  the  canal  for  the  passage  of  the  obturator  vessels 
and  nerves.  The  fibres  converging  pass  backward,  outward,  and  upAvard,  and 
terminate  in  a  tendon  which  runs  under  and  across  the  back  part  of  the  hip- 
joint  and  is  inserted  into  the  digital  fossa  of  the  femur. 

Relations. — By  its  anterior  surface,  with  the  Psoas,  Iliacus,  Pectineus, 
Adductor  magnus,  Adductor  brevis,  and  Gracilis,  and  more  externally,  with  the 
neck  of  the  femur  and  capsule  of  the  hip-joint;  by  its  posterior  surface,  with  the 
obturatoV  membrane  and  Quadratus  femoris. 

Nerves. — The  Gluteus  maximus  is  supplied  by  the  inferior  gluteal  nerve  from 
the  sacral  plexus  ;  the  Gluteus  medius  and  minimus,  by  the  superior  gluteal ;  the 
Pyriformis,  Gemelli,  Obturator  internus,  and  Quadratus  femoris,  by  branches  from 
the  sacral  plexus ;  and  the  Obturator  externus,  by  the  obturator  nerve. 

Actions. — The  Gluteus  maximus,  when  it  takes  its  fixed  point  from  the  pelvis, 
extends  the  femur  and  brings  the  bent  thigh  into  a  line  with  the  body.  Taking 
its  fixed  point  from  below,  it  acts  upon  the  pelvis,  supporting  it  and  the  Avhole 
trunk  upon  the  head  of  the  femur,  which  is  especially  obvious  in  standing  on  one 
leg.  Its  most  powerful  action  is  to  cause  the  body  to  regain  the  erect  position 
after  stooping  by  drawing  the  pelvis  backward,  being  assisted  in  this  action  by 
the  Biceps,  Semitendinosus,  and  Semimembranosus.  The  Gluteus  maximus  is  a 
tensor  of  the  fascia  lata,  and  by  its  connection  with  the  ilio-tibial  band  it  steadies 
the  femur  on  the  articular  surface  of  the  tibia  during  standing,  when  the  extensor 
muscles  are  relaxed.  The  lower  part  of  the  muscle  also  acts  as  an  abductor  and 
external  rotator  of  the  limb.  The  Gluteus  medius  and  minimus  abduct  the 
thigh  when  the  limb  is  extended,  and  are  principally  called  into  action  in 
supporting  the  body  on  one  limb,  in  conjunction  with  the  Tensor  vaginae  femoris. 
Their  anterior  fibres,  by  drawing  the  great  trochanter  forward,  rotate  the 
thigh  inward,  in  which  action  they  are  also  assisted  by  the  Tensor  vaginge 
femoris.  Their  posterior  fibres  rotate  the  thigh  outward.  The  remaining  muscles 
are  powerful  rotators  of  the  thigh  outward.  In  the  sitting  posture,  when  the  thigh 
is  flexed  upon  the  pelvis,  their  action  as  rotator  ceases,  and  they  become  abductors, 
with  the  exception  of  the  Obturator  externus,  which  still  rotates  the  femur  out- 
ward. When  the  femur  is  fixed,  the  Pyriformis  and  Obturator  muscles  serve  to 
draw  the  pelvis  forward  if  it  has  been  inclined  backward,  and  assist  in  steadying 
it  upon  the  head  of  the  femur. 

Posterior  Femoral  Region. 

Biceps.  Semitendinosus.  Semimembranosus. 

Dissection  (Fig.  328). — Make  a  vertical  incision  along  the  middle  of  the  thigh,  from  the 
lower  fold  of  the  nates  to  about  three  inches  below  the  back  of  the  knee-joint,  and  there 
connect  it  with  a  transverse  incision  carried  from  the  inner  to  the  outer  side  of  the  leg.  Make 
a  third  incision  transversely  at  the  junction  of  the  middle  with  the  lower  third  of  the  thigh. 
The  integument  having  been  removed  from  the  back  of  the  knee  and  the  boundaries  of 
the  popliteal  space  examined,  the  removal  of  the  integument  from  the  remaining  part  of  the 
thigh  should  be  continued,  when  the  fascia  and  muscles  of  this  region  will  be  exposed. 

The  Biceps  (Biceps  flexor  cruris)  is  a  large  muscle,  of  considerable  length, 
situated  on  the  posterior  and  outer  aspect  of  the  thigh  (Fig.  329).  It  arises  by 
two  heads.  One,  the  long  head,  arises  from  the  lower  and  inner  facet  on  the 
back  part  of  the  tuberosity  of  the  ischium  by  a  tendon  common  to  it  and  the 
Semitendinosus.  The  femoral,  or  short  head,  arises  from  the  outer  lip  of  the 
linea  aspera,  between  the  Adductor  magnus  and  Vastus  externus,  extending  up 
almost  as  high  as  the  insertion  of  the  Gluteus  maximus,  and  from  the  external  supra- 
condylar  line  to  within  two  inches  of  the  outer  condyle ;  it  also  arises  from  the 


THE   POSTERIOR   FEMORAL    REGION.  519 

external  intermuscular  septum.  The  fibres  of  the  long  head  form  a  fusiform 
belly,  which,  passing  obliquely  doAvnward  and  a  little  outward,  terminates  in  an 
aponeurosis  which  covers  the  posterior  surface  of  the  muscle  and  receives  the 
fibres  of  the  short  head :  this  aponeurosis  becomes  gradually  contracted  into  a 
tendon,  which  is  inserted  into  the  outer  side  of  the  head  of  the  fibula,  and  by 
a  small  slip  into  the  lateral  surface  of  the  external  tuberosity  of  the  tibia.  At 
its  insertion  the  tendon  divides  into  two  portions,  which  embrace  the  long 
external  lateral  ligament  of  the  knee-joint,  a  strong  prolongation  being  sent  for- 
ward to  the  outer  tuberosity  of  the  tibia,  which  gives  off  an  expansion  to  the  fascia 
of  the  leg.  The  tendon  of  this  muscle  forms  the  outer  hamstring. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  above,  with 
the  fascia  lata  and  integument  in  the  rest  of  its  extent;  by  its  deep  surface, 
with  the  Semimembranosus,  Adductor  magnus,  and  Yastus  externus,  the  great 
sciatic  nerve,  and,  near  its  insertion,  with  the  external  head  of  the  Gastro- 
cnemius,  Plantaris,  the  superior  external  articular  artery,  and  the  external  popliteal 
nerve. 

The  Semitendinosus,  remarkable  for  the  great  length  of  its  tendon,  is  situated 
at  the  posterior  and  inner  aspect  of  the  thigh.  It  arises  from  the  lower  and  inner 
facet  on  the  tuberosity  of  the  ischium  by  a  tendon  common  to  it  and  the  long  head 
of  the  Biceps ;  it  also  arises  from  an  aponeurosis  which  connects  the  adjacent 
surfaces  of  the  two  muscles  to  the  extent  of  about  three  inches  after  their  origin. 
Ir  forms  a  fusiform  muscle,  which,  passing  downward  and  inward,  terminates  a 
little  below  the  middle  of  the  thigh  in  a  long  round  tendon  which  lies  along  the 
inner  side  of  the  popliteal  space,  then  curves  around  the  inner  tuberosity  of  the 
tibia,  and  is  inserted  into  the  upper  part  of  the  inner  surface  of  the  shaft  of  that 
bone  nearly  as  far  forward  as  its  anterior  border.  This  tendon  is  surrounded  by 
the  tendon  of  the  Sartorius,  and  lies  below  that  of  the  Gracilis,  to  which  it  is 
united.  A  tendinous  intersection  is  usually  observed  about  the  middle  of  the 
muscle. 

Relations. — By  its  superti<--ial  surface,  with  the  Gluteus  maximus  and  fascia 
lata :  by  its  deep  surface,  with  the  Semimembranosus,  Adductor  magnus,  inner 
head  of  the  Gastrocnemius,  and  internal  lateral  ligament  of  the  knee-joint. 

The  Semimembranosus,  so  called  from  the  membranous  expansion  on  its 
anterior  and  posterior  surfaces,  is  situated  at  the  back  part  and  inner  side  of  the 
thigh.  It  arises  by  a  thick  tendon  from  the  upper  and  outer  facet  on  the  back 
part  of  the  tuberosity  of  the  ischium,  above  and  to  the  outer  side  of  the  Biceps 
and  Semitendinosus.  and  is  inserted  into  the  groove  on  the  inner  and  back  part  of 
the  inner  tuberosity  of  the  tibia,  beneath  the  internal  lateral  ligament.  The 
tendon  of  the  muscle  at  its  origin  expands  into  an  aponeurosis  which  covers  the 
upper  part  of  its  anterior  surface :  from  this  aponeurosis  muscular  fibres  arise, 
and  converge  to  another  aponeurosis,  which  covers  the  lower  part  of  its  posterior 
surface  and  contracts  into  the  tendon  of  insertion.  The  tendon  of  the  muscle  at 
its  insertion  gives  off  two  fibrous  expansions ;  one  of  these,  of  considerable  size, 
passes  upward  and  outward  to  be  inserted  into  the  back  part  of  the  outer  con- 
dyle  of  the  femur,  forming  part  of  the  posterior  ligament  of  the  knee-joint.  The 
second  is  continued  downward  to  the  fascia  which  covers  the  Popliteus  muscle. 
The  tendon  also  sends  a  few  fibres  to  join  the  internal  lateral  ligament  of  the 
joint. 

The  tendons  of  the  two  preceding  muscles,  with  that  of  the  Gracilis,  form  the 
inner  hamstring. 

Relations. — By  its  superficial  surface,  with  the  Semitendinosus,  Biceps,  and 
fascia  lata  :  by  its  deep  surface,  with  the  popliteal  vessels,  Adductor  magnus,  and 
inner  head  of  the  Gastrocnemius,  from  which  it  is  separated  by  a  synovial  bursa ; 
by  its  inner  border,  with  the  Gracilis;  by  its  outer  border,  with  the  great  sciatic 
nerve  and  its  internal  popliteal  branch. 

Nerves. — The  muscles  of  this  region  are  supplied  by  the  great  sciatic  nerve. 

Actions. — The  hamstring  muscles  flex   the  leg  upon  the  thigh.     When  the 


520 


THE   MUSCLES  AND    FASCIAE. 


Tibi 


rr 


leg. 


FIG.  330.— Muscles  of  the  front  of  the 


knee  is  semiflexed,  the  Biceps,  in  consequence 
of  its  oblique  direction  downward  and  outward, 
rotates  the  leg  slightly  outward ;  and  the  Semi- 
tendinosus,  and  to  a  slight  extent  the  Semimem- 
branosus,  rotate  the  leg  inward,  assisting  the  Pop- 
liteus.  Taking  their  fixed  point  from  below,  these 
muscles  serve  to  support  the  pelvis  upon  the  head 
of  the  femur  and  to  draw  the  trunk  directly  back- 
ward, as  in  feats  of  strength,  when  the  body  is 
thrown  backward  in  the  form  of  an  arch. 

Surgical  Anatomy.— The  tendons  of  these  muscles 
occasionally  require  subcutaneous  division  in  some  forms  of 
spurious  ankylosis  of  the  knee-joint  dependent  upon  per- 
manent contraction  and  rigidity  of  the  Flexor  muscles,  or 
from  stiffening  of  the  ligamentous  and  other  tissues  sur- 
rounding the  joint,  the  result  of  disease.  This  is  effected  by 
putting  the  tendon  upon  the  stretch,  and  inserting  a  nar- 
row, sharp-pointed  knife  between  it  and  the  skin  :  the  cut- 
ting edge  being  then  turned  toward  the  tendon,  it  should 
be  divided,  taking  great  care  that  the  wound  in  the  skin  is 
not  at  the  same  time  enlarged.  The  relation  of  the  external 
popliteal  nerve  to  the  tendon  of  the  Biceps  must  always  be 
borne  in  mind  in  dividing  this  tendon. 

THE  LEG. 

Dissection  (Fig.  325). — The  knee  should  be  bent,  a 
block  placed  beneath  it,  and  the  foot  kept  in  an  extended 
position ;  then  make  an  incision  through  the  integument  in 
the  middle  line  of  the  leg  to  the  ankle,  and  continue  it  along 
the  dorsum  of  the  foot  to  the  toes.  Make  a  second  incision 
transversely  across  the  ankle,  and  a  third  in  the  same  direc- 
tion across  the  bases  of  the  toes ;  remove  the  flaps  of  integu- 
ment included  between  these  incisions  in  order  to  examine 
the  deep  fascia  of  the  leg. 

The  Deep  fascia  of  the  Leg  forms  a  complete 
investment  to  the  muscles,  but  is  not  continued 
over  the  subcutaneous  surfaces  of  the  bones.  It  is 
continuous  above  with  the  fascia  lata,  receiving  an 
expansion  from  the  tendon  of  the  Biceps  on  the 
outer  side,  and  from  the  tendons  of  the  Sartorius, 
Gracilis,  and  Semitendinosus  on  the  inner  side ;  in 
front  it  blends  with  the  periosteum  covering  the 
subcutaneous  surface  of  the  tibia,  and  with  that 
covering  the  head  and  external  malleolus  of  the 
fibula ;  below  it  is  continuous  with  the  annular 
ligaments  of  the  ankle.  It  is  thick  and  dense  in 
the  upper  and  anterior  part  of  the  leg,  and  gives 
attachment,  by  its  deep  surface,  to  the  Tibialis 
anticus  and  Extensor  longus  digitorum  muscles, 
but  thinner  behind,  where  it  covers  the  Gastro- 
cnemius  and  Soleus  muscles.  Over  the  popliteal 
space  it  is  much  strengthened  by  transverse  fibres 
which  stretch  across  from  the  inner  to  the  outer 
hamstring  muscles,  and  it  is  here  perforated  by  the 
external  saphenous  vein.  Its  deep  surface  gives 
off,  on  the  outer  side  of  the  leg,  two  strong  inter- 
muscular  septa  which  enclose  the  Peronei  muscles, 
and  separate  them  from  the  muscles  on  the  anterior 
and  posterior  tibial  regions  and  several  smaller  and 
more  slender  processes  which  enclose  the  indi- 


THE   ANTERIOR    TIBIO-FIBULAR   REGION.  521 

vidual  muscles  in  each  region ;  at  the  same  time  a  broad  transverse  intermuscular 
septum,  called  the  deep  transverse  fascia  of  the  leg,  intervenes  between  the  super- 
ficial and  deep  muscles  in  the  posterior  tibio-fibular  region. 

Xovr  remove  the  fascia  by  dividing  it  in  the  same  direction  as  the  integument,  excepting 
opposite  the  ankle,  where  it  should  be  left  entire.  Commence  the  removal  of  the  fascia  from 
below,  opposite  the  tendons,  and  detach  it  in  the  line  of  direction  of  the  muscular  fibres. 

Muscles  of  the  Leg. — These  may  be  subdivided  into  three  groups :  those  on  the 
anterior,  those  on  the  posterior,  and  those  on  the  outer  side. 

Anterior  Tibio-fibular  Region. 

Tibialis  anticus.  Extensor  longus  digitorum. 

Extensor  proprius  hallucis.  Peroneus  tertius. 

The  Tibialis  anticus  is  situated  on  the  outer  side  of  the  tibia ;  it  is  thick  and 
fleshy  at  its  upper  part,  tendinous  below.  It  arises  from  the  outer  tuberosity  and 
upper  two-thirds  of  the  external  surface  of  the  shaft  of  the  tibia  ;  from  the  adjoin- 
ing part  of  the  interosseous  membrane  ;  from  the  deep  surface  of  the  fascia  ;  and 
from  the  intermuscular  septum  between  it  and  the  Extensor  longus  digitorum : 
the  fibres  pass  vertically  downward,  and  terminate  in  a  tendon  which  is  apparent 
on  the  anterior  surface  of  the  muscle  at  the  lower  third  of  the  leg.  After  passing 
through  the  innermost  compartment  of  the  anterior  annular  ligament,  it  is  inserted 
into  the  inner  and  under  surface  of  the  internal  cuneiform  bone  and  base  of  the 
metatarsal  bone  of  the  great  toe. 

Relations. — By  its  anterior  surface,  with  the  fascia  and  with  the  annular  liga- 
ment :  by  its  posterior  surface,  with  the  interosseous  membrane,  tibia,  ankle-joint, 
and  inner  side  of  the  tarsus:  this  surface  also  overlaps  the  anterior  tibial  vessels 
and  nerve  in  the  upper  part  of  the  leg.  By  its  inner  surface,  with  the  tibia;  by 
its  outer  surface,  with  the  Extensor  longus  digitorum  and  Extensor  proprius  hal- 
lucis, and  the  anterior  tibial  vessels  and  nerve. 

The  Extensor  proprius  hallucis  is  a  thin,  elongated,  and  flattened  muscle  situ- 
ated between  the  Tibialis  anticus  and  Extensor  longus  digitorum.  It  arises  from 
the  anterior  surface  of  the  fibula  for  about  the  middle  two-fourths  of  its  extent,  its 
origin  being  internal  to  that  of  the  Extensor  longus  digitorum ;  it  also  arises  from 
the  interosseous  membrane  to  a  similar  extent.  The  fibres  pass  downward,  and 
terminate  in  a  tendon  which  occupies  the  anterior  border  of  the  muscle,  passes 
through  a  distinct  compartment  in  the  horizontal  portion  of  the  annular  ligament, 
crosses  the  anterior  tibial  vessels  near  the  bend  of  the  ankle,  and  is  inserted  into 
the  base  of  the  last  phalanx  of  the  great  toe.  Opposite  the  metatarso-phalangeal 
articulation  the  tendon  gives  off  a  thin  prolongation  on  each  side,  which  covers 
the  surface  of  the  joint.  It  usually  sends  an  expansion  from  the  inner  side  of  the 
tendon,  to  be  inserted  into  the  base  of  the  first  phalanx. 

Eelations. — By  its  anterior  surface,  with  the  fascia  and  the  anterior  annular 
ligament:  by  its  posterior  surface,  with  the  interosseous  membrane,  fibula,  tibia, 
ankle-joint,  and  Extensor  brevis  digitorum  ;  by  its  outer  side,  with  the  Extensor 
longus  digitorum  above,  the  dorsalis  pedis  vessels  and  anterior  tibial  nerve  below ; 
by  its  inner  •*''</••.  with  the  Tibialis  anticus  and  the  anterior  tibial  vessels  above. 

The  Extensor  longus  digitorum  is  an  elongated,  flattened,  semipennifonn 
muscle  situated  the  most  externally  of  all  the  muscles  on  the  fore  part  of  the  leg. 
It  arises  from  the  outer  tuberosity  of  the  tibia  ;  from  the  upper  three-fourths  of 
the  anterior  surface  of  the  shaft  of  the  fibula ;  from  the  interosseous  membrane ; 
from  the  deep  surface  of  the  fascia  ;  and  from  the  intermuscular  septa  between  it 
and  the  Tibialis  anticus  on  the  inner  and  the  Peronei  on  the  outer  side.  The  tendon 
enters  a  canal  in  the  annular  ligament  with  the  Peroneus  tertius,  and  divides  into 
four  slips,  which  run  across  the  dorsum  of  the  foot  and  are  inserted  into  the  second 
and  third  phalanges  of  the  four  lesser  toes.  The  mode  in  which  the  tendons 
are  inserted  is  the  following :  The  three  inner  tendons  opposite  the  metatarso- 
phalangeal  articulation  are  joined,  on  their  outer  side,  by  a  tendon  of  the  Extensor 


522  THE  MUSCLES  AND   FASCIAE. 

brevis  digitorum.  They  all  receive  a  fibrous  expansion  from  the  Interossei  and 
Lumbricales,  and  then  spread  out  into  a  broad  aponeurosis,  which  covers  the  dorsal 
surface  of  the  first  phalanx :  this  aponeurosis,  at  the  articulation  of  the  first  with 
the  second  phalanx,  divides  into  three  slips — a  middle  one,  Avhich  is  inserted  into 
the  base  of  the  second  phalanx,  and  two  lateral  slips,  which,  after  uniting  on  the 
dorsal  surface  of  the  second  phalanx,  are  continued  onward,  to  be  inserted  into 
the  base  of  the  third. 

Relations. — By  its  anterior  surface,  Avith  the  fascia  and  the  annular  ligament ; 
by  its  posterior  surface,  with  the  fibula,  interosseous  membrane,  ankle-joint,  and 
Extensor  brevis  digitorum ;  by  its  inner  side,  with  the  Tibialis  anticus,  Extensor 
proprius  hallucis,  and  anterior  tibial  vessels  and  nerve ;  by  its  outer  side,  with  the 
Peroneus  longus  and  brevis. 

The  Peroneus  tertius  is  a  part  of  the  Extensor  longus  digitorum,  and  might 
be  described  as  its  fifth  tendon.  The  fibres  belonging  to  this  tendon  arise  from 
the  lower  fourth  of  the  anterior  surface  of  the  fibula,  from  the  lower  part  of  the 
interosseous  membrane,  and  from  an  intermuscular  septum  between  it  and  the 
Peroneus  brevis.  The  tendon,  after  passing  through  the  same  canal  in  the 
annular  ligament  as  the  Extensor  longus  digitorum,  is  inserted  into  the  dorsal 
surface  of  the  base  of  the  metatarsal  bone  of  the  little  toe,  on  its  inner  side.  This 
muscle  is  sometimes  wanting. 

Nerves. — These  muscles  are  supplied  by  the  anterior  tibial  nerve. 

Actions. — The  Tibialis  anticus  and  Peroneus  tertius  are  the  flexors  of  the 
tarsus  upon  the  leg  ;  the  former  muscle,  from  the  obliquity  in  the  direction  of  its 
tendon,  raises  the  inner  border  of  the  foot ;  and  the  latter,  acting  with  the  Pero- 
neus brevis  and  longus,  draws  the  outer  border  of  the  foot  upward  and  the  sole 
outward.  The  Extensor  longus  digitorum  and  Extensor  proprius  hallucis  extend 
the  phalanges  of  the  toes,  the  action  being  the  same  as  that  of  the  corresponding 
muscles  of  the  hand,  and  flex  the  tarsus.  Taking  their  fixed  point  from  below  in 
the  erect  posture,  all  these  muscles  serve  to  fix  the  bones  of  the  leg  in  the  perpen- 
dicular position. 

Posterior  Tibio-fibular  Region. 

Dissection  (Fig.  328). — Make  a  vertical  incision  along  the  middle  line  of  the  back  of  the 
leg,  from  the  lower  part  of  the  popliteal  space  to  the  heel,  connecting  it  below  by  a  transverse 
incision  extending  between  the  two  malleoli ;  the  flaps  of  integument  being  removed,  the  fascia 
and  muscles  should  be  examined. 

The  muscles  in  this  region  of  the  leg  are  subdivided  into  two  layers — super- 
ficial and  deep.  The  superficial  layer  constitutes  a  powerful  muscular  mass, 
forming  the  calf  of  the  leg.  Their  large  size  is  one  of  the  most  characteristic 
features  of  the  muscular  apparatus  in  man,  and  bears  a  direct  connection  with  his 
ordinary  attitude  and  mode  of  progression. 

Superficial  Layer. 
Gastrocnemius.  Soleus.  Plantaris. 

The  Gastrocnemius  is  the  most  superficial  muscle,  and  forms  the  greater  part 
of  the  calf.  It  arises  by  two  heads,  which  are  connected  to  the  condyles  of 
the  femur  by  two  strong  flat  tendons.  The  inner  head,  the  larger  and  a  little 
the  more  posterior,  arises  from  a  depression  at  the  upper  and  back  part  of  the 
inner  condyle.  The  outer  head  arises  from  the  upper  and  back  part  of  the 
external  condyle,  immediately  above  the  origin  of  the  Popliteus.  Both  heads,  also, 
arise  by  a  few  tendinous  and  fleshy  fibres  from  the  ridges  which  are  continued 
upward  from  the  condyles  to  the  linea  aspera.  Each  tendon  spreads  out  into  an 
aponeurosis  which  covers  the  posterior  surface  of  that  portion  of  the  muscle  to 
which  it  belongs,  that  covering  the  inner  head  being  longer  and  thicker  than 
the  outer.  From  the  anterior  surface  of  these  tendinous  expansions  muscular 
fibres  are  given  off.  The  fibres  in  the  median  line,  which  correspond  to  the 


THE  POSTERIOR    TIBIO-FIBULAR   REGION. 


523 


accessory  portions  of  the  muscle  derived  from  the  bifurcations  of  the  linea  aspera, 

unite  at  an  angle  upon  a  median  tendinous 

raphe  below  :   the  remaining  fibres  converge 

to  the   posterior  surface   or    an   aponeurosis 

which    covers   the   anterior   surface   of  the 

muscle,     and    this,     gradually    contracting, 

unites  with  the  tendon   of  the   Soleus,   and 

forms  with  it  the  tendo  Achillis. 

Relations. — By  its  superficial  surface, 
with  the  fascia  of  the  leg,  which  separates 
it  from  the  external  saphenous  vein  and 
nerve ;  by  its  deep  surface,  with  the  posterior 
ligament  of  the  knee-joint,  the  Popliteus, 
Soleus,  Plantaris,  popliteal  vessels,  and  in- 
ternal popliteal  nerve.  The  tendon  of  the 
inner  head  corresponds  with  the  back  part 
of  the  inner  condyle,  from  which  it  is  sepa- 
rated by  a  synovial  bursa,  which,  in  some 
cases,  communicates  with  the  cavity  of  the 
knee-joint.  The  tendon  of  the  outer  head 
contains  a  sesamoid  fibro-cartilage  (rarely 
osseous)  where  it  plays  over  the  correspond- 
ing outer  condyle  ;  and  one  is  occasionally 
found  in  the  tendon  of  the  inner  head. 

The  Gastrocnemius  should  be  divided  across, 
just  below  its  origin,  and  turned  downward,  in  order 
to  expose  the  next  muscles. 

The  Soleus  is  a  broad  flat  muscle  situated 
immediately  beneath  the  Gastrocnemius.  It 
has  received  its  name  from  its  resemblance 
in  shape  to  a  sole-fish.  It  arises  by  ten- 
dinous fibres  from  the  back  part  of  the  head 
of  the  fibula  and  from  the  upper  third  of  the 
posterior  surface  of  its  shaft ;  from  the  oblique 
line  of  the  tibia  and  from  the  middle  third 
of  its  internal  border ;  some  fibres  also  arise 
from  a  tendinous  arch  placed  between  the 
tibial  and  fibular  origins  of  the  muscle,  be- 
neath which  the  posterior  tibial  vessels  and 
nerve  pass.  The  fibres  pass  backward  to  an 
aponeurosis  which  covers  the  posterior  sur- 
face of  the  muscle,  and  this,  gradually  be- 
coming thicker  and  nai'rower,  joins  with  the 
tendon  of  the  Gastrocnemius,  and  forms  with 
it  the  tendo  Achillis. 

Relations. — By  its  superficial  surface, 
with  the  Gastrocnemius  and  Plantaris ;  by 
its  deep  surface,  with  the  Flexor  longus 
digitorum.  Flexor  longus  hallucis,  Tibialis 
posticus,  and  posterior  tibial  vessels  and  nerve,  from  which  it  is  separated  by  the 
transverse  intermuscular  septum  or  deep  transverse  fascia  of  the  leg. 

The  Tendo  Achillis,  the  common  tendon  of  the  Gastrocnemius  and  Soleus,  is 
the  thickest  and  strongest  tendon  in  the  body.  It  is  about  six  inches  in  length, 
and  commences  about  the  middle  of  the  leg,  but  receives  fleshy  fibres  on  its 
anterior  surface  nearly  to  its  lower  end.  Gradually  becoming  contracted  below,  it 
is  inserted  into  the  lower  part  of  the  posterior  surface  of  the  os  calcis,  a  synovial 


Tendons  of 

PERONEUS    LONGUS 

and  BREVIS. 


FIG.  331.— Muscles  of  the  back  of  the  leg. 
Superficial  layer. 


524  THE  MUSCLES  AND   FASCIA. 

bursa  being  interposed  between  the  tendon  and  the  upper  part  of  this  surface.  The 
tendon  spreads  out  somewhat  at  its  lower  end,  so  that  its  narrowest  part  is  usually 
about  an  inch  and  a  half  above  its  insertion.  The  tendon  is  covered  by  the  fascia 
and  the  integument,  and  is  separated  from  the  deep  muscles  and  vessels  by  a 
considerable  interval  filled  up  with  areolar  and  adipose  tissue.  Along  its  outer 
side,  but  superficial  to  it,  is  the  external  saphenous  vein. 

The  Plantaris  is  an  extremely  diminutive  muscle  placed  between  the  Gastro- 
cnemius  and  Soleus,  and  remarkable  for  its  long  and  delicate  tendon.  It  arises 
from  the  lower  part  of  the  outer  prolongation  of  the  linea  aspera  and  from  the 
posterior  ligament  of  the  knee-joint.  It  forms  a  small  fusiform  belly,  about  three 
or  four  inches  in  length,  terminating  in  a  long  slender  tendon  which  crosses 
obliquely  between  the  two  muscles  of  the  calf,  and,  running  along  the  inner  border 
of  the  tendo  Achillis,  is  inserted  with  it  into  the  posterior  part  of  the  os  calcis. 
This  muscle  is  occasionally  double,  and  is  sometimes  wanting.  Occasionally,  its 
tendon  is  lost  in  the  internal  annular  ligament  or  in  the  fascia  of  the  leg. 

Nerves. — These  muscles  are  supplied  by  the  internal  popliteal  nerve,  the  Soleus 
receiving  an  additional  branch  from  the  posterior  tibial  nerve. 

Actions. — The  muscles  of  the  calf  are  constantly  called  into  use  in  standing, 
walking,  dancing,  and  leaping.  In  walking  these  muscles  draw  powerfully  upon 
the  os  calcis,  raising  the  heel,  and  with  it  the  entire  body,  from  the  ground ;  the 
body  being  thus  supported  on  the  raised  foot,  the  opposite  limb  can  be  carried 
forward.  In  standing,  the  Soleus,  taking  its  fixed  point  from  below,  steadies  the 
leg  upon  the  foot,  and  prevents  the  body  from  falling  forward,  to  which  there  is  a 
constant  tendency  from  the  superincumbent  weight.  The  Gastrocnemius,  acting 
from  below,  serves  to  flex  the  femur  upon  the  tibia,  assisted  by  the  Popliteus.  The 
Plantaris  is  the  rudiment  of  a  large  muscle  which  exists  in  some  of  the  lower 
animals  and  serves  as  a  tensor  of  the  plantar  fascia.  In  man  it  is  merely  an 
accessory  to  the  Gastrocnemius,  extending  the  ankle  if  the  foot  is  free  or  bending 
the  knee  if  the  foot  is  fixed. 

Deep  Layer. 

Popliteus.  Flexor  longus  digitorum. 

Flexor  longus  hallucis.  Tibialis  posticus. 

Dissection. — Detach  the  Soleus  from  its  attachment  to  the  fibula  and  tibia,  and  turn  it 
downward,  when  the  deep  layer  of  muscles  is  exposed,  covered  by  the  deep  transverse  fascia  of 
the  leg. 

The  Deep  Transverse  Fascia  of  the  leg  is  a  broad,  transverse,  intermuscular 
septum  interposed  between  the  superficial  and  deep  muscles  in  the  posterior 
tibio-fibular  region.  On  either  side  it  is  connected  to  the  margins  of  the  tibia  and 
fibula.  Above,  where  it  covers  the  Popliteus,  it  is  thick  and  dense,  and  receives  an 
expansion  from  the  tendon  of  the  Semimembranosus ;  it  is  thinner  in  the  middle 
of  the  leg,  but  below,  where  it  covers  the  tendons  passing  behind  the  malleoli,  it 
is  thickened.  It  is  continued  onward  in  the  interval  between  the  ankle  and  the 
heel,  where  it  covers  the  vessels  and  is  blended  with  the  internal  annular 
ligament. 

This  fascia  should  now  be  removed,  commencing  from  below  opposite  the  tendons,  and 
detaching  it  from  the  muscles  in  the  direction  of  their  fibres. 

The  Popliteus  is  a  thin,  flat,  triangular  muscle,  which  forms  part  of  the  floor 
of  the  popliteal  space,  and  is  covered  by  a  tendinous  expansion  derived  from  the 
Semimembranosus  muscle.  It  arises  by  a  strong  tendon,  about  an  inch  in  length, 
from  a  deep  depression  on  the  outer  side  of  the  external  condyle  of  the  femur, 
and  from  the  posterior  ligament  of  the  knee-joint,  and  is  inserted  into  the  inner 
two-thirds  of  the  triangular  surface  above  the  oblique  line  on  the  posterior  surface 
of  the  shaft  of  the  tibia,  and  into  the  tendinous  expansion  covering  the  surface 
of  the  muscle.  The  tendon  of  the  muscle  is  covered  by  that  of  the  Biceps  and  the 
external  lateral  ligament  of  the  knee-joint;  it  grooves  the  outer  border  of  the 


THE   POSTERIOR    TIBIO-FIBULAR    REGIOX. 


525 


'  Femur. ( 


external  semilunar  fibro-cartilage,  and  is  invested  by  the  synovia!  membrane 
of  the  knee-joint. 

Relations.  —  By  its  superficial  surface,  with  the  fascia  above  mentioned,  which 
separates  it  from  the  Gastrocnemius,  Plantaris,  popliteal 
vessels,  and  internal  popliteal  nerve;  by  its  deep  sur- 
face,  with   the    superior   tibio-fibular    articulation    and 
back  of  the  tibia. 

The  Flexor  longus  hallucis  is  situated  on  the  fibular 
side  of  the  leg.  It  arises  from  the  lower  two- 
thirds  of  the  posterior  surface  of  the  shaft  of  the 
fibula,  with  the  exception  of  an  inch  at  its  lowest 
part  ;  from  the  lower  part  of  the  interosseus  mem- 
brane ;  from  an  intermuscular  septum  between  it 
and  the  Peronei,  externally  ;  and  from  the  fascia 
covering  the  Tibialis  posticus,  which  is  attached  to 
the  inner  border  of  the  fibula  externally  and  to 
the  posterior  surface  of  the  tibia  between  the 
origins  of  the  Tibialis  posticus  and  the  Flexor 
longus  digitorum,  internally.  The  fibres  pass  ob- 
liquely downward  and  backward,  and  terminate 
round  a  tendon  which  occupies  nearly  the  whole 
length  of  the  posterior  surface  of  the  muscle. 
This  tendon  passes  through  a  groove  on  the  pos- 
terior surface  of  the  lower  end  of  the  tibia;  it 
then  passes  through  another  groove  on  the  pos- 
terior surface  of  the  astragalus,  and  along  a  third 
groove,  beneath  the  sustentaculum  tali  of  the  os 
calcis,  into  the  sole  of  the  foot,  where  it  runs 
forward  between  the  two  heads  of  the  Flexor  brevis 
hallucis,  and  is  inserted  into  the  base  of  the  last 
phalanx  of  the  great  toe.  The  grooves  in  the  ,  » 
astragalus  and  os  calcis,  which  contain  the  tendon  ID 
of  the  muscle,  are  converted  by  tendinous  fibres 
into  distinct  canals  lined  by  synovial  membrane  ; 
and  as  the  tendon  crosses  the  sole  of  the  foot, 
it  is  connected  to  the  common  flexor  by  a  tendinous 

T  J 

slip. 

Relations.  —  By  its  superficial  surface,  with  the 
Soleus  and  tendo  Achillis,  from  which  it  is  sepa- 
rated by  the  deep  transverse  fascia;  by  its  deep  sur- 
face, with  the  fibula,  Tibialis  posticus,  the  peroneal 
vessels,  the  lower  part  of  the  interosseous  membrane, 
and  the  ankle-joint;  by  its  outer  border,  with  the 
Peronei  :  by  its  inner  border,  with  the  Tibialis 
posticus  and  posterior  tibial  vessels  and  nerve. 

The  Flexor  longus  digitorum  (perforans)  is  situated 
on  the  tibial  side  of  the  leg.  At  its  origin  it  is  thin 
and  pointed,  but  gradually  increases  in  size  as  it 
descends.  It  arises  from  the  posterior  surface  of  the 
shaft  of  the  tibia,  immediately  below  the  oblique  line,  to 
within  three  inches  of  its  extremity  internal  to  the 
tibial  origin  of  the  Tibialis  posticus  ;  some  fibres  also 
arise  from  the  fascia  covering  the  Tibialis  posticus.  The 

fibres  terminate  in  a  tendon  which  runs  nearly  the  whole  length  of  the  posterior 
surface  of  the  muscle.  This  tendon  passes  behind  the  internal  malleolus  in  a  groove 
common  to  it  and  the  Tibiali.<  posticus,  but  separated  from  the  latter  by  a  fibrous 
septum,  each  tendon  being  contained  in  a  special  sheath  lined  by  a  separate  synovial 


"•14 


33-2.—  Muscles  of  the 


526  THE  MUSCLES  AND   FASCIAE. 

membrane.  It  then  passes  obliquely  forward  and  outward,  crossing  over  the 
internal  lateral  ligament  into  the  sole  of  the  foot  (Fig.  334),  where,  crossing 
superficially  to  the  tendon  of  the  Flexor  longus  hallucis,1  to  which  it  is  connected 
by  a  strong  tendinous  slip,  it  becomes  expanded,  is  joined  by  the  Flexor  acces- 
sorius,  and  finally  divides  into  four  tendons  which  are  inserted  into  the  bases 
of  the  last  phalanges  of  the  four  lesser  toes,  each  tendon  passing  through  a  fissure 
in  the  tendon  of  the  Flexor  brevis  digitorum  opposite  the  base  of  the  first 
phalanges. 

Relations. — In  the  leg :  by  its  superficial  surface,  with  the  posterior  tibial 
vessels  and  nerve,  and  the  deep  transverse  fascia,  which  separates  it  from  the 
Soleus  muscle ;  by  its  deep  surface,  with  the  Tibia  and  Tibialis  posticus.  In  the 
foot  it  is  covered  by  the  Abductor  hallucis  and  Flexor  brevis  digitorum,  and 
crosses  superficial  to  the  Flexor  longus  hallucis. 

The  Tibialis  posticus  lies  between  the  two  preceding  muscles,  and  is  the  most 
deeply  seated  of  all  the  muscles  in  the  leg.  It  commences  above  by  two  pointed 
processes,  separated  by  an  angular  interval,  through  which  the  anterior  tibial 
vessels  pass  forward  to  the  front  of  the  leg.  It  arises  from  the  whole  of  the 
posterior  surface  of  the  interosseous  membrane,  excepting  its  lowest  part,  from 
the  posterior  surface  of  the  shaft  of  the  tibia,  external  to  the  Flexor  longus 
digitorum,  between  the  commencement  of  the  oblique  line  above,  and  the  middle 
of  the  external  border  of  the  bone  below,  and  from  the  upper  two-thirds  of  the 
internal  surface  of  the  fibula ;  some  fibres  also  arise  from  the  deep  transverse 
fascia  and  from  the  intermuscular  septa,  separating  it  from  the  adjacent  muscles 
on  each  side.  This  muscle,  in  the  lower  fourth  of  the  leg,  passes  in  front  of  the 
Flexor  longus  digitorum,  and  terminates  in  a  tendon  which  passes  through  a 
groove  behind  the  inner  malleolus  with  the  tendon  of  that  muscle^  but  enclosed  in 
a  separate  sheath  ;  it  then  passes  through  another  sheath,  over  the  internal  lateral 
ligament  into  the  foot,  and  then  beneath  the  inferior  calcaneo-navicular  ligament, 
and  is  inserted  into  the  tuberosity  of  the  navicular  and  internal  cuneiform  bones. 
The  tendon  of  this  muscle  contains  a  sesamoid  fibro-cartilage  as  it  passes  over  the 
navicular  bone,  and  gives  off  fibrous  expansions,  one  of  which  passes  backward  to 
the  sustentaculum  tali  of  the  os  calcis,  others  outward  to  the  middle  and  external 
cuneiform  and  cuboid,  and  some  forward  to  the  bases  of  the  second,  third,  and 
fourth  metatarsal  bones  (Fig.  335). 

Relations. — By  its  superficial  surface,  with  the  Soleus,  from  which  it  is 
separated  by  the  deep  transverse  fascia,  the  Flexor  longus  digitorum,  the  posterior 
tibial  vessels  and  nerve,  and  the  peroneal  vessels ;  by  its  deep  surface,  with  the 
interosseous  ligament,  the  tibia,  fibula,  and  ankle-joint. 

Nerves. — The  Popliteus  is  supplied  by  the  internal  popliteal  nerve,  the 
remaining  muscles  of  this  group  by  the  posterior  tibial  nerve. 

Actions. — The  Popliteus  assists  in  flexing  the  leg  upon  the  thigh ;  when  the 
leg  is  flexed  it  will  rotate  the  tibia  inward.  It  is  especially  called  into  action  at 
the  commencement  of  the  act  of  bending  the  knee,  inasmuch  as  it  produces  a 
slight  inward  rotation  of  the  tibia,  which  is  essential  in  the  early  stage  of  this 
movement.  The  Tibialis  posticus  is  a  direct  extensor  of  the  tarsus  upon  the  leg ; 
acting  in  conjunction  with  the  Tibialis  anticus,  it  turns  the  sole  of  the  foot  inward, 
antagonizing  the  Peroneus  longus,  which  turns  it  outward.  The  Flexor  longus 
digitorum  and  Flexor  longus  hallucis  are  the  direct  flexors  of  the  phalanges,  act- 
ing as  do  the  similar  muscles  of  the  hand,  and,  continuing  their  action,  extend 
the  foot  upon  the  leg;  they  assist  the  Gastrocnemius  and  Soleus  in  extending 
the  foot,  as  in  the  act  of  walking  or  in  standing  on  tiptoe. 

In  consequence  of  the  oblique  direction  of  the  tendon  of  the  long  flexor  the  toes 
would  be  drawn  inward  were  it  not  for  the  Flexor  accessorius  muscle,  which  is 
inserted  into  the  outer  side  of  its  tendon  and  draws  it  to  the  middle  line  of  the  foot 
during  its  action.  Taking  their  fixed  point  from  the  foot,  these  muscles  serve  to 
maintain  the  upright  posture  by  steadying  the  tibia  and  fibula  perpendicularly 
1  That  is,  in  the  order  of  dissection  of  the  sole  of  the  foot. 


THE    OUTER    OR   FIBULAR   REGION.  527 

upon  the  ankle-joint.     They  also  serve  to  raise  these  bones  from  the  oblique  position 
they  assume  in  the  stooping  posture. 

Outer  or  Fibular  Region. 
Peroneus  longus.  Peroneus  brevis. 

Dissection.— The  muscles  are  readily  exposed  by  removing  the  fascia  covering  their  surf  aw, 
from  below  upward,  in  the  line  of  direction  of  their  fibres. 

The  Peroneus  longus  is  situated  at  the  upper  part  of  the  outer  side  of  the  leg, 
and  is  the  more  superficial  of  the  two  muscles.  It  arises  from  the  head  and  upper 
two-thirds  of  the  outer  surface  of  the  shaft  of  the  fibula,  from  the  deep  surface  of 
the  fascia,  and  from  the  intermuscular  septa  between  it  and  the  muscles  on  the 
front,  and  those  on  the  back  of  the  leg.  It  terminates  in  a  long  tendon  which 
passes  behind  the  outer  malleolus,  in  a  groove  common  to  it  and  the  Peroneus 
brevis.  the  groove  being  converted  into  a  canal  by  a  fibrous  band,  and  the  tendons 
invested  by  a  common  synovial  membrane ;  it  is  then  reflected,  obliquely  forward, 
across  the  outer  side  of  the  os  calcis,  being  contained  in  a  separate  fibrous  sheath 
lined  by  a  prolongation  of  the  synovial  membrane  from  that  which  lines  the  groove 
behind  the  malleolus.  Having  reached  the  outer  side  of  the  cuboid  bone,  it  runs 
in  a  groove  on  the  under  surface  of  that  bone,  which  is  converted  into  a  canal 
by  the  long  calcaneo-cuboid  ligament,  and  is  lined  by  a  synovial  membrane :  the 
tendon  then  crosses  obliquely  the  sole  of  the  foot,  and  is  inserted  into  the  outer 
side  of  the  base  of  the  metatarsal  bone  of  the  great  toe  and  the  internal  cuneiform 
bone.  Occasionally  it  sends  a  slip  to  the  base  of  the  second  metatarsal  bone.  The 
tendon  changes  its  direction  at  two  points  ;  first,  behind  the  external  malleolus ; 
secondly,  on  the  outer  side  of  the  cuboid  bone ;  in  both  of  these  situations  the 
tendon  is  thickened,  and  in  the  latter  a  sesamoid  fibre-cartilage,  or  sometimes  a 
bone,  is  usually  developed  in  its  substance. 

Relations. — By  its  superficial  surface,  with  the  fascia  and  integument ;  by  its 
deep  surface,  with  the  fibula,  the  Peroneus  brevis,  os  calcis,  and  cuboid  bone ;  by 
its  anterior  border,  with  an  intermuscular  septum  which  intervenes  between  it 
and  the  Extensor  longus  digitorum;  by  its  posterior  border,  with  an  intermuscular 
septum  which  separates  it  from  the  Soleus  above  and  the  Flexor  longus  hallucis 
below. 

The  Peroneus  brevis  lies  beneath  the  Peroneus  longus,  and  is  shorter  and 
smaller  than  it.  It  arises  from  the  lower  two-thirds  of  the  external  surface  of  the 
shaft  of  the  fibula,  internal  to  the  Peroneus  longus.  and  from  the  intennuscular 
septa  separating  it  from  the  adjacent  muscles  on  the  front  and  back  part  of  the 
leg.  The  fibres  pass  vertically  downward,  and  terminate  in  a  tendon  which 
runs  in  front  of  that  of  the  preceding  muscle  through  the  same  groove,  behind  the 
external  malleolus,  being  contained  in  the  same  fibrous  sheath  and  lubricated  by 
the  same  synovial  membrane.  It  then  passes  through  a  separate  sheath  on  the 
outer  side  of  the  os  calcis,  above  that  for  the  tendon  of  the  Peroneus  longus,  and 
is  finally  inserted  into  the  tuberosity  at  the  base  of  the  metatarsal  bone  of  the  little 
toe.  on  its  outer  side. 

Relations. — By  its  superficial  surface,  with  the  Peroneus  longus  and  the  fascia 
of  the  leg  and  foot ;  by  its  deep  surface,  with  the  fibula  and  outer  side  of  the  os 
calcis. 

Nerves. — The  Peroneus  longus  and  brevis  are  supplied  by  the  musculo-cuta- 
neous  branch  of  the  external  popliteal  nerve. 

Actions. — The  Peroneus  longus  and  brevis  extend  the  foot  upon  the  leg  in 
conjunction  with  the  Tibialis  posticus.  antagonizing  the  Tibialis  anticus  and 
Peroneus  tertius.  which  are  flexors  of  the  foot.  The  Peroneus  longus  also  everts 
the  sole  of  the  foot ;  hence  the  extreme  eversion  occasionally  observed  in  fractui'e 
of  the  lower  end  of  the  fibula,  where  that  bone  offers  no  resistance  to  the  action 
of  this  muscle.  Taking  their  fixed  point  below,  the  Peronei  serve  to  steady  the 
leg  upon  the  foot.  This  is  especially  the  case  in  standing  upon  one  leg,  when  the 


528  THE  MUSCLES  AND   FASCIA 

tendency  of  the  superincumbent  weight  is  to  throw  the  leg  inward :  the  Peroneus 
longus  overcomes  this  tendency  by  drawing  on  the  outer  side  of  the  leg,  and  thus 
maintains  the  perpendicular  direction  of  the  limb. 

Surgical  Anatomy. — The  student  should  now  consider  the  position  of  the  tendons  of  the 
various  muscles  of  the  leg,  their  relation  with  the  ankle-joint  and  surrounding  blood-vessels,  and 
especially  their  action  upon  the  foot,  as  their  rigidity  and  contraction  give  rise  to  one  or  other  of 
the  kinds  of  deformity  known  as  club-foot.  The  most  simple  and  .common  deformity,  and  one 
that  is  rarely,  if  ever,  congenital,  is  the  talipes  equinus,  the  heel  being  raised  by  rigidity  and  con- 
traction of  the  Grastrocnemius  muscle,  and  the  patient  walking  upon  the  ball  of  the  foot.  In  the 
talipes  varus  the  foot  is  forcibly  adducted  and  the  inner  side  of  the  sole  raised,  sometimes  to  a 
right  angle  with  the  ground,  by  the  action  of  the  Tibialis  anticus  and  posticus.  In  the  talipes 
valgus  the  outer  edge  of  the  foot  is  raised  by  the  Peronei  muscles,  and  the  patient  walks  on  the 
inner  ankle.  In  the  talipes  cakaneus  the  toes  are  raised  by  the  extensor  muscles,  the  heel  is 
depressed,  and  the  patient  walks  upon  it.  Other  varieties  of  deformity  are  met  with,  as  the 
talipes  equino-varus,  equino-valgus,  and  calcaneo-valgus,  whose  names  sufficiently  indicate  their 
nature.  Of  these,  the  talipes  equino-varus  is  the  most  common  congenital  form  :  the  heel  is 
raised  by  the  tendo  Achillis,  the  inner  border  of  the  foot  drawn  upward  by  the  Tibialis  anticus, 
the  anterior  two-thirds  twisted  inward  by  the  Tibialis  posticus,  and  the  arch  increased  by  the 
contraction  of  the  plantar  fascia,  so  that  the  patient  walks  on  the  middle  of  the  outer  border  of 
the  foot.  Each  of  these  deformities  may  be  successfully  relieved  (after  other  remedies  fail)  by 
division  of  the  opposing  tendons  and  fascia  :  by  this  means  the  foot  regains  its  proper  position, 
and  the  tendons  heal  by  the  organization  of  lymph  thrown  out  between  the  divided  ends.  The 
operation  is  easily  performed  by  putting  the  contracted  tendon  upon  the  stretch,  and  dividing 
it  by  means  of  a  narrow,  sharp-pointed  knife  inserted  beneath  it. 

Rupture  of  a  few  of  the  fibres  of  the  Grastrocnemius  or  rupture  of  the  Plantaris  tendon  not 
uncommonly  occurs,  especially  in  men  somewhat  advanced  in  life,  from  some  sudden  exertion, 
and  frequently  occurs  during  the  game  of  lawn  tennis,  and  is  hence  known  as  "lawn-tennis  leg." 
The  accident  is  accompanied  by  a  sudden  pain,  and  produces  a  sensation  as  if  the  individual  had 
been  struck  a  violent  blow  on  the  part.  The  tendp  Achillis  is  also  sometimes  ruptured.  It  is 
stated  that  John  Hunter  ruptured  his  tendo  Achillis  whilst  dancing  at  the  age  of  forty. 

THE  FOOT. 

The  fibrous  bands  which  bind  down  the  tendons  in  front  of  and  behind  the  ankle  in  their 
passage  to  the  foot  should  now  be  examined  ;  they  are  termed  the  annular  ligaments,  and  are 
three  in  number — anterior,  internal,  and  external. 

The  Anterior  Annular  Ligament  consists  of  a  superior  or  vertical  portion, 
which  binds  down  the  extensor  tendons  as  they  descend  on  the  front  of  the  tibia 
and  fibula,  and  an  inferior  or  horizontal  portion,  which  retains  them  in  connection 
with  the  tarsus,  the  two  portions  being  connected  by  a  thin  intervening  layer  of 
fascia.  The  vertical  portion  is  attached  externally  to  the  lower  end  of  the  fibula, 
internally  to  the  tibia,  and  above  is  continuous  with  the  fascia  of  the  leg ;  it  con- 
tains only  one  synovial  sheath,  for  the  tendon  of  the  Tibialis  anticus,  the  other 
tendons  and  the  anterior  tibial  vessels  and  nerve  passing  beneath  it,  but  without 
any  distinct  synovial  sheath.  The  horizontal  portion  is  attached  externally  to  the 
upper  surface  of  the  os  calcis,  in  front  of  the  depression  for  the  interosseous 
ligament ;  it  passes  upward  and  inward  as  a  double  layer,  one  lamina  passing  in 
front,  and  the  other  behind,  the  Peroneus  tertius  and  Extensor  longus  digitorum. 
At  the  inner  border  of  the  latter  tendon  these  two  layers  join  together,  forming  a 
sort  of  loop  or  sheath  in  which  the  tendons  are  enclosed,  surrounded  by  a  synovial 
membrane.  From  the  inner  extremity  of  this  loop  two  bands  are  given  off:  one 
passes  upward  and  inward  to  be  attached  to  the  internal  malleolus,  passing  over 
the  Extensor  proprius  hallucis  and  vessels  and  nerves,  but  enclosing  the  Tibialis 
anticus  and  its  synovial  sheath  by  a  splitting  of  its  fibres.  The  other  limb  passes 
downward  and  inward  to  be  attached  to  the  navicular  and  internal  cuneiform 
bones,  and  passes  over  both  the  tendon  of  the  Extensor  proprius  hallucis  and  the 
Tibialis  anticus,  and  also  the  vessels  and  nerves.  These  two  tendons  are  contained 
in  separate  synovial  sheaths  situated  beneath  the  ligament.  It  will  thus  be  seen 
that  the  horizontal  portion  of  the  ligament  is  like  the  letter  Y>  the  foot  of  the  letter 
being  attached  to  the  os  calcis,  and  the  two  diverging  arms  to  the  tibia  and  navic- 
ular and  internal  cuneiform  respectively. 

The  Internal  Annular  Ligament  is  a  strong  fibrous  band  which  extends  from 
the  inner  malleolus  above  to  the  internal  margin  of  the  os  calcis  below,  converting 


OF   THE  FOOT.  529 

a  series  of  grooves  in  this  situation  into  canals  for  the  passage  of  the  tendons  of 
the  Flexor  muscles  and  vessels  into  the  sole  of  the  foot.  It  is  continuous  by  its 
upper  border  with  the  deep  fascia  of  the  leg,  and  by  its  lower  border  with  the 
plantar  fascia  and  the  fibres  of  origin  of  the  Abductor  hallucis  muscle.  The  three 
canals  which  it  forms  transmit,  from  within  outward,  first,  the  tendon  of  the  Tibi- 
alis  posticus ;  second,  the  tendon  of  the  Flexor  longus  digitorum  ;  then  the  pos- 
terior tibial  vessels  and  nerve,  which  run  through  a  broad  space  beneath  the  liga- 
ment :  lastly,  in  a  canal  formed  partly  by  the  astragalus,  the  tendon  of  the  Flexor 
longus  hallucis.  Each  of  these  canals  is  lined  by  a  separate  synovial  membrane. 
The  External  Annular  Ligament  extends  from  the  extremity  of  the  outer  mal- 
leolus  to  the  outer  surface  of  the  os  calcis  :  it  binds  down  the  tendons  of  the  Pero- 
nei  muscles  in  their  passage  beneath  the  outer  ankle.  The  two  tendons  are 
enclosed  in  one  synovial  sac. 

Dissection  of  the  Sole  of  the  Foot. — The  foot  should  be  placed  on  a  high  block  with  the 
sole  uppermost,  and  firmly  secured  in  that  position.  Carry  an  incision  round  the  heel  and  along 
the  inner  and  outer  borders  of  the  foot  to  the  great  and  little  toes.  This  incision  should  divide 
the  internment  and  thick  layer  of  granular  fat  beneath  until  the  fascia  is  visible ;  the  skin  and 
tar  should  then  be  removed  from  the  fascia  in  a  direction  from  behind  forward,  as  seen  in  Fig. 

The  Plantar  Fascia,  the  densest  of  all  the  fibrous  membranes,  is  of  great  strength, 
and  consists  of  dense  pearly-white  glistening  fibres,  disposed,  for  the  most  part, 
longitudinally :  it  is  divided  into  a  central  and  two  lateral  portions. 

The  central  portion,  the  thickest,  is  narrow  behind  and  attached  to  the  inner 
tubercle  of  the  os  calcis,  behind  the  origin  of  the  Flexor  brevis  digitorum,  and, 
becoming  broader  and  thinner  in  front,  divides  near  the  heads  of  the  metatarsal 
bones  into  five  processes,  one  for  each  of  the  toes.  Each  of  these  processes  divides 
opposite  the  metatarso-phalangeal  articulation  into  two  strata,  superficial  and  deep. 
The  superficial  stratum  is  inserted  into  the  skin  of  the  transverse  sulcus  which 
divides  the  toes  from  the  sole.  The  deeper  stratum  divides  into  two  slips  which 
embrace  the  sides  of  the  flexor  tendons  of  the  toes,  and  blend  with  the  sheaths  of 
the  tendons,  and  laterally  with  the  transverse  metatarsal  ligament,  thus  forming  a 
series  of  arches  through  which  the  tendons  of  the  short  and  long  flexors  pass  to 
the  toes.  The  intervals  left  between  the  five  processes  allow  the  digital  vessels  and  M 
nerves  and  the  tendons  of  the  Lumbricales  muscles  to  become  superficial.  At  the// 
point  of  division  of  the  fascia  into  processes  and  slips  numerous  transverse  fibres 
are  superadded.  which  serve  to  increase  the  strength  of  the  fascia  at  this  part  by 
binding  the  processes  together  and  connecting  them  with  the  integument.  The 
central  portion  of  the  plantar  fascia  is  continuous  with  the  lateral  portions  at  each 
side,  and  sends  upward  into  the  foot,  at  their  point  of  junction,  two  strong  vertical 
intermuscular  septa,  broader  in  front  than  behind,  which  separate  the  middle  from 
the  external  and  internal  plantar  group  of  muscles  ;  from  these,  again,  thinner 
transverse  septa  are  derived,  which  separate  the  various  layers  of  muscles  in  this 
region.  The  upper  surface  of  this  fascia  gives  attachment  behind  to  the  Flexor 
brevis  digitorum  muscle. 

The  lateral  portions  of  the  plantar  fascia  are  thinner  than  the  central  piece,  and 
cover  the  sides  of  the  foot. 

The  outer  portion  covers  the  under  surface  of  the  Abductor  minimi  digiti ;  it  is 
thick  behind,  thin  in  front,  and  extends  from  the  os  calcis,  forward,  to  the  base  of 
the  fifth  metatarsal  bone,  into  the  outer  side  of  which  it  is  attached  ;  it  is  con- 
tinuous internally  with  the  middle  portion  of  the  plantar  fascia,  and  externally 
with  the  dorsal  fascia. 

The  inner  portion  is  very  thin,  and  covers  the  Abductor  hallucis  muscle  ;  it  is 
attached  behind  to  the  internal  annular  ligament,  and  is  continuous  around  the 
side  of  the  foot  with  the  dorsal  fascia,  and  externally  with  the  middle  portion  of 
the  plantar  fascia. 

The  Muscles  of  the  Foot  are  found  in  two  regions :  1.  On  the  dorsum ;  2.  On 
the  plantar  surface. 


530  THE  MUSCLES  AND   FASCIA 

1.  Dorsal  Region. 

Extensor  brevis  digitorum. 

The  Fascia  on  the  dorsum  of  the  foot  is  a  thin  membranous  layer  continuous 
above  with  the  anterior  margin  of  the  annular  ligament ;  it  becomes  gradually 
lost  opposite  the  heads  of  the  metatarsal  bones,  and  on  each  side  blends  with  the 
lateral  portions  of  the  plantar  fascia ;  it  forms  a  sheath  for  the  tendons  placed  on 
the  dorsum  of  the  foot.  On  the  removal  of  this  fascia  the  muscles  and  tendons  of 
the  dorsal  region  of  the  foot  are  exposed. 

The  Extensor  brevis  digitorum  (Fig.  330)  is  a  broad  thin  muscle  which  arises 
from  the  fore  part  of  the  upper  and  outer  surfaces  of  the  os  calcis,  in  front  of  the 
groove  for  the  Peroneus  brevis,  from  the  external  calcaneo-astragaloid  ligament, 
and  from  the  horizontal  portion  of  the  anterior  annular  ligament.  It  passes 
obliquely  across  the  dorsum  of  the  foot,  and  terminates  in  four  tendons.  The 
innermost,  which  is  the  largest,  is  inserted  into  the  dorsal  surface  of  the  base  of 
the  first  phalanx  of  the  great  toe,  crossing  the  Dorsalis  pedis  artery  ;  the  other 
three,  into  the  outer  sides  of  the  long  extensor  tendons  of  the  second,  third,  and 
fourth  toes. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  foot,  the  tendons 
of  the  Extensor  longus  digitorum  and  Extensor  proprius  hallucis;'by  its  deep 
surface,  with  the  tarsal  and  metatarsal  bones  and  the  Dorsal  interossei  muscles. 

Nerves. — It  is  supplied  by  the  anterior  tibial  nerve. 

Actions. — The  Extensor  brevis  digitorum  is  an  accessory  to  the  long  Extensor, 
extending  the  first  phalanges  of  all  four  inner  toes.  The  obliquity  of  its  direc- 
tion counteracts  the  oblique  movement  given  to  the  toes  by  the  long  Extensor, 
so  that,  both  muscles  acting  together,  the  toes  are  evenly  extended. 

2.  Plantar  Region. 

The  muscles  in  the  plantar  region  of  the  foot  may  be  divided  into  three  groups, 
in  a  similar  manner  to  those  in  the  hand.  Those  of  the  internal  plantar  region 
are  connected  with  the  great  toe,  and  correspond  with  those  of  the  thumb  ;  those 
of  the  external  plantar  region  are  connected  with  the  little  toe,  and  correspond 
with  those  of  the  little  finger ;  and  those  of  the  middle  plantar  region  are  con- 
nected with  the  tendons  intervening  betAveen  the  two  former  groups.  But  in  order 
to  facilitate  the  dissection  of  these  muscles  it  will  be  found  more  convenient  to 
divide  them  into  four  layers,  as  they  present  themselves,  in  the  order  in  which 
they  are  successively  exposed. 

First  Layer. 

Abductor  hallucis.  Flexor  brevis  digitorum. 

Abductor  minimi  digiti. 

Dissection.— Remove  the  fascia  on  the  inner  and  outer  sides  of  the  foot,  commencing  in 
front  over  the  tendons  and  proceeding  backward.  The  central  portion  should  be  divided  trans- 
versely in  the  middle  of  the  foot,  and  the  two  flaps  dissected  forward  and  backward. 

The  Abductor  hallucis  lies  along  the  inner  border  of  the  foot.  It  arises  from 
the  inner  tubercle  on  the  under  surface  of  the  os  calcis ;  from  the  internal  annular 
ligament ;  from  the  plantar  fascia ;  and  from  the  intermuscular  septum  between  it 
and  the  Flexor  brevis  digitorum.  The  fibres  terminate  in  a  tendon  which  is 
inserted,  together  with  the  innermost  tendon  of  the  Flexor  brevis  hallucis,  into 
the  inner  side  of  the  base  of  the  first  phalanx  of  the  great  toe. 

Relations. — By  its  superficial  surface,  Avith  the  plantar  fascia ;  by  its  deep  sur- 
face, with  the  Flexor  brevis  hallucis,  the  Flexor  acccssorius,  and  the  tendons  of 
the  Flexor  longus  digitorum  and  Flexor  longus  hallucis,  the  Tibialis  anticus  and 
posticus,  the  plantar  vessels  and  nerves,  and  the  articulations  of  the  tarsus. 

The  Flexor  brevis  digitorum  (perforatus)  lies  in  the  middle  of  the  sole  of  the 
foot,  immediately  beneath1  the  plantar  fascia,  with  which  it  is  firmly  united.  It 
1  That  is,  in  order  of  dissection  of  the  sole  of  the  foot. 


OF    THE  FOOT. 


531 


arise*  by  a  narrow  tendinous  process,  from  the  inner  tubercle  of  the  os  calcis, 
from  the  central  part  of  the  plantar  fascia,  and  from  the  intermuscular 
septa  between  it  and  the  adjacent  muscles. 
It  passes  forward,  and  dividesJnto  four  tendons. 
Opposite  the  bases  of  the  first  phalanges  each 
tendon  divides  into  two  slips,  to  allow  of  the 
_re  of  the  corresponding  tendon  of  the 
Flexor  l<>ngus  digitorum  :  the  two  portions  of 
the  tendon  then  unite  and  form  a  grooved 
channel  for  the  reception  of  the  accompanying 
long  flexor  tendon.  Finally,  they  divide  a 
second  time,  to  be  inserted  into  the  sides  of 
the  second  phalanges  about  their  middle. 
The  mode  of  division  of  the  tendons  of  the 
Flexor  brevis  digitorum  and  their  insertion 
into  the  phalanges  is  analogous  to  the  Flexor 
sublimis  in  the  hand. 

Relations. — By  its  superficial  surface,  with 
the  plantar  fascia :  by  its  deep  surface,  with 
the  Flexor  accessorius,  the  Lumbricales.  the 
tendons  of  the  Flexor  longus  digitorum.  and 
the  external  plantar  vessels  and  nerve,  from 
which  it  is  separated  by  a  thin  layer  of  fascia. 
The  outer  and  inner  border*  are  separated  from 
the  adjacent  muscles  by  means  of  vertical  pro- 
longations of  the  plantar  fascia. 

Fibrous  Sheaths  of  the  Flexor  Tendons. — 
These  are  not  so  well  marked  as  in  the  fingers. 
The  flexor  tendons  of  the  toes  as  they  run 
along  the  phalanges  are  retained  agains't  the 
bones  by  a  fibrous  sheath,  forming  osseo-apo- 
neurotic  canals.  These  sheaths  are  formed 
by  strong  fibrous  bands  which  arch  across  the 
tendons  and  are  attached  on  each  side  to  the 
margins  of  the  phalanges.  Opposite  the 
middle  of  the  proximal  and  second  phalanges 
the  sheath  is  very  strong,  and  the  fibres  pass 
transversely,  but  opposite  the  joints  it  is  much 
thinner,  and  the  fibres  pass  obliquely.  Each 
sheath  is  lined  by  a  synovial  membrane  which 
is  reflected  on  the  contained  tendon. 

The  Abductor  minimi  digiti  lies  along  the 
outer  border  of  the  foot.  It  arises,  by  a  very  broad  origin,  from  the  outer  tuber- 
cle of  the  os  caleis,  from  the  under  surface  of  the  os  caleis  in  front  of  both  tuber- 
cles, from  the  fore  part  of  the  inner  tubercle,  from  the  plantar  fascia  and  the 
intermuscular  septum  between  it  and  the  Flexor  brevis  digitorum.  Its  tendon, 
after  gliding  over  a  smooth  facet  on  the  under  surface  of  the  base  of  the  fifth 
metatarsal  bone,  is  inserted  with  the  short  Flexor  of  the  little  toe  into  the  outer 
side  of  the  base  of  the  first  phalanx  of  the  little  toe. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia ;  by  its  deep  sur- 
face, with  the  Flexor  accessorius,  the  Flexor  brevis  minimi  digiti,  the  long  plantar 
ligament,  and  the  tendon  of  the  Peroneus  longus.  On  its  inner  side  are  the 
external  plantar  vessels  and  nerve,  and  it  is  separated  from  the  Flexor  brevis 
digitorum  by  a  vertical  septum  of  fascia. 

Dissection. — The  muscles  of  the  superficial  layer  should  be  divided  at  their  origin  by  insert- 
ing the  knife  beneath  each,  and  cutting  obliquely  backward,  so  as  to  detach  them  from  the 
bone ;  they  should  then  be  drawn  forward,  in  order  to  expose  the  second  layer,  but  not  cut 


FIG.  333.— Muscles  of  the  sole  of  the  foot. 
First  Layer. 


532 


THE   MUSCLES  AND    FASCIA. 


away  at  their  insertion.     The  two  layers  are  separated  by  a  thin  membrane,  the  d<< ••/> 
fascia,  on  the  removal  of  which  is  seen  the  tendon  of  the  Flexor  longus  digitorum,  the  Flexor 

accessorius,  the  tendon  of  the  Flexor  longus  hallu- 
cis, and  the  Lumbricales.  The  long  flexor  tendons 
cross  each  other  at  an  acute  angle,  the  Flexor 
longus  hallucis  running  along  the  inner  side  of 
the  foot,  on  a  plane  superior  to  that  of  the  Flexor 
longus  digitorum,  the  direction  of  which  is  ob- 
liquely outward. 

Second  Layer. 
Flexor  accessorius.  Lumbricales. 

The  Flexor  accessorius  arises  by  two 
heads ;  the  inner  or  larger,  which  is  mus- 
cular, being  attached  to  the  inner  concave 
surface  of  the  os  calcis,  and  to  the  inferior 
calcaneo-navicular  ligament ;  the  outer  head, 
flat  and  tendinous,  to  the  under  surface  of 
the  os  calcis,  in  front  of  its  outer  tubercle, 
and  to  the  long  plantar  ligament ;  the  two 
portions  join  at  an  acute  angle,  and  are 
inserted  into  the  outer  margin  and  upper 
and  under  surfaces  of  the  tendon  of  the 
Flexor  longus  digitorum,  forming  a  kind  of 
groove  in  which  the  tendon  is  lodged.1 

Relations. — By  its  superficial  surface, 
with  the  muscles  of  the  superficial  layer, 
from  which  it  is  separated  by  the  external 
plantar  vessels  and  nerves  ;  by  its  deep  sur- 
face, with  the  os  calcis  and  long  calcaneo- 
cuboid  ligament. 

The  Lumbricales  are  four  small  muscles 
accessory  to  the  tendons  of  the  Flexor 
longus  digitorum :  they  arise  from  the 
tendons  of  the  long  Flexor,  as  far  back  as 
their  angle  of  division,  each  arising  from 
two  tendons,  except  the  internal  one. 
Each  muscle  terminates  in  a  tendon, 
which  passes  forward  on  the  inner  side 
of  each  of  the  lesser  toes,  and  is  inserted 
into  the  expansion  of  the  long  Extensor 
second  ia3y3er7Muscles  °f  the  sole  °f  the  ***•  and  base  of  the  first  phalanx  of  the  cor- 
responding toe. 

Dissection. — The  flexor  tendons  should  be  divided  at  the  back  part  of  the  foot,  and  the 
Flexor  accessorius  at  its  origin,  and  drawn  forward,  in  order  to  expose  the  third  layer. 


Third  Layer. 

Flexor  brevis  hallucis. 
Adductor  obliquus  hallucis. 
Flexor  brevis  minimi  digiti. 
Adductor  transversus  hallucis. 

The  Flexor  brevis  hallucis  arises,  by  a  pointed  tendinous  process,  from  the 
inner  border  of  the  cuboid  bone,  from  the  contiguous  portion  of  the  external 
cuneiform,  and  from  the  prolongation  of  the  tendon  of  the  Tibialis  posticus,  which 

1  According  to  Turner,  the  fibres  of  the  Flexor  accessorius  end  in  aponeurotic  bands,  which  con- 
tribute slips  to  the  second,  third,  and  fourth  digits. 


OF    THE   FOOT. 


533 


is  attached  to  that  bone.  The  muscle  divides,  in  front,  into  two  portions,  which 
are  inserted  into  the  inner  and  outer  sides  of  the  base  of  the  first  phalanx  of 
the  great  toe,  a  sesaruoid  bone  being  developed  in  each  tendon  at  its  insertion. 
The  inner  portion  of  thia  muscle  is 
blended  with  the  Abductor  hallucis  pre- 
vious to  its  insertion,  the  outer  with  the 
Adductor  obliquus  hallucis.  and  the  ten- 
don of  the  Flexor  longus  hallucis  lies  in 
a  groove  between  them. 

Relations. — By  its  xup'-rlii-ial  surface, 
with  the  Abductor  hallucis,  the  tendon  of 
the  Flexor  longus  hallucis,  and  plantar  fas- 
cia :  by  its  deep  surf <«.•?.  with  the  tendon 
of  the  Peroneus  longus  and  metatarsal 
bone  of  the  great  toe ;  by  its  inner  bor- 
der, with  the  Abductor  hallucis;  by  its 
outer  border,  with  the  Adductor  obliquus 
hallucis. 

The  Adductor  obliquus  hallucis  is  a 
large,  thick,  fleshy  mass  passing  obliquely 
across  the  foot  and  occupying  the  hollow 
space  between  the  four  inner  metatarsal 
bones.  It  arises  from  the  tarsal  extrem- 
ities of  the  second,  third  and  fourth  met- 
atarsal b'.tiies  and  from  the  sheath  of  the 
tendon  of  the  Peroneus  longus,  and  is 
inserted,  together  with  the  outer  portion 
of  the  Flexor  brevis  hallucis,  into  the 
outer  side  of  the  base  of  the  first  phalanx 
of  the  great  toe. 

The  small  muscles  of  the  great  toe, 
the  Abductor.  Flexor  brevis.  Adductor 
obliquus.  and  Adductor  transversus.  like 
the  similar  muscles  of  the  thumb,  give 
off  fibrous  expansions,  at  their  inser- 
tions, to  blend  with  the  long  Extensor 
tendon. 

The  Flexor  brevis  minimi  digiti  lies 
on  the  metatarsal  bone  of  the  little  toe, 
and  much  resembles  one  of  the  Interossei. 
It  arises  from  the  base  of  the  metatarsal 
bone  of  the  little  toe.  and  from  the  sheath 
of  the  Peroneus  longus ;  its  tendon  is 
inserted  into  the  base  of  the  first  phalanx  of  the  little  toe  on  its  outer  side. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia  and  tendon 
of  the  Abductor  minimi  digiti ;  by  its  deep  surface,  with  the  fifth  metatarsal 
bone. 

The  Adductor  transversus  hallucis  (Transversus  pedis)  is  a  narrow,  flat,  muscular 
fasciculus,  stretched  transversely  across  the  heads  of  the  metatarsal  bones,  between 
them  and  the  flexor  tendons.  It  arises  from  the  inferior  metatarso-phalangeal 
ligaments  of  the  three  outer  toes,  sometimes  only  from  the  third  and  fourth  and 
from  the  transverse  ligament  of  the  metatarsus  ;  and  is  inserted  into  the  outer  side 
of  the  first  phalanx  of  the  great  toe.  its  fibres  being  blended  with  the  tendon  of 
insertion  of  the  Adductor  obliquus  hallucis. 

Relations. — By  its  mperficial  surface,  with  the  tendons  of  the  long  and  short 
Flexors  and  Lumbricales ;  by  its  deep  surface,  with  the  Interossei. 


FIG.  335.— Muscles  of  the  sole  of  the  foot.    Third 
layer. 


534 


THE  MUSCLES  AND    FASCIA. 


Fourth  Layer. 
The  Interossei. 

The  Interossei  muscles  in  the  foot  are  similar  to  those  in  the  hand,  with  this 
exception,  that  they  are  grouped  around  the  middle  line  of  the  second  toe,  instead 
of  the  middle  line  of  the  third  finger,  as  in  the  hand.  They  are  seven  in  number, 
and  consist  of  two  groups,  dorsal  and  plantar. 

The  Dorsal  interossei,  four  in  number,  are  situated  between  the  metatarsal 
bones.  They  are  bipenniform  muscles,  arising  by  two  heads  from  the  adjacent 
sides  of  the  metatarsal  bones,  between  which  they  are  placed  ;  their  tendons  are 
inserted  into  the  bases  of  the  first  phalanges,  and  into  the  aponeurosis  of  the 
common  extensor  tendon.  In  the  angular  interval  left  between  the  heads  of 


FIG.  336.— The  Dorsal  interossei.    Left  foot. 


FIG.  337.— The  Plantar  interossei.    Left  foot. 


each  muscle  at  its  posterior  extremity  the  perforating  arteries  pass  to  the 
dorsum  of  the  foot,  except  in  the  First  interosseous  muscle,  where  the  interval 
allows  the  passage  of  the  communicating  branch  of  the  dorsalis  pedis  artery. 
The  First  dorsal  interosseous  muscle  is  inserted  into  the  inner  side  of  the  second 
toe ;  the  other  three  are  inserted  into  the  outer  sides  of  the  second,  third,  and 
fourth  toes. 

The  Plantar  interossei,  three  in  number,  lie  beneath,  rather  than  between,  the 
metatarsal  bones.  They  are  single  muscles,  and  are  each  connected  with  but  one 
metatarsal  bone.  They  arise  from  the  base  and  inner  sides  of  the  shaft  of  the 
third,  fourth,  and  fifth  metatarsal  bones,  and  are  inserted  into  the  inner  sides  of 
the  bases  of  the  first  phalanges  of  the  same  toes,  and  into  the  aponeurosis  of  the 
common  extensor  tendon. 

Nerves. — The  Flexor  brevis  digitorum,  the  Flexor  brevis  and  ^  Abductor 
hallucis,  and  the  two  inner  Lumbricales  are  supplied  by  the  internal  plantar 
nerve ;  all  the  other  muscles  in  the  sole  of  the  foot  by  the  external  plantar.  The 
First  and  Second  dorsal  interossei  muscles  receive  extra  filaments  from  the  gan- 
glionic  enlargement  of  the  anterior  tibial  nerve  on  the  dorsum  of  the  foot. 

Actions. — All  the  muscles  of  the  foot  act  upon  the  toes,  and  for  purposes  of 
description  as  regards  their  action  may  be  grouped  as  Abductors,  Adductors, 


SURFACE   FORM   OF    THE  LOWER    EXTREMITY.  535 

Flexors,  or  Extensors.  The  Abdwtors  are  the  Dorsal  interossei,  the  Abductor 
hallucis.  and  the  Abductor  minimi  digiti.  The  Dorsal  interossei  are  abductors 
from  an  imaginary  line  passing  through  the  axis  of  the  second  toe,  so  that  the 
first  muscle  draws  the  second  toe  inward,  toward  the  great  toe ;  the  second 
muscle  draws  the  same  toe,  outward ;  the  third  draws  the  third  toe,  and  the 
fourth  draws  the  fourth  toe,  in  the  same  direction.  Like  the  interossei  in  the 
hand,  they  also  flex  the  proximal  phalanges  and  extend  the  two  terminal  pha- 
langes. The  Abductor  hallucis  abducts  the  great  toe  from  the  others,  and  also 
flexes  the  proximal  phalanx  of  this  toe.  And  in  the  same  way  the  action  of  the 
Abductor  minimi  digiti  is  twofold — as  an  abductor  of  this  toe  from  the  others, 
and  also  as  a  flexor  of  the  proximal  phalanx.  The  Adductors  are  the  Plantar 
interossei,  the  Adductor  obliquus  hallucis,  and  the  Adductor  transversus  hallucis. 
The  plantar  interosseous  muscles  adduct  the  third,  fourth,  and  fifth  toes  toward 
the  imaginary  line  passing  through  the  second  toe,  and  by  means  of  their  inser- 
tion into  the  aponeurosis  of  the  extensor  tendon  they  flex  the  proximal  phalanges 
and  extend  the  two  terminal  phalanges.  The  Adductor  obliquus  hallucis  is 
chiefly  concerned  in  adducting  the  great  toe  toward  the  second  one,  but  also 
assists  in  flexing  this  toe.  The  Adductor  transversus  hallucis  approximates  all 
the  toes,  and  thus  increases  the  curve  of  the  transverse  arch  of  the  metatarsus. 
The  Flexors  are  the  Flexor  brevis  digitorum.  the  Flexor  accessorius.  the  Flexor 
brevis  hallucis.  the  Flexor  brevis  minimi  digiti,  and  the  Lumbricales.  The 
Flexor  brevis  digitorum  flexes  the  second  phalanges  upon  the  first,  and,  con- 
tinuing its  action,  may  flex  the  first  phalanges  also  and  bring  the  toes  together. 
The  Flexor  accessorius  assists  the  Long  flexor  of  the  toes,  and  converts  the 
oblique  pull  of  the  tendons  of  that  muscle  into  a  direct  backward  pull  upon  the 
toes.  The  Flexor  brevis  minimi  digiti  flexes  the  little  toe  and  draws  its  meta- 
tarsal  bone  downward  and  inward.  The  Lumbricales,  like  the  corresponding 
muscles  in  the  hand,  assist  in  flexing  the  proximal  phalanges,  and  by  their  inser- 
tion into  the  long  Extensor  tendon  aid  in  straightening  the  two  terminal  pha- 
langes. The  only  muscle  in  the  Extensor  group  is  the  Extensor  brevis  digi- 
torum. It  extends  the  first  phalanx  of  the  great  toe,  and  assists  the  long  Exten- 
sor in  extending  the  next  three  toes,  and  at  the  same  time  gives  to  the  toes  an 
outward  direction  when  they  are  extended. 

Surface  Form. — Of  the  muscles  of  the  thigh,  those  of  the  iliac  region  have  no  influence 
on  surface  form,  while  those  of  the  anterior  femoral  region,  being  to  a  great  extent  superficial, 
largely  contribute  to  the  surface  form  of  this  part  of  the  body.  The  Tensor  vaginae  femoris 
produces  a  broad  elevation  immediately  below  the  anterior  portion  of  the  crest  of  the  ilium  and 
behind  the  anterior  superior  spinous  process.  From  its  lower  border  a  longitudinal  groove, 
corresponding  to  the  ilio-tibial  band,  may  be  seen  running  down  the  outer  side  of  the  thigh  to 
the  outer  side  of  the  knee-joint.  The  Sartoriut  muscle,  when  it  is  brought  into  action  by 
flexing  the  leg  on  the  thigh  and  the  thigh  on  the  pelvis,  and  rotating  the  thigh  outward, 
presents  a  well-marked  surface  form.  At  its  upper  part,  where  it  constitutes  the  outer 
boundary  of  Scarpa's  triangle,  it  forms  a  prominent  oblique  ridge,  which  becomes  changed  into 
a  flattened  plane  below,  and  this  gradually  merges  in  a  general  fulness  on  the  inner  side  of  the 
knee-joint.  When  the  Sartorius  is  not  in  action,  a  depression  exists  between  the  Extensor 
quadriceps  and  the  Adductor  muscles,  running  obliquely  downward  and  inward  from  the  apex 
of  Scarpa's  triangle  to  the  inner  side  of  the  knee,  which  corresponds  to  this  muscle.  In  the 
depressed  angle  formed  by  the  divergence  of  the  Sartorius  and  Tensor  vaginae  femoris  muscles, 
just  below  the  anterior  superior  spinous  process  of  the  ilium,  the  Rechufemoru  muscle  appears, 
and.  below  this,  determines  to  a  great  extent  the  convex  form  of  the  front  of  the  thigh. 
In  a  well- developed  subject  the  borders  of  the  muscle,  when  in  action,  are  clearly  to  be  defined. 
The  Vnstiis  extennts  forms  a  long  flattened  plane  on  the  outer  side  of  the  thigh,  traversed  by 
the  longitudinal  groove  formed  by  the  ilio-tibial  band.  The  Vast  us  interims,  on  the  inner  side 
of  the  lower  half  of  the  thigh,  gives  rise  to  a  considerable  prominence,  which  increases  toward 
the  knee  and  terminates  somewhat  abruptly  in  this  situation  with  a  full,  curved  outline.  The 
Crnrem  and  Subcrureus  are  completely  hidden,  and  do  not  directly  influence  surface  form.  The 
Aibiuctnr  nt  !'.«•/<*.  constituting  the  internal  femoral  group,  are  not  to  be  individually  distin- 
guished from  each  other,  with  the  exception  of  the  upper  tendon  of  the  Adductor  longus  and 
the  lower  tendon  of  the  Adductor  magnus.  The  upper  tendon  of  the  Adductor  longus,  when 
the  muscle  is  in  action,  stands  out  as  a  prominent  ridge,  which  runs  obliquely  downward  and 
outward  from  the  neighborhood  of  the  pubic  spine,  and  forms  the  inner  boundary  of  a  flattened 
triangular  space  on  the  upper  part  of  the  front  of  the  thigh,  known  as  Scarpa's  triangle.  The 


536  THE  MUSCLES  AND    FASCIA. 

lower  tendon  of  the  Adductor  magnus  can  be  distinct!}'  felt  as  a  short  ridge  extending  down  to 
the  Adductor  tubercle  on  the  internal  condyle,  between  the  Sartorius  and  Vastus  internus. 
The  Adductor  group  of  muscles  fills  in  the  triangular  space  at  the  upper  part  of  the  thigh, 
formed  between  the  oblique  femur  and  the  pelvic  wall,  and  to  them  is  due  the  contour  of  the 
inner  border  of  the  thigh,  the  Gracilis  largely  contributing  to  the  smoothness  of  the  outline. 
These  muscles  are  not  marked  off  on  the  surface  from  those  of  the  posterior  femoral  region  by 
any  intermuscular  marking ;  but  on  the  outer  side  of  the  thigh  these  latter  muscles  are  denned 
from  the  Vastus  externus  by  a  distinct  marking,  corresponding  to  the  external  intermuscular 
septum.  The  Glutens  maximus  and  a  part  of  the  Glutens  medius  are  the  only  muscles  of  the 
buttock  which  influence  surface  form.  The  other  part  of  the  Gluteus  medius,  the  Gluteus 
minimus,  and  the  External  rotators  are  completely  hidden.  The  Gluteus  maximus  forms  the 
full  rounded  outline  of  the  buttock :  it  is  more  prominent  behind,  compressed  in  front,  and 
terminates  at  its  tendinous  insertion  in  a  depression  immediately  behind  the  great  trochanter. 
Its  lower  border  does  not  correspond  to  the  gluteal  fold,  but  is  much  more  oblique,  being 
marked  by  a  line  drawn  from  the  side  of  the  coccyx  to  the  lower  part  of  the  great  trochanter. 
From  beneath  the  fold  of  the  buttock  the  hamstring  muscles  appear,  at  first  narrow  and  not  well 
marked,  but  as  they  descend  becoming  more  prominent  and  widened  out,  and  eventually  divid- 
ing into  two  well-marked  ridges,  which  form  the  upper  boundaries  of  the  popliteal  space, 
being  formed  by  the  tendons  of  the  inner  and  outer  hamstring  muscles  respectively.  In  the 
upper  part  of  the  thigh  these  muscles  are  not  to  be  individually  distinguished  from  each  other, 
but  lower  down,  the  separation  between  the  Semitendinosus  and  Semimembranosus  is  denoted 
by  a  slight  intermuscular  marking.  The  external  hamstring  tendon  formed  by  the  Biceps  is 
seen  as  a  thick  cord  running  down  to  the  head  of  the  fibula.  The  inner  hamstring  tendons 
comprise  the  Semitendinosus,  the  Semimembranosus,  and  the  Gracilis.  The  Semitendinosus  is  the 
most  internal  of  these,  and  can  be  felt,  in  certain  positions  of  the  limb,  as  a  sharp  cord ;  the 
Semimembranosus  is  thick,  and  the  Gracilis  is  situated  a  little  farther  forward  than  the  other 
two.  All  the  muscles  on  the  front  of  the  leg  appear  to  a  certain  extent  somewhere  on  the 
surface,  but  the  form  of  this  region  is  mainly  dependent  upon  the  Tibialis  anticus  and  the 
Extensor  longus  digitorum.  The  Tibialis  anticus  is  well  marked,  and  presents  a  fusiform 
enlargement  at  the  outer  side  of  the  tibia,  and  projects  beyond  the  crest  of  the  shin-bone. 
From  the  muscular  mass  its  tendon  may  be  traced  downward,  standing  out  boldly,  when  the 
muscle  is  in  action,  on  the  front  of  the  tibia  and  ankle-joint,  and  coursing  down  to  its  insertion 
along  the  inner  border  of  the  foot.  A  well-marked  groove  separates  this  muscle  externally 
from  the  Extensor  longiis  digitorum,  which  fills  up  the  rest  of  the  space  between  the  upper 
part  of  the  shaft  of  the  tibia  and  fibula.  It  does  not  present  so  bold  an  outline  as  the  Tibialis 
anticus,  and  its  tendon  below,  diverging  from  the  tendon  of  the  Tibialis  anticus,  forms  a  sort  of 
plane,  in  which  may  be  seen  the  tendon  of  the  Extensor  proprius  hallucis.  A  groove  on  the 
outer  side  of  the  Extensor  longus  digitorum,  seen  most  plainly  when  the  muscle  is  in  action, 
separates  from  it  a  slight  eminence  corresponding  to  the  Peroneus  tertius.  The  fleshy  fibres  of 
the  Peroneus  longus  are  strongly  marked  at  the  upper  part  of  the  outer  side  of  the  leg,  especi- 
ally when  the  muscle  is  in  action.  It  forms  a  bold  swelling,  separated  by  furrows  from  the 
Extensor  longus  digitorum  in  front  and  the  Soleus  behind.  Below,  the  fleshy  fibres  terminate 
abruptly  in  a  tendon  which  overlaps  the  more  flattened  form  of  the  Peroneus  brevis.  At  the 
external  malleolus  the  tendon  of  the  Peroneus  brevis  is  more  marked  than  that  of  the  Peroneus 
longus.  On  the  dorsum  of  the  foot  the  tendons  of  the  Extensor  muscles,  emerging  from 
beneath  the  anterior  annular  ligament,  spread  out  and  can  be  distinguished  in  the  following 
order :  The  most  internal  and  largest  is  the  Tibialis  anticus,  then  the  Extensor  proprius  hallucis  : 
next  comes  the  Extensor  longus  digitorum,  dividing  into  four  tendons  to  the  four  outer  toes ;  and 
lastly,  most  externally,  is  the  Peroneus  tertius.  The  flattened  form  of  the  dorsum  of  the  foot  is 
relieved  by  the  rounded  outline  of  the  fleshy  belly  of  the  Extensor  brevis  digitorum,  which  forms  a 
soft  fulness  on  the  outer  side  of  the  tarsus  in  front  of  the  external  malleolus,  and  by  the  Dorsal 
interossei,  which  bulge  between  the  metatarsal  bones.  At  the  back  of  the  knee  is  the  popliteal 
space,  bounded  above  by  the  tendons  of  the  hamstring  muscle  ;  below,  by  the  two  heads  of  the 
Gastrocnemius.  Below  this  space  is  the  prominent  fleshy  mass  of  the  calf  of  the  leg,  produced 
by  the  Gastrocnemius  and  Soleus.  When  these  muscles  are  in  action,  as  in  standing  on  tiptoe, 
the  borders  of  the  Gastrocnemius  are  well  defined,  presenting  two  curved  lines,  which  converge 
to  the  tendon  of  insertion.  Of  these  borders,  the  inner  is  more  prominent  than  the  outer. 
The  fleshy  mass  of  the  calf  terminates  somewhat  abruptly  below  in  the  tendo  Achillis.  which 
stands  out  prominently  on  the  lower  part  of  the  back  of  the  leg.  It  presents  a  somewhat 
tapering  form  in  the  upper  three-fourths  of  its  extent,  but  widens  out  slightly  below.  When 
the  muscles  of  the  calf  are  in  action,  the  lateral  portions  of  the  Soleus  may  be  seen,  forming 
curved  eminences,  of  which  the  outer  is  the  longer,  on  either  side  of  the  Gastrocnemius. 
Behind  the  inner  border  of  the  lower  part  of  the  shaft  of  the  tibia  a  well-marked  ridge,  pro- 
duced by  the  tendon  of  the  Tibialis  posticus,  is  visible  when  this  muscle  is  in  a  state  of  con- 
traction. 

On  the  sole  of  the  foot  the  superficial  layer  of  muscles  influences  surface  form ;  the 
Abductor  minimi  digiti  most  markedly.  This  muscle  forms  a  narrow  rounded  elevation  along 
the  outer  border  of  the  foot,  while  the  Abductor  hallucis  does  the  same,  though  to  a  less  ex- 
tent, on  the  inner  side.  The  Flexor  brevis  digitorum,  bound  down  by  the  plantar  fascia,  is  not 
very  apparent ;  it  produces  a  flattened  form,  covered  by  the  thickened  skin  of  the  sole,  which 
is  here  thrown  into  numerous  wrinkles. 


SURGICAL    AXATOMY   OF    THE   LOWER    EXTREMITY.        537 


EMELLUS   SUPERIOR. 

OBTURATOR    INTERNUS 

GEMELLUS    INFERIOR. 

BTURATOR    EXTERNUS 

UAORATUS    FEMORIS. 


SURGICAL   ANATOMY   OF  THE   LOWER   EXTREMITY. 

The  student  should  now  consider  the  effects  produced  by  the  action  of  the  various  muscles 
in  fractures  of  the  bones  of  the  lower  extremity.  The  more  common  forms  of  fractures  are 

selected  for  illustration  and 
description. 

In  fracture  of  the  neck 
of  the  femur  internal  to  the 
capsular  ligameiit  (Fig.  338) 
the  characteristic  marks  are 
slight  shortening  of  the 
limb  and  eversion  of  the 
foot,  neither  of  which  symp- 
toms occurs,  however,  in 
some  cases  until  some  time 
after  the  injury.  The 
eversion  is  caused  by  the 

-PYRIFORMIS.  weight  of  the  limb  rotating 

it  outward.  The  shorten- 
ing is  produced  by  the 
action  of  the  Glutei,  and 
by  the  Rectus  femoris  in 
front  and  the  Biceps, 
Semitendinosus,  and  Serni- 
membranosus  behind. 

In  fracture  of  the 
femur  just  below  thetrochan- 
ters  (Fig.  339)  the  upper 
fragment,  the  portion  chiefly 
displaced,  is  tilted  forward 


FIG.  338.— Fracture  of  the  neck  of  the   femur    within    the  capsular 
ligament. 

almost  at  right  angles  with  the  pelvis  by  the  combined  action  of 
the  Psoas  and  Iliacus.  and.  at  the  same  time,  everted  and  drawn 
outward  by  the  External  rotator  and  Glutei  muscles,  causing  a 
marked  prominence  at  the  upper  and  outer  side  of  the  thigh,  and 
much  pain  from  the  bruising  and  laceration  of  the  muscles.  The 
limb  is  shortened,  in  consequence  of  the  lower  fragment  being 
drawn  upward  by  the  rectus  in  front,  and  the  Biceps.  Semi- 
membranosus.  and  Semitendinosus  behind,  and.  at  the  same 
time,  everted,  and  the  upper  end  thrown  outward  and  the  lower 
inward  by  the  Pectineus  and  Adductor  muscles.  This  fracture 
may  be  reduced  in  two  different  methods  :  either  by  direct  relax- 
ation of  all  the  opposing  muscles,  to  effect  which  the  limb  should 
be  placed  on  a  double  inclined  plane ;  or  by  overcoming  the  con- 
traction of  the  muscles  by  continued  extension,  which  may  be 
effected  by  means  of  the  long  splint. 

Oblique  fracture  of  the  femur  immf-dintihi  above  the  condyles 
Fi-r.  34<i  is  a  formidable  injury,  and  attended  with  considerable 
displacement.  On  examination  of  the  limb  the  lower  fragment 
may  be  felt  deep  in  the  popliteal  space,  being  drawn  backward 
by  the  Gastrocnemiua  and  Plantaris  muscles,  and  upward  by 
the  posterior  Femoral  and  Rectus  muscles.  The  pointed  end 
of  the  upper  fragment  is  drawn  inward  by  the  Pectineus  and  Ad- 
ductor muscles,  and  tilted  forward  by  the  Psoas  and  Iliacus,  pierc- 
ing the  Rectus  muscle  and  occasionally  the  integument.  Relaxation 
of  these  muscles  and  direct  approximation  of  the  broken  frag- 
ments are  effected  by  placinsr  the  limb  on  a  double  inclined  plane. 
The  greatest  care  is  requisite  in  keeping  the  pointed  extremity 
of  the  upper  frasnient  in  proper  position  ;  otherwise,  after  union 
of  the  fracture,  the  power  of  extension  of  the  limb  is  partially 
destroyed,  from  the  Rectus  muscle  being  held  down  by  the  frac- 
tiirv'l  end  of  the  bone,  and  from  the  patella,  when  elevated, 
beinsr  drawn  upward  atrainst  the  projectins  fragment.  FIG.  339.— Fracture  of  the  femur 

In  fracture  of  the  paUUa  (Fig.  341)  the  fragments  are  sepa-    below  the  trochanters. 
rated    by  the   effusion    which   takes    place    into  the  joint,   and 
possibly  by  the  action  of  the   Quadriceps  extensor;   the  extent  of  separation  of  the  two 


MEMBRANOSUS. 


TENDINOSUS. 


538 


THE   MUSCLES   AND    FASCIA. 


fragments  depending  upon  the  degree  of  laceration   of  the  ligamentous  structures  around 
the  bone. 

In  oblique  fracture  of  the  shaft  of  the  tibia  (Fig.  342),  if  the  'fracture  has  taken  place 
obliquely  from  above,  downward  and  forward,  the  fragments  ride  over  one  another,  the  lower 

fragments  being  drawn  backward  and  upward 
by  the  powerful  action  of  the  muscles  of  the 
calf;  the  pointed  extremity  of  the  upper 
fragment  projects  forward  immediately  be- 
neath the  integument,  often  protruding 
through  it  and  rendering  the  fracture  a 
compound  one.  If  the  direction  of  the 
fracture  is  the  reverse  of  that  shown  in  the 
figure,  the  pointed  extremity  of  the  lower 
fragment  projects  forward,  riding  upon  the 
lower  end  of  the  upper  one.  By  bending  the 
knee,  which  relaxes  the  opposing  muscles, 
and  making  extension  from  the  ankle  and 
counter-extension  at  the  knee,  the  fragments 
may  be  brought  into  apposition.  It  is  often 
necessary,  however,  in  compound  fracture,  to 
remove  a  portion  of  the  projecting  bone  with 
the  saw  before  complete  adaptation  can  be 
effected. 

Fracture  of  the  fibula  with  dislocation 
of  the  foot  outward   (Fig.   343),  commonly 
known  as  "Pott's  Fracture,"  is  one  of  the 
most  frequent  injuries  of  the   ankle-joint. 
FIG.  341. —  Fracture  The  end  of  the  tibia  is  displaced  from  the 
of  the  patella.  corresponding  surface  of  the  astragalus ;  the 

internal  lateral  ligament  is  ruptured  ;    and 

the  inner  malleolus  projects  inward  beneath  the  integument,  which  is  tightly  stretched  over 

it  and  in  danger  of  bursting.  The  fibula  is  broken,  usually 
from  two  to  three  inches  above  the  ankle,  and  occasionally 
that  portion  of  the  tibia  with  which  it  is  more  directly 
connected  below ;  the  foot  is  everted  by  the  action  of 
the  Peroneus  longus,  its  inner  border  resting  upon  the 
ground,  and  at  the  same  time  the  heel  is  drawn  up  by 
the  muscles  of  the  calf.  This  injury  may  be  at  once 
reduced  by  flexing  the  leg  at  right  angles  with  the  thigh, 
which  relaxes  all  the  opposing  muscles,  and  by  making 
extension  from  the  ankle  and  counter-extension  at  the  knee. 


FIG.  340.— Fracture  of  the 
femur  above  the  condyles. 


FIG.  342.— Oblique  fracture  of 
the  shaft  of  the  tibia. 


FIG.  343.— Fracture  of  the  fibula  with  dislocation  of  the 
foot  outward — "  Pott's  Fracture." 


THE    ARTERIES. 


Arteries  are  cylindrical  tubular  vessels  which  serve  to  convey  blood  from 
_L  both  ventricles  of  the  heart  to  every  part  of  the  body.  These  vessels  were 
named  arteries  (dr/to.  air :  -r^titv,  to  contain)  from  the  belief  entertained  bv  the 
ancients  that  they  contained  air.  To  Galen  is  due  the  honor  of  refuting  this 
opinion  :  he  showed  that  these  vessels,  though  for  the  most  part  empty  after  death, 
contain  blood  in  the  living  body. 

The  pulmonary  artery,  which  arises  from  the  right  ventricle  of  the  heart, 
carries  venous  blood  directly  into  the  lungs,  whence  it  is  returned  by  the  pul- 
monary veins  into  the  left  auricle.  This  constitutes  the  lesser  or  pulmonic  circu- 
lation. The  great  artery  which  arises  from  the  left  ventricle,  the  aorta,  conveys 
arterial  blood  to  the  body  generally,  whence  it  is  brought  back  to  the  right 
side  of  the  heart  by  means  of  the  veins.  This  constitutes  the  greater  or  systemic 
circulation. 

The  distribution  of  the  systemic  arteries  is  like  a  highly  ramified  tree,  the 
common  trunk  of  which,  formed  by  the  aorta,  commences  at  the  left  ventricle  of 
the  heart,  the  smallest  ramifications  corresponding  to  the  circumference  of 
the  body  and  the  contained  organs.  The  arteries  are  found  in  nearly  every 
part  of  the  body,  with  the  exception  of  the  hairs,  nails,  epidermis,  cartilages, 
and  cornea  :  and  the  larger  trunks  usually  occupy  the  most  protected  situa- 
tions, running,  in  the  limbs,  along  the  flexor  side,  where  they  are  less  exposed 
to  injury. 

There  is  considerable  variation  in  the  mode  of  division  of  the  arteries  :  occa- 
sionally a  short  trunk  subdivides  into  several  branches  at  the  same  point,  as  we 
observe  in  the  coeliac  and  thyroid  axes ;  or  the  vessel  may  give  off  several  branches 
in  succession,  and  still  continue  as  the  main  trunk,  as  is  seen  in  the  arteries  of 
the  limbs;  but  the  usual  division  is  dichotomous;  as,  for  instance,  the  aorta 
dividing  into  tne  two  common  iliacs.  and  the  common  carotid  into  the  external 
and  internal. 

The  branches  of  arteries  arise  at  very  variable  angles :  some,  as  the  superior 
intercostal  arteries  from  the  aorta,  arise  at  an  obtuse  angle :  others,  as  the  lumbar 
arteries,  at  a  right  angle :  or.  as  the  spermatic,  at  an  acute  angle.  An  artery  from 
which  a  branch  is  given  off  is  smaller  in  size,  but  retains  a  uniform  diameter  until 
a  second  branch  is  derived  from  it.  A  branch  of  an  artery  is  smaller  than  the 
trunk  from  which  it  arises ;  but  if  an  artery  divides  into  two  branches,  the  com- 
bined area  of  the  two  vessels  is,  in  nearly  every  instance,  somewhat  greater  than 
that  of  the  trunk :  and  the  combined  area  of  all  the  arterial  branches  greatlv 
exceeds  the  area  of  the  aorta;  so  that  the  arteries  collectively  may  be  regarded 
as  a  cone,  the  apex  of  which  corresponds  to  the  aorta,  the  base  to* the  capillary 
system. 

The  arteries,  in  their  distribution,  communicate  freely  with  one  another,  form- 
ing what  is  called  an  i.'fn-'tst'.'/iiosis  (d^d.  between;  <rro(«a,  mouth),  or  inosculation  ; 
and  this  communication  is  very  free  between  the  large  as  well  as  between  the 
smaller  branches.  The  anastomosis  between  trunks  of  equal  size  is  found  where 
great  freedom  and  activity  of  the  circulation  are  requisite,  as  in  the  brain;  here 
the  two  vertebral  arteries  unite  to  form  the  basilar.  and  the  two  internal  carotid 
arteries  are  connected  by  a  short  communicating  trunk ;  it  is  also  found  in  the 
abdomen,  the  intestinal  arteries  having  verv  free  anastomoses  between  their  larger 

539 


540  THE  ARTERIES. 

branches.  In  the  limbs  the  anastomoses  are  most  frequent  and  of  largest  size 
around  the  joints,  the  branches  of  an  artery  above  freely  inosculating  with 
branches  from  the  vessels  below ;  these  anastomoses  are  of  considerable  interest  to 
the  surgeon,  as  it  is  by  their  enlargement  that  a  collateral  circulation  is  established 
after  the  application  of  a  ligature  to  an  artery  for  the  cure  of  aneurism.  The 
smaller  branches  of  arteries  anastomose  more  frequently  than  the  larger,  and 
between  the  smallest  twigs  these  inosculations  become  so  numerous  as  to  constitute 
a  close  network  that  pervades  nearly  every  tissue  of  the  body. 

Throughout  the  body  generally  the  larger  arterial  branches  pursue  a  perfectly 
straight  course,  but  in  certain  situations  they  are  tortuous ;  thus,  the  facial  artery 
in  its  course  over  the  face,  and  the  arteries  of  the  lips,  are  extremely  tortuous  in 
their  course,  to  accommodate  themselves  to  the  movements  of  the  parts.  The 
uterine  arteries  are  also  tortuous,  to  accommodate  themselves  to  the  increase  of 
size  which  the  organ  undergoes  during  pregnancy.  Again,  the  internal  carotid 
and  vertebral  arteries,  previous  to  their  entering  the  cavity  of  the  skull,  describe 
a  series  of  curves,  which  are  evidently  intended  to  diminish  the  velocity  of  the 
current  of  blood  by  increasing  the  extent  of  surface  over  which  it  moves  and 
adding  to  the  amount  of  impediment  which  is  produced  by  friction. 

The  arteries  are  dense  in  structure,  of  considerable  strength,  highly  elastic, 
and,  when  divided,  they  preserve,  although  empty,  their  cylindrical  form. 

The  minute  structure  of  these  vessels  has  been  described  in  the  chapter  on 
General  Anatomy. 

In  the  description  of  the  arteries  we  shall  first  consider  the  efferent  trunk  of 
the  pulmonic  circulation,  the  pulmonary  artery,  and  then  the  efferent  trunk  of  the 
systemic  circulation,  the  aorta  and  its  branches. 

THE  PULMONARY  ARTERY  (Fig.  344). 

The  pulmonary  artery  conveys  the  venous  blood  from  the  right  side  of  the  heart 
to  the  lungs.  It  is  a  short,  wide  vessel,  about  two  inches  in  length,  arising  from 
the  left  side  of  the  base  of  the  right  ventricle,  in  front  of  the  aorta.  It  passes 
obliquely  upward  and  backward,  passing  at  first  in  front  of,  and  then  to  the  left 
of,  the  ascending  aorta  as  far  as  the  under  surface  of  the  transverse  aorta,  where 
it  divides  into  two  branches  of  nearly  equal  size — the  right  and  left  pulmonary 
arteries. 

Relations. — The  whole  of  this  vessel  is  contained,  together  with*  the  ascending 
aorta,  in  the  pericardium,  being  enclosed  with  it  in  a  tube  of  serous  membrane, 
continued  upward  from  the  base  of  the  heart,  and  has  attached  to  it,  above,  the 
fibrous  layer  of  the  membrane.  Behind,  it  rests  at  first  upon  the  ascending 
aorta,  and  higher  up  lies  in  front  of  the  left  auricle.  On  each  side  of  its  origin 
is  the  appendix  of  the  corresponding  auricle  and  a  coronary  artery ;  and  higher 
up  it  passes  to  the  left  side  of  the  ascending  aorta. 

The  right  pulmonary  artery,  longer  and  larger  than  the  left,  pierces  the  peri- 
cardium and  runs  horizontally  outward,  behind  the  ascending  aorta  and  superior 
vena  cava,  to  the  root  of  the  right  lung,  where  it  divides  into  two  branches,  of 
which  the  lower,  which  is  the  smaller,  supplies  the  lower  lobe ;  the  upper  supplies 
the  upper  lobe,  giving  a  branch  to  the  middle  lobe. 

The  left  pulmonary  artery,  shorter  and  somewhat  smaller  than  the  right, 
pierces  the  pericardium  and  passes  horizontally  in  front  of  the  descending  aorta 
and  left  bronchus  to  the  root  of  the  left  lung,  where  it  divides  into  two  branches 
for  the  two  lobes. 

The  root  of  the  left  pulmonary  artery  is  connected  to  the  under  surface  of  the 
arch  of  the  aorta  (transverse  aorta)  by  a  short  fibrous  cord,  the  remains  of  a  vessel 
peculiar  to  foetal  life,  the  ductus  arteriosus. 

The  terminal  branches  of  the  pulmonary  artery  will  be  described  with  the 
anatomy  of  the  lung. 


THE   AORTA. 


541 


THE  AORTA. 

The  aorta  (do/>ny,  arteria  magna)  is  the  main  trunk  of  a  series  of  vessels  which 
convey  the  oxygenated  blood  to  every  part  of  the  body  for  its  nutrition.  This 
vessel  commences  at  the  upper  part  of  the  left  ventricle,  and,  after  ascending  for 
a  short  distance,  arches  backward  to  the  left  side,  over  the  root  of  the  left  lung, 
then  descends  within  the  thorax  on  the  left  side  of  the  vertebral  column,  passes 
through  the  aortic  opening  in  the  Diaphragm,  and,  entering  the  abdominal  cavity, 
terminates,  considerably  diminished  in  size,  opposite  the  fourth  lumbar  vertebra, 


Right  vagus.  -X 
Recurrent  laryngeal.    \ 


Left  vagus. 
Left  phrenic. 
Thoracic  duct. 


Bight 
coronary 


Left 
oronary. 


FIG.  345.— Plan  of  the 
branches. 


FIG.  344.— The  arch  of  the  aorta  and  its  branches. 


where  it  divides  into  the  right  and  left  common  iliac  arteries.  Hence  its  division 
into  the  ascending  aorta,  the  arch  of  the  aorta  or  transverse  aorta,  and  the 
descending  aorta,  which  last  is  again  divided  into  thoracic  aorta  and  abdominal 
aorta,  from  the  position  of  these  part.<. 

THE  ASCENDING  AORTA. 

The  ascending  aorta  is  about  two  inches  in  length.  It  commences  at  the 
upper  part  of  the  left  ventricle,  on  a  level  with  the  lower  border  of  the  third  costal 
cartilage  behind  the  left  half  of  the  sternum  ;  it  passes  obliquely  upward,  forward, 


542  THE   ARTERIES. 

and  to  the  right  in  the  direction  of  the  heart's  axis,  as  high  as  the  upper  border  of 
the  second  right  costal  cartilage,  describing  a  slight  curve  in  its  course,  and  being 
situated,  when  distended,  about  a  quarter  of  an  inch  behind  the  posterior  surface 
of  the  sternum.  A  little  above  its  commencement  it  is  somewhat  enlarged,  and 
presents  three  small  dilatations,  called  the  sinuses  of  the  aorta  (sinuses  of 
Valsalva),  opposite  to  Avhich  are  attached  the  three  semilunar  valves,  which  serve 
the  purpose  of  preventing  any  regurgitation  of  blood  into  the  cavity  of  the 
ventricle.  A  section  of  the  aorta  opposite  this  part  has  a  somewhat  triangular 
figure,  but  below  the  attachment  of  the  valves  it  is  circular.  This  portion  of  the 
aorta  is  contained  in  the  cavity  of  the  pericardium,  and,  together  with  the  pul- 
monary artery,  is  invested  in  a  tube  of  serous  membrane,  continued  on  to  them 
from  the  surface  of  the  heart. 

Relations. — The  ascending  aorta  is  covered  at  its  commencement  by  the 
trunk  of  the  pulmonary  artery  and  the  right  auricular  appendix,  and,  higher  up,  is 
separated  from  the  sternum  by  the  pericardium  over  which  lie : — the  right  pleura, 
and  anterior  margin  of  right  lung,  some  loose  areolar  tissue,  and  the  remains  of 
the  thymus  gland;  behind,  it  rests  upon  the  right  pulmonary  artery  and  left 
auricle.  On  the  right  side  it  is  in  relation  with  the  superior  vena  cava  and  right 
auricle ;  on  the  left  side,  with  the  main  pulmonary  artery. 

PLAN  OF  THE  RELATIONS  OF  THE  ASCENDING  AORTA. 

In  front. 

Pulmonary  artery. 
Right  auricular  appendix. 
Pericardium. 

Right  side.  /ArchofAortaX  Leftside. 

Superior  cava.  (     ^ortioL^  Pulmonary  artery. 

Right  auricle.  j 

Behind. 

Eight  pulmonary  artery. 
Left  auricle. 
Pericardium. 

BRANCHES  OF  THE  ASCENDING  AORTA. 

The  only  branches  of  the  ascending  aorta  are  the  two  coronary  arteries. 
They  supply  the  heart,  and  are  two  in  number,  right  and  left,  arising  near  the 
commencement  of  the  aorta  immediately  above  the  free  margin  of  the  semilunar 
valves. 

THE  CORONARY  ARTERIES. 

The  Right  Coronary  Artery,  about  the  size  of  a  crow's  quill,  arises  from  the 
aorta  immediately  above  the  free  margin  of  the  anterior  semilunar  valve.  It 
passes  forward  between  the  pulmonary  artery  and  the  right  auricular  appendix, 
then  runs  obliquely  to  the  righTside  in  lhe"groove  between  the  right  auricle  and 
ventricle,  and,  curving  around  the  right  border  of  the  heart,  runs  along  its  posterior 
surface  as  far  as  the  posterior  interventricular  groove,  where  it  divides  into  two 
branches,  one  of  which  (transverse]  continues  onward  in  the  groove  between  the 
left  auricle  and  ventricle,  and  anastomoses  with  the  left  coronary ;  the  other  (de- 
scending} descends  along  the  posterior  interventricular  furrow,  supplying  branches 
to  both  ventricles  and  to  the  septum,  and  anastomosing  at  the  apex  of  the  heart 
with  the  descending  branches  of  the  left  coronary. 

This  vessel  sends  a  large  branch  (marginal)  along  the  thin  margin  of  the  right 
ventricle  to  the  apex,  and  numerous  small  branches  to  the  right  auricle  and  ven- 
tricle, and  the  commencement  of  the  pulmonary  artery  (infundibular). 

The  Left  Coronary,  larger  than  the  former,  arises  immediately  above  the  free 


THE   ARCH    OF    THE   AORTA. 


543 


ed<ie  of  the  left  posterior  semilunar  valve,  a  little  higher  than  the  right;  it' passes 
forward  between  the  pulmonary  artery  and  theJlelt^uTicjilar_app£iidix,  and  divides 
into  two  branches.  OTTfieseT  "ou^tfansverse)  passes  transversely  outward  in  the 
left  auriculo-ventricular  groove,  and  winds  around  the  left  border  of  the  heart 
into  its  posterior  surface,  where  it  anastomoses  with  the  transverse  branch  of  the 
right  coronary ;  the  other  (descending)  descends  along  the  anterior  interventricu- 
lar  groove  to  the  apex  of  the  heart,  where  it  anastomoses  with  the  descending 
branches  of  the  right  coronary %  The  left  coronary  supplies  the  left  auricle  and 
its  appendix,  both  ventricles,  and  numerous  small  branches  to  the  pulmonary 
artery,  and  commencement  of  the  aorta.1 

Peculiarities. — These  vessels  occasionally  arise  by  a  common  trunk,  or  their  number  may 
be  increased  to  three,  the  additional  branch  being  of  small  size.  More  rarely,  there  are  two 
additional  branches. 

THE   ARCH  OF  THE  AORTA. 

The  arch,  or  transverse  aorta,  commences  at  the  upper  border  of  the  second 
chondro-sternal  articulation  of  the  right  side,  and  passes  from  right  to  left,  and 
from  before  backward,  to  the  left  side  of  the  lower  border  of  the  fourth  dorsal 
vertebra  behind.  Its  upper  border  is  usually  about  an  inch  below  the  upper  mar- 
gin of  the  sternum. 

Relations. — Its  anterior  surface  is  covered  by  the  pleurae  and  lungs  and  the 
remains  of  the  thymus  gland,  and  crossed  toward  the  left  side  by  the  left  pneumo- 
gastric  and  phrenic  nerves  and  superior  cardiac  branches  of  the  left  sympathetic, 
and  by  the  left  superior  intercostal  vein.  Its  posterior  surface  lies  on  the  trachea, 
just  above  its  bifurcation,  on  the  great,  or  deep,  cardiac  plexus,  the  oesophagus, 
thoracic  duct,  and  left  recurrent  laryngeal  nerve.  Its  upper  border  is  in  relation 
with  the  left  innominate  vein,  and  from  its  upper  part  are  given  off  the  innom- 
inate, left  common  carotia,  and  left  subclavian  arteries.  Its  loicer  border  is  in 
relation  with  the  bifurcation  of  the  pulmonary  artery,  the  remains  of  the  ductus 
arteriosus.  which  is  connected  with  the  left  division  of  that  vessel,  and  the  super- 
ficial cardiac  plexus :  the  left  recurrent  laryngeal  nerve  winds  round  it  from 
before  backward,  whilst  the  left  bronchus  passes  below  it. 

PLAN  OF  THE  RELATIONS  OF  THE  ARCH  OF  THE  AORTA. 

Above. 

Left  innominate  vein. 
Innominate  artery. 
Left  carotid. 
J.ieft  subclavian. 
In  From. 
Pleurae  and  lungs. 
Remains  of  thymus  gland. 
Left  pneumogastric  nerve. 
Left  phrenic  nerve. 
Left  superior  cardiac  ner 
Left  superior  intercostal  vein. 

Below. 

Bifurcation  of  pulmonary  artery. 
Remains  of  ductus  arteriosus. 
Superficial  cardiac  plexus. 
Left  recurrent  nerve. 
Left  bronchus. 

Peculiarities.— The  height  to  which  the  aorta  rises  in  the  chest  is  usually  about  an  inch 
below  the  upper  border  of  the  sternum :  but  it  may  ascend  nearly  to  the  top  of  that  bone. 
Occasionally  it  is  found  an  inch  and  a  half,  more  rarely  two  or  even  three  inches,  below  this 
point. 

1  According  to  Dr.  Samuel  West,  there  is  a  very  free  and  complete  anastomosis  between  the  two 
coronary  arteries  < Lancet,  June  '2.  1<S3.  p.  945  .  This,  however,  is  not  the  view  generally  held  by 
anatomist.«,  for,  with  the  exception  of  the  anastomosis  mentioned  above  in  the  auriculo-ventricular  and 
interventricular  grooves,  it  is  believed  that  the  two  arteries  only  communicate  by  very  small  vessels 
:n  the  substance  of  the  heart. 


Behind. 
Trachea. 

Deep  cardiac  plexus. 
(Esophagus. 
Thoracic  duct. 
Left  recurrent  nerve. 


544  THE  ARTERIES. 

In  Direction. — Sometimes  the  aorta  arches  over  the  root  of  the  right  instead  of  the  left 
lung,  as  in  birds,  and  passes  down  on  the  right  side  of  the  spine.  In  such  cases  all  of  the 
viscera  of  the  thoracic  and  abdominal  cavities  are  transposed.  Less  frequently,  the  aorta,  after 
arching  over  the  root  of  the  right  lung,  is  directed  to  its  usual  position  on  the  left  side  of  the 
spine,  this  peculiarity  not  being  accompanied  by  any  transposition  of  the  viscera. 

In  Conformation. — The  aorta  occasionally  divides,  as  in  some  quadrupeds,  into  an  ascend- 
ing and  descending  trunk,  the  former  of  which  is  directed  vertically  upward,  and  subdivides 
into  three  branches,  to  supply  the  head  and  upper  extremities.  Sometimes  the  aorta  subdivides 
soon  after  its  origin  into  two  branches,  which  soon  reunite.  In  one  of  these  cases  the  oesophagus 
and  trachea  were  found  to  pass  through  the  interval  left  by  their  division  ;  this  is  the  normal 
condition  of  the  vessel  in  the  reptilia. 

Surgical  Anatomy. — Of  all  the  vessels  of  the  arterial  system,  the  aorta,  and  more  espe- 
cially its  arch,  is  most  frequently  the  seat  of  disease  ;  hence  it  is  important  to  consider  some  of 
the  consequences  that  may  ensue  from  aneurism  of  this  part. 

It  will  be  remembered  that  the  ascending  aorta  is  contained  in  the  pericardium,  just  behind 
the  sternum,  being  crossed  at  its  commencement  by  the  pulmonary  artery  and  right  auricular 
appendix,  and  having  the  root  of  the  right  lung  behind,  the  vena  cava  on  the  right  side,  and 
the  pulmonary  artery  and  left  auricle  on  the  left  side. 

Aneurism  of  the  ascending  aorta,  in  the  situation  of  the  aortic  sinuses,  in  the  great  majority 

Vein  azygos  major. 
Right 
pulmonary  veil 


Right ' 
innom.  vein. 

Right  subclav.  / 

Right  common  carotid.  Left  subclav. 

Inferior  thyroid.         "*~  '    ~  \ 

Left  innominate  win.1**  common  caroti(L 

FIG.  346.— Relation  of  great  vessels  at  base  of  heart,  seen  from  above.    (From  a  preparation  in  the  Museum 
of  the  Royal  College  of  Surgeons.) 

of  cases,  affects  the  right  anterior  sinus ;  this  is  mainly  owing  to  the  fact  that  the  regurgitation 
of  blood  upon  the  sinuses  takes  place  chiefly  on  the  right  anterior  aspect  of  the  vessel.  As  the 
aneurismal  sac  enlarges  it  may  compress  any  or  all  of  the  structures  in  immediate  proximity  with 
it,  but  chiefly  projects  toward  the  right  anterior  side,  and,  consequently,  interferes  mainly  with 
those  structures  that  have  a  corresponding  relation  with  the  vessel.  In  the  majority  of  cases  it 
bursts  into  the  cavity  of  the  pericardium,  the  patient  suddenly  drops  down  dead,  and,  upon  a 
post-mortem  examination,  the  pericardial  sac  is  found  full  of  blood ;  or  it  may  compress  the 
right  auricle,  or  the  pulmonary  artery,  and  adjoining  part  of  the  right  ventricle,  and  open  into 
one  or  the  other  of  these  parts,  or  may  press  upon  the  superior  vena  cava. 

Aneurism  of  the  ascending  aorta,  originating  above  the  sinuses,  most  frequently  implicates 
the  right  anterior  wall  of  the  vessel;  this  is  probably  mainly  owing  to  the  blood  being  impelled 
against  this  part.  The  direction  of  the  aneurism  is  also  chiefly  toward  the  right  of  the  median 
line.  If  it  attains  a  large  size  and  projects  forward,  it  may  absorb  the  sternum  and  the  cartilages 
of  the  ribs,  usually  on  the  right  side,  and  appear  as  a  pulsating  tumor  on  the  front  of  the  chest, 
just  below  the  manubrium  ;  or  it  may  burst  into  the  pericardium,  or  may  compress  or  open  into 
the  right  lung,  the  trachea,  bronchi,  or  oesophagus. 

Regarding  the  transverse  aorta,  the  student  is  reminded  that  the  vessel  lies  on  the  trachea, 
the  oesophagus,  and  thoracic  duct ;  that  the  recurrent  laryngeal  nerve  winds  around  it ;  and  that 
from  its  upper  part  are  given  off  three  large  trunks,  which  supply  the  head,  neck,  and  upper 
extremities.  Now,  an  aneurismal  tumor,  taking  origin  from  the  posterior  part  or  right  aspect  of 
the  vessel,  its  most  usual  site,  may  press  upon  the  trachea,  impede  the  breathing,  or  produce 
cough,  haemoptysis,  or  stridulous  breathing,  or  it  may  ultimately  burst  into  that  tube,  producing 
fatal  haemorrhage.  Again,  its  pressure  on  the  laryngeal  nerves  may  give  rise  to  symptoms  which 
so  accurately  resemble  those  of  laryngitis  that  the  operation  of  tracheotomy  has  in  some  cases 


THE   INNOMINATE  ARTERY.  545 

been  reported  to.  from  the  supposition  that  disease  existed  in  the  larynx ;  or  it  may  press  up.on 
the  thoracic  duct  and  destroy  lite  by  inanition ;  or  it  may  involve  the  oesophagus,  producing 
dysphairia  :  or  may  burst  into  the  oesophagus,  when  fatal  haemorrhage  will  occur.  Again,  the 
innominate  artery,  or  the  subclavian,  or  left  carotid,  may  be  so  obstructed  by  clots  as  to  produce 
a.  weakness,  or  even  a  disappearance,  of  the  pulse  in  one  or  the  other  wrist  or  in  the  left  tem- 
poral artery ;  or  the  tumor  may  present  itself  at  or  above  the  manubrium,  generally  either  in  the 
median  line  or  to  the  right  of  the  sternum,  and  may  simulate  an  aneurism  of  one  of  the  arteries 
of  the  neck. 

t 

BRANCHES  OF  THE  ARCH  OF  THE  AORTA  (Figs.  344,  345). 

The  branches  given  off  from  the  arch  of  the  aorta  are  three  in  number :  the 
innominate  artery,  the  left  common  carotid,  and  the  left  subclavian. 

Peculiarities. — Position  of  the  Branches. — The  branches,  instead  of  arising  from  the  high- 
est part  of  the  arch  (their  usual  position),  may  be  moved  more  to  the  right,  arising  from  the 
commencement  of  the  transverse  or  upper  part  of  the  ascending  portion  :  or  the  distance  from 
one  another  at  their  origin  may  be  increased  or  diminished,  the  most  frequent  change  in  this 
:  being  the  approximation  of  the  left  carotid  toward  the  innominate  artery. 

Tin  J\  n  mix  /•  of  the  primary  branches  may  be  reduced  to  two :  the  left  carotid  arising  from 
the  innominate  artery,  or  (more  rarely)  the  carotid  and  subclavian  arteries  of  the  left  side  aris- 
inir  from  a  left  innominate  artery.  But  the  number  may  be  increased  to  four,  from  the  right 
carotid  and  subclavian  arteries  arising  directly  from  the  aorta,  the  innominate  being  absent.  ~In 
most  of  these  latter  cases  the  right  subclavian  has  been  found  to  arise  from  the  left  end  of  the 
arch  :  in  other  cases  it  was  the  second  or  third  branch  given  off  instead  of  the  first.  Lastly,  the 
number  of  trunks  from  the  arch  may  be  increased  to  five  or  six ;  in  these  instances  the  external 
and  internal  carotids  arise  separately  from  the  arch,  the  common  carotid  being  absent  on  one  or 
both  sides. 

Number  Usual,  Arrangement  Different.— When  the  aorta  arches  over  to  the  right  side, 
the  three  brandies  have  an  arrangement  the  reverse  of  what  is  usual  the  innominate  supplying 
the  left  side,  and  the  carotid  and  subclavian  (which  arise  separately)  the  right  side.  In  other 
where  the  aorta  takes  its  usual  course,  the  two  carotids  may  be  joined  in  a  common  trunk, 
and  the  sul»clavians  arise  separately  from  the  arch,  the  right  subclavian  generally  arising  from 
the  left  end  of  the  arch. 

Secondary  Branches  sometimes  arise  from  the  arch;  most  commonly  such  a  secondarv 
branch  is  the  left  vertebral,  which  usually  takes  origin  between  the  left  carotid  and  left  subcla- 
vian. or  beyond  them.  Sometimes,  a  thyroid  branch  is  derived  from  the  arch,  or  the  right 
internal  mammary,  or  right  vertebral,  or.  more  rarely,  both  vertebral.1 

THE  INNOMINATE  ARTERY. 

The  innominate  artery  (brachio-cephalic)  is  the  largest  branch  given  off  from 
the  arch  of  the  aorta,  It  arises  opposite  the  fourth  dorsal  vertebra  from  the 
commencement  of  the  arch  of  the  aorta  in  front  of  the  left  carotid,  and,  ascending 
obliquely  to  the  upper  border  of  the  right  sterno-clavicular  articulation,  divides 
into  the  right  common  carotid  and  right  subclavian  arteries.  This  vessel  varies 
from  an  inch  and  a  half  to  two  inches  in  length. 

Relations. — In  front,  it  is  separated  from  the  first  bone  of  the  sternum  by  the 
Stemo-hyoid  and  Sterno-thyroid  muscles,  the  remains  of  the  thymus  gland,  the 
left  innominate  and  right  inferior  thyroid  veins  which  cross  its  Yoot,  and  some- 
times the  inferior  cervical  cardiac  branch  of  the  right  pneumogastric.  Behind,  it 
lies  upon  the  trachea,  which  it  crosses  obliquely.  On  the  right  side  is  the  right 
innominate  vein,  right  pneumogastric  nerve,  and  the  pleura ;  and  on  the  left  side, 
the  remains  of  the  thymus  gland,  the  origin  of  the  left  carotid  artery,  the  left 
inferior  thyroid  vein,  and  the  trachea. 

Branches. — The  innominate  usually  gives  off  no  branches,  but  occasionally  a 
small  brunch,  the  thyroidea  ima,  is  given  off  from  this  vessel.  It  also  sometimes 
gives  off  a  thymic  or  Irom-hiid.  launch.  The  Thyroidea  ima  ascends  in  front  of 
the  trachea  to  the  lower  part  of  the  thyroid  body,  which  it  supplies.  It  varies 
greatly  in  size,  and  appears  to  compensate  for  deficiency  or  absence  of  one  of  the 
other  thyroid  vessels.  It  occasionally  is  found  to  arise  from  the  subclavian  or 
internal  mammary  vessel. 

1  The  anomalies  of  the  aorta  and  its  branches  are  minutely  described  by  Krause  in  Henle's 
Anatomy  (Brunswick,  1868),  vol.  iii.  p.  203  et  seq. 


546  THE   ARTERIES. 

PLAN  OF  THE  RELATIONS  OF  THE  INNOMINATE  ARTERY. 

In  front. 
Sternum. 

Sternq-hyoid  and  Sterno-thyroid  muscles. 
Remains  of  thymus  gland. 
Left  innominate  and  right  inferior  thyroid  veins. 
Inferior  cervical  cardiac  branch  from  right  pneumogastric  nerve. 

Right  side.  f  \  Left  side. 

Right  innominate  vein.  [    innominate    \  Remains  of  thymus. 

Right  pneumogastric  nerve.  1      Artery.       I  Left.  parotid. 

Pleura.  V  Left  inferior  thyroid  vein. 

Trachea. 

Behind. 
Trachea. 

Peculiarities  in  Point  of  Division. — When  the  bifurcation  of  the  innominate  artery  varies 
from  the  point  above  mentioned,  it  sometimes  ascends  a  considerable  distance  above  the  sternal 
end  of  the  clavicle  ;  less  frequently  it  divides  below  it,  In  the  former  class  of  cases  its  length 
may  exceed  two  inches,  and  in  the  latter  be  reduced  to  an  inch  or  less.  These  are  points  of  con- 
siderable interest  for  the  surgeon  to  remember  in  connection  with  the  operation  of  tying  this  vessel. 

Position. — When  the  aorta  arches  over  to  the  right  side,  the  innominate  is  directed  to  the 
left  side  of  the  neck  instead  of  the  right. 

Collateral  Circulation. — Allan  Burns  demonstrated,  on  the  dead  subject,  the  possibility  of 
the  establishment  of  the  collateral  circulation  after  ligature  of  the  innominate  artery,  by  tying 
and  dividing  that  artery,  after  which,  he  says,  "Even  coarse  injection,  impelled  into  the  aorta, 
passing  freely  by  the  anastomosing  branches  into  the  arteries  of  the  right  arm,  filling  them  and 
all  the  vessels  of  the  head  completely"  (Surgical  Anatomy  of  the  Head  and  Neck,  p.  62). 
The  branches  by  which  this  circulation  would  be  carried  on  are  very  numerous ;  thus,  all  the 
communications  across  the  middle  line  between  the  branches  of  the  carotid  arteries  of  oppoMii- 
sides  would  be  available  for  the  supply  of  blood  to  the  right  side  of  the  head  and  neck  ;  while 
the  anastomosis  between  the  superior  intercostal  of  the  subclavian  and  the  first  aortic  intercostal 
(see  infra  on  the  collateral  circulation  after  obliteration  of  the  thoracic  aorta)  would  bring  the 
blood,  by  a  free  and  direct  course,  into  the  right  subclavian :  the  numerous  connections,  also, 
between  the  intercostal  arteries  and  the  branches  of  the  axillary  and  internal  mammary  arteries 
would,  doubtless,  assist  in  the  supply  of  blood  to  the  right  arm,  while  the  epigastric,  from  the 
external  iliac,  would,  by  means  of  its  anastomosis  with  the  internal  mammary,  compensate  for 
any  deficiency  in  the  vascularity  of  the  wall  of  the  chest. 

Surgical  Anatomy. — Although  the  operation  of  tying  the  innominate  artery  has  been 
performed  by  several  surgeons  for  aneurism  of  the  right  subclavian  extending  inward  as  far  as 
the  Scalenus,  in  only  two  instances  has  the  patient  survived.1  Mott's  patient,  however,  on  whom 
the  operation  was  first  performed,  lived  nearly  four  weeks,  and  Graefe's  more  than  two  months. 
The  main  obstacles  to  the  operation  are,  as  the  student  will  perceive  from  his  dissection  of  this 
vessel,  the  deep  situation  of  the  artery  behind  and  beneath  the  sternum  and  the  number  of 
important  structures  which  surround  jt  in  every  part. 

In  order  to  apply  a  ligature  to  this  vessel,  the  patient  is  to  be  placed  upon  his  back,  with  the 
thorax  slightly  raised,  the  head  bent  a  little  backward,  and  the  shoulder  on  the  side  of  the  aneu- 
rism strongly  depressed,  so  as  to  draw  out  the  artery  from  behind  the  sternum  into  the  neck. 
An  incision  three  or  more  inches  long  is  then  made  along  the  anterior  border  of  the  Sterno-mas- 
toid  muscle,  terminating  at  the  sternal  end  of  the  clavicle.  From  this  point  a  second  incision  is 
carried  about  the  same  length  along  the  upper  border  of  the  clavicle.  The  skin  is  then  dissected 
back,  and  the  Platysma  divided  on  a  director :  the  sternal  end  of  the  Sterno-mastoid  is  now 
brought  into  view,  and,  a  director  being  passed  beneath  it  and  close  to  its  under  surface,  so  as  to 
avoid  any  small  vessels,  it  is  to  be  divided  ;  in  like  manner  the  clavicular  origin  is  to  be  divided 
throughout  the  whole  or  greater  part  of  its  attachment.  By  pressing  aside  any  loose  cellular 
tissue  or  vessels  that  may  now  appear  the  Sterno-hyoid  and  Sterno-thyroid  muscles  will  be 
exposed,  and  must  be  divided,  a  director  being  previously  passed  beneath  them.  The  inferior 
thyroid  veins  may  come  into  view,  and  must  be  carefully  drawn,  either  upward  or  downward,  by 
means  of  a  blunt  hook,  or  tied  with  double  ligatures  and  divided.  After  tearing  through  a 
strong  fibro-cellular  lamina,  the  right  carotid  is  brought  into  view,  and,  being  traced  downward. 
the  arteria  innominata  is  arrived  at.  The  left  innominate  vein  should  now  be  depressed ;  the 
right  innominate  vein,  the  internal  jugular  vein,  and  the  pneumogastric  nerve  drawn  to  the  ridit 
side ;  and  a  curved  aneurism  needle  may  then  be  passed  around  the  vessel,  close  to  its  surface, 
and  in  a  direction  from  below  upward  and  inward,  care  being  taken  to  avoid  the  right  pleura! 
sac,  the  trachea,  and  cardiac  nerves.  The  Jigature  should  be  applied  to  the  artery  as  high  ;is 
possible,  in  order  to  allow  room  between  it  and  the  aorta  for  the  formation  of  the  coaguhni). 

1  In  one  of  these  the  operation  was  performed  by  Dr.  Smyth  of  New  Orleans.  See  the  New 
Sydenham  Society's  Biennial  Retrospect  for  1865-6,  p.  346.  In  the  other,  the  operation  was  performed 
by  Dr.  Mitchell  Banks  in  the  Liverpool  Infirmary.  The  case  is  recorded  by  Mr.  Jacobson  in  Oper- 
ations of  Suryery,  p.  536. 


THE    COMMOX   CAROTID    ARTERIES. 


547 


The  importance  of  avoiding  the  thyroid  plexus  of  veins  during  the  primary  steps  of  the  opera- 
tion, and  the  pleural  sac  whilst  including  the  vessel  in  the  ligature,  should  be  most  carefully 
borne  in  ruind.  The  niu*t  frequent  cause  of  death  after  operation  is  secondary  haemorrhage, 
which  has  occurred  in  almost  every  case.  Other  causes  are  pleurisy,  pericarditis,  and  suppura- 
tive  cellulitk 

THE  COMMON  CAROTID  ARTERIES. 

The  common  carotid  arteries,  although  occupying  a  nearly  similar  position  in 
the  neck,  differ  in  position,  and,  consequently,  in  their  relation  at  their  origin. 
The  right  carotid  arises  from  the  innominate  artery,  behind  the  right  sterno- 
clavicular  articulation  ;  the  left  from  the  highest  part  of  the  arch  of  the  aorta. 
The  left  carotid  is,  consequently,  longer,  and  at  its  origin  is  contained  within  the 
thorax.  The  course  and  relations  of  that  portion  of  the  left  carotid  which  inter- 
venes between  the  arch  of  the  aorta  and  the  left  sterno-clavicular  articulation  will 
first  be  described  (see  Fig.  344). 

The  left  carotid  within  the  thorax  ascends  obliquely  outward  from  the  arch  of 
the  aorta  to  the  root  of  the  neck.  In  front,  it  is  separated  from  the  first  piece  of 
the  sternum  by  the  Sterno-hyoid  and  Sterno-thyroid  muscles,  the  left  innominate 
vein,  and  the  remains  of  the  thymus  gland ;  behind,  it  lies  on  the  trachea,  oesoph- 
agus, and  thoracic  duct.  Internally^  it  is  in  relation  with  the  innominate 
artery,  inferior  thyroid  veins  and  remains  of  thymus  gland ;  externally,  with  the 
left  pneurnogastric  nerve,  left  pleura,  and  lung.  The  left  subclavian  artery  is 
posterior  and  external  to  it. 

PLAN  OF  THE  RELATIONS  OF  THE  LEFT  COMMON  CAROTID. 
THORACIC  PORTION. 

In  front. 
Sternum. 

Sterno-hyoid  and  Sterno-thyroid  muscles. 
Left  innominate  vein. 
Remains  of  thymus  gland. 


Internally. 

Innominate  artery. 
Inferior  thyroid  veins. 
Remains  of  thymus  gland. 


Externally. 

Left  pneumogastric  nerve. 
Left  pleura  and  lung. 
Left  subclavian  artery. 


Behind. 

Trachea. 
(Esophagus. 
Thoracic  duct. 

In  the  neck  the  two  common  carotids  resemble  each  other  so  closely  that  one 
description  will  apply  to  both.  Each  vessel  passes  obliquely  upward  from  behind 
the  sterno-clavicular  articulation  to  a  level  with  the  upper  border  of  the  thyroid 
cartilage,  opposite  the  third  cervical  vertebra,  where  it  divides  into  the  external 
and  internal  carotid ;  these  names  being  derived  from  the  distribution  of  the 
arteries  to  the  external  parts  of  the  head  and  face  and  to  the  internal  parts  of  the 
cranium  and  orbit  respectively. 

At  the  lower  part  of  the  neck  the  two  common  carotid  arteries  are  separated 
from  each  other  by  a  small  interval,  which  contains  the  trachea;  but  at  the  upper 
part,  the  thyroid  body,  the  larynx  and  pharynx  project  forward  between  the 
two  vessels,  and  give  the  appearance  of  their  bemg  placed  farther  back  in  that 
situation.  The  common  carotid  artery  is  contained  in  a  sheath  derived  from  the 
deep  cervical  fascia,  which  also  encloses  the  internal  jugular  vein  and  pneumo- 
gastric nerve,  the  vein  lying  on  the  outer  side,  of  the  artery,  and  the  nerve  between 
the  artery  and  vein,  on  a  plane  posterior  to  both.  On  opening  the  sheath  these 
three  structures  are  seen  to  be  separated  from  one  another,  each  being  enclosed  in 
a  separate  fibrous  investment. 

Relations. — At  the  lower  part  of  the  neck  the  common  carotid  artery  is  very 


548 


THE   ARTERIES. 


deeply  seated,  being  covered  by  the  integument,  superficial  fascia,  Platysma,  and 
deep  cervical  fascia,  the  Sterno-mastoid,  Sterno-hyoid,  and  Sterno-thyroid  muscles, 
and  by  the  Omo-hyoid,  opposite  the  cricoid  cartilage  ;  but  in  the  upper  part  of  its 
course,  near  its  termination,  it  is  more  superficial,  being  covered  merely  by  the 
integument,  the  superficial  fascia,  Platysma,  deep  cervical  fascia,  and  inner  margin 
of  the  Sterno-mastoid,  and  is  contained  in  a  triangular  space,  bounded  behind  by 


FIG.  348.— Plan  of  the 
branches  of  the  external 
carotid. 


FIG.  347.— Surgical  anatomy  of  the  arteries  of  the  neck.    Right  side. 

the  Sterno-mastoid,  above  by  the  posterior  belly  of  the  Digastric,  and  below  by 
the  anterior  belly  of  the  Omo-hyoid.  This  part  of  the  artery  is  crossed  obliquely, 
from  within  outward,  by  the  sterno-mastoid  artery ;  it  is  crossed  also  by  one,  or 
sometimes  two  superior  thyroid  veins,  which  terminate  in  the  internal  jugular ; 
and,  descending  on  its  sheath  in  front,  is  seen  the  descendens  hypoglossi  nerve, 
this  filament  being  joined  by  one  or  two  branches  from  the  cervical  nerves,  which 
cross  the  vessel  from  without  inward.  Sometimes  the  descendens  hypoglossi  is 
contained  within  the  sheath.  The  middle  thyroid  vein  crosses  the  artery  about 


THE    COMMOX   CAROTID    ARTERIES.  549 

its  middle,  and  the  anterior  jugular  vein  below.  Behind,  the  artery  lies  in  front 
of  the  cervical  portion  of  the  spine,  resting  first  on  the  Longus  colli  muscle,  then 
on  the  Rectus  capitis  auticus  major,  from  which  it  is  separated  by  the  sympathetic 
nerve.  The  recurrent  laryngeal  nerve  and  inferior  thyroid  artery  cross  behind  the 
1  at  its  lower  part.  Internally,  it  is  in  relation  with  the  trachea  and  thyroid 
gland,  the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve  being  interposed : 
higher  up.  with  the  larynx  and  pharynx.  On  its  outer  side  are  placed  the  internal 
jugular  vein  and  pneumogastric  nerve 

At  the  lower  part  of  the  neck  the  internal  jugular  vein  on  the  right  side 
diverges  from  the  artery,  but  on  the  left  side  it  approaches  it.  and  often  cr<:»-  - 
its  lower  part.  This  is  an  important  fact  to  bear  in  mind  during  the  performance 
of  any  operation  on  the  lower  part  of  the  left  common  carotid  artery. 

PLAN  OF  THE  RELATIONS  OF  THE  COMMON  CAROTID  ARTERY. 

Externally. 

Integument,  and  superficial  fascia. 
Deep  cervical  fascia. 
Platysma. 

Sterno-mastoid.  Internally. 

Sterno-hyoid.  /^^     ^X  Trachea. 

Sterno-thyroid.  /  Thyroid  gland. 

Oruo-hyoid.  Common  Recurrent  laryngeal  nerve. 

Descendens  and  Couimunicans  by-  Inferior  thyroid  artery. 

poglossi  nerves.  Larynx. 

Sterno-mastoid  artery.  Pharynx. 

Superior  and  middle  thyroid  veins. 
Anterior  jugular  vein. 
Internal  jugular  vein. 
Pneumogastric  nerve. 

Behind. 

Longus  colli.  Sympathetic  nerve. 

Rectus  capitis  anticus  major.  Inferior  thyroid  artery. 

Recurrent  laryngeai  nerve. 

Peculiarities  as  to  Origin. — The  right  common  carotid  may  arise  above  or  below  its  usual 
point,  the  upper  border  of  the  sterno-clavicular  articulation.  This  variation  occurs  in  one  out  of 
about  eiirht  cases  and  a  halt',  and  the  origin  is  more  frequently  above  than  below  the  usual  point ; 
or  the  artery  may  arise  as  a  separate  branch  from  the  arch  of  the  aorta  or  in  conjunction  with  the 
left  carotid.  The  hit  common  carotid  varies  more  frequently  in  its  origin  than  the  right.  In 
the  majority  of  abnormal  cases  it  arises  with  the  innominate  artery,  or.  if  the  innominate  artery 
is  absent,  the  two  carotids  arise  usually  by  a  single  trunk.  The  left  carotid  is  occasionally  the 
first  branch  given  off  from  the  arch  of  the  aorta.  It  rarely  joins  with  the  left  subclavian,  except 
in  cases  of  transposition  of  the  arch. 

Peculiarities  as  to  Point  of  Division. — The  most  important  peculiarities  of  this  vessel, 
in  a  surgical  point  of  view,  relate  to  its  place  of  division  in  the  neck.  In  the  majority  of 
abnormal  cases  this  occurs  higher  than  usual,  the  artery  dividing  into  two  branches  opposite 
the  hyoid  bone,  or  even  higher;  more  rarely,  it  occurs  below  its  usual  place,  opposite  the 
middle  of  the  larynx  or  the  lower  border  of  the  cricoid  cartilage ;  and  one  case  is  related  by 
Morgairni  where  the  common  carotid,  only  an  inch  and  a  half  in  length,  divided  at  the  root  of 
the  neck.  Very  rarely  the  common  carotid  ascends  in  the  neck  without  any  subdivision,  the 
internal  carotid  being  wanting:  and  in  a  few  cases  the  common  carotid  has  been  found  to  be 
absent,  the  external  and  internal  carotids  arising  directly  from  the  arch  of  the  aorta.  This 
peculiarity  existed  on  both  sides  in  some  instances,  on  one  side  in  others. 

Occasional  Branches. — The  common  carotid  usually  gives  off  no  branch  previous  to  its 
bifurcation  :  but  it  occasionally  gives  origin  to  tbe  superior  thyroid  or  its  laryngeal  branch,  the 
inferior  thyroid,  or.  more  rarely,  the  vertebral  artery. 

Surface  Marking. — The  carotid  arteries  are  overlapped  throughout  their  entire  extent  by 
tbe  anterior  border  of  the  Sterno-mastoid  muscle,  but  their  course  does  not  correspond  to  the 
border  of  tbe  muscle,  which  passes  in  a  somewhat  curved  direction  from  the  mastoid  process  to 
the  sterno-clavicular  joint.  The  course  of  the  artery  is  indicated  more  exactly  by  a  line  drawn 
from  tbe  sternal  end  of  the  clavicle  below,  to  a  point  midway  between  the  angle  of  the  jaw  and 
tbe  mastoid  process  above.  That  portion  of  the  line  below  the  Wei  of  the  upper  border  of  the 
thyroid  cartilage  would  represent  the  course  of  tbe  vessel. 

Surgical  Anatomy. — The  operation  of  tying  the  common  carotid  artery  may  be  necessary 
in  a  case  of  wound  of  that  vessel  or  its  branches,  in  aneurism,  or  in  a  case  of  pulsating  tumor  of 
tbe  orbit  or  skull.  If  the  wound  involves  tbe  trunk  of  the  common  carotid,  it  will  be  necessary 
to  tie  the  artery  above  and  below  the  wounded  part.  But  in  cases  of  aneurism,  or  where  one  of 


550  THE   ARTERIES. 

the  branches  of  the  common  carotid  is  wounded  in  an  inaccessible  situation,  it  may  be  judged 
necessary  to  tie  the  trunk.  In  such  cases  the  whole  of  the  artery  is  accessible,  and  any  part  may 
be  tied  except  close  to  either  end.  When  the  case  is  such  as  to  allow  of  a  choice  being  made, 
the  lower  part  of  the  carotid  should  never  be  selected  as  the  spot  upon  which  to  place  a  ligature, 
for  not  only  is  the  artery  in  this  situation  placed  very  deeply  in  the  neck,  but  it  is  covered 
by  three  layers  of  muscles,  and,  on  the  left  side,  the  internal  jugular  vein,  in  the  great  majority 
of  cases,  passes  obliquely  in  front  of  it.  Neither  should  the  upper  end  be  selected,  for  here  the 
superior  thyroid  vein  and  its  tributaries  would  give  rise  to  very  considerable  difficulty  in  the 
application  of  a  ligature.  The  point  most  favorable  for  the  operation  is  that  part  of  the  vessel 
which  is  at  the  level  of  the  cricoid  cartilage.  It  occasionally  happens  that  the  carotid 
artery  bifurcates  below  its  usual  position  :  if  the  artery  be  exposed  at  its  point  of  bifurcation, 
both  divisions  of  the  vessel  should  be  tied  near  their  origin,  in  preference  to  tying  the  trunk 
of  the  artery  near  its  termination  ;  and  if,  in  consequence  of  the  entire  absence  of  the  common 
carotid  or  from  its  early  division,  two  arteries,  the  external  and  internal  carotids,  are  met  with, 
the  ligature  should  be  placed  on  that  vessel  which  is  found  on  compression  to  be  connected  with 
the  disease. 

In  this  operation  the  direction  of  the  vessel  and  the  inner  margin  of  the  Sterno-mastoid  are 
the  chief  guides  to  its  performance.  The  patient  should  be  placed  on  his  back  with  the  head 
thrown  back  and  turned  slightly  to  the  opposite  side:  an  incision  is  to  be  made,  three  inches 
long,  in  the  direction  of  the  anterior  border  of  the  Sterno-mastoid,  so  that  the  centre  corresponds 
to  the  level  of  the  cricoid  cartilage :  after  dividing  the  integument,  superficial  fascia,  and 
Platysma,  the  deep  fascia  must  be  cut  through  on  a  director,  so  as  to  avoid  wounding 
numerous  small  veins  that  are  usually  found  beneath.  The  head  may  now  be  brought  forward 
so  as  to  relax  the  parts  somewhat,  and  the  margins  of  the  wound  held  asunder  by  retractors. 
The  descendens  hypoglossi  nerve  may  now  be  exposed,  and  must  be  avoided,  and,  the  sheath  of 
the  vessel  having  been  raised  by  forceps,  is  to  be  opened  to  a  small  extent  over  the  artery  at  its 
inner  side.  The  internal  jugular  vein  may  present  itself  alternately  distended  and  relaxed  ;  this 
should  be  compressed  both  above  and  below,  and  drawn  outward,  in  order  to  facilitate  the  opera- 
tion. The  aneurism  needle  is  passed  from  the  outside,  care  being  taken  to  keep  the  needle  in 
close  contact  with  the  artery,  and  thus  avoid  the  risk  of  injuring  the  internal  jugular  vein  or 
including  the  vagus  nerve.  Before  the  ligature  is  tied  it  should  be  ascertained  that  nothing  but 
the  artery  is  included  in  it. 

Ligature  of  the  Common  Carotid  at  the  Lower  Part  of  the  Neck.— This  operation  is 
sometimes  required  in  cases  of  aneurism  of  the  upper  part  of  the  carotid,  especially  if  the  sac  is 
of  large  size.  It  is  best  performed  by  dividing  the  sternal  origin  of  the  Sterno-mastoid  muscle, 
but  may  be  done  in  some  cases,  if  the  aneurism  is  not  of  very  large  size,  by  an  incision 
along  the  anterior  border  of  the  Sterno-mastoid,  extending  down  to  the  sterno-clavicular  articula- 
tion, and  by  then  retracting  the  muscle.  The  easiest  and  best  plan,  however,  is  to  make  an 
incision  two  or  three  inches  long  down  the  lower  part  of  the  anterior  border  of  the  Sterno- 
mastoid  muscle  to  the  sterno-clavicular  joint,  and  a  second  incision,  starting  from  the  termination 
of  the  first,  along  the  upper  border  of  the  clavicle  for  about  two  inches.  This  incision  is  made 
through  the  superficial  and  deep  fascia,  and  the  sternal  origin  of  the  muscle  exposed.  This  is  to 
be  divided  on  a  director,  and  turned  up,  with  the  superficial  structures,  as  a  triangular  flap. 
Some  loose  connective  tissue  is  to  be  divided  or  torn  through,  and  the  outer  border  of  the 
Sterno-hyoid  muscle  exposed.  In  doing  this  care  must  be  taken  not  to  wound  the  anterior 
jugular  vein,  which  crosses  the  muscle  to  reach  the  external  jugular  or  subclavian  vein.  The 
Sterno-hyoid,  and  with  it  the  Sterno-thyroid.  are  to  be  drawn  inward  by  means  of  a  retractor, 
and  the  sheath  of  the  vessel  is  exposed.  This  must  be  opened  with  great  care  on  its  inner 
or  tracheal  side,  so  as  to  avoid  the  internal  jugular  vein.  This  is  especially  necessary  on 
the  left  side,  where  the  artery  is  commonly  overlapped  by  the  vein.  On  the  right  side  there  is 
usually  an  interval  between  the  artery  and  the  vein,  and  not  the  same  risk  of  wounding  the 
latter. 

The  common  carotid  artery,  being  a  long  vessel  without  any  branches,  is  particularly  suitable 
for  the  performance  of  Brasdor's  operation  for  the  cure  of  an  aneurism  of  the  lower  part  of  the 
vessel.  Brasdor's  procedure  consists  in  ligaturing  the  artery  on  the  distal  side  of  the  aneurism, 
and  in  the  case  of  the  common  carotid  there  are  no  branches  given  off  from  the  vessel  between 
the  aneurism  and  the  site  of  the  ligature ;  hence  little  or  no  blood  passes  through  the  sac  of  the 
aneurism,  and  consequently  it  and  the  vessel  shrinks,  and  a  cure  is  effected. 

Collateral  Circulation. — After  ligature  of  the  common  carotid  the  collateral  circulation 
can  be  perfectly  established,  by  the  free  communication  which  exists  between  the  carotid  arteries 
of  opposite  sides,  both  without  and  within  the  cranium,  and  by  enlargement  of  the  branches  of 
the  subclavian  artery  on  the  side  corresponding  to  that  on  which  the  vessel  has  been  tied — the 
chief  communication  outside  the  skull  taking  place  between  the  superior  and  inferior  thyroid 
arteries,  and  the  profunda  cervicis  and  arteria  princeps  cervicis  of  the  occipital ;  the  vertebral 
taking  the  place  of  the  internal  carotid  within  the  cranium. 

Sir  A.  Cooper  had  an  opportunity  of  dissecting,  thirteen  years  after  the  operation,  the  case 
in  which  he  first  successfully  tied  the  common  carotid  (the  second  case  in  which  he  performed 
the  operation).1  The  injection,  however,  does  not  seem  to  have  been  a  successful  one.  It 
showed  merely  that  the  arteries  at  the  base  of  the  brain  (circle  of  Willis)  were  much  enlarged  on 

1  Guy's  Hospital  Reports,  i.  56. 


THE   EXTERXAL    CAROTID    ARTERY.  V»l 

the  side  of  the  tied  artery,  and  that  the  anastomosis  between  the  branches  of  the  external  carotid 
on  the  affected  side  and  those  of  the  same  artery  on  the  sound  side  was  free,  so  that  the  external 
carotid  was  pervious  throughout. 

The  External  Carotid  Artery. 

The  external  carotid  artery  (Fig.  347)  commences  opposite  the  upper  border  of 
the  thyroid  cartilage,  and  taking  a  slightly  curved  course,  passes  upward  and  for- 
ward, and  then  inclines  backward  to  the  space  between  the  neck  of  the  condyle 
of  the  lower  jaw  and  the  external  meatus.  where  it  divides  into  the  superficial 
temporal  and  internal  maxillary  arteries.  It  rapidly  diminishes  in  size  in  its 
course  up  the  neck,  owing  to  the  number  and  large  size  of  the  branches  given 
off  from  it.  In  the  cbild  it  is  somewhat  smaller  than  the  internal  carotid,  but  in 
the  adult  the  two  vessels  are  of  nearly  equal  size.  At  its  commencement  this 
artery  is  more  superficial,  and  placed  nearer  the  middle  line  than  the  internal 
carotid,  and  is  contained  in  the  triangular  space  bounded  by  the  Sterno-mastoid 
behind,  the  Omo-hyoid  below,  and  the  posterior  belly  of  the  Digastric  and  Stylo- 
hyoid  above. 

Relations.— It  is  covered  by  the  skin,  superficial  fascia.  Platysma,  deep  fascia, 
and  anterior  margin  of  the  Sterno-mastoid,  crossed  by  the  hypoglossal  nerve,  and 
by  the  lingual  and  facial  veins ;  it  is  afterward  crossed  by  the  Digastric  and 
Stylo-hyoid  muscles,  and  higher  up  passes  deeply  into  the  substance  of  the  parotid 
gland,  where  it  lies  beneath  the  facial  nerve  and  the  junction  of  the  temporal  and 
internal  maxillary  veins. 

InttrnMy  is  the  hyoid  bone,  wall  of  the  pharynx,  the  superior  laryngeal 
nerve,  and  higher  up  it  is  separated  from  the  internal  carotid  by  the  Stylo-glossus 
and  Stylo-pharyngeus  muscles,  the  glosso-pharyngeal  nerve,  and  part  of  the  paro- 
tid gland.  Anteriorly  is  the  ramus  of  the  jaw,  from  which  it  is  separated  by  a 
portion  of  the  parotid  gland.  Externally,  in  the  lower  part  of  its  course,  is  the 
internal  carotid  artery. 

Surface  Marking. — The  position  of  the  external  carotid  artery  may  be  marked  out  with 
sufficient  accuracy  by  a  line  drawn  from  the  front  of  the  meatus  of  the  external  ear  to  the  side 
of  the  cricoid  cartilage,  slightly  arching  the  line  forward. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  external  carotid  may  be  required 
in^  case  of  wounds  of  this  vessel,  or  of  its  branches  when  these  cannot  be  tied,  and  in  some  cases 
of  pulsating  tumor  of  the  scalp  or  face.  The  operation  has  not  received  the  attention  which  it 
deserves,  owing  to  the  fear  which  surgeons  have  entertained  of  secondary  haemorrhage,  on 
account  of  the  number  of  branches  given  off  from  the  vessel.  This  fear,  however,  has  been 
shown  by  Mr.  Cripps  not  to  be  well  founded.1  To  tie  this  vessel  near  its  origin,  below  the  point 
where  it  is  crossed  by  the  Digastric,  an  incision  about  three  inches  in  length  should  be  made 
along  the  margin  of  the  Sterno-mastoid.  from  the  angle  of  the  jaw  to  the  upper  border  of  the 
thyroid  cartilage.  The  ligature  should  be  applied  between  the  lingual  and  superior  thyroid 
branches.  To  tie  the  vessel  above  the  Digastric,  between  it  and  the  parotid  gland,  an  incision 
should  be  made,  from  the  lobe  of  the  ear  to  the  great  cornu  of  the  os  hyoides.  dividing  succes- 
sively the  skin.  Platysma.  and  fascia.  By  drawing  the  Sterno-mastoid  outward,  and  the  posterior 
belly  of  the  Digastric  and  Stylo-hyoid  muscles  downward,  and  separating  them  from  the  parotid 
gland,  the  vessel  will  be  exposed,  and  a  ligature  may  be  applied  to  it.  The  circulation  is  at  once 
re-established  by  the  free  communication  between  most  of  the  large  branches  of  the  artery 
(facial,  lingual,  superior  thyroid,  occipital)  and  the  corresponding  arteries  of  the  opposite  side, 
and  by  the  anastomosis  of  its  branches  with  those  of  the  internal  carotid,  and  of  the  occipital 
with  the  branches  of  the  subclavian.  etc. 

PLAX  OF  THE  RELATIONS  OF  THE  EXTERNAL  CAROTID. 

Externally. 

Skin,  superficial  fascia. 
Platysma  and  deep  fascia. 
Anterior  border  of  Sterno-mastoid. 
Hypoglossal  nerve. 
Lingual  and  facial  veins. 
Digastric  and  Stylo-hyoid  muscles. 

Parotid  gland  with  facial  nerve  and  temporo-maxillary  vein  in  its  substance. 
Internal  carotid  artery. 

1  Med.-Chir.  Trnn.*.,  Ixi.  229. 


552  THE  ARTERIES. 


In  front.  I     External      ]  Behind. 

Ramus  of  jaw.  V  J  Parotid  gland. 

Internally. 
Hyoid  bone. 
Pharynx. 

Superior  laryngeal  nerve. 
Stylo-glossus. 
Stylo-pharyngeus. 
Glosso-pharyngeal  nerve. 
Parotid  gland. 

Branches. — The  external  carotid  artery  gives  off  eight  branches,  which,  for 
convenience  of  description,  may  be  divided  into  four  sets.  (See  Fig.  348,  Plan  of 
the  Branches). 

Anterior.  Posterior.  Ascending.  Terminal. 

Superior  Thyroid.     Occipital.  Ascending  Pha-       Superficial  Temporal. 

Lingual.  Posterior  Auricular,     ryngeal.  Internal  Maxillary. 

Facial. 

The  student  is  here  reminded  that  many  variations  are  met  with  in  the 
number,  origin,  and  course  of  these  branches  in  different  subjects;  but  the  above 
arrangement  is  that  which  is  found  in  the  great  majority  of  cases. 

The  Superior  Thyroid  Artery  (Figs.  347  and  352)  is  the  first  branch  given  off 
from  the  external  carotid,  being  derived  from  that  vessel  just  below  the  great 
cornu  of  the  hyoid  bone.  At  its  commencement  it  is  quite  superficial,  being 
covered  by  the  integument,  fascia,  and  Platysma,  and  is  contained  in  the 
triangular  space  bounded  by  the  Sterno-mastoid,  Digastric,  and  Omo-hyoid  muscles. 
After  running  upward  and  inward  for  a  short  distance,  it  curves  downward 
and  forward,  in  an  arched  and  tortuous  manner,  to  the  upper  part  of  the  thyroid 
gland,  passing  beneath  the  Omo-hyoid,  Sterno-hyoid,  and  Sterno-thyroid  muscles, 
and  distributes  numerous  branches  to  the  anterior  surface  of  the  gland, 
anastomosing  with  its  fellow  of  the  opposite  side  and  with  the  inferior  thyroid 
arteries.  Besides  the  arteries  distributed  to  the  muscles  by  which  it  is  covered 
and  the  substance  of  the  gland,  the  branches  of  the  superior  thyroid  are  the 
following : 

Hyoid.  Superior  Laryngeal. 

Superficial  descending  branch  (Sterno-mastoid).        Crico-thyroid. 

The  hyoid  is  a  small  branch  which  runs  along  the  lower  border  of  the  os 
hyoides  beneath  the  Thyro-hyoid  muscle  ;  after  supplying  the  muscles  connected  to 
that  bone  it  forms  an  arch,  by  anastomosing  with  the  vessels  of  the  opposite  side. 

The  superficial  descending  branch  runs  downward  and  outward  across  the 
sheath  of  the  common  carotid  artery,  and  supplies  the  Sterno-mastoid  and  neigh- 
boring muscles  and  integument.  There  is  also  often  a  distinct  branch  from  the 
external  carotid  distributed  to  the  Sterno-mastoid  muscle. 

The  superior  laryngeal,  larger  than  either  of  the  preceding,  accompanies  the 
superior  laryngeal  nerve,  beneath  the  Thyro-hyoid  muscle :  it  pierces  the  thyro- 
hyoid  membrane,  and  supplies  the  muscles,  mucous  membrane,  and  glands  of  the 
larynx,  anastomosing  with  the  branch  from  the  opposite  side. 

The  crico-thyroid  is  a  small  branch  which  runs  transversely  across  the  crico- 
thyroid  membrane,  communicating  with  the  artery  of  the  opposite  side. 

Surgical  Anatomy. — The  superior  thyroid,  or  some  of  its  branches,  is  often  divided  in 
cases  of  cut  throat,  giving  rise  to  considerable  haemorrhage.  In  such  cases  the  artery  should  be 
secured,  the  wound  being  enlarged  for  that  purpose,  if  necessary.  The  operation  may  be  easily 
performed,  the  position  of  the  artery  beinu  very  superficial,  and  the  only  structures  of  importance 
covering  it  being  a  few  small  veins.  The  operation  of  tying  the  superior  thyroid  artery  in 
bronchocele  has  been  performed  in  numerous  instances  with  partial  or  temporary  success.  When, 


BRANCHES    OF    THE   EXTERNAL    CAROTID.  553 

however,  the  collateral  circulation  between  this  vessel  and  the  artery  of  the  opposite  side,  and 
the  inferior  thyroid,  is  completely  re-established,  the  tumor  usually  regains  its  former  size. 

The  position  of  the  superficial  descending  branch  is  of  importance  in  connection  with  the 
operation  of  ligature  of  the  common  carotid  artery.  It  crosses  and  lies  on  the  sheath  of  this 
vessel,  and  may  chance  to  be  wounded  in  opening  the  sheath.  The  position  of  the  crico-thyrpid 
branch  should  be  remembered,  as  it  may  prove  the  source  of  troublesome  haemorrhage  during 
the  operation  of  laryngotomy. 

The  Lingual  Artery  (Fig.  352)  arises  from  the  external  carotid  between  the 
superior  thyroid  and  facial ;  it  runs  obliquely  upward  and  inward  to  the  great 
cornu  of  the  hyoid  bone,  then  passes  horizontally  forward  parallel  with  the  great 
cornu,  and.  ascending  perpendicularly  to  the  under  surface  of  the  tongue,  turns 
forward  on  its  under  surface  as  far  as  the  tip  of  that  organ,  under  the  name  of 
the  ranine  artery. 

Relations. — Its  first,  or  oblique,  portion  is  superficial,  being  contained  in  the 
triangular  space  already  described,  resting  upon  the  middle  constrictor  of  the 
pharynx,  and  covered  by  the  Platysina  and  fascia  of  the  neck.  Its  second,  or 
horizontal,  portion  also  lies  upon  the  middle  constrictor,  being  covered  at  first  by 
the  tendon  of  the  Digastric  and  the  Stylo-hyoid  muscle,  and  afterward  by  the 
Hyo-glossus.  the  latter  muscle  separating  it  from  the  hypoglossal  nerve.  Its 
third,  or  ascending,  portion  lies  between  the  Hyo-glossus  and  Genio-hyo-glossus 
muscles.  The  fourth,  or  terminal,  part,  under  the  name  of  the  ranine,  runs  along 
the  under  surface  of  the  tongue  to  its  tip  :  it  is  very  superficial,  being  covered 
only  by  the  mucous  membrane,  and  rests  on  the  Lingualis  on  the  outer  side  of 
the  Genio-hyo-glossus.  The  hypoglossal  nerve  crosses  the  lingual  artery,  and  then 
becomes  separated  from  it,  in  the  second  part  of  its  course,  by  the  Hyo-glossus 
muscle. 

The  branches  of  the  lingual  artery  are — the 

Hyoid.  Sublingual. 

Dorsalis  Linguae.  Ranine. 

The  hyoid  branch  rims  along  the  upper  border  of  the  hyoid  bone,  supplying 
the  muscles  attached  to  it  and  anastomosing  with  its  fellow  of  the  opposite  side. 

The  dorsalis  linguae  (Fig.  352)  arises  from  the  lingual  artery  beneath  the  Hyo- 
glossus  muscle  (which,  in  the  figure,  has  been  partly  cut  away  to  show  the  vessel)  ; 
ascending  to  the  dorsum  of  the  tongue,  it  supplies  the  mucous  membrane,  the 
tonsil,  soft  palate,  and  epiglottis,  anastomosing  with  its  fellow  from  the  opposite 
side. 

The  sublingual,  which  may  be  described  as  a  branch  of  bifurcation  of  the 
lingual  artery,  arises  at  the  anterior  margin  of  the  Hyo-glossus  muscle,  and 
runs  forward  between  the  Genio-hyo-glossus  and  the  sublingual  gland.  It 
supplies  the  substance  of  the  gland,  giving  branches  to  the  Mylo-hyoid  and 
neighboring  muscles,  the  mucous  membrane  of  the  mouth  and  gums.  One 
branch  runs  behind  the  alveolar  process  of  the  lower  jaw  in  the  substance  of  the 
gum  to  anastomose  with  a  similar  artery  from  the  other  side. 

The  ranine  may  be  regarded  as  the  other  branch  of  bifurcation,  or,  as  is  more 
usual,  as  the  continuation  of  the  lingual  artery  ;  it  runs  along  the  under  surface 
of  the  tongue,  resting  on  the  Inferior  lingualis.  and  covered  by  the  mucous 
membrane  of  the  mouth ;  it  lies  on  the  outer  side  of  the  Genio-hyo-glossus, 
accompanied  by  the  lingual  nerve.  On  arriving  at  the  tip  of  the  tongue  it  has 
been  said  to  anastomose  with  the  artery  of  the  gpposite  side,  but  this  is  denied 
by  Hyrtl.  These  vessels  in  the  mouth  are  placed  one  on  each  side  of  the  fraenum. 

Surgical  Anatomy.— The  lingual  artery  may  be  divided  near  its  origin  in  cases  of  cut 
throat,  a  complication  that  not  unf'requently  happens  in  this  class  of  wounds ;  or  severe 
haemorrhage  which  cannot  be  restrained  by  ordinary  means  may  ensue  from  a  wound  or  deep 
ulcer  of  the  tongue.  In  the  former  case  the  primary  wound  may  be  enlarged  if  necessary,  and 
the  bleeding  vessels  secured.  In  the  latter  ease  it  has  been  suggested  that  the  lingual  artery 
should  be  tied  near  its  origin.  Ligature  of  the  lingual  artery  is  also  occasionally  practised,  as  a 
palliative  measure,  in  cases  of  cancer  of  the  tongue,  in  order  to  check  the  progress  of  the 
disease  by  starving  the  growth,  and  it  is  sometimes  tied  as  a  preliminary  measure  to  removal  of 


554 


THE   ARTERIES. 


the  tongue.  The  operation  is  a  difficult  one,  on  account  of  the  depth  of  the  artery,  the  number 
of  important  parts  by  which  it  is  surrounded,  the  loose  and  yielding  nature  of  the  parts  upon 
which  it  is  supported,  and  its  occasional  irregularity  of  origin.  An  incision  is  to  be  made  in 
a  curved  direction  from  a  finger's  breadth  external  to  the  symphysis  of  the  jaw  downward  to  the 
cornu  of  the  hyoid  bone,  and  then  upward  to  near  the  angle  of  the  jaw.  Care  must  be  taken 
not  to  carry  this  incision  too  far  backward,  for  fear  of  endangering  the  facial  vein.  In  the  first 
incision  the  skin,  superficial  fascia,  and  Platysma  will  be  divided,  and  the  deep  fascia  exposed. 
This  is  then  to  be  incised  and  the  submaxillary  gland  exposed  and  pulled  upward  by  retractors. 
A  triangular  space  is  now  exposed,  bounded  internally  by  the  posterior  border  of  the  Mylo- 
hyoid  muscle :  below  and  externally,  by  the  tendon  of  the  Digastric ;  and  above,  by  the  hypo- 
glossal  nerve.  The  floor  of  the  space  is  formed  by  the  Hyo-glossus  muscle,  beneath  which  the 
artery  lies.  The  fibres  of  this  muscle  are  now  to  be  cut  through  horizontally  and  the  vessel 
exposed,  care  being  taken,  while  near  the  vessel,  not  to  open  the  pharynx. 

Troublesome  haemorrhage  may  occur  in  the  division  of  the  fraenum  in  children  if  the  ranine 
artery,  which  lies  on  each  side  of  it,  is  wounded.  The  student  should  remember  that  the  opera- 
tion is  always  to  be  performed  with  a  pair  of  blunt-pointed  scissors,  and  the  mucous  membrane 
only  is  to  be  divided  by  a  very  superficial  cut,  which  cannot  endanger  any  vessel.  The  scissors, 
also,  should  be  directed  away  from  the  tongue.  Any  further  liberation  of  the  tongue  which  may 
be  necessary  can  be  effected  by  tearing. 

The  Facial  Artery  (Fig.  349)  arises  a  little  above  the  lingual,  and  passes 
obliquely  upward,  beneath  the  Digastric  and  Stylo-hyoid  muscles  ;  it  then  runs 


Arteria  septi  nasi. 
Superior  coronary. 


Inferior  coronary. 
Inferior  labial. 


I 
FIG.  349.— The  arteries  of  the  face  and  scalp.1 

forward  under  cover  of  the  body  of  the  lower  jaw,  lodged  in  a  groove  on  the 
posterior  surface  of  the  submaxillary  gland ;  this  may  be  called  the  cervical  part 
of  the  artery.  It  then  curves  upward  over  the  body  of  the  jaw  at  the  anterior 
inferior  angle  of  the  Masseter  muscle ;  passes  forward  and  upward  across  the 

1  The  muscular  tissue  of  the  lips  must  be  supposed  to  have  been  cut  away,  in  order  to  show  the 
course  of  the  coronary  arteries. 


BRANCHES   OF   THE  EXTERNAL    CAROTID.  555 

cheek  to  the  angle  of  the  mouth,  then  upward  along  the  side  of  the  nose,  and 
terminates  at  the  inner  canthus  of  the  eye,  under  the  name  of  the  angular  artery. 
This  vessel,  both  in  the  neck  and  on  the  face,  is  remarkably  tortuous :  in  the 
former  situation,  to  accommodate  itself  to  the  movements  of  the  pharynx  in 
deglutition,  and  in  the  latter  to  the  movements  of  the  jaw  and  the  lips  and  cheeks. 

Relations. — In  the  neck  its  origin  is  superficial,  being  covered  by  the 
integument,  Platysma,  and  fascia  ;  it  then  passes  beneath  the  Digastric  and  Stylo- 
hyoid  muscles  and  the  submaxillary  gland.  On  the  face,  where  it  passes  over  the 
body  of  the  lower  jaw,  it  is  comparatively  superficial,  lying  immediately  beneath 
the  Platysma.  In  this  situation  its  pulsation  may  be  distinctly  felt,  and  com- 
pression of  the  vessel  effectually  made  against  the  bone.  In  its  course  over  the 
face  it  is  covered  by  the  integument,  the  fat  of  the  cheek,  and,  near  the  angle  of 
the  mouth,  by  the  Platysma,  Risorius,  and  Zygomatic  muscles.  It  rests  on  the 
Buccinator,  the  Levator  anguli  oris,  and  the  Levator  labii  superioris  (sometimes 
piercing  or  else  passing  under  this  last  muscle).  It  is  accompanied  by  the  facial 
vein  throughout  its  entire  course ;  the  vein  is  not  tortuous  like  the  artery,  and,  on 
the  face,  is  separated  from  that  vessel  by  a  considerable  interval,  lying  to  its  outer 
side.  The  branches  of  the  facial  nerve  cross  the  artery,  and  the  infra-orbital  nerve 
lies  beneath  it. 

The  branches  of  this  vessel  may  be  divided  into  two  sets  :  those  given  off  below 
the  jaw  (cervical),  and  those  on  the  face  (facial). 

Cervical  Branches.  Facial  Branches. 

Inferior  or  Ascending  Palatine.  Muscular. 

Tonsillar.  Inferior  Labial. 

Submaxillary.  Inferior  Coronary. 

Submental.  Superior  Coronary. 

Muscular.  Lateralis  Nasi. 

Angular. 

The  inferior  or  ascending  palatine  (Fig.  352)  passes  up  between  the  Stylo- 
glossus  and  Stylo-pharyngeus  to  the  outer  side  of  the  pharynx.  After  supplying 
these  muscles,  the  tonsil,  and  Eustachian  tube,  it  divides,  near  the  Levator  palati, 
into  two  branches  :  one  follows  the  course  of  the  Levator  palati,  and,  winding  over 
the  upper  border  of  the  Superior  constrictor,  supplies  the  soft  palate  and  the  pal- 
atine glands ;  the  other  pierces  the  Superior  constrictor,  supplies  the  tonsil,  anas- 
tomosing with  the  tonsillar  artery.  These  vessels  also  anastomose  with  the  pos- 
terior palatine  branch  of  the  internal  maxillary  artery. 

The  tonsillar  branch  (Fig.  352)  passes  up  between  the  Internal  Pterygoid  and 
Stylo-glossus,  and  then  ascends  along  the  side  of  the  pharynx,  perforating  the 
Superior  constrictor,  to  ramify  in  the  substance  of  the  tonsil  and  root  of  the  tongue. 

The  submaxillary  consists  of  three  or  four  large  branches,  which  supply  the 
submaxillary  gland,  some  being  prolonged  to  the  neighboring  muscles,  lymphatic 
glands,  and  integument. 

The  submental,  the  largest  of  the  cervical  branches,  is  given  off  from  the  facial 
artery  just  as  that  vessel  quits  the  submaxillary  gland  :  it  runs  forward  upon  the 
Mylo-hyoid  muscle,  just  below  the  body  of  the  jaw  and  beneath  the  Digastric; 
after  supplying  the  surrounding  muscles,  and  anastomosing  with  the  sublingual 
artery  by  branches  which  perforate  the  Mylo-hyoid  muscle,  it  arrives  at  the  sym- 
physis  of  the  chin,  where  it  turns  over  the  border  of  the  jaw  and  divides  into  a 
superficial  and  a  deep  branch  ;  the  former  passes  between  the  integument  and 
Depressor  labii  inferioris,  supplies  both,  and  anastomoses  with  the  inferior  labial. 
The  deep  branch  passes  between  the  latter  muscle  and  the  bone,  supplies  the  lip, 
and  anastomoses  with  the  inferior  labial  and  mental  arteries. 

The  muscular  branches  are  distributed  to  the  Internal  pterygoid  and  Stylo-hyoid 
in  the  neck,  and  to  the  Masseter  and  Buccinator  on  the  face. 

The  inferior  labial   passes  beneath  the  Depressor  anguli  oris.  to  supply  the 


556  THE   ARTERIES. 

muscles  and  integument  of  the  lower  lip,  anastomosing  with  the  inferior  coronary 
and  submental  branches  of  the  facial,  and  with  the  mental  branch  of  the  inferior 
dental  artery. 

The  inferior  coronary  is  derived  from  the  facial  artery,  near  the  angle  of  the 
mouth :  it  passes  upward  and  inward  beneath  the  depressor  anguli  oris.  and,  pen- 
etrating the  Orbicularis  oris  muscle,  runs  in  a  tortuous  course  along  the  edge  of 
the  lower  lip  between  this  muscle  and  the  mucous  membrane,  inosculating  with 
the  artery  of  the  opposite  side.  This  artery  supplies  the  labial  glands,  the  mucous 
membrane,  and  muscles  of  the  lower  lip,  and  anastomoses  with  the  inferior  labial 
and  the  mental  branch  of  the  inferior  dental  artery. 

The  superior  coronary  is  larger  and  more  tortuous  in  its  course  than  the  pre- 
ceding. It  follows  the  same  course  along  the  edge  of  the  upper  lip,  lying  between 
the  mucous  membrane  and  the  Orbicularis  oris,  and  anastomoses  with  the  artery 
of  the  opposite  side.  It  supplies  the  textures  of  the  upper  lip,  and  gives  off  in  its 
course  two  or  three  vessels  which  ascend  to  the  nose.  One,  named  the  inferior 
artery  of  the  septum,  ramifies  on  the  septum  of  the  nares  as  far  as  the  point  of  the 
nose  ;  another,  the  artery  of  the  ala,  supplies  the  ala  of  the  nose. 

The  lateralis  nasi  is  derived  from  the  facial,  as  that  vessel  is  ascending  along 
the  side  of  the  nose ;  it  supplies  the  ala  and  dorsum  of  the  nose,  anastomosing 
with  its  fellow,  the  nasal  branch  of  the  ophthalmic,  the  inferior  artery  of  the 
septum,  the  artery  of  the  ala,  and  the  infra-orbital. 

The  angular  artery  is  the  termination  of  the  trunk  of  the  facial ;  it  ascends  to 
the  inner  angle  of  the  orbit,  imbedded  in  the  fibres  of  the  Levator  labii  superioris 
alaeque  nasi,  and  accompanied  by  a  large  vein,  the  angular  ;  it  distributes  some 
branches  on  the  cheek  which  anastomose  with  the  infra-orbital,  and  after  supplying 
the  lachrymal  sac  and  Orbicularis  palpebrarum  muscle,  terminates  by  anastomos- 
ing with  the  nasal  branch  of  the  ophthalmic  artery. 

The  anastomoses  of  the  facial  artery  are  very  numerous,  not  only  with  the 
vessel  of  the  opposite  side,  but,  in  the  neck,  with  the  sublingual  branch  of  the 
lingual ;  with  the  ascending  pharyngeal ;  with  the  posterior  palatine,  a  branch  of 
the  internal  maxillary,  by  its  inferior  or  ascending  palatine  and  tonsillar  branches  ; 
on  the  face,  with  the  mental  branch  of  the  inferior  dental  as  it  emerges  from  the  mental 
foramen,  with  the  transverse  facial,  a  branch  of  the  temporal ;  with  the  infra-orbital, 
a  branch  of  the  internal  maxillary,  and  with  the  nasal  branch  of  the  ophthalmic. 

Peculiarities. — The  facial  artery  not  unfrequently  arises  by  a  common  trunk  with  the 
lingual.  This  vessel  is  also  subject  to  some  variations  in  its  size  and  in  the  extent  to  which  it 
supplies  the  face.  It  occasionally  terminates  as  the  submental,  and  not  unfrequently  supplies 
the  face  only  as  high  as  the  angle  of  the  mouth  or  nose.  The  deficiency  is  then  supplied  by 
enlargement  of  one  of  the  neighboring  arteries. 

Surgical  Anatomy.— The  passage  of  the  facial  artery  over  the  body  of  the  jaw  would 
appear  to  afford  a  favorable  position  for  the  application  of  pressure  in  case  of  haemorrhage 
from  the  lips,  the  result  either  of  an  accidental  wound  or  during  an  operation  ;  but  its  applica- 
tion is  useless,  except  for  a  very  short  time,  on  account  of  the  free  communication  of  this 
vessel  with  its  fellow  and  with  numerous  branches  from  different  sources.  In  a  wound  involv- 
ing the  lip  it  is  better  to  seize  the  part  between  the  fingers,  and  evert  it,  when  the  bleeding 
vessel  may  be  at  once  secured  with  pressure -forceps.  In  order  to  prevent  haemorrhage  in  cases 
of  removal  of  diseased  growths  from  the  part,  the  lip  should  be  compressed  on  each  side 
between  the  fingers  and  thumb  or  by  a  pair  of  specially  devised  clamp-forceps,  whilst  the  surgeon 
excises  the  diseased  part.  In  order  to  stop  haemorrhage  where  the  lip  has  been  divided  in  an 
operation,  it  is  necessary,  in  uniting  the  edges  of  the  wound,  to  pass  the  sutures  through  the 
cut  edges,  almost  as  deep  as  its  mucous  surface ;  by  these  means  not  only  are  the  cut  surfaces 
more  neatly  and  securely  adapted  to  each  other,  but  the  possibility  of  haemorrhage  is  prevented 
by  including  in  the  suture  the  divided  artery.  If  the  suture  is,  on  the  contrary,  passed  through 
merely  the  cutaneous  portion  of  the  wound,  haemorrhage  occurs  into  the  cavity  of  the  mouth. 
The  student  should,  lastly,  observe  the  relation  of  the  angular  artery  to  the  lachrymal  sac.  and 
it  will  be  seen  that,  as  the  vessel  passes  up  along  the  inner  margin  of  the  orbit,  it  ascends  on 
its  nasal  side.  In  operating  for  fistula  luchrymalis  the  sac  should  always  be  opened  on  its  outer 
side,  in  order  that  this  vessel  may  be  avoided. 

The  Occipital  Artery  (Fig.  349)  arises  from  the  posterior  part  of  the  external 
carotid,  opposite  the  facial  near  the  lower  margin  of  the  Digastric  muscle.  At  its 
origin  it  is  covered  by  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid  muscles, 


BRANCHES    OF    THE   EXTERNAL    CAROTID.  557 

and  the  hypoglossal  nerve  winds  around  it  from  behind  forward ;  higher  up,  it 
passes  across  the  internal  carotid  artery,  the  internal  jugular  vein,  and  the  pneumo- 
gastric  and  spinal  accessory  nerves ;  it  then  ascends  to  the  interval  between  the 
transverse  process  of  the  atlas  and  the  inastoid  process  of  the  temporal  bone,  and 
|ia-<es  horizontally  backward,  grooving  the  surface  of  the  latter  bone,  being  covered 
bv  the  Sterno-mastoid,  Splenius,  Trachelo-mastoid,  and  Digastric  muscles,  and 
resting  upon  the  Rectus  lateralis,  the  Superior  oblique,  and  Complexus  muscles; 
it  then  changes  its  course  and  passes  vertically  upward,  pierces  the  fascia  which 
connects  the  cranial  attachment  of  the  Trapezius  with  the  Sterno-mastoid,  and 
asct-nds  in  a  tortuous  course  over  the  occiput,  as  high  as  the  vertex,  where  it 
divides  into  numerous  branches.  It  is  accompanied  in  the  latter  part  of  its  course 
by  the  great  occipital  and  a  cutaneous  filament  from  the  suboccipital  nerve. 
The  branches  given  oft'  from  this  vessel  are — 

Muscular.  Auricular. 

Sterno-mastoid.  Meningeal. 

Arteria  Princeps  Cervicis. 

The  Muscular  branches  supply  the  Digastric,  Stylo-hyoid,  Splenius,  and 
Trachelo-mastoid  muscles. 

The  sterno-mastoid  is  a  large  and  constant  branch,  generally  arising  from  the 
artery  close  to  its  commencement.  It  first  passes  upward  and  backward,  and 
then  turns  downward  over  the  hypoglossal  nerve,  and  enters  the  substance  of  the 
muscle,  frequently  in  company  with  the  spinal  accessory  nerve. 

The  auricular  branch  supplies  the  back  part  of  the  concha.  It  frequently 
gives  off  a  branch,  which  enters  the  skull  through  the  mastoid  foramen  and 
supplies  the  dura  mater. 

The  meningeal  branch  ascends  with  the  internal  jugular  vein,  and  enters  the 
skull  through  the  foramen  lacerum  posterius,  to  supply  the  dura  mater  in  the 
posterior  fossa. 

The  arteria  princeps  cervicis  (Fig.  352)  is  a  large  branch  which  descends 
along  the  back  part  of  the  neck  and  divides  into  a  superficial  and  deep  branch. 
The  former  runs  beneath  the  Splenius,  giving  off  branches  which  perforate  that 
muscle  to  supply  the  Trapezius  which  anastomose  with  the  superficial  cervical 
artery,  a  branch  of  the  transversalis  colli :  the  latter  passes  beneath  the  Corn- 
plexus  between  it  and  the  Semispinalis  colli  and  anastomoses  with  branches  from 
the  vertebral  and  \\ith  the  deep  cervical  artery,  a  branch  of  the  superior  inter- 
c.-D-tal.  The  anastomosis  between  these  vessels  serves  mainly  to  establish  the  col- 
lateral circulation  after  ligature  of  the  carotid  or  subclavian  artery. 

The  cranial  branches  of  the  occipital  artery  are  distributed  upon  the  occiput; 
they  are  very  tortuous,  and  lie  between  the  integument  and  Occipito-frontalis, 
anastomosing  with  the  artery  of  the  opposite  side,  the  posterior  auricular  and 
temporal  arteries.  They  supply  the  back  part  of  the  Occipito-frontalis  muscle, 
the  integument,  and  pericranium. 

The  Posterior  Auricular  Artery  (Fig.  349)  is  a  small  vessel  which  arises  from 
the  external  carotid,  above  the  Digastric  and  Stylo-hyoid  muscles,  opposite  the 
apex  of  the  styloid  process.  It  ascends,  under  cover  of  the  parotid  gland,  to  the 
groove  between  the  cartilage  of  the  ear  and  the  mastoid  process,  immediately 
above  which  it  divides  into  two  branches :  an  anterior,  auricular,  passing  forward 
to  supply  the  back  of  the  auricle  and  anastomose  with  the  posterior  division  of  the 
temporal :  and  a  posterior,  mastoid,  to  the  scalp  above  and  behind  the  ear, 
communicating  with  the  occipital.  Just  before  arriving  at  the  mastoid  process  this 
artery  is  crossed  by  the  facial  nerve,  and  has  beneath  it  the  spinal  accessory  nerve. 

Besides  several  small  branches  to  the  Digastric,  Stylo-hyoid,  and  Sterno-mastoid 
muscles  and  to  the  parotid  gland,  this  vessel  gives  off  three  branches : 

Stylo-mastoid.  .        Auricular.  Mastoid. 

The  stylo-mastoid  branch  enters   the  stylo-mastoid  foramen,  and  supplies  the 


558  THE  ARTERIES. 

tympanum,  mastoid  cells,  and  semicircular  canals.  In  the  young  subject  a  branch 
from  this  vessel  forms,  with  the  tympanic  branch  from  the  internal  maxillary,  a 
vascular  circle,  which  surrounds  the  auditory  meatus,  and  from  which  delicate 
vessels  ramify  on  the  membrana  tympani.  It  anastomoses  with  the  petrosal 
branch  of  the  middle  meningeal  artery  by  a  twig  which  enters  the  hiatus  Fallopii. 

The  auricular  branch  is  distributed  to  the  back  part  of  the  cartilage  of  the  ear, 
upon  which  it  ramifies  minutely,  some  branches  curving  round  the  margin  of  the 
fibre-cartilage,  others  perforating  it,  to  supply  its  anterior  surface.  It  anastomoses 
with  the  anterior  auricular  branches  of  the  temporal. 

The  mastoid  branch  passes  backward,  over  the  Sterno-mastoid  muscle,  to  the 
scalp  above  and  behind  the  ear.  It  supplies  the  posterior  belly  of  the  Occipito-fron- 
talis  muscle  and  the  scalp  in  this  situation.  It  anastomoses  with  the  occipital  artery. 

The  Ascending  Pharyngeal  Artery  (Fig.  352),  the  smallest  branch  of  the 
external  carotid,  is  a  long,  slender  vessel,  deeply  seated  in  the  neck,  beneath  the 
other  branches  of  the  external  carotid  and  the  Stylo-pharyngeus  muscle.  It  arises 
from  the  back  part  of  the  external  carotid,  near  the  commencement  of  that  vessel, 
and  ascends  vertically  between  the  internal  carotid  and  the  side  of  the  pharynx,  to 
the  under  surface  of  the  base  of  the  skull,  lying  on  the  Rectus  capitis  anticus  major. 
Its  branches  may  be  subdivided  into  three  sets : 

Prevertebral.  Pharyngeal.  Meningeal. 

The  prevertebral  branches  are  numerous  small  vessels  which  supply  the  Recti 
capitis  antici  and  Longus  colli  muscles,  the  sympathetic,  hypoglossal,  and 
pneumogastric  nerves,  and  the  lymphatic  glands  of  the  neck,  anastomosing  with 
the  ascending  cervical  artery. 

The  pharyngeal  branches  are  three  or  four  in  number.  Two  of  these  descend 
to  supply  the  middle  and  inferior  Constrictors  and  the  Stylo-pharyngeus,  ramifying 
in  their  substance  and  in  the  mucous  membrane  lining  them.  The  largest  of  the 
pharyngeal  branches  passes  inward,  running  upon  the  Superior  constrictor,  and 
sends  ramifications  to  the  soft  palate  and  tonsil,  which  take  the  place  of  the 
ascending  palatine  branch  of  the  facial  artery  when  that  vessel  is  of  small  size. 
A  twig  from  this  branch  passes  up  the  Eustachian  tube  to  supply  the  tympanum. 

The  meningeal  branches  consist  of  several  small  vessels,  which  pass  through 
foramina  in  the  base  of  the  skull,  to  supply  the  dura  mater.  One,  the  posterior 
meningeal,  enters  the  cranium  through  the  foramen  lacerum  posterius ;  a  second 
passes  through  the  foramen  lacerum  medium  ;  and  occasionally  a  third  through 
the  anterior  condyloid  foramen.  They  are  all  distributed  to  the  dura  mater. 

Surgical  Anatomy. — The  ascending  pharyngeal  artery  has  been  wounded  from  the  throat, 
as  in  the  case  in  which  the  stem  of  a  tobacco-pipe  was  driven  into  the  vessel,  causing  fatal 
haemorrhage. 

The  Superficial  Temporal  Artery  (Fig.  349),  the  smaller  of  the  two  terminal 
branches  of  the  external  carotid,  appears,  from  its  direction,  to  be  the  continu- 
ation of  that  vessel.  It  commences  in  the  substance  of  the  parotid  gland,  in  the 
interspace  between  the  neck  of  the  condyle  of  the  lower  jaw  and  the  external 
meatus,  crosses  over  the  posterior  root  of  the  zygoma,  passes  beneath  the  Attra- 
hens  aurem  muscle,  and  divides,  about  two  inches  above  the  zygornatic  arch,  into 
two  branches,  an  anterior  and  a  posterior. 

The  anterior  temporal  inclines  forward  over  the  forehead,  supplying  the 
muscles,  integument,  and  pericranium  in  this  region,  and  anastomoses  with  the 
supra-orbital  and  frontal  arteries. 

The  posterior  temporal,  larger  than  the  anterior,  curves  upward  and  backward 
along  the  side  of  the  head,  lying  superficial  to  the  temporal  fascia,  and  inosculates 
with  its  fellow  of  the  opposite  side,  and  with  the  posterior  auricular  and  occipital 
arteries. 

The  superficial  temporal  artery,  as  it  crosses  the  zygoma,  is  covered  by  the 
Attrahens  aurem  muscle  and  by  a  dense  fascia  given  off  from  the  parotid  gland: 
it  is  also  usually  crossed  by  one  or  two  veins,  and  accompanied  by  branches  of  the 


BRANCHES    OF    THE   EXTERNAL    CAROTID.  559 

facial  and  auriculo-temporal  nerves.    Besides  some  twigs  to  the  parotid  gland,  the 
articulation  of  the  jaw,  and  the  Masseter  muscle,  its  branches  are — the 

Transverse  Facial.  Middle  Temporal. 

Anterior  Auricular. 

The  transverse  facial  is  given  off  from  the  temporal  before  that  vessel  quits 
the  parotid  gland ;  running  forward  through  its  substance,  it  passes  transversely 
across  the  face,  between  Stenson's  duct  and  the  lower  border  of  the  zygoma,  and 
divides  on  the  side  of  the  face  into  numerous  branches,  which  supply  the  parotid 
gland,  the  Masseter  muscle,  and  the  integument,  anastomosing  with  the  facial, 

-•teric.  and  infra-orbital  arteries.  This  vessel  rests  on  the  Masseter,  and  is 
accompanied  by  one  or  two  branches  of  the  facial  nerve.  It  is  sometimes  a  branch 
of  the  external  carotid. 

The  middle  temporal  artery  arises  immediately  above  the  zygomatic  arch,  and, 
perforating  the  temporal  fascia,  supplies  the  Temporal  muscle,  anastomosing  with 
the  deep  temporal  branches  of  the  internal  maxillary.  It  occasionally  gives  off 
an  orbital  branch,  which  runs  along  the  upper  border  of  the  zygoma,  between 
the  two  lavers  of  the  temporal  fascia,  to  the  outer  angle  of  the  orbit.  This 
branch  supplies  the  Orbicularis  palpebrarum,  and  anastomoses  with  the  lachrymal 
and  palpebral  branches  of  the  ophthalmic  artery. 

The  anterior  auricular  branches  are  distributed  to  the  anterior  portion  of  the 
pinna,  the  lobule,  and  part  of  the  external  meatus,  anastomosing  with  branches 
of  the  posterior  auricular. 

Surgical  Anatomy. — It  occasionally  happens  that  the  surgeon  is  called  upon  to  perform 
the  operation  of  arteriotomy  upon  this  vessel  in  cases  of  inflammation  of  the  eye  or  brajn.  If 
the  student  will  consider  the  relations  of  the  trunk  of  this  vessel  as  it  crosses  the  zygomatic  arch 
with  the  surrounding  structures,  he  will  observe  that  it  is  covered  by  a  thick  and  dense  fascia. 
1  by  one  or  two  veins,  and  accompanied  by  branches  of  the  facial  and  auriculo-tem- 
poral  nerves.  Bleeding  should  not  be  performed  in  this  situation,  as  much  difficulty  may  arise 
from  the  dense  fascia  over  the  vessel  preventing  a  free  flow  of  blood,  and  considerable  pressure 
is  requisite  afterward  to  repress  the  haemorrhage.  Again,  a  varicose  aneurism  may  be  formed 
by  the  accidental  opening  of  one  of  the  veins  in  front  of  the  artery,  or  severe  neuralgic  pain 
may  arise  from  the  operation  implicating  one  of  the  nervous  filaments  in  the  neighborhood.  The 
anterior  branch,  on  the  contrary,  is  subcutaneous,  is  a  large  vessel,  and  is  readily  compressed :  it 
should  consequently  always  be  selected  for  the  operation. 

The  Internal  Maxillary  (Fig.  350),  the  larger  of  the  two  terminal  branches  of 
the  external  carotid,  passes  inward,  at  right  angles  from  that  vessel,  to  the  inner 
side  of  the  neck  of  the  condyle  of  the  lower  jaw,  to  supply  the  deep  structures  of 
the  face.  At  its  origin,  it  is  imbedded  in  the  substance  of  the  parotid  gland, 
being  on  a  level  with  the  lower  extremity  of  the  lobule  of  the  ear. 

In  the  first  part  of  its  course  (maxillary  portion}  the  artery  passes  horizontally 
forward  and  inward,  between  the  ramus  of  the  jaw  and  the  internal  lateral  lig- 
ament. The  artery  here  lies  parallel  with  the  auriculo-temporal  nerve ;  it  crosses 
the  inferior  dental  nerve,  and  lies  along  the  lower  border  of  the  External 
ptervgoid  muscle. 

In  the  second  part  of  its  course  (pterygoid  portion)  it  runs  obliquely  forward 
and  upward  upon  the  outer  surface  of  the  External  ptervgoid  muscle,  being 
covered  by  the  ramus  of  the  lower  jaw  and  lower  part  of  the  Temporal  muscle. 

In  the  third  part  of  its  course  (spheno-maxillary  portion)  it  approaches  the 
superior  maxillary  bone,  and  enters  the  spheno-maxillary  fossa  in  the  interval 
between  the  two  heads  of  the  External  ptervgoid,  where  it  lies  in  relation  with 
Meckel's  ganglion,  and  gives  off  its  terminal  branches. 

Peculiarities. — Occasionally,  this  artery  passes  between  the  two  Ptervgoid  muscles.  The 
vessel  in  this  case  passes  forward  to  the  interval  between  the  processes  of  origin  of  the  External 
ptervgoid.  in  order  to  reach  the  superior  maxillary  bone.  Sometimes  the  vessel  escapes  from 
beneath  the  External  pterygoid  by  perforating  the  middle  of  that  muscle. 

The  branches  of  this  vessel  may  be  divided  into  three  groups,  corresponding 
with  its  three  divisions. 


560 


THE   ARTERIES. 


BRANCHES  OF  THE  FIRST  OR   MAXILLARY   PORTION   OF  THE  INTERNAL  MAX- 
ILLARY (Fig.  351). 

Tympanic  (anterior).  Small  Meningeal. 

Middle  Meningeal.  Inferior  Dental. 

The  tympanic  branch  passes  upward  behind  the  articulation  of  the  lower  jaw, 
enters  the  tympanum  through  the  Glaserian  fissure,  and   ramifies  upon  the  mem- 


Incisor. 


FIG.  350  —The  internal  maxillary  artery,  and  its  branches. 

Ptery  go- Palatine. 
Vidian. 

Descending  Palatine. 
l.-"±i8ph.eno  Palatine. 
Deep  Temporal. \«  V^)/j 

Middle  Meningeal. 
Meningea  Parva.- 
Tympanic. 

Inferior  Dental.- 

\  \       \V^       _ 

v%,.    <s 

Q  *?     ' 
FIG.  351.— Plan  of  the  branches. 

brana  tympani,  forming  a  vascular  circle  around  the  membrane  with  the  stylo- 
mastoid  artery,  and  anastomosing  with  the  Vidian  and  the  tympanic  branch  from 
the  internal  carotid.  It  gives  off  a  branch  (deep  auricular)  to  the  external  meatus, 
supplying  its  lining  and  the  outer  surface  of  the  membrana  tympani. 

The  middle  meningeal  is  the  largest  of  the  branches  which  supply  the  dura 
mater.  It  arises  from  the  internal  maxillary,  between  the  internal  lateral  liga- 
ment and  the  neck  of  the  jaw,  and  passes  vertically  upward  between  the  two 
roots  of  the  auriculo-temporal  nerve  to  the  foramen  spinosum  of  the  sphenoid 
bone.  On  entering  the  cranium  it  divides  into  two  branches,  anterior  and  poste- 
rior. The  anterior  branch,  the  larger,  crosses  the  great  ala  of  the  sphenoid,  and 
reaches  the  groove,  or  canal,  in  the  anterior  inferior  angle  of  the  parietal  bone  : 
it  then  divides  into  branches  which  spread  out  between  the  dura  mater  and  internal 
surface  of  the  cranium,  some  passing  upward  over  the  parietal  bone  as  far  as  the 
vertex,  and  others  backward  to  the  occipital  bone.  The  posterior  branch  crosses 
the  squamous  portion  of  the  temporal,  and  on  the  inner  surface  of  the  parietal 


BRAXCHE*    O/     THE    EXTERXAL    CAROTID.  561 

bone  divides  into  branches  which  supply  the  posterior  part  of  the  dura  mater  and 
cranium.  The  branches  of  this  vessel  are  distributed  partly  to  the  dura  mater, 
but  chiefly  to  the  bones ;  they  anastomose  with  the  arteries  "of  the  opposite  side, 
and  with  the  anterior  and  posterior  meningeal. 

The  middle  meningeal  on  entering  the  cranium  gives  off  the  following  collat- 
eral branches  :  1.  Numerous  small  vessels  to  the  ganglion  of  the  fifth  nerve  and 
to  the  dura  mater  in  this  situation :  2.  A  branch  (petrosal  branch),  which  enters 
the  hiatus  Fallopii.  supplies  the  facial  nerve,  and  anastomoses  with  the  stvlo- 
mastoid  branch  of  the  posterior  auricular  artery ;  3.  Orbital  branches,  which  pass 
through  the  sphenoidal  fissure  or  through  separate  canals  in  the  great  win»  of  the 
sphenoid  to  anastomose  with  the  lachrymal  or  other  branches  of  the  ophthalmic 
artery :  4.  Temporal  branches,  which  pass  through  foramina  in  the  great  win»  of 
the  sphenoid,  and  anastomose  in  the  temporal  fossa  with  the  deep  temporal  arteries. 

Surgical  Anatomy. — The  middle  meoingeal  is  an  artery  of  considerable  surgical  import- 
ance, as  it  may  be  injured  in  fractures  of  the  temporal  region  of  the  skull,  and  the  injury  may 
be  followed  by  considerable  haemorrhage  between  the  bone  and  dura  mater,  which  niay"  cause 
compression  of  the  brain  and  require  the  operation  of  trephining  for  its  relief.  This  artery 
crosses  the  anterior  inferior  angle  of  the  parietal  bone  at  a  point  li  inches  behind  the  external 
angular  process  of  the  frontal  bone,  and  If  inches  above  the  zygoma.  From  this  point  the  ante- 
rior branch  passes  upward  and  sliehtly  backward  to  the  sagittal  suture,  lying  about  i  inch  to 
f  inch  behind  the  coronal  suture.  The  posterior  branch  passes  upward  and  backward  over  the 
squamous  portion  of  the  temporal  bone.  In  order  to  expose  the  artery  as  it  lies  in  the  canal  in 
the  parietal  bone,  a  semilnnar  incision,  with  its  convexity  upward,  should  be  made,  commencing 
an  inch  behind  the  external  angular  process,  and  carried  backward  for  2  inches.  The  structures 
cut  through  are  :  1 1 )  skin :  (2)  superficial  fascia,  with  branches  of  the  superficial  temporal  vessels 
and  nerves:  )3)  the  fascia  continued  down  from  the  aponenrosis  of  the  Oeeipito-frontali- 
the  two  layers  of  the  temporal  fascia:  (5)  the  temporal  muscle:  (6)  die  deep  temporal  vessels; 

'..e  pericranium ;  and  (8;  the  bone. 

The  small  meningeal  is  sometimes  derived  from  the  preceding.  It  enters  the 
skull  through  the  foramen  ovale.  and  supplies  the  Gasserian  ganglion  and  dura 
mater.  Before  entering  the  cranium  it  gives  off  a  branch  to  the  nasal  fossa,  soft 
palate,  and  tonsil. 

The  inferior  dental  descends  with  the  dental  nerve  to  the  foramen  on  the  inner 
side  of  the  ram  us  of  the  jaw.  It  runs  along  the  dental  canal  in  the  substance 
of  the  bone,  accompanied  by  the  nerve,  and  opposite  the  first  bicuspid  tooth  divides 
into  rwo  branches,  incisor  and  mental ;  the  former  is  continued  forward  beneath 
the  incisor  teeth  as  far  as  the  symphysis.  where  it  anastomoses  with  the  arterv  of 
the  opposite  side :  the  mental  branch  escapes  with  the  nerve  at  the  mental  foramen, 
supplies  the  structures  com;  -sing  the  chin,  and  anastomoses  with  the  submental. 
inferior  labial,  and  inferior  coronary  arteries.  As  the  dental  artery  enters  the 
foramen  it  gives  off  a  mylo-hyoid  branch,  which  runs  in  the  mylo-hyoid  groove, 
and  ramifies  on  the  under  surface  of  the  Mylo-hyoid  muscle.  "  The  dental  and 
incisor  arteries  during  their  course  through  the  substance  of  the  bone  give  off  a 
few  twigs  which  are  lost  in  the  cancellous  tissue,  and  a  series  of  branches  which 
correspond  in  number  to  the  roots  of  the  teeth  :  these  enter  the  minute  apertures 
at  the  extremities  of  the  fangs  and  supply  the  pulp  of  the  teeth. 

BRANCHES  OF  TH     -       \D  OR  PTERTGOID  PORTION  OF  INTERNAL  MAXILLARY. 
Deep  Temporal.  Masseteric. 

Pterygoid.  Buccal. 

These  branches  are  distributed,  as  their  names  imply,  to  the  muscles  in  the 
maxillary  region. 

The  deep  temporal  arteries,  two  in  number,  anterior  and  posterior,  each  occupy 
that  part  of  the  temporal  fossa  indicated  by  its  name.  Ascending  between 
the  Temporal  muscle  and  pericranium,  they  supply  that  muscle  and  anastomose 
with  the  other  temporal  arteries,  the  anterior  branch  communicating  with  the 
lachrymal  through  small  branches  which  perforate  the  malar  bone  and  great  win<* 
of  the  sphenoid. 


562  THE   ARTERIES. 

The  pterygoid  branches,  irregular  in  their  number  and  origin,  supply  the 
Pterygoid  muscles. 

The  masseteric  is  a  small  branch  which  passes  outward,  above  the  sigmoid 
notch  of  the  lower  jaw,  to  the  deep  surface  of  the  Masseter.  It  supplies  that 
muscle,  and  anastomoses  with  the  masseteric  branches  of  the  facial  and  with  the 
transverse  facial  artery. 

The  buccal  is  a  small  branch  which  runs  obliquely  forward  between  the  Internal 
pterygoid  and  the  ramus  of  the  jaw,  to  the  outer  surface  of  the  Buccinator,  to 
which  it  is  distributed,  anastomosing  with  branches  of  the  facial  artery. 

BRANCHES  OF  THE  THIRD  OR  SPHENO-MAXILLARY  PORTION  OF  INTERNAL 

MAXILLARY. 

Alveolar.  Vidian. 

Infra-orbital.  Pterygo-palatine. 

Posterior  or  Descending  Palatine.  Naso-  or  Spheno-palatine. 

The  alveolar  or  posterior  dental  branch  is  given  off  from  the  internal  maxillary 
by  a  common  branch  with  the  infra-orbital,  and  just  as  the  trunk  of  the  vessel  is 
passing  into  the  spheno-maxillary  fossa.  Descending  upon  the  tuberosity  of  the 
superior  maxillary  bone,  it  divides  into  numerous  branches,  some  of  which  enter 
the  posterior  dental  canals,  to  supply  the  molar  and  bicuspid  teeth  and  the  lining 
of  the  antrum,  and  others  are  continued  forward  on  the  alveolar  process  to  supply 
the  gums. 

The  infra-orbital  appears,  from  its  direction,  to  be  the  continuation  of  the  trunk 
of  the  internal  maxillary.  It  arises  from  that  vessel  by  a  common  trunk  with  the 
preceding  branch,  and  runs  along  the  infra-orbital  canal  with  the  superior  maxil- 
lary nerve,  emerging  upon  the  face  at  the  infra-orbital  foramen,  beneath  the  Levator 
labii  superioris.  Whilst  contained  in  the  canal,  it  gives  off  branches  which  ascend 
into  the  orbit,  and  supply  the  Inferior  rectus  and  Inferior  oblique  muscles  and  the 
lachrymal  gland.  Other  branches  (anterior  dental)  descend  through  canals  in 
the  bone  to  supply  the  mucous  membrane  of  the  antrum  and  the  front  teeth  of 
the  upper  jaw.  On  the  face  some  branches  pass  inward  toward  the  nose,  anasto- 
mosing with  the  angular  branch  of  the  facial  artery  and  nasal  branch  of  the 
ophthalmic ;  and  other  branches  descend  beneath  the  Levator  labii  superioris  and 
anastomose  with  the  transverse  facial  and  buccal  branches. 

The  four  remaining  branches  arise  from  that  portion  of  the  internal  maxillary 
which  is  contained  in  the  spheno-maxillary  fossa. 

The  descending  palatine  passes  down  the  posterior  palatine  canal  with  the 
anterior  palatine  branch  of  Meckel's  ganglion,  and,  emerging  from  the  posterior 
palatine  foramen,  runs  forward  in  a  groove  on  the  inner  side  of  the  alveolar  border 
of  the  hard  palate  to  the  anterior  palatine  canal,  where  the  terminal  branch  of  the 
artery  passes  upward  through  the  foramen  of  Stenson  to  anastomose  with  the 
naso-palatine  artery.  Its  branches  are  distributed  to  the  gums,  the  mucous 
membrane  of  the  hard  palate,  and  the  palatine  glands.  Whilst  it  is  contained  in 
the  palatine  canal  it  gives  off  branches,  which  descend  in  the  accessory  palatine 
canals  to  supply  the  soft  palate  and  tonsil,  anastomosing  with  the  ascending 
palatine  artery. 

The  Vidian  branch  passes  backward  along  the  Vidian  canal  with  the  Vidian 
nerve.  It  is  distributed  to  the  upper  part  of  the  pharynx  and  Eustachian  tube, 
sending  a  small  branch  into  the  tympanum,  which  anastomoses  with  the  anterior 
tympanic. 

The  pterygo-palatine  is  also  a  very  small  branch,  which  passes  backward 
through  the  pterygo-palatine  canal  with  the  pharyngeal  nerve,  and  is  distributed 
to  the  upper  part  of  the  pharynx  and  Eustachian  tube. 

The  spheno-palatine  passes  through  the  spheno-palatine  foramen  into  the 
cavity  of  the  nose,  at  the  back  part  of  the  superior  meatus,  and  divides  into  two 
branches :  one  internal,  the  naso-palatine  or  superior  artery  of  the  septum,  passes 


THE   ANTERIOR    TRIAXGLE    OF   THE   NECK.  563 

obliquely  downward  and  forward  along  the  septum  nasi,  supplies  the  mucous 
membrane,  and  anastomoses  in  front  with  the  terminal  branch  of  the  descending 
palatine.  The  external  branches,  two  or  three  in  number,  supply  the  mucous 
membrane  covering  the  lateral  wall  of  the  nose,  the  antrum,  and  the  ethmoid  and 
sphenoid  cells. 

SURGICAL  ANATOMY  OF  THE  TRIANGLES  OF  THE  NECK. 

The  student  having  considered  the  relative  anatomy  of  the  large  arteries  of  the 
neck  and  their  branches,  and  the  relations  they  bear  to  the  veins  and  nerves,  should 
now  examine  these  structures  collectively,  as  they  present  themselves  in  certain 
regions  of  the  neck,  in  each  of  which  important  operations  are  constantly  being 
performed. 

The  side  of  the  neck  presents  a  somewhat  quadrilateral  outline,  limited,  above, 
by  the  lower  border  of  the  body  of  the  jaw,  and  an  imaginary  line  extending  from 
the  angle  of  the  jaw  to  the  mastoid  process  ;  below,  by  the  prominent  upper  border 
of  the  clavicle ;  in  front,  by  the  median  line  of  the  neck ;  behind,  by  the  anterior 
margin  of  the  Trapezius  muscle.  This  space  is  subdivided  into  two  large  triangles 
by  the  Sterno-niastoid  muscle,  which  passes  obliquely  across  the  neck,  from  the 
sternum  and  clavicle  below  to  the  mastoid  process  above.  The  triangular  space 
in  front  of  this  muscle  is  called  the  anterior  triangle  ;  and  that  behind  it,  the 
posterior  trianyh-. 

ANTERIOR  TRIANGLE  OF  THE  NECK. 

The  anterior  triangle  is  bounded,  in  front,  by  a  line  extending  from  the  chin 
to  the  sternum :  behind,  by  the  anterior  margin  of  the  Sterno-mastoid ;  its  base, 
directed  upward,  is  formed  by  the  lower  border  of  the  body  of  the  jaw  and  a  line 
extending  from  the  angle  of  the  jaw  to  the  mastoid  process ;  its  apex  is  below,  at 
the  sternum.  This  space  is  subdivided  into  three  smaller  triangles  by  the  Digastric 
muscle  above  and  the  anterior  belly  of  the  Omo-hyoid  below.  These  smaller 
triangles  are  named,  from  below  upward,  the  inferior  carotid,  the  superior  carotid, 
and  the  submaxillary  triangle. 

The  Inferior  Carotid  Triangle  is  bounded,  in  front,  by  the  median  line  of  the 
neck  ;  behind,  by  the  anterior  margin  of  the  Sterno-mastoid ;  above,  by  the  anterior 
belly  of  the  Omo-hyoid ;  and  is  covered  by  the  integument,  superficial  fascia, 
Platysma.  and  deep  fascia,  ramifying  between  which  is  the  descending  branch  of 
the  superficialis  colli  nerve.  Beneath  these  superficial  structures  are  the  Sterno- 
hyoid  and  Sterno-thyroid  muscles,  which,  together  with  the  anterior  margin  of 
the  Sterno-mastoid,  conceal  the  lower  part  of  the  common  carotid  artery.1 

This  vessel  is  enclosed  within  its  sheath,  together  with  the  internal  jugular 
vein  and  pneumogastric  nerve ;  the  vein  lying  on  the  outer  side  of  the  artery  on 
the  right  side  of  the  neck,  but  overlapping  it,  or  passing  directly  across  it  on  the 
left  side ;  the  nerve  lying  between  the  artery  and  vein,  on  a  plane  posterior  to 
both.  In  front  of  the  sheath  are  a  few  filaments  descending  from  the  loop  of  com- 
munication between  the  descendens  and  communicans  hypoglossi ;  behind  the  sheath 

-een  the  inferior  thyroid  artery,  the  recurrent  laryngeal  nerve,  and  the  sym- 
pathetic nerve ;  and  on  its  inner  side,  the  trachea,  the  thyroid  gland — much  more 
prominent  in  the  female  than  in  the  male — and  the  lower  part  of  the  larynx.  By  cut- 
ting into  the  upper  part  of  this  space  and  slightly  .displacing  the  Sterno-mastoid 
muscle  the  common  carotid  artery  may  be  tied  below  the  Omo-hyoid  muscle. 

The  floor  of  the  inferior  carotid  triangle  is  formed  by  the  Longus  colli  muscle 
below,  by  the  Scalenus  anticus  above  (see  Fig.  284.  page  424),  between  which 

1  Therefore  the  common  carotid  artery  and  internal  jugular  vein  are  not,  strictly  speaking,  con- 
tained in  this  triangle,  since  they  are  covered  by  the  Sterno-mastoid  muscle ;  that  is  to  say,  lie  behind 
the  anterior  border  of  that  muscle,  which  forms  the  posterior  border  of  the  triangle.  But  as  they  lie 
very  close  to  the  structures  which  are  really  contained  in  the  triangle,  and  whose  position  it  is 
essential  to  remember  in  operating  on  this  part  of  the  artery,  it  has  seemed  expedient  to  study  the 
relations  of  all  these  parts  together. 


564  THE   ARTERIES. 

muscles  the  vertebral  artery  and  vein  will  be  found  passing  into  the  foramen  in  the 
sixth  transverse  process  ;  a  small  portion  of  the  origin  of  the  Rectus  capitis  anticus 
major  may  also  be  seen  in  the  floor  of  the  space. 

The  Superior  Carotid  Triangle  is  bounded,  behind,  by  the  Sterno-mastoid ; 
below,  by  the  anterior  belly  of  the  Omo-hyoid ;  and  above,  by  the  posterior  belly 
of  the  Digastric  muscle.  It  is  covered  by  the  integument,  superficial  fascia, 
Platysma,  and  deep  fascia,  ramifying  between  which  are  branches  of  the  facial 
and  superficialis  colli  nerves.  Its  floor  is  formed  by  parts  of  the  Thyro-hyoid, 
Hyo-glossus,  and  the  inferior  and  middle  Constrictor  muscles  of  the  pharynx. 
This  space  contains  the  upper  part  of  the  common  carotid  artery,  which  bifurcates 
opposite  the  upper  border  of  the  thyroid  cartilage  into  the  external  and  internal 
carotid.  These  vessels  are  occasionally  somewhat  concealed  from  view  by  the 
anterior  margin  of  the  Sterno-mastoid  muscle,  which  overlaps  them.  The  external 
and  internal  carotids  lie  side  by  side,  the  external  being  the  more  anterior  of  the 
two.  The  following  branches  of  the  external  carotid  are  also  met  with  in  this 
space :  the  superior  thyroid,  running  forward  and  downward ;  the  lingual, 
directly  forward ;  the  facial,  forward  and  upward ;  the  occipital,  backward ; 
and  the  ascending  pharyngeal  directly  upward  on  the  inner  side  of  the  internal 
carotid.  The  veins  met  with  are:  the  internal  jugular,  which  lies  on  the  outer 
side  of  the  common  and  internal  carotid  arteries,  and  veins  corresponding  to  the 
above-mentioned  branches  of  the  external  carotid — viz.  the  superior  thyroid,  the 
lingual,  facial,  ascending  pharyngeal,  and  sometimes  the  occipital, — all  of  which 
accompany  their  corresponding  arteries  and  terminate  in  the  internal  jugular. 
The  nerves  in  this  space  are  the  following :  In  front  of  the  sheath  of  the  common 
carotid  is  the  descendens  hypoglossi.  The  hypoglossal  nerve  crosses  both  carotids 
above,  curving  round  the  occipital  artery  at  its  origin.  Within  the  sheath,  between 
the  artery  and  vein,  and  behind  both,  is  the  pneumogastric  nerve ;  behind  the 
sheath,  the  sympathetic.  On  the  outer  side  of  the  vessels  the  spinal  accessory 
nerve  runs  for  a  short  distance  before  it  pierces  the  Sterno-mastoid  muscle ;  and 
on  the  inner  side  of  the  external  carotid,  just  below  the  hyoid  bone,  may  be  seen 
the  superior  laryngeal  nerve ;  and,  still  more  inferiorly,  the  external  laryngeal 
nerve.  The  upper  part  of  the  larynx  and  lower  part  of  the  pharynx  are  also  found 
in  the  front  part  of  this  space. 

The  Submaxillary  Triangle  corresponds  to  the  part  of  the  neck  immediately 
beneath  the  body  of  the  jaw.  It  is  bounded,  above,  by  the  lower  border  of  the 
body  of  the  jaw  and  a  line  drawn  from  its  angle  to  the  mastoid  process ;  below, 
by  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid  muscles ;  in  front,  by  the 
anterior  belly  of  the  Digastric.  It  is  covered  by  the  integument,  superficial  fascia, 
Platysma,  and  deep  fascia,  ramifying  between  which  are  branches  of  the  facial  and 
ascending  filaments  of  the  superficial  cervical  nerves.  Its  floor  is  formed  by  the 
anterior  belly  of  the  Digastric,  the  Mylo-hyoid,  and  the  Hyo-glossus  muscles.  This 
space  contains,  in  front,  the  submaxillary  gland,  imbedded  in  the  substance  of 
which  are  the  facial  artery  and  vein  and  their  glandular  branches ;  beneath  this 
gland,  on  the  surface  of  the  Mylo-hyoid  muscle,  are  the  submental  artery  and  the 
mylo-hyoid  artery  and  nerve.  The  back  part  of  this  space  is  separated  from  the 
front  part  by  the  stylo-maxillary  ligament :  it  contains  the  external  carotid  artery, 
ascending  deeply  in  the  substance  of  the  parotid  gland :  this  vessel  here  lies  in 
front  of,  and  superficial  to,  the  internal  carotid,  being  crossed  by  the  facial  nerve, 
and  gives  off  in  its  course  the  posterior  auricular,  temporal,  and  internal  maxil- 
lary branches :  more  deeply  are  the  internal  carotid,  the  internal  jugular  vein, 
and  the  pneumogastric  nerve,  separated  from  the  external  carotid  by  the  Stylo- 
glossus  and  Stylo-pharyngeus  muscles  and  the  glosso-pharyngeal  nerve.1 

1  The  same  remark  will  apply  to  this  triangle  as  was  made  about  the  inferior  carotid  triangle. 
The  structures  enumerated  as  contained  in  the  back  part  of  the  space  lie,  strictly  speaking,  beneath 
the  muscles  which  form  the  posterior  boundary  of  the  triangle ;  but  as  it  is  very  important  to  bear  in 
mind  their  close  relation  to  the  parotid  gland  and  its  boundaries  (on  account  of  the  frequency  of  sur- 
gical operations  on  this  gland),  all  these  parts  are  spoken  of  together. 


THE   IXTERXAL    CAROTID   ARTERY.  565 

POSTERIOR  TRIANGLE  OF  THE  XEOK. 

The  posterior  triangle  is  bounded,  in  front,  by  the  Sterno-mastoid  muscle; 
behind,  by  the  anterior  margin  of  the  Trapezius ;  its  base  corresponds  to  the 
upper  border  of  the  clavicle;  its  apex,  to  the  occiput.  The  space  is  crossed, 
about  an  inch  above  the  clavicle,  by  the  posterior  belly  of  the  Omo-hyoid,  which 
divides  it  unequally  into  two,  an  upper  or  occipital  and  a  lower  or  subclavian 
triangle. 

The  Occipital,  the  larger  of  the  two  posterior  triangles,  is  bounded,  in  front, 
by  the  Sterno-mastoid  ;  behind,  by  the  Trapezius ;  below,  by  the  Omo-hyoid.  Its 
floor  is  formed  from  above  downward  by  the  Splenius  capitis,  Levator  anguli 
scapulae,  and  the  middle  and  posterior  Scaleni  muscles.  It  is  covered  by  the 
integument,  the  Platysma  below,  the  superficial  and  deep  fasciae  ;  the  spinal  acces- 
sory nerve  is  directed  obliquely  across  the  space  from  the  Sterno-mastoid, 
which  it  pierces,  to  the  under  surface  of  the  Trapezius;  below,  the  descending 
branches  of  the  cervical  plexus  and  the  transversalis  colli  artery  and  vein  cross 
the  space.  A  chain  of  lymphatic  glands  is  also  found  running  along  the  pos- 
terior border  of  the  Sterno-mastoid,  from  the  mastoid  process  to  the  root  of  the 
neck. 

The  Subclavian,  the  smaller  of  the  two  posterior  triangles,  is  bounded,  above, 
by  the  posterior  belly  of  the  Omo-hyoid ;  below,  by  the  clavicle,  its  base,  directed 
forward,  being  formed  by  the  Sterno-mastoid.  The  size  of  the  subclavian  trian- 
gle varies  according  to  the  extent  of  attachment  of  the  clavicular  portion  of  the 
Sterno-mastoid  and  Trapezius  muscles,  and  also  according  to  the  height  at  which 
the  Omo-hyoid  crosses  the  neck  above  the  clavicle.  Its  height  also  varies  much 
according  to  the  position  of  the  arm,  being  much  diminished  by  raising  the  limb, 
on  account  of  the  ascent  of  the  clavicle,  and  increased  by  drawing  the  arm  down- 
ward, when  that  bone  is  depressed.  This  space  is  covered  by  the  integument, 
superficial  and  deep  fascine,  and  crossed  by  the  descending  branches  of  the  cervical 
plexus.  Just  above  the  level  of  the  clavicle  the  third  portion  of  the  subclavian 
artery  curves  outward  and  downward  from  the  outer  margin  of  the  Scalenus 
anticus.  across  the  first  rib.  to  the  axilla.  Sometimes  this  vessel  rises  as  high  as 
an  inch  and  a  half  above  the  clavicle,  or  to  any  point  intermediate  between  this 
and  its  usual  level.  Occasionally,  it  passes  in  front  of  the  Scalenus  anticus  or 
pierces  the  fibres  of  that  muscle.  The  subclavian  vein  lies  behind  the  clavicle, 
and  is  usually  not  seen  in  this  space ;  but  it  occasionally  rises  as  high  up  as  the 
artery,  and  has  even  been  seen  to  pass  with  that  vessel  behind  the  Scalenus 
anticus.  The  brachial  plexus  of  nerves  lies  above  the  artery,  and  in  close  contact 
with  it.  Passing  transversely  across  the  clavicular  margin  of  the  space  are  the 
suprascapular  vessels,  and  traversing  its  upper  angle  in  the  same1  direction,  the 
transversalis  colli  artery  and  vein.  The  external  jugular  vein  runs  vertically 
downward  behind  the  posterior  border  of  the  Sterno-mastoid,  to  terminate  in  the 
subclavian  vein:  it  receives  the  transverse  cervical  and  suprascapular  veins,  which 
occasionally  form  a  plexus  in  front  of  the  artery,  and  a  small  vein  whicn  crosses 
the  clavicle  from  the  cephalic.  The  small  nerve  to  the  Subclavius  muscle  also 
crosses  this  triangle  about  its  middle.  A  lymphatic  gland  is  also  foundVin  the 
space.  Its  floor  is  formed  by  the  first  rib  with  the  first  digitation  of  the  Serratus 
magnus. 

The  Internal  Carotid  Artery.      I          J  ' 

The  internal  carotid  artery  supplies  the  anterior  part  of  the  brain,  the  eye. 
and  its  appendages,  and  sends  branches  to  the  forehead  and  nose.  Its  size  in 
the  adult  is  equal  to  that  of  the  external  carotid,  though  in  the  child  it  is  larger 
than  that  vessel.  It  is  remarkable  for  the  number  of  curvatures  that  it  presents 
in  different  parts  of  its  course.  In  its  cervical  portion  it  occasionally  presents 
one  or  two  flexures  near  the  base  of  the  skull,  whilst  through  the  rest  of  its  extent 
it  describes  a  double  curvature  which  resembles  the  italic  letter  s  placed  horizon- 
tally. These  curvatures  most  probably  diminish  the  velocity  of  the  current  of 


566  THE  ARTERIES. 

blood,  by  increasing  the  extent  of  surface  over  which  it  moves  and  adding  to  the 
amount  of  impediment  produced  from  friction. 

In  considering  the  course  and  relations  of  this  vessel  it  may  be  conveniently 
divided  into  four  portions :  a  cervical,  petrous,  cavernous,  and  cerebral. 

Cervical  Portion. — This  portion  of  the  internal  carotid  commences  at  the  bifur- 
cation of  the  common  carotid,  opposite  the  upper  border  of  the  thyroid  cartilage, 
and  runs  perpendicularly  upward,  in  front  of  the  transverse  processes  of  the  three 
upper  cervical  vertebrae,  to  the  carotid  canal  in  the  petrous  portion  of  the  temporal 
bone.  It  is  superficial  at  its  commencement,  being  contained  in  the  superior 
carotid  triangle,  and  lying  on  the  same  level  as  the  external  carotid,  but  behind 
that  artery  overlapped  by  the  Sterno-mastoid  and  covered  by  the  deep  fascia, 
Platysma,  and  integument :  it  then  passes  beneath  the  parotid  gland,  being  crossed 
by  the  hypoglossal  nerve,  the  Digastric  and  Stylo-hyoid  muscles,  and  the  external 
carotid  and  occipital  arteries.  Higher  up,  it  is  separated  from  the  external  carotid 
by  the  Stylo-glossus  and  Stylo-pharyngeus  muscles,  the  glosso-pharyngeal  nerve, 
and  pharyngeal  branch  of  the  pneumogastric.  It  is  in  relation,  behind,  with  the 
Rectus  capitis  anticus  major,  the  superior  cervical  ganglion  of  the  sympathetic, 
and  superior  laryngeal  nerve ;  externally,  with  the  internal  jugular  vein  and  pneu- 
mogastric nerve ;  internally,  with  the  pharynx,  tonsil,  the  superior  laryngeal  nerve, 
and  ascending  pharyngeal  artery. 

Petrous  Portion. — When  the  internal  carotid  artery  enters  the  canal  in  the 
petrous  portion  of  the  temporal  bone,  it  first  ascends  a  short  distance,  then  curves 
forward  and  inward,  and  again  ascends  as  it  leaves  the  canal  to  enter  the  cavity 
of  the  skull.  In  this  canal  the  artery  lies  at  first  anterior  to  the  tympanum,  from 
which  it  is  separated  by  a  thin,  bony  lamella,  which  is  cribriform  in  the  young 
subject,  and  often  absorbed  in  old  age.  It  is  separated  from  the  bony  wall  of  the 
carotid  canal  by  a  prolongation  of  dura  mater,  and  is  surrounded  by  filaments  of 
the  carotid  plexus. 

Cavernous  Portion. — The  internal  carotid  artery  in  this  part  of  its  course  is 
situated  between  the  layers  of  the  dura  mater  forming  the  cavernous  sinus,  but 
covered  by  the  lining  membrane  of  the  sinus.  It  at  first  ascends  to  the  posterior 
clinoid  process,  then  passes  forward  by  the  side  of  the  body  of  the  sphenoid  bone, 
and  again  curves  upward  on  the  inner  side  of  the  anterior  clinoid  process,  and 
perforates  the  dura  mater  forming  the  roof  of  the  sinus.  In  this  part  of  its  course 
it  is  surrounded  by  filaments  of  the  sympathetic  nerve,  and  has  in  relation  with  it 
externally  the  sixth  nerve. 

Cerebral  Portion. — Having  perforated  the  dura  mater  on  the  inner  side  of  the 
anterior  clinoid  process,  the  internal  carotid  enters  the  inner  extremity  of  the 
fissure  of  Sylvius,  where  it  gives  off  its  terminal  or  cerebral  branches.  This 
portion  of  the  artery  has  the  optic  nerve  on  its  inner  side,  and  the  third  nerve 
externally. 

PLAN  OF  THE  RELATIONS  OF  THE  INTERNAL  CAROTID  ARTERY  IN  THE  NECK. 

Externally. 

Skin,  superficial  and  deep  fasciae. 

Platysma. 

Sterno-mastoid. 

External  carotid  and  occipital  ar-  /^       ~^\  Internally. 

teries.  /  \  Pharynx. 

Hypoglossal  nerve.  (      carot?d       ]  Superior  laryngeal  nerve. 

Parotid  gland.  I      Artery.       I  Ascending  pharyngeal  artery. 

Stylo-glossus  and  Stylo-pharyngeus  J  Tonsil, 

muscles. 

Glosso-pharyngeal  nerve. 

Pharyngeal  branch  of  the  pneumo- 
gastric. 

Internal  jugular  vein. 

Pneumogastric  nerve. 


THE   IXTERXAL    CAROTID    ARTERY.  567 

Behind. 

Rectus  capitis  anticus  major. 
Sympathetic. 
Superior  laryngeal  nerve. 

Peculiarities. — The  length  of  the  internal  carotid  varies  according  to  the  length  of  the 
neck,  and  also  according  to  the  point  of  bifurcation  of  the  common  carotid.     Its  origin  some- 


1U  Aortic 


FIG.  352.—  The  internal  carotid  and  vertebral  arteries.    Right  side. 


times  takes  place  from  the  arch  of  the  aorta  ;  in  such  rare  instances  this  vessel  has  been  found 
to  be  placed  nearer  the  middle  line  of  the  neck  than  the  external  carotid,  as  far  upward  as  the 
larynx,  when  the  latter  vessel  crossed  the  internal  carotid.  The  course  of  the  vessel,  instead  of 
being  straight,  may  be  very  tortuous.  A  few  instances  are  recorded  in  which  this  vessel  was 
altogether  absent  :  in  one  of  these  the  common  carotid  passed  up  the  neck,  and  gave  off  the 
usual  branches  of  the  external  carotid,  the  cranial  portion  of  the  internal  carotid  being  replaced 
by  two  branches  of  the  internal  maxillary,  which  entered  the  skull  through  the  foramen  rotundum 
and  ovale  and  joined  to  form  a  single  vessel. 


568  THE   ARTERIES. 

Surgical  Anatomy. — The  cervical  part  of  the  internal  carotid  is  very  rarely  wounded. 
Mr.  Cripps,  in  an  interesting  paper  in  the  Medico-  Chirurgical  Transactions,  compares  the  rare- 
ness of  a  wound  of  the  internal  carotid  with  one  of  the  external  or  its  branches.  It  is,  however, 
sometimes  injured  by  a  stab  or  gunshot  wound  in  the  neck,  or  even  occasionally  by  a  stab  from 
within  the  mouth,  as  when  a  person  receives  a  thrust  from  the  end  of  a  parasol  or  falls  down 
with  a  tobacco-pipe  in  his  mouth.  The  relation  of  the  internal  carotid  with  the  tonsil  should  be 
especially  remembered,  as  instances  have  occurred  in  which  the  artery  has  been  wounded  during 
the  operation  of  scarifying  the  tonsil,  and  fatal  haemorrhage  has  supervened.  The  indications 
for  ligature  are  wounds,  when  the  vessel  should  be  exposed  by  a  careful  dissection  and  tied 
above  and  below  the  bleeding  point ;  and  aneurism,  which  if  non-traumatic  may  be  treated  by 
ligature  of  the  common  carotid,  but  if  traumatic  in  origin  by  exposing  the  sac  and  tying  the 
vessel  above  and  below.  The  incision  for  ligature  of  the  cervical  portion  of  the  internal  carotid 
should  be  made  along  the  anterior  border  of  the  Sterno-mastoid,  from  the  angle  of  the  jaw  to 
the  upper  border  of  the  thyroid  cartilage.  The  superficial  structures  being  divided  and  the 
Sterno-mastoid  defined  and  drawn  outward,  the  cellular  tissue  must  be  carefully  separated  and 
the  posterior  belly  of  the  Digastric  and  hypoglossal  nerve  sought  for  as  guides  to  the  vessel. 
When  the  artery  is  found  the  external  carotid  should  be  drawn  inward  and  the  Digastric  muscles 
upward,  and  the  aneurism  needle  passed  from  without  inward. 

The  branches  given  off  from  the  internal  carotid  are — 

From  the  Petrous  portion     .     Tympanic  (internal  or  deep). 

(  Arterise  Receptaculi. 
From  the  Cavernous  portion    <  Anterior  Meningeal. 

(  Ophthalmic. 

f  Anterior  Cerebral. 

TTT         .7     n     z,     7        *•  I  Middle  Cerebral. 

from  the  Cerebral  portion       <  ^  ~  .      . 

.Posterior  Communicating. 

(^Anterior  Choroid. 

The  cervical  portion  of  the  internal  carotid  gives  off  no  branches. 

The  tympanic  is  a  small  branch  which  enters  the  cavity  of  the  tympanum 
through  a  minute  foramen  in  the  carotid  canal,  and  anastomoses  with  the  tympanic 
branch  of  the  internal  maxillary,  and  with  the  stylo-mastoid  artery. 

The  arteriae  receptaculi  are  numerous  small  vessels,  derived  from  the  internal 
carotid  in  the  cavernous  sinus ;  they  supply  the  pituitary  body,  the  Gasserian 
ganglion,  and  the  walls  of  the  cavernous  and  inferior  petrosal  sinuses.  Some  of 
these  branches  anastomose  with,  branches  of  the  middle  meningeal. 

The  anterior  meningeal  is  a  small  branch  which  passes  over  the  lesser  wing  of 
the  sphenoid  to  supply  the  dura  mater  of  the  anterior  fossa;  it  anastomoses  with 
the  meningeal  branch  from  the  posterior  ethmoidal  artery. 

The  Ophthalmic  Artery  arises  from  the  internal  carotid,  just  as  that  vessel 
is  emerging  from  the  cavernous  sinus,  on  the  inner  side  of  the  anterior  clinoid 
process,  and  enters  the  orbit  through  the  optic  foramen,  below  and  on  the  outer 
side  of  the  optic  nerve.  It  then  passes  over  the  nerve  to  the  inner  wall  of  the 
orbit,  and  thence  horizontally  forward,  beneath  the  lower  border  of  the  Superior 
oblique  muscle,  to  a  point  behind  the  internal  angular  process  of  the  frontal  bone, 
where  it  divides  into  two  terminal  branches,  the  frontal  and  nasal. 

Branches. — The  branches  of  this  vessel  may  be  divided  into  an  orbital  group, 
which  are  distributed  to  the  orbit  and  surrounding  parts,  and  an  ocular  group, 
which  supply  the  muscles  and  globe  of  the  eye : 

Orbital  Grroup.  Ocular  Group. 

Lachrymal.  Muscular. 

Supra-orbital.  Anterior  Ciliary. 

Posterior  Ethmoidal.  Short  Ciliary. 

Anterior  Ethmoidal.  Long  Ciliary. 

Palpebral.  Arteria  Centralis  Retinae. 
Frontal. 
Nasal. 

The  lachrymal  is  the  first  and  one  of  the  largest  branches  derived  from  the 
ophthalmic,  arising  close  to  the  optic  foramen :  not  unfrequently  it  is  given  off 


BRAXCHES    OF   THE   IXTERXAL    CAROTID.  569 

from  the  arterv  before  it  enters  the  orbit.  It  accompanies  the  lachrymal  nerve 
along  the  upper  border  of  the  External  rectus  muscle,  and  is  distributed  to  the 
lachrymal  crland.  Its  terminal  branches,  escaping  from  the  gland,  are  distributed 
to  the  evelids  and  conjunctiva,  anastomosing  with  the  palpebral  arteries.  The 
lachrymal  artery  gives  off  one  or  two  malar  branches*  one  of  which  passes  through 
a  foramen  in  the  malar  bone,  to  reach  the  temporal  fossa,  and  anastomoses  with 
the  deep  temporal  arteries  ;  the  other  appears  on  the  cheek  and  anastomoses  with 

Xasal.         Palpebral. 

Froiiial.  Supra-orbitaL 


-Internal  carotid. 
FIG.  353.— The  ophthalmic  artery  and  its  branches,  the  roof  of  the  orbit  having  been  removed. 

the  transverse  facial.  A  branch  is  also  sent  backward  through  the  sphenoidal 
fissure  to  the  dura  mater,  which  anastomoses  with  a  branch  of  the  middle  menin- 
geal  artery. 

Peculiarities.— The  lachrymal  artery  is  sometimes  derived  from  one  of  the  anterior  branches 
of  the  middle  meningeal  artery. 

The  supra-orbital  artery  arises  from  the  ophthalmic  as  that  vessel  is  crossing 
over  the  optic  nerve.  Ascending  so  as  to  arise  above  all  the  muscles  of  the  orbit, 
it  passes  forward,  with  the  supra-orbital  nerve,  between  the  periosteum  and 
Levator  palpebra :  and.  passing  through  the  supra-orbital  foramen,  divides  into  a 
superficial  and  deep  branch,  which  supply  the  integument,  the  muscles,  and  the 
pericranium  of  the  forehead,  anastomosing  with  the  frontal,  the  anterior  branch 
of  the  temporal,  and  the  artery  of  the  opposite  side.  This  artery  in  the  orbit 
supplies  the  Supei'ior  rectus  and  the  Levator  palpebrae,  and  sends  a  branch 
inward,  across  the  pulley  of  the  Superior  oblique  muscle,  to  supply  the  parts  at  the 
inner  canthus.  At  the  supra-orbital  foramen  it  frequently  transmits  a  branch  to 
the  diploe. 

The  ethmoidal  branches  are  two  in  number — posterior  and  anterior.  The 
former,  which  is  the  smaller,  passes  through  the  posterior  ethmoidal  foramen, 
supplies  the  posterior  ethmoidal  cells,  and.  entering  the  cranium,  gives  off  a 
meningeal  branch,  which  supplies  the  adjacent  dura  mater,  and  nasal  branches 
which  descend  into  the  nose  through  apertures  in  the  cribriform  plate,  anasto- 


570  THE   ARTERIES. 

mosing  with  branches  of  the  spheric-palatine.  The  anterior  ethmoidal  artery 
accompanies  the  nasal  nerve  through  the  anterior  ethmoidal  foramen,  supplies  the 
anterior  ethmoidal  cells  and  frontal  sinuses,  and,  entering  the  cranium,  gives  off 
a  meningeal  branch,  which  supplies  the  adjacent  dura  mater,  and  nasal  branches, 
which  descend  into  the  nose,  through  apertures  in  the  cribriform  plate. 

The  palpebral  arteries,  two  in  number,  superior  and  inferior,  arise  from  the 
ophthalmic,  opposite  the  pulley  of  the  Superior  oblique  muscle ;  they  leave  the 
orbit  to  encircle  the  eyelids  near  their  free  margin,  forming  a  superior  and  an 
inferior  arch,  which  lie  between  the  Orbicularis  muscle  and  tarsal  plates ;  the 
superior  palpebral  inosculating  at  the  outer  angle  of  the  orbit  with  the  orbital 
branch  of  the  temporal  artery,  and  with  a  branch  from  the  lachrymal  artery — the 
inferior  palpebral  inosculating,  at  the  outer  angle  of  the  orbit  with  a  branch 
from  the  lachrymal  and  transverse  facial  arteries,  and  at  the  inner  side  of  the 
lid  with  a  branch  from  the  angular  artery.  From  this  anastomosis  a  branch 
passes  to  the  nasal  duct,  ramifying  in  its  mucous  membrane,  as  far  as  the  inferior 
meatus. 

The  frontal  artery,  one  of  the  terminal  branches  of  the  ophthalmic,  passes  from 
the  orbit  at  its  inner  angle,  and,  ascending  on  the  forehead,  supplies  the  integument, 
muscles,  and  pericranium,  anastomosing  with  the  supraorbital  artery  and  with  the 
artery  of  the  opposite  side. 

The  nasal  artery,  the  other  terminal  branch  of  the  ophthalmic,  emerges  from 
the  orbit  above  the  tendo  oculi,  and,  after  giving  a  branch  to  the  upper  part  of 
the  lachrymal  sac,  divides  into  two  branches,  one  of  which  anastomoses  with  the 
angular  artery ;  the  other,  the  dorsalis  nasi,  runs  along  the  dorsum  of  the  nose, 
supplies  its  entire  surface,  and  anastomoses  with  the  artery  of  the  opposite  side. 

The  ciliary  arteries  are  divisible  into  three  groups,  the  short,  the  long,  and  ante- 
rior. The  short  ciliary  arteries,  from  six  to  twelve  in  number,  arise  from  the  ophthal- 
mic or  some  of  its  branches  ;  they  surround  the  optic  nerve  as  they  pass  forward 
to  the  posterior  part  of  the  eyeball,  pierce  the  sclerotic  coat  around  the  entrance  of 
the  nerve,  and  supply  the  choroid  coat  and  ciliary  processes.  The  long  ciliary 
arteries,  two  in  number,  also  pierce  the  posterior  part  of  the  sclerotic,  and  run 
forward,  along  each  side  of  the  eyeball,  between  the  sclerotic  and  choroid,  to  the 
ciliarv  muscle,  where  they  divide  into  two  branches  ;  these  form  an  arterial  circle 
around  the  circumference  of  the .  iris,  from  which  numerous  radiating  branches 
pass  forward,  in  its  substance,  to  its  free  margin,  where  they  form  a  second  arterial 
circle  around  its  pupillary  margin.  The  anterior  ciliary  arteries  are  derived  from 
the  muscular  branches ;  they  pierce  the  sclerotic  a  short  distance  from  the  cornea, 
and  terminate  in  the  great  arterial  circle  of  the  iris. 

The  arteria  centralis  retinae  is  one  of  the  smallest  branches  of  the  ophthalmic 
artery.  It  arises  from  the  ophthalmic  as  that  vessel  is  about  to  cross  over  the 
optic  nerve ;  it  pierces  the  optic  nerve  obliquely,  and  runs  forward  in  the  centre  of 
its  substance,  and  enters  the  globe  of  the  eye  through  the  porus  opticus.  Its  mode 
of  distribution  will  be  described  in  the  account  of  the  anatomy  of  the  eye. 

The  muscular  branches,  two  in  number,  superior  and  inferior,  supply  the  mus- 
cles of  the  eyeball.  The  superior,  the  smaller,  often  wanting,  supplies  the  Levator 
palpebrae,  Superior  rectus,  and  Superior  oblique.  The  inferior,  more  constant  in 
its  existence,  passes  forward  between  the  optic  nerve  and  Inferior  rectus,  and  is 
distributed  to  the  External,  Internal,  and  Inferior  recti,  and  Inferior  oblique. 
This  vessel  gives  off  most  of  the  anterior  ciliary  arteries. 

The  cerebral  branches  of  the  internal  carotid  are — the  anterior  cerebral,  the 
middle  cerebral,  the  posterior  communicating,  and  the  anterior  choroid. 

The  anterior  cerebral  arises  from  the  internal  carotid  at  the  inner  extremity  of 
the  fissure  of  Sylvius.  It  passes  forward  in  the  great  longitudinal  fissure  between 
the  two  anterior  lobes  of  the  brain,  being  connected,  soon  after  its  origin,  with  the 
vessel  of  the  opposite  side  by  a  short  anastomosing  trunk,  about  two  lines  in  length, 
the  anterior  communicating.  The  two  anterior  cerebral  arteries,  lying  side  by 
side,  curve  round  the  anterior  border  of  the  corpus  callosum,  and  run  along  its 


BRANCHES    OF   THE   IXTERXAL    CAROTID. 


571 


upper  surface  to  its  posterior  part,  where  they  terminate  by  anastomosing  with  the 
posterior  cerebral  arteries.     In  their  course  they  give  off  the  following  branches : 

Antero-median  ganglkmic.  Middle  and  Internal  Frontal. 

Anterior  and  Internal  Frontal.  Posterior  and  Internal  Frontal. 


FIG.  3M.— The  arteries  of  the  base  of  the  brain.    The  right  half  of  the  cerebellum  and  pons  have  been 
removed. 

X.B. — It  will  be  noticed  that  in  the  illustration  the  two  anterior  cerebral  arteries  have  been 
drawn  at  a  considerable  distance  from  each  other :  this  makes  the  anterior  communicating  artery 
appear  very  much  longer  than  it  really  is. 

The  antero-median  ganglionic  is  a  group  of  small  arteries  which  arise  at  the 


572 


THE  ARTERIES. 


commencement  of  the  anterior  cerebral  artery  ;  they  pierce  the  anterior  perforated 
space  and  lamina  cinerea,  and  supply  the  head  of  the  caudate  nucleus. 

The  anterior  and  internal  frontal  branches  supply  the  two  inferior  frontal 
convolutions.  The  middle  and  internal  frontal  branches  supply  the  corpus 
callosum,  the  convolution  of  the  corpus  callosum,  the  inner  surface  of  the  first 
frontal  convolution,  and  the  upper  part  of  the  ascending  frontal  convolution.  The 
posterior  and  internal  frontal  branches  supply  the  lobus  quadratus. 

The  anterior  communicating  artery  is  a  short  branch,  about  two  lines  in 
length,  but  of  moderate  size,  connecting  together  the  two  anterior  cerebral 


Fissure  of  Rolando. 

/*"•••» 


FIG.  355.— Vascular  arese  of  the  internal  surface  of  the  cerebrum.    (After  Charcot.)    The  regions  marked  off 

by  the  line  ( )  represent  the  area  of  distribution  of  the  anterior  cerebral  artery :  I.  Anterior  and  internal 

frontal  arteries.    II.  Middle  and  internal   frontal  arteries.    III.  Posterior  and  internal  frontal  arteries.    The 

regions  marked  off  by  the  line  ( )  represent  the  area  of  distribution  of  the  posterior  cerebral 

arteries  :  IV.  to  the  temporo-sphenoidal  lobe ;  V.  to  the  cuneus  and  occipital  lobe  ;  a  third  branch  supplies  the 
uncinate  gyrus. 

arteries  across  the  longitudinal  fissure.  Sometimes  this  vessel  is  wanting,  the 
two  arteries  joining  together  to  form  a  single  trunk,  which  afterward  divides.  Or 
the  vessel  may  be  wholly  or  partially  divided  into  two ;  frequently  it  is  longer 
and  smaller  than  usual.  It  gives  off  some  of  the  antero-median  ganglionic  group 
of  vessels,  which  are,  however,  principally  derived  from  the  anterior  cerebral. 

The  middle  cerebral  artery  (Fig.  356),  the  largest  branch  of  the  internal  car- 
otid, passes  obliquely  outward  along  the  fissure  of  Sylvius,  and  opposite  the  island 
of  Reil  divides  into  its  terminal  branches.  The  branches  of  the  middle  cerebral 
artery  are — 

Antero-lateral  Ganglionic. 
External  and  Inferior  Frontal. 


Ascending  Frontal. 
Ascending  Parietal. 


Parieto-sphenoidal. 

The  antero-lateral  ganglionic  branches  are  a  group  of  small  arteries  which 
arise  at  the  commencement  of  the  middle  cerebral  artery  ;  they  pierce  the  ante- 
rior perforated  space  and  supply  the  greater  part  of  the  caudate  nucleus,  the  len- 
ticular nucleus,  the  internal  capsule,  and  a  part  of  the  optic  thalamus.  One 
artery  of  this  group,  distributed  to  the  lenticular  nucleus,  is  of  larger  size  than 
the  rest,  and  is  of  special  importance,  as  being  the  artery  in  the  brain  most  fre- 
quently ruptured;  it  has  been  termed  by  Charcot  the  "artery  of  cerebral  haemor- 
rhage." The  external  and  inferior  frontal  supplies  the  third  or  inferior  frontal 
convolution  (Broca's  convolution).  The  ascending  frontal  supplies  the  ascending 
frontal  convolution.  The  ascending  parietal  supplies  the  ascending  parietal  con- 


THE   BLOOD-VESSELS    OF    THE   BRAIN. 


573 


volution.     The  parieto-sphenoidal  supplies  the  superior  temporo-sphenoidal  con- 
volution and  the  angular  gyms. 

The  posterior  communicating  artery  arises  from  the  back  part  of  the  internal 
carotid,   runs  directly  backward,  and  anastomoses  with  the  posterior  cerebral,  a 


FISSURE  OF 
ROLANDO. 


Perforating 

Branches. 

Middle  Cerebral 
Artery. 

FIG.  356.— The  distribution  of  the  middle  cerebral  artery.    (After  Charcot.) 

branch  of  the  basilar.  This  artery  varies  considerably  in  size,  being  sometimes 
small,  and  occasionally  so  large  that  the  posterior  cerebral  may  be  considered  as 
arising  from  the  internal  carotid  rather  than  from  the  basilar.  It  is  frequently 
larger  on  one  side  than  on  the  other  side.  From  the  posterior  half  of  this  vessel 
are  given  off  a  number  of  small  branches,  the  postero-median  ganglionic  branches, 
which,  with  similar  vessels  from  the  posterior  cerebral,  pierce  the  posterior  perfo- 
rated space  and  supply  the  internal  surfaces  of  the  optic  thalami  and  the  walls  of 
the  third  ventricle. 

The  anterior  choroid  is  a  small  but  constant  branch  which  arises  from  the 
back  part  of  the  internal  carotid,  near  the  posterior  communicating  artery. 
Passing  backward  and  outward,  it  enters  the  descending  horn  of  the  lateral  ven- 
tricle beneath  the  edge  of  the  middle  lobe  of  the  brain.  It  is  distributed  to  the 
hippocampus  major,  corpus  fimbriatum,  velum  interpositum,  and  choroid  plexus. 

The  Blood-vessels  of  the  Brain. 

Recent  investigations  have  tended  to  show  that  the  mode  of  distribution  of 
the  vessels  of  the  brain  has  an  important  bearing  upon  a  considerable  number  of 
the  anatomical  lesions  of  which  this  part  of  the  nervous  system  may  be  the  seat ; 
it  therefore  becomes  important  to  consider  a  little  more  in  detail  the  way  in  which 
the  cerebral  vessels  are  distributed. 

The  cerebral  arteries  are  derived  from  the  internal  carotid  and  the  vertebral, 
which  at  the  base  of  the  brain  form  a  remarkable  anastomosis  known  as  the  circle 
of  Willis.  It  is  formed  in  front  by  the  anterior  cerebral  arteries,  branches  of  the 
internal  carotid,  which  are  connected  together  by  the  anterior  communicating; 
behind  by  the  two  posterior  cerebrals,  branches  of  the  basilar  which  are  connected 
on  each  side  with  the  internal  carotid  by  the  posterior  communicating  (Fig.  354, 
p.  573).  The  parts  of  the  brain  included  within  this  arterial  circle  are  the  lamina 
cinerea,  the  commissure  of  the  optic  nerves,  the  infundibulum,  the  tuber  cinereum, 
the  corpora  albicantia,  and  the  posterior  perforated  space. 

From  the  circle  of  Willis  arise  the  three  trunks  which  together  supply  each 
cerebral  hemisphere.  From  its  anterior  part  proceed  the  two  anterior  cerebrals, 
from  its  antero-lateral  part  the  middle  cerebral,  and  from  its  posterior  part  the 


574 


THE  ARTERIES. 


posterior  cerebrals.  Each  of  these  principal  arteries  gives  origin  to  two  very 
different  systems  of  secondary  vessels.  One  of  these  systems  has  been  named  the 
central  ganglionic  system,  and  the  vessels  belonging  to  it  supply  the  central  ganglia 
of  the  brain ;  the  other  has  been  named  the  cortical  arterial  system,  and  its  vessels 
ramify  in  the  pia  mater  and  supply  the  cortex  and  subjacent  medullary  matter. 
These  two  systems,  though  they  have  a  common  origin,  do  not  communicate  at  any 
point  of  their  peripheral  distribution,  and  are  entirely  independent  of  each  other. 
Though  some  of  the  arteries  of  the  cortical  system  approach,  at  their  terminations, 
the  regions  supplied  by  the  central  ganglionic  system,  no  communication  between 
the  two  sets  of  vessels  takes  place,  and  there  is  between  the  parts  supplied  by 
the  two  systems  a  borderland  of  diminished  nutritive  activity,  where,  it  is  said, 
softening  is  especially  liable  to  occur  in  the  brains  of  old  people. 

The  Central  Ganglionic  System. — All  the  vessels  belonging  to  this  system  are 
given  off  from  the  circle  of  Willis  or  from  the  vessels  immediately  after  their  origin 


->-  Anterior  cerebral  artery, 
tid  artery. 
Middle  cerebral  artery. 


^Posterior  cerebral  artery. 


FIG.  3f>7.— Diagram  of  the  arterial  circulation  at  the  base  of  the  brain.    (After  Charcot.) 


I.  Antero-median 
IV.  Right 


group  of  ganglionic  branches.    II.  Postero-median  group.    III.  Right  and  left  antero-lateral  group, 
and  left  postero-lateral  group.    The  dotted  line  shows  the  limit  of  the  ganglionic  circle. 

from  it,  so  that  if  a  circle  is  drawn  at  a  distance  of  about  an  inch  from  the  circle 
of  Willis,  it  will  include  the  origin  of  all  the  arteries  belonging  to  this  system  (Fig. 
357).  The  vessels  of  this  system  form  six  principal  groups :  (I.)  the  antero-median 
group,  derived  from  the  anterior  cerebrals  and  anterior  communicating ;  (II.)  the 
postero-median  group,  from  the  posterior  cerebrals  and  posterior  communicating ; 
(III.)  the  right  and  left  antero-lateral  group,  from  the  middle  cerebrals :  and  (IV.) 
the  right  and  left  postero-lateral  group,  from  the  posterior  cerebrals,  after  they  have 
wound  round  the  crura  cerebri.  The  vessels  belonging  to  this  system  ate  larger 
than  those  of  the  cortical  system,  and  are  what  Cohnheim  has  termed  "  terminal  " 
arteries ;  that  is  to  say,  vessels  which  from  their  origin  to  their  termination  neither 
supply  nor  receive  any  anastomotic  branch,  so  that  by  one  of  the  small  vessels 
only  a  limited  area  of  the  central  ganglia  can  be  injected ;  and  the  injection  cannot 
be  driven  beyond  the  area  of  the  part  supplied  by  the  particular  vessel  which  is  the 
subject  of  the  experiment. 

The  Cortical  Arterial  System. — The  vessels  forming  this  system  are  the  terminal 
branches  of  the  anterior,  middle,  and  posterior  cerebral  arteries,  described  above. 


THE   ARTERIES    OF    THE    UPPER    EXTREMITY. 

These  vessels  divide  and  ramify  in  the  substance  of  the  pia  mater,  and  give  off 
nutrient  arteries  which  penetrate  the  cortex  perpendicularly.  These  nutrient  vessels 
are  divisible  into  two  classes — the  long  and  short.  The  long — or,  as  they  are  some- 
times called,  the  medullary — arteries  pass  through  the  gray  matter  to  penetrate  the 
centrum  ovale  to  the  depth  of  about  an  inch  and  a  half,  without  intercommunica- 
ting otherwise  than  by  very  fine  capillaries,  and  thus  constitute  so  many  independ- 


FIG.  358.— Distribution  of  the  cortical  arteries.  (After  Charcot.)  1.  Medullary  arteries.  1'.  Group  of  medullary 
arteries  in  the  sulcus  between  two  adjacent  convolutions.  1".  Arteries  situated  among  Gratiolet's  commis- 
sural  fibres.  2,  2.  Cortical  arteries,  a.  Capillary  network  with  fairly  wide  meshes,  situated  beneath  the  pia 
mater,  b.  Network  with  more  compact,  polygonal  meshes,  situated  in  the  cortex,  c.  Transitional  network  with 
wider  meshes,  d.  Capillary  network  in  the  white  matter. 

ent  small  systems.  The  short  vessels  are  confined  to  the  cortex,  where  they  form 
with  the  long  vessels  a  compact  network  in  the  middle  zone  of  the  gray  matter,  the 
outer  and  inner  zones  being  sparingly  supplied  with  blood  (Fig.  358).  The  vessels 
of  the  cortical  arterial  system  are  not  so  strictly  "terminal"  as  those  of  the 
central  ganglionic  system,  but  they  approach  this  type  very  closely,  so  that  injec- 
tion of  one  area  from  the  vessel  of  another  area,  though  it  may  be  possible,  is 
frequently  very  difficult,  and  is  only  effected  through  vessels  of  small  calibre.  As 
a  result  of  this,  obstruction  of  one  of  the  main  branches  or  its  divisions  may  have 
the  effect  of  producing  softening  in  a  very  limited  area  of  the  cortex.1 

ARTERIES  OF   THE  rPPER  EXTREMITY. 

The  artery  which  supplies  the  upper  extremity  continues  as  a  single  trunk 
from  its  commencement  down  to  the  elbow,  but  different  portions  of  it  have 
received  different  names  according  to  the  region  through  which  it  passes.  That 
part  of  the  vessel  which  extends  from  its  origin  to  the  lower  border  of  the  first 
rib  is  termed  the  subclavian ;  beyond  this  point  to  the  lower  border  of  the  axilla 
it  is  termed  the  axillary :  and  from  the  lower  margin  of  the  axillary  space  to  the 
bend  of  the  elbow  it  is  termed  brachial ;  here  the  single  trunk  terminates  by 
dividing  into  two  branches,  the  radial  and  ulnar — an  arrangement  precisely  similar 
to  what  occurs  in  the  lower  limb. 

1  The  student  who  desires  further  information  on  this  subject  is  referred  to  Charcot's  Localisation 
of  Cei-ebral  and  Spinal  Disease*,  p.  42  et  seq.,  whence  the  facts  above  given  have  been  principally 
derived. 


576 


THE   ARTERIES. 


THE  SUBCLAVIAN  ARTERIES  (Fig.  359). 

The  subclavian  artery  on  the  right  side  arises  from  the  innominate  artery 
opposite  the  right  sterno-clavicular  articulation ;  on  the  left  side  it  arises  from  the 
arch  of  the  aorta.  It  follows,  therefore,  that  these  two  vessels  must,  in  the  first 
part  of  their  course,  differ  in  their  length,  their  direction,  and  their  relation  with 
neighboring  parts. 

In  order  to  facilitate  the  description  of  these  vessels,  more  especially  from  a 


Phrenic  nerve. 
I  Vertebral  artery. 

I 


Inferior  thyroid  artery. 


Supra-scapular  artery 

I 

Supra-scapular  nerve. 
I 

i 


Pneumogastric 
nerve. 


^Int.  mammary  artery. 

Innominate  vein. 
nominate  artery. 


Musculo-cutaneous  j 
nerve. 


\-\Profunda  artery. 


FIG.  359.— The  subclavian  artery,  showing  its  relations.    (From  a  preparation  in  the  Museum  of  the  Royal 
College  of  Surgeons.) 

surgical  point  of  view,  each  subclavian  artery  has  been  divided  into  three  parts. 
The  first  portion,  on  the  right  side,  passes  upward  and  outward  from  the  origin 
of  the  vessel  to  the  inner  border  of  the  Scalenus  anticus.  On  the  left  side  it  ascends 
nearly  vertically,  to  gain  the  inner  border  of  that  muscle.  The  second  part  passes 
outward,  behind  the  Scalenus  anticus ;  and  the  third  part  passes  from  the  outer 
margin  of  that  muscle,  beneath  the  clavicle,  to  the  lower  border  of  the  first  rib, 
where  it  becomes  the  axillary  artery.  The  first  portion  of  these  two  vessels 
differs  so  much  in  its  course  and  in  its  relation  with  neighboring  parts  that  it 
will  be  described  separately.  The  second  and  third  parts  are  alike  on  the  two 
sides. 


THE   SCBCLAVIAX   ARTERIES.  577 

FIRST  PART  OF  THE  RICHT  SUBCLAYIAN  ARTERY  (Figs.  344,  359)x 

The  right  subclavian  artery  arises  from  the  arteria  innominata,  opposite  the 
right  stern  '-clavicular  articulation,  and  passes  upward  and  outward  to  the  inner 
margin  of  the  Scalenus  anticus  muscle.  In  this  part  of  its  course  it  ascends  & 
little  above  the  clavicle,  the  extent  to  which  it  does  so  varying  in  different  cases. 
It  is  covered,  in  front,  by  the  integument,  superficial  fascia.  Platysma,  deep  fascia, 
the  clavicular  origin  of  the  Sterno-mastoid,  the  Sterno-hyoid,  and  Sterno-thyroid 
muscles,  and  another  layer  of  the  deep  fascia.  It  is  crossed  by  the  internal  jugular 
and  vertebral  veins  and  by  the  pneumogastric.  the  cardiac  branches  of  the 
sympathetic,  and  the  phrenic  nerve.  Beneath,  the  artery  is  invested  by  the 
pleura,  and  behind,  it  is  separated  by  a  cellular  interval  from  the  Longus  colli, 
the  neck  of  the  first  rib,  and  the  cord  of  the  sympathetic  nerve;  the  recurrent 
laryngeal  nerve  winds  round  the  lower  and  back  part  of  the  vessel.  The  subclavian 
vein  lies  below  the  subclavian  artery,  immediately  behind  the  clavicle. 

PLAN  OF  RELATIONS  OF  FIRST  PORTION  OF  THE  RIGHT  SUBCLAVIAN  ARTERY. 

In  front. 

Skin,  superficial  fascia. 

Platysma.  deep  fascia. 

Clavicular  origin  of  Sterno-mastoid. 

Sterno-hyoid  and  Sterno-thyroid. 

Internal  jugular  and  vertebral  veins. 

Pneumogastric,  cardiac,  and  phrenic  nerves. 

Beneath. 
Pleura, 


Behind. 

Recurrent  laryngeal  nerve. 
Sympathetic. 
Longus  colli. 
Neck  of  first  rib. 

FIRST  PART  OF  THE  LEFT  SUBCLAVIAN  ARTERY  (Fig.  344). 

The  left  subclavian  artery  arises  from  the  end  of  the  arch  of  the  aorta, 
opposite  the  fourth  dorsal  vertebra,  and  ascends  nearly  vertically  to  the  inner 
margin  of  the  Scalenus  anticus  muscle.  This  part  of  the  vessel  is.  therefore, 
longer  than  the  right,  situated  more  deeply  in  the  cavity  of  the  chest,  and  directed 
nearly  vertically  upward,  instead  of  arching  outward  like  the  vessel  of  the 
opposite  side. 

It  is  in  relation,  in  front,  with  the  pleura,  the  left  lung,  the  pneumogastric. 
cardiac,  and  phrenic  nerves,  which  lie  parallel  with  it :  the  left  carotid  artery,  left 
internal  jugular  and  vertebral  veins,  and  the  commencement  of  the  left  innominate 
vein  :  and  is  covered  by  the  Sterno-thyroid,  Sterno-hyoid.  and  Sterno-mastoid 
muscles :  it  has  the  left  carotid  in  front  of,  but  not  in  contact  with,  it ;  behind,  it 
is  in  relation  with  the  oesophagus,  thoracic  duct,  inferior  cervical  ganglion  of  the 
sympathetic.  Longus  colli,  and  vertebral  column.  To  its  inner  side  are  the 
oesophagus,  trachea,  and  thoracic  duct;  to  its  outer  side,  the  pleura. 

PLAN  OF  RELATIONS  OF  FIRST  PORTION  OF  LEFT  SUBCLAVIAN  ARTERY. 

In  front. 

Pleura  and  left  lung. 

Pneumogastric.  cardiac,  and  phrenic  nerves. 
Left  carotid  artery. 

Left  internal  jugular,  vertebral,  and  innominate  veins. 
Sterno-thyroid,  Sterno-hyoid,  and  Sterno-mastoid  muscles. 


578 


THE   ARTERIES. 


Inner  side. 

Trachea. 
(Esophagus. 
Thoracic  duct. 


Outer  side. 
Pleura. 


Behind. 

(Esophagus  and  thoracic  duct. 
Inferior  cervical  ganglion  of  sympathetic. 
Longus  colli  and  vertebral  column. 

SECOND  AND  THIRD  PARTS  OF  THE  SUBCLAVIAN  ARTERY  (Fig.  347). 

The  Second  Portion  of  the  Subclavian  Artery  lies  behind  the  Scalenus  anticus 
muscle ;  it  is  very  short,  and  forms  the  highest  part  of  the  arch  described  by  that 
vessel. 

Kelatious. — It  is  covered,  in  front,  by  the  skin,  superficial  fascia,  Platysma, 
deep  cervical  fascia,  Sterno-mastoid,  and  by  the  phrenic  nerve,  which  is  separated 
from  the  artery  by  the  ScaTenus  anticus  muscle.  BeJtind,  it  is  in  relation  with 
the  pleura  and  the  middle  Scalenus ;  above,  with  the  brachial  plexus  of  nerves ; 
below,  with  the  pleura.  The  subclavian  vein  lies  below  and  in  front  of  the  artery, 
separated  from  it  by  the  Scalenus  anticus. 

PLAN  or  RELATIONS  OF  SECOND  PORTION  OF  SUBCLAVIAN  ARTERY. 

In  front. 

Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 
Sterno-mastoid. 
Phrenic  nerve. 
Scalenus  anticus. 
Subclavian  vein. 


Above. 
Brachial  plexus. 


Below. 
Pleura. 


Behind. 

Pleura  and  Middle  Scalenus. 

The  Third  Portion  of  the  Subclavian  Artery  passes  downward  and  outward 
from  the  outer  margin  of  the  Scalenus  anticus  to  the  lower  border  of  the  first  rib, 
where  it  becomes  the  axillary  artery.  This  portion  of  the  vessel  is  the  most 
superficial,  and  is  contained  in  a  triangular  space,  the  base  of  which  is  formed  in 
front  by  the  Sterno-mastoid,  and  the  two  sides  by  the  Omo-hyoid  above  and  the 
clavicle  below. 

PLAN  OF  RELATIONS  OF  THIRD  PORTION  OF  SUBCLAVIAN  ARTERY. 

In  front. 

Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 

Descending  branches  of  cervical  plexus.     Nerve  to  Subclavius  muscle. 
Subclavius  muscle,  suprascapular  artery,  and  vein. 
The  external  jugular  and  transverse  cervical  veins. 
The  clavicle. 


Above. 

Brachial  plexus. 
Omo-hyoid. 


Below. 
First  rib. 


Behind. 
Scalenus  medius. 


THE   SUBCLAVIAN  ARTERIES.  579 

Relations. — It  is  covered,  in  front,  by  the  skin,  the  superficial  fascia,  the 
Platysma,  deep  cervical  fascia ;  by  the  clavicle,  the  Subclavius  muscle  and  the 
suprascapular  artery  and  vein,  and  the  transverse  cervical  vein  ;  the  clavicular 
descending  branches  of  the  cervical  plexus  and  the  nerve  to  the  Subclavius  muscle 
pass  vertically  downward  in  front  of  the  artery.  The  external  jugular  vein  crosses 
it  at  its  inner  side,  and  receives  the  suprascapular  and  transverse  cervical  veins, 
which  occasionally  form  a  plexus  in  front  of  it.  The  subclavian  vein  is  below  the 
artery,  lying  close  behind  the  clavicle.  Behind,  it  lies  on  the  middle  Scalenus 
muscle;  above  it,  and  to  its  outer  side,  is  the  brachial  plexus  and  Omo-hyoid mus- 
cle ;  below,  it  rests  on  the  upper  surface  of  the  first  rib. 

Peculiarities. — The  subclavian  arteries  vary  in  their  origin,  their  course,  and  the  height  to 
which  they  rise  in  the  neck. 

The  origin  of  the  right  subclavian  from  the  innominate  takes  place,  in  some  cases,  above  the 
sterno-clavicular  articulation,  and  occasionally,  but  less  frequently,  in  the  cavity  of  the  thorax, 
below  that  joint.  Or  the  artery  may  arise  as  a  separate  trunk  from  the  arch  of  the  aorta.  In 
such  cases  it  may  be  either  the  first,  second,  third,  or  even  the  last  branch  derived  from  that  ves- 
sel ;  in  the  majority  of  cases  it  is  the  first  or  last,  rarely  the  second  or  third.  When  it  is  the  first 
branch,  it  occupies  the  ordinary  position  of  the  innominate  artery ;  when  the  second  or  third,  it 
gains  its  usual  position  by  passing  behind  the  right  carotid  ;  and  when  the  last  branch,  it  arises 
from  the  left  extremity  of  the  arch,  at  its  upper  or  back  part,  and  passes  obliquely  toward  the 
right  side,  usually  behind  the  oesophagus  and  right  carotid,  sometimes  between  the  oesophagus 
and  trachea  to  the  upper  border  of  the  first  rib,  whence  it  follows  its  ordinary  course.  In  very 
rare  instances  this  vessel  arises  from  the  thoracic  aorta,  as  low  down  as  the  fourth  dorsal  verte- 
bra. Occasionally  it  perforates  the  anterior  Scalenus ;  more  rarely  it  passes  in  front  of  that 
muscle.  Sometimes  the  subclavian  vein  passes  with  the  artery  behind  the  Scalenus.  The 
artery  sometimes  ascends  as  high  as  an  inch  and  a  half  above  the  clavicle  or  an}'  intermediate 
point  between  this  and  the  upper  border  of  the  bone,  the  right  subclavian  usually  ascending 
higher  than  the  left. 

The  left  subclavian  is  occasionally  joined  at  its  origin  with  the  left  carotid. 

Surface  Marking. — The  course  of  the  subclavian  artery  in  the  neck  may  be  mapped  out 
by  describing  a  curve,  with  its  convexity  upward  at  the  base  of  the  posterior  triangle.  The  inner 
end  of  this  curve  corresponds  to  the  sterno-clavicular  joint,  the  outer  end  to  the  centre  of  the 
lower  border  of  the  clavicle.  The  curve  is  to  be  drawn  with  such  an  amount  of  convexity  that 
its  mid-point  reaches  half  an  inch  above  the  upper  border  of  the  clavicle.  The  left  subclavian 
artery  is  more  deeply  placed  than  the  right  in  the  first  part  of  its  course,  and,  as  a  rule,  does  not 
reach  quite  as  high  a  level  in  the  neck.  It  should  be  borne  in  mind  that  the  posterior  border  of 
the  Sterno-mastoid  muscle  corresponds  to  the  outer  border  of  the  Scalenus  anticus,  so  that  the 
third  portion  of  the  artery,  that  part  most  accessible  for  operation,  lies  immediately  external  to 
the  posterior  border  of  the  Sterno-mastoid. 

Surgical  Anatomy. — The  relations  of  the  subclavian  arteries  of  the  two  sides  having  been 
examined,  the  student  should  direct  his  attention  to  a  consideration  of  the  best  position  in  which 
compression  of  the  vessel  may  be  effected,  or  in  what  situation  a  ligature  may  be  best  applied  in 
cases  of  aneurism  or  wound. 

Compression  of  the  subclavian  artery  is  required  in  cases  of  operations  about  the  shoul- 
der, in  the  axilla,  or  at  the  upper  part  of  the  arm ;  and  the  student  will  observe  that  there  is 
only  one  situation  in  which  it  can  be  effectually  applied — viz.  where  the  artery  passes  across  the 
outer  surface  of  the  first  rib.  In  order  to  compress  the  vessel  in  this  situation,  the  shoulder 
should  be  depressed,  and  the  surgeon,  grasping  the  side  of  the  neck,  should  press  with  his 
thumb  in  the  angle  formed  by  the  posterior  border  of  the  Sterno-mastoid  with  the  upper  border 
of  the  clavicle,  downward,  backward,  and  inward  against  the  rib  ;  if  from  any  cause  the  shoulder 
cannot  be  sufficiently  depressed,  pressure  may  be  made  from  before  backward,  so  as  to  compress 
the  artery  against  the  middle  Scalenus  and  transverse  process  of  the  seventh  cervical  vertebra. 
In  appropriate  cases,  a  preliminary  incision  may  be  made  through  the  cervical  fascia,  and  the 
finger  may  be  pressed  down  directly  upon  the  artery. 

Ligature  of  the  subclavian  artery  may  be  required  in  cases  of  wounds  or  of  aneurism  in 
the  axilla,  or  in  cases  of  aneurism  on  the  cardiac  side  of  the  point  of  ligature  ;  and  the  third  part 
of  the  artery  is  that  which  is  most  favorable  for  an  operation,  on  account  of  its  being  compara- 
tively superficial  and  most  remote  from  the  origin  of  the  large  branches.  In  those  cases  where 
the  clavicle  is  not  displaced,  this  operation  may  be  performed  with  comparative  facility ;  but 
where  the  clavicle  is  pushed  up  by  a  large  aneurismal  tumor  in  the  axilla  the  artery  is  placed  at 
a^great  depth  from  the  surface,  which  materially  increases  the  difficulty  of  the  operation. 
Under  these  circumstances  it  becomes  a  matter  of  importance  to  consider  the  height  to  which 
this  vessel  reaches  above  the  bone.  In  ordinary  cases  its  arch  is  about  half  an  inch  above  the 
clavicle,  occasionally  as  high  as  an  inch  and  a  half  and  sometimes  so  low  as  to  be  on  a  level  with 
its  upper  border.  If  the  clavicle  is  displaced,  these  variations  will  necessarily  make  the  opera- 
tion more  or  less  difficult  according  as  the  vessel  is  more  or  less  accessible. 

The  chief  points  in  the  operation  of  tyinir  the  third  portion  of  the  subclavian  artery  are  as 
follows :  The  patient  being  placed  on  a  table  in  the  horizontal  position,  with  the  head  drawn 


580  THE   ARTERIES. 

over  to  the  opposite  side  and  the  shoulder  depressed  as  much  as  possible,  the  integument  should 
be  drawn  downward  upon  the  clavicle,  and  an  incision  made  through  it,  upon  that  bone,  from 
the  anterior  border  of  the  Trapezius  to  the  posterior  border  of  the  Sterno-mastoid,  to  which  may 
be  added  a  short  vertical  incision  meeting  the  preceding  in  its  centre.  The  object  in  drawing 
the  skin  downward  is  to  avoid  any  risk  of  wounding  the  external  jugular  vein,  for  as  it  perforates 
the  deep  fascia  above  the  clavicle,  it  cannot  be  drawn  downward  with  the  skin.  The  cervical 
fascia  should  be  divided  upon  a  director,  and  if  the  interval  between  the  Trapezius  and  Sterno- 
mastoid  muscles  be  insufficient  for  the  performance  of  the  operation,  a  portion  of  one  or  both 
may  be  divided.  The  external  jugular  vein  will  now  be  seen  toward  the  inner  side  of  the  wound  : 
this  and  the  suprascapular  and  transverse  cervical  veins,  which  terminate  in  it,  should  be  held 
aside.  If  the  external  jugular  vein  is  at  all  in  the  way  and  exposed  to  injury,  it  should  be  tied 
in  two  places  and  divided.  The  suprascapular  artery  should  be  avoided,  and  the  Omo-hyoid 
muscle  held  aside  if  necessary.  In  the  space  beneath  this  muscle  careful  search  must  be  made 
for  the  vessel :  a  deep  la.yer  of  fascia  and  some  connective  tissue  having  been  divided  carefully, 
the  outer  margin  of  the  Scalenus  anticus  muscle  must  be  felt  for,  and,  the  finger  being  guided  by 
it  to  the  first  rib,  the  pulsation  of  the  subclavian  artery  will  be  felt  as  it  passes  over  the  rib. 
The  aneurism  needle  may  then  be  passed  around  the  vessel  from  above  downward  and  inward,  so  as 
to  avoid  including  any  of  the  branches  of  the  brachial  plexus.  If  the  clavicle  is  so  raised  by  the 
tumor  that  the  application  of  the  ligature  cannot  be  effected  in  this  situation,  the  artery  may  be 
tied  above  the  first  rib,  or  even  behind  the  Scalenus  anticus  muscle  ;  the  difficulties  of  the  ope- 
ration in  such  a  case  will  be  materially  increased,  on  account  of  the  greater  depth  of  the  artery 
and  the  alteration  in  position  of  the  surrounding  parts. 

The  second  part  of  the  subclavian  artery,  from  being  that  portion  which  rises  highest  in 
the  neck,  has  been  considered  favorable  for  the  application  of  the  ligature  when  it  is  difficult  to 
tie  the  artery  in  the  third  part  of  its  course.  There  are,  however,  many  objections  to  the  ope- 
ration in  this  situation.  It  is  necessary  to  divide  the  Scalenus  anticus  muscle,  upon  which  lies 
the  phrenic  nerve,  and  at  the  inner  side  of  which  is  situated  the  internal  jugular  vein  ;  and  a 
wound  of  either  of  these  structures  might  lead  to  the  most  dangerous  consequences.  Again, 
the  artery  is  in  contact,  below,  with  the  pleura,  which  must  also  be  avoided ;  and,  lastly,  the 
proximity  of  so  many  of  its  large  branches  arising  internal  to  this  point  must  be  a  still  further 
objection  to  the  operation.  In  cases,  however,  where  the  sac  of  an  axillary  aneurism  encroaches 
on  the  neck,  it  may  be  necessary  to  divide  the  outer  half  or  two-thirds  of  the  Scalenus  anticus 
muscle,  so  as  to  place  the  ligature  on  the  vessel  at  a  greater  distance  from  the  sac.  The  opera- 
tion is  performed  exactly  in  the  same  way  as  ligature  of  the  third  portion,  until  the  Scalenus 
anticus  is  exposed,  when  it  is  to  be  divided  on  a  director  (never  to  a  greater  extent  than  its  outer 
two-thirds),  and  it  immediately  retracts.  The  operation  is  therefore  merely  an  extension  of  liga- 
ture of  the  third  portion  of  the  vessel. 

In  those  cases  of  aneurism  of  the  axillary  or  subclavian  artery  which  encroach  upon  the 
outer  portion  of  the  Scalenus  muscle  to  such  an  extent  that  a  ligature  cannot  be  applied  in  that 
situation,  it  may  be  deemed  advisable,  as  a  last  resource,  to  tie  the  first  portion  of  the  subcla- 
vian artery.  On  the  left  side  this  operation  is  almost  impracticable ;  the  great  depth  of  the 
artery  from  the  surface,  its  intimate  relation  with  the  pleura,  and  its  close  proximity  to  the 
thoracic  duct  and  to  so  many  important  veins  and  nerves,  present  a  series  of  difficulties  which  it 
is  next  to  impossible  to  overcome.1  On  the  right  side  the  operation  is  practicable,  and  has  been 
performed,  though  never  with  success.  The  main  objection  to  the  operation  in  this  situation  is 
the  smallness  of  the  interval  which  usually  exists  between  the  commencement  of  the  vessel  and 
the  origin  of  the  nearest  branch.  The  operation  may  be  performed  in  the  following  manner  : 
The  patient  being  placed  on  the  table  in  the  horizontal  position  with  the  neck  extended,  an  incis- 
ion should  be  made  along  the  upper  border  of  the  inner  part  of  the  clavicle,  and  a  second 
along  the  inner  border  of  the  Sterno-mastoid,  meeting  the  former  at  an  angle.  The  sternal 
attachment  of  the  Sterno-mastoid  may  now  be  divided  on  a  director  and  turned  outward ;  a  few 
small  arteries  and  veins,  and  occasionally  the  anterior  jugular,  must  be  avoided,  or,  if  necessary, 
ligatured  in  two  places  and  divided,  and  the  Sterno-hyoid  and  Sterno-thyroid  muscles  divided  in 
the  same  manner  as  the  preceding  muscle.  After  tearing  through  the  deep  fascia  with  the  finger- 
nail, the  internal  jugular  vein  will  be  seen  crossing  the  subclavian  artery ;  this  should  be  pressed 
aside  and  the  artery  secured  by  passing  the  needle  from  below  upward,  by  which  the  pleura  is 
more  effectually  avoided.  The  exact  position  of  the  vagus  nerve,  the  recurrent  laryngeal,  the 
phrenic  and  sympathetic  nerves  should  be  remembered,  and  the  ligature  should  be  applied  near 
the  origin  of  the  vertebral,  in  order  to  afford  as  much  room  as  possible  for  the  formation  of  a 
cpagulum  between  the  ligature  and  the  origin  of  the  vessel.  It  should  be  remembered  that  the 
right  subclavian  artery  is  occasionally  deeply  placed  in  the  first  part  of  its  course  when  it  arises 
from  the  left  side  of  the  aortic  arch,  and  passes  in  such  cases  behind  the  oesophagus  or  between 
it  and  the  trachea. 

Collateral  Circulation. — After  ligature  of  the  third  part  of  the  subclavian  artery  the  col- 
lateral circulation  is  mainly  established  by  three  sets  of  vessels,  thus  described  in  a  dissection  : 

''  ].  A  posterior  set,  consisting  of  the  suprascapular  and  posterior  scapular  branches  of  the 
subclavian,  anastomosing  with  the  median  branch  from  the  subscapular  from  the  axillary. 

''  "2.  An  internal  set  produced  by  the  connection  of  the  internal  mammary  on  the  one  hand, 

1  The  operation  was,  however,  performed  in  New  York  by  Dr.  J.  K.  Rodgers,  and  the  case  is 
related  in  A  System  of  Surgery,  edited  by  T.  Holmes,  2d  ed.  vol.  iii.  pp.  620,  etc. 


BRANCHES    OF    THE   SUBCLAVIAN  ARTERY. 


581 


with  the  superior  and  long  thoracic  arteries,  and  the  branches  from  the  subscapular  on  the 
other. 

A  middle  or  axillary  set.  which  consisted  of  a  number  of  small  vessels  derived  from 
branches  of  the  subclavian.  above,  and.  passing  through  the  axilla,  terminated  either  in  the 
main  trunk  or  some  of  the  branches  of  the  axillary  below.  This  last  set  presented  most  con- 
spicuously the  peculiar  character  of  newly-formed  or,  rather,  dilated  arteries,  being  excessively 
tortuous,  and  funning  a  complete  plexus. 

••  The  chief  agent  in  the  restoration  of  the  axillary  artery  below  the  tumor  was  the  sub- 
scapular  artery,  which  communicated  most  freely  with  the  internal  mammary,  suprascapular, 
and  posterior  scapular  branches  of  the  subclavian,  from  all  of  which  it  received  so  great  an 
influx  of  blood  as  to  dilate  it  to  three  times  its  natural  size.'  l 

When  a  ligature  is  applied  to  the  first  part  of  the  subclavian  artery,  the  collateral  circula- 
tion is  carried  on  by — 1.  the  anastomosis  between  the  superior  and  inferior  thyroid ;  2.  the  anas- 
Kimosis  of  the  two  vertebrals ;  3.  the  anastomosis  of  the  internal  mammary  with  the  deep 
epitrastrie  and  the  aortic  intercostals :  4.  the  superior  intercostal  anastomosing  with  the  aortic 
intercostals :  5.  the  profunda  cervicis  anastomosing  with  the  princeps  cervicis ;  6,  the  scapular 
branches  of  the  thyroid  axis  anastomosing  with  the  branches  of  the  axillary ;  and  7,  the  thoracic 
branches  of  the  axillary  anastomosing  with  the  aortic  intercostals. 

BRANCHES  OF  THE  SUBCLAYIAX  ARTERY. 

These  are  four  in  number.  On  the  left  side  all  four  branches,  the  vertebral, 
the  int>-rn>tl.  mammary,  the  thyroid  axis,  and  the  superior  intercostal,  generally 
arise  from  the  first  portion  of  the  vessel ;  but  on  the  right  side  the  superior  inter- 
costal usually  arises  from  the  second  portion  of  the  vessel.  On  both  sides  of  the 
body  the  first  three  branches  arise  close  together  at  the  inner  margin  of  the  ^ca- 
lenus  anticus.  in  the  majority  of  cases  a  free  interval  of  half  an  inch  to  an  inch 
existing  between  the  commencement  of  the 
artery  and  the  origin  of  the  nearest  branch  ; 
in  a  smaller  number  of  cases  an  interval 
of  more  than  an  inch  exists,  never  exceed- 
ing an  inch  and  three-quarters.  In  a  very 
few  instances  the  interval  had  been  found 
to  be  less  than  half  an  inch. 

The  Vertebral  Artery  (Fig.  352)  is  gen- 
erally the  first  and  largest  branch  of  the 
subclavian :  it  arises  from  the  upper  and 
back  part  of  the  first  portion  of  the  vessel, 
and.  passing  upward,  enters  the  foramen 
in  the  transverse  process  of  the  sixth  cerv- 
ical vertebra.2  and  ascends  through  the  for- 
amina in  the  transverse  processes  of  all  the 
vertebrae  above  this.  Above  the  upper  bor- 
der of  the  axis  it  inclines  outward  and  upward  to  the  foramen  in  the  transverse 
process  of  the  atlas,  through  which  it  passes  ;  it  then  winds  backward  behind  its 
articular  process,  runs  in  a  deep  groove  on  the  upper  surface  of  the  posterior 
arch  of  this  bone.  and.  passing  beneath  the  posterior  occipito-atlantal  ligament, 
pierces  the  dura  mater  and  enters  the  skull  through  the  foramen  magnum.  It 
then  passes  forward  and  upward  to  the  front  of  the  medulla  oblongata,  and  unites 
with  the  vessel  of  the  opposite  side  at  the  lower  border  of  the  pons  Varolii  to 
form  the  baxilar  '//•/•/•//. 

Relations. — At  its  origin  it  is  situated  behind  the  internal  jugular  vein  and 
inferior  thyroid  artery  :  and  near  the  spine  it  lies  between  the  Longus  colli  and 
Scalenus  anticus  muscles,  having  the  thoracic  duct  in  front  of  it  on  the  left  side. 
Within  the  foramina  formed  by  the  transverse  processes  of  the  vertebrae  it  is 
accompanied  by  a  plexus  of  nerves  from  the  inferior  cervical  ganglion  of  the 
sympathetic,  and  is  surrounded  by  a  dense  plexus  of  veins  which  unite  to  form  the 

1  Guy's  Hospital  Reports,  vol.  i.  1836:  case  of  axillary  aneurism,  in  which  Mr.  Aston  Key  had 
tied  the  subclavian  artery  on  the  outer  edge  of  the  Scalenus  muscle  twelve  years  previously. 

2  The  vertebral  artery  sometimes  enters  the  foramen  in  the  transverse  process  of  the  fifth  ver- 
tebra.    Dr.  Smyth,  who  tied  this  artery  in  the  living  subject,  found  it,  in  one  of  his  dissections,  pass- 
ing into  the  foramen  in  the  seventh  vertebra. 


FIG.  360.— Plan  of  the  branches  of  the  right 
subclavian  artery. 


582  THE  ARTERIES. 

vertebral  vein  at  the  lower  part  of  the  neck.  It  is  situated  in  front  of  the  cervical 
nerves  as  they  issue  from  the  intervertebral  foramina.  Whilst  winding  round  the 
articular  process  of  the  atlas  it  is  contained  in  a  triangular  space  (suboccipital 
triangle)  formed  by  the  Rectus  capitis  posticus  major,  the  Superior  and  the  Inferior 
oblique  muscles ;  and  at  this  point  is  covered  by  the  Complexus  muscle.  Within 
the  skull,  as  it  winds  round  the  medulla  oblongata,  it  is  placed  between  the  hypo- 
glossal  nerve  and  the  anterior  root  of  the  suboccipital  nerve,  beneath  the  first 
digitation  of  the  ligamentum  denticulatum,  and  finally  lies  between  the  dura  mater 
covering  the  basilar  process  of  the  occipital  bone  and  the  anterior  surface  of  the 
medulla  oblongata. 

Branches. — These  may  be  divided  into  two  sets — those  given  off  in  the  neck 
and  those  within  the  cranium. 

Cervical  Branches.  Cranial  Branches. 

Lateral  Spinal.  Posterior  Meningeal. 

Muscular.  Anterior  Spinal. 

Posterior  Spinal. 

Posterior  Inferior  Cerebellar. 

The  lateral  spinal  branches  enter  the  spinal  canal  through  the  intervertebral 
foramina  and  divide  into  two  branches.  Of  these,  one  passes  along  the  roots  of 
the  nerves  to  supply  the  spinal  cord  and  its  membranes,  anastomosing  with  the 
other  arteries  of  the  spinal  cord ;  the  other  divides  into  an  ascending  and  a 
descending  branch,  which  unite  with  similar  branches  from  the  artery  above  and 
below,  so  that  two  lateral  anastomotic  chains  are  formed  on  the  posterior  surface 
of  the  bodies  of  the  vertebrae  near  the  attachment  of  the  pedicles.  From  these 
anastomotic  chains  branches  are  given  off  to  supply  the  periosteum  and  the  bodies 
of  the  vertebrae,  and  to  communicate  with  similar  branches  from  the  opposite  side  ; 
from  these  latter  small  branches  are  given  off  which  join  similar  branches  above 
and  below,  so  that  a  central  anastomotic  chain  is  formed  on  the  posterior  surface 
of  the  bodies  of  the  vertebrae. 

Muscular  branches  are  given  off  to  the  deep  muscles  of  the  neck,  where  the 
vertebral  artery  curves  round  the  articular  process  of  the  atlas.  They  anastomose 
with  the  occipital  and  with  the  ascending  and  deep  cervical  arteries. 

The  posterior  meningeal  are  one  or  two  small  branches  given  off  from  the 
vertebral  opposite  the  foramen  magnum.  They  ramify  between  the  bone  and  dura 
mater  in  the  cerebellar  fossae,  and  supply  the  falx  cerebelli. 

The  anterior  spinal  is  a  small  branch,  though  larger  than  the  posterior  spinal, 
which  arises  near  the  termination  of  the  vertebral,  and,  descending  in  front  of  the 
medulla  oblongata,  unites  Avith  its  fellow  of  the  opposite  side  at  about  the  level  of 
the  foramen  magnum.  The  single  trunk,  thus  formed,  descends  on  the  front 
of  the  spinal  cord,  and  is  reinforced  by  a  succession  of  small  branches  which 
enter  the  spinal  canal  through  the  intervertebral  foramina ;  these  branches  are 
derived  from  the  vertebral  and  ascending  cervical  of  the  inferior  thyroid  in  the 
neck ;  from  the  intercostal  in  the  dorsal  region ;  and  from  the  lumbar,  ilio- 
lumbar,  and  lateral  sacral  arteries  in  the  lower  part  of  the  spine.  They  unite,  by 
means  of  ascending  and  descending  branches,  to  form  a  single  anterior  median 
artery,  Avhich  extends  as  far  as  the  lower  part  of  the  spinal  cord.  This  vessel  is 
placed  in  the  pia  mater  along  the  anterior  median  fissure :  it  supplies  that  mem- 
brane and  the  substance  of  the  cord,  and  sends  off  branches  at  its  lower  part  to 
be  distributed  to  the  cauda  equina,  and  ends  on  the  central  fibrous  prolongation 
of  the  cord. 

The  posterior  spinal  arises  from  the  vertebral  at  the  side  of  the  medulla 
oblongata :  passing  backward  to  the  posterior  aspect  of  the  spinal  cord,  it  descends 
on  each  side,  lying  behind  the  posterior  roots  of  the  spinal  nerves,  and  is 
reinforced  by  a  succession  of  small  branches  which  enter  the  spinal  canal  through 
the  intervertebral  foramina,  and  by  which  it  is  continued  to  the  lower  part  of  the 


BBAXCHES    OF    THE   SUBCLAVIAX  ARTERY.  583 

cord  and  to  the  eauda  equina.  Branches  from  these  vessels  form  a  free  anasto- 
mosis round  the  posterior  roots  of  the  spinal  nerves,  and  communicate,  by  means 
of  very  tortuous  transverse  branches,  with  the  vessel  of  the  opposite  side.  At  its 
commencement  it  gives  off  an  ascending  branch,  which  terminates  on  the  side  of 
the  fourth  ventricle. 

The  posterior  inferior  cerebellar  artery  (Fig.  354).  the  largest  branch  of  the 
vertebral,  winds  backward  round  the  upper  part  of  the  medulla  oblongata,  passing 
between  the  origin  of  the  pneurnogastric  and  spinal  accessory  nerves,  over  the 
restiform  body  to  the  under  surface  of  the  cerebellum,  where  it  divides  into  two 
branches — an  internal  one.  which  is  continued  backward  to  the  notch  between 
the  two  hemispheres  of  the  cerebellum ;  and  an  external  one.  which  supplies  the 
under  surface  of  the  cerebellum  as  far  as  its  outer  border,  where  it  anastomoses 
with  the  anterior  inferior  cerebellar  and  the  superior  cerebellar  branches  of  the 
basilar  artery.  Branches  from  this  artery  supply  the  choroid  plexus  of  the  fourth 
ventricle. 

Surgical  Anatomy. — The  vertebral  artery  has  been  tied  in  several  instances:  1.  tor 
wounds  or  traumatic  aneurism  :  '2.  after  ligature  of  the  innominate,  either  at  the  same  time  to 
prevent  haemorrhage,  or  later  on  to  arrest  bleeding  where  it  has  occurred  at  the  seat  of  ligature ; 
and  3.  in  epilepsy.  In  these  latter  cases  the  treatment  has  been  recommended  by  Dr. 
Alexander  of  Liverpool,  in  the  hope  that  by  diminishing  the  supply  of  blood  to  the  posterior 
part  of  the  brain  and  the  spinal  cord  a  diminution  or  cessation  of  the  epileptic  fits  would  result 
The  operation  of  ligature  of  the  vertebral  is  performed  by  making  an  incision  along  the  posterior 
border  of  the  Sterno-mastoid  muscle,  just  above  the  clavicle.  The  muscle  is  pulled  to  the 
inner  side,  and  the  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra 
sought  for.  A  deep  layer  of  fascia  bejng  now  divided,  the  interval  between  the  Scalenus  anticus 
and  the  Longus  colli  just  below  their  insertion  into  the  tubercle  is  defined,  and  the  artery  and 
vein  found  in  the  interspace.  The  vein  is  to  be  drawn  to  the  outer  side,  and  the  aneurism 
needle  passed  from  without  inward.  Drs.  Raniskill  and  Bright  have  pointed  out  that  severe 
pain  at  the  back  of  the  head  may  be  symptomatic  of  disease  of  the  vertebral  artery  just 
before  it  enters  the  skull.  This  is  explained  by  the  close  connection  of  the  artery  with  the  sub- 
occipital  nerve  in  the  groove  on  the  posterior  arch  of  the  atlas.  Disease  of  the  same  artery  has 
been  also  said  to  affect  speech,  from  pressure  on  the  hypoglossal  where  it  is  in  relation  with 
the  vessel,  leading  to  paralysis  of  the  muscles  of  the  tongue. 

The  Basilar  Artery,  so  named  from  its  position  at  the  base  of  the  skull,  is 
a  single  trunk  formed  by  the  junction  of  the  two  vertebral  arteries ;  it  extends 
from  the  posterior  to  the  anterior  border  of  the  pons  Varolii,  lying  in  its 
median  groove,  under  cover  of  the  arachnoid.  It  ends  by  dividing  into  two 
branches,  the  posterior  cerebral  arteries.  Its  branches  are,  on  each  side,  the 
following : 

Transverse.  Superior  Cerebellar. 

Anterior  Inferior  Cerebellar.  Posterior  Cerebral. 

The  transverse  branches  supply  the  pons  Varolii  and  adjacent  parts  of  the 
brain,  one  branch,  the  internal  auditory,  accompanies  the  auditory  nerve  into 
the  internal  auditory  ineatus :  and  another,  the  anterior  inferior  cerebellar  artery, 
passes  across  the  crus  cerebelli,  to  be  distributed  to  the  anterior  border  of  the 
under  surface  of  the  cerebellum. 

The  superior  cerebellar  arteries  arise  near  the  termination  of  the  basilar. 
They  wind  round  the  crus  cerebri  close  to  the  fourth  nerve,  and,  arriving  at  the 
upper  surface  of  the  cerebellum,  divide  into  branches  which  ramify  in  the  pia 
mater  and  anastomose  with  the  branches  of  the  inferior  cerebellar  artery.  Sev- 
eral branches  are  given  to  the  pineal  gland  and  also  to  the  velum  interpositum. 

The  posterior  cerebral  arteries,  the  two  terminal  branches  of  the  basilar,  are 
larger  than  the  preceding,  from  which  they  are  separated  near  their  origin  by  the 
third  nerves.  Winding  round  the  cms  cerebri,  they  pass  to  the  under  surface  of 
the  occipital  lobes  of  the  cerebrum  and  divide  into  three  main  branches.  Xear 
their  origin  they  receive  the  posterior  communicating  arteries  from  the  internal 
carotid.  The  branches  of  the  posterior  cerebral  artery  are — 

Postero-median  Ganglionic.  Postero-lateral  Ganglionic. 

Posterior  Choroid.  Three  Terminal. 


584  THE   ARTERIES. 

The  postero-medidn  ganglionic  branches  (Fig.  357)  are  a  group  of  small  arteries 
which  arise  at  the  commencement  of  the  posterior  cerebral  artery ;  these,  with 
similar  branches  from  the  posterior  communicating,  pierce  the  posterior  perforated 
space  and  supply  the  internal  surfaces  of  the  optic  thalami  and  the  walls  of  the 
third  ventricle.  The  posterior  choroid  enters  the  interior  of  the  brain  beneath  the 
posterior  border  of  the  corpus  callosum  and  supplies  the  velum  interpositum  and 
the  choroid  plexus.  The  postero-lateral  ganglionic  branches  are  a  group  of  small 
arteries  which  arise  from  the  posterior  cerebral  artery  after  it  has  turned  round 
the  crus  cerebri ;  they  supply  a  considerable  portion  of  the  optic  thalamus.  The 
terminal  branches  are  distributed  as  follows  :  the  first  to  the  uncinate  gyrus ;  the 
second  to  the  temporo-sphenoidal  lobe ;  and  the  third  to  the  cuneus  or  the  occip- 
ital lobule. 

Circle  of  Willis. — The  remarkable  anastomosis  which  exists  betAveen  the 
branches  of  the  internal  carotid  and  vertebral  arteries  at  the  base  of  the  brain 
constitutes  the  circle  of  Willis.  It  is  formed,  in  front,  by  the  anterior  cerebral 
arteries,  branches  of  the  internal  carotid,  which  are  connected  together  by  the 
anterior  communicating ;  behind,  by  the  two  posterior  cerebrals,  branches  of  the 
basilar,  which  are  connected  on  each  side  with  the  internal  carotid  by  the  pos- 
terior communicating  arteries  (Fig.  354).  It  is  by  this  anastomosis  that  the  cere- 
bral circulation  is  equalized,  and  provision  made  for  effectually  carrying  it  on  if 
one  or  more  of  the  branches  are  obliterated.  The  parts  of  the  brain  included 
within  this  arterial  circle  are — the  lamina  cinerea,  the  commissure  of  the  optic 
nerves,  the  infundibulum,  the  tuber  cinereum,  the  corpora  albicantia,  and  the 
posterior  perforated  space. 

The  Thyroid  Axis  (Fig.  347)  is  a  short  thick  trunk  which  arises  from  the  fore 
part  of  the  first  portion  of  the  subclavian  artery,  close  to  the  inner  border  of  the 
Scalenus  anticus  muscle,  and  divides,  almost  immediately  after  its  origin,  into 
three  branches — the  inferior  thyroid,  suprascapular,  and  transversalis  colli. 

The  Inferior  Thyroid  Artery  passes  upward,  in  a  serpentine  course,  behind  the 
sheath  of  the  common  carotid  vessel  and  sympathetic  nerve  (the  middle  cervical 
ganglion  resting  upon  it),  and  in  front  of  the  vertebral  artery,  recurrent  laryngeal 
nerve  (sometimes  behind  the  nerve),  and  Longus  colli  muscle,  and  is  distributed 
to  the  posterior  surface  of  the  thyroid  gland,  anastomosing  with  the  superior  thy- 
roid and  with  the  corresponding  artery  of  the  opposite  side.  Its  branches  are — the 

Inferior  Laryngeal.  (Esophageal. 

Tracheal.  Ascending  Cervical. 

Muscular. 

The  inferior  laryngeal  branch  ascends  upon  the  trachea  to  the  back  part  of  the 
larynx,  in  company  with  the  recurrent  laryngeal  nerve,  and  supplies  the  muscles 
and  mucous  membrane  of  this  part,  anastomosing  with  the  branch  from  the  oppo- 
site side  and  with  the  laryngeal  branch  from  the  superior  thyroid  artery. 

The  tracheal  branches  are  distributed  upon  the  trachea,  anastomosing  below 
with  the  bronchial  arteries. 

The  cesophageal  branches  are  distributed  to  the  oesophagus,  and  anastomose 
with  the  oesophageal  branches  of  the  aorta. 

The  ascending  cervical  is  a  small  branch  which  arises  from  the  inferior  thyroid 
just  where  that  vessel  is  passing  behind  the  common  carotid  artery,  and  runs  up 
on  the  anterior  tubercles  of  the  transverse  processes  of  the  cervical  vertebrae  in 
the  interval  between  the  Scalenus  anticus  and  Rectus  capitis  anticus  major.  It 
gives  branches  to  the  muscles  of  the  neck,  which  anastomose  with  branches  of  the 
vertebral,  and  sends  one  or  two  branches  into  the  spinal  canal  through  the  inter- 
vertebral  foramina  to  be  distributed  to  the  spinal  cord  and  its  membranes,  and  to 
the  bodies  of  the  vertebrae  in  the  same  manner  as  the  lateral  spinal  branches  from 
the  vertebral.  It  anastomoses  with  the  ascending  pharyngeal  artery. 

The  muscular  branches  supply  the  depressors  of  the  hyoid  bone,  the  Longus 
colli,  the  Scalenus  anticus,  and  the  Inferior  constrictor  of  the  pharynx. 


BRANCHES   OF   THE  SUBCLAVIAN    ARTERY.  585 

Surgical  Anatomy. — This  artery  is  sometimes  tied,  in  conjunction  with  the  superior  thy- 
roid, in  cases  of  bronchocele.  An  incision  is  made  along  the  anterior  border  of  the  Sterno-mas- 
toid  down  to  the  clavicle.  After  the  deep  fascia  has  been  divided,  the  Sterno-mastoid  and  caro- 
tid vessels  are  drawn  outward  and  the  carotid  (Chassaignac's)  tubercle  sought  for.  The  vessel 
will  be  found  just  below  this  tubercle,  between  the  carotid  sheath  on  the  outer  side  of  the  trachea 
and  oesophagus  on  the  inner  side.  In  passing  the  ligature  great  care  must  be  exercised  to  avoid 
including  the  recurrent  laryngeal  nerve. 

The  Suprascapular  Artery  (transversalis  humeri),  smaller  than  the  transversalis 
colli.  passes  obliquely  from  within  outward,  across  the  root  of  the  neck.  It  at 
first  lies  on  the  lower  part  of  the  Scalenus  anticus,  being  covered  by  the  Sterno- 
mastoid  :  it  then  crosses  the  subclavian  artery,  and  runs  outward  behind  and  par- 
allel with  the  clavicle  and  Subclavius  muscle,  and  beneath  the  posterior  belly  of 
the  Omo-hyoid,  to  the  superior  border  of  the  scapula,  where  it  passes  over  the 
transverse  ligament  of  the  scapula  to  the  supraspinous  fossa.  In  this  situation  it 
lies  close  to  the  bone,  and  ramifies  between  it  and  the  Supraspinatus  muscle,  to 
which  it  is  mainly  distributed,  giving  off  a  communicating  branch  which  crosses 

Posterior  scapular. 

tiiprascapular.  Acromiat  branch 

Of  Thoracico-acromialis. 

Anterior 
circumflex. 


I 

-Termination  of 
subscapular. 

FIG.  36L— The  scapular  and  circumflex  arteries. 

the  neck  of  the  scapula,  to  reach  the  infraspinous  fossa,  where  it  anastomoses  with 
the  dorsal  branch  of  the  subscapular  artery.  Besides  distributing  branches  to  the 
Sterno-mastoid  and  neighboring  muscles,  it  gives  off  a  supra-acromial  branch, 
which,  piercing  the  Trapezius  muscle,  supplies  the  cutaneous  surface  of  the  acro- 
mion.  anastomosing  with  the  acromial  thoracic  artery.  As  the  artery  passes  over 
the  transverse  ligament  of  the  scapula  a  branch  descends  into  the  subscapular 
fossa,  ramifies  beneath  that  muscle,  and  anastomoses  with  the  posterior  and  sub- 
scapular  arteries.  It  also  supplies  the  shoulder-joint  and  a  nutrient  branch  to  the 
clavicle. 

The  Transversalis  Colli  passes  transversely  outward,  across  the  upper  part  of 
the  subclavian  triangle,  to  the  anterior  margin  of  the  Trapezius  muscle,  beneath 
which  it  divides  into  two  branches,  the  superficial  cervical  and  the  posterior  scap- 
ular. In  its  passage  across  the  neck  it  crosses  in  front  of  the  Scaleni  muscles  and 
the  brachial  plexus,  between  the  divisions  of  which  it  sometimes  passes,  and  is 
covered  by  the  Platysma,  Sterno-mastoid,  Omo-hyoid,  and  Trapezius  muscles. 

The  superficial  cervical  ascends  beneath  the  anterior  margin  of  the  Trapezius, 
distributing  branches  to  it  and  to  the  neighboring  muscles  and  glands  in  the  neck, 
and  anastomoses  with  the  supei'ficial  branch  of  the  arteria  princeps  cervicis. 

The    posterior    scapular,   the   continuation   of  the   transversalis    colli,   passes 


586  THE   ARTERIES. 

beneath  the  Levator  anguli  scapulae  to  the  superior  angles  of  the  scapula.  It  now 
descends  along  the  posterior  border  of  that  bone  as  far  as  the  inferior  angle,  where 
it  anastomoses  with  the  subscapular  branch  of  the  axillary.  In  its  course  it 
is  covered  by  the  Rhomboid  muscles,  supplying  them  and  the  Latissimus  dorsi  and 
Trapezius,  and  anastomosing  with  the  suprascapular  and  subscapular  arteries  and 
with  the  posterior  branches  of  some  of  the  intercostal  arteries. 

Peculiarities. — The  superficial  cervical  frequently  arises  as  a  separate  branch  from  the 
thyroid  axis ;  and  the  posterior  scapular,  from  the  third,  more  rarely  from  the  second,  part  of 
the  subclavian.  This  arrangement  is  almost  as  common  as  the  one  already  given. 

The  Internal  Mammary  arises  from  the  under  surface  of  the  first  portion  of 
the  subclavian  artery,  opposite  the  thyroid  axis.  It  descends  behind  the  costal 
cartilage  of  the  first  rib  to  the  inner  surface  of  the  anterior  wall  of  the  chest, 
resting  against  the  costal  cartilages  about  half  an  inch  from  the  margin  of  the 
sternum ;  and  at  the  interval  between  the  sixth  and  seventh  cartilages  divides 
into  two  branches,  the  musculo-phrenic  and  superior  epigastric. 

Relations. — At  its  origin  it  is  covered  by  the  internal  jugular  and  subclavian 
veins  and  crossed  by  the  phrenic  nerve.  In  the  upper  part  of  the  thorax  it  lies 
against  the  costal  cartilages  and  Internal  intercostal  muscles  in  front,  and  is 
covered  by  the  pleura  behind.  At  the  lower  part  of  the  thorax  the  Triangularis 
sterni  separates  the  artery  from  the  pleura. 

The  branches  of  the  internal  mammary  are — 

Comes  Nervi  Phrenici  (Superior  Phrenic).  Anterior  Intercostal. 

Mediastinal.  Perforating. 

Pericardiac.  Musculo-phrenic. 

Sternal.  Superior  Epigastric. 

The  comes  nervi  phrenici  (superior  phrenic),  is  a  long  slender  branch  which 
accompanies  the  phrenic  nerve,  between  the  pleura  and  pericardium,  to  the 
Diaphragm,  to  which  it  is  distributed,  anastomosing  with  the  other  phrenic 
arteries  from  the  internal  mammary  and  abdominal  aorta. 

The  mediastinal  branches  are  small  vessels  Avhich  are  distributed  to  the  areolar 
tissue  and  lymphatic  glands  in  the  anterior  mediastinum  and  the  remains  of  the 
thymus  gland. 

The  pericardiac  branches  supply  the  upper  part  of  the  anterior  surface  of  the 
pericardium,  the  lower  part  receiving  branches  from  the  musculo-phrenic  artery. 

The  sternal  branches  are  distributed  to  the  Triangularis  sterni  and  to  the 
posterior  surface  of  the  sternum. 

The  mediastinal,  pericardiac,  and  sternal  branches,  together  with  some  twigs 
from  the  comes  nervi  phrenici,  anastomose  with  branches  from  the  intercostal  and 
bronchial  arteries,  and  form  a  minute  plexus  beneath  the  pleura,  which  has  been 
named  by  Turner  the  subpleural  mediastinal  plexus. 

The  anterior  intercostal  arteries  supply  the  five  or  six  upper  intercostal  spaces. 
The  branch  corresponding  to  each  space  soon  divides  into  two,  or  the  two 
branches  may  come  off  separately  from  the  parent  trunk.  The  small  vessels  pass 
outward  in  the  intercostal  spaces,  one  lying  near  the  lower  margin  of  the  rib 
above,  and  the  other  near  the  upper  margin  of  the  rib  below,  and  anastomose 
with  the  intercostal  arteries  from  the  aorta.  They  are  at  first  situated  between 
the  pleura  and  the  Internal  intercostal  muscles,  and  then  between  the  Internal 
and  External  intercostal  muscles.  They  supply  the  Intercostal  muscles,  and,  by 
branches  which  perforate  the  External  intercostal  muscle,  the  Pectoral  muscles 
and  the  mammary  gland. 

The  perforating  arteries  correspond  to  the  five  or  six  upper  intercostal  spaces. 
They  arise  from  the  internal  mammary,  pass  forward  through  the  intercostal 
spaces,  and,  curving  outward,  supply  the  Pectoralis  major  and  the  integument. 
Those  which  correspond  to  the  second,  third,  and  fourth  spaces  are  distributed  to 
the  mammary  gland.  In  females,  during  lactation,  these  branches  are  of  large  size. 

The   musculo-phrenic    artery    is    directed   obliquely  downward  and  outward, 


si'RGICAL    AXATOMY   OF   THE   AXILLA. 

behind  the  cartilages  of  the  false  ribs,  perforating  the  Diaphragm  at  the  eighth  or 
ninth  rib,  and  terminating,  considerably  reduced  in  size,  opposite  the  last  inter- 
costal space.  It  gives  off  anterior  intercostal  arteries  to  each  of  the  intercostal 
spaces  across  which  it  passes;  these  diminish  in  size  as  the  spaces  decrease  in 
length,  and  are  distributed  in  a  manner  precisely  similar  to  the  anterior  intercostals 
from  the  internal  mammary.  The  musculo-phrenic  also  gives  branches  to  the 
lower  part  of  the  pericardium,  and  others  which  run  backward  to  the  Diaphragm 
and  downward  to  the  abdominal  muscles. 

The  superior  epigastric  continues  in  the  original  direction  of  the  internal 
mammary  :  it  descends  through  the  cellular  interval  between  the  costal  and  sternal 
attachments  of  the  Diaphragm,  and  enters  the  sheath  of  the  ftectus  abdominis 
muscle,  at  first  lying  behind  the  muscle,  and  then  perforating  it  and  supplying  it, 
and  anastomosing  with  the  deep  epigastric  artery  from  the  external  iliac.  Some 
Is  perforate  the  sheath  of  the  Rectus,  and  supply  the  muscles  of  the  abdomen 
and  the  integument,  and  a  small  branch,  which  passes  inward  upon  the  side  of  the 
ensiform  appendix,  anastomoses  in  front  of  that  cartilage  with  the  artery  of  the 
opposite  side. 

Surgical  Anatomy. — The  course  of  the  internal  mammary  artery  may  be  defined  by  draw- 
ing a  line  across  the  six  upper  intercostal  spaces  half  an  inch  from  and  parallel  with  the  sternum. 
The  position  of  the  vessel  must  be  remembered,  as  it  is  liable  to  be  wounded  in  stabs  of  the 
chest-wall.  It  is  most  easily  reached  by  a  transverse  incision  in  the  second  intercostal  space. 

The  Superior  Intercostal  (Fig.  352)  arises  from  the  upper  and  back  part  of  the 
subclavian  artery,  behind  the  Anterior  scalenus  on  the  right  side,  and  to  the  inner 
side  of  the  muscle  on  the  left  side.  Passing  backward,  it  gives  off  the  deep  cervical 
branch,  and  then  descends  behind  the  pleura  in  front  of  the  necks  of  the  first  two 
ribs,  and  inosculates  with  the  first  aortic  intercostal.1  In  the  first  intercostal 
space  it  gives  off  a  branch  which  is  distributed  in  a  manner  similar  to  the  distri- 
bution of  the  aortic  intercostals.  The  branch  for  the  second  intercostal  space 
usually  joins  with  one  from  the  aortic  intercostals.  Each  intercostal  gives  off  a 
branch  to  the  posterior  spinal  muscles,  and  a  small  one,  spinal,  which  passes  through 
the  corresponding  intervertebral  foramen  to  the  spinal  cord  and  its  membranes. 

The  deep  cervical  branch  (profunda  cervicis)  "arises,  in  most  cases,  from  the 
superior  intercostal,  and  is  analogous  to  the  posterior  branch  of  an  aortic  inter- 
costal artery.  Passing  backward,  between  the  transverse  process  of  the  seventh 
cervical  vertebra  and  the  first  rib.  it  runs  up  the  back  part  of  the  neck,  between 
the  Complexus  and  Semispinalis  colli  muscles,  as  high  as  the  axis,  supplying 
these  and  adjacent  muscles,  and  anastomosing  with  the  deep  branch  of  the  arteria 
princeps  cervicis  of  the  occipital  and  with  branches  which  pass  outward  from  the 
vertebral. 

SURGICAL  ANATOMY  OF  THE  AXILLA. 

The  Axilla  is  a  pyramidal  space,  situated  between  the  upper  and  lateral  part  of 
the  chest  and  the  inner  side  of  the  arm. 

Boundaries. — Its  apei\  which  is  directed  upward  toward  the  root  of  the  neck, 
corresponds  to  the  interval  between  the  first  rib.  the  upper  edge  of  the  scapula, 
and  the  clavicle,  through  which  the  axillary  vessels  and  nerves  pass.  The  base, 
directed  downward,  is  formed  by  the  integument,  and  a  thick  layer  of  fascia 
extending  between  the  lower  border  of  the  Pectoralis  major  in  front,  and  the  lower 
border  of  the  Latissimus  dorsi  behind ;  it  is  broad  internally  at  the  chest,  but 
narrow  and  pointed  externally  at  the  arm.  The  anterior  boundary  is  formed  by 
the  Pectoralis  major  and  minor  muscles,  the  former  covering  the  whole  of  the 
anterior  wall  of  the  axilla,  the  latter  covering  only  its  central  part.  The  posterior 
boundary,  which  extends  somewhat  lower  than  the  anterior,  is  formed  by  the  Sub- 
scapularis  above,  the  Teres  major  and  Latissimus  dorsi  below.  On  the  inner  side 
are  the  first  four  ribs  with  their  corresponding  Intercostal  muscles,  and  part  of  the 
Serratus  magnus.  On  the  outer  side,  where  the  anterior  and  posterior  boundaries 

1  See  foot-note,  p.  607. 


588 


THE   ARTERIES. 


converge,  the  space  is  narrow,  and  bounded  by  the  humerus,  the  Coraco-brachialis 
and  Biceps  muscles. 

Contents. — This  space  contains  the  axillary  vessels  and  brachial  plexus  of 
nerves,  with  their  branches,  some  branches  of  the  intercostal  nerves,  and  a  large 
number  of  lymphatic  glands,  all  connected  together  by  a  quantity  of  fat  and  loose 
areolar  tissue. 

Their  Position. — The  axillary  artery  and  vein,  with  the  brachial  plexus  of 
nerves,  extend  obliquely  along  the  outer  boundary  of  the  axillary  space,  from  its 
apex  to  its  base,  and  are  placed  much  nearer  the  anterior  than  the  posterior  wall, 
the  vein  lying  to^the  inner  or  thoracic  side  of  the  artery  and  partially  concealing 
it.  At  the  fore  part  of  the  axillary  space,  in  contact  with  the  Pectoral  muscles, 
are  the  thoracic  branches  of  the  axillary  artery,  and  along  the  anterior  margin 


Anterior 
circumflex. 


FIG.  362.— The  axillary  artery  and  its  branches. 

of  the  axilla  the  long  thoracic  artery  extends  to  the  side  of  the  chest.  At  the 
back  part,  in  contact  with  the  lower  margin  of  the  Subscapularis  muscle,  are  the 
subscapular  vessels  and  nerves ;  winding  around  the  lower  border  of  this  muscle 
is  the  dorsalis  scapulae  artery  and  veins ;  and  toward  the  outer  extremity  of  the 
muscle  the  posterior  circumflex  vessels  and  the  circumflex  nerve  are  seen  curving 
backward  to  the  shoulder. 

Along  the  inner  or  thoracic  side  no  vessel  of  any  importance  exists,  the  upper 
part  of  the  space  being  crossed  merely  by  a  few  small  branches  from  the  superior 
thoracic  artery.  There  are  some  important  nerves,  however,  in  this  situation— 
viz.  the  posterior  thoracic  or  external  respiratory  nerve,  descending  on  the  sur- 
face of  the  Serratus  magnus,  to  which  it  is  distributed ;  and  perforating  the  upper 
and  anterior  part  of  this  wall,  the  intercosto-humeral  nerve  or  nerves,  passing 
across  the  axilla  to  the  inner  side  of  the  arm. 

The  cavity  of  the  axilla  is  filled  by  a  quantity  of  loose  areolar  tissue  and  a  large 
number  of  small  arteries  and  veins,  all  of  which  are,  however,  of  inconsiderable 


THE  AXILLARY  ARTERY.  589 

size,  and  numerous  lymphatic  glands  :  these  are  from  ten  to  twelve  in  number,  and 
situated  chiefly  on  the  thoracic  side  and  lower  and  back  part  of  this  space. 

Surgical  Anatomy. — The  axilla  is  a  space  of  considerable  surgical  importance.  It  trans- 
mits the  large  vessels  and  nerves  to  the  upper  extremity,  and  these  may  be  the  seat  of  injury  or 
disease  :  it  contains  numerous  lymphatic  glands  which  may  require  removal  when  diseased ;  in  it 
is  a  quantity  of  loose  connective  and  adipose  tissue  which  may  be  readily  infiltrated  with  blood 
or  inflammatory  exudation,  and  it  may  be  the  seat  of  rapidly-growing  tumors.  Moreover,  it  is 
covered  at  its  base  by  thin  skin,  largely  supplied  with  sebaceous  and  sweat  glands,  which  is  fre- 
quently the  seat  of  small  cutaneous  abscesses  and  boils,  and  of  eruptions  due  to  irritation. 

In  suppuration  in  the  axilla  the  arrangement  of  the  fasciae  plays  a  very  important  part  in  the 
direction  which  the  pus  takes.  As  described  on  page  468,  the  costo-coracoid  membrane,  after 
covering  in  the  space  between  the  clavicle  and  the  upper  border  of  the  Peetoralis  minor,  splits 
to  enclose  this  muscle,  and.  reblending  at  its  lower  border,  becomes  incorporated  with  the  fascia 
covering  the  Peetoralis  major  muscle  at  the  anterior  fold  of  the  axilla.  This  is  known  as  the 
clavi-pectoral  fascia.  Suppuration  may  take  place  either  superficial  to  or  beneath  this  layer  of 
fascia  :  that  is.  either  between  the  pectorals  or  below  the  pectoralis  minor :  in  the  former  case, 
it  would  point  either  at  the  anterior  border  of  the  axillary  fold  or  in  the  groove  between  the  Del- 
toid and  the  Pectoralis  major ;  in  the  latter,  the  pus  would  have  a  tendency  to  surround  the  vessels 
and  nerves  and  ascend  into  the  neck,  that  being  the  direction  in  which  there  is  least  resistance. 
Its  progress  toward  the  skin  is  prevented  by  the  axillary  fascia  ;  its  progress  backward,  by  the 
Serratus  magnus ;  forward,  by  the  clavi-pectoral  fascia  ;  inward,  by  the  wall  of  the  thorax ;  and 
outward,  by  the  upper  limb.  The  pus  in  these  cases,  after  extending  into  the  neck,  has  been 
known  to  spread  through  the  superior  opening  of  the  thorax  into  the  mediastinum. 

In  opening  an  axillary  abscess  the  knife  should  be  entered  in  the  floor  of  the  axilla,  midway 
between  the  anterior  and  posterior  margins  and  near  the  thoracic  side  of  the  space.  It  is  well 
to  use  a  director  and  dressing  forceps  after  an  incision  has  been  made  through  the  skin  and  fascia 
in  the  manner  directed  by  the  late  Mr.  Hilton. 

The  student  should  attentively  consider  the  relation  of  the  vessels  and  nerves  in  the  several 
parts  of  the  axilla,  for  it  not  unfrequently  happens  that  the  surgeon  is  called  upon  to  extirpate 
diseased  glands  or  to  remove  a  tumor  from  this  situation.  In  performing  such  an  operation  it 
will  be  necessary  to  proceed  with  much  caution  in  the  direction  of  the  outer  wall  and  apex  of  the 
spun-,  as  here  the  axillary  vessels  will  be  in  danger  of  being  wounded.  Toward  the  posterior  wall 
it  will  be  necessary  to  avoid  the  subscapular,  dorsalis  scapulas,  and  posterior  circumflex  vessels. 
All  HI  2  the  anterior  wall  it  \\i\\  be  necessary  to  avoid  the  thoracic  branches.  It  is  only  along  the 
inner  or  thoracic  wall,  and  in  the  centre  of  the  axillary  cavity,  that  there  are  no  vessels  of  any 
importance — a  fortunate  circumstance,  for  it  is  in  this  situation  more  especially  that  tumors 
requiring  removal  are  usually  situated. 

THE  AXILLARY  ARTERY. 

The  Axillary  Artery,  the  continuation  of  the  subclavian,  commences  at  the 
lower  border  of  the  first  rib,  and  terminates  at  the  lower  border  of  the  tendon  of 
the  Teres  major  muscle,  where  it  takes  the  name  of  brachial.  Its  direction  varies 
with  the  position  of  the  limb :  when  the  arm  lies  by  the  side  of  the  chest,  the 
vessel  forms  a  gentle  curve,  the  convexity  being  upward  and  outward ;  when  it  is 
directed  at  right  angles  with  the  trunk,  the  vessel  is  nearly  straight ;  and  when 
it  is  elevated  still  higher,  the  artery  describes  a  curve  the  concavity  of  which  is 
directed  upward.  At  its  commencement  the  artery  is  very  deeply  situated,  but 
near  its  termination  is  superficial,  being  covered  only  by  the  skin  and  fascia.  The 
description  of  the  relations  of  this  vessel  is  facilitated  by  its  division  into  three 
portions,  the  first  portion  being  that  above  the  Pectoralis  minor ;  the  second  por- 
tion, behind ;  and  the  third  below,  that  muscle. 

The  first  portion  of  the  axillary  artery  is  in  relation,  in  front,  with  the  clavic- 
ular portion  of  the  Pectoralis  major,  the  costo-coracoid  membrane,  the  external 
anterior  thoracic  nerve,  and  the  acromio-thoracic  and  cephalic  veins ;  behind,  with 
the  first  intercostal  space,  the  corresponding  Intercostal  muscle,  the  second  and 
third  serrations  of  the  Serratus  magnus,  and  the  posterior  thoracic  nerve ;  on  its 
outer  side,  with  the  brachial  plexus,  from  which  it  is  separated  by  a  little  cellular 
interval ;  on  its  inner  or  thoracic  side,  with  the  axillary  vein. 

KELATIONS  OF  THE  FIRST  PORTION  OF  THE  AXILLARY  ARTERY. 

In  front. 
Pectoralis  major. 
Costo-coracoid  membrane. 
External  anterior  thoracic  nerve. 
Acromio-thoracic  and  Cephalic  veins. 


590 


THE   ARTERIES. 


Outer  side. 
Brachial  plexus. 


Inner  side. 
Axillary  vein. 


Behind. 

Firat  Intercostal  space,  and  Intercostal  muscle. 
Second  and  third  serrations  of  Serratus  magnus. 
Posterior  and  Internal  anterior  thoracic  nerves. 

The  second  portion  of  the  axillary  artery  lies  behind  the  Pectoralis  minor.  It 
is  covered  in  front,  by  the  Pectoralis  major  and  minor  muscles ;  behind,  it  is 
separated  from  the  Subscapularis  by  a  cellular  interval ;  on  the  inner  side  is  the 
axillary  vein.  The  cords  of  the  brachial  plexus  of  nerves  surround  the  artery,  and 
separate  it  from  direct  contact  with  the  vein  and  adjacent  muscles. 

RELATIONS  OF  THE  SECOND  PORTION  OF  THE  AXILLARY  ARTERY. 

In  front. 
Pectoralis  major  and  minor. 


Outer  side. 
Outer  cord  of  plexus. 


Inner  side. 
Axillary  vein. 
Inner  cord  of  plexus. 


Behind. 
Subscapularis. 
Posterior  cord  of  plexus. 

The  third  portion  of  the  axillary  artery  lies  below  the  Pectoralis  minor.  It  is 
in  relation,  in  front,  with  the  lower  part  of  the  Pectoralis  major  above,  being 
covered  only  by  the  integument  and  fascia  below,  where  it  is  crossed  by  the  inner 
head  of  the  median  nerve ;  behind,  with  the  lower  part  of  the  Subscapularis  and 
the  tendons  of  the  Latissimus  dorsi  and  Teres  major;  on  its  outer  side,  with  the 
Coraco-brachialis ;  on  its  inner  or  thoracic  side,  with  the  axillary  vein.  The  nerves 
of  the  brachial  plexus  bear  the  following  relation  to  the  artery  in  this  part  of  its 
course :  on  the  outer  side  is  the  median  nerve,  and  the  musculo-cutaneous  for  a 
short  distance;  on  the  inner  side,  the  ulnar,  the  internal,  and  lesser  internal 
cutaneous  nerves ;  and  behind,  the  musculo-spiral  and  circumflex,  the  latter 
extending  only  to  the  lower  border  of  the  Subscapularis  muscle. 

Peculiarities. — The  axillary  artery,  in  about  one  case  out  of  every  ten,  gives  off  a  large 
branch,  which  forms  either  one  of  the  arteries  of  the  forearm  or  a  large  muscular  trunk.  In  the 
first  set  of  cases  this  artery  is  most  frequently  the  radial  (1  in  33),  sometimes  the  ulnar  (1  in  72), 
and,  very  rarely,  the  interosseous  (1  in  506).  In  the  second  set  of  cases  the  trunk  has  been 
found  to  give  origin  to  the  subscapular,  circumflex,  and  profunda  arteries  of  the  arm.  Some- 
times only  one  of  the  circumflex,  or  one  of  the  profunda  arteries,  arose  from  the  trunk. 
In  these  cases  the  brachial  plexus  surrounded  the  trunk  of  the  branches,  and  not  the  main 
vessel. 

RELATIONS  OF  THE  THIRD  PORTION  OF  THE  AXILLARY  ARTERY. 

In  front. 

Integument  and  fascia. 
Pectoralis  major. 
Inner  head  of  median  nerve. 


Outer  side. 
Coraco-brachialis. 
Median  nerve. 
Musculo-cutaneous  nerve. 


Inner  side. 
Ulnar  nerve. 

Internal  cutaneous  nerves. 
Axillary  veins. 


Behind. 
Subscapularis. 

Tendons  of  Latissimus  dorsi  and  Teres  major. 
Musculo-spiral  and  circumflex  nerves. 


THE   AXILLARY  ARTERY.  591 

Surface  Marking. — The  course  of  the  axillary  artery  may  be  marked  out  by  raising  the 
arm  to  a  right  angle  and  drawing  a  line  from  the  middle  of  the  clavicle  to  the  point  where  the 
tendon  of  the  Pectoralis  major  crosses  the  prominence  caused  by  the  Coraco-brachialis  as  it 
emerges  from  under  cover  of  the  anterior  fold  of  the  axilla.  The  third  portion  of  the  artery  can 
be  felt  pulsating  beneath  the  skin  and  fascia,  at  the  junction  of  the  anterior  with  the  middle 
third  of  the  space  between  the  anterior  and  posterior  folds  of  the  axilla,  close  to  the  inner  border 
of  the  Coraoo-brachi&li& 

Surgical  Anatomy. — The  student,  having  carefully  examined  the  relations  of  the  axillary 
artery  in  its  various  parts,  should  now  consider  in  what  situation  compression  of  this  vessel 
may  be  most  easily  effected,  and  the  best  position  for  the  application  of  a  ligature  to  it  when 
necessary. 

Compression  of  the  vessel  may  be  required  in  the  removal  of  tumors  or  in  amputation  of 
the  upper  part  of  the  arm;  and  the  only  situation  in  which  this  can  be  effectually  made  is  in  the 
lower  part  of  its  course ;  by  pressing  on  it  in  this  situation  from  within  outward  against  the 
huinerus  the  circulation  may  be  effectually  arrested. 

The  axillary  artery  is  perhaps  more  frequently  lacerated  than  any  other  artery  in  the  body, 
with  the  exception  of  the  popliteal,  by  violent  movements  of  the  upper  extremity,  especially  in 
those  cases  where  its  coats  are  diseased.  It  has  occasionally  been  ruptured  in  attempts  to  reduce 
old  dislocations  of  the  shoulder-joint.  This  lesion  is  most  likely  to  occur  during  the  preliminary 
breaking  down  of  adhesions,  in  consequence  of  the  artery  having  contracted  adhesions  to  the 
capsule  of  the  joint.  Aneurism  of  the  axillary  artery  is  of  frequent  occurrence,  a  large  percentage 
of  the  cases  being  traumatic  in  their  origin,  due  to  the  violence  to  which  it  is  exposed  in  the 
varied,  extensive,  and  often  violent  movement  of  the  limb. 

The  application  of  a  ligature  to  the  axillary  artery  may  be  required  in  cases  of 
aneurism  of  the  upper  part  of  the  brachial  or  as  a  distal  operation  for  aneurism  of  the  sub- 
clavian :  and  there  are  only  two  situations  in  which  it  can  be  secured — viz.  in  the  first  and  in  the 
third  parts  of  its  course  ;  for  the  axillary  artery  at  its  central  part  is  so  deeply  seated,  and,  at  the 
same  time,  so  closely  surrounded  with  large  nervous  trunks,  that  the  application  of  a  ligature  to 
it  in  that  situation  would  be  almost  impracticable. 

In  the  third  part  of  its  course  the  operation  is  most  simple,  and  may  be  performed  in  the 
following  manner:  The  patient  being  placed  on  a  bed  and  the  arm  separated  from  the  side,  with 
the  hand  supinated.  an  incision  is  made  through  the  integument  forming  the  floor  of  the  axilla 
about  two  inches  in  length,  a  little  nearer  to  the  anterior  than  the  posterior  fold  of  the  axilla. 
After  carefully  dissecting  through  the  areolar  tissue  and  fascia,  the  median  nerve  and  axillary 
vein  are  exposed  ;  the  former  having  been  displaced  to  the  outer  and  the  latter  to  the  inner  side 
of  the  arm,  the  elbow  being  at  the  same  time  bent,  so  as  to  relax  the  structures  and  facilitate 
their  separation,  the  ligature  may  be  passed  round  the  artery  from  the  ulnar  to  the  radial  side. 
This  portion  of  the  artery  is  occasionally  crossed  by  a  muscular  slip  derived  from  the  Latissimus 
dorsi.  which  may  mislead  the  surgeon  during  an  operation.  The  occasional  existence  of  this 
muscular  fasciculus  was  spoken  of  in  the  description  of  the  muscles.  It  may  easily  be  recognized 
by  the  transverse  direction  of  its  fibres. 

The  first  portion  of  the  axillary  artery  may  be  tied  in  cases  of  aneurism  encroaching  so  far 
upward  that  a  ligature  cannot  be  applied  in  the  lower  part  of  its  course.  Notwithstanding  that 
this  operation  has  been  performed  in  some  few  cases,  and  with  success,  its  performance  is 
attended  with  much  difficulty  and  danger.  The  student  will  remark  that  in  this  situation  it 
would  be  necessary  to  divide  a  thick  muscle,  and,  after  separating  the  costo-coracoid  membrane, 
the  artery  would  be  exposed  at  the  bottom  of  a  more  or  less  deep  space,  with  the  cephalic  and 
axillary  veins  in  such  relation  with  it  as  must  render  the  application  of  a  ligature  to  this  part 
of  the  vessel  particularly  hazardous.  Under  such  circumstances  it  is  an  easier,  and  at  the 
same  time  more  advisable,  operation  to  tie  the  subclavian  artery  in  the  third  part  of  its  course. 

The  vessel  can  be  best  secured  by  a  curved  incision  with  the  convexity  downward  from  a 
point  half  an  inch  external  to  the  Sterno-clavicular  joint  to  a  point  half  an  inch  internal  to  the 
coracoid  process.  The  linib  is  to  be  well  abducted  and  the  head  inclined  to  the  opposite  side, 
and  this  incision  carried  through  the  superficial  structures,  care  being  taken  of  the  cephalic  vein 
at  the  outer  angle  of  the  incision.  The  clavicular  origin  of  the  Pectoralis  major  is  then  divided 
in  the  whole  extent  of  the  wound.  The  arm  is  now  to  be  brought  to  the  side,  and  the  upper 
edge  of  the  Pectoralis  minor  defined  and  drawn  downward.  The  costo-coracoid  membrane  is  to 
be  carefully  torn  through  with  a  director  close  to  the  coracoid  process,  and  the  axillary  sheath 
exposed  :  this  is  to  be  opened  with  especial  care  on  account  of  the  vein  overlapping  the  artery. 
The  needle  should  be  passed  from  below,  so  as  to  avoid  wounding  the  vein. 

In  a  case  of  wound  of  the  vessel  the  general  practice  of  cutting  down  upon,  and  tying  it 
above  and  below  the  wounded  point  should  be  adopted  in  all  cases. 

Collateral  Circulation  after  Ligature  of  the  Axillary  Artery.— If  the  artery  be  tied 
above  the  origin  of  the  acrornial  thoracic,  the  collateral  circulation  will  be  carried  on  by  the  same 
branches  as  after  the  ligature  of  the  subclavian  :  if  at  a  lower  point,  between  the  acromial 
thoracic  and  subscapular  arteries,  the  latter  vessel,  by  its  free  anastomoses  with  the  other 
scapular  arteries,  branches  of  the  subclavian.  will  become  the  chief  agent  in  carrying  on  the  cir- 
culation, to  which  the  long  thoracic,  if  it  be  below  the  ligature,  will  materially  contribute  by  its 
anastomoses  with  the  intercostal  and  internal  mammary  arteries.  If  the  point  included  in  the 
ligature  be  below  the  origin  of  the  subscapular  artery,  it  will  most  probably  also  be  below  the 
origins  of  the  two  circumflex  arteries.  The  chief  agents  in  restoring  the  circulation  will  then  be 


592  THE   ARTERIES. 

the  subscapular  and  the  two  circumflex  arteries  anastomosing  with  the  superior  prof'unda  from 
the  brachial. 

BRANCHES  OF  THE  AXILLARY  ARTERY. 
The  branches  of  the  axillary  artery  are — 

r,          -?  .  f  Superior  Thoracic.  ^  -,        .  (  Long  Thoracic. 

From  first  part  |  A(£omial  Thoracic  From  second  part  j  AlargThoracic 

(  Subscapular. 

From  third  parti  Anterior  Circumflex. 
(Posterior  Circumflex. 

The  superior  thoracic  is  a  small  artery  which  arises  from  the  axillary  sepa- 
rately or  by  a  common  trunk  with  the  acromial  thoracic.  Running  forward  and 
inward  along  the  upper  border  of  the  Pectoralis  minor,  it  passes  between  it  and  the 
Pectoralis  major  to  the  side  of  the  chest.  It  supplies  these  muscles  and  the  parietes 
of  the  thorax,  anastomosing  with  the  internal  mammary  and  intercostal  arteries. 

The  acromial  thoracic  is  a  short  trunk  which  arises  from  the  fore  part  of  the 
axillary  artery.  Projecting  forward  to  the  upper  border  of  the  Pectoralis  minor, 
it  divides  into  three  sets  of  branches — thoracic,  acromial,  and  descending  or 
humeral.  The  thoracic  branches,  two  or  three  in  number,  are  distributed  to  the 
Serratus  magnus  and  Pectoral  muscles,  anastomosing  with  the  intercostal 
branches  of  the  internal  mammary.  The  acromial  branches  are  directed  outward 
toward  the  acromion,  supplying  the  Deltoid  muscle,  and  anastomosing,  on  the  sur- 
face of  the  acromion,  with  the  suprascapular  and  posterior  circumflex  arteries. 
The  humeral  branch  passes  in  the  space  between  the  Pectoralis  major  and  Deltoid 
in  the  same  groove  as  the  cephalic  vein,  and  supplies  both  muscles.  The  artery 
also  gives  off  a  very  small  branch,  the  clavicular,  which  passes  upward  to  the  Sub- 
clavius  muscle. 

The  long  thoracic  (external  mammary')  passes  downward  and  inward  along  the 
lower  border  of  the  Pectoralis  minor  to  the  side  of  the  chest,  supplying  the  Serra- 
tus magnus,  the  Pectoral  muscles,  and  mammary  gland,  and  sending  branches 
across  the  axilla  to  the  axillary  glands  and  Subscapularis ;  it  anastomoses  with 
the  internal  mammary  and  intercostal  arteries.  An  accessory  external  mammary 
branch  is  often  found  running  to  the  chest  behind  the  long  thoracic. 

The  alar  thoracic  is  a  small  branch  which  supplies  the  glands  and  areolar 
tissue  of  the  axilla.  Its  place  is  frequently  supplied  by  branches  from  some  of  the 
other  thoracic  arteries. 

The  subscapular,  the  largest  branch  of  the  axillary  artery,  arises  opposite  the 
lower  border  of  the  Subscapularis  muscle,  and  passes  downward  and  backward 
along  its  lower  margin  to  the  inferior  angle  of  the  scapula,  where  it  anastomoses 
with  the  long  thoracic  and  intercostal  arteries  and  with  the  posterior  scapular. 
About  an  inch  and  a  half  from  its  origin  it  gives  off  a  large  branch,  the  dorsalis  scap- 
ulae, and  terminates  by  supplying  branches  to  the  muscles  in  the  neighborhood. 

The  dorsalis  scapulae  is  given  off  from  the  subscapular  about  an  inch  from  its 
origin,  and  is  generally  larger  than  the  continuation  of  the  vessel.  It  curves  round 
the  axillary  border  of  the  scapula,  leaving  the  axilla  through  the  space  between 
the  Teres  minor  above,  the  Teres  major  below,  and  the  long  head  of  the  Triceps 
externally  (Fig.  361),  and  enters  the  infraspinous  fossa,  where  it  anastomoses  with 
the  posterior  scapular  and  suprascapular  arteries.'  In  its  course  it  gives  off  two 
sets  of  branches :  one  enters  the  subscapular  fossa  beneath  the  Subscapularis, 
which  it  supplies,  anastomosing  with  the  posterior  scapular  and  suprascapular 
arteries ;  the  other  is  continued  along  the  axillary  border  of  the  scapula,  between 
the  Teres  major  and  minor,  and,  at  the  dorsal  surface  of  the  inferior  angle  of  the 
bone,  anastomoses  with  the  posterior  scapular.  In  addition  to  these,  small  branches 
are  distributed  to  the  back  part  of  the  Deltoid  muscle  and  the  long  head  of  the 
Triceps,  anastomosing  with  an  ascending  branch  of  the  superior  profunda  of  the 
brachial. 


THE   BRACHIAL   ARTERY.  593 

The  circumflex  arteries  wind  round  the  neck  of  the  humerus.  The  posterior 
cif  'I'm ilex  (Fig.  361),  the  larger  of  the  two,  arises  from  the  back  part  of  the  axillary 
opposite  the  lower  border  of  the  Subscapularis  muscle,  and,  passing  backward  with 
the  circumflex  veins  and  nerve  through  the  quadrangular  space  bounded  by  the 
Teres  major  and  minor,  the  scapular  head  of  the  Triceps  and  the  humerus.  winds 
round  the  neck  of  that  bone  and  is  distributed  to  the  Deltoid  muscle  and  shoulder- 
joint,  anastomosing  with  the  anterior  circumflex  and  acromial  thoracic  arteries,  and 
with  the  superior  profunda  branch  of  the  brachial  artery.  The  anterior  circumflex 
(Figs.  361,  362),  considerably  smaller  than  the  preceding,  arises  just  below  that 

•  •I  from  the  outer  side  of  the  axillary  artery.  It  passes  horizontally  outward 
beneath  the  Coraco-brachialis  and  short  head  of  the  Biceps,  lying  upon  the  fore  part 
of  the  neck  of  the  humerus,  and,  on  reaching  the  bicipital  groove,  gives  oft"  an 
ascending  branch  which  passes  upward  along  the  groove  to  supply  the  head  of  the 
bone  and  the  shoulder-joint.  The  trunk  of  the  vessel  is  then  continued  outward 
beneath  the  Deltoid,  which  it  supplies,  and  anastomoses  with  the  posterior  circum- 
flex artery.  The  axillary  cutaneous  branch,  long  and  slender,  is  often  found 
ramifying  in  the  superficial  fascia  of  the  floor  of  the  axilla. 

THE  BRACHIAL  ARTERY  (Fig.  363). 

The  Brachial  Artery  commences  at  the  lower  margin  of  the  tendon  of  the  Teres 
major,  and,  passing  down  the  inner  and  anterior  aspect  of  the  arm,  terminates  about 
half  an  inch  below  the  bend  of  the  elbow,  where  it  divides  into  the  radial  and 

ulnar  arteries. 

PLAN  OF  THE  RELATIONS  OF  THE  BRACHIAL  ARTERY. 

In  front. 

Integument  and  fasciae. 
Bicipital  fascia,  median  basilic  vein. 
Median  nerve. 

Outer  side.  /^          ^\  Inner  side. 

Vt-na  comes.  /     Braci,iai      |        Vena  comes. 

Median  nerve  (above).  Artery.  Internal  cutaneous  and  Ulnar  nerves. 

Coraco-brachialis.  V  J        Median  nerve  (below). 

Biceps.  Basilic  vein  (upper  half). 

Behind. 
Triceps. 

Musculo-spiral  nerve. 
Superior  profunda  artery. 
Coraco-brachialis  (insertion). 
Brachialis  anticus. 

Relations. — This  artery  is  superficial  throughout  its  entire  extent,  being  covered, 
in  front,  by  the  integument,  the  superficial  and  deep  fascia;  the  bicipital  fascia 
separates  it  opposite  the  elbow  from  the  median  basilic  vein  ;  the  median  nerve 
crosses  it  at  its  middle.  Behind,  it  is  separated  from  the  inner  side  of  the 
humerus.  above,  by  the  long  and  inner  heads  of  the  Triceps,  the  musculo-spiral 
nerve  and  superior  profunda  artery  intervening,  and  from  the  front  of  the  bone, 
below,  by  the  insertion  of  the  Coraco-brachialis  muscle  and  by  the  Brachialis 
anticus.  By  its  outer  side  it  is  in  relation  with  the  commencement  of  the 
median  nerve  and  the  Coraco-brachialis  and  Biceps  muscles,  which  slightly 
overlap  the  artery.  By  its  inner  side  its  upper  half  is  in  relation  with  the  inter- 
nal cutaneous  and  ulnar  nerves,  its  lower  half  with  the  median  nerve.  The 
basilic  vein  lies  on  the  inner  side  of  the  artery,  but  is  separated  from  it  in  the 
lower  part  of  the  arm  by  the  deep  fascia.  It  is  accompanied  by  two  vense  comites, 
which  lie  in  close  contact  with  the  artery,  being  connected  together  at  inter- 
vals bv  short  transverse  communicating  branches. 

V  '._ 

SURGICAL   ANATOMY   OF   THE   BEND   OF   THE   ELBOW. 
At   the  bend    of  the    elbow  the  brachial    artery  sinks    deeply  into  a  trian- 
gular   interval,    the    base    of  which    is    directed    upward    toward  the    humerus, 

38 


594 


THE   ARTERIES. 


and  the  sides  of  which  are  bounded,  externally,  by  the  Supinator  longus ;  inter- 
nally, by  the  Pronator  radii  teres  ;  its  floor  is  formed  by  the  Brachialis  anticus  and 

Supinator  brevis.  This  space,  culltnl 
fossa,  contains  the  brachial  artery  with 
its  accompanying  veins,  the  radial  and 
ulnar  arteries,  the  median  and  musculo- 
spiral  nerves,  and  the  tendon  of  the 
Biceps.  The  brachial  artery  occupies 
the  middle  line  of  this  space,  and  divides 
opposite  the  neck  of  the  radius  into  the 
radial  and  ulnar  arteries ;  it  is  covered, 
in  front,  by  the  integument,  the  super- 
ficial fascia,  and  the  median  basilic  vein, 
the  vein  being  separated  from  direct 
contact  with  the  artery  by  the  bicipital 
fascia.  Behind,  it  lies  on  the  Brachialis 
anticus,  which  separates  it  from  the 
elbow  -joint.  The  median  nerve  lies  on 
the  inner  side  of  the  artery,  close  to 
it  above,  but  separated  from  it  below 
by  the  coronoid  head  of  the  Pronator 
radii  teres.  The  tendon  of  the  Biceps 
lies  to  the  outer  side  of  the  space,  and 
the  musculo-spiral  nerve  still  more  ex- 
ternally, lying  upon  the  Supinator 
brevis  and  partly  concealed  by  the 
Supinator  longus. 

Peculiarities  of  the  Brachial  Artery  as 
regards  its  Course. — The  brachial  artery,  ac- 
companied by  the  median  nerve,  may  leave  the 
inner  border  of  the  Biceps,  and  descend  toward 
the  inner  condyle  of  the  humerus,  where  it 
usually  curves  round  a  prominence  of  bone,  to 
which  it  is  connected  by  a  fibrous  band  ;  it  then 
inclines  outward,  beneath  or  through  the  sub- 
stance of  the  Pronator  radii  teres  muscle,  to 
the  bend  of  the  elbow.  The  variation  bears 
considerable  analogy  with  the  normal  condition 
of  the  artery  in  some  of  the  carnivora :  it  has 
been  referred  to  above  in  the  description  of 
the  humerus  (page  250). 

As  regards  its  Division. — Occasionally, 
the  artery  is  divided  for  a  short  distance  at 
its  upper  part  into  two  trunks,  which  are 
united  above  and  below.  A  similar  peculiarity 
occurs  in  the  main  vessel  of  the  lower  limb. 

The  point  of  bifurcation  may  be  above  or 
below  the  usual  point,  the  former  condition  being  by  far  the  more  frequent.  Out  of  481  exam- 
inations recorded  by  Mr.  Quain,  some  made  on  the  right  and  some  on  the  left  side  of  the  body, 
in  386  the  artery  bifurcated  in  its  normal  position.  In  one  case  only  was  the  place  ot  division 
lower  than  usual,  being  two  or  three  inches  below  the  elbow-joint.  "  In  94  cases  out  of  481,  or 
about  1  in  5£.  there  were  two  arteries  instead  of  one  in  some  part  or  in  the  whole  of  the  arm. 

There  appears,  however,  to  be  no  correspondence  between  the  arteries  of  the  two  arms  with 
respect  to  their  irregular  division  ;  for  in  61  bodies  it  occurred  on  one  side  only  in  43  ;  on  both 
sides,  in  different  positions,  in  13;  on  both  sides,  in  the  same  position,  in  5. 

The  point  of  bifurcation  takes  place  at  different  parts  of  the  arm,  being  most  frequent  in  the 
upper  part,  less  so  in  the  lower  part,  and  least  so  in  the  middle,  the  most  usual  point  tor  the 
application  of  a  ligature  :  under  any  of  these  circumstances  two  large  arteries  would  be  found  in 
the  arm  instead  of  one.  The  most  frequent  (in  three  out  of  four)  of  these  peculiarities  is  the 
high  division  of  the  radial.  That  artery  often  arises  from  the  inner  side  of  the  brachial,  and 
runs  parallel  with  the  main  trunk  to  the  elbow,  where  it  crosses  it,  lying  beneath  the  fascia  ;  or  it 
may  perforate  the  fascia  and  pass  over  the  artery  immediately  beneath  the  integument, 

The  ulnar  sometimes  arises  from  the  brachial  high  up,  and  then  occasionally  leaves  that  ves- 
sel at  the  lower  part  of  the  arm,  and  descends  toward  the  inner  condyle.  In  the  forearm  it  gen- 


FIG.  363. — The  surgical  anatomy  of  the  brachial  artery. 


BRANCHES    OF    THE   BRACHIAL.  595 

erally  lies  beneath  the  deep  fascia,  superficial  to  the  flexor  muscles :   occasionally  between  the 
integument  and  deep  fascia,  and  very  rarely  beneath  the  flexor  muscles. 

The  interosseous  artery  BometOWB  arises  from  the  upper  part  of  the  brachial  or  axillary  :  as 
it  passes  down  the  arm  it  lies  behind  the  main  trunk,  and  at  the  bend  of  the  elbow  regains  its  usual 
position. 

In  some  eases  of  high  division  of  the  radial  the  remaining  trunk  (ulnar  interosseous)  occa- 
sionally passes,  together  with  the  median  nerve,  along  the  inner  margin  of  the  arm  to  the  inner 
condyle.  and  then  passing  from  within  outward,  beneath  or  through  the  Pronator  radii  teres, 
regains  its  usual  position  at  the  bend  of  the  elbow. 

Occasionally  the  two  arteries  representing  the  brachial  are  connected  at  the  bend  of  the 
elbow  by  a  short  transverse  branch,  and  are  even  sometimes  reunited. 

Sometimes,  ling  slender  vessels,  vasa  aberrantia,  connect  the  brachial  or  axillary  arteries 
with  one  of  the  arteries  of  the  forearm  or  a  branch  from  them.  These  vessels  usually  join  the 
radial. 

Varieties  in  Muscular  Relations.1 — The  brachial  artery  is  occasionally  concealed  in  some 
part  of  its  course  by  muscular  or  tendinous  slips  derived  from  the  Coraco-brachialis.  Biceps, 
Brachialis  anticus  and  Pronator  radii  teres  muscles. 

Surface  Marking. — The  direction  of  the  brachial  artery  is  marked,  when  the  arm  is 
extended  and  supinated.  by  a  line  drawn  from  the  junction  of  the  anterior  and  middle  third  of 
the  space  between  the  anterior  and  posterior  folds  of  the  axilla  ;  that  is  to  say  from  the  inner 
side  of  the  prominence  of  the  Coraco-brachialis  muscle  to  the  point  midway  between  the  condyles 
of  the  humerus  which  corresponds  to  the  depression  along  the  inner  border  of  the  Coraco-bra- 
chialis and  Biceps.  In  the  upper  part  of  its  course  the  artery  lies  internal  to  the  humerus.  but 
below  it  is  in  front  of  that  bone. 

Surgical  Anatomy.— Compression  of  the  brachial  artery  is  required  in  cases  of  amputation 
and  some  other  operations  in  the  arm  and  forearm  ;  and  it  will  be  observed  that  it  may  be  effected 
in  almost  any  part  of  the  course  of  the  artery.  If  pressure  is  made  in  the  upper  part  of  the 
limb,  it  should  be  directed  from  within  outward  :  and  if  in  the  lower  part,  from  before  backward, 
as  the  artery  lies  on  the  inner  side  of  the  humerus  above  and  in  front  below.  The  most  favor- 
able situation  is  about  the  middle  of  the  arm.  where  it  lies  on  the  tendon  of  the  Coraco-brachialis 
on  the  inner  flat  side  of  the  humerus. 

The  application  of  a  ligature  to  the  brachial  artery  may  be  required  in  case  of  wound  of 
the  vessel  and  in  some  cases  of  wound  of  the  palmar  arch.  It  is  also  sometimes  necessary  in 
cases  of  aneurism  of  the  brachial,  the  radial,  ulnar,  or  interosseous  arteries.  The  artery  may 
be  secured  in  any  part  of  its  course.  The  chief  guides  in  determining  its  position  are  the  sur- 
face markings  produced  by  the  inner  margin  of  the  Coraco-brachiaKs  and  Biceps,  the  known 
course  of  the  vessel,  and  its  pulsation,  which  should  be  carefully  felt  for  before  any  operation  is 
performed,  as  the  vessel  occasionally  deviates  from  its  usual  position  in  the  arm.  In  whatever 
situation  the  operation  is  performed,  great  care  is  necessary,  on  account  of  the  extreme  thinness 
of  the  parts  covering  the  artery  and  the  intimate  connection  which  the  vessel  has  throughout  its 
whole  course  with  important  nerves  and  veins.  Sometimes  a  thin  layer  of  muscular  fibre  is 
met  with  concealing  the  artery :  if  such  is  the  case,  it  must  be  cut  across  in  order  to  expose  the 
vessel. 

In  the  upper  third  of  the  arm  the  artery  may  be  exposed  in  the  following  manner :  The 
patient  being  placed  horizontally  upon  a  table,  the  affected  limb  should  be  raised  from  the  side 
and  the  hand  supinated.  An  incision  about  two  inches  in  length  should  be  made  on  the  inner 
side  of  the  Coraco-brachialis  muscle,  and  the  subjacent  fascia  cautiously  divided,  so  as  to  avoid 
wounding  the  internal  cutaneous  nerve  or  basilic  vein,  which  sometimes  runs  on  the  surface  of 
the  artery  as  high  as  the  axilla.  The  fascia  having  been  divided,  it  should  be  remembered  that 
the  ulnar  and  internal  cutaneous  nerves  lie  on  the  inner  side  of  the  artery,  the  median  on  the 
outer  side,  the  latter  nerve  being  occasionally  superficial  to  the  artery  in  this  situation,  and  that 
the  vena?  comites  are  also  in  relation  with  the  vessel,  one  on  either  side.  These  being  carefully 
separated,  the  aneurism  needle  should  be  passed  round  the  artery  from  the  inner  to  the  outer 

s'nk'. 

If  two  arterit-s  are  present  in  the  arm  in  consequence  of  a  high  division,  they  are  usually 
placed  side  by  side:  and  if  they  are  exposed  in  an  operation,  the  surgeon  should  endeavor  to 
ascertain,  by  alternately  pressing  on  each  vessel,  which  of  the  two  communicates  with  the  wound 
or  aneurism,  when  a  ligature  may  be  applied  accordingly ;  or  if  pulsation  or  haemorrhage  ceases 
only  when  both  vessels  are  compressed,  both  vessels  may  be  tied,  as  it  may  be  concluded  that 
the  two  communicate  above  the  seat  of  disease  or  are  reunited. 

It  should  also  be  remembered  that  two  arteries  may  be  present  in  the  arm  in  a  case  of  high 
division,  and  that  one  of  these  may  be  found  along  the  inner  intermuscular  septum,  in  a  line 
toward  the  inner  condyle  of  the  humerus.  or  in  the  usual  position  of  the  brachial,  but  deeply 
placed  beneath  the  common  trunk :  a  knowledge  of  these  facts  will  suggest  the  precautions 

-ury  in  even-  case,  and  indicate  the  measures  to  be  adopted  when  anomalies  are  met 
with. 

In  the  middle  of  the  arm  the  brachial  artery  may  be  exposed  by  making  an  incision  along 
the  inner  margin  of  the  Biceps  muscle.  The  forearm  being  bent  so  as  to  relax  the  muscle,  it 
should  be  drawn  slightly  aside,  and,  the  fascia  being  carefully  divided,  the  median  nerve  will  be 

1  See  Struther's  Anatomical  and  Physiological  Observations. 


596  THE   ARTERIES. 

exposed  lying  upon  the  artery  (sometimes  beneath) ;  this  being  drawn  inward  and  the  muscle 
outward,  the  artery  should  be  separated  from  its  accompanying  veins  and  secured.  In  this 
situation  the  inferior  profunda  may  be  mistaken  for  the  main  trunk,  especially  if  enlarged,  from 
the  collateral  circulation  having  become  established ;  this  may  be  avoided  by  directing  the  incis- 
ion externally  toward  the  Biceps,  rather  than  inward  or  backward  toward  the  Triceps. 

The  lower  part  of  the  brachial  artery  is  of  interest  in  a  surgical  point  of  view,  on  account 
of  the  relation  which  it  bears  to  the  veins  most  commonly  opened  in  venesection.  Of  these 
vessels,  the  median  basilic  is  the  largest  and  most  prominent,  and,  consequently,  the  one  usually 
selected  for  the  operation.  It  should  be  remembered  that  this  vein  runs  parallel  with  the 
brachial  artery,  from  which  it  is  separated  by  the  bicipital  fascia,  and  that  care  should  be  taken 
in  opening  the  vein  not  to  carry  the  incision  too  deeply,  so  as  to  endanger  the  artery. 

Collateral  Circulation. — After  the  application  of  a  ligature  to  the  brachial  artery  in  the 
upper  third  of  the  arm,  the  circulation  is  carried  on  by  branches  from  the  circumflex  and 
subscapular  arteries,  anastomosing  with  ascending  branches  from  the  superior  profunda.  If  the 
brachial  is  tied  below  the  origin  of  the  profunda  arteries,  the  circulation  is  maintained  by  the 
branches  of  the  profundse,  anastomosing  with  the  recurrent  radial,  ulnar,  and  interosseous 
arteries.  In  two  cases  described  by  Mr.  South,1  in  which  the  brachial  artery  had  been  tied  some 
time  previously,  in  one  ''a  long  portion  of  the  artery  had  been  obliterated,  and  sets  of  vessels 
are  descending  on  either  side  from  above  the  obliteration,  to  be  received  into  others  which  ascend 
in  a  similar  manner  from  below  it.  In  the  other  the  obliteration  is  less  extensive,  and  a  single 
curved  artery  about  as  big  as  a  crow-quill  passes  from  the  upper  to  the  lower  open  part  of  the 
artery. ' ' 

The  branches  of  the  brachial  artery  are — the 

Superior  Profunda.  Inferior  Profunda. 

Nutrient.  Anastomotica  Magna. 

Muscular. 

The  superior  profunda  arises  from  the  inner  and  back  part  of  the  brachial,  just 
below  the  lower  border  of  the  Teres  major,  and  passes  backward  to  the  interval 
between  the  outer  and  inner  heads  of  the  Triceps  muscle,  accompanied  by  the 
musculo-spiral  nerve ;  it  winds  round  the  back  part  of  the  shaft  of  the  humerus 
in  the  spiral  groove,  between  the  Triceps  and  the  bone,  to  the  outer  side  of  the 
humerus  just  above  the  external  condyle,  where  it  divides  into  two  terminal 
branches.  One  of  these  pierces  the  external  intermuscular  septum,  and  descends 
to  the  space  between  the  Brachialis  anticus  and  Supinator  longus,  where  it  anasto- 
moses with  the  recurrent  branch  of  the  radial  artery  ;  while  the  other,  the  posterior 
articular,  descends  along  the  back  of  the  external  intermuscular  septum  to  the 
back  part  of  the  elbow-joint,  where  it  anastomoses  with  the  posterior  interosseous 
recurrent,  and  across  the  back  of  the  humerus  with  the  posterior  ulnar  recurrent, 
the  anastomotica  magna,  and  inferior  profunda  (Fig.  366).  The  superior  profunda 
supplies  the  Triceps  muscle  and  gives  off  a  nutrient  artery  to  the  upper  end  of  the 
humerus.  Near  its  commencement  it  sends  off  a  branch  which  passes  upward 
between  the  external  and  long  heads  of  the  Triceps  muscle  to  anastomose  with 
the  posterior  circumflex  artery,  and,  while  in  the  groove,  a  small  branch  which 
accompanies  a  branch  of  the  musculo-spiral  nerve  through  the  substance  of  the 
Triceps  muscle  and  ends  in  the  Anconeus  below  the  outer  condyle  of  the 
humerus. 

The  nutrient  artery  of  the  shaft  of  the  humerus  arises  from  the  brachial,  about 
the  middle  of  the  arm.  Passing  downward  it  enters  the  nutrient  canal  of  that 
bone  near  the  insertion  of  the  Coraco-brachialis  muscle. 

The  inferior  profunda,  of  small  size,  arises  from  the  brachial,  a  little  below  the 
middle  of  the  arm ;  piercing  the  internal  intermuscular  septum,  it  descends  on  the 
surface  of  the  inner  head  of  the  Triceps  muscle  to  the  space  between  the  inner 
condyle  and  olecranon,  accompanied  by  the  ulnar  nerve,  and  terminates  by  anasto- 
mosing with  the  posterior  ulnar  recurrent  and  anastomotica  magna.  It  also 
supplies  a  branch  to  the  front  of  the  internal  condyle,  which  anastomoses  with  the 
anterior  ulnar  recurrent. 

The  anastomotica  magna  arises  from   the  brachial  about  two  inches  above  the 

1  Chelius's  Surgery,  vol.  ii.  p.  254.  See  also  White's  engraving,  referred  to  by  Mr.  South,  of  the 
anastomosing  branches  after  ligature  of  the  brachial,  in  White's  Cases  in  Surgery.  Porta  also  gives  a 
case  (with  drawings)  of  the  circulation  after  ligature  of  both  brachial  and  radial  (Alterazioni 
Patoligiche  delle  Arterie). 


THE   RADIAL    ARTERY.  597 

elbow-joint.  It  passes  transversely  inward  upon  the  Brachialis  anticus,  and,  piercing 
the  internal  intermuscular  septum,  winds  round  the  back  part  of  the  humerus 
between  the  Triceps  and  the  bone,  forming  an  arch  above  the  olecranon  fossa  by  its 
junction  with  the  posterior  articular  branch  of  the  superior  profunda.  As  this  vessel 
lies  on  the  Brachialis  anticus,  branches  ascend  to  join  the  inferior  profunda,  and 
others  descend  in  front  of  the  inner  condyle  to  anastomose  with  the  anterior  ulnar 
recurrent.  Behind  the  internal  condyle  an  offset  is  given  off  which  anastomoses 
with  the  inferior  profunda  and  posterior  ulnar  recurrent  arteries  and  supplies  the 
Triceps. 

The  muscular  are  three  or  four  large  branches,  which  are  distributed  to  the 
muscles  in  the  course  of  the  artery.  They  supply  the  Coraco-brachialis,  Biceps, 
and  Brachialis  anticus  muscles. 

The  Anastomosis  around  the  Elbow-joint  (Fig.  366). — The  vessels  engaged  in 
this  anastomosis  may  be  conveniently  divided  into  those  situated  in  front  and 
behind  the  internal  and  external  condyles.  The  branches  anastomosing  in  front 
of  the  internal  condyle  are  the  anastomotica  magna,  the  anterior  ulnar  recurrent, 
and  the  anterior  terminal  branch  of  the  inferior  profunda.  Those  behind  the  internal 
condyle  are  the  anastomotica  magna,  the  posterior  ulnar  recurrent,  and  the 
posterior  terminal  branch  of  the  inferior  profunda.  The  branches  anastomosing  in 
i'r<>nt  of  the  external  condyle  are  the  radial  recurrent  and  one  of  the  terminal 
branches  of  the  superior  profunda.  Those  behind  the  external  condyle  (perhaps 
more  properly  described  as  being  situated  between  the  external  condyle  and  the 
olecranon)  are  the  anastomotica  magna,  the  interosseous  recurrent,  and  one  of 
the  terminal  branches  of  the  superior  profunda.  There  is  also  a  large  arch  of 
anastomosis  above  the  olecranon,  formed  by  the  interosseous  recurrent,  joining  with 
the  anastomotica  magna  and  posterior  ulnar  recurrent  (Fig.  366). 

From  this  description  it  will  be  observed  that  the  anastomotica  magna  is  the 
vessel  most  engaged,  the  only  part  of  the  anastomosis  in  which  it  is  not  employed 
being  that  in  front  of  the  external  condyle. 

Radial  Artery. 

The  Radial  Artery  appears,  from  its  direction,  to  be  the  continuation  of  the 
brachial,  but  in  size  it  is  smaller  than  the  ulnar.  It  commences  at  the  bifurca- 
tion of  the  brachial,  just  below  the  bend  of  the  elbow,  and  passes  along  the  radial 
side  of  the  forearm  to  the  wrist ;  it  then  winds  backward,  round  the  outer  side 
of  the  carpus,  beneath  the  extensor  tendons  of  the  thumb,  and,  finally,  passes 
forward,  between  the  two  heads  of  the  First  dorsal  interosseous  muscle,  into  the 
palm. of  the  hand,  where  it  crosses  the  metacarpal  bones  to  the  ulnar  border  of  the 
hand,  to  form  the  deep  palmar  arch.  At  its  termination  it  ini>jculates_jwjth  the 
deep  branch  of  the  ulnar  artery.  The  relations  of  this  vessel  may  thus  be  con- 
veniently divided  into  three  parts — viz.  in  the  forearm,  at  the  back  of  the  wrist, 
and  in  the  hand. 

Relations. — In  the  forearm  this  vessel  extends  from  opposite  the  neck  of  the 
radius  to  the  fore  part  of  the  styloid  process,  being  placed  to  the  inner  side  of  the 
shaft  of  the  bone  above  and  in  front  of  it  below.  It  is  superficial  throughout  its 
entire  extent,  being  covered  by  the  integument,  the  superficial  and  deep  fasciae, 
and  slightly  overlapped  above  by  the  Supinator  longus.  In  its  course  downward 
it  lies  upon  the  tendon  of  the  Biceps,  the  Supinator  brevis,  the  radial  origin  of  the 
Flexor  sublimis  digitorum,  the  Pronator  radii  teres,  the  Flexor  longus  pollicis,  the 
Pronator  quadratus,  and  the  lower  extremity  of  the  radius.  In  the  upper  third 
of  its  course  it  lies  between  the  Supinator  longus  and  the  Pronator  radii  teres ; 
in  its  lower  two-thirds,  between  the  tendons  of  the  Supinator  longus  and  the 
Flexor  carpi  radialis.  The  radial  nerve  lies  along  the  outer  side  of  the  artery 
in  the  middle  third  of  its  course,  and  some  filaments  of  the  musculo-cutaneous 
nerve,  after  piercing  the  deep  fascia,  run  along  the  lower  part  of  the  artery  as  it 
winds  round  the  wrist.  The  vessel  is  accompanied  by  venae  comites  throughout  its 
whole  course. 


598  THE   ARTERIES. 

PLAN  OF  THE  RELATIONS  OF  THE  RADIAL  ARTERY  IN  THE  FOREARM. 

In  front. 

Skin,  superficial  and  deep  fasciae. 
Supinator  longus. 

Inner  side.  /  \  Outer  side. 

Pronator  radii  teres.  i^FoVearm7  Supinator  longus. 

Flexor  carpi  radialis.  \  I  Radial  nerve  (middle  third). 

Behind. 

Tendon  of  Biceps. 
Supinator  breyis. 
Flexor  sublimis  digitorum. 
Pronator  radii  teres. 
Flexor  longus  pollicis. 
Pronator  quadratus. 
Radius. 

At  the  wrist,  as  it  winds  round  the  outer  side  of  the  carpus  from  the  styloid 
process  to  the  first  interosseous  space,  it  lies  upon  the  external  lateral  ligament, 
and  then  upon  the  scaphoid  bone  and  trapezium,  being  covered  by  the  extensor 
tendons  of  the  thumb,  subcutaneous  veins,  some  filaments  of  the  radial  nerve,  and 
the  integument.  It  is  accompanied  by  two  veins  and  a  filament  of  the  musculo- 
cutaneous  nerve. 

In  the  hand  it  passes  from  the  upper  end  of  the  first  interosseous  space, 
between  the  heads  of  the  Abductor  indicis  or  First  dorsal  interosseous  muscle, 
transversely  across  the  palm,  to  the  base  of  the  metacarpal  bone  of  the  little 
finger,  where  it  inosculates  with  the  communicating  branch  from  the  ulnar  artery, 
forming  the  deep  palmar  arch.  It  lies  upon  the  carpal  extremities  of  the  metacarpal 
bones  and  the  Interossei  muscles,  being  covered  by  the  Adductor  obliquus  pollicis, 
the  flexor  tendons  of  the  fingers,  the  Lumbricales,  the  Opponens,  and  Flexor 
brevis  minimi  digiti.  Alongside  of  it  is  the  deep  branch  of  the  ulnar  nerve,  but 
running  in  the  opposite  direction ;  that  is  to  say,  from  within  outward. 

Peculiarities. — The  origin  of  the  radial  artery,  according  to  Quain,  is,  in  nearly  one  case 
in  eight,  higher  than  usual ;  more  frequently  arising  from  the  axillary  or  upper  part  of  the 
brachial  than  from  the  lower  part  of  this  vessel.  The  variations  in  the  position  of  this  vessel 
in  the  arm  and  at  the  bend  of  the  elbow  have  been  already  mentioned.  In  the  forearm  it 
deviates  less  frequently  from  its  position  than  the  ulnar.  It  has  been  found  lying  over  the  fascia 
instead  of  beneath  it.  It  has  also  been  observed  on  the  surface  of  the  Supinator  longus,  instead 
of  along  its  inner  border ;  and  in  turning  round  the  wrist  it  has  been  seen  lying  over,  instead  of 
beneath,  the  extensor  tendons. 

Surface  Marking. — The  position  of  the  radial  artery  in  the  forearm  is  represented  by  a 
line  drawn  from  the  outer  border  of  the  tendon  of  the  Biceps  in  the  centre  of  the  hollow  in  front 
of  the  elbow-joint  with  a  straight  course  to  the  inner  side  of  the  fore  part  of  the  styloid  process 
of  the  radius. 

Surgical  Anatomy. — The  radial  artery  is  much  exposed  to  injury  in  its  lower  third,  and  is 
frequently  wounded  by  the  hand  being  driven  through  a  pane  of  glass,  by  the  slipping  of  a 
knife  or  chisel  held  in  the  other  hand,  and  such-like  accidents.  The  injury  is  often  followed  by 
a  traumatic  aneurism,  for  which  the  old  operation  of  laying  open  the  sac  and  securing  the  vessel 
above  and  below  is  required. 

The  operation  of  tying  the  radial  artery  is  required  in  cases  of  wounds  either  of  its  trunk  01 
of  some  of  its  branches,  or  for  aneurism  ;  and  it  will  be  observed  that  the  vessel  may  be  exposed 
in  any  part  of  its  course  through  the  forearm  without  the  division  of  any  muscular  fibres.  The 
operation  in  the  middle  or  inferior  third  of  the  forearm  is  easily  performed,  but  in  the  upper 
third,  near  the  elbow,  it  is  attended  with  some  difficulty,  from  the  greater  depth  of  the  vessel 
and  from  its  being  overlapped  by  the  Supinator  longus  muscle. 

To  tie  the  artery  in  the  upper  third  an  incision  three  inches  in  length  should  be  made 
through  the  integument,  in  a  line  drawn  from  the  centre  of  the  bend  of  the  elbow  to  the  front 
of  the  styloid  process  of  the  radius,  avoiding  the  branches  of  the  median  vein ;  the  fascia  of 
the  arm  being  divided  and  the  Supinator  longus  drawn  a  little  outward,  the  artery  will  be 
exposed.  The  venae  comites  should  be  carefully  separated  from  the  vessel,  and  the  ligature 
passed  from  the  radial  to  the  ulnar  side. 

In  the  middle  third  of  the  forearm  the  artery  may  be  exposed  by  making  an  incision  of 
similar  length  on  the  inner  margin  of  the  Supinator  longus.  In  this  situation  the  radial  nerve 


THE   RADIAL    ARTERY. 


599 


lie?  in  dose  relation  with  the  outer  side  of  the  artery,  and  should,  as  well  as  the  veins,  be  care- 
fully avoided. 

In  tlit-  lower  third  the  artery  is  easily  secured  by  dividing  the  integument  and  fascia  in  the 
interval  between  the  tendons  of  the  Su- 
pinator  longus  and  Flexor  carpi  radialis 
iraadea 

The  branches  of  the  radial  ar- 
tery may  be  divided  into  three 
groups,  corresponding  with  the 
three  region?  in  which  the  vessel  is 
situated. 

f  Radial  Recurrent. 
In  tlis      !    Muscular. 

j   Anterior  Carpal. 

I  Superficial  Volae. 

|   Posterior  Carpal. 

)   Metacarpal. 


Baditd  recurrent. 


Wrt'*t . 


Dorsales  Pollicis. 
Dorsalis  Indicis. 
Princeps  Pollicis. 
Radialis  Indicis. 
Perforating. 
Interosseous. 
Palmar  Recurrent. 


The  radial  recurrent  is  given 
off  immediately  below  the  elbow. 
It  ascends  between  the  branches 
of  the  inusculo-spiral  nerve  lying 
on  the  Supinator  brevis,  and  then 
between  the  Supinator  longus  and 
Brachialia  anticus.  supplying  these 
muscles  and  the  elbow-joint,  and 
anastomosing  with  one  of  the  ter- 
minal branches  of  the  superior 
profunda. 

The  muscular  branches  are  dis- 
tributed to  the  muscles  on  the  ra- 
dial side  of  the  forearm. 

The  anterior  carpal  is  a  small 
vessel  which  arises  from  the  radial 
artery  near  the  lower  border  of  the 
Pronator  quadratus.  and,  running 
inward  in  front  of  the  radius,  an- 
astomoses with  the  anterior  carpal 
branch  of  the  ulnar  artery.  From 
the  arch  thus  formed  branches  de- 
scend to  supply  the  articulations 
of  the  wrist. 

The  superficialis  volae  arises 
from  the  radial  artery,  just  where 
this  vessel  is  about  to  Avind  round 
the  wrist.  Running  forward,  it 
passes  between  the  muscles  of  the 
thumb,  which  it  supplies,  and  some- 
times anastomoses  with  the  palmar 
portion  of  the  ulnar  artery,  com- 
pleting the  superficial  palmar  arch. 


Deep  branch 
of  ulnar. 


Superficial™  votee. 


FIG.  364.— The  surgical  anatomy  of  the  radial  and  ulner 
arteries. 

This  vessel  varies    considerably  in   size: 


600 


THE    ARTERIES. 


recurrent. 


Posterior 
interosseous. 


usually  it  is  very  small,  and  terminates  in  the  muscles  of  the  thumb  ;  sometimes 
it  is  as  large  as  the  continuation  of  the  radial. 

The  posterior  carpal  arises  from  the  radial  artery  beneath  the  extensor  tendons 

of  the  thumb ;   crossing  the  carpus 
transversely  to   its  inner  border,  it 
anastomoses  -with  the  posterior  car- 
_Anastomotica       pal  branch  of  the  ulnar,  forming  the 
magna.  posterior  carpal  arch,  Avhich  is  joined 

by  the  termination  of  the  posterior 
interosseous  artery.  From  this  arch 
are  given  off  descending  branches, 
the  dorsal  interosseous  arteries  for 
the  third  and  fourth  interosseous 
spaces,  which  run  forward  on  the 
-Anterior ulnar  muscies  an(j  Divide  into  dorsal  digi- 

recurrent.  9 

Posterior  ulnar  tal  branches  which  supply  the  adja- 
cent sides  of  the  middle,  ring,  and 
little  fingers  respectively,  communi- 
cating with  the  digital  arteries  of 
the  superficial  palmar  arch.  At 
their  origin  they  anastomose  with 
the  superior  perforating  branches 
from  the  deep  palmar  arch,  and  at 
the  clefts  of  the  fingers  send  off 
inferior  perforating  branches  to  the 
corresponding  palmar  digital  ar- 
teries. 

The  metacarpal  (first  dorsal  inter- 
osseous branch)  arises  beneath  the  ex- 
tensor tendons  of  the  thumb,  some- 
times with  the  posterior  carpal 
artery ;  running  forward  on  the 
Second  dorsal  interosseus  muscle,  it 
communicates,  behind,  with  the 
corresponding  superior  perforating 
branch  of  the  deep  palmar  arch  : 
and  in  front  it  divides  into  two 
dorsal  digital  branches,  which  supply 
the  adjoining  sides  of  the  index  and 
middle  fingers,  inosculating  with  the 
digital  branch  of  the  superficial 
palmar  arch.  It  also  has  a  similar 
but  more  constant  inferior  perfor- 
ating branch, 

The  dorsales  pollicis  are  two 
vessels  which  run  along  the  sides  of 
the  .dorsal  aspect  of  the  thumb. 
They  arise  separately,  or  by  a  com- 
mon trunk,  near  the  base  of  the  first 
metacarpal  bone. 

The  dorsalis  indicis  runs  along  the  radial  side  of  the  back  of  the  index  finger, 
sending  a  few  branches  to  the  Abductor  indicis. 

The  princeps  pollicis  arises  from  the  radial  just  as  it  turns  inward  to  the  deep 
part  of  the  hand;  it  descends  anterior  to  the  Abductor  indicis  and  between  the 
Adductor  pollicis  muscles,  along  the  ulnar  side  of  the  metacarpal  bone  of  the  thumb, 
to  the  base  of  the  first  phalanx,  where  it  divides  into  two  branches,  which  run  along 
the  sides  of  the  palmar  aspect  of  the  thumb  and  form  an  arch  on  the  under  surface 


Muscular. 


Anterior  carpal. 
Superficialis  wise. 


Anterior  carpal. 


Deep  branch  of 
ulnar. 


FIG.  365.— Ulnar  and  radial  arteries.    Deep  view. 


THE    ULXAR    ARTERY.  601 

of  the  last  phalanx,  from  which  branches  are  distributed  to  the  integument  and 
pulp  of  the  thumb. 

The  radialis  indicis  arises  close  to  the  preceding,  descends  between  the 
Abductor  indicis  and  Adductor  transversus  pollicis.  and  runs  along  the  radial 
side  of  the  index  finger  to  its  extremity,  where  it  anastomoses  with  the  collateral 
digital  artery  from  the  superficial  palmar  arch.  At  the  lower  border  of  the 
Adductor  transversus  pollicis  this  vessel  anastomoses  with  the  princeps  pollicis, 
and  gives  a  communicating  branch  to  the  superficial  palmar  arch. 

The  superior  perforating  arteries,  three  in  number,  pass  backward  between  the 
heads  of  the  last  three  Dorsal  interossei  muscles,  to  inosculate  with  the  dorsal 
interosseous  arteries. 

The  palmar  interosseous,  three  or  four  in  number,  are  branches  of  the  deep 
palmar  arch :  they  run  forward  upon  the  Interossei  muscles,  and  anastomose  at 
the  clefts  of  the  fingers  with  the  digital  branches  of  the  superficial  arch. 

The  palmar  recurrent  branches  arise  from  the  concavity  of  the  deep  palmar 
arch.  They  pass  upward  in  front  of  the  wrist,  supplying  the  carpal  articulations 
and  anastomosing  with  the  anterior  carpal  arch. 

Ulnar  Artery. 

The  Ulnar  Artery,  the  larger  of  the  two  terminal  branches  of  the  brachial, 
commences  a  little  below  the  bend  of  the  elbow,  and  crosses  obliquely  the  inner 
side  of  the  forearm,  to  the  commencement  of  its  lower  half;  it  then  runs  along  its 
ulnar  border  to  the  wrist,  crosses  the  annular  ligament  on  the  radial  side  of  the 
pisiform  bone,  and  immediately  beyond  this  bone  divides  into  two  branches, 
superficial  and  deep  palmar. 

Relations  in  the  Forearm. — In  its  upper  half  it  is  deeply  seated,  being  covered 
by  all  the  superficial  flexor  muscles,  excepting  the  Flexor  carpi  ulnaris ;  it  is 
crossed  by  the  median  nerve  (deep  head  of  Pronator  radii  teres  intervening), 
which  lies  just  above  to  its  inner  side,  and  it  lies  upon  the  Brachialis 
anticus  and  Flexor  profundus  digitorum  muscles.  In  the  lower  half  of 
the  forearm  it  lies  upon  the  Flexor  profundus,  being  covered  by  the  integu- 
ment, the  superficial  and  deep  fasciae,  and  is  placed  between  the  Flexor 
carpi  ulnaris  and  Flexor  sublimis  digitorum  muscles.  It  is  accompanied 
by  two  venae  comites ;  the  ulnar  nerve  lies  on  its  inner  side  for  the  lower  two- 
thirds  of  its  extent,  and  a  small  branch  from  the  nerve  descends  on  the  lower  part 
of  the  vessel  to  the  palm  of  the  hand. 

PLAN  OF  RELATIONS  OF  THE  ULNAR  ARTERY  IN  THE  FOREARM. 

In  front. 

fl^ifnter^61"  °f  **™  "^  }  UPP«  half' 
Superficial  and  deep  fasciae.  Lower  half. 

Lu.fr  Me.  ,       ,,„..  Outer  Me, 


Behind. 

Brachialis  anticus. 
Flexor  profundus  digitorum. 

At  the  wrist  (Fig.  364)  the  ulnar  artery  is  covered  by  the  integument  and 
fascia  and  lies  upon  the  anterior  annular  ligament.  On  its  inner  side  is  the 
pisiform  bone.  The  ulnar  nerve  lies  at  the  inner  side,  and  somewhat  behind  the 
artery. 

Peculiarities. — The  ulnar  artery  has  been  found  to  vary  in  its  origin  nearly  in  the  propor- 
tion of  one  in  thirteen  cases,  in  one  case  arising  lower  than  usual,  about  two  or  three  inches 
below  the  elbow,  and  in  all  other  cases  much  higher,  the  brachial  being  a  more  frequent  source 
of  origin  than  the  axillary. 


602  THE   ARTERIES. 

Variations  in  the  position  of  this  vessel  are  more  frequent  than  in  the  radial.  When  its 
origin  is  normal  the  course  of  the  vessel  is  rarely  changed.  When  it  arises  high  up  it  is  almost 
invariably  superficial  to  the  flexor  muscles  in  the  forearm,  lying  commonly  beneath  the  fascia, 
more  rarely  between  the  fascia  and  integument.  In  a  few  cases  its  position  was  subcutaneous 
in  the  upper  part  of  the  forearm,  subaponeurotic  in  the  lower  part. 

Surface  Marking. — On  account  of  the  curved  direction  of  the  ulnar  artery  the  line  on  the  sur- 
face of  the  body  which  indicates  its  course  is  somewhat  complicated.  First,  draw  a  line  from  the 
front  of  the  internal  condyle  of  the  humerus  to  the  radial  side  of  the  pisiform  bone  ;  the  lower 
two-thirds  of  this  line  represents  the  course  of  the  middle  and  lower  third  of  the  ulnar  artery. 
Secondly,  draw  a  line  from  the  centre  of  the  hollow  in  front  of  the  elbow -joint  to  the  junction  of  the 
upper  and  middle  third  of  the  first  line  ;  this  represents  the  course  of  the  upper  third  of  the  artery. 

Surgical  Anatomy. — The  application  of  a  ligature  to  this  vessel  is  required  in  cases  of 
wound  of  the  artery  or  of  its  branches,  or  in  consequence  of  aneurism.  In  the  upper  half  of 
the  forearm  the  artery  is  deeply  seated  beneath  the  superficial  flexor  muscles,  and  the  applica- 
tion of  a  ligature  in  this  situation  is  attended  with  some  difficulty.  An  incision  is  to  be  made 
in  the  course  of  a  line  drawn  from  the  front  of  the  internal  condyle  of  the  humerus  to  the  outer 
side  of  the  pisiform  bone,  so  that  the  centre  of  the  incision  is  three  fingers'  breadth  below  the 
internal  condyle.  The  skin  and  superficial  fascia  having  been  divided  and  the  deep  fascia 
exposed,  the  white  line  which  separates  the  Flexor  carpi  ulnaris  from  the  other  flexor  muscles 
is  to  be  sought  for,  and  the  fascia  incised  in  this  line.  The  Flexor  carpi  ulnaris  is  now  to  be 
carefully  separated  from  the  other  muscles,  when  the  ulnar  nerve  will  be  exposed,  and  must  be 
drawn  aside.  Some  little  distance  below  the  nerve  the  artery  will  be  found  accompanied  by  its 
vense  comites,  and  may  be  ligatured  by  passing  the  needle  from  within  outward.  In  the  middle 
and  lower  third  of  the  forearm  this  vessel  may  be  easily  secured  by  making  an  incision  on  the 
radial  side  of  the  tendon  of  the  Flexor  carpi  ulnaris  :  the  deep  fascia  being  divided,  and  the 
Flexor  carpi  ulnaris  and  its  companion  muscle,  the  Flexor  sublimis,  being  separated  from  each 
other,  the  vessel  will  be  exposed,  accompanied  by  its  venae  comites,  the  ulnar  nerve  lying  on  its 
inner  side.  The  veins  being  separated  from  the  artery,  the  ligature  should  be  passed  from  the 
ulnar  to  the  radial  side,  taking  care  to  avoid  the  ulnar  nerve. 

The  branches  of  the  ulnar  artery  may  be  arranged  in  the  following  groups  : 

(  Anterior  Ulnar  Recurrent. 
Posterior  Ulnar  Recurrent. 

Forearm.  f  Anterior  Interosseous. 

)  Interosseous     <  -n  T    . 

\  Posterior  Interosseous. 

^  Muscular. 
Wri«t  f  Anterior  Carpal. 

\  Posterior  Carpal. 
IT     j  /  Superficial  Palmar  Arch. 

(  Deep  Palmar  or  Communicating. 

The  anterior  ulnar  recurrent  (Fig.  365)  arises  immediately  below  the  elbow- 
joint,  passes  upward  and  inward  between  the  Brachialis  anticus  and  Pronator 
radii  teres,  supplies  those  muscles,  and,  in  front  of  the  inner  condyle,  anastomoses 
with  the  anastomotica  magna  and  inferior  profunda. 

The  posterior  ulnar  recurrent  is  much  larger,  and  arises  somewhat  lower  than 
the  preceding.  It  passes  backward  and  inward,  beneath  the  Flexor  sublimis, 
and  ascends  behind  the  inner  condyle  of  the  humerus.  In  the  interval  between 
this  process  and  the  olecranon  it  lies  beneath  the  Flexor  carpi  ulnaris,  ascend- 
ing between  the  heads  of  that  muscle,  beneath  the  ulnar  nerve;  it  supplies  the 
neighboring  muscles  and  joint,  and  anastomoses  with  the  inferior  profunda,  anas- 
tomotica magna,  and  interosseous  recurrent  arteries  (Fig.  366). 

The  interosseous  artery  (Fig.  365)  is  a  short  trunk  about  an  inch  in  length, 
and  of  considerable  size,  which  arises  immediately  below  the  tuberosity  of  the 
radius,  and,  passing  backward  to  the  upper  border  of  the  interosseous  membrane, 
divides  into  two  branches,  the  anterior  and  posterior  inter  osseous. 

The  anterior  interosseous  passes  down  the  forearm  on  the  anterior  surface  of 
the  interosseous  membrane,  to  which  it  is  connected,  by  a  thin  aponeurotic  arch. 
It  is  accompanied  by  the  interosseous  branch  of  the  median  nerve,  and  overlapped 
by  the  contiguous  margins  of  the  Flexor  profundus  digitorum  and  Flexor  longus 
pollicis  muscles,  giving  off  in  this  situation  muscular  branches  and  the  nutrient 
arteries  of  the  radius  and  ulna.  At  the  upper  border  of  the  Pronator  quadratus 
a  branch  descends  traaeath  the  muscle  to  anastomose  in  front  of  the  carpus  with 


OF    THE    ULXAR    ARTERY. 


603 


.  Descending  branch  from 
superior  profunda. 


Anastomotica 
magna. 


Posterior  idnar 
recurrent. 


Posterior  interosoeons. 


branches  from  the  anterior  carpal  and  deep  palmar  arch.  The  continuation  of 
the  artery  passes  behind  the  Pronator  quadratus,  and,  piercing  the  interosseous 
membrane,  gets  to  the  back  of  the  forearm,  and  anastomoses  with  the  posterior 
interosseous°arterv  (Fig.  366).  It  then  descends  to  tne  back  of  the  wrist  to  join  the 
posterior  carpal  arch.  The 
anterior  interosseous  gives  off 
a  Ion  or,  slender  branch,  the 

• 

median  artery,  which  accom- 
panies the  median  nerve  and 
gives  offsets  to  its  substance. 
This  artery  is  s  unetimes  much 
enlarged.  It  also  gives  off 
nutrient  branches  to  the  radius 
and  ulna  about  the  middle  of 
the  forearm. 

The  posterior  interosse- 
ous artery  passes  backward 
through  the  interval  between 
the  oblique  ligament  and  the 
upper  border  of  the  interos- 
seous membrane.  It  appears 
between  the  contiguous  bor- 
ders of  the  Supinator  brevis 
and  the  Extensor  ossis  meta- 
carpi  pollicis.  and  runs  down 
the  back  part  of  the  forearm, 
between  the  superficial  and 
deep  layer  of  muscles,  to 
both  of  which  it  distributes 
branches.  At  the  lower  part 
of  the  forearm  it  anastomoses 
with  the  termination  of  the 
anterior  interosseous  artery. 
Then,  continuing  its  course 
over  the  head  of  the  ulna,  it 
joins  the  posterior  carpal 
branch  of  the  ulnar  artery. 
This  artery  gives  off.  near  its 
origin,  the  interosseous  recur- 
rent branch. 

The  interosseous  recurrent 
artery  is  a  large  vessel  which 
ascends  to  the  interval  be- 
tween the  external  condyle 
and  olecranon,  on  or  through 
the  fibres  of  the  Supinator 
brevis,  but  beneath  the  Anco- 
neus.  anastomosing  with  a 
branch  from  the  superior  pro- 
funda, and  with  the  posterior 
ulnar  recurrent  and  anas- 
tomotica  magna. 

The  muscular  branches  are  distributed  to  the  muscles  along  the  ulnar  side  of 
the  forearm. 

The  anterior  carpal  is  a  small  vessel  which  crosses  the  front  of  the  carpus 
beneath  the  tendons  of  the  Flexor  profundus,  and  inosculates  with  a  correspond- 
ing branch  of  the  radial  artery. 


Posterior  carpal 
(idnar). 


Termination  of  an- 
terior interosseous. 


Posterior  carpal 
(radial). 

•Eadial. 

.Dorsalis  pollicis. 
rsalis  indicis. 


FIG.  366.— Arteries  of  the  back  of  the  forearm  and  baud. 


604  THE   ARTERIES. 

The  posterior  carpal  arises  immediately  above  the  pisiform  bone,  and  winds 
backward  beneath  the  tendon  of  the  Flexor  carpi  ulnaris :  it  passes  across  the 
dorsal  surface  of  the  carpus  beneath  the  extensor  tendons,  anastomosing  with  a 
corresponding  branch  of  the  radial  artery,  and  forming  the  posterior  carpal  arch. 
Immediately  after  its  origin  it  gives  off  a  small  branch  which  runs  along  the 
ulnar  side  of  the  metacarpal  bone  of  the  little  finger,  forming  one  of  the  meta- 
carpal  arteries,  and  supplies  the  ulnar  side  of  the  dorsal  surface  of  the  little 
finger.  (See  also  page  600.) 

The  deep  palmar  or  communicating  branch  (Fig.  365)  passes  deeply  inward 
between  the  Abductor  minimi  digiti  and  Flexor  brevis  minimi  digiti  near  their 
origins ;  it  anastomoses  with  the  termination  of  the  radial  artery,  completing  the 
deep  palmar  arch. 

The  Superficial  Palmar  Arch. — The  superficial  palmar  arch  passes  outward 
across  the  palm  of  the  hand,  describing  a  curve,  with  its  convexity  forward  to  the 
space  between  the  ball  of  the  thumb  and  the  index  finger,  where  the  arch  is  com- 
pleted by  its  anastomosing  with  a  branch  from  the  radialis  indicis,  though  some- 
times the  arch  is  completed  by  its  anastomosing  with  the  superficialis  volge 
branch  of  the  radial  artery. 

Relations. — The  superficial  palmar  arch  is  covered  by  the  skin,  the  Palmaris 
brevis,  and  the  palmar  fascia.  It  lies  upon  the  annular  ligament,  origin  of  the 
muscles  of  the  little  finger,  the  tendons  of  the  superficial  flexor  of  the  fingers, 
and,  the  divisions  of  the  median  and  ulnar  nerves. 

RELATIONS  OF  THE  SUPERFICIAL  PALMAR  ARCH. 

In  front. 
Skin. 

Palmaris  brevis. 
Palmar  fascia. 


Behind. 

Annular  ligament. 
Origin  of  muscles  of  little  finger. 
Superficial  flexor  tendons. 
Divisions  of  median  and  ulnar  nerves. 

BRANCHES  OF  THE  SUPERFICIAL  PALMAR  ARCH. 
Digital. 

The  digital  branches  (Fig.  364),  four  in  number,  are  given  off  from  the  con- 
vexity of  the  superficial  palmar  arch.  They  supply  the  ulnar  side  of  the  little 
finger  and  the  adjoining  sides  of  the  little,  ring,  middle,  and  index  fingers,  the 
radial  side  of  the  index  finger  and  thumb  being  supplied  from  the  radial  artery. 
The  digital  arteries  at  first  lie  superficial  to  the  flexor  tendons,  but  as  they  pass 
forward  with  the  digital  nerves  to  the  clefts  between  the  fingers  they  lie  between 
them,  and  are  there  joined  by  the  interosseous  branches  from  the  deep  palmar 
arch.  The  digital  arteries  on  the  sides  of  the  fingers  lie  behind  the  digital 
nerves ;  and  about  the  middle  of  the  last  phalanx  the  two  branches  for  each 
finger  form  an  arch,  from  the  convexity  of  which  branches  pass  to  supply  the 
pulp  of  the  finger. 

Surface  Marking. — The  superficial  palmar  arch  is  represented  by  a  curved  line,  starting 
from  the  outer  side  of  the  pisiform  bone  and  carried  downward  as  far  as  the  middle  third  of 
the  palm,  and  then  curved  outward  on  a  level  with  the  upper  end  of  the  cleft  between  the 
thumb  and  index  finger. 

The  deep  palmar  arch  is  situated  about  half  an  inch  nearer  to  the  carpus. 


THE    THORACIC  AORTA.  605 

Surgical  Anatomy. — Wounds  of  the  palmar  arches  are  of  special  interest,  and  are  always 
difficult  to  deal  with.  Wheu  the  wound  in  the  superficial  tissues  is  extensive,  it  may  be  possible 
to  secure  the  bleeding  ends  of  the  vessel :  but  when  there  is  a  small  punctured  wound,  as  from 
a  penknife  or  piece  of  glass,  pressure  systematically  applied  is  probably  the  best  course  of  treat- 
ment, as  there  is  difficult}7  in  reaching  the  wounded  vessel  without  d'amaging  important  struc- 
tures.  At  the  same  time  it  must  be  admitted  that  pressure  applied  to  the  palm  of  the  hand  to 
arrest  hemorrhage  from  a  wound  of  one  of  the  palmar  arches,  especially  the  deep  arch,  is  apt 
to  be  followed  by  sloughing,  owing  to  the  rigidity  of  the  parts  and  the  facility  with  which  a  con- 
siderable amount  of  pressure  can  be  applied.  In  wounds  of  the  deep  palmar  arch  a  ligature 
may  be  applied  to  the  bleeding  points  from  the  dorsum  of  the  hand  by  resection  of  the  upper 
part  of  the  third  metacarpal  bone.  It  is  useless  in  these  cases  to  ligature  one  of  the  arteries  of 
the  forearm  alone,  and  indeed  simultaneous  ligature  of  both  radial  and  ulnar  arteries  above  the 
wrist  is  often  unsuccessful,  on  account  of  the  anastomosis  carried  on  by  the  carpal  arches. 
Therefore,  upon  the  failure  of  pressure  to  arrest  haemorrhage  it  is  expedient  to  apply  a  liga- 
ture to  the  brachial  artery. 

THE  DESCENDING  AORTA. 

ARTERIES   OF   THE   TRUNK. 

The  Descending  Aorta  is  divided  into  two  portions,  the  thoracic  and  abdominal, 
in  correspondence  with  the  two  great  cavities  of  the  trunk  in  which  it  is  situated. 

THE  THOEACIC  AORTA. 

The  Thoracic  Aorta  commences  at  the  lower  border  of  the  fourth  dorsal  ver- 
tebra, on  the  left  side,  and  terminates  at  the  aortic  opening  in  the  Diaphragm,  in 
fp.»nt  of  the  last  dorsal  vertebra.  At  its  commencement  it  is  situated  on  the  left 
side  of  the  spine  :  it  approaches  the  median  line  as  it  descends,  and  at  its  termina- 
tion lies  directly  in  front  of  the  column.  The  direction  of  this  vessel  being  influ- 
enced by  the  spine,  upon  which  it  rests,  it  describes  a  curve  which  is  concave  forward 
in  rhe  dorsal  region.  As  the  branches  given  off  from  it  are  small,  the  diminution 
in  the  size  of  the  vessel  is  inconsiderable.  It  is  contained  in  the  back  part  of  the 
posterior  mediastinum. 

Eelations. — It  is  in  relation,  in  front*  from  above  downward,  with  the  left  pul- 
monary artery,  the  left  bronchus,  the  pericardium,  and  the  oesophagus ;  behind. 
with  the  vertebral  column  and  the  vena  azygos  minor ;  on  the  right  side,  with  the 
vena  azygos  major  and  thoracic  duct;  on  the  left  side,  with  the  left  pleura  and 
lung.  The  oesophagus  with  its  accompanying  nerves  lies  at  first  on  the  right  side 
of  the  aorta,  but  at  the  lower  part  of  the  thorax  it  gets  in  front  of  the  aorta,  and 
close  to  the  Diaphragm  is  situated  to  its  left  side. 

PLAN  OF  THE  RELATIONS  OF  THE  THORACIC  AORTA. 

In  front. 

Left  pulmonary  artery. 
Left  bronchus. 
Pericardium. 
(Esophagus  (below). 

Right  side.  \  Left  side. 

(Esophagus  Thoracic     \  Pleura. 

Vena  azygos  major.  y      Aoru.        I  Left  lung. 

Thoracic  duct.  V  J  (Esophagus  (below). 

Behind. 

Vertebral  column. 
Vena  azygos  minor. 

The  aorta  is  occasionally  found  to  be  obliterated  at  a  particular  spot — viz.  at  the  junction  of 
the  arch  with  the  thoracic  aorta,  just  below  the  ductus  arteriosus.  \\  hether  this  is  the  result  of 
disease  or  of  congenital  malformation  is  immaterial  to  our  present  purpose ;  it  affords  an  interest- 
ing opportunity  ot  observing  the  resources  of  the  collateral  circulation.  The  course  of  the  anas- 
tomosing vessels,  by  which  the  blood  is  brought  from  the  upper  to  the  lower  part  of  the  artery, 
will  be  found  well  described  in  an  account  of  two  cases  in  the  Pathological  Transactions,  vols.  viii. 
and  x.  In  the  former  (p.  160 j  Mr.  Sydney  Jones  thus  sums  up  the  detailed  description  of  the 


606  THE   ARTERIES. 

anastomosing  vessels:  "The  principal  communications  by  which  the  circulation  was  carried  on, 
WITH— Firstly,  the  internal  mammary,  anastomosing  with  the  intercostal  arteries,  with  the  phrenic 
of  the  abdominal  aorta  by  means  of  the  musculo-phrenic  and  comes  nervi  phrenici,  and  largely 
with  the  deep  epigastric.  Secondly,  the  superior  intercostal,  anastomosing  anteriorly  by  means 
of  a  large  branch  with  the  first  aortic  intercostal,  and  posteriorly  with  the  posterior  branch  of  the 
same  artery.  Thirdly,  the  inferior  thyroid,  by  means  of  a  branch  about  the  size  of  an  ordinary 
radial,  formed  a  communication  with  the  first  aortic  intercostal.  Fourthly,  the  transversalis  colli, 
by  means  of  very  large  communications  with  the  posterior  branches  of  the  intercostals.  Fifthly, 
the  branches  (of  the  subclavian  and  axillary)  going  to  the  side  of  the  chest  were  large,  and 
anastomosed  freely  with  the  lateral  branches  of  the  intercostals."  In  the  second  case  also  (vol. 
x.  p.  97)  Mr.  Wood  describes  the  anastomoses  in  a  somewhat  similar  manner,  adding  the  remark 
that  "  the  blood  which  was  brought  into  the  aorta  through  the  anastomoses  of  the  intercostal 
arteries  appeared  to  be  expended  principally  in  supplying  the  abdomen  and  pelvis,  while  the  sup- 
ply to  the  lower  extremities  had  passed  through  the  internal  mammary  and  epigastrics. " 

Surgical  Anatomy. — The  student  should  now  consider  the  effects  likely  to  be  produced  by 
aneurism  of  the  thoracic  aorta,  a  disease  of  common  occurrence.  When  we  consider  the  great 
depth  of  the  vessel  from  the  surface  and  the  number  of  important  structures  which  surround  it 
on  every  side,  it  may  easily  be  conceived  what  a  variety  of  obscure  symptoms  may  arise  from  dis- 
ease of  this  part  of  the  arterial  system,  and  how  they  may  be  liable  to  be  mistaken  for  those  of 
other  affections.  Aneurism  of  the  thoracic  aorta  most  usually  extends  backward  along  the  left 
side  of  the  spine,  producing  absorption  of  the  bodies  of  the  vertebrae,  with  curvature  of  the  spine ; 
whilst  the  irritation  or  pressure  on  the  cord  will  give  rise  to  pain,  either  in  the  chest,  back,  or 
loins,  with  radiating  pain  in  the  left  upper  intercostal  spaces,  from  pressure  on  the  intercostal 
nerves ;  at  the  same  time  the  tumor  may  project  backward  on  each  side  of  the  spine,  beneath  the 
integument,  as  a  pulsating  swelling,  simulating  abscess  connected  with  diseased  bone,  or  it  may 
displace  the  oesophagus  and  compress  the  lung  on  one  or  the  other  side.  If  the  tumor  extend 
forward,  it  may  press  upon  and  displace  the  heart,  giving  rise  to  palpitation  and  other  symptoms 
of  disease  of  that  organ  ;  or  it  may  displace,  or  even  compress,  the  oasophagus,  causing  pain  and 
difficulty  of  swallowing,  as  in  stricture  of  that  tube  ;  and  ultimately  even  open  into  it  by  ulcera- 
tion.  producing  fatal  haemorrhage.  If  the  disease  extends  to  the  right  side,  it  may  press  upon 
the  thoracic  duct ;  or  it  may  burst  into  the  pleural  cavity  or  into  the  trachea  or  lung ;  and  lastly, 
it  may  open  into  the  posterior  mediastinum. 

BRANCHES  OF  THE  THORACIC  AORTA. 

Pericardiac.  (Esophageal. 

Bronchial.  Posterior  Mediastinal. 

Intercostal. 

The  pericardiac  are  a  few  small  vessels,  irregular  in  their  origin,  distributed  to 
the  pericardium. 

The  bronchial  arteries  are  the  nutrient  vessels  of  the  lungs,  and  vary  in  num- 
ber, size,  and  origin.  That  of  the  right  side  arises  from  the  first  aortic  intercostal, 
or  by  a  common  trunk  with  the  left  bronchial  from  the  front  of  the  thoracic  aorta. 
Those  of  the  left  side,  usually  two  in  number,  arise  from  the  thoracic  aorta,  one  a 
little  lower  than  the  other.  Each  vessel  is  directed  to  the  back  part  of  the  corre- 
sponding bronchus  along  which  it  runs,  dividing  and  subdividing  upon  the  bron- 
chial tube,  supplying  them,  the  cellular  tissue  of  the  lungs,  the  bronchial  glands, 
and  the  oesophagus. 

The  cesophageal  arteries,  usually  four  or  five  in  number,  arise  from  the  front 
of  the  aorta,  and  pass  obliquely  downward  to  the  oesophagus,  forming  a  chain  of 
anastomoses  along  that  tube,  anastomosing  with  the  oesophageal  branches  of  the 
inferior  thyroid  arteries  above,  and  with  ascending  branches  from  the  phrenic  and 
gastric  arteries  below. 

The  posterior  mediastinal  arteries  are  numerous  small  vessels  which  supply  the 
glands  and  loose  areolar  tissue  in  the  mediastinum. 

The  Intercostal  arteries  arise  from  the  back  part  of  the  aorta.  They  are  usu- 
ally eleven  in  number  on  each  side,  the  superior  intercostal  space  being  supplied 
by  the  superior  intercostal,  a  branch  of  the  subclavian,  and  the  second  intercostal 
space  being  supplied  by  a  branch  from  the  superior  intercostal  joining  with  the  first 
aortic  intercostal.  The  lowest  of  these  branches,  the  subcostal  artery,  underlies 
the  last  rib.  The  right  intercostals  are  longer  than  the  left,  on  account  of  the 
position  of  the  aorta  on  the  left  side  of  the  spine :  they  pass  outward,  across  the 
bodies  of  the  vertebras,  to  the  intercostal  spaces,  being  covered  by  the  pleura,  the 


BRAX<'Hi:s    r>r    THE    THORACIC  AORTA. 


607 


oesophagus,  thoracic  duct,  sympathetic  nerve,  and  the  vena  azygos  major :  the  left 
ng^beneath  the  superior  intercostal  vein,  the  vena  azygos  minor,  and  sympa- 
thetic.^   In  the  intercostal  spaces  each  artery  divides  into  two  branches — an  ante- 
rior, or  proper  intercostal  branch  :  and  a  posterior,  or  dorsal  branch.1 

The  anterior  branch  passes  outward,  at  first  lying  upon  the  External  inter- 


FIG.  367. — The  abdominal  aorta  and  its  branches. 

costal  muscle,  covered  in  front  by  the  pleura  and  a  thin  fascia.  It  then  passes 
between  the  two  layers  of  Intercostal  muscles,  and,  having  ascended  obliquely  to 
the  lower  border  of  the  rib  above,  divides,  near  the  angle  of  that  bone,  into  two 
branches :  of  these  the  larger  runs  in  the  groove  on  the  lower  border  of  the  rib 
above ;  the  smaller  branch  along  the  upper  border  of  the  rib  below ;  passing 

1  Mr.  W.  J.  Walsham  describes  a  small  twig  as  being  given  off  from  eacb  intercostal  close  to  its 
origin.  He  states  that  they  can  be  traced  running  between  the  neck  of  the  rib  and  the  transverse 
process  of  the  corresponding  vertebra  ;  they  anastomose  with  similar  twigs  given  off  from  the  inter- 
costal artery  next  below.  In  the  first  and  second  spaces  similar  anastomosing  twigs  are  given  off  from 
the  superior  intercostal  (Journal  of  Anatomy  and  Physiology,  vol.  xvi.  part  iii.  p.  443). 


608  THE   ARTERIES. 

forward,  they  supply  the  Intercostal  muscle,  and  anastomose  with  the  anterior 
intercostal  branches  of  the  internal  mammary,  and  with  the  thoracic  branches  of 
the  axillary  artery.  The  first  aortic  intercostal  anastomoses  with  the  superior 
intercostal,  and  the  last  three  pass  between  the  abdominal  muscles,  inosculating 
with  the  epigastric  in  front  and  with  the  phrenic  and  lumbar  arteries.  Each 
intercostal  artery  is  accompanied  by  a  vein  and  nerve,  the  former  being  above, 
and  the  latter  below,  except  in  the  upper  intercostal  spaces,  where  the  nerve  is  at 
first  above  the  artery.  The  arteries  are  protected  from  pressure  during  the  action 
of  the  Intercostal  muscles  by  fibrous  arches  thrown  across,  and  attached  by  each 
extremity  to  the  bone.  The  lower  intercostal  arteries  are  continued  anteriorly 
from  the  intercostal  spaces  into  the  abdominal  wall,  except  the  last,  the  subcostal, 
which  lies  throughout  its  whole  course  in  the  abdominal  wall,  since  it  is  placed 
below  the  last  rib.  They  pass  behind  the  costal  cartilages  between  the  Internal 
oblique  and  Transversalis  muscle  to  the  sheath  of  the  Rectus,  where  they 
anastomose  with  the  internal  mammary  and  the  deep  epigastric  arteries.  Behind, 
the  subcostal  artery  anastomoses  with  the  first  lumbar  artery. 

The  posterior  or  dorsal  branch  of  each  intercostal  artery  passes  backward 
to  the  inner  side  of  the  anterior  costo-transverse  ligament,  and  divides  into  a 
muscular  branch  which  is  distributed  to  the  muscles  and  integument  of  the  back, 
and  a  spinal  branch  which  enters  the  spinal  canal  through  the  intervertebral 
foramina  to  be  distributed  to  the  spinal  cord  and  its  membranes,  and  to  the 
bodies  of  the  vertebrae  in  the  same  manner  as  the  lateral  spinal  branches  from  the 
vertebral. 

THE  ABDOMINAL  AORTA  (Fig.  367). 

The  Abdominal  Aorta  commences  at  the  aortic  opening  of  the  Diaphragm,  in 
front  of  the  body  of  the  last  dorsal  vertebra,  and,  descending  a  little  to  the  left 
side  of  the  vertebral  column,  terminates  on  the  body  of  the  fourth  lumbar  vertebra, 
commonly  a  little  to  the  left  of  the  middle  line,1  where  it  divides  into  the  two 
common  iliac  arteries.  It  diminishes  rapidly  in  size,  in  consequence  of  the  many 
large  branches  which  it  gives  off.  As  it  lies  upon  the  bodies  of  the  vertebrae 
the  curve  which  it  describes  is  convex  forward,  the  greatest  convexity  correspond- 
ing to  the  third  lumbar  vertebra,  which  is  a  little  above  and  to  the  left  side  of  the 
umbilicus. 

Relations. — It  is  covered,  in  front,  by  the  lesser  omentum  and  stomach,  behind 
which  are  the  branches  of  the  coeliac  axis  and  the  solar  plexus ;  below  these,  by 
the  splenic  vein,  the  pancreas,  the  left  renal  vein,  the  transverse  portion  of  the 
duodenum,  the  mesentery,  and  aortic  plexus.  Behind,  it  is  separated  from  the 
lumbar  vertebrae  by  the  left  lumbar  veins,  the  receptaculum  chyli,  and  thoracic 
duct.  On  the  right  side  it  is  in  relation  with  the  inferior  vena  cava  (the  right 
crus  of  the  Diaphragm  being  interposed  above),  the  vena  azygos  major,  thoracic 
duct,  and  right  semilunar  ganglion ;  on  the  left  side,  with  the  sympathetic  nerve 
and  left  semilunar  ganglion. 

PLAN  OF  THE  RELATIONS  OP  THE  ABDOMINAL  AORTA. 

In  front. 

Lesser  omentum  and  stomach. 

Branches  of  the  coeliac  axis  and  solar  plexus. 

Splenic  vein. 

Pancreas. 

Left  renal  vein. 

Transverse  duodenum. 

Mesentery. 

Aortic  plexus. 

1  Sir  Joseph  Lister,  having  accurately  examined  30  bodies  in  order  to  ascertain  the  exact  point 
of  termination  of  this  vessel,  found  it  "either  absolutely,  or  almost  absolutely,  mesial  in  15,  while  in 
13  it  deviated  more  or  less  to  the  left,  and  in  2  was  slightly  to  the  right"  (System  of  Surgery,  edited  by 
T.  Holmes,  2d  ed.  vol.  v.  p.  652). 


THE   ABDOMINAL    AORTA.  609 

Right  side.  ^x*"~    ~^v 

Right  eras  of  Diaphragm.  \  j^fft  side. 

Interior  vena  cava.  Abdominal  Q  '  . 

Vena   azveos  major.  Aorta-       j  Sympathetic  nerve 

Thoracic  duct.  ^  sem«l™»  ganghon. 

Right  semilunar  ganglion, 

Behind. 

Left  lumbar  veins. 

Receptaculum  chyli. 

Thoracic  duct. 

Vertebral  column. 

Surface  Marking.— In  order  to  map  out  the  abdominal  aorta  on  the  surface  of  the  abdomen, 
a  line  must  be  drawn  from  the  middle  line  of  the  body,  on  a  level  with  the  distal  extremity  of 
the  seventh  costal  cartilage,  downward  and  slightly  to  the  left,  so  that  it  just  skirts  the  umbilicus, 
to  a  zone  drawn  round  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium.  This 
point  is  generally  halt'  an  inch  below  and  to  the  left  of  the  umbilicus,  but  as  the  position  of  this 
structure  varies  with  the  obesity  of  the  individual,  it  is  not  a  reliable  landmark  as  to  the  situation 
of  the  bifurcation  of  the  aorta. 

Surgical  Anatomy. — Aneurisms  of  the  abdominal  aorta  near  the  creliac  axis  communicate 
in  nearly  equal  proportion  with  the  anterior  and  posterior  parts  of  the  artery. 

When  an  aneurismal  sac  is  connected  with  the  back  part  of  the  abdominal  aorta,  it  usually 
produces  absorption  of  the  bodies  of  the  vertebrae,  and  forms  a  pulsating  tumor  that  presents 
itself  in  the  left  hypochondriac  or  epigastric  regions,  and  is  accompanied  by  symptoms  of  dis- 
turbance in  the  alimentary  canal.  Pain  is  invariably  present,  and  is  usually  of  two  kinds — a 
fixed  and  constant  pain  in  the  back,  caused  by  the  tumor  pressing  on  or  displacing  the  branches 
of  the  solar  plexus  and  splanchnic  nerves  ;  and  a  sharp  lancinating  pain,  radiating  along  those 
branches  of  the  lumbar  nerves  which  are  pressed  on  by  the  tumor ;  hence  the  pain  in  the  loins, 
the  testes.  the  hypogaatnnm,  and  in  the  lower  limb  (usually  of  the  left  side).  This  form  of 
aneurism  usually  bursts  into  the  peritoneal  cavity  or  behind  the  peritoneum  in  the  left  hypo- 
chondriac region :  or  it  may  form  a  large  aneurismal  sac,  extending  down  as  low  as  Poupart's 
ligament :  haemorrhage  in  these  cases  being  generally  very  extensive,  but  slowly  produced,  and 
not  rapidly  fatal. 

When  an  aneurismal  sac  is  connected  with  the  front  of  the  aorta  near  the  coeliac  axis,  it 
forms  a  pulsating  tumor  in  the  left  hypochondriac  or  epigastric  regions,  usually  attended  with 
symptoms  of  disturbance  of  the  alimentary  canal,  as  sickness,  dyspepsia,  or  constipation,  and 
accompanied  by  pain,  which  is  constant,  but  nearly  always  fixed  in  the  loins,  epigastrium,  or 
some  part  of  the  abdomen :  the  radiating  pain  being  rare,  as  the  lumbar  nerves  are  seldom 
implicated.  This  form  of  aneurism  may  burst  into  the  peritoneal  cavity  or  behind  the  peritoneum, 
between  the  layers  of  the  mesentery,  or,  more  rarely,  into  the  duodenum  ;  it  rarely  extends  back- 
ward so  as  to  affect  the  spine. 

The  abdominal  aorta  has  been  tied  several  times,  and  although  none  of  the  patients  perma- 
nently recovered,  still,  as  one  of  them  lived  as  long  as  ten  days,  the  possibility  of  the  re- 
establishment  of  the  circulation  may  be  considered  to  be  proved.  In  the  lower  animals  this 
artery  has  been  often  successful!}'  tied.  The  vessel  may  be  reached  in  several  ways.  In  the 
original  operation,  performed  by  Sir  A.  Cooper,  an  incision  was  made  in  the  linea  alba,  the 
peritoneum  opened  in  front,  the  finger  carried  down  amongst  the  intestines  toward  the  spine,  the 
peritoneum  again  opened  behind  by  scratching  through  the  mesentery,  and  the  vessel  thus  reached. 
Or  either  of  the  operations  described  below  for  securing  the  common  iliac  artery  may,  by  extend- 
inrr  the  dissection  a  sufficient  distance  upward,  be  made  use  of  to  expose  the  aorta.  The  chief 
dim  julty  in  the  dead  subject  consists  in  isolating  the  artery  in  consequence  of  its  great  depth  ;  but 
in  the  living  subject  the  embarrassment  resulting  from  the  proximity  of  the  aneurismal  tumor,  and 
the  great  probability  of  disease  in  the  vessel  itself,  add  to  the  dangers  and  difficulties  of  this  for- 
midable operation  so  greatly  that  it  is  very  doubtful  whether  it  ought  ever  to  be  performed. 

The  collateral  circulation  would  be  carried  on  by  the  anastomosis  between  the  internal 
mammary  and  the  deep  epigastric  ;  by  the  free  communication  between  the  superior  and  inferior 
m«->'.-nterics  if  the  ligature  were  placed  above  the  latter  vessel ;  or  by  the  anastomosis  between 
the  inferior  inesenteric  and  the  internal  pudic  when  (as  is  more  common)  the  point  of  ligature  is 
below  the  origin  of  the  inferior  inesenteric :  and  possibly  by  the  anastomoses  of  the  lumbar 
arteries  with  the  branches  of  the  internal  iliac. 

The  circulation  through  the  abdominal  aorta  may  be  commanded,  in  thin  persons,  by  firm 
pressure  with  the  fingers.  A  tourniquet  has  been  invented  for  this  purpose  which  is  sometimes 
used  in  amputation  at  the  hip-joint  and  some  other  operations. 

BRANCHES  OF  THE  ABDOMINAL  AORTA. 

Phrenic.  Superior  Mesenteric.          Ovarian  in  female. 

j'  Gastric.  Suprarenal.                           Inferior  Mesenteric. 

Coeliac  Axis.   -    Hepatic.  Renal.                                    Lumbar. 

(  Splenic.  Spermatic  in  male.             Sacra  Media. 


610 


THE   ARTERIES. 


The  branches  may  be  divided  into  two  sets  :  1.  Those  supplying  the  viscera. 
2.   Those  distributed  to  the  Avails  of  the  abdomen. 


Visceral  Branches. 

(  Gastric. 
Coeliac  Axis.  <  Hepatic. 

(  Splenic. 

Superior  Mesenteric. 
Inferior  Mesenteric. 
Suprarenal. 


Renal. 

Spermatic  or  Ovarian. 

Parietal  Branches. 

Phrenic. 
Lumbar. 
Sacra  Media. 


Visceral  Brandies  of  the  Abdominal  Aorta. 
The  Coeliac  Axis  (Fig.  368). 

To  expose  this  artery  raise  the  liver,  draw  down  the  stomach,  and  then  tear  through  the 
layers  of  the  lesser  omentum. 

The  Coeliac  Axis  is  a  short  thick  trunk,  about  half  an  inch  in  length,  which 


Cystic  artery 


FIG.  368.— The  cceliacaxis  and  its  branches,  the  liver  having  been  raised  and  the  lesser  omentum  removed. 

arises  from  the  aorta  opposite  the  margin  of  the  Diaphragm,  and,  passing  nearly 
horizontally  forward  (in  the  erect  posture),  divides  into  three  large  branches,  the 
gastric,  hepatic,  and  splenic,  occasionally  giving  off  one  of  the  phrenic  arteries. 

Eelations. — It  is  covered  by  the  lesser  omentum.  On  the  right  side  it  is  in 
relation  with  the  right  semilunar  ganglion,  and  the  lobus  Spigelii ;  on  the  left  side, 
with  the  left  semilunar  ganglion  and  cardiac  end  of  the  stomach.  Below,  it  rests 
upon  the  upper  border  of  the  pancreas. 


THE    CfELIAC  AXIS.  611 

The  Gastric  Artery  (Coronaria  ventriculi),  the  smallest  of  the  three  branches 
of  the  coeliac  axis,  passes  upward  and  to  the  left  side,  to  the  cardiac  orifice  of 
the  stomach,  distributing  branches  to  the  oesophagus  which  anastomose  with  the 
aortic  oesophageal  arteries ;  others  supply  the  cardiac  end  of  the  stomach,  inoscu- 
lating with  branches  of  the  splenic  artery  ;  it  then  passes  from  left  to  right, 
along  the  lesser  curvature  of  the  stomach  to  the  pylorus,  lying  in  its  course 
between  the  layers  of  the  lesser  omentum,  and  giving  branches  to  both  surfaces 
of  the  organ  :  at  its  termination  it  anastomoses  with  the  pyloric  branch  of  the 
hepatic. 

The  Hepatic  Artery  in  the  adult  is  intermediate  in  size  between  the  gastric  and 
splenic ;  in  the  foetus  it  is  the  largest  of  the  three  branches  of  the  coeliac  axis.  It 
is  first  directed  forward  and  to  the  right,  to  the  upper  margin  of  the  pyloric  end 
of  the  stomach,  crossing  under  the  foramen  of  Winslow.  It  then  passes  upward 
between  the  layers  of  the  lesser  omentum,  near  the  anterior  margin  of  the  fora- 
men of  Winslow,  to  the  transverse  fissure  of  the  liver,  where  it  divides  into  two 
branches,  right  and  left,  which  supply  the  corresponding  lobes  of  that  organ, 
accompanying  the  ramifications  of  the  vena  portse  and  hepatic  duct.  The  hepatic 
artery,  in  its  course  along  the  right  border  of  the  lesser  omentum,  is  in  relation 
with  the  ductus  communis  choledochus  and  portal  veins,  the  duct  lying  to  the 
right  of  the  artery  and  the  vena  portse  behind. 

Its  branches  are — the 

Pyloric. 

i      ,       v       (  Gastro-epiploica  Dextra. 
(jastro-duodenahs    <  ^  5      j     j       r    a 

\  Pancreatico-duodenahs  Superior. 

Cystic. 

The  pyloric  branch  arises  from  the  hepatic,  above  the  pylorus,  descends  to  the 
pyloric  end  of  the  stomach,  and  passes  from  right  to  left  along  its  lesser  curvature, 
supplying  it  with  branches  and  inosculating  with  the  gastric  artery. 

The  gastro-duodenalis  (Fig.  369)  is  a  short  but  large  branch  which  descends, 
near  the  pylorus,  behind  the  first  portion  of  the  duodenum,  at  the  lower  border  of 
which  it  divides  into  two  branches,  the  gastro-epiploica  dextra  and  the pancreatico- 
duodenalis  superior.  Previous  to  its  division  it  gives  off  two  or  three  small  inferior 
pyloric  branches  to  the  pyloric  end  of  the  stomach  and  pancreas. 

The  gastro-epiploica  dextra  runs  from  right  to  left  along  the  greater  curvature 
of  the  stomach,  between  the  layers  of  the  great  omentum,  anastomosing  about  the 
middle  of  the  lower  border  of  the  stomach  with  the  gastro-epiploica  sinistra  from 
the  splenic  artery.  This  vessel  gives  off  numerous  branches,  some  of  which  ascend 
to  supply  both  surfaces  of  the  stomach,  whilst  others  descend  to  supply  the  great 
omentum. 

The  pancreatico-duodenalis  superior  descends  between  the  contiguous  margins 
of  the  duodenum  and  pancreas.  It  supplies  both  these  organs,  and  anastomoses 
with  the  inferior  pancreatico-duodenal  branch  of  the  superior  mesenteric  artery 
and  with  the  pancreatic  branches  of  the  splenic. 

The  cystic  artery  (Fig.  368),  usually  a  branch  of  the  right  hepatic,  passes 
upward  and  forward  along  the  neck  of  the  gall-bladder,  and  divides  into  two 
branches,  one  of  which  ramifies  on  its  free  surface,  the  other  between  it  and  the 
substance  of  the  liver. 

The  Splenic  Artery,  in  the  adult,  is  the  largest  of  the  three  branches  of  the 
coeliac  axis,  and  is  remarkable  for  the  extreme  -tortuosity  of  its  course.  It  passes 
horizontally  to  the  left  side  along  the  upper  border  of  the  pancreas,  accompanied 
by  the  splenic  vein,  which  lies  below  it,  and  on  arriving  near  the  spleen  divides 
into  branches,  some  of  which  enter  the  hilum  of  that  organ  to  be  distributed  to  its 
structure,  whilst  others  are  distributed  to  the  great  end  of  the  stomach.  Its 
branches  are — the 

Pancreaticse  Parvae.  Gastric  (Vasa  Brevia). 

Pancreatica  Magnu.  Gastro-epiploica  Sinistra. 


612 


THE   ARTERIES. 


The  pancreatic  are  numerous  small  branches  derived  from  the  splenic  as  it 
runs  behind  the  upper  border  of  the  pancreas,  supplying  its  middle  and  left  parts. 
One  of  these,  larger  than  the  rest,  is  given  off  from  the  splenic  near  the  left 
extremity  of  the  pancreas ;  it  runs  from  left  to  right  near  the  posterior  surface  of 
the  gland,  following  the  course  of  the  pancreatic  duct,  and  is  called  the  pancreatica 
magna.  These  vessels  anastomose  with  the  pancreatic  branches  of  the  pancreatico- 


Great 


FIG.  369. — The  coeliac  axis  and  its  branches,  the  stomach  having  been  raised  and  the  transverse  meso-colon 
removed  (semi-diagrammatic). 

duodenal  arteries,  derived  from  the  hepatic  on  the  one  hand  and  superior  mesenteric 
on  the  other. 

The  gastric  (vasa  brevia)  consists  of  from  five  to  seven  small  branches,  which 
arise  either  from  the  termination  of  the  splenic  artery  or  from  its  terminal  branches, 
and,  passing  from  left  to  right,  between  the  layers  of  the  gastro-splenic  omentum, 
are  distributed  to  the  great  curvature  of  the  stomach,  anastomosing  with  branches 
of  the  gastric  and  gastro-epiploica  sinistra  arteries. 

The  gastro-epiploica  sinistra,  the  largest  branch  of  the  splenic,  runs  from  left 
to  right  along  the  great  curvature -of  the  stomach,  between  the  layers  of  the  great 
omentum,  and  anastomoses  with  the  gastro-epiploica  dextra.  In  its  course  it 
distributes  several  branches  to  the  stomach,  which  ascend  upon  both  surfaces ; 
others  descend  to  supply  the  omentum. 

The  Superior  Mesenteric  Artery  (Fig.  370). 

In  order  to  expose  this  vessel  raise  the  great  omentum  and  transverse  colon,  draw  down  the 
small  intestines,  and  cut  through  the  peritoneum  where  the  transverse  meso-colon  and  mesen- 


THE   SUPERIOR    MESEXTERIC  ARTERY. 


613 


tery  join :  the  artery  will  then  be  exposed  just  as  it  issues  from  beneath  the  lower  border  of  the 
pancreas. 

The  Superior  Mesenteric  Artery  supplies  the  whole  length  of  the  small  intestine, 
except  the  first  part  of  the  duodenum ;  it  also  supplies  the  caecum,  ascending 
and  transverse  colon  ;  it  is  a  vessel  of  large  size,  arising  from  the  fore  part  of  the 
aorta  about  a  quarter  of  an  inch  below  the  coeliac  axis  :  being  covered  at  its  origin 
bv  the  splenic  vein  and  pancreas.  It  passes  forward,  between  the  pancreas  and 
transverse  portion  of  the  duodenum,  crosses  in  front  of  this  portion  of  the  intes- 


FIG.  370.— The  superior  mesenteric  artery  and  its  branches. 


tine,  and  descends  between  the  layers  of  the  mesentery  to  the  right  iliac  fossa, 
where  it  terminates,  considerably  diminished  in  size.  In  its  course  it  forms  an 
arch,  the  convexity  of  which  is  directed  forward  and  downward  to  the  left  side, 
the  concavity  backward  and  upward  to  the  right.  It  is  accompanied  by  the 
superior  mesenteric  vein,  and  is  surrounded  by  a  superior  mesenteric  plexus  of 
nerves.  Its  branches  are — the 

Inferior  Pancreatico-duodenal.  Heo-colic. 

Vasa  Intestini  Tenuis.  Colica  Dextra. 

Colica  Media. 

The  Inferior  pancreatico-duodenal  is  given  off  from   the   superior  mesenteric 
behind  the  pancreas,  and  is   distributed  to  the  head  of  the   pancreas  with   the 


614  THE   ARTERIES. 

transverse  and  descending  portions  of  the  duodenum,  anastomosing  with  the 
superior  pancreatico-duodenal  artery. 

The  vasa  intestini  tenuis  arise  from  the  convex  side  of  the  superior  mesenteric 
artery.  They  are  usually  from  twelve  to  fifteen  in  number,  and  are  distributed  to 
the  jejunum  and  ileum.  They  run  parallel  with  one  another  between  the  layers 
of  the  mesentery,  each  vessel  dividing  into  two  branches,  which  unite  with  a  sim- 
ilar branch  on  each  side,  forming  a  series  of  arches  the  convexities  of  which  are 
directed  toward  the  intestine.  From  this  first  set  of  arches  branches  arise, 
which  again  unite  with  similar  branches  from  either  side,  and  thus  a  second  series 
of  arches  is  formed ;  and  from  these  latter,  a  third,  and  a  fourth,  or  even  fifth, 
series  of  arches  is  constituted,  diminishing  in  size  the  nearer  they  approach  the 
intestine.  From  the  terminal  arches  numerous  small  straight  vessels  arise  which 
encircle  the  intestine,  upon  which  they  are  distributed,  ramifying  thickly  between 
its  coats. 

The  ileo-colic  artery  is  the  lowest  branch  given  off  from  the  concavity  of  the 
superior  mesenteric  artery.  It  descends  between  the  layers  of  the  mesentery  to 
the  right  iliac  fossa,  where  it  divides  into  two  branches.  Of  these,  the  inferior 
one  inosculates  with  the  lowest  branches  of  the  vasa  intestini  tenuis,  from  the 
convexity  of  which  branches  proceed  to  supply  the  termination  of  the  ileum,  the 
caecum  and  appendix  caeci,  and  the  ileo-caecal  valve.  The  superior  division  inos- 
culates with  the  colica  dextra  and  supplies  the  commencement  of  the  colon. 

The  colica  dextra  arises  from  about  the  middle  of  the  concavity  of  the  superior 
mesenteric  artery,  and,  passing  behind  the  peritoneum  to  the  middle  of  the 
ascending  colon,  divides  into  two  branches — a  descending  branch,  which  inoscu- 
lates with  the  ileo-colic ;  and  the  ascending  branch,  which  anastomoses  with  the 
colica  media.  These  branches  form  arches,  from  the  convexity  of  which  vessels 
are  distributed  to  the  ascending  colon.  The  branches  of  this  vessel  are  covered 
with  peritoneum  only  on  their  anterior  aspect. 

The  colica  media  arises  from  the  upper  part  of  the  concavity  of  the  superior 
mesenteric,  and,  passing  forward  between  the  layers  of  the  transverse  meso-colon, 
divides  into  two  branches,  the  one  on  the  right  side  inosculating  Avith  the  colica 
dextra ;  that  on  the  left  side,  with  the  colica  sinistra,  a  branch  of  the  inferior 
mesenteric.  From  the  arches  formed  by  their  inosculation  branches  are  distrib- 
uted to  the  transverse  colon.  The  branches  of  this  vessel  lie  between  two  layers 
of  peritoneum. 

The  Inferior  Mesenteric  Artery  (Fig.  371). 

In  order  to  expose  this  vessel  draw  the  small  intestines  and  mesentery  over  to  the  right 
side  of  the  abdomen,  raise  the  transverse  colon  toward  the  thorax,  and  divide  the  peritoneum 
covering  the  left  side  of  the  aorta. 

The  Inferior  Mesenteric  Artery  supplies  the  descending  and  sigmoid  flexure  of 
the  colon  and  the  greater  part  of  the  rectum.  It  is  smaller  than  the  superior 
mesenteric,  and  arises  from  the  left  side  of  the  aorta,  between  one  and  two 
inches  above  its  division  into  the  common  iliacs.  It  passes  downward  to  the  left 
iliac  fossa,  and  then  descends,  between  the  layers  of  the  meso-rectum,  into  the 
pelvis,  under  the  name  of  the  superior  hcemorrhoidal  artery.  It  lies  at  first  in  close 
relation  with  the  left  side  of  the  aorta,  and  then  passes  as  the  superior  haemor- 
rhoidal  in  front  of  the  left  common  iliac  artery.  Its  branches  are — the 

Colica  Sinistra.  Sigmoid. 

Superior  Haemorrhoidal. 

The  colica  sinistra  passes  behind  the  peritoneum,  in  front  of  the  left  kidney, 
to  reach  the  descending  colon,  and  divides  into  two  branches — an  ascending 
branch,  which  inosculates  with  the  colica  media;  and  a  descending  branch,  which 
anastomoses  with  the  sigmoid  artery.  From  the  arches  formed  by  these  inoscu- 
lations branches  are  distributed  to  the  descending  colon. 

The  sigmoid  artery  runs  obliquely  downward  across  the  Psoas  muscle  to  the 


THE   8l'Pn.\UKXAL    ARTERIES. 


615 


sigmoid  flexure  of  the  colon,  and  divides  into  branches  which  supply  that  part  of 
the  intestine,  anastomosing  above  with  the  colica  sinistra,  and  below  with  the 
superior  hteniorrhoidal  artery.  This  vessel  is  sometimes  replaced  by  three  or  four 
small  branches. 

The  superior  haemorrhoidal  artery,  the  continuation  of  the  inferior  mesenteric, 
descends  into  the  pelvis  between  the  layers  of  the  meso-rectum,  crossing,  in  its 


Middle  7we 
Inferior  hxmorrhoidaL' 


TIG.  371. — The  inferior  mesenteric  and  its  branches. 

course,  the  ureter  and  left  common  iliac  vessels.  It  divides  into  two  branches, 
which  descend  one  on  each  side  of  the  rectum,  and  about  five  inches  from  the  anus 
break  up  into  several  small  branches,  which  are  distributed  between  the  mucous 
and  muscular  coats  of  that  tube,  nearly  as  far  as  its  lower  end,  anastomosing 
with  each  other,  with  the  middle  haemorrhoidal  arteries,  branches  of  the  internal 
iliac,  and  with  the  inferior  haemorrhoidal  branches  of  the  internal  pudic. 


The  Suprarenal  Arteries. 

The  suprarenal  arteries  ( Fig.  367)  (middle  suprarenal)  are  two  small  vessels 
which  arise,  one  on  each  side  of  the  aorta,  opposite  the  superior  mesenteric  artery. 
They  pass  obliquely  upward  and  outward,  over  the  crura  of  the  Diaphragm,  to 
the  under  surface  of  the  suprarenal  capsules,  to  which  they  are  distributed,  anasto- 
mosing with  capsular  branches  from  the  phrenic  and  renal  arteries.  In  the  adult 
these  arteries  are  of  small  size  ;  in  the  foetus  they  are  as  large  as  the  renal  arteries. 


616  THE   ARTERIES. 

The  Renal  Arteries. 

The  renal  arteries  are  two  large  trunks  which  arise  from  the  sides  of  the 
aorta  immediately  below  the  superior  mesenteric  artery.  Each  is  directed 
outward  across  the  crus  of  the  Diaphragm,  so  as  to  form  nearly  a  right  angle 
with  the  aorta.  The  right  is  longer  than  the  left,  on  account  of  the  position  of 
the  aorta ;  it  passes  behind  the  inferior  vena  cava.  The  left  is  somewhat  higher 
than  the  right.  Previously  to  entering  the  kidney  each  artery  divides  into  four 
or  five  branches  which  are  distributed  to  its  substance.  At  the  hilum  these 
branches  lie  between  the  renal  vein  and  ureter,  the  vein  being  usually  in  front,  the 
ureter  behind.  Each  vessel  gives  off  some  small  branches  (inferior  suprarenal}  to 
the  suprarenal  capsule,  the  ureter,  and  the  surrounding  cellular  tissue  and  muscles. 
Frequently  there  is  a  second  renal  artery,  which  is  given  off  from  the  abdominal 
aorta  at  a  lower  level  and  supplies  the  lower  portion  of  the  kidney.  It  is  termed 
the  inferior  renal  artery. 

The  Spermatic  Arteries. 

The  spermatic  arteries  are  distributed  to  the  testes  in  the  male  and  to  the 
ovaria  in  the  female.  They  are  two  slender  vessels,  of  considerable  length,  which 
arise  from  the  front  of  the  aorta  a  little  below  the  renal  arteries.  Each  artery 
passes  obliquely  outward  and  downward  behind  the  peritoneum,  resting  on  the 
Psoas  muscle,  the  right  spermatic  lying  in  front  of  the  inferior  vena  cava,  the  left 
behind  the  sigmoid  flexure  of  the  colon.  It  then  crosses  obliquely  over  the  ureter 
and  the  lower  part  of  the  external  iliac  artery  to  reach  the  internal  abdominal 
ring,  through  which  it  passes,  and  accompanies  the  other  constituents  of  the 
spermatic  cord  along  the  inguinal  canal  to  the  scrotum,  where  it  becomes  tortuous, 
and  divides  into  several  branches,  two  or  three  of  Avhich  accompany  the  vas 
deferens  and  supply  the  epididymis,  anastomosing  with  the  artery  of  the  vas 
deferens  ;  others  pierce  the  back  part  of  the  tunica  albuginea,  and  supply  the 
substance  of  the  testis. 

The  Ovarian  Arteries. 

The  ovarian  arteries  are  shorter  than  the  spermatic,  and  do  not  pass  out  of 
the  abdominal  cavity.  The  origin  and  course  of  the  first  part  of  the  artery  are  the 
same  as  the  spermatic  in  the  male,  but  on  arriving  at  the  margin  of  the  pelvis  the 
ovarian  artery  passes  inward,  between  the  two  laminae  of  the  broad  ligament  of 
the  uterus,  to  be  distributed  to  the  ovary.  One  or  two  small  branches  supply  the 
Fallopian  tube ;  another  passes  on  to  the  side  of  the  uterus  and  anastomoses  with 
the  uterine  arteries.  Other  offsets  are  continued  along  the  round  ligament, 
through  the  inguinal  canal,  to  the  integument  of  the  labium  and  groin. 

At  an  early  period  of  foetal  life,  when  the  testes  or  ovaries  lie  by  the  side  of  the 
spine  below  the  kidneys,  the  spermatic  or  ovarian  arteries  are  short ;  but  as  these 
organs  descend  from  the  abdomen  into  the  scrotum  the  arteries  become  gradually 
lengthened. 

Parietal  Branches  of  the  Abdominal  Aorta. 
The  Phrenic  Arteries. 

The  phrenic  arteries  are  two  small  vessels  which  present  much  variety  in 
their  origin.  They  may  arise  separately  from  the  front  of  the  aorta,  immediately 
above  the  cceliac  axis,  or  by  a  common  trunk,  which  may  spring  either  from  the 
aorta  or  from  the  cceliac  axis.  Sometimes  one  is  derived  from  the  aorta,  and  the 
other  from  one  of  the  renal  arteries.  In  only  one  out  of  thirty-six  cases  examined 
did  these  arteries  arise  as  two  separate  vessels  from  the  aorta.  They  diverge  from 
one  another  across  the  crura  of  the  Diaphragm,  and  then  pass  obliquely  upward 
and  outward  upon  its  under  surface.  The  left  phrenic  passes  behind  the  oesoph- 
agus and  runs  forward  on  the  left  side  of  the  cesophageal  opening.  The  right 
phrenic  passes  behind  the  inferior  vena  cava,  and  ascends  along  the  right  side  of 
the  aperture  for  transmitting  that  vein.  Near  the  back  part  of  the  central  tendon 
each  vessel  divides  into  two  branches.  The  internal  branch  runs  forward  to  the 
front  of  the  thorax,  supplying  the  Diaphragm  and  anastomosing  with  its  fellow  of 


THE   SACRA    MEDIA.  617 

the  opposite  side,  and  with  the  musculo-phrenic  and  comes  nervi  phrenici,  branches 
of  the  internal  mammary.  The  external  branch  passes  toward  the  side  of  the 
thorax  and  inosculates  with  the  intercostal  arteries.  The  internal  branch  of  the 
right  phrenic  gives  off  a  few  vessels  to  the  inferior  vena  cava.  and  the  left  one 
some  branches  to  the  oesophagus.  Each  vessel  also  sends  capsular  branches 
/•/"/•  supr<ir'  nal)  to  the  suprarenal  capsule  of  its  own  side.  The  spleen  on  the 
left  side  and  the  liver  on  the  right  also  receive  a  few  branches  from  these  vessels. 

The  Lumbar  Arteries. 

The  lumbar  arteries  are  analogous  to  the  intercostal.  They  are  usually  four 
in  number  on  each  side,  and  arise  from  the  back  part  of  the  aorta,  nearly  at  right 
angles  with  that  vessel.  They  pass  outward  and  backward,  around  the  sides  of 
the  body  of  the  lumbar  vertebra,  behind  the  sympathetic  nerve  and  the  Psoas 
magnus  muscle,  those  on  the  right  side  being  covered  by  the  inferior  vena  cava, 
and  the  two  upper  ones  on  each  side  by  the  crura  of  the  Diaphragm.  In  the 
interval  between  the  transverse  processes  of  the  vertebrae  each  artery  divides  into 
a  'lor&.d  and  an  abdominal  branch. 

The  dorsal  branch  gives  off,  immediately  after  its  origin,  a  spinal  branch,  which 
enters  the  spinal  canal :  it  then  continues  its  course  backward  between  the  trans- 
verse pr  £  md  is  distributed  to  the  muscles  and  integument  of  the  back, 
anastomosing  with  the  similar  branches  of  the  adjacent  lumbar  arteries  and  with 
the  posterior  branches  of  the  intercostal  arteries. 

The  spinal  branch  enters  the  spinal  canal  through  the  intervertebral  foramen, 
to  be  distributed  to  the  spinal  cord  and  its  membranes  and  to  the  bodies  of  the 
vertebrae  in  the  same  manner  as  the  lateral  spinal  branches  from  the  vertebral 
page  582). 

The  abdominal  branches  pass  outward,  having  a  variable  relation  to  the 
Quadratus  lurnborum  muscle.  Most  frequently  the  first  branch  passes  in  front 
:>f  the  muscle  and  the  others  behind  it ;  sometimes  the  order  is  reversed  and  the 
lowest  branch  passes  in  front  of  the  muscle.  At  the  outer  border  of  the  Quadratus 
they  are  continued  between  the  abdominal  muscles,  anastomose  with  branches  of 
the  epigastric  and  internal  mammary  in  front,  the  intercostals  above,  and  those  of 
the  ilio-lumbar  and  circumflex  iliac  below. 

The  Sacra  Media. 

The  Middle  Sacral  Artery  is  a  small  vessel  about  the  size  of  a  crow-quill, 
which  arises  from  the  back  part  of  the  aorta  just  at  its  bifurcation.  It  descends 
upon  the  last  lumbar  vertebra,  and  along  the  middle  line  of  the  front  of  the 
sacrum,  to  the  upper  part  of  the  coccyx,  where  it  anastomoses  with  the  lateral 
sacral  arteries,  and  terminates  in  a  minute  branch,  which  runs  down  to  the  situation 
of  the  body  presently  to  be  described  as  "  Luschka's  gland."  From  it  branches 
arise  which  run  through  the  meso-rectum  to  supply  the  posterior  surface  of  the  rec- 
tum. Other  branches  are  given  off  on  each  side,  which  anastomose  with  the  lateral 
sacral  arteries,  and  send  off  small  offsets  which  enter  the  anterior  sacral  foramina. 

The  artery  is  the  representative  of  the  caudal  prolongation  of  the  aorta  of 
animals,  and  its  lateral  branches  correspond  to  the  intercostal  and  lumbar  arteries 
in  the  dorsal  and  lumbar  regions. 

Coccygeal  Gland,  or  Luschka's  Gland. — Lying  near  the  tip  of  the  coccyx  in  a 
small  tendinous  interval  formed  by  the  union  of  the  Levator  ani  muscles  of  each 
side,  and  just  above  the  coccygeal  attachment  of  the  Sphincter  ani,  is  a  small 
conglobate  body  about  as  large  as  a  lentil  or  a  pea.  first  described  by  Luschka  .' 
and  named  by  him  the  coccygeal  gland.  Its  most  obvious  connections  are  with  the 
arteries  of  the  part. 

Structure. — It  consists  of  a  congeries  of  small  arteries  with  little  aneurismal 
dilatations  derived  from  the  middle  sacral  and  freely  communicating  with  each 

1  Der  Hirnanhang  und  die  Stelesdruse  des  Mensehen,  Berlin,  1860 ;  Anatomie  des  Menschen,  Tubingen, 
1864,  vol.  ii.  pt.  -2,  p.  187. 


618 


THE   ARTERIES. 


other.  These  vessels  are  enclosed  in  one  or  more  layers  of  polyhedral  granular  cells, 
and  the  whole  structure  is  invested  in  a  capsule  of  connective  tissue  which  sends 
in  trabeculse,  dividing  the  interior  into  a  number  of  spaces  in  which  the  vessels 
and  cells  are  contained.  Nerves  pass  into  this  little  body  from  the  sympathetic, 
but  their  mode  of  termination  is  unknown.  Macalister  believes  the  glomerulus  of 
vessels  "  consists  of  the  condensed  and  convoluted  metameric  dorsal  arteries  of  the 
caudal  segments  imbedded  in  tissue  which  is  possibly  a  small  persisting  fragment 
of  the  neurenteric  canal." 


THE  COMMON  ILIAC  ARTERIES. 

The  abdominal  aorta  divides  into  the  two  common  iliac  arteries.  The  bifurca- 
tion usually  takes  place  on  the  left  side  of  the  body  of  the  fourth  lumbar  vertebra. 
This  point  corresponds  to  the  left  side  of  the  umbilicus,  and  is  on  a  level  with  a 
line  drawn  from  the  highest  point  of  one  iliac  crest  to  the  other.  The  common 
iliac  arteries  are  about  two  inches  in  length ;  diverging  from  the  termination  of 
the  aorta,  they  pass  downward  and  outward  to  the  margin  of  the  pelvis,  and 
divide  opposite  the  intervertebral  substance,  between  the  last  lumbar  vertebra 
and  the  sacrum  into  two  branches,  the  external  and  internal  iliac  arteries,  the 
former  supplying  the  lower  extremity  ;  the  latter,  the  viscera  and  parietes  of  the 
pelvis. 

The  right  common  iliac  is  somewhat  larger  than  the  left,  and  passes  more  ob- 
liquely across  the  body  of  the  last  lumbar  vertebra.  In  front  of  it  are  the  perito- 
neum, the  small  intestine,  branches  of  the  sympathetic  nerve,  and,  at  its  point  of 
division,  the  ureter.  Behind,  it  is  separated  from  the  last  two  lumbar  vertebrae  by 
the  two  common  iliac  veins.  On  its  outer  side,  it  is  in  relation  with  the  inferior  vena 
cava  and  the  right  common  iliac  vein  above,  and  the  Psoas  magnus  muscle  below. 

The  left  common  iliac  is  in  relation,  in  front,  with  the  peritoneum,  the  small  in- 
testine, branches  of  the  sympathetic  nerve,  and  the  superior  haemorrhoidal  artery, 
and  is  crossed  at  its  point  of  bifurcation  by  the  ureter.  The  left  common  iliac  vein 
lies  partly  on  the  inner  side  and  partly  beneath  the  artery ;  on  its  outer  side  the 
artery  is  in  relation  with  the  Psoas  magnus  muscle. 

PLAN  OF  THE  RELATIONS  OF  THE  COMMON  ILIAC  ARTERIES. 


In  front. 
Peritoneum. 
Small  intestines. 
Sympathetic  nerves. 
Ureter. 

Outer  side. 

Vena  cava. 
Right  common 

iliac  vein. 
Psoas  muscle. 


Inner  side. 


In  front. 

Peritoneum,  small  intestines. 
Sympathetic  nerves. 
Superior  haemorrhoidal  artery. 
Ureter. 

Outer  side. 


Left  common     / 
iliac  vein. 


Psoas  muscle. 


Beld 'ml. 

Last  two  lumbar  vertebrae. 
Left  common  iliac 


Behind. 

Last  two  lumbar  vertebrae. 
Right  and  left  common 

iliac  veins.  vein. 

Branches. — The  common  iliac  arteries  give  off  small  branches  to  the  peritoneum 
Psoas  magnus,  ureters,  and  the  surrounding  cellular  tissue,  and  occasionally  give 
origin  to  the  ilio-lumbar  or  renal  arteries. 

o 

Peculiarities. — The  point  of  origin  varies  according  to  the  bifurcation  of  the  aorta.  In 
three-fourths  of  a  large  number  of  cases  the  aorta  bifurcated  cither  upon  the  fourth  lumbar 
vertebra  or  upon  the  intervertebral  disk  between  it  and  the  fifth,  the  bifurcation  being,  in  one 
case  out  of  nine  below,  and  in  one  out  of  eleven  above,  this  point.  In  ten  out  of  every  thirteen 
cases  the  vessel  bifurcated  within  half  an  inch  above  or  below  the  level  of  the  crest  of  the  ilium 
more  frequently  below  than  above. 

The  point  of  division  is  subject  to  great  variety.  In  two-thirds  of  a  large  number  of  cases 
it  was  between  the  last  lumbar  vertebra  and  the  upper  border  of  the  sacrum  being  above  that 


THE    COMMOX  ILIAC   ARTERIES. 


619 


point  in  one  case  out  of  eight ;  and  below  it  in  one  ease  out  of  six.  The  left  common  iliac 
artery  divides  lower  down  more  frequently  than  the  right. 

The  rilntir,  /myth.  also,  of  the  two  common  iliac  arteries  varies.  The  right  common  iliac 
was  the  lonirer  in  sixty-three  cases,  the  left  in  fifty-two,  whilst  they  were  both  equal  in  fifty- 
three.  The  length  of  the  arteries  varied  in  five-sevenths  of  the  cases  examined  from  an  inch 
and  a  half  to  three  inches :  in  about  half  of  the  remaining  cases  the  artery  was  longer  and  in 
the  other  half  shorter,  the  minimum  length  being  less  than  half  an  inch,  the  maximum  four 
and  a  half  inches.  In  two  instances  the  right  common  iliac  has  been  found  wanting,  the 
external  and  internal  iliacs  arising  directly  from  the  aorta. 

Surface  Marking. — Draw  a  zone  round  the  body  opposite  the  highest  part  of  the  crest 
of  the  ilium  :  in  this  line  take  a  point  half  an  inch  to  the  left  of  the  middle  line.  From  this 


Heo-lttmbar. 


Gluteal. 


FIG.  372.— Arteries  of  the  pelvis. 

draw  two  lines  to  points  midway  between  the  anterior  superior  spines  of  the  ilium  and  the 
symphysis  pubis.  These  two  diverging  lines  will  represent  the  course  of  the  common  and 
external  iliac  arteries.  Draw  a  second  zone  round  the  body  corresponding  to  the  level  of  the 
anterior  superior  spines  of  the  ilium  :  the  portion  of  the  diverging  lines  between  the  two  zones 
will  represent  the  course  of  the  common  iliac  artery :  the  portion  below  the  lower  zone,  that  of 
the  external  iliac  artery. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  common  iliac  artery  may  be 
required  on  account  of  aneurism  or  haemorrhage  implicating  the  external  or  internal  iliacs. 
The  artery  may  be  tied  by  one  or  two  incisions :  1 .  an  anterior  or  iliac  incision,  by  which  the  vessel 
is  approached  more  directly  from  the  front :  and  2.  a  posterior  abdominal  or  lumbar  incision,  by 
which  the  vessel  is  reached  from  behind.  If  the  surgeon  select  the  iliac  region,  a  curved  incis- 
ion, from  five  to  eight  inches  in  length  according  to  the  amount  of  fat.  is  made,  commencing  just 
outside  the  middle  of  Poupart's  ligament  and  a  finger's  breadth  above  it.  and  carried  outward 
toward  the  anterior  superior  iliac  spine,  then  upward  toward  the  ribs,  and  finally  curving  inward 


620  THE  ARTERIES. 

toward  the  umbilicus.  The  abdominal  muscles  and  transversalis  fascia  are  divided,  and  the  peri- 
toneum raised  upward  and  inward  until  the  Psoas  is  reached.  The  artery  will  be  found  on  the 
inner  side  of  this  muscle,  and  is  to  be  cleared  with  a  director,  especial  care  being  taken  on  the  right 
side,  as  here  the  common  iliac  veins  lie  behind  the  artery.  The  aneurism  needle  is  to  be  passed 
from  within  outward.  But  if  the  aneurismal  tumor  should  extend  high  up  in  the  abdomen,  along 
the  external  iliac,  it  is  better  to  select  the  posterior  or  lumbar,  by  making  an  incision  partly  in 
the  abdomen,  partly  in  the  loin.  The  incision  is  commenced  at  the  anterior  extremity  of  the 
last  rib,  proceeding  directly  downward  to  the  ilium ;  it  is  then  curved  forward  along  the  crest  of 
the  ilium  and  a  little  above  it  to  the  anterior  superior  spine  of  that  bone.  The  abdominal  mus- 
cles having  been  cautiously  divided  in  succession,  the  transversalis  fascia  must  be  carefully  cut 
through,  and  the  peritoneum,  together  with  the  ureter,  separated  from  the  artery  and  pushed 
aside  ;  the  sacro-iliac  articulation  must  then  be  felt  for,  and  upon  it  the  vessel  will  be  felt  pulsat- 
ing, and  may  be  fully  exposed  in  close  connection  with  its  accompanying  vein.  On  the  right 
side  both  common  iliac  veins,  as  well  the  inferior  vena  cava,  are  in  close  connection  with  the 
artery,  and  must  be  carefully  avoided.  On  the  left  side  the  vein  usually  lies  on  the  inner  side 
and  behind  the  artery  ;  but  it  occasionally  happens  that  the  two  common  iliac  veins  are  joined  on 
the  left  instead  of  the  right  side,  which  would  add  much  to  the  difficulty  of  an  operation  in  such 
a  case.  The  common  iliac  artery  may  be  so  short  that  danger  may  be  apprehended  from  second- 
ary haemorrhage  if  a  ligature  is  applied  to  it.  It  would  be  preferable,  in  such  a  case,  to  tie  both 
the  external  and  internal  iliacs  near  their  origin. 

Collateral  Circulation. — The  principal  agents  in  carrying  on  the  collateral  circulation  after 
the  application  of  a  ligature  to  the  common  iliac  are — the  anastomoses  of  the  hsemorrhoidal 
branches  of  the  internal  iliac  with  the  superior  haemorrhoidal  from  the  inferior  mesenteric ;  the 
anastomoses  of  the  uterine  and  ovarian  arteries  and  of  the  vesical  arteries  of  opposite  sides  ;  of 
the  lateral  sacral  with  the  middle  sacral  artery  ;  of  the  epigastric  with  the  internal  mammary, 
inferior  intercostal,  and  lumbar  arteries ;  of  the  circumflex  iliac  with  the  lumbar  arteries  ;  of  the 
ilio-lumbar  with  the  last  lumbar  artery ;  of  the  obturator  artery,  by  means  of  its  pubic  branch, 
with  the  vessel  of  the  opposite  side  and  with  the  deep  epigastric. 

Compression  of  the  Common  Iliac  Arteries.— The  common  iliac  arteries  are  most  effi- 
ciently compressed  by  Davy's  lever.  The  instrument  consists  of  a  gum-elastic  tube  about  two 
feet  long,  in  which  fits  a  round  wooden  "  lever  "  considerably  longer  than  the  tube.  A  small 
quantity  of  olive  oil  having  been  injected  into  the  rectum,  the  gum-elastic  tube,  softened  in  hot 
water,  is  passed  into  the  bowel  sufficiently  far  to  permit  its  pressing  upon  the  common  iliac  artery 
as  it  lies  in  the  groove  between  the  last  lumbar  vertebra  and  the  Psoas  muscle.  The  wooden 
lever  is  then  inserted  into  the  tube,  and  the  projecting  end  carried  toward  the  opposite  thigh 
and  raised,  when  it  acts  as  a  lever  of  the  first  order,  the  anus  being  the  fulcrum.  In  cases 
where  the  meso-rectum  is  abnormally  short  it  may  be  impossible,  without  unjustifiable  force,  to 
compress  the  artery  on  the  right  side. 

Internal  Iliac  Artery  (Fig.  372). 

The  internal  iliac  artery  supplies  the  walls  and  viscera  of  the  pelvis,  the  gen- 
erative organs,  and  inner  side  of  the  thigh.  It  is  a  short,  thick  vessel,  smaller 
in  the  adult  thar  the  external  iliac,  and  about  an  inch  and  a  half  in  length.  It 
arises  at  the  point  of  bifurcation  of  the  common  iliac,  and,  passing  downward  to 
the  upper  margin  of  the  great  sacro-sciatic  foramen,  divides  into  two  large  trunks, 
an  anterior  and  posterior  ;  from  its  point  of  bifurcation  a  partially  obliterated  cord, 
the  hypogastric  artery,  extends  forward  to  the  bladder. 

Relations. — In  front,  with  the  ureter,  which  separates  it  from  the  peritoneum. 
Behind,  with  the  internal  iliac  vein,  the  lumbo-sacral  nerve,  and  Pyriformis  mus- 
cle. By  its  outer  side,  near  its  origin,  with  the  Psoas  magnus  muscle. 

PLAN  OF  THE  RELATIONS  OF  THE  INTERNAL  ILIAC  ARTERY. 

In  front. 

Peritoneum. 
Ureter. 

/- 

Outer  side.  /  \  Inner  side. 

Psoas  magnus. 


£  eh  i  n<  I. 

External  iliac  vein  (above). 
Internal  iliac  vein. 
TAimbo-sacral  nerve. 
Sacrum. 


THE   INTERNAL    ILIAC   ARTERY.  621 

In  the  foetus  the  internal  iliac  artery  (hypogastric]  is  twice  as  large  as  the 
external  iliac,  and  appears  to  be  the  continuation  of  the  common  iliac.  Instead 
of  dipping  into  the  pelvis,  it  passes  forward  to  the  bladder,  and  ascends  along 
the  sides  of  that  viscus  to  its  summit,  to  which  it  gives  branches;  it  then  passes 
upward  along  the  back  part  of  the  anterior  wall  of  the  abdomen  to  the  umbilicus, 
converging  toward  its  fellow  of  the  opposite  side.  Having  passed  through  the 
umbilical  opening,  the  two  arteries  twine  round  the  umbilical  vein,  forming  with 
it  the  umbilical  cord,  and  ultimately  ramify  in  the  placenta.  The  portion  of  the 
1  within  the  abdomen  is  called  the  hypogastric  artery,  and  that  external  to 
that  cavity,  the  umbilical  artery. 

At  birth,  when  the  placental  circulation  ceases,  the  upper  portion  of  the 
hypogastric  artery,  extending  from  the  summit  of  the  bladder  to  the  umbilicus, 
contracts,  and  ultimatelv  dwindles  to  a  solid  fibrous  cord ;  but  the  lower  portion, 
extending  from  its  origin  (in  what  is  now  the  internal  iliac  artery)  for  about  an 
inch  and  a  half  to  the  wall  of  the  bladder,  and  thence  to  the  summit  of  that  organ, 
is  not  totally  impervious,  though  it  becomes  considerably  reduced  in  size,  and 
serves  to  convey  blood  to  the  bladder  under  the  name  of  the  superior  vesical 
artery. 

Peculiarities  as  regards  Length. — In  two-thirds  of  a  large  number  of  cases  the  length  of 
the  internal  iliac  varied  between  an  inch  and  an  inch  and  a  half:  in  the  remaining  third  it 
was  more  frequently  longer  than  shorter,  the  maximum  length  being  three  inches,  the  minimum 
half  an  inch. 

The  lengths  of  the  common  and  internal  iliac  arteries  bear  an  inverse  proportion  to 
each  other,  the  internal  iliac  artery  being  long  when  the  common  iliac  is  short,  and  vice 
r<  /•>•»;. 

As  regards  its  Place  of  Division. — The  place  of  division  of  the  internal  iliac  varies 
between  the  upper  margin  of  the  sacrum  and  the  upper  border  of  the  sacro-sciatic  for- 
amen. 

The  arteries  of  the  two  sides  in  a  series  of  cases  often  differed  in  length,  but  neither  seemed 
constantly  to  exceed  the  other. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  internal  iliac  artery  may  be 
require  1  in  case?  of  aneurism  or  haemorrhage  affecting  one  of  its  branches.  The  vessel  may  be 
secured  by  making  an  incision  through  the  abdominal  parietes  in  the  iliac  region  in  a  direction 
and  to  an  extent  similar  to  that  for  securing  the  common  iliac :  the  transversalis  fascia  having 
been  cautiously  divided,  and  the  peritoneum  pushed  inward  from  the  iliac  fossa  toward  the 
pelvis,  the  finger  may  feel  the  pulsation  of  the  external  iliac  at  the  bottom  of  the  wound,  and  by 
tracing  this  vessel  upward  the  internal  iliac  is  arrived  at,  opposite  the  sacro-iliac  articulation.  It 
should  be  remembered  that  the  vein  lies  behind  and  on  the  right  side,  a  little  external  to 
the  artery,  and  in  close  contact  with  it :  the  ureter  and  peritoneum,  which  lie  in  front,  must  also 
be  avoided.  The  degree  of  facility  in  applying  a  ligature  to  this  vessel  will  mainly  depend  upon 
its  length.  It  has  been  seen  that  in  the  great  majority  of  the  cases  examined  the  artery  was 
short,  varying  from  an  inch  to  an  inch  and  a  half;  in  these  cases  the  artery  is  deeply  seated  in 
tbe  pelvis:  when,  on  the  contrary,  the  vessel  is  longer,  it  is  found  partly  above  that  cavity.  If 
the  artery  is  very  short,  as  occasionally  happens,  it  would  be  preferable  to  apply  a  ligature  to  the 
common  iliac  or  upon  the  external  and  internal  iliacs  at  their  origin. 

Probably  a  better  method  of  tying  the  internal  iliac  artery  is  by  an  abdominal  section  in  the 
median  line  and  reaching  the  vessel  through  the  peritoneal  cavity.  This  plan  has  been 
advocated  by  Dennis  of  New  York  on  the  following  grounds :  (1 )  It  no  way  increases  the  danger 
of  the  operation  :  -'  it  prevents  a  series  of  accidents  which  have  occurred  during  ligature  of  the 
artery  by  the  older  methods;  (3)  it  enables  the  surgeon  to  ascertain  the  exact  extent  of  disease 
in  the  main  arterial  trunk,  and  select  his  spot  for  the  application  of  the  ligature ;  and  (4)  it 
occupies  much  less  time. 

Collateral  Circulation. — In  Professor  Owen's  dissection  of  a  case  in  which  the  internal 
iliac  artery  had  been  tied  by  Stevens  ten  years  before  death  for  aneurism  of  the  sciatic  artery, 
the  internal  iliac  was  found  impervious  for  about  an  inch  above  the  point  where  the  ligature  had 
been  applied,  but  the  obliteration  did  not  extend  to  the  origin  of  the  external  iliac,  as  the  ilio- 
lumbar  artery  arose  just  above  this  point.  Below  the  point  of  obliteration  the  artery  resumed 
its  natural  diameter,  and  continued  so  for  half  an  inch,  the  obturator,  lateral  sacral,  and  gluteal 
arising  in  succession  from  the  latter  portion.  The  obturator  artery  was  entirely  obliterated. 
The  lateral  sacral  artery  was  as  large  as  a  crow's  quill,  and  had  a  very  free  anastomosis  with  the 
artery  of  the  opposite  side  and  with  the  middle  sacral  artery.  The  sciatic  artery  was  entirely 
obliterated  as  far  as  its  point  of  connection  with  the  aneurismal  tumor,  but  on  the  distal  side  of 
the  sac  it  was  continued  down  along  the  back  of  the  thigh  nearly  as  large  in  size  as  the  femoral, 
being  pervious  about  an  inch  below  the  sac  by  receiving  an  anastomosing  vessel  from  the  pro- 
funda.1  The  circulation  was  carried  on  by  the  anastomoses  of  the  uterine  and  ovarian  arteries; 

1  Jfedico-Chirurgical  Trans.,  vol.  xvi. 


622  THE  ARTERIES. 

of  the  opposite  vesical  arteries ;  of  the  haemorrhoidal  branches  of  the  internal  iliac  with 
those  from  the  inferior  mesenteric;  of  the  obturator  artery,  by  means  of  its  pubic  branch, 
with  the  vessel  of  the  opposite  side  and  with  the  epigastric  and  internal  circumflex ;  of  the 
circumflex  and  perforating  branches  of  the  profunda  femoris  with  the  sciatic ;  of  the  gluteal 
with  the  posterior  branches  of  the  sacral  arteries;  of  the  ilio-lumbar  with  the  last  lumbar;  of 
the  lateral  sacral  with  the  middle  sacral ;  and  of  the  circumflex  iliac  with  the  ilio-lumbar  and 
gluteal. 

BRANCHES  OF  THE  INTERNAL  ILIAC. 

From  the  Anterior  Trunk.  From  the  Posterior  Trunk. 

Superior  Vesical.  Ilio-lumbar. 

Middle  Vesical.  Lateral  Sacral. 

Inferior  Vesical.  Gluteal. 

Middle  Hsemorrhoidal. 
Obturator. 
Internal  Pudic. 
Sciatic. 

T    j.       7    f  Uterine. 
In  female  ^^ 

The  superior  vesical  is  that  part  of  the  foetal  hypogastric  artery  which  remains 
pervious  after  birth.  It  extends  to  the  side  of  the  bladder,  distributing  numerous 
branches  to  the  apex  and  body  of  the  organ.  From  one  of  these  a  slender  vessel 
is  derived  which  accompanies  the  vas  deferens  in  its  course  to  the  testis,  where  it 
anastomoses  with  the  spermatic  artery.  This  is  the  artery  of  the  vas  deferens. 
Other  branches  supply  the  ureter. 

The  middle  vesical,  usually  a  branch  of  the  superior,  is  distributed  to  the  base 
of  the  bladder  and  under  surface  of  the  vesiculse  seminales. 

The  inferior  vesical  arises  from  the  anterior  division  of  the  internal  iliac, 
frequently  in  common  with  the  middle  haemorrhoidal,  and  is  distributed  to  the 
base  of  the  bladder,  the  prostate  gland,  and  vesiculse  seminales.  The  branches 
distributed  to  the  prostate  communicate  with  the  corresponding  vessel  of  the 
opposite  side. 

The  middle  hsemorrhoidal  artery  usually  arises  together  with  the  preceding 
vessel.  It  supplies  the  rectum,  anastomosing  with  the  other  hsemorrhoidal 
arteries. 

The  uterine  artery  passes  inward  from  the  anterior  trunk  of  the  internal 
iliac  to  the  neck  of  the  uterus.  Ascending,  in  a  tortuous  course  on  the  side  of 
this  viscus,  between  the  layers  of  the  broad  ligament,  it  distributes  branches 
to  its  substance,  anastomosing,  near  its  termination,  with  a  branch  from  the 
ovarian  artery.  Branches  from  this  vessel  are  also  distributed  to  the  bladder  and 
ureter. 

The  vaginal  artery  is  analogous  to  the  inferior  vesical  in  the  male ;  it  descends 
upon  the  vagina,  supplying  its  mucous  membrane,  and  sending  branches  to  the 
neck  of  the  bladder  and  contiguous  part  of  the  rectum. 

The  Obturator  Artery  usually  arises  from  the  anterior  trunk  of  the  internal 
iliac,  frequently  from  the  posterior.  It  passes  forward,  below  the  brim  of  the 
pelvis,  to  the  upper  part  of  the  obturator  foramen,  and,  escaping  from  the  pelvic 
cavity  through  a  short  canal  formed  by  a  groove  on  the  under  surface  of  the 
horizontal  ramus  of  the  os  pubis  and  the  arched  border  of  the  obturator  mem- 
brane, it  divides  into  an  internal  and  external  branch.  In  the  pelvic  cavity  this 
vessel  lies  upon  the  pelvic  fascia,  beneath  the  peritoneum,  and  a  little  below  the 
obturator  nerve. 

Branches. —  Within  the  pelvis,  the  obturator  artery  gives  off  an  iliac  branch  to 
the  iliac  fossa,  which  supplies  the  bone  and  the  Iliacus  muscle,  and  anastomoses 
with,  the  ilio-lumbar  artery ;  a  vesical  branch,  which  runs  backward  to  supply  the 
bladder;  and  a  pubic  branch,  which  is  given  off  from  the  vessel  just  before  it 
leaves  the  pelvic  cavity.  This  branch  ascends  upon  the  back  of  the  os  pubis, 


BRANCHES    OF    THE   IXTEPXAL    ILIAC.  623 

sommunicating  with  offsets  from  the  deep  epigastric  artery  and  with  the  corre- 
sponding vessel  of  the  opposite  side.  This  branch  is  placed  on  the  inner  side  of 
the  femoral  ring.  External  to  the  pelvis,  the  obturator  artery  divides  into  an 
iial  and  an  external  branch,  which  are  deeply  situated  beneath  the  Obturator 
externus  muscle. 

The  internal  branch  curves  downward  along  the  inner  margin  of  the  obturator 
foramen,  distributing  branches  to  the  Obturator  externus  muscle,  Pectineus. 
Adductors,  and  Gracilis.  and  anastomoses  with  the  external  branch  and  with  the 
internal  circumflex  artery. 

The  external  branch  curves  round  the  outer  margin  of  the  foramen  to  the 

space  between  the  Gemellus  inferior  and  Quadratus  femoris.  where  it  anastomoses 

with    the   sciatic   artery.      It   supplies  the   Obturator  muscles,  anastomoses,  as  it 

a  backward,  with  the  internal  branch  and  with  the  internal  circumflex,  and 


FIG.  373.— Variations  in  origin  and  course  of  obturator  artery. 


sends  a  branch  to  the  hip-joint  through  the  cotyloid  notch,  which  ramifies  on  the 
round  ligament  as  far  as  the  head  of  the  femur. 

Peculiarities.— In  two  out  of  every  three  cases  the  obturator  arises  from  the  internal  iliac  . 
in  one  case  in  three  and  a  half  from  the  epigastric ;  and  in  about  two  and  a  half  in  seventy-two 
iiy  two  routs  from  both  vessels.  It  arises  in  one  and  two-tenths  per  cent,  from  the  exter- 
nal iliac  artery.  The  origin  of  the  obturator  from  the  epigastric  is  not  commonly  found  on  both 
sides  of  the  same  body. 

When  the  obturator  artery  arises  at  the  front  of  the  pelvis  from  the  epigastric,  it  descends 
almost  vertically  to  the  upper  part  of  the  obturator  foramen.  The  artery  in  this  course  usually 
lies  in  contact  with  the  external  iliac  vein  and  on  the  outer  side  of  the  femoral  ring  (Fig.  373,  A)  ; 
in  such  cases  it  would  not  be  endangered  in  the  operation  for  femoral  hernia.  Occasionally. 
however.it  curves  inward  along  the  free  margin  of  Gimbernat's  ligament  I  Fig.  373.  B'.  and 
under  such  circumstances  would  almost  completely  encircle  the  neck  of  a  hernial  sac  (supposing 
a  hernia  to  exist  in  such  a  case),  and  would  be  in  great  danger  of  being  wounded  if  an  operation 
was  performed. 

The  internal  pudic  is  the  smaller  of  the  two  terminal  branches  of  the  anterior 
trunk  of  the  internal  iliac,  and  supplies  the  external  organs  of  generation. 
Though  the  course  of  the  artery  is  the  same  in  the  two  sexes,  the  vessel  is  much 
smaller  in  the  female  than  in  the  male,  and  the  distribution  of  its  branches 
somewhat  different.  The  description  of  its  arrangement  in  the  male  will  first  be 
given,  and  subsequently  the  differences  which  it  presents  in  the  female  will  be 
mentioned. 

The  Internal  Pudic  Artery  in  the  Male  passes  downward  and  outward  to  the 
lower  border  of  the  great  sacro-sciatic  foramen,  and  emerges  from  the  pelvis 
between  the  Pyriformis  and  Coccygeus  muscles  :  it  then  crosses  the  spine  of  the 
ischium  and  re-enters  the  pelvis  through  the  lesser  sacro-sciatic  foramen.  The 
artery  now  crosses  the  Obturator  internus  muscle  along  the  outer  Avail  of  the  ischio- 
rectal  fossa,  being  .situated  about  an  inch  and  a  half  above  the  lower  margin  of  the 
ischial  tuberosity.  It  is  here  contained  in  a  sheath  of  the  obturator  fascia,  and 
gradually  approaches  the  margin  of  the  ramus  of  the  ischium.  along  which  it  passes 
forward  and  upward,  pierce?  the  posterior  layer  of  the  deep  perineal  fascia,  and 
runs  forward  along  the  inner  margin  of  the  ramus  of  the  os  pubis  ;  finally,  it 
perforates  the  anterior  layer  of  the  deep  perineal  fascia  and  divides  into  its  two 


624 


THE   ARTERIES. 


terminal   branches,  the  dorsal  artery  of  the  penis  and  the  artery  of  the 

cavernosum. 

Relations.  —  In  the  first  part  of  its  course,  within  the  pelvis,  it  lies  in  front  of 

the  Pyriforruis  muscle  and  sacral  plexus  of  nerves,  and  on  the  outer  side  of  the 

rectum  (on  the  left  side). 
As  it  crosses  the  spine 
of  the  ischium  it  is  cov- 

Ileo-lumbar 


Deep 
epigastric 


Obturatoi 


Inf.  hxmorrhoidal 


maximus.  In  the  pelvis 
it  lies  on  the  outer  side 
of  the  ischio-rectal  fossa, 
upon  the  surface  of  the 
Obturator  internus  mus- 
cle, contained  in  a  fibi'ous 
canal  formed  by  the  ob- 
turator fascia  and  the 
falciform  process  of  the 
great  sacro-sciatic  liga- 
ment. It  is  accompa- 
nied by  the  pudic  veins 
and  the  internal  pudic 
nerve,  which  lies  inter- 
nal to  it  on  the  ischial 
spine. 

Peculiarities,—  The  in- 

ternal pudic  is  sometimes 
smaller  than  usual,  or  i'ails 
to  give  off  one  or  two  of  its 
usual  branches  ;  in  such 
cases  the  deficiency  is  sup- 
plied by  branches  derived 
from  an  additional  vessel. 
the  accessor  pudic,  which 
generally  arises  from  the  in- 
ternal pudic  artery  before  its 
exit  from  the  great  sacro- 
sciatic  foramen.  It  passes 
forward  along  the  lower  part 
hypogastnc  of  th(^  bladder  and  across 

nLpudic  the  side  of  the  Prostate 
gland  to  the  root  of  the 
penis,  where  it  perforates 
the  triangular  ligament  and 
gives  off  the  branches  usu- 
ally derived  from  the  pudic 


Gluteal 


Oblit. 


Dorsal  artery 
Artery  of  Corp.  cav. 

Perinea! 
FIG.  374.-  The  internal  pudic  artery  and  its  branches  in  the  male.   (Gegenbaur.)  artery.    The  deficiency  most 

frequently  met  with  is  that 

in  which  the  internal  pudic  ends  as  the  artery  of  the  bulb,  the  artery  of  the  corpus  cavernosum 
and  arteria  dorsalis  penis  being  derived  from  the  accessory  pudic.  Or  the  pudic  may  terminate 
as  the  superficial  perineal,  the  artery  of  the  bulb  being  derived,  with  the  other  two  branches, 
from  the  accessory  vessel. 

Surgical  Anatomy. — The  relation  of  the  accessory  pudic  to  the  prostate  gland  and  urethra 
is  of  the  greatest  interest  in  a  surgical  point  of  view,  as  this  vessel  is  in  danger  of  being  wounded 
in  the  lateral  operation  of  lithotomy.  The  student  should  also  study  the  position  of  the  internal 
pudic  artery  and  its  branches,  when  running  a  normal  course,  with  regard  to  the  same  operation. 
The  superficial  and  the  transverse  perineal  arteries  are,  of  necessity,  divided  in  this  operation, 
but  the  haemorrhage  from  these  vessels  is  seldom  excessive ;  should  a  ligature  be  required,  it  can 
readily  be  applied  on  account  of  their  superficial  position.  The  artery  of  the  bulb  may  be 
divided  if  the  incision  be  carried  too  far  forward,  and  injury  of  this  vessel  maybe  attended  with 
serious  or  even  fatal  consequences.  The  main  trunk  of  the  internal  pudic  artery  may  be  wounded 
if  the  incision  be  carried  too  far  outward  ;  bat,  being  bound  down  by  the  strong  obturator  fascia 
and  under  cover  of  the  ram  us  of  the  ischiuin,  the  accident  is  not  very  likely  to  occur  unless  the 
vessel  runs  an  anomalous  course. 


BRAXCHE8    OF    THE   INTERNAL    ILIAC.  625 

Branches. — The  branches  of  the  internal  pudic  artery  are — 

Muscular.  Transverse  Perineal. 

Inferior  Haemorrhoidal.  Artery  of  the  Bulb. 

Superficial  Perineal.  Artery  of  "the  Corpus  Cavernosum. 

Dorsal  Artery  of  the  Penis. 

The  muscular  branches  consist  of  two  sets — one  given  off  in  the  pelvis,  the 
other  as  the  vessel  crosses  the  ischial  spine.  The  former  are  several  small  offsets 
which  supply  the  Levator  ani,  the  Obturator  internus,  the  Pyriformis,  and  the 
Coccygeus  muscles.  The  branches  given  off  outside  the  pelvis  are  distributed  to 
the  adjacent  part  of  the  Gluteus  maximus  and  External  rotator  muscles.  They 
anastomose  with  branches  of  the  sciatic  artery. 

The  inferior  haemorrhoidal  are  two  or  three  small  arteries  which  arise  from  the  in- 
ternal pudic  as  it  passes  above  the  tuberosity  of  the  ischium.  Crossing  the  ischio- 
rectal  fossa,  they  are  distributed  to  the  muscles  and  integument  of  the  anal  region. 

The  superficial  perineal  artery  supplies  the  scrotum  and  muscles  and  integu- 
ment of  the  perinaeum.  It  arises  from  the  internal  pudic  in  front  of  the  preceding 
branches,  and  turns  upward,  crossing  either  over  or  under  the  Transversus  perinaei 
muscle,  and  runs  forward,  parallel  to  the  pubic  arch,  in  the  interspace  between  the 
Accelerator  urinae  and  Erector  penis  muscles,  both  of  which  it  supplies,  and  is 
finally  distributed  to  the  skin  and  dartos  of  the  scrotum.  In  its  passage  through 
the  perinteum  it  lies  beneath  the  superficial  perineal  fascia. 

The  transverse  perineal  is  a  small  branch  which  arises  either  from  the  internal 
pudic  or  from  the  superficial  perineal  artery  as  it  crosses  the  Transversus  perinaei 
muscle.  It  runs  transversely  inward  along  the  cutaneous  surface  of  the  Trans- 
versus perinaei  muscle,  which  it  supplies,  as  well  as  the  structures  between  the  anus 
and  bulb  of  the  urethra,  and  anastomoses  with  the  one  of  the  opposite  side. 

The  artery  of  the  bulb  is  a  large  but  very  short  vessel  which  arises  from  the 
internal  pubic  between  the  two  layers  of  the  deep  perineal  fascia,  and,  passing 
nearly  transversely  inward,  pierces  the  bulb  of  the  urethra,  in  which  it  ramifies. 
It  gives  off  a  small  branch  which  descends  to  supply  Cowper's  gland. 

Surgical  Anatomy. — This  artery  is  of  considerable  importance  in  a  surgical  point  of  view, 
as  it  is  in  danger  of  being  wounded  in  the  lateral  operation  of  lithotomy — an  accident  usually 
attended  in  the  adult  with  alarming  haemorrhage.  The  vessel  is  sometimes  very  small,  occasion- 
ally wanting,  or  even  double.  It  sometimes  arises  from  the  internal  pudic  earlier  than  usual,  and 
•s  the  perinasum  to  reach  the  back  part  of  the  bulb.  In  such  a  case  the  vessel  could  hardly 
fail  to  be  wounded  in  the  performance  of  the  lateral  operation  of  lithotomy.  If,  on  the  contrary, 
it  should  arise  from  an  accessory  pudic,  it  lies  more  forward  than  usual  and  is  out  of  danger  in 
the  operation. 

The  artery  of  the  corpus  cavernosum,  one  of  the  terminal  branches  of  the  inter- 
nal pudic,  arises  from  that  vessel  while  it  is  situated  between  the  crus  penis  and 
the  ramus  of  the  os  pubis ;  piercing  the  crus  penis  obliquely,  it  runs  forward  in  the 
centre  of  the  corpus  cavernosum,  to  which  its  branches  are  distributed. 

The  dorsal  artery  of  the  penis  ascends  between  the  crus  and  pubic  symphysis, 
and.  piercing  the  suspensory  ligament,  runs  forward  on  the  dorsum  of  the  penis  to 
the  glans.  where  it  divides  into  two  branches  which  supply  the  glans  and  prepuce. 
On  the  dorsurn  of  the  penis  it  lies  immediately  beneath  the  integument,  parallel 
with  the  dorsal  vein  and  the  corresponding  artery  of  the  opposite  side  with  the 
nerve  external.  It  supplies  the  integument  and  fibrous  sheath  of  the  corpus  caver- 
nosum, sending  branches  through  the  sheath  to  anastomose  with  the  preceding 
vessel. 

The  Internal  Pudic  Artery  in  the  Female  is  smaller  than  in  the  male.  Its 
origin  and  course  are  similar,  and  there  is  considerable  analogy  in  the  distribution 
of  its  branches.  The  superficial  artery  supplies  the  labia  pudendi ;  the  artery  of 
the  bulb  supplies  the  bulbi  vestibuli  and  the  erectile  tissue  of  the  vagina ;  the 
artery  of  the  corpus  cavernosum  supplies  the  cavernous  body  of  the  clitoris ;  and 
the  arteria  dorsalis  clitoridis  supplies  the  dorsum  of  that  organ,  and  terminates  in 
the  glans  and  in  the  membranous  fold  corresponding  to  the  prepuce  of  the  male. 

40 


626 


THE   ARTERIES. 


The  Sciatic  Artery  (Fig.  375),  the  larger  of  the  two  terminal  branches  of  the 
anterior  trunk  of  the  internal  iliac,  is  distributed  to  the  muscles  at  the  back  of  the 
pelvis.  It  passes  down  to  the  lower  part  of  the  great  sacro-sciatic  foramen  behind 
the  internal  pudic  artery,  resting  on  the  sacral  plexus  of  nerves  and  Pyriformis 
muscle,  and  escapes  from  the  pelvis  through  this  foramen  between  the  Pyriformis 
and  Coccygeus.  It  then  descends  in  the  interval  between  the  trochanter  major  and 

tuberosity  of  the  ischium,  ac- 
companied by  the  sciatic  nerves, 
and  covered  by  the  Glutens 
maximus,  and  is  continued  down 
the  back  of  the  thigh  supplying 
the  skin,  and  anastomosing  with 
branches  of  the  perforating  arte- 
ries. 

Within  the  pelvis  it  distrib- 
utes branches  to  the  Pyriformis, 
Coccygeus,  and  Levator  ani 
muscles ;  some  haemorrhoidal 
branches,  which  supply  the 
rectum,  and  occasionally  take 
the  place  of  the  middle  hsemor- 
rhoidal  artery;  and  vesical 
branches  to  the  base  and  neck 
of  the  bladder,  vesiculae  semi- 
nales,  and  prostate  gland.  Ex- 
ternal to  the  pelvis  it  gives  off 
the  following  branches : 

Coccygeal. 

Inferior  Gluteal. 

Comes  Nervi  Ischiadici. 

Muscular. 

Articular. 

The  coccygeal  branch  runs 
inward,  pierces  the  great  sacro- 
sciatic  ligament,  and  supplies 
the  Gluteus  maximus,  the  in- 
tegument, and  other  structures 

O  ' 

on  the  back  of  the  coccyx. 

The  inferior  gluteal  branches, 
three  or  four  in  number,  supply 
the  Gluteus  maximus  muscle, 
anastomosing  with  the  gluteal 
artery  in  the  substance  of  the 
muscle. 

The  comes  nervi  ischiadici 
is  a  long,  slender  vessel  which 
accompanies  the  great  sciatic 
nerve  for  a  short  distance ;  it 
then  penetrates  it  and  runs  in 
its  substance  to  the  lower  part 
of  the  thigh. 

The  muscular  branches  supply  the  muscles  on  the  back  part  of  the  hip,  anas- 
tomosing with  the  gluteal,  external  branch  of  the  obturator,  internal  and  exter- 
nal circumflex,  and  superior  perforating  arteries. 

Some  articular  branches  are  distributed  to  the  capsule  of  the  hip-joint. 

The  Ilio-lumbar  Artery,  given  off  from  the  posterior  trunk  of  the  internal 


Termination 
of  internal 
circumflex. 


JSuperior 
perforating. 


Middle 
perforating. 

Inferior 
perforating. 


Termination  of 
proftinda. 


Superior  muscular. 


Superior  external 

articular. 


Inferior  muscular. 


Fio.  375. — The  arteries   of  the   gluteal  and  posterior  femoral 
regions. 


Superior  internal 
articular. 


BRANCHES    OF    THE   INTERNAL    ILIAC.  627 

iliac,  turns  upward  and  outward  between  the  obturator  nerve  and  lumbo-sacral 
cord,  to  the  inner  margin  of  the  Psoas  muscle,  behind  which  it  divides  into  a  lum- 
bar and  an  iliac  branch. 

The  lumbar  branch  supplies  the  Psoas  and  Quadratus  lumborum  muscles, 
anastomosing  with  the  last  lumbar  artery,  and  sends  a  small  spinal  branch  through 
the  intervertebral  foramen,  between  the  last  lumbar  vertebra  and  the  sacrum,  into 
the  spinal  canal,  to  supply  the  spinal  cord  and  its  membranes. 

The  iliac  branch  descends  to  supply  the  Iliacus  muscle ;  some  offsets,  running 
between  the  muscle  and  the  bone,  anastomose  with  the  iliac  branch  of  the 
obturator ;  one  of  these  enters  an  oblique  canal  to  supply  the  diploe,  whilst  others 
run  along  the  crest  of  the  ilium,  distributing  branches  to  the  Gluteal  and  Abdom- 
inal muscles,  and  anastomose  in  their  course  with  the  gluteal,  circumflex  iliac, 
and  external  circumflex  arteries. 

The  Lateral  Sacral  Arteries  (Fig.  372)  are  usually  two  in  number  on  each  side, 
superior  and  inferior. 

The  superior,  which  is  of  large  size,  passes  inward,  and,  after  anastomosing 
with  branches  from  the  middle  sacral,  enters  the  first  or  second  sacral  foramen,  is 
distributed  to  the  contents  of  the  sacral  canal  in  the  same  manner  as  the  lateral 
spinal  branches  from  the  vertebral,  and,  escaping  by  the  corresponding  posterior 
sacral  foramen,  supplies  the  skin  and  muscles  on  the  dorsum  of  the  sacrum,  anas- 
tomosing with  the  gluteal. 

The  inferior  passes  obliquely  across  the  front  of  the  Pyriformis  muscle  and 
sacral  nerves  to  the  inner  side  of  the  anterior  sacral  foramina,  descends  on  the 
front  of  the  sacrum,  and  anastomoses  over  the  coccyx  with  the  sacra  media  and 
opposite  lateral  sacral  arteries.  In  its  course  it  gives  off  branches  which  enter 
the  anterior  sacral  foramina;  these,  after  giving  off  branches  to  be  distributed  to 
the  contents  of  the  sacral  canal  in  the  same  manner  as  the  lateral  spinal  branches 
from  the  vertebral,  escape  by  the  posterior  sacral  foramina,  and  are  distributed  to 
the  muscles  and  skin  on  the  dorsal  surface  of  the  sacrum,  anastomosing  with  the 
gluteal. 

The  Gluteal  Artery  is  the  largest  branch  of  the  internal  iliac,  and  appears  to 
be  the  continuation  of  the  posterior  division  of  that  vessel.  It  is  a  short,  thick 
trunk,  which  passes  out  of  the  pelvis  above  the  upper  border  of  the  Pyriformis 
muscle,  and  immediately  divides  into  a  superficial  and  deep  branch.  Within  the 
pelvis  it  gives  off  a  few  muscular  branches  to  the  Iliacus,  Pyriformis,  and  Obtu- 
rator internus,  and,  just  previous  to  quitting  that  cavity,  a  nutrient  artery,  which 
enters  the  ilium. 

The  superficial  branch  passes  beneath  the  Gluteus  maximus  and  divides  into 
numerous  branches,  some  of  which  supply  that  muscle,  whilst  others  perforate  its 
tendinous  origin,  and  supply  the  integument  covering  the  posterior  surface  of  the 
sacrum,  anastomosing  with  the  posterior  branches  of  the  sacral  arteries. 

The  deep  branch  runs  between  the  Gluteus  medius  and  minimus,  and  sub- 
divides into  two.  Of  these,  the  superior  division,  continuing  the  original  course 
of  the  vessel,  passes  along  the  upper  border  of  the  Gluteus  minimus  to  the 
anterior  superior  spine  of  the  ilium,  anastomosing  with  the  circumflex  iliac  and 
ascending  branches  of  the  external  circumflex  artery.  The  inferior  division 
crosses  the  Gluteus  minimus  obliquely  to  the  trochanter  major,  distributing 
branches  to  the  Glutei  muscles,  and  inosculates  with  the  external  circumflex 
artery.  Some  branches  pierce  the  Gluteus  minimus  to  supply  the  hip-joint. 

Surface  Marking. — The  position  of  the  three  main  branches  of  the  internal  iliac,  the 
sciatic,  internal  pudic.  and  gluteal,  which  may  occasionally  be  the  object  of  surgical  interference, 
is  indicated  on  the  surface  in  the  following  way :  A  line  is  to  be  drawn  from  the  posterior  supe- 
rior iliac  spine  to  the  posterior  superior  angle  of  the  great  trochanter.  with  the  limb  slightly 
flexed  and  rotated  inward :  the  point  of  emergence  of  the  gluteal  artery  from  the  upper  part  of 
the  sciatic  notch  will  correspond  with  the  junction  of  the  upper  with  tbe  middle  third  of  tbis 
line.  A  second  line  is  to  be  drawn  from  tbe  same  point  to  the  middle  of  tbe  tuberosity  of  the 
ischium  ;  tbe  junction  of  the  lower  with  the  middle  third  marks  the  point  of  emergence  of  the 
sciatic  and  pudic  arteries  from  the  great  sciatic  notch. 


628  THE   ARTERIES. 

Surgical  Anatomy. — Any  of  these  three  vessels  may  require  ligaturing  for  a  wound  or  for 
aneurism,  which  is  generally  traumatic,  and  the  operation  may  be  performed  by  an  incision, 
three  or  four  inches  long,  in  the  direction  of  the  fibres  of  the  Gluteus  maximus  muscle,  the 
middle  of  the  cut  corresponding  to  the  point  indicating  their  respective  positions. 

The  External  Iliac  Artery  (Fig.  372). 

The  external  iliac  artery  is  larger  in  the  adult  than  the  internal  iliac,  and 
passes  obliquely  downward  and  outward  along  the  inner  border  of  the  Psoas 
muscle,  from  the  bifurcation  of  the  common  iliac  to  Poupart's  ligament,  where  it 
enters  the  thigh  and  becomes  the  femoral  artery. 

Relations. — In  front,  with  the  peritoneum,  subperitoneal  areolar  tissue,  the 
intestines,  ileum  on  right  side,  sigmoid  flexure  on  left,  and  a  tHin  layer  of  fascia 
derived  from  the  iliac  fascia,  which  surrounds  the  artery  and  vein,  At  its 
origin  it  is  occasionally  crossed  by  the  ureter.  The  spermatic  vessels  descend  for 
some  distance  upon  it  near  its  termination,  and  it  is  crossed  in  this  situation  by 
the  genital  branch  of  the  genito-crural  nerve  and  the  circumflex  iliac  vein ;  the 
vas  deferens  curves  down  along  its  inner  side.  Behind,  it  is  in  relation  with  the 
external  iliac  vein,  which,  at  Poupart's  ligament,  lies  at  its  inner  side.  Exter- 
nally, it  rests  against  the  Psoas  muscle,  from  which  it  is  separated  by  the  iliac 
fascia.  The  artery  rests  upon  this  muscle,  near  Poupart's  ligament,  similarly 
separated  by  the  fascia.  Numerous  lymphatic  vessels  and  glands  are  found  lying 
on  the  front  and  inner  side  of  the  vessel. 

PLAN  OF  THE  RELATIONS  OF  THE  EXTERNAL  ILIAC  ARTERY. 

In  front. 

Peritoneum,  intestines,  and  fascia. 
Near          f  Spermatic  vessels. 
Poupart's      •<  Genito-crural  nerve  (genital  branch). 
Ligament.       (  Circumflex  iliac  vein. 

Lymphatic  vessels  and  glands. 


Outer  aide.  /  \  Inner  side. 

Psoas  magnus.  (        iiiac™  External  iliac  vein  and  vas  deferens 

Iliac  fascia.  /  at  femoral  arch. 

Behind. 

External  iliac  vein. 
Psoas  magnus. 
Iliac  fascia. 

Surface  Marking. — The  surface  line  indicating  the  course  of  the  external  iliac  artery  has 
been  already  given  (see  page  619). 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  external  iliac  may  be  required  in 
cases  of  aneurism  of  the  femoral  artery  or  for  a  wound  of  the  artery.  This  vessel  may  be 
secured  in  any  part  of  its  course,  excepting  near  its  upper  end,  which  is  to  be  avoided  on 
account  of  the  proximity  of  the  great  stream  of  blood  in  the  internal  iliac,  and  near  its  lower 
end,  which  should  also  be  avoided,  on  account  of  the  proximity  of  the  epigastric  and  circumflex 
iliac  vessels.  One  of  the  chief  points  in  the  performance  of  the  operation  is  to  secure  the  ves- 
sel without  injury  to  the  peritoneum.  The  patient  having  been  placed  in  the  recumbent  posi- 
tion, an  incision  should  be  made,  commencing  below  at  a  point  about  three-quarters  of  an  inch 
above  Poupart's  ligament,  and  a  little  external  to  its  middle,  and  running  upward  and  outward, 
parallel  to  Poupart's  ligament,  to  a  point  above  the  anterior  superior  spine  of  the  ilium.  When 
the  artery  is  deeply  seated  more  room  will  be  required,  and  may  be  obtained  by  curving  the 
incision  from  the  point  last  named  inward  toward  the  umbilicus  for  a  short  distance,  or,  if  the 
lower  part  of  the  artery  is  to  be  reached,  the  surgeon  may  adopt  the  plan  advocated  by  Sir 
Astley  Cooper,  by  making  an  incision  close  to  Poupart's  ligament  from  about  half  an  inch  out- 
side of  the  external  abdominal  ring  to  one  inch  internal  to  the  anterior  superior  spine  of  the 
ilium.  This  incision,  being  made  in  the  course  of  the  fibres  of  the  aponeurosis  of  the  external 
oblique,  is  less  likely  to  be  followed  by  a  ventral  hernia,  but  there  is  danger  of  wounding  the 
epigastric  artery.  Abernethy,  who  first  tied  this  artery,  made  his  incision  in  the  course  of  the 
vessel.  The  abdominal  muscles  and  transversalis  fascia  having  been  cautiously  divided,  the  peri- 
toneum should  be  separated  from  the  iliac  fossa  and  raised  toward  the  pelvis ;  and  on  introducing 
the  finger  to  the  bottom  of  the  wound  the  artery  may  be  felt  pulsating  along  the  inner  border  of 
the  Psoas  muscle.  The  external  iliac  vein  is  generally  found  on  the  inner  side  of  the  artery, 


THE    EXTERNAL    ILIAC  ARTERY.  629 

and  must  be  cautiously  ,>e panted  from  it  by  the  finger-nail  or  handle  of  the  knife,  and  the  aneu- 
rism needle  should  be  introduced  on  the  inner  side,  between  the  artery  and  the  vein. 

I.  .  iiure  of  the  external  iliac  artery  has  recently  been  performed  in  three  or  more  cases  by 
a  transperitoneal  method.  An  incision  four  inches  in  length  is  made  in  the  semilunar  line,  com- 
mencing about  an  inch  below  the  umbilicus  and  carried  through  the  abdominal  wall  into  the 
peritoneal  cavity.  The  intestines  are  then  pushed  upward  and  held  out  of  the  way  by  a  broad 
abdominal  retractor,  and  an  incision  made  through  the  peritoneum  at  the  margin  of  the  pelvis 
in  the  course  of  the  artery,  and  the  vessel  secured  in  any  part  of  its  course  which  may  seem 
desirable  to  the  operator.  The  advantages  of  this  operation  appear  to  be  that  if  it  is  found 

—ary  the  common  iliac  artery  can  be  ligatured  instead  of  the  external  iliac  without  extension 
or  modification  of  the  incision :  and  secondly,  that  the  vessel  can  be  ligatured  without  in  any 
way  interfering  with  the  coverings  of  the  sac.  Possibly  a  disadvantage  may  exist  in  the  greater 
risk  of  hernia  after  this  method. 

Collateral  Circulation. — The  principal  anastomoses  in  carrying  on  the  collateral  circulation, 
after  the  application  of  a  ligature  to  the  external  iliac,  are — the  ilio-lumbar  with  the  circumflex 
iliac  :  the  gluteal  with  the  external  circumflex  ;  the  obturator  with  the  internal  circumflex  :  the 
sciatic  with  the  superior  perforating  and  circumflex  branches  of  the  profunda  artery ;  and  the 
internal  pudic  with  the  external  pudic.  When  the  obturator  arises  from  the  epigastric,  it  is 
supplied  with  blood  by  branches,  either  from  the  internal  iliac,  the  lateral  sacral,  or  the  inter- 
nal pudic.  The  epigastric  receives  its  supply  from  the  internal  mammary  and  inferior 
intercostal  arteries,  and  from  the  internal  iliac  by  the  anastomoses  of  its  branches  with  the 
obturator. 

In  the  dissection  of  a  limb  eighteen  years  after  the  successful  ligature  of  the  external  iliac 
artery  by  Sir  A.  Cooper,  which  is  to  be  found  in  Guys  Hospital  Reports,  vol.  i.  p.  50.  the 
anastomosing  branches  are  described  in  three  sets:  An  anterior  set. — 1.  a  very  large  branch 
from  the  ilio-lumbar  artery  to  the  circumflex  iliac :  '2.  another  branch  from  the  ilio-lumbar, 
joined  by  one  from  the  obturator,  and  breaking  up  into  numerous  tortuous  branches  to  anastomose 
with  the  external  circumflex  :  3.  two  other  branches  from  the  obturator,  which  passed  over  the 
brim  of  the  pelvis,  communicated  with  the  epigastric,  and  then  broke  up  into  a  plexus  to  anas- 
tomose with  the  internal  circumflex.  An  internal  set. — Branches  given  off  from  the  obturator, 
after  quitting  the  pelvis,  which  ramified  among  the  adductor  muscles  on  the  inner  side  of  the 
hip-joint,  and  joined  most  freely  with  branches  of  the  internal  circumflex.  A  posterior  set. — 
1.  three  large  branches  from  the  gluteal  to  the  external  circumflex:  2.  several  branches  from  the 
sciatic  around  the  great  sciatic  notch  to  the  internal  and  external  circumflex,  and  the  perforating 
branches  of  the  profunda. 

Branches. — Besides  several  small  branches  to  the  Psoas  muscle  and  the  neigh- 
boring lymphatic  glands,  the  external  iliac  gives  off  two  branches  of  considerable 
size — the 

Deep  Epigastric  and  Deep  Circumflex  Iliac. 

The  Deep  Epigastric  Artery  arises  from  the  external  iliac  a  few  lines  above 
Poupart's  ligament.  It  at  first  descends  to  reach  this  ligament,  and  then  ascends 
obliquely  along  the  inner  margin  of  the  internal  abdominal  ring,  lying  between 
the  trans versalis  fascia  and  peritoneum,  and,  continuing  its  course  upward,  it 
pierces  the  transversalis  fascia,  and,  passing  over  the  semilunar  fold  of  Douglas, 
enters  the  sheath  of  the  Rectus  muscle.  It  then  ascends  on  the  posterior  surface 
of  the  muscle,  and  finally  divides  into  numerous  branches,  which  anastomose, 
above  the  umbilicus,  with  the  terminal  branches  of  the  internal  mammary  and 
inferior  intercostal  arteries.  The  deep  epigastric  artery  bears  a  very  important 
relation  to  the  internal  abdominal  ring  as  it  passes  obliquely  upward  and  inward 
from  its  origin  from  the  external  iliac.  In  this  part  of  its  course  it  lies  along  the 
lower  and  inner  margin  of  the  ring  and  beneath  the  commencement  of  the  sper- 
matic cord.  As  it  winds  round  the  internal  abdominal  ring  it  is  crossed  by  the  vas 
deferens  in  the  male  and  the  round  ligament  in  the  female. 

Branches. — The  branches  of  this  vessel  are  the  following :  The  ere  waster  ic\ 
which  accompanies  the  spermatic  cord,  and  supplies  the  Cremaster  muscle  and 
other  coverings  of  the  cord,  anastomosing  with  the  spermatic  artery :  a  pubic 
branch,  which  runs  along  Poupart's  ligament,  and  then  descends  behind  the  pubes 
to  the  inner  side  of  the  femoral  ring,  and  anastomoses  with  offsets  from  the 
obturator  artery  :  HI  titular  £/••/  me  of  which  are  distributed  to  the  abdominal 

muscles  and  peritoneum,  anastomosing  with  the  lumbar  and  circumflex  iliac  arteries : 
others  perforate  the  tendon  of  the  External  oblique,  and  supply  the  integument, 
anastomosing  with  branches  of  the  superficial  epigastric. 


630  THE  ARTERIES. 

Peculiarities. — The  origin  of  the  epigastric  may  take  place  from  any  part  of  the  external 
iliac  between  Poupart's  ligament  and  two  inches  and  a  half  above  it,  or  it  may  arise  below  this 
ligament,  from  the  femoral  or  from  the  deep  femoral. 

Union  with  Branches. — It  frequently  arises  from  the  external  iliac  by  a  common  trunk 
with  the  obturator.  Sometimes  the  epigastric  arises  from  the  obturator,  the  latter  vessel  being 
furnished  by  the  internal  iliac,  or  the  epigastric  may  be  formed  of  two  branches,  one  derived 
from  the  external  iliac,  the  other  from  the  internal  iliac. 

Surgical  Anatomy.— The  deep  epigastric  artery  follows  a  line  drawn  from  the  middle  of 
Poupart's  ligament  toward  the  umbilicus;  but  shortly  after  this  line  crosses  thelineasemilunaris 
the  direction  changes,  and  the  course  of  the  vessel  is  directly  upward  in  the  line  of  junction  of 
the  inner  third  with  the  outer  two-thirds  of  the  Rectus  muscle.  It  has  important  surgical 
relations,  in  addition  to  the  fact  that  it  is  one  of  the  principal  means,  through  its  anastomosis 
with  the  internal  mammary,  in  establishing  the  collateral  circulation  after  ligature  of  either  the 
common  or  external  iliac  arteries.  It  lies  close  to  the  internal  abdominal  ring,  and  is  therefore 
internal,  to  an  oblique  inguinal  hernia,  but  external  to  a  direct  inguinal  hernia,  as  it  emerges 
from  the  abdomen.  It  forms  the  outer  boundary  of  Hesselbach  s  triangle.  It  is  in  close  rela- 
tionship with  the  spermatic  cord,  which  lies  in  front  of  it  in  the  inguinal  canal,  separated  only 
by  the  transversalis  fascia.  The  vas  deferens  hooks  round  its  outer  side. 

The  Deep  Circumflex  Iliac  Artery  arises  from  the  outer  side  of  the  external 
iliac  nearly  opposite  the  epigastric  artery.  It  ascends  obliquely  outward  behind 
Poupart's  ligament,  contained  in  a  fibrous  sheath  formed  by  the  junction  of  the 
transversalis  and  iliac  fasciae,  to  the  anterior  superior  spinous  process  of  the  ilium. 
It  then  runs  along  the  inner  surface  of  the  crest  of  the  ilium  to  about  its  middle, 
where  it  pierces  the  Transversalis,  and  runs  backward  between  that  muscle  and 
the  Internal  oblique,  to  anastomose  with  the  ilio-lumbar  and  gluteal  arteries. 
Opposite  the  anterior  superior  spine  of  the  ilium  it  gives  off  a  large  branch,  which 
ascends  between  the  Internal  oblique  and  Transversalis  muscles,  supplying  them, 
and  anastomosing  with  the  lumbar  and  epigastric  arteries. 

AETERIES  OF  THE  LOWER  EXTREMITY. 
The  Femoral  Artery  (Fig.  376). 

The  femoral  artery  is  the  continuation  of  the  external  iliac.  It  commences 
immediately  behind  Poupart's  ligament,  midway  between  the  anterior  superior 
spine  of  the  ilium  and  the  symphysis  pubis,  and,  passing  down  the  fore  part  and 
inner  side  of  the  thigh,  terminates  at  the  opening  in  the  Adductor  magnus,  at  the 
junction  of  the  middle  with  the  lower  third  of  the  thigh,  where  it  becomes  the 
popliteal  artery.  The  vessel,  at  the  upper  part  of  thigh,  lies  a  little  internal  to 
the  head  of  the  femur ;  in  the  lower  part  of  its  course,  on  the  inner  side  of  the 
shaft  of  the  bone,  and  between  these  two  parts  the  vessel  is  far  away  from  the  bone. 
In  the  upper  third  of  the  thigh  it  is  contained  in  a  triangular  space  called  Scarpa's 
triangle.  In  the  middle  third  of  the  thigh  it  is  contained  in  an  aponeurotic  canal 
called  Hunter's  canal. 

Scarpa's  Triangle. — Scarpa's  triangle  corresponds  to  the  depression  seen 
immediately  below  the  fold  of  the  groin.  It  is  a  triangular  space,  the  apex  of 
which  is  directed  downward,  and  the  sides  formed  externally  by  the  Sartorius, 
internally  by  the  Adductor  longus,  and  above  by  Poupart's  ligament.  The  floor  of 
the  space  is  formed  from  without  inward  by  the  Iliacus,  Psoas,  Pectineus,  a  small 
part  of  the  Adductor  brevis  and  the  Adductor  longus  muscles  ;  and  it  is  divided 
into  two  nearly  equal  parts  by  the  femoral  vessels,  which  extend  from  the  middle  of 
its  base  to  its  apex,  the  artery  giving  off  in  this  situation  its  cutaneous  and 
profunda  branches,  the  vein  receiving  the  deep  femoral  and  internal  saphenous. 
On  the  outer  side  of  the  femoral  artery  is  the  anterior  crural  nerve  dividing  into 
its  branches.  Besides  the  vessels  and  nerves,  this  space  contains  some  fat  and 
lymphatics. 

Hunter's  Canal. — This  is  the  aponeurotic  space  in  the  middle  third  of  the 
thigh,  extending  from  the  apex  of  Scarpa's  triangle  to  the  femoral  opening  in  the 
Adductor  magnus  muscle.  It  is  bounded,  externally,  by  the  Vastus  internus  ; 
postero-internally  by  the  Adductor  longus  and  magnus  ;  and  antero-internally  by 
a  strong  aponeurosis  which  extends  transversely  from  the  Vastus  internus,  across 


THE    FEMORAL    ARTERY. 


631 


Scrotum, 


the  femoral  vessels  to  the  Adductor  longus  and  magnus  muscles,  lying  on  which 
apoueurosis  is  the  Sartorius  muscle.  It  contains  the  femoral  artery  and  vein 
enclosed  in  their  own  sheath  of  areolar  tissue,  the  vein  being  behind  and  on  the 
outer  side  of  the  artery,  and  the  internal  or  long  saphenous  nerve  lying  on  the 
outer  side  of  the  vessels. 

Fur  convenience  of  description,  and  also  in  reference  to  its  surgical  anatomy, 
the  femoral  artery  is  divided  into 
a  short  trunk,  about  an  inch  and 
a  half  or  two  inches  long,  which 
is  known  as  the  t.-ommon  femoral 
•//.  and  the  remainder  of  the 
vessel,  which  is  known  as  the 
ntpcrficial femorcU,  to  distinguish 
it  from  the  deep  femoral  (pro- 
funda  femoris).  which  is  a  large 
branch  given  off  from  the  com- 
mon femoral  at  its  termination, 
and  which  by  its  derivation  from 
the  parent  trunk  marks  the  com- 
mencement of  the  superficial  fem- 
oral artery. 

The  common  femoral  artery  is 
very  superficial,  being  covered 
by  the  skin  and  superficial 
fascia,  superficial  inguinal  lym- 
phatic glands,  the  iliac  portion 
of  the  fascia  lata,  and  the  prolon- 
gation downward  of  the  Trans- 
versalis  fascia,  which  forms  the 
sheath  of  the  vessels.  It  has  in 
front  of  it  filaments  from  the 
crural  branch  of  the  genito- 
crural  nerve,  the  superficial  cir- 
cumflex iliac  vein,  and  occa- 
sionally the  superficial  epigastric 
vein.  It  rests  on  the  inner  mar- 
gin of  the  Psoas  muscle,  which 
separates  it  from  the  capsular 
ligament  of  the  hip-joint,  and  a 
little  lower  on  the  Pectineus 
muscle :  and  crossing  behind  it 
is  the  branch  to  the  Pectineus 
from  the  anterior  crural  nerve. 
Separating  the  artery  from  the 

is  and  Pectineus  muscles  is 
the  pubic  portion  of  the  fascia 
lata  and  the  prolongation  from 
the  fascia  covering  the  Iliacus 
muscle,  which  forms  the  poste- 
rior layer  of  the  sheath  of  the 
Is.  The  anterior  crural 
nerve  lies  about  half  an  inch  to 
the  outer  side  of  the  common 
femoral  artery,  lying  between  the  Psoas  and  Iliacus  muscles.  To  the  inner  side 
of  the  artery  is  the  femoral  vein,  between  the  margins  of  the  Pectineus  and  Psoas 
muscles.  The  two  vessels  are  enclosed  in  a  strong  fibrous  sheath  formed  by  the 
proper  sheath  of  the  vessels  strengthened  by  the  fascia  lata  (see  page  507) ;  the 


Long  saphenous 
nerve. 


Superior  external 
articular. 


Inferior  internal 
articular. 


Anterior  tibial 
recurrent. 


AiuuUmotica 

magna. 

? — Superior  internal 
articular. 


Inferior  internal 
articular. 


FIG.  376.— Surgical  anatomy  of  the  femora!  artery. 


632  THE   ARTERIES. 

artery  and   vein  are  separated,  however,  from   one  another  by  a  thin  fibrous 
partition. 

PLAN  OF  RELATIONS  OF  THE  COMMON  FEMORAL  ARTERY. 

In  front. 

Skin  and  superficial  fascia. 
Superficial  inguinal  glands. 
Iliac  portion  of  fascia  lata. 
Prolongation  of  transversalis  fascia. 
Crural  branch  of  genito-crural  nerve. 
Superficial  circumflex  iliac  vein. 
Superficial  epigastric  vein. 


7-  •  7  /        Common       \  _  .  7 

inner  side.  Femoral  Outer  side. 

Femoral  vein.  Anterior  crural  nerve. 

^_^ 

Behind. 

Prolongation  of  fascia  covering  Iliacus  muscle. 
Pubic  portion  of  fascia  lata. 
Nerve  to  Pectineus. 
Psoas  muscle. 
Pectineus  muscle. 
Capsule  of  hip-joint. 

The  superficial  femoral  artery  is  only  superficial  where  it  lies  in  Scarpa's  tri- 
angle. Here  it  is  covered  by  the  skin,  superficial  and  deep  fascia,  and  crossed 
by  the  internal  cutaneous  branch  of  the  anterior  crural  nerve.  In  Hunter's  canal 
it  is  more  deeply  seated,  being  covered  by  the  integument,  the  superficial  and 
deep  fascia,  the  Sartorius  and  aponeurotic  covering  of  Hunter's  canal.  The 
internal  saphenous  nerve  crosses  the  artery  from  '.vithout  inward.  Behind,  the 
artery  lies  at  its  upper  part  on  the  femoral  vein  and  the  profunda  artery  and 
vein,  which  separate  it  from  the  Pectineus  muscle,  and  lower  down  on  the  Adduc- 
tor longus  and  Adductor  magnus  muscles.  To  the  outer  side  is  the  long  saphe- 
nous nerve  and  the  nerve  to  the  Vastus  internus,  the  Vastus  internus  muscle, 
and,  at  its  lower  part,  the  femoral  vein.  To  the  inner  side  is  the  Adductor 
longus  above  and  the  Adductor  magnus  and  Sartorius  below. 

PLAN  OF  RELATIONS  OF  THE  SUPERFICIAL  FEMORAL  ARTERY. 

In  front. 

Skin,  superficial  and  deep  fasciae. 
Internal  cutaneous  nerve. 
Sartorius. 

Aponeurotic  covering  of  Hunter's  canal. 
Internal  saphenous  nerve. 

Inner  side.  \^  Outer  side. 

Adductor  longus.  /    femoral '     |  Long  saphenous  nerve. 

Adductor  magnus.  I      Artery.       I  Nerve  to  vastus  internus. 

Sartorius.  /  Vastus  internus. 

Femoral  vein  (below). 

Behind. 
Femoral  vein. 
Profunda  artery  and  vein. 
Pectineus  muscle. 
Adductor  longus. 
Adductor  magnus. 

Ike  femoral  vein,  at»Poupart's  ligament,  lies  close  to  the  inner  side  of  the 
artery,  separated  from  it  by  a  thin  fibrous  partition;  but  lower  down  it  is  behind 
it,  and  then  to  its  outer  side. 

The  internal  saphenous  nerve  is  situated  on  the  outer  side  of  the  artery,  in  the 


THE   FEMORAL    ARTERY.  633 

middle  third  of  the  thigh,  beneath  the  aponeurotic  covering  of  Hunter's  canal,  but 
nut  usually  within  the  sheath  of  the  vessels.  The  internal  cutaneous  nerve  passes 
obliquely  across  the  upper  part  of  the  sheath  of  the  femoral  artery. 

Peculiarities.— Double  Femoral  reunited. — Several  cases  are  recorded  in  which  the  femoral 
artery  divided  into  two  trunks  below  the  origin  of  the  profunda,  and  became  reunited  near  the 
opening  in  the  Adductor  niagnus  so  as  to  form  a  single  popliteal  artery.  One  of  them  occurred 
in  a  patient  operated  upon  for  popliteal  aneurism. 

Change  of  Position. — A  tew  cases  have  been  recorded  in  which  the  femoral  artery  was 

situated  at  the  back  of  the  thigh,  the  vessel  being  continuous  above  with  the  internal  iliac, 

ing  from  the  pelvis  through  the  great  sacro-sciatic  foramen,  and  accompanying  the  great 

sciatic  nerve  to  the  popliteal  space,  where  its  division  occurred  in   the  usual  manner.     The 

external  iliac  in  these  cases  was  small,  and  terminated  in  the  profunda. 

Position  of  the  Vein. — The  femoral  vein  is  occasionally  placed  along  the  inner  side  of  the 
artery,  throughout  the  entire  extent  of  Scarpa's  triangle,  or  it  may  be  slit  so  that  a  large  vein  is 
placed  on  each  side  of  the  artery  fur  a  greater  or  less  extent. 

Origin  of  the  Profunda. — This  vessel  occasionally  arises  from  the  inner  side,  and,  more 
rarely,  from  the  back  of  the  common  trunk;  but  the  more  important  peculiarity,  in  a  surgical 
point  of  view,  is  that  which  relates  to  the  height  at  which  the  vessel  arises  from  the  femoral.  In 
three-fourths  of  a  large  number  of  cases  it  arose  between  one  or  two  inches  below  Poupart's 
ligament ;  in  a  few  cases  the  distance  was  less  than  an  inch  ;  more  rarely,  opposite  the  ligament ; 
and  in  one  case,  above  Poupart's  ligament,  from  the  external  iliac.  Occasionally,  the  distance 
between  the  origin  of  the  vessel  and  Poupart's  ligament  exceeds  two  inches,  and  in  one  case  it 
was  found  to  be  as  much  as  four  inches. 

Surface  Marking.— The  upper  two-thirds  of  a  line  drawn  from  a  point  midway  between 
the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis  to  the  prominent  tuberosity  on 
the  inner  condyle  of  the  femur,  with  the  thigh  abducted  and  rotated  outward,  will  indicate  the 
course  of  the  femoral  artery. 

Surgical  Anatomy. — Compression  of  the  femoral  artery,  which  is  constantly  requisite  in 
amputations  and  other  operations  on  the  lower  limb,  and  also  for  the  cure  of  popliteal  aneurisms, 
is  most  effectually  made  immediately  below  Poupart's  ligament.  In  this  situation  the  artery  is 
very  superficial,  and  is  merely  separated  from  the  horizontal  ramus  of  the  os  pubis  by  the  Psoas 
muscle  :  so  that  the  surgeon,  by  means  of  his  thumb  or  a  compressor,  may  effectually  control  the 
circulation  through  it.  This  vessel  may  also  be  compressed  in  the  middle  third  of  the  thigh  by 
placing  a  compress  over  the  artery,  beneath  the  tourniquet,  and  directing  the  pressure  from 
within  outward,  so  as  to  compress  the  vessel  against  the  inner  side  of  the  shaft  of  the  femur. 

The  application  of  a  ligature  to  the  femoral  artery  may  be  required  in  the  cases  of 
wound  or  aneurism  of  the  arteries  of  the  leg.  of  the  popliteal  or  femoral ;  *  and  the  vessel  may 
be  exposed  and  tied  in  any  part  of  its  course.  The  great  depth  of  this  vessel  at  its  lower  part, 
its  close  connection  with  important  structures,  and  the  density  of  its  sheath  render  the  opera- 
tion in  this  situation  one  of  much  greater  difficulty  than  the  application  of  a  ligature  at  its  upper 
part,  where  it  is  more  superficial. 

Ligature  of  the  common  femoral  artery  is  usually  considered  unsafe,  on  account  of  the  con- 
nection of  larse  branches  with  it — viz.  the  deep  epigastric  and  the  deep  circumflex  iliac  arising 
just  above  Poupart's  ligament ;  on  account  of  the  number  of  small  branches  which  arise  from 
it  in  its  short  course :  and  on  account  of  the  uncertainty  of  the  origin  of  the  profunda  femoris, 
which,  if  it  arise  high  up.  would  be  too  close  to  the  ligature  for  the  formation  of  a  firm  coagu- 
lum.  The  profunda  sometimes  arises  higher  than  the  point  above  mentioned,  and  rarely  between 
two  or  three  inches  (in  one  case  four)  below  Poupart's  ligament.  It  would  appear,  then,  that 
the  most  favorable  situation  for  the  application  of  a  ligature  to  the  femoral  is  between  four  and 
five  inches  from  its  point  of  origin.  In  order  to  expose  the  artery  in  this  situation,  an  incision 
between  two  and  three  inches  long  should  be  made  in  the  course  of  the  vessel,  the  patient  lying 
in  the  recumbent  position,  with  the  limb  slightly  flexed  and  abducted.  A  large  vein  is  frequently 
met  with,  passing  in  the  course  of  the  artery  to  join  the  saphena:  this  must  be  avoided,  and, 
the  fas  -ia  lata  having  been  cautiously  divided  and  the  Sartorius  exposed,  that  muscle  must  be 
drawn  outward  in  order  to  fully  expose  the  sheath  of  the  vessels.  The  finger  being  introduced 
into  the  wound  and  the  pulsation  of  the  artery  felt,  the  sheath  should  be  opened  on  the  outer 
side  of  the  vessel  to  a  sufficient  extent  to  allow  of  the  introduction  of  the  ligature,  but  no  farther ; 
otherwise  the  nutrition  of  the  coats  of  the  vessel  may  be  interfered  with,  or  muscular  branches 
which  arise  from  the  vessel  at  irregular  intervals  may  be  divided.  In  this  part  of  the  operation 
the  long  saphenous  nerve  and  the  nerve  to  the  Yastus  internus.  which  is  in  close  relation  with 
the  sheath,  should  be  avoided.  The  aneurism  needle  must  be  carefully  introduced  and  kept 
close  to  the  artery,  to  avoid  the  femoral  vein,  which  lies  behind  the  vessel  in  this  part  of  its 
course. 

To  expose  the  artery,  in  Hunter's  canal,  an  incision  should  be  made  through  the  integument, 
between  three  and  four  inches  in  length,  a  finger's  breadth  internal  to  the  line  of  the  artery,  in 
the  middle  of  the  thigh — i.  c.  midway  between  the  groin  and  the  knee.  The  fascia  lata  having 
been  divided  and  the  Sartorius  muscle  exposed,  it  should  be  drawn  inward,  when  the  stronir 

1  Ligature  of  the  femoral  artery  has  been  also  recommended  and  performed  for  elephantiasis  of 
the  leg  and  acute  inflammation  of  the  knee-joint  (Maunder,  Clin.  Soc.  Trans.,  vol.  ii.  p.  37). 


634  THE   ARTERIES. 

fascia  which  is  stretched  across  from  the  Adductors  to  the  Vastus  interims  will  be  exposed,  and 
must  be  freely  divided  ;  the  sheath  of  the  vessels  is  now  seen,  and  must  be  opened,  and  the 
artery  secured  by  passing  the  aneurism  needle  between  the  vein  and  artery  in  the  direction  from 
without  inward.  The  femoral  vein  in  this  situation  lies  on  the  outer  side  of  the  artery,  the  long 
saphenous  nerve  on  its  anterior  and  outer  side. 

It  has  been  seen  that  the  femoral  artery  occasionally  divides  into  two  trunks  below  the  origin 
of  the  profunda.  If  in  the  operation  for  tying  the  femoral  two  vessels  are  met  with,  the  surgeon 
should  alternately  compress  each,  in  order  to  ascertain  which  vessel  is  connected  with  the 
aneurismal  tumor  or  with  the  bleeding  from  the  wound,  and  that  one  only  should  be  tied  which 
controls  the  pulsation  or  haemorrhage.  If,  however,  it  is  necessary  to  compress  both  vessels 
before  the  circulation  in  the  tumor  is  controlled,  both  should  be  tied,  as  it  would  be  probable  that 
they  became  reunited,  as  in  the  instances  referred  to  above. 

In  wounds  of  the  femoral  artery  the  question  of  the  mode  of  treatment  is  of  considerable 
importance.  If  the  wound  in  the  superficial  structures  is  a  large  one,  the  injured  vessel  must 
be  exposed  and  tied ;  but  if  the  wound  is  a  punctured  one  and  the  bleeding  has  ceased,  the 
question  will  arise  whether  to  cut  down  upon  the  artery  or  to  trust  to  pressure.  Mr.  Cripps l 
advises  that  if  the  wound  is  in  the  "  upper  part  of  the  thigh — that  is  to  say,  in  a  position  where 
the  femoral  artery  is  comparatively  superficial — the  surgeon  may  enlarge  the  opening  with  a 
good  prospect  of  finding  the  wounded  vessel  without  an  extensive  or  prolonged  operation.  If 
the  wound  be  in  the  lower  half  of  the  thigh,  owing  to  the  greater  depth  of  the  artery  and  the 
possibility  of  its  being  the  popliteal  that  is  wounded,  the  search  is  rendered  a  far  more  severe 
and  hazardous  operation,  and  it  should  not  be  undertaken  until  a  thorough  trial  of  pressure  has 
proved  ineffectual." 

Great  care  and  attention  are  necessary  for  the  successful  application  of  pressure.  The  limb 
should  be  carefully  bandaged  from  the  foot  upward  to  the  wound,  which  is  not  covered,  and  then 
onward  to  the  groin.  The  wound  is  then  dusted  with  iodoform  or  boracic  powder  and  a  conical 
pad  applied  over  the  wound.  Rollers  the  thickness  of  the  index  finger  are  then  placed  along 
the  course  of  the  vessel  above  and  below  the  wound,  and  the  whole  carefully  bandaged  to  a  back 
splint  with  a  foot-piece. 

Collateral  Circulation. — When  the  common  femoral  is  tied  the  main  channels  for  carrying 
on  the  circulation  are  the  anastomoses  of  the  gluteal  and  circumflex  iliac  arteries  above  with  the 
external  circumflex  below ;  of  the  obturator  and  sciatic  above  with  the  internal  circumflex  below ; 
and  of  the  comes  nervi  ischiadici  with  the  arteries  in  the  ham. 

The  principal  agents  in  carrying  on  the  collateral  circulation  after  ligature  of  the  superficial 
femoral  artery  are,  according  to  Sir  A.  Cooper,  as  follows  : 

"  The  arteria  profunda  formed  the  new  channel  for  the  blood."  "The  first  artery  sent  off 
passed  down  close  to  the  back  of  the  thigh-bone,  and  entered  the  two  superior  articular  branches 
of  the  popliteal  artery." 

"The  second  new  large  vessel,  arising  from  the  profunda  at  the  same  part  with  the  former, 
passed  down  by  the  inner  side  of  the  Biceps  muscle  to  a  branch  of  the  popliteal  which  was  dis- 
tributed to  the  Gastrocnemius  muscle ;  whilst  a  third  artery,  dividing  into  several  branches, 
passed  down  with  the  sciatic  nerve  behind  the  knee-joint,  and  some  of  its  branches  united  them- 
selves with  the  inferior  articular  arteries  of  the  popliteal,  with  some  recurrent  branches  of  those 
arteries,  with  arteries  passing  to  the  Gastrocnemii,  and,  lastly,  with  the  origin  of  the  anterior 
and  posterior  tibial  arteries." 

"It  appears,  then,  that  it  is  those  branches  of  the  profunda  which  accompany  the  sciatic 
nerve  that  are  the  principal  supporters  of  the  new  circulation."  2 

In  Porta's  work  3  (tab.  xii.,  xiii. )  is  a  good  representation  of  the  collateral  circulation  after 
the  ligature  of  the  femoral  artery.  The  patient  had  survived  the  operation  three  years.  The 
lower  part  of  the  artery  is  at  least  as  large  as  the  upper ;  about  two  inches  of  the  vessel  appear 
to  have  been  obliterated.  The  external  and  internal  circumflex  arteries  are  seen  anastomosing 
by  a  great  number  of  branches  with  the  lower  branches  of  the  femoral  (muscular  and  anasto- 
motica  magna)  and  with  the  articular  branches  of  the  popliteal.  The  branches  from  the 
external  circumflex  are  extremely  large  and  numerous.  One  very  distinct  anastomosis  can  be 
traced  between  this  artery  on  the  outside  and  the  anastomotica  magna  on  the  inside  through  the 
intervention  of  the  superior  external  articular  artery,  with  which  they  both  anastomose  ;  and 
blood  reaches  even  the  anterior  tibial  recurrent  from  the  external  circumflex  by  means  of 
anastomosis  with  the  same  external  articular  artery.  The  perforating  branches  of  the  profunda 
are  also  seen  bringing  blood  round  the  obliterated  portion  of  the  artery  into  long  brandies 
(muscular)  which  have  been  given  off  just  below  that  portion.  The  termination  of  the  profunda 
itself  anastomoses  most  freely  with  the  superior  external  articular.  A  long  branch  of  anasto- 
mosis is  also  traced  down  from  the  internal  iliac  by  means  of  the  comes  nervi  ischiadici  of  the 
sciatic,  which  anastomoses  on  the  popliteal  nerves  with  branches  from  the  popliteal  and  posterior 
tibial  arteries.  In  this  case  the  anastomosis  had  been  too  free,  since  the  pulsation  and  growth 
of  the  aneurism  recurred,  and  the  patient  died  after  ligature  of  the  external  iliac. 

There  is  an  interesting  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  a 
limb  on  which  John  Hunter  had  tied  the  femoral  artery  fifty  years  before  the  patient's  death. 
The  whole  of  the  superficial  femoral  and  popliteal  artery  seems  to  have  been  obliterated.  The 

1  Heath's  Dictionary  of  Practical  Surgery,  vol.  i.  p.  525. 

*  Med.-Chir.  Trans.,  vol.  ii.  1811.  3  Allerazioni  patologiche  ddle  Arterie. 


THE   FEMORAL    ARTERY.  635 

anastomosis  by  means  of  the  comes  nervi  ischiadici,  which  is  shown  in  Porta's  plate,  is  distinctly 
seen :  the  external  circumflex  and  the  termination  of  the  profunda  artery,  seem  to  have  been 
the  chief  channels  of  anastomosis ;  but  the  injection  has  not  been  a  very  successful  one. 

Branches. — The  branches  of  the  femoral  artery  are — the 

Superficial  Epigastric.  (  External  Circumflex. 

Superficial  Circumflex  Iliac.  Profunda <  Internal  Circumflex. 

Superficial  External  Pudic.  (Three  Perforating. 

Deep  External  Pudic.  Muscular. 

Anastomotica  Magna. 

The  superficial  epigastric  arises  from  the  femoral  about  half  an  inch  below  Pou- 
part's  ligament,  and.  passing  through  the  saphenous  opening  in  the  fascia  lata, 
asrt  ii-ls  on  the  abdomen,  in  the  superficial  fascia  covering  the  External  oblique 
muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches  to  the  superficial 
inguinal  glands,  the  superficial  fascia,  and  the  integument,  anastomosing  with 
branches  of  the  deep  epigastric. 

The  superficial  circumflex  iliac,  the  smallest  of  the  cutaneous  branches,  arises 
close  to  the  preceding,  and,  piercing  the  fascia  lata.  runs  outward,  parallel  with 
Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches  which 
supply  the  integument  of  the  groin,  the  superficial  fascia,  and  the  superficial  ingui- 
nal lymphatic  glands,  anastomosing  with  the  circumflex  iliac  and  with  the  gluteal 
and  external  circumflex  arteries. 

The  superficial  external  pudic  (superior)  arises  from  the  inner  side  of  the  femoral 
artery,  close  to  the  preceding  vessels,  and.  after  passing  through  the  saphenous 
opening,  courses  inward,  across  the  spermatic  cord  or  round  ligament,  to  be  dis- 
tributed to  the  integument  on  the  lower  part  of  the  abdomen,  the  penis  and  scro- 
tum in  the  male,  and  the  labium  in  the  female,  anastomosing  with  branches  of  the 
internal  pudic. 

The  deep  external  pudic  (inferior),  more  deeply  seated  than  the  preceding, 
passes  inward  on  the  Pectineus  muscle,  covered  by  the  fascia  lata.  which  it  pierces 
ar  the  inner  border  of  the  thigh,  its  branches  being  distributed,  in  the  male,  to  the 
integument  of  the  scrotum  and  perinseum  ;  and  in  the  female,  to  the  labium,  anas- 
tomosing with  branches  of  the  superficial  perineal  artery. 

The  Profunda  Femoris  (deep  femoral  artery)  nearly  equals  the  size  of  the 
superficial  femoral.  It  arises  from  the  outer  and  back  part  of  the  femoral  artery, 
from  one  to  two  inches  below  Poupart's  ligament.  It  at  first  lies  on  the  outer  side 
of  the  superficial  femoral,  and  then  passes  behind  it  and  the  femoral  vein  to  the 
inner  side  of  the  femur,  and,  passing  downward  beneath  the  Adductor  longus, 
terminates  at  the  lower  third  of  the  thigh  in  a  small  branch  which  pierces  the 
Adductor  magnus  (and  from  this  circumstance  is  sometimes  called  the  fourth 
perforating  artery),  and  is  distributed  to  the  flexor  muscles  on  the  back  of  the 
thigh,  anastomosing  with  branches  of  the  popliteal  and  inferior  perforating 
arteries. 

Relations. — Behind,  it  lies  first  upon  the  Iliacus.  and  then  on  the  Pectineus, 
Adductor  brevis.  and  Adductor  magnus  muscles.  In  front,  it  is  separated  from 
the  femoral  artery,  above  by  the  femoral  and  profunda  veins,  and  below  by  the 
Adductor  longus.  On  its  outer  side  the  origin  of  the  Vastus  internus  separates  it 
from  the  femur. 


636  THE  ARTERIES. 

PLAN  OF  THE  RELATIONS  OF  THE  PROFUNDA  ARTERY. 

In  front. 

Femoral  and  Profunda  veins. 
Adductor  longus. 

Outer  side. 
Vastus  internus. 


Behind. 
Iliacus. 
Pectin  eus. 
Adductor  brevis. 
Adductor  niagnus. 

The  External  Circumflex  Artery  supplies  the  muscles  on  the  front  of  the  thigh. 
It  arises  from  the  outer  side  of  the  profunda,  passes  horizontally  outward,  between 
the  divisions  of  the  anterior  crural  nerve  and  behind  the  Sartorius  and  Rectus 
muscles,  and  divides  into  three  sets  of  branches — ascending,  transverse,  and 
descending. 

The  ascending  branches  pass  upward,  beneath  the  Tensor  vaginas  femoris 
muscle,  to  the  outer  side  of  the  hip,  anastomosing  with  the  terminal  branches  of 
the  gluteal  and  circumflex  iliac  arteries. 

The  descending  branches,  three  or  four  in  number,  pass  downward,  behind  the 
Rectus,  upon  the  Vasti  muscles,  to  which  they  are  distributed,  one  or  two  passing 
beneath  the  Vastus  extern  us  as  far  as  the  knee,  anastomosing  with  the  superior 
articular  branches  of  the  popliteal  artery.  These  are  accompanied  by  the  branch 
of  the  anterior  crural  nerve  to  the  Vastus  externus. 

The  transverse  branches,  the  smallest  and  least  numerous,  pass  outward  over 
the  Crureus,  pierce  the  Vastus  externus,  and  wind  round  the  femur  to  its  back 
part,  just  below  the  great  trochanter,  anastomosing  at  the  back  of  the  thigh  with 
the  internal  circumflex,  sciatic,  and  superior  perforating  arteries. 

The  Internal  Circumflex  Artery,  smaller  than  the  external,  arises  from  the  inner 
and  back  part  of  the  profunda.  and  winds  round  the  inner  side  of  the  femur, 
between  the  Pectineus  and  Psoas  muscles.  On  reaching  the  upper  border  of  the 
Adductor  brevis  it  gives  off  two  branches,  one  of  which  passes  inward  to  be  dis- 
tributed to  the  Adductor  muscles,  the  Gracilis,  and  Obturator  externus,  anasto- 
mosing with  the  obturator  artery ;  the  other  descends,  and  passes  beneath  the 
Adductor  brevis,  to  supply  it  and  the  great  Adductor ;  while  the  continuation  of 
the  vessel  passes  backward,  between  the  Quadratus  femoris  and  upper  border  of 
the  Adductor  magnus,  anastomosing  with  the  sciatic,  external  circumflex,  and 
superior  perforating  arteries  ("  the  crucial  anastomosis  ").  Opposite  the  hip-joint 
this  branch  gives  off  an  articular  vessel,  which  enters  the  joint  beneath  the  trans- 
verse ligament,  and,  after  supplying  the  adipose  tissue,  passes  along  the  round 
ligament  to  the  head  of  the  bone. 

The  Perforating  Arteries  (Fig.  375),  usually  three  in  number,  are  so  called  from 
their  perforating  the  tendon  of  the  Adductor  magnus  muscle  to  reach  the  back  of 
the  thigh.  The  first  is  given  off  above  the  Adductor  brevis,  the  second  in  front 
of  that  muscle,  and  the  third  immediately  below  it. 

The  first  or  superior  perforating  artery  passes  backward  between  the  Pectineus 
and  Adductor  brevis  (sometimes  perforates  the  latter) ;  it  then  pierces  the  Adductor 
magnus  close  to  the  linea  aspera,  and  divides  into  branches  which  supply  the 
Adductor  brevis,  the  Adductor  magnus,  the  Biceps,  and  Gluteus  maximus  muscles, 
anastomosing  with  the  sciatic,  internal  and  external  circumflex,  and  middle  per- 
forating arteries. 

The  second  or  middle  perforating  artery,  larger  than  the  first,  pierces  the 
tendons  of  the  Adductor  brevis  and  Adductor  magnus  muscles,  and  divides  into 
ascending  and  descending  branches,  which  supply  the  flexor  muscles  of  the  thigh, 


THE   POPLITEAL    ARTERY.  637 

anastomosing  with  the  superior  and  inferior  perforating.  The  nutrient  artery  of  the 
femur  is  usually  given  off  from  this  branch. 

The  third  or  inferior  perforating  artery  is  given  off  below  the  Adductor  brevis ; 
it  pierces  the  Adductor  magnus,  and  divides  into  branches  which  supply  the  flexor 
muscles  of  the  thigh,  anastomosing  above  with  the  perforating  arteries,  and  below 
with  the  terminal  branches  of  the  profunda  and  the  muscular  branches  of  the 
popliteal. 

Muscular  branches  are  given  off  from  the  superficial  femoral  throughout  its 
entire  course.  They  vary  from  two  to  seven  in  number,  and  supply  chiefly  the 
Sartorius  an<l  Vastus  internus. 

The  Anastomotica  Magna  arises  from  the  femoral  artery  just  before  it  passes 
through  the  tendinous  opening  in  the  Adductor  magnus  muscle,  and  divides  into  a 
superficial  and  deep  branch. 

The  superficial  branch  accompanies  the  long  saphenous  nerve  beneath  the 
Sartorius.  and.  piercing  the  fascia  lata,  is  distributed  to  the  integument. 

The  deep  branch  descends  in  the  substance  of  the  Vastus  internus,  lying  in 
front  of  the  tendon  of  the  Adductor  magnus.  to  the  inner  side  of  the  knee,  where  it 
anastomoses  with  the  superior  internal  articular  artery  and  anterior  recurrent 
branch  of  the  anterior  tibial.  A  branch  from  this  vessel  crosses  outward  above 
the  articular  surface  of  the  femur,  forming  an  anastomotic  arch  with  the  superior 
external  articular  artery,  and  supplies  branches  to  the  knee-joint. 

Popliteal  Artery. 

The  popliteal  artery  commences  at  the  termination  of  the  femoral  at  the 
opening  in  the  Adductor  magnus.  and.  passing  obliquely  downward  and  outward 
behind  the  knee-joint  to  the  lower  border  of  the  Popliteus  muscle,  divides  into 
the  ant: r /•/<</•  and  posterior  tibial  arteries.  A  portion  of  the  artery  lies  in  the 
popliteal  space :  but  above,  to  a  slight  extent,  and  below,  to  a  considerable  extent, 
it  is  covered  by  the  muscles  which  form  the  boundaries  of  the  space,  and  is  therefore 
beyond  the  confines  of  the  hollow. 

THE  POPLITEAL  SPACE   (Fig.  377). 

Dissection. — A  vertical  incision  about  eight  inches  in  length  should  be  made  along  the 
back  part  of  the  knee-joint,  connected  above  and  below  by  a  transverse  incision  from  the  inner 
to  the  outer  side  of  the  limb.  The  flaps  of  integument  included  between  these  incisions  should 
be  reflected  in  the  direction  shown  in  Fig.  328,  page  514. 

Boundaries. — The  popliteal  space. is  lozenge-shaped,  widest  at  the  back  part  of 
the  knee-joint.  It  is  bounded  externally,  above  the  joint,  by  the  Biceps,  and, 
below  the  joint,  by  the  Plantaris  and  external  head  of  the  Gastrocneinius  ;  in- 
ternally, above  the  joint,  by  the  Semimembranosus  and  Semitendinosus.  the  latter, 
however,  lying  on  (posterior  to}  the  former,  whose  edge  is  the  real  boundary;  below 
the  joint,  by  the  inner  head  of  the  Gastrocnemius. 

Above,  it  is  limited  by  the  apposition  of  the  inner  and  outer  hamstring 
muscles:  beL»w.  by  the  junction  of  the  two  heads  of  the  Gastrocnemius. 
The  floor  is  formed  by  the  lower  part  of  the  posterior  surface  of  the  shaft  of 
the  femur,  the  posterior  ligament  of  the  knee-joint,  the  upper  end  of  the  tibia, 
and  the  fascia  covering  the  Popliteus  muscle,  and  the  space  is  covered  in  by  the 
fascia  lata. 

Contents. — It  contains  the  popliteal  vessels  and  their  branches,  together  with 
the  termination  of  the  external  saphenous  vein,  the  internal  and  external  popliteal 
nerves  and  some  of  their  branches,  the  lower  extremity  of  the  small  sciatic  nerve, 
the  articular  branch  from  the  obturator  nerve,  a  few  small  lymphatic  glands,  and 
a  considerable  quantity  of  loose  adipose  tissue. 

Position  of  Contained  Parts. — The  internal  popliteal  nerve  descends  in  the 
middle  line  of  the  space,  lying  superficial  and  crossing  the  artery  from  without 
inward.  The  external  popliteal  nerve  descends  on  the  outer  side  of  the  space, 


638  THE   ARTERIES. 

lying  close  to  the  tendon  of  the  Biceps  muscle.  More  deeply  at  the  bottom  of  the 
space  are  the  popliteal  vessels,  the  vein  lying  superficial  and  a  little  external  to  the 
artery,  to  which  it  is  closely  united  by  dense  areolar  tissue  ;  sometimes  the  vein 
is  placed  on  the  inner  instead  of  the  outer  side  of  the  artery  ;  or  the  vein  may  be 
double,  the  artery  lying  between  the  two  vengecomites,  which  are  usually  connected 
by  short  transverse  branches.  More  deeply,  and,  at  its  upper  part,  close  to  the 
surface  of  the  bone,  is  the  popliteal  artery,  and  passing  off  from  it  at  right  angles 
are  its  articular  branches.  The  articular  branch  from  the  obturator  nerve  descends 
upon  the  popliteal  artery  to  supply  the  knee,  and  occasionally  there  is  found  deep 
in  the  space  an  articular  filament  from  the  great  sciatic  nerve.  The  popliteal 
lymphatic  glands,  four  or  five  in  number,  are  found  surrounding  the  artery :  one 
usually  lies  superficial  to  the  vessel ;  another  is  situated  between  it  and  the  bone, 
and  the  rest  are  placed  on  either  side  of  it. 

The  Popliteal  Artery,  in  its  course  downward  from  the  aperture  in  the  Adductor 
magnus  to  the  lower  border  of  the  Popliteus  muscle,  rests  first  on  the  inner  surface 
of  the  femur,  and  is  then  separated  by  a  little  fat  from  the  hollowed  popliteal 
surface  of  the  bone ;  in  the  middle  of  its  course  it  rests  on  the  posterior  ligament 
of  the  knee-joint,  and  below  on  the  fascia  covering  the  Popliteus  muscle.  Super- 
ficially, it  is  covered  above  by  the  Semimembranosus  ;  in  the  middle  of  its  course, 
by  a  quantity  of  fat,  which  separates  it  from  the  deep  fascia  and  integument ;  and 
below  it  is  overlapped  by  the  Gastrocnemius,  Plantaris,  and  Soleus  muscles,  the 
popliteal  vein,  and  the  internal  popliteal  nerve.  The  popliteal  vein,  which  is 
intimately  attached  to  the  artery,  lies  superficial  and  external  to  it  until  near  the 
termination  of  the  artery,  when  the  vein  crosses  it  and  lies  to  its  inner  side.  The 
internal  popliteal  nerve  is  still  more  superficial  and  external  above,  but  below  the 
joint  it  crosses  the  artery  and  lies  on  its  inner  side.  Laterally,  the  artery  is 
bounded  by  the  rcuscles  which  are  situated  on  either  side  of  the  popliteal  space. 

PLAN  or  RELATIONS  OF  POPLITEAL  ARTERY. 

In  front. 
Femur. 

Ligamentum  posticum. 
Popliteus. 

Inner  side.  f  Outer  side. 

Semimembranosus.  I     popiiteal      ]  Biceps. 

Internal  condyle.  1       Artery.       I  Outer  condyle. 

Gastrocnemius  (inner  head).  V  Gastrocnemius  (outer  head). 

Internal  popliteal  nerve  (below).  Plantaris. 

Internal  popliteal  nerve  (above). 
Behind. 

Semimembranosus. 

Fascia. 

Popliteal  vein. 

Internal  popliteal  nerve. 

Gastrocnemius. 

Plantaris. 

Soleus. 

Peculiarities  in  Point  of  Division. — Occasionally  the  popliteal  artery  divides  prematurely 
into  its  terminal  branches ;  this  unusual  division  occurs  most  frequently  opposite  the  knee-joint. 

Unusual  Branches. — The  artery  sometimes  divides  into  the  anterior  tibial  and  peroneal, 
the  posterior  tibial  being  wanting  or  very  small.  Occasionally  the  popliteal  is  found  to  divide 
into  three  branches,  the  anterior  and  posterior  tibial  and  peroneal. 

Surface  Marking.— The  course  of  the  upper  part  of  the  popliteal  artery  is  indicated  by 
a  line  drawn  from  the  outer  border  of  the  Semimembranosus  muscle  at  the  junction  of  the 
middle  and  lower  third  of  the  thigh  obliquely  downward  to  the  middle  of  the  popliteal  space, 
exactly  behind  the  knee-joint.  From  this  point  it  passes  vertically  downward  to  the  level  of  a 
line  drawn  through  the  lower  part  of  the  tubercle  of  the  tibia. 

Surgical  Anatomy. — The  popliteal  artery  is  not  infrequently  the  seat  of  injury.  It  may  be 
torn  by  direct  violence,  as  by  the  passage  of  a  cart-wheel  over  the  knee  or  by  hyper-extension  of 
the  knee  ;  and  in  the  dead  body,  at  all  events,  the  middle  and  internal  coats  may  be  ruptured  by 
extreme  flexion.  It  may  also  be  lacerated  by  fracture  of  the  lower  part  of  the  shaft  of  the 


BRANCHES    OF    THE  POPLITEAL    ARTERY.  639 

femur  or  by  antero-posterior  dislocation  of  the  knee-joint.  It  has  been  torn  in  breaking  down 
adhesions  in  cases  of  fibrous  ankylosis  of  the  knee,  and  is  in  danger  of  being  wounded,  and  in 
fact  has  been  wounded,  in  performing  Macewen's  operation  of  osteotomy  of  the  lower  end  of  the 
femur  for  genu  valgum.  In  addition.  Spencer  records  a  case  in  which  the  popliteal  artery  was 
wounded  from  in  front  by  a  stab  just  below  the  knee,  the  knife  passing  through  the  interosseous 
space.  The  popliteal  artery  is  more  frequently  the  seat  of  aneurism  than  is  any  other  artery 
in  the  body,  with  the  exception  of  the  thoracic  aorta.  This  is  due  no  doubt,  in  a  great 
measure  to  the  amount  of  movement  to  which  it  is  subjected,  and  to  the  fact  that  it  is  supported 
by  loose  and  lax  tissue  only,  and  not  by  muscles,  as  is  the  case  with  most  arteries. 

Ligature  of  the  popliteal  artery  is  required  in  cases  of  wound  of  that  vessel,  but  for  aneurism 
of  the  posterior  tibial  it  is  preferable  to  tie  the  superficial  femoral.  The  popliteal  may  be  tied 
in  the  upper  or  lower  part  of  its  course :  but  in  the  middle  of  the  ham  the  operation  is  attended 
with  considerable  difficult}',  from  the  great  depth  of  the  artery  and  from  the  extreme  degree  of 
tension  of  the  lateral  boundaries  of  the  space. 

In  order  to  expose  the  vessel  in  the  upper  part  of  its  course  the  patient  should  be  placed  in 
the  prone  position,  with  the  limb  extended.  An  incision  about  three  inches  in  length  should 
then  be  made  through  the  integument,  along  the  posterior  margin  of  the  Semimembranosus, 
and.  the  fascia  lata  having  been  divided,  this  muscle  must  be  drawn  inward.  The  internal  pop- 
liteal nerve  will  be  first  exposed,  lying  very  superficial  and  external  to  the  artery ;  beneath  this 
will  be  seen  the  popliteal  vein,  and,  still  deeper  and  to  its  inner  side,  the  artery.  The  vein  and 
nerve  must  be  cautiously  separated  from  the  artery,  and  the  aneurism  needle  passed  around  the 
vessel  from  without  inward. 

To  expose  the  vessel  in  the  lower  part  of  its  course,  where  the  artery  lies  between  the  two 
heads  of  the  Gastrocnemius.  the  patient  should  be  placed  in  the  same  position  as  in  the  preceding 
operation.  An  incision  should  then  be  made  through  the  integument  in  the  middle  line,  com- 
mencing  opposite  the  bend  of  the  knee-joint,  care  being  taken  to  avoid  the  external  saphenous 
vein  and  nerve.  After  dividing  the  deep  fascia  and  separating  some  dense  cellular  membrane, 
the  artery,  vein,  and  nerve  will  be  exposed,  descending  between  the  two  heads  of  the  Gastrocne- 
mius. Some  muscular  branches  of  the  popliteal  should  be  avoided  if  possible,  or,  if  divided,  tied 
immediately.  The  leg  being  now  flexed,  in  order  the  more  effectually  to  separate  the  two  heads 
of  the  Gastrocnemius  the  nerve  should  be  drawn  inward  and  the  vein  outward,  and  the 
aneurism  needle  passed  between  the  artery  and  vein  from  without  inward. 

In  cases  where  the  artery  has  been  wounded  during  an  osteotomy  of  the  lower  end  of  the 
femur  it  would  be  most  conveniently  secured  from  the  front  at  the  inner  side  of  the  thigh.  The 
knee  is  flexed  and  the  limb  placed  on  its  outer  side.  An  incision,  three  inches  long,  is  made 
parallel  to  and  immediately  behind  the  tendon  of  the  Adductor  magnus  from  the  junction  of  the 
middle  and  lower  third  of  the  thigh.  Skin,  superficial  and  deep  fascia  are  to  be  divided,  care 
being  taken  of  the  internal  saphenous  vein  ;  the  Adductor  magnus  is  to  be  drawn  forward  and 
the  inner  hamstring  tendons  backward,  and  the  artery  will  be  found  surrounded  by  fat.  The 
nerve  and  vein  are  usually  not  seen,  as  they  lie  to  the  outer  side  of  the  artery. 

The  branches  of  the  popliteal  artery  are — the 

•tr        i    .  f  Superior.  Superior  Internal  Articular. 

^Muscular  's  T  /•    •  01  A  *    ^-     i 

(  Interior  or  bural.  Azygos  Articular. 

Cutaneous.  Inferior  External  Articular. 

Superior  External  Articular.  Inferior  Internal  Articular. 

The  superior  muscular  branches,  two  or  three  in  number,  arise  from  the  upper 
part  of  the  popliteal  artery,  and  are  distributed  to  the  Vastus  externus  and  flexor 
muscles  of  the  thigh,  anastomosing  with  the  inferior  perforating  and  terminal 
branches  of  the  profunda. 

The  inferior  muscular  (sural)  are  two  large  branches  which  are  distributed  to 
the  two  heads  of  the  Gastrocnemius  and  to  the  Plantaris  muscle.  They  arise  from 
the  popliteal  artery  opposite  the  knee-joint. 

Cutaneous  branches  descend  on  each  side  and  in  the  middle  of  the  limb,  between 
the  Gastrocnemius  and  integument ;  they  arise  separately  from  the  popliteal  artery 
or  from  some  of  its  branches,  and  supply  the  integument  of  the  calf. 

The  superior  articular  arteries,  two  in  number,  arise  one  on  each  side  of  the 
popliteal,  and  wind  round  the  femur  immediately  above  its  condyles  to  the  front 
of  the  knee-joint.  The  internal  branch  passes  beneath  the  tendon  of  the  Adductor 
magnus,  and  divides  into  two,  one  of  which  supplies  the  Yastus  internus,  inoscu- 
lating with  the  anastomotica  magna  and  inferior  internal  articular ;  the  other 
ramifies  close  to  the  surface  of  the  femur,  supplying  it  and  the  knee-joint,  and 
anastomosing  with  the  superior  external  articular  artery.  The  external  branch 
passes  above  the  outer  condyle.  beneath  the  tendon  of  the  Biceps,  and  divides  into 


640  THE   ARTERIES. 

a  superficial  and  deep  branch:   the  superficial  branch  supplies  the  Vastus  exter- 


-Sural  arteries. 


•Anterior  peroneal. 


FIG.  377.— The  popliteal,  posterior  tibial,  and 
peroneal  arteries. 


Inferior 
external 
articular, 


'Inferior  internal 
articular. 


Communicating. 


FIG.  378.— Surgical  anatomy  of  the  anterior  tibial 
and  dorsalis  pedi?  arteries. 


nus   and  anastomoses  with  the  descending  branch  of  the  external  circumflex,  and 
the  inferior  external  articular  arteries ;  the  deep  branch  supplies  the  lower  part 


THE   ANTERIOR    TIBIA L    ARTERY.  641 

of  the  femur  and  knee-joint,  and  forms  an  anastomotic  arch  across  the  bone  with 
the  anastomotica  magna  and  the  inferior  internal  articular  arteries. 

The  azygos  articular  is  a  small  branch  arising  from  the  popliteal  artery  oppo- 
site the  bend  of  the  knee-joint.  It  pierces  the  posterior  ligament,  and  supplies 
the  ligaments  and  synovial  membrane  in  the  interior  of  the  articulation. 

The  inferior  articular  arteries,  two  in  number,  arise  from  the  popliteal  beneath 
the  Gastrocnemius.  and  wind  round  the  head  of  the  tibia  below  the  joint.  The 
nal  one  passes  below  the  inner  tuberosity.  beneath  the  internal  lateral  lig- 
ament, at  the  anterior  border  of  which  it  ascends  to  the  front  and  inner  side  of 
the  joint,  to  supply  the  head  of  the  tibia  and  the  articulation  of  the  knee,  anasto- 
mosing with  the  inferior  external  articular  and  superior  internal  articular  arteries. 
The  txt>rnal  one  passes  outward  above  the  head  of  the  fibula,  to  the  front  of  the 
knee-joint,  passing  in  its  course  beneath  the  outer  head  of  the  Gastrocnemius, 
the  external  lateral  ligament,  and  the  tendon  of  the  Biceps  muscle,  and  divides 
into  branches  which  anastomose  with  the  inferior  internal  articular  artery,  the 
superior  external  articular  artery,  and  the  anterior  recurrent  branch  of  the 
anterior  tibial. 

Circumpatellar  Anastomosis. — Around  and  above  the  patella,  and  on  the  con- 
tiguous ends  of  the  femur  and  tibia,  is  a  large  network  of  vessels,  forming  a 
superficial  and  deep  plexus  from  which  numerous  offsets  proceed  into  the  interior 
of  the  joint.  The  arteries  from  which  this  plexus  is  formed  are  the  two  internal 
and  two  external  articular  branches  of  the  popliteal,  the  anastomotica  magna,  the 
terminal  branch  of  the  profunda,  the  descending  branch  from  the  external  cir- 
cumflex, and  the  anterior  recurrent  branch  of  the  anterior  tibial. 

The  Anterior  Tibial  Artery  (Fig.  378). 

The  anterior  tibial  artery  commences  at  the  bifurcation  of  the  popliteal  at  the 
lower  border  of  the  Popliteus  muscle,  passes  forward  between  the  two  heads  of 
the  Tibialis  posticus.  and  through  the  large  oval  aperture  above  the  upper  border 
of  the  interosseous  membrane  to  the  deep  part  of  the  front  of  the  leg :  it  then 
descends  on  the  anterior  surface  of  the  interosseous  membrane,  gradually 
approaching  the  tibia  :  and  at  the  lower  part  of  the  leg  lies  on  this  bone,  and 
then  on  the  anterior  ligament  of  the  ankle  to  the  bend  of  the  ankle-joint,  where 
it  lies  more  superficially,  and  becomes  the  dorsalis  pedis. 

Relations. — In  the  upper  two-thirds  of  its  extent  it  rests  upon  the  interosseous 
membrane,  to  which  it  is  connected  by  delicate  fibrous  arches  thrown  across  it ; 
in  the  lower  third,  upon  the  front  of  the  tibia  and  the  anterior  ligament  of  the 
ankle-joint.  In  the  upper  third  of  its  course  it  lies  between  the  Tibialis  anticus 
and  Extensor  longus  digitorum ;  in  the  middle  third,  between  the  Tibialis  anticus 
and  Extensor  proprius  hallucis.  At  the  bend  of  the  ankle  it  is  crossed  by  the 
tendon  of  the  Extensor  proprius  hallucis.  and  lies  between  it  and  the  innermost 
tendon  of  the  Extensor  longus  digitorum.  It  is  covered,  in  the  upper  two-thirds 
of  its  course,  by  the  muscles  which  lie  on  either  side  of  it  and  by  the  deep  fascia ; 
in  the  lower  third,  by  the  integument,  anterior  annular  ligament,  and  fascia. 

The  anterior  tibial  artery  is  accompanied  by  two  veins  (venae  comites),  which 
lie  one  on  each  side  of  the  artery  ;  the  anterior  tibial  nerve  lies  at  first  to  its  outer 
side,  and  about  the  middle  of  the  leg  is  placed  superficial  to  it ;  at  the  lower  part 
of  the  artery  the  nerve  is  generally  again  on  the  outer  side. 

41 


642  THE   ARTERIES. 

PLAN  OF  THE  RELATIONS  OF  THE  ANTERIOR  TIBIAL  ARTERY. 

In  front. 

Integument,  superficial  and  deep  fasciae. 
Anterior  tibial  nerve. 

Tibialis  anticus  (overlaps  it  in  the  upper  part  of  the  leg). 
Extensor  longus  digitorum  )  /     n  ,  ^  •,    i-  1,1   v 
Extensor  proprius  hallucis  \  (overlaP  xt  sllghtly)- 
Anterior  annular  ligament. 

Inner  side.  ^  ^\  Outer  side. 

Tibialis  anticus.  /    Anterior    \  Anterior  tibial  nerve. 

Extensor  proprius  hallucis  (        Tibiai°  Extensor  longus  digitorum. 

(crosses  it  at  its  lower  V  /  Extensor  proprius  hallucis. 

part).  </ 

Behind. 

Interosseous  membrane. 
Tibia. 
Anterior  ligament  of  ankle-joint. 

Peculiarities  in  Size. — This  vessel  may  be  diminished  in  size,  may  be  deficient  to  a  greatei 
or  less  extent,  or  may  be  entirely  wanting,  its  place  being  supplied  by  perforating  branches  from 
the  posterior  tibial  or  by  the  anterior  division  of  the  peroneal  artery. 

Course. — The  artery  occasionally  deviates  in  its  course  toward  the  fibular  side  of  the  leg, 
regaining  its  usual  position  beneath  the  annular  ligament  at  the  front  of  the  ankle.  In  two 
instances  the  vessel  has  been  found  to  approach  the  surface  in  the  middle  of  the  leg,  being 
covered  merely  by  the  integument  and  fascia  below  that  point. 

Surface  Marking. — A  line  drawn  from  the  inner  side  of  the  head  of  the  fibula  to  midway 
between  the  two  malleoli  will  mark  the  course  of  the  artery,  the  point  where  the  artery  comes 
in  front  of  the  interosseous  membrane  being  in  this  line,  one  and  a  quarter  inches  below  the 
level  of  the  head  of  the  fibula. 

Surgical  Anatomy. — The  anterior  tibial  artery  may  be  tied  in  the  upper  or  lower  part 
of  the  leg.  In  the  upper  part  the  operation  is  attended  with  great  difficulty,  on  account  of  the 
depth  of  the  vessel  from  the  surface.  An  incision  about  four  inches  in  length,  should  be  made 
through  the  integument,  midway  between  the  spine  of  the  tibia  and  the  outer  margin  of  the 
fibula,  the  fascia  and  intermuscular  septum  between  the  Tibialis  anticus  and  Extensor  longus 
digitorum  being  divided  to  the  same  extent.  The  foot  must  be  flexed  to  relax  these  muscles, 
and  they  must  be  separated  from  each  other  by  the  finger.  The  artery  is  then  exposed  deeply 
seated,  lying  upon  the  interosseous  membrane,  the  nerve  lying  externally,  and  one  of  the  venae 
comites  on  either  side ;  these  must  be  separated  from  the  artery  before  the  aneurism  needle  is 
passed  round  it. 

To  tie  the  vessel  in  the  lower  third  of  the  leg  above  the  ankle-joint  an  incision  about  three 
inches  in  length  should  be  made  through  the  integument  between  the  tendons  of  the  Tibialis 
anticus  and  Extensor  proprius  hallucis  muscles,  the  deep  fascia  being  divided  to  the  same  extent. 
The  tendon  on  either  side  should  be  held  aside,  when  the  vessel  will  be  seen  lying  upon  the 
tibia,  with  the  nerve  superficial  to  it  and  one  of  the  venae  comites  on  either  side. 

The  branches  of  the  anterior  tibial  artery  are — the 

Posterior  Recurrent  Tibial.  Muscular. 

Superior  Fibular.  Internal  Malleolar. 

Anterior  Recurrent  Tibial.  External  Malleolar. 

The  posterior  recurrent  tibial  is  not  a  constant  branch,  and  is  given  off  from 
the  anterior  tibial  before  that  vessel  passes  through  the  interosseous  space.  It 
ascends  beneath  the  Popliteus  muscle,  which  it  supplies,  and  anastomoses  with  the 
lower  articular  branches  of  the  popliteal  artery,  giving  off  an  offset  to  the 
superior  tibio-fibular  joint. 

The  superior  fibular  is  sometimes  given  off  from  the  anterior  tibial,  sometimes 
from  the  posterior  tibial.  It  passes  outward,  round  the  neck  of  the  fibula,  through 
the  Soleus,  which  it  supplies,  and  ends  in  the  substance  of  the  Peroneus  longus 
muscle. 

The  anterior  recurrent  tibial  branch  arises  from  the  anterior  tibial  as  soon  as 
that  vessel  has  passed  through  the  interosseous  space ;  it  ascends  in  the  Tibialis 
anticus  muscle,  and  ramifies  on  the  front  and  sides  of  the  knee-joint,  anastomos- 
ing with  the  articular  branches  of  the  popliteal  and  with  the  anastomotica  magna. 

The  muscular  branches  are  numerous :    they  are  distributed  to  the  muscles 


THE   DORSAL  IS   PEDIS  ARTERY.  643 

which  lie  on  each  side  of  the  vessel,  some  piercing  the  deep  fascia  to  supply  the 
integument,  others  passing  through  the  interosseous  membrane,  and  anastomosing 
with  branches  of  the  posterior  tibial  and  peroneal  arteries. 

The  malleolar  arteries  supply  the  ankle-joint.  The  internal  arises  about  two 
inches  above  the  articulation,  and  passes  beneath  the  tendons  of  the  Extensor 
proprius  hallucis  and  Tibialis  anticus  to  the  inner  ankle,  upon  which  it  ramifies, 
anastomosing  with  branches  of  the  posterior  tibial  and  internal  plantar  arteries 
and  with  the  internal  calcanean  from  the  posterior  tibial.  The  external  passes 
beneath  the  tendons  of  the  Extensor  longus  digitorum  and  Peroneus  tertius,  and 
supplies  the  outer  ankle,  anastomosing  with  the  anterior  peroneal  artery  and  with 
ascending  branches  from  the  tarsal  branch  of  the  dorsalis  pedis. 

The  Dorsalis  Pedis  Artery  (Fig.  378). 

The  dorsalis  pedis,  the  continuation  of  the  anterior  tibial,  passes  forward  from 
the  bend  of  the  ankle  along  the  tibial  side  of  the  foot  to  the  back  part  of  the  first 
intermetatarsal  space,  where  it  divides  into  two  branches,  the  dorsalis  hallucis,  and 
communicating,  or  first  dorsal  interosseous  artery  and. plantar  digital  respectively. 

Relations. — This  vessel,  in  its  course  forward,  rests  upon  the  astragalus,  navic- 
ular.  and  internal  cuneiform  bones  and  the  ligaments  connecting  them,  being  cov- 
ered by  the  integument  and  fascia,  anterior  annular  ligament,  and  crossed  near 
its  termination  by  the  innermost  tendon  of  the  Extensor  brevis  digitorum.  On 
its  tibial  side  is  the  tendon  of  the  Extensor  proprius  hallucis ;  on  its  fibular  side, 
the  innermost  tendon  of  the  Extensor  longus  digitorum,  and  the  termination  of  the 
anterior  tibial  nerve.  It  is  accompanied  by  two  veins. 

PLAX  OF  THE  RELATIONS  OF  THE  DORSALIS  PEDIS  ARTERY. 

In  front. 

Integument  and  fascia. 

Anterior  annular  ligament. 

Innermost  tendon  of  Extensor  brevis  digitorum. 


Tibial  side.  I        _lia     \  Fibular  side. 


Extensor  proprius  hallucis.  *««••       j  Extensor  long™  digitorum. 

Anterior  tibial  nerve. 


Behind. 

Astragalus. 
Navicular. 
Internal  cuneiform, 
and  their  ligaments. 

Peculiarities  in  Size. — The  dorsal  artery  of  the  foot  may  be  larger  than  usual,  to  compen- 
sate for  a  deficient  plantar  artery;  or  it  may  be  deficient  in  its  terminal  branches  to  the  toes, 
which  are  then  derived  from  the  internal  plantar ;  or  its  place  may  be  supplied  altogether  by  a 
large  anterior  peroneal  artery. 

Position. — This  artery  frequently  curves  outward,  lying  external  to  the  line  between  the 
middle  of  the  ankle  and  the  back  part  of  the  first  interosseous  space. 

Surface  Marking. — The  dorsalis  pedis  artery  is  indicated  on  the  surface  of  the  dorsum  of 
the  foot  by  a  line  drawn  from  the  centre  of  the  space  between  the  two  malleoli  to  the  back  of  the 
first  internietatarsal  space. 

Surgical  Anatomy. — This  artery  may  be  tied,  by  making  an  incision  through  the  integu- 
ment between  two  and  three  inches  in  length,  on  the  fibular  side  of  the  tendon  of  the  Extensor 
proprius  hallucis.  in  the  interval  between  it  and  the  inner  border  of  the  short  Extensor  muscle. 
The  incision  should  not  extend  farther  forward  than  the  back  part  of  the  first  intermetatarsal 
space,  as  the  artery  divides  in  that  situation.  The  deep  fascia  being  divided  to  the  same  extent, 
the  artery  will  be  exposed,  the  nerve  lying  upon  its  outer  side. 


644  THE  ARTERIES. 

Branches. — The  branches  of  the  dorsalis  pedis  are — the 

Tarsal.  Dorsalis  Hallucis. 

Metatarsal — Interosseous.  Communicating. 

The  tarsal  artery  arises  from  the  dorsalis  pedis,  as  that  vessel  crosses  the  navic- 
ular  bone ;  it  passes  in  an  arched  direction  outward,  lying  upon  the  tarsal  bones, 
and  covered  by  the  Extensor  brevis  digitorum  ;  it  supplies  that  muscle  and  the 
articulations  of  the  tarsus,  and  anastomoses  with  branches  from  the  metatarsal, 
external  malleolar,  peroneal,  and  external  plantar  arteries. 

The  metatarsal  arises  a  little  anterior  to  the  preceding ;  it  passes  outward  to 
the  outer  part  of  the  foot,  over  the  bases  of  the  metatarsal  bones,  beneath  the  ten- 
dons of  the  short  Extensor,  its  direction  being  influenced  by  its  point  of  origin ; 
and  it  anastomoses  with  the  tarsal  and  external  plantar  arteries.  This  vessel 
gives  off  three  branches,  the  interosseous  arteries,  which  pass  forward  upon  the 
three  outer  Dorsal  interossei  muscles,  and,  in  the  clefts  between  the  toes,  divide 
into  two  dorsal  collateral  branches  for  the  adjoining  toes.  At  the  back  part  of 
each  interosseous  space  these  vessels  receive  the  posterior  perforating  branches 
from  the  plantar  arch,  and  at  the  fore  part  of  each  interosseous  space  they  are 
joined  by  the  anterior  perforating  branches  from  the  digital  arteries.  The  outer- 
most interosseous  artery  gives  off  a  branch  which  supplies  the  outer  side  of  the 
little  toe. 

The  dorsalis  hallucis  (first  dorsal  interosseous)  runs  forward  along  the  outer 
border  of  the  first  metatarsal  bone,  and  at  the  cleft  between  the  first  and  second 
toes  divides  into  two  branches,  one  of  which  passes  inward,  beneath  the  tendon  of 
the  Extensor  proprius  hallucis,  and  is  distributed  to  the  inner  border  of  the  great 
toe;  the  outer  branch  bifurcates,  to  supply  the  adjoining  sides  of  the  great  and 
second  toes. 

The  communicating  artery  or  Plantar  digital  dips  down  into  the  sole  of  the  foot, 
between  the  two  heads  of  the  First  dorsal  interosseous  muscle,  and  inosculates  with 
the  termination  of  the  external  plantar  artery  to  complete  the  plantar  arch.  It  here 
gives  off  two  digital  branches  :  one  runs  along  the  inner  side  of  the  great  toe  on 
its  plantar  surface  ;  the  other  passes  forward  along  the  first  interosseous  space,  and 
bifurcates  at  the  cleft  for  the  supply  of  the  adjacent  sides  of  the  great  and  second 
toes. 

The  Posterior  Tibial  Artery. 

The  posterior  tibial  is  an  artery  of  large  size,  which  extends  obliquely  down- 
ward from  the  lower  border  of  the  Popliteus  muscle,  along  the  tibial  side  of  the 
leg,  to  the  fossa  between  the  inner  ankle  and  the  heel,  where  it  divides  beneath 
the  origin  of  the  Abductor  hallucis,  on  a  level  with  a  line  drawn  from  the  point  of 
the  internal  malleolus  to  the  centre  of  the  convexity  of  the  heel,  into  the  internal 
and  external  plantar  arteries.  At  its  origin  it  lies  opposite  the  interval  between 
the  tibia  and  fibula;  as  it  descends,  it  approaches  the  inner  side  of  the  leg,  lying 
behind  the  tibia,  and,  in  the  lower  part  of  its  course,  is  situated  midway  between 
the  inner  malleolus  and  the  tuberosity  of  the  os  calcis. 

Relations. — It  lies  successively  upon  the  Tibialis  posticus,  the  Flexor  longus 
digitorum,  the  tibia,  and  the  back  part  of  the  ankle-joint.  It  is  covered  by  the 
deep  transverse  fascia,  which  separates  it  above  from  the  Gastrocnemius  and 
Soleus  muscles.  In  the  lower  third,  where  it  is  more  superficial,  it  is  covered  only 
by  the  integument  and  fascia,  and  runs  parallel  with  the  inner  border  of  the  tendo 
Achillis.  It  is  accompanied  by  two  veins,  and  by  the  posterior  tibial  nerve, 
which  lies  at  first  to  the  inner  side  of  the  artery,  but  soon  crosses  it,  and  is,  in  the 
greater  part  of  its  course,  on  its  outer  side. 


THE   POSTERIOR    TIBIAL    ARTERY.  645 

PLAN  OF  THE  RELATIONS  OF  THE  POSTERIOR  TIBIAL  ARTERY. 

In  front. 
Tibialis  posticus. 
Flexor  longus  digitorum. 
Tibia. 
Ankle-joint. 

Inner  side.  /  \  Outer  side. 

Posterior  tibial  nerve,  PTiw3?r      I  Posterior  tibial  nerve, 

upper  third.  y  )  lower  two-thirds. 

Behind. 

Integument  and  fascia. 
Gastrocnemius. 
Soleus. 

Deep  transverse  fascia. 
Posterior  tibial  nerve. 

Behind  the  Inner  ankle  the  tendons  and  blood-vessels  are  arranged  in  the 
following  order,  from  within  outward :  First,  the  tendons  of  the  Tibialis  posticus 
and  Flexor  longus  digitorum,  lying  in  the  same  groove,  behind  the  inner  malleolus, 
the  former  being  the  most  internal.  External  to  these  is  the  posterior  tibial 
artery,  having  a  vein  on  either  side  ;  and,  still  more  externally,  the  posterior 
tibial  nerve.  About  half  an  inch  nearer  the  heel  is  the  tendon  of  the  Flexor 
longus  hallucis. 

Peculiarities  in  Size. — The  posterior  tibial  is  not  unfrequently  smaller  than  usual,  or 
absent,  its  place  being  supplied  by  a  large  peroneal  artery  which  passes  inward  at  the  lower  end 
of  the  tibia,  an  I  either  joins  the  small  tibial  artery  or  continues  alone  to  the  sole  of  the  foot.  . 

Surface  Marking. — The  course  of  the  posterior  tibial  artery  is  indicated  by  a  line  drawn 
from  a  point  one  inch  below  the  centre  of  the  popliteal  space  to  midway  between  the  tip  of  the 
internal  malleolus  and  the  centre  of  the  convexity  of  the  heeL 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  posterior  tibial  may  be  required 
in  cases  of  wound  of  the  sole  of  the  foot  attended  with  great  haemorrhage,  when  the  vessel 
should  be  tied  at  the  inner  ankle.  In  cases  of  wound  of  the  posterior  tibial  it  will  be  necessary 
to  enlarge  the  opening  so  as  to  expose  the  vessel  at  the  wounded  point,  excepting  where  the 
vessel  is  injured  by  a  punctured  wound  from  the  front  of  the  leg.  In  cases  of  aneurism  from 
wound  of  the  artery  low  down,  the  vessel  should  be  tied  in  the  middle  of  the  leg.  But  in 
aneurism  of  the  posterior  tibial  high  up  it  would  be  better  to  tie  the  femoral  artery. 

To  tie  the  posterior  tibial  artery  at  the  ankle,  a  semilunar  incision  should  be  made  through 
the  integument,  about  two  inches  and  a  half  in  length,  midway  between  the  heel  and  inner  ankle 
or  a  little  nearer  the  latter.  The  subcutaneous  cellular  tissue  haying  been  divided,  a  strong 
and  dense  fascia,  the  internal  annular  ligament,  is  exposed.  This  ligament  is  continuous  above 
with  the  deep  fascia  of  the  leg,  covers  the  vessels  and  nerves,  and  is  intimately  adherent  to  the 
sheaths  of  the  tendons.  This  having  been  cautiously  divided  upon  a  director,  the  sheath  of 
the  vessels  is  exposed,  and,  being  opened,  the  artery  is  seen  with  one  of  the  venae  comites  on  each 
side.  The  aneurism  needle  should  be  passed  round  the  vessel  from  the  heel  toward  the  ankle,  in 
order  to  avoid  the  posterior  tibial  nerve,  care  being  at  the  same  time  taken  not  to  include  the 
vena?  comites. 

The  vessel  may  also  be  tied  in  the  lower  third  of  the  leg  by  making  an  incision,  about  three 
inches  in  length,  parallel  with  the  inner  margin  of  the  tendo  Achillis.  The  internal  saphenous 
vein  being  carefully  avoided,  the  two  layers  of  fascia  must  be  divided  upon  a  director,  when  the 
artery  is  exposed  along  the  outer  margin  of  the  Flexor  longus  digitorum,  with  one  of  its  venae 
comites  on  either  side  and  the  nerve  lying  external  to  it, 

To  tie  the  posterior  tibial  in  the  middle  of  the  leg  is  a  very  difficult  operation,  on  account  of 
the  great  depth  of  the  vessel  from  the  surface.  The  patient  being  placed  in  the  recumbent  posi- 
tion, the  injured  limb  should  rest  on  its  outer  side,  the  knee  being  partially  bent  and  the  foot 
extended,  so  as  to  relax  the  muscles  of  the  calf.  An  incision  about  four  inches  in  length  should 
then  be  made  through  the  integument  a  finger's  breadth  behind  the  inner  margin  of  the  tibia, 
taking  care  to  avoid  the  internal  saphenous  vein.  The  deep  fascia  having  been  divided,  the 
margin  of  the  Gastrocnemius  is  exposed,  and  must  be  drawn  aside,  and  the  tibial  attachment  of 
the  Soleus  divided,  a  director  being  previously  passed  beneath  it.  The  artery  may  now  be 
felt  pulsating  beneath  the  deep  fascia  about  an  inch  from  the  margin  of  the  tibia.  The  fascia 
having  been  divided,  and  the  limb  placed  in  such  a  position  as  to  relax  the  muscles  of  the 
calf  as  much  as  possible,  the  veins  should  be  separated  from  the  artery,  and  the  aneurism 
needle  passed  round  the  vessel  from  without  inward,  so  as  to  avoid  wounding  the  posterior 
tibial  nerve. 


646  THE  ARTERIES. 

The  branches  of  the  posterior  tibial  artery  are — the 

Peroneal.  Nutrient. 

Muscular.  Communicating. 

Internal  Calcanean. 

The  Peroneal  Artery  lies,  deeply  seated,  along  the  back  part  of  the  fibular  side 
of  the  leg.  It  arises  from  the  posterior  tibial  about  an  inch  below  the  lower 
border  of  the  Popliteus  muscle,  passes  obliquely  outward  to  the  fibula,  and  then 
descends  along  the  inner  border  of  that  bone  to  the  lower  third  of  the  leg,  where 
it  gives  off  the  anterior  peroneal.  It  then  passes  as  the  posterior  peroneal,  across 
the  articulation  between  the  tibia  and  fibula  to  the  outer  side  of  the  os  calcis, 
where  it  gives  off  its  terminal  branches,  the  external  calcanean. 

Relations. — This  vessel  rests  at  first  upon  the  Tibialis  posticus,  and  then,  for 
the  greater  part  of  its  course,  in  a  fibrous  canal  between  the  origins  of  the  Flexor 
longus  hallucis  and  Tibialis  posticus,  covered  or  surrounded  by  the  fibres  of  the 
Flexor  longus  hallucis.  It  is  covered,  in  the  upper  part  of  its  course,  by  the  Soleus 
and  deep  transverse  fascia ;  below,  by  the  Flexor  longus  hallucis. 

PLAN  OF  THE  RELATIONS  OF  THE  PERONEAL  ARTERY. 

In  front. 
Tibialis  posticus. 
Flexor  longus  hallucis. 

Outer  side.  I  \  Inner  side. 

Fibula.  A6™^  Flexor  longus  hallucis. 

Flexor  longus  hallucis. 

Bell  ind. 
Soleus. 

Deep  transverse  fascja. 
Flexor  longus  hallucis. 

Peculiarities  in  Origin. — The  peroneal  artery  may  arise  three  inches  below  the  Popliteus, 
or  from  the  posterior  tibial  high  up,  or  even  from  the  popliteal. 

Its  size  is  more  frequently  increased  than  diminished ;  and  then  it  either  reinforces  the 
posterior  tibial  by  its  junction  with  it,  or  altogether  takes  the  place  of  the  posterior  tibial  in  the 
lower  part  of  the  leg  and  foot,  the  latter  vessel  only  existing  as  a  short  muscular  branch.  In 
those  rare  cases  where  the  peroneal  artery  is  smaller  than  usual  a  branch  from  the  posterior 
tibial  supplies  its  place,  and  a  branch  from  the  anterior  tibial  compensates  for  the  diminished 
anterior  peroneal  artery.  In  one  case  the  peroneal  artery  has  been  found  entirely  wanting. 

The  anterior  peroneal  is  sometimes  enlarged,  and  takes  the  place  of  the  dorsal  arterv  of  the 
foot 

The  branches  of  the  peroneal  are — the 

Muscular.  Communicating. 

Nutrient.  Posterior  Peroneal. 

Anterior  Peroneal.  External  Calcanean. 

Muscular  Branches. — The  peroneal  artery  in  its  course  gives  off  branches  to 
the  Soleus,  Tibialis  posticus,  Flexor  longus  hallucis,  and  Peronei  muscles. 

The  nutrient  artery  supplies  the  fibula. 

The  Anterior  peroneal  pierces  the  interosseous  membrane,  about  two  inches 
above  the  outer  malleolus,  to  reach  the  fore  part  of  the  leg,  and,  passing  down 
beneath  the  Peroneus  tertius  to  the  outer  ankle,  ramifies  on  the  front  and  outer 
side  of  the  tarsus,  anastomosing  with  the  external  malleolar  and  tarsal  arteries. 

The  communicating  is  given  off  from  the  peroneal  about  an  inch  from  its 
lower  end,  and,  passing  inward,  joins  the  communicating  branch  of  the  posterior 
tibial. 

The  Posterior  peroneal  passes  down  behind  the  outer  ankle  to  the  back  of  the 
external  malleolus,  to  terminate  in  branches  which  ramify  on  the  outer  surface 
and  back  of  the  os  calcis. 


THE   PL  Ay  TAR    ARTERIES. 


The  External  r<dca**a*  are  the  terminal  branches  of  the  peroneal  artery  ;  they 
pass  DO  the  outer  side  of  the  heel,  and  communicate  with  the  external  malleolar. 
and.  on  the  back  of  the  heel,  -with  the  internal  calcanean  arteries. 

The  nutrient  artery  of  the  tibia  arises  from  the  posterior  tibial  near  its  origin. 
and,  after  supplying  a  few  muscular  branches,  enters  the  nutrient  canal  of  that 
bone,  which  ii  tra\erses  obliquely  from  above  downward.  This  is  the  largest 
nutrient  artery  of  bone  in  the  body. 

The  muscular  branches  of  the  posterior  tibial  are  distributed  to  the  Soleus  and 

-  .iking  i he  back  of  the  leg. 

communicating  branch,  to  join  a  similar  branch  of  the  peroneal,  runs  trans- 
-s  the  hack  of  the  tibia,  about  two  inches  above  its  lower  end,  passing 

r  longus  hallucis. 
The  internal  calcanean  are  several  large  arteries  which  arise  from  the  posterior 


Ite.  SJ9.— T%e  plmtai 


FIG.  S80.— The  plantar  arteries.    Deep  view. 


tibial  just  before  its  division :  they  are  distributed  to  the  fat  and  integument 
behind  the  tendo  Achillis  and  about  the  heel,  and  to  the  muscles  on  the  inner  side 
of  the  sole,  anastomosing  with  the  peroneal  and  internal  malleolar,  and.  on  the  back 
of  the  heel,  with  the  external  calcanean  arteries. 

The  Internal  Plantar  Artery  (Figs.  379,  380).  much  smaller  than  the  external. 
passes  forward  along  the  inner  side  of  the  foot.  It  is  at  first  situated  above1  the 
Abductor  hallucis,  and  then  between  it  and  the  Flexor  brevis  digitorum.  both  of 
which  it  supplies.  At  the  base  of  the  first  metatarsal  bone,  where  it  has  become 
much  diminished  in  size,  it  passes  along  the  inner  border  of  the  great  toe,  inoscu- 
lating with  its  digital  branch. 

Tne  External  Plantar  Artery,  much  larger  than  the  internal,  passes  obliquely 
outward  and  forward  to  the  base  of  the  fifth  metatarsal  bone.  It  then  turns 
obliquely  inward  to  the  interval  between  the  bases  of  the  first  and  second  meta- 
tarsal bones,  where  it  anastomoses  with  the  plantar  digital  branch  from  the 
dorsalis  pedis  artery,  thus  completing  the  plantar  arch.  As  this  artery  passes 

1  This  refers  to  the  erect  position  of  the  body.  In  the  ordinary  position  for  dissection  the  artery 
is  deeper  than  the  muscle. 


348  THE   ARTERIES. 

outward,  it  is  first  placed  between  the  os  calcis  and  Abductor  hallucis,  and  then 
between  the  Flexor  brevis  digitorum  and  Flexor  accessorius,  and  as  it  passes 
forward  to  the  base  of  the  little  toe,  it  lies  more  superficially  between  the  Flexor 
brevis  digitorum  and  Abductor  minimi  digiti,  covered  by  the  deep  fascia  and 
integument.  The  remaining  portion  of  the  vessel  is  deeply  situated :  it  extends 
from  the  base  of  the  metatarsal  bone  of  the  little  toe  to  the  back  part  of  the 
first  interosseous  space,  and  forms  the  plantar  arch ;  it  is  convex  forward,  lies 
upon  the  Interossei  muscles  opposite  the  tarsal  ends  of  the  metatarsal  bones,  and 
is  covered  by  the  Adductor  obliquus  hallucis,  the  flexor  tendons  of  the  toes,  and 
the  Lumbricales. 

Surface  Marking. — The  course  of  the  internal  plantar  artery  is  represented  by  a  line 
drawn  from  the  mid-point  between  the  tip  of  the  internal  malleolus  and  the  centre  of  the  con- 
vexity of  the  heel  to  the  middle  of  the  under  surface  of  the  great  toe ;  the  external  plantar  by 
a  line  from  the  same  point  to  within  a  finger's  breadth  of  the  tuberosity  of  the  fifth  metatarsal 
bone.  The  plantar  arch  is  indicated  by  a  line  drawn  from  this  point ;  i.  e.  a  finger's  breadth 
internal  to  the  tuberosity  of  the  fifth  metatarsal  bone  transversely  across  the  foot  to  the  back  of 
the  first  interosseous  space. 

Surgical  Anatomy. — Wounds  of  the  plantar  arch  are  always  serious,  on  account  of  the 
depth  of  the  vessel  and  the  important  structures  which  must  be  interfered  with  in  an  attempt 
to  ligature  it.  Delorrne  has  shown  that  it  may  be  ligatured  from  the  dorsum  of  the  foot  in 
almost  any  part  of  its  course  by  removing  a  portion  of  one  of  the  three  middle  metatarsal  bones. 

Branches. — The  plantar  arch,  besides  distributing  numerous  branches  to  the 
muscles,  integument,  and  fasciae  in  the  sole,  gives  off  the  following  branches: 

Posterior  Perforating.  Digital — Anterior  Perforating. 

The  Posterior  Perforating  are  three  small  branches  which  ascend  through  the 
back  part  of  the  three  outer  interosseous  spaces,  between  the  heads  of  the  Dorsal 
interossei  muscles,  and  anastomose  with  the  interosseous  branches  from  the  meta- 
tarsal artery. 

The  Digital  Branches  are  four  in  number,  and  supply  the  three  outer  toes  and 
half  the  second  toe.  The  first  passes  outward  from  the  outer  side  of  the  plantar 
arch,  and  is  distributed  to  the  outer  side  of  the  little  toe,  passing  in  its  course 
beneath  the  Abductor  and  short  Flexor  muscles.  The  second,  third,  and.  fourth 
run  forward  along  the  interosseous  spaces,  and  on  arriving  at  the  clefts  between 
the  toes  divide  into  collateral  branches,  which  supply  the  adjacent  sides  of  the 
three  outer  toes  and  the  outer  side  of  the  second.  At  the  bifurcation  of  the  toes 
each  digital  artery  sends  upward,  through  the  fore  part  of  the  corresponding 
interosseous  space,  a  small  branch,  which  inosculates  with  the  interosseous  branches 
of  the  metatarsal  artery.  These  are  the  anterior  perforating  branches. 

From  the  arrangement  already  described  of  the  distribution  of  the  vessels  to 
the  toes  it  will  be  seen  that  both  sides  of  the  three  outer  toes  and  the  outer  side 
of  the  second  toe  are  supplied  by  branches  from  the  plantar  arch ;  both  sides  of 
the  great  toe  and  the  inner  side  of  the  second  are  supplied  by  the  plantar  digital 
branch  of  the  dorsalis  pedis. 


THE  VEINS. 


THE  Veins  are  the  vessels  which  serve  to  return  the  blood  from  the  capillaries 
of  the  different  parts  of  the  body  to  the  heart.  They  consist  of  two  distinct 
sets  of  vessels,  the  pulmonary  and  systemic. 

The  Pulmonary  Veins  are  concerned  in  the  circulation  in  the  lungs.  Unlike 
other  vessels  of  this  kind,  they  contain  arterial  blood,  which  they  return  from  the 
lungs  to  the  left  auricle  of  the  heart. 

The  Systemic  Veins  are  concerned  in  the  general  circulation ;  they  return  the 
venous  blood  from  the  body  generally  to  the  right  auricle  of  the  heart. 

The  Portal  Vein,  an  appendage  to  the  systemic  venous  system,  is  confined  to 
the  abdominal  cavity,  returning  the  venous  blood  from  the  viscera  of  digestion, 
and  carrying  it  to  the  liver  by  a  single  trunk  of  large  size,  the  vena  portce.  This 
vessel  ramifies  in  the  substance  of  the  liver  and  breaks  up  into  a  minute  network 
of  capillaries.  These  capillaries  then  re-collect  to  form  the  hepatic  veins,  by  which 
the  blood  is  conveyed  to  the  inferior  vena  cava. 

The  veins,  like  the  arteries,  are  found  in  nearly  every  tissue  of  the  body. 
They  commence  by  minute  plexuses  which  receive  the  blood  from  the  capillaries. 
The  branches  which  have  their  commencement  in  these  plexuses  unite  together 
into  trunks,  and  these,  in  their  passage  toward  the  heart,  constantly  increase  in 
size  as  they  receive  tributaries  or  join  other  veins.  The  veins  are  larger  and 
altogether  more  numerous  than  the  arteries  ;  hence  the  entire  capacity  of  the 
venous  svstem  is  much  greater  than  that  of  the  arterial,  the  pulmonary  veins 
excepted.  which  do  not  exceed  in  capacity  the  pulmonary  arteries.  From  the 
combined  area  of  the  smaller  venous  branches  being  greater  than  the  main  trunks, 
it  results  that  the  venous  system  represents  a  cone,  the  summit  of  which  corresponds 
to  the  heart,  its  base  to  the  circumference  of  the  body.  In  form  the  veins  are  not 
perfectly  cylindrical  like  the  arteries,  their  walls  being  collapsed  when  empty,  and 
the  uniformity  of  their  surface  being  interrupted  at  intervals  by  slight  constric- 
tions, which  indicate  the  existence  of  valves  in  their  interior.  They  usually 
retain,  however,  the  same  calibre  as  long  as  they  receive  no  branches. 

The  veins  communicate  very  freely  with  one  another,  especially  in  certain 
regions  of  the  body,  and  this  communication  exists  between  the  larger  trunks  as 
well  as  between  the  smaller  branches.  Thus,  in  the  cavity  of  the  cranium  and 
between  the  veins  of  the  neck,  where  obstruction  would  be  attended  with  immi- 
nent danger  to  the  cerebral  venous  system,  we  find  that  the  sinuses  and  larger 
veins  have  large  and  very  frequent  anastomoses.  The  same  free  communication 
exists  between  the  veins  throughout  the  whole  extent  of  the  spinal  canal,  and 
between  the  veins  composing  the  various  venous  plexuses  in  the  abdomen  and  pel- 
vis, as  the  spermatic,  uterine,  vesical,  and  prostatic. 

The  systemic  veins  are  subdivided  into  three  sets :  superficial,  deep,  and  sinuses. 

The  Superficial  or  Cutaneous  Veins  are  found  between  the  layers  of  the  super- 
ficial fascia,  immediately  beneath  the  integument ;  they  return  the  blood  from 
these  structures,  and  communicate  with  the  deep  veins  by  perforating  the  deep  fascia. 

The  Deep  Veins  accompanv  the  arteries,  and  are  usually  enclosed  in  the  same 
sheath  with  th<  se  vessels.  With  the  smaller  arteries — as  the  radial,  ulnar,  brachial, 
tibial.  peroneal — they  exist  generally  in  pairs,  one  lying  on  each  side  of  the  ves- 
sel, and  are  called  vence  comites.  The  larger  arteries — as  the  axillary,  subclavian, 
popliteal,  and  femoral — have  usually  only  one  accompanying  vein.  In  certain 

619 


650  THE    VEINS 

organs  of  the  body,  however,  the  deep  veins  do  not  accompany  the  arteries ;  for 
instance,  the  veins  in  the  skull  and  spinal  canal,  the  hepatic  veins  in  the  liver,  and 
the  larger  veins  returning  blood  from  the  osseous  tissue. 

Sinuses  are  venous  channels  which,  in  their  structure  and  mode  of  distribution, 
differ  altogether  from  the  veins.  They  are  found  only  in  the  interior  of  the  skull, 
and  are  formed  by  a  separation  of  the  layers  of  the  dura  mater,  their  outer  coat 
consisting  of  fibrous  tissue,  their  inner  of  an  endothelial  layer  continuous  with  the 
lining  membrane  of  the  veins. 

Veins  have  thinner  walls  than  arteries,  the  difference  in  thickness  being  due  to 
the  small  amount  of  elastic  and  muscular  tissues  which  the  veins  contain.  The 
superficial  veins  usually  have  thicker  coats  than  the  deep  veins,  and  the  veins  of 
the  lower  limb  are  thicker  than  those  of  the  upper. 

The  minute  structure  of  these  vessels  has  been  described  in  the  section  on 
General  Anatomy. 

THE  PULMONARY  VEINS. 

The  Pulmonary  Veins  return  the  arterial  blood  from  the  lungs  to  the  left 
auricle  of  the  heart.  They  are  four  in  number,  two  for  each  lung.  The  pulmo- 
nary differ  from  other  veins  in  several  respects  :  1.  They  carry  arterial  instead  of 
venous  blood.  2.  They  are  destitute  of  valves.  3.  They  are  only  slightly  larger 
than  the  arteries  they  accompany.  4.  They  accompany  those  vessels  singly. 
They  commence  in  a  capillary  network  upon  the  walls  of  the  air-cells,  where 
they  are  continuous  with  the  ramifications  of  the  pulmonary  artery,  and,  uniting 
together,  form  a  single  trunk  for  each  lobule.  These  branches,  uniting  succes- 
sively, form  a  single  trunk  for  each  lobe,  three  for  the  right  and  two  for  the  left 
lung.  The  vein  from  the  middle  lobe  of  the  right  lung  unites  with  that  from  the 
upper  lobe,  in  most  cases,  forming  two  trunks  on  each  side,  which  open  separately 
into  the  left  auricle.  Occasionally  they  remain  separate ;  there  are  then  three 
veins  on  the  right  side.  Not  unfrequently  the  two  left  pulmonary  veins  termi- 
nate by  a  common  opening. 

Within  the  lung,  the  branches  of  the  pulmonary  artery  are  in  front,  the  veins 
behind,  and  the  bronchi  between  the  two. 

At  the  root  of  the  lung,  the  veins  are  in  front,  the  artery  in  the  middle,  and  the 
bronchus  behind. 

Within  the  pericardium,  their  anterior  surface  is  invested  by  the  serous  layer 
of  this  membrane.  The  right  pulmonary  veins  pass  behind  the  right  auricle  and 
ascending  aorta ;  the  left  pass  in  front  of  the  thoracic  aorta  with  the  left  pulmo- 
nary artery. 

THE  SYSTEMIC  VEINS. 

The  systemic  veins  may  be  arranged  into  three  groups :  1.  Those  of  the  head 
and  neck,  upper  extremity,  and  thorax,  which  terminate  in  the  superior  vena  cava. 
2.  Those  of  the  lower  limb,  pelvis,  and  abdomen,  which  terminate  in  the  inferior 
vena  cava.  3.  The  cardiac  veins,  which  open  directly  into  the  right  auricle  of 
the  heart. 

VEINS  OF  THE  HEAD  AND  NECK. 

The  veins  of  the  head  and  neck  may  be  subdivided  into  three  groups :  1.  The 
veins  of  the  exterior  of  the  head  and  face.  2.  The  veins  of  the  neck.  3.  The 
veins  of  the  diploe  and  interior  of  the  cranium. 

Veins  of  the  Exterior  of  the  Head. 
The  veins  of  the  exterior  of  the  head  and  face  are — the 

Frontal.  Temporal. 

Supra-orbital.  Internal  Maxillary. 

Angular.  Temporo-maxillary. 

Facial.  Posterior  Auricular. 
Occipital. 


OF  THE  EXTERIOR  OF  THE  HEAD. 


651 


The  frontal  vein  commences  on  the  anterior  part  of  the  skull  by  a  venous 
plexus  which  communicates  with  the  anterior  tributaries  of  the  temporal  vein. 
The  veins  converge  to  form  a  single  trunk,  which  runs  downward  near  the 
middle  line  of  the  forehead  parallel  with  the  vein  of  the  opposite  side,  and  unites 
with  it  at  the  root  of  the  nose  by  a  transverse  branch  called  the  nasal  arch. 
Occasionally  the  frontal  veins  join  to  form  a  single  trunk,  which  bifurcates  at  the 


FrontaL 

'ommunicatiiig 
branch  uith 
hthalmic  rein. 
Angular. 


\  Superior  thyroid. 


FIG.  38L-Veins  of  the  head  and  neck. 

root  of  the  nose  into  the  two  angular  veins.  At  the  root  of  the  nose  the  veins 
diverge  and  join  the  supra-orbital  vein,  at  the  inner  angle  of  the  orbit,  to  form 
the  angular  vein. 

The  supra-orbital  vein  commences  on  the  forehead,  communicating  with  the 
anterior  temporal  vein,  and  runs  downward  and  inward,  superficial  to  the 
Occipito-frontalis  muscle,  receiving  tributaries  from  the  neighboring  structures, 
and  joins  the  frontal  vein  at  the  inner  angle  of  the  orbit  to  form  the  angular 
vein. 

The  angular  vein,  formed  by  the  junction  of  the  frontal  and  supra-orbital 
veins,  runs  obliquely  downward  and  outward  on  the  side  of  the  root  of  the  nose, 
and  receives  the  veins  of  the  ala  nasi  on  its  inner  side  and  the  superior  palpebral 
veins  on  its  outer  side ;  it  moreover  communicates  with  the  ophthalmic  vein,  thus 


652  THE    VEINS 

establishing  an  important  anastomosis  between  this  vessel  and  the  cavernous 
sinus.  Some  small  veins  from  the  dorsum  of  the  nose  terminate  in  the  nasal 
arch. 

The  facial  vein  commences  at  the  side  of  the  root  of  the  nose,  being  a  direct 
continuation  of  the  angular  vein.  It  passes  obliquely  downward  and  outward 
beneath  the  Zygomaticus  major  and  minor  muscles,  descends  along  the  anterior 
border  of  the  Masseter,  crosses  over  the  body  of  the  lower  jaw  with  the  facial 
artery,  and,  passing  obliquely  outward  and  backward  beneath  the  Platysma  and 
cervical  fascia,  unites  with  a  branch  of  communication  from  the  temporo-max- 
illary  vein  to  form  a  trunk  of  large  size  which  enters  the  internal  jugular.  From 
near  its  termination  a  communicating  branch  often  runs  down  the  anterior  border 
of  the  Sterno-mastoid  to  join  the  lower  part  of  the  anterior  jugular. 

Tributaries. — The  facial  vein  receives,  near  the  angle  of  the  mouth,  communi- 
cating tributaries  of  considerable  size  (the  deep  facial  or  anterior  internal  maxil- 
lary vein)  from  the  pterygoid  plexus.  It  is  also  joined  by  the  inferior  palpebral, 
the  superior  and  inferior  labial  veins,  the  buccal  veins  from  the  cheek,  and  the 
masseteric  veins.  Below  the  jaw  it  receives  the  submental ;  the  inferior  palatine, 
which  returns  the  blood  from  the  plexus  around  the  tonsil  and  soft  palate ;  the 
submaxillary  vein,  which  commences  in  the  submaxillary  gland  ;  and,  generally, 
the  ranine  vein. 

Surgical  Anatomy. — There  are  some  points  about  the  facial  vein  which  render  it  of  great 
importance  in  surgery.  It  is  not  so  flaccid  as  are  most  superficial  veins,  and,  in  consequence  of 
this,  remains  more  patent  when  divided.  It  has,  moreover,  no  valves.  It  communicates  freely 
with  the  intracranial  circulation,  not  only  at  its  commencement  by  its  tributaries,  the  angular 
and  supra-orbital  veins,  communicating  with  the  ophthalmic  vein,. a  tributary  of  the  cavernous 
sinus,  but  also  by  its  deep  branch,  which  communicates  through  the  pterygoid  plexus  with  the 
cavernous  sinus  by  branches  which  pass  through  the  foramen  ovale  and  foramen  lacerum 
medium  (see  page  661).  These  facts  have  an  important  bearing  upon  the  surgery  of  some 
diseases  of  the  face,  for  on  account  of  its  patency  the  facial  vein  favors  septic  absorption,  and 
therefore  any  phlegmonous  inflammation  of  the  face  following  a  poisoned  wound  is  liable  to  set 
up  thrombosis  in  the  facial  vein.  And  on  account  of  its  communications  with  the  cerebral 
sinuses  these  thrombi  are  apt  to  extend  upward  into  them,  and  detached  portions  may  give  rise 
to  purulent  foci  in  other  parts  of  the  body,  and  so  induce  a  fatal  issue. 

The  Temporal  Vein  commences  by  a  minute  plexus  on  the  side  and  vertex  of 
the  skull,  which  communicates  with  the  frontal  and  supra-orbital  veins  in  front, 
the  corresponding  vein  of  the  opposite  side,  and  the  posterior  auricular  and 
occipital  veins  behind.  From  this  network  anterior  and  posterior  branches  are 
formed  which  unite  above  the  zygoma,  forming  the  trunk  of  the  vein.  This 
trunk  is  joined  in  this  situation  by  a  large  vein,  the  middle  temporal,  which 
receives  the  blood  from  the  substance  of  the  Temporal  muscle  and  pierces  the 
fascia  at  the  upper  border  of  the  zygoma.  The  temporal  vein  then  descends 
between  the  external  auditory  meatus  and  the  condyle  of  the  jaw,  enters  the  sub- 
stance of  the  parotid  gland,  and  unites  with  the  internal  maxillary  vein  to  form 
the  temporo-maxillary  vein. 

Tributaries. — The  temporal  vein  receives  in  its  course  some  parotid  veins,  an 
articular  branch  from  the  articulation  of  the  jaw,  anterior  auricular  veins  from 
the  external  ear,  and  a  vein  of  large  size,  the  transverse  facial,  from  the  side  of 
the  face.  The  middle  temporal  vein,  previous  to  its  junction  with  the  temporal 
vein,  receives  a  branch,  the  orbital  vein,  which  is  formed  by  some  external  palpe- 
bral branches,  and  passes  backward  between  the  layers  of  the  temporal  fascia. 

The  Internal  Maxillary  Vein  is  a  vessel  of  considerable  size,  receiving  branches 
which  correspond  with  those  of  the  internal  maxillary  artery.  Thus  it  receives 
the  middle  meningeal  veins,  the  deep  temporal,  the  pterygoid,  masseteric,  buccal, 
alveolar,  some  palatine  veins,  and  the  inferior  dental.  These  branches  form  a 
large  plexus,  the  pterygoid,  which  is  placed  between  the  Temporal  and  External 
pterygoid  and  partly  between  the  Pterygoid  muscles.  This  plexus  communicates 
very  freely  with  the  facial  vein  and  with  the  cavernous  sinus  by  branches  through 
the  foramen  Vesalii  at  the  base  of  the  skull.  The  trunk  of  the  vein  then  passes 


OF    THE  NECK. 

backward  behind  the  neck  of  the  lower  jaw,  and  unites  with  the  temporal  vein, 
forming  the  temporo-ruaxillary  vein. 

The  Temporo-Maxillary  Vein,  formed  by  the  union  of  the  temporal  and  internal 
maxillary  veins,  descends  in  the  substance  of  the  parotid  gland  on  the  outer  surface 
of  the  external  carotid  artery,  between  the  ramus  of  the  jaw  and  the  Sterno-mastoid 
muscle,  and  divides  into  two  branches,  one  of  which  passes  inward  to  join  the 
facial  vein :  the  other  is  joined  by  the  posterior  auricular  vein  and  becomes  the 
external  jugular. 

The  Posterior  Auricular  Vein  commences  upon  the  side  of  the  head  by  a 
plexus  which  communicates  with  the  tributaries  of  the  temporal  and  occipital  veins. 
The  vein  descends  behind  the  external  ear  and  joins  the  temporo-maxillary  vein, 
forming  the  external  jugular.  This  vessel  receives  the  stylo-mastoid  vein  and 
some  tributaries  from  the  back  part  of  the  external  ear. 

The  Occipital  Veins  commence  at  the  back  part  of  the  vertex  of  the  skull  by 
a  plexus  in  a  similar  manner  to  the  other  veins.  These  unite  and  form  one  or 
two  veins,  which  follow  the  course  of  the  occipital  artery,  passing  deeply  beneath 
the  muscles  of  the  back  part  of  the  neck,  and  terminate  in  the  internal  jugular, 
occasionally  in  the  external  jugular  vein.  As  these  veins  pass  across  the  mastoid 
portion  of  the  temporal  bone,  one  of  them  receives  the  mastoid  vein,  which  thus 
establishes  a  communication  with  the  lateral  sinus. 

The  Veins  of  the  Neck. 
The  veins  of  the  neck,  which  return  the  blood  from  the  head  and  face,  are — the 

External  Jugular.  Anterior  Jugular. 

Posterior  External  Jugular.  Internal  Jugular. 

Vertebral. 

The  External  Jugular  Vein  receives  the  greater  part  of  the  blood  from  the 
exterior  of  the  cranium  and  deep  parts  of  the  face,  being  formed  by  the  junction  of 
the  posterior  division  of  the  temporo-maxillary  and  posterior  auricular  veins.  It 
commences  in  the  substance  of  the  parotid  gland,  on  aTevel  with  the  angle  of  the 
lower  jaw.  and  runs  perpendicularly  down  the  neck  in  the  direction  of  a  line 
drawn  from  the  angle  of  the  jaw  to  the  middle  of  the  clavicle.  In  its  course  it 
crosses  the  Sterno-mastoid  muscle,  and  runs  parallel  with  its  posterior  border  as 
far  as  its  attachment  to  the  clavicle,  where  it  perforates  the  deep  fascia,  and 
terminates  in  the  subclavian  vein,  on  the  outer  side  of  or  in  front  of  the  Scalenus 
anticus  muscle.  In  the  neck  it  is  separated  from  the  Sterno-mastoid  by  the  anterior 
layer  of  the  deep  cervical  fascia,  and  is  covered  by  the  Platysma.  the  superficial 
fascia,  and  the  integument.  This  vein  is  crossed  about  its  middle  by  the  super- 
ficialis  colli  nerve,  and  its  upper  half  is  accompanied  by  the  auricularis  magnus 
nerve.  The  external  jugular  vein  varies  in  size,  bearing  an  inverse  proportion  to 
that  of  the  other  veins  of  the  neck  :  it  is  occasionally  double.  It  is  provided  with 
two  pairs  of  valves,  the  lower  pair  being  placed  at  its  entrance  into  the  subclavian 
vein,  the  upper  pair  in  most  cases  about  an  inch  and  a  half  above  the  clavicle. 
The  portion  of  vein  between  the  two  sets  of  valves  is  often  dilated,  and  is  termed 
the  .«/>/?/.*.  These  valves  do  not -prevent  the  regurgitation  of  the  blood  or  the 
passage  of  injection  from  below  upward.1 

Surgical  Anatomy. — Venesection  used  formerly  to  be  performed  on  the  external  jugular 
vein,  but  is  now  probably  never  resorted  to.  The  anatomical  point  to  be  remembered  in  per- 
forming this  operation  is  to  cut  across  the  fibres  of  the  Plat.vsma  myoides  in  opening  the  vein, 
so  that  by  their  contraction  they  will  expose  the  orifice  in  the  vein  and  so  allow  the  flow  of 
blood. 

Tributaries. — This  vein  receives  the  occipital  occasionally,  the  posterior  external 
jugular,  and  near  its  termination,  the  suprascapular  and  transverse  cervical  veins. 

1  The  student  may  refer  to  an  interesting  paper  by  Dr.  Struthers,  "  On  Jugular  Venesection  in 
Asphyxia,  anatomically  and  experimentally  considered,  including  the  Demonstration  of  Valves-  in 
the  Veins  of  the  Xeck,"  in  the  Edinburgh  Medical  Journal  for  November,  1856. 


654  THE    VEINS 

It  communicates  with  the  anterior  jugular,  and,  in  the  substance  of  the  parotid, 
receives  a  large  branch  of  communication  from  the  internal  jugular. 

The  Posterior  External  Jugular  Vein  commences  in  the  occipital  region,  and 
returns  the  blood  from  the  integument  and  superficial  muscles  in  the  upper  and 
back  part  of  the  neck,  lying  between  the  Splenius  and  Trapezius  muscles.  It  runs 
down  the  back  part  of  the  neck,  and  opens  into  the  external  jugular  just  below 
the  middle  of  its  course. 

The  Anterior  Jugular  Vein  commences  near  the  hyoid  bone  from  the  con- 
vergence of  several  superficial  veins  from  the  submaxillary  region.  It  passes 
down  between  the  median  line  and  the  anterior  border  of  the  Sterno-mastoid, 
and  at  the  lower  part  of  the  neck  passes  beneath  that  muscle  to  open  into  the 
termination  of  the  external  jugular  or  into  the  subclavian  vein  (Fig.  388).  This 
vein  varies  considerably  in  size,  bearing  almost  always  an  inverse  proportion  to  the 
external  jugular.  Most  frequently  there  are  two  anterior  jugulars,  a  right  and 
left,  but  occasionally  only  one.  This  vein  receives  some  laryngeal  veins,  and 
occasionally  a  small  thyroid  vein.  Just  above  the  sternum  the  two  anterior 
jugular  veins  communicate  by  a  transverse  trunk,  which  receives  tributaries  from 
the  inferior  thyroid  veins.  It  also  communicates  with  the  internal  jugular.  There 
are  no  valves  in  this  vein. 

The  Internal  Jugular  Vein  collects  the  blood  from  the  interior  of  the  cranium, 
from  the  superficial  parts  of  the  face,  and  from  the  neck.  It  commences  just 
external  to  the  jugular  foramen,  at  the  base  of  the  skull,  being  formed  by  the 
coalescence  of  the  lateral  and  inferior  petrosal  sinuses  (Fig.  386).  At  its  origin  it 
is  somewhat  dilated,  and  this  dilatation  is  called  the  sinus,  or  gulf,  of  the  internal 
jugular  vein.  It  runs  down  the  side  of  the  neck  in  a  vertical  direction,  lying  at 
first  on  the  outer  side  of  the  internal  carotid,  and  then  on  the  outer  side  of  the 
common  carotid,  and  at  the  root  of  the  neck  unites  with  the  subclavian  vein  to 
form  the  innominate  vein.  The  internal  jugular  vein,  at  its  commencement,  lies 
upon  the  Rectus  capitis  lateralis,  and  behind  the  internal  carotid  and  the  nerves 
passing  through  the  jugular  foramen  ;  lower  down,  the  vein  and  artery  lie  upon 
the  same  plane,  the  glosso-pharyngeal  and  hypoglossal  nerves  passing  forward 
between  them ;  the  pneumogastric  descends  between  and  behind  them  in  the 
same  sheath,  and  the  spinal  accessory  passes  obliquely  outward  behind  the 
vein.  At  the  root  of  the  neck  the  vein  of  the  right  side  is  placed  at  a  little 
distance  from  the  artery ;  on  the  left  side  it  usually  lies  over  the  artery  at  its 
lower  part.  The  right  internal  jugular  vein  crosses  the  first  part  of  the  subclavian 
artery.  The  vein  is  of  considerable  size,  but  varies  in  different  individuals,  the 
left  one  being  usually  the  smaller.  It  is  provided  with  a  pair  of  valves,  which 
are  placed  at  its  point  of  termination  or  from  half  to  three-quarters  of  an  inch 
above  it. 

Tributaries. — This  vein  receives  in  its  course  the  facial,  lingual,  pharyngeal, 
superior  and  middle  thyroid  veins,  and  sometimes  the  occipital.  At  its  point  of 
junction  with  the  branch  common  to  the  temporo-maxillary  and  facial  veins  it 
becomes  greatly  increased  in  size. 

The  lingual  veins  commence  on  the  dorsum,  sides,  and  under  surface  of  the 
tongue,  and,  passing  backward,  following  the  course  of  the  lingual  artery  and  its 
branches,  terminate  in  the  internal  jugular.  Sometimes  the  ranine  vein,  which  is 
a  branch  of  considerable  size  commencing  below  the  tip  of  the  tongue,  joins  the 
lingual.  Generally,  however,  it  passes  backward,  crosses  the  Hyo-glossus  muscle 
in  company  with  the  hypoglossal  nerve,  and  joins  the  facial. 

The  pharyngeal  vein  commences  in  a  minute  plexus,  the  pharyngeal,  at  the 
back  part  and  sides  of  the  pharynx,  and,  after  receiving  meningeal  tributaries 
and  the  Vidian  and  spheno-palatine  veins,  terminates  in  the  internal  jugular.  It 
occasionally  opens  into  the  facial,  lingual,  or  superior  thyroid  vein. 

The  superior  thyroid  vein  commences  in  the  substance  and  on  the  surface  of 
the  thyroid  gland  by  tributaries  corresponding  with  the  branches  of  the  superior 
thyroid  artery,  and  terminates  in  the  upper  part  of  the  internal  jugular  vein. 


OF    THE   DIPLOE.  655 

The  middle  thyroid  vein  collects  the  blood  from  the  lower  part  of  the  lateral 
lobe  of  the  thyroid  gland,  and,  being  joined  by  some  veins  from  the  larynx  and 
trachea,  terminates  in  the  lower  part  of  the  internal  jugular  vein. 

The  facial  and  occipital  veins  have  been  described  above. 

Surgical  Anatomy. — The  internal  jugular  vein  occasionally  requires  ligature  in  cases  of 
septic  thrombosis  of  the  lateral  sinus  from  suppuration  in  the  middle  ear,  in  order  to  prevent 
embolism  of  the  thoracic  viscera.  This  operation  has  been  performed  recently  in  several  cases 
with  the  most  satisfactory  results.  The  cases  are  generally  those  of  chronic  disease  of  the  middle 
ear.  with  discharge  of  pus  which  perhaps  has  existed  for  many  years.  The  patient  is  seized  with 
acute  septic  inflammation,  spreading  to  the  mastoid  cells,  and  consequent  on  this  septic  throm- 
bosis of  the  lateral  sinus  extending  to  the  internal  jugular  vein.  Such  cases  are  always  extremely 
grave,  for  there  is  a  danger  of  a  portion  of  the  septic  clot  being  detached  and  causing  septic 
embolism  in  the  thoracic  viscera.  This  may  be  mechanically  prevented  by  ligature  of  the  inter- 
nal jugular  vein  in  the  middle  of  the  neck.  The  operation  is  a  comparatively  simple  one,  and 
may  be  performed  by  an  incision  similar  to  that  employed  in  ligature  of  the  common  carotid 
artery. 

The  Vertebral  Vein  commences  in  the  occipital  region  by  numerous  small 
tributaries  from  the  deep  muscles  at  the  upper  and  back  part  of  the  neck ;  these 
pass  outward  and  enter  the  foramen  in  the  transverse  process  of  the  atlas,  and 
descend,  forming  a  dense  plexus  around  the  vertebral  artery  in  the  canal  formed 
by  the  transverse  processes  of  the  cervical  vertebrae.  This  plexus  unites  at  the 
lower  part  of  the  neck  into  two  main  trunks,  one  of  which  emerges  from  the 
foramen  in  the  transverse  process  of  the  sixth  cervical  vertebra,  and  the  other 
through  that  of  the  seventh,  and,  uniting,  form  a  single  vessel,  which  terminates 
at  the  root  of  the  neck  in  the  back  part  of  the  innominate  vein  near  its  origin,  its 
mouth  being  guarded  by  a  pair  of  valves.  On  the  right  side  it  crosses  the  first 
part  of  the  subclavian  arterv. 

Tributaries. — The  vertebral  vein  receives  in  its  course  a  vein  from  the  inside 
of  the  skull  through  the  posterior  condvloid  foramen ;  muscular  veins  from  the 
muscles  in  the  prevertebral  region ;  dorsi-spinal  veins,  from  the  back  part  of  the 
cervical  portion  of  the  spine ;  meningo-rachidian  veins,  from  the  interior  of  the 
spinal  canal :  the  anterior  and  posterior  vertebral  veins ;  and  close  to  its  termina- 
tion it  is  joined  by  a  small  vein  from  the  first  intercostal  space  which  accompanies 
the  superior  intercostal  artery.  (See  page  666.) 

The  anterior  vertebral  vein  commences  in  a  plexus  around  the  transverse  pro- 
cesses of  the  upper  cervical  vertebrae,  descends  in  company  with  the  ascending 
cervical  artery  between  the  Scalenus  anticus  and  Rectus  capitis  anticus  major 
muscles,  and  opens  into  the  vertebral  vein  just  before  its  termination. 

The  posterior  vertebral  vein  (the  deep  cervical)  accompanies  the  profunda  cer- 
vicis  artery,  lying  between  the  Complexus  and  Semispinalis  colli.  It  commences 
in  the  suboccipital  region  bv  communicating  branches  from  the  occipital  vein  and 
tributaries  from  the  deep  muscles  at  the  back  of  the  neck.  It  receives  tribu- 
taries from  the  plexuses  around  the  spinous  processes  of  the  cervical  vertebrae,  and 
terminates  in  the  lower  end  of  the  vertebral  vein. 

The  Veins  of  the  Diploe. 

The  diploe  of  the  cranial  bones  is  channelled  in  the  adult  by  a  number  of 
tortuous  canals,  which  are  lined  by  a  more  or  less  complete  layer  of  compact 
tissue. 

The  veins  they  contain  are  large  and  capacious,  their  walls  being  thin,  and 
formed  only  of  endothelium  resting  upon  a  layer  of  elastic  tissue,  and  they  pre- 
sent at  irregular  intervals  pouch-like  dilatations,  or  culs-de-sac,  which  serve  as 
reservoirs  for  the  blood.  These  are  the  veins  of  the  diploe ;  they  can  only  be 
displayed  by  removing  the  outer  table  of  the  skull. 

In  adult  life,  as  long  as  the  cranial  bones  are  distinct  and  separable,  these 
veins  are  confined  to  the  particular  bones ;  but  in  old  age,  when  the  sutures  are 
united,  they  communicate  with  each  other  and  increase  in  size.  These  vessels 
communicate,  in  the  interior  of  the  cranium,  with  the  meningeal  veins  and  with 


656  THE    VEINS. 


the  sinuses  of  the  dura  mater,  and  on  the  exterior  of  the  skull  with  the  veins  of 
the  pericranium.  They  are  divided  into  the  frontal,  which  opens  into  the  supra- 
orbital  vein  by  an  aperture  in  the  supra-orbital  notch  ;  the  anterior  temporal, 
which  is  confined  chiefly  to  the  frontal  bone,  and  opens  into  one  of  the  deep 
temporal  veins,  after  escaping  by  an  aperture  in  the  great  wing  of  the  sphenoid  ; 


(  FIG.  382.— Veins  of  the  Diploe  as  displayed  by  the  removal  of  the  outer  table  of  the  skull. 

the  posterior  temporal,  which  is  confined  to  the  parietal  bone,  and  terminates  in 
the  lateral  sinus  by  an  aperture  at  the  posterior  inferior  angle  of  the  parietal 
bone  ;  and  the  occipital,  the  largest  of  the  four,  which  is  confined  to  the  occipital 
bone,  and  opens  either  into  the  occipital  vein  or  internally  into  the  lateral  sinus 
or  torcular  Herophili. 

The  Cerebral  Veins. 

The  Cerebral  Veins  are  remarkable  for  the  extreme  thinness  of  their  coats  in 
consequence  of  the  muscular  tissue  in  them  being  wanting,  and  for  the  absence 
of  valves.  They  may  be  divided  into  two  sets :  the  superficial,  which  are  placed 
on  the  surface,  and  the  deep  veins,  which  occupy  the  interior  of  the  organ. 

The  Superficial  Cerebral  Veins  ramify  upon  the  surface  of  the  brain,  being 
lodged  in  the  sulci  between  the  convolutions,  a  few  running  across  the  convolu- 
tions. They  receive  branches  from  the  substance  of  the  brain  and  terminate  in 
the  sinuses.  They  are  named,  from  the  position  they  occupy,  superior,  median, 
and  inferior  cerebral  veins. 

The  Superior  Cerebral  Veins,  eight  to  twelve  in  number  on  each  side,  return 
the  blood  from  the  convolutions  on  the  superior  surface  of  the  hemisphere ;  they 
pass  forward  and  inward  toward  the  great  longitudinal  fissure,  where  they  receive 
the  median  cerebral  veins  ;  near  their  termination  they  become  invested  with  a 
tubular  sheath  of  the  arachnoid  membrane,  and  open  into  the  superior  longitudi- 
nal sinus  in  the  opposite  direction  to  the  course  of  the  blood. 

The  Median  Cerebral  Veins  return  the  blood  from  the  convolutions  of  the  mesial 
surface  of  the  corresponding  hemisphere ;  they  open  into  the  superior  cerebral 
veins,  or  occasionally  into  the  inferior  longitudinal  sinus. 

The  Inferior  Cerebral  Veins  ramify  on  the  lower  part  of  the  outer  and  on  the 
under  surface  of  the  cerebral  hemisphere.  Some,  collecting  tributaries  from  the 
under  surface  of  the  anterior  lobes  of  the  brain,  terminate  in  the  cavernous  sinus. 
One  vein  of  large  size,  the  middle  cerebral  vein,  commences  on  the  under  surface 


THE   SIXUSES    OF    THE   DURA    MATER.  657 

of  the  temporo-sphenoidal  lobe,  and,  running  along  the  fissure  of  Sylvius,  opens 
in:  >  ihe  cavernous  sinus.  Another  large  vein,  the  great  anastomotic  vein  of  Tro- 
1'ird,  commences  on  the  parietal  lobe,  runs  along  the  horizontal  limb  of  the  fissure 
of  Sylvius  and  opens  into  theanterior  part  of  the  cavernous  sinus  under  the  lesser 
wing  of  the  sphenoid.  Others  commence  on  the  under  surface  of  the  base  of  the 
brain,  and  unite  to  form  from  three  to  five  veins,  which  open  into  the  superior 
petrosal  and  lateral  sinuses  from  before  backward. 

The  Deep  Cerebral,  or  Ventricular  Veins  (vence  Galeni),  are  two  in  number. 
They  are  formed  by  the  union  of  two  veins,  the  vena  corporis  striati.  and  the 
chor  .  on  either  side.  They  run  backward,  parallel  with  one  another, 

between  the  layers  of  the  velum  interpositum,  and  pass  out  of  the  brain  at 
the  great  transverse  fissure,  between  the  posterior  extremity,  or  splenium,  of  the 
corpus  callosum  and  the  tubercula  quadrigemina,  to  enter  the  straight  sinus.  The 
two  veins  usually  unite  to  firm  one  before  opening  into  the  straight  sinus. 

The  vena  corporis  striati  commences  in  the  groove  between  the  corpus  striatum 
and  thalaimis  opticus.  receives  numerous  veins  from  both  of  these  parts,  and  unites 
behind  the  anterior  pillar  of  the  fornix  with  the  choroid  vein  to  form  one  of  the 
vena;  Galeni. 

The  choroid  vein  runs  along  the  whole  length  of  the  outer  border  of  the  choroid 
plexus,  receiving  veins  from  the  hippocampus  major,  the  fornix  and  corpus  callosum, 
and  unites,  at  the  anterior  extremity  of  the  choroid  plexus,  with  the  vein  of  the 
corpus  striatum. 

The  Cerebellar  Veins  occupy  the  surface  of  the  cerebellum,  and  are  disposed  in 
three  sets,  superior,  inferior,  and  lateral.  The  superior  pass  forward  and  inward 
across  the  superior  vermiform  process,  and  terminate  in  the  straight  sinus ;  some 
open  into  the  venae  Galeni.  The  inferior  cerebellar  reins,  of  large  size,  run  trans- 
versely outward,  and  terminate  by  two  or  three  trunks  in  the  lateral  sinuses.  The 
lateral  cerebellar  veins  terminate  in  the  superior  petrosal  sinuses. 

The  perivasc-ular  lymph-sheaths  alluded  to  above  (see  page  87)  are  especially  found  in  con- 
nection with  the  vessels  of  the  brain.  These  vessels  are  enclosed  in  a  sheath  which  acts  as  a 
lymphatic  channel,  through  which  the  lymph  is  carried  to  the  subarachnoid  and  subdural  spaces, 
from  which  it  is  returned  into  the  general  circulation. 

The  Sinuses  of  the  Dura  Mater. 

The  sinuses  of  the  dura  mater  are  venous  channels,  analogous  to  the  veins,  their 
outer  coat  being  formed  by  the  dura  mater :  their  inner,  by  a  continuation  of  the 
lining  membrane  of  the  veins.  They  are  fifteen  in  number,  and  are  divided  into 
tw..  sets:  1,  those  situated  at  the  upper  and  back  part  of  the  skull;  2,  those  at 
the  base  of  the  skull.  The  former  are — the 

Superior  Longitudinal.  Straight  Sinus. 

Inferior  Longitudinal.  Lateral  Sinuses. 

Occipital  Sinus. 

The  Superior  Longitudinal  Sinus  occupies  the  attached  margin  of  the  falx 
cerebri.  Commencing  at  the  foramen  ca?cum.  through  which  it  constantly  com- 
municates by  a  small  branch  with  the  veins  of  the  nasal  fossie.  it  runs  from  before 
backward,  grooving  the  inner  surface  of  the  frontal,  the  adjacent  margins  of  the 
two  parietal,  and  the  superior  division  of  the  crucial  ridge  of  the  occipital  bone, 
and  terminates  by  opening  into  the  torcular  Herophili.  The  sinus  is  triangular 
in  form,  narrow  in  front,  and  gradually  increasing  in  size  as  it  passes  backward. 
On  examining  its  inner  surface  it  presents  the  internal  openings  of  the  superior 
cerebral  veins,  which  run.  for  the  most  part,  from  behind  forward,  and  open  chiefly 
at  the  back  part  of  the  sinus,  their  orifices  being  concealed  by  fibrous  folds; 
numerous  fibrous  bands  (chordae  Willisii)  are  also  seen,  extending  transversely 
across  the  inferior  angle  of  the  sinus :  and.  lastly,  some  small,  white,  projecting 
bodies,  the  glundulie  Pacchioni.  This  sinus  receives  the  superior  cerebral  veins, 
numerous  veins  from  the  diploe  and  dura  mater,  and,  at  the  posterior  extremity 

-12 


658 


THE    VEIN8. 


of  the  sagittal  suture,  veins  from  the  pericranium,  which  pass  through  the  parietal 
foramen. 

The  torcular  Herophili  is  the  dilated  extremity  of  the  superior  longitudinal 
sinus.  It  is  of  irregular  form,  and  is  lodged  on  one  side  (generally  the  right) 
of  the  internal  occipital  protuberance.  From  it  the  lateral  sinus  of  the  side 
to  which  it  is  deflected  is  derived.  It  receives  also  the  blood  from  the  occipital 
sinus. 

The  Inferior  Longitudinal  Sinus,  more  correctly  described  as  the  inferior  longi 
tudinal  vein,  is  contained  in  the  posterior  part  of  the  free  margin  of  the  falx 
cerebri.  It  is  of  a  cylindrical  form,  increases  in  size  as  it  passes  backward,  and 
terminates  in  the  straight  sinus.  It  receives  several  veins  from  the  falx  cerebri, 
and  occasionally  a  few  from  the  mesial  surface  of  the  hemispheres. 

The  Straight  Sinus  is  situated  at  the  line  of  junction  of  the  falx  cerebri  with 
the  tentorium.  It  is  triangular  in  form,  increases  in  size  as  it  proceeds  backward, 
and  runs  obliquely  downward  and  backward  from  the  termination  of  the  inferior 
longitudinal  sinus  to  the  lateral  sinus  of  the  opposite  side  to  that  into  which  the 
superior  longitudinal  sinus  is  prolonged.  It  communicates  by  a  cross  branch 


Torcular  herophili. 


Foramen  csecum. 


FIG.  383. —Vertical  section  of  the  skull,  showing  the  sinuses  of  the  dura  mater. 


with  the  torcular  Herophili.  Beside  the  inferior  longitudinal  sinus,  it  receives 
the  venae  Galeni  and  the  superior  cerebellar  veins.  A  few  transverse  bands  cross 
its  interior. 

The  Lateral  Sinuses  are  of  large  size,  and  are  situated  in  the  attached  margin 
of  the  tentorium  cerebelli.  They  commence  at  the  internal  occipital  protuberance, 
the  one,  generally  the  right,  being  the  direct  continuation  of  the  superior  longi- 
tudinal sinus,  the  other  of  the  straight  sinus.  They  pass  horizontally  outward 
to  the  base  of  the  petrous  portion  of  the  temporal  bone,  then  curve  downward  and 
inward  on  each  side  to  reach  the  jugular  foramen,  where  they  terminate  in  the 
internal  jugular  vein.  Each  sinus  rests,  in  its  course,  upon  the  inner  surface  of 
the  occipital,  the  posterior  inferior  angle  of  the  parietal,  the  mastoid  portion  of  the 
temporal,  and  on  the  occipital,  again  just  before  its  termination.  These  sinuses 
are  frequently  of  unequal  size,  that  formed  by  the  superior  longitudinal  sinus  being 
the  larger,  and  they  increase  in  size  as  they  proceed  from  behind  forward.  The 
horizontal  portion  is  of  a  triangular  form,  the  curved  portion  semicylindrical. 
Their  inner  surface  is  smooth,  and  not  crossed  by  the  fibrous  bands  found  in  the 
other  sinuses.  These  sinuses  receive  the  blood  from  the  superior  petrosal  sinuses 
at  the  base  of  the  petrous  portion  of  the  temporal  bone,  and  they  unite  with  the 
inferior  petrosal  sinus,  just  external  to  the  jugular  foramen,  to  form  the  internal 


THE   SISl'SES    OF   THE   DURA    JfATER. 

jugular  vein  (Fig.  386).  They  communicate  with  the  veins  of  the  pericranium 
by  means  of  the  mastoid  and  posterior  condyloid  veins,  and  thev  receive 
some  of  the  inferior  cerebral  and  inferior  cerebellar  veins  and  some  veins  from 
the  diploe. 

The  Occipital  is  the  smallest  of  the  cranial  sinuses.  It  is  generally  single,  but 
occasionally  there  are  two.  It  is  situated  in  the  attached  margin  of  the  falx  cere- 
belli.  It  commences  by  several  small  veins  around  the  margin  of  the  foramen 
magnum,  one  of  which  joins  the  termination  of  the  lateral  sinus  ;  it  communicates 
with  the  posterior  spinal  veins  and  terminates  in  the  torcular  Herophili. 

The  sinuses  at  the  base  of  the  skull  are — the 

Cavernous.  Superior  Petrosal. 

Circular.  Inferior  Petrosal. 

Transverse. 

The  Cavernous  Sinuses  are  named  from  their  presenting  a  reticulated  structure. 
They  are  two  in  number,  of  large  size,  and  placed  one  on  each  side  of  the  sella 


Dura  mater  limn 


^Lining  membrane  of  sinus. 
"Third  nerte. 


nerve. 
Internal  carotid. 


r  ^^^^        fourth  nerve, 

First  division  of  fifth  nerve, 


FIG.  3S4. — Plan  showing  the  relative  position  of  the  structures  in  the  right  cavernous  sinus,  viewed  from 
behind. 

turcica.  extending  from  the  sphenoidal  fissure  to  the  apex  of  the  petrous  portion 
of  the  temporal  bone :  they  receive  anteriorly  the  ophthalmic  vein  through  the 
sphenoidal  fissure,  and  open  behind  into  the  petrosal  sinuses.  On  the  inner  wall 
of  each  sinus  is  found  the  internal  carotid  artery,  accompanied  by  filaments  of  the 
carotid  plexus  and  by  the  sixth  nerve  ;  and  on  its  outer  wall,  the  third,  fourth,  and 
ophthalmic  division  of  the  fifth  nerve.  These  parts  are  separated  from  the  blood 
flowing  along  the  sinus  by  the  lining  membrane,  which  is  continuous  with  the 
inner  coat  of  the  veins.  The  cavity  of  the  sinus,  which  is  larger  behind  than  in 
front,  is  intersected  by  filaments  of  fibrous  tissue  and  small  vessels.  The  cavernous 
sinuses  receive  some  of  the  cerebral  veins  :  they  communicate  with  the  lateral 
sinuses  by  means  of  the  superior  and  inferior  petrosal.  and  with  the  facial  vein 
through  the  ophthalmic.  They  also  communicate  with  each  other  by  means  of  the 
circular  sinus. 

Surgical  Anatomy. — An  arterio-venous  communication  may  be  established  between  the 
cavernous  sinus  and  the  carotid  artery,  as  it  lies  in  it.  giving  rise  to  a  pulsating  tumor  in  the 
orbit.  These  communications  may  be  the  result  of  injury,  such  as  a  bullet  wound,  a  stab,  or  a 
blow  or  fall  sufficiently  severe  to  cause  a  fracture  of  the  base  of  the  skull  in  this  situation,  or 
they  may  occur  idiopathically  from  the  rupture  of  an  aneurism  or  a  diseased  condition  of  the 
internal  carotid  artery.  The  disease  begins  with  sudden  noise  and  pain  in  the  head,  followed  by 
exophthalmic,  and  development  of  a  pulsating  tumor  at  the  margin  of  the  orbit,  with  thrill 
and  the  characteristic  bruit.  In  some  cases  the  opposite  orbit  becomes  affected  by  the  passage 
of  the  arterial  blood  into  the  opposite  sinus  by  means  of  the  circular  sinus.  Or  the  arterial 
blood  may  find  its  way  through  the  emissary  veins  (see  page  663)  into  the  pterygoid  plexus,  and 
thence  into  the  veins  of  the  face.  Pulsating  tumors  of  the  orbit  may  also  be  due  to  traumatic 
aneurism  of  one  of  the  orbital  arteries,  and  symptoms  resembling  those  of  pulsating  tumor  may 
be  produced  by  pressure  on  the  ophthalmic  vein,  as  it  enters  the  sinus,  by  an  aneurism  of  the 
internal  carotid  artery. 

The  ophthalmic  is  a  large  vein  which  connects  the  angular  vein  at  the  inner 
angle  of  the  orbit  with  the  cavernous  sinus  :  it  pursues  the  same  course  as 
the  ophthalmic  artery,  and  receives  tributaries  corresponding  to  the  branches 
derived  from  that  vessel.  Forming  a  short  single  trunk,  it  passes  through 


060 


THE    VEINS. 


the  inner  extremity  of  the  sphenoidal  fissure  and  terminates  in  the  cavernous 
sinus. 

The  Inferior  Ophthalmic  Vein. — Sometimes  the  veins  from  the  floor  of  the  orbit 
collect  into  a  separate  trunk,  the  inferior  ophthalmic  vein,  which  either  passes  out 
of  the  orbit  through  the  spheno-maxillary  fissure  to  join  the  pterygoid  plexus  of 
veins,  or  else,  passing  backward  through  the  sphenoidal  fissure,  it  enters  the 
cavernous  sinus,  either  by  a  separate  opening  or  in  common  with  the  ophthalmic 
vein. 

The  Circular  Sinus  is  formed  by  two  transverse  vessels  which  connect  together 
the  two  cavernous  sinuses,  the  one  passing  in  front  and  the  other  behind  the 
pituitary  body,  and  thus  forming  with  the  cavernous  sinuses  a  venous  circle  around 
the  body.  The  anterior  one  is  usually  the  larger  of  the  two,  and  one  or  other  is 
occasionally  found  to  be  absent. 

The  Superior  Petrosal  Sinus  is  situated  along  the  superior  border  of  the  petrous 
portion  of  the  temporal  bone,  in  the  front  part  of  the  attached  margin  of  the 
tentorium.  It  is  small  and  narrow,  and  connects  together  the  cavernous 


Opening  of  mastoid 
vein. 


1  Torcular  HerophiK. 
FIG.  385.— The  sinuses  at  the  base  of  the  skull. 

and  lateral  sinuses  at  each  side.  It  receives  a  cerebellar  vein  (anterior  lateral 
cerebellar)  from  the  anterior  border  of  the  cerebellum,  and  a  vein  from  the 
internal  ear. 

The  Inferior  Petrosal  Sinus  is  situated  in  the  groove  formed  by  the  junction  of 
the  posterior  border  of  the  petrous  portion  of  the  temporal  with  the  basilar  process 
of  the  occipital.  It  commences  in  front  at  the  termination  of  the  cavernous  sinus, 
and  behind  joins  the  lateral  sinus  after  it  has  passed  through  the  jugular  foramen, 
the  junction  of  these  two  sinuses  forming  the  commencement  of  the  internal 
jugular  vein. 

The  junction  of  the  two  sinuses  takes  place  at  the  lower  border  of,  or  just 
external  to,  the  jugular  foramen.  The  exact  relation  of  the  parts  to  one  another 
in  the  foramen  is  as  follows :  The  inferior  petrosal  sinus  is  in  front,  with  the 
meningeal  branch  of  the  ascending  pharyngeal  artery,  and  is  directed  obliquely 
downward  and  backward  ;  the  lateral  sinus  is  situated  at  the  back  part  of  the  fora- 


THE 


OF    THE    DURA     HATER. 


661 


men  with  a  meningeal  branch  of  the  occipital  artery,  and  between  the  two  are 
the  glosso-pharvngeal,  pneurnogastric.  and  spinal  accessory  nerves.  These  three 
sets  of  structures  are  divided  from  each  other  by  two  processes  of  fibrous  tissue. 
The  junction  of  the  sinuses  takes  place  superficial  to  the  nerves,  so  that  these  latter 
lie  a  little  internal  to  the  venous  channels  in  the  foramen  (see  Fig.  386).  These 
sinuses  are  semicylindrical  in  form. 

The  Transverse  Sinus,  or  basilar  sinus,  consists  of  several  interlacing  veins 
between  the  layers  of  the  dura  mater  over  the  basilar  process  of  the  occipital  bone, 
which  serve  to  connect  the  two  inferior  petrosal  sinuses.  With  them  the  anterior 
spinal  veins  communicate. 

Emissary  Veins. — The  emissary  veins  are  vessels  which  pass  through  apertures 


Falx  cerebri 


Optic  nerve 
Int.  carotid  artery 

Motor  oculi  nerre 


Inferior 
petrosal  fi 


Dorsum  sellse 


9th.  10th.  and  llt'.t 
cranial  nerves 


Lateral  finus 
Fin.  3S6. — Relation  of  nerves  to  sinuses  in  jugular  foramen.    (Henle.) 

in  the  cranial  wall  and  establish  communications  between  the  sinuses  inside  the 
skull  and  the  veins  external  to  it.  Some  of  these  are  always  present,  others  only 
occasionally  so.  They  vary  much  in  size  in  different  individuals.  The  principal 
emissary  veins  are  the  following:  1.  A.  vein,  almost  always  present,  which  passes 
through  the  mastoid  foramen  and  connects  the  lateral  sinus  with  the  posterior 
auricular  or  with  an  occipital  vein.  2.  A  vein  which  passes  through  the  parietal 
foramen  and  connects  the  superior  longitudinal  sinus  with  the  veins  of  the  scalp. 

3.  A  plexus  of  minute  veins  which  pass  through  the  anterior  condyloid  foramen 
and  connect  the  occipital  sinus  with  the  vertebral  vein  and  deep  veins  of  the  neck. 

4.  An  inconstant  vein  which  passes  through  the  posterior  condyloid  foramen  and 
connects  the  lateral  sinus  with  the  deep  veins  of  the  neck.     5.   One  or  two  veins 
of  considerable  size  which  pass  through  the  foramen  ovale  and  connect  the  cav- 
ernous sinus  with  the  pterygoid  and  pharvngeal  plexuses.     6.   Two  or  three  small 
veins  which  pass  through  fhe  foramen  lacerum  medium  and  connect  the  cavernous 
sinus  with  the  pterygoid  and  pharyngeal  plexuses.     7.   There  is  sometimes  a  small 


662 


THE    VEINS 


vein  passing  through  the  foramen  of  Vesalius  connecting  the  same  parts.  8.  A 
plexus  of  veins  passing  through  the  carotid  canal  and  connecting  the  Cav- 
ernous sinus  with  the  internal  jugular 
vein. 

Surgical  Anatomy.— These  emissary 
veins  are  of  great  importance  in  surgery.  In 
addition  to  them  there  are,  however,  other  com- 
munications between  the  intra-  and  extra-cra- 
nial circulation,  as.  for  instance,  the  communi- 
cation of  the  angular  and  supra-orbital  veins 
with  the  ophthalmic  vein  at  the  inner  angle  of 
the  orbit  (page  653),  and  the  communication 
of  the  veins  of  the  scalp  with  the  diploic  veins 
(page  658).  Through  these  communications 
inflammatory  processes  commencing  on  the  out- 
side of  the  skull  may  travel  inward,  leading  to 
osteo-phlebitis  of  the  diploe  and  inflammation 
of  the  membranes  of  the  brain.  To  this  must 
be  attributed  one  of  the  principal  dangers  of 
scalp  wounds  and  other  injuries  of  the  scalp. 

By  means  of  these  emissary  veins  blood 
may  be  abstracted  almost  directly  from  the 
intracranial  circulation.  For  instance,  leeches 
applied  behind  the  ear  abstract  blood  almost 
directly  from  the  lateral  sinus  through  the  vein 
passing  through  the  mastoid  foramen.  Again, 
epistaxis  in  children  will  frequently  relieve  severe 
headache,  the  blood  which  flows  from  the  nose 
being  derived  from  the  longitudinal  sinus  by 
means  of  the  vein  which  passes  through  the 
foramen  caecum,  which  is  another  communica- 
tion between  the  intracranial  and  extracranial 
circulation  which  is  constantly  found  in  children. 


Median  cephalic, 

External 
cutaneous  nerce. 


FIG.  387.— The  superficial  veins  of  the  upper  extremity. 


VEINS  OF  THE  UPPER  EXTREMITY 
AND  THORAX. 

The  veins  of  the  Upper  Extremity  are 
divided  into  two  sets,  superficial  and  deep. 

The  Superficial  Veins  are  placed  im- 
mediately beneath  the  integument  he- 
tween  the  two  layers  of  superficial  fascia. 

The  Deep  Veins  accompany  the  ar- 
teries, and  constitute  the  venae  comites 
of  those  vessels. 

Both  sets  of  vessels  are  provided  with 
valves,  which  are  more  numerous  in  the 
deep  than  in  the  superficial. 

The  superficial  veins  of  the  upper 
extremity  are — the 

Superficial  veins  of  the  Hand. 

Anterior  Ulnar. 

Posterior  Ulnar. 

Common  Ulnar. 

Radial. 

Median. 

Median  Basilic. 

Median  Cephalic. 

Basilic. 

Cephalic.. 


The  Superficial  Veins  of  the  Hand  and  Fingers  are  principally  situated  on  the 


OF    THE    UPPER    EXTREMITY  AXD    THORAX.  663 

dorsal  surface,  and  form  two  plexuses,  an  inner  and  outer,  on  the  back  of  the 
hand.  The  inner  plexus  is  formed  by  the  veins  from  the  little  finger  (vena  salva- 
t>  //'/).  the  ring  finger,  and  the  ulnar  side  of  the  middle  finger  ;  from  it  the  anterior 
and  posterior  ulnar  veins  are  derived.  The  outer  plexus  is  formed  by  veins  from 
the  thumb,  the  index  finger,  and  radial  side  of  the  middle  finger ;  from  it  the 
radial  vein  is  derived.  These  two  plexuses  communicate  on  the  back  of  the  hand, 
forming  the  superficial  arch  of  veins  in  this  situation.  The  superficial  veins  from 
the  palm  of  the  hand  form  a  plexus  in  front  of  the  wrist,  from  which  the  median 
vein  is  derived. 

The  Anterior  Ulnar  Vein  commences  on  the  anterior  surface  of  the  ulnar  side 
of  the  hand  and  wrist,  and  ascends  along  the  anterior  surface  of  the  ulnar  side  of 
the  forearm  to  the  bend  of  the  elbow,  where  it  joins  with  the  posterior  ulnar  vein 
to  form  the  common  ulnar.  Occasionally  it  opens  separately  into  the  median 
basilic  vein.  It  communicates  with  branches  of  the  median  vein  in  front  and 
with  the  posterior  ulnar  behind. 

The  Posterior  Ulnar  Vein  commences  on  the  posterior  surface  of  the  ulnar  side 
of  the  wrist.  It  runs  on  the  posterior  surface  of  the  ulnar  side  of  the  forearm, 
and  just  below  the  elbow  unites  with  the  anterior  ulnar  vein  to  form  the  common 
ulnar,  or  else  joins  the  median  basilic  to  form  the  basilic.  It  communicates  with 
the  deep  veins  of  the  palm  by  a  branch  which  emerges  from  beneath  the  Abductor 
minimi  digiti  muscle. 

The  Common  Ulnar  is  a  short  trunk  which  is  not  constant.  When  it  exists  it 
is  formed  by  the  junction  of  the  two  preceding  veins,  and,  passing  upward  and 
outward,  joins  the  median  basilic  to  form  the  basilic  vein.  When  it  does  not 
exis:  the  anterior  and  posterior  ulnar  veins  open  separately  into  the  median 
basilic  vein. 

The  Radial  Vein  commences  from  the  dorsal  surface  of  the  wrist,  communi- 
cating with  the  deep  veins  of  the  palm  by  a  branch  which  passes  through  the 
first  interosseous  space.  It  forms  a  large  vessel,  which  ascends  along  the  radial 
side  of  the  forearm  and  receives  numerous  veins  from  both  its  surfaces.  At 
the  bend  of  the  elbow  it  unites  with  the  median  cephalic  to  form  the  cephalic 
vein. 

The  Median  Vein  ascends  on  the  front  of  the  forearm,  and  communicates  with 
the  anterior  ulnar  and  radial  veins.  At  the  bend  of  the  elbow  it  receives  a  branch 
of  communication  from  the  deep  veins,  and  divides  into  two  branches,  the  median 
cephalic  and  median  basilic,  which  diverge  from  each  other  as  they  ascend. 

The  Median  Cephalic,  usually  the  smaller  of  the  two,  passes  outward  in  the 
groove  between  the  Supinator  longus  and  Biceps  muscles,  and  joins  with  the 
radial  to  form  the  cephalic  vein.  The  branches  of  the  external  cutaneous  nerve 
pass  beneath  this  vessel. 

The  Median  Basilic  Vein  passes  obliquely  inward,  in  the  groove  between  the 
Biceps  and  Pronator  radii  teres.  and  joins  the  common  ulnar  to  form  the  basilic. 
This  vein  passes  in  front  of  the  brachial  artery,  from  which  it  is  separated  by  a 
fibrous  expansion  (the  bicipital fascia]  which  is  given  off  from  the  tendon  of  the 
Biceps  to  the  fascia  covering  the  Flexor  muscles  of  the  forearm.  Filaments  of 
the  internal  cutaneous  nerve  pass  in  front  as  well  as  behind  this  vessel.1* 

Venesection  is  usually  performed  at  the  bend  of  the  elbow,  and  as  a  matter  of  practice  the 
largest  vein  in  this  situation  is  commonly  selected.  This  is  usually  the  median  basilic,  and  there 
are  anatomical  advantages  and  disadvantages  in  selecting  this  vein.  The  advantages  are,  that 
in  addition  to  its  being  the  largest,  and  therefore  yielding  a  greater  supply  of  blood,  it  is  the 
least  movable  and  can  be  easily  steadied  on  the  bieipital  fascia  on  which  it  rests.  The  disadvan- 
are.  that  it  is  in  close  relationship  with  the  brachial  artery,  separated  only  by  the  bieipital 
fascia ;  and  formerly,  when  venesection  was  frequently  practised,  arterio-venous  aneurism  was 

1  Cruveilhier  says:   "Numerous  varieties  are  observed  in  the  disposition  of  the  veins  of  the 
elbow;  sometimes  the  common  median  vein  is  wanting:  but  in  those  cases  its  two  branches  are  fur- 
nished by  the  radial  vein,  and  the  cephalic  is  almost  always  in  a  rudimentary  condition.     In  other 
.nly  two  veins  are  found  at  the  bend  of  the  elbow,  the  radial  and  ulnar,  which  are  continuous, 
without  any  demarcation,  with  the  cephalic  and  bnsilic." 


664  THE    VEINS. 

no  uncommon  result  of  this  practice.  Another  disadvantage  is,  that  the  median  basilic  is 
crossed  by  some  of  the  branches  of  the  internal  cutaneous  nerve,  and  these  may  be  divided  in 
the  operation,  giving  rise  to  ''traumatic  neuralgia  of  extreme  intensity  "  (Tillaux). 

The  Basilic  Vein  is  of  considerable  size,  formed  by  the  coalescence  of  the 
common  ulnar  vein  with  the  median  basilic.  It  passes  upward  along  the  inner 
side  of  the  Biceps  muscle,  pierces  the  deep  fascia  a  little  below  the  middle  of  the 
arm,  and,  ascending  in  the  course  of  the  brachial  artery,  terminates  in  the  axil- 
lary vein,  which  receives,  a  little  higher  up,  the  brachial  venae  comites. 

The  Cephalic  Vein  courses  along  the  outer  border  of  the  Biceps  muscle,  lying 
in  the  same  groove  with  the  upper  external  cutaneous  branch  of  the  musculo-spival 
nerve,  to  the  upper  third  of  the  arm  ;  it  then  passes  in  the  interval  between  the 
Pectoralis  major  and  Deltoid  muscles,  lying  in  the  same  groove  with  the  descending 
branch  of  the  acromial-thoracic  artery.  It  pierces  the  costo-coracoid  membrane, 
and  terminates  in  the  axillary  vein  just  below  the  clavicle.  This  vein  is  occa- 
sionally connected  with  the  external  jugular  or  subclavian  by  a  branch  which 
passes  from  it  upward  in  front  of  the  clavicle. 

The  Deep  Veins  of  the  Upper  Extremity  follow  the  course  of  the  arteries, 
forming  their  venae  comites.  They  are  generally  two  in  number,  one  lying  on 
each  side  of  the  corresponding  artery,  and  they  are  connected  at  intervals  by 
short  transverse  branches. 

There  are  two  digital  veins  accompanying  each  artery  along  the  sides  of  the 
fingers :  these,  uniting  at  their  base,  pass  along  the  interosseous  spaces  in  the 
palm,  and  terminate  in  the  two  venae  comites  which  accompany  the  superficial 
palmar  arch.  Branches  from  these  vessels  on  the  radial  side  of  the  hand  accom- 
pany the  superficialis  volae,  and  on  the  ulnar  side  terminate  in  the  deep  ulnar 
veins.  The  deep  ulnar  veins,  as  they  pass  in  front  of  the  wrist,  communicate  with 
the  interosseous  and  superficial  veins,  and  at  the  elbow  unite  with  the  deep  radial 
veins  to  form  the  venae  comites  of  the  brachial  artery. 

The  Interosseous  Veins  accompany  the  anterior  and  posterior  interosseous 
arteries.  The  anterior  interosseous  veins  commence  in  front  of  the  wrist,  where 
they  communicate  with  the  deep  radial  and  ulnar  veins  ;  at  the  upper  part  of  the 
forearm  they  receive  the  posterior  interosseous  veins,  and  terminate  in  the  venae 
comites  of  the  ulnar  artery. 

The  Deep  Palmar  Veins  accompany  the  deep  palmar  arch,  being  formed  by 
tributaries  which  accompany  the  ramifications  of  that  vessel.  They  communicate 
with  the  deep  ulnar  veins  at  the  inner  side  of  the  hand,  and  on  the  outer  side 
terminate  in  the  venae  comites  of  the  radial  artery.  At  the  wrist  they  receive  a 
dorsal  and  a  palmar  tributary  from  the  thumb,  and  unite  with  the  deep  radial 
veins.  Accompanying  the  radial  artery,  these  vessels  terminate  in  the  venae 
comites  of  the  brachial  artery. 

The  Brachial  Veins  are  placed  one  on  each  side  of  the  brachial  artery, 
receiving  tributaries  corresponding  with  the  branches  given  off  from  that  vessel ; 
just  above  the  lower  margin  of  the  tendon  of  the  Latissimus  dorsi  they  empty 
into  the  axillary  vein. 

These  deep  veins  have  numerous  anastomoses,  not  only  with  each  other,  but 
also  with  the  superficial  veins. 

The  Axillary  Vein  is  of  large  size,  and  is  the  continuation  of  the  basilic  vein, 
receiving  the  venae  comites  of  the  brachial  artery.  It  commences  at  the  lower 
part  of  the  axillary  space,  increases  in  size  as  it  ascends  by  receiving  tributaries 
corresponding  with  the  branches  of  the  axillary  artery,  and  terminates  imme- 
diately beneath  the  clavicle  at  the  lower  border  of  the  first  rib,  where  it  becomes 
the  subclavian  vein.  This  vessel  is  covered  in  front  by  the  Pectoral  muscles  and 
costo-coracoid  membrane,  and  lies  on  the  thoracic  side  of  the  axillary  artery, 
which  it  partially  overlaps.  Near  its  termination  it  receives  the  cephalic  vein. 
This  vein  is  provided  with  a  pair  of  valves  opposite  the  lower  border  of  the  Sub- 
scapularis  muscle ;  valves  are  also  found  at  the  termination  of  the  cephalic  and 
subscapular  veins. 


THE  INNOMINATE    VEIX*.  665 

Surgical  Anatomy.— There  are  several  points  of  surgical  interest  in  connection  with  the 
axillary  vein.  Being  more  superficial,  larger,  and  slightly  overlapping  the  axillary  artery,  it  is 
more  liable  to  be  wounded  in  the  operation  of  extirpation  of  the  axillary  glands,  especially  as 
these  glands,  when  diseased,  are  apt  to  become  adherent  to  the  vessel.  When  wounded  there 
is  always  a  danger  of  air  being  drawn  into  its  interior,  and  death  resulting.  This  is  due  not  only 
to  the  fact  that  it  is  near  the  thorax,  and  therefore  liable  to  be  influenced  by  the  respiratory 
movements,  but  also  because  it  is  adherent  by  its  anterior  surface  to  the  costo-coracoid  membrane, 
and  therefore  if  wounded  is  likely  to  remain  patulous  and  favor  the  chance  of  air  being  sucked 
in.  This  adhesion  of  the  vein  to  the  fascia  prevents  its  collapsing,  and  therefore  favors  the 
furious  bleeding  which  takes  place  in  these  cases. 

To  avoid  wounding  the  axillary  vein  in  the  extirpation  of  cancerous  glands  from  the  axilla, 
no  sharp  cuttinir  instruments  should  be  used  after  the  axillary  cavity  has  been  freely  exposed, 
and  care  should  be  taken  to  use  no  undue  force  in  isolating  the  glands.  Should  the  vein  be  so 
imbedded  in  the  malignant  deposit  that  the  latter  cannot  be  removed  without  taking  away  a  part 
of  the  vein,  this  must  be  done,  the  vessel  having  been  first  ligatured  above  and  below. 

The  Subclavian  Vein,  the  continuation  of  the  axillary,  extends  from  the  lower 
border  of  the  first  rib  to  the  inner  end  of  the  sterno-clavicular  articulation,  where 
it  unites  with  the  internal  jugular  to  form  the  innominate  vein.  It  is  in  relation, 
in  front,  with  the  clavicle  and  Subclavius  muscle ;  behind,  with  the  subclavian 
artery,  from  which  it  is  separated  internally  by  the  Scalenus  anticus  muscle  and 
phrenic  nerve.  Below,  it  rests  in  a  depression  on  the  first  rib  and  upon  the  pleura. 
Above,  it  is  covered  by  the  cervical  fascia  and  integument. 

The  subclavian  vein  occasionally  rises  in  the  neck  to  a  level  with  the  third  part 
of  the  subclavian  artery,  and  in  two  instances  has  been  seen  passing  with  this  vessel 
behind  the  Scalenus  anticus.  This  vessel  is  usually  provided  with  valves  about 
an  inch  from  its  termination  in  the  innominate,  just  external  to  the  entrance  of  the 
external  jugular  vein. 

Tributaries. — It  receives  the  external  and  anterior  jugular  veins  and  a  small 
branch  from  the  cephalic,  outside  the  Scalenus,  and  on  the  inner  side  of  that 
muscle  the  internal  jugular  vein.  At  the  angle  of  junction  with  the  internal 
jugular  the  left  subclavian  vein  receives  the  thoracic  duct,  while  the  right  sub- 
clavian vein  receives  the  right  lymphatic  duct. 

The  Innominate  or  Brachio-cephalic  Veins  (Fig.  388)  are  two  large  trunks, 
placed  one  on  each  side  of  the  root  of  the  neck,  and  formed  by  the  union  of  the 
internal  jugular  and  subclavian  veins  of  the  corresponding  side. 

The  Right  Innominate  Vein  is  a  short  vessel,  an  inch  in  length,  which  com- 
mences at  the  inner  end  of  the  clavicle,  and.  passing  almost  vertically  downward, 
joins  with  the  left  innominate  vein  just  below  the  cartilage  of  the  first  rib,  close  to 
the  right  border  of  the  sternum,  to  form  the  superior  vena  cava.  It  lies  superficial 
and  external  to  the  innominate  artery ;  on  its  right  side  the  pleura  is  interposed 
between  it  and  the  apex  of  the  lung.  This  vein,  at  the  angle  of  junction  of  the 
internal  jugular  with  the  subclavian,  receives  the  right  vertebral  vein,  and,  lower 
down,  the  right  internal  mammary,  right  inferior  thyroid,  and  sometimes  the 
right  superior  intercostal  veins. 

The  Left  Innominate  Vein,  about  two  and  a  half  inches  in  length,  and  larger 
than  the  right,  passes  from  left  to  right  across  the  upper  and  front  part  of  the  chest, 
at  the  same  time  inclining  downward,  to  unite  with  its  fellow  of  the  opposite 
side,  forming  the  *''/"  ri.»r  vena  cava.  It  is  in  relation,  in  front,  with  the  first 
piece  of  the  sternum,  from  which  it  is  separated  by  the  Sterno-hyoid  and  Sterno- 
thyroid  muscles,  the  thynius  gland  or  its  remains,  and  some  loose  areolar  tissue. 
Behind,  it  lies  across  the  roots  of  the  three  large  arteries  arising  from  the  arch  of 
the  aorta.  This  vessel  is  joined  by  the  left  vertebral,  left  internal  mammary,  left 
inferior  thyroid,  and  the  left  superior  intercostal  veins,  and  occasionally  some  thymic 
and  pericardiac  veins.  There  are  no  valves  in  the  innominate  veins. 

Peculiarities.— Sometimes  the  innominate  veins  open  separately  into  the  right  auricle  ;  in 
such  cases  the  right  vein  takes  the  ordinary  course  of  the  superior  vena  cava  ;  but  the  left  vein, 
after  communicating  by  a  small  branch  with  the  right  one.  passes  in  front  of  the  root  of  the  left 
lung.  and.  turninir  to  the  back  of  the  heart,  receives  the  cardiac  veins  and  terminates  in  the  back 
of  the  right  auricle.  This  occasional  condition  of  the  veins  in  the  adult  is  a  regular  one  in  the 
foetus  at  an  early  period,  and  the  two  vessels  are  persistent  in  birds  and  some  mammalia.  The 


666 


THE    VEINS. 


subsequent  changes  which  take  place  in  these  vessels  are  the  following  :  The  communicating 
branch  between  the  two  trunks  enlarges  and  forms  the  future  left  innominate  vein ;  the  re- 
maining part  of  the  left  trunk  is 
obliterated  as  i'ar  as  the  heart, 
where  it  remains  pervious  and 
forms  the  coronary  sinus :  a 
remnant  of  the  obliterated  vessel 

-External  jugular.        is  seen  in  adult   life  as  a  fibroiis 


Anterior  jugular. 


Superior  thyroid. 


Middle  thyi 


Mediastinal  1 

and        ' , 

pericardiac.  p 


band  passing  along  the  back  of 
the  left  auricle  and  in  front  of 
the  root  of  the  left  lung,  called 
by  Mr.  Marshall  the  vestigial 
fold  of  the  pericardium. 

The  internal  mammary 
veins,  two  in  number  to 
each  artery,  follow  the 
course  of  that  vessel, 
and  receive  corresponding 
branches.  The  two  veins 
of  each  side  unite  into  a 
single  trunk,  which  termi- 
nates in  the  corresponding 
innominate  vein. 

The  inferior  thyroid  veins, 
two,  frequently  three  or 
four,  in  number,  arise  in 
the  venous  plexus  on  the 
thyroid  body,  communicat- 
ing with  the  middle  and 
superior  thyroid  veins.  The 
left  one  descends  in  front 
of  the  trachea  behind  the 
Sterno-thyroid  muscle,  com- 
municating with  its  fellow 
by  transverse  branches,  and 
terminates  in  the  left  in- 
nominate vein.  The  right 
one,  which  is  placed  a  little 
to  the  right  of  the  median 
line,  opens  into  the  right 
innominate  vein  just  at  its 
junction  with  the  superior 
vena  cava.  These  veins 
receive  oesophageal,  tra- 
cheal,  and  inferior  laryn- 
geal  veins,  and  are  pro- 
vided with  valves  at  their 
termination  in  the  innom- 
inate veins. 

The  Superior  Intercos- 
tal Veins  return  the  blood 
from  the  upper  intercostal 
spaces,  below  the  first. 

The  rigid  superior  inter- 
costal, much  smaller  than 
the  left,  closely  corresponds 
with  the  superior  intercos- 
tal artery,  receiving  the 
blood  from  the  second  or  second  and  third  intercostal  spaces,  and,  passing  do\vn- 


Tntrrna 


FIG.  388  -The  venae  cavse  and  azygos  veins,  with  their  formative 
branches. 


THE    VENA    CAVA.  667 

ward,  terminates  in  the  vena  azygos  major.  Occasionally  it  opeas  into  the  right 
innominate  vein. 

The  Ifft  x)if» •/•("/•  int-  r<-"*t<il  is  always  larger  than  the  right,  but  varies  in  size 
in  different  subjects,  being  small  when  the  left  upper  azygos  vein  is  large,  and  vice 
'.  It  is  usually  formed  by  branches  from  two  or  three  upper  intercostal 
spaces  below  the  first,  and.  passing  across  the  arch  of  the  aorta,  terminates  in  the 
left  innominate-vein.  The  left  bronchial  vein  and  the  left  superior  phrenic  open 
into  it. 

The  Superior  Vena  Cava  receives  the  blood  which  is  conveyed  to  the  heart  from 
the  whole  of  the  upper  half  of  the  body.  It  is  a  short  trunk,  varying  from  two 
inches  and  a  half  to  three  inches  in  length,  formed  by  the  junction  of  the  two 
innominate  veins.  It  commences  immediately  below  the  cartilage  of  the  first  rib 
close  to  the  sternum  on  the  right  side,  and,  descending  vertically,  enters  the  peri- 
cardium about  an  inch  and  a  half  above  the  heart,  and  terminates  in  the  upper  part 
of  the  right  auricle  opposite  the  upper  border  of  the  third  left  costal  cartilage.  In 
its  course  it  describes  a  slight  curve,  the  convexity  of  which  is  turned  to  the  right 
side. 

Relations. — In  front,  with  the  pericardium  and  process  of  cervical  fascia  which 
i-  continuous  with  it:  this  separates  it  from  the  thymus  gland  and  from  the  ster- 
num :  behind,  with  the  root  of  the  right  lung:  on  its  right  side,  with  the  phrenic 
nerve  and  right  pleura  :  on  its  left  side,  with  the  commencement  of  the  innominate 
artery  and  ascending  part  of  the  aorta.  The  portion  contained  within  the  peri- 
cardium is  covered  by  the  serous  layer  of  that  membrane  in  its  anterior  three- 
fourths.  It  receives  the  vena  azygos  major  just  before  it  enters  the  pericardium, 
and  several  small  veins  from  the  pericardium  and  parts  in  the  mediastinum.  The 
superior  vena  cava  has  no  valves. 

The  Azygos  Veins  connect  together  the  superior  and  inferior  venae  cava,  taking 
the  place  of  those  vessels  in  thaf  part  of  the  chest  occupied  by  the  heart. 

The  larger,  or  right  azygos  vein  (vena  azygos  major),  commences  opposite  the 
first  or  second  lumbar  vertebra  by  a  branch  from  the  right  lumbar  veins  (the 
/'/>//  lumbar);  sometimes  by  a  branch  from  the  right  renal  vein  or  from  the 
inferior  vena  cava.  It  enters  the  thorax  through  the  aortic  opening  in  the  Dia- 
phragm, and  passes  along  the  right  side  of  the  vertebral  column  to  the  fourth  dorsal 
vertebra,  where  it  arches  forward  over  the  root  of  the  right  lung,  and  terminates 
in  the  superior  vena  cava  just  before  that  vessel  enters  the  pericardium.  Whilst 
] uissing  through  the  aortic  opening  of  the  Diaphragm  it  lies  with  the  thoracic 
duct  on  the  right  side  of  the  aorta,  and  in  the  thorax  it  lies  upon  the  intercostal 
arteries  on  the  right  side  of  the  aorta  and  thoracic  duct,  and  is  partly  covered  by 
pleura. 

Tributaries. — It  receives,  excepting  those  of  the  first  three  spaces,  the  intercostal 
veins  of  the  right  side,  the  vena  azygos  minor,  the  left  upper  azygos  vein,  several 
cesophageal.  rnediastinal,  and  pericardial  veins ;  near  its  termination,  the  right 
bronchial  vein  :  and  generally  the  right  superior  intercostal  vein.  A  few  imperfect 
valves  are  found  in  this  vein,  but  its  tributaries  are  provided  with  complete  valves. 

The  intercostal  veins  on  the  left  side,  below  the  two  or  three  upper  intercostal 
spaces,  form  two  trunks,  named  the  left  lower  and  the  left  upper  azygos  veins. 

The  l'-ff  !<,>r>-r.  or  *>/><tHi  /•  <i-'/<:/o$  vein  (vena  azygos  minor),  commences  in  the 
lumbar  region  by  a  branch  from  one  of  the  lumbar  veins  (ascending  lumbar)  or 
from  the  left  renal.  It  passes  into  the  thorax  through  the  left  cms  of  the  Dia- 
phragm, and.  ascending  on  the  left  side  of  the  spine  as  high  as  the  seventh  or 
eighth  dorsal  vertebra,  passes  across  the  column,  behind  the  aorta  and  thoracic 
duct,  to  terminate  in  the  right  azygos  vein.  It  receives  the  four  or  five  lower  inter- 
C'>stal  veins  of  the  left  side,  and  some  oesophageal  and  mediastinal  veins. 

The  left  upper  azygos  vein  varies  according  to  the  size  of  the  left  superior 
intercostal,  with  which  it  communicates  above.  It  receives  veins  from 
the  intercostal  spaces  between  the  left  superior  intercostal  vein  and  highest 
tributary  of  the  left  lower  azygos.  They  are  usually  two  or  three  in  number, 


668 


THE    VEINS. 


and  join  to  form  a  trunk  which  ends  in  the  right  azygos  vein  or  in  the  left  lower 
azygos.  It  sometimes  receives  the  left  bronchial  vein.  When  this  vein  is  small 
or  altogether  wanting,  the  left  superior  intercostal  vein  will  extend  as  low  as  the 
fifth  or  sixth  intercostal  space.1 

Surgical  Anatomy. — In  obstruction  of  the  superior  vena  cava  the  azygos  veins  are  one  of 
the  principal  means  by  which  the  venous  circulation  is  carried  on,  connecting  as  they  do  the  superior 
and  inferior  venae  cavae.  and  communicating  with  the  common  iliac  veins  by  the  ascending  lumbar 
veins,  and  with  many  of  the  tributaries  of  the  inferior  vena  cava. 

The  bronchial  veins  return  the  blood  from  the  substance  of  the  lungs ;  that  of 
the  right  side  opens  into  the  vena  azygos  major  near  its  termination ;  that  of  the 
left  side,  into  the  left  superior  intercostal  vein  or  left  upper  azygos  vein. 

THE  SPINAL  VEINS. 

The  numerous  venous  plexuses  placed  upon  and  within  the  spine  may  be 
arranged  into  four  sets  : 

1.  Those  placed  on  the  exterior  of  the  spinal  column  (the  dorsi-spinal  veins). 

2.  Those  situated  in  the  interior  of  the  spinal  canal,  between  the  vertebrae  and 
the  theca  vertebralis  (meningo-rachidian  veins). 

3.  The  veins  of  the  bodies  of  the  vertebrae  (venae  basis  vertebraruni). 

4.  The  veins  of  the  spinal  cord  (medulli-spinat). 

1.  The  Dorsi-spinal  Veins  commence  by  small  branches  which  receive  their 


The  dor  si- spinal  veins. 


FIG.  389.— Transverse  section  of  a  dorsal  vertebra,  showing  the  spinal  veins. 


blood  from  the  integument  of  the  back  of  the  spine  and  from  the  muscles  in  the 
vertebral  grooves.  They  form  a  complicated  network,  which  surrounds  the  spinous 
processes,  the  laminae,  and  the  transverse  and  articular  processes  of  all  the  ver- 
tebrae. At  the  bases  of  the  transverse  processes  they  communicate,  by  means  of 
ascending  and  descending  branches,  with  the  veins  surrounding  the  contiguous 
vertebrae,  and  they  join  with  the  veins  in  the  spinal  canal  by  branches  which 
perforate  the  ligamenta  subflava.  Other  branches  pass  obliquely  forward, 
between  the  transverse  processes,  and  communicate  with  the  intraspinal  veins 
through  the  intervertebral  foramina.  They  terminate  by  joining  the  vertebral 

1  For  an  account  of  the  arrangement  of  the  azygos  and  superior  intercostal  veins  in  a  number  of 
consecutive  cases  from  the  same  dissecting-room,  see  a  paper  by  Mr.  B.  G.  Morison  (Jom~nal  of  Anat- 
<)my  and  Physiology,  vol.  xiii.  p.  346).  The  most  important  difference  between  his  description  and  that 
in  the  text  is,  that  he  always  found  two  superior  intercostal  veins  on  both  sides,  the  vein  from  the  first 
space  being  separate,  and  joining  the  corresponding  innominate  vein.  The  lower  (and  larger)  supe- 
rior intercostal  vein  he  describes  as  opening  into  the  azygos  on  the  right  and  innominate  on  the  left 
side. 


THE  SPINAL    VEIXS.  669 

veins  in  the  neck,  the  intercostal  veins  in  the  thorax,  and  the  lumbar  and  sacral 
veins  in  the  loins  and  pelvis 

'2.  The  Meningo-rachidian  Veins. — The  principal  veins  contained  in  the  spinal 
canal  are  situated  between  the  theca  vertebralis  and  the  vertebrae.  They  consist 
of  two  longitudinal  plexuses,  one  of  which  runs  along  the  posterior  surface  of  the 
bodies  of  the  vertebrae  (anterior  longitudinal  spinal  veins).  The  other  plexus 
(posterior  longitudinal  spinal  veins)  is  placed  on  the  inner  or  anterior  surface  of 
the  lamina?  of  the  vertebne. 

The  Anterior  Longitudinal  Spinal  Veins  consist  of  two  large,  tortuous  veins 
which  extend  along  the  whole  length  of  the  vertebral  column,  from  the  foramen 
magnum  where  they  communicate  by  a  venous  ring  around  that  opening,  to  the 
base  of  the  coccyx,  being  placed  one  on  each  side  of  the  posterior  surface  of  the 
bodies  of  the  vertebrae  along  the  margin  of  the  posterior  common  ligament. 
These  veins  communicate  together  opposite  each  vertebra  by  transverse  trunks 
which  pass  beneath  the  ligament,  and  receive  the  large  vence  basis  vertebrarum 
from  the  interior  of  the  body  of  each  vertebra.  The  anterior  longitudinal  spinal 
veins  are  least  developed  in  the  cervical  and  sacral  regions.  They  are  not  of 


FIG.  390. — Vertical  section  of  two  dorsal  vertebrae,  showing  the  spinal  veins. 

uniform  size  throughout,  being  alternately  enlarged  and  constricted.  At  the 
intervertebral  foramina  they  communicate  with  the  dorsi-spinal  veins,  and  with 
the  vertebral  veins  in  the  neck,  with  the  intercostal  veins  in  the  dorsal  region, 
and  with  the  lumbar  and  sacral  veins  in  the  corresponding  regions. 

The  Posterior  Longitudinal  Spinal  Veins,  smaller  than  the  anterior,  are 
situated  one  on  each  side,  between  the  inner  surface  of  the  laminae  and  the  theca 
vertebralis.  They  communicate  (like  the  anterior)  opposite  each  vertebra  by 
transverse  trunks,  and  with  the  anterior  longitudinal  veins  by  lateral  transverse 
branches  which  pass  from  behind  forward.  These  veins,  by  branches  which  per- 
forate the  ligamenta  subflava,  join  with  the  dorsi-spinal  veins.  From  them 
branches  are  given  off  which  pass  through  the  intervertebral  foramina  and  join 
the  vertebral,  intercostal,  lumbar,  and  sacral  veins. 

3.  The  Veins  of  the  Bodies  of  the  Vertebrae  (vence  basis  vertebrarum)  emerge 
from  the  foramina  on  their  posterior  surface,  and  join  the  transverse  trunk  con- 
necting the  anterior  longitudinal  spinal  veins.     They  are  contained  in  large,  tor- 
tuous channels  in  the  substance  of  the  bones,  similar  in  every  respect  to  those 
found  in  the  diploe  of  the  cranial  bones.      These  canals  lie  parallel  to  the  upper 
and  lower  surface  of  the  bones.      They  commence  by  small  openings  on  the  front 
and  sides  of  the  bodies  of  the  vertebrae,  through  which  communicating  branches 
fr<»in  the  veins  external  to  the  bone  pass  into  its  substance,  and  converge  to  the 
principal  canal,  which   is  sometimes  double   toward  its  posterior  part,  and  open 
into  the  corresponding  transverse  branch  uniting  the  anterior  longitudinal  veins. 
They  become  greatly  developed  in  advanced  age. 

4.  The  Veins  of  the  Spinal  Cord  (  nuditlK-fpmat)  consist  of  a  minute,  tortuous, 


670  THE    VEINS 

venous  plexus  which  covers  the  entire  surface  of  the  cord,  being  situated  between 
the  pia  mater  and  arachnoid.  These  vessels  emerge  chiefly  from  the  median 
furrows,  and  are  largest  in  the  lumbar  region.  Near  the  base  of  the  skull  they 
unite  and  form  two  or  three  small  trunks,  which  communicate  with  the  vertebral 
veins,  and  then  terminate  in  the  inferior  cerebellar  veins  or  in  the  inferior  petro- 
sal  sinuses.  Each  of  the  spinal  nerves  is  accompanied  by  a  branch  as  far  as  the 
intervertebral  foramina,  where  they  join  the  other  veins  from  the  spinal  canal. 
There  are  no  valves  in  the  spinal  veins. 

VEINS  OF  THE  LOWER  EXTREMITY,  ABDOMEN,  AND  PELVIS. 

The  Veins  of  the  Lower  Extremity  are  subdivided,  like  those  of  the  upper, 
into  two  sets,  superficial  and  deep,  the  superficial  veins  being  placed  beneath  the 
integument,  between  the  two  layers  of  superficial  fascia,  the  deep  veins  accom- 
panying the  arteries  and  forming  the  venae  comites  of  those  vessels.  Both  sets 
of  veins  are  provided  with  valves,  which  are  more  numerous  in  the  deep  than  in 
the  superficial  set.  These  valves  are  also  more  numerous  in  the  lower  than  in 
the  upper  limb. 

The  Superficial  Veins  of  the  Lower  Extremity  are  the  internal  or  long  saphen- 
ous  and  the  external  or  short  saphenous. 

On  the  dorsum  of  the  foot  is  a  venous  arch  situated  in  the  superficial  struc- 
tures over  the  anterior  extremities  of  the  metatarsal  bones.  It  has  its  convexity 
directed  forward,  and  receives  digital  tributaries  from  the  upper  surface  of  the 
toes;  at  its  concavity  it  is  joined  by  numerous  small  veins  which  form  a  plexus 
on  the  dorsum  of  the  foot.  The  arch  terminates  internally  in  the  long  saphenous, 
externally  in  a  short  saphenous  vein. 

The  internal  or  long  saphenous  vein  (Fig.  391)  commences  at  the  inner  side  of 
the  arch  on  the  dorsum  of  the  foot ;  it  ascends  in  front  of  the  inner  malleolus 
and  along  the  inner  side  of  the  leg,  behind  the  inner  margin  of  the  tibia,  accom- 
panied by  the  internal  saphenous  nerve.  At  the  knee  it  passes  backward  behind 
the  inner  condyle  of  the  femur,  ascends  along  the  inside  of  the  thigh,  and,  pass- 
ing through  the  saphenous  opening  in  the  fascia  lata,  terminates  in  the  femoral 
vein  about  an  inch  and  a  half  below  Poupart's  ligament.  This  vein  receives  in 
its  course  cutaneous  tributaries  from  the  leg  and  thigh,  and  at  the  saphenous 
opening  the  superficial  epigastric,  superficial  circumflex  iliac,  and  external  pudic 
veins.  The  veins  from  the  inner  and  back  part  of  the  thigh  frequently  unite  to 
form  a  large  vessel,  which  enters  the  main  trunk  near  the  saphenous  opening ; 
and  sometimes  those  on  the  outer  side  of  the  thigh  join  to  form  another  large 
vessel ;  so  that  occasionally  three  large  veins  are  seen  converging  from  different 
parts  of  the  thigh  toward  the  saphenous  opening.  The  internal  saphenous  vein 
communicates  in  the  foot  with  the  internal  plantar  vein  ;  in  the  leg,  with  the 
posterior  tibial  veins  by  branches  which  perforate  the  tibial  origin  of  the  Soleus 
muscle,  and  also  with  the  anterior  tibial  veins ;  at  the  knee,  with  the  articular 
veins  ;  in  the  thigh,  with  the  femoral  vein  by  one  or  more  branches.  The  valves 
in  this  vein  vary  from  two  to  six  in  number  ;  they  are  more  numerous  in  the 
thigh  than  in  the  leg. 

The  external  or  short  saphenous  vein  (Fig.  392)  commences  at  the  outer  side 
of  the  arch  on  the  dorsum  of  the  foot ;  it  ascends  behind  the  outer  malleolus, 
and  along  the  outer  border  of  the  tendo  Achillis,  across  which  it  passes  at  an 
acute  angle  to  reach  the  middle  line  of  the  posterior  aspect  of  the  leg.  Passing 
directly  upward,  it  perforates  the  deep  fascia  in  the  lower  part  of  the  popliteal 
space,  and  terminates  in  the  popliteal  vein,  between  the  heads  of  the  Gastro- 
cnemius  muscle.1  It  receives  numerous  large  tributaries  from  the  back  part  of 

1  Mr.  Gay  calls  attention  to  the  fact  that  the  external  saphenous  vein  often  (he  says  invariably) 
penetrates  the  fascia  at  or  about  the  point  where  the  tendon  of  the  Gastrocnemius  commences,  and  runs 
below  the  fascia  in  the  rest  of  its  course,  or  sometimes  among  the  muscular  fibres,  to  join  the  popliteal 
vein.  (See  Gay  on  Varicose  Disease  of  the  Loiuer  Extremities,  p.  24,  where  there  is  also  a  careful  and 
elaborate  description  of  the  branches  of  the  saphena  veins.) 


OF    THE    LOWER    EXTREMITY. 


671 


the  leg,  and   communicates  with  the  deep  veins  on  the  dorsum  of  the  foot  and 
behind  the   outer  malleolus.     Before   it  perforates   the  deep  fascia  it  gives  off 

a  communicating  branch,  which 
passes  upward  and  inward  to  join 

the  internal  saphenous  vein,      this 

i  -1,1  i,  c 

vein     has    a    variable    number    ol 

valves,   from  three   to  nine    (Gay), 

/      *\.(f^     —  Jfc  one  °f  which  is  always  found  near 

its  termination  in  the  popliteal 
vein.  The  external  saphenous 
nerve  lies  close  beside  this  vein. 


Surgical  Anatomy.— The  saphena 
veins  are  of  considerable  surgical  import- 
ance, since  a  varicose  condition  of  these 
vessels  is  more  frequently  met  with  than 
of  those  in  other  parts  of  the  body,  except 
perhaps  the  spermatic  and  hjemorrhoidal 
veins.  The  course  of  the  internal 
saphenous  is  in  front  of  tbe  tip  of  the 
malleolus,  over  the  subcutaneous  surface 
of  the  lower  end  of  tbe  tibia,  and  tben 
alon<r  the  internal  border  of  this  bone 
to  tbe  back  part  of  the  internal  condyle  of 
the  femur,  whence  it  follows  the  course 
of  the  Sartorius  muscle,  and  is  represented 
on  the  surface  by  a  line  drawn  from  tbe 
posterior  border  of  tbe  Sartorius  on  a 
level  with  the  internal  condyle  to  the 
saphenous  opening.  The  short  saphenous 
lies  behind  the  external  malleolus.  and 
from  this  follows  the  middle  line  of  the 
calf  to  just  below  tbe  ham.  It  is  not 
generally  so  apparent  beneath  the  skin  as 
tbe  internal  saphenous.  Both  these  veins 
in  the  leg  are  accompanied  by  nerves,  the 
internal  saphenous  being  joined  by  its 
companion  nerve  just  below  tbe  level  of 
the  knee-joint.  $p  doubt  much  of  the 
pain  of  varicose  veins  in  the  leg  is  due  to 
this  fact.  On  the  Continent  the  internal 
sapbenous  vein  as  it  rests  on  the  tibia 
just  above  tbe  malleolus  is  sometimes 
selected  for  venesection. 


FIG.  392.— External 
or  short  saphenous 
vein. 


The   Deep    Veins  of  the  Lower 

Extremity  accompany  the  arteries  and  their  branches, 
and  are  called  the  ve nee  comites  of  those  vessels. 

The  external  and  internal  plantar  veins  unite  to  form 
the  posterior  tibial.  They  accompany  the  posterior 
tibial  artery  and  are  joined  by  \\ieperoneal  veins. 

The  anterior  tibial  veins  are  formed  by  a  con- 
tinuation upward  of  the  venae  comites  of  the  dorsalis 
pedis  artery.  They  pass  between  the  tibia  and  fibula, 
through  the  large  oval  aperture  above  the  interosse- 
ous  membrane,  and  form,  by  their  junction  with  the 
posterior  tibial.  the  popliteal  vein. 

The  valves  in  the  deep  veins  are  very  numerous. 

The  Popliteal  Vein  is  formed  by  the  junction  of  the 
venae  comites  of  the  anterior  and' posterior  tibial  ves- 
sels ;  it  ascends  through  the  popliteal  space  to  the 

tendinous  aperture  in  the  Adductor  magnus,  where  it  becomes  the  femoral  veirf. 
In  the  lower  part  of  its  course  it  is  placed  internal  to  the  artery ;  between  the 


672  THE    VEINS 

heads  of  the  Gastrocnemius  it  is  superficial  to  that  vessel ;  but  above  the  knee- 
joint  it  is  close  to  its  outer  side.  It  receives  the  sural  veins  from  the  Gastro- 
cnemius muscle,  the  articular  veins,  and  the  external  saphenous.  The  valves  in 
this  vein  are  usually  four  in  number. 

The  Femoral  Vein  accompanies  the  femoral  artery  through  the  upper  two- 
thirds  of  the  thigh.  In  the  lower  part  of  its  course  it  lies  external  to  the  artery  ; 
higher  up  it  is  behind  it;  and  at  Poupart's  ligament  it  lies  to  its  inner  side  and 
on  the  same  plane.  It  receives  numerous  muscular  tributaries :  the  profunda 
femoris  and  deep  external  pudic  veins  join  it  near  Poupart's  ligament  and  about 
an  inch  and  a  half  below  the  internal  saphenous  vein.  The  valves  in  this  vein  are 
four  or  five  in  number. 

The  External  Iliac  Vein  commences  at  the  termination  of  the  femoral,  beneath 
the  crural  arch,  and,  passing  upward  along  the  brim  of  the  pelvis,  terminates 
opposite  the  sacro-iliac  synchondrosis  by  uniting  with  the  internal  iliac  to  form 
the  common  iliac  vein.  On  the  right  side  it  lies  at  first  along  the  inner  side  of 
the  external  iliac  artery,  but  as  it  passes  upward  gradually  inclines  behind  it. 
On  the  left  side  it  lies  altogether  on  the  inner  side  of  the  artery.  It  receives, 
immediately  above  Poupart's  ligament,  the  deep  epigastric  and  deep  circumflex 
iliac  veins  and  a  small  pubic  vein,  corresponding  to  the  pubic  branch  of  the 
obturator  artery.  According  to  Friedreich,  it  frequently  contains  one,  and  some- 
times two  valves. 

The  Deep  Epigastric  Veins. — Two  veins  accompany  the  deep  epigastric  artery ; 
they  usually  unite  into  a  single  trunk  before  their  termination  in  the  external 
iliac  vein. 

The  Deep  Circumflex  Iliac  Veins. — Two  veins  accompany  the  deep  circumflex 
iliac  artery.  These  unite  into  a  single  trunk  which  crosses  the  external  iliac 
artery  just  above  Poupart's  ligament  and  terminates  in  the  external  iliac 
vein. 

The  Internal  Iliac  Vein  is  formed  by  the  venae  comites  of  the  branches  of  the 
internal  iliac  artery,  the  umbilical  arteries  excepted.  It  receives  the  blood  from 
the  exterior  of  the  pelvis  by  the  gluteal,  sciatic,  internal  pudic,  and  obturator 
veins,  and  from  the  organs  in  the  cavity  of  the  pelvis  by  the  haemorrhoidal  and 
vesico-prostatic  plexuses  in  the  male,  and  the  uterine  and  vaginal  plexuses  in  the 
female.  The  vessels  forming  these  plexuses  are  remarkable  for  their  large  size, 
their  frequent  anastomoses,  and  the  number  of  valves  which  they  contain.  The 
internal  iliac  vein  lies  at  first  on  the  inner  side,  and  then  behind  the  inter- 
nal iliac  artery,  and  terminates  opposite  the  sacro-iliac  articulation  by  uniting 
with  the  external  iliac  to  form  the  common  iliac  vein.  This  vessel  has  no 
valves. 

The  internal  pudic  veins  (venaz  comites)  have  the  same  course  as  the 
internal  pudic  artery.  They  receive  tributaries  corresponding  to  the  branches 
of  the  artery,  except  the  tributary  corresponding  to  the  dorsal  artery  of  the 
penis ;  that  is,  the  dorsal  vein  of  the  penis,  which  opens  into  the  prostatic 
plexus. 

The  hfemorrhoidal  plexus  surrounds  the  lower  end  of  the  rectum,  being  formed 
by  the  superior  hsemorrhoidal  veins  (tributaries  of  the  inferior  mesenteric),  and 
the  middle  and  inferior  hgemorrhoidal,  which  terminate  in  the  internal  iliac.  The 
portal  and  general  venous  systems  have  a  free  communication  by  means  of  the 
branches  composing  this  plexus. 

Surgical  Anatomy. — The  veins  of  this  plexus  are  apt  to  become  dilated  and  varicose  and 
form  piles.  This  is  partly  due  to  the  free  communication  between  the  portal  and  systemic  circu- 
lation which  here  exists,  so  that  any  obstruction  to  the  flow  of  blood  through  either  the  inferior 
vena  cava  or  its  main  tributaries,  or  through  the  portal  vein,  tends  to  produce  passive  congestion 
of  this  plexus.  The  condition  is  also  partly  due  to  the  fact  that  the  vessels  are  contained  in 
very  loose,  lax  connective  tissue,  so  that  they  get  less  support  from  surrounding  structures 
than  most  other  veins,  and  are  less  capable  of  resisting  increased  blood-pressure.  And, 
finally,  the  condition  is  favored  by  gravitation,  inasmuch  as  the  portal  vein  contains  no 
valves. 


OF    THE   LOWER    EXTREMITY.  673 

The  vesico-prostatic  plexus  surrounds  the  neck  and  base  of  the  bladder  and 
prostate  gland.  It  communicates  with  the  haemorrhoidal  plexus  behind,  and 
receives  the  dorsal  vein  of  the  penis,  which  enters  the  pelvis  beneath  the  subpubic 
ligament.  This  plexus  is  supported  upon  the  sides  of  the  bladder  by  a  reflection 
of  the  pelvic  fascia.  The  veins  composing  it  are  very  liable  to  become  varicose, 
and  often  contain  hard,  earthy  concretions,  called  phlebolit/t*. 

Surgical  Anatomy. — This  plexus  is  wounded  in  the  lateral  operation  of  lithotomy,  and  it  is 
through  it  that  septic  matter  finds  its  way  into  the  general  circulation  after  this  operation. 

The  dorsal  vein  of  the  penis  is  a  vessel  of  large  size  which  returns  the  blood 
from  the  body  of  that  organ.  At  first  it  consists  of  two  branches,  which  are 
contained  in  the  groove  on  the  dorsum  of  the  penis,  and  it  receives  veins  from  the 
glans.  the  corpus  spongiosum,  and  numerous  superficial  veins  ;  these  unite  near  the 
ro«it  of  the  penis  into  a  single  trunk,  which  passes  through  the  suspensory  ligament 
of  the  penis,  pierces  the  triangular  ligament  beneath  the  pubic  arch,  and  divides 
into  two  branches,  which  enter  the  prostatic  plexus. 

The  vaginal  plexus  surrounds  the  mucous  membrane,  being  especially  developed 
at  the  orifice  of  the  vagina ;  it  communicates  with  the  vesical  plexus  in  front,  and 
with  the  hiernorrhoidal  plexus  behind. 

The  uterine  plexus  is  situated  along  the  sides  and  superior  angles  of  the  uterus, 
between  the  layers  of  the  broad  ligament,  receiving  large  venous  canals  (the  uterine 
sinuses)  from  the  substance  of  the  uterus.  The  veins  composing  this  plexus 
anastomose  frequently  with  each  other  and  with  the  ovarian  veins.  They  are  not 
tortuous  like  the  arteries. 

The  Common  Iliac  Veins  are  formed  by  the  union  of  the  external  and  internal 
iliac  veins  in  front  of  the  sacro-iliac  articulation :  passing  obliquely  upward 
toward  the  right  side,  they  terminate  upon  the  intervertebral  substance  between 
the  fourth  and  fifth  lumbar  vertebrae,  where  the  veins  of  the  two  sides  unite  at  an 
acute  angle  to  form  the  inferior  vena  cava.  The  right  common  iliac  is  shorter 
than  the  left,  nearly  vertical  in  its  direction,  and  ascends  behind  and  then  to  the 
outer  side  of  its  corresponding  artery.  The  left  common  iliac,  longer  and  more 
oblique  in  its  coarse,  is  at  first  situated  on  the  inner  side  of  the  corresponding 
artery,  and  then  behind  the  right  common  iliac.  Each  common  iliac  receives  the 
ilio-lumbar,  and  sometimes  the  lateral  sacral,  veins.  The  left  receives,  in  addition, 
the  middle  sacral  vein.  Xo  valves  are  found  in  these  veins. 

The  middle  sacral  veins  accompany  the  corresponding  artery  along  the  front 
of  the  sacrum,  and  terminate  in  the  left  common  iliac  vein  ;  occasionally  in  the 
angle  of  junction  of  the  two  iliac  veins. 

Peculiarities. — The  left  common  iliac  vein,  instead  of  joining  with  the  right  in  its  usual 
position,  occasionally  ascends  on  the  left  side  of  the  aorta  as  high  as  the  kidney,  where,  after 
receiving  the  left  renal  vein,  it  crosses  over  the  aorta,  and  then  joins  with  the  right  vein  to  form 
the  vena  cava.  In  these  cases  the  two  common  iliacs  are  connected  by  a  small  communicating 
branch  at  the  spot  where  they  are  usually  united.1 

The  Inferior  Vena  Cava  returns  to  the  heart  the  blood  from  all  the  parts  below 
the  Diaphragm.  It  is  formed  by  the  junction  of  the  two  common  iliac  veins  on 
the  right  side  of  the  intervertebral  substance  between  the  fourth  and  fifth  lumbar 
vertebrae.  It  passes  upward  along  the  front  of  the  spine  on  the  right  side  of  the 
aorta,  and.  having  reached  the  under  surface  of  the  liver,  is  contained  in  a  groove 
on  its  posterior  surface.  It  then  perforates  the  central  tendon  of  the  Diaphragm, 
enters  the  pericardium,  where  it  is  covered  by  its  serous  layer,  and  terminates  in 
the  lower  and  back  part  of  the  right  auricle.  At  its  termination  in  the  auricle  it 
is  provided  with  a  valve,  the  Euxtaehian.  which  is  of  large  size  during  foetal  life. 

Eelations. — In  front,  from  below  upward,  with  the  mesentery,  right  spermatic 
artery,  transverse  portion  of  the  duodenum,  the  pancreas,  portal  vein,  and  the 

1  See  two  case?  which   have  been  described  by  Mr.  Walsham  in  the  St.  Bartholomew's   Hospital 
Reports,\o\s.  xvi.  and  xvii. 
43 


674  THE    VEINS. 

posterior  surface  of  the  liver,  which  partly  and  occasionally  completely  surrounds 
it ;  behind,  with  the  vertebral  column,  the  right  crus  of  the  Diaphragm,  the  right 
renal  and  lumbar  arteries,  right  semilunar  ganglion  ;  on  the  left  side,  with  the 
aorta. 

Tributaries. — It  receives  in  its  course  the  following  veins  : 

Lumbar.  Suprarenal. 

Right  Spermatic.  Phrenic. 

Renal.  Hepatic. 

Peculiarities. — In  Position. — This  vessel  is  sometimes  placed  on  the  left  side  of  the  aorta, 
as  high  as  the  left  renal  veins,  after  receiving  which  it  crosses  over  to  its  usual  position  on  the 
right  side ;  or  it  may  be  placed  altogether  on  the  left  side  of  the  aorta,  as  far  upward  as  its  ter- 
mination in  the  heart :  in  such  cases  the  abdominal  and  thoracic  viscera,  together  with  the  great 
vessels,  are  all  transposed. 

Point  of  Termination. — Occasionally  the  inferior  vena  cava  joins  the  right  azygos  vein, 
which  is  then  of  large  size.  In  such  cases  the  superior  cava  receives  the  whole  of  the  blood 
from  the  body  before  transmitting  it  to  the  right  auricle,  except  the  blood  from  the  hepatic  veins, 
which  passes  directly  into  the  right  auricle. 

The  lumbar  veins,  four  in  number  on  each  side,  collect  the  blood  by  dorsal 
tributaries  from  the  muscles  and  integument  of  the  loins  and  by  abdominal  tribu- 
taries from  the  walls  of  the  abdomen,  where  they  communicate  with  the  epigastric 
veins.  At  the  spine  they  receive  veins  from  the  spinal  plexuses,  and  then  pass 
forward,  round  the  sides  of  the  bodies  of  the  vertebrae  beneath  the  Psoas  magrms, 
and  terminate  at  the  back  part  of  the  inferior  cava.  The  left  lumbar  veins  are 
longer  than  the  right,  and  pass  behind  the  aorta.  The  lumbar  veins  are  connected 
together  by  a  longitudinal  vein  which  passes  in  front  of  the  transverse  processes  of  the 
lumbar  vertebrae,  and  is  called  the  ascending  lumbar.  It  forms  the  most  frequent 
origin  of  the  corresponding  vena  azygos,  and  serves  to  connect  the  common  iliac, 
ilio-lumbar,  lumbar,  and  azygos  veins  of  the  corresponding  side  of  the  body. 

The  spermatic  veins  emerge  from  the  back  of  the  testis,  and  receive  tributaries 
from  the  epididymis  ;  they  unite  and  form  a  convoluted  plexus  called  the  spermatic 
plexus  (plexus  pampiniformis),  which  forms  the  chief  mass  of  the  cord  :  the  vessels 
composing  this  plexus  are  very  numerous,  and  ascend  along  the  cord  in  front  of 
the  vas  deferens  ;  below  the  external  abdominal  ring  they  unite  to  form  three  or 
four  veins,  which  pass  along  the  spermatic  canal,  and,  entering  the  abdomen  through 
the  internal  abdominal  ring,  coalesce  to  form  two  veins,  which  ascend  on  the  Psoas 
muscle  behind  the  peritoneum,  lying  one  on  each  side  of  the  spermatic  artery,  and 
unite  to  form  a  single  vein,  which  opens  on  the  right  side  into  the  inferior  vena 
cava  at  an  acute  angle ;  on  the  left  side  into  the  left  renal  vein  at  a  right  angle. 
The  spermatic  veins  are  provided  with  valves.1  The  left  spermatic  vein  passes 
behind  the  sigmoid  flexure  of  the  colon,  and  is  thus  exposed  to  pressure  from  the 
contents  of  that  bowel. 

Surgical  Anatomy. — The  spermatic  yeins  are  very  frequently  varicose,  constituting  the 
disease  known  as  varicocele.  Though  it  is  quite  possible  that  the  originating  cause  of  this 
affection  may  be  a  congenital  abnormality  either  in  the  size  or  number  of  the  veins  of  the 
pampiniform  plexus,  still  it  must  be  admitted  that  there  are  many  anatomical  reasons  why  these 
veins  should  become  varicose — viz.  the  imperfect  support  afforded  to  them  by  the  loose  tissue  of 
the  scrotum ;  their  great  length  ;  their  vertical  course  ;  their  dependent  position  ;  their  plexiform 
arrangement  in  the  scrotum,  with  their  termination  in  one  small  vein  in  the  abdomen  ;  their  few 
and  imperfect  valves;  and  the  fact  that  they  may  be  subjected  to  pressure  in  their  passage 
through  the  abdominal  wall. 

The  ovarian  veins  are  analogous  to  the  spermatic  in  the  male ;  they  form  a 
plexus  near  the  ovary  and  in  the  broad  ligament  and  Fallopian  tube,  communi- 
cating with  the  uterine  plexus.  They  terminate  in  the  same  way  as  the  spermatic 
veins  in  the  male.  Valves  are  occasionally  found  in  these  veins.  These  vessels. 
like  the  uterine  veins,  become  much  enlarged  during  pregnancy. 

1  Rivington  has  pointed  out  that  a  valve  is  usually  found  at  the  orifices  of  both  the  right  and 
left  spermatic  veins.  When  no  valves  exist  at  the  opening  of  the  left  spermatic  vein  into  the  left 
renal  vein,  valves  are  generally  present  in  the  left  renal  vein  within  a  quarter  of  an  inch  from 
the  orifice  of  the  spermatic  vein  (Jouiiud  of  Anatomy  and  Physiology,  vol.  vii.  p.  163). 


THE   PORTAL    SYSTEM.  675 

The  renal  veins  are  of  large  size,  and  placed  in  front  of  the  renal  arteries.1 
The  left  is  longer  than  the  right,  and  passes  in  front  of  the  aorta,  just  below  the 
origin  of  the  superior  mesenteric  artery.  It  receives  the  left  spermatic,  the  left 
inferior  phrenic,  and.  generally,  the  left  suprarenal  veins.  It  opens  into  the  vena 
cava  a  little  higher  than  the  right. 

The  suprarenal  veins  terminate,  on  the  right  side,  in  the  vena  cava  ;  on  the 
left  side,  in  the  left  renal  or  phrenic  vein. 

The  phrenic  veins  follow  the  course  of  the  phrenic  arteries.  The  tu'o  superior, 
of  small  size,  accompany  the  phrenic  nerve  and  comes  nervi  phrenici  artery,  and 
join  the  internal  mammary.  The  two  inferior  phrenic  veins  follow  the  course  of 
the  phrenic  arteries,  and  terminate,  the  right  in  the  inferior  vena  cava.  the  left  in 
the  left  renal  vein. 

The  hepatic  veins  commence  in  the  substance  of  the  liver,  in  the  capillary 
terminations  of  the  portal  vein  and  hepatic  artery  :  these  tributaries,  gradually 
uniting,  usuallv  form  three  large  veins,  which  converge  toward  the  posterior 
surface  of  the  liver  and  open  into  the  inferior  vena  cava,  whilst  that  vessel  is 
situated  in  the  -groove  at  the  back  part  of  this  organ.  Of  these  three  veins,  one 
from  the  right,  and  another  from  the  left  lobe,  open  obliquely  into  the  inferior 
vena  cava.  that  from  the  middle  of  the  organ  and  lobulus  Spigelii  having  a  straight 
course.  The  hepatic  veins  run  singly,  and  are  in  direct  contact  with  the  hepatic 
tissue.  Thev  are  destitute  of  valves. 

»' 

The  Portal  System  of  Veins. 

The  portal  venous  system  is  composed  of  four  large  veins  which  collect  the 
venous  blood  from  the  viscera  of  digestion.  The  trunk  formed  by  their  union 
/  portcp)  enters  the  liver  and  ramifies  throughout  its  substance,  and  its 
branches,  again  emerging  from  that  organ  as  the  hepatic  veins,  terminate  in  the 
inferior  vena  cava.  The  branches  in  this  vein  are  in  all  cases  single  and  destitute 
of  valves. 

The  veins  forming  the  portal  system  are — the 

Superior  Mesenteric.  Inferior  Mesenteric. 

Splenic.  Gastric. 

The  superior  mesenteric  vein  returns  the  blood  from  the  small  intestines  and 
from  the  caecum  and  ascending  and  transverse  portions  of  the  colon,  correspond- 
ing with  the  distribution  of  the  branches  of  the  superior  mesenteric  artery.  The 
large  trunk  formed  by  the  union  of  these  branches  ascends  along  the  right  side 
and  in  front  of  the  corresponding  artery,  passes  in  front  of  the  transverse  por- 
tion of  the  duodenum,  and  unites,  behind  the  upper  border  of  the  pancreas,  with 
the  splenic  vein  to  form  the  vena  portse.  It  receives  the  right  gastro-epiploic  vein. 

The  splenic  vein  commences  by  five  or  six  large  branches  which  return  the 
blood  from  the  substance  of  the  spleen.  These,  uniting,  form  a  single  vessel,  which 
passes  from  left  to  right,  grooving  the  upper  and  back  part  of  the  pancreas  below 
the  artery,  and  terminates  at  its  greater  end  by  uniting  at  a  right  angle  with  the 
superior  mesenteric  to  form  the  vena  portte.  The  splenic  vein  is  of  large  size,  and 
not  tortuous  like  the  artery.  It  receives  the  vasa  brevia  from  the  left  extremity  of 
the  stomach,  the  left  gastro-epiploic  vein,  pancreatic  branches  from  the  pancreas, 
the  pancreatico-duodenal  vein,  and  the  inferior  mesenteric  vein. 

The  inferior  mesenteric  vein  returns  the  blood  from  the  rectum,  sigmoid  flexure, 
and  descending  colon,  corresponding  with  the  ramifications  of  the  branches  of 
the  inferior  mesenteric  artery.  Ascending  beneath  the  peritoneum  in  the  lumbar 
region,  it  passes  behind  the  transverse  portion  of  the  duodenum  and  pancreas  and 
terminates  in  the  splenic  vein.  Its  haemorrhoidal  branches  inosculate  with  those 

1  The  student  may  observe  that  all  veins  above  the  Diaphragm,  which  do  not  lie  on  the  same 
plane  as  the  arteries  which  they  accompany,  lie  in  front  of  them,  and  that  all  veins  below  the 
Diaphragm,  which  do  not  lie  on  the  same  plane  as  the  arteries  which  they  accompany,  lie  behind 
them,  except  the  renal  and  profunda  femoris  vein. 


676 


THE     VEINS. 


of  the  internal  iliac,  and  thus  establish  a  communication  between  the  portal  and 
the  general  venous  system.1 

The  gastric  veins  are  two  in  number :  one,  a  small  vein,  corresponds  to  the 
pyloric  branch  of  the  hepatic  artery  ;  the  other,  considerably  larger,  corresponds 
to  the  gastric  artery.  The  former  (pyloric,  Walsham)  runs  along  the  lesser  cur- 


FIG.  393.— Portal  vein  and  its  branches. 

NOTE.— In  this  diagram  the  right  gastro-epiploic  vein  opens  into  the  splenic  vein  ;  generally 
it  empties  itself  into  the  superior  mesenteric,  close  to  its  termination. 

vature  of  the  stomach  toward  the  pyloric  end,  receives  branches  from  the  pylorus 
and  duodenum,  and  ends  in  the  vena  portse.  The  latter  (coronary,  Walsham) 
begins  near  the  pylorus,  runs  along  the  lesser  curvature  of  the  stomach  toward  the 

1  Besides  this  anastomosis  between  the  portal  vein  and  the  branches  of  the  vena  caya,  other 
anastomoses  between  the  portal  and  systemic  veins  are  formed  by  the  communication  between  the 
gastric  veins  and  the  cesophageal  veins,  which  empty  themselves  into  the  vena  azygos  minor  ;  between 
the  left  renal  vein  and  the  veins  of  the  intestines,  especially  of  the  colon  and  duodenum ;  between  the 
veins  of  the  round  ligament  of  the  liver  and  the  portal  veins ;  and  between  the  superficial  branches 
of  the  portal  veins  of  the  liver  and  the  phrenic  veins,  as  pointed  out  by  Mr.  Kiernan.  (See  Physio- 
logical Anatomy,  by  Todd  and  Bowman,  1859,  vol.  ii.  p.  348.) 


THE    CARDIAC    I'AV.V.v.  677 

oesophageal  opening,  and  then  curves  downward  and  backward  between  the  folds 
of  the  lesser  omentum,  to  end  in  the  vena  port*. 

The  Portal  Vein  is  formed  by  the  junction  of  the  superior  mesenteric  and 
splenic  veins,  their  union  taking  place  in  front  of  the  vena  cava  and  behind  the 
upper  border  of  the  great  end  of  the  pancreas.  Passing  upward  through  the  right 
border  of  the  lesser  omentum  to  the  under  surface  of  the  liver,  it  enters  the  trans- 
verse fissure,  where  it  is  somewhat  enlarged,  forming  the  sinu*  of  the  portal  vein, 
and  divides  into  two  branches  which  accompany  the  ramifications  of  the  hepatic 
artery  and  hepatic  duct  throughout  the  substance  of  the  liver.  Of  these  two 
branches,  the  right  is  the  larger,  but  the  shorter,  of  the  two.  The  portal  vein  is 
about  three  or  four  inches  in  length,  and.  whilst  contained  in  the  lesser  omentum. 
lies  behind  and  between  the  hepatic  duct  and  artery,  the  former  being  to  the  right, 
the  latter  to  the  left.  These  structures  are  accompanied  by  filaments  of  the  hepatic 
plexus  of  nerves  and  numerous  lymphatics,  surrounded  by  a  quantity  of  loose 
areolar  tissue  (•-•<ij}*u?e  of  G-fasoti),  and  placed  between  the  layers  of  the  lesser 
omentum.  The  vena  port*  receives  the  gastric  and  cystic  veins  :  the  latter  vein 
sometimes  terminates  in  the  right  branch  of  the  vena  port*.  Within  the  liver  the 
portal  vein  receives  the  blood  from  the  branches  of  the  hepatic  artery. 

THE  CARDIAC  VEINS. 
The  veins  which  return  the  blood  from  the  substance  of  the  heart  are — the 

Anterior  Cardiac  Vein.  Right  Cardiac  Veins. 

Posterior  Cardiac  Vein.  Right  or  Small  Coronary  Sinus. 

Left  Cardiac  Veins.  Left  or  Great  Coronary  Sinus. 

Ven*  Thebesii. 

The  Anterior  Cardiac  Vein  (sometimes  called  Great  Cardiac  l^ein)  is  a  vessel 
of  considerable  size  which  commences  at  the  apex  of  the  heart  and  ascends  along 
the  anterior  interventricular  groove  to  the  base  of  the  ventricles.  It  then  curves 
to  the  left  side,  around  the  auriculo-ventricular  groove,  between  the  left  auricle 
and  ventricle,  to  the  back  part  of  the  heart,  and  opens  into  the  great  coronary 
sinus,  its  aperture  being  guarded  by  two  valves.  It  receives,  in  its  course,  tribu- 
taries from  both  ventricles,  but  especially  the  left,  and  also  from  the  left  auricle  ; 
one  of  these,  ascending  along  the  thick  margin  of  the  left  ventricle,  is  of  consider- 
able size.  The  vessels  joining  it  are  provided  with  valves. 

The  Middle  Cardiac  Vein  commences  by  small  tributaries  at  the  apex  of  the 
heart,  communicating  with  those  of  the  preceding.  It  ascends  along  the  posterior 
interveutricular  groove  to  the  base  of  the  heart,  and  terminates  in  the  great  coro- 
nary sinus,  its  orifice  being  guarded  by  a  valve.  It  receives  the  veins  from  the 
posterior  surface  of  both  ventricles. 

The  Left  or  Posterior  Cardiac  Veins  are  three  or  four  small  vessels  which  col- 
lect the  blood  from  the  posterior  surface  of  the  left  ventricle,  and  open  into  the 
lower  border  of  the  great  coronary  sinus. 

The  Bight  or  Anterior  Cardiac  Veins  are  three  or  four  small  vessels  which  col- 
lect the  blood  from  the  anterior  surface  of  the  right  ventricle.     One  of  these  (the 
••f  G<il>  n}.  larger    than  the   rest,  runs  along  the  right   border  of  the  heart. 
They  open  separately  into  the  lower  part  of  the  right  auricle. 

The  Right  or  Small  Coronary  Sinus  runs  along  the  groove  between  the  right 
auricle  and  ventricle,  to  open  into  the  right  extremity  of  the  great  coronary  sinus. 
It  receives  blood  from  the  back  part  of  the  right  auricle  and  ventricle. 

The  Left  or  Great  Coronary  Sinus  is  that  portion  of  the  anterior  cardiac  vein 
which  is  situated  in  the  posterior  part  of  the  left  auriculo-ventricular  groove.  It 
is  about  an  inch  in  length,  presents  a  considerable  dilatation,  and  is  covered  by 
the  muscular  fibres  of  the  left  auricle.  It  receives  the  veins  enumerated  above, 
and  an  oblique  vein  from  the  back  part  of  the  left  auricle,  the  remnant  of  the 
obliterated  left  innominate  trunk  of  the  foetus,  described  by  Mr.  Marshall.  The 


678  THE    VEINS. 

great  coronary  sinus  terminates  in  the  right  auricle  between  the  inferior  vena  cava 
and  the  auriculo-ventricular  aperture,  its  orifice  being  guarded  by  a  semilunar 
fold  of  the  lining  membrane  of  the  heart,  the  coronary  valve.  All  the  veins  join- 
ing this  vessel,  excepting  the  oblique  vein  above  mentioned,  are  provided  •with 
valves. 

The  Venae  Thebesii  are  numerous  minute  veins,  which  return  the  blood 
directly  from  the  muscular  substance,  without  entering  the  venous  current.  They 
open  by  minute  orifices  {foramina  Thebesii)  on  the  inner  surface  of  the  right 
auricle.  Similarly  minute  veins  are  said  to  open  into  the  left  auricle  and  both 
ventricles. 


THE    LYMPHATICS. 


THE  Lymphatics  have  derived  their  name  from  the  appearance  of  the  fluid  con- 
tained in  their  interior  (lympha,  water).  They  are  also  called  absorbents, 
from  the  property  they  possess  of  absorbing  certain  materials  from  the  tissues  and 
conveying  them  into  the  circulation. 

The  lymphatic  system  includes  not  only  the  lymphatic  vessels  and  the  glands 
through  which  they  pass,  but  also  the  lacteal  or  chyliferous  vessels.  The  lacteals 
are  the  lymphatic  vessels  of  the  small  intestine,  and  differ  in  no  respect  from  the 
lymphatics  generally,  excepting  that  they  contain  a  milk-white  fluid,  the  chyle, 
during  the  process  of  digestion,  and  convey  it  into  the  blood  through  the  thoracic 
duct. 

The  lymphatics  are  exceedingly  delicate  vessels,  the  coats  of  which  are  so 
transparent  that  the  fluid  they  contain  is  readily  seen  through  them.  They  retain 
a  nearly  uniform  size,  being  interrupted  at  intervals  by  constrictions,  which  give 
them  a  knotted  or  beaded  appearance.  These  constrictions  are  due  to  the  pres- 
ence of  valves  in  their  interior.  Lymphatics  have  been  found  in  nearly  every 
texture  and  organ  of  the  body  which  contain  blood-vessels.  Such  non-vascular 
structures  as  cartilage,  the  nails,  cuticle,  and  hair  have  none,  but  with  these 
exceptions  it  is  probable  that  eventually  all  parts  will  be  found  to  be  permeated 
by  these  vessels. 

The  lymphatics  are  arranged  into  a  superficial  and  deep  set.  The  superficial 
lymphatics,  on  the  surface  of  the  body,  are  placed  immediately  beneath  the  integ- 
ument, accompanying  the  superficial  veins  ;  they  join  the  deep  lymphatics  in  cer- 
tain situations  by  perforating  the  deep  fascia.  In  the  interior  of  the  body  they 
lie  in  the  submucous  areolar  tissue  throughout  the  whole  length  of  the  gastro- 
pulmonary  and  genito-urinary  tracts,  and  in  the  subserous  tissue  in  the  cranial, 
thoracic,  and  abdominal  cavities.  The  method  of  their  origin  has  been  described 
along  with  the  other  details  of  their  minute  anatomy  (page  86).  Here  it  will  be 
sufficient  to  say  that  a  plexiform  network  of  minute  lymphatics  may  be  found 
interspersed  among  the  proper  elements  and  blood-vessels  of  the  several  tissues, 
the  vessels  composing  which,  as  well  as  the  meshes  between  them,  are  much  larger 
than  those  of  the  capillary  plexus.  From  these  networks  small  vessels  emerge, 
which  pass  either  to  a  neighboring  gland  or  to  join  some  larger  lymphatic  trunk. 
The  deep  lymphatics,  fewer  in  number  and  larger  than  the  superficial,  accompany 
the  deep  blood-vessels.  Their  mode  of  origin  is  probably  similar  to  that  of  the 
superficial  vessels.  The  lymphatics  of  any  part  or  organ  exceed  the  veins  in 
number,  but  in  size  they  are  much  smaller.  Their  anastomoses  also,  especially 
those  of  the  large  trunks,  are  more  frequent,  and  are  effected  by  vessels  equal  in 
diameter  to  those  which  they  connect,  the  continuous  trunks  retaining  the  same 
diameter. 

The  lymphatic  or  absorbent  glands,  named  also  conglobate  glands,  are  small, 
solid,  glandular  bodies  situated  in  the  course  of  the  lymphatic  and  lacteal  ves- 
sels. In  size  they  vary  from  a  hemp-seed  to  an  almond,  and  their  color,  on  sec- 
tion, is  of  a  pinkish-gray  tint,  excepting  the  bronchial  glands,  which  in  the  adult 
are  mottled  with  black.  Each  gland  has  a  layer  or  capsule  of  cellular  tissue 
investing  it,  from  which  prolongations  dip  into  its  substance,  forming  partitions. 
JThe  lymphatic  and  lacteal  vessels  pass  through  these  bodies  in  their  passage  to 
the  thoracic  and  lymphatic  ducts.  A  lymphatic  or  lacteal  vessel,  previous  to 

679 


680 


THE   LYMPHATICS 


entering  a  gland,  divides  into  several  small  branches,  which  are  named  afferent 
vessels.     As  they  enter  their  external  coat  becomes  continuous  with  the  capsule  of 

the  gland,  and  the  vessels,  much 
thinned,  and  consisting  only  of 
their  internal  or  endothelial  coat, 
pass  into  the  gland,  and  branch 
out  upon  and  in  the  tissue  of  the 
capsule,  these  branches  opening 
into  the  lymph-sinuses  of  the 
gland.  From  these  sinuses  fine 
branches  proceed  to  form  a  plex- 
us, the  vessels  of  which  unite  to 
form  a  single  efferent  vessel,  which, 
on  emerging  from  the  gland,  is 
again  invested  with  an  external 
coat.  (Further  details  on  the  mi- 
^  nute  anatomy  of  the  lymphatic  ves- 

sels and  glands  will  be  found  in  the 
chapter  on  General  Anatomy.) 

THE  THORACIC  DUCT. 

The  thoracic  duct  (Fig.  394) 
conveys  the  great  mass  of  lymph 
and  chyle  into  the  blood.  It  is  the 
common  trunk  of  all  the  lymphatic 
vessels  of  the  body,  excepting  those 
of  the  right  side  of  the  head,  neck, 
and  thorax,  and  right  upper  ex- 
tremity, the  right  lung,  right  side 
of  the  heart,  and  the  convex  sur- 
face of  the  liver.  It  varies  in 
length  from  fifteen  to  eighteen 
inches  in  the  adult,  and  extends 
from  the  second  lumbar  vertebra 
to  the  root  of  the  neck.  It  com- 
mences in  the  abdomen  by  a  trian- 
gular dilatation,  the  receptaculum 
chyli  (reservoir  or  cistern  of  Pec- 
quet),  which  is  situated  upon  the 
front  of  the  body  of  the  second 
lumbar  vertebra,  to  the  right  side 
and  behind  the  aorta,  by  the  side 
of  the  right  crus  of  the  Diaphragm. 
It  ascends  into  the  thorax  through 
the  aortic  opening  in  the  Dia- 
phragm, lying  to  the  right  of  the 
aorta,  and  is  placed  in  the  pos- 
terior mediastinum  in  front  of  the 
vertebral  column,  lying  between 
the  aorta  and  vena  azygos  major. 
Opposite  the  fourth  dorsal  ver- 
tebra it  inclines  toward  the  left 
side,  and  ascends  behind  the  arch  of  the  aorta  on  the  left  side  of  the 
oesophagus,  and  behind  the  first  portion  of  the  left  subclavian  artery,  to  the 
upper  orifice  of  the  thorax.  Opposite  the  seventh  cervical  vertebra  it  turns 
outward  and  then  curves  downward  over  the  subclavian  artery  and  in  front  of 
the  Scalenus  anticus  muscle,  so  as  to  form  an  arch,  and  terminates  in  the  left 


FIG.  394.— The  thoracic  and  right  lymphatic  duct. 


OF    THE   HEAD,  FACE,  AND    XECK.  681 

subclavian  vein  at  its  angle  of  junction  with  the  left  internal  jugular  vein.  The 
thoracic  duct,  at  its  commencement,  is  about  equal  in  size  to  the  diameter  of  a 
goosequill,  diminishes  considerably  in  its  calibre  in  the  middle  of  the  thorax,  and 
is  again  dilated  just  before  its~  termination.  It  is  generally  flexuous  in  its  course, 
and  constricted  at  intervals  so  as  to  present  a  varicose  appearance.  The  thoracic 
duct  not  unfrequently  divides  in  the  middle  of  its  course  into  two  branches  of 
unequal  size,  which  soon  reunite,  or  into  several  branches,  which  form  a  plexiform 
interlacement.  It  occasionally  divides,  at  its  upper  part,  into  two  branches,  of 
which  the  one  on  the  left  side  terminates  in  the  usual  manner,  while  that  on  the 
right  opens  into  the  right  subclavian  vein,  in  connection  Avith  the  right  lymphatic 
duct.  The  thoracic  duct  has  numerous  valves  throughout  its  whole  course,  but 
they  are  more  numerous  in  the  upper  than  in  the  lower  part :  at  its  termination  it 
is  provided  with  a  pair  of  valves,  the  free  borders  of  which  are  turned  toward  the 
vein,  so  as  to  prevent  the  passage  of  venous  blood  into  the  duct. 

Tributaries. — The  thoracic  duct,  at  its  commencement,  receives  four  or  five 
large  trunks  from  the  abdominal  lymphatic  glands,  and  also  the  trunk  of  the 
lacteal  vessels.  Within  the  thorax  it  is  joined  by  the  lymphatic  vessels  from  the 
left  half  of  the  wall  of  the  thoracic  cavity,  the  lymphatics  from  the  sternal  and 
intercostal  glands,  those  of  the  left  lung,  left  side  of  the  heart,  trachea,  and 
oesophagus;  and,  just  before  its  termination,  it  receives  the  lymphatics  of  the  left 
side  of  the  head  and  neck  and  left  upper  extremity. 

Structure  (Fig.  61). — The  thoracic  duct  is  composed  of  three  coats,  which 
differ  in  some  respects  from  those  of  the  lymphatic  vessels.  The  internal  coat 
consists  of  a  single  layer  of  flattened  lanceolate-shaped  endothelial  cells  with 
serrated  borders ;  of  a  subendothelial  layer,  similar  to  that  found  in  the  arteries ; 
and  an  elastic  fibrous  coat,  the  fibres  of  which  run  in  a  longitudinal  direction. 
The  middle  coat  consists  of  a  longitudinal  layer  of  white  connective  tissue  with 
elastic  fibres,  external  to  which  are  several  laminae  of  muscular  tissue,  the  fibres  of 
which  are  for  the  most  part  disposed  transversely,  but  some  are  oblique  or 
longitudinal  and  intermixed  with  elastic  fibres.  The  external  coat  is  composed  of 
areolar  tissue,  with  elastic  fibres  and  isolated  fasciculi  of  muscular  fibres. 

The  Right  Lymphatic  Duct  is  a  short  trunk,  about  half  an  inch  in  length  and 
a  line  or  a  line  and  a  half  in  diameter.  It  terminates  in  the  right  subclavian  vein 
at  its  angle  of  junction  with  the  right  internal  jugular  vein.  Its  orifice  is  guarded 
by  two  semilunar  valves,  which  prevent  the  passage  of  venous  blood  into  the  duct. 

Tributaries. — It  receives  the  lymph  from  the  right  side  of  the  head  and  neck, 
the  right  upper  extremity,  the  right  side  of  the  thorax,  the  right  lung  and  right 
side  of  the  heart,  and  from  part  of  the  convex  surface  of  the  liver. 

LYMPHATICS  OF  THE  HEAD,  FACE,  AND  NECK. 

The  Lymphatic  Glands  of  the  Head  (Fig.  395)  are  of  small  size,  few  in  number, 
and  confined  to  its  posterior  region.  They  are  the  occipital  and  posterior 
auricular.  The  occipital  set  are  placed  at  the  back  of  the  head  along  the  attach- 
ment of  the  Occipito-frontalis  muscle.  The  posterior  auricular  set  are  placed  near 
the  upper  end  of  the  Sterno^mastoid  muscle.  Both  these  sets  of  glands  are 
affected  in  cutaneous  eruptions  and  other  diseases  of  the  scalp.  In  the  face  the 
superficial  lymphatic  glands  are  more  numerous  :  they  are  the  parotid,  some  of 
which  are  superficial,  and  others  deeply  placed  in  the  substance  of  the  parotid 
gland ;  the  zygomatic,  situated  under  the  zygoma ;  the  buccal,  on  the  surface  of  the 
Buccinator  muscle  ;  and  the  internal  maxillary,  the  largest,  beneath  the  ramus  of 
the  lower  jaw. 

•  The  lymphatic  vessels  of  the  scalp  are  divided  into  an  anterior  and  a  posterior 
set,  which  follow  the  course  of  the  temporal  and  occipital  vessels.  The  temporal 
set  accompany  the  temporal  artery  in  front  of  the  ear,  to  the  parotid  lymphatic 
glands,  from  which  they  proceed  to  the  lymphatic  glands  of  the  neck.  The 
occipital  set  follow  the  course  of  the  occipital  artery,  descend  to  the  occipital 


682 


THE   LYMPHATICS 


and  posterior  auricular  lymphatic  glands,  and  from  thence  join  the  cervical 
glands. 

The  Lymphatic  Vessels  of  the  Face  are  divided  into  two  sets,  superficial  and 
deep. 

The  superficial  lymphatic  vessels  of  the  face  are  more  numerous  than  those  of 
the  head,  and  commence  over  its  entire  surface.  Those  from  the  frontal  region 
accompany  the  frontal  vessels ;  they  then  pass  obliquely  across  the  face,  running 


FIG.  395.— The  superficial  lymphatics  and  glands  of  the  head,  face,  and  neck. 

with  the  facial  vein,  pass  through  the  buccal  glands  on  the  surface  of  the  Bucci- 
nator muscle,  and  join  the  submaxillary  lymphatic  glands.  The  latter  receive  the 
lymphatic  vessels  from  the  lips,  and  are  often  found  enlarged  in  cases  of  malignant 
disease  of  those  parts. 

The  deep  lymphatic  vessels  of  the  face  are  derived  from  the  pituitary  membrane 
of  the  nose,  the  mucous  membrane  of  the  mouth  and  pharynx,  and  the  contents 
of  the  temporal  and  orbital  fossae  ;  they  accompany  the  branches  of  the  internal 
maxillary  artery,  and  terminate  in  the  internal  maxillary  and  cervical  lymphatic 
glands. 

The  lymphatic  vessels  of  the  cranium  consist  of  tAvo  sets,  the  meningeal  and 
cerebral.  The  meningeal  lymphatics  accompany  the  meningeal  vessels,  escape 
through  foramina  at  the  base  of  the  skull,  and  join  the  deep  cervical  lymphatic 
glands.  The  cerebral  lymphatics  are  described  by  Eshmann  as  being  situated 
between  the  arachnoid  and  pia  mater,  as  well  as  in  the  choroid  plexuses  of  the 


OF    THE 


683 


lateral  ventricles  ;  they  accompany  the  trunks  of  the  carotid  and  vertebral  arteries, 
and  probably  pass  through  foramina  at  the  base  of  the  skull  to  terminate  in  the 
deep  cervical  glands.  They  have  not  at  present  been  demonstrated  in  the  dura 
mater  or  in  the  substance  of  the  brain. 

The  Lymphatic  Glands  of  the  Neck  are  divided  into  two  sets,  superficial  and 
deep. 

The  superficial  cervical  glands  may  be  arranged  in  three  sets:  (1)  The 
axillary,  ten  to  fifteen  in  number,  situated  beneath  the  body  of  the  lower 


FIG.  396.— The  deep  lymphatics  and  glands  of  the  neck  and  thorax. 

jaw  in  the  submaxillary  triangle ;  (2)  suprahyoid '.  situated  in  the  middle  line  of  the 
neck,  between  the  anterior  bellies  of  the  two  digastric  muscles ;  and  (3)  cervical. 
placed  in  the  course  of  the  external  jugular  rein  between  the  Platysma  and  deep 
fascia.  They  are  most  numerous  at  the  root  of  the  neck,  in  the  triangular 
interval  between  the  clavicle,  the  Sterno-mastoid,  and  the  Trapezius,  where  they 
are  continuous  with  the  axillary  glands.  A  few  small  glands  are  also  found  on 
the  front  and  sides  of  the  larynx. 

The  deep  cervical  glands  (Fi'g.  396)  are  numerous  and  of  large  size ;  they  form 
a  chain  along  the  sheath  of  the  carotid  artery  and  internal  jugular  vein,  lying  by 
the  side  of  the  pharynx,  oesophagus,  and  trachea,  and  extending  from  the  base  of 
the  skull  to  the  thorax,  where  they  communicate  with  the  lymphatic  glands  in  that 
cavity.  They  are  subdivided  into  two  sets :  an  upper,  ten  to  twenty  in  number, 


684  THE   LYMPHATICS 

situated  about  the  bifurcation  of  the  common  carotid  and  along  the  upper  part 
of  the  internal  jugular  vein  ;  and  a  loiver,  ten  to  fifteen  in  number,  clustered  around 
the  lower  part  of  the  internal  jugular  vein,  and  extending  outward  into  the  supra- 
clavicular  fossa,  where  they  are  continuous  with  the  axillary  glands.  Internally, 
this  set  is  continuous  with  the  mediastinal  glands. 

The  superficial  and  deep  cervical  lymphatic  vessels  are  a  continuation  of  those 
already  described  on  the  cranium  and  face.  After  traversing  the  glands  in  those 
regions,  they  pass  through  the  chain  of  glands  which  lie  along  the  sheath  of  the 
carotid  vessels,  being  joined  by  the  lymphatics  from  the  pharynx,  oesophagus, 
larynx,  trachea,  and  thyroid  gland.  At  the  lower  part  of  the  neck,  after  receiving 
some  lymphatics  from  the  thorax,  they  unite  into  a  single  trunk,  which  terminates, 
on  the  left  side,  in  the  thoracic  duct;  on  the  right  side,  in  the  right  lymphatic 
duct. 

Surgical  Anatomy. — The  cervical  glands  tare  very  frequently  the  seat  of  tuberculous 
trouble.  This  condition  is  most  usually  set  up  by  some  lesion  in  those  parts  from  which  they 
receive  their  lymph.  This  excites  some  inflammation,  which  subsequently  takes  on  a  tuberculous 
character.  It  is  very  desirable,  therefore,  for  the  surgeon,  in  dealing  with  these  cases,  to  possess 
a  knowledge  of  the  relation  of  the  respective  groups  of  glands  to  the  periphery.  The  following 
table  is  extracted  from  Mr.  Treves's  work  on  Scrofula  audits  Gland  Diseases : 

Scalp. — Posterior  part  =  suboccipital  and  mastoid  glands.  Frontal  and  parietal  portions  = 
parotid  glands. 

Lymphatic  vessels  from  the  scalp  also  enter  the  superficial  cervical  set  of  glands. 

Skin  of  face  and  neck  =  submaxillary,  parotid,  and  superficial  cervical  glands. 

External  ear  =  superficial  cervical  glands. 

Lower  lip  =  submaxillary  and  suprahyoid  glands. 

Buccal  cavity  =  submaxillary  and  upper  set  of  deep  cervical  glands. 

Gums  of  lower  jaw  =  submaxillary  glands. 

Tongue. — Anterior  portion  =  suprahyoid  and  submaxillary  glands.  Posterior  portion  = 
upper  set  of  deep  cervical  glands. 

Tonsils  and  palate  =  upper  set  of  deep  cervical  glands. 

Pharynx. — Upper  part  =  parotid  and  retro-pharyngeal  glands.  Lower  part  =  upper  set  of 
deep  cervical  glands. 

Larynx,  orbit,  and  roof  of  mouth  =  upper  set  of  deep  cervical  glands. 

Nasal  fossa?  =  retro-pharyngeal  glands,  upper  set  of  deep  cervical  glands.  Some  lymphatic 
vessels  from  posterior  part  of  tbe  fossae  enter  tbe  parotid  glands. 

LYMPHATICS  OF  THE  UPPER  EXTREMITY. 

The  Lymphatic  Glands  of  the  Upper  Extremity  (Fig.  397)  are  divided  into  two 
sets,  superficial  and  deep. 

The  superficial  lymphatic  glands  are  few  and  of  small  size.  There  are  occa- 
sionally two  or  three  in  front  of  the  elbow,  and  one  or  two  above  the  internal 
condyle  of  the  hurnerus,  near  the  basilic  vein. 

The  deep  lymphatic  glands  are  few  in  number,  and  are  subdivided  into 
those  in  the  forearm,  the  arm,  and  the  axilla.  In  the  forearm  a  few  small 
ones  are  occasionally  found  in  the  course  of  the  radial  and  ulnar  vessels.  In  the 
arm  there  is  a  chain  of  small  glands  along  the  inner  side  of  the  brachial  artery. 
One,  sometimes  two,  fairly  constant  glands  are  situated  a  little  above  and  in  front 
of  the  inner  condyle  of  the  humerus.  In  the  axilla  they  are  of  large'  size,  and 
usually  ten  or  twelve  in  number.  A  chain  of  these  glands  surrounds  the  axillary 
vessels,  imbedded  in  a  quantity  of  loose  areolar  tissue ;  they  receive  the  lymphatic 
vessels  from  the  arm  ;  others  are  dispersed  in  the  areolar  tissue  of  the  axilla ;  the 
remainder  are  arranged  in  two  series,  a  small  chain  running  along  the  lower 
border  of  the  Pectoralis  major,  receiving  the  lymphatics  from  the  front  of  the 
chest  and  mamma  ;  and  others  are  placed  along  the  lower  margin  of  the  posterior 
wall  of  the  axilla,  which  receive  the  lymphatics  from  the  integument  of  the  back. 
Two  or  three  subclavian  lymphatic  glands  are  placed  immediately  beneath  the 
clavicle;  it  is  through  these  that  the  axillary  and  deep  cervical  glands  communi- 
cate with  each  other. 

Surgical  Anatomy. — In  malignant  diseases,  tumors,  or  other  affections  implicating  tbe 
upper  part  of  the  back  and  shoulder,  the  front  of  the  chest  and  mamma,  the  upper  part  of  tbe 


OF    THE    UPPER    EXTREMITY. 


685 


front  and  side  of  the  abdomen,  or  the  hand,  forearm,  and  arm,  the  axillary  glands  are  liable  to 
be  found  enlarged. 

The  lymphatic  vessels  of  the  upper  extremity  are  divided  into  two  sets,  super- 
ficial and  deep. 

The  superficial  lymphatic  vessels  of  the  upper  extremity  commence  on  the  fin- 
gers, two  vessels  running  along  either  side  of  each  finger,  one  on  the  palmar  and 
the  other  on  the  dorsal  surface.  Those  on  the  palmar  surface  form  an  arch  in  the 


Axillary  glands. 


FIG.  397.— The  superficial  lymphatics  and  glands  of  the  upper  extremity. 

palm  of  the  hand,  from  which  are  derived  two  sets  of  vessels,  which  pass  up  the 
forearm,  taking  the  course  of  the  subcutaneous  veins.  The  lymphatics  from  the 
dorsal  surface  of  the  fingers  form  a  plexus  on  the  back  of  the  hand,  and,  winding 
around  the  inner  and  outer  borders  of  the  forearm,  unite  with  those  in  front.  Those 
from  the  inner  border  of  the  hand  accompany  the  ulnar  veins  along  the  inner  side 
of  the  forearm  to  the  bend  of  the  elbow,  where  they  are  joined  by  some  lymphatics 
from  the  outer  side  of  the  forearm  :  they  then  follow  the  course  of  the  basilic  vein, 
communicate  with  the  glands  immediately  above  the  elbow,  and  terminate  in  the 
axillary  glands,  joining  with  the  deep  lymphatics.  The  superficial  lymphatics  from 


686  THE   LYMPHATICS 

the  outer  and  back  part  of  the  hand  accompany  the  radial  veins  to  the  bend  of  the 
elbow.  They  are  less  numerous  than  the  preceding.  At  the  bend  of  the  elbow 
the  greater  number  join  the  basilic  group  ;  the  rest  ascend  with  the  cephalic  vein 
on  the  outer  side  of  the  arm,  some  crossing  the  upper  part  of  the  Biceps  obliquely, 
to  terminate  in  the  axillary  glands,  whilst  one  or  two  accompany  the  cephalic  vein 
in  the  cellular  interval  between  the  Pectoralis  major  and  Deltoid,  and  enter  the 
subclavian  lymphatic  glands. 

The  deep  lymphatic  vessels  of  the  upper  extremity  accompany  the  deep  blood- 
vessels. In  the  forearm  they  consist  of  four  sets,  corresponding  with  the  radial, 
ulnar,  and  interosseous  arteries  ;  they  pass  through  the  glands  occasionally  found 
in  the  course  of  those  vessels,  and  communicate  at  intervals  with  the  superficial 
lymphatics.  In  their  course  upward  some  of  them  pass  through  the  glands  which 
lie  upon  the  brachial  artery ;  they  then  enter  the  axillary  and  subclavian  glands, 
and  at  the  root  of  the  neck  terminate  on  the  left  side  in  the  thoracic  duct,  and  on 
the  right  side  in  the  right  lymphatic  duct. 

LYMPHATICS  OF  THE  LOWER  EXTREMITY. 

The  Lymphatic  Glands  of  the  Lower  Extremity  are  divided  into  two  sets,  super- 
ficial and  deep.  The  superficial  are  confined  to  the  inguinal  region,  forming  the 
superficial  inguinal  lymphatic  glands. 

The  superficial  inguinal  lymphatic  glands,  placed  immediately  beneath  the 
integument,  are  of  large  size,  and  vary  from  eight  to  ten  in  number.  They  are 
divisible  into  two  groups  :  an  upper  oblique  set,  disposed  irregularly  along  Pou- 
part's  ligament,  which  receive  the  lymphatic  vessels  from  the  integument  of  the 
scrotum,  penis,  parietes  of  the  abdomen,  perineal  and  gluteal  regions,  and  the 
mucous  membrane  of  the  urethra ;  and  an  inferior  vertical  set,  which  surround  the 
saphenous  opening  in  the  fascia  lata,  a  few  being  sometimes  continued  along  the 
saphenous  vein  to  a  variable  extent.  This  latter  group  receive  the  superficial 
lymphatic  vessels  from  the  lower  extremity. 

Surgical  Anatomy. — These  glands  frequently  become  enlarged  in  diseases  implicating  the 
parts  from  which  their  lymphatics  originate.  Thus  in  malignant  or  syphilitic  affections  of  the 
prepuce  and  penis,  or  of  the  labia  majora  in  the  female,  in  cancer  scroti,  in  abscess  in  the  peri- 
nseum,  or  in  any  other  diseases  affecting  the  integument  and  superficial  structures  in  those  parts, 
or  the  subumbijical  part  of  the  abdominal  wall  or  the  gluteal  region,  the  upper  chain  of  glands 
is  almost  invariably  enlarged,  the  lower  chain  being  implicated  in  diseases  affecting  the  lower 
limb. 

The  deep  lymphatic  glands  are  the  anterior  tibial,  popliteal,  deep  inguinal, 
gluteal,  and  ischiatic. 

The  anterior  tibial  gland  is  not  constant  in  its  existence.  It  is  gener- 
ally found  by  the  side  of  the  anterior  tibial  artery,  upon  the  interosseous  mem- 
brane at  the  upper  part  of  the  leg.  Occasionally,  two  glands  are  found  in 
this  situation. 

The  popliteal  glands,  four  or  five  in  number,  are  of  small  size ;  they  surround 
the  popliteal  vessels,  imbedded  in  the  cellular  tissue  and  fat  of  the  popliteal  space. 

The  deep  inguinal  glands  are  placed  beneath  the  deep  fascia  around  the  femoral 
artery  and  vein.  They  are  of  small  size,  and  communicate  with  the  superficial 
inguinal  glands  through  the  saphenous  opening. 

The  gluteal  and  ischiatic  glands  are  placed,  the  former  above,  the  latter  below, 
the  Pyriformis  muscle,  resting  on  their  corresponding  vessels  as  they  pass  through 
the  great  sacro-sciatic  foramen. 

The  Lymphatic  Vessels  of  the  Lower  Extremity,  like  the  veins,  may  be  divided 
into  two  sets,  superficial  and  deep. 

The  superficial  lymphatic  vessels  are  placed  beneath  the  integument  in  the 
superficial  fascia,  and  are  divisible  into  two  groups :  an  internal  group,  which 
follow  the  course  of  the  internal  saphenous  vein ;  and  an  external  group,  which 
accompany  the  external  saphenous.  The  internal  group,  the  larger,  commence  on 
the  inner  side  and  dorsum  of  the  foot ;  they  pass,  some  in  front  and  some  behind 


OF    THE    LOWER    EXTREMITY. 


687 


Superficial 
inguinal 
glands. 


the  inner  ankle,  run  up  the  leg  with 
the  internal  saphenous  vein,  pass  with  it 
behind  the  inner  condyle  of  the  femur, 
and  accompany  it  to  the  groin,  where 
they  terminate  in  the  group  of  super- 
ficial inguinal  lymphatic  glands  which 
surround  the  saphenous  opening.  Some 
of  the  efferent  vessels  from  these  glands 
pierce  the  cribriform  fascia  and  sheath 
of  the  femoral  vessels,  and  terminate  in 
a  lymphatic  gland  contained  in  the 
femoral  canal,  thus  establishing  a  com- 
munication between  the  lymphatics  of 
the  lower  extremity  and  those  of  the 
trunk  :  others  pierce  the  fascia  lata  and 
join  the  deep  inguinal  glands.  The  ex- 
ternal group  arise  from  the  outer  side 
of  the  foot,  ascend  in  front  of  the  leg, 
and.  just  below  the  knee,  cross  the  tibia 
fr»m  without  inward,  to  join  the  lym- 
phatics on  the  inner  side  of  the  thigh. 
Others  commence  on  the  outer  side  of 
the  foot,  pass  behind  the  outer  malleolus, 
and  accompany  the  external  saphenous 
vein  along  the  back  of  the  leg,  where  they 
enter  the  popliteal  glands. 

The  deep  lymphatic  vessels  of  the 
lower  extremity  are  few  in  number  and 
accompany  the  deep  blood-vessels.  In 
the  leg  they  consist  of  three  sets,  the 
anterior  tibial.  peroneal,  and  posterior 
tibial.  which  accompany  the  correspond- 
ing blood-vessels,  two  or  three  to  each 
artery :  they  ascend  with  the  blood- 
vessels and  enter  the  lymphatic  glands 
in  the  popliteal  space ;  the  efferent 

-els  from  these  glands  accompany 
the  femoral  vein  and  join  the  deep 
inguinal  glands ;  from  these,  the  vessels 
pass  beneath  Poupart's  ligament  and  com- 
municate with  the  chain  of  glands  sur- 
rounding the  external  iliac  vessels. 

The  deep  lymphatic  vessels  of  the 
gluteal  and  ischiatic  regions  follow  the 
course  of  the  blood-vessels,  and  join  the 
gluteal  and  ischiatic  glands  at  the  great 
Bacro-sciatic  foramen. 


LYMPHATICS  OF  THE  PELVIS  AND 
ABDOMEN. 

The  Lymphatic  Glands  in  the  Pelvis 
are  the  external  iliac,  the  internal  iliac, 
and  the  sacral.  Those  of  the  abdomen 
are  the  lumbar  glands. 

The  external  iliac  glands  form  an  unin-         FIG.  m-The  superficial  lymphatics  and  glands 
terrupted  chain  round  the  external  iliac    <>f  the  lower  extremity, 
vessels,  three  being  placed  round  the  commencement  of  the  vessels  just  behind  the 


688 


THE   LYMPHATICS 


crural  arch.  They  communicate  below  with  the  deep  inguinal  lymphatic  glands, 
and  above  with  the  lumbar  glands. 

The  internal  iliac  glands  surround  the  internal  iliac  vessels ;  they  receive  the 
lymphatic  vessels  corresponding  to  the  branches  of  the  internal  iliac  artery,  and 
communicate  with  the  lumbar  glands. 

The  sacral  glands  occupy  the  sides  of  the  anterior  surface  of  the  sacrum,  some 


Lumbar 
glands. 


Sacral  glands. 


Internal 


W  iliac  glands, 


External 
iliac  glands 


Deep 
inguinal 
glands. 


FIG.  399.— The  deep  lymphatic  vessels  and  glands  of  the  abdomen  and  pelvis. 


being  situated  in  the  meso-rectal  fold.     These  and  the  internal  iliac  glands  are 
affected  in  malignant  disease  of  the  bladder,  rectum,  or  uterus. 

The  lumbar  glands  are  very  numerous ;  they  are  situated  on  the  front  of  the 
lumbar  vertebrae,  surrounding  the  common  iliac  vessels,  the  aorta,  and  vena  cava ; 
they  receive  the  lymphatic  vessels  from  the  lower  extremities  and  pelvis,  as  well  as 
from  the  testes  and  some  of  the  abdominal  viscera :  the  efferent  vessels  from  these 
glands  unite  into  a  few  large  trunks,  which,  with  the  lacteals,  form  the  commence- 


OF   THE  ABDOMEN  AXD   PELVIS.  689 

ment  of  the  thoracic  duct.  In  addition  to  these  there  are  a  few  small  lateral  lum- 
bar  t/?'i/t •/.>•  which  lie  between  the  transverse  processes  of  the  vertebrae,  behind  the 
Psoas  muscle,  and  receive  lymphatics  from  the  back.  In  some  cases  of  malignant 
disease  these  glands  become  enormously  enlarged,  completely  surrounding  the  aorta 
and  vena  cava.  and  occasionally  greatly  contracting  the  calibre  of  those  vessels. 
In  all  cases  of  malignant  disease  of  the  testes  and  in  malignant  disease  of  the  lower 
limb,  before  any  operation  is  attempted,  careful  examination  of  the  abdomen  should 
be  made,  in  order  to  ascertain  if  any  enlargement  exists ;  and  if  any  should  be 
detected,  all  operative  measures  should  be  avoided  as  fruitless. 

The  Lymphatic  Vessels  of  the  Abdomen  and  Pelvis  may  be  divided  into  two  sets, 
ttiperjicial  and  deep. 

The  superficial  lymphatic  vessels  of  the  walls  of  the  abdomen  and  pelvis  follow 
the  course  of  the  superficial  blood-vessels.  Those  derived  from  the  integument 
of  the  loAver  part  of  the  abdomen  below  the  umbilicus  follow  the  course  of  the 
superficial  epigastric  vessels  and  converge  to  the  superior  group  of  the  superficial 
inguinal  glands :  a  deeper  set  accompany  the  deep  epigastric  vessels,  and  commu- 
nicate Avith  the  external  iliac  glands.  The  superficial  lymphatics  from  the  sides 
of  the  lumbar  part  of  the  abdominal  wall  wind  round  the  crest  of  the  ilium, 
accompanying  the  superficial  circumflex  iliac  vessels,  to  join  the  superior  group 
of  the  superficial  inguinal  glands :  the  greater  number,  however,  run  back- 
ward along  Avith  the  ilio-lumbar  and  lumbar  vessels,  to  join  the  lateral  lumbar 
glands. 

The  superficial  lymphatic  vessels  of  the  gluteal  region  turn  horizontally  round 
the  outer  side  of  the  nates,  and  join  the  superficial  inguinal  glands. 

The  superficial  lymphatic  vessels  of  the  scrotum  and  perinaeum  folloAT  the  course 
of  the  external  pudic  vessels,  and  terminate  in  the  superficial  inguinal  glands. 

The  superficial  lymphatic  vessels  of  the  penis  occupy  the  sides  and  dorsum  of 
the  organ,  the  latter  receiving  the  lymphatics  from  the  skin  covering  the  glans 
penis  :  they  all  converge  to  the  upper  chain  of  the  superficial  inguinal  glans.  The 
deep  lymphatic  vessels  of  the  penis  folloAv  the  course  of  the  internal  pudic  vessels, 
and  join  the  internal  iliac  glands. 

In  the  female  the  lymphatic  vessels  of  the  mucous  membrane  of  the  labia, 
nymphae,  and  clitoris  terminate  in  the  upper  chain  of  the  inguinal  glands. 

The  deep  lymphatic  vessels  of  the  abdomen  and  pelvis  take  the  course  of  the 
principal  blood-vessels.  Those  of  the  parietes  of  the  pelvis,  which  accompany 
the  gluteal.  ischiatic.  and  obturator  vessels,  follow  the  course  of  the  internal  iliac 
arterv.  and  ultimately  join  the  lumbar  lymphatics. 

The  efferent  vessels  from  the  inguinal  glands  enter  the  pelvis  beneath  Poupart's 
ligament.  A\  here  they  lie  in  close  relation  with  the  femoral  vein ;  they  then  pass 
through  the  chain  of  glands  surrounding  the  external  iliac  vessels,  and  finally  ter- 
minate in  the  lumbar  glands.  They  receive  the  deep  epigastric  and  circumflex 
iliac  lymphatics. 

The  lymphatic  vessels  of  the  bladder  arise  from  the  entire  surface  of  the 
organ : l  the  greater  number  run  beneath  the  peritoneum  on  its  posterior  surface, 
and.  after  passing  through  the  lymphatic  glands  in  that  situation,  join  with  the 
lymphatics  from  the  prostate  and  vesiculae  seminales,  and  enter  the  internal  iliac 
glands. 

The  lymphatic  vessels  of  the  rectum  are  of  large  size ;  after  passing  through 
some  small  glands  that  lie  upon  its  outer  Avail  and  in  the  meso-rectum  they  pass  to 
the  sacral  glands. 

The  lymphatic  vessels  of  the  uterus  consist  of  two  sets,  superficial  and  deep, 
the  former  being  placed  beneath  the  peritoneum,  the  latter  in  the  substance  of  the 
organ.  The  lymphatics  of  the  cervix  uteri,  together  with  those  from  the  vagina, 
enter  the  internal  iliac  and  sacral  glands :  those  from  the  body  and  fundus  of  the 
uterus  pass  outward  in  the  broad  ligaments,  and,  being  joined  by  the  lymphatics 

1  Curnow  states  that  they  are  confined  to  the  base  of  the  organ. 
44 


690  THE   LYMPHATICS 

from  the  ovaries,  broad  ligaments,  and  Fallopian  tubes,  ascend  with  the  ovarian 
vessels  to  open  into  the  lumbar  glands.  In  the  unimpregnated  uterus  they  are 
small,  but  during  gestation  they  become  very  greatly  enlarged. 

The  lymphatic  vessels  of  the  testicle  consist  of  two  sets,  superficial  and  deep :  the 
former  commence  on  the  surface  of  the  tunica  vaginalis,  the  latter  in  the  epididy- 
mis  and  body  of  the  testis.  They  form  several  large  trunks  which  ascend  with 
the  spermatic  cord,  and,  accompanying  the  spermatic  vessels  into  the  abdomen, 
terminate  into  the  lumbar  glands ;  hence  the  enlargement  of  these  glands  in 
malignant  disease  of  the  testis. 

The  lymphatic  vessels  of  the  kidney  arise  on  the  surface,  and  also  in  the  inte- 
rior of  the  organ  ;  they  join  at  the  hilum,  and,  after  receiving  the  lymphatic  vessels 
from  the  ureter  and  suprarenal  capsules,  open  into  the  lumbar  glands. 

The  lymphatic  vessels  of  the  liver  are  divisible  into  two  sets,  superficial  and  deep. 
The  former  arise  in  the  subperitoneal  areolar  tissue  over  the  entire  surface  of  the 
organ.  Those  on  the  convex  surface  may  be  divided  into  four  groups :  1.  Those 
which  pass  from  behind  forward,  consisting  of  three  or  four  branches,  which  ascend 
in  the  longitudinal  ligament  and  unite  to  form  a  single  trunk,  which  passes  up 
between  the  fibres  of  the  Diaphragm,  behind  the  ensiform  cartilage,  to  enter  the 
anterior  mediastinal  glands,  and  finally  ascends  to  the  root  of  the  neck,  to  ter- 
minate in  the  right  lymphatic  duct.  2.  Another  group,  which  also  incline  from 
behind  forward,  are  reflected  over  the  anterior  margin  of  the  liver  to  its  under 
surface,  and  from  thence  pass  along  the  longitudinal  fissure  to  the  glands  in  the 
gastro-hepatic  omentum.  3.  A  third  group  incline  outward  to  the  right  lateral 
ligament,  and,  uniting  into  one  or  two  large  trunks,  pierce  the  Diaphragm,  and 
run  along  its  upper  surface  to  enter  the  anterior  mediastinal  glands,  or,  instead 
of  entering  the  thorax,  turn  inward  across  the  crus  of  the  Diaphragm  and  open 
into  the  commencement  of  the  thoracic  duct.  4.  The  fourth  group  incline  out- 
Avard  from  the  surface  of  the  left  lobe  of  the  liver  to  the  left  lateral  ligament, 
pierce  the  Diaphragm,  and,  passing  forward,  terminate  in  the  glands  in  the  ante- 
rior mediastinum. 

The  superficial  lymphatics  on  the  under  surface  of  the  liver  are  divided  into 
three  sets  :  1.  Those  on  the  right  side  of  the  gall-bladder  enter  the  lumbar  glands. 

2.  Those  surrounding  the  gall-bladder  form  a  remarkable  plexus ;  they  accom- 
pany the  hepatic  vessels,  and  open  into  the  glands  in  the  gastro-hepatic  omentum. 

3.  Those  on  the  left  of  the  gall-bladder  pass  to  the  cesophageal  glands  and  to  the 
glands  which  are  situated  along  the  lesser  curvature  of  the  stomach. 

The  deep  lymphatics  accompany  the  branches  of  the  portal  vein  and  the  hepatic 
artery  and  duct  through  the  substance  of  the  liver;  passing  out  at  the  transverse 
fissure,  they  enter  the  lymphatic  glands  along  the  lesser  curvature  of  the  stomach 
and  behind  the  pancreas,  or  join  with  one  of  the  lacteal  vessels  previous  to  its 
termination  in  the  thoracic  duct. 

The  lymphatic  glands  of  the  stomach  are  of  small  size ;  they  are  placed  along 
the  lesser  and  greater  curvatures,  some  within  the  gastro-splenic  omentum,  whilst 
others  surround  the  cardiac  -^nd  pyloric  orifices. 

The  lymphatic  vessels  of  the  stomach  consist  of  two  sets,  superficial  and  deep, 
the  former  originating  in  the  subserous,  and  the  latter  in  the  submucous,  coat. 
They  follow  the  course  of  the  blood-vessels,  and  may  consequently  be  arranged 
into  three  groups:  The  first  group  accompany  the  gastric  vessels  along  the  lesser 
curvature,  receiving  branches  from  both  surfaces  of  the  organ,  and  pass  to  the 
glands  around  the  pylorus.  The  second  group  pass  from  the  great  end  of  the 
stomach,  accompanying  the  vasa  brevia,  and  enter  the  splenic  lymphatic  glands. 
The  third  group  run  along  the  greater  curvature  with  the  right  gastro-epiploic 
vessels,  and  terminate  at  the  root  of  the  mesentery  in  one  of  the  principal  lacteal 
vessels. 

The  lymphatic  glands  of  the  spleen  occupy  the  hilum.  Its  lymphatic  vessels 
consist  of  two  sets,  superficial  and  deep :  the  former  are  placed  beneath  its 
peritoneal  covering,  the  latter  in  the  substance  of  the  organ  ;  they  accompany  the 


O.F   THE    THORAX.  691 

blood-vessels,  passing  through  a  series  of  small  glands,  and,  after  receiving  the 
lymphatics  from  the  pancreas,  ultimately  pass  into  the  thoracic  duct. 

THE  LYMPHATIC  SYSTEM  OF  THE  INTESTINES. 

The  lymphatic  glands  of  the  small  intestine  are  placed  between  the  layers  of 
the  mesentery,  occupying  the  meshes  formed  by  the  superior  mesenteric  vessels, 
and  hence  called  mesenteric  glands.  They  vary  in  number  from  a  hundred  to  a 
hundred  and  fifty,  and  in  size  from  that  of  a  pea  to  that  of  a  small  almond. 
These  glands  are  most  numerous,  and  largest  above,  near  the  duodenum,  and 
below,  opposite  the  termination  of  the  ileum  in  the  colon.  This  latter  group 
becomes  enlarged  and  infiltrated  with  deposit  in  cases  of  fever  accompanied  with 
ulceration  of  the  intestine*. 

The  lymphatic  glands  of  the  large  intestine  are  much  less  numerous  than  the 
mesenteric  glands ;  they  are  situated  along  the  vascular  arches  formed  by  the 
arteries  previous  to  their  distribution,  and  even  sometimes  upon  the  intestine 
itself.  They  are  fewest  in  number  along  the  transverse  colon,  where  they  form 
an  uninterrupted  chain  with  the  mesenteric  glands. 

The  lymphatic  vessels  of  the  small  intestine  are  called  lacteals,  from  the  milk- 
white  fluid  they  usually  contain :  they  consist  of  two  sets,  superficial  and  deep, 
the  former  lie  between  the  layers  of  the  muscular  coat  and  between  the  muscular 
and  peritoneal  coats,  taking  a  longitudinal  course  along  the  outer  side  of  the 
intestine  :  the  latter  occupy  the  submucous  tissue,  and  course  transversely  round 
the  intestine,  accompanied  by  the  branches  of  the  mesenteric  vessels;  they  pass 
between  the  layers  of  the  mesentery,  enter  the  mesenteric  glands,  and  finally 
unite  to  form  two  or  three  large  trunks  which  terminate  in  the  thoracic  duct. 

The  lymphatic  vessels  of  the  large  intestine  consist  of  two  sets :  those  of  the 
caecum,  ascending  and  transverse  colon,  which,  after  passing  through  their  proper 
glands,  enter  the  mesenteric  glands  ;  and  those  of  the  descending  colon,  sigmoid 
flexure,  and  rectum,  which  pass  to  the  lumbar  glands. 

THE  LYMPHATICS  OF  THE  THORAX. 

The  Lymphatic  Glands  of  the  Thoracic  Wall  are  the  intercostal,  internal  mam- 
mary, anterior  mediastinal.  and  posterior  mediastinal. 

The  intercostal  glands  are  small,  irregular  in  number,  and  situated  on  each 
side  of  the  spine,  near  the  costo-vertebral  articulations,  some  being  placed  between 
the  two  planes  of  intercostal  muscles. 

The  internal  mammary  glands  are  placed  at  the  anterior  extremity  of  each 
intercostal  space,  by  the  side  of  the  internal  mammary  vessels. 

The  anterior  mediastinal  glands  are  placed  in  the  loose  areolar  tissue  of  the 
anterior  mediastinum,  some  lying  upon  the  Diaphragm  in  front  of  the  pericardium, 
and  others  round  the  great  vessels  at  the  base  of  the  heart. 

The  posterior  mediastinal  glands  are  situated  in  the  areolar  tissue  in  the  poste- 
rior mediastinum,  forming  a  continuous  chain  by  the  side  of  the  aorta  and  oesoph- 
agus :  they  communicate  on  each  side  with  the  intercostal,  below  with  the  lumbar, 
and  above  with  the  deep  cervical  glands. 

The  Superficial  Lymphatic  Vessels  of  the  Front  of  the  Thorax  run  across  the 
great  Pectoral  muscle,  and  those  on  the  back  part  of  this  cavity  lie  upon  the 
Trapezius  and  Latissimus  dorsi ;  they  all  converge  to  the  axillary  glands.  The 
lymphatics  from  the  greater  part  of  the  mammary  gland  pass  outward  to  the 
lower  border  of  the  Pectoralis  major  muscle,  where  they  enter  a  chain  of  small 
glands  situated  in  the  axillary  space  along  the  lower  border  of  its  anterior 
boundary.  Some  few  lymphatics  from  the  inner  side  of  the  mammary  gland  pass 
through  the  intercostal  spaces  to  reach  the  anterior  mediastinal  glands. 

The  Deep  Lymphatic  Vessels  of  the  Thoracic  Wall  are  the  intercostal,  internal 
mammary,  and  diaphragmatic. 

The  intercostal  lymphatic  vessels  follow  the  course  of  the  intercostal  vessels. 


692  THE  LYMPHATICS. 

receiving  lymphatics  from  the  intercostal  muscles  and  pleura  ;  they  pass  backward 
to  the  spine,  and  unite  with  lymphatics  from  the  back  part  of  the  thorax  and  spinal 
canal.  After  traversing  the  intercostal  glands,  they  pass  down  the  spine  and 
terminate  in  the  thoracic  duct. 

The  internal  mammary  lymphatic  vessels  follow  the  course  of  the  internal 
mammary  vessels ;  they  commence  in  the  muscles  of  the  abdomen  above  the 
umbilicus,  communicating  with  the  epigastric  lymphatics,  ascend  between  the 
fibres  of  the  Diaphragm  at  its  attachment  to  the  ensiform  appendix,  and  in  their 
course  behind  the  costal  cartilages  are  joined  by  the  intercostal  lymphatics;  they 
terminate  on  the  righ^  side  in  the  right  lymphatic  duct,  on  the  left  side  in  the 
thoracic  duct. 

The  lymphatic  vessels  of  the  Diaphragm  follow  the  course  of  their  correspond- 
ing vessels,  and  terminate,  some  in  front  in  the  anterior  mediastinal  and  internal 
mammary  glands,  some  behind,  in  the  intercostal  and  posterior  mediastinal  lymph- 
atics. 

The  Lymphatic  Glands  of  the  Viscera  are  the  bronchial  glands. 

The  bronchial  glands  are  situated  round  the  bifurcation  of  the  trachea  and 
roots  of  the  lungs.  They  are  ten  or  twelve  in  number,  the  largest  being  placed 
opposite  the  bifurcation  of  the  trachea,  the  smallest  round  the  bronchi  and  their 
primary  divisions  for  some  little  distance  within  the  substance  of  the  lungs.  In 
infancy  they  present  the  same  appearance  as  lymphatic  glands  in  other  situations ; 
in  the  adult  they  assume  a  brownish  tinge,  and  in  old  age  a  deep  black  color. 
Occasionally  they  become  sufficiently  enlarged  to  compress  and  narrow  the  canal 
of  the  bronchi,  and  they  are  often  the  seat  of  tubercle  or  cretaceous  deposits. 

The  lymphatic  vessels  of  the  lung  consist  of  two  sets,  superficial  and  deep  : 
the  former  are  placed  beneath  the  pleura,  forming  a  minute  plexus  which  covers 
the  outer  surface  of  the  lung ;  the  latter  accompany  the  blood-vessels  and  run  along 
the  bronchi :  they  both  terminate  at  the  root  of  the  lungs  in  the  bronchial  glands. 
The  efferent  vessels  from  these  glands,  two  or  three  in  number,  ascend  upon  the 
trachea  to  the  root  of  the  neck,  traverse  the  tracheal  and  oesophageal  glands,  and 
terminate  on  the  left  side  in  the  thoracic  duct  and  on  the  right  side  in  the  right 
lymphatic  duct. 

The  cardiac  lymphatic  vessels  consist  of  two  sets,  superficial  and  deep  :  the 
former  arise  in  the  subserous  areolar  tissue  of  the  surface,  and  the  latter  in  the 
deeper  tissues  of  the  heart.  They  follow  the  course  of  the  coronary  vessels  :  those 
of  the  right  side  unite  into  a  trunk  at  the  root  of  the  aorta,  which,  ascending  across 
the  arch  of  that  vessel,  passes  backward  to  the  trachea,  upon  which  it  ascends, 
to  terminate  at  the  root  of  the  neck  in  the  right  lymphatic  duct.  Those  of  the 
left  side  unite  into  a  single  vessel  at  the  base  of  the  heart,  which,  passing  along 
the  pulmonary  artery  and  traversing  some  glands  at  the  root  of  the  aorta,  ascends 
on  the  trachea  to  terminate  in  the  thoracic  duct. 

The  thymic  lymphatic  vessels  arise  from  the  under  surface  of  the  thymus  gland, 
and  terminate  on  each  side  in  the  internal  jugular  veins. 

The  thyroid  lymphatic  vessels  arise  from  either  lateral  lobe  of  this  organ :  they 
converge  to  form  a  short  trunk,  which  terminates  on  the  right  side  in  the  right 
lymphatic  duct,  on  the  left  side  in  the  thoracic  duct. 

The  lymphatic  vessels  of  the  oesophagus  form  a  plexus  round  that  tube,  traverse 
the  glands  in  the  posterior  mediastinum,  and,  after  communicating  with  the 
pulmonary  lymphatic  vessels  near  the  roots  of  the  lungs,  terminate  in  the  thoracic 
duct, 


THE    NERVOUS    SYSTEM. 


THE  Xervous  System  is  composed — 1.  Of  a  series  of  large  centres  of  nerve-matter, 
called,  collectively,  the  cerebro-spinal  centre  or  axis.     2.   Of  smaller  centres, 
termed  ganglia.     3.  Of  nerves*  connected  either  with  the  cerebro-spinal  axis  or 
the  ganglia.    And  4.  Of  certain  modifications  of  the  peripheral  terminations  of  the 
nerves,  forming  the  organs  of  the  external  senses. 

The  Cerebro-spinal  Centre  consists  of  two  parts,  the  spinal  cord  and  the 
encephalon :  the  latter  may  be  subdivided  into  the  cerebrum,  the  cerebellum,  the 
pons  Varolii,  and  the  medulla  oblongata. 

THE  SPINAL  CORD  AND  ITS  MEMBRANES. 

Dissection.— To  dissect  the  cord  and  its  membranes  it  will  be  necessary  to  lay  open  the 
whole  length  of  the  spinal  canal.  For  this  purpose  the  muscles  must  be  separated  from  the 
vertebral  erooves.  so  as  to  expose  the  spinous  processes  and  laminae  of  the  vertebrae ;  and  the 
latter  must  be  sawn  through  on  each  side,  close  to  the  roots  of  tbe  transverse  processes,  from 
the  third  or  fourth  cervical  vertebra  above  to  the  sacrum  below.  The  vertebral  arches  having 
been  displaced  by  means  of  a  chisel  and  the  separate  fragments  removed,  the  dura  mater  will  be 
exposed,  covered  by  a  plexus  of  veins  and  a  quantity  of  loose  areolar  tissue,  often  infiltrated  with 
serous  fluid.  The  arches  of  the  upper  vertebrae  are  best  divided  by  means  of  a  strong  pair  of 
cutting  bone-forceps. 

MEMBRANES   OF   THE   CORD. 

The  membranes  which  envelop  the  spinal  cord  are  three  in  number.  The  most 
external  is  the  dur"  m.-it,  /•.  a  strong  fibrous  membrane  which  forms  a  loose  sheath 
around  the  cord.  The  most  internal  is  the  pia  mater*  a  cellulo-vascular  membrane 
which  closely  invests  the  entire  surface  of  the  cord.  Between  the  two  is  the 

•iinoid  membrane,  a  non-vascular  membrane  which  envelops  the  cord  and  is 
connected  to  the  pia  mater  by  slender  filaments  of  connective  tissue. 

The  Dura  Mater  of  the  cord,  continuous  with  that  which  invests  the  brain,  is 
a  loose  sheath  which  surrounds  the  cord,  and  is  separated  from  the  bony  walls  of 
the  spinal  canal  by  a  quantity  of  loose  areolar  tissue  and  a  plexus  of  veins.  It 
is  attached  to  the  circumference  of  the  foramen  magnum  and  to  the  posterior 
common  ligament,  especially  at  the  lower  end  of  the  spinal  canal,  by  fibrous 
slips,  and  extends  below  as  far  as  the  third  piece  of  the  sacrum ;  but  beyond  this 
point  it  is  impervious,  being  continued  in  the  form  of  a  slender  cord  to  the  back 
of  the  coccyx,  where  it  blends  with  the  periosteum.  This  sheath  is  much  larger 
than  is  necessary  for  its  contents,  and  its  size  is  greater  in  the  cervical  and  lumbar 
regions  than  in  the  dorsal.  Its  inner  surface  is  smooth.  On  each  side  may  be 
seen  the  double  openings  which  transmit  the  two  roots  of  the  corresponding  spinal 
nerve,  the  fibrous  layer  of  the  dura  mater  being  continued  in  the  form  of  a  tubular 
prolongation  on  them  as  they  pass  through  these  apertures.  On  opening  the 
lower  part  of  the  dura  mater — i.  e.  below  the  termination  of  the  cord  proper — 
the  root*  of  the  lumbar  and  sacral  nerves  are  seen.  These  roots,  taken  together, 
form  what  is  known  as  the  cauda  equina.  In  the  midst  of  the  cauda  equina  is  a 
delicate  process  of  gray  matter  within  a  tube  of  pia  mater.  This  is  the  filnm 
terminal?.  This  comes  off  from  the  conus  terminalis  (Fig.  402)  or  cone-like  end- 
ing of  the  cord,  and  blends,  below,  with  the  slender  cord-like  prolongation  of  the 
dura  mater  just  mentioned.  (See  page  695.) 

693 


THE   NERVOUS  SYSTEM. 


The  chief  peculiarities  of  the  dura  mater  of  the  cord,  as  compared  with  that 
investing  the  brain,  are  the  following : 

The  dura  mater  of  the  cord  is  not  adherent  to  the  bones   of  the  spinal  canal, 
which  have  an  independent  periosteum. 

It  does  not  send  partitions  into  the  fissures  of  the  cord,  as  in  the  brain. 
Its  fibrous  laminae  do  not  separate  to  form  venous  sinuses,  as  in  the  brain. 
Structure. — The  dura  mater  consists  of  white  fibrous  and  elastic  tissue  arranged 
in  bands  or  lamellae,  which,  for  the  most  part,  are  par- 
allel with  one  another.     Its  internal  surface  is  covered 
by  a  layer  of  endothelial  cells  which  gives  this  surface 
its  smooth  appearance.     It  is  sparingly  supplied  with 
vessels,  and  some  few  nerves  have  been  traced  into  it. 

The  Arachnoid  is  exposed  by  slitting  up  the  dura 
mater  and  reflecting  that  membrane  to  either  side  (Fig. 
400).  It  is  a  thin,  delicate,  tubular  membrane  which 
invests  the  surface  of  the  cord,  and  is  connected  to  the 
pia  mater  by  slender  filaments  of  connective  tissue. 
Above,  it  is  continuous  with  the  cerebral  arachnoid ; 
on  each  side  it  is  continued  on  the  various  nerves,  so 
as  to  form  a  sheath  for  them  as  they  pass  outward  to 
the  intervertebral  foramina.  The  outer  surface  of  the 
arachnoid  is  in  contact  with  the  inner  surface  of  the 
dura  mater,  and  the  two  are,  here  and  there,  connected 
together  by  isolated  connective-tissue  trabeculre,  especi- 
ally on  the  posterior  surface  of  the  cord.  For  the 
most  part,  however,  the  membranes  are  not  connected 
together,  and  the  interval  between  them  is  named  the 
subdural  space.  The  inner  surface  of  the  arachnoid  is 
separated  from  the  pia  mater  by  a  considerable  interval, 
which  is  called  the  subarachnoidean  space.  The  space 
is  the  largest  at  the  lower  part  of  the  spinal  canal,  and 
encloses  the  mass  of  nerves  which  form  the  cauda 

equina.  Superiorly  it  is  continuous  with  the  cranial  subarachnoid  space,  and 
communicates  with  the  general  ventricular  cavity  of  the  brain  by  means  of  an 
opening  in  the  pia  mater  at  the  inferior  boundary  of  the  fourth  ventricle  (for- 
amen of  Majendie).  It  contains  an  abundant  serous  secretion,  the  cerebro-spinal 

fluid.  This  secretion  is  sufficient  in 
amount  to  expand  the  arachnoid  mem- 
brane, so  as  to  completely  fill  up  the 
whole  of  the  space  included  in  the  dura 
mater.  The  subarachnoidean  space  is 
occupied  by  trabeculae  of  delicate  con- 
nective tissue,  connecting  the  pia  mater 
on  the  one  hand  with  the  arachnoid  mem- 
brane on  the  other. 
arachnoid  tissue.  In 
partially  subdivided 

membranous  partition,  which  serves  to 
connect  the  arachnoid  with  the  pia  mater, 
opposite  the  posterior  median  fissure.  This 
partition  is  incomplete  and  cribriform  in 
structure,  consisting  of  bundles  of  white 
fibrous  tissue  interlacing  with  each  other. 
This  space  is  to  be  regarded  as,  in  reality,  a  great  lymph-space,  from  which  the 
lymph  carried  to  it  by  the  perivascular  lymph-sheath  (see  page  87)  is  conveyed 
back  into  the  circulation. 


FIG.  400.— The  spinal  cord  and 
its  membranes. 


Dura,  mater 

Arachnoid 
fost.  root 

Ant.  root 


This  is  named  sub- 
addition  to  this  it  is 
by  a  longitudinal 


Dura  mater 

Plexus  venosus 


a  vertebralia 


FIG.  401.— Transverse  section  of  the  spinal  cord 
and  its  membranes.    (Gegenbaur.) 


THE  SPINAL    CORD.  695 

Structure. — The  arachnoid  is  a  delicate  membrane  made  up  of  closely  arranged 
interlacing  bundles  of  connective  tissue  in  several  layers. 

The  Pia  Mater  of  the  cord  is  exposed  on  the  removal  of  the  arachnoid  (Fig.  400). 
It  covers  the  entire  surface  of  the  cord,  to  which  it  is  very  intimately  adherent, 
forming  its  neurilemma,  and  sending  a  process  downward  into  its  anterior  fissure. 
It  also  forms  a  sheath  for  each  of  the  filaments  of  the  spinal  nerves,  and  invests 
the  nerves  themselves.  A  longitudinal  fibrous  band  extends  along  the  middle 
line  on  its  anterior  surface,  called  by  Haller  the  linea  xplendens  ;  and  a  some- 
what similar  band,  the  ligamentum  dentu'idatum,  is  situated  on  each  side.  At 
the  point  where  the  cord  terminates  the  pia  mater  becomes  contracted,  and  is  con- 
tinued down  as  a  long,  slender  filament  (filum  terminale),  which  descends  through 
the  centre  of  the  mass  of  nerves  forming  the  cauda  equina,  and  is  blended  with 
the  impervious  sheath  of  dura  mater  on  a  level  with  the  third  sacral  vertebra.  It 
assists  in  maintaining  the  cord  in  its  position  during  the  movements  of  the  trunk, 
and  is  from  this  circumstance  called  the  central  ligament  of  the  spinal  cord.  It 
contains  a  little  gray  nervous  substance,  which  may  be  traced  for  some  dis- 
tance into  its  upper  part,  and  is  accompanied  by  a  small  artery  and  vein. 
At  the  upper  part  of  the  cord  the  pia  mater  presents  a  grayish,  mottled  tint, 
which  is  owing  to  yellow  or  brown  pigment-cells  scattered  among  the  elastic 
fibres. 

Structure. — The  pia  mater  of  the  cord  is  less  vascular  in  structure,  but  thicker 
and  denser,  than  the  pia  mater  of  the  brain,  with  which  it  is  continuous.  It 
consists  of  two  layers :  an  outer  composed  of  bundles  of  connective-tissue  fibres, 
arranged  for  the  most  part  longitudinally ;  and  an  inner,  consisting  of  stiff 
bundles  of  the  same  tissue,  which  present  peculiar  angular  bends,  and  is  covered 
on  both  surfaces  by  a  layer  of  endothelium.  Between  the  two  layers  are  a 
number  of  cleftlike  lymphatic  spaces  which  communicate  with  the  subarachnoid 
cavity,  and  a  number  of  blood-vessels  which  are  enclosed  in  a  peri  vascular 
sheath,  derived  from  the  inner  layer  of  the  pia  mater,  into  which  the  lymphatic 
spaces  open.  It  is  also  supplied  with  nerves,  which  are  derived  from  the  sympa- 
thetic. 

The  Ligamentum  Denticulatum  (Fig.  400)  is  a  narrow  fibrous  band,  situated 
on  each  side  of  the  spinal  cord,  throughout  its  entire  length,  and  separating  the 
anterior  from  the  posterior  roots  of  the  spinal  nerves.  It  has  received  its  name 
from  the  serrated  appearance  which  it  presents.  Its  inner  border  is  continuous 
with  the  pia  mater  at  the  side  of  the  cord.  Its  outer  border  presents  a  series  of 
triangular,  dentated  serrations,  the  points  of  which  are  fixed  at  intervals  to  the 
dura  mater.  These  serrations  are  twenty-one  in  number  on  each  side,  the  first 
being  attached  to  the  dura  mater,,  opposite  the  margin  of  the  foramen  magnum 
between  the  vertebral  artery  and  the  hypoglossal  nerve,  and  the  last  near  the 
lower  end  of  the  cord.  Its  use  is  to  support  the  cord  in  the  fluid  by  which  it  is 
surrounded.  4 

THE    SPINAL    CORD  (Fig.  402). 

The  Spinal  Cord  (medulla  spinalis)  is  the  cylindrical,  elongated  part  of  the 
cerebro-spinal  axis  which  is  contained  in  the  vertebral  canal.  Its  length  is 
usually  about  seventeen  or  eighteen  inches,  and  its  weight,  when  divested  of  its 
membranes  and  nerves,  about  one  ounce  and  a  half,  its  proportion  to  the  encepha- 
lon  being  about  1  to  33.  It  does  not  nearly  fill  the  canal  in  which  it  is  con- 
tained, its  investing  membranes  being  separated  from  the  surrounding  walls  by 
art-' )lar  tissue  and  a  plexus  of  veins.  It  occupies,  in  the  adult,  the  upper  two- 
thirds  of  the  vertebral  canal,  extending  from  the  upper  border  of  the  atlas  to  the 
lower  border  of  the  body  of  the  first  lumbar  vertebra,  where  it  terminates  in  a 
slender  filament  of  gray  substance,  which  is  continued  for  some  distance  into  the 
Ilium  terminale.  In  the  foetus,  before  the  third  month,  it  extends  to  the  bottom  of 
the  sacral  canal,  but  after  this  period  it  gradually  recedes  from  below,  as  the 
growth  of  the  bones  composing  the  canal  is  more  rapid  in  proportion  than  that 


696 


THE   NERVOUS   SYSTEM. 


of  the  cord,  so  that  in  the  child  at  birth  the  cord  extends  as  far  as  the  third  lum- 
bar vertebra.     Its  position  varies  also  according  to  the  degree  of  curvature  of  the 


Pyramid 

Decussation 

of  the 
pyramids 


Ant.  med. 
fissure 


Antero-lat.. 


Posterior 
— Median  Fissure. 


Intumescentia 
lumbalis,  or 
lumbar  en- 
largement 


Conus 
terminalis 


Beginning  of 
thefllum  term. 

FIG.  402.— The  spinal  cord :  A,  from  in  front.    B,  from 
behind.    (Gegenbaur  and  Ouain.) 


FIG.  403.— Spinal  cord.  Side 
view.  Plan  of  the  fissures  and 
columns. 


spinal  column,  being  raised  somewhat 
in  flexion  of  the  spine.  On  exam- 
ining its  surface  it  presents  a  differ- 
ence in  its  diameter  in  different  parts, 
being  marked  by  two  enlargements, 
an  upper  or  cervical,  and  a  lower  or 
lumbar.  The  cervical  enlargement, 
which  is  the  larger,  extends  from 
about  the  third  cervical  to  the  first 
or  second  dorsal  vertebra :  its  great- 
est diameter  is  in  the  transverse  di- 
rection, and  it  corresponds  with  the 
origin  of  the  nerves  which  supply  the 
upper  extremities.  The  lower,  or  lum- 
bar, enlargement  (intumescentia)  is 
situated  opposite  the  last  two  or  three 
dorsal  vertebrae,  its  greatest  diameter 
being  from  before  backward.  It  cor- 
responds with  the  origin  of  the  nerves 
which  supply  the  lower  extremities. 
In  form  the  spinal  cord  is  a  flattened 
cylinder  (Fig.  402). 

Fissures. — It  presents  on  its  ante- 
rior surface,  along  the  middle  line,  a 
longitudinal  fissure,  the  anterior  me- 
dian fissure,  and  on  its  posterior  sur- 
face another  fissure,  which  also  ex- 
tends along  the  entire  length  of  the 
cord,  the  posterior  median  fissure. 
These  fissures  penetrate  through  the 
greater  part  of  the  thickness  of  the 
cord,  and  incompletely  divide  the 
cord  into  two  symmetrical  halves, 
united  in  the  middle  line  by  a  trans- 
verse band  of  nervous  substance,  the 
commissure. 

The  Anterior    Median  Fissure   is 

wider,  but  of  less  depth,  than  the  posterior,  extending  into  the  cord  for  about 
one-third  of  its  thickness,  and  is  deepest  at  the  lower  part  of  the  cord.     It  con- 


THE   SPINAL    CORD.  697 

tains  a  prolongation  from  the  pia  mater,  and  its  floor  is  formed  by  the  anterior 
white  commi**ni-i\  which  is  perforated  by  numerous  blood-vessels  passing  to  the 
centre  of  the  cord. 

The  Posterior  Median  Fissure  is  not  an  actual  fissure,  as  the  space  between 
the  lateral  halves  of  the  posterior  part  of  the  cord  is  crossed  by  connective  tissue 
and  numerous  blood-vessels,  so  that  no  actual  hiatus  exists,  and  there  is  conse- 
quently no  prolongation  of  the  pia  mater  into  it.  It  extends  into  the  cord  to 
about  one  half  its  depth,  and  its  floor  is  formed  by  the  posterior  gray  commissure. 

Lateral  Fissures. — On  each  side  of  the  anterior  median  fissure  a  linear  series 
of  foramina  may  be  observed,  indicating  the  points  where  the  anterior  roots  of 
the  spinal  nerves  emerge  from  the  cord.  This  is  called,  by  some  anatomists,  the 
antero-lateral  fissure  of  the  cord,  although  no  actual  fissure  exists  in  this  situation. 
And  on  each  side  of  the  posterior  median  fissure,  along  the  line  of  attachment  of 
the  posterior  roots  of  the  nerves,  a  delicate  fissure  may  be  seen,  leading  down  to 
the  gray  matter  which  approaches  the  surface  in  this  situation ;  this  is  called  the 
postero-lateral  fissure  of  the  spinal  cord.  On  the  posterior  surface  of  the  spinal 
cord,  between  the  posterior  median  and  the  postero-lateral  fissure  on  each  side,  is 
a  slight  longitudinal  furrow  (posterior  intermediate  furrow}  marking  off  two  tracts, 
the  posterior  median  columns.  These  are  most  distinct  in  the  cervical  region,  but 
are  stated  by  Foville  to  exist  throughout  the  whole  length  of  the  cord. 

Columns  of  the  Cord. — Each  half  of  the  spinal  cord  is  thus  divided  into  three 
main  columns :  an  antero-lateral  column,  a  postero-lateral  column,  and  a  postero- 
median  column. 

The  antero-lateral  column,  which  forms  rather  more  than  two-thirds  of  the 
entire  circumference  of  the  cord,  includes  all  the  portion  of  the  cord  between  the 
anterior  median  fissure  and  the  postero-lateral  fissure. 

By  some  anatomists  the  antero-lateral  column  is  subdivided  into  an  anterior 
column,  which  includes  all  the  portion  of  the  cord  between  the  anterior  median 
fissure  and  the  line  from  which  the  anterior  roots  of  the  nerves  arise;  and  a  lat- 
eral column,  which  includes  all  the  portion  between  the  line  of  origin  of  the  ante- 
rior roots  of  the  spinal  nerves  and  the  postero-lateral  fissure. 

The  postero-lateral  column  is  situated  between  the  postero-lateral  fissure  and 
the  posterior  intermediate  furrow. 

The  posterior  median  column  is  that  narrow  segment  of  the  cord  which  is  seen 
on  each  side  of  the  posterior  median  fissure,  usually  included  with  the  preceding 
as  the  posterior  column. 

Structure  of  the  Cord. — If  a  transverse  section  of  the  spinal  cord  be  made,  it 
will  be  seen  to  consist  of  white  and  gray  nervous  substance.  The  white  matter  is 
situated  externally,  and  constitutes  the  greater  part.  The  gray  substance  occupies 
the  centre,  and  is  so  arranged  as  to  present  on  the  surface  of  the  section  two  cres- 
centic  masses,  placed  one  in  each  lateral  half  of  the  cord,  united  together  by  a 
transverse  band  of  gray  matter,  the  gray  commissure.  Each  crescentic  mass  has 
an  anterior  and  posterior  horn.  The  posterior  horn  is  long  and  narrow,  and 
approaches  the  surface  of  the  postero-lateral  fissure,  near  which  it  presents  a  slight 
enlargement,  the  caput  cornu  :  from  this  it  tapers  to  form  the  apex  cornu,  which  at 
the  surface  of  the  cord  becomes  continuous  with  the  fibres  of  the  posterior  roots  of 
the  spinal  nerves.  The  anterior  horn  is  short  and  thick,  and  does  not  quite  reach 
the  surface,  but  extends  toward  the  point  of  attachment  of  the  anterior  roots  of  the 
nerves.  Its  margin  presents  a  dentate  or  stellate  appearance.  Owing  to  the  pro- 
jections toward  the  surface  of  the  anterior  and  posterior  horns  of  the  gray  matter, 
each  half  of  the  cord  is  divided,  more  or  less  completely,  into  three  columns, 
anterior,  middle,  and  posterior,  the  anterior  and  middle  being  joined  to  form  the 
antero-lateral  column,  as  the  anterior  horn  does  not  quite  reach  the  surface. 

The  commissure  of  the  spinal  cord  is  composed  of  white  and  gray  fibres,  hence 
called  the  white  and  gray  commissures.  The  -white  commissure  is  formed  of  fibres 
which,  for  the  most  part,  pass  horizontally  between  the  gray  matter  of  the  ante- 
rior horn  of  one  side  and  the  anterior  white  column  of  the  opposite  side. 


698 


THE   NERVOUS  SYSTEM. 


The  gray  commissure,  which  connects  the  two  crescentic  masses  of  gray  mat- 
ter, is  separated  from  the  bottom  of  the  anterior  median  fissure  by  the  anterior 

white  commissure.    It  consists  of  transverse  fibres, 

a,  x"T~X  with  a  considerable  quantity  of  neuroglia  between 

them.      The  fibres  when  they  reach  the  lateral 
crescents    diverge :    some    pass    backward    to    the 
posterior    roots ;    others    spread    out,    at    various 
angles,  into  the  cervix  cornu. 
/CT~^\  Running  through  the  gray  commissure  of  the 

Post,  commissure 


Epithelium  oj 
the  central  canal 


f 


Ant.  com- 
missure 


FIG.  404.— Diagram  of  cross-sections  of  the  cord  at  various  levels,  a,  beginning  of  the  cervical  portion,  b, 
cervical  enlargement,  c,  thoracic  or  dorsal  region,  d,  lumbar  enlargement,  e,  end  of  the  same.  /,  end  of  the 
cord.  (Gegenbaur.) 

FIG.  40o.— Cross-section  of  the  cervical  portion  of  the  spinal  cord  of  a  six  weeks'  embryo.    (Kolliker.) 

whole  length  of  the  cord  is  a  minute  canal,  which  is  barely  visible  to  the  naked 
eye  in  the  human  cord,  but  is  proportionally  larger  in  some  of  the  lower  verte- 
brata.  It  is  called  the  central  canal,  and  opens  above  into  the  fourth  ventricle, 
and  terminates  below  in  a  somewhat  dilated  extremity.  It  is  lined  in  the  foetus 
by  columnar  ciliated  epithelium,  but  in  the  adult  very  often  the  cilia  have  disap- 
peared, and  the  canal  is  filled  with  their  remains.  The  cells  are  supported  on  a 
layer  of  neuroglia,  which  is  sometimes  called  the  substantia  gelatinosa  centralis. 

The  mode  of  arrangement  of  the  gray  matter,  and  its  amount  in  proportion  to 
the  white,  vary  in  different  parts  of  the  cord.  Thus,  the  posterior  horns  are  long 
and  narrow  in  the  cervical  region ;  short  and  narrower  in  the  dorsal ;  short,  but 
wider,  in  the  lumbar  region.  In  the  cervical  region  the  crescentic  portions  are 
small,  and  the  white  matter  more  abundant  than  in  any  other  region  of  the  cord. 
In  the  dorsal  region  the  gray  matter  is  least  developed,  the  white  matter  being 
also  small  in  quantity.  In  the  lumbar  region  the  gray  matter  is  more  abundant 
than  in  any  other  region  of  the  cord.  Toward  the  lower  end  of  the  cord  the  white 
matter  gradually  ceases.  The  crescentic  portions  of  the  gray  matter  soon  blend  into 
a  single  mass,  which  forms  the  only  constituent  of  the  extreme  point  of  the  cord. 

Minute  Anatomy  of  the  Cord. — The  cord  consists  of  an  outer  part,  composed 
of  medullated  nerve-fibres,  which  is  the  white  substance  ;  and  of  a  central  part,  the 
gray  matter,  both  supported  in  a  peculiar  kind  of  tissue,  called  neuroglia. 

The  neuroglia  consists  of  a  homogeneous  transparent  matrix,  of  a  network  of 
very  delicate  fibrillae,  and  of  small  stellate  or  branched  cells,  the  neuroglia-cells. 

In  addition  to  forming  a  ground  substance,  in  which  the  nerve-fibres,  nerve- 
cells,  and  blood-vessels  are  imbedded,  a  considerable  accumulation  of  neuroglia 
takes  place  in  three  situations — (1)  on  the  surface  of  the  cord,  beneath  the  pia 
mater ;  (2)  around  the  central  canal ;  and  (3)  in  the  posterior  part  of  the  posterior 
horn,  forming  the  substantia  cinerea  gelatinosa. 


THE   SPIRAL    CORD. 


699 


The  white  substance  of  the  cord  consists  of  medullated  nerve-fibres,  with 
blood-vessels  and  neuroglia.  On  transverse  section  of  the  white  substance  of  the 
cord  a  very  striking  object  is  presented.  It  is  seen  to  be  studded  all  over  with 
minute  dots,  surrounded  by  a  white  area,  and  this  again  by  a  dark  circle  (Fig.  410). 
This  is  due  to  the  longitudinal  medullated  fibres  seen  on  section.  The  dot  is  the 
axis-cylinder,  the  white  area  the  substance  of  Schwann.  and  the  dark  circle  the 
tubular  membrane  of  the  fibres,  which  seems  to  consist  of  several  laminae. 
Externally,  the  neuroglia  is  seen  to  form  a  delicate  connective  sheath  round  the 
outer  surface  of  the  cord  immediately  beneath  the  pia  mater,  from  which  numerous 


-White  matter. 


Septa  of 
connect i 
(MMO. 


Central  canaL 


\  Gray  matter. 


Divided  nerve- 
fibre*. 


-^— J 

FIG.  406.— Transverse  section  through  the  cervical  portion  of  the  spinal  cord  of  the  calf.    Magnified  40 
diameters.    (Klein  and  Noble  Smith.) 


septa  pass  in  to  separate  the  respective  bundles  of  fibres  and  extend  between  the 
individual  nerve-fibres,  acting  as  a  supporting  medium  in  which  they  are  im- 
bedded. Thus  it  will  be  seen  that  the  greater  bulk  of  the  white  matter  of  the 
cord  is  made  up  of  longitudinal  medullated  fibres,  which  are  arranged  in  groups 
forming  the  antero-lateral  and  posterior  columns. 

There  are,  however,  also  oblique  and  transverse  fibres  in  the  white  substance. 
These  are  principally  found  (1)  at  the  bottom  of  the  anterior  median  fissure, 
forming  the  white  commissure,  the  fibres  passing  from  the  gray  matter  of  the 
anterior  horn  on  one  side  to  the  white  matter  of  the  anterior  column  of  the  oppo- 
site side ;  (2)  horizontal  or  oblique  fibres  passing  from  the  roots  of  the  nerves  into 


700 


THE   NERVOUS  SYSTEM. 


the  gray  matter ;  and  (3)  fibres  leaving  the  gray  matter,  and  pursuing  a  longer  or 
shorter  horizontal  course  between  the  bundles  of  longitudinal  fibres,  with  which 
many  of  them  are  continuous. 

The  investigation  of  pathological  lesions  has  shown  that  of  the  main  columns 
of  the  cord  each  consists  of  certain  sub-columns  or  tracts  of  fibres,  for  it  has  been 
found  that  separate  lesions  are  strictly  limited  to  certain  well-determined  parts  of 
the  organ  without  involving  neighboring  regions.  That  these  parts  or  fasciculi 
correspond  to  so  many  distinct  anatomical  systems,  each  endowed  with  special 
functions,  seems  abundantly  proved  by  the  researches  of  Flechsig  and  others  on 
the  development  of  the  cord  during  the  later  periods  of  utero-gestation  and  in  the 
newly-born  infant.  Thus,  on  either  side  of  the  anterior  median  fissure  a  portion 
of  the  antero-lateral  column  is  divided  off  us  the  direct  pyramidal  tract  (fasciculus 


FIG.  407.— Columns  of  the  cord. 


Atitr.  Medn.  Fitsure. 


FIG.  408. — Transverse  section  of  the  gray  substance  of 
the  spinal  cord,  near  the  middle  of  the  dorsal  region.  Mag- 
nified 13  diameters. 


of  Turck),  which  can  be  traced  to  be  continuous  with  the  non-decussating  fibres 
of  the  pyramid  of  the  medulla.  The  remainder  of  the  antero-lateral  column  of 
the  cord  is  formed  of  six  tracts  or  columns,  which,  as  to  actual  size,  may  be 
divided  into  three  large  and  three  small  tracts.  The  three  former  are :  (1)  The 
crossed  pyramidal  tract,  whose  fibres  when  traced  upward  form  the  decussating 
portion  '  f  the  pyramid  of  the  medulla  oblongata ;  (2)  the  direct  cerebellar  tract, 
which  passes  above  into  the  restiform  body  of  the  medulla ;  (3)  the  antero-lateral 
ground  bundle,  the  fibres  of  which  are  continued  into  the  formatio  reticularis  of 
the  medulla.  The  three  latter  are :  (1)  The  antero-lateral  descending  cerebellar 
tract  (Loewenthal);  (2)  the  antero-lateral  ascending  cerebellar  tract  (Gowers);  (3) 
the  tract  if  Lissauer.  For  the  prolongations  of  the  first  two,  see  Structure  of 
the  Medulla.  The  last  is  not  apparently  found  in  the  medulla.  All  these  small 
tracts  occupy  the  surface  of  the  cord  (see  Fig.  407). 

The  posterior  column  of  the  cord  is  divided  into  two :  the  portion  which  lies 
next  the  posterior  median  fissure  is  called  the  column  of  Goll  (postero-median), 
and  if  traced  upward  is  found  to  be  continuous  with  the  funiculus  gracilis  of  the 
medulla.  The  remainder  of  the  posterior  column  is  called  the  postero-lateral  or 
Eurdach's  column,  and  is  prolonged  into  the  medulla  under  the  name  of  funiculus 
cuneatus. 

Collateral  Fibres. — The  posterior  nerve-roots,  on  entering  the  cord,  separate 
into  the  component  fibres,  each  of  which  bifurcates  into  an  ascending  and  descend- 
ing branch,  which  run  upward  and  downward  in  the  posterior  column  and  in  the 
posterior  cornu.  Furthermore,  each  of  these  fibres  before  bifurcating  and  each 
of  its  bifurcations  gives  off  at  intervals  collateral  branches,  which  penetrate  the 


THE  SPIRAL    CORD. 


701 


gray  matter  and  there  break  up  into  an  arborization  of  nerve-fibrils  which  appears 
to  have  some,  though  not  direct,  connection  with  a  similar  arborization  of  the 
branched  processes  from  the  nerve-cells  (see  Fig.  411). 

The  gray  substance  of  the  cord  occupies  its  central  part  in  the  shape  of  two 
crescentic  horns,  joined  together  by  a  commissure.  Each  of  these  crescents  has 
an  anterior  and  posterior  cornu. 

The  posterior  horn  consists  of  two  parts— the  caput  cornu,  or  expanded 
extremity  of  the  horn  (Fig.  409),  round  which  is  a  lighter  space  or  lamina  of 


isr   isar   f  i  I 

Fissure. 

FK;.  409.— Transverse  section  of  the  gray  substance  of  the  spinal  cord  through  the  middle  of  the  lumbai 
enlargement.  On  the  left  side  of  the  figure"  groups  of  large  cells  are  seen ;  on  the  right  side,  the  course  of  the 
fibres  is  shown  without  the  cells.  Magnified  13  diameters. 

gelatinous  substance :  and  the  cervix  cornu,  or  narrower  portion,  which  connects 
it  with  the  rest  of  the  gray  substance. 

The  gelatinous  substance  is  a  peculiar  accumulation  of  neuroglia  (Klein),  and 
has  been  named  by  Rolando  the  substantia  cinerea  gelatinosa. 

The  anterior  horn  of  the  gray  substance  in  the  cervical  and  lumbar  swellings, 
where  it  gives  origin  to  the  nerves  of  the  extremities,  is  much  larger  than  in  any 
other  region,  and  contains  several  distinct  groups  of  large  and  variously  shaped 
cells. 

In  addition  to  this,  in  certain  parts  of  the  cord  other  horns  or  projections  of 
the  gray  matter  may  be  seen  on  transverse  section.  One  of  these,  the  lateral 
horn,  is  found  projecting  outward  from  the  lateral  region  of  the  gray  matter  on  a 
level  with  the  gray  commissure  in  the  cervical  and  upper  part  of  the  dorsal  region 
of  the  cord;  and  a  second,  Clarke's  vesicular  column,  is  found  on  the  inner 
side  of  the  posterior  horn  near  the  gray  commissure,  in  the  upper  cervical  or 
dorsal  regions  or  at  the  point  of  exit  of  the  lower  lumbar  nerves. 

The  gray  commissure  is  situated  behind  the  white  commissure,  which  sep- 
arates it  from  the  bottom  of  the  anterior  median  fissure. 

The  gray  substance  of  the  cord  consists  of — (1)  nerve-fibres  of  variable  but 
smaller  average  diameter  than  those  of  the  columns ;  (2)  nerve-cells  of  various 
shapes  and  sizes,  with  from  two  to  eight  processes ;  (3)  blood-vessels  and 
neuroglia. 

The  nerve-fibres  of  the  gray  matter  of  the  posterior  horn  are  for  the  most  part 


702 


THE  NERVOUS   SYSTEM. 


w:  s. 


Gr.  S. 


composed  of  a  minute  and  dense  network  of  minute  fibrils,  which  is  termed 
"  Gerlach's  nerve-network,"  intermingled  with  nerves  of  a  larger  size.  This 
network  is  continuous  with  the  medullated  fibres  of  the  posterior  nerve-roots  on 
the  one  hand  (Deiters),  and  with  the  branched  processes  of  the  ganglion-cells  on 
the  other  (Gerlach),  so  that  the  ganglion-cells  are  connected  with  the  medullated 
fibres  of  the  posterior  nerve-roots  only  indirectly  through  the  nerve-network. 
The  arrangement  of  the  fibres  in  the  anterior  horn  of  the  gray  matter  appears 
to  be  somewhat  different :  here  the  medullated 
fibres  of  the  anterior  nerve-roots  are  for  the 
most  part  directly  continuous  with  the  axis-cyl- 
inder processes  of  the  ganglion-cells  (Fig.  411). 

The  nerve-cells  of  the  gray  matter  are  of  two 
kinds,  large  branched  nerve-vesicles  which  are 
collected  into  groups,  and  small  round  cells 
which  resemble  free  nuclei  and  are  found  scat- 
tered throughout  the  whole  of  the  gray  matter. 

In  the  anterior  horn  is  a  constant  group, 
situated  at  the  anterior  part  of  the  cornu,  and 
sometimes  termed  the  vesicular  column  of  tlie 
anterior  cornu.  It  consists  of  two  groups  of 

Sinus  long.  sup. 


FIG.  410.— Transverse  vertical  section  of  the  head, 
occipital  region,  showing  hemispheres  and  cerebel- 
lum. (Gegenbaur.) 


FIG.  411.— Diagram  showing  collator;;!  fibres  (C) 
and  arborizations  (6).  S,  arborization  of  the  branched 
processes  of  a  cell,  whose  axis-cylinder  process  is  seen 
prolonged  as  a  nerve-fibre.  II'.  N.  and  Gr.  S.,  white 
and  gray  substance.  (Gegenbaur.) 


cells :  one  mesial,  near  the  anterior  column  ;  the  other  lateral,  near  the  lateral 
column.  At  the  base  of  the  posterior  horn  on  its  inner  side,  and  joining  the 
gray  commissure,  is  a  group  of  nerve-cells,  which  give  rise  to  the  projection  men- 
tioned above  as  being  seen  on  transverse  section  in  the  upper  part  of  the  cord, 
which  is  called  Clarke's  posterior  vesicular  column. 

At  the  junction  of  the  anterior  and  posterior  cornu,  in  the  outer  portion  of 
the  gray  matter,  is  a  third  group  of  cells,  the  tractus  intermedio-lateralis.  In  cer- 
tain regions  of  the  cord  these  cells  extend  in  amongst  the  fibres  of  the  white 
matter  of  the  lateral  column,  and  give  rise  to  the  lateral  horn.  In  addition  to 
these  groups  a  few  large  scattered  cells  are  found  in  the  posterior  horn,  extending 
into  the  substantia  cinerea  gelatinosa. 

THE   BRAIN  AND  ITS  MEMBRANES. 

Dissection. — To  examine  the  brain  with  its  membranes  the  skull-cap  must  be  removed.  In 
order  to  effect  this,  saw  through  the  external  table,  the  section  commencing,  in  front,  about  an 
inch  above  the  margin  of  the  orbit,  and  extending,  behind,  to  a  level  with  the  occipital  protu- 
berance. Then  break  the  internal  table  with  the  chisel  and  hammer,  to  avoid  injuring  the  invest- 
ing membranes  or  brain  ;  loosen  and  forcibly  detach  the  skull-cap,  when  the  dura  mater  will  be 
exposed.  The  adhesion  between  the  bone  and  the  dura  mater  is  very  intimate,  and  much  more 
so  in  the  young  subject  than  in  the  adult. 


THE  BRAIN  AND   ITS  MEMBRANES.  703 

MEMBRANES  OF  THE  BRAIN. 

The  membranes  of  the  brain  are  the  dura  mater,  arachnoid  membrane,  and 
pia  mater. 

The  Dura  Mater. 

The  Dura  Mater  (Fig.  410)  is  a  thick  and  dense  inelastic  fibrous  membrane  which 
lines  the  interior  of  the  skull.  Its  outer  surface  is  rough  and  fibrillated,  and  adheres 
closely  to  the  inner  surface  of  the  bones,  forming  their  internal  periosteum,  this 
adhesion  being  most  marked  opposite  the  sutures  and  at  the  base  of  the  skull.  Its 
inner  surface  is  smooth  and  lined  by  a  layer  of  endothelial  cells.  It  sends  three 
processes  inward,  into  the  cavity  of  the  skull,  for  the  support  and  protection  of 
the  different  parts  of  the  brain,  and  is  prolonged  to  the  outer  surface  of  the  skull 
through  the  various  foramina  which  exist  at  the  base,  and  thus  becomes  continuous 
with  the  pericranium ;  its  fibrous  layer  forms  sheaths  for  the  nerves  which  pass 
through  these  apertures.  At  the  base  of  the  skull  it  sends  a  fibrous  prolongation 
into  the  foramen  caecum ;  it  sends  a  series  of  tubular  prolongations  round  the 
filaments  of  the  olfactory  nerves  as  they  pass  through  the  cribriform  plate,  and 
also  round  the  nasal  nerve  as  it  passes  through  the  nasal  slit ;  a  prolongation  is 
also  continued  through  the  sphenoidal  fissure  into  the  orbit,  and  another  is  con- 
tinued into  the  same  cavity  through  the  optic  foramen,  forming  a  sheath  for  the 
optic  nerve,  which  is  continued  as  far  as  the  eyeball.  In  the  posterior  fossa  it 
sends  a  process  down  the  internal  auditory  meatus,  ensheathing  the  facial  and 
auditory  nerves;  another  through  the  jugular  foramen,  forming  a  sheath  for  the 
structures  which  pass  through  this  opening ;  and  a  third  through  the  anterior 
condyloid  foramen.  Around  the  margin  of  the  foramen  magnum  it  is  closely 
adherent  to  the  bone,  and  is  continuous  with  the  dura  mater  lining  the  spinal 
canal.  In  certain  situations,  as  already  mentioned  (page  650),  the  fibrous  layers 
of  this  membrane  separate,  to  form  sinuses  for  the  passage  of  venous  blood. 
Upon  the  outer  surface  of  the  dura  mater,  in  the  situation  of  the  longitudinal 
sinus,  may  be  seen  numerous  small  whitish  bodies,  the  glandulce  Pacchioni. 

Structure. — The  dura  mater  consists  of  white  fibrous  and  elastic  tissues 
arranged  in  flattened  laminae,  which  are  divisible  into  two  layers,  the  fibres  of  the 
two  layers  intersecting  each  other  obliquely.  A  layer  of  nucleated  endothelial 
cells,  similar  to  those  found  on  serous  membranes,  lines  its  inner  surface ;  these 
were  formerly  regarded  as  belonging  to  the  arachnoid  membrane. 

Its  arteries  are  very  numerous,  but  are  chiefly  distributed  to  the  bones.  Those 
found  in  the  anterior  fossa  are  the  anterior  meningeal  branches  of  the  anterior  and 
posterior  ethmoidal  and  internal  carotid,  and  a  branch  from  the  middle  meningeal. 
In  the  middle  fossa  are  the  middle  and  small  meningeal  branches  of  the  internal 
maxillary,  a  branch  from  the  ascending  pharyngeal,  which  enters  the  skull  through 
the  foramen  lacerum  medium  basis  cranii,  branches  from  the  internal  carotid,  and 
a  recurrent  branch  from  the  lachrymal.  In  the  posterior  fossa  are  meningeal 
branches  from  the  occipital,  one  of  which  enters  the  skull  through  the  jugular 
foramen,  and  the  other  through  the  mastoid  foramen ;  the  posterior  meningeal, 
from  the  vertebral ;  occasionally  meningeal  branches  from  the  ascending  pharyngeal, 
which  enter  the  skull,  one  at  the  jugular  foramen,  the  other  at  the  anterior 
eondyloid  foramen,  and  a  branch  from  the  middle  meningeal. 

The  veins,  which  return  the  blood  from  the  dura  mater,  and  partly  from  the 
bones,  anastomose  with  the  diploic  veins.  These  vessels  terminate  in  the  various 
sinuses,  with  the  exception  of  two  which  accompany  the  middle  meningeal  artery, 
and  pass  out  of  the  skull  at  the  foramen  spinosum  to  join  the  internal  maxillary 
vein. 

The  nerves  of  the  dura  mater  are,  the  recurrent  branch  of  the  fourth  and 
filaments  from  the  Gasserian  ganglion,  from  the  ophthalmic  and  hypoglossal  nerves, 
and  from  the  sympathetic. 

The  so-called  glandulee  Pacchioni  are  numerous  small  whitish  granulations, 
usually  collected  into  clusters  of  variable  size,  which  are  found  in  the  following 


704  THE  NERVOUS  SYSTEM. 

situations :  1.  Upon  the  outer  surface  of  the  dura  mater,  in  the  vicinity  of  the 
superior  longitudinal  sinus,  being  received  into  little  depressions  on  the  inner 
surface  of  the  calvarium.  2.  On  the  inner  surface  of  the  dura  mater.  3.  In  the 
superior  longitudinal  sinus.  4.  On  the  pia  mater,  near  the  margin  of  the 
hemispheres. 

These  bodies  are  not  glandular  in  structure,  but  simply  enlarged  normal  villi 
of  the  arachnoid.  In  their  growth  they  perforate  the  dura  mater,  and  are  thus 
found  on  its  outer  surface,  and  when  of  large  size  they  cause  absorption  of  the 
bone,  and  come  to  be  lodged  in  pits  or  depressions  on  the  inner  table  of  the  skull. 
The  manner  in  which  they  perforate  the  dura  mater  is  as  follows :  At  an  early 
period  of  their  growth  they  project  through  minute  holes  in  the  inner  layer  of  the 
dura  mater,  which  open  into  large  venous  spaces  situated  in  the  tissues  of  the 
membrane  on  either  side  of  the  longitudinal  sinus  and  communicating  with  it. 
In  their  onward  growth  the  villi  push  the  outer  layer  of  the  dura  mater  before 
them,  and  this  forms  over  them  a  delicate  membranous  sheath.  In  structure  they 
consist  of  trabeculse  of  connective  tissue  covered  over  by  a  layer  of  endothelium. 
The  spongy  tissue  of  which  they  are  composed  is  continuous  with  the  trabecular 
tissue  of  the  subarachnoid  space. 

These  bodies  are  not  found  in  infancy,  and  very  rarely  until  the  third  year. 
They  are  usually  found  after  the  seventh  year,  and  from  this  period  they  increase 
in  number  as  age  advances.  Occasionally  they  are  wanting. 

Processes  of  the  Dura  Mater. — The  processes  of  the  dura  mater,  sent  inward 
into  the  cavity  of  the  skull,  are  three  in  number :  the  falx  cerebri,  the  tentorium 
cerebelli,  and  the  falx  cerebelli. 

The  falx  cerebri,  so  named  from  its  sickle-like  form,  is  a  strong  arched  process 
of  the  dura  mater,  which  descends  vertically  in  the  longitudinal  fissure  between 
the  two  hemispheres  of  the  brain.  It  is  narrow  in  front,  where  it  is  attached  to 
the  crista  galli  of  the  ethmoid  bone,  and  broad  behind,  where  it  is  connected  with 
the  upper  surface  of  the  tentorium.  Its  upper  margin  is  convex,  and  attached  to 
the  inner  surface  of  the  skull  as  far  back  as  the  internal  occipital  protuberance. 
In  this  situation  it  is  broad,  and  contains  the  superior  longitudinal  sinus.  Its 
lower  margin  is  free,  concave,  and  presents  a  sharp  curved  edge,  which  contains 
the  inferior  longitudinal  sinus. 

The  tentorium  cerebelli  is  an  arched  lamina  of  dura  mater,  elevated  in  the 
middle  and  inclining  downward  toward  the  circumference.  It  covers  the  upper 
surface  of  the  cerebellum,  and  supports  the  occipital  lobes  of  the  brain,  and 
prevents  them  pressing  upon  the  cerebellum.  It  is  attached,  behind,  by  its  convex 
border  to  the  transverse  ridges  upon  the  inner  surface  of  the  occipital  bone,  and 
there  encloses  the  lateral  sinuses ;  in  front,  to  the  superior  margin  of  the  petrous 
portion  of  the  temporal  bone,  enclosing  the  superior  petrosal  sinuses ;  and  at  the 
apex  of  this  bone  the  free  or  internal  border  and  the  attached  or  external  border 
meet,  and,  forming  two  processes,  cross  one  another  and  are  continued  forward,  to 
be  attached  to  the  anterior  and  posterior  clinoid  processes  respectively.  Along  the 
middle  line  of  its  upper  surface  the  posterior  border  of  the  falx  cerebri  is  attached, 
the  straight  sinus  being  placed  at  their  point  of  junction.  Its  anterior  border  is 
free  and  concave,  and  presents  a  large  oval  opening  for  the  transmission  of  the 
crura  cerebri. 

The  falx  cerebelli  is  a  small  triangular  process  of  dura  mater  received  into  the 
indentation  between  the  two  lateral  lobes  of  the  cerebellum  behind.  Its  base  is 
attached,  above,  to  the  under  and  back  part  of  the  tentorium  ;  its  posterior  margin, 
to  the  lower  division  of  the  vertical  crest  on  the  inner  surface  of  the  occipital  bone. 
As  it  descends  it  sometimes  divides  into  two  smaller  folds,  which  are  lost  on  the 
sides  of  the  foramen  magnum. 

The  Arachnoid  Membrane. 

The  arachnoid  (dpd%vy  e?ooc,  like  a  spider's  web),  so  named  from  its  extreme 
thinness,  is  a  delicate  membrane  which  envelops  the  brain,  lying  between  the  pia 


THE   BRAIN  AND    ITS   MEMBRANES.  705 

mater  internally  and  the  dura  mater  externally  ;  from  this  latter  membrane  it  is 
separated  by  a  space,  the  subdural  space. 

It  invests  the  brain  loosely,  being  separated  from  direct  contact  with  the 
cerebral  substance  by  the  pia  mater,  and  a  quantity  of  loose  areolar  tissue,  the 
ntbaracknoidean.  On  the  upper  surface  of  the  cerebrum  the  arachnoid  is  thin  and 
transparent,  and  may  be  easily  demonstrated  by  injecting  a  stream  of  air  beneath 
it  by  means  of  a  blowpipe;  it  passes  over  the  convolutions  without  dipping  down 
into  the  sulci  between  them.  At  the  base  of  the  brain  the  arachnoid  is  thicker, 
and  slightly  opaque  toward  the  central  part ;  it  covers  the  anterior  lobes,  and 
extends  across  between  the  two  temporo-sphenoidal  lobes,  so  as  to  leave  a  consid- 
erable interval  between  it  and  the  brain,  the  anterior  subarachnoidean  space;  it 
is  in  contact  with  the  pons  and  under  surface  of  the  cerebellum,  but  between  the 
hemispheres  of  the  cerebellum  and  the  medulla  oblongata  another  considerable 
interval  is  left  between  it  and  the  brain,  called  the  posterior  subarachnoidean  space. 
These  two  spaces  communicate  together  across  the  crura  cerebelli.  The  arachnoid 
membrane  surrounds  the  nerves  which  arise  from  the  brain,  and  encloses  them  in 
loose  sheaths  as  far  as  their  point  of  exit  from  the  skull. 

The  subarachnoid  space  is  the  interval  between  the  arachnoid  and  pia  mater  : 
this  space  is  narrow  on  the  surface  of  the  hemispheres,  but  at  the  base  of  the 
brain  a  wide  interval  is  left  between  the  two  temporo-sphenoidal  lobes,  and,  behind, 
between  the  hemispheres  of  the  cerebellum  and  the  medulla  oblongata.  This 
space  is  the  seat  of  an  abundant  serous  secretion,  the  cerebro-spinal  fluid,  which 
fills  up  the  interval  between  the  arachnoid  and  pia  mater.  The  subarachnoid 
space  usually  communicates  with  the  general  ventricular  cavity  of  the  brain  by 
means  of  an  opening  in  the  inferior  boundary  of  the  fourth  ventricle. 

The  subdural  space  also  contains  fluid;  this  is,  however,  small  in  quantity 
compared  with  the  cerebro-spinal  fluid. 

Structure. — The  arachnoid  consists  of  bundles  of  white  fibrous  and  elastic 
tissue  intimately  blended  together.  Its  outer  surface  is  covered  with  a  laver  of 
emlothelium.  From  its  inner  surface  are  given  off  a  number  of  bundles  of  fine 
connective  tissue,  which  form  a  sponge-like  trabecular  network  in  the  subarachnoid 
space,  in  the  interstices  of  which  the  cerebro-spinal  fluid  is  contained.  Vessels  of 
considerable  size,  but  few  in  number,  and,  according  to  Bochdalek,  a  rich  plexus  of 
nerves  derived  from  the  motor  division  of  the  fifth,  the  facial,  and  the  spinal 
accessory  nerves,  are  found  in  the  arachnoid. 

The  cerebro-spinal  fluid  fills  up  the  subarachnoid  space.  It  is  a  clear,  limpid 
fluid,  having  a  saltish  taste  and  a  slightly  alkaline  reaction.  According  to 
Lassaigne,  it  consists  of  98.5  parts  of  water,  the  remaining  1.5  per  cent,  being 
solid  matters,  animal  and  saline.  It  varies  in  quantity,  being  most  abundant 
in  old  persons,  and  is  quickly  reproduced.  Its  chief  use  is  probably  to  afford 
mechanical  protection  to  the  nervous  centres  and  to  prevent  the  effects  of  concus- 
sions communicated  from  without. 

The  Pia  Mater. 

The  pia  mater  is  a  vascular  membrane,  and  derives  its  blood  from  the  internal 
carotid  and  vertebral  arteries.  It  consists  of  a  minute  plexus  of  blood-vessels, 
held  together  by  an  extremely  fine  areolar  tissue.  It  invests  the  entire  surface  of 
the  brain,  dipping  down  between  the  convolutions  and  laminae,  and  is  prolonged 
into  the  interior,  forming  the  velum  interpositum  and  choroid  plexuses  of  the 
fourth  ventricle.  It  represents  only  the  inner  layer  of  the  pia  mater  of  the  cord. 
Upon  the  surfaces  of  the  hemispheres,  where  it  covers  the  gray  matter  of  the 
convolutions,  it  is  very  vascular,  and  gives  off  from  its  inner  surface  a  multitude 
of  minute  vessels,  which  extend  perpendicularly  for  some  distance  into  the  cerebral 
substance.  At  the  base  of  the  brain,  in  the  situation  of  the  anterior  and  posterior 
perforated  spaces,  a  number  of  long  straight  vessels  are  given  off,  which  pass 
through  the  white  matter  to  reach  the  gray  substance  in  the  interior.  On  the 

45 


706  THE   NERVOUS  SYSTEM. 

cerebellum  the  membrane  is  more  delicate,  and  the  vessels  from  its  inner  surface 
are  shorter.  Upon  the  crura  cerebri  and  pons  Varolii  its  characters  are  altogether 
changed ;  it  here  presents  a  dense  fibrous  structure,  marked  only  by  slight  traces 
of  vascularity. 

According  to  Fohmann  and  Arnold,  this  membrane  contains  numerous 
lymphatic  vessels.  Its  nerves  are  derived  from  the  sympathetic,  and  also  from 
the  third,  fifth,  sixth,  facial,  glosso-pharyngeal,  pneumogastric,  and  spinal  acces- 
sory. They  accompany  the  branches  of  the  arteries. 

THE  BRAIN. 

[By  BEEN  B.  GALLAXJDET.  M.  D., 

Demonstrator  of  Anatomv,  College  of  Physicians  and  Surgeons  (Columbia  University)  -,  Surgeon  to  Bellevue 

Hospital,  New  York  City.] 

GENERAL  CONSIDERATIONS  AND  DIVISIONS. 

THE  Brain,  or  encephalon,  is  that  portion  of  the  cerebro-spinal  axis  which  is 
contained  in  the  cranial  cavity.  It  may  be  divided  into  five  portions,  which,  from 
below  upward,  are  as  follows :  1.  The  medulla  oblongata ;  2.  The  pons  Varolii 
and  cerebellum  ;  3.  The  mid-brain  ;  4.  The  inter-brain  ;  5.  The  two  hemispheres. 
The  inter-brain  and  the  two  hemispheres  are  sometimes  grouped  together  as  the 
cerebrum.  Commonly,  however,  the  word  "cerebrum"  means  the  two  hemi- 
spheres only. 

These  various  subdivisions  of  the  brain  are  based  on  the  method  of  development 
of  the  brain,  each  of  which  corresponds  to  one  of  the  five  cerebral  vesicles  into 
which  the  original  foetal  brain,  a  mere  tube,  is  soon  divided. 

Authorities  differ  as  to  the  precise  method  of  development  of  the  early  foetal 
brain  after  it  has  become  a  closed  tube.  Some  observers  state  that  this  brain- 
tube  becomes  partially  constricted  in  two  places,  thus  giving  rise  to  three  primary 
cerebral  vesicles,  and  that  no  further  constrictions  as  such  occur.  Others  claim 
that,  while  this  is  true,  soon  afterward  the  anterior  and  posterior  vesicles  are  fur- 
ther subdivided  by  similar,  though  not  so  well-marked,  constrictions. 

This  latter  method  seems,  perhaps,  the  simpler,  and  is  the  one  which  will  be 
followed  in  the  present  description. 

There  are  thus  formed,  first,  three  primary  cerebral  vesicles,  and  then  five 
secondary  cerebral  vesicles.  The  three  former  are  known  respectively  as  the 
fore-brain,  the  mid-brain,  and  the  hind-brain.  Of  the  five  secondary  vesicles,  the 
first  and  second  result  from  constriction  of  the  fore-brain ;  the  third  is  the  orig- 
inal mid-brain  unchanged,  Avhile  the  fourth  and  fifth  are  derived  from  the  hind- 
brain  in  a  manner  similar  to  that  in  which  the  first  two  are  formed  from  the  fore- 
brain.  The  first  secondary  vesicle  is  known  as  the  prosencephalon  ;  the  second, 
as  the  thalamencephalon ;  the  third,  as  the  mesencephalon,  or  mid-brain;  the  fourth, 
as  the  epencephalon ;  and  the  fifth,  as  the  metencephalon  (Fig.  412).  Each  of 
these  subdivisions,  of  course,  contains  its  own  portion  of  the  original  brain- 
cavity,  and  these  various  portions  are  all  in  direct  continuity,  one  with  the 
other. 

In  comparing  these  divisions  of  the  embryonal  brain  with  those  of  the  adult 
brain  already  mentioned,  it  is  found  that  the  prosencephalon,  together  with  the 
thalamencephalon,  develop  into  or  go  to  form  the  inter-brain,  and  hence  their 
cavities  make  up  the  third  ventricle,  which  is  the  name  given  to  that  portion  of 
the  general  brain-cavity,  in  the  adult,  included  in  the  inter-brain.  It  is  common, 
however,  in  describing  the  adult  brain  to  use  the  names  "  inter-brain  "  and 
"thalamencephalon  "  interchangeably,  thus  disregarding  the  prosencephalon.  The 
reason  for  this  is  that  the  latter,  in  the  adult  brain,  is  merely  the  extreme  ante- 
rior part  of  the  true  thalamencephalon,  while  its  cavity  holds  a  similar  relation 
to  the  third  ventricle — i.  e.  it  is  only  the  anterior  end  of  the  ventricle.  It  is 
that  portion  of  the  third  ventricle  which  has  on  each  side  the  opening  known  as 
the  foramen  of  Monro,  the  significance  of  which  will  be  dwelt  upon  later. 


THE   BRAIN  AND    ITS   MEMBRANES. 


707 


The  mesencephalon,  or  mid-brain,  simply  develops  into  the  corresponding  por- 
tion of  the  adult  brain  which  is  known  by  the  same  name,  mid-brain.  The  epen- 
cephalon  becomes  the  future  pons  Varolii  and  cerebellum,  while  the  metencephalon 
develops  into  the  medulla  oblongata.  These  names,  "  prosencephalon,"  etc.,  which 
have  been  given  to  the  five  secondary  cerebral  vesicles,  are  also  used,  sometimes, 
to  designate  the  corresponding  divisions  of  the  adult  brain.  The  terms  "  hind- 
brain  "  and  "•  after-brain  "  are  often  employed,  the  former  as  a  name  for  the  pons 
and  cerebellum,  the  latter  for  the  medulla.* 

It  will  be  observed  that  in  making  the  above  comparison  there  has  been  no 
mention  of  the  hemispheres  nor  of  a 
corresponding  portion  of  the  embryonal 
brain.  This  point  will  now  be  touched 
upon.  Soon  after  the  formation  of  the 
primary,  or  simultaneously  with  that  of 
the  secondary,  cerebral  vesicles  there 
grows  out  from  each  side  of  the  front 
part  of  the  fore-brain  or  prosencephalon 


Mid-brain 


Inter-brain 


'ind-bratn 


After-brain 


brain) 


Mid-brain 


a  hollow  protrusion.     These  protrusions 
from  the  sides  of  the  prosencephalon  are  Waetory  lobe 
known  as  the  "  hemisphere  "  vesicles,  and  Optic  lobe 

each  one  is  to  form  the  corresponding 
•<i'h'/)-i}  of  the  adult  brain  (Fig.  412). 

mi  •      j         i  -  111 

1  his  development  is  brought  about  by  a 
process  of  extension  and  growth  in  all 
directions,  forward,  backward,  upward, 
and  downward,  until,  as  the  hemispheres, 
the  enormously  enlarged  hemisphere 
vesicles  come  close  together  above,  and 
overlie  from  above  downward  all  the 
remaining  divisions  of  the  encephalon. 
(The  term  "  fore-brain  "  is  sometimes 
used  to  designate  the  prosencephalon  and  the  hemispheres.) 

It  will  be  remembered  that  the  name  "  third  ventricle  "  means  the  cavity  of 
the  inter-brain.     The  cavities  of  the  other  divisions  are  known  as  follows  :  That 


Hemisphere 
tarn  '• 


FIG.  412.— Brain  of  a  seven  weeks'  old  embryo,  seen, 
A,  from  the  side.    B,  from  above.    (Mihalkovics.) 


Choroid 
plexus 


Com  mun  i  cation 

between  both 
lateral  ventricles 


Spinal  cord 
FIG.  413. — Diagram  showing  intercommunication 


Jfid-brain 


Afler-brain 


N  opt. 


X.  ma. 


FIG.  414.— A,  brain  of  a  rabbit  embryo.  B.  of  a 
foetal  calf.  In  both  the  lateral  wall  of  the  left  hemi 
sphere  vesicle  is  removed.  (Mihalkovics.i 


of  each  of  the  hemispheres  is  the  lateral  ventricle  of  the  corresponding  side ;  that 
of  the  mid-brain  is  the  aqueduct  of  Sylvius  ;  while  that  of  the  pons  and  cerebellum 


708 


THE  NERVOUS  SYSTEM. 


and  of  the  medulla  is  described  as  one  cavity  under  the  name  of  the  fourth 
ventricle.  These  spaces  all  communicate  with  one  another  (Fig.  413).  Thus  the 
fourth  ventricle  opens  above  into  the  aqueduct  of  Sylvius,  which  in  its  turn  leads 
into  the  back  part  of  the  third  ventricle,  and  this,  from  its  front  portion  laterally, 
communicates  with  each  lateral  ventricle  by  means  of  the  corresponding  foramen 
of  Monro.  It  is  thus  seen  that  this  foramen  was  originally  the  simple  orifice 
formed  by  the  protrusion  of  the  hemisphere  vesicle  from  the  side  of  the  prosen- 
cephalon  (Fig.  414). 

THE  MEDULLA  OBLONGATA  (Figs.  415  and  416). 
General  Description. 

The  medulla  oblongata,  or  spinal  bulb,  is  the  first  division  of  the  brain,  pro- 
ceeding from  below  upward.  It  has  two  extremities,  superior  and  inferior,  and 
four  surfaces,  dorsal,  ventral,  and  two  lateral.  The  inferior  extremity  is  directly 
connected  with  the  spinal  cord  ;  the  upper  has  a  similarly  direct  connection  with 
the  pons  Varolii  (Fig.  415).  The  surfaces  in  the  upper  half  of  the  medulla  are 
distinct  from  each  other ;  in  the  lower  half  each  runs  into  the  other  by  insensible 


Brachium' 
corp.  quad- 
rig,  post. 

FrsenuLum 

Crusta      N.  trochle- 
(mid-brain)        aris 
-Jf.  trig.  Lingula 


Basilar 
sulcus 


Olive 
Pyramid 


Decussation  of 
the  pyramids 


Funiculus 
teres 


Epiphysis 


Restiform 
body 
Ligala  • 

Obex 


Strife  aci 

Ala  cinerea 
Clava 


.  Fun 


S  ((o 


the  left  of  the  li 

Funiculut  ffracilis  (to 

the  left  of  the  line) 

Post.  med.  fissure 


FIG.  415.— Ventral  surfaces  of  medulla,  pons,  and 
mid-brain.    (Gegenbaur.) 


FIG.  416.— Dorsal  surfaces  of  medulla,  pons,  and 
mid-brain,    c.  q.a.  and  c.q.  p.,  corpora  quad.  aut.  and 

Eost.  adpont.=  cut  surface  of  middle  ped.  of  cerebel- 
im.  act  med.  =  cut  surface  of  inf.  ped.  of  cerebel- 
lum, ad  cer.  =  cut  surface  of  sup.  ped.  of  cerebellum. 
(Gegenbaur.) 

gradations.  Hence  the  outline  of  a  cross-section  of  the  upper  half  would  show 
each  of  these  surfaces  distinctly,  while  a  similar  outline  of  the  lower  half  would 
be  almost  that  of  a  circle. 

The  lateral  diameter  of  the  medulla  increases  from  below  upward,  that  of  the 
lower  end  being  about  equal  to  that  of  the  cord,  while  that  of  the  upper  is  but 
little  less  than  that  of  the  pons.  The  dorso-ventral  diameter  also  increases 
slightly  from  below  upward,  but  is  always  less,  at  any  given  level,  than  the 
corresponding  lateral  diameter.  Hence  the  medulla  is  somewhat  flattened  dorso- 
ventrally  and  expands  laterally  as  it  ascends.  It  is  directed  obliquely  from  below 
upward  and  forward,  and  its  lower  end,  which  joins  the  cord,  is  on  a  level  with 
the  lower  margin  of  the  foramen  magnum.  Its  ventral  surface  rests  on  the 
basilar  groove  of  the  occipital  bone,  while  its  dorsal  surface  lies  under  the  space 
which  separates  the  two  hemispheres  of  the  cerebellum.  Ventrally  its  upper  end 


THE   BRAIN  AND    ITS  MEMBRANES.  709 

is  clearly  marked  off  from  the  pons  by  prominent  transversely  directed  fibres 
belonging  to  the  latter ;  dorsally,  however,  there  is  no  such  line  of  separation, 
the  dorsal  surface  passing  directly  and  smoothly  into  that  of  the  pons.  The 
length  of  the  medulla  is  nearly  1  inch  (20  to  24  mm.) ;  its  greatest  lateral 
diameter  is  about  three-quarters  of  an  inch  (17  to  18  mm.) ;  its  greatest  dorso- 
ventral  diameter  is  somewhat  less  (15  mm.).  % 

The  further  description  of  the  medulla  will  be  divided  into  that  of  its  surface 
and  that  of  its  internal  structure. 

Surface. 

The  Surfaces  of  the  Medulla. — The  ventral  surface  of  the  medulla  is  divided 
into  two  symmetrical  lateral  halves  by  the  continuation  upward  of  the  anterior 
median  fissure  of  the  spinal  cord.  This  continues  up  to  the  pons,  where  it  ter- 
minates in  a  recess,  the  foramen  cacum  of  Vicq  d'Azyr.  It  is  interrupted,  how- 
ever, for  a  short  distance  after  its  passage  into  the  medulla  by  the  decussation  of 
the  crossed  pyramidal  tracts  of  the  cord.  The  dorsal  surface  of  the  lower  half 
of  the  medulla  is  similarly  divided  by  the  posterior  median  fissure  of  the  cord, 
which  does  not  extend  on  to  the  dorsal  surface  of  the  upper  half.  This  surface 
is,  however,  bisected  by  a  groove  or  sulcus  which  lies  in  the  middle  line  and 
extends  from  the  junction  of  the  upper  and  lower  halves  of  the  medulla  on  to 
the  dorsal  surface  of  the  pons  as  far  as  its  upper  extremity. 

Each  lateral  surface  of  the  medulla  is  separated  from  the  adjacent  halves  of 
the  dorsal  and  ventral  surfaces  by  a  groove,  well  marked  above,  less  distinct 
below.  These  grooves  may  be  called,  respectively,  the  dorso-lateral  and  ventro- 
lafcral  grooves  of  the  medulla. 

The  dorso-lateral  groove  is  the  continuation  upward  of  the  postero-lateral 
groove  of  the  cord,  and  from  it  emerge  the  fibres  of  the  accessory  portion  of  the 
spinal  accessory  nerve,  of  the  vagus,  of  the  glosso-pharyngeal,  and,  from  the 
extreme  upper  part,  close  to  the  pons,  the  fibres  of  the  seventh  and  mesial  root 
of  the  eighth.  There  are  two  points  to  be  noted  in  connection  with  this  groove : 
First,  it  is  interrupted  at  its  lower  end  by  the  change  in  position  of  the  direct 
cerebellar  tract  of  the  cord.  In  the  cord  this  tract  is  anterior  to  the  postero- 
lateral  groove,  but  as  it  passes  upward  into  the  medulla  it  becomes  dorsal  to  the 
groove,  and  thus  belongs  to  the  corresponding  half  of  the  medullary  dorsal  sur- 
face. Secondly,  its  direction  is  not  straight  up  and  down,  but  is  upward,  for- 
ward, and  outward.  The  reason  for  this  change  of  direction,  as  well  as  for  the 
cessation  of  the  posterior  median  fissure,  will  be  explained  below. 

The  ventro-lateral  groove  is  the  direct  continuation  upward  of  the  line  of 
emergence  of  the  anterior  roots  of  the  spinal  nerves,  although  in  the  cord  there 
is  no  similar  sulcus.  Out  of  this  groove,  in  the  upper  half  of  the  medulla,  wh«re 
it  is  very  distinct,  pass  the  fibres  of  the  hypoglossal  nerve. 

These  various  surfaces  will  now  be  considered  in  detail. 

THE  VENTRAL  SURFACE  OF  THE  MEDULLA. — Its  lower  half  is  made  up, 
mesially,  of  the  decussation  of  the  crossed  pyramidal  tracts,  and,  laterally,  of 
the  continuations  upward  of  the  direct  pyramidal  tracts  of  the  cord.  Hence  it 
is  undivided,  and  extends  laterally  from  the  lower  part  of  one  ventro-lateral 
groove  of  the  medulla  to  the  other.  Its  upper  half  is  divided  in  two,  as  already 
stated,  by  the  anterior  median  fissure.  These  two  halves  are  known  as  the 
pyramids. 

The  pyramids  are  two  prominent,  somewhat  pyramidally  shaped  bundles  of 
white  matter  or  nerve-fibres,  placed  one  on  either  side  of  the  anterior  median 
fissure,  each  being  separated  from  the  upper  half  of  the  corresponding  lateral 
surface  by  the  upper  part  of  the  ventro-lateral  groove.  Superiorly,  they  reach 
to  the  pons,  at  the  lower  border  of  which  they  are  somewhat  constricted.  Each, 
as  it  descends,  becomes  somewhat  enlarged,  and  then  tapers  at  its  lower  extrem- 
ity. The  fibres  of  which  each  pyramid  is  composed  are  disposed  in  two  bundles, 


710  THE   NERVOUS  SYSTEM. 

a  large  mesial  and  a  smaller  lateral  one.  The  fibres  of  the  former  are  directly 
continuous  with  those  of  the  crossed  pyramidal  tract  of  the  opposite  side  of  the 
cord  by  means  of  the  decussation  already  referred  to.  This  decussation  is  more 
commonly  spoken  of  as  the  decussation  of  the  pyramids.  The  fibres  of  the  lateral 
bundle  are  directly  continuous  with  those  of  the  direct  pyramidal  tract  of  the 
same  side  of  the  cord.  This  tract,  it  will  be  remembered,  in  the  cord  is  next  to 
the  anterior  median  fissure.  Hence  in  the  pyramid  it  is  displaced  laterally  by 
the  passage  upward,  next  to  the  median  fissure,  of  the  crossed  pyramidal  tract 
after  its  decussation  with  its  fellow  of  the  opposite  side.  Each  pyramid,  close  to 
the  pons,  is  often  crossed  by  a  fairly-well  marked  band  of  fibres,  the  ponticulus 
of  Arnold.  The  fibres  of  the  pyramid  are  continued  directly  upward  into  the 
pons  Varolii. 

THE  LATERAL  SURFACE  OF  THE  MEDULLA. — Each  of  these  surfaces,  as 
already  stated,  is  separated  from  the  corresponding  half  of  the  ventral  and  dorsal 
surface  respectively  by  the  ventro-lateral  and  dorso-lateral  groove.  The  entire 
upper  half  of  this  surface  is  occupied  by  a  well-marked  olive-shaped  prominence, 
the  olive  or  olivary  body.  The  lower  half,  below  the  olive,  is  often  spoken  of  as 
the  "  lateral  tract "  of  the  medulla.  It  is  not  raised  up  from  the  general  surface, 
as  is  the  olive,  and  consists  of  white  fibres  derived  from  the  antero-lateral  ground 
bundle  and  antero-lateral  ascending  and  descending  cerebellar  tracts  of  the  cord. 
These  fibres  pass  upward,  some  going  beneath  the  olive  (the  major  part),  while 
others  proceed  over  its  surface,  thus  forming  part  of  its  structure,  and  still 
others  are  found  in  the  grooves  on  each  side  of  the  olive.  The  fibres  in  the 
grooves  may  be  considered  as  coming  from  the  cerebellar  tracts  (ascending  and 
descending),  while  those  on  the  surface,  and  those  which  dip  under  or  beneath  the 
olive,  are  direct  prolongations  of  the  antero-lateral  ground  bundle.  The  further 
destination  of  all  these  fibres  will  be  noted  later  on. 

The  Olive  or  Olivary  Body. — This  has  just  been  partially  described.  It  is 
made  up  of  the  white  fibres  above  mentioned,  and  also  of  a  nucleus  of  gray 
matter  in  its  substance,  the  projection  of  which  really  causes  the  prominence 
itself,  or  the  olive.  This  nucleus  is  the  olivary  nucleus  or  dentate  nucleus  of  the 
olivary  body.  It  will  be  further  considered  below.  The  upper  end  of  the  olive 
reaches  nearly  to  the  pons,  only  a  short  but  deep,  transversely  directed  groove 
intervening.  This  small  groove  really  connects  the  upper  ends  of  the  dorso- 
lateral  and  ventro-lateral  grooves,  between  which  the  olive  is  placed,  and  which 
are  here  nearer  together  than  their  lower  portions,  owing  to  the  forward  tend- 
ency of  the  former.  Between  the  olive  and  pyramid  (ventro-lateral  groove) 
emerge  the  fibres  of  the  hypoglossal  nerve.  The  olive  is  equal  in  breadth  to  the 
pyramid,  is  a  little  broader  above  than  below,  and  is  about  half  an  inch  in 
length.  Numerous  white  fibres  (superficial  arciform  fibres}  are  seen  winding 
across  the  lower  half  of  the  pyramid  and  the  olivary  body  to  enter  the  restiform 
body  (see  below). 

THE  DORSAL  SURFACE  OF  THE  MEDULLA. — The  lower  half  of  this  surface  is 
divided  in  two  by  the  posterior  median  fissure  continued  upward  from  the  cord. 
Each  of  these  halves  of  the  lower  half  of  the  dorsal  surface  of  the  medulla  is  sep- 
arated from  the  so-called  lateral  tract  or  area  by  the  inferior  portion  of  the  dorso- 
lateral  groove,  and  receives  the  upward  prolongation  of  the  direct  cerebellar  tract 
of  the  cord,  as  already  mentioned. 

Situated  in  and  forming  parts  of  this  same  portion  of  the  dorsal  surface  of 
the  medulla  are  three  other  columns  or  tracts  of  white  matter,  besides  the  one 
just  mentioned.  These  columns  are  known  as  funiculi,  and  are  placed  side  by 
side,  separated  by  slight  grooves,  between  the  direct  cerebellar  tract  laterally 
and  the  posterior  median  fissure  mesially.  The  one  next  to  the  direct  cerebellar 
tract  is  the  funiculus  of  Rolando,  adjoining  which  is  the  funiculus  cuneatus,  and 
the  innermost,  next  to  the  fissure,  is  the  funiculus  gracilis. 

The  upper  half  of  the  dorsal  surface  of  the  medulla  is  considerably  wider 
than  the  lower,  this  increase  in  width  being  progressive  from  below  upward.  Its 


THE   BRAIN   AND    ITS   MEMBRANES.  711 

appearance  is  therefore  somewhat  like  that  of  an  equilateral  triangle,  base  upper- 
most and  with  thick  rounded  sides.  It  is  divided  in  two,  as  before  stated,  by  a 
longitudinal  mesial  sulcus  or  groove.  The  lateral  boundary  of  each  of  these 
halves  of  the  upper  half  of  the  dorsal  surface  is  the  superior  portion  of  the 
dorso-lateral  groove,  immediately  beyond  which  is,  of  course,  the  olivary  body  on 
the  lateral  surface.  The  thick  rounded  sides  of  the  "triangle"  are  the  restiform 
bodies,  and  the  space  between  them,  including  the  longitudinal  mesial  groove,  is 
the  lower  half  of  the  floor  of  the  fourth  ventricle.  The  restiform  bodies  project 
dorsally,  so  that  they  are  slightly  elevated  above  this  part  of  the  floor  of  the 
fourth  ventricle,  which  they  bound. 

The  Funiculus  Gracilis — Open  and  Closed  Portions  of  the  Medulla. — The 
funiculus  grac His  is  the  column  immediately  next  to  the  posterior  median  fissure 
on  the  dorsal  surface  of  the  lower  half  of  the  medulla,  and  its  fibres  are  continued 
directly  up  from  the  postero-mesial  column  (column  of  Goll)  of  the  spinal  cord. 
Its  upper  end  is  slightly  enlarged,  and  is  somewhat  more  prominent  than  the 
rest  of  the  column.  This  enlargement  and  prominence  are  due  to  the  nucleus 
found  in  its  substance  at  this  point  (Fig.  417).  The  term  clava  is  given  to  this 
enlarged  upper  end.  The  two  clavce  diverge  from  each  other,  and  each  encroaches 
somewhat  on  the  inner  aspect  of  the  lower  part  of  the  restiform  body,  thus  exclud- 
ing this  particular  part  of  the  restiform  body  from  its  place  as  lateral  boundary 
of  this  the  lowest  portion  of  the  floor  of  the  fourth  ventricle,  and  becoming  itself 
such  boundary.  As  each  clava  ascends  it  tapers  gradually  to  a  point,  and  is  lost 
on  the  restiform  body.  The  course  of  the  fibres  of  the  gracilis  and  its  nucleus 
will  be  described  under  the  "internal  structure  "  of  the  medulla.  The  fibres  do 
not  join  with  those  of  the  restiform  body.  The  angle  of  divergence  of  the  clavae 
indicates  the  points  of  cessation  of  the  posterior  median  fissure  and  of  the  begin- 
ning of  the  groove  which  lies  along  the  middle  of  the  floor  of  the  fourth  ven- 
tricle. In  other  words,  it  is  at  this  spot  that  the  lower  half  of  the  medulla,  which 
contains  the  upper  part  of  the  central  canal  of  the  spinal  cord,  now  begins  to 
widen  out  and  become  somewhat  flattened  dorso-ventrally.  This  wide  separation 
of  its  edges  necessarily  destroys  the  median  fissure  and  brings  to  the  surface  the 
central  canal  of  the  cord,  covered  in  only  by  the  dorsal  part  of  its  lining  epi- 
thelium and  a  delicate  layer  of  gray  matter.  The  canal  now  shares  in  the  widen- 
ing-out  process  and  becomes  the  lower  half  of  the  fourth  ventricle,  the  roof  of 
which  is  the  same  layer  of  epithelium  and  gray  matter,  but  which  now  stretches 
across,  as  a  delicate  triangular-shaped  lamina,  between  the  inner  margins  of  the 
restiform  bodies  and  the  clavce,  with  its  apex  necessarily  right  in  the  angle  of 
divergence  of  the  clavge.  This  layer  always  comes  away  with  the  removal  of  the 
pia  mater ;  hence  in  specimens  stripped  of  pia  there  is  seen,  of  the  lower  half  of 
the  fourth  ventricle,  only  its  floor  and  lateral  boundaries.  For  this  reason  also 
the  lower  half  of  the  medulla  is  often  called  the  closed  portion,  and  the  upper 
half  the  open  or  ventricular  portion.  (See  Tela  choroidea  inferior.) 

The  Funiculus  Cuneatus. — This  column  is  next  to  the  gracilis,  and  the  fibres 
of  which  it  is  composed  are  the  direct  continuations  upward  of  the  fibres  of  the 
postero-lateral  column  (column  of  Burdach)  of  the  cord.  Its  upper  end,  lying 
immediately  under  the  restiform  body,  is  enlarged  and  prominent,  like  that  of 
the  gracilis,  but  to  a  less  extent.  This  prominence  is  known  as  the  cuneate 
tubercle,  and  is  due  to  the  projection  of  a  nucleus  within  its  substance  (Fig.  417). 

The  Funiculus  of  Rolando. —  This  column  is  lateral  to  the  funiculus  cuneatus, 
and,  like  it,  its  upper  end  is  somewhat  enlarged  and  prominent,  this  prominence 
being  known  as  the  tubercle  of  Rolando.  There  is  also  a  nucleus  (Fig.  417) 
within  its  substance,  and  its  upper  end  lies  immediately  beneath  the  restiform 
body.  This  column  is  found  only  in  the  medulla,  it  having,  apparently,  no  cor- 
responding column  in  the  cord. 

The  Lower  Half  of  the  Floor  of  the  Fourth  Ventricle. — This  is  the  triangular 
space  already  mentioned  as  lying  between  the  restiform  bodies  and  clavse  of  the 
funiculi  graciles.  Its  base  joins  that  of  a  similar  triangular  space  (upper  half  of 


712  THE  NERVOUS  SYSTEM. 

the  floor  of  the  fourth  ventricle)  found  on  the  dorsum  of  the  pons.  Its  further 
consideration  -will  be  postponed  until  the  floor  as  a  whole  is  described. 

The  Restiform  Bodies. — These  are  the  largest  and  thickest  "  columns  "  found 
on  the  medulla.  Each  is  a  well-rounded  mass  of  white  fibres,  and  is  directed 
from  below  upward,  outward,  and  somewhat  forward,  diverging  from  its  fellow. 
Its  upper  extremity  is  at  the  widest  part  of  the  medulla,  where  it  bends,  almost 
at  a  right  angle,  directly  dorsally  away  from  the  medulla,  and  immediately  enters 
the  cerebellum.  Hence  a  synonym  of  the  restiform  body  is  the  inferior  peduncle 
of  the  cerebellum.  Its  lower  extremity  is  somewhat  tapering,  and  not  so  rounded 
and  prominent  as  are  the  succeeding  portions.  This  is  due  to  the  fact  that  the 
upper  ends  of  the  gracilis,  cuneatus,  and  Rolandic  columns  are  not  quite  on  the 
same  level,  the  cuneatus  reaching  a  little  higher  than  the  gracilis,  and  the 
Rolandic  column  a  little  higher  than  the  cuneatus.  The  fibres  of  these  three 
columns  end  here  in  a  manner  to  be  subsequently  described.  They  do  not  enter 
the  restiform  body,  which  does  receive,  on  the  contrary,  all  the  fibres  of  the  direct 
cerebellar  tract,  previously  mentioned.  The  "  widening-out "  of  the  medulla  in 
its  growth  explains  the  divergence  and  oblique  position  of  the  restiform  body,  as 
well  as  the  change  in  direction  of  the  dorso-lateral  groove,  which  separates  the 
restiform  body  from  the  olive,  and  out  of  which  emerge  the  fibres  of  origin  of 
the  seventh  to  the  eleventh,  inclusive,  cranial  nerves  (except  the  lateral  root  of 
the  eighth). 

External  Arciform  Fibres. — The  external  arciform  or  arcuate  fibres  are  seen 
on  all  three  surfaces  of  the  medulla.  They  are  small,  but  vary  in  number  in  dif- 
ferent medullse.  They  emerge  from  the  anterior  median  fissure,  between  the 
pyramids,  and  curve  doi'sally  on  both  sides.  They  pass  over  the  pyramid  and 
olive,  and  then  turn  upward  to  join  the  restiform  body.  In  doing  so  they  often 
conceal  from  view  the  upper  part  of  the  cuneate  and  Rolandic  funiculi.  Often 
these  fibres  are  collected  into  a  well-marked  bundle  which  crosses  inferior  to  the 
olive,  thus  obscuring  the  "lateral  tract"  and  portions  of  the  grooves  between 
the  pyramid,  olive,  and  restiform  body.  Sometimes  they  spread  out  over  the 
entire  surface  of  the  olivary  body. 

Internal  Structure. 

The  internal  structure  of  the  medulla  includes  that  of  the  whole  medulla — i.  e. 
its  various  surfaces,  already  described,  as  well  as  the  deep  portion  surrounded  and 
included  by  these  surfaces. 

The  deep  portion  is  divided  into  three  bilateral  areas,  separated  by  a  median 
raphe  or  septum,  each  of  which  is  known  respectively  as  the  anterior,  lateral,  and 
posterior  area  of  the  medulla,  and  each  of  which  corresponds  to,  or  may  be 
regarded  as  having  for  its  superficial  or  "  surface  "  aspect,  one  of  the  subdivisions 
of  the  surface  of  the  medulla.  Thus,  the  anterior  area  corresponds  to  one-half 
of  the  decussation  of  the  pyramids  and  to  the  pyramid  of  its  own  side ;  the  late- 
ral area,  to  the  olive  and  lateral  tract ;  the  posterior  area,  to  the  restiform  body, 
floor  of  fourth  ventricle,  and  the  four  small  columns  below — viz.  the  direct  cere- 
bellar tract,  the  funiculus  of  Rolando,  cuneatus,  and  gracilis.  These  areas, 
observed  in  transverse  sections,  are  seen  to  be  somewhat  wedge-shaped,  especially 
in  the  lower  half  of  the  medulla,  and  each  to  be  separated  from  the  adjacent  one 
by  a  line  of  nerve-jibres  running  dorso-ventrally  through  the  substance  of  the 
bulb  (Fig.  417).  Furthermore,  the  two  anterior  areas  have  between  them  the 
raphe,  while  the  two  posterior,  in  the  lower  half  of  the  medulla,  are  separated  by 
the  posterior  median  fissure.  The  nerve-fibres  referred  to  above  are  the  root- 
bundles  of  the  hypoglossal  nerve  on  the  one  hand,  and,  depending  on  the  level 
of  the  section,  of  either  the  seventh,  glosso-pharyngeal,  vagus,  or  spinal  acces- 
sory on  the  other ;  the  root-bundles  of  these  last  being,  of  course,  in  the  same 
perpendicular  plane.  These  fibres  are  all  proceeding  from  their  various  nuclei 
of  origin  in  the  dorsal  part  of  the  medulla,  to  emerge,  those  of  the  hypoglossal 


THE   BRAIN  AND    ITS  MEMBRANES. 


713 


between  the  pyramid  and  olive,  those  of  the  last-named  group  between  the  olive 
and  restiform  body.  It  is  thus  seen  that  these  fibres,  traced  dorsally,  are  right 
in  line  with  the  corresponding  groove,  ventro-lateral  and  dorso-lateral,  and  the 
similarity  between  the  methods  of  division  of  the  4>  deep  portion  "  of  the  medulla 
and  its  ••surface"  is  rendered  complete;  thus,  the  root-bundles  of  the  twelfth 
separate  the  anterior  and  lateral  areas,  while  those  of  the  seventh  (some  of  the 
eighth),  ninth,  tenth,  and  eleventh,  according  to  the  level,  run  between  the  lateral 
and  posterior  areas. 

Each  of  the  above  "areas  "  is  made  up  of  gray  and  white  matter,  the  former 
being  derived  in  part  from  that  of  the  cord.     The  latter  is  composed  of  fibres, 


yucleus  offuniculus  teres. 


yucleus  anting. 

Raphe- 
Formatio  reticuiaris 


Vagus  nuclei.        Ligula. 
Hypoglossal 


niculus  Soil/arms. 
Xucleus  gracilis. 


Continuation  of  antero-.- 
lateral  ground-bundle 


.Accessory  olivary  nuclei -f- 


'ucleus  citneahts. 


Corpus  restiforme. 


Nucleus  of  Rolando 

'Ascending  root  of 
fifth,  nerve. 


'agus  root. 

•Arciform  fibres. 
•^Nucleus  lateralis. 


ivary  nucleus. 

Hypoglossal  nerve, 
cleus  of  ext.  arc.  fibres, 
ternal  arciform  fibres. 
Anterior  median  fissure. 

FIG  417.— Section  of  the  medulla  oblongata  at  about  the  middle  of  the  olivary  body.    (Schwalbe.) 

some  longitudinal,  directly  continued  up  from  the  cord,  and  others  running  for 
the  most  part  transversely,  but  with  a  slight  dorso-ventral  curve,  and  intersecting 
the  preceding  ones.  Between  these  intersecting  fibres  are  scattered  the  various 
cells  and  nuclei  of  gray  matter  which,  together  with  their  processes,  form  a  net- 
work. This  network,  together  with  the  intersection  of  the  white  fibres,  gives  a 
reticular  appearance  to  cross-sections  of  the  medulla,  which  is  known  as  the 
for/r>af>"  rt'ti'.'iilaris. 

As  there  is  quite  a  difference  between  the  structure  and  appearance  of  both 
af'-'is  and  f«n/i<itio  reticuiaris  as  they  occur  in  the  upper  (ventricular)  or  lower 
(closed)  portion  of  the  medulla,  as  well  as  between  that  of  the  corresponding  sur- 

*.  it  will  be  more  convenient  to  describe  the  internal  structure  of  each  half 
of  the  medulla  separately. 

THE  LOWER  OR  CLOSED  PART  OF  THE  MEDULLA. — The  gray  matter  is  here 
more  directly  continuous  with  that  of  the  cord,  the  central  canal  of  which  is  still 
present,  but  placed  dorsally,  and  the  posterior  median  fissure  and  decussation  of 
the  pyramids  are  also  seen.  The  '"widening-out "  of  the  medulla  and  the  decus- 
sation of  the  crossed  pyramidal  tracts  of  the  cord  are  the  prime  factors  in  bring- 
ing about  the  following  changes  in  arrangement  of  the  gray  matter  as  compared 
to  that  of  the  cord  (see  Figs.  418,  419,  and  420).  The  anterior  cornu  (in  the 
cord)  is  broken  up  by  the  crossed  pyramidal  tract  passing  through  it  from  behind 
forward  and  inward  to  gain  the  pyramid  of  the  opposite  side.  The  caput  cornu 


714  THE  NERVOUS  SYSTEM. 

is  thus  separated  from  the  base,  and  becomes  pushed  over  laterally.     At  first  it  is 


Nucl.  gracilis 
Nucl.  cuneat., 

Cornu  post.~H 
Decussation^^. 

Cornu  ant. — ^f 

Pyramid 

FIG.  418.— Transverse  section  through  the  begin- 
ning of  the  medulla  X  \ .    (Gegenbaur.) 


Nucl.  gracilis 
Nucl.  cuneat.^ 

Cornu  post. 


FIG.  419.— Transverse  section  through  the  closed 
portion  of  the  medulla,  at  a  higher  level  than  the  pre- 
ceding X  f .  (Gegenbaur.) 


Pyramid 


Cornu  post. 
Eaphe 

Main  oli- 
vary nucleus 

XII. 

Accessory  olivary  nucleus 


FIG.  420.— Transverse  section  of  the 
medulla  at  the  junction  of  the  open  and 
closed  portions  X  f.  (Gegenbaur.) 


somewhat  distinct,  but  as  seen  in  sections  immediately  above  (Fig.  420)  it  rap- 
idly becomes  disintegrated,  as  it  were,  into  the  gray 
gracilis  matter  of  the  formatio  reticularis  of  the  anterior 

and  lateral  areas  (see  above).  The  base  of  the 
cornu  remains  as  a  portion  of  gray  matter  close  to 
the  ventro-lateral  aspect  of  the  central  canal.  The 
lateral  horn  (Fig.  417)  of  the  cord  is  also  somewhat 
isolated,  and  is  seen  in  the  lateral  area  near  the 
surface  as  the  nucleus  lateralis. 

The  posterior  cornu  (Figs.  418,  419,  420)  is 
changed  thus :  The  caput  of  the  posterior  horn 
becomes  enlarged,  and  gradually  shifted  outward, 
so  that  it  forms  a  rounded  mass,  which  produces 
the  prominence  on  the  surface  called  the  funiculus 
of  Rolando  and  its  tubercle.  The  neck  of  the  cornu 
diminishes  in  size,  and  is  broken  up  into  a  reticular  formation,  which  blends  with 
that  derived  from  the  anterior  cornu,  by  the  passage  of  longitudinal  and  trans- 
verse fibres  through  it,  so  that  the  caput  is  separated  from  the  rest  of  the  gray 
matter. 

Just  before  and  as  the  central  canal  expands  into  the  fourth  ventricle  the  base 
of  the  posterior  horn  of  gray  matter  is  pushed  outward  into  the  funiculus  cuneatus 
and  funiculus  gracilis ;  in  each  of  these  funiculi  it  forms  a  distinct  accumulation 
of  gray  matter,  constituting  the  nucleus  cuneatus  and  the  nucleus  gracilis.  These 
nuclei  may  be  regarded  as  helping  to  form  the  "formatio  reticularis  "  of  the  pos- 
terior area,  although  the  reticular  appearance  is  much  less  marked  than  in  the 
lateral  or  anterior  area.  On  the  surface  these  nuclei  produce,  respectively,  the 
cuneate  tubercle  and  clava.  A  small  portion  of  the  base  of  the  posterior  horn  is 
separated  from  the  remainder,  and  is  placed  lateral  to  the  cuneate  nucleus ;  it  is 
known  as  the  accessory  cuneate  nucleus,  probably  derived  from  Clarke's  vesicular 
column  (gray  matter)  of  the  cord.  Fibres  from  this  nucleus  run  to  the  restiform 
body. 

The  white  matter  of  the  closed  portion  of  the  medulla  is  made  up  of  white 
fibres,  some  collected  into  large  bundles  on  the  surface,  while  others  are  found  in 
the  formatio  reticularis.  The  latter,  being  directly  continued  upward  into  the 
fibres  of  the  formatio  reticularis  of  the  upper  or  open  portion  of  the  medulla, 
•will  be  taken  up  in  the  description  of  that  region. 
The  fibres  on  the  surface  : 

Of  these  the  decussation  of  the  pyramids,  the  "lateral  tract,"  and  direct 
cerebellar  tract  have  been  already  dwelt  upon.  They  will  again  be  referred  to, 
however,  in  connection  with  the  upper  part  of  the  bulb. 

The  funiculus  of  Rolando  is  due  to  the  enlarged  head  of  the  posterior  cornu  of 
the  gray  matter,  which  is  displaced  laterally  in  consequence  of  the  increase  in 
size  of  the  posterior  columns  of  the  medulla,  so  that  it  lies  almost  at  right  angles 


THE   BRAIN  AND    ITS  MEMBRANES. 


715 


to  the  posterior  median  fissure,  and  approaching  the  surface  forms  a  prominence 
which  is  covered  over  by  a  very  thin  layer  of  white  matter  derived  from  the 
funiculus  cuneatus.  Its  most  prominent  part  is  its  upper  end,  which  is  called 
the  tubercle  of  Rolando. 

The  funiculus  cuneatus  is  the  direct  continuation  upward  of  the  postero- 
lateral  column  of  the  cord  —  L  e.  its  white  fibres  are  derived  from  this  region  of 
the  cord.  The  fibres  end  in  the  gray  matter  which  forms  the  so-called  nucleus 
of  this  column  :  this  nucleus,  at  first  narrow,  gradually  enlarges,  and  produces, 
externally,  the  eminence  mentioned  above  as  the  tuberculum  cuneatum. 

The  funiculus  gracilis  is  the  direct  continuation  upward  of  the  posterior 
median  column  of  the  cord.  It  consists  entirely  of  white  fibres,  which  are 
continuous  with  those  of  this  region  of  the  cord.  Like  the  funiculus  cuneatus, 
its  fibres  end  in  its  so-called  nucleus,  which  produces  externally  the  prominence 
mentioned  above  as  the  clava. 

THE  UPPER,  OPEN,  OR  VENTRICULAR  PART  OF  THE  MEDULLA.  —  The  gray 
matter,  as  in  the  lower  part,  contributes  to  form  a  formatio  reticularis,  but  this 
is  confined  chiefly  to  the  anterior  and  lateral  "  areas."  In  the  posterior  "  area  " 
the  gray  matter,  dorsally,  is  found  to  consist  mainly  of  numerous  individual 
masses  of  cells  or  nuclei  scattered  among  fibres 
which  are  mostly  longitudinal,  while  ventrally  there 
is  a  small  amount  of  reticular  formation. 

There  are  also  other  individual  nuclei  found  in 
the  anterior  and  lateral  areas. 

Gray  Matter  of  the  Anterior  and  Lateral  Areas. 
—  This  is  chiefly  seen  in  the  formatio  reticularis, 
dorsal  to  the  pyramids  and  olives  (Figs.  417  and 
421).  It  is  practically  a  continuation  upward  of 
the  same  structure  in  the  closed  portion  of  the  bulb. 
In  the  anterior  area  the  nerve-cells  are  infrequent 
and  small  as  compared  with  those  in  the  lateral 
area,  Diving  a  whiter  appearance  on  section.  Hence 

,  p     i       />  i      •         v-    u   •     •      J.U 

that  part  of  the  formatio  reticularis  which  is  m  the 
anterior  area  is  called  the  formatio  reticularis  alba, 
while  that  of  the  lateral  area  is  known  as  the  formatio  reticularis  grisea.  Just 
anterior  to  the  latter  —  in  fact,  projecting  into  the  olive,  the  prominence  of  which 
it  produces  —  is  a  large  isolated  nucleus,  the  nucleus  of  the  olivary  body  (Figs. 
417.  420,  and  421).  This  is  really  a  hollow  capsule,  with  an  opening  or  hilum 
directed  toward  the  middle  line.  White  fibres  extend  into  and  proceed  out  of 
this  capsule  through  the  hilum,  constituting  the  so-called  olivary  peduncle.  On 
section  the  wall  of  this  capsule  is  seen  to  be  wavy  and  irregular  in  outline:  hence 
the  nucleus  is  often  called  the  corpus  dentatum  or  dentate  nucleus  of  the  olivary 
body.  Microscopically,  the  wall  of  the  nucleus  appears  to  be  made  up  of  neur- 
oglia,  in  which  are  placed  small  multipolar  nerve-cells.  From  the  surface  this 
nucleus  is  not  seen,  being  concealed  by  the  fibres  of  the  olive. 

In  addition  to  the  main  olivary  nucleus  there  are  two  accessory  olivary  nuclei 
(Fig.  417),  "inner"  and  "outer"  respectively.  The  former  is  in  the  anterior 
area,  dorsal  to  the  pyramid  ;  the  latter  in  the  lateral  area,  dorsal  to  the  main 
nucleus. 

Gray  Matter  of  the  Posterior  Area  (Figs.  417,  420,  and  421).  —  Inferiorly, 
close  to  the  lower  half  of  the  bulb,  are  seen  the  upper  ends  of  the  nuclei  of  the 
funiculus  cuneatus  and  gracilis.  The  bulk  of  this  gray  matter,  however,  is 
observed,  on  section,  to  consist  of  numerous  nuclei,  ventral  and  mesial  to  which 
is  a  small  area  of  reticular  formation. 

The  Nuclei  (Fig.  417).  —  It  must  be  remembered  that  the  region  now  being 
considered  is  just  ventral  to  the  floor  of  the  fourth  ventricle  and  the  restiform 
bodies.  In  other  words,  owing  to  the  "  widening-out  "  process  which  has  occurred 
in  this  part  of  the  medulla  the  posterior  "  area  "  has  dorsal  to  it,  laterally,  the 


Pyramid 


FIG.  421.—  Transverse  section  of  the 

upper  part  of  the  medulla  X  f.    (Ge- 


716  THE  NERVOUS  SYSTEM. 

restiform  bodies,  and  mesially  the  lower  half  of  the  floor  of  the  fourth  ventricle. 
It  is  therefore  more  convenient  to  regard  these  nuclei  in  their  relations  to  the 
floor  of  the  fourth  ventricle  and  the  restiform  body,  and  especially  to  the  former, 
as  there  is  practically  but  one  nucleus  in  relation  with  the  latter — viz.  the  fol- 
lowing :  Just  ventral  to  the  latter  is  the  end  of  the  gray  matter  of  the  tubercle 
of  Rolando,  showing  somewhat  indistinctly  as  a  rounded  mass  traversed  by  the 
root-bundles  of  the  vagus  (Fig.  417). 

Nuclei  in  Relation  to  Floor  of  Fourth  Ventricle. — As  before  stated,  in  the  closed 
portion  of  the  medulla  the  base  of  the  anterior  cornua  is  found  close  to  the  cen- 
tral canal,  on  its  ventro-lateral  aspect.  As  the  floor  of  the  canal  becomes  the 
floor  of  the  fourth  ventricle  in  passing  into  the  upper  part  of  the  medulla,  it 
necessarily  follows  that  this  gray  matter  is  shifted  still  more  dorsally  arid  comes 
to  lie  beneath  (ventral  to)  the  floor  of  the  ventricle  on  each  side  of  the  median 
groove.  In  this  gray  matter  is  a  column  of  large  nerve-cells  from  which  the 
roots  of  the  hypoglossal  nerve  arise.  Hence  these  cells  are  called  the  hypoglossal 
nucleus.  This  nucleus  extends  upward  to  the  pons,  and  is  covered  dorsally  by 
white  fibres,  which  are  known  as  the  funieulus  teres  (see  below,  floor  of  fourth 
ventricle).  In  these  fibres,  dorsal  and  mesial  to  the  hypoglossal  nucleus,  there 
is  also  a  smaller  group  of  cells,  the  nucleus  of  the  funieulus  teres,  from  which  fibres 
are  traceable  to  the  vago-glossopharyngeal  roots. 

The  remaining  nuclei  in  this  region  are  those  of  the  auditory,  glossopharyn- 
geal,  vagus,  and  spinal  accessory  nerves. 

The  Nucleus  of  the  Spinal  Accessory  Nerve. — This  group  of  cells  begins  in  the 
closed  part  of  the  medulla,  close  to  the  base  of  the  posterior  cornu,  and  extends 
upward,  lying  beneath  the  beginning  of  the  floor  of  the  fourth  ventricle,  and 
lateral  to  the  hypoglossal  nucleus.  Its  upper  extremity  reaches  to  the  eminentia 
cinerea  (see  below,  floor  of  fourth  ventricle).  This  is  the  nucleus  of  the  accessory 
part  of  the  nerve. 

Nuclei  of  the  Vagus  and  G-lossopharyngeal  Nerves. — These  are  known  as  prin- 
cipal and  accessory.  The  principal  nuclei  of  both  these  nerves  are  groups  of 
cells  practically  in  continuity  upward  with  the  nucleus  of  the  spinal  accessory 
nerve.  These  cells  lie  beneath  (ventral  to)  the  ala  cinerea  and  inferior  fovea  in 
the  floor  of  the  fourth  ventricle  (which  see),  that  of  the  ninth  being  above  the 
tenth. 

The  accessory  nuclei  are  the  upper  and  lower  portions  respectively  of  a  small, 
detached  pear-shaped  mass  of  gray  matter  (nucleus  ambiguus)  containing  nerve- 
cells,  which  is  found  in  the  reticular  formation  of  the  posterior  area  at  some  dis- 
tance from  the  floor  of  the  ventricle,  and  about  on  a  line,  ventrally,  with  the  ala 
cinerea.  Its  stalk  is  seen  to  extend  mesially  and  dorsally,  and  fibres  run  in  this, 
and  then  turn  outward  and  forward  to  join  the  main  bundles  of  their  respective 
nerves.  The  nucleus  of  the  funieulus  teres  (see  above)  is  also  an  accessory 
nucleus  of  these  nerves. 

Nuclei  of  the  Auditory  Nerve. — These  are  two,  dorsal  and  ventral.  The  dorsal 
nucleus  lies  external  to  the  vago-glossopharyngeal  nucleus  and  underneath  the 
trigonum  acoustici,  which  is  on  the  floor  of  the  ventricle  just  lateral  to  the  inferior 
fovea.  The  ventral  or  accessory  nucleus  lies  between  the  two  roots  of  the  auditory 
nerve  (which  see),  ventral  and  close  to  the  restiform  body ;  above,  in  the  pons, 
it  unites  with  the  ganglion  of  the  lateral  root,  which  in  this  region  is  found  mixed 
in  with  the  fibres  of  this  root  as  it  passes  around  the  restiform  body. 

The  white  matter  of  the  upper  part  of  the  medulla  is,  like  that  of  the  lower, 
found  on  the  surface  in  comparatively  large  bundles  of  fibres  and,  as  smaller 
bundles  or  even  as  individual  fibres,  in  the  formatio  reticularis  of  the  various 
"  areas  "  of  the  deep  portion. 

The  surface  fibres  are  those  of  the  pyramid,  the  olivary  body,  and  restiform 
body,  together  with  small  bundles  in  the  ventro-lateral  and  dorso-lateral  grooves. 

The  pyramid  has  already  been  described  in  discussing  the  ventral  surface  of 
the  medulla.  It  only  remains  to  state  here  that  its  fibres  all  proceed  directly 


THE   BRAIN  AND    ITS   MEMBRANES.  717 

upward  into  the  pons,  of  which  they  should  be  considered  a  part,  and  then  pass 
into  the  cms  cerebri  (mid-brain)  and  internal  capsule  (hemisphere)  of  the  same 
side  (Fig.  422). 

The  olivary  body,  due  to  the  projection  of  its  dentate  nucleus  (see  above),  has 
on  its  surface  (or  is  made  up  of)  longitudinal  fibres  continued  up  from  the  lateral 
tract  immediately  beneath  it.  The  fibres  of  this  lateral  tract  have  already  been 
traced  upward  from  the  cord.  Some  now  pass  upward  over  the  surface  of  the 
olive  to  its  upper  end,  where  they  dip  into  the  deep  portion  of  the  medulla  and 
join  the  fibres  from  the  lateral  tract,  which  have  already  passed  beneath  the  olive 


Superficial 
fibres  of  pons 
reflected. 


FIG.  422.— Superficial  dissection  of  the  medulla  oblongata  and  pons.    (Ellis.) 

(see  "  lateral  surface  "  of  medulla  for  this  and  paragraphs  immediately  preceding 
and  following). 

Fibres  in  the  Grooves. — Those  in  the  dorse-lateral  groove  are  the  continuations 
upward  of  the  antero-latcral  ascending  cerebellar  tract  (column  of  Gowers)  of  the 
cord.  At  the  upper  end  of  the  groove  they  dip  into  the  formatio  reticularis,  and 
pass  at  once  into  the  dorsal  part  of  the  pons.  Here  they  reach  the  corresponding 
superior  peduncle  of  the  cerebellum,  turn  backward  and  mesially  in  this,  and 
then  pass  into  the  superior  medullary  velum,  and  are  thus  continued  into  the 
white  matter  of  the  worm  or  middle  lobe  of  the  cerebellum. 

Those  in  the  vcntro-lateral  groove  on  reaching  its  upper  end  maybe  considered 
to  dip  into  the  formatio  reticularis,  and  then  bend  dorsally  over  the  top  of  the 
olive  to  join  the  fibres  of  the  restiform  body,  and  thus  reach  the  cerebellum. 
They  are  the  upward  prolongations  of  the  antero-lateral  descending  cerebellar 
tract  (column  of  Loewenthal)  of  the  cord. 

The  Restiform  Body. — As  before .  stated,  each  of  these  columns  is  the  largest 
tract  on  its  own  half  of  the  medulla,  and  receives  the  fibres  of  the  direct  cerebellar 
tract  (dorso-lateral  ascending  cerebellar  tract — Flechsig's  column),  the  antero- 
lateral  descending  cerebellar  tract  of  the  cord,  and  the  external  arciform  fibres. 
It  receives  also  other  bands  of  fibres  from  the  formatio  reticularls  of  the  medulla, 


718  THE  NERVOUS  SYSTEM. 

which  will  be  mentioned  below.  Each  restiform  body  passes  into  the  cerebellum 
(see  under  "  dorsal  surface  "  of  the  medulla),  and  is  therefore  known,  also,  as  the 
inferior  peduncle  of  the  cerebellum. 

The  white  fibres  of  the  deep  portion,  or  formatio  reticularis,  will  now  be 
described. 

Fibres  of  formatio  reticularis  in  both  closed  and  open  portions  of  the  medulla. 
— These  fibres  are  described  as  longitudinal,  transverse,  and  dorso-ventral.  The 
longitudinal  fibres  really  make  up  the  bulk  of  the  deep  portion  (ail  three  "  areas  ") 
of  the  medulla.  Most  of  them  come  directly  from  the  antero-lateral  ground  bundle 
of  the  cord,  while  others  are  derived  from  cells  in  the  gray  matter  of  the  formatio 
reticularis  itself.  They  are  all  more  or  less  directly  continued  upward  into  the  pons, 
and  thence  into  the  mid-brain  and  inter-brain.  All  of  them  have  by  no  means 
been  traced  definitely  from  origin  to  destination.  This  last  statement  is  equally 
true  of  the  transverse  and  dorso-ventral  fibres.  But  there  are  certain  bundles  in 
all  these  fibres  which  have  been  quite  clearly  made  out,  and  these  will  at  once  be 
described. 

Longitudinal  Fibres  of  the  Formatio  Reticularis. — In  each  anterior  area,  just 
dorsal  to  the  pyramid,  is  seen  on  section  a  well-marked  bundle  of  fibres.  This  is 
the  fillet,  or  lemniscus.  Traced  downward,  each  fillet,  at  about  the  level  of  the 
lower  end  of  the  pyramid,  bends  dorsally  and  mesially,  and  then  most  of  its  fibres 
decussate  across  the  middle  line  (raphe)  with  the  corresponding  fibres  of  the  oppo- 
site fillet,  and  proceed  to  the  cuneate  and  gracilis  nuclei  of  the  opposite  side,  in 
the  cells  of  which  they  terminate.  This  decussation  of  the  fillet  is  dorsal  to  and 
above  the  decussation  of  the  pyramids.  The  remaining  fibres  of  each  fillet  are 
traceable  downward  on  the  same  side  to — (1)  the  lateral  tract  of  the  medulla, 
and  thence  to  the  antero-lateral  ground  bundle  of  the  cord ;  (2)  a  few  fibres  run 
through  the  trapezium  of  the  pons  to  the  ventral  auditory  nucleus  of  the  opposite 
side. 

The  Posterior  Longitudinal  Bundle. — This  is  a  band  of  fibres  running  upward 
in  each  anterior  area  dorsal  to  the  fillet.  Below,  its  fibres  are  continued  directly 
into  the  "lateral  tract,"  and  thence  into  the  antero-lateral  ground  bundle  of  the 
cord.  Both  this  and  the  fillet  are  continued  upward  into  the  pons  and  mid-brain, 
where  their  final  distribution  will  be  described. 

In  the  lateral  area  the  longitudinal  fibres  do  not  appear  in  any  well-marked 
bundles.  Those  on  each  side  of  and  in  front  of  the  olive  have  been  described. 
Those  dorsal  are  merely  indeterminate  fibres  of  the  formatio  reticularis  or  belong 
to  the  internal  arciform  fibres  (see  page  719). 

In  the  posterior  area,  besides  the  indeterminate  fibres,  two  rather  distinct 
bundles  are  to  be  noted.  One  is  ihefuniculus  solitarius,  and  the  other  the  ascend- 
ing root  of  the  fifth  nerve. 

The  Ascending  Boot  of  the  Fifth  Nerve. — This  is  seen  on  section  (Fig.  417) 
to  lie  just  external  to  the  gray  matter  of  the  tubercle  of  Rolando  and  dorsal  to 
the  issuing  root-bundles  of  the  vagus.  Lower  down,  its  fibres  may  take  origin 
from  the  cells  of  the  tubercle  of  Rolando,  but  this  is  considered  doubtful. 
Passing  upward,  this  root  enters  the  pons,  and  contributes  most  of  the  fibres  of 
the  regular  sensory  root  of  the  fifth  nerve  (see  page  722). 

The  Funiculus  Solitarius. — This  lies  just  ventral  to  the  principal  nuclei  of  the 
vagus  and  glossopharyngeal  nerves.  It  is  round  on  section,  and  is  surrounded 
by  graj  matter.  Traced  downward,  this  bundle  gradually  disappears  ;  upward, 
its  fibres  join  with  the  roots  of  origin  of  the  ninth  and  tenth,  especially  the 
former.  It  may  thus  be  regarded  somewhat  as  an  "  ascending  root "  of  these 
nerves. 

Transverse  and  Dorso-ventral  Fibres. — The  transverse  fibres  are  found  chiefly 
in  the  formatio  reticularis  of  the  upper  half  of  the  medulla.  Of  these  the  most 
important — or,  rather,  those  which  have  been  more  or  less  definitely  traced — are 
known  as  external  and  internal  arciform  fibres. 

The  external  arciform  fibres  have  already  been  described  on  the  surface  of  the 


THE  BRAIN  AND    ITS  MEMBRANES.  719 

medulla  (see  page  712).  They  join  the  restiform  body,  and  emerge  from  the 
anterior  median  fissure.  Traced  backward  into  the  fissure,  they  enter  the  raphe, 
cross  over  the  median  line,  still  in  the  raphe,  and  then  bend  upward  and  become 
longitudinal,  after  which  their  course  is  not  traceable.  As  these  fibres  emerge 
from  between  the  pyramids  a  few  fibres  from  each  pyramid  are  said  to  join  with 
them.  As  they  pass  across  the  ventro-lateral  groove  and  olive  they  are  joined 
bv  some  of  the  internal  arciform  fibres  (see  below).  Scattered  amongst  these 
fibres,  or  between  them  and  adjacent  parts  of  the  medulla,  are  small  masses  of 
gray  matter  with  nerve-cells.  These  masses  are  the  nuclei  of  the  external  arci- 
form fibres.  The  largest  on  each  side  is  ventral  to  the  pyramid. 

The  Internal  or  Deep  Arciform  Fibres. — A  portion  of  these  have  already  been 
mentioned.  Traced  upward,  they  start  from  the  nuclei  of  the  gracilis  and  cuneate 
columns,  and  then  constitute  the  decussation  of  the  fillet  (see  page  718).  The 
remainder  of  the  internal  arciform  fibres  are  known  as  the  olivary  peduncle  (see 
page  715).  The  fibres  of  this  peduncle  decussate  across  the  median  line  (through 
the  raphe)  with  those  of  the  opposite  peduncle.  It  must  be  remembered  that 
this  peduncle,  as  a  whole,  is  really  a  lamina  of  superimposed  transversely  run- 
ning fibres,  and  not  the  mere  bundle  it  appears  to  be  on  section.  Traced  from 
one  side  to  the  other,  they  start  from  the  cells  in  the  gray  matter  of  the  olivary 
nucleus  (see  page  715),  and  pass  mesially  out  through  the  hilum.  They  then 
decussate,  as  above  mentioned,  with  the  opposite  peduncle,  and  enter,  through 
its  hilum,  the  opposite  olivary  nucleus.  Here  they  diverge  as  they  approach  the 
gray  lamina  of  the  nucleus,  and  proceed  in  different  directions,  after  passing 
through  the  lamina.  This  "passing  through"  the  lamina  is  not  true  for  all  the 
fibres,  for  some  end  in  the  nuclei,  which  in  their  turn  give  rise  to  new  fibres 
which  continue  the  course  of  the  old  ones.  On  "passing  through,"  then,  the 
lamina,  the  most  posterior  fibres  run  backward  through  the  lateral  area  and  join 
the  restiform  body,  and  thus  reach  the  cerebellum ;  the  uppermost  pass  upward  as 
longitudinal  fibres  in  the  formatio  reticularis  of  the  lateral  area  (see  page  718), 
and  have  been  traced  on  up  to  the  cerebral  hemisphere  of  the  same  side ;  the 
more  anterior  fibres  run  between  the  longitudinal  fibres  on  the  surface  of  the 
olive  or  between  those  in  the  grooves  on  each  side  of  the  olive,  and  there  bend 
backward  and  join  the  external  arciform  fibres,  and  are  continued  to  the  restiform 
body  and  cerebellum. 

The  Raphe. — The  raphe  is  situated  in  the  middle  line  of  the  medulla,  above 
the  decussation  of  the  pyramids.  It  consists  of  nerve-fibres  intermingled  with 
nerve-cells.  The  fibres  have  different  directions  which  can  only  be  seen  in  suitable 
microscopic  sections  ;  thus  : 

1.  Some  are  dorso-ventral ;  these  are  continuous  ventrally  with  the  superficial 
arciform  fibres,  and  dorsally  with  fibres  from  the  striae  acusticae. 

2.  Some  are  longitudinal ;  these  are  derived  from  the  arciform  fibres,  both 
sets,  which  on  entering  the  raphe  change  their  direction  and  become  longitudinal. 

3.  Some  are  oblique  ;  these  are  continuous  with  the  deep  arciform  fibres  which 
pass  from  the  raphe. 

Some  of  the  fibres  of  the  raphe  arise  from  the  nuclei  ventral  to  the  floor  of 
the  fourth  ventricle. 

THE  PONS  VAROLH  (Figs.  415,  416). 

The  pons  Varolii  is  the  ventral  portion  of  the  hind-brain,  the  dorsal  portion 
being  the  cerebellum.  The  pons  is  in  direct  continuity  below  with  the  medulla, 
all  the  longitudinal  fibres  of  each  being  directly  continuous  from  one  to  the 
other,  with  the  exceptions  of  the  restiform  bodies  of  the  medulla,  which  go  to  the 
cerebellum  (inferior  peduncles),  and  the  superior  peduncles  of  the  cerebellum, 
which,  as  will  be  seen,  belong  to  the  structure  of  the  pons,  after  they  leave  or 
before  they  enter,  according  as  they  are  traced,  the  cerebellum. 

The  pons  is  about  one  inch  long,  and  somewhat  more  in  width.  Dorso- 
ventrally,  it  is  about  three-fourths  of  an  inch  (17-18  mm.),  hence  its  thickness  is 


720  THE  NERVOUS  SYSTEM. 

greater  than  that  of  the  medulla.  There  are  four  surfaces  to  the  pons — superior, 
inferior,  ventral,  and  dorsal;  the  two  latter  are  free.  The  superior  and  inferior 
surfaces  are  seen  only  on  section,  the  former  being  attached,  by  direct  continuation 
of  fibres,  to  the  mid-brain,  while  the  latter  is  similarly  attached  to  the  medulla. 

The  ventral  surface  is  markedly  convex  from  side  to  side ;  it  rests  upon  the 
grooved  dorsal  surface  of  the  dorsum  sellce  of  the  body  of  the  sphenoid  bone.  It 
presents  along  the  middle  line  a  longitudinal  groove,  wider  in  front  than  behind, 
which  lodges  the  basilar  artery.  This  surface  consists  entirely  of  a  rather  thick 
layer  of  well-marked  transversely  running  fibres,  extending  across  the  median 
groove  from  side  to  side.  The  lowermost  fibres  slightly  overlap  the  upper  ends 
of  the  pyramids  and  cross  over  the  extreme  upper  end  of  the  anterior  median 
fissure.  The  uppermost  fibres,  similarly  but  to  a  greater  extent,  overlap  the 
lower  part  of  the  ventral  surface  of  the  mid-brain  (crura  cerebri  or  crustae). 
Hence  it  follows  that  this  surface  has  an  upper  and  lower  curved  free  margin, 
and  each  somewhat  rounded  and  distinct  from  the  medulla  on  the  one  hand  and 
the  crura  cerebri  on  the  other,  and  that  these  margins  have  nothing  to  do  with 
the  respective  attached  surfaces  of  the  pons.  Furthermore,  after  crossing  the 
middle  line  the  superior  fibres  bend  downward  and  the  inferior  upward.  The 
middle  fibres  are  exactly  transverse ;  hence  their  extremities  are  overlapped  by 
those  of  the  other  two  sets.  The  extremities  of  all  these  sets  of  fibres  are  seen, 
in  horizontal  section,  on  the  dorsal  aspect  of  the  pons,  and  they  here  form, 
together  with  other  transverse  fibres  coming  from  the  deep  part  of  the  pons,  a 
large  rounded  bundle  of  fibres  on  each  side,  which  is  directed  dorsally  into  the 
cerebellum,  and  is  known  as  the  middle  peduncle  of  the  cerebellum  of  the  corre- 
sponding side.  Owing  to  its  prominence  this  surface  is  often  called  the  tuber 
annulare. 

The  dorsal  surface  of  the  pons  is  almost  flat,  and,  though  free,  is  concealed 
from  above  by  the  cerebellum.  It  is  divided  into  a  mesial  and  two  lateral  por- 
tions. Each  lateral  portion  is  raised  up  somewhat  from  the  mesial,  and  is  seen 
to  be  a  rather  broad,  flat  band  of  white  fibres.  These  bands  are  not  parallel,  but 
.converge  from  below  upward.  Superiorly,  the  fibres  of  each  are  continued  into 
the  mid-brain ;  inferiorly,  they  pass  into  the  cerebellum.  These  bands  are  the 
superior  peduncles  of  the  cerebellum.  Besides  being  raised  from  the  mesial  por- 
tion, each  of  these  peduncles  overhangs  it  a  little  by  its  inner  margin.  Between 
the  inner  margins  of  these  peduncles  stretches  a  delicate  layer  of  Avhite  matter 
(valve  of  Vieussens)  roofing  over  the  following  : 

The  mesial  portion  of  the  dorsal  surface  of  the  pons  is  the  upper  half  of  the 
floor  of  the  fourth  ventricle.  Like  the  lower  half  (see  page  711),  it  is  triangular 
in  shape,  but  its  apex  is  upward.  Its  base  corresponds  to  that  of  the  lower  or 
medullary  half.  As  these  two  portions  of  the  floor  of  the  ventricle  run  into  each 
other  without  any  line  of  demarkation,  it  follows  that  the  entire  floor  of  the  fourth 
ventricle  is  rhomboidal  or  diamond-shaped.  The  widest  part  of  the  floor  is  the 
line  of  union  of  the  two  bases  of  the  triangles,  and,  if  this  line  is  continued 
ventrally,  it  will  be  found  to  run  close  along  the  lower  free  margin  of  the  tuber 
annulare  (ventral  surface  of  pons).  The  floor,  as  a  whole,  will  be  described  after 
the  description  of  the  pons  is  completed. 

Relations  of  the  Cerebellar  Peduncles  to  Each  Other. — If  the  cerebellum  be 
removed  from  the  pons  and  medulla  by  cutting  through  the  three  peduncles  on 
each  side  close  to  the  pons  and  medulla,  it  will  be  found  that  the  cut  ends  are 
all  grouped  together  in  an  area  immediately  external  to  the  widest  part  of  the 
floor  of  the  ventricle.  In  this  group  the  cut  end  of  the  middle  is  external  to  the 
cut  ends  of  the  superior  and  inferior  peduncles,  which  here  are  in  contact  (see 
Fig.  416). 

Deep  Portion  of  the  Pons. — This  is  comprised  between  the  dorsal  and  ventral 
surfaces.  It  is  made  up  of  both  longitudinal  and  transverse  fibres  and  gray 
matter.  The  longitudinal  and  transverse  fibres  in  each  lateral  half  of  the  pons 
are  arranged  in  two  groups,  ventral  and  dorsal. 


THE   BRAIN  AND    ITS  MEMBRANES.  721 

The  ventral  longitudinal  fibres  are  placed  just  dorsal  to,  and  are  concealed 
from  below  by,  the  transverse  fibres  of  the  ventral  surface  just  described.  They 
are  the  direct  continuations  of  the  fibres  of  the  pyramid.  Each  of  these  pyram- 
idal bundles  soon  after  entering  the  pons  breaks  up  into  smaller  bundles  which 
are  intersected  by  certain  transverse  fibres  (see  below).  Superiorly,  they  are 
continued  upward  into  the  crusta  of  the  mid-brain.  These  fibres  lie  on  each  side 
of  the  middle  line,  and  cause  a  corresponding  bulging  of  the  tuber  annulare. 
Thus  is  produced  the  median  groove  (sulcus  basilaris)  for  the  basilar  artery.  As 
they  pass  upward  through  the  pons  these  fibres  are  somewhat  increased  in  number 
from  being  reinforced  by  fibres  derived  from  the  nerve-cells  in  the  ventral  trans- 
verse fibres  (see  below.). 

The  dorsal  longitudinal  fibres  are  separated  by  quite  an  interval  from  the  pre- 
ceding. This  interval  is  filled  in  by  transverse  fibres,  especially  the  trapezium 
(see  below).  They  are  continued  upward  from  the  formatio  reticularis  of  the 
medulla,  and  among  them  are  especially  to  be  noted  the  ascending  root  of  the  fifth 
nerve,  the  fillet,  and  the  posterior  longitudinal  bundle. 

The  Transverse  Fibres. — These  comprise  ventral  and  dorsal,  and  must  not  be 
confounded,  especially  the  former,  with  the  superficial  transverse  fibres  of  the 
ventral  surface  (tuber  annulare},  already  described.  These  transverse  fibres  now 
under  discussion  belong  to  the  "  deep  portion  "  of  the  pons,  dorsal  to  those  of  the 
ventral  surface. 

The  ventral  transverse  fibres  of  the  deep  portion  of  the  pons  intersect  the 
bundles  of  the  pyramidal  fibres  (see  above),  and  then  curve  dorsally  and  join 
with  those  of  the  ventral  surface  to  make  up  the  middle  peduncle  of  the  cerebellum. 
These  transverse  fibres,  taken  together,  form  a  much  thicker  layer  than  the  super- 
ficial set,  and  contain  much  gray  matter  between  them.  Across  the  median  line, 
intersecting  or  dorsal  to  the  pyramidal  bundle,  they  meet  and  interlace  with 
those  coming  from  the  opposite  side.  Furthermore,  all  of  these  fibres  do  not  join 
the  middle  peduncle,  many  of  them  joining  the  nerve-cells,  which  are  situated  in 
the  gray  matter  (nuclei  pontis)  of  this  layer.  From  these  cells  other  fibres  are 
given  off  which  proceed  to  the  pyramidal  bundles  (see  above). 

The  dorsal  transverse  fibres  of  the  deep  portion  of  the  pons,  especially  in  its 
lower  half,  are  collected  into  a  distinct  mass  called,  from  its  shape,  the  trapezium. 

The  trapezium  is  situated  just  dorsal  to  the  pyramidal  bundles,  and  its  fibres 
proceed  laterally  on  each  side,  tapering  as  they  go,  until  they  reach  the  cells  (with 
which  they  become  connected)  of  the  accessory  (ventral)  auditory  nucleus  (Fig.  488), 
and,  through  this,  the  lateral  root  of  the  auditory  nerve.  Some  of  the  fibres  of  the 
trapezium  are  connected  with  the  cells  of  the  superior  olivary  nucleus  (see  below), 
which  lies  just  dorsally  on  each  side,  and  others  pass  to  the  fillet. 

The  Septum  or  Raphe. — This  is  the  upward  prolongation  of  the  medullary 
raphe.  It  is  found  in  that  portion  of  the  pons  which  is  dorsal  to  the  trapezium, 
and  does  not  extend  to  the  ventral  surface  except  at  the  upper  and  lower  extrem- 
ities of  the  pons.  At  these  places  certain  of  the  raphe  fibres  pass  out  of  the 
median  line,  and  then  bend  laterally  to  join  with  and  become  part  of  the  upper 
and  lower  margins,  respectively,  of  the  tuber  annulare.  It  follows,  therefore 
(see  page  720),  that  some  of  the  fibres  of  the  upper  margin  of  the  tuber  annulare 
actually  encircle  the  corresponding  crus  cerebri. 

The  Gray  Matter  of  the  Pons. — This  may  be  arranged  as  follows : 

(a)  The  nuclei  pontis,  which  are  small  masses  of  gray  matter,  containing  small 
multipolar  nerve-cells,  found  scattered  between  the  bundles  of  the  ventral  trans- 
verse fibres  (see  above),  and  also  to   a  less  extent,  between  those  of  the  tuber 
annulare.     Some  of  the  fibres  of  the  latter  may  have  an  arrangement — i.  e.  inter- 
lacing and  taking  origin  from  these  nuclei — similar  to  that  already  described  as 
occurring  in  many  of  the  fibres  of  the  ventral  transverse  set. 

(b)  Gray  Matter  of  the  Formatio  Reticularis. — This  formatio,  as  before  stated, 
lies   dorsal   to  the   trapezium.     Its  gray   matter   comprises,    first,   its  own  gray 
matter — /'.  c.  small  reticularly  arranged  masses  with  nerve-cells,  exactly  similar  to 

46 


722  THE   NERVOUS  SYSTEM. 

those  of  the  formatio  reticularis  of  the  medulla.  Secondly,  and  more  important, 
a  group,  in  each  lateral  half,  of  much  more  distinct  nuclei,  some  of  which  are 
close  under  the  floor,  upper  half,  of  the  fourth  ventricle,  while  others  are  more 
deeply,  as  Avell  as  laterally,  situated.  These  distinct  nuclei  merit,  each,  a  separate 
description,  as  follows : 

The  Superior  Olivary  Nucleus. — This  is  a  mass  of  small  nerve-cells  situated 
just  dorsal  to  the  lateral  part  of  the  trapezium,  and  between  the  issuing  root- 
bundles  of  the  sixth  and  seventh  cranial  nerves.  Its  structure  is  similar  to  that 
of  the  inferior  olivary  nucleus  of  the  medulla,  though  it  has  not  the  capsular 
form  of  the  latter  (see  p.  715).  Its  cells  give  origin  to  some  of  the  fibres  of 
the  trapezium  (see  p.  721),  and  these  fibres,  crossing  the  median  line,  pass  to  the 
accessory  auditory  nucleus  of  the  opposite  side  (see  p.  721). 

The  remaining  "  distinct  "  nuclei  are  those  of  various  cranial  nerves  :  One  of 
these  forms  the  nucleus  of  the  sensory  root  of  the  fifth  nerve ;  a  second,  the 
nucleus  of  the  motor  part  of  the  same  nerve;  a  third,  the  nucleus  of  the  sixth 
nerve ;  and  a  fourth,  the  nucleus  of  the  facial  nerve.  The  nuclei  of  the  auditory 
nerve  are  also  prolonged  upward  into  the  pons. 

Nuclei  of  the  Auditory  Nerve. — The  dorsal  nucleus  (see  p.  716)  is  prolonged 
upward  into  the  pons,  beneath  the  upper  half  of  the  floor  of  the  ventricle,  where 
it  is  shifted  laterally  and  soon  tapers  away.  It  is  widest  at  the  junction  betAveen 
the  pons  and  medulla.  The  ventral  or  accessory  nucleus  lies  entirely  external  to 
the  floor  of  the  ventricle,  and  rather  deeply  in  the  formatio  reticularis  of  the 
pons.  Extremely  dorsal  to  it  is  the  upper  end  of  the  corresponding  inferior 
peduncle  (restiform  body)  of  the  cerebellum.  It  is  the  united  accessory  auditory 
nucleus  of  the  medulla  and  nucleus  of  the  lateral  auditory  root  (see  p.  716). 

Nucleus  of  the  Facial  Nerve. — The  nucleus  of  the  seventh  or  facial  nerve  lies 
deeply  in  the  substance  of  the  formatio  reticularis  of  the  pons  just  dorsal  to  the 
superior  olivary  nucleus.  The  fibres  of  origin,  of  the  facial  nerve  proceed  from 
this  nucleus  dorsally  and  mesially  until  they  are  close  under  the  floor  of  the  ven- 
tricle, where  they  are  collected,  on  each  side,  into  a  rounded  bundle.  This 
bundle  now  runs  upward  (ascending  part  of  the  root)  for  a  short  distance  close  to 
the  median  line,  having  beneath  it  the  nucleus  of  the  sixth,  and  then  makes  a 
sharp  bend,  ventro-laterally,  and  continues  its  course  in  this  direction  through  the 
substance  of  the  pons,  to  emerge  close  under  the  inferior  margin  of  the  tuber 
annulare  in  the  extreme  upper  end  of  the  dorso-lateral  medullary  groove. 

Nucleus  of  the  Sixth  Nerve. — This  is  situated  immediately  ventral  to  the  upper 
half  of  the  funiculus  teres  in  the  floor  of  the  ventricle.  It  is  external  to  and 
.beneath  the  ascending  root  of  the  seventh,  just  described.  The  fibres  of  origin 
of  the  sixth  nerve  proceed  from  this  nucleus  obliquely  ventrally  and  downward 
and  through  the  pons,  and  emerge  at  the  lower  margin  of  the  tuber  annulare  at  a 
point  corresponding  to  the  upper  end  of  the  ventro-lateral  medullary  groove  close 
to  the  pyramid. 

Nuclei  of  the  Fifth  Nerve. — The  motor  nucleus  is  higher  up  in  the  pons 
than  the  nucleus  of  the  seventh  nerve,  but  is  about  on  the  same  line.  It  is, 
furthermore,  nearer  the  surface  of  the  floor  of  the  ventricle,  being  just  ventral 
to  the  lateral  margin  of  the  latter.  The  sensory  nucleus  is  larger  than  the  motor 
and  lies  to  its  outer  side.  It  would  therefore  lie  beneath  the  superior  peduncle 
of  the  cerebellum,  and  be  outside  of  the  limits  of  the  floor  of  the  ventricle.  The 
cells  of  this  nucleus  are,  however,  smaller  than  those  of  the  motor.  Special  fibres 
are  seen  to  pass  from  each  of  these  nuclei  to  the  raphe  of  the  pons,  but  the  reg- 
ular fibres  are  those  of  the  root-bundles  of  the  motor  and  sensory  roots,  respect- 
ively, of  the  fifth  nerve.  These  root-bundles  proceed  ventrally  and  somewhat 
laterally  through  the  substance  of  the  pons,  and  emerge  on  the  surface  of  the 
tuber  annulare,  nearer  its  superior  than  its  inferior  margin,  and  having  between 
them  some  of  its  transverse  fibres.  All  the  fibres  of  each  of  these  roots  do  not 
come,  however,  from  its  respective  nucleus,  for,  if  traced  inward  or  dorsally, 
each  root  is  seen  to  divide,  just  before  reaching  its  nucleus,  into  two  bundles,  the 


THE   BRAIN  AND   ITS  MEMBRANES.  723 

smaller  of  which,  in  each  case,  goes  to  the  nucleus,  while  the  other  takes  a  dis- 
tinct course,  differing  for  the  two  roots,  thus:  The  "non-nuclear"  division  of  the 
motor  root  passes  upward  as  a  distinct  bundle  through  the  dorsal  part  of  the  pons 
and  into  the  mid-brain,  where  its  fibres  terminate  in  a  group  of  large  nerve-cells 
situated  in  the  gray  matter  on  the  side  of  the  aqueduct  of  Sylvius.  This  is  the 
so-called  descending  root  of  the  fifth  nerve  The  "non-nuclear"  division  of  the 
sensory  root  is  the  so-called  ascending  root  of  the  fifth  nerve,  already  sufficiently 
described. 

Floor  of  the  Fourth  Ventricle  (Fig.  423). 

A?  already  stated,  the  floor  of  the  fourth  ventricle  is  made  up  of  the  mesial 
portions  of  the  dorsal  surfaces  of,  the  pons  Varolii  above  and  upper  half  of  the1 
medulla  oblongata  below.     It  is  lozenge-  or  diamond-shaped ;    that  is  to  say,  it  is 
composed  of  two  triangles,  with  their  bases  opposed  to  each  other.     Hence  it  is 
often  called  the  fossa  rhomboidaUs. 

The  lower  triangle  is  formed  by  the  divergence  of  the  clavae  of  the  funiculi 
graciles  and  the  restiform  bodies.     These  columns  pass  upward  and  outward  at  an 

Pnst.  corp.  quad. 

Wge  •-••• ' 

sup.  ped.  of  cerdt. 

ip.Jovea 


^ 

Fun.  tun. 
Fun.grac. 

FIG.  423.— Floor  of  the  fourth  ventricle.    (Henle.) 

acute  angle,  leaving  by  their  divergence  a  triangular  space  which  forms  the  lower 
half  of  the  floor  of  the  fourth  ventricle.  In  like  manner  the  upper  triangle  is 
formed  by  the  divergence  of  the  superior  peduncles  of  the  cerebellum.  These, 
traced  downward,  as  they  emerge  from  beneath  the  corpora  quadrigemina  of  the 
mid-brain,  are  almost  in  ontact  by  their  inner  margins,  but  they  gradually 
diverge,  passing  downward,  backward,  and  outward,  to  reach  the  cerebellum,  thus 
enclosing  a  triangular  space  which  forms  the  upper  half  of  the  floor  of  the  fourth 
ventricle. 

The  floor  presents  four  angles.  The  upper  angle  reaches  as  high  as  the  upper 
border  of  the  pons ;  it  presents  the  lower  opening  of  the  aqueduct  of  Sylvius,  by 
which  this  ventricle  communicates  with  the  third  ventricle.  The  lower  angle  is 
the  angle  of  divergence  of  the  clavse,  and  is  about  on  a  level  with  the  lower 
end  of  the  olivary  body.  It  presents  a  minute  opening,  the  aperture  of  the 
central  canal  of  the  spinal  cord. 

The  two  lateral  angles  are  situated  each  at  an  end  of  the  conjoined  bases  of 
the  triangles.  The  distance  between  them  is  the  widest  part  of  the  floor.  Each 
lateral  angle  is  also  the  point  of  the  "coming  together  "of  the  superior  and 
inferior  peduncle  (restiform  body)  just  as  they  pass  into  the  cerebellum. 

In  the  median  line  of  the  floor  is  a  longitudinal  groove  which  extends  between 


724  THE   NERVOUS   SYSTEM. 

the  upper  and  lower  angles.  From  the  fancied  resemblance  in  the  combined 
lower  end  of  this  groove  and  lower  angle,  to  the  nib  of  a  writing  pen,  this  lower 
angle  has  been  named  the  calamus  scriptorius. 

On  jeach  side  of  the  median  fissure  are  two  spindle-shaped  longitudinal  emi- 
nences, the  fasciculi  or  funiculi  teretes;  they  extend  the  entire  length  of  the  Moor. 
Each  eminence  consists  of  Avhite  fibres,  and  is  due  to  a  portion  of  the  base  of  the 
anterior  cornu  of  gray  matter  of  the  cord  which  comes  to  the  surface  of  the  floor 
of  the  fourth  ventricle  after  the  central  canal  of  the  spinal  cord  has  opened  out 
into  this  cavity,  This  gray  matter  of  the  "base  of  the  anterior  cornu"  now 
constitutes  the  nuclei  of  origin  of  the  hypoglossal  and  sixth  cranial  nerves.  The 
white  fibres  of  the  funiculus  teres  are  partially  those  of  the  "  ascending  part "  of 
*the  root  of  the  seventh  nerve  (see  page  722)  and  those  of  the  formatio  reticularis 
of  the  posterior  "  area  "  of  the  medulla. 

The  widest  part  of  the  floor  of  the  ventricle  is  crossed  by  several  white  trans- 
verse lines,  linece  transverse?,  auditory  strice,  or  striae  acusticse ;  they  emerge  from 
the  posterior  median  fissure,  and,  passing  over  the  fasciculus  teres  of  the  same 
side,  some  of  the  fibres  enter  the  lateral  root  of  origin  of  the  auditory  nerve, 
while  others  may  be  traced  to  the  flocculus  of  the  cerebellum.  Ventrally.  through 
the  posterior  median  fissure,  these  fibres  are  traceable  to  the  raphe. 

Below  these  striae,  on  each  side,  and  external  to  the  fasciculus  teres,  is  a  little 
fossa,  called  the  fovea  inferior ;  while  above,  similarly  placed,  is  a  fossa,  called 
the  fovea  superior.  Extending  upward  to  the  top  of  the  ventricle  from  each 
superior  fovea  is  a  shallow  groove ;  this  groove  is  called  the  locus  coeruleus,  which 
presents  a  bluish  tint  through  the  thin  stratum  covering  it.  This  tint  is  due  to 
an  underlying  stratum  of  pigmented  nerve-cells  (substantia  ferruginea).  The 
locus  coeruieus  lies  along  the  extreme  lateral  limit  of  the  upper  half  of  the  floor  of 
the  ventricle,  and  hence  converges  upward  toward  its  fellow  of  the  opposite  side. 
It  is  slightly  overhung  by  the  inner  margin  of  the  cerebellar  superior  peduncle. 
Just  ventral  to  the  locus  coeruleus  in  the  substance  of  the  pons  is  the  motor 
nucleus  of  the  fifth  nerve  (see  page  722). 

The  fovea  inferior  is  the  depressed  apex,  which  is  directed  upward,  of  a  tri- 
angular area.  The  floor  of  this  triangular  area  is  darker  in  color  than  the  rest 
of  the  floor  of  the  ventricle;  hence  it  is  called  the  ala  cinerea.  The  base,  being 
elevated  in  consequence  of  the  depression  of  the  apex,  is  knoAvn  as  the  eminentia, 
cinerea.  The  triangular  area  itself,  as  a  whole,  including  inferior  fovea  (apex), 
ala  cinerea  (floor),  and  eminentia  cinerea  (base),  is  known  as  the  trigonum  vagi. 
Immediately  ventral  to  this  trigonum  is  the  nucleus  of  origin  of  the  vagus,  and 
at  the  apex  is  that  of  the  glossopharyngeal  nerve. 

Between  the  trigonum  vagi  and  the  mesial  groove  is  the  lower  half  of  the 
funiculus  teres.  This  is  triangular  in  shape,  its  base  turned  upward  toward  the 
striae  acusticae.  This  lower  half  of  the  funiculus  teres  is  the  trigonum  hypoglossi. 
Ventral  to  it  is  the  nucleus  of  origin  of  the  hypoglossal  nerve. 

Between  the  trigonum  vagi  and  the  restiform  body  is  another  triangular  area, 
whose  base  is  also  directed  upward,  and  across  which  the  striae  acusticae  pass. 
This  area  is  the  trigonum  acustici.  On  its  base  is  a  slight  eminence,  the  tuber- 
culum  acusticum.  Ventral  to  this  trigonum  and  tubercle  is  the  dorsal  nucleus  of 
the  auditory  nerv^. 

Between  the  superior  fovea  (above  the  striae  acusticae)  and  the  middle  groove  is 
the  upper  half  of  the  funiculus  teres.  Just  ventral  to  this,  but  not  close  to  the 
middle  line,  is  the  nucleus  of  origin  of  the  sixth  rferve,  while  the  superior  fovea 
itself  may  be  taken  as  indicating  the  position  of  the  nucleus  of  the  seventh  nerve> 
which,  however,  is  quite  deeply  situated  in  the  pons  (see  page  722). 

THE  CEREBELLUM. 

The  cerebellum,  together  with  the  pons  Varolii,  forms  the  hind-brain.  It  is, 
morphologically,  the  enormously  thickened  and  hjpertrophied  middle  portion  of 
the  brain-matter  forming  the  r.oof  of  that  part  of  the  brain-cavity  known  as  the 


THE   BRAIN  AND    ITS   MEMBRANES. 


725 


FIG.  424.— Diagram  showing  development 
of  cerebellum,  e:  A,  a.  simple  thickening  of 
the  roof;  B,  more  fully  advanced.  (Gegen- 
baur.) 


fourth  ventricle  (Fig.  424).   of  which  the  ventral  boundaries  are,   as  already 
described,  parts  of  the  dorsal  surfaces  of  the 
pons  and  medulla  (after-brain). 

The  Cerebellum  is  contained  in  the  inferior 
occipital  fossae.  It  is  situated  beneath  the  oc- 
cipital lobes  of  the  cerebrum,  from  which  it  is 
separated  by  the  tentorium.  In  form  the  cere- 
bellum is  oblong,  and  flattened  from  above 
downward,  its  great  diameter  being  from  side 
to  side.  It  measures  from  three  and  a  half  to 
four  inches  (10  centimetres)  transversely,  and 
from  two  to  two  and  a  half  inches  from  before 
backward,  being  about  two  inches  thick  in  the  centre  and  about  six  lines  at  the 
circumference,  which  is  the  thinnest  part.  It  consists  of  gray  and  white  matter : 
the  former,  darker  than  that  of  the  cerebrum,  occupies  the  surface ;  the  latter, 
the  interior.  The  surface  of  the  cerebellum  is  not  convoluted  like  the  cerebrum, 
but  traversed  by  numerous  curved  furrows  or  sulci,  which  vary  in  depth  at  dif- 
ferent parts,  and  separate  the  laminae  of  which  its  exterior  is  composed. 

Weight  of  the  Cerebellum. — Its  average  weight  in  the  male  is  5  ozs.  4  drs.  It 
attains  its  maximum  weight  between  the  twenty-fifth  and  fortieth  year,  its  increase 
in  weight  after  the  fourteenth  year  being  relatively  greater  in  the  female  than  in 
the  male.  The  proportion  between  the  cerebellum  and  cerebrum  is,  in  the  male, 
as  1  to  Si.  and  in  the  female,  as  1  to  8J.  In  the  infant  the  cerebellum  is  propor- 
tionately much  smaller  than  in  the  adult,  the  relation  between  it  and  the  cerebrum 
being,  according  to  Chaussier,  between  1  to  13  and  1  to  26 ;  by  Cruveilhier  the 
proportion  was  found  to  be  1  to  20. 

Main  Lobes  of  the  Cerebellum. — The  cerebellum  is  divided  into  three  large 
lobes,  a  middle  and  two  lateral.  The  middle  lobe  is  the  worm,  and  the  two  lateral 
are  the  hemispheres.  These  lobes  are  not  separable  from  each  other,  being  joined 
together  by  their  sides.  Hence  the  upper  surface  of  the  cerebellum,  as  a  whole, 


Dadfee— 


Lobuspott. 
in/eiw 

FIG.  425.— Upper  surface  of  cerebellum,  x  i-    (Gegenbaur.) 

is  the  upper  surfaces  of  the  two  hemispheres  connected  in  the  middle  line  by  the 
upper  surface  of  the  u-orm,  which  last  appears  as  a  slightly  elevated  narrow  ridge, 
about  1  centimetre  wide,  from  which  the  upper  surfaces  of  the  hemispheres  slope 
away  laterally  and  posteriorly,  and  are  therefore  flattened  or  slightly  concave 
(Fig.  425).  *The  inferior  surfaces  (Fig.  426)  of  the  hemispheres  are  markedly 
convex  both  from  before  backward  and  from  side  to  side.  In  the  middle  line  they 
partially  overlap  and  conceal  the  inferior  surface  of  the  tvorm  ;  but  on  separating 
them — which  can  be  done  to  a  certain  degree  without  tearing  any  tissue — the 
entire  inferior  surface  of  the  worm  is  brought  into  view.  This  is  far  more  dis- 


726 


THE  NERVOUS  SYSTEM. 


tinct  than  the  upper  surface,  and  has  on  each  side  of  it,  marking  it  off  from  the 
hemisphere,  a,  deep  groove  which  runs  antero-posteriorly.  The  inferior  surface  of 
the  worm  can  be  seen  as  a  whole  only  after  removal  of  the  pons  and  medulla. 
The  space  or  fossa  between  the  inferior  surfaces  of  the  hemispheres,  and  which  con- 
tains the  inferior  worm,  is  called  the  vallecula,  and  the  grooves  above  mentioned, 
one  on  each  side  of  the  lower  surface  of  the  worm,  are  known  as  the  sulci  vallec- 
ulce.  The  upper  or  anterior  part  of  the  vallecula  lies  dorsal  to  the  medulla,  and 
is  continued  upward  into  the  anterior  cerebellar  notch;  the  lower  or  posterior 


Sup.  Fed.  of  Cerebel. 
Mid.  Fed. 


Inf.  Fed. 


Great  Horiz.  Fissure 
FIG.  426.— Under  surface  of  the  cerebellum. 


part  contains  the  lower  portion  of  the  falx  cerebelli,  and  is  continued  into  the 
posterior  cerebellar  notch  (see  below). 

Although  in  the  adult  human  brain  each  hemisphere  is  much  larger  than  the 
worm,  still  the  latter  is  morphologically  the  more  important,  being  the  part  first 
developed  in  mammals,  and,  in  many  of  them  lower  than  man,  constituting  a  large 
median  lobe  quite  distinct  from  the  hemispheres.  Furthermore,  in  fishes  and 
reptiles  it  is  the  only  part  which  exists,  the  hemispheres  being  additions  and 
attaining  their  maximum  size  in  man. 

The  Notches  of  the  Cerebellum. — The  hemispheres  are  separated  in  front  in  the 
middle  line  by  a  deep  notch,  the  anterior  cerebellar  notch  (incisura  cerebelli  ante- 


Incimira 

cerebelli  posterior. 
FIG.  427. — Upper  surface  of  the  cerebellum. 


rior\  and  also  behind  (similarly)  by   a  smaller  notch,  posterior  cerebellar  notch 
ineisura  cerebelli  posterior]  (Fig.  427).     The  anterior  notch  is  much  wider,  and 


THE    BRAIN   AND    ITS   MEMBRANES.  727 

its  sides  are  much  more  curved,  than  those  of  the  posterior.  This  notch  is  really 
the  deeply  hollowed-out  "anterior  margin"  of  the  cerebellum.  It  lies  close  to  the 
pons  and'upper  part  of  the  medulla,  while  the  upper  edge  of  the  notch  extends  to 
or  encircles  the  posterior  pair  of  corpora  quadrigemina  of  the  mid-brain.  This 
edge  can  be  raised,  however,  and  then  can  be  seen  the  superior  cerebellar  pedun- 
cles and  valve  of  Vieussens  (see  below).  The  posterior  notch  is  free.  When 
within  the  cranium  it  contains  the  upper  part  of  the  falx  cerebelli.  The  sides  of 
each  notch  are  formed  by  the  respective  hemispheres,  while  the  bottom  of  each 
notch,  or  its  centre,  is  the  anterior  and  posterior  extremity,  respectively,  of  the 
worm, 

The  fissures  of  the  cerebellum  are  very  numerous  and  dip  deeply  into  its 
substance.  Of  these  the  largest  and  deepest  is  the  great  horizontal  fissure. 
This  passes  completely  around  the  cerebellum,  forming  its  circumference  as  it 
were,  and  its  plane  is  horizontal.  As  it  crosses  the  median  line,  in  front  and 
behind,  it  cuts  into  the  respective  extremities  of  the  worm,  and  splits  the  sides 
of  each  of  the  notches  as  well  (see  above).  Hence  this  fissure  divides  each  hemi- 
sphere and  the  worm  (the  entire  cerebellum)  into  an  upper  and  a  lower  half.  The 
edges  and  sides  of  this  fissure  are  everywhere  in  contact,  and  lined  by  gray  mat- 
ter, except  where  it  runs  across  the  anterior  cerebellar  notch,  where  its  edges, 
upper  and  lower,  are  separated  by  the  passage  between  them  of  the  u'hite  matter 
of  the  cerebellum. 

All  the  remaining  fissures  of  the  cerebellum  are  lined  by  gray  matter  ;  their 
edges  are  everywhere  in  contact,  and  they  all  terminate,  by  one  extremity  at  least, 
in  the  great  horizontal  fissure  (see  below  for  further  details  of  these  fissures). 

The  Worm. — This,  as  already  stated,  is  the  middle  lobe  of  the  cerebellum.  It 
has  an  upper  and  a  lower  surface,  and  two  extremities,  anterior  and  posterior. 
The  upper  surface  is  called  either  the  superior  vermiform  process  or  the  upper 

'/>  ;  and  the  lower  surface,  either  the  inferior  vermiform  process  or  the  lower 
Its  tides  are  attached  directly  to  the  mesial  sides  of  the  hemispheres,  and 
are  not  seen  except  on  section.  Each  extremity  is  divided  by  that  portion  of  the 
great  horizontal  fissure  which  dips  into  the  corresponding  notch  into  an  upper  and 
a  lower  half.  Hence  each  of  these  anterior  halves  is  the  anterior  extremity, 
respectively,  of  the  upper  and  lower  worm  ;  and  each  posterior  half  is,  similarly, 
the  posterior  extremity  of  the  corresponding  worm.  The  horizontal  fissure  does 
not  dip  into  the  extremities  of  the  worm  nearly  so  deeply  as  it  does  into  the 
im'!  rgin  of  the  hemispheres. 

Each  surface  of  the  worm,  or  the  upper  and  lower  worm  respectively,  is  sub- 
divided into  lobules  by  transversely  directed  fissures  which  are  continued  laterally 
into  and  across  the  corresponding  surfaces  of  the  hemisphere  to  the  margin,  where 
they  terminate  in  the  great  horizontal  fissure.  Hence  any  tAvo  of  these  fissures 
contain  between  them  a  lobule  of  the  upper  or  lower  worm  in  the  middle,  and, 
laterally,  a  portion  of  the  corresponding  surfaces  of  the  hemispheres.  These 
fissures  are  known  as  mler$0ftnl(ir  fissures. 

The  Hemispheres. — Each  hemisphere  has  a  side,  an  upper  surface,  a  lower  sur- 
face, and  a  margin.  The  side  of  each  is  directly  attached  to  the  corresponding 
side  of  the  worm.  The  margin  is  curved  and  extends  around  from  the  side  of 
the  posterior  extremity  of  the  worm  to  the  corresponding  side  of  the  anterior 
extremity  of  the  worm.  Hence  in  the  notches  this  margin  is  the  same  thing  as 
the  side  of  the  notch.  The  margins  of  both  hemispheres,  together  with  both 
extremities  of  the  worm,  contain  the  great  horizontal  fissure — /.  e.  the  upper  edge 
of  the  Jissure  is  made  up  of  the  anterior  extremity  of  the  upper  worm,  the  margin 
of  the  upper  half  of  one  hemisphere,  the  posterior  extremity  of  the  upper  worm, 
the  margin  of  the  upper  half  of  the  other  hemisphere.  The  lower  edge  of  the 
fissure  is  similarly  made  up. 

The  surfaces,  both  lower  and  upper,  are,  like  those  of  the  worm,  subdivided 
into  lobules  by  the  lateral  prolongations  of  the  interlobular  fissures,  already  men- 
tioned. On  the  upper  surface  of  each  hemisphere  these  fissures  are  disposed 


728  THE   NERVOUS   SYSTEM. 

quite  regularly  and  with  a  direction,  somewhat  curved,  concavity  forward,  which 
is  outward  and  forward.  On  the  lower  surface  the  interlobular  fissures  have  not 
such  a  regular  arrangement,  but  are  much  more  curved,  concavity  forward,  the 
curves  being  greater  in  those  placed  anteriorly. 

The  general  outline  of  each  surface  has  already  been  mentioned. 

UPPER  SURFACE  OF  WORM  AND  HEMISPHERES. — Each  of  these,  as  already 
stated,  is  subdivided  into  lobules  by  the  interlobular  fissures.  There  are  five 
lobules  and  four  fissures  on  the  upper  surfaces  of  the  worm  and  hemispheres, 
which,  from  before  backward,  are  as  follows  (Fig.  425)  : 

Lobules  of  superior  worm :  lingula,  lobulus  centralis,  culmen,  clivus,  folium 
cacuminis  ;  lobules  of  hemisphere  (upper  surface) :  frcenulum,  ala,  anterior  cres- 
centic lobule,  posterior  crescentic  lobule,  postero-superior  lobule. 

The  interlobular  fissures  are  the  precentral,  the  post-central,  the  preclival,  and 
the  post-clival. 

The  complete  arrangement  is  as  follows :  On  each  side  of  the  lingula  is  the 
frcenulum ;  these  three  lobules  are  separated  by  the  precentral  fissure  from  the 
lobulus  centralis  with  its  ala  on  each  side.  These  three  are  in  turn  separated  by 
the  post-central  fissure  from  the  eulmen,  with  the  anterior  crescentic  lobule  on  each 
side.  Posteriorly  to  these  is  the  preclival  fissure,  behind  which  are  the  clivus  and 
two  posterior  crescentic  lobules,  which  are  separated  by  the  post-clival  fissure  from 
the  folium  cacuminis  and  postero-superior  lobules,  and  these  last  are  limited  below 
by  the  great  horizontal  fissure. 

LOWER  SURFACE  OF  WORM  AND  HEMISPHERES. — The  lobules  of  each  of  these 
surfaces  are  four  in  number,  separated  by  three  fissures  (Fig.  426).  They  are, 
from  behind  forward,  as  follows : 

Lobules  of  inferior  worm :  tuber  valvulce,  pyramid,  uvula,  nodulus  ;  lobules  of 
hemisphere  (lower  surface) :  postero-inferior  lobule,  digastric  lobule,  amygdala  or 
tonsil,  flocculus. 

The  interlobular  fissures  are  the  post-nodular,  the  prepyramidal,  and  the  post- 
pyramidal. 

The  complete  arrangement  is  as  follows :  The  post-nodular  fissure  separates 
the  nodulus  and  the  two  flocculi  in  front  from  the  uvula  and  two  amyydalce 
behind ;  the  prepyramidal  fissure  lies  between  the  three  last-mentioned  lobules, 
and  the  pyramid  with  a  digastric  lobule  on  each  side,  which  in  their  turn  are  sepa- 
rated by  the  post-pyramidal  fissure  from  the  tuber  valvulce  and  postero-inferior 
lobules,  while  between  these  last  and  the  folium  cacuminis  and  postero-superior 
lobules  of  the  upper  surface  runs  the  great  horizontal  fissure,  which,  in  front,  also 
runs  between  the  lingula  and  nodulus  and  their  prolongations. 

LOBULES  OF  THE  CEREBELLUM. — As  above  mentioned,  each  group  of  three 
lobules  (central  of  the  worm,  lateral  of  the  hemispheres)  is  limited  either  by  two 
interlobular  fissures  or  by  one  such  fissure  and  a  portion  of  the  great  horizontal 
fissure.  Besides  these  there  are  other  smaller  fissures,  known  as  intralobular, 
which  also  run  more  or  less  transversely  and  cut  up  each  lobule  into  still  smaller 
subdivisions  or  lamince,  and  which  are  quite  irregularly  disposed,  especially  in  the 
hemisphere  lobules,  where  they  may  run  obliquely,  and,  many  of  them,  stop  short 
of  the  margin.  Furthermore,  the  lobules  vary  greatly  in  size  and,  on  the  under 
surface,  in  symmetry. 

The  structure  of  each  lobule  (Fig.  428)  is  seen,  on  an  antero-posterior  section, 
to  consist  of  white  matter  surrounded  by  an  irregular  margin  of  gray  matter,  these 
irregularities  or  indentations  being  due  to  the  intralobular  fissures ;  while  the 
interlobular  fissures  are  seen  to  be  deep  clefts  separating  the  lobules.  Hence  the 
cut  surface  of  each  lobule,  whether  of  worm  or  hemisphere,  looks  like  a  dentated 
leaf  or  folium,  the  branching  stems  of  which  are  white  matter,  and  the  mar<jiii* 
gray  matter ;  which  last  is  also  continued  from  lobule  to  lobule  at  the  bottom  of 
each  fissure  (see  also  page  734). 

On  the  other  hand,  should  the  cerebellum  be  sliced  from  side  to  side,  the  plane 
of  each  transverse  section  corresponding  as  nearly  as  possible  to  that  of  each  inter- 


THE   BRAIN  AND   ITS  MEMBRANES. 


729 


lobular  fissure,  it  would  appear  that  each  group  of  three  lobules  would  really  con- 
stitute a  single  lamina,  or  sheet,  of  white  matter  reaching  from  margin  to  margin 
of  the  cerebellum,  the  central  part  (worm)  being  more  prominent  than  the  lateral 
portions  (hemispheres);  while  from  each  surface  of  this  lamina  would  appear  pro- 
jecting ridges  also  of  white  matter,  the  entire  lamina  and  ridges  being  covered  by 


Tuber  ralv. 


Culmen  and 


Post.  corp.    / 
auad.        I 


nid 


quad. 


Sup.  med.  veL 


ffoduie 


FIG.  428. — Antero-posterior  median  section  of  the  worm.    (Henle.) 

gray  matter.     The  spaces  between  the  ridges  would  be,  of  course,  the  intralobular 
fissures. 

The  Lingula  and  Fraenula. — The  lingula  is  the  smallest  lobule  of  the  upper  worm 
{Figs.  428,  429,  430).  It  is  peculiar  from  all  the  other  lobules  in  that  its  cut 
surface  is  not  like  a  folium,  but  appears  merely  as  a  series  of  three  or  four 


Lob.  centralit 


Pyramid 


/.  ^7>;> 


Abdufe 
FIG.  429.— Antero-posterior  median  section  of  the  worm,  also  showing  fourth  ventricle,  X§-    (Gegenbaur.) 

small  elevations  on  the  dorsal  surface  of  a  layer  of  white  matter  (valve  of 
Vi-'U.itt'-ns).  which  is  here  emerging  from  the  middle  part  of  the  great  hori- 
zontal fissure  at  the  bottom  of  the  anterior  cerebellar  notch.  These  elevations 
are  white  matter  (derived  directly  from  the  valve  of  Yieussens)  covered  by  a 
layer  of  gray  matter  which  dips  in  between  them.  Posteriorly,  this  gray 
matter  is  continuous  with  that  of  the  central  lobule;  anteriorly,  it  disappears 
or  is  continued  merely  as  an  epithelial  layer  over  the  dorsal  surface  of  the  valve 
of  Yieussens. 

The  frcenula  (Fig.  430)  stretch  laterally  from  each  side  of  the  lingula.  They 
are  short,  not  reaching  beyond  the  superior  peduncles  of  the  cerebellum,  over 
which  they  lie.  Each  fnenulum  is  overlapped  considerably  by  the  ala. 

Lobulus  Centralis  and  Alae  i  Ficrs.  428.  429). — The  central  lobule,  though  of  good 
size,  is  much  smaller  than  the  culmen.  immediately  behind,  and  by  which  it  is 
overlapped.  It.  in  its  turn,  overlaps  the  lingula.  and  together  with  it  forms  the 
bottom  of  the  anterior  notch. 

The  airs  are  slender,  and  are  prolonged  almost  to  the  lateral  limits  of  the 
anterior  notch.  Hence  each  is  curved,  with  the  concavity  forward. 

Of  the  remaining  lobules  of  the  upper  surface  it  may  be  noted  that  the  culmen 


730 


THE  NERVOUS  SYSTEM. 


and  clivus  or  declive  are  each  very  large  as  compared  to  the  other  divisions  of  the 
upper  worm  (Figs.  425,  428,  429).  Taken  together,  they  constitute  the  bulk  of 
the  upper  worm,  and  are  the  only  parts  seen  in  the  natural  position,  for  the  cul- 
men  must  be  lifted  anteriorly  to  show  the  central  lobule,  and  the  clivus  posteriorly 


Sup.  med.  vd. 


Lingula 


FIG.  430.— Anterior  part  of  cerebellum  from  above.    The  central  lobule  and  alse  are  drawn  backward  to  dis- 
close lingula.    (Henle.) 

to  show  the  folium  cacuminis.  On  antero-posterior  section  each  appears  as  made 
up  of  a  number  of  secondary  folia  with  well-marked  intralobular  fissures.  The 
term  monticulus  is  often  applied  to  the  combined  culmen  and  clivus.  The  cres- 
centic  lobules,  anterior  and  posterior,  or  lunate  lobules,  are  large  and  have  numerous 
intralobular  fissures.  Taken  together,  on  each  side  they  constitute  the  so-called 
quadrate  or  quadrangular  or  square  lobule.  The  anterior  crescentic  overlaps  the 
ala  and  reaches  to  beyond  the  lateral  limits  of  the  anterior  notch.  The  folium 
cacuminis  (see  also  Fig.  431)  is  smaller  than  any  of  the  lobules  of  the  upper  worm 


Oudmen     Folium  cacuminis 

Post,  cresc.  lob. 


Tuber  valvulse 


Postero-sup.  lobe 


Pyramid  ^Digastric  lobe 

FIG.  431.— The  cerebellum  from  behind.    (Henle.) 


except  the  lingula.  Its  cut  surface  looks  like  a  single  leaf  or  folium.  Its  lateral 
prolongations,  however,  the  postero-superior  lobules  (superior  semilunar),  are  large, 
each  being  fully  as  large,  and  beset  with  as  many  intralobular  fissures,  as  either 
of  the  crescentic  lobules. 

Tuber  Valvulae  and  Postero-inferior  Lobules  (Fig.  431).— The  tuber  valvulce  is 
the  posterior  extremity  of  the  inferior  worm.  It  is  decidedly  larger  than  the 
folium  cacuminis,  and  its  cut  surface  shows  at  least  one  secondary  folium  in  addi- 
tion to  that  of  its  own  cut  surface.  Its  point  of  junction,  on  each  side,  with  the 
postero-inferior  lobule  is  slightly  grooved.  This  groove  is  the  posterior  extremity 


THE  BRAIN  AND   ITS  MEMBRANES. 


731 


of  the  corresponding  sulcus  valleculce  (see  above),  which  deepens  as  it  runs  for- 
ward along  the  side  of  the  inferior  worm.  The  postero-inferior  lobule  is  as  large, 
taken  as  a  whole,  as  the  larger  lobules  of  the  upper  surface  of  the  hemisphere. 
It  resembles  them  also  in  general  appearance,  except  that  it  is  much  more  convex 
and  its  intralobular  fissures  are  very  large.  These  fissures  are  also  considerably 
more  curved,  concavity  forward,  than  those  of  the  upper  surface.  Two  of  them 
are  of  especial  depth  ;  hence  the  postero-inferior  lobule  is  often  described  as  being 
made  up  of  three  subdivisions,  the  most  posterior  being  called  the  inferior  semi- 
lunar  lobule  ;  the  middle  one,  the  posterior  slender  lobule  ;  and  the  anterior,  the 
anterior  slender  lobule  (lobuli  graciles).  In  examining  the  mesial  extremities  of 
these  "  sublobules  "  it  is  found  that  only  that  of  the  inferior  semilunar  actually 
joins  with  the  tuber  valvulse,  while  those  of  the  other  two  terminate  abruptly  in 
the  sulcus  valleculse,  and  do  not  join  with  any  lobule  of  the  inferior  worm. 

Central  lobule 

.Sup.  med.  velum 

Sup.  cerebel.  ped. 
Module 


Mid.  cerebel.  ped. 
Inf.  cerebel.  ped. 
(the  inf.  velum  is  seen 
just  beyond  the  end 
>f  the  line). 


Post.-sup. 
fofetfa 


Cut  surface 
of  flocculus 


Cut  surface  of 
part  of  mid.  ped. 


Digastric  lobe  \plocculus 
Amyqdala     (mesial  to  the 
Ime) 


FIG.  432.— The  cerebellum  from  in  front,  with  pens  and  medulla  removed.    (Henle.) 


Therefore  the  post-pyramidal  fissure  (see  above)  is  prolonged,  on  the  hemisphere, 
in  front  of  the  anterior  slender  lobule. 

Pyramid  and  Digastric  Lobules  (Figs.  432,  433 ;  also  preceding  ones). — The 
pyramid  is  a  large  laminated,  somewhat  conical  projection.     Its  cut  surface  shows 


Cut  surface  of 
mid. 


Sup.  velum       Kbdulug 


Inf.  velum 


Vvula 


Pott,  pyram.        Hollow  after  removal 

oj "tonsil  TOnsU 

FIG.  433.— The  cerebellum  from  in  front  and  below.    (Henle.) 


numerous  intralobular  fissures.  On  each  side  of  it  is  the  sulcus  valleculae,  here 
quite  deep,  and  it  is  connected,  across  this  sulcus,  with  the  digastric  lobule  by 
means  of  a  narrow  connecting  ridge  of  gray  matter. 

The  digastric  (biventral)  lobule  (see  also  Fig.  434)  is  triangular  in  general  out- 


732 


THE   NERVOUS  SYSTEM. 


line,  with  the  apex  at  the  "  connecting  ridge  "  just  mentioned.  Its  laminae  or  subdi- 
visions, due  to  its  intralobular  fissures,  are  curved,  concavity  forward  and  inward, 
but  short,  and  tend  more  antero-posteriorly  ;  hence  the  lobule  is  embraced  pos- 
teriorly by  the  anterior  slender  lobe  and  post-pyramidal  fissure,  both  of  which  are 
decidedly  concave,  while  the  laminae  of  the  former  are  much  longer  than  those 
of  the  digastric  lobule.  The  base  is  anterior,  and  is  on  a  line  with  the  ante- 
rior extremity  of  the  amygdala,  and  is  separated  from  the  flocculus,  just  in 
front,  by  the  prolongation  of  the  post-nodular  fissure.  Mesially  the  digastric 
lobule  is  separated  from  the  amygdala  by  the  prepyramidal  fissure,  which  on 
the  hemisphere  runs  almost  antero-posteriorly,  while  on  the  inferior  worm  it  is 
transverse. 

Uvula  and  Amygdalae  (Fig.  434  and  those  preceding).  —  The  uvula  is  longer 
than  the  pyramid.     It  is  more  prominent  posteriorly  than  anteriorly.     It  has 


Sup.  med.  vel. 
Lob.  centr. 


•  cerebel.  ped. 


Nodulus      Uvula  Horizontal  fissure 

FIG.  434.— The  cerebellum  from  in  front  and  somewhat  from  below,  X  §.    (Gegeiibaur.) 

three  or  four  well-marked  transversely  running  intralobular  fissures,  clearly  seen 
on  antero-posterior  section.  It  is  connected  Avith  the  amygdala  on  each  side  by 
means  of  a  corrugated  ridge  of  gray  matter,  the  furrowed  band,  which  lies  in  the 
sulcus  valleculse.  The  amygdala  or  tonsil  is  a  rounded  mass  smaller  than  the 
digastric  lobule.  It  has  a  large  number  of  intralobular  fissures  and  laminae. 
These  last  are  short  and  directed  sagittally.  Externally  is  the  prepyramidal  fis- 
sure, between  it  and  the  digastric.  On  removal  of  the  amygdala  a  marked  hol- 
low (Fig.  433)  is  seen  on  the  mesial  side  of  the  digastric.  This  hollow  is  the 
nidus  avis  (bird's  nest).  Internally,  the  amygdala  is  connected  to  the  uvula  by 
the  furrowed  band,  and  besides  has  a  free  surface  bounded  by  the  sulcus  valleculse. 
In  the  natural  position  this  surface  is  applied  closely  to  the  side  of  the  uvula, 
which,  together  with  that  of  the  opposite  tonsil,  it  conceals  from  view.  Ante- 
riorly is  the  post-nodular  fissure. 

Nodulus  and  Flocculi  (Figs.  426-434). — The  nodule  is  the  most  anterior  as 
well  as  the  smallest  lobule  of  the  lower  worm.  Its  cut  surface  shows  a  single 
folium  indented  by  a  few  intralobular  fissures.  It  is  larger  than  the  lingula. 
Its  white  matter  is  usually  a  single  stem,  which  branches  peripherally.  This 
stem,  furthermore,  like  the  small  projections  of  white  matter  in  the  lingula  (see 
page  729),  which  are  derived  from  the  valve  of  Vieussens,  is  seen  in  its  turn  to 
come  from  a  similar,  but  more  curved,  lamina  of  white  matter  which  lies  at  first 
ventral  and  anterior  to  the  nodulus,  and  then  dorsally  or  over  it.  This  lamina  is 
the  inferior  medullary  velum  (see  below).  The  sulcus  valleculae  on  each  side  of 
the  nodulus  is  deep  and  wider  than  it  is  posteriorly. 

The  post-nodular  fissure,  transverse  between  nodule  and  uvula,  becomes  irreg- 
ularly curved  on  the  hemisphere.  On  leaving  the  worm  it  is  at  first  concave  for- 
ward in  the  sulcus  valleculse,  then  bends,  convexity  forward,  around  the  front  of 
the  amygdala  and  runs  laterally,  between  the  base  of  the  digastric  lobe  behind 
and  the  flocculus  in  front,  to  terminate  in  the  great  horizontal  fissure.  In  its 
course  it  receives  the  anterior  end  of  the  prepyramidal  fissure,  and  at  its  termi- 
nation in  the  horizontal  fissure  is  joined  by  the  anterior  end  of  the  post-pyram- 


THE   BRAIN  AND    ITS  MEMBRANES.  733 

idal  fissure.  As  it  lies  in  the  sulcus  valleculae  it  separates  the  furrowed  band 
from  a  very  slender  lamina  of  gray  matter  which  is  continuous  with  the  gray 
matter  of  the  nodule  mesially,  and,  laterally,  follows  the  course  of  the  post- 
nodular  fissure  until  it  reaches  the  flocculus,  with  the  gray  matter  of  which  it  is 
continuous.  This  slender  lamina  is  known  as  the  peduncle  of  the  flocculus. 

The  flocculus  is  the  smallest  of  the  lobules  of  the  inferior  surface  of  the 
hemisphere,  and  is  situated  farther  away  from  its  corresponding  lobule  of  the 
inferior  worm  than  any  of  the  others.  It  is  a  rounded,  tuft-like  body,  its 
expanded  extremity  looking  forward,  and  it  tapers  toward  its  peduncle.  It  is 
situated  below  the  middle  peduncle  of  the  cerebellum ;  its  surface  is  composed  of 
gray  matter,  subdivided  into  a  few  small  laminae ;  it  is  sometimes  called  the 
pneumogastric  lobule,  from  being  situated  behind  the  pneumogastric  nerve. 

It  is  thus  seen  that  the  flocculus,  amygdala,  and  digastric  lobule  differ  in 
regularity,  both  of  outline  and  position,  from  all  the  other  lobules  of  the  hemi- 
sphere ;  also  that  the  prepyramidal  fissure  differs  from  the  other  interlobular  fis- 
sures in  that  it,  as  a  whole,  is  almost  "horseshoe"  in  shape,  while  they  have  a 
generally  transverse  direction. 

WHITE  MATTER  OF  THE  CEREBELLUM. — Traced  from  within  the  cerebellum, 
all  the  white  matter  is  found  to  emerge  from  between  the  edges  of  the  great  hori- 
zontal Ussure.  where  that  fissure  lies  in  the  anterior  cerebellar  notch  (Figs.  432, 
433,  434).  It  may  be  described  (after  removal  of  pons  and  medulla  by  cutting 
close  to  the  cerebellum)  as  consisting  of  two  layers,  an  upper  and  a  lower.  In 
other  words,  this  white  matter  on  emerging  from  the  cerebellum  may  be  said  to 
split  into  two  diverging  layers.  The  cleft-like  space  between  these  two  layers 
extends  entirely  across  the  anterior  cerebellar  notch,  at  the  lateral  extremities  of 
which  the  two  layers  are  continuous.  It  has  already  been  noted  (see  page  727), 
that  the  edges  of  the  great  horizontal  fissure,  in  close  contact  everywhere  else, 
are  separated  in  the  anterior  notch.  Hence  the  space  between  the  layers  might 
be  regarded  as  a  part  of  the  horizontal  fissure  lined  with  white  matter.  Of  these 
two  layers,  the  upper  is  much  the  thicker  and  more  substantial,  the  lower  being 
merely  a  thin,  delicate  white  lamina. 

The  upper  layer  is  divisible  into  a  mesial  and  two  lateral  portions,  of  which 
the  mesial  is  much  thinner  than  the  lateral.  This  mesial  portion  is  the  valve  of 
Yieussens  or  superior  medullary  velum.  It  is  of  uniform  thickness  from  side  to 
side.  On  transverse  section,  close  to  the  cerebellum,  its  width  is  seen  to  be  about 
equal  to  that  of  the  upper  worm.  It  has  above  it  the  lingula,  together  with  the 
central  lobule  resting  on  the  lingula.  The  lateral  portions  increase  in  thickness 
from  within  outward,  so  that  the  cut  surface  of  each  looks  somewhat  racket- 
shaped.  Each  lateral  portion  occupies  the  side  of  the  anterior  notch,  and  is  made 
up  of  the  three  peduncles  of  the  cerebellum,  the  handle  of  the  racket-shaped  sur- 
face representing  the  superior  peduncle,  while  the  rounded,  expanded  head  repre- 
sents, externally,  the  middle,  and,  inferiorly  and  mesially,  the  inferior,  peduncle. 

The  lower  layer  is  the  inferior  medullary  velum.  It  is  an  exceedingly  delicate 
white  lamina  stretching  from  the  white  matter  of  one  flocculus  across  the  middle 
line  to  the  white  matter  of  the  other  flocculus.  These  different  subdivisions  will 
now  be  considered  in  detail. 

Peduncles  of  the  Cerebellum  (Figs.  426,  432,  433). — The  superior  peduncles 
(Fig.  430)  are  on  the  dorsal  surface  of  the  pons  Varolii,  as  previously  described, 
diverging  from  each  other  from  above  downward.  Each  enters  the  corresponding 
hemisphere  of  the  cerebellum  beneath  the  frcenulum  and  ala  (Fig.  430),  where  its 
fibres  blend  with  those  of  the  two  other  peduncles  and  a  part  of  the  inferior  medul- 
lary velum,  to  form  the  white  matter  of  the  hemisphere.  The  superior  peduncles 
form  the  lateral  boundaries  of  the  upper  part  of  the  fourth  ventricle. 

The  middle  peduncles  are  large  rounded  bundles  made  up  of  most  of  the  trans- 
verse fibres  of  the  pons,  as  already  described.  Each,  bending  dorsally  from  the 
pons,  enters  the  cerebellum  between  the  edges  of  the  horizontal  fissure  at  the 
lateral  limits  of  the  anterior  notch — i.  e.  between  the  ala  and  the  edge  of  anterior 


734  THE   NERVOUS  SYSTEM. 

crescentic  lobule  above  and  flocculus  below — and  its  fibres  contribute  to  form  part 
of  the  white  matter  of  the  hemisphere. 

The  inferior  peduncle,  restiform  body  of  medulla,  as  it  enters  the  cerebellum 
lies  a  little  deeper  in  the  anterior  notch  than,  and  inferior  to,  the  middle  pedun- 
cle. Within  the  cerebellum  its  fibres  blend  with  those  of  the  preceding  to  form 
the  white  matter  of  the  hemisphere.  Just  as  this  peduncle  bends  sharply  back- 
ward from  the  medulla,  and  just  before  it  actually  enters  the  hemisphere,  its  under 
surface  is  free,  and  forms,  in  this  situation,  the  upper  boundary  of  the  cleft,  above 
referred  to,  between  the  layers  of  the  white  matter  of  the  cerebellum.  The  lower 
boundary  of  this  part  of  the  cleft  is  the  lateral  part  of  the  inferior  medullary  velum. 

Inferior  Medullary  Velum  (Figs.  426,  429,  432,  433). — As  already  mentioned, 
this  is  the  lower  layer  of  the  white  matter  of  the  cerebellum,  and  is  very  thin.  Its' 
central  portion  enters  the  cerebellum  over  or  dorsal  to  the  nodulus  at  the  centre  of 
the  anterior  notch ;  and  at  the  bottom  of  this  part  of  the  great  horizontal  fissure 
it  joins  with  the  superior  medullary  velum  to  enter  the  cerebellum  as  the  white 
matter  of  the  worm.  As  it  passes  over  the  nodulus  it  is  adherent  to  it — i.  e.  it 
sends  into  the  nodule  a  stem  of  white  matter. 

As  the  velum  passes  laterally  it  has  a  curved  direction,  concavity  forward,  and 
extends  almost  to  the  limits  of  the  anterior  notch,  where  it  blends  with  the  Avhite 
matter  of  the  flocculus.  These  curving  portions,  lateral  to  the  nodulus,  are  the 
so-called  lateral  parts  of  the  velum.  Each  of  these  lateral  parts,  traced  into  the 
horizontal  fissure,  passes  above  or  dorsal  to  the  peduncle  of  the  flocculus  (see  above), 
and  blends  with  the  under  surfaces  of  the  three  peduncles  to  form  the  white  matter 
of  the  hemisphere.  Thus  it  is  seen  that  the  white  matter  of  the  worm  is  made  up 
of  the  union  of  the  superior  medullary  velum  above  and  the  central  part  of  the 
inferior  medullary  velum  below,  while  that  of  the  hemispheres  is  the  conjoined 
three  peduncles  and  lateral  part  of  the  inferior  velum. 

Tent  and  Lateral  Recess. — The  cleft  between  these  layers  of  white  matter  is, 
like  them,  divisible  into  a  central  and  two  lateral  portions.  The  central  part  lies 
between  the  superior  velum  above  and  the  central  portion  of  the  inferior  velum 
below.  It  is  called  the  tent,  from  its  pointed  appearance  on  section.  The  lateral 
portions,  when  closed  in  by  the  upper  ends  of  the  restiform  bodies  (see  page  738), 
are  known  as  the  lateral  recesses  of  the  fourth  ventricle,  while  the  tent  forms  the 
roof  of  the  central  part  of  the  fourth  ventricle  (see  page  738). 

Superior  Medullary  Velum. — The  superior  medullary  velum,  or  valve  of  Vieus- 
sens,  has  been  partially  described.  It  is  a  thin  lamina  of  white  matter  stretched 
between  the  inner  margins  of  the  superior  cerebellar  peduncles ;  it  forms  the  roof 
of  the  upper  half  of  the  fourth  ventricle.  It  is  narrow  above,  where  it  passes 
beneath  the  lower  corpora  quadrigemina  (mid-brain),  and  broader  below  at  its 
connection  with  the  upper  vermiform  process  of  the  cerebellum.  A  slight  elevated 
ridge,  the  frcenulum,  descends  upon  the  upper  part  of  the  valve  from  between  the 
lower  corpora  quadrigemina,  and  on  either  side  of  it  may  be  seen  the  fourth  nerve. 
Its  lower  half  is  covered  by  a  thin,  transversely-grooved  lobule  of  gray  matter 
prolonged  from  the  anterior  border  of  the  cerebellum  ;  this  is  the  lingula. 

Arbor  Vitse  (Figs.  428,  429). — This  is  the  name  given  to  the  white  matter  of 
either  worm  or  hemisphere  when  viewed  on  antero-posterior  section.  On  such  a 
section  the  white  matter  looks  like  a  tree  with  a  central  trunk  and  branches,  with 
the  branches  also  subdividing  into  stems.  These  stems,  being  surrounded  by  gray 
matter,  resemble  leaves  or  folia  ;  and  there  may  also  be  secondary  folia  whose 
stems  come  from  a  primary  stem,  and  not  from  the  main  trunk  of  white  matter. 
These  folia,  as  already  explained  (page  728),  are  merely  the  cut  surfaces  of  the 
corresponding  lobules,  whether  of  worm  or  hemisphere.  The  main  trunk  of  the 
arbor  vitae  of  the  worm  is  slender,  while  that  of  the  arbor  vitae  of  each  hemisphere 
is  thick  and  bulky.  This  difference  is  due  to  the  large  amount  of  white  matter 
resulting  from  the  conjoined  peduncles  and  lateral  part  of  inferior  velum  as  com- 
pared with  that  resulting  from  the  union  of  the  comparatively  thin  superior  velum 
with  the  central  part  of  the  inferior  velum. 


THE   BRAIN  AND   ITS  MEMBRANES. 


735 


Fibres  of  the  Peduncles  (Fig.  435). — The  fibres  of  the  superior  peduncles  on 
entering  the  hemisphere  pass  to  a  great  extent  into  the  interior  of  the  corpus 
dentatum  (see  below),  though  some  wind  round  it  and  reach  the  gray  cortical 
matter,  especially  on  its  inferior  surface,  while  others  pass  into  the  white  matter 


Cut  surface 
of  pong\* 


Sup. 


,Xid.  ped.  (cut) 
.  ped.  (cut) 


Dentate  nucleus. 


Fie*.  435.— A  section  of  the  cerebellum  to  show  dentate  nucleus.    (Henle.) 

of  the  worm.  Into  the  white  matter  of  the  worm  pass  the  fibres  of  the  superior 
velum,  of  which  certain  longitudinal  ones  are  quite  distinct.  These  last  are  the 
antero-lateral  ascending  cerebellar  tracts  of  cord  and  medulla  (see  page  717). 

The  fibres  of  the  middle  peduncles  on  entering  the  hemisphere  have  a  gen- 
erally dorsal  tendency,  after  which  they  go  in  various  directions :  the  upper  fibres 
of  the  tuber  annulare  pass  to  the  lower  part  of  the  hemisphere ;  the  lower  fibres 
of  the  tuber  pass  into  the  upper  part  of  the  hemisphere ;  while  the  remaining 
fibres  (middle  of  tuber  and  dorsal  transverse ;  see  Pons)  pass  for  the  most  part 
into  the  middle  region  of  the  hemisphere. 

The  fibres  of  the  inferior  peduncles  on  entering  the  cerebellum  are  placed 
between  the  middle  peduncle  externally  and  superior  internally.  They  then  pass 
upward,  and  radiate  into  the  upper  part  of  the  hemisphere,  curving  over  the 
corpus  dentatum  ;  some  are  extended  into  the  white  matter  of  the  worm.  These 
last  are  the  continuations  of  the  direct  cerebellar  tract. 

The  Hbres  already  described,  which  make  up  the  inferior  peduncle  or  restiform 
body,  may  be  summarized  as  follows :  1.  Direct  cerebellar  tract ;  2.  External 
arciform  fibres ;  3.  Internal  arciform  fibres  (from  opposite  olivary  nucleus) ;  4. 
Fibres  from  accessory  cuneate  nucleus ;  5.  Fibres  from  antero-lateral  descending 
cerebellar  tract  of  cord ;  6.  Fibres  of  Solly.  These  last  are  occasionally  found, 
and  are  seen  on  the  surface  of  the  medulla  running  upward  and  backward  from 
the  direct  pyramidal  tract  of  the  cord  just  before  it  enters  the  pyramid. 

The  fibrae  propriae  of  the  cerebellum  are  of  two  kinds :  (1)  commissural  fibres, 
which  cross  the  middle  line  to  connect  the  opposite  halves  of  the  hemispheres, 
some  at  the  anterior  part,  and  others  at  the  posterior  part,  of  the  vermiform  pro- 
cess ;  (2)  arcuate  or  association  fibres,  which  connect  one  lamina  with  another, 
arching  across  the  fissures  between  the  laminae. 

The  GRAY  MATTER  OF  THE  CEREBELLUM  is  found  in  two  situations :  (1)  on  the 
surface,  forming  the  cortex ;  (2)  as  independent  masses  in  the  interior. 

(1)  The  gray  matter  of  the  cortex  presents  a  characteristic  foliated  appearance, 
due  to  the  series  of  laminae  which  are  given  off  from  the  central  white  matter : 
these  laminae  give  off  secondary  laminae  which  are  covered  with  gray  matter. 
This  arrangement  gives  to  the  cut  surface  of  the  organ  the  foliated  appearance 
already  described.  Externally  the  cortex  is  covered  by  pia  mater,  and  internally 
is  the  medullary  centre,  consisting  mainly  of  nerve-fibres. 


736 


THE   NERVOUS  SYSTEM. 


Microscopical  Appearance  of  the  Cortex. — The  cortex  presents  a  remarkable 
structure,  consisting  of  two  distinct  layers — viz.  an  external  gray  or  cellular  layer, 
and  an  internal  rust-colored  granular  layer.  Between  the  two  layers,  or  rather 
situated  in  the  deepest  part  of  the  gray  or  cellular  layer,  is  an  incomplete  stratum 
of  the  characteristic  cells  of  the  cerebellum,  the  corpuscles  of  Purkinje. 

The  external  gray  or  cellular  layer  (Fig.  436)  consists  of  fibres  and  cells.  The 
fibres  are  delicate  fibrillse,  some  running  at  right  angles  to  the  surface-fibres  of 
Bergman.  These  are  the  dendritic  processes  of  large  glia-cells  situated  in  the  gran- 


External  gray  or 
cellular  layer. 


Corpuscles  of  Purkinje. 


Internal  or  rust- 
colored  layer. 


— -  White  substance. 

Fio.  436. — Vertical  section  through  the  gray  matter  of  the  human  cerebellum.    Magnified  about  100  diame- 
ters.   (Klein  and  Noble  Smith.) 

ular  layer.  On  reaching  the  periphery  these  fibres  expand  into  small  cones,  bases 
superficially,  and  here  form  a  delicate  supporting  connective-tissue-like  membrane, 
which  spreads  out  into  a  broad  base  against  the  inner  surface  of  the  pia  mater. 
Other  fibres  are  horizontal,  and  can  be  observed  to  unite,  by  means  of  a  T-  or  Y- 
shaped  junction,  with  the  long  axis-cylinder  processes  of  the  granule-cells  in  the 
granular  layer. 

The  cells  are  small,  and  are  in  two  layers,  outer  and  inner.  .  All  have  numer- 
ously branching  axis-cylinder  and  protoplasmic  processes,  the  former  of  which, 
from  the  inner  cells  (basket-cells),  give  oft'  descending  vertical  branches  which 
ramify  like  a  basket  around  the  corpuscles  of  Purkinje. 

The  corpuscles  of  Purkinje  (Fig.  436)  are  flask-shaped  cells  in  the  deepest  part 
of  the  external  gray  or  cellular  layer,  resting  against  the  internal  rust-colored 


THE    BRA IX  AXD    ITS    MEMBRANES. 


737 


layer.  From  their  under  surface  a  slender  axis-cylinder  process  arises,  which 
passes  through  the  internal  layer,  and  becomes  continuous  with  the  axis-cylinder 
of  a  medullated  nerve-fibre  in  the  medullary  (white)  substance  beneath.  From 
the  other  extremity  a  number  of  protoplasmic  processes  (dendrites)  are  given  off, 
which  branch  in  an  antler-like  manner  in  the  external  layer,  all  having  free 
terminations. 

The  internal  or  rust-colored  layer  (Fig.  436)  is  characterized  by  containing 
multitudes  of  granular-looking  cells.  There  are  also  minute  stellate  cells  and 
glia-cells.  Between  the  cells  is  a  fine  nerve-network,  with  which  the  processes 
of  all  the  cells  are  continuous,  except  the  axis-cylinder  processes  of  the  granule- 
cells. 

There  are  still  other  fibres  to  be  found  in  the  cerebellar  cortex.  These  come 
directly  from  the  white  centre,  and  penetrate  through  the  entire  cortex.  Each 
fibre,  thus  penetrating,  gives  off  branches  in  the  granular  layer,  the  ramuscles 
exhibiting  peculiar  moss-like  appendages,  hence  are  called  "  moss-fibres  "  (Ramon 
y  Cajal).  Other  ramifications  are  also  found  around  Purkinje's  corpuscles. 
Finally,  in  the  external  layer  these  fibres  terminate  by  becoming  longitudinal  and 


FIG.  437.— A  corpuscle  of  Purkinje, 
with  its  dichotomously  branched  pro- 


P 

FIG.  438.— Vertical  section  of  the  cerebellum. 


horizontal.  The  cell-origin  of  these  fibres  is  probably  situated  in  the  gray  matter 
of  the  spinal  cord. 

(2)  The  independent  centres  of  gray  matter  in  the  cerebellum  are — (1)  the  cor- 
pus dentatum  :  (2)  the  roof  nuclei  of  Stilling. 

The  corpus  dentatum  (Fisrs.  435.  438),  or  ganglion  of  the  cerebellum*  is  situated 
a  little  to  the  inner  side  of  the  centre  of  the  stem  of  white  matter.  It  consists  of 
an  open  bag  or  capsule  of  gray  matter,  the  section  of  which  presents  a  grav  den- 
tated  outline,  open  at  its  anterior  part.  It  is  surrounded  by  white  fibres ;  'white 
fibres  are  also  contained  in  its  interior,  which  are  derived  from  the  superior 
peduncles. 

The  roof  nuclei  of  Stilling  are  two  small  gray  masses  situated  in  the  anterior 
part  of  the  white  matter  of  the  worm,  close  to  where  the  valve  of  Yieussens 
begins  to  assist  in  the  formation  of  the  roof  of  the  fourth  ventricle.  These  can 
only  be  seen  in  microscopic  preparations. 

The  Fourth  Ventricle  (Fig?.  423,  429). 

The  Fourth  Ventricle,  or  ventricle  of  the  cerebellum,  is  the  space  between  the 
mesial  portions  of  the  dorsal  surfaces  of  the  medulla  oblongata  and  pons  ventrally 
and  the  cerebellum  dorsally.  It  consists  of  a  floor,  roof,  and  lateral  boundaries. 

47 


738  THE   NERVOUS  SYSTEM. 

The  floor  has  already  been  described  in  detail.  It  is  flat  and  lozenge-shaped,  its 
upper  half  being  on  the  dorsal  surface  of  the  pons,  its  lower  half  lying  between 
the  restiform  bodies  on  the  upper  portion  of  the  dorsal  surface  of  the  medulla. 
Its  widest  or  central  portion  is  at  the  junction  between  pons  and  medulla.  Like 
the  floor,  the  ventricle  itself  is  divided  into  an  upper,  a  lower,  and  a  middle  portion. 

Boundaries  of  the  Fourth  Ventricle. — The  upper  portion  has  for  its  floor  the  cen- 
tral part  of  the  dorsal  surface  of  the  pons  ;  for  its  lateral  boundaries,  the  inner 
surfaces  of  the  superior  cerebellar  peduncles  ;  for  its  roof,  the  superior  medullary 
velum. 

The  middle  portion  has  for  its  roof  the  tent,  or  space  between  central  part  of 
inferior  medullary  velum,  below  ;  and  that  part  of  superior  medullary  velum  which 
is  below  the  lingula,  above  ;  and  their  line  of  junction  dorsally.  The  tent,  on  section, 
appears  pointed,  the  angle  projecting  dorsally  from  pons  and  medulla  into  the 
worm,  between  lingula  above  and  nodulus  below.  In  the  complete  ventricle  the 
tent  lies  dorsal  to  the  widest  part  of  the  floor  ;  and  the  lateral  boundaries  of  this  par- 
ticular region  of  the  ventricle  are  the  lateral  angles  (see  page  723),  each  lateral 
angle  being  the  point  of  contact  of  the  lower  end  of  the  inner  surface  of  the 
superior  peduncle  with  the  upper  end  of  the  inner  surface  of  the  inferior  peduncle, 
just  as  each  peduncle  bends  dorsally  to  enter  the  hemisphere. 

The  lower  portion  has  for  its  floor  that  part  of  the  dorsal  surface  of  the 
medulla  which  is  between  the  restiform  bodies,  and  for  its  lateral  boundaries  the 
clavcetf  the  funiculi  graciles  and  the  inner  surf  aces  of  the  restiform  bodies.  The 
inner  surface  of  the  restiform  body  is  merely  the  inner  aspect  of  its  generally 
rounded,  elevated  surface.  Hence  it  is  not  so  marked  as  that  of  the  flattened 
superior  peduncle,  which  also  has  an  inner  margin,  to  which  is  attached  the  supe- 
rior medullary  velum ;  while  the  inner  margin  of  the  rounded  inferior  peduncle 
would  be  merely  the  line  drawn  between  its  inner  and  dorsal  aspects.  The  roof 
of  the  lower  portion  of  the  fourth  ventricle  is  the  tela  choroidea  inferior,  which 
will  now  be  described,  together  with  the  lateral  recesses  of  the  fourth  ventricle. 

Roof  of  Lower  Portion  of  Fourth  Ventricle ;  Lateral  Recess ;  Tela  Choroidea 
Inferior. — In  the  description  of  the  white  matter  of  the  cerebellum,  as  it  lies 
between  the  edges  of  the  great  horizontal  fissure  in  the  anterior  notch,  it  was 
stated  that  this  white  matter  was  split  into  two  layers,  the  lower  of  which  is  the 
inferior  medullary  velum.  An  important  difference  between  these  two  layers  must 
now  be  noted,  in  addition  to  the  others  already  given.  This  difference  is  that,  in 
the  complete  specimen,  the  inferior  medullary  velum,  as  such,  has  a  free  edge, 
while  the  upper  layer  is  continued  directly  into  the  prolongations  of  its  com- 
ponent parts,  superior  medullary  velum  and  the  peduncles  of  the  cerebellum. 

This/ree  edge  of  the  inferior  velum  is  directed,  in  the  natural  position,  down- 
ward and  forward.  The  free  edge  of  the  mesial  part  lies  over  the  nodulus,  which 
projects  somewhat  beyond  it.  Being  very  thin,  it  cannot  be  made  out  distinctly 
except  on  antero-posterior  section.  The  free  edges  of  the  lateral  portions,  how- 
ever, are  well  seen  on  removal  of  cerebellum  from  pons  and  medulla  and  after 
separating  the  edges  of  the  great  horizontal  fissure.  In  the  complete  condition 
each  of  these  lateral  free  edges  of  the  velum  lies  just  dorsal  to  the  upper  extrem- 
ity of  the  corresponding  restiform  body  just  before  it  bends  backward  into  the 
cerebellum,  and  curves  around  it,  as  it  were,  reaching  out  laterally  to  the  floc- 
culus, which,  in  the  complete  specimen,  lies  just  external  to  the  lateral  aspect  of 
the  restiform  body. 

Having  thus  located  the  free  edge  of  the  entire  inferior  medullary  velum,  it 
now  remains  to  establish  its  connection  with  the  subjacent  parts.  This  connec- 
tion is  effected  by  a  layer  of  epithelial  cells  prolonged  from  the  general  epithelial 
lining  of  the  ventricle.  It  is  understood,  of  course,  that  all  the  ventricles  of  the 
brain,  as  well  as  the  central  canal  of  the  cord,  are  lined  with  epithelium.  There- 
fore in  the  fourth  ventricle  this  epithelium  lines  the  under  surface  of  the  superior 
velum  ;  the  inner  surface  of  the  superior  cerebellar  peduncle ;  covers  the  entire 
floor,  and  is  also  found  in  the  tent  and  its  lateral  prolongations.  Therefore  it 


THE   BRA IX  AXD    IT*   MEM-BRACES.  739 

must  also  cover  the  upper  surface  of  the  entire  inferior  medullary  velum  ;  and  it 
is  the  prolongation  of  this  particular  layer  which  was  just  referred  to. 

The  epithelium  covering  the  central  part  of  the  inferior  velum  on  arriving  at 
its  free  edge  is  continued  over  the  projecting  portion  of  the  upper  surface  of  the 
nodulus.  and  then  bends  sharply  downward  and  backward  around  the  anterior 
extremity  of  the  nodulus.  and  is  continued  on  down  to  the  calamus  scriptorius — 
angle  of  divergence  of  the  clavae — where  it  dips  into  the  upper  (medullary) 
part  of  the  central  canal  of  the  cord,  and  becomes  continuous  with  its  dorsal  lin- 
ing epithelium.  This  layer  of  epithelium,  thus  traced  from  above  downward,  has, 
of  course,  lateral  attachments,  and  on  each  side  this  attachment  is  mainly  the  line, 
already  referred  to,  which  marks  off  the  inner  from  the  dorsal  aspect  of  the  resti- 
form  body.  Below,  this  line  of  attachment  is  continued  down  on  the  clava,  and 
at  the  calamus  scriptorius  meets  the  line  from  the  opposite  side.  Along  this  line 
for  its  entire  extent  the  layer  of  epithelium  is  continuous  with  the  epithelium 
lining  the  slightly  elevated  inner  aspect  of  the  restiform  body  and  that  covering 
the  floor,  but  is  not  prolonged  over  the  dorsal  aspect  of  the  restiform  body,  which 
is  closely  invested  with  pia  mater.  Owing  to  the  divergence  of  the  restiform 
bodies  and  clava?.  it  is  evident  that  this  layer  of  epithelium  is  triangular  in  shape, 
with  its  apex  at  the  calamus  scriptorius.  This  triangular  layer  of  epithelium  is 
the  /•"//  /-"of  of  the  lower  portion  of  the  fourth  ventricle. 

Lateral  Recess. — The  epithelium  covering  each  lateral  portion  of  the  inferior 
medullary  velum  on  arriving  at  its  free  edge  is  prolonged  directly  on  to  the  upper 
extremity  of  the  restiform  body,  close  to  which  the  free  edge  lies,  and  is  then 
reflected  upward  for  a  very  short  distance — i.  e.  to  where  the  restiform  body  bends 
backward  to  enter  the  hemisphere.  The  epithelium  then  bends  backward  also, 
covering  the  (now)  under  surface  of  the  inferior  cerebellar  peduncle,  and  thus 
enters  the  Jaf<-ral  portion  of  the  cleft  (see  page  734)  between  the  "  laminae  "  of 
the  cerebellar  white  matter :  arriving  at  the  bottom  of  this  cleft,  it  is  reflected 
back  again  over  the  upper  surface  of  the  lateral  part  of  the  inferior  medullary 
velum  to  its  free  edge,  at  which  point  its  tracing  was  commenced. 

The  line  of  attachment  of  the  epithelium  to  the  upper  end  of  the  restiform 
body  just  after  its  reflection  from  the  edge  of  the  inferior  velum  is,  of  course, 
directed  transversely.  Its  inner  end  bends  downward  and  becomes  continuous 
with  the  line  already  mentioned  on  the  restiform  body,  along  which  the  '"roof" 
epithelium  blends  with  that  of  the  side  and  floor. 

Thus  is  formed  the  complete  lateral  recess,  which,  when  all  the  parts  are  con- 
nected, is  really  a  triangular-shaped,  tunnel-like  prolongation  of  the  cavity  of 
the  fourth  ventricle,  curving  around  the  extreme  upper  end  of  the  restiform  body 
just  before  that  body  bends  backward  into  the  hemisphere  of  the  cerebellum. 

The  outer  extremity  of  the  lateral  recess  may  be  regarded  as  a  pointed  cul-de- 
sac.     At  its  in.  ii>  r  •  sir-  /t»'t>/  is  an  aperture  through  which  its  lining  epithelium  is 
continuous  with  that  of  the  fourth  ventricle.     This  aperture  is  situated  just  at  the 
//  '//>//••  (see  above)  of  the  ventricle.      The  cul-de-sac  is  situated  just  between 
the  flocculus  externally  and  the  outer  aspect  of  the  restiform  body  internally. 

Tela  Choroidea  Inferior. — The  pia  mater  which  invests  the  inferior  worm  is 
continued  upward  and  forward,  dipping  in  and  out  of  the  various  fissures,  until 
it  reaches  the  nodulus.  It  now  closely  invests  the  nodulus  and  bends  sharply 
around  it.  forward,  upward,  and  a  little  backward,  following  exactly  the  course 
of,  but  lying  posterior  to,  the  epithelial  roof  of  the  ventricle,  already  described, 
until  it  reaches  the  free  edge  of  the  inferior  velum  lying  on  the  nodulus.  At  this 
point  it  is  reflected  at  an  acute  angle  right  back  on  itself,  and  now  follows  the 
"epithelial  roof"  down  to  the  calamus  scriptorius.  In  its  course  this  reflected 
lui/'ji-  of  pia  mater  lies,  naturally,  dorsal  to  the  epithelial  roof,  and  so  closely  adhe- 
to  it  that  the  two  form  one  structure.  This  structure  is  the  tela  choroidea 
inferior.  It  is  the  practical  mof  of  the  lower  portion  of  the  fourth  ventricle, 
because  when  the  pia  mater  is  pulled  away  the  epithelial  layer  comes  with  it, 
and  thus  this  portion  of  the  ventricle  is  exposed. 


740  THE   NERVOUS  SYSTEM. 

If  the  pia  mater  covering  the  hemisphere  on  each  side  of  that  covering  the 
inferior  worm  (the  lateral  extension  of  the  same  layer)  be  traced,  it  will  be  found 
to  follow  a  similar  course,  thus  :  After  passing  upward  it  reaches  the  under  sur- 
face, and  then  the  free  edge,  of  the  lateral  part  of  the  inferior  velum.  It  is  now 
sharply  reflected  on  itself,  and  passes  downward  on  the  dorsal  aspect  of  the  resti- 
form  body.  This  is  merely  the  lateral  extension  of  the  pia  matral  portion  of  the 
tela  choroidea  inferior.  As  this  layer  passes  from  the  edge  of  the  inferior  velum 
(lateral  part)  to  the  restiform  body  it  is  in  contact,  just  at  its  downward  bend, 
with  the  epithelium  of  the  lateral  recess  just  where  it  is  being  reflected  on  to  the 
extreme  upper  end  of  the  restiform  body.  It  is  therefore  evident  that  along  the 
free  edge  of  the  entire  inferior  medullary  velum  there  is  attached  a  margin  of  pia 
mater  consisting  of  two  layers  folded  on  themselves.  For  some  distance  down- 
ward these  two  layers  are  somewhat  adherent  to  each  other. 

The  Ligula. — In  the  fourth  ventricle,  as  well  as  in  the  other  ventricles,  the 
lining  epithelium  has  between  it  and  the  surrounding  brain-tissue  a  delicate  layer 
of  neuroglia  known  as  the  ependyma.  The  upper  surface  of  the  inferior  velum 
also  has  on  it  some  of  this  ependyma.  At  the  free  edge  of  the  velum,  however, 
this  ependyma  ceases  abruptly,  and  the  epithelium  comes  in  direct  contact  with 
the  pia  mater.  But  where  the  epithelium  leaves  the  pia  mater  to  be  reflected 
upward  on  the  restiform  body  (lateral  recess),  or  where  it  leaves  the  under  sur- 
face of  the  tela  choroidea  inferior  to  be  reflected  on  the  inner  aspect  of  the  resti- 
form body  and  floor  of  the  ventricle,  the  ependyma  reappears.  Hence  this  edge 
of  ependyma  follows  the  line  of  reflection  of  epithelium  all  the  way  from  the 
calamus  scriptorius  obliquely  upward  and  outward,  and  then  outward  around  the 
upper  end  of  the  restiform  body.  It  is  not  visible  to  the  naked  eye  until  the  pia 
mater  is  pulled  away.  This  tearing  away  of  the  pia  mater  necessarily  brings 
with  it  the  epithelium  lining  it,  and  there  is  seen  a  very  delicate,  jagged  line  of 
tissue  following  the  course  of  the  "line  of  reflection  "  just  described.  This  line 
of  tissue  is  the  edge  of  the  ependyma  plus  the  torn  edge  of  epithelium,  and  is  the 
ligula,  not  to  be  confounded  with  the  lingula.  The  union  of  the  lower  ends  of 
the  two  ligulse  in  the  calamus  scriptorius  is  known  as  the  obex. 

This  tearing  away  of  the  pia  mater  and  epithelium  also  brings  into  view  the 
free  edge  of  the  inferior  medullary  velum,  especially  its  lateral  portions  on  each 
side  of  the  nodulus. 

Choroid  Plexuses. — The  under  surface  of  the  pia-matral  portion  of  the  tela 
choroidea  inferior  is  not  smooth.  It  has  a  linear  series,  on  each  side  of  the  mid- 
dle line,  of  minute  vascular  tufts  of  pia-mater  tissue  projecting  ventrally.  These 
tufts,  however,  do  not  pierce  the  epithelial  "roof,"  but  are  covered,  ventrally, 
everywhere  by  the  epithelium.  These  lines  of  tufts  with  their  epithelium  are  the 
choroid  plexuses  of  the  fourth  ventricle. 

Similar,  but  longer,  tufts  of  pia-mater  tissue  are  also  prolonged  from  the  pia 
mater  which  lies  beneath  the  epithelium,  closing  in  the  lateral  recess.  These  last 
are  collected  into  quite  a  distinct  bunch,  resembling  a  group  of  small  villi,  which 
is  seen  between  the  flocculus  and  outer  aspect  of  the  restiform  body.  In  the 
middle  of  these  villi  is  the  pointed  cul-de-sac  of  the  lateral  recess,  which  by  some 
observers  is  said  to  be  perforated  by  a  minute  foramen. 

A  similar  foramen  is  said  to  be  present  in  the  tela  choroidea  inferior  just  above 
the  calamus  scriptorius.  This  is  the  so-called  foramen  of  Majendie. 

THE  MID-BRAIN  (Figs.  415,  416,  and  439). 

The  mid-brain,  or  mesencephalon,  is  that  portion  of  the  brain  which  connects 
the  pons  Varolii  below  with  the  cerebrum  (inter-brain  and  hemispheres)  above.  On 
this  account  it  is  sometimes  called  the  isthmus  or  the  cms  cerebri.  It  has  four 
surfaces — a  superior,  an  inferior,  a  dorsal,  and  a  ventral.  The  first  two  are  flat- 
tened and  are  attached,  the  superior  to  the  cerebrum,  the  inferior  to  the  pons. 
They  are  also  nearly  parallel  with  each  other.  The  two  latter  are  somewhat  curved 


THE   BRAIN  AND    ITS  MEMBRANES. 


741 


transversely,  and  meet  each  other  on  the  side  of  the  mid-brain,  being  separated 
only  by  a  groove,  the  sulcus  lateralis,  which  runs  from  below  upward  and  forward. 
The  dorsal  surface  is  free,  but  is  concealed  from  view,  from  above,  in  the  com- 
plete brain  by  the  overhanging  hemispheres.  The  ventral  surface  is  also  free, 
and  also  concealed,  from  below,  by  portions  of  the  hemispheres,  apices  of  tem- 
poral lobes,  which  overlap  it.  These  two  surfaces  are  not  parallel,  as  the  ventral 
surface,  besides  being  convex  from  side  to  side,  is  slightly  concave  from  below 
upward  and  forward.  The  cavity  of  the  mid-brain  is  the  smallest  of  all  the  brain 
••  ventricles."  It  is  called  the  aqueduct  of  Sylvius,  and  is  a  mere  tube  whose 


N.  opticu* 


Corp.     f«* 
quadr^-\poist 


Inf.      Hypophysis 
.  oculomotor 


y.  access. 


-V.  facialis 

'.  acusticus 

hypoglossus 


Ant.  roots  of  the 
Jirst  spinal  nerves 


FIG.  439.—  Medulla,  pons.  and  mid-brain  seen  from  the  right  side,  X  \.   (Gegenbaur.) 

diameter  is  very  small  compared  to  the  bulk  of  the  mid-brain  in  which  it  lies.  It 
is  situated  close  under  the  dorsal  surf  ace  in  the  middle  line;  hence  its  direction 
is  upward  and  forward.  It  opens  below  into  the  fourth  ventricle  and  above  into 
the  third  ventricle. 

Main  Divisions.  —  The  mid-brain,  as  a  whole,  is  divided  into  two  portions  (Fig. 
440),  a  postero-superior  and  an  antero-inferior,  by  a  lamina  of  gray  matter,  the 
substantia  nigra,  which  is  seen  to  be  convex 
downward  and  from  side  to  side  in  sections 
made  both  dorso-ventrally  and  from  above 
downward.  Hence  this  lamina,  as  a  whole,  has 
an  antero-posterior  curve,  with  the  concavity 
looking  ventrally.  Its  two  edges  lie  along  and 
in  the  sul"ii.<*  lateralis. 

All  of  the  mid-brain  dorsal  to  and  above  (pos- 
tero-superior) the  substantia  nigra  is  called  the 
tegmentum.  while  that  portion  which  is  below  and 
anterior  (antero-inferior)  is  known  as  the  crustce. 

Crustse.  —  There  are  two  crustae,  which  diverge  from  each  other  from  below 
upward.  The  lower  end  of  each  is  overlapped  by  the  upper  margin  of  the  tuber 
annulare  of  the  pons.  Each  crusta  is  a  thick,  wide,  rounded  bundle  of  longitudi- 
nal white  fibres,  its  outer  margin  being  limited  by  the  sulcus  lateralis.  Its  inner 
margin  is  free,  and  in  the  interval  between  it  and  the  opposite  crusta  is  the  sub- 
stantia nigra  passing  across.  Dorsal  to  each  crusta  is  the  substantia  nigra,  and 
on  the  inner  margin  of  each,  where  the  substantia  nigra  is  about  to  cross  over,  is 
a  groove,  the  mesial  sulcus,  or  sulcus  oculo-motorius,  out  of  which  the  roots  of  the 


FlG"  ^- 


Corpus  quad- 
rigem.  ant. 
Aquxducius 

Sylvii 
Tegmentum 

Subst.  nigra 


Crusta 

mid-brain, 


742  THE   NERVOUS   SYSTEM, 

third  nerve  pass.  The  two  crustce  are  often  spoken  of  as  the  crura  or  pedunculi 
cerebri. 

Fibres  of  the  Crusta. — These  are — (1)  the  upward  continuations  of  the  fibres 
of  the  pyramids,  pyramidal  tract,  which  in  passing  through  the  pons  are  known 
as  its  ventral  longitudinal  fibres :  this  pyramidal  tract  forms  about  the  middle 
third  of  the  crusta.  Superiorly,  it  is  continued  into  the  middle  part  of  the  internal 
capsule  of  the  hemisphere,  and  thence  to  the  fronto-parietal  or  Rolandic  region 
of  the  cortex.  (2)  The  direct  sensory  tract :  these  fibres  occupy  the  outer  third 
of  the  crusta ;  below,  they  probably  come  from  the  nuclei  pontis ;  above,  they 
pass  into  the  posterior  part  of  the  internal  capsule,  and  thence  to  the  cortex  of 
the  occipito-ternporal  regions  of  the  hemisphere.  (3)  Fibres  of  the  inner  third 
of  the  crusta :  the  lower  origin  of  most  of  these  is  not  well  defined.  They  pos- 
sibly arise  from  the  cells  of  the  substantia  nigra.  Above,  they  pass  through  the 
anterior  part  of  the  internal  capsule  to  the  cortex  of  the  prefrontal  region  of  the 
hemisphere.  One  bundle,  however,  is  distinct.  It  is  the  mesial  fillet  (see  below). 
As  it  passes  upward  it  crosses  obliquely  outward  through  the  other  fibres  of  the 
crusta,  and  its  fibres  are  finally  lost  in  the  subthalamic  region,  where  they  prob- 
ably become  continuous  with  the  ansa  lenticularis  (see  page  747).  Below,  it  is 
one  of  the  three  divisions  of  the  fillet. 

The  substantia  nigra  or  locus  niger  is,  as  already  mentioned,  a  lamina  of  gray 
matter  situated  between  the  crustse  and  tegmenturn  and  projecting  here  and  there 
between  the  bundles  of  the  former.  It  is  thicker  at  the  inner  than  at  the  outer 
side,  and  is  traversed  in  its  mesial  part  by  the  fibres  of  origin  of  the  third  nerve. 
It  contains  irregular  nerve-cells,  in  which  are  lodged  numerous  dark  pigment- 
granules.  The  portion  between  the  crustae,  together  with  the  crustse,  form  the 
ventral  surface  of  the  mid-brain,  which,  on  each  side,  is  limited  by  the  sulcus 
lateralis. 

The  Tegmentum. — This  comprises  all  that  part  of  the  mid-brain  dorsal  to  and 
superior  to  the  substantia  nigra.  Its  longitudinal  fibres  run  up  through  the 
"dorsal"  part,  and  then  bend  forward  in  the  "superior"  part,  from  which  they 
pass  to  their  destination.  There  are  really  two  tegmenta,  but  each  is  united  with 
its  fellow  of  the  opposite  side  by  a  prolongation  of  the  median  septum  or  raphe 
of  the  pons. 

The  tegmentuin  consists  of  longitudinal  bundles  of  white  fibres  interlaced  by 
transverse  fibres,  together  with  a  quantity  of  gray  matter  with  scattered  nerve- 
cells.  It  forms  a  well-marked  formatio  reticularis  similar  to  that  found  in  the 
pons  and  medulla,  with  which  it  is  continuous,  receiving,  however,  a  bundle  of 
fibres  (superior  peduncle]  from  the  cerebellum. 

The  most  distinct  of  the  longitudinal  fibres  comprise  the  following  bundles, 
whose  course  in  medulla  arid  pons  has  already  been  described:  (1)  The  posterior 
longitudinal  bundle:  this  lies  on  each  side  of  the  median  line  and  just  below  the 
aqueduct  of  Sylvius.  In  the  mid-brain  it  gives  off  fibres  to  the  nuclei  of  the 
third  and  fourth  cranial  nerves,  and  receives  fibres,  in  the  pons,  from  the  nucleus 
of  the  sixth.  At  the  junction  between  the  dorsal  and  superior  surface  of  the 
mid-brain  each  posterior  longitudinal  bundle  passes  dorsal  to  the  aqueduct  and 
across  to  the  opposite  side  in  the  posterior  commissure;  some  fibres,  however,  pass 
to  the  subthalamic  region  of  the  same  side ;  there  are  also  decussating  fibres 
between  the  two  "bundles  "  in  the  raphe.  (2)  The  fillet :  its  mode  of  origin  and 
course  in  the  medulla  and  pons  have  been  described.  Arrived  at  the  mid-brain,  it 
divides  into  three  subdivisions — the  mesial  fillet,  the  upper  fillet,  the  lower  or 
lateral  fillet.  The  first  has  already  been  described  with  the  crusta.  The  upper 
fillet  passes  to  the  superior  corpus  quadrigeminum.  The  lower  fillet  appears  on 
the  dorsal  surface  (see  below).  Above,  its  fibres  pass  to  the  inferior  corpus  quad- 
rigeminum, being  reinforced  by  some  fibres  from  the  superior  medullary  velum. 
It  also  receives,  through  the  trapezium  of  the  pons,  some  fibres  from  the  ventral 
auditory  nucleus  of  the  opposite  side.  (3)  Fibres  from  the  superior  peduncle  of 
the  cerebellum :  these  on  leaving  the  pons  dip  ventrally,  and  beneath  the  corpora 


THE  BRAIX   AXD    ITS   MEMBRANES.  743 

quadrigemina  the  fibres  of  each  peduncle  decussate  with  each  other,  so  that  fibres 
from  one  half  of  the  cerebrum  are  continued  in  the  other  half  of  the  cerebellum. 
The  fibres  thus  pass  upward  into  the  optic  thalamus,  surrounding,  as  they  go, 
the  red  /tu<-J>-t(s.  from  and  to  the  cells  of  which  they  receive  and  give  fibres. 
(4)  Certain  fibres  from  the  olivary  nucleus  of  the  medulla:  above,  these  are  trace- 
able into  the  internal  capsule  of  the  hemisphere. 

The  red  nucleus  (Fig.  451),  or  nucleus  of  the  tegmentum,  is  a  cylindrical  mass 
of  gray  matter  on  each  side  of  the  middle  line.  On  cross-section  it  is  seen  as  a 
reddish  circle  in  about  the  middle  of  the  tegmentum  ventral  to  the  aqueduct  of 
Sylvius. 

The  following  structures  are  all  grouped  on  the  dorsal  surface  of  the  mid-brain. 
They  belong  to  the  tegmentum,  since  they  are  dorsal  to  the  substantia  nigra. 
This  dorsal  surface  is  limited  by  the  sulcus  lateralis  on  each  side. 

The  corpora  or  tubercula  quadrigemina  are  four  rounded  eminences  placed  in 
pairs,  two  in  front  and  two  behind,  and  separated  from  one  another  by  a  median 
longitudinal  and  a  transverse  groove. 

They  are  situated  immediately  behind  the  third  ventricle  and  posterior  com- 
missure, and  beneath  the  posterior  border  of  the  corpus  callosum.  Below,  they 
rest  upon  a  layer  of  white  matter,  the  quadrigeminal  lamina,  immediately  beneath 
which,  in  the  median  line,  is  the  aqueduct  of  Sylvius.  The  anterior  or  upper 
pair  are  the  larger,  oblong  from  betore  backward,  and  of  a  gray  color.  The  pos- 
terior or  loicer  pair  are  hemispherical  in  f  >rm  and  lighter  in  color  than  the  pre- 
ceding. From  the  outer  side  of  each  of  these  eminences  a  prominent  white 
band,  termed  braeki/um,  is  continued.  Those  from  the  anterior  pair  (brachia 
iinti-riora)  are  long  and  slender,  and  each  passes  at  first  obliquely  outward,  and 
then  curves  backward,  downward,  and  forward  around  the  posterior  extremity 
of  the  optic  thalamus,  which  overhangs  it,  and  then  between  the  inner  and 
outer  geniculate  bodies  into  the  optic  tract.  Those  from  the  posterior  pair 
(In-ti'-lda  posterior  d)  are  comparatively  short  and  broad,  and  each  passes  to  an 
oval  prominence,  the  internal  geniculate  body,  beneath  which  it  apparently  dis- 
appears. Both  pairs  of  these  bodies  are  composed  of  white  matter  externally 
and  gray  matter  within.  In  fishes,  reptiles,  and  birds  these  bodies  are  only  two 
in  number,  and  are  called  the  optic  lobes,  from  their  connection  with  the  optic 
nerves ;  but  in  mammalia  they  are  four  in  number,  as  in  man.  In  the  human 
fcetus  they  are  developed  at  a  very  early  period,  and  form  a  large  proportion 
of  the  cerebral  mass. 

These  bodies  are  apparently  connected  with  the  cerebellum  by  means  of  the 
superior  peduncles  of  the  cerebellum,  which  are  continued  onward  to  the  optic 
thalami  through  the  tegmentum,  as  already  mentioned. 

Arching  over  the  upper  ends  of  these  peduncles  is  a  flattish  triangular-shaped 
band  of  white  fibres,  the  lemniscus  or  lower  fillet,  which  issues  from  beneath  the 
transverse  fibres  of  the  pons  to  pass  obliquely  round  the  upper  end  of  the  superior 
peduncle  of  the  cerebellum  and  become  lost  in  the  inferior  quadrigeminal  body. 

The  corpora  geniculata  are  two  small,  flattened,  oblong  masses,  placed  on  the 
under  and  back  part  of  each  optic  thalamus,  and  named,  from  their  positions, 
corpus  geniculatum  externum  and  internum.  The  two  bodies  are  separated  from 
one  another  by  the  brachium  anterius  from  the  anterior  corpus  quadrigeminum. 

Structure  of  the  Corpora  Quadrigemina  and  Geniculata. — The  peripheral 
///•"//  matter  of  the  corpora  quadrigemina  differs  somewhat  in  the  posterior  and 
anterior  bodies.  The  posterior  are  composed  almost  entirely  of  gray  matter, 
covered  over  by  a  thin  stratum  of  white  matter,  and  separated  from  the  central 
.'//•"//  matter  of  the  aqueduct  by  tracts  of  transverse  white  fibres  derived  from,  and 
forming  part  of,  the  lower  fillet.  The  anterior  are  covered  superficially  by  a  thin 
stratum  of  white  matter :  beneath  this  is  a  layer  of  gray  matter,  termed  the 
xtrntuni  '•i/'creutn,  and  consisting,  as  well  as  the  gray  matter  of  the  posterior 
l<>bes,  of  small  multipolar  cells  imbedded  in  a  fine  network  of  nerves.  Beneath 
this,  again,  is  a  characteristic  mass  of  gray  matter,  termed  the  stratum  opticum. 


744  THE   NERVOUS  SYSTEM. 

which  is  made  up  of  fine  nerve-fibres,  coursing  in  a  longitudinal  direction,  and 
containing  between  them  small  masses  of  gray  substance,  consisting  of  small  mul- 
tipolar nerve-cells  imbedded  in  gray  matter.  Lastly,  between  this  body  and  the 
central  gray  matter  around  the  Sylvian  aqueduct  is  a  thin  lamina  of  white  matter, 
derived  from  the  upper  fillet. 

The  geniculate  bodies  are  continuous  with  the  gray  substance  of  the  optic 
thalamus,  and  the  external  one  (corpus  genjculatum  extcrnum]  is  peculiar  on 
account  of  its  dark  color,  due  to  its  cells  containing  pigment.  It  presents 
a  laminated  arrangement,  and  consists  of  alternate  thick  layers  of  gray 
matter  and  tkin  layers  of  white  matter.  Its  cells  are  multipolar.  The  internal 
body  (corpus  geniculatum  internuni)  is  of  lighter  color,  does  not  present  a  lami- 
nated arrangement,  arid  its  cells  are  smaller  in  size  and  fusiform  in  shape. 
These  bodies,  strictly  speaking,  belong,  the  external  to  the  inter-brain,  and  the 
internal  to  the  mid-brain. 

The  locus  niger,  or  gray  matter  of  the  crus  cerebri,  like  the  external  geniculate 
body,  is  peculiar  from  the  large  number  of  dark  pigment-granules  which  are 
contained  in  its  ganglion-cells,  and  which  give  to  it  its  dark  color,  from  which  it 
has  derived  its  name.  Its  cells  are  small  and  multipolar. 

The  Aqueduct  of  Sylvius. — This  is  the  "  ventricle  "  of  the  mid-brain.  It  is  a 
narrow  tube  into  which  the  fourth  ventricle  opens  below,  and  which  opens  into 
the  third  ventricle  above.  Hence  it  is  sometimes  called  the  iter  a  tertio  ad 
quartum  ventriculum.  It  is  a  little  over  half  an  inch  long.  It  lies  in  the  teg- 
mentum,  and  its  course  is  upward  and  forward,  the  same  direction  as  that  of  the 
dorsal  surface  of  the  tegmentum,  on  which  the  groove  between  the  right  and  left 
corpora  quadrigemina  indicates  its  position.  It  lies  immediately  ventral  to  this 
groove.  Its  roof  is  the  lamina  quadrigemina,  the  white  layer  which  supports  the 
corpora  quadrigemina,  and  into  which  are  prolonged  the  fibres  of  the  superior 
medullary  velum.  Its  shape,  on  transverse  section,  varies,  being  T-shaped  near 
the  fourth  ventricle,  shield-shaped  about  midway  in  its  course,  and  triangular 
near  the  third  ventricle,  into  which  it  opens  just  at  the  bend  between  end  of 
dorsal  surface  and  beginning  of  the  superior  surface  of  the  mid-brain. 

In  all  cross-sections  through  the  aqueduct — /.  e.  at  right  angles  to  the  plane 
of  the  dorsal  surface,  from  its  beginning  to  end — a  large  amount  of  tegment'tl 
tissue  is  to  be  seen  between  it  and  the  ntfatantia  niqra,  ventrally.  Hence  the 
latter  can  have  nothing  to  do  with  the  formation  of  the  floor  of  the  aqueduct. 

The  central  gray  matter  surrounding  the  Sylvian  aqueduct  presents  some 
features  requiring  especial  mention.  It  forms  a  tolerably  thick  layer  surround- 
ing the  canal,  but  is  thicker  on  the  lower  wall — that  is,  below  the  canal — than 
above.  The  cells,  which  are  multipolar,  are  here  collected  into  groups,  and  form 
nuclei  for  the  origin  of  the  third  and  fourth  cranial  nerves.  The  nucleus  for  the 
third  and  fourth  consists  of  a,  column  of  cells  of  large  size  on  either  side  of,  and 
close  to,  the  median  line.  In  addition  to  these  cells  there  are  found  at  the  per- 
iphery of  the  zone  of  gray  matter  surrounding  the  aqueduct  some  other,  and 
larger,  cells,  sometimes  single,  sometimes  grouped  in  tAvos  or  threes,  or  even 
more.  They  are  globular,  and  lie  in  the  midst  of  well-marked  nerve-fibres,  with 
which  their  processes  appear  to  be  continuous.  Close  to  the  Lateral  margin  of 
this  gray  matter,  in  its  lower  part,  is  the  upper  end  of  the  upper  nucleus  of  the 
fifth  nerve. 

The  third  nerve  passes  from  its  nucleus  in  a  somewhat  curved  manner  through 
the  tegmentum,  and  emerges  from  the  oculo-motor  groove  on  the  inner  margin  of 
the  crusta.  Some  of  its  fibres,  however,  from  the  dorsal  part  of  the  nucleus, 
decussate. 

The  fourth  nerve  passes  downward  from  its  nucleus  toward  the  pons,  on  enter- 
ing which  it  turns  dorsally,  and  then  runs  transversely  in  the  superior  medullary 
velum,  crossing  the  middle  line  and  decussating  with  its  fellow,  to  emerge  from 
the  dorsal  surface  of  the  velum.  It  then  curves  obliquely  downward  and  for- 
ward, resting  on  the  crusta. 


THE   BRAiy   A XI)    ITS    irKMBRAXES.  74o 

Superior  Surface  of  Mid-brain. — The  superior  surface  of  the  mid-brain  begins 
just  anterior  to  the  anterior  pair  of  the  corpora  quadrigemina.  It  is  directed 
downward  and  forward,  and  meets  the  upper  extremity  of  the  ventral  surface  at 
quite  an  acute  angle.  The  central  portion  of  this  surface  is  narrow  and  free.  It 
consists  of  tegmentum,  and  forms  the  first  part  (from  behind  forward)  of  the  floor 
of  the  thii-'l  ventricle  (Fig.  442).  Of  each  lateral  portion  the  area  immediately 
u,ljo<;-nt  to  the  central  portion  is  also  tegmentum.  and  has  resting  on  it  and  is 
closely  connected  with  the  optic  ?/<<//<//////.«  of  the  inter-brain.  External  to  this 
area  is  the  "margin  "  of  the  superior  surface,  which,  when  the  mid-brain  is  iso- 
lated by  dissection,  is  seen  to  consist  of  the  upper  ends  of  the  fibres  of  the  crusta, 
cut  across  just  as  they  are  about  to  be  continuous  with  those  of  the  internal  cap- 
sule of  the  hemisphere  (see  Figs.  460  and  461). 

Posterior  Perforated  Lamina. — In  vertical  transverse  sections  through  the  pos- 
t-  /•!"/•  i»irt  of  the  optic  thalami  and  superior  surface  of  the  mid-brain  the  tegmen- 
tum is  clearly  to  be  distinguished,  both  the  portions  beneath  the  optic  thalami 
and  the  central  free  portion  between  them  (beginning  of  floor  of  third  ventricle). 
In  all  similar  sections  made  anterior  to  this,  however,  the  tegmentum  is  seen  to 
become  less  and  less  distinct,  until  it  finally  disappears,  and  we  have  only  the 
optic  thalami  lying  dorsal  to  the  substantia  nigra,  which  last  also  bridges  over 
the  interval  < third  ventricle)  between  them.  Tli*  portion  of  the  substantia  nigra 
is  the  anterior  part  of  that  (already  mentioned)  which  is  seen  in  the  interval 
between  the  crustre.  It  is  called  the  pout •  /•>»/•  perforated  lamina,  and  is  the 
second  structure,  from  behind  forward,  forming  the  floor  of  the  third  ventricle. 

Subthalamic    Region. — The  gradual  disappearance  of  the  tegmentum  in  the 

cross-sections  just  referred  to  is  due  to  the  blending  of  the  tegmental  tissue  with 

that  of  the  superjacent  portion  of  the  optic  thalamus,  the  central  tegmeutal  tissue 

also  thinning  out  as  the  lateral  parts  are  thus  absorbed.     To  this  tissue,  thus 

made  up   of  tegmentum   and   optic   thalamus,    the   name   subthalamic  tegmental 

•  n  is  given.     In  it  are  seen  the  remnant  of  the  red  nucleus  on  each  side, 

together   with   what  corresponds  to  the  lateral  parts  of  the  substantia  nigra — 

r'  Z, >'//.*.     Dorsal  to  this  is  the  zona  incerta.  a  layer  of  reticular  formation 

derived  from  that  of  the  tegmentum  proper,  and  still  more  dorsally  is  the  stratum 

•  il>.  a  layer  of  longitudinal  fibres  derived  from  the  posterior  longitudinal 
bundle  and  superior  peduncle  of  the  cerebellum  (see  page  742). 

THE  INTER-BRAIN  (Fig.  441). 

The  inter-brain,  or  thalamencephalon  ( /.  <• .  thalamencephalon  proper  and  prosen- 
cephalon,  see  page  706),  together  with  the  hemispheres,  constitutes  the  cerebrum. 

Anteriorly,  the  inter-brain  is  connected  with  the  combined  frontal  lobes  of  each 
hemisphere:  laterally,  it  is  connected  with  the  inner  aspect  of  each  hemisphere; 
•/"/•///.  it  has  resting  on  it.  but  with  two  layers  of  pia  mater  interposed,  the 
under  surface  of  the  combined  hemispheres ;  posteriorly,  it  is  connected,  mesially. 
with  the  lamina  quadrigemina  of  the  mid-brain,  beyond  which  connection,  on 
each  side,  it  is  free,  this  free  portion  being  the  rounded  posterior  extremity 
pulvinar)  of  the  optic  thalamus. 

The  cavity  of  the  inter-brain  is  the  third  ventricle,  a  vertical  antero-posterior 
slit  lying  between  the  optic  thalami.  which  are  the  thick  side-walls  of  the  inter- 
brain  (see  also  Figs.  447  and  451).  The  roof  proper  of  the  ventricle  is  a  layer  of 
epithelium,  like  that  of  the  lower  half  of  the  fourth  ventricle,  which  stretches 
between  the  optic  thalami.  and,  together  with  their  superior  surfaces,  constitutes 
the  upper  surface  of  the  inter-brain.  Hence  (see  above)  the  under  surface  of  the 
combined  hemispheres  lies,  in  the  middle  line,  on  the  roof  of  the  third  ventricle, 
but  with  two  layers  of  pia  mater  (velum  interpositum)  interposed.  The  floor  of 
the  third  ventricle  almost  meets  the  roof  posteriorly,  being  separated  from  it  only 
by  the  orifice  of  the  Sylvian  aqueduct,  and  then  proceeds  downward  and  forward 
until  it  attains  its  greatest  distance  from  the  roof  (infundibulum),  where  it  turns 
upward  and  forward,  and  finally  upward  to  meet  the  anterior  end  of  the  roof 


746 


THE   NERVOUS   SYSTEM. 


proper.  This  "upward  prolongation"  of  the  floor  is  known  as  the  "anterior 
boundary  "  of  the  ventricle. 

The  Optic  Thalamus. — Each  optic  thalamus  is  a  large  oblong  mass  of,  chiefly, 
gray  matter.  It  has  two  rounded  extremities,  anterior  and  posterior,  and  four 
surfaces,  superior,  inferior,  external,  and  internal. 

The  inferior  surface  rests  upon,  and  is  united  with  its  corresponding  part  of 
the  tegmentum.  The  external  surface  lies  in  contact  with  the  internal  capsule  of 
the  hemisphere.  Its  internal  surface  forms  the  lateral  boundary  or  wall  of  the 


Anterior  cornu 
Fifth  ventricle 

Septum 
pellucidum 


Orifice  of 
infundibulum 

Tsenia  semicirc. 

Peduncle  of 
'pineal  gland 


Orifice  of  Syl- 
^/wan  aqueduct 


^Epiphysis 


Fillet  (lat.) 


'trise.  acusticx 


Intermed.  lat.  furrow 
Post.  med.  fissure 

FIG.  441.— Superior  surface  of  inter-brain ;  dorsal  surfaces  of  mid-brain,  pons,  and  medulla.    Most  of  the 
cerebral  hemispheres  and  cerebellum  are  removed,  X  i-    (Gegenbaur.) 

third  ventricle  (Figs.  447,  442,  441).  Its  upper  surface  is  free,  and  is  traversed 
by  a  groove  from  behind  forward  and  inward.  The  portion  external  to  this 
groove  is  seen  in  the  floor  of  the  body  of  the  lateral  ventricle,  but  it  is  covered 
by  a  layer  of  epithelium  continuous  with  that  lining  the  lateral  ventricle.  It  is 
marked  in  front  by  an  eminence,  the  anterior  tubercle.  The  portion  of  the  upper 
surface  internal  to  the  groove  is  covered  by  the  velum  interpositum. 

The  posterior  extremity  of  the  optic  thalamus  projects  beyond  the  level  of  the 
corpora  quadrigemina,  and  forms  a  well-marked  prominence,  the  posterior  tubercle 
or  pulvinar  in  close  connection  with  which  are  two  small  rounded  eminences,  the 
internal  and  external  geniculate  bodies,  the  internal  lying  in  the  groove  between 
the  dorsally  projecting  pulvinar  and  side  of  the  mid-brain,  the  external  being  placed 


THE   BRAIX  AXD    ITS   MEMBRANES. 


747 


immediately  beneath  the  pulvinar  (Figs.  439  and  443).  Its  anterior  extremity, 
which  is  rounded  and  smaller  than  the  posterior,  forms  the  posterior  boundary  of 
the  foramen  of  Monro. 

Structure  of  the  Optic  Thalamus. — The  optic  thalamus  is  chiefly  formed. of  gray 
matter,   covered  over  by  a   superficial  layer  of  white,   which  on  the  outer  side 


Genu  of  the 
corp.  call. ' 


Anterior 
eoMiisntre 


Chiasma  opt 


Infund.  Corp.  Middle  Fed.  Epi-  Aqux-  Lamina 
mam-  comm.ofpin.phy-  duct,      quad- 
millare  gl.     sis    Sylvii    rigcm. 

FIG.  442.— The  right  side  of  an  antero-posterior  median  section  of  the  parts  immediately  around  the  third 

ventricle.    (Gegenbaur.) 

(external  medullary  lamina)  separates  it  from  the  internal  capsule.  This  layer 
on  the  upper  surface  is  known  as  the  stratum  zonale,  and  is  prolonged  downward 
on  the  internal  surface. 

The  gray  matter  is  arranged  in  two  masses,  the  outer  and  inner  nuclei,  par- 
tially divided  by  a  vertical  white  septum,  S-shaped  on  section,  the  internal  medul- 
lary lamina.  The  thalamus  is  traversed  by  numerous  nerve-fibres,  which  for  the 


Corp. 
gcnicul 


Tractus  options 


Optic  chiasma 


FIG.  443.— Geniculate  bodies  seen  from  below.    The  cut-surface  is  through  the  plane  of  junction  between 
pons  and  mid-brain,  X  {•    (Gegenbanr.) 

most  part  have  no  definite  direction :  some,  however,  converge  and  form  various 
bundles  which  pass  out  of  the  optic  thalamus  to  blend  with  the  white  matter  of  the 
hemispheres,  as  follows  :  (1)  from  its  anterior  extremity  to  the  frontal  lobes  (anterior 
stalk  of  thalamus) :  (2)  from  its  lower  part  (subthalamic  region)  to  (a)  lenticular 
nucleus  of  corpus  striatum  (ansa  lenticulan's)  and  (/>)  internal  capsule  (ansapedun- 
cularis),  the  fibres  of  which  pass  below  the  lenticular  nucleus  and  into  the 
"external  capsule"  of  the  hemisphere;  (3)  from  its  outer  surface  through  inter- 
nal capsule  to  parietal  and  temporal  lobes :  (4)  from  pulvinar  (outer  aspect)  to 
occipital  lobe.  These  last  are  long  and  curve  backward,  and  radiate  toward  the 
cortex.  They  are  called  the  optic  radiations.  They  connect,  through  the  pulvinar, 
with  the  outer  root  of  the  optic  tract.  The  gray  matter  contains  comparatively 
large  nerve-cells,  both  multipolar  and  fusiform.  The  inner  nucleus  is  connected 


748  THE  NERVOUS  SYSTEM. 

across  the  middle  line  with  the  inner  nucleus  of  the  opposite  side  by  the  middle 
commissure  of  the  third  ventricle.  The  outer  nucleus  is  continued  into  the 
pulvinar. 

There  are  two  other  smaller  nuclei  in  the  optic  thalamus — one  the  nucleus  of 
the  anterior  tubercle,  and  the  other,  just  beneath  the  trigonum  habenulce  (see 
below),  the  ganglion  of  the  habenula.  There  are  also  two  bundles  of  fibres  in 
addition  to  those  just  described.  One  of  these  runs  through  the  anterior  part  of 
the  optic  thalamus.  It  is  the  anterior  pillar  of  the  fornix,  and  will  be  again 
referred  to,  as  will  also  the  other,  much  smaller,  the  bundle  of  Vicq  d'  Azyr,  whose 
fibres  run  downward  from  their  origin  in  the  cells  of  the  nucleus  of  the  anterior 
tubercle,  just  mentioned. 

The  third  ventricle  (Figs.  442,  447,  451)  is  the  fissure  placed  between  the  optic 
thalami  and  extending  to  the  base  of  the  brain.  It  is  bounded,  above,  by  the 
posterior  commissure  and  the  under  surface  of  the  velum  interpositum,  lined  with 
epithelium,  from  which  are  suspended  the  choroid  plexuses  of  the  third  ventricle. 
Its  floor,  somewhat  oblique  in  its  direction,  -is  formed,  from  before  backward,  by 
the  lamina  cinerea,  the  tuber  cinereum  and  infundibulum,  the  locus  perforatus 
posticus  (posterior  perforated  lamina)  and  behind  these  by  the  tegmentum  of  the 
mid-brain ;  its  sides  are  formed  by  the  internal  surfaces  of  the  optic  thalami.  It 
is  bounded,  in  front,  by  the  lamina  cinerea,  while  the  extreme  upper  part  of  its 
"  anterior  boundary  "  is  a  layer  of  epithelium  covering,  posteriorly,  and  through 
which  are  seen,  from  within  the  ventricle,  the  anterior  pillars  of  the  fornix  and 
middle  part  of  the  anterior  commissure. 

These  last-named  structures  belong  to  the  hemispheres,  and  the  epithelium 
covering  them  posteriorly  is  the  same  layer  as  that  which  lies  in  contact  with  the 
lamina  cinerea,  which  itself,  on  reaching  the  anterior  commissure,  passes  in  front 
of  it,  and  is  continuous  with  the  corpus  callosum  of  the  hemispheres.  This  extreme 
upper  part  of  the  lamina  cinerea  is  often  called  the  lamina  terminalis.  It  is  the 
representative  in  the  adult  brain  of  the  anterior  end  of  the  primary  fore-brain, 
around  and  in  front  of  which  have  grown  the  anterior  parts  of  the  hemisphere 
vesicles  to  form  the  frontal  lobes  of  the  hemispheres. 

The  lateral  extension  of  this  epithelial  layer  is  through  the  corresponding  fora- 
men of  Monro,  which  lies  just  behind  each  anterior  pillar  of  the  fornix. 

The  various  structures  which  enter  into  the  formation  of  the  third  ventricle 
will  now  be  described  more  in  detail,  beginning  with  those  of  the  ROOF  (Fig.  442). 

The  posterior  commissure  is  a  distinct  rounded  bundle  of  white  fibres  running 
transversely  just  above  the  opening  of  the  Sylvian  aqueduct.  The  pineal  gland 
is  placed  above  it  and  connected  to  its  upper  surface.  It  is  made  up  of:  (1)  the 
combined  upper  ends  of  the  two  posterior  longitudinal  bundles  (see  tegmentum  of 
mid-brain)  as  each  bends  to  the  opposite  side  in  order  to  pass  through  the  opposite 
optic  thalamus  and  reach  the  white  substance  of  the  hemisphere ;  (2)  commissural 
fibres  between  the  optic  thalami ;  (3)  fibres  from  one  anterior  corpus  quadrigem- 
inum  to  the  opposite  upper  fillet. 

The  pineal  gland  (epiphysis  cerebri],  so  named  from  its  peculiar  shape  (pinus, 
a  fir-cone),  is  a  small  reddish-gray  body,  conical  in  form  (hence  its  synonym, 
conarium),  placed  immediately  behind  the  posterior  commissure  and  between  the 
anterior  corpora  quadrigemina.  It  is  retained  in  its  position  by  a  duplicature  of 
pia  mater  derived  from  the  under  layer  of  the  velum  interpositum,  which  almost 
completely  invests  it.  The  pineal  gland  is  about  four  lines  in  length  and  from 
two  to  three  in  width  at  its  base,  and  is  said  to  be  larger  in  the  child  than  in  the 
adult,  and  in  the  female  than  in  the  male.  Its  base  is  connected  to  the  optic 
thalami  by  a  stalk,  which  consists  of  two  laminre,  an  upper  and  a  lower,  the  inter- 
vening space,  apex  toward  the  gland,  being  known  as  the  pineal  recess.  The 
lower  or  ventral  lamina  is  derived  from  the  lower  aspect  of  the  posterior  commis- 
sure, and  is  reflected  upward  and  backward  to  meet  the  upper  or  dorsal  layer  at 
the  base  of  the  gland.  The  dorsal  lamina  is  the  direct  continuation  backward  of 
the  epithelial  roof  of  the  third  ventricle.  When  this  is  torn  away  the  dorsal 


THE   BRAIX  AND    ITS   MKMltHAXES.  749 

lamina  necessarily  has  a  free  edge  looking  forward.  On  each  side  this  lamina  is 
prolonged  into  a  somewhat  triangular-shaped,  depressed  area  on  the  upper  surface 
of  the  optic  thalaums.  known  as  the  trigonum  habenulce,  because  the  word  "ha- 
benula"  (bridle)  is  often  applied  to  this  dorsal  lamina  of  the  stalk.  The  free  edge 
of  the  lamina  is  also  prolonged  as  a  delicate  whitish  band  on  to  the  optic  thalamus, 
on  which  it  runs  forward  along  the  sharp  margin  which  separates  the  superior 
from  the  internal  surface  of  the  thalamus.  These  bands  are  the  pineal  strice  or 
peduncles  of  the  pineal  gland.  Anteriorly  each  blends  with  the  corresponding 
anterior  pillar  of  the  fornix. 

Structure. — The  pineal  gland  consists  of  a  number  of  follicles  lined  by  epithe- 
lium and  connected  together  by  ingrowths  of  connective  tissue.  The  follicles 
contain  a  transparent  viscid  fluid,  and  a  quantity  of  sabulous  matter,  named 

'•ulus  cerebri,  composed  of  phosphate  and  carbonate  of  lime,  phosphate  of 
magnesia  and  ammonia,  with  a  little  animal  matter.  These  concretions  are 
almost  constant  in  their  existence,  and  are  found  at  all  periods  of  life.  At  times 
the  sabulous  matter  is  found  upon  its  surface,  and  occasionally  upon  its  peduncles. 
In  the  foetal  brain  the  pineal  gland  is  a  hollow  protrusion  from  the  posterior  part 
of  the  roof  of  the  inter-brain. 

The  Epithelial  Roof. — This  stretches  across  the  third  ventricle  from  one  pineal 
to  the  other,  and  then  is  reflected  downward  to  become  continuous  with  the 
epithelium  covering  the  side  of  the  ventricle  (internal  surfaces  of  thalami).  The 
epithelium  is  not  continued  on  to  that  part  of  the  superior  surface  of  the  thala- 
mus which  is  adjacent  to  the  pineal  stria,  and  which  is  internal  to  the  oblique 
shallow  groove,  already  referred  to.  which  runs  along  this  surface.  External  to 
the  groove,  however,  this  upper  surface  is  covered  by  epithelium,  but  this  epithe- 
lium belongs  to  the  lateral  ventricle. 

The  roof  epithelium  of  the  third  ventricle  is  continued  anteriorly  between  the 
pineal  stria?  until  just  before  they  join  the  down-curving  anterior  pillars  of  the 
fornix.  where  it  is  interrupted  by  the  foramen  of  Monro,  around  the  margin  of 
which  it  passes  into  continuity  with  the  epithelium,  lining  its  own  ventricle  and 
the  lateral  ventricle. 

The  velum  interposition  (Fig.  458)  is  a  vascular  membrane,  a  prolongation 
from  the  pia  mater.  It  is  of  a  triangular  form,  and  separates  the  under  surfaces 
of  the  body  of  the  fornix,  posterior  pillars  of  the  fornix,  and  posterior  part  of 
corpus  callosum  above  (the  last-named  structures  representing  the  Bunder  surface 
of  the  combined  hemispheres"),  from  the  cavity  of  the  third  ventricle  and  the 
inner  portions  of  the  superior  surfaces  of  the  optic  thalami  below.  Its  anterior 
extremity,  or  »/»>./•.  is  bifid,  each  bifurcation  lying  close  to  and  behind  the  corre- 
sponding anterior  pillar  of  the  fornix,  and  hence  "•  in,"  but  covered  by  epithelium, 
the  foramen  of  Monro.  Its  base  lies  beneath  the  posterior  rounded  border  of  the 
corpus  callosum  above,  and  the  optic  thalami,  the  corpora  quadrigemina,  and 
pineal  gland  below 

The  velum  interpositum  is  composed  of  two  layers  of  pia  mater,  which  sepa- 
rate from  each  other  at  its  base,  the  upper  layer  passing  backward  on  the  under 
surface  of  the  occipital  lobes  of  the  hemispheres,  the  lower  layer  passing  down- 
ward over  the  mid-brain,  pons.  and  cerebellum.  At  the  apex  the  two  layers  are 
continuous  with  each  other,  as  well  as  at  the  margins,  which  are  free  and  lie  along 
and  project  a  little  beyond  the  groove,  already  referred  to,  which  runs  forward  and 
inward  on  the  superior  surface  of  the  thalamus.  Along  this  margin  is  the 
ehoroid  plexiu  «f  t/><-  lutiTul  >•, •////•/ .-1,\  which  is  covered  by  the  mesial  prolongation 
of  the  layer  of  epithelium  covering  the  outer  portion  of  the  upper  surface  of  the 
thalamus.  After  investing  the  margin  of  the  velum  interpositum  the  epithelium, 
still  prolonged  mesially.  is  attached  to  the  edge  of  the  fornix,  under  which  the 
velum  lies  and  beyond  which  it  projects.  As  will  be  seen  later,  the  fornix  forms 
part  of  the  floor  of  this  district  of  the  lateral  ventricle;  hence  the  roughened 
thickened  margin  (choroid  plexus)  of  the  velum  interpositum  really  invaginates 
into  the  lateral  ventricle,  that  part  of  its  floor  which  has  become  thinned  out  to  a 


750  THE  NERVOUS  SYSTEM. 

layer  of  epithelium,  and  which  stretches  from  the  edge  of  the  fornix  outward  over 
the  thalaraus  (outer  part  of  its  superior  surface)  to  the  teenia  semicircularis  (a 
structure  forming  part  of  the  floor  of  the  lateral  ventricle),  which  lies  along  that 
margin  of  the  optic  thalamus  which  separates  its  superior  from  its  external  surface. 

Tela  Choroidea  Superior. — From  the  preceding  it  is  clear  that  the  under  layer 
of  the  velum  interpositum  has  three  districts — a  mesial  and  two  lateral,  the  latter 
resting  on  the  upper  surfaces  of  the  thalami,  the  former  on  the  "  roof  epithelium  " 
of  the  third  ventricle,  with  which  it  forms  practically  one  membrane.  This  mem- 
brane is  the  tela  choroidea  superior,  and  is  exactly  similar  to  the  tela  choroidea 
inferior  of  the  fourth  ventricle. 

The  reason,  on  embryological  grounds,  for  the  existence  of  two  layers  of  the 
velum  interpositum  will  be  given  in  describing  the  choroid  plexuses  of  the  lateral 
ventricles. 

Of  the  structures  forming  the  FLOOR  (Figs.  442,  446)  of  the  third  ventricle,  the 
tegmentum  of  the  mid-brain  has  been  described.  The  rest  of  the  floor,  including 
the  "  anterior  boundary,"  is  a  gray  lamina  prolonged  from  the  substantia  nigra, 
and  its  ventral  surface  appears  at  the  base  of  the  brain,  where,  however,  the 
tegmentum  cannot  be  seen  (Fig.  473).  Various  portions  of  this  lamina  have 
received  diiferent  names.  Each  of  these  will  now  be  considered,  beginning  pos- 
teriorly. 

The  posterior  perforated  lamina  succeeds  the  tegmentum.  It  is  the  anterior 
part  of  that  portion  of  the  substantia  nigra  which  appears  in  the  interval  between 
the  diverging  crustae  of  the  mid-brain  on  each  side  and  the  upper  margin  of  the 
tuber  annulare  of  the  pons  Varolii  posteriorly  and  below.  Together  with  that 
portion  it  is  often  called  the  posterior  perforated  space  (pons  Tarini).  It  reaches 
forward  as  far  as  the  mamillary  tubercles,  beyond  which  the  gray  lamina  is  known 
as  the  tuber  cinereum. 

The  "  space  "  is  perforated  by  numerous  small  orifices  for  the  passage  of  the 
postero-median  ganglionic  branches  of  the  posterior  cerebral  and  posterior  commu- 
nicating arteries. 

The  corpora  albicantia,  or  mamillaria,  or  mamillary  tubercles,  are  two  small, 
round,  white  masses,  each  about  the  size  of  a  small  pea,  placed  side  by  side  imme- 
diately behind  the  tuber  cinereum.  Each  projects  downward  from  the  under 
surface  of  the  optic  thalamus,  the  exceedingly  narrow  interval  between  them  being 
bridged  over  by  a  gray  commissure  continuous  with  the  posterior  perforated  lamina 
behind  and  the  tuber  cinereum  in  front.  Each  is  composed  externally  of  white 
substance  and  internally  of  gray  matter,  the  gray  matter  of  the  two  being  con- 
nected by  the  transverse  commissure  of  the  same  material  just  mentioned. 

The  fibres  of  the  white  substance  terminate  in  the  cells  of  the  gray  matter, 
and  they  are  derived  from  two  distinct  bundles :  one,  deeply  situated  in  the  sub- 
stance of  the  optic  thalamus,  is  the  bundle  of  Vicq  d'Azyr,  already  mentioned ; 
the  other,  much  larger,  is  the  anterior  pillar  of  the  fornix,  which,  after  bending 
sharply  downward  around  the  foramen  of  Monro,  passes  obliquely,  downward  and 
backward,  through  the  substance  of  the  anterior  portion  of  the  thalamus,  to  ter- 
minate in,  and  thus  help  to  form,  the  corresponding  corpus  albicans  or  bulb  of  the 
fornix.  In  its  course  through  the  thalamus  it  lies  quite  near  the  internal  surface, 
and  may  even  cause  a  slight  projection  on  the  side  of  the  third  ventricle. 

The  tuber  cinereum  is  the  next  portion  of  the  general  lamina  of  the  floor. 
It  is  wider  than  the  posterior  perforated  lamina,  and  blends  laterally  with  the  sub- 
stance of  the  lower  and  anterior  part  of  the  thalamus,  while  antero-laterally,  pass- 
ing dorsal  to  the  optic  tract,  it  extends  beyond  the  limits  of  the  thalamus  into  the 
gray  matter  of  the  anterior  perforated  space  on  the  under  surface  of  the  hemi- 
sphere. Anteriorly,  it  is  attached  to  the  posterior  edge  of  the  optic  commissure. 
From  the  middle  of  its  under  surface  a  conical  tubular  process  of  gray  matter, 
about  two  lines  in  length,  is  continued  downward  and  forward,  to  be  attached  to 
the  posterior  lobe  of  the  pituitary  body  :  this  is  the  infundibulum.  Its  canal, 
which  is  funnel-shaped,  communicates  with  the  third  ventricle. 


THE   BRAIN  AND    ITS   MEMBRANES.  751 

The  pituitary  body  ( hypophysis  cerebri)  is  a  small  reddish-gray  vascular  mass 
weighing  from  five  to  ten  grains,  and  of  an  oval  form,  situated  in  the  sella  Tur- 
cica,  in  connection  with  which  it  is  retained  by  a  process  of  dura  mater  derived 
from  the  inner  wall  of  the  cavernous  sinus.  This  process  covers  in  the  pituitary 
fossa,  enclosing  the  pituitary  body,  and  having  a  small  hole  in  the  centre  through 
which  the  infundibulum  passes.  The  pituitary  body  is  very  vascular,  and  consists 
of  two  lobes,  separated  from  one  another  by  a  fibrous  lamina.  Of  these,  the  ante- 
rior is  the  larger,  of  an  oblong  form,  and  somewhat  concave  behind,  where  it 
receives  the  posterior  lobe,  which  is  round.  The  two  lobes  differ  both  in  develop- 
ment and  structure.  The  anterior  lobe,  of  a  dark,  yellowish-gray  color,  is  devel- 
oped as  a  tubular  prolongation  of  the  epiblast  of  the  buccal  cavity,  and  resembles 
to  a  considerable  extent,  in  microscopic  structure,  the  thyroid  body.  It  consists 
of  a  number  of  isolated  vesicles  and  slightly  convoluted  alveoli  lined  by  epithe- 
lium aud  united  together  by  connective  tissue.  The  epithelium  is  columnar,  and 
occasionally  ciliated.  The  alveoli  sometimes  contain  a  colloid  material  similar 
to  that  found  in  the  thyroid  body,  and  their  walls  are  surrounded  by  a  close  net- 
work of  lymphatics  and  capillary  blood-vessels.  The  posterior  lobe  is  developed 
by  a  hollow  outgrowth  from  the  embryonic  brain,  and  during  foetal  life  contains  a 
cavity  which  communicates  through  the  infundibulum  with  the  cavity  of  the  third 
ventricle.  In  the  adult  it  becomes  firmer  and  more  solid,  owing  to  the  growing 
in  of  a  sponge-like  connective  tissue  arranged  in  the  form  of  reticulating  bundles, 
between  which  are  branched  cells,  some  of  them  containing  pigment. 

The  lamina  cinerea  begins  at  the  posterior  border  of  the  optic  commissure,  in 
continuity  with  the  tuber  cinereum.  It  passes  forward  and  downward  over  the 
commissure,  to  which  it  is  adherent,  and  then  turns  upward,  forms  the  anterior 
boundary  of  the  third  ventricle,  and  terminates,  as  the  lamina  terminalis,  by 
blending  with  the  middle  portion  of  the  anterior  extremity  of  the  corpus  cal- 
losum.  It  is  continuous  on  each  side  with  the  gray  matter  of  the  anterior  per- 
forated space.  The  angle  made  by  the  upward  bend  of  the  lamina  is  known  as 
the  optic  recess. 

The  anterior  boundary  of  the  third  ventricle  is  the  lamina  cinerea  below ; 
above  this,  for  a  very  short  distance,  the  anterior  boundary  is  the  layer  of  epithe- 
lium covering  portions  of  the  posterior  aspects  of  the  anterior  commissure  and 
anterior  pillars  of  the  fornix,  as  already  explained. 

The  SIDES  of  the  ventricle  are  the  internal  surfaces  of  the  thalami.  Each  is 
slightly  convex,  and  just  in  front  of  the  middle  point  of  each  is  attached  the  cor- 
responding extremity  of  the  middle  commissure,  a  band  of  gray  matter  which 
passes  right  across  the  ventricle.  It  is  frequently  broken  in  examining  the  brain, 
and  might  then  be  supposed  to  be  wanting.  A  little  more  anteriorly  is  seen  a 
somewhat  curved,  from  above  downward  and  backward,  elevation  (anterior  pillar 
of  fornix.  already  explained).  As  these  pillars,  traced  upward,  become  free,  they 
bend  sharply  upward  and  backward,  thus  forming  a  completed  curve,  each  enclos- 
ing in  front  and  above  the  foramen  of  Monro,  which  has  for  its  posterior  boundary 
a  part  of  the  anterior  extremity  of  the  optic  thalamus. 

Antero-inferiorly  to  the  curved  elevations  is  still,  on  each  side,  a  small  portion 
left  of  the  internal  surface  of  the  thalamus,  connected  to  the  similar  opposite  por- 
tion, below  and  in  front,  by  the  tuber  cinereum  and  lamina  cinerea.  It  is  thus 
seen  that  all  these  structures  really  form  the  anterior  extremity  of  the  third  ven- 
tricle (see  page  706),  which  is  the  prosencephalon,  or,  in  the  foetal  brain,  the  first 
secondary  cerebral  vesicle.  Hence  the  "curved  elevations"  may  be  regarded  as 
indicating,  approximately,  the  line  of  division  or  constriction  between  the  first 
and  second  secondary  cerebral  vesicles  (prosencephalon  and  thalmencephalon 
proper),  while  the  foramina  of  Monro  are  to  be  regarded  as  opening  from  the 
prosencephalon,  and  thus  represent  the  foetal  foramina  caused  by  the  bulging  out 
of  the  hemisphere  vesicles  (see  Figs.  412,  413,  414). 

The  choroid  plexuses  of  the  third  ventricle,  formed  like  those  of  the  fourth, 
lie  along  the  roof,  projecting  downward,  one  on  each  side  of  the  middle  line. 


752  THE  NERVOUS  SYSTEM. 

They  are  covered  with  epithelium,  and  are  derived  from  the  lower  layer  of  the 
velum  interpositum.  Of  the  arteries  of  the  velum  interposituru,  some  branches 
from  the  superior  cerebellar  and  posterior  cerebral  enter  from  behind  beneath  the 
corpus  callosum.  The  veins  of  the  velum  interpositum,  the  vence  Galeni,  two  in 
number,  run  between  its  layers ;  they  are  formed  by  the  venae  corporis  striati  and 
the  veins  of  the  choroid  plexuses ;  the  venae  Galeni  unite  posteriorly  into  a  single 
trunk,  which  terminates  in  the  straight  sinus  (Fig.  383). 

Openings. — The  third  ventricle  has  four  openings  connected  with  it.  In  front 
are  the  two  foramina  of  Monro,  one  on  each  side,  through  which  the  third  com- 
municates with  the  lateral  ventricles.  Behind  is  a  third  opening,  that  of  the 
aqueduct  of  Sylvius,  or  iter  a  tertio  ad  quartum  ventriculum.  The  fourth,  sit- 
uated in  the  anterior  part  of  the  floor  of  the  ventricle,  is  a  deep  pit,  which  leads 
downward  to  the  funnel-shaped  cavity  of  the  infundibulum  (iter  ad  infundibulum). 
A  fifth  opening  exists  in  the  foetus  which  communicates  behind  with  the  cavity 
in  the  pineal  gland. 

The  lining  membrane  of  the  lateral  ventricles  is  continued  through  the 
foramen  of  Monro  into  the  third  ventricle,  and  extends  along  the  iter  a  tertio 
(aqueduct  of  Sylvius)  into  the  fourth  ventricle ;  at  the  bottom  of  the  iter  ad 
infundibulum  it  ends  in  a  cul-de-sac. 

The  Optic  Tracts  (Figs.  415,  443). — These  are  two  well-marked  flattened  bun- 
dles of  fibres  which  lie  along  the  upper  parts  of  the  crustae.  They  are  attached 
only  by  their  upper  edges,  which  also  serve  to  mark  the  transition  between  upper 
limit  of  crusta  and  internal  capsule  of  hemisphere.  These  edges  also  mark  the 
limit  of  separation,  without  tearing,  between  the  temporo-sphenoidal  lobes  of  the 
hemispheres,  which,  at  the  base  of  the  brain,  overlap  the  optic  tracts  and  the 
crustae.  Each  tract  was  originally  a  hollow  outgrowth  (optic  vesicle)  from  the 
back  part  of  the  fore-brain.  Anteriorly  each  unites  with  the  other  to  form  the 
optic  commissure.  The  fibres  of  each  are  described  in  connection  with  the  optic 
nerve  (which  see). 

THE  HEMISPHERES. 
General  Considerations  and  Development. 

The  two  hemispheres  are  by  far  the  largest  portion  of  the  encephalon,  each 
one  in  bulk  exceeding  somewhat  all  the  other  divisions  of  the  brain.  Together 
with  the  fore  part  of  the  third  ventricle  they  form  what  is  called  by  some  writers 
the  prosencephalon  or  fore-brain. 

Each  hemisphere  is  an  enormously  developed  "  hemisphere  vesicle  "  whose 
cavity  is  the  lateral  ventricle,  and  whose  walls,  originally  smooth,  thin,  and 
spherical,  are  convoluted,  elongated  in  various  directions,  arid,  for  the  most  part, 
exceedingly  thick.  Although  the  two  hemispheres  in  the  adult  brain  are  con- 
nected with  each  other  by  means  of  the  corpus  callosum  and  anterior  commissure, 
this  connection  is  merely  between  the  adjacent  walls,  and  in  no  wise  involves  the 
cavities,  each  cavity  being  as  distinct  from  the  opposite  one  as  it  is  in  early  foetal 
life  before  the  intermural  connection  is  established.  Each  lateral  ventricle  is, 
therefore,  a  complete  cavity,  communicating  only  with  the  third  ventricle  through 
the  corresponding  foramen  of  Monro. 

The  development  of  each  hemisphere  vesicle  may  be  described  approximately 
as  follows  (Figs.  412,  413,  414) :  After  becoming  a  rounded  hollow  projection 
from  the  side  of  the  prosencephalon,  each  hemisphere  vesicle  expands  in  an 
anterior  direction  and  approaches  close  to  its  fellow.  At  the  same  time  it  grows 
upward  over  the  inter-brain  and  backward  along  its  side,  while  from  this  latter 
portion  two  projections  may  be  said  to  take  place — one  still  farther  backward, 
covering  over  the  dorsal  surface  of  the  mid-brain  and  cerebellum  ;  and  the  other, 
downward  and  forward,  overlapping  somewhat  the  external  surface  of  the  portion 
from  which  it  is  derived,  until  its  lower  end  projects  below,  and  also  overlaps  the 
ventral  surface  of  the  mid-brain  (crustae).  We  can  thus  distinguish  four  main 
divisions  of  the  developing  hemisphere  vesicle :  an  anterior,  a  superior,  the  latter 


THE   BRAIN  AND   ITS  MEMBRANES.  753 

giving  off  an  inferior,  and  a  posterior  division.  As  these  four  divisions  repre- 
sent sufficiently  accurately  the  four  large  divisions  or  lobes  of  the  adult  hemi- 
sphere, it  will  be  more  convenient,  in  tracing  their  further  development,  to  give 
them  the  same  names,  thus :  the  anterior  division  will  be  called  the  frontal  lobe  ; 
the  superior,  the  parietal  lobe  ;  the  posterior,  the  occipital  lobe  ;  and  the  inferior, 
the  temporal  or  temporo-sphenoidal  lobe.  Each  of  these  has  its  portion  of  the 
original  cavity,  all  of  which  naturally  intercommunicate. 

The  frontal  lobes  are  now  closely  approximated  in  front  of  the  inter-brain, 
while  there  is  also  to  be  noted  the  formation  of  the  optic  thalami,  which  are  merely 
the  thickened  sides  of  the  inter-brain  (prosencephalon  and  thalamencephalon). 

The  parietal  lobes  are  similarly  approximated  above  the  optic  thalami,  but  they 
have  now  enlarged,  so  that  the  inner  aspect  of  each  comprises  two  regions  (see 
Fig.  459) — one,  just  mentioned,  close  to  its  fellow  above  the  inter-brain  ;  the  other, 
lower  region,  lying  external  to  the  external  surface  of  the  optic  thalamus. 
Furthermore,  the  upper  region  is  the  inner  wall  of  the  cavity  of  the  parietal  lobe, 
which  also  comes  above  the  inter-brain,  while  the  lower  region  is  simply  the  inner 
aspect  of  solid  matter — i.  e.  a  downward  thickening  of  the  original  wall.  Along 
the  floor  of  that  portion  of  the  ventricle  contained  in  the  parietal  lobe  is  now  seen 
a  thickening  which  soon  resolves  itself  into  a  bundle  of  fibres.  This  band  of 
fibres,  when  traced  forward,  is  found  to  be  continuous  with  a  similar  thickening 
around  the  foramen  of  Monro,  which  in  its  turn  is  continued  down  through  the 
optic  thalamus  (anterior  pillar  of  fornix  ;  see  page  761).  The  curve  of  this  band 
is  due  to  the  marked  antero-posterior  flexure  of  the  entire  foetal  brain  which  has 
already  taken  place,  while  its  transition  in  position — L  e.  to  the  floor  of  the  "  pari- 
etal cavity  " — is  due  to  a  certain  twisting  or  rotation  which  the  hemisphere 
vesicle  now  undergoes. 

The  approximation  of  the  parietal  lobes  brings  these  bands  very  close  together 
as  they  curve  upward,  and,  as  neither  one  is  developed  in  the  cavity  of  the  cor- 
responding frontal  lobe,  each  serves,  just  here,  as  a  line  of  demarkation  between 
the  inner  wall  of  the  frontal  lobe  in  front  and  that  of  the  parietal  lobe  behind. 
Traced  backward,  these  bands  are  necessarily  found  to  lie  dorsal  to  the  inter- 
brain,  since  each  is  in  the  floor  of  the  corresponding  cavity  of  the  parietal  lobe. 

Fornix. — The  next  point  to  be  noted  is  the  absolute  approximation  of  the  two 
frontal  and  of  the  "  upper  regions  "  of  the  inner  aspects  of  the  two  parietal  lobes. 
As  a  result  of  the  latter  approximation,  the  two  anterior  pillars  of  the  fornix,  just 
above  the  foramen  of  Monro,  are  brought  together  edge  to  edge,  and  an  actual 
union  takes  place  between  them.  This  union  extends  posteriorly  for  more  than 
half  the  length  of  the  floor  of  each  cavity  of  the  parietal  lobe,  and  is  known  as 
the  body  of  the  fornix,  or  as  "  the  fornix  "  in  the  adult  brain.  The  anterior 
pillars,  however,  as  they  curve  downward,  are  not  united,  this  slight  separation 
persisting  in  the  adult  brain. 

Anterior  Commissure. — Immediately  anterior  to  and  connected  with  each  of 
these  pillars,  just  previous  to  its  passage  through  the  optic  thalamus,  is  a  portion 
of  the  inner  wall  of  the  cavity  of  the  frontal  lobe,  which  is  now  in  close  contact 
with  the  opposite  one.  Just  at  this  point  there  now  occurs  an  interchange  of 
fibres  between  the  inner  walls  of  each  frontal  cavity.  These  fibres  (anterior  com- 
missure) run  transversely  across  the  front  of  the  upper  part  of  the  anterior 
boundary  of  the  prosencephalon,  and  causes  an  absorption  of  its  tissue,  its  epi- 
thelial lining  excepted.  so  that  the  latter  comes  to  lie  directly  on  the  centre  part 
of  the  posterior  aspect  of  the  anterior  commissure,  in  the  interval  between  the 
anterior  pillars  of  the  fornix. 

The  lower  part  of  the  anterior  boundary  of  the  prosencephalon  persists  in  the 
adult  brain  as  the  upper  limit  of  the  lamina  cinerea  (lamina  terminalis). 

Corpus  Callosum. — The  frontal  lobes  having  now  grown  well  forward,  and  hav- 
ing also  curve*.!  upward  to  form  the  parietal  lobes,  and  the  inner  surface  of  each 
frontal  and  the  "  upper  region  "  of  the  inner  surface  of  the  corresponding  parietal 
lobe  having  met  the  same  structures  of  the  opposite  hemisphere,  there  is  formed 


754  THE  NERVOUS  SYSTEM. 

a  curved  line  of  actual  contact,  all  along  \vbich  occurs  an  interchange  of  fibres 
running  transversely  from  one  hemisphere  to  the  other.  Another  factor,  besides 
the  upward  curve  of  the  parietal  lobe,  in  causing  this  line  of  contact  to  be  curved 
is  doubtless  the  antero-posterior  flexure  of  the  whole  foetal  brain,  already  re- 
ferred to.  This  large  transverse  commissure,  thus  formed,  curved  anteriorly,  is 
the  corpus  callosum  of  the  adult  brain. 

This  curved  line,  along  which  the  above-mentioned  interchange  of  fibres  takes 
place,  has  two  extremities,  an  anterior  and  a  posterior. 

The  anterior  extremity  is  immediately  in  front  of,  and  in  direct  contact  with, 
the  lateral  part  of  the  anterior  commissure.  Here  the  corpus  callosum  itself  is 
thin  and  conceals  the  anterior  commissure  from  in  front  and  below  ;  it  is  also 
adherent  to  it  and  blends  inferiorly  with  the  lamina  terminalis. 

The  posterior  extremity  of  the  curved  line  is  at  the  posterior  part  of  the  inner 
wall  of  the  cavity  of  the  parietal  lobe.  Here  the  corpus  callosum  itself  is  very 
thick  and  with  a  free  posterior  edge,  beyond  which  project,  posteriorly,  the  inner 
surfaces  of  the  occipital  lobes,  entirely  separate  from  each  other. 

This  curved  line — or  the  cut  surface  of  the  corpus  callosum,  which  is  the  same 
thing — will  now  be  traced  from  the  posterior  to  the  anterior  extremity. 

As  it  passes  along  anteriorly  in  the  inner  wall  of  the  "  parietal  cavity"  it  is 
quite  near  the  floor,  so  that  it  soon  reaches  and  becomes  adherent  to  the  corre- 
sponding half  of  the  "body  of  the  fornix  "  immediately  below  it.  As  it  goes 
forward  from  this  point  it  separates  from  its  half  of  the  fornix,  which  is  now  curv- 
ing around  the  foramen  of  Monro.  Continuing  forward,  the  cut  edge  of  the  corpus 
callosum  is  now  on  the  inner  wall  of  the  "frontal  cavity."  It  continues  this 
course  for  a  distance,  and  then  bends  sharply  downward,  after  which  it  runs  lack- 
ward  until  it  reaches  the  anterior  commissure,  by  which  it  is  separated  from  the 
anterior  pillar  of  the  fornix,  just  as  the  latter  is  about  to  run  downward  through 
the  optic  thalamus. 

Septum  Lucidum. — There  is  thus  formed  a  somewhat  oval-shaped  interval, 
tapering  posteriorly,  bounded  above  and  in  front  by  the  corpus  callosum ;  below, 
by  the  corpus  callosum  (reflected  part)  and  anterior  commissure;  behind  and  below, 
by  the  anterior  pillar  of  the  fornix  and  body  of  the  fornix,  respectively. 

This  interval  is  filled  in  by  a  lamina  on  each  side,  which  is  a  portion  of  the  inner 
Avails  of  both  frontal  and  parietal  cavities.  This  lamina  is  necessarily  in  close 
contact  with  the  opposite  one,  and  they  both  together  constitute  the  septum  lucidum 
of  the  adult  brain  (Figs.  448,  461). 

The  corpus  callosum  in  addition  to  forming  the  commissure  just  described 
spreads  outwardly,  also,  in  the  frontal  and  parietal  lobes,  and,  as  it  is  now  quite 
thick,  its  under  surface  forms  the  roof  of  the  "parietal  and  frontal  cavities;" 
its  posterior  surface  (at  the  bend)  is  the  anterior  boundary  of  the  "  frontal  cav- 
ity," while  the  upper  surface  of  its  reflected  portion  is  the  floor  of  the  frontal 
cavity. 

Along  the  outer  wall  of  both  frontal  and  parietal  cavities  the  corpus  strict  nm 
is  developed  as  a  marked  thickening,  and  close  above  it  passes  the  corpus  cal- 
losum. All  portions  of  the  frontal  and  parietal  lobes  external  to  the  corpus  stri- 
atum  and  above  the  corpus  callosum,  and  those  portions  of  the  frontal  lobe  ante- 
rior to  and  below  the  corpus  callosum,  develop  into  thick,  solid  matter  and 
project  for  a  considerable  distance,  but  without  uniting  with  the  opposite  side, 
beyond  the  corpus  callosum  in  the  corresponding  directions.  This  solid  mattrr 
constitutes  the  bulk  of  the  lobe. 

The  "lower  region  "  of  the  internal  surface  of  the  parietal  lobe  (internal  cap*ul<' 
of  adult  brain)  is  eventually  closely  united  to  the  external  surface  of  the  optic 
thalamus  (Figs.  461,  460). 

The  occipital  lobe  is  the  backward  extension  of  the  hemisphere.  It  is  entirely 
separate  from  the  opposite  one.  Its  cavity  is  roofed  over  by  backward  curved 
prolongations  from  the  corpus  callosum. 

The  temporal  lobe   (temporo-sphenoidoT)    grows   downward   and   forward,    as 


THE   BRA  IX.  AXD    ITS   MEMBRANES. 


755 


already  described.  It  carries  with  it,  in  its  floor,  a  prolongation  of  its  corre- 
sponding half  of  the  for  nix,  which,  consequently, 
in  the  adult  brain,  is  described  as  dividing  poste- 
riorly into  its  two  posterior'  pillars.  As  this  lobe 
curves  downward  it  embraces,  but  does  not  adhere  to, 
the  pulvinar  of  the  optic  thalauius. 

In  the  foetal  brain  a  wide  shallow  cleft  (Fig. 
444)  lies  between  the  temporal  and  portions  of  the 
frontal  and  parietal  lobes,  but  this  deepens  and  nar- 
rows (/?'.>•.<;//•'  "/  Xi/l>'iiis)  as  the  lobe  develops.  The 
•  '•ai-ity  of  the  temporal  lobe  lies  close  to  its  inner 
aspect,  the  bulk  of  the  lobe  developing  externally. 
A  portion  of  the  corpus  callosum  roofs  over  the 
beginning  of  the  temporal  cavity. 

The  Lateral  Ventricles,  and  Structures  in  Connection  therewith. 

The  lateral  ventricles  are  the  cavities  of  the  hemispheres,  each  being  distinct 
from  the  other.  In  each  hemisphere  the  lateral  ventricle  is  situated  in^its  lower 
and  inner  regions,  being  surrounded  above,  in  front  and  externally,  by  the  solid, 
chiefly  white,  matter  of  the  hemisphere.  Each  lateral  ventricle*  communicates 
through  the  foramen  of  Monro  with  the  third  ventricle,  and  is  lined  by  a  thin 
diaphanous  membrane  (the  ependymd),  covered  by  nucleated  epithelium  with 
cilia,  scattered  here  and  there  in  patches.  It  is  moistened  by  a  serous  fluid, 
which  is  sometimes,  even  in  health,  secreted  in  considerable  quantity.  Each  is 
separated  from  the  other  by  a  vertical  septum,  the  septum  lucidum. 

Each    lateral   ventricle    consists    (Fig.   445)    of  a    central    cavity,    or   body, 

and  three  accessory  cavities  or  cor- 
nua.  The  anterior  cornu  curves 
forward  and  outward  into  the  sub- 
stance of  the  frontal  lobe.  It  com- 
prises that  portion  of  the  ventricle 
which  is  anterior  to  the  foramen  of 
Monro.  The  body  comprises  that 
portion  of  the  ventricle  which  lies 
between  the  foramen  of  Monro  and 
the  posterior  part  of  the  corpus  cal- 
losum. It  is  situated  low  down  in 
the  parietal  lobe.  From  its  poste- 
rior extremity  diverge  the  two  fol- 
lowing:  The  posterior  cornu,  called 
the  digital  cavity,  curves  backward 
into  the  occipital  lobe;  the  middle 
cornu  descends  into  the  temporal 
lobe. 

If  the  upper  part  of  both  hemi- 
spheres is  removed,  about  half  an 
inch  above  the  level  of  the  corpus 
callosum,  the  internal  white  matter 
will  be  exposed.  It  is  an '  oval- 
shaped  centre,  of  white  substance, 
surrounded  on  all  sides  by  a  narrow 
convoluted  margin  of  gray  matter, 
which  presents  an  equal  thickness  in 
nearly  every  part.  This  white  cen- 
tral mass  has  been  called  the  centrum 
ovale  minus.  Its  surface  is  studded  with  numerous  minute  red  dots  (puncta  vascu- 


FIG.  -Wo.— Right  later* 
(Gegenbaur.) 


seen  from  above. 


756 


THE  NERVOUS  SYSTEM. 


losd),  produced  by  the  escape  of  blood  from  divided  blood-vessels.  In  inflammation 
or  great  congestion  of  the  brain  these  are  very  numerous  and  of  a  dark  color.  If 
the  remaining  portion  of  one  hemisphere  is  slightly  separated  from  the  other,  a 
broad  band  of  white  substance  will  be  observed  connecting  them  at  the  bottom  of 
the  longitudinal  fissure ;  this  is  the  corpus  callosum.  The  margins  of  the  hemi- 
spheres which  overlap  this  portion  of  the  brain  are  called  the  labia  cerebri.  Each 
labium  is  part  of  the  convolution  of  the  corpus  callosum  (gyrns  fornicatus),  and 
the  space  between  it  and  the  upper  surface  of  the  corpus  callosum  has  been  termed 
the  ventricle  of  the  corpus  callosum  (Fig.  446). 

The  hemispheres  should  now  be  sliced  off  to  a  level  with  the  corpus  callosum, 
when  the  white  substance  of  that  structure  will  be  seen  connecting  the  tAvo 
hemispheres.  The  large  expanse  of  medullary  matter  now  exposed,  surrounded 
by  the  convoluted  margin  of  gray  substance,  is  called  the  centrum  ovale  majus  of 
Vieussens. 

The  corpus  callosum  (Figs.  442,  446)  is  a  thick  stratum  of  transverse  fibres 
exposed  at  the  bottom  of  the  longitudinal  fissure.  It  connects  the  two  herni- 


Sept  luc.  Corp  caU 


Mid.  com 


Pin.  gland 

Lam.  quadrig. 


Splenium 
•Aq.  Sylv. 


Hipp. 

gyms 


Opt.  ch/ ^  body  I        Pons\ 


FIG.  446.— Antero-posterior  median  section  of  the  brain,  X  §.    (Henle.) 

spheres  of  the  brain,  forming  their  great  transverse  commissure,  and  forms  the 
roof  of  the  lateral  ventricles.  It  is  about  four  inches  in  length,  extending  to 
within  an  inch  and  a  half  of  the  anterior,  and  to  within  two  inches  and  a  half 
of  the  posterior,  end  of  the  hemispheres.  It  is  somewhat  broader  behind  than  in 
front,  and  is  thicker  at  either  end  than  in  its  central  part,  being  thickest  behind. 
It  presents  a  somewhat  arched  form  (Fig.  446)  from  before  backward,  and  termi- 
nates anteriorly  by  curving  downward  and  backward  between  the  frontal  lobes. 
This  distinct  bend  is  named  the  genu,  whence  it  is  still  continued  downward  and 
backward  to  the  base  of  the  brain,  where  it  blends  with  the  lamina  cinerea.  The 
reflected  portion  of  the  corpus  callosum  is  called  the  beak  or  rostrum :  it  becomes 
gradually  narrower  as  it  passes  backward,  and  is  attached  by  its  lateral  margins 
to  the  frontal  lobes.  At  its  termination,  besides  blending  with  the  lamina  cinerea, 
the  corpus  callosum  gives  off  two  small  bundles  of  white  substance,  which,  diverg- 
ing from  one  another,  pass  backward,  across  the  corresponding  anterior  perforated 
space,  to  the  entrance  of  the  fissure  of  Sylvius,  to  enter  the  end  of  the  temporal 


THE  BRAIN  AND    ITS  MEMBRANES. 


757 


lobe,  where  they  meet  the  outer  olfactory  roots.  They  are  called  the  peduncles 
•A'  the  corpus  callosum.  Posteriorly,  the  corpus  callosum  forms  a  thick  rounded 
fold,  called  the  splenium  or  pad,  which  is  free  for  a  little  distance  as  it  curves 
forward,  and  is  then  continuous  with  the  fornix  below.  On  its  upper  surface 
the  structure  of  the  corpus  callosum  is  very  apparent,  being  collected  into  coarse 
transverse  bundles.  Along  the  middle  line  is  a  linear  depression,  the  raplie, 
bounded  laterally  by  two  or  more  slightly  elevated  longitudinal  bands,  called  the 

w      .   w  O  •/ 

stria  longitudinales  or  nerves  of  Lancisi ;  and,  still  more  externally,  other  longi- 
tudinal stride  are  seen  beneath  the  convolutions  which  rest  on  the  corpus  callo- 
sum. These  are  the  strife  longitudinales  laterales  or  tcenice  tectce.  The  under 
surface  of  the  corpus  callosum  is  continuous  behind  with  the  fornix,  being  sepa- 
rated from  it  in  front  by  the  septum  lucidum,  which  forms  a  vertical  partition 
between  the  two  ventricles.  On  each  side  the  fibres  of  the  corpus  callosum 
extend  into  the  substance  of  the  hemispheres,  connecting  them  together.  The 
greater  thickness  of  the  two  extremities  of  this  commissure  is  explained  by  the 
fact  that  the  fibres  from  the  anterior  and  posterior  parts  of  each  hemisphere  do 
not  pass  directly  across,  but  take  a  curved  direction.  The  peduncles  of  the  cor- 
pus callosurn  may  be  traced  upward  around  the  genu  to  become  continuous  with 
the  strice  longitudinales,  or  nerves  of  Lancisi,  on  the  upper  surface  of  the  corpus 
callosum. 

The  fibres  from  the  splenium,  which  curve  backward  to  roof  in  the  poste- 
rior cornu  are  known  as  the  forceps  major ;  those  from  just  above  the  genu. 
which  curve  forward  to  roof  in  the  front  part  of  the  anterior  cornu  constitute 


Nucleus 
eaudatus\ 


Corpus 

M0M     • 


Will'/' 


FIG.  447.— Transverse  vertical  section  of  the  brain,  X  §.  anterior  to  the  middle  commissure;  the  cut  surface 
s  forward.    1.  putamen.    2  and  3.  globus  pallidus.    (Gegenbaur.) 

the  forceps  minor ;  while  the  term  tapetum  is  given  to  the  main  body  of  the 
fibres. 

The  central  cavity,  or  body,  of  the  lateral  ventricle  is  comparatively  wide,  but 
is  a  mere  slit  as  regards  its  perpendicular  diameter.  It  is  (Fig.  447)  bounded, 
above,  by  the  under  surface  of  the  corpus  callosum,  which  forms  the  roof  of  the 
cavity.  Internally  i.<  a  vertical  partition,  the  posterior  portion  of  the  septum 
lucid mn,  which  separates  it  from  the  opposite  ventricle,  and  connects  the  under 
surface  of  the  corpus  callosum  with  the  fornix.  Its  floor  is  formed  by  the  fol- 
lowing parts,  enumerated  in  their  order  of  position  from  without  inward :  the 


758 


THE   NERVOUS  SYSTEM. 


corpus  striatum  (caudate  nucleus),  tcenia  semicircularis,  optic  thalamus,  clwroid 
plexus,  one-half  of  body  of  for  nix,  and  corresponding  posterior  pillar. 

The    anterior    cornu    is    deep    and 

narrow, 

frontal 

Oenu  of  the 

corpus 

callosum 


passing  outward  into  the 
lobe  and  curving  round  the 
anterior  extremity  of  the  corpus  stri- 
atum. Its  apex  points  outward.  It 
is  bounded,  above,  by  the  corpus  cal- 
losum ;  externally,  by  the  corpus  stri- 
atum (head  of  caudate  nucleus) ;  in 
front,  by  the  posterior  surface  of  the 
genu  of  the  corpus  callosum  ;  inter- 
nally, by  the  anterior  or  broad  por- 
tion of  the  septum  lucidurn ;  infe- 
riorly,  by  the  upper  surface  of  the 
rostrum  (each  side  of  its  middle  line) 
of  the  corpus  callosum.  This  last  is 
the  floor  of  the  cornu,  and  is  exceed- 
ingly narrow,  the  outer  Avail,  convex 
toward  the  cavity,  almost  meeting  the 
lower  part  of  the  septum  lucidurn  be- 
low (Figs.  448  and  449). 

The  posterior  cornu,  or  digital  cav- 
ity (Fig.  445),  curves  backward  into 
the  substance  of  the  occipital  lobe, 
its  direction  being  backward  and  out- 
ward, and  then  inward.  On  its  inner 
wall  is  seen  a  longitudinal  eminence 
which  is  produced  by  the  extension 
inward  of  the  calcarine  sulcus  ;  this  is 
called  the  hippocampus  minor,  or  cal- 
car  avis.  Just  above  this  is  a  smaller 
projection,  bulb  of  the  posterior  horn 
(Fig.  456),  caused  by  the  bulging  of  the  fibres  of  the  forceps  major  of  the  corpus 
callosum. 

Between  the  middle  and  posterior 
horns  a  smooth  triangular  surface  is 
observed.  It  is  called  the  trigonum 
ventriculi. 

The  middle  or  descending  cornu, 
the  longest  of  the  three  (Fig.  445), 
traverses  the  temporal  lobe  of  the 
brain,  forming  in  its  course  a  remark- 
able curve  round  the  back  of  the  optic 
thalamus  (pulvinar}.  It  passes,  at 
first,  backward,  outward,  and  down- 
ward, and  then  curves  round  the 
crusta  forward  and  inward,  nearly 
to  the  apex  of  the  middle  lobe,  close 
to  the  fissure  of  Sylvius.  Its  upper 
boundary,  or  roof,  is  formed  by  the 
under  surface  of  the  corpus  callosum, 
the  small  portion  of  the  pulvinar  of 
the  optic  thalamus  covered  by  epithe- 
lium, and  by  the  white  matter  (internal  capsule)  of  the  temporal  lobe,  with  which 
are  incorporated  the  reflected  parts  of  the  nucleus  caudatus  of  the  corpus  striatum 
and  tsenia  semicircularis,  which  are  prolonged  into  it.  Its  lower  boundary,  or 


Anterior 
cornu 


Nucleus 
caudatus 

Sept.  luc. 

Ant.  pillars  oj 
thefornix 

(ext. 
Capsule  < 

(int. 

Claustnm, 
Optic  thalam. 

Lenticular 
nucleus 

Svlenium  of 
the  corp. 
callosum 


Post,  part 
of  the    . 
nucleus 
caudatus 

Post,  cornu 


FIG.  448. -Horizontal  section  of  the  right  half  of  the 
cerebrum,  X  §•  2.  putaraen.  a,  b,  and  c  nuclei  of  the 
optic  thalamus.  (Gegenbaur.) 


Corpus 
callosun, 

Sept. 
pellucid 


Claustrum 


FIG.  449.— Transverse  vertical  section  < 
spheres  through  the  anterior  eornua,  X  §• 
face  looks  forward.  (Gegenbaur.) 


f  the  hcmi- 
The  cut  sur- 


THE   BKAIX   AXD    ITS 


759 


floor,  presents  for  examination  the  following  parts:  the  hippocampus  major,  pes 
hippocampi,  eminently  <.;>Uuteralis  or  pes  accessorius,  and  corpus  fimbriatum  from 
the  for  nix.  The  o//f>  r  "-all  is  white  matter  of  the  temporal  lobe.  The  inner  icall 
is  a  layer  of  epithelium,  prolonged  from  that  covering  the  pulvinar,  just  mentioned, 
which  is  ini'ii'iiii'iti'd  by  a  fold  of  pia  mater,  and  thus  is  formed  the  choroid  plexus. 
The  corpus  striatum  (Fig.  450)  has  received  its  name  from  the  striped  appear- 
ance which  its  section  presents,  in  consequence  of  diverging  white  fibres  being 
mixed  with  the  gray  matter  which  forms  the  greater  part  of  its  substance.  The 
greater  portion  of  this  body  is  imbedded  in  the  white  substance  of  the  hemisphere, 
and  is  therefore  external  to  the  ventricle.  It  is  termed  the  extraventricular  por- 


FIG.  450.— Middle  part  of  a  horizontal  section  through  the  cerebrum  at  the  level  of  the  dotted  line  in  the 
small  figure  of  one  hemisphere.    (From  Ellis,  after  Dalton). 

tion,  or  the  nucleus  lenticularis :  a  part,  however,  is  visible  in  the  ventricle  and 
its  anterior  cornu;  this  is  the  intraventricular  portion,  or  the  nucleus  caudatus. 
The  intra ventricular  portion  is  a  pear-shaped  mass  of  gray  matter :  its  broad  ante- 
rior extremity  is  the  convex  outer  wall  of  the  anterior  cornu.  Its  narrow  end  is 
directed  backward,  and  lies  on  the  outer  part  of  the  floor  of  the  body  of  the  ven- 
tricle. It  is  continued,  by  a  sharp  anterior  bend,  into  the  roof  of  the  descending 
cornu :  it  is  covered  by  the  lining  of  the  cavity  and  crossed  by  some  veins  of 
considerable  size.  It  is  separated  from  the  extraventricular  portion  by  a  lamina 
of  white  matter,  the  internal  capsule,  in  contradistinction  to  a  lamina  of  white 
matter  which  covers  the  outer  surface  of  the  extraventricular  portion  of  the  corpus 
striatum,  and  which  is  called  the  external  capsule. 

The  extraventricular  portion  of  the  corpus  striatum,  or  nucleus  lenticularis, 
is  oval  in  form.     It  does  not  extend  as  far  forward  or  backward  as  the  nucleus 


760  THE  NERVOUS  SYSTEM. 

caudatus.  It  is  bounded  externally  by  a  lamina  of  white  matter  called  the  exter- 
nal capsule,  which  is  covered  on  its  outer  surface  by  a  thin  layer  of  gray  matter 
termed  the  claustrum.  The  claustrum  presents  ridges  and  furrows  on  its  outer 
surface,  corresponding  to  the  convolutions  and  sulci  of  the  island  of  Reil,  with 
the  white  matter  of  which  it  is  in  immediate  relation. 

Antero-inferiorly  the  ends  of  the  two  nuclei  of  the  corpus  striatum  are  united 
by  a  thin  gray  lamina  which  appears  at  the  base  of  the  brain  in  the  anterior 
perforated  space.  The  caudate  nucleus  terminates,  after  running  downward  and 
forward  in  the  roof  of  the  descending  cornu,  in  the  nucleus  amygdalae,  a  collec- 
tion of  gray  matter  in  the  apex  of  the  temporal  lobe.  The  base  of  the  claustrum 
is  also  in  connection  with  this  nucleus. 

The  gray  matter  (Fig.  449)  of  the  corpus  striatum  is  permeated  by  tracts  of 
medullated  nerve-fibres,  some  of  which  probably  originate  in  it.  The  nerve-cells 
are  multipolar,  both  large  and  small,  the  larger  being  principally  found  in  the 
lenticular  nucleus. 

On  section,  the  substance  of  the  corpus  striatum  appears  of  reddish-gray 
color.  On  a  transverse  vertical  section,  the  lenticular  nucleus  shows  two  laminae 
of  white  matter  parallel  with  its  outer  surface,  forming  three  areas  of  gray  matter, 
the  two  inner  of  which  are  knoAvn  as  the  globus  pallidus,  the  outer  as  the  putamen 
(Fig.  447).  The  fibres  of  the  nucleus  enter  and  leave  it,  the  former  chiefly  derived 
from  the  ansa  lenticularis  (see  page  747),  the  latter  proceeding  into  the  internal 
capsule  and  corona  radiata,  which  last  is  made  up  of  the  radiating  diverging 
fibres  of  the  upward  prolongation  of  the  internal  capsule  which  extend  to  the 
cortex. 

The  internal  capsule  is  formed  by  fibres  of  the  crusta  of  the  crus  cerebri,  sup- 
plemented by  fibres  derived  from  the  optic  thalamus  and  corpus  striatum  on  each 
side.  In  horizontal  section  it  is  seen  to  be  somewhat  abruptly  curved,  with  its 
convexity  inward ;  the  prominence  of  the  curve  is  called  the  genu,  and  projects 
between  the  intraventricular  portion  of  the  corpus  striatum  and  the  optic  thal- 
amus (Figs.  447,  448,  450).  In  front  of  the  genu  the  internal  capsule  separates 
the  two  portions  of  the  corpus  striatum ;  behind,  it  lies  between  the  optic  thal- 
amus and  lenticular  nucleus.  The  portions  of  the  internal  capsule,  anterior  and 
posterior  to  the  genu,  are  known,  respectively,  as  the  anterior  and  posterior 
segments.  The  fibres  of  the  former  proceed  to  the  prefrontal  region  of  the 
cortex ;  of  the  latter,  to  the  occipito-temporal  region ;  while  those  of  the  mid- 
dle third  go  to  the  Rolandic  region  (motor)  of  the  cortex.  Other  fibres,  in 
the  internal  capsule,  than  those  of  the  crusta  are  derived  from  the  nuclei  of  the 
corpus  striatum,  the  optic  thalamus,  the  subthalamic  tegmerital  region,  and  from 
the  cortex  of  the  opposite  side  through  the  corpus  callosurn  (see  also  page  785). 

The  taenia  semicircularis  (Figs.  445,  447,  and  461)  is  a  narrow,  whitish  band 
of  medullary  substance  situated  in  the  depression  between  the  nucleus  caudatus 
and  optic  thalamus.  Anteriorly,  it  descends,  between  the  head  of  the  caudate 
nucleus  and  the  anterior  extremity  of  the  optic  thalamus,  to  join  the  anterior 
pillar  of  the  fornix,  below  the  level  of  the  foramen  of  Monro,  where  most  of  the 
fibres  continue  with  those  of  the  pillar,  while  the  remainder  pass  over  the  anterior 
commissure  and  terminate  in  the  gray  matter  of  the  anterior  perforated  space. 
Behind,  it  is  continued  into  the  roof  of  the  middle  or  descending  horn  of  the 
lateral  ventricle,  lying  parallel  with  the  caudate  nucleus,  to  enter,  with  it,  the 
nucleus  amygdalae.  Beneath  it  is  a  large  vein  (vena  corporis  striati],  which 
receives  numerous  small  veins  from  the  surface  of  the  corpus  striatum  and  optic 
thalamus,  and  joins  the  venae  Galeni.  On  transverse  vertical  section  the  tcenia 
is  seen  to  lie  upon  a  projection  from  the  internal  capsule. 

The  fornix  (Figs.  442,  447,  451)  is  a  longitudinal  band  of  white  matter  situ- 
ated beneath  the  corpus  callosum,  with  which  it  is  continuous  behind,  but  sep- 
arated from  it  in  front  by  the  septum  lucidum.  It  may  be  described  as  consisting 
of  two  symmetrical  halves,  one  for  either  hemisphere.  These  two  portions  are 
joined  together  in  the  middle  line  (along  which  is  attached  the  lower  edge  of  the 


THE 


Aiy  AXD    ITS   MEMBRANES. 


761 


septum  lucidum),  where  they  form  the-body,  but  are  separated  from  one  another 
in  front  and  behind,  forming  the  anterior  and  posterior  pillars,  or  columnce  forni- 
cis  and  t-rura  t\>rnicis,  respectively. 

The  body  of  the  for nh-  is  triangular;  narrow  in  front,  broad  behind.  Its 
upper  surface  is  connected,  in  the  median  line,  to  the  septum  lucidum  in  front 
and  the  corpus  callosum  behind,  while  laterally  this  surface  forms  part  of  the 
floor  of  the  body  of  each  lateral  ventricle.  Its  under  surface  rests  upon  the  velum 
mterpositum.  which  separates  it  from  the  third  ventricle  and  from  the  inner  por- 
tion of  the  superior  surfaces  of  the  optic  thalami.  Its  free  outer  edge,  on  each  side, 
is  in  contact  with  the  choroid  plexus,  which  projects  from  under  it.  This  edge, 
running  from  behind  forward  and  inward,  rests  in  the  groove  already  referred  to, 
having  a  similar  direction,  on  the  superior  surface  of  the  thalamus,  but  with  a 
portion  of  the  velum  interpositum,  of  course,  separating  it  from  the  groove. 

The  anterior  pillars  are  rounded  bundles  which  arch  downward  toward  the  base 
of  the  brain,  separated  from  each  other  by  a  narrow  interval,  and  each  descends 


Nucleus 
caudatus 


Beginning 
of  the  post, 
pillar  $  the 
Jornix 


Subst.  nil 


Chuta 


Hippocampu 


FIG.  451.— Transverse  vertical  section  of  brain  behind  the  middle  commissure.    The  cut-surface  looks  back- 
ward, X  §.    (Gegenbaur.) 

through  the  anterior  portion  of  the  optic  thalamus.  Each  is  placed  immediately 
behind  the  anterior  commissure.  At  the  base  of  the  brain  the  white  fibres  of  each 
pillar  make  a  sudden  curve  and  form  the  outer  part  of  the  corresponding  corpus  albi- 
<•<//'.«  (see  page  750).  from  which  point  they  may  be  traced  upward  into  the  substance 
of  the  corresponding  optic  thalamus.  The  anterior  pillars  of  the  fornix  are  con- 
nected in  their  course  with  the  peduncles  of  the  pineal  gland  and  the  superficial 
fibres  of  the  trenia  semicircularis.  and  receive  fibres  from  the  septum  lucidum. 

Between  the  anterior  pillars  of  the  fornix  and  the  anterior  extremities  of  the 
optic  thalami  an  oval  aperture  is  seen  on  each  side :  this  is  the  foramen  of  Monro 
(Fig.  442).  The  two  openings  descend  toward  the  middle  line  and  lead  into  the 
upper  part  of  the  third  ventricle.  Through  these  openings  the  lateral  ventricles 
on  each  side  communicate  with  the  third  ventricle,  and  consequently  with  each 
other.  Its  boundaries  are,  therefore,  in  front,  the  anterior  pillars  of  the  fornix; 
behind,  the  anterior  extremity  of  the  optic  thalamus ;  above,  the  body  of  the  for- 
nix :  and  below,  the  junction  between  the  anterior  pillars  of  ihe  fornix  and  the 
optic  thalamus. 

The  posterior  pillars  are  flattened  bands,  and  at  their  commencement  are  inti- 
mately connected  by  their  upper  surfaces  with  the  corpus  callosum  ;  diverging 
from  one  another,  each  passes  downward  around  and  behind  the  pulvinar  of  the 


762 


THE   NERVOUS   SYSTEM. 


optic  thalamus,  and  then  along  the  floor  of  the  descending  horn  of  the  lateral 
ventricle,  where  some  of  its  fibres  blend  with  the  white  matter  of  the  hippocampus 
major.,  while  the  remainder  are  prolonged  along  its  inner  border  as  the  corpus 
fimbriatum  (Figs.  445,  454),  which  extends  into  the  white  matter  of  the  uncus 
of  the  hippocampal  gyrus.  Upon  examining  the  under  surface  of  the  fornix, 
between  its  diverging  posterior  pillars  a  triangular  portion  of  the  under  surface 
of  the  corpus  callosum  may  be  seen,  the  base  of  which  is  the  splenium.  On  it 
are  a  number  of  lines,  some  transverse,  others  longitudinal  or  oblique.  This 


FIG.  462.— The  fornix,  velum  interpositum,  and  middle  or  descending  cornu  of  the  lateral  ventricle. 


portion  has  been  termed  the  lyra,  from  the  fancied  resemblance  it  bears  to  the 
strings  of  a  harp  (Fig.  452).  The  corpus  fimbriatum  is  often  called  the  fimbria. 

The  anterior  commissure  is  a  round  bundle  of  white  fibres  placed  in  front  of 
the  anterior  pillars  of  the  fornix,  and  appears  to  connect  together  the  corpora 
striata.  It  passes  outward  through  the  corpus  striatum  on  each  side,  and  then 
curves  backward  into  the  substance  of  the  temporal  lobe. 

The  septum  lucidum  (or  pellucidum)  (Figs.  446,  449)  forms  the  internal  bound- 
ary of  the  body  and  anterior  cornu  of  the  lateral  ventricle.  It  is  a  thin  septum 
attached,  above,  to  the  under  surface  of  the  corpus  callosum ;  belong  to  the  ante- 
rior part  of  the  fornix,  and  in  front  of  this  to  the  reflected  portion  of  the  corpus 
callosum  and  anterior  commissure ;  behind,  to  the  anterior  pillars  of  the  fornix ; 
in  front,  to  the  posterior  surface  of  genu  of  the  corpus  callosum.  It  is  broad  in 
front,  and  narrow  behind,  its  external  surfaces  looking  toward  the  cavities  of  the 
ventricles.  The  septum  consists  of  two  laminae,  separated  by  a  narrow  interval, 
the  fifth  ventricle. 


THE   BRAIN  AND    ITS   MEMBRANES.  763 

Fifth  Ventricle. — The  fifth  ventricle  was  originally  a  part  of  the  great  longi- 
tudinal fissure  which  separated  the  two  hemisphere  vesicles,  but  has  become  shut 
off  bv  the  union  of  the  hemispheres  in  the  formation  of  the  corpus  callosum  and 
the  fornix.  Its  Avails  are  therefore  formed  by  the  median  wall  of  the  hemispheres, 
and  each  consists  of  an  internal  layer  of  gray  matter  derived  from  the  gray  mat- 
ter of  the  cortex  and  an  external  layer  of  white  substance  continuous  with  the 
white  matter  of  the  cerebral  hemispheres.  This  is  lined  on  its  external  surface 
by  the  ependyma  of  the  corresponding  lateral  ventricle.  The  fifth  ventricle  is 
not  lined  bv  epithelium,  but  by  a  delicate  layer  of  modified  pia  mater.  It  has  no 
connection  "with  any  of  the  "regular"  ventricles. 

The  structures*  of  the  floor  of  the  descending  cornu  will  now  be  con- 
sidered. 

The  hippocampus  major,  or  cornu  Ammonis  (Figs.  445.  452.  456),  so  called  from 
its  resemblance  to  a  ram's  horn,  is  a  white  eminence,  of  a  curved  elongated  form, 
extending  throughout  the  entire  length  of  the 
floor  of  the  middle  horn  of  the  lateral  ventricle. 

At  its  lower  extremity  it  becomes  enlarged,  and  -^^^^^ 

presents  a  number  of  rounded  elevations  with  — ^^*^.^^^^P^l     Eminent 

intervening  depressions,  which,  from  presenting          C~  ^lyl/  coU(U- 

some  resemblance  to  the  paw  of  an  animal,  is 
called  the  pes  hippocampi.     If  a  transverse  sec- 
tion  is   made   through   the  hippocampus   major 
(Fig.  453).  it  will  be  seen  that  this  eminence  is 
produced  by  the  extension  inward  of  the  dentate    Hipp./ 
(hippocarnpal)  fissure  on  the  mesial  aspect  of  the    ' 
temporal  lobe.     This  fissure,  like  all  the  other  fis- 
sures of  the  hemisphere,  is  lined  by  a  dipping  in      ^  ^  _part  of  left  desc  cornu 
and  out  a<?ain  of  the  orav  cortex;  but,  whereas  in  The  cut  surface  looks  forward.   (Henie.) 

c      •-  7 

fissures  the  gray  lining,  after  coming  out,  is 

continuous  with  that  of  an  adjacent  fissure,  the  gray  lining  of  the  hippocarnpal 
ri*sun.  after  turning  on  itself,  comes  out  and  terminates  in  a  free  edge,  forming  a 
notched  ridge,  the  fascia  dentata  (Figs.  453,  454).  The  hippocampus  is  covered 

Corpus 

OaUoso-marffinal    caUosutn 
Jbwn 


Genu  of  tte 
corp.  call. 


Corpus 

^^ _^__    . fimbrialum 

Olfactory,  " 
lobe 

FIG.  451.— The  mesial,  or  internal  surface  of  the  right  tiemispkere  of  a  six  months'  foetus.    (Schmidt.) 

on  its  ventricular  surface  by  the  lining  membrane  of  the  ventricle,  beneath  which 
is  a  thin  lamina  of  Avhite  matter  (alveus),  which  is  continuous  with  the  corpus 
fimbriaturu  of  the  fornix,  and  beneath  this  is  the  "gray  matter"  of  the  hippo- 
campus— i.  e.  the  cortical  lining  of  the  hippocampal  fissure,  just  described.  This 
gray  matter  is  seen,  on  cross-section,  to  make  a  secondary  turn  which  embraces  a 
slender  process  of  white  matter  derived  from  the  white  lamina  before  it  emerges 
as  the  free  edge. 

The  corpus  fimbriatum  (Figs.  445.  454.  456)  (tcenia  hippocampi)  is  a  narrow 
white  band  situated  immediately  below  the  choroid  plexus.  It  is  the  thin  pro- 
longation of  the  posterior  pillar  of  the  fornix,  and  is  attached  by  its  inner  margin 


764  THE   NERVOUS  SYSTEM. 

along  the  curved  inner  border  of  the  hippocampus  major  as  it  descends  into  the 


FIG.  4^.— Horizontal  section  of  the  hemispheres  at  the  level  of  the  corpus  callosum.    (Henle.) 


Post,  pillar  J| 
of  fornix  "~ 

Corp 

call. 


Corp.fimb. 


FTG.  456.— Descending  and  part  of  posterior  cornu  of  left  side.    (Henle.) 

middle  horn  of  the  lateral  ventricle.    It  may  be  traced  as  far  as  the  crochet  or  hook 


THE  BRAIN  AND    ITS  MEMBRANES. 


765 


of  the  hippoeampal  convolution.  Its  outer  edge  is  free,  and  lies  on  the  surface 
of  the  hippocampus.  This  edge  is  directed  toward  the  cavity  of  the  descending 
cornu. 

The  eminentia  collateralis  (Fig.  453).  or  pes  accessorius,  is  a  white  eminence, 
varvino-  in  size,  placed  between  the  hippocampus  major  and  the  outer  wall  of  the 
cornu.  It  is  formed  by  the  protrusion  inward  of  the  collateral  fissure. 

Fascia  Dentata  (Figs.  453,  454.  456). — On  separating  the  inner  border  of  the 
corpus  fimbriatum  from  the  choroid  plexus,  and  raising  the  edge  of  the  former,  a 

Genu  of  corp.  call. 

Sept.  luc. 


Foramen  of  Jfonro 
Corp.  striatum. 


Posterior  cornu 


FIG.  457. — The  lateral  ventricles  from  above,  showing  choroid  plexuses;  the  left  is  in  its  natural  position  : 
the  right  plexus  is  somewhat  laterally  displaced  to  show  the  edge  of  the  fornix.    (Henle.) 

serrated  band  of  gray  substance,  the  edge  of  the  gray  substance  in  the  dentate  or 
hippoeampal  fissure,  will  be  seen  beneath  it:  this  is  the  fascia  dentata.  Correctly 
speaking,  it  is  not  placed  within  the  cavity  of  the  descending  cornu.  The  fascia 
•Itntata  has  a  curved  direction,  following  the  course  of  the  hippocampus,  and  also 
runs  obliquely  from  above  downward  and  forward.  Its  lower  extremity  is  lost 
in  the  gray  matter  of  the  uncus  or  hook  of  the  hippoeampal  gyrus,  where  it  is 
>feii  as  a  small  band  (Giacomini)  passing  transversely  over  the  hook.  Its  upper 
extremity  is  well  marked  (fasciola  cinerea],  and  lies  immediately  behind  and  below 
the  splenium  of  the  corpus  callosum,  over  and  above  which  it  is  continuous  with 
the  lateral  and  mesial  longitudinal  striae  of  that  body  (Fig.  455). 


766 


THE   NERVOUS  SYSTEM. 


The  choroid  plexuses  (Figs.  457,  458)  of  each  lateral  ventricle  are  two  in 
number,  one  in  the  floor  of  the  body,  and  the  other  in  the  descending  cornu. 
Each  is  a  vascular  fringe-like  membrane  with  a  free  edge  looking  toward  the 
ventricular  cavity,  and  an  attached  margin  which  is  continuous  with  two  layers 
of  pia  mater. 

The  choroid  plexus  of  the  body  of  the  ventricle  is,  as  before  stated,  the  thick- 
ened, convoluted  side  of  the  velum  interpositum,  which  is  made  up  of  two  layers 
of  pia  mater.  The  reasons  for  the  presence  of  two  layers  in  the  velum  interpo- 
situm, as  well  as  for  their  continuity  with  one  another  at  their  free  margins,  and 


Gcnu  of  corp.  call. 


th  ventricle 


Caud.  nucl. 

- — Ant  pillar  of  fornix 
Velum  interpos. 

Optic  thalaiuus 


Pes  hippocampus 


Pineal  gland 
Ant.  corp.  q. 
Chor,  pi.  of  3d  v 


Vena  Galeni 


Posterior  cornu 


Pia  mater 

FIG.  458.— Choroid  plexus  of  body  of  ventricle  and  of  descending  cornu  of  left  side.    The  velum  interposi- 
tum is  split  on  the  left  side,  showing  choroid  plexus  of  third  ventricle.    (Henle.) 

for  the  fact  of  the  existence  of  such  free  margins,  must  be  sought  for  in  the  method 
of  development. 

In  the  brief  account  given  of  the  development  of  the  hemisphere  vesicles  no 
mention  was  made  of  the  pia  mater.  But  it  must  be  understood,  of  course,  that 
the  pia  mater  covers  the  entire  brain-tube,  and  takes  part  in,  and  adapts  itself  to, 
all  the  diiferent  changes  in  shape  and  position  which  the  various  portions  of  the 
brain  undergo. 

We  thus  have,  at  a  certain  point  of  development,  three  "  tubes  "  of  pia  mater 
— one  encircling  the  inter-brain,  and  one  investing  each  hemisphere  vesicle  (see 
Fig.  459).  As  the  latter  approaches  its  fellow  it  also  grows  in  toward  the  inter- 
brain.  Finally,  as  already  described,  actual  adhesions  take  place  between  the 
mesial  aspects  of  each  hemisphere  above  the  inter-brain,  and  between  that  portion 
of  the  hemisphere  which  lies  external  to  the  inter-brain  and  the  side  of  the  inter- 
brain  (optic  thalamus) ;  while  the  under  surfaces  of  the  hemispheres  (corpus  cal- 
losum  and  fornix)  merely  rest  on,  and  are  not  adherent  to,  the  superior  surface  of 
the  inter-brain.  The  effect  on  the  pia  mater  (see  Figs.  460,  461)  mesially  and 


THE  BRAIN  AND    ITS   MEMBRANES. 


767 


above  the  inter-brain,  is  thus  clear :  (1)  The  pia  lining  the  mesial  aspect  of  each 
hemisphere  is  absorbed  by  the  formation  of  the  corpus  callosum  and  the  coming 
together  of  the  two  halves  of  the  fornix ;  hence  (2),  the  part  above  the  corpus  cal- 
losum becomes  continuous  with  that  of  the  other  side  across  the  upper  surface  of 
the  corpus  callosum :  while  (3)  the  pia  on  the  under  surface  of  each  hemisphere 
(tif-lnir  the  corpus  callosum  and  fornix)  becomes  continuous  with  that  on  the  under 
surface  of  the  other,  and  forms  one  layer  from  side  to  side  (upper  layer  of  velum 
interpositum  I.  This  upper  layer  of  the  velum  interpositum  is  now  in  close  con- 
tact with  the  layer  of  the  pia  covering  the  superior  surface  of  the  inter-brain 
(lower  layer  of  the  velum  interpositum),  but  they  are  not  absorbed,  because  no 
adhesions  take  place  between  the  corresponding  portions  of  the  brain. 

(hi  tli.'-  */</,•.>••  the  effect  of  the  adhesion  between  the  hemisphere  and  the  optic 
thalarnus    is    to    cause    absorption    of   the    layer   of  pia   mater    covering    each; 


FIG.  459.— Diagram  of  cross-section  of  hemisphere  vesicles,  inlet-brain,  and  mid-brain  to  explain  formation 
of  velum  interpositum  and  choroid  plexuses.    The  red  line  is  the  pia  mater.    (B.  B.  G.) 

hence,  as  the  pia  mater  on  the  hemisphere  is  originally  continuous  with  the  upper 
1<i)j:-r  of  the  velum  interpositum,  and  the  pia  mater  on  the  outer  side  of  the  optic 
thalamus  with  the  lower  layer  of  the  same,  it  follows  that  the  two  layers  become 
continuous  at  their  margins  or  along  the  line  where  each  is  "cut  off,"  as  it  were, 
from  its  original  prolongation  (Figs.  460,  461). 

This  in  / >v/;"  is  at  first  ///'/////  the  border  between  the  superior  and  external  sur- 
face of  the  thalamus,  but  soon  becomes  shifted  mesially.  so  that  it  comes  to  lie 
along  the  groove  on  the  superior  surface  of  the  thalamus.  This  shifting  is  due 
to  the  absorption  of  the  pia-mater  layers  external  to  the  groove,  caused  by  the 
adhesion  which  has  taken  place  between  the  subjacent  portion  of  the  thalamus 
and  the  superjacent  portion  (epithelial  floor,  see  below)  of  the  hemisphere. 

The  anterior  extremity  of  the  velum  interpositum,  narrow  and  bifid,  as  already 
described,  is  necessarily  limited  by  the  curve  of  the  anterior  pillars  of  the  fornix, 
behind  which  the  two  layers  are  continuous,  because  it  is  at  and  around  this  point, 
which  might  be  regarded  as  a  sort  of  hinge,  that  the  hemispheres  swing  up  and 
over  the  inter-brain,  carrying  with  them  each  one  half  of  the  future  upper  layer 
of  the  velum  interpositum. 


768 


THE   NERVOUS  SYSTEM. 


Epithelial  Floor  of  the  Body  of  the  Ventricle. — The  margin  of  the  velum  inter- 
positum  thus  formed  is  necessarily  situated  between  the  under  surface  of  the  floor 
of  the  body  of  lateral  ventricle  above  and  the  upper  surface  of  optic  thalamus 
below,  but  it  does  not  reach  out  over  all  of  this  surface,  but  lies  only  on  its  inner 
half,  as  already  explained.  Hence  a  portion  of  the  under  surface  of  the  floor  of 
the  ventricle  must  rest  on  the  outer  half  of  the  upper  surface  of  the  thalamus. 
Now,  this  portion  of  the  floor,  together  with  that  immediately  superjacent  to  the 
margin  of  the  velum  interpositum,  becomes  reduced  to  a  layer  of  epithelium 
which  stretches  from  the  edge  of  the  fornix  over  to  the  tcenia  semicircularis.  This 
epithelium  is  continuous  with  that  lining  the  ventricle  both  at  the  edge  of  the 
fornix  and  at  the  tgenia.  As  it  passes  over  the  fringe-like  margin  of  the  velum 
interpositum  it  invests  all  its  processes,  and  thus  forms  the  true  choroid  plexus. 
As  it  passes  over  the  optic  thalamus  it  has  ependyma  beneath  it,  as  also  where  it 


'ody  of  Ventricle 


Fornix 


White  Matter 
(Temporal  Lobe) 


Inner  Wall 
of 


FIG.  460.— The  same  as  preceding  figure,  but  at  a  supposedly  later  stage  of  development.    (B.  B.  G.) 

covers  tsenia  semicircularis,  caudate  nucleus,  under  surface  of  corpus  callosum, 
ventricular  aspect  of  septum  lucidum,  and  upper  surface  of  corresponding  half 
of  fornix. 

Epithelial  Inner  Wall  of  Descending  Cornu. — The  entire  inner  wall  of  this 
cornu  is  reduced  to  a  layer  of  epithelium.  It  is,  morphologically,  the  continua- 
tion of  the  epithelium  forming  part  of  the  floor  of  the  body  of  the  ventricle  just 
described,  and  it  stretches  between  the  same  structures,  or  rather  their  prolonga- 
tions— i.  e.  tcenia  semicircularis  in  roof  of  descending  cornu  and  corpus  fimbriatum 
in  floor  (Figs.  460  and  461).  In  the  region  of  transition  from  body  to  descend- 
ing cornu,  just  at  the  curve,  the  epithelium  curves  downward  also,  and  stretches, 
now,  between  edge  of  posterior  pillar  of  fornix  (posterior  part)  across,  on  the 
rounded  pulvinar  of  the  optic  thalamus,  to  the  curved  part  of  the  tcenia,  which 
is  immediately  external  to  and  lies  against  the  outer  aspect  of  the  pulvinar. 
Hence  this  part  of  the  epithelium  is,  strictly  speaking,  a  portion  of  the  roof  of 
the  descending  cornu  (see  p.  758).  Just  beyond  this  point  the  epithelium  assumes 
the  mesial  position  and  becomes  the  regular  inner  wall  of  the  cornu. 


THE   BRAIN  AND    ITS   MEMBRANES. 


f69 


Choroid  Plexus  of  Descending  Cornu. — The  epithelial  inner  wall,  just  described, 
is  invaginated  by  and  closely  invests  a  fringe-like  margin  of  pia  mater  (Fig.  461), 
•which  apparently  passes  into  the  ventricle,  turns  on  itself,  and  passes  out  again, 
but  is  everywhere  covered,  toward  the  cavity  of  the  cornu,  by  the  latter's  now 
greatly  convoluted  inner  epithelial  Avail.  This  is  the  choroid  plexus  of  the 
descending  cornu,  and  when  seen  from  above  it  lies  over  the  hippocampus  major 
and  conceals  it  from  view,  as  well  as  the  corpus  fimbriatum. 

The  two  layers  of  pia  mater,  of  which  the  margins,  covered  by  epithelium, 
make  up  the  choroid  plexus,  are  in  continuity  with  the  two  layers  of  the  velum 
interpositum.  whose  margins,  also  covered  by  epithelium,  form  the  choroid  plexuses 
of  the  bodies  of  the  ventricles.  But  the  upper  layer  of  the  velum  is  continuous 


FIG.  461.— The  same  as  the  two  preceding  figures.  The  velum  interpositum  and  choroid  plexuses  are  now  com- 
plete. In  the  roof  of  the  descending  cornu  are  seen  the  prolongations  of  ta?nia  semicircularis  and  caudate 
nucleus.  (B.  B.  G.) 

with  the  lower  layer  of  the  choroid  plexus  of  the  cornu,  and,  vice  versd,  this  rela- 
tion being  due  to  the  bending  downward,  forward,  and  inward  of  the  temporal 
lobe  and  the  descending  cornu.  This  relation  may  perhaps  be  better  appreciated 
by  tracing  these  layers  separately,  thus : 

The  loicer  layer  of  the  "choroid  plexus"  of  the  descending  cornu,  if  traced 
out  of  the  cornu — /.  e.  toward  the  median  line — passes,  at  its  lower  part,  right 
around  the  under  surface  of  the  temporal  lobe ;  if  traced  at  its  upper  part — i.  e. 
at  the  curve  of  junction  between  this  cornu  and  body  of  ventricle — this  same 
layer  will  be  found  to  bend  sharply  forward  on  itself  and  to  come  forward  under 
the  edge  of  the  now  superiorly  placed  fornix,  and  be  continuous  with  the  upper 
layer  of  the  velum.  Posteriorly  and  externally,  this  layer  is  in  continuity  with 
the  pia  mater  covering  the  under  surfaces  of  the  occipital  and  temporal  lobes. 

The  upper  layer  of  the  "  choroid  plexus  "  of  the  descending  cornu,  if  traced 
in  the  same  manner — i.  e.  at  two  levels — is  found,  at  the  lower  level,  to  be  con- 
tinuous with  the  pia  mater  covering  the  crustse  of  the  mid-brain ;  at  the  upper 
level  it  also  bends  sharply  forward,  comes  forward  under  the  fornix,  and  is  con- 

49 


770  77 IK    NERVOUN    NYNTEM. 

tinued  into  the  lower  layer  of  the  velum  interpositum.  Just  at  the  forward 
bend  this  layer  is  really  anterior  to  the  other  one.  Posteriorly,  this  same  layer  is 
in  continuity  with  the  pia  mater  covering  the  corpora  quadrigemina,  which,  in  its 
turn,  if  traced  ventrally,  is  seen  to  be  continuous  with  that  already  mentioned 
covering  the  crustae. 

It  would  appear,  then,  from  the  foregoing,  that  this  whole  arrangement  of  pia 
mater  is  a  complicated  invagination  or  tucking-in  process  of  an  originally  single 
layer.  Morphologically,  however,  we  find  this  arrangement  to  be  caused  by  the 
absorption  of  the  contiguous  layers  of  the  three  "  tubes  "  of  pia  mater  already 
referred  to.  Thus  (cf.  Figs.  459,  460,  461),  the  pia  mater  covering  the  crustae 
should  be  considered,  as  it  really  does  in  an  early  stage  of  development,  as  run- 
ning up  on  the  outer  side  of,  and  around  and  behind  the  pulvinar  of,  the  optic 
thalamus  to  its  upper  surface,  and  thence  inward  to  pass  into  continuity  with  the 
lower  layer  of  the  velum  interpositum,  thus  making  one  tube ;  while,  similarly, 
the  upper  layer  of  the  pia  from  the  choroid  plexus  of  the  descending  cornu  should 
be  considered,  not  as  being  reflected  mesially  on  to  the  crustoe,  but  as  running 
upward  along  the  inner  aspect  of  the  internal  capsule  to  the  tsenia  semicircularis, 
and  thence  inward  along  the  under  surface  of  the  floor  of  the  body  of  the  ventricle 
to  join  with  the  upper  layer  of  the  velum  interpositum,  which,  in  its  turn,  should 
be  considered  as  splitting  along  its  middle  line,  each  half  to  bend  upward,  lying 
mesial  to  the  corresponding  half  of  the  fornix,  septum  lucidum,  and  corpus  cal- 
losum,  to  meet  the  corresponding  layer  of  pia  mater  lining  the  mesial  aspect  of 
the  hemisphere  above  the  corpus  callosum  ;  thus  forming  two  tubes. 

At  the  junction  betAveen  the  choroid  plexus  of  the  body  and  that  of  the 
descending  cornu  in  the  adult  brain  there  is  a  twisting  backward  of  the  latter,  so 
that  its  free  edge  is  directed  posteriorly,  while  that  of  the  former  looks  antero- 
externally  (Fig-  457).  It  may  sometimes  look  mesially,  bending  over  the  fornix. 

Structure  of  Choroid  Plexus. — The  plexus  consists  of  minute  and  highly  vas- 
cular villous  processes,  composed  of  large  round  corpuscles,  containing,  besides  a 
central  nucleus,  several  yellowish  granules  and  fat-molecules,  and  covered  by  a 
single  layer  of  flattened  epithelium.  The  arteries  of  the  choroid  plexus  enter 
along  the  descending  cornu,  and,  after  ramifying  through  its  substance,  send 
branches  into  the  substance  of  the  brain.  A  constant  branch,  the  anterior 
choroid,  enters  at  the  extremity  of  the  middle  horn  of  the  lateral  ventricle,  and 
supplies  the  velum  interpositum  and  the  choroid  plexus.  The  veins  of  the  choroid 
plexus  terminate  in  the  venae  Galeni. 

The  Transverse  Fissure  (Fig.  454). — The  descending  cornu  is  a  mere  cleft ; 
that  is,  its  roof  and  floor  are  very  close  together.  Hence  the  tcenia  semicircular/'* 
of  the  roof,  which  runs  along  in  the  substance  of  the  white  matter  of  the  tem- 
poral lobe,  this  white  matter  being  the  outer  and  under  aspect  of  the  beginning 
of  the  internal  capsule,  is  quite  near  the  corpus  fimbriatum  in  the  floor.  Between 
the  two  pass  the  two  layers  of  the  pia  mater  which  form  the  choroid  plexus.  If 
this  pia  mater  be  pulled  out,  the  epithelial  inner  wall  will  necessarily  come  with 
it,  and  a  cleft-like  orifice  into  the  cornu  be  produced.  A  similar  cleft  above  will 
be  caused  by  removal  of  the  velum  interpositum  and  choroid  plexuses  of  the 
bodies  of  the  ventricles,  and  if  the  plexus  of  the  other  cornu  be  removed  also, 
there  will  remain  two  large  curved  fissures,  one  on  each  side,  extending  from  the 
end  of  the  descending  cornu  to  the  corresponding  foramen  of  Monro.  Begin- 
ning at  the  foramen,  the  fissure  will  be  bounded  by  edge  of  body  and  posterior 
pillar  of  fornix  above,  and  upper  surface  of  optic  thalamus  beloiv  (Fig.  462).  At 
the  curve  of  the  descending  cornu  the  cleft  will  lie  between  pulvinar  of  optic 
thalamus  in  front  and  edge  of  posterior  pillar  of  fornix  (now  beginning  to  twist 
into  its  position  in  the  floor  of  the  descending  cornu  as  corpus  fimbriatum)  behind; 
while  along  the  cornu  it  is  bounded  below  by  corpus  fimbriatum,  and  above  by  edge 
of  white  matter  of  temporal  lobe,  along  which  is  running  the  tcenia  semicircularis. 
These  two  fissures,  taken  together,  are  known  as  the  transverse  fissure  of  the  brain, 
and  only  exist  when  the  pia  mater  and  choroid  plexuses  are  removed.  Hence  it 


THE   BRAIN   AND    ITS   MEMBRANES. 


771 


is  not  a  real  fissure  or  sulcus,  but  a  rent  in  part  of  the  floor  of  the  body  and  in 
the  inner  wall  of  the  descending  cornu  of  the  lateral  ventricle.  The  cleft  formed 
by  removal  of  the  plexus  of  the  body  of  the  ventricle  leads  mesially  into  a  space 
whose  upper  boundary  is  the  under  surface  of  fornix  and  corpus  callosum,  the 
lower  boundary  being  the  upper  surfaces  of  the  optic  thalami  on  each  side,  while 
in  the  middle  part  is  seen  the  cavity  of  the  third  ventricle,  which  has  necessarily 
been  unroofed  by  the  removal  of  the  velum  interpositum.  Posteriorly,  this  space 
continues  into  the  larger  one  separating  splenium  of  corpus  callosum  above  and 
pineal  gland  and  corpora  quadrigemina  below ;  while  in  its  turn  this  interval  is 


Oenu 


Post,  pillar  of  fomix 
Pe«  hipp. 
Corp.ftmb. 


.  major 
.  collect. 


Hipp,  minor 


FIG.  462.— The  lateral  ventricles  from  above.    The  corpus  callosum  is  removed  and  the  velum  interpositum 
has  been  pulled  out  from  beneath  the  fornix.    (Henle.) 

prolonged  posteriorly  into  the  still  larger  interspace  between  under  surfaces  of 
occipital  lobes  and  upper  surface  of  cerebellum  (Fig.  463). 

The  Surface  Aspect  of  the  Hemispheres. 

Each  hemisphere,  as  already  stated,  has  four  main  lobes,  frontal,  parietal,  tem- 
i-nl  or  temporo-sphenoidal,  and  occipital.  The  white  substance  or  medullary 
centre  of  each  of  these  lobes  lies  next  to  the  corresponding  portion  of  the  ventri- 
cle, and  is  of  course  directly  continuous  with  that  of  an  adjacent  lobe,  so  that,  as 
far  as  the  white  matter  is  concerned,  there  is  no  actual  demarkation  between  the 
lobes.  The  surfaces  of  these  lobes,  however,  can  be  fairly  accurately  separated 
from  each  other;  but,  since  they  constitute,  all  taken  together,  the  surface  of  the 
entire  hemisphere,  it  is  more  convenient  to  consider  this  first,  and  it  is  to  be 
remembered  that  the  various  "  lobes  "  to  be  mentioned  are  really  the  surfaces  of 
these  lobes. 

The  surface  of  each  hemisphere  presents  the  following  general  points  for  con- 
sideration :  Its  un<I>  r  surface  or  base  is  of  an  irregular  form,  resting  in  front  on 
the  anterior  and  middle  fossae  of  the  skull,  behind  upon  the  tentorium  cerebelli. 
There  is  a  small  portion  of  the  under  surface  which  is  adherent.  This  is  equal 
in  width  to  the  internal  capsule,  and  is  the  line  of  junction  between  its  fibres  and 
those  of  the  crusta  (see  Fig.  460).  Its  upper  surface  is  of  an  ovoid  form, 
broader  behind  than  in  front,  convex  in  its  general  outline,  and  separated  from 


772 


THE   NERVOUS   SYSTEM. 


that  of  its  fellow  by  the  great  longitudinal  fissure,  which  extends  throughout  the 
entire  length  of  the  cerebrum  in  the  middle  line,  reaching  down  to  the  base  of 
the  brain  in  front  and  behind,  but  interrupted  in  the  middle  by  a  broad  transverse 
commissure  of  white  matter,  the  corpus  callosum,  which  connects  the  two  hemi- 
spheres together.  This  fissure  lodges  the  falx  cerebri,  and  indicates  the  original 
development  of  the  hemispheres  by  two  lateral  halves. 

Each  hemisphere  presents  also  an  outer  surface,  which  is  convex  to  correspond 
with  the  vault  of  the  cranium ;  an  inner  surface,  which  is  flattened  and  in  contact 
with  the  opposite  hemisphere  (the  two  inner  surfaces  forming  the  sides  of  the 
longitudinal  fissure) ;  that  is,  above,  in  front  of,  and  below  (reflected  portion) 
corpus  callosum ;  the  lower  part  of  the  mesial  surface  (inner  aspect  of  internal 


Splenium 


Part  of 
trans. fissure 


Pin.  gland 


Pulvinar  of 
optic  thai. 

,Brachium  of 
C     tup.  c.  q. 

j|\       Brachium 
WL^    inf.  c.  q. 


Vncus  of 
hipp.  gyrus 


IV.  N. 
FIG.  463.-The  brain  from  behind.    The  hemispheres  and 


him  are  widely  separated.    (Henle.) 


capsule)  resting  against  and  being  adherent  to  outer  side  of  optic  thalamus 
(Fig.  461). 

If  the  arachnoid  and  pia  mater  are  removed,  the  entire  surface  of  each  hemi- 
sphere will  be  seen  to  present  a  number  of  depressions  (fissures  and  sulci)  sepa- 
rating a  number  of  convoluted  eminences  (convolutions  or  gyri}. 

The  depressions  are  of  two  kinds,  fissures  and  sulci.  The  fissures  are  few  in 
number;  they  are  constant  in  their  arrangement,  and  are  produced  by  marked 
foldings  of  the  hemisphere  during  the  process  of  development.  There  are  seven 
— fissure  of  Sylvius,  fissure  of  Rolando,  parieto-occipital,  calloso-marginal,  hippo- 
campal,  calcarine,  and  collateral  fissures.  The  first  four  serve  to  mark  off  from 
each  other  the  larger  lobes  of  the  hemisphere — i.  e.  frontal,  parietal,  temporal, 
and  occipital — and  also  two  others,  the  island  of  Reil  or  central  lobe,  and  the 
limbic  lobe.  There  is  still  one  other  lobe,  the  olfactory.  The  three  last-named 
fissures  cause  elevations  in  the  ventricle — viz.  hippocampus  major  and  minor 
and  eminentia  collaterals. 

The  sulci  are  much  more  numerous ;  they  are  depressions  of  the  gray  matter, 
which  is  folded  inward  and  only  indents  the  central  white  substance ;  they  vary 
in  different  brains  and  in  different  parts  of  the  same  brain. 


THE   BKAIX    AXD    ITS 


773 


The  terms  "  fissure'    and  "sulcus"  are  often  used  interchangeably. 

The  Gyri  or  Convolutions. — There  is  no  accurate  resemblance  between  the  con- 
volutions in  different  brains,  nor  are  they  exactly  symmetrical  on  the  two  sides  of 
the  same  brain,  but  their  general  arrangement  or  plan  is  fairly  constant.  Certain 
infoldings  of  the  cerebrum  take  place  at  an  early  period  of  development  and  form 
important  landmarks,  which  are  constant  and  can  without  difficulty  be  recognized, 
but  the  secondary  depressions  and  convolutions  vary  considerably. 

The  number  and  extent  of  the  convolutions,  as  well  as  their  depth,  appear  to 
bear  a  close  relation  to  the  intellectual  power  of  the  individual,  as  is  shown  in 


Lower 
frontal 


fissure  of 
~  Rolando. 


'Porieto-occtptfcrf  fiuure. 
FIG.  4&4.— Upper  surface  of  the  brain,  the  arachnoid  having  been  removed. 

their  increasing  complexity  of  arrangement  as  we  ascend  from  the  lowest  mammalia 
up  to  man.  Thus  they  are  absent  in  some  of  the  lower  orders  of  mammalia,  and 
they  increase  in  number  and  extent  through  the  higher  orders.  In  man  they 
present  the  most  complex  arrangement.  Again,  in  the  child  at  birth,  before  the 
intellectual  faculties  are  exercised,  the  convolutions  have  a  very  simple  arrange- 
ment, presenting  few  undulations,  and  the  sulci  between  them  are  less  deep  than 
in  the  adult. 

The  convolutions  on  the  outer  convex  surface  of  the  hemisphere  are  the  largest 
and  most  complicated ;  their  general  direction  is  more  or  less  oblique ;  they  fre- 
quently branch  like  the  letter  Y  in  their  course  upward  and  backward  toward  the 
longitudinal  fissure:  these  convolutions  attain  their  greatest  development  in  man, 
and  are  especially  characteristic  of  the  human  brain. 


774 


THE    NERVOUS   SYSTEM. 


Structure  of  the  Convolutions. — The  outer  surface  of  each  convolution,  as  well 
as  the  sides  and  bottom  of  the  sulci  between  them,  are  composed  of  gray  matter, 
which  is  here  called  the  cortical  substance.  The  interior  of  each  convolution  is 
composed  of  white  matter,  medullary  centre,  the  white  fibres  of  which  blend  with 
the  gray  matter  not  only  on  the  surface  of  the  gyrus,  but  at  the  sides  and  bottom 
of  the  sulci  as  well.  By  this  arrangement  the  convolutions  are  adapted  to 
increase  the  amount  of  gray  matter  without  occupying  much  additional  space, 
and  to  afford  a  greater  extent  of  surface  for  the  termination  of  the  white 
fibres. 

EXTERNAL  LOBES  AND  FISSURES  OF  THE  HEMISPHERE. — Each  hemisphere  of 


Splenivm 


Lyra 


Ant.  pillar 
of  fornix 


Ant. 


Post,  pillar 
ofjornix 


Hipp. 

gyrus 


Fascia 
dent. 

FIG.  465.— Mesial  or  inner  aspect  of  part  of  left  hemisphere.    Tbe  large  central  concavity  shows  place  of 
removal  of  optic  thalamus.    (Heule.) 

the  brain  on  its  external  surface  is  divided  into  five  lobes,  the  division  being  made 
by  the  main  fissures  and  by  imaginary  lines  drawn  to  connect  them  (Fig.  466). 

The  fissures  dividing  the  five  lobes  on  the  external  surface  of  the  hemispheres 
are  three  in  number,  and  are  named  fissure  of  Sylvius,  fissure  of  Rolando,  and 
parieto-occipital  fissure. 

The  fissure  of  Sylvius  separates  the  frontal  froir  the  temporal  lobe,  and 
lodges  the  middle  cerebral  artery.  It  begins,  at  the  base  of  the  brain,  at  the 
outer  side  of  a  depression  at  the  bottom  of  which  is  the  anterior  perforated  space. 
This  depression  is  called  the  vallecula  Sylvii.  It  then  passes  outward  to  the  exter- 
nal surface  of  the  hemisphere,  and  gives  off  a  short  anterior  limb,  which  passes 
forward,  and  another,  ascending  limb,  which  passes  upAvard  into  the  inferior  frontal 
convolution.  It  is  then  continued  backward  as  the  horizontal  limb,  and  terminates 
in  the  parietal  lobe  after  curving  upward  for  a  short  distance.  It  separates  the 
frontal  and  parietal  lobes  from  the  temporal,  and  occupies  about  the  middle  third 
of  the  lateral  surface  of  the  hemisphere. 

The  fissure  of  Rolando  is  situated  about  the  middle  of  the  outer  surface  of  the 
hemisphere.  It  commences  at  or  near  the  longitudinal  fissure,  and  runs  downward 
and  forward  to  terminate  a  little  above  the  beginning  of  the  horizontal  limb  of  the 
fissure  of  Sylvius,  and  about  half  an  inch  behind  the  ascending  limb  of  the  same 
fissure.  It  separates  the  frontal  from  the  parietal  lobe. 

The  parieto-occipital  fissure  is  only  seen  to  a  slight  extent  on  the  outer  surface 
of  the  hemisphere,  and  is  not  so  distinctly  marked  as  the  others.  The  portion  on 
the  outer  surface  of  the  hemisphere  is  sometimes  called  the  external  /><>/ •!<•  to-occip- 
ital fissure,  to  distinguish  it  from  the  continuation  of  the  sulcus  on  the  internal 
surface  of  the  hemisphere,  which  would  then  be  termed  the  internal  parieto-occip- 
ital fissure.  It  commences  about  midway  between  the  posterior  extremity  of  the 


THE   BRAIX  AXD    ITU   MEMBRANES. 


775 


brain  and  the  fissure  of  Rolando,  and  runs  downward  and  forward  for  somewhat 
less  than  an  inch.  It  separates  the  parietal  and  occipital  lobes. 

These  three  fissures  divide  the  external  surface  of  the  hemisphere  into  five 
lobes — the  frontal,  the  parietal,  the  occipital,  the  temporal,  and  the  central  or 
island  of  JieiL 

The  frontal  lobe  is  that  portion  of  the  brain  which  is  situated  in  front  of  the 
fissure  of  Rolando  and  above  the  horizontal  limb  of  the  fissure  of  Sylvius.  Its 
under  surface  rests  on  the  orbital  plate  of  the  frontal  bone,  and  is  termed  the 
orbital  lobe. 

The  outer  surface  of  the  frontal  lobe  presents  three  sulci,  which  divide  it  into 
four  primary  convolutions :  1.  The  precentral  sulcus  runs  upward  through  this 
lobe,  parallel  to  the  fissure  of  Rolando.  It  may  be  interrupted  by  annectant 

End  of  calloso- 
marginal  fissure. 


Ascending  fissure 
of  Sylvius. 


FIG.  466.— Convolutions  and  fissures  of  the  outer  surface  of  the  cerebral  hemisphere. 

gyri.  It  divides  off  a  convolution  which  lies  between  it  and  the  fissure  of  Rolando, 
and  which  is  called  the  ascending  frontal  convolution.  2  and  3.  From  it  two  sulci, 
the  superior  and  inferior  frontal  sub-i,  run  forward  and  downward,  and  divide  the 
remainder  of  the  outer  surface  of  the  lobe — namely,  that  part  in  front  of  the  pre- 
central sulcus — into  three  principal  convolutions,  named,  respectively,  the  superior, 
middle,  and  inferior  frontal  convolutions  (or  "lobes"). 

The  under  surface  of  the  frontal  lobe,  which  rests  on  the  orbital  plate  of  the 
frontal  bone,  is  named  the  orbital  lobe  (Fig.  467).  This  surface  of  the  frontal 
lobe  is  divided  into  three  convolutions  by  a  well-marked  sulcus,  the  orbital  sub-it*. 
These  are  named,  from  their  positions,  the  iiitcnmL  anterior,  and  posterior  orbital 
'•"//'•olutions,  and  are  the  continuations  respectively  of  the  superior,  middle,  and 
inferior  frontal  convolutions.  The  internal  orbital  convolution  presents  or  is 
subdivided  by  a  well-marked  groove  or  sulcus  (olfactory  sulcus)  for  the  olfactory 
tract. 

The  ascending  frontal  convolution  is  a  simple  convolution,  bounded  in  front  by 
the  precentral  sulcus,  behind  by  the  fissure  of  Rolando,  and  extending  from  the 


776 


THE   NERVOUS   SYSTEM. 


upper  margin  of  the  hemisphere  above  to  a  little  behind  the  bifurcation  of  the 

fissure  of  Sylvius  below. 

The  superior  frontal  convolution 
is  situated  between  the  margin  of 
the  longitudinal  fissure  and  the  su- 
perior frontal  sulcus.  It  extends 
above  on  to  the  inner  aspect  of  the 
hemisphere,  forming  the  marginal 
convolution,  and  in  front  and  below 
on  to  the  orbital  surface,  forming 
the  internal  orbital  convolution.  It 
is  much  divided  by  secondary  sulci. 
The  middle  frontal  convolution 
is  situated  between  the  superior  and 
inferior  frontal  sulci,  and  extends 
from  the  precentral  •  sulcus  to  the 
lower  margin  of  the  lobe,  where  it 
forms  the  anterior  orbital  convolu- 
tion. 

The  inferior  frontal  convolution 
is  situated  below  the  inferior  frontal 
sulcus,  and  extends  from  the  lower 
part  of  the  precentral  sulcus,  circling 
round  the  ascending  and  anterior 
limbs  of  the  fissure  of  Sylvius,  to 
the  under  surface  of  the  lobe,  where 
it  forms  the  posterior  orbital  convo- 
lution. 

The  parietal  lobe  is  situated  be- 
tween the  frontal  and  occipital  lobes, 
and  is  not  much  more  than  half  the 
size  of  the  former.  It  is  bounded  in 
front  by  the  fissure  of  Rolando  ;  be- 
hind, by  the  external  parieto-occip- 
ital  fissure  and  a  line  drawn  in  continuation  of  that  sulcus  over  the  hemisphere ; 
and  below,  by  the  horizontal  limb  of  the  fissure  of  Sylvius  and  a  line  connecting 
this  with  the  lower  end  of  the  superior  occipital  sulcus.  Above,  it  extends  to  the 
longitudinal  fissure.  It  presents  for  examination  two  sulci  and  three  convolutions. 
The  intraparietal  sulcus  commences  close  to  the  horizontal  limb  of  the  fissure 
of  Sylvius,  about  midway  between  the  fissure  of  Rolando  arid  the  upturned 
extremity  of  the  fissure  of  Sylvius.  It  first  runs  upward  parallel  to  and  behind 
the  lower  half  of  the  fissure  of  Rolando,  and  then  turns  backward,  extending 
nearly  to  the  termination  of  the  external  parieto-occipital  fissure,  where  it  some- 
times becomes  continuous  with  the  superior  occipital  sulcus.  The  ascending  por- 
tion of  this  sulcus  separates  off  a  convolution,  the  ascending  parietal,  which  lies 
between  it  and  the  fissure  of  Rolando,  whilst  the  horizontal  portion  divides  the 
remainder  of  the  parietal  lobe  into  two  other  convolutions,  the  superior  and 
inferior  parietal. 

The  post-central  sulcus  is  a  slightly  marked  groove,  which  is  sometimes  a 
branch  of  the  intraparietal  sulcus,  being  given  off  where  the  ascending  portion 
of  this  sulcus  turns  backward.  It  lies  parallel  to  and  behind  the  upper  part  of 
the  fissure  of  Rolando,  and  separates  the  ascending  from  the  superior  parietal 
convolution.1 

1  Professor  Cunningham  describes  these  two  sulci,  intraparietal  and  post  central,  somewhat  differ- 
ently. He  regards  them  as  both  belonging  to  the  intraparietal  sulcns,  which  he  divides  into  three 
parts:  the  ascending  portion  of  the  intraparietal,  as  described  above,  he  terms  the  ramus  vertical  is  infe- 
rior; the  horizontal  portion  as  the  ramus  horizontal  is ;  while  the  post-central  sulcus  he  denominates 
the  ramus  vertically  superior.  He  states  that  considerable  variability  is  exhibited  in  the  relation  to  each 


FIG.  467.— Convolutions  and  fissures  of  the  under  surface 
of  the  anterior  lobe. 


THE   BRA IX  A XI)    ITS   MEMBRAXES.  777 

The  aticemliti'/  parietal  <-<>n>-<>hition  is  bounded  in  front  by  the  fissure  of  Rolando, 
behind  by  the  ascending  portion  of  the  intraparietal  and  the  post-central  sulci.  It 
extends  from  the  great  longitudinal  fissure  above  to  the  horizontal  limb  of  the 
fissure  of  Sylvius  below.  It  lies  parallel  with  the  ascending  frontal  convolution, 
with  which  it  is  connected  below,  and  also  generally  above,  the  termination  of 
the  fissure  of  Rolando. 

The  mi / «//•/"/•  purii-fiiJ  convolution  is  bounded  in  front  by  the  post-central  sulcus, 
which  separates  it  from  the  previous  convolution,  but  with  which  it  is  usually 
connected  above  the  upper  extremity  of  the  sulcus ;  behind,  it  is  bounded  by  the 
external  parieto-occipital  fissure,  below  the  termination  of  which  it  is  connected 
with  the  occipital  lobe  by  a  narrow  convolution,  the  first  annectant  gyrus.  Below, 
it  is  separated  from  the  inferior  parietal  convolution  by  the  horizontal  portion  of 
the  intraparietal  sulcus ;  and  above  it  is  continuous  on  the  inner  surface  of  the 
hemisphere  with  the  quadrate  lobe. 

The  inferior  parietal  convolution  is  that  portion  of  the  parietal  lobe  which  is 
situated  between  the  ascending  portion  of  the  intraparietal  sulcus  in  front,  the 
horizontal  portion  of  the  same  sulcus  above,  the  horizontal  limb  of  the  fissure  of 
Sylvius  below,  and  the  posterior  boundary  of  the  parietal  lobe  behind.  It  is  sub- 
divided into  two  convolutions  by  an  indistinct  groove.  One,  the  supra  marginal, 
lies  behind  the  lower  end  of  the  intraparietal  sulcus  and  above  the  horizontal  limb 
of  the  fissure  of  Sylvius.  It  is  connected,  in  front,  with  the  ascending  parietal 
convolution  beneath  the  intraparietal  sulcus,  and  with  the  superior  temporal  con- 
volution behind,  around  the  posterior  extremity  of  the  fissure  of  Sylvius.  The 
other,  the  angular,  is  connected  in  front  with  the  foregoing  and  with  the  middle 
temporal  convolution  by  a  process  which  curves  round  the  superior  temporal  or 
parallel  sulcus.  It  is  connected  with  the  occipital  lobe  by  the  second  annectant 
yyrus. 

The  occipital  lobe  is  triangular  in  shape  and  forms  the  posterior  extremity  of 
the  hemisphere.  It  rests  upon  the  tentoriuin.  Its  external  surface  is  bounded 
in  front  by  the  external  parieto-occipital  fissure  and  a  line  drawn  from  the 
extremity  of  this  in  the  direction  of  the  fissure  across  the  outer  surface  of  the 
hemisphere.  It  is  continuous  below  and  in  front  with  the  temporal  lobe,  and 
above  and  in  front  with  the  parietal.  It  is  divided  on  the  outer  surface  of  the 
hemisphere  into  three  convolutions  by  two  indistinct  sulci — the  superior  and 
//*•  1-,,-,-ijiitiiJ  fill.-!.  They  are  directed  backward  across  the  lobe,  being  fre- 
quently small  and  ill-marked ;  the  superior  is  sometimes  continuous  with  the 
horizontal  portion  of  the  intraparietal  sulcus. 

The  x//y«  /•''«/•  -i-'-ipital  convolution  is  situated  above  the  superior  sulcus,  and  is 
connected  to  the  superior  parietal  convolution  by  the  first  annectant  gyra*. 

The  mi'ldle  occipital  convolution  is  situated  between  the  superior  and  middle 
occipital  sulci.  and  is  connected  to  the  angular  convolution  by  the  second  annectant 
'jiiriix.  and  to  the  middle  temporal  by  the  third  annectant  gyrus. 

The  ////</•/"/•  o.v/y ///•///  r,,  involution  is  situated  below  the  middle  occipital  sulcus. 
and  is  sometimes  separated  from  the  external  occipito-temporal  (fourth  temporal] 
convolution  on  the  under  surface  of  the  hemisphere  by  an  inconstant  sulcus,  the 

rior  n>-i-ipital  sulcus  (posterior  extension  of  third  temporal  sulcus;  see  next 
page).  The  fourth  annectant  gyrus  unites  it  with  the  third  temporal  gyrus. 

The  temporal  (temporo-sphenoidciT)  lobe  is  that  portion  of  the  hemisphere  which 
is  lodged  in  the  middle  fossa  of  the  base  of  the  skull.  In  front  and  above  it  is 

other  of  these  different  parts  of  the  intraparietal  sulcus.  but  that  the  one  in  which  the  three  parts  of 
the  sulcus  are  confluent  is  by  far  the  most  constant  condition.  Sometimes,  however,  the  three  parts 
of  the  siilcus  may  be  all  separate,  or  the  ramns  horizontalis  confluent  with  the  ramus  verticalis  infe- 
rior, the  ramus  verticalis  superior  remaining  separate ;  or,  again,  the  vertical  limbs  may  be  confluent 
and  the  horizontal  limb  separate;  or,  finally,  the  ramus  horizontalis  may  be  joined  to  the  lower  end 
of  the  ramus  verticalis  superior,  while  the  lower  vertical  limb  is  separate.  The  connection  which 
sometimes  exists  between  the  intraparietal  sulcus  and  the  occipital  lobe  he  calls  the  ramus  occipitfiJi*. 
In  the  majority  of  cases,  however,  the  occipital  ramus  is  separated  from  the  main  portion  of  the  infra- 
parietal  sulcus  by  a  superficial  or  deep  bridging  convolution  (Journal  of  Anatomy  and  Physiology,  vol. 
xxiv.  part  ii.  p.  135). 


778  THE   NERVOUS  SYSTEM. 

limited  by  the  fissure  of  Sylvius ;  behind,  on  its  external  surface,  it  is  connected 
with  the  parietal  and  occipital  lobes,  and  is  limited  artificially  by  a  line  continuing 
the  direction  of  the  external  parieto-occipital  fissure  across  the  outer  surface  of  the 
hemisphere.  It  is  divided  into  three  convolutions  by  two  sulci.  The  superior  of 
these  runs  parallel  to  the  horizontal  limb  of  the  fissure  of  Sylvius.  It  is  named 
the  superior  or  first  temporal  or  parallel  sulcus,  and  it  is  well  marked  and  con- 
stant. The  second,  the  middle  or  second  temporal,  is  not  so  well  marked  or  con- 
stant ;  it  takes  the  same  course  at  a  lower  level. 

The  superior  or  first  temporal  convolution  is  situated  between  the  horizontal 
limb  of  the  fissure  of  Sylvius  and  the  superior  temporal  sulcus.  It  is  continuous 
behind  with  the  supramarginal  convolution. 

The  middle  or  second  temporal  convolution  is  situated  between  the  superior 
and  middle  sulci  of  the  same  name,  and  is  continuous  behind  with  the  angular 
and  middle  occipital  convolutions. 

The  inferior  or  third  temporal  convolution  is  situated  below  the  middle  tem- 
poral sulcus,  and  is  separated  from  the  external  occipito-temporal  (fourth  tem- 
poral) convolution,  on  the  under  (mesial)  surface  of  the  hemisphere,  by  a  sulcus 
which  is  called  the  inferior  or  third  temporal  sulcus.  It  is  connected  with  the 
inferior  occipital  convolution. 

The  central  lobe,  or  island  of  Reil  (Figs.  467,  468),  is  situated  in  the  fissure 
of  Sylvius;  at  the  base  of  the  brain  it  is  separated,  in  front,  from  the  posterior 
orbital  convolution  by  a  nearly  transverse  sulcus,  the  anterior  sulcus  of  Reil : 

externally,  from  the  inferior  frontal  con- 
volution and  the  lower  ends  of  the  ascend- 
ing frontal  and  parietal  convolutions  by 
another  deep  sulcus,  the  external  side  us 
of  Reil ;  and  posteriorly,  from  the  tem- 
poral lobe  by  a  third  sulcus,  the  pos- 
terior sulcus  of  Reil.  It  is  a  triangu- 
lar-shaped (apex  downward)  prominent 
cluster  of  about  six  convolutions,  the 
gyri  operti,  so  called  from  being  covered 
in  by  the  gyri  bounding  the  fissure.  By 
the  removal  of  these  convolutions  the  ex- 
traventricular  part  of  the  corpus  striatum 

FIG.  468.— External  surface  of  left  hemisphere.  Wrt,1'M  KQ  ^r>o«li«rl 

The  island  of  Reil  is  shown  by  raising  the  opercula  W(n  BU- 

and  bending  outward  the  upper  edge  of  the  tern-  These    Various     Sulci     of     Reil,     taken 

poral  lobe,    a  and  b  are  the  portions  of  the  insula  .  ' . 

separated  by  the  sulcus  centralis  insulx.  (Gegenbaur.)  together,    Constitute    the     SulcUS     limitans 

insulce.  The  sulcus  centralis  insulce  di- 
vides the  lobe  into  a  pre-central  and  a  post-central  lobule,  of  which  the  former 
corresponds  to,  or  may  be  regarded  as  part  of,  the  frontal  lobe ;  and  the  latter  to 
the  parietal  and  temporal  lobes.  Those  portions  of  the  corresponding  lobes  from 
which  the  above-mentioned  sulci  separate  the  island  overlap  it  in  the  normal  con- 
dition, and  are  known  as  the  opercula. 

THE  MESIAL  LOBES  AND  FISSURES  OF  THE  HEMISPHERE. — The  arrangement 
of  the  convolutions  in  this  region  is  less  complex:  they  are  generally  well  defined, 
and,  some  of  them  being  of  great  length,  there  is  not  the  same  subdivision  into 
smaller  lobes  as  on  the  external  surface  (Figs.  469,  470).  The  fissures  on  the 
internal  surface  are  five  in  number,  and  are  named  the  calloso-marginal,  the 
parieto-occipital,  the  calcarine,  the  collateral,  and  the  dentate. 

The  calloso-marginal  fissure  is  seen  in  front,  commencing  below  the  anterior 
extremity  of  the  corpus  callosum  :  it  at  first  runs  forward  and  upward,  parallel 
with  the  rostrum  of  the  corpus  callosum,  and,  winding  round  the  genu  of  that 
body,  it  continues  from  before  backward,  between  the  upper  margin  of  the  hemi- 
sphere and  the  convolution  of  the  corpus  callosum,  to  about  midway  between  the 
anterior  and  posterior  extremities  of  the  brain,  where  it  turns  upward  to  reach  the 
upper  margin  of  the  inner  surface  of  the  hemisphere  (paracentral  fissure  of 


THE   BRAIX   AXD    ITS   MEMBRAXES. 


779 


Wilder)  a  short  distance  behind  the  superior  extremity  of  the  furrow  of  Rolando. 
It  separates  the  marginal  convolution  from  the  gyrus  fornicatus  or  convolution  of 
the  corpus  callosum  (limbic  lobe). 

The  parieto-occipital  fissure  (internal  parieto-occipital}  is  the  continuation  of 
the  fissure  of  the  same  name  seen  on  the  outer  surface  of  the  hemisphere.  It 
extends  in  an  oblique  direction  downward  and  forward  to  join  the  calcarine 
fissure  on  a  level  with  the  hinder  end  of  the  corpus  callosum.  It  separates  the 
quadrate  from  the  cuneate  lobe. 

The  calcarine  fissure  commences,  usually  by  two  branches,  at  the  back  of  the 
hemisphere,  runs  nearly  horizontally  forward,  and  is  joined  by  the  parieto-occipital 
fissure,  and  continues  nearly  as  far  as  the  posterior  extremity  of  the  corpus  callosum, 
to  terminate  a  little  below  the  level  of  this  commissure.  It  separates  the  cuneate 


Pulv.  of 

optic  thai. 

\ 


Cbrp.  quad. 


Subst.  nigra 


FIG.  469.— Mesial  or  inner  aspect  of  left  hemisphere,  together  with  optic  thalamus  and  part  of  mid-brain. 
The  temporal  lobe  is  drawn  downward  and  backward  away  from  the  optic  thalamus.  The  septum  lucidum 
is  removed.  'Henle.) 

lobe  from  the  fifth  temporal  or  infracalcarine  gyrus,  and  causes  the  prominence  in 
the  posterior  cornu  known  as  the  hippocampus  minor  or  calcar  avis,  whence  its  name. 

The  collateral  fissure  (fourth  temporal  sulcus)  is  situated  below  the  preceding, 
being  separated  from  it  by  the  infracalcarine  gyrus.  It  runs  forward,  from  the 
posterior  extremity  of  the  brain,  nearly  as  far  as  the  commencement  of  the  fissure 
of  Sylvius.  It  runs,  at  first,  between  the  fourth  temporal  (below)  and  infracalcarine 
(above)  convolutions,  and  then  lies  beneath  the  hippocampal  gyrus.  It  lies  below 
the  posterior  and  middle  horn  of  the  lateral  ventricle,  and  causes  the  prominence  in 
the  latter  known  as  the  eminentia  collateralis. 

The  dentate  or  hippocampal  fissure  commences  immediately  below  the  posterior 
extremity  of  the  corpus  callosum,  and  runs  forward  to  terminate  at  the  recurved 
part  of  the  hippocampal  gyrus.  It  corresponds  with  the  prominence  of  the  hippo- 
campus major  in  the  descending  horn  of  the  lateral  ventricle. 

The  lobes  or  convolutions  seen  on  the  internal  surface  of  the  hemisphere  are 
as  follows :  gyfiu  fonticatiu,  iimrnimiL  'iii<i<lr<it>\  atm-atr,  hippocampal,  uncinate, 
.'••///,  •, i  !•',,(,•.  fourth  temporal,  and  th>/  paracentral  lolntJ' . 

The  gyrus  fornicatus,  or  convolution  of  the  corpus  callosum,  is  a  well-marked 


780 


THE   NERVOUS  SYSTEM. 


lobe  which  begins  just  in  front  of  the  anterior  perforated  space  at  the  base  of  the 
brain  :  it  passes  forward  below  the  rostrum,  and  then  ascends  in  front  of  the  genu 
of  the  corpus  callosum,  and  runs  backward  along  the  upper  surface  of  this  body 
to  its  posterior  extremity,  around  which  it  bends  to  join  the  hippocampal  convo- 
lution by  a  constriction,  the  isthmus.  It  is  bounded  below,  in  front,  and  above, 
in  the  greater  part  of  its  extent,  by  the  calloso-marginal  fissure,  which  separates 
it  from  the  marginal  convolution ;  above  and  behind  its  bend  it  is  separated  by 
the  post-limbic  fissure  from  the  quadrate  lobe.  Between  it  and  the  corpus  callosum 
is  the  eallosal  sulcus. 

The  marginal  convolution  is  situated  parallel  with  the  anterior  portion  of  the 
preceding,  and  has  received  its  name  from  its  position  along  the  border  of  the 
hemisphere.  It  commences  in  front  of  the  anterior  perforated  space,  runs  along 
the  margin  of  the  longitudinal  fissure  on  the  under  surface  of  the  orbital  lobe, 
being  subdivided  by  the  sulcus  for  the  olfactory  tract ;  it  then  turns  upward  to  the 


FIG.  470. — Convolutions  and  fissures  of  the  inner  surface  of  the  cerebral  hemisphere. 

upper  surface  of  the  hemisphere  and  runs  backward,  forming  the  marginal  convo- 
lution, on  the  inner  surface,  to  the  point  where  the  calloso-marginal  fissure  turns 
upward  to  reach  the  superior  border  of  the  hemisphere.  At  this  point,  together 
with  the  upper  extremities  of  the  ascending  frontal  and  parietal  gyri,  which  are 
bent  over  on  the  inner  surface  of  the  hemisphere,  it  forms  the  paracentral  lobule. 
This  convolution  is  regarded  as  being  on  the  mesial  aspect  of  the  frontal  lobe. 

The  quadrate  lobe  (precuneus)  is  the  "marginal"  convolution  of  the  longitu- 
dinal fissure  behind  the  posterior  portion  (paracentral  fissure)  of  the  calloso-marginal 
sulcus,  lying  between  this  fissure  in  front  and  the  internal  parieto-occipital  behind. 
It  is  separated  by  the  post-limbic  fissure  from  the  gyrus  fornicatus  below,  and  is 
continuous  above  with  the  superior  parietal  convolution. 

The  cuneate  or  occipital  lobule  is  triangular  in  shape,  being  situated  between 
the  internal  parieto-occipital  and  calcarine  fissures,  which,  as  above  mentioned, 
meet  behind  the  isthmus  of  the  gyrus  fornicatus. 

The  infracalcarine  (fifth  temporal)  convolution  extends  from  the  posterior  ex- 
tremity of  the  temporal  lobe  to  join  the  hippocampal  gyrus,  being  bounded  above 
by  the  calcarine  and  its  anterior  prolongation,  after  its  junction  with  the  parieto- 
occipital  fissure,  and  separated  below  from  the  fourth  temporal  convolution  by  the 
collateral  fissure.  The  back  part  of  this  convolution — that  is,  the  part  below  the 


THE   BRAIN  AND    ITS   MEMBRAS1.S. 


781 


posterior  portion  of  the  calcarine  fissure — is  sometimes  known  as  the  lingual  lobule 
or  gyrus. 

The  fourth  temporal  convolution  is  of  considerable  length,  and  lies  on  the  inner 
aspect  of  the  temporal  lobe,  between  the  collateral  fissure  above  and  the  inferior 
(third)  temporal  sulcus  below,  which  latter  separates  it  from  the  inferior  (third) 
temporal  convolution  on  the  outer  surface  of  the  temporal  lobe.  Its  posterior  part 
is  called,  ar  times,  the  fusiform  lobule. 

The  hippocampal  convolution  is  the  downward  and  forward  prolongation,  on  the 
mesial  surface  of  the  temporal  lobe,  of  the  gyrus  fornicatus,  just  after  the  latter 
has  bent  around  and  beneath  the  splenium  of  the  corpus  callosum.  Its  direction 
is  toward  the  apex  of  the  temporal  lobe,  just  before  reaching  which,  however,  its 
anterior  extremitv  is  recurved  or  bent  backward  in  the  form  of  a  hook,  which  is 


FIG.  471. — Side  view  of  the  brain  of  man,  showing  the  localization  of  various  functions.    (After  Ferrier.) 

I.  Centre  for  movements  of  opposite  leg  and  foot.    2,  3.  4.  Centres  for  complex  movements  of  the  arms  and  legs, 
as  in  swimming.    5.  Extension  forward  of  the  arm  and  hand.    6.  Supination  of  the  hand  and  flexion  of  the 
forearm.    7,  S.  Elevators  and  depressors  of  the  angle  of  the  mouth.    9, 10.  Movements  of  the  lips  and  tongue. 

II.  Retraction  of  the  angle  of  the  mouth.    12.  Movements  of  the  eyes.    13, 13'.  Vision.    14.  Hearing,    a,  b,  c,  d. 
Movements  of  the  wrists  and  fingers. 

sometimes  called  the  crochet  or  uncus.  It  is  bounded  below  by  the  collateral  Jis- 
mtre  (anterior  portion),  and  above  by  the  hippocampal  or  dentate  fissure. 

The  Uncinate  Gyrus. — The  hippocampal  and  infracalcarine  gyri  are,  taken 
together,  often  described  as  one  gyrus.  the  uitcinate. 

Besides  the  great  primary  convolutions  above  named  and  described,  and 
which  can  be  recognized  in  almost  any  well-developed  brain,  there  are  a  great 
number  of  secondary  convolutions  which  pass  from  one  primary  convolution  to 
another,  and  often  render  the  arrangement  of  the  latter  somewhat  obscure :  of 
these  annc'-t'int  <-,,/, r,,hitions  the  connections  of  the  occipital  lobe,  above  mentioned, 
may  be  taken  as  examples. 

THE  LIMBIC  LOBE. — By  this  term  is  understood  a  grouping  together  of  certain 
portions  of  the  hemisphere  which  have  a  peculiar  course.  That  is,  beginning 
anteriorly,  they  curve  forward,  upward,  and  backward,  then  downward  and  for- 
ward, so  that  their  two  extremities  lie  quite  close  together.  The  structures  of  the 
limbic  lobe  have  all  been  described,  and  are  as  follows :  (1)  Gyrus  fornicatus  and 
hippocampal  gyrus  :  (2)  the  supracallosal  gyrus  (see  below) ;  (3)  each  half  of  the 


782 


THE   NERVOUS   SYSTEM. 


fornix,  with  its  corresponding  anterior  and  posterior  pillar  and  half  of  the  septum 
lucidum. 

The  supracallosal  gyrus,  just  mentioned,  may  be  regarded  as  made  up  of  the 
peduncles  of  the  corpus  callosum,  the  longitudinal  striae  on  the  upper  surface  of  the 
same,  and  the  fascia  dentata  with  its  upper  part,  the  fasciola  cinerea.  These 
structures  are  continuous  with  each  other,  as  has  already  been  mentioned  in  the 
description  of  each.  The  name  dentate  gyrus  is  often  used  to  designate  the  com- 
bined fasciola  cinerea  and  fascia  dentata. 

The  boundaries  of  the  limbic  lobe  are  the  calloso-marginal  fissure,  the  collateral 
fissure,  and  the  post-limbic  fissure. 


FIG.  472. — Top  view  of  the  brain  of  man,  showing  the  localization  of  various  functions.  (After  Ferrier.) 
References  the  same  as  in  the  preceding  figure. 

THE  OLFACTORY  LOBE  (Fig.  473). — This  is  situated  on  the  orbital  lobe  (under 
surface  of  frontal  lobe).  In  general  outline  it  is  long  and  slender,  widest  behind. 
It  is  divisible  into  two,  anterior  and  posterior,  olfactory  lobules.  The  olfactory 
lobe  is  developed  as  a  hollow  outgrowth  from  the  ventral  and  lateral  part  of  the 
corresponding  hemisphere  vesicle,  the  cavity  of  which,  in  man  and  primates,  is 
eventually  obliterated.  In  the  adult  condition  the  posterior  lobule  is  found  to  have 
remained  on  the  hemisphere,  and  thus  to  form  a  part  of  it,  while  most  of  the  ante- 
rior lobule  is  attached  only  by  a  stalk  to  the  posterior,  it  being  freely  separable  in 
the  rest  of  its  extent ;  that  is,  after  removal  of  the  membranes. 

The  anterior  olfactory  lobule  is  made  up  of  (1)  the  olfactory  bulb ;  (2)  the 
olfactory  tract ;  (3)  the  trigonum  olfactorium  ;  and  (4)  the  area  of  Broca. 

The  olfactory  bulb  is  an  oval  mass  of  a  grayish  color,  Avhich  rests  on  the  crib- 
riform plate  of  the  ethmoid  bone,  and  forms  the  anterior  expanded  extremity  of 
the  slender  process  of  brain-substance,  the  olfactory  tract  (see  page  792).  From 
the  under  part  of  this  bulb  are  given  off  the  olfactory  nerves,  which  pass  through 
the  cribriform  foramina  and  are  distributed  to  the  mucous  membrane  of  the  nose. 


THE   BRAIN   AND    ITS   MEMBRANES. 


783 


The  olfactory  tract ,  when  traced  backward,  divides  into  two  slips  or  roots, 
external  and  internal,  at  its  base.  The  so-called  middle  or  gray  root  is  the  tri- 
(•fn,t>ii/i  olfii'-toriniii.  which  is  enclosed  by  the  two  roots.  Traced  forward,  these  two 
roots  unite  and  form  the  tract,  which  is  a  flat  band,  narrower  in  front  than  behind, 
and  of  a  somewhat  prismoid  form  on  section.  It  is  soft  in  texture  and  contains 
gray  matter  (neuroglia)  in  its  substance.  As  it  passes  forward  it  is  contained  in 
a  deep  sulcus,  the  olfactory  sulcus,  which  subdivides  the  internal  orbital  convolu- 
tion, lying  on  the  under  surface  of  the  frontal  lobe  on  each  side  of  the  longi- 
tudinal fissure,  and  is  retained  in  position  by  the  membrane  (pia  mater),  which 


Frontal  lobe. 


Temporal  lobe. 

rncus  of  hippo- 
campal  gyrus. 


l_Part  of  fourth 
temporal  gyms. 


Occipital 
lobe. 


FIG.  473.— Base  of  the  brain. 


covers  it.     On  reaching  the  cribriform  plate  of  the  ethmoid  bone  it  expands  into 
the  i jl factory  bulb. 

The  trigonum  olfactorium  and  the  area  of  Broca  constitute  one  and  the  same 
area  of  cortical  gray  matter,  bounded  internally  and  posteriorly  by  a  fissure 
(fasura  prima).  which  separates  it  from  the  anterior  part  of  the  peduncle  of  the 
corpus  callosum  on  its  inner  aspect,  and  from  the  anterior  perforated  space  pos- 
teriorly. Externally,  this  area  passes  into  continuity  with  the  cortical  gray 
matter  of  the  internal  orbital  gyrus.  This  area  is  divided  into  three  districts  by 
the  passage  across  it,  from  before  backward,  of  the  two  roots  of  the  olfactory  tract. 
The  internal  district,  lying  between  the  internal  root  and  anterior  part  of  pedun- 
cle of  corpus  callosum  (fissura  prima  intervening)  is  the  area  of  Broca,  continu- 
ous with  the  beginning  of  the  gyrus  fornicatus.  The  middle  district,  included 


784  THE   NERVOUS  SYSTEM. 

between  the  two  roots,  is  the  trigonum  olfactorium.  The  external  district, 
external  to  the  external  root,  is  very  small  and  has  no  especial  name. 

The  posterior  olfactory  lobule  or  anterior  perforated  space  (anterior  perforated 
lamina)  is  situated  at  the  inner  side  of  the  fissure  of  Sylvius.  It  is  bounded 
in  front  by  the  fissura  prima  (transverse  part)  and  the  orbital  convolutions 
of  the  frontal  lobe ;  behind,  by  the  optic  tract ;  externally,  by  the  temporal 
lobe  and  commencement  of  the  fissure  of  Sylvius  (valleeula) ;  internally,  it  is 
continuous  with  the  lamina  cinerea.  It  is  crossed  internally  and  posteriorly  by 
the  posterior  part  of  the  peduncle  of  the  corpus  callosum,  and  externally  by  the 
external  olfactory  root.  It  is  of  a  grayish  color,  and  corresponds  to  the  under 
surface  of  the  corpus  striatum  (lenticular  nucleus)  and  part  of  the  claustrum.  It 
has  received  its  name  from  being  perforated  by  numerous  minute  apertures  for 
the  transmission  of  small  straight  vessels  into  the  substance  of  the  corpus  stri- 
atum, constituting  the  antero-median  and  antero-lateral  ganglionic  branches  of  the 
anterior  and  middle  cerebral  arteries. 

The  Olfactory  Roots. — The  external  root  passes  outward  across  the  anterior 
perforated  space  and  the  fissure  of  Sylvius  to  the  temporal  lobe — i.  e.  end  of 
hippocampal  gyrus  (possibly  nucleus  amygdalae  also) — where  it  meets  the  termi- 
nation of  the  peduncle  of  the  corpus  callosum. 

The  internal  root  passes  inward  and  joins  the  lower  end  of  the  gyrus  forni- 
catus  after  bending  around  and  behind  the  area  of  Broca,  into  which  also  some 
of  its  fibres  pass. 

The  trigonum  receives  a  few  fibres  directly  from  the  end  of  the  tract — /.  e. 
between  the  divergence  of  its  roots.  When  these  fibres  are  well  marked  they 
constitute  the  so-called  "  middle  root."  From  the  end  of  the  tract  a  few  fibres 
also  pass  directly  dorsally  into  the  white  matter  of  the  frontal  lobe,  upper  or 
dorsal  root  (Henle). 

Each  root  of  the  olfactory  tract  is  thus  seen  to  be  connected  with  an  extrem- 
ity of  the  limbic  lobe — the  external  with  the  end  of  the  hippocampal  gyrus, 
and  the  internal  with  the  beginning  of  the  gyrus  fornicatus. 

Under  Surface  or  "Base"  of  the  Encephalon. — The  various  objects  exposed  to 
view  on  the  under  surface  of  the  brain,  in  and  near  the  middle  line,  are  here 
arranged  in  the  order  in  which  they  are  met  with  from  before  backward  (Fig. 
473)  : 

In  the  Middle  Line.  Each  Side  of  the  Middle  Line. 

Longitudinal  fissure.  Under  surface  of  frontal  lobe. 
Under  surface  of  rostrum  of  corpus         Olfactory  bulb, 

callosum  and  its  peduncles.  Olfactory  tract. 

Lamina  cinerea.  Olfactory  roots. 

Optic  commissure.  Anterior  perforated  space. 

Pituitary  body.  Fissure  of  Sylvius. 

Infundibulum.  Optic  tract. 

Tuber  cinereum.  Crusta. 

Corpora  albicantia.  Under  surface  of  temporal  lobe. 

Posterior  perforated  space.  Under  surface  of  hemisphere  of 
Tuber  annulare  of  pons.  cerebellum. 

Medulla  oblongata  (ventral  surface). 

The  longitudinal  fissure  partially  separates  the  two  hemispheres  from  each 
other :  it  divides  the  two  frontal  lobes  in  front,  and  on  raising  the  cerebellum  and 
pons  it  will  be  seen  completely  separating  the  two  occipital  lobes.  Of  these  two 
portions  of  the  longitudinal  fissure,  that  which  separates  the  occipital  lobes  is  tlic 
longer.  The  intermediate  portion  of  the  fissure  is  filled  up  by  the  great  transverse 
band  of  white  matter,  the  corpus  callosum.  In  the  fissure  between  the  two  frontal 
lobes  the  anterior  cerebral  arteries  ascend  on  the  corpus  callosum. 

Interpeduncular  Space. — Immediately  behind  the  diverging  optic  tracts,  and 


THE   BRAIN  AND   ITS  MEMBRANES.  785 

between  them  and  the  inner  margins  of  the  crustae  or  peduncles  of  the  cerehrum 
(mira  cerebri),  is  a  lozenge-shaped  interval,  the  interpeduncular  space,  in  which 
are  found  the  following  parts :  the  tuber  cinereum,  infundibulum,  pituitary  body, 
corpora  albicantia,  and  the  posterior  perforated  space. 

The  remaining  structures  above  enumerated  have  all  been  previously  described, 
each  in  its  own  region. 

Structure  of  the  Hemispheres. 

Each  hemisphere  is  made  up  of  gray  and  white  matter.  The  latter  constitutes 
nearly  the  whole  of  the  deeper  portion  (medullary  centre),  and  enters  into  the 
.structure  of  the  convolutions.  The  gray  matter  covers  in  the  convolutions,  form- 
ing the  cortex  of  the  hemisphere,  and  also  is  collected  into  three  masses  or  nuclei 
situated  in  the  hemisphere — the  corpus  striatum,  the  claustrum,  and  the  nucleus 
amygdalce.  These  last  might  be  regarded  as  subdivisions  of  one  large  nucleus, 
since  they  are  more  or  less  connected  in  the  anterior  perforated  space. 

The  WHITE  MATTER  OF  THE  HEMISPHERES  consists  of  medullated  fibres,  vary- 
ing in  size  and  arranged  in  bundles,  separated  by  neuroglia.  They  may  be 
divided  into  three  distinct  systems,  according  to  the  course  which  they  take : 
1.  Projection  fibres,  which  connect  the  hemispheres  with  the  medulla  oblongata 
and  cord.  2.  Transverse  or  commissural  fibres,  which  connect  together  the  two 
hemispheres.  3.  Association-fibres  (Meynert),  which  connect  different  structures 
in  the  same  hemisphere. 

1.  The  projection  or  peduncular  fibres  consist  of  a  main  body,  which  originates 
in  the  cord  and  medulla  oblongata,  forms  the  longitudinal  fibres  of  the  pons,  which 
last  are  then  continued  up  into  the  mid-brain,  where,  as  has  been  before  described, 
the  fibres  are  arranged  in  two  strata,  which  are  separated  by  the  locus  niger,  the 
ventral  or  superficial  stratum  forming  the  crusta,  and  the  dorsal  or  deeper  stratum 
the  bulk  of  the  tegmentum.  The  fibres  derived  from  these  two  sources  take  a  dif- 
ferent course,  and  will  have  to  be  separately  considered. 

The  fibres  of  the  crusta  are  derived  from  the  pyramid  of  the  medulla,  which 
fibres  are  continued  upward  through  the  pons  to  form  the  crusta ;  they  are  rein- 
forced in  their  passage  through  the  crus  by  accessory  fibres  derived  from  the  cen- 
tral gray  matter  around  the  Sylvian  aqueduct,  from  the  nuclei  pontis,  and  from 
the  locus  niger  (see  page  742).  Most  of  the  fibres  of  the  crusta  (except  the 
mesial  fillet,  p.  742)  pass  into  the  hemisphere  as  part  of  the  internal  capsule, 
which  last,  passing  upward,  diverges  into  fibres  which  radiate  forward,  upward, 
and  backward,  thus  constituting  the  corona  radiata,  Each  fibre  of  this  last- 
named  structure  proceeds  to  the  corresponding  portion  of  the  cortex,  where  it 
becomes  the  direct  prolongation  of  an  axis-cylinder  process  of  a  pyramidal  cell 
(see  below).  Some,  if  not  all,  of  the  fibres  of  the  internal  capsule  give  off  col- 
laterals to  the  optic  thalamus  and  the  nucleus  caudatus  and  lenticularis  of  the 
corpus  striatum. 

From  these  ganglia  (see  pages  747,  760)  there  are  also  fibres  which  proceed 
into  the  internal  capsule  and  the  corona  radiata,  thus  forming  parts  of  each  in 
addition  to  the  fibres  from  the  crusta.  The  fibres  which  arise  from  the  ganglia 
are  more  numerous  than  those  which  terminate  in  the  ganglia,  so  that  more  fibres 
pass  out  of  the  ganglia  than  pass  into  them. 

The  fibres  of  the  tegmentum  are  continuous  with  those  longitudinal  fibres  of 
the  pons  which  are  derived  from  the  formatio  reticularis  of  the  medulla  (which 
see),  including  also  fillet  (per  corpora  quadrigemina)  and  posterior  longitudinal 
bundle.  They  are  reinforced  by  fibres  from  the  corpora  quadrigemina  and  cor- 
pora geniculata,  and  from  the  superior  peduncle  of  the  cerebellum.  Superiorly, 
some  are  lost  in  the  subthalamic  region,  while  others  enter  the  optic  thalamus  and 
terminate  in  its  gray  matter,  whence  they  are  continued  into  the  internal  capsule 
as  the  various  bundles  of  fibres  which  have  been  already  referred  to  both  in  the 
description  of  the  optic  thalamus  and  just  above.  Thus,  the  tegmental  fibres 

50 


786  THE   NERVOUS  SYSTEM. 

Avhich  help  make  up  the  projection  fibres  do  so,  not  directly,  but  by  the  interpo- 
sition of  the  optic  thalarni  and  corpora  striata,  between  which  there  are  also  con- 
necting fibres  which  run  through  the  internal  capsule. 

2.  The  transverse  or  commissural  fibres  connect  together  the  two  hemispheres. 
They  include  (a)  the  transverse  fibres  of  the  corpus  callosum,  and  (6)  the  anterior 
commissure. 

The  corpus  callosum,  which  has  already  been  described,  connects  together  the 
two  hemispheres  of  the  brain,  forming  their  great  transverse  commissure,  pene- 
trating into  the  medullary  substance  of  the  convolutions  and  intersecting  the 
fibres  of  the  corona  radiata.  The  fibres  of  the  corpus  callosum  can  each  be  traced 
either  as  a  direct  prolongation  of  an  axis-cylinder  process  of  a  pyramidal  cell  in 
the  gray  matter  of  the  cortex,  or  as  a  collateral  from  one  of  the  projection-fibres 
just  described. 

The  anterior  commissure  is  a  round  bundle  of  white  fibres  Avhich  is  placed  in 
front  of  the  anterior  pillars  of  the  fornix,  and  appears  to  connect  the  corpora  stri- 
ata. It  passes  outward  through  the  lenticular  nucleus  of  the  corpus  striatum  on 
each  side,  and  then  curves,  somewhat  twisted  on  itself,  downward  and  backward 
into  the  substance  of  the  temporal  lobe,  where  its  fibres  radiate  from  each  other. 

3.  Association-fibres  connecting  Different  Structures  in  the  Same  Hemisphere. — 
These  fibres  are  of  two  kinds  :  (1)  those  which  connect  adjacent  convolutions,  and 
which  are  termed  short  association-fibres  ;  (2)  those  which  connect  more  distant 
parts  in  the  same  hemisphere — the  long  association-fibres. 

The  short  association-fibres  are  situated  immediately  beneath  the  gray  substance 
of  the  cortex  of  the  hemispheres,  and  connect  together  adjacent  convolutions, 
arching  beneath  the  cortical  matter  which  lies  at  the  bottom  of  the  fissures. 

The  long  association-fibres  include  the  following : 

(a)  The  uncinate  fasciculus  connects  the  convolutions  of  the  frontal  and  tem- 
poral lobe.  It  passes  across  the  bottom  of  the  Sylvian  fissure  and  traverses  the 
claustrum. 

(6)  The  fillet  of  the  gyrus  fornicatus  or  cingulum  is  a  band  of  white  matter 
which  encircles  the  hemisphere  in  an  antero-posterior  direction,  lying  in  the  sub- 
stance of  the  convolution  of  the  corpus  callosum.  Commencing  in  front  at  the 
anterior  perforated  space,  it  passes  forward  and  upward  parallel  with  the  rostrum, 
winds  round  the  genu,  runs  in  the  convolution  from  before  backward  immediately 
above  the  corpus  callosum,  turns  round  its  posterior  extremity,  and  is  continued 
downward  and  forward  in  the  hippocampal  gyrus  to  its  extremity.  In  its  course 
it  is  connected  with  the  secondary  convolutions  of  the  gyrus  fornicatus  by  short 
arcuate  fibres. 

(c)  The  superior  longitudinal  fasciculus  runs  along  the  convex  surface  of  the 
hemisphere  and  connects  the  frontal  lobe  with  the  temporal  and  occipital. 

(d)  The  inferior  longitudinal  fasciculus  is  a  collection  of  fibres  which  connects 
the  temporal  and  occipital  lobes,  running  along  the  outer  wall  of  the  middle  and 
posterior  cornu. 

(e)  The  perpendicular  fasciculus  passes  vertically  through  the  front  part  of  the 
occipital  lobe,  and  connects  the  inferior  parietal  convolution  above  with  the  pos- 
terior part  (fusiform  lobule)  of  the  fourth  temporal  convolution  below. 

(/)  The  fornix  connects  the  corpus  albicans  with  the  crochet  or  uncus  of  the 
hippocampal  convolution  in  the  manner  which  has  already  been  described. 

THE  GRAY  MATTER  OF  THE  HEMISPHERE  is  disposed  in  two  regions :  1.  The 
gray  matter  of  the  cerebral  cortex  ;  2.  The  gray  matter  of  the  basal  ganglia ; 
that  is,  the  corpus  striatum  and  nucleus  amygdalae.  As  the  last  two  have  already 
been  described,  there  remains  only  the  cortex  to  be  considered. 

The  gray  matter  of  the  cortex  (Fig.  474)  invests  the  surface  of  the  hemi- 
spheres, covering  in  the  convolutions  or  gyri  and  lining  the  intervening  fissures 
or  sulci.  When  a  vertical  section  is  made  through  a  gyrus,  it  is  found  to  be 
made  up  of  a  white  centre  invested  by  a  portion  of  the  cortex,  which  last,  if 
examined  microscopically,  is  found  to  consist  of  five  separate  layers,  but  to  this 


THE   BRAIN  AND    ITS   MEMBRANES. 


787 


there  are  some  exceptions.     According  to  Meynert,  these  exception*  are  to  be 
found — (1)  in  the  posterior  portion  of  the  occip- 
ital lobe;  (2)  in  the  gray  cortex  of  the  hippo- 
campus major;  (3)  in  the  wall  of  the  fissure  of 
Sylvius ;  and  (4)  in  the  olfactory  bulb. 

The  five  layers  in  the  common  type  (from 
parietal  lobe)  are  as  follows :  (1)  The  first  (super- 
ficial or  molecular)  layer  is  principally  composed 
of  a  matrix  of  neuroglia,  through  which  a  few 
small  ganglion-cells  are  irregularly  distributed, 
and  a  nerve-fibre  network  of  both  non-medullated 
and  medullated  fibres,  the  latter  constituting  a 
delicate  white  lamina  almost  in  contact  with  the 
pia  mater.  Of  the  former,  the  majority  come 
from  the  processes  of  the  pyramidal  cells  in  the 
next  layer,  the  remainder  being  made  up  of  both 
dendrites  (protoplasmic  processes)  and  axis-cyl- 
inder processes  of  the  ganglion-cells  in  this  layer. 

(2)  The    second    layer    consists  of  numerous 
small  pryamidal  cells,  which  have  their  long  axes 
vertical  to  the  surface  of  the   convolutions,  and 
are   closely   aggregated  together  so   as   to   com- 
pletely fill  the  layer.     The  dendrites  of  each  of 
these  cells  extend  into  the  preceding  layer,  while 
the  axis-cylinder  process,  starting  from  the  base 
of  the  cell,  gives  off  a  few  collaterals  and  extends 
through  the  white  centre  of  the  convolution,  and 
thence  to  the  corpus  striatum,  as  a  projection-fibre. 

(3)  The  third  layer  is  made  up  of  cells,  which 
are  the  same  kind  as  those  in  the  formation  of 
the    cornu   Ammonis.      These    cells    are    large 
pyramidal  cells,  arranged  vertically  to  the  sur- 
face, as  was  found  in  the  preceding  layer,  but 
they  are  of  very  much  larger  size,  and  increase 
progressively    toward    the    deeper   parts    of  the 
layer,  and  they  are  much  more  widely  separated 
from  each  other,  thus  forming  groups  between 
which  are  radiating  nerve-fibres.     This  layer  is 
the  principal  and  broadest  one  of  the  series,  and 
is  at  least  twice  as  deep  as  the  preceding  layer. 
The  axis-cylinder  processes  of  these   cells  pass 
into  the  white  substance,  and  there  become  med- 
ullated.    Previously  each  gives  off  a  number  of  collaterals,  which  also  become 
medullated  and  form  ramifications  in  the  layer. 

(4)  The  fourth  layer  is  termed  the  layer  of  polymorphous  cells,  and  consists 
of  numerous,  small,  irregular  cells,  each  of  which  has  numerous  dendrites,  but 
only  one  axis-cylinder  process.     This  last,  from  most  of  the  cells,  passes  into 
the  white  centre,  but  from  some  it  goes  peripherally  to  the  first  layer  and  becomes 
continuous  with  one  of  its  fibres. 

(5)  The  fifth  layer  (layer  of  fusiform  cells)  consists  of  a  very  large  proportion 
of  spindle-shaped  or  fusiform  cells,  which  are  the  peculiar  elements  of  this  layer. 
They  are  especially  numerous  in  the  inner  half,  and  are  arranged  horizontally, 
extending  parallel  to  the  surface.      The  claustrum  is  made  up  almost  entirely  of 
an  accumulation  of  cells  of  the  same  kind. 

The  white  centre  lies  just  beneath  the  fifth  layer,  which  gradually  blends  with 
it.  As  its  fibres  radiate  into  the  cortex  they  become  finer,  and  most  of  them  are 
continuous,  as  stated  above,  with  the  axis-cylinder  processes  of  the  large  pyr- 


FIG.  474.— Gray  matter  of  the  cerebral 
cortex.    (Meynert.) 


788  THE   NERVOUS  SYSTEM. 

amidal  cells  in  the  third  layer  of  the  cortex.  The  collaterals,  already  referred  to, 
of  these  processes  become  medullated  and  form  two  plexuses,  one  along  each 
border  of  the  third  layer.  These  plexuses  appear  to  the  naked  eye  as  two  fine 
white  lines  (Baillarger)  in  sections  of  the  cortex  of  a  fresh  brain. 

Special  Types  of  the   Gray  Matter  of  the  Cortex. — The  special  types  of  gray 
matter  of  the  cortex  are  the  following: 

(1)  On  the  posterior  portion  of  the  occipital  lobe,  near  the  calcarine  fissure, 
the  gray  matter  consists  of  six  or  eight  layers.     This  is  produced  by  the  inter- 
calation of  intermediate  small,  irregular  cells,  similar  to  those  forming  the  fourth 
layer  of  the  typical  cortex.     Furthermore,  the  large  pyramidal  cells  of  the  typical 
third  layer  are  very  few,  while,  on  the  other  hand,  in  the  upper  part  of  the  ascend- 
ing frontal  convolution  (psycho-motor  region)  these  pyramidal  cells  of  the  third 
layer  are,  many  of  them,  of  unusual  size. 

(2)  In   the  gray  matter  of  the   cortex   of  the  hippocampus  major   or   cornu 
Ammonis  pyramidal  cells  are  found,   such  as  have  been   described  in  the  third 
layer  of  the  typical  cortex.     They  constitute  the  greater  part  of  the  structure, 
the  fourth  and  fifth  layers  being  absent.      Hence  this  layer  is  called  the  formation 
of  the  cornu  Ammonis.     The  bases  of  these   cells  are   close  under  the  white 
lamina  (alveus)  which  covers  the  hippocampus  on  its  ventricular  aspect.     The 
second  layer — i.  e.   toward  the  hippocampal   fissure — contains   no    cells.      It    is 
represented  by  a  closely  interwoven  arborization  of  the  dendrites  (protoplasmic 
processes)  of  the  pyramidal  cells  just  mentioned,  of  which  the  axis-cylinder  pro- 
cesses pass,  in  the  opposite   direction,    into  the   alveus.      Finally,   beyond  the 
second  layer  is  the  first  layer  of  the  gray  matter  of  the  hippocampus,  or,  as  it 
is  termed,  the  granular  formation  (Meynert),  and  consists  of   numerous  small, 
irregular  cells,  which  resemble  the  nerves-corpuscles  found  in  the  internal  granule- 
layer  of  the  retina. 

(3)  In  the  Sylvian  fissure  the  fifth  layer  of  the  cortex  contains  an  unusual 
number  of  fusiform  cells  ;  hence  this  layer,  in  this  region,  is   called  the   "  claus- 
tral  formation,"  because  of  the  number  of  the  same  kind  of  cells  in  the  structure 
of  the  claustrum. 

(4)  In  the  olfactory  bulb,  which  is  a  portion  of  the  cerebral  hemispheres,  form- 
ing "a  cap  superimposed  upon  a  conical  process  of  the  cerebrum,"  is  another 
variety  of  structure,  differing  from  the  type  of  the  cortex  of  the  hemispheres. 
The  bulb  consists  of  both  gray  and  white  matter,  and  in  most  of  the  lower  animals 
retains  a  central  cavity  lined  by  epithelium,  around  which  is  a  layer  of  neuroglia, 
surrounded  in  its  turn  by  white  fibres,  the  whole  being  enclosed  by  gray  matter. 
In  man  the  central  cavity  is  obliterated,  and  in  the  "  centre  "  of  the  bulb  is  found 
neuroglia  surrounded  in  section  by  a  flattened  ring  (medullary  ring)  of  white 
fibres.     The  gray  matter  is  now  exceedingly  thin  dorsally,  but  very  thick  ven- 
trally,  and  in  section  this  ventral  portion  shows  the  following  layers  from  below 
upward  :    1.  The  olfactory  nerve-layer,  consisting  of  a  plexus  of  non-medullated 
nerve-fibres  derived  from  the  nerves  which  supply  the  olfactory  region.      These 
fibres  pass  downward  through  the  foramina  in  the  cribriform  plate  of  the  ethmoid, 
and  dorsally  into  the  glomeruli  of  2,  the  stratum  glomerulosum,  consisting  of 
nodulated  masses  (the  glomeruli),  each  mass  consisting  of  a  dense  interlacement 
of  fibres,  which  are  partly  the  prolongations  of  the  olfactory  fibres  just  mentioned, 
and  partly  the  dendrites  of  the  mitral  cells  in  the  superjacent  part  of  the  next  layer. 
Small  neuroglia-cells  also  are  found  in  these  glomeruli.     3.  The  granular  layer, 
consisting  of  (a)  small  irregular  nerve-cells  resembling  those  of  the  granule-layer 
of  the  cortex  of  the  cerebellum  ;  (b)  a  deeper  layer  (next  to  the  stratum  glomeru- 
losum)  of  large,  conical  cells  (mitral  cells).     The  dendrites  of  these  pass  down  to 
the  glomeruli  (see  above),  while  their  axis-cylinder  processes  (medullated)  pass 
upward  between  small  cells  of  the  granule-layer  to  the  medullary  ring,  with  the 
fibres  of  which,  after  bending  sharply  backward,  they  become  continuous,  and 
thence  pass  backward  along  the  olfactory  tract  toward  the  base  of  the  brain ;  that 
is,  the  fibres  of  the  medullary  ring  are  the  continuations  of  these  processes. 


THE   BRAIN  AND    ITS  MEMBRANES.  789 

Weight  of  the  Encephalon. — The  average  weight  of  the  brain  in  the  adult  male 
is  4UJ  oz.,  or  a  little  more  than  3  Ibs.  avoirdupois;  that  of  the  female  44  oz. ;  the 
average  difference  between  the  two  being  from  5  to  6  oz.  The  prevailing  weight 
of  the  brain  in  the  male  ranges  between  46  oz.  and  53  oz.,  and  in  the  female 
between  41  oz.  and  47  oz.  In  the  male  the  maximum  weight  out  of  278  cases  A\as 
65  oz.,  and  the  minimum  weight  34  oz.  The  maximum  weight  of  the  adult  female 
brain,  out  of  191  cases,  was  -Itj  oz.,  and  the  minimum  weight  31  oz.  According  to 
Luschka,  the  average  weight  of  a  man's  brain  is  1424  grammes  (about  45  oz.), 
of  a  woman's  1272  grammes  (about  41  oz.),  and,  according  to  Krause,  1570 
grammes  (about  48|  oz.)  for  the  male,  and  1350  (about  43  oz.)  for  the  female.  It 
appears  that  the  weight  of  the  brain  increases  rapidly  up  to  the  seventh  year,  more 
slowly  to  between  sixteen  and  twenty,  and  still  more  slowly  to  between  thirty  and 
forty,  when  it  reaches  its  maximum.  Beyond  this  period,  as  age  advances  and  the 
mental  faculties  decline,  the  brain  diminishes  slowly  in  weight,  about  an  ounce 
for  each  subsequent  decennial  period.  These  results  apply  alike  to  both  sexes. 

The  size  of  the  brain  was  formerly  said  to  bear  a  general  relation  to  the  intel- 
lectual capacity  of  the  individual.  Cuvier's  brain  weighed  rather  more  than  64  oz., 
that  of  the  late  Dr.  Abercrombie  63  oz.,  and  that  of  Dupuytren  62J  oz.  On  the 
other  hand,  the  brain  of  an  idiot  seldom  weighs  more  than  23  oz.  But  these  facts 
are  by  no  means  conclusive,  and  it  is  well  known  that  these  weights  have  been 
equalled  by  the  brains  of  persons  who  never  displayed  any  remarkable  intellect. 
Dr.  Haldennan  of  Cincinnati  has  recorded  the  case  of  a  mulatto,  aged  forty-five, 
whose  brain  weighed  68|  oz. ;  he  had  been  a  slave,  and  was  never  regarded  as 
particularly  intelligent ;  he  was  illiterate,  but  is  said  to  have  been  reserved,  medi- 
tative, and  economical.  Dr.  Ensor,  district  medical  officer  at  Port  Elizabeth, 
reports  that  the  brain  of  Carey,  the  Irish  informer,  weighed  61  oz.  M.  Xikiforoff 
has  published  an  article  on  the  subject  of  the  weight  of  brains  in  the  Novosti. 
According  to  him.  the  weight  of  the  brain  has  no  influence  whatever  on  the 
mental  faculties.  It  ought  to  be  remembered  that  the  significance  of  the  weight 
of  the  brain  should  depend  upon  the  proportion  it  bears  to  the  dimensions  of  the 
whole  body  and  to  the  age  of  the  individual.  It  is  equally  important  to  know 
what  was  the  cause  of  death,  for  long  illness  or  old  age  exhausts  the  brain.  To 
define  the  real  degree  of  development  of  the  brain  it  is  therefore  necessarv  to 
have  a  knowledge  of  the  condition  of  the  whole  body,  and,  as  this  is  usually 
lacking,  the  mere  record  of  weight  possesses  little  significance. 

The  human  brain  is  heavier  than  that  of  all  the  lower  animals,  excepting  the 
elephant  and  whale.  The  brain  of  the  former  weighs  from  eight  to  ten  pounds ; 
and  that  of  a  whale,  in  a  specimen  seventy-five  feet  long,  weighed  rather  more 
than  five  pounds. 

Cerebral  Localization  and  Topography.  —Within  the  last  few  years  physiological  and 
pathological  research  have  gone  far  to  prove  that  the  surface  of  the  brain  may  be  mapped  out 
into  series  of  definite  areas,  each  one  of  which  is  intimately  connected  with  some  well-defined 
function.  Ami  this  is  especially  true  with  regard  to  the  convolutions  on  either  side  of  the  fis- 
sure of  Rolando,  which  are  believed  by  most  physiologists  of  the  present  day  to  be  concerned  in 
motion,  those  grouped  around  the  fissure  being  associated  with  movements  of  the  extremities 
of  the  opposite  side  of  the  body,  and  those  around  the  lower  end  of  the  fissure  being  related  to 
movements  of  the  mouth  and  tongue. 

This  is  not  the  place,  nor  can  space  be  given,  to  describe  these  localities.  But  the  two 
accompanying  woodcuts  from  Ferrier  (Figs.  471,  472)  have  been  introduced,  and  will  serve  to 
indicate  the  position  of  these  areas  as  far  as  they  have  been  at  present  ascertained. 

The  relation  of  the  principal  fissures  and  convolutions  of  the  cerebrum  to  the  outer  surface 
of  the  scalp  has  been  the  subject  of  much  recent  investigation,  and  many  systems  have  been 
devised  by  which  one  may  localize  these  parts  from  an  examination  of  the  external  surface  of 
the  head. 

These  plans  can  only  be  regarded  as  approximately  correct  for  several  reasons  :  in  the  first 
place,  because  the  relations  of  the  convolutions  and  sulci  to  the  surface  are  found  to  be  very 
variable  in  different  individuals ;  secondly,  because  the  surface  area  of  the  scalp  is  greater  than 
the  surface  area  of  the  brain,  so  that  lines  drawn  on  the  one  cannot  correspond  exactly  to  sulci 
or  convolutions  on  the  other ;  and  thirdly,  because  the  sulci  and  convolutions  in  two  individuals 
are  never  precisely  alike.  Nevertheless,  the  principal  fissures  and  convolutions  can  be  mapped 


790 


THE   NERVOUS  SYSTEM. 


out  with  sufficient  accuracy  for  all  practical  purposes,  so  that  any  particular  convolution  can  be 
generally  exposed  by  removing  with  the  trephine  a  certain  portion  of  the  skull's  area. 

Ihe  various  landmarks  on  the  outside  of  the  skull,  which  can  be  easily  felt,  and  which  serve 


Superior  frontal  fissure. 


End  of  calloso- 
marginal  fissure.^ 


Inferior  frontal 
lobe. 


Parieto-  __  _ 

occipital 

fissure. 


Fissure  of 
Sylvius. 


FIG.  475.— Drawing  to  illustrate  cranio-cerebral  topography. 
Professor  Cunningham. 


(Macalister.)    Taken  from  a  cast  prepared  by 


as  indications  of  the  position  of  the  parts  beneath,  have  been  already  referred  to  (see  page  222), 
and  the  relation  of  the  fissures  and  convolutions  to  these  landmarks  is  as  follows : 

Longitudinal  Fissure. — This  corresponds  to  a  line  drawn  from  the  glabella  at  the  root  of 
the  nose  to  the  external  occipital  protuberance. 

The  Fissure  of  Sylvius. — The  position  of  the  fissure  of  Sylvius  and  its  horizontal  limb  is 
marked  by  a  line  starting  from  a  point  one  inch  and  a  quarter  horizontally  behind  the  external 
angular  process  of  the  frontal  bone  to  a  point  three-quarters  of  an  inch  below  the  most  promi- 
nent point  of  the  parietal  eminence.  The  first  three-quarters  of  an  inch  will  represent  the  main 
fissure,  the  remainder  the  horizontal  limb.  The  bifurcation  of  the  fissure  is,  therefore,  two 
inches  behind  and  about  a  quarter  of  an  inch  above  the  level  of  the  external  angular  process. 
The  ascending  limb  of  the  fissure  passes  ..upward  from  this  point  parallel  to,  and  immediately 
behind,  the  coronal  suture. 

Fissure  of  Rolando. — To  find  the  upper  end  of  the  fissure  of  Rolando,  a  measurement 
should  be  taken  from  the  glabella  to  the  external  occipital  protuberance.  The  position  of  the 
top  of  the  sulcus  will  be,  measuring  from  in  front,  55.6  per  cent,  of  the  whole  distance  from  the 
glabella  to  the  external  occipital  protuberance.  Professor  Thane  adopts  a  somewhat  simpler 
method.  He  divides  the  distance  from  the  glabella  to  the  external  occipital  protuberance  over 
the  top  of  the  head  into  two  equal  parts,  and,  having  thus  defined  the  middle  point  of  the  ver- 
tex, he  takes  half  an  inch  behind  it  as  the  top  of  the  sulcus.  This  is  not  quite  so  accurate  as 
the  former  method,  but  it  is  sufficiently  so  for  all  practical  purposes,  and  on  account  of  its  sim- 
plicity is  very  generally  adopted.  From  this  point  the  fissure  runs  downward  and  forward  for  3$ 
inches,  its  axis  making  an  angle  of  61  with  the  middle  line.  In  order  to  mark  this  groove,  two 
strips  of  metal  may  be  employed — one,  the  shorter,  being  fixed  to  the  middle  of  the  other  at  the 
angle  mentioned.  If  the  longer  strip  is  now  placed  along  the  sagittal  suture  so  that  the  junction  of 
the  two  strips  is  over  the  point  corresponding  to  the  top  of  the  furrow,  the  shorter,  oblique 
strip  will  indicate  the  direction  and  3|  inches  will  mark  the  length  of  the  furrow.  Dr.  Wilson 
has  devised  an  instrument,  called  a  cyrtometer,  which  combines  the  scale  of  measurements  for 


THE   BRAIX  AXD    ITS  MEMBRANES. 


791 


localizing  the  fissure  with  data  for  representing  its  length  and  direction.1  Professor  Thane 
gives  the  lower  end  of  the  furrow  as  "close  to  the  posterior  limb,  and  about  half  an  inch 
behind  the  bifurcation  of  the  fissure  of  Sylvius."  So  that,  according  to  this  anatomist,  a  line 
drawn  from  a  point  half  an  inch  behind  the  mid-point  between  the  glabella  and  external  occipi- 
tal protuberance  to  this  spot  would  mark  out  the  fissure  of  Rolando.  Dr.  Reid  adopts  a  differ- 
ent method  (Fig.  476).  He  first  indicates,  on  the  surface  the  longitudinal  fissure  and  the  hori- 
zontal limb  of  the  fissure  of  Sylvius  (as  above).  He  then^draws  two  perpendicular  lines  from 


. 

FIG.  47f>.— Relations  of  the  principal  fissures  and  convolutions  of  the  cerebrum  to  the  outer  surface  of 
scalp.    (Reid.) 


his  "base-line"  (that  is,  a  line  from  the  lowest  part  of  the  infra-orbital  margin  through  the 
middle  of  the  external  auditory  meatus  to  the  back  of  the  head)  to  the  top  of  the  cranium,  one 
(D  E,  Fig.  476)  from  the  depression  'in  front  of  the  external  auditory  meatus,  and  the. other 
(F  o,  Fig.  476)  from  the  posterior  border  of  the  mastoid  process  at  its  root.  He  has  thus 
described  on  the  surface  of  the  head  a  four-sided  figure  (p  D  G  E,  Fig.  476),  and  a  diagonal  line 
from  the  posterior  superior  angle  to  the  anterior  perpendicular  line  where  it  is  crossed  by  the 
fissure  of  Sylvius  will  represent  the  furrow. 

The  parieto-occipital  fissure  on  the  upper  surface  of  the  cerebrum  runs  outward  at  right 
angles  to  the  great  longitudinal  fissure  for  about  an  inch,  from  a  point  one-fifth  of  an  inch  in 
front)  of  the  lambda  (posterior  fontanelle).  Reid  states  that  if  the  horizontal  limb  of  the  fissure 
of  Sylvius  be  continued  onward  to  the  sagittal  suture,  the  last  inch  of  this  line  will  indicate  the 
position  of  the  suleus. 

The  precentral  suJciis  lies  in  a  line  drawn  vertically  downward  from  the  point  of  junction  of 
the  sagittal  and  coronal  sutures.  It  begins  four-fifths  of  an  inch  in  front  of  the  middle  of  the 
fissure  of  Rolando,  and  extends  nearly,  but  not  quite,  to  the  horizontal  limb  of  the  fissure  of 
Sylvius. 

The  superior  frontal  fissure  runs  backward  from  the  supra-orbital  notch,  parallel  with  the 
line  of  the  longitudinal  fissure  to  two-fifths  of  an  inch  in  front  of  the  line  indicating  the  position 
of  the  fissure  of  Rolando. 

The  inferior  frontal  fissure  follows  the  course  of  the  superior  temporal  ridge  on  the  frontal 
bone. 

The  infra  parietal  fissure  begins  on  a  level  with  the  junction  of  the  middle  and  lower  third 
of  the  fissure  of  Rolando,  on  a  line  carried  across  the  head  from  the  back  of  the  root  of  one 
auricle  to  that  of  the  other.  After  passing  upward  it  curves  backward,  lying  parallel  to  the 
longitudinal  fissure,  midway  between  it  and  the  parietal  eminence ;  it  then  curves  downward  to 
en  1  midway  between  the  posterior  fontanelle  and  the  parietal  eminence. 


1  Lancet,  vol.  i.,  1888,  p.  408. 


792  THE  NERVOUS  SYSTEM. 


THE  CRANIAL  NERVES. 

The  cranial  nerves  arise  from  some  part  of  the  cerebro-spinal  centre,  and 
are  transmitted  through  foramina  in  the  base  of  the  cranium.  They  have  been 
named  numerically,  according  to  the  order  in  which  they  pass  through  the  dura 
mater  lining  the  base  of  the  skull.  Other  names  are  also  given  to  them,  derived 
from  the  parts  to  which  they  are  distributed  or  from  their  functions.  Taken  in 
their  order,  from  before  backward,  they  are  as  follows  : 

1st.  Olfactory.  7th.  Facial  (Portio  dura). 

2d.    Optic.  8th.  Auditory  (Portio  mollis). 

3d.    Motor  oculi.  9th.  Glosso-pharyngeal. 

4th.  Pathetic.  10th.  Pneumogastric  (Par  vagum). 

5th.  Trifacial  (Trigeminus).  llth.  Spinal  accessory. 

6th.  Abducent.  12th.  Hypoglossal. 

All  the  cranial  nerves  are  connected  to  some  part  of  the  surface  of  the  brain. 
This  is  termed  their  superficial  or  apparent  origin.  But  their  fibres  may,  in  all 
cases,  be  traced  deeply  into  the  substance  of  the  brain  to  some  special  centre  of 
gray  matter,  termed  a  nucleus.  This  is  called  their  deep  or  real  origin.  The 
nerves,  after  emerging  from  the  brain  at  their  apparent  origin,  pass  through 
foramina  or  tubular  prolongations  in  the  dura  mater,  leave  the  skull  through 
foramina  in  its  base,  and  pass  to  their  final  distribution. 

First  Nerve  (Fig.  473,  page  783). 

The  First  Cranial  or  Olfactory  Nerves,  the  special  nerves  of  the  sense  of  smell, 
are  about  twenty  in  number.  They  are  given  off  from  the  under  surface  of  the 
olfactory  bulb,  an  oval  mass  of  a  grayish  color,  which  rests  on  the  cribriform 
plate  of  the  ethmoid  bone,  and  forms  the  anterior  expanded  extremity  of  a  slender 
process  of  brain-substance,  named  the  olfactory  tract  (see  page  783).  The  olfactory 
tract,  when  traced  backward,  divides  into  three  slips  or  roots  at  its  base.  The 
middle  root  is  attached  to  the  under  surface  of  the  frontal  lobe,  just  in  front  of 
the  anterior  perforated  space.  The  external  root  passes  outward,  round  the 
anterior  perforated  space,  across  the  fissure  of  Sylvius  to  the  temporo-sphenoidal 
lobe.  The  internal  root  passes  inward,  and  joins  the  lower  end  of  the  gyrus 
fornicatus. 

These  three  roots  unite  and  form  a  flat  band,  narrower  in  the  middle  than 
at  either  extremity,  and  of  a  somewhat  prismoid  form  on  section.  It  is  soft  in 
texture  and  contains  a  considerable  amount  of  gray  matter  in  its  substance.  As  it 
passes  forward  it  is  contained  in  a  deep  sulcus,  the  olfactory  suleus,  between  two 
convolutions,  lying  on  the  under  surface  of  the  frontal  lobe,  on  either  side  of  the 
longitudinal  fissure,  and  is  retained  in  position  by  the  arachnoid  membrane,  which 
covers  it.  On  reaching  the  cribriform  plate  of  the  ethmoid  bone  it  expands  into 
the  olfactory  bulb.  From  the  under  part  of  this  bulb  are  given  off  the  olfactory 
nerves,  which  pass  through  the  cribriform  foramina  and  are  distributed  to  the 
mucous  membrane  of  the  nose.  Each  nerve  is  surrounded  by  a  tubular  prolonga- 
tion from  the  dura  mater  and  pia  mater ;  the  former  being  lost  on  the  periosteum 
lining  the  nose ;  the  latter,  in  the  neurilemma  of  the  nerve.  The  nerves,  as  they 
enter  the  nares,  are  divisible  into  three  groups  :  an  inner  group,  larger  than  those 
on  the  outer  Avail,  spread  out  over  the  upper  third  of  the  septum  ;  a  middle  set, 
confined  to  the  roof  of  the  nose ;  and  an  outer  set,  which  are  distributed  over  the 
superior  and  middle  turbinated  bones  and  the  surface  of  the  ethmoid  in  front 
of  them.  As  the  filaments  descend  they  unite  in  a  plexiform  network,  and  are 
believed  by  most  observers  to  terminate  in  the  cells  of  Schultze. 

The  olfactory  differ  in  structure  from  other  nerves  in  being  composed  exclu- 
sively of  non-medullated  fibres.  They  are  deficient  in  the  white  substance  of 
Schwann,  and  consist  of  axis-cylinders,  with  a  distinct  nucleated  sheath,  in  which 
there  are,  however,  fewer  nuclei  than  in  ordinary  non-medullated  fibres. 


THE  SECOXD    OR    OPTIC  NERVE. 


793 


FIG.  477.- 
tracts. 


-The  left  optic  nerve  and  optic 


Surgical  Anatomy. — In  severe  injuries  to  the  head  the  olfactory  bulb  may  become  sepa- 
rated from  the  olfactory  nerves,  thus  producing  loss  of  the  sense  of  smelling  (anosmia),  and 
with  this  a  considerable  loss  in  the  sense  of  taste,  as  much  of  the  perfection  of  the  sense  of 
taste  is  due  to  the  sapid  substances  being  also  odorous  and  simultaneously  exciting  the  sense  of 
smell. 

Second  Nerve  (Fig.  477). 

The  Second  or  Optic  Nerve,  the  special  nerve  of  the  sense  of  sight,  is  distributed 
exclusively  to  the  eyeball.     The  nerves  of  opposite  sides  are  connected  together 
at  the  commissure,  and  from  the  back  of  the 
commissure  they  may  be  traced  to  the  brain, 
under  the  name  of  the  optic  tracts. 

The  optic  tract;  at  its  connection  with  the 
brain,  is  divided  into  two  bands,  external  and 
internal.  The  external  arises  from  the  ex- 
ternal geniculate  body  and  from  the  under 
part  of  the  pulvinar  of  the  optic  thalamus,  and 
receives  most  of  the  fibres  of  the  brachium  of 
the  superior  Corpus  quadrigeminum.  The  in- 
''•/•nal  arises  from  beneath  the  internal  genic- 
ulate body,  from  which  it  derives  fibres,  and 
joins  with  the  other  band  to  form  the  optic 
tract.  From  this  origin  the  tract  winds  ob- 
liquely across  the  surface  of  the  crusta  in  the 
form  of  a  flattened  band,  destitute  of  neuri- 
lernma  and  attached  to  the  crusta  by  its  an- 
tero-superior  margin.  It  then  assumes  a  cyl- 
indrical form,  and,  as  it  passes  forward,  is 
connected  with  the  tuber  cinereum  and  lam- 
ina cinerea.  It  finally  joins  with  the  tract  of  the  opposite  side  to  form  the  optic 
/•  rmmisture. 

The  commissure  or  chiasma,  somewhat  quadrilateral  in  form,  rests  upon  the 
optic  groove  of  the  sphenoid  bone,  being  bounded,  above,  by  the  lamina  cinerea ; 

behind,  by  the  tuber  cinereum ;  on  either  side,  by  the 
anterior  perforated  space.  Within  the  commissure  the 
optic  nerves  of  the  two  sides  undergo  a  partial  decus- 
sation.  The  fibres  which  form  the  inner  margin  (in- 
'o  optic  nerve  ferior  commissure  of  Gudden)  of  each  tract  are  con- 

y  same  side.     •  .  ,  ,      J     ,  .  ,         „     ,       , 

of  opposite  tinned  across  from  one  to  the  other  side  of  the  brain. 
These  may  be  regarded  as  commissural  fibres  (inter- 
cerebraT)  between  the  internal  geniculate  bodies.  Some 
fibres  are  continued  across  the  anterior  border  of  the 
chiasma,  and  connect  the  optic  nerves  of  the  two  sides,  having  no  relation  with 
the  optic  tracts.1  They  may  be  regarded  as  commissural  fibres  between  the  two 
retime  (inter-retinal  fibres).  The  outer  fibres  of  each  tract  are  continued  into  the 
optic  nerve  of  the  same  side.  The  central  fibres  of  each  tract  are  continued  into 
the  optic  nerve  of  the  opposite  side,  decussating  in  the  commissure  with  similar 
fibres  of  the  opposite  tract.2 

The  optic  nerves  arise  from  the  fore  part  of  the  commissure,  and,  diverging  from 
one  another,  become  rounded  in  form  and  firm  in  texture,  and  are  enclosed  in  a 
sheath  derived  from  the  arachnoid.  As  each  nerve  passes  through  the  correspond- 
ing optic  foramen  it  receives  a  sheath  from  the  dura  mater ;  and  as  it  enters  the 
orbit  this  sheath  subdivides  into  two  layers,  one  of  which  becomes  continuous  with 
the  periosteum  of  the  orbit ;  the  other  forms  the  proper  sheath  of  the  nerve  and 

1  The  presence  of  these  fibres  has  been  doubted  by  some  observers,  but  they  have  been  recently 
asserted  to  exist  by  Stilling. 

2  A  specimen  of  congenital  absence  of  the  optic  commissure  is  to  be  found  in  the  Museum  of  the 
Westminster  Hospital.     (See  also  Henle,  Nervenlehre,  p.  393,  ed.  2.) 


side. 


FIG.  478.— Course  of  the  fibres 
in  the  optic  commissure. 


794  THE  NERVOUS  SYSTEM. 

surrounds  it  as  far  as  the  sclerotic.  The  nerve  passes  through  the  cavity  of  the 
orbit,  pierces  the  sclerotic  and  choroid  coats  at  the  back  part  of  the  eyeball,  a  little 
to  the  nasal  side  of  its  centre,  and  expands  into  the  retina.  Arnold  describes  a 
communication  between  the  optic  nerve  in  the  orbit  and  the  ascending  branches 
of  Meckel's  ganglion.  A  small  artery,  the  arteria  centralis  retince,  perforates  the 
optic  nerve  a  little  behind  the  globe,  and  runs  along  its  interior  in  a  tubular  canal 
of  fibrous  tissue.  It  supplies  the  inner  surface  of  the  retina,  and  is  accompanied 
by  corresponding  veins. 

Surgical  Anatomy. — The  optic  nerve  is  peculiarly  liable  to  become  the  seat  of  neuritis  or 
undergo  atrophy  in  affections  of  the  central  nervous  system,  and,  as  a  rule,  the  pathological 
relationship  between  the  two  affections  is  exceedingly  difficult  to  trace.  There  are,  however, 
certain  points  in  connection  with  the  anatomy  of  this  nerve  which  tend  to  throw  light  upon  the 
frequent  association  of  these  affections  with  intracranial  disease:  (1)  From  its  mode  of 
development  (see  page  123)  and  from  its  structure  the  optic  nerve  must  be  regarded  as  a  prolonga- 
tion of  the  brain-substance,  rather  than  as  an  ordinary  cerebro-spinal  nerve.  (2)  As  it  passes 
from  the  brain  it  receives  sheaths  from  the  three  cerebral  membranes — a  perineural  sheath  from 
the  pia  mater,  an  intermediate  sheath  from  the  arachnoid,  and  an  outer  sheath  from  the  dura 
mater,  which  is  also  connected  with  the  periosteum  as  it  passes  through  the  optic  foramen. 
These  sheaths  are  separated  from  each  other  by  spaces  which  communicate  with  the  subdural  and 
subarachnoid  spaces  respectively.  The  innermost  or  perineural  sheath  sends  a  process  around 
the  arteria  centralis  retinas  into  the  interior  of  the  nerve,  and  enters  intimately  into  the  struc- 
ture of  the  nerve.  Tims  inflammatory  affections  of  the  meninges  or  of  the  brain  may  readily 
extend  themselves  along  these  spaces  or  along  the  interstitial  connective  tissue  in  the  nerve. 

The  course  of  the  fibres  in  the  optic  commissure  has  an  important  pathological  bearing,  and 
has  been  the  subject  of  much  controversy.  Microscopic  examination,  experiments,  and  pathology 
all  seem  to  point  to  the  fact  that  there  is  a  partial  decussation  of  the  fibres,  each  tract  supplying 
the  corresponding  half  of  each  eye,  so  that  the  right  tract  supplies  the  right  half  of  each  eye, 
and  the  left  tract  the  left  half  of  each  eye.  At  the  same  time,  Charcot  believes — and  his  view 
has  met  with  general  acceptation — that  the  fibres  which  do  not  decussate  at  the  optic  commis- 
sure have  already  decussated  in  the  corpora  quadrigemina,  so  that  lesion  of  the  cerebral  centre 
of  one  side  causes  complete  blindness  of  the  opposite  eye,  because  both  sets  of  decussating  fibres 
are  destroyed.  Whereas  should  one  tract — say  the  right — be  destroyed  by  disease,  there  will  be 
blindness  of  the  right  half  of  both  retinae. 

An  antero-posterior  section  through  the  commissure  would  divide  the  decussating  fibres, 
and  would  therefore  produce  blindness  of  the  inner  half  of  each  eye  ;  while  a  section  at  the 
margin  of  the  side  of  the  optic  commissure  would  produce  blindness  of  the  external  half  of  the 
retina  of  the  same  side. 

The  optic  nerve  may  also  be  affected  in  injuries  or  diseases  involving  the  orbit,  in  fractures 
of  the  anterior  fossa  of  the  base  of  the  skull,  in  tumors  of  the  orbit  itself,  or  those  invading  this 
cavity  from  neighboring  parts. 

Third  Nerve  (Figs.  384,  479,  480,  481,  486). 

The  Third  or  Motor  Oculi  Nerve  supplies  all  the  muscles  of  the  orbit,  except 
the  Superior  oblique  and  External  rectus ;  it  also  sends  motor  filaments  to  the  iris 
and  the  ciliary  muscle.  It  is  a  rather  large  nerve,  of  rounded  form  and  firm 
texture.  Its  apparent  origin  is  from  the  inner  surface  of  the  crus  cerebri, 
immediately  in  front  of  the  pons  Varolii. 

The  deep  origin  may  be  traced  through  the  locus  niger  and  tegmentum  of  the 
crus  to  a  nucleus  situated  on  either  side  o£  the  median  line  beneath  the  floor  of 
the  aqueduct  of  Sylvius.  On  emerging  from  the  brain  the  nerve  is  invested  with 
a  sheath  of  pia  mater,  and  enclosed  in  a  prolongation  from  the  arachnoid.  It 
then  pierces  the  dura  mater  in  front  of  and  external  to  the  posterior  clinoid  pro- 
cess, passing  between  the  two  processes  from  the  free  and  attached  borders  of  the 
tentorium,  which  are  prolonged  forward  to  be  connected  with  the  anterior  and 
posterior  clinoid  processes  of  the  sphenoid  bone.  It  passes  along  the  outer  wall 
of  the  cavernous  sinus,  above  the  other  orbital  nerves,  receiving  in  its  course  one 
or  two  filaments  from  the  cavernous  plexus  of  the  sympathetic  and  from  the  oph- 
thalmic division  of  the  fifth  nerve.  It  then  divides  into  two  branches,  which 
enter  the  orbit  through  the  sphenoidal  fissure  between  the  two  heads  of  the 
External  rectus  muscle.  On  passing  through  the  fissure  the  nerve  is  placed  below 
the  fourth  and  the  frontal  and  lachrymal  branches  of  the  ophthalmic  nerve,  and 
has  passing  between  its  two  divisions  the  nasal  nerve. 


THE    THIRD    OR    MOTOR    OCULI  NERVE. 


795 


The  superior  division,  the  smaller,  passes  inward  over  the  optic  nerve,  an;l 
supplies  the  Superior  rectus  and  Levator  palpebrae.  It  occasionally  communi- 
cates with  the  ganglionic  branch  of  the  nasal  nerve. 

The  //(/'<•/•/'//•  din'xitin,  the  Jarger,  divides  into  three  branches.  One  passes 
beneath  the  optic  nerve  to  the  Internal  rectus ;  another,  to  the  Inferior  rectus ; 
and  the  third,  the  largest  of  the  three,  passes  forward  between  the  Inferior  and 


Infratrochlear 
nerve. 


Motor  root. 
Sensory  root. 


Recurrent  filament 
to  dura  mater. 


FIG.  479. — Nerves  of  the  orbit.    Seen  from  sibove. 

External  recti  to  the  Inferior  oblique.  From  this  latter  a  short,  thick  branch  is 
given  off  to  the  lower  part  of  the  lenticular  ganglion,  which  forms  its  inferior 
root.  It  also  gives  off  one  or  two  filaments  to  the  Inferior  rectus.  All  these 
branches  enter  the  muscles  on  their  ocular  surface,  except  that  to  the  Inferior 
oblique,  which  enters  its  posterior  border. 

Surgical  Anatomy. — Paralysis  of  the  third  nerve  may  be  the  result  of  many  causes :  as 
cerebral  disease;  conditions  causing  pressure  on  the  cavernous  sinus;  periostitis  of  the  bones 
entering  into  the  formation  of  the  sphenoidal  fissure.  It  results,  when  complete,  in  (1)  ptosis, 
or  drooping  of  the  upper  eyelid,  in  consequence  of  the  Levator  palpebrae  being  paralyzed  ;  (2) 
external  strabismus,  on  account  of  the  unopposed  action  of  the  External  rectus  muscle,  which 
is  not  supplied  by  the  third  nerve,  and  is  not  therefore  paralyzed ;  (3)  dilatation  of  the  pupil, 
because  the  sphincter  fibres  of  the  iris  are  paralyzed;  (4)  loss  of  power  of  accommodation,  as 
the  sphincter  pupillae,  the  ciliary  muscle,  and  the  Internal  rectus  are  paralyzed ;  (5)  slight 
prominence  of  the  eyeball,  from  the  compressing  action  of  the  Superior  oblique,  which  is  not 
paralyzed.  Occasionally  paralysis  may  affect  only  a  part  of  the  nerve ;  that  is  to  say,  there  may 
be,  for  example,  a  dilated  and  fixed  pupil,  with  ptosis,  but  no  other  signs.  Irritation  of  the 
nerve  causes  spasm  of  one  or  other  of  the  muscles  supplied  by  it ;  thus,  there  may  be  internal 
strabismus  from  .spasm  of  the  Internal  rectus ;  accommodation  for  near  objects  only  from  spasm 
of  the  ciliary  muscle,  or  myosis,  contraction  or  the  pupil,  from  irritation  of  the  sphincter  of  (he 
pupil. 


796 


THE    NERVOUS  SYSTEM. 
Fourth  Nerve  (Figs.  384,  479,  486). 


The  Fourth  or  Trochlear  Nerve  (pathetic),  the  smallest  of  the  cranial  nerves, 
supplies  the  Superior  oblique  muscle.  Its  apparent  origin  is  behind  the  corpora 
quadrigemina,  from  the  valve  of  Vieussens,  in  the  upper  surface  of  which  the 
two  nerves  decussate.  Its  deep  origin  may  be  traced  to  the  nucleus  in  the  floor 
of  the  aqueduct  of  Sylvius  immediately  below  that  of  the  third  nerve,  with  which 
it  is  continuous.  After  emergence  from  the  surface  of  the  valve  of  Vieussens, 


FIG.  480.— Plan  of  the  motor  oculi  nerve.    (After  Flower.) 

the  nerve  winds  across  the  superior  peduncle  of  the  cerebellum  and  round  the 
crusta  of  the  mid-brain,  immediately  above  the  pons  Varolii,  pierces  the  dura 
mater  in  the  free  border  of  the  tentorium  cerebelli  just  behind,  arid  external 
to,  the  posterior  clinoid  process,  and  passes  forward  in  the  outer  wall  of  the  cav- 
ernous sinus,  between  the  third  nerve  and  the  ophthalmic  division  of  the  fifth. 
It  then  crosses  the  third  nerve,  and  enters  the  orbit  through  the  sphenoidal  fissure. 
It  now  lies  at  the  inner  extremity  of  the  fissure  internal  to  the  frontal  nerve.  In 
the  orbit  it  passes  inward  above  the  origin  of  the  Levator  palpebrse,  and  finally 
enters  the  orbital  surface  of  the  Superior  oblique  muscle. 

In  the  outer  wall  of  the  cavernous  sinus  this  nerve  receives  some  filaments 
from  the  ophthalmic  division  of  the  fifth  as  well  as  from  the  cavernous  plexus  of 
the  sympathetic,  and  gives  off  a  recurrent  branch,  which  passes  backward  between 
the  layers  of  the  tentorium,  dividing  into  two  or  three  filaments  which  may  be 
traced  as  far  back  as  the  Avail  of  the  lateral  sinus.  In  the  sphenoidal  fissure 
it  occasionally  gives  off  a  branch  to  assist  in  the  formation  of  the  lachrymal 
nerve. 

Surgical  Anatomy. — The  fourth  nerve  when  paralyzed  causes  loss  of  function  in  the 
Superior  oblique,  so  that  the  patient  is  unable  to  turn  his  eye  downward  and  outward.  Should 
the  patient  attempt  to  do  this,  the  eye  on  the  affected  side  is  twisted  inward,  producing  diplopia 
or  double  vision.  Accordingly,  it  is  said  that  the  first  symptom  of  this  disease  which  presents 
itself  is  giddiness  when  going  down  hill  or  in  descending  stairs,  owing  to  the  double  vision 
induced  by  the  patient  looking  at  his  steps  while  descending. 

Fifth  Nerve. 

The  Fifth  or  Trifacial  Nerve  (trigeminus)  is  the  largest  cranial  nerve.  It 
resembles  a  spinal  nerve  (1)  in  arising  by  two  roots ;  (2)  in  having  a  ganglion 
developed  on  its  posterior  root;  and  (3)  in  its  function,  since  it  is  a  compound 
nerve.  It  is  the  great  sensory  nerve  of  the  head  and  face  and  the  motor  nerve 
of  the  muscles  of  mastication.  Its  upper  two  divisions  are  entirely  sensory ;  the 


THE   FIFTH   OR    TRIFACIAL    NERVE.  797 

third  division  is  partly  sensory  and  partly  motor.  It  arises  by  two  roots:  of  these 
the  anterior  is  the  smaller,  and  is  the  motor  root ;  the  posterior,  the  larger  and 
sensory.  Its  superficial  origin  is  from  the  side  of  the  pons  Varolii,  nearer  to  the 
upper  than  the  lower  border.  The  smaller  root  consists  of  three  or  four  bundles ; 
the  larger  root  consists  of  numerous  bundles  of  fibres,  varying  in  number  from 
seventy  to  a  hundred.  The  two  roots  are  separated  from  one  another  by  a  few  of 
the  transverse  fibres  of  the  pons.  The  deep  origin  of  the  larger  or  sensory  root 
is  from  a  nucleus  in  the  pons,  just  below  the  floor  and  just  internal  to  the  mar- 
gin of  the  upper  half  of  the  fourth  ventricle.  The  deep  origin  of  the  smaller  or 
motor  root  is  from  a  nucleus  internal  to  the  sensory  root,  and  just  external  to  the 
fasciculus  teres  on  the  upper  half  of  the  floor  of  the  fourth  ventricle.  The  two 
roots  of  the  nerve  pass  forward  through  an  oval  opening  (cavum  Meckelit)  in  the 
dura  mater,  on  the  superior  border  of  the  petrous  portion  of  the  temporal  bone, 
above  the  internal  auditory  meatus :  they  then  run  between  the  bone  and  the 
dura  mater  to  the  apex  of  the  petrous  portion  of  the  temporal  bone,  where  the 
fibres  of  the  sensory  root  form  a  large,  semilunar  ganglion  (G-asserian},  while  the 
motor  root  passes  beneath  the  ganglion  without  having  any  connection  with  it, 
and  joins  outside  the  cranium  with  one  of  the  trunks  derived  from  it. 

The  Gasserian  or  semilunar  ganglion  *  is  lodged  in  a  depression  near  the  apex 
of  the  petrous  portion  of  the  temporal  bone.  It  is  of  somewhat  crescentic  form, 
with  its  convexity  turned  forward.  Its  upper  surface  is  intimately  adherent  to 
the  dura  mater.  Besides  the  small  or  motor  root,  the  large  superficial  petrosal 
nerve  lies  underneath  the  ganglion. 

Branches  of  Communication. — This  ganglion  receives,  on  its  inner  side,  fila- 
ments from  the  carotid  plexus  of  the  sympathetic.  Branches  of  Distribution. — It 
gives  off  minute  branches  to  the  tentorium  cerebelli  and  the  dura  mater  in  the 
middle  fossa  of  me  cranium.  From  its  anterior  border,  which  is  directed  forward 
and  outward,  three  large  branches  proceed — the  ophthalmic,  superior  maxillary, 
and  inferior  maxillary.  The  ophthalmic  and  superior  maxillary  consist  exclu- 
sively of  fibres  derived  from  the  larger  root  and  ganglion,  and  are  solely  nerves 
of  common  sensation.  The  third  division,  or  inferior  maxillary,  is  joined  outside 
the  cranium  by  the  motor  root.  This,  therefore,  strictly  speaking,  is  the  only 
portion  of  the  fifth  nerve  which  can  be  said  to  resemble  a  spinal  nerve. 

Ophthalmic  Nerve  (Figs.  384,  479,  481,  482,  486). 

The  Ophthalmic,  or  first  division  of  the  fifth,  is  a  sensory  nerve.  It  supplies 
the  eyeball,  the  lachrymal  gland,  the  mucous  lining  of  the  eye  and  nasal  fossae, 
and  the  integument  of  the  eyebrow,  forehead,  and  nose.  It  is  the  smallest  of 
the  three  divisions  of  the  fifth,  arising  from  the  upper  part  of  the  Gasserian 
ganglion.  It  is  a  short,  flattened  band,  about  an  -inch  in  length,  which  passes 
forward  along  the  outer  wall  of  the  cavernous  sinus,  below  the  other  nerves,  and 
just  before  entering  the  orbit,  through  the  sphenoidal  fissure,  divides  into  three 
branches — lachrymal,  frontal,  and  nasal. 

Branches  of  Communication. — The  ophthalmic  nerve  is  joined  by  filaments 
from  the  cavernous  plexus  of  the  sympathetic,  communicates  with  the  third  and 
sixth  nerves,  and  is  not  unfrequently  joined  with  the  fourth. 

Branches  of  Distribution. — It  gives  off  recurrent  filaments  (nervi  tentorii) 
which  pass  between  the  layers  of  the  tentorium  along  with  a  branch  from  the 
fourth  nerve,  and  then  divides  into 

Lachrymal.  Frontal.  Nasal. 

1  A  Viennese  anatomist,  Raimund  Balthasar  Hirsch  (1765),  was  the  first  who  recognized  the 
ganglionic  nature  of  the  swelling  on  the  sensory  root  of  the  fifth  nerve,  and  called  it,  in  honor  of  his 
otherwise  unknown  teacher,  Jon.  Laur.  Gasser,  the  "  Ganglion  Gasseri."  Julius  Casserius,  whose 
name  is  given  to  the  musculo-cutaneous  nerve  of  the  arm,  was  professor  at  Padua,  1545-1605.  (See 
Hyrtl,  Lehrbuch  der  Anatomie,  p.  895  and  p.  55.) 


798 


THE  NERVOUS  SYSTEM. 


The  Lachrymal  is  the  smallest  of  the  three  branches  of  the  ophthalmic.  Not 
(infrequently  it  arises  by  two  filaments,  one  from  the  ophthalmic,  the  other  from 
the  fourth.  It  passes  forward  in  a  separate  tube  of  dura  mater  and  enters  the 


Internal  carotid  artery 
and  carotid  plexus, 


Sensory 
root. 

Motor  root: 


FIG.  481.— Nerves  of  the  orbit  and  ophthalmic  ganglion.    Side  view. 

orbit  through  the  narrowest  part  of  the  sphenoidal  fissure.  In  the  orbit  it  runs 
along  the  upper  border  of  the  External  rectus  muscle  with  the  lachrymal  artery, 
and  sends  off  a  recurrent  branch  which  joins  the  orbital  branch  of  the  superior 
maxillary  nerve,  and  occasionally  takes  the  place  of  the  temporal  branch  of  this 
nerve,  which  is  then  absent.  Within  the  lachrymal  gland  it  gives  off  several 
filaments,  which  supply  the  gland  and  the  conjunctiva.  Finally,  it  pierces  the 
tarsal  ligaments,  and  terminates  in  the  integument  of  the  upper  eyelid,  joining 
with  filaments  of  the  facial  nerve. 

The  Frontal  is  the  largest  division  of  the  ophthalmic,  and  may  be  regarded, 
both  from  its  size  and  direction,  as  the  continuation  of  the  nerve.  It  enters  the 
orbit  above  the  muscles  through  the  highest  and  broadest  part  of  the  sphenoidal 
fissure,  and  runs  forward  along  the  middle  line,  between  the  Levator  palpebne 
and  the  periosteum.  Midway  between  the  apex  and  base  of  the  orbit  it  divides 
into  two  branches,  supratrochlear  and  supra-orbital. 

The  supratrochlear  branch,  the  smaller  of  the  two,  passes  inward  above  the 
pulley  of  the  Superior  oblique  muscle,  and  gives  off  a  descending  filament,  which 
joins  with  the  infratrochlear  branch  of  the  nasal  nerve.  It  then  escapes  from  the 
orbit  between  the  pulley  of  the  Superior  oblique  and  the  supra-orbital  foramen, 
curves  up  on  to  the  forehead  close  to  the  bone,  and  ascends  beneath  the  Corrugator 
supercilii  and  Occipito-frontalis  muscles,  and  supplies  the  integument  of  the  lower 
part  of  the  forehead  on  either  side  of  the  middle  line. 

The  supra-orbital  branch  passes  forward  through  the  supra-orbital  foramen, 
and  gives  off,  in  this  situation,  palpebral  filaments  to  the  upper  eyelid.  It  then 
ascends  upon  the  forehead,  and  terminates  in  cutaneous  and  pericranial  branches. 
The  cutaneous  branches,  two  in  number,  an  inner  and  an  outer,  supply  the 
integument  of  the  cranium  as  far  back  as  the  occiput.  They  are  at  first  situated 
beneath  the  Occipito-frontalis,  the  inner  branch  perforating  the  frontal  portion  of 
the  muscle,  the  outer  branch  its  tendinous  aponeurosis.  The  pericrttm'nl  branches 
are  distributed  to  the  pericranium  over  the  frontal  and  parietal  bones. 

The  Nasal  nerve  is  intermediate  in  size  between  the  frontal  and  lachrymal,  and 
more  deeply  placed  than  the  other  branches  of  the  ophthalmic.  It  enters  the  orbit 


BRANCHES    OF    THE  FIFTH  XEItVE.  799 

between  the  two  beads  of  tbe  External  rectus,  and  between  tbe  two  divisions  of 
the  third  nerve,  and  passes  obliquely  inward  across  the  optic  nerve,  beneath  the 
Superior  oblique  and  Superior  rectus  muscles,  to  the  inner  wall  of  the  orbit, 
where  it  enters  the  anterior  ethmoidal  foramen.  It  then  enters  the  cavity  of  the 
cranium,  traverses  a  shallow  groove  on  the  cribriform  plate  of  the  ethmoid  bone, 
and  passes  down,  through  the  slit  by  the  side  of  the  crista  galli,  into  the  nose, 
where  it  gives  off  two  branches,  an  internal  and  an  external.  The  internal 
branch  supplies  the  mucous  membrane  near  the  fore  part  of  the  septum  of  the 
nose.  The  external  branch  supplies  a  few  filaments  to  the  mucous  membrane 
covering  the  fore  part  of  the  outer  wall  of  the  nares  as  far  as  the  inferior  spongy 
bone.  The  nerve  then  descends  in  a  groove  on  the  back  of  the  nasal  bone  and 
leaves  the  cavity  of  the  nose,  between  the  lower  border  of  the  nasal  bone  and  the 
upper  lateral  cartilage  of  the  nose.  and.  passing  down  beneath  the  Compressor 
nasi,  supplies  the  integument  of  the  ala  and  the  tip  of  the  nose,  joining  with  the 
facial  nerve. 

The  branches  of  the  nasal  nerve  are  the  ganglionic,  ciliary,  and  infratroch- 
lear. 

The  gangl.ionic  is  a  slender  branch,  about  half  an  inch  in  length,  which  usually 
arises  from  the  nasal,  between  the  two  heads  of  the  External  rectus.  It  passes 
forward  on  the  outer  side  of  the  optic  nerve,  and  enters  the  superior  and  posterior 
angle  of  the  ciliary  ganglion,  forming  its  superior  or  long  root.  It  is  sometimes 
joined  by  a  filament  from  the  cavernous  plexus  of  the  sympathetic  or  from  the 
superior  division  of  the  third  nerve. 

The  long  ciliary  nerves^  two  or  three  in  number,  are  given  off  from  the  nasal 
as  it  crosses  the  optic  nerve.  They  join  the  short  ciliary  nerves  from  the  ciliary 
ganglion,  pierce  the  posterior  part  of  the  sclerotic,  and,  running  forward  between 
it  and  the  choroid,  are  distributed  to  the  ciliary  muscles,  iris,  and  cornea. 

The  mfratrocUear  branch  is  given  off  just  before  the  nasal  nerve  passes 
through  the  anterior  ethmoidal  foramen.  It  runs  forward  along  the  upper  border 
of  the  Internal  rectus.  and  is  joined,  beneath  the  pulley  of  the  Superior  oblique, 
by  a  filament  from  the  supratrochlear  nerve.  It  then  passes  to  the  inner  angle 
of  the  eye.  and  supplies  the  integument  of  the  eyelids  and  side  of  the  nose,  the 
conjunctiva,  lachrymal  sac.  and  caruncula  lachrymalis. 

Ophthalmic  Ganglion  (Figs.  481,  482). 

Connected  with  the  three  divisions  of  the  fifth  nerve  are  four  small  ganglia. 
With  the  first  division  is  connected  the  ophthalmic  ganglion  ;  with  the  second 
division,  the  tphcHO-palatine  or  MeckeVs  ganglion  :  and  with  the  third,  the  otic 
and  submajcillary  ganglia.  All  the  four  receive  sensory  filaments  from  the  fifth, 
and  motor  and  sympathetic  filaments  from  various  sources ;  these  filaments  are 
called  the  roots  of  the  ganglia. 

The  Ophthalmic,  Lenticular,  or  Ciliary  Ganglion  is  a  small,  quadrangular, 
flattened  ganglion,  of  a  reddish-gray  color,  and  about  the  size  of  a  pin's  head, 
situated  at  the  back  part  of  the  orbit  between  the  optic  nerve  and  the  External 
rectus  muscle,  lying  generally  on  the  outer  side  of  the  ophthalmic  artery.  It  is 
enclosed  in  a  quantity  of  loose  fat.  which  makes  its  dissection  somewhat  difficult. 

Its  branches  of  communication,  or  roots,  are  three,  all  of  which  enter  its 
posterior  border.  One,  the  long  or  sensory  root,  is  derived  from  the  nasal  branch 
of  the  ophthalmic  and  joins  its  superior  angle.  The  second,  the  short  or  motor 
root,  is  a  short,  thick  nerve,  occasionally  divided  into  two  parts,  which  is  derived 
from  the  branch  of  the  third  nerve  to  the  Inferior  oblique  muscle,  and  is  connected 
with  the  inferior  angle  of  the  ganglion.  The  third,  the  sympathetic  root,  is  a 
slender  filament  from  the  cavernous  plexus  of  the  sympathetic.  This  is  frequently 
blended  with  the  long  root,  though  it  sometimes  passes  to  the  ganglion  separately. 
According  to  Tiedemann.  this  ganglion  receives  a  filament  of  communication  from 
the  spheno-palatine  ganglion. 


800 


THE  NERVOUS  SYSTEM. 


FIG.  482.— Plan  of  the  fifth  cranial  nerve.    (After  Flower.) 


Its  branches  of  distribution  are  the  short  ciliary  nerves.     These  are  delicate 
filaments,  from  six  to  ten  in  number,  which  arise  from  the  fore  part  of  the  ganglion 


BRANCHES    OF    THE   FIFTH  NERVE.  801 

in  two  bundles,  connected  with  its  superior  and  inferior  angles ;  the  lowrer  bundle 
is  the  larger.  They  run  forward  with  the  ciliary  arteries  in  a  wavy  course,  one 
set  above  and  the  other  below  the  optic  nerve,  and  are  joined  by  the  long  ciliary 
nerves  from  the  nasal.  They  pierce  the  sclerotic  at  the  back  part  of  the  globe,  pass 
forward  in  delicate  grooves  on  its  inner  surface,  and  are  distributed  to  the  ciliary 
muscle,  iris,  and  cornea.  Tiedemann  has  described  one  small  branch  as  penetrating 
the  optic  nerve  with  the  arteria  centralis  retinae. 

• 

Superior  Maxillary  Nerve  (Fig.  483). 

The  Superior  Maxillary,  or  second  division  of  the  fifth,  is  a  sensory  nerve.  It 
is  intermediate,  both  in  position  and  size,  between  the  ophthalmic  and  inferior 
maxillary.  It  commences  at  the  middle  of  the  Gasserian  ganglion  as  a  flattened 
plexiform  band,  and  passes  forward  through  the  foramen  rotundum,  where  it 
becomes  more  cylindrical  in  form  and  firmer  in  texture.  It  then  crosses  the 
spheno-maxillary  fossa,  enters  the  orbit  through  the  spheno-maxillary  fissure, 
traverses  the  infra-orbital  canal  in  the  floor  of  the  orbit,  and  appears  upon  the  face 
at  the  infra-orbital  foramen.1  At  its  termination  the  nerve  lies  beneath  the 
Levator  labii  superioris  muscle,  and  divides  into  a  leash  of  branches,  which  spread 
out  upon  the  side  of  the  nose,  the  lower  eyelid,  and  upper  lip,  joining  with  filaments 
of  the  facial  nerve. 

Branches  of  Distribution. — The  branches  of  this  nerve  may  be  divided  into  four 
groups  :  1.  Those  given  off  in  the  cranium.  2.  Those  given  off  in  the  spheno- 
maxillary  fossa.  3.  Those  in  the  infra-orbital  canal.  4.  Those  on  the  face. 

In  the  cranium     .    .    .         Meningeal. 

(  Orbital  or  temporo-malar. 
Spheno-maxillary  fossa  <    Spheno-palatine. 

(^  Posterior  superior  dental. 

T  f        ,  .    ,  f    Middle  superior  dental. 

Infra-orbital  canal  <     »  ,  , 

(   Anterior  superior  dental. 

(  Palpebral. 

On  the  face       .       .        <    Nasal. 

(  Labial. 

The  meningeal  branch  is  given  off  directly  after  its  origin  from  the  Gasserian 
ganglion,  and  supplies  the  dura  mater,  communicating  with  a  meningeal  branch 
from  the  inferior  maxillary  nerve. 

The  orbital  or  temporo-malar  branch  arises  in  the  spheno-maxillary  fossa, 
enters  the  orbit  by  the  spheno-maxillary  fissure,  and  divides  at  the  back  of  that 
cavity  into  two  branches,  temporal  and  malar. 

The  temporal  branch  runs  in  a  groove  along  the  outer  wall  of  the  orbit  (in  the 
malar  bone),  receives  a  branch  of  communication  from  the  lachrymal,  and, 
passing  through  a  foramen  in  the  malar  bone,  enters  the  temporal  fossa.  It 
ascends  between  the  bone  and  substance  of  the  Temporal  muscle,  pierces  this 
muscle  and  the  temporal  fascia  about  an  inch  above  the  zygoma,  and  is  distributed 
to  the  integument  covering  the  temple  and  side  of  the  forehead,  communicating 
with  the  facial  and  auriculo-temporal  branch  of  the  inferior  maxillary  nerve.  As 
it  pierces  the  temporal  fascia  it  gives  off  a  slender  twig,  which  runs  between  the 
two  layers  of  the  fascia  to  the  outer  angle  of  the  orbit. 

The  malar  Branch  passes  along  the  external  inferior  angle  of  the  orbit,  emerges 
upon  the  face  through  a  foramen  in  the  malar  bone,  and,  perforating  the  Orbicu- 
laris  palpebrarum  muscle,  supplies  the  skin  on  the  prominence  of  the  cheek,  and 
is  named  subcutaneus  malce.  It  joins  with  the  facial  and  the  palpebral  branches 
of  the  superior  maxillary. 

The  spheno-palatine  branches,  two  in  number,  descend  to  the  spheno-palatine 
ganglion. 

1  After  it  enters  the  infra-orbital  canal,  the  nerve  is  frequently  called  the  infra-orbitui. 
51 


802 


THE   NERVOUS  SYSTEM. 


The  posterior  superior  dental  branches  arise  from  the  trunk  of  the  nerve  just 
as  it  is  about  to  enter  the  infra-orbital  canal ;  they  are  generally  two  in  number. 


Sensory  root. 
Motor  root. 


Auriculo-temporal\ 
nerve. 


FIG.  483.— Distribution  of  the  second  and  third  divisions  of  the  fifth  nerve  and  submaxillary  ganglion. 

but  sometimes  arise  by  a  single  trunk,  and  immediately  divide  and  pass  downward 
on  the  tuberosity  of  the  superior  maxillary  bone.  They  give  off  several  twigs  to 
the  gums  and  neighboring  parts  of  the  mucous  membrane  of  the  cheek  (superior 
gingival  branches).  They  then  enter  the  posterior  dental  canals  on  the  zygomatic 
surface  of  the  superior  maxillary  bone,  and,  passing  from  behind  forward  in  the 
substance  of  the  bone,  communicate  with  the  middle  dental  nerve,  and  give  off' 
branches  to  the  lining  membrane  of  the  antrum  and  three  twigs  to  each  of  the 
molar  teeth.  These  twigs  enter  the  foramina  at  the  apices  of  the  fangs  and 
supply  the  pulp. 

The  middle  superior  dental  branch  is  given  off  from  the  superior  maxillary  nerve 
in  the  back  part  of  the  infra-orbital  canal,  and  runs  downward  and  forward  in  a 
special  canal  in  the  outer  wall  of  the  antrum  to  supply  the  two  bicuspid  teeth.  It 
communicates  with  the  posterior  and  anterior  dental  branches.  At  its  point  of 
communication  with  the  posterior  branch  is  a  slight  thickening  Avhich  has  received 
the  name  of  the  ganglion  of  Valentin  ;  and  at  its  point  of  communication  with  the 
anterior  branch  is  a  second  enlargement,  which  is  called  the  ganglion  of  Bochdalek. 
Neither  of  these  is  probably  a  true  ganglion. 

The  anterior  superior  dental  branch,  of  large  size,  is  given  off  from  the  supe- 
rior maxillary  nerve  just  before  its  exit  from  the  infra-orbital  foramen  ;  it  enters  a 
special  canal  in  the  anterior  wall  of  the  antrum,  and,  coursing  from  before  back- 
ward, divides  into  a  series  of  branches  which  supply  the  incisor  and  canine  teeth. 
It  communicates  with  the  middle  dental  branch,  and  gives  off  a  nasal  branch,  which 
passes  through  a  minute  canal  into  the  nasal  fossa,  and  supplies  the  mucous  mem- 


BRANCHES    OF    THE    FIFTH   XERVE. 


803 


lirane  of  the  fore  part  of  the  inferior  meatus  and  the  floor  of  this  cavity,  communi- 
cating with  the  naso-palatine  nerve  from  Meckel's  ganglion. 


Termination  of 

naso-palatine 

nerre. 


FIG.  484. — The  spheno-palatine  ganglion  and  its  branches. 

The  palpebral  branches  pass  upward  beneath  the  Orbicularis  palpebrarum. 
They  supply  the  integument  and  conjunctiva  of  the  lower  eyelid  with  sensation, 
joining  at  the  outer  angle  of  the  orbit  with  the  facial  nerve  and  malar  branch  of 
the  orbital. 

The  nasal  branches  pass  inward ;  they  supply  the  integument  of  the  side  of 
the  nose  and  join  with  the  nasal  branch  of  the  ophthalmic. 

The  labial  branches,  the  largest  and  most  numerous,  descend  beneath  the 
Levator  labii  superioris,  and  are  distributed  to  the  integument  of  the  upper  lip, 
the  mucous  membrane  of  the  mouth,  and  labial  glands. 

All  these  branches  are  joined,  immediately  beneath  the  orbit,  by  filaments  from 
the  facial  nerve,  forming  an  intricate  plexus,  the  infra-orbital. 

Spheno-palatine  Ganglion  (Fig.  484). 

The  spheno-palatine  ganglion  (JleckeVs),  the  largest  of  the  cranial  ganglia,  is 
deeply  placed  in  the  spheno-maxillary  fossa,  close  to  the  spheno-palatine  foramen. 
It  is  triangular  or  heart-shaped,  of  a  reddish-gray  color,  and  is  situated  just  below 
the  superior  maxillary  nerve  as  it  crosses  the  f<> 

Its  Branches  of  Communication. — Like  the  other  ganglia  of  the  fifth  nerve,  it 
possesses  a  motor,  a  sensory,  and  a  sympathetic  root.  Its  sensory  root  is  derived 
from  the  superior  maxillary  nerve  through  its  two  spheno-palatine  branches.  These 
branches  of  the  nerve,  given  off  in  the  spheno-maxillary  fossa,  descend  to  the 
ganglion.  Their  fibres,  for  the  most  part,  pass  in  front  of  the  ganglion,  as  they 
proceed  to  their  destination,  in  the  palate  and  nasal  fossa,  and  are  not  incorporated 
in  the  ganglionic  mass ;  some  few  of  the  fibres,  however,  enter  the  ganglion, 
constituting  its  sensory  root.  Its  motor  root  is  derived  from  the  facial  nerve 
through  the  large  superficial  petrosal  nerve,  and  its  sympathetic  root  from  the 
carotid  plexus,  through  the  large  deep  petrosal  nerve.  These  two  nerves  join  together 
to  form  a  single  nerve,  the  Vidian.  before  their  entrance  into  the  ganglion. 


804  THE  NERVOUS   SYSTEM. 

The  large  superficial  petrosal  branch  (nervus  petrosus  superficialis  major]  is 
given  off  from  the  intumescentia  ganglioformis  in  the  aqueductus  Fallopii;  it 
passes  through  the  hiatus  Fallopii ;  enters  the  cranial  cavity,  and  runs  forward 
contained  in  a  groove  on  the  anterior  surface  of  the  petrous  portion  of  the 
temporal  bone,  lying  beneath  the  dura  mater  and  the  Gasserian  ganglion.  It 
then  enters  the  fibrous  substance  which  fills  in  the  foramen  lacerum  medium  basis 
cranii,  and,  joining  with  the  large  deep  petrosal  branch,  forms  the  Vidian  nerve. 

The  large  deep  petrosal  branch  (nervus  petrosus  profundus)  is  given  off  from 
the  carotid  plexus,  and  runs  through  the  carotid  canal  on  the  outer  side  of  the 
internal  carotid  artery.  It  then  enters  the  fibrous  substance  which  fills  in  the 
foramen  lacerum  medium,  and  joins  with  the  large  superficial  petrosal  nerve  to 
form  the  Vidian. 

The  Vidian  nerve,  thus  formed,  passes  forward  through  the  Vidian  canal 
with  the  artery  of  the  same  name,  receives  the  sphenoidal  filament  from  the  otic 
ganglion,  and,  entering  the  spheno-maxillary  fossa,  joins  the  posterior  angle  of 
Meckel's  ganglion. 

Its  Branches  of  Distribution. — These  are  divisible  into  four  groups  :  ascending, 
which  pass  to  the  orbit ;  descending,  to  the  palate ;  internal,  to  the  nose ;  and 
posterior  branches,  to  the  pharynx  and  nasal  fossae. 

The  ascending  branches  are  two  or  three  delicate  filaments  which  enter  the 
orbit  by  the  spheno-maxillary  fissure  and  supply  the  periosteum.  Arnold  describes 
and  delineates  these  branches  as  ascending  to  the  optic  nerve.  Bock  describes  a 
branch  as  going  to  the  cavernous  sinus  to  communicate  with  the  sixth  nerve,  and 
Tiedemann,  a  communicating  branch  to  the  ophthalmic  ganglion. 

The  descending  or  palatine  branches  are  distributed  to  the  roof  of  the  mouth, 
the  soft  palate,  tonsil,  and  lining  membrane  of  the  nose.  They  are  almost  a  direct 
continuation  of  the  spheno-palatine  branches  of  the  superior  maxillary  nerve,  and 
are  three  in  number — anterior,  middle,  and  posterior. 

The  anterior  or  large  palatine  nerve  descends  through  the  posterior  palatine 
canal,  emerges  upon  the  hard  palate  at  the  posterior  palatine  foramen,  and  passes 
forward  through  a  groove  in  the  hard  palate  nearly  as  far  as  the  incisor  teeth.  It 
supplies  the  gums,  the  mucous  membrane  and  glands  of  the  hard  palate,  and 
communicates  in  front  with  the  termination  of  the  naso-palatine  nerve.  While  in 
the  posterior  palatine  canal  it  gives  off  inferior  nasal  branches,  which  enter  the 
nose  through  openings  in  the  palate  bone,  and  ramify  over  the  middle  meatus  and 
the  middle  and  inferior  spongy  bones ;  and,  at  its  exit  from  the  canal  a  palatine 
branch  is  distributed  to  both  surfaces  of  the  soft  palate. 

The  middle  or  external  palatine  nerve  descends  through  one  of  the  accessory 
palatine  canals,  distributing  branches  to  the  uvula,  tonsil,  and  soft  palate.  It  is 
occasionally  wanting. 

The  posterior  or  small  palatine  nerve  descends  with  a  small  artery  through  the 
small  posterior  palatine  canal,  emerging  by  a  separate  opening  behind  the  posterior 
palatine  foramen.  It  supplies  the  Levator  palati  and  Azygos  uvulae  muscles,  the 
soft  palate,  tonsil,  and  uvula.  The  middle  and  posterior  palatine  join  with  the 
tonsillar  branches  of  the  glosso-pharyngeal  to  form  the  plexus  around  the  tonsil 
(circulus  tonsillaris). 

The  internal  branches  are  distributed  to  the  septum  and  outer  wall  of  the  nasal 
fossae.  They  are  the  superior  nasal  (anterior)  and  the  naso-palatine. 

The  superior  nasal  branches  (anterior),  four  or  five  in  number,  enter 
the  back  part  of  the  nasal  fossa  by  the  spheno-palatine  foramen.  They 
supply  the  mucous  membrane  covering  the  superior  and  middle  spongy  bones, 
and  that  lining  the  posterior  ethmoidal  cells,  a  few  being  prolonged  to  the 
upper  and  back  part  of  the  septum.  One  branch  is  continued  on  to  the  inner 
surface  of  the  anterior  wall  of  the  antrum,  and  there  forms  a  communication 
with  the  anterior  dental  nerve.  At  the  point  of  communication  a  swelling 
exists,  denominated  "the  ganglion  of  Bochdalek,"  the  nature  of  which  seems 
to  be,  however,  uncertain. 


BRANCHES    Or    THE   FIFTH   NERVE.  805 

The  naso-palatine  nerve  (Cotunnius)  also  enters  the  nasal  fossa  through  the 
spheno-palatine  foramen,  and  passes  inward  across  the  roof  of  the  nose,  below 
the  orifice  of  the  sphenoidal  sinus,  to  reach  the  septum  ;  it  then  runs  obliquely 
downward  and  forward  along  the  lower  part  of  the  septum,  to  the  anterior  palatine 
foramen,  lying  between  the  periosteum  and  mucous  membrane.  It  descends  to  the 
roof  of  the  mouth  through  the  anterior  palatine  canal.  The  two  nerves  are  here 
contained  in  separate  and  distinct  canals,  situated  in  the  intermaxillary  suture, 
and  termed  the  foramina  of  Scarpa,  the  left  nerve  being  usually  anterior  to  the 
right  one.  In  the  mouth  they  become  united,  supply  the  mucous  membrane 
behind  the  incisor  teeth,  and  join  with  the  anterior  palatine  nerve.  The  naso- 
palatine  nerve  occasionally  furnishes  a  few  small  filaments  to  the  mucous  mem- 
brane of  the  septum. 

The  posterior  branches  are  the  pharyngeal  (pterygo-palatine)  and  the  upper 
posterior  nasal  branches. 

The  pharyngeal  nerve  (pterygo-palatine)  is  a  small  branch  arising  from  the 
back  part  of  the  ganglion,  being  generally  blended  with  the  Vidian  nerve.  It 
passes  through  the  pterygo-palatine  canal  with  the  pterygo-palatine  artery,  and  is 
distributed  to  the  mucous  membrane  of  the  upper  part  of  the  pharynx,  behind  the 
Eustachian  tube. 

The  upper  posterior  nasal  branches  are  a  few  twigs  given  off  from  the  posterior 
part  of  the  ganglion,  which  run  backward  in  the  sheath  of  the  Vidian  nerve  to 
the  mucous  membrane  at  the  back  part  of  the  roof,  septum,  and  superior  meatus 
of  the  nose  and  that  covering  the  end  of  the  Eustachian  tube. 

Inferior  Maxillary  Nerve  (Fig.  483). 

The  Inferior  Maxillary  Nerve  distributes  branches  to  the  teeth  and  gums  of 
the  lower  jaw,  the  integument  of  the  temple  and  external  ear,  the  lower  part  of 
the  face  and  lower  lip,  and  the  muscles  of  mastication ;  it  also  supplies  the  tongue 
with  a  large  branch.  It  is  the  largest  of  the  three  divisions  of  the  fifth,  and  is 
made  up  of  two  roots :  a  large  or  sensory  root  proceeding  from  the  inferior  angle 
of  the  Gasserian  ganglion ;  and  a  small  or  motor  root,  which  passes  beneath  the 
ganglion,  and  unites  with  the  sensory  root  just  after  its  exit  through  the  foramen 
ovale.  Immediately  beneath  the  base  of  the  skull  this  nerve  divides  into  two 
trunks,  anterior  and  posterior.  Previous  to  its  division  the  primary  trunk  gives 
off  from  its  inner  side  a  recurrent  (meningeal)  branch  and  the  nerve  to  the  Internal 
pterygoid  muscle. 

The  recurrent  branch  is  given  off  directly  after  its  exit  from  the  foramen 
ovale.  It  passes  backward  into  the  skull  through  the  foramen  spinosum  with  the 
middle  meningeal  artery.  It  divides  into  two  branches,  anterior  and  posterior, 
which  accompany  the  main  divisions  of  the  artery  and  supply  the  dura  mater. 
The  anterior  branch  communicates  with  the  meningeal  branch  of  the  superior 
maxillary  nerve. 

The  internal  Pterygoid  Nerve,  given  off  from  the  inferior  maxillary  previous 
to  its  division,  is  intimately  connected  at  its  origin  with  the  otic  ganglion.  It  is  a 
long  and  slender  branch,  which  passes  inward  to  enter  the  deep  surface  of  the 
Internal  pterygoid  muscle. 

The  anterior  and  smaller  division,  which  receives  nearly  the  whole  of  the 
motor  root,  divides  into  branches  which  supply  the  remaining  muscles  of  masti- 
cation. They  are  the  masseteric,  deep  temporal,  buccal,  and  external  pterygoid. 

The  masseteric  branch  passes  outward,  above  the  External  pterygoid  muscle, 
in  front  of  the  temporo-maxillary  articulation,  and  crosses  the  sigmoid  notch  with 
the  masseteric  artery  to  the  Masseter  muscle,  in  which  it  ramifies  nearly  as  far  as 
its  anterior  border.  It  occasionally  gives  a  branch  to  the  Temporal  muscle  and 
a  filament  to  the  articulation  of  the  jaw. 

The  deep  temporal  branches  supply  the  deep  surface  of  the  Temporal  muscle. 
The  posterior  branch,  of  small  size,  is  placed  at  the  back  of  the  temporal  fossa. 
It  is  sometimes  joined  with  the  masseteric  branch.  The  anterior  branch  is 


806  THE  NERVOUS  SYSTEM. 

reflected  upward  at  the  pterygoid  ridge  of  the  sphenoid  to  the  front  of  the  tem- 
poral fossa.  It  is  often  given  off  from  the  buccal  branch  after  the  latter  has 
pierced  the  external  pterygoid  muscle.  The  third  branch  (middle  deep  temporal) 
passes  outward  over  the  External  pterygoid  muscle  and  enters  the  deep  surface 
of  the  Temporal  muscle. 

The  buccal  branch  passes  forward  between  the  two  heads  of  the  External 
pterygoid,  and  downward  beneath  the  inner  surface  of  the  coronoid  process  of  the 
lower  jaw,  or  through  the  fibres  of  the  Temporal  muscle,  to  reach  the  surface  of 
the  Buccinator,  upon  which  it  divides  into  a  superior  and  an  inferior  branch.  It 
gives  the  branch  to  the  External  pterygoid  during  its  passage  through  that 
muscle,  and  is  usually  joined  with  the  anterior  branch  of  the  deep  temporal  nerve. 
The  upper  branch  supplies  the  integument  and  upper  part  of  the  Buccinator 
muscle,  joining  with  the  facial  nerve  round  the  facial  vein.  The  lower  branch 
,,/passes  forward  to  the  angle  of  the  mouth  :  it  supplies  the  integument  and'Bucci- 
'  nator  muscle,  as  well  as  the  mucous  membrane  lining  the  inner  surface  of  that 
muscle,  and  joins  the  facial  nerve.1 

The  External  Pterygoid  Nerve  is  most  frequently  derived  from  the  buccal,  but 
it  may  be  given  off  separately  from  the  anterior  trunk  of  the  nerve.  It  enters  the 
muscle  on  its  inner  surface. 

The  posterior  and  larger  division  of  the  inferior  maxillary  nerve  is  for  the 
most  part  sensory,  but  receives  a  few  filaments  from  the  motor  root.  It  divides 
into  three  branches  :  auriculo-temporal,  lingual  (gustatory),  and  inferior  dental. 

The  Auriculo-temporal  Nerve  generally  arises  by  two  roots,  beneath  which  the 
middle  meningeal  artery  passes.  It  runs  backward  beneath  the  External  ptery- 
goid muscle  to  the  inner  side  of  the  neck  of  the  lower  jaw.  It  then  turns  upward 
with  the  temporal  artery,  between  the  external  ear  and  condyle  of  the  jaw,  under 
cover  of  the  parotid  gland,  and,  escaping  from  beneath  this  structure,  ascends 
over  the  zygoma  and  divides  into  two  temporal  branches. 

The  branches  of  communication  are  with  the  facial  and  with  the  otic  ganglion. 
The  branches  of  communication  with  the  facial,  usually  two  in  number,  pass 
forward  from  behind  the  neck  of  the  condyle  of  the  jaw,  to  join  the  temporo-facial 
division  of  this  nerve  .at^the  posterior  border  of  the  Masseter  muscle.  They  form 
one  of  the  principal  branches" of  coTnmuni cation  between  the  facial  and  the  fifth 
nerve.  The  filaments  of  communication  with  the  otic  ganglion  are  derived  from 
the  commencement  of  the  auriculo-temporal  nerve. 

The  branches  of  distribution  are — 

Auricular,  inferior  and  superior.  Articular. 

Branches  to  the  meatus  auditorius.  Parotid. 

Temporal,  anterior  and  posterior. 

The  inferior  auricular  arises  behind  the  articulation  of  the  jaw,  and  is  distrib- 
uted to  the  ear  below  the  external  meatus :  other  filaments  twine  round  the 
internal  maxillary  artery  and  communicate  with  the  sympathetic.  The  superior 
auricular  arises  in  front  of  the  external  ear,  and  supplies  the  integument  cover- 
ing the  tragus  and  pinna. 

Branches  to  the  meatus  auditorius,  upper  and  lower,  arise  from  the  point 
of  communication  between  the  auriculo-temporal  and  facial  nerves,  and  are 
distributed  to  the  meatus.  A  filament  from  the  upper  passes  to  the  membrana 
tympani. 

A  branch  to  the  temporo-maxillary  articulation  is  usually  derived  from  the 
auriculo-temporal  nerve. 

The  parotid  branches  supply  the  parotid  gland. 

The  anterior  temporal  accompanies  the  temporal  artery  to  the  vertex  of  the 
skull,  and  supplies  the  integument  of  the  temporal  region,  communicating  with 
the  facial  nerve  and  the  temporal  branch  of  the  temporo-malar  from  the  superior 

1  There  seems  to  be  no  reason  to  doubt  that  the  branch  supplying  the  Buccinator  muscle  is  entire- 
ly a  nerve  of  ordinary  sensation,  and  that  the  true  motor-supply  of  this  muscle  is  from  the  facial. 


BRANCHES    OF   THE  FIFTH  NERVE.  807 

maxillary.  The  posterior  temporal,  the  smaller  of  the  two,  is  distributed  to  the 
upper  part  of  the  pinna  and  the  neighboring  tissues. 

The  Lingual  Nerve  (gustatory)  supplies  the  papillae  and  mucous  membrane  of 
the  tongue.  It  is  deeply  placed  throughout  the  whole  of  its  course.  It  lies  at 
first  beneath  the  External  pterygoid  muscle,  together  with  the  inferior  dental 
nerve,  being  placed  to  the  inner  side  of  the  latter  nerve,  and  is  occasionally 
joined  to  it  by  a  branch  which  crosses  the  internal  maxillary  artery.  The  chorda 
tympani  also  joins  it  at  an  acute  angle  in  this  situation.  The  nerve  then  passes 
between  the  Internal  pterygoid  muscle  and  the  inner  side  of  the  ramus  of  the 
jaw,  and  crosses  obliquely  to  the  side  of  the  tongue  over  the  Stylo-glossus 
muscle,  and  then  between  the  Hyo-glossus  muscle  and  deep  part  of  the  submaxil- 
lary  gland  :  the  nerve  lastly  runs  across  Wharton's  duct,  and  along  the  side  of 
the  tongue  to  its  apex,  lying  immediately  beneath  the  mucous  membrane. 

The  branches  of  communication  are  with  the  facial  through  the  chorda  tympani, 
the  inferior  dental  and  hypoglossal  nerves,  and  the  submaxillary  ganglion.  The 
branches  to  the  submaxillary  ganglion  are  two  or  three  in  number ;  those  con- 
nected with  the  hypoglossal  nerve  form  a  plexus  at  the  anterior  margin  of  the 
Hyo-glossus  muscle. 

The  branches  of  distribution  are  few  in  number.  They  supply  the  mucous 
membrane  of  the  mouth,  the  gums,  and  the  sublingual  gland,  while  the  lingual 
or  terminal  branches  supply  the  mucous  membrane  of  the  tongue  over  its  anterior 
two-thirds,  terminating  in  the  filiform  and  fungiform  papillae. 

The  Inferior  Dental  is  the  largest  of  the  three  branches  of  the  inferior  max- 
illary nerve.  It  passes  downward  with  the  inferior  dental  artery,  at  first  beneath 
the  External  pterygoid  muscle,  and  then  between  the  internal  lateral  ligament 
and  the  ramus  of  the  jaw  to  the  dental  foramen.  It  then  passes  forward  in  the 
dental  canal  of  the  inferior  maxillary  bone,  lying  beneath  the  teeth,  as  far  as  the 
mental  foramen,  where  it  divides  into  two  terminal  branches,  incisor  and  mental. 

The  branches  of  the  inferior  dental  are,  the  mylo-hyoid,  dental,  incisive,  and 
mental. 

The  mylo-hyoid  is  derived  from  the  inferior  dental  just  as  that  nerve  is  about 
to  enter  the  dental  foramen.  It  descends  in  a  groove  on  the  inner  surface  of  the 
ramus  of  the  jaw,  in  which  it  is  retained  by  a  process  of  fibrous  membrane.  It 
reaches  the  under  surface  of  the  Mylo-hyoid  muscle,  and  supplies  it  and  the 
anterior  belly  of  the  Digastric,  occasionally  sending  one  or  two  filaments  to  the 
submaxillary  gland. 

The  dental  branches  supply  the  molar  and  bicuspid  teeth.  They  correspond 
in  number  to  the  fangs  of  those  teeth :  each  nerve  entering  the  orifice  at  the 
point  of  the  fang  and  supplying  the  pulp  of  the  tooth. 

The  incisive  branch  is  continued  onward  within  the  bone  to  the  middle  line, 
and  supplies  the  canine  and  incisor  teeth. 

The  mental  branch  emerges  from  the  bone  at  the  mental  foramen,  and  divides 
beneath  the  Depressor  anguli  oris  into  two  or  three  branches ;  one  descends  to 
supply  the  skin  of  the  chin,  and  another  (sometimes  two)  ascends  to  supply  the 
skin  and  mucous  membrane  of  the  lower  lip.  These  branches  communicate  freely 
with  the  facial  nerve. 

Two  small  ganglia  are  connected  with  the  inferior  maxillary  nerve — the  otic 
with  the  trunk  of  the  nerve,  and  the  submaxillary  with  its  lingual  branch. 

Otic  Ganglion  (Fig.  485). 

The  Otic  Ganglion  (Arnold's)  is  a  small,  oval-shaped,  flattened  ganglion  of  a 
reddish-gray  color,  situated  immediately  below  the  foramen  ovale,  on  the  inner 
surface  of  the  inferior  maxillary  nerve,  and  round  the  origin  of  the  internal  ptery- 
goid nerve.  It  is  in  relation,  externally,  with  the  trunk  of  the  inferior  maxillary 
nerve,  at  the  point  where  the  motor  root  joins  the  sensory  portion ;  internally. 
with  the  cartilaginous  part  of  the  Eustachian  tube,  and  the  origin  of  the  Tensor 
palati  muscle ;  behind  it  is  the  middle  meningeal  artery. 


808 


THE   NERVOUS   SYSTEM. 


Branches  of  Communication. — This  ganglion  is  connected  with  the  internal 
pterygoid  branch  of  the  inferior  maxillary  nerve  by  two  or  three  short,  delicate 
filaments.  From  this  it  may  obtain  a  motor  root,  and  possibly  also  a  sensory  root, 
as  these  filaments  from  the  nerve  to  the  Internal  pterygoid  may  contain  sensory 


FIG.  485.— The  otic  ganglion  and  its  branches. 

fibres.  It  communicates  with  the  glosso-pharyngeal  and  facial  nerves  through  the 
small  superficial  petrosal  nerve  continued  from  the  tympanic  plexus  (pages  811  and 
818),  and  through  this  communication  it  probably  receives  its  sensory  root  from  the 
glosso-pharyngeal  and  its  motor  root  from  the  facial ;  its  communication  with  the 
sympathetic  is  effected  by  a  filament  from  the  plexus  surrounding  the  middle 
meningeal  artery.  The  ganglion  also  communicates  with  the  auriculo-temporal 
nerve.  This  is  probably  a  branch  from  the  glosso-pharyngeal  which  passes 
to  the  ganglion,  and  through  it  and  the  auriculo-temporal  nerve  to  the  parotid 
gland.  The  sphenoidal  filament  joins  the  Vidian  nerve. 

Its  branches  of  distribution  are  a  filament  to  the  Tensor  tympani  and  one  to  the 
Tensor  palati.  The  former  passes  backward  on  the  outer  side  of  the  Eustachian 
tube  ;  the  latter  arises  from  the  ganglion,  near  the  origin  of  the  internal  pterygoid 
nerve,  and  passes  forward.  The  fibres  of  these  nerves  are,  however,  mainly  derived 
from  the  nerve  to  the  Internal  pterygoid  muscle.  It  also  gives  off  a  small  com- 
municating branch  to  the  chorda  tympani  and  one  to  the  buccal  nerve  (Rauber). 


Submaxillary  Ganglion  (Fig.  483). 

The  submaxillary  ganglion  is  of  small  size,  fusiform  in  shape,  and  situated 
above  the  deep  portion  of  the  submaxillary  gland,  near  the  posterior  border  of  the 
Mylo-hyoid  muscle,  being  connected  by  filaments  with  the  lower  border  of  the 
lingual  (gustatory)  nerve. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  lingual 
(gustatory)  nerve  by  a  few  filaments  which  join  it  separately  at  its  fore  and  back 
part.  It  also  receives  a  branch  from  the  chorda  tympani,  by  which  it  communicates 
with  the  facial,  and  communicates  with  the  sympathetic  by  filaments  from  the 
sympathetic  plexus  around  the  facial  artery. 

Branches  of  Distribution. — These  are  five  or  six  in  number:  they  arise  from 
the  lower  part  of  the  ganglion,  and  supply  the  mucous  membrane  of  the  mouth  and 


BRANCHES    OF    THE   FIFTH  XERVE.  809 

Wharton's  duct,  some  being  lost  in  the  submaxillary  gland.  The  branch  of  com- 
munication from  the  lingual  to  the  fore  part  of  the  ganglion  is  by  some  regarded 
'•ranch  of  distribution,  by  which  filaments  of  the  chorda  tympani  pass  from 
the  ganglion  to  the  nerve,  and  by  it  are  conveyed  to  the  sublingual  gland  and  the 
tongue. 

Surface  Marking. — It  will  be  seen  from  the  above  description  that  the  three  terminal 
branches  of  the  three  divisions  of  the  fifth  nerve  emerge  from  foramina  in  the  bones  of  the  skull 
and  face  on  to  the  face :  the  terminal  branch  of  the  first  division  emerging  through  the  supra- 
orbital  foramen  :  that  of  the  second  through  the  infra-orbital  foramen ;  and  the  third  through 
the  mental  foramen.  The  supra-orbital  foramen  is  situated  at  the  junction  of  the  internal 
and  middle  third  of  the  supra-orbital  arch  between  the  internal  and  external  angular  processes. 
It'  a  straight  line  is  drawn  from  this  point  to  the  lower  border  of  the  inferior  maxillary  bone,  so 
that  it  passes  between  the  two  bicuspid  teeth  in  both  jaws,  it  will  pass  over  the  infra-orbital  and 
mental  foramina,  the  former  being  situated  about  one  centimetre  (two-fifths  of  an  inch)  below  the 
margin  of  the  orbit,  and  the  latter  varying  in  position  according  to  the  age  of  the  individual. 
In  the  adult  it  is  midway  between  the  upper  and  lower  borders  of  the  inferior  maxillary  bone  ; 
in  the  child  it  is  nearer  the  lower  border ;  and  in  the  edentulous  jaw  of  old  age  it  is  close  to  the 
upper  margin. 

Surgical  Anatomy. — The  fifth  nerve  may  be  affected  in  its  entirety,  or  its  sensory  or  motor 
root  may  be  affected,  or  one  of  its  primary  main  divisions.  In  injury  to  the  sensory  root  there  is 
anaesthesia  of  the  whole  of  the  side  of  the  face  on  the  side  of  the  lesion,  with  the  exception  of 
the  skin  over  the  parotid  gland  ;  insensibility  of  the  conjunctiva,  followed  by  destructive  inflam- 
mation of  the  cornea,  partly  from  loss  of  trophic  influence,  and  partly  from  the  irritation  pro- 
duced by  the  presence  of  foreign  bodies  on  it.  which  are  not  perceived  by  the  patient,  and  there- 
fore not  expelled  by  the  act  of  winking  ;  dryness  of  the  nose,  loss  to  a  considerable  extent  of  the 
sense  of  taste,  and  diminished  secretion  of  the  lachrymal  and  salivary  glands.  In  injury  to  the 
motor  root  there  is  impaired  action  of  the  lower  jaw  from  paralysis  of  the  muscles  of  mastication 
on  tbe  affected  side. 

The  fifth  nerve  is  often  tbe  seat  of  neuralgia,  and  each  of  the  three  divisions  has  been 
divided  or  a  portion  of  the  nerve  excised  for  this  affection.  The  supra-orbital  nerve  may  be 
exposed  by  making  an  incision  an  inch  and  a  half  in  length  along  the  supra-orbital  margin  below 
the  eyebrow,  which  is  to  be  drawn  upward,  the  centre  of  the  incision  corresponding  to  the  supra- 
orbital  notch.  The  skin  and  Orbicularis  palpebrarum  having  been  divided,  the  nerve  can  be 
easily  found  emerging  from  the  notch  and  lying  in  some  loose  cellular  tissue.  It  should  be  drawn 
up  by  a  blunt  hook  and  divided,  or,  what  is  better,  a  portion  of  it  removed.  The  infra-orbital 
nerve  has  !>een  divided  at  its  exit  by  an  incision  on  the  cheek  ;  or  the  floor  of  the  orbit  has  been 
exposed,  the  infra-orbital  canal  opened  up,  and  the  anterior  part  of  the  nerve  resected  ;  or  the 
whole  nerve,  together  with  Meek  el's  ganglion  as  far  back  as  the  foramen  rotundum,  has  been 
removed.  This  latter  operation,  though  undoubtedly  a  severe  proceeding,  appears  to  have  been 
followed  by  the  best  results.  The  operation  is  performed  as  follows :  The  superior  maxillary 
bone  is  first  exposed  by  a  T-shaped  incision,  one  limb  passing  along  the  lower  margin  of  the  orbit, 
the  other  from  the  centre  of  this  vertically  down  the  cheek  to  the  angle  of  the  mouth.  The 
nerve  is  then  found,  divided,  and  a  piece  of  silk  tied  to  it  as  a  guide.  A  small  trephine  (one- 
half  inch  I  is  then  applied  to  the  bone  below,  but  including,  the  infra-orbital  foramen,  and  the 
antrum  opened.  The  trephine  is  now  applied  to  the  posterior  wall  of  the  antrum,  and  the 
spheno-maxillary  fossa  exposed.  The  infra-orbital  canal  is  now  opened  up  from  below  by  fine 
cutting-pliers  or  a  chisel,  and  the  nerve  drawn  down  into  the  trephine  hole,  it  being  held  on  the 
stretch  by  means  of  the  piece  of  silk ;  it  is  severed  with  fine  curved  scissors  as  near  the  foramen 
rotundum  as  possible,  any  branches  coming  off  from  the  ganglion  being  also  divided.1  The 
inferior  dental  nerve  has  been  divided  at  its  exit  from  the  foramen  by  an  incision  made  through 
the  mucous  membrane  where  it  is  reflected  from  the  alveolar  process  on  to  the  lower  lip ;  or  a 
portion  of  the  nerve  has  been  resected  by  an  incision  on  the  cheek  through  the  Masseter  muscle, 
exposing  the  outer  surface  of  the  ramus  of  the  jaw.  A  trephine  was  then  applied  over  the 
position  of  the  inferior  dental  foramen  and  the  outer  table  removed,  so  as  to  expose  the  inferior 
dental  canal.  The  nerve  was  dissected  out  of  the  portion  of  the  canal  exposed,  and,  having  been 
divided  after  its  exit  from  the  mental  foramen,  it  was  by  traction  on  the  end  exposed  in  the 
trephine  hole,  drawn  out  entire,  and  cut  off  as  high  up  as  possible.1  The  inferior  dental  nerve 
has  also  been  divided  by  an  incision  within  the  mouth,  the  bony  point  guarding  the  inferior 
dental  foramen  forming  the  guide  to  the  nerve.  The  buccal  nerve  may  be  divided  by  an  incision 
through  the  mucous  membrane  of  the  mouth  and  the  Buccinator  just  in  front  of  the  anterior 
border  of  the  ramus  of  the  lower  jaw  (Stiinson). 

The  lingual  (gustatory  nerve  is  occasionally  divided  with  the  view  of  relieving  the  pain  in 
cancerous  disease  of  the  tongue.  This  may  be  done  in  that  part  of  its  course  where  it  lies  below 
and  behind  the  last  molar  tooth.  If  a  line  is  drawn  from  the  middle  of  the  crown  of  the  last 
molar  tooth  to  the  angle  of  the  jaw.  it  will  cross  the  nerve,  which  lies  about  half  an  inch  behind 
the  tooth,  parallel  to  the  bulging  alveolar  ridge  on  the  inner  side  of  the  bod}'  of  the  bone.  If 
the  knife  is  entered  three-quarters  of  an  inch  behind  and  below  the  last  molar  tooth  and  carried 

1  Carnochan,  Amer.  Journ.  Med.  Scienfe,  1858,  p.  136. 

2  Means,  Tran#.  Amer.  Surg.  Assoc.,  vol.  ii.  p.  469. 


810  THE   NERVOUS  SYSTEM. 

down  to  the  bone,  the  nerve  will  be  divided.  Hilton  divided  it  opposite  the  second  molar  tooth, 
where  it  is  covered  only  by  the  mucous  membrane,  and  Lucas  pulls  the  tongue  forward  and  over 
to  the  opposite  side,  when  the  nerve  can  be  seen  standing  out  as  a  firm  cord  under  the  mucous 
membrane  by  the  side  of  the  tongue,  and  can  be  easily  seized  with  a  sharp  hook  and  divided  or 
a  portion  excised.  This  is  a  simple  enough  operation  on  the  cadaver,  but  when  the  disease  is 
extensive  and  has  extended  to  the  floor  of  the  mouth,  as  is  generally  the  case  when  division  of 
the  nerve  is  required,  the  operation  is  not  practicable. 

Sixth  Nerve  (Figs.  384,  481). 

The  Sixth  or  Abducent  Nerve  supplies  the  External  rectus  muscle.  Its  super- 
ficial origin  is  by  several  filaments  from  the  constricted  part  of  the  pyramid  close 
to  the  pons,  or  from  the  lower  border  of  the  pons  itself  in  the  groove  between  this 
body  and  the  medulla.  Its  deep  origin  is  a  little  lower  than  the  motor  root  of  the 
fifth,  and  close  to  the  median  line,  beneath  the  superior  portion  (above  the  audi- 
tory striae)  of  the  fasciculus  teres  on  the  floor  of  the  fourth  ventricle. 

The  nerve  pierces  the  dura  mate.r  on  the  basilar  surface  of  the  sphenoid  bone, 
runs  through  a  notch  immediately  below  the  posterior  clinoid  process,  and  enters 
the  cavernous  sinus.  It  passes  forward  through  the  sinus,  lying  on  the  outer  side 
of  the  internal  carotid  artery.  It  enters  the  orbit  through  the  sphenoidal  fissure, 
and  lies  above  the  ophthalmic  vein,  from  which  it  is  separated  by  a  lamina  of  dura 
mater.  It  then  passes  between  the  two  heads  of  the  External  rectus,  and  is  dis- 
tributed to  that  muscle  on  its  ocular  surface. 

Branches  of  Communication. — It  is  joined  by  several  filaments  from  the  carotid 
and  cavernous  plexus,  by  one  from  Meek  el's  ganglion  (Bock),  and  another  from 
the  ophthalmic  nerve. 

The  above-mentioned  nerve,  as  well  as  the  third,  fourth,  and  the  ophthalmic 
division  of  the  fifth,  as  they  pass  to  the  orbit,  bear  a  certain  relation  to  each  other 
in  the  cavernous  sinus,  at  the  sphenoidal  fissure,  and  in  the  cavity  of  the  orbit, 
which  will  now  be  described. 

In  the  cavernous  sinus  (Fig.  384)  the  third,  fourth,  and  ophthalmic  division  of 
the  fifth  are  placed  on  the  outer  wall  of  the  sinus,  in  their  numerical  order  both 
from  above  downward  and  from  within  outward.  The  sixth  nerve  lies  at  the 
outer  side  of  the  internal  carotid  artery.  As  these  nerves  pass  forward  to  the 
sphenoidal  fissure,  the  third  and  fifth  nerves  become  divided  into  branches,  and 
the  sixth  approaches  the  rest,  so  that  their  relative  position  becomes  considerably 
changed. 

In  the  sphenoidal  fissure  (Fig.  486)  the  fourth  and  the  frontal  and  lachrymal 
divisions  of  the  ophthalmic  lie  upon  the  same  plane,  the  former  being  most 

Lachrymal. 
Frontal. 


Superior  division  of  3d. 
Nasal. 

'Inferior  division  of  3d. 
"6th. 
~0phthalnir  vein. 


FIG.  486. — Relations  of  structures  passing  through  the  sphenoidal  fissure. 

internal,  the  latter  external,  and  they  enter  the  cavity  of  the  orbit  above  the  mus- 
cles. The  remaining  nerves  enter  the  orbit  between  the  two  heads  of  the 
External  rectus.  The  superior  division  of  the  third  is  the  highest  of  these; 
beneath  this  lies  the  nasal  branch  of  the  ophthalmic ;  then  the  inferior  division  of 
the  third  ;  and  the  sixth  lowest  of  all. 


THE   SEVENTH    OR    FACIAL    NERVE.  811 

In  the  orbit  the  fourth  and  the  frontal  and  lachrymal  divisions  of  the  ophthal- 
mic lie  on  the  same  plane  immediately  beneath  the  periosteum,  the  fourth  nerve 
being  internal  and  resting  on  the  Superior  oblique,  the  frontal  resting  on  the 
Levator  palpebne.  and  the  lachrymal  on  the  External  re*ctus.  Next  in  order 
comes  the  superior  division  of  the  third  nerve,  lying  immediately  beneath  the 
Superior  rectus,  and  then  the  nasal  branch  of  the  ophthalmic,  crossing  the  optic 
nerve  from  the  outer  to  the  inner  side  of  the  orbit.  Beneath  these  is  found  the 
optic  nerve,  surrounded  in  front  by  the  ciliary  nerves,  and  having  the  lenticular 
ganglion  on  its  outer  side,  between  it  and  the  External  rectus.  Below  the  optic 
is  the  inferior  division  of  the  third  and  the  sixth,  which  lies  on  the  outer  side  of 
the  orbit. 

Surgical  Anatomy. — The  sixth  nerve  is  more  frequently  involved  in  fractures  of  the  base 
of  the  skull  than  any  other  of  the  cranial  nerves.  The  result  of  paralysis  of  this  nerve  is  internal 
or  convergent  squint.  When  injured  so  that  its  function  is  destroyed,  there  is,  in  addition  to 
the  paralysis  of  the  External  rectus  muscle,  often  a  certain  amount  of  contraction  of  the  pupil, 
because  some  of  the  sympathetic  fibres  to  the  radiating  muscle  of  the  iris  pass  along  with  this 
nerve. 

Seventh  Nerve   (Figs.  487   and  489).  *•  (VHVVVUAANA^C^  tf 

" — " " — ~\— — 

The  Seventh  or  Facial  Nerve  (portio  dura)  is  the  motor  nerve  of  all  the  mus- 
cles of  expression  in  the  face  and  of  the  Platysma  and  Buccinator,  the  muscles 
of  the  External  ear,  the  posterior 
belly  of  the  Digastric,  and  the  Stylo- 

hyoid.     Through   its   chorda  tym-  Elienial  petrosal    _ 

pani  it  supplies  the  Lingualis;  by      *-J «jgg 8tt2=SJj§g^ 

its  tvmpanic  branch  the  btapedms. 

T.      *  /•    •   7         ••       •      f  Au      Intumescentia  ganglicformu. 

Its  superficial   origin    is  trom   the 

upper  end  of  the   medulla   oblon- 

gata.   in    the    groove    between    the  Seventh  pair  { 

olivary  and  restiform  bodies.     Its 

•  h-ep  origin  is  from  a  nucleus  in  the 

pons,  below  the  floor  of  the  fourth 

ventricle,    somewhat   ventral   and   external   to   the   nucleus  of  the   sixth   nerve. 

The  auditory  nerve  (portio  mollis)  lies  to  its  outer  side,  and  between  the  two 
is  a  small  fasciculus  (portio  inter  duram  et  mollem  of  Wrisberg,  or  pars  intermedia), 
which  arises  from  the  medulla  and  joins  the  facial  nerve  in  the  internal  auditory 
meatus.  At  its  origin  it  is  frequently  connected  with  both  the  nerves  between 
which  it  lies. 

The  facial  nerve,  firmer,  rounder,  and  smaller  than  the  auditory,  passes 
forward  and  outward  together  with  that  nerve,  and  with  it  enters  the  internal 
auditory  meatus.  Within  the  meatus  the  facial  nerve  lies  in  a  groove  along 
the  upper  and  anterior  part  of  the  auditory  nerve.  The  pars  intermedia 
is  placed  between  the  facial  and  auditory  nerves  in  the  internal  auditory 
meatus ;  a  few  of  its  fibres  frequently  pass  into  the  auditory  nerve,  while 
the  remainder  join  the  facial.  At  the  bottom  of  the  meatus  it  is  connected  to  this 
nerve  by  one  or  two  slender  filaments. 

At  the  bottom  of  the  meatus  the  facial  nerve  enters  the  aqueductus  Fallopii, 
and  follows  the  serpentine  course  of  that  canal  through  the  petrous  portion  of  the 
temporal  bone,  from  its  commencement  at  the  internal  meatus  to  its  termination 
at  the  stylo-mastoid  foramen.  It  is  at  first  directed  outward  toward  the  inner 
wall  of  the  tympanum,  where  it  forms  a  reddish  gangliform  swelling  (intumescentia 
ganglioformis,  or  geniculate  ganglion),  and  is  joined  by  several  nerves  ;  then  bending 
suddenly  , backward,  it  runs  in  the  internal  wall  of  the  tympanum,  above  the 
fenestra  ovalis.  and  at  the  back  of  that  cavity  passes  vertically  downward  behind 
the  tympanum  to  the  stylo-mastoid  foramen.  On  emerging  from  this  aperture  it 
runs  forward  in  the  substance  of  the  parotid  gland,  crosses  the  external  carotid 
artery,  and  divides  behind  the  ramus  of  the  lower  jaw  into  two  primary  branches. 
temporo-facial  and  cervico-facial,  from  which  numerous  offsets  are  distributed  over 


812  THE  NERVOUS  SYSTEM. 

the  side  of  the  head,  face,  and  upper  part  of  the  neck,  supplying  the  superficial 
muscles  in  these  regions.  As  the  primary  branches  and  their  offsets  diverge  from 
each  other  they  present  somewhat  the  appearance  of  a  bird's  claw  ;  hence  the 
name  of  pes  anserinus  is  given  to  the  divisions  of  the  facial  nerve  in  and  near  the 
parotid  gland. 
The  branches  of  communication  of  the  facial  nerve  may  be  thus  arranged : 

In     the     internal     auditory      ™T-,I    .  r, 

J       VV  ith  the  auditory  nerve, 
meatus  .... 

With  Meckel's  ganglion  by  the  large  superficial 

potrosal  nerve. 
With  the  otic  ganglion  by  the  small  superficial 

petrosal  nerve. 


In  the  aquseductus  Fallopii 


With  the  sympathetic  on  the  middle  meningeal 


Jby  the  external  superficial  petrosal  nerve. 

'auricular    branch    of    the    pneumo- 
ga'Stric. 
^--With  the  glosso-pharyngeal  (Digastric). 

With  the  pneumogastric  (Posterior  auricular). 

After  its  exit  from  the  stylo-       -IIT-..I    .1  ,•  i     i          /ox  i    u     -j\ 

,,  J        <    With  the  carotid  plexus  (fetylo-hyoid). 

mastoid  foramen     .          •    I   •nrvLi.  ±1.          •     i     •  VD  •     i     \ 

With  the  auricularis  magnus  (Posterior  auricular). 

^  With  the  auriculo-temporal  (Temporal). 
On  the  face         .          .          .       With  the  three  divisions  of  the  fifth. 

In  the  internal  auditory  meatus  some  minute  filaments  pass  between  the  facial 
and  auditory  nerves. 

Opposite  the  hiatus  Fallopii  the  gangliform  enlargement  on  the  facial  nerve 
communicates  with  Meckel's  ganglion  by  means  of  the  large  superficial  petrosal 
nerve,  which  forms  its  motor  root ;  with  the  otic  ganglion,  by  the  small  superficial 
petrosal  nerve ;  and  with  the  sympathetic  filaments  accompanying  the  middle 
meningeal  artery,  by  the  external  petrosal  (Bidder).  From  the  gangliform  enlarge- 
ment, according  to  Arnold,  a  twig  is  sent  back  to  the  auditory  nerve. 

Just  before  leaving  the  aqueduct  a  twig  joins  the  auricular  branch  of  the 
pneumogastric  nerve. 

Just  after  its  exit  from  the  stylo-mastoid  foramen  it  communicates  with  the 
following  nerves  by  means  of  its  respective  branches :  With  the  auricular  branch 
of  the  pneumogastric  and  auricularis  magnus  of  the  cervical  plexus,  by  the  Pos- 
terior auricular  branch ;  with  the  glosso-pharyngeal,  by  the  digastric ;  with  the 
carotid  plexus,  by  the  stylo-hyoid;  and  with  the  auriculo-temporal,  by  its  tem- 
poral branches. 

BRANCHES  OF  DISTRIBUTION. 

Within  the  aqueductus  Fallopii  . 

,   •  i   (  Posterior  Auricular. 
At  its  exit  from  the  stylo-mastoid  J  j)jgagtric 

ft^n \Stylo-hyoid. 

(  Temporal. 
,  Temporo-facial  <  Malar. 

I  Infra-orbital. 
On  the  face <  fBuccal. 

^  Cervico-facial    <  Supramaxillary. 
(Inframaxillarx . 

The  tympanic  branch  arises  from  the  nerve  opposite  the  pyramid  ;  it  passes 
through  a  small  canal  in  the  pyramid  and  supplies  the  Stapedius  muscle. 

The  chorda  tympani  is  given  off  from  the  facial  as  it  passes  vertically  down- 


THE  SEVENTH   OR    FACIAL    NERVE. 


813 


ward  at  the  back  of  the  tympanum,  about  a  quarter  of  an  inch  before  its  exit 
from  the  stvlo-mastoid  foramen.     It  passes  from  below  upward  and  forward  in  a 


Ganglion  of_ 
Lateral  Root 


Mesial  Root 


(Accessory)  Ventral  Auditory 
Nitcleus 


FIG.  488.— Mode  of  origin  of  auditory  nerve  (diagrammatic).    [The  section  is  dorso-ventrally,  between  pons 
and  medulla.] 

distinct  canal,  and  enters  the  cavity  of  the  tympanum  through  an  aperture  (iter 
chordae  posterius)  on  its  posterior  Avail  between  the  opening  of  the  mastoid  cells 
and  the  attachment  of  the  membrana  tympani,  and  becomes  invested  with  mucous 
membrane.  It  passes  forward  through  the  cavity  of  the  tympanum,  between  the 
handle  of  the  malleus  and  vertical  ramus  of  the  incus,  to  its  anterior  inferior 
angle,  and  emerges  from  that  cavity  through  a  foramen  at  the  inner  end  of  the 
Glaserian  fissure,  which  is  called  the  iter  chordce  anterius,  or  canal  of  Huguier. 
It  then  descends  between  the  two  Pterygoid  muscles,  meets  the  lingual  nerve 
at  an  acute  angle,  and  accompanies  it  to  the  submaxillary  gland ;  part  of  it  then 
joins  the  submaxillary  ganglion ;  the  rest  is  continued  onward  into  the  proper 
muscular  fibres  of  the  tongue — the  Inferior  lingualis  muscle.  A  few  of  its  fibres 
probably  pass  through  the  submaxillary  ganglion  to  the  sublingual  gland.  Before 
joining  the  lingual  nerve  it  receives  a  small  communicating  branch  from  the 
otic  ganglion. 

The  Posterior  auricular  nerve  arises  close  to  the  stylo-mastoid  foramen,  and 
passes  upAvard  in  front  of  the  mastoid  process,  where  it  is  joined  by  a  filament 
from  the  auricular  branch  of  the  pneumogastric,  and  communicates  with  the 
mastoid  branch  of  the  auricularis  magnus  and  with  the  small  occipital.  As  it 
ascends  between  the  meatus  and  mastoid  process  it  divides  into  two  branches. 
The  auricular  branch  supplies  the  Retrahens  aurem  and  the  small  muscles  on  the 
cranial  surface  of  the  pinna.  The  occipital  branch,  the  larger,  passes  backward 
along  the  superior  curved  line  of  the  occipital  bone,  and  supplies  the  occipital 
portion  of  the  Occipito-frontalis. 

The  digastric  branch  usually  arises  by  a  common  trunk  with  the  Stylo-h-yoid 
branch :  it  divides  into  several  filaments,  which  supply  the  posterior  belly  of  the 
Digastric;  one  of  these  perforates  that  muscle  to  join  the  glosso-pharyngeal  nerve. 

The  stylo-hyoid  is  a  long  slender  branch,  which  passes  inward,  entering  the 
Stylo-hyoid  muscle  about  its  middle;  it  communicates  with  the  sympathetic 
filaments  on  the  external  carotid  artery. 

The  Temporo-facial,  the  larger  of  the  two  terminal  branches,  passes  upward 
and  forward  through  the  parotid  glands,  crosses  the  external  carotid  artery  and 


THE  NERVOUS  SYSTEM. 


temporo-maxillary  vein,  and  passes  over  the  neck  of  the  condyle  of  the  jaw,  being 
connected  in  this  situation  with  the  auriculo-temporal  branch  of  the  inferior 
maxillary  nerve,  and  divides  into  branches  which  are  distributed  over  the  temple 
and  upper  part  of  the  face ;  these  are  divided  into  three  sets — temporal,  malar,  and 
infra-orbital. 


Terminatio'iis 
of  snpratrochlear. 

)f  infratrochlear 
of  nasal. 


FIG.  489.— The  nerves  of  the  scalp,  face,  and  side  of  the  neck. 

The  temporal  branches  cross  the  zygoma  to  the  temporal  region,  supplying  the 
Attrahens  and  Attollens  aurem  muscles,  and  join  with  the  temporal  branch  of  the 
temporo-malar,  a  branch  of  the  superior  maxillary,  and  with  the  auriculo-tem- 
poral branch  of  the  inferior  maxillary.  The  more  anterior  branches  supply  the 
frontal  portion  of  the  Occipito-frontalis,  the  Orbicularis  palpebrarum,  and  Corruga- 
tor  supercilii  muscles,  joining  with  the  supra-orbital  and  lachrymal  branches  of 
the  ophthalmic. 

The  malar  branches  pass  across  the  malar  bone  to  the  outer  angle  of  the  orbit, 
where  they  supply  the  Orbicularis  palpebrarum  muscle,  joining  with  filaments  from 
the  lachrymal  nerve;  others  supply  the  lower  eyelid,  joining  with  filaments  of  the 
malar  branch  (subcutaneus  malce)  of  the  superior  maxillary  nerve. 

The  infra-orbital,  of  larger  size  than  the  rest,  pass  horizontally  forward  to  be 
distributed  between  the  lower  margin  of  the  orbit  and  the  mouth.  The  superficial 
branches  run  beneath  the  skin  and  above  the  superficial  muscles  of  the  face,  which 
they  supply  :  some  branches  are  distributed  to  the  Pyramidalis  nasi,  joining  at  the 


THE   SEVENTH    OR   FACIAL    NERVE.  815 

inner  angle  of  the  orbit  with  the  infratrochlear  and  nasal  branches  of  the 
ophthalmic.  The  deep  branches  pass  beneath  the  Zygomatici  and  the  Levator  labii 
superioris.  supplying  them  and  the  Levator  anguli  oris,  and  form  a  plexus  (infra- 
orbital)  by  joining  with  the  mfra-orbital  branch  of  the  superior  maxillary  nerve 
and  the  buccal  branches  of  the  cervico-facial.  This  branch  also  supplies  the 
Levator  labii  superioris  alaeque  nasi  and  the  small  muscles  of  the  nose. 

The  Cervico-facial  division  of  the  facial  nerve  passes  obliquely  downward  and 
:V>rward  through  the  parotid  gland,  crossing  the  external  carotid  artery.  In  this 
situation  it  is  joined  by  branches  from  the  great  auricular  nerve.  Opposite  the 
angle  of  the  lower  jaw  it  divides  into  branches  which  are  distributed  on  the  lower 
half  of  the  face  and  upper  part  of  the  neck.  These  may  be  divided  into  three  sets 
— buccal,  supramaxillary,  and  inframaxillary. 

The  buccal  branches  cross  the  Masseter  muscle.  They  supply  the  Buccinator 
and  Orbicularis  oris,  and  join  with  the  infra-orbital  branches  of  the  temporo-facial 
division  of  the  nerve,  and  with  filaments  of  the  buccal  branch  of  the  inferior 
maxillary  nerve. 

The  supramaxillary  or  mandibular  branches  pass  forward  beneath  the  Platysma 
and  Depressor  anguli  oris.  supplying  the  muscles  of  the  lower  lip  and  chin,  and 
communicating  with  the  mental  branch  of  the  inferior  dental  nerve. 

The  inframaxiUary  or  cervical  branches  run  forward  beneath  the  Platysma, 
and  form  a  series  of  arches  across  the  side  of  the  neck  over  the  suprahyoid 
region.  One  of  these  branches  descends  vertically  to  join  with  the  superficialis 
colli  nerve  from  the  cervical  plexus :  others  supply  the  Platysma. 

Surgical  Anatomy. — The  facial  nerve  is  more  frequently  paralyzed  than  any  of  the  other 
of  the  cranial  nerves.  The  paralysis  may  depend  either  upon  (1)  central  causes — i.  e.  blood-clots 
or  intracranial  tumors  pressing  on  the  nerve  before  its  entrance  into  the  internal  auditory  meat  us. 
It  is  also  one  of  the  nerves  involved  in  "  bulbar  paralysis."  Or  (2)  it  may  be  paralyzed  in  its 
passage  through  the  petrous  bone  by  damage  due  to  middle-ear  disease  or  by  fractures  of  the 
base.  Or  (3)  it  may  be  affected  at  or  after  its  exit  from  the  stylo-mastoid  foramen.  This  is 
commonly  known  as  "  Bell's  paralysis."  It  may  be  due  to  exposure  to  cold  or  to  injury  of  the 
nerve,  either  from  accidental  wounds  of  the  face  or  during  some  surgical  operation,  as  removal 
of  parotid  tumors,  opening  of  abscesses,  or  operations  on  the  lower  jaw. 

The  facial  nerve  is  at  fault  in  cases  of  so-called  "histrionic  spasm,"  which  consists  in  an 
almost  constant  and  uncontrollable  twitching  of  the  muscles  of  the  face.  This  twitching  is 
sometimes  so  severe  as  to  cause  great  discomfort  and  annoyance  to  the  patient  and  to  interfere 
with  sleep,  ami  fur  its  relief  the  facial  nerve  has  been  stretched.  The  operation  is  performed 
by  making  an  incision  behind  the  ear  from  the  root  of  the  mastoid  process  to  the  angle  of  the 
jaw.  The  parotid  is  turned  forward,  and  the  dissection  carried  along  the  anterior  border  of  the 
Sterno-mastotd  muscle  and  mastoid  process  until  the  upper  border  of  the  posterior  belly  of  the 
Digastric  is  found.  The  nerve  is  parallel  to  this  on  about  a  level  of  the  middle  of  the  mastoid 
process.  When  found,  the  nerve  must  be  stretched  by  passing  a  blunt  hook  beneath  it  and 
pulling  it  forward  and  outward.  Too  great  force  must  not  be  used,  for  fear  of  permanent  injury 
to  the  nerve. 

Eighth  Nerve. 

The  Eighth  or  Auditory  Nerve  (portio  mollis)  is  the  special  nerve  of  the  sense 
of  hearing,  being  distributed  exclusively  to  the  internal  ear. 

Its  mperficuU  origin  is  by  two  roots.  One,  the  mesial,  is  from  the  groove 
between  the  olivary  and  restiform  bodies  at  the  lower  border  of  the  pons.  The 
other,  or  lateral  root,  winds  around  the  upper  end  of  the  restiform  body,  dorsally, 
and  joins  the  former  at  its  exit  in  the  groove.  This  root  is  apparently  cont?nuous 
with  the  auditory  striae.  The  nerve,  thus  formed,  lies  external  to  the  facial  nerve. 
Each  root  has  a  deep  origin  :  1.  The  mesial  root  is  traceable  dorsally,  through 
the  substance  of  the  medulla,  lying  close  to  the  mesial  or  attached  surface  of  the 
restiform  body,  to  the  dorsal  auditory  nucleus,  which  lies  immediately  ventral  to 
a  prominence,  the  acoustic  tubercle,  on  the  outer  side  of  the  inferior  fovea  on  the 
floor  of  the  fourth  ventricle.  2.  The  fibres  of  the  lateral  root  are  traceable  dor- 
sally to  four  different  sources:  (a)  To  the  accessory  or  ventral  auditory  nucleus. 
which  lies  close  in  front  of  the  restiform  body  and  between  this  root  and  the 
mesial ;  (6)  to  its  own  ganglion,  or  ganglion  of  the  lateral  root,  situated  among 
the  fibres  where  they  bend  around  the  restiform  body ;  (c)  to  the  auditory  striae ; 


816 


THE   NERVOUS  SYSTEM. 


and  (d)  trapezium  of  the  pons.  The  first-mentioned  origin,  however,  gives  most 
of  the  fibres  (see  Fig.  488).  The  auditory  nerve  passes  forward  across  the  pos- 
terior border  of  the  middle  peduncle  of  the  cerebellum,  in  company  with  the 
facial  nerve,  from  which  it  is  partially  separated  by  a  small  artery  (auditory). 
It  then  enters  the  internal  auditory  meatus,  with  the  facial  nerve  in  a  groove 
along  its  upper  and  fore  part.  At  the  bottom  of  the  meatus  it  receives  one  or 
two  filaments  from  the  facial  nerve,  and  then  divides  into  two  branches,  cochlear 
and  vestibular.  The  auditory  nerve  is  soft  in  texture  (hence  the  name  portio 
mollis),  and  is  destitute  of  neurilemma.  The  distribution  of  the  auditory  nerve 
in  the  internal  ear  will  be  found  described  along  with  the  anatomy  of  that  organ 
in  a  subsequent  page. 

Surgical  Anatomy. — The  auditory  nerve  is  frequently  injured,  together  with  the  facial 
nerve,  in  fractures  of  the  middle  fossa  of  the  base  of  the  skull  implicating  the  internal  auditory 
meatus.  The  nerve  may  be  either  torn  across,  producing  permanent  deafness,  or  it  may  be 
bruised  or  pressed  upon  by  extravasated  blood  or  inflammatory  exudation,  when  the  deafness 
will  in  all  probability  be  temporary.  The  nerve  may  also  be  injured  by  violent  blows  on  the 
head  without  fracture,  and  deafness  may  arise  from  loud  explosions  from  dynamite,  etc. ,  prob- 
ably from  some  lesion  of  this  nerve,  which  is  more  liable  to  be  injured  than  the  other  cranial 
nerves  on  account  of  its  structure.  The  test  that  the  nerve  is  destroyed  and  that  the  deafness  is 
not  due  to  some  lesion  of  the  auditory  apparatus  is  obtained  by  placing  a  vibrating  tuning-fork 
on  the  head.  The  vibrations  will  be  heard  in  cases  where  the  auditory  apparatus  is  at  fault,  but 
not  in  cases  of  destruction  of  the  auditory  nerve. 

Ninth  Pair  (Figs.  490,  491,  492). 

The  Ninth  or  G-losso-pharyngeal  Nerve  is  distributed,  as  its  name  implies,  to 
the  tongue  and  pharynx,  being  the  nerve  of  sensation  to  the  mucous  membrane 
of  the  pharynx,  fauces,  and  tonsil,  and  a  special  nerve  of  taste  to  all  the  parts  of 
the  tongue  to  which  it  is  distributed.  Its  superficial  origin  is  by  three  or  four 
filaments  closely  connected  together,  from  the  upper  part  of  the  medulla  oblon- 
gata,  in  the  groove  between  the  olivary  and  the  restiform  body. 

Its  deep  origin  may  be  traced  through  the  fasciculi  which  lie  betAveen  the 
lateral  and  posterior  areas  of  the  medulla  to  a  nucleus  of  gray  matter  in  the 
lower  part  of  the  floor  of  the  fourth  ventricle,  beneath  the  inferior  fovea,  above 
the  nucleus  of  the  pneumogastric.  From  its  superficial  origin  it  passes  outward 
across  the  flocculus,  and  leaves  the  skull  at  the  central  part  of  the  jugular  fora- 
men, in  a  separate  sheath  of  the  dura  mater,  external  to  and  in  front  of  the 
pneumogastric  and  spinal  accessory  nerves  (Fig.  386).  In  its  passage  through 
the  jugular  foramen  it  grooves  the  lower  border  of  the  petrous  portion  of  the 
temporal  bone,  and  at  its  exit  from  the  skull  passes  forward  between  the  jugular 
vein  and  internal  carotid  artery,  and  descends  in  front  of  the  latter  vessel,  and  be- 
neath the  styloid  process  and  the  muscles  connected  with  it,  to  the  lower  border  of 
the  Stylo-pharyngeus.  The  nerve  now  curves  inward,  forming  an  arch  on  the  side 

of  the  neck,  and  lying  upon  the  Stylo-pharyngeus 
and  Middle  constrictor  of  the  pharynx,  above  the 
superior  laryngeal  nerve.  It  then  passes  beneath 
the  Hyoglossus,  and  is  finally  distributed  to  the  mu- 
cous membrane  of  the  fauces  and  base  of  the  tongue, 
and  the  mucous  glands  of  the  mouth  and  tonsil. 

In  passing  through  the  jugular  foramen  the  nerve 
™>,«,^^  presents,    in    succession,    two    gangliform   enlarge- 

Spinal  accessory.  W  '«„,  ,^  -.&  n     i    ,,        -° 

V%£Va        ments.     The  superior,  the  smaller,  is  called  the  jug- 
c.  ***?**  ular  ganglion  ;  the  inferior  and  larger,  the  petrous 
FIG.  490.— 9th,ioth,andiithneryes,  ganglion,  or  the  gant//it>n  nf  Andefteh. 

their  origin,  ganglia,  and  communica-    '         Vp^  superior>  Qr  jugular,'  ganglion  is  situated  ill  the 

u-pper  part  of  the  groove  in  which  the  nerve  is  lodged 

during  its  passage  through  the  jugular  foramen.  It  is  of  very  small  size,  and 
involves  only  the  lower  part  of  the  trunk  of  the  nerve.  It  is  usually  regarded 
as  a  segmentation  from  the  lower  ganglion. 


^Jugular  ganglion. 
Petrous  ganglion, 
tympanic  br. 


THE   NINTH    OR    GLOSSO-PHARYNGEAL    NERVE. 


81' 


FIG.  491.— Plan  of  the  glosso-pharyngeal,  pneumogastric,  and  spinal  accessor}-  nerves.    (After  Flower.) 


The  inferior,  or  petrous,  ganglion  is  situated  in  a  depression  in  the  lower  bor- 
der of  the  petrous  portion  of  the  temporal  bone ;  it  is  larger  than  the  former  and 


i       '/ 


818  THE  NERVOUS  SYSTEM. 

involves  the  whole  of  the  fibres  of  the  nerve.  From  this  ganglion  arise  those 
filaments  which  connect  the  glosso-pharyngeal  with  the  pneumogastric  and  sym- 
pathetic nerves. 

The  branches  of  communication  are  with  the  pneumogastric,  sympathetic,  and 
facial. 

The  branches  to  the  pneumogastric  are  two  filaments,  arising  from  the  petrous 
ganglion,  one  to  its  auricular  branch,  and  one  to  the  upper  ganglion  of  the 
pneumogastric. 

The  branch  to  the  sympathetic,  also  arising  from  the  petrous  ganglion,  is  con- 
nected with  the  superior  cervical  ganglion. 

The  branch  of  communication  with  the  facial  perforates  the  posterior  belly  of 
the  Digastric.  It  arises  from  the  trunk  of  the  nerve  below  the  petrous  ganglion, 
and  joins  the  digastric  branch  of  the  facial  (see  page  813). 

The  branches  of  distribution  are  the  tympanic,  carotid,  pharyngeal,  muscular, 
tonsillar,  and  lingual. 

The  tympanic  branch  (Jacobsons  nerve)  arises  from  the  petrous  ganglion,  and 
enters  a  small  bony  canal  in  the  lower  surface  of  the  petrous  portion  of  the  tem- 
poral bone,  the  lower  opening  of  which  is  situated  on  the  bony  ridge  which  sep- 
arates the  carotid  canal  from  the  jugular  fossa.  It  ascends  to  the  tympanum, 
enters  that  cavity  by  an  aperture  in  its  floor  close  to  the  inner  wall,  and  divides 
into  branches  which  are  contained  in  grooves  upon  the  surface  of  the  promontory, 
forming  the  tympanic  plexus. 

Its  branches  of  distribution  are — one  to  the  fenestra  rotunda,  one  to  thefenestra 
ovalis,  and  one  to  the  lining  membrane  of  the  tympanum  and  Eustachian  tube 

Its  branches  of  communication  are  three,  and  occupy  separate  grooves  on  the 
surface  of  the  promontory.  One,  the  small  deep  petrosal,  arches  forward  and 
downward  to  the  carotid  canal  (piercing  the  bone)  to  join  the  carotid  plexus.  A 
second,  the  long  petrosal  nerve,  runs  forward  through  a  canal  in  the  processus 
cochleariformis  and  enters  the  foramen  lacerum  medium,  where  it  joins  the 
carotid  plexus  of  the  sympathetic,  and  generally  the  large  superficial  petrosal 
nerve.  The  third  branch  runs  upward  through  the  substance  of  the  petrous  por- 
tion of  the  temporal  bone.  In  its  course  it  passes  by  the  gangliform  enlargement 
of  the  facial  nerve,  and,  receiving  a  connecting  filament  from  it,  becomes  the 
small  superficial  petrosal  nerve.  This  nerve  enters  the  skull  through  a  small 
aperture  situated  external  to  the  hiatus  Fallopii  on  the  anterior  surface  of  the 
petrous  bone,  courses  forward  across  the  base  of  the  skull,  and  emerges  through 
the  petro-sphenoidal  fissure  or  a  foramen  in  the  great  wing  of  the  sphenoid,  and 
joins  the  otic  ganglion. 

The  carotid  branches  descend  along  the  trunk  of  the  internal  carotid  artery 
as  far  as  its  commencement,  communicating  with  the  pharyngeal  branch  of  the 
pneumogastric  and  with  branches  of  the  sympathetic. 

The  pharyngeal  branches  are  three  or  four  filaments  which  unite  opposite  the 
Middle  constrictor  of  the  pharynx  with  the  pharyngeal  branches  of  the  pneumo- 
gastric, the  external  laryngeal,  and  sympathetic  nerves  to  form  the  pharyngeal 
plexus,  branches  from  which  perforate  the  muscular  cdat  of  the  pharynx  to  sup- 
ply the  muscles  and  mucous  membrane. 

The  muscular  branch  is  distributed  to  the  Stylo-pharyngeus. 

The  tonsillar  branches  supply  the  tonsil,  forming  a  plexus  (circulus  tonsillaris) 
around  this  body,  from  which  branches  are  distributed  to  the  soft  palate  and 
fauces,  where  they  communicate  with  the  palatine  nerves. 

The  lingual  branches  (terminal]  are  two:  one  supplies  the  circumvallate  papillae, 
the  mucous  membrane  covering  the  base  of  the  tongue,  and  the  anterior  surface 
of  the  epiglottis ;  the  other  supplies  the  mucous  membrane  of  the  side  of  the 
tongue  for  about  one-half  its  length. 


THE    TENTH   OR    PNEUMOGASTRIC  NERVE. 


819 


Spinal  accessory. 


ryngeal 


laryngeal. 


Tenth  Pair  (Figs.  491,  492). 

The  Tenth  or  Pneumogastric  Nerve  (nervus  vagus  or  par  vagum)  has  a  more 
extensive  distribution  than  any  of  the  other  cranial  nerves,  passing  through  the 
neck  and  thorax  to  the  upper 

part      of     the      abdomen.         It      is  Glosso-pharyngeal. 

composed  of  both  motor  and 
sensory  fibres.  It  supplies  the 
organs  of  voice  and  respiration 
with  motor  and  sensory  fibres, 
and  the  pharynx,  oesophagus, 
stomach,  and  heart  with  motor 
fibres.  Its  superficial  origin  is 
by  eight  or  ten  filaments  from 
the  groove  between  the  olivary 
and  the  restiform  body  below 
the  glosso-pharyngeal ;  its  deep 
origin  may  be  traced  through 
the  fasciculi  of  the  medulla  to 
its  nucleus  of  gray  matter  in  the 
lower  part  of  the  floor  of  the 
fourth  ventricle  beneath  the  ala 
cinerea  below  and  continuous 
with  the  nucleus  of  origin  of 
the  glosso-pharyngeal.  The  fil- 
aments become  united  and  form 
a  flat  cord,  which  passes  outward 
beneath  the  flocculus  to  the  jug- 
ular foramen,  through  which  it 
emerges  from  the  cranium.  In 
passing  through  this  opening  the 
pneumogastric  accompanies  the 
spinal  accessory,  being  contained 
in  the  same  sheath  of  dura  mater 
with  it,  a  membranous  septum 
separating  it  from  the  glosso- 
pharyngeal,  which  lies  in  front 
(Fig.  386).  The  nerve  in  this 
situation  presents  a  well-marked 
ganglionic  enlargement,  which  is 
called  the  jugular  ganglion,  or 
the  ganglion  of  the  root  of  the 
pneumogastric :  to  it  the  acces- 
sory part  of  the  spinal  accessory 
nerve  is  connected  by  one  or  two 
filaments.  After  the  exit  of  the 
nerve  from  the  jugular  foramen 
the  nerve  is  joined  by  the  acces- 
sory portion  of  the  spinal  acces- 
sory, and  enlarged  into  a  second 
gangliform  swelling,  called  the 
ganglion  inferius,  or  the  gan- 
glion of  the  trunk  of  the  nerve, 
over  which  the  fibres  of  the  spi- 
nal accessory  pass  unchanged, 
being  principally  distributed  to  the  pharyngeal  and  superior  laryngeal  branches 
of  the  vagus ;  but  some  of  the  filaments  from  it  are  continued  into  the  trunk  of 


FIG.  492.— Course  and  distribution  of  the  ninth,  tenth,  and 
eleventh  nerves. 


820  THE   NERVOUS  SYSTEM. 

the  vagus  below  the  ganglion,  to  be  distributed  with  the  recurrent  laryngeal 
nerve,  arid  probably  also  with  the  cardiac  nerves.  The  nerve  passes  vertically 
down  the  neck  within  the  sheath  of  the  carotid  vessels  lying  between  the  internal 
carotid  artery  and  internal  jugular  vein  as  far  as  the  thyroid  cartilage,  and  then 
between  the  same  vein  and  the.  common  carotid  to  the  root  of  the  neck.  Here 
the  course  of  the  nerve  becomes  different  on  the  two  sides  of  the  body. 

On  the  right  side  the  nerve  passes  across  the  subclavian  artery  between  it  and 
the  right  innominate  vein,  and  descends  by  the  side  of  the  trachea  to  the  back  part 
of  the  root  of  the  lung,  where  it  spreads  out  in  a  plexiform  network  (posterior  pul- 
monary], from  the  lower  part  of  which  two  cords  descend  upon  the  oesophagus,  on 
which  they  divide,  forming,  with  branches  from  the  opposite  nerve,  the  cesophageal 
plexus  (plexus  gulce);  below,  these  branches  are  collected  into  a  single  cord,  which 
runs  along  the  back  part  of  the  oesophagus,  enters  the  abdomen,  and  is  distributed 
to  the  posterior  surface  of  the  stomach,  joining  the  left  side  of  the  solar  plexus,  and 
sending  filaments  to  the  splenic  plexus  and  a  considerable  branch  to  the  coeliac 
plexus. 

On  the  left  side  the  pneumogastric  nerve  enters  the  chest  between  the  left 
carotid  and  subclavian  arteries,  behind  the  left  innominate  vein.  It  crosses  the 
arch  of  the  aorta  and  descends  behind  the  root  of  the  left  lung,  forming  the  poste- 
rior pulmonary  plexus,  and  along  the  anterior  surface  of  the  oesophagus,  where  it 
unites  with  the  nerve  of  the  right  side  in  forming  the  plexus  guise,  to  the  stomach, 
distributing  branches  over  its  anterior  surface,  some  extending  over  the  great 
cul-de-sac,  and  others  along  the  lesser  curvature.  Filaments  from  these  branches 
enter  the  gastro-hepatic  omentum  and  join  the  hepatic  plexus. 

The  ganglion  of  the  root  is  of  a  grayish  color,  circular  in  form,  about 
two  lines  in  diameter,  and  resembles  the  ganglion  on  the  large  root  of  the  fifth 
nerve. 

Connecting  Branches. — To  this  ganglion  the  accessory  portion  of  the  spinal 
accessory  nerve  is  connected  by  several  delicate  filaments  ;  it  also  has  a  communi- 
cating twig  with  the  petrous  ganglion  of  the  glosso-pharyngeal,  with  the  facial 
nerve  by  means  of  its  (the  ganglion's)  auricular  branch,  and  with  sympathetic 
by  means  of  an  ascending  filament  from  the  superior  cervical  ganglion. 

The  ganglion  of  the  trunk  (inferior)  is  a  plexiform  cord,  cylindrical  in 
form,  of  a  reddish  color,  and  about  an  inch  in  length ;  it  involves  the  whole 
of  the  fibres  of  the  nerve,  and  passing  through  it  is  the  accessory  portion  of 
the  spinal  accessory  nerve,  which  blends  with  the  pneumogastric  below  the 
ganglion,  and  is  then  principally  continued  into  its  pharyngeal  and  superior 
laryngeal  branches. 

Connecting  Branches. — This  ganglion  is  connected  with  the  hypoglossal,  the 
superior  cervical  ganglion  of  the  sympathetic,  and  the  loop  between  the  first  and 
second  cervical  nerves. 

The  branches  of  the  pneumogastric  are — 

In  the  iugular  fossa     .         .         .    <          .    *2 

\  Auricular. 

j  Pharyngeal. 
In  the  neck  J  Superior  laryngeal. 

All     tilt     licCJV  •  •  i  •        \     -T-fc  ,     i  i 

.Recurrent  laryngeal. 
(^Cervical  cardiac. 
|  Thoracic  cardiac. 
In  the  thorax  J  Anterior  pulmonary. 

All     tilt/     t  1 1  <  M  (I  A  *  •  •  »        \      |  ,  •  i 

-Posterior  pulmonary. 
(^(Esophageal. 
In  the  abdomen  ....       Gastric. 

The  meningeal  branch  is  a  recurrent  branch  given  off  from  the  ganglion  of  the 
root  in  the  jugular  foramen.  It  passes  backward,  and  is  distributed  to  the  dura  mater 
covering  the  posterior  fossa  of  the  base  of  the  skull. 


THE    TENTH   OR   PNEUMOGASTRIC  NERVE.  821 

The  auricular  branch  (Arnold's)  arises  from  the  ganglion  of  the  root,  and  is 
joined  soon  after  its  origin  by  a  filament  from  the  petrous  ganglion  of  the  glosso- 
pharvngeal ;  it  passes  outward  behind  the  jugular  vein,  and  enters  a  small  canal 
on  the  outer  wall  of  the  jugular  fossa.  Traversing  the  substance  of  the  temporal 
bone,  it  crosses  the  aqueductus  Fallopii  about  two  lines  above  its  termination  at 
the  stylo-mastoid  foramen ;  here  it  gives  off  an  ascending  branch,  which  joins  the 
facial :  the  continuation  of  the  nerve  reaches  the  surface  by  passing  through  the 
auricular  fissure  between  the  mastoid  process  and  the  external  auditory  meatus,  and 
divides  into  two  branches,  one  of  which  communicates  with  the  posterior  auricular 
nerve,  while  the  other  supplies  the  integument  at  the  back  part  of  the  pinna  and 
the  posterior  part  of  the  external  auditory  meatus. 

The  pharyngeal  branch,  the  principal  motor  nerve  of  the  pharynx,  arises  from 
the  upper  part  of  the  inferior  ganglion  of  the  pneumogastric.  It  consists  principally 
of  filaments  from  the  accessory  portion  of  the  spinal  accessory :  it  passes  across 
the  internal  carotid  artery  (in  front  or  behind)  to  the  upper  border  of  the  Middle 
constrictor,  where  it  divides  into  numerous  filaments,  which  join  with  those  from 
the  glosso-pharyngeal,  superior  laryngeal  (its  external  branch),  and  sympathetic, 
to  form  the  pharyngeal  plexus,  from  which  branches  are  distributed  to  the  muscles 
and  mucous  membrane  of  the  pharynx  and  the  muscles  of  the  soft  palate.  From 
the  pharyngeal  plexus  a  minute  filament  (lingual  branch)  is  given  off,  which 
descends  and  joins  the  hypoglossal  nerve  as  it  winds  round  the  occipital  artery. 

The  superior  laryngeal  is  the  nerve  of  sensation  to  the  larynx.  It  is  larger  than 
the  preceding,  and  arises  from  the  middle  of  the  inferior  ganglion  of  the  pneumo- 
gastric. It  consists  principally  of  filaments  from  the  accessory  portion  of  the  spinal 
accessory.  In  its  course  it  receives  a  branch  from  the  superior  cervical  ganglion 
of  the  sympathetic.  It  descends  by  the  side  of  the  pharynx  behind  the  internal 
carotid,  where  it  divides  into  two  branches,  the  external  and  internal  laryngeal. 

The  external  laryngeal  branch,  the  smaller,  descends  by  the  side  of  the  larynx, 
beneath  the  Sterno-thyroid.  to  supply  the  Crico-thvroid  muscle.  It  gives  branches 
to  the  pharyngeal  plexus  and  the  Inferior  constrictor,  and  communicates  with  the 
superior  cardiac  nerve,  behind  the  common  carotid. 

The  internal  laryngeal  branch  descends  to  the  opening  in  the  thyro-hyoid 
membrane,  through  which  it  passes  with  the  superior  laryngeal  artery,  and  is 
distributed  to  the  mucous  membrane  of  the  larynx.  A  small  branch  communicates 
with  the  recurrent  laryngeal  nerve.  The  branches  to  the  mucous  membrane  are 
distributed,  some  in  front  to  the  epiglottis,  the  base  of  the  tongue,  and  the 
epiglottidean  glands  ;  while  others  pass  backward,  in  the  aryteno-epiglottidean 
fold,  to  supply  the  mucous  membrane  surrounding  the  superior  orifice  of  the 
larynx,  as  well  as  the  membrane  which  lines  the  cavity  of  the  larynx  as  low  down 
as  the  vocal  cord.  The  filament  which  joins  with  the  recurrent  laryngeal  descends 
beneath  the  mucous  membrane  on  the  inner  surface  of  the  thyroid  cartilage,  where 
the  two  nerves  become  united. 

The  inferior  or  recurrent  laryngeal.  so  called  from  its  reflected  course,  is  the 
motor  nerve  of  the  larynx.  It  arises  on  the  right  side,  in  front  of  the  subclavian 
artery :  winds  from  before  backward  round  that  vessel,  and  ascends  obliquely  to 
the  side  of  the  trachea,  behind  the  common  carotid  and  behind  or  in  front  of  tl.e 
inferior  thyroid  artery.  On  the  left  side  it  arises  in  front  of  the  arch  of  the 
aorta,  and  winds  from  before  backward  round  the  aorta  just  beyond  where  the 
remains  of  the  ductus  arteriosus  are  connected  with  it,  and  then  ascends  to  the 
side  of  the  trachea.  The  nerves  on  both  sides  ascend  in  the  groove  between  the 
trachea  and  oesophagus,  and,  passing  under  the  lower  border  of  the  Inferior  con- 
strictor muscle,  enter  the  larynx  behind  the  articulation  of  the  inferior  cornu  of 
the  thyroid  cartilage  with  the  cricoid,  being  distributed  to  all  the  muscles  of  the 
larynx,  except  the  Crico-thyroid.  It  communicates  with  the  Superior  laryngeal 
nerve  and  sends  twigs  to  the  mucous  membrane  below  the  true  cords.  The  recur- 
rent laryngeal,  as  it  winds  round  the  subclavian  artery  and  aorta,  gives  off 
several  cardiac  filaments.  "which  unite  with  the  cardiac  branches  from  the  pneu- 


822  THE  NERVOUS  SYSTEM. 

mogastric  and  sympathetic.  As  it  ascends  in  the  neck  it  gives  off  oesophageal 
branches,  more  numerous  on  the  left  than  on  the  right  side,  which  supply  the 
mucous  membrane  and  muscular  coat  of  the  oesophagus  ;  tracheal  branches  to  the 
mucous  membrane  and  muscular  fibres  of  the  trachea  :  and  some  pharyngeal 
filaments  to  the  Inferior  constrictor  of  the  pharynx. 

The  cervical  cardiac  branches,  two  or  three  in  number,  arise  from  the  pneumo- 
gastric,  at  the  upper  and  lower  part  of  the  neck. 

The  superior  branches  are  small,  and  communicate  with  the  cardiac  branches 
of  the  sympathetic.  They  can  be  traced  to  the  great  or  deep  cardiac  plexus. 

The  inferior  branches,  one  on  each  side,  arise  at  the  lower  part  of  the  neck, 
just  above  the  first  rib.  On  the  right  side  this  branch  passes  in  front  or  by  the 
side  of  the  arteria  innominata,  and  communicates  with  one  of  the  cardiac  nerves 
proceeding  to  the  great  or  deep  cardiac  plexus.  On  the  left  side  it  passes  in  front 
of  the  arch  of  the  aorta  and  joins  the  superficial  cardiac  plexus. 

The  thoracic  cardiac  branches,  on  the  right  side,  arise  from  the  trunk  of  the 
pneumogastric  as  it  lies  by  the  side  of  the  trachea,  and  from  its  recurrent  laryngeal 
branch,  but  on  the  left  side  from  the  recurrent  nerve  only;  passing  inward,  they 
terminate  in  the  deep  cardiac  plexus. 

The  anterior  pulmonary  branches,  two  or  three  in  number,  and  of  small 
size,  are  distributed  on  the  anterior  aspect  of  the  root  of  the  lungs.  They  join 
with  filaments  from  the  sympathetic,  and  form  the  anterior  pulmonary  plexus. 

The  posterior  pulmonary  branches,  more  numerous  and  larger  than  the  anterior, 
are  distributed  on  the  posterior  aspect  of  the  root  of  the  lung,  some  filaments 
going  to  the  pericardium  ;  they  are  joined  by  filaments  from  the  third  and  fourth 
(sometimes  also  first  and  second)  thoracic  ganglia  of  the  sympathetic,  and  form 
the  posterior  pulmonary  plexus.  Branches  from  both  plexuses  accompany  the 
ramification  of  the  air-tubes  through  the  substance  of  the  lungs. 

o  o 

The  oesophageal  branches  are  given  off  from  the  pneumogastric  both  above 
and  below  the  pulmonary  branches.  The  lower  are  more  numerous  and  larger 
than  the  upper.  They  form,  together  with  branches  from  the  opposite  nerve,  the 
oesophageal  plexus,  or  plexus  gulce,  which  also  supplies  the  pericardium. 

The  gastric  branches  are  the  terminal  filaments  of  the  pneumogastric  nerve. 
The  nerve  on  the  right  side  is  distributed  to  the  posterior  surface  of  the  stomach, 
and  joins  the  left  side  of  the  coeliac  plexus  and  the  splenic  plexus.  The  nerve 
on  the  left  side  is  distributed  over  the  anterior  surface  of  the  stomach,  some 
filaments  passing  across  the  great  cul-de-sac,  and  others  along  the  lesser  curvature. 
They  unite  with  branches  of  the  right  nerve  and  with  the  sympathetic,  some  fila- 
ments passing  through  the  lesser  omentum  to  the  hepatic  plexus. 

Surgical  Anatomy. — The  laryngeal  nerves  are  of  considerable  importance  in  considering 
some  of  the  morbid  conditions  of  the  larynx.  When  the  peripheral  terminations  of  the  superior 
laryngeal  nerve  are  irritated  by  some  foreign  body  passing  over  them,  reflex  spasm  of  the  glottis 
is  the  result.  When  the  trunk  of  this  same  nerve  is  pressed  upon  by,  for  instance,  a  goitre  or 
an  aneurism  of  the  upper  part  of  the  carotid,  we  have  a  peculiar  dry,  brassy  cough.  When  the 
nerve  is  paralyzed,  we  have  anaesthesia  of  the  mucous  membrane  of  the  larynx,  so  that  foreign 
bodies  can  readily  enter  the  cavity,  and,  in  consequence  of  its  supplying  the  crico-thyroid  muscle, 
the  vocal  cords  cannot  be  made  tense,  and  the  voice  is  deep  and  hoarse.  Paralysis  of  the 
superior  laryngeal  nerves  may  be  the  result  of  bulbar  paralysis,  may  be  a  sequel  to  diphtheria, 
when  both  nerves  are  usually  involved,  or  it  may,  though  less  commonly,  be  caused  by  the 
pressure  of  tumors  or  aneurisms,  when  the  paralysis  is  generally  unilateral.  Irritation  of  the 
inferior  laryngeal  nerves  produces  spasm  of  the  muscles  of  the  larynx.  When  both  these 
recurrent  nerves  are  paralyzed,  the  vocal  cords  are  motionless,  in  the  so-called  "cadaveric  posi- 
tion " — that  is  to  say,  in  the  position  in  which  they  are  found  in  ordinary  tranquil  respiration — 
neither  closed  as  in  phonation,  nor  open  as  in  deep  inspiratory  eiforts.  When  one  recurrent 
nerve  is  paralyzed,  the  cord  of  the  same  side  is  motionless,  while  the  opposite  one  crosses  the 
middle  line  to  accommodate  itself  to  the  affected  one ;  hence  phonation  is  present,  but  the  voice 
is  altered  and  weak  in  timbre.  The  recurrent  laryngeal  nerves  may  be  paralyzed  in  bulbar 
paralysis  or  after  diphtheria,  when  it  usually  affects  both  sides ;  or  they  may  be  affected  by  the 
pressure  of  aneurisms  of  the  aorta,  innominate  or  subclavian  arteries  ;  by  mediastinal  tumors  ; 
by  bronchocele  ;  or  by  cancer  of  the  upper  part  of  the  oesophagus,  when  the  paralysis  is  often 
unilateral. 


THE  ELEVENTH   OR   SPINAL    ACCESSORY  NERVE. 

Eleventh  Pair  (Figs.  491,  492). 

The  Eleventh  or  Spinal  Accessory  Nerve  consists  of  two  parts — one  the  acces- 
sory part  to  the  vagus,  and  the  other  the  spinal  portion. 

The  accessory  part  is  the  smaller  of  the  two.  Its  superficial  origin  is  by  four 
or  five  delicate  filaments  from  the  side  of  the  medulla,  below  the  roots  of  the  vagus. 
Its  deep  origin  may  be  traced  to  a  nucleus  of  gray  matter  in  the  medulla,  just 
dorsal  to  the  lower  third  of  the  olive  and  dorso-lateral  to  the  hypoglossal 
nucleus.  It  passes  outward  to  the  jugular  foramen,  where  it  joins  with  the 
spinal  portion,  and  is  connected  with  the  upper  ganglion  of  the  vagus  by  one  or 
two  filaments.  It  then  separates  from  the  spinal  portion,  passes  through  the 
foramen,  and  is  continued  over  but  adherent  to  the  surface  of  the  inferior  gan- 
glion, or  ganglion  of  the  trunk  of  the  vagus,  to  be  distributed  principally  to  the 
pharyngeal  and  superior  laryngeal  branches  of  the  pneumogastric.  Through  the 
pharyngeal  branch  it  probably  supplies  the  muscles  of  the  soft  palate  (see  page 
425).  Some  few  filaments  from  it  are  continued  into  the  trunk  of  the  vagus 
below  the  ganglion,  to  be  distributed  with  the  recurrent  laryngeal  nerve  and 
probably  also  with  the  cardiac  nerves. 

The  spinal  portion  is  firm  in  texture.  Its  superficial  origin  is  by  several  fila- 
ments from  the  lateral  tract  of  the  cord,  as  low  down  as  the  sixth  cervical  nerve. 
Its  deep  orijin  may  be  traced  to  the  intermedio-lateral  tract  (lateral  horn)  of  the 
gray  matter  of  the  cord,  where  it  forms  a  column  of  cells  reaching,  above,  to  the 
lower  end  of  the  nucleus  of  the  accessory  part  of  the  nerve.  This  portion  of  the 
nerve  ascends  between  the  ligamentum  denticulatum  and  the  posterior  roots  of 
the  spinal  nerves,  enters  the  skull  through  the  foramen  magnum,  and  is  then 
directed  outward  to  the  jugular  foramen,  through  which  it  passes,  lying  in  the  same 
sheath  as  the  pneumogastric,  but  separated  from  it  by  a  fold  of  the  arachnoid.  In  the 
jugular  foramen  it  joins  with  the  accessory  portion.  At  its  exit  from  the  jugular 
foramen  it  passes  backward,  either  in  front  of  or  behind  the  internal  jugular  vein, 
and  descends  obliquely  behind  the  Digastric  and  Stylo-hyoid  muscles  to  the  upper 
part  of  the  Sterno-mastoid.  It  pierces  that  muscle,  and  passes  obliquely  across 
the  occipital  triangle,  to  terminate  in  the  deep  surface  of  the  Trapezius.  This 
nerve  gives  several  branches  to  the  Sterno-mastoid  during  its  passage  through  it, 
and  joins  in  its  substance  with  branches  from  the  second  cervical,  which  supply 
the  muscle.  In  the  occipital  triangle  it  joins  with  the  second  and  third  cervical 
nerves  and  assists  in  the  formation  of  the  cervical  plexus.  Beneath  the  Trapezius 
it  joins  with  the  third  and  fourth  cervical  nerves  to  form  a  sort  of  plexus,  from 
which  fibres  are  distributed  to  the  muscle. 

Surgical  Anatomy. — In  cases  of  spasmodic  torticollis  in  which  all  palliative  treatment  has 
failed,  division  or  excision  of  a  portion  of  the  spinal  accessory  nerve  has  oeen  resorted  to.  This 
may  be  done  either  along  the  anterior  or  posterior  border  of  the  Sterno-mastoid  muscle.  The 
former  operation  is  performed  by  making  an  incision  from  the  apex  of  the  mastoid  process, 
three  inches  in  length,  along  the  anterior  border  of  the  Sterno-mastoid  muscle.  The  anterior 
border  of  the  muscle  is  defined  and  pulled  backward,  so  as  to  stretch  the  nerve,  which  is  then  to 
be  sought  for  beneath  the  Digastric  muscle,  about  two  inches  below  the  apex  of  the  mastoid 
process.  The  other  operation  consists  in  making  an  incision  along  the  posterior  border  of  the 
muscle,  so  that  the  centre  of  the  incision  corresponds  to  the  middle  of  this  border  of  the  mus- 
cle. The  superficial  structures  having  been  divided  and  the  border  of  the  muscle  defined,  the 
nerve  is  to  be  sought  for  as  it  emerges  from  the  muscle  to  cross  the  occipital  triangle.  When 
found,  it  is  to  be  traced  upward  through  the  muscle,  and  a  portion  of  it  excised  above  the  point 
where  it  gives  off  its  branches  to  the  Sterno-mastoid.  In  this  operation  one  of  the  descending 
branches  of  the  superficial  cervical  plexus  is  liable  to  be  mistaken  for  the  nerve. 

Twelfth  Pair  (Fig.  493). 

The  Twelfth  or  Hypoglossal  Nerve  is  the  motor  nerve  of  the  tongue.  Its 
superficial  origin  is  by  several  filaments,  from  ten  to  fifteen  in  number,  from  the 
groove  between  the  pyramid  and  olivary  body,  in  a  continuous  line  with  the 
anterior  roots  of  the  spinal  nerves.  Its  deep  origin  can  be  traced  to  a  nucleus  of 
gray  matter  lying  under  the  lower  part  of  the  fasciculus  teres  (trigonum  hypo- 


824 


THE   NERVOUS  SYSTEM. 


Communication  between  1st  and  2d 
Cervical  Nerves  and  Hypoglossal 


glossi)  in  the  floor  of  the  fourth  ventricle,  and   extending   downward    into  the 
closed  portion  of  the  medulla.     The  filaments  of  this  nerve  are  collected  into  two 

bundles  which  perforate  the  dura 
mater  separately,  opposite  the  an- 
terior condyloid  foramen,  and 
unite  together  after  their  passage 
through  it.  In  those  cases  in 
which  the  anterior  condyloid  for- 
amen in  the  occipital  bone  is 
double  these  two  portions  of  the 
nerve  are  separated  by  the  small 
piece  of  bone  which  divides  the 
foramen.  The  nerve  descends  al- 
most vertically  to  a  point  corre- 
sponding with  the  angle  of  the 
jaw.  It  is  at  first  deeply  seated 
beneath  the  internal  carotid  artery 
and  internal  jugular  vein,  and  in- 
timately connected  with  the  pneu- 
mogastric nerve ;  it  then  passes 
forward  between  the  vein  and 
artery,  and  lower  down  in  the 
neck  becomes  superficial  below 
the  Digastric  muscle.  The  nerve 
then  loops  round  the  occipital 
artery,  the  sterno-mastoid  branch 
of  which  hooks  over  the  nerve, 
and  crosses  the  external  carotid 
and  its  lingual  branch  below  the 
tendon  of  the  Digastric  muscle. 

It  then  passes  beneath  the  tendon  of  the  digastric,  the  stylo-hyoid,  and  the  Mylo- 
hyoid  muscles,  lying  on  the  Hyo-glossus,  accompanied  by  the  ranine  vein,  and 
communicates  at  the  anterior  border  of  the  latter  muscle  with  the  lingual  (gusta- 
tory) nerve ;  it  is  then  continued  forward  in  the  fibres  of  the  Genio-hyo-glossus 
muscle  as  far  as  the  tip  of  the  tongue,  distributing  branches  to  its  substance. 
The  branches  of  communication  are — with  the 


Infra-hyoid  Muscles 

FIG.  493.— Plan  of  communicantes  and  descendens  hypo 
i  nerves. 


Pneumogastric. 
Sympathetic. 


First  and  Second  Cervical  Nerves. 
Lingual  (gustatory). 


The  first  mentioned  takes  place  close  to  the  exit  of  the  nerve  from  the  skull, 
numerous  filaments  passing  between  the  hypoglossal  and  lower  ganglion  of  the 
pneumogastric  through  the  mass  of  connective  tissue  which  here  unites  the  two 
nerves.  It  also  communicates  with  the  pharyngeal  plexus  by  a  minute  filament 
as  it  winds  round  the  occipital  artery  (lingual  branch,  see  page  821). 

The  communication  with  the  sympathetic  takes  place  opposite  the  atlas  by 
branches  derived  from  the  superior  cervical  ganglion,  and  in  the  same  situation 
the  nerve  is  joined  by  filaments  derived  from  the  loop  connecting  the  first  two 
cervical  nerves. 

The  communication  with  the  lingual  (gustatory)  takes  place  near  the  anterior 
border  of  the  Hyo-glossus  muscle  by  numerous  filaments  which  ascend  upon  it. 

The  branches  of  distribution  are — the 


Meningeal. 
Descendens  hypoglossi. 


Thyro-hyoid. 
Muscular. 


Meningeal  Branches. — As  the  hypoglossal  nerve  passes  through  the  anterior 


THE    TWELFTH   OR    HYPOGLOSSAL    NERVE. 


825 


condyloid  foramen  it  gives  off,  according  to  Luschka,  several  filaments  (recurrent) 
to  the  dura  mater  in  the  posterior  fossa  of  the  base  base  of  the  skull. 

The  descendens  hypoglossi  is  a  long  slender  branch  which  quits  the  hypoglossal 
where  it  turns  round  the  occipital  artery.  It  descends  obliquely  across  the  sheath 
of  the  carotid  vessels,  and  joins  the  communicating  branches  from  the  second  and 
third  cervical  nerves,  just  below  the  middle  of  the  neck,  to  form  a  loop.  From  the 
convexity  of  this  loop  branches  pass  forward  to  supply  the  Sterno-hyoid,  Sterno- 
thyroid,  and  both  bellies  of  the  Omo-hyoid.  According  to  Arnold,  another  filament 
descends  in  front  of  the  vessels  into  the  chest  and  joins  the  cardiac  and  phrenic 
nerves.  The  descendens  hypoglossi  is  occasionally  contained  in  the  sheath  of  the 
carotid  vessels,  being  sometimes  placed  over,  and  sometimes  beneath,  the  internal 


•'*\       ,  Hypo-glossal  nen-e. 

PHtniinogastric  nerve. 


FIG.  4W.— Hypoglossal  nerve,  cervical  plexus,  and  their  branches. 

jugular  vein.  The  fibres  of  this  nerve  are  chiefly  derived  from  the  first  and 
second  cervical  nerves  by  means  of  the  filaments  of  communication  already  men- 
tioned. 

The  thyro-hyoid  is  a  small  branch  arising  from  the  hypoglossal  near  the  poste- 
rior border  of  the  Hyo-glossus ;  it  passes  obliquely  across  the  great  cornu  of  the 
hyoid  bone  and  supplies  the  Thyro-hyoid  muscle. 

The  muscular  branches  are  distributed  to  the  Stylo-glossus,  Hyo-glossus,  Genio- 
hyoid.  and  Genio-hyo-glossus  muscles.  At  the  under  surface  of  the  tongue  numer- 
ous slender  branches  pass  upward  into  the  substance  of  the  organ  to  supply  its 
muscular  structure. 

Surgical  Anatomy. — The  hypoglossal  nerve  is  an  important  guide  in  the  operation  of  liga- 
ture of  the  lingual  artery  (see  page  553). 


826  THE  NERVOUS  SYSTEM. 

THE   SPINAL  NERVES. 

The  spinal  nerves  are  so  called  because  they  take  their  origin  from  the  spinal 
cord,  and  are  transmitted  through  the  intervertebral  foramina  on  either  side  of  the 
spinal  column.  There  are  thirty-one  pairs  of  spinal  nerves,  which  are  arranged 
into  the  following  groups,  corresponding  to  the  region  of  the  spine  through  which 
they  pass : 

Cervical 8  pairs. 

Dorsal 12     " 

Lumbar  . 5     " 

Sacral 5      " 

Coccygeal 1  pair. 

It  will  be  observed  that  each  group  of  nerves  corresponds  in  number  with  the 
vertebne  in  that  region,  except  the  cervical  and  coccygeal. 

Each  spinal  nerve  arises  by  two  roots,  an  anterior  or  motor  root,  and  a  pos- 
terior or  sensory  root. 

Roots  of  the  Spinal  Nerves. 

The  Anterior  Roots. — The  superficial  origin  is  from  a  somewhat  irregular  series 
of  depressions  which  map  out  a  longitudinal  area  opposite  the  anterior  cornu  of 
gray  matter  on  the  antero-lateral  column  of  the  spinal  cord,  gradually  approach- 
ing toward  the  anterior  median  fissure  as  they  descend.  To  the  deep  origin  the 
fibres  can  be  traced  through  the  antero-lateral  column  ;  the  roots,  after  penetrat- 
ing horizontally  through  the  longitudinal  fibres  of  this  tract,  enter  the  gray  sub- 
stance of  the  anterior  cornu,  where  their  fibrils  diverge  in  several  directions  : 
some,  passing  inward,  are  continued  across  the  anterior  commissure  in  front  of 
the  central  canal,  to  become  continuous  with  the  axis-cylinder  processes  of  the 
large  cells  of  the  anterior  cornu  of  the  opposite  side ;  others  terminate  in  the 
mesial  group  of  cells  of  the  anterior  column  of  the  same  side ;  other  fibrils  pass 
outward,  some  to  become  continuous  with  the  axis-cylinder  processes  of  the  group 
of  cells  in  the  lateral  part  of  the  anterior  column ;  and  others  enter  the  lateral 
column  of  the  same  side,  where,  turning  upward,  they  pursue  their  course  as 
longitudinal  fibres.  The  remaining  fibrils  pass  backward  to  the  posterior  horn, 
where  they  are  continuous  with  the  axis-cylinders  of  the  cells  at  the  base  of  the 
posterior  cornu. 

The  Posterior  Boots. — The  superficial  origin  is  from  the  postero-lateral  fissure 
of  the  cord.  The  deep  origin  is  from  the  gray  substance  of  the  posterior  cornu, 
either  directly  through  the  substantia  gelatinosa,  or  indirectly,  by  first  passing 
through  the  white  matter  of  the  posterior  column  and  winding  round  in  front  of 
the  caput  cornu.  Those  which  enter  the  gray  matter  at  once  for  the  most  part 
turn  upward  and  downward,  and  become  continuous  with  the  fine  nerve-plexus  in 
the  central  portion  of  the  gray  matter ;  some  few  fibres  pass  transversely  through 
the  posterior  commissure  to  the  opposite  side,  and  others  into  the  anterior  cornu 
of  the  same  side.  Those  fibres  which  enter  the  gray  matter  in  front  of  the  caput 
cornu  reach  the  posterior  vesicular  column  (Clark's  column)  and  blend  with  it,  a 
few  fibres  passing  through  it,  to  become  longitudinal  in  the  posterior  column  of 
the  cord. 

The  anterior  roots  are  smaller  than  the  posterior,  devoid  of  ganglionic  enlarge- 
ment, and  their  component  fibrils  are  collected  into  two  bundles  near  the  inter- 
vertebral  foramina. 

The  posterior  roots  of  the  nerves  are  larger,  but  the  individual  filaments  are 
finer  and  more  delicate  than  those  of  the  anterior.  As  their  component  fibrils 
pass  outward,  toward  the  aperture  in  the  dura  mater,  they  coalesce  into  two  bun- 
dles, receive  a  tubular  sheath  from  that  membrane,  and  enter  the  ganglion  which 
is  developed  upon  each  root. 

The  posterior  root  of  the  first  cervical  nerve  forms  an  exception  to  these  cha- 
racters. It  is  smaller  than  the  anterior,  has  frequently  no  ganglion  developed 
upon  it,  and  when  the  ganglion  exists  it  is  often  situated  within  the  dura  mater. 


THE   SPIRAL    SERVE*. 


827 


Ganglia  of  the  Spinal  Nerves. 

A  ganglion  is  developed  upon  the  posterior  root  of  each  of  the  spinal  nerves. 
These  cranglia  are  of  an  oval  form  and  of  a  reddish  color ;  they  bear  a  proportion 
in  size  to  the  nerves  upon  which  they  are  formed,  and  are  placed  in  the  interver- 
tebral  foramina,  external  to  the  point  where  the  nerves  perforate  the  dura 
mater.  Each  ganglion  is  bifid  internally,  where  it  is  joined  by  the  two  bundles 
of  the  posterior  root,  the  two  portions  being  united  into  a  single  mass  externally. 
The  ganglion  upon  the  first  and  second  cervical  nerves  forms  an  exception  to 
these  characters,  being  placed  on  the  arches  of  the  vertebrae  over  which  the  nerves 
pass.  The  ganglia,  also,  of  the  sacral  nerves  are  placed  within  the  spinal  canal ;  and 
that  on  the  coccygeal  nerve,  also  in  the  canal,  about  the  middle  of  its  posterior  root. 

DISTRIBUTION  OF  THE  SPINAL  XERYES. 

Immediately  beyond  the  ganglion  the  two  roots  coalesce,  their  fibres  inter- 
mingle, and  the  trunk  thus  formed  passes  out  of  the  intervertebral  foramen,  and 
divides  into  a  posterior  division  for  the  supply  of  the  posterior  part  of  the  body, 
and  an  anterior  division  for  the  supply  of  the  anterior  part  of  the  body,  each  con- 
taining fibres  from  both  roots.  Before  division  each  trunk  gives  off  a  recurrent 
branch  to  the  dura  mater  of  the  cord. 

The  posterior  divisions  of  the  spinal  nerves  are  generally  smaller  than  the 
anterior ;  they  arise  from  the  trunk  resulting  from  the  union  of  the  roots  in 
the  intravertebral  foramina,  and,  passing  backward,  divide  into  internal  and 
external  branches,  which  are  distributed  to  the  muscles  and  integument  behind 
the  spine.  The  first  cervical,  the  fourth  and  fifth  sacral,  and  the  coccygeal 
nerves  are  exceptions  to  these  characters. 

The  anterior  divisions  of  the  spinal  nerves  supply  the  parts  of  the  body  in  front 
of  the  spine,  including  the  limbs.  They  are  for  the  most  part  larger  than  the 
posterior  divisions.  Each  division  is  connected  Avith  the  sympathetic  by  slender 
filaments  from  which  a  communicating  branch  runs  to  the  recurrent  filament  from 
the  trunk.  In  the  dorsal  region  the  anterior  divisions  of  the  spinal  nerves  are 
completely  separate  from  each  other,  and  are  uniform  in  their  distribution ;  but 
in  the  cervical,  lumbar,  and  sacral  regions  they  form  intricate  plexuses  previous 
to  their  distribution. 

Points  of  Emergence  of  the  Spinal  Nerves. 

The  roots  of  the  spinal  nerves  from  their  origin  in  the  cord  run  obliquely 
downward  to  their  point  of  exit  from  the  intervertebral  foramina,  the  amount  of 
obliquity  varying  in  different  regions  of  the  spine,  and  being  greater  in  the  lower 
than  the  upper  part.  The  level  of  their  emergence  from  the  cord  is  within  certain 


Level  of                                             Level  of  tip                Level  of         j     „       fv^ 
Body  of                                                of  Spine  of                Body  of              No.  of  Nerve. 

Level  of  tip 
of  Spine  of 

C.  1                         C.  1 

_ 

D.  8 

9 

7  d. 

f 

2 

— 

9                       10 

8  d. 

I 

3 

1  c. 

10                        11 

9  d. 

3 

4 

2c. 

—                        12 

10  d. 

4 

5 

3c. 

11                    L.  1 

11  d. 

5 

6 

4c. 

2 

— 

6 

7 
8 

5  c. 
6c. 

3 
4 

' 

>  12  d. 

7 
D.  1 

D.  1 

2 

7  c. 
Id. 

\ 

5 
S.I 

: 

•- 

2 

3 

— 

L.  l\ 

2 

3 

4 

2d. 

3 

4 

5 

3d. 

L 

4 

-   1L. 

5 

6 

4d. 

5 

6 

7 

5d. 

— 

G.  1 

i 

8 

6  d.                      L.  2 

— 

— 

828  THE  NERVOUS  SYSTEM. 

limits  variable,  and  of  course  does  not  correspond  to  the  point  of  emergence  of 
the  nerve  from  the  intervertebral  foramina.  The  preceding  table,  from  Mac- 
alister,  shows  as  accurately  as  can  be  shown  the  relation  of  these  points  of  origin 
from  the  spinal  cord  to  the  bodies  and  spinous  processes  of  the  vertebrae. 

THE  CERVICAL  NERVES. 

The  roots  of  the  cervical  nerves  increase  in  size  from  the  first  to  the  fifth,  and 
then  remain  the  same  size  to  the  eighth.  The  posterior  roots  bear  a  proportion 
to  the  anterior  as  3  to  1,  which  is  much  greater  than  in  any  other  region,  the 
individual  filaments  being  also  much  larger  than  those  of  the  anterior  roots.  In 
direction  the  roots  of  the  cervical  are  less  oblique  than  those  of  the  other  spinal 
nerves.  The  first  cervical  nerve  is  directed  a  little  upward  and  outward ;  the 
second  is  horizontal ;  the  others  are  directed  obliquely  downward  and  outward, 
the  lowest  being  the  most  oblique,  and  consequently  longer  than  the  upper,  the 
distance  between  their  place  of  origin  and  their  point  of  exit  from  the  spinal  canal 
never  exceeding  the  depth  of  one  vertebra. 

The  trunk  of  the  first  cervical  nerve  (suboccipitaT)  leaves  the  spinal  canal  between 
the  occipital  bone  and  the  posterior  arch  of  the  atlas ;  the  second,  between  the 
posterior  arch  of  the  atlas  and  the  lamina  of  the  axis ;  and  the  eighth  (the  last), 
between  the  last  cervical  and  first  dorsal  vertebrae. 

Each  nerve,  at  its  exit  from  the  intervertebral  foramen,  divides  into  a  posterior 
and  an  anterior  division.    The  anterior  divisions  of  the  four  upper  cervical  nerves . 
form  the  cervical  plexus.    The  anterior  divisions  of  the  four  lower  cervical  nerves, 
together  with  the  first  dorsal,  form  the  brachial  plexus. 

Posterior  Divisions  of  the  Cervical  Nerves  (Fig.  495). 

The  posterior  division  of  the  first  cervical  (subocdpitaT)  nerve  differs  from  the 
posterior  divisions  of  the  other  cervical  nerves  in  not  dividing  into  an  internal 
and  external  branch.  It  is  larger  than  the  anterior  division,  and  escapes  from  the 
spinal  canal  between  the  occipital  bone  and  the  posterior  arch  of  the  atlas,  lying 
behind  the  vertebral  artery./  It  enters  the  suboccipital  triangle  formed  by  the 
Rectus  capitis  posticus  major,  the  Obliquus  superior,  and  Obliquus  inferior,  and 
supplies  the  Recti  and  Obliqui  muscles,  and  the  Complexus.  From  the  branch 
which  supplies  the  Inferior  oblique  a  filament  is  given  off  which  joins  the  second 
cervical  nerve.  This  nerve  also  occasionally  gives  off  a  cutaneous  filament,  which 
accompanies  the  occipital  artery  and  communicates  with  the  occipitalis  major  and 
minor  nerves. 

The  posterior  division  of  the  second  cervical  nerve  is  three  or  four  times  greater 
than  the  anterior  division,  and  the  largest  of  all  the  posterior  cervical  divisions. 
It  emerges  from  the  spinal  canal  between  the  posterior  arch  of  the  atlas  and 
lamina  of  the  axis,  below  the  Inferior  oblique.  It  supplies  this  muscle,  and 
receives  a  communicating  filament  from  the  first  cervical.  It  then  divides  into  an 
internal  and  external  branch. 

The  internal  branch,  called,  from  its  size  and  distribution,  the  occipitalis  major, 
ascends  obliquely  inward  between  the  Obliquus  inferior  and  Complexus,  and  pierces 
the  latter  muscle  and  the  Trapezius  near  their  attachments  to  the  cranium.  It  is  now 
joined  by  a  filament  (third  occipital)  from  the  posterior  division  of  the  third  cervical 
nerve,  and,  ascending  on  the  back  part  of  the  head  with  the  occipital  artery,  di- 
vides into  two  branches,  which  supply  the  integument  of  the  scalp  as  far  forward 
as  the  vertex,  communicating  with  the  occipitalis  minor.  It  gives  off  an  auricular 
branch  to  the  back  part  of  the  ear  and  muscular  branches  to  the  Complexus. 
The  external  branch  is  often  joined  by  the  external  branch  of  the  posterior 
division  of  the  third,  and  supplies  the  Splenius,  Trachelo-mastoid,  and  Complexus. 

The  posterior  division  of  the  third  cervical  is  smaller  than  the  preceding,  but 
larger  than  the  fourth ;  it  differs  from  the  posterior  divisions  of  the  remaining 
cervical  nerves  in  its  supplying  an  additional  filament,  the  third  occipital  nerve, 


THE   CERVICAL   NERVES.  *29 

to  the  integument  of  the  occiput.  The  posterior  division  of  the  third  nerve,  like 
the  others,  divides  into  an  internal  and  external  branch.  The  internal  branch 
passes  between  the  Complexus  and  Semispinalis,  and,  piercing  the  Splenius  and 
Trapezius,  supplies  the  skin  over  the  latter  muscle  ;  the  external  branch  joins  with 
that  of  the  posterior  division  of  the  second  to  supply  the  Splenius,  Trachelo-mas- 
toid,  and  Complexus. 

The  third  occipital  nerve  arises  from  the  internal  or  cutaneous  branch  beneath 
the  Trapezius ;  it  then  pierces  that  muscle,  and  supplies  the  skin  on  the  lower  and 


FIG.  495.— Posterior  divisions  of  the  upper  cervical  nerves. 

back  part  of  the  head.  It  lies  to  the  inner  side  of  the  occipitalis  major,  with 
which  it  is  connected. 

The  posterior  division  of  the  suboccipital  nerve  and  the  internal  branches  of 
the  posterior  divisions  of  the  second  and  third  cervical  nerves  are  occasionally 
joined  beneath  the  Complexus  by  communicating  branches.  This  communication 
is  described  by  Cruveilhier  as  the  posterior  cervical  plexus. 

The  posterior  divisions  of  the  fourth,  fifth,  sixth,  seventh,  and  eighth  cervical 
nerves  (Fig.  502)  pass  backward,  and  divide,  behind  the  Posterior  intertransverse 


830  THE  NERVOUS  SYSTEM. 

muscles,  into  internal  and  external  branches.  The  internal  branches,  the  larger, 
are  distributed  differently  in  the  upper  and  lower  part  of  the  neck.  Those 
derived  from  the  fourth  and  fifth  nerves  pass  between  the  Com  plexus  and  Semi- 
spinalis  muscles,  and,  having  reached  the  spinous  processes,  perforate  the 
aponeurosis  of  the  Splenius  and  Trapezius,  and  are  continued  outward  to  the 
integument  over  the  Trapezius,  whilst  those  derived  from  the  three  lowest  cervical 
nerves  are  the  smallest,  and  are  placed  beneath  the  Semispinalis  colli,  Avhich  they 
supply,  and  then  pass  into  the  Interspinales,  Multifidus  spinse,  and  Complexus, 
and  send  twigs  through  this  latter  muscle  to  supply  the  integument  near  the 
spinous  processes  (Hirschfeld).  The  external  branches  supply  the  muscles  at  the 
side  of  the  neck — viz.  the  Cervicalis  ascendens,  Transversalis  colli,  and  Trachelo- 
mastoid. 

Anterior  Divisions  of  the  Cervical  Nerves. 

The  anterior  division  of  the  first  or  suboccipital  nerve  is  of  small  size.  It 
escapes  from  the  spinal  canal  through  a  groove  upon .  the  posterior  arch  of  the 
atlas.  In  this  groove  it  lies  beneath  the  vertebral  artery,  to  the  inner  side  of 
the  Rectus  capitis  lateralis.  As  it  crosses  the  foramen  in  the  transverse  process 
of  the  atlas  it  receives  a  filament  from  the  sympathetic  on  the  vertebral  artery. 
It  then  descends,  in  front  of  this  process,  to  j^in  with  the  ascending  branch  from 
the  second  cervical  nerve. 

Communicating  filaments  from  the  loop  between  this  nerve  and  the  second 
join  the  pneumogastric,  the  hypoglossal,  and  sympathetic'  (superior_jcervical 
ganglion),  and  some  branches  are  distributed  to  the  Rectus  lateraTis~and  the  two 
Anterior  recti.  The  fibres  communicating  with  the  hypoglossal  are  mostly  con- 
tinued into  its  descendens  hypoglossi  branch  (see  page  825). l 

The  anterior  division  of  the  second  cervical  nerve  escapes  from  the  spinal 
canal,  between  the  posterior  arch  of  the  atlas  and  the  lamina  of  the  axis,  and, 
passing  forward  on  the  outer  side  of  the  vertebral  artery,  divides  in  front  of  the 
Intertransverse  muscle  into  an  ascending  branch,  which  joins  the  first  cervical, 
and  descending  branches,  which  join  branches  from  the  third.  These  last-named 
intercommunicating  branches  of  the  second  and  third  cervical  nerves,  give  off 
the  small  occipital,  the  great  auricular,  and  the  superficial  cervical  nerves.  .  The 
nerve  also  gives  off  one  of  the  communicantes  hypoglossi,  and  a  filament  to  the 
Sterno-mastoid  which  communicates  in  the  substance  of  the  muscle  with  the 
spinal  accessory. 

The  anterior  division  of  the  third  cervical  nerve  is  double  the  size  of  the 
preceding.  At  its  exit  from  the  intervertebral  foramen  it  passes  downward  and 
outward  beneath  the  Sterno-mastoid,  and  divides  into  branches.  The  ascend- 
ing ones  join  with  branches  of  the  second  cervical,  and  this  combination  gives  off, 
as  already  stated,  the  small  occipital,  the  great  auricular,  and  the  superficial 
cervical  nerves.  The  descending  branches  pass  down  in  front  of  the  Scalenus 
anticus,  and  are  as  follows  :  One  of  the  communicantes  hypoglossi ;  a  branch  to 
the  supraclavicular  nerves  ;  a  filament  to  assist  in  forming  the  phrenic ;  and 
muscular  branches  to  the  Levator  anguli  scapulae  and  Trapezius ;  this  latter 
nerve  communicates  beneath  the  muscle  with  the  spinal  accessory.  Sometimes  ^ 
the  nerve  to  the  Scaleuus  medius  is  derived  from  this  source. 

The  anterior  division  of  the  fourth  cervical  is  of  the  same  size  as  the  preceding. 
It  sends  a  communicating  branch  to  the  fifth  cervical,  and,  passing  downward 
and  outward^  unites  with  a  branch  from  the  third,  and  from  this  union  are  derived 
numerous  filaments  which  cross  the  posterior  triangle  of  the  neck,  forming  the 
supraclavicular  nerves.  It  also  gives  a  branch  to  the  phrenic  nerve  whilst  it  is 
contained  in  the  intertransverse  space,  and  sometimes  a  branch  to  the  Scalenus 
medius  muscle.  It  also  gives  a  branch  to  the  Levator  anguli  scapulae  and  to  the 

1  According  to  Valentin,  the  anterior  division  of  the  suboccipital  also  distributes  filaments  to 
the  occipito-atlantal  articulation  and  mastoid  process  of  the  temporal  bone. 


THE    CERVICAL   PLEXUS.  831 

Trapezius,  which  unites  with  the  branch  given  off  from  the  third  nerve,  and 
communicates  beneath  the  muscle  with  the  spinal  accessory. 

The  anterior  divisions  of  the  fifth,  sixth,  seventh,  and  eighth  cervical  nerves 
are  remarkable  for  their  large  size.  They  are  much  larger  than  the  preceding 
nerves,  and  are  all  of  equal  size.  They  assist  in  the  formation  of  the  brachial 
plexus. 

The  Cervical  Plexus. 

The  cervical  plexus  (Fig.  496)  is  formed,  as  above  described,  by  the  anterior 
divisions  of  the  four  upper  cervical  nerves.  It  is  situated  opposite  the  four  upper 
cervical  vertebrae,  resting  upon  the  Levator  anguli  scapulae  and  Scalenus  medius 
muscles,  and  covered  in  by  the  Sterno-mastoid. 

Its  branches  may  be  divided  into  two  groups,  superficial  and  deep,  which  may 
be  thus  arranged : 

(  Occipitalis  minor, 
f  Ascending    .  •<  Auricularis  magnus. 
(^  Superficialis  colli. 

Superficial    \ 

(  Suprasternal. 

^Descending  .       Supraclavicular    -I  Supraclavicular. 

(  Supra-acromial. 
C  Communicating. 
rT  ,  J  Muscular. 

1  Communicans  hypoglossi. 
Deep  .    .   .    -<  ^Phrenic. 

(  Communicating. 
^External  .    .  j  Musculai, 

Superficial  Branches  of  the  Cervical  Plexus, 

The  Occipitalis  minor  (Fig.  502)  arises  from  the  second  and  third  cervical 
nerves ;  it  curves  round  the  posterior  border  of  the  Sterno-mastoid,  and  ascends, 
running  parallel  to  the  posterior  border  of  the  muscle,  to  the  back  part  of  the 
side  of  the  head.  Xear  the  cranium  it  perforates  the  deep  fascia,  and  is  continued 
upward  along  the  side  of  the  head  behind  the  ear,  supplying  the  integument,  and 
communicating  with  the  occipitalis  major,  the  auricularis  magnus,  and  with  the 
posterior  auricular  branch  of  the  facial. 

This  nerve  gives  off  an  auricular  branch,  which  supplies  the  integument  of 
the  upper  and  back  part  of  the  auricle,  communicating  with  the  mastoid  branch 
of  the  auricularis  magnus.  This  branch  is  occasionally  derived  from  the  great 
occipital  nerve.  The  occipitalis  minor  varies  in  size ;  it  is  occasionally  double. 

The  Auricularis  Magnus  is  the  largest  of  the  ascending  branches.  It  arises 
from  the  second  and  third  cervical  nerves,  winds  round  the  posterior  border  of 
the  Sterno-mastoid,  and.  after  perforating  the  deep  fascia,  ascends  upon  that 
muscle  beneath  the  Platysma  to  the  parotid  gland,  where  it  divides  into  facial, 
auricular,  and  mastoid  branches. 

The/'/'-/'//  branches  pass  across  the  parotid,  and  are  distributed  to  the  integ- 
ument of  the  face  over  the  parotid  gland ;  others  penetrate  the  substance  of  the 
gland  and  communicate  with  the  facial  nerve. 

The  auricular  branches  ascend  to  supply  the  integument  of  the  back  part  of 
the  pinna,  except  at  its  upper  part,  communicating  with  the  auricular  branches 
of  the  facial  and  pneumogastric  nerves. 

The  rnastoii.l  branch  communicates  with  the  occipitalis  minor  and  the  posterior 
auricular  branch  of  the  facial,  and  is  distributed  to  the  integument  behind  the  ear. 

The  Superficialis  Colli  arises  from  the  second  and  third  cervical  nerves,  turns 
round  the  posterior  border  of  the  Sterno-mastoid  about  its  middle,  and,  passing 
obliquely  forward  beneath  the  external  jugular  vein  to  the  anterior  border  of  that 


832 


THE  NERVOUS  SYSTEM. 


muscle,  perforates  the  deep  cervical  fascia,  and  divides  beneath  the  Platysma  into 
two  branches  which  are  distributed  to  the  antero-lateral  parts  of  the  neck. 

The  ascending  branch  gives  a  filament  which  accompanies  the  external  jugular 
vein  ;  it  then  passes  upward  to  the  submaxillary  region,  and  divides  into  branches, 
some  of  which  form  a  plexus  with  the  cervical  branches  of  the  facial  nerve  beneath 


Sect.  Cap.  Lat. 


t.  Ant.  Major 
)Rect.  Ant,  Minor 

'To  Sympathetic 
)  To  Hypoglossal 

0  Scalp  and  Occipito  Frontalis 

1  To  Auricle 


Ill 


Trapezius 
C.  with  Spin.  Accessory 


FIG.  496.— Plan  of  the  cervical  plexus. 

the  Platysma;  others  pierce  that  muscle,  supply  it,  and  are  distributed  to  the 
integument  of  the  upper  half  of  the  neck,  at  its  fore  part,  as  high  as  the  chin. 

The  descending  branch  (occasionally  represented  by  two  or  more  filaments) 
pierces  the  Platysma,  and  is  distributed  to  the  integument  of  the  side  and  front 
of  the  neck,  as  low  as  the  sternum. 

The  Descending  or  supra  ^avicular  branches  arise  from  the  third  and  fourth 
cervical  nerves :  emerging  t.  Uh  the  posterior  border  of  the  Sterno-mastoid, 
they  descend  in  the  interval  between  that  muscle  and  the  Trapezius,  and  divide 
into  branches,  which  are  arranged,  according  to  their  position,  into  three  groups. 

The  inner  or  suprasternal  branches  cross  obliquely  over  the  clavicular  and 
sternal  attachments  of  the  Sterno-mastoid,  and  supply  the  integument  as  far  as 
the  median  line. 

The  middle  or  supraclavicular  branches  cross  the  clavicle,  and  supply  the 
integument  over  the  Pectoral  and  Deltoid  muscles,  communicating  with  the 
cutaneous  branches  of  the  upper  intercostal  nerves. 

The  external  or  supra-acromial  branches  pass  obliquely  across  the  outer  surface 
of  the  Trapezius  and  the  acromion,  and  supply  the  integument  of  the  upper  and 
back  part  of  the  shoulder. 


DEEP  BRANCHES    OF   THE    CERVICAL   PLEXUS.  833 

Deep  Branches  of  the  Cervical  Plexus.    Internal  Series. 

The  communicating  branches  consist  of  several  filaments  which  pass  from  the 
loop  between  the  first  and  second  cervical  nerves  in  front  of  the  atlas  to  the 
pneumogastric,  hypoglossal  (see  page  825  and  Fig.  493)  and  sympathetic,  and  a 
communicating  branch  between  the  fourth  and  fifth  cervical. 

Muscular  branches  supply  the  Anterior  recti  and  the  Rectus  lateralis  mus- 
cles ;  they  proceed  from  the  first  cervical  nerve  and  from  the  loop  formed 
between  it  and  the  second.  The  Longus  colli  is  supplied  from  the  third  and 
the  fourth. 

The  Communicans  Hypoglossi  (Fig.  493)  consists  usually  of  two  filaments,  one 
being  derived  from  the  second,  and  the  other  from  the  third  cervical.  These 
filaments  pass  downward  on  the  outer  side  of  the  internal  jugular  vein,  cross  in 
front  of  the  vein  a  little  below  the  middle  of  the  neck,  and  form  a  loop  with  the 
descendens  hvpoglossi  in  front  of  the  sheath  of  the  carotid  vessels  (see  page  825). 
Occasionally,  the  junction  of  these  nerves  takes  place  within  the  sheath. 

The  Phrenic  Nerve  (internal  respiratory  of  Bell)  arises  chiefly  from  the  fourth 
cervical  nerve,  with  a  few  filaments  from  the  third  and  a  communicating  branch 
from  the  fifch.  It  descends  to  the  root  of  the  neck,  running  obliquely  across  the 
front  of  the  Scalenus  anticus,  passes  over  the  first  part  of  the  subclavian  artery, 
between  it  and  the  subclavian  vein,  and,  as  it  enters  the  chest,  crosses  the 
internal  mammary  artery  near  its  origin.  Within  the  chest  it  descends  nearly 
vertically  in  front  of  the  root  of  the  lung  and  by  the  side  of  the  pericardium, 
between  it  and  the  mediastinal  portion  of  the  pleura,  to  the  Diaphragm,  where  it 
divides  into  branches,  which  separately  pierce  that  muscle  and  are  distributed  to 
its  under  surface. 

The  two  phrenic  nerves  differ  in  their  length,  and  also  in  their  relations  at 
the  upper  part  of  the  thorax. 

The  right  nerve  is  situated  more  deeply,  and  is  shorter  and  more  vertical  in 
direction  than  the  left ;  it  lies  en  the  outer  side  of  the  right  vena  innominata  and 
superior  vena  cava. 

The  left  nerve  is  rather  longer  than  the  right,  from  the  inclination  of  the 
heart  to  the  left  side,  and  from  the  Diaphragm  being  lower  on  this  than  on  the 
opposite  side.  At  the  upper  part  of  the  thorax  it  crosses  in  front  of  the  arch  of 
the  aorta  to  the  root  of  the  lung. 

Each  nerve  supplies  filaments  to  the  pericardium  and  pleura,  and  near  the 
chest  is  joined  by  a  fiian.ent  from  the  sympathetic,  and  occasionally  by  one  from 
the  union  of  the  descendens  hypoglossi  with  the  spinal  nerves  :  this  filament  is 
found,  according  to  Swan,  only  on  the  left  side.  It  is  also  usually  connected  by 
a  filament  with  the  nerve  to  the  Subclavius  muscle.  Branches  have .  been 
described  as  passing  to  the  peritoneum. 

From  the  right  nerve  one  or  two  filaments  pass  to  join  in  a  small  ganglion 
with  phrenic  branches  of  the  solar  plexus  ;  and  branches  from  this  ganglion  are 
distributed  to  the  hepatic  plexus,  the  suprarenal  capsule,  and  inferior  vena  cava. 
From  the  left  nerve  filaments  pass  to  join  the  phrenr'1* plexus  of  the  sympathetic, 
but  without  any  ganglionic  enlargement. 

Deep  Branches  of  the  Cervical  Plexus.    External  Series. 

Communicating  Branches. — The  deep  branches  of  the  external  series  of  the 
cervical  plexus  communicate  with  the  spinal  accessory  nerve,  in  the  substance  of 
the  Sterno-mastoid  muscle,  in  the  occipital  triangle,  and  beneath  the  Trapezius. 

Muscular  branches  are  distributed  to  the  Sterno-mastoid,  Trapezius,  Levator 
anguli  scapulae  and  Scalenus  medius. 

The  branch  for  the  Sterno-mastoid  is  derived  from  the  second  cervical;  the 
Trapezius  and  Levator  anguli  scapulae  receive  branches  from  the  third  and 
fourth.  The  Scalenus  medius  is  supplied  sometimes  from  the  third,  sometimes 
the  fourth,  and  occasionally  from  both  nerves. 


834 


THE   NERVOUS  SYSTEM. 


The  Brachial  Plexus  (Fig.  497). 

The  Brachial  Plexus  is  formed  by  the  union  of  the  anterior  branches  of  the 
four  lower  cervical  and  the  greater  part  of  the  first  dorsal  nerves,  receiving  also  a 
fasciculus  from  the  fourth  cervical  nerve.  It  extends  from  the  lower  part  of  the 
side  of  the  neck  to  the  axilla.  It  is  very  broad,  and  presents  little  of  a  plexiform 
arrangement  at  its  commencement.  It  is  narrow  opposite  the  clavicle,  becomes 
broad  and  forms  a  more  dense  interlacement  in  the  axilla,  and  divides  opposite 
the  coracoid  process  into  numerous  branches  for  the  supply  of  the  upper  limb. 
The  nerves  which  form  the  plexus  are  all  similar  in  size,  and  their  mode  of  com- 
munication is  subject  to  considerable  variation,  so  that  no  one  plan  can  be  given 
as  applying  to  every  case.  The  following  appears,  however,  to  be  the  most  con- 
stant arrangement :  the  fifth  and  sixth  cervical  unite  together  soon  after  their 
exit  from  the  intervertebral  foramina  to  form  a  common  trunk.  The  eighth  cervi- 
cal and  first  dorsal  also  unite  to  form  one  trunk.  So  that  the  nerves  forming  the 
plexus,  as  they  lie  on  the  Scalenus  medius  external  to  the  outer  border  of  the 


TROM  4. !£ 


A-SCAPULAR 


BRS  TO  LOW 
US  COULI 
SCALEN 


XT:   ANT:   THORACIC 

UPPER    SUB-SCAPULAH. 

SUB-SCAPULAR 
CIRCUMFLEX 


FIG.  497.— Plan  of  the  brachial  plexus. 

Scalenus  anticus,  are  blended  into  three  trunks — an  upper  one,  formed  by  the 
junction  of  the  fifth  and  sixth  cervical  nerves ;  a  middle  one,  consisting  of  the 
seventh  cervical  nerve;  and  a  lower  one,  formed  by  the  junction  of  the  eighth 
cervical  and  first  dorsal  nerves.  As  they  pass  beneath  the  clavicle,  each  of  these 
three  trunks  divides  into  two  branches,  an  anterior  and  a,  posterior.  The  anterior 
divisions  of  the  upper  and  middle  trunks  then  unite  to  form  a  common  cord, 
which  is  situated  on  the  outer  side  of  the  middle  part  of  the  axillary  artery,  and 
is  called  the  outer  cord  of  the  brachial  plexus.  The  anterior  division  of  the 


THE  BRACHIAL    PLEXUS. 


835 


lower  trunk,  formed  by  the  union  of  the  eighth  cervical  and  first  dorsal,  passes 
down  on  the  inner  side  of  the  axillary  artery  in  the  middle  of  the  axilla,  and 
forms  the  inner  cord  of  the  brachial  plexus.  The  posterior  divisions  of  the  upper 


FIG.  498.— Cutaneous  nerves  of  right  upper 
extremity.    Anterior  view. 


FIG.  -199. — Cutaneous  nerves  of  right  upper 
extremity.    Posterior  view. 


trunk  (formed  by  the  junction  of  the  fifth  and  sixth  nerves)  and  of  the  middle 
trunk  (the  seventh  nerve)  unite  together  to  form  the  posterior  cord  of  the  brachial 
plexus,  which  is  situated  behind  the  second  portion  of  the  axillary  artery.  From 
this  posterior  cord  are  given  off  the  two  lower  subscapular  nerves,  the  upper  sub- 
scapular  nerve  being  given  off  from  the  posterior  division  of  the  outer  trunk 
prior  to  its  junction  with  the  posterior  division  of  the  middle  trunk.  The  pos- 
terior cord  divides  into  the  circumflex  and  musculo-spiral  nerves.  The  musculc- 


836 


THE  NERVOUS  SYSTEM. 


External  anterior  thoracic. 

Internal  anterior  thoracic. 

-  cutaneous. 


Musculo-spiral. 
Posterior 

interosseous. 


Anterior 
interosseous. 


FIG.  500.— Nerves  of  the  left  upper  extremity. 


spiral  nerve  is  subsequently  joined  by  the  posterior  division  of  the  inner  trunk, 
formed  by  the  union  of  the  eighth  cervical  and  first  dorsal. 


THE   BRACHIAL    PLEX  837 

The  brachial  plexus  communicates  with  the  cervical  plexus  by  a  branch  from 
the  fourth  to  the  fifth  nerve,  and  with  the  phrenic  nerve  by  a  branch  from  the 
fifth  cervical,  which  joins  that  nerve  on  the  Anterior  scalenus  muscle :  the  cervi- 
cal and  first  dorsal  nerves  are  also  joined  by  filaments  from  the  middle  and 
inferior  cervical  ganglia  of  the  sympathetic,  close  to  their  exit  from  the  interver- 
tebral  foramina. 

Relations. — In  the  neck  the  brachial  plexus  lies  at  the  first  between  the  Anterior 
and  Middle  scaleni  muscles,  and  then  above  and  to  the  outer  side  of  the  subclavian 
artery :  it  then  passes  behind  the  clavicle  and  Subclavius  muscle,  lying  upon  the 
first  serration  of  the  Serratus  magnus,  and  the  Subscapularis  muscles.  In  the 
axilla  it  is  placed  on  the  outer  side  of  the  first  portion  of  the  axillary  artery ;  it 
surrounds  the  artery  in  the  second  part  of  its  course,  one  cord  lying  upon  the  outer 
side  of  that  vessel,  one  on  the  inner  side,  and  one  behind  it,  and  at  the  lower  part 
of  the  axillary  space  gives  off  its  terminal  branches  to  the  upper  extremity. 

Branches. — The  branches  of  the  brachial  plexus  are  arranged  in  two  groups —  — 
viz.  those  given  off  above  the  clavicle,  and  those  below  that  bone. 

Branches  above  the  Clavicle. 

Communicating.  Posterior  thoracic. 

Muscular.  Suprascapular. 

The  communicating  branch  with  the  phrenic  is  derived  from  the  fifth  cervical 
nerve  or  from  the  loop  between  the  fifth  and  sixth  ;  it  joins  the  phrenic  on  the 
Anterior  scalenus  muscle. 

The  muscular  branches  supply  the  Longus  colli,  Scaleni,  Rhomboidei,  and 
Subclavius  muscles.  Those  for  the  Longus  colli  and  Scaleni  arise  from  the  lower 
cervical  nerves  at  their  exit  from  the  intervertebral  foramina.  The  Rhomboid 
branch  arises  from  the  fifth  cervical,  pierces  the  Scalenus  medius,  and  passes 
beneath  the  Levator  anguli  scapulas,  which  it  occasionally  supplies,  to  the  Rhomboid 
muscles.  The  nerve  to  the  Subclavius  is  a  small  filament  which  arises  from  the 
fifth  cervical  at  its  point  of  junction  with  the  sixth  nerve:  it  descends  in  front 
of  the  subclavian  artery  to  the  Subclavius  muscle,  and  is  usually  connected  by  a 
filament  with  the  phrenic  nerve. 

The  posterior  thoracic  nerve  (long  thoracic,  external  respiratory  of  Bell) 
(Fig.  500)  supplies  the  Serratus  magnus,  and  is  remarkable  for  the  length  of  its 
course.  It  sometimes  arises  by  two  roots  from  the  fifth  and  sixth  cervical  nerves 
immediately  after  their  exit  from  the  intervertebral  foramina,  but  generally  by 
three  roots  from  the  fifth,  sixth,  and  seventh  nerves.  These  unite  in  the  substance 
of  the  Middle  scalenus  muscle,  and,  after  emerging  from  it,  the  nerve  passes  down 
behind  the  brachial  plexus  and  the  axillary  vessels,  resting  on  the  outer  surface  of 
the  Serratus  magnus.  It  extends  along  the  side  of  the  chest  to  the  lower  border 
of  that  muscle,  supplying  filaments  to  each  of  its  digitations. 

The  suprascapular  nerve  (Fig.  501)  arises  from  the  cord  formed  by  the  fifth  and 
sixth  cervical  nerves  :  passing  obliquely  outward  beneath  the  Trapezius,  it  enters 
the  supraspinous  fossa,  through  the  notch  in  the  upper  border  of  the  scapula,  and, 
passing  beneath  the  Supraspinatus  muscle,  curves  in  front  of  the  spine  of  the 
scapula  to  the  infraspinous  fossa.  In  the  supraspinous  fossa  it  gives  off  two 
branches  to  the  Supraspinatus  muscle,  and  an  articular  filament  to  the  shoulder- 
joint  :  and  in  the  infraspinous  fossa  it  gives  off  two  branches  to  the  Infraspinatus 
muscle,  besides  some  filaments  to  the  shoulder-joint  and  scapula. 

Branches   below  the  Clavicle. 

The  branches  below  the  clavicle  are  derived  from  the  three  cords,  as  follows : 
Fi-fttn  the  oittfr  eorJ  arise  the  external  of  the  two  anterior  thoracic  nerves,  the 

musculo-cutaneous  nerve,  the  nerve  to  the  Coraco-brachialis  muscle,  and  the  outer 

head  of  the  median. 


838  THE  NERVOUS  SYSTEM, 

From  the  inner  cord  arise  the  internal  of  the  two  anterior  thoracic  nerves,  the 
internal  cutaneous,  the  lesser  internal  cutaneous  (nerve  of  Wrisberg),  the  ulnar,  and 
inner  head  of  the  median. 

From  the  posterior  cord  arise  two  of  the  three  subscapular  nerves,  the  third 
arising  from  the  posterior  division  of  the  trunk  formed  by  the  fifth  and  sixth 
cervical  nerves ;  the  cord  then  divides  into  the  musculo-spiral  and  circumflex 
nerves. 

These  may  be  arranged  according  to  the  parts  they  supply : 

To  the  chest         ....         Anterior  thoracic. 

To  the  shoulder  .  {  Subscapular. 

(  Circumflex. 
Musculo-cutaneous. 
Internal  cutaneous. 

m    ,1  c  i  Lesser  internal  cutaneous. 

To  the  arm,  forearm,  and  hand  .        ^  M  d' 

Ulnar.  ' 
^  Musculo-spiral. 

The  fasciculi  of  which  these  nerves  are  composed  may  be  traced  through  the 
plexus  to  the  spinal  nerves  from  which  they  originate.  They  are  as  follows : 

External  anterior  thoracic  from  5th,  6th,  and  7th  cervical. 

Internal  anterior  thoracic  "  8th  cervical  and  1st  dorsal. 

Subscapular  "  5th,  6th,  7th,  and  8th  cervical. 

Circumflex  "  5th,  6th,  7th,  and  8th  cervical. 

Musculo-cutaneous  "  5th,  6th,  and  7th  cervical. 

Internal  cutaneous  "  8th  cervical  and  1st  dorsal. 

Lesser  internal  cutaneous  "  1st  dorsal. 

Median  "  6th,  7th,  and  8th  cervical,  and  1st  dorsal. 

Ulnar  "  8th  cervical  and  1st  dorsal. 

Musculo-spiral  "  6th,  7th,  and  8th  cervical,  and  1st  dorsal. 

The  Anterior  Thoracic  Nerves  (Fig.  500),  two  in  number,  supply  the  Pectoral 
muscles. 

The  external  or  superficial  nerve,  the  larger  of  the  two,  arises  from  the  outer 
cord  of  the  brachial  plexus,  through  which  its  fibres  may  be  traced  to  the  fifth, 
sixth,  and  seventh  cervical  nerves.  It  passes  inward,  across  the  axillary  artery 
and  vein,  pierces  the  costo-coracoid  membrane,  and  is  distributed  to  the  under 
surface  of  the  Pectoralis  major.  It  sends  down  a  communicating  filament  to  join 
the  internal  nerve,  which  forms  a  loop  round  the  inner  side  of  the  axillary 
artery. 

The  internal  or  deep  nerve  arises  from  the  inner  cord,  and  through  it  from 
the  eighth  cervical  and  first  dorsal.  It  passes  upward  between  the  axillary  artery 
and  vein,  and  joins  with  the  filament  from  the  superficial  nerve.  It  then  passes 
to  the  under  surface  of  the  Pectoralis  minor  muscle,  where  it  divides  into  a  number 
of  branches,  which  supply  the  muscle  on  its  under  surface.  Some  of  the  branches 
pass  through  the  muscle  ;  others  wind  round  its  upper  border  and  pierce  the  costo- 
coracoid  membrane  to  supply  the  Pectoralis  major. 

The  Subscapular  Nerves,  three  in  number,  supply  the  Subscapularis,  Teres 
major,  and  Latissimus  dorsi  muscles.  The  fasciculi  of  which  they  are  composed 
may  be  traced  to  the  fifth,  sixth,  seventh,  and  eighth  cervical  nerves. 

The  upper  subscapular  nerve,  the  smallest,  enters  the  upper  part  of  the  Sub- 
scapularis muscle. 

The  lower  subscapular  nerve  enters  the  axillary  border  of  the  Subscapularis 
and  terminates  in  the  Teres  major.  The  latter  muscle  is  sometimes  supplied  by  a 
separate  branch. 

The  middle  or  long  subscapular,  the  largest  of  the  three,  follows  the  course  of 


THE  BRACHIAL    PLEXUS.  839 

the  subscapular  artery,  along  the  posterior  wall  of  the  axilla  to  the  Latissimus 
dorsi,  through  which  it  mav  be  traced  as  far  as  its  lower  border. 

The  Circumflex  Nerve  (Fig.  501)  supplies  some  of  the  muscles  and  the  integu- 
ment of  the  shoulder  and  the  shoulder-joint.  It  arises  from  the  posterior  cord  of 
the  brachial  plexus,  in  common  with  the  musculo-spiral  nerve,  and  its  fibres  may 
be  traced  through  the  posterior  cord  to  the  fifth,  sixth,  seventh,  and  eighth  cer- 
vical nerves.  It  is  at  first  placed  behind  the  axillary  artery,  between  it  and  the 
Subscapularis  muscle,  and  passes  downward  and  outward  to  the  lower  border  of 
that  muscle.  It  then  winds  backward  in  company  with  the  posterior  circumflex 
artery,  through  a  quadrilateral  space  bounded  above  by  the  Teres  minor,  below 
by  the  Teres  major,  internally  by  the  long  head  of  the  Triceps,  and  externally  by 
the  neck  of  the  humerus,  and  divides  into  t\vo  branches. 

The  upper  branch  winds  round  the  surgical  neck  of  the  humerus,  beneath  tb-e 
Deltoid,  with  the  posterior  circumflex  vessels,  as  far  as  the  anterior  border  of  that 
muscle,  supplying  it,  and  giving  off  cutaneous  branches,  which  pierce  the  muscle 
and  ramify  in  the  integument  covering  its  lower  part. 

The  loiver  branch,  at  its  origin,  distributes  filaments  to  the  Teres  minor  and 
back  part  of  the  Deltoid  muscles.  Upon  the  filament  to  the  former  muscle  a 
gangliform  enlargement  usually  exists.  The  nerve  then  pierces  the  deep  fascia, 
and  supplies  the  integument  over  the  lower  two-thirds  of  the  posterior  surface  of 
the  Deltoid,  as  well  as  that  covering  the  long  head  of  the  Triceps. 

The  circumflex  nerve,  before  its  division,  gives  off  an  articular  filament,  which 
enters  the  shoulder-joint  below  the  Subscapularis. 

The  Musculo-cutaneous  Nerve  (Fig.  500)  (external  cutaneous  or  perforans  Cas- 
serii)  supplies  some  of  the  muscles  of  the  arm  and  the  integument  of  the  fore- 
arm. It  arises  from  the  outer  cord  of  the  brachial  plexus,  opposite  the  lower  border 
of  the  Pectoralis  minor,  receiving  filaments  from  the  fifth,  sixth,  and  seventh 
cervical  nerves.  It  perforates  the  Coraco-brachialis  muscle,  passes  obliquely  between 
the  Biceps  and  Brachialis  anticus  to  the  outer  side  of  the  arm,  and,  a  little  above 
the  elbow,  winds  round  the  outer  border  of  the  tendon  of  the  Biceps,  and,  perfo- 
rating the  deep  fascia,  becomes  cutaneous.  This  nerve  in  its  course  through  the 
arm  supplies  the  Coraco-brachialis  (this  branch  often  arises  separately  from  the 
outer  cord).  Biceps,  and  part  of  the  Brachialis  anticus  muscles.  It  sends  a  small 
branch  to  the  bone,  which  enters  the  nutrient  foramen  with  the  accompanying 
artery  and  a  filament,  from  the  branch  supplying  the  Brachialis  anticus,  to  the 
elbow-joint. 

The  cutaneous  portion  of  the  nerve  passes  behind  the  median  cephalic  vein,  and 
divides,  opposite  the  elbow-joint,  into  an  anterior  and  a  posterior  branch. 

The  anterior  branch  descends  along  the  radial  border  of  the  forearm  to  the 
wrist,  and  supplies  the  integument  over  the  outer  half  of  the  anterior  surface.  At 
the  wrist-joint  it  is  placed  in  front  of  the  radial  artery,  and  some  filaments, 
piercing  the  deep  fascia,  accompany  that  vessel  to  the  back  of  the  wrist,  supplying 
the  carpus.  The  nerve  then  passes  downward  to  the  ball  of  the  thumb,  where  it 
terminates  in  cutaneous  filaments.  It  communicates  with  a  branch  from  the  radial 
nerve  and  the  palmar  cutaneous  branch  of  the  median. 

The  posterior  branch  passes  downward  along  the  back  part  of  the  radial  side 
of  the  forearm  to  the  wrist.  It  supplies  the  integument  of  the  lower  third  of  the 
forearm,  communicating  with  the  radial  nerve  and  the  lower  external  cutaneous 
branch  of  the  musculo-spiral. 

The  Internal  Cutaneous  Nerve  (Fig.  500)  is  one  of  the  smallest  branches  of  the 
brachial  plexus.  It  arises  from  the  inner  cord  in  common  with  the  ulnar  and 
internal  head  of  the  median,  and  at  its  commencement  is  placed  on  the  inner 
side  of  the  axillary  artery.  It  derives  its  fibres  from  the  eighth  cervical  and  first 
dorsal  nerves.  It  passes  down  the  inner  side  of  the  arm,  pierces  the  deep  fascia 
Avith  the  basilic  vein,  about  the  middle  of  the  limb,  and,  becoming  cutaneous, 
divides  into  two  branches,  anterior  and  posterior. 

This  nerve  gives  off,  near  the  axilla,  a  cutaneous  filament,  which  pierces  the 


846  THE   NERVOUS  SYSTEM. 

fascia  and  supplies  the  integument  covering  the  Biceps  muscle  nearly  as  far  as 
the  elbow.  This  filament  lies  a  little  external  to  the  common  trunk,  from  which 
it  arises. 

The  anterior  branch,  the  larger  of  the  two,  passes  usually  in  front  of,  but 
occasionally  behind,  the  median  basilic  vein.  It  then  descends  on  the  anterior 
surface  of  the  ulnar  side  of  the  forearm,  disti'ibuting  filaments  to  the  integument 
as  far  as  the  wrist,  and  communicating  with  a  cutaneous  branch  of  the  ulnar 
nerve. 

The  posterior  branch  passes  obliquely  downward  on  the  inner  side  of  the 
basilic  vein,  passes  in  front  of,  or  over,  the  internal  condyle  of  the  humerus  to  the 
back  of  the  forearm,  and  descends  on  the  posterior  surface  of  its  ulnar  side  as  far 
as  the  wrist,  distributing  filaments  to  the  integument.  It  communicates,  above 
the  elbow,  with  the  lesser  internal  cutaneous,  and  above  the  wrist  Avith  the  dorsal 
cutaneous  branch  of  the  ulnar  nerve  (Swan). 

The  Lesser  Internal  Cutaneous  Nerve  (nerve  of  Wrisbery)  (Fig.  500)  is  distrib- 
uted to  the  integument  on  the  inner  side  of  the  arm.  It  is  the  smallest  of  the 
branches  of  the  brachial  plexus,  and,  arising  from  the  inner  cord  with  the  internal 
cutaneous  and  ulnar  nerves,  receives  its  fibres  from  the  first  dorsal  nerve.  It 
passes  through  the  axillary  space,  at  first  lying  behind,  and  then  on  the  inner  side 
of,  the  axillary  vein,  and  communicates  with  the  intercosto-humeral  nerve.  It 
descends  along  the  inner  side  of  the  brachial  artery  to  the  middle  of  the  arm, 
where  it  pierces  the  deep  fascia,  and  is  distributed  to  the  integument  of  the  back 
part  of  the  lower  third  of  the  arm,  extending  as  far  as  the  elbow,  where  some 
filaments  are  lost  in  the  integument  in  front  of  the  inner  condyle,  and  others 
over  the  olecranon.  It  communicates  with  the  posterior  branch  of  the  internal 
cutaneous  nerve. 

In  some  cases  the  nerve  of  Wrisberg  and  intercosto-humeral  are  connected  by 
two  or  three  filaments  which  form  a  plexus  at  the  back  part  of  the  axilla.  In 
other  cases  the  intercosto-humeral  is  of  large  size,  and  takes  the  place  of  the 
nerve  of  Wrisberg,  receiving  merely  a  filament  of  communication  from  the  brachial 
plexus,  which  represents  the  latter  nerve.  In  other  cases  this  filament  is  wanting, 
the  place  of  the  nerve  of  Wrisberg  being  supplied  entirely  from  the  intercosto- 
humeral. 

The  Median  Nerve  (Fig.  500)  has  received  its  name  from  the  course  it  takes 
along  the  middle  of  the  arm  and  forearm  to  the  hand,  lying  between  the  ulnar 
and  the  musculo-spiral  and  radial  nerves.  It  arises  by  two  roots,  one  from  the 
outer,  and  one  from  the  inner,  cord  of  the  brachial  plexus  ;  these  embrace  the  lower 
part  of  the  axillary  artery,  uniting  either  in  front  or  on  the  outer  side  of  that 
vessel.  It  receives  filaments  from  the  sixth,  seventh,  and  eighth  cervical  and  the 
first  dorsal.  As  it  descends  through  the  arm,  it  lies  at  first  on  the  outer  side  of 
the  brachial  artery,  crosses  that  vessel  in  the  middle  of  its  course,  usually  in 
front,  but  occasionally  behind  it,  and  lies  on  its  inner  side  to  the  bend  of  the 
elbow,  where  it  is  placed  beneath  the  bicipital  fascia,  and  is  separated  from  the 
elbow-joint  by  the  Brachialis  anticus.  In  the  forearm  it  passes  between  the  two 
heads  of  the  Pronator  radii  teres,  and  descends  beneath  the  Flexor  sublimis,  lying 
on  the  Flexor  profundus,  to  within  two  inches  above  the  annular  ligament,  where 
it  becomes  more  superficial,  lying  between  the  tendons  of  the  Flexor  sublimis 
and  Flexor  carpi  radialis,  beneath,  or  rather  to  the  ulnar  side  of,  the  tendon  of 
the  Palmaris  longus,  covered  by  the  integument  and  fascia.  It  then  passes  beneath 
the  annular  ligament  into  the  hand.  In  its  course  through  the  forearm  it  is 
accompanied  by  a  small  artery. 

Branches. — No  branches  are  given  off  from  the  median  nerve  in  the  arm.  In 
the  forearm  its  branches  are  muscular,  anterior  interosseous,  and  palmar  cuta- 
neous, and,  according  to  Rudinger  and  Macalister,  tAvo  articular  twigs  to  the 
elbow-joint. 

The  muscular  branches  supply  all  the  superficial  muscles  on  the  front  of  the 
forearm,  except  the  Flexor  carpi  ulnaris.  These  branches  are  derived  from  the 


THE   BR ACTUAL    PLEXl'X. 

nerve  near  the  elbow.  The  radial  head  and  index  finger  belly  of  the  Flexor 
sublirais.  each  has  a  separate  filament. 

The  anterior  interosseous  supplies  the  deep  muscles  on  the  front  of  the  fore- 
arm, except  the  inner  half  of  the  Flexor  profundus  digitorum.  It  accompanies 
the  anterior  interosseous  artery  along  the  interosseous  membrane,  in  the  interval 
between  the  Flexor  longus  pollicis  and  Flexor  profundus  digitorum  muscles,  both 
of  which  it  supplies,  and  terminates  below  in  the  Pronator  quadratus. 

The  palmar  cutaneous  branch  arises  from  the  median  nerve  at  the  lower  part 
of  the  forearm.  It  pierces  the  fascia  above  the  annular  ligament,  and,  descending 
over  that  ligament,  divides  into  two  branches :  of  which  the  outer  supplies  the 
skin  over  the  ball  of  the  thumb,  and  communicates  with  the  anterior  cutaneous 
branch  of  the  musculo-cutaneous  nerve  ;  and  the  inner  supplies  the  integument  of 
the  palm  of  the  hand,  communicating  with  the  cutaneous  branch  of  the  ulnar. 

In  the  palm  of  the  hand  the  median  nerve  is  covered  by  the  integument  and 
palmar  fascia  and  crossed  by  the  superficial  palmar  arch.  It  rests  upon  the 
tendons  of  the  flexor  muscles.  In  this  situation  it  becomes  enlarged,  somewhat 
flattened,  of  a  reddish  color,  and  divides  into  two  branches.  Of  these,  the 
external  supplies  a  muscular  branch  to  some  of  the  muscles  of  the  thumb  and 
digital  branches  to  the  thumb  and  index  finger ;  the  internal  supplies  digital 
branches  to  the  contiguous  sides  of  the  index  and  middle  and  of  the  middle  and 
ring  fingers. 

The  branch  to  the  muscles  of  the  thumb  is  a  short  nerve  which  subdivides 
to  supply  the  Abductor,  Opponens,  and  outer  head  of  the  Flexor  brevis  pollicis 
muscles,  the  remaining  muscles  of  this  group  being  supplied  by  the  ulnar 
nerve. 

The  digital  branches  are  five  in  number.  The  first  and  second  pass  along  the 
borders  of  the  thumb,  the  external  branch  communicating  with  branches  of  the 
radial  nerve.  The  third  passes  along  the  radial  side  of  the  index  finger,  and 
supplies  the  First  lumbricalis  muscle.  The  fourth  subdivides  to  supply  the  adjacent 
sides  of  the  index  and  middle  fingers,  and  sends  a  branch  to  the  Second  lumbrical 
muscle.  The  fifth  supplies  the  adjacent  sides  of  the  middle  and  ring  fingers,  and 
communicates  with  a  branch  from  the  ulnar  nerve. 

Each  digital  nerve,  opposite  the  base  of  the  first  phalanx,  gives  off  a  dorsal 
branch,  which  joins  the  dorsal  digital  nerve  from  the  radial  and  runs  along  the 
side  of  the  dorsum  of  the  finger,  to  end  in  the  integument  over  the  last  phalanx. 
At  the  end  of  the  finger  the  digital  nerve  divides  into  a  palmar  and  a  dorsal 
branch,  the  former  of  which  supplies  the  extremity  of  the  finger,  and  the  latter 
ramifies  round  and  beneath  the  nail.  The  digital  nerves,  as  they  run  along  the 
fingers,  are  placed  superficial  to  the  digital  arteries. 

The  Ulnar  Nerve  (Fig.  500)  is  placed  along  the  inner  or  ulnar  side  of  the  upper 
limb,  and  is  distributed  to  the  muscles  and  integument  of  the  forearm  and  hand. 
It  is  smaller  than  the  median,  behind  which  it  is  placed,  diverging  from  it  in  its 
course  down  the  arm.  It  arises  from  the  inner  cord  of  the  brachial  plexus,  in 
common  with  the  inner  head  of  the  median  and  the  internal  cutaneous  nerve,  and 
derives  its  fibres  from  the  eighth  cervical  and  first  dorsal  nerves.  At  its  commence- 
ment it  lies  at  the  inner  side  of  the  axillary  artery,  and  holds  the  same  relation 
with  the  brachial  artery  to  the  middle  of  the  arm.  From  this  point  it  runs  obliquely 
across  the  internal  head  of  the  Triceps,  pierces  the  internal  intermuscular  septum, 
and  descends  to  the  groove  between  the  internal  condyle  and  the  olecranon.  accom- 
panied by  the  inferior  profunda  artery.  At  the  elbou'  -it  rests  upon  the  back  of  the 
inner  condyle.  and  passes  into  the  forearm  between  the  two  heads  of  the  Flexor 
carpi  ulnaris.  In  the  forearm  it  descends  in  a  perfectly  straight  course  along  its 
ulnar  side,  lying  upon  the  Flexor  profundus  digitorum,  its  upper  half  being  covered 
by  the  Fiexor  carpi  ulnaris,  its  lower  half  lying  on  the  outer  side  of  the  muscle, 
covered  by  the  integument  and  fascia.  The  ulnar  artery,  in  the  upper  third  of  its 
course,  is  separated  from  the  ulnar  nerve  by  a  considerable  interval,  but  in  the 
>f  its  extent  the  nerve  lies  to  its  inner  side.  At  the  wrist  the  ulnar  nerve 


842  THE  NERVOUS  SYSTEM. 

crosses  the  annular  ligament  on  the  outer  side  of  the  pisiform  bone,  to  the  inner 
side  and  a  little  behind  the  ulnar  artery,  and  immediately  beyond  this  bone  divides 
into  two  branches,  superficial  and  deep  palmar. 
The  branches  of  the  ulnar  nerve  are — 

^Articular  (elbow). 
Muscular.  /•  q         fi  •  i       i 

In  the  forearm  <  Cutaneous.  In  the  hand  <  \ 

\  T\        i  I  Deep  palmar. 

Dorsal  cutaneous. 

^Articular  (wrist). 

The  articular  branches  distributed  to  the  elbow-joint  consist  of  several  small 
filaments.  They  arise  from  the  nerve  as  it  lies  in  the  groove  between  the  inner 
condyle  and  olecranon. 

The  muscular  branches  are  two  in  number — one  supplying  the  Flexor  carpi 
ulnaris  ;  the  other,  the  inner  half  of  the  Flexor  profundus  digitorum.  They  arise 
from  the  trunk  of  the  nerve  near  the  elbow. 

The  cutaneous  branch  arises  from  the  ulnar  nerve  about  the  middle  of  the  fore- 
arm, and  divides  into  two  branches. 

One  branch  (frequently  absent)  pierces  the  deep  fascia  near  the  wrist,  and  is 
distributed  to  the  integument,  communicating  with  a  branch  of  the  internal 
cutaneous  nerve. 

The  second  branch  (palmar  cutaneous)  lies  on  the  ulnar  artery,  which  it 
accompanies  to  the  hand,  some  filaments  entwining  round  the  vessel ;  it  ends  in 
the  integument  of  the  palm,  communicating  with  branches  of  the  median  nerve. 

The  dorsal  cutaneous  branch  arises  about  two  inches  above  the  wrist ;  it  passes 
backward  beneath  the  Flexor  carpi  ulnaris,  perforates  the  deep  fascia,  and,  along 
the  ulnar  side  of  the  back  of  the  wrist  and  hand,  divides  into  two  digital  branches, 
of  which  one  supplies  the  inner  side  of  the  little  finger,  and  the  other  bifurcates 
to  supply  the  adjoining  sides  of  the  little  and  ring  fingers ;  it  communicates  with 
the  posterior  branch  of  the  internal  cutaneous  nerve,  and  sends  a  communicating 
filament  to  that  branch  of  the  radial  nerve  which  supplies  the  adjoining  sides  of 
the  middle  and  ring  fingers.  Sometimes  there  is  a  third  digital  branch  which 
goes  to  the  adjacent  sides  of  the  middle  and  ring  fingers.  In  this  case  the  radial 
nerve-supply  is  correspondingly  diminished. 

The  superficial  palmar  branch  supplies  the  Palmaris  brevis  and  the  integu- 
ment on  the  inner  side  of  the  hand,  and  terminates  in  two  digital  branches,  which 
are  distributed,  one  to  the  ulnar  side  of  the  little  finger,  the  other  to  the  adjoining 
sides  of  the  little  and  ring  fingers,  the  latter  communicating  with  a  branch  from 
the  median.  The  digital  branches  are  distributed  to  the  fingers  in  the  same 
manner  as  the  digital  branches  of  the  median.  The  dorsal  digital  branches, 
except  those  on  the  little  finger,  do  not  extend,  as  a  rule,  beyond  the  second 
phalanx,  the  remaining  portion  of  the  skin  being  supplied  by  filaments  from  the 
corresponding  palmar  digital  branch. 

The  deep  palmar  branch  passes  between  the  Abductor  and  Flexor  brevis 
minimi  digiti  muscles,  and  follows  the  course  of  the  deep  palmar  arch  beneath  the 
flexor  tendons.  At  its  origin  it  supplies  the  muscles  of  the  little  finger.  As  it 
crosses  the  deep  part  of  the  hand  it  sends  two  branches  to  each  interosseous 
space,  one  for  the  Dorsal  and  one  for  the  Palmar  interosseous  muscle,  the  branches 
to  the  Second  and  Third  palmar  interossei  supplying  filaments  to  the  two  inner 
Lumbrical  muscles.  At  its  termination  between  the  thumb  and  index  finger  it 
supplies  the  Adductores  transversus  et  obliquus  pollicis  and  the  inner  head  of  the 
Flexor  brevis  pollicis.  Articular  branches  to  the  wrist  are  derived  from  this 
nerve. 

The  Musculo-spiral  Nerve  (Fig.  501),  the  largest  branch  of  the  brachial  plexus, 
supplies  the  muscles  of  the  back  part  of  the  arm  and  forearm  and  the  integument 
of  the  same  parts,  as  well  as  that  of  the  back  of  the  hand.  It  arises  from  the 
posterior  cord  of  the  brachial  plexus  by  a  common  trunk  with  the  circumflex 


THE   BRACHIAL    PLEXUS. 


843 


Suprascapular. 


Circumflex, 


nerve,  and  is  afterward  joined  by  the  posterior  division  of  the  trunk,  formed  by 
the  junction  of  the  eighth  cervical  and  first  dorsal  nerves.  It  receives  filaments 
from  the  sixth,  seventh,  and  eighth  cervical  and  first  dorsal  nerves.  At  its  com- 
mencement it  is  placed  behind  the  axillary  and  upper  part  of  the  brachial  arteries, 
passing  down  in  front  of  the 
tendons  of  the  Latissimus  dorsi 
and  Teres  major.  It  winds 
round  the  humerus  in  the  mus- 
culo-spiral  groove  with  the  su- 
perior profunda  artery,  passing 
from  the  inner  to  the  outer  side 
of  the  bone,  between  the  inter- 
nal and  external  heads  of  the 
Triceps  muscle.  It  pierces  the 
external  intermuscular  septum, 
and  descends  between  the 
Brachialis  anticus  and  Supi- 
nator  longus  to  the  front  of 
the  external  condyle,  where  it 
divides  into  the  radial  and 
posterior  interosseous  nerves. 

The  branches  of  the  mus- 
culo-spiral  nerve  are — 
Muscular. 
Cutaneous. 
Radial. 
Posterior  interosseous. 

The  muscular  brandies  are 
divided  into  internal,  posterior, 
and  external ;  they  supply  the 
Triceps.  Anconeus,  Supinator 
longus,  Extensor  carpi  radialis 
longior,  and  Brachialis  anti- 
cus. These  branches  are  de- 
rived from  the  nerve  at  the 
inner  side,  back  part,  and 
outer  side  of  the  arm. 

The  internal  muscular 
branches  supply  the  inner  and 
middle  heads  of  the  Triceps 
muscle.  That  to  the  inner 
head  of  the  Triceps  is  a  long, 
slender  filament  which  lies 
close  to  the  ulnar  nerve,  as  far 
as  the  lower  third  of  the  arm. 
and  is  often  intimately  con- 
nected with  it  (ulnar  collateral 
branch). 

The  posterior  muscular 
branch,  of  large  size,  arises 
from  the  nerve  in  the  groove 
between  the  Triceps  and  the 
humerus.  It  divides  into  branches  which  supply  the  outer  and  inner  head  of  the 
Triceps  and  Anconeus  muscles.  The  branch  for  the  latter  muscle  is  a  long,  slen- 
der filament  which  descends  in  the  substance  of  the  Triceps  to  the  Anconeus. 

The  external  muscular  branches  supply  the  Supinator  longus,  Extensor  carpi- 
radial  is  longior,  and  (usually)  the  outer  part  of  the  Brachialis  anticus. 


FIG.  501.— The  suprascapular,  circumflex,  and  musculo-spiral 

nerves. 


844  THE  NERVOUS  SYSTEM. 

The  cutaneous  brandies  are  three  in  number,  one  internal  and  two  external. 

The  internal  cutaneous  branch  arises  in  the  axillary  space  with  the  inner  mus- 
cular branch.  It  is  of  small  size,  and  passes  through  the  axilla  to  the  inner  side 
of  the  arm,  supplying  the  integument  on  its  posterior  aspect  nearly  as  far  as  the 
olecranon.  In  its  course  it  crosses  beneath  the  intercosto-humeral,  with  which 
it  communicates. 

The  two  external  cutaneous  branches  perforate  the  outer  head  of  the  Triceps 
at  its  attachment  to  the  humerus.  The  upper  and  smaller  one  passes  to  the 
front  of  the  elbow,  lying  close  to  the  cephalic  vein,  and  supplies  the  integu- 
ment of  the  lower  half  of  the  arm  on  its  anterior  aspect.  The  lower  branch 
pierces  the  deep  fascia  below  the  insertion  of  the  Deltoid,  and  passes  down  along 
the  outer  side  of  the  arm  and  elbow,  and  then  along  the  back  part  of  the  radial 
side  of  the  forearm  to  the  wrist,  supplying  the  integument  in  its  course,  and  join- 
ing, near  its  termination,  with  the  posterior  cutaneous  branch  of  the  musculo- 
cutaneous  nerve. 

The  radial  nerve  passes  along  the  front  of  the  radial  side  of  the  forearm  to 
the  commencement  of  its  lower  third.  It  lies  at  first  a  little  to  the  outer  side  of 
the  radial  artery,  concealed  beneath  the  Supinator  longus.  In  the  middle  third 
of  the  forearm  it  lies  beneath  the  same  muscle,  in  close  relation  with  the  outer 
side  of  the  artery.  It  quits  the  artery  about  three  inches  above  the  wrist,  passes 
beneath  the  tendon  of  the  Supinator  longus,  and,  piercing  the  deep  fascia  at  the 
outer  border  of  the  forearm,  divides  into  two  branches. 

The  external  branch,  the  smaller  of  the  two,  supplies  the  integument  of  the 
radial  side  and  ball  of  the  thumb,  joining  with  the  anterior  branch  of  the  musculo- 
cutaneous  nerve. 

The  internal  branch  communicates,  above  the  wrist,  with  the  posterior  cuta- 
neous branch  from  the  musculo-cutaneous,  and  on  the  back  of  the  hand  forms  an 
arch  with  the  dorsal  cutaneous  branch  of  the  ulnar  nerve.  It  then  divides  into 
three  digital  nerves,  which  are  distributed  as  follows :  The  first  supplies  the  ulnar 
side  of  the  thumb  and  the  radial  side  of  the  index  finger;  the  second,  the  adjoin- 
ing sides  of  the  index  and  middle  fingers ;  and  the  third,  the  adjacent  borders  of 
the  middle  and  ring  fingers.1  The  latter  nerve  communicates  with  a  filament 
from  the  dorsal  branch  of  the  ulnar  nerve. 

The  Posterior  Interosseous  Nerve  winds  to  the  back  of  the  forearm  through 
the  fibres  of  the  Supinator  brevis,  and  passes  down,  between  the  superficial 
and  deep  layer  of  muscles,  to  the  middle  of  the  forearm.  Considerably  dimin- 
ished in  size,  it  descends  on  the  interosseous  membrane,  beneath  the  Extensor 
longus  pollicis,  to  the  back  of  the  carpus,  where  it  presents  a  gangliform 
enlargement  from  which  filaments  are  distributed  to  the  ligaments  and  artic- 
ulations of  the  carpus.  It  supplies  all  the  muscles  of  the  radial  and  posterior 
brachial  regions,  excepting  the  Anconeus,  Supinator  longus,  and  Extensor  carpi 
radialis  longior. 

Surgical  Anatomy. — The  brachial  plexus  may  be  ruptured  by  traction  on  the  limb  leading 
to  complete  paralysis.  In  these  cases  the  lesion  would  appear  to  be  rather  a  tearing  away  of 
the  nerves  from  the  spinal  cord  than  a  solution  of  continuity  of  the  nerve-fibres  themselves.  In 
the  axilla  any  of  the  nerves  forming  the  brachial  plexus  may  be  injured  in  a  wound  of  this  part, 
the  median  being  the  one  which  is  most  frequently  damaged  from  its  exposed  position,  and  the 
musculo-spiral,  on  account  of  its  sheltered  and  deep  position,  being  the  least  often  wounded. 
The  brachial  plexus  in  the  axilla  is  often  damaged  from  the  pressure  of  a  crutch,  producing  the 
condition  known  as  "crutch  paralysis."  In  these  cases  the  musculo-spiral  appears  to  be  the 
nerve  which  is  most  frequently  implicated  to  the  greatest  extent,  the  ulnar  nerve  being  the  one 
that  appears  to  suffer  next  in  frequency. 

The  circumflex  nerve  is  of  particular  surgical  interest.  On  account  of  its  course  round  the 
joint  it  is  liable  to  be  torn  in  fractures  of  the  surgical  neck  of  the  humerus  and  in  dislocations 
of  the  shoulder-joint,  leading  to  paralysis  of  the  deltoid,  and,  according  to  Erb,  inflammation  of 
the  shoulder-joint  is  liable  to  be  followed  by  a  neuritis  of  this  nerve  from  extension  of  the 
inflammation  to  it. 

1  According  to  Hutchinson,  the  digital  nerve  to  the  thumb  reaches  only  as  high  as  the  root  of  the 
nail ;  the  one  to  the  fort-linger  as  high  as  the  middle  of  the  second  phalanx;  and  the  one  to  the  mid 
die  and  ring  lingers  not  higher  than  the  first  phalangeal  joint  (London  Hasp.  Gas.  vol.  iii.  p.  319.) 


THE   BRACHIAL    PLEXUS.  845 

Mr.  Hilton  takes  the  circumflex  nerve  as  an  illustration  of  a  law  which  he  lays  down,  that 
"  the  same  trunks  of  nerves  whose  branches  supply  the  groups  of  muscles  moving  a  joint  furnish 
also  a  distribution  of  nerves  to  the  skin  over  the  insertions  of  the  same  muscles,  and  the  interior 
of  the  joint  receives  its  nerves  from  the  same  source."  In  this  way  he  explains  the  fact  that  an 
inflamed  joint  becomes  rigid,  because  the  same  nerves  which  supply  the  interior  of  the  joint 
supply  the  mus vies  also  which  move  that  joint. 

The  median  //••/•?•••  is  liable  to  injury  in  wounds  of  the  forearm.  When  paralyzed,  there  is 
f  flexion  of  the  second  phalanges  of  all  the  fingers  and  of  the  terminal  phalanges  of  the 
index  and  middle  fingers.  Flexion  of  the  terminal  phalanges  of  the  ring  and  middle  fingers  is 
effected  by  that  portion  of  the  Flexor  profundus  digitorum  which  is  supplied  by  the  ulnar  nerve. 
There  is  power  to  flex  the  proximal  phalanges  through  the  Interossei.  The  thumb  cannot  be 
flexed  or  opposed,  and  is  maintained  in  a  position  of  extension  and  adduction.  All  power  of 
pronation  is  lust.  The  wrist  can  be  flexed,  if  the  hand  is  first  adducted.  by  the  action  of  the 
Flexor  carpi  ulnaris.  There  is  loss  or  impairment  of  sensation  on  the  palmar  surface  of  the 
thumb,  index,  middle,  and  outer  half  of  the  ring  fingers,  and  on  the  dorsal  surface  of  the  same 
fingers  over  the  last  two  phalanges  :  except  in  the  thumb,  where  the  loss  of  sensation  would  be 
limited  to  the  back  of  the  last  phalanx.  In  order  to  expose  the  median  nerve  for  the  purpose 
of  stretching  an  incision  should  be  made  along  the  ulnar  side  of  the  tendon  of  the  Palmaris 
longus.  which  serves  as  a  guide  to  the  nerve. 

The  ii.finn'  nerve  is  also  liable  to  be  injured  in  wounds  of  the  forearm.  When  paralyzed, 
there  is  loss  of  power  of  flexion  in  the  ring  and  little  fingers  :  there  is  impaired  power  of  ulnar 
flexion  and  adduction  :  there  is  inability  to  spread  out  the  fingers  from  paralysis  of  the  Inter- 
and  there  is  inability  to  adduct  the  thumb.  Sensation  is  lost  or  impaired  in  the  skin  sup- 
plied by  the  nerve.  In  order  to  expose  the  nerve  in  the  lower  part  of  the  forearm,  an  incision 
should  be  made  along  the  outer  border  of  the  tendon  of  the  Flexor  carpi  ulnaris.  and  the  nerve 
will  be  found  lying  on  the  ulnar  side  of  the  ulnar  artery. 

The  musculo-spira!  nerve  is  probably  more  frequently  injured  than  any  other  nerve  of  the 
upper  extremity.  In  consequence  of  its  close  relationship  to  the  humerus  as  it  lies  in  the  mus- 
culo-spiral  groove,  it  is  frequently  torn  or  injured  in  fractures  of  this  bone,  or  subsequently 
involved  in  the  callus  that  may  be  thrown  out  around  a  fracture,  and  thus  pressed  upon  and  its 
functions  interfered  with.  It  is  also  liable  to  be  contused  against  the  bone  by  kicks  or  blows  or 
to  be  divided  by  wounds  of  the  arm.  When  paralyzed,  the  hand  is  flexed  at  the  wrist  and  lies 
flaccid.  This  is  known  as  "  drop-wrist"  The  fingers  are  also  flexed,  and  on  an  attempt  being 
made  to  extend  them  the  last  two  phalanges  only  wilTbe  extended  through  the  action  of  the  Inter- 
the  first  phalanges  remaining  flexed.  There  is  no  power  of  extending  the  wrist.  Supina^ 
tion  is  completely  lost  when  the  forearm  is  extended  on  the  arm.  but  it  is  possible  to  a  certain 
extent  if  the  forearm  is  flexed  so  as  to  allow  of  the  action  of  the  Biceps.  The  power  of  exten- 
sion of  the  forearm  is  lost  on  account  of  paralysis  of  the  Triceps.  The  best  position  in  which 
to  expose  the^  nerve  for  the  purpose  of  stretching  is  to  make  an  incision  along  the  inner 
border  of  the  Supinator  longiis.  just  above  the  level  of  the  elbow-joint.  The  skin  and  super- 
ficial structures  are  to  be  divided  and  the  deep  fascia  exposed.  The  white  line  in  this  struc- 
ture indicating  the  border  of  the  muscle  is  to  be  defined,  and  the  deep  fascia  divided  in  this 
line.  By  now  raising  the  Supinator  longus  the  nerve  will  be  found  lying  beneath  it,  on  the 
Brachialis  antieus. 

THE   DOESAL   NERVES  (Fig.  502). 

The  Dorsal  Nerves  are  twelve  in  number  on  each  side.  The  first  appears 
between  the  first  and  second  dorsal  vertebrae,  and  the  last  between  the  last  dorsal 
and  first  lumbar. 

The  roots  of  tln>  dorsal  nerves  are  of  small  size,  and  vary  but  slightly  from  the 
second  to  the  last.  Both  roots  are  very  slender,  the  posterior  roots  only  slightly 
exceeding  the  anterior  in  thickness.  They  gradually  increase  in  length  from 
above  downward,  and  pass  down  in  contact  with  the  spinal  cord  for  a  distance 
equal  to  the  height  of,  at  least,  two  vertebrae,  in  the  lower  part  of  the  dorsal  region, 
before  they  emerge  from  the  spinal  canal.  They  then  join  in  the  intervertebral 
foramen,  and  at  their  exit  divide  into  two  primary  divisions,  a  posterior  (dorsal) 
and  an  anterior  (intercostal). 

The  first  and  last  dorsal  nerves  are  peculiar  in  some  respects. 

Posterior  Divisions  of  the  Dorsal  Nerves. 

The  posterior  divisions  of  the  dorsal  nerves,  which  are  smaller  than  the  ante- 
rior, pass  backward  between  the  transverse  processes,  and  divide  into  internal  and 
external  branches. 

The  internal  branches  of  the  six  upper  nerves  pass  inward  between  the  Semi- 
spinalis  dorsi  and  Multifidus  spinae  muscles,  which  they  supply,  and  then,  piercing 


846  THE   NERVOUS  SYSTEM. 

the  origins  of  the  Rhomboidei  and  Trapezius  muscles,  become  cutaneous  by  the 
side  of  the  spinous  processes  and  ramify  in  the  integument.  The  internal  branches 
of  the  six  lower  nerves  are  distributed  to  the  Multifidus  spinae,  without  giving  off 
any  cutaneous  filaments. 

The  external  branches  increase  in  size  from  above  downward.  They  pass 
through  the  Longissimus  dorsi  to  the  cellular  interval  between  it  and  the  Ilio- 
costalis,  and  supply  those  muscles,  as  well  as  their  continuations  upward  to  the 
head,  and  the  Levatores  costarum ;  the  five  or  six  lower  nerves  also  give  off 
cutaneous  filaments,  which  pierce  the  Serratus  posticus  inferior  and  Latissimus  dorsi 
in  a  line  with  the  angles  of  the  ribs,  and  then  ramify  in  the  integument. 

The  cutaneous  branches  of  the  dorsal  nerves  are  twelve  in  number.  The  six 
upper  cutaneous  nerves  are  derived  from  the  internal  branches  of  the  posterior 
divisions  of  the  dorsal  nerves.  They  pierce  the  origins  of  the  Rhomboidei  and 
Trapezius  muscles,  and  become  cutaneous  by  the  side  of  the  spinous  processes, 
and  then  ramify  in  the  integument.  They  are  frequently  furnished  with  gangliform 
enlargements.  The  six  lower  cutaneous  nerves  are  derived  from  the  external 
branches  of  the  posterior  divisions  of  the  dorsal  nerves.  They  pierce  the  Serratus 
posticus  inferior  and  Latissimus  dorsi  in  a  line  with  the  angles  of  the  ribs,  and 
then  ramify  in  the  integument. 

Anterior  Divisions  of  the  Dorsal  Nerves. 

The  anterior  divisions  of  the  dorsal  nerves  (intercostal  nerves)  are  twelve  in 
number  on  each  side.  They  are,  for  the  most  part,  distributed  to  the  parietes  of 
the  thorax  and  abdomen,  separately  from  each  other,  without  being  joined  in  a 
plexus ;  in  which  respect  they  differ  from  the  other  spinal  nerves.  Each  nerve  is 
connected  with  the  adjoining  ganglia  of  the  sympathetic  by  one  or  two  filaments. 
The  intercostal  nerves  may  be  divided  into  two  sets,  from  the  difference  they 
present  in  their  distribution.  The  six  upper,  with  the  exception  of  the  first  and 
the  intercosto-humeral  branch  of  the  second,  are  limited  in  their  distribution  to  the 
parietes  of  the  chest.  The  six  lower  supply  the  parietes  of  the  chest  and  abdomen, 
the  last  one  sending  a  cutaneous  filament  to  the  hip. 

The  First  Dorsal  Nerve. — The  anterior  division  of  the  first  dorsal  nerve  divides 
into  two  branches :  one,  the  larger,  leaves  the  thorax  in  front  of  the  neck  of  the 
first  rib,  and  enters  into  the  formation  of  the  brachial  plexus  ;  the  other  and 
smaller  branch  runs  along  the  first  intercostal  space,  forming  the  first  intercostal 
nerve,  and  terminates  on  the  front  of  the  chest  by  forming  the  first  anterior 
cutaneous  nerve  of  the  thorax.  Occasionally  this  anterior  cutaneous  branch  is 
wanting.  The  first  intercostal  nerve,  as  a  rule,  gives  off  no  lateral  cutaneous 
branch,  but  sometimes  a  small  branch  is  given  off  which  communicates  with  the 
intercosto-humeral. 

The  Upper  Dorsal  Nerves. — The  anterior  divisions  of  the  second,  third,  fourth, 
fifth,  and  sixth  dorsal  nerves  and  the  small  branch  from  the  first  dorsal  are 
confined  to  the  parietes  of  the  thorax,  and  are  named  upper  or  pectoral  intercostal 
nerves.  They  pass  forward  in  the  intercostal  spaces  with  the  intercostal  vessels, 
being  situated  below  them.  At  the  back  of  the  chest  they  lie  between  the  pleura 
and  the  External  intercostal  muscle,  but  are  soon  placed  between  the  tAvo  planes 
of  Intercostal  muscles  as  far  as  the  middle  of  the  rib.  They  then  enter  the 
substance  of  the  Internal  intercostal  muscles,  and,  running  amidst  their  fibres  as  far 
as  the  costal  cartilages,  they  gain  the  inner  surface  of  the  muscles  and  lie  between 
them  and  the  pleura.  Near  the  sternum  they  cross  the  internal  mammary  artery 
and  Triangularis  sterni  muscle,  pierce  the  Internal  intercostal  and  Pectoralis  major 
muscles,  and  supply  the  integument  of  the  front  of  the  chest  and  over  the 
mammary  gland,  forming  the  anterior  cutaneous  nerves  of  the  thorax,  the  branch 
from  the  second  nerve  becoming  joined  with  the  supraclavicular  nerves  of  the 
cervical  plexus. 

Branches. — Numerous  slender  muscular  filaments  supply  the  Intercostals,  the 
Infracostales,  the  Levatores  costarum,  Serratus  posticus  superior,  and  Triangularis 


THE   DORSAL    NERVES. 


847 


FIG.  50i— Superficial  and  deep  distribution  of  the  posterior  branches  of  the  spinal  nerves  (after  Hirschfeld 
and  Leveille).  On  the  left  side  the  cutaneous  branches  are  represented  lying  on  the  superficial  layer  of  mus- 
cles. On  the  right  side  the  superficial  muscles  have  been  removed,  the  Splenius  capitis  and  Complexus  divided 
in  the  neck,  and  the  Erector  spinae  divided  and  partly  removed  in  the  back,  so  as  to  expose  the  posterior  divis- 
ions of  the  spinal  nerves  near  their  origin,  a  a.  Lesser  occipital  nerve  from  the  cervical  plexus.  1.  External 
muscular  branches  of  the  first  cervical  nerve,  and  union  by  a  loop  with  the  second.  2,  placed  on  the  Rectus 
capitis  posticus  major  muscle,  marks  the  great  occipital  nerve,  passing  round  the  short  muscles  and  piercing 
:nplexus  :  the  external  branch  is  seen  to  the  outside.  3.  External  branch  from  the  posterior  division  of 
the  third  nerve.  3'.  Its  internal  branch,  sometimes  called  the  third  occipital.  4'  to  8'.  The  internal  branches 
of  the  several  corresponding  nerves  on  the  left  side.  The  external  branches  of  these  nerves,  proceeding  to 
mu-cles,  are  displayed  on  the  right  side,  d  1  to  d  6,  and  thence  to  d  12.  External  muscular  branches  of  the  pos- 
terior divisions  of  the  twelve  dorsal  nerves  on  the  right  side,  d  1'  to  d  6'.  The  internal  cutaneous  branches  of 
the  six  upper  dorsal  nerves  on  the  left  side,  d  7'  to  -7  U  .  Cutaneous  twigs  from  the  external  branches  of  the 
six  lower  dorsal  nerves.  1 1.  External  branches  from  the  posterior  divisions  of  several  lumbar  nerves  on  the 
ri"ht  side,  piercing  the  muscles,  the  lower  descending  over  the  gluteal  region.  I'  I'.  The  same,  more  super- 
ficially, on  the  left  side,  s  s.  The  issue  and  union  by  loops  of  the  posterior  divisions  of  four  sacral  nerves  on  the 
right  side,  if  «*.  Some  of  those  distributed  to  the  skin  on  the  left  side. 

sterni  muscles.     Some  of  these  branches,  at  the  front  of  the  chest,  cross  the  costal 
curtilages  from  one  to  another  intercostal  space. 


848  THE  NERVOUS  SYSTEM. 

Lateral  Cutaneous  Nerves. — These  are  derived  from  the  intercostal  nerves, 
midway  between  the  vertebrae  and  sternum :  they  pierce  the  External  intercostal 
and  Serratus  magnus  muscles,  and  divide  into  two  branches,  anterior  and  posterior. 

The  anterior  branches  are  reflected  forward  to  the  side  and  the  fore  part  of  the 
chest,  supplying  the  integument  of  the  chest  and  mamma  and  the  upper  digitations 
of  the  External  oblique. 

The  posterior  branches  are  reflected  backward  to  supply  the  integument  over 
the  scapula  and  over  the  Latissimus  dorsi. 

The  lateral  cutaneous  branch  of  the  second  intercostal  nerve  is  of  large  size, 
and  does  not  divide,  like  the  other  nerves,  into  an  anterior  and  posterior  branch. 
It  is  named,  from  its  origin  and  distribution,  the  intercosto-humeral  nerve  (Fig.  500). 
It  pierces  the  External  intercostal  muscle,  crosses  the  axilla  to  the  inner  side  of 
the  arm,  and  joins  with  a  filament  from  the  nerve  of  Wrisberg.  It  then  pierces 
the  fascia,  and  supplies  the  skin  of  the  upper  half  of  the  inner  and  back  part  of 
the  arm,  communicating  with  the  internal  cutaneous  branch  of  the  musculo-spiral 
nerve.  The  size  of  this  nerve  is  in  inverse  proportion  to  the  size  of  the  other 
cutaneous  nerves,  especially  the  nerve  of  Wrisberg.  A  second  intercosto-humeral 
nerve  is  frequently  given  off  from  the  third  intercostal.  It  supplies  filaments  to 
the  armpit  and  inner  side  of  the  arm. 

The  Lower  Dorsal  Nerves. — The  anterior  divisions  of  the  seventh,  eighth,  ninth, 
tenth,  and  eleventh  dorsal  nerves  are  continued  anteriorly  from  the  intercostal 
spaces  into  the  abdominal  wall,  hence  these  nerves  are  named  lower  or  abdominal 
intercostal  nerves  ;  the  twelfth  dorsal  is  continued  throughout  its  whole  course  in 
the  abdominal  wall,  since  it  is  placed  below  the  last  rib  (subcostal  nerve).  They 
have  (except  the  last)  the  same  arrangement  as  the  upper  ones  as  far  as  the 
anterior  extremities  of  the  intercostal  spaces,  where  they  pass  behind  the  costal 
cartilages,  and  between  the  Internal  oblique  and  Transversalis  muscles,  to  the 
sheath  of  the  Rectus,  which  they  perforate.  They  supply  the  Rectus  muscle,  and 
terminate  in  branches  which  become  subcutaneous  near  the  linea  alba.  These 
branches  are  named  the  anterior  cutaneous  nerves  of  the  abdomen.  They  are 
directed  outward  as  far  as  the  lateral  cutaneous  nerves,  supplying  the  integument 
of  the  front  of  the  belly.  The  lower  intercostal  nerves  supply  the  Intercostals, 
Serratus  posticus  inferior,  and  Abdominal  muscles.  Filaments  have  been  traced 
to  the  costal  part  of  the  Diaphragm.  About  the  middle  of  their  course  they 
give  off  lateral  cutaneous  branches,  which  pierce  the  External  intercostal  and 
External  oblique  muscles,  in  the  same  line  as  the  lateral  cutaneous  nerves  of  the 
thorax,  and  divide  into  anterior  and  posterior  branches,  which  are  distributed 
to  the  integument  of  the  abdomen  and  back,  the  anterior  branches  passing  nearly 
as  far  forward  as  the  margin  of  the  Rectus,  the  posterior  branches  passing 
backward  to  supply  the  skin  over  the  Latissimus  dorsi,  where  they  join  the  dorsal 
cutaneous  nerves. 

The  last  dorsal  is  larger  than  the  other  dorsal  nerves.  Its  anterior  division 
runs  along  the  lower  border  of  the  last  rib  in  front  of  the  Quadratus  lumborum, 
perforates  the  Transversalis,  and  passes  forward  between  it  and  the  Internal 
oblique  to  be  distributed  in  the  same  manner  as  the  lower  intercostal  nerves.  It 
communicates  with  the  ilio-hypogastric  branch  of  the  lumbar  plexus,  and  is 
frequently  connected  with  the  first  lumbar  nerve  by  a  slender  branch,  the  dorso- 
lumbar  nerve,  which  descends  in  the  substance  of  the  Quadratus  lumborum. 

The  lateral  cutaneous  branch  of  the  last  dorsal  is  remarkable  for  its  large  size : 
it  perforates  the  Internal  and  External  oblique  muscles,  passes  downward  over 
the  crest  of  the  ilium  in  front  of  the  iliac  branch  of  the  ilio-hypogastric  (Fig.  509), 
and  is  distributed  to  the  integument  of  the  front  of  the  hip,  some  of  its  filaments 
extending  as  low  down  as  the  trochanter  major.  It  does  not  divide  into  an  anterior 
and  posterior  branch  like  the  other  lateral  cutaneous  branches  of  the  intercostal 
nerves. 

Surgical  Anatomy. — The  lower  seven  intercostal  nerves  and  the  ilio-hypogastric  from  the 
first  lumbar  nerve  supply  the  skin  of  the  abdominal  wall.  They  run  downward  and  inward 


THE   LUMBAR    .Y£7?T7>.  849 

fairly  equidistant  from  each  other.  The  sixth  and  seventh  supply  the  skin  over  the  "  pit  of  the 
stomach:  "  the  eighth  corresponds  to  about  the  position  of  the  middle  linea  transversa  ;  the 
tenth  to  the  umbilicus  :  and  the  ilio-hypogastric  supplies  the  skin  over  the  pubes  and  external 
abdominal  ring.  There  are  several  points  of  surgical  importance  about  the  distribution  of  these 
nerves,  and  it  is  important  to  remember  their  origin  and  course,  for  in  many  diseases  affecting 
the  nerve-trunks  at  or  near  the  origin  the  pain  is  referred  to  their  peripheral  terminations. 
Thus  in  Pott's  disease  of  the  spine  children  will  often  be  brought  to  the  surgeon  suffering  from 
pain  in  the  belly.  This  is  due  to  the  fact  that  the  nerves  are  irritated  at  the  seat  of  disease  as 
they  issue  from  the  spinal  canal.  When  the  irritation  is  confined  to  a  single  pair  of  nerves,  the 
sensation  complained  of  is  often  a  feeling  of  constriction,  as  if  a  cord  were  tied  round  the  abdo- 
men ;  and  in  these  cases  the  situation  of  the  sense  of  constriction  may  serve  to  localize  the 
disease  in  the  spinal  column.  In  other  cases,  where  the  bone  disease  is  more  extensive  and  two 
or  more  nerves  are  involved,  a  more  general  diffused  pain  in  the  abdomen  is  complained  of.  A 
similar  condition  is  sometimes  present  in  affections  of  the  cord  itself,  as  in  tabes  dorsalis. 

Again,  it  must  be  borne  in  mind  that  the  same  nerves  which  supply  the  skin  of  the  abdomen 
supply  also  the  planes  of  muscle  which  constitute  the  greater  part  of  the  abdominal  wall.  Hence 
it  follows  that  any  irritation  applied  to  the  peripheral  terminations  of  the  cutaneous  branches  in 
the  skin  of  the  abdomen  is  immediately  followed  by  reflex  contraction  of  the  abdominal  muscles. 
A  good  practical  illustration  of  this  may  sometimes  be  seen  in  watching  two  surgeons  examine 
the  abdomen  of  the  same  patient.  One.  whose  hand  is  cold,  causes  the  muscles  of  the  abdominal 
wall  to  at  once  contract  and  the  belly  to  become  rigid,  and  thus  not  nearly  so  suitable  for  examina- 
tion :  the  other,  who  has  taken  the  precaution  to  warm  his  hand,  examines  the  abdomen  with- 
out exciting  any  reflex  contraction.  The  supply  of  both  muscles  and  skin  from  the  same  source 
is  of  importance  in  protecting  the  abdominal  viscera  from  injury.  A  blow  on  the  abdomen, 
even  of  a  severe  character,  will  do  no  injury  to  the  viscera  if  the  muscles  are  in  a  condition  of 
firm  contraction  :  whereas  in  cases  where  the  muscles  have  been  taken  unawares,  and  the  blow 
has  been  struck  while  they  were  in  a  state  of  rest,  an  injury  insufficient  to  produce  any  lesion  of 
the  abdominal  wall  has  been  attended  with  rupture  of  some  of  the  abdominal  contents.  The 
importance,  therefore,  of  immediate  reflex  contraction  upon  the  receipt  of  an  injury  cannot  be 
overestimated,  and  the  intimate  association  of  the  cutaneous  and  muscular  fibres  in  the  same 
nerve  produces  a  much  more  immediate  response  on  the  part  of  the  muscles  to  any  peripheral 
stimulation  of  the  cutaneous  filaments  than  would  be  the  case  if  the  two  sets  of  fibres  were  derived 
from  independent  sources. 

Again,  the  nerves  supplying  the  abdominal  muscles  and  skin  derived  from  the  lower  inter- 
costal nerves  are  intimately  connected  with  the  sympathetic  supplying  the  abdominal  viscera 
through  the  lower  thoracic  ganirlia  from  which  the  splanchnic  nerves  are  derived.  In  con- 
sequence of  this,  in  laceration  of  the  abdominal  viscera  and  in  acute  peritonitis  the  muscles  of  the 
belly-wall  become  firmly  contracted,  and  thus  as  far  as  possible  preserve  the  abdominal  contents 
in  a  condition  of  rest. 

THE  LUMBAR  NERVES. 

The  lumbar  nerves  are  five  in  number  on  each  side.  The  first  appears  between 
the  first  and  second  lumbar  vertebra?,  and  the  last  between  the  last  lumbar  and  the 
base  of  the  sacrum. 

The  roots  of  the  lower  lumbar  (and  upper  sacral)  nerves  are  the  largest,  and  their 
filaments  the  most  numerous,  of  all  the  spinal  nerves,  and  they  are  closely  aggre- 
gated together  upon  the  lower  end  of  the  cord.  The  anterior  roots'are  the 
smaller,  but  there  is  not  the  same  disproportion  between  them  and  the  posterior 
roots  as  in  the  cervical  nerves.  The  roots  of  these  nerves  have  a  vertical  direction, 
and  are  of  considerable  length,  more  especially  the  lower  ones,  since  the  spinal 
cord  does  not  extend  beyond  the  first  lumbar  vertebra.  The  roots  become  joined 
in  the  intervertebral  foramina,  and  the  nerves  so  formed  divide  at  their  exit  into 
two  divisions,  posterior  and  anterior. 

Posterior  Divisions  of  the  Lumbar  Nerves. 

The  posterior  divisions  of  the  lumbar  nerves  (Fig.  502)  diminish  in  size  from 
above  downward;  they  pass  backward  beneath  the  transverse  processes,  and 
divide  into  internal  and  external  branches. 

The  internal  branches,  the  smaller,  pass  inward  close  to  the  articular 
processes  of  the  vertebra?,  and  supply  the  Multifidus  spina?  and  Interspinales 
muscles. 

The  external  branches  supply  the  Erector  spina?  and  Intertransverse  muscles. 
From  the  three  upper  branches  cutaneous  nerves  are  derived  which  pierce  the 
aponeurosis  of  the  Latissimus  dorsi  muscle  and  descend  over  the  back  part  of  the 

54 


850 


THE   NERVOUS   SYSTEM. 


crest  of  the  ilium,  to  be  distributed  to  the  integument  of  the  gluteal  region,  some 
of  the  filaments  passing  as  far  as  the  trochanter  major  (nervi  clunium  superiores). 

Anterior  Divisions  of  the  Lumbar  Nerves. 

The  anterior  divisions  of  the  lumbar  nerves  increase  in  size  from  above  doAvn- 
ward.  At  their  origin  they  communicate  with  the  lumbar  ganglia  of  the  sym- 
pathetic by  long,  slender  filaments,  which  accompany  the  lumbar  arteries  round 
the  sides  of  the  bodies  of  the  vertebrae,  beneath  the  Psoas  muscle.  The  nerves 
pass  obliquely  outward  behind  the  Psoas  magnus  or  between  its  fasciculi,  dis- 
tributing filaments  to  it  and  the  Quadratus  lumborum.  The  anterior  divisions 
of  the  four  upper  nerves  give  off  their  branches  by  a  series  of  anastomotic  loops, 
which  are  called  the  lumbar  plexus.  The  anterior  division  of  the  fifth  lumbar, 
joined  with  a  branch  from  the  fourth,  descends  across  the  base  of  the  sacrum  to 
join  the  anterior  division  of  the  first  sacral  nerve  and  assist  in  the  formation  of 
the  sacral  plexus.  The  cord  resulting  from  the  union  of  the  fifth  lumbar  and  the 
branch  from  the  fourth  is  called  the  lumbo-sacral  nerve. 


The  Lumbar  Plexus. 

The  lumbar  plexus,  so  called,  is  formed  by  the  anastomotic  loops  above  men- 
tioned.    The  plexus  is  narrow  above,  and  often  connected  with  the  last  dorsal  by 


C.  withlgthDJI 
jjio-hypogastric  // 


FIG.  503.— Plan  of  the  lumbar  plexus. 

a  slender  branch,  the  (torso-lumbar  nerve;  it  is  broad  below,  where  it  is  joined  to 
the  sacral  plexus  by  the  lumbo-sacral  cord.  It  is  situated  in  the  substance  of  the 
Psoas  muscle  near  its  posterior  part,  in  front  of  the  transverse  processes  of  the 
lumbar  vertebrae. 

The  mode  in  which  the  plexus  is  formed  varies  greatly  in  different  subjects. 
A  plan  which  is  often  found  is  the  following :  The  first  lumbar  nerve  receives  a 
branch  from  the  last  dorsal,  and  gives  off  two  branches,  the  upper  of  which  sub- 


THE  LUMBAR   PLEXUS.  851 

divides  into  the  ilio-hypogastric  and  ilio-inguinal ;  the  lower  one  descends  and 
subdivides  into  two  branches,  an  anterior  and  a  posterior.  The  second  lumbar 
nerve  sends  a  branch  to  join  with  the  anterior  of  the  two  preceding,  to  form  the 
genito-crural  nerve ;  the  rest  of  the  nerve  then  receives  the  posterior  of  the  two 
above  mentioned,  and  proceeds  downward,  giving  off  an  external,  a  middle,  and 
an  internal  branch.  The  third  lumbar  nerve  gives  off  three  branches,  known  as 
dorsal,  middle,  and  ventral.  The  fourth  lumbar  nerve  also  divides  into  three 
branches,  known  as  anterior,  posterior,  and  inferior.  These  various  subdivisions 
now  unite  as  follows :  The  external  from  the  second  joins  the  dorsal  from  the 
third  to  form  the  external  cutaneous  nerve.  The  middle  branches  from  the  second 
and  third  together  with  the  posterior  from  the  fourth,  unite  to  form  the  anterior 
crural  nerve ;  while  the  remaining  (internal  and  ventral)  branches  of  the  second 
and  third  lumbar  nerves  unite  with  the  anterior  of  the  fourth  to  form  the  obturator 
nerve.  The  remainder  of  the  anterior  division  of  the  fourth  nerve  passes  down 
to  communicate  with  the  fifth  lumbar  nerve.  The  accessory  obturator,  when  it 
exists,  is  formed  by  a  small  branch  from  the  third  nerve  joining  with  a  small 
branch  from  the  fourth. 

From  this  arrangement  it  follows  that  the  ilio-hypogastric  and  ilio-inguinal 
are  derived  entirely  from  the  first  lumbar  nerve ;  the  genito-crural  from  the  first 
and  second  nerves ;  the  external  cutaneous  from  the  second  and  third ;  the  ante- 
rior crural  and  obturator  by  fibres  derived  from  the  second,  third,  and  fourth ; 
and  the  accessory  obturator,  when  it  exists,  from  the  third  and  fourth. 

The  branches  of  the  lumbar  plexus  are — the 

Ilio-hypogastric.  Anterior  crural. 

Ilio-inguinal.  Obturator. 

Genito-crural.  Accessory  obturator. 
External  cutaneous. 

The  nio-hypogastric  Nerve  (superior  musculo-cutaneous)  arises  from  the  firsi 
lumbar  nerve.  It  emerges  from  the  outer  border  of  the  Psoas  muscle  at  its  upper 
part,  and  crosses  obliquely  in  front  of  the  Quadratus  lumborum  to  the  crest  of  the 
ilium.  It  then  perforates  the  Transversalis  muscle  at  its  posterior  part,  near  the 
crest  of  the  ilium,  and  divides  between  it  and  the  Internal  oblique  into  two 
branches,  iliac  and  hypogastric. 

The  iliac  branch  pierces  the  Internal  and  External  oblique  muscles  imme- 
diately above  the  crest  of  the  ilium,  and  is  distributed  to  the  integument  of  the 
gluteal  region,  behind  the  lateral  cutaneous  branch  of  the  last  dorsal  nerve  (Fig. 
509).  The  size  of  this  nerve  bears  an  inverse  proportion  to  that  of  the  cutaneous 
branch  of  the  last  dorsal  nerve. 

The  hypogastric  branch  (Fig.  505)  continues  onward  between  the  Internal 
oblique  and  Transversalis  muscles.  It  then  pierces  the  Internal  oblique,  and 
near  the  middle  line  perforates  the  aponeurosrs  of  the  External  oblique,  about  an 
inch  above  and  a  little  to  the  outer  side  of  the  external  abdominal  ring,  and  is 
distributed  to  the  integument  of  the  hypogastric  region. 

The  ilio-hypogastric  nerve  communicates  with  the  last  dorsal  and  ilio-inguinal 
nerves. 

The  Ilio-inguinal  Nerve  (inferior  musculo-cutaneous),  smaller  than  the  pre- 
ceding, arises  with  it  from  the  first  lumbar  nerve.  It  emerges  from  the  outer 
border  of  the  Psoas  just  below  the  ilio-hypogastric,  and,  passing  obliquely  across 
the  Quadratus  lumborum  and  Iliacus  muscles,  perforates  the  Transversalis  near 
the  fore  part  of  the  crest  of  the  ilium,  and  communicates  with  the  ilio-hypogastric 
nerve  between  that  muscle  and  the  Internal  oblique.  The  nerve  then  pierces  the 
Internal  oblique,  distributing  filaments  to  it ;  and,  accompanying  the  spermatic 
cord  through  the  inguinal  canal,  it  escapes  at  the  external  abdominal  ring,  and  is 
distributed  to  the  integument  of  the  upper  and  inner  part  of  the  thigh,  and  to  the 
scrotum  in  the  male  and  to  the  labium  in  the  female.  The  size  of  this  nerve  is  in 


852  THE  NERVOUS  SYSTEM. 

inverse  proportion  to  that  of  the  ilio-hypogastic.  Occasionally  it  is  very  small, 
and  ends  by  joining  the  ilio-hypogastric ;  in  such  cases  a  branch  from  the  ilio- 
hypogastric  takes  the  place  of  the  ilio-inguinal,  or  the  latter  nerve  may  be  alto- 
gether absent. 

The  Genito-crural  Nerve  arises  from  the  first  and  second  lumbar  nerves.  It 
passes  obliquely  through  the  substance  of  the  Psoas,  and  emerges  from  its  inner 
border  at  a  level  corresponding  to  the  intervertebral  substance  between  the  third 
and  fourth  lumbar  vertebrae.  It  descends  on  its  surface  for  a  variable  distance, 
and  divides  into  a  genital  and  crural  branch. 


FIG.  504.— The  lumbar  plexus  and  its  branches. 

The  genital  branch  passes  outward  on  the  Psoas  magnus,  near  the  external 
iliac  artery,  to  which  it  gives  a  twig.  It  then  pierces  the  fascia  transversalis  or 
passes  through  the  internal  abdominal  ring,  descends  along  the  back  part  of  the 
spermatic  cord  to  the  scrotum  in  the  male,  and  supplies  the  Cremaster  muscle. 
In  the  female  it  accompanies  the  round  ligament. 

The  crural  branch  descends  on  the  external  iliac  artery,  sending  a  few  fila- 
ments round  it,  and,  passing  beneath  Poupart's  ligament  into  the  thigh,  enters  the 
sheath  of  the  femoral  vessels  lying  superficial  and  a  little  external  to  the  femoral 
artery,  to  which  it  also  supplies  a  few  filaments.  It  pierces  the  anterior  layer  of 
the  sheath  of  the  vessels,  and,  becoming  superficial  by  passing  through  the  fascia 
lata,  it  supplies  the  skin  of  the  anterior  aspect  of  the  thigh  as  far  as  midway 
between  the  pelvis  and  knee.  On  the  front  of  the  thigh  it  communicates  with 
the  outer  branch  of  the  middle  cutaneous  nerve,  derived  from  the  anterior  crural. 


THE   LUMBAR   PLEXUS. 


853 


Anterior  cruroL 


External 
saphenous. 


-Anterior  tibial. 


interior  division 

of  obturator. 
Internal 
cutaneous. 


Internal 
saphenous. 


FIG.  505.— Cutaneous  nerves  of  lower  ex- 
tremity.   Front  view. 


FIG.  506.— Kerves  of  the  lower  extremity.    Front  view. 


The  External  Cutaneous  Nerve  arises  from  the  second  and  third  lumbar  nerves. 
It  emerges  from  the  outer  border  of  the  Psoas  muscle    about  its   middle,  and 


854  THE  NERVOUS  SYSTEM. 

crosses  the  Iliacus  muscle  obliquely,  to  the  notch  immediately  beneath  the  ante- 
rior superior  spine  of  the  ilium,  where  it  passes  under  Poupart's  ligament  into 
the  thigh,  and  divides  into  two  branches,  anterior  and  posterior. 

The  anterior  branch  descends  in  an  aponeurotic  canal  formed  in  the  fascia 
lata,  becomes  superficial  about  four  inches  below  Poupart's  ligament,  and  divides 
into  branches  which  are  distributed  to  the  integument  along  the  anterior  and 
outer  part  of  the  thigh,  as  far  down  as  the  knee.  This  nerve  occasionally  com- 
municates with  a  branch  of  the  long  saphenous  nerve  in  front  of  the  knee- 
joint. 

The  posterior  branch  pierces  the  fascia  lata,  and  subdivides  into  branches  which 
pass  backward  across  the  outer  and  posterior  surface  of  the  thigh,  supplying  the 
integument  from  the  crest  of  the  ilium  as  far  as  the  middle  of  the  thigh. 

The  Obturator  Nerve  supplies  the  obturator  externus  and  Adductor  muscles  of 
the  thigh,  the  articulations  of  the  hip  and  knee,  and  occasionally  the  integument 
of  the  thigh  and  leg.  It  arises  by  three  branches — from  the  second,  the  third,  and 
the  fourth  lumbar  nerves.  It  descends  through  the  inner  fibres  of  the  Psoas  muscle 
and  emerges  from  its  inner  border  near  the  brim  of  the  pelvis ;  it  then  runs  along 
the  lateral  wall  of  the  pelvis,  above  the  obturator  vessels,  to  the  upper  part  of  the 
obturator  foramen,  where  it  enters  the  thigh,  and  divides  into  an  anterior  and  a 
posterior  branch,  separated  by  some  of  the  fibres  of  the  Obturator  externus,  and 
lower  down  by  the  Adductor  brevis  muscle. 

The  anterior  branch  (Fig.  506)  passes  down  in  front  of  the  Adductor  brevis, 
being  covered  by  the  Pectineus  and  Adductor  longus,  and  at  the  lower  border  of 
the  latter  muscle  communicates  with  the  internal  cutaneous  and  internal  saphenous 
nerves,  forming  a  kind  of  plexus.  It  then  descends  upon  the  femoral  artery,  upon 
which  it  is  finally  distributed.  The  nerve,  near  the  obturator  foramen,  gives  off  an 
articular  branch  to  the  hip-joint.  Behind  the  Pectineus  it  distributes  muscular 
branches  to  the  Adductor  longus  and  Gracilis,  occasionally  to  the  Adductor  brevis, 
and  rarely  to  the  Pectineus,  and  receives  a  communicating  branch  from  the  acces- 
sory obturator  nerve. 

Occasionally  the  communicating  branch  to  the  internal  cutaneous  and  internal 
saphenous  nerves  is  continued  down,  as  a  cutaneous  branch,  to  the  thigh  and  leg. 
When  this  is  so,  this  occasional  cutaneous  branch  emerges  from  beneath  the  lower 
border  of  the  Adductor  longus,  descends  along  the  posterior  margin  of  the  Sartorius 
to  the  inner  side  of  the  knee,  where  it  pierces  the  deep  fascia,  communicates  with 
the  long  saphenous  nerve,  and  is  distributed  to  the  integument  of  the  inner  side 
of  the  leg  as  low  down  as  its  middle.  When  this  communicating  branch  is  small, 
its  place  is  supplied  by  the  internal  cutaneous  nerve. 

The  posterior  branch  of  the  obturator  nerve  pierces  the  Obturator  externus, 
sending  branches  to  supply  it,  and  passes  behind  the  Adductor  brevis  on  the  front 
of  the  Adductor  magnus,  where  it  divides  into  numerous  muscular  branches,  which 
supply  the  Adductor  magnus,  and  occasionally  the  Adductor  brevis.  One  of  the 
branches  gives  off  a  filament  to  the  knee-joint. 

The  articular  branch  for  the  knee-joint  perforates  the  lower  part  of  the  Adductor 
magnus  and  enters  the  popliteal  space ;  it  then  descends  upon  the  popliteal  artery 
as  far  as  the  back  part  of  the  knee-joint,  where  it  perforates  the  posterior  ligament, 
and  is  distributed  to  the  synovial  membrane.  It  gives  filaments  to  the  artery  in 
its  course. 

The  Accessory  Obturator  Nerve  (Fig.  504)  is  not  constantly  present.  It  is  of 
small  size,  and  arises  by  separate  filaments  from  the  third  and  fourth  lumbar  nerves. 
It  descends  along  the  inner  border  of  the  Psoas  muscle,  crosses  the  horizontal 
ramus  of  the  os  pubis,  and  passes  under  the  outer  border  of  the  Pectineus  muscle, 
where  it  divides  into  numerous  branches.  One  of  these  supplies  the  Pectineus, 
penetrating  its  under  surface;  another  is  distributed  to  the  hip-joint ;  while  a  third 
communicates  with  the  anterior  branch  of  the  obturator  nerve.  When  this  nerve 
is  absent  the  hip-joint  receives  two  branches  from  the  obturator  nerve.  Occasion- 
ally it  is  very  small,  and  becomes  lost  in  the  capsule  of  the  hip-joint. 


THE   LUMBAR    PLEXUS.  855 

The  Anterior  Crural  Nerve  (Figs.  504,  506)  is  the  largest  branch  of  the  lumbar 
plexus.  It  supplies  muscular  branches  to  the  Iliacus,  Pectineus,  and  all  the 
muscles  on  the  front  of  the  thigh,  excepting  the  Tensor  vaginae  femoris  ;  cutaneous 
filaments  to  the  front  and  inner  side  of  the  thigh  and  to  the  leg  and  foot ;  and 
articular  branches  to  the  hip  and  knee.  It  arises  from  the  second,  third,  and 
fourth  lumbar  nerves.  It  descends  through  the  fibres  of  the  Psoas  muscle, 
emerorino'  from  it  at  the  lower  part  of  its  outer  border,  and  passes  down  between 
it  and  the  Iliacus,  and  beneath  Pouparf s  ligament,  into  the  thigh,  where  it  becomes 
somewhat  flattened,  and  divides  into  an  anterior  part  which  passes  superficial  to 
the  external  circumflex  vessels,  and  a  posterior  part  which  passes  beneath  these 
vessels.  Under  Poupart's  ligament  it  is  separated  from  the  femoral  artery  by  the 
Ps  'as  muscle,  and  lies  beneath  the  iliac  fascia. 

Within  the  pelvis  the  anterior  crural  nerve  gives  off  from  its  outer  side  some 
small  branches  to  the  Iliacus.  and  a  branch  to  the  femoral  artery  which  is  distrib- 
uted upon  the  upper  part  of  that  vessel.  The  origin  of  this  branch  varies :  it 
occasionally  arises  higher  than  usual,  or  it  may  arise  lower  down  in  the  thigh. 

External  to  the  pelvis  the  following  branches  are  given  off: 

From  the  Anterior  Division.  From  the  Posterior  Division. 
Middle  cutaneous.  Long  saphenous. 

Internal  cutaneous.  Muscular. 

Muscular.  Articular. 

Anterior  Division. — The  middle  cutaneous  nerve  (Fig.  505)  pierces  the  fascia 
lata  about  three  inches  below  Poupart's  ligament,  and  divides  into  two  branches, 
which  descend  in  immediate  proximity  along  the  fore  part  of  the  thigh,  dis- 
tributincr  numerous  branches  to  the  integument  as  low  as  the  front  of  the  knee. 

O  C3 

where  it  communicates  Avith  the  nervus  cutaneus  patellce,  a  branch  of  the  internal 
saphenous  nerve,  helping  to  form  the  patellar  plexus.  Its  outer  branch  communi- 
cates, above,  with  the  crural  branch  of  the  genito-crural  nerve,  and  the  inner 
branch  with  the  internal  cutaneous  nerve  below.  The  Sartorius  muscle  is  fre- 
quently pierced  by  this  nerve  or  by  its  outer  branch. 

The  internal  cutaneous  nerve  passes  obliquely  across  the  upper  part  of  the 
sheath  of  the  femoral  artery,  and  divides  in  front  or  at  the  inner  side  of  that  vessel 
into  two  branches,  anterior  and  posterior  or  internal. 

The  anterior  branch  runs  downward  on  the  Sartorius,  perforates  the  fascia  lata 
at  the  lower  third  of  the  thigh,  and  divides  into  two  branches,  one  of  which 
supplies  the  integument  as  low  down  as  the  inner  side  of  the  knee  ;  the  other 
crosses  to  the  outer  side  of  the  patella,  communicating  in  its  course  with  the 
nervus  cutaneus  patellae,  a  branch  of  the  internal  saphenous  nerve. 

The  posterior  or  internal  branch  descends  along  the  inner  border  of  the 
Sartorius  muscle  to  the  knee,  where  it  pierces  the  fascia  lata,  communicates  with 
the  long  saphenous  nerve,  and  gives  off  several  cutaneous  branches.  The  nerve 
then  passes  clown  the  inner  side  of  the  leg,  to  the  integument  of  which  it  is 
distributed.  This  nerve,  beneath  the  fascia  lata,  at  the  lower  border  of  the 
Adductor  longus,  joins  in  a  plexiform  network  by  uniting  with  branches  of  the 
long  saphenous  and  obturator  nerves  (Fig.  506).  When  the  communicating  branch 
from  the  obturator  nerve  is  large  and  continued  to  the  integument  of  the  leg,  the 
inner  branch  of  the  internal  cutaneous  is  small  and  terminates  at  the  plexus, 
occasionally  giving  off  a  few  cutaneous  filaments. 

The  internal  cutaneous  nerve,  before  dividing,  gives  off  a  few  filaments,  which 
pierce  the  fascia  lata.  to  supply  the  integument  of  the  inner  side  of  the  thigh, 
accompanying  the  long  saphenous  vein.  One  of  these  filaments  passes  through 
the  saphenous  opening ;  a  second  becomes  subcutaneous  about  the  middle  of  the 
thigh ;  and  a  third  pierces  the  fascia  at  its  lower  third. 

The  muscular  branches  supply  the  Pectineus  and  Sartorius.  Those  to  the 
Pectineus,  often  united  with  the  internal  cutaneous  nerve  at  their  origin,  are 


856  THE  NERVOUS  SYSTEM. 

usually  two  in  number  and  pass  inward  behind  the  femoral  vessels,  and  enter  the 
muscle  on  its  anterior  surface.  Sometimes  one  of  these  nerves  is  given  off  in  the 
pelvis,  and  is  then  often  united  with  the  accessory  obturator.  The  Sartorius  is 
supplied  by  filaments  which  arise  in  common  with  the  middle  cutaneous  nerve  and 
enter  the  upper  part  of  the  muscle. 

Posterior  Division. — The  long  or  internal  saphenous  nerve  is  the  largest  of  the 
cutaneous  branches  of  the  anterior  crural.  It  approaches  the  femoral  artery 
where  this  vessel  passes  beneath  the  Sartorius,  and  lies  at  first  on  its  outer  side 
and  then  crosses  over  it,  beneath  the  aponeurotic  covering  of  Hunter's  canal,  as 
far  as  the  opening  in  the  lower  part  of  the  Adductor  magnus.  It  then  quits  the 
artery,  and  descends  vertically  along  the  inner  side  of  the  knee,  beneath  the  Sar- 
torius, pierces  the  fascia  lata,  opposite  the  interval  between  the  tendons  of  the 
Sartorius  and  Gracilis,  and  becomes  subcutaneous.  The  nerve  then  passes  along 
the  inner  side  of  the  leg,  accompanied  by  the  internal  saphenous  vein,  descends 
behind  the  internal  border  of  the  tibia,  and,  at  the  lower  third  of  the  leg,  divides 
into  two  branches :  one  continues  its  course  along  the  margin  of  the  tibia,  termi- 
nating at  the  inner  ankle ;  the  other  passes  in  front  of  the  ankle,  and  is  distrib- 
uted to  the  integument  along  the  inner  side  of  the  foot,  as  far  as  the  great  toe, 
communicating  with  the  internal  branch  of  the  musculo-cutaneous  nerve. 

The  long  saphenous  nerve  about  the  middle  of  the  thigh  gives  off  a  communi- 
cating branch  which  joins  the  plexus  formed  by  the  obturator  and  internal  cuta- 
neous nerves. 

At  the  inner  side  of  the  knee  it  gives  off  a  large  branch  (nervus  cutaneus 
patellce)  which  pierces  the  Sartorius  and  fascia  lata,  and  is  distributed  to  the 
integument  in  front  of  the  patella.  This  nerve  communicates  above  the  knee 
with  the  anterior  branch  of  the  internal  cutaneous  and  with  the  middle  cutaneous  ; 
below  the  knee,  with  other  branches  of  the  long  saphenous ;  and  on  the  outer  side 
of  the  joint,  with  branches  of  the  external  cutaneous  nerve,  forming  a  plexiform 
network,  the  plexus  patellae.  The  cutaneous  nerve  of  the  patella  is  occasionally 
small,  and  terminates  by  joining  the  internal  cutaneous,  which  supplies  its  place 
in  front  of  the  knee. 

Beloiv  the  knee  the  branches  of  the  long  saphenous  nerve  are  distributed  to  the 
integument  of  the  front  and  inner  side  of  the  leg,  communicating  with  the  cutaneous 
branches  from"  the  internal  cutaneous  or  from  the  obturator  nerve. 

The  muscular  branches  are  as  follows : 

The  branch  to  the  Rectus  muscle  enters  its  under  surface  high  up,  sending  off 
a  small  filament  to  the, hip-joint. 

The  branch  to  the  Vastus  externus,  of  large  size,  follows  the  course  of  the 
descending  branch  of  the  external  circumflex  artery  to  the  lower  part  of  the  muscle. 
It  gives  off  an  articular  filament  to  the  knee-joint. 

The  branch  to  the  Vastus  internus  is  a  long  branch  which  runs  down  on  the 
outer  side  of  the  femoral  vessels  in  company  with  the  internal  saphenous  nerve  for 
its  upper  part.  It  enters  the  muscle  about  its  middle,  and  gives  off  a  filament 
which  can  usually  be  traced  downward  on  the  surface  of  the  muscle  to  the  knee- 
joint. 

The  branch  to  the  Crureus  enters  the  muscle  on  its  anterior  surface  about 
the  middle  of  the  thigh,  and  sends  a  filament  through  the  muscle  to  the  Sub- 
crureus.  Articular  branches  to  the  hip-joint  are  derived  from  some  of  the  other 
muscular  branches  as  well  as  from  the  nerve  to  the  Rectus. 

The  articular  branches  to  the  knee-joint  are  two  in  number.  One,  a  long, 
slender  filament,  is  derived  from  the  nerve  to  the  Vastus  externus.  It  penetrates 
the  capsular  ligament  of  the  joint  on  its  anterior  aspect.  The  other  is  derived 
from  the  nerve  to  the  Vastus  internus.  It  can  usually  be  traced  downward  on 
the  surface  of  this  muscle  to  near  the  joint;  it  then  penetrates  the  muscular  fibres, 
and  accompanies  the  deep  branch  of  the  anastomotica  magna  artery,  pierces 
the  capsular  ligament  of  the  joint  on  its  inner  side,  and  supplies  the  synovial 
membrane. 


THE  SACRAL   NERVES. 


857 


THE  SACRAL  AND   COCCYGEAL  NERVES. 

The  sacral  nerves  are  five  in  number  on  each  side.  The  four  upper  ones  pass 
from  the  sacral  canal  through  the  sacral  foramina ;  the  fifth  through  the  foramen 
between  the  sacrum  and  coccyx. 

The  roots  of  origin  of  the  upper  sacral  (and  lower  lumbar)  nerves  are  the 
largest  of  all  the  spinal  nerves,  whilst  those  of  the  lowest  sacral  and  coccygeal 
nerve  are  the  smallest. 

The  roots  of  these  nerves  are  of  very  considerable  length,  being  longer  than 
those  of  any  of  the  other  spinal  nerves,  on  account  of  the  spinal  cord  not  extending 
beyond  the  first  lumbar  vertebra.  From  their  great  length  and  the  appearance 
they  present  in  connection  with  the  spinal  cord  the  roots  of  origin  of  these  nerves 
are  called  collectively  the  cauda  equina.  Each  sacral  and  coccygeal  nerve  divides 
into  two  divisions,  posterior  and  anterior. 

The  posterior  divisions  of  the  sacral  nerves  (Fig.  507)  are  small,  diminish  in 


FIG.  507. — The  posterior  sacral  nerves. 

size  from  above  downward,  and  emerge,  except  the  last,  from  -the  sacral  canal 
by  the  posterior  sacral  foramina. 

The  three  upper  ones  are  covered,  at  their  exit  from  the  sacral  canal,  by  the 
Multifidus  spinse,  and  divide  into  internal  and  external  branches. 

The  internal  branches    are  small,  and  supply  the  Multifidus  spinse. 

The  external  branches  join  with  one  another  and  with  the  last  lumbar  and 
fourth  sacral  nerves  by  means  of  communicating  loops.  These  branches  pass  out- 
ward to  the  outer  surface  of  the  great  sacro-sciatic  ligament,  where  they  form  a 
second  series  of  loops  beneath  the  Gluteus  maximus.  Cutaneous  branches  from 
this  second  series  of  loops,  usually  three  in  number,  pierce  the  Gluteus  maximus : 
one  near  the  posterior  inferior  spine  of  the  ilium  ;  another  opposite  the  end  of  the 
sacrum ;  and  the  third  midway  between  the  other  two.  They  supply  the  integu- 
ment over  the  posterior  part  of  the  gluteal  region  (nervi  clunium  medii). 


858 


THE   NERVOUS  SYSTEM. 


The  posterior  divisions  of  the  two  lower  sacral  nerves  are  situated  below  the 
Multifidus  spinse.  They  are  of  small  size,  and  do  not  divide  into  internal  and 
external  branches,  but  join  with  each  other,  and  with  the  coccygeal  nerve,  so  as 
to  form  loops  on  the  back  of  the  sacrum,  filaments  from  which  supply  the  Extensor 
coccygis  and  the  integument  over  the  coccyx. 

The  coccygeal  nerve  divides  into  its  anterior  and  posterior  divisions  in  the  spinal 
caual.  The  posterior  division  is  the  smaller.  It  does  not  divide,  but  receives,  as 
already  mentioned,  a  communicating  branch  from  the  last  sacral,  and  is  lost  in  the 
fibrous  structure  on  the  back  of  the  coccyx. 

The  anterior  divisions  of  the  sacral  nerves   diminish  in  size   from  above  down- 


Femoral  a 


COCCYGEUS. 


Coccygeal. 
Br.  to 

LEVATOH  AMI.    SPH  I  NCTER  AN  I . 

FIG.  508.— Side  view  of  pelvis,  showing  sacral  nerves. 

ward.  The  four  upper  ones  emerge  from  the  anterior  sacral  foramina :  the  ante- 
rior division  of  the  fifth,  after  emerging  from  the  spinal  canal  through  its  termi- 
nal opening,  curves  forward  between  the  sacrum  and  the  coccyx.  All  the  anterior 
sacral  nerves  communicate  with  the  sacral  ganglia  of  the  sympathetic  at  their 
exit  from  the  sacral  foramina.  The  first  nerve,  of  large  size,  unites  with  the 
lumbo-sacral  cord,  formed  by  the  fifth  lumbar,  and  a  branch  from  the  fourth  lum- 
bar. The  second,  equal  in  size  to  the  preceding,  and  the  third,  about  one-fourth 
the  size  of  the  second,  unite,  together  with  a  small  fasciculus  from  the  fourth,  to 
form  the  sacral  plexus,  a  visceral  branch  being  given  off  from  the  third  nerve  to 
the  bladder. 

The  fourth  anterior  sacral  nerve  sends  a  branch  to  join  the  sacral  plexus.  The 
remaining  portion  of  the  nerve  divides  into  visceral  and  muscular  branches,  and 
a  communicating  filament  descends  to  join  the  fifth  sacral  nerve.  The  visceral 
branches  are  distributed  to  the  viscera  of  the  pelvis,  communicating  with  the 
sympathetic  nerve.  These  branches  ascend  upon  the  rectum  and  bladder,  and 
in  the  female  upon  the  vagina,  communicating  with  branches  of  the  sympathetic 
from  the  pelvic  plexus.  The  muscular  branches  are  distributed  to  the  Levator 


THE  SACRAL    PLEXUS.  859 

ani,  Coccygeus,  and  Sphincter  ani.  The  branch  to  the  Sphincter  ani  pierces  the 
Levator  ani,  so  as  to  reach  the  ischio-rectal  fossa,  where  it  is  found  lying  in  front 
of  the  coccyx.  Cutaneous  filaments  arise  from  the  latter  branch,  which  supply 
the  integument  between  the  anus  and  coccyx.  Another  cutaneous  branch  is  fre- 
quentlv  given  off  from  this  nerve,  though  sometimes  from  the  pudic  (Schwalbe). 
It  perforates  the  great  sacro-sciatic  ligament,  and,  winding  round  the  lower  bor- 
der of  the  Gluteus  maximus,  supplies  the  skin  over  the  lower  and  inner  part  of 
this  muscle. 

The  fifth  anterior  sacral  nerve,  after  passing  from  the  lower  end  of  the  sacral 
canal,  curves  forward  through  the  fifth  sacral  foramen,  formed  between  the  lower 
part  of  the  sacrum  and  the  transverse  process  of  the  first  piece  of  the  coccyx.  It 
pierces  the  Coccygeus  muscle,  and  descends  upon  its  anterior  surface  to  near  the 
tip  of  the  coccyx,  where  it  again  perforates  the  muscle,  to  be  distributed  to  the 
integument  over  the  back  part  and  side  of  the  coccyx.  This  nerve  communicates 
above  with  the  fourth  sacral  and  below  with  the  coccygeal  nerve,  and  supplies  the 
Coccygeus  muscle. 

The  anterior  division  of  the  coccygeal  nerve  is  a  delicate  filament  which  escapes 
at  the  termination  of  the  sacral  canal ;  it  passes  downward  behind  the  rudiment- 
ary transverse  process  of  the  first  piece  of  the  coccyx,  and  curves  forward  through 
the  notch  between  the  first  and  second  pieces,  piercing  the  Coccygeus  muscle,  and 
descending  on  its  anterior  surface  to  near  the  tip  of  the  coccyx,  where  it  again 
pierces  the  muscle,  to  be  distributed  to  the  integument  over  the  back  part  and  side 
of  the  coccyx.  It  is  joined  by  a  branch  from  the  fifth  anterior  sacral  as  it 
descends  on  the  surface  of  the  Coccygeus  muscle. 

The   Sacral  Plexus  (Fig.  508). 

The  sacral  plexus  is  formed  by  the  lumbo-sacral  cord,  the  anterior  divisions  of 
the  three  upper  sacral  nerves,  and  part  of  that  of  the  fourth.  These  nerves  proceed 
in  different  directions ;  the  upper  ones  obliquely  downward  and  outward,  the 
lower  ones  nearly  horizontally.  The  sacral  plexus  is  triangular  in  form,  its  base 
corresponding  with  the  exit  of  the  nerves  from  the  sacrum,  its  apex  with  the  lower 
part  of  the  great  sacro-sciatic  foramen.  It  rests  upon  the  anterior  surface  of  the 
Pyriformis,  and  is  covered  in  front  by  the  pelvic  fascia,  which  separates  it  from 
the  sciatic  and  pudic  branches  of  the  internal  iliac  artery  and  from  the  viscera  of 
the  pelvis. 

The  special  method  of  the  formation  of  the  plexus  is  as  follows :  The  lumbo- 
sacral  cord,  first,  second  and  larger  part  of  the  third  sacral  nerves  unite  to  form  a 
large  upper  cord  or  band.  The  smaller  part  of  the  third,  together  with  the  branch 
of  the  fourth  nerve,  already  mentioned  as  going  to  the  sacral  plexus,  unite  to 
form  a  smaller,  lower,  cord  or  band.  The  larger  is  continued  into  the  great  sciatic 
nerve  ;  the  smaller  is  continuous  with  the  pudic  nerve.  The  remaining  branches 
of  the  plexus  are  derived  separately  or  by  more  or  less  intercommunication  from 
the  sacral  nerves  before  the  latter  form  the  two  principal  cords  just  mentioned. 

The  branches  of  the  sacral  plexus  are — 

Muscular.  Perforating  cutaneous. 

Superior  gluteal.  Pudic. 

Inferior  gluteal.  Small  sciatic. 

Great  sciatic. 

The  muscular  branches  supply  the  Pyriformis,  Obturator  internus,  the  two 
Gemelli,  and  the  Quadratus  femoris.  The  branches  to  the  Pyriformis  arise  from 
the  back  of  the  first  and  second  sacral  nerves  before  they  enter  the  plexus ;  the 
branch  to  the  Obturator  internus  arises  from  the  lumbo-sacral  and  first  two  sacral 
nerves :  it  passes  out  of  the  pelvis  through  the  great  sacro-sciatic  foramen,  crosses 
the  spine  of  the  ischium,  and  re-enters  the  pelvis  through  the  lesser  sacro-sciatic 
foramen  to  the  inner  surface  of  the  Obturator  internus ;  the  branch  to  the 
Gemellus  superior  arises  in  common  with  the  nerve  to  the  Obturator  internus :  it 


860 


THE     NERVOUS     SYSTEM. 


/ 


Superior 
gluteal.  ~      \\ 

Pudic., 

Nerve  to 
obturator  internus. 


Small  sciatic.  - 


Inferior . 
pudendal. 


Descending_ 
cutaneous. 


Internal 
popliteal." 


External 

-popliteal,  or 

peroneal. 


Communicans  _ 
poplitei. 
Posterior 
tibial. 


Communicans 
peronei. 


k 


\ 


Plantar , 
cutaneous. 


FIG.  509.— Cutaneous  nerves  of 
lower  extremity.    Posterior  view. 


FIG.  510.— Nerves  of  the  lower  extremity.1  Posterior 
view. 


1  N.  B. — In  this  diagram  the  external  saphenous  and  comraunicans  peronei  are  not  in  their  nor- 
mal position.     They  have  been  displaced  by  the  removal  of  the  superficial  muscles. 


THE  SACRAL    PLEXU8.  861 

enters  the  muscle  at  the  upper  part  of  its  posterior  surface ;  the  small  branch  to  the 
Gemellus  inferior  and  Quadratus  femoris  arises  from  the  lumbo-sacral  cord  and 
first  sacral  nerve :  it  passes  through  the  great  sacro-sciatic  foramen,  and  courses 
down  beneath  the  Gemelli  and  tendon  of  the  Obturator  internus,  and  sup- 
plies the  muscles  on  their  deep  or  anterior  surface.  It  gives  off  an  articular 
branch  to  the  hip-joint.  Another  articular  branch  is  occasionally  derived  from 
the  upper  part  of  the  great  sciatic  nerve. 

The  Superior  Gluteal  Nerve  (Fig.  510)  arises  from  the  back  part  of  the  lumbo- 
sacral  cord  and  first  sacral  nerve :  it  passes  from  the  pelvis  through  the  great 
sacro-sciatic  foramen  above  the  Pyriformis  muscle,  accompanied  by  the  gluteal 
vessels,  and  divides  into  a  superior  and  an  inferior  branch. 

The  superior  branch  follows  the  line  of  origin  of  the  Gluteus  minimus,  and 
supplied  the  Gluteus  medius. 

The  inferior  branch  crosses  obliquely  between  the  Gluteus  minimus  and 
medius,  distributing  filaments  to  both  these  muscles,  and  terminates  in  the  Tensor 
vaginae  femoris,  extending  nearly  to  its  lower  end. 

The  Inferior  Gluteal  arises  from  the  lumbo-sacral  cord  and  first  and  second 
sacral  nerves,  and  is  often  intimately  connected  with  the  small  sciatic  at  its  origin. 
It  passes  out  of  the  pelvis  through  the  great  sciatic  notch,  beneath  the  Pyriformis 
muscle,  and,  dividing  into  a  number  of  branches,  enters  the  Gluteus  maximus 
muscle  on  its  under  surface. 

The  Perforating  Cutaneous  Nerve  is  derived  from  the  second  and  third  sacral 
nerves.  It  pierces  the  great  sacro-sciatic  ligament  and  winds  round  the  lower 
border  of  the  Gluteus  maximus  muscle  to  supply  the  skin  of  the  buttock. 

The  Pudic  Nerve  arises  from  the  lower  cord  of  the  sacral  plexus  (sometimes 
containing  fibres  derived  from  the  second  and  even  first  sacral  nerves),  and  leaves 
the  pelvis,  through  the  great  sacro-sciatic  foramen,  below  the  Pyriformis.  It  then 
crosses  the  spine  of  the  ischium,  and  re-enters  the  pelvis  through  the  lesser  sacro- 
sciatic  foramen.  It  accompanies  the  pudic  vessels  upward  and  forward  for  a  short 
distance  along  the  outer  wall  of  the  ischio-rectal  fossa,  and  then  divides  into 
three  branches,  the  perineal  nerve,  the  dorsal  nerve  of  the  penis,  and  the  inferior 
haemorrhoidal  nerve. 

The  inferior  hcemorrhoidal  nerve  is  occasionally  derived  separately  from  the 
sacral  plexus.  It  passes  across  the  ischio-rectal  fossa,  with  its  accompanying  ves- 
sels, toward  the  lower  end  of  the  rectum,  and  is  distributed  to  the  integument 
round  the  anus.  Branches  of  this  nerve  communicate  with  the  inferior  pudendal 
and  superficial  perineal  nerves  at  the  fore  part  of  the  perinaeum. 

The  perineal  nerve,  the  largest  of  the  branches  of  the  pudic,  is  situated 
below  the  pudic  artery.  It  accompanies  the  superficial  perineal  artery  in  the 
peringeurn,  dividing  into  cutaneous  and  muscular  branches. 

The  cutaneous  branches  (superficial  perineal)  are  two  in  number,  posterior 
and  anterior.  The  posterior  or  external  branch  passes  forward  along  the  outer 
side  of  the  perineal  space  parallel  to  the  inferior  pudendal  nerve,  and  is  distrib- 
uted to  the  skin  of  the  scrotum.  It  communicates  with  the  inferior  hgemorrhoid- 
al,  the  inferior  pudendal,  and  the  other  superficial  perineal  nerve.  The  anterior 
or  internal  branch  passes  forward  nearer  to  the  middle  line,  to  be  distributed  to 
the  inner  and  back  part  of  the  scrotum.  Both  these  nerves  supply  the  labia 
majora  in  the  female. 

The  muscular  branches  are  distributed  to  the  Transversus  perinaei,  Accelerator 
urinre.  Erector  penis,  External  sphincter  and  Levator  ani,  and  Compressor  urethrae. 
A  distinct  branch  is  given  off  from  the  nerve  to  the  Accelerator  urinae,  which 
pierces  this  muscle  and  supplies  the  corpus  spongiosum,  ending  in  the  mucous 
membrane  of  the  urethra.  This  is  the  nerve  to  the  bulb. 

The  dorsal  nerve  of  the  penis  is  the  deepest  division  of  the  pudic  nerve ;  it 
accompanies  the  pudic  artery  along  the  ramus  of  the  ischium :  piercing  the  pos- 
terior layer  of  the  deep  perineal  fascia,  it  runs  forward  along  the  inner  margin 
of  the  ramus  of  the  os  pubis,  between  the  two  layers  of  the  deep  fascia.  It  then 


862  THE  NERVOUS  SYSTEM. 

pierces  the  anterior  layer,  and,  in  company  with  the  dorsal  artery  of  the  penis, 
passes  through  the  suspensory  ligament,  and,  running  forward,  is  distributed  to 
the  glans.  On  the  penis  this  nerve  gives  off  a  cutaneous  branch  which  runs 
along  the  side  of  the  organ ;  it  is  joined  with  branches  of  the  sympathetic,  and 
supplies  the  integument  of  the  upper  surface  and  sides  of  the  penis  and  prepuce, 
giving  a  large  branch  to  the  corpus  cavernosum. 

In  the  female  the  dorsal  nerve  is  very  small  and  supplies  the  clitoris. 

The  Small  Sciatic  Nerve  (Fig.  510)  supplies  the  integument  of  the  perinreum 
and  back  part  of  the  thigh  and  leg.  It  is  usually  formed  by  the  union  of  three 
branches,  which  arise  from  the  first,  second,  and  third  nerves  of  the  sacral  plexus. 
It  issues  from  the  pelvis  through  the  great  sacro-sciatic  foramen  below  the  Pyri- 
formis  muscle,  descends  beneath  the  Gluteus  maximus  with  the  sciatic  artery,  and 
at  the  lower  border  of  that  muscle  passes  along  the  back  part  of  the  thigh, 
beneath  the  fascia  lata,  to  the  lower  part  of  the  popliteal  region,  where  it  pierces 
the  fascia  and  becomes  cutaneous.  It  then  accompanies  the  external  saphenous 
vein  to  about  the  middle  of  the  leg,  its  terminal  filaments  communicating  with 
the  external  saphenous  nerve. 

The  branches  of  the  small  sciatic  nerve  are  all  cutaneous,  and  are  as  follows : 
perineal,  femoral,  and  ascending. 

The  perineal  cutaneous  branches  are  distributed  to  the  skin  at  the  upper  and 
inner  side  of  the  thigh,  on  its  posterior  aspect,  and  to  the  perineeum.  One  branch, 
longer  than  the  rest,  the  inferior  pudendal,  curves  forward  below  the  tuber  ischii, 
pierces  the  fascia  lata,  and  passes  forward  beneath  the  superficial  fascia  of  the 
peringeum  to  be  distributed  to  the  integument  of  the  scrotum  in  the  male  and  the 
labium  in  the  female,  communicating  with  the  superficial  perineal  and  inferior 
haemorrhoidal  nerves. 

The  femoral  cutaneous  branches  consist  of  filaments,  which  are  derived  from 
both  sides  of  the  nerve  and  are  distributed  to  the  skin  of  the  inner  and  outer  side 
of  the  thigh  on  its  posterior  aspect,  as  far  down  as  the  middle  of  that  region,  and 
also  to  the  skin  of  the  back  part  of  the  thigh,  popliteal  region,  and  upper  part 
of  the  leg. 

The  ascending  cutaneous  branches  consist  of  two  or  three  filaments,  which  turn 
upward  round  the  lower  border  of  the  gluteus  maximus,  to  supply  the  integument 
covering  its  surface  (nervi  clunium  infer  lores). 

The  Great  Sciatic  Nerve  (Fig.  510)  supplies  nearly  the  whole  of  the  integu- 
ments of  the  leg,  the  muscles  of  the  back  of  the  thigh,  and  those  of  the  leg  and 
foot.  It  is  the  largest  nervous  cord  in  the  body,  measuring  three-quarters  of  an 
inch  in  breadth,  and  is  the  continuation  of  the  lower  cord  of  the  sacral  plexus. 
It  passes  out  of  the  pelvis  through  the  great  sacro-sciatic  foramen,  below  the 
Pyriformis  muscle.  It  descends  between  the  trochanter  major  and  tuberosity  of 
the  ischium,  along  the  back  part  of  the  thigh  to  about  its  lower  third,  where  it 
divides  into  two  large  branches,  the  internal  and  external  popliteal  nerves. 

This  division  may  take  place  at  any  point  between  the  sacral  plexus  and  the 
lower  third  of  the  thigh.  When  the  division  occurs  at  the  plexus,  the  two  nerves 
descend  together,  side  by  side ;  or  they  may  be  separated  at  their  commencement 
by  the  interposition  of  part  or  the  whole  of  the  Pyriformis  muscle.  As  the  nerve 
descends  along  the  back  of  the  thigh  it  rests  at  first  upon  the  External  rotator 
muscles,  in  company  with  the  small  sciatic  nerve  and  artery,  being  covered  by 
the  Gluteus  maximus  ;  lower  down,  it  lies  upon  the  Adductor  magnus  and  is 
covered  by  the  long  head  of  the  Biceps. 

The  branches  of  the  nerve,  before  its  division,  are  articular  and  muscular. 

The  articular  branches  arise  from  the  upper  part  of  the  nerve ;  they  supply 
the  hip-joint,  perforating  its  fibrous  capsule  posteriorly.  These  branches  are 
sometimes  derived  from  the  sacral  plexus. 

The  muscular  branches  are  distributed  to  the  Flexors  of  the  leg — viz.  the 
Biceps,  Semitendinosus,  and  Semimembranosus,  and  a  branch  to  the  Adductor 
magnus.  These  branches  are  given  off  beneath  the  Biceps  muscle. 


THE    POPLITEAL,    TIBIA L,  AND  PLANTAR    NERVES.          863 

The  Internal  Popliteal  Nerve,  the  larger  of  the  two  terminal  branches  of  the 
great  sciatic,  descends  along  the  back  part  of  the  thigh,  through  the  middle  of 
the  popliteal  space,  to  the  lower  border  of  the  Popliteus  muscle,  where  it  passes 
with  the  artery  beneath  the  arch  of  the  Soleus  and  becomes  the  posterior  tibial. 
It  is  overlapped  by  the  hamstring  muscles  above,  and  then  becomes  more  super- 
ficial, and  lies  to  the  outer  side  of,  and  some  distance  from,  the  popliteal  vessels ; 
opposite  the  knee-joint  it  is  in  close  relation  with  the  vessels,  and  crosses  to  the 
inner  side  of  the  artery.  Below,  it  is  overlapped  by  the  Gastrocnemius. 

The  branches  of  this  nerve  are — articular,  muscular,  and  a  cutaneous  branch, 
the  commuiii<-<nix  /><>j>!/'t>-i  nerve. 

The  arti'-al'ir  branches,  usually  three  in  number,  supply  the  knee-joint:  two  of 
these  branches  accompany  the  superior  and  inferior  internal  articular  arteries, 
and  a  third,  the  azygos  articular  artery. 

The  muscular  branches,  four  or  five  in  number,  arise  from  the  nerve  as  it  lies 
between  the  two  heads  of  the  Gastrocnemius  muscle ;  they  supply  that  muscle, 
the  Plantaris,  Soleus,  and  Popliteus.  The  filaments  which  supply  the  Popliteus 
turn  round  its  lower  border  and  are  distributed  to  its  deep  surface. 

The  eommunieans  poplitei  descends  between  the  tAvo  heads  of  the  Gastrocne- 
mius muscle,  and  about  the  middle  of  the  back  of  the  leg  pierces  the  deep  fascia, 
and  joins  a  communicating  branch  (communicans  peronef)  from  the  external 
popliteal  nerve  to  form  the  external  or  short  saphenous  (Fig.  509).  The  exter- 
nal saphenous  nerve,  formed  by  the  cutaneous  branches  of  the  internal  and 
external  popliteal  nerves,  passes  downward  and  outward  near  the  outer  margin  of 
the  tendo  Achillis,  lying  close  to  the  external  saphenous  vein,  to  the  interval 
between  the  external  malleolus  and  the  os  calcis.  It  winds  round  the  outer  mal- 
leolus,  and  is  distributed  to  the  integument  along  the  outer  side  of  the  foot  and 
little  toe,  communicating  on  the  dorsum  of  the  foot  with  the  musculo-cutaneous 
nerve.  In  the  leg  its  branches  communicate  with  those  of  the  small  sciatic. 

The  Posterior  Tibial  Nerve  (Fig.  510)  commences  at  the  lower  border  of  the 
Popliteus  muscle,  and  passes  along  the  back  part  of  the  leg  with  the  posterior 
tibial  vessels  to  the  interval  between  the  inner  malleolus  and  the  heel,  where  it 
divides  into  the  external  and  internal  plantar  nerves.  It  lies  upon  the  deep 
muscles  of  the  leg,  and  is  covered  in  the  upper  part  by  the  muscles  of  the  calf, 
lower  down  by  the  skin  and  fascia.  In  the  upper  part  of  its  course  it  lies  to  the 
inner  side  of  the  posterior  tibial  artery,  but  it  soon  crosses  that  vessel,  and  lies  to 
its  outer  side  as  far  as  the  ankle.  In  the  lower  third  of  the  leg  it  is  placed 
parallel  with  the  inner  margin  of  the  tendo  Achillis. 

The  branches  of  the  posterior  tibial  nerve  are — muscular,  plantar  cutaneous,  and 
articular. 

The  muscular  branches  arise  either  separately  or  by  a  common  trunk  from  the 
upper  part  of  the  nerve.  They  supply  the  Tibialis  posticus,  Flexor  longus  digito- 
rum,  and  Flexor  longus  hallucis  muscles,  the  branch  to  the  latter  muscle  accom- 
panying the  peroneal  artery.  A  branch  is  also  given  to  the  Soleus. 

The  plantar  cutaneous  branch  perforates  the  internal  annular  ligament  and 
supplies  the  integument  of  the  heel  and  inner  side  of  the  sole  of  the  foot. 

The  arti-ulnr  branch  is  given  off  just  above  the  bifurcation  of  the  nerve  and 
supplies  the  ankle-joint. 

The  internal  plantar  nerve  (Fig.  511),  the  larger  of  the  two  terminal  branches 
of  the  posterior  tibial,  accompanies  the  internal  plantar  artery  along  the  inner  side 
of  the  foot.  From  its  origin  at  the  inner  ankle  it  passes  beneath  the  Abductor 
hallucis,  and  then  forward  between  this  muscle  and  the  Flexor  brevis  digitorum, 
divides  opposite  the  bases  of  the  metatarsal  bones  into  four  digital  branches,  and 
communicates  with  the  external  plantar  nerve. 

Branches. — In  its  course  the  internal  plantar  nerve  gives  off  cutaneous 
branches,  which  pierce  the  plantar  fascia  and  supply  the  integument  of  the  sole 
of  the  foot ;  muscular  branches,  which  supply  the  Abductor  hallucis  and  Flexor 
brevis  digitorum ;  articular  branches,  to  the  articulations  of  the  tarsus  and  meta- 


864 


THE   NERVOUS  SYSTEM. 


Internal 
plantar. 


External 
plantar. 


Deep 
branch. 


tarsus ;  and  four  digital  branches.  These  pass  between  the  divisions  of  the 
plantar  fascia  in  the  clefts  between  the  toes,  and  are  distributed  in  the  fol- 
lowing manner:  The  first  supplies  the  inner  border  of  the  great  toe,  and 
sends  a  filament  to  the  Flexor  brevis  hallucis  muscle ;  the  second  bifurcates 
to  supply  the  adjacent  sides  of  the  great  and  second  toes,  sending  a  filament 
to  the  First  lumbrical  muscle;  the  third  digital  branch  supplies  the  adjacent 
sides  of  the  second  and  third  toes,  and  the  Second  lumbrical  muscle ;  the 

fourth  supplies  the  corresponding  sides  of 
the  third  and  fourth  toes,  and  receives  a 
communicating  branch  from  the  external 
plantar  nerve.  It  will  be  observed  that 
the  distribution  of  these  branches  is  pre- 
cisely similar  to  that  of  the  median  nerve 
in  the  hand.  Each  digital  nerve  gives  off 
cutaneous  and  articular  filaments,  and  oppo- 
site the  last  phalanx  sends  a  dorsal  branch, 
which  supplies  the  structure  round  the  nail, 
the  continuation  of  the  nerve  being  dis- 
tributed to  the  ball  of  the  toe. 

The  external  plantar  nerve,  the  smaller 
of  the  two,  completes  the  nervous  supply  to 
the  structures  of  the  sole  of  the  foot,  being 
distributed  to  the  little  toe  and  one-half 
of  the  fourth,  as  well  as  to  most  of  the 
deep  muscles,  its  distribution  being  similar 
to  that  of  the  ulnar  in  the  hand.  It  passes 
obliquely  forward  with  the  external  plantar 
artery  to  the  outer  side  of  the  foot,  lying 
between  the  Flexor  brevis  digitorum  and 
Flexor  accessorius,  and  in  the  interval  be- 
tween the  former  muscle  and  Abductor 
minimi  digiti  divides  into  a  superficial  and 
a  deep  branch.  Before  its  division  it  sup- 
plies the  Flexor  accessorius  and  Abductor 
minimi  digiti. 

The  superficial  branch  separates  into 
two  digital  nerves :  one,  the  smaller  of 

the  two,  supplies  the  outer  side  of  the  little  toe,  the  Flexor  brevis  minimi  digiti, 
and  the  two  Interosseous  muscles  of  the  fourth  metatarsal  space  ;  the  other  and 
larger  digital  branch  supplies  the  adjoining  sides  of  the  fourth  and  fifth  toes,  and 
communicates  with  the  internal  plantar  nerve. 

The  deep  or  muscular  branch  accompanies  the  external  plantar  artery  into  the 
deep  part  of  the  sole  of  the  foot,  beneath  the  tendons  of  the  Flexor  muscles  and 
Adductor  transversus  hallucis,  and  supplies  all  the  Interossei  (except  those  in  the 
fourth  metatarsal  space),  the  two  outer  Lumbricales,  the  Adductor  obliquus  hal- 
lucis, and  the  Adductor  transversus  hallucis. 

The  External  Popliteal  or  Peroneal  Nerve  (Fig.  510),  about  one-half  the  size  cf 
the  internal  popliteal,  descends  obliquely  along  the  outer  sides  of  the  popliteal 
space  to  the  head  of  the  fibula,  close  to  the  inner  margin  of  the  Biceps  muscle.  It 
is  easily  felt  beneath  the  skin  behind  the  head  of  the  fibula  at  the  inner  side  of 
the  tendon  of  the  Biceps.  It  passes  between  the  tendon  of  the  Biceps  and  outer 
head  of  the  Gastrocnemius  muscle,  winds  round  the  neck  of  the  fibula,  pierces  the 
origin  of  the  Peroneus  longus,  and  divides  beneath  that  muscle  into  the  anterior 
tibial  and  musculo-cutaneous  nerves. 

The  branches  of  the  peroneal  nerve,  previous  to  its  division,  are  articular  and 
cutaneous. 

The  articular  branches  are  three  in  number;    two  of  these  accompany  the 


FIG.  511.— The  plantar  nerves. 


THE    TIBIAL    AND    MUSCULO-CUTANEOUS  NERVES.  865 

superior  and  inferior  external  articular  arteries  to  the  outer  side  of  the  knee.  The 
upper  one  occasionally  arises  from  the  great  sciatic  nerve  before  its  bifurcation. 
The  third  (recurrent)  articular  nerve  is  given  off  at  the  point  of  division  of  the 
peroneal  nerve ;  it  ascends  with  the  anterior  recurrent  tibial  artery  through  the 
Tibialis  anticus  muscle  to  the  front  of  the  knee,  which  it  supplies. 

The  cut'incons  branches,  two  or  three  in  number,  supply  the  integument  along 
the  back  part  and  outer  side  of  the  leg  as  far  as  its  middle  or  lower,  part ;  one  of 
these,  larger  than  the  rest,  the  communicant  peronei,  arises  near  the  head  of  the 
fibula,  crosses  the  external  head  of  the  Gastrocnemius  to  the  middle  of  the 
leg.  and  joins  with  the  communicans  poplitei  to  form  the  external  saphenous. 
This  nerve  occasionally  exists  as  a  separate  branch,  which  is  continued  down  as 
far  as  the  heel. 

The  Anterior  Tibial  Nerve  (Fig.  506)  commences  at  the  bifurcation  of  the  per- 
oneal nerve,  between  the  fibula  and  upper  part  of  the  Peroneus  longus,  passes 
obliquely  forward  beneath  the  Extensor  longus  digitorum  to  the  fore  part  of  the 
interosseous  membrane,  and  reaches  the  outer  side  of  the  anterior  tibial  arterv 
above  the  middle  of  the  leg;  it  then  descends  with  the  artery  to  the  front  of  the 
ankle-joint,  where  it  divides  into  an  external  and  an  internal  branch.  This  nerve 
lies  at  first  on  the  outer  side  of  the  anterior  tibial  artery,  then  in  front  of  it,  and 
again  at  its  outer  side  at  the  ankle-joint. 

The  branches  of  the  anterior  tibial  nerve  in  its  course  through  the  leg  are  the 
muscular  branches  to  the  Tibialis  anticus,  Extensor  longus  digitorum,  Peroneus 
tertius.  and  Extensor  proprius  hallucis  muscles,  and  an  articular  branch  to  the 
ankle-joint. 

The  external  or  tarsal  branch  of  the  anterior  tibial  passes  outward  across  the 
tarsus,  beneath  the  Extensor  brevis  digitorum,  and,  having  become  ganglionic, 
like  the  posterior  interosseous  nerve  at  the  wrist,  supplies  the  Extensor  brevis 
digitorum.  From  the  ganglion  are  given  off  three  minute  interosseous  branches 
which  supply  the  tarsal  joints  and  the  metatarso-phalangeal  joints  of  the  second, 
third,  and  fourth  toes.  The  first  of  these  sends  a  filament  to  the  second  dorsal 
in'erosseous  muscle. 

The  internal  branch,  the  continuation  of  the  nerve,  accompanies  the  dorsalis 
pedis  artery  along  the  inner  side  of  the  dorsum  of  the  foot,  and  at  the  first  inter- 
osseous space  divides  into  two  branches,  which  supply  the  adjacent  sides  of  the 
great  and  second  toes,  communicating  with  the  internal  branch  of  the  musculo- 
cutaneous  nerve.  Before  it  divides  it  gives  off  an  interosseous  branch  to  the  first 
space,  which  supplies  the  metatarso-phalangeal  joint  of  the  great  toe  and  sends  a 
filament  to  the  First  dorsal  interosseous  muscle. 

The  Musculo-cutaneous  Nerve  (Fig.  506)  supplies  the  muscles  on  the  fibular 
side  of  the  leg  and  the  integument  of  the  dorsum  of  the  foot.  It  passes  forward 
betAveen  the  Peronei  muscles  and  the  Extensor  longus  digitorum,  pierces  the  deep 
fascia  at  the  lower  third  of  the  leg  on  its  front  and  outer  side,  and  divides  into 
two  branches.  This  nerve  in  its  course  between  the  muscles  gives  off  muscular 
branches  to  the  Peroneus  longus  and  brevis,  and  cutaneous  filaments  to  the 
integument  of  the  lower  part  of  the  leg. 

The  internal  branch  of  the  musculo-cutaneous  nerve  passes  in  front  of  the 
ankle-joint  and  along  the  dorsum  of  the  foot,  supplying  the  inner  side  of  the  great 
roe  and  the  adjoining  sides  of  the  second  and  third  toes.  It  also  supplies  the 
integument  of  the  inner  ankle  and  inner  side  of  the  foot,  communicating  with 
the  internal  saphenous  nerve,  and  communicates  with  the  anterior  tibial  nerve 
between  the  great  and  second  toes. 

The  external  branch,  the  larger,  passes  along  the  outer  side  of  the  dorsum  of 
the  foot,  to  be  distributed  to  the  adjoining  sides  of  the  third,  fourth,  and  fifth  toes. 
It  also  supplies  the  integument  of  the  outer  ankle  and  outer  side  of  the  foot,  com- 
municating with  the  short  saphenous  nerve.  These  dorsal  digital  nerves  reach 
as  far  as  the  last  phalanges. 

The  distribution  of  these  branches  of  the  musculo-cutaneous  nerve  will  be 

55 


866  THE   NERVOUS  SYSTEM. 

found  to  vary ;  together,  they  supply  all  the  toes  excepting  the  outer  side  of  the 
little  toe  and  the  adjoining  sides  of  the  great  and  second  toes,  the  former  being 
supplied  by  the  external  saphenous,  and  the  latter  by  the  internal  branch  of  the 
anterior  tibia!. 

Surgical  Anatomy. — The  lumbar  plexus  passes  through  the  Psoas  muscle,  and,  therefore 
in  psoas  abscess  any  or  all  of  its  branches  may  be  irritated,  causing  severe  pain  in  the  part  to 
which  the  irritated  nerves  are  distributed.  The  genito-crural  nerve  is  the  one  which  is  most 
frequently  implicated.  This  nerve  is  also  of  importance,  as  it  is  concerned  in  one  of  the  princi- 
pal reflexes  employed  in  the  investigation  of  diseases  of  the  spine.  If  the  skin  over  the  inner 
side  of  the  thigh  just  below  Poupart's  ligament,  the  part  supplied  by  the  crural  branch  of  the 
genito-crural  nerve,  be  gently  tickled  in  a  male  child,  the  testicle  will  be  noticed  to  be  drawn 
upward  through  the  action  of  the  Cremaster  muscle,  supplied  by  the  genital  branch  of  the  same 
nerve.  The  same  result  may  sometimes  be  noticed  in  adults,  and  can  almost  always  be  produced 
by  severe  stimulation.  This  reflex,  when  present,  shows  that  the  portion  of  the  cord  from  which 
the  first  and  second  lumbar  nerves  are  derived  is  in  a  normal  condition. 

The  anterior  crural  nerve  is  in  danger  of  being  injured  in  fractures  of  the  true  pelvis,  since 
the  fracture  most  commonly  takes  place  through  the  horizontal  minus  of  the  os  pubis,  at  or 
near  the  point  where  this  nerve  crosses  the  bone.  It  is  also  liable  to  be  injured  in  fractures  and 
dislocations  of  the  femur,  and  is  likely  to  be  pressed  upon  and  its  functions  impaired  in  some 
tumors  growing  in  the  pelvis.  Moreover,  on  account  of  its  superficial  position  it  is  exposed  to 
injury  in  wounds  and  stabs  in  the  groin.  When  this  nerve  is  paralyzed,  there  is  loss  of  motion 
in  the  Iliacus,  in  the  Quadriceps  extensor  cruris,  in  the  Sartorius,  and  partial  paralysis  of  the 
Pectineus.  There  is  loss  of  sensation  down  the  front  and  inner  side  of  the  thigh,  except  in  that 
part  supplied  by  the  crural  branch  of  the  genito-crural  and  by  the  ilio-inguinal,  as  well  as  down 
the  inner  side  of  the  leg  and  foot  as  far  as  the  ball  of  the  great  toe. 

The  obturator  nerve  is  of  special  surgical  interest.  It  is  rarely  paralyzed  alone,  but  occa- 
sionally in  association  with  the  anterior  crural.  The  principal  interest  attached  to  it  is  in  con- 
nection with  its  supply  to  the  knee,  pain  in  the  knee  being  symptomatic  of  many  diseases  in 
which  the  trunk  of  this  nerve  or  one  of  its  branches  is  irritated.  Thus  it  is  well  known  that  in 
the  earlier  stages  of  hip-joint  disease  the  patient  does  not  complain  of  pain  in  that  articulation, 
but  on  the  inner  side  of  the  knee  or  in  the  knee-joint  itself.  Again,  the  same  thing  occurs  in 
sacro-iliac  disease.  The  obturator  nerve  is  in  close  relationship  with  the  sacro-iliac  articulation, 
passing  over  it,  and,  according  to  some  anatomists,  distributing  filaments  to  it.  Again,  in  cancer 
of  the  sigmoid  flexure,  and  even  in  cases  where  masses  of  hardened  faeces  are  impacted  in  this 
portion  of  the  gut,  pain  is  complained  of  in  the  knee.  Finally,  pain  in  the  knee  forms  an 
important  diagnostic  sign  in  obturator  hernia.  The  hernial  protrusion  as  it  passes  out  through 
the  opening  in  the  obturator  membrane  presses  upon  the  nerve  and  causes  pain  in  the  parts  sup- 
plied by  its  peripheral  filaments.  When  the  obturator  nerve  is  paralyzed,  the  patient  is  unable 
to  press  his  knees  together  or  to  cross  one  leg  over  the  other,  on  account  of  paralysis  of  the 
Adductor  muscles.  Kotation  outward  of  the  thigh  is  impaired  from  paralysis  of  the  Obturator 
externus. 

The  great  sciatic  nerve  is  liable  to  be  pressed  upon  by  various  forms  of  pelvic  tumors  grow- 
ing from  the  pelvic  viscera  or  bones,  by  aneurisms  of  some  of  the  branches  of  the  internal  iliac 
artery,  calculus  in  the  bladder  when  of  large  size,  accumulation  of  faeces  in  the  rectum,  giving 
rise  to  pain  along  its  trunk,  to  which  the  term  sciatica  is  applied.  Outside  the  pelvis  exposure 
to  cold,  violent  movements  of  the  hip-joint,  exostoses  or  other  tumors  growing  from  the  margin 
of  the  sacro-sciatic  foramen,  may  also  give  rise  to  the  same  condition.  When  paralyzed  there 
is  loss  of  motion  in  all  the  muscles  below  the  knee,  and  loss  of  sensation  in  the  regions  sup- 
plied by  it. 

The  sciatic  nerve  has  been  frequently  cut  down  upon  and  stretched  for  the  relief  of  sciatica, 
and  also  in  cases  of  locomotor  ataxy,  the  anaesthesia  of  leprosy,  etc.  In  order  to  define  it  on 
the  surface,  a  point  is  taken  at  the  junction  of  the  middle  and  lower  third  of  a  line  stretching 
from  the  posterior  superior  spine  of  the  ilium  to  the  outer  part  of  the  tuber  ischii,  and  a  line 
drawn  from  this  to  the  middle  of  the  upper  part  of  the  popliteal  space.  The  operation  of 
stretching  the  sciatic  nerve  is  performed  by  making  an  incision  over  the  course  of  the  nerve 
about  the  centre  of  the  thigh.  The  overlying  structures  having  been  divided,  the  interval 
between  the  inner  and  outer'hamstrings  is  to  be  defined,  and  these  muscles  pulled  inward  and 
outward  with  retractors.  The  nerve  will  be  found  a  little  to  the  inner  side  of  the  Biceps.  It 
is  to  be  separated,  hooked  up  with  the  finger,  and  stretched  by  steady  and  continuous  traction 
for  two  or  three  minutes.  The  sciatic  nerve  may  also  be  stretched  by  what  is  known  as  the 
"  dry  "  plan.  The  patient  is  laid  on  his  back,  the  foot  is  extended,  the  leg  flexed  on  the  thigh, 
and  the  thigh  strongly  flexed  on  the  abdomen.  While  the  thigh  is  maintained  in  this  position 
the  leg  is  forcibly  extended  to  its  full  extent  and  the  foot  as  fully  flexed  on  the  leg. 

The  position  of  the  external  popliteal,  close  behind  the  tendon  of  the  Biceps  on  the  outer 
side  of  the  ham,  should  be  remembered  in  subcutaneous  division  of  the  tendon. 


THE  SYMPATHETIC  NERVE.  867 


THE  SYMPATHETIC   NERVE. 

The  Sympathetic  Nervous  System  consists  of  (1)  a  series  of  ganglia,  connected 
together  by  intervening  cords,  extending  from  the  base  of  the  skull  to  the  coccyx, 
one  on  each  side  of  the  middle  line  of  the  body,  partly  in  front  and  partly  on  each 
side  of  the  vertebral  column  ;  (2)  of  three  great  gangliated  plexuses  or  aggregations 
of  nerves  and  ganglia,  situated  in  front  of  the  spine  in  the  thoracic,  abdominal,  and 
pelvic  cavities  respectively ;  (3)  of  smaller  ganglia,  situated  in  relation  with  the 
abdominal  viscera ;  and  (4)  of  numerous  nerve-fibres.  These  latter  are  of  two 
kinds:  i.-niinnnnli-ntiiH'^  by  which  the  ganglia  communicate  with  each  other  and 
with  the  cerebro-spinal  nerves;  and  distributor^,  supplying,  in  general,  all  the 
internal  viscera  and  the  coats  of  the  blood-vessels. 

Each  gangliated  cord  may  be  traced  upward  from  the  base  of  the  skull  into 
its  cavity  by  an  ascending  branch,  which  passes  through  the  carotid  canal,  forms 
a  plexus  on  the  internal  carotid  artery,  and  communicates  with  the  ganglia  on  the 
first  and  second  divisions  of  the  fifth  nerve.  According  to  some  anatomists,  the 
two  cords  are  joined,  at  their  cephalic  extremities,  by  these  ascending  branches 
communicating  in  a  small  ganglion  (the  ganglion  of  Ribes),  situated  upon  the 
anterior  communicating  artery.  The  ganglia  of  these  cords  are  distinguished  as 
cervical,  dorsal,  lumbar,  and  sacral,  and  except  in  the  neck  they  correspond  pretty 
nearly  in  number  to  the  vertebrae  against  which  they  lie.  They  may  be  thus 
arranged : 

Cervical  portion         .         .         3  pairs  of  ganglia. 
Dorsal         "  12  " 

Lumbar       "  4           "         " 

Sacral         "  .          .4  or  5  "         " 

In  the  neck  they  are  situated  in  front  of  the  transverse  processes  of  the  verte- 
brae ;  in  the  dorsal  region,  in  front  of  the  heads  of  the  ribs ;  in  the  lumbar  region, 
on  the  sides  of  the  bodies  of  the  vertebrse  ;  and  in  the  sacral  region,  in  front  of  the 
sacrum.  As  the  two  cords  pass  into  the  pelvis  they  converge  and  unite  together 
in  a  single  ganglion  (ganglion  impar)  placed  in  front  of  the  coccyx.  Each 
ganglion  may  be  regarded  as  a  distinct  centre,  and,  in  addition  to  its  branches  of 
distribution,  possesses  also  branches  of  communication  which  communicate  with 
other  ganglia  and  with  the  cerebro-spinal  nerves. 

The  branches  of  communication  between  the  ganglia  are  composed  of  gray 
and  white  nerve-fibres,  the  latter  being  continuous  with  those  fibres  of  the  spinal 
nerves  which  pass  to  the  ganglia.  • 

The  branches  of  communication  between  the  ganglia  and  the  cerebro-spinal 
nerves  also  consist  of  a  white  and  gray  portion,  the  former  proceeding  from  the 
spinal  nerve  to  the  ganglion,  the  latter  passing  from  the  ganglion  to  the  spinal 
nerve,  so  that  a  double  interchange  takes  place  between  the  two  systems. 

The  three  great  gangliated  plexuses  are  situated  in  front  of  the  spine  in  the 
thoracic,  abdominal,  and  pelvic  regions,  and  are  named,  respectively,  the  cardiac, 
the  solar  or  epigastric,  and  the  Tiypogastric  plexus.  They  consist  of  collections  of 
nerves  and  ganglia,  the  nerves  being  derived  from  the  gangliated  cords  and  from 
the  cerebro-spinal  nerves.  They  distribute  branches  to  the  viscera. 

Smaller  ganglia  are  also  found  lying  amidst  the  nerves,  some  of  them  of 
microscopic  size,  in  certain  viscera — as,  for  instance,  in  the  heart,  the  stomach,  and 
the  uterus.  They  serve  as  additional  centres  for  the  origin  of  nerve-fibres. 

The  branches  of  distribution  derived  from  the  gangliated  cords,  from  the 
prevertebral  plexuses,  and  also  from  the  smaller  ganglia,  are  principally  destined 
for  the  blood-vessels  and  thoracic  and  abdominal  viscera,  supplying  the  involuntary 
muscular  fibre  of  the  coats  of  the  vessels  and  the  hollow  viscera,  and  the  secreting 
cells,  as  well  as  the  muscular  coats  of  the  vessels  in  the  glandular  viscera. 


868 


THE  NERVOUS  SYSTEM. 


Superior  cervical  ganglion.--\^: 

Middle  cervical  ganglion. 

/ 
Inferior  cervical  ganglion. 


^Pharyngeal  branches. 
Cardiac  branches. 

Deep  cardiac  plexus. 

Superficial  cardiac  plexus. 


Solar  plexus. 


Aortic  plexus. 


Hypogastric  plexus 


Sacral  ganglia. 


Ganglion  impar. 


FIG.  512.— The  sympathetic  nerve. 


CERVICAL   PORTION   OF   THE    GANGLIA  TED    CORD.         869 

In  addition  to  these  various  divisions  of  the  sympathetic,  the  ganglia  con- 
nected with  the  three  branches  of  the  fifth  cranial  nerve  are  believed  by  some 
to  constitute  a  part  of  the  sympathetic  system.  These  ganglia  have  already  been 
described  (page  799  et  seq.). 

THE  GANGLIATED  CORD. 
Cervical  Portion  of  the  Gangliated  Cord. 

The  cervical  portion  of  the  gangliated  cord  consists  of  three  ganglia  on  each 
side,  which  are  distinguished,  according  to  their  position,  as  the  superior,  middle, 
and  inferior  cervical. 

The  Superior  Cervical  Ganglion,  the  largest  of  the  three,  is  placed  opposite  the 
second  and  third  cervical  vertebrae,  and  sometimes  as  low  as  the  fourth  or  fifth.  It 
is  of  a  reddish-gray  color,  and  usually  fusiform  in  shape,  sometimes  broad,  and 
occasionally  constricted  at  intervals,  so  as  to  give  rise  to  the  opinion  that  it  consists 
of  the  coalescence  of  several  smaller  ganglia  ;  and  it  is  usually  believed  that  it  is 
formed  by  the  coalescence,  of  the  four  ganglia,  corresponding  to  the  four  upper 
cervical  nerves.  It  is  in  relation,  in  front,  with  the  sheath  of  the  internal  carotid 
artery  and  internal  jugular  vein;  behind,  it  lies  on  the  Rectus  capitis  anticus 
major  muscle. 

Its  branches  may  be  divided  into  superior,  inferior,  external,  internal,  and 
anterior. 

The  superior  branch  appears  to  be  a  direct  prolongation  of  the  ganglion.  It 
is  soft  in  texture  and  of  a  reddish  color.  It  ascends  by  the  side  of  the  internal 
carotid  artery,  and,  entering  the  carotid  canal  in  the  temporal  bone,  divides  into  two 
branches,  which  lie,  one  on  the  outer,  and  the  other  on  the  inner,  side  of  that  vessel. 

The  outer  branch,  the  larger  of  the  two,  distributes  filaments  to  the  internal 
carotid  artery  and  forms  the  carotid  plexus. 

The  inner  branch  also  distributes  filaments  to  the  internal  carotid,  and,  con- 
tinuing onward,  forms  the  cavernous  plexus. 

The  Carotid  Plexus. 

The  carotid  plexus  is  situated  on  the  outer  side  of  the  internal  carotid.  Fila- 
ments from  this  plexus  occasionally  form  a  small  gangliform  swelling  on  the  under 
surface  of  the  artery,  which  is  called  the  carotid  ganglion.  The  carotid  plexus 
communicates  with  the  Gasserian  ganglion,  with  the  sixth  nerve,  and  the  spheno- 
palatine  ganglion,  and  distributes  filaments  to  the  wall  of  the  carotid  artery  and 
to  the  dura  mater  (Valentin),  while  in  the  carotid  canal  it  communicates  with 
Jacobson's  nerve,  the  tympanic  branch  of  the  glosso-pharyngeal. 

The  communicating  branches  ivith  the  sixth  nerve  consist  of  one  or  two  fila- 
ments which  join  that  nerve  as  it  lies  upon  the  outer  side  of  the  internal  carotid. 
Other  filaments  are  also  connected  with  the  Gasserian  ganglion.  The  communi- 
cation with  the  spheno-palatine  ganglion  is  effected  by  a  branch,  the  large  deep 
petrosal,  which  is  given  off  from  the  plexus  on  the  outer  side  of  the  artery,  and 
which  passes  through  the  cartilage  filling  up  the  foramen  lacerum  medium,  and 
joins  the  great  superficial  petrosal  to  form  the  Vidian  nerve.  The  Vidian  nerve 
then  proceeds  along  the  pterygoid  or  Vidian  canal  to  the  spheno-palatine  ganglion. 
The  communication  with  Jacobson's  nerve  is  effected  by  two  branches,  one  of 
which  is  called  the  small  deep  petrosal  nerve,  and  the  other  the  long  petrosal. 

The  Cavernous  Plexus. 

The  cavernous  plexus  is  situated  below  and  internal  to  that  part  of  the  internal 
carotid  which  is  placed  by  the  side  of  the  sella  Turcica  in  the  cavernous  sinus, 
and  is  formed  chiefly  by  the  internal  division  of  the  ascending  branch  from  the 
superior  cervical  ganglion.  It  communicates  with  the  third,  the  fourth,  the 
ophthalmic  division  of  the  fifth,  and  the  sixth  nerves,  and  with  the  ophthalmic 


870 


THE   NERVOUS  SYSTEM. 


'Accompanying  brandies  of  internal 


carotid  artery.    I  //  L 


To  ophthalmic  ganglion. 


To  tympanic  branch 


of  glosso-pharyngeal.  .A  -mj 

II  //     -•tALiiJffl; 


•.To  third  nerve. 

Large  superficial  petrosal  from  facial  nerve. 


To  ganglion  of  root 
of  pneumogastric.  ^ 
To  petrosal  ganglion    \ 
of  glosso  pharyngeal.==~^i 


From  1st  cervical  nerve. 
From  2d  cervical  nerve. 


Accompanying  branches  of 
•^—external,  carotid  artery. 


From  3d  cervical  nerve. 


From  Uh  cervical  nerve. 


Uniting,  with  branches  of  pneumogas- 
'.ric  and  glosso-pharyngeal,  to  form 
tfte  pharyngeal  plexus. 


From  5th  cervical  nerved 


From  6th  cervical  nerve. 


lor  thyroid  branches  surrounding  artery. 


Plexus  sur- 
rounding  vert- 
al  artery, 


From  8th  cerv- 
ical nerve.     ' 


" "?  is  S       From  1st 


*  «  i  s    dorsal  nerve, 


Cardiac  branches  from  pneumo- 
gastric and  recurrent  laryngeal 


From  3d 

dorsal 

nerve. 


Ganglion  of  Wnsberg. 


To  left  an- 
erior  pul- 
monary 


FIG.  513.— Plan  of  the  cervical  portion  of  the  sympathetic.    (After  Flower.) 


THE  SYMPATHETIC,  MIDDLE    CERVICAL    GANGLION.        871 

ganglion,  and  distributes  filaments  to  the  wall  of  the  internal  carotid.  The 
branch  of  communication  with  the  third  nerve  joins  it  at  its  point  of  division; 
the  branch  to  the  fourth  nerve  joins  it  as  it  lies  on  the  outer  wall  of  the  cavernous 
sinus ;  other  filaments  are  connected  with  the  under  surface  of  the  trunk  of  the 
ophthalmic  nerve;  and  a  second  filament  of  communication  joins  the  sixth  nerve. 

The  filament  of  connection  with  the  ophthalmic  ganglion  arises  from  the 
anterior  part  of  the  cavernous  plexus ;  it  accompanies  the  nasal  nerve  or  con- 
tinues forward  as  a  separate  branch. 

The  terminal  filaments  from  the  carotid  and  cavernous  plexuses  are  prolonged 
along  the  internal  carotid,  forming  plexuses  which  entwine  round  the  cerebral  and 
ophthalmic  arteries ;  along  the  former  vessels  they  may  be  traced  on  to  the  pia 
mater ;  along  the  latter,  into  the  orbit,  where  they  accompany  each  of  the  sub- 
divisions of  the  vessel,  a  separate  plexus  passing,  with  the  arteria  centralis  retinae, 
into  the  interior  of  the  eyeball.  The  filaments  prolonged  on  to  the  anterior  com- 
municating artery  form  a  small  ganglion,  the  ganglion  of  Ribes,1  which  serves,  as 
mentioned  above,  to  connect  the  sympathetic  nerves  of  the  right  and  left  sides. 

The  inferior  or  descending  branch  of  the  superior  cervical  ganglion  communi- 
cates with  the  middle  cervical  ganglion. 

The  external  branches  are  numerous,  and  communicate  with  the  cranial  nerves 
and  with  the  four  upper  spinal  nerves.  Sometimes  the  branch  to  the  fourth 
s.->inal  nerve  may  come  from  the  cord  connecting  the  upper  and  middle  cervical 
ganglia.  The  branches  of  communication  with  the  cranial  nerves  consist  of 
delicate  filaments,  which  pass  from  the  superior  cervical  ganglion  to  the  ganglion 
of  the  trunk  of  the  pneumogastric  and  to  the  hypoglossal  nerve.  A  separate 
filament  from  the  cervical  ganglion  subdivides  and  joins  the  petrosal  ganglion  of 
the  glosso-pharyngeal  and  the  ganglion  of  the  root  of  the  pneumogastric  in  the 
jugular  foramen. 

The  internal  branches  are  three  in  number — the  pharyngeal,  laryngeal,  and 
tup <•!•{<.»•  cardiac  nerve.  The  pharyngeal  branches  pass  inward  to  the  side  of  the 
pharynx,  where  they  join  with  branches  from  the  glosso-pharyngeal,  pneumogastric, 
and  external  laryngeal  nerves  to  form  the  pharyngeal  plexus.  The  laryngeal 
hi- mi-lies  unite  with  the  superior  laryngeal  nerve  and  its  branches. 

The  superior  cardiac  nerve  (nervus  superficialis  cordis)  arises  by  two  or  more 
branches  from  the  superior  cervical  ganglion,  and  occasionally  receives  a  filament 
from  the  cord  of  communication  between  the  first  and  second  cervical  ganglia.  It 
runs  down  the  neck  behind  the  common  carotid  artery,  lying  upon  the  Longus 
colli  muscle,  and  crosses  in  front  of  the  inferior  thyroid  artery  and  recurrent 
larvngeal  nerve. 

The  right  superior  cardiac  nerve,  at  the  root  of  the  neck,  passes  either  in  front 
of  or  behind  the  subclavian  artery,  and  along  the  arteria  innominata,  to  the  back 
part  of  the  arch  of  the  aorta,  where  it  joins  the  deep  cardiac  plexus.  This  nerve, 
in  its  course,  is  connected  with  other  branches  of  the  sympathetic  :  about  the 
middle  of  the  neck  it  receives  filaments  from  the  external  laryngeal  nerve ;  lower 
down,  one  or  two  twigs  from  the  pneumogastric  ;  and  as  it  enters  the  thorax  it  is 
joined  by  a  filament  from  the  recurrent  laryngeal.  Filaments  from  this  nerve 
communicate  with  the  thyroid  branches  from  the  middle  cervical  ganglion. 

The  left  superior  cardiac  nerve,  in  the  chest,  runs  by  the  side  of  the  left  com- 
mon carotid  artery  and  in  front  of  the  arch  of  the  aorta  to  the  superficial  cardiac 
plexus,  but  occasionally  it  passes  behind  the  aorta  and  terminates  in  the  deep 
cardiac  plexus. 

The  anterior  branches  ramify  upon  the  external  carotid  artery  and  its  branches, 
forming  round  each  a  delicate  plexus,  on  the  nerves  composing  which  small  ganglia 
are  occasionally  found.  These  ganglia  have  been  named,  according  to  their  posi- 
tion, intercarotid 2  (placed  at  the  angle  of  bifurcation  of  the  common  carotid), 
lingual,  temporal,  and  pharyngeal.  The  plexuses  accompanying  some  of  these 

1  The  existence  of  this  ganglion  is  doubted  by  some  observers. 

2  This  ganglion  is  of  the  same  structure  as  the  coccygeal  gland  (Luschka). 


872  THE   NERVOUS  SYSTEM. 

arteries  have  important  communications  with  other  nerves.  That  surrounding  the 
external  carotid  is  connected  with  the  branch  of  the  facial  nerve  to  the  stylo-hyoid 
muscle;  that  surrounding  the  facial  communicates  with  the  submaxillary  ganglion 
by  one  or  two  filaments ;  and  that  accompanying  the  middle  meningeal  artery 
sends  offsets  which  pass  to  the  otic  ganglion  and  to  the  intumescentiaganglioformis 
of  the  facial  nerve  (external  petrosal). 

The  Middle  Cervical  Ganglion  (thyroid  ganglion}  is  the  smallest  of  the  three 
cervical  ganglia,  and  is  occasionally  altogether  wanting.  It  is  placed  opposite  the 
sixth  cervical  vertebra,  usually  upon,  or  close  to,  the  inferior  thyroid  artery ; 
hence  the  name,  "thyroid  ganglion,"  assigned  to  it  by  Haller.  It  is  probably 
formed  by  the  coalescence  of  two  ganglia  corresponding  to  the  fifth  and  sixth  cer- 
vical nerves. 

Its  superior  branches  ascend  to  communicate  with  the  superior  cervical  gan- 
glion. 

Its  inferior  branches  descend  to  communicate  with  the  inferior  cervical  ganglion. 

Its  external  branches  pass  outward  to  join  the  fifth  and  sixth  spinal  nerves. 
These  branches  are  -not  constantly  found. 

Its  internal  branches  are  the  thyroid  and  the  middle  cardiac  nerve. 

The  thyroid  branches  are  small  filaments  which  accompany  the  inferior  thyroid 
artery  to  the  thyroid  gland ;  they  communicate,  on  the  artery,  with  the  superior 
cardiac  nerve,  and,  in  the  gland,  with  branches  from  the  recurrent  and  external 
laryngeal  nerves. 

The  middle  cardiac  nerve  (nervus  cardiacus  magnus),  the  largest  of  the  three 
cardiac  nerves,  arises  from  the  middle  cervical  ganglion  or  from  the  cord  between 
the  middle  and  inferior  ganglia.  On  the  right  side  it  descends  behind  the  common 
carotid  artery,  and  at  the  root  of  the  neck  passes  either  in  front  of  or  behind  the 
subclavian  artery;  it  then  descends  on  the  trachea,  receives  a  few  filaments  from 
the  recurrent  laryngeal  nerve,  and  joins  the  deep  cardiac  plexus.  In  the  neck  it 
communicates  with  the  superior  cardiac  and  recurrent  laryngeal  nerves.  On  the 
left  side  the  middle  cardiac  nerve  enters  the  chest  between  the  left  carotid  and  sub- 
clavian arteries,  and  joins  the  left  side  of  the  deep  cardiac  plexus. 

The  Inferior  Cervical  G-anglion  is  situated  between  the  base  of  the  transverse 
process  of  the  last  cervical  vertebra  and  the  neck  of  the  first  rib  on  the  inner  side 
of  the  superior  intercostal  artery.  Its  form  is  irregular;  it  is  larger  in  size  than 
the  preceding,  and  frequently  joined  with  the  first  thoracic  ganglion.  It  is  proba- 
bly formed  by  the  coalescence  of  two  ganglia  which  correspond  to  the  two  last 
cervical  nerves. 

Its  superior  branches  communicate  with  the  middle  cervical  ganglion. 

Its  inferior  branches  descend,  some  in  front  of,  others  behind,  the  subclavian 
artery,  to  join  the  first  thoracic  ganglion. 

Its  internal  branch  is  the  inferior  cardiac  nerve. 

The  inferior  cardiac  nerve  (nervus  cardiacus  minor)  arises  from  the  inferior 
cervical  or  first  thoracic  ganglion.  It  passes  down  behind  the  subclavian  artery 
and  along  the  front  of  the  trachea  to  join  the  deep  cardiac  plexus.  It  communi- 
cates freely  behind  the  subclavian  artery  with  the  recurrent  laryngeal  and  middle 
cardiac  nerves. 

The  external  branches  consist  of  several  filaments,  some  of  which  communi- 
cate with  the  seventh  and  eighth  spinal  nerves ;  others  accompany  the  vertebral 
artery  along  the  vertebral  canal,  forming  a  plexus  round  the  vessel,  supplying  it 
with  filaments,  and  communicating  with  the  cervical  spinal  nerves  as  high  as  the 
fourth. 

Thoracic  Portion  of  the  Gangliated  Cord. 

The  thoracic  portion  of  the  gangliated  cord  consists  of  a  series  of  ganglia 
which  usually  correspond  in  number  to  that  of  the  vertebrae,  but,  from  the  occa- 
sional coalescence  of  two,  their  number  is  uncertain.  These  ganglia  are  placed 
on  each  side  of  the  spine,  resting  against  the  heads  of  the  ribs  and  covered  by  the 


THE  LUMBAR   PORTION    OF   THE    GANGLIATED    CORD.     873 

pleura  costalis ;  the  last  two  are,  however,  anterior  to  the  rest,  being  placed  on  the 
side  of  the  bodies  of  the  eleventh  and  twelfth  dorsal  vertebrae.  The  ganglia  are 
small  in  size  and  of  a  grayish  color.  The  first,  larger  than  the  rest,  is  of  an 
elongated  form  and  frequently-  blended  with  the  last  cervical.  They  are  connected 
together  by  cord-like  prolongations  from  their  substance. 

The  t>.rter/ial  branches  from  each  ganglion,  usually  two  in  number,  communi- 
cate with  each  of  the  dorsal  spinal  nerves. 

The  internal  branches  from  the  six  upper  ganglia  are  very  small ;  they  supply 
filaments  to  the  thoracic  aorta  and  its  branches,  besides  small  branches  to  the 
bodies  of  the  vertebrae  and  their  ligaments.  Branches  from  the  third  and  fourth, 
and  sometimes  also  from  the  first  and  second  ganglia,  form  part  of  the  posterior 
pulmonary  plexus. 

The  internal  branches  from  the  six  lower  ganglia  are  large  and  white  in  color; 
they  distribute  filaments  to  the  aorta  and  unite  to  form  the  three  splanchnic  nerves. 
These  are  named  the  great,  the  lesser,  and  the  smallest  or  renal  splanchnic. 

The  great  splanchnic  nerve  is  of  a  white  color,  firm  in  texture,  and  bears  a 
marked  contrast  to  the  ganglionic  nerves.  It  is  formed  by  branches  from  the 
thoracic  ganglia  between  the  sixth  and  tenth,  receiving  filaments  (according  to  Dr. 
Beck)  from  all  the  thoracic  ganglia  above  the  sixth.  These  roots  unite  to  form  a 
large  round  cord  of  considerable  size.  It  descends  obliquely  inward  in  front  of 
the  bodies  of  the  vertebrae  along  the  posterior  mediastinum,  perforates  the  crus  of 
the  Diaphragm,  and  terminates  in  the  semilunar  ganglion,  distributing  filaments 
to  the  renal  and  suprarenal  plexus. 

The  lesser  splanchnic  nerve  is  formed  by  filaments  from  the  tenth  and  eleventh 
ganglia  and  from  the  cord  between  them.  It  pierces  the  Diaphragm  with  the 
preceding  nerve  and  joins  the  coeliac  plexus.  It  communicates  in  the  chest  with 
the  great  splanchnic  nerve,  and  occasionally  sends  filaments  to  the  renal  plexus. 

The  smallest,  or  renal,  splanchnic  nerve  arises  from  the  last  ganglion,  and, 
piercing  the  Diaphragm,  terminates  in  the  renal  plexus  and  lower  part  of  the 
coeliac  plexus.  It  occasionally  communicates  with  the  preceding  nerve. 

A  striking  analogy  appears  to  exist  between  the  splanchnic  and  the  cardiac 
nerves.  The  cardiac  nerves  are  three  in  number;  they  arise  from  the  three 
cervical  ganglia,  and  are  distributed  to  a  large  and  important  organ  in  the  thoracic 
cavity.  The  splanchnic  nerves,  also  thi-ee  in  number,  are  connected  probably  with 
all  the  dorsal  ganglia,  and  are  distributed  to  important  organs  in  the  abdominal 
cavity. 

The  Lumbar  Portion  of  the  Gangliated  Cord. 

The  lumbar  portion  of  the  gangliated  cord  is  situated  in  front  of  the  vertebral 
column  along  the  inner  margin  of  the  Psoas  muscle.  It  consists  usually  of  four 
ganglia,  connected  together  by  interganglionic  cords.  The  ganglia  are  of  small 
size,  of  a  grayish  color,  shaped  like  a  barleycorn,  and  placed  much  nearer  the 
median  line  than  the  thoracic  ganglia. 

The  xn/»',->'i>r  and  inferior  branches  of  the  lumbar  ganglia  serve  as  communi- 
cating branches  between  the  chain  of  ganglia  in  this  region.  They  are  usually 
single  and  of  a  white  color. 

The  external  branches  communicate  with  the  lumbar  spinal  nerves.  From  the 
situation  of  the  lumbar  ganglia  these  branches  are  longer  than  in  the  other  regions. 
They  are  usually  two  in  number  from  each  ganglion,  but  their  connection  with  the 
spinal  nerves  is  not  so  uniform  as  in  other  regions.  They  accompany  the  lumbar 
arteries  around  the  sides  of  the  bodies  of  the  vertebrae,  passing  beneath  the  fibrous 
arches  from  which  some  of  the  fibres  of  the  Psoas  muscle  arise. 

Of  the  internal  branches,  some  pass  inward,  in  front  of  the  aorta,  and  help  to 
form  the  aortic  plexus.  Other  branches  descend  in  front  of  the  common  iliac 
arteries,  and  join  over  the  pi'omontory  of  the  sacrum,  helping  to  form  the  hypo- 
gastric  plexus.  Numerous  delicate  filaments  are  also  distributed  to  the  bodies  of 
the  vertebras  and  the  ligaments  connecting  them. 


874  THE   NERVOUS  SYSTEM. 

Pelvic  Portion  of  the  Gangliated  Cord. 

The  pelvic  portion  of  the  gangliated  cord  is  situated  in  front  of  the  sacrum 
along  the  inner  side  of  the  anterior  sacral  foramina.  It  consists  of  four  or  five 

o 

small  ganglia  on  each  side,  connected  together  by  interganglionic  cords.  Below, 
these  cords  converge  and  unite  on  the  front  of  the  coccyx  by  means  of  a  small 
ganglion  (the  coccygeal  ganglion  or  ganglion  impar). 

The  superior  and  inferior  branches  are  the  cords  of  communication  between  the 
ganglia  above  and  below. 

The  external  branches,  exceedingly  short,  communicate  with  the  sacral  nerves. 
They  are  two  in  number  from  each  ganglion.  The  coccygeal  nerve  communicates 
either  with  the  last  sacral  or  coccygeal  ganglion. 

The  internal  branches  communicate,  on  the  front  of  the  sacrum,  with  the 
corresponding  branches  from  the  opposite  side ;  some,  from  the  first  two  ganglia, 
pass  to  join  the  pelvic  plexus,  and  others  form  a  plexus  which  accompanies  the 
middle  sacral  artery  and  sends  filaments  to  the  coccygeal  gland. 

THE  GREAT  PLEXUSES  OF  THE  SYMPATHETIC. 

The  great  plexuses  of  the  sympathetic  are  the  large  aggregations  of  nerves 
and  ganglia,  above  alluded  to,  situated  in  the  thoracic,  abdominal,  and  pelvic 
cavities  respectively.  From  them  are  derived  the  branches  which  supply  the 
viscera. 

The  Cardiac  Plexus. 

The  cardiac  plexus  is  situated  at  the  base  of  the  heart,  and  is  divided  into  a 
superficial  part,  which  lies  in  the  concavity  of  the  arch  of  the  aorta,  and  a  deep 
part,  which  lies  between  the  trachea  and  aorta. 

The  great  or  deep  cardiac  plexus  (plexus  magnus  profundus,  Scarpa)  is 
situated  in  front  of  the  trachea  at  its  bifurcation,  above  the  point  of  division  of 
the  pulmonary  artery  and  behind  the  arch  of  the  aorta.  It  is  formed  by  the 
cardiac  nerves  derived  from  the  cervical  ganglia  of  the  sympathetic  and  the 
cardiac  branches  of  the  recurrent  laryngeal  and  pneumogastric.  The  only  cardiac 
nerves  which  do  not  enter  into  the  formation  of  this  plexus  are  the  left  superior 
cardiac  nerve  and  the  left  inferior  cervical  cardiac  branch  from  the  pneumogastric. 

The  branches  from  the  right  side  of  this  plexus  pass,  some  in  front  of,  and 
others  behind,  the  right  pulmonary  artery ;  the  former,  the  more  numerous, 
transmit  a  few  filaments  to  the  anterior  pulmonary  plexus,  and  are  then  continued 
onward  to  form  part  of  the  anterior  coronary  plexus  ;  those  behind  the  pulmonary 
artery  distribute  a  few  filaments  to  the  right  auricle,  and  are  then  continued 
onward  to  form  part  of  the  posterior  coronary  plexus. 

The  branches  from  the  left  side  of  the  deep  cardiac  plexus  distribute  a  few 
filaments  to  the  superficial  cardiac  plexus,  to  the  left  auricle  of  the  heart,  and  to 
the  anterior  pulmonary  plexus,  and  then  pass  on  to  form  the  greater  part  of  the 
posterior  coronary  plexus. 

The  superficial  (anterior)  cardiac  plexus  lies  beneath  the  arch  of  the  aorta,  in 
front  of  the  right  pulmonary  artery.  It  is  formed  by  the  left  superior  cardiac 
nerve,  the  left  (and  occasionally  the  right)  inferior  cervical  cardiac  branches  of  the 
pneumogastric,  and  filaments  from  the  deep  cardiac  plexus.  A  small  ganglion 
(cardiac  ganglion  of  Wrisberg]  is  occasionally  found  connected  with  these  nerves 
at  their  point  of  junction.  This  ganglion,  when  present,  is  situated  immediately 
beneath  the  arch  of  the  aorta,  on  the  right  side  of  the  ductus  arteriosus.  The 
superficial  cardiac  plexus  forms  the  chief  part  of  the  anterior  coronary  plexus,  and 
several  filaments  pass  along  the  pulmonary  artery  to  the  left  anterior  pulmonary 
plexus. 

The  posterior  coronary  plexus  is  chiefly  formed  by  filaments  prolonged  from 
the  left  side  of  the  deep  cardiac  plexus,  and  by  a  few  from  the  right  side.  It 
surrounds  the  branches  of  the  coronary  artery  at  the  back  of  the  heart,  and  its 


THE   EPIGASTRIC    OR   SOLAR   PLEXUS.  875 

filaments  are  distributed  with  those  vessels  to  the  muscular  substance  of  the 
ventricles. 

The  anterior  coronary  plexus  is  formed  chiefly  from  the  superficial  cardiac 
plexus,  but  receives  filaments  from  the  deep  cardiac  plexus.  Passing  forward 
between  the  aorta  and  pulmonary  artery,  it  accompanies  the  left  coronary  artery 
on  the  anterior  surface  of  the  heart. 

Valentin  has  described  nervous  filaments  ramifying  under  the  endocardium  ; 
and  Remak  has  found,  in  several  mammalia,  numerous  small  ganglia  on  the  cardiac 
nerves,  both  on  the  surface  of  the  heart  and  in  its  muscular  substance. 

The  Epigastric  or  Solar  Plexus  (Figs.  512,  514). 

The  Epigastric  or  Solar  plexus  supplies  all  the  viscera  in  the  abdominal  cavity. 
It  consists  of  a  great  network  of  nerves  and  ganglia,  situated  behind  the  stomach 
and  in  front  of  the  aorta  and  crura  of  the  Diaphragm.  It  surrounds  the  coeliac 
axis  and  root  of  the  superior  mesenteric  artery,  extending  downward  as  low  as  the 
pancreas  and  outward  to  the  suprarenal  capsules.  This  plexus,  and  the  ganglia 
connected  with  it,  receive  the  great  splanchnic  nerve  of  both  sides,  and  some 
filaments  from  the  right  pneumogastric.  It  distributes  filaments  which  accompany, 
under  the  name  of  plexuses,  all  the  branches  from  the  front  of  the  abdominal 
aorta. 

The  semilunar  ganglia  of  the  solar  plexus,  two  in  number,  one  on  each  side, 
are  the  largest  ganglia  in  the  body.  They  are  large  irregular  gangliform  masses 
formed  by  the  aggregation  of  smaller  ganglia,  having  interspaces  between  them. 
They  are  situated  in  front  of  the  crura  of  the  Diaphragm,  close  to  the  suprarenal 
capsules :  the  one  on  the  right  side  lies  beneath  the  inferior  vena  cava ;  the  upper 
part  of  each  ganglion  is  joined  by  the  greater  splanchnic  nerve,  and  to  the  inner 
side  of  each  the  branches  of  the  solar  plexus  are  connected. 

From  the  epigastric  or  solar  plexus  are  derived  the  following : 

Phrenic  or  Diaphragmatic  plexus.  (  Gastric  plexus. 

Suprarenal  plexus.  Coeliac  plexus  <  Splenic  plexus. 

Renal  plexus.  (  Hepatic  plexus. 

Spermatic  plexus.  Superior  mesenteric  plexus. 

Aortic  plexus. 

The  phrenic  plexus  accompanies  the  phrenic  artery  to  the  Diaphragm,  which 
it  supplies,  some  filaments  passing  to  the  suprarenal  capsule.  It  arises  from  the 
upper  part  of  the  semilunar  ganglion,  and  is  larger  on  the  right  than  on  the  left 
side.  It  receives  one  or  two  branches  from  the  phrenic  nerve.  In  connection 
with  this  plexus,  on  the  right  side,  at  its  point  of  junction  with  the  phrenic  nerve, 
is  a  small  ganglion  (ganglion  diapTiragmaticuni).  This  ganglion  is  placed  on  the 
under  surface  of  the  Diaphragm,  near  the  suprarenal  capsule.  Its  branches  are 
distributed  to  the  inferior  vena  cava,  suprarenal  capsule,  and  hepatic  plexus. 
There  is  no  ganglion  on  the  left  side. 

The  suprarenal  plexus  is  formed  by  branches  from  the  solar  plexus,  from  the 
semilunar  ganglion,  and  from  the  phrenic  and  great  splanchnic  nerves,  a  ganglion 
being  formed  at  the  point  of  junction  of  the  latter  nerve.  It  supplies  the  supra- 
renal capsule.  The  branches  of  this  plexus  are  remarkable  for  their  large  size  in 
comparison  with  the  size  of  the  organ  they  supply. 

The  renal  plexus  is  formed  by  filaments  from  the  solar  plexus,  the  outer  part 
of  the  semilunar  ganglion,  and  the  aortic  plexus.  It  is  also  joined  by  filaments 
from  the  lesser  and  smallest  splanchnic  nerves.  The  nerves  from  these  sources, 
fifteen  or  twenty  in  number,  have  numerous  ganglia  developed  upon  them.  They 
accompany  the  branches  of  the  renal  artery  into  the  kidney,  some  filaments  on 
the  right  side  being  distributed  to  the  inferior  vena  cava,  and  others  to  the  sper- 
matic plexus  on  both  sides. 

The  spermatic  plexus  is  derived  from  the  renal  plexus,  receiving  branches  from 
the  aortic  plexus.  It  accompanies  the  spermatic  vessels  to  the  testes. 


876 


THE   NERVOUS  SYSTEM. 


Diaphragmatic  ganglion. . 
Suprarenal  capsule. 

Great 

splanchni 

nerve. 

Right 
semilunar 
ganglion. 

Renal  ganglion. 
Small  splanchnic  nerve. 


Hepatic 
artery.  \ 


Renal  artery. 

Gangliated  cord. 

Communicating  branch. 


Left  semilunar  ganglion. 
Superior  mesenteric  artery. 
Great  splanchnic  nerve. 
Small  splanchnic  nerve. 

Renal  ganglion. 


Renal  artery. 
Superior  mesenteric  ganglion. 


Branch  to  aortic  plexus. 


Branch  to  aortic  plexus. 


Gangliated  cord  of 
sympathetic. 


Inferior  mesenteric  artery. 


Inferior  mesenteric  ganglion. 


Sacro-vertebral  angle. 
Common  iliac  vein. 
Common  iliac  artery. 


FIG.  514.— Lumbar  portion  of  the  gangliated  cord,  with  the  solar  and  hypogastric  plexuses.    (After  Hcnle.) 

In  the  female  the  ovarian  plexus  is  distributed  to  the  ovaries  and  fundus  of  the 
uterus. 

The  coeliac  plexus,  of  large  size,  is  a  direct  continuation  from  the  solar  plexus  : 
it  surrounds  the  coeliac  axis  and  subdivides  into  the  gastric,  hepatic,  and  splenic 


THE   HYPOGASTRIC  PLEXUS.  877 

plexuses.  It  receives  branches  from  the  lesser  splanchnic  nerves,  and,  on  the  left 
side,  a  filament  from  the  right  pneumogastric. 

The  gastric  or  coronary  plexus  accompanies  the  gastric  artery  along  the  lesser 
curvature  of  the  stomach,  and  joins  with  branches  from  the  left  pneumogastric 
nerve.  It  is  distributed  to  the  stomach. 

The  hepatic  plexus,  the  largest  offset  from  the  coeliac  plexus,  receives  filaments 
from  the  left  pneumogastric  and  right  phrenic  nerves.  It  accompanies  the  hepatic 
artery,  ramifying  in  the  substance  of  the  liver  upon  its  branches  and  upon  those 
of  the  vena  portte. 

Branches  from  this  plexus  accompany  all  the  divisions  of  the  hepatic  arterv. 
Thus  there  is  a  pyloric  plexus  accompanying  the  pyloric  branch  of  the  hepatic, 
which  joins  with  the  gastric  plexus  and  pneumogastric  nerves.  There  is  also  a 
goitre-duodenal  plexus,  which  subdivides  into  the  pancreatico-duodenal  plexus, 
which  accompanies  the  pancreatico-duodenal  artery,  to  supply  the  pancreas  and 
duodenum,  joining  with  branches  from  the  mesenteric  plexus;  and  a  gastro-epi- 
ploic  plexus,  which  accompanies  the  right  gastro-epiploic  artery  along  the  greater 
curvature  of  the  stomach  and  anastomoses  with  branches  from  the  splenic  plexus. 
A  -  i>}--jru8,  which  supplies  the  gall-bladder,  also  arises  from  the  hepatic  plexus 
near  the  liver. 

The  splenic  plexus  is  formed  by  branches  from  the  eceliac  plexus,  the  left  semi- 
lunar  ganglia,  and  from  the  right  pneumogastric  nerve.  It  accompanies  the 
splenic  artery  and  its  branches  to  the  substance  of  the  spleen,  giving  off,  in  its 
course,  filaments  to  the  pancreas  (pancreatic  jlexitz)  and  the  left  gastro-epiploic 
plexus,  which  accompanies  the  gastro-epiplpica  sinistra  artery  along  the  convex 
border  of  the  stomach. 

The  superior  mesenteric  plexus  is  a  continuation  of  the  lower  part  of  the  great 
solar  plexus,  receiving  a  branch  from  the  junction  of  the  right  pneumogastric 
nerve  with  the  coeliac  plexus.  It  surrounds  the  superior  mesenteric  artery,  which  it 
accompanies  into  the  mesentery,  and  divides  into  a  number  of  secondary  plexuses, 
which  are  distributed  to  all  the  parts  supplied  by  the  artery — viz.  pancreatic  branches 
to  the  pancreas ;  intestinal  branches,  which  supply  the  whole  of  the  small  intestine  ; 
and  ileo-colic,  right  colic,  and  middle  colic  branches,  which  supply  the  correspond- 
ing parts  of  the  great  intestine.  The  nerves  composing  this  plexus  are  white  in 
color  and  firm  in  texture,  and  have  numerous  ganglia  developed  upon  them  near 
their  origin. 

The  aortic  plexus  is  formed  by  branches  derived,  on  each  side,  from  the  solar 
plexus  and  the  semilunar  ganglia,  receiving  filaments  from  some  of  the  lumbar 
ganglia.  It  is  situated  upon  the  sides  and  front  of  the  aorta,  between  the  origins 
of  the  superior  and  inferior  mesenteric  arteries.  From  this  plexus  arise  part  of 
the  spermatic,  the  inferior  mesenteric,  and  the  hypogastric  plexuses ;  and  it  dis- 
tributes filaments  to  the  inferior  vena  cava. 

The  nesenteric  plexu*  is  derived  chiefly  from  the  left  side  of  the  aortic 

plexus.  It  surrounds  the  inferior  mesenteric  artery,  and  divides  into  a  number  of 
secondary  plexuses,  which  are  distributed  to  all  the  parts  supplied  by  the  artery — 
viz.  the  left  colic  and  sigmoid  plexuses,  which  supply  the  descending  and  sigmoid 
flexure  of  the  colon ;  and  the  superior  haemorrhoidal  plexus,  which  supplies  the 
upper  part  of  the  rectum  and  joins  in  the  pelvis  with  branches  from  the  pelvic 
plexus. 

The  Hypogastric  Plexus. 

The  Hypogastric  Plexus  supplies  the  viscera  of  the  pelvic  cavity.  It  is  situated 
in  front  of  the  promontory  of  the  sacrum,  between  the  two  common  iliac  arteries, 
and  is  formed  by  the  union  of  numerous  filaments,  which  descend  on  each  side 
from  the  aortic  plexus  and  from  the  lumbar  ganglia.  This  plexus  contains  no 
ganglia,  and  bifurcates,  below,  into  two  lateral  portions,  which  form  the  pelvic 


878  THE  NERVOUS  SYSTEM. 

The  Pelvic  Plexus. 

The  Pelvic  Plexus  (sometimes  called  inferior  hypogastric)  supplies  the  viscera 
of  the  pelvic  cavity,  is  situated  at  the  side  of  the  rectum  and  bladder  in  the  male, 
and  at  the  side  of  the  rectum,  vagina,  and  bladder  in  the  female.  It  is  formed  by 
a  continuation  of  the  hypogastric  plexus,  by  branches  from  the  second,  third,  and 
fourth  sacral  nerves,  and  by  a  few  filaments  from  the  first  two  sacral  ganglia.  At 
the  point  of  junction  of  these  nerves  small  ganglia  are  found.  From  this  plexus 
numerous  branches  are  distributed  to  all  the  viscera  of  the  pelvis.  They  accom- 
pany the  branches  of  the  internal  iliac  artery. 

The  inferior  hsemorrhoidal  plexus  arises  from  the  back  part  of  the  pelvic 
plexus.  It  supplies  the  rectum,  joining  with  branches  of  the  superior  hsemor- 
rhoidal  plexus. 

The  vesical  plexus  arises  from  the  fore  part  of  the  pelvic  plexus.  The  nerves 
composing  it  are  numerous,  and  contain  a  large  proportion  of  spinal  nerve-fibres. 
They  accompany  the  vesical  arteries,  and  are  distributed  at  the  side  and  base  of 
the  bladder.  Numerous  filaments  also  pass  to  the  vesiculae  seminales  and  vas 
deferens ;  those  accompanying  the  vas  deferens  join,  on  the  spermatic  cord,  with 
branches  from  the  spermatic  plexus. 

The  prostatic  plexus  is  continued  from  the  lower  part  of  the  pelvic  plexus. 
The  nerves  composing  it  are  of  large  size.  They  are  distributed  to  the  pros- 
tate gland,  vesicuke  seminales,  and  erectile  structure  of  the  penis.  The  nerves 
supplying  the  erectile  structure  of  the  penis  consist  of  two  sets,  the  small  and 
large  cavernous  nerves.  They  are  slender  filaments,  which  arise  from  the  fore 
part  of  the  prostatic  plexus,  and,  after  joining  with  branches  from  the  internal 
pudic  nerve,  pass  forward  beneath  the  pubic  arch. 

The  small  cavernous  nerves  perforate  the  fibrous  covering  of  the  penis  near  its 
roots. 

The  large  cavernous  nerve  passes  forward  along  the  dorsum  of  the  penis, 
joins  with  the  dorsal  branch  of  the  pudic  nerve,  and  is  distributed  to  the  corpus 
cavernosum  and  spongiosum. 

The  vaginal  plexus  arises  from  the  lower  part  of  the  pelvic  plexus.  It  is  lost 
on  the  walls  of  the  vagina,  being  distributed  to  the  erectile  tissue  at  its  anterior 
part  and  to  the  mucous  membrane.  The  nerves  composing  this  plexus  contain, 
like  the  vesical,  a  large  proportion  of  spinal  nerve-fibres. 

The  uterine  plexus  arises  from  the  upper  part  of  the  pelvic  plexus  above  the 
point  where  the  branches  from  the  sacral  nerves  join  the  plexus.  Its  branches 
accompany  the  uterine  arteries  to  the  side  of  the  organ  between  the  layers  of  the 
broad  ligament,  and  are  distributed  to  the  cervix  and  lower  part  of  the  body  of  the 
uterus,  penetrating  its  substance. 

Other  filaments  pass  separately  to  the  body  of  the  uterus  and  Fallopian  tube. 

Branches  from  the  plexus  accompany  the  uterine  arteries  into  the  substance 
of  the  uterus.  Upon  these  filaments  ganglionic  enlargements  are  found. 


THE  ORGANS  OF  SENSE. 


Organs  of  the  Senses  are  five  in  number — viz.  those  of  Touch,  of  Taste,  of 
Smell,  of  Hearing,  and  of  Sight.      The  skin,  which  is  the  principal  seat  of  the 
sense  of  touch,  has  been  described  in  the  chapter  on  General  Anatomy. 

THE  TONGUE. 

The  Tongue  is  the  organ  of  the  special  sense  of  taste.  It  is  situated  in  the 
floor  of  the  mouth,  in  the  interval  between  the  two  lateral  portions  of  the  body  of 
the  lower  jaw. 

Its  base  or  root  is  directed  backward,  and  connected  with  the  os  hyoides  by 
the  Hyo-glossi  and  Genio-hyo-glossi  muscles  and  the  hyo-glossal  membrane ;  with 
the  epiglottis  by  three  folds  of  mucous  membrane 
which  form  the  glosso-epiglottic  ligaments  ;  with 
the  soft  palate  by  means  of  the  anterior  pillars 
of  the  fauces  ;  and  with  the  pharynx  by  the  Su- 
perior constrictor  and  the  mucous  membrane. 
Its  apex  or  tip,  thin  and  narrow,  is  directed  for- 
ward against  the  inner  surface  of  the  lower  in- 
cisor teeth.  The  under  surface  of  the  tongue  is 
connected  with  the  lower  jaw  by  the  Genio-hyo- 
glossi  muscles  ;  from  its  sides  the  mucous  mem- 
brane is  reflected  to  the  inner  surface  of  the 
gums :  and  in  front  a  distinct  fold  of  that  mem- 
brane, the //•<?>?  H/»  linguce,  is  formed  beneath  its 
under  surface. 

The  tip  of  the  tongue,  part  of  the  under 
surface,  its  sides  and  dorsum.  are  free. 

The  dorsum  of  the  tongue  is  convex,  marked 
along  the  middle  line  by  a  raphe,  which  divides 
it  into  symmetrical  halves ;  this  raphe  terminates 
behind,  about  an  inch  from  the  base  of  the  organ, 
in  a  depression,  the  foramen  ccecum.  The  ante- 
rior two-thirds  of  this  surface  are  rough  and 
covered  with  papillae ;  the  posterior  third  is 
smoother,  and  covered  by  the  projecting  orifices 
of  numerous  muciparous  glands. 

Structure  of  the  Tongue. — The  tongue  is 
partly  invested  by  mucous  membrane  and  a  sub- 
mucous  fibrous  layer.  It  consists  of  symmetri- 
cal halves,  separated  from  each  other,  in  the  middle  line,  by  a  fibrous  septum. 
Each  half  is  composed  of  muscular  fibres  arranged  in  various  directions,  contain- 
ing much  interposed  fat,  and  supplied  by  vessels  and  nerves. 

The  mucous  membrane  invests  the  entire  extent  of  the  free  surface  of  the 
tongue.  On  the  dorsum  it  is  thicker  behind  than  in  front,  and  is  continuous  with 
the  sheath  of  the  muscles  attached  to  it,  through  the  submucous  fibrous  layer. 
On  the  under  surface  of  the  organ  it  can  be  traced  on  each  side  of  the  fraenum 
through  the  ducts  of  the  submaxillary  and  the  sublingual  glands.  As  it  passes 
over  the  borders  of  the  organ  it  gradually  assumes  its  papillary  character. 

The  structure  of  the  mucous  membrane  of  the  tongue  differs  in  different  parts. 
That  covering  the  under  surface  of  the  organ  is  thin,  smooth,  and  identical  in 

879 


-dfie 

FIG.  515.— Upper  surface  of  the  tongue. 


880 


THE    ORGANS    OF  SENSE. 


structure  with  that  lining  the  rest  of  the  oral  cavity.  The  mucous  membrane  on 
the  anterior  part  of  the  dorsum  of  the  tongue  is  thin  and  intimately  adherent  to 
the  muscular  tissue,  whilst  that  at  the  root  is  much  thicker  and  looser.  It  consists 


Filiform. 


Fungi  form. 


Secondary 
papillae. 


Circumvallate. 


Artery.  ^\  JpVein. 


A  rtery. 
Vein. 


FIG.  516.— The  three  kinds  of  papillae,  magnified. 


of  a  layer  of  connective  tissue,  the  corium  or  mucosa,  supporting  numerous  papillce 
and  covered,  as  well  as  the  papillae,  with  epithelium. 

The  epithelium  is  of  the  scaly  variety,  like  that  of  the  epidermis.  It  covers  the 
free  surface  of  the  tongue,  as  may  be  easily  demonstrated  by  maceration  or  boiling, 
when  it  can  be  easily  detached  entire :  it  is  much  thinner  than  on  the  skin :  the 
intervals  between  the  large  papillae  are  not  filled  up  by  it,  but  each  papilla  has 
a  separate  investment  from  root  to  summit.  The  deepest  cells  may  sometimes 
be  detached  as  a  separate  layer,  corresponding  to  the  rete  mucosum,  but  they 
never  contain  coloring  matter. 

The  corium  consists  of  a  dense  feltwork  of  fibrous  connective  tissue,  with 
numerous  elastic  fibres,  firmly  connected  with  the  fibrous  tissue  forming  the  septa 
between  the  muscular  bundles  of  the  tongue.  It  contains  the  ramifications  of  the 
numerous  vessels  and  nerves  from  which  the  papillae  are  supplied,  large  plexuses 
of  lymphatic  vessels,  and  the  glands  of  the  tongue. 

The  Papillce  of  the  Tongue. — These  are  papillary  projections  of  the  corium. 
They  are  thickly  distributed  over  the  anterior  two-thirds  of  its  upper  surface,  giving 
to  it  its  characteristic  roughness.  The  varieties  of  papillae  met  with  are — the 
papillae  maximae  (circumvallatce),  papillae  mediae  (fungiformes),  papillae  minimae 
(conicce  or  filiformes),  and  papillae  simplices. 

The  papillce  maxima  (circumvallatae)  are  of  large  size,  and  vary  from  eight  to 
twelve  in  number.  They  are  situated  at  the  back  part  of  the  dorsum  of  the  tongue, 
near  its  base,  forming  a  row  on  each  side,  which,  running  backward  and  inward, 
meet  in  the  middle  line,  like  the  two  lines  of  the  letter  V  inverted.  Each  papilla 
consists  of  a  projection  of  mucous  membrane  from  ^V  to  y1^  of  an  inch  wide, 
attached  to  the  bottom  of  a  cup-shaped  depression  of  the  mucous  membrane ;  the 
papilla  is  in  shape  like  a  truncated  cone,  the  smaller  end  being  directed  down- 
ward and  attached  to  the  tongue,  the  broader  part  or  base  projecting  on  the  sur- 
face and  being  studded  with  numerous  small  secondary  papillae,  which,  however, 
are  covered  by  a  smooth  layer  of  the  epithelium.  The  cup-shaped  depression 
forms  a  kind  of  fossa  round  the  papilla,  having  a  circular  margin  of  about  the 
same  elevation  covered  with  smaller  papillae.  At  the  point  of  junction  of  the  two 
rows  of  papillae  is  the  deep  depression,  the  foramen  ccecum,  mentioned  above. 

The  papillce  mediae  (fungiformes),  more  numerous  than  the  preceding,  are 
scattered  irregularly  and  sparingly  over  the  dorsum  of  the  tongue,  but  are  found 
chiefly  at  its  sides  and  apex.  They  are  easily  recognized  among  the  other 
papillae,  by  their  large  size,  rounded  eminences,  and  deep-red  color.  They  are 
narrow  at  their  attachment  to  the  tongue,  but  broad  and  rounded  at  their  free 


THE    TONGUE. 


881 


FIG.  517.— Circumvallate  papillae  of  tongue 
of  rabbit,  showing  position  of  taste-goblets. 
(Stohr.)  a.  Duct  of  gland,  d.  Serous  gland.  <?. 
Taste-goblets.  I.  Primary  septa,  and  r,  second- 
ary septa,  of  papillae,  n.  Medullated  nerve. 
M.  Muscular  fibres. 


extremities,  and  covered  with  secondary  papillae.     Their  epithelial  investment  is 
very  thin. 

The  papillce  minima  (conicae  or  filiformes)  cover  the  anterior  two-thirds  of  the 
dorsum  of  the  tongue.  They  are  very  mi- 
nute, more  or  less  conical  or  filiform  in  shape, 
and  arranged  in  lines  corresponding  in  di- 
rection with  the  two  rows  of  the  papillae  cir- 
cumvallatae,  excepting  at  the  apex  of  the 
organ,  where  their  direction  is  transverse. 
They  have  projecting  from  their  apices  nu- 
merous filiform  processes  or .  secondary  pa- 
pillae, which  are  of  a  whitish  tint,  owing  to 
the  thickness  and  density  of  the  epithelium 
of  which  they  are  composed,  and  which  has 
here  undergone  a  peculiar  modification,  the 
cells  having  become  cornified  and  elongated 
into  dense,  imbricated,  brush-like  processes. 
They  contain  also  a  number  of  elastic  fibres, 
which  render  them  firmer  and  more  elastic 
than  the  papillae  of  mucous  membrane  gen- 
erally. 

Simple  papillce,  similar  to  those  of  the 
skin,  cover  the  whole  of  the  mucous  mem- 
brane of  the  tongue,   as  well  as   the  larger 
papillae.     They  consist  of  closely-set,  microscopic  elevations  of  the  corium,  con- 
taining a  capillary  loop,  covered  by  a  layer  of  epithelium. 

Structure  of  the  Papilla?. — The  papillae  apparently  resemble  in  structure  those 
of  the  cutis.  consisting  of  a  cone-shaped  projection  of  connective  tissue,  covered 
with  a  thick  layer  of  squamous  epithelium,  and  contain  one  or  more  capillary 
loops,  amongst  which  nerves  are  distributed  in  great  abundance.  If  the  epithe- 
lium is  removed,  it  will  be  found  that  they  are  not  simple  elevations  like  the 
papillae  of  the  skin,  for  the  surface  of  each  is  studded  with  minute  conical  pro- 
cesses of  the  mucous  membrane,  which  form  secondary  papillae  (Todd  and  Bow- 
man). In  the  papillae  circumvallatae  the  nerves  are  numerous  and  of  large  size; 
in  the  papillae  fungiformes  they  are  also  numerous,  and  terminate  in  a  plexiform 
network,  from  which  brush-like  branches  proceed ;  in  the  papillae  filiformes  their 

mode  of  termination  is  uncertain.  Buried  in  the 
epidermis  of  the  papillae  circumvallatae,  and  in  some 
of  the  fungiformes,  certain  peculiar  bodies  called 
taste-goblets  have  been  described.1  They  are  flask- 
like  in  shape,  their  broad  base  resting  on  the  co- 
rium, and  their  neck  opening  by  an  orifice  between 
the  cells  of  the  epithelium.  They  are  formed  by 
two  kinds  of  cells :  the  external  (cortical)  are 
arranged  in  several  layers ;  they  are  long  and  flat- 
tened, with  tapering  ends,  and  in  contact  by  their 
edges,  the  tapering  extremities  extending  from  the 
base  to  the  apex  of  the  organ.  Their  apical  ends 
bound  the  orifice  (gustatory  pore)  just  mentioned. 
They  thus  enclose  the  central  cells  (gustatory  cells), 
which  are  spindle-shaped  and  have  a  large  spherical  nucleus  about  the  middle  of 
the  cell.  Both  extremities  of  a  gustatory  cell  are  filamentous ;  the  inner  process 
is  described  (denied  by  G.  Retzius)  as  continuous  with  the  terminal  fibril  of  a 
nerve  (glosso-pharyngeal),  while  the  outer  one  projects  as  an  extremely  fine  hair 
through  the  orifice  of  the  taste-goblet.2 

1  These  bodies  are  also  found  in  considerable  numbers  at  the  side  of  the  base  of  the  tongue,  just 
in  front  of  the  anterior  pillars  of  the  fauces. 

2  See  Englemann,  in  Strieker's  Handbook  (New  Syd.  Soc.  Trans.),  vol.  iii.  p.  2. 

56 


FIG.  518.— Taste-goblets,    a.  Central 
cell.    6.  Cortical  cell. 


882  THE    ORGANS    OF  SENSE. 

G-lands  of  the  Tongue. — The  tongue  is  provided  with  mucous  and  serous 
glands  and  lymphoid  follicles. 

The  mucous  glands  are  similar  in  structure  to  the  labial  and  buccal  glands. 
They  are  found  all  over  the  surface  of  the  mucous  membrane  of  the  tongue, 

especially  at  the  back  part,  behind 
the  circurnvallate  papillae,  but  also 

-Bristles  in  Gland        at  tne  aPex  an(1   marginal  parts. 
Ducts.  [n  connection  with  these  glands  a 

_  Gland  of  Bland  in   special  one  has  been  described  by 

Jfttn/R.  -fi,  ,.  1      TVT       1  T         •  •  1 

J31andm  and  JNuhn.  It  is  situated 
near  the  apex  of  the  tongue  on 
either  side  of  the  frsenum,  and  is 
covered  over  by  a  fasciculus  of 
muscular  fibre  derived  from  the 
Stylo-glossus  and  Inferior  lin- 
gualis.  It  is  from  half  an  inch 
to  nearly  an  inch  long  and  about 
the  third  of  an  inch  broad.  It 
has  from  four  to  six  ducts,  which 
open  on  the  under  surface  of  the 

Lingual  Nerve.  apex. 
FIG.  519.— Under  surface  of  tongue,  showing  position  and  Lhe  SCTOUS    (/lands    OCCUr   Only 

relations  of  gland  of  Blandin  and  Nuhn.  (From  a  prepara-  at  the  back  of  the  tongue  in  the 
tion  in  the  Museum  of  the  Royal  College  of  Surgeons.) 

neighborhood  ot  the  taste-goblets, 

their  ducts  opening  for  the  most  part  into  the  fossae  of  the  circumvallate  papillae. 
These  glands  are  racemose,  the  duct  branching  into  several  minute  ducts,  which 
terminate  in  alveoli  lined  by  a  single  layer  of  more  or  less  columnar  epithelium. 
Their  secretion  is  of  a  watery  nature,  and  probably  assists  in  the  distribution  of 
the  substance  to  be  tasted  over  the  taste-area  (Ebner). 

The  Lymphoid  Follicles. — The  lymphoid  tissue  is  situated,  for  the  most  part  at 
the  back  of  the  tongue,  between  the  epiglottis  and  the  circumvallate  papillae,  and 
is  collected  at  numerous  points  into  distinct  masses  known  as  lymphoid  follicles. 
Here  and  there  in  this  situation  are  depressions  in  the  mucous  membrane, 
surrounded  by  nodules  of  lymphoid  tissue,  similar  to  the  structure  found  in  the 
tonsil :  into  them  open  some  of  the  ducts  of  the  mucous  glands. 

The  fibrous  septum  consists  of  a  vertical  layer  of  fibrous  tissue,  extending 
throughout  the  entire  length  of  the  middle  line  of  the  tongue,  from  the  base 
to  the  apex,  though  not  quite  reaching  the  dorsum.  It  is  thicker  behind  than 
in  front,  and  occasionally  contains  a  small  fibro-cartilage  about  a  quarter  of 
an  inch  in  length.  It  is  well  displayed  by  making  a  vertical  section  across  the 
organ. 

The  Hyo-glossal  membrane  is  a  strong  fibrous  lamina  which  connects  the 
under  surface  of  the  base  of  the  tongue  to  the  body  of  the  hyoid  bone.  This 
membrane  receives,  in  front,  some  of  the  fibres  of  the  Genio-hyo-glossi. 

Vessels  of  the  Tongue. — The  arteries  of  the  tongue  are  derived  from  the  lingual, 
the  facial,  and  ascending  pharyngeal.  The  veins  of  the  tongue  accompany  the 
arteries. 

Muscles  of  the  Tongue. — The  muscular  fibres  of  the  tongue  run  in  various 
directions.  These  fibres  are  divided  into  two  sets,  Extrinsic  and  Intrinsic. 

The  Extrinsic  muscles  of  the  tongue  are  those  which  have  their  origin  external 
to  it,  and  only  their  terminal  fibres  contained  in  the  substance  of  the  organ.  They 
are  the  Stylo-glossus,  the  Hyo-glossus,  the  Palato-glossus,  the  Genio-hyo-glossus, 
and  part  of  the  Superior  constrictor  of  the  pharynx  (Pharyngo-glossus). 

The  Intrinsic  muscles  are  those  which  are  contained  entirely  within  the  tongue 
and  form  the  greater  part  of  its  substance.  Both  sets  have  been  already  described 
(page  415). 

The  lymphatic  vessels  from  the  tongue  pass  to  one  or  two  small  glands  situated 


THE    TONGUE. 


883 


on  the  Hyo-glossus  muscle  in  the  submaxillary  region,  and  from  thence  to  the  deep 
glands  of  the  neck. 

The  nerves  of  the  tongue  are  four  in  number  in  each  half:  the  lingual  branch 
of  the  fifth,  which  is  distributed  to  the  papillae  at  the  fore  part  and  sides  of  the 
tongue  ;  the  lingual  branch  of  the  glosso-pharyngeal,  which  is  distributed  to  the 
mucous  membrane  at  the  base  and  side  of  the  tongue  and  to  the  papillae  circum- 


SubmaxiUary  artery. 


• Cartilage.^ 


Glosso- 
phai-yngeal  nerve. 


'Lingual  artery. 


Superior  laryngew 


FIG.  520.— Under  surface  of  the  tongue,  showing  the  distribution  of  nerves  to  this  organ.    (From  a  prepara- 
tion in  the  Museum  of  the  Royal  College  of  Surgeons.) 

vallatse :  the  hypoglossal  nerve,  which  is  distributed  to  the  muscular  substance 
of  the  tongue ;  and  the  chorda  tympani  to  the  Lingualis  muscle.  Sympathetic 
filaments  also  pass  to  the  tongue  from  the  nervi  molles  on  the  lingual  and  other 
arteries  supplying  it.  The  glosso-pharyngeal  branch  is  the  special  nerve  of  the 
sense  of  taste,  the  lingual  (gustatory)  is  the  nerve  of  common  sensation,  and  the 
hypoglossal  is  the  motor  nerve  of  the  tongue,  except  for  the  Inferior  lingualis, 
which  is  supplied  by  the  chorda  tympani. 

Surgical  Anatomy. — The  diseases  to  which  the  tongue  is  liable  are  numerous,  and  its 
surgical  anatomy  of  importance,  since  an}7  or  all  the  structures  of  which  it  is  composed — muscles, 
connective  tissue,  mucous  membrane,  glands,  vessels,  nerves,  and  lymphatics — may  be  the  seat 
of  morbid  changes.  It  is  not  often  the  seat  of  congenital  defects,  though  a  few  cases  of  vertical 
cleft  have  been  recorded,  and  it  is  occasionally,  though  much  more  rarely  than  is  commonly  sup- 
pose*!, the  seat  of  "tongue-tie,"  from  shortness  of  the  fra?num.  (See  page  554.) 

There  is,  however,  one  condition  which  must  be  regarded  as  congenital,  though  it  does  not 
sometimes  evidence  itself  until  a  year  or  two  after  birth,  which  is  not  uncommon.  This  is  an 
enlargement  of  the  tongue  which  is  due  primarily  to  a  dilatation  of  the  lymph-channels  and  a 
greatly  increased  development  of  the  lymphatic  tissue  throughout  the  tongue.  This  is  often 


884  THE    ORGANS    OF  SENSE. 

aggravated  by  inflammatory  changes  Induced  by  injury  or  exposure,  and  the  tongue  may  assume 
enormous  dimensions  and  hang  out  of  the  mouth,  giving  the  child  an  imbecile  expression.  The 
treatment  consists  in  excising  a  V-shaped  portion  and  bringing  the  cut  surfaces  together  with 
deeply-placed  silver  sutures.  Compression  has  been  resorted  to  in  some  cases  and  with  success, 
but  it  is  difficult  to  apply.  Acute  inflammation  of  the  tongue,  which  may  be  caused  by  injury 
and  the  introduction  of  some  septic  or  irritating  matter,  is  attended  by  great  swelling  from 
infiltration  of  its  connective  tissue,  which  is  in  considerable  quantity.  This  renders  the  patient 
incapable  of  swallowing  or  speaking,  and  may  seriously  impede  respiration.  It  may  run  on  to 
suppuration  and  the  formation  of  an  acute  abscess.  Chronic  abscess,  which  has  been  mistaken 
for  cancer,  may  also  occur  in  the  substance  of  the  tongue. 

The  mucous  membrane  of  the  tongue  may  become  chronically  inflamed,  and  presents 
different  appearances  in  different  stages  of  the  disease,  to  which  the  terms  leucoplakia,  psoriasis, 
and  ichthyosis  have  been  given. 

The  tongue,  being  very  vascular,  is  often  the  seat  of  nsevoid  growths,  and  these  have  a  tend- 
ency to  grow  rapidly. 

The  tongue  is  frequently  the  seat  of  ulceration,  which  may  arise  from  many  causes,  as  from 
the  irritation  of  jagged  teeth,  dyspepsia,  tubercle,  syphilis,  and  cancer.  Of  these  the  cancerous 
ulcer  is  the  most  important,  and  probably  also  the  most  common.  The  variety  is  the  squamous 
epithelioma,  which  soon  develops  into  an  ulcer  with  an  indurated  base.  It  produces  great  pain, 
which  speedily  extends  to  all  parts  supplied  with  sensation  by  the  fifth  nerve,  especially  to  the 
region  of  the  ear.  The  pain  in  these  cases  is  conducted  to  the  ear  and  temporal  region  by  the 
lingual  nerve,  and  from  it  to  the  other  branches  of  the  inferior  maxillary  nerve,  especially  the 
auriculo-temporal.  Possibly  pain  in  the  ear  itself  may  be  due  to  implication  of  the  fibres  of 
the  glosso-pharyngeal  nerve,  which  by  its  tympanic  branch  is  conducted  to  the  tympanic 
plexus. 

Cancer  of  the  tongue  may  necessitate  removal  of  a  part  or  the  whole  of  the  organ,  and 
many  different  methods  have  been  adopted  for  its  excision.  It  may  be  removed  from  the  mouth 
by  the  ecraseur  or  the  scissors.  Probably  the  better  method  is  by  the  scissors,  usually  known 
as  Whitehead's  method.  <  The  mouth  is  widely  opened  with  a  gag.  the  toninie  transfixed  with  a 
stout  silk  ligature,  by  which  to  hold  and  make  traction  on  it  and  the  reflection  of  mucous  mem- 
brane from  the  tongue  to  the  jaw,  and  the  insertion  of  the  Genio-hyo-glossus  first  divided  with 
a  pair  of  curved  blunt  scissors.  The  Palato-glossus  is  also  divided.  The  tongue  can  now  be 
pulled  well  out  of  the  mouth.  The  base  of  the  tongue  is  cut  through  by  a  series  of  short  snips, 
each  bleeding  vessel  being  dealt  with  as  soon  as  divided,  until  the  situation  of  the  ranine  artery 
is  reached.  The  remaining  undivided  portion  of  tissue  is  to  be  seized  with  a  pair  of  Wells' s 
forceps,  the  tongue  removed,  and  the  vessel  secured.  In  the  event  of  the  ranine  artery  being 
accidentally  injured  haemorrhage  can  be  at  once  controlled  by  passing  two  fingers  over  the 
dorsum  of  the  tongue  as  far  as  the  epiglottis  and  dragging  the  root  of  the  tongue  forcibly 
forward. 

In  cases  where  the  disease  is  confined  to  one  side  of  the  tongue  this  operation  may  be 
modified  by  splitting  the  tongue  down  the  centre  and  removing  only  the  affected  half.  In 
cases  where  the  submaxillary  glands  are  involved  Kocher's  operation  should  be  performed. 
He  removes  the  tongue  from  the  neck,  having  performed  a  preliminary  tracheotomy,  by  an  incis- 
ion from  near  the  lobule  of  the  ear,  down  the  anterior  border  of  the  Sterno-mastoid  to  the  level 
of  the  great  cornu  of  the  hyoid  bone,  then  forward  to  the  body  of  the  hyoid  bone,  and  upward 
to  near  the  symphysis  of  the  jaw.  The  lingual  artery  is  now  secured,  and  by  a  careful  dissec- 
tion the  submaxillary  lymphatic  glands  and  the  tongue  removed,  llegnoli  advocated  the  removal 
of  the  tongue  by  a  semilunar  incision  in  the  submaxillary  triangle  along  the  line  of  the  lower 
jaw,  and  a  vertical  incision  from  the  centre  of  the  semilunar  one  backward  to  the  h^-oid  bone. 
Care  must  be  taken  not  to  carry  the  first  incision  too  far  backward,  so  as  to  wound  the  facial 
arteries.  The  tongue  is  thus  reached  through  the  floor  of  the  mouth,  pulled  out  through  the 
external  incision,  and  removed  with  the  ecraseur  or  knife.  The  great  objection  to  this  operation 
is  that  all  the  muscles  which  raise  the  hyoid  bone  and  larynx  are  divided,  and  that  therefore  the 
movements  of  deglutition  and  respiration  are  interfered  with. 

Finally,  where  both  sides  of  the  floor  of  the  mouth  are  involved  in  the  disease,  or  where 
very  free  access  is  required  on  account  of  the  extension  backward  of  the  disease  to  the  pillars 
of  the  fauces  and  the  tonsil,  or  where  the  lower  jaw  is  involved,  the  operation  recommended  by 
Syme  must  be  performed.  This  is  done  by  an  incision  through  the  central  line  of  the  lip,  across 
the  chin,  and  down  as  far  as  the  hyoid  bone.  The  lower  jaw  is  sawn  through  at  the  symphysis, 
and  the  two  halves  of  the  bone  forcibly  separated  from  each  other.  The  mucous  membrane  is 
separated  from  the  bone,  and  the  Genio-hyo-glossi  detached  from  the  bone,  and  the  Hyo-glossi 
divided.  The  tongue  is  then  drawn  forward  and  removed  close  to  its  attachment  to  the  hyoid 
bone.  Any  glands  which  are  enlarged  can  be  removed,  and  if  the  bone  is  implicated  in  the 
disease,  it  can  also  be  removed  by  freeing  it  from  the  soft  parts  externally  and  internally,  and 
making  a  second  section  with  the  saw  beyond  the  diseased  part. 

Formerly  many  surgeons  before  removing  the  tongue  performed  a  preliminary  tracheotomy : 
(1)  to  prevent  blood  entering  the  air-passages  ;  and  (2)  to  allow  the  patient  to  breathe  through 
the  tube  and  not  inspire  air  which  had  passed  over  a  .sloughy  wound,  and  which  was  loaded  with 
septic  organisms  and  likely  to  induce  septic  pneumonia.  By  the  judicious  use  of  iodoform  this 
secondary  evil  may  be  obviated,  and  the  preliminary  tracheotomy  is  now  usually  dispensed 
with. 


THE    NOISE. 


885 


THE  NOSE. 

The  nose  is  the  special  organ  of  the  sense  of  smell  :  by  means  of  the  peculiar 
properties  of  its  nerves  it  protects  the  lungs  from  the  inhalation  of  deleterious 
gases  and  assists  the  organ  of-  taste  in  discriminating  the  properties  of  food. 


Seen  from  below. 


Side  view. 


Lower  lateral  cartilage. 


Sesamoid  cartilages. 


FIGS.  521,  522.— Cartilages  of  the  nose. 

The  organ  of  smell  consists  of  two  parts — one  external,  the  nose  ;  the  other 
internal,  the  nasal  fossce. 

The  nose  is  the  more  anterior  and  prominent  part  of  the  organ  of  smell.  It  is 
of  a  triangular  form,  directed  vertically  downward,  and  projects  from  the  centre 
of  the  face  immediately  above  the  upper  lip.  Its  summit  or  root  is  connected 
directly  with  the  forehead.  Its  inferior  part,  the  base  of  the  nose,  presents  two 
elliptical  orifices,  the  nostrils,  separated  from  each  other  by  an  antero-posterior 
septum,  the  columna.  The  margins  of  these  orifices  are  provided  with  a  number 
of  stiff  hairs,  or  vibrissce,  which  arrest  the  passage  of  foreign  substances  carried 
with  the  current  of  air  intended  for  respiration.  The  lateral  surfaces  of  the  nose 
form,  by  their  union,  the  dorsum,  the  direction  of  which  varies  considerably  in 
different  individuals.  The  dorsum  terminates  below  in  a  rounded  eminence,  the 
lobe  of  the  nose. 

The  nose  is  composed  of  a  framework  of  bones  and  cartilages,  the  latter  being 
slightly  acted  upon  by  certain  muscles.  It  is  covered  externally  by  the  integument, 
internally  by  mucous  membrane,  and  supplied  with  vessels  and  nerves. 

The  bony  framework  occupies  the  upper  part  of  the  organ  :  it  consists  of  the 
nasal  bones  and  the  nasal  processes  of  the  superior  maxillary. 

The  cartilaginous  frametvork  consists  of  five  pieces,  the  two  upper  and  the  two 
lower  lateral  cartilages  and  the  cartilage  of  the  septum. 

The  upper  lateral  cartilages  are  situated  below  the  free  margin  of  the  nasal 
bones ;  each  cartilage  is  flattened  and  triangular  in  shape.  Its  anterior  margin  is 
thicker  than  the  posterior,  and  connected  with  the  fibro-cartilage  of  the  septum. 
Its  posterior  margin  is  attached  to  the  nasal  process  of  the  superior  maxillary  and 
nasal  bones.  Its  inferior  margin  is  connected  by  fibrous  tissue  with  the  lower 
lateral  cartilage  :  one  surface  is  turned  outward,  the  other  inward  toward  the 
nasal  cavity. 

The  lower  lateral  cartilages  are  two  thin,  flexible  plates  situated  immediately 
below  the  preceding,  and  bent  upon  themselves  in  such  a  manner  as  to  form  the 
inner  and  outer  walls  of  each  orifice  of  the  nostril.  The  portion  which  forms  the 
inner  wall,  thicker  than  the  rest,  is  loosely  connected  with  the  same  part  of  the 
opposite  cartilage,  and  forms  a  small  part  of  the  columna.  Its  inferior  border, 
free,  rounded,  and  projecting,  forms,  with  the  thickened  integument  and  subja- 


886 


THE    ORGANS    OF  SEN^E. 


FIG.  523.— Bones  and  cartilages  of  septum  of  nose. 
Right  side. 


cent  tissue  and  the  corresponding  parts  of  the  opposite  side,  the  tip  of  the  nose. 
The  part  which  forms  the  outer  wall  is  curved  to  correspond  with  the  ala  of  the 

nose ;  it  is  oval  and  flattened,  narrow 
behind,  where  it  is  connected  with  the 
nasal  process  of  the  superior  maxilla 
by  a  tough  fibrous  membrane,  in  which 
are  found  three  or  four  small  cartilagi- 
nous plates  (sesamoid  cartilages),  car- 
tilagines  minores.  Above,  it  is  con- 
nected to  the  upper  lateral  cartilage 
and  front  part  of  the  cartilage  of  the 
septum ;  below,  it  is  separated  from 
the  margin  of  the  nostril  by  dense 
cellular  tissue ;  and  in  front,  it  forms, 
with  its  fellow,  the  lobe  of  the  nose. 

The  cartilage  of  the  septum  is  some- 
what quadrilateral  in  form,  thicker  at 
its  margins  than  at  its  centre,  and 
completes  the  separation  between  the 
nasal  fossae  in  front.  Its  anterior  mar- 
gin, thickest  above,  is  connected  from 
above  downward  with  the  nasal  bones,  the  anterior  margin  of  the  two  upper  lateral 
cartilages,  and  the  inner  portion  of  the  two  lower  lateral  cartilages.  Its  posterior 
margin  is  connected  with  the  perpendicular  lamella  of  the  ethmoid,  its  inferior 
margin  with  the  vomer  and  the  palate  processes  of  the  superior  maxillary  bones. 
These  various  cartilages  are  connected  to  each  other  and  to  the  bones  by  a 
tough  fibrous  membrane,  which  allows  the  utmost  facility  of  movement  between 
them. 

The  muscles  of  the  nose  are  situated  immediately  beneath  the  integument : 
they  are  (on  each  side)  the  Pyramidalis  nasi,  the  Levator  labii  superioris  alaeque 
nasi,  the  Dilatator  naris,  anterior  and  posterior,  the  Compressor  nasi,  the  Com- 
pressor narium  minor,  and  the  Depressor  alae  nasi.  They  have  been  described 
above  (page  399). 

The  integument  covering  the  dorsum  and  sides  of  the  nose  is  thin,  and  loosely 
connected  with  the  subjacent  parts,  but  where  it  forms  the  tip  or  lobe  and  the 
alae  of  the  nose  it  is  thicker  and  more  firmly  adherent.  It  is  furnished  with  a  large 
number  of  sebaceous  follicles,  the  orifices  of  which  are  usually  very  distinct. 

The  mucous  membrane  lining  the  interior  of  the  nose  is  continuous  with  the 
skin  externally  and  with  that  which  lines  the  nasal  fossae  within. 

The  arteries  of  the  nose  are  the  lateralis  nasi  from  the  facial,  and  the  inferior 
artery  of  the  septum  from  the  superior  coronary,  which  supply  the  alae  and 
septum,  the  sides  and  dorsum  being  supplied  from  the  nasal  branch  of  the 
ophthalmic  and  the  infra-orbital. 

The  veins  of  the  nose  terminate  in  the  facial  and  ophthalmic. 
The  nerves  of  the  nose  are  branches   from  the  facial,  infra-orbital,  and  infra- 
trochlear,  and  a  filament  from  the  nasal  branch  of  the  ophthalmic. 

Nasal  Fossae. 

The  nasal  fossae  are  two  irregular  cavities  situated  in  the  middle  of  the  face 
and  extending  from  before  backward.  They  open  in  front  by  the  two  anterior 
nares,  and  terminate  in  the  pharynx,  behind,  by  the  posterior  nares.  The  anterior 
nares  are  somewhat  pear-shaped  apertures,  each  measuring  about  one  inch  vertically 
and  half  an  inch  transversely  at  their  widest  part.  The  posterior  nares  are  two 
oval  openings  situated  at  the  upper  part  of  the  anterior  wall  of  the  pharynx. 
They  are  smaller  in  the  body  than  in  the  skeleton,  because  narrowed  by  the 
mucous  membrane.  Each  opening  measures  an  inch  in  the  vertical  and  half  an 
inch  in  the  transverse  direction  in  a  well-developed  adult  skull. 


THE  NASAL    FOSSAE. 


887 


The  mucous  membrane  lining  the  nasal  fossae  is  called  the  pituitary,  from  the 
nature  of  its  secretion ;  or  Schneiderian,  from  Schneider,  the  first  anatomist  who 
showed  that  the  secretion  proceeded  from  the  mucous  membrane,  and  not,  as  was 
formerly  imagined,  from  the  brain.  It  is  intimately  adherent  to  the  periosteum 
or  perichondrium,  over  which  it  lies.  It  is  continuous  externally  with  the  skin 
through  the  anterior  nares,  and  with  the  mucous  membrane  of  the  pharynx 
through  the  posterior  nares.  From  the  nasal  fossae  its  continuity  may  be  traced 
with  the  conjunctiva  through  the  nasal  duct  and  lachrymal  canals;  with  the 
lining  membrane  of  the  tympanum  and  mastoid  cells  through  the  Eustachian 
tube ;  and  with  the  frontal,  ethmoidal,  and  sphenoidal  sinuses,  and  the  antrum  of 
Highmore  through  the  several  openings  in  the  meatuses.  The  mucous  membrane 
is  thickest  and  most  vascular  over  the  turbinated  bones.  It  is  also  thick  over  the 


Hiatus  Ant.  ethm. 

semilunaris  cells 


Eye-ball 


Groove  (hiatus  semilunaris) 
leading  to  infundibulum 
Middle  turbinated  bone 

•Middle  meatus 
Antrum  of  Highmore 
'nferior  meatus 

Inferior  turbinated  bone 


f  Buccal  cavity 

\  Space  between  cheek  and  gum 
Molar  tooth,  upper  jaw 


Koot  of  molar  tooth 


^^  Inferior  dental  nerve 

Tunrjue    I      Hard  palate 

Septum 
nasi 

FIG.  524.— Transverse  vertical  section  of  the  nasal  fossae.    The  section  is  made  anterior  to  the  superior 
turbinated  bones.    (Cryer.) 

septum,  but  in  the  intervals  between  the  spongy  bones  and  on  the  floor  of  the 
nasal  fossae  it  is  very  thin.  Where  it  lines  the  various  sinuses  and  the  antrum  of 
Highmore  it  is  thin  and  pale. 

Owing  to  the  great  thickness  of  this  membrane,  the  nasal  fossae  are  much 
narrower,  and  the  turbinated  bones,  especially  the  lower  ones,  appear  larger  and 
more  prominent  than  in  the  skeleton.  From  the  same  circumstance  also  the 
various  apertures  communicating  with  the  meatuses  are  either  narrowed  or 
completely  closed. 

In  the  superior  meatus  the  aperture  of  communication  with  the  posterior 
ethmoidal  cells  is  considerably  diminished  in  size,  and  the  spheno-palatine  foramen 
completely  covered  in. 

In  the  middle  meatus  the  opening  of  the  infundibulum  is  partially  hidden  by 


888 


THE    ORGANS    OF  SENSE. 


a  projecting  fold  of  mucous  membrane,  and  the  orifice  of  the  antrum  is  contracted 
to  a  small  circular  aperture,  much  narrower  than  in  the  skeleton. 

In  the  inferior  meatus  the  orifice  of  the  nasal  duct  is  partially  hidden  by  either 
a  single  or  double  valvular  mucous  fold,  and  the  anterior  palatine  canal  either 
completely  closed  in  or  a  tubular  cul-de-sac  of  mucous  membrane  is  continued  a 
short  distance  into  it.  This  cul-de-sac  is  termed  the  organ  of  Jacobson,  and  is 
present  in  all  mammals  as  well  as  man.  In  the  former  it  consists  of  a  bilateral 
tube,  situated  in  the  nasal  septum  and  supported  by  hyaline  cartilage,  the  cartilage 
of  Jacobson. 

In  the  roof  the  opening  leading  to  the  sphenoidal  sinus  is  narrowed,  and  the 
apertures  in  the  cribriform  plate  of  the  ethmoid  completely  closed  in. 

Structure  of  the  Mucous  Membrane. — The  epithelium  covering  the  mucous 
membrane  differs  in  its  character  according  to  the  functions  of  the  part  of  the 
nose  in  which  it  is  found.  Near  the  orifice  of  the  nostril,  the  vestibule,  where 
common  sensation  is  chiefly  or  alone  required,  the  epithelium  is  of  the  ordinary 
pavement  or  scaly  variety.  In  the  rest  of  the  cavity,  below  the  distribution  of  the 


Middle  meatus, 

Infundibulum 
Opening  of  nasal  duct 


Anterior  ethmoid  cells 


•nj 

Floor  of  orbft-Sjwyjit  • 

F 

Middle  ethmoid  cells  — > « 


Post,  ethmoid 
cells 

FIG.  525.— Horizontal  section,  high  up,  of  the  nasal  fossae,  viewed  from  above.    (Cryer.) 

olfactory  nerves — i.  e.  in  the  respiratory  portion  of  the  nasal  cavity — the  epithelium 
is  columnar  and  ciliated.  This  is  the  case  also  in  the  meatuses  of  the  nose.  In 
this  region,  beneath  the  epithelium  and  its  basement  membrane,  is  a  fibrous  layer 
infiltrated  with  lymph-corpuscles,  so  as  to  form  in  many  parts  a  diffuse  adenoid 
tissue,  and  beneath  this  a  nearly  continuous  layer  of  smaller  and  larger  glands, 
some  mucous  and  some  serous,  the  ducts  of  which  open  upon  the  surface.  In  the 
olfactory  region — i.e.  the  region  in  which  the  terminal  filaments  from  the  olfactory 
nerves  are  distributed  (see  page  889) — the  epithelial  cells  are  columnar  and,  for  the 
most  part,  non-ciliated :  their  free  surface  presents  a  sharp  outline,  and  their  deep 
extremity  is  prolonged  into  a  process  which  runs  inward,  branching  to  commu- 
nicate with  similar  processes  from  neighboring  cells,  so  as  to  form  a  network  in 
the  deep  part  of  the  mucous  membrane.  Lying  between  them  are  cells  (termed  by 
Max  Schultze,  olfactory  cells],  which  consist  of  a  nucleated  body  and  two  processes, 
of  which  one  runs  outward  between  the  columnar  epithelial  cells  and  projects  on 
the  surface  of  the  mucous  membrane ;  the  other  (the  deep)  process  runs  inward, 
is  frequently  beaded  like  a  nerve-fibre,  and  is  believed  by  most  observers  to  be  in 
connection  with  one  of  the  terminal  filaments  of  the  olfactory  nerve.  Amongst 


THE   XASAL    FOSSAE. 


889 


n 
mem- 


the branched  ends  of  the  columnar  cells  there  is  a  deep  layer  of  epithelial  cells  of 
a  conical  shape,  their  broad  end  resting  on  the  basement  membrane,  and  their 
tapering  extremity  projecting  between  the  other  cells.  Beneath  the  epithelium, 
extending  through  the  thickness  of  the  mucous  membrane,  is  a  layer  of  glands,  the 
ijl,in<1*  of  Bowman.  identical  in  structure  with  serous  glands. 

The  mucous  membrane  is  pigmented  in  the  olfactory,  but  not  in  the  other 
regions,  being  of  a  light  yellow  color,  at  least  in  the  white  races.1 

The  arteries  of  the  nasal  fossa?  are  the  anterior  and  posterior  ethmoidal,  from 
the  ophthalmic,  which  supply  the  ethmoidal  cells,  frontal  sinuses,  and  roof  of  the 
nose;  a  minute  twig  from  the  small  meningeal  ;  the  spheno-palatine,  from  the 
internal  maxillary,  which  supplies  the  mucous  membrane  covering  the  spongy 
bones,  the  meatuses,  and  septum  ;  the  inferior  artery  of  the  septum  from 
the  superior  coronary  of  the  facial  ;  and  the  alveolar  branch  of  the  internal 
maxillary,  which  supplies  the  lining  membrane  of  the  antrum.  The  ramifica- 
tions of  these  vessels  form  a  close, 
plexiform  network  beneath  and 
the  substance  of  the  mucous 
brane. 

The  veins  of  the  nasal  fossa*  form  a 
close  network  beneath  the  mucous 
membrane.  They  pass,  some  with 
the  veins  accompanying  the  spheno- 
palatine  artery,  through  the  spheno- 
palatine  foramen,  and  others  through 
the  alveolar  branch,  to  join  the  facial 
vein  :  some  accompany  the  ethmoidal 
arteries  and  terminate  in  the  ophthal- 
mic vein  :  and.  lastly,  a  few  communi- 
cate with  the  veins  in  the  interior  of 
the  skull  through  the  foramina  in  the 
cribriform  plate  of  the  ethmoid  bone 
and  the  foramen  csecum. 

The  nerve*  are  —  the  olfactory,  the 

nasal  branch  of  the  ophthalmic,  filaments  from  the  anterior  dental  branch  of  the 
superior  maxillary,  the  Yidian.  naso-palatine,  descending  anterior  palatine,  and 
nasal  branches  of  Meckel's  ganglion. 

The  olfactory,  the  special  nerve  of  the  sense  of  smell,  is  distributed  over  the 
upper  third  of  the  septum  and  over  the  surface  of  the  superior  and  middle  spongy 
bones. 

The  n<i*:il  hraneJi  of  the  ophthalmic  distributes  filaments  to  the  fore  part  of  the 
septum  and  outer  wall  of  the  nasal  fossae. 

Filaiif-ntitfi''.,,!!  th>'  'interior  dental  branch  of  the  superior  maxillary  supply  the 
inferior  meatus  and  inferior  turbinated  bone. 

The  Vi'lian  nerve  supplies  the  upper  and  back  part  of  the  septum  and  superior 
spongy  bone,  and  the  upper  anterior  nasal  branches  from  the  spheno-palatine 
ganglion  have  a  similar  distribution. 

The  naso-palatine  nerve  supplies  the  middle  of  the  septum. 

The  larger  or  anterior  palatine  nerve  supplies  the  middle  and  lower  spongy 
bones. 

Surgical  Anatomy.  —  Instances  of  congenital  deformity  of  the  nose  are  occasionally  met 
with,  such  as  complete  absence  of  the  nose,  an  aperture  only  being  present,  or  perfect  develop- 
ment on  one  side,  and  suppression  or  malformation  on  the  other  ;  or  there  may  be  imperfect 
apposition  of  the  nasal  bones,  so  that  the  nose  presents  a  median  cleft  or  furrow.  Deformities 
which  have  been  acquired  are  much  more  common,  such  as  flattening  of  the  nose,  the  result  of 

1  An  interesting  speculation  has  been  suggested  by  Dr.  W.  Ogle,  <  Med.  Chir.  Trans.,  vol.  liii.  p. 
277  as  to  the  possible  connection  between  the  presence  and  abundance  of  this  pigment  and  the  per- 
fection of  the  sense  of  smell. 


FIG.  526.— Nerves  ot  septum  of  nose.    Right  side. 


890  THE    ORGANS    OF  SENSE. 

syphilitic  necrosis,  or  imperfect  development  of  the  nasal  bones  in  cases  of  congenital  syphilis,  or 
a  lateral  deviation  of  the  nose  may  result  from  fracture. 

The  skin  over  the  alee  and  tip  of  the  nose  is  thick  and  closely  adherent  to  subjacent  parts. 
Inflammation  of  this  part  is  therefore  very  painful,  on  account  of  the  tension.  It  is  largely  sup- 
plied with  blood,  and,  the  circulation  here  being  terminal,  vascular  engorgement  is  liable  to  occur, 
especially  in  women  at  the  menopause  and  in  both  sexes  from  disorders  of  digestion,  exposure  to 
cold,  etc.  The  skin  of  the  nose  also  contains  a  large  number  of  sebaceous  follicles,  and  these,  as 
the  result  of  intemperance,  are  apt  to  become  affected  and  the  nose  reddened,  congested,  and 
irregularly  swollen.  To  this  the  term  "  grog-blossom  ' '  is  popularly  applied.  In  some  of  these  cases 
there  is  enormous  hypertrophy  of  the  skin  and  subcutaneous  tissues,  producing  pendulous  masses, 
termed  lipomata  nasi.  Epitheliorna  and  rodent  ulcer  may  attack  the  nose,  the  latter  being  the 
more  common  of  the  two.  Lupus  and  syphilitic  ulceration  frequently  attack  the  nose,  and  may 
destroy  the  whole  of  the  cartilaginous  portion.  In  fact,  lupus  vulgaris  begins  more  frequently  on 
the  ala  of  the  nose  than  in  any  other  situation. 

Cases  of  congenital  occlusion  of  one  or  both  nostrils,  or  adhesion  between  the  ala  and  septum 
may  occur,  and  may  require  immediate  operation,  since  the  obstruction  much  interferes  with  suck- 
ing. Bony  closure  of  the  posterior  nares  may  also  occur. 

To  examine  the  nasal  cavities,  the  head  should  be  thrown  back  and  the  nose  drawn  upward, 
the  parts  being  dilated  by  some  form  of  speculum.  It  can  also  be  examined  with  the  little  finger 
or  a  probe,  and  in  this  way  foreign  bodies  detected.  A  still  more  extensive  examination  can  be 
made  by  Rouge's  operation,  which  was  introduced  for  the  cure  of  ozaena  by  the  removal  of  any 
dead  bone  which  may  be  present  in  this  disease.  The  whole  framework  of  the  nose  is  lifted  up 
by  an  incision  made  inside  the  mouth,  through  the  junction  of  the  upper  lip  with  the  bone ;  the 
septum  nasi  and  the  lateral  cartilages  are  divided  with  strong  scissors  till  the  anterior  nares  are 
completely  exposed.  The  posterior  nares  can  be  explored  by  reflected  light  from  the  mouth,  by 
which  the  posterior  nares  can  be  illuminated.  The  examination  is  very  difficult  to  carry  out, 
and,  as  a  rule,  sufficient  information  regarding  the  presence  of  foreign  bodies  or  tumors  in  the 
naso-pharynx  can  be  obtained  by  the  introduction  of  the  finger  behind  the  soft  palate  through 
the  mouth.  The  septum  of  the  nose  may  be  displaced  or  deviate  from  the  middle  line :  this 
may  be  the  result  of  an  injury  or  from  some  congenital  defect  in  its  development.  Sometimes 
the  deviation  may  be  so  great  that  the  septum  may  come  in  contact  with  the  outer  wall  of  the 
nasal  fossae,  and  may  even  become  adherent  to  it,  thus  producing  complete  obstruction.  Per- 
foration of  the  septum  is  not  an  uncommon  affection,  and  may  arise  from  several  causes:  syph- 
ilitic or  tubercular  ulceration,  blood-tumor  or  abscess  of  the  septum,  and  especially  in  workmen 
exposed  to  the  vapor  of  bichromate  of  potash,  from  the  irritating  and  corrosive  action  of  the 
fumes.  When  small,  the  perforation  may  cause  a  peculiar  whistling  sound  during  respiration. 
When  large,  it  may  lead  to  the  falling  in  of  the  bridge  of  the  nose. 

Epistaxis  is  a  very  common  affection  in  children.  It  is  rarely  of  much  consequence,  and 
will  almost  always  subside,  but  in  the  more  violent  haemorrhages  of  later  life  it  may  be 
necessary  to  plug  the  posterior  nares.  In  performing  this  operation  it  is  desirable  to  remember 
the  size  of  the  posterior  nares.  A  ready  method  of  regulating  the  size  of  the  plug  to  fit 
the  opening  is  to  make  it  of  the  same  size  as  the  terminal  phalanx  of  the  thumb  of  the  patient 
to  be  operated  on. 

Nasal  polypus  is  a  very  common  disease,  and  presents  itself  in  three  forms :  the  gelatinous, 
the  fibrous,  and  the  malignant.  The  first  is  by  far  the  most  common.  It  grows  from  the 
mucous  membrane  of  the  outer  wall  of  the  nasal  fossa,  where  there  is  an  abundant  layer  of 
highly  vascular  submucous  tissue ;  rarely  from  the  septum,  where  the  mucous  membrane  is 
closely  adherent  to  the  cartilage  and  bone,  without  the  intervention  of  much,  if  any,  submucous 
tissue.  Their  most  common  seat  is  probably  the  middle  turbinated  bone.  The  fibrous  polypus 
generally  grows  from  the  base  of  the  skull  behind  the  posterior  nares  or  from  the  roof  of  the  nasal 
fossae.  The  malignant  polypi,  both  sarcomatous  or  carcinomatous,  may  arise  in  the  nasal  cavities 
and  the  naso-pharynx ;  or  they  may  originate  in  the  antrum,  and  protrude  through  its  inner  wall 
into  the  nasal  fossa. 

Rhinoliths,  or  nose-stones,  may  sometimes  be  found  in  the  nasal  cavities,  from  the  formation 
of  phosphate  of  lime  upon  either  a  foreign  body  or  a  piece  of  inspissated  secretion. 

THE  EYE. 

The  eyeball  is  contained  in  the  cavity  of  the  orbit.  In  this  situation  it  is 
securely  protected  from  injury,  whilst  its  position  is  such  as  to  ensure  the  most 
extensive  range  of  sight.  It  is  acted  upon  by  numerous  muscles,  by  which  it  is 
capable  of  being  directed  to  any  part ;  it  is  supplied  by  vessels  and  nerves,  and  is 
additionally  protected  in  front  by  several  appendages,  such  as  the  eyebrow,  eye- 
lids, etc. 

The  eyeball  is  imbedded  in  the  fat  of  the  orbit,  but  is  surrounded  by  a  thin 
membranous  sac,  the  capsule  of  Tenon,  which  isolates  it,  so  as  to  allow  of  free 
movement. 

The  capsule  of  Tenon  (tunica  vaginalis  oculi)  may  be  regarded  as  a  distinct 


THE   EYE.  891 

serous  membrane,  consisting  of  a  parietal  and  visceral  layer.  The  latter  invests 
the  posterior  part  of  the  globe  from  the  ciliary  margin  of  the  cornea  backward  to 
the  entrance  of  the  optic  nerve,  and  is  connected  to  it  by  very  delicate  connective 
tissue :  the  former  (parietal)  lines  the  hollow  in  the  fat  in  which  the  eyeball  is 
imbedded.  Both  layers  are  lined  on  their  free  surfaces  by  endothelial  cells.  The 
cavity  between  them  is  continuous  with  the  spaces  between  the  different  layers  of 
the  sheath  of  the  optic  nerve — that  is  to  say,  with  the  subarachnoidean  between  the 
pia-matral  and  the  arachnoid  sheath,  and  the  subdural  between  the  arachnoid  and 
dural  sheath — and  into  it  empty  the  lymphatic  vessels  of  the  sclerotic.  The  capsule 
is  pierced  by  the  muscles  of  the  eyeball  near  their  insertion,  and  sends  tubular 
prolongations  on  them,  which  become  continuous  with  the  sheath  of  the  muscles. 
From  the  outer  surface  of  these  sheaths  expansions,  consisting  of  elastic  fibres  and 
muscle-cells,  are  given  off  to  the  margin  of  the  orbit,  which  serve  to  limit  the 
degree  of  contraction  of  the  muscles.1 

The  eyeball  is  composed  of  segments  of  two  spheres  of  different  sizes.  The 
anterior  segment  is  one  of  a  small  sphere,  and  forms  about  one-sixth  of  the  eyeball. 
It  is  more  prominent  than  the  posterior  segment,  which  is  one  of  a  much  larger 
sphere,  and  forms  about  five-sixths  of  the  globe.  The  segment  of  the  larger  sphere 
is  opaque,  and  formed  by  the  sclerotic,  the  tunic  of  protection  to  the  eyeball ;  the 
smaller  sphere  is  transparent,  and  formed  by  the  cornea.  The  axes  of  the  eyeballs 
are  nearly  parallel,  and  do  not  correspond  to  the  axes  of  the  orbits,  which  are 
directed  outward.  The  optic  nerves  follow  the  direction  of  the  axes  of  the  orbits, 
and  are  therefore  not  parallel ;  they  enter  the  eyeball  a  little  to  their  inner  or  nasal 
side.  The  eyeball  measures  rather  more  in  its  transverse  than  in  its  antero- 
posterior  and  vertical  diameters,  the  former  amounting  to  about  an  inch,  the  latter 
to  about  nine-tenths  of  an  inch. 

The  eyeball  is  composed  of  several  investing  tunics,  and  of  fluid  and  solid 
refracting  media,  called  humors. 

The  tunics  are  three  in  number: 

1.  Sclerotic  and  Cornea. 

2.  Choroid,  Iris,  and  Ciliary  Processes. 

3.  Retina. 

The  refracting  media,  or  humors,  are  also  three : 

Aqueous.  Crystalline  (lens)  and  Capsule.  Vitreous. 

The  sclerotic  and  cornea  form  the  external  tunic  of  the  eyeball ;  they  are 
essentially  fibrous  in  structure,  the  sclerotic  being  opaque,  and  forming  the 
posterior  five-sixths  of  the  globe  ;  the  cornea,  which  forms  the  remaining  sixth, 
being  transparent. 

The  Sclerotic  (ax).rtrio~.  hard)  (Fig.  527)  has  received  its  name  from  its  extreme 
density  and  hardness  ;  it  is  a  firm,  unyielding,  fibrous  membrane,  serving  to  main- 
tain the  form  of  the  globe.  It  is  much  thicker  behind  than  in  front.  Its  external 
surface  is  of  a  white  color,  quite  smooth,  except  at  the  points  where  the  Recti  and 
Obliqui  muscles  are  inserted  into  it,  and  covered,  for  part  of  its  extent,  by  the 
conjunctival  membrane;  hence  the  whiteness  and  brilliancy  of  the  front  of  the 
eyeball.  Its  inner  surface  is  stained  of  a  brown  color,  marked  by  grooves,  in 
which  are  lodged  the  ciliary  nerves,  and  connected  by  an  exceedingly  fine  cellular 
tissue  (lamina  fusca)  with  the  outer  surface  of  the  choroid.  Behind,  it  is  pierced 
by  the  optic  nerve  a  little  to  its  inner  or  nasal  side,  and  is  continuous  with  the 
fibrous  sheath  of  the  nerve,  which  is  derived  from  the  dura  mater.  At  the  point 
where  the  optic  nerve  passes  through  the  sclerotic  this  membrane  forms  a  thin 
cribriform  lamina  (the  lamina  cribrosa) ;  the  minute  orifices  in  this  layer  serve 
for  the  transmission  of  the  nervous  filaments,  and  the  fibrous  septa  dividing  them 
from  one  another  are  continuous  with  the  membranous  processes  which  separate 
the  bundles  of  nerve-fibres.  One  of  these  openings,  larger  than  the  rest,  occupies 

1  See  a  paper  by  Mr.  C.  B.  Lockwood  (Journal  of  Anatomy  and  Physioloyy,  vol.  xx.,  part  i.  p.  1). 


892 


THE   ORGANS   OF  SENSE. 


the  centre  of  the  lamella  ;  it  is  called  the  porus  opticus,  and  transmits  the  arteria 
centralis  retinae'  to  the  interior  of  the  eyeball.  Around  the  cribriform  lamella  are 
numerous  small  apertures  for  the  transmission  of  the  ciliary  vessels  and  nerves 
In  front  the  sclerotic  is  continuous  with  the  cornea  by  direct  continuity  of  tissue, 
but  the  opaque  sclerotic  overlaps  the  cornea  rather  more  on  its  outer  than  on  ita 
inner  surface. 

Structure.  —  The  sclerotic  is  formed  of  white  fibrous  tissue  intermixed  with  fine 
elastic  fibres,  and  of  flattened  connective-  tissue  corpuscles,  some  of  which  are 
pigmented,  contained  in  cell-spaces  between  the  fibres.  These  fibres  are  aggre- 
gated into  bundles  which  are  arranged  chiefly  in  a  longitudinal  direction.  It  yields 
gelatin  on  boiling.  Its  vessels  are  not  numerous,  the  capillaries  being  of  small 
size,  uniting  at  long  and  wide  intervals.  The  existence  of  nerves  in  it  is  doubtful. 


Canal  of  Schlemm. 


Retina. 


Choroid  coat. 


Sclerotic  coat. 

Nerve  sheath 


Canal  for 
entral  artery. 


!  'vrJ Optic  nerve. 

FIG.  527.— A  horizontal  section  of  the  eyeball.    (Allen.) 

The  Cornea  is  the  projecting  transparent  part  of  the  external  tunic  of  the 
eyeball,  and  forms  the  anterior  sixth  of  the  globe.  It  is  almost  circular  in  shape, 
occasionally  a  little  broader  in  the  transverse  than  in  the  vertical  direction.  It 
is  convex  anteriorly,  and  projects  forward  from  the  sclerotic  in  the  same  manner 
that  a  Avatch-glass  does  from  its  case.  Its  degree  of  curvature  varies  in  different 
individuals,  and  in  the  same  individual  at  different  periods  of  life,  it  being  more 
prominent  in  youth  than  in  advanced  life,  when  it  becomes  flattened.  The 
cornea  is  dense  and  of  uniform  thickness  throughout ;  its  posterior  surface  is 
perfectly  circular  in  outline,  and  exceeds  the  anterior  surface  slightly  in  extent, 
from  the  latter  being  overlapped  by  the  sclerotic. 

Structure. — The  cornea  consists  of  four  layers — namely,  (1)  several  strata 
of  epithelial  cells,  continuous  with  those  of  the  conjunctiva ;  (2)  a  thick  central 
fibrous  structure,  the  cornea  proper;  (3)  a  homogeneous  elastic  lamina;  and  (4) 
a  single  layer  of  epithelial  cells,  forming  part  of  the  lining  membrane  of  the 
anterior  chamber  of  the  eyeball.  The  name  of  membrane  of  Descemet  or  Demours 
is  given  to  this  posterior  elastic  lamina  and  its  endothelial  coating. 


THE    CORNEA.  893 

The  conjunctival  epithelium,  which  covers  the  front  of  the  cornea  proper, 
consists  of  several  strata  of  epithelial  cells.  The  lowermost  cells  are  columnar  : 
then  follow  two  or  three  layers  of  polyhedral  cells,  some  of  which  present  ridges 
and  furrows  similar  to  those  found  in  the  cuticle.  Lastly,  there  are  three  or  four 
layers  of  scaly  epithelium  with  flattened  nuclei. 

The  proper  substance  of  the  cornea  is  fibrous,  tough,  unyielding,  perfectly 
transparent,  and  continuous  with  the  sclerotic,  with  which  it  is  identical  in 
structure.  It  is  composed  of  about  sixty  flattened  lamellae,  superimposed  one  on 
another.  These  lamellae  are  made  up  of  bundles  of  fibrous  connective  tissue,  the 
fibres  of  which  are  directly  continuous  with  the  fibres  of  the  sclerotic.  The  fibres 
of  each  lamella  are  for  the  most  part  parallel  with  each  other  ;  those  of  alternat- 
ing lamellae  at  right  angles  to  each  other.  Fibres,  however,  frequently  pass  from 
one  lamella  to  the  next. 

The  lamellae  are  connected  with  each  other  by  an  interstitial  cement-substance, 
in  which  are  spaces,  the  corneal  spaces.  The  spaces  are  stellate  in  shape,  and 
have  numerous  offsets  by  which  they  communicate  with  other  spaces.  Each  space 
contains  a  cell,  the  corneal  corpuscle,  which  resembles  in  form  the  space  in  which 
it  is  contained,  but  does  not  entirely  fill  it. 

Immediately  beneath  the  conjunctival  epithelium  the  cornea  proper  presents 
certain  characteristic  differences,  which  have  led  some  anatomists  to  regard  it  as  a 
distinct  membrane,  and  it  has  been  named  by  Bowman  the  anterior  elastic  lamina. 
It  differs,  however,  from  the  true  elastic  lamina  or  membrane  of  Descemet  in 
many  essential  particulars,  presenting  evidence  of  fibrillar  structure,  and  not 
having  the  same  tendency  to  curl  inward  or  to  undergo  fracture  when  detached 
from  the  other  layers  of  the  cornea.  It  consists  of  extremely  closely  interwoven 
fibrils,  similar  to  those  found  in  the  rest  of  the  cornea  proper,  but  contains  no 
corneal  corpuscles.  It  seems,  therefore,  more  proper  to  regard  it  as  a  part  of  the 
proper  tissue  of  the  cornea.1 

The  posterior  elastic  lamina,  which  covers  the  proper  structure  of  the  cornea 
behind,  presents  no  structure  recognizable  under  the  microscope.  It  consists  of  a 
hard,  elastic,  and  perfectly  transparent  homogeneous  membrane,  of  extreme  thin- 
ness, which  is  not  rendered  opaque  by  either  water,  alcohol,  or  acids.  It  is  very 
brittle,  but  its  most  remarkable  property  is  its  extreme  elasticity,  and  the  tend- 
ency which  it  presents  to  curl  up  or  roll  upon  itself,  with  the  attached  surface 
innermost,  when  separate  from  the  proper  substance  of  the  cornea.  Its  use 
appears  to  be  (as  suggested  by  Dr.  Jacob)  "  to  preserve  the  requisite  permanent 
correct  curvature  of  the  flaccid  cornea  proper." 

At  the  margin  of  the  cornea  this  posterior  elastic  membrane  breaks  up  into 
fibres  to  form  a  reticular  structure  at  the  outer  angle  of  the  anterior  chamber, 
the  intervals  between  the  fibres  forming  small  cavernous  spaces,  the  spaces  of 
Fontana.  These  little  recesses  communicate  with  a  somewhat  larger  space  in  the 
substance  of  the  sclerotic  close  to  its  junction  with  the  cornea.  This  is  the  canal 
of  Schlemm,  or  sinus  circularis  iridis,  and,  according  to  some  authors,  is  a  lymph- 
canal,  but  according  to  others  is  a  venous  sinus.  Some  of  the  fibres  of  this 
reticulated  structure  are  continued  into  the  front  of  the  iris,  forming  the  liga- 
mentum  pectinatum  iridis,  while  others  are  connected  with  the  fore  part  of  the 
sclerotic  and  choroid. 

The  endoiheKal  fining  of  the  aqueous  chamber  covers  the  posterior  surface  of 
the  posterior  elastic  lamina.  It  consists  of  a  single  layer  of  polygonal  flattened 
transparent  nucleated  cells,  similar  to  those  found  lining  other  serous  cavities. 

Arteries  and  Nerves. — The  cornea  is  a  non-vascular  structure,  the  capillary 
vessels  terminating  in  loops  at  its  circumference.  Lymphatic  vessels  have  not  as 
yet  been  demonstrated  in  it,  but  are  represented  by  the  channels  in  which  the 
bundles  of  nerves  run  ;  these  are  lined  by  an  endothelium  and  are  continuous 
with  the  cell-spaces.  The  nerves  are  numerous,  twenty-four  to  thirty-six  in 

1  This  layer  has  been  called  by  Reichert  the  "  anterior  limiting  layer  " — a  name  which  appears 
more  applicable  to  it  than  that  of  "anterior  elastic  lamina." 


894 


THE    ORGANS    OF  SENSE. 


number  (Kdlliker),  forty  to  forty-five  (Waldeyer  and  Sumisch) ;  they  are  derived 
from  the  ciliary  nerves  and  enter  the  laminated  tissue  of  the  cornea.  They 
ramify  throughout  its  substance  in  a  delicate  network,  and  their  terminal  fila- 
ments form  a  firm  and  closer  plexus  on  the  surface  of  the  cornea  proper  beneath 
the  epithelium.  This  is  termed  the  subepithelial  plexus,  and  from  it  fibrils  are 
given  off  which  ramify  between  the  epithelial  cells,  forming  a  network  which  is 
termed  the  intra-epithelial  plexus. 

Dissection. — In  order  to  separate  the  sclerotic  and  cornea,  so  as  to  expose  the  second  tunic, 
the  eyeball  should  be  immersed  in  a  small  vessel  of  water  and  held  between  the  finger  and 
thumb.  The  sclerotic  is  then  carefully  incised,  in  the  equator  of  the  globe,  till  the  choroid  is 
exposed.  One  blade  of  a  pair  of  probe-pointed  scissors  is  now  introduced  through  the  opening 
thus  made,  and  the  sclerotic  divided  around  its  entire  circumference,  and  removed  in  separate 
portions.  The  front  segment  being  then  drawn  forward,  the  handle  of  the  scalpel  should  be 
pressed  gently  against  it  at  its  connection  with  the  iris,  and,  these  being  separated,  a  quantity 
of  perfectly  transparent  fluid  will  escape ;  this  is  the  aqueous  humor.  In  the  course  of  the 
dissection  the  ciliary  nerves  may  be  seen  lying  in  the  loose  cellular  tissue  between  the  choroid 
and  sclerotic  or  contained  in  delicate  grooves  on  the  inner  surface  of  the  latter  membrane. 

Second  Tunic. — This  is  formed  by  the  choroid  behind,  the  iris  and  ciliary 
processes  in  front,  and  by  the  Ciliary  muscle,  opposite  the  junction  of  the  scle- 
rotic and  cornea. 


FIG.  528.— The  choroid  and  iris.    (Enlarged.) 

The  choroid  is  the  vascular  and  pigmentary  tunic  of  the  eyeball  investing  the 
posterior  five-sixths  of  the  globe,  and  extending  as  far  forward  as  the  cornea, 
the  ciliary  processes  being  appendages  of  the  choroid  developed  from  its  inner 
surface  in  front.  The  iris  is  the  circular  muscular  septum  which  hangs  vertical- 
ly behind  the  cornea,  presenting  in  its  centre  a  large  circular  aperture,  the  pupil. 
The  Ciliary  muscle  forms  the  white  ring  observed  at  the  point  where  the  choroid 
and  iris  join  with  each  other  and  with  the  sclerotic  and  cornea. 

The  Choroid  is  a  thin,  highly  vascular  membrane,  of  a  dark  brown  or  chocolate 
color,  which  invests  the  posterior  five-sixths  of  the  central  part  of  the  globe.  It  is 
pierced  behind  by  the  optic  nerve,  and  extends  in  front  as  far  forward  as  the 
ciliary  ligament,  where  it  is  connected  with  the  iris,  and  bends  inward,  forming 
on  its  inner  surface  a  series  of  folds  or  plaitings,  the  ciliary  processes.  It  is  thicker 


THE  EYE.  895 

behind  than  in  front.  Externally  it  is  connected  by  a  fine  cellular  web  (membrana 
/)  with  the  inner  surface  of  the  sclerotic.  Its  inner  surface  is  smooth  and 
lies  in  contact  with  the  retina. 

Structure. — The  choroid  consists  mainly  of  a  dense  capillary  plexus  and  of 
small  arteries  and  veins,  carrying  the  blood  to  and  returning  it  from  this  plexus. 
On  its  external  surface — i.  >'.  the  surface  next  the  sclerotic — is  a  thin  membrane 
of  fine  elastic  fibres  arranged  in  lamellae,  which  are  covered  with  endothelium  and 
form  spaces,  which  communicate  by  perforations  in  the  sclerotic,  through  which 
the  vessels  and  nerves  enter,  with  the  capsule  of  Tenon.  This  layer  is  named  the 
lamina  mprackoroidea,  and  is  continuous  with  the  lamina  fusca  of  the  sclerotic. 

Internal  to  this  is  the  choroid  proper,  and,  in  consequence  of  the  small  arteries 
and  veins  being  arranged  on  the  outer  surface  of  the  capillary  network,  it  is  cus- 
tomary to  describe  this  as  consisting  of  two  layers,  the  outermost  composed  of 
small  arteries  and  veins,  with  pigment-cells  interspersed  between  them,  and  the 


FIG.  529.— The  veins  of  the  choroid.    (Enlarged.) 

inner  consisting  of  a  capillary  plexus.  The  external  layer  consists,  in  part,  of 
the  larger  branches  of  the  short  ciliary  arteries,  which  run  forward  between  the 
veins  before  they  bend  inward  to  terminate  in  the  capillaries  ;  but  is  formed 
principally  of  veins,  which  are  named,  from  their  arrangement,  vence  vorticosce. 
Thev  converge  to  four  or  five  equidistant  trunks,  which  pierce  the  sclerotic  mid- 
way between  the  margin  of  the  cornea  and  the  entrance  of  the  optic  nerve.  Inter- 
spersed between  the  vessels  are  lodged  dark  star-shaped  pigment-cells,  the  fibrous 
offsets  from  which,  communicating  with  similar  branchings  from  neighboring  cells, 
form  a  delicate  network  or  stroma,  which  toward  the  inner  surface  of  the  choroid 
loses  its  pigmentary  character.  The  internal  layer  consists  of  an  exceedingly  fine 
capillary  plexus,  formed  by  the  short  ciliary  vessels,  and  is  known  as  the  tunica 
Ruii*<:-liinna.  The  network  is  close,  and  finer  at  the  hinder  part  of  the  choroid 
than  in  front.  About  half  an  inch  behind  the  cornea  its  meshes  become  larger, 
and  are  continuous  with  those  of  the  ciliary  processes.  On  the  inner  surface  of 
this  tunic  is  a  very  thin,  structureless — or,  according  to  Kolliker,  faintly  fibrous — 
membrane,  called  the  lamina  vitrea  ;  it  is  closely  connected  with  the  stroma  of  the 
choroid.  and  separates  it  from  the  pigmentary  layer  of  the  retina. 

The  ciliary  processes  should  now  be  examined.  They  may  be  exposed,  either  by  detaching 
the  iris  from  its  connection  with  the  Ciliary  muscle,  or  by  making  a  transverse  section  of  the 
globe  and  examining  them  from  behind. 

The  ciliary  processes  are  formed  by  the  plaiting  and  folding  inward  of  the 
various  layers  of  the  choroid  (i.  e.  the  choroid  proper  and  the  lamina  vitrea)  at  its 
anterior  margin,  and  are  received  between  corresponding  foldings  of  the  suspensory 


896  THE    ORGANS   OF  SENSE. 

ligament  of  the  lens,  thus  establishing  a  connection  between  the  choroid  and  inner 
tunic  of  the  eye.  They  are  arranged  in  a  circle,  and  form  a  sort  of  plaited  frill 
behind  the  iris  round  the  margin  of  the  lens.  They  vary  between  sixty  and 
eighty  in  number,  lie  side  by  siae,  ana  may  be  divided  into  large  and  small ;  the 
latter,  consisting  of  about  one-third  of  the  entire  number,  are  situated  in  the 
spaces  between  the  former,  but  without  regular  alternation.  The  larger  processes 
are  each  about  one-tenth  of  an  inch  in  length,  and  are  attached  by  their  periphery 
to  the  Ciliary  muscle,  and  are  continuous  with  the  layers  of  the  choroid :  the 
opposite  margin  is  free,  and  rests  upon  the  circumference  of  the  lens.  Their 
anterior  surface  is  turned  toward  the  back  of  the  iris,  with  the  circumference  of 
which  they  are  continuous.  The  posterior  surface  is  closely  connected  with  the 
suspensory  ligament  of  the  lens. 

Structure. — The  ciliary  processes  are  similar  in  structure  to  the  choroid,  but 
the  vessels  are  larger,  and  have  chiefly  a  longitudinal  direction.     They  are  covered 


Anterior  ciliary  artery. 


Short  ciliary  arteries. ' 

vLnierior  ciliary  artery. 

FIG.  530.— The  arteries  of  the  choroid  and  iris.    The  sclerotic  has  been  mostly  removed.    (Enlarged.) 

on  their  inner  surface  with  a  layer  of  black  pigment-cells  continuous  with  the  cells 
of  the  pigmentary  layer  of  the  retina,  and  in  their  stroma  are  also  other,  stellate, 
pigment-cells,  which,  however,  are  not  so  numerous  as  in  the  choroid  itself,  and 
toward  the  free  extremities  of  the  folds  are  devoid  of  pigment. 

The  Iris  (iris,  a  rainbow)  has  received  its  name  from  its  various  colors  in  dif- 
ferent individuals.  It  is  a  thin,  circular-shaped,  contractile  curtain,  suspended 
in  the  aqueous  humor  behind  the  cornea  and  in  front  of  the  lens,  being  perforated 
a  little  to  the  nasal  side  of  its  centre  by  a,  circular  aperture,  the  pupil,  for  the 
transmission  of  light.  By  its  circumference  it  is  intimately  connected  with  the 
choroid  ;  externally  to  this  is  the  Ciliary  muscle,  by  which  it  is  connected  to  the 
sclerotic  and  cornea  ;  its  inner  edge  forms  the  margin  of  the  pupil ;  its  surfaces 
are  flattened,  and  look  forward  and  backward,  the  anterior  surface  toward  the 
cornea,  the  posterior  toward  the  ciliary  processes  and  lens.  The  circumference 
of  the  iris  is  connected  to  the  cornea  by  a  reticular  structure  denominated  the 
ligamentum  pectinatum  iridis.  The  anterior  surface  of  the  iris  is  variously 
colored  in  different  individuals,  and  marked  by  lines  which  converge  toward  the 
pupil.  The  posterior  surface  is  of  a  deep  purple  tint,  from  being  covered  by  dark 
pigment ;  it  is  hence  named  uvea,  from  its  resemblance  in  color  to  a  ripe  grape. 

Structure. — The  iris  is  composed  of  the  following  structures  : 

1.  In   front  is   a  layer  of  polyhedral  cells   on  a  delicate   hyaline    basement 
membrane.     This  layer  is  continuous  with  the  epithelial  layer  of  the  membrane  of 
Descemet,  and  in  men  with  dark-colored  irides  the  cells  contain  pigment-granules. 

2.  Stroma. — The  stroma  consists  of  fibres  and  cells.     The  former  are  made  up 


THE   EYE. 


897 


of  fine  delicate  bundles  of  fibrous  tissue,  of  which  some  few  fibres  have  a  circular 
direction  at  the  circumference  of  the  iris,  but  the  chief  mass  consists  of  fibres 
radiating  toward  the  pupil.  They  form,  by  their  interlacement,  a  delicate  mesh, 
in  which  the  vessels  and  nerves  are  contained.  Interspersed  between  the  bundles 
of  connective  tissue  are  numerous  branched  cells  with  fine  processes.  Many  of 
them  in  dark  eyes  contain  pigment-granules,  but  in  blue  eyes  and  the  pink  eyes  of 
albinos  they  are  unpigniented. 

3.  The  muscular  fibre  is  involuntary,  and  consists  of  circular  and  radiating 
fibres.  The  circular  fibres  (sphincter  of  the  pupil)  surround  the  margin  of  the 
pupil  on  the  posterior  surface  of  the  iris,  like  a  sphincter,  forming  a  narrow  band 


Circ.  fibres 
of  sclerotic. 


^_  f  Pars  ciliaris 
~\      retime. 

jssy. 

Circ.  fibres    /     \ 
of  Ciliary  muscle 

FIG.  531.— Section  of  the  eye,  showing  the  relations  of  the  cornea,  sclerotic,  and  iris,  together  with  the 
Ciliary  muscle  and  the  cavernous  spaces  near  the  angle  of  the  anterior  chamber.    (Waldeyer.) 

about  one-thirtieth  of  an  inch  in  width,  those  near  the  free  margin  being  closely 
aggregated ;  those  more  external  somewhat  separated,  and  forming  less  complete 
circles.  The  radiating  fibres  (dilator  of  the  pupil)  converge  from  the  circumfer- 
ence toward  the  centre,  and  blend  with  the  circular  fibres  near  the  margin  of 
the  pupil. 

4.  Pigment. — The  situation  of  the  pigment-cells  differs  in  different  irides.  In 
the  various  shades  of  blue  eyes  the  only  pigment-cells  are  several  layers  of  small 
round  or  polyhedral  cells  filled  with  dark  pigment,  situated  on  the  posterior  surface 
of  the  iris  and  continuous  with  the  pigmentary  lining  of  the  ciliary  processes.  The 
color  of  the  eye  in  these  individuals  is  due  to  this  coloring  matter  showing  more 
or  less  through  the  texture  of  the  iris.  In  the  albino  even  this  pigment  is  absent. 
In  the  gray,  brown,  and  black  eye  there  are,  as  mentioned  above,  pigment-granules 
to  be  found  in  the  cells  of  the  stroma  and  in  the  epithelial  layer  on  the  front  of  the 
iris,  to  which  the  color  of  the  eye  is  due. 

The  arteries  of  the  iris  are  derived  from  the  long  and  anterior  ciliary  and  from 
the  vessels  of  the  ciliary  processes  (see  page  570). 

The  nerves  of  the  iris  are  derived  from  the  ciliary  branches  of  the  lenticular 
ganglion  and  the  long  ciliary  from  the  nasal  branch  of  the  ophthalmic  division  of 
the  fifth.  After  reaching  the  iris  in  the  manner  described  above  (page  797)  they  form 
a  plexus  around  the  attached  margin  of  the  iris ;  from  this  are  derived  non- 
57 


898  THE    ORGANS   OF  SENSE. 

medullated  fibres  which  terminate  in  the  circular  and  radiating  muscular  fibres. 
Their  exact  mode  of  termination  has  not  been  ascertained.  Other  fibres  from  the 
plexus  terminate  in  a  network  on  the  anterior  surface  of  the  iris.  The  fibres 
derived  from  the  motor  root  of  the  lenticular  ganglion  (third  nerve)  supply  the 
circular  fibres,  while  those  derived  from  the  sympathetic  supply  the  radiating 
fibres. 

Membrana  Pupillaris. — In  the  foetus  the  pupil  is  closed  by  a  delicate  transparent 
vascular  membrane,  the  membrana  pupillaris,  which  divides  the  space  into  which 
the  iris  is  suspended  into  two  distinct  chambers.  This  membrane  contains  numerous 
minute  vessels,  continued  from  the  margin  of  the  iris  to  those  on  the  front  part  of 
the  capsule  of  the  lens.  These  vessels  have  a  looped  arrangement,  and  converge 
toward  each  other  without  anastomosing.  Between  the  seventh  and  eighth  months 
the  membrane  begins  to  disappear,  by  its  gradual  absorption  from  the  centre 
toward  the  circumference,  and  at  birth  only  a  few  fragments  remain.  It  is  said 
sometimes  to  remain  permanent  and  produce  blindness. 

The  Ciliary  muscle  (Bowman)  consists  of  unstriped  fibres :  it  forms  a  grayish, 
semitransparent,  circular  band,  about  one-eighth  of  an  inch  broad,  on  the  outer 
surface  of  the  fore  part  of  the  choroid.  It  is  thickest  in  front,  and  gradually 
becomes  thinner  behind.  It  consists  of  two  sets  of  fibres,  radiating  and  circular. 
The  former,  much  the  more  numerous,  arise  at  the  point  of  junction  of  the  cornea 
and  sclerotic,  and,  passing  backward,  are  attached  to  the  choroid  opposite  to  the 
ciliary  processes.  One  bundle,  according  to  Waldeyer,  is  continued  backward  to 
be  inserted  into  the  sclerotic.  The  circular  fibres  are  internal  to  the  radiating  ones, 
and  to  some  extent  unconnected  with  them,  and  have  a  circular  course  around  the 
attachment  of  the  iris.  They  are  sometimes  called  the  "  ring  muscle  "  of  Miiller, 
and  were  formerly  described  as  the  ciliary  ligament.  The  Ciliary  muscle  is  admitted 
to  be  the  chief  agent  in  accommodation — i.  e.  in  adjusting  the  eye  to  the  vision  of 
near  objects.  Mr.  Bowman  believed  that  this  was  effected  by  its  compressing  the 
vitreous  body,  and  so  causing  the  lens  to  advance ;  but  the  view  which  now 
prevails  is  that  the  contraction  of  the  muscle,  by  drawing  on  the  ciliary  processes, 
relaxes  the  suspensory  ligament  of  the  lens,  thus  allowing  the  anterior  surface 
of  the  lens  to  become  more  convex.  The  pupil  is  at  the  same  time  slightly 
contracted.1 

The  Retina  is  a  delicate  nervous  membrane  upon  the  surface  of  which  the 
images  of  external  objects  are  received.  Its  outer  surface  is  in  contact  with  the 
choroid,  the  inner  surface  with  the  vitreous  body.  Behind  it  is  continuous  with 
the  optic  nerve  ;  it  gradually  diminishes  in  thickness  from  behind  forward,  and 
in  front  extends  nearly  as  far  forward  as  the  Ciliary  muscle,  where  it  terminates 
by  a  jagged  margin,  the  ora  serrata.  It  is  soft,  and  semitransparent  in  the  fresh 
state,  but  soon  becomes  clouded,  opaque,  and  of  a  pinkish  tint.  Exactly  in  the 
centre  of  the  posterior  part  of  the  retina,  and  at  a  point  corresponding  to  the  axis 
of  the  eye,  in  which  the  sense  of  vision  is  most  perfect,  is  a  round,  elevated, 
yellowish  spot,  called,  after  its  discoverer,  the  yellow  spot  or  limbus  Iriteus  (macula 
luted)  of  Sbmmerring,  having  a  central  depression  at  its  summit,  the  fovea 
centralis.  The  retina  in  the  situation  of  the  fovea  centralis  is  exceedingly  thin  ;  so 
much  so  that  the  dark  color  of  the  choroid  is  distinctly  seen  through  it ;  so  that 
it  presents  more  the  appearance  of  a  foramen,  and  hence  the  name  "foramen  of 
Sbmmerring  "  at  first  given  to  it.  It  exists  only  in  man,  the  quadrumana,  and 
some  saurian  reptiles.  About  one-tenth  of  an  inch  to  the  inner  side  of  the  yellow 
spot  is  the  point  of  entrance  of  the  optic  nerve  ( porus  opticus) ;  here  the  nervous 
substance  is  slightly  raised  so  as  to  form  an  eminence  (colliculus  nervi  optici);  the 
arteria  centralis  retinae  pierces  its  centre.  This  is  the  only  part  of  the  surface  of 
the  retina  from  which  the  power  of  vision  is  absent. 

Structure. — The  retina  is  an  exceedingly  complex  structure,  and,  when  exam- 
ined microscopically  by  means  of  sections  made  perpendicularly  to  its  surface, 

1  See  explanation  and  diagram  in  Power's  Illustrations  of  Some  of  the  Principal  Diseases  of  the  Eye. 
p.  590. 


THE   EYE. 


899 


is   found    to  consist  of  ten    layers,   which    are  named  from   within  outward  as 
fellows  : 

1.  Membrana  limitans  interna. 

2.  Fibrous  layer,  consisting  of  nerve-fibres. 

3.  Vesicular  layer,  consisting  of  nerve-cells. 

4.  Inner  molecular,  or  granular,  layer. 

5.  Inner  nuclear  layer. 

6.  Outer  molecular,  or  granular,  layer. 

7.  Outer  nuclear  layer. 

8.  Membrana  limitans  externa. 

9.  Layer  of  rods  and  cones  (Jacob's  membrane). 
10.  Pigmentary  layer. 

1.  The  membrana  limitans  interna  is  the  most  internal  layer  of  the  retina,  and 
is  in  contact  with  the  hyaloid  membrane  of  the  vitreous  humor.  It  is  derived  from 
the  supporting  framework  of  the  retina,  with  which  tissue  it  will  be  described. 


FIG.  532.— The  arteria  centralis  retina,  yellow  spot,  etc.,  the  anterior  half  of  the  eyeball  being  removed. 
(Enlarged.) 

2.  The  fibrous  layer  is  made  up  of  nerve-fibres,  the  direct  continuation  of  the 
fibres  of  the  optic  nerve.     This  nerve  therefore  passes  through  all  the  other  layers 
of  the  retina,  except  the  one  previously  mentioned,  to  reach  its  destination  in  the 
fibrous  layer.     As  the  nerve  passes  through   the  lamina  cribrosa  of  the  sclerotic 
coat  the  fibres  of  which   it  is  composed  lay  aside   their  medullary  sheaths   and 
are  continued  onward,  through  the  choroid  and  retina,  as  simple  axis-cylinders. 
When  these  non-medullated  fibres  reach  the  internal  surface  of  the  retina,  they 
radiate  from  their  point  of  entrance  over   the  surface  of  the  retina,  grouped  in 
bundles,  and  in  many  places,  according   to  Michel,  arranged   in  plexuses.     The 
layer  is  thickest  at  the  optic  nerve  entrance,  and  gradually  diminishes  in  thick- 
ness toward  the  ora  serrata. 

3.  The  vesicular  layer  consists  of  a  single  layer  of  large  ganglion-cells,  except 
in  the  macula  lutea,  where  there  are  several  layers.    The  cells  are  somewhat  flask- 
shaped  ;  their  rounded  internal  margin  resting  on  the  preceding  layer,  and  sending 
off  a  single  process,  which  is  prolonged  into  the  fibrous  layer,  and  is  believed  to  be 
continuous  with  a  nerve-fibre.     From  the  opposite  extremity  of  the  cell  one  or 
more  thicker  processes  extend  into  the  inner  molecular  layer,  where  they  divide 
dichotomously   and  become  lost  in   its   reticulum,   or,   according   to    some,  pass 
through  this  layer  to  reach  the  inner  nuclear  layer. 

4.  The  inner  molecular  layer  consists  of  a  stratum  of  granular-looking  sub- 
stance, from  which  circumstance  it  is  sometimes  called  the  "  inner  granular"  layer. 


900 


THE    ORGANS    OF  SENSE. 


It  is  made  up  of  a  dense  reticulum  of  minute  fibrils,  intermingled  with  the  fine 
processes  of  the  ganglion-cells  and  also  processes  derived  from  certain  cells 
contained  in  the  next  layer,  immediately  to  be  described.  No  direct  connection 
between  these  sets  of  processes  has  yet  been  demonstrated,  but  it  is  considered 
probable  that  they  do  communicate,  and  that  there  is  therefore  a  direct  connection 
between  the  ganglion-cells  of  the  vesicular  layer  and  the  nuclear  cells  of  the  inner 
nuclear  layer.  Within  the  reticulum  formed  by  these  fibrils  minute  clear  granules, 
of  unknown  nature,  are  imbedded. 

5.  The  inner  nuclear  layer  is  made  up  of  nuclear  bodies,  of  which  there  are 


FIGS.  533,  534.— Vertical  sections  of  the  human  retina.  Fig.  533,  half  an  inch  from  the  entrance  of  the  optic 
nerve.  Fig.  534,  close  to  the  latter.  1.  Layer  of  rods  and  cones  (columnar  layer),  bounded  underneath  by  the 
membrana  limitans  externa.  2.  External  nuclear  layer.  3.  Outer  molecular  layer.  4.  Internal  nuclear  layer. 
f>.  Inner  molecular  layer.  6.  Layer  of  the  ganglion-cells.  7.  Expansion  of  optic  fibres.  8.  Sustentacular  fibres 
of  Miiller.  9.  Their  a'ttachment'to  the  membrana  limitans  interna. 

three  different  kinds  :  (1)  A  large  number  of  oval  nuclei,  which  are  commonly 
regarded  as  bipolar  nerve-cells,  and  are  much  more  numerous  than  either  of  the 
other  kind.  They  consist  of  a  large  oval  nuclear  body  placed  vertically  to  the 
surface,  containing  a  distinct  nucleolus  :  they  are  surrounded  by  a  small  amount 
of  protoplasm,  which  is  prolonged  into  two  processes :  one  of  these  passes  inward 
into  the  inner  molecular  layer,  is  varicose  in  appearance,  and,  as  stated  above,  is 
believed  to  be  continuous  with  the  processes  of  the  ganglion-cells.  The  other 
process  passes  outward  into  the  outer  molecular  layer,  and  there  bifurcates. 
According  to  some  observers,  the  divisions  thus  formed  communicate  with  the  rod- 
and  cone-fibres  (Merkel).  (2)  At  the  innermost  part  of  this  inner  nuclear  layer 
is  a  stratum  of  cells  which  are  not  branched.  (3)  Some  few  cells  are  also  found 
in  this  layer  connected  with  the  fibres  of  Miiller,  and  will  be  described  with  those 
structures. 

6.  The  outer  molecular  layer  is  much  thinner  than  the  inner  molecular  layer, 
but,  like  it,  consists  of  a  dense  network  of  minute  fibrils,  and  presents  the  same 
granular  appearance.  It  differs,  however,  from  the  inner  molecular  layer  in  con- 
taining branched  stellate  cells,  the  processes  of  which  are  extremely  fine  and 
exhibit  varicosities  like  nerve-fibrils.  They  are  therefore  considered  by  Schultze 
to  be  ganglion-cells. 

1.  The  Outer  Nuclear  Layer. — Like  the  inner  nuclear  layer,  this  layer  contains 
several  strata  of  clear  oval  nuclear  bodies ;  they  are  of  two  kinds,  and,  on  account 
of  their  being  respectively  connected  with  the  rods  and  cones  of  Jacob's  membrane. 


THE    KYK.  901 

are  named  rod-granules  and  cone-granules.  The  rod-granules  are  much  the  more 
numerous,  and  are  placed  at  different  levels  throughout  the  layer.  They  present  a 
peculiar  cross-striped  appearance,  and  have  prolonged  from  either  extremity  a  fine 
process :  the  outermost  is  continuous  with  a  single  rod  of  Jacob's  membrane;  the 
innermost  passes  inward  toward  the  outer  molecular  layer,  and  terminates  in  an 
enlarged  extremity,  from  which  are  given  off  a  number  of  minute  fibrils,  which 
enter  the  outer  molecular  layer.  In  its  course  it  presents  numerous  varicosities. 
The  cone-granules,  fewer  in  number  than  the  rod-granules,  are  placed  close  to  the 
membrana  limitans  externa.  and  are  closely  connected  with  the  cones  of  Jacob's 
membrane.  They  do  not  present  any  cross-striping,  but  contain  a  pyriform 
nucleus,  which  almost  completely  fills  the  cell.  From  their  inner  extremity  a 
thick  process  passes  inward  to  the  outer  molecular  layer,  where,  like  the  processes 
of  the  rod-cells,  it  terminates  in  an  enlargement,  from  which  are  given  off  numerous 
fine  fibrils  which  enter  the  outer  molecular  layer. 

8.  The  Membrana  Limitans  Externa. — This  layer,  like  the  membrana  limitans 
interna.  is  derived  from  the  fibres  of  Miiller,  with   which  structures  it  will  be 
described. 

9.  Ji.n.-nb' $   Membrane  (bacillary  layer). — The   elements   which   compose   this 
layer  are  of  two  kinds,  rods  and  cones,  the  former  being  much  more  numerous  than 
the  latter.     The  rods  are  solid,  of  nearly  uniform  size,  and  arranged  perpendicularly 
to  the  surface.     Each  rod  consists  of  two  portions,  an  outer  and  inner,  which  are 
joined  together  by  a  cement-substance  and  are  of  about  equal  length.    They  differ 
from    each    other    as    regards    refraction    and    in    their    behavior   with   coloring 
reagents,  the  inner  portion  becoming  stained  by  carmine,  iodine,  etc.,  the  outer 
portion  remaining  unstained.   The  outer  portion  of  each  rod  is  marked  by  transverse 
stride,  and  is  made  up  of  a  number  of  thin  disks  superimposed  on  one  another.    It 
also  exhibits  faint   longitudinal  markings.     The  inner  portion  of  each  rod  at  its 
inner  extremity,  where  it  is  joined  to  the  processes  of  the  rod-granules,  is  indistinctly 
granular  :   at   its  outer  extremity  it   presents  a  fine  longitudinal  striation.  being 
composed  of  fine,  bright,  highly  refracting  fibrils. 

The  cones  are  conical  or  flask-shaped,  their  broad  ends  resting  upon  the 
membrana  limitans  externa.  the  narrow  pointed  extremity  being  turned  to  the 
choroid.  Like  the  rods,  they  are  made  up  of  two  portions,  outer  and  inner ;  the 
outer  portion  being  a  short  conical  process,  which,  like  the  outer  segment  of  the  rods, 
presents  transverse  stria?.  The  inner  portion  resembles  the  inner  portion  of  the 
rods  in  structure,  presenting  an  outer  striated  and  an  inner  granular  appearance, 
but  differs  from  it  in  size,  being  bulged  out  laterally  and  presenting  a  flask  shape. 

10.  The  Pigmentary  Z<///- /•.  ••/•  Tapettun  ^ic/nun. — The  most  external  layer  of 
the  retina,  formerly  regarded  as  a  part  of  the  choroid,  consists  of  a  single  layer  of 
hexagonal  epithelium  cells  loaded  with  pigment-granules  (Fig.  21).   In  the  eyes  of 
albinos  the  cells  of  the  pigmentary  layer  are  present,  but  they  contain  no  coloring 
matter.     In  many  of  the  mammals  also,  as  in  the  horse,  and  many  of  the  carnivora, 
there  is  no  pigment  in  the  cells  of  this  layer,  and  the  choroid  possesses  a  beautiful 
iridescent  lustre,  which  is  termed  the  tapetum  lucidum. 

nectit'e-tissue  Framework  of  the  Retina. — Almost  all  these  layers  of  the 
retina  are  connected  together  by  a  sort  of  supporting  connective  tissue,  which  has 
been  named  the  fibres  of  J/// //</•.  or  radiating  fibres,  from  which  the  membrana 
limitans  interna  et  externa  are  derived.  These  fibres  are  found  stretched  between 
the  two  limiting  layers.  "  as  columns  between  a  floor  and  a  ceiling."  and  passing 
through  all  the  nervous  layers  except  Jacob's  membrane.  They  commence  on 
the  inner  surface  of  the  retina  by  a  conical  base,  the  edges  of  the  bases  of  adjoining 
fibres  being  united,  and  thus  forming  a  boundarv-line  which  is  the  membrana 
limitans  interna.  As  they  pass  through  the  various  lavers  they  present  a  roughness 
on  their  surface,  as  if  a  number  of  membranous  processes  had  been  abruptly 
broken  off.  By  these  they  are  continuous  with  the  reticulum  of  the  inner  and  outer 
molecular  layer  and  with  a  sponge-like  stroma,  in  which  the  nuclei  of  the  inner 
nuclear  lavers  are  imbedded.  In  the  inner  nuclear  laver  each  fibre  of  Miiller 


902 


THE    ORGANS    OF  SENSE. 


presents  a  clear  oval  nucleus,  referred  to  above,  which  is  sometimes  situated  at  the 
side  of,  sometimes  altogether  within,  the  fibre.  In  the  outer  nuclear  layer  the  fibre 
breaks  up  into  fine  lamellae,  which  form  a  fenestrated  or  sponge-like  tissue,  in 
which  the  rod-  and  cone-granules  are  enclosed,  and  at  the  outer  border  of  this 
layer  these  lamellae  unite  along  a  definite  line,  forming  the  mernbrana  limitans 
externa. 

Macula  Lutea  and  Fovea  Centralis. — The  structure  of  the  retina  at  the  yellow 
spot  presents  some  modifications.     In  the  macula  lutea  (1)  the  nerve-fibres  are 


Pigmentary  layer. 


Jacob's  membrane. 


•&-  Membrana  limitans  externa. 


Outer  nuclear  layer. 


Outer  molecular  layer. 


Fibre  of  Milller. 


Inner  nuclear  layer. 


Inner  molecular  layer. 


Vesicular  layer. 
Fibrous  layer. 

Membrana  limitans  interna. 
FIG.  535.— The  layers  of  the  retina  (diagrammatic).    (After  Schultze.) 

wanting  as  a  continuous  layer ;  (2)  the  vesicular  layer  consists  of  several  strata  of 
cells,  instead  of  a  single  layer;  (3)  in  Jacob's  membrane  there  are  no  rods,  but 
only  cones,  and  these  are  longer  and  narrower  than  in  other  parts ;  and  (4)  in  the 
outer  nuclear  layer  there  are  only  cone-fibres,  which  are  very  long  and  arranged  in 
curved  lines.  At  the  fovea  centralis  the  only  parts  which  exist  are  the  cones  of 
Jacob's  membrane,  the  outer  nuclear  layer,  the  cone-fibres  of  which  are  almost 
horizontal  in  direction,  and  an  exceedingly  thin  inner  granular  layer.  The  color 
of  the  spot  seems  to  imbue  all  the  layers  except  Jacob's  membrane ;  it  is  of  a  rich 
yellow,  deepest  toward  the  centre,  and  does  not  appear  to  consist  of  pigment-cells, 
but  simply  a  staining  of  the  constituent  parts. 

At  the  ora  serrata  the  layers  of  the  retina  for  the  most  part  terminate  abruptly, 
and  the  radiating  fibres  of  Muller,  covered  by  the  pigmentary  layer,  can  be  traced 
forward,  as  the  pars  ciliaris,  to  the  iris.  The  fibres  of  Muller  here  present  the 
appearance  of  columnar  epithelial  cells  arranged  in  a  single  stratum. 

The  arteria  centralis  retince  and  its  accompanying  vein  pierce  the  optic  nerve, 
and  enter  the  globe  of  the  eye  through  the  porus  opticus.  It  immediately  divides 


THE    VITREOUS   BODY.  903 

into  four  or  five  branches,  which  at  first  run  between  the  hyaloid  membrane  and 
the  nervous  layer,  but  they  soon  enter  the  latter  membrane,  and  pass  forward, 
dividing  dichotomously.  From  these  bi'anches  a  minute  capillary  plexus  is  given 
off.  which  does  not  extend  beyond  the  inner  nuclear  layer.  In  the  foetus  a  small 
vessel  passes  forward,  through  the  vitreous  humor,  to  the  posterior  surface  of  the 
capsule  of  the  lens. 

Humors  of  the  Eye. 

The  aqueous  humor  completely  fills  the  anterior  and  posterior  chambers  of  the 
eyeball.  It  is  small  in  quantity  (scarcely  exceeding,  according  to  Petit,  four  or 
five  grains  in  weight),  has  an  alkaline  reaction,  in  composition  is  little  more  than 
water,  less  than  one-fiftieth  of  its  weight  being  solid  matter,  chiefly  chloride  of 
sodium. 

The  anterior  chamber  is  a  space  bounded  in  front  by  the  cornea,  behind  by  the 
front  of  the  iris.  The  posterior  chamber  was  the  name  formerly  given  to  a  space 
which  was  believed  to  exist  between  the  iris  in  front  and  the  capsule  of  the  lens, 
its  suspensory  ligament,  and  the  ciliary  processes  behind.  It  is  now  known  that 
the  posterior  surface  of  the  iris  is  in  immediate  contact  with  the  lens  throughout 
the  greater  part  of  its  extent.  The  only  space  which  remains  to  represent  the 
posterior  chamber  is  a  narrow  chink  between  the  peripheral  part  of  the  iris,  the 
suspensory  ligament,  and  the  ciliary  processes. 

In  the  adult  these  two  chambers  communicate  through  the  pupil ;  but  in  the 
foetus  in  the  seventh  month,  Avhen  the  pupil  is  closed  by  the  membrana  pupillaris, 
the  two  chambers  are  quite  separate. 

The  Vitreous  Body. 

The  vitreous  body  forms  about  four-fifths  of  the  entire  globe.  It  fills  the  con- 
cavity of  the  retina,  and  is  hollowed  in  front  for  the  reception  of  the  lens  and  its 
capsule.  It  is  perfectly  transparent,  of  the  consistence  of  thin  jelly,  and  is  com- 
posed of  an  albuminous  fluid  enclosed  in  a  delicate  transparent  membrane,  the 
hyaloid.  This  membrane  invests  the  surface  of  the  vitreous  body ;  at  the  pars  ciliaris 
rctince  it  splits  into  two  layers,  an  anterior,  the  suspensory  ligament  of  the  lens,  and 
a  posterior,  which  passes  over  the  front  of  the  vitreous  body.  It  has  been  supposed, 
by  Hannover,  that  from  its  inner  surface  numerous  thin  lamellae  are  prolonged 
inward  in  a  radiating  manner,  forming  spaces  in  which  the  fluid  is  contained.  In 
the  adult  these  lamellae  cannot  be  detected  even  after  careful  microscopic  exami- 
nation ;  but  in  the  foetus  a  peculiar  fibrous  texture  pervades  the  mass,  the  fibres 
joining  at  numerous  points,  and  presenting  minute  nuclear  granules  at  their 
point  of  junction.  In  the  centre  of  the  vitreous  humor,  running  from  the  posi- 
tion of  the  entrance  of  the  optic  nerve  on  the  retina  to  the  posterior  surface  of  the 
lens,  is  a  canal  filled  with  fluid  and  lined  by  a  prolongation  of  the  hyaloid  mem- 
brane. This  is  the  canal  of  Stilling,  and  is  the  canal  which  in  the  embryonic 
vitreous  humor  conveyed  the  minute  artery  from  the  central  artery  of  the  retina 
to  the  back  of  the  lens.  The  fluid  from  the  vitreous  body  resembles  nearly  pure 
water ;  it  contains,  however,  some  salts  and  a  little  albumen. 

The  hyaloid  membrane  encloses  the  whole  of  the  vitreous  humor,  that  portion 
on  its  anterior  surface,  which  is  hollowed  out  for  the  reception  of  the  lens,  being 
the  posterior  layer  just  mentioned  ;  while  the  anterior  layer  is  the  suspensory 
ligament.  It  is  a  delicate  structureless  membrane,  except  where  it  forms  the  sus- 
pensory ligament,  where  it  contains  longitudinal  elastic  fibres.  Immediately 
beneath  the  hyaloid  membrane  are  found  small,  granular,  nucleated  cells  which 
are  said  to  be  possessed  of  amoeboid  movements. 

In  the  foetus  the  centre  of  the  vitreous  humor  presents  a  tubular  canal,  through 
which  a  minute  artery  passes  along  the  vitreous  body  to  the  capsule  of  the  lens. 
In  the  adult  no  vessels  penetrate  its  substance,  so  that  its  nutrition  must  be 
carried  on  by  the  vessels  of  the  retina  and  ciliary  processes  situated  upon  its 
exterior. 


904  THE    ORGANS    OF  SENSE. 


The  Crystalline  Lens  and  its  Capsule. 

The  crystalline  lens,  enclosed  in  its  capsule,  is  situated  immediately  behind 
the  pupil,  in  front  of  the  vitreous  body,  and  surrounded  by  the  ciliary  processes, 
which  slightly  overlap  its  margin. 

The  capsule  of  the  lens  is  a  transparent,  highly  elastic,  and  brittle  membrane 
which  closely  surrounds  the  lens.  It  rests,  behind,  in  a  depression  in  the  fore  part 
of  the  vitreous  body  ;  in  front  it  is  in  contact  with  the  free  border  of  the  iris,  this 
latter  receding  from  it  at  the  circumference,  thus  forming  the  posterior  chamber 
of  the  eye  ;  and  it  is  retained  in  its  position  chiefly  by  the  suspensory  ligament  of 
the  lens.  The  capsule  is  much  thicker  in  front  than  behind,  structureless  in  text- 
ure, and  when  ruptured  the  edges  roll  up  with  the  outer  surface  innermost,  like 
the  elastic  lamina  of  the  cornea.  The  anterior  surface  of  the  lens  is  connected  to 
the  inner  surface  of  the  capsule  by  a  single  layer  of  transparent,  polygonal,  nucle- 
ated cells.  At  the  circumference  of  the  lens  these  cells 
undergo  a  change  in  form  :  they  become  elongated,  and 
Babucin  states  that  he  can  trace  the  gradual  transition 
of  the  cells  into  proper  lens-fibres,  with  which  they  are 
directly  continuous.  There  is  no  epithelium  on  the 
posterior  surface. 

In  the  foetus  a  small  branch  from  the  arteria  centralis 
retinae  runs  forward,  as  already  mentioned,  through  the 
vitreous  humor  to  the  posterior  part  of  the  capsule  of  the 
lens,  where   its   branches   radiate  and  form  a  plexiform 
FIG  536.— The  crystalline     network  which    covers  its   surface,  and  they  are  continu- 
&arhgaedd)ned  and  ***        ous  round  the  margin  of  the  capsule  with  the  vessels  of 
the   pupillary  membrane   and  with  those  of  the  iris.     In 
the  adult  no  vessels  enter  its  substance. 

The  lens  is  a  transparent,  double-convex  body,  the  convexity  being  greater  on 
the  posterior  than  on  the  anterior  surface.  It  measures  about  a  third  of  an  inch 
in  the  transverse  diameter,  and  about  one-fourth  in  the  antero-posterior.  It  con- 
sists of  concentric  layers,  of  which  the  external  in  the  fresh  state  are  soft  and 
easily  detached ;  those  beneath  are  firmer,  the  central  ones  forming  a  hardened 
nucleus.  These  laminae  are  best  demonstrated  by  boiling,  or  immersion  in  alcohol. 
The  same  reagents  demonstrate  that  the  lens  consists  of  three  triangular  segments, 
the  sharp  edges  of  which  are  directed  toward  the  centre,  the  bases  toward  the 
circumference.  The  laminae  consist  of  minute  parallel  fibres  which  are  hexagonal 
prisms,  the  edges  being  dentated,  and  the  dentations  fitting  accurately  into  each 
other;  their  breadth  is  about  g-^oT^b-  of  an  inch.  They  run  from  the  sutures  or 
lines  of  junction  of  the  triangular  segments  on  the  one  surface  to  the  periphery  of 
the  lens,  and,  curving  round  its  margin,  they  terminate  at  the  line  of  junction  of 
the  segments  on  the  other.  No  fibres  pass  from  pole  to  pole,  but  they  are 
arranged  in  such  a  way  that  fibres  which  commence  near  the  pole  on  the  one 
aspect  of  the  lens — that  is  to  say,  near  the  apex  of  the  triangular  segment — 
terminate  near  the  peripheral  extremity  of  the  plane  on  the  other,  or  near  the  base 
of  the  triangular  segment,  and  vice  versa.  The  fibres  of  the  outer  layers  of  the 
lens  each  contain  a  nucleus,  which  together  form  a  layer  (nuclear  layer)  on  the 
surface  of  the  lens,  most  distinct  toward  its  circumference.  The  meridians,  or 
lines  of  junction  of  the  three  segments,  are  composed  of  an  amorphous  granular 
substance  which  sometimes  becomes  opaque,  when  the  lines  are  seen  forming  a 
distinct  star  on  the  lens.  The  lines  on  one  surface  do  not  lie  immediately  opposite 
those  on  the  other,  but  are  intermediate. 

The  changes  produced  in  the  lens  by  age  are  the  following : 
In  the  foetus  its  form  is  nearly  spherical,  its  color  of  a  slightly  reddish  tint,  it 
is  not  perfectly  transparent,  and  is  so  soft  as  to  break  down  readily  on  the  slightest 
pressure. 


THE    CRYSTALLINE  LENS   AND    ITS    CAPSULE.  905 

In  the  adult  the  posterior  surface  is  more  convex  than  the  anterior ;  it  is  color- 
less, transparent,  and  firm  in  texture. 

In  old  age  it  becomes  flattened  on  both  surfaces,  slightly  opaque,  of  an  amber 
tint,  and  increases  in  density. 

The  suspensory  ligament  of  the  lens  is  a  thin,  transparent,  membranous  struc- 
ture placed  at  first  between  the  vitreous  body  and  the  ciliary  processes  of  the 
choroid,  and  then  passing  from  these  same  processes  to  the  anterior  surface  of 
the  lens  near  its  circumference.  It  assists  in  retaining  the  lens  in  its  position. 
Its  outer  surface  presents  a  number  of  folds  or  plaitings  in  which  the  corresponding 
folds  of  the  ciliary  processes  are  received.  These  plaitings  are  arranged  round  the 
lens  in  a  radiating  form,  and  are  stained  by  the  pigment  of  the  ciliary  processes. 
The  suspensory  ligament  is  that  part  of  the  hyaloid  membrane,  which,  as  described 
above,  is  continued  forward  to  the  anterior  part  of  the  margin  of  the  lens.  It  is 
covered  on  its  outer  surface  by  the  pars  ciliaris,  or  connective-tissue  framework 
of  the  retina,  prolonged  forward  from  the  ora  serrata.  That  portion  of  this  mem- 
brane which  intervenes  between  the  ciliary  processes  and  the  capsule  of  the  lens 
forms  part  of  the  boundary  of  the  posterior  chamber  of  the  eye.  The  posterior 
surface  of  this  layer  is  turned  toward  the  vitreous  humor,  being  separated  from  it 
at  the  circumference  of  the  lens  by  a  space  called  the  canal  of  Petit. 

The  canal  of  Petit  is  about  one-tenth  of  an  inch  wide.  It  is  bounded  in  front 
by  the  suspensory  ligament;  behind  by  the  "posterior  layer"  of  the  hyaloid 
membrane,  its  base  being  formed  by  the  capsule  of  the  lens.  When  inflated  with 
air  it  is  sacculated  at  intervals,  owing  to  the  foldings  on  its  anterior  surface. 

The  arteries  of  the  globe  of  the  eye  are  the  short,  long,  and  anterior  ciliary 
arteries  and  the  arteria  centralis  retinae.  They  have  been  already  described  (see 
page  570). 

The  ciliary  veins  are  seen  on  the  outer  surface  of  the  choroid,  and  are  named, 
from  their  arrangement,  the  vence  vorticosa.  They  converge  to  four  or  five 
equidistant  trunks,  which  pierce  the  sclerotic  midway  between  the  margin  of  the 
cornea  and  the  entrance  of  the  optic  nerve.  Another  set  of  veins  accompany  the 
anterior  ciliary  arteries  and  open  into  the  ophthalmic  vein. 

The  ciliary  nerves  are  derived  from  the  nasal  branch  of  the  ophthalmic  and 
from  the  ciliary  or  ophthalmic  ganglion. 

Surgical  Anatomy. — Foreign  bodies  frequently  get  into  the  conjunctival  sac  and  cause 
great  pain,  especially  if  they  come  in  contact  with  the  corneal  surface  during  the  movements  of 
the  lid  and  the  eye  on  each  other.  The  conjunctiva  is  frequently  involved  in  severe  injuries  of 
the  eyeball,  but  is  seldom  ruptured  alone ;  the  most  common  form  of  injury  to  the  conjunctiva 
alone  is  from  a  burn,  either  from  fire,  strong  acids,  or  lime.  In  these  cases  union  is  liable  to  take 
place  between  the  eyelid  and  the  eyeball.  The  conjunctiva  is  often  the  seat  of  inflammation 
arising  from  many  different  causes,  and  the  arrangement  of  the  conjunctival  vessels  should  be 
remembered  as  affording  a  means  of  diagnosis  between  this  condition  and  injection  of  the  sclero- 
tic, which  is  present  in  inflammations  of  the  deeper  structures  of  the  globe.  The  inflamed  con- 
junctiva is  bright  red ;  the  vessels  are  large  and  tortuous,  and  greatest  at  the  circumference, 
shading  off  toward  the  corneal  margin ;  they  anastomose  freely  and  form  a  dense  network,  and 
they  can  be  emptied  or  displaced  by  gentle  pressure. 

From  a  surgical  point  of  view  the  cornea  may  be  regarded  as  consisting  of  three  layers:  (1) 
of  an  external  epithelial  layer,  developed  from  the  epiblast,  and  continuous  with  the  external 
epithelial  covering  of  the  rest  of  the  body,  and  therefore  in  its  lesions  resembling  those  of  the 
epidermis  and  superficial  layers  of  the  derma ;  (2)  of  the  cornea  proper,  derived  from  the  meso- 
blast,  and  associated  in  its  diseases  with  the  fibre-vascular  structures  of  the  body;  and  (3)  the 
posterior  elastic  layer  with  its  endothelium.  also  derived  from  the  mesoblast  and  having  the 
characters  of  a  serous  membrane,  so  that  inflammation  of  it  resembles  inflammation  of  the  other 
serous  and  synovial  membranes  of  the  body. 

The  cornea  contains  no  blood-vessels,  except  at  its  periphery,  where  numerous  delicate 
loops,  derived  from  the  anterior  ciliary  arteries,  may  be  demonstrated  on  the  anterior  surface  of 
the  cornea.  The  rest  of  the  cornea  is  nourished  by  lymph,  which  gains  access  to  the  proper  sub- 
stance of  the  cornea  and  the  posterior  layer  through  the  spaces  of  Fpntana.  This  lack  of  a 
direct  blood-supply  renders  the  cornea  very  apt  to  inflame  in  the  cachectic  and  ill-nourished.  In 
cases  of  granular  lids  there  is  a  peculiar  affection  of  the  cornea,  called  pannus,  in  which  the 
anterior  layers  of  the  cornea  become  vascularized,  and  a  rich  network  of  blood-vessels  may  be 
seen  on  the  cornea ;  and  in  interstitial  keratitis  new  vessels  extend  into  the  cornea,  giving  it  a 
pinkish  hue.  to  which  the  term  "  salmon  patch  -'  is  applied.  The  cornea  is  richly  supplied  with 


906  THE    ORGANS    OF  SENSE. 

nerves,  derived  from  the  ciliary,  which  enter  the  cornea  through  the  fore  part  of  the  sclerotic 
and  form  plexuses  in  the  stroma,  terminating  between  the  epithelial  cells  by  free  ends  or  in  cor- 
puscles. In  cases  of  glaucoma  the  ciliary  nerves  may  be  pressed  upon  as  they  course  between 
the  choroid  and  sclerotic,  and  the  cornea  becomes  anaesthetic.  The  sclerotic  has  very  few  blood- 
vessels and  nerves.  The  blood-vessels  are  derived  from  the  anterior  ciliary,  and  form  an  open 
plexus  in  its  substance.  As  they  approach  the  corneal  margin  this  arrangement  is  peculiar. 
Some  branches  pass  through  the  sclerotic  to  the  ciliary  body ;  others  become  superficial  and  lie 
in  the  episeleral  tissue,  and  form  arches,  by  anastomosing  with  each  other,  some  little  distance 
behind  the  corneal  margin.  From  these  arches  numerous  straight  vessels  are  given  off,  which 
run  forward  to  the  cornea,  forming  its  marginal  plexus.  In  inflammation  of  the  sclerotic  and 
episeleral  tissue  these  vessels  become  conspicuous,  and  form  a  pinkish  zone  of  straight  vessels 
radiating  from  the  corneal  margin,  commonly  known  as  the  zone  of  ciliary  injection.  In  inflam- 
mation of  the  iris  and  ciliary  body  this  zone  is  present,  since  the  sclerotic  speedily  becomes 
involved  when  these  structures  are  inflamed.  But  in  inflammation  of  the  cornea  the  sclerotic  is 
seldom  much  affected,  though  the  cornea  and  sclerotic  are  structurally  continuous.  This  would 
appear  to  be  due  to  the  fact  that  the  nutrition  of  the  cornea  is  derived  from  a  different  source 
from  that  of  the  sclerotic.  The  sclerotic  may  be  ruptured  subcutaneously  without  any  laceration  of 
the  conjunctiva,  and  the  rupture  usually  occurs  near  the  corneal  margin,  where  the  tunic  is  thin- 
nest. It  may  be  complicated  with  lesions  of  adjacent  parts — laceration  of  the  choroid,  retina, 
iris,  or  suspensory  ligament  of  the  lens — and  is  then  often  attended  with  haemorrhage  into  the 
anterior  chamber,  which  masks  the  nature  of  the  injury.  In  some  cases  the  lens  has  escaped 
through  the  rent  in  the  sclerotic,  and  has  been  found  under  the  conjunctiva.  Wounds  of  the 
sclerotic  are  always  dangerous,  and  are  often  followed  by  inflammation,  suppuration,  and  by 
sympathetic  ophthalmia. 

The  function  of  the  choroid  is  to  provide  nutrition  for  the  retina  and  to  convey  vessels  and 
nerves  to  the  ciliary  body  and  iris.  Inflammation  of  the  choroid  is  therefore  followed  by  grave 
disturbance  in  the  nutrition  of  the  retina,  and  is  attended  with  early  interference  with  vision. 
In  its  diseases  it  bears  a  considerable  analogy  to  those  which  affect  the  skin,  and,  like  it, 
is  one  of  the  places  from  which  melanotic  sarcomata  may  grow.  These  tumors  contain  a  large 
amount  of  pigment  in  their  cells,  and  grow  only  from  those  parts  where  pigment  is  naturally 
present.  The  choroid  may  be  ruptured  without  injury  to  the  other  tunics,  as  well  as  participa- 
ting in  general  injuries  of  the  eyeball.  In  cases  of  uncomplicated  rupture  the  injury  is  usually 
at  its  posterior  part,  and  is  the  result  of  a  blow  on  the  front  of  the  eye.  It  is  attended  by  con- 
siderable haemorrhage,  which  for  a  time  may  obscure  vision,  but  in  most  cases  this  is  restored  as 
soon  as  the  blood  is  absorbed. 

The  iris  is  the  seat  of  a  malformation,  termed  coloboma,  which  consists  in  a  deficiency  or 
cleft,  which  in  a  great  number  of  cases  is  clearly  due  to  an  arrest  in  development.  In  these  cases 
it  is  found  at  the  lower  aspect,  extending  directly  downward  from  the  pupil,  and  the  gap 
frequently  extends  through  the  choroid  to  the  entrance  of  the  optic  nerve.  In  some  rarer  cases 
the  gap  is  found  in  other  parts  of  the  iris,  and  is  then  not  associated  with  any  deficiency  of  the 
choroid.  The  iris  is  abundantly  supplied  with  blood-vessels  and  nerves,  and  is  therefore  very 
prone  to  become  inflamed.  And  when  inflamed,  in  consequence  of  the  intimate  relationship 
which  exists  between  the  vessels  of  the  iris  and  choroid  this  latter  tunic  is  very  apt  to  participate 
in  the  inflammation.  And,  in  addition,  inflammation  of  adjacent  structures,  the  cornea  and 
sclerotic,  is  apt  to  spread  into  the  iris.  The  iris  is  covered  with  epithelium,  and  partakes  of  the 
character  of  a  serous  membrane,  and,  like  these  structures,  is  liable  to  pour  out  a  plastic  exuda- 
tion when  inflamed,  and  contract  adhesions,  either  to  the  cornea  in  front  (synechia  anterior),  or 
to  the  capsule  of  the  lens  behind  (synechia  posterior).  In  iritis  the  lens  may  become  involved, 
and  the  condition  known  as  secondary  cataract  may  be  set  up.  Tumors  occasionally  commence  in 
the  iris ;  of  these,  cysts,  which  are  usually  congenital  and  sarcomatous  tumors,  are  the 
most  common  and  require  removal.  Gumrnata  are  not  unfrequently  found  in  this  situa- 
tion. In  some  forms  of  injury  of  the  eyeball,  as  the  impact  of  a  spent  shot,  the  rebound  of  a 
twig,  or  a  blow  with  a  whip,  the  iris  may  be  detached  from  the  Ciliary  muscle,  the  amount  of 
detachment  varying  from  the  slightest  degree  to  the  separation  of  the  whole  iris  from  its  ciliary 
connection. 

•  The  retina,  with  the  exception  of  its  pigment-layer  and  its  vessels,  is  perfectly  transparent, 
so  as  to  be  invisible  when  examined  by  the  ophthalmoscope,  so  that  its  diseased  conditions  are 
recognized  by  its  loss  of  transparency.  In  retinitis,  for  instance,  there  is  more  or  less  dense  and 
extensive  opacity  of  its  structure,  and  not  unfrequently  extravasations  of  blood  into  its  sub- 
stance. Haemorrhages  may  also  take  place  into  the  retina  from  rupture  of  a  blood-vessel  with- 
out inflammation. 

The  retina  may  become  displaced  from  effusion  of  serum  between  it  and  the  choroid  or  by 
blows  on  the  eyeball,  or  may  occur  without  apparent  cause  in  progressive  myopia,  and  in  this 
case  the  ophthalmoscope  shows  an  opaque,  tremulous  cloud.  Glioma,  a  form  of  sarcoma,  and 
essentially  a  disease  of  early  life,  is  occasionally  met  with  in  connection  with  the  retina. 

The  lens  has  no  blood-vessels,  nerves,  or  connective  tissue  in  its  structure,  and  therefore  is 
not  subject  to  those  morbid  changes  to  which  tissues  containing  these  structures  are  liable.  It 
does,  however,  present  certain  morbid  or  abnormal  conditions  of  various  kinds.  Thus,  variations 
in  shape,  absence  of  the  whole  or  a  part  of  the  lens,  and  displacements  are  amongst  its  congeni- 
tal defects.  Opacities  may  occur  from  injury,  senile  changes,  malnutrition,  or  errors  in  growth 
or  development.  Senile  changes  may  take  place  in  the  lens,  impairing  its  elasticity  and  render- 


THE   APPENDAGES    OF    THE   EYE.  907 

iiiir  it  harder  than  in  youth,  so  that  its  curvature  can  only  be  altered  to  a  limited  extent  by  the 
Ciliary  muscle.  And,  finally,  the  lens  may  be  dislocated  or  displaced  by  blows  upon  the  eyeball, 
and  its  relations  to  surrounding  structures  altered  by  adhesions  or  the  pressure  of  new  growths. 
There  are  two  particular  regions  of  the  eye  which  require  special  notice :  one  of  these  is 
known  as  the  "  filtration  area,"  and  the  other  as  the  "  dangerous  area."  The  filtration  area  is 
the  circumcoraeal  zone  immediately  in  front  of  the  iris.  Here  are  situated  the  cavernous  spaces 
of  Fontana.  which  communicate  with  the  canal  of  Schlemm,  through  which  the  chief  transuda- 
tion  of  fluid  from  the  eye  is  now  believed  to  take  place.  The  dangerous  area  of  the  eye  is  the 
region  in  the  neighborhood  of  the  ciliary  body,  and  wounds  or  injuries  in  this  situation  are 
peculiarly  dangerous  ;  for  inflammation  of  the  ciliary  body  is  liable  to  spread  to  many  of  the 
other  structures  of  the  eye,  especially  to  the  iris  and  chorpid,  which  are  intimately  connected  by 
nervous  and  vascular  supplies.  Moreover,  wounds  which  involve  the  ciliary  region  are  especially 
liable  to  be  followed  by  sympathetic  ophthalmia,  in  which  destructive  inflammation  of  one  eye 
is  excited  by  some  irritation  in  the  other. 

The  Appendages  of  the  Eye. 

The  appendages  of  the  eye  (tutamina  oculi)  include  the  eyebrows,  the  eyelids, 
the  conjunctiva,  and  the  lachrymal  apparatus — viz.  the  lachrymal  gland,  the 
lachrymal  sac,  and  the  nasal  duct. 

The  eyebrows  (supercilid)  are  two  arched  eminences  of  integument  which 
surmount  the  upper  circumference  of  the  orbit  on  each  side,  and  support  numer- 
ous short,  thick  hairs,  directed  obliquely  on  the  surface.  In  structure  the  eye- 
brows consist  of  thickened  integument,  connected  beneath  with  the  Orbicularis 
palpebrarum,  Corrugator  supercilii,  and  Occipito-frontalis  muscles.  These  mus- 
cles serve,  by  their  action  on  this  part,  to  control  to  a  certain  extent  the  amount 
of  light  admitted  into  the  eye. 

The  eyelids  (palpebrce)  are  two  thin,  movable  folds  placed  in  front  of  the 
eve.  protecting  it  from  injury  by  their  closure.  The  upper  lid  is  the  larger 
and  the  more  movable  of  the  two,  and  is  furnished  with  a  separate  elevator 
muscle,  the  Levator  palpebrce  superioris.  When  the  eyelids  are  opened  an 
elliptical  space  (fissura  palpebraruni)  is  left  between  their  margins,  the  angles 
of  which  correspond  to  the  junction  of  the  upper  and  lower  lids,  and  are 
called  eanthi. 

The  outer  canthus  is  more  acute  than  the  inner,  and  the  lids  here  lie  in  close 
contact  with  the  globe ;  but  the  inner  canthus  is  prolonged  for  a  short  distance 
inward  toward  the  nose,  and  the  two  lids  are  separated  by  a  triangular  space,  the 
lurus  lachrymalis.  At  the  commencement  of  the  lacus  lachrymalis,  on  the  margin 
of  each  eyelid,  is  a  small  conical  elevation,  the  lachrymal  papilla,  or  tubercle,  the 
apex  of  which  is  pierced  by  a  small  orifice,  the  punctum  lachrymale,  the  com- 
mencement of  the  lachrymal  canal. 

The  eyelashes  (cilia)  are  attached  to  the  free  edges  of  the  eyelids  ;  they  are 
short,  thick,  curved  hairs,  arranged  in  a  double  or  triple  row  at  the  margin  of  the 
lids :  those  of  the  upper  lid,  more  numerous  and  longer  than  the  lower,  curve 
upward ;  those  of  the  lower  lid  curve  downward,  so  that  they  do  not  interlace  in 
closing  the  lids.  Near  the  attachment  of  the  eyelashes  are  the  openings  of  a 
number  of  glands,  glands  of  Mohl,  arranged  in  several  rows  close  to  the  free 
margin  of  the  lid.  They  resemble  in  structure  a  portion  of  a  sweat-gland,  and 
are  regarded  as  the  modified  sweat-glands  of  this  region. 

Structure  of  the  Eyelids. — The  eyelids  are  composed  of  the  following  struc- 
tures, taken  in  their  order  from  without  inward  : 

Integument,  areolar  tissue,  fibres  of  the  Orbicularis  muscle,  tarsal  plate 
(cartilage),  and  its  ligament,  Meibomian  glands  and  conjunctiva.  The  upper  lid 
has,  in  addition,  the  aponeurosis  of  the  Levator  palpebrse. 

The  integument  is  extremely  thin,  and  continuous  at  the  margin  of  the  lids 
with  the  conjunctiva. 

The  subcutaneous  areolar  tissue  is  very  lax  and  delicate,  seldom  contains  any 
fat,  and  is  extremely  liable  to  serous  infiltration. 

The  fibres  of  the  Orbicularis  muscle,  where  they  cover  the  palpebrae,  are  thin, 
pale  in  color,  and  possess  an  involuntary  action. 


908  THE    ORGANS    OF  SENSE. 

The  tarsal plates  (cartilages} l  are  two  thin  elongated  plates  of  dense  connect- 
ive tissue  about  an  inch  in  length.  They  are  placed  one  in  each  lid,  contribut- 
ing to  their  form  and  support. 

The  superior,  the  larger,  is  of  a  semilunar  form,  about  one-third  of  an  inch  in 
breadth  at  the  centre,  and  becoming  gradually  narrowed  at  each  extremity.  Into 
the  anterior  surface  of  this  plate  the  aponeurosis  of  the  Levator  palpebrse  is 
attached. 

The  inferior  tarsal  plate,  the  smaller,  is  thinner  and  of  an  elliptical  form. 

The  free  or  ciliary  margin  of  these  plates  is  thick,  and  presents  a  perfectly 
straight  edge.  The  attached  or  orbital  margin  is  connected  to  the  circumference 
of  the  orbit  by  the  fibrous  membrane  of  the  lids  with  which  it  is  continuous.  The 
outer  angle  of  each  plate  is  attached  to  the  malar  bone  by  the  external  palpebral 
or  tarsal  ligament.  The  inner  angles  of  the  two  plates  terminate  at  the  com- 
mencement of  the  lacus  lachrymalis,  being  fixed  to  the  margins  of  the  orbit  by 
the  tendo  oculi. 

The  tarsal  ligament,  or  fibrous  membrane  of  the  lids,  is  a  layer  of  fibrous 
membrane  beneath  the  Orbicularis,  attached  marginally  to  the  edge  of  the  orbit, 
where  it  becomes  continuous  with  the  periosteum,  and  centrally  to  the  tarsal 
plate,  near  its  ciliary  margin,  with  the  tissue  of  which  it  is  continuous.  It  is 
thickest  and  densest  at  the  outer  part  of  the  orbit.  Upon  its  under  surface  is  a 
layer  of  unstriped  muscle,  which  in  the  upper  lid  passes  from  the  aponeurosis  of 
the  Levator  palpebrse  muscle  to  the  tarsal  plate.  This  ligament  serves  to  support 
the  eyelids,  and  retains  the  tarsal  plates  in  their  position. 

The  Meibomian  glands  (Fig.  537)  are  situated  upon  the  inner  surface  of  the 
eyelids  between  the  tarsal  plates  and  conjunctiva,  and  may  be  distinctly  seen 
through  the  mucous  membrane  on  everting  the  eyelids,  presenting  the  appear- 
ance of  parallel  strings  of  pearls.  They  are  about  thirty  in  number  in  the  upper 
eyelid,  and  somewhat  fewer  in  the  lower.  They  are  imbedded  in  grooves  in  the 
inner  surface  of  the  tarsal  plates,  and  correspond  in  length  with  the  breadth  of 
each  plate  ;  they  are,  consequently,  longer  in  the  upper  than  in  the  lower  eyelid. 
Their  ducts  open  on  the  free  margin  of  the  lids  by  minute  foramina,  which  cor- 
respond in  number  to  the  follicles.  The  peculiar  parallel  arrangement  of  these 
glands,  side  by  side,  forms  a  smooth  layer  adapted  to  the  surface  of  the  globe, 
over  which  they  constantly  glide.  The  use  of  their  secretion  is  to  prevent  adhe- 
sions of  the  lids. 

Structure  of  the  Meibomian  G-lands. — These  glands  are  a  variety  of  the  cuta- 
neous sebaceous  glands,  each  consisting  of  a  single  straight  tube  or  follicle,  hav- 
ing a  caecal  termination,  and  with  numerous  small  secondary  follicles  opening 
into  it.  The  tubes  consist  of  basement  membrane,  covered  by  a  layer  of  scaly 
epithelium ;  the  secondary  follicles  are  lined  by  a  layer  of  polyhedral  cells  con- 
tinuous with  the  cells  of  the  tube.  The  remainder  of  the  follicle  is  filled  with 
large  polyhedral  cells  charged  with  fat.  They  are  thus  identical  in  structure 
with  the  sebaceous  glands. 

The  conjunctiva  is  the  mucous  membrane  of  the  eye.  It  lines  the  inner  surface 
of  the  eyelids,  and  is  reflected  over  the  fore  part  of  the  sclerotic  and  cornea.  In 
each  of  these  situations  its  structure  presents  some  peculiarities. 

The  palpebral  portion  of  the  conjunctiva  is  thick,  opaque,  highly  vascular,  and 
covered  with  numerous  papillae,  its  deeper  parts  presenting  a  considerable  amount 
of  lymphoid  tissue.  At  the  margin  of  the  lids  it  becomes  continuous  with  the 
lining  membrane  of  the  ducts  of  the  Meibomian  glands,  and,  through  the  lachrymal 
canals,  with  the  lining  membrane  of  the  lachrymal  sac  and  nasal  duct.  At  the 
outer  angle  of  the  upper  lid  it  may  be  traced  along  the  lachrymal  ducts  into  the 
lachrymal  gland,  and  at  the  inner  angle  of  the  eye  it  forms  a  semilunar  fold, 
the  plica  semilunaris.  The  folds  formed  by  the  reflection  of  the  conjunctiva  from 
the  lids  on  to  the  eye  are  called  the  superior  and  inferior  palpebral  folds,  the 

'Recent  observations  have  proved  that  the  so-cnlled  "tarsal  cartilages"  do  not  contain  any  carti- 
lage-cells, and  that  the  name  is  a  misnomer. 


THE   LACHRYMAL    APPARATUS. 


909 


former  being  the  deeper  of  the  two.  Upon  the  sclerotic  the  conjunctiva  is  loosely 
connected  to  the  globe:  it  becomes  thinner,  loses  its  papillary  structure,  is 
transparent,  and  only  slightly  vascular  in  health.  Upon  the  cornea  the  con- 
junctiva consists  only  of  epithelium,  constituting  the  anterior  layer  of  the  cornea 
(conj unc rival  epithelium)  already  described  (see  page  893).  Lymphatics  arise  in  the 
conjunctiva  in  a  delicate  zone  around  the  cornea,  from  which  the  vessels  run  to 
the  ocular  conjunctiva. 

At  the  point  of  reflection  of  the  conjunctiva  from  the  lid  on  to  the  globe  of  the 
eye.  termed  the/"/-///'./-  ••••njunctivce,  are  a  number  of  mucous  glands  which  are  much 
convoluted.  They  are  chiefly  found  in  the  upper  lid.  Other  glands,  analogous  to 


Piincta  lachrymalia. 


FIG.  537.— The  Meibomian  glands,  etc..  seen  from  the  inner  surface  of  the  eyelids. 

lymphoid  follicles,  and  called  by  Henle  trachoma  glands,  are  found  in  the  con- 
junctiva, and.  according  to  Strohmeyer,  are  chiefly  situated  near  the  inner  canthus 
of  the  eye.  They  were  first  described  by  Brush,  in  his  description  of  Peyer's 
patches  of  the  small  intestines,  as  "identical  structures  existing  in  the  under  eye- 
lid of  the  ox." 

The  nerves  in  the  conjunctiva  are  numerous  and  form  rich  plexuses.  According 
to  Krause.  they  terminate  in  a  peculiar  form  of  tactile  corpuscle,  which  he  terms 
the  "  terminal  bulb." 

The  caruncula  lachrymaUs  is  a  small,  reddish,  conical-shaped  body,  situated  at 
the  inner  canthus  of  the  eye.  and  filling  up  the  small  triangular  space  in  this  situa- 
tion, the  lacus  lachrymdti*.  It  consists  of  a  cluster  of  follicles  similar  in  structure 
to  the  Meibomian,  covered  with  mucous  membrane,  and  is  the  source  of  the  whitish 
secretion  which  constantly  collects  at  the  inner  angle  of  the  eye.  A  few  slender 
hairs  are  attached  to  its  surface.  On  the  outer  side  of  the  caruncula  is  a  slight 
semilunar  fold  of  mucous  membrane,  the  concavity  of  which  is  directed  toward  the 
cornea  :  it  is  called  the  plica  semilunaris.  Miiller  found  smooth  muscular  fibres 
in  this  fold,  and  in  some  of  the  domesticated  animals  a  thin  plate  of  cartilage  has 
been  discovered.  This  structure  is  considered  to  be  the  rudiment  of  the  third  eyelid 
in  birds,  the  membrana  nictitans. 

The  Lachrymal  Apparatus  (Fig.  538). 

The  lachrymal  apparatus  consists  of  the  lachrymal  gland,  which  secretes  the 
tears,  and  its  excretory  ducts,  which  convey  the  fluid  to  the  surface  of  the  eye. 
This  fluid  is  carried  away  by  the  lachrymal  canals  into  the  lachrymal  sac,  and  along 
the  nasal  duct  into  the  cavity  of  the  nose. 

The  lachrymal  gland  is  lodged  in  a  depression  at  the  outer  angle  of  the  orbit, 
on  the  inner  side  of  the  external  angular  process  of  the  frontal  bone.  It  is  of  an 


910  THE    ORGANS    OF  SENSE. 

oval  form,  about  the  size  and  shape  of  an  almond.  Its  upper  convex  surface  is  in 
contact  with  the  periosteum  of  the  orbit,  to  which  it  is  connected  by  a  few  fibrous 
bands.  Its  under  concave  surface  rests  upon  the  convexity  of  the  eyeball  and 
upon  the  Superior  and  External  recti  muscles.  Its  vessels  and  nerves  enter  its 
posterior  border,  whilst  its  anterior  margin  is  closely  adherent  to  the  back  part  of 
the  upper  eyelid,  where  it  is  covered  to  a  slight  extent  by  the  reflection  of  the  con- 
junctiva.  The  fore  part  of  the  gland  is  separated  from  the  rest  by  a  fibrous  septum  ; 
hence  it  is  sometimes  described  as  a  separate  lobe,  called  the  palpebral  portion  of 
the  gland  (accessory  gland  of  Rosenmuller).  Its  ducts,  about  seven  in  number, 
run  obliquely  beneath  the  mucous  membrane  for  a  short  distance,  and,  separating 
from  each  other,  open  by  a  series  of  minute  orifices  on  the  upper  and  outer  half 


FIG.  538.— The  lachrymal  apparatus.    Right  side. 

of  the  conjunctiva  near  its  reflection  on  to  the  globe.  These  orifices  are  arranged 
in  a  row,  so  as  to  disperse  the  secretion  over  the  surface  of  the  membrane. 

Structure  of  the  Lachrymal  Grland. — In  structure  and  general  appearance  the 
lachrymal  resembles  the  serous  salivary  glands  (page  946).  In  the  recent  state  the 
cells  are  so  crowded  with  granules  that  their  limits  can  hardly  be  defined.  They 
contain  an  oval  nucleus,  and  the  cell-protoplasm  is  finely  fibrillated. 

The  lachrymal  canals  commence  at  the  minute  orifices,  puncta  lachrymalia, 
on  the  summit  of  a  small  conical  elevation,  the  lachrymal  papilla,  seen  on  the 
margin  of  the  lids  at  the  oute*r  extremity  of  the  lacus  lachrymalis.  The  superior 
canal,  the  smaller  and  shorter  of  the  two,  at  first  ascends,  and  then  bends  at  an 
acute  angle,  and  passes  inward  and  downward  to  the  lachrymal  sac.  The 
inferior  canal  at  first  descends,  and  then,  abruptly  changing  its  course,  passes 
almost  horizontally  inward  to  the  lachrymal  sac.  These  canals  are  dense  and 
elastic  in  structure  and  somewhat  dilated  at  their  angle.  The  mucous  membrane 
is  covered  with  scaly  epithelium. 

The  lachrymal  sac  is  the  upper  dilated  extremity  of  the  nasal  duct,  and  is 
lodged  in  a  deep  groove  formed  by  the  lachrymal  bone  and  nasal  process  of  the 
superior  maxillary.  It  is  oval  in  form,  its  upper  extremity  being  closed  in  and 
rounded,  whilst  below  it  is  continued  into  the  nasal  duct.  It  is  covered  by  a  fibrous 
expansion  derived  from  the  tendo  oculi.  and  on  the  inner  side  it  is  crossed  by  the 
Tensor  tarsi  muscle  (Horner's  muscle,  page  395),  which  is  attached  to  the  ridge 
on  the  lachrymal  bone. 

Structure. — It  consists  of  a  fibrous  elastic  coat,  lined  internally  by  mucous 
membrane,  the  latter  being  continuous,  through  the  lachrymal  canals,  with  the 
mucous  lining  of  the  conjunctiva,  and,  through  the  nasal  duct,  with  the  pituitary 
membrane  of  the  nose. 


THE  LACHRYMAL    APPARATUS.  911 

The  nasal  duct  is  a  membranous  canal,  about  three-quarters  of  an  inch  in 
length,  which  extends  from  the  lower  part  of  the  lachrymal  sac  to  the  inferior 
meatus  of  the  nose,  where  it  terminates  by  a  somewhat  expanded  orifice,  provided 
with  an  imperfect  valve,  the  valve  of  Hasner,  formed  by  the  mucous  membrane.  It 
is  contained  in  an  osseous  canal  formed  by  the  superior  maxillary,  the  lachrymal,  and 
the  inferior  turbinated  bones,  is  narrower  in  the  middle  than  at  each  extremity, 
and  takes  a  direction  downward,  backward,  and  a  little  outward.  It  is  lined 
by  mucous  membrane,  which  is  continuous  below  with  the  pituitary  lining  of  the 
nose.  This  membrane  in  the  lachrymal  sac  and  nasal  duct  is  covered  with  ciliated 
epithelium  as  in  the  nose. 

Surface  Form. — The  palpebral  fissure,  or  opening  between  the  eyelids,  is  elliptical  in  shape, 
and  differs  in  size  in  different  individuals  and  in  different  races  of  mankind.  In  the  Mongolian 
races,  for  instance,  the  opening  is  very  small,  merely  a  narrow  fissure,  and  this  makes  the  eye- 
ball appear  small  in  these  races,  whereas  the  size  of  the  eye  is  relatively  very  constant.  The 
normal  direction  of  the  fissure  is  slightly  oblique,  in  a  direction  upward  and  outward,  so  that  the 
outer  angle  is  on  a  slightly  higher  level  than  the  inner.  This  is  especially  noticeable  in  the  Mon- 
golian races,  in  whom,  owing  to  the  upward  projection  of  the  malar  bone  and  the  shortness  of 
the  external  angular  process  of  the  frontal  bone,  the  tarsal  plate  of  the  upper  lid  is  raised  at  its 
outer  part  and  gives  an  oblique  direction  to  the  palpebral  fissure. 

When  the  eyes  are  directed  forward,  as  in  ordinary  vision,  the  upper  part  of  the  cornea  is 
covered  by  the  upper  lid.  and  the  lower  margin  of  the  cornea  corresponds  to  the  level  of  the 
lower  lid.  so  that  about  the  lower  three-fourths  of  the  cornea  is  exposed  under  ordinary  circum- 
stances. On  the  margins  of  the  lids,  about  a  quarter  of  an  inch  from  the  inner  canthus.  are  two 
small  openings,  the  puncta  lachrymalia,  the  commencement  of  the  lachrymal  canals.  They  are 
best  seen  by  everting  the  eyelids.  In  the  natural  condition  they  are  in  contact  with  the  con- 
junctiva of  the  eyeball,  and  are  maintained  in  this  position  by  the  Tensor  tarsi  muscle,  so  that 
the  tears  running  over  the  surface  of  the  globe  easily  find  their  way  into  the  lachrymal  canals. 
The  position  of  the  lachrymal  sac  into  which  the  canals  open  is  indicated  by  a  little  tubercle 
(page  224).  which  is  plainly  to  be  felt  on  the  lower  margin  of  the  orbit.  The  lachrymal  sac  lies 
immediately  above  and  to  the  inner  side  of  this  tubercle,  and  a  knife  passed  through  the  skin 
in  this  situation  would  open  the  cavity.  The  position  of  the  lachrymal  sac  may  also  be  indicated 
by  the  tendp  oculi  or  internal  tarsal  ligament.  If  both  lids  be  drawn  outward,  so  as  to  tense  the 
skin  at  the  inner  angle,  a  prominent  cord  will  be  seen  beneath  the  tightened  skin.  This  is  the 
tendo  oculi.  which  lies  immediately  over  the  lachrymal  sac,  bisecting  it,  and  thus  forming  a  use- 
ful guide  to  its  situation.  A  knife  entered  immediately  beneath  the  tense  cord  would  open  the 
lower  part  of  the  sac.  A  probe  introduced  through  this  opening  can  be  readily  passed  down- 
ward through  the  duct  into  the  inferior  meatus  of  the  nose.  The  direction  of  the  duct  is  down- 
ward, outward,  and  backward,  and  this  course  should  be  borne  in  mind  in  passing  the  probe, 
otherwise  the  point  may  be  driven  through  the  thin  bony  walls  of  the  canal.  A  convenient 
plan  is  to  direct  the  probe  in  such  a  manner  that  if  it  were  pushed  onward  it  would  strike  the 
first  molar  tooth  of  the  lower  jaw  on  the  same  side  of  the  body.  In  other  words,  the  surgeon 
standing  in  front  of  his  patient  should  carry  in  his  mind  the  position  of  the  first  molar  tooth, 
and  should  push  his  probe  onward  in  such  a  way  as  if  he  desired  to  reach  this  structure. 

Beneath  the  internal  angular  process  of  the  frontal  bone  the  pulley  of  the  Superior  oblique 
muscle  of  the  eye  can  be  plainly  felt  by  pushins  the  finger  backward  between  the  upper  and 
inner  angle  of  the  eye  and  the  roof  of  the  orbit ;  passing  backward  and  outward  from  this 
pulley,  the  tendon  can  be  felt  for  a  short  distance. 

Surgical  Anatomy. — The  eyelids  are  composed  of  various  tissues,  and  consequently  are 
liable  to  a  variety  of  diseases.  The  skin  which  covers  them  is  exceedingly  thin  and  delicate,  and 
is  supported  on  a  quantity  of  loose  and  lax  subcutaneous  tissue  which  contains  no  fat.  In  conse- 
quence of  this  it  is  very  freely  movable,  and  is  liable  to  be  drawn  down  by  the  contraction  of 
neighboring  cicatrices,  and  thus  produce  an  eversion  of  the  lid  known  as  ectropion.  Inversion 
of  the  lids  (entropion)  from  spasm  of  the  Orbicularis  palpebrarum  or  from  chronic  inflammation 
of  the  palpebral  conjunctiva  may  also  occur.  The  eyelids  are  richly  supplied  with  blood,  and  are 
often  the  seat  of  vascular  growths,  such  as  naevi.  Rodent  ulcer  also  frequently  commences  in 
this  situation.  The  loose  cellular  tissue  beneath  the  skin  is  liable  to  become  extensively  infil- 
trated either  with  blood  or  inflammatory  products,  producing  very  great  swelling.  Even  from 
very  slight  injuries  to  this  tissue  the  extravasation  of  blood  may  be  so  great  as  to  produce  consid- 
erable swelling  of  the  lids  and  complete  closure  of  the  eye,  and  the  same  is  the  case  when  inflam- 
matory products  are  poured  out.  The  follicles  of  the  eyelashes  or  the  sebaceous  glands  associated 
with  these  follicles  may  be  the  seat  of  inflammation,  constituting  the  ordinary  "sty."  The 
Meiboinian  glands  are  affected  in  the  so-called  "  tarsal  tumor  ;  "  the  tumor,  according  to  some, 
being  caused  by  the  retained  secretion  of  these  glands ;  by  others  it  is  believed  to  be  a  neoplasm 
connected  with  the  gland.  The  ciliary  follicles  are  liable  to  become  inflamed,  constituting  the 
disease  known  as  blepharitis  dliaris,  or  "blear-eye."  Irregular  or  disorderly  growth  of  the  eye- 
lashes not  unfrequently  occurs,  some  of  them  being  turned  toward  the  eyeball  and  producing 
inflammation  and  ulceration  of  the  cornea,  and  possibly  eventually  complete  destruction  of  the 
eye.  The  Orbicularis  palpebrarum  may  be  the  seat  of  spasm,  either  in  the  form  of  slight  quiv- 


912  THE    ORGANS   OF  SENSE. 

ering  of  the  lids  or  repeated  twitchings,  most  commonly  due  to  errors  of  refraction  in  children, 
or  more  continuous  spasm,  due  to  some  irritation  of  the  fifth  or  seventh  cranial  nerve.  The 
Orbicularis  may  be  paralyzed,  generally  associated  with  paralysis  of  the  other  facial  muscles. 
Under  these  circumstances  the  patient  is  unable  to  close  the  lids,  and,  if  he  attempts  to  do  so, 
rolls  the  eyeball  upward  under  the  upper  lid.  The  tears  overflow  from  displacement  of  the 
lower  lid,  and  the  conjunctiva  and  cornea,  being  constantly  exposed  and  the  patient  being  unable 
to  wink,  become  irritated  from  dust  and  foreign  bodies.  In  paralysis  of  the  Levator  palpebrae 
superioris  there  is  drooping  of  the  upper  eyelid  and  other  symptoms  of  implication  of  the  third 
nerve.  The  eyelids  may  be  the  seat  of  bruises,  wounds,  or  burns.  In  these  latter  injuries  adhe- 
sions of  the  margins  of  the  lids  to  each  other  or  adhesion  of  the  lids  to  the  globe  may  take 
place.  The  eyelids  are  sometimes  the  seat  of  emphysema  after  fracture  of  some  of  the  thin 
bones  forming  the  inner  wall  of  the  orbit.  If  shortly  after  such  an  injury  the  patient  blows  his 
nose,  air  is  forced  from  the  nostril  through  the  lacerated  structures  into  the  connective  tissue  of 
the  eyelids,  which  suddenly  swell  up  and  present  the  peculiar  crackling  characteristic  of  tin's 
affection. 

The  lachrymal  gland  is  occasionally,  though  rarely,  the  seat  of  inflammation,  either  acute 
or  chronic ;  it  is  also  sometimes  the  seat  of  tumors,  benign  or  malignant,  and  for  these  may 
require  removal.  This  may  be  done  by  an  incision  through  the  skin  just  below  the  eyebrow  ; 
and  the  gland,  being  invested  with  a  special  capsule  of  its  own,  may  be  isolated  and  removed 
without  opening  the  general  cavity  of  the  orbit.  The  canaliculi  may  be  obstructed,  either  as  a 
congenital  defect  or  by  some  foreign  body,  as  an  eyelash  or  a  dacryolith,  causing  the  tears  to  run 
over  the  cheek.  The  canaliculi  may  also  become  occluded  as  the  result  of  burns  or  injury ;  over- 
flow of  the  tears  may  in  addition  result  from  deviation  of  the  puncta  or  from  chronic  inflamma- 
tion of  the  lachrymal  sac.  This  latter  condition  is  set  up  by  some  obstruction  to  the  nasal  duct 
frequently  occurring  in  tubercular  subjects.  In  consequence  of  this  the  tears  and  mucus  accumu- 
late in  the  lachrymal  sac,  distending  it.  Suppuration  in  the  lachrymal  sac  is  sometimes  met 
with  ;  this  may  be  the  sequel  of  a  chronic  inflammation  ;  or  may  occur  after  some  of  the  erup- 
tive fevers  in  cases  where  the  lachrymal  passages  were  previously  quite  healthy.  It  may  lead  to 
lachrymal  fistula. 

THE  EAR. 

The  organ  of  hearing  is  divisible  into  three  parts — the  external  ear,  the  middle 
ear  or  tympanum,  and  the  internal  ear  or  labyrinth. 

The  external  ear  consists  of  an  expanded  portion  named  pinna  or  auricle,  and 
the  auditory  canal,  or  meatus.  The  former  serves  to  collect  the  vibrations  of  the  air 
by  which  sound  is  produced ;  the  latter  conducts  those  vibrations  to  the  tympanum. 

The  pinna,  or  auricle  (Fig.  539),  is  of  an  ovoid  form,  with  its  larger  end  directed 
upward.  Its  outer  surface  is  irregularly  concave,  directed  slightly  forward,  and 
presents  numerous  eminences  and  depressions  which  result  from  the  foldings  of  its 
nbro-cartilaginous  element.  To  each  of  these  names  have  been  assigned.  Thus 
the  external  prominent  rim  of  the  auricle  is  called  the  helix.  Another  curved 
prominence,  parallel  with  and  in  front  of  the  helix,  is  called  the  antihelix ;  this 
bifurcates  above,  so  as  to  enclose  a  triangular  depression,  the  fossa  of  the.  antihelix. 
The  narrow  curved  depression  between  the  helix  and  antihelix  is  called  the  fossa 
of  the  helix  (fossa  innominata  or  scaphoidea) ;  the  antihelix  describes  a  curve 
round  a  deep,  capacious  cavity,  the  concha,  which  is  partially  divided  into  two 
parts  by  the  commencement  of  the  helix.  In  front  of  the  concha,  and  projecting 
backward  over  the  meatus,  is  a  small  pointed  eminence,  the  tragns,  so  called 
from  its  being  generally  covered  on  its  under  surface  with  a  tuft  of  hair  resem- 
bling a  goat's  beard.  Opposite  the  tragus,  and  separated  from  it  by  a  deep  notch 
(incisura  intertragica)  is  a  small  tubercle,  the  antitragus.  Below  this  is  the  lobule, 
composed  of  tough  areolar  and  adipose  tissue,  wanting  the  firmness  and  elasticity 
of  the  rest  of  the  pinna. 

Structure  of  the  Pinna. — The  pinna  is  composed  of  a  thin  plate  of  yellow  fibro- 
cartilage  covered  with  integument,  and  connected  to  the  surrounding  parts  by  the 
extrinsic  ligaments  and  muscles,  and  to  the  commencement  of  the  external 
auditory  canal. 

The  integument  is  thin,  closely  adherent  to  the  cartilage,  and  furnished  with 
sebaceous  glands,  which  are  most  numerous  in  the  concha  and  scaphoid  fossa. 

The  cartilage  of  the  pinna  consists  of  one  single  piece :  it  gives  form  to  this 
part  of  the  ear,  and  upon  its  surface  are  found  all  the  eminences  and  depressions 
above  described.  It  does  not  enter  into  the  construction  of  all  parts  of  the 
auricle :  thus  it  does  not  form  a  constituent  part  of  the  lobule ;  it  is  deficient 


THE   EAR. 


913 


also  between  the  tragus  and  beginning  of  the  helix,  the  notch  between  them  being 
filled  up  by  dense  fibrous  tissue.  At  the  front  part  of  the  pinna,  where  the  helix 
bends  upward,  is  a  small  projection  of  cartilage,  called  the  process  of  the  helix. 
The  cartilage  of  the  pinna  presents  several  intervals  or  fissures  in  its  substance 
which  partially  separate  the  different  parts.  The  fissure  of  the  helix  is  a  short 
vertical  slit  situated  at  the  fore  part  of  the  pinna,  immediately  behind  a  small 
conical  projection  of  cartilage,  opposite  the  first  curve  of  the  helix  (process  of  the 
helix).  Another  fissure,  the  fissure  of  the  tragus,  is  seen  upon  the  anterior  sur- 
face of  the  tragus.  The  antihelix 
is  divided  below,  by  a  deep  fissure, 
into  two  parts  :  one  part  termi- 
nates by  a  pointed,  tail-like  ex- 
tremity (processus  caudatus);  the 
other  is  continuous  with  the  anti- 

tragus.       The    cartilage    of    the  ^\ \\\\\\ 

V    IVB 


FIG.  ."39.— The  pinna,  or  auricle. 
Outer  surface. 


FIG.  540.— The  muscles  of  the  pinna. 


pinna  is  very  pliable,  elastic,  of  a  yellowish  color,  and  belongs  to  that  form  of 
cartilage  which  is  known  under  the  name  of  yellow  fibro-cartilage. 

The  ligaments  of  the  pinna  consist  of  two  sets :  1.  The  extrinsic  set,  or  those 
connecting  it  to  the  side  of  the  head.  2.  The  intrinsic  set,  or  those  connecting  the 
various  parts  of  its  cartilage  together. 

The  extrinsic  ligaments,  the  most  important,  are  two  in  number,  anterior  and 
posterior.  The  anterior  ligament  extends  from  the  process  of  the  helix  to  the  root 
of  the  zygoma.  A  few  fibres  connect  the  tragus  to  the  root  of  the  zygoma.  The 
posterior  ligament  passes  from  the  posterior  surface  of  the  concha  to  the  outer 
surface  of  the  mastoid  process  of  the  temporal  bone. 

The  intri/txt'-  ligaments  are  also  two  in  number.  Of  these,  one  is  a  strong 
fibrous  band  stretching  across  from  the  tragus  to  the  commencement  of  the  helix, 
completing  the  meatus  in  front  and  partly  encircling  the  boundary  of  the  concha ; 
the  other  extends  between  the  concha  and  the  processus  caudatus. 

The  muscles  of  the  pinna  (Fig.  540)  consist  of  two  sets:  1.  The  extrinsic, 
which  connect  it  with  the  side  of  the  head,  moving  the  pinna  as  a  whole — viz.  the 
Attollens.  Attrahens,  and  Retrahens  aurem  (page  394);  and  2.  The  intrinsic,  which 
extend  from  one  part  of  the  auricle  to  another — viz. : 


Helicis  major. 
Helicis  minor. 
Trasicus. 


Antitragicus. 
Transversus  auriculae. 
Obliquus  auris. 


914  THE    ORGANS    OF  SENSE. 

The  Musculus  helicis  major  is  a  narrow  vertical  band  of  muscular  fibres,  situated 
upon  the  anterior  margin  of  the  helix.  It  arises  below  from  the  process  of  the 
helix,  and  is  inserted  into  the  anterior  border  of  the  helix,  just  where  it  is  about 
to  curve  backward.  It  is  pretty  constant  in  its  existence. 

The  Musculus  helicis  minor  is  an  oblique  fasciculus,  attached  to  that  part  of 
the  helix  which  commences  from  the  bottom  of  the  concha. 

The  Tragicus  is  a  short,  flattened  band  of  muscular  fibres  situated  upon  the 
outer  surface  of  the  tragus,  the  direction  of  its  fibres  being  vertical. 

The  Antitragicus  arises  from  the  outer  part  of  the  antitragus :  its  fibres  are 
inserted  into  the  processus  caudatus  of  the  helix.  This  muscle  is  usually  very 
distinct. 

The  Transversus  auricula?  is  placed  on  the  cranial  surface  of  the  pinna.  It 
consists  of  radiating  fibres,  partly  tendinous  and  partly  muscular,  extending  from 
the  convexity  of  the  concha  to  the  prominence  corresponding  with  the  groove  of 
the  helix. 

The  Obliquus  auris  (Todd)  consists  of  a  few  fibres  extending  from  the  upper 
and  back  part  of  the  concha  to  the  convexity  immediately  above  it. 

The  arteries  of  the  pinna  are — the  posterior  auricular  from  the  external  carotid, 
the  anterior  auricular  from  the  temporal,  and  an  auricular  branch  from  the 
occipital  artery. 

The  veins  accompany  the  corresponding  arteries. 

The  nerves  are — the  auricularis  magnus,  from  the  cervical  plexus  ;  the  posterior 
auricular,  from  the  facial  to  the  muscles  of  the  pinna ;  the  auricular  branch  of 
the  pneumogastric ;  the  auriculo-temporal  branch  of  the  inferior  maxillary  nerve ; 
the  occipitalis  minor  from  the  cervical  plexus  ;  and  the  occipitalis  major  or  internal 
branch  of  the  posterior  division  of  the  second  cervical  nerve. 

The  Auditory  Canal  (meatus  auditorius  externus}  extends  from  the  bottom 
of  the  concha  to  the  membrana  tympani.  It  is  about  an  inch  and  a  quarter 
in  length ;  its  direction  is  obliquely  forward,  inward,  and  downward.  At  first  it 
slightly  ascends,  while  in  the  middle  portion  it  makes  a  sharp  bend  backward.  It 
forms  an  oval  cylindrical  canal,  the  greatest  diameter  being  in  the  vertical  direction 
at  the  external  orifice,  but  in  the  transverse  direction  at  the  tympanic  end.  The 
calibre  of  the  canal  is  narrowest  about  the  middle.  The  membrana  tympani,  which 
occupies  the  termination  of  the  meatus,  is  obliquely  directed,  in  consequence  of 
which  the  floor  of  the  canal  is  longer  than  the  roof,  and  the  anterior  wall  longer 
than  the  posterior.  The  auditory  canal  is  formed  partly  by  cartilage  and  mem- 
brane, and  partly  by  bone,  and  is  covered  by  skin. 

The  cartilaginous  portion  is  about  half  an  inch  in  length,  being  rather  less  than 
half  the  canal ;  it  is  formed  by  the  cartilage  of  the  concha  and  tragus,  prolonged 
inward,  and  firmly  attached  to  the  circumference  of  the  auditory  process  of  the 
temporal  bone.  The  cartilage  is  deficient  at  its  upper  and  back  part,  its  place 
being  supplied  by  fibrous  membrane.  This  part  of  the  canal  is  rendered  extremely 
movable  by  two  or  three  deep  fissures  (incisurce  Santorini],  which  extend  through 
the  cartilage  in  a  vertical  direction. 

The  osseous  portion  is  about  three-quarters  of  an  inch  in  length,  and  narrower 
than  the  cartilaginous  portion.  Its  inner  end  is  marked,  except  at  its  upper  part, 
by  a  narrow  groove  (sulcus  tympanicus]  for  the  insertion  of  the  membrana  tym- 
pani. The  bony  ridge,  external  to  the  sulcus,  is  the  remnant  of  the  foetal  tym- 
panic ring.  It  also  is  deficient  above,  and  this  deficiency  is  known  as  the  notch 
of  Eivinus.  The  ends  of  the  incomplete  ring  bound  the  notch,  and  are  known 
as  the  anterior  and  posterior  tympanic  spines.  Its  outer  end  is  dilated,  and  rough, 
in  the  greater  part  of  its  circumference,  for  the  attachment  of  the  cartilage  of  the 
pinna.  Its  vertical  transverse  section  is  oval,  the  greatest  diameter  being  from 
above  downward.  The  front  and  lower  parts  of  this  canal  are  formed  by  a  curved 
plate  (tympanic  plate)  of  bone,  which,  in  the  foetus,  exists  as  a  separate  ring 
(tympanic  ring)  incomplete  at  its  upper  part. 

The  skin  lining  the  meatus  is  very  thin,  adheres  closely  to  the  cartilaginous 


THE   EAR.  915 

ami  osseous  portion  of  the  tube,  and  covers  the  surface  of  the  membrana  tympani, 
forming  its  outer  layer.  After  maceration  the  thin  pouch  of  epidermis,  when 
withdrawn,  preserves  the  form  of  the  meatus.  In  the  thick  subcutaneous  tissue 
of  the  cartilaginous  part  of  the  meatus  are  numerous  ceruminous  glands,  which 

Cartilage  of 
the  piniut ' 

Promonl. 


Cartilage  of  the  act. 
auditory  meatus 

FIG.  511. — Transverse  section  of  external  auditory  meatus  and  tympanum.    Left  side.    (Gegenbaur.) 

secrete  the  ear-wax.  They  resemble  in  structure  sweat-glands,  and  their  ducts 
open  on  the  surface  of  the  skin. 

The  a rtf i-(>'*  supplying  the  meatus  are  branches  from  the  posterior  auricular, 
internal  maxillary,  and  temporal. 

The  a >'/•>.•<'*  are  chiefly  derived  from  the  auriculo-temporal  branch  of  the  inferior 
maxillary  nerve. 

Surface  Form. — At  the  point  of  junction  of  the  osseous  and  cartilaginous  portions  the  tube 
forms  an  obtuse  angle,  which  projects  into  the  tube  at  its  antero-inferior  wall.  This  produces  a 
sort  of  constriction  in  this  situation,  and  renders  it  the  narrowest  portion  of  the  canal — an  im- 
portant point  to  be  borne  in  mind  in  connection  with  the  presence  of  foreign  bodies  in  the  ears. 
The  cartilaginous  is  connected  to  the  bony  part  by  fibrous  tissue,  which  renders  the  outer  part 
of  the  tube  very  movable,  and  therefore  by  drawing  the  pinna  upward  and  backward  the  canal 
is  rendered  almost  straight.  At  the  external  orifice  are  a  few  short,  crisp  hairs  which  serve  to 
prevent  the  entrance  of  small  particles  of  dust,  or  flies  or  other  insects.  In  the  external  auditory 
meatus  the  secretion  of  the  ceruminous  glands  serves  to  catch  any  small  particles  which  may 
find  their  way  into  the  canal,  and  prevent  their  reaching  the  membrana  tympani,  where  their 
I'lVM/nce  mi-rht  excite  irritation.  In  young  children  the  meatus  is  very  short,  the  osseous  part 
being  very  deficient,  and  consisting  merely  of  a  bony  ring  (the  tympanic  plate),  which  supports 
the  membrana  tympani.  In  the  foetus  the  osseous  part  is  entirely  absent.  The  shortness  of  the 
canal  in  children  should  be  borne  in  mind  in  introducing  the  aural  speculum,  so  that  it  be  not 
pushed  in  too  far.  at  the  risk  of  injuring  the  membrana  tympani ;  indeed,  even  in  the  adult  the 
speculum  should  never  be  introduced  beyond  the  constriction  which  marks  the  junction  of  the 

is  and  cartilaginous  portions.  In  using  this  instrument  it  is  advisable  that  the  pinna 
should  be  drawn  upward,  backward,  and  a  little  outward,  so  as  to  render  the  canal  as  straight  as 
possible,  and  thus  assist  the  operator  in  obtaining,  by  the  aid  of  reflected  light,  a  good  view  of 
tiie  mernbrana  tympani.  Just  in  front  of  tbe  membrane  is  a  well-marked  depression,  situated 
on  the  floor  of  the  canal  and  bounded  by  a  somewhat  prominent  ridge ;  in  this  foreign  bodies 
may  ber-.mie  lodged.  By  aid  of  tbe  speculum,  combined  with  traction  of  the  auricle  upward  and 
backward,  the  whole  of  the  membrana  tympani  is  rendered  visible.  It  is  a  pearly-gray  mem- 
brane, slightly  "listening  in  the  adult,  placed  obliquely,  so  as  to  form  with  the  floor  of  the  meatus 
a  very  acute  angle,  while  with  the  roof  it  forms  an  obtuse  angle.  At  birth  it  is  more  horizontal, 
situated  in  almost  tbe  same  plane  as  the  base  of  the  skull.  About  midway  between  the  anterior 
and  posterior  margins  of  the  membrane,  and  extending  from  the  centre  obliquely  upward,  is  a 
reddish-yellow  streak  :  this  is  the  handle  of  the  malleus,  which  is  inserted  into  the  membrane. 
At  the  upper  part  of  this  streak,  close  to  the  roof  of  the  meatus.  a  little  white  rounded  promi- 
nence is  plainly  to  be  seen :  this  is  the  processus  brevis  of  the  malleus,  projecting  against  the 
membrane.  The  roembrana  tympani  does  not  present  a  plane  surface  ;  on  the  contrary,  its  centre 

twn  inward,  on  account  ol  its  connecnoii  Vuii  the  handle  of  the  malleus,  and  thus  the 
external  surface  is  rendered  concave. 


916  THE    ORGANS    OF  SENSE. 

Middle  Ear,  or  Tympanum. 

The  middle  ear,  or  tympanum,  is  an  irregular  cavity,  compressed  from  without 
inward,  and  situated  within  the  petrous  bone.  It  is  placed  above  the  jugular  fossa ; 
the  carotid  canal  lying  in  front,  the  mastoid  cells  behind,  the  meatus  auditorius 
externally,  and  the  labyrinth  internally.  It  is  filled  with  air,  and  communicates  Avith 
the  pharynx  by  the  Eustachian  tube.  The  tympanum  is  traversed  by  a  chain  of 
movable  bones,  which  connect  the  membrana  tympani  with  the  labyrinth,  and  serve 
to  convey  the  vibrations  communicated  to  the  membrana  tympani  across  the  cavity 
of  the  tympanum  to  the  internal  ear. 

The  cavity  of  the  tympanum  measures  about  five  lines  from  before  backward, 
three  lines  in  the  vertical  direction,  and  between  two  and  three  in  the  transverse, 
being  a  little  broader  behind  and  above  than  it  is  below  and  in  front.  It  is  bounded 
externally  by  the  membrana  tympani  and  meatus,  internally,  by  the  outer  surface 
of  the  internal  ear,  and  communicates,  behind,  with  the  mastoid  cells,  and  in  front 
with  the  Eustachian  tube  and  canal  for  the  Tensor  tympani.  "Its  roof  and  floor  are 
formed  by  thin  osseous  laminae,  the  one  forming  the  roof  being  a  thin  plate  situated 
on  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone,  close  to  its 
angle  of  junction  with  the  squamous  portion  of  the  same  bone. 

The  roof  is  broad,  flattened,  and  formed  of  a  thin  plate  of  bone  which  separates 
the  cranial  and  tympanic  cavities. 

The  floor  is  narrow,  and  corresponds  to  the  jugular  fossa,  which  lies  beneath, 
It  presents,  near  the  inner  wall,  a  small  aperture  for  the  passage  of  Jacobson's 
nerve. 

The  outer  wall  is  formed  mainly  by  the  membrana  tympani,  partly  by  the  ring 
of  bone  into  which  this  membrane  is  inserted.  Close  to  it  are  three  small  apertures — 
the  iter  chordae  posterius,  the  Glaserian  fissure,  and  the  her  chordae  anterius. 

The  aperture  of  the  iter  chordce  posterius  is  in  the  angle  of  junction  between  the 
posterior  and  external  Avails  of  the  tympanum,  immediately  behind  the  membrana 
tympani  and  on  a  level  Avith  its  centre ;  it  leads  into  a  minute  canal,  Avhich  descends 
in  front  of  the  aqueductus  Fallopii  and  terminates  in  that  canal  near  the  stylo- 
mas  toid  foramen.  Through  it  the  chorda  tympani  nerve  enters  the  tympanum. 

The  Grlaserian  fissure  opens  just  above  and  in  front  of  the  ring  of  bone  into 
which  the  membrana  tympani  is  inserted;  in  this  situation  it  is  a  mere  slit  about 
a  line  in  length.  It  lodges  the  long  process  of  the  malleus  and  gives  passage  to 
some  tympanic  vessels. 

The  aperture  of  the  iter  chordce  anterius  is  seen  just  above  the  preceding  fissure  ; 
it  leads  into  a  canal  (canal  of  Huguier},  Avhich  runs  parallel  Avith  the  Glaserian 
fissure.  Through  it  the  chorda  tympani  nerve  leaves  the  tympanum. 

The  internal  wall  of  the  tympanum  (Fig.  542)  is  vertical  in  direction  and  looks 
directly  outAvard.  It  presents  for  examination  the  folloAving  parts : 

Fenestra  ovalis.  Ridge  of  the  aqueductus  Fallopii. 

Fenestra  rotunda.  Promontory. 

The  fenestra  ovalis  is  a  reniform  opening  leading  from  the  tympanum  into 
the  vestibule ;  its  long  diameter  is  directed  horizontally,  and  its  convex  border  is 
upward.  The  opening  in  the  recent  state  is  occupied  by  the  base  of  the  stapes, 
which  is  connected  to  the  margin  of  the  foramen  by  an  annular  ligament. 

The  fenestra  rotunda  is  an  aperture  placed  at  the  bottom  of  a  funnel-shaped 
depression  leading  into  the  cochlea.  It  is  situated  beloAv  and  rather  behind  the 
fenestra  ovalis,  from  Avhich  it  is  separated  by  a  rounded  elevation,  the  promontory; 
it  is  closed  in  the  recent  state  by  a  membrane  (membrana  tympani  secundaria, 
Scarpa).  This  membrane  is  concave  toward  the  tympanum,  convex  toward  the 
cochlea.  It  consists  of  three  layers :  the  external,  or  mucous,  derived  from  the 
mucous  lining  of  the  tympanum  ;  the  internal,  or  serous,  from  the  lining  membrane 
of  the  cochlea  ;  and  an  intermediate,  or  fibrous  layer. 

The  promontory  is  a  rounded  hollow  prominence,  formed  by  the  projection 
outward  of  the  first  turn  of  the  cochlea  ;  it  is  placed  between  the  fenestrae,  and 


THE    TYMPA  X  f  -.V. 


917 


is  furrowed  on  its  surface  by  three  small  grooves  which  lodge  branches  of  the 
tympanic  plexus. 

The  r<>un<l>'J  eminence  of  the  aqueductus  FaUopii.  the  prominence  of  the  bony 
canal  in  which  the  portio  dura  is  contained,  traverses  the  inner  wall  of  the  tym- 
panum above  the  fenestra  ovalis.  and  behind  that  opening  curves  nearly  vertically 
downward  along  the  posterior  wall. 

The  posterior  wall  of  the  tympanum  is  wider  above  than  below,  and  presents 
for  examination  the  Opening  of  the  mastoid  antrum. 

Pyramid. 

The  mastoid  antrum  is  an  irregular  cavity  with  several  small  apertures  opening 
into  it.  situated  above  and  behind  the  tympanum  proper;  the  smaller  openings 
lead  into  canals  which  communicate  with  large  irregular  cavities  contained  in  the 
interior  of  the  mastoid  process.  These  cavities  vary  considerably  in  number, 

Fenestra  ovalit 
Pyramid  \  Proc.  cocMearif. 
Hiatus  PaUop. 

Canal  for  tens.  tymp. 


Canal  of  Eust.  tube 
Groove  for  Jacobton's  nerve 
Fenettra  rotunda 
Can.  for  chorda  tympani 

FIG.  542.— Antero-posterior  section  through  the  tympanum.    (Gegenbaur.) 

size,  and  form  :  they  are  lined  by  mucous  membrane  continuous  with  that  lining 
the  cavity  of  the  tympanum.  Just  below  the  opening  of  the  antrum  is  the 
pyramid.  The  antrum  really  opens  into  an  upward  and  backward  prolongation 
of  the  tympanum,  known  as  the  attic  or  epitympanic  recess,  in  which  are  situated 
the  head  of  the  malleus  and  greater  part  of  the  incus  (Fig.  543). 

The  pyramid  is  a  conical  eminence  situated  immediately  behind  the  fenestra 
ovalis.  and  in  front  of  the  vertical  portion  of  the  Fallopian  eminence  above 
described :  it  is  hollow  in  the  interior,  and  contains  the  Stapedius  muscle ;  its 
summit  projects  forward  toward  the  fenestra  ovalis.  and  presents  a  small  aperture 
which  transmits  the  tendon  of  the  muscle.  The  cavity  in  the  pyramid  is  pro- 
longed into  a  minute  canal,  which  communicates  with  the  aqueductus  Fallopii 
and  transmits  the  nerve  which  supplies  the  Stapedius. 

The  anterior  wall  of  the  tympanum  corresponds  to  the  carotid  canal,  from 
which  it  is  separated  by  a  thin  plate  of  bone.  It  presents  the 

Canal  for  the  Tensor  tympani  muscle.          Orifice  of  the  Eustachian  tube. 
The  processus  cochleariformis. 

The  orifices  of  the  canal  for  the  Tensor  tympani  and  of  the  Eustachian  tube 

are  separated  from  each  other  by  a  thin,  delicate,  horizontal  plate  of  bone,  the 

x    coeUeariformit.     These    canals    run    from   the   tympanum,   forward. 

inward,  and  a  little  downward,  to  the  retiring  angle  between  the  squamous  and 

petrous  portions  of  the  temporal  bone. 

The  canal  for  the  Tensor  tympani  muscle  is  the  superior  and  the  smaller 
of  the  two :  it  is  rounded,  and  lies  beneath  the  upper  surface  of  the  petrous  bone, 
close  to  the  hiatus  Fallopii  (Fig.  542). 

The  Eustachian  tube  is  the  channel  through  which  the  tympanum  communi- 
cates with  the  pharynx.  Its  length  is  from  an  inch  and  a  half  to  two  inches,  and 
its  direction  downward,  forward,  and  inward.  It  is  formed  partly  of  bone,  partly 
of  cartilage  and  fibrous  tissue. 


918 


THE    ORGANS    OF  SENSE. 


Epitympanic  recess 


Proc.  cochlearif. 

Anterior  watt 


rotico-tymp.  canal 


Floor 

Prorrcontor. 
Aq.  Fallop. 

FIG.  543.— Antero-posterior  section  through 
the  tympanum.    (Gegenbaur.) 


i 


FIG.  544.— Transverse  section 
of  the  Eustachiau  tube.  a. 
Above,  b.  At  about  its  middle. 
c.  At  its  lower  part. 


The  osseous  portion  is  about  half  an  inch  in  length.  It  commences  in  the  lower 
part  of  the  anterior  wall  of  the  tympanum,  below  the  processus  cochleariformis, 

and,  gradually  narrowing,  terminates  in  an 
oval  dilated  opening  at  the  angle  of  junction 
of  the  petrous  and  squamous  portions,  its  ex- 
tremity presenting  a  jagged  margin  which 
serves  for  the  attachment  of  the  cartilaginous 
portion. 

The  cartilaginous  portion,  about  an  inch 
in  length,  is  formed  of  a  triangular  plate  of 
elastic  fibro.-cartilage,  curled  upon  itself,  an 
interval  being  left  below,  between  the  margins 
of  the  cartilage,  which  is  completed  by  fibrous 
and  muscular  tissue.  Its  canal  is  narrow 
behind,  wide,  expanded,  and  somewhat  trum- 
pet-shaped in  front,  terminating  by  an  oval 
orifice  at  the  upper  part  and  side  of  the  pharynx,  behind  the  back  part  of  the  infe- 
rior meatus.  Through  this  canal  the  mucous  membrane  of  the  pharynx  is  contin- 
uous with  that  which  lines  the  tympanum.  The  mucous 
membrane  is  covered  with  ciliated  epithelium  (Fig.  544). 
The  membrana  tympani  separates  the  cavity  of  the 
tympanum  from  the  bottom  of  the  external  meatus.  It 
is  a  thin,  semi-transparent  membrane,  nearly  oval  in 
form,  somewhat  broader  above  than  below,  and  directed 
very  obliquely  downward  and  inward.  Its  circumfer- 
ence is  contained  in  a  groove  at  the  inner  end  of  the 
meatus,  which  skirts  the  circumference  of  this  part,  ex- 
cepting above.  The  portion  filling  in  the  notch  of  Rivinus  (see  above)  is  looser 
in  texture  than  the  remainder,  and  is  known  as  the  membrana  flaccida.  The 
handle  of  the  malleus  descends  vertically  between  the  inner  and  middle  layers  of 
this  membrane  as  far  down  as  its  centre,  where  it  is  firmly  attached,  drawing  the 
membrane  inward,  so  that  its  outer  surface  is  concave,  its  inner  convex.  The 
middle  of  the  concavity  is  known  as  the  umbo. 

Structure. — This  membrane  is  composed  of  three  layers,  an  external  (cuticular), 
a  middle  (fibrous),  and  an  internal  (mucous).  The  cuticular  lining  is  derived  from 
the  integument  lining  the  meatus.  The  fibrous  layer  consists  of  fibrous  and  elastic 
tissues  ;  some  of  the  fibres  radiate  from  near  the  centre  to  the  circumference  ;  others 
are  arranged,  in  the  form  of  a  dense  circular  ring,  round  the  attached  margin  of 
the  membrane.  The  mucous  lining  is  derived  from  the  mucous  lining  of  the 
tympanum.  The  vessels  pass  to  the  membrana  tympani  along  the  handle  of  the 
malleus,  and  are  distributed  between  its  layers. 

Ossicles  of  the  Tympanum  (Fig.  545). 

The  tympanum  is  traversed  by  a  chain  of  movable  bones  three  in  number,  the 
malleus,  incus,  and  stapes.  The  former  is  attached  to  the  membrana  tympani,  the 
latter  to  the  fenestra  ovalis,  the  incus  being  placed  between  the  two,  to  both  of 
which  it  is  connected  by  delicate  articulations. 

The  Malleus,  so  named  from  its  fancied  resemblance  to  a  hammer,  consists  of 
a  head,  neck,  and  three  processes — the  handle  or  manubrium,  the  processus  gracilis, 
and  the  processus  brevis. 

The  head  is  the  large  upper  extremity  of  the  bone ;  it  is  oval  in  shape,  and 
articulates  posteriorly  with  the  incus,  being  free  in  the  rest  of  its  extent. 

The  neck  is  the  narrow  contracted  part  just  beneath  the  head,  and  below  this 
is  a  prominence  to  which  the  various  processes  are  attached. 

The  manubrium  is  a  vertical  process  of  bone  which  is  connected  by  its  outer 
margin  with  the  membrana  tympani.  It  decreases  in  size  toward  its  extremity, 
where  it  is  curved  slightly  forward,  and  flattened  from  within  outward.  On  the 


Tin:  miPA.\rjf.  919 

inner  side,  near  its  upper  end.  is  a  slight  projection,  into  which  the  tendon  of  the 
Tensor  tympani  is  inserted. 

The  processes  gracilis  is  a  long  and  very  delicate  process  which  passes  from 
the  eminence  below  the  neck  forward  and  outward  to  the  Glaserian  fissure,  to  which 
it  is  connected  by  bone  and  ligamentous  fibres. 

The  pro<->  **>/>•  bt'i'-'-i*  is  a  slight  conical  projection  which  springs  from  the  root 
of  the  manubrium.  and  lies  in  contact  with  the  membrana  tympani. 

The  Incus  lias  received  its  name  from  its  supposed  resemblance  to  an  anvil, 
but  it  is  more  like  a  bicuspid  tooth,  with  two  roots,  which  differ  in  length  and  are 
widely  separated  from  each  other.  It  consists  of  a  body  and  two  processes. 

The  body  is  somewhat  quadrilateral,  but  compressed  laterally.     On  the  anterior 
surface  of  its  summit  is  a  deeply  concavo-convex  facet,  which  articulates  with  the 
malleus  ;  in  the  fresh  state  it  is  covered  with 
cartilage  and  lined  with  synovial  membrane. 

The  two  processes  diverge  from  one  another 
nearly  at  right  angles. 

The    short  process,    somewhat    conical    in  Ssj^  ^^j&~\ P™/.,«.«  fc^m*. 

shape,  projects  nearly  horizontally  backward, 
and  is  attached  to  the  margin  of  the  opening 
leading  into  the  mastoid  cells  by  ligamentous 

fibres.  o.—.  m  TV*  n 

„„       7  .  ,  ,        ,  JjEJ-Osorbicularc. 

Ihe  long  process,  longer  and  more  slender 
than  the  preceding,  descends  nearly  verticallv 
behind  and  parallel  to  the  handle  of  the  mal- 

,  i      i         i-          •  i  •  •  FIG.  545. — The  small  bones  of  the  ear,  seen 

lens.   and.    bending  inward,    terminates    in  a     from  the  outside.  (Enlarged.) 
rounded  globular  projection,  the  os  orbiculare, 

or  lenticular  ///•/»'«  .<x.  which  is  tipped  with  cartilage  and  articulates  with  the  head 
of  the  stapes.  In  the  foetus  the  os  orbiculare  exists  as  a  separate  bone,  but 
becomes  united  to  the  long  process  of  the  incus  in  the  adult. 

The  Stapes,  so  called  from  its  close  resemblance  to  a  stirrup,  consists  of  a  head, 
neck,  two  branches,  and  a  base.  The  head  presents  a  depression,  tipped  with 
cartilage,  which  articulates  with  the  os  orbiculare.  The  neck,  the  constricted 
part  of  the  bone  below  the  head,  receives  the  insertion  of  the  Stapedius  muscle. 
The  two  brain-In-*  (i-rura]  diverge  from  the  neck,  and  are  connected  at  their  ex- 
tremities by  a  flattened,  oval-shaped  plate  (the  base),  which  forms  the  foot  of  the 
stirrup,  and  is  fixed  to  the  margin  of  the  fenestra  ovalis  by  ligamentous  fibres. 

Ligaments  of  the  Ossicula. — These  small  bones  are  connected  with  each  other 
and  with  the  walls  of  the  tympanum  by  ligaments,  and  moved  by  small  muscles. 
The  articular  surfaces  of  the  malleus  and  incus  and  the  orbicular  process  of  the 
incus  and  head  of  the  stapes  are  covered  with  cartilage,  connected  together  by 
delicate  capsular  ligaments  and  lined  by  synovial  membrane.  The  ligaments  con- 
necting the  ossicula  with  the  Avails  of  the  tympanum  are  four  in  number — two  for 
the  malleus,  one  for  the  incus,  and  one  for  the  stapes. 

The  anterior  li-jament  of  the  malleus  was  formerly  described  by  Sommerring  as 
a  muscle  (Laxator  tympani).  It  is  now,  however,  believed  by  most  observers  to 

-:>t  of  ligamentous  fibres  only.  It  is  attached  by  one  extremity  to  the  neck 
of  the  malleus,  just  above  the  processus  gracilis,  and  by  the  other  to  the  anterior 
wall  of  the  tympanum,  close  to  the  Glaserian  fissure,  some  of  its  fibres  being  pro- 
longed through  the  fissure. 

The  suspensory  ligament  of  the  malleus  is  a  delicate,  round  bundle  of  fibres 
which  descends  perpendicularly  from  the  roof  of  the  tympanum  to  the  head  of  the 
malleus. 

The  posterior  ligament  of  the  incus  is  a  short,  thick,  ligamentous  band  which 
connects  the  extremity  of  the  short  process  of  the  incus  to  the  posterior  wall  of  the 
tympanum,  near  the  margin  of  the  opening  of  the  mastoid  cells. 

The  annular  ligament  of  the  stapes  connects  the  circumference  of  the  base  of 
this  bone  to  the  margin  of  the  fenestra  ovalis. 


920  THE    ORGANS    OF  SENSE. 

A  suspensory  ligament  of  the  incus  has  been  described  by  Arnold,  descending 
from  the  roof  of  the  tympanum  to  the  upper  part  of  the  incus,  near  its  articulation 
with  the  malleus. 

The  muscles  of  the  tympanum  are  two  : 

Tensor  tympani.  Stapedius. 

The  Tensor  tympani,  the  larger,  is  contained  in  the  bony  canal  above  the 
osseous  portion  of  the  Eustachian  tube,  from  which  it  is  separated  by  the  processus 
cochleariformis.  It  arises  from  the  under  surface  of  the  petrous  bone,  from  the 
cartilaginous  portion  of  the  Eustachian  tube,  and  from  the  osseous  canal  in  which 
it  is  contained.  Passing  backward  through  the  canal,  it  terminates  in  a  slender 
tendon  which  enters  the  tympanum  and  makes  a  sharp  bend  outward  round  the 
extremity  of  the  processus  cochleariformis,  and  is  inserted  into  the  handle  of  the 
malleus  near  its  root.  It  is  supplied  by  a  branch  from  the  otic  ganglion. 

The  iStapedius  arises  from  the  side  of  a  conical  cavity  hollowed  out  of  the  inte- 
rior of  the  pyramid;  its  tendon  emerges  from  the  orifice  at  the  apex  of  the  pyra- 
mid, and,  passing  forward,  is  inserted  into  the  neck  of  the  stapes.  Its  surface  is 
aponeurotic,  its  interior  fleshy,  and  its  tendon  occasionally  contains  a  slender  bony 
spine,  which  is  constant  in  some  mammalia.  It  is  supplied  by  the  tympanic 
branch  of  the  facial  nerve. 

Actions. — The  Tensor  tympani  draws  the  membrana  tympani  inward  and  thus 
heightens  its  tension.  The  Stapedius  draws  the  head  of  the  stapes  backward,  and 
thus  causes  the  base  of  the  bone  to  rotate  on  a  vertical  axis  drawn  through  its  own 
centre :  in  doing  this  the  back  part  of  the  base  would  be  pressed  inward  toward 
the  vestibule,  while  the  fore  part  would  be  drawn  from  it.  It  probably  compresses 
the  contents  of  the  vestibule. 

The  mucous  membrane  of  the  tympanum  is  thin,  slightly  vascular,  and  continuous 
with  the  mucous  membrane  of  the  pharynx  through  the  Eustachian  tube.  It 
invests  the  ossicula  and  the  muscles  and  nerves  contained  in  the  tympanic  cavity, 
forms  the  internal  layer  of  the  membrana  tympani,  covers  the  foramen  rotundum, 
and  is  reflected  into  the  mastoid  cells,  which  it  lines  throughout.  In  the  tympanum 
and  mastoid  cells  this  membrane  is  pale,  thin,  slightly  vascular,  and  covered  with 
ciliated  epithelium.  In  the  osseous  portion  of  the  Eustachian  tube  the  membrane 
is  thin,  but  in  the  cartilaginous  portion  it  is  very  thick,  highly  vascular,  covered 
with  laminar  ciliated  epithelium,  and  provided  with  numerous  mucous  glands. 

The  arteries  supplying  the  tympanum  are  six  in  number.  Three  of  them  are 
larger  than  the  rest — viz.  the  tympanic  branch  of  the  internal  maxillary,  which 
supplies  the  membrana  tympani ;  the  Vidian  and  the  stylo-mastoid  branch  of  the 
posterior  auricular,  which  supplies  the  back  part  of  the  tympanum  and  mastoid 
cells.  The  smaller  branches  are — the  petrosal  branch  of  the  middle  meningeal, 
which  enters  through  the  hiatus  Fallopii  ;  a  branch  from  the  ascending  pharyngeal, 
and  another  from  the  Vidian  which  pass  up  the  Eustachian  tube ;  and  the  tympanic 
branch  from  the  internal  carotid,  given  off  in  the  carotid  canal  and  perforating  the 
thin  anterior  wall  of  the  tympanum. 

The  veins  of  the  tympanum  terminate  in  the  temporo-maxillary  vein  and  in 
the  superior  petrosal  sinus. 

The  nerves  of  the  tympanum  may  be  divided  into — 1,  those  supplying  the 
muscles ;  2,  those  distributed  to  the  lining  membrane  ;  3,  branches  communicating 
with  other  nerves. 

Nerves  to  Muscles. — The  Tensor  tympani  is  supplied  by  a  branch  from  the  otic 
ganglion ;  the  Stapedius,  by  the  tympanic  branch  of  the  facial  (Sbmmerring). 

The  nerves  distributed  to  the  lining  membrane  are  derived  from  the  tympanic 
plexus. 

The  communications  which  take  place  in  the  tympanum  are  between  the 
tympanic  branch  of  the  glosso-pharyngeal  with  the  sympathetic  and  with  filaments 
derived  from  the  intumescentia  ganglioformis  of  the  facial. 

The  tympanic  branch  of  the  glosso-pharyngeal  (Jacobson's    nerve)  enters  the 


THE   INTERNAL    EAR.  921 

tympanum  by  an  aperture  in  its  floor,  close  to  the  inner  wall,  and  divides  into 
branches  which  are  contained  in  grooves  upon  the  surface  of  the  promontory 
forming  the  tympanic  plexus. 

Ir<  branches  of  distribution  are — one  to  the  fenestra  rotunda,  one  to  the  fenestra 
ovalis,  and  one  to  the  lining  membrane  of  the  tympanum  and  Eustachian  tube. 

Its  branches  of  communication  are  three,  and  occupy  separate  grooves  on  the 
surface  of  the  promontory.  One  branch,  the  small  deep  petrosal,  arches  forward 
and  downward  to  the  carotid  canal  to  join  the  carotid  plexus.  A  second,  the  long 
petrvsiil  //»'/•/•/',  runs  forward  through  a  canal  close  to  or  in  the  processus  cochleari- 
formis.  and  enters  the  foramen  lacerum  medium,  where  it  joins  the  carotid  plexus 
of  the  sympathetic,  and  generally  the  large  superficial  petrosal  nerve.  The  third 
branch  runs  upward  through  the  substance  of  the  petrous  portion  of  the  temporal 
bone.  In  its  course  it  passes  by  the  gangliform  enlargement  of  the  facial  nerve, 
and.  receiving  a  connecting  filament  from  it,  becomes  the  small  superficial  petrosal 
ni'i-i'i'.  It  then  enters  the  skull  through  a  small  aperture,  situated  external  to  the 
hiatus  Fallopii  on  the  anterior  surface  of  the  petrous  bone,  courses  forward  across 
the  base  of  the  skull,  and  emerges  through  a  foramen  in  the  middle  fossa  (sometimes 
through  the  foramen  ovale)  and  joins  the  otic  ganglion. 

The  chorda  tympani  leaves  the  facial  about  a  quarter  of  an  inch  above  the 
exit  of  the  latter.  It  enters  the  tympanum  through  the  iter  chordce  posterius, 
and  liecomes  invested  with  mucous  membrane.  It  passes  forward,  between  the 
handle  of  the  malleus  and  vertical  ramus  of  the  incus,  and  leaves  the  tympanum 
through  the  iter  chordre  anterius. 

The  Internal  Ear,  or  Labyrinth  (Fig.  546). 

The  internal  ear  has  two  main  divisions,  the  osseous  and  membranous  laby- 
rinths. They  are  called  labyrinths  from  the 

complexity  of  their  shapes.     The  osseous  laby-  Sup.  «mof. 

rinth   consists   of  three   parts — the   vestibule,  Aq- 

semicircular  canals,  and  cochlea.     It  is  formed 
by  a  series  of  cavities  channelled  out  of  the 
substance  of  the  petrous  bone,  communicating          ^ 
externally  with  the  cavity  of  the  tympanum 

through  the  fenestrae  ovalis  and  rotunda,  and  

internally  with  the  meatus  auditorius  internus,  Prommt    Fen-roL     > 

bv  means  of  minute  bonv  canals  which  contain 

J  ,„.  ,  .         ,  FIG.  ->46.— The  bony  labyrinth  of  the  left 

the  auditory  nerve-filamentS.        Within   the  OS-       ear,  seen  from  the  outer  side  and  somewhat 
i    i      "'•     ,  i     •  .    •       j    ,  i  i  from  below  ?  (Gegenbaur). 

seous  labyrinth  is  contained  the  membranous 

labyrinth,  upon  which  the  ramifications  of  the  auditory  nerve  are  distributed. 
The  Vestibule  (Fig.  547)  is  the  common  central  cavity  of  communication  between 
the  parts  of  the  internal  ear.  It  is  situated  on  the  inner  side  of  the  tympanum, 
behind  the  cochlea,  and  in  front  of  the  semicircular  canals.  It  is  somewhat  ovoidal 
in  shape  from  before  backward,  flattened  from  within  outward,  and  measures 
about  one-fifth  of  an  inch  from  before  backward,  as  well  as  from  above  downward, 
being  narrower  from  without  inward.  On  its  outer  or  tympanic  wall  is  the 
fenestra  ovalis,  closed,  in  the  recent  state,  by  the  base  of  the  stapes  and  its  annular 
ligament.  On  its  inner  wall,  at  the  fore  part,  is  a  small  circular  depression,  fovea 
hemispherica,  which  is  perforated,  at  its  anterior  and  inferior  part,  by  several 
minute  holes  (macula  cribrosd)  for  the  passage  of  the  filaments  of  the  auditory 
nerve ;  and  behind  this  depression  is  a  vertical  ridge,  the  pyramidal  eminence 
(crista  vestibuli).  At  the  hinder  part  of  the  inner  wall  is  the  orifice  of  the  aque- 
ductus  vestibuli,  which  extends  to  the  posterior  surface  of  the  petrous  portion  of 
the  temporal  bone.  It  transmits  a  small  vein,  and  contains  a  tubular  prolonga- 
tion (ductus  cndolymphaticus)  which,  derived  from  the  saccule  and  utricle,  in  a 
manner  to  be  described  later,  ends  in  a  cul-de-sac.  On  the  upper  wall  or  roof  is 
a  transverse  oval  depression,  fovea  semi-elliptica,  separated  from  the  fovea  hem- 


922 


THE    ORGANS    OF  SENSE. 


ispherica  by  the  pyramidal  eminence  already  mentioned.  Behind,  the  semicir- 
cular canals  open  into  the  vestibule  by  five  orifices.  In  front  is  a  large  oval 
opening  which  communicates  with  the  scala  vestibuli  of  the  cochlea  by  a  single 
orifice,  apertura  scalce  vestibuli  cochlece. 

The  Semicircular  canals  are  three  bony  canals  situated  above  and  behind  the 
vestibule.  They  are  of  unequal  length,  compressed  from  side  to  side,  and  describe 
the  greater  part  of  a  circle.  They  measure  about  one-twentieth  of  an  inch  in 
diameter,  and  each  presents  a  dilatation  at  one  end,  called  the  ampulla,  which 
measures  more  than  twice  the  diameter  of  the  tube.  These  canals  open  into  the 
vestibule  by  five  orifices,  one  of  the  apertures  being  common  to  two  of  the  canals. 

The  superior  semicircular  canal  is  vertical  in  direction,  and  stretches  across 
the  petrous  portion  of  the  temporal  bone,  at  right  angles  to  its  posterior  surface ; 
its  arch  forms  a  round  projection  on  the  anterior  surface  of  the  petrous  bone.  It 
describes  about  two-thirds  of  a  circle.  Its  outer  extremity,  which  is  ampullated, 
commences  by  a  distinct  orifice  in  the  upper  part  of  the  vestibule  ;  the  opposite  end 


Opening  of  aqueductm  vestibuli. 
Bristle  passed  through  foramen  rotundum. 

Opening  of  aqueductus  cochlese. 
FIG.  547. — The  osseous  labyrinth  laid  open.    (Enlarged.) 

of  the  canal,  which  is  not  dilated,  joins  with  the  corresponding  part  of  the  pos- 
terior canal,  and  opens  by  a  common  orifice  with  it  in  the  back  part  of  the 
vestibule. 

The  posterior  semicircular  canal,  also  vertical  in  direction,  is  directed  back- 
ward, nearly  parallel  to  the  posterior  surface  of  the  petrous  bone ;  it  is  the 
longest  of  the  three :  its  ampullated  end  commences  at  the  lower  and  back 
part  of  the  vestibule,  its  opposite  end  joining  to  form  the  common  canal  already 
mentioned. 

The  external  or  horizontal  canal  is  the  shortest  of  the  three,  its  arch  being 
directed  outward  and  backward ;  thus  each  semicircular  canal  stands  at  right 
angles  to  the  other  two.  Its  ampullated  end  corresponds  to  the  upper  and  outer 
angle  of  the  vestibule,  just  above  the  fenestra  ovalis;  its  opposite  end  opens  by  a 
distinct  orifice  at  the  upper  and  back  part  of  the  vestibule. 

The  Cochlea  bears  some  resemblance  to  a  common  snail-shell :  it  forms  the 
anterior  part  of  the  labyrinth,  is  conical  in  form,  and  placed  almost  horizontally 
in  front  of  the  vestibule ;  its  apex  is  directed  forward  and  outward  toward  the 
upper  and  front  part  of  the  inner  wall  of  the  tympanum  ;  its  base  corresponds  with 
the  anterior  depression  at  the  bottom  of  the  internal  auditory  meatus,  and  is 
perforated  by  numerous  apertures  for  the  passage  of  the  cochlear  branch  ot  the 


THE   IXTERXAL    EAR.  923 

auditory  nerve.  It  measure?  about  a  quarter  of  an  inch  in  length,  and  its  breadth 
toward  the  base  is  about  the  same.  It  consists  of  a  conical-shaped  central  axis, 
the  modiohi*  or  cfilumella  ;  of  a  canal  wound  spirally  round  the  axis  for  two  turns 
ind  a  half,  from  the  base  to  the  apex  :  and  of  a  delicate  lamina  (the  lamina  apiralis) 
contained  within  the  canal,  which  follows  its  windings  and  partially  subdivides  it 
:nto  tw..;. 

The  o.ntral  axis,  or  //>«'7"</>/>-.  is  conical  in  form,  and  extends  from  the  base  to 
the  apex  of  the  cochlea.  Its  base  is  broad,  corresponds  with  the  first  turn  of  the 
cochlea,  and  is  perforated  by  numerous  orifices,  which  transmit  filaments  of  the 
cochlear  branch  of  the  auditory  nerve ;  the  axis  diminishes  rapidly  in  size  in 
the  second  coil,  and  terminates  within  the  last  half-coil,  or  cupola,  in  an  expanded 
delicate,  bony  lamella,  which  resembles  the  half  of  a  funnel  divided  longitudinally, 
and  is  called  the  infundibulum  ;  the  broad  part  of  this  funnel  is  directed  toward 
the  summit  of  the  cochlea,  and  blends  with  the  cupola  or  last  half-turn  of  the 
spiral  canal  of  the  cochlea.  At  this  point  the  two  larger  scalte  of  the  cochlea,  the 
scala  tympani  and  .seal a  vestibuli,  communicate  by  an  opening  called  the  helico- 
tr>  •///'./.  The  outer  surface  of  the  modiolus  forms  part  of  the  wall  of  the  spiral 
canal,  and  is  dense  in  structure;  but  its  centre  is  channelled,  as  far  as  the  last 
half-coil,  by  numerous  branching  canals,  which  transmit  nervous  filaments  in 
regular  succession  into  the  canal  of  the  cochlea  or  on  to  the  surface  of  the 
lamina  spiralis.  One  of  these,  larger  than  the  rest,  occupies  the  centre  of  the 
modiolus,  and  is  named  the  canalis  centralis  modioli ;  it  extends  from  the  base  to 
the  extremity  of  the  modiolus,  and  transmits  a  small  nerve  and  artery  (arteria 
centralis  modioli). 

The  spiral  canal  (Fig.  5-48)  takes  two  turns  and  a  half  round  the  modiolus. 
It  is  about  an  inch  and  a  half  in  length,  measured  along  its  outer  wall,  and 


FIG.  548.— The  cochlea  laid  open.    (Enlarged,  i 

diminishes  gradually  in  size  from  the  base  to  the  summit,  where  it  terminates  in 
a  cul-de-zac.  the  cupola,  which  forms  the  apex  of  the  cochlea.  The  commence- 
ment of  this  canal  is  about  the  tenth  of  an  inch  in  diameter;  it  diverges 
from  the  modiolna  toward  the  tympanum  and  vestibule  and  presents  three  open- 
ings. One.  the  fenestra  rotunda,  communicates  with  the  tympanum ;  in  the 
recent  state  this  aperture  is  closed  by  a  membrane,  the  membrana  tympani 

••daria.  Another  aperture,  of  an  oval  form,  enters  the  vestibule.  The 
third  is  the  aperture  of  the  aqueductus  cochlea?,  leading  to  a  minute  funnel-shaped 
canal,  which  opens  on  the  basilar  surface  of  the  petrous  bone  and  transmits  a 
small  vein. 

The  interior  of  the  spiral  canal  (Fig.  549)  is  partially  divided  into  two.  in  the 
dry  state,  by  a  thin  bony  plate,  the  lamina  spiral!*,  which  consists  of  two  thin 
lamellae  of  bone,  between  which  are  numerous  canals  for  the  passage  of  nerve- 
fibres.  This  lamina  projects  from  the  modiolus  into  the  canal,  but  does  not  reach 
more  than  halfway  toward  the  outer  wall  of  the  tube.  From  its  extremity  a  thin 
membrane  extends  to  the  outer  wall,  and  completes  the  division  of  the  canal  into 
an  upper  compartment,  the  scala  vestibuli.  and  a  lower  one.  the  scala  tympani. 


THE    ORGANS    OF  SENSE. 


By  a  second  membrane  a  portion  of  the  upper  of  these  two  canals  is  cut  off  from 
the  rest,  constituting  the  scala  media.  The  lamina  spiralis  ends  above  in  a  hook- 
shaped  process  (hamuhts)  -which  partly  bounds  the  helicotrema.  At  the  point  where 
the  osseous  lamina  is  attached  to  the  rnodiolus  is  a  small  canal,  -which  winds  round 
the  modiolus,  and  was  denominated  by  Rosenthal  the  canalis  spiralis  modioli ;  it 
is  occupied  by  a  swelling  of  the  cochlear  nerve,  the  ganglion  spirale,  in  which 


FIG.  549.— Longitudinal  section  of  the  cochlea,  showing  the  relations  of  the  scalae,  the  ganglion  spirale,  etc. 
S.  V.  Scala  vestibuli.  S.  T.  Scala  tympani.  S.  M.  Scala  media.  L.  S.  Ligamentum  spirale.  G.  S.  Ganglion  spi- 
rale. 

ganglion-cells  are  found,  and  from  which  the  nerves  pass  to  the  osseous  lamina  and 
organ  of  Corti.     The  scala  media  belongs  to  the  membranous  labyrinth. 

The  osseous  lamina,  as  above  stated,  extends  only  part  of  the  distance  between 
the  modiolus  and  the  outer  bony  wall  of  the  cochlea.  Near  its  outer  end  the 
periosteum  on  the  upper  or  vestibular  surface  of  the  lamina  swells  up  into  an 
elevation  which  is  called  the  limbus  laminae  spiralis  ("•  denticulate  lamina  "  of  Todd 
and  Bowman).  The  lamina  spiralis  terminates  in  a  grooved  extremity,  the  sulcus 
spiralis,  which  presents  the  form  of  the  letter  C :  the  upper  part  of  the  letter, 
being  formed  by  the  overhanging  extremity  of  the  limbus,  is  named  the  labium 
vestibulare  ;  the  lower  part,  prolonged  and  tapering,  is  called  the  labium  ty'mpani- 
cum  (Fig.  550).  From  the  labium  tympanicum  a  thin  membrane  extends  over  to 
the  bony  wall  of  the  cochlea,  completing  the  scala  tympani.  This  membrane  is 
called  the  membrana  basilaris.  At  its  outer  attachment  it  swells  out  so  as  to  form 
a  thick  triangular  structure,  which  was  regarded  as  a  muscle  by  Todd  and  Bowman 
(cochlearis),  but  is  now  recognized  as  ligamentous — the  lie/amentum  spirale. 
Between  the  labium  vestibulare  and  the  attachment  of  the  membrane  of  Reissner, 
presently  to  be  described,  a  very  delicate  membrane  extends  over  to  the  outer 
wall  of  the  cochlea,  running  nearly  parallel  to  the  membrana  basilaris.  It  was 
described  by  Corti,  and  covers  over  the  organ  which  is  called  after  his  name,  and 
is  therefore  called  membrane  of  Corti,  or  membrana  tectoria.  Farther  inward, 
near  the  commencement  of  the  limbus  laminae  spiralis,  another  delicate  mem- 
brane, the  membrane  of  Reissner,  is  attached  to  the  vestibular  surface  of  the 
periosteum  of  the  osseous  lamina  and  stretches  across  to  the  outer  wall  of  the 
cochlea.  The  canal  which  lies  below  the  osseous  lamina  and  membrana  basilaris 
is  the  scala  tympani ;  that  which  is  bounded  by  the  osseous  lamina  and  membrane 
of  Reissner,  the  scala  vcstibuli;  while  the  space  between  the  membrane  of 
Reissner  and  membrana  basilaris  is  generally  described  as  the  Scala  media,  Can- 
alis membranacea,  or  Canalis  cochlea*,  and  this  is  the  nomenclature  which  will  be 
used  here.  Others,  however,  apply  the  name  canalis  cochlea?  only  to  the  canal 


THE   INTERNAL    EAR. 


925 


lying  between  the  membrane  of  Reissner  and  the  membrana  tectoria,  which  con- 
tains no  object  for  description,  while  the  space  lying  between  the  membrana  tec- 
toria and  membrana  basilaris  is  described  by  itself  as  a  fourth  canal — the  ductm 
cochharis  or  duct  us  auditor/ us.1  The  latter  is  the  space  in  which  the  organ  of 
C"/it'2  is  contained.  This  organ  (Fig.  550)  is  situated  upon  the  membrana  basila- 
ris, and  appears  at  first  sight  as  a  papilla,  winding  spirally  with  the  turns  of  this 
membrane  throughout  the  whole  length  of  the  cochlea,  from  which  circumstance 
it  has  been  designated  the  papilla  spiralis.  More  accurately  viewed,  it  is  seen  +o 


FIG.  550.— Floor  of  scala  media,  showing  the  organ  of  Corti,  etc. 

be  composed  of  a  remarkable  arrangement  of  cells  which  may  be  likened  to  the 
kevboard  of  a  pianoforte.  Of  these  cells,  the  two  central  ones  are  rod-like 
bodies,  and  are  called  the  inner  and  outer  rods  of  Corti.  They  are  placed  erect 
on  the  basilar  membrane  at  some  little  distance  from  each  other,  the  space 
between  them  being  denominated  the  zona  arcuata;  they  are  inclined  toward 
each  other,  so  as  to  meet  at  their  opposite  extremities  and  form  a  series  of  arches 
roofing  over  the  zona  arcuata,  thus  forming  a  minute  tunnel  between  them  and 
the  basilar  membrane,  which  ascends  spirally  through  the  whole  length  of  the 
cochlea.  They  are  estimated  at  over  three  thousand  in  number. 

The  inner  rods,  which  are  more  numerous  than  the  outer  ones,  rest  on  the 
basilar  membrane,  close  to  the  labium  tympanic-urn:  they  project  obliquely  for- 
ward and  outward,  and  terminate  above  in  expanded  extremities,  which  resemble 
in  shape  the  upper  end  of  the  ulna,  with  its  sigmoid  cavity,  coronoid  and  olecra- 
non  processes.  On  the  outer  side  of  the  rod,  in  the  angle  formed  between  it  and 
the  basilar  membrane,  is  a  protoplasmic  cell,  whilst  on  the  inner  side  is  a  row  of 
epithelial  cells  surmounted  by  a  brush  of  fine,  stiff,  hair-like  processes,  these  cells 
being  continuous  with  the  cubical  cells  lining  the  sulcus  spiralis. 

The  outer  rods  also  rest  by  a  broad  foot  on  the  basilar  membrane :  they 
incline  forward  and  inward,  and  their  upper  extremity  resembles  the  head  and 
bill  of  a  swan,  the  head  fitting  into  the  concavity — the  analogue  of  the  sigmoid 
cavity — of  one  or  more  of  the  internal  rods,  and  the  bill  resting  against  the 
phalanges  of  the  lamina  reticularis.  presently  to  be  described. 

In  the  head  of  these  outer  rods  is  an  oval  portion,  where  the  fibres  of  which 
the  rod  appears  to  be  composed  are  deficient,  and  which  stains  more  deeply  with 
carmine  than  the  rest  of  the  rod.  This  is  supposed  to  represent  the  nucleus  of 
the  cell  from  which  the  rod  was  originally  developed.  At  the  base  of  the  rod.  on 
its  internal  side — that  is  to  say,  in  the  angle  formed  by  the  rod  with  the  basilar 
membrane — is  a  similar  protoplasmic  cell  to  that  found  on  the  outer  side  of  the 
base  of  the  inner  rod,  whilst  external  to  the  outer  rod  are  three  or  four  successive 

1  In  reading  the  older  descriptions  of  the  organ  of  hearing  the  student  must  bear  in  mind  that  the 
membranes  bounding  the  ductus  auditorius,  together  with  the  organ  contained  between  them,  were  de- 
scribed together  as  the  "  lamina  spiralis  membranacea.v  while  the  membrane  of  Reissner  was  not  recog- 
nized, the  parts  being,  in  fact,  as  shown  in  the  second  turn  of  the  cochlea  on  the  right  hand  of  Fig.  549. 

1  Corti's  original  paper  is  in  the  Zeitschrift  f.  Wissen.  Zool.,  iii.  109. 


926  THE    ORGANS    OF  SENSE. 

rows  of  epithelial  cells,  more  elongated  than  those  found  on  the  internal  side  of 
the  inner  rod,  but,  like  them,  furnished  with  minute  hairs  or  cilia.  These  are 
termed  the  outer  hair-cells,  in  contradistinction  to  the  inner  set,  which  are  termed 
the  inner  hair-cells.  They  are  attached  by  their  bases  to  the  basilar  membrane, 
whilst  from  the  opposite  extremity  a  brush  of  hairs  or  cilia  projects  through  the 
reticular  membrane.  They  are  continuous  externally  with  the  cubical  cells  on 
the  lateral  part  of  the  basilar  membrane. 

The  reticular  lamina  or  membrane  of  Kolliker  is  a  delicate  framework  perfo- 
rated by  rounded  holes.  It  extends  from  the  inner  rods  of  Corti  to  the  external 
row  of  the  outer  hair-cells,  and  is  formed  by  several  rows  of  "•  minute  fiddle- 
shaped  cuticular  structures,"  called  phalanges,  between  which  are  holes  for  the 
projection  of  the  cilise  of  the  outer  hair-cells. 

Covering  over  these  structures,  but  not  touching  them,  is  the  membrana  tec- 
toria,  or  membrane  of  Corti,  which  is  attached  to  the  vestibular  surface  of  the 
lamina  spiralis  close  to  the  attachment  of  the  membrane  of  Reissner ;  it  courses 
over  the  denticulate  lamina,  and,  passing  outward  parallel  to  the  basilar  mem- 
brane, is  blended  with  the  ligamentum  spirale  on  the  outer  wall  of  the  spiral 
canal.1 

The  inner  surface  of  the  osseous  labyrinth  is  lined  by  an  exceedingly  thin 
fibro-serous  membrane,  analogous  to  a  periosteum  from  its  close  adhesion  to  the 
inner  surfaces  of  these  cavities,  and  performing  the  office  of  a  serous  membrane 
by  its  free  surface.  It  lines  the  vestibule,  and  from  this  cavity  is  continued  into 
the  semicircular  canals  and  the  scala  vestibuli  of  the  cochlea,  and  through  the 
helicotrema  into  the  scala  tympani.  This  membrane  is  continued  across  the 
fenestrae  ovalis  and  rotunda,  and  consequently  has  no  communication  with  the 
lining  membrane  of  the  tympanum.  Its  attached  surface  is  rough  and  fibrous, 
and  closely  adherent  to  the  bone ;  its  free  surface  is  smooth  and  pale,  covered 
with  a  layer  of  epithelium,  and  secretes  a  thin,  limpid  fluid,  the  aqua  labyrinthi, 
liquor  Cotunnii,  or  perilymph  (Blainville). 

The  Membranous  Labyrinth. 

The  membranous  labyrinth  (Fig.  551)  is  a  closed  sac,  containing  fluid,  on  the 
walls  of  which  the  ramifications  of  the  auditory  nerve  are  distributed.  It  has  the 
same  general  form  as  the  cochlea,  vestibule,  and  semicircular  canals  in  which  it 
is  enclosed,  but  is  considerably  smaller,  and  the  vestibular  and  canalicular  por- 
tions are  more  or  less  surrounded  by  the  perilymph. 

The  scala  media,  already  described  in  connection  with  the  cochlea,  is  closed 
above  and  below.  The  upper  blind  extremity  is  attached  to  the  cupola  at  the 
upper  part  of  the  helicotrema ;  the  lower  end  fits  into  the  angle  at  the  com- 
mencement of  the  osseous  lamina  on  the  floor  of  the  vestibule.  Near  this  blind 
extremity  the  scala  media  receives  the  canalis  reuniens  (Fig.  551),  a  very  delicate 
canal  by  which  the  ductus  cochlearis  is  brought  into  continuity  with  the  saccule. 

The  vestibular  portion  consists  of  two  sacs,  the  utricle  and  the  saccule. 

The  utricle  is  the  larger  of  the  two,  of  an  oblong  form,  compressed  laterally, 
and  occupies  the  upper  and  back  part  of  the  vestibule,  lying  in  contact  with  the 
fovea  semi-elliptica.  Numerous  filaments  of  the  auditory  nerve  are  distributed 
on  the  wall  of  this  sac,  and  its  cavity  communicates  behind  with  the  membra- 
nous semicircular  canals  by  five  orifices.  It  also  sends  off  a  minute  canal  into 
the  aqueductus  vestibuli,  which  unites  with  the  ductus  endolymphaticus,  a  similar 
but  somewhat  larger  tubular  prolongation  from  the  saccule. 

The  saccule  is  the  smaller  of  the  two  vestibular  sacs ;  it  is  globular  in  form, 
lies  in  the  fovea  hemispherica  near  the  opening  of  the  vestibular  scala  of  the 
cochlea,  and  receives  numerous  nervous  filaments  which  enter  from  the  bottom 
of  the  depression  in  Avhich  it  is  contained.  Its  cavity  communicates  with  that 
of  the  scala  media  by  means  of  the  canalis  reuniens  and  with  that  of  the  utricle 
in  the  manner  just  mentioned. 

1  In  Fig.  550  only  the  inner  half  of  the  membrane  is  represented. 


THE   MEMBRANOUS   LABYRINTH   OF    THE   EAR. 


927 


The  membranous  *>  mi<-ir<-ular  canals  are  about  one-third  the  diameter  of  the 
osseous  canals,  but  in  number,  shape,  and  general  form  they  are  precisely  simi- 
lar: they  are  hollow,  and  open  by  five  orifices  into  the  utricle,  one  opening  being 
common  to  two  canal-?.  Their  ampullae  are  thicker  than  the  rest  of  the  tubes, 
and  nearly  fill  the  cavities  in  which  they  are  contained. 

Numerous  fibrous  bands  stretch  across  between  the  membranous  and  bony 
labyrinths.  These  fibrous  bands  convey  the  blood-vessels  and  nervous  fila- 
ments distributed  to  the  utricle,  to  the  saccule,  and  to  the  ampulla  of  each 
canal. 

Structure. — The  wall  of  the  membranous  labyrinth  is  semi-transparent,  and 
consists  of  three  layers.  The  outer  layer  is  a  loose  and  flocculent  structure, 
apparently  composed  of  ordinary  fibrous  tissue,  containing  blood-vessels  and 
numerous  pigment-cells  analogous  to  those  in  the  pigment-coat  of  the  retina.  The 
middle  layer,  thicker  and  more  transparent,  bears  some  resemblance  to  the  hyaloid 


/AMPULLyE 


DUCTUS 

ENDO-LYMPHATICU8 


CANALISREUNIENS 
FIG.  551.— The  membranous  labyrinth.    (Enlarged.) 

membrane,  but  it  presents  on  its  internal  surface  numerous  papilliform  projections, 
and  on  the  addition  of  acetic  acid  presents  an  appearance  of  longitudinal  fibrilla- 
tion and  elongated  nuclei.  The  inner  layer  is  formed  of  polygonal  nucleated  epi- 
thelial cells,  which  secrete  the  endolvmph. 

The  endolymph  (liquor  Scarpce)  is  a  limpid  serous  fluid  which  fills  the  membra- 
nous labyrinth ;  in  composition  it  closely  resembles  the  perilymph. 

The  otoliths  are  two  small  rounded  bodies  consisting  of  a  mass  of  minute  crys- 
talline grains  of  carbonate  of  lime,  held  together  in  a  mesh  of  delicate  fibrous 
tissue,  and  contained  in  the  walls  of  the  utricle  and  saccule,  opposite  the  distribu- 
tion of  nerves.  A  calcareous  material  is  also,  according  to  Bowman,  sparingly 
scattered  in  the  cells  lining  the  ampulla  of  each  semicircular  canal. 

The  arteries  of  the  labyrinth  are — the  internal  auditory,  from  the  basilar;  the 
stylo-mastoid,  from  the  posterior  auricular  ;  and,  occasionally,  branches  from  the 
occipital.  The  internal  auditory  divides  at  the  bottom  of  the  internal  meatus  into 
two  branches,  cochlear  and  vestibular. 

The  cochlear  branch  subdivides  into  from  twelve  to  fourteen  twigs,  which 
traverse  the  canals  in  the  modiolus.  and  are  distributed,  in  the  form  of  a  capillary 
network,  in  the  substance  of  the  lamina  spiralis. 

The  vestibular  branches  accompany  the  nerves,  and  are  distributed,  in  the  form 
of  a  minute  capillary  network,  in  the  substance  of  the  membranous  labyrinth. 

The  veins  (auditory)  of  the  vestibule  and  semicircular  canals  accompany  the 
arteries,  and,  receiving  those  of  the  cochlea  at  the  base  of  the  modiolus,  terminate 
in  the  superior  petrosal  sinus. 

The  auditory  uerve,  the  special  nerve  of  the  sense  of  hearing,  divides,  at  the 


928  THE    ORGANS    OF  XENSE. 

bottom  of  the  internal  auditory  meatus,  into  two  branches,  the  cochlear  and  ves- 
tibular.  The  trunk  of  the  nerve,  as  well  as  the  branches,  contains  numerous 
ganglion-cells  with  caudate  prolongations. 

The  vestibular  nerve,  the  posterior  of  the  two,  divides  into  three  branches — 
superior,  middle,  and  inferior. 

The  superior  vestibular  branch,  the  largest,  divides  into  numerous  filaments, 
which  pass  through  minute  openings  at  the  upper  and  back  part  of  the  cul-de- 
sac  at  the  bottom  of  the  meatus,  and,  entering  the  vestibule,  are  distributed 
to  the  utricle  and  to  the  ampulla  of  the  external  and  superior  semicircular 
canals. 

The  middle  vestibular  branch  consists  of  numerous  filaments,  which  enter  the 
vestibule  by  a  smaller  cluster  of  foramina  placed  below  those  above  mentioned, 
and  which  correspond  to  the  bottom  of  the  fovea  hemispherica ;  they  are  distributed 
to  the  saccule. 

The  inferior  and  smallest  branch  passes  backward  in  a  canal  behind  the  fora- 
mina for  the  nerves  of  the  saccule,  and  is  distributed  to  the  ampulla  of  the  pos- 
terior semicircular  canal. 

The  nervous  filaments  enter  the  ampullary  enlargements  at  a  deep  depression 
seen  on  their  external  surface,  with  a  corresponding  elevation  when  seen  from 
within  ;  the  nerve-fibres  ending  in  loops  and  in  free  extremities.  In  the  utricle 
and  saccule  the  nerve-fibres  spread  out,  some  blending  with  the  calcareous  matter ; 
others,  radiating  on  the  inner  surface  of  the  wall  of  each  cavity,  become  blended 
with  a  layer  of  nucleated  cells  and  terminate  in  a  thin  fibrous  film. 

The  cochlear  nerve  divides  into  numerous  filaments  at  the  base  of  themodiolus, 
which  ascend  along  its  canals,  and  then,  bending  outward  at  right  angles,  pass 
between  the  plates  of  the  bony  lamina  spiralis,  close  to  its  tympanic  surface. 
Between  the  plates  of  the  spiral  lamina  the  nerves  form  a  plexus  which  contains 
ganglion  cells  forming  the  ganglion  spirale.  From  this  ganglion  delicate  filaments 
pass  between  the  layers  of  the  osseous  lamina  to  the  sulcus  spiralis  and  pass  out- 
ward to  the  organ  of  Corti.  Their  exact  termination  is  uncertain.  Waldeyer 
describes  them  as  collected  into  two  groups,  one  group  ending  in  the  outer  and  the 
other  in  the  inner  hair-cells. 

The  bottom  of  the  internal  auditory  meatus,  known  as  the  lamina  cribrosa,  is 
subdivided  by  a  horizontal  ridge,  the  crista  falciformis,  into  a  superior  and  an 
inferior  fossa.  In  the  superior  fossa  is  seen  anteriorly  the  for  amen  faciale  or 
orifice  of  the  aqueductus  Fallopii ;  and  posteriorly  is  a  group  of  foramina,  area 
cribrosa  superior,  for  the  nerve-filaments  to  the  utricle,  superior  and  external 
semicircular  canals  (superior  vestibular  branch).  In  the  inferior  fossa  are :  (1) 
a  group  of  foramina,  area  cribrosa  media,  for  the  filaments  to  the  saccule  (middle 
vestibular  branch) ;  (2)  posteriorly,  the  foramen  singulare,  for  the  nerve  to  the 
posterior  semicircular  canal  (inferior  vestibular  branch) ;  (3)  antero-inferiorly,  the 
foramina  for  the  filaments  of  the  cochlear  branch,  grouped  in  a  spiral,  tract  us 
spiralis  for aminulentus,  and  at  the  end  of  the  spiral  is  the  foramen  centrale  coch- 
lea? or  orifice  of  the  central  canal  of  the  modiolus. 

Surgical  Anatomy.— Malformations,  such  as  imperfect  development  of  the  external  parts, 
absence  of  the  meatus,  or  supernumerary  auricles,  are  occasionally  met  with.  Or  the  pinna  may 
present  a  congenital  fistula  which  is  due  to  defective  closure  of  the  first  visceral  cleft,  or  rather 
of  that  portion  of  it  which  is  not  concerned  in  the  formation  of  the  Eustachian  tube,  tympanum, 
and  meatus.  The  skin  of  the  aui-icle  is  thin  and  richly  supplied  with  blood,  but  in  spite  of  this 
it  is  frequently  the  seat  of  frost-bite,  due  to  the  fact  that  it  is  much  exposed  to  cold,  and  lacks 
the  usual  covering  of  subcutaneous  fat  found  in  most  other  parts  of  the  body.  A  collection  of 
blood  is  sometimes  found  between  the  cartilage  and  perichondrium  (licematoma  auris),  usually 
the  result  of  traumatism,  but  not  necessarily  due  to  this  cause.  It  is  said  to  occur  moet  fre- 
quently in  the  ears  of  the  insane.  Keloid  sometimes  grows  in  the  auricle  around  the  puncture 
made  for  earrings,  and  epithelioma  occasionally  affects  this  part.  Deposits  of  urate  of  soda  are 
often  met  with  in  the  pinna  in  gouty  subjects. 

The  external  auditory  meatus  can  be  most  satisfactorily  examined  by  light  reflected 
down  a  funnel-shaped  speculum;  by  gently  moving  the  latter  in  different  directions  the 
whole  of  the  canal  and  membrana  tympani  can  be  brought  into  view.  The  points  to  be  noted 


SURGICAL   ANATOMY   OF   THE  EAR.  929 

are.  the  presence  of  wax  or  foreign  bodies,  the  size  of  the  canal,  and  the  condition  of  the  niern- 
brana  tympani.  The  accumulation  of  wax  is  often  the  cause  of  deafness,  and  may  give  rise  to 
very  serious  consequences,  causing  ulceration  of  the  membrane  and  even  absorption  of  the  bony 
wall  of  the  canal.  Foreign  bodies  are  not  infrequently  introduced  into  the  ear  by  children,  and, 
when  situated  in  the  first  portion  of  the  canal,  may  be  removed  with  tolerable  facility  by  means 
of  a  minute  hook  or  loop  of  fine  wire,  with  reflected  light;  but  when  they  have  slipped  beyond 
the  narrow  middle  part  of  the  meatus.  their  removal  is  in  no  wise  easy,  and  attempts  to  effect 
it.  in  inexperienced  hands,  may  be  followed  by  destruction  of  the  membrana  tympani  and  possi- 
bly the  contents  of  the  tympanum.  The  calibre  of  the  external  auditory  canal  may  be  narrowed 
by  inflammation  of  its  lining  membrane,  running  on  to  suppuration  ;  by  periostitis  :  by  polypi, 
sebaceous  tumors,  and  exostoses.  The  membrana  tyrnpani.  when  seen  in  a  healthy  ear.  "  reflects 
light  strongly,  and.  owing  to  its  peculiar  curvature,  presents  a  bright  spot  of  triangular  shape  at 
its  lower  and  anterior  portion. ' '  From  the  apex  of  this,  proceeding  upward  and  slightly  forward, 
is  a  white  streak  formed  by  the  handle  of  the  malleus,  while  at  the  upper  and  middle  part  of  the 
membrane  may  be  seen  a  slight  projection,  caused  by  the  short  process  of  the  malleus.  In 
disease  alterations  in  color,  lustre,  curvature  or  inclination,  and  perforation  must  be  noted.  Such 
perforations  may  be  caused  by  a  blow  or  a  loud  report  or  by  a  wound. 

The  upper  wall  of  the  meatus  is  separated  from  the  cranial  cavity  by  a  thin  plate  of  bone ; 
the  anterior  wall  is  separated  from  the  temporo-maxillary  joint  and  parotid  gland  by  the  bone 
forming  the  glenoid  fossa ;  and  the  posterior  wall  is  in  relation  with  the  mastoid  cells ;  hence 
inflammation  of  the  external  auditory  meatus  may  readily  extend  to  the  membranes  of  the  brain, 
to  the  temporo-rnaxillary  joint,  or  to  the  mastoid  cells ;  and,  in  addition  to  this,  blows  on  the  chin 
may  cause  fracture  of  the  wall  of  the  meatus. 

The  nerves  supplying  the  meatus  are  the  auricular  branch  of  the  pneumogastric,  the 
auriculo-temporal.  and  the  auricularis  magnus.  The  connections  of  these  nerves  explain  the 
fact  of  the  occurrence,  in  cases  of  any  irritation  of  the  meatus,  of  constant  coughing  and  sneez- 
ing from  implication  of  the  pneumogastric.  or  of  yawning  from  implication  of  the  auriculo- 
temporal.  No  doubt  also  the  association  of  earache  with  toothache  in  cancer  of  the  tongue  is 
due  to  implication  of  the  same  nerve,  a  branch  of  the  fifth,  which  supplies  also  the  teeth  and 
the  tongue.  The  vessels  of  the  meatus  and  membrana  tympani  are  derived  from  the  posterior 
auricular,  temporal,  and  internal  maxillary  arteries.  The  upper  half  of  the  membrana  tympani 
is  much  more  richly  supplied  with  blood  than  the  lower  half.  For  this  reason,  and  also  to  avoid 
the  chorda  tympani  nerve  and  ossicles,  incisions  through  the  membrane  should  be  made  at  the 
lower  and  posterior  part. 

The  principal  point  in  connection  with  the  surgical  anatomy  of  the  tympanum  is  its  relations 
toother  parts.  Its  roof  is  formed  by  a  thin  plate  of  bone,  which,  with  the  dura  mater,  is  all  that 
separates  it  from  the  temporo-sphenoidal  lobe  of  the  brain.  Its  floor  is  immediately  above  the 
jugular  fossa  behind  and  the  carotid  canal  in  front.  Its  posterior  wall  presents  the  openings  of 
the  mastoid  cells.  On  its  anterior  wall  is  the  opening  of  the  Eustachian  tube.  Thus  it  follows 
that  in  disease  of  the  middle  ear  we  may  get  subdural  abscess,  septic  meningitis,  or  abscess  of 
the  cerebrum  or  cerebellum  from  extension  of  the  inflammation  through  the  bony  roof;  throm- 
bosis of  the  lateral  sinus,  with  or  without  pyaemia,  by  extension  through  the  floor ;  or  mastoid 
abscess  by  extension  backward.  In  addition  to  this,  we  may  get  fatal  haemorrhage  from  the 
internal  carotid  in  destructive  changes  of  the  middle  ear ;  and  in  throat  disease  we  may  get  the 
inflammation  extending  up  the  Eustachian  tube  to  the  middle  ear.  The  Eustachian  tube  is 

-- ible  from  the  nose.  If  the  nose  and  mouth  be  closed  and  an  attempt  made  to  expire  air. 
-e  of  pressure  with  dulness  of  hearing  is  produced  in  both  ears,  from  the  air  finding  its 
way  up  the  Eustachian  tube  and  bulging  out  the  membrana  tympani.  During  the  act  of 
swallowing  the  pharyngeal  orifice  of  the  tube,  which  is  normally  closed,  is  opened,  probably  by 
the  action  of  the  Tensor  tympani.  This  fact  was  employed  by  Politzer  in  devising  an  easy 
method  of  inflating  the  tube.  The  nozzle  of  an  india-rubber  syringe  is  inserted  into  the  nostril ; 
the  patient  takes  a  mouthful  of  water  and  holds  it  in  his  mouth ;  both  nostrils  are  closed  with 
the  finger  and  thumb  to  prevent  the  escape  of  air,  and  the  patient  is  then  requested  to  swallow ; 
as  he  does  so  the  air  is  forced  out  of  the  syringe  into  his  nose,  and  is  driven  into  the  Eustachian 
tube,  which  is  now  open.  The  impact  of  the  air  against  the  membrana  tympani  can  be  heard,  if 
the  membrane  is  sound,  by  means  of  a  piece  of  india-rubber  tubing,  one  end  of  which  is  inserted 
into  the  meatus  of  the  patient's  ear.  the  other  into  that  of  the  surgeon.  The  direct  examination 
of  the  Eustachian  tube  is  made  by  the  Eustachian  catheter.  This  is  passed  along  the  floor  of 
the  nostril,  with  the  curve  downward,  to  the  posterior  wall  of  the  pharynx.  When  this  is  felt, 
the  catheter  is  to  be  withdrawn  about  half  an  inch,  and  the  point  rotated  outward  through  a 
quarter  of  a  circle,  and  pushed  again  slightly  backward,  when  it  will  enter  the  orifice  of  the  tube, 
and  will  be  found  to  be  caught,  and  air  forced  into  the  catheter  will  be  heard  impinging  on  the 
tympanic  membrane  if  the  ears  of  the  patient  and  surgeon  are  connected  by  an  india-rubber 
tube. 

59 


THE  ORGANS  OF  DIGESTION. 


Apparatus  for  the  Digestion  of  the  Food  consists  of  the  alimentary  canal 
_L    and  of  certain  accessory  organs. 

The  alimentary  canal  is  a  musculo-membranous  tube,  about  thirty  feet  in 
length,  extending  from  the  mouth  to  the  anus,  and  lined  throughout  its  entire 
extent  by  mucous  membrane.  It  has  received  different  names  in  the  various  parts 
of  its  course :  at  its  commencement,  the  mouth,  we  find  provision  made  for  the 
mechanical  division  of  the  food  (mastication),  and  for  its  admixture  with  a  fluid 
secreted  by  the  salivary  glands  (insalivatioii) ;  beyond  this  are  the  organs  of 
deglutition,  the  pharynx  and  the  oesophagus,  which  convey  the  food  into  that  part 
of  the  alimentary  canal  (the  stomach)  in  which  the  principal  chemical  changes 
occur,  and  in  which  the  reduction  and  solution  of  the  food  take  place  ;  in  the  small 
intestines  the  nutritive  principles  of  the  food  (the  chyle)  are  separated,  by  its 
admixture  with  the  bile  and  pancreatic  fluid,  from  that  portion  which  passes  into 
the  large  intestine,  most  of  which  is  expelled  from  the  system. 

Alimentary   Canal. 

f  Duodenum. 

Mouth.  Small  intestines  Jejunum. 

Pharynx.  ( Ileum. 

(Esophagus.  T  Caecum. 

Stomach.  Large  intestines  Colon. 

(  Rectum. 


Accessory    Organs. 
Teeth. 

(  Parotid. 
Salivary  glands  <  Submaxillary. 

(  Sublingual. 


Liver. 

Pancreas. 

Spleen. 


THE  MOUTH. 


The  mouth  (oral  or  buccal  cavity)  (Fig.  552)  is  the  vestibule  to  the  alimentary 
canal.  It  is  a  nearly  oval-shaped  cavity,  bounded  in  front  by  the  lips,  upon  the 
sides  by  the  cheeks,  behind  by  the  soft  palate  and  fauces.  The  upper  and  lower 
dental  arches,  together  with  their  alveolar  processes,  subdivide  the  general  cavity 
into  a  lingual  and  a  buccal  cavity.  The  latter  has  as  its  inner  wall  the  external 
faces  of  the  teeth  and  gums  of  both  jaws ;  its  external  wall  is  formed  by  the  lips 
and  cheeks.  The  lingual  cavity  is  bounded  anteriorly  and  laterally  by  the  lingual 
surfaces  of  both  dental  arches ;  above,  by  the  hard  and  the  soft  palates ;  below,  by 
the  floor  of  the  mouth  and  the  tongue. 

The  mucous  membrane  lining  the  mouth  is  continuous  with  the  integument  at 
the  free  margin  of  the  lips  and  with  the  mucous  lining  of  the  fauces  behind  ;  it  is 
of  a  rose-pink  tinge  during  life,  and  very  thick  where  it  covers  the  hard  parts 
bounding  the  cavity.  It  is  covered  by  stratified  epithelium. 

The  lips  are  two  fleshy  folds  which  surround  the  orifice  of  the  mouth,  formed 
externally  of  integument  and  internally  of  mucous  membrane,  between  which  are 
found  the  Orbicularis  oris,  muscle,  the  coronary  vessels,  some  nerves,  areolar  tissue, 
and  fat,  and  numerous  small  labial  glands.  The  inner  surface  of  each  lip  is  con- 

930 


THE  MOUTH. 


931 


nected  in  the  middle  line  to  the  gum  of  the  corresponding  jaw  by  a  fold  of  mucous 
membrane,  the  fr&num  labii  su^erioris  and  inferioris — the  former  being  the  larger 
of  the  two. 

The  labial  glands  are  situated  between  the  mucous  membrane  and  the  Orbicu- 
laris  oris  round  the  orifice  of  the  mouth.  They  are  rounded  in  form,  about  the 
size  of  small  peas,  their  ducts  opening  by  small  orifices  upon  the  mucous  mem- 
brane. In  structure  they  resemble  the  salivary  glands. 

The  cheeks  form  the  sides  of  the  face  and  are  continuous  in  front  with  the  lips. 
They  are  composed  externally  of  integument,  internally  of  mucous  membrane, 
and  between  the  two  of  a  muscular  stratum,  besides  a  large  quantity  of  fat,  areolar 
tissue,  vessels,  nerves,  and  buccal  glands. 

The  mu--  : nine  lining  the  cheek  is  reflected  above  and  below  upon  the 

gums,  where  its  color  becomes  lighter ;  it  is  continuous  behind  with  the  lining  mem- 


Opening  of  nasal  dvxL 


Bristle  passed  through 
Stenson's  duct. 


FIG.  552.— Sectional  view  of  the  nose,  month,  pharynx,  etc. 

brane  of  the  soft  palate.  Opposite  the  second  molar  tooth  of  the  upper  jaw  is  a 
papilla,  the  summit  of  which  presents  the  aperture  of  the  duct  of  the  parotid  gland. 
The  principal  muscle  of  the  cheek  is  the  Buccinator,  but  numerous  other  muscles 
enter  into  its  formation — viz.  the  Zygomatici,  Risorius  Santorini,  and  Platysma 
myoides. 

The  buccal  glands  are  placed  between  the  mucous  membrane  and  Buccinator 
muscle :  they  are  similar  in  structure  to  the  labial  glands,  but  smaller.  Two  or 
three  of  larger  size  than  the  rest  are  placed  between  the  Masseter  and  Buccinator 
muscles ;  their  ducts  open  into  the  mouth  opposite  the  last  molar  tooth.  They  are 
called  iii'jlir  ,/lmds. 

The  gums  are  composed  of  a  dense  fibrous  tissue  closely  connected  to  the 


932 


THE    ORGANS    OF  DIGESTION. 


periosteum  of  the  alveolar  processes  and  surrounding  the  necks  of  the  teeth.  They 
are  covered  by  smooth  and  vascular  mucous  membrane,  which  is  remarkable  for  its 
limited  sensibility.  Around  the  necks  of  the  teeth  this  membrane  presents  numer- 
ous fine  papillae.  The  deep  fibrous  layer  is  continuous  with  the  periosteum  lining 
the  alveoli,  (the  pericementum). 

THE  TEETH. 

The  human  subject  is  provided  with  two  sets  of  teeth,  which  make  their  appear- 
ance at  different  periods  of  life.  The  first  set  appear  in  childhood,  and  are  called 

the  temporary,  deciduous,  or  milk  teeth.    The 
second  set  are  named  permanent. 

The  temporary  teeth  are  twenty  in  num- 
ber— four  incisors,  two  canine,  and  four 
molars,  in  each  jaw  (Fig.  553). 

The  permanent  teeth  are  thirty-two  in 
number — four  incisors  (two  central  and  two 
lateral),  two  canines,  four  bicuspids,  and  six 
molars  in  each  jaw  (Fig.  554). 

General  Characters. — Each  tooth  consists 
of  three  portions :  the  crown,  or  body,  pro- 
jecting above  the  gum;  the  root,  or  fang, 
entirely  concealed  within  the  alveolus ;  and 
the  neck,  the  constricted  portion,  between  the 
root  and  crown. 

The  surfaces  of  a  tooth  are  named  thus :  that  which  looks  toward  the  lips  is 
the  labial;  that  toward  the  tongue  is  the  lingual ;  that  toward  the  mesial  line, 
proximal;  that  away  from  the  same,  distal;  that  toward  the  cheek,  the  buccal 
surface.  This  applies  to  the  roots  as  well  as  to  the  crowns  of  teeth. 


FIG.  553. — Deciduous  teeth.    Left  side. 


FIG.  554.— Permanent  teeth.    Right  side  (Burchanl). 

The  roots  of  the  teeth  are  firmly  implanted  within  the  alveoli  (Fig.  558) ;  these 
depressions  are  lined  with  periosteum  (the  pericementum)  which  is  reflected  on  to 
the  tooth  at  the  point  of  the  root  and  covers  it  as  far  as  the  neck.  At  the  margin 
of  the  alveolus  the  periosteum  becomes  continuous  with  the  fibrous  structure  of 
the  gums. 

Permanent  Teeth  (Figs.  555  and  556). 

The  incisors,  or  cutting  teeth,  are  so  named  from  their  presenting  a  sharp  cut- 
ting edge,  adapted  for  incising  the  food.  They  are  eight  in  number,  and  comprise 
the  four  front  teeth  in  each  jaw. 


THE    TEETH. 


933 


FIG.  555.— Right  halt  of  upper 
jaw  (from  below),  with  the  cor- 
responding teeth.  The  letters 
and  numbers  point  to  the 
classes  of  teeth  and  the  num- 
bers in  classes. 


The  crown  is  directed  almost  vertically  and  is  spade-like  in  form  ;  it  has  the  form 
of  a  truncated  cone  whose  top  has  been  compressed  into  a  sharp  horizontal  cutting 
edge.     Before  being  subjected  to  attrition  this  edge  pre- 
sents three  small  elevations.    The  labial  surface  is  convex, 
and  marked  by  three  longitudinal  ridges  extending  from 
the  edge  tubercles  toward  the  neck  of  the  tooth.     The 
lingual  surface  is  concave,  and  is  marked  by  two  marginal 
ridges  extending  from  an  encircling  ridge  at  the  neck  to 
the  angles  of  the  cutting  edge  of  the  tooth.    The  ridge  at 
the  neck  is  termed  the  cingulum  or  basal  ridge. 

The  mesial  and  distal  *urf<u'i'8  are  triangular,  the 
apex  of  the  triangle  at  the  cutting  edge. 
The  neck  of  the  tooth  is  constricted. 
The  root  is  long,  single,  and  has  the  form  of  a  trans- 
versely flattened  cone,  thicker  before  than  behind.     The 
root  may  be  curved. 

The  incisor*  of  tie  upju-r  j>nc  are  altogether  larger 
and  stronger  than  those  of  the  lower  jaw.  the  central 
incisors  being  larger  and  flatter  than  the  laterals.  They 
are  directed  obliquely  downward  and  forward. 

The  //<r/.v, ,/-.>•  ,;,f  tJt,'  lower  jaw  are  smaller  and  flatter 
than  the  upper,  and  the  elevations  upon  their  lingual 
faces  are  not  marked.  The  two  central  are  smaller  than 
the  two  lateral  incisors,  being  the  smallest  of  all  the 

teeth.  The  roots  of  these  teeth  are  flattened  laterally. 
The  canine  teeth  (cuspidati)  are  four  in  number,  two 
in  the  upper,  two  in  the  lower  jaw — one  being  placed 
distal  to  each  lateral  incisor.  They  are  larger  and 
stronger  than  the  incisors,  especially  in  the  roots,  which 
are  deeply  implanted  and  cause  well-marked  prominence 
of  the  process  at  the  places  of  insertion. 

The  crown  is  large,  of  spear-head,  form  and  its  very 
convex  labial  surface  is  marked  by  three  longitudinal 
ridges.  The  concave  labial  surface  is  also  marked  by 
three  ridges  which  unite  at  a  basal  ridge.  The  point  or 
cusp  is  longer  than  in  the  other  teeth,  and  is  the  point  of 
division  between  a  short  mesial  and  a  long  distal  cutting 
edge. 

The  root  is  oval  or  elliptical  in  transverse  section,  and 
is  longer  and  more  prominent  than  the  roots  of  the 
incisors. 

The  upper  canines  or  cuspids  (vulgarly  called  the  eye 
teeth)  are  larger  and  longer  than  the  two  lower,  and 
in  occlusion  are  distal  to  them  to  the  extent  of  half  the 
width  of  the  crown. 

The  lower  canines  (vulgarly  called  the  stomach  teeth) 
have  the  general  form  of  the  upper  cuspids,  but  their  lin- 
gual surfaces  are  much  more  flattenec.  owing  to  the 
absence  of  the  elevations  marking  the  upper.  Their  roots  are  more  flattened  and 
may  be  bifid  at  their  apices. 

The  bicuspid  teeth  (premolars)  are  eight  in  number,  four  in  each  jaw  :  they  are 

placed  distal  to  the  cuspid  teeth,  two  upon  each  side.    They  are  double  cuspids  in  form. 

The  crown  is  surmounted  by  two  cusps,  one  buccal  and  one  lingual,  separated 

by  a  groove,  the  buccal  being  more  prominent  and  larger  than  the  lingual.     The 

lower  bicuspids  are  not  truly  bicuspid,  the  first  having  but  a  primitive  lingual  cusp,  the 

second  having  the  lingual  cusp  divided  into  two  sections — i.  e.  it  is  usually  tricuspid. 

The  necks  of  the  teeth  are  oval ;  the  roots  are  laterally  compressed,  that  of  the 


FIG.  556.— Right  half  of 
lower  jaw.  with  the  corre- 
sponding teeth.  The  letter 
and  numbers  point  to  the 
various  cusps  or  their  modifi- 
cations on  the  different  teeth 
(Burchard). 


934 


THE    ORGANS    OF  DIGESTION. 


first  upper  bicuspid  being  frequently  bifid.  The  first  upper  bicuspid  is  usually  the 
largest  of  the  series. 

The  molar  teeth  (multicuspidati ;  or  grinders)  are  the  largest  teeth  of  the  den- 
ture. They  are  adapted  by  their  forms  for  the  crushing  and  grinding  of  the  food. 
They  are  twelve  in  number,  six  in  each  jaw,  three  being  placed  posterior  to  each 
second  bicuspid. 

The  crowns  are  cuboidal  in  form,  are  convex  buccally  and  lingually ;  they  are 
flattened  mesially  and  distally.  They  are  formed  by  the  fusion  of  three  primitive 
cuspids  in  the  upper  and  four  in  the  lower.  To  these  are  added  in  the  first  and 
second  upper  molars  a  disto-lingual  tubercle,  and  in  the  first  and  third  molars  of 
the  lower  jaw  a  disto-buccal  tubercle.  The  unions  of  the  primitive  forms  are 
marked  by  sulci.  The  necks  of  these  teeth  are  large  and  rhomboidal  in  form. 

The  roots  of  the  upper  molars  are  three  in  number — one  large  lingual  and  two 
smaller  buccal  roots.  In  the  lower,  two  roots  are  found,  a  mesial  and  a  distal,  each 
of  which  is  much  flattened  from  before  backward. 

The  first  molar  teeth  are  the  largest  of  the  dental  series :  they  have  four  cusps 
on  the  upper  and  five  in  the  lower — three  buccal  and  two  lingual. 

The  second  molars  are  smaller ;  the  crown  of  the  upper  is  compressed  until  the 
disto-lingual  cusp  is  reduced.  The  crowns  of  the  lower  are  almost  rectangular,  with 
a  cusp  at  each  angle. 

The  third  molars  are  called  the  wisdom  teeth  (denies  sapientice)  from  their  late 
eruption :  they  have  three  cusps  upon  the  upper  and  five  upon  the  lower.  The 
three  roots  of  the  upper  are  frequently  fused  together,  forming  a  grooved  cone, 
which  is  usually  curved  backward.  The  roots  of  the  lower,  two  in  number,  are 
compressed  together  and  curve  backward. 


Right  upper. 


Temporary  Teeth  (Figs.  553  and  557). 

The  temporary  or  milk  teeth  are  smaller,  but 
resemble  in  form  those  of  the  permanent  set.  The 
neck  is  more  marked,  owing  to  the  greater  degree 
of  convexity  of  the  labial  and  lingual  surfaces  of 
the  crown.  The  hinder  of  the  two  temporary  mo- 
lars is  the  largest  of  all  the  deciduous  teeth,  and  is 
succeeded  by  the  second  bicuspid.  The  first  upper 
molar  has  only  three  cusps — two  labial,  one  lin- 
gual ;  the  second  upper  molar  has  four  cusps.  The 
first  lower  molar  has  four  cusps ;  the  second  lower 
molar  has  five.  The  roots  of  the  temporary  molar 
teeth  are  smaller  and  more  diverging  than  those 
of  the  permanent  set,  but  in  other  respects  bear  a 
strong  resemblance  to  them. 


Lin- 


Arrangement  of  the  Teeth.1 

The  human  teeth  are  arranged  in  two  parabolic  arches,  the  upper  arch  being 
larger,  its  teeth  overlapping  the  lower.  The  average  distance  between  the  centres 
of  the  condyles  of  the  inferior  maxillary  bones  is  about  four  inches,  which  is  also 
the  distance  from  either  of  these  points  to  the  line  of  junction  between  the  lower 
incisor  teeth.  Whether  the  jaw  be  large  or  small,  the  equilateral  triangle  indicated 
is  included  in  it ;  the  range  of  size  is  between  3^"— 4^-". 

Owing  to  the  smaller  sizes  of  the  lower  incisors,  the  teeth  of  the  lower  jaw  are 
each  one  half  a  tooth  in  advance  of  its  upper  fellow,  so  that  each  tooth  of  the  dental 
series  has  two  antagonists,  with  the  exception  of  the  lower  central  incisors  and 
upper  third  molars  (Figs.  558,  559). 

The  grinding  faces  of  the  upper  bicuspids  and  molars  curve  progressively  up- 
ward and  point  outward,  the  first  molar  being  at  the  lowest  point  of  the  curve, 

1  After  Dr.  W.  G.  A.  Bonwill. 


OF    THE    TEETH. 


935 


the  third  molar  at  the  highest.  The  curve  of  the  lower  dental  arch  is  the  reverse, 
the  first  molar  at  its  deepest  part,  the  third  molar  at  its  extremity.  The  greater 
the  depth  to  which  the  upper  incisors  overlap  the  lower,  the  more  marked  this 
curve  and  the  more  pointed  are  the  cusps  of  the  grinding  teeth. 


,J£>*  •    :-          ^WA  /-  '  ".*\, 

i*C  %'  "*  ;-^^     -*  If.''*'  N  -  «     "*  *5 

J?%^  '  "' V' „"  ^f^fr1  r*  i  MB  3V^|  "*'"'•  ^. 

^  *  "Mw 

«•/'  _^^     ; 

-  --  *   " 


FIG.  5f*.— View  of  teeth  in  «7u,  with  the  external  plates  of  the  alveolar  processes  removed  (Cryer). 

The  movement  of  the  human  mandible  is  forward  and  downward,  the  resultant 
of  these  directions  being  an  oblique  line,  upon  an  average  35°  from  the  horizontal 
plane.1  When  the  lower 
jaw  is  advanced  until  the 
cutting  edges  of  the  in- 
cisors are  in  contact,  the 
jaws  are  separated,  but 
as  the  highest  point  of 
the  lower  arch,  its  third 
molar  advances,  it  meets 

and    rests    upon    a    high    J  V  'V^f    ^ 

point,  second  molar  of  the 
upper  arch,  and  thus  un- 
due strain  of  the  incisors 
is  obviated. 

In  the  lateral  move- 
ments of  the  mandible  but 
one  side  is  in  effective  action 
at  one  time;  the  oblique 
positions  of  the  cusps  of 
the  opposite  teeth  are  such 
that  when  either  side  is  in  action  the  other  is  balanced  at  two  or  more  points. 


\ 


FIG.  559.— Front  and  side  views  of  the  teeth  and  jaws. 


1  W.  E.  Walker,  Dental  Cosmos,  1896. 


936 


THE    ORGANS    OF  DIGESTION. 


There  is  an  anatomical  correspondence  between  the  forms  and  arrangement 
of  the  teeth,  the  form  of  the  condyle  of  the  inferior  maxilla,  and  the  mus- 
cular arrangement.  Individuals  who  have  teeth  with  long  cusps  have  the  head 
of  the  bone  much  rounded  from  before  behind,  and  have  a  preponderance  of 
the  direct  over  the  oblique  muscles  of  mastication,  and  vice  versd ;  teeth  with 
short  or  no  cusps  are  associated  with  a  flattened  condyle  and  strong  oblique 
muscles. 

Very  great  aberrations  in  the  dental  arrangement  are  frequently  followed  by 
accomodative  changes  in  the  heads  of  the  inferior  maxilla. 


Structure  of  the  Teeth. 

The  Dental  Pulp. — A  longitudinal  section  of  a  tooth  will  show  the  presence  of  a 
central  chamber  having  the  general  form  of  the  crown  of  the  tooth.  Processes  of 
the  chamber  pass  from  its  body,  one  for  each  root  and  down  each  root,  and  open  at 


Pulp 
cavity. 


Root. 


FIG.  560. — Vertical  section  of  a  molar  tooth. 

the  apex  by  a  minute  orifice,  the  apical 
foramen.  This  cavity  is  known  as  the 
pulp-chamber,  the  minute  canals  the 
pulp-canals.  The  cavity  contains  a  soft, 
vascular,  and  sensitive  organ  called  the 
dental  pulp.  It  is  made  up  of  myxoma- 
tous  tissues,  and  contains  numerous  blood- 
vessels and  nerves,  which  enter  by  way 
of  the  apical  foramina.  It  does  not  pos- 
sess lymphatics.  The  periphery  of  the 
pulp  is  bounded  by  a  layer  of  cells  ar- 
ranged like  columnar  epithelium,  each 
cell  sending  one  or  more  branched  pro- 
cesses through  the  basic  substance  of  the 
dentine.  These  are  the  dentine-forming 
cells,  the  odontoblasts  of  Waldeyer.  The 
blood-vessels  break  up  into  innumerable 
capillary  loops  which  lie  beneath  the 
layer  of  odontoblasts.  The  nerve-fibrils 
break  up  into  numberless  non-medullary 
filaments,  which  spread  out  beneath  the 
odontoblasts,  and  probably  send  terminal 
filaments  to  the  extreme  periphery  of  the 
pulp  outside  the  odontoblasts. 

The  matrix  cells  and  their  processes 
are  irregularly  arranged  in  the  body  of 
the  pulp,  but  in  the  canal  portion  the 
fibrillse  are  in  the  direction  of  the  axis 
of  the  root. 

The  section  will  exhibit  three  hard  tissues  in  a  tooth,  one  forming  the  greater 
mass  of  the  tooth ;  hence  its  name  dentine  (the  ivory).  The  dentine  upon  the 
crown  is  sheathed  by  a  layer  called  the  enamel ;  the  dentine  of  the  root  is  enclosed 


FIG.  561.— Vertical  section  of  a  tooth  in  situ  (15 
diameters),  c  is  placed  in  the  pulp-cavity,  opposite 
the  cervix  or  neck  of  the  tooth  :  the  part  above  is  the 
crown,  that  below  is  the  root  (fang).  1.  Enamel  with 
radial  and  concentric  markings.  2.  Dentine  with 
tubules  and  incremental  lines.  3.  Cement  or  crusta 
petrosa,  with  bon  corpuscles.  4.  Dental  periosteum. 
5.  Bone  of  lower  jaw. 


STRUCTURE    OF   THE    TEETH. 


937 


T^yift 


in  a  distinct  tissue,  the  cementum  or  crusta  petrosa ;  both  cementum  and  enamel  are 
thinnest  at  the  neck  and  thickest  upon  their  distal  portions. 

The  solid  portion  of  the  tooth  consists  of  three  distinct  structures — viz.  the 
proper  dental  substance,  which  forms  the  larger  portion  of  the  tooth,  the  ivory  or 
dentine:  a  layer  which  covers  the 
exposed  part  of  the  crown,  the 
enamel :  and  a  thin  layer,  which  is 
disposed  on  the  surface  of  the  fang, 
the  cement  or  crust  a  />ctrosa. 

The  ivory,  or  dentine  (Fig.  561), 
forms  the  principal  rua^s  of  a  tooth ; 
in  its  central  part  is  the  cavity  en- 
closing the  pulp.  It  is  a  modi- 
fication of  osseous  tissue,  from 
which  it  differs,  however,  in  struc- 
ture. On  microscopic  examination 
it  is  seen  to  consist  of  a  number 
of  minute  wavy  and  branching 
tubes  having  distinct  parictcs. 
They  are  called  the  dentinal  tu- 
buli. and  are  imbedded  in  a  dense 
homogeneous  substance,  the  inter- 
tubular tissue. 

The  dentinal  tubuli  (Fig.  562) 
are  placed  parallel  with  one  an- 
other, and  open  at  their  inner  ends 
into  the  pulp-cavity.  In  their 
course  to  the  periphery  they  present 
two  or  three  curves,  and  are  twisted 
on  themselves  in  a  spiral  direc- 
tion. The  direction  of  these  tubes 
varies  :  they  are  vertical  in  the  up- 
per portion  of  the  crown,  oblique 
in  the  neck  and  upper  part  of  the  root,  and  toward  the  lower  part  of  the  root 
they  are  inclined  downward.  The  tubuli,  at  their  commencement,  are  about 
43*00  of  an  inch  in  diameter ;  in  their  course  they  divide  and  subdivide  dichoto- 
mously.  so  as  to  give  to  the  cut  surface  of  the  dentine  a  striated  appearance. 
From  the  sides  of  the  tubes,  especially  in  the  root,  ramifications  of  extreme 
minuteness  are  given  off,  which  join  together  in  loops  in  the  intertubular  sub- 
stance, or  terminate  in  small  dilatations,  from  which  branches  are  given  off. 
Near  the  periphery  of  the  dentine  the  finer  ramifications  of  the  tubuli  terminate 
in  a  layer  of  irregular  branched  spaces  which  communicate  with  each  other. 
These  are  called  the  interglobular  spaces  of  Czermale,  or  the  granular  layer  of 
Tomes  (Fig.  502.  J).  The  dentinal  tubuli  have  comparatively  thick  walls,  and  con- 
tain slender  cylindrical  prolongations  from  the  processes  of  the  cells  of  the  pulp- 
tissue  already  mentioned,  and  first  described  by  Mr.  Tomes  and  named  Tomes's 
fibres  or  dentinal  fibres.  These  dentinal  fibres  are  analogous  to  the  soft  contents 
of  the  canaliculi  of  bone.  Between  Tomes's  fibres  and  the  ivory  around  the  canals 
there  is  a  tissue  which  is  markedly  resistant  to  the  action  of  acids — the  dentinal 
sheath  of  3~  unn'mn. 

The  intertubular  substance  or  tissue  is  translucent,  and  contains  the  chief  part 
of  the  earthy  matter  of  the  dentine.  After  the  earthy  matter  has  been  removed 
by  steeping  a  tooth  in  weak  acid  the  animal  basis  remaining  may  be  torn  into 
laminae  which  run  parallel  with  the  pulp-cavity  across  the  direction  of  the  tubules. 
These  laminae  show  the  method  of  growth  to  be  by  deposition  of  successive  strata 
of  dentine.  Fibrils  have  been  found  in  the  matrix  of  the  intertubular  substance, 
and  are  probably  continuous  with  the  dentinal  fibres  of  Tomes.  In  a  dry  tooth  a 


' 

'"._..•...,.; *;.--B------ .    --         =      •     --  ,-;*-...  ."*  -i-~- -»-    -- 

Fir;.  562. — Ground  section  through  the  root  of  a  human 
premolar :  D,  dentine  :  A',  cement  corpuscles ;  O,  osteoblasts ; 
Ep.,  remains  of  Hertwig's  epithelial  sheath,  200  diameters ; 
J,  interglobular  spaces  (Rose). 


938 


THE    ORGANS    OF   DIGESTION. 


section  of  dentine  often  displays  a  series  of  lines — the  incremental  lines  of  Salter — 
which  are  parallel  with  the  laminae  above  mentioned.  These  lines  are  caused  by 
two  facts :  (1)  The  imperfect  calcification  of  the  dentinal  laminae  immediately 
adjacent  to  the  line;  (2)  The  drying  process,  which  reveals  these  defects  in  the 
calcification.  These  lines  are  wide  or  narrow  according  to  the  number  of  lamina 
involved,  and  along  their  course,  in  consequence  of  the  imperfection  in  the  calci- 
fying process,  little  irregular  cavities  are  left,  which  are  the  inter  globular  spaces 
already  referred  to.  They  have  received  their  name  from  the  fact  that  they  are 
surrounded  by  minute  nodules  or  globules  of  dentine.  Other  curved  lines  may 
be  seen  parallel  to  the  surface.  These  are  the  lines  of  Sclireger,  and  are  due  to 
the  optical  effect  of  simultaneous  curvature  of  the  dentinal  tubules. 

Chemical  Composition. — According  to  Berzelius  and  Bibra,  dentine  consists  of 
28  parts  of  animal  and  72  of  earthy  matter.  The  animal  matter  is  resolvable  by 
boiling  into  gelatin.  The  earthy  matter  consists  of  phosphate  and  carbonate  with 
calcium,  with  a  trace  of  fluoride  of  calcium,  phosphate  of  magnesia,  and  other 
salts. 

The  enamel  is  the  hardest  and  most  compact  part  of  a  tooth,  and  forms  a  thin 
crust  over  the  exposed  part  of  the  crown  as  far  as  the  commencement  of  the  root. 
It  is  thickest  on  the  grinding  surface  of  the  crown  until  worn  away  by  attrition, 
and  becomes  thinner  toward  the  neck.  It  consists  of  a  congeries  of  minute 
hexagonal  rods,  columns,  or  prisms.  They  lie  parallel  with  one  another,  resting 
by  one  extremity  upon  the  dentine,  which  presents  a  number  of  minute  depres- 
sions for  their  reception,  and  forming  the  free  surface  of  the  crown  by  the  other 
extremity.  These  fibres  are  directed  vertically  on  the  summit  of  the  crown, 


FIG.  563.— Enamel  prisms  (350  diameters).   A.  Fragments  and  single  fibres  of  the  enamel  isolated  by  the  action 
of  hydrochloric  acid.    B.  Surface  of  a  small  fragment  of  enamel,  showing  the  hexagonal  ends  of  the  fibres. 

horizontally  at  the  sides ;  they  are  about  the  -j-jW  of  an  inch  in  diameter,  and 
pursue  a  more  or  less  wavy  course.  Each  enamel  rod  is  crossed  by  a  series  of 
dark  transverse  lines,  which  mark  the  mode  of  the  formation  of  the  rods  (Fig. 
563).  Another  series  of  lines,  having  a  brown  appearance,  and  denominated  the 
parallel  stria?  of  Retzius,  or  the  colored  lines,  are  seen  on  a  section  of  the  enamel. 
These  lines  are  concentric  and  cross  the  enamel  rods.  They  are  caused  by  the 
mode  of  enamel  deposition.  Inasmuch  as  the  enamel  columns,  when  near  the  den- 
tine, cross  each  other  and  only  become  parallel  farther  away,  a  series  of  radial 
markings,  light  and  dark  alternately,  is  obtained  (Fig.  561). 

Numerous  minute  interstices  intervene  between  the  enamel-fibres  near  their 
dentinal  surface.  It  is  noted  in  rare  cases  that  the  dentinal  fibres  penetrate 
a  certain  distance  between  the  rods  of  the  enamel.  No  nutritive  canals  exist 
in  the  enamel. 

Chemical  Composition. — According  to  Bibra,  enamel  consists  of  96.5  per  cent, 
of  earthy  matter  and  3.5  per  cent,  of  animal  matter.  The  earthy  matter  consists 


THE  DEVELOPMENT   OF    THE    TEETH.  939 

of  the  phosphate  with  the  carbonate  of  calcium,  with  traces  of  fluoride  of  calcium, 
phosphate  of  magnesia,  and  other  salts. 

The  cortical  substance,  or  cementum  (crusta  petrosa),  is  disposed  as  a  thin  layer 
on  the  roots  of  the  teeth,  from  the  termination  of  the  enamel  as  far  as  the  apex  of 
the  root,  where  it  is  usually  very  thick.  In  structure  and  chemical  composition 
it  resembles  bone.  It  contains,  sparingly,  the  lacunae  and  canaliculi  which 
characterize  true  bone;  the  lacunae  placed  near  the  surface  have  the  canaliculi 
radiating  from  the  side  of  the  lacunas  toward  the  periodontal  membrane,  dental 
pi-ri'.-'xti-'tiii.  and  those  more  deeply  placed  join  with  adjacent  dentinal  tubuli.  In 
the  thicker  portions  of  the  crusta  petrosa  the  lamellae  and  Haversian  canals  pecu- 
liar to  bone  are  also  occasionally  found. 

A.-  age  advances  the  cement  increases  in  thickness,  and  gives  rise  to  those  bony  growths,  or 

exostoses.  so  common  in  the  teeth  of  the  aged ;  the  pulp-cavity  becomes  also  partially  filled  up 

by  a  hard  substance  intermediate  in  structure  between  dentine  and  bone  (osteo-dentine.  Owen  : 

lary  dentine.  Tomes).     It  is  formed  by  the  odontoblasts,  the  dental  pulp  lessening  in 

volume. 

Development  of  the  Teeth. 

The  teeth  are  an  evolution  from  the  dermoid  system,  and  not  of  the  bony  skele- 
ton :  they  are  developed  from  two  of  the  blastodermic  layers,  the  epiblast  and 
rnesoblast.  From  the  former  the  enamel  is  developed,  from  the  latter  the  dental 
pulp,  dentine,  cementum,  and  pericementum.  It  is  customary  to  view  the  develop- 
ment of  the  permanent  and  temporary  teeth  as  separate  studies. 

The  earliest  evidence  of  tooth-formation  in  the  human  embryo  is  observed  in 
about  the  seventh  week.  The  mucous  membrane  covering  the  embryonic  jaws  is 
seen  to  rise  as  a  longitudinal  ridge  along  the  summit  of  each  jaw.1  A  transverse 
section  through  the  jaws  will  show  the  elevation  to  be  due  to  a  linear  and  outlined 
activity  of  the  germinal  epithelial  layer :  a  corresponding  epithelial  growth  is  seen 
to  sink  as  a  band  into  the  mesoblastic  tissue  beneath.  The  local  cell-activity  con- 
tinues, and  in  its  descent  the  band  appears  to  meet  with  a  resistance  which  causes  a 
flattening  of  its  extremity  into  a  continuous  lamina.  From  the  inner  (toward  the 
tongue)  edge  of  the  lamina  epithelial  cords  are  given  off,  ten  in  number,  one  for 
each  temporary  tooth. 

The  growth  of  each  cord  continues,  and  each  expands  into  a  flask -like  form,  the 
walls  covered  by  a  layer  of  germinal  cells,  its  interior  by  swollen  mature  cells. 
The  ingrowing  bulb  is  now  seen  to  flatten  upon  its  lower  surface,  as  though  it  had 
met  with  an  outlined  resistance  from  the  mesoblastic  tissue  beneath.  The  epithelial 
ingrowth  assumes  the  general  form  of  the  several  teeth  :  it  is  the  enamel-organ  of 
the  tooth  (Fig.  o04).  At  this  period  the  mesoblastic  tissue  around  each  enamel- 
organ  is  seen  to  become  differentiated  into  fibrous  tissue  surrounding  the  enamel- 
organs,  but  at  some  distance  from  them.  Islets  of  bone  are  also  seen  to  be  forming 
the  beginning  of  the  bony  maxillae. 

The  indentation  of  the  base  of  the  enamel-organ  continues  until  it  assumes 
the  form  of  the  future  teeth.  The  cells  bounding  the  organ  assume  a  cylin- 
drical form  :  the  cells  of  the  interior  become  much  expanded,  irregular  in  size 
and  form. 

The  mesoblastic  tissue  underlying  the  enamel-organ  is  much  condensed  :  evi- 
dences of  cellular  differentiation  and  a  vascular  system  appear.  Bone  continues  to 
develop  until  all  of  the  tooth-follicles  are  embraced  in  a  gutter  of  bone.  From  the 
lingual  side  of  the  cords  of  the  temporary  teeth  epithelial  buds  are  given  off,  which 
sink  into  the  mesoblastic  tissue  and  form  the  enamel-organs  of  the  permanent  teeth. 
The  condensation  of  fibrous  tissue  continues  until  each  embryonic  tooth  is  enveloped 
in  a  sac.  the  dental  sac  :  this,  together  with  all  of  its  contents,  is  called  the  dental 
follicle. 

The  cells  of  the  enamel-organ  now  undergo  a  series  of  differentiations  :  the 
inner  layer  is  arranged  as  columnar  epithelium,  and  is  called  the  ameloblastic  or 

1  The  maxillary  rampart  of  Kolliker  "Waldeyer. 


940 


THE    ORGANS    OF  DIGESTION. 


enamel-forming  layer  (Figs.   565  and  566).     The  cells  of  the  outer  wall  remain 
cuboidal ;  the  cells  which  lie  between  become  much  distended,  and  on  account  of 


FIG.  561— Diagram  of  method  of  development  of  the  teeth.    1.  Early  stage.    4.  Later  stage.    2,  3.  Interme- 
diate stages,    s.  Common  dental  germ.    o.  Special  dental  germ  (milk),    o'.  Special    " 


p.  Papilla,    e.  Dental  furrow.    (Gegenbaur.) 


ial  dental  germ  (permanent). 


their  appearance  when  seen  in  section  this  portion  of  the  organ  is  called  the  stellate 
reticulum  (the  enamel-jelly).  The  layer  of  cells  immediately  contiguous  to  the 
ameloblasts  form  a  layer  called  the  stratum  intermedium  (Fig.  566A — D). 

The  enclosed  mesoblastic  papilla  (the  future  dental  pulp)  has  its  peripheral  cells 
differentiated  into  columnar  bodies  disposed  as  a  layer,  each  cell  having  a  large 


Dental  furrow 


Remains  of  ' '  neck  "  of 
enamel  organ,  or  of  the— 
common  dental  germ 


Permanent  special 
dental  germ 


MeckeVs  cartilage. — 


Internal  enamel  layer, 
or  adamantoblasts 


Dental  sac 


lamel  pulp 
External  enamel 
layer 
Papilla 


Lower  jaw. 


FIG.  565.— Vertical  section  of  the  inferior  maxilla  of  an  early  human  foetus.    (Magnified  25  diameters.) 


nucleus.  The  vascular  supply  of  the  pulp  is  now  well  marked.  A  section  of  a 
follicle  at  this  period  will  exhibit  the  follicular  wall  springing  from  the  base  of  the 
dental  papilla  and  having  a  well-marked  blood-supply.  The  bony  alveolar  walls 
are  well  outlined,  and  evidences  of  a  periosteum  appear  (Figs.  565  and  566). 

Development  of  Enamel. — In  point  of  time,  the  deposition  of  dentine  actually 
begins  before  that  of  enamel,  so  that  the  first-formed  layer  of  enamel  is  deposited 
against  a  layer  of  immature  dentine.  The  enamel  is  built  up  of  two  distinct  sub- 
stances— globules  of  uniform  size  which  are  formed  by  the  ameloblasts,  and  a 
cementing  substance,  probably  an  albuminate  of  calcium  (calco-globulin),  the  basis 
of  all  the  calcified  tissues.  At  the  ends  of  the  ameloblasts,  next  to  the  dentine, 
the  secretion  calco-globulin  is  deposited,  and  into  the  plastic  mass  the  enamel- 
globules  are  extruded,  each  globule  remaining  connected  with  the  ameloblasts  by 
plasmic  strings,  which  also  join  the  globules  laterally.1 

The  first  deposit  of  enamel  begins  in  the  tips  of  the  cusps,  and  is  quickly  fol- 
lowed by  a  disappearance  of  the  stellate  reticulum  at  that  point ;  the  stellate  retic- 
ulum now  appears  to  atrophy,  so  that  the  vascular  follicular  wall  is  brought  into 
direct  apposition  with  the  stratum  intermedium,  which  becomes  differentiated  into  a 
glandular  (secreting)  tissue  which  elaborates  the  calcic  albuminous  basis  of  the 
enamel.  The  secretion  passes  from  the  cells  of  the  stratum  intermedium  through  a 
membrane  into  the  ameloblasts,  where  it  is  in  part  combined  with  the  cellular 

1  J.  L.  Williams,  Dental  Cosmos,  1896. 


THE   DEVELOPMENT   OF    THE    TEETH. 


941 


globules,  and  irregular  masses  of  it  extruded  as  cementing  substance.  The  deposi- 
tion continues  until  tbe  enamel-cap  has  its  typical  form.  The  deposition  of  the 
layers  of  globules  is  indicated  by  parallel  lines  transverse  to  the  axes  of  the  enamel- 


Eu±  ud. 


E 


FIG.  506.— A.  Section  through  tooth-follicle — human  caiiine  ~\  months :  A,  follicular  wall :  B,  outer  epithelial 
coat :  C.  stellate  reticulum  :  1>.  stratum  intermedium :  E.  ameloblasts  :  F,  odontoblasts  ;  G,  pulp. 

B.  Diagram  after  Williams  (Dental  Cosmos,  1896),  mode  of  enamel  deposition:  A,  blood  supply  to  B, secreting 
papillae ;  f\  layer  of  ameloblasts  containing  enamel  globules  and  droplets  of  calcoglobulin  ;  D,  enamel-globules 
•ited:  E,  formed  dentine;  F,  forming  dentine;  G,  layer  of  odontoblasts;  H,  blood  supply  to  odonto- 
blastic  layer. 

rods.     At  the  completion  of  amelification  the  ameloblasts  are  partially  calcified  and 
form  the  eutieuJa  dentis  or  Xasmyth's  membrane. 

Formation  of  Dentine. — The  layer  of  columnar  cells  bounding  the  periphery  of 
the  pulp  (the  odontoblasts)  are  in  apposition  with 
a  plexus  of  capillary  vessels  (Fig.  566,  .4).  Each 
cell  is  a  secreting  body  which  selects  the  mate- 
rial for  dentine-building.  Against  the  layer  of 
ameloblasts  covering  the  dental  papilla  the  odon- 
toblasts deposit  globules  of  the  calcium  albu- 
minate,  and,  receding  as  the  deposits  are  made, 
leave  one  or  more  protoplasmic  processes  in 
the  calcic  deposit  (Tomes's  fibres).  The  process 
continues  until  the  normal  dentine  thickness  is 
formed.  The  deposit  is  laid  down  in  a  scaffold- 
ing of  finely  fibrillated  tissue.  The  layer  of 
formative  cells  remains  constant. 

Formation  of  Cementum. — Hertwig  asserts 
that  the  epithelial  edge  of  the  enamel-organ 
formed  by  the  inner  and  outer  epithelial  layers 
of  the  organ  grows  downward,  or  rather  the 
developing  tooth  grows  upward  until  the  future  root-form  of  the  tooth  is  outlined 
by  a  double  layer  of  epithelial  cells  (the  root-sheath  of  Hertwig).  The  growth  of 
alveolar  process  is  synchronous. 

Upon  the  pulp  side  of  the  sheath  a  layer  of  odontoblasts  is  developed  :  upon 
the  outer  side  the  fibrous  encasement  becomes  closely  attached  to  the  sheath  and  a 
layer  of  osteogenetic  cells  (cementoblasts)  is  differentiated.  The  growth  of  the 
dentine  of  the  root  is  the  same  as  in  the  crown.  The  epithelial  sheath  undergoes 
atrophic  changes,  leaving  epithelial  whorls  which  remain  in  the  pericementum. 
The  cementum  is  developed  as  subperiosteal  bone.  The  cementum  over  the  apex 
of  the  root  is  not  formed  until  after  the  eruption  of  the  tooth. 

Formation  of  Alveoli. — Bv  the  time  the  crowns  of  the  teeth  have  formed,  each 


FIG.  567.— Part  of  section  of  developing 
tooth  of  young  rat,  showing  the  mode  of 
deposition  of  the  dentine  (highly  magni- 
fied), a.  Outer  layer  of  fully -calcined  den- 
tine. 6.  Uncalcified  matrix  with  a  few  nod- 
ules of  calcareous  matter,  o.  Odontoblasts 
with  processes  extending  into  the  dentine. 
d.  Pulp.  The  section  is  stained  with  car- 
mine, which  colors  the  uncalcified  matrix, 
but  not  the  calcified  part. 


942  THE   ORGANS   OF  DIGESTION. 

is  enclosed  in  a  loculus  of  bone  which  has  developed  around  it  and  at  some  distance 
from  it ;  the  loculus  is  open  at  the  top  toward  the  gums,  where  it  is  closed  by 
fibrous  tissue ;  the  developing  permanent  tooth  is  contained  in  the  same  loculus, 
but  is  later  separated  from  the  temporary  tooth  by  a  growth  of  bone.  The  alveolar 
process  is  not  completed  until  after  the  eruption  of  the  teeth.  During  eruption 
that  portion  of  the  process  overlying  the  crown  undergoes  absorption,  and  as  soon 
as  the  immature  tooth  has  erupted  the  alveolar  process  is  developed  about  the  root, 
whose  formation  is  also  completed  after  eruption. 

Development  of  the  Permanent  Teeth. — The  permanent  teeth  as  regards  their 
development  may  be  divided  into  two  sets :  (1)  those  which  replace  the  temporary 
teeth,  and  which,  like  them,  are  ten  in  number :  these  are  the  successional  per- 
manent teeth ;  and  (2)  those  which  have  no  temporary  predecessors,  but  are 
superadded  at  the  back  of  the  dental  series.  These  are  three  in  number  on  either 
side  in  each  jaw,  and  are  termed  the  superadded  permanent  teeth.  They  are  the 
three  molars  of  the  permanent  set,  the  molars  of  the  temporary  set  being  replaced 
by  the  prernolars  or  bicuspids  of  the  permanent  set. 

The  development  of  the  successional  permanent  teeth — the  ten  anterior  ones 
in  either  jaw — will  be  first  considered.  As  already  stated,  the  germ  of  each 
milk  tooth  is  a  special  thickening  of  the  "  free  "  edge  of  the  common  dental  germ 
or  dental  lamina.  In  like  manner  is  formed  the  special  dental  germ  of  each 
of  the  successional  permanent  teeth.  But  these  thickenings  are  not  at  the 
"free"  edge  of  the  dental  lamina,  but  occur  behind  and  lateral  to  each  of  the 
milk-tooth  germs  (Fig.  564).  There  are  ten  of  these,  and  they  appear  in  order, 
about  the  sixteenth  week,  on  each  side,  the  central  incisor  germs  being  the 
first. 

These  special  dental  germs  now  go  through  the  same  transformations  (and 
become  enamel-organs)  as  were  described  in  connection  with  those  of  the  milk 
teeth ;  that  is,  they  recede  into  the  substance  of  the  gum  behind  the  germs  of  the 
temporary  teeth.  As  they  recede  they  become  flask-shaped,  form  an  expansion 
of  their  distal  extremity,  and  finally  meet  a  papilla,  which  has  been  formed  in 
the  mesoblast,  just  in  the  same  manner  as  was  the  case  in  the  temporary  teeth. 
The  apex  of  the  papilla  indentates  the  dental  germ,  which  encloses  it,  and  form- 
ing a  cap  for  it,  undergoes  analogous  changes  to  those  described  in  the  develop- 
ment of  the  milk  teeth,  and  becomes  converted  into  the  enamel,  whilst  the  papilla 
forms  the  dentine,  of  the  permanent  tooth.  In  its  development  it  becomes  en- 
closed in  a  dentinal  sac  which  adheres  to  the  back  of  the  sac  of  the  temporary 
tooth.  The  sac  of  each  permanent  tooth  is  also  connected  with  the  fibrous  tissue 
of  the  gum  by  a  slender  band  or  gubernaculum,  which  passes  to  the  margin  of 
the  jaw  behind  the  corresponding  milk  tooth  (see  above). 

The  superadded  permanent  teeth — three  on  each  side  in  each  jaw — arise  from 
successive  extensions  backward — i.  e.  along  the  line  of  the  jaw — of  the  common 
dental  germ  from  the  back  part  of  the  special  dental  germ  of  the  immediately 
preceding  tooth.  During  the  fourth  month  or  seventeenth  week,  in  that  portion 
of  the  common  dental  germ  which  lies  behind — i.  e.  lateral  to  the  special  dental 
germ  of  the  last  temporary  molar  tooth,  and  which  has  hitherto  remained  unal- 
tered, there  is  developed  the  special  dental  germ  of  the  first  permanent  molar 
into  which  a  papilla  projects.  In  a  similar  manner,  about  the  fourth  month 
after  birth  the  second  molar  is  formed,  and  about  the  third  year  the  third 
molar. 

Eruption. — When  the  calcification  of  the  different  tissues  of  the  milk  tooth 
is  sufficiently  advanced  to  enable  it  to  bear  the  pressure  to  which  it  will  be  after- 
ward subjected,  its  eruption  takes  place,  the  tooth  making  its  way  through  the 
gum.  The  gum  is  absorbed  by  the  pressure  of  the  crown  of  the  tooth  against  it, 
which  is  itself  pressed  up  by  the  increasing  size  of  the  fang.  At  the  same  time 
the  septa  between  the  dentinal  sacs,  at  first  fibrous  in  structure,  ossify  and  thus 
form  the  loculi  or  alveoli ;  these  firmly  embrace  the  necks  of  the  teeth  and  afford 
them  a  solid  basis. 


THE   DEVELOPMENT   OF    THE    TEETH. 


943 


Previous  to  the  i«  rmnn> 'at  teeth  penetrating  the  gum,  the  bony  partitions 
which  separate  their  sacs  from  the  deciduous  teeth  are  absorbed,  the  roots  of 
the  temporary  teeth  disappear  by  absorption  through  the  agency  of  particular 
multinucleated  cells,  called  odontoclasts,  which  are  developed  at  the  time  in  the 
neighborhood  of  the  root,  and  the  permanent  teeth  become  placed  under  the 
loose  crown  of  the  deciduous  teeth ;  the  latter  finally  become  detached,  and  the 
permanent  teeth  take  their  place  in  the  mouth  (Fig.  568). 


FIG.  568.— The  milk-teeth  in  a  child  of  about  four  years.    The  permanent  teeth  are  seen  in  their  alveoli. 

L*f*r  "\ 


(Cryer.) 

Calcification  of  the  permanent  teeth  proceeds  in  the  following  order :  First 
molar,  soon  after  birth  ;  the  central  incisor,  lateral  incisor,  and  cuspid,  about  six 
months  after  birth ;  the  bicuspids,  .at  the  second  year  or  later ;  second  molar,  end 
of  second  year ;  third  molar,  about  the  twelfth  year. 

The  eruption  of  the  temporary  teeth  commences  at  the  seventh  month,  and  is 
complete  about  the  end  of  the  second  year. 

The  periods  for  the  eruption  of  the  temporary  set  are  (C.  S.  Tomes) — 


Lower  central  incisors 

Upper  incisors 

Lower  lateral  incisors  and  first  molars 

Canines 

Second  molars 


6  to    9  months. 
8  to  10        " 

15  to  21        " 

16  to  20        " 
20  to  24       " 


The  eruption  of  tin'  permanent  teeth  takes   place  at  the  following  periods,  the 
teeth  of  the  lower  jaw  preceding  those  of  the  upper  by  a  short  interval  : 


6i  years,  first  molars. 
7th  year,  two  middle  incisors. 
8th  year,  two  lateral  incisors. 
9th  year,  first  bicuspid. 


10th  year,  second  bicuspid, 
llth  to  12th  year,  canine. 
12th  to  loth  year,  second  molars. 
17th  to  21st  year,  third  molars. 


944  THE    ORGANS   OF  DIGESTION. 


THE  PALATE. 

The  palate  forms  the  roof  of  the  mouth :  it  consists  of  two  portions,  the  hard 
palate  in  front,  the  soft  palate  behind. 

The  hard  palate  is  bounded  in  front  and  at  the  sides  by  the  alveolar  arches 
and  gums ;  behind,  it  is  continuous  with  the  soft  palate.  It  is  covered  by  a  dense 
structure  formed  by  the  periosteum  and  mucous  membrane  of  the  mouth,  which 
are  intimately  adherent  together.  Along  the  middle  line  is  a  linear  ridge  or 
raphe,  which  terminates  anteriorly  in  a  small  papilla  (incisive  pad)  correspond- 
ing with  the  inferior  opening  of  the  anterior  palatine  fossa.  This  papilla 
receives  filaments  from  the  naso-palatine  and  anterior  palatine  nerves.  On  either 
side  and  in  front  of  the  raphe  the  mucous  membrane  is  thick,  pale  in  color,  and 
corrugated ;  behind,  it  is  thin,  smooth,  and  of  a  deeper  color :  it  is  covered  with 
squamous  epithelium,  and  furnished  with  numerous  glands  (palatal  glands), 
which  lie  between  the  mucous  membrane  and  the  surface  of  the  bone. 

The  soft  palate  (velum  pendulum  palati)  is  a  movable  fold  suspended  from  the 
posterior  border  of  the  hard  palate,  and  forming  an  incomplete  septum,  between 
the  mouth  and  pharynx.  It  consists  of  a  fold  of  mucous  membrane  enclosing 
muscular  fibres,  an  aponeurosis,  vessels,  nerves,  adenoid  tissue,  and  mucous 
glands.  When  occupying  its  usual  position  (i.  e.  relaxed  and  pendent)  its  anterior 
surface  is  concave,  continuous  with  the  roof  of  the  mouth,  and  marked  by  a 
median  ridge  or  raphe,  which  indicates  its  original  separation  into  two  lateral 
halves.  Its  posterior  surface  is  convex,  and  continuous  with  the  mucous 
membrane  covering  the  floor  of  the  posterior  nares.  Its  upper  border  is  attached 
to  the  posterior  margin  of  the  hard  palate,  and  its  sides  are  blended  with  the 
pharynx.  Its  lower  border  is  free. 

Hanging  from  the  middle  of  its  lower  border  is  a  small,  conical-shaped 
pendulous  process,  the  uvula,  and  arching  outward  and  downward  from  the  base 
of  the  uvula  on  each  side  are  two  curved  folds  of  mucous  membrane,  containing 
muscular  fibres,  called  the  arches  or  pillars  of  the  soft  palate. 

The  anterior  pillars  run  downward,  outward,  and  forward  to  the  sides  of  the 
base  of  the  tongue,  and  are  formed  by  the  projection  of  the  Palato-glossi  muscles, 
covered  by  mucous  membrane. 

The  posterior  pillars  are  nearer  to  each  other  and  larger  than  the  anterior ;  they 
run  downward,  outward,  and  backward  to  the  sides  of  the  pharynx,  and  are 
formed  by  the  projection  of  the  Palato-pharyngei  muscles,  covered  by  mucous 
membrane.  The  anterior  and  posterior  pillars  are  separated  below  by  a  triangular 
interval  in  which  the  tonsil  is  lodged. 

The  space  left  between  the  arches  of  the  palate  on  the  two  sides  is  called  the 
isthmus  of  the  fauces.  It  is  bounded,  above,  by  the  free  margin  of  the  soft  palate  ; 
below,  by  the  back  of  the  tongue ;  and  on  each  side,  by  the  pillars  of  the  soft 
palate  and  the  tonsil. 

The  mucous  membrane  of  the  soft  palate  is  thin,  and  covered  with  squamous 
epithelium  on  its  under  surface,  while  on  its  superior  surface  the  epithelium 
is  columnar  and  ciliated.1  Beneath  the  mucous  membrane  on  the  oral  surface 
of  the  soft  palate  is  a  considerable  amount  of  adenoid  tissue.  The  palatine  glands 
form  a  continuous  layer  on  its  posterior  surface  and  round  the  uvula. 

The  aponeurosis  of  the  soft  palate  is  a  thin  but  firm  fibrous  layer  attached  above 
to  the  posterior  border  of  the  hard  palate,  and  becoming  thinner  toward  the  free 
margin  of  the  velum.  Laterally,  it  is  continuous  with  the  pharyngeal  aponeurosis. 
It  forms  the  framework  of  the  soft  palate,  and  is  joined  by  the  tendon  of  the  Tensor 
palati  muscle. 

The  muscles  of  the  soft  palate  are  five  on  each  side  :  the  Levator  palati, 
Tensor  palati,  Azygos  uvulae,  Palato-glos'sus,  and  Palato-pharyngeus  (see  page  421). 
The  following  is  the  relative  position  of  these  structures  in  a  dissection  of  the  soft 

1  According  to  Klein,  the  mucous  membrane  on  the  nasal  surface  of  the  soft  palate  is  in  the 
foetus  covered  throughout  by  columnar  ciliated  epithelium,  which  subsequently  becomes  squamous. 


THE  SALIVARY   GLAXDS.  945 

palate  from  the  posterior  or  nasal  to  the  anterior  or  oral  surface :  Immediately 
beneath  the  nasal  mucous  membrane  is  a  thin  stratum  of  muscular  fibres,  the 
posterior  fasciculus  of  the  Palato-pharyngeus  muscle,  joining  with  its  fellow  of 
the  opposite  side  in  the  middle  line.  Beneath  this  is  the  Azygos  uvulae,  consist- 
ing of  two  rounded  fleshy  fasciculi,  placed  side  by  side  in  the  median  line  of  the 
soft  palate.  Next  come  the  fibres  of  the  Levator  palati,  joining  with  the  muscle 
of  the  opposite  side  in  the  middle  line.  Fourthly,  the  anterior  fasciculus  of  the 
Palato-pharvngeus,  thicker  than  the  posterior,  and  separating  the  Levator  palati 
from  the  next  muscle,  the  Tensor  palati.  This  muscle  terminates  in  a  tendon 
which,  after  winding  round  the  hamular  process,  expands  into  a  broad  aponeurosis 
in  the  soft  palate,  anterior  to  the  other  muscles  which  have  been  enumerated. 
Finally,  we  have  a  thin  muscular  stratum,  the  Palatp-glossus  muscle,  placed  in 
front  of  the  aponeurosis  of  the  Tensor  palati.  and  separated  from  the  oral  mucous 
membrane  by  adenoid  tissue. 

The  tonsils  (amygdcdce)  are  two  glandular  organs,  situated  one  on  each  side  of 
the  fauces,  between  the  anterior  and  posterior  pillars  of  the  soft  palate.  They  are 
of  a  rounded  form,  and  vary  considerably  in  size  in  different  individuals.  Exter- 
nally the  tonsil  is  in  relation  with  the  inner  surface  of  the  Superior  constrictor, 
which  separates  it  from  the  internal  carotid  and  ascending  pharyngeal  arteries. 
It  corresponds  to  the  angle  of  the  lower  jaw.  Its  inner  surface  presents  from 
twelve  to  fifteen  orifices,  leading  into  small  recesses,  from  which  numerous  follicles 
branch  out  into  the  substance  of  the  gland.  These  follicles  are  lined  by  a  continua- 
tion of  the  mucous  membrane  of  the  pharynx,  covered  with  epithelium ;  around 
each  follicle  is  a  layer  of  closed  capsules  imbedded  in  the  submucous  tissue.  These 
capsules  are  analogous  to  those  of  Fever's  glands,  consisting  of  adenoid  tissue. 
No  openings  from  the  capsules  into  the  follicles  can  be  recognized.  They  contain 
a  thick  grayish  secretion.  Surrounding  each  follicle  is  a  close  plexus  of  lymphatic 
."essels.  From  these  plexuses  the  lymphatic  vessels  pass  to  the  deep  cervical 
glands  in  the  upper  part  of  the  neck,  which  frequently  become  enlarged  in  affec- 
tions of  these  organs. 

The  arteries  supplying  the  tonsil  are  the  dorsalis  linguae  from  the  lingual,  the 
ascending  palatine  and  tonsillar  from  the  facial,  the  ascending  pharyngeal  from  the 
external  carotid,  the  descending  palatine  branch  of  the  internal  maxillary,  and  a 
twig  from  the  small  meningeal. 

The  veins  terminate  in  the  tonsillar  plexus,  on  the  outer  side  of  the 
tonsil. 

The  nerves  are  derived  from  Meckel's  ganglion  and  from  the  glosso-pharyngeal. 

THE  SALIVARY  GLANDS  (Fig.  569). 

The  principal  salivary  glands  communicating  with  the  mouth  and  pouring 
their  secretion  into  its  cavity  are  the  parotid,  submaxillary.  and  sublingual. 

The  parotid  gland,  so  called  from  being  placed  near  the  ear  (~af>d,  near ;  ouz, 
o»roc,  the  ear),  is  the  largest  of  the  three  salivary  glands,  varying  in  weight  from 
half  an  ounce  to  an  ounce.  It  lies  upon  the  side  of  the  face  immediately  below 
and  in  front  of  the  external  ear.  It  is  limited  above  by  the  zygoma ;  below,  by 
the  angle  of  the  jaw  and  by  a  line  drawn  between  it  and  the  mastoid  process: 
anteriorly,  it  extends  to  a  variable  extent  over  the  Masseter  muscle;  posteriorly, 
it  is  bounded  by  the  external  meatus,  the  mastoid  process,  and  the  Sterno-mastoid 
and  Digastric  muscles,  slightly  overlapping  the  latter. 

Its  anterior  surface  is  grooved  to  embrace  the  posterior  margin  of  the  ramus  of 
the  lower  jaw,  and  advances  forward  beneath  the  ramus,  between  the  two  Pterygoid 
muscles  and  in  front  of  the  ramus  over  the  Masseter  muscle.  Its  outer  surface, 
slightly  lobulated,  is  covered  by  the  integument  and  parotid  fascia,  and  has  one  or 
two  lymphatic  glands  resting  on  it.  Its  inn>  /•  surf  ace  extends  deeply  into  the  neck 
by  means  of  two  large  processes,  one  of  which  dips  behind  the  styloid  process  and 
projects  beneath  the  mastoid  process  and  the  Sterno-mastoid  muscle ;  the  other  is 

60 


946 


THE    ORGANS    OF  DIGESTION. 


situated  in  front  of  the  styloid  process,  and  passes  into  the  back  part  of  the  glenoid 
fossa,  behind  the  articulation  of  the  lower  jaw.  The  structures  passing  through 
the  parotid  gland  are — the  external  carotid  artery,  giving  off  its  three  terminal 
branches :  the  posterior  auricular  artery  emerges  from  the  gland  behind ;  the 
temporal  artery  above ;  the  transverse  facial,  a  branch  of  the  temporal,  in  front ; 


FIG.  569.  —The  salivary  glands. 

and  the  internal  maxillary  winds  through  it  as  it  passes  inward,  behind  the  neck 
of  the  jaw.  Superficial  to  the  external  carotid  is  the  trunk  formed  by  the  union 
of  the  temporal  and  internal  maxillary  veins ;  a  branch,  connecting  this  trunk 
with  the  internal  jugular,  also  passes  through  the  gland.  It  is  also  traversed  by 
the  facial  nerve  and  its  branches,  which  emerge  at  its  anterior  border ;  branches  of 
the  great  auricular  nerve  pierce  the  gland  to  join  the  facial,  and  the  auriculo- 
temporal  branch  of  the  inferior  maxillary  nerve  emerges  from  the  upper  part  of  the 
gland.  The  internal  carotid  artery  and  internal  jugular  vein  lie  close  to  its  deep 
surface. 

The  duct  of  the  parotid  gland  (Stenson's)  is  about  two  inches  and  a  half  in 
length.  It  commences  by  numerous  branches  from  the  anterior  part  of  the  gland, 
crosses  the  Masseter  muscle,  and  at  its  anterior  border  dips  down  into  the  substance 
of.  the  Buccinator  muscle,  which  it  pierces ;  it  then  runs  for  a  short  distance  obliquely 
forward  between  the  Buccinator  and  mucous  membrane  of  the  mouth,  and  opens 
upon  the  inner  surface  of  the  cheek  by  a  small  orifice  opposite  the  second  molar 
tooth  of  the  upper  jaw.  While  crossing  the  Masseter  it  receives  the  duct  of  a  small 
detached  portion  of  the  gland,  soda  parotidis,  which  occasionally  exists  as  a  separate 
lobe,  just  beneath  the  zygomatic  arch.  In  this  position  it  has  the  transverse  facial 
artery  above  it  and  some  branches  of  the  facial  nerve  below  it. 

Structure. — The  parotid  duct  is  dense,  of  considerable  thickness,  and  its  canal 
about  the  size  of  a  crowquill ;  it  consists  of  an  external  or  fibrous  coat,  of 
considerable  density,  containing  contractile  fibres,  and  of  an  internal  or  mucous 
coat  lined  with  short  columnar  epithelium. 


THE   SALIVARY    GLANDS.  947 

Surface  Form.  —  The  direction  of  the  duct  corresponds  to  a  line  drawn  across  the  face  about 
a  finger  >  breadth  below  the  zygoma  :  that  is.  from  the  lower  part  of  the  tragus  to  midway 
between  the  tree  margin  of  the  upper  lip  and  the  ala  of  the  nose. 


Vessels  and  Nerves.  —  The  art^ri-'*  supplying  the  parotid  gland  are  derived  from 
the  external  carotid,  and  from  the  branches  given  off  by  that  vessel  in  or  near  its 
substance.  The  veins  empty  themselves  into  the  external  jugular  through  some 
of  its  tributaries  The  lymphnti<>$  terminate  in  the  superficial  and  deep  cervical 


M  Cresccnt  of  Gianuza. 


FIG.  570.— A  highly  magnified  section  of  the  submaxillary  gland  of  the  dog,  stained  with  carmine.    (Kolliker.) 

glands,  passing  in  their  course  through  two  or  three  lymphatic  glands  placed  on 
the  surface  and  in  the  substance  of  the  parotid.  The  nerves  are  derived  from  the 
carotid  plexus  of  the  sympathetic,  the  facial,  the  auriculo-temporal,  and  great 
auricular  nerves. 

It  is  probable  that  the  branch  from  the  auriculo-temporal  nerve  is  derived 
from  the  glosso-pharyngeal  through  the  otic  ganglion  (which  see).  At  all  events, 
in  some  of  the  lower  animals  this  has  been  proved  experimentally  to  be  the 
case. 

The  submaxillary  gland  is  situated  below  the  jaw,  in  the  anterior  part  of  the 
submaxillary  triangle  of  the  neck.  It  is  irregular  in  form  and  weighs  about  two 
drachms  (8-10  grammes).  It  is  covered  by  the  integument,  Platysma,  deep  cer- 
vical fascia,  and  the  body  of  the  lower  jaw.  corresponding  to  a  depression  on  the 
inner  surface  of  the  bone,  and  lies  upon  the  Mylo-hyoid,  Hyo-glossus,  and  Stylo- 
glossus  muscles,  a  portion  of  the  gland  passing  beneath  the  posterior  border  of 
the  Mylo-hyoid.  In  front  of  it  is  the  anterior  belly  of  the  Digastric ;  behind,  it 
is  separated  from  the  parotid  gland  by  the  stylo-maxillary  ligament,  and  from  the 
sublingual  gland  in  front  by  the  Mylo-hyoid  muscle.  The  facial  artery  lies  im- 
bedded in  a  groove  in  its  posterior  and  upper  border. 

The  duct  of  the  submaxillary  gland  ( Whartons)  is  about  two  inches  in  length, 
and  its  walls  are  much  thinner  than  those  of  the  parotid  duct..  It  commences  by 
numerous  branches  from  the  deep  portion  of  the  gland,  and  passes  forward  and 
inward  between  the  Mylo-hyoid  and  the  Hyo-glossus  and  Genio-hyo-glossus  mus- 
cles, then  between  the  sublingual  gland  and  the  Genio-hyo-glossus,  and  opens  bv 
a  narrow  orifice  on  the  summit  of  a  small  papilla  at  the  side  of  the  fraenum  linguae. 
On  the  Hyo-glossus  muscle  it  lies  between  the  lingual  and  hypoglossal  nerves,  but 
at  the  anterior  border  of  the  muscle  it  crosses  under  the  lingual  nerve,  and  is  then 
placed  above  it. 

Vessels  and  Nerves. — The  arteries  supplying  the  submaxillary  gland  are 
branches  of  the  facial  and  lingual.  Its  wins  follow  the  course  of  the  arteries. 
The  nerves  are  derived  from  the  submaxillary  ganglion,  through  which  it  receives 
filaments  from  the  chorda  tympani  of  the  facial  and  lingual  branch  of  the 
inferior  maxillary,  from  the  mylo-hyoid  branch  of  the  inferior  dental,  and  from 
the  sympathetic. 


THE    ORGANS    OF  DIGESTION. 

The  sublingual  gland  is  the  smallest  of  the  salivary  glands.  It  is  situated 
beneath  the  mucous  membrane  of  the  floor  of  the  mouth,  at  the  side  of  the  fraenum 
linguae,  in  contact  with  the  inner  surface  of  the  lower  jaw,  close  to  the  symphysis. 
It  is  narrow,  flattened,  in  shape  somewhat  like  an  almond,  and  weighs  about  a 
drachm.  It  is  in  relation,  above,  with  the  mucous  membrane  ;  below,  with  the 
Mylo-hyoid  muscle;  in  front,  with  the  depression  on  the  side  of  the  symphysis  of 
the  lower  jaw,  and  with  its  fellow  of  the  opposite  side ;  behind,  with  the  deep 
part  of  the  submaxillary  gland ;  and  internally,  with  the  Genio-hyo-glossus, 
from  which  it  is  separated  by  the  lingual  nerve  and  Wharton's  duct.  Its 
excretory  ducts  (ducts  of  Rivinus),  from  eight  to  twenty  in  number,  open 
separately  into  the  mouth,  on  the  elevated  crest  of  mucous  membrane  caused  by 
the  projection  of  the  gland,  on  either  side  of  the  fraenum  linguae.  One  or  more 
join  to  form  a  tube  which  opens  into  the  Whartonian  duct ;  this  is  called  the  duct 
of  Bartholin. 

Vessels  and  Nerves. — The  sublingual  gland  is  supplied  with  blood  from  the 
sublingual  and  submental  arteries.  Its  nerves  are  derived  from  the  lingual. 

Structure  of  Salivary  Glands. — The  salivary  are  compound  racemose  glands, 
consisting  of  numerous  lobes,  which  are  made  up  of  smaller  lobules  connected 
together  by  dense  areolar  tissue,  vessels,  and  ducts.  Each  lobule  consists  of  the 
ramifications  of  a  single  duct,  "  branching  frequently  in  a  tree-like  manner,"  the 
branches  terminating  in  dilated  ends  or  alveoli,  on  which  the  capillaries  are 
distributed.  These  alveoli,  however,  as  Pfliiger  points  out,  are  not  necessarily 
spherical,  though  sometimes  they  assume  that  form ;  sometimes  they  are  perfectly 
cylindrical,  and  very  often  they  are  mutually  compressed.  The  alveoli  are  enclosed 
by  a  basement  membrane  which  is  continuous  with  the  membrana  propria  of  the 
duct.  It  presents  a  peculiar  reticulated  structure,  having  the  appearance  of  a 
basket  with  open  meshes,  and  consisting  of  a  network  of  branched  and  flattened 
nucleated  cells. 

The  alveoli  of  the  salivary  glands  are  of  two  kinds,  which  differ  both  in  the 
appearance  of  their  secreting  cells,  in  their  size,  and  in  the  nature  of  their 
secretion.  The  one  variety  secretes  a  ropy  fluid  which  contains  mucin,  and 
has  therefore  been  named  the  mucous,  whilst  the  other  secretes  a  thinner  and 
more  watery  fluid,  which  contains  serum-albumin,  and  has  been  named  serous 
or  albuminous.  The  sublingual  gland  may  be  regarded  as  an  example  of  the 
former  variety,  the  parotid  of  the  latter.  The  submaxillary  is  of  the  mixed 
variety,  containing  both  mucous  and  serous  alveoli,  the  latter,  however,  prepon- 
derating. 

Both  alveoli  are  lined  bv  cells,  and  it  is  by  the  character  of  these  cells  that  the 
nature  of  the  gland  is  chiefly  to  be  determined,  In  addition,  however,  the  alveoli 
of  the  serous  glands  are  smaller  than  those  of  the  mucous  ones. 

The  cells  in  the  mucous  alveoli  are  spheroidal  in  shape,  glassy,  transparent,  and 
dimly  striated  in  appearance.  The  nucleus  is  usuallv  situated  in  the  part  of  the 
cell  which  is  next  the  basement  membrane,  against  which  it  is  sometimes  flattened. 
The  most  remarkable  peculiarity  presented  by  these  cells  is,  that  they  give  off  an 
extremely  fine  process,  which  is  curved  in  a  direction  parallel  to  the  surface  of  the 
alveolus,  lies  in  contact  with  the  membrana  propria,  and  overlaps  the  process  of 
neighboring  cells.  The  cells  contain  a  quantity  of  mucin,  to  which  their  clear, 
transparent  appearance  is  due. 

Here  and  there  in  the  alveoli  are  seen  peculiar  half-moon-shaped  bodies  lying 
between  the  cells  and  the  membrana  propria  of  the  alveolus.  They  are  termed 
the  crescents  of  Crianuzzi  or  the  demilunes  of  Heidenhain  (Fig.  570),  and  are 
regarded  by  Pfliiger  as  due  to  post-mortem  change,  but  by  most  other  later 
observers  they  are  believed  to  be  composed  of  polyhedral  granular  cells,  which 
Heidenhain  regards  as  young  epithelial  cells  destined  to  supply  the  place  of  those 
salivary  cells  which  have  undergone  disintegration.  This  view,  however,  is  not 
accepted  by  Klein. 

Serous  Alveoli. — In  the  serous  alveoli  the  cells  almost  completely  fill  the  cavity. 


THE  SALIVARY   GLANDS.  949 

.<•)  that  there  is  hardly  any  lumen  perceptible.  Instead  of  presenting  the  clear, 
transparent  appearance  of  the  cells  of  the  mucous  alveoli,  they  present  a  granular 
appearance,  due  to  distinct  granules  of  an  albuminous  nature  imbedded  in  a  closely- 
reticulated  protoplasm.  The  ducts  which  originate  out  of  the  alveoli  are  lined  at 
their  commencement  by  epithelium  which  differs  little  from  the  pavement  type. 
A-  the  ducts  enlarge  the  epithelial  cells  change  to  the  columnar  type,  and  they  are 
described  by  Pfiiiger  as  attached  to  the  basement  membrane  by  a  brush  of  fine 
hair-like  processes,  which  he  believes  to  be  continuous  with  the  nerve-fibres. 
Other  anatomists  regard  these  cells  as  merely  striated  on  their  deep  surface. 
The  lobules  of  the  salivary  glands  are  richly  supplied  with  blood-vessels  which 
form  a  dense  network  in  the  interalveolar  spaces.  Fine  plexuses  of  nerves  are 
als'»  found  in  the  interlobular  tissue. 
Pfluger  describes  the  nerves  as  being 
directly  continuous  with  the  salivary 
cells  of  the  alveolus,  the  nerve  some- 


FIG.  571.— Illustrating  Pfluger  s  views  of  the  termination  of  the  nerves  in  the  alveolar  cells.  (From  Strieker's 
•  Handbook.")  A.  Direct  passage  of  nerve  into  a  salivary  cell.  B.  By  the  medium  of  a  multipolar  ganglion-cell,  g. 

times  passing  through  a  ganglion-cell  just  before  joining  the  alveolus  (Fig.  571, 
A  and  B).  This  fact  has  not.  however,  been  corroborated  by  other  observers. 
There  is  no  doubt  that  ganglia  are  to  be  found  in  some  salivary  glands  in  connec- 
tion with  the  nerve-plexuses  in  the  interlobular  tissue;  thus  they  are  to  be 
found  in  the  submaxillary.  but  not  in  the  parotid,  but  whether  the  ultimate 
fibrils  are  connected  with  the  salivary  cells,  as  asserted  by  Pfluger,  remains  to  be 
proved 

In  the  submaxillary  and  sublingual  glands  the  lobes  are  larger  and  more 
loosely  united  than  in  the  parotid. 

Jftfcotu  Glands. — Besides  the  salivary  glands  proper,  numerous  other  glands 
are  found  in  the  mouth.  They  appear  to  secrete  mucus  only,  which  serves  to  keep 
the  mouth  moist  during  the  intervals  of  the  salivary  secretion,  and  which  is  mixed 
Avith  that  secretion  in  swallowing.  Many  of  these  glands  are  found  at  the  posterior 
part  of  the  dorsum  of  the  tongue,  behind  the  circumvallate  papillae,  and  also  along 
its  margins  as  far  forward  as  the  apex.1  Others  lie  around  and  in  the  tonsil 
between  its  crypts,  and  a  large  number  in  the  soft  palate.  These  glands  are  of 
the  ordinary  compound  racemose  type. 

Surface  Form. — The  orifice  of  the  mouth  is  bounded  by  the  lips,  two  thick,  fleshy  folds 
covered  externally  by  integument  and  internally  by  mucous  membrane,  and  consisting  of 
muscles,  vessels,  nerves,  areolar  tissue,  and  numerous  small  glands.  The  size  of  the  orifice  of 
the  mouth  varies  considerably  in  different  individuals,  but  seems  to  bear  a  close  relation  to  the 
size  and  prominence  of  the  teeth.  Its  corners  correspond  pretty  accurately  to  the  outer  border 
of  the  canine  teeth.  In  the  Mongolian  tribes,  where  the  front  teeth  are  large  and  inclined  for- 
ward, the  mouth  is  large ;  and  this;  combined  with  the  thick  and  everted  lips  which  appear  to 
be  associated  with  prominent  teeth,  gives  to  the  negro's  face  much  of  the  peculiarity  by  which 
it  is  characterized.  The  smaller  teeth  and  the  slighter  prominence  of  the  alveolar  arch  of  the 

1  It  has  recently  been  shown  by  Ebner  that  many  of  these  glands  open  into  the  trenches  around 
the  circumvallate  papillae,  and  that  their  secretion  is  more  watery  than  that  of  ordinary  mucous 
glands.  He  supposes  that  they  assist  in  the  more  rapid  distribution  of  the  substance  to  be  tasted  over 
the  region  where  the  special  apparatus  of  the  sense  of  taste  is  situated. 


950  THE    ORGANS    OF  DIGESTION. 

more  highly  civilized  races  render  the  orifice  of  the  mouth  much  smaller,  and  thus  a  small 
mouth  is  an  indication  of  intelligence,  and  is  regarded  as  an  evidence  of  the  higher  civilization 
of  the  individual. 

Upon  looking  into  the  mouth,  the  first  thing  we  may  note  is  the  tongue,  the  upper  surface 
of  which  will  be  seen  occupying  the  floor  of  the  cavity.  This  surface  is  convex,  and  is  marked 
along  the  middle  line  by  a  raphe  which  divides  it  into  two  symmetrical  portions.  The  anterior 
two-thirds  is  rough  and  studded  with  papillae  ;  the  posterior  third  smooth  and  tuberculated, 
covered  by  numerous  glands  which  project  from  the  surface.  Upon  raising  the  tongue  the 
mucous  membrane  which  invests  the  upper  surface  may  be  traced  covering  the  sides  of  the 
under  surface,  and  then  reflected  over  the  floor  of  the  mouth  on  to  the  inner  surface  of  the 
Vower  jaw,  a  part  of  which  it  covers.  As  it  passes  over  the  borders  of  the  tongue  it  changes  its 
character,  becoming  thin  and  smooth  and  losing  the  papillse  which  are  to  be  seen  on  the  upper 
surface.  In  the  middle  line  the  mucous  membrane  on  the  under  surface  of  the  tip  of  the 
tongue  forms  a  distinct  fold,  the  frcenum  linguae,  by  which  this  organ  is  connected  to  the  sym- 
physis  of  the  jaw.  Occasionally  it  is  found  that  this  fraenum  is  rather  shorter  than  natural, 
and,  acting  as  a  bridle,  prevents  the  complete  protrusion  of  the  tongue.  When  this  condition 
exists  and  an  attempt  is  made  to  protrude  the  organ,  the  tip  will  be  seen  to  remain  buried  in 
the  floor  of  the  mouth,  and  the  dorsum  of  the  tongue  is  rendered  very  convex,  and  more  or 
less  extruded  from  the  mouth  ;  at  the  same  time  a  deep  furrow  will  be  noticed  to  appear  in  the 
middle  line  of  the  anterior  part  of  the  dorsum.  Sometimes,  a  little  external  to  the  fraenum, 
the  ranine  vein  may  be  seen  immediately  beneath  the  mucous  membrane.  The  corresponding 
artery,  being  more  deeply  placed,  does  not  come  into  view,  nor  can  its  pulsation  be  felt  with  the 
finger.  On  either  side  of  the  fraenum,  in  the  floor  of  the  mouth,  is  a  longitudinal  elevation  or 
ridge,  produced  by  the  projection  of  the  sublingual  gland,  which  lies  immediately  beneath  the 
mucous  membrane.  And  close  to  the  attachment  of  the  fraenum  to  the  tip  of  the  tongue  may 
be  seen  on  either  side  the  slit-like  orifices  of  Wharton's  ducts,  into  which  a  fine  probe  may  be 
passed  without  much  difficulty.  By  everting  the  lips  the  smooth  mucous  membrane  lining  them 
may  be  examined,  and  may  be  traced  from  them  on  to  the  outer  surface  of  the  alveolar  arch. 
En  the  middle  line,  both  of  the  upper  and  lower  lip,  a  small  fold  of  mucous  membrane  passes 
from  the  lip  to  the  bone,  constituting  the  frcena ;  these  are  not  so  large  as  the  fraenum  linguae. 
By  pulling  outward  the  angle  of  the  mouth,  the  mucous  membrane  lining  the  cheeks  can  be 
seen,  and  on  it  may  be  perceived  a  little  papilla  which  marks  the  position  of  the  orifice  of  Sten- 
son's  duct — the  duct  of  the  parotid  gland.  The  exact  position  of  the  orifice  of  the  duct  will  be 
found  to  be  opposite  the  second  molar  tooth  of  the  upper  jaw.  The  introduction  of  a  probe 
into  this  duct  is  attended  with  considerable  difficulty.  The  teeth  are  the  next  objects  which 
claim  our  attention  upon  looking  into  the  mouth.  There  are,  as  stated  above,  ten  in  either  jaw 
in  the  temporary  set,  and  sixteen  in  the  permanent  set.  The  gums,  in  which  they  are  implanted, 
are  dense,  firm,  and  vascular. 

At  the  back  of  the  mouth  is  seen  the  isthmus  of  the  fauces,  or,  as  it  is  popularly  called, 
"the  throat:"  this  is  the  space  between  the  pillars  of  the  fauces  on  either  side,  and  is  the 
means  by  which  the  mouth  communicates  with  the  pharynx.  Above,  it  is  bounded  by  the  soft 
palate,  the  anterior  surface  of  which  is  concave  and  covered  with  mucous  membrane,  which  is 
continuous  with  that  lining  the  roof  of  the  mouth.  Projecting  from  the  middle  of  its  lower 
border  is  a  conical-shaped  projection,  the  uvula.  On  either  side  of  the  isthmus  of  the  fauces 
are  the  anterior  and  posterior  pillars,  formed  by  the  Palato-glossus  and  Palato-pharyngeus 
muscles  respectively,  covered  over  by  mucous  membrane.  Between  the  two  pillars  on  either 
side  is  situated  the  tonsil.  By  their  external  surface  these  glands  are  in  close  relationship  with 
the  internal  carotid  artery,  being  separated  from  this  vessel  only  by  the  thin  plane  of  muscular 
fibres  forming  the  wall  of  the  pharynx.  It  is  stated  that  this  vessel  may  be  wounded  in  remov- 
ing the  tonsil.  The  extirpation  of  this  glandular  body  is  not  unattended  with  danger  of 
haemorrhage  from  other  sources.  Dr.  Weir  has  stated  that  he  believes  that  when  haemorrhage 
occurs  after  their  removal  it  arises  from  one  of  the  palatine  arteries  having  been  wounded. 
These  vessels  are  large :  they  lie  in  the  muscular  tissue  of  the  palate,  and  when  wounded  are 
constantly  exposed  to  disturbance  from  the  contraction  of  the  palatine  muscles.  The  vessels  of 
the  tonsil,  Dr.  Weir  states,  are  small  and  lie  in  the  soft  tissue,  and  readily  contract  when 
wounded. 

When  the  mouth  is  wide  open  a  prominent  tense  fold  of  mucous  membrane  may  be  seen 
and  felt,  extending  upward  and  backward  from  the  position  of  the  fang  of  the  last  molar  tooth 
to  the  posterior  part  of  the  hard  palate.  This  is  caused  by  the  Pterygo-maxillary  ligament, 
which  is  attached  by  one  extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other 
to  the  posterior  extremity  of  the  mylo-hyoid  ridge  of  the  lower  jaw.  It  connects  the  Buccina- 
tor with  the  Superior  constrictor  of  the  pharynx.  The  fang  of  the  last  molar  tooth  indicates 
the  position  of  the  lingual  (gustatory)  nerve,  where  it  is  easily  accessible,  and  can  with  readiness 
be  divided  in  cases  of  cancer  of  the  tongue  (see  page  810).  On  the  inner  side  of  the  last  molar 
tooth  we  can  feel  the  hamular  process  of  the  internal  pterygoid  plate  of  the  sphenoid  bone, 
around  which  the  tendon  of  the  Tensor  palati  plays.  The  exact  position  of  this  process  is  of 
importance  in  performing  the  operation  of  staphylorraphy.  About  one-third  of  an  inch  in 
front  of  the  hamular  process,  and  the  same  distance  directly  inward  from  the  last  molar  tooth, 
is  the  situation  of  the  opening  of  the  posterior  palatine  canal,  through  which  emerges  the  pos- 
terior or  descending  palatine  branch  of  the  internal  maxillary  artery  and  one  of  the  descending 
palatine  nerves  from  Meckel's  ganglion.  The  exact  position  of  the  opening  on  the  subject  may 


THE   PHARYNX.  951 

lie  ascertained  by  driving  a  needle  through  the  tissues  of  the  palate  in  this  situation,  when  it 
will  be  at  once  felt  to  enter  the  canal.  The  artery  emerging  from  the  opening  runs  forward  in  a 
groove  in  the  bone  just  internal  to  the  alveolar  border  of  the  hard  palate,  and  may  be  wounded 
in  the  operation  for  the  cure  of  cleft  palate.  Under  these  circumstances  the  palatine  canal  may 
require  plugging.  By  introducing  the  finger  into  the  mouth  the  anterior  border  of  the  coronoid 
process  of  the  jaw  can  be  felt,  and  is  especially  prominent  when  the  jaw  is  dislocated.  By 
throwing  the  head  well  back  a  considerable  portion  of  the  posterior  wall  of  the  pharynx  may  be 
seen  throush  the  isthmus  faucium,  and  on  introducing  the  finger  the  anterior  surface  of  the 
bodies  of  the  upper  cervical  vertebrae  may  be  felt  immediately  beneath  the  thin  muscular  stra- 
tum forming  the  wall  of  the  pharynx.  The  finger  can  be  hooked  around  the  posterior  border 
of  the  soft  palate,  and  by  turning  it  forward  the  posterior  nares,  separated  by  the  septum,  can 
be  felt,  or  the  presence  of  any  adenoid  or  other  growths  in  the  naso-pharynx  ascertained. 

THE  PHARYNX. 

The  pharynx  is  that  part  of  the  alimentary  canal  which  is  placed  behind  the 
nose,  mouth,  and  larynx.  It  is  a  musculo-membranous  sac,  somewhat  conical  in 
form,  with  the  base  upward  and  the  apex  downward,  extending  from  the  under 
surface  of  the  skull  to  the  cricoid  cartilage  in  front  and  the  intervertebral  disk 
between  the  fifth  and  sixth  cervical  vertebne  behind. 

The  pharynx  is  about  four  inches  and  a  half  in  length,  and  broader  in  the 
transverse  than  in  the  autero-posterior  diameter.  Its  greatest  breadth  is  opposite 
the  cornua  of  the  hyoid  bone ;  its  narrowest  point,  at  its  termination  in  the 
oesophagus.  It  is  limited,  above,  by  the  body  of  the  sphenoid  and  basilar  process 
of  the  occipital  bone ;  belotv,  it  is  continuous  with  the  oesophagus ;  posteriorly,  it 
is  connected  by  loose  areolar  tissue  with  the  cervical  portion  of  the  vertebral 
column  and  the  Longi  colli  and  Recti  capitis  antici  muscles ;  anteriorly,  it  is 
incomplete,  and  is  attached  in  succession  to  the  internal  pterygoid  plate,  the 
pterygo-maxillary  ligament,  the  lower  jaw,  the  tongue,  hyoid  bone,  and  thyroid  and 
cricoid  cartilages ;  lateral!//,  it  is  connected  to  the  styloid  processes  and  their  mus- 
cles, and  is  in  contact  with  the  common  and  internal  carotid  arteries,  the  internal 
jugular  veins,  and  the  glosso-pharyngeal,  pneumogastric,  hypoglossal,  and  sym- 
pathetic nerves,  and  above  with  a  small  part  of  the  Internal  pterygoid  muscles. 

It  has  seven  openings  communicating  with  it — the  two  posterior  nares,  the 
two  Eustachian  tubes,  the  mouth,  larynx,  and  oesophagus. 

The  posterior  nares  are  the  two  oval  openings  (see  page  222)  situated  at  the 
upper  part  of  the  anterior  wall  of  the  pharynx. 

The  two  Eustachian  tubes  open  one  at  each  side  of  the  upper  part  of  the 
pharynx,  at  the  back  part  of  the  inferior  meatus.  Below  the  posterior  nares  are 
the  posterior  surface  of  the  soft  palate  and  uvula,  the  large  aperture  of  the 
mouth,  the  base  of  the  tongue,  the  epiglottis,  and  the  cordiform  opening  of  the 
larynx. 

The  cewphageal  opening  is  the  lower  contracted  portion  of  the  pharynx. 

Structure. — The  pharynx  is  composed  of  three  coats — mucous,  fibrous,  and 
muscular. 

The  pharyngeal  aponeurosis,  or  fibrous  coat,  is  situated  between  the  mucous 
and  muscular  layers.  It  is  thick  above,  where  the  muscular  fibres  are  wanting,  and 
is  firmly  connected  to  the  basilar  process  of  the  occipital  and  petrous  portion  of  the 
temporal  bones.  As  it  descends  it  diminishes  in  thickness,  and  is  gradually  lost. 
It  is  strengthened  posteriorly  by  a  strong  fibrous  band  which  is  attached  above  to 
the  pharyngeal  spine  on  the  under  surface  of  the  basilar  portion  of  the  occipital 
bone,  and  passes  downward,  forming  a  median  raphe,  which  gives  attachment  to 
the  Constrictor  muscles  of  the  pharynx. 

The  mucous  coat  is  continuous  with  that  lining  the  Eustachian  tubes,  the  nares, 
the  mouth,  and  the  larynx.  It  is  covered  by  columnar  ciliated  epithelium,  as  low 
down  as  on  a  level  with  the  floor  of  the  nares  ;  below  that  point  the  epithelium  is  of 
the  squamous  variety.  Beneath  the  mucous  membrane  are  found  racemose  mucous 
glands  ;  they  are  especially  numerous  at  the  upper  part  of  the  pharynx  around  the 
orifices  of  the  Eustachian  tubes.  Throughout  the  pharynx  are  also  numerous  crvpts 
or  recesses,  the  walls  of  which  are  surrounded  by  lymphoid  tissue  similar  to  what 


952  THE    ORGANS    OF  DIGESTION. 

is  found  in  the  tonsils.  Across  the  back  part  of  the  pharyngeal  cavity,  between  the 
two  Eustachian  tubes,  a  considerable  mass  of  this  tissue  exists,  and  has  been  named 
the  pharyngeal  tonsil.  Just  below  this  in  the  middle  line  is  the  orifice  of  an 
irregular,  flask-shaped  recess  of  the  mucous  membrane,  extending  up  as  far  as 
the  basilar  process  of  the  occipital  bone.  It  is  known  as  the  bursa  pharyngea, 
and  is  the  remains  of  the  diverticulum  of  the  alimentary  canal,  which  is  con- 
cerned in  the  development  of  the  pituitary  body  (which  see).  It  is  only  occa- 
sionally present  in  the  adult. 

The  muscular  coat  has  been  already  described  (page  419). 

Surgical  Anatomy. — The  internal  carotid  artery  is  in  close  relation  with  the  pharynx,  so 
that  its  pulsations  can  be  felt  through  the  mouth.  It  has  been  occasionally  wounded  by  sharp- 
pointed  instruments  introduced  into  the  mouth  and  thrust  through  the  wall  of  the  pharynx. 
In  aneurism  of  this  vessel  in  the  neck  the  tumor  necessarily  bulges  into  the  pharynx,  as  this  is 
the  direction  in  which  it  meets  with  the  least  resistance,  nothing  lying  between  the  vessel  and 
the  mucous  membrane  except  the  thin  Constrictor  muscle,  whereas  on  the  outer  side  there  is 
the  dense  cervical  fascia,  the  muscles  descending  from  the  styloid  process,  and  the  margin  of  the 
Sterno-mastoid. 

The  mucous  membrane  of  the  pharynx  is  very  vascular,  and  is  often  the  seat  of  inflamma- 
tion, frequently  of  a  septic  character,  and  dangerous  on  account  of  its  tendency  to  spread  to  the 
larynx.  On  account  of  the  tissue  which  surrounds  the  pharyngeal  wall  being  loose  and  lax,  the 
inflammation  is  liable  to  spread  through  it  far  and  wide,  extending  downward  into  the  posterior 
mediastinum  along  the  oesophagus.  Abscess  may  form  in  the  connective  tissue  behind  the 
pharynx,  between  it  and  the  vertebral  column,  constituting  what  is  known  as  post- pharyngeal 
abscess.  This  is  most  commonly  due  to  caries  of  the  cervical  vertebrae,  but  may  also  be  caused 
by  suppuration  of  a  lymphatic  gland  which  is  situated  in  this  position  opposite  the  axis,  and 
which  receives  lymphatics  from  the  nares,  or  by  a  gumrna  or  by  acute  pharyngitis.  The  abscess 
may  be  most  easily  evacuated  by  an  incision,  with  a  guarded  bistoury,  through  the  mouth.  It 
has  recently  been  proposed  to  open  the  abscess  aseptically  by  an  incision  in  the  neck  behind  the 
Sterno-mastoid.  The  operation,  however,  is  a  difficult  one,  unless  the  abscess  is  pointing  later- 
ally, and  does  not  give  such  free  access  to  the  seat  of  disease  for  the  removal  of  necrosed  bone,  if 
any  exists,  and  does  not  appear  to  present  sufficient  advantages  to  warrant  its  performance. 

Foreign  bodies  not  unfrequently  become  lodged  in  the  pharynx,  and  most  usually  at  its 
termination  at  about  the  level  of  the  cricoid  cartilage,  just  beyond  the  reach  of  the  finger,  as  the 
distance  from  the  arch  of  the  teeth  to  the  commencement  of  the  oasophagus  is  about  six 
inches. 

The  position  of  the  openings  of  the  Eustachian  tubes  should  be  studied  with  a  view  to 
catheterism  of  these  tubes.  This  is  to  be  done  by  introducing  the  instrument  through  the 
anterior  nares,  so  that  its  points  rest  on  the  floor  of  the  nasal  cavity  close  to  the  septum  ;  it  is 
then  pushed  gradually  and  slowly  backward  until  the  posterior  wall  of  the  pharynx  is  reached. 
Then  having  been  slightly  withdrawn  so  as  to  free  the  point  from  the  wall  of  the  pharynx,  it  is 
rotated  outward  and  upward,  so  that  the  ring  of  the  instrument  is  turned  toward  the  external 
ear,  and  it  can  then  be  made  to  glide  into  the  Eustachian  tube. 

THE  (ESOPHAGUS. 

The  oesophagus,  or  gullet,  is  a  muscular  canal,  about  nine  inches  (23  centim.) 
in  length,  extending  from  the  pharynx  to  the  stomach.  When  empty  its  lumen 
appears  as  a  transverse  slit.  Its  diameter  varies  from  1.8  to  2.4  centim.  It 
commences  at  the  upper  border  of  the  cricoid  cartilage,  opposite  the  iriterverte- 
bral  disk  between  the  fifth  and  sixth  cervical  vertebrae,  descends  along  the  front 
of  the  spine  through  the  posterior  mediastinum,  passes  through  the  Diaphragm, 
and,  entering  the  abdomen,  terminates  at  the  cardiac  orifice  of  the  stomach  oppo- 
site the  tenth  dorsal  vertebra  or  the  intervertebral  disk  between  the  tenth  and 
eleventh  dorsal  vertebrae.  The  general  direction  of  the  oesophagus  is  vertical, 
but  it  presents  two  or  three  slight  curves  in  its  course.  At  its  commencement  it 
is  placed  in  the  median  line,  but  it  inclines  to  the  left  side  as  far  as  the  root  of 
the  neck,  gradually  passes  to  the  middle  line  again,  and  finally  again  deviates  to 
the  left  as  it  passes  forward  to  the  oesophageal  opening  of  the  Diaphragm.  The 
oesophagus  also  presents  an  antero-posterior  flexure,  corresponding  to  the  curva- 
ture of  the  cervical  and  thoracic  portions  of  the  spine.  It  is  the  narrowest  part 
of  the  alimentary  canal,  being  most  contracted  at  its  commencement  and  at  the 
point  where  it  passes  through  the  Diaphragm. 

Relations. — In  the  neck  the  oesophagus  is  in  relation,  in  front,  with  the 
trachea,  and  at  the  lower  part  of  the  neck,  where  it  projects  to  the  left  side,  with 


THE    (ESOPHAGUS.  953 

the  thyroid  gland  and  thoracic  duct ;  behind,  it  rests  upon  \he  vertebral  column 
and  Longi  colli  muscles;  on  each  side,  it  is  in  relation  with  the  common  carotid 
artery  (especially  the  left,  as  it  inclines  to  that  side)  and  part  of  the  lateral  lobes 
of  the  thyroid  gland:  the  recurrent  laryngeal  nerves  ascend  between  it  and  the 
trachea. 

In  the  thorax  it  is  at  first  situated  a  little  to  the  left  of  the  median  line ;  it  then 
passes  behind  the  left  side  of  the  aortic  arch,  and  descends  in  the  posterior 
mediastinum,  along  the  right  side  of  the  aorta,  nearly  to  the  Diaphragm,  where 
it  passes  in  front  and  a  little  to  the  left  of  the  artery,  previous  to  entering  the 
abdomen.  It  is  in  relation,  in  front,  with  the  trachea,  the  arch  of  the  aorta, 
left  carotid,  and  left  subclavian  arteries,  the  left-  bronchus,  and  the  posterior 
surface  of  the  pericardium ;  behind,  it  rests  upon  the  vertebral  column,  the  Longi 
colli  muscles,  the  thoracic  duct  (opposite  middle  dorsal  vertebrae),  the  right  inter- 
costal vessels,  and  below,  near  the  Diaphragm,  upon  the  front  of  the  aorta : 
lateral.?'/,  it  is  covered  by  the  pleurae :  the  vena  azygos  major  lies  on  the  right 
and  the  descending  aorta  on  the  left  side.  The  pneumogastric  nerves  descend  in 
close  contact  with  it  on  each  side;  lower  down  the  right  nerve  passes  behind,  and 
the  left  nerve  in  front  of  it. 

Structure. — The  oesophagus  has  three  coats — an  external  or  muscular;  a 
middle  or  areolar ;  and  an  internal  or  mucous  coat. 

The  muscular  coat  is  composed  of  two  planes  of  fibres  of  considerable  thickness, 
an  external  longitudinal  and  an  internal  circular. 

The  longitudinal  fibres  are  arranged,  at  the  commencement  of  the  tube,  in  three 
fasciculi :  one  in  front,  which  is  attached  to  the  vertical  ridge  on  the  posterior 
surface  of  the  cricoid  cartilage ;  and  one  at  each  side,  which  is  continuous  with 
the  fibres  of  the  Inferior  constrictor  :  as  they  descend  they  blend  together  and 
form  a  uniform  layer,  which  covers  the  outer  surface  of  the  tube. 

Accessory  slips  of  muscular  fibres  are  described  by  Dr.  Cunningham  as 
passing  between  the  oesophagus  and  the  pleura,  where  it  covers  the  thoracic 
aorta  (almost  always),  or  the  root  of  the  left  bronchus  (usually),  or  the  back  of 
the  pericardium  or  corner  of  the  mediastinum  (more  rarely),  as  well  as  other  still 
more  rare  accessory  fibres.  In  Fig.  572,  taken  from  a  dissection  in  the  Museum 
of  the  Royal  College  of  Surgeons,  several  of  these  accessory  slips  may  be  seen 
passing  from  the  oesophagus  to  the  pleura,  and  two  slips  to  the  back  of  the  trachea 
just  above  its  bifurcation. 

The  circular  fibres  are  continuous  above  with  the  Inferior  constrictor;  their 
direction  is  transverse  at  the  upper  and  lower  parts  of  the  tube,  but  oblique  in  the 
central  part. 

The  muscular  fibres  in  the  upper  part  of  the  oesophagus  are  of  a  red  color,  and 
consist  chiefly  of  the  striped  variety,  but  below  they  consist  for  the  most  part  of 
involuntary  muscular  fibre. 

The  areolar  coat  connects  loosely  the  mucous  and  muscular  coats. 

The  mucous  coat  is  thick,  of  a  reddish  color  above  and  pale  below.  It  is 
disposed  in  longitudinal  folds,  which  disappear  on  distension  of  the  tube.  Its 
surface  is  studded  with  minute  papillae,  and  it  is  covered  throughout  with  a  thick 
layer  of  stratified  pavement  epithelium.  Beneath  the  mucous  membrane,  between 
it  and  the  are  :>lar  coat,  is  a  layer  of  longitudinally  arranged  non-striped 
muscular  fibres.  This  is  the  muscularis  mucosw.  At  the  commencement  it  is 
absent,  or  only  represented  by  a  few  scattered  bundles ;  lower  down  it  forms  a 
considerable  stratum. 

The  aesophageal  glands  are  numerous  small  compound  racemose  glands 
scattered  throughout  the  tube ;  they  are  lodged  in  the  submucous  tissue,  and  open 
upon  the  surface  by  a  long  excretory  duct.  They  are  most  numerous  at  the  lower 
part  of  the  tube,  where  they  form  a  ring  round  the  cardiac  orifice. 

Vessels  of  the  (Esophagus. — The  arteries  supplying  the  oesophagus  are  de- 
rived from  the  inferior  thyroid  branch  of  the  thyroid  axis  of  the  subclavian. 
from  the  descending  thoracic  aorta,  and  from  the 'gastric  branch  of  the  coeliac 


954 


THE    ORGANS    OF    DIGESTION. 


axis   from   the   abdominal   aorta.      They  have  for  the  most  part  a  longitudinal 
direction. 

Nerves  of  the  (Esophagus. — The  nerves  are  derived  from  the  pneumogastric 
and  from  the  sympathetic ;  they  form  a  plexus  in  which  are  groups  of  ganglion- 
cells  between  the  two  layers  of  the  muscular  coats,  and  also  a  second  plexus  in 
the  submucous  tissue. 

Surgical  Anatomy. — The  relations  of  the  oesophagus  are  of  considerable  practical  interest 
to  the  surgeon,  as  he  is  frequently  required,  in  cases  of  stricture  of  this  tube,  to  dilate  the  canal 

by  a  bougie,  when  it  is  of  importance  that  the  direction  of  the 
oesophagus  and  its  relations  to  surrounding  parts  should  be 
remembered.  In  cases  of  malignant  disease  of  the  oesophagus, 
where  its  tissues  have  become  softened  from  infiltration  of  the 
morbid  deposit,  the  greatest  care  is  requisite  in  directing  the 
bougie  through  the  strictured  part,  as  a  false  passage  may 
easily  be  made,  and  the  instrument  may  pass  into  the  medi- 
astinum, or  into  one  or  the  other  pleural  cavity,  or  even  into 
the  pericardium. 

The  student  should  also  remember  that  contraction  of  tbe 
oesophagus,  and  consequent  symptoms  of  stricture,  are  occa- 
sionally produced  by  an  aneurism  of  some  part  of  the  aorta 
pressing  upon  this  tube.  In  such  a  case  the  passage  of  a 
bougie  could  only  hasten  the  fatal  issue. 

In  passing  a  bougie  the  left  fore  finger  should  be  intro- 
duced into  the  mouth  and  the  epiglottis  felt  for,  care  being 
taken  not  to  throw  the  head  too  far  backward.  The  bougie  is 
then  to  be  passed  beyond  the  finger  until  it  touches  the  pos- 
terior wall  of  the  pharynx.  The  patient  is  now  asked  to  swal- 
low, and  at  the  moment  of  swallowing  the  bougie  is  passed 
gently  onward,  all  violence  being  carefully  avoided. 

It  occasionally  happens  that  a  foreign  body  becomes  im- 
pacted in  the  oesophagus  which  can  neither  be  brought  upward 
nor  moved  downward.  When  all  ordinary  means  for  its  re- 
moval have  failed,  excision  is  the  only  resource.  This,  of 
course,  can  only  be  performed  when  it  is  not  very  low  down. 
If  the  foreign  body  is  allowed  to  remain,  extensive  inflamma- 
tion and  ulceration  of  the  oesophagus  may  ensue.  In  one  case 
the  foreign  body  ultimately  penetrated  the  intervertebral  sub- 
stance, and  destroyed  life  by  inflammation  of  the  membranes 
and  substance  of  the  cord. 

The  operation  of  oesophagotomy  is  thus  performed  :  The 
patient  being  placed  upon  his  back,  'with  the  head  and  shoul- 
ders slightly  elevated,  an  incision,  about  four  inches  in  length, 
should  be  made  on  the  left  side  of  the  trachea,  from  the  thy- 
roid cartilage  downward,  dividing  the  skin  and  Platysma. 
The  edges  of  the  wound  being  separated,  the  Omo-hyoid 
muscle  should,  if  necessary,  be  divided,  and  the  fibres  of  the 
Sterno-hyoid  and  Sterno-thyroid  muscles  drawn  inward ;  the 
sheath  of  the  carotid  vessels,  being  exposed,  should  be  drawn 
outward,  and  retained  in  that  position  by  retractors  :  the  oesoph- 
agus will  now  be  exposed,  and  should  be  divided  over  the  foreign  body,  which  can  then  be 
removed.  Great  care  is  necessary  to  avoid  wounding  the  thyroid  vessels,  the  thyroid  gland,  and 
the  laryngeal  nerves. 

The  oesophagus  may  be  obstructed  not  only  by  foreign  bodies,  but  also  by  changes  in 
its  coats,  producing  stricture,  or  by  pressure  on  it  from  without  of  new  growths  or  aneurism. 
etc. 

The  different  forms  of  stricture  are:  (1)  the  spasmodic,  usually  occurring  in  nervous 
women,  and  intermittent  in  character,  so  that  the  dysphagia  is  not  constant ;  (2)  fibrous,  due  to 
cicatrization  after  injuries,  such  as  swallowing  corrosive  fluids  or  boiling  water  ;  and  (3)  malig- 
nant, usually  epitheliomatous  in  its  nature.  This  is  situated  generally  either  at  the  upper  end 
of  the  tube,  opposite  to  the  cricoid  cartilage,  or  at  its  lower  end  at  the  cardiac  orifice,  but  is 
also  occasionally  found  at  that  part  of  the  tube  where  it  is  crossed  by  the  left  bronchus. 

The  operation  of  oesophagostomy  has  occasionally  been  performed  in  cases  where  the 
stricture  in  the  oesophagus  is  at  the  upper  part,  \yith  a  view  to  making  a  permanent  opening 
below  the  stricture  through  which  to  feed  the  patient,  but  the  operation  has  been  far  from  a 
successful  one,  and  the  risk  of  setting  up  diffuse  inflammation  in  the  loose  planes  of  con- 
nective tissue  deep  in  the  neck  is  so  great  that  it  would  appear  to  be  better  to  perform  gas- 
trostomy. 


FIG.  572. — Accessory  muscular  fi- 
bres between  the  oesophagus  and 
pleura,  and  oesophagus  and  trachea. 
(From  a  preparation  in  the  Museum 
of  the  Royal  College  of  Surgeons.) 


THE   ABDOMEN. 


955 


THE    ABDOMEN. 

[BY  FRED  J.  BBOCKWAY,  M.  D., 
I'emonstrator  of  Anatomy,  College  of  Physicians  and  Surgeons  (Columbia  University)  Xew  York  City.] 

In  the  early  stages  of  the  embryo  the  "body-cavity"  (pleuro-peritoneal 
cavity)  is  of  large  size.  Anteriorly  (*".  e.  superiorly  in  the  erect  posture)  there 
is  developed  a  comparatively  enormous  space,  called  the  pericardio-thoracic 
cavity  (Fig.  573.  .4..  B  and  C).  There  also  appears  a  transverse  fold  marking 


Ptrural  Carities 
Pleurae 
Perifardial  Gorily 


Ftri!o*eum 


ABC 

FIG.  573. —Schematic  representation  of  the  serous  cavities.    (Gegenbanr.) 

off  this  cavity  in  part  from  the  future  abdominal  cavity.  This  fold,  associated 
with  many  large  veins,  is  next  developed  into  the  primary  diaphragm,  but  its 
dorsal  part  is  incomplete.  This  is  completed  later,  constituting  the  diaphragm 
as  we  know  it  in  the  adult.  The  diaphragm  is  thus  made  up  of  a  ventral  younger 
part  and  a  dorsal  older  part.  When  this  posterior  part  fails  of  development, 
there  is  an  opportunity  for  the  *•  congenital  diaphragmatic  hernia  "'  to  be  present. 

The  superior  or  pericardio-thoracic  cavity  becomes  separated  into  three  dis- 
tinct compartments  (Fig.  573.  B  and  C').  the  two  lateral  being  continuous  for  a 
time  with  the  abdominal  cavity.  Thus  are  formed  the  four  large  serous  spaces 
of  the  body,  each  one  lined  with  serous  membrane.  Two  are  thoracic  or  pleural, 
lined  with  pleura,  one  is  cardiac,  defined  by  the  pericardial  sac,  and  one  is  ab- 
dominal, lined  with  peritoneum. 

The  word  abdomen  l  is  applied  to  the  part  of  the  body  lying  between  the 
thorax  and  pelvis :  it  refers  to  the  largest  cavity  of  the  adult  body,  and  is  often 
applied  incorrectly  to  the  anterior  wall  of  this  cavity.  It  contains  nearly  all  the 
digestive  apparatus  and  a  part  of  the  urinary  system. 

Superficially  the  abdomen  is  marked  from  the  thorax  above  by  the  costal 
arches,  and  below  from  the  pelvis  by  the  crests  of  the  ilia,  and  from  the  thighs 
by  Poupart's  ligaments.  These  limits,  however,  do  not  correspond  with  those  of 
the  abdominal  cavity.  This  extends  high  into  the  thorax  to  the  cupola  of  the 
diaphragm.  The  lowest  limit  is  the  so-called  "  diaphragm  of  the  pelvis  "  made 
by  the  Levator  ani  and  Coccygeus  muscles  on  either  side.  This  great  cavity 
shows  a  smaller  artificial  subdivision,  the  pelvic  cavity  (Fig.  577)  The  two  are 
not  separated,  but  the  limit  between  them  is  taken  as  the  brim  of  the  true  pelvis. 

1  Abdo'men  comes  perhaps  from  abdere,  to  conceal.  Hyrtl  says  it  is  an  ancient  word  applied  to 
the  belly  of  a  pregnant  pig.  Cicero  transferred  it  from  swine  to  man  in  a  sense  of  contempt.  Venter 
and  alrnf  were  used  for  belly ;  abdomen  and  its  adjective  abdominalis  finally  came  into  general  use. 


956 


THE    ORGANS    OF   DIGESTION. 


the  linea  innominata.     The  larger  upper  cavity  is  called  the  abdominal  cavity 
proper. 

The  form  and  extent  of  the  abdomen  vary  with  age  and  sex.     In  the  adult 
male  with  intestines  moderately  distended  it  is  barrel-shaped  or  oval,  somewhat 


A 


Male  Type 


Infantile  Type 


FIG.  574. — Schematic  outlines  of  the  abdomen. 


flattened  from  before  backward  (Fig.  574,  A,  B,  and  (7).     The  infantile  type  is 
conical  with  apex  below,  as  the  pelvis  is  undeveloped.     In  woman  the  type  is  a 

fe<£%Vi>7 ;" .       \ 

fr;l»iWH&!w«:    \ 

,:?>^b'P'-«4i-      \ 
SS^S: 

•'^iVVv>;T?-v  , 

*$®§51K< 

•?H>wB!b« 

"r*-;^^  i^^-rVv  ;• 


Skin— 

Superficial  layer  of     P 
superficial  fascia 

Deep  layer  of  super- 
ficial fascia 

Areolar  tissue  and-£ 
intercolumnar  fascia 

Apoiieurosis  of  M. 
obliquus  externus 

M.  obliquus  interims 
M.  transversal!* 
Fascia  transversalis — 

Sub-peritoneal  area- 
lar  tissue 


FIG.  575.— Antero-posterior  vertical  section  through  the  outer  third  of  Poupart's  ligament,  showing  the 
layers  of  the  abdominal  walls.    Schematic.    (After  Tillaux.) 

reversed  infantile,  regardless  of  so-called  civilized  dress.  The  circumference  of 
the  fully-developed  pelvis  here  is  always  larger  than  that  of  the  lower  end  of  the 
thorax. 


THE    ABDOMKX.  957 

Boundaries. — The  al»l<>in>  //  ^  roper  is  divided  for  description  into  the  abdominal 
ii'dll  or  boundaries  and  the  abdominal  cavity  and  contents.  The  boundaries  are 
a  /••"/.  a  floor,  and  the  trail,  which  includes  an  antero-lateral  and  a  posterior  por- 
tion ;  the  former  is  soft  and  contractile,  muscular  on  the  sides,  fibrous  and 
aponeurotic  in  the  centre ;  the  posterior  wall  is  partly  osseous,  ligamentous  and 
muscular. 

Several  facts  depend  on  the  character  of  the  antero-lateral  wall.  It  does  not 
offer  to  the  viscera  and  great  vessels  a  passive  protection  as  does  the  skull  to  its 
contents,  but  allows  a  mutual  reaction  which  is  of  the  greatest  importance.  It 
yields  lightly  to  every  pressure  and  corresponds  to  the  changing  volume  of  the 
intestines  and  to  the  changes  of  position  and  form  of  the  viscera.  Atmospheric 
pressure  acts  on  every  side,  but  this  is  overlooked  when  the  many  muscles  are 
considered  which  exert  a  constant  tension.  The  relations  of  each  organ  to  its 
neighbor  are  modified  by  this  tension,  and  soft  organs  like  the  liver,  pancreas,  or 
spleen  are  moulded  by  it  and  show  the  imprint  of  nearly  every  viscus  that  touches 
them.  The  tension  is  seen  in  cases  of  penetrating  wounds,  where  the  movable 
intestines  tend  to  flow  toward  the  spot  of  least  resistance  and  are  replaced  or 
restrained  with  difficulty.  The  same  pressure  helps  to  develop  hernife  and  forces 
the  portal  circulation  through  the  liver. 

The  shape  of  the  soft  antero-lateral  wall  depends  upon  the  degree  of  disten- 
tion  of  the  alimentary  canal,  the  size  of  the  parenchymatous  organs,  and  espe- 
cially upon  the  deposit  of  fat  in  the  subcutaneous  tissue,  in  the  peritoneal  folds, 
and  in  the  great  omentum.  All  gradations  occur  between  the  great  fat  belly 
which  depends  over  the  thighs  and  the  concave  trough-like  one  of  a  thin  person. 
The  pliability  and  thinness  of  the  wall  allow  palpation  to  be  of  more  value  here 
in  diagnosis  than  percussion. 

The  component  parts  of  the  walls  have  already  been  discussed.  A  brief 
review  is  here  added  (Fig.  575). 

In  the  antero-lateral  wall  from  without  inward  are  found  in  order : 

1.  Skin. 

2.  Superficial  fascia,  two  layers. 

3.  Cellular  tissue  covering  the  External  oblique  muscle,  and  intercolumnar 
fascia  from  the  external  abdominal  ring. 

4.  Muscles  of  the  wall.     Broad  muscles — the  External  oblique  and  aponeur- 
osis.  the  Internal  oblique  and  aponeurosis,  the  Transversalis  and  aponeurosis. 
Longitudinal  muscles — the  Rectus  and  Pyramidalis. 

5.  Fascia  transversalis. 

6.  Subperitoneal  cellular  tissue. 

7.  Peritoneum. 

In  this  wall  several  regions  are  described :  the  inguinal,  inguino-femoral,  and 
umbilical. 

The  arteries  of  the  antero-lateral  wall  are  superficial  and  deep ;  the  super- 
ficial epigastric  and  superficial  circumflex-iliac  from  the  femoral,  the  lower  two 
intercostals  from  the  thoracic  aorta,  the  lumbar  from  the  abdominal  aorta,  and 
ilio-lumbar  from  the  internal  iliac.  Above  are  the  superior  epigastric  and  mus- 
culo-phrenic  from  the  internal  mammary — all  forming  the  superficial  set.  Below 
are  the  deep  circumflex-iliac  and  deep  epigastric  (inferior  epigastric)  from  the 
external  iliac.  The  latter  is  the  most  important  and  gives  off  the  cremasteric 
artery,  pubic  and  muscular  branches.  There  is  an  anastomosis  between  the  two 
lower  epigastrics  and  between  the  deep  epigastric  and  the  internal  mammary. 

The  veins  are  also  divided  into  a  superficial  and  deep  set.  Superficial  are  the 
superficial  epigastric  and  superficial  circumflex-iliac  and  another  which  passes 
subcutaneously  along  the  side  of  the  thorax,  connecting  above  with  the  axillary 
vein  and  emptying  below  into  either  the  superficial  epigastric  vein  or  into  the 
femoral  through  the  saphenous  opening.  It  is  dignified  by  the  name  l^cna 
thoracico-epi<!<ixtr<<-'i  /••/#;/•/  t>-;-niriit>ntox<i  ( Braune).  The  deep  veins  accompany 
their  corresponding  arteries  and  are  usually  double.  The  superficial  veins  do  not 


958 


THE    ORGANS    OF   DIGESTION. 


exactly  correspond  to  their  arteries,  and  are  usually  single.  The  superficial  epi- 
gastric anastomoses  with  the  deep  epigastric,  and  both  with  the  internal  mammary. 

Pressure  upon  the  vena  cava  inferior  forces  blood  into  the  superficial  epigas- 
tric vein.  A  dilatation  of  the  superficial  abdominal  veins  to  the  size  of  the  little 
finger  (caput  Medusae)  may  thus  be  caused  by  cirrhosis  of  the  liver.  This  is 
explained  by  the  anastomosis  between  the  superficial  epigastric  vein  and  the 
portal  system :  the  superficial  veins  communicate  with  the  deep  epigastrics  and 
these  with  the  portal  system  by  means  of  a  little  vena  parumbilicalis  running  in 
the  falciform  ligament  of  the  liver. 

Depending  upon  the  seat  of  obstruction,  whether  in  the  vena  cava  inferior  or 
in  the  portal  system,  the  course  of  the  blood-stream  in  the  dilated  veins  may  be 
in  one  of  two  directions :  toward  the  umbilicus  in  the  former  case,  and  from  it  in 
the  latter. 

The  deep  veins  are  the  venae  comites  of  the  deep  epigastric  and  deep  circum- 
flex-iliac arteries.  They  communicate  with  the  superficial  set,  the  internal  mam- 
mary, the  portal  system,  and  behind  the  sheath  of  the  Rectus  with  a  plexus  in 
the  parietal  peritoneum. 

The  superficial  lymphatic  vessels  above  the  umbilicus  empty  into  the  axillary 
glands,  below  the  umbilicus  into  the  inguinal  glands.  The  deep  lymphatics  prob- 
ably empty  above  into  the  sternal  glands  arid  below  into  the  iliac  glands. 


M.  rectus  abdominii 


M.  obliquus 
externus 


Peritoneum 


M.  quadratm 
lumborum 


Posterior  M.  latissimus  dorsi 

layer  Lumbar  aponeitrosis,  anterior  layer 

Middle  layer 

FIG.  576.— Horizontal  section  of  the  posterior  abdominal  wall  through  the  second  lumbar  vertebra,  right 
side.  (Tillaux.) 

The  nerves  supplying  the  whole  musculature  are  the  lower  five  intercostal, 
the  anterior  part  of  the  first  lumbar,  viz.  the  ilio-hypogastric  and  ilio-inguinal. 
Twigs  from  the  lower  seven  intercostal  and  from  the  ilio-hypogastric  and  ilio- 
inguinal  furnish  the  sensory  supply. 


THE   ABDOMEX.  959 

There  may  exist  a  congenital  deformity  in  the  anterior  wall,  a  partial  lack  of 
development  and  an  ununited  symphysis  pubis ;  with  this  the  anterior  wall  of  the 
bladder  is  lacking  and  its  posterior  wall,  with  ureters,  exposed.  This  condition 
is  called  exstrophy  of  the  bladder. 

The  jioxfr /•/'•>/•  "'nil  of  the  abdomen  proper  has  no  special  line  of  demarcation 
from  the  antero-lateral  Avail ;  its  vertical  length  is  of  much  less  extent  than  the 
latter  (Fig.  570). 

It  is  the  part  into  which  the  skeleton  enters,  composed  of  the  five  lumbar 
vertebrae  connected  by  ligaments  and  disks.  Laterally  are  the  Psoas  and  Quad- 
ratus  lumborum  muscles,  and  behind  these  the  Sacro-spinalis  mass  (Erector  spinse 
muscle). 

Through  the  lumbar  region  on  either  side  of  the  vertebral  column  the  folio w- 

c  •         i 

ing  structures  are  met  in  order : 

1.  Skin. 

2.  Subcutaneous  fascia  and  cellular  tissue. 

3.  Lumbar  aponeurosis,  posterior  layer. 

4.  Erector  spinse  muscle. 

5.  Transverse  process  and  lumbar  aponeurosis,  middle  layer. 

6.  Quadratus  lumborum  muscle. 

7.  Lumbar  aponeurosis,  anterior  layer. 

8.  Psoas  muscle. 

9.  Visceral  layer  of  kidney,  cellular  tissue,  and  colon. 

10.  Subperitoneal  tissue  and  peritoneum. 

This  region  presents  the  special  districts,  lumbar  and  iliac,  already  described. 
The  arteries,  veins,  nerves,  and  lymphatics  are  all  called  lumbar. 

The  roof  and  floor  of  the  abdomen  are  elsewhere  described. 

The  apertures  found  in  the  walls  of  the  abdomen  for  the  transmission  of 
structures  to  or  from  it  are — the  umbilicus,  for  the  transmission  (in  the  foetus)  of 
the  umbilical  vessels ;  the  caval  opening  in  the  Diaphragm,  for  the  transmission 
of  the  inferior  vena  cava  :  the  aortic  opening,  for  the  passage  of  the  aorta,  vena 
azygos,  and  thoracic  duct ;  and  the  oesophageal  opening,  for  the  ossophagus  and 
pneumogastric  nerves.  Beloiv,  there  are  two  apertures  on  each  side,  one  for  the 
passage  of  the  femoral  vessels,  and  the  other  for  the  transmission  of  the  spermatic 
cord  in  the  male  and  the  round  ligament  in  the  female. 

THE  ABDOMINAL  CAVITY  AND  CONTEXTS. 

It  must  be  carefully  noted  that  there  is  a  difference  between  the  abdominal 
cavity  proper  and  the  peritoneal  cavity.  The  peritoneum  does  not  closely  cover 
everywhere  the  abdominal  walls,  but  is  pushed  in  and  out,  leaving  spaces  and 
diverticula  so  that  some  organs  will  be  extraperitoneal,  others  intraperitoneal, 
yet  all  will  be  inside  the  abdominal  cavity. 

Before  studying  the  peritoneum  it  will  be  best  to  become  more  familiar  with 
the  names  and  location  of  the  important  viscera.  This  can  be  shown  in  a  topo- 
graphical way  by  dividing  off  the  surface  of  the  abdomen  into  districts  and  con- 
sidering the  chief  organs  lying  in  each. 

Regions. 

Many  authors  have  devised  many  means  for  this  subdivision,  all  of  which 
consist  in  allowing  two  horizontal  planes  to  cross  two  perpendicular  ones ;  the 
edges  of  these  planes  are  indicated  by  lines  on  the  abdomen.  An  old  way  was 
to  let  the  edge  of  one  horizontal  plane  intersect  the  anterior  extremities  of  the 
ninth  ribs,  and  to  let  the  lower  plane  pass  through  the  highest  points  of  the 
crests  of  the  ilia.  The  perpendicular  planes  passed  each  one  through  the  centre 
of  Poupart's  ligament. 

The  advantage  of  the  following  method  (Joessel)  is  that  all  its  planes  pass 
through  bony  points  and  its  two  perpendicular  planes  through  the  brim  of  the 


960 


THE    ORGANS    OF  DIGESTION. 


pelvis.  Here  the  highest  plane  is  subcostal,  passing  just  under  the  lowest  margin 
of  the  thorax  in  a  line  drawn  through  the  cartilaginous  ends  of  the  tenth  ribs. 
The  lower  plane  is  interspinous  and  passes  through  the  anterior  superior  spines 
of  the  ilia  (Fig.  577). 

This  marks  off  three  zones  or  regions :  1.  Epigastric.  2.  Mesogastric.  3. 
Hypogastric.  Each  one  is  again  subdivided  into  three  parts  by  the  two  sagittal 
planes  which  pass  through  on  either  side  the  ileo-pectineal  eminence  and  end  on 
the  horizontal  line  connecting  the  tenth  ribs  (Fig-  578). 


Fio.  577.— Outline  of  the  ab- 
dominal cavity  as  seen  in  mesial 
section.  The  planes  of  subdivis- 
ion are  indicated  by  dotted  lines. 
(Cunningham.) 


Emincntia,  ilia-peclinea, 
FIG.  578.— Regions  of  the  abdominal  cavity.    Anterior  view.    (Joessel. 


The  epigastric  zone  contains,  in  order,  the  riff  Tit  hypochondrium  (UTTO,  under ; 
•fcovdpot,  cartilages),  epigastrium  (£rci,  upon ;  yaarrjp,  stomach)  and  the  left  hypo- 
chondrium.  The  mesogastric  zone  contains  the  right  lumbar,  the  umbilical,  and 
the  left  lumbar  regions  (the  lateral  regions  may  be  called  lateral  abdominal). 
The  hypogastric  zone  contains  the  right  iliac,  the  pubic,  and  left  iliac  regions. 
Sometimes  the  iliac  regions  are  called  inguinal ;  then  a  subinguinal  region  is  dis- 
tinguished below  Poupart's  ligament. 

The  limits  of  the  epigastric  zone  are  the  diaphragm  above  and  below  the 
horizontal  plane  through  the  anterior  ends  of  the  tenth  ribs.  The  lateral  and 
posterior  limits  follow  the  eleventh  and  twelfth  ribs  to  end  with  the  last  on  the 


THE   ABDOMEN. 


961 


spinal  column.  The  epigastric  surface  of  this  region  is  triangular,  placed  between 
the  costal  arches  and  horizontal  line  below.  The  transverse  colon  corresponds 
to  this  horizontal  line.  Somewhat  higher,  opposite  the  ninth  rib.  is  the  greater 
curvature  of  the  stomach  in  moderate  distention.  In  the  middle  of  the  epigas- 
trium farthest  above  is  a  depression  called  the  gastric  or  cardiac  fossa  (scrobiculus 
cordis) ;  corresponding  to  this  place  is  the  liver  and  pyloric  end  of  stomach. 

The  hypochondriac  regions  include  the  spaces  between  the  diaphragm  supe- 
riorly, posteriorly,  and  externally,  the  costal  cartilages  internally,  and  the  hori- 
zontal plane  below.  The  right  one  is  filled  by  the  liver.  The  left  one  contains 
the  spleen,  the  splenic  flexure  of  the  colon,  the  greater  part  of  the  stomach,  and 
after  distention  of  the  stomach  a  large  part  of  the  great  omentum. 


FIG.  579.— Regions  of  the  abdominal  cavity.    Posterior  view.    (Joessel.) 

The  mesogastric  zone  is  bounded  above  by  the  epigastric  zone  and  below  by 
the  horizontal  plane  passing  through  the  anterior  superior  spines  of  the  ilia. 
Laterally  and  behind  are  the  crests  of  the  ilia.  In  the  umbilical  region  lie  the 
great  omentum.  the  loops  of  small  intestine,  and  their  mesentery.  In  the  lumbar 
nt,  which  extend  from  the  perpendicular  lines  drawn  through  the  ileo-pec- 
tineal  eminences  around  to  the  vertebral  column,  are  also  small  intestines,  the 
kidneys,  the  ascending  and  descending  colons. 

The  hypogastric  zone  is  bounded  above  by  the  mesogastric  and  below  by  the 
brim  of  the  true  pelvis.  The  pubic  region  in  the  centre  contains  the  bladder,  the 
right  iliac,  the  caecum,  and  the  left  iliac,  a  part  of  the  sigmoid  flexure. 

61 


962 


THE    ORGANS    OF  DIGESTION. 


To  recapitulate : 

Right  Hypochondrium . 
Liver. 


Right  Lumbar. 
Right  kidney. 
Small  intestines. 
Ascending  colon. 

Right  Iliac. 
Caecum. 


Epigastrium. 
Liver. 
Stomach. 


Umbilical  Region. 
Great  omenturn. 
Small  intestines. 
Mesentery. 

Pubic. 
Bladder. 


Left  Hypochondria > n. 
Greater  part  of  stomach. 
Spleen. 

Splenic  flexure  of  colon. 
Great  omentum. 

Left  Lumbar. 
Left  kidney. 
Small  intestines. 
Descending  colon. 

Left  Iliac. 
Part  of  sigmoid  flexure. 


Fig.  579  gives  a  posterior  view  of  the  abdominal  cavity,  showing  a  vertebral 
region  and  the  two  lateral  regions  of  the  mesogastric  zone  continued  posteriorly, 
the  right  and  left  lumbar.  There  are  to  be  seen  the  outlines  of  the  kidneys,  the 
spleen,  the  ascending  and  descending  colons.  The  dotted  line  meeting  the  ver- 
tebral column  at  the  eleventh  rib  is  the  lower  lung  limit ;  the  line  at  the  twelfth 
rib  is  the  lower  pleural  limit.  The  vertebral  region  includes  the  vertebral  column 
and  part  of  the  Quadratus  lumborum  muscles. 

THE  PERITONEUM. 

Let  us  now  suppose  the  student  has  finished  the  dissection  of  the  antero- 
lateral  abdominal  wall,  has  studied  the  anatomy  of  inguinal  and  femoral  hernia, 
the  sheath  of  the  Rectus  muscle,  and  has  seen  the  adminiculum  linea;  albce.  The 
semilunar  folds  of  Douglas  are  before  him,  and  he  is  ready  to  incise  the  trans- 
versalis  fascia  and  the  parietal  peritoneum. 

The  Recti  muscles  should  have  been  cut  transversely  a  little  below  the  umbil- 
icus and  both  turned  down  together  from  their  sheath  without  dividing  the  linea 
alba. 


FIG.  580. — Posterior  view  of  the  Recti  abdominis  muscles.    (Luschka.) 

Behind  the  Recti  on  the  lower  and  posterior  part  of  the  linea  alba  is  a  trian- 
gular band  of  fibrous  tissue  called  adminiculum  linece  albce  (adminiculum,  "  prop 
on  which  a  vine  grows  ")  (Fig.  580,  4).  It  passes  up  4  or  5  cm.  to  strengthen  the 


THE   PERITONEUM. 


963 


•white  line,  its  apex  being  above  and  its  base  below.  It  rises  from  the  crests  of 
the  pubic  bones  and  arches  over  the  upper  edge  of  the  symphjsis  pubis.  This 
should  not  be  mistaken  for  the  urachus  which  lies  behind  it,  separated  by  the 
tran sversalis  fascia ;  both  are  outside  the  peritoneum. 

Xow  open  the  peritoneal  cavity.  Do  not  make  a  median  incision  from  the 
ensiform  cartilage  to  the  symphysis  pubis.  Start  at  the  umbilicus  and  make  two 
oblique  cuts  from  it,  one  to  each  Poupart's  ligament  near  the  anterior  superior 
spine  of  the  ilium  ;  make  one  more  from  the  umbilicus  to  the  ensiform  cartilage. 
Make  a  transverse  cut  on  either  side  when  more  room  is  desired.  To  the  riorht 
of  the  upper  incision  will  be  seen  a  round  cord  passing  from  the  umbilicus  to  the 
under  surface  of  the  liver  and  enclosed  in  a  double  layer  of  serous  tissue.  The 
latter  is  peritoneum,  called  the  broad,  suspensory,  or  falciform  ligament  of  the 
liver ;  the  cord  is  the  round  ligament  of  the  liver,  or  a  part  of  the  obliterated 
wnbiUcal  vein,  which  in  the  foetal  state  carried  arterial  blood  from  the  placenta 
to  the  liver  first  and  thence  over  the  body. 

Turn  down  the  lower  triangular  flap  and  the  view  presented  is  shown  in  Fig. 
•jsl.  Three  distinct  bands  or  cords  are  seen  passing  from  below  upward  toward 


Plica  hypoffcutrica 


P.ica  uractd 


P>ica  epigae- 
trica' 


Middle 
inffuinalfosaa 


Internal  inguinal 
fossa 

Superior  vesi- 
cal  artery 


in  US  10Wer  half    The  Peritoneum  is  in  place,  and 


the  umbilicus.  They  are  all  foetal  structures.  The  middle  one  is  the  urachus, 
the  remnant  of  the  stalk  of  the  allantois  ;  it  may  remain  pervious.  The  two 
lateral  ones  are  the  obliterated  Jiupogastric  arteries  which  conveyed  venous  blood 


964  THE    ORGANS    OF  DIGESTION. 

from  the  foetus  to  the  placenta  for  oxygenation  which  was  returned,  as  we  have 
seen,  by  the  umbilical  vein.  The  younger  the  subject  under  dissection,  the 
bigger  are  these  two  cords.  Near  the  umbilicus  they  subdivide  into  numerous 
threads  which  in  part  join  the  urachus,  in  part  run  free  toward  the  umbilicus, 
and  only  the  smallest  part  reaches  it.  The  proximal  part  of  this  artery  is  still 
pervious  after  birth  as  far  as  the  bladder  under  the  name  of  superior  vesical. 

To  either  side  of  the  three  cords  is  seen  the  deep  epigastric  artery  passing  in 
behind  the  Rectus  at  the  semilunar  fold  of  Douglas.  These  five  bands  are  cov- 
ered posteriorly  by  peritoneum,  which  is  thrown  backward  in  five  folds  or  ridges 
(plica,  fold)  forming  in  all  six  fossae,  or  three  to  a  side.  Sometimes  the  obliter- 
ated hypogastric  artery  is  identical  in  position  with  the  deep  epigastric,  in  which 
case  folds  and  fossae  are  less  in  number.  The  middle  fold  is  called  plica  umbil- 
icalis  media  or  superior  ligament  of  the  bladder ;  the  next  on  either  side  the  plica 
umbilicalis  lateralis,  or  lateral  ligament  of  the  bladder ;  the  fold  over  the  deep 
epigastric  artery  is  the  plica  epigastrica.  The  simplest  nomenclature  is  plica 
urachi,  plica  hypogastrica,  plica  epigastrica.  The  fossae  included  between  these 
folds  are  named — the  most  external,  outside  the  epigastric  artery  and  above  Pou- 
part's  ligament,  the  external  inguinal  fossa  ;  between  the  urachus  and  the  cord 
of  the  obliterated  hypogastric  artery  is  the  internal  inguinal  fossa,  and  the 
remaining  depression  is  the  middle  inguinal  fossa.  This  one  may  be  very  narrow 
and  quite  deep.  The  external  fossa  has  on  its  floor  the  internal  abdominal  ring, 
and  admits  the  oblique  inguinal  hernia ;  either  of  the  other  two  alloAvs  a  direct 
inguinal  hernia.  To  the  inner  side  of  the  femoral  vein  is  the  femoral  or  crural 
fossa,  the  site  of  femoral  hernia.  All  the  above  points  should  be  noticed  when 
the  abdomen  is  opened. 

The  structures  now  presented  for  study,  more  or  less  preliminary  at  first  and 
in  detail  later,  are  here  presented. 

1.  Peritoneum  which  lines  the  cavity  and  clothes  the  viscera. 

2.  Abdominal  part  of  alimentary  canal : 

(  Duodenum. 

Small  Intestines  Jejunum. 
|^  Ileum. 

!  Caecum. 
Ascending  colon. 
Transverse  colon. 
T>  J'  1 

Descending  colon. 
Sigmoid  Flexure. 
[  Rectum. 
(  Liver. 

3.  Accessory  Glands  <  Gall-bladder. 

(  Pancreas. 

4.  Spleen. 

5.  Two  Kidneys,  Ureters.  Adrenals  or  Suprarenal  Capsules,  and  Bladder. 

6.  In  female,  Uterus,  Ovaries,  and  Fallopian  Tubes. 

7.  Lymphatic  Glands,  Vessels,  and  beginning  of  Thoracic  Duct. 

8.  Abdominal  Aorta  and  nine  sets  of  branches. 

9.  Vena  cava  inferior  and  tributaries ;  beginning  of  Vena  azygos  major  and 
minor. 

10.  Portal  venous  system. 

11.  Lumbar    Plexus   of    cerebro-spinal    nerves;     Sympathetic    Nerves    and 
Plexuses. 

We  get  but  a  partial  view  of  all  when  the  viscera  are  undisturbed  (Fig.  584). 
Like  a  curtain  the  great  omentum  conceals  most  of  the  small  intestines,  but  it 
may  be  short  or  turned  up  or  to  one  side.  The  parts  to  be  seen  are  indicated  in 
the  diagram.  To  find  the  transverse  colon,  throw  the  great  omentum  and  stom- 
ach well  up  over  the  ribs ;  now  the  whole  colon  can  be  traced,  beginning  in  the 


THE   PERITONEUM. 


965 


Gall-bladder 


Right  suprarenal 
"  capsule 


Greater  curvature 
of  stomach 


Left  kidney 

Trans,  mesocolon 
Transverse  colon 
Jejunum 


FIG.  582. — Anterior  view  of  His'  models  of  the  abdominal  contents.    Drawn  from  photographs. 


966 


THE    ORGANS   OF   DIGESTION. 


Left  lobe  of  liver . 

Lobus  Spigelii 


'.e  of  left 
'ney 


Splenic  vein — 


Vena  cava  inferior 


Non-peritoneal 
surface 

Right  lobe  of  liver 


Impressio  renalis 
Gall-bladder 


Impressio  colica 


Capsule  of  right 
kidney 


Vena  portse 
.Common  bile-duct 
— ~Sup.  mesen.  vessels 


Inferior  mcsenteric 
vein 


Mesocolon 


Back  of  peritoneum 


Csecum 


Bladder 


Caput  femoris 
Prostate  gland 


FIG.  583.— Posterior  view  of  His'  models.    Drawn  from  photographs. 


THE   PERITONEUM. 


967 


right  iliac  fossa  at  the  caecum,  then  upward,  across,  downward,  and  into  the  sig- 
moid  flexure  and  rectum.     This  surrounds  the  coils  of  the  small  intestines. 


Liver 


A.  gastro-epi- 
pluica  dextrd 


A.  gaslrchepi- 
ploica  sinistra 


PUF Omentum  majui 


Small  intestine 
FIG.  584.— Position  of  abdominal  organs  in  a  state  of  moderate  distention.    (Joessel.) 

The  other  structures  not  evident  without  dissection  or  manipulation  can  be 
located  by  aid  of  Figs.  582,  583.  The  organs  there  are  all  spaced  and  so  are 
not  in  their  exact  positions. 

It  is  customary  to  study  the  peritoneum  before  taking  up  the  separate  viscera. 
This  membrane  has  quite  a  reputation.  Whenever  in  Human  Anatomy  any- 
thing is  difficult  or  obscure,  one  should  leave  the  complex  adult  form  and  study 
the  more  primitive  simple  type  of  the  embryo  or  new-born ;  if  that  be  not  wholly 
satisfactory,  go  to  the  lower  animals  (Comparative  Anatomy),  while  the  ambi- 
tious student  investigates  even  fossil  animals  (Palaeontology).  It  is  meant  by 
this  that  the  medical  student  should  first  study  something  of  the  development  of 
the  peritoneum  before  opening  the  abdominal  cavity  and  destroying  important 
structures. 

Some  Essential  Facts  in  the  Development  of  the  Peritoneum. 

In  the  early  development  of  the  alimentary  canal,  before  the  twelfth  day  in 
the  human  embryo,  all  three  germ-layers  push  forward,  are  folded  over,  and  pro- 
duce the  head  and  the  anterior  part  of  the  fore-gut.  This  is  blind  at  the  front 
end,  and  the  mouth  is  developed  later  by  an  invagination  from  the  exterior.  The 
middle  part  of  the  future  alimentary  tract,  mid-gut,  is  in  free  communication  for 
some  time  with  the  blastodermic  vesicle  which  is  later  called  the  yolk-sac.  The 
approximation  of  the  body-walls  at  the  umbilicus  gradually  pinches  the  yolk-stalk 
off  into  the  vitelline  duct,  so  the  sac  finally  lies  wholly  outside  the  body  of  the 


968 


THE    ORGANS    OF  DIGESTION. 


embryo  and  that  part  of  it  enclosed  within  is  the  pleuro-peritoneal  cavity  (Fig. 
585).  Finally,  at  the  caudal  end  a  hind-gut  is  formed  and  an  anus  added  by  a 
process  of  imagination. 


Amnion 


Fore-gut  /  Heart 

Chorda  Dorsalis 


FIG.  585. — Diagram  of  a  longitudinal  section  of  a  mammalian  embryo.    Very  early.    (After  Quain.) 

Thus  the  whole  alimentary  canal  was   originally  a  straight  tube  placed  in 
front  of  the  aorta,  or  the  original  two  primary  aortse,  and  that  in  front  of  the 


Fore-gut 


Mid-gut 


Hind-gut 


FIG.  586.— Schematic  median  section  of  a  human  embryo.    (After  Dexter.) 

future    vertebral    column,  the    chorda    dorsalis  (Fig.    586).      Along   its    middle 
region,  the  anterior  wall  is  lacking  as  it  opens  here  into  the  yolk-sac. 


THE  PERITONEUM. 


969 


The  fore-gut  contracts  to  form  the  oesophagus,  which  is  very  short  (Fig.  587). 
This  gradually  widens  into  a  spindle-like  dilatation  indicating  the  stomach.     The 


Ol?    ,.    /.'.I 


Stomach 


L; 


Jlid-gut 


FIG.  5S7.— Schematic  median  section  of  a  human  embryo  of  fourth  week.    (After  Dexter.) 
small  intestine  is  short  and  straight  Avith  a  wide  opening  into  the  yolk-sac.     Just 

ophagus 


Duodenal  Loop 

Aorta 
Chorda  Dorsalis 


FIG.  588.— Schematic  median  section  of  a  human  embryo  of  fifth  or  sixth  week.    (After  Dexter.) 

below  the  stomach,  the  liver  is  budding  out  from  the  duodenum.     This  stage  is 
attained  in  the  fourth  week  in  the  human  embrvo.      There  are  now  five  successive 


970 


THE    ORGANS    OF  DIGESTION. 


districts  in  the  whole  canal,  mouth,  throat  and  visceral  clefts,  oesophagus,  spindle- 
shaped  stomach,  and  the  remaining  tube  connected  with  the  yolk-sac. 

By  the  fifth  or  sixth  week,  the  stomach,  at  first  straight  and  parallel  with  the 
axis  of  the  body,  begins  to  show  a  convex  greater  curvature  toward  the  vertebral 

column  and  a  concave  lesser  curvature  on  the  opposite 
side.  This  is  covered  by  the  voluminous  liver.  The 
pyloric  end  is  tilted  away  from  the  column  and  this 
forms  the  duodenal  loop  (Fig.  588).  As  the  commu- 
nication with  the  yolk-sac  becomes  constricted  and 
absorbed  there  is  developed  a  long  umbilical  loop  of 
intestine  opposite  the  vitelline  duct.  The  end  of  this 
loop  passes  for  a  time  into  the  umbilical  cord  sur- 
rounded by  a  protrusion  of  the  peritoneum.  This 
loop  passes  downward  and  forward,  and  consists  of 
two  nearly  parallel  arms  between  which  is  stretched 
the  mesentery.  At  a  little  distance  from  the  vitelline 
duct  on  the  lower  arm  of  the  loop  is  seen  a  small  en- 
largement ;  this  marks  the  future  ccecum  and  begin- 
ning of  the  colon  and  end  of  small  intestine.  Five 
portions  of  intestine  are  now  to  be  distinguished: 
the  short  part  passing  back  from  the  stomach  toward 
the  spinal  column  becomes  duodenum  ;  at  the  turn- 
ing-point into  the  umbilical  loop  is  the  duodeno-jejunal 
junction ;  the  anterior  descending  arm  and  bend  of 
the  loop  become  small  intestine  ;  most  of  the  ascending  posterior  arm  becomes 
colon,  and  the  terminal  part,  sigmoid  flexure  and  rectum. 

At  first  the  alimentary  tract  is  mostly  in  contact  with  the  chorda  dorsal  is 
held  by  a  broad  mass  of  embryonal  connective  tissue.     This  tissue  contains  two 


, tenor 

Mesentery 

'  Umbilicus 
Alimentary  Tract 
Posterior  Mesentery 

Aorta 
Chorda  Dorsalis 


FIG.  589.— Fig.  586  with  mesen- 
teries added.    (Dexter.) 


Spleen 

Lesser  Curvature 
'renter  Curvature 
•Mesogastrium 


'esentery 


Colon 


Vitelline 
Duct 


FIG.  590.— Diagram  to  show  the  original  positions  of  the  liver,  stomach,  duodenum,  pancreas  and  spleen, 
and  the  mesenteries  connected.    A  longitudinal  section.    (Hertwig.) 

primitive  aortae.  The  right  and  left  portions  of  the  body-cavity  approach  each 
other  and  compress  this  tissue  into  a  mesentery,  which  is  attached  to  the  whole 
length  of  the  tube  beginning  with  the  stomach,  connecting  it  with  the  chorda. 
The  special  part  of  this  membrane  attached  to  the  stomach  posteriorly  is  called 
mesogastrium,  that  to  the  small  intestine  is  called  mesentery  (medium  intestinum 


THE   PERITONEUM, 


971 


or  fj.eaov  svrepois,  middle  intestine);  that  to  the  colon,  the  mesocolon ;  that  to  the 
sigmoid  flexure,  the  mesosigmoidea  or  sigmoid  mesocolon  ;  and  that  to  the  rectum, 
the  mesorectum.  This  has  not  been  represented  in  the  above  figures  for  the  sake 
of  simplicity.  There  is  also  a  ventral  mesentery,  but  not  of  such  extent  as  the 
dorsal.  It  extends  along  the  front  of  the  alimentary  canal  from  the  throat  to 
the  lower  end  of  the  duodenum  and  in  front  as  far  down  as  the  umbilicus 
(Fig.  589).  It  almost  makes  the  body-cavity  a  paired  structure.  In  the  upper 
part  of  this  mesentery  is  developed  the  heart,  the  part  enclosing  it  being  called 
mesocardium  anterius  and  posterius.  The  lower  part  extends  from  the  stomach 
and  duodenum  to  the  anterior  wall  and  has  many  names — ventral  gastric  and 
duodenal  mesentery,  liver-ridge  and  prohepaticus ;  it  is  never  called  anterior 
mesogastrium. 

The  liver  is  here  developed  anterior  to  the  stomach,  budding  from  the  anterior 
part  of  the  beginning  of  the  duodenum  (Fig.  590). 

The  pancreas  buds  from  the  posterior  part  of  the  duodenum,  vertical  at  first 
and  covered  on  both  sides  by  the  mesentery  of  the  small  intestine ;  it  passes  into 
the  mesogastrium  later  and  becomes  transverse. 

The  spleen  is  developed  in  the  second  month  in  the  mesogastrium  and  is  not 
connected  directly  with  the  alimentary  canal. 

At  this  stage*,  passing  from  before  backward,  we  find  the  structures  arranged : 
anteriorly,  liver;  in  the  centre,  stomach;  posteriorly,  spleen  and  pancreas.  The 
anterior  mesentery  in  front  of  the  liver  becomes  the  suspensory  or  falciform  liga- 
ment of  the  liver,  extending  to  the  umbilicus  below  and  embracing  the  intra- 
abdominal  part  of  the  umbilical  vein.  The  anterior  mesentery  between  the  liver 
and  stomach  becomes  the  lesser  amentum  or  lig.  hepato-gastro-duodenale.  The 
mesogastrium  between  stomach  and  spleen  becomes  g astro-splenic  omentum,  and 
that  part  between  the  spleen  and  vertebral  column  forms  the  great  omentum. 

Fig.  591  is  a  cross-section  of  the  same  embryo.  Anteriorly  are  the  two  sacs 
of  the  liver  projecting  one  into  each  side  of  the  body-cavity.  The  right  sac 
grows  to  a  larger  size  than  the  left;  they  form  respectively  the  right  and  left  lobes. 
Behind  these  is  the  duodenum  and  behind  that  the  pancreas.  The  intervening 


Posterior  Wa, 
Dorsal  Mesentery 
Pancreas 


Lig.  Suspensorium 
Hepatis 


FIG.  591.— Cross  section  in  duodenal 
region  to  show  same  structures  as  in 
Fig.  590.  (Hertwig.) 


Stomach 


Geliacaxis 
Mesogastrium 

Superior  mes- 
enteric  artery 

Splenic  flexure 

of  colon 
Inferior  mes- 
enteric artery 
'Mesentery 

FIG.  592.— Schematic  representation  of  the  mesentery  in  a  six- 
weeks'  human  embryo.    (Toldt.) 


parts  of  the  mesentery  are  called  ligaments,  viz.  first,  suspensory  ligament  of 
liver,  next  Jtepato-duodenal  ligament,  next  duodeno-pancreatic  ligament,  and  lastly 
the  dorsal  mesentery.  Note  that  pancreas  and  duodenum  are  wholly  enclosed. 

The  vascular  arrangement  of  this  stage  is  shown  in  Fig.  592.  The  coeliac 
axis,  the  superior  mesenteric  and  inferior  mesenteric  arteries  have  their  points  of 
supply  definitely  marked  out  even  in  the  sixth  week.  They  pass  from  the  aorta 
between  the  two  layers  of  the  mesogastrium  and  mesentery  to  their  destinations, 
which  never  change.  The  creliac  axis  goes  to  the  stomach,  spleen,  pancreas, 
liver  and  part  of  duodenum ;  the  superior  mesenteric,  to  part  of  duodenum,  the 


972 


THE    ORGANS    OF   DIGPISTION. 


small  intestines,  and  part  of  colon ;  the  inferior  mesenteric,  to  the  remainder  of 
the  tube. 

The  length  of  the  intestine  continually  increases,  and  it  becomes  more  bent 
and  tortuous,  till  from  the  third  month  on  there  occur  two  important  changes,  one 


FIG.  593.— Torsion  of  the  umbilical  loop.    Initial 
position.    (Jonnesco.) 


\Vitelline  Duct 


FIG.  594.— Torsion  of  the  umbilical  loop.    Ac- 
quired position.    (Jonnesco.) 


in  regard  to  a  twist  of  the  intestinal  loop  and  one  in  regard  to  a  change  in  posi- 
tion of  the  stomach.  The  ascending  and  descending  arms  of  the  umbilical  loop 
have  been  lying  side  by  side  one  above  the  other ;  now  the  lower  arm,  which 
becomes  caecum  and  colon,  begins  to  pass  over  the  upper  arm  and  crosses  the  small 
intestine  transversely  (Fig.  598).  The  upper  arm  moves  but  little  or  none,  as  it 


Smatt  in- 
testine 

Vitettine 
duct 


Greater  curva- 
ture 


Greater  omen- 
turn 


Place  where  the 
intestines  cross 

Large  intestine 


Rectum 


Duodenum 


Appendix 
Mesentery 

Vitelline 
duct 


Greater 
curvature 

Greater  omen- 
turn 

Placeuihere  the 
intestines  cross 
x 

Metocolon 
Large  intes- 
tine 
Small  intestine 


Rectum 


FIG.  595.— Development  of  human  alimentary 
canal  and  mesentery.    Earlier  stage.    (Hertwig.) 


^a& 

FIG.  596. — Development  of  human  alimentary  canal 
and  mesentery.     Later  stage.    (Hertwig.) 

is  already  fixed  to  the  vertebral  column  at  its  upper  duodeno-jejunal  end,  perhaps 
by  the  muscle  of  Treitz. 

The  caecum,  which  has  already  developed  an  appendix,  is  thus  landed  wholly  on 
the  right  side  of  the  body  up  under  the  liver  (Figs.  594  and  596).  At  first  there 
is  no  ascending  colon,  the  transverse  colon  running  across  the  duodenum  inferior 
to  the  stomach  and  up  to  the  spleen,  making  a  splenic  flexure  ;  it  passes  through 


THE  PERITOXEUM. 


973 


the  left  lumbar  region  and  is  continued  into  the  sigmoid  flexure  and  rectum.  The 
csecum  increases  in  length  and,  finding  least  resistance  below,  finally  settles  into 
the  rio-ht  iliac  fossa,  dragging  down  a  short  ascending  colon. 

The  mesentery,  seen  in  the  loop  of  Fig.  592,  makes  a  half  rotation  as  does 
the  loop,  and  its  anterior  surface  becomes  posterior,  as  may  be  inferred  from  Figs. 
595  and  596. 

Fig.  597  shows  the  arterial  supply  after  the  twist  of  the  umbilical  loop,  with 
the  coeliac  axis  behind  the  stomach,  the  superior  mesen- 
teric  artery  fastening  the  duodenum  between  itself  and 
the  aorta,  and  the  inferior  mesenteric  coming  off  below. 

During  this  period  of  intestinal  torsion,  the  stomach 
has  suffered  a  double  change.  First  the  stomach  twists 
around  an  antero-posterior  axis,  so  its  cardiac  or  oesoph- 
ageal  end  moves  to  the  left  and  downward,  while  its  py- 
loric  end  moves  a  little  to  the  right  and  upward  ;  and 
its  vertical  position  becomes  more  transverse. 

Secondly,  its  long  axis  having  been  parallel  to  the 
vertebral  column,  it  originally  presented  a  right  and  left 
surface,  supplied  respectively  by  the  right  and  left  vagus 
nerves.  It  now  falls  over  so  that  its  right  side  becomes 
posterior  and  its  left  side  anterior,  and  the  greater  curv- 
ature becomes  more  inferior,  and  the  lesser  curvature 
more  superior.  The  vagus  nerves  still  supply  the  same 
surfaces,  which  have  changed  their  positions  :  the  right 
nerve  now  goes  to  the  posterior  surface  and  the  left  one 
to  the  anterior  surface. 

The  lower  end  of  the  oesophagus  also  experiences 
the  same  torsion. 

The  mesogastrium  is  modified  by  this  rotation  to 
the  right.  In  the  anterior  mesentery  is  the  liver  (Fig. 
590),  but  in  the  adult  we  find  it  shifted  to  the  right  side 

rtf  tKo  K/^rlT-         TVio  cv.loon   wna  nncrprirvr  tn  tVip  afrrvmarh  • 

ot  tne  Douy.      me  bpieen  was  po?  >  me  biomacu  , 

in  the  adult  it  is  to  its  left.      So  these  three  antero-pos- 
terior  organs  have  become  laterally  placed,  and  from 

.    i  .          ,    «,  ,.         f          -.      i  •   '  i  1 

right  to  left  are  hereafter  found  :  liver,  stomach,  spleen, 


FlG.  597.—  Final  disposition 

of  the  intestines  and  their  vas- 

cular  relati<)ns    A  Aorta.   H. 


rior  mesenteric  artery.  «,  mr. 

Branches  of  inferior  mesenteric 

artery.    (Jonneseo.) 


Chorda  Dorsalis 


2Ifsoyastriitm 


Cavity  of 
reat  Omentum 


FIG.  598.— Wood  and  cloth  to  illustrate  stom- 
ach and  mesogastrium  of  two  layers  viewed 
from  the  side.  (G.  S.  H.) 


FIG.  599.— Stomach  turned  to  right  enclosing  a  space 
behind  it,  representing  the  great  omentum  and  its  cavity 
viewed  from  the  front.  (G.  8.  H.) 


Again  connected  with  this  torsion  of  the  stomach  is  associated  the  formation 
of  the  great  omentum.     To  illustrate  this,  carve  a  piece  of  wood  to  represent  the 


974 


THE    ORGANS    OF  DIGESTION. 


stomach ;  let  two  layers  of  cloth  attached  to  the  posterior  border  represent  the 
mesogastrium  attached  to  the  vertebral  column  (Fig.  598).  This  was  the  original 
condition  (Fig.  592).  Now  turn  the  stomach  to  the  right,  allowing  the  cloth  to 
fall  loosely  to  the  left,  and  immediately  a  cavity  is  formed  included  between  two 
layers  of  cloth  anteriorly  and  two  layers  posteriorly  (Fig.  599).  In  the  embryo 
a  similar  cavity  is  formed  called  the  cavity  of  the  great  omentum,  the  lesser  sac 
of  peritoneum,  bursa  omentalis  ;  and  a  similar  fold  of  four  layers  is  formed  called 
the  great  omentum  which  in  the  embryo  and  infant  contains  this  cavity. 

The  entrance  to  this  cavity  is  indicated  by  the  arrow  in  Figs.  595,  596,  and 
599,  and  the  bulging  of  the  great  omentum  is  seen  to  the  left  of  and  below  the 
greater  curvature  of  the  stomach.  Compare  the  above  with  Fig.  600,  and  the 
position  of  the  sac  will  be  better  understood. 

The  front  wall  of  the  bursa  omentalis  is  formed  by  the  stomach  ;  the  posterior 
wall  by  the  mesogastrium,  which  at  first  completely  invests  the  pancreas,  touches 
the  spleen,  and  covers  part  of  the  left  suprarenal  capsule.  The  opening  is  turned 
to  the  right  and  covered  anteriorly  by  the  lesser  omentum.  The  space  between 


Right 

suprarenal 

captule 


Liver 


Right 

suprarenal 

capsule 


Left 

supraienal 
capsule 


Liver 


FIG.  600.— Schematic  and  enlarged  cross  section 
through  the  body  of  a  human  embryo  in  the  region 
of  the  mesogastrium.  Beginning  of  third  month. 
(Toldt.) 


Left 

suprarenal 
capsule 


Liver 


FIG.  601.— Same  section  as  in  Fig.  600,  at  end  of 
third  month.    (.Toldt.) 


the  lesser  omentum  and  right  end  of  pancreas  is  the  atrium  bnrsa?  omentalis  or 
the  antechamber  or  lesser  omental pocket.  It  lies  below  and  behind  the  Spigelian 
lobe  of  the  liver.  The  bursa  proper,  or  lesser  sac,  is  that  part  behind  the  stomach. 

By  the  end  of  the  third  month  the  pancreas  touches  the  left  suprarenal  cap- 
sule (Fig.  601),  the  layer  of  mesogastrium  separating  the  two  becomes  later 
absorbed,  and  the  pancreas  is  then  an  extraperitoneal  organ  separated  from  the 
kidney  or  capsule  by  connective  tissue.  By  further  development  this  lesser  sac 
continues  to  push  between  the  layers  of  the  great  omentum  downward  and  to  the 
left,  and  fuses  with  neighboring  viscera.  The  great  omentum,  formerly  a  part 
of  the  mesogastrium,  comes  to  hang  freely  down  over  the  transverse  colon  and 
then  in  front  of  the  small  intestines,  as  about  to  do  in  Figs.  596  and  602. 

The  lamellae  composing  the  bursa  omentalis  or  lesser  sac  are  each  composed 
of  two  layers ;  they  are  placed  close  together  and  are  continuous  below  (Figs. 
602  and  603).  The  more  anterior  one  is  attached  to  the  greater  curvature  of 
the  stomach  and  the  posterior  one  lying  on  the  intestines  was  originally  attached 
to  the  vertebral  column  and  enclosed  most  of  the  pancreas  (Figs.  600  and  602). 
In  many  mammals  no  further  change  occurs.  In  man  fusions  follow :  the  pos- 


THE   PERITOXE I  'U. 


975 


terior  lamella  covers  a  large  part  of  the  posterior  abominal  wall,  and  its  original 
line  of  vertebral  attachment  gets  displaced  to  the  left ;  it  joins  the  diaphragm  and 
forms  the  liy.  phreno-lien-ih1.  suspensory  ligament  of  the  spleen.  Below  it  be- 
comes fused  to  the  upper  layer  of  the  transverse  mesocolon  and  to  the  trans- 
verse colon  (Fig.  603).  These  two  contiguous  layers,  i.  e.  the  posterior  layer  of 
the  mesogastrium  and  the  upper  layer  of  the  transverse  mesocolon,  may  present 
a  fissure  at  birth  in  many  mammals.  During  early  infancy  in  the  human  species 
they  form  a  single  lamella  with  a  deposit  of  fat  (Fig.  603).  In  adult  life  no  trace 
of  the  extra  layer  is  seen. 

There  are  then  three  types  of  relation  of  the  posterior  layer  of  the  great 
omentum  to  the  transverse  mesocolon :  foetal,  where  they  are  separate  (Fig.  602); 
infantile,  where  they  are  fused  into  one  layer  (Fig.  603);  and  adult,  where  all 
trace  of  this  layer  has  disappeared  and  the  posterior  lamella  of  the  great  omen- 
turn  seems  to  enclose  the  transverse  colon  (Fig.  606). 


Diaphragm 


Liver 


Stomach 

Greater  curvature 

Anterior  lamella  of  greater  omentum 
Posterior  lamella  of  greater  omentum 

Transverse  colon 


Greater  omentum 


Letter  omentum 

Pancreas 

Transverse  mesocolon 
Duodenum 

Mesentery 


SmaU  intestine 


FIG.  602.— Diagram  to  illustrate  the  development  of  the  bursa  omentalis,  cavity  of  the  great  omentum  or 
lesser  sac.    Fcetalstage.    *.  Lesser  sac.    (Hertwig.) 

The  lesser  sac  of  peritoneum  (bursa  omentalis)  is  still  continuous  with  the 
greater  sac  or  general  peritoneal  cavity,  something  like  the  two  cavities  of  an 
hour-glass,  only  the  upper  cavity  (lesser  sac)  is  comparatively  small  and  bent 
down  behind  the  other.  In  Fig.  603  the  cavity  behind  the  stomach  is  connected 


Diaphragm 


Liver 


Stomach 

Greater  curvaturi 

Pusierior  lamella  of  greater  omentu 
Transverte  colon 


Greater  omentum 


Lesser  omentum 


Part  of  omentum  enclosing  pancreas 

TViJ  >/.-->••.  r.».    l' 

Duodenum 


Small  intestine 


FIG.  603. — Development  of  bursa  omentalis.  Infantile  stage.    Great  omentum  covers  the  intestines  and  has 
fused  with  the  transverse  mesocolon.    Pancreas  is  free  of  peritoneum  posteriorly.    (Hertwig.) 

with  the  larger  cavity  in  front  of  it  by  means  of  a  foramen  to  the  right  of  the 
lesser  omentum.  It  is  the  foramen  of  Win*l.f>>i\  and  is  to  be  found  just  under 
the  hilus  (the  black  spot  on  a  bean)  of  the  liver  to  the  right  side  of  the  neck  of 
the  gall-bladder. 

After  childhood  the  cavity  of  the  lesser  sac  descending  into  the  great  omen- 
tum is  obliterated  and  the  four  layers  are  fused  into  an  omcntal  plate. 


976 


THE    ORGANS    OF   DIGESTION. 


Mesentery  of  the  Small  Intestine  and  Colon. 

The  mesentery  is  influenced  by  the  increase  in  length  of  the  small  intestine. 
It  becomes  fan-shaped,  and  its  length  at  its  insertion  into  the  intestine  is  many 
times  that  of  its  origin  from  the  lumbar  vertebrae ;  so  it  lies  in  folds  and  is  called 
a  frill.  In  man  after  the  fourth  month,  this  becomes  more  complicated  by  fusions 
with  the  posterior  body-wall  or  neighboring  viscera.  It  aifects  especially  the 
mesentery  of  the  duodenum  and  colon. 

The  duodenum  at  first  is  completely  invested  Avith  peritoneum  (Fig.  595) ; 
later  other  viscera  growing  faster  are  thought  to  pull  it  away  and  appropriate  it, 
and  so  posteriorly  it  comes  to  lie  on  the  posterior  wall  of  the  body  and  becomes  an 
immovable  organ  (Fig.  603). 

The  large  intestine  possesses  a  susperisorium  attached  to  the  vertebral  column 
and  designated  the  mesocolon.  When  the  twist  of  the  umbilical  loop  occurred, 
the  transverse  colon  and  its  mesocolon  were  drawn  transversely  across  the  duode- 
num, and  a  new  secondary  line  of  attachment  was  thus  formed.  This  explains 
why  in  the  adult  we  find  the  body-cavity  divided  by  the  transverse  colon  and 
transverse  mesocolon  into  chambers,  an  upper  and  a  lower.  In  the  upper  are  the 
stomach,  liver,  pancreas,  spleen  and  part  of  duodenum ;  in  the  lower,  part  of 
duodenum  and  the  small  intestines.  The  duodenum,  in  order  to  get  from  the 
upper  to  the  lower  space,  passes  underneath  the  transverse  colon  or  apparently 
through  the  mesocolon  (Fig.  596). 

The  caecum,  ascending  and  descending  colon,  also  lie  with  their  posterior 
walls  more  or  less  in  contact  with  the  body-wall,  but  sometimes  they  have  a  more 

Small  intestine 

Mesentery 


Colon 


'Mesocolon 


Kidney 


Eetroperitoneal 

space 
FIG.  604.  —  Cross  section  of  alimentary  canal  of  Fig.  596  to  show  mesenteries.     (Dexter,) 

or  less  distinct  mesentery  as  they  did  originally.     The  original  disposition  can  be 
seen  by  taking  a  cross  section  of  the  alimentary  canal  in  Fig.  596  along  the 


Serous  Cavity 
Intestine 


Visceral  Layer 
Parietal  Layer 


FIG.  605. — Schematic  drawing  of  a  cross  section  of  a  serous  cavity.    (Gegenbaur.) 


line  X.  Each  colon  and  the  small  intestine  are  fixed  to  the  aorta  and  vertebral 
column  by  its  special  mesentery,  which  allows  freedom  of  motion  (Fig.  604). 
The  mesentery  is  seen  to  be  formed  of  two  layers  of  peritoneum  which  surround 
an  intestine  completely,  except  at  a  posterior  line  where  there  is  opportunity  for 


THE   PERITONEUM.  977 

vessels,  nerves,  and  lymphatics  to  enter  or  return.  Two  layers  of  peritoneal  con- 
nective tissue,  which  lodge  vessels,  nerves,  and  lymphatics,  constitute  a  mesentery. 
The  intestine  looks  as  though  it  had  pushed  its  way  into  the  sac  of  peritoneum  as 
a  finger  enters  a  glove.  That  comparison  is  incorrect,  for  intestine  and  perito- 
neum are  developed  simultaneously.  The  intestine  is  not  first  made  and  then 
pushed,  as  would  appear  (Fig.  605). 

The  intestine  and  the  two  layers  of  peritoneum  are  formed  together.  As  the 
intestine  recedes,  the  serous  membrane  comes  from  the  wall  to  it  in  a  duplicature. 
The  layer  covering  the  intestine  is  called  visceral;  that  reflected  upon  the 
parietes  or  wall  is  the  parietal  layer,  and  the  passage  from  one  to  the  other  is  the 
mesentery. 

In  the  adult  the  small  intestine  is  unchanged,  but  the  mesentery  of  the  right 
and  left  colon  has  been  widely  separated  posteriorly,  and  it  and  some  of  the  pari- 
etal peritoneum  have  been  changed  to  connective  tissue,  so  each  colon  becomes 
fixed  and  partly  extraperitoneal,  like  the  duodenum  and  pancreas  (Fig.  603). 
The  kidneys  were  always  outside,  being  developed  in  the  retroperitoneal  space. 

Summary. 

Separation  of  the  alimentary  tube  and  its  mesentery  into  distinct  regions 
(Hertwig) : 

1.  The  alimentary  canal  is  originally  a  straight  tube  from  mouth  to  anus, 
near  the  middle  of  which  the  yolk-sac  is  attached  by  the  vitelline  duct  (Figs.  586 
and  587). 

2.  The  alimentary  tube  is  attached  throughout  its  whole  length  to  the  verte- 
bral column  by  a  narrow  dorsal  mesentery ;  it  is  also  connected  with  the  anterior 
wall,  as  far  as  the  umbilicus,  by  means  of  a  ventral  mesentery. 

3  At  some  distance  behind  (below)  the  visceral  clefts,  the  stomach  arises  as 
a  spindle-shaped  enlargement ;  its  dorsal  mesentery  is  designated  as  mesogas- 
triurn. 

4.  The  portion  which  follows  the  stomach  grows  more  rapidly  in  length  than 
does  the  trunk,  and  therefore  forms  a  loop  with  an  upper,  descending,  narrower 
arm.  which  becomes  the  small  intestine,  and  a  lower  ascending  more  capacious 
arm  which  produces  the  large  intestine. 

5.  The  stomach  takes  on  the  form  of  a  sac  and  becomes  so  turned  that  its 
long  axis  coincides  with  the  transverse  axis  of  the  body  and  that  the  line  of  attach- 
ment of  the  rnesogastrium.  or  its  greater  curvature,  which  at  first  was  dorsal, 
comes  to  lie  below  or  caudad. 

6.  The  intestinal  loop  undergoes  such  a  twisting  that  its  lower  ascending  arm 
(large  intestine)  is  laid  over  (ventrad  to)  the  upper  descending  arm  (small  intes- 
tine) from  right  to  left  and  crosses  it  near  its  origin  at  the  stomach. 

7.  The  twisting  of  the  intestinal  loop  explains  why  in  the  adult  the  duodenum, 
as  it  merges  into  the  jejunum,  passes  under  the  transverse  colon  and  through  its 
mesocolon  (crossing  and  crossed  parts  of  the  intestine). 

8.  The  lower  arm  of  the  loop,  during  and  after  its  twisting  and  crossing  of  the 
upper  arm,  assumes  the  form  of  a  horseshoe,  and  permits  one  to  distinguish  the 
c^cum,  the  colon  ascendens,  colon  transversum,  and  colon  descendens. 

9.  Within  the  space  bounded  by  the  horseshoe,  the  upper  arm  of  the  loop 
becomes  folded  to  form  the  convolutions  of  the  small  intestine. 

10.  The  mesentery,   which   is   at  first  common  to  the  whole  tube,  becomes 
differentiated  into  separate  regions  and  adapts  itself  to  the  different  folds  and 
elongations.     It  is  elongated  and  here  and  there  undergoes  fusion  with  the  peri- 
toneum of  the  body-cavity,  by  means  of  which  it  acquires  new  points  of  attach- 
ment, or  in  certain  tracts  wholly  disappears ;  some  portions  of  the  intestine  are 
thus  deprived  of  their  mesentery  (Fig.  614). 

11.  The  mesentery  of  the  duodenum,  and  in  part  that  of  the  colon  ascendens 
and  descendens,  fuses  with  the  wall  of  the  body. 

62 


978  THE    ORGANS    OF  DIGESTION. 

12.  The  mesentery  of  the  colon  transversum  acquires  a  new  line  of  attachment 
running  from  right  to  left,  and  becomes   differentiated  from  the   mesentery  as 
mesoeolon. 

13.  The  mesogastrium  of  the  stomach  follows  the  torsions  of  the  latter,  and  is 
converted  into  the  greater  omentum,  which  grows  out  from  the  greater  curvature 
of  the  stomach  to  cover  all  the  viscera  lying  below. 

14.  Fusion  of  the  walls  of  the  omentum  occur  with  the  adjacent  serous  mem- 
branes :  (1)  on  the  posterior  wall  of  the  body,  where  its  line  of  origin  from  the 
vertebral  column  is  displaced  to  the  left  side  of  the  body  (Fig.  614) ;  (2)  with  the 
transverse  colon  and  mesoeolon  (Fig.  603) ;  (3)  anterior  and  posterior  walls  come 
into  close  contact  and  fuse  into  an  omental  plate. 

Development  of  special  organs  out  of  the  walls  of  the  alimentary  tube  : 

1.  From  the  intestinal  canal  proper  there  are  formed  only  two  glands,  devel- 
oped from  the  duodenum,  viz.  the  liver  and  pancreas. 

2.  The  liver  is  developed  as  a  branched  tubular  gland  which  becomes  a  net- 
work :  (a)  There  grow  out  from  the  duodenum  into  the  ventral  mesentery  or  pre- 
hepaticus  two  liver-tubes,  the  fundaments  of  the  right  and  left  lobes  of  the  liver. 
(&)  The  tubes  form  hollow  or  solid  branches,  the  hepatic  cylinders,  which  become 
in  part  bile-ducts  and  in  part  parenchyma  of  the  liver.     (<?)  The  common  bile-duct 
rises  as  an  evagination  of  the  wall  of  the  duodenum  receiving  the  two  hepatic  tubes, 
and  at  one  place  an  evagination  which  becomes  the  gall-bladder  and  cystic  duct. 

3.  From  the  ventral  mesentery  into  which  the  liver  grows  are  derived  the  sus- 
pensory ligament  of  the  liver  (falciform)  and  the  lesser  omentum. 

4.  The  pancreas  grows  from  the  duodenum  into  the  dorsal  mesentery  and  into 
the  mesogastrium. 

The  mesentery,  which  the  pancreas  originally  possesses,  disappears  and  fuses 
with  the  posterior  body-wall.  By  reason  of  the  twist  of  the  stomach,  the  long 
vertical  axis  of  the  pancreas  becomes  transverse. 

ADULT  PERITONEUM. 

During  life  and  before  dissection  of  the  dead  subject  the  abdominal  cavity  is 
air-tight.  Atmospheric  pressure  and  muscular  tension  allow  no  space  to  be  vacant. 
The  peritoneum  (iteptrefvetv,  to  extend  around)  is  the  shiny  serous  membrane 
lining  the  abdominal  walls  and  posteriorly  either  lining  the  wall  or  covering  the 
viscera.  If  one  is  asked  to  touch  the  liver  or  stomach  it  is  the  peritoneum  cover- 
ing those  organs  which  is  touched.  The  peritoneal  cavity  was  opened  when  the 
anterior  abdominal  wall  was  incised,  and  does  not  exist  till  artificially  produced 
by  the  surgeon  or  dissector. 

In  the  male  it  is  a  closed  sac  with  its  two  walls  approximated,  and  consequently 
perfectly  empty  except  for  a  small  amount  of  yellowish-green  lubricating  fluid, 
liquor  peritonei.  Its  anterior  wall  has  already  been  opened  and  is  called  the 
parietal  peritoneum.  Its  posterior  wall  is  tucked  into  every  crevice  and  corner 
around  and  between  the  viscera,  which  may  be  regarded  as  lying  behind  the  whole 
sac.  This  layer  is  largely  visceral  and  the  spaces  between  single  organs  are  only 
capillary.  In  the  female,  the  peritoneum  has  two  openings ;  there  is  a  single 
region  on  either  side  where  mucous  membrane  is  continued  into  serous  membrane, 
viz.  where  the  Fallopian  tube  opens  into  the  peritoneal  cavity. 

Other  serous  membranes  are  comparatively  small,  and,  like  the  pleura,  serous 
pericardium,  or  tunica  vaginalis,  surround  one  organ.  In  these  it  is  very  easy  to 
trace  the  layer  around  the  walls,  then  its  reflection  upon  the  viscus  and  off  again 
to  the  starting-point.  In  the  peritoneum,  or  really  behind  it,  we  have  many 
organs  involved,  nearly  all  of  which  have  experienced  changes  in  size  or  position 
during  foetal  life,  so  that  the  task  is  somewhat  more  complex.  It  is  to  trace  the 
peritoneal  layers  from  one  organ  to  another  or  from  an  organ  to  a  wall,  and  to 
show  that  the  layers  are  continuous,  making  a  closed  sac. 


THE   PERITONEUM.  979 

We  may  say  that  the  peritoneum  has  two  surfaces,  i.  e.  one  attached  to  the 
wall  or  visciis  and  the  other  is  free  and  shiny  :  there  are  two  layers,  parietal  and 
visceral,  and  two  sacs,  since  the  large  one  has  a  posterior  subdivision  formed  when 
the  stomach  rotated  to  the  right  in  the  embryo. 

The  various  folds  and  bands  formed  by  the  peritoneum  in  passing  from  the 
different  viscera  or  walls  have  definite  names. 

An  Omentum  means  a  fold  of  peritoneum  which  connects  the  stomach  with 
other  viscera,  viz.  great  and  gastro-colic  amentum,  small  or  gastro-hepatic,  and 
i/'i."tro-sp!enic.  These  are  situated  respectively  below,  above,  and  to  the  left  of 
the  stomach. 

A  Mesentery  is  a  fold  of  peritoneum  connecting  any  part  of  the  small  intestine 
to  the  posterior  wall.  It  is  used  also  in  a  wider  sense.  The  name  of  the  fold 
connecting  any  part  of  the  alimentary  canal  below  the  oesophagus  to  vertebral 
column  or  posterior  abdominal  wall  may  be  found  by  prefixing  the  Greek  adjective 
mesos  (usaoz)  or  Latin  medium  to  the  Greek  or  Latin  name  of  the  part  fixed,  as 
itixtriuii).  me*''»luf>fl>:num,  mesentery,  mesenteriolum  (little  mesentery  for  ver- 
miform appendix).  There  is  no  mesocaecum  in  the  adult,  but  sometimes  an 
ascending  or  descending  mesocolon ;  always  a  transverse  mesocolon,  a  sigmoid 
mesocolon.  and  a  mesorectum. 

Ligament  is  a  term  applied  to  folds  connecting  viscera  not  belonging  to  the 
intestinal  canal,  to  the  abdominal  walls,  or  to  folds  which  bind  viscera  to  the 
diaphragm.  The  German  anatomists  apply  this  term  also  to  omenta.  There 
are  ligaments  of  the  bladder,  uterus,  and  liver,  and  others,  as  lieno-renal,  hepato- 
renal,  and  gastro-phrenic. 

We  will  now  trace  the  peritoneum  in  a  vertical  direction  simply  to  show  its 
continuitv  and  to  see  from  a  side  view  how  it  surrounds  viscera  or  forms  bridges 
from  one  organ  to  another  (Fig.  606). 

We  may  begin  anywhere,  perhaps  best  at  a  point  above  the  liver,  where  the 
parietal  layer  of  peritoneum  is  reflected  from  the  diaphragm  to  the  liver,  becoming 
visceral  layer. 

The  student  is  supposed  to  have  read  carefully  all  the  description  of  the 
peritoneal  development.  Now  he  follows  by  hand  the  parts  in  the  subject  and 
the  diagram  by  eye.  Lifting  up  the  diaphragm  the  hand  passes  over  the  glisten- 
ing superior  surface  of  the  liver  in  the  middle  line  till  it  is  stopped  posteriorly 
by  a  fold  called  the  coronary  ligament.  The  peritoneum  covers  all  the  surface 
of  the  liver  to  its  anterior  acute  margin.  Next  lift  up  the  liver  from  the  stomach 
and  trace  the  layer  backward  on  the  under  surface  of  the  liver  to  the  transverse 
fissure  or  hilus.  and  the  hand  is  again  stopped,  this  time  by  the  peritoneum 
ending  to  the  lesser  curvature  of  the  stomach,  making  one  layer  of  the  lesser 

ntum  ;  or,  giving  the  names  of  the  viscera  connected,  hepato-gastric  amentum . 
This  layer  now  covers  the  anterior  surface  of  the  stomach  and  reaches  the  greater 
curvature ;  here  it  falls  directly  downward  to  a  varying  extent,  usually  to  the 
pubic  region,  making  the  anterior  superficial  layer  of  the  great  amentum.  Just 
below  the  stomach  the  transverse  colon  may  be  seen  shining  through.  This 
layer  in  the  foetus  and  young  child  should  not  be  attached  to  it,  however.  Now  lift 
up  the  great  omentum  over  the  stomach  and  this  layer  may  be  seen  to  be  reflected 
up  to  the  under  surface  of  the  transverse  colon,  making  the  posterior  superficial 
layer  of  the  great  omentum.  Fig.  602  shows  that  the  great  omentum  has  not 
always  been  present ;  this  layer  we  are  now  tracing  used  to  pass  above  the  trans- 
verse colon  and  go  to  the  pancreas  and  then  return,  making  two  layers.  Fig.  603 
shows  how  these  two  layers  united  into  one ;  and  Fig.  606  shows  how  one  has 
disappeared  as  such,  and  how  this  layer  passes  beneath  the  "transverse  colon  and 
on  to  the  vertebral  column  and  anterior  margin  of  the  pancreas,  making  the 
lower  layer  of  the  transverse  mesocolon. 

This  laver  is  closelv  connected  with  the  vertebral  column,  aorta,  and  vena  cava 

•  * 

inferior,  and  on  leaving  the  pancreas  meets  the  superior  mesenteric  vessels  and 
surrounds  them.      It  covers  only  anteriorly  the  pre-aortic  portion  of  the  duode- 


980 


THE    ORGANS    OF  DIGE8TION. 


num,  and  makes  another  excursion  to  surround  the  small  intestines  and  returns 
under  the  vessels  forming  the  two  layers  of  the  mesentery  proper.  (Take  a 
definite  portion  of  the  small  intestine  and  prove  this — that  the  mesentery  has  an 
upper  and  a  lower  layer  and  the  intestine  is  fastened  to  the  spinal  colum  by  it.) 


Lesser  amentum 
Lesser  sac  (bursa  omentalis) 

Greater  sac 


Cavity  of  great  amentum 
Small  intestine 


Pre-vesical  space  of 
Relzius 

Symphysis  pitbis 


Liver 

Foramen  of  Winslow 
Codiac  axis 

Pancreas 

Superior  mesenteric  vessels 

Transverse  duodenum 
Transverse  mesocolon 


Mesentery 


Rectum 
Uterus 

Cul-de-sac  of  Louglas 


Fio.  606.— Diagram  to  illustrate  the  reflections  and  continuity  of  the  peritoneum  in  a  vertical  direction  in 
the  female  body.    Section  is  a  little  to  the  right  of  a  median  plane.    (After  Allan  Thomson.) 

Next,  this  layer  descends  into  the  pelvis  and  forms  a  mesentery  for  the  intes- 
tine, there  surrounding  it  as  low  down  as  the  middle  of  the  third  sacral  vertebra. 
If  anatomists  agree  to  call  that  intestine  the  upper  part  of  the  rectum,  the  fold  is 
mesorectum,  but  if  the  intestine  be  called  the  lower  part  of  the  sigmoid  flexure,  the 
fold  is  sigmoid  mesocolon,  and  there  is  no  mesorectum.  Just  at  the  third  sacral 
vertebra  the  peritoneum  leaves  the  posterior  surface  of  the  intestine,  then  the 
sides,  and  then  the  front,  and  is  reflected  in  the  female  next  upon  the  upper  fifth 


THE   PERITONEUM.  981 

or  fourth  of  the  posterior  wall  of  the  vagina  and  then  upon  the  uterus,  covering 
its  posterior  wall,  its  fundus.  its  anterior  surface,  but  it  does  not  pass  on  to 
the  vagina  in  front.  About  the  level  of  the  internal  os  it  passes  over  the  summit 
of  the  bladder  as  far  as  the  urachus.  The  deep  pouch  behind  the  uterus  and 
vagina  is  called  the  recto-vaginal  pouch,  or  cul-de-sac  of  Douglas,  or  recto-uterine 
pouch.  The  more  shallow  anterior  pouch  is  the  vesico-uterine.  In  the  male  the 
peritoneum  passes  from  the  rectum  directly  upon  the  posterior  wall  and  summit 
of  the  bladder  to  the  urachus,  forming  behind  the  recto-vesical  pouch.  In  either 
sex  the  peritoneum  passes  directly  from  the  bladder  to  the  anterior  abdominal  wall 
and  does  not  cover  the  bladder  anteriorly.  The  surgeon  makes  use  of  this  fact  in 
operating  upon  the  bladder  through  this  space  below  the  peritoneum  and  above 
the  symphysis  pubis.  It  is  called  the  pre-vesical  space  of  Retzius,  and  is  much 
increased  in  size  by  distending  the  bladder.  By  putting  420  c.c.  of  fluid  into 
a  rubber  bag  in  the  rectum  and  500  c.c.  into  the  bladder,  the  rectum  will  so 
push  up  the  bladder  and  the  bladder  will  so  push  up  the  peritoneum  that  a  space  of 
8.5  cm.  will  exist  between  the  lowest  fold  of  peritoneum  and  the  symphysis  pubis. 

This  parietal  layer  is  then  simply  traced,  lining  the  anterior  abdominal  wall 
around  to  our  starting-point  between  the  liver  and  diaphragm.  We  see  then  that 
this  is  a  closed  sac  and  the  parietal  layer  is  continuous  with  the  visceral.  This  is 
the  cavity  of  the  greater  peritoneal  sac. 

We  have  not  yet  brought  the  peritoneum  into  contact  with  the  Spigelian  lobe 
of  the  liver  or  the  posterior  surface  of  the  stomach  or  internal  surface  of  the 
spleen.  Behind  the  upper  part  of  the  large  cavity  and  running  into  its  lower 
part  is  another  artificial  cavity  which  we  have  not  traced,  viz.  the  cavity  of  the 
lesser  sa  \  or  the  bursa  omentalis.  We  have  seen  that  these  two  sacs  are.  con- 
tinuous with  each  other  through  the  foramen  of  Winslow.  That  is  best  shown  in 
a  cross  section,  but  is  indicated  in  the  diagram. 

The  boundaries  of  the  lesser  sac  cannot  be  well  seen  at  this  stage,  and  for  the 
present  must  be  mostly  studied  by  diagram  till  the  anterior  parts  are  dissected. 
Remember  the  diagram  is  only  true  for  the  median  line  or  near  it,  and  nowhere 
else  but  in  the  region  of  the  Spigelian  lobe  of  the  liver  does  the  lesser  sac  reach 
up  behind  it  as  here  represented.  Imagine  the  hand  introduced  through  the 
foramen  of  Winslow  from  right  to  left  into  the  lesser  sac ;  push  the  finger  up 
behind  the  liver  and  in  front  of  the  diaphragm  till  stopped  by  the  fornix  made  by 
the  transition  of  parietal  to  visceral  layer.  This  layer  invests  the  Spigelian  lobe 
only  behind  and  inferiorly  till  the  transverse  fissure  is  reached ;  it  then  descends, 
as  did  the  layer  of  greater  sac  in  front  of  it.  to  the  lesser  curvature  of  the  stomach 
forming  the  posterior  layer  of  the  lesser  omentuin.  Next  it  descends  behind  the 
stomach  and  in  front  of  the  transverse  colon  into  the  great  omentum,  passing 
nearly  to  the  free  border  of  that  apron.  It  now  turns  and  ascends  and  covers 
the  upper  surface  of  the  transverse  colon  and  goes  back  to  the  vertebral  column, 
forming  the  superior  layer  of  the  transverse  mesocolon.  It  now  covers  the  ante- 
rior surface  of  the  pancreas,  next  the  vertebral  column  and  crura  of  diaphragm 
and  great  vessels  to  the  reflection  on  to  the  liver. 

It  is  advised  that  the  above  tracings  for  both  sacs  be  followed  in  Fig.  607. 
which  represents  the  organs  in  greater  detail.  This  diagram  shows  two  sections 
of  the  duodenum,  one  in  its  first  and  one  in  its  second  portion.  A  median  sec- 
tion would  show  its  third  portion  about  at  the  root  of  the  mesentery  (Fig.  606). 

We  have  traced  the  layers  singly,  and  some  new  features  may  be  presented 
if  we  take  two  layers  together,  beginning  above  at  the  liver. 

Anteriorly,  a  layer  passes  back  under  the  diaphragm  and  from  behind  another 
approaches  it ;  one  is  from  the  greater  sac  and  the  other  from  the  lesser  (if  sec- 
tion be  near  median  line).  They  both  turn  down  upon  the  liver,  making  these 
the  anterior  and  posterior  layers  of  the  coronari/  ligament,  including  between 
them  a  small  surface  of  liver  directly  connected  to  the  diaphragm  and  uncovered 
by  peritoneum.  These  two  layers  then  surround  the  liver,  forming  its  serous 
coat,  and  meet  again  at  the  transverse  fissure.  The  two  now  descend  to  the 


982 


THE    ORGANS    OF  DIGESTION. 


lesser  curvature  of  the  stomach,  forming  the  lesser  omentum  or  hepato-gastric 
omentum,  the  right  free  margin  of  which,  also  made  of  two  layers,  is  called  the 
lig.  hepato-duodenale,  because  it  passes  between  liver  and  duodenum.  Between 
the  two  layers  of  this  ligament  to  the  right  are  the  common  bile-duct,  the  hepatic 
artery,  and  portal  vein,  all  surrounded  by  connective  tissue,  the  capsule  of 
Crlisson.  These  layers  next  invest  the  stomach,  meeting  at  its  greater  curvature. 
They  next  pass  down  in  front  of  the  transverse  colon  and  small  intestines  and 
form  the  anterior  lamella  of  the  great  omentum  ;  they  turn  on  themselves  and 


Diaphragm 


Liver 


Foramen 
Winslowi 

Superior  curve 

of  duodenum 

Sight  renal  artery 

Right  renal  vein 

Pancreas 

Superior  mesen-. 


Posterior  layer  of 
transverse  mesocolui 


Omentum  minus 


Anterior  surface 
of  stomach, 

Bursa  omentalis 

Anterior  layer  of 
transverse  mesocolon 


ft —  Colon  transversum 

Descending  layer  of 
omentum  majus 


Ascending  layer  of 
omentum  majus 

Two  layers  of 
mesentery 


all  intestine 


Pouch  of 
Douglas 


FIG.  607.— Sagittal  section  of  abdominal  cavity  after  Farabeuf.    The  cut  runs  a  little  to  the  right  of  the 
median  line.    A  probe  passes  through  the  foramen  of  Winslow  to  the  lesser  sac. 


reach  the  transverse  colon,  forming  the  posterior  lamella  of  the  great  omentum, 
and  next  surround  the  transverse  colon.  Then  they  pass  to  the  vertebral  column, 
forming  the  transverse  mesocolon  with  its  upper  and  lower  layers,  and  covering 
the  anterior  and  inferior  surfaces  of  the  pancreas  by  their  bifurcation,  one  layer 
passing  upward  and  the  other  downward.  These  layers  now  diverge  to  complete 
their  respective  sacs,  which  have  been  traced,  and  meet  again  as  the  coronary 
ligaments  of  the  liver  at  the  starting-point. 


THE  PERITONEUM. 


983 


So  far  we  have  seen  the  reflections  and  pouches  in  a  longitudinal  section  in  or 
near  the  median  line. 

It  is  the  arrangement  as  found  in  the  infant  up  to  the  age  of  two  years ;  after 
that  age  the  great  omentum  does  not  usually  show  a  cavity. 

We  should  next  trace  the  peritoneum  transversely  in  cross  sections.  This  is 
simplest  low  doAvn  in  the  abdomen,  where  only  the  greater  sac  is  involved.  Let 
the  section  be  made  through  the  lumbar  region  somewhat  above  the  level  of  the 
umbilicus  (Fig.  608).  Beginning  at  the  linea  alba,  trace  the  parietal  layer 


Mesentery  Aorta 


Small      Lymphatic    Vena  cava,  Ascending 
intestine       gland         inferior          colon 


Perito 


Left  kidney 


FIG.  608. — Peritoneal  reflections  in  a  transverse  section  of  lumbar  region  below  transverse  colon.    Seen 
from  above.    Schematic.    (From  Tillaux.) 

around  to  the  right  until  it  nearly  reaches  the  outer  border  of  the  Quadratus 
lumborum  muscle.  It  then  passes  up  over  part  of  the  anterior  surface  of  the 
right  kidney  and  meets  the  ascending  colon.  It  partly  surrounds  it,  forming 
sometimes  a  proper  mesocolon,  but  usually  leaving  one-third  of  the  posterior  sur- 
face exposed.  At  birth  only  the  anterior  and  external  surfaces  are  covered. 

This  layer  then  passes  from  the  right  kidney  over  the  Psoas  muscle,  over  the 
vena  cava.  and.  meeting  the  superior  mesenteric  vessels  from  the  side,  is  led  by 
them  to  surround  the  small  intestine,  enclosing  blood-vessels,  lacteals,  lymphatics, 
and  nerves  in  the  mesentery  proper.  It  next  passes  over  the  vertebral  column  and 
aorta,  anterior  to  the  left  Psoas  muscle  and  left  kidney,  and  covers  the  anterior 
surface  and  sides  of  the  descending  colon,  forming  sometimes  a  true  descending 
mesocolon.  It  next  is  reflected  upon  the  antero-lateral  abdominal  wall  and  is 
continuous  with  itself  at  the  linea  alba. 

Notice  that  the  lower  end  of  each  kidne^  mav  be  best  felt  by  palpating  to  the 
•   I-A     *         t.     ii  J         *  J   r     r 

right  ot  each  colon. 

By  taking  a  cross  section  higher  up,  just  above  the  transverse  colon,  both 
cavities  are  involved,  making  the  tracing  more  complex,  but  the  continuity  of  one 
with  the  other  is  well  seen.  The  spleen  is  met  in  this  section,  and  all  parts  of 
the  colon  are  belonv  (Fig.  609).  Begin  again  in  front  at  the  linea  alba  and  trace 
to  the  right ;  soon  the  layer  makes  a  fold  open  to  the  front  and  encloses  the 
obliterated  umbilical  vein,  now  called  the  round  ligament  of  the  liver.  The  fold 
is  a  part  of  the  foetal  anterior  mesentery,  now  called  falciform  or  suspensory  liga- 
ment of  the  liver.  The  layer  is  a  parietal  one,  passes  to  the  posterior  abdominal 
wall  and  covers  the  anterior  surface  of  the  right  kidney  and  then  passes  in  front 


984 


THE    ORGANS    OF  DIGESTION. 


of  the  vena  cava  and  behind  the  margin  of  the  hepato-duodenal  ligament  which  is 
the  right  free  edge  of  the  lesser  omentum.     This  layer  now  forms  the  posterior 


Aorta 


Vessels  in  lesser 
omentum 


Liff.  teres 


FIG.  609.— Transverse  section  of  peritoneum  above  the  transverse  colon.    The  arrow  points  to  the  lesser  sac 
and  passes  through  the  foramen  of  Winslow. 


wall  of  the  lesser  sac  and  is  directly  continuous  with  the  layers  of  the  greater 
sac. 


Lip.  teres 


Vessels  in  lesser 
omentum 


FIG.  610.— Horizontal  section  through  the  abdomen  at  the  level  of  the  foramen  of  Winslow.    (Modified  from 
Godlee.) 

It  passes  over  the  vertebral  column,  the  crura  of  the  diaphragm  and  great 
vessels,  in  front  of  the  left  kidney  to  the  hilus  of  the  spleen,  forming  with  the 


THE   PERITONEUM. 


985 


greater  sac.  behind,  a  double  fold,  the  lieno-renal  ligament  (lien,  lienis,  spleen)  in 
which  run  the  splenic  and  pancreatic  vessels.  Anteriorly  it  forms  with  the 
greater  sac  another  double  fold,  the  lieno-gastric  ligament  or  g astro-splenic  omen- 
turn,  in  which  pass  the  vasa  brevia  to  the  fundus  of  the  stomach.  This  layer 
then  covers  the  posterior  surface  of  the  stomach  and  makes  the  posterior  layer  of 
the  lesser  omentum,  surrounding  the  three  vessels  and  forming  the  anterior 
boundary  of  the  foramen  of  Winslow.  Now  it  forms  a  part  of  the  greater  sac 
and  makes  the  anterior  layer  of  the  lesser  omentum,  covers  the  stomach  ante- 
riorly, dips  down  between  it  and  the  spleen  to  the  anterior  lip  of  the  hilus  to 
meet  the  lesser  sac,  and  so  forms  the  gastro-splenic  omentum.  It  then  covers  the 
whole  phrenic  surface  of  the  spleen,  approaching  the  hilus  from  all  sides,  and 
meeting  the  lesser  sac  again  from  behind.  Completing  the  lieno-renal  ligament, 
it  turns  back  on  the  left  kidney  to  the  abdominal  wall  and  courses  as  parietal 
peritoneum  to  the  middle  line  again. 

If  we  trace  a  section  through  the  level  of  the  foramen  of  Winslow,  the  pan- 
creas and  liver  are  introduced  (Fig.  610). 

Here  again  the  peritoneum  is  traced  from  the  mid-line  anteriorly  where  it 
invests  the  round  ligament  of  the  liver,  then  it  covers  the  right  abdominal  wall 
and  posteriorly  touches  the  diaphragm,  passes  anterior  to  the  right  kidney  and 
crosses  the  inferior  vena  cava,  where  it  makes  the  posterior  boundary  of  the 
foramen  of  Winslow.  It  then  extends  to  the  left  as  the  posterior  wall  of  the 
lesser  sac.  in  front  of  the  aorta,  splenic  vessels,  pancreas  and  left  kidney  to  the 
hilus  of  the  spleen.  Xow  the  pancreas  is  interposed  between  this  layer  and 
the  left  kidney,  and  the  splenic  vessels  pass  behind  or  just  above  the  pancreas  in 
the  lieno-renal  ligament  as  before.  The  lesser  sac  makes  a  small  blind  pouch 
near  the  hilus  of  the  spleen,  and  its  peritoneum  covers  the  posterior  wall  of  the 
stomach,  makes  the  posterior  layer  of  the  lesser  omentum,  bounds  the  foramen 
of  AA  inslow  anteriorly,  and  is  then  traced  as  in  the  last  figure. 

The  peritoneum  simply  surrounds  this  section  of  the  liver,  not  showing  any 
coronary  ligament.  The  peritoneal  relations  between  stomach,  kidnev,  pancreas, 
and  spleen  are  shown  m  more  detail  in  Fig.  611. 


Renal  surface 
Pouch  of  greater  sac 

Lieno-renal  ligament 
Phrenic  surface 
Gastro-splenic  omentum 
Pouch  of  greater  sac 

Gastric  surf  ace 


FIG.  611. -Horizontal  section  through  the  stomach,  pancreas,  spleen,  and  the  left  kidney  to  show  peritoneal 
reflections  at  hilus  of  spleen.    Schematic.    (G.  S.  H.) 

Here  we  see  three  pouches  of  peritoneum  centering  at  the  hilus  of  the  spleen. 
Anteriorly  and  posteriorly  are  two  from  the  greater  sac  and  in  the  centre  is  the 
left  blind  extremity  of  the  lesser  sac.  Should  the  structures  at  the  hilus  be 
grasped,  the  hand  would  enclose  anteriorly  a  layer  of  the  greater  sac,  then  two 
of  the  lesser  sac.  then  one  of  the  greater,  or  four  in  all,  and  a  section  through 
them  would  show  their  cut  edges  standing  out  as  two  concentric  rings  (Fig.  612). 


986  THE    ORGANS    OF  DIGESTION. 

The  layer  of  peritoneum  covering  the  pancreas  and  attached  to  the  spleen  may 
be  called  the  lieno-pancreatic  ligament ;  it  is  really  the  anterior  layer  of  the  lieno- 
renal  ligament. 


Peritoneum  of  greater  sac 
Renal  surface—  if§$&^  ^-Peritoneum  of  lesser  sac. 

»™«^««,  _^-^.«.  •  •      •.        •...,,.-.....:,    Gastric  surface 
Posterior  border 

K'-:-'-~--:*r:'3m~mli It  il-:'v"X"     S  >.._'.  1  ',        '     .-  J 

-  Anterior  border 


FIG.  612.— Inner  surface  of  spleen,  showing  "  peritoneal  lines  "  at  hilus.    (From  model  of  His.) 

We  are  now  prepared  to  follow  a  whole  layer  of  peritoneum  instead  of  tracing 
it  in  certain  lines. 

Parietal  Peritoneum. 

The  wall-implanted  peritoneum  follows  essentially  the  wall  of  the  abdomen 
and  that  of  the  pelvis,  being  bound  firmly  to  the  latter  and  quite  loosely  to  the 
former.  In  most  places  it  possesses  a  greater  thickness  than  the  visceral  layer 
arid  a  marked  resistance.  A  separate  piece  will  resist  a  pull  of  about  fifty 
pounds.  In  the  greater  part  of  its  extent  it  is  intimately  connected  with  the 
endo-abdominal  fascia  (transversalis  and  iliac  fascia)  which  covers  it  as  does  the 
endo-thoracic  fascia  cover  the  pleura ;  or  as  the  fibrous  pericardium  covers  the 
serous  pericardium. 

Anterior  Wall  of  the  Peritoneal  Sac. 

From  the  umbilicus  down  along  the  inner  surface  of  the  anterior  abdominal 
wall  the  parietal  layer  descends  to  the  top  of  the  bladder  and  Poupart's  ligaments, 
and  extends  from  here  into  the  pelvis.  In  its  course  it  is  thin  on  the  linea  alba 
and  umbilicus,  and  is  fused  with  the  parts  beneath.  On  both  sides  of  the  linea 
alba,  especially  below  in  the  pubic  region,  and  close  above  Poupart's  ligaments, 
the  peritoneum  is  thicker  and  does  not  lie  so  close  to  the  abdomiual  wall,  as  a 
well-developed  properitoneal  fatty  layer  comes  between  and  separates  them. 
Higher  up  along  the  linea  alba  the  peritoneum  is  rather  loosely  attached  and 
very  often  covers  numerous,  knobby,  overlapped  processes  of  fat  which  project 
inward,  plicce  adiposce. 

Lower  down  the  processes  of  the  fatty  layer  project  in  the  opposite  direction 
toward  the  linea  alba,  arid  may  push  out  through  aponeurotic  holes  and  make  a 
fat  hernia  of  variable  size. 

Above  the  umbilicus  the  peritoneum  forms  itself  into  a  sheath  which  contains 
the  beginning  of  the  round  ligament  of  the  liver.  It  forms  a  pocket  open  from 
above  which  is  in  a  position  to  receive  a  loop  of  intestine  and  to  share  in  the  for- 
mation of  an  umbilical  hernia. 


THE  PERITONEUM.  987 

Below  the  umbilicus  we  have  already  noted  the  five  longitudinal  folds  and  the 
inguinal  fossae  (p.  963). 

The  parietal  layer  passes  from  the  anterior  wall  to  the  under  surface  of  the 
diaphragm  and  clothes  it  up  to  the  central  tendon  where  the  oesophagus  and  vena 
cava  inferior  pass  through.  From  here  it  spreads  out  on  one  side  to  the  liver,  on 
the  other  to  the  stomach  and  spleen,  and  so  changes  into  the  visceral  layer. 

The  parietal  peritoneum  of  the  posterior  abdominal  wall  rests  on  small  and 
limited  spaces  and  passes  over  such  structures  as  the  kidneys,  transverse  duo- 
denum, right  and  left  colons,  great  vessel  trunks,  many  lymph-glands  and  vessels 
and  nerve-plexuses. 

By  means  of  a  loose  fatty  connective  tissue  called  retroperitoneal  cellular  tissue 
these  structures  fasten  themselves  together  and  themselves  to  the  peritoneum. 
On  this  posterior  wall  to  the  left  of  the  duodenum  there  may  be  as  many  as  three 
infoldings  or  retroperitoneal  pouches  which  will  be  described  later. 

Upper  Wall  of  the  Peritoneal  Sac. 

The  lower  surface  of  the  diaphragm  representing  the  roof  of  the  abdomen  is 
not  covered  wholly  by  peritoneum.  Behind  the  central  tendon  it  is  partly  free 
where  the  surface  of  the  liver  rests  upon  it  and  where  the  suprarenal  capsules  and 
kidneys  come  in  contact  with  it.  The  greater  part  of  the  diaphragmatic  covering 
is  directly  continuous  Avith  the  anterior  and  lateral  parietal  layers,  and  is  distin- 
guished by  its  extreme  delicacy  and  firm  connection,  with  the  endo-abdominal 
fascia.  In  the  cleft-like  holes  left  between  the  costal  and  sternal  parts  of  the 
diaphragm  and  between  the  costal  and  vertebral  parts,  peritoneum  and  pleura 
meet;  these  are  called  "weak  places,"  and  here  a  diaphragmatic  hernia  can  be 
acquired. 

A  small  surface  of  the  diaphragm  situated  behind  the  lobus  Spigelii  gets  a 
covering  from  the  upper  end  of  the  posterior  wall  of  the  lesser  sac  which  does  not 
enter  into  continuity  with  the  serous  covering  of  either  side,  but  on  the  left  it  turns 
into  the  mesial  layer  of  the  gastro-splenic  omentum  and  on  the  right  into  the 
mesial  layer  of  the  hepatico-renal  ligament. 

Inferior  Wall  of  the  Peritoneal  Sac. 

This  belongs  in  part  to  the  false  pelvis  and  in  part  to  the  true  pelvis.  In  the 
former  it  is  connected  with  the  fascia  iliaca.  In  the  iliac  fossa  the  peritoneum  ex- 
tends itself  underneath  and  behind  the  caecum  so  that  that  structure  hangs  free  in 
the  peritoneal  cavity.  There  is  usually  no  mesocaecum  in  the  adult.  Near  the 
caecum  there  are  periccecal  fossce,  for  later  description.  On  the  left  side  the  peri- 
toneum passes  from  within  and  Avithout  over  the  iliacus  muscle  and  fascia  to  the 
formation  of  a  very  movable  fold  Avhich  surrounds  the  siginoid  flexure,  the  meso- 
ngmoidea  or  sigmoid  mesocolon.  Where  this  attaches  to  the  intestine,  opposite 
the  brim  of  the  true  pelvis,  the  peritoneum  raises  itself  into  a  fold  Avhich  has  been 
called  lig.  mesenterico-mesoeolicum  (W.  Gruber),  which  on  one  side  runs  into  the 
mesentery  proper  and  on  the  other  into  the  mesocolon  of  this  flexure.  It  seems 

to  have  the  purpose  of  limiting  the  deep  descent  of  the  rectal  limb  of  the  sicrmoid 

° 
flexure. 

In  the  left  leaf  of  the  mesosigmoidea  is  usually  to  be  found  the  fossa  subsig- 
moidea  or  intersigmoidea. 

In  the  hollow  of  the  true  pelvis  the  peritoneum  clothes  that  region  of  the  lateral 
wall  Avhich  in  man  extends  between  rectum  and  bladder,  in  Avoman  betAveen  rec- 
tum and  vagina,  also  between  rectum  and  uterus.  In  the  first  it  forms  a  pouch 
open  abo\re,  excavatio  recto-vesicaUs  or  recto-vesical  pouch.  The  mouth  of  the 
pouch  is  bounded  by  a  crescentic  fold  of  peritoneum  on  each  side,  the  plica  semi- 
lunaris.  The  left  one  is  usually  the  larger.  They  form  the  posterior  false  liga- 
ments of  the  bladder.  The  depth  of  this  pouch  extends  to  Avithin  one  inch  of  the 
prostate  or  Avithin  about  8  cm.  of  the  anal  orifice. 


988  THE    ORGANS    OF  DIGESTION. 

In  the  female  we  have  seen  that  two  pouches  exist  at  the  lower  end  of  the 
peritoneal  sac  ;  a  shallow  one  between  bladder  and  uterus,  excavatio  vesico-uterina  ; 
a  posterior  deep  one  between  rectum  behind  and  uterus  and  cervix  and  upper  end  of 
vagina  in  front.  The  deepest  part  is  bounded  on  each  side  by  a  sharp  semilunar 
fold  as  in  the  male,  which  folds  are  called  sacro-uterine  ligaments,  or,  according  to 
some,  recto-uterine.  They  pass  from  the  upper  part  of  the  cervix  in  front  and 
extend  backward  to  the  sides  of  the  rectum  toward  the  sacrum.  This  pouch  has 
anteriorly  the  supravaginal  cervix  uteri  and  the  upper  fifth  of  the  posterior  wall 
of  the  vagina,  and  posteriorly  the  rectum  and  sacrum  ;  it  is  the  recto-vaginal  pouch 
or  the  proper  cul-de-sac  of  Douglas.  The  space  above  this,  between  rectum  and 
uterus,  is  called  the  recto-uterine  pouch. 

On  either  side  of 'the  uterus  the  peritoneum  forms  a  broad  double  layer  pass- 
ing to  the  side  of  the  pelvis.  It  is  called  the  broad  ligament,  and  each  contains 
three  important  structures,  anteriorly  the  round  ligament  of  the  uterus,  in  the 
middle  and  highest  up  the  Fallopian  tube,  and  posteriorly  the  ovary. 

In  a  distended  condition  of  the  pelvic  organs  the  pouches  are  filled  by  them, 
otherwise  coils  of  small  intestines  and  usually  a  part  of  the  sigmoid  flexure  fall 
into  the  pelvic  cavity. 

The  Visceral  Peritoneum. 

By  this  term  one  understands  in  general  the  prolongations  of  the  peritoneum 
into  its  own  cavity,  usually  from  behind,  covering  or  nearly  surrounding  a  viscus. 
It  is  also  applied  to  prolongations  from  parietal  layers  and  those  Avhich  pass  bridge- 
like  from  one  organ  to  another. 

In  the  middle  line,  the  peritoneum  accompanies  in  its  course  from  the 
umbilicus  to  the  diaphragm  the  extraperitoneal  obliterated  umbilical  vein,  forms 
a  fold  around  it  which  on  one  hand  follows  the  vein  (lig.  teres)  to  the  under  sur- 
face of  the  liver,  and  on  the  other  continues  itself  to  the  upper  surface  of  the 
liver,  and  from  there  passes  to  the  diaphragm  as  the  lig.  suspensorium  hepatis. 
It  covers  the  concave  surface  of  the  diaphragm  as  far  as  the  spot  where  the  liver 
comes  into  direct  contact  with  it  and  then  passes  upon  the  liver  in  a  frontal  direc- 
tion as  the  anterior  (or  upper)  layer  of  the  lig.  coronarium  hepatis  (coronary  and 
lateral  ligaments).  The  left  leaf  of  the  suspensory  ligament  passes  out  over  the 
upper  surface  of  the  left  lobe  of  the  liver,  meeting  above  the  left  part  of  the  coro- 
nary ligament,  and  the  right  leaf  passes  over  the  upper  surface  of  the  right  lobe 
in  the  same  manner.  After  clothing  the  convex  surface  of  the  liver  it  advances 
over  the  anterior  acute  margin  and  then  covers  the  quadrate  lobe  to  the  portal 
fissure,  the  gall-bladder  except  where  adherent  to  the  liver,  and  under  surfaces 
of  the  right  and  left  lobes,  to  turn  finally  back  to  the  diaphragm,  forming  the 
lower  layer  of  the  coronary  and  lateral  ligaments.  There  is  but  one  place,  the 
portal  fissure,  where  this  layer  does  not  turn  back.  Here  by  the  out-  and  ingoing 
vessels  it  is  obliged  to  descend  to  the  stomach. 

Farther  to  the  left  the  peritoneum  goes  from  the  diaphragm  to  the  stomach 
(cardia)  as  the  lig.  phrenico-gastricum  covering  the  anterior  and  left  surfaces 
of  the  oesophagus ;  it  descends  from  the  diaphragm  to  the  spleen  as  the  lig. 
phrenic o-lienale  or  suspensory  ligament ;  and  to  the  splenic  flexure  of  the  colon 
as  the  lig.  phrenic  o-colicum. 

From  the  fundus  of  the  stomach,  the  peritoneum  passes  in  a  duplicature  to  the 
spleen  as  the  lig.  gastr o-lienale  (gastro-splenic  omentum),  which  covers  the  gastric 
surface  of  the  spleen  and  is  continued  over  its  phrenic  and  renal  surfaces  as  we 
have  seen. 

This  omentum  descends  over  the  splenic  flexure  of  the  colon  and  there  may 
be  called  omentum  colicum;  thence  it  is  connected  with  the  posterior  abdominal 
wall  and  descending  colon. 

The  peritoneum  leaves  about  one-third  of  the  posterior  surface  of  the  left 
colon  uncovered,  forming  no  mesocolon  usually  ;  below,  it  surrounds  the  sigmoid 
flexure,  forming  a  long  mesentery,  which  follows  it  into  the  pelvis. 


THE   PERITOXECM. 


989 


Turning  to  the  right  side  and  above,  we  have  seen  the  right  part  of 
the  coronary  and  lateral  ligament  descending  in  two  layers  from  the  dia- 
phragm. 

Below  the  liver,  the  peritoneum  passes  to  the  stomach  and  duodenum  as  the 
liy.  hepato-f/astricum  and  lig.  kepato-duodenale,  both  of  which  make  the  lesser 
omentum  of  two  layers.  A  part  of  the  right  edge  of  this  omentum  passes  to  the 
hepatic  flexure  of  the  colon,  called  lig.  hepato-colicum.  The  peritoneum  from  the 
neck  of  the  gall-bladder  to  the  duodenum  is  the  lig.  cystico-duodenale.  Behind 
the  foramen  of  Winslow  and  beneath  the  neck  of  the  gall-bladder  another  thin 
layer  passes  to  the  right  kidney,  lig.  hepato-renale  (Fig.  615).  Farther  down  the 


Siffmoid  flexure 
FIG.  613.— Mesentery.    Small  intestines  pushed  to  the  right  and  above.    (Tillaux.) 

peritoneum  from  the  posterior  abdominal  wall,  continuous  with  the  hepato-colic 
ligament,  covers  about  two-thirds  of  the  ascending  colon  as  on  the  left  side, 
making  no  mesocolon,  and  covers  the  whole  of  the  caecum,  making  no  meso- 
coecurn.  because  the  layers  have  fused  into  a  close-fitting  pocket  with  no  attach- 
ments except  above.  This,  as  the  mesentery  proper,  forms  a  little  mesentery 
for  the  appendix  (mesenteriolum)  and  descends  into  the  pelvis. 

Mesentery. — When  the  peritoneum  on  the  vertebral  column  reaches  the  ante- 


990 


THE    ORGANS    OF  DIGESTION. 


rior  surface  of  the  superior  mesenteric  vessels,  it  follows  them  down  to  the  loops 
of  small  intestine  surrounding  all  the  jejunum  and  ileum,  but  not  the  duodenum; 
it  returns  to  the  spinal  column,  constituting  the  mesentery.  It  has  a  right  upper 
and  a  left  lower  layer,  between  which  are  the  mesenteric  arteries  and  veins, 
lacteals,  lymphatics,  and  nerves,  all  fused  together  by  fatty  connective  tissue. 
The  point  of  origin  of  the  two  layers  is  called  "root  of  the  mesentery  "  (Radix 
mesenterii)  (Fig.  613). 

It  runs  obliquely  from  the  left  side  of  the  body  of  the  second  lumbar  vertebra 
across  the  vertebral  column,  aorta,  vena  cava  inferior,  and  third  pai't  of  the  duo- 


Kight  lati 
ligament  of  liv 


I          Falci/i 


Left  lateral 
ligament  of  liver. 


Vena  cava  inferior: 

(Esophagus. 
Right  phrenic  artery. 

Coronary  artery. 
Hepatic  artery.  --. 

Splenic  artery 
Pancreas 

Inf.  pane. -duo.  artery 

Colica  media 

Superior  mesenteric 

Duodenum  (3rd  part) 

Aorta 

Duodenum  (2nd  part) 

Hiijttt  and  left  kidneys. 

/Superior  mesenteric. 

Aorta. 

Colica  sinistra 
Colica  dextra. 
Yasa  infest, 


Siffmoid  artery. t 

Slip,  hoimorrhoidal  artery. ,J« 


Common  iliac  artery.' 


External  iliac  artery.  "" 

Epigastric  artery. 

Bladder.  "~ 


•  'Extra-peritoneal  tissue. 

"          J  Diaphragmatic  end  of 


Costo-colic  ligament. 
Dot  between  two  anterior 
layers  of  great  omcntut 
Transverse  meso-culon. 


J  Bare  surface  for  2nd  par 
~  t    of  rectum. 

«  Left  lateral  false  Uga- 
"  (    ment  of  bladder. 


FIG.  614.-Diagram  devised  by  Dr.  Delepine  to  show  the  lines  along  which  the  peritoneum  leaves  the  wall 
of  the  abdomen  to  invest  the  viscera. 

denum  to  the  right  sacro-iliac  articulation  or  to  the  right  iliac  fossa  (Fig.  614). 
It  is  three-cornered  or  fan-shaped,  with  its  root  six  inches  long  and  its  convex 
intestinal  edge  about  twenty-one  feet  long;  its  average  width  is  eight  or  nine 
inches.  It  is  widest — i.  e.  gives  greatest  freedom  to  the  intestine,  20  to  25  cm. 
above  the  caecum,  and  then  suddenly  shortens.  The  middle  and  lower  loops  of 
intestine  have  the  longest  mesentery,  and  are  more  movable  and  more  liable  to 
hernia.  They  usually  lie  in  the  pelvis.  From  its  obliquity,  fluid  exudate  of  any 


THE   PERITONEUM.  991 

kind  on  the  right  side  would  press  upon  the  right  inguinal  region ;  if  upon  the 
left  side,  would  have  an  inclination  to  gravitate  to  the  true  pelvic  cavity.  At 
the  root,  the  right  layer  is  continued  into  the  lower  layer  of  the  transverse  meso- 
colon ;  on  both  sides  the  layers  continue  themselves,  one  into  the  inner  lamella 
of  the  left  colon  and  the  other  into  that  one  of  the  right  colon.  The  left  layer 
continues  downward  into  the  peritoneum,  covering  the  lumbar  vertebrae,  which 
passes  over  the  promontory  to  the  pelvic  organs. 

The  Omenta  and  Bursa  Omentalis. 

The  great  omentum  we  have  seen  consists  of  four  layers  formed  by  an  anterior 
descending  lamella  of  two  and  a  posterior  ascending  lamella  of  two.  It  was 
derived  from  the  mesogastrium  (Fig.  599).  Its  two  middle  layers  (Fig.  606)  con- 
stitute the  walls  of  the  lesser  sac  and  come  from  the  right  leaf  of  the  mesogastrium; 
its  two  superficial  layers  belong  to  the  greater  peritoneal  cavity  and  come  from  the 
left  leaf  of  the  mesogastrium. 

Only  in  foetal  life  could  the  first  and  second  or  third  and  fourth  layers  be 
separated  and  only  up  to  about  the  age  of  two  years  does  the  cavity  exist  between 
the  second  and  third  layers.  Before  that  age  and  sometimes  in  adults  the  cavity 
of  the  great  omentum  can  be  distended  by  air  introduced  through  the  foramen  of 
Winslow  or  a  finger  could  be  inserted  into  it  through  an  incision  made  just  below 
the  stomach  dividing  the  two  anterior  layers.  This  finger  would  come  in  contact 
with  another  introduced  from  right  to  left  through  the  foramen  of  Winslow.  This 
can  rarely  be  done  in  the  adult  without  breaking  down  adhesions,  for  the  reason 
that  at  about  the  age  mentioned  the  anterior  lamella  of  two  layers  fell  back  upon 
the  transverse  colon  and  became  adherent  to  the  posterior  lamella,  obliterating 
the  cavity  of  the  great  omentum,  which  may  now  be  called  the  omental  plate. 
Figure  606  shows  the  opportunity.  This  arrangement  gives  the  stomach  a  direct 
connection  with  the  transverse  colon  and  the  two  layers  descending  from  the 
greater  curvature  cannot  be  lifted  from  it.  Our  former  great  omentum  may  now 
be  called  yastro-colic  omentum  ;  some  speak  of  the  layers  between  stomach  and 
colon  only  as  the  gastro-colic  part  of  the  great  omentum. 

This  part  connects  on  the  left  with  the  gastro-splenic  omentum  and  on  the 
right  with  the  hepatic  flexure  of  the  colon  and  descending  colon,  meeting  there 
the  hepato-colic  ligament,  and  is  distinguished  at  those  points  as  omentum  colicum 
(Haller).  In  later  time,  the  great  omentum  is  a  four-cornered  curtain  which 
hangs  down  from  the  great  curvature  of  the  stomach  in  front  of  the  small  intes- 
tines fused  with  the  transverse  colon,  ending  usually  in  a  free  edge  and  descend- 
ing a  little  lower  on  the  left  side  as  evidenced  by  its  greater  frequency  in  left 
hernise.  It  may  be  tucked  between  the  intestines  or  wholly  pushed  upward.  It 
may  accumulate  much  fat. 

Its  vessels — vasa  epiploica — are  chiefly  derived  from  the  art.  gastro-epiploica 
sinistra,  only  the  smallest  part  from  the  dextra.  It  is  poorly  supplied  with 
lymphatics.  Its  nerves  are  from  the  coeliac  plexus. 

The  gastro-splenic  omentum  we  have  seen  (Figs.  610  and  611)  as  a  double 
fold,  dipping  in  between  the  fundus  of  the  stomach  and  the  gastric  surface  of  the 
spleen.  It  is  where  the  greater  sac  has  opportunity  to  touch  the  lesser  sac 
between  these  two  organs.  In  this  fold,  made  by  two  sacs,  the  splenic  artery 
sends  its  vasa  brevia  to  the  stomach. 

The  lesser  omentum  (omentum  minus)  or  g  astro-hepatic  omentum  or  lig.  hepato- 
gastricum  passes  nearly  vertically  between  the  transverse  fissure  of  the  liver  and  the 
lesser  curvature  of  the  stomach,  continuous  to  the  right  upon  the  first  part  of  the 
duodenum.  This  right  free  edge  going  to  the  duodenum,  containing  vessels,  is 
called  the  lig.  hepato-duodenale.  The  lesser  omentum  and  hepato-duodenal  liga- 
ment are  made  of  two  layers,  one  from  the  greater  and  one  from  the  lesser  sac. 
An  index  finger  passed  into  the  foramen  of  Winslow,  if  approximated  to  the  thumb 
placed  upon  the  anterior  surface,  includes  the  two  layers,  thin  as  they  are.  The 


992 


THE    ORGANS    OF   DIGESTION. 


anterior  layer  at  the  right  free  border  turns  behind  the  vessels,  now  belongs  to 
the  lesser  sac,  and  makes  the  posterior  layer  of  the  hepato-duodenal  ligament  and 
of  the  lesser  omentum.  These  two  layers  below  enclose  the  stomach,  and  to  the 
left  side  form  the  gastro-splenic  omentum.  Above,  the  anterior  layer  is  attached 
in  front  of  the  transverse  fissure  and  then  spreads  over  all  the  inferior  surface  of 
the  liver.  The  posterior  layer  above  is  attached  just  behind  the  transverse  fissure, 
and  here  separates  from  the  anterior  to  pass  backward  and  upward  over  the 
Spigelian  lobule  only.  The  combined  layers  leave  the  left  end  of  the  transverse 
fissure  and  run  along  the  edges  of  the  fissure  for  the  ductus  venosus,  passing  to 
the  diaphragm  and  on  that  forward  to  the  oesophagus,  which  the  two  layers  partly 
surround,  the  anterior  one  covering  its  anterior  and  left  side,  the  posterior  one  its 
posterior  and  right  side,  in  part.  The  anterior  one  is  the  phrenico-gastric  liga- 
ment. Between  the  two  layers  of  the  hepato-duodenal  ligament  at  the  right 

Lig.  teres  in  lig. 
suspensorium^ 


Cystic  duct ' 
Hepatic  duct  • 

Common  bile-duct 
Vena  portse , 
Hepatic  artery . 

Lig.  hepatico-reiwlf. 

Lifj.  hepatico- 

duodenale 

FIG.  615.— Upper  part  of  abdominal  cavity  of  a  child.  The  liver  has  been  drawn  upward  and  the  lig.  hepato- 
duodenale,  containing  the  hepatic  vessels,  has  been  put  on  the  stretch  ;  its  anterior  layer  has  been  opened  by 
a  vertical  incision.  A  probe  passes  behind  it  through  the  foramen  of  Winslow  into  the  lesser  sac.  (Henle.) 

edge  of  the  lesser  omentum,  the  outgoing  and  ingoing  vessels  are  arranged  as 
represented  in  Fig.  615. 

Near  the  duodenum  there  are  three  vessels,  the  common  bile-duct  to  the  right, 
the  hepatic  artery  to  the  left,  and  behind  and  between  the  two  the  portal  vein. 
At  the  transverse  fissure  of  the  liver  the  artery  and  vein  divide  into  right  and 
left  branches  for  the  right  and  left  lobes,  and  the  common  bile-duct  receives  the 
cystic  duct  and  the  hepatic  ducts  descending  from  the  two  lobes.  Besides  these 
are  lymph-glands  and  vessels  and  nerves,  all  surrounded  by  connective  tissue 
which  is  called  Grlissoris  capsule. 

The  foramen  of  Winslow  (J.  B.  Winslow,  1743)  or  orificium  epiploicum,  is 
the  point  of  communication  between  the  bursa  omentalis  (lesser  sac)  and  the 
greater  sac.  It  may  be  round  in  shape,  triangular  or  semilunar.  It  should 
admit  about  two  fingers.  It  is  best  shown  when  the  liver  is  tilted  upward  and  to 
the  right,  and  the  intestines,  with  the  first  part  of  the  duodenum,  downward  and 
to  the  left.  Its  boundaries  are — above,  the  caudate  lobe  of  the  liver ;  below,  the 
first  part  of  the  duodenum  and  the  first  part  of  the  hepatic  artery  as  it  passes 
forward ;  in  front  are  the  right  free  border  of  the  lesser  omentum,  lig.  hepato- 
duodenale,  with  its  contained  vessels,  hepatic  artery,  vena  portse  and  common 
bile-duct;  behind  are  the  lig.  hepato-renale  and  vena  cava  inferior. 


THE   PERITONEUM. 


993 


As  a  result  of  closure  of  this  foramen  due  to  adhesive  inflammation,  a  hydrops 
saccatus  can  be  formed  by  a  collection  of  serum  in  the  lesser  sac,  and  the  stomach 
will  rest  on  a  sort  of  water-bed. 

Another  rare  anomaly  is  a  hernia  through  this  foramen.  A  great  part  of  the 
small  intestines  have  worked  their  way  through  it  by  peristalsis  into  the  lesser  sac. 

The  Lesser  Sac  or  Bursa  Omentalis. — Between  the  mesogastrium  and  posterior 
wall  of  the  stomach  there  was  originally  a  three-cornered  space  with  its  apex 
turned  to  the  left  and  base  to  the  right  (Figs.  599  and  600).  During  develop- 
ment the  base  has  been  narrowed  to  the  foramen  of  Winslow.  The  cavity  is 
called  the  lesser  sac  or  omental  bursa.  Figure  606  shows  that  it  sends  a  diver- 
ticulum  up  behind  the  Spigelian  lobe  of  the  liver,  another  downward  known  as 
the  cavity  of  the  great  omentum,  and  in  figure  610  we  see  the  main  chamber 
behind  the  stomach  sending  off  a  third  pouch  to  the  spleen  and  left  kidney. 

When  the  finger  enters  the  foramen  of  Winslow  it  is  able  to  mark  out  a  cir- 
cumscribed region  confined  by  the  Spigelian  lobe  anteriorly  and  the  diaphragm 
behind.  Push  the  finger  to  the  left  until  it  is  obstructed  and  let  it  descend ;  at  a 
level  below  the  papillary  tubercle  of  the  liver  it  will  slip  under  a  prominent  band, 
and  can  now  ascend  under  the  fundus  of  the  stomach  up  to  the  posterior  surface 
of  the  resophagus ;  we  call  then  push  over  to  the  spleen,  or,  if  the  subject  be 
young  enough,  down  into  the  great  omentum. 

The  lesser  sac  seems  to  be  subdivided.  Huschke  called  the  first  portion, 
which  receives  the  Spigelian  lobe,  the  bursa  omenti  minoris,  because  it  is  just 
behind  the  lesser  omentum. 

The  second  large  division  going  upward  behind  the  stomach  and  downward 
into  the  omentum  and  over  to  the  spleen  was  the  bursa  omenti  majoris.  Each 


Papillary  tubercle 


Cut  edfje  of  peritoneum 


Descending 
duodenum 


Spleen  covered 
'by  peritoneum 


Cut  edge  of  peritoneum 


FIG.  616. — Bursa  omentalis,  opened  from  the  front  by  an  incision  through  the  gastro-colic  omentum     A 
probe  passes  through  the  foramen  of  Winslow  and  rests  o'u  the  gastro-pancreatic  ligament.    (Henle.) 

communicates  with  the  other  by  the  foramen  omenti  majoris.     These  subdivisions 
are  still  found,  and  the  constricting  band  is  still  present,  caused  by  the  gastric 

63 


994  THE    ORGANS    OF  DIGESTION. 

artery,  throwing  forward  a  fold  of  peritoneum  in  relief.  This  is  called  the  lig. 
gastro-pancreaticum  (Fig.  616). 

The  figure  shows  the  posterior  wall  of  the  bursa  lying  in  front  of  the  pan- 
creas. Through  the  opening  to  the  right  and  above  may  be  seen  the  papillary 
tubercle  of  the  Spigelian  lobe. 

The  connection  of  the  two  bursse  is  narrowed  by  the  tuber  omentale  of  the 
pancreas  and  the  gastro-pancreatic  ligament  which  runs  obliquely  from  the  cardia 
to  the  anterior  surface  of  the  pancreas  in  about  the  middle  line. 

It  is  now  proposed  to  call  the  first  bursa  the  atrium  bursce  omentalis  or  ante- 
chamber, and  the  second  bursa  the  bursa  omentalis  proper. 

The  part  behind  the  stomach  persists  throughout  life.  The  surfaces  are  in 
immediate  contact,  and  by  their  smoothness  and  moisture  permit  easy  movements 
of  the  stomach  in  its  various  degrees  of  distention. 

Recessus  Peritonei  or  Retro -peritoneal  Fossae. 

In  four  or  five  different  parts  of  the  abdominal  cavity  there  are  regions  of  sur- 
gical interest  from  the  possibility  of  the  occurrence  of  retro-peritoneal  hernice.  One 
we  have  already  noted,  the  foramen  of  Winslow,  another  is  a  plirenico-hepatic  fossa 
at  the  left  lobe  of  the  liver.  As  many  as  three  may  occur  at  the  upper  end  of  the 
root  of  the  mesentery:  a  duodeno-jejunal  and  duodenal  fossae ;  an  intersigmoid 
fossa  to  the  outer  side  of  the  sigmoid  flexure,  &  fossa  iliaco-subfascialis  connected 
with  a  left  Psoas  minor  muscle.  Finally  three  fossae  may  exist  in  the  neighbor- 
hood of  the  caecum. 

Henle  says  of  the  first  one,  "It  is  remarkable  that  a  hitherto  overlooked 
pocket  has  been  brought  to  light  by  Von  Brunn,  1874.  It  is  on  the  under  sur- 
face of  the  diaphragm,  of  various  dimensions,  and  can  be  found  in  about  one-half 
of  the  adults.  It  opens  to  the  right  from  the  left  margin  of  the  liver  and  extends 
to  the  left,  parallel  to  the  coronary  ligament,  sometimes  only  deep  enough  for  the 
introduction  of  the  point  of  a  probe  and  sometimes  distensible  to  a  length  of  13  to 
16  cm.  and  to  a  diameter  of  3  to  4  cm.  Its  existence  depends  on  the  atrophy  of 
the  left  lobe  of  the  liver.  When  the  gland  substance  retracts,  a  flat  peritoneal 
fold  remains  on  the  under  surface  of  the  diaphragm,  penetrated  by  vessels  and  vasa 
aberrantia  of  the  liver  and  often  lodging  separate  particles  of  gland  tissue.  The 
pocket  fossa  phrenico-hepatis  originates  therefore  when  the  anterior  or  posterior 
"edge  of  the  atrophied  lobe,  by  far  most  frequently  the  anterior,  fuses  with  the 
diaphragm.  It  develops  after  birth.  In  new-born  and  children  it  is  not  to  be 
found." 

Duodenal  Fossae. 

Jonnesco  has  found  a  series  of  three  fossas  in  the  vicinity  of  the  ascending 
duodenum  and  duodeno-jejunal  angle.  They  have  all  generally  been  called  the 
duodeno-jejunal  fossa,  or  fossa  of  Treitz. 

1.  The  inferior  duodenal  fossa  (Fig.  617)  is  most  frequent,  and  occurs  in 
about  75  per  cent,  of  cases.  It  is  situated  to  the  left  of  the  upper  part  of  the 
ascending  duodenum  and  has  the  shape  of  a  cornucopia  bound  to  the  intestine. 
The  apex  of  the  fossa  is  directed  to  the  right  and  almost  touches  the  root  of  the 
mesentery. 

Its  widened  mouth  is  turned  upward  and  circumscribed  by  the  free  edge  of 
the  inferior  duodenal  fold.  This  fold  is  triangular,  has  a  falciform  edge  with  its 
concavity  turned  upward ;  its  right  margin  rests  on  the  anterior  surface  of  the 
duodenum  and  its  left  on  the  prerenal  peritoneum  and  is  continuous  with  the 
parietal  peritoneum.  It  contains  no  vessels,  nor  fat,  and  the  duodenum  is  readily 
seen  through  it.  The  boundaries  of  the  fossa  are — this  fold  to  the  front  and  left, 
the  ascending  duodenum  to  the  right,  and  the  left  side  of  the  third  lumbar  verte- 
bra behind.  Its  tip  may  extend  to  the  anterior  surface  of  the  fourth  lumbar  ver- 
tebra. The  depth  may  attain  3  cm. ;  its  orifice  admits  the  tip  of  the  index  finger. 


THE   PERITONEUM. 


995 


Sometimes  the  fold  is  bound  to  the  intestine  and  the  fossa  is  then   apparently 
lacking. 

The  vascular  relations  of  this  fossa  are  not  close.  The  inferior  mesenteric 
vein  is  about  one  finger's  breadth  to  the  left  and  the  art.  colica  sinistra  is  as  far 
below.  The  vessels  have  no  causal  relations  and  the  fossa  is  non-vascular.  Jon- 
nesco  met  one  case  where  the  artery  and  vein  were  related  to  the  fold. 


FIG.  617.— Inferior  and  superior  duodenal  fossfe. 
The  inferior  mesenteric  vein  is  some  distance  from 
the  inferior  fossa  but  near  the  left  border  of  the  su- 
perior fossa.  Transverse  colon  and  mesocolon  are 
turned  up.  On  the  left  is  the  descending  colon,  as- 
cending duodenum  on  the  right,  and  jejunum  is 
pulled  to  the  right.  (Jonnesco.) 


FIG.  618.— Duodeno-jejunal  fossa  of  Treitz.  (From 
Treitz  in  Jonnesco.)  D.  Ascending  duodenum.  P. 
Duodenal  fold.  Vm.  Inferior  mesenteric  vein.  Ac. 
Art.  colica  sinistra.  Jft.  Transverse  mesocolon.  Ifd. 
Descending  mesocolon. 


The  fossa  described  by  Treitz  and  known  as  the  duodeno-jejunal  fossa  of 
Treitz  is  this  one,  but  it  is  "vascular,"  in  which  the  inferior  mesenteric  vein 
runs  in  the  edge  of  the  crescentic  fold  and  the  inferior  extremity  of  the  fossa  is 
formed  by  the  colica  sinistra  artery.  Treitz  regarded  the  formation  of  the  fossa 
due  to  the  presence  of  the  vessels  (Fig.  618). 

"  The  orifice  of  the  fossa  was  limited  on  the  right  by  the  duodenum,  on  the 
left  by  the  free  edge  of  the  duodenal  fold.  The  fossa  lay  on  the  third  lumbar 
vertebra  left  side,  and  in  the  bottom  of  a  depression  of  the  posterior  abdominal 
wall  limited  by  the  pancreas,  left  kidney  and  aorta." 

'2.  The  superior  dnoJ- .rc.il  fU-.*</  is  present  in  about  50  per  cent.  It  often  co- 
exists with  the  inferior  one  (Fig.  617).  It  is  always  at  the  level  of  the  superior 
extremity  of  the  ascending  duodenum,  and  its  orifice  looks  downward,  opposed  to 
the  preceding.  The  orifice  is  limited  by  the  edge  of  the  superior  duodenal  fold, 
which  presents  the  free  semilunar  base  turned  below.  The  summit  of  the  fold  is 
lost  above  in  the  inferior  layer  of  the  transverse  mesocolon,  its  left  side  passes 
over  into  prerenal  peritoneum,  and  its  right  side  on  to  the  duodenum  and  left  leaf 
of  mesentery. 

The  fossa  is  limited  in  front  by  this  fold,  to  the  right  by  the  duodenum  and  is 
stopped  above  by  the  body  of  the  pancreas  and  rests  on  the  second  lumbar  verte- 
bra in  the  angle  formed  by  the  left  renal  vein  crossing  the  aorta.  Its  greatest 
depth  is  2  cm.  This  fossa  is  always  vascular,  i.  e.  is  related  to  the  inferior  mesen- 
teric vein  which  passes  to  its  left  along  its  adherent  parietal  border  and  disap- 
pears under  the  pancreas :  sometimes  it  enters  the  free  fold  covering  the  orifice. 

3.  The  duodeno-jejunal  or  mesocolic  fossa.  This  is  found  in  16  per  cent.  ;  it 
does  not  coexist  with  anv  other.  Its  existence  necessitates  that  the  duodeno- 


996 


THE    ORGANS    OF   DIGESTION. 


jejuna!  angle  should  penetrate  the  root  of  the  transverse  mesocolon.     This  occurs 

in  two  forms :  (1)  a  single  simple  fossa  (Fig.  619),  and  (2)  a  double  fossa.     Below 

the  duodenum  is  the  inferior  mesenteric 
artery,  giving  off  the  colica  sinistra ; 
passing  over  the  fossa  is  the  inferior 
mesenteric  vein.  This  was  originally 
described  by  Huschke  in  1844.  In 
drawing  the  jejunum  forward  and  to  the 
right,  the  mesocolon  being  raised,  the 
duodeno-mesocolic  ligaments  are  seen 
stretched  between  the  duodeno-jejunal 
angle  and  mesocolon.  They  seem  to  be 
layers  of  mesentery  passing  into  the 
mesocolon.  Limited  by  these  folds  and 
by  the  upper  surface  of  the  duodeno- 
jejunal  angle  and  the  inferior  mesenteric 
vein  there  appears  an  almost  circular 
opening  leading  into  a  deep  fossa.  This 
plunges  into  the  mesocolon  and  occupies 
a  retro-peritoneal  space  to  the  left  of  the 
second  lumbar  vertebra,  limited  above  by 
the  pancreas,  on  the  right  by  the  aorta, 
and  on  the  left  by  the  left  kidney.  In 

this  cavity  is  the  angle  of  the  duodeno-jejunal  flexure  and  higher  up  can  be  seen 

under  it  the  left  renal  vein.     The  orifice  admits  the  little  finger  and  its  depth  is 

2  or  3  cm. 

The  inferior  mesenteric  vein  passes  at  first  along  the  adherent  mesocolic 

border  of  the  left  fold  and  then  its  concavity  crosses  near  the  orifice. 

Jonnesco  has  seen  one  case  of  a  double  duodeno-jejunal  fossa  where  there  were 

three  ligaments.     All  these  are  related  to  the  inferior  mesenteric  vein. 

It  is  not  believed  that  any  of  these  are  pathological.     They  are  more  or  less 

developed  in  children  and  new-born. 


FIG.  619.— Simple  duodeno-jejunal  fossa.    (Jonnesco.) 


Classification. 


I.  Duodenal  fossae  (may  co- 
exist). 


(  Inferior 
(  Superior 


II.  Duodeno-jejunal  or  meso-  ^   Q.      -, 

colic  fossa  (never   coexists  with   >  ^ 

,,  j-     \  I   Double 

the  preceding). 


Non-vascular  most  often.    If  vas- 
cular, is  the  fossa  of  Treitz. 

Always  vascular,  simple 
venous. 

Always  vascular,  venous. 


Fossa  Intersigmoidea. 

Under  the  name  intersigmoid  or  subsigmoid  fossa,  Treitz  described  a  funnel- 
shaped  recess  of  the  peritoneum,  commonly  found  in  the  foetus,  next  most  often 
in  the  child,  and  rather  rarely  in  the  adult.  Its  mouth  opens  below  in  the  left 
iliac  fossa  on  the  left  side  of  the  root  of  the  mesentery  of  the  sigmoid  flexure. 
To  find  it,  turn  the  flexure  over  to  the  right  (Fig.  620). 

The  opening  usually  lies  upon  the  left  external  iliac  vessels  at  the  interval 
between  the  edges  of  the  Iliacus  and  Psoas  muscles. 

The  pouch  runs  up  under  the  parietal  peritoneum  of  the  posterior  abdominal 
wall  and  ends  blind  at  the  point  of  division  of  the  inferior  mesenteric  artery  into 
the  colica  sinistra  and  its  descending  branch.  More  often  the  fossa  is  incom- 
pletely subdivided  by  a  falciform  projection  of  the  wall.  Sometimes  two  separate 
fossae  extend  from  a  single  opening.  Probably  the  fossa  is  formed  by  the  separa- 
tion of  the  two  layers  of  the  peritoneum  behind  the  descending  colon  which 


THE   PERITONEUM. 


997 


formerly  made  the  descending  mesocolon.     On  the  right  side  the  subccecal  fossa 
is  made  in  a  similar  way. 

"  The  Psoas  minor  muscle  can  raise  the  peritoneum  into  a  fold  by  the  spread- 
in»  out  of  its  tendon  of  insertion  into  the  fascia  iliaca ;  at  the  side  of  this  a  peri- 


Inter- 
sigmoid 
fossa. 


Spermatic 

MttEb 


FIG.  620.— Fossa-intersigmoidea.    Sigmoid  flexure  of  a  new-born,  drawn  upward.    (Henle). 


toneal  fossa  may  exist  which  in  some  cases  receives  a  part  of  the  descending 
colon."  Biesiadecki,  who  described  it,  gave  it  the  naine/ossa  iliaco-subfascialis. 
This  fossa,  of  course,  is  of  slight  importance. 

Pericaecal  Fossae. 

At  least  three  fossae  are  to  be  found  in  the  csecal  region.  There  is  no  agree- 
ment upon  their  frequency  and  nomenclature.  Just  above  the  ileo-colic  junction 
between  the  end  of  the  ileum  and  ascending  colon,  bounded  in  front  by  an  ileo- 
colic  fold  may  be  the  ileo-colic  fossa,  also  called  superior  ileo-ccecal.  (Luschka.) 

It  is  just  where  the  mesentery  changes  into  the  peritoneal  coat  of  the  ascend- 
ing colon.  It  is  smaller  and  less  constant  than  the  next. 

Underneath  the  ileum,  between  it  and  the  caecum,  is  the  ileo-ccecal  fossa,  which 
may  be  called  the  inferior  ileo-ccecal,  and  has  been  described  as  the  subcaecal.  It 
lies  between  two  definite  folds  of  peritoneum,  the  formation  of  which  requires 
explanation.  Originally  in  the  human  foetus  there  were  three  folds  passing 
between  the  contiguous  surfaces  of  the  ileum  and  caecum.  These  are  normal 
in  the  spider  monkey  (Fig.  621). 

They  are  called  anterior  vascular,  posterior  vascular,  and  intermediate  non- 

•i ilar  foil*.  In  the  human  subject  the  anterior  vascular  and  the  middle  non- 
vascular  folds  unite  on  the  caecum,  but  do  not  descend  upon  the  appendix ;  the 
posterior  vascular  fold  with  its  contained  posterior  ileo-caecal  artery  passes  to  the 
appendix  and  forms  its  mesentery.  The  space  left  between  this  fold  behind  and 
the  middle  non-vascular  fold  in  front  is  the  ileo-caecal  fossa  (Fig.  622). 

The  subccecal  fossa  is  directly  behind  the  crecurn  ;  it  is  really  post-caecal.  Its 
fundus  may  pass  up  behind  the  ascending  colon,  i.  e.  the  coecuui  in  descending 


998 


THE    ORGANS    OF   DIGESTION. 


from  its  subhepatic  position  has  never  contracted  extensive  adhesions  to  the  pos- 
terior abdominal  wall,  and  a  fossa  is  left  between  the  layers  of  its  mesocolon. 


Anterior 
vascular  fold 


Non-vascular  interme- 
diate fold 

Posterior  vascular  fold 


FIG.  621.— The  three  ileo-csecal  folds  of  Ateles  ater.    (Huntington.) 


The  ascending  colon  can  be  easily  separated  from  its  posterior  connections. 

These  fossae  may  nearly  all  be  the  site  of  retro-peritoneal  hernias.     Attention 

was  first  called  to  such  hernias   as   early  as  1778,  and  a  most  important  work  on 


Posterior  vascular  fold 
'      (proximal  part) 


/       Posterior  vascular  fold 
'or  mesenteriolum 


Non-vascular  inter- 
mediate fold 


lleo-cxcal  fossa-  -/'- 


Entrance  of  appendicu- 
lar  artery 


FIG.  622. — Human  caecum  and  ileo-colon,  showing  ileo-csecal  fossa.    (Huntington.') 

the  subject  appeared  in  1857  by  Treitz,  who  described  the  fossa  of  his  name  and 
reported  cases  of  "  retro-peritoneal "  hernia  through  his  fossa. 


THE   STOMACH. 


999 


Such   cases  are  sometimes  seen  in  the  dissecting-room,  say  about  3  in  1000 

subjects. 

Contents  of  the  Abdominal  Cavity. 

They  are  intra-peritoneal  and  retro-peritoneal,  two  groups.  The  stomach, 
small  and  large  intestine,  liver,  and  spleen  receive  a  more  or  less  complete 
investment  of  peritoneum,  and  are  called  intra-peritoneal  organs.  The  other 
group,  to  which  belong  the  kidneys,  suprarenal  capsules,  pancreas,  and  great 
vessels  are  only  covered  on  the  side  turned  toward  the  abdominal  cavity  by 
parietal  peritoneum  and  are  retro-peritoneal. 

THE   STOMACH. 

Form  and  Size  (Figs.  623  and  624). — The  stomach  is  a  sac-like,  pear-shaped 
dilatation  of  the  alimentary  canal  placed  between  the  oesophagus  and  beginning 


Ant  rum  pyloricum 


FIG.  623.— Anterior  outlines  of  stomach.    His'  model. 


of  the  small  intestine.     Its  big  end  is  directed  above  and  to  the  left,  to  the  dia- 
phragm, its  small  end  below  and  to  the  right.      The  beginning  of  the  stomach  or 


Orificiitm  pyloricum 
Valvula  pylorica 


Antrum  pyloricum 


FIG.  624.— Posterior  outlines  of  stomach.    His'  model. 

its  mouth  is  the  cardia  or  cardiac  opening,  which  passes  from  the  oesophagus  like 


1000 


THE    ORGANS    OF    DIGESTION. 


an  inverted  funnel  without  visible  external  limit.  On  the  inner  surface  a  defi- 
nite line  is  seen  between  the  oesophagus  and  cardia.  Above  the  line  the  mucous 
membrane  is  whitish  and  made  largely  of  pavement  epithelium,  while  below  the 
color  is  red  and  the  mucous  membrane  shows  characteristic  cylindrical  epithe- 
lium. Sometimes  an  external  ring  as  well  as  an  internal  projection  is  found 
between  cardia  and  the  rest  of  the  stomach,  forming  a  kind  of  antrum  cardiacum. 
Passing  from  the  cardia  to  the  left  and  above,  we  find  the  first  great  pouch, 
the  blind  sac  QY  fundus,  whose  relative  size  varies  with  age.  In  early  youth  it  is 
slightly  developed,  in  adult  man  it  forms  about  one-fifth  of  the  stomach. 

This  continues  on  the  right  into  the  body  of  the  stomach,  which  has  two  sur- 
faces— anterior  and  posterior — and  two  borders.  The  anterior  surface  looks 
upward  and  forward,  the  posterior  backward  and  downward,  and  they  are 
included  between  the  borders  lesser  curvature,  concave  and  turned  to  the  right 
and  above,  and  larger  curvature,  convex  and  three  or  four  times  as  large  as  the 
lesser,  turned  to  the  left  and  below  (Figs.  623  and  624). 

At  the  right  the  body  of  the  stomach  gradually  contracts  toward  its  duodenal 
end.  Then  follows  a  second  smaller  part  of  the  stomach,  the  portio  pylorica,  which 
includes  the  antrum  pyloricum,  whose  form  and  size  vary.  Usually  the  antrum 
appears  as  a  double  pouch ;  the  flatter  one  is  higher  and  extends  from  the  lesser 
curvature  to  the  beginning  of  the  duodenum.  It  is  not  very  distinctly  marked 
off  from  the  body.  The  other  lies  laterally  and  is  separated  by  a  more  or  less 
deep  notch  from  the  greater  curvature  (Fig.  627). 

Sometimes  a  third  one  is  found  under  this  last  one.  On  the  inner  surface  of 
the  stomach  there  is  sometimes  a  mucous  fold,  plica  prcepylorica,  separating  the 
antrum  from  the  body  of  the  stomach.  The  pouches  representing  the  antrum 
pylori  are  caused  by  two  flat  ligamentous  bands  some  millimeters  wide,  one  run- 
ning along  the  anterior  wall,  one  on  the  posterior.  They  are  called  pyloric  liga- 
ments (lig.  pyloricum)  and  lie  between  the  muscular  and  serous  coats  and  are 
closely  fused  with  the  latter  (Fig.  627). 

The  division  between  the  stomach  and  intestine  is  marked  externally  by  a 
circular  constriction,  sulcus  pyloricus,  and  more  deeply  by  a  muscular  ring, 

sphincter  pyloricus,  and  internally 
by  a  corresponding  projection  of 
mucous  membrane  called  valvula 
pylorica  or  pylorus  (Fig.  625). 

The  valve  usually  presents  a 
round  opening,  bigger  or  smaller — 
orificium  duodenale — which  may  have 
a  central  or  eccentric  position.  It 
may  not  be  an  enclosing  ring  but  a 
crescentic  projection,  and  rarely  con- 
sists of  two  halves  lying  opposite 
each  other. 

The  first   part  of  the  duodenum   is   often  pouched,   called  antrum  duodeni. 
The  size  of  the  stomach  varies  according  to  age,  sex,  individual,  and  degree 
of  distention. 

A  woman's  stomach  increases  more  in  length,  is  more  slender,  and  in  general 
smaller  than  that  of  a  man.  In  moderate  distention  Sappey  found  the  greatest 
diameter  of  the  stomach  to  be  24-26  cm.  (10-12  inches),  from  the  lesser  to  the 
greater  curvature  10—12  cm.  (4-5  inches),  and  from  the  anterior  to  the  posterior 
wall  8—9  cm.  (3J  inches).  The  distance  between  the  two  orifices  is  three  to  six 
inches.  Luschka,  by  blowing  up  the  stomach,  found  its  long  axis  to  measure  34 
cm.,  greatest  vertical  diameter  15  cm.,  greatest  antero-posterior  diameter  11.5 
cm.,  and  smallest  antero-posterior  diameter,  at  pylorus,  3.7  cm. 

In  the  empty  condition,  as  in  the  dead  subject,  the  greatest  diameter  is  reduced 
to  18-20  cm.,  the  second  diameter  is  7—8  cm.,  and  the  third  disappears  as  the  two 
walls  touch. 


Gastric  mucous  membrane 
Circular  muscular  fibres 
Longitudinal  muscular  fibres 
Peritoneum 


FIG.  625.— Diagrammatic  view  of  coats  of  the  stom- 
ach, duodenum,  and  pylorus.    (Allan  Thomson.) 


THE   STOMACH. 


1001 


The  weight  of  the  freed  stomach  is  in  the  male  about  four  and  a  half  ounces. 
Its  normal  capacity  in  the  adult  male  is  2.5-4  litres  (5-8  pints). 

A  blown-up    stomach  dried    contained  5   pounds  of  water,  female;    and    8 
pounds,  male. 

Position  and  Relations  of  the  Stomach. 

It  lies  in  the  epigastric  region  and  left  hypochondrium,  rarely  in  the  right 
hypochondriuni,  about  five-sixths  to  the  left  of  the  median  line,  and  one-sixth  to 


Lower  lung 
limit 

'eural 
limit 


Diaphraffn 


•  Heart-contour 


Stomach 


Umbilicus  • 


Cxcum  -  <• 


Peritoneum  — 


7 


J 


Small  inUstine 


^Sigmoid 

J-.J-:        , 


-/;:  id  ler 


FIG.  626.— Relations  of  the  abdominal  viscera.    (Joessel.) 

the  right.  Of  the  left  segment  the  greater  part  lies  in  the  left  hypochondrium. 
viz.  the  cardia.  fundus.  and  the  most  curved  part  of  the  body ;  the  rest  of  the 
body  and  a  part  of  the  pars  pylorica  fall  in  the  left  part  of  the  epigastrium.  The 
only  part  belonging  to  the  right  half  includes  a  very  small  portion  of  the  pars 
pylorica  and  the  pylorus.  The  stomach  then  lies  under  the  diaphragm  and  liver, 
above  the  jejunum,  ileum.  and  transverse  colon,  extending  its  greater  part  into 
the  left  hypochondrium  and  smaller  part  into  the  epigastrium  between  the  spleen 
on  the  left  and  gall-bladder  on  the  right  It  does  not  lie  transversely  nor  yet  so 


1002  THE    ORGANS    OF  DIGESTION. 

vertically  as  Luschka  puts  it,  unless  in  the  infant  or  in  the  female  deformed  by 
corsets.  It  is  directed  from  above  and  the  left  downward  and  forward  to  the 
right.  An  empty  stomach  may  hang  nearly  vertically  and  present  an  anterior 
and  a  posterior  surface,  but  there  is  usually  some  obliquity.  If  the  small  intes- 
tines are  much  distended  it  may  be  transverse,  or  if  rigor  mortis  be  rapid  it  may 
be  cylindrical,  especially  below. 

In  moderate  distention  the  cardia  lies  2—3  cm.  (1  inch)  below  the  cesophageal 
opening  of  the  diaphragm  (Fig.  626). 

This  point  is  distant  about  11  cm.  from  the  anterior  body-wall,  is  opposite  the 
sternal  junction  of  the  left  seventh  costal  cartilage,  and  that  corresponds  to  the 
left  side  of  the  eleventh  thoracic  vertebra.  A  horizontal  line  drawn  backward 
from  the  ziphoid  cartilage  to  the  vertebral  column  marks  the  transition  from  cardia 
to  oesophagus.  The  fundus  is  3-5  cm.  higher  than  the  cardia.  It  lies  in  the  left 
hypochondrium  and,  if  distended,  against  the  left  cupola  of  the  diaphragm,  which 
separates  it  from  the  overlying  lung.  Its  highest  point  on  the  cadaver  reaches  a 
horizontal  line  connecting  the  sternal  end  of  the  left  sixth  costal  cartilage  and  the 
vertebral  end  of  the  tenth  rib. 

In  its  full  condition  the  fundus  lies  upon  the  upper  half  of  the  inner  surface 
of  the  spleen,  connected  by  the  gastro-splenic  omentum.  A  full  stomach  there- 
fore may  intrude  upon  respiration,  or  it  may  touch  the  left  part  of  the  central 
tendon  and  exert  an  influence  on  the  heart's  action,  or  may  compress  the  big  ves- 
sel trunks  on  the  vertebral  column. 

The  anterior  surface  of  the  body  of  the  stomach  touches  on  the  left  the  poste- 
rior surface  of  the  anterior  thoracic  Avail,  where  it  is  covered  by  the  anterior  parts 
of  the  seventh,  eighth  and  ninth  ribs.  The  part  of  the  lesser  curvature  lying 
next  is  covered  by  the  liver.  Thus  one  finds  in  the  so-called  gastric  fossa  of  the 
abdomen  not  only  the  stomach  but  the  liver  in  front  of  it.  Between  the  part 
covered  by  the  liver  and  that  covered  by  the  left  ribs,  there  is  a  triangular  section 
of  about  40  sq.  cm.  of  the  anterior  wall  of  the  stomach  in  contact  with  the 
abdominal  wall.  It  is  bounded  on  the  left  by  the  cartilaginous  ends  of  the 
seventh,  eighth  and  ninth  ribs,  on  the  right  by  the  anterior  margin  of  the  liver, 
and  below  by  the  transverse  colon.  This  is  the  only  part  of  the  stomach  to  be 
actually  seen  when  the  subject  is  opened.  This  is  the  part  which  the  surgeon 
can  readily  approach  in  operation.  In  the  new-born  the  stomach  is  wholly  covered 
by  the  left  lobe  of  the  liver. 

The  posterior  surface  of  the  body  covers,  in  moderate  distention,  the  end  of 
the  transverse  colon  and  its  splenic  flexure.  The  greater  part  of  the  posterior 
surface  of  the  stomach  rests  on  a  "bed  "  formed  largely  by  the  transverse  colon 
and  its  upper  layer  of  mesocolon.  If  the  organs  are  hardened  in  situ,  the  trans- 
verse mesocolon  Avill  be  found  to  present  a  concavity  directed  upward,  correspond- 
ing to  the  convex  shape  of  the  stomach,  and  thus  the  latter  receives  great  support. 
Still  in  this  bed  are  the  pancreas  with  the  splenic  vessels  running  along  its  upper 
border,  the  upper  part  of  the  left  kidney,  the  left  suprarenal  capsule,  spleen, 
bursa  omentalis,  duodenum,  and  left  crus  of  diaphragm  .(Fig.  680).  Cases  are 
known  where  ulcers  on  this  surface  of  the  stomach  have  perforated  branches  of 
the  splenic  artery  and  caused  fatal  haemorrhage. 

The  lesser  curvature,  with  its  concavity  directed  to  the  right  and  upward  toward 
the  under  surface  of  the  liver,  descends  in  front  of  the  vertebral  portion  of  the 
diaphragm  at  first  quite  obliquely  along  the  left  side  of  the  eleventh  and  twelfth 
thoracic  vertebrae,  then  crosses  the  vertebral  column  at  the  level  of  the  first  lumbar 
vertebra,  and  then  ascends  into  the  pylorus.  The  greater  curvature  forms  a  con- 
vex arch  directed  below.  In  moderate  distention  it  crosses  the  epigastrium  in  a 
line  which  connects  the  cartilages  of  the  two  ninth  or  tenth  ribs.  This  line 
usually  lies  two  fingers'  breadth  above  the  umbilicus.  In  great  distention  the 
great  curvature  can  reach  it,  and  in  pathological  cases  can  descend  far  below  it. 
The  portio  pylorica,  bent  backward  and  outward,  lying  in  the  epigastrium,  is 
covered  by  the  quadrate  lobe  of  the  liver.  The  pylorus  is  to  the  right  and  some- 


THE  STOMACH.  1003 

what  below  the  ziphoid  process  between  the  sternal  and  parasternal  lines  on  a 
level  with  the  upper  edge  of  the  first  lumbar  vertebra.  This  may  extend  into  the 
right  hypochondriurn.  In  an  empty,  fasting  stomach  these  relations  are  all 
changed  and  the  surfaces  of  contact  are  small.  In  a  well-filled  stomach  a 
twist  of  the  organ  occurs,  so  that  the  anterior  surface  comes  to  be  more  superior 
and  the  posterior  surface  more  inferior.  The  lesser  curvature  is  more  directed 
toward  the  vertebral  column  and  the  greater  curvature  toward  the  anterior  abdomi- 
nal wall.  The  pylorus  also  moves  more  to  the  right. 

Relations  of  Stomach  in  Detail. 

Cardia.  opposite  left  7th  chondro-sternal  junction. 

Fundus  reaches  left  6th  costal  cartilage  and  left  cupola  of  diaphragm. 

Pylorus  reaches  upper  border  of  1st  L.  vertebra  to  the  right  of  the  median 
line. 

Lowest  edge  of  greater  curvature  in  median  line  reaches  to  within  two  fingers' 
breadth  of  the  umbilicus. 

Anteriorly : 

Diaphragm ;  . 

Thoracic  wall  formed  by  anterior  parts  of  7th,  8th,  and  9th  ribs ; 

Quadrate  and  left  lobes  of  liver; 

Anterior  abdominal  wall. 

Posteriorly,  or  "bed:" 
Diaphragm  ; 

Left  crus  of  diaphragm  ; 
Aorta  and  vena  cava  inferior ; 
1st  lumbar  vertebra; 
Coeliac  axis ; 

Bursa  omentalis  (lesser  sac) ; 
Splenic  flexure_of  colon; 
Transverse  colon ; 

Transverse  mesocolon  (upper  layer)  ; 
Gastric  surface  of  spleen  ; 
Left  kidney  and  capsule ; 
Pancreas ; 
Splenic  vessels; 
4th  part  of  duodenum. 

Right  End : 

Junction  of  transverse  colon  and  under  surface  of  liver. 
Left  End: 

Spleen ; 

Diaphragm. 

The  peritoneal  relations  of  the  stomach  have  in  general  been  described.  It 
presents  double  "peritoneal  lines"  on  both  curvatures  and  fundus,  showing  the 
cut  edges  of  peritoneum.  Above,  in  front  of  the  cardia  is  the  attachment  of  the 
gastro-phrenic  ligament  running  down  along  the  lesser  curvature  as  the  anterior 
layer  of  the  lesser  omentum.  Behind  it,  separated  by  a  linear  space  where  the 
stomach  is  uncovered,  is  the  line  for  the  posterior  layer  of  the  lesser  omentum. 
Larger  triangular  spaces  are  left  uncovered  at  either  end  of  the  stomach.  On 
the  greater  curvature  is  the  double  line  indicating  the  two  layers  of  the  anterior 
lamella  of  the  great  omentum  running  on  the  left  into  the  two  lines  of  the  gastro- 
splenic  omentum. 

Points  of  Fixation  of  the  Stomach. — It  is  a  part  very  well  secured,  especially 
by  the  oesophagus  fastened  to  the  diaphragm  and  by  the  duodenum  firmly  bound 


THE    ORGANS    OF   DIGESTION. 


to  the  vertebral  column.  Some  peritoneal  folds  also  aid,  as  the  lig.  phrenico- 
gastricuni  connecting  the  cardia  to  the  diaphragm.  To  the  right  this  joins  the 
lesser  omentum,  which  is  very  thin,  but  farther  to  the  right  is  the  strong  lig. 
hepato-duodenale,  which  confines  the  pylorus.  The  great  omentum  and  gastro- 
splenic  afford  no  fixation  to  the  stomach.  The  spleen  has  no  firmness  of  position, 
so  the  stomach  gains  nothing  by  that  attachment.  The  great  omentum  hangs 
free  in  front  of  the  intestines,  and  could  only  modify  the  position  of  the  stomach 
when  caught  in  a  hernia. 

Alterations  in  Position. — There  is  no  organ  in  the  body  the  position  and  connections  of 
which  present  such  frequent  alterations  as  the  stomach.  During  inspiration  it  is  displaced 
downward  by  the  descent  of  the  Diaphragm,  and  elevated  by  the  pressure  of  the  abdominal 
muscles  during  expiration.  Its  position  in  relation  to  the  surrounding  viscera  is  also  changed 
according  to  the  empty  or  distended  state  of  the  organ.  When  empty  it  lies  at  the  back  part 
of  the  abdomen,  some  distance  from  the  surface.  The  left  lobe  of  the  liver  covers  it  in  front. 
and  the  under  surface  of  the  heart  rests  upon  it  above  and  in  front,  being  separated  from  it  by 
the  left  lobe  of  the  liver,  besides  the  Diaphragm  and  pericardium.  This  close  relation  between 
the  stomach  and  the  heart  explains  the  fact  that  in  gastralgia  the  pain  is  generally  referred  to 
the  heart,  and  is  often  accompanied  by  palpitation  and  intermission  of  the  pulse.  When  f/if 
stomach  is  distended  the  greater  curvature  is  elevated  and  carried  forward,  so  that  the  anterior 
surface  is  turned  upward  and  the  posterior  surface  downward,  and  the  stomach  brought  well 
against  the  anterior  wall  of  the  abdomen.1  The  Diaphragm  at  the  same  time  is  forced  upward, 
contracting  the  cavity  of  the  chest ;  hence  the  dyspnoea  complained  of,  from  inspiration  being 
impeded.  The  heart  is  also  displaced  upward ;  hence  the  oppression  in  this  region  and  the 
palpitation  experienced  in  extreme  distention  of  the  stomach.  Pressure  from  vrim&ut,  as  from 
tight  lacing,  pushes  the  stomach  down  toward  the  pelvis.  In  disease  also  the  position  and  con- 
nections of  the  organ  may  be  greatly  changed,  from  the  accumulation  of  fluid  in  the  chest  or 
abdomen  or  from  alteration  in  size  of  any  of  the  surrounding  viscera. 

Structure. — Its  walls  are  composed  of  four  coats  named  in  order — serous,  mus- 
cular, submucous  or  areolar,  and  mucous. 

The  serous  coat,  peritoneum,  is  thin,  smooth,  and  moist,  allowing  some  -mo- 
bility of  the  organ.  It  encloses  the  stomach  between  two  layers,  derived  from 

the  lesser  omentum.  Where  the 
layers  come  upon  the  surface  and 
leave  it  again — greater  and  lesser 
curvature — they  lie  loosely  and 
leave  a  small  interspace,  in  which 
blood-vessels,  nerves,  lymph-vessels 
and  glands,  take  their  course.  Else- 
where the  serous  layer  is  held  so 
tightly  by  subserous  tissue  to  the 
muscular  coat  that  it  can  only  be 
removed  artificially  in  small  bits. 
There  is  a  small  posterior  area 
near  the  cardia  not  covered  by 
peritoneum  which  touches  the  dia- 
phragm. 

Musculature.  —  Three  sets  of 
unstriated  muscular  tissue  are  here 
included  —  longitudinal,  circular, 
and  oblique.  Their  purpose  is  to 
set  the  stomach  contents  in  motion, 
to  push  them  on,  and  to  empty 
glandular  secretion. 

The  external  or  Ionfii1u<li»«l 
layer  is  very  incomplete  and  is 
directly  continuous  Avith  the  longitudinal  fibres  of  the  oesophagus  (Fig.  627). 
There  is  a  connected  layer  on  the  outer  side  of  the  cardia,  from  which  fibres 

1  This  is  denied  by  Dr.  Lesshaft  of  St.  Petersburg,  who  states  that  "  if  the  stomach  is  enlarged, 
no  one  part  can  be  alone  displaced,  but  all  parts  are  equally  moved  by  the  distention"  (Lancet, 
March  11,  1882,  p.  406). 


FIG.  627.— The  external  muscular  coat  of  the  stomach. 
(Luschka.)  1.  (Esophagus.  2.  Cardia.  3.  Fundus.  4.  Pars 
pylorica.  5.  Lig.  pyloricum.  6.  Sulcus  pyloricus.  7.  Lesser 
curvature.  8.  Greater  curvature.  9.  Antrum  duodcui. 


THE   STOMACH. 


1005 


stream  outward  in  all  directions  with  unequal  lengths.  They  are  thickest  along 
the  lesser  curvature.  At  the  fundus  and  anterior  and  posterior  walls  there  are 
only  a  few  delicate  bundles  which  seem  to  pass  deeply  between  the  circular  fibres. 
The  substantial  longitudinal  layer  is  united  at  the  pylorus,  where  it  is  firmly 
bound  to  the  serous  coat  and  wholly  covers  the  circular  layer.  To  this  layer 
belong  the  tigamtnt'i.  />///"/•/••<•/.  This  layer  passes  over  the  pylorus  to  the  duode- 
nal wall.  The  longitudinal  layer  stands  in  closest  relation  to  the  apertures  of 
the  stomach. 

Circ  itl'.tr  fibres  cover  the  whole  length  of  the  stomach  in  an  uninterrupted 
layer,  but  they  are  not  everywhere  collected  with  the  same  thickness  and  strength 
(Fig.  628).  They  are  fewest  on 
the  fundus.  where  there  is  a  sort 
of  whorl.  They  pass  along  the 
stomach  in  circles  at  right  angles 
to  its  axis,  and  become  thickest 
at  the  pylorus,  where  they  form 
the  sphincter  pyloricus.  On  the 
margin  of  the  duodenum  they 
abruptly  cease.  Above  they  seem 
connected  with  the  circular  coat 
of  the  O2sophagus.  By  this  set 
the  peristaltic  movements  of  the 
stomach  are  produced,  carrying 
the  contents  to  the  pyloric  end, 
where  is  experienced  a  strong 
compression  and  after  that  a  re- 
laxation of  the  antrum  pylori- 
cam  and  of  the  pylorus,  and 
then  the  longitudinal  fibres  can 
exercise  their  expulsive  strength 
on  the  whole  circumference. 

The  oblique  lib  res.  like  the  longitudinal,  form  an  imperfect  layer.  They  lie 
under  the  circular  layer,  and  are  thought  to  be  derived  from  it.  They  can  best 
be  seen  when  the  stomach  is  turned  inside  out  and  the  mucous  membrane  is 
removed.  This  group  is  said  to  have  no  counterpart  in  any  region  of  the  digest- 
ive tract.  They  are  not  believed  to  represent  the  ring  fibres  of  the  oesophagus. 
They  form  a  loose  layer  to  the  left  of  the  cardia  and  pass  superiorly  and  poste- 
riorly toward  the  greater  curvature.  The  upper  edge  of  these  fibres  forms  a 
raised  ligamentous  strip  on  either  side  of  the  lesser  curvature,  about  a  finger's 
breadth  below  it ;  this  goes  in  a  flat  curve  (seen  on  inner  surface  of  stomach)  from 
the  left  of  the  cardia  on  both  sides  toward  the  portio  pylorica.  At  the  apex  of 
the  fundus  and  toward  the  greater  curvature  the  fibres  grow  smaller  and  paler. 
The  bundles  are  apt  to  split  into  a  sort  of  wicker-work,  leaving  longitudinal 
clefts.  Delicate  fibres  run  from  these  to  the  submucosa  and  to  the  circular 
fibres 

These  fibres  seem  able  to  bring  nearer  together  the  cardia  and  pylorus,  the 
greater  and  lesser  curvatures,  and  also  the  contiguous  surfaces  of  the  anterior 
and  posterior  walls,  resulting  in  the  function  of  the  pharyngeal  groove  in  rumi- 
nants. A  sort  of  half  canal  is  formed  along  the  lesser  curvature,  where  fluid 
could  be  sent  directly  from  oesophagus  to  pylorus  or  various  juices  could  be  sent 
in  the  opposite  direction. 

The  mbmucmu  <->:».it  consists  of  loose,  filamentous,  areolar  tissue,  connecting 
the  mucous  and  muscular  layers,  thus  allowing  free  movement  to  the  former.  It 
supports  the  blood-vessels  previous  to  their  distribution  to  the  mucous  membrane. 
The  rugre  of  the  stomach  involve  the  mucous  and  submucous  coats. 

The  mucous  membrane  is  thick,  its  surface  smooth,  soft,  and  velvety.  In  the 
fresh  state  it  is  of  a  pinkish  tinge  at  the  pyloric  end,  and  of  a  red  or  reddish- 


FIG.  6-28.— Musculature  of  the  stomach  from  within.  The 
stomach  has  been  turned  inside  out.  Circular  and  oblique 
fibres.  (Luschka.)  1.  (Esophagus.  2.  Antrum  duodeni.  3.  Cir- 
cular fibres.  4.  Oblique  fibres. 


1006 


THE    ORGANS   OF  DIGESTION. 


brown  color  over  the  rest  of  its  surface.  In  infancy  it  is  of  a  brighter  hue,  the 
vascular  redness  being  more  marked.  It  is  thin  at  the  cardiac  extremity,  but 
thicker  toward  the  pylorus.  During  the  contracted  state  of  the  organ  it  is  thrown 
into  numerous  plaits  or  rugse,  which  for  the  most  part  have  a  longitudinal  direc- 
tion, and  are  most  marked  toward  the  lesser  end  of  the  stomach  and  along  the 
greater  curvature.  These  folds  are  entirely  obliterated  when  the  organ  becomes 
distended. 

Structure  of  the  Mucous  Membrane. — When  examined  with  a  lens  the  inner 
surface  of  the  mucous  membrane  presents  a  peculiar  honeycomb  appearance, 
from  being  covered  with  small  shallow  depressions  or  alveoli  of  a  polygonal 
or  hexagonal  form,  which  vary  from  y^-g  to  -^-^  of  an  inch  in  diameter,  and 
are  separated  by  slightly  elevated  ridges.  In  the  bottom  of  the  alveoli  are 
seen  the  orifices  of  minute  tubes,  the  gastric  follicles,  which  are  situated 
perpendicularly  side  by  side  throughout  the  entire  substance  of  the  mucous  mem- 
brane. 

The  gastric  glands  are  of  two  kinds,  which  differ  from  each  other  in  structure, 


FIG.  629.— Pylorio  gland. 


FIG.  630.— Peptic  gastric  gland. 


and  it  is  believed  also  in  the  nature  of  their  secretion.  They  are  named  respectively 
pyloric  and  peptic  glands.  They  are  both  tubular  in  character,  and  are  formed  of 
a  delicate  basement  membrane,  supporting  epithelium.  The  basement  membrane 
consists  of  flattened  transparent  endothelial  cells,  with  processes  which  extend  and 
support  the  epithelium.  The  pyloric  glands  (Fig.  629)  are  most  numerous  at  the 
pyloric  end  of  the  stomach,  and  from  this  fact  have  received  their  name.  They  were 
formerly  termed  mucous  glands,  and  were  supposed  to  secrete  mucus ;  but,  as  Klein 
points  out,  "  the  cells  are  serous,  not  mucous,  and  the  secretion  of  the  glands  cannot 
therefore  be  mucus."  They  consist  of  two  or  three  short  closed  tubes  opening 
into  a  common  duct,  the  external  orifice  of  which  is  situated  at  the  bottom  of  an 
alveolus.  The  caeca!  tubes- are  wavy,  and  are  of  about  equal  length  with  the  duct. 
The  tubes  and  duct  are  lined  throughout  with  epithelium,  the  duct  being  lined 
by  columnar  cells  continuous  with  the  epithelium  lining  the  surface  of  the  mucous 


THE   STOMACH.  1007 

membrane  of  the  stomach,  the  tubes  with  shorter  and  more  cubical  cells,  which  are 
finely  granular.  The  y/cy//<-  ///<//?</«  (Fig.  630)  are  found  all  over  the  surface  of  the 
stomach.  Like  the  pyloric  glands,  they  consist  of  a  duct  into  which  open  two  or 
more  ciecal  tubes.  The  duct,  however,  in  these  glands  is  shorter  than  in  the  other 
variety,  sometimes  not  amounting  to  more  than  one-sixth  of  the  whole  length  of 
the  gland  ;  it  is  lined  throughout  by  columnar  epithelium.  At  the  point  where 
the  terminal  tubes  open  into  the  duct,  and  which  is  termed  the  neck,  the  epithe- 
lium alters,  the  cells  becoming  much  shorter  and  opaque:  the  lumen  also  becomes 
suddenly  constricted,  and  is  continued  down  to  the  bottom  of  the  tubes  as  a  very 
fine  channel.  Here  also  are  found,  between  the  epithelium  and  the  basement 
membrane,  large  spheroidal,  coarsely  granular  cells,  which  were  formerly  termed 
fn'l>ti''  'V//X.  and  which  produce  an  outward  bulging  of  the  basement  membrane. 
They  are  seen  throughout  the  remainder  of  the  tube  at  intervals,  and  give  it  a 
beaded  or  varicose  appearance.  Below  the  neck  the  terminal  tubes,  in  addition 
to  these  isolated  spheroidal  cells,  are  occupied  with  finely  granular,  angular  cells 
(columnar,  Klein),  leaving  only  a  small  channel  in  the  centre.  They  are  continuous 
with  the  short  columnar  cells  of  the  neck,  and  are  termed  the  central  or  chief  cells, 
because  they  are  believed  to  be  principally  concerned  in  the  secretion  of  the  gastric 
juice.  The  peptic  cells,  Avhich  were  formerly  supposed  to  possess  this  office,  are 
now  termed  parietal  or  oxyntic  cells.  Between  the  glands  the  mucous  membrane 
consists  of  a  connective  tissue  framework,  with  lymphoid  tissue.  In  places  this 
latter  tissue,  especially  in  early  life,  is  collected  into  little  masses,  which  to  a  certain 
extent  resemble  the  solitary  glands  of  the  intestine,  and  are  bv  some  termed  the 
lenticular  glands  of  the  stomach.  They  are  not,  however,  so  distinctly  circum- 
scribed as  the  solitary  glands.  The  epithelium  lining  the  mucous  membrane  of 
the  stomach  and  its  alveoli  is  of  the  columnar  variety.  Beneath  the  mucous 
membrane,  and  between  it  and  the  submucous  coat,  is  a  thin  stratum  of  involuntary 
muscular  fibre  (muscnlaris  mucosce),  which  in  some  parts  consists  only  of  a  single 
longitudinal  layer ;  in  others,  of  two  layers,  an  inner,  circular,  and  an  outer, 
longitudinal. 

Vessels  and  Nerves. — The  arteries  supplying  the  stomach  are — the  gastric,  the 
pyloric  and  right  gastro-epiploic  branches  of  the  hepatic,  the  left  gastro-epiploic 
and  vasa  brevia  from  the  splenic.  They  supply  the  muscular  coat,  ramify  in  the 
submucous  coat,  and  are  finally  distributed  to  the  mucous  membrane.  The 
arrangement  of  the  vessels  in  the  mucous  membrane  is  somewhat  peculiar.  The 
arteries  break  up  at  the  base  of  the  gastric  tubules  into  a  plexus  of  fine  capillaries 
Avhich  run  upward  between  the  tubules,  anastomosing  with  each  other,  and  ending 
in  a  plexus  of  larger  capillaries,  which  surround  the  mouths  of  the  tubes  and  also 
form  hexagonal  meshes  around  the  alveoli.  From  these  latter  the  veins  arise,  and 
pursue  a  straight  course  backward  between  the  tubules,  to  the  submucous  tissue, 
and  terminate  either  in  the  splenic  and  superior  mesenteric  veins  or  directly  in 
the  portal  vein.  The  lymphatics  are  numerous;  they  consist  of  a  superficiarand 
deep  set,  which  pass  through  the  lymphatic  glands  found  along  the  two  curvatures 
of  the  organ.  The  nerves  are  the  terminal  branches  of  the  right  and  left  pneumo- 
gastric.  the  former  being  distributed  upon  the  back,  and  the  latter  upon  the  front 
part  of  the  organ.  A  great  number  of  branches  from  the  sympathetic  also  supply 
the  organ. 

Surgical  Anatomy. — Operations  on  the  stomach  are  frequently  performed.  By 
strotomy"  is  meant  an  incision  into  the  stomach  for  the  removal  of  "a  foreign  body,  the 
opening  being  immediately  afterward  closed— in  contradistinction  to  ''gastrostoniy/'  the 
making  of  a  more  or  less  permanent  fistulous  opening.  Gastrotomy  is  probably  best  performed 
by  an  incision  in  the  linea  alba,  especially  if  the  foreign  body  is  large.  l»y  a  cut  from  the 
ensifonn  cartilage  to  the  umbilicus,  but  may  be  performed  by  an  incision  over  the  body  itself, 
where  this  can  be  felt,  or  by  one  of  the  incisions  for  gastrostoniy,  to  be  mentioned  immediately. 
The  peritoneal  cavity  is  opened,  and  the  point  at  which  the  stomach  is  to  be  incised  decided 
upon.  This  pardon  is  then  brought  out  of  the  abdominal  wound  and  sponges  carefully 
packed  around.  The  stomach  is  now  opened  by  a  transverse  incision  and  the  foreign  body 
extracted.  The  wound  in  the  stomach  is  then  closed  by  Lembert's  sutures — i.  e.  by"  sutures 
i  through  the  peritoneal  and  muscular  coats  in  such  a  way  that  the  peritoneal  surfaces 


1008  THE    ORGANS    OF  DIGESTION. 

on  each  side  of  the  wound  are  brought  into  apposition,  and  in  this  way  the  wound  i& 
closed.  Gastrostomy  is  performed  in  two  stages:  The  first  stage  consists  in  opening  the 
peritoneal  cavity  and  stitching  the  stomach  to  the  abdominal  wall.  The  second  stage  consists  in 
opening  the  stomach  after  a*few  clays  have  elapsed  and  adhesions  formed  between  the  peritoneal 
surfaces  of  the  stomach  and  abdominal  wall.  The  operation  is  usually  performed  by  an 
oblique  incision  about  one  finger's  breadth  below  and  parallel  with  the  margin  of  the 
left  costal  cartilages,  commencing  an  inch  and  a  half  from  the  median  line  and  being  about 
three  inches  in  length.  Some  surgeons  prefer  a  straight  incision,  beginning  opposite  to  the 
end  of  the  eighth  intercostal  space,  and  passing  down  for  three  inches  over  the  Rectus  abdominia 
muscle.  The  skin,  fasciae,  and  muscles  are  to  be  severally  divided  down  to  the  peritoneum. 
Howse  recommends  that  the  sheath  of  the  Rectus  should  be  opened  longitudinally,  and  the  fibres 
of  this  muscle  separated,  and  not  cut,  in  the  same  direction,  so  as  to  secure  a  sphincter-like  action 
around  the  opening.  After  the  peritoneum  has  been  opened  the  stomach  is  recognized  by  its 
pink-red  color  and  smooth  surface.  It  is  to  be  pulled  up  into  the  wound  and  sutured  to  the 
opening.  This  may  be  done  in  several  ways,  but  in  whatever  way  it  is  done  the  following  points 
should  be  carefully  attended  to:  (1)  In  taking  up  the  stomach  only  to  pass  the  needle  through 
the  serous  and  muscular  coats,  and  avoid  puncturing  the  mucous  membrane.  (2)  To  take  up 
plenty  of  the  muscular  coat.  (3)  In  passing  the  needle  through  the  parietes  of  the  abdomen  to 
be  careful  to  include  the  parietal  peritoneum.  (4)  To  enclose  a  circle  of  the  stomach  at  least  an 
inch  in  diameter.  If  the  symptoms  admit  of  it,  the  parts  are  now  to  be  left  quiet  for  four  01 
five  days,  and  a  small  puncture  is  then  to  be  made  through  the  exposed  portion  of  the  stomach. 
and  a  gum  elastic  catheter  passed  through  it  into  the  viscus,  through  which  fluid  can  be  injected, 
in  small  quantities  at  first.  In  more  urgent  cases  it  may  be  necessary  to  make  the  opening  much 
earlier. 

Excision  of  the  pylorus  has  occasionally  been  performed,  but  the  results  of  this  operation  are 
by  no  means  favorable,  and  in  cases  of  cancer  of  the  pylorus  gastro-enterostomy  is  generally  pre- 
ferred. The  object  of  this  operation  is  to  make  a  fistulous  communication  between  the  stomach, 
on  the  cardiac  side  of  the  disease,  and  the  small  intestine,  as  high  up  as  is  possible. 

THE  INTESTINAL  CANAL. 

This,  in  the  form  of  a  curved  tube,  passes  uninterruptedly  from  the  pylorus 
to  the  anus.  It  has  a  remarkable  length  of  about  six  times  the  height  of  its  pos- 
sessor, though  in  the  adult  it  may  be  independent  of  the  age,  height,  or  weight. 
In  this  relation  man  stands  midway  between  the  herbivores,  e.  g.  rabbit  with  very 
long  intestine,  and  carnivores,  e.  g.  lion,  whose  intestine  is  three  times  the  length 
of  its  body.  There  is  some  evidence  to  prove  that  vegetarians  may  have  a  longer 
intestine  than  those  living  on  a  mixed  or  a  flesh  diet.  The  wall  of  the  intestine 
offers  throughout  a  serous,  muscular  and  mucous  coat  presenting  many  modifica- 
tions, by  which  the  upper  four-fifths  is  distinguished  as  small  intestine  and  the 
lower  fifth  as  large  intestine. 

The  Small  Intestine. 

By  this  term  is  understood  the  part  of  the  alimentary  canal  extending  from 
the  pylorus  to  the  ileo-csecal  valve.  Its  average  length  is  about  8  metres  or 
(Luschka)  25  feet,  or  6  metres  longer  than  the  whole  body ;  Treves  says  22£  feet, 
and  Quain  22-  feet.  The  extremes  found  are  34  feet  and  8  feet.  Its  circumfer- 
ence decreases  from  the  stomach  toward  the  large  intestine  from  12.8  cm.  to  9.5 
cm.  Its  capacity,  inflated  and  dried,  is  15  pints.  The  wall  of  the  ileum  is  so  thin 
and  translucent  that  a  newspaper  may  be  read  through  it. 

The  small  intestine  is  divided  into  three  parts : 

1.  Duodenum  (12-finger  intestine) ; 

2.  Jejunum  (empty  intestine) ; 

3.  Ileum  (curved  or  twisted  intestine). 

The  Duodenum. 

The  duodenum,  begins  at  the  sulcus  pyloricus  and  ends  at  the  duodena- jejunal 
angle  or  flexure,  where  it  becomes  jejunum.  It  was  named  by  Herophilus,  but  it 
possesses  neither  the  length  nor  the  breadth  of  twelve  fingers. 

A  better  name  would  be  intestinum  pancreaticum  (Luschka)  on  account  of  its 
intimate  relation  to  the  pancreas.  In  the  adult  male  its  axial  length  is  30  cm. 
(or  10-12  inches),  and  its  usual  circumference  12  or  13  cm.  (1.5  to  2  inches  in 
diameter).  Authors  fail  to  agree  on  its  direction  and  form. 


THE   INTESTINAL    CANAL. 


1009 


1.   French  authors  give  three  portions,  ending  it  at  the  superior  mesenteric 

Is  :  superior  horizontal,  vertical,  and  inferior  horizontal  parts. 
-.   To  this  third  part  Henle,  Krause,  Quain,  and  others  add  a  fourth  oblique 
part  ascending  from  right  to  left. 

3.  Luschka.   His.   and   Braune    describe   an 
annular  form. 

4.  Cruvielhier,  Young,  and  Treves  describe 
a  fourth  portion  2  cm.  long,  coming  forward  at 
the  end  of  duodenum,  by  joining  the  duodeno- 
jejunal  junction.     They  are  all  described  as  dif- 
ferent types,  of  which,  according  to  Jonnesco,1 
there  are  three. 

1.  Annular  or  circular  type,  infantile; 

±    V-*Ji«ped  type,  \  ^^      rare     in    infent 

3.  V '-shaped  type,  J 

(Figs.  632  and  633). 

The  typical  annular  form  is  always  found  in 
the  child  up  to  about  the  age  of  seven  (Fig. 
631). 

The  terminal  point  of  this  variety  is  strongly 
fixed  to  the  left  side  of  the  first  lumbar  vertebra 
and  is  exactly  on  the  same  level  as  the  begin- 
ning of  the  duodenum,  and  hence  is  behind  the  stomach  (Fig.  634). 

Between  these  points,  the  one  fastened  by  tbe  muscle  of  Treitz  and  the  other 
by  the  hepato-duodenal  ligament,  the  duodenum  describes  a  regular  curve  in  front 
of  the  vertebral  column.  This  ring  is  filled  and  its  margins  overlapped  by  the 


FIG.  631.— Annular  duodenum.  Infan- 
tile type,  from  boy  of  three  years.  (Jon- 
nesco.) 


Aorta 


Aorta 


Musclf  of  Treitz 


FIG.  632. — Duodenum  in  U-    (Jonnesco.) 


FIG.  633. — Duodenum  in  V.    (Jonnesco.) 


head  of  the  pancreas,  the  neck  of  which  is  limited  by  the  two  extremities  of  the 
ring. 

In  the  adult  this  type  may  be  found,  but  the  terminal  point  does  not  usually 
attain  the  same  level  that  the  origin  has ;  it  is  pushed  back  more  to  the  left  as 
though  the  developing  neck  of  the  pancreas  had  forced  the  duodenal  ring  to  open 
more  widely  for  its  lodgment. 

Course  of  the  Adult  Duodenum. — Separated  from  the  pylorus  at  the  right  of 
the  upper  edge  of  the  first  lumbar  vertebra  there  is  usually  at  first  a  bottle-shaped 
dilatation,  the  antrum  duodeni.  The  direction  of  the  first  portion  depends  on  the 
condition  and  length  of  the  stomach  and  position  of  the  pylorus.  With  an  empty 
stomach  the  first  part  is  nearly  horizontal  and  transverse.  With  a  distended 
stomach,  it  is  nearly  antero-posterior :  its  distal  end  is  stationary  and  its  proxi- 
1  ''  Anat.  topographique  du  duodenum,"  Jonnesco,  Paris,  1889. 


1010 


THE    ORGANS    OF  DIGESTION. 


mal  end  is  not.  In  general,  it  is  directed  upward  to  the  right  and  backward 
under  the  quadrate  lobe  of  the  liver  and  curves  backward  under  the  neck  of  the 
gall-bladder  to  make  a  sharp  turn  to  the  right  surface  of  the  lumbar  column. 
This  is  the  initial  curve.  It  is  so  closely  related  to  the  liver  and  gall-bladder 
that  it  is  stained  by  bile  soon  after  death.  Behind  it  are  the  common  bile-duct, 
vena  portne,  and  gastro- duodenal  artery.  Behind  and  to  the  left  is  the  neck  of 
the  pancreas,  and  below,  the  head  of  the  pancreas.  Its  anterior  surface  and  a 
part  of  its  posterior  surface  near  the  pylorus  are  wholly  covered  by  peritoneum, 
derived  from  the  lig.  hepato-duodenale.  The  length  of  this  portion  is  so  variable, 
"  two  inches  "  (Quain),  "  often  almost  inappreciable  "  (Jonnesco),  that  the  latter 
author  unites  it  and  the  curve  which  follows  it  under  one  name,  the  superior 
hepatic  curve  of  the  duodenum  (Fig.  634).  Placed  on  the  vena  cava  inferior  and 


Portal  veta 

Hepatic  duct 

Cystic  duct 

Hepatic  artery 

Right  suprarenal 

capsule 

Pyloric  orifice \ 

Rigid  gastro-epiploic 
artery 


Superior  mesenteric 
vein 


Spermatic  vessels 


Spermatic  vessels 
Inferior  mesenteric  artery 


FIG.  634.— View  of  duodenum  and  its  five  parts,  a,  6,  c,  d,  and  e,  and  pancreas.    The  part  of  stomach 
removed  is  indicated  by  dotted  lines.    (Testut.) 


right  kidney,  it  next  descends  along  the  right  side  of  the  vertebral  column  a 
variable  length,  usually  to  the  body  of  the  fourth  lumbar  vertebra,  starting  from 
the  right  side  of  the  first.  This  is  called  the  vertical,  descending,  or  second  por- 
tion. It  is  three  or  four  inches  long  and  divided  into  two  parts,  supracolic  and 
infracolic,  since  the  transverse  colon  crosses  its  middle  third.  The  two  layers  of 
transverse  mesocolon  (Fig.  679)  leave  an  interspace  uncovered  by  peritoneum 
Avhere  the  approximated  surfaces  of  duodenum  and  transverse  colon  touch  except 
for  a  little  areolar  tissue.  Above  and  below  this  place  its  anterior  surface  and 


THE  INTESTINAL    CANAL.  1011 

sides  are  covered  with  peritoneum.  Above  it  is  in  contact  with  the  right  lobe  of 
the  liver,  leaving  its  "impression."  Posteriorly  there  is  no  peritoneum,  areolar 
tissue  connecting  it  with  the  kidney,  vessels  at  its  hilus.  and  vena  cava.  The 
pancreatic  and  common  bile-ducts  open  into  its  postero-internal  wall  below  the 
middle.  The  head  of  the  pancreas  is  to  its  inner  side. 

Now  the  duodenum  changes  its  direction  and  passes  more  or  less  horizontally 
from  right  to  left  in  front  of  the  great  vessel-trunks  and  crura  of  the  diaphragm, 
moulding  itself  over  the  third  or  fourth  lumbar  vertebra.  This  is  the  transverse 
or  pre-aortii-  portion  and  is  two  or  three  inches  long.  The  head  of  the  pancreas 
is  above  it.  It  is  crossed  by  the  superior  mesenteric  vessels  and  mesentery.  Its 
anterior  surface  is  covered  by  the  peritoneum  of  the  mesentery,  but  is  separated 
from  it  when  the  superior  mesenteric  vessels  cross  it  from  above.  On  the  right 
its  posterior  surface  has  no  peritoneal  covering,  but  on  the  left  the  posterior  layer 
of  the  mesentery  may  be  prolonged  behind  it.  In  the  middle  line  this  part  of 
the  duodenum  is  situated  at  the  point  of  divergence  of  the  two  layers  of  the  root 
of  the  mesentery  (Fig.  606). 

Thence  the  duodenum  ascends  along  the  left  side  of  the  vertebral  column  and 
aorta,  touches  the  left  kidney,  lies  upon  the  left  crus  of  the  diaphragm,  and  ends 
at  the  left  side  of  the  second  or  first  lumbar  vertebra.  This  part  is  about  two 
inches  long  and  is  called  the  fourth  or  ascending  portion. 

It  often  turns  abruptly  forward  to  unite  with  the  jejunum  and  form  the  duo- 
deno-jejunal  angle.  This  terminal  portion,  about  2  cm.  long  (less  than  one  inch), 
has  been  described  as  the  fourth  portion,  but  with  the  U-shaped  duodenum  it 
makes  the  fifth  portion. 

The  duodenum  begins  with  a  short  portion  looking  backward  and  ends  with  a 
short  portion  looking  forward. 

The  five  parts  are — 1.  Superior  hepatic  curve,  or  pars  superior  horizontalis. 
'2.  Descending  or  vertical  portion.  3.  Pre-aortic  or  transverse  portion.  4.  Ascend- 
ing portion.  5.  Terminal  portion  to  form  (6)  the  duodeno-jejunal  angle. 

When  the  above  arrangement  is  complete,  the  duodenum  has  the  form  of  the 
letter  U,  considering  the  second,  third,  and  fourth  portions  (Figs.  632  and  634). 
When,  however,  the  descending  and  ascending  portions  unite  by  a  short  curve 
or  angle,  the  transverse  portion  is  practically  lacking,  and  the  duodenum  is  then 
V-shaped  (Fig.  633).  The  angle  of  the  V  is  thrown  to  the  right  against  the  vena 
cava,  and  the  ascending  portion  crosses  the  abdominal  aorta  at  a  sharp  angle. 
The  U-shaped  duodenum  usually  descends  to  the  fourth  lumbar  vertebra,  and 
seems  to  occur  in  foetal  life  when  the  ascending  colon  obstructs  the  way.  The 
V-shaped  duodenum  usually  descends  to  the  fifth  lumbar  vertebra,  and*  occurs 
when  there  is  plenty  of  room  and  no  obstruction  by  the  descent  of  the  ascending 
colon. 

The  lengths  of  the  parts  vary  in  the  two  types  thus  (measured  from  fifteen 
subjects) : 

Duodenum— 
In  U-         In  V. 

Superior  curve 4  cm.        4  cm. 

Descending  portion 10.5  "         12     " 

Pre-aortic  portion 9.5  "  2     " 

Ascending  portion 7     "         13     " 

3l  31 

Peritoneal  Relations  of  the  Duodenum. — The  duodenum  is  included  among  the 
extra-peritoneal  viscera.  In  the  foetus  it  is  completely  invested,  but  the  two 
layers  of  its  mesentery  have  been  separated  or  perhaps  appropriated  by  the  rapidly 
growing  kidneys,  and  its  posterior  surface  has  adhered  to  the  posterior  abdominal 
wall.  Its  visceral  layer  has  become  parietal  peritoneum.  To  get  at  this  peri- 
toneum it  is  necessary,  on  the  cadaver,  to  practise  certain  manipulations :  to 
disclose  the  initial  superior  parts,  draw  the  hepatic  flexure  of  the  colon  down  and 
to  the  left,  and  lift  up  the  anterior  margin  of  the  liver.  The  pylorus  and  supe- 


1012 


THE    ORGANS    OF  DIGESTION. 


rior  curve  of  the  duodenum  can  be  seen  attached  to  the  liver  by  a  ligament  in 
which  can  be  felt  three  cords,  the  lig.  hepato-duodenale,  and  to  the  gall-bladder 
by  a  simple  fold,  the  lig.  cystico-duodenale. 

Now  pull  toward  the  left  this  superior  curve  of  the  duodenum,  and  a  deep 
space  is  formed  bounded  above  by  the  right  lobe  of  the  liver.  Below  this  is  the 
right  kidney,  and  to  the  left  a  series  of  organs  all  bound  together  by  the  same 
layer  of  peritoneum.  The  peritoneum  covering  the  anterior  surface  of  the  right 
kidney  passes  from  right  to  left,  above,  upon  the  vena  cava  inferior,  thence  behind 
an  orifice,  foramen  of  Winslow,  into  a  large  cavity  which  cannot  be  seen,  the 
atrium  bursce  omentalis  (Fig.  635).  As  this  layer  covers  the  vena  cava  it  passes 
to  the  posterior  surface  of  the  liver,  and  is  the  lig.  hepato-renale.  A  little  lower 
than  this,  where  the  vein  is  covered  by  the  superior  angle  of  the  duodenum,  the 
peritoneum  from  the  kidney  covers  the  right  and  anterior  surface  of  the  first  por- 
tion and  part  of  the  surface  of  the  descending  portion,  running  below  into  the 


Diaphragm 


Lat.  lig.  of  liver 

Recessus  hepatico- 

renalis 

Lig.  hepatico-renale 
Diaphragm 


Vena  cava 
Foramen  of  Winslow 

Lig.  duodeno-renal 


Ligamentnm  teres 


Liy.  hepatico-duod. 
Posterior  layer  of 
lesser  amentum. 
'Hepatic  artery 


Lig 


hepatico-colicum 

Common  bile-duct     ' Vena  Porta 


FIG.  636.— Peritoneal  relations  of  the  liver,  first  portion  of  duodenum,  and  entrance  to  the  lesser  sac. 
(Luschka). 

gastro-colic  part  of  the  great  omentum.  Often  the  renal  peritoneum  passing  to 
the  first  part  of  duodenum  is  raised  into  a  fold,  from  the  summit  of  the  kidney  to 
the  summit  of  the  curve  of  the  duodenum,  called  lig.  duodeno-renole  (Huschke). 
Finally,  still  lower,  where  the  hepatic  flexure  of  the  colon  crosses  about  the  mid- 
dle of  the  descending  duodenum,  the  renal  peritoneum  passes  directly  over  the 
hepatic  flexure  of  colon  and  fixes  it.  Three  organs  are  thus  bound  together  by  a 
continuous  layer,  hepatic  flexure  of  colon,  duodenum,  and  right  kidney.  In  other 
cases  the  hepatic  flexure  and  ascending  colon  present  a  mesentery  ;  here  the  renal 
peritoneum  loses  itself  on  the  right  leaf  of  this  mesentery,  which  now  covers  in 
the  descending  duodenum.  To  see  another  side  of  the  descending  duodenum, 
incise  the  two  anterior  layers  of  the  great  omentum  along  the  inner  side  of  the 
duodenum  and  upper  side  of  the  transverse  colon.  This  will  open  the  bursa 
omentalis  (Fig.  616).  The  large  peritoneal  surface  which  forms  the  posterior 
wall  of  this  sac  covers  the  pancreas  and  the  left  side  of  the  descending  duodenum. 
The  rest  of  the  duodenum  still  remains  concealed  under  thick  coverings.  To  see 


THE   INTESTINAL    CANAL.  1013 

the  transverse  and  ascending  portions  and  duodeno-jejimal  angle,  displace  the 
intestines  in  two  ways.  Seize  the  lower  end  of  the  omentum  and  turn  it  and  the 
transverse  colon  up  over  the  chest-wall :  then  push  the  coils  of  the  small  intestine 
below  and  to  the  left.  There  is  now  uncovered  a  large  peritoneal  surface  formed 
above  by  the  lower  layer  of  the  transverse  mesocolon,  on  the  right  by  a  layer  of 
peritoneum  to  cover  the  ascending  colon,  on  the  left  by  the  right  layer  of  the 
mesentery,  and  below  by  the  ileo-caecal  angle.  Shining  through  this  common 
layer  one  usually  perceives  a  part  of  the  duodenum,  its  inferior  angle  or  trans- 
verse portion. 

Sometimes  none  of  it  can  be  seen  here ;  that  means  a  low  duodenum,  and  in 
order  to  disclose  it,  turn  all  the  small  intestines  upward  and  to  the  right  (Fig. 
613).  Then  one  sees  perhaps  a  portion  of  the  descending  part,  the  pre-aortic 
part,  and  always  the  ascending  part,  and  duodeno-jejunal  angle,  escaping  from 
the  mesocolon.  *  It  has  been  noticed  that  when  the  transverse  colon  is  held  verti- 
cally up  above  the  body  (the  subject  being  supine)  the  transverse  mesocolon  forms 
a  horizontal  partition.  It  divides  the  peritoneal  cavity  into  two  chambers — a 
superior  gastro-spleno-hepatic,  and  an  inferior  intestinal.  The  ceiling  of  the 
upper  chamber  is  formed  by  the  diaphragm,  the  sides  by  the  inner  surface  of 
the  short  ribs,  and  the  floor  by  the  upper  layer  of  the  transverse  mesocolon. 
The  liver,  spleen,  and  stomach  form  its  contents.  The  inferior  chamber  is 
limited  above  by  the  lower  layer  of  the  transverse  mesocolon,  on  the  sides  by 
the  ascending  and  descending  colons,  below  by  the  iliac  fossse,  while  the  middle 
of  this  floor  has  been  broken  open  to  allow  free  communication  between  abdomen 
and  pelvis.  This  chamber  contains  small  intestines.  The  duodenum  makes  a 
bas-relief  on  the  posterior  walls  of  these  two  stories.  The  superior  angle  and  a 
part  of  the  descending  portion  is  in  the  upper  one ;  the  rest  of  the  descending 
portion,  all  the  pre-aortic  and  ascending  portion,  and  often  the  duodeno-jejunal 
angle,  belong  to  the  inferior  story.  Sometimes  the  duodeno-jejunal  angle  is  in 
the  thickness  of  the  mesocolon  forming  the  partition. 

To  describe  the  duodenal  peritoneum  of  the  lower  chamber,  reverse  the  great 
omentum  as  before,  isolate  the  mesentery  and  hold  it  tense,  then  follow  the  course 
of  its  two  layers.  The  left  layer  at  first  covers  the  part  of  the  duodenum  situated 
to  the  left  of  this  mesentery  and  then  proceeds  to  lose  itself  below  in  the  right 
leaf  of  the  sigmoid  mesocolon,  passing  over  the  inferior  mesenteric  vessels ;  to 
the  left  it  is  continuous  with  the  left  prerenal  peritoneum  and  right  layer  of  peri- 
toneum covering  the  descending  colon  ;  farther  above,  this  layer  passes  over  the 
left  surface  of  the  duodeno-jejunal  angle  and  is  continued  into  the  inferior  layer 
of  the  transverse  mesocolon.  The  right  leaf  of  the  mesentery  covers  the  duode- 
num to  the  right  of  this  root  and  continues  to  cover  the  ascending  colon ;  below 
it  covers  the  ileo-csecal  angle.  Above,  it  passes  upon  the  inferior  layer  of  the 
transverse  mesocolon  and  on  the  right  surface  of  the  duodeno-jejunal  angle. 
Sometimes  the  two  leaves  of  the  mesentery  embrace  the  duodeno-jejunal  angle, 
and,  instead  of  immediately  reuniting  beyond,  they  leave  a  space  between,  form- 
ing the  orifice  of  the  duodeno-jejunal  fossa.  The  duodenum  is  crossed  by  two 
mesenteries,  the  second  portion  by  the  transverse  mesocolon,  and  the  third  or 
fourth  portion  by  the  root  of  the  mesentery. 

The  first  part  of  the  duodenum  is  almost  completely  covered  by  peritoneum 
derived  from  the  two  layers  of  the  lesser  omentum.  Only  a  part  of  its  posterior 
surface  near  the  vena  cava  and  neck  of  the  gall-bladder  is  uncovered.  The  supra- 
colic  part  of  the  descending  portion  has  no  posterior  covering.  Its  right  and 
anterior  surface  are  covered  by  peritoneum  from  the  anterior  surface  of  the  right 
kidney  :  its  left  side  is  covered  by  peritoneum  of  the  lesser  sac.  Next  on  its 
anterior  surface  is  a  non-serous  region  corresponding  to  the  interspace  between 
the  layers  of  the  transverse  mesocolon.  The  infracolic  part  of  the  second  portion 
is  covered  by  the  right  leaf  of  the  mesentery. 

A  part  of  the  pre-aortic  portion  has  only  an  anterior  covering  from  the  right 
leaf  of  the  mesentery.  Depending  on  the  position  of  the  radix  mesenterii  and 


1014  THE    ORGANS    OF  DIGESTION. 

of  the  duodenum,  the  remaining  parts  would  be  covered  anteriorly  by  the  left 
leaf  of  mesentery  until  the  intestine  is  called  jejunum,  when  it  is  wholly  invested 
by  mesentery. 

The  different  layers  of  mesocolon  cannot  be  regarded  as  forming  any  covering 
in  the  above  list,  because  their  attachments  are  all  secondary. 

A  persistence  of  the  mesoduodenum  is  normal  in  many  animals,  abnormal 
in  man. 

Ligaments  of  the  Duodenum. 

These  are  peritoneal  folds  connecting  it  to  neighboring  viscera  or  to  the  poste- 
rior abdominal  wall. 

1.  Lig.  suspensorium  duodeni  or  lig.  hepato-duodenale  is  the  right  edge  of  the 
lesser  omentum,  and  passes  from  the  hilus  of  the  liver  to  invest  by  two  layers  the 
first  portion  of  the  duodenum,  except  a  part  of  its  posterior  surface. 

2.  Lig.  cystico-duodenale,  from  the  neck  of  the  gall-bladder  to  the  superior 
curve  of  the  duodenum. 

3.  Lig.  duodeno-renale,  triangular  in  form,  from  the  right  surface  of  the  supe- 
rior curve  of  the  duodenum  to  the  summit  of  the  right  kidney.     The  lig.  hepato- 
renale  is  posterior  to  this  one. 

4.  On  the  left  of  the  ascending  duodenum,  where  the  left  layer  of  the  mesen- 
tery runs  into  the  lower  layer  of  the  transverse  mesocolon  or  into  prerenal  peri- 
toneum, one  or  two  ligaments  may  limit  certain  fossae :  they  are  lig.  duodeno- 
mesocolica. 

For  duodenal  fossae,  see  p.  994. 

Eelations  of  Duodenum. 

The  duodenum,  occupying  a  fixed  position  against  the  posterior  abdominal 
wall,  comes  into  relation  with  all  the  abdominal  organs  except  the  spleen,  which 
is  fixed  in  the  left  cupola  of  the  diaphragm.  We  may  describe  the  relations  with 
(1)  Movable  organs  of  the  abdominal  cavity,  (2)  Fixed  organs  of  the  posterior 
abdominal  wall,  (3)  Lumbar  skeleton. 

(1)  The  relation  with  movable  organs  can  be  determined  at  once  on  opening 
the  cavity.     The  stomach,  in  its  empty  state,  touches  by  its   antrum   pylori   the 
duodeno-jejunal  angle  (Braune),  (Fig.  634).     This  occurs  behind  the  posterior 
wall  of  the  stomach,  and  the  two  are  separated  by  the  transverse  mesocolon.     If 
the  stomach  be  distended  the  pylorus  is  deflected  farther  to  the  right,  and  the 
above  relation  is  lost. 

The  hepatic  flexure  of  the  colon  passes  over  the  lower  part  of  the  anterior 
surface  of  the  right  kidney,  and  the  beginning  of  the  transverse  colon  over  the 
middle  part  of  the  descending  duodenum,  as  we  have  seen.  The  movable  small 
intestines,  being  included  in  the  ring  of  the  colon,  cover  the  duodenum  as 
it  lies  in  the  lower  chamber,  and  so  render  it  almost  inaccessible. 

(2)  The  relations  with  fixed  organs  are  with  liver,  the  two  kidneys,  and  the 
pancreas.     The  first  and  second  portions  are  related  to  the  liver  and  neck  of  gall- 
bladder.    An  impressio  duodenalis  is  not  always   made  on  the  quadrate  lobe, 
although  the  first  part  of  the  duodenum  passes  under  it.     The  initial  curve  is 
fixed  at  the  inferior  vena,  cava  and  neck  of  gall-bladder  where  the  peritoneum  is 
broken  and  the  investment  is  incomplete.     The  impressio  duodenalis  is  on  the 
inferior  surface  of  the  right  lobe  to  the  right  of  the  gall-bladder,  to  the  left  of 
the  renal  impression,  and  behind  the  colic  impression. 

In  respect  to  the  kidneys,  not  all  authors  speak  of  the  left  as  being  related. 
Luschka  has  always  found  the  ascending  duodenum  related  to  the  left  kidney,  as 
well  as  the  descending  duodenum  to  the  right  kidney,  but  the  two  duodenal 
parts  always  behave  differently  to  their  respective  kidneys. 

The  descending  duodenum  is  thrown  strongly  backward  on  the  right  of  the 
lumbar  column,  and  immediately  meets  the  right  kidney  and  suprarenal  capsule  as 
they  all  leave  the  liver.  It  then  rests  on  the  inner  margin  of  the  anterior  surface 


THE   INTESTINAL    CANAL. 


1015 


of  the  kidney  and  on  the  renal  vessels  at  the  hilus.  Sometimes  it  only  abuts 
against  the  inner  margin,  not  covering  its  surface  at  all.  This  is  thought  to  be 
due  to  a  changed  position  of  kidney  and  not  of  duodenum.  The  adhesion  by  con- 
nective tissue  between  the  duodenum  and  kidney  is  especially  close  where  the 
hepatic  flexure  crosses  the  kidney  and  then  crosses  the  duodenum  as  transverse 
colon  (Fig.  636). 

In  case  the  duodenum  descends  very  low  to  the  fifth  lumbar  vertebra,  it  then 
borders  the  lower  extremity  of  the  kidney.     The  relations  of  the  ascending  por- 


yon-peritoneal  part 
Peritoneal  part 


Left  suprarenal 
capsule 


Right  suprarenal 
capsule 


Duodenum 


Duodenum 


Mesocolic  area 


Descending 
'colon 


Mesocolic  area 
FIG.  636.— Diagram  to  show  relations  of  duodenum  to  both  kidneys. 

tion  with  the  left  kidney  are  much  more  variable.  A  light  traction  from  left 
to  right  displaces  them.  There  are  no  adhesions,  and  the  ascending  duodenum 
glides  ^asily  over  the  subjacent  tissue. 

The  annular  or  the  U-shaped  duodenum  usually  overlies  the  inner  margin  of 
the  lower  third  or  half  of  the  left  kidney ;  with  the  V-shaped  duodenum,  only  the 
ascending  portion  or  the  duodeno-jejunal  angle  may  touch  the  lower  part  of  its 
inner  margin.  Ureters  and  spermatic  vessels  are  covered  on  the  two  sides  by  the 
duodenal  arch. 

Between  the  duodenum  and  pancreas  there  exists  not  only  a  relation  of  con- 
tiguity but  one  of  continuity  of  tissue,  which  is  explained  by  the  duodenal  origin 
of  the  pancreas.  The  head  of  the  pancreas  fills  the  space  limited  by  the  duode- 
nal arch  and  then  escapes  as  the  neck  by  the  opening  of  the  intestinal  ring.  It  is 
to  be  noted  that  the  head  is  always  proportional  in  extent  to  the  duodenum,  and 
assumes  the  form  allowed  by  that  intestine.  In  the  adult  the  head  of  the  pancreas 
embraces  the  duodenum  much  as  the  parotid  gland  embraces  the  ramus  of  the 
lower  jaw.  It  advances  in  front  and  behind,  covering  about  one-half  of  the  cir- 
cumference of  the  intestinal  wall,  generally  more  anteriorly  than  posteriorly. 

The  second  portion  is  much  more  enveloped  than  any  other.  Union  between 
the  intestine  and  pancreas  is  established  by  cellulo-fibrous  tissue,  by  pancreatico- 
duodenal  vessels,  by  excretory  ducts,  and  perhaps  by  longitudinal  muscular  fibres 
from  the  intestines  which  run  between  the  lobules  of  the  gland.  Yerneuil  and 
Treitz  believe  the  duodenum  holds  the  pancreas  in  place  and  not  vice  versd. 

By  lifting  all  the  viscera  from  the  abdominal  cavity,  the  vertebral  column 
with  its  prevertebral  vessels  are  disclosed  behind  the  duodenum.  There  is  the 
aorta,  often  a  little  to  the  left  of  the  median  line,  which  nearly  always  divides 


1016  THE    ORGANS    OF  DIGESTION. 

at  the  fourth  lumbar  vertebra  into  its  two  primitive  iliacs.  A  little  to  the  right 
is  the  inferior  vena  cava,  having  just  received  the  two  common  iliac  veins.  It 
also  receives,  behind  the  descending  and  ascending  part  of  the  duodenum,  the 
renal  veins — the  right  on  the  level  of  the  lower  part  of  the  second  lumbar  verte- 
bra, and  the  left  a  little  higher  on  the  level  of  the  upper  part  of  the  same  vertebra, 
having  passed  in  front  of  the  aorta. 

The  superior  hepatic  curve  of  the  duodenum  rests  on  the  vena  cava  at  the 
first  lumbar  vertebra  right  side.  The  descending  portion  covers  about  the  two 
external  thirds  of  the  anterior  surface  of  the  vena  cava  and  the  right  renal 
vessels. 

The  horizontal  portion  of  the  duodenum  in  the  U-form  applies  itself  in  one 
part  to  the  vena  cava,  and  in  another  to  the  aorta,  and  sometimes  passes  over  the 
common  iliacs.  In  the  duodenum  in  the  V-form  the  inferior  angle  lies  upon  the 
vena  cava  to  the  right  of  the  aorta,  then  the  ascending  portion  crosses  the  aorta 
sharply,  from  right  to  left,  then  borders  it  on  the  left  and  crosses  the  left  renal 
vein  and  ends  in  the  duodeno-jejunal  angle. 

The  ascending  portion  in  the  U-form  runs  along  the  left  surface  of  the  aorta 
and  finally  over  the  left  renal  vein  as  the  above. 

(3)  Relations  to  the  Lumbar  Column. — By  fixing  the  duodenum  with  pins 
while  in  situ,  Jonnesco  examined  thirty  subjects  and  found  that  the  first  portion 
of  the  duodenum  lies  to  the  right  of  the  first  lumbar  vertebra.  Its  pyloric  end 
in  the  median  line  is  on  the  level  of  the  inferior  extremity  of  this  vertebra,  and 
it  is  directed  up  to  the  right  and  backward  to  reach  the  upper  border  of  the 
same  vertebra. 

The  pre-aortic  portion,  or  inferior  angle,  reaches  a  variable  point;  in  children, 
the  superior  border  of  the  fourth  lumbar,  or  the  disk  between  it  and  the  third. 
In  adults  with  the  duodenum  in  U-form,  this  pre-aortic  portion  moulds  itself 
over  the  convexity  of  the  fourth  lumbar  vertebra  in  12  out  of  20  cases.  In  some 
cases  it  passes  over  the  fifth  vertebra.  In  the  duodenum  in  V-form  the  inferior 
angle  applies  itself  most  often  to  the  right  of  the  column,  and  the  lower  border 
of  the  fourth  lumbar  vertebra,  in  5  out  of  8  cases.  Again  it  may  go  to  the  side 
of  the  fifth  lumbar  three  times  in  8  cases. 

There  may  be  three  types :  a  high  type,  corresponding  to  the  superior  border 
of  the  fourth,  or  articulation  between  it  and  the  third,  seen  in  the  child ;  middle 
type,  to  the  body  of  the  fourth  lumbar ;  lotv  type,  to  the  body  of  the  fifth  lumbar, 
confined  almost  wholly  to  the  V-type. 

The  duodeno-jejunal  angle  corresponds  to  the  left  of  the  vertebral  column, 
may  be  to  the  first  lumbar  vertebra  (infantile  type),  or  to  the  second  (adult  type 
in  U  or  V).  In  the  first  case  the  angle  approaches  the  median  line,  in  the  latter 
it  is  thrown  to  the  side  of  the  column. 

Relations  of  Duodenum  in  Detail. 

Superior  Hepatic  Curve,  First  Portion. 

Above  and  in  front: 

Quadrate  lobe  of  liver ; 
Neck  of  gall-bladder; 
Foramen  of  Winslow ; 
Hepatic  artery. 

Behind : 

Common  bile-duct ; 

Vena  portse ; 

Gastro-duodenal  artery ; 

Vena  cava  inferior  (at  summit  of  curve) ; 

First  lumbar  vertebra  (on  the  left). 


THE  INTESTINAL    CANAL.  1017 


Below  : 

Neck  of  pancreas ; 
Head  of  pancreas. 

Descending,  or  Second  Portion. 

Anterior!//  : 

Right  lobe  of  liver  (impressio  duodenalis) ; 

Right  end  of  transverse  colon ; 

Two  layers  of  transverse  mesocolon  ; 

Small  intestine ; 

Right  leaf  of  mesentery. 

Posteriorly : 

Right  kidney  and  suprarenal  capsule  (at  times) ; 

Structures  at  hilus ; 

Common  bile  and  pancreatic  ducts  ; 

Vena  cava  inferior ; 

Spermatic  vessels. 

Internally : 

Head  of  pancreas ; 

Pancreatico-duodenal  vessels ; 

Common  bile  and  pancreatic  ducts ; 

First,  second,  third,  fourth,  or  fifth  lumbar  vertebras. 

Pre-aortic,  or  Third  Portion. 

Superiorly : 

Head  of  pancreas ; 
Superior  mesenteric  vessels. 

Anterior!//  : 

Root  of  mesentery ; 
Right  and  left  layers  of  mesentery ; 
Superior  mesenteric  vessels ; 
Small  intestine. 

Posteriori'/  : 

Vena  cava  inferior ; 

Aorta  ; 

Crura  of  diaphragm ; 

Third  or  fourth  lumbar  vertebra. 

Ascending,  or  Fourth  Portion. 
Anteriorly  : 

Antrum  pylori  (at  times)  : 

Transverse  colon ; 

Transverse  mesocolon  (lower  layer); 

Small  intestine ; 

Left  layer  of  mesentery. 

Posteriorly : 

Left  Psoas  muscle ; 
Left  renal  vessels  ; 
Spermatic  vessels ; 
Lower  part  of  inner  edge  of  left  kidney. 


1018  THE    ORGANS    OF  DIGESTION. 

Internally : 

Head  and  neck  of  pancreas ; 
Aorta ; 

Fourth,  third,  and  second  lumbar  vertebrae ; 
(Third,  second,  and  first  in  child). 

Terminal,  or  Fifth  Portion. 

Superiorly : 

Body  of  pancreas. 

Anteriorly : 

Duodeno-jejunal  angle ; 
Left  layer  of  mesentery. 


Externally  : 

Inner  margin  of  left  kidney. 


Means  of  Fixation. — Neither  peritoneal  adhesions  nor  peritoneal  ligaments 
really  fix  an  organ ;  if  the  latter  ever  does,  it  is  because  it  contains  vessels  and 
nerves  and  cellular  tissue  between  its  layers. 

The  means  here  are — 1.  Biliary  and  pancreatic  ducts.  2.  Arteries  which  are 
the  conductors  and  support  of  fibro-nervous  tissue.  3.  Suspensory  muscle  of 
Treitz  supporting  the  duodeno-jejunal  angle.  4.  A  cellular  fold  under  the  pan- 
creas. (Treitz.) 

1.  The  ducts  of  the  two  glands,  common  bile-duct  and  the  pancreatic,  con- 
tribute to  the  fixation  of  the  duodenum,  yet  the  lig.  hepato-duodenale  must 
render  service  in  resisting  a  downward  pull,  whereby  the  ducts  would  be  stretched 
and  their  functions  disturbed. 

2.  Two  abdominal  arteries  are  important  in  fixing  the  duodenum  to  the  poste- 
rior Avail:  the  coeliac  axis  above  it  and  superior  mesenteric  above  and  in  front, 
which  have  retained  their  original  positions  of  foetal  life.     There  is  a  complete 
anastomosis  or  arterial  circle  between   these  vessels,   connecting  the  posterior 
abdominal  wall  to  the  liver,  stomach,  pancreas,  duodenum,  and  spleen. 

3.  Fibro-nervous  investments  accompany  the  arterial  circle  formed  of  cellular 
tissue  and  sympathetic  nerve-plexuses.     They  have  two  roles :  first,  innervation 
of  the  vessels,  and  secondly,  support.     The  coeliac  and  solar  plexuses  support  as 
one  the  duodenum  and  its  neighboring  organs  the  liver,  stomach,  and  pancreas. 

4.  Muscle  of  Treitz. 

In  1853  Treitz  described  a  muscle  running  from  the  duodeno-jejunal  angle  to 
the  diaphragm.  Many  have  since  described  it  for  him.  If  the  beginning  of  the 
jejunum  be  pressed  down,  after  turning  up  the  stomach  and  transverse  colon,  a 
ridge  of  peritoneum  will  be  seen  to  extend  from  the  duodeno-jejunal  angle  up 
under  the  pancreas  to  the  left  crus  of  the  diaphragm.  This  ridge  is  called  the 
ligament  of  Treitz.  The  original  article l  reads  in  substance  thus — 

"Raise  the  pancreas  and  detach  it  from  the  diaphragm.  The  duodeno-jejunal  angle  is 
seen  attached  to  the  posterior  abdominal  wall  by  a  muscle  (Fig.  637).  This  muscle  is  small  and 
triangular  and  rises  by  its  base  from  the  superior  border  of  the  duodeno-jejunal  curve  and  from 
a  part  of  the  ascending  duodenum.  It  passes  toward  the  aortic  orifice  of  the  diaphragm  and 
near  its  centre  continues  into  a  tendon  which  becomes  more  narrow  and  loses  itself  in  the  ten- 
dinous tissue  surrounding  the  superior  mesenteric  artery  and  coeliac  trunk,  enveloping  the 
ganglia  and  nerves  of  the  coeliac  plexus.  By  traction  these  fibrous  bands  can  be  seen  connected 
with  the  inner  pillars  of  the  diaphragm,  and  commonly  with  the  right  border  of  the  oesophageal 
orifice.  All  subjects  possess  it;  it  is  best  developed  in  muscular  individuals  and  with  a  low- 
placed  duodenum.  Its  tendon  is  1.5  mm.  long;  the  muscle  1  mm.  thick.  As  to  its  function, 
it  does  not^merit  the  name  Levator  duodeni ;  its  action  is  of  little  importance  as  a  muscle;  it 
plays  the  r61e  of  a  suspensory  ligament  and  ought  to  be  called  Muscidus  suspensnn'it*  <lu,i<l,  ni." 

The  muscle  is  continuous  with  the  longitudinal  muscular  layer  of  the  duode- 
num and  is  stronger  the  older  the  subject. 

1  Prager  Vierteljahrcsschrifl,  1853,  s.  113. 


THE  INTESTINAL    CANAL. 


1019 


FIG.  637.— Muscle  of  Treitz.  The  large  intes- 
tine, jejunum,  mesentery,  and  pancreas  are 
removed.  (After  Treitz  in  Jonnesco.)  D.  In- 
ferior surface  of  diaphragm.  E.  Posterior  sur- 
face of  stomach.  F.  Liver.  Ls.  Spigelian  lobe. 
Vb.  Gall-bladder  and  duct.  VCI.  Vena  cava. 
Ac.  Codiac  axis.  PC.  Coeliac  plexus.  ADJ. 
Duodeno-jejunal  angle.  Ms.  Muscle  of  Treitz. 
MB.  Original  mesoduodenum. 


Treitz  indicates  a  cellular  membrane  (Fig.  637)  stretching  between  the  supe- 
rior mesenteric  artery  on  one  side,  the  pylorus,  duodeno-jejunal  angle,  and  con- 
cavity of  the  duodenum  on  the  other,  which  forms  a  floor  to  the  posterior  surface 
•  if  the  pancreas  and  represents  the  foetal  mes- 
entery of  the  duodenum.    He  says  on  account 
of  its'tenuity  it  is  unable  to  offer  any  fixation. 

Such  are  the  means  of  fixation  in  general. 
The  duodenal  ring  is  fixed  in  all  its  length, 
but  unequally ;  it  is  suspended  by  two  fixed 
extremities.  Its  superior  hepatic  angle  is 
fixed  by  the  total  of  organs  attached  to  the 
liver  and  by  the  thick  cellular  tissue  which 
fastens  it  to  the  inferior  vena  cava.  There 
are  also  the  structures  forming  the  hepatic 
pedicle,  artery,  duct,  and  portal  vein,  all  sur- 
rounded by  fibre-nervous  layers  and  all  united 
into  one  by  the  serous  membrane  forming  the 
lig.  hepato-duodenale.  Finally,  the  fibro-ner- 
vous tissue  contained  in  the  lig.  cystico- 
duodenale  serves  to  render  the  first  part  of 
the  duodenum  solid  to  the  liver.  The  liver 
is  fixed,  not  by  peritoneal  folds,  as  is  com- 
monly said,  but  by  a  thick  cellular  tissue  and 
numerous  subhepatic  veins  emptying  into  the 
inferior  cava — nailed,  so  to  speak,  to  the  pos- 
terior abdominal  wall.  By  such  attachment 
to  the  vena  cava  and  liver,  the  superior  angle 
is  secure. 

The  duodeno-jejunal  angle  is  fixed  by  the 
muscle  and  ligament  of  Treitz.  When  this  angle  penetrates  the  thickness  of  the 
transverse  mesocolon  its  fixation  is  still  more  assured.  The  branches  of  the  supe- 
rior mesenteric  artery  given  to  this  angle  reinforce  the  support.  More  than  the 
ends  of  the  duodenal  arch  must  be  supported  or  its  lower  part  would  separate 
from  the  posterior  abdominal  wall  and  come  forward  on  a  hinge-movement.  As 
long  as  nothing  presses  this  part  of  the  duodenum  backward  this  forward  move- 
ment does  occur,  as  in  early  human  embryos  or  in  case  of  a  mesoduodenum,  as  in 
many  animals. 

Normally  the  adult  human  duodenum  cannot  separate  from  the  posterior  wall, 
owing  to  many  agencies  which  come,  in  turn,  to  hold  it  down. 

The  descending  duodenum  is  fixed  to  the  inferior  vena  cava  and  right  kid- 
ney by  thick  cellular  tissue.  This  is  further  strengthened  by  the  hepatic 
flexure  and  transverse  colon,  which  apply  themselves  directly  to  the  kidney  and 
duodenum. 

The  pre-aortic  portion  is  fixed  by  two  agents — (a)  by  fibrous  tissue  between  it 
and  the  aorta  and  vena  cava  inferior :  (b)  by  the  superior  mesenteric  artery  sur- 
rounded by  its  fibro-nervous  tissue,  which  forms  the  root  of  the  mesentery  and 
presses  this  part  of  the  duodenum  down  upon  the  aorta.  So  the  mesenteric 
artery  and  aorta,  passing  one  behind  the  other,  constitute  a  sort  of  vascular 
press,  lessening  the  calibre  to  what  may  be  called  the  isthmus  of  the  duode- 
num. 

The  ascending  portion  is  much  less  fixed  than  any  other  part  to  the  posterior 
wall  and  left  kidney.  It  is  easily  displaced  from  left  to  right,  and  peritoneal 
covering  is  its  sole  agency  of  fixation. 

R£sum$. — The  duodenal  ring  is  fixed  against  the  posterior  abdominal  Avail, 
or,  better,  against  the  fixed  organs  which  cover  it.  This  fixity  is  assured  in 
part  by  the  vascular  system  and  by  the  fibro-nervous  layers  connected,  and  in 
another  part  by  the  muscle  of  Treitz. 


1020  THE    ORGANS    OF  DIGESTION. 

Jejunum  and  Ileum  (Intestinum  mesenteriale). 

Following  the  duodenum,  about  the  upper  two-fifths  of  the  remaining  small 
intestine  is  called  jejunum  and  the  lower  three-fifths  ileum  There  is  no  mor- 
phological line  of  distinction  between  these  two,  but  there  is  considerable  differ- 
ence between  the  beginning  of  the  jejunum  and  end  of  ileum.  The  diameter  of 
the  first  is  about  one  and  a  half  inches;  of  the  latter,  one  and  one-fourth  inches; 
the  walls  of  the  jejunum  are  thicker  and  a  given  length  weighs  more  than  the 
same  of  the  ileum ;  the  character  of  the  mucous  membrane  and  of  the  contents 
markedly  changes,  but  very  gradually.  The  ileum  possesses  none  or  poorly- 
formed  valvulae  conniventes.  The  jejunum  is  usually  in  the  umbilical  region  and 
left  iliac  fossa,  while  the  coils  of  the  ileum  are  more  on  the  right  side  and  right 
iliac  fossa  and  true  pelvis.  Both  these  parts  of  the  intestine  retain  the  mesentery, 
which  the  duodenum  does  not. 

There  is  but  little  fixation  to  the  loops  of  the  small  intestine ;  the  mesentery 
allows  the  freest  motion.  Every  moment  the  coil  must  accommodate  itself  to 
changes  in  form  and  position  of  the  peritoneal  cavity  or  be  prepared  to  fill  some 
hole.  Contraction  of  the  diaphragm  and  abdominal  muscles,  the  filling  and 
emptying  of  viscera,  presence  of  tumors,  position  of  body,  must  all  occasion 
changes  of  position  in  the  small  intestines.  With  this  great  motility,  no  definite 
shape  can  be  ascribed  for  the  coils,  but  frequently  the  upper  loops  of  the  jejunum 
are  transverse  and  the  lower  ofLthe  ileum  are  more  vertical. 

The  terminal  part  of  the  ileum  is  more  fixed  than  any  other,  as  its  mesentery 
passing  over  the  right  Psoas  muscle  is  very  short.  At  the  point  of  transition 
from  the  duodenum  to  the  jejunum  or  from  the  small  to  the  large  intestine  the 
various  fossae  have  been  noticed  (p.  994). 

The  vitelline  duct  coming  from  the  original  convexity  of  the  intestinal  loop 
(Fig.  588)  may  persist  in  adult  life  ;  it  is  then  called  MeckeVs  diverticulum.  It 
is  a  blind  intestine,  having  the  same  layers  as  the  ileum,  with  the  lumen  of  which 
it  directly  communicates.  It  is  two  or  three  inches  long  (one-half  to  seven 
inches),  and  rises  about  forty-three  inches  from  the  ileo-colic  junction  (from  one 
to  ten  feet) ;  originally  it  passes  toward  the  umbilicus,  but  usually  hangs  free  in 
the  cavity.  It  may  be  connected  with  the  umbilicus  or  other  points  by  a  solid 
band,  which  attains  great  firmness  and  is  the  enlarged  remains  of  the  omphalo- 
mesenteric  vessels.  It  may  be  conical,  cylindrical,  or  hour-glass  in  shape.  It 
occurs  about  once  in  fifty  cases,  and  may  cause  surgical  complications. 

Structure  of  the  Wall  of  the  Small  Intestine. — Like  the  stomach,  the  wall 
is  composed  of  four  layers,  serous,  muscular,  submucous,  and  mucous.  It  is 
much  thinner  than  that  of  the  stomach,  only  |— 1  mm.  thick. 

The  external  or  serous  coat  is  peritoneum,  which  surrounds  the  whole  of  the 
ileum  and  jejunum  except  along  the  little  interspace  left  at  the  mesenteric  border 
of  the  intestine.  Here  a  sort  of  linear  hilus  is  left  between  the  two  layers  where 
vessels,  nerves,  veins,  and  lymphatics  have  their  entrance  or  exit.  In  case  of 
the  duodenum,  each  part  is  covered  to  a  different  degree. 

The  muscular  coat  consists  of  two  layers ;  as  usual  for  the  alimentary  canal, 
the  external  is  made  of  longitudinal  fibres,  and  the  internal  of  circular  fibres. 
The  longitudinal  fibres  are  best  developed  at  the  beginning  of  the  duodenum  and 
end  of  the  ileum,  and  are  here  closely  attached  to  the  serous  coat.  They  are 
most  marked  on  the  free  border  of  the  intestine,  and  may  be  wholly  lacking  on 
the  mesenteric  attachment.  The  circular  set  is  three  times  thicker  than  the 
longitudinal,  and  consists  of  complete  muscular  rings  which  are  pressed  so  closely 
together  as  to  only  leave  clefts  for  the  passage  of  vessels  and  nerves  to  deeper 
parts.  This  double  coat  gets  thinner  below,  is  pale,  and  made  of  unstriated  mus- 
cular tissue.  It  produces  peristalsis,  by  which  food  is  pushed  onward. 

The  submucous  coat  acts  as  a  bed  for  the  mucosa,  is  connected  more  closely  with 
it  than  with  the  muscular  coat,  and  is  made  of  areolar  tissue.  Here  are  lymphatic 
vessels  and  nerve-plexuses,  and  the  blood-vessels  divide  up  for  the  mucosa. 


THE   IXTESTIXAL    CAXAL. 


1021 


The  mucous  membrane  is  thick,  red,  and  highly  vascular  at  the  upper  part 
of  the  intestine,  but  paler  and  thinner  below.  Its  inner  surface  is  shaggy  like 
velvet ;  this  is  due  to  the  presence  of  minute  processes  called  I'iUi.  Next  the 
submucous  coat  is  a  layer  of  unstriped  muscle  fibres,  the  muscularis  mucosce. 
This  thin  layer  from  the  sheep  makes  the  "  catgut "  of  commerce.  Internal  to 
this  is  a  quantity  of  retifonn  tissue  containing  goblet-cells  and  migratory  leuco- 
cytes supporting  tubular  glands,  blood-vessels,  nerves,  and  lacteals.  Most  inter- 
nally the  uiucosa  is  covered  by  a  single  layer  of  columnar  epithelial  cells  resting 
upon  a  basement  membrane.  The  prismatic  cells  contain  granular  protoplasm 
and  oval  nuclei.  The  free  ends  of  the  cells  are  invested  by  a  cuticular  zone  or 
basilar  border,  a  well-defined  band  exhibiting  a  fine  vertical  striation.  Some 
interpret  these  as  parallel  canals  for  absorption  of  chyle. 

The  mucous  membrane  presents  in  its  different  parts  the  following  structures : 


conniventes  ; 


Villi; 

Intestinal  true  glands 

7  ^  77  •  7      f  Solitary  glands  ; 
Intestinal  lumph-folhcles  |  Agmil^ed  glandS)  w  Peyer^  patcnes. 


(  Grlands  of  Lieberkilhn ; 
\  Grlands  of  Brunner  ; 


conniventes  (valves  of  Kerkring,  1670),  who  gave  the  incorrect  name, 
conniventes  (connivere,  to  close  the  eyelids)  (Fig.  638)  are  permanent  crescentic 
folds  of  mucous  membrane  and  submucosa  ; 
each  contains  two  layers  of  mucous  mem- 
brane, placed  back  to  back  and  separated 
by  the  submucosa.  They  contain  no  part 
of  the  muscular  coats,  and  are  not  obliter- 
ated by  distention  of  the  intestine.  They 
extend  transversely  across  the  axis  of  the 
tube  for  about  one-half  or  two-thirds  of  its 
circumference.  Some  form  complete  circles 

i         ,1  i  -i  FIG.  638.—  Diagram  of  valvulae  conniventes. 

and  others  spirals;  the   spirals  rarely  may     (Brinton.) 

Valvulae  conniventes 


Vittiu 

Mucous  membrane 


Sub-mucogai 


Circular  muscular  coat 


Longitudinal  muscular  coat 


FIG  639.— Longitudinal  section  of  human  small  intestine  to  show  relations  of  villi,  valvulae  conniventes, 
and  muscular -coats.    Schematic.    (From  Piersol.) 

extend  two  or  three  times  around  the  internal  circumference.     This  is  of  interest, 
as  a  spiral  valve  is  the  characteristic  of  the  intestine  of  certain  fishes — e.  g.  the 


1022 


THE    ORGANS    OF    DIGESTION. 


/o, 


shark  family.  The  large  folds  project  about  one-third  inch  into  the  lumen,  and 
often  connect  at  one  end  obliquely  with  a  smaller  fold.  Sometimes  a  valve  ter- 
minates abruptly,  or  it  bifurcates  at  one  or  both  ends.  They  are  so  close  that  in 

a  relaxed  condition  they  cover  the  intes- 
tinal surface  like  roof-tiles.  These  valves 
are  most  abundant  in  the  duodenum  and 
jejunum ;  they  decrease  and  disappear  at 
the  lower  end  of  the  ileum.  Their  total 
number  is  800  or  900.  They  begin  with 
the  commencement  of  the  descending  duode- 
num, there  being  usually  none  in  the  first 
portion.  Just  beyond  the  point  of  entrance 
of  the  bile  and  pancreatic  ducts  they  are 
very  large  and  regular  and  closely  packed. 
About  two  feet  from  the  lower  end  of  the 
ileum  they  cease.  From  this  point  up  to 
the  middle  of  the  jejunum  they  are  indis- 
tinct and  irregular,  smaller,  and  farther 
apart.  They  are  seen  at  their  best  from  the  lower  part  of  the  descending  duode- 
num through  the  upper  half  of  the  jejunum.  Their  function  is  to  retard  the 
passage  of  food  and  to  afford  an  extensive  absorptive  surface. 


Mouth  of  crypt  of 

Lieberkiihn 

FIG.  640.— Small   portion  of  mucous  mem- 
brane of  the  small  intestine.    (Rauber.) 


FIG.  641.— Diagrammatic  section  of  a  villus.  (Watney.)  ep.  Epithelium  only  partially  shaded  in.  /.Cen- 
tral chyle-vessel:  the  cells  forming  the  vessel  have  been  less  shaded  to  distinguish  them  from  the  cells  of  the 
parenchyma  of  the  villas,  m.  Muscle-fibres  running  up  by  the  side  of  the  chyle-vessel.  It  will  be  noticed  that 


membrana  propria.  It  will  be  seen  that  there  is  hardly  any  difference  between  the  cells  of  the  parenchyma, 
the  endothelium  of  the  upper  part  of  the  chyle-vessel,  and  the  cells  of  the  ineiubrana  propria.  v.  mood-vessels. 
z.  Dark  line  at  the  base  of  the  epithelium  formed  by  the  reticulum.  It  will  be  seen  that  the  reticulum  IK  'ni- 
trates between  all  the  other  elements  of  the  villus.  The  reticulum  contains  thickenings  or  "nodal  points." 
The  diagram  shows  that  the  cells  of  the  upper  part  of  the  villus  are  larger  and  contain  a  lanrer  zone  of  proto- 
plasm than  those  of  the  lower  part.  The  cells  of  the  upper  part  of  the  chyle-vessel  differ  somewhat  from  those 
of  the  lower  part,  in  that  they  more  nearly  resemble  the  cells  of  the  parenchyma. 

The  villi  are  minute  vascular  processes,  consisting  entirely  of  tissues  of  the 
mucosa,  projecting  from   every  part  of  the  inner  surface  of  the   small  intestine 


THE   IXTESTIXAL    CAXAL. 


1023 


over  the  valvuhe  conniventes  as  well  as  between  them  (Fig.  639).  They  give  to 
the  surface  its  velvety  appearance.  Between  the  bases  of  the  viili,  wherever  they 
are.  the  mouths  of  the  glands  of  Lieberkiihn  are  seen  (Figs.  640  and  642).  They 
are  lar-ot  and  most  numerous  in  the  duodenum  and  jejunum,  resembling  the 
valvulaT  conniventes  in  distribution.  They  are  smaller  and  fewer  in  the  ileum. 
and  stop  abruptly  at  the  ileo-c*cal  orifice.  There  are  none  in  the  large  intestine. 
Thev  measure  .5*  to  .7  mm.  in  length,  and  are  present  to  the  number  of  about 
four*  millions  (Krause) ;  10  to  18  per  sq.  mm.  in  the  upper  intestine,  and  8  to  14 
to  the  same  space  in  the  ileum.  They  are  apt  to  be  leaf-shaped  in  the  duode- 
num, tongue-shaped  in  the  jejunum,  and  filiform  in  the  ileum. 

Structure  of  the  Villi  (Fig.  641). — The  structure  of  the  villi  has  been  studied 
recentlv  bv  many  eminent  anatomists.  We  shall  here  follow  the  description  of 
Dr.  Watney,1  whose  researches  have  a  most  important  bearing  on  the  physiology 


Capillaries.  1ft  r |»    g>~  4 

J    ^ 

Lymph  trunk.'-K^^^ 

\ "' " 


-1*  ^    -  t     =--%=-!  »»5    =   ' 

Ma  's;l  ss|ii\ 

^  I  I^Vml 

^^1      lAf'lift: 


-I-" 


"  ~  Capillaries. 


Small  artery.'  LtfmpJtatic  plexus. 

FIG.  fri2.— Villi  of  small  intestine.    (Cadiat.) 

of  that  which  is  the  peculiar  function  of  this  part  of  the  intestine,  the  absorp- 
tion of  fat. 

The  essential  parts  of  a  villus  are — the  lacteal  vessel,  the  blood-vessels,  the 
epithelium,  the  basement  membrane  and  muscular  tissue  of  the  mucosa,  these 
structures  being  supported  and  held  together  by  retiform  lymphoid  tissue. 

These  structures  are  arranged  in  the  following  manner :  situated  in  the  centre 
of  the  villus  is  the  lacteal,  terminating  near  the  summit  in  a  blind  extremity ; 
running  along  this  vessel  are  unstriped  muscular  fibres  :  surrounding  it  is  a  plexus 
of  capillary  vessels,  the  whole  being  enclosed  by  a  basement  membrane,  supporting 
columnar  epithelium.  Those  structures  which  are  contained  within  the  basement 
membrane — namely,  the  lacteal,  the  muscular  tissue,  and  the  blood-vessels — are 
surrounded  and  enclosed  by  a  delicate  reticulum  which  forms  tbe  matrix  of  the 
villus.  and  in  the  meshes  of  which  are  found  large  flattened  cells,  with  an  oval 
nucleus,  and.  in  smaller  numbers,  lymph-corpuscles.  These  latter  are  to  be 
distinguished  from  the  larger  cells  of  the  villus  by  their  behavior  with  reagents,  by 
their  size,  and  by  the  shape  of  their  nucleus,  which  is  spherical.  Transitional 
forms,  however,  of  all  kinds  are  met  with  between  the  lymph-corpuscle  and  the 
proper  cells  of  the  villus. 

The  lacteals  are  in  some  cases  double,  and  in  some  animals  multiple.     Situated 

1  Phil.  Trans.,  vol.  clxvi.  pt.  ii. 


1024 


THE    ORGANS    OF   DIGESTION. 


in  the  axis  of  the  villi,  they  commence  by  dilated  caecal  extremities  near  to,  but 
not  quite  at,  the  summit  of  the  villus.  The  walls  are  composed  of  a  single  layer 
of  endothelial  cells,  the  interstitial  substance  between  the  cells  being  continuous 
with  the  reticulum  of  the  matrix. 

The  muscular  fibres  are  derived  from  the  muscularis  mucosse,  and  are  arranged 
in  bundles  around  the  lacteal  vessel,  extending  from  the  base  to  the  summit  of  the 
villus,  and  giving  off  laterally,  individual  muscle-cells,  which  are  enclosed  by  the 
reticulum,  and  by  it  are  attached  to  the  basement  membrane. 

The  blood-vessels  form  a  plexus  between  the  lacteal  and  the  basement  mem- 
brane, and  are  enclosed  in  the  reticular  tissue ;  in  the  interstices  of  the  capillary 
plexus,  which  they  form,  are  contained  the  cells  of  the  villus. 

These  structures  are  surrounded  by  the  basement  membrane,  which  is  made 
up  of  a  stratum  of  endothelial  cells,  and  upon  which  is  placed  a  layer  of  columnar 
epithelium.  The  reticulum  of  the  matrix  is  continuous  through  the  basement 
membrane  (that  is,  through  the  interstitial  substance  between  the  individual 
endothelial  cells)  with  the  interstitial  cement  substance  of  the  columnar  cells  on 
the  surface  of  the  villus.  Thus  we  are  enabled  to  trace  a  direct  continuity  between 
the  interior  of  the  lacteal  and  the  surface  of  the  villus  by  means  of  the  reticular 
tissue,  and  it  is  along  this  path  that,  according  to  Dr.  Watney,  the  chyle  passes 
in  the  process  of  absorption  by  the  villi.  That  is  to  say,  it  passes  through  the 
interstitial  substance  between  the  epithelium  cells,  through  the  interstitial  sub- 
stance of  the  basement  membrane,  the  reticulum  of  the  matrix,  and  the  interstitial 
substance  between  the  endothelial  plates  of  the  lacteal,  all  which  structures  have 
been  shown  to  be  continuous  with  one  another,  and,  being  probably  semifluid,  do 
not  offer  any  obstacle  to  the  passage  of  the  molecular  basis  of  the  chyle. 

Among  the  structures  of  the  intestinal  wall  called  glands  there  are  two  kinds 
— true  and  false ;  the  latter  belong  to  the  lymphatic  system.  The  true  glands 
are  those  of  Lieberkiihn  and  Brunner. 

The  follicles,  crypts,  or  glands  of  Lieberkiihn  (Figs.  643  and  644)  are  very 
numerous,  forming  an  almost  continuous  layer  of  tubu- 
lar depressions  throughout  the  intestines,  large  and 
small.  They  are  in  every  part  of  the  small  intestine, 
opening  between  the  villi  (Figs.  640  and  642).  Their 
small  circular  mouths  may  be  seen  by  the  aid  of  a 
lens.  They  occupy  nearly  the  whole  depth  of  the 
mucosa,  are  upon  the  valvulse  conniventes,  their  blind 
ends  approaching  nearly  perpendicularly  the  muscu- 
laris mucosse.  They  consist  of  thin  tubes,  Avhose 
walls  are  made  of  basement  membrane,  lined  by  the 
columnar  epithelium  from  the  free  surface.  Many 
of  these  cells  change  to  spherical  secreting  cells,  some 
of  which  become  goblet-cells  (Fig.  644).  They  are 
2  to  3  mm.  long  and  about  .04  mm.  in  diameter. 


FIG.  643.— Transverse  section 
of  crypts  of  Lieberkiihn.  (Klein 
and  Noble  Smith.) 


FIG.  644. — Longitudinal  section  of  crypts  of  Lieberkiihn.    Goblet-cells  seen  among  the  columnar  epithelial 
cells.    (Klein  and  Noble  Smith.) 

The  duodenal  or  Brunner's  glands  are  limited  to  the  duodenum  and  first  part 
of  the  jejunum.  They  are  most  numerous  in  the  first  part  of  the  duodenum, 
within  one  or  two  inches  of  the  pylorus.  They  are  small  compound  tubular  glands, 
consisting  of  a  number  of  tubular  alveoli  opening  into  a  slender  duct,  much  like 


THE  INTESTINAL    CAXAL. 


1025 


the  salivary  glands  of  the  mouth,  which  are  more  compact.  They  are  probably 
direct  continuations  and  higher  specializations  of  the  pyloric  glands.  They  are 
situated  in  the  submucosa  or  in  part  in  the  mucous  membrane.  Their  ducts 
penetrate  the  muscularis  inucosae,  pass  between  the  glands  of  Lieberkiihn  and 
open  upon  the  inner  surface  of  the  intestine,  or  in  some  cases  into  the  bases  of 
the  crypts. 

The  solitary  glands  (Fig.  645)  are  found  scattered  throughout  the  mucous 
membrane  of  the  small  intestine,  but  are  most  numerous  in  the  lower  part  of  the 
ileum.  They  are  small,  round,  whitish  and  slightly  prominent  bodies  6  mm.  to 
3  mm.  in  diameter.  They  are  formed  on  the  mesenteric  as  well  as  free  border, 
between  and  upon  the  valvulae  conniventes.  The  free  surface  of  the  follicle  may 
have  villi  upon  it,  but  at  the  centre  or  cupola  they  are  lacking.  Each  gland  is 
surrounded  irregularly  by  the  openings  of  the  glands  of  Lieberkiihn.  These  so- 
called  glands  have  a  structure  similar  to  that  of  a  lymph-node,  consisting  of 
dense  retiform  tissue  closely  packed  with  lymph-corpuscles,  and  permeated  by  fine 
capillaries.  They  have  no  ducts.  The  interspaces  of  the  retiform  tissue  are  con- 
tinuous with  larger  lymph-spaces  at  the  base  of  the  gland  by  which  they  commu- 
nicate with  the  lacteal  system,  or  they  may  even  hang  into  a  lacteal  sinus  which 
may  nearly  surround  the  nodule.  The  base  of  the  nodule  is  in  the  subumcous 
tissue.  They  penetrate  the  muscularis  mucosse  and  enter  the  mucous  membrane, 
where  they  form  slight  projections  of  its  epithelial  layer. 

Agminated  glands  or  Peyers  glands  (1677)  may  be  regarded  as  aggregations 
of  the  solitary  glands,  forming  circular  or  oval  patches  (Fig.  646).  They  number 
from  twenty  to  thirty,  and  vary  in  length  from  one-half  to  four  inches ;  in  width 
from  one  and  a  half  to  two  inches.  They  are  largest  and  most  numerous  in  the 
lower  two-thirds  of  the  ileum.  In  the  lower  part  of  the  jejunum  they  are  small 


FIG.  645. — Section  of  a  solitary  gland  of  the  small  intestine. 
.t.i    n.  Solitary  gland,  which  has  become  partly  broken 
away.    6.  Epithelium  of  cupola,    c,  c.  Villi.    d.  Crypt  of  Lieber- 
kuhh.    e,  e.  Muscularis  mucosae.   /.  Submucous  coat. 


FIG.  646.— Patch  of  Fever's  glands  from 
the  ilenm,  slightly  magnified.    (Boehm.) 


and  few  and  of  a  circular  form.  They  are  occasionally  seen  in  the  lower  duode- 
num. They  are  placed  lengthwise  to  the  intestine,  covering  that  portion  of  the 
tube  opposite  the  attachment  of  the  mesentery,  hence  to  see  them  well  open  the 
bowel  along  its  mesenteric  attachment. 

Each  patch  is  formed  of  a  group  of  lymph-nodes  which  are  similar  to  the  sol- 
itary glands  above  described.  Each  follicle  becomes  somewhat  pyramidal,  due  to 
pressure,  and  they  lose  much  of  their  individuality,  being  most  distinct  along  the 

65 


1026 


THE    ORGANS    OF  DIGESTION. 


outer  boundary.    The  surface  of  a  patch  is  usually  free  from  villi;  it  is  surrounded 
by  a  row  of  the  crypts  of  Lieberkiihn.     They  are  best  marked  in  young  subjects, 

where  as  many  as  45  have  been  observed ; 
they  become  indistinct  in  middle  life  and 
...-Capillary  network,  even  disappear  in  old  age.  Their  resem- 
blance to  lymph-glands  is  seen  in  any  in- 
fectious disease  of  the  intestines,  especially 
in  typhoid  fever,  where  they  may  ulcerate 
and  perforate  to  the  peritoneal  cavity, 
causing  fatal  haemorrhage. 

They  have  a  large  vascular  supply 
which  forms  an  abundant  plexus  around 
each  follicle.  This  gives  off  fine  capil- 
laries, which,  supported  by  the  retiform 
tissue,  converge  toward  the  centre  (Fig. 
647).  The  lacteal  plexuses,  which  are 
abundant  throughout  the  small  intestine, 
are  especially  so  around  the  follicles  of  a 
Peyer's  patch,  often  forming  sinuses 
around  them  (Fig.  648), 

Resume. — The  valvulge  conniventes 
and  villi  are  most  abundant  in  the  upper 
part  of  the  small  intestine. 

Brunner's  glands  are  mostly  in  the 
duodenum. 

Solitary  glands  and  Peyer's  patches  are  most  abundant  in  the  lower  part  of 
the  small  intestine. 

The  crypts  of  Lieberkiihn  are  abundant  in  both  large  and  small  intestines. 
The  large  intestine  possesses  the  crypts  of  Lieberkiihn  and  solitary  glands. 


FIG.  647.— Transverse  section  through  the  equato- 
rial plane  of  three  of  Peyer's  follicles  from  the  rabbit. 


FIG  648— Vertical  section  of  one  of  Peyer's  patches  from  man,  injected  through  its  lymphatic  canals,  a. 
Villi  with  their  chyle-passages,  b.  Follicles  of  Lieberkiihn.  c.  Muscular  mucosse.  rf.  Cupola  or  apex  of  solitary 
glands  e  Mesial  zone  of  glands.  /.  Base  of  glands,  g.  Points  of  exit  of  the  chyle-passages  from  the  villi,  and 
entrance  into  the  true  mucous  membrane,  h.  Eetiform  arrangement  of  the  lymphatics  in  the  mesial  zone.  i. 
Course  of  the  latter  at  the  base  of  the  glands,  k.  Confluence  of  the  lymphatics  opening  into  the  vessels  of  the 
submucous  tissue.  I.  Follicular  tissue  of  the  latter. 

Vessels  and  Nerves  of  the  Small  Intestine. 

The  arteries  supplying  the  duodenum  are  the  pyloric,  the  superior  pancreatico- 
duodenal,  from  the  gastro-duodenal,  all  of  which  come  from  the  hepatic,  and  the 
inferior  pancreatico-duodenal,  from  the  superior  mesenteric. 

The  jejunum  and.  ileum  are  supplied  by  the  superior  mesenteric  artery,  the 


THE  INTESTINAL    CANAL.  1027 

branches  of  which,  having  reached  the  attached  border  of  the  bowel,  run  between 
the  serous  and  muscular  coats,  with  frequent  inosculations  to  the  free  border, 
where  they  also  anastomose  with  other  branches  running  round  the  opposite  sur- 
face of  the  gut.  From  these  vessels  numerous  branches  are  given  off  which  pierce 
the  muscular  coat,  supplying  it  and  forming  an  intricate  plexus  in  the  submucous 
tissue.  From  this  plexus  minute  vessels  pass  to  the  glands  and  villi  of  the  mucous 
membrane.  The  veins  have  a  similar  course  and  arrangement  to  the  arteries. 
Each  artery  has  only  one  vein.  The  lymphatics  of  the  small  intestine  (lacteals) 
are  those  of  the  mucous  membrane  and  those  of  the  muscular  coat.  The  lymph- 
atics of  the  villi  commence  in  these  structures  in  the  manner  described  above,  and 
form  an  intricate  plexus  in  the  mucous  and  submucous  tissue,  being  joined  by  the 
lymphatics  from  the  lymph-spaces  at  the  bases  of  the  solitary  glands  (Fig.  648), 
and  from  this  pass  to  larger  vessels  at  the  mesenteric  border  of  the  gut.  The 
lymphatics  of  the  muscular  coats  are  situated  to  a  great  extent  between  the  two 
layers  of  muscular  fibres,  where  they  form  a  close  plexus,  and  throughout  their 
course  communicate  freely  with  the  lymphatics  from  the  mucous  membrane,  and 
empty  themselves  in  the  same  manner  into  the  commencement  of  the  lacteal  ves- 
sels at  the  attached  border  of  the  gut. 

According  to  Sappey  the  vessels  from  a  villas  have  two  functions,  one  set  is  to 
carry  chyle  and  the  other  lymph.  The  former  either  contains  chyle  only  or  is 
empty.  After  the  vessels  have  entered  the  mesentery,  then  they  interchangeably 
carry  chyle  or  lymph.  The  nerves  of  the  small  intestine  are  derived  from  the 
plexuses  of  sympathetic  nerves  around  the  superior  mesenteric  artery.  Those 
nerves  come  from  the  cceliac  plexus,  the  semilunar  ganglia,  and  largely  from  the 
right  vagus  nerve.  From  this  source  they  run  to  a  plexus  of  nerves  and  ganglia 
situated  between  the  circular  and  longitudinal  muscular  fibres  (Auerbach's  plexus) 
from  which  the  nervous  branches  are  distributed  to  the  muscular  coats  of  the 
intestine.  From  this  plexus  a  secondary  plexus  is  derived  (Meissner's  plexus), 
which  is  formed  by  branches  which  have  perforated  the  circular  muscular  fibres. 
This  plexus  lies  between  the  muscular  and  mucous  coats  of  the  intestine.  It  is 
also  gangliated,  and  from  it  the  ultimate  fibres  pass  to  the  muscularis  mucosae  and 
to  the  mucous  membrane. 

The  Large  Intestine. 

The  large  intestine  extends  from  the  termination  of  the  ileum  to  the  anal 
orifice.  It  differs  from  the  small  intestine  in  its  larger  size,  more  fixed  position, 
saccular  form  and  appendices  epiploicae.  It  is  about  five  or  six  feet  in  length  or 
one-fifth  that  of  the  whole  intestinal  canal  (Sappey  1.68  m.).  Its  capacity  in 
moderate  distention  averages  twenty-two  ounces  pe/foot,  or  seven  and  a  half  to 
eight  pints  for  the  whole  length.  Its  circumference  decreases  from  beginning  to 
end.  except  at  the  ampulla  of  the  rectum  ;  it  measures  28.5  cm.  at  its  widest 
part,  junction  of  colon  and  caecum,  20.5  cm.  at  the  end  of  the  ascending  portion. 
14.5  cm.  in  the  descending  portion.  Diameter  varies  from  two  and  a  half  inches 
to  less  than  one  inch.  By  accumulation  of  fecal  matter  or  gas  the  colon  may  be 
distended  to  double  its  normal  size. 

Sometimes  in  the  fresh  body  of  a  robust  suicide  the  descending  colon  or  sig- 
moid  flexure  or  even  part  of  transverse  colon  may  be  contracted  to  the  thickness 
of  a  thumb.  The  tube  is  hard  and  can  scarcely  be  opened  by  inflation.  It  is  not 
pathological,  as  coroners  say,  but  a  high  degree  of  rigor  mortis,  which  will  dis- 
appear. In  the  greater  part  of  the  colon  its  external  surface  is  very  uneven  from 
the  presence  of  pouches  or  saccules,  protrusions  arranged  in  rows  of  three  columns. 
These  are  separated  by  three  ligamentous  tapes  about  the  width  of  the  little 
finger. 

In  its  course  the  large  intestine  describes  a  horseshoe-shaped  arch  which  sur- 
rounds the  convolutions  of  the  small  intestine.  It  begins  in  a  blind  sac  in  the 
right  iliac  fossa,  ascends  along  the  right  posterior  abdominal  wall  to  the  right 
hypochondrium,  where  it  is  in  contact  with  the  under  surface  of  the  liver.  It  here 


1028  THE    ORGANS    OF  DIGESTION. 

bends  to  the  left,  and  takes  a  transverse  somewhat  ascending  course  to  the  spleen. 
In  the  left  hypochondrium  it  bends  again  and  descends  along  the  left  posterior 
abdominal  wall  to  the  left  iliac  fossa,  then  becomes  convoluted  as  the  sigmoid 
flexure :  it  finally  enters  the  pelvis  and  descends  as  the  rectum  along  its  posterior 
wall  to  the  anus. 

There  are  to  be  distinguished,  then : 

1.  Caecum  (intestinum  caecum),  or  Caput  coli ; 

2.  Colon  ascendens,  or  Right  colon ; 

3.  Hepatic  flexure,  or  Flexura  coli  dextra ; 

4.  Colon  transversum ; 

5.  Splenic  flexure,  or  Flexura  coli  sinistra ; 

6.  Colon  descendens,  or  Left  colon ; 

7.  Flexura  sigmoidea  (Colon  sigmoideum),  or  S.  romanum. 

8.  Rectum  (intestinum  rectum). 

Structure  of  the  Large  Intestine. 

We  find  here  the  same  four  coats  which  have  been  seen  in  the  canal  above  : 
serous,  muscular,  submucous,  and  mucous. 

The  serous  coat  is  the  peritoneal  covering  investing  parts  of  the  large  intes- 
tine to  a  variable  extent. 

The  caecum  is  completely  invested.  The  ascending  and  descending  colons  in 
the  adult  have  usually  only  a  third  of  the  posterior  surface  left  bare.  It  is  a 
question  when  to  declare  the  folds  near  enough  to  call  them  a  mesocolon. 

Treves  says  a  mesocolon  may  be  expected  on  the  left  side  in  36  per  cent,  of 
all  cases,  on  the  right  side  in  26  per  cent. 

The  transverse  colon  is  almost  completely  invested,  having  a  proper  meso- 
colon ;  the  great  omentum  is  attached  to  its  anterior  surface. 

The  sigmoid  flexure  has  a  mesocolon,  and  the  upper  part  of  the  rectum  has  a 
mesorectum.  In  the  second  part  of  the  rectum  the  peritoneum  covers  its  ante- 
rior surface  and  parts  of  the  sides ;  its  third  portion  loses  it  altogether.  The 
peritoneum  covering  the  internal  taenia  along  the  colon,  especially  the  transverse 
and  after  part,  is  thrown  into  many  external  pouches  containing  fat  in  well- 
nourished  people ;  they  are  called  appendices  epiploicce,  or  omentula. 

The  muscular  coat  consists  of  an  external  longitudinal  and  an  internal  circu- 
lar layer. 

The  longitudinal  fibres  are  partly  collected  into  three  flat  longitudinal  bands, 
each  about  half  an  inch  wide  and  one  twenty-fifth  inch  thick.  They  are  found 
on  the  caecum  and  colon  and  each  is  called  ligamentum  or  tcenia  coli  Between 
these  bands  the  longitudinal  layer  is  present,  but  very  thin.  On  the  appendix 
the  layer  is  uniform.  These  bands  spread  out  from  the  root  of  the  vermiform 
appendix  to  the  caecum.  Thence  they  can  be  traced  as  far  as  the  rectum,  where 

they  form  two  bundles.  The  posterior  band  passes 
^uca sijjmoidea  along  the  mesenteric  attachment  of  the  intestine; 
another,  the  largest,  runs  along  the  anterior  border 
of  the  ascending  and  descending  colons  and  on  the 
transverse  colon  corresponds  to  the  attachment  of 
the  great  omentum.  The  third  or  internal  band 
runs  along  the  inner  borders  of  the  ascending  and 
descending  colons,  but  becomes  inferior  on  the  trans- 
verse  colon. 

The  three  bands  are  about  one-half  shorter  than 
the  real  walls  of  the  intestine  and  so  form  sacculi  or 
haustra  (buckets).  If  the  bands  be  dissected  away 
the  sacculi  will  be  wholly  effaced  and  the  colon  be- 
comes much  elongated  and  cylindrical.  The  transverse  constrictions  seen  on  the 
outside  of  the  intestine  between  the  sacculi  appear  on  the  inside  as  sharp  ridges 


THE  INTESTINAL    CANAL. 


1029 


which  separate  the  pouches,  cellulte,  or  haustra.  The  whole  projection  is  made 
up  of  all  the  coats  of  the  intestine  and  is  called  the  plica  or  valvula  sigmoidea 
(Fig.  649).  A  valve  passes  between  two  trenire  Avhere  otherwise  a  transverse  fold 
would  exist.  Only  rarely  do  two  or  three  valves  lie  in  the  same  plane,  so  that 
they  would  be  in  position  to  effect  a  scissor-like  motion  and  cut  a  mass  of  faecal 
matter  into  scybalse  or  round  balls. 

The  circular  fibres  form  a  thin  continuous  layer  and  are  especially  collected 
in  the  constrictions  between  the  sacculi.  In  the  rectum  they  form  the  Internal 
sphincter  muscle. 

The  xubmiu-ous  coat  is  in  the  same  position  and  serves  the  same  purpose  as  in 
the  small  intestine. 

The  mucous  membrane  is  pale,  smooth,  destitute  of  villi  and  raised  into  cres- 
centic  folds,  separating  the  pouches  and  corresponding  to  the  external  constric- 
tions separating  the  sacculi. 

As  in  the  small  intestine,  the  mucous  membrane  consists  of  a  muscular  layer, 
the  muscularis  mucostie ;  of  a  quantity  of  retiform  tissue,  in  which  the  vessels 
ramify ;  of  a  basement  membrane  and  epithelium,  which  is  of  the  columnar 
variety  and  exactly  resembles  the  epithelium  found  in  the  small  intestine.  The 
mucous  membrane  of  this  portion  of  the  bowel  presents  for  examination  crypts 
of  Lieberkiihu  and  solitary  glands. 

The  crypts  of  Lieberkiikn  are  tubular  prolongations  of  the  mucous  mem- 
brane, arranged  perpendicularly,  side  by  side,  over  its  entire  surface ;  they  are 
longer,  more  numerous,  and  placed  in  much  closer  apposition  than  those  of  the 
small  intestine,  and  they  open  by  minute  rounded  orifices  upon  the  surface,  giving 
it  a  cribriform  appearance. 

The  solitary  glands  (Fig.  650)  in  the  large  intestine  are  most  abundant  in 

Surface  of  mucous  membrane, 
with  openings  of  Lieberkuhn't 
follicle*. 


Lieberkiihn'i  foUidet. 

Muscularis  mucoste  (two  layers). 
Submucous  connective  tissue. 


Solitary  gland. 
FIG.  650. — Minute  structure  of  large  intestine. 

the  cfKcum  and  appendix  vermiformis,  but  are  irregularly  scattered  also  over  the 
rest  of  the  intestine.  They  are  similar  to  those  of  the  small  intestine. 

Vessels  and  Nerves. — The  arteries  supplying  the  large  intestine  give  off  large 
branches,  which  ramify  between  the  muscular  coats,  supplying  them,  and,  after 
dividing  into  small  vessels  in  the  submucous  tissue,  pass  to  the  mucous  membrane. 
Those  arteries  are  the  ileo-colic,  colica  dextra,  colica  media  from  the  superior 
mesenteric,  colica  sinistra  and  sigmoidea  from  the  inferior  mesenteric. 

The  lymphatic  vessels  consist  of  two  layers ;  the  deep  set  lie  under  the  glands 
of  Lieberkuhn,  and  the  superficial  forms  a  wide-meshed  network  which  penetrates 
the  submucosa  in  all  directions.  The  lymphatics  of  the  ascending,  transverse,  and 
descending  colons  open  into  the  mesenteric  glands,  those  of  the  sigmoid  flexure 
into  the  lumbar  glands. 


1030 


THE    ORGANS    OF  DIGESTION. 


The  nerves  which  supply  the  caecum,  ascending  and  right  half  of  the  trans- 
verse colon  are  sympathetic,  coming  from  the  superior  mesenteric  plexus  derived 
from  the  coeliac  plexus.  Those  which  supply  the  left  half  of  the  transverse  colon, 
the  descending  and  sigmoid  colon  come  from  the  inferior  mesenteric  plexus 
derived  from  the  aortic  plexus.  In  their  course  they  accompany  the  arteries. 

The  caecum  (ccecus,  blind)  (Fig.  653)  is  the  head  of  the  colon,  or  that  part  of 
the  large  intestine  situated  below  the  ileo-caecal  valve,  some  say  below  the  ileurn. 
Its  length  and  breadth  are  never  equal,  the  breadth  being  always  the  greater. 
The  opinions  vary  thus — 

Average  length.  Average  breadth. 

Quain 2J  inches                            3  inches 

Berry 6   cm.                                 7  cm. 

Treves 6     "                                    8    " 

Struthers       6     "                                    6    " 

Luschka 4-12     " 

Sappey 8-10     " 

Henle" 5.5" 

The  discrepancies  are  due  largely  to  methods  of  measurement.  Treves  takes 
as  the  upper  limit  of  the  caecum  the  lower  edge  of  the  ileum.  Berry  states  this 
is  too  short,  and  the  upper  limit  of  caecum  is  on  the  level  of  the  ileo-caecal  valve, 
or  Struthers'  "  fraenal  furrows,"  which  are  continuations  of  the  ileo-caecal  valve. 
If  these  furrows  cannot  be  seen  externally,  take  as  the  upper  limit  an  "  approxi- 
mation line,"  drawn  transversely  across  the  colon  from  a  point  midway  between 
the  upper  and  lower  edges  of  the  ileum.  In  100  cases  this  gave  Berry's  figures, 
6  and  7  cm.,  for  average  length  and  breadth.  "  Sex  has  no  influence  upos  size, 
but  it  varies  with  age,  being  absolutely  and  relatively  larger  in  the  adult.  Caeca 
of  insane  persons  are  apt  to  be  abnormal "  (Berry). 

The  caecum  lies  in  the  right  iliac  fossa  above  the  outer  half  of  Poupart's 
ligament,  its  point  being  at  about  the  middle,  immediately  behind  the  anterior 


FIG.  651. — A.  Caecum  of  Mangabey  monkey.    B.  Caecum  of  spider  monkey.    (Treves.) 

abdominal  wall  in  front  of  the  ilio-psoas  muscle  (Fig.  578).     Should  it  be  long 
it  may  extend  more  or  less  into  the  pelvic  cavity  (Fig.  626). 

Many  statements  are  made  as  to  its  peritoneal  relations.  Bardeleben  first 
stated  it  was  wholly  invested  by  peritoneum  ;  Luschka,  Treves,  very  positively, 
Struthers  and  Jonnesco  all  agree.  Quain  states  that  in  5  per  cent,  of  cases  the 


THE  INTESTINAL    CANAL. 


1031 


peritoneal  covering  is  not  complete,  but  is  reflected  just  below  its  upper  end, 
leaving  the  upper  part  of  its  posterior  surface  uncovered  and  connected  to  the 
iliac  fascia  by  areolar  tissue.  Berry  has  seen  the  same  thing  in  6  per  cent,  of 
cases.  The  reflected  peritoneum  never  makes  a  true  mesocaecum.  It  may  have 
sufficient  motility  or  length  to  enter  a  right  inguinal  or  femoral  hernia,  and  in 
rare  cases  a  left 'one.  According  to  Treves,  any'human  caecum  can  be  classified 
under  one  of  four  types  (Fig.  652).  In  certain  monkeys  we  see  a  primitive  form 


FIG.  Gol.—A,  B,  C,  D,  four  types  of  human  cseca.    (Treves. ) 

where  the  crecum  is  short,  conical,  and  broad  at  the  base,  with  its  apex  turned 
up  and  in  toward  the  ileo-colic  junction  (Fig.  651,  A).  This  type  is  seen  early 
in  the  human  foetus.  Next  it  grows  in  length  more  than  in  breadth,  and  this 
type  is  seen  in  the  human  fcetus  in  Fig.  651,  B.  As  development  goes  on  the 
lower  part  of  the  tube  ceases  to  grow  and  the  upper  part  becomes  greatly  in- 
creased, so  that  a  narrow  tube  is  formed  hanging  from  a  conical  projection.  The 
latter  is  the  csecum.  and  the  small  tube  the  vermiform  appendix.  This  is  the  foetal 
or  infantile  type  (Fig.  652,  ^1).  It  may  persist  throughout  life.  Treves  found  it 


1032  THE    ORGANS    OF  DIGESTION, 

in  adults  to  the  extent  of  2  per,  cent.  The  caecum  is  conical,  and  the  appendix 
rises  from  its  apex  in  line  with  the  axis  of  the  colon.  The  three  longitudinal 
bands  of  the  colon  start  at  the  root  of  the  foetal  appendix  about  equidistant,  and 
pass  up  over  the  caecum  and  colon  as  described,  dividing  them  into  three  rows  of 
sacculations.  The  second  type  (Fig.  652,  B}  has  substituted  the  conical  caecum 
for  a  more  quadrate  one.  The  appendix  is  in  the  centre  of  two  sacculi  of  equal 
size  instead  of  at  the  apex  of  a  cone.  There  is  an  equal  extent  of  intestine  on 
each  side  of  the  anterior  band.  The  higher  apes  have  this  type — e.  g.  gibbon. 
In  the  human  subject  it  occurs  in  3  per  cent.  The  third  type  (Fig.  652,  (7)  is 
the  normal  type  found  in  man.  The  walls  of  the  caecum  have  grown  at  unequal 
rates.  The  right  saccule  and  anterior  wall,  probably  due  to  better  blood-supply, 
have  outstripped  the  left  saccule  and  posterior  wall.  The  appendix  still  rises 
from  the  true  apex,  the  three  bands  still  start  from  its  root,  but  they  are  all  now 
found  to  the  left  and  posteriorly  near  the  ileo-colic  junction.  A  new  or  false 
apex  has  appeared,  which  really  is  the  exaggerated  convexity  of  the  right  sac- 
cule situated  between  the  anterior  and  postero-external  bands.  This  form  occurs 
in  90  per  cent.,  and  hence  is  of  great  surgical  importance,  as  it  simplifies  the 
location  of  the  appendix.  In  the  fourth  type  the  condition  of  the  third  has  gone 
still  farther.  The  right  saccule  and  parts  to  the  right  of  the  anterior  band  have 
excessive  development,  while  the  parts  to  the  left  of  the  band  are  atrophied. 
Here  the  anterior  band  runs  to  the  inferior  angle  of  the  ileum,  while  the  cgecum 
and  the  appendix  seem  to  rise  from  the  ileo-colic  junction  (Fig.  652,  7>).  This 
occurs  in  4  or  5  per  cent. 

Berry  has  gone  over  the  same  work  and  obtained  nearly  the  same  percentages, 
proving  that  in  about  90  cases  out  of  100  the  base  of  the  appendix  bears  a  definite 
relationship  to  the  ileo-caecal  junction. 

Sometimes  the  caecum  is  small  and  insignificant,  may  be  enormous ;  may  be 
rotated  so  the  ileum  passes  behind  and  enters  on  the  right  side ;  or  the  left  parts 
may  be  so  developed  that  the  ileum  enters  anteriorly. 

Vermiform  Appendix. — Starting  from  what  was  originally  the  apex  of  the 
tube,  the  inner  and  back  portion  of  the  caecum,  usually  1.7  cm.  below  the 
ileo-colic  opening,  is  a  famous  narrow  round  part  of  the  intestine  called  the 
appendix  cceci,  or,  on  account  of  its  worm-like  appearance,  appendix  vermi- 
formis.  This  is  first  seen  low  down  among  the  mammals,  in  the  marsupial 
group,  in  the  wombat.  No  sign  of  it  again  appears  till  the  ichneumon  and 
pig  are  reached,  but  not  then  is  it  a  proper  appendix.  It  is  next  seen  in  the 
lemurs  and  higher  apes,  as  chimpanzee,  orang,  gibbon,  and  gorilla.  Finally  in 
man  it  is  present  as  a  functionless  and  dangerous  structure.  Its  length,  aver- 
aged from  eleven  authors,  is  9.2  cm.  Its  extremes  are  1  to  9  inches,  or  3.1 
cm.  to  23  cm.  It  attains  its  greatest  length  between  the  twentieth  and  for- 
tieth years  (Berry).  Its  length  compared  to  that  of  the  large  intestine  is  1  to 
10  in  the  new-born,  and  1  to  20  in  the  adult.  There  is  no  relation  between 
size  of  caecum  and  length  of  appendix.  Its  diameter  is  6  mm.  at  base  and  5 
mm.  at  apex. 

The  appendix  has  no  set  position.  Treves  considers  it  to  pass  most  frequently 
up  from  behind  the  caecum  to  the  left  behind  the  ileum  and  mesentery  toward  the 
spleen.  Others  regard  this  position  as  nearly  abnormal.  Turner  of  Russia  finds 
it  hanging  into  the  true  pelvis  in  51  out  of  83  cases,  and  transversely  across  the 
promontory  in  20  more  of  those  cases. 

Berry  gives  order  of  frequency  as  :  1.  Pelvic  position  ;  2.  Retro-csecal ;  3.  In- 
ternal caecal  (toward  spleen) ;  4.  Variable. 

The  order  of  frequency  found  in  this  country  by  J.  D.  Bryant1  was  most 
often  "inward,"  then  "behind  caecum,"  "downward  and  inward,"  "into  true 
pelvis." 

The  explanation  of  an  up-turned  or  down-turned  appendix  is  probably  to  be 
sought  in  fcetal  life.  If  the  distal  end  of  the  appendix  gain  adhesions  with  the 

1  Ann.  Surg.,  vol.  17,  1893,  p.  164. 


THE  INTESTINAL    CANAL.  1033 

mesentery  or  abdominal  wall  when  it  is  still  high  up  beneath  the  liver,  the  caecum 
will  drag  it  down  in  an  inverted  position.  If  no  such  adhesions  occur,  then  it 
will  descend  freely,  and  perhaps  dip  into  the  pelvis.  It  takes  a  somewhat  spiral 
form,  due  to  its  short  mesentery. 

/!<  lotions  to  ccecum  have  been  noted  above  under  Caecum,  where  the  data  are 
quite  constant. 

Relations  to  the  anterior  abdominal  wall  for  clinical  purposes  do  not  agree. 
Clado  draws  two  lines,  one  along  the  outer  edge  of  the  right  Rectus,  and  another 
connecting  the  anterior  superior  spines  of  the  ilia.  The  point  where  these  inter- 
sect Clado"  uses  as  a  guide  to  the  base  of  the  appendix,  which  brings  it  into  the 
hypogastrium.  McBurney  draws  an  imaginary  line  from  the  right  anterior  supe- 
rior spine  to  the  umbilicus.  His  ''point"  is  situated  on  this  line  two  inches  from 
the  spine.  This  is  used  as  a  guide  to  the  base  of  the  appendix.  This  point  is  in 
the  right  iliac  fossa. 

Relations  to  peritoneum  are  that  a  mesentery  is  always  present,  but  it  does 
not  extend  the  whole  length  of  the  tube,  leaving  the  distal  third  or  so  free  and 
•completely  covered  by  peritoneum.  This  meso-appendix  is  triangular  and  comes 
from  the  left  leaf  of  the  mesentery,  and  contains  in  its  fold  the  posterior  branch 
of  the  ileo-caecal  artery,  which  is  derived  from  the  ileo-colic. 

Its  walls  present  the  same  layers  as  seen  in  the  colon,  and  its  whole  mucous 
membrane  is  closely  studded  with  solitary  glands.  It  is  usually  hollow  to  its 
extremity  and  its  lumen  communicates  with  the  caecum  by  a  small  orifice  often 
guarded  by  a  valve. 

Gerlach  in  1847  described  a  "  semilunar  fold  of  mucous  membrane  guarding 
the  appendico-caecal  orifice."  It  was  only  .5  to  1  mm.  high  and  was  so  turned  as 
to  cause  retention  of  the  normal  secretion  in  the  appendix.  The  existence  of 
Gerlach's  valve  is  now  doubted.  It  is  inconstant  and  unimportant. 

There  is  usually  another  bigger  crescentic  fold  near  the  orifice  (Fig.  654),  but 
with  no  function  of  a  valve. 

According  to  Ribbert  and  Zuckerkandl  the  cavity  of  the  vermiform  appendix 
tends  to  undergo  obliteration,  not  as  a  pathological  process,  but  a  physiological 
one.  In  children  the  lymph-follicles  of  the  appendix  are  very  numerous  and  close. 
After  the  twentieth  or  thirtieth  year  it  is  normal  for  them  to  atrophy.  Oblitera- 
tion of  the  process  occurs  to  some  degree  in  99  cases  out  of  400  (25  per  cent,) ; 
total  obliteration  in  3.5  per  cent.  (Ribbert).  Or  obliteration  occurred  in  23.7  per 
cent. ;  total  obliteration  in  13.8  per  cent.,  and  partial  (distal  half  most  common) 
in  9.9  per  cent.  (Zuckerkandl).  It  never  occurs  in  new-born.  After  sixty  years 
of  age  more  than  half  are  obliterated.  It  occurs  more  often  in  a  short  process,  5 
to  6  cm.  long.  One  can  never  tell  by  macroscopic  appearance  as  to  the  presence 
of  obliteration. 

The  pathology  seems  to  be  an  involution-change  in  a  functionless  organ. 
There  are  no  signs  of  inflammation  or  cicatrices.  As  a  first  step  there  is  atrophy 
of  the  mucous  membrane,  and  its  glands  disappear.  The  submucosa  thickens  and 
accumulates  fat.  The  muscular  coat  is  either  unchanged  or  becomes  hypertro- 
phied.  The  adenoid  tissue  is  finally  lost.  There  are  four  authentic  cases  of 
absence  of  the  appendix.  For  the  fossce  of  this  region  see  p.  997. 

The  Ileo-colic,  Ileo-caecal  valve  or  Valvula  Bauhini. 

The  end  of  the  ileum  passes  obliquely  upward  and  to  the  right,  and  opens 
into  the  large  intestine  on  its  postero-internal  surface ;  it  opens  upon  the  summit 
of  a  plica  sigmoidea  which  marks  the  junction  between  the  caecum  and  ascending 
colon. 

This  orifice  appears  as  a  transversely  oblique  or  a  double  convex  slit.  It  is 
often  rounded  on  the  left  and  presents  a  sharp  apex  to  the  right  (Fig.  654).  It- 
is  bounded  by  a  valve  having  two  semilunar  segments,  a  colic  and  a  caecal  one, 
which  project  into  the  lumen  of  the  large  intestine.  The  upper  of  these  seg- 
ments is  more  horizontal,  the  lower  more  concave  and  longer.  At  each  end  they 


1034 


THE    ORGANS    OF  DIGESTION. 


coalesce  and  are  prolonged  intofrcena  or  retinacula  of  the  valve.     The  segments 
are  made  by  an  invagination  of  parts  of  the  wall  of  the  ileum  into  those  of  the 


FIG.  653.— Caecum  and  vermiform  appendix.  (Sap- 
pey.)  1.  Ileum.  2.  Orifice  of  valve.  3.  Inf.  segment. 
4.  sup.  segment.  5.  Long  muscular  fibres  from  ileum. 
6.  Cul-de-sac  of  caecum.  7.  Appendix.  8.  Post,  taenia. 
9.  Int.  taenia.  10.  Ant.  taenia.  11.  Sacculus. 


FIG.  654. — Ileo-caecal  valve.  fSappey.)  1.  Edge  of 
caecum.  2.  Orifice  of  valve.  3.  Inf.  segment.  4.  Sup. 
segment:  5  and  6.  Fraena.  7.  Appendix.  8.  Its  mouth. 
9.  Semilunar  fold.  10.  Post,  taenia.  11,  12,  12.  Ant. 
taenia.  13.  Int.  taenia. 


colon  (Fig.  655). 


Each  segment  of  the  valve  consists  of  two  layers  of  mucous 
membrane  continued  around  the  free  border, 
one  from  the  small  intestine  and  one  from  the 
large,  including  between  them  submucosa  and 
circular  muscular  fibres  ;  the  longitudinal  fibres 
and  peritoneum  are  continued  uninterruptedly 
across  from  one  intestine  to  the  other  and  do 
not  enter  their  composition.  If  these  two  coats 
be  incised  and  traction  made  on  the  ileum,  these 
valves  can  be  unfolded  and  drawn  out  of  the 
colon,  the  ileum  appearing  to  open  into  the 
intestine  by  a  large  funnel-shaped  orifice.  The 
opposed  mucous  surfaces  of  the  segments  look- 
ing toward  the  ileum  are  covered  by  villi  and 
present  the  structure  of  the  small  intestine.  In 
foetal  life  the  other  two  surfaces  possessed  yilli 
too,  but  by  birth  the  latter  have  disappeared. 
The  surfaces  turned  toward  the  large  intestine 
present  the  follicles  and  glands  of  Lieberkuhn 
peculiar  to  the  large  intestine. 

The  function  of  the  valve  is  to  prevent  re- 
gurgitation  of  intestinal  contents  back  into  the 
small  intestine.  When  the  caecum  is  distended, 
the  segments  are  approximated.  They  act  even  in  the  cadaver,  proving  that 
muscular  action  is  not  essential.  When  in  an  experiment  water  was  injected 
into  the  colon,  not  a  drop  passed  through  the  valve ;  when  the  pressure  was 
increased  to  a  height  of  two  or  three  metres  the  valves  did  not  yield,  but  the 
walls  ruptured.  In  intestinal  obstruction  there  is  evidence  of  a  return  of  con- 
tents from  the  large  intestine.  This  is  probably  due  to  a  slow,  gradual  disten- 
tion  of  the  walls  of  the  large  intestine,  and  hence  a  relative  insufficiency  of  the 
valve.  High  enemata  may  pass  this  valve  in  two  out  of  three  cases,  but  such  a 
valve  is  regarded  as  imperfectly  developed  and  incompetent  from  the  first. 


FIG.  655.— Vertical  section  through  the 
caecum  and  ileo-caecal  valve.  (Gegen- 
baur.)  Col.  Colon.  C.  Caecum,  pv.  Pro- 
cessus  vermiformis. 


THE  INTESTINAL    CANAL.  1035 

This  valve  has  been  named  after  nearly  all  the  following  men.  It  was  discovered  in  1573 
by  Varolius,  who  called  it  an  opercuJum.  Six  years  later  Bauhin  called  it  vahula.  Fabricius 
in  1618  first  tried  its  function  by  insufflation.  Casserius,  Tulpius.  and  Bartholin  repeated  the 
experiments.  Morgagni  in  1719  gave  the  best  description.  Window  and  Albinus  followed 
him. 

Colon. — As  in  the  csecum,  the  outer  surface  of  the  colon  is  prismatic  and  tri- 
angular. Four  characteristics  are  observed :  1.  Three  taenise  which  start  from 
th^ root  of  the  appendix;  2.  Three  rows  of  sacculi  between  the  bands;  3.  Con- 
strictions which  separate  the  sacculi  of  each  row ;  4.  Appendices  epiploicse. 
The  internal  surface  has  a  reverse  conformation,  the  projections  between  the 
pouches  being  called  plicce  sigmoidece. 

The  ascending  colon  is  smaller  than  the  caecum,  with  which  it  is  continuous, 
and  larger  than  the  transverse  colon.  It  is  very  short.  It  passes  up  through 
the  right  lumbar  region  into  the  right  hypochondrium  until  it  reaches  the  inferior 
surface  of  the  right  lobe  of  the  liver  to  the  right  of  the  gall-bladder,  the  impressio 
colica.  It  is  retained  in  contact  with  the  posterior  abdominal  wall  by  peritoneum 
which  covers  its  anterior  surface  and  sides,  its  posterior  surface  being  connected 
by  loose  areolar  tissue  with  the  fascia  covering  the  Quadratus  lumborum  and 
Transversalis  muscles,  and  with  the  front  of  the  lower  and  outer  part  of  the  right 
kidney.  An  abscess  of  the  right  kidney  could  thus  break  through  into  the  ascend- 
ing colon  and  not  wound  the  peritoneum.  It  is  in  relation  in  front  with  the 
abdominal  wall  and  convolutions  of  the  ileum.  Sometimes  the  peritoneum  nearly 
surrounds  the  colon  and  forms  a  short  mesocolon.1  On  the  under  surface  of  the 
liver  in  the  region  of  the  gall-bladder,  the  ascending  colon  forms  a  sharp  angle 
from  the  posterior  abdominal  wall  to  the  front  and  the  left,  becomes  somewhat 
superficial,  and  continues  into  the  transverse  colon.  This  is  the  hepatic  or  right 
colic  flexure,  bound  to  the  under  surface  of  the  liver  by  the  lig.  hepato-colicum. 

The  transverse  colon  is  the  longest  part  of  the  large  intestine,  averaging 
twenty  inches,  while  the  ascending  colon  is  eight  inches,  and  the  descending, 
from  the  splenic  flexure  to  the  crest  of  the  ilium,  is  eight  and  a  half  inches.  It 
passes  from  the  hepatic  flexure  in  the  right  hypochondrium  transversely  and 
slightly  upward  from  right  to  left  along  the  anterior  abdominal  wall  to  the  splenic 
flexure  in  the  left  hypochondrium  (Fig.  626).  Since  the  colon  is  longer  than 
the  width  of  the  abdomen  it  describes  an  arch,  transverse  arch  of  the  colon,  Avith 
its  convexity  directed  downward  and  forward. 

It  is  the  most  movable  part  of  the  colon,  for  it  has  a  very  long  mesentery, 
the  transverse  mesocolon,  which  allows  it  a  variable  position.  Its  usual  position 
corresponds  to  the  line  separating  the  umbilical  and  epigastric  regions.  In  four 
times  out  of  five  it  is  above  the  umbilicus.  It  is  in  relation  by  its  upper  surface 
with  the  under  surface  of  the  liver  and  gall-bladder,  greater  curvature  of  the 
stomach  and  lower  end  of  the  spleen ;  by  its  under  surface  with  the  small  intes- 
tine ;  by  its  anterior  surface  with  the  great  omentum  and  abdominal  walls  ;  by- 
its  posterior  surface  with  the  transverse  mesocolon  ;  on  the  right  with  the  second 
part  of  the  duodenum,  and  to  the  left  of  this  with  some  convolutions  of  the 
small  intestine.  If  this  colon  has  a  very  direct  and  obliquely  ascending  course, 
the  greater  curvature  of  the  stomach  will  be  behind  its  left  portion. 

In  some  cases  the  transverse  colon  may  present  a  V-  or  U-shaped  bend  de- 
scending as  far  as  the  pubes.  These  bends  are  always  downward,  abrupt,  and 
angular.  Treves  thinks  they  are  due  to  habitual  distention  or  to  congenital 
causes  (Fig.  656).  They  are  normal  in  many  animals. 

The  descending  colon  is  continuous  with  the  transverse  by  the  splenic  flexure, 

1  Mr.  Treves  states  that,  after  a  careful  examination  of  one  hundred  subjects,  he  found  that  in 
fifty-two  there  was  neither  an  ascending  nor  a  descending  mesocolon.  In  twenty-two  there  was  a 
descending  mesocolon,  but  no  trace  of  a  corresponding  fold  on  the  other  side.  In  fourteen  subjects 
there  was  a  mesocolon  to  both  the  ascending  and  the  descending  segments  of  the  bowel,  while  in  the 
remaining  twelve  there  was  an  ascending  mesocolon,  but  no  corresponding  fold  on  the  left  side.  It 
follows,  therefore,  that  in  performing  lumbar  colotomy  a  mesocolon  may  be  expected  upon  the  left 
side  in  36  per  cent,  of  all  cases,  and  on  the  right  in  26  per  cent.  (The  Anatomy  of  the  Intestinal  Canal 
and  Peritoneum  in  Man,  1885,  p.  55.) 


1036 


THE    ORGANS   OF  DIGESTION. 


FIG.  656. — Extreme  downward  bend  in  the  trans- 
verse colon.    Found  in  four  cases.    (Treves.) 


or  left  colic  flexure,  which  is  higher  up  and  farther  back  than  the  hepatic  flexure. 
To  this  bend  a  fold  of  peritoneum  is  attached,  rising  from  the  diaphragm  between 
the  tenth  and  eleventh  ribs.  It  is  the  phreno-colic  ligament,  rather  than  "  costo- 

colic,"  as  it  does  not  touch  a  rib.  The 
spleen  happens  to  lie  just  above  it,  so  it 
acts  as  a  support  to  that  organ  though 
not  connected  with  it,  and  thus  receives 
a  second  name,  sustentaculum  lienis  (sup- 
porter of  the  spleen).  The  colon  then 
descends  along  the  outer  border  of  the 
left  kidney,  then  turns  in  a  little,  and 
descends  to  the  crest  of  the  ilium  or  to  a 
point  where  the  peritoneum  begins  to 
surround  the  intestine  and  form  a  meso- 
colon  for  the  sigmoid  flexure. 

It  has  passed  along  the  outer  border 
of  the  Psoas  muscle  in  front  of  part  of 
the  Quadratus  lumborum,  and  more  largely 
in  front  of  the  Transversalis  muscle.    The 
relations  of  the  descending  colon  on  the 
left  side  are  much  like  those  of  the  as- 
cending on   the   right,  only   the  former 
reaches  a  little  higher  and  is  placed  more 
laterally,  so  it  can  be  more  easily  reached 
through  the  posterior  abdominal  wall  for  the  establishment  of  an  artificial  anus. 
This  colon  is  smaller  and  deeper  than  the  ascending  colon  and  more  liable  to 
have  a  mesocolon. 

The  sigmoid  colon  or  flexure  is  in  the  left  iliac  fossa,  commencing  above  at  the 
iliac  crest  and  ending  below  in  the  rectum  at  the  brim  of  the  true  pelvis  opposite 
the  left  sacro-iliac  articulation,  or  just  as  often  opposite  the  upper  edge  of  the 
sacrum.  In  general  it  is  described  as  an  S-shaped  curve  in  which  can  be  distin- 
guished an  upper  colic  limb  turned  toward  Poupart's  ligament,  and  a  lower  rectal 
limb  which  hangs  more  or  less  into  the  true  pelvis. 

This  first  part  usually  passes  downward,  inward,  and  somewhat  forward, 
approaching  the  anterior  abdominal  wall  and  outer  part  of  Poupart's  ligament. 
This  portion  may  have  peritoneum  only  in  front  and  on  the  sides.  The  next 
part  is  more  movable,  its  mesentery  is  about  three  inches  long,  and  it  constitutes 
the  sigmoid  loop  proper.  When  it  does  not  hang  down  into  the  pelvis,  the  blad- 
der and  rectum  are  distended  and  push  it  up,  in  rare  cases  as  high  as  the  umbili- 
cus or  even  liver.  This  loop  may  lie  in  the  iliac  fossa  outside  the  first  part ;  if 
its  mesocolon  is  short,  it  passes  obliquely  across  the  iliac  fossa  and  is  covered  by 
small  intestine. 

The  sigmoid  mesocolon  is  inserted  into  a  line  running  from  the  left  at  the 
crest  of  the  ilium  across  the  psoas  muscle  and  left  iliac  vessels  at  right  angles  to 
the  anterior  surface  of  the  sacral  promontory,  where  it  is  continuous  Avith  the 
mesorectum  (Fig.  614).  In  the  left  layer  of  this  mesentery  is  the  intersigmoid 
fossa  (page  996).  The  position  of  the  flexure  in  the  new-born  demands  notice, 
for  here  the  mesentery  is  very  long  and  the  flexure  may  reach  over  on  the  right 
to  the  caecum.  This  flexure  is  usually  filled  with  meconium. 

Relations  of  Large  Intestine  in  Detail. 

Caecum. 
Anteriorly : 

Anterior  abdominal  wall  above  outer  half  of  Poupart's  ligament. 
Posteriorly : 

Right  ilio-psoas  muscle  ;  Origin  of  appendix. 


THE  INTESTINAL    CANAL.  1037 


Superiorly  : 

Ileo-cjecal  valve  ;  and  aperture. 

Inner  Side : 

End  of  ileum. 

Ascending  Colon. 

Anteriorly  : 
Ileum ; 
Abdominal  wall. 

Posteriorly/ : 

Quadratus  lumborum  muscle ; 

Transversalis  abdominis ; 

Lower  and  outer  part  of  the  right  kidney. 

Superiorly : 

Under  surface  right  lobe  of  liver. 

Transverse  Colon. 
Anteriorly: 

Anterior  abdominal  wall ; 
Great  omentum. 

Posteriorly : 

Transverse  mesocolon  ; 

Descending  duodenum  ; 

Small  intestine ; 

Greater  curvature  of  stomach  (sometimes). 

Superiorly : 

Under  surface  of  liver  and  gall-bladder; 
Greater  curvature  of  stomach  ; 
Lower  end  of  spleen  ; 
Tail  of  pancreas. 

Inferiorly  : 

Small  intestines. 

Descending  Colon. 
Anteriorly: 

Jejunum ; 
Abdominal  wall. 

Posteriorly  : 

Quadratus  lumborum  muscle ; 
Transversalis  abdominis  muscle; 
Outer  margin  of  Psoas  muscle  ; 
Lower  part  left  edge  of  left  kidney. 

Superiorly : 

Spleen  ; 

Phreno-colic  ligament. 

Sigmoid  Colon, 
Anteriorly  : 

Anterior  abdominal  wall; 

Small  intestines. 

Posteriorly  : 

Left  ilio-psoas  muscle ; 
Posterior  wall  of  pelvis; 
Rectum. 


1038 


THE    ORGANS    OF  DIGESTION. 


The  rectum  constitutes  the  terminal  portion  of  the  intestinal  tube.  It  received 
its  name  intestinum  rectum  from  its  straight  course  in  animals.  In  the  human 
subject  its  course  is  nearly  vertical,  but  it  presents  four  curves  and  should  be 
called  intestinum  curvum  (Lisfranc). 

The  ancient  and  much-copied  method  of  description  divides  it  into  three 
parts.  We  hesitate  to  introduce  a  change  in  old  nomenclature,  but  will  mention 
those  proposed  and  allow  the  reader  to  make  his  choice. 

Treves  in  1885  called  attention  to  the  fact  that  there  Avas  no  demarcation  be- 
tween the  sigmoid  flexure  and  the  first  part  of  the  rectum  at  the  brim  of  the  pelvis. 
So  he  concludes  the  intestines  should  be  called  sigmoid  flexure  until  the  mesocolon 
is  lost,  i.  e.  until  it  reaches  the  third  sacral  vertebra.  This  rectum,  therefore, 
has  the  two  lower  parts  of  the  three  usually  described  and  no  inesorectum.  Cun- 
ningham and  Quain  take  for  the  rectum  the  upper  two  of  the  three  usually 
described,  the  third  being  regarded  as  a  separate  part  called  anal  canal. 

The  rectum  in  three  parts  is  situated  in  the  pelvic  cavity  and  on  its  floor.  It 
is  attached  to  its  posterior  wall,  whose  curve  it  follows.  Its  inferior  limit  is  a 

circular  line  separating  the  skin 
from  the  mucous  membrane — the 
anal  orifice.  Its  superior  limit  can- 
not be  determined  precisely ;  it  is 
continuous  with  the  sigmoid  flexure, 
but  there  is  only  an  arbitrary  line 
of  demarcation.  This  is  the  pelvic 
brim,  most  usually  opposite  the  left 
sacro-iliac  articulation,  quite  often 
the  sacro-vertebral  angle,  or  rarely 
on  the  right  of  the  base  of  the 
sacrum.  Superiorly,  it  is  united  to 
the  sacrum  by  a  fold  of  peritoneum, 
the  mesorectum.  Lower  down  the 
peritoneum  only  covers  the  sides 
and  front,  much  as  in  the  case  of 
the  descending  duodenum  (Fig. 
657).  Still  lower  down,  at  a  height 
of  about  one  inch  above  the  prostate 
gland,  it  entirely  abandons  the  rec- 
tum and  is  reflected  upon  the  neigh- 
boring organs,  making,  according  to 
sex,  the  recto-vesical  pouch  or  the 
recto-vaginal  and  recto-uterine.  The 
height  of  the  recto-vesical  pouch  in 
the  male  is  never  more  than  8  cm. 
above  the  anus.  The  height  of  the 
recto-vaginal  in  the  female  is  always 
less,  about  6  cm.  The  length  of  the 
rectum,  measured  along  its  anterior 
wall  (in  the  body),  is  18  to  22  cm., 
or  about  eight  inches.  Outside  the 

FIG.  657.— Relations  of  peritoneum  to  rectum  and  bladder,    i      i      •,  or  mr.  7-1 

Outline  of  rectum.  (Tiiiaux.)  body  it  measures  z5  cm.    Ihe  calibre 

varies    according  to   circumstances. 

When  empty  it  is  less  than  that  of  the  other  portions  of  the  large  intestine. 
When  it  contains  a  certain  amount  of  faecal  matter  its  middle  portion  is  more  or 
less  dilated,  but  not  to  the  size  of  the  caecum.  The  calibre  of  the  remainder,  in 
general,  is  not  circular.  In  the  lower  part  of  the  rectum  it  presents  a  transverse 
slit,  and  the  anterior  and  posterior  walls  lie  upon  each  other,  mainly  from  the 
pressure  of  the  anterior  organs  forcing  the  rectum  back  on  the  sacrum  and 
coccyx.  Just  at  the  turn  of  the  rectum  into  its  third  portion,  and  especially 


THE  INTESTINAL    CANAL. 


1039 


marked  anteriorly  at  the  apex  of  the  prostate,  is  the  largest  part,  the  ampulla 
of  the  rectum. 

The  lowest  inch  of  the  rectum,  the  anal  canal,  is  an  antero-posterior  slit,  the 
lateral  walls  resting  on  each  other  (Fig.  658).  In  pathological  cases  the  calibre 
may  be  so  distended  as  to  occupy  the 
whole  pelvis. 

The  ilirsi-tioit  of  the  rectum,  starting 
usually  from  the  left  of  the  base  of  the  sa- 
crum, is  obliquely  downward,  backward, 
and  to  the  right.  When  it  comes  to  the 
level  of  the  third  sacral  vertebra  it  has 
reached  themiddle  line.  It  now  passes  that 
line  a  little  and  runs  along  the  right  lat- 
eral part  of  the  fourth  sacral  vertebra. 
It  again  returns  to  the  middle  line  at 
about  the  sacro-coccygeal  junction  and 
passes  downward  and  forward,  and  may 
cross  it  a  second  time  till  it  reaches  the 
level  of  a  transverse  line  drawn  between 
the  anterior  parts  of  the  ischial  tuberos- 
ities.  This  point  is  also  opposite  the 
apex  of  the  prostate  gland  (Fig.  657). 
This  point  is  not  opposite  the  lower  end 
of  the  coccyx,  as  often  stated,  but  fully 
one  inch  below  that. 

Sappey  thus  describes  two  lateral 
curves,  and,  with  two  antero-posterior 
curves,  makes  four  altogether.  The 
first  turn  of  the  rectum  from  left  to 
right  he  does  not  consider  a  curve.  The  lateral  curves  are  of  little  importance, 
and  run  into  each  other.  The  first  is  the  more  pronounced,  and  corresponds  to 
the  junction  of  the  third  and  fourth  pieces  of  the  sacrum,  with  its  concavity  to 
the  left.  The  second  corresponds  to  the  sacro-coccygeal  junction,  with  its  con- 
cavitv  to  the  ri^ht.  Thev  are  best  seen  with  an  emptv  rectum,  and  are  almost 

•  O  «/  i      v 

effaced  when  it  is  distended. 

The  <tnt>-ro-]>,jxterior  cun-e*  are  more  pronounced  and  independent  of  the 
degrees  of  dilatation.  The  first  or  sacral  curve  is  due  to  the  conformation  of 
the  sacro-coccygeal  column.  It  has  its  concavity  forward,  its  convexity  being 
most  marked  at  the  junction  of  the  third  and  fourth  sacral  vertebrae.  The 
second  or  perinc'il  /•»/•>>'  has  its  convexity  forward,  corresponding  to  the  apex 
of  the  prostate  gland  in  the  male  and  posterior  wall  of  the  vagina  in  the  female. 
Its  concavity  looks  downward  and  backward.  The  sacral  curve  represents  the 
arc  of  a  circle.  The  last  one  is  angular. 

According  to  its  direction,  then,  the  rectum  is  divided  into  three  parts — a 
superior  portion,  passing  obliquely  downward  and  backward  :  a  middle  portion 
passing  obliquely  downward  and  forward ;  an  inferior  or  anal  portion,  passing 
obliquely  downward  and  backward.  They  are  not  of  equal  lengths :  that  of  the 
first  is  8  to  9  cm. ;  second.  10  to  11  cm. ;  third,  2  to  3  cm.  in  the  male,  1.5  to 
2  cm.  in  the  female.  According  to  Quain,  in  order,  the  first  part  is  five  or  four 
inches ;  second,  three  or  four  inches ;  anal  canal,  one-half  to  one  inch.  In  the 
infant  the  rectum  is  straighter,  less  flexuous,  and  relatively  larger  than  in  the 
adult.  In  the  female  it  is  said  to  be  larger  and  straighter  than  in  the  male. 

The  first,  or  superior,  portion  includes  about  half  the  length  of  the  tube,  and 
extends  obliquely  from  the  pelvic  brim,  opposite  either  the  left  sacro-iliac  artic- 
ulation or  the  sacro-vertebral  angle  or  the  right  side  of  the  base  of  the  sacrum, 
to  the  body  of  the  third  sacral  vertebra.  It  is  almost  completely  surrounded 
by  peritoneum,  which  is  connected  to  the  anterior  surface  of  the  sacrum  by  the 


FIG.  658. — Coronal  section  through  the  anal  canal. 
(Symington.)  B.  Cavity  of  bladder.  VD.  Vas  deferens. 
SV.  Seminal  vesicle.  R.  Second  part  of  rectum.  AC. 
Anal  canal.  LA.  Levator  ani.  1*.  Internal  sphincter. 
£.?.  External  sphincter. 


1040  THE    ORGANS   OF  DIGESTION. 

double  fold  called  mesorectum.  This  is  continued  above  with  the  sigmoid  meso- 
colon,  is  triangular,  and  ends  below  in  an  apex  at  the  third  sacral  vertebra.  Some 
convolutions  of  the  ileum,  or  a  loop  of  the  sigmoid  flexure,  usually  lie  in  front 
of  this  part  of  the  rectum.  They  separate  it  from  the  bladder  in  the  male  and 
posterior  surface  of  the  uterus  in  the  female  when  the  rectum  is  empty.  If  dis- 
tended, one  of  these  organs,  according  to  sex,  rests  on  its  anterior  surface,  the 
intestine  being  pushed  up.  Posteriorly  is  the  mesorectum,  left  Pyriformis  muscle, 
left  sacral  plexus  of  nerves,  branches  of  left  internal  iliac  vessels,  left  portion  of 
anterior  surface  of  two  and  a  half  sacral  vertebrae.  To  the  left  side  are  the  left 
ureter  and  left  internal  iliac  vessels.  If  this  part  of  the  rectum  come  down  in  the 
middle  line  or  from  the  right,  these  relations  will  differ. 

The  middle  or  second  part  of  the  rectum  is  three  or  four  inches  long,  and  ex- 
tends from  the  middle  of  the  third  sacral  vertebra  to  a  point  opposite  the  apex  of 
the  prostate  gland.  Here  the  course  of  the  rectum  changes  to  a  posterior  one,  and 
that  is  one  inch  below  the  tip  of  the  coccyx.  It  is  only  partially  covered  by 
peritoneum.  It  has  no  mesorectum  and  its  posterior  surface  has  no  peritoneal 
covering.  At  first  it  is  covered  anteriorly  and  laterally,  but  gradually  the  peri- 
toneum leaves  the  sides,  and  finally,  about  one  inch  above  the  prostate  or  at  the 
length  of  an  index  finger  above  the  anus,  never  more  than  8  cm.,  it  is  reflected 
from  the  anterior  surface  of  the  rectum  to  the  bladder  or  to  the  upper  fifth  of  the 
posterior  wall  of  the  vagina,  making  the  pouches  as  above  noted.  Distention  of 
bladder  or  rectum  would  diminish  the  depth  of  these  pouches.  This  part  of  the 
rectum  is  in  relation  anteriorly  in  the  male  with  the  recto-vesical  pouch,  with  the 
triangular  portion  of  the  base  of  the  bladder,  the  vesiculae  seminales  and  vasa 
deferentia,  and  beyond  them  with  the  under  surface  of  the  prostate.  In  the  female 
it  is  related  anteriorly  to  the  posterior  wall  of  the  vagina,  with  which  it  is  adherent, 
with  the  recto-vaginal  and  recto-uterine  pouches  and  small  intestines  therein. 

The  posterior  wall  lies  upon  the  lower  part  of  the  sacrum,  middle  sacral  artery, 
origin  of  Pyriformis  muscles,  coccyx  and  ano-coccygeal  body,  and  Coccygei  mus- 
cles. The  ano-coccygeal  body  is  a  dense  mass  of  musculo-fibrous  tissue  situated 
between  the  tip  of  the  coccyx  and  anus. 

The  lower  portion  or  anal  canal  is  about  one  inch  long  when  the  rectum  is 
empty;  it  is  shorter  when  the  rectum  is  distended.  It  turns  downward  and  back- 
ward at  the  lower  part  of  the  prostate  gland  and  ends  at  the  anal  orifice.  It  has 
no  peritoneal  covering.  It  is  invested  by  the  sphincter  muscles  and  supported  by 
the  Levatores  ani.  Behind  it  is  in  relation  to  the  ano-coccygeal  body  and  Coc- 
cygei muscles;  on  the  sides  to  the  fat  of  the  ischio-rectal  fossae  and  the  Levatores 
ani  muscles. 

Anteriorly  in  the  male  is  the  bulb  of  the  urethra  and  its  membranous  por- 
tion ;  in  the  female  it  is  separated  from  the  lower  end  of  the  vagina  by  the  peri- 
neal  body. 

The  skin  about  the  anus  is  provided  with  a  ring  of  sweat-glands  called  circum- 
anal  glands.  The  skin  is  also  thrown  into  minute  corrugations  by  means  of  little 
dermal  muscles,  the  Corrugator  cutis  ani.  The  anal  orifice  is  not  situated  alike 
in  the  sexes ;  it  is  farther  forward  in  the  female,  and  less  concealed  between  the 
ischial  tuberosities.  It  is  3  cm.  in  front  of  the  coccyx  or  just  at  the  bi-ischial 
line,  a  little  elongated,  and  the  skin  is  destitute  of  hair.  In  the  male  it  is  2.5  cm. 
in  front  of  the  coccyx  just  behind  the  bi-ischial  line  and  deeply  placed.  The  skin 
is  covered  by  hair  more  or  less  abundantly,  and  the  orifice  is  circular  and  pre- 
sents little  skin  folds  vertically  arranged  like  rays  toward  a  centre.  Between 
these,  where  they  continue  into  the  mucous  membrane,  linear  excoriations  may 
occur — fissure  of  the  anus. 

Structure  of  the  Rectum. 

Four  coats  are  again  met,  but  the  muscular  and  mucous  ones  differ  from  those 

yet  seen.   The  walls  are  3  to  4  mm.  thick,  while  those  of  the  colon  are  1  to  1.5  mm. 

The  peritoneal  coat  surrounds  the  first  portion  only  and  forms  a  mesorectum. 


Till:   INTESTINAL    ('AXAL. 


1041 


In  the  second  portion  it  covers  the  upper  part  of  the  anterior  surface,  a  part  of  the 
sides,  and  none  of  the  posterior  surface.  The  lower  part  is  devoid  of  serous 
covering.  The  peritoneum  of  the  upper  part  of  the  rectum  is  thrown  into  a  few 
pouches,  the  appendices  epiploicce.  In  women,  where  the  cul-de-sac  is  lower  than 
in  men.  the  peritoneum  covers  the  whole  of  the  anterior  part  of  the  middle 
portion. 

The  in>is<-nlar  coat  is  thick  ;  the  three  bands  of  the  colon  do  not  spread  out  and 
form  the  uniform  layer  as  described.  The  anterior  band  descends  along  the  mid- 
dle portion  of  the  rectum  and  continues  to  the  anus.  The  external  band  joins  the 
anterior  near  the  end  of  the  sigmoid  flexure  and  runs  with  it  over  the  first  part 
of  the  rectum.  The  internal  band  is  most  marked  along  the  middle  portion  of 
the  rectum  and  runs  posteriorly  to  the  anus.  The  three  bands  of  the  caecum  and 
colon  are  reduced  to  two  on  the  rectum,  an  anterior  and  a  posterior  one.  In  pro- 
portion as  they  descend  they  get  larger.  The  endings  of  these  fibres  are  various : 
into  pelvic  fascia,  anterior  surface  of  coccyx,  and  deep  surface  of  skin,  just  out- 
side the  anus.  Tendencies  to  sacculation  are  described,  as  the  longitudinal  fibres 
are  rather  short.  The  longitudinal  layer  is  more  or  less  complete  between  the 
two  bands. 

The  c-ir<-ul.ai'  fibres  are  well  developed  and  especially  thick  between  the  sac- 
culations.  Below,  in  the  anal  portion,  they  become  much  augmented  as  the 
Intern  '/  itpliinctcr.  This  muscle  is  3  cm.  high,  and  3  to  4  mm.  thick ;  below  it  is 
precisely  limited  by  the  circular  line,  "white  line,"  which  marks  the  mucous 
membrane  from  the  skin.  It  surrounds  the  whole  length  of  the  anal  canal  and 
ends  very  abruptly  above  in  the  thinner  circular  fibres.  All  these  fibres  are  un- 
striated. 

Posteriorly  two  Recto-coccygei  muscles  pass  from  the  second  or  third  vertebra 
of  the  coccyx  to  the  posterior  part  of  the  anal  canal. 

The  other  muscles  directly  connected  are  the  External  sphincter,  which  de- 
scends a  little  lower  than  the  Internal  and  surrounds  the  anal  orifice  (Fig.  658), 
and  the  Levator  ani  giving  support  on  the  sides.  These  have  been  described. 

The  mni-i-'ii.it  membrane  of  the  rectum  is  thicker  and  more  vascular  than  that 
of  the  colon,  and,  moving  quite  freely  on  the  muscular  coat,  makes  a  kind  of 
independent  tube.  When  contracted  it  shows  many  folds  of  no  special  direction, 
most  of  which  can  be  obliterated :  some,  however,  are  more  permanent,  and  are 


FIG.  659. — Coronal  section  of  pelvis.    Posterior  wall  of  rectum  seen  from  in  front.    (Henle.) 

called  valves  of  the  rectum,  or  of  Houston,  or  plicce  recti.  Usually  three  are 
present,  sometimes  two  or  four.  One  of  these,  the  largest  and  usually  constant. 
is  situated  on  the  right  side  of  the  rectum,  about  at  the  point  where  the  perito- 

66  * 


1042 


THE    ORGANS    OF  DIGESTION. 


neum  is  reflected  upon  the  bladder,  i.  e.  6  to  8  cm.  above  the  anal  orifice.  It  is 
historical,  and  has  been  described  by  Ndlaton  and  Yelpeau  as  sphincter  superior  ; 
as  Houston's  "most  frequent"  valve;  as  Hyrtl's  sphincter  tertius ;  and  Kohl- 
rausch's  plica  transversalis.  This  extends  from  the  right  to  the  anterior  Avail  of 
the  rectum,  and  cannot  be  obliterated,  as  it  does  not  contain  longitudinal  muscu- 
lar fibres.  It  projects  15  mm.  into  the  lumen  of  the  gut  and  extends  around  one- 
half  or  two-thirds  of  its  inner  circumference  (Fig.  659).  There  are  generally  two 
other  folds  on  the  left  side,  one  about  one  inch  above  and  the  other  one  inch 
below,  this  one  of  the  right  side.  These  two  contain  all  the  coats  of  the  wall  and 
may  be  obliterated  by  distention.  Note  the  tendency  of  the  three  to  the  forma- 
tion of  a  spiral  valve.  They  may  all  be  called  valves  or  folds  of  Houston.  The 
dilatation  between  the  lowest  valve  and  the  anal  canal  is  the  rectal  ampulla. 
The  presence  of  these  valves  may  cause  difficulty  in  the  passage  of  bougies  or  in 
digital  examinations.  In  function  they  seem  to  assist  the  sphincters  and  act  as 
shelves  in  supporting  the  fgecal  masses. 

In  the  anal  canal  the  mucous  membrane  is  thrown  into  three  to  eight  longi- 

D  O 

tudinal  folds  containing  muscular  fibres,  probably  of  the  muscularis  mucosae ; 
they  are  called  columnce  ani  or  columns  of  Morgagni.  They  commence  just  above 
the  anal  orifice  and  extend  7  to  14  mm.  up  the  anal  canal,  rising  1  to  2  mm. 
above  the  level  of  the  mucous  membrane.  Stretched  between  these  columns  at 
their  inferior  extremities  are  semilunar  valves  or  folds  made  of  mucous  membrane 
with  concavities  turned  upward.  They  are  unequal  in  length,  varying  inversely 
with  the  number  of  columns. 

Behind  each  valve  and  between  any  two  contiguous  columns  is  a  little  con- 
cavity or  sinus  with  mouth  directed  upward.  Thus,  there  are  columns,  valves, 
and  sinuses  of  Morgagni  (Fig.  660). 


Column  of  Morgugni 


Sinus  of  Morgagni 
Valve  of  Morgagni 


FIG.  660.— Mucous  membrane  of  anal  canal  showing  columns,  valves,  and  sinuses  of  Morgagni.    (Schematic.) 

The  characteristic  cells  of  the  mucous  membrane  are  cylindrical  epithelium. 
The  glands  present  are  those  of  Lieberkiihn  and  the  solitary  lymph-follicles. 
Inferiorly  on  the  anal  canal  there  is  a  narrow  zone  of  mucous  membrane  desti- 
tute of  glands. 

Vessels  and  Nerves  of  the  Rectum. — The  arteries  spring  from  five  or  six 
sources,  three  of  which  are  named  hsemorrhoidal :  the  superior  hcemorrhoidal 
from  the  inferior  mesenteric  artery ;  the  middle  hcemorrhoidal  from  the  internal 
iliac  ;  and  the  inferior  hcemorrhoidal  from  the  internal  pudic.  The  sacra  media 
and  sciatic  arteries  also  send  unnamed  branches  to  the  rectum,  and  in  the  female 
the  vaginal  artery  does  the  same.  These  arteries  coming  from  above  form  loops 
on  either  side  of  the  rectum  with  convexities  pointing  downward.  These  are 
three  or  four  inches  above  the  anus ;  from  these  loops  several  branches  rise,  and 
pass  longitudinally  downward,  pierce  the  muscular  coats  and  enter  the  submu- 
cosa,  and  anastomose  freely.  In  the  anal  canal  they  are  longitudinal  in  folds  of 
mucous  membrane,  and  reach  to  the  anal  orifice. 

The  veins  return  the  blood  in  a  similar  way,  starting  by  dilatations  below  and 
making  a  plexus  higher  up  under  the  mucous  membrane.  Most  of  this  blood  is 
returned  by  the  superior  hsemorrhoidal  vein  to  the  inferior  mesenteric  vein  and 
portal  system.  The  rest  of  it  reaches  the  systemic  circulation  and  vena  cava  infe- 
rior. The  rectum  furnishes  an  anastomosis  between  these  two  systems.  It  is  very 
strange  that  the  anatomical  text-books  apply  the  term  hcemorrhoidal  to  all  vessels 


THE   IXTESTIXAL    CANAL.  1043 

connected  with  the  rectum.  Of  course  those  vessels  supply  haemorrhoids  when 
the  latter  are  present,  but  the  implication  is,  they  are  always  present.  The 
term  rectal  would  seem  to  be  correct  and  the  one  intended. 

The  lymphatics,  from  mucous  and  from  muscular  coats,  enter  glands  anterior 
to  the  sacrum.  Those  near  the  anus  enter  inguinal  glands. 

The  »</•>>•>•  are  from  the  sacral  plexus  (cerebro-spinal),  and  from  the  inferior 
mesenteric  and  hypogastric  plexuses  (sympathetic). 

In  animals  the  longitudinal  muscular  fibres  have  a  motor  supply  from  the 
sacral  nerves. 

Relations  of  the  Rectum  in  Detail. 

FIRST  PORTION. 
Anteriorly : 

^:uall  intestines; 

Sigmoid  flexure ; 

Posterior  surface  of  bladder  in  male  ; 

Posterior  surface  of  uterus  in  female. 

Posteriorly  : 

Mesorectum ; 

Left  Pyriformis  muscle ; 

Left  sacral  plexus ; 

Left  internal  iliac  vessels; 

Anterior  surface  of  first  two  and  a  half  sacral  vertebrae. 

Externally  : 

Left  ureter ; 

Left  internal  iliac  vessels. 

SECOND  PORTION. 
Anteriorly : 
(Male)      Recto- vesical  pouch  ; 

^mall  intestines; 

Triangular  portion  of  bladder ; 

Vesiculae  seminales : 

Vasa  deferentia ; 

Under  surface  of  prostate  gland. 
(Female)  Posterior  wall  of  vagina ; 

Recto-vaginal  pouch ; 

Recto-uterine  pouch ; 

Small  intestines. 

Posteriorly : 

Lower  part  of  sacrum ; 
Coccyx ; 

Ano-coccygeal  body ; 
Middle  sacral  vessels; 
Origin  of  Pyriformis  muscles. 

THIRD  PORTION,  OR  ANAL  CANAL. 
Anteriorly : 
(Male)      Bulb  of  urethra  ; 

Membranous  urethra. 
(Female)  Perineal  body. 

Posteriorly : 

Ano-coccvgeal  bodv ; 

a«/  o  **    ' 

Coccygei  muscles. 


1044 


THE    ORGANS    OF  DIGESTION. 


Laterally : 

Fat  of  ischio-rectal  fossae  ; 
Levatores  ani  muscles. 

The  other  ways  of  describing  the  rectum  (page  1038)  only  affect  its  method 
of  subdivision. 

Treves  describes  the  two  lower  parts  of  the  rectum  and  includes  the  first  in 
the  sigmoid  flexure.  This  is  doubtless  an  improvement  on  the  old  method.  He 
says :  l  "  The  segments  of  the  gut  termed  the  sigmoid  flexure  and  first  part  of 
the  rectum  form  together  a  single  loop  which  cannot  be  divided  into  parts.  This 
loop  begins  where  the  descending  colon  ends,  and  ends  at  the  spot  where  the 
mesorectum  ceases  opposite  the  third  piece  of  the  sacrum.  This  loop  when  un- 
folded describes  a  figure  that  may  be  compared  to  the  capital  omega  "  (Fig.  661). 

"  The  average  length  of  this  adult  omega  loop  is  seventeen  and  a  half  inches, 
varying  from  six  to  twenty-seven.  Its  normal  position  is  not  in  the  left  iliac 
fossa,  but  in  the  pelvis.  Its  most  usual  arrangement  is  this  :  the  descending  colon 
ends  just  at  the  outer  border  of  the  Psoas.  The  gut  crosses  the  muscle  at  right 


Psoas 


•Jb- Internal  iliac 
«     vessels 


FIG.  661.— Omega  loop  of  sigmoid  flexure.    (Treves.) 


Bladder 
FIG.  662.— Usual  course  of  the  omega  loop.    (Treves.) 


angles  and  descends  vertically  along  the  left  pelvic  wall,  and  may  at  once  reach 
the  pelvic  floor.  It  then  passes  more  or  less  horizontally  and  transversely  across 
the  pelvis  from  left  to  right  and  commonly  comes  into  contact  with  the  right  pelvic 
wall.  Here  it  is  bent  upon  itself,  and  passing  once  more  toward  the  left  reaches 
the  middle  line  and  descends  to  the  anus  "  (Fig.  662). 

The  line  of  attachment  of  the  mesocolon  that  fastens  the  omega  loop  is  as 
follows  (Fig.  661):  "  It  crosses  the  Psoas  at  a  right  angle,  and  then  takes  a  slight 
curve  upward  so  as  to  pass  over  the  iliac  vessels  about  at  their  bifurcation.  The 
curve  ends  at  the  point  Jf,  which  is  most  frequently  at  the  bifurcation  of  the 
vessels.  From  here  the  line  of  attachment  proceeds  vertically  down  to  termi- 
nate at  N.  Its  course  is  to  the  left  of  the  middle  line,  while  its  ending  will  be 
upon  that  line.  At  the  point  X  the  mesocolon  is  folded  a  little,  and  here  there 
arises  that  part  of  the  membrane  which  goes  to  the  summit  of  the  loop  Y.  Here 
the  mesocolon  attains  its  greatest  length,  and  at  this  spot  the  sigmoid  artery 
enters.  The  average  length  of  the  mesocolon  is  over  the  Psoas  one  and  a  half 
inches ;  at  the  point  X  three  and  a  half  inches ;  on  the  sacrum  one  and  three- 
fourths  inches.  The  distance  between  the  ends  of  the  loop  M  and  N  is  three 
inches." 

1  Hunterian  Lectures,  1885:  "The  Anatomy  of  the  Intestinal  Canal  and  Peritoneum  in  Man." 


SURGICAL    ANATOMY   OF    THE   IXTESTIXAL    CASAL.      1045 

Surface  Form. — The  coils  of  the  small  intestine  occupy  the  front  of  the  abdomen  below  the 
transverse  enlon.  and  are  covered  more  or  less  completely  by  the  great  omentum.  For  the  most 
part  the  coil.-  of  the  jejunum  occupy  the  left  side  of  the  abdominal  cavity — i.  e.  the  left  lumbar 
and  inguinal  regions  and  the  left  half  of  the  umbilical  region — whilst  the  coils  of  the  ileum  are 
situated  to  the  right,  in  the  right  lumbar  and  inguinal  regions,  in  the  right  half  of  the  umbilical 
region,  ami  also  the  hypogastric.  The  caecum  is  situated  in  the  right  inguinal  region.  Its  posi- 
tion varies  slightly,  but  the  mid-point  of  a  line  drawn  from  the  anterior  superior  spinous  process 
of  the  ilium  to  the  symphysis  pubis  will  alxnt  mark  the  .iddle  of  its  lower  border.  It  is  com- 
paratively superficial  From  it  the  ascending  colon  passes  upward  through  the  right  lumbar 
and  hypochondriac  regions,  and  becomes  more  deeply  situated  as  it  ascends  to  the  hepatic  flexure, 
which  is  deeply  placed  under  cover  of  the  liver.  The  transverse  coion  crosses  the  belly  trans- 
versely on  the  confines  of  the  umbilical  and  epigastric  regions,  its  lower  border  being  on  a  level 
slightly  above  the  umbilicus,  its  upper  border  just  below  the  greater  curvature  of  the  stomach. 
The  splenic  flexure  of  the  colon  is  situated  behind  the  stomach  in  the  left  hypochondrium.  and 
is  on  a  higher  level  than  the  hepatic  flexure.  The  descending  colon  is  deeply  seated,  passing 
down  through  the  left  hypochondriac  and  lumbar  regions  to  the  sigmoid  flexure,  which  is  situ- 
ated in  the  left  inguinal  regions,  and  which  can  be  felt  in  thin  persons,  with  relaxed  abdominal 
walls,  rolling  under  the  fingers  when  empty,  and  when  distended  forming  a  distinct  tumor. 

Surgical  Anatomy.— The  small  intestines  are  much  exposed  to  injury,  but,  in  consequence 
of  their  elasticity  and  the  ease  with  which  one  fold  glides  over  another,  they  are  not  so  frequently 
ruptured  as  would  otherwise  be  the  case.  Any  part  of  the  small  intestine  may  be  ruptured,  but 
probably  the  most  common  situation  is  the  transverse  duodenum,  on  account  of  its  being  more 
fixed  than  other  portions  of  the  bowel,  and  because  it  is  situated  in  front  of  the  bodies  of  the 
vertebrse.  so  that  if  this  portion  of  the  abdomen  is  struck  by  a  sharp  blow,  as  from  the  kick  of 
a  horse,  it  is  unable  to  glide  out  of  the  way.  but  is  compressed  against  the  bone  and  so  lacerated. 
Woundfl  of  the  intestine  sometimes  occur.  If  the  wound  is  a  srnaH  puncture,  under,  it  is  said, 
three  lines  in  length,  no  extravasation  of  the  contents  of  the  bowel  takes  place.  The  mucous 
membrane  becomes  everted  and  plugs  the  little  opening.  The  bowels,  therefore,  may  be  safely 
punctured  with  a  fine  capillary  trocar,  in  cases  of  excessive  distension  of  the  intestine  with  gas, 
without  fear  of  extravasation.  A  longitudinal  wound  gapes  more  than  a  transverse,  owing  to 
the  greater  amount  of  circular  muscular  fibres.  The  small  intestine,  and  most  frequently  the 
ileum.  may  become  strangulated  by  internal  bands,  or  through  apertures,  normal  or  abnormal. 
The  bands  may  be  formed  in  several  different  ways :  they  may  be  old  peritoneal  adhesions  from 
previous  attacks  of  peritonitis ;  or  an  adherent  omentum  from  the  same  cause ;  or  the  band 
may  be  formed  by  Meckel's  diverticulum,  which  has  contracted  adhesions  at  its  distal  extremity  ; 
or  the  band  may  be  the  result  of  the  abnormal  attachment  of  some  normal  structure,  as  the 
adhesion  of  two  appendices  epiploicae,  or  an  adherent  vermiform  appendix  or  Fallopian  tube. 
Intussusception  or  imagination  of  the  small  intestine  may  take  place  in  any  part  of  the  jejunum 
and  ileum.  but  the  most  frequent  situation  is  at  the  ileo-caecal  valve,  the  valve  forming  the  apex 
of  the  entering  tube.  This  form  may  attain  great  size,  and  it  is  not  uncommon  in  these  cases  to 
fin  1  the  valve  projecting  from  the  anus.  Stricture,  the  impaction  of  foreign  bodies,  and  twist- 
ing of  the  gut  (vuh-tilug)  may  lead  to  intestinal  obstruction. 

Foreign  bodies  and  small  hardened  masses  of  faecal  matter  are  very  liable  to  become  lodged 
in  the  vermiform  appendix.  Here  they  set  up  inflammation,  often  cause  perforation  of  the 
appendix  and  formation  of  abscess  in  the  loose  connective  tissue  around.  This  may  require 
operative  interference,  and  in  some  cases  of  recurrent  attacks  of  appendicitis  this  little  divertic- 
ulum of  the  bowel  has  been  removed.  In  external  hernia  the  ileum  is  the  portion  of  bowel 
most  frequently  herniated.  When  a  part  of  the  large  intestine  is  involved,  it  is  usually  the 
ca?:-um.  and  this  may  occur  even  on  the  left  side.  In  some  few  cases  the  vermiform  appendix 
has  been  the  part  implicated  in  cases  of  strangulated  hernia,  and  has  given  rise  to  serious  symp- 
toms of  obstruction.  Occasionally  ulceration  of  the  duodenal  glands  may  occur  in  cases  of  burns, 
but  is  not  a  very  common  complication.  The  ulcer  may  perforate  one  of  the  large  duodenal 
vessels,  and  may  cause  death  from  haemorrhage,  or  it  may  perforate  the  coats  of  the  intestine 
and  produce  fatal  acute  peritonitis.  The  diameter  of  the  large  intestine  gradually  diminishes 
from  the  caecum,  which  has  the  greatest  diameter  of  any  part  of  the  bowel,  to  the  point  of 
junction  of  the  sigmoid  flexure  with  the  rectum,  at  or  a  little  below  which  point  stricture  most 
commonly  occurs  and  diminishes  in  frequency  as  one  proceeds  upward  to  me  caecum.  When 
distended  by  some  obstruction  low  down,  the  outline  of  the  large  intestine  can  be  defined 
throughout  nearly  the  whole  of  its  course — all,  in  fact,  except  the  hepatic  and  splenic  flexures, 
which  are  more  deeply  placed :  the  distension  is  most  obvious  in  the  two  flanks  and  on  the  front 
of  the  abdomen  just  above  the  umbilicus.  The  caecum,  however,  is  that  portion  of  the  bowel 
which  is.  of  all.  most  distended.  It  sometimes  assumes  enormous  dimensions,  and  has  been 
known  to  be  perforated  from  the  pressure,  causing  fatal  peritonitis.  The  hepatic  flexure  and 
the  right  extremity  of  the  transverse  colon  is  in  close  relationship  with  the  liver,  and  abscess  of 
this  vis':-us  sometimes  bursts  into  the  gut  in  this  situation.  The  gall-bladder  may  become  adherent 
to  the  colon,  and  gall-stones  may  find  their  way  through  into  the  gut,  where  they  may  become 
impacted  or  may  be  discharged  per  anum.  The  mobility  of  the  sigmoid  flexure  renders  it  more 
liable  to  become  the  seat  of  a  vol vulus  or  twist  than  any  other  part  of  the  intestine.  It  gener- 
ally occurs  in  patients  who  have  been  the  subjects  of  habitual  constipation,  and  in  whom,  there- 
fore, the  meso-sigmoid  flexure  is  elongated.  The  gut  at  this  part  being  loaded  with  faeces,  from 
its  weight  falls  over  the  gut  below,  and  so  gives  rise  to  the  twist. 


1046  THE    ORGANS    OF   DIGESTION. 

The  surgical  anatomy  of  the  rectum  is  of  considerable  importance.  There  may  be  congen- 
ital malformation  due  to  arrest  or  imperfect  development.  Thus,  there  may  be  no  inflection  of 
the  epiblast  (see  page  134),  and  consequently  a  complete  absence  of  the  anus;  or  the  hind-gut 
may  be  imperfectly  developed,  and  there  may  be  an  absence  of  the  rectum,  though  the  anus  is 
developed  ;  or  the  inflection  of  the  epiblast  may  not  communicate  with  the  termination  of  the 
hind-gut  from  want  of  solution  of  continuity  in  ';he  septum  which  in  early  foetal  life  exists 
between  the  two.  The  mucous  membrane  is  thick  and  but  loosely  connected  to  the  muscular 
coat  beneath,  and  thus  favors  prolapse,  especially  in  children.  The  vessels  of  the  rectum  are 
arranged,  as  mentioned  above,  longitudinally,  and  are  contained  in  the  loose  cellular  tissue  between 
the  mucous  and  muscular  coats,  and  receive  no  support  from  surrounding  tissues,  and  this  favors 
varicosity.  Moreover,  the  blood  from  these  vessels  is  returned  into  the  general  circulation 
through  two  distinct  channels — part  through  the  systemic  system  and  part  through  the  portal 
system — so  that  they  may  be  said  to  be  placed  between  the  portal  and  systemic  circulations,  and 
thus  predisposed  to  congestion  and  consequent  dilatation.  In  addition  to  this,  there  are  no 
valves  in  the  superior  hfemorrhoidal  veins,  and  the  vessels  of  the  rectum  are  placed  in  a  depend- 
ent position,  and  are  liable  to  be  pressed  upon  and  obstructed  by  hardened  faeces.  The  anatom- 
ical arrangement,  therefore,  of  the  haemorrhoidal  vessels  explains  the  great  tendency  to  the 
occurrence  of  piles.  Again,  the  presence  of  the  Sphincter  ani  is  of  surgical  importance,  since 
it  is  the  constant  contraction  of  this  muscle  which  prevents  an  ischiq-rectal  abscess  from  healing 
and  causes  it  to  become  a  fistula.  Also,  the  reflex  contraction  of  this  muscle  is  the  cause  of  the 
severe  pain  complained  of  in  fissure  of  the  anus.  The  relations  of  the  peritoneum  to  the  rectum 
are  of  importance  in  connection  with  the  operation  of  removal  of  the  lower  end  of  the  rectum 
for  malignant  disease.  This  membrane  gradually  leaves  the  rectum  as  it  descends  into  the 
pelvis ;  first  leaving  its  posterior  surface,  then  the  sides,  and  then  the  anterior  surface  to  become 
reflected  in  the  male  on  to  the  posterior  wall  of  the  bladder,  forming  the  recto-vesical  pouch,  and 
in  the  female  on  to  the  posterior  wall  of  the  vagina,  forming  Douglas's  pouch.  The  recto-vesical 
pouch  of  peritoneum  extends  to  within  three  and  a  half  or  four  inches  from  the  anus,  so  that  it 
is  not  safe  to  remove  more  than  three  inches  of  the  entire  circumference  of  the  bowel  for  fear 
of  the  risk  of  opening  the  peritoneum.  When,  however,  the  disease  is  confined  to  the  posterior 
surface  of  the  rectum,  or  extends  farther  in  this  direction,  a  greater  amount  of  the  posterior 
wall  of  the  gut  may  be  removed,  as  the  peritoneum  does  not  extend  on  this  surface  to  a  lower 
level  than  five  inches  from  the  margin  of  the  anus.  The  recto-vaginal  or  Douglas's  pouch  in 
the  female  extends  somewhat  lower  than  the  recto-vesical  pouch  of  the  male,  and  therefore  it  is 
necessary  to  remove  a  less  length  of  the  tube  in  this  sex.1  Upon  introducing  the  finger  into  the 
rectum  the  membranous  portion  of  the  urethra  can  be  felt,  if  an  instrument  has  been  introduced 
into  the  bladder,  exactly  in  the  middle  line ;  behind  this  the  prostate  gland  can  be  recognized 
by  its  shape  and  hardness  and  any  enlargement  detected ;  behind  the  prostate  the  fluctuating 
wall  of  the  bladder  when  full  can  be  felt,  and  if  thought  desirable  it  can  be  tapped  in  this  situ- 
ation ;  on  either  side  and  behind  the  prostate  the  vesiculae  seniinales  can  be  readily  felt,  espe- 
cially if  enlarged  by  tubercular  disease.  Behind,  the  coccyx  is  to  be  felt,  and  on  the  mucous 
membrane  one  or  two  of  Houston's  folds.  The  ischio-rectal  fossae  can  be  explored  on  either 
side,  with  a  view  to  ascertaining  the  presence  of  deep-seated  collections  of  pus.  Finally,  it  will 
be  noted  that  the  finger  is  firmly  gripped  by  the  sphincter  for  about  an  inch  up  the  bowel. 

By  gradual  dilatation  of  the  sphincter  the  whole  hand  can  be  introduced  into  the  rectum  so 
as  to  reach  the  descending  colon.  This  method  of  exploration  is  rarely,  however,  required  for 
diagnostic  purposes. 

The  colon  frequently  requires  opening  in  cases  of  intestinal  obstruction,  the  descending  colon 
being  usually  the  portion  of  bowel  selected  for  this  operation.  The  operation  of  colotomy  may 
be  performed  either  without  opening  the  peritoneum  by  an  incision  in  the  loin  (lumbar  colotomy), 
or  by  an  opening  through  the  peritoneum  (inguinal  colotomy).  Lumbar  colotomy  is  performed 
by  placing  the  patient  on  the  side  opposite  to  the  one  to  be  operated  on,  with  a  firm  pillow  under 
the  loin.  A  line  is  then  drawn  from  the  anterior  superior  to  the  posterior  superior  spine  of  the 
ilium,  and  the  mid-point  of  this  line  (Heath)  or  half  an  inch  behind  the  mid-point  (Allingham) 
is  taken,  and  a  line  drawn  vertically  upward  from  it  to  the  last  rib.  This  line  represents^  with 
sufficient  correctness,  the  position  of  the  normal  colon.  An  oblique  incision  four  inches  in  length 
is  now  made  midway  between  the  last  rib  and  the  crest  of  the  ilium,  so  that  its  centre  bisects 
the  vertical  line,  and  the  following  parts  successively  divided:  (1)  The  skin,  superficial  fascia, 
with  cutaneous  vessels  and  nerves  and  deep  fascia.  (2)  The  posterior  fibres  of  the  External 
oblique  and  anterior  fibres  of  the  Latissimus  dorsi.  (3)  The  Internal  oblique.  (4)  The  lumbar 
fascia  and  the  external  border  of  the  Quadratus  luniborum.  The  edges  of  the  wound  are  now 
to  be  held  apart  with  retractors,  and  the  transversalis  fascia  will  be  exposed.  This  is  to  be 
opened  with  care,  commencing  at  the  posterior  angle  of  the  incision.  If  the  bowel  is  distended, 
it  will  bulge  into  the  wound,  and  no  difficulty  will  be  found  in  dealing  with  it.  If,  however,  the 
gut  is  empty,  this  bulging  will  not  take  place,  and  the  colon  will  have  to  be  sought  for.  The 
guides  to  it  are  the  lower  end  of  the  kidney,  which  will  be  plainly  felt,  and  the  outer  edge  of 
the  Quadratus  lumborum.  The  bowel  having  been  found,  is  to  be  drawn  well  up  into  the 
wound,  and  it  may  be  opened  at  once  and  the  margins  of  the  openings  stitched  to  the  skin  at 
the  edge  of  the  wound ;  or,  if  the  case  is  not  an  urgent  one.  it  may  be  retained  in  this  position 
by  two  harelip  pins  passed  through  the  muscular  coat,  the  rest  of  the  wound  closed,  and  the 

1  Allingham  says  one  inch  less  in  the  female. 


THE  LIVER.  1047 

bowel  opened  in  three  or  four  days,  when  adhesion  of  the  bowel  to  the  edges  of  the  wound  has 
taken  place. 

Iiir/niiiit1  <-<>l>ti>my  is  preferred  by  many  surgeons  in  those  cases  where  there  is  no  urgent 
obstruction,  aivl  where,  therefore,  there  is  no  necessity  to  open  the  bowel  at  once.  The  main 
reason  for  preferring  this  operation  is  that  a  spur-shaped  process  of  the  meso-colon  can  be  formed 
which  prevents  any  fecal  matter  finding  its  way  past  the  artificial  anus  and  becoming  lodged  on 
the  diseased  structures  below.  The  sigmoid  flexure  being  almost  entirely  surrounded  by  peri- 
toneum. a  coil  can  be  drawn  out  of  the  wound  and  the  greater  part  of  its  calibre  removed,  leav- 
ing the  remainder  attached  to  the  meso-colon,  which  forms  a  spur,  much  the  same  as  in  an 
artificial  anus  caused  by  sloughing  of  the  gut  after  a  strangulated  hernia,  and  this  prevents  any 
fecal  matter  finding  its  way  from  the  gut  above  the  opening  into  that  below.  The  operation  is 
performed  by  making  an  incision  two  or  three  inches  in  length  from  a  point  one  inch  internal  to 
the  anterior  superior  spinous  process  of  the  ilium,  parallel  to  Poupart's  ligament.  The  various 
layers  of  abdominal  muscles  are  cut  through,  and  the  peritoneum  opened  and  sewn  to  the 
external  skin.  The  sigmoid  flexure  is  now  sought  for.  and  pulled  out  of  the  wound  and  fixed  by 
passing  a  needle  threaded  with  carbolized  silk  through  the  meso-colon  close  to  the  gut  and  then 
through  the  abdominal  wall.  The  intestine  is  now  sewn  to  the  skin  all  round,  the  suture  passing 
only  through  the  serous  and  muscular  coats.  The  wound  is  dressed,  and  on  the  second  to  the 
fourth  day.  according  to  the  requirements  of  the  case,  the  protruded  coil  of  intestine  is  opened 
and  removed  with  scissors. 

THE  LIVER. 

The  Liver  (Hepar)  is  a  gland  intended  for  the  secretion  of  sugar  and  bile, 
remarkable  for  its  size,  equalling  that  of  all  the  other  glands  put  together,  and 
for  its  connections  with  the  system  of  the  portal  vein  which  ramifies  in  its  sub- 
stance. It  may  be  described  under  two  heads:  (1)  External  conformation;  (2) 
Structure  or  Histology.  First  we  shall  study  its  sit- 
uation. its  volume,  its  weight,  its  consistence  and  color. 
its  form,  its  relations,  and  its  means  of  fixation.  This 
organ  fills  almost  all  the  right  hypochondrium.  a  great 
part  of  the  epigastrium,  and  advances  into  the  left  hypo- 
chondrium as  far  as  the  mammary  line  in  the  neighbor- 
hood of  the  spleen.  It  is  situated,  consequently,  below 
the  diaphragm,  which  separates  it  from  the  lungs  and 
heart  :  above  the  stomach,  duodenum,  transverse  colon. 
and  small  intestines,  which  form  a  sort  of  pillow  ;  and 
behind  are  the  right  false  ribs,  which  protect  it.  In  an 
embryo  of  three  weeks  this  organ  fills  the  greater  part 
of  the  abdomen  (Fig.  663).  During  the  first  half  of 
intra-uterine  life  its  anterior  border  is  below  the  umbil- 
icus.  In  a  child  of  six  or  eight  years  it  gets  behind  the 
free  border  of  the  right  false  ribs.  In  the  adult  its 
average  transverse  dimension  is  28  cm.  (eleven  inches),  FIG.  ees.—  Embryo  of  twelve 

,.  .          .       -.„  /    •    -i       •       i       \        weeks  with  open  thoracic  and 

its  antero-posterior  dimension  is  20   cm.  (eight  inches),     abdominal  cavity  in  which  the 
and  vertical  dimension  is  6  cm.  (two  and  a  half  inches)  1111  ' 


(Sappey).  Quain's  figures  are  —  greatest  vertical  diam- 
eter on  the  right  lobe,  five  to  seven  inches,  greatest  transverse  is  one  or  two 
inches  more  ;  its  greatest  antero-posterior  diameter  is  above  the  right  kidney. 
four  to  six  inches,  and  in  front  of  the  vertebral  column  is  two  and  a  half  to  four 
inches.  All  this  varies  with  the  individual,  the  amount  of  blood  contained,  and 
the  state  of  digestion  and  pathological  state. 

Its  volume  is  90  to  100  cubic  inches. 

The  absolute  weight  of  the  liver  is  proportional  to  its  volume  and  amount  of 
blood  contained.  The  average  is  in  bloodless  livers  1.451  kg.  :  in  physiological 
livers  containing  blood,  1.937  kg.,  or  about  one-thirty-second  of  the  body-weight. 
At  birth  it  is  one-eighteenth  of  the  body-weight.  This  is  50  or  60  ounces  avoir- 
dupois in  the  male,  a  little  heavier  than  the  brain,  and  40  to  50  ounces  in  the 
female.  Its  specific  gravity  is  1.046.  The  consistence  of  the  liver  is  soft,  but 
harder  than  that  of  other  glands.  It  has  a  certain  friability.  Its  tissue  is  more 
easily  crushed  than  depressed. 

The  physiological  color  is  a  dark,  reddish  brown.      In  the  young  it  takes  on  a 


1048 


THE    ORGANS    OF  DIGESTION. 


brighter  tone,  due  to  the  milk  diet,  and  in  later  years  may  assume  other  shades, 
due  to  pathological  changes.  After  death  it  may  be  red-brown  at  one  place, 
yellow  at  another,  with  all  variations ;  sometimes  the  colors  occur  in  wavy  lines. 
This  means  only  unequal  repletion  of  the  vessels.  The  liver  possesses  no  shape 
peculiar  to  itself.  Like  the  lachrymal,  or  parotid  gland,  or  pancreas,  it  is 
moulded  to  neighboring  organs.  Its  general  contour,  how:ever,  is  wedge-shaped, 
with  the  base  to  the  right.  Many  compare  it  to  the  upper  section  of  an  ovoid 

cut  by  a  plane  passing  from  below 
upward  to  the  left  (Fig.  664).  The 
right  end  is  thick  and  the  left  end 
thin. 

The  various  surfaces  ascribed  to 
the  liver  are  from  two  to  five,  result- 
ing from  the  method  of  observation. 
A  pathological,  bloodless,  decayed 
liver  placed  on  the  dissecting  table 
as  usually  seen  by  the  student,  Avill 
always  have  two  surfaces.  It  does 
not  follow  that  that  liver  shows 
anything  of  its  normal  appearance 
FIG.  664,-Figure  to  illustrate  the  shape  of  the  liver.  during  life.  The  inferior  vena  cava 

d 

of  this    liver    is    horizontal    on    its 

inferior  surface,  yet  we  know  that  vessel  runs  vertically  along  the  spinal  column. 
A  liver  removed  from  the  body  and  injected  does  not  give  the  correct  form. 
Hardening  in  situ  by  chromic  acid  or  formalin  injections  leaves  the  shape  of  the 
viscera  as  in  life.  The  liver  treated  thus  shows  three  surfaces,  a  superior,  infe- 
rior, and  posterior  ;  an  anterior  border,  a  right,  and  a  left  extremity.  That  which 
was  formerly  called  the  posterior  blunt  margin  is  now  seen  to  be  a  posterior 
surface.  Symington  regards  the  shape  of  the  liver  as  that  "of  a  right-angled 
triangular  prism,  and  describes  five  surfaces,  right  basal  or  lateral,  anterior, 
superior,  posterior,  and  inferior. 

The  convex,  upper,  smooth  surface  of  the  liver  is  subdivided  by  a  sagittal  fold 
of  peritoneum  drawn  down  from  the  diaphragm,  called  the  suspensory,  broad,  or 

Gull-bladder 


Left  lateral 
ligament 


Vena  cava  inferior 
FIG.  665.— Superior  surface  of  the  liver.    Drawn  from  His'  models. 


falciform  ligament.  To  its  right  is  a  Lirger,  broader  convex  lobe,  and  on  the 
left  a  smaller,  more  slender,  flatter  lobe  (Fig.  665).  This  broad  ligament  corre- 
sponds on  the  under  concave  surface  of  the  liver  to  the  left  longitudinal  fissure 


THE   £717.7.'. 


(Fig.  666)  running  from  before  backward.     This  fissure  also  divides  the  under 
surface  into  a  right  and  left  lobe.     The  left  lobe  is  variable,  and  usually  consti- 
tutes one-sixth  of  the  gland.     Three  more  lobes  are  seen  on  the  inferior  and  pos- 
terior surfaces  of  the  right 
one.    from    before    back- 
ward,   the   ijuadrate,  the 

or    tubereulum 

,  and  Spigelian 

Surfaces. — The    »upe- 

or  phrenic  surface  is 
convex,  directed  upward 
and  forward  and  covered 
by  peritoneum  except  for 
the  linear  space  between 
the  layers  of  the  broad 
ligament.  It  includes  the 
upper  surface  of  the  right 
and  left  lobes,  the  former 
being  convex  and  the  lat- 
ter more  flat.  Between 
and  upon  the  two  is  a 
shallow  depression  or 
flattening  corresponding 
to  the  central  tendon  of 
the  diaphragm  and  to  the 
heart. 

This  separation  of 
lobes  continues  below  in 
the  attachment  of  the 
falciform  ligament  and  in- 
•  •/>•///•//  umbili<-alix.  umbil- 
i'-'il  or  interl'ibular  notch. 

To  the  right  of  the 
notch  is  a  concavity  in- 
truding upon  this  surface, 
occupied  by  the  fundus 
of  the  gall-bladder,  the 
///•  '  <  >  cah's.  This 

whole  surface  is  in  rela- 
tion to  the  under  surface 
of  the  diaphragm,  and 
below  to  a  small  extent 
with  the  anterior  abdom-  ?  I  ^  ?  1 

inal  wall. 

The  inferior  or  visceral  surface  is  uneven,  concave,  and  directed  backward, 
downward,  and  to  the  left.  It  is  in  relation  with  the  stomach,  duodenum,  the 
hepatic  flexure  of  the  colon,  the  right  kidney,  and  suprarenal  capsule.  This 
surface,  as  we  have  seen,  is  divided  into  a  right  and  left  portion  by  the  left 
longitudinal  fissure.  It  is  invested  by  peritoneum  of  the  greater  sac.  except 
where  the  <rall-bladder  is  adherent  to  it,  and  at  the  transverse  fissure  or  hilus 
where  the  two  layers  of  lesser  omentum  are  attached. 

The  u/td,  r  sur/.n-e  of  the  left  lobe  is  moulded  over  the  cardia  of  the  stomach. 
Near  the  centre  and  right  part  of  this  surface  a  result  of  moulding  is  seen  in  a 
large  rounded  tubercle,  the  tuber  omentale,  which  fits  into  the  concavity  of  the 
lesser  curvature  of  the  stomach.  The  whole  tubercle  is  made  from  the  under  sur- 
face of  the  left  lobe  and  the  lower  left  corner  of  the  Spigelian.  It  is  in  front  of 


. 
=     -     ''•       ~-  * 

1    =-  ^  f -i 

§*  I.  I  &§ 
=  ?  2  ~s 


1050  THE    ORGANS    OF   DIGESTION. 

the  anterior  layer  of  the  lesser  omentum.  Here  it  meets  another  tuber  omentale 
coming  upward  and  forward  from  the  pancreas. 

The  under  surface  of  the  right  lobe  has  a  middle  piece  cut  off  from  it  by  the 
fossa  for  the  gall-bladder,  fossa  vesicalis.  This  forms  a  quadrate  or  anterior  lobe 
which  is  just  above  the  pyloric  end  of  the  stomach  and  the  superior  curvature 
of  the  duodenum.  To  the  right  of  the  quadrate  lobe  and  gall-bladder,  the  under 
surface  of  the  right  lobe  shows  two  marked  concavities  separated  by  a  ridge.  The 
anterior  concavity  is  made  by  the  hepatic  flexure  of  the  colon,  impressio  colica ; 
we  have  seen  how  this  ascends  in  front  of  the  right  kidney,  so  posteriorly  the 
next  concavity  is  the  impressio  renalis. 

At  the  inner  border  of  the  renal  impression  is  another  for  the  second  part  of 
the  duodenum,  impressio  duodenalis  ;  this  lies  outside  the  neck  of  the  gall-bladder 
and  is  limited  internally  by  the  cystic  duct.  The  superior  curve  of  the  duodenum 
crosses  the  neck  of  the  gall-bladder  or  even  the  transverse  fissure,  and  comes 
under  the  caudate  lobe.  The  pyloric  end  of  the  stomach  touches  the  quadrate 
lobe,  starting  from  its  anterior  border.  Sometimes  there  is  an  impressio  pylorica. 

The  impression  for  the  right  suprarenal  capsule  is  farther  back  than  the 
impressio  renalis  and  close  to  the  inferior  vena  cava.  Its  basal  part  rests  upon 
the  under  surface  of  the  liver  at  the  posterior  tip  of  the  renal  impression.  This 
part  of  the  impression  is  covered  by  peritoneum.  Its  apex  extends  up  on  the 
posterior  surface  of  the  liver  just  to  the  right  of  the  vena  cava.  This  part  of 
its  impression  is  not  covered  by  peritoneum.  So  the  impressio  suprarenalis  has 
two  parts,  one  covered  with  peritoneum  on  the  inferior  surface  of  the  liver  and 
one  uncovered  by  peritoneum  on  the  posterior  surface. 

Just  anterior  to  the  vena  cava  is  a  narrow  area  of  liver  tissue  connecting  the 
right  lower  corner  of  the  Spigelian  lobe  to  the  under  surface  of  the  right  lobe. 
It  is  the  tuberculum  caudatum,  not  always  big  enough  to  be  called  the  caudate 
lobe  (cauda,  tail).  This  lies  above  the  foramen  of  Winslow. 

The  posterior  surface  is  rounded  and  broad  behind  the  right  lobe,  but  narrow 
on  the  left.  To  the  right  is  not  covered  by  peritoneum  for  a  space  about  three 
inches  broad  and  two  inches  high.  This  is  in  direct  contact  with  the  diaphragm 
and  posterior  abdominal  wall,  and  is  marked  off  from  the  upper  surface  by  the 
line  of  reflection  of  the  peritoneum  from  the  diaphragm  to  the  liver.  This  part 
constitutes  the  anteriofr  layer  of  the  coronary  and  right  lateral  ligaments.  It  is 
marked  off  from  the  under  surface  of  the  liver  by  a  similar  line  of  reflected  peri- 
toneum from  the  posterior  part  of  the  diaphragm  to  the  liver,  which  here  forms 
the  inferior  or  posterior  layer  of  the  coronary  and  right  lateral  ligaments.  A 
small  peritoneal  area  exists  on  the  posterior  surface  to  the  right  of  the  rough 
area. 

At  the  lower  and  inner  part  of  this  rough  surface  is  the  non-peritoneal  part 
of  the  impressio  suprarenalis.  The  inner  border  of  the  surface  projects  over  the 
vena  cava,  and  not  rarely  encloses  it  in  a  canal  of  liver  tissue.  The  centre  of 
the  posterior  surface  is  deeply  grooved  for  the  vertebral  column  and  aorta. 

The  lobe  so  grooved  is  the  Spigelian  ;  it  rests  against  the  tenth  and  eleventh 
dorsal  vertebrae,  the  aorta  and  crura  of  the  diaphragm,  but  upon  the  right  crus 
more  than  the  left.  The  right  crus  grooves  it  from  the  right  lower  corner  to  the 
left  upper  corner;  here  also  is  the  oesophagus.  The  end  of  the  thoracic  aorta 
lies  behind  the  left  lower  corner  separated  by  the  diaphragm.  To  its  right  is  the 
fossa  or  canal  for  the  inferior  vena  cava ;  to  its  left  is  the  furrow  for  the  obliterated 
remains  of  the  ductus  venosus  Arantii.  In  foetal  life  this  duct  establishes  com- 
munication between  the  vena  umbilicalis  and  vena  cava  inferior.  Still  farther  to 
the  left  of  this  is  a  groove  for  the  oesophagus  and  beginning  of  the  cardia. 

The  free  surface  of  the  Spigelian  lobe  looks  backward,  is  nearly  vertical,  and 
is  concave  from  side  to  side.  Its  superior  border  slopes  toward  the  upper  surface 
of  the  liver,  but  is  separated  from  it  by  a  double  layer  of  peritoneum.  Below,  its 
inferior  margin  shows  a  slight  notch  separating  a  right  part,  which  joins  the  cau- 
date tubercle  or  lobe,  and  a  left  part  called  papillary  tubercle,  tuber  papiUare. 


THE   LIVER. 


1051 


This  is  seen  as  the  most  prominent  part  of  the  lobe  when  the  lesser  omentum  is 
divided  in  front.  This  lobe  is  the  only  part  of  the  liver  covered  by  the  peritoneum 
of  the  lesser  sac.  The  finger  goes  under  the  caudate  lobe,  through  the  foramen 
of  Winslow,  and  passes  up  behind  the  Spigelian  lobe.  Above,  it  is  limited  by  the 
posterior  layer  of  the  coronary  ligament ;  to  the  right  it  is  obstructed  by  the  layer 
of  the  lesser  sac  attached  to  the  caval  fossa ;  and  to  the  left  the  finger  cannot  pass 
over  to  the  stomach  by  reason  of  the  double  layer  attached  to  the  fissure  of  the 
ductus  venosus.  All  of  the  right  lobe,  except  its  posterior  part,  and  all  of  the  left 
and  quadrate  lobes  are  covered  by  peritoneum  of  the  greater  sac.  That  on  the 
caudate  is  divided  between  the  two  sacs. 

Finally,  to  the  extreme  left  of  the  posterior  surface  we  have  the  thin  posterior 
edge  of  the  left  lobe  sharply  under-cut  by  the  inferior  surface.  His  regards  the 
tuber  omentale  as  on  the  posterior  surface. 

The  anterior  border  is  thin  and  sharp  and  marked  opposite  the  attachment  of 
the  falciform  ligament  by  the  umbilical  notch  (incisura  umbilicalis),  and  opposite 
the  cartilage  of  the  ninth  rib  by  a  second  notch  for  the  fundus  of  the  gall-bladder 
(incisura  vesicalis).  In  adult  males  this  border  usually  corresponds  with  the  free 
margin  of  the  ribs;  in  women  and  children  it  may  project  below. 

The  right  extremity  of  the  liver  is  thick  and  rounded,  convex  from  before  back- 
ward and  usually  from  above  downward.  Its  upper  and  anterior  angles  are 
rounded.  Below  it  forms  an  acute  margin  with  the  under  surface. 

The  left  extremity  is  thin  and  flattened  from  above  downward. 

The  fissures  of  the  liver  closely  follow  the  lines  of  the  letter  H  (Meckel),  suppos- 
ing them  projected  upon  a  flat  surface  (Fig.  667).  They  are  five  in  number, 
situated  upon  the  inferior  and  poste- 
rior surfaces  of  the  liver,  often  called 
fossce  instead  of  fissures.  The  trans- 
verse fissure,  or  porta  hepatis  (gate 
of  the  liver),  is  the  most  important, 
because  the  great  vessels  and  nerves 
enter  here  and  the  hepatic  ducts  and 
lymphatics  pass  out.  It  is  a  short, 
deep  fissure,  5  cm.  long  (two  inches) 
and  12  to  15  mm.  wide  (one-half 
inch) ;  it  is  on  the  under  surface  of 
the  right  lobe,  passing  transversely  a 
little  nearer  the  posterior  surface  than 
the  anterior  margin  and  nearer  the 
left  extremity  than  the  right.  It 

separates  the  quadrate  lobe  in  front  from  the  caudate  and  Spigelian  lobes  behind, 
and  joins  the  two  longitudinal  fissures  at  nearly  right  angles.  The  two  vertical 
arms  of  the  H  are  represented  by  the  two  longitudinal  fissures,  right  and  left. 

The  left  longitudinal,  or  sagittal,  fissure  (fossa  longitudinalis  sinistra)  separates 
the  right  from  the  left  lobe,  and  is  divided  into  an  anterior  and  posterior  part  by 
its  junction  with  the  transverse  fissure.  The  anterior  part  is  the  umbilical  fissure, 
which  contains  the  umbilical  vein  in  the  foetus  and  its  remains  in  the  adult,  which 
is  then  called  the  round  ligament  (Lig.  teres).  It  lies  between  the  quadrate  and 
left  lobes  of  the  liver.  This  fissure,  and  the  one  for  the  ductus  venosus,  are  often 
bridged  over  by  liver  tissue  (pons  hepatis),  converting  a  fissure  wholly  or  partially 
into  a  canal. 

The  posterior  part  of  the  left  longitudinal  fissure  is  not  so  marked  as  the  ante- 
rior part ;  it  passes  between  the  lobe  of  Spigelius  and  the  left  lobe,  and  is  called 
the  fissure  of  the  ductus  venosus.  In  the  foetus  it  lodges  a  vein,  but  in  the  adult 
this  vein  becomes  a  slender  cord,  lig.  venosum. 

The  right  longitudinal  fissure  (fossa  longitudinalis  dextra)  runs  parallel  to  the 
left  one.  and  has  an  anterior  and  posterior  part.  It  meets  one  interruption  just 
behind  the  transverse  fissure,  where  the  caudate  lobe  connects  the  Spigelian  and 


FIG.  667. — Diagram  of  fissures  of  liver.    Schematic. 
Seen  from  behind  and  below. 


1052  THE    ORGANS    OF  DIGESTION. 

right  lobe.  The  posterior  part  is  the  fossa  of  the  vena  cava,  which  separates  the 
Spigelian  from  the  right  lobe,  and  is  separated  from  the  transverse  fissure  by  the 
caudate  lobe.  It  is  a  deep  fossa,  sometimes  a  canal ;  at  its  upper  part  the  hepatic 
veins  enter  the  floor  of  the  fossa  and  end  in  the  vena  cava.  The  anterior  part  of 
this  longitudinal  fissure  is  the  fossa  for  the  gall-bladder,  fossa  vesicalis.  The  pro- 
posed name  is  fossa  vesicse  fellese.  It  is  a  shallow,  oblong  fossa  on  the  under  sur- 
face of  the  right  lobe,  and  runs  from  the  incisura  vesica'lis  to  near  the  right  end 
of  the  transverse  fissure. 

The  transverse,  umbilical,  and  vesical  fissures  are  on  the  under  surface  of  the 
liver,  and  the  fissures  for  the  ductus  venosus  and  vena  cava  are  on  the  posterior 
surface. 

Lobes. 

We  have  seen  five  lobes,  though  one,  the  caudate,  is  very  small.  The  bound- 
aries between  right  and  left  are,  superiorly,  the  attachment  of  the  falciform  ligament; 
anteriorly,  the  umbilical  incisure ;  inferiorly,  the  lig.  teres  in  the  umbilical  fissure ; 
posteriorly,  the  lig.  venosum  in  the  fissure  for  the  ductus  venosus. 

The  right  lobe  is  much  larger  than  the  left,  and  is  of  quadrate  form.  Three 
fissures  are  on  its  under  and  posterior  surfaces  :  the  transverse,  and  those  for  gall- 
bladder and  vena  cava.  These  separate  three  more  lobes,  all  belonging  to  the  right 
one.  Three  impressions  are  seen — renal  and  suprarenal,  colic,  and  duodenal. 

The  left  lobe  is  convex  above,  but  less  so  than  the  right,  and  concave  below, 
where  it  rests  on  the  stomach.  This  impression  is  in  front  of  the  groove  for  the 
oesophagus,  and  is  separated  from  the  longitudinal  fissure  by  the  omental  tuberosity 
which  lies  against  the  lesser  omentum  and  lesser  curvature  of  the  stomach. 

The  quadrate  or  square  lobe  on  the  under  surface  of  the  right  is  bounded  ante- 
riorly by  the  acute  margin  of  the  liver ;  to  the  right  by  the  fossa  for  the  gall- 
bladder ;  to  the  left  by  the  umbilical  fissure  and  behind  by  the  transverse  fissure. 
Its  length  is  greater  from  before  backward  than  from  side  to  side.  It  may  present 
an  impressio  pylorica. 

The  caudate  lobe  or  tubercle  is  on  the  under  surface  of  the  right  lobe  between 
the  fossa  for  the  gall-bladder  and  that  for  the  vena  cava,  at  the  right  end  of  the 
transverse  fissure.  It  connects  the  right  lobe  with  the  right  lower  corner  of  the 
Spigelian  lobe. 

The  Spigelian  lobe  is  on  the  posterior  surface  of  the  right  one,  looks  directly 
backward,  and  is  wholly  included  in  the  atrium  bursce  omentalis.  It  reaches  below 
as  far  as  the  pancreas  and  coeliac  axis.  It  is  bounded  above  by  the  coronary  lig- 
ament ;  to  the  right  by  the  fossa  for  the  vena  cava ;  to  the  left  by  the  fissure  for 
the  ductus  venosus,  and  below  by  the  transverse  fissure.  Its  left  upper  angle  is 
partly  grooved  for  the  oesophagus.  Its  papillary  tubercle  looks  directly  downward. 

The  technical  names  of  the  parts  seen  on  the  three  surfaces  of  the  liver  are,  in 
order  from  left  to  right — 

Superior  surface :  Upper  surface  left  lobe,  umbilical  incisure,  attachment  of 
falciform  ligament,  cardiac  impression  on  both  lobes,  vesical  incisure,  upper  surface 
of  right  lobe  (Fig.  665). 

Posterior  surface :  Thin  margin  of  left  lobe,  oesophageal  incisure,  lig.  venosum 
in  fissure  for  ductus  venosus,  lobus  Spigelii  in  front  of  the  tenth  and  eleventh  dorsal 
vertebrae ;  papillary  tubercle ;  fossa  for  the  vena  cava  and  hepatic  veins ;  non- 
peritoneal  impression  for  part  of  the  right  suprarenal  capsule ;  non-peritoneal  sur- 
face of  right  lobe  for  the  diaphragm  (Fig.  666). 

Inferior  surface :  Gastric  impression  on  the  under  surface  of  left  lobe ;  tuber 
omentale  which  includes  lower  left  part  of  Spigelian  lobe;  umbilical  fissure  and  lig. 
teres ;  quadrate  lobe  with  impressio  pylorica  and  duodenalis  (first  portion) ;  fossa 
for  gall-bladder ;  remainder  of  under  surface  of  right  lobe ;  impressio  duodenalis 
(second  portion) ;  peritoneal  impression  for  suprarenal  capsule :  impressio  renalis 
posteriorly,  and  colica,  anteriorly. 

There  are  some  abnormal  forms  of  the  liver.     Frequently  the  left  lobe  is  so 


THE  LIVER.  1053 

elongated  it  may  reach  the  spleen  or  even  be  hooked  around  it  or  inseparably  fused 
with  it.  The  papillary  tubercle  may  be  so  developed  as  to  form  a  separate  lobule. 
An  accessory  lobe  may  be  attached  to  the  left  one,  united  by  peritoneum  and  blood- 
vessels. Many  times  the  number  of  lobes  are  diminished  and  the  form  becomes 
square  or  spherical.  More  often  the  number  of  lobes  increases,  separated  by  short 
deep  clefts  called  rimce  ccecce. 

Besides  congenital  changes,  others  may  be  acquired  by  pressure.  By  excessive 
lacing  in  women  the  superficial  part  of  the  liver  will  become  atrophic  and  the  peri- 
toneal coat  will  become  thicker.  On  the  convex  surface  of  the  liver  a  transverse 
furrow  will  be  established  dividing  off  an  anterior  portion,  especially  of  the  right 
lobe.  This  part  will  be  pushed  down  into  the  abdominal  cavity,  and  may  become 
almost  separated  from  the  rest — the  "corset  liver."  If  the  liver  be  more  resistant, 
its  surface  may  show  the  flat,  stripe-like  impressions  occasioned  by  the  ribs. 

Ligaments  and  Peritoneal  Relations. — The  liver  is  connected  in  part  by  peri- 
toneum to  the  roof  of  the  abdominal  cavity,  to  the  anterior  wall,  to  the  stomach, 
duodenum,  right  kidney,  and  hepatic  flexure  of  colon,  whereby  the  following  peri- 
toneal folds  or  ligaments  are  to  be  distinguished.  With  one  exception  they  are 
peritoneal  folds. 

The  coronary  ligament  connects  the  posterior  surface  of  the  liver  to  the  dia- 
phragm. Its  two  layers  surround  the  rough  triangular  surface  seen  on  the  pos- 
terior part  of  the  right  lobe,  which  is  connected  directly  to  the  diaphragm  by 
areolar  tissue.  These  layers  are  reflections  from  the  parietal  peritoneum  descending 
from  the  diaphragm.  This  ligament  has  three  portions  (Fig.  668).  The  right 
part  is  much  the  bigger  and  its  layers  are  far  apart,  enclosing  the  posterior  rough 
surface  of  the  right  lobe.  The  two  layers  are  derived  from  the  peritoneum  of  the 
greater  sac.  A  middle  portion  is  seen  above  the  Spigelian  lobe.  The  two  layers 
are  close  together ;  the  anterior  one  belongs  to  the  greater  sac,  and  the  posterior 
one  to  the  lesser.  Farther  to  the  left  is  a  third  narrow  portion  continued  into  the 
left  lateral  ligament.  Both  layers  here  belong  to  the  greater  sac.  On  either  end 
of  the  coronary  ligament  the  two  layers  of  peritoneum  gradually  approach,  and 
finally  unite,  thus  forming  the  right  and  left  lateral  ligaments  as  prolongations  of 
the  coronary.  As  they  enclose  a  triangular  space,  they  are  also  called  triangular 
ligaments  ;  the  left  is  the  longer,  and  lies  in  front  of  the  ossophagus.  The  right  is 
often  imperceptible. 

The  suspensory,  longitudinal,  falciform,  or  broad  ligament  is  a  part  of  the  old 
anterior  mesentery  of  the  stomach  and  duodenum.  The  liver  was  developed  in  it, 
budding  out  from  the  duodenum,  where  its  duct  is  still  attached.  This  is  a  thin 
membrane  which  passes  antero-posteriorly  above  the  liver  and  below  it.  Above  it 
meets  the  coronary  ligament  at  right  angles.  By  one  of  its  margins  it  is  connected 
with  the  posterior  layer  of  the  sheath  of  the  right  Rectus  abdominis  muscle  as  far 
as  the  umbilicus,  and  above  to  the  under  surface  of  the  diaphragm,  where  it  spreads 
out  to  the  right  and  left.  By  its  other  margin  it  is  attached  along  the  upper  sur- 
face of  the  liver,  its  left  layer  passing  over  the  left  lobe  and  continuing  into  the 
left  part  of  the  coronary  and  left  lateral  ligament.  Its  right  layer  passes  over  the 
right  lobe  and  corresponding  ligaments.  The  remaining  margin  is  free  and 
rounded,  and  passes  from  the  interlobular  notch  to  the  transverse  fissure  of  the 
liver.  It  contains  between  its  two  layers  the  intra-abdominal  part  of  the  umbilical 
vein  of  the  foetus,  now  a  fibrous  cord,  the  round  ligament  (lig.  hepato-umbilicalis), 
which  is  lodged  in  the  umbilical  fissure.  Also  between  the  two  layers  run  some 
branches  of  the  epigastric  veins  anastomosing  with  the  portal  system,  little  twigs 
of  the  phrenic  arteries,  numerous  lymphatics,  and  branches  of  the  phrenic  nerve 
which  are  destined  for  the  serosa  of  the  liver  and  for  the  peritoneum  of  the  anterior 
abdominal  wall.  In  its  natural  position  the  falciform  ligament  forms  a  pocket, 
which,  with  the  diaphragm  and  abdominal  wall,  enclose  the  convex  upper  part  of 
the  left  lobe  of  the  liver.  This  ligament  has  no  function  of  suspension. 

Besides  these  there  are  others  hardly  less  marked  which  we  have  noted  in  the 
study  of  the  peritoneum.  The  lesser  omentum  (lig.  gastro-hepaticum)  with  its 


1054  THE    ORGANS    OF  DIGESTION. 

two  layers  attached  to  the  anterior  and  posterior  borders  of  the  transverse  fissure, 
descends  to  the  lesser  curvature  of  the  stomach,  containing  between  its  layers 
some  ascending  branches  of  the  left  vagus  nerve.  The  posterior  layer  descends 
behind  the  stomach  as  the  anterior  wall  of  the  bursa  omentalis,  and  arches  behind 
the  cardia  into  the  posterior  wall  of  this  bursa.  On  the  right  both  layers 
unite,  forming  a  free  edge,  constituting  the  anterior  margin  of  the  foramen  of 
Winslow. 

This  edge,  whose  layers  separate  below  and  nearly  enclose  the  whole  of  the 
superior  curve  of  the  duodenum,  constitutes  the  lig.  hepato-duodenale,  which  con- 
tains the  portal  vein,  hepatic  artery,  common  bile-duct,  lymphatics  and  nerves 
(not  hepatic  veins). 

A  part  of  this  ligament  passes  on  over  the  duodenum  into  the  great  omentum 
and  reaches  the  transverse  colon.  This  is  the  hepato-colic  ligament  (Fig.  635). 

The  lig.  hepato-renale  passes  down  from  the  under  surface  of  the  right  lobe 
rising  near  the  neck  of  the  gall-bladder  and  vena  cava  and  behind  the  foramen  of 
Winslow  to  the  upper  part  of  the  right  kidney.  It  possesses  a  free  edge  directed 
forward.  Between  this  and  the  right  lateral  ligament  of  the  liver  is  often  a  recess, 
recessus  hepato-renalis,  into  which  fits  the  right  end  of  the  inferior  and  posterior 
surfaces  of  the  liver.  The  posterior  wall  of  this  recess  touches  in  part  the  right 
suprarenal  capsule  and  in  part  the  right  kidney.  That  part  of  th^e  hepato-duode- 
nal  ligament  which  rises  from  the  gall-bladder  is  the  lig.  cystico-duodenale. 

The  ligaments  of  the  liver  are  coronary,  right  and  left  lateral  or  triangular, 
falciform  or  suspensory,  round  or  lig.  hepato-umbilicalis,  lesser  omentum,  which 
consists  of  lig.  Jiepato-gastricum  and  lig.  hepato-duodenale,  lig.  cystico-duodenale, 
lig.  hepato-colicum,  and  lig.  hepato-renale  (Figs.  615  and  635). 

Peritoneal  Lines. — Beginning  at  the  left,  we  see  the  space  between  the  two  layers 
of  the  left  lateral  ligament  (Figs.  668  and  665).  The  anterior  layer  belongs  wholly 

Falciform 
ligament 


Left  lateral 
ligament 


Right  lateral 
ligament 


FIG.  668. — "  Peritoneal  lines  "  of  the  liver.    Schematic. 


to  the  greater  sac.  It  passes  from  the  left  lateral  ligament  to  the  left  layer  of  the 
falciform,  forming  a  part  of  the  coronary.  This  becomes  continuous  with  the 
right  layer  at  the  umbilicus.  The  right  layer  runs  along  the  upper  margin  of  the 
liver,  making  the  middle  part  of  the  coronary  ligament,  and  then  goes  to  the  right, 
forming  the  rest  of  the  coronary  in  front  of  the  posterior  rough  surface  on  the 
liver,  finally  ending  in  the  right  lateral  ligament.  Taking  the  posterior  layer 
from  this  point,  we  shall  see  it  belongs  mostly  to  the  greater  sac.  It  first  completes 
the  right  lateral  ligament,  then  runs  behind  the  rough  surface  and  enters  into  the 
impressio  renalis,  forming  the  lig.  hepato-renale.  It  then  passes  under  the  rough 
impressio  suprarenale  in  front  of  the  vena  cava  and  behind  the  tuberculum  cauda- 
tum  to  the  lobus  Spigelii.  It  ascends  on  high  to  the  left  of  the  vena  cava,  sur- 
rounds the  upper  end  of  the  Spigelian  lobe,  descends  on  its  left  side,  turns  in 
front  of  the  papillary  tubercle,  follows  the  anterior  edge  of  the  caudate  tubercle, 
and  goes  back  to  the  right  lobe.  It  here  enters  upon  the  under  surface  of  the 


THE   LIVER.  1055 

gall-bladder  and  undergoes  a  more  or  less  sharp  bend,  and  passes  to  the  anterior 
margin  of  the  transverse  fissure,  following  the  posterior  edge  of  the  quadrate  lobe 
to  the  left.  It  now  reaches  the  tuber  omentale.  ascends  on  the  left  side  of  the 
fissure  for  the  ductus  venosus,  and,  making  nearly  a  right  angle,  is  prolonged  above 
upon  the  left  lobe.  Here  it  forms  the  posterior  edge  of  the  lateral  ligament.  All 
the  parts  between  the  lines  thus  traced  are  not  covered  by  peritoneum.  This  all 
belongs  to  the  peritoneum  of  the  greater  sac  except  that  which  surrounds  the 
Spigelian  lobe ;  this  belongs  to  the  lesser  sac  or  atrium  of  the  omental  bursa. 

Relations  of  the  Liver. 

It  lies  in  both  hypochondria  and  in  the  epigastrium.  It  completely  fills  the 
right  hypochondrium  and  sometimes  enters  the  right  lumbar  region.  Its  entire 
right  lobe  lies  in  the  right  side  of  the  abdominal  cavity  ;  only  the  left  lobe  reaches 
the  left  half  of  the  body.  The  left  longitudinal  fissure  and  the  attachment  of  the 
broad  ligament,  and  the  interlobar  incisure  which  mark  the  limits  between  the  right 
and  left  lobes,  correspond  almost  always  to  the  median  line  of  the  body  (Fig-  626). 
Its  convex  upper  surface  fits  itself  to  the  concavity  of  the  diaphragm,  in  which  it 
glides  as  if  in  a  joint-socket.  The  upper  limit  of  the  liver  corresponds  to  that  of 
the  diaphragm.  On  the  right  side  in  the  mammary  line  it  is  at  the  middle  of  the 
fourth  intercostal  space ;  on  the  left  in  the  mammary  line  it  is  at  the  upper  bordet 
of  the  fifth  space.  It  does  not  usually  go  beyond  this  line.  Above  the  right  lobe 
rests  the  concave  base  of  the  right  lung.  In  percussing  the  side  of  the  chest  down- 
ward three  regions  are  noted — first,  one  of  relative  liver  dulness,  where  it  is  covered 
by  the  lung ;  second,  the  region  of  costo-phrenic  sinus,  where  diaphragm  and  not 
lung  intervenes  ;  third,  absolute  liver  dulness  below  the  diaphragm.  A  stab  here 
could  wound  at  the  same  time  the  pleura,  right  lung,  diaphragm,  peritoneum,  and 
convex  surface  of  the  liver.  Above  the  right  and  left  lobes  are  the  heart  and  then 
the  left  lung.  The  convex  surface  of  the  liver  is  covered  on  the  right  side  by  the 
greater  part  of  the  lower  six  or  seven  ribs,  but  usually  stops  at  the  eleventh.  *  An- 
teriorly it  is  behind  the  fifth,  sixth,  seventh,  eighth,  and  ninth  costal  cartilages 
and  the  ensiform  cartilage.  A  part  of  the  liver  surface  comes  into  direct  contact 
with  the  anterior  abdominal  wall.  From  between  the  ninth  and  tenth  rib  cartilages 
the  liver  passes  under  the  right  costal  arch  into  the  epigastrium.  Close  under  the 
ensiform  process,  at  a  spot  usually  called  gastric  fossa,  lies  a  part  of  the  liver  which 
is  turned  forward  and  touches  the  abdominal  wall  more  closely.  In  women  with  a 
"corset  liver"  the  part  in  direct  contact  with  the  wall  is  much  greater.  Here 
some  loops  of  intestine  or  transverse  colon  may  intervene  and  a  dulness  will  be 
found  in  percussing  the  mesogastrium,  modified  by  a  tympanitic  sound. 

The  under  surface  of  the  liver  is  in  contact  by  its* right  lobe  directly  with  the 
upper  two-thirds  of  the  right  kidney,  and  internal  to  that,  with  the  descending 
duodenum,  and  above  both,  near  the  vena  cava,  with  the  suprarenal  capsule  which 
also  touches  the  posterior  surface  (His).  Lateral  to  the  gall-bladder  is  the  colon, 
internal  to  it  the  quadrate  lobe  with  the  portio  pylorica  of  the  stomach  in  relation. 
Going  to  the  left  and  above,  we  find  the  tuber  omentale.  and  still  more  laterally 
the  whole  concavity  of  the  left  lobe  covering  the  lesser  curvature,  the  cardia,  and 
adjacent  part  of  the  anterior  surface  of  the  stomach.  In  an  empty  contracted 
stomach  it  may  cover  the  fundus. 

The  posterior  edge  and  surface  rest  against  the  tenth  and  eleventh  dorsal  ver- 
tebrae and  the  posterior  ends  of  those  ribs.  This  part  also  rests  on  the  crura  of  the 
diaphragm,  covers  the  oesophagus,  and  embraces  the  vena  cava.  Against  it  are 
the  aorta,  thoracic  duct,  nerves,  and  small  vessels  which  rise  from  the  vertebral 
column,  but  are  separated  from  the  liver  by  the  diaphragm. 

The  anterior  edge  of  the  liver  follows,  in  the  right  hypochondrium,  the  tenth 
and  eleventh  ribs,  but  normally  does  not  extend  over  the  anterior  end  of  the  last. 
Should  one  in  quiet  respiration  feel  the  liver  lower  than  this  point,  there  is  enlarge- 
ment or  displacement.  Between  the  ninth  and  tenth  ribs  the  anterior  edge  of  the 


1056  THE    ORGANS    OF  DIGESTION. 

liver  leaves  the  costal  arch  and  passes  obliquely  from  right  to  left,  ascending  to  the 
anterior  end  of  the  left  eighth  rib.  In  case  of  a  thin  abdominal  wall  this  anterior 
edge  of  the  liver  can  be  felt  as  it  passes  through  the  epigastrium.  This  part  can 
contract  adhesions  with  the  wall. 

Relations  in  Detail. 

Antero-swperiorly : 

Diaphragm  ; 
Right  and  left  lungs  ; 
Pericardium  and  heart ; 
Anterior  abdominal  wall ; 
r\    +1       •  1,+  f  Six  or  seven  lowrer  ribs  : 

riSnt  j  Fifth  to  ninth  costal  cartilage. 

Inferiorty : 

Right  kidney  and  capsule  ; 

Hepatic  flexure  of  colon  ; 

Descending  duodenum  ; 

Gall-bladder  and  cystic  duct ; 

Vessels  at  portal  fissure  ; 

Pyloric  end  of  stomach  ; 

Superior  curve  of  duodenum  ; 

Cardia ; 

Lesser  curvature  of  stomach  ; 

Anterior  surface  stomach,  small  part  (sometimes  fundus  of  stomach). 

Posteriorly : 

Diaphragm  ; 

Tenth  and  eleventh  dorsal  vertebrae  ; 

End  of  tenth  and  eleventh  ribs ; 

Crura  of  diaphragm ; 

(Esophagus ; 

Aorta ; 

Vena  cava  inferior ; 

Thoracic  duct ; 

Non-peritoneal  impression  for  right  suprarenal  capsule. 

The  Fixation  of  the  Liver. — The  liver,  compared  Avith  other  intraperitoneal 
organs,  has  a  firm  position,  due  to  its  fusion  with  the  diaphragm.  The  peritoneal 
folds  aid  this  fixation  by  connecting  the  liver  to  the  concavity  of  the  dia- 
phragm. They  are  the  falciform,  or  suspensory,  coronary,  and  right  and  left  lateral 
ligaments.  In  spite  of  this  fixation,  the  liver  experiences  certain  physiological 
changes  and  variations  of  position.  It  passes  downward  and  forward  in  inspira- 
tion, and  in  expiration  is  pushed  upward  and  backward.  It  moves  up  and  down 
1  to  1.5  cm.  In  inspiration  Hasse  finds  a  stretching  of  the  liver ;  in  expiration,  a 
compression.  -  These  changes  exert  an  influence  over  the  circulation  of  the  liver. 
The  dilatation  of  the  vessels  accompanying  the  expansion  of  the  liver  during  inspi- 
ration favors  the  influx  of  portal  blood ;  during  expiration  and  the  accompanying 
compression  the  blood  in  the  open  hepatic  veins  is  pressed  into  the  vena  cava. 

Also  the  liver  suffers  small  displacements  occasioned  by  changes  in  the  position 
of  the  body.  In  the  horizontal  supine  position  it  falls  back  upon  the  diaphragm, 
and  its  anterior  margin  is  more  concealed  behind  the  ribs.  In  the  erect  position 
the  liver  descends  a  little  below  the  costal  arch.  The  horizontal  lateral  position  of 
body  also  has  influence,  displacing  it  a  little  toward  the  left  or  the  right,  as  the  case 
may  be.  Furthermore,  by  relaxation  of  ligaments,  sometimes  in  women  after  child- 
birth, a  "dislocation"  of  the  liver  results,  or  "  wandering  liver."  Any  pathological 
displacements  of  the  diaphragm  also  affect  the  liver,  as  effusions  into  the  thoracic 
cavity  ;  also  ascites,  tympanites,  or  tumors  in  the  abdominal  cavity. 


THE   LIVER.  1057 

Vessels. — The  blood-supply  of  the  liver  follows  a  double  course  through  the 
portal  vein  and  hepatic  artery.  The  greatest  amount  of  blood  flowing  through 
the  liver,  thus  differing  from  other  organs,  comes  from  the  veins  of  the  digestive 
tract  and  of  the  spleen,  which  unite  into  a  great  vessel,  the  vena  portarum  or  portce. 

The  hepatic  artery  and  portal  vein,  accompanied  by  numerous  lymphatics  and 
nerves,  ascend  to  the  transverse  fissure  between  the  layers  of  the  gastro-hepatic 
omentum.  The  hepatic  duet,  lying  in  company  with  them,  descends  from  the 
transverse  fissure  between  the  layers  of  the  same  omentum.  The  relative  position 
of  the  three  structures  is  as  follows :  the  hepatic  duct  lies  to  the  right,  the  hepatic 
artery  to  the  left,  and  the  portal  vein  behind  and  between  the  other  two.  Thev 
are  enveloped  in  a  loose  areolar  tissue,  the  capsule  of  Glisson,  which  accompanies 
the  vessels  in  their  course  through  the  portal  canals  in  the  interior  of  the  organ. 

In  the  transverse  fissure  this  portal  vein  splits  into  two  trunks,  the  right  and 
left,  for  lobes  of  the  same  name.  At  the  point  of  division  is  an  enlargement,  the 
sinus  vena? portce.  They  enter  the  liver  substance  and  subdivide  dichotomously  into 
smaller  branches,  which  do  not  anastomose.  They  end  in  the  interlobular  connec- 
tive tissue  in  three  to  five  twigs,  and  form  a  rich  plexus  around  each  lobule,  inter- 
lobular '•-//<*.  These  lose  themselves  in  a  capillary  network,  which  penetrates  the 
lobule  in  a  ray-shaped  manner,  and  are  collected  at  its  centre  into  a  little  vein,  the 
vena  centralis  or  mtralobufar  vein.  These  are  the  roots  of  the  hepatic  veins. 

The  characteristic  point  of  the  blood-current  of  the  portal  system  consists  in 
this :  it  must  first  pass  through  a  capillary  circulation  before  it  enters  the  inferior 
vena  cava. 

Accompanying  the  portal  vein  is  the  hepatic  artery,  a  branch  of  the  coeliac 
axis,  which  divides  at  the  transverse  fissure  into  a  right  and  left  branch.  The 
twigs  of  the  chief  branches  follow  those  of  the  portal  vein,  which  accompany  them 
singly  or  doubly.  The  hepatic  artery  supplies  chiefly  the  connective  tissue  and 
the  capsule  of  the  liver.  In  the  serous  covering  it  anastomoses  with  the  phrenic 
and  internal  mammary  arteries. 

The  intralobular  veins  form,  so  to  speak,  the  pedicles  of  the  lobules,  and,  after 
their  exit  from  each  empty  at  an  acute  angle  into  bigger  veins,  the  sublobular. 
These  larger  veins  unite  with  each  other  and  form  numerous  valveless  hepatic  veins, 
which,  draining  the  blood  from  the  circulation  of  the  portal  vein  and  hepatic 
artery,  make  their  way  to  the  posterior  surface  of  the  liver  and  empty,  as  three 
large  trunks  and  a  number  of  small  ones,  into  the  vena  cava.  These  hepatic  veins 
have  no  cellular  investment,  and  their  walls  are  directly  adherent  to  the  surround- 
ing liver  substance,  while  the  branches  of  the  portal  vein,  hepatic  artery,  and 
hepatic  duct  are  enclosed  by  loose  connective  tissue,  and  the  three  go  together  in 
a  portal  canal. 

"V\  hen  the  arterial,  portal,  and  biliary  twigs  are  seen  in  the  same  connective  tissue 
sheath,  the  portal  twigs  are  the  strongest,  and  the  arteries  have  the  smallest  lumen. 

On  section  of  a  piece  of  liver  the  open  solitary  holes  are  the  cut  hepatic  veins, 
unable  to  collapse  on  account  of  their  close  relation  to  the  liver-tissue.  For  this 
reason  hemorrhage  is  so  dangerous  in  wounds  of  the  liver.  The  branches  of  the 
portal  vein  collapse  on  cross-section. 

According  to  Sappey.  there  are  five  sets  of  accessory  portal  veins.  The  liver 
does  not  receive  all  its  blood  from  the  hepatic  artery  and  vena  portse. 

The  first  group  occupies  the  lesser  omentum,  and  consists  of  venules  from  the 
lesser  curvature  of  the  stomach.  When  the  pyloric  vein  rises  high  it  joins  this 
group,  which  is  distributed  to  the  lobes  just  in  front  of  and  just  behind  the  trans- 
verse fissure. 

The  second  group  is  more  important,  and  consists  of  twelve  to  fifteen  little  veins 
rising  from  the  fundus  of  the  gall-bladder  and  distributed  to  the  fossa  vesicalis. 
Two  cystic  veins  here  usually  open  into  the  right  branch  of  the  portal  vein. 

The  third  group  includes  all  the  venules  rising  in  the  walls  of  the  portal  vein, 
hepatic  artery,  and  hepatic  duct.  They  lose  themselves  in  the  subjacent  lobules. 

The  fourth  group  consists  of  veins  descending  from  the  middle  portion  of  the 

67 


1058  THE    ORGANS    OF  DIGESTION. 

diaphragm  in  the  falciform  ligament.  They  ramify  in  the  lobes  adjoining  the 
ligament.  They  are  almost  capillary  and  anastomose  with  each  other. 

The  fifth  group  is  formed  of  veins  passing  from  the  sub  umbilical  part  of  the 
abdominal  wall  to  the  left  longitudinal  fissure  of  the  liver.  They  are  situated  in 
the  inferior  part  of  the  falciform  ligament.  The  most  important  end  at  the  umbili- 
cal incisure  of  the  liver  ;  others  end  in  the  umbilical  fissure ;  and  others,  very  deli- 
cate, surround  the  round  ligament :  one  or  two  constantly  empty  into  the  left  portal 
branch.  At  their  origin  these  veins  communicate  with  the  epigastric  veins,  inter- 
nal mammary,  and  the  tegumentary  veins  of  the  abdomen. 

The  fourth  and  fifth  groups  do  not  come  from  the  alimentary  tract,  and  hence 
establish  an  anastomosis  between  the  portal  and  general  venous  systems.  These 
branches  would  dilate  in  some  chronic  diseases  of  the  liver  and  aid  the  obstructed 
portal  system. 

The  hepatic  duct  is  formed  at  the  transverse  fissure  by  two  tributaries,  one 
from  the  right  and  one  from  the  left  lobe.  The  calibre  of  each  nearly  equals  that 
of  the  trunk  formed.  The  tributaries  to  these  two  branches  start  from  the  inter- 
lobular  spaces  in  company  with  the  portal  and  arterial  twigs. 

The  lymph-vessels  form  a  superficial  and  deep  set. 

The  superficial  lymph-vessels  of  the  convex  surface  belong  either  to  the  poste- 
rior half  or  to  the  anterior  half  of  the  liver.  Those  of  the  posterior  half  form 
several  groups,  and  from  right  to  left  are  found  first  on  the  right  edge,  a  larger 
lymph-vessel  which  runs  around  to  the  right  lateral  ligament,  and  from  there  to 
the  inferior  surface,  and  empties  into  a  gland  on  the  head  of  the  pancreas. 

Then  comes  a  series  of  lymph-vessels  which  go  over  to  the  coronary  ligament, 
and  from  there  to  the  posterior  surface  of  the  liver,  and  empty  into  the  lymphatic 
glands  which  lie  on  the  inferior  vena  cava  just  above  the  Diaphragm.  Along  the 
falciform  ligament  from  the  right  as  well  as  from  the  left  lobe  is  developed  a  rich 
network  of  vessels  which  unite  into  several  larger  trunks.  These  run  between 
both  layers  of  the  falciform  ligament,  and  join  finally  to  form  a  big  trunk  which 
pierces  the  Diaphragm  and  empties  into  glands  situated  above  this  at  its  point  of 
fusion  with  the  pericardium. 

Those  vessels  springing  more  laterally  from  the  left  lobe  of  the  liver  empty 
into  glands  situated  more  to  the  right,  lying  on  the  vena  cava ;  the  vessels  rising 
to  the  left  of  the  left  lateral  ligament,  and  from  it,  empty  into  glands  situated  on 
the  lower  part  of  the  oesophagus. 

Those  vessels  springing  from  the  anterior  half  of  the  convex  surface  arch 
around  the  anterior  margin  of  the  liver  and  run  into  the  glands  situated  in  the 
transverse  fissure.  The  vessels  of  the  under  surface  also  pass  to  those  same 
glands.  Only  a  few  twigs  arising  on  the  posterior  surface  of  the  liver  end  in  the 
glands  lying  on  the  vena  cava. 

Of  the  deeper  lymph-vessels,  some  accompany  the  portal  veins,  and  others  the 
hepatic  veins.  The  first,  fifteen  or  eighteen  in  number,  empty  into  the  glands  sur- 
rounding the  neck  of  the  gall-bladder.  The  last  accompany  the  hepatic  veins  to 
the  vena  cava,  five  or  six  in  number,  and  pass  through  the  foramen  venae  cavae  of 
the  Diaphragm,  and  empty  into  glands  situated  just  above  it. 

Microscopically  the  lymphatics  are  seen  in  Glisson's  capsule  in  the  interlobular 
spaces,  where  they  accompany  the  blood-vessels.  They  rise  from  lymph-spaces  in 
the  intralobular  plexus. 

The  nerves  come  from  two  sources,  left  vagus  and  coeliac  plexus.  The  left 
vagus  after  its  passage  through  the  oesophageal  opening  gives  off  twigs  which  turn 
from  left  to  right  along  the  lesser  curvature  of  the  stomach,  between  the  two  layers 
of  the  lesser  omentum,  to  accompany  the  branches  of  the  portal  veins.  Those 
twigs  from  the  coeliac  plexus  are  much  more  numerous,  and  come  from  three 
sources,  right  vagus,  phrenic,  and  great  sympathetic.  They  meet  the  hepatic 
artery  and  follow  this  to  the  transverse  fissure.  The  nerves  all  divide  into  right 
and  left  sets,  which  accompany  the  branches  of  the  artery,  of  the  portal  vein,  and 
the  tributaries  of  the  hepatic  duct.  They  terminate  in  fine  tree-like  endings,  show- 


THE  LIVER. 


1059 


ing  varicosities,  and  are  distributed  to  the  blood-vessels  and  ducts,  and  to  spaces 
between  the  liver-cells,  and  follow  the  biliary  canaliculi  (Berkeley).  The  phrenic 
nerves  supply  part  of  the  external  surface  of  the  liver. 

Structure.  —  The  substance  of  the  liver  is  composed  of  lobules  held  together  by 
an  extremely  fine  areolar  tissue,  and  of  the  ramifications  of  the  portal  vein,  hepatic 
duct,  hepatic  artery,  hepatic  veins,  lymphatics,  and  nerves,  the  whole  being 
invested  by  a  serous  and  a  fibrous  coat. 

The  serous  coat  is  derived  from  the  peritoneum,  and  invests  the  greater  part 
of  the  surface  of  the  organ.  It  is  intimately  adherent  to  the  fibrous  coat. 

The  fibrous  coat  lies  beneath  the  serous  investment  and  covers  the  entire  sur- 
face of  the  organ.  It  is  difficult  of  demonstration,  excepting  where  the  serous 
coat  is  deficient.  At  the  transverse  fissure  it  is  continuous  with  the  capsule  of 
Glisson,  and  on  the  surface  of  the  organ  with  the  areolar  tissue  separating  the 
lobules. 

The  lobules  form  the  chief  mass  of  the  hepatic  substance  ;  they  may  be  seen 
either  on  the  surface  of  the  organ  or  by  making  a  section  through  the  gland. 


Hepatic 

artery. 


Portal  vein. 


Orifices  of  intralobular  veins. 


FIG.  669.— Longitudinal  section  of  an  hepatic 
vein.    (.After  Kiernan.) 


Portion  of 
canal  from 
which  vein 
has  been 
removed. 

FIG.  670. — Longitudinal  section  of  a  small  portal 
vein  and  canal.    (After  Kiernan.; 


They  are  small  granular  bodies  about  the  size  of  a  millet-seed,  measuring  from 
one-twentieth  to  one-tenth  of  an  inch  in  diameter.  In  the  human  subject  their 
outline  is  very  irregular,  but  in  some  of  the  lower  animals  (for  example,  the  pig) 
they  are  well-defined,  and  when  divided  transversely  have  a  polygonal  outline. 
If  divided  longitudinally  they  are  more  or  less  foliated  or  oblong.  The  bases  of 
the  lobules  are  clustered  round  the  smallest  radicles  (sublobular)  of  the  hepatic 
veins,  to  which  each  is  connected  by  means  of  a  small  branch  which  issues  from 
the  centre  of  the  lobule  (intralobular).  The  remaining  part  of  the  surface  of  each 
lobule  is  imperfectly  isolated  from  the  surrounding  lobules  by  a  thin  stratum  of 
areolar  tissue  in  which  is  contained  a  plexus  of  vessels  (the  interlobular  plexus) 
and  ducts.  In  some  animals,  as  the  pig,  the  lobules  are  completely  isolated  one 
from  another  by  this  interlobular  areolar  tissue. 

If  one  of  the  sublobular  veins  be  laid  open,  the  bases  of  the  lobules  may  be 
seen  through  the  thin  wall  of  the  vein  on  which  they  rest,  arranged  in  the  form 
of  a  tesselated  pavement,  the  centre  of  each  polygonal  space  presenting  a  minute 
aperture,  the  mouth  of  an  intralobular  vein  (Figs.  669  and  671). 

Microscopic  Appearance. — Each  lobule  is  composed  of  a  mass  of  cells  (hepatic 
cells)  surrounded  by  a  dense  capillary  plexus,  composed  of  vessels  which  penetrate 
from  the  circumference  to  the  centre  of  the  lobule,  and  terminate  in  a  single 


1060 


THE    ORGANS    OF  DIGESTION. 


straight  vein,  which  runs  through  its  centre,  to  open  at  its  base  into  one  oi 
the  radicles  of  the  hepatic  vein.  Between  the  cells  are  also  the  minute  com- 
mencements of  the  bile-ducts.  Therefore  in  the  lobule  we  have  all  the  essen- 
tials of  a  secreting  gland ;  that  is  to  say :  (1)  cells,  by  which  the  secretion  is 
formed ;  (2)  blood-vessels,  in  close  relation  with  the  cells,  containing  the  blood 
from  which  the  secretion  is  derived ;  and  (3)  ducts,  by  which  the  secretion, 
when  formed,  is  carried  away.  Each  of  these  structures  will  have  to  be  further 
considered. 

(1)  The  hepatic  cells  are  of  more  or  less  spheroidal  form,  but  may  be  rounded, 
flattened,  or  many-sided  from  mutual  compression.      They  vary  in  size  from  the 
.  A      to  the  ^Qfr  of  an  inch  in  diameter.     They  consist  of  a  honeycomb  net- 
work (Klein)  without  any  cell-wall,  and  contain   one  or  sometimes   two  distinct 
nuclei.    In  the  nucleus  is  a  highly  refracting  nucleolus  with  granules.    Embedded 
in  the  honeycomb  network  are  numerous  yellow  particles,  the  coloring  matter  of 
the  bile,  and  oil-globules.     The  cells  adhere   together  by  their  surfaces  so  as  to 
form  rows,  which  radiate  from  the  centre  to  the  circumference  of  the  lobules.    As 
stated  above,  they  are  the  chief  agents  in  the  secretion  of  the  bile. 

(2)  The  Blood-vessels. — The  blood   in   the   capillary  plexus  around  the  liver- 
cells  is  brought  to  the  liver  principally  by  the   portal  vein,  but  also  to  a  certain 
extent  by  the  hepatic  artery.     For  the  sake  of  clearness  the  distribution  of  the 
blood  derived  from  the  hepatic  artery  may  be  considered  first. 

The  hepatic  artery,  entering  the  liver  at  the  transverse  fissure  with  the  portal 
vein  and  hepatic  duct,  ramifies  with  these  vessels  through  the  portal  canals.  It 
gives  off  vaginal  branches  which  ramify  in  the  capsule  of  Glisson,  and  appear  to 
be  destined  chiefly  for  the  nutrition  of  the  coats  of  the  large  vessels,  the  ducts, 
and  the  investing  membranes  of  the  liver.  It  also  gives  oif  capsular  branches 
which  reach  the  surface  of  the  organ,  terminating  in  its  fibrous  coat  in  stellate 
plexuses.  Finally  it  gives  off  interlobular  branches  which  form  a  plexus  on  the 
outer  side  of  each  lobule,  to  supply  its  wall  and  the  accompanying  bile-ducts. 
From  this,  lobular  branches  enter  the  lobule  and  end  in  the  capillary  network 
between  the  cells.  Some  anatomists,  however,  doubt  whether  it  transmits  any 
blood  directly  to  the  capillary  network. 


FIG  671  — Cross  section  of  a  lobule  of  the  human  liver,  showing  capillary  network  between  portal  and 
hepatic  veins.  (Sappey.)  1.  Section  of  intralobular  vein.  2,  2.  Tributaries  from  capillary  net-work.  3,  3. 
Interlobular  veins  from  vena  portee. 

The  portal  vein  (Fig.  670)  also  enters  at  the  transverse  fissure  and  run3 
through  the  portal  canals,  enclosed  in  Glisson's  capsule,  dividing  into  branches  in 
its  course,  which  finally  break  up  into  a  plexus  (the  interlobular  plexus]  in  the 
interlobular  spaces  between  the  lobules.  In  their  course  these  branches  receive 
the  vaginal  and  capsular  veins,  corresponding  to  the  vaginal  and  capsular 


THE   LIVER. 


1061 


branches  of  the  hepatic  artery  (Fig.  670).  Thus  it  will  be  seen  that  all  the 
blood  carried  to  the  liver  by  the  portal  vein  and  hepatic  artery,  except  perhaps 
that  derived  from  the  interlobular  branches  of  the  hepatic  artery,  directly  or 
indirectly  finds  its  way  into  the  interlobular  plexus.  From  this  plexus  the  blood 
is  carried  into  the  lobule  by  fine  branches  which  pierce  its  wall  and  then  converge 
from  the  circumference  to  the  centre  of  the  lobule,  forming  a  number  of  longitu- 
dinal vessels  which  are  connected  by  transverse  or  horizontal  branches  (Fig.  671). 
In  the  interstices  of  the  network  of  vessels  thus  formed  are  situated,  as  before 
said,  the  liver-cells  :  and  here  it  is  that,  the  blood  being  brought  into  intimate 
connection  with  the  liver-cells,  the  bile  is  secreted.  Arrived  at  the  centre  of  the 
lobule,  all  these  minute  vessels  empty  themselves  into  one  vein,  of  considerable 
size,  which  runs  down  the  centre  of  the  lobules  from  apex  to  base  and  is  called 
the  intral'-ibular  vein.  At  the  base  of  the  lobule  this  vein  opens  directly  into  the 
sublobular  •.'•-in.  with  which  the  lobule  is  connected,  and  which,  as  before  men- 


FIG.  672.— Origin  of  the  hepatic  veins.    (Sappey.)    1.  Sublobular  vein.    2,  2.  Intralobular  veins.    3,  3.  Trib- 
utaries to  2.    4.  4.  Capillary  network  between  portal  and  hepatic  systems. 

tioned,  is  a  radicle  of  the  hepatic  vein  (Fig.  672).     The  sublobular  veins,  uniting 

into  larger  and  larger  trunks,  end  at  last 
in  the  hepatic  veins,  which  do  not  receive 
any  intralobular  veins.  Finally,  the  he- 
patic veins,  as  mentioned  at  page  1057, 

Biliary  .^-N 

"  duct. 


Hepatic 
cells. 


Capillary. 


Biliary  duct. 


FIG.  673.— Section  of  liver. 


Fig.  674.— A  transverse  section  of  a  small  portal 
canal  and  its  vessels.  (After  Kiernan.)  L  Portal  vein. 
2.  Interlobular  branches.  3.  Vaginal  branches.  4. 
Hepatic  duct.  5.  Hepatic  artery. 


converge  to  form  three  large  trunks  which  open  into  the  inferior  vena  cava,  while 
that  vessel  is  situated  in  the  fissure  appropriated  to  it  at  the  back  of  the  liver. 


1062 


THE    ORGANS    OF  DIGESTION. 


(3)  The  Ducts. — Having  shown  how  the  blood  is  brought  into  intimate  relation 
with  the  hepatic  cells  in  order  that  the  bile  may  be  secreted,  it  remains  now  only 
to  consider  the  way  in  which  the  secretion,  having  been  formed,  is  carried  away. 
Several  views  have  prevailed  as  to  the  mode  of  origin  of  the  hepatic  ducts ;  it 
seems,  however,  to  be  clear  that  they  commence  by  little  passages  which  are 
formed  between  the  cells,  and  which  have  been  termed  intercellular  biliary  pas- 
sages or  bile-canaliculi  (Fig.  673).  These  passages  are  merely  little  channels  or 
interspaces  left  between  the  contiguous  surfaces  of  two  cells  or  in  the  angle  where 
three  or  more  liver-cells  meet,  and  it  seems  doubtful  whether  there  is  any  delicate 
membrane  forming  the  wall  of  the  space.  The  channels  thus  formed  radiate  to 
the  circumference  of  the  lobule,  and,  piercing  its  wall,  form  a  plexus  (interlobular') 
between  the  lobules.  From  this  plexus  ducts  are  derived  which  pass  into  the  por- 
tal canals,  become  enclosed  in  Glisson's  capsule,  and,  accompanying  the  portal 
vein  and  hepatic  artery  (Fig.  674),  join  with  other  ducts  to  form  two  main  trunks, 
which  leave  the  liver  at  the  transverse  fissure,  and  by  their  union  form  the  hepatic 
duct. 

Structure  of  the  Ducts. — Those  in  the  interlobular  spaces  have  walls  of  con- 
nective tissue  lined  by  columnar  epithelium.  They  probably  contain  muscle-cells 


FIG.  675.— Blind  tubules  of  the  bil- 
iary ducts  of  a  horse.    (Sappey.) 


FIG.  676.— Liver  tissue  over  the  posterior  surface  of  the  vena 
cava  inferior,  with  injected  vasa  aberrantia.    (Henle.) 


arranged  longitudinally  and  circularly.  As  they  lie  in  the  lobule  the  columnar 
epithelium  is  very  short  and  flat  and  the  lumen  very  small.  The  bile-canaliculi 
open  directly  into  them,  liver-cells  abutting  against  the  epithelium.  The  ducts  in 
the  portal  canals  are  larger,  and  present  numerous  openings  on  the  inner  surface, 
sometimes  arranged  in  two  rows.  Sappey  considers  them  the  orifices  of  mucous 
glands  (Fig.  675),  and  compares  their  appearance  to  that  of  the  vegetable  pai-asites. 
Their  function  is  much  discussed,  arid  at  present  they  are  regarded  only  as  tubular 
recesses.  They  occasionally  anastomose,  and  from  their  sides  saccular  dilatations 
are  given  off. 

Sometimes  certain  parts  of  the  liver  gradually  atrophy  or  completely  disappear, 
while  the  corresponding  biliary  ducts  remain  and,  on  the  contrary,  become  hyper- 
trophied.  They  are  called  vasa  aberrantia.  They  are  not  found  in  the  foetus  or 
child,  are  not  rare  in  the  adult,  and  are  most  frequent  in  old  age.  Accompanying 
them  are  all  the  other  vessels  which  supplied  the  part,  branches  of  the  portal  vein, 
hepatic  vein,  and  artery.  They  are  situated  at  either  extremity  of  the  liver,  most 
often  in  the  left  lateral  ligament,  at  the  attachment  of  the  falciform,  or  in  the  posi- 
tions of  atrophied  "bridges,"  as  over  the  left  longitudinal  fissure  or  vena  cava 
(Fig.  676).  They  present  certain  common  characteristics.  All  communicate  with 


THE   LIVER. 


1063 


the  biliary  ducts ;  they  have  a  yellowish  color,  have  epithelial  lining,  and  fibrous 
coat,  and  in  proportion  as  the  lobe  has  atrophied,  they  have  hypertrophied.  They 
present  the  tubular  recesses,  and  anastomose  with  each  other.  These  vessels  are 
found  in  certain  mammals. 

The  Excretory  Apparatus  of  the  Liver. — This  apparatus  consists  of  the  bile- 
canaliculi  and  ducts,  which  we  have  seen  in  and  between  the  lobules;  of  the  hepatic 
duct  formed  by  the  union  of  these  ;  of  a  diverticuluin  or  reservoir  the  (/all-bladder  ; 
of  the  communicating  tube,  cystic  duct,  and  of  the  united  cystic  and  hepatic  ducts, 
the  common  bile-duct  or  ductus  choledochus  (Fig.  677). 


Gall-bladder 


Hepatic  duct 


Common  bile-duct 


Duodenal 
orifice 


FIG.  677.— Biliary  vessels  and  gall-bladder,  dried  and  insufflated.    (Tillaux.) 

The  hepatic  duct  is  formed  by  the  union  of  the  right  and  left  bile -ducts 
descending  from  the  liver.  They  unite  at  an  obtuse  angle  at  the  right  end  of  the 
transverse  fissure.  Their  point  of  union  is  usually  near  the  spot  where  they 
emerge  from  the  liver.  Often  this  happens  lower  down  and  the  hepatic  duct  is 
shortened.  Its  usual  length  is  3-5  cm.  (one  to  two  inches)  and  diameter  4  mm. 
It  joins  with  the  cystic  duct  at  an  acute  angle  to  form  the  common  bile-duct.  It 
descends  in  the  right  margin  of  the  gastro-hepatic  onientum  with  the  vena  cava 
behind  and  the  hepatic  artery  to  the  left.  The  passage  of  bile  into  the  gall-bladder 
only  occurs  when  its  exit  to  the  duodenum  is  closed.  The  bile  then  from  the 
beginning  of  the  common  duct  has  a  passage  provided  upward  and  backward  to  a 
reservoir  which  is  the  gall-bladder. 


1064  THE    ORGANS    OF  DIGESTION. 

The  gall-bladder  is  pear-shaped.  It  is  directed,  with  its  broader  rounded  end 
downward  and  forward  and  to  the  right  to  the  anterior  margin  of  the  liver,  and  with 
its  sharper  end  backward  and  upward  toward  the  transverse  fissure.  It  is  7  to  8 
cm.  long  (three  or  four  inches)  and  near  the  fundus  2.5—3  cm.  broad  (over  an  inch), 
and  will  contain  30-50  cc.  of  bile  (1-1J  ounces).  There  are  to  be  distinguished 
&fundus<  a  body,  and  a  neck.  It  is  fastened  to  the  liver  by  connective  tissue  and 
vessels,  and  lies  in  the  fossa  vesicalis.  The  fundus  extends  beyond  the  anterior 
margin  of  the  liver  in  the  region  of  the  incisura  vesicalis.  But  in  a  normal  posi- 
tion of  the  liver,  the  gall-bladder  may  be  placed  more  or  less  behind  this  edge. 
The  position  of  the  fundus  is  usually  at  the  lower  edge  of  the  ninth  costal  carti- 
lage on  the  outer  edge  of  the  right  Rectus  muscle.  Here  it  rests  directly  on  the 
abdominal  wall.  When  it  extends  beyond  the  liver  it  can  be  percussed.  Its 
function  is  more  than  a  storehouse.  It  forms  some  of  the  constituents  of  the  bile. 
Exceptionally  it  lies  more  to  the  right  or  more  to  the  left. 

The  fundus  rests  usually  on  the  transverse  colon  and  farther  back  on  the  upper 
end  of  the  descending  duodenum,  or  on  the  pylorus.  This  part  is  usually  stained 
by  biliary  coloring  matter  after  death.  The  neck  of  the  bladder  usually  extends 
in  the  posterior  arid  upper  part  of  the  vesical  fossa  close  to  the  transverse  fissure. 
It  is  continued  in  a  spiral  curve  into  the  cystic  duct.  This  curving  corresponds  on 
the  inner  surface  to  a  constant  more  or  less  well  developed  screw-like  valve  which 
runs  through  the  Avhole  cystic  duct,  Valvula  Heisteri. 

The  upper  surface  is  attached  to  the  liver  by  areolar  tissue  and  vessels.  Its 
under  surface  and  fundus  are  covered  by  peritoneum  reflected  from  the  liver  sur- 
face. Sometimes  the  peritoneum  completely  surrounds  the  bladder,  suspending  it 
by  a  mesentery  from  the  under  surface  of  the  liver.  The  gall-bladder  is  not  present 
in  all  vertebrates.  It  is  lacking  in  some  mammals  and  birds,  but  is  present  in  all 
reptiles,  and  nearly  all  fishes.  The  ass,  horse,  elephant,  and  rhinoceros  do  not 
have  it. 

Relations  of  the  Gall-bladder. 

Superiorly : 

Liver  (Fossa  vesicalis). 
Anteriorly : 

Abdominal  wall ;  and  ninth  costal  cartilage. 
Inferiorly : 

Hepatic  flexure  of  colon  ; 

Beginning  of  transverse  colon  ; 

Duodenum,  first  and  second  parts ; 

Pyloric  end  of  stomach. 

Vessels  and  Nerves. — It  is  supplied  by  the  cystic  artery  from  the  right  branch 
of  the  hepatic.  Two  cystic  veins  usually  empty  into  right  branch  of  the  vena 
portse.  Twelve  or  fifteen  from  the  fundus  go  directly  into  liver. 

The  nerves  are  from  the  coeliac  plexus. 

The  lymphatics  are  numerous  and  empty  into  a  gland  on  the  neck  of  the 
bladder. 

The  cystic  duct,  the  smallest  of  the  three,  running  from  the  neck  of  the  gall- 
bladder is  3—7  cm.  long  (one  to  three  inches)  and  2.3  mm.  wide.  Its  course  is 
toward  the  left,  at  first  a  little  curved  and  then  straight.  It  joins  the  hepatic  duct 
at  an  acute  angle  to  form  the  common  duct.  This  is  contained  in  the  edge  of  the 
lesser  omentum. 

The  ductus  choledochus  (xokq,  bile,  doxo^,  which  receives)  is  the  largest  of  the 
three,  and  is  the  common  excretory  duct  of  both  liver  and  gall-bladder  and  con- 
veys the  bile  to  the  duodenum.  The  length  is  various  depending  upon  the  point 
of  meeting  of  its  two  tributaries:  7—8  cm.  (Sappey) ;  2—4.5  (Luschka) ;  6—7  cm., 
or  about  three  inches  (Joessel),  and  5.6  mm.  to  7.5  mm.  wide  (one-fourth  inch).  It 


THE  LIVER.  1065 

continues  the  course  of  the  hepatic  duct,  running  downward  and  backward  in  the 
hepato-duodenal  ligament  in  front  of  the  portal  vein  and  to  the  right  of  the 
hepatic  a'-tery.  It  passes  behind  the  first  portion  of  the  duodenum  and  then 
behind  and  to  the  inner  side  of  the  second  portion,  lying  here  in  a  furrow  between 
duodenum  and  head  of  pancreas ;  or  it  may  be  enclosed  by  the  pancreas  till  it 
meets  the  pancreatic  duct.  For  a  short  space  it  is  in  contact  with  the  right  side 
of  this  duct.  The  two  perforate  the  duodenal  wall  and  run  obliquely  for  three- 
fourths  of  an  inch  between  the  coats.  They  finally  open  into  a  little  pouch  and 
that  upon  a  papilla  of  the  mucous  membrane  by  a  common  orifice,  situated  near 
the  junction  of  middle  and  lower  third  of  the  duodenum  on  its  posterior  internal 
wall.  This  is  three  or  four  inches  beyond  the  pylorns.  (See  Pancreas.) 

When  the  gall-bladder  is  distended  with  bile  or  calculi,  the  fundus  may  be  felt  through  the 
abdominal  parietes,  especially  in  an  emaciated  subject :  the  relations  of  this  sac  will  also  serve  to 
explain  the  occasional  occurrence  of  abdominal  biliary  fistuia3,  through  which  biliary  calculi  may 
pass  out.  and  of  the  passage  of  calculi  from  the  gall-bladder  into  the  stomach,  duodenum,  or 
colon,  which  occasionally  happens. 

Structure. — The  gall-bladder  consists  of  three  coats — serous,  fibrous  and  mus- 
cular, and  mucous. 

The  external  or  serous  coat  is  derived  from  the  peritoneum  ;  it  completely 
invests  the  fundus,  but  covers  the  body  and  neck  only  on  their  under  surface. 

The  fibro-muscular  coat  is  a  thin  but  strong  layer  which  forms  the  framework 
of  the  sac,  consisting  of  dense  fibrous  tissue  which  interlaces  in  all  directions  and 
is  mixed  with  plain  muscular  fibres  which  are  disposed  chiefly  in  a  longitudinal 
direction,  a  few  running  transversely. 

The  internal  or  mucous  coat  is  loosely  connected  with  the  fibrous  layer.  It  is 
generally  tinged  with  a  yellowish-brown  color,  and  is  everywhere  elevated  into 
minute  rugse,  by  the  union  of  which  numerous  meshes  are  formed, 
the  depressed  intervening  spaces  having  a  polygonal  outline.  The 
meshes  are  smaller  at  the  fundus  and  neck,  being  most  developed 
about  the  centre  of  the  sac. 

The  mucous  membrane  is  covered  with  columnar  epithelium 
and  secretes  an  abundance  of  thick  viscid  mucus  ;  it  is  continuous 
through  the  hepatic  duct  with  the  mucous  membrane  lining  the 
ducts  of  the  liver,  and  through  the  ductus  communis  choledochus 
with  the  mucous  membrane  of  the  alimentary  canal. 

In  the  cystic  duct  the  mucous  membrane  is  raised  into  ob- 
lique crescentic  folds  much  as  in  the  neck  of  the  bladder.  It 
presents  the  appearance  of  a  continuous  spiral  valve  of  which 
we  have  seen  indications  in  the  small  intestine  and  rectum  (Fi**. 
678).  This  is  the  valve  of  Heister  (1758).  The  outer  surface 
of  the  duct  presents  indentations  at  the  attachment  of  these  folds, 
giving  it  a  sacculated  or  twisted  appearance  (Fig.  677). 

The  coats  of  the  larger  ducts  are  an  external  or  fibrous  and  an  internal  or 
mucous.  The  fibrous  coat  is  composed  of  strong  fibro-areolar  tissue,  with  a  cer- 
tain amount  of  muscular  tissue  arranged  for  the  most  part  in  a  circular  manner 
around  the  duct.  The  mucous  coat  is  continuous  with  the  lining  membrane  of 
the  hepatic  duet  and  gall-bladder,  and  also  with  that  of  the  duodenum,  and,  like 
the  mucous  membrane  of  these  structures,  its  epithelium  is  of  the  columnar 
variety.  It  is  provided  with  numerous  tubules,  which  are  lobulated  and  open  by 
minute  orifices  scattered  irregularly  (Fig.  675). 

Surface  Form. — The  liver  is  situated  in  the  right  hypochondriac  and  the  epigastric  regions, 
and  is  moulded  to  the  arch  of  the  Diaphragm.  In  the  greater  part  of  its  extent  it  lies  under 
cover  of  the  lower  ribs  and  their  c-artilasres,  but  in  the  epigastric  region  it  comes  in  contact  with 
the  abdominal  wall  in  the  subcostal  angle.  The  upper  limit  of  the  right  lobe  of  the  liver  may  be 
defined  by  a  line  drawn  from  the  articulation  of  the  fifth  right  costal  cartilage  to  the  sternum 
horizontally  outward  to  a  little  below  the  nipple,  and  then  inclined  downward  to  reach  the 
seventh  rib  at  the  side  of  the  chest.  The  upper  limit  of  the  left  lobe  may  be  defined  by  continu- 
ing this  line  to  the  left,  with  an  inclination  downward  as  it  crosses  the  gladiolus,  to  a  point  about 


1066  THE    ORGANS    OF   DIGESTION. 

two  inches  to  the  left  of  the  sternum  on  a  level  with  the  sixth  left  costal  cartilage.  The  lower 
limit  of  the  liver  may  be  indicated  by  a  line  drawn  half  an  inch  below  the  lower  border  of  the 
thorax  on  the  right  side  as  far  as  the  ninth  right  costal  cartilage,  and  thence  obliquely  upward 
across  the  subcostal  angle  to  the  eighth  left  costal  cartilage.  A  slight  curved  line  with  its  con- 
vexity to  the  left  from  this  point — i.  e.  the  eighth  left  costal  cartilage — to  the  termination  of  the 
line  indicating  the  upper  limit  will  denote  the  left  margin  of  the  liver.  The  fundus  of  the  gall- 
bladder approaches  the  surface  behind  the  anterior  extremity  of  the  ninth  costal  cartilage,  close 
to  the  outer  margin  of  the  Right  rectus  muscle. 

It  must  be  remembered  that  the  liver  is  subject  to  considerable  alterations  in  position,  and 
the  student  should  make  himself  acquainted  with  the  different  circumstances  under  which  this 
occurs,  as  they  are  of  importance  in  determining  the  existence  of  enlargement  or  other  diseases 
of  the  organ. 

Its  position  varies  according  to  the  posture  of  the  body.  In  the  erect  position  in  the  adult 
male  the  edge  of  the  liver  projects  about  half  an  inch  below  the  lower  edge  of  the  right  costal 
cartilages,  and  its  anterior  border  can  be  often  felt  in  this  situation  if  the  abdominal  wall  is  thin. 
In  the  supine  position  the  liver  gravitates  backward  and  recedes  above  the  lower  margin  of  the 
ribs,  and  cannot  then  be  detected  by  the  finger.  In  the  prone  position  it  falls  forward,  and  can 
then  generally  be  felt  in  a  patient  with  loose  and  lax  abdominal  walls.  Its  position  varies  also 
with  the  ascent  or  descent  of  the  Diaphragm.  In  a  deep  inspiration  the  liver  descends  below 
the  ribs;  in  expiration  it  is  raised  behind  them.  Again,  in  emphysema,  where  the  lungs  are 
distended  and  the  Diaphragm  descends  very  low,  the  liver  is  pushed  down ;  in  some  other 
diseases,  as  phthisis,  where  the  Diaphragm  is  much  arched,  the  liver  rises  very  high  up.  Pres- 
sure from  without,  as  in  tight-lacing,  by  compressing  the  lower  part  of  the  chest,  displaces  the 
liver  considerably,  its  anterior  edge  often  extending  as  low  as  the  crest  of  the  ileum  ;  and  its 
convex  surface  is  often  at  the  same  time  deeply  indented  from  the  pressure  of  the  ribs.  Again, 
its  position  varies  greatly  according  to  the  greater  or  less  distension  of  the  stomach  and  intestines. 
When  the  intestines  are  empty  the  liver  descends  in  the  abdomen,  but  when  they  are  distended 
it  is  pushed  upward.  Its  relations  to  surrounding  organs  may  also  be  changed  by  the  growth  of 
tumors  or  by  collections  of  fluid  in  the  thoracic  or  abdominal  cavities. 

Surgical  Anatomy. — On  account  of  its  large  size,  its  fixed  position,  and  its  friability,  the 
liver  is  more  frequently  ruptured  than  any  of  the  abdominal  viscera.  The  rupture  may  vary 
considerably  in  extent,  from  a  slight  scratch  to  an  extensive  laceration  completely  through  its 
substance,  dividing  it  into  two  parts.  Sometimes  an  internal  rupture  without  laceration  of  the 
peritoneal  covering  takes  place,  and  such  injuries  are  most  susceptible  of  repair ;  but  small  tears 
of  the  surface  may  also  heal ;  when,  however,  the  laceration  is  extensive,  death  usually  takes 
place  from  haemorrhage,  on  account  of  the  fact  that  the  hepatic  veins  are  contained  in  rigid 
canals  in  the  liver-substance  and  are  unable  to  contract,  and  are  moreover  unprovided  with 
valves.  The  liver  may  also  be  torn  by  the  end  of  a  broken  rib  perforating  the  Diaphragm. 
The  liver  may  be  injured  by  stabs  or  other  punctured  wounds,  and  when  these  are  inflicted 
through  the  chest-wall  both  pleural  and  peritoneal  cavities  may  be  opened  up  and  both  lung  and 
liver  be  wounded.  In  cases  of  wound  of  the  liver  from  the  front,  hernia  of  a  part  of  this  viscus 
may  take  place,  but  can  generally  easily  be  replaced.  Abscess  of  the  liver  is  of  not  unfrequent 
occurrence,  and  may  open  in  many  different  ways  on  account  of  the  relations  of  this  viscus  to 
other  organs.  Thus,  it  has  been  known  to  burst  into  the  lungs,  and  the  pus  been  coughed  up, 
or  into  the  stomach  and  the  pus  vomited ;  it  may  burst  into  the  colon  or  into  the  duodenum  ; 
or,  by  perforating  the  Diaphragm,  it  may  empty  itself  into  the  pleural  cavity.  Frequently  it 
makes  its  way  forward  and  points  on  the  anterior  abdominal  wall,  and  finally  it  may  burst  into 
the  peritoneal  or  pericardiac  cavities.  Abscesses  of  the  liver  frequently  require  opening,  and 
this  should  be  done  preferably  by  an  incision  in  the  right  semilunar  line,  in  two  stages :  the 
peritoneal  ctivity  being  opened  and  the  liver  over  the  summit  of  the  abscess  being  stitched  to  the 
parietal  peritoneum  on  the  first  occasion,  and  three  or  four  days  subsequently  the  abscess  being 
evacuated.  Hydatid  cysts  are  more  often  found  in  the  liver  than  in  any  other  of  the  viscera. 
The  reason  of  this  is  not  far  to  seek.  The  embryo  of  the  egg  of  the  taenia  echinococcus,  being 
liberated  in  the  stomach  by  the  disintegration  of  its  shell,  bores  its  way  through  the  gastric 
walls,  and  usually  enters  a  blood-vessel  and  is  carried  by  the  blood-stream  to  the  hepatic  capil- 
laries, where  its  onward  course  is  arrested,  and  where  it  undergoes  development  into  the  fully- 
formed  hydatid. 

When  the  gall-bladder  is,  ruptured,  or  one  of  its  main  ducts,  which  may  occur  indepen- 
dently of  laceration  of  the  liver,  the  injury  is  necessarily  fatal  from  peritonitis  caused  by  the 
extravasation  of  bile  into  the  peritoneal  cavity. 

The  gall-bladder  may  become  distended  with  bile  in  cases  of  obstruction  of  its  duct  or  the 
common  bile-duct,  or  from  a  collection  of  gall-stones  within  its  interior,  thus  forming  a  large 
tumor.  The  swelling  is  pear-shaped,  and  projects  downward  and  forward  to  the  umbilicus.  It 
moves  with  respiration,  since  it  is  attached  to  the  liver.  To  relieve  this  condition  the  gall-blad- 
der must  be  opened  and  the  gall-stones  removed.  The  operation  is  performed  by  an  incision 
two  or  three  inches  long  in  the  right  semilunar  line,  commencing  an  inch  below  the  costal  mar- 
gin. The  peritoneal  cavity  is  opened,  and,  the  tumor  having  been  found,  sponges  are  packed 
round  it  to  protect  the  peritoneal  cavity,  and  it  is  aspirated.  When  the  contained  fluid  has  been 
evacuated  the  flaccid  bladder  is  drawn  out  of  the  abdominal  wound  and  its  \yall  incised  to  the 
extent  of  an  inch ;  any  gall-stones  in  the  bladder  are  now  removed  and  the  interior  of  the  sac 
sponged  dry.  If  the  case  is  one  of  obstruction  of  the  duct,  an  attempt  must  be  made  to  dislodge 


THE   PANCREAS. 


1067 


the  stone  by  manipulation  through  the  wall  of  the  duct,  or  it  must  be  crushed  from  without  by 
carefully  padded  forceps.  After  all  obstruction  has  been  removed  a  drainage-tube  is  to  be 
inserted  and  the  external  wound  closed  around  it,  the  stitches  being  passed  through  the  parietal 
peritoneum  and  also  through  the  peritoneum  covering  the  gall-bladder  around  the  incision,  so  as 
to  bring  these  two  surfaces  into  apposition.  The  fistulous  opening  generally  closes  in  the  course 
of  a  few  weeks, 

THE  PANCREAS. 

Dissection.  —  The  pancreas  may  be  exposed  for  dissection  in  three  different  ways  :  1.  By 
raising  the  liver,  drawing  down  the  stomach,  and  tearing  through  the  gastro-hepatic  omentum 
and  the  ascending  layer  of  the  transverse  meso-colon.  2.  By  raising  the  stomach,  the  arch  of 
the  colon,  and  great  omentum,  and  then  dividing  the  inferior  layer  of  the  transverse  meso-colon 
and  raising  the  ascending  layer  of  the  transverse  meso-colon.  3.  By  dividing  the  two  layers  of 
peritoneum  which  descend  from  the  great  curvature  of  the  stomach  to  form  the  great  omentum, 
turning  the  stomach  upward,  and  then  cutting  through  the  ascending  layer  of  the  transverse 
meso-colon  (see  Figs.  606  and  616). 


The  pancreas  (xav-xpsaz,  all  flesh)  or  the  abdominal  salivary  gland,  is  a  com- 
pound racemose  gland,  similar  in  structure  to  the  salivary  glands,  though  softer 
and  less  compact.  It  is  long  and  lies  transversely  across  the  posterior  wall  of  the 
abdomen  and  when  hardened  in  situ  is  prismatic,  with  three  surfaces.  But 
usually,  when  removed  from  the  body,  it  appears  flattened,  with  only  two  surfaces 
and  two  borders.  It  lies  deep  in  the  epigastrium  at  the  level  of  the  second  lumbar 
vertebra  ;  behind  the  stomach  ;  between  the  duodenum  on  the  right  and  the  spleen 
on  the  left,  so  that  for  clinical  and  surgical  purposes  it  is  scarcely  approachable. 
In  shape,  Meckel  compared  it  to  a  sort  of  hammer  ;  Verneuil,  to  a  cross  placed 
on  its  side,  the  short  vertical  arm  representing  the  head.  Winslow  compared  it 
to  a  dog's  tongue.  Its  right  extremity  being  broad  is  termed  the  head  ;  then  fol- 
lows a  constriction  made  by  the  two  terminal  parts  of  the  duodenal  loop  called 
the  neck,  which  connects  head  and  body.  The  body  is  the  free  portion  passing  to 
the  left,  and  finally  it  abuts  against  the  spleen  as  the  tail  (Figs.  634  and  679). 


yon-perito- 
ncal  surface 


,-Lefl  suprarenal 

capsule 
Left  kidney 

Splenic  vessels 


Transverse 
mesocolon 
'Left  kidney 
'Descending  colon 

"Jejunum 


•"Superior  mesenteric 
vessels 

~3fesentery 
FIG.  679. — Pancreas  and  adjoining  viscera  from  before.    His'  model.    (F.  E.) 

In  color  the  pancreas  is  grayish-white  in  the  intervals  of  digestion,  turning  to 
a  rosy  hue  during  secretion. 

Its  volume  presents  many  variations.  In  general  it  is  bigger  in  man  than  in 
woman.  It  is  usually  15-16  cm.  long  (six  inches) ;  its  width  is  not  one-fourth  or 
one-fifth  of  its  length  ;  its  thickness  is  15-18  mm.  (one-half  to  one  inch).  Length, 
23  cm. ;  width.  4.5  cm. ;  thickness,  2.8  cm.  (Luschka).  Its  volume  is  54-90  c.c. 
Its  weight  is  about  70  gm.  in  the  male  and  60  in  the  female,  two  and  one-fourth  to 
three  and  a  half  ounces.  A  maximum  weight  is  105  gm. 

The  head  of  the  pancreas  is  called  disc-shaped,  or,  since  it  is  elongated  both 
above  and  below,  hammer-shaped.  It  is  flattened  from  before  backward,  and  con- 
forms to  the  whole  concavity  of  the  duodenum  made  up  of  its  four  parts,  and  not  vice 


1068 


THE    ORGANS    OF   DIGESTION. 


versd.     Its  edges  overlap  the  surface  of  the  duodenum  and  may  be  connected  by 
muscular  tissue.     There  is  an  interruption  at  one  place,  below  and  to  the  left  in 


Stomach. ; 


Right  suprarenal 

capsule 
-Mesocolon 
'—  Vena  portx 
j— Splenic  vein 
Common  bile-duct 

'uperior  mesenteric 

vessels 


Mesentery 


FIG.  680.— View  of  the  abdominal  viscera  from  behind,  after  removal  of  spinal  column  and  posterior 
abdominal  wall.    (Drawn  from  His'  model.) 

front  of  the  preaortic  portion  of  the  duodenum,  where  the  root  of  the  mesentery 
passes,  in  which  are  contained  the  superior  mesenteric  vessels,  the  vein  to  the 
right  and  the  artery  to  the  left  (Figs.  634  and  679).  Both  vessels  run  in  a 


.  Tuber  culum 

caudatum 

Venaportx 

Common  bile-duct 
Mesocolon 

Superior  mesen- 
teric vessels 


—  Mesentery 


FIG.  681.—  Same  as  previous  figure,  but  with  right  kidney  and  spleen   removed.     (Drawn  from  His'  model.) 

groove  on  the  posterior  surface  of  the  head,  and  near  the  descending  duodenum 
in  a  groove  or  canal  is  the  common  bile-duct.  A  part  of  the  pancreatic  tissue  is 
bent  around  behind  the  vessels,  which  is  called  the  lesser  head.  The  posterior 


THE   PANCREAS.  1069 

surface  of  the  head  is  bound  by  loose  tissue  to  and  rests  upon  the  inferior  vena 
cava  and  right  crus  of  diaphragm,  coeliac  plexus,  left  renal  vein,  and  right  renal 
vessels :  the  descending  duodenum  intervenes  between  it  and  the  right  kidney. 
Near  its  lower  end  it  is  crossed  in  front  by  the  transverse  colon  and  transverse 
mesocolon.  The  superior  and  inferior  pancreatico-duodenal  vessels  are  in  front 
of  the  head. 

The  neck  is  about  one  inch  long,  passing  upward  and  forward  to  the  left :  it 
is  bounded  above  by  the  first  part  of  the  duodenum  and  below  by  the  end  of  the 
ascending  portion.  The  stomach,  if  distended,  touches  this  portion  by  the  poste- 
rior surface  of  the  pylorus.  Behind  it  is  the  junction  of  the  superior  mesenteric 
vein  with  the  vena  porta?  (Fig.  681).  To  the  right  it  is  grooved  by  the  gastro- 
duodenal  and  superior  pancreatico-duodenal  arteries. 

The  body  and  tail  constitute  the  prismatic  portion  presenting  three  surfaces 
and  three  borders:  '!/if. ,ri»r.  posterior,  and  inferior  surfaces;  superior  and  two 
•lor  borders.  Some  regard  the  surfaces  as  posterior,  antero-superior,  and 
antero-inferior.  making  an  anterior  border  more  distinct.  This  part  of  the  pan- 
creas passes  from  the  right  to  the  left  and  is  moulded  to  different  structures, 
following  the  example  of  the  liver.  Its  anterior  surface  is  fitted  to  the  convexity 
of  the  filled  stomach  :  its  posterior  surface  is  more  flat  except  where  it  covers  the 
left  kidney :  the  tail  passes  upward  and  backward  to  the  spleen.  The  anterior 
surface  is  concave,  looks  upward  and  forward  ;  the  posterior  surface  of  the  stomach 
lies  upon  it.  separated  by  the  bursa  omentalis,  or  two  layers  of  the  lesser  sac. 
Perforating  ulcers  of  the  stomach  can  reach  the  pancreas  and  result  in  fusion  of 
these  two  organs,  or  in  hemorrhage  from  the  splenic  vessels. 

The  post»:ri>~>r  surface  (Figs.  680  and  681)  corresponds  internally  to  the  aorta 
and  left  crus  of  the  diaphragm  and  the  origin  of  the  superior  mesenteric  artery. 
It  crosses  the  second  or  third  lumbar  vertebra.  Near  the  upper  edge  are  two  fur- 
r-.iws — one  for  the  somewhat  tortuous  splenic  artery  and  a  straight  one  for  the 
splenic  vein.  The  surface  shows  a  shallow  furrow  for  the  splenic  vein,  which 
ascends  from  the  middle  of  the  lower  edge  toward  the  left  to  the  upper  edge. 
This  edge  carries  a  furrow  from  the  middle  along  the  left  half,  in  which  the 
splenic  artery  takes  part  of  its  course.  The  splenic  vein  in  its  outer  half  runs 
above  the  edge  to  reach  the  hilus  of  the  spleen.  To  the  left  is  the  left  kidney 
and  its  vessels,  and  sometimes  the  left  suprarenal  capsule.  The  relations  to  the 
left  kidney  show  two  types :  one  is  seen  in  the  His  models  and  Fig.  636.  where 
the  pancreas  runs  directly  over  the  hilus  and  centre  of  the  kidney,  exposing  the 
suprarenal  capsule,  and  a  considerable  part  of  the  anterior  kidney  surface  above, 
the  tail  touching  the  lower  part  of  the  spleen. 

The  other  type  is  seen  in  Fig.  634.  Here  the  pancreas  is  higher,  and  crosses 
the  upper  part  of  the  kidney,  leaving  exposed  above  its  edge  the  whole  or  only  a 
part  of  the  left  suprarenal  capsule.  The  tail  touches  the  same  part  of  the  spleen 
in  each  case,  showing  it  is  also  elevated  with  the  pancreas.  (Compare  Figs. 
634  and  679.) 

The  *nrfa?e  is  narrow,  only  1  to  -  cm.  broad,  and  shows,  in  the  organ 

hardened  in  situ,  internally  a  cavity  and  laterally  a  convexity,  each  directed 
downward.  It  rests  by  the  concavity  on  the  duodeno-jejunal  flexure,  and  often 
on  some  coils  of  the  jejunum,  and  to  the  left  on  the  transverse  colon. 

The  fup-.-rior  border  of  the  body  on  the  right  is  prominent,  blunt,  and  flat ; 
laterally,  near  the  tail,  it  is  narrower  and  sharper.  The  inner  blunt  elevation  is 
covered  by  the  lesser  omentum.  and  fits  into  and  behind  the  lesser  curvature  of 
the  stomach  :  it  is  the  tuber  omentale  of  the  pancreas.  Between  it  and  the  tuber 
omentale  of  the  liver  is  the  lesser  sac.  This  border  is  related  above  to  the  coeliac 
axi.s  and  solar  plexus,  and  to  two  of  the  branches  of  the  former,  the  hepatic 
artery  passing  to  the  right,  the  splenic  to  the  left. 

The  inferior  or  anterior  border  is  the  dividing  line  for  the  two  layers  of  the 
transverse  mesocolon.  The  upper  layer  passes  up  over  the  anterior  surface  and 
here  constitutes  the  posterior  wall  of  the  lesser  sac.  The  lower  layer  passes  down 


1070 


THE    ORGANS    OF   DIGESTION. 


over  the  narrow  inferior  surface  (Fig.  679).  Thus  the  posterior  surface  is  devoid 
of  peritoneum. 

The  tail  of  the  pancreas  rests  upon  the  lower  part  of  the  inner  surface  of  the 
spleen,  or  is  bound  to  it  by  a  fold  of  peritoneum,  the  lig.  pancreatico-lienale.  It 
crosses  over  the  middle  of  the  left  kidney,  or  kidney  and  capsule,  or  capsule 
alone.  In  front  of  this  portion  is  the  left  gastro-epiploic  artery. 

The  excretory  duct  of  the  gland,  ductus  pancreaticus  or  canal  of  Wirsung  runs 
(1643)  from  left  to  right  in  the  long  axis  of  the  gland,  sometimes  approaching 
the  anterior  surface,  but  more  often  the  posterior  surface.  It  begins  with  a  very 
small  calibre,  formed  by  union  of  small  ducts  from  the  lobules,  in  the  tail  part, 
and  gradually  increases  in  size  on  the  receipt  of  tributaries  from  every  side ;  so 
that  near  its  mouth  it  attains  the  size  of  the  classical  quill,  about  one-ninth  of  an 
inch  in  diameter.  It  can  be  found  by  its  white  color  and  close  relation  to  the 
large  pancreatic  artery.  After  reaching  the  neck  it  turns  downward,  backward, 
and  to  the  right  in  the  head,  and  reaches  the  left  side  of  the  common  bile-duct, 
and  both  go  to  the  descending  duodenum. 

It  receives  numerous  branches  in  the  head  of  the  gland,  a  large  one  from 
below,  and  the  ductus  pancreaticus  accessorius  or  ductus  Santorini  from  above 
(1775)  (Fig.  682). 

This  latter  duct  opens  into  the  duodenum  independently  on  a  papilla  about 
one  inch  above  the  orifice  of  the  others.1  The  usual  course  of  its  contents,  how- 


FIG.  682.— Pancreas  and  duodenum  from  behind.  The  pan- 
creatic duct  is  dissected  free  and  the  posterior  wall  of  the  du- 
odenum removed.  (Henle.) 


Ductus 
choledochus      Wau  of  duodenum 


Fold  of  mucous 
membrane 


Diverticuhtm  Vateri 
Papilla  Vateri 


FIG.  683.— Section  of  duodenal  wall 
through  the  papilla  on  which  the  bile 
and  pancreatic  ducts  open.  (Henle.) 


ever,  is  below  into  the  pancreatic  duct.  Should  this  become  occluded  near  its 
orifice  then  a  reverse  flow  might  occur  in  the  duct  of  Santorini. 

The  bile  and  pancreatic  ducts  do  not  unite  outside  the  duodenal  wall.  They 
enter  it  obliquely  and  run  obliquely  a  short  distance  between  its  coats  and  then 
unite  at  an  acute  angle  and  empty  into  a  common  receptacle  just  under  the 
mucous  membrane  (Fig.  683).  This  little  bladder-like  pouch  is  called  the  diver- 
ticulum  Vateri  (1720).  It  throws  up  a  papilla  of  mucous  membrane  situated  on 
the  free  edge  of  one  of  the  valvulae  conniventes.  This  is  the  papilla  of  Voter. 
It  has  a  single  opening,  which  can  be  best  found  by  the  presence  of  a  drop 
of  fluid  intruded  by  pressure  on  the  gall-bladder  or  pancreas.  The  papilla 
is  still  farther  concealed  by  a  mucous  fold,  which  covers  it  from  above 
(Fig.  683). 

Abnormal  forms  occur ;  the  descending  duodenum  mny  be  surrounded  by  a 
ring  of  pancreatic  tissue ;  the  tail  may  be  bifid  ;  a  part  of  the  head  curving 
around  behind  the  mesenteric  vessels  may  form  the  lesser  pancreas.  Accessory 
glands  (pancreas  accessorium)  are  found  most  often  in  the  walls  of  the  jejunum 
and  in  those  of  the  stomach. 

1  This  is  of  interest,  as  the  pancreas  originally  budded  from  the  duodenum  as  two  outgrowths. 
At  about  the  sixth  week  the  processes  and  their  ducts  join,  as  here  seen. 


THE  PANCREAS. 


1071 


HECTUS    MUSCLE. 


Sth  Costal  Cartilage. 

7th  Costal  Cartilage. 


7th  Rib. 


^~8th  Eib. 


—9th  Rib. 


DIAPHRAGM. 


Abdominal  Aorta. 


12th  Bib.    nth  Rib. 


FIG.  684.— Transverse  section  through  the  middle  of  the  first  lumbar  vertebra,  showing  the  relations  of  the 
pancreas.    <  Braune.  i 

Relations  in  Detail  (Fig.  684). 
Superiorly : 

First  part  of  duodenum  ; 
Coeliac  axis,  solar  plexus  : 
Splenic  and  hepatic  arteries ; 
Tuber  omentale  of  liver. 

Anteriorly  : 

Bursa  omentalis  (lesser  sac)  ; 
Posterior  surface  of  stomach ; 
Gastro-duodenal  artery ; 
Pancreatico-duodenal  arteries ; 
Upper  layer  of  transverse  mesocolon  ; 
Transverse  colon. 


To  rigid  : 

Concavity  of  duodenum. 


To  left : 

Lower  part  of  inner  surface  of  spleen. 


Posteriorly : 

Second  (third  or  first)  lumbar  vertebra ; 

Pancreatic  and  common  bile-ducts ; 

Vena  cava  inferior : 

Origin  of  thoracic  duct ; 

Crura  of  diaphragm ; 

Coeliac  plexus ; 

Aorta  : 

Sup.  roesenteric  artery ; 

Splenic,  sup.  and  inf.  mesenteric  veins ; 

Vena  portre : 

Right  and  left  renal  vessels  : 

Left  kidney  (or  kidney  and  capsule  or  capsule  alone). 


1072 


THE    ORGANS    OF  DIGESTION, 


Inferiorly : 

Duodeno-jejunal  flexure; 

Third  and  fourth  parts  of  duodenum ; 

Jejunum  ; 

Transverse  colon ; 

Lower  layer  of  transverse  mesocolon ; 

Superior  mesenteric  vessels ; 

Inferior  mesenteric  vein ; 

Mesentery. 

Vessels  and  Nerves. — The  pancreas  is  the  only  abdominal  organ  which  does  not 
have  a  special  artery  from  the  aorta.  Its  supply  comes  from  the  coeliac  axis  and 
superior  mesenteric.  The  splenic  artery  gives  the  pancreaticoe  parvce  and  pan- 
creatica  magna,  which  supply  the  tail  and  body.  The  pancreatico-duodenalis 
superior  comes  from  the  gastro-duodenalis  of  the  hepatic.  These  all  come  from 
the  coeliac  axis.  The  superior  mesenteric  gives  off  the  pancreatico-duodenalis 
inferior,  which,  with  the  superior,  supplies  the  head. 

The  veins  are  of  the  same  names,  and  empty  into  the  splenic  and  superior 
mesenteric  veins,  all  belonging  to  the  portal  system. 

The  lymphatic  vessels  are  numerous,  divided,  according  to  their  course,  in 
upper,  lower,  right,  and  left  sets  (Sappey). 

The  upper  open  into  a  row  of  lymph-glands  along  the  splenic  artery ;  the 
lower  open  into  glands  on  the  posterior  surface  around  the  superior  mesenteric 
vessels ;  the  right  open  into  three  or  four  glands  found  between  the  head  of  the 
pancreas  and  descending  duodenum  ;  the  left,  into  a  group  of  glands  situated 
between  the  tail  of  the  pancreas  and  spleen  in  the  pancreatico-lienal  ligament. 

The  nerves  rise  from  the  coeliac  plexus,  and  probably  have  some  elements  of 
the  right  vagus,  and  accompany  the  vessels  which  supply  the  pancreas ;  the  most 
of  them  go  with  the  splenic  artery.  They  are  non-medullated  and  gangliated. 
In  the  gland  they  run  independently  of  the  vessels. 

In  structure  the  pancreas  closely  resembles  the  parotid  gland.  It  differs  in 
certain  particulars,  and  is  looser  and  softer  in  its  texture  It  is  not  enclosed  in  a 


Larger  duct 


-  Commencement  of  duct 

Inner  zone  of  alveolar 
cells 


FIG.  686.— Section  of  alveoli  and  duct.    Human  pancreas.    (Bohm  and  Davidoff.) 


distinct  capsule,  but  is  surrounded  by  areolar  tissue  which  dips  down  into  its 
interstices  and  divides  the  gland  tissue  into  lobes,  and  these  are  subdivided  by 
septa  into  lobules  which  in  turn  are  composed  of  groups  of  alveoli,  connected 


THE  SPLEEN.  1073 

with  one  of  the  ramifications  of  the  main  duct  (Fig.  685).  This  interalveolar 
connective  tissue  supports  the  blood-vessels,  and  in  certain  parts  of  it  are  seen 
collections  of  cells,  interalveolar  cell-islets.  They  are  permeated  by  a  network  of 
capillaries,  and  are  very  characteristic  of  the  pancreas.  Their  function  is  un- 
known. The  minute  ducts  are  lined  by  short  columnar  epithelium,  shorter  than 
that  found  in  the  salivary  ducts,  and  with  no  striation.  The  alveoli  are  tubular, 

»/  ' 

wavy,  and  convoluted,  lined  by  columnar  cells  which  presents  two  zones:  an 
outer  one  presenting  the  nucleus,  clear  and  faintly  striated ;  and  an  inner  granu- 
lar one,  next  the  lumen.  These  are  the  secreting  cells  ;  after  their  activity  the 
granular  zone  occupies  most  of  the  cell,  whereas,  in  the  earliest  stage  of  digestion, 
the  clear  zone  did  this.  The  lumen  of  the  alveolus  is  hardly  visible,  being  filled 
by  spindle-shaped  cells,  the  centro-acinar  cells  of  Langerhaus.  Piersol  considers 
these  as  imperfectly  developed  acini,  and  calls  them  bodies  of  Langerhaus. 

The  pancreatic  duct  presents  two  coats,  fibro-elastic  and  mucous.  There  is  no 
sign  of  muscular  tissue.  Fine  intercellular  canaliculi  have  been  seen,  compar- 
able to  those  of  the  liver,  passing  from  between  the  cells  to  the  lumen  of  an 
alveolus. 

Surface  Form. — The  pancreas  lies  in  front  of  the  second  lumbar  vertebra,  and  can  some- 
times be  felt,  in  emaciated  subjects,  when  the  stomach  and  colon  are  empty,  by  making  deep 
pressure  in  the  middle  line  about  three  inches  above  the  umbilicus. 

Surgical  Anatomy. — The  pancreas  presents  but  little  of  surgical  importance.  It  is  occa- 
sionally the  seat  of  cancer,  which  usually  affects  the  bead  or  duodenal  end,  and  therefore  often 
speedily  involves  the  common  bile-duct,  leading  to  persistent  jaundice.  Cysts  are  also  occasion- 
ally found  in  it.  which  may  present  in  the  epigastric  region,  above  and  to  the  right  of  the  umbil- 
icus, and  may  require  opening  and  drainage.  The  fluid  in  them  contains  some  of  the  elements 
of  the  pancreatic  secretion  and  is  very  irritating,  so  that,  if  allowed  to  come  in  contact  with  the 
skin  of  the  abdominal  wall,  it  is  likely  to  produce  intractable  eczema.  It  has  been  said  that  the 
pancreas  is  the  only  abdominal  viscus  which  has  never  been  found  in  a  hernial  protrusion ;  but 
even  this  organ  has  been  found,  in  company  with  other  viscera,  in  rare  cases  of  diaphragmatic 
hernia.  The  pancreas  has  been  known  to  become  invaginated  into  the  intestine,  and  portions 
of  the  organ  have  sloughed  off.  In  cases  of  excision  of  the  pylorus  great  care  must  be  exer- 
cised to  avoid  wounding  the  pancreas,  as  the  escape  of  the  pancreatic  fluid  may  be  attended 
with  serious  results.  According  to  Billroth,  it  is  likely,  in  consequence  of  its  peptonizing  quali- 
ties, to  dissolve  the  cicatrix  of  the  stomach. 

THE  SPLEEN. 

The  spleen  is  the  largest  and  most  important  ductless  gland.  It  is  probably 
related  to  the  vascular  system,  yet  its  anatomical  relations  to  the  stomach  and 
physiological  relation  to  the  liver,  may  allow  it  to  be  described  as  an  accessory  to 
the  digestive  tract. 

It  is  placed  deep  in  the  left  hypochondrium,  between  the  fundus  of  the  stom- 
ach and  diaphragm,  above  the  descending  colon. 

In  number  there  is  but  one,  yet  various  observations  show  it  may  be  congeni- 
tally  lacking,  or  may  be  multiple;  as  many  as  twenty-three  in  one  body.  These 
are  called  accessory  or  supernumerary  spleens  (lienculi\  probably  occasioned  by 
the  deep  notching  of  the  anterior  margin  and  separation  of  the  included  parts. 
They  may  be  connected  with  the  mother-organ  by  thin  bridges  of  splenic  tissue 
or  only  by  a  portion  of  capsule.  They  are  generally  wholly  isolated,  and  situ- 
ated in  the  gastro-splenic  omentum,  great  omentum,  transverse  mesocolon,  or 
in  the  pancreas  on  a  branch  of  the  splenic  artery.  Frequently,  one  or  two  are 
in  the  region  of  the  hilus.  They  are  of  the  size  of  a  hazelnut,  red  to  almost 
black  in  color  and  of  a  rounded  form. 

Xo  organ  varies  more  in  volume  than  the  spleen.  In  children  it  is  relatively 
well  developed.  In  old  age  it  is  usually  atrophied.  It  varies  with  the  same 
individual,  w  ith  sex,  degree  of  fulness  of  portal  vein,  state  of  health  or  of  dis- 
ease, and  with  the  influence  of  certain  drugs.  It  is  hypertrophied  in  all  infec- 
tious diseases  and  in  all  depending  upon  malarial  poison  or  leukaemia.  It  may 
be  so  large  as  to  reach  the  pelvis  and  weigh  many  pounds. 

Its   average   length   in  ten  adult  men  was  found  to  be  12  cm.  (five  or  six 


1074 


THE    ORGANS    OF  DIGESTION. 


inches) ;  breadth,  8  cm. ;  thickness,  3  cm.  (Sappey).  In  children  its  proportion 
to  body-weight  is  1  to  350 ;  in  adults  1  to  320 ;  in  old  age  1  to  700. 

Its  average  cadaveric  weight  in  the  above  ten  specimens  was  195  gm.  If 
filled  with  blood  its  physiological  weight  would  be  225  gm.  (or  7  ounces).  Its 
specific  gravity  is  1.054,  showing  greater  density  than  the  liver.  Its  volume  is 
200  to  300  cc. 

Its  color  in  the  living  animal  is  dark  red  and  probably  the  same  in  living  man. 
After  death  it  is  dark  purple  to  a  grayish  red,  due  to  the  presence  of  venous 
blood. 

In  consistence  it  is  soft  and  distensible  and  liable  to  laceration. 
Form  and  Relations. — The  spleen  may  be  ellipsoid,  tongue-shaped  in  length, 
or  it  may  be  rectilinear  with  its  four  corners  rounded  off.     An  internal  view  of 

tho  model  by  His  (Fig.  612),  shows  it 
to  be  somewhat  broader  above  than 
below,  while  typical  forms  presented 
by  Luschka  show  two  types  both  larger 
below.  One  is  rectangular  which  is 
most  frequent,  and  one  is  oval  (Fig. 
686). 

Three  surfaces  may  be  distin- 
guished, phrenic  or  external,  basal,  and 
internal,  which  is  subdivided  by  the 
intermediate  ridge  (mar go  intermedium) 
into  an  an terior  gastric  portion  (super- 
ficies gastrica),  and  a  posterior  renal 
portion  (superficies  renalis). 

There  are  two  margins,  anterior 
or  crenated  (margo  crenatus,  and  pos- 
terior (rnargo  obtusus}. 

The  spleen  lies  obliquely  with  its 
long  axis  placed  deep  in  the  left  hypo- 

chondrium  and  nearly  parallel  to  the  ribs.  It  lies  between  the  concave  surface 
of  the  diaphragm,  placed  to  the  left,  behind  and  above,  and  the  fundus  of  the  stom- 
ach, placed  to  the  right  and  in  front.  It  is  above  the  left  kidney  and  splenic 
flexure  of  colon  (Fig.  680).  This  figure  will  repay  study  as  we  do  not  always 
appreciate  that  the  suprarenal  capsule  and  kidney  and  spleen  rise  nearly  to  the 
cardia  with  the  pancreas,  transverse  colon,  and  splenic  flexure  in  immediate 
contact. 

Its  large  convex  phrenic  surface  lies  against  the  costal  part  of  the  diaphragm 
and  looks  upward,  backward,  and  to  the  left  or  even  a  little  inward  above.  It  is 
covered  by  the  ninth,  tenth,  and  eleventh  ribs,  but  separated  from  them  by  the 
peritoneum,  diaphragm,  costo-phrenic  sinus,  and  in  part  by  the  left  pleura  and 
lung.  In  some  cases  the  left  lobe  of  the  liver  extends  between  this  surface  of 
the  spleen  and  diaphragm.  This  is  normal  at  birth  when  the  hepatic  surface  of 
the  spleen  is  the  biggest  of  all. 

The  internal  surface,  directed  toward  the  abdominal  cavity  is  divided  by  a 
prominent  ridge  into  two  parts,  of  which  the  posterior  is  narrow  and  the  anterior 
broad. 

The  hilus  of  the  spleen  may  be  on  the  ridge,  but  is  usually  anterior  to  it.  It 
is  represented  by  an  irregular  longitudinal  row  of  depressions,  in  which  the  arteries 
and  nerves  enter  and  through  which  the  lymphatics  and  veins  emerge. 

The  surface  posterior  to  the  ridge  is  the  renal  surface,  flat  and  not  reaching 
as  high  as  the  gastric  surface,  it  is  turned  inward  and  downward  toward  the  left 
crus  of  the  diaphragm,  and  is  in  contact  with  the  upper  and  outer  margin  of  the 
left  kidney,  and  usually  the  suprarenal  capsule. 

The  gastric  surface,  broad  and  concave,  is  directed  inward  and  forward. 
When  the  stomach  is  distended  in  the  greater  part  of  its  extent,  this  surface  lies 


Lower  end 


FIG.  686.— The  two  type-forms  of  the  human  spleen. 
A.  Rhomboidal  form  of  spleen.  B.  Oval  form  of  spleen. 
(Luschka.) 


THE   SPLEEX. 


1075 


against  the  posterior  wall  of  the  fundus  and  body  of  the  stomach  (Fig.  680). 
Lower  down  it  touches  the  tail  of  the  pancreas. 

The  basal  surface  forms  the  lower  and  outer  end  of  the  spleen,  and  is  trian- 
gular in  shape.  This  does  not  rest  on  the  left  kidney,  but  frequently  is  in  con- 
tact with  the  tail  of  the  pancreas  and  regularly  with  the  splenic  flexure  of  the 
colon  and  phreno-colic  ligament. 

The  anterior  or  cr>-nate  margin  is  sharp  and  thin  and  usually  marked  by  a 
few.  two  to  four,  notches  more  or  less  deeply  cut.  It  separates  the  internal  from 


Lung- 


f  Diaphragm 


FIG.  6S7.— Relations  of  abdominal  viscera.    Posterior  view.    (Joessel.) 

the  phrenic  surface.  Traced  from  the  upper  end  of  the  spleen,  this  border  passes 
outward,  convex  above.  This  lies  between  the  diaphragm  and  stomach  nearly  as 
high  as  the  cardia.  The  border  then  passes  downward  and  forward,  and  is  in 
close  contact  with  the  chest-wall  at  the  mid-axillary  line. 

The  inner  or  int^i'irn-iUfite  border  lies  on  the  interior  surface  posterior  to  the 
hilus,  and  separates  the  gastric  and  renal  surfaces.  The  posterior  or  blunt  border 
separates  the  internal  and  phrenic  surfaces.  It  dips  in  between  the  diaphragm 
and  left  kidnev,  and  runs  downward  and  outward  along  the  lower  border  of  the 


1076  THE    ORGANS    OF  DIGESTION. 

eleventh  rib.  A  lower  border  may  be  described  between  the  phrenic  and  basal 
surfaces. 

The  upper  end  of  the  spleen  lies  on  the  level  of  the  tenth  dorsal  vertebra. 
It  approaches  the  vertebral  column  to  within  2  or  3  cm.,  and  often  touches  it. 
It  is  covered  behind  by  the  ribs  and  the  great  Sacro-spinalis  muscle. 

The  lower  end  of  the  spleen  extends  more  or  less  forward,  but  normally,  even 
in  deep  inspiration,  does  not  extend  beyond  the  costo-clavicular  line,  which  con- 
nects the  left  sterno-clavicular  articulation  to  the  anterior  end  of  the  eleventh 
rib.  Frequently  it  only  reaches  the  axillary  line.  In  regard  to  the  relations  of 
the  spleen  to  the  thoracic  cavity  and  lung  three  zones  can  be  distinguished  (Fig. 
687)  :  (1)  The  upper  part  of  the  spleen  is  completely  covered  by  the  left  lung ; 
(2)  the  middle  part  corresponds  to  the  costo-phrenic  sinus ;  (3)  the  lower  part 
extends  over  the  lower  pleural  limit  and  projects  down  over  the  costal  origin  of 
the  diaphragm.  Its  relations  to  the  pleura  and  pleural  cavity  explain  why 
wounds  of  the  spleen  can  be  accompanied  by  wounds  of  the  lung  and  why  abscess 
of  the  spleen  may  open  through  the  diaphragm  into  the  left  pleural  cavity. 

It  can  also  be  seen  how  the  limit  of  percussion  is  very  narrow.  The  upper 
part  is  covered  by  the  lung  and  thick  muscles  of  the  back.  The  part  not  covered 
by  the  lung  applies  itself  to  the  left  kidney  and  splenic  flexure  of  colon  whereby 
the  percussion  note  may  be  modified,  especially  if  faecal  masses  be  in  the  colon 
or  if  the  fundus  of  the  stomach  be  filled  with  food.  Abnormal  enlargements  of 
the  spleen  may  be  diagnosed  by  palpation  as  well  as  by  percussion. 

Relations. 

Externally  and  above: 

Peritoneum  and  left  costal  part  of  diaphragm ; 

Ninth,  tenth,  and  eleventh  ribs ; 

Costo-phrenic  sinus ; 

Left  lung  and  pleura  ; 

(At  birth)  left  lobe  of  liver; 

Great  muscles  of  back. 

Internally : 

Posterior  surface  of  fundus  of  stomach ; 
Left  kidney  and  capsule  ; 
Tail  of  pancreas ; 
Sometimes  vertebral  column. 

Inferiorly : 

Tail  of  pancreas  sometimes  ; 

Splenic  flexure  of  colon  ; 

Lig.  phreno-colicum ;  saccus  lienalis. 

Fixation  of  Spleen  and  Peritoneal  Relations. — The  position  of  the  spleen  is 
secured  by  peritoneal  folds  which  connect  it  with  the  diaphragm  and  neighboring 
organs. 

The  lig.  pJireno-lienale  comes  from  the  left  crus  of  the  diaphragm,  and  passes 
in  the  direction  of  the  long 'axis  of  the  spleen  to  its  point  of  insertion,  which  is 
directly  behind  the  inner  border  (margo  intermedius).  The  ligament  consists  of 
firm  connective  tissue  strands,  and  deserves  the  name  suspensory  ligament  of  the 
spleen  (lig.  suspensorium  lienis). 

The  lig.  gastro-lienale  or  g astro-splenic  omentum  connects  the  hilus  of  the 
spleen  with  the  fundus  of  the  stomach.  It  consists  of  an  anterior  layer  formed  of 
peritoneum  of  the  greater  sac,  and  a  posterior  layer  which  helps  form  the  anterior 
wall  of  the  lesser  sac  (Fig.  611).  It  only  receives  a  strong  consistency  by  the 
presence  of  the  vasa  gastrica  brevia,  Avhich  run  in  this  fold  from  the  hilus  of  the 
spleen  to  the  stomach.  The  insertion  of  the  ligament  into  the  fundus  of  the 
stomach  has  no  firm  hold  and  can  offer  but  little  fixation  to  the  spleen,  but 


THE  SPLEEX.  1077 

rather  serves  to  fasten  the  fundus  of  the  stomach,  which,  in  an  empty  state,  needs 
support. 

The  lig.  lieno-renale  (Fig.  611)  is  made  of  a  posterior  layer  from  the  greater 
.iul  an  anterior  layer  which  forms  part  of  the  posterior  wall  of  the  lesser  sac. 
It  contains  the  splenic  vessels. 

The  l.i;i.  pkreno-coticwn  (incorrectly  costo-colic)  contributes  to  the  security  of 
the  spleen,  although  unconnected  with  it.  It  arises  from  the  diaphragm  opposite 
the  anterior  ends  of  the  tenth  and  eleventh  ribs,  and  passes  below  the  spleen 
downward  and  inward  to  the  splenic  flexure  of  the  colon  and  to  the  anterior  sur- 
face of  the  descending  colon.  It  forms  a  pocket,  with  its  concavity  directed 
upward  and  inward,  the  saccus  lienalis,  which,  in  the  new-born,  regularly  receives 
the  spleen.  This  ligament  may  also  be  called  the  sustentaculum  Jienis.  supporter 
of  the  spleen.  By  the  normal  condition  of  the  suspensory,  and  especially  phreno- 
colic  ligament,  the  spleen  retains  its  position.  Should  the  phreno-colic  be  re- 
laxed then  the  spleen  is  displaced  and  its  long  axis  becomes  more  vertical.  In 
rare  cases  the  normal  spleen  may  sink  deep  into  the  abdominal  cavity,  even  to 
the  pelvis.  This  is  called  the  "  wandering  spleen."  It  is  liable  to  atrophy  when 
the  splenic  artery  suffers  torsion.  There  are  still  two  more  inconstant  ligaments, 
the  U-j.  :  nale  and  colico-lienale.  The  former  is  present  when  the 

tail  of  the  pancreas  does  not  reach  the  lower  part  of  the  inner  surface  of  the 
spleen  ;  then  the  visceral  peritoneum  from  below  and  the  lesser  sac  from  above 
form  a  short  band  between  these  two  organs,  a  part  of  the  lig.  lieno-renale. 

The  lig.  colico-lienale,  when  present,  passes  from  the  basal  surface  of  the 
spleen  downward  and  outward  to  the  descending  colon  and  joins  the  great  omen- 
turn.  It  contributes  to  the  formation  of  the  saccus  lienalis. 

The  ligaments,  altogether,  are  the  lig.  gastro-lienale  or  gastro-splenic  omen- 
turn  :  lig.  phreno-KenaU  or  suspensory  ligament;  lig.  pTireno-colicum  or  supporter 
of  the  spleen ;  lig.  lieno-renale,  lig.  pancreatico-lienale,  and  lig.  colico-lienale,  six 
in  number. 

llt-xpirotifin  exerts  an  influence  upon  the  position  of  the  spleen,  and  especially 
on  the  percussion  limits.  In  inspiration  it  sinks  somewhat,  and  its  area  of  dul- 
ness  is  lessened  from  the  overlapping  of  the  lungs.  Yet  the  respiratory  motility 
of  the  spleen  is  much  less  than  that  of  the  liver,  because  the  diaphragm  exercises 
less  influence  over  it  than  upon  the  liver.  Hasse1  states  that  in  inspiration  the 
spleen  is  compressed  from  above  downward,  and  in  expiration  it  passes  upward 
and  backward  along  the  tenth  rib.  Pathological  changes  in  the  thoracic  cavity, 
as  effusions',  will  push  the  spleen  down,  or  ascites  and  tumors  in  the  abdominal 
cavity  will  push  it  up. 

Vessels  and  Nerves  of  the  Spleen. — The  arteries  are  branches  of  the  splenic ; 
it  divides  about  3  cm.  internal  to  the  hilus  into  three  or  four  branches  which 
soon   subdivide  into  twelve  or  fifteen  twigs,  which  enter  the  gland.      The  splenic 
is  about  twice  as  large  as  the  accompanying  artery. 

The  lymphatic  vessels  are  divided  into  a  superficial  and  deep  set.  Sappey  con- 
tends for  a  superficial  set-  in  man,  which  is  proven  in  the  horse,  deer,  and  pig. 
The  deeper  lymphatic  vessels  follow  the  blood-vessels,  one  for  each  of  the  larger 
veins.  At  the  hilus  there  are  five  or  six  trunks  which  empty  into  the  glands 
situated  there.  In  their  farther  course  they  follow  the  blood-vessels  and  unite 
with  the  lymphatics  of  the  liver  and  stomach  to  form  the  thoracic  duct. 

The  nerves  come  from  the  coeliac  plexus  and  right  vagus,  and  accompany, 
sparingly,  the  splenic  artery. 

Structure. — The  spleen  is  invested  by  two  coats — an  external  serous  and  an 
internal  fibro-elastic  coat  (tunica  propria). 

The  external  or  serous  coat  is  derived  from  the  peritoneum  :  it  is  thin,  smooth, 
and  in  the  human  subject  intimately  adherent  to  the  fibro-elastic  coat.     It  in 
almost  the  entire  organ,  being  reflected  from  it.  at  the  hilus,  on  to  the  great  end 
of  the  stomach,  and  at  the  upper  end  of  the  organ  on  to  the  Diaphragm. 

lAnh.  f.  Anat.  u.  Phys.,  1886,  s.  208. 


1078  THE    ORGANS    OF   DIGESTION. 

The  fibro-elastic  coat  forms  the  framework  of  the  spleen.  It  invests  the 
exterior  of  the  organ,  and  at  the  hilus  is  reflected  inward  upon  the  vessels  in  the 
form  of  vaginae  or  sheaths.  From  these  sheaths,  as  well  as  from  the  inner  surface 
of  the  fibro-elastic  coat,  numerous  small  fibrous  bands,  trabeculce  (Fig.  688),  are 


FIG.  688.— Transverse  section  of  the  spleen,  showing  the  trabecular  tissue  and  the  splenic  vein  and  its  branches. 

given  off  in  all  directions ;  these,  uniting,  constitute  the  areolar  framework  of  the 
spleen.  The  framework  of  the  spleen  resembles,  therefore,  a  sponge-like  material, 
consisting  of  a  number  of  small  spaces  or  areolce,  formed  by  the  trabeculse  which 
are  given  off  from  the  inner  surface  of  the  capsule,  or  from  the  sheaths  prolonged 
inward  on  the  blood-vessels.  And  in  these  spaces  or  areolae  is  contained  the 
splenic  pulp. 

The  proper  coat,  the  sheaths  of  the  vessels  and  the  trabeculae,  consist  of  a 
dense  mesh  of  white  and  yellow  elastic  fibrous  tissues,  the  latter  considerably  pre- 
dominating. It  is  owing  to  the  presence  of  this  tissue  that  the  spleen  possesses 
a  considerable  amount  of  elasticity,  which  allows  of  the  very  great  variations  in 
size  that  it  presents  under  certain  circumstances.  In  addition  to  these  con- 
stituents of  this  tunic,  there  is  found  in  man  a  small  amount  of  non-striped  muscu- 
lar fibre,  and  in  some  mammalia  (e.  g.  dog,  pig,  and  cat)  a  very  considerable 
amount,  so  that  the  trabeculae  appear  to  consist  chiefly  of  muscular  tissue.  It  is 
probably  owing  to  this  structure  that  the  spleen  exhibits,  when  acted  upon  by  the 
galvanic  current,  faint  traces  of  contractility. 

The  proper  substance  of  the  spleen  or  spleen-pulp  is  a  soft  mass  of  a  dark 
reddish-brown  color,  resembling  grumous  blood.  When  examined,  by  means  of  a 
thin  section,  under  a  microscope,  it  is  found  to  consist  of  a  number  of  branching 
cells  and  an  intercellular  substance.  The  cells  are  connective-tissue  corpuscles, 
and  have  been  named  the  sustentacular  or  supporting  cells  of  the  pulp.  The 
processes  of  these  branching  cells  communicate  with  each  other,  thus  forming  a 
delicate  reticulated  tissue  in  the  interior  of  the  areolae  formed  by  the  trabeculae  of 
the  capsule ;  so  that  each  primary  space  may  be  considered  to  be  divided  into  a 
number  of  smaller  spaces  by  the  junction  of  these  processes  of  the  branching 
corpuscles.  These  secondary  spaces  contain  blood,  in  which,  however,  the  white 
corpuscles  are  found  to  be  in  larger  proportions  than  they  are  in  ordinary  blood. 
The  sustentacular  cells  are  either  small  uni-nucleated  or  larger  multi-nucleated 
cells ;  they  do  not  become  deeply  stained  with  carmine,  like  the  cells  of  the 
Malpighian  bodies,  presently  to  be'described  (W.  Miiller),  but  like  them  they  pos- 
sess amoeboid  movements  (Cohnheim).  In  manv  of  them  may  be  seen  deep  red 


THE   SPLEEN. 


1079 


or  reddish-yellow  granules  of  various  sizes  which  present  the  characters  of  the 
haematin  of^the  blood.  Sometimes,  also,  unchanged  blood-disks  are  seen  included 
in  these  cells,  but  more  frequently  blood-disks  are  found  which  are  altered  both 
in  form  and  color.  In  fact,  blood-corpuscles  in  all  stages  of  disintegration  may 
be  noticed  to  occur  within  them.  Klein  has  recently  pointed  out  that  some- 
times these  cells  in  the  young  spleen  contain  a  proliferating  nucleus ;  that  is  to 
say.  the  nucleus  is  of  large  size,  and  presents  a  number  of  knob-like  projections, 
as  if  small  nuclei  were  budding  from  it  by  a  process  of  gemmation.  This  observa- 
tion is  of  importance,  as  it  may  explain  one  possible  source  of  the  colorless  blood- 
corpuscles. 

The  interspaces  or  areolne  formed  by  the  framework  of  the  spleen  are  thus  filled 
by  a  delicate  reticulum  of  branched  connective-tissue  corpuscles  the  interstices  of 
which  are  occupied  by  blood,  and  in  which  the  blood-vessels  terminate  in  the 
manner  now  to  be  described. 

Blood-vessels  of  the  Spleen. — The  splenic  artery  is  remarkable  for  its  large 
size  in  proportion  to  the  size  of  the  organ,  and  also  for  its  tortuous  course. 


FIG.  689.— Transverse  section  of  the  human  spleen,  showing  the  distribution  of  the  splenic  artery  and  its 
branches. 

It  divides  into  twelve  to  fifteen  branches,  which  enter  the  hilus  of  the  spleen 
and  ramify  throughout  its  substance  (Fig.  689),  receiving  sheaths  from  an 
involution  of  the  external  fibrous  tissue.  Similar  sheaths  also  invest  the  nerves 
and  veins. 

Each  branch  runs  in  the  transverse  axis  of  the  organ  from  within  outward, 
diminishing  in  size  during  its  transit,  and  giving  off  in  its  passage  smaller 
branches,  some  of  which  pass  to  the  anterior,  others  to  the  posterior  part.  These 
ultimately  leave  the  trabecular  sheaths,  and  terminate  in  the  proper  substance  of 
the  spleen  in  small  tufts  or  pencils  of  minute  arterioles,  which  open  into  the 
interstices  of  the  reticulum  formed  by  the  branched  sustentacular  cells.  Each  of 
the  larger  branches  of  the  artery  supplies  chiefly  that  region  of  the  organ  in 
which  the  branch  ramifies,  having  no  anastomosis  with  the  majority  of  the  other 
branches. 

The  arterioles,  supported  by  the  minute  trabeculae.  traverse  the  pulp  in 
all  directions  in  bundles  or  penicilli  of  straight  vessels.  Their  external  coat,  on 
leaving  the  trabecular  sheaths,  consists  of  ordinary  connective  tissue,  but  it  gradu- 
ally undergoes  a  transformation,  becomes  much  thickened,  and  is  converted  into 
a  lymphoid  material.1  This  change  is  effected  by  the  conversion  of  the  con- 
nective tissue  into  a  cystogenous  tissue,  the  bundles  of  connective  tissue  becoming 

1  According  to  Klein,  it  is  the  sheath  of  the  small  vessel  which  undergoes  this  transformation, 
and  forms  a  "  solid  mass  of  adenoid  tissue  which  surrounds  the  vessel  like  a  cylindrical  sheath  "  (Atlas 
of  Hisloloyy,  p. 


1080 


THE    ORGANS    OF    DIGESTION. 


•If 


looser  and  laxer,  their  fibrils  more  delicate,  and  containing  in  their  interstices 
an  abundance  of  lymph-corpuscles  (W.  Miiller).  This  lymphoid  material  is 
supplied  with  blood  by  minute  vessels  derived  from  the  artery  with  which  they 
are  in  contact,  and  which  terminates  by  breaking  up  into  a  network  of  capillary 
vessels. 

The  altered  coat  of  the  arterioles,  consisting  of  lymphoid  tissue,  presents  here 
and  there  thickenings  of  a  spheroidal  shape,  the  Malpiyliian  bodies  of  the  spleen. 
These  bodies  vary  in  size  from  about  the  yj-^  of  an  inch  to  the  -^  of  an  inch  in 
diameter.  They  are  merely  local  expansions  or  hyperplasise  of  the  lymphoid 
tissue  of  which  the  external  coat  of  the  smaller  arteries  of  the  spleen  is  formed. 
They  are  most  frequently  found  surrounding  the  arteriole,  which  thus  seems  to 

tunnel  them,  but  occasionally  they  grow  from 
one  side  of  the  vessel  only,  and  present  the 
appearance  of  a  sessile  bud  growing  from  the 
arterial  wall.  Klein,  however,  denies  this, 
and  says  it  is  incorrect  to  describe  the  Mal- 
pighian  bodies  as  isolated  masses  of  adenoid 
tissue,  but  that  they  are  always  formed  around 
an  artery,  though  there  is  generally  a  greater 
amount  on  one  side  than  the  other,  and  that, 
therefore,  in  transverse  sections  the  artery  in 
the  majority  of  cases  is  found  in  an  eccentric 
position.  These  bodies  are  visible  to  the  naked 
eye  on  the  surface  of  a  fresh  section  of  the 
organ,  appearing  as  minute  dots  of  semi- 
opaque  whitish  color  in  the  dark  substance 
of  the  pulp.  In  minute  structure  they  re- 
semble the  adenoid  tissue  of  lymphatic  glands, 
consisting  of  a  delicate  reticulum  in  the  meshes 
of  which  lie  ordinary  lymphoid  cells  (Fig. 

The  reticulum  of  the  tissue  is  made  up 
of  extremely  delicate  fibrils,  and  is  comparatively  open  in  the  centre  of  the 
corpuscle,  becoming  closer  at  the  periphery  of  the  body.  The  cells  which  it 
encloses,  like  the  supporting  cells  of  the  pulp,  are  possessed  of  amoeboid  move- 


Arte>-y 


FIG.  690.— Artery   from   a   dog's   spleen, 
showing  Malpighian  corpuscles.    (Kolliker.) 


Supporting  cell. 


Vessel  undergoing  lymphoid  change. 


' 


Small 
artery. ' 


Vessel  continuous 
loith  procesw  of 
supporting  cells. 


Supporting  cell. 


FIG.  691.— Section  of  spleen,  showing  the  termination  of  the  small  blood-vessels. 

ments,   but  when  treated  with   carmine  become  deeply  stained,  and  can  thus 
easily  be  recognized  from  those  of  the  pulp. 

The  arterioles  terminate  in  capillaries,  Avhich  traverse  the  pulp  in  all  directions ; 


THE  SPLEEN.  1081 

their  walls  become  much  attenuated,  lose  their  tubular  character,  and  the  cells  of 
the  lymphoid  tissue  of  which  they  are  composed  become  altered,  presenting  a 
branched  appearance  and  acquiring  processes  which  are  directly  connected  Avith 
the  processes  of  the  sustentacular  cells  of  the  pulp  (Fig.  691).  In  this  manner  the 
capillary  vessels  terminate,  and  the  blood  flowing  through  them  finds  its  way  into 
the  interstices  of  the  reticulated  tissue  formed  by  the  branched  connective-tissue 
corpuscles  of  the  splenic  pulp.  Thus  the  blood  passing  through  the  spleen  is 
brought  into  intimate  relation  with  the  elements  of  the  pulp,  and  no  doubt  under- 
goes important  chan.i 

After  these  changes  have  taken  place  the  blood  is  collected  from  the  interstices 
of  the  tissue  by  the  rootlets  of  the  veins,  which  commence  much  in  the  same  way 
as  the  arteries  terminate.  Where  a  vein  is  about  to  commence  the  connective- 
tissue  corpuscles  of  the  pulp  arrange  themselves  in  rows  in  such  a  way  as  to  form 
an  elongated  space  or  sinus.  They  become  changed  in  shape,  being  elongated 
and  spindle-shaped,  and  overlap  each  other  at  their  extremities.  They  thus  form 
t  of  endothelial  lining  of  the  path  or  sinus,  which  is  the  radicle  of  a  vein. 
On  the  outer  surface  of  these  cells  arc  seen  delicate  transverse  lines  or  markings 
which  are  due  to  minute  elastic  fibrillse  arranged  in  a  circular  manner  around  the 
sinus.  Thus  the  channel  obtains  a  continuous  external  investment,  and  gradually 
becomes  converted  into  a  small  vein,  which  after  a  time  presents  a  coat  of 
ordinary  connective  tissue,  lined  by  a  layer  of  fusiform  epithelial  cells  which  are 
continuous  with  the  supporting  cells  of  the  pulp.  The  smaller  veins  unite  to  form 
larger  ones  which  do  not  accompany  the  arteries,  but  soon  enter  the  trabecular 
sheaths  of  the  capsule,  and  by  their  junction  form  from  four  to  six  branches  which 
emerge  from  the  hilum  and.  uniting,  form  the  splenic  vein,  the  largest  radicle  of 
the  vena  porta. 

The  veins  are  remarkable  for  their  numerous  anastomoses,  while  the  arteries 
hardly  anastomose  at  all. 

The  lymphatics  originate  in  two  ways — i.  e.  a  trabecular  set  and  a  perivascu- 
lar  set.  The  former  run  on  the  trabeculae  and  empty  into  the  superficial  network 
of  the  capsule.  The  peri  vascular  is  the  deep  set,  rising  in  the  lymphoid  tissue 
surrounding  the  arteries  and  forming  Malpighian  corpuscles.  At  first  they  have 
no  walls.  They  are  seen  to  run  with  an  artery  in  pairs  and  singly  with  each  larger 
vein,  forming  many  anastomoses.  Both  sets  join  at  the  hilus  (see  page  1077). 

Surface  Form. — The  spleen  is  situated  under  cover  of  the  ribs  of  the  left  side,  being  sepa- 
rated from  them  by  the  Diaphragm,  and  above  by  a  small  portion  of  the  lower  margin  of  the 
left  kins:.  Its  position  corresponds  to  the  ninth,  tenth,  and  eleventh  ribs.  It  is  placed  very 
obliquely.  "It  is  oblique  in  two  directions,  viz.  from  above  downward  and  outward,  and  also 
from  above  downward  and  forward"  (Cunningham).  "  Its  highest  and  lowest  points  are  on  a 
level  respectively  with  the  ninth  dorsal  and  first  lumbar  spines ;  its  inner  end  is  distant  about  an 
inch  and  a  halt'  from  the  median  plane  of  the  body,  and  its  outer  end  about  reaches  the  mid- 
axillary  line  Quain  . 

Surgical  Anatomy. — Injury  of  the  spleen  is  less  common  than  that  of  the  liver,  on  account 
of  its  protected  situation  and  connections.  It  may  be  ruptured  by  direct  or  indirect  violence, 
torn  by  a  broken  rib.  or  injured  by  a  punctured  or  gunshot  wound.  When  the  organ  is  enlarged 
the  eliaiK-e  of  rupture  is  increased.  The  great  risk  is  haemorrhage,  owing  to  the  great  vascu- 
larity  of  the  organ,  and  the  absence  of  a  proper  system  of  capillaries.  The  injury  is  not.  how- 
ever, necessarily  fatal,  and  this  would  appear  to  be  due  in  a  great  measure  to  the  contractile 
power  of  its  capsule,  which  narrows  the  wound  and  prevents  the  escape  of  blood.  In  cai«es 
where  the  diasmosis  is  clear  and  the  symptoms  indicate  danger  to  life  laparotomy  must  be  per- 
formed :  and  if  the  haemorrhage  cannot  be  stayed  by  ordinary  surgical  methods  the  spleen  must 
be  removed.  The  spleen  may  become  displaced,  producing  great  pain  from  stretching  of  the 
-  and  nerves,  and  this  may  require  removal  of  the  organ.  The  spleen  may  become  enor- 
mously enlarged  in  certain  diseased  conditions,  such  as  ague,  syphilis,  valvular  disease  of  the 
heart,  or  without  any  obtainable  history  of  previous  disease.  It  may  also  become  enlarged  in 
lymphadenoma  as  a  part  of  a  general  blood-disease.  In  these  cases  the  tumor  may  sometimes 
till  the  abdomen  and  extend  into  the  pelvis,  and  may  be  mistaken  for  ovarian  or  uterine 
disease. 

The  spleen  is  sometimes  the  seat  of  cystic  tumors,  especially  hydatids.  and  of  abscess. 
These  cases  require  treatment  by  incision  and  drainage :  and  in  abscess  great  case  must  be  taken 
if  there  are  no  adhesions  between  the  spleen  and  abdominal  cavity,  to  prevent  the  escape  of  any 
of  the  pus  into  the  peritoneal  cavitv.  If  possible,  the  operation  should  be  performed  in  two 


1082  THE    ORGANS    OF   DIGESTION. 

stages,  as  in  abscess  of  the  liver.     Sarcoma  and  carcinoma  are  occasionally  found  in  the  spleen, 
but  very  rarely  as  a  primary  disease. 

Extirpation  of  the  spleen  has  been  performed  for  wounds  or  injuries,  in  floating  spleen,  in 
simple  hypertrophy,  and  in  leukaemic  enlargement :  but  in  these  latter  cases  the  operation  is 
now  regarded  as  unjustifiable,  as  every  case  in  which  it  has  been  performed  has  terminated 
fatally.  The  incision  is  best  made  in  the  left  semilunar  line  :  the  spleen  is  isolated  from  its  sur- 
roundings, and  the  pedicle  transfixed  and  ligatured  in  two  portions,  before  the  tumor  is  turned 
out  of  the  abdominal  cavity,  if  this  is  possible,  so  as  to  avoid  any  traction  on  the  pedicle,  which 
may  cause  tearing  of  the  splenic  vein.  In  applying  the  ligature  care  must  be  taken  not  to 
include  the  tail  of  the  pancreas,  and  in  lifting  out  the  organ  to  avoid  rupturing  the  capsule. 


THE  THORAX. 


THE  Thorax  is  a  cone-shaped  cavity  containing  and  protecting  the  heart, 
enclosed  in  its  membranous  bag,  the  pericardium,  and  the  lungs,  invested  by 
the  pleura.  Its  shape  and  boundaries  have  already  been  described  (see  page 

The  Cavity  of  the  Thorax. — The  size  of  the  cavity  of  the  thorax  does  not 
correspond  with  its  apparent  size  externally,  because  (1)  the  space  enclosed  by  the 
lower  ribs  is  occupied  by  some  of  the  abdominal  viscera,  and  (2)  the  cavity  extends 
above  the  first  rib  into  the  neck.  The  size  of  the  cavity  of  the  thorax  is  constantly 
varying  during  life  with  the  movements  of  the  ribs  and  Diaphragm  and  with  the 
degree  of  distension  of  the  abdominal  viscera.  From  the  collapsed  state  of  the 
lungs  in  the  dead  body  it  would  appear  as  if  the  viscera  only  partly  filled  the 
cavity  of  the  thorax,  but  during  life  there  is  no  vacant  space,  that  which  is  seen 
after  death  being  filled  up  by  the  expanded  lungs. 

The  Upper  Opening  of  the  Thorax. — The  parts  which  pass  through  the  upper 
opening  of  the  thorax  are,  from  before  backward  in  the  middle  line,  the  Sterno- 
hyoid  and  Sterno-thyroid  muscles,  the  remains  of  the  thymus  gland,  the  trachea, 
oesophagus,  thoracic  duct,  and  the  Longus  colli  muscle  of  each  side ;  at  the  sides, 
the  innominate  artery,  the  left  common  carotid  and  left  subclavian  arteries,  the 
internal  mammary  and  superior  intercostal  arteries,  the  right  and  left  innom- 
inate veins,  and  the  inferior  thyroid  veins,  the  pneumogastric,  cardiac,  phrenic, 
and  sympathetic  nerves,  the  anterior  branch  of  the  first  dorsal  nerve,  and  the 
recurrent  laryngeal  nerve  of  the  left  side.  The  apex  of  each  lung,  covered  by 
the  pleura,  also  projects  through  this  aperture,  a  little  above  the  margin  of  the 
first  rib. 

The  Lower  Opening  of  the  Thorax  is  wider  transversely  than  from  before  back- 
ward. It  slopes  obliquely  downward  and  backward,  so  that  the  cavity  of  the 
thorax  is  much  deeper  behind  than  in  front.  The  Diaphragm  (see  page  444)  closes 
in  the  opening,  forming  the  floor  of  the  thorax.  The  floor  is  flatter  at  the  centre 
than  at  the  sides,  and  is  higher  on  the  right  side  than  on  the  left,  corresponding  in 
the  dead  body  to  the  upper  border  of  the  fifth  costal  cartilage  on  the  former,  and 
to  the  corresponding  part  of  the  sixth  costal  cartilage  on  the  latter.  From  the 
highest  point  on  each  side  the  floor  slopes  suddenly  downward  to  the  attachment 
of  the  Diaphragm  to  the  ribs ;  this  is  more  marked  behind  than  in  front,  so  that 
only  a  narrow  space  is  left  between  it  and  the  wall  of  the  thorax. 

For  measurements  of  the  thorax  see  page  1099. 

THE  PERICARDIUM. 

The  Pericardium  (Figs.  692,  693)  is  a  conical  membranous  sac  in  which  the 
heart  and  the  commencement  of  the  great  vessels  are  contained.  It  is  placed 
behind  the  sternum  and  the  cartilages  of  the  third,  fourth,  fifth,  sixth,  and  seventh 
ribs  of  the  left  side,  in  the  interval  between  the  pleurae. 

Irs  a/»-x  is  directed  upward,  and  surrounds  the  great  vessels  about  two  inches 
above  their  origin  from  the  base  of  the  heart.  Its  base  is  attached  to  the  central 
tendon  and  part  of  the  adjoining  muscular  structure  of  the  Diaphragm,  extending 
a  little  farther  to  the  left  than  to  the  right  side.  In  front  it  is  separated  from  the 
sternum  by  the  remains  of  the  thymus  gland  above  and  a  little  loose  areolar  tissue 
below,  and  is  covered  by  the  margins  of  the  lungs,  especially  the  left.  Behind,  it 
rests  upon  the  bronchi,  the  oesophagus,  and  the  descending  aorta.  Laterally,  it  is 
covered  by  the  pleurae,  the  phrenic  nerve  with  its  accompanying  vessels  descending 
between  the  two  membranes  on  either  side. 

1083 


THE    THORAX. 


Structure  of  the  Pericardium. — The  pericardium  is  a  fibro-serous  membrane, 
and  consists,  therefore,  of  two  layers,  an  external  fibrous  and  an  internal  serous. 

The  fibrous  layer  is  a  strong,  dense  membrane.  Above,  it  surrounds  the  great 
vessels  arising  from  the  base  of  the  heart,  on  which  it  is  continued  in  the  form 
of  tubular  prolongations  which  are  gradually  lost  upon  their  external  coat,  the 
strongest  being  that  which  encloses  the  aorta.  The  pericardium  may  be  traced 
over  these  vessels,  to  become  continuous  with  the  deep  layer  of  the  cervical  fascia. 
On  each  side  of  the  ascending  aorta  it  sends  upward  a  di vertical um  :  the  one  on. 


Right 
common 
carotid  J 
artery 


Inf.  thyroid  vein 
Right  innom. 
vein. 


^Right  subdavian  artery. 

fT.eft  carotid. 


Left  subdavian. 


Dtictua 
arteriosus. 


FIG.  692. — Pericardium,  from  in  front.  The  sac  has  been  distended  with  plaster.    (From  a  preparation  in  the 
Museum  of  the  Royal  College  of  Surgeons.) 

the  left  side,  somewhat  conical  in  shape,  passes  upward  and  outward,  between  the 
arch  of  the  aorta  and  the  left  pulmonary  artery,  as  far  as  the  ductus  arteriosus, 
where  it  terminates  in  a  csecal  extremity,  which  is  attached  by  loose  connective 
tissue  to  the  obliterated  duct  (Fig.  692).  The  one  on  the  right  side  passes  up- 
ward and  to  the  right,  between  the  ascending  aorta  and  vena  cava  superior,  and 
also  terminates  in  a  caecal  extremity.  Below,  the  fibrous  layer  is  attached  to  the 
central  tendon  of  the  Diaphragm,  and  on  the  left  side  to  its  muscular  fibres. 
Anteriorly  the  pericardium  is  connected  to  the  sternum  by  two  variable  bands  of 
fascia,  the  superior  and  inferior  sterno-pericardial  ligankents  of  Luschka. 

The  vessels  receiving  fibrous  prolongations  are  the  aorta,  the  superior  vena  cava, 
the  right  and  left  pulmonary  arteries,  and  the  four  pulmonary  veins.  As  the  infe- 
rior vena  cava  enters  the  pericardium,  it  receives  no  covering  from  the  fibrous  layer. 


THE   PERICARDIUM. 


1085 


The  >•'.•/••></.«  layer  invests  the  heart,  and  is  then  reflected  on  the  inner  surface 
of  the  pericardium.  It  consists,  therefore,  of  a  visceral  and  parietal  portion. 
The  former  invests  the  surface  of  the  heart  and  the  commencement  of  the  great 
vessels  to  the  extent  of  one  inch  and  a  half  from  their  origin ;  from  these  it  is 
reflected  upon  the  inner  surface  of  the  fibrous  layer.  The  serous  membrane 
encloses  the  aorta  and  pulmonary  artery  in  a  single  tube ;  hence  between  these 
Is  and  the  auricles  posteriorly  is  a  passage,  the  transverse  pericardial  sinus  ; 
but  it  only  partially  covers  the  superior  and  inferior  vena  cava  and  the  four  pul- 


Lffl  subdarian  art. 
Sight  pulmonary  art. 


Right 
subdavian 
Left  comm. 
carotid  artery. 


FIG.  693. — Pericardium,  from  behind.    (From  the  same  preparation  as  the  preceding  figure.) 

monary  veins.  Its  inner  surface  is  smooth  and  glistening,  and  secretes  a  thin 
fluid  which  serves  to  facilitate  the  movements  of  the  heart. 

Arteries  <>f  the  Pericardium. — These  are  derived  from  the  internal  mammary 
and  its  umsculo-phrenic  branch  and  from  the  descending  thoracic  aorta. 

^\-  rces  of  the  Pericardium. — These  are  branches  from  the  vagus,  the  phrenic, 
and  the  sympathetic. 

The  Vestigial  Foil  of  the  Pericardium. — AYhen  the  pericardium  is  opened 
there  is  seen  lying  between  the  left  pulmonary  artery  and  subjacent  pulmonary 
vein  a  triangular  fold  (vestigial  fold  of  Marshall)  of  the  serous  layer,  which  encloses 
between  its  layers  the  remains,  a  fibrous  cord,  of  the  left  superior  vena  cava.  This 
cord  may  sometimes  be  traced  upward  to  the  left  superior  intercostal  vein. 


1086  THE    THORAX. 

Surgical  Anatomy. — Paracentesis  of  the  pericardium  is  sometimes  required  in  cases  of  effu- 
sion into  its  cavity.  The  operation  is  best  performed  in  the  fifth  intercostal  space,  one  inch  to 
the  left  of  the  sternum.  The  operation  has  been  performed,  however,  in  the  fourth,  sixth,  and 
seventh  spaces,  and  also  on  the  right  side  of  the  sternum. 

THE  HEART. 

The  Heart  is  a  hollow  muscular  organ,  of  a  conical  form,  placed  between  the 
lungs  and  enclosed  in  the  cavity  of  the  pericardium. 

Position. — The  heart  is  placed  obliquely  in  the  chest :  the  broad  attached  end, 
or  base,  is  directed  upward,  backward,  and  to  the  right,  and  corresponds  to  the 


FIG.  694.— Front  view  of  the  thorax.  The  ribs  and  sternum  are  represented  in  relation  to  the  lungs,  heart, 
and  other  internal  organs.  1.  Pulmonary  orifice.  2.  Aortic  orifice.  3.  Left  auriculo-ventricular  orifice.  4.  Right 
auriculo-ventricular  orifice. 

interval  between  the  fifth  and  ninth  dorsal  vertebrae — that  is,  it  lies  opposite  the 
sixth,  seventh,  and  eighth  vertebrae ;  the  apex  is  directed  downward,  forward, 
and  to  the  left,  and  corresponds  to  the  space  between  the  cartilage  of  the  fifth 
and  sixth  ribs,  three-quarters  of  an  inch  to  the  inner  side  and  an  inch  and  a 
half  below  the  left  nipple.  The  heart  is  placed  behind  the  lower  two-thirds  of 
the  sternum,  and  projects  farther  into  the  left  than  into  the  right  cavity  of  the 
chest,  extending  from  the  median  line  about  three  inches  in  the  former  direction, 
and  only  one  and  a  half  in  the  latter.  The  anterior  surface  of  the  heart  is  round 
and  convex,  directed  upward  and  forward,  and  formed  chiefly  by  the  right  ven- 
tricle and  part  of  the  left.  Its  posterior  surface  is  flattened  and  rests  upon  the 
Diaphragm,  and  is  formed  chiefly  by  the  left  ventricle.  The  right  border  is  long, 
thin,  and  sharp ;  the  left  border  short,  but  thick  and  round. 


THE   HEART. 


1087 


Size. — The  heart  in  the  adult  measures  five  inches  in  length,  three  inches  and 
a  half  in  breadth  in  the  broadest  part,  and  two  inches  and  a  half  in  thickness. 
The  prevalent  weight,  in  the  male,  varies  from  ten  to  twelve  ounces  ;  in  the  female, 
from  eight  to  ten  :  its  proportions  to  the  body  being  as  1  to  169  in  males,  1  to 
149  in  females.  The  heart  continues  increasing  in  weight,  and  also  in  length, 
breadth,  and  thickness,  up  to  an  advanced  period  of  life :  this  increase  is  more 
marked  in  men  than  in  women. 

Component  Parts. — The  heart  is  subdivided  by  a  longitudinal  muscular  septum 
into  two  lateral  halves,  which  are  named  respectively,  from  their  position,  right 
and  left;  and  a  transverse  constriction  subdivides  each  half  of  the  organ  into  two 
cavities,  the  upper  cavity  on  each  side  being  called  the  auricle,  the  lower  the  ven- 
tricle. The  right  is  the  venous  side  of  the  heart,  receiving  into  its  auricle  the 


Bristle  passed  through 
Right  Auriculo-  Ventricular  opening. 

FIG.  695.— The  right  auricle  and  ventricle  laid  open,  the  anterior  walls  of  both  being  removed. 

dark  venous  blood  from  the  entire  body,  by  the  superior  and  inferior  vena  cava 
and  coronary  sinus.  From  the  right  auricle  the  blood  passes  into  the  right 
ventricle,  and  from  the  right  ventricle,  through  the  pulmonary  artery,  into  the 
lungs.  The  blood,  arterialized  by  its  passage  through  the  lungs,  is  returned  to 
the  left  side  of  the  heart  by  the  pulmonary  veins,  which  open  into  the  left  auricle ; 
from  the  left  auricle  the  blood  passes  into  the  left  ventricle,  and  from  the  left 
ventricle  is  distributed,  by  the  aorta  and  its  subdivisions,  through  the  entire  body. 
This  constitutes  the  circulation  of  the  blood  in  the  adult. 

The  great  transverse  groove  separates  the  auricles  from  the  ventricles,  and  is 
called  the  auricula-ventricular  groove.  It  is  deficient,  in  front,  from  being  crossed 
by  the  root  of  the  pulmonary  artery.  The  two  ventricles  are  also  separated  from 
each  other  on  the  surface  by  two  longitudinal  furrows,  the  interventricular  grooves, 
which  are  situated  one  on  the  anterior,  the  other  on  the  posterior  surface;  these  ex- 
tend from  the  base  of  the  ventricle  to  a  little  to  the  right  of  the  apex  of  the  organ, 
where  they  are  continuous,  the  former  being  situated  nearer  to  the  left  border  of 
the  heart,  and  the  latter  to  the  right.  It  follows,  therefore,  that  the  right  ventricle 
forms  the  greater  portion  of  the  anterior  surface  of  the  heart,  and  the  left  ventricle 
more  of  its  posterior  surface,  while  the  apex  is  made  up  entirely  of  the  left  ventri- 


1088  THE    THORAX. 

cle.     The  grooves  contain  the  coronary  arteries,  cardiac  veins,  lymphatics,  nerves, 
and  fat,  all  covered  by  the  visceral  layer  of  the  serous  pericardium. 
Each  of  these  cavities  should  now  be  separately  examined. 

To  examine  the  interior  of  the  right  auricle,  an  incision  should  be  made  along  its  right  bor- 
der from  the  entrance  of  the  superior  vena  cava  to  that  of  the  inferior.  A  second  cut  is  to  be 
made  from  the  centre  of  this  first  incision  to  the  tip  of  the  auricular  appendix,  and  the  flaps 
raised. 

The  Right  Auricle  is  a  little  larger  than  the  left,  its  walls  somewhat  thinner, 
measuring  about  one  line,  and  its  cavity  is  capable  of  containing  about  two  ounces. 
It  consists  of  two  parts — a  principal  cavity,  or  sinus,  venosus  or  atrium,  and  an 
appendix  auriculae. 

The  sinus  is  the  large  quadrangular  cavity  placed  between  the  two  venae  cavae  ; 
its  walls  are  extremely  thin ;  it  is  connected  below  with  the  right  ventricle,  and 
internally  with  the  left  auricle,  being  free  in  the  rest  of  its  extent. 

The  appendix  auricula?,  so  called  from  its  fancied  resemblance  to  a  dog's  ear, 
is  a  small  conical  muscular  pouch  the  margins  of  which  present  a  dentated  edge. 
It  projects  from  the  sinus  forward  and  to  the  left  side,  overlapping  the  root  of  the 
aorta. 

The  internal  surface  of  the  right  auricle  is  smooth,  except  in  the  appendix  and 
adjacent  part  of  the  anterior  or  right  wall  of  the  sinus  venosus,  where  it  is  thrown 
into  parallel  ridges  (musculi  pectinati). 

It  presents  the  following  parts  for  examination : 

Superior  cava. 


Inferior  cava.  V  1  r     /  Eustachian. 

Openings  \    Coronary  sinus.  \  Coronary. 

I   Foramina  Thebesii. 
(^  Auriculo-ventricular. 

Relics  of  foetal  f  Annulus  ovalis. 
structure       \  Fossa  ovalis. 
Musculi  pectinati. 
Tuberculum  Loweri. 

The  superior  vena  cava  returns  the  blood  from  the  upper  half  of  the  body,  and 
opens  into  the  upper  and  back  part  of  the  auricle,  the  direction  of  its  orifice  being 
downward  and  forward. 

The  inferior  vena  cava,  larger  than  the  superior,  returns  the  blood  from  the 
lower  half  of  the  body,  and  opens  into  the  lowest  part  of  the  auricle  near  the 
septum,  the  direction  of  its  orifice  being  upward  and  inward.  The  direction  of 
a  current  of  blood  through  the  superior  vena  cava  would  consequently  be  toward 
the  auriculo-ventricular  orifice,  whilst  the  direction  of  the  blood  through  the 
inferior  cava  would  be  toward  the  auricular  septum.  This  is  the  normal  direction 
of  the  two  currents  in  foetal  life. 

The  tuberculum  Loweri  is  a  small  projection  on  the  right  wall  of  the  auricle, 
between  the  two  venae  cavse.  It  is  most  distinct  in  the  hearts  of  quadrupeds  ;  in 
man  it  is  scarcely  visible.  It  was  supposed  by  Lower  to  direct  the  blood  from  the 
superior  cava  toward  the  auriculo-ventricular  opening. 

The  coronary  sinus  opens  into  the  auricle,  between  the  inferior  vena  cava  and 
the  auriculo-ventricular  opening.  It  returns  the  blood  from  the  substance 
of  the  heart,  and  is  protected  by  a  semicircular  fold  of  the  lining  membrane 
of  the  auricle,  the  coronary  valve  (valve  of  Thebesius).  The  sinus,  before  enter- 
ing the  auricle,  is  considerably  dilated — nearly  to  the  size  of  the  end  of  the  little 
finger.  Its  wall  is  partly  muscular,  and  at  its  junction  with  the  great  coronary 
vein  is  somewhat  constricted  and  furnished  with  a  valve  consisting  of  two  unequal 
segments. 

Theforamini  Thebesii  are  numerous  minute  apertures,  the  mouths  of  small 
veins  (vena*  cordis  minima?),  which  open  on  various  parts  of  the  inner  surface  of 
the  auricle.  They  return  the  blood  directly  from  the  muscular  substance  of  the 


THE   HEART.  1089 

heart.      Some  of  these  foramina  are  minute  depressions  in  the  walls  of  the  heart, 
presenting  a  closed  extremity. 

The  auricula-ventricular  opening  is  the  large  oval  aperture  of  communication 
between  the  auricle  and  the  ventricle,  to  be  presently  described. 

The  Eustaehian  valve  is  situated  between  the  anterior  margin  of  the  inferior 
vena  cava  and  the  auriculo-ventricular  orifice.  It  is  semilunar  in  form,  its  convex 
margin  being  attached  to  the  wall  of  the  vein ;  its  concave  margin,  which  is  free, 
terminating  in  two  cornua,  of  which  the  left  is  attached  to  the  anterior  edge  of 
the  annulus  ovalis,  the  right  being  lost  on  the  wall  of  the  auricle.  The  valve  is 
formed  by  a  duplicature  of  the  lining  membrane  of  the  auricle  containing  a  few 
muscular  fibres. 

In  the  foetus  this  valve  is  of  large  size,  and  serves  to  direct  the  blood  from  the 
inferior  vena  cava,  through  the  foramen  ovale,  into  the  left  auricle. 

In  the  adult  it  is  occasionally  persistent,  and  may  assist  in  preventing  the 
reflux  of  blood  into  the  inferior  vena  cava :  more  commonly  it  is  small,  and  its 
free  margin  presents  a  cribriform  or  filamentous  appearance ;  occasionally  it  is 
altogether  wanting. 

The  coronary   valve  (valve  of  Thebesius)  is  a  semicircular  fold  of  the  lining 
membrane  of  the  auricle,  protecting  the  orifice  of  the  coronary  sinus.    It  prevents 
the  regurgitation  of  blood  into  the  sinus  during  the  contraction  of  the  auricle 
This  valve  is  occasionally  double. 

The  fossa  ovalis  is  an  oval  depression  corresponding  to  the  situation  of  the 
foramen  ovale  in  the  foetus.  It  is  situated  at  the  lower  part  of  the  septum  auricu- 
larum.  above  and  to  the  left  of  the  orifice  of  the  inferior  vena  cava. 

The  annulus  ovalis  is  the  prominent  oval  margin  of  the  foramen  ovale.  It  is 
most  distinct  above  and  at  the  sides ;  below,  it  is  deficient.  A  small  slit-like 
valvular  opening  is  occasionally  found,  at  the  upper  margin  of  the  fossa  ovalis, 
which  leads  upward  beneath  the  annulus  into  the  left  auricle,  and  is  the  remains 
of  the  aperture  between  the  two  auricles  in  the  foetus. 

The  musculi  pectinati  are  small,  prominent  muscular  columns  which  run  across 
the  inner  surface  of  the  appendix  auriculae  and  adjoining  portion  of  the  wall  of  the 
sinus.  Posteriorly,  they  join  a  vertical  ridge,  the  crista  terminalis  of  His.  They 
are  called  pectinati  from  their  fancied  resemblance  to  the  teeth  of  a  comb. 

The  Eight  Ventricle  i?  triangular  in  form,  and  extends  from  the  right  auricle 
to  near  the  apex  of  the  heart.  Its  anterior  or  upper  surface  is  rounded  and 
convex,  and  forms  the  larger  part  of  the  front  of  the  heart.  Its  under  surface  is 
flattened,  rests  upon  the  Diaphragm,  and  forms  only  a  small  part  of  the  back  of 
the  heart.  Its  posterior  wall  is  formed  by  the  partition  between  the  two 
ventricles,  the  septum  ventriculorum,  the  surface  of  which  is  convex  and  bulges 
into  the  cavity  of  the  right  ventricle.  Its  upper  and  left  angle  is  prolonged 
into  a  conical  pouch,  the  infundibulum  or  conns  arteriosus,  from  which  the  pul- 
monary artery  arises.  The  walls  of  the  right  ventricle  are  thinner  than  those 
of  the  left,  the  proportion  between  them  being  as  1  to  3.  The  wall  is  thickest 
at  the  base,  and  gradually  becomes  thinner  toward  the  apex.  The  cavity,  which 
equals  that  of  the  left  ventricle,  is  capable  of  containing  about  three  fluidounces.1 

To  examine  the  interior  of  the  right  ventricle,  an  incision  should  be  made  a  little  to  the 
right  of  the  anterior  interventricular  groove  from  the  pulmonary  artery  to  the  apex  of  the 
heart,  and  should  be  carried  up  from  thence  a  little  to  the  right  of  the  posterior  interventricular 
groove,  as  far  as  the  auriculo-ventricular  opening. 

The  following  parts  present  themselves  for  examination : 

Q       •          f  Auriculo-ventricular. 

G:>  \  Opening  of  the  pulmonary  artery. 

Valves       /  Tricuspid. 
~-  milunar. 

1  Morrant  Baker  says  that  ''  taking  the  means  of  various  estimates,  it  may  be  inferred  that  each 
ventricle  is  able  to  contain  four  to  six  ounces  of  blood ''  (Kirke's  Physiology,  10th  edition,  p.  156). 
69 


1090  THE    THORAX. 

And  a  muscular  and  tendinous  apparatus  connected  with  the  tricuspid  valve : 
Columns  carneae.  Chordae  tendineae. 

The  auriculo-ventricular  orifice  is  the  large  oval  aperture  of  communication 
between  the  auricle  and  ventricle.  It  is  situated  at  the  base  of  the  ventricle,  near 
the  right  border  of  the  heart.  The  opening  is  about  an  inch  in  diameter,1  oval 
from  side  to  side,  surrounded  by  a  fibrous  ring,  covered  by  the  lining  membrane 
of  the  heart,  and  rather  larger  than  the  corresponding  aperture  on  the  left  side.  It 
is  guarded  by  the  tricuspid  valve. 

The  opening  of  the  pulmonary  artery  is  circular  in  form,  and  situated  at  the 
summit  of  the  conus  arteriosus,  close  to  the  septum  ventriculorum.  It  is  placed  on 
the  left  side  of  the  auriculo-ventricular  opening,  upon  the  anterior  aspect  of  the 
heart,  and,  when  viewed  from  above,  on  cross-section,  the  aortic  opening  is  seen 
intervening.  Its  orifice  is  guarded  by  the  pulmonary  semilunar  valves. 

The  tricuspid  valve  consists  of  three  segments  of  a  triangular  or  trapezoidal 
shape,  formed  by  a  duplicature  of  the  lining  membrane  of  the  heart,  reflected  on 
both  sides  of  a  layer  of  fibrous  tissue,  which  contains,  according  to  Kurschner  and 
Senac,  muscular  fibres.  These  segments  are  connected  by  their  bases  to  the  auriculo- 
ventricular  orifice,  and  to  one  another,  so  as  to  form  a  continuous  annular  membrane 
which  is  attached  round  the  margin  of  the  auriculo-ventricular  opening,  their  free 
margins  and  ventricular  surfaces  affording  attachment  to  a  number  of  delicate  ten- 
dinous cords,  the  chordae  tendinece.  The  largest  and  most  movable  segment,  placed 
toward  the  left  and  anterior  side  of  the  auriculo-ventricular  opening,  is  directed 
downward  between  that  opening  and  the  infundibulum  (left  or  infundibular  flap). 
Another  segment  corresponds  to  the  front  and  right  of  the  ventricle  (right  flap), 
and  a  third  to  its  posterior  wall  (posterior  or  septal  flap].  The  central  part  of  each 
segment  is  thick  and  strong ;  the  lateral  margins  are  thin  and  indented.  The 
chordce  tendinece  are  connected  with  the  segments  of  the  valve  in  the  following 
manner :  1.  Three  or  four  reach  the  attached  margin  of  each  segment,  where 
they  are  continuous  with  the  auriculo-ventricular  tendinous  ring.  2.  Others, 
four  to  six  in  number,  are  attached  to  the  central  thickened  part  of  each  segment. 
3.  The  most  numerous  and  finest  are  connected  with  the  marginal  portion  of  each 
segment. 

The  columnce  carnece  are  muscular  columns  which  project  from  the  inner  sur- 
face, excepting  near  the  opening  of  the  pulmonary  artery,  where  the  wall  becomes 
smooth.  They  may  be  classified  into  three  sets :  The  first  merely  form  prominent 
ridges ;  the  second  set  (trabeculce)  are  attached  by  their  two  extremities  only ; 
whilst  the  third  set  (musculi  papillares)  are  attached  by  one  extremity  to  the  wall 
of  the  heart,  the  opposite  extremity  giving  attachment  to  the  chordce  tendinece. 
There  are  two  papillary  muscles,  anterior  and  posterior.  The  chordce  tendinece  of 
the  former  go  to  the  left  and  right  segments.  Those  of  the  latter,  which  is  often 
replaced  by  two  or  three  smaller  ones,  pass  to  the  right  and  septal  segments.  There 
is  still  another  set  of  chordae  which  arise  directly  from  the  septum  and  pass  to  the 
septal  and  left  segments. 

The  semilunar  valves,  three  in  number,2  guard  the  orifice  of  the  pulmonary 
artery.  They  consist  of  three  semicircular  folds,  two  anterior  (right  and  left)  and 
one  posterior,  formed  by  a  fibrous  membrane,  covered  above  by  the  inner  coat  of 
the  artery  and  below  by  a  reflection  of  the  endocardium.  They  are  attached  by 

1  In  the  Pathological  Transactions,  vol.  vi.  p.  119,  Dr.  Peacock  has  given  some  careful  researches 
upon  the  weight  and  dimensions  of  the  heart  in  health  and  disease.     He  states,  as  the  result  of  his 
investigations,  that  in  the  healthy  adult  heart  the  right  auriculo-ventricular  aperture  has  a  mean  cir- 
cumference of  54.4  lines,  or  4|f  inches ;  the  left  auriculo-ventricular  aperture,  a  mean  circumference 
of  44.3  lines,  or  Sff  inches;   the  pulmonic  orifice,  of  40  lines,  or  3|f  inches;  and  the  aortic  orifice, 
of  35.5  lines,  or  3fa  inches;    but  the  dimensions  of  the  orifices  varied  greatly  in  different  cases, 
the  auriculo-ventricular  aperture  having  a  range  of  from  45  to  60  lines,  and  the  others  in  the  same 
proportion. 

2  The  pulmonary  semilunar  valves  have  been  found  to  be  two  in  number,  instead  of  three  (Dr. 
Hand,  of  St.  Paul,  Minn.,  in  the  North-  Western  Med.  and  Surg.  Jour.,  July,  1873),  and  the  same 
variation  is  more  frequently  noticed  in  the  aortic  semilunar  valves. 


THE  HEART.  1091 

their  convex  margins  to  the  wall  of  the  artery  at  its  junction  with  the  ventricle,  the 
straight  border  being  free,  and  directed  somewhat  upward  in  the  lumen  of  the 
•1.  The  free  margin  of  each  is  somewhat  thicker  than  the  rest  of  the  valve, 
is  strengthened  by  a  bundle  of  tendinous  fibres,  and  presents  at  its  middle  a  small 
projecting  thickened  nodule  called  corpus  Arantii.1  From  this  nodule  tendinous 
fibres  radiate  through  the  valve  to  its  attached  margin,  and  these  fibres  form  a  con- 
stituent part  of  its  substance  throughout  its  whole  extent,  excepting  two  narrow 
lunated  portions  (lunulce)  placed  on  each  side  of  the  nodule  immediately  behind 
the  free  margin  ;  here  the  valve  is  thin  and  formed  merely  by  the  lining  membrane. 
During  the  passage  of  the  blood  along  the  pulmonary  artery  these  valves  are  pressed 
against  the  sides  of  the  cylinder  and  the  course  of  the  blood  along  the  tube  is  unin- 
terrupted :  but  during  the  ventricular  diastole,  when  the  current  of  blood  along  the 
pulmonary  artery  is  checked  and  partly  thrown  back  by  its  elastic  walls,  these  valves 
become  immediately  expanded  and  effectually  close  the  entrance  of  the  tube.  When 
the  valves  are  closed  the  lunated  portions  of  each  are  brought  into  contact  with  one 
another  by  their  opposed  surfaces,  the  three  corpora  Arantii  filling  up  the  small 
triangular  space  that  would  be  otherwise  left  by  the  approximation  of  the  three 
semilunar  valves. 

Between  the  semilunar  valves  and  the  commencement  of  the  pulmonary  artery 
are  three  pouches  or  dilatations,  one  behind  each  valve.  These  are  the  pulmonary 
sinuses  (*!nu*e%  of  Vahalva).  Similar  sinuses  exist  between  the  semilunar  valves 
and  the  commencement  of  the  aorta  :  they  are  larger  than  the  pulmonary  sinuses. 
The  blood,  in  its  regurgitation  toward  the  heart,  finds  its  way  into  these  sinuses, 
and  so  shuts  down  the  valve-flaps. 

Iu  order  to  examine  the  interior  of  the  left  auricle,  make  an  incision  on  the  posterior  surface 
of  the  auricle  from  the  pulmonary  veins  on  one  side  to  those  on  the  other,  the  incision  being 
carried  a  little  way  into  the  vessels.  Make  another  incision  from  the  middle  of  the  horizontal 
one  to  the  appendix. 

The  Left  Auricle  is  rather  smaller  than  the  right ;  its  walls  thicker,  measuring 
about  one  line  and  a  half;  it  consists,  like  the  right,  of  two  parts,  a  principal  cavity, 
atrium  or  sinus  and  an  appendix  auriculce. 

The  sinus  is  cuboidal  in  form,  and  concealed  in  front  by  the  pulmonary  artery 
and  aorta :  internally,  it  is  separated  from  the  right  auricle  by  the  septum  auricu- 
larum  :  behind,  it  receives  on  each  side  two  pulmonary  veins,  being  free  in  the  rest 
of  its  extent. 

The  appendix  auriculce  is  somewhat  constricted  at  its  junction  with  the  auricle; 
it  is  longer,  narrower,  and  more  curved  than  that  of  the  right  side,  and  its  margins 
are  more  deeply  indented,  presenting  a  kind  of  foliated  appearance.  Its  direction 
is  forward  and  toward  the  right  side,  overlapping  the  root  of  the  pulmonary  artery. 

Within  the  auricle  the  following  parts  present  themselves  for  examination : 

The  openings  of  the  four  pulmonary  veins. 
Auriculo-ventricular  opening. 
Musculi  pectinati. 

The  pulmonary  veins,  four  in  number,  open,  two  into  the  right,  and  two  into 
the  left  side  of  the  auricle.  The  two  left  veins  frequently  terminate  by  a  common 
opening.  They  are  not  provided  with  valves. 

The  auriculo-ventricular  opening  is  the  large  oval  aperture  of  communication 
between  the  auricle  and  ventricle.  It  is  rather  smaller  than  the  corresponding 
opening  on  the  opposite  side  (see  note,  page  1090). 

1  In  former  editions,  as  well  as  in  other  text-books  on  anatomy,  these  little  nodules  have  been 
described  as  fibro-cartilaginous  in  structure.  At  my  request,  Dr.  Le  Cronier  Lancaster,  Demonstrator 
of  Anatomy  at  St.  George's  Hospital,  has  investigated  this  subject,  and  reports  that  the  "corpora 
Arantii "  appear  to  consist  of  bundles  of  interlacing  connective-tissue  fibres  with  branched  connective- 
tissue  cells,  and  some  few  elastic  fibres.  Occasionally  a  rounded  cell,  with  indistinct  capsule,  resem- 
bling a  cartilage-cell  wa.<  seen  ;  but  there  were  not  many  of  them.  At  the  free  edge  of  the  corpus  the 
structure  is  denser,  there  being  a  larger  proportion  of  fibres  to  cells  than  in  the  central  portion.  He 
thinks  the  structure  of  the  corpus  should  be  put  down  as  fibrous  and  not  fibro-cartilaginous. 


1092 


THE    THORAX. 


The  musculi  pectinati  are  fewer  in  number  and  smaller  than  on  the  right  side  ; 
they  are  confined  to  the  inner  surface  of  the  appendix. 

On  the  inner  surface  of  the  septum  auricularum  may  be  seen  a  lunated 
impression  bounded  below  by  a  crescentic  ridge  the  concavity  of  which  is  turned 
upward.  The  depression  is  just  above  the  fossa  ovalis  in  the  right  auricle. 

To  examine  the  interior  of  the  left  ventricle,  make  an  incision  a  little  to  the  left  of  the 
anterior  inter  ventricular  groove  from  the  base  to  the  apex  of  the  heart,  and  carry  it  up  from 
thence,  a  little  to  the  left  of  the  posterior  interventricular  groove,  nearly  as  far  as  the  auriculo- 
ventricular  groove. 

The  Left  Ventricle  is  longer  and  more  conical  in  shape  than  the  right 
ventricle.  It  forms  a  small  part  of  the  left  side  of  the  anterior  surface  of  the 


Bristle  passed  through  left 
auriculo-ventricular  opening. 


Passed  through  aortic  opening. 


FIG.  696.— The  left  auricle  and  ventricle  laid  open,  the  posterior  walls  of  both  being  removed. 

heart,  and  a  considerable  part  of  its  posterior  surface.  It  also  forms  the  apex  of 
the  heart  by  its  projection  beyond  the  right  ventricle.  Its  walls  are  much  thicker 
than  those  of  the  right  side,  the  proportion  being  as  3  to  1.  They  are  also  thickest 
in  the  broadest  part  of  the  ventricle,  becoming  gradually  thinner  toward  the  base, 
and  also  toward  the  apex,  which  is  the  thinnest  part. 

The  following  parts  present  themselves  for  examination  within  the  ventricle  : 

f  Auriculo-ventricular.  ^T  i        f  Mitral. 

Openmgs-J  Anrf.^  Valves^  gemilunar. 


Aortic. 
Chordae  tendinese. 


Columnae  carneae. 


The  auriculo-ventricular  opening  is  placed  below  and  to  the  left  of  the  aortic 
orifice.  It  is  a  little  smaller  than  the  corresponding  aperture  of  the  opposite  side, 
and,  like  it,  is  broader  in  the  transverse  than  in  the  antero-posterior  diameter.  It 
is  surrounded  by  a  dense  fibrous  ring,  covered  by  the  lining  membrane  of  the 
heart,  and  guarded  by  the  mitral  valves. 

The  aortic  opening  is  a  circular  aperture  in  front  and  to  the  right  side  of  the 
auriculo-ventricular,  from  which  it  is  separated  by  one  of  the  segments  of  the 
mitral  valve.  Its  orifice  is  guarded  by  the  semilunar  valves. 


THE   HEART. 


1093 


The  mitral  or  bicuspid  valve  is  attached  to  the  circumference  of  the  auriculo- 
ventricular  orifice  in  the  same  way  that  the  tricuspid  valve  is  on  the  opposite  side. 
It  is  formed  by  fibrous  membrane  covered  on  both  surfaces  by  endocardium,  and 
contains  a  few  muscular  fibres.  It  is  large  in  size,  thicker,  and  altogether  stronger 
than  the  tricuspid,  and  consists  of  two  segments  of  unequal  size.  The  large  seg- 
ment is  placed  in  front  and  to  the  right,  between  the  auriculo-ventricular  and 
aortic  orifices.  Two  smaller  segments  are  usually  found  at  the  angles  of  junction 
of  the  larger.  Similar  segments  are  less  constantly  found  between  the  main  ones 
of  the  tricuspid  valve.  The  mitral  valve-flaps  are  furnished  with  chordae  tendinese, 
the  mode  of  attachment  of  which. is  precisely  similar  to  that  of  those  on  the  right 
side,  but  they  are  thicker,  stronger,  and  less  numerous. 

The  semilunar  valves  surround  the  orifice  of  the  aorta ;  two  are  posterior  (right 
and  left),  and  one  anterior ;  they  are  similar  in  structure  and  mode  of  attachment  to 
the  pulmonary  valves.  They  are,  however,  larger,  thicker,  and  stronger,  the  lunulae 
are  more  distinct,  and  the  corpora  Arantii  larger  and  more  prominent.  Between  each 
valve  and  the  cylinder  of  the  aorta  is  a  deep  depression,  the  sinus  aortici  (sinuses 
of  Valsalva)  ;  they  are  larger  than  those  of  the  root  of  the  pulmonary  artery.  The 
right  coronary  artery  arises  from  the  anterior ;  the  left  from  the  left  posterior. 

The  columnce  carnece  admit  of  a  subdivision  into  three  sets,  like  those  upon  the 
right  side,  but  they  are  smaller,  more  numerous,  and  present  a  dense  interlace- 
ment, especially  at  the  apex  and  upon  the  posterior  wall.  Those  attached  by  one 
extremity  only,  the  musculi  papillares,  are  two  in  number,  being  connected  one  to 

Vena  cava  inf.  Right  inf.  puJm.  vein 


\ 


EiistacJtinn  riilr 


Valve  of 

Thebesiits 


Trabeculx 


Left  inf. 
pulm.  vein 


Coronary 
mlcus 


Chordse  tendin. 


Muse,  papill. 


Muse.  pupil!. 


FIG.  697.— Section  of  the  heart,  showing  the  inturarticular  and  interventricular  septa.    (Gegenbaur.) 

the  anterior,  the  other  to  the  posterior  wall ;  they  are  of  large  size,  and  terminate 
by  free  rounded  extremities  from  which  the  chordae  tendineae  arise. 

The  septum  between  the  two  ventricles  is  thick,  especially  below  (Fig.  697)- 


1094  THE    THORAX. 

At  its  upper  part  it  suddenly  tapers  off  and  loses  its  muscular  fibres,  consisting 
only  of  fibrous  tissue  covered  by  two  layers  of  endocardium,  and  on  the  right  side 
it  is  also,  during  diastole,  in  contact  with  the  septal  flap  of  the  tricuspid  valve.  It 
continues  upward,  and  forms  the  septum  between  the  aortic  vestibule  and  the  right 
auricle.  It  is  derived  from  the  lower  part  of  the  aortic  septum  of  the  foetus,  and 
an  abnormal  communication  may  exist  at  this  part  owing  to  defective  development. 
The  aortic  vestibule  (Sibson)  is  a  small  portion  of  the  ventricular  cavity  immedi- 
ately under  the  root  of  the  aorta. 

The  Endocardium  is  a  thin  membrane  which  lines  the  internal  surface  of  the 
heart ;  it  assists  in  forming  the  valves  by  its  reduplications,  and  is  continuous  with 
the  lining  membrane  of  the  great  blood-vessels.  It  is  a  smooth,  transparent 
membrane,  giving  to  the  inner  surface  of  the  heart  its  glistening  appearance.  It 
is  more  opaque  on  the  left  than  on  the  right  side  of  the  heart,  thicker  in  the 
auricles  than  in  the  ventricles,  and  thickest  in  the  left  auricle.  It  is  thin  on  the 
musculi  pectinati  and  on  the  columnae  carneae,  but  thicker  on  the  smooth  part  of 
the  auricular  and  ventricular  walls  and  on  the  tips  of  the  musculi  papillares. 

Structure. — The  heart  consists  of  muscular  fibres  and  of  fibrous  rings  which 
serve  for  their  attachment. 

The  fibrous  rings  surround  the  auriculo- ventricular  and  arterial  orifices  :  they  are 
stronger  upon  the  left  than  on  the  right  side  of  the  heart.  The  auriculo-ventricular 
rings  serve  for  the  attachment  of  the  muscular  fibres  of  the  auricles  and  ventricles, 
and  also  for  the  mitral  and  tricuspid  valves ;  the  ring  on  the  left  side  is  closely 
connected  by  its  right  margin  with  the  aortic  arterial  ring.  Between  these  and 
the  right  auriculo-ventricular  ring  is  a  mass  of  fibrous  tissue,  and  in  some  of  the 
larger  animals,  as  the  ox  and  elephant,  a  nodule  of  bone. 

The  fibrous  rings  surrounding  the  arterial  orifices  serve  for  the  attachment  of 
the  great  vessels  and  semilunar  valves.  Each  ring  receives,  by  its  ventricular 
margin,  the  attachment  of  the  muscular  fibres  of  the  ventricles  ;  its  opposite  margin 
presents  three  deep  semicircular  notches,  within  which  the  middle  coat  of  the 
artery  (which  presents  three  convex  semicircular  segments)  is  firmly  fixed,  the 
attachment  of  the  artery  to  its  fibrous  ring  being  strengthened  by  the  thin  cellular 
coat  and  serous  membrane  externally  and  by  the  endocardium  within.  It  is 
opposite  the  margins  of  these  semicircular  notches,  in  the  arterial  rings,  that  the 
endocardium  by  its  reduplication,  forms  the  semilunar  valves,  the  fibrous  structure 
of  the  ring  being  continued  into  each  of  the  segments  of  the  valve  at  this  part. 
The  middle  coat  of  the  artery  in  this  situation  is  thin,  and  the  sides  of  the  vessel 
are  dilated  to  form  the  sinuses  of  Valsalva. 

The  muscular  structure  of  the  heart  (myocardiuni)  consists  of  bands  of  fibres 
which  present  an  exceedingly  intricate  interlacement.  They  are  of  a  deep  red 
color  and  marked  with  transverse  striae  (page  65). 

The  muscular  fibres  of  the  heart  admit  of  a  subdivision  into  two  kinds,  those  of  the 
auricles  and  those  of  the  ventricles,  which  are  quite  independent  of  one  another. 

Fibres  of  the  Auricles. — These  are  disposed  in  two  layers — a  superficial  layer 
common  to  both  cavities,  and  a  deep  layer  proper  to  each.  The  superficial  fibres 
are  more  distinct  on  the  anterior  surface  of  the  auricles,  across  the  bases  of  which 
they  run  in  a  transverse  direction,  forming  a  thin,  but  incomplete  layer.  Some  of 
these  fibres  pass  into  the  septum  auricularum.  The  internal  or  deep  fibres  proper 
to  each  auricle  consist  of  two  sets,  looped  and  annular  fibres.  The  looped  fibres 
pass  upward  over  each  auricle,  being  attached  by  two  extremities  to  the  corre- 
sponding auriculo-ventricular  rings  in  front  and  behind.  The  annular  fibres 
surround  the  whole  extent  of  the  appendices  auricularum,  and  are  continued  upon 
the  walls  of  the  venae  cavae  and  coronary  sinus  on  the  right  side,  and  upon  the 
pulmonary  veins  on  the  left  side,  at  their  connection  with  the  heart.  In  the 
appendices  they  interlace  with  the  longitudinal  fibres. 

Fibres  of  the  Ventricles. — These  are  arranged  in  an  exceedingly  complex  man- 
ner, and  the  accounts  given  by  various  anatomists  differ  considerably.  This  is  prob- 
ably due  partly  to  the  fact  that  the  various  layers  of  muscular  fibres  of  which  the 


THE   HEART.  1095 

heart  is  said  to  be  composed  are  not  independent,  but  their  fibres  are  interlaced 
to  a  considerable  extent,  and  therefore  any  separation  into  layers  must  be  to 
a  great  extent  artificial :  and  also  no  doubt  partly  due  to  the  fact,  pointed  out  by 
Henle,  that  there  are  varieties  in  the  arrangement  due  to  individual  differences. 
If  the  epi'-'ardiuni  (visceral  layer  of  pericardium)  and  the  subjacent  fat  is  removed 
from  a  heart  which  has  been  subjected  to  prolonged  boiling,  so  as  to  dissolve  the 
connective  tissues,  the  superficial  fibres  of  the  ventricles  will  be  exposed.  They 
will  be  seen  to  commence  at  the  base  of  the  heart,  where  they  are  attached  to 
the  tendinous  rings  around  the  orifices,  and  to  pass  obliquely  downward  toward 
the  apex,  with  a  direction  from  right  to  left.  At  the  apex  the  fibres  turn  suddenly  in- 
ward, forming  what  is  called  the  vortex,  into  the  interior  of  the  left  ventricle.  On 
the  back  of  the  heart  it  will  be  seen  that  the  fibres  pass  continuously  from  one 
ventricle  to  the  other  over  the  interventricular  groove  ;  and  the  same  thing  will  be 
noticed  on  the  front  of  the  heart  at  the  upper  and  lower  end  of  the  anterior 
interventricular  groove,  but  in  the  middle  portion  of  this  groove  the  fibres  passing 
from  one  ventricle  to  the  other  are  interrupted  by  fibres  emerging  from  the  septum 
along  the  groove  ;  many  of  the  superficial  fibres  pass  in  also  at  this  groove  to  the 
septum.  The  vortex  is  produced,  as  stated  above,  by  the  sudden  turning  inward 
of  the  superficial  fibres  in  a  peculiar  spiral  manner  into  the  interior  of  the  left 
ventricle.  Those  fibres  which  descended  on  the  posterior  surface  of  the  heart 
enter,  at  the  vortex,  the  left  ventricle,  and,  ascending,  form  part  of  the  inner  layer 
of  muscular  fibres  lining  this  cavity  and  the  right  (posterior)  musculus  papillaris : 
those  fibres  which  descend  on  the  front  of  the  heart,  and  which  pass  to  the  apex, 
also  pass,  at  the  vortex,  into  the  interior  of  the  ventricle,  where  they  also  form  the 
remainder  of  the  innermost  layer  of  the  ventricle  and  the  left  (anterior)  musculus 
papillaris.  The  fibres  forming  the  inner  layer  of  the  wall  of  the  ventricle  ascend 
to  be  attached  to  the  fibrous  rings  around  the  orifices. 

By  dissection  these  superficial  fibres  may  be  removed  as  a  thin  stratum,  and  it 
will  then  be  found  that  the  ventricles  are  made  up  of  oblique  fibres  superimposed  in 
layers  one  on  the  top  of  another,  and  assuming  gradually  a  less  oblique  direction  as 
they  pass  to  the  middle  of  the  thickness  of  the  ventricular  wall,  so  that  in  the  centre 
of  the  wall  the  fibres  are  transverse.  Internal  to  this  central  transverse  layer  the 
fibres  become  oblique  again,  but  in  the  opposite  direction  to  the  external  ones.  This 
division  into  distinct  layers  is.  however,  to  a  great  extent  artificial,  as  the  fibres 
pass  lu-n-s  from  one  layer  to  another,  and  have  therefore  to  be  divided  in  the 
dissection,  and  the  change  in  the  direction  of  the  fibres  is  very  gradual.  These 
oblique  fibres  commence  above  at  the  fibrous  rings  at  the  base  of  the  heart,  and, 
descending  toward  the  apex,  they  enter  the  septum  near  its  lower  end.  In  the 
septum  the  fibres  which  form  the  left  ventricle  may  be  traced  in  three  directions : 
1.  Some  pass  upward  to  be  attached  to  the  central  fibro-cartilage.  2.  Others 
pass  through  the  septum  to  become  continuous  with  the  fibres  of  the  right  ventricle. 
3.  The  remainder  pass  through  the  septum  to  encircle  the  ventricle  as  annular 
fibres.  Of  the  fibres  of  the  right  ventricle,  some  on  entering  the  septum  pass 
upward  to  be  attached  to  the  central  fibro-cartilage ;  some,  entering  the  septum 
from  behind,  pass  forward  to  become  continuous  with  the  fibres  on  the  anterior 
surface  of  the  left  ventricle  ;  and  others,  entering  in  front,  pass  backward  to  join 
the  fibres  on  the  posterior  wall  of  the  left  ventricle.  The  septum  therefore^consists 
of  three  varieties  of  fibres — viz.  annular  fibres,  special  to  the  left  ventricle ; 
ascending  fibres,  derived  from  both  ventricles  and  ascending  through  the  septum 
to  the  central  fibro-cartilage  ;  and  decussating  fibres,  derived  from  the  anterior  wall 
of  one  ventricle  and  passing  to  the  posterior  wall  of  the  other  ventricle,  or  from 
the  posterior  wall  of  the  right  ventricle  and  passing  to  the  anterior  wall  of  the  left. 
In  addition  to  these  fibres  there  are  a  considerable  number  which  appear  to 
encircle  both  ventricles  and  which  pass  across  the  septum  without  turning  into  it. 

Vessels  and  Nerves. — The  arteries  supplying  the  heart  are  the  left  or  anterior 
and  right  or  posterior  coronary  (page  542). 

The  veins  accompany  the  arteries,  and  terminate  in  the  right  auricle.     They  are 


1096  THE    THORAX. 

the  great,  the  middle,  anterior,  and  posterior,  cardiac  veins,  the  right  or  small  and  the 
left  or  great  coronary  sinuses,  and  the  venae  cordis  minimae  (vence  Thebesii)  (p.  677). 

The  lymphatics  terminate  in  the  thoracic  and  right  lymphatic  ducts. 

The  nerves  are  derived  from  the  cardiac  plexuses,  which  are  formed  partly  from 
the  cranial  nerves  and  partly  from  the  sympathetic.  They  are  freely  distributed 
both  on  the  surface  and  in  the  substance  of  the  heart,  the  separate  filaments  being 
furnished  with  small  ganglia. 

Surface  Form. — In  order  to  show  the  extent  of  the  heart  in  relation  to  the  front  of  the 
chest,  draw  a  line  from  the  lower  border  of  the  second  left  costal  cartilage,  one  inch  from  the 
sternum,  to  the  upper  border  of  the  third  right  costal  cartilage,  half  an  inch  from  the  sternum. 
This  represents  the  base-line  or  upper  limit  of  the  organ.  Take  a  point  an  inch  and  a  half 
below  and  three-quarters  of  an  inch  internal  to  the  left  nipple — that  is,  about  three  and  a  half 
inches  to  the  left  of  the  median  line  of  the  body.  This  represents  the  apex  of  the  heart. 
Draw  a  line  from  this  apex-point,  with  a  slight  convexity  downward,  to  the  junction  of  the 
seventh  right  costal  cartilage  to  the  sternum.  This  represents  the  lower  limit  of  the  heart. 
Join  the  right  extremity  of  the  first  line — that  is,  the  base-line — with  the  right  extremity  of 
this  line — that  is,  to  the  seventh  rigbt  chondro-sternal  joint — with  a  slight  curve  outward,  so 
that  it  projects  about  an  inch  and  a  half  from  the  middle  line  of  the  sternum.  Lastly,  join  the 
left  extremity  of  the  base-line  and  the  apex-point  by  a  line  curved  slightly  to  the  left. 

The  position  of  the  various  orifices  is  as  follows :  viz.  the  pulmonary  orifice  is  situated  in 
the  upper  angle  formed  by  the  articulation  of  tbe  third  left  costal  cartilage  with  the  sternum  ; 
the  aortic  orifice  is  a  little  below  and  internal  to  this,  behind  the  left  border  of  the  sternum, 
close  to  the  articulation  of  the  third  left  costal  cartilage  to  this  bone.  The  left  auriculo-yentric- 
ular  opening  is  behind  the  sternum,  rather  to  the  left  of  the  median  line,  and  opposite  the 
fourth  costal  cartilages.  The  right  auriculo- ventricular  opening  is  a  little  lower,  opposite  the 
fourth  interspace  and  in  the  middle  line  of  the  body. 

A  portion  of  the  area  of  the  heart  thus  mapped  out  is  uncovered  by  lung,  and  therefore 
gives  a  dull  note  on  percussion ;  tbe  remainder,  being  overlapped  by  the  lung,  gives  a  more  or 
less  resonant  note.  The  former  is  known  as  the  area  of  superficial  cardiac  dulness ;  the  latter 
as  the  area  of  deep  cardiac  dulness.  The  area  of  superficial  cardiac  dulness  is  included  between 
a  line  drawn  from  the  centre  of  tbe  sternum,  between  the  fourth  costal  cartilages,  to  the  apex 
of  the  heart  and  a  line  drawn  from  the  same  point  down  tbe  lower  third  of  the  middle  line  of 
the  sternum.  Below,  this  area  merges  into  the  dulness  which  corresponds  to  the  liver.  Dr. 
Latham  lays  down  the  following  rule  as  a  sufficient  practical  guide  for  the  definition  of  the  por- 
tion of  the  heart  which  is  uncovered  by  lung  or  pleura :  "  Make  a  circle  of  two  inches  in  diam- 
eter round  a  point  midway  between  the  nipple  and  the  end  of  the  sternum, ' '  that  is,  the  gladiolus. 

Peculiarities  in  the  Vascular  System  of  the  Foetus. 

The  chief  peculiarities  in  the  heart  of  the  foetus  are  the  direct  communication 
between  the  two  auricles  through  the  foramen  ovale  and  the  large  size  of  the 
Eustachian  valve.  There  are  also  several  minor  peculiarities.  Thus,  the  position 
of  the  heart  is  vertical  until  the  fourth  month,  when  it  commences  to  assume  an 
oblique  direction.  Its  size  is  also  very  considerable  as  compared  with  the  body,  the 
proportion  at  the  second  month  being  1  to  50 ;  at  birth  it  is  as  1  to  120 ;  whilst 
in  the  adult  the  average  is  about  1  to  160.  At  an  early  period  of  foetal  life  the 
auricular  portion  of  the  heart  is  larger  than  the  ventricular,  the  right  auricle  being 
more  capacious  than  the  left ;  but  toward  birth  the  ventricular  portion  becomes 
the  larger.  The  thickness  of  both  ventricles  is  at  first  about  equal,  but  toward 
birth  the  left  becomes  much  the  thicker  of  the  two. 

The  foramen  ovale  is  situated  at  the  lower  and  back  part  of  the  septum  auricu- 
larum,  forming  a  communication  between  the  auricles.  It  remains  as  a  free  oval 
opening  from  the  time  of  the  formation  of  the  auricular  septum  (about  the  eighth 
week)  until  the  middle  period  of  fcetal  life.  About  this  period  a  fold  grows  up 
from  the  posterior  wall  of  the  auricle  to  the  left  of  the  foramen  ovale,  and  advances 
over  the  opening  so  as  to  form  a  sort  of  valve,  which  allows  the  blood  to  pass  only 
from  the  right  to  the  left  auricle,  and  not  in  the  opposite  direction. 

The  Eustachian  valve  is  developed  from  the  anterior  border  of  the  inferior  vena 
cava  at  its  entrance  into  the  auricle.  It  is  directed  upward  on  the  left  side  of  the 
opening  of  this  vein,  and  serves  to  direct  the  blood  from  the  inferior  vena  cava 
through  the  foramen  ovale  into  the  left  auricle. 

The  peculiarities  in  the  arterial  system  of  the  foetus  are  the  communication 
between  the  pulmonary  artery  and  the  descending  aorta  by  means  of  the  ductus 


THE   HEART.  1097 

arteriosus,  and  the  communication  between  the  internal  iliac  arteries  and  the 
placenta  by  means  of  the  umbilical  arteries. 

The  duetus  arteriosus  is  a  short  tube,  about  half  an  inch  in  length  at  birth,  and 
of  the  diameter  of  a  goosequill.  In  the  early  condition  it  forms  the  continuation  of 
the  pulmonary  artery,  and  opens  into  the  descending  aorta  just  below  the  origin 
of  the  left  subclavian  artery,  and  so  conducts  the  chief  part  of  the  blood  from  the 
right  ventricle  into  this  vessel.  When  the  branches  of  the  pulmonary  artery  have 
become  larger  relatively  to  the  duetus  arteriosus,  the  latter  is  chiefly  connected 
to  the  left  pulmonary  artery ;  and  the  fibrous  cord,  which  is  all  that  remains 
of  the  duetus  arteriosus  in  later  life,  will  be  found  to  be  attached  to  the  root  of 
that  vessel. 

The  umbilical  or  hypogastrie  arteries  arise  from  the  internal  iliacs,  in  addition 
to  the  branches  given  off  from  those  vessels  in  the  adult.  Ascending  along  the 
sides  of  the  bladder  to  its  fundus.  they  pass  out  of  the  abdomen  at  the  umbilicus, 
and  are  continued  along  the  umbilical  cord  to  the  placenta,  coiling  round  the 
umbilical  vein.  They  return  to  the  placenta  the  blood  which  has  circulated  in 
the  system  of  the  foetus. 

The  peculiarity  in  the  venous  system  of  the  foetus  is  the  communication  estab- 
lished between  the  placenta  and  the  liver  and  portal  vein  through  the  umbilical 
vein,  and  the  inferior  vena  cava  through  the  duetus  venosus. 

FCETAL  CIRCULATION. 

The  blood  destined  for  the  nutrition  of  the  foetus  is  carried  from  the  placenta 
to  the  foetus,  along  the  umbilical  cord,  by  the  umbilical  vein.  The  umbilical  vein 
enters  the  abdomen  at  the  umbilicus,  and  passes  upward  along  the  free  margin 
of  the  suspensory  ligament  of  the  liver  to  the  under  surface  of  that  organ,  where 
it  gives  off  two  or  three  branches  to  the  left  lobe,  one  of  which  is  of  large  size,  and 
others  to  the  lobus  quadratus  and  lobulus  Spigelii.  At  the  transverse  fissure  it 
divides  into  two  branches  :  of  these,  the  larger  is  joined  by  the  portal  vein  and 
enters  the  right  lobe  ;  the  smaller  branch  continues  onward,  under  the  name  of 
the  duetus  venosus.  and  joins  the  left  hepatic  vein  at  the  point  of  junction  of  that 
vessel  with  the  inferior  vena  cava.  The  blood,  therefore,  which  traverses  the 
umbilical  vein  reaches  the  inferior  vena  cava  in  three  different  ways :  the  greater 
quantity  circulates  through  the  liver  with  the  portal  venous  blood  before  entering 
the  vena  cava  by  the  hepatic  veins ;  some  enters  the  liver  directly,  and  is  also 
returned  to  the  inferior  cava  by  the  hepatic  veins ;  the  smaller  quantity  passes 
directly  into  the  vena  cava  by  the  junction  of  the  duetus  venosus  with  the  left 
hepatic  vein. 

In  the  inferior  cava  the  blood  carried  by  the  duetus  venosus  and  hepatic  veins 
becomes  mixed  with  that  returning  from  the  lower  extremities  and  wall  of  the 
abdomen.  It  enters  the  right  auricle,  and,  guided  by  the  Eustachian  valve,  passes 
through  the  foramen  ovale  into  the  left  auricle,  where  it  becomes  mixed  with  a 
small  quantity  of  blood  returned  from  the  lungs  by  the  pulmonary  veins.  From 
the  left  auricle  it  passes  into  the  left  ventricle,  and  from  the  left  ventricle  into 
the  aorta,  by  means  of  which  it  is  distributed  almost  entirely  to  the  head  and 
upper  extremities,  a  small  quantity  being  probably  carried  into  the  descending 
aorta.  From  the  head  and  upper  extremities  the  blood  is  returned  by  the  branches 
of  the  superior  vena  cava  to  the  right  auricle,  where  it  becomes  mixed  with  a  small 
portion  of  the  blood  from  the  inferior  cava.  From  the  right  auricle  it  descends 
over  the  Eustachian  valve  into  the  right  ventricle,  and  from  the  right  ventricle 
passes  into  the  pulmonary  artery.  The  lungs  of  the  foetus  being  solid  and  almost 
impervious,  only  a  small  quantity  of  the  blood  of  the  pulmonary  artery  is  distrib- 
uted to  them  by  the  right  and  left  pulmonary  arteries,  and  is  returned  by  the 
pulmonary  veins  to  the  left  auricle ;  the  greater  part  passes  through  the  duetus 
arteriosus  into  the  commencement  of  the  descending  aorta,  where  it  becomes  mixed 
with  a  small  quantity  of  blood  transmitted  by  the  left  ventricle  into  the  aorta. 


1098 


THE    THORAX. 


Along  this  vessel  it  descends  to  supply  the  lower  extremities  and  viscera  of  the 
abdomen  and  pelvis,  the  chief  portion  being,  however,  conveyed  by  the  umbilical 
arteries  to  the  placenta. 

From  the  preceding  account  of  the  circulation  of  the  blood  in  the  foetus  it  will 
be  seen — 

1.  That  the  placenta  serves  the  double  purpose  of  a  respiratory  and  nutritive 


Ductus  arteriosus. 


Internal  iliac  artery. 


FIG.  698.— Plan  of  the  foetal  circulation.    In  this  plan  the  figured  arrows  represent  the  kind  of  blood,  as 

well  as  the  direction  which  it  takes  in  the  vessels.  Thus,  arterial  Wood  is  figured  ^> — — > ;  venous  blood1 

•^yr >;  mixed  (arterial  and  venous)  blood,  ^^ >. 

organ,  receiving  the  venous  blood  from  the  foetus,  and  returning  it  again  re-oxy- 
genated and  charged  with  additional  nutritive  material. 

2.   That  nearly  the  whole  of  the  blood  of  the  umbilical  vein  traverses  the  liver 


THE  HEART.  1099 

before  entering  the  inferior  cava ;  hence  the  large  size  of  this  organ,  especially  at 
an  early  period  of  foetal  life. 

3.  That   the   right   auricle  is  the  point  of  meeting  of  a  double  current,  the 
blood  in   the  inferior  cava  being  guided  by  the  Eustachian  valve  into  the  left 
auricle,  whilst  that  in  the  superior  cava  descends  into  the  right  ventricle.     At  an 
early  period  of  foetal  life  it  is  highly  probable  that  the  two  streams  are  quite  dis- 
tinct, for  the  inferior  cava  opens  almost  directly  into  the  left  auricle,  and  the 
Eustachian  valve  would  exclude  the  current  along  the  vein  from  entering  the 
right  ventricle.     At  a  later  period,  as  the  separation  between  the  two  auricles 
becomes  more  distinct,  it  seems  probable  that  some  mixture  of  the  two  streams 
must  take  place. 

4.  The  blood  carried  from  the  placenta  to  the  foetus  by  the  umbilical  vein, 
mixed  with  the  blood  from  the  inferior  cava,  passes  almost  directly  to  the  arch 
of  the  aorta,  and  is  distributed  by  the  branches  of  that  vessel  to  the  head  and 
upper  extremities ;  hence  the  large  size  and  perfect  development  of  those  parts  at 
birth. 

5.  The  blood  contained  in  the  descending  aorta,  chiefly  derived  from  that 
which  has  already  circulated  through  the  head  and  upper  limbs,  together  with  a 
small  quantity  from  the  left  ventricle,  is  distributed  to  the  lower  extremities ; 
hence  the  small  size  and  imperfect  development  of  these  parts  at  birth. 

CHANGES  IN  THE  VASCULAR  SYSTEM  AT  BIRTH. 

At  birth,  when  respiration  is  established,  an  increased  amount  of  blood 
from  the  pulmonary  artery  passes  through  the  lungs,  which  now  perform  their 
office  as  respiratory  organs,  and  at  the  same  time  the  placental  circulation 
is  cut  off.  The  foramen  ovale  becomes  gradually  closed  by  about  the  tenth 
day  after  birth ;  the  valvular  fold  above  mentioned  becomes  adherent  to  the 
margins  of  the  foramen  for  the  greater  part  of  its  circumference,  but  above 
a  slit-like  opening  is  left  between  the  two  auricles  which  sometimes  remains  per- 
sisrent. 

The  Justus  nrteriosus  begins  to  contract  immediately  after  respiration  is  estab- 
lished, becomes  completely  closed  from  the  fourth  to  the  tenth  day,  and  ultimately 
degenerates  into  an  impervious  cord  which  serves  to  connect  the  left  pulmonary 
artery  to  the  descending  aorta. 

Of  the  umbilical  or  hypogastric  arteries,  the  portion  continued  on  to  the 
bladder  from  the  trunk  of  the  corresponding  internal  iliac  remains  pervious 
as  the  superior  vesical  artery,  and  the  part  between  the  fundus  of  the  bladder 
and  the  umbilicus  becomes  obliterated  between  the  second  and  fifth  days  after 
birth,  and  projects  into  the  peritoneal  sac  so  as  to  form  the  two  fossae  of  the 
peritoneum  spoken  of  in  the  section  on  the  surgical  anatomy  of  direct  inguinal 
hernia. 

The  umbilical  vein  and  ductus  venoms  become  completely  obliterated  between 
the  second  and  fifth  days  after  birth,  and  ultimately  dwindle  to  fibrous  cords,  the 
former  becoming  the  round  ligament  of  the  liver,  the  latter  the  fibrous  cord,  which 
in  the  adult  may  be  traced  along  the  fissure  of  the  ductus  venosus. 

Measurements  of  the  Thorax. 
Perimeters. 

At  the  level  of  the  highest  point  of  the  axilla 89.52  cm. 

nipple 86.64cm. 

storno-xiphoid  articulation 81.88  cm. 

Diameters. 

Transverse,  between  the  eighth  intercostal  spaces 28     cm. 

Antero-posterior.  at  the  level  of  the  ensiform  cartilage 20     cm. 

Vertical,  anterior  wall 15.5cm. 

posterior  wall 31.5  cm. 

(2.54  cm.  =  1  inch.)  (Joessel.) 


THE  ORGANS  OF  VOICE  AND  RESPIRATION. 


THE    LARYNX. 

fTlHE  Larynx  is  the  organ  of  voice,  placed  at  the  upper  part  of  the  air-passage. 
X  It  is  situated  between  the  trachea  and  base  of  the  tongue,  at  the  upper  and 
fore  part  of  the  neck,  where  it  forms  a  considerable  projection  in  the  middle  line. 
On  either  side  of  it  lie  the  great  vessels  of  the  neck  ;  behind,  it  forms  part  of  the 
anterior  boundary  of  the  pharynx,  and  is  covered  by  the  mucous  membrane  lining 
that  cavity. 

The  larynx  is  broad  above,  where  it  presents  the  form  of  a  triangular 
box,  flattened  behind  and  at  the  sides,  and  bounded  in  front  by  a  prominent 
vertical  ridge.  Below,  it  is  narrow  and  cylindrical.  It  is  composed  of  cartilages 
which  are  connected  together  by  ligaments  and  moved  by  numerous  muscles  ; 
the  interior  is  lined  by  mucous  membrane  and  supplied  with  vessels  and  nerves. 

The  Cartilages  of  the  Larynx  are  nine  in  number,  three  single  and  three  pairs : 


Two  Arytenoid. 

Two  Cornicula  Laryngis. 

Two  Cuneiform. 


Thyroid. 

Cricoid. 

Epiglottis. 

The  Thyroid  (dupeoz,  a  shield)  is  the  largest 
cartilage  of  the  larynx.  It  consists  of  two 
lateral  lamellae  or  alse,  united  at  an  acute 
angle  in  front,  forming  a  vertical  projection 
in  the  middle  line  which  is  prominent  above 
and  called  the  pomum  Adami.  This  projec- 
tion is  subcutaneous,  more  distinct  in  the  male 
than  in  the  female,  and  occasionally  separated 
from  the  integument  by  a  bursa  mucosa. 

Each  lamella  is  quadrilateral  in  form.  Its 
outer  surface  presents  an  oblique  ridge  which 
passes  downward  and  forward  from  a  tubercle 
situated  near  the  root  of  the  superior  cornu. 
This  ridge  gives  attachment  to  the  Sterno- 
thyroid  and  Thyro-hyoid  muscles,  and  the  por- 
tion of  cartilage  included  between  it  and  the 
posterior  border,  to  part  of  the  Inferior  con- 
strictor muscle. 

The  inner  surface  of  each  ala  is  smooth, 
slightly  concave,  and  covered  by  mucous  mem- 
brane above  and  behind ;  but  in  front,  in  the 
receding  angle  formed  by  their  junction,  are 
attached  the  epiglottis,  the  true  and  false  vocal 
cricoid-c6^tnKsViewofthethyr°idand  cords,  the  Thyro-arytenoid  and  Thyro-epiglot- 

tidean  muscles. 

The  upper  border  of  the  thyroid  cartilage  is  sinuously  curved,  being  concave  at 
its  posterior  part,  just  in  front  of  the  superior  cornu,  and  then  rising  into  a  convex 
outline,  which  dips,  in  front,  to  form  the  sides  of  a  notch  or  incisura  in  the  middle 
line  immediately  above  the  pomum  Adami.  This  border  gives  attachment  through- 
out its  whole  extent  to  the  thyro-hyoid  membrane. 
1100 


THE   LARYNX. 


1101 


Epiglottis. 


From  above  the  lower  border  posteriorly,  there  passes  to  the  cricoid  cartilage, 
in  and  on  each  side  of  the  median  line,  the  crico-thyroid  membrane,  on  each  side 
of  which  is  the  Crico-thyroid  muscle. 

The  posterior  borders  terminate  above  in  the  superior  cornua,  and  below  in  the 
inferior  cornua.  The  two  superior  cornua,  long  and  narrow,  directed  upward, 
backward,  and  inward,  terminate  each  in  a  conical  extremity  which  gives  attach- 
ment to  the  lateral  thyro-hyoid  lig- 
ament. The  two  inferior  cornua 
are  short  and  thick ;  they  pass 
downward,  with  a  slight  inclina- 
tion forward  and  inward,  and  pre- 
sent each  on  its  inner  surface  a  small 
oval  articular  facet  for  articulation 
with  the  side  of  the  cricoid  carti- 
lage. On  the  posterior  border  are 
inserted  the  Stylo-pharyngeus  and 
Palato-pharyngeus  muscles. 

The  Cricoid  Cartilage  is  so  called 
from  its  resemblance  to  a  signet- 
ring  (xfjcxo;.  a  ring).  It  is  smaller, 
but  thicker  and  stronger  than  the 
thyroid  cartilage,  and  forms  the 
lower  part  of  the  cavity  of  the 
larynx. 

Its  anterior  half  (annulus)  is 
narrow,  convex,  affording  attach- 
ment at  the  sides  to  the  Crico- 
thyroid  muscles,  and  behind  to 
part  of  the  Inferior  constrictor. 

Its  post •:/•<<>/•  half  (lamina)  is 
very  broad  both  from  side  to  side 
and  from  above  downward :  it  pre- 
sents posteriorly  in  the  middle  line 
a  vertical  ridge  (linea  eminens)  for 
the  attachment  of  the  longitudinal 
fibres  of  the  oesophagus,  and  on 
either  side  a  broad  depression  (fo- 
vea)  for  the  Crico-arytenoideus  pos- 
ticus  muscle. 

At  the  point  of  junction  of  the 
two  halves  of  the  cartilage  on 
either  side  is  a  small  round  ele- 
vated facet  for  articulation  with 
the  inferior  cornu  of  the  thyroid 
cartilage. 

The  lower  border  of  the  cricoid 
cartilage  is  horizontal  and  connected  to  the  upper  ring  of  the  trachea  by  fibrous 
membrane. 

Its  upper  border  is  directed  obliquely  upward  and  backward,  owing  to  the 
height  of  the  lamina.  The  upper  border  of  the  lamina  is  surmounted  on  each 
end  by  a  smooth,  oval  facet  for  articulation  with  the  arytenoid  cartilage.  Between 
these  articular  surfaces  is  a  slight  notch.  To  the  rest" of  the  upper  border  of  the 
entire  cartilage,  all  the  way  around  from  one  arytenoid  facet  to  the  other,  is 
attached  the  Crico-thyro-arytenoid  ligament,  and  externally  to  this,  at  the  sides, 
the  lateral  Crico-arytenoid  muscle. 

The  inner  surface  of  the  cricoid  cartilage  is  smooth  and  lined  by  mucous 
membrane. 


Posterior 
surface. 


Arytenoid  cartilages,  bate. 


Insertion  of 

CRICO-ARYTENOIDEUS 
POSTICUS  ET  LATERALIS 


Cricoid. 
Articular  facet  for 
arytenoid  cartilage. 


Articular  facet  for_  _ 
inferior  cornu  of 
thyroid  cartilage. 


FIG.  TOO.— The  cartilages  of  the  larynx.    Posterior  view. 


1102  THE    ORGANS    OF    VOICE   AND   RESPIRATION. 

The  Arytenoid  Cartilages,  so  called  from  dp'jraiva,  a  ladle,  are  two  in  number, 
and  each  is  situated  at  the  end  of  the  upper  border  of  the  lamina  of  the  cricoid 
cartilage.  Each  cartilage  is  pyramidal  in  form,  and  presents  for  examination  three 
surfaces,  a  base,  and  an  apex. 

The  posterior  surface  is  triangular,  smooth,  concave,  and  gives  attachment  to 
the  Arytenoid  muscle. 

The  antero-external  surface  is  convex  and  rough.  It  gives  attachment  to  the 
Thyro-arytenoid  muscle ;  and  to  the  false  vocal  cord  immediately  above  a  depres- 
sion, the  fossa  triangularis,  situated  at  about  its  centre. 

The  internal  surface  is  narrow,  smooth,  and  flattened,  covered  by  mucous  mem- 
brane, and  lies  almost  in  apposition  with  the  cartilage  of  the  opposite  side. 

The  base  of  each  cartilage  is  broad,  and  presents  a  concave  (antero-posteriorly) 
smooth  surface  for  articulation  with  the  cricoid  cartilage.  Projecting  from  the  base 
are  two  processes,  one  postero-externally  and  the  other  anteriorly.  Between  the  two 
is  the  base  of  the  antero-external  surface.  The  former,  known  as  the  muscu- 
lar process,  is  short,  rounded,  and  prominent,  and  receives  the  insertion  of  the 
Posterior  and  Lateral  crico-arytenoid  muscles.  The  latter  also  prominent,  but 
more  pointed  and  flattened,  gives  attachment  to  the  true  vocal  cord.  This  is  the 
vocal  process. 

The  apex  of  each  cartilage  is  pointed,  curved  backward  and  inward,  and  sur- 
mounted by  a  small,  cone-shaped,  cartilaginous  nodule,  the  corniculum  laryngis. 

The  cornicula  laryngis  (cartilages  of  Santorini)  are  two  small,  conical  nodules, 
consisting  of  yellow  fibro-cartilage,  which  are  attached  to  the  summit  of  the  ary- 
tenoid  cartilages  and  serve  to  prolong  them  backward  and  inward.  To  them  are 
attached  the  aryteno-epiglottic  folds.  They  are  sometimes  united  to  the  arytenoid 
cartilages. 

The  cuneiform  cartilages  (cartilages  of  Wrisberg)  are  two  small,  elongated,  car- 
tilaginous bodies,  placed  one  on  each  side  in  the  fold  of  mucous  membrane,  which 
extends  from  the  apex  of  the  arytenoid  cartilage  to  the  side  of  the  epiglottis  (aryteno- 
epiglottic  fold) ;  they  give  rise  to  small  whitish  elevations  on  the  free  edge  of  the 
mucous  fold,  just  in  front  of  the  cartilages  of  Santorini. 

The  epiglottis  is  a  thin  lamella  of  fibro-cartilage,  of  a  yellowish  color,  shaped 
like  a  leaf,  and  placed  behind  the  tongue,  in  front  of  the  superior  opening  of  the 
larynx.  During  respiration  its  direction  is  vertically  upward,  its  free  extremity 
curving  forward  toward  the  base  of  the  tongue;  but  when  the  larynx  is  drawn  up 
beneath  the  base  of  the  tongue  during  deglutition,  it  is  carried  downward  and 
backward  so  as  to  close,  more  or  less  completely,  the  opening  of  the  larynx.  Its 
free  extremity  is  broad  and  rounded;  its  attached  end  is  long  and  narrow,  and 
connected  to  the  receding  angle  between  the  two  alse  of  the  thyroid  cartilage,  just 
below  the  median  notch,  by  a  ligamentous  band,  the  thyro-epiglottic  ligament.  It 
is  also  connected  to  the  posterior  surface  of  the  body  of  the  hyoid  bone  by  an 
elastic  ligamentous  band,  the  hyo-efriglottic  ligament. 

Its  anterior  or  lingual  surface  is  curved  forward  toward  the  tongue,  and  covered 
at  its  upper  part  by  mucous  membrane,  which  is  reflected  on  to  the  sides  and  base 
of  the  organ,  forming  a  median  and  two  lateral  folds,  the  glosso-epiglottic  folds. 

Its  posterior  or  laryngeal  surface  is  smooth,  concave  from  side  to  side,  concavo- 
convex  from  above  downward,  and  covered  by  mucous  membrane ;  when  this  is 
removed  the  surface  of  the  cartilage  is  seen,  to  be  studded  with  a  number  of  little 
pits  for  the  lodgment  of  mucous  glands.  To  its  sides  the  aryteno-epiglottic  folds 
are  attached.  It  is  somewhat  prominent  just  below  its  centre  (tubercle  or  cushion 
of  the  epiglottis). 

Structure. — The  cornicula  laryngis,  cuneiform  cartilages,  and  epiglottis  are  com- 
posed of  yellow  fibro-cartilage  which  shows  little  tendency  to  calcification,  but  the 
other  cartilages  are  hyaline,  becoming  more  or  less  calcified  in  old  age. 

LIGAMENTS. — The  ligaments  of  the  larynx  connect  the  thyroid  cartilage  and 
epiglottis  with  the  hyoid  bone,  thg  cricoid  cartilage  with  the  trachea,  and  the 
several  cartilages  of  the  larynx  to  each  other. 


THE  LARYNX.  1103 

The  Thyro-hyoid  Ligaments. — These  constitute  the  thyro-hyoid  membrane,  and 
the  middle  and  two  lateral  Uiyro-hyoid  ligaments. 

The  middle  thyro-hyoid  ligament  consists  of  tough,  yellowish  fibro-elastic  tissue. 
Its  lower  border  is  attached  in  the  thyroid  notch  ;  its  upper  to  the  upper  border  of 
the  posterior  surface  of  the  body  of  the  hyoid  bone,  thus  passing  behind  its  pos- 
terior surface,  and  being  separated  from  it  by  a  synovial  bursa  (sub-hyoid  bursa). 
When  the  thyro-hyoid  membrane  is  removed,  the  lateral  borders  of  this  ligament 
are  seen  to  be  free. 

The  tivo  lateral  thyro-hyoid  ligaments  are  rounded  elastic  cords,  which  pass 
between  the  superior  cornua  of  the  thyroid  cartilage  and  the  extremities  of  the 
greater  cornua  of  the  hyoid  bone.  A  small  cartilaginous  nodule  (cartilago  triticea), 
sometimes  bony,  is  frequently  found  in  each. 

The  tkyro-hyrid  membrane  fills  in  the  interval  between  each  lateral  thyro- 
hyoid  ligament  and  the  free  edge  of  the  middle  one.  In  this  situation  it  is  made 
up  of  two  layers,  cellular  tissue  externally  and  mucous  membrane  internally  and, 
just  in  front  of  the  lateral  ligament,  its  cellular  layer  is  pierced  by  the  superior 
laryngeal  vessels  and  nerve.  The  cellular  layer  is  attached  all  the  way  around, 
above  to  the  cornua  and  body  of  the  hyoid  bone,  and  below  to  the  entire  upper 
border,  incisura  as  well,  of  the  thyroid  cartilage.  It  thus  passes  in  front  of  the 
middle  thyro-hyoid  ligament,  and  here  forms  the  anterior  wall  of  the  sub-hyoid 
bursa.  A*t  the  free  edge  of  the  middle  ligament  the  mucous  membrane  passes 
behind  the  epiglottis ;  at  the  lateral  ligament  it  is  reflected  on  to  the  posterior 
wall  of  the  pharynx. 

The  hyo-epigiottic  ligament  is  a  fibrous  band,  which  extends  from  the  anterior 
surface  of  the  epiglottis  to  the  upper  border  of  the  body  of  the  hyoid  bone.  The 
thyro-epiglottic  ligament  connects  the  apex  of  the  epiglottis  with  the  receding  angle 
of  the  thyroid  cartilage  just  beneath  the  median  notch. 

The  Crico-thyro-arytenoid  Ligament. — This  is  a  strong  fibrous  lamina,  bent  on 
itself  anteriorly.  Its  attachments  are  as  follows  :  (1)  Posteriorly,  it  is  attached  to  the 
vocal  process  of  one  arytenoid  cartilage,  whence  it  extends  as  &free  edge  in  a  prac- 
tically straight  line,  forward  and  a  little  inward,  to  the  posterior  aspect  of  the  angle 
between  the  alae  of  the  thyroid  cartilage.  Here  it  bends  on  itself  at  an  acute 
angle,  is  attached  to  the  thyroid,  and  passes  backward  and  a  little  outward,  as  a 
second  free  edge,  to  be  attached  to  the  vocal  process  of  the  other  arytenoid  carti- 
lage. (2)  From  these  two  free  edges,  as  an  upper  limit,  the  lamina  passes  down- 
ward, with  an  outward  slope,  to  the  curved  sloping  upper  border  of  the  cricoid 
cartilage  which  lies  anterior  to  the  lamina  of  the  same,  and  becomes  attached  to  it 
in  its  entire  extent.  The  ligament,  as  a  whole,  is  thus  seen  to  be  V-shaped  above, 
apex  forward,  but  of  a  curved  outline  below.  Furthermore,  its  vertical  diameter 
varies,  being  smallest  behind  and  greatest  in  front  at  the  middle  line,  this  variation 
being  due  to  the  upper  border  of  the  cricoid,  which  slopes  upward  posteriorly  until 
it  almost  reaches  the  vocal  process  of  the  arytenoid. 

In  the  middle  line  the  angle  which  is  formed  in  front  by  the  bending  on  itself 
of  this  ligament  is  acute  above,  but  obtuse  or  "rounded"  below.  The  upper  part 
of  this  "  angle  "  lies  behind  and  attached  to  the  angle  of  the  thyroid  cartilage,  its 
upper  limit  (i.  e.  the  angle  of  the  free  edges)  being  at  some  distance  (almost  half- 
way up)  from  the  lower  edge  of  the  cartilage.  The  lower  or  "  rounded  "  part  is 
the  direct  continuation  downward  of  the  upper,  and  passes  to  the  middle  of  the 
upper  border  of  the  cricoid.  This  last  is  known  as  the  crico-thyroid  membrane,  is 
subcutaneous,  and  is  crossed  by  a  small  anastomotic  arterial  arch  from  the  two 
crico-thyroid  arteries. 

Latt'i'iiH.}!*  there  is  a  considerable  interval  between  the  outer  surface  of  this  liga- 
ment and  the  inner  surface  of  the  corresponding  half  of  the  thyroid  cartilage,  which 
is  filled  in  by  the  Thyro-arytenoid  and  Lateral  crico-arytenoid  muscles. 

The  upper  free  edges  of  this  ligament  are  thicker  than  the  remainder,  and  are 
known  as  the  inferior  thyro-arytenoid  ligaments.  When  covered  with  mucous  mem- 
brane they  constitute  the  true  vocal  cords.  The  inner  surfaces  of  the  crico-thyro- 


1104 


THE    ORGANS    OF  VOICE   AND    RESPIRATION. 


arytenoid  ligament  are  covered  by  mucous  membrane  prolonged  from  that  of  the 
true  cords,  and  are  the  lateral  boundaries  of  this  portion  of  the  cavity  of  the  larynx. 
The  Crico-thyroid  Ligaments. — These  are  capsular  ligaments  which  enclose  on 
each  side  the  articulation  of  the  inferior  cornu  of  the  thyroid  with  the  cricoid 
cartilage.  The  articulation  is  lined  by  synovial  membrane,  and  strengthened  by 
accessory  (kerato-cricoid)  ligaments  which  pass  from  the  tip  of  the  cornu  in  various 
directions  to  the  cricoid. 

The  crico-arytenoid  ligaments  are  two  capsular  and  two  posterior.  The  cap- 
sular are  thin  and  loose  capsules  attached  to  the  margins  of  the  articular  surfaces ; 
they  are  lined  internally  by  synovial  membrane.  The  posterior  extend  from  the 
cricoid  to  the  inner  and  back  part  of  the  base  of  the  arytenoid  cartilage. 

The  crico-tracheal  ligament  connects  the  cricoid  cartilage  with  the  first  ring  of 
the  trachea.  It  resembles  the  fibrous  membrane,  which  connects  the  rings  of  the 
trachea  to  each  other. 

INTERIOR  OF  THE  LARYNX. — The  superior  aperture  of  the  larynx  (Fig.  701)  is 
a  cordiform  opening,  wide  in  front,  narrow  behind,  and  sloping  obliquely  downward 
and  backward.  It  is  bounded  in  front  by  the  epiglottis,  behind  by  the  inter-ary- 
tenoid  fold  of  mucous  membrane  passing  between  the  arytenoid  cartilages,  and  lat- 
erally, by  a  fold  of  mucous  membrane  enclosing  areolar  tissue  and  muscular  fibres, 
stretched  between  the  sides  of  the  epiglottis  and  the  apex  of  the  arytenoid  carti- 
lages :  these  are  the  aryteno-epiglottic  folds,  on  the  margins  of  which  the  cuneiform 
cartilages  and  cornicula  form  more  or  less  distinct  whitish  prominences. 

The  cavity  of  the  larynx  extends  from  the  superior  aperture  to  the  lower 
border  of  the  cricoid  cartilage.  It  is  divided  into  two  parts  by  the  projection 
inward  of  the  true  vocal  cords  ;  between  the  two  cords  is  a  long  and  narrow  trian- 
gular fissure  or  chink,  the  glottis,  of  which  the  boundary  is  the  rima  glottidis.  The 
portion  of  the  cavity  of  the  larynx  above  the  true  vocal  cords  is  broad,  and  contains 
the  false  vocal  cords,  between  each  of  which  and  the  corresponding  true  vocal  cord 
is  the  corresponding  ventricle  of  the  larynx.  The  portion  below  the  true  vocal 
cords  is  at  first  elliptical,  and  lower  down  circular,  in  form. 

The  glottis  is  the  narrow  fissure  or  chink  between  the  inferior  or  true  vocal 
cords  in  front  (inter-ligamentous  portion),  and  the  vocal  processes  of  the  arytenoid 

cartilages  behind  (intercartilag- 
inous  portion).  It  is  the  nar- 
rowest part  of  the  cavity  of  the 
larynx.  Its  length  in  the  male 
measures  rather  less  than  an 
inch,  its  breadth  when  dilated 
varying  at  its  widest  part  from 
a  third  to  half  an  inch.  The 
form  of  the  glottis  varies.  In 
its  half-closed  condition  it  is  a 
narrow  fissure,  a  little  enlarged 
and  rounded  behind.  In  quiet 
breathing  it  is  somewhat  trian- 
gular, the  base  of  the  triangle 
directed  backward,  and  corre- 
sponding to  the  space  between 
the  arytenoid  cartilages.  When 
widely  open  it  is  lozenge -shaped. 
In  forcible  expiration  it  is 
smaller  than  during  inspiration. 
When  sound  is  produced  it  is 

more  narrowed,  the  edges  of  the  vocal  cords  being  approximated  and  made  parallel, 
the  approximation  and  tension  corresponding  to  the  height  of  the  note  produced.1 

1  On  the  shape  of  the  rima  glottidis  in  the  various  conditions  of  breathing  and  speaking,  see 
Czermak,  On  the  Laryngoscope,  translated  for  the  New  Sydenham  Society. 


V 

FIG.  701.— The  larynx  and  adjacent  parts,  seen  from  above. 


THE    LARYNX. 


1105 


The  *ni.>i:i'i"i-  or  false  vocal  cords,  so  called  because  they  are  not  directly 
concerned  in  the  production  of  the  voice,  are  two  folds  of  mucous  membrane, 
each  enclosing  a  delicate  rounded  band,  the  superior  thyro-arytenoid  ligament. 
This  ligament  consists  of  areolar  tissue,  attached  in  front  to  the  angle  of  the  thy- 
roid cartilage  below  the  epiglottis,  and  behind  to  the  antero-external  surface  of  the 
arytenoid  cartilage,  just  above  the  fossa  triangularis.  This  ligament,  enclosed  in 
mucous  membrane,  forms  a  free  margin,  which  constitutes  the  upper  boundary  of 
the  corresponding  ventricle  of  the  larynx. 

The  inferior  or  true  vocal  cords,  so  called  from  their  being  concerned  in  the 
production  of  sound,  are  two  strong  fibrous  bands  (inferior  ihyro-arytenoid  liga- 
nicut*).  covered  on  their  surface  by  a  thin  layer  of  mucous  membrane.  These 
ligaments  have  already  been  described.  Each  forms  the  lower  boundary  of  the 
corresponding  ventricle  of  the  larynx.  Externally,  the  Thyro-arytenoideus  (inner 
portion)  muscle  lies  parallel  with  it. 

The  ventricle  of  the  larynx  is  an  oblong  fossa  situated  between  the  superior 
and  inferior  vocal  cords  on  each  side,  and  extending  nearly  their  entire  length. 
This  fossa  is  bounded  above  by  the  free  crescentric  edge  of  the  superior  vocal 
cord,  below  bv  the  straight  margin  of 

•/  O  O 

the  true  vocal  cord,  externally  by  the 
mucous  membrane  covering  the  inner 
surface  of  the  corresponding  Thyro-ary- 
tenoideus muscle  (outer  portion).  The 
anterior  part  of  the  ventricle  leads  up 
by  a  narrow  opening  into  a  caecal  pouch 
of  mucous  membrane  of  variable  size 
called  the  laryngeal  pouch. 

The  saccuhis  laryngis,  or  laryngeal 
pouch,  is  a  membranous  sac  placed 
between  the  superior  vocal  cord  and 
the  inner  surface  of  the  thyroid  carti- 
lage, occasionally  extending  as  far  as 
its  upper  border ;  it  is  conical  in  form, 
and  curved  slightly  backward.  On  the 
surface  of  its  mucous  membrane  are  the 
openings  of  sixty  or  seventy  small  fol- 
licular  glands  which  are  lodged  in  the 
sub  mucous  areolar  tissue.  This  sac  is 
enclosed  in  a  fibrous  capsule  continuous 
below  with  the  superior  thyro-arytenoid 
ligament :  its  laryngeal  surface  is  cov- 
ered by  muscular  fibres  derived  from 
from  those  found  in  the  aryteno-epiglot- 
tic  fold  (Aryteno-epiglottideus  inferior 
muscle.  Compressor  sacculi  laryngis, 
Hilton),  whilst  its  exterior  is  covered  by  the  Thyro-arytenoideus  and  Thvro-epi- 
glottideus  muscles. 

Muscles.— The  muscles  of  the  larynx  are  eight  in  number,  and  are  as  follows : 

The  Orieoid-thyroid  is  triangular  *in  form,  and  situated  at  the  fore  part  and  side 
of  the  cricoid  cartilage.  It  arises  from  the  front  and  lateral  part  of  the  cricoid 
cartilage  :  its  fibres  diverge,  passing  obliquely  upward  and  outward  to  be  inserted 
into  the  lower  border  of  the  thyroid  cartilage  and  into  the  anterior  border  of  the 
lower  cornua. 

The  inner  borders  of  these  two  muscles  are  separated  in  the  middle  line  by  a 
triangular  interval  occupied  by  the  crico-thyroid  membrane. 

The   Orico-arytenoideu*  posticu*  arises  from  the  broad  depression  occupying 
each  lateral  half  of  the  posterior  surface  of  the  lamina  of  the  cricoid  cartilage ;  its 
fibres  pass  upward  and  outward,  converging  to  be  inserted  into  the  muscular  pro- 
70 


Vocal  cords, 

ventricle  - 

between  thtm 


Aryteno- 
•piglottic  fold. 


Arytenoid 
cartilage. 


.RYTENCIDCUS 
MUSCLE. 


Crico-thyroid 
membrane.  ~ 


Trachea. 

FIG.  702.— Vertical  section  of  the  larynx  and  upper 
part  of  the  trachea. 


1106 


THE    ORGANS    OF   VOICE   AND    RESPIRATION. 


cess  of  the  base  of  the  arytenoid  cartilage.     The  upper  fibres  are  nearly  horizontal, 
the  middle  oblique,  and  the  lower  almost  vertical.1 

The  Crico-arytenoideus  lateralis  is  smaller  than  the  preceding,  and  of  an 
oblong  form.  It  arises  from  the  upper  border  of  the  side  of  the  cricoid  cartilage, 
and,  passing  obliquely  upward  and  backward,  is  inserted  into  the  muscular  process 
of  the  base  of  the  arytenoid  cartilage  in  front  of  the  preceding  muscle. 

The  Arytenoideus  is  a  single  muscle  filling  up  the  posterior  concave  surface 
of  the  arytenoid  cartilages.  It  arises  from  the  posterior  surface  and  outer  border 

of  one  arytenoid  cartilage,  and  is  in- 
serted into  the  corresponding  parts  of 
the  opposite  cartilage.  It  consists  of 
three  planes  of  fibres,  two  oblique  and 
one  transverse.  The  oblique  fibres, 
the  most  superficial,  form  two  fasciculi, 


Cornicida 
laryngis. 


Articular  facet  for 
inferior  cornu  of 
thyroid  cartilage. 


FIG.  70S.— Muscles  of  larynx, 
of  thyroid  cartilage  removed. 


Side  view.    Right  ala 


FIG.  704.— Interior   of  the   larynx,   seen 
above.    (Enlarged.) 


from 


which  pass  from  the  base  of  one  cartilage  to  the  apex  of  the  opposite  one.  The 
transverse  fibres,  the  deepest  and  most  numerous,  pass  transversely  across  between 
the  two  cartilages ;  hence  the  Arytenoideus  was  formerly  considered  as  several  mus- 
cles, under  the  name  of  transversi  and  obliqui.  A  few  of  the  oblique  fibres  are 
usually  continued  round  the  outer  margin  of  the  cartilage,  and  blend  with  the 
Thyro-arytenoid  or  the  Aryteno-epiglottideus  superior  muscle.2 

The  Thyro-arytenoideus  is  a  broad,  flat  muscle,  which  lies  parallel  with  the  outer 
side  of  the  true  vocal  cord.  It  arises  in  front  from  the  lower  half  of  the  receding 
angle  of  the  thyroid  cartilage  and  from  the  crico-thyroid  membrane.  Its  fibres 
pass  backward  and  outward,  to  be  inserted  into  the  arytenoid  cartilage.  This 
muscle  consists  of  two  fasciculi.  The  inner  portion,  the  thicker,  is  inserted  into 
the  vocal  process  of  the  base  of  the  arytenoid  cartilage  and  into  the  adjacent  por- 

1  Dr.  Merkel  of  Leipsic  has  described  a  muscular  slip  which  occasionally  extends  between  the 
outer  border  of  the  posterior  surface  of  the  cricoid  cartilage  and  the  posterior  margin  of  the  inferior 
cornu  of  the  thyroid;  this   he  calls  the  "Musculus   kerato-cricoideus."     It  is  not  found  in  every 
larynx,  and  when  present  exits  usually  only  on  one  side,  but  is  occasionally  found  on  both  sides. 
Sir  William  Turner  (Edinburgh  Medictd  Journal,  Feb.,  1860)  states  that  it  is  found  in  about  one  case 
in  five.     Its  action  is  to  fix  the  lower  horn  of  the  thyroid  cartilage  backward  and  downward,  oppos- 
ing in  some  measure  the  part  of  the  Crico-thyroid  muscle  which  is  connected  to  the  anterior  margin 
of  the  horn. 

2  The  arytenoideus  reclus  (Luschka)  is  a  small  slip  passing  between  the  posterior  surface  of  the 
arytenoid  cartilage  below  to  the  cartilage  of  Santorini  (corniculum)  above.    Anatomy,  Hyrtl,  p.  718. 


THE   LARYXX.  1107 

tion  of  its  antero-external  surface ;  it  lies  parallel  with  the  true  vocal  cord,  to 
which  it  is  adherent.  The  outer  or  superior  fasciculus,  the  thinner,  is  inserted 
into  the  muscular  process  and  outer  border  of  the  arytenoid  cartilage  above  the 
preceding  fibres ;  it  lies  on  the  outer  side  of  the  sacculus  laryngis.1 

The  TJtyro-epiglottideus  is  a  delicate  fasciculus  which  arises  from  the  angle  of 
the  thyroid  cartilage,  close  to  the  origin  of  the  Thyro-arytenoid,  and  spreads  out 
upon  the  outer  surface  of  the  sacculus  laryngis ;  some  of  its  fibres  are  lost  in  the 
aryteno-epiglottic  fold,  whilst  others  pass  to  the  margin  of  the  epiglottis  (Depressor 
epiglottidis). 

The  Aryteno-epiglottideus  superior  consists  of  a  few  delicate  fasciculi,  which 
arise  from  the  apex  of  the  arytenoid  cartilage  and  become  lost  in  the  aryteno-epi- 
glottic  fold. 

The  Aryt:  no-epiglottideus  inferior  (Compressor  sacculi  laryngis,  Hilton),  arises 
from  the  arytenoid  cartilage  just  below  the  preceding ;  and  passes  forward  and  up- 
ward, it  spreads  out  upon  the  inner  surface  of  the  laryngeal  pouch.2 

Actions. — In  considering  the  action  of  the  muscles  of  the  larynx,  they  may 
be  conveniently  divided  into  two  groups,  viz. :  1.  Those  which  open  and  close 
the  glottis.  '2.  Those  which  regulate  the  degree  of  tension  of  the  vocal  cords. 

1.  The  muscles  which  open  the  glottis  are  the  Crico-arytenoidei  postici ;  and 
those  which  close  it  are  the  Arvtenoideus  and  the  Crico-arytenoidei  laterales. 
'2.  The  muscles  which  regulate  the  tension  of  the  vocal  cords  are  the  Crico- 
thyroidei.  which  tense  and  elongate  them  :  and  the  Thyro-arytenoidei,  which  relax 
and  shorten  them.  The  Thyro-epiglottideus  is  a  depressor  of  the  epiglottis,  and 
the  Aryteno-epiglottidei  constrict  the  superior  aperture  of  the  larynx,  compress 
the  sacculi  laryngis,  and  empty  them  of  their  contents. 

The  Cricn-arytfnoidt ! posti<-i  separate  the  chordae  vocales.  and  consequently  open  the  glottis, 
by  rotating  the  arytenoid  cartilages  outward  around  a  vertical  axis  passing  through  the  crico- 
arytenoid  joints,  so  that  their  anterior  angles  and  the  ligaments  attached  to  them  become  widely 
separated,  the  vocal  cords  at  the  same  time  being  made  tense. 

The  Grioo-arytaioidt  i  laterales  close  the  glottis  by  rotating  the  arytenoid  cartilages  inward 
so  as  to  approximate  their  anterior  angles. 

The  Aryttitni'i]'  »/.*  muscle*  approximate  the  arytenoid  cartilages,  and  thus  close  the  opening 
of  the  glottis,  especially  at  its  back  part. 

The  Crtco-thyroi'l  un!.«-les  produce  tension  and  elongation  of  the  vocal  cords.  This  is 
effected  as  follows :  the  thyroid  cartilage  is  fixed  by  the  Thyro-hyoid  muscles ;  then  the 
Crico-thyroid  muscles,  when  they  act.  draw  upward  the  front  of  the  cricoid  cartilage,  and  so 
depress  the  posterior  portion,  which  carries  with  it  the  arytenoid  cartilages,  and  thus  elongate 
the  vocal  o'.rils. 

The  Tkyro-cerytauHdei  muscles,  consisting  of  two  parts  having  different  attachments  and 
different  directions,  are  rather  complicated  as  regards  their  action.  Their  main  use  is  to  draw 
the  ar.vte.noid  cartilages  forward  toward  the  thyroid,  and  thus  shorten  and  relax  the  vocal  cords. 
But.  owing  to  the  connection  of  the  inner  portion  with  the  vocal  cord,  this  part,  if  acting  sep- 
arately, is  supposed  to  modify  its  elasticity  and  tension,  and  the  outer  portion,  being  inserted 
into  the  outer  part  of  the  anterior  surface  of  the  arytenoid  cartilage,  may  rotate  it  inward,  and 
thus  narrow  the  rima  elottidis  by  bringing  the  two  cords  together. 

The  Thyro-qpiglottidei  depress  the  epiglottis  and  assist  in  compressing  the  sacculi  laryngis. 
The  Aryteno-epiglottideus  superior  constricts  the  superior  aperture  of  the  larynx,  when  it 
is  drawn  upward,  during  deglutition,  and  the  opening  closed  by  the  epiglottis.  The  Aryteno- 
epiglottideus  inferior,  together  with  some  fibres  of  the  Thyro-arytenoidei,  compress  the  sacculus 
laryngis. 

The  Mucous  Membrane  of  the  Larynx  is  continuous  above  with  that  lining  the 
mouth  and  pharynx,  and  is  prolonged  through  the  trachea  and  bronchi  into  the 
lungs.  It  lines  the  posterior  and  upper  part  of  the  anterior  surface  of  the  epiglot- 
tis, to  which  it  is  closely  adherent,  and  forms  the  aryteno-epiglottic  folds  which 

1  Henle  describes  these  two  portions  as  separate  muscles,  under  the  names  of  External  and 
Internal  thyro-arytenoid. 

:  MuscTLfs  TRiTiCEO-GLOssrs,  Bochdalek.  jun.  (Prager  VierteljaArssehrift,  2d  part,  1866), 
describes  a  muscle  hitherto  entirely  OTerlooked,  except  a  brief  statement  in  Henle's  Anatomy,  which 
arises  from  the  nodule  of  cartilage  (corpus  triticeum]  in  the  posterior  thyro-hyoid  ligament,  and  passes 
forward  and  upward  to  enter  the  tongue  along  with  the  Hyo-glossus  muscle.  He  met  with  this 
muscle  eight  times  in  twenty -two  subjects.  It  occurred  in  both  sexes,  sometimes  on  both  sides,  at  others 
ou  one  onlv. 


1108  THE    ORGANS    OF    VOICE   AND    RESPIRATION. 

encircle  the  superior  aperture  of  the  larynx.  It  lines  the  whole  of  the  cavity  of 
the  larynx ;  forms,  by  its  reduplication,  the  chief  part  of  the  superior  or  false 
vocal  cord ;  and,  from  the  ventricle,  is  continued  into  the  sacculus  larvngis.  It 
is  then  reflected  over  the  true  vocal  cords,  where  it  is  thin  and  very  intimately 
adherent;  covers  the  inner  surface  of  the  crico-thyroid  membrane  and  cricoid 
cartilage ;  and  is  ultimately  continuous  with  the  lining  membrane  of  the  trachea. 
It  is  covered  with  columnar  ciliated  epithelium  below  the  superior  vocal  cord, 
but  above  this  point  the  cilia  are  found  only  in  front,  as  high  as  the  middle 
of  the  epiglottis.  In  the  rest  of  its  extent  the  epithelium  is  of  the  squamous 
variety ;  as  is  also  that  covering  the  true  vocal  cords. 

Grlands. — The  mucous  membrane  of  the  larynx  is  furnished  with  numerous 
muciparous  glands,  the  orifices  of  which  are  found  in  nearly  every  part ;  they 
are  very  numerous  upon  the  epiglottis,  being  lodged  in  little  pits  in  its  substance ; 
they  are  also  found  in  large  numbers  along  the  posterior  margin  of  the  aryteno- 
epiglottidean  fold,  in  front  of  the  arytenoid  cartilages,  where  they  are  termed  the 
arytenoid  glands.  They  exist  also  in  large  numbers  upon  the  inner  surface  of  the 
sacculus  laryngis.  None  are  found  on  the  vocal  cords. 

Vessels  and  Nerves. — The  arteries  of  the  larynx  are  the  laryngeal  branches 
derived  from  the  superior  and  inferior  thyroid.  The  veins  accompany  the  arteries : 
those  accompanying  the  superior  laryngeal  artery  join  the  superior  thyroid  vein 
which  opens  into  the  internal  jugular  vein ;  while  those  accompanying  the  inferior 
laryngeal  artery  join  the  inferior  thyroid  vein  which  opens  into  the  innominate 
vein.  The  lymphatics  terminate  in  the  deep  cervical  glands.  The  nerves  are  the 
superior  laryngeal  and  the  inferior  or  recurrent  laryngeal  branches  of  the  pneumo- 
gastric  nerves,  joined  by  filaments  from  the  sympathetic.  The  superior  laryngeal 
nerves  supply  the  mucous  membrane  of  the  larynx  and  the  Crico-thyroid  muscles. 
The  inferior  laryngeal  nerves  supply  the  remaining  muscles.  The  Arytenoid 
muscle  is  supplied  by  both  nerves. 

THE  TRACHEA  (Fig.  705). 

The  Trachea,  or  Windpipe,  is  a  cartilaginous  and  membranous  cylindrical  tube, 
flattened  posteriorly,  which  extends  from  the  lower  part  of  the  larynx,  on  a  level 
with  the  sixth  cervical  vertebra,  to  opposite  the  fourth,  or  sometimes  the  fifth, 
dorsal,  where  it  divides  into  the  two  bronchi,  one  for  each  lung.  The  trachea 
measures  about  four  inches  and  a  half  in  length  (10-11  cm.) ;  its  diameter,  from 
side  to  side,  is  from  three-quarters  of  an  inch  to  an  inch  (2-2J  cm.),  being  always 
greater  in  the  male  than  in  the  female. 

Relations. — The  anterior  surface  of  the  trachea  is  convex,  and  covered  in  the 
neck,  from  above  downward,  by  the  isthmus  of  the  thyroid  gland,  the  inferior 
thyroid  veins,  the  arteria  thyroidea  ima  (when  that  vessel  exists),  the  Sterno-hyoid 
and  Sterno-thyroid  muscles,  the  cervical  fascia,  and  more  superficially,  by  the 
anastomosing  branches  between  the  anterior  jugular  veins  :  in  the  thorax  it  is 
covered  from  before  backward  by  the  first  piece  of  the  sternum,  the  remains  of  the 
thymus  gland,  the  left  innominate  vein,  the  arch  of  the  aorta,  the  innominate  and 
left  common  carotid  arteries,  and  the  deep  cardiac  plexus.  Posteriorly,  it  is  in 
relation  with  the  oesophagus ;  laterally,  in  the  neck,  it  is  in  relation  with  the  com- 
mon carotid  arteries,  the  lateral  lobes  of  the  thyroid  gland,  the  inferior  thyroid 
arteries,  and  recurrent  laryngeal  nerves ;  and  in  the  thorax  it  lies  in  the  space 
between  the  pleurae  (superior  mediastinum) ;  having  the  pneumogastric  nerve  on 
each  side  of  it. 

The  Right  Bronchus,  wider,  shorter,  and  more  horizontal  in  direction  than  the 
left,  is  about  an  inch  in  length,  and  enters  the  right  lung  opposite  the  fifth  dorsal 
vertebra.  The  vena  azygos  major  arches  over  it  from  behind,  and  the  right  pul- 
monary artery  lies  below  and  then  in  front  of  it.  About  three-quarters  of  an  inch 
from  its  origin  it  gives  off  a  branch  to  the  upper  lobe  of  the  right  lung.  This 
branch  is  known  as  eparterial  because  it  is  given  off  above  the  right  pulmonary 
artery,  below  which  the  main  bronchus  now  passes  and  is  known  as  hyparterial ; 


THE    TRACHEA. 


1109 


this  subdivides  into  two  branches  for  the  middle  and  lower  lobes  of  the  right 
lung. 

The  Left  Bronchus  is  smaller,  longer,  and  more  oblique  than  the  right,  being 
nearly  two  inches  in  length.  It  enters  the  root  of  the  left  lung  opposite  the  sixth 
dorsal  vertebra,  about  an  inch  lower  than  the  right  bronchus.  It  passes  beneath 
the  arch  of  the  aorta,  crosses,  in  front  of  the  oesophagus,  the  thoracic  duct  and 


Superior 
Cornu. 


FIG.  705. — Front  view  of  cartilages  of  larynx;  the  trachea  and  bronchi. 


the  descending  aorta,  and  has  the  left  pulmonary  artery  lying  at  first  above  and 
then  in  front  of  it.  It  is  entirely  hyparterial,  having  no  eparterial  branch,  and 
divides  into  two  branches  for  the  upper  and  lower  lobes  of  the  left  lung.  If  a 
transverse  section  is  made  across  the  trachea  a  short  distance  above  its  point  of 
bifurcation,  it  is  seen,  in  many  cases,  on  looking  down  the  tube  that  the  right 
bronchus  appears  to  continue  the  direction  of  the  trachea  more  directly  than  does 
the  left. 

Subdivisions  of  the  Bronchi. — According  to  Aeby,  whose  observations  are  based 
on  casts  of  the  trachea  and  bronchi  made  with  Roser's  fusible  alloy,  the  following 
is  the  arrangement  of  the  bronchi  and  larger  bronchial  tubes  (Fig.  706) :  The  right 
{'/••-'itchus,  after  giving  off  the  eparterial  branch,  becomes  hyparterial,  which  the  left 
bronchus  is  from  the  beginning.  Each  bronchus  then  passes  downward  and  back- 


1110 


THE    ORGANS    OF    VOICE   AND    RESPIRATION. 


ward,  constantly  diminishing  in  calibre  until  it  ends,  as  such,  in  the  lower  and  pos- 
terior part  of  the  inferior  lobe  of  the  corresponding  lung.  In  its  course  each  bronchus 
gives  off  four  ventral  and  four  dorsal  branches,  the  right  bronchus  also  giving  off 
an  additional  or  accessory  bronchus,  the  so-called  "heart-bronchus"  which  passes 
mesially  and  dorsally  into  the  inferior  lobe.  Its  name  comes  from  the  fact  that  it 
is  the  homologue  of  a  bronchus  which,  in  certain  animals,  runs  to  the  infracardiac 


Bight  bronchus 
Eparterial  branch 


End  of  bronchus 


End  of  bronchus 


FIG.  706.— Diagram  (after  Aeby)  of  a  cast  of  the  "bronchial-tree:"    v1,  v2,  v3,  v4,  the  ventral  branches; 
d1,  d2,  d3,  d4,  the  dorsal  branches ;  C,  the  "  heart-bronchus." 

lobe.  Of  the  right  bronchus,  the  first  ventral  branch  goes  to  the  middle  lobe  ;  the 
other  ventral  and  all  the  dorsal  passing  to  the  inferior  lobe.  Of  the  left  bronchus, 
the  first  ventral  branch  passes  to  the  superior  lobe,  all  the  others,  ventral  and 
dorsal,  going  to  the  inferior  lobe.  All  these  branches,  on  both  sides,  are  hyp- 
arterial  as  well  as  the  "  heart-bronchus."  The  characteristic  general  course  of  each 
bronchus  is  outlined  in  the  Diagram. 

Structure. — The  trachea  is  composed  of  imperfect  cartilaginous  rings,  fibrous 
membrane,  muscular  fibres,  mucous  membrane,  and  glands. 

The  cartilages  vary  from  sixteen  to  twenty  in  number ;  each  forms  an  imper- 
fect ring  which  surrounds  about  two-thirds  of  the  cylinder  of  the  trachea,  which  is 
completed  behind  by  fibrous  membrane.  The  cartilages  are  placed  horizontally 
above  each  other,  separated  by  narrow  membranous  intervals.  They  measure 
about  two  lines  in  depth  and  half  a  line  in  thickness.  Their  outer  surfaces  are 
flattened,  but  internally  they  are  convex  from  being  thicker  in  the  middle  than  at 
the  margins.  Two  or  more  of  the  cartilages  often  unite  partially  or  completely, 
and  are  sometimes  bifurcated  at  their  extremities.  They  are  highly  elastic,  but 
sometimes  become  calcified  in  advanced  life.  In  the  right  bronchus  the  cartilages 
vary  in  number  from  six  to  eight ;  in  the  left,  from  nine  to  twelve.  They  are 
shorter  and  narrower  than  those  of  the  trachea. 


THE  TRACHEA.  1111 

The  first  cartilage  is  broader  than  the  rest,  and  sometimes  divided  at  one  end ; 
it  is  connected  by  fibrous  membrane  with  the  lower  border  of  the  cricoid  cartilage, 
with  which  or  with  the  succeeding  cartilage  it  is  sometimes  blended. 

The  last  cartilage  is  thick  and  broad  in  the  middle,  in  consequence  of  its  lower 
border  being  prolonged  into  a  triangular  hook-shaped  process  which  curves  down- 
ward and  backward  between  the  two  bronchi.  It  terminates  on  each  side  in  an 
imperfect  ring  which  encloses  the  commencement  of  the  bronchi.  The  cartilage 
above  the  last  is  somewhat  broader  than  the  rest  at  its  centre. 

The  Fibrous  Membrane. — The  cartilages  are  enclosed  in  an  elastic  fibrous 
membrane  which  forms  a  double  layer,  one  layer,  the  thicker  of  the  two,  passing 
over  the  outer  surface  of  the  ring,  the  other  over  the  inner  surface ;  at  the  upper 
and  lower  margins  of  the  cartilages  these  two  layers  blend  together  to  form  a  single 
membrane,  which  connects  the  rings  one  with  another.  They  are  thus,  as  it  were, 
imbedded  in  the  membrane.  In  the  space  behind,  between  the  extremities  of  the 
rings,  the  membrane  forms  a  single  distinct  layer. 

The  muscular  fibres  are  of  the  unstriped  variety  and  are  disposed  in  two  layers, 
transverse  and  longitudinal. 

The  transverse  fibres  (Trachealis  muscle,  Todd  and  Bowman),  the  most  inter- 
nal, form  a  thin  layer  which  extends  transversely  between  the  ends  of  the  carti- 
lages in  the  intervals  between  them  at  the  posterior  part  of  the  trachea.  Outside 
of  or  posterior  to  these  are  a  few  bundles  of  longitudinal  fibres. 

The  Mucous  Membrane  is  continuous  above  with  that  of  the  larynx,  and  below 
with  that  of  the  bronchi.  Microscopically,  it  presents  a  well-marked  basement 
membrane  supporting  a  layer  of  columnar  ciliated  epithelium,  between  the  deeper 
ends  of  which  are  smaller  round  or  elongated  cells.  It  contains  a  large  amount 
of  lymphoid  tissue  and  some  tracheal  glands.  Next  to  the  submucous  tissue,  the 
mucous  membrane  contains  elastic  fibres,  most  abundant  posteriorly,  where  they  are 
collected  into  distinct  longitudinal  bundles.  They  are  especially  numerous  about 
the  bifurcation  of  the  trachea. 

The  Tracheal  Glands  (racemose)  are  found  in  great  abundance  at  the  posterior 
part  of  the  trachea.  They  are  small,  placed  upon  the  outer  surface  of  the  fibrous 
layer ;  each  is  furnished  with  an  excretory  duct,  which  pierces  the  fibrous  and 
muscular  layers  and  opens  on  the  surface  of  the  mucous  membrane.  Some  glands 
of  smaller  size  are  also  found  at  the  sides  of  the  trachea,  between  the  layers  of 
fibrous  tissue  connecting  the  rings,  and  others  immediately  beneath  the  mucous 
coat.  The  secretion  from  these  glands  serves  to  lubricate  the  inner  surface  of  the 
trachea. 

Vessels  and  Nerves. — The  trachea  is  supplied  with  blood  by  the  inferior  thyroid 
arteries.  The  veins  terminate  in  the  thyroid  venous  plexus.  The  nerves  are  de- 
rived from  the  pneumogastric  and  its  recurrent  branches  and  from  the  sympathetic. 

Surface  Form. — In  the  middle  line  of  the  neck  some  of  the  cartilages  of  the  larynx  can  be 
readily  distinguished.  In  the  receding  angle  below  the  chin  the  hyoid  bone  can  easily  be  made 
out  ( see  page  230),  and  a  finger's  breadth  below  it  is  the  pomum  Adanii,  the  prominence  between 
the  upper  borders  of  the  two  alae  of  the  thyroid  cartilage.  About  an  inch  below  this,  in  the 
middle  line,  is  a  depression  corresponding  to  the  crico-thyroid  space,  in  which  the  operation  of 
laryngotomy  is  performed.  This  depression  is  bounded  below  by  a  prominent  arch,  the  anterior 
ring  of  the  cricoid  cartilage,  below  which  the  trachea  can  be  felt,  though  it  is  only  in  the  emaci- 
ated adult  that  the  separate  rings  can  be  distinguished.  The  lower  part  of  the  trachea  is  not 
easily  made  out,  for  as  it  descends  it  is  farther  removed  from  the  surface.  The  level  of  the 
vocal  nords  corresponds  to  the  middle  of  the  anterior  margin  of  the  thyroid  cartilage. 

With  the  laryngoscope  the  following  structures  can  be  seen :  The  base  of  the  tongue  and 
the  upper  surface  of  the  epiglottis,  with  the  glosso-epiglottic  folds,  the  superior  aperture  of  the 
larynx,  bounded  on  either  side  by  the  aryteno-epiglottic  folds,  in  which  may  be  seen  two  rounded 
eminences  corresponding  to  the  cornicula  and  cuneiform  cartilages.  Beneath  these,  the  true 
and  false  vocal  cords,  with  the  ventricle  between  them.  Still  deeper,  the  cricoid  cartilage  and 
some  of  the  anterior  parts  of  the  rings  of  the  trachea,  and  sometimes,  in  deep  inspiration,  the 
bifurcation  of  the  trachea. 

Surgical  Anatomy. — Foreign  bodies  often  find  their  way  into  the  air- passages.  These  may 
be  large  substance?,  as  a  piece  of  meat,  which  becomes  lodged  in  the  upper  aperture  of  the 
larynx  or  in  the  rima  glottidis,  and  cause  speedy  suffocation  unless  rapidly  got  rid  of  or  unless 


1112  THE    ORGANS    OF  VOICE   AND    RESPIRATION. 

an  opening  is  made  into  the  air- passages  below.  Smaller  bodies,  such  as  cherry-  or  plum-stones, 
small  pieces  of  bone,  buttons,  etc. ,  may  find  their  way  into  the  trachea  or  bronchus,  or  may 
become  lodged  in  the  ventricle  of  the  larynx.  The  dangers  then  depend  not  so  much  upon  the 
mechanical  obstruction  as  upon  the  spasm  of  the  glottis  which  they  excite.  When  lodged  in  the 
ventricle  of  the  larynx  they  may  produce  very  few  symptoms  beyond  sudden  loss  of  voice  or  alter- 
ation in  the  voice  sounds  immediately  following  the  inhalation  of  the  foreign  body.  When,  how- 
ever, they  are  situated  in  the  trachea,  they  are  constantly  striking  against  the  vocal  cords  during 
expiratory  efforts,  and  produce  attacks  of  dyspnosa  from  spasm  of  the  glottis.  When  lodged  in 
the  bronchus  they  usually  become  fixed  there,  and,  occluding  the  lumen  of  the  tube,  cause  a  loss 
of  the  respiratory  murmur  on  the  affected  side,  which  is  usually  the  right. 

Beneath  the  mucous  membrane  of  the  upper  part  of  the  air-passages  there  is  a  considerable 
amount  of  submucous  tissue  which  is  liable  to  become  much  swollen  from  effusion  in  inflamma- 
tory affections,  constituting  the  disease  known  as  "oedema  of  the  glottis."  This  effusion  does 
not  extend  below  the  level  of  the  vocal  cords,  on  account  of  the  mucous  membrane  being  closely 
adherent  to  these  structures.  So  that  in  cases  of  this  disease  the  operation  of  laryrigotomy  is 
sufficient. 

Chronic  laryngitis,  which  occurs  in  those  who  speak  much  in  public,  is  known  as  "clergy- 
man's sore  throat."  It  is  due  to  the  large  amount  of  cold  air  drawn  into  the  air-passages  during 
prolonged  speaking. 

Ulceration  of  the  larynx  may  occur  from  syphilis,  either  superficial  or  from  the  softening  of 
a  gumma,  from  tubercular  disease  (laryngeal  phthisis),  or  from  malignant  disease  (epithelioma). 

The  air-passages  may  be  opened  in  two  different  situations :  through  the  crico-thyroid  mem- 
brane (laryngotoniy) ,  or  in  some  part  of  the  trachea  (tracheotomy] ;  and  to  these  some  surgeons 
have  added  a  third  method,  by  opening  the  crico-thyroid  membrane  and  dividing  the  cricoid 
cartilage  with  the  upper  ring  of  the  trachea  (laryngo-tracheotomy). 

Larytigotomy  is  the  most  simple,  and  should  always  be  preferred  when  particular  circum- 
stances do  not  render  the  operation  of  tracheotomy  absolutely  necessary.  The  crico-thyroid 
membrane  is  very  superficial,  being  covered  only  in  the  middle  line  by  the  skin,  superficial  fascia, 
and  the  deep  fascia.  On  each  side  of  the  middle  line  it  is  also  covered  by  the  Sterno-hyoid  and 
Sterno-thyroid  muscles,  which  diverge  slightly  from  each  other  at  their  upper  parts,  leaving  a 
slight  interval  between  them.  On  these  muscles  rests  the  anterior  jugular  vein.  The  only  vessel 
of  any  importance  in  connection  with  this  operation  is  the  crico-thyroid  artery,  which  crosses  the 
crico-thyroid  membrane,  and  which  may  be  wounded,  but  rarely  gives  rise  to  any  trouble.  The 
operation  is  performed  thus :  The  crico-thyroid  depression  having  been  felt  for  and  found,  a 
vertical  incision  is  then  made  through  the  skin  in  the  middle  line  over  this  spot,  and  carried 
down  through  the  fascia  until  the  crico-thyroid  membrane  is  exposed.  Across  cut  is  then  made 
through  the  membrane,  close  to  the  upper  border  of  the  cricoid  cartilage,  so  as  to  avoid,  if  pos- 
sible, the  crico-thyroid  artery,  and  a  tracheotomy-tube  introduced. 

Tracheotomy  may  be  performed  either  above  or  below  the  isthmus  of  the  thyroid  body,  or 
this  structure  may  be  divided  and  the  trachea  opened  beneath  it. 

The  isthmus  of  the  thyroid  gland  usually  crosses  the  second  and  third  rings  of  the  trachea ; 
along  its  upper  border  is  frequently  to  be  found  a  large  transverse  communicating  branch  between 
the  superior  thyroid  veins ;  and  the  isthmus  itself  is  covered  by  a  venous  plexus  formed  between 
the  thyroid  veins  of  the  opposite  sides.  Theoretically,  therefore,  it  is  advisable  to  avoid  dividing 
this  structure  in  opening  the  trachea. 

Above  the  isthmus  the  trachea  is  comparatively  superficial,  being  covered  by  the  skin,  super- 
ficial fascia,  deep  fascia,  Sterno-hyoid  and  Sterno-thyroid  muscles,  and  a  second  layer  of  the 
deep  fascia,  which,  attached  above  to  the  lower  border  of  the  hyoid  bone,  descends  beneath  the 
muscles  to  the  thyroid  body,  where  it  divides  into  two  layers  and  encloses  the  isthmus. 

Below  the  isthmus  the  trachea  lies  much  more  deeply,  and  is  covered  by  the  Sterno-hyoid 
and  the  Sterno-thyroid  muscles  and  a  quantity  of  loose  areolar  tissue  in  which  is  a  plexus  of 
veins,  some  of  them  of  large  size;  they  converge  to  two  trunks,  the  inferior  thyroid  veins,  which 
descend  on  either  side  of  the  median  line  on  the  front  of  the  trachea  and  open  into  the  innomi- 
nate veins.  In  the  infant  the  thyinus  gland  ascends  a  variable  distance  along  the  front  of  the 
trachea,  and  opposite  the  episternal  notch  the  windpipe  is  crossed  by  the  left  innominate  vein. 
Occasionally  also,  in  young  subjects,  the  innominate  artery  crosses  the  tube  obliquely  above  the 
level  of  the  sternum.  The  thyroidea  iina  artery,  when  that  vessel  exists,  passes  from  below  up- 
ward along  the  front  of  the  trachea. 

From  these  observations  it  must  be  evident  that  the  trachea  can  be  more  readily  opened 
above  than  below  the  isthmus  of  the  thyroid  body. 

Tracheotomy  above  the  isthmus  is  performed  thus :  An  incision  is  made  from  an  inch  and 
a  half  to  two  inches  in  length  exactly  in  the  median  line  of  the  neck  from  the  top  of  the  cricoid 
cartilage.  After  the  superficial  structures  have  been  divided  the  interval  between  the  Sterno- 
hyoid  muscles  must  be  found,  the  raphe  divided,  and  the  muscles  drawn  apart.  The  lower 
border  of  the  cricoid  cartilage  must  now  be  felt  for,  and  the  upper  part  of  the  trachea  exposed 
from  this  point  downward  in  the  middle  line.  Bose  has  recommended  that  the  layer  of  fascia 
in  front  of  the  trachea  should  be  divided  transversely  at  the  level  of  the  lower  border  of  the 
cricoid  cartilage,  and,  having  been  seized  with  a  pair  of  forceps,  pressed  downward  with  the 
handle  of  the  scalpel.  By  this  means  the  isthmus  of  the  thyroid  gland  is  depressed,  and  is 
saved  from  all  danger  of  being  wounded,  and  the  trachea  cleanly  exposed.  The  trachea  is  now 
transfixed  with  a  sharp  hook  and  drawn  forward  in  order  to  steady  it,  and  is  then  opened  by 


THE   PLEURA. 


1113 


inserting  the  knife  into  it  and  dividing  the  two  or  three  upper  rings  from  below  upward.  If 
the  trachea  is  to  be  opened  below  the  isthmus,  the  incision  must  be  made  from  a  little  below 
the  cricoid  cartilage  to  the  top  of  the  sternum. 

In  the  child  the  trachea  is  smaller,  more  deeply  placed,  and  more  movable  than  in  the  adult. 

A  portion  of  the  larynx  or  the  whole  of  it  has  been  removed  for  malignant  disease,  laryng- 
ict<,m\j.  The  results  which  have  been  obtained  from  the  removal  of  the  whole  of  it  have  not 
been  very  satisfactory,  and  the  cases  in  which  the  operation  is  justifiable  are  very  few.  It  may 
be  removed  by  a  median  incision  through  the  soft  parts,  freeing  the  cartilage  from  the  muscles 
and  other  structures  in  front,  separating  the  larynx  from  the  trachea  below,  and  dissecting  off 
the  deeper  structure  from  below  upward. 

THE  PLEURA. 

Each  lung  is  invested,  upon  its  external  surface,  by  an  exceedingly  delicate 
serous  membrane,  the  pleura,  which  encloses  the  organ  as  far  as  its  root,  and  is 
then  reflected  upon  the  inner  surface  of  the  thorax.  The  portion  of  the  serous 
membrane  investing  the  surface  of  the  lung  is  called  the  pleura  pulmonalis 
(visceral  layer  of  pleura),  while  that  which  lines  the  inner  surface  of  the  chest  is 
called  the  yleiira  costalis  (parietal  layer  of  pleura).  The  space  between  these  two 
lavers  is  called  the  cavity  of  the  pleura.,  but  it  must  be  borne  in  mind  that  in  the 
healthy  condition  the  two  layers  are  in  contact,  and  there  is  no  real  cavity  until  the 
lung  becomes  collapsed  and  a  separation  of  it  from  the  wall  of  the  chest  takes 
place.  Each  pleura  is  therefore  a  shut  sac.  one  occupying  the  right,  the  other  the 
left  half  of  the  thorax,  and  they  are  perfectly  separate,  not  communicating  with 
each  other.  The  two  pleurae  do  not  meet  in  the  middle  line  of  the  chest,  excepting 
anteriorly  opposite  the  upper  part  of  the  second  piece  of  the  sternum — a  space 
being  left  between  them,  which  contains  all  the  viscera  of  the  thorax  excepting 
the  lungs :  this  is  the  mediastinum. 

Reflections  of  the  Pleura  (Fig.  707). — Commencing  at  the  sternum,  the  pleura 
passes  outward,  covers  the  costal  cartilages,  the  inner  surface  of  the  ribs  and 


TRIANGULARIS    STERNI. 

Internal  Mammary  Vessels. 


Left  Phrenic  Serve 


Pleura  Pulmonalis. 
Pleura  Costalis. 


Vena  Azygos  Major}  Posterior 
Pneumogastric  Ferees  > 

FIG.  707.— A  transverse  section  of  the  thorax,  showing  the  relative  position  of  the  viscera  and  the  reflections 
of  the  uleura:. 

Intercostal  muscles,  and  at  the  back  part  of  the  thorax  passes  over  the  thoracic 
ganglia  and  their  branches,  and  is  reflected  upon  the  sides  of  the  bodies  of  the 


1114  THE    ORGANS   OF    VOICE  AND   RESPIRATION. 

vertebrae,  where  it  is  separated  by  a  narrow  interval,  the  posterior  mediastinum, 
from  the  opposite  pleura.  From  the  vertebral  column  the  pleura  passes  to  the  side 
of  the  pericardium,  which  it  covers  to  a  slight  extent ;  it  then  covers  the  back  part 
of  the  root  of  the  lung,  from  the  lower  border  of  which  a  triangular  fold  descends 
vertically  by  the  side  of  the  posterior  mediastinum  to  the  Diaphragm.  This  fold 
is  the  broad  ligament  of  the  lung,  the  ligamentum  latum  pulmonis,  and  serves  to 
retain  the  lower  part  of  that  organ  in  position.  From  the  root  the  pleura  may  be 
traced  over  the  convex  surface  of  the  lung,  the  summit  and  base,  and  also  over  the 
sides  of  the  fissures  between  the  lobes  on  to  its  anterior  surface  and  the  front  part 
of  its  root ;  from  this  it  is  reflected  upon  the  side  of  the  pericardium  to  the  inner 
surface  of  the  sternum.  Below,  it  covers  the  upper  surface  of  the  Diaphragm,  and 
extends  in  front  as  low  as  the  costal  cartilage  of  the  seventh  rib  ;  at  the  side  of  the 
chest,  as  low  as  the  tenth  rib  on  the  left  side  and  the  ninth  on  the  right  side ;  and 
behind,  it  reaches  as  low  as  the  twelfth  rib,  and  sometimes  even  beyond  it,  as  low 
as  the  transverse  process  of  the  first  lumbar  vertebra.  Above,  its  apex  projects,  in 
the  form  of  a  cul-de-sac,  through  the  superior  opening  of  the  thorax  into  the  neck, 
extending  from  one  to  two  inches  above  the  margin  of  tha  first  rib,  and  receives 
the  summit  of  the  corresponding  lung ;  this  sac  is  strengthened,  according  to  Dr. 
Sibson,  by  a  dome-like  expansion  of  fascia,  attached  in  front  to  the  posterior  border 
of  the  first  rib,  and  behind  to  the  anterior  border  of  the  transverse  process  of  the 
seventh  cervical  vertebra.  This  is  covered  and  strengthened  by  a  few  spreading 
muscular  fibres  derived  from  the  Scaleni  muscles. 

A  little  above  the  middle  of  the  sternum,  the  contiguous  surfaces  of  the  two 
pleurae  are  sometimes  in  contact  for  a  slight  extent ;  but  above  and  below  this  point 
the  interval  left  between  them  forms  part  of  the  mediastinum. 

The  inner  surface  of  the  pleura  is  smooth,  polished,  and  moistened  by  a 
serous  fluid ;  its  outer  surface  is  intimately  adherent  to  the  surface  of  the  lung 
and  to  the  pulmonary  vessels  as  they  emerge  from  the  pericardium ;  it  is  also 
adherent  to  the  upper  surface  of  the  Diaphragm  :  throughout  the  rest  of  its 
extent  it  is  somewhat  thicker,  and  may  be  easily  separated  from  the  adjacent  parts. 

The  right  pleural  sac  is  shorter  and  wider  than  the  left. 

A  portion  of  the  Diaphagm  below  and  behind,  i.  e.  a  narrow  interval  around 
this  part  of  its  circumference,  is  not  covered  by  pleura  and  is  in  direct  contact  with 
the  costal  parietes.  Furthermore,  it  is  to  be  noted  that  there  are  certain  localities 
in  the  pleural  sac  in  which  the  surfaces  of  two  portions  of  parietal  pleura  are  always 
in  contact,  even  when  the  lung  is  in  a  state  of  complete  inspiration.  These  localities 
are  known  as  sinuses  or  complementary  spaces.  The  largest  and  most  distinct  of 
these  is  the  costo-phrenic  sinus,  which  follows  the  line  of  reflection  of  the  costal 
pleura  on  to  the  diaphragm. 

Vessels  and  Nerves. — The  arteries  of  the  pleura  are  derived  from  the  inter- 
costal, the  internal  mammary,  the  musculo-phrenic,  thymic,  pericardiac,  and 
bronchial.  The  veins  correspond  to  the  arteries.  The  lymphatics  are  very 
numerous.  The  nerves  are  derived  from  the  phrenic  and  sympathetic  (Luschka). 
Kolliker  states  that  nerves  accompany  the  ramification  of  the  bronchial  arteries 
in  the  pleura  pulmonalis. 

Surgical  Anatomy. — In  operations  upon  the  kidney  it  must  be  borne  in  mind  that  the 
pleura  may  sometimes  extend  below  the  level  of  the  last  rib,  and  may  therefore  be  opened  in 
these  operations,  especially  when  the  last  rib  is  removed  in  order  to  give  more  room. 

THE  MEDIASTINUM. 

The  Mediastinum  is  the  space  left  in  the  median  portion  of  the  chest  by  the  non- 
approximation  of  the  two  pleurae.  It  extends  from  the  sternum  in  front  to  the 
spine  behind,  and  contains  all  the  viscera  in  the  thorax  excepting  the  lungs.  The 
mediastinum  may  be  divided  for  purposes  of  description  into  two  parts — an 
upper  portion,  above  the  upper  level  of  the  pericardium,  which  is  named  the 
Superior  mediastinum,  (Struthers) ;  and  a  lower  portion,  below  the  upper  level  of 
the  pericardium.  This  lower  portion  is  again  subdivided  into  three — that  part 


THE   MEDIASTINUM. 


1115 


which  contains  the  pericardium  and  its  contents,  the  middle  mediastinum ;  that 
part  which  is  in  front  of  the  pericardium,  the  anterior  mediastinum ;  and  that 
part  which  is  behind  the  pericardium,  the  posterior  mediastinum. 


FIG.  708. — The  posterior  mediastinum. 

The  superior  mediastinum  is  that  portion  of  the  interpleural  space  which  lies 
above  the  upper  level  of  the  pericardium,  between  the  manubrium  sterni  in  front  and 
the  upper  dorsal  vertebrae  behind.  It  is  bounded  below  by  a  plane  passing  back- 
ward from  the  junction  of  the  manubrium  and  gladiolus  sterni  to  the  lower  part 
of  the  body  of  the  fourth  dorsal  vertebra.  It  contains  the  origins  of  the  Sterno- 
hyoid  and  Sterno-thyroid  muscles  and  the  lower  ends  of  the  Longi  colli  muscles ; 
the  transverse  portion  of  the  arch  of  the  aorta  ;  the  innominate,  the  thoracic 
portion  of  the  left  carotid  and  subclavian  arteries  ;  the  upper  half  of  the  superior 


1116 


THE    ORGANS    OF    VOICE    AND    RESPIRATION. 


vena  cava  and  the  innominate  veins,  and  the  left  superior  intercostal  vein ;  the 
pneumogastric,  cardiac,  phrenic,  and  left  recurrent  laryngeal  nerves  ;  the  trachea, 
oesophagus,  and  thoracic  duct ;  the  remains  of  the  thymus  gland  and  lymphatics. 
The  anterior  mediastinum  is  bounded  in  front  by  the  sternum,  on  each  side  by 
the  pleura,  and  behind  by  the  pericardium.  Owing  to  the  oblique  position  of  the 


Left  Inom-     Left  Carotid     Thymus 
inate  Vein.  Artery.  Gland. 


Pneumogastric 
Nerve. 


Pneumogastric 
Nerve. 
\ 


Internal  Mammary 
Artery. 


Right  Innom- 
-  inate  Vein. 
1st  Rib. 

—  Trachea. 


Vertebral 
Artery..-  — 
Left  Sublcavian, 
Artery. 

(Esophagus.-'' 


2nd  Rib. 


V 

3rd  Rib. 

FIG.  709.— Transverse  section  through  the  upper  margin  of  the  third  dorsal  vertebra.    (Braune.) 

heart  toward  the  left  side,  this  space  is  not  parallel  with  the  sternum,  but  directed 
obliquely  from  above  downward  and  to  the  left  of  the  median  line ;  it  is  broad 
below,  narrow  above,  very  narrow  opposite  the  first  segment  of  the  gladiolus  of  the 
sternum,  the  contiguous  surfaces  of  the  two  pleurae  being  occasionally  united  over  a 
small  space.  The  anterior  mediastinum  contains  the  origins  of  the  Triangularis 
sterni  muscles,  and  a  quantity  of  loose  areolar  tissue  in  which  some  lymphatic 
vessels  are  found  ascending  from  the  convex  surface  of  the  liver,  and  two  or  three 
lymphatic  glands  (anterior  mediastinal  glands). 

The  middle  mediastinum  is  the  broadest  part  of  the  interpleural  space.  It 
contains  the  heart  enclosed  in  the  pericardium,  the  ascending  aorta,  the  lower 
half  of  the  superior  vena  cava,  with  the  vena  azygos  major  opening  into  it,  the 
bifurcation  of  the  trachea  and  the  two  bronchi,  the  pulmonary  artery  dividing  into 
its  two  branches  and  the  right  and  left  pulmonary  veins,  the  phrenic  nerves,  and 
some  bronchial  lymphatic  glands. 

The  posterior  mediastinum  is  an  irregular  triangular  space  running  parallel 
with  the  vertebral  column ;  it  is  bounded  in  front  by  the  pericardium  and  roots  of 
the  lungs,  behind  by  the  vertebral  column  from  the  lower  border  of  the  fourth 
dorsal  vertebra,  and  on  either  side  by  the  pleura.  It  contains  the  descend- 
ing thoracic  aorta,  the  greater  and  lesser  azygos  veins,  the  pneumogastric  and 
splanchnic  nerves,  the  oesophagus,  thoracic  duct,  and  some  lymphatic  glands. 


THE    LUNGS. 


The  Lungs  are  the  essential   organs  of  respiration  ;  they  are  two  in  number, 
placed  one  on  each  side  of  the  chest,  separated  from  each  other  by  the  heart  and 


THE  LUNGS. 


1117 


other  contents  of  the  mediastinum.     Each  lung  is  conical  in  shape,  and  presents 
for  examination  an  apex,  a  base,  two  borders,  and  two  surfaces  (Fig.  710). 


\ 


FIG.  710. — Front  view  of  the  heart  and  lungs. 

The  apex  forms  a  tapering  cone  which  extends  into  the  root  of  the  neck  about 
an  inch  to  an  inch  and  a  half  above  the  level  of  the  first  rib. 

The  base  is  broad,  concave,  and  rests  upon  the  convex  surface  of  the  Dia- 
phragm :  its  circumference  is  thin,  and  fits  into  the  space  between  the  lower  ribs 
and  the  costal  attachment  of  the  Diaphragm,  extending  lower  down  externally 
and  behind  than  in  front. 

The  external  or  thoracic  surface  is  smooth,  convex,  of  considerable  extent, 
and  corresponds  to  the  form  of  the  cavity  of  the  chest,  being  deeper  behind  than 
in  front. 

The  inner  surface  is  concave.  It  presents  in  front  a  depression  corresponding 
to  the  convex  surface  of  the  pericardium,  and  behind  a  deep  fissure  (the  hilum 
pulmonis)  which  gives  attachment  to  the  root  of  the  lung. 

The  posterior  border  is  rounded  and  broad,  and  is  received  into  the  deep  con- 
cavity on  either  side  of  the  spinal  column.  It  is  much  longer  than  the  anterior 
border,  and  projects  below  between  the  ribs  and  the  Diaphragm. 

The  anterior  border  is  thin  and  sharp,  and  overlaps  the  front  of  the  peri- 
cardium. 

Each  lung  is  divided  into  two  lobes,  an  upper  and  lower,  by  a  long  and  deep 
fissure  which  extends  from  the  upper  part  of  the  posterior  border  of  the  organ, 
about  three  inches  from  its  apex,  downward  and  forward  to  the  lower  part  of  its 
anterior  border.  This  fissure  penetrates  nearly  to  the  root.  In  the  right  lung 
the  upper  lobe  is  partially  subdivided  by  a  second  and  shorter  fissure  which  extends 
from  the  middle  of  the  preceding,  forward  and  slightly  upward,  to  the  anterior 
margin  of  the  organ,  marking  off  a  small  triangular  portion,  the  middle  lobe. 


1118  THE    ORGANS    OF    VOICE   AND    RESPIRATION. 

The  right  lung  is  the  larger  and  heavier ;  it  is  broader  than  the  left,  owing  to 
the  inclination  of  the  heart  to  the  left  side  ;  it  is  also  shorter  by  an  inch,  in  conse- 
quence of  the  Diaphragm  rising  higher  on  the  right  side  to  accommodate  the  liver. 

The  Eoot  of  the  Lungs. — A  little  above  the  middle  of  the  inner  surface  of  each 
lung,  and  nearer  its  posterior  than  its  anterior  border,  is  its  root,  by  which  the 
lung  is  connected  to  the  heart  and  the  trachea.  The  root  is  formed  by  the  bronchial 
tube,  the  pulmonary  artery,  the  pulmonary  veins,  the  bronchial  arteries  and  veins, 
the  pulmonary  plexus  of  nerves,  lymphatics,  bronchial  glands,  and  areolar  tissue,  all 
of  which  are  enclosed  by  a  reflection  of  the  pleura.  The  root  of  the  right  lung  lies 
behind  the  superior  vena  cava  and  ascending  portion  of  the  aorta  and  below  the 
vena  azygos  major.  That  of  the  left  lung  passes  beneath  the  arch  of  the  aorta  and 
in  front  of  the  descending  aorta ;  the  phrenic  nerve  and  the  anterior  pulmonary 
plexus  lie  in  front  of  each,  and  the  pneumogastric  and  posterior  pulmonary  plexus 
behind  each. 

The  chief  structures  composing  the  root  of  each  lung  are  arranged  in  a  similar 
manner  from  before  backward  on  both  sides — viz.  the  pulmonary  veins  most 
anterior ;  the  pulmonary  artery  in  the  middle ;  and  the  bronchus,  together  with 
the  bronchial  vessels,  behind.  From  above  downward,  on  the  two  sides,  their 
arrangement  differs,  thus : 

On  the  right  side  their  position  is — bronchus  (undivided  portion),  pulmonary 
artery,  pulmonary  veins ;  but  on  the  left  side  their  position  is — pulmonary  artery, 
bronchus,  pulmonary  veins ;  this  is  accounted  for  by  the  bronchus  being  placed  on 
a  lower  level  on  the  left  than  on  the  right  side,  in  order  that  it  may  pass  under 
the  arch  of  the  aorta. 

The  weight  of  both  lungs  together  is  about  forty-two  ounces,  the  right  lung 
being  two  ounces  heavier  than  the  left ;  but  much  variation  is  met  with  according 
to  the  amount  of  blood  or  serous  fluid  they  may  contain.  The  lungs  are  heavier 
in  the  male  than  in  the  female,  their  proportion  to  the  body  being  in  the  former 
as  1  to  37,  in  the  latter  as  1  to  43.  The  specific  gravity  of  the  lung-tissue  varies 
from  0.345  to  0.746,  water  being  1000. 

The  color  of  the  lungs  at  birth  is  a  pinkish-white ;  in  adult  life  a  dark 
slate-color,  mottled  in  patches ;  and  as  age  advances  this  mottling  assumes  a 
black  color.  The  coloring  matter  consists  of  granules  of  a  carbonaceous  substance 
deposited  in  the  areolar  tissue  near  the  surface  of  the  organ.  It  increases  in 
quantity  as  age  advances,  and  is  more  abundant  in  males  than  in  females.  The 
posterior  border  of  the  lung  is  usually  darker  than  the  anterior. 

The  surface  of  the  lung  is  smooth,  shining,  and  marked  out  into  numerous 
polyhedral  spaces,  indicating  the  lobules  of  the  organ ;  the  area  of  each  of  these 
spaces  is  crossed  by  numerous  lighter  lines. 

The  substance  of  the  lung  is  of  a  light,  porous,  spongy  texture ;  it  floats  in 
water  and  crepitates  when  handled,  owing  to  the  presence  of  air  in  the  tissue ;  it 
is  also  highly  elastic ;  hence  the  collapsed  state  of  these  organs  when  they  are 
removed  from  the  closed  cavity  of  the  thorax. 

Structure. — The  lungs  are  composed  of  an  external  serous  coat,  a  subserous 
areolar  tissue,  and  the  pulmonary  substance  or  parenchyma. 

The  serous  coat  is  the  visceral  layer  of  the  pleura. 

The  subserous  areolar  tissue  contains  a  large  proportion  of  elastic  fibres ; 
it  invests  the  surface  of  the  lung,  and  extends  inward  between  the  lobules. 

The  parenchyma  is  composed  of  lobules  which,  although  closely  connected 
together  by  an  interlobular  areolar  tissue,  are  quite  distinct  from  one  another,  and 
may  be  teased  asunder  without  much  difficulty  in  the  foetus.  The  lobules  vary  in 
size ;  those  on  the  surface  are  large,  of  pyramidal  form,  the  base  turned  toward 
the  surface ;  those  in  the  interior,  smaller  and  of  various  forms.  Each  lobule  is 
composed  of  one  of  the  ramifications  of  a  bronchial  tube  and  its  terminal  air-cells, 
and  of  the  ramifications  of  the  pulmonary  and  bronchial  vessels,  lymphatics,  and 
nerves,  all  of  these  structures  being  connected  together  by  areolar  tissue. 

The  bronchus,  upon  entering  the  substance  of  the  lung,  divides  and  subdivides 


THE   LUNGS.  1119 

dichotomously,  or  rather  bipinnately,  throughout  the  entire  organ.  Sometimes 
three  branches  arise  together,  and  occasionally  small  lateral  branches  are  given  off 
from  the  sides  of  a  larger.  Each  of  the  smaller  subdivisions  of  the  bronchi  enters 
a  pulmonary  lobule,  and  is  termed  a  lobular  bronchial  tube  or  bronchiole.  Its  wall 
now  begins  to  present  irregular  dilatations,  air-cells  or  alveoli,  at  first  sparingly 
and  on  one  side  of  the  tube  only,  but  as  it  proceeds  onward  these  dilatations 
become  more  numerous  and  surround  the  tube  on  all  sides,  so  that  it  loses  its  cyl- 
indrical character.  The  lobular  bronchiole  now  becomes  enlarged,  and  is  known  as 
the  atrium  or  alveolar  passage.  From  the  atrium  are  now  given  off  in  all  direc- 
tions somewhat  elongated  blind  pouches  (1  mm.  in  diameter),  the  infundibula. 
Each  infundibulum  is,  in  its  turn,  closely  beset  with  alveoli.  Within  the  lungs 
the  bronchial  tubes  are  circular,  not  flattened,  and  present  certain  peculiarities  of 
structure. 

Changes  in  the  Structure  of  the  Bronchi. — As  the  bronchial  tubes  become 
smaller  and  smaller  the  following  changes  take  place :  The  cartilages  consist  of 
thin  lamina,  of  varied  form  and  size,  scattered  irregularly  along  the  sides  of  the 
tube,  being  most  distinct  at  the  points  of  division  of  the  tubes.  They  may  be 
traced  into  tubes  the  diameter  of  which  is  only  one-fourth  of  a  line.  Beyond  this 
point  the  tubes  are  wholly  membranous.  The  fibrous  coat  and  the  longitudinal 
elastic  fibres  are  continued  into  the  smallest  ramifications  of  the  bronchi.  The 
muscular  coat  is  disposed  in  the  form  of  a  continuous  layer  of  annular  fibres,  which 
may  be  traced  upon  the  smallest  bronchial  tubes.  The  mucous  membrane  lines 
the  bronchi  and  its  ramifications  throughout,  and  is  covered  with  columnar  ciliated 
epithelium. 

In  the  lobular  bronchial  tubes  and  in  the  infundibula  the  following  changes 
take  place :  The  muscular  tissue  begins  to  disappear ;  the  longitudinal  elastic  fibres 
begin  to  break  up,  so  that  in  the  infundibula  they  form  an  interlacement  around 
the  mouths  of  the  air-cells.  The  epithelium  becomes  non-ciliated  and  flattened. 
This  occurs  gradually ;  thus,  in  the  lobular  bronchioles  patches  of  non-ciliated 
flattened  epithelium  may  be  found  scattered  amongst  the  columnar  ciliated  epithe- 
lium ;  then  these  patches  of  non-ciliated  flattened  epithelium  become  more  and 
more  numerous,  until  in  the  infundibula  and  air-cells  all  the  epithelium  is  of  the 
non-ciliated  pavement  variety.  In  addition  to  these  flattened  cells,  there  are  small 
polygonal  granular  cells  in  the  air-sacs,  in  clusters  of  two  or  three,  between  the 
others. 

The  air-cells  are  small,  polyhedral,  recesses  composed  of  a  fibrillated  connec- 
tive tissue  and  surrounded  by  a  few  involuntary  muscular  and  elastic  fibres.  Free 
within  their  cavities  are  granular  leucocytes,  often  containing  carbonaceous  parti- 
cles. The  air-cells  are  well  seen  on  the  surface  of  the  lung,  and  vary  from  gr^th 
to  7o-th  of  an  inch  in  diameter,  being  largest  on  the  surface  at  the  thin  borders 
and  at  the  apex,  and  smallest  in  the  interior. 

The  pulmonary  artery  conveys  the  venous  blood  to  the  lungs ;  it  divides  into 
branches  which  accompany  the  bronchial  tubes,  and  terminates  in  a  dense  capillary 
network  upon  the  walls  of  the  intercellular  passages  and  air-cells.  In  the  lung 
the  branches  of  the  pulmonary  artery  are  usually  above  and  behind  a  bronchial 
tube,  the  vein  below  and  in  front. 

The  pulmonary  capillaries  form  plexuses  which  lie  immediately  beneath  the 
mucous  membrane  in  the  walls  and  septa  of  the  air-cells  and  of  the  infundibula. 
In  the  septa  between  the  air-cells  the  capillary  network  forms  a  single  layer.  The 
capillaries  form  a  very  minute  network,  the  meshes  of  which  are  smaller  than  the 
vessels  themselves  ;  *  their  walls  are  also  exceedingly  thin.  The  arteries  of  neigh- 
boring lobules  are  distinct  from  each  other,  and  do  not  anastomose,  whereas  the 
corresponding  venous  anastomosis  is  extremely  free. 

The  radicles  of  the  pulmonary  veins  commence  in  the  pulmonary  capillaries, 
and  coalesce  into  larger  branches,  which  accompany  the  arteries  and  return  the 

1  The  meshes  are  only  0.002'"  to  0.008'"  in  width,  while  the  vessels  are  0.003'"  to  0.005'" 
(Kolliker,  Human  Microscopic  Anatomy). 


1120  THE    ORGANS   OF    VOICE  AND   RESPIRATION. 

oxygenated  blood  to  the  left  auricle  of  the  heart.  The  radicles  come  together  in 
the  septa  between  the  infundibula,  entirely  separate  from  the  small  arterial  ramifi- 
cations. Those  which  are  near  the  surface  of  the  lung  have  an  undivided  course 
for  some  distance  and  then  either  unite  with  some  deeper  lying  vein  or  form,  with 
their  companions,  a  wide-meshed  superficial  plexus. 

The  bronchial  arteries  supply  blood  for  the  nutrition  of  the  lung :  they  are 
derived  from  the  thoracic  aorta,  and,  accompanying  the  bronchial  tubes,  are  dis- 
tributed to  the  bronchial  glands  and  upon  the  walls  of  the  larger  bronchial  tubes 
and  pulmonary  vessels.  Those  supplying  the  bronchial  tubes  form  a  capillary 
plexus  in  the  muscular  coat,  from  which  branches  are  given  off  to  form  a  second 
plexus  in  the  mucous  coat.  This  plexus  in  the  lobular  branchioles  is  continuous 
with  that  of  the  pulmonary  artery,  and  the  blood  which  the  bronchial  artery  brings 
is  thus  carried  back  by  the  pulmonary  vein.  Others  are  distributed  in  the  inter- 
lobular  areolar  tissue,  and  terminate  partly  in  the  deep,  partly  in  the  superficial, 
bronchial  veins.  Lastly,  some  ramify  upon  the  surface  of  the  lung  beneath  the 
pleura,  where  they  form  a  capillary  network. 

The  bronchial  vein  is  formed  at  the  root  of  the  lung,  receiving  superficial  and 
deep  veins  corresponding  to  branches  of  the  bronchial  artery.  It  does  not,  how- 
ever, receive  all  the  blood  supplied  by  the  artery,  as  some  of  it  passes  into  the 
pulmonary  vein.  It  terminates  on  the  right  side  in  the  vena  azygos  major,  and 
on  the  left  side  in  the  superior  intercostal  or  left  upper  azygos  vein.  Some  author- 
ities, especially  Zuckerkandl,  state  that,  in  other  parts  of  the  lung  than  in  the 
lobular  branchioles,  bronchial  veins,  even  those  coming  from  the  larger  bronchial 
tubes,  join  more  or  less  freely  with  pulmonary  veins.  The  intercostal  arteries  give 
small  branches  to  the  surface  of  the  lung,  by  way  of  the  ligamentum  latum  pul- 
monis.  (Turner.) 

The  lymphatics  consist  of  a  superficial  and  deep  set :  they  terminate  at  the 
root  of  the  lung,  in  the  bronchial  glands. 

Nerves. — The  lungs  are  supplied  from  the  anterior  and  posterior  pulmonary 
plexuses,  formed  chiefly  by  branches  from  the  sympathetic  and  pneumogastric. 
The  filaments  from  these  plexuses  accompany  the  bronchial  tubes,  upon  which 
they  are  lost.  Small  ganglia  are  found  upon  these  nerves. 

Surface  Form. — The  apex  of  the  lung  is  situated  in  the  neck,  behind  the  interval  between 
the  two  heads  of  origin  of  the  Sterno-mastoid.  The  height  to  which  it  rises  above  the  clavicle 
varies  very  considerably,  but  is  generally  about  one  inch.  It  may,  however,  extend  as  much  as 
an  inch  and  a  half  or  an  inch  and  three-quarters,  or,  on  the  other  hand,  it  may  scarcely  project 
above  the  level  of  this  bone.  In  order  to  mark  out  the  anterior  margin  of  the  lung,  a  line  is 
to  be  drawn  from  the  apex-point,  one  inch  above  the  level  of  the  clavicle,  and  rather  nearer  the 
posterior  than  the  anterior  border  of  the  Sterno-mastoid  muscle,  downward  and  inward  across 
the  sterno-clavicular  articulation  and  first  piece  of  the  sternum  until  it  meets,  or  .almost  meets, 
its  fellow  of  the  other  side  opposite  the  articulation  of  the  manubrium  and  gladiolus.  From  this 
point  the  two  lines  are  to  be  drawn  downward,  one  on  either  side  of  the  mesial  line  and  close  to 
it,  as  far  as  the  level  of  the  articulation  of  the  fourth  costal  cartilages  to  the  sternum.  From 
here  the  two"  lines  diverge  ;  the  left  is  to  be  drawn  at  first  passing  outward  with  a  slight  inclina- 
tion downward,  and  then  taking  a  bend  downward  with  a  slight  inclination  outward  to  the  apex 
of  the  heart^  and  thence  to  the  sixth  costo-chondral  articulation.  The  direction  of  the  anterior 
border  of  this  part  of  the  left  lung  is  denoted  with  sufficient  accuracy  by  a  curved  line  with  its 
convexity  directed  upward  and  outward  from  the  articulation  of  the  fourth  right  costal  cartilage 
of  the  sternum  to  the  fifth  intercostal  space,  an  inch  and  a  half  below  and  three-quarters  of  an 
inch  internal  to  the  left  nipple.  The  continuation  of  the  anterior  border  of  the  right  lung  is 
marked  by  a  prolongation  of  its  line  from  the  level  of  the  fourth  costal  cartilages  vertically 
downward  as  far  as  the  sixth,  when  it  slopes  off  along  the  line  of  the  sixth  costal  cartilage  to  its 
articulation  with  the  rib. 

The  lower  border  of  the  lung  is  marked  out  by  a  slightly  curved  line  with  its  convexity  down- 
ward from  the  articulation  of  the  sixth  costal  cartilage  to  its  rib  to  the  spinous  process  of  the 
tenth  dorsal  vertebra.  If  vertical  lines  are  drawn  downward  from  the  nipple,  the  mid-axillary 
line,  and  the  apex  of  the  scapula,  while  the  arms  are  raised  from  the  sides,  they  should  intersect 
this  convex  line,  the  first  at  the  sixth,  the  second  at  the  eighth,  and  the  third  at  the  tenth  rib. 
It  will  thus  be  seen  that  the  pleura  (seepage  11 14) extends  farther  down  than  the  lung,  so  that 
it  may  be  wounded,  and  a  wound  pass  through  its  cavity  into  the  Diaphragm,  and  even  injure 
the  abdominal  viscera,  without  the  lung  being  involved. 

The  posterior  border  of  the  lung  is  indicated  by  a  line  drawn  from  the  level  of  the  spinous 


THE   LUNGS. 


1121 


Recur, 
lar.  nerve 


Epart. 
bronchus 


Pulm. 
veins 


Great 
cor  on.  vein 


ilmfil  JO 

(esophagus 
FIG.  711. — Thoracic  contents  seen  from  behind.    (Joessel.) 


71 


1122  THE    ORGANS    OF    VOICE   AND    RESPIRATION. 

process  of  the  seventh  cervical  vertebra,  down  either  side  of  the  spine,  corresponding  to  the 
costo-vertebral  joints  as  low  as  the  spinous  process  of  the  tenth  dorsal  vertebra.  The  trachea 
bifurcates  opposite  the  spinous  process  of  the  fourth  dorsal  vertebra,  and  from  this  point  the  two 
bronchi  are  directed  outward,  the  right  one  almost  horizontally,  the  left  with  a  considerable 
inclination  downward. 

The  position  of  the  great  fissure  in  the  right  lung  may  be  indicated  by  a  line  drawn  from 
the  fourth  dorsal  vertebra  round  the  side  of  the  chest  to  the  anterior  margin  of  the  lung  opposite 
the  seventh  rib,  and  the  smaller  or  secondary  fissure  by  a  line  drawn  from  the  preceding  where 
it  bisects  the  mid-axillary  line  to  the  junction  of  the  fourth  costal  cartilage  to  the  sternum.  The 
great  fissure  in  the  left  lung  is  a  little  higher,  extending  from  the  third  dorsal  vertebra  round  the 
side  of  the  chest  to  reach  the  anterior  margin  of  the  lung  opposite  the  sixth  costal  cartilage. 

Surgical  Anatomy. — The  lungs  may  be  wounded  or  torn  in  three  ways:  (1)  By  compres- 
sion of  the  chest,  without  any  injury  to  the  ribs.  (2)  By  a  fractured  rib  penetrating  the  lung. 
(3)  By  stabs,  gunshot  wounds,  etc. 

The  first  form  is  very  rare,  and  usually  occurs  in  young  children,  and  affects  the  root  of  the 
lung — i.  e.  the  most  fixed  part — and  thus,  implicating  the  great  vessels,  is  frequently  fatal.  Its 
exact  mode  of  causation  is  difficult  to  interpret.  The  probable  explanation  is  that  immediately 
before  the  compression  is  applied  a  deep  inspiration  is  taken  and  the  lungs  are  fully  inflated ; 
owing  then  to  spasm  of  the  glottis  at  the  moment  of  compression,  the  air  is  unable  to  escape 
from  the  lung,  which  is  not  able  to  recede,  and  consequently  gives  way. 

In  the  second  variety  both  the  pleura  costalis  and  pulmonalis  must  necessarily  be  injured, 
arid  consequently  the  air  taken  into  the  wounded  air-cells  may  find  its  way  through  these  wounds 
into  the  cellular  tissue  of  the  parietes  of  the  chest.  This  it  may  do  without  collecting  in  the 
pleural  cavity ;  the  two  layers  of  the  pleura  are  so  intimately  in  contact  that  the  air  passes 
straight  through  from  the  wounded  lung  into  the  subcutaneous  tissue.  Emphysema  constitutes, 
therefore,  the  most  important  sign  of  injury  to  the  lung  in  cases  of  fracture  of  the  ribs.  Pneu- 
mothorax,  or  air  in  the  pleural  cavity,  is  much  more  likely  to  occur  in  injuries  to  the  lung  of 
the  third  variety,  in  which  cases  air  passes  either  from  the  wound  of  the  lung  or  from  external 
wound  into  the  cavity  of  the  pleura  during  the  respiratory  movements.  In  these  cases  there  is 
generally  no  emphysema  of  the  subcutaneous  tissue  unless  the  external  wound  is  small  and  val- 
vular, so  that  the  air  drawn  into  the  wound  during  inspiration  is  then  forced  into  the  cellular 
tissue  around  during  expiration  because  it  cannot  escape  from  the  external  wound.  Occasion- 
ally in  wounds  of  the  parietes  of  the  chest  no  air  finds  its  way  into  the  cavity  of  the  pleura, 
because  the  lung  at  the  time  of  the  accident  protrudes  through  the  wound  and  blocks  the  open- 
ing. This  occurs  where  the  wound  is  large,  and  constitutes  one  form  of  hernia  of  the  lung. 
Another  form  of  hernia  of  the  lung  occurs,  though  very  rarely,  after  wounds  of  the  chest-wall, 
when  the  wound  has  healed  and  the  cicatrix  subsequently  yields  from  the  pressure  of  the  viscus 
behind.  It  forms  a  globular,  elastic,  crepitating  swelling,  which  enlarges  during  expiratory 
efforts,  falls  in  during  inspiration,  and  disappears  on  holding  the  breath. 

THE  THYROID  GLAND. 

The  thyroid  gland  bears  much  resemblance  in  structure  to  other  glandular 
organs,  and  is  classified,  together  with  the  thymus,  suprarenal  capsules,  and 


FIG.  712.— Two  lobules  from  the  thyroid  of  an  infant,  a.  Small  glandular  vesicles  with  their  cells,  />.  The 
same,  with  incipient  colloid  metamorphosis,  more  strongly  marked  at  c.  d.  Coarse  lymph-canals,  e.  Fine  rad- 
icles of  the  same.  f.  An  efferent  vessel  of  considerable  size. 

spleen,  under  the  head  of  ductless  glands,  since  when  fully  developed  it  has  no 
excretory  duct.  From  its  situation  in  connection  with  the  trachea  and  larynx, 
the  thyroid  body  is  usually  described  with  those  organs,  although  it  takes  no  part 


THE    THYROID    GLAND.  1123 

in  the  function  of  respiration.  It  is  situated  at  the  upper  part  of  the  trachea,  and 
consists  of  two  lateral  lobes,  placed  one  on  each  side  of  that  tube  and  connected 
together  by  a  narrow  transverse  portion,  the  isthmus. 

Its  anterior  surface  is  convex,  and  covered  by  the  Sterno-hyoid,  Sterno-thyroid, 
and  Omo-hyoid  muscles. 

Its  lateral  surfaces,  also  convex,  lie  in  contact  with  the  sheath  of  the  common 
carotid  artery. 

Its  posterior  surface  is  concave,  and  embraces  the  trachea  and  larynx.  The 
posterior  borders  of  the  gland  extend  as  far  back  as  the  lower  part  of  the  pharynx, 
and  on  the  left  side  to  the  oesophagus. 

The  thyroid  varies  in  weight  from  one  to  two  ounces.  It  is  larger  in  females 
than  in  males,  and  becomes  slightly  increased  in  size  during  menstruation.  Each 
lobe  is  somewhat  conical  in  shape,  about  two  inches  in  length,  and  three-quarters 
of  an  inch  to  an  inch  and  a  quarter  in  breadth,  the  right  lobe  being  the  larger  of 
the  two. 

The  isthmus  connects  the  lower  third  of  the  two  lateral  lobes;  it  measures 
about  half  an  inch  in  breadth  and  the  same  in  depth,  and  usually  covers  the  second 
and  third  rings  of  the  trachea.  Its  situation  presents,  however,  many  variations — 
a  point  of  importance  in  the  operation  of  tracheotomy.  Sometimes  the  isthmus 
is  altogether  wanting. 

A  third  lobe,  of  conical  shape,  called  the  pyramid,  occasionally  arises  from  the 
upper  part  of  the  isthmus  or  from  the  adjacent  portion  of  either  lobe,  but  most 
commonly  the  left,  and  ascends  as  high  as  the  hyoid  bone.  It  is  occasionally  quite 
detached,  or  divided  into  two  parts,  or  altogether  wanting. 

A  few  muscular  bands  are  occasionally  found  attached  above  to  the  body  of 
the  hyoid  bone,  and  below  to  the  isthmus  of  the  gland  or  its  pyramidal  process. 
These  form  a  muscle  which  was  named  by  Sommerring  the  Levator  glandules 
thy roiJ <  i':. 

Structure. — The  thyroid  body  is  invested  by  a  thin  capsule  of  connective  tissue 
which  projects  into  its  substance  and  imperfectly  divides  it  into  masses  or  lobules 
of  irregular  form  and  size.  When  the  organ  is  cut  into  it  is  of  a  brownish-red 
color,  and  is  seen  to  be  made  up  of  a  number  of  closed  vesicles  containing  a 
yellow  glairy  fluid  and  separated  from  each  other  by  intermediate  connective 
tissue. 

According  to  Dr.  Baber,  who  has  recently  published  some  important  observa- 
tions on  the  minute  structure  of  the  thyroid,1  the  vesicles  of  the  thyroid  of  the 
adult  animal  are  generally  closed  cavities;  but  in  some  young  animals  (e.g.  young 
dogs)  the  vesicles  are  more  or  less  tubular  and  branched.  This  appearance  he 
supposes  to  be  due  to  the  mode  of  growth  of  the  gland,  and  merely  indicating  that 
an  increase  in  the  number  of  vesicles  is  taking  place.  Each  vesicle  is  lined  by  a 
single  layer  of  epithelium,  the  cells  of  which,  though  differing  somewhat  in  shape 
in  different  animals,  have  always  a  tendency  to  assume  a  columnar  form.  Between 
the  epithelial  cells  exists  a  delicate  reticulum.  The  vesicles  are  of  various  sizes 
and  shapes,  and  contain  as  a  normal  product  a  viscid,  homogeneous,  semi-fluid, 
slightly  yellowish  material  which  frequently  contains  blood,  the  red  corpuscles 
of  which  are  found  in  it  in  various  stages  of  disintegration  and  decolorization,  the 
yellow  tinge  being  probably  due  to  the  haemoglobin,  which  is  thus  set  free  from 
the  colored  corpuscles.  Baber  has  also  described  in  the  thyroid  gland  of  the 
dog  large  round  cells  ("  parenchymatous  cells  "),  each  provided  with  a  single  oval- 
shaped  nucleus,  which  migrate  into  the  interior  of  the  gland-vesicles. 

The  capillary  blood-vessels  form  a  dense  plexus  in  the  connective  tissue  around 
the  vesicles,  between  the  epithelium  of  the  vesicles  and  the  endothelium  of  the 
lymph-spaces,  which  latter  surround  a  greater  or  smaller  part  of  the  circumference 
of  the  vesicle.  These  lymph-spaces  empty  themselves  into  lymphatic  vessels 
which  run  in  the  interlobular  connective  tissue,  not  uncommonly  surrounding  the 
arteries  which  they  accompany,  and  communicate  with  a  network  in  the  capsule 

1  "Researches  on  the  Minute  Structure  of  the  Thyroid  Gland,"  Phil.  Trans.,  part  iii.,  1881. 


1124  THE   ORGANS    OF    VOICE  AND    RESPIRATION. 

of  the  gland.     Baber  has  found  in  the  lymphatics  of  the  thyroid  a  viscid  mate- 
rial which  is  morphologically  identical  with  the  normal  constituent  of  the  vesicle. 
Vessels  and  Nerves. — The  arteries  supplying  the  thyroid  are  the  superior  and 
inferior  thyroid,  and  sometimes  an  additional  branch  (thyroidea  media  or  ima) 

Vesicle. 

i     ^v  *r**~~.  it      \     i— \».Vi:M     /  •      ,v 

Lymphatic  vessel. 


\    1.  '' 

Vv  -v  V" 


Wall  of  gland-vesicle.  • 

FIG.  713.— Minute  structure  of  thyroid.    From  a  transverse  section  of  the  thyroid  of  a  dog.    (Semi-diagram- 
matic.)   (Baber.) 

from  the  innominate  artery  or  the  arch  of  the  aorta,  which  ascends  upon  the 
front  of  the  trachea.  The  arteries  are  remarkable  for  their  large  size  and  frequent 
anastomoses.  The  veins  form  a  plexus  on  the  surface  of  the  gland  and  on  the 
front  of  the  trachea,  from  which  arise  the  superior,  middle,  and  inferior  thyroid 
veins,  the  two  former  terminating  in  the  internal  jugular,  the  latter  in  the  innom- 
inate vein.  The  lymphatics  are  numerous,  of  large  size,  and  terminate  in  the 
thoracic  and  right  lymphatic  ducts.  The  nerves  are  derived  from  the  middle  and 
inferior  cervical  ganglia  of  the  sympathetic. 

Surgical  Anatomy. — The  thyroid  gland  is  subject  to  enlargement,  which  is  called  goitre. 
This  may  be  due  to  hypertrophy  of  any  of  the  constituents  of  the  gland.  The  simplest 
(parenchymatous  goitre)  is  due  to  an  enlargement  of  the  follicles.  The  fibroid  is  due  to  increase 
of  the  interstitial  connective  tissue.  The  cystic  is  that  form  in  which  one  or  more  large  ^cysts 
are  formed  from  dilatation  and  possibly  coalescence  of  adjacent  follicles.  The  pulsating  goitre  is 
where  the  vascular  changes  predominate  over  the  parenchymatous,  and  the  vessels  of  the 
gland  are  especially  enlarged.  Finally,  there  is  exophthalmic  goitre  (Graves's  disease),  where 
there  is  great  vascularity  and  often  pulsation,  accompanied  by  exophthalmos,  palpitation,  and 
rapid  pulse. 

For  the  relief  of  these  growths  various  operations  have  been  resorted  to,  such  as  injection 
of  tincture  of  iodine  or  perchloride  of  iron,  especially  applicable  to  the  cystic  form  of  the  disease, 
ligature  of  the  thyroid  arteries,  excision  of  the  isthmus,  and  extirpation  of  the  whole  or  a  part 
of  the  gland.  This  latter  operation  is  one  of  difficulty,  and  when  the  entire  gland  has  been 
removed  the  operation  has  been  followed  by  a  condition  resembling  myxoedema.  In  removing 
the  organ  great  care  must  be  taken  to  avoid  tearing  the  capsule /K  if  this  happens  the  gland- 
tissue  bleeds  profusely.  The  thyroid  arteries  should  be  ligatured  before  an  attempt  is  made  to 
remove  the  mass,  and  in  ligaturing  the  inferior  thyroids  the  position  of  the  recurrent  laryngeal 
nerve  must  be  borne  in  mind,  so  as  not  to  include  it  in  the  ligature. 

THE  THYMUS  GLAND. 

The  thymus  gland  presents  much  resemblance  in  structure  to  other  glandular 
organs,  and  is  another  of  the  organs  which  are  denominated  ductless  glands. 

The  thymus  gland  is  a  temporary  organ,  attaining  its  full  size  at  the  end  of  the 
second  year,  when  it  ceases  to  grow,  and  gradually  dwindles,  until  at  puberty  it 
has  almost  disappeared.  If  examined  when  its  growth  is  most  active,  it  will  be 


THE    THYMUS    GLAND.  1125 

found  to  consist  of  two  lateral  lobes  placed  in  close  contact  along  the  middle  line, 
situated  partly  in  the  superior  mediastinum,  partly  in  the  neck,  and  extending 
from  the  fourth  costal  cartilage  upward  as  high  as  the  lower  border  of  the 
thyroid  gland.  It  is  covered  by  the  sternum  and  by  the  origins  of  the  Sterno- 
hyoid  and  Sterno-thyroid  muscles.  Below,  it  rests  upon  the  pericardium,  being 
separated  from  the  arch  of  the  aorta  and  great  vessels  by  a  layer  of  fascia.  In 
the  neck  it  lies  on  the  front  and  sides  of  the  trachea,  behind  the  Sterno-hyoid 
and  Sterno-thyroid  muscles.  The  two  lobes  generally  differ  in  size;  they  are 


FIG.  714.— 1.  Upper  portion  of  the  thymus  of  a  foetal  pig  of  2"  in  length,  showing  the  bud-like  lobuli  and 
glandular  elements.  2.  Cells  of  the  thymus,  mostly  from  a  man.  a.  Free  nuclei,  b.  Small  cells,  c.  Larger. 
d.  Larger,  with  oil-globules,  from  the  ox.  e,f.  Cells  completely  filled  with  fat,  at  /  without  a  nucleus,  g,  h. 
Concentric  bodies,  g.  An  encapsulated  nucleated  cell.  h.  A  composite  structure  of  a  similar  nature. 

occasionally  united  so  as  to  form  a  single  mass,  and  sometimes  separated  by  an 
intermediate  lobe.  The  thymus  is  of  a  pinkish-gray  color,  soft,  and  lobulated  on  its 
surfaces.  It  is  about  two  inches  in  length,  one  and  a  half  in  breadth  below,  and 
about  three  or  four  lines  in  thickness.  At  birth  it  weighs  about  half  an  ounce. 

Structure. — Each  lateral  lobe  is  composed  of  numerous  lobules  held  together 
by  delicate  areolar  tissue,  the  entire  gland  being  enclosed  in  an  investing  capsule 
of  a  similar  but  denser  structure.  The  primary  lobules  vary  in  size  from  a  pin's 
head  to  a  small  pea,  and  are  made  up  of  a  number  of  small  nodules  or  follicles 
which  are  irregular  in  shape  and  are  more  or  less  fused  together,  especially 
toward  the  interior  of  the  gland.  According  to  AVatney.  each  follicle  consists  of 
a  medullary  and  cortical  portion,  which  differ  in  many  essential  particulars  from 
each  other.  The  cortical  portion  is  mainly  composed  of  lymphoid  cells  supported 
by  a  delicate  reticulum.  In  addition  to  this  reticulum,  of  which  traces  only  are 
found  in  the  medullary  portion,  there  is  also  a  network  of  finely-branched  cells 
which  is  continuous  with  a  similar  network  in  the  medullary  portion.  This 
network  forms  an  adventitia  to  the  blood-vessels.  In  the  medullary  portion  there: 
are  but  few  lymphoid  cells,  but  there  are,  especially  toward  the  centre,  granular* 
cells  and  concentric  corpuscles.  The  granular  cells  are  rounded  or  flask-shaped 
masses  attached  (often  by  fibrillated  extremities)  to  blood-vessels  and  to  newly- 
formed  connective  tissue.  The  concentric  corpuscles  are  composed  of  a  central 
mass  consisting  of  one  or  more  granular  cells,  and  of  a  capsule  which  is  formed 
of  epithelioid  cells  which  are  continuous  with  the  branched  cells  forming  the 
network  mentioned  above. 

Each  follicle  is  surrounded  by  a  capillary  plexus  from  which  vessels  pass  into 
the  interior  and  radiate  from  the  periphery  toward  the  centre,  and  form  a  second 
zone  just  within  the  margin  of  the  medullary  portion.  In  the  centre  of  the  medulla 
there  are  verv  few  vessels,  and  they  are  of  minute  size. 


1126 


THE    ORGANS    OF    VOICE   AND    RESPIRATION. 


Dr.  Watney  has  recently  made  the  important  observation  that  haemoglobin  is 
found  in  the  thymus  either  in  cysts  or  in  cells  situated  near  to  or  forming  part 

,Vein. 


Artery. 


FIG.  715.— Minute  structure  of  the  thymus  gland.  Frllirk>  of  injected  thymus  from  calf,  four  days  old, 
slightly  diagrammatic,  magnified  about  50  diameters.  The  large  vessels  are  disposed  in  two  rings,  one  of  which 
surrounds  the  follicle,  the  other  lies  just  within  the  margin  of  the  medulla.  (Watney.)  A  and  B.  From  thy- 
mus of  camel,  examined  without  addition  of  any  reagent.  Magnified  about  400  diameters.  A.  Large  colorless 
cell  containing  small  oval  masses  of  haemoglobin.  Similar  cells  are  found  in  the  lymph-glands,  spleen,  and 
medulla  of  bone.  B.  Colored  blood-corpuscles. 

of  the  concentric  corpuscles.  This  haemoglobin  varies  from  granules  to  masses 
exactly  resembling  colored  blood-corpuscles,  oval  in  the  bird,  reptile,  and  fish  ; 
circular  in  all  mammals  except  in  the  camel.  Dr.  Watney  has  also  discovered 
in  the  lymph  issuing  from  the  thymus  similar  cells  to  those  found  in  the  gland, 
and,  like  them,  containing  haemoglobin  either  in  the  form  of  granules  or  masses. 
From  these  facts  he  arrives  at  the  physiological  conclusion  that  the  thymus  is  one 
source  of  the  colored  blood-corpuscles. 

Vessels  and  Nerves. — The  arteries  supplying  the  thymus  are  derived  from 
the  internal  mammary  and  from  the  superior  and  inferior  thyroid.  The  veins 
terminate  in  the  left  innominate  vein  and  in  the  thyroid  veins.  The  lymphatics 
are  of  large  size,  arise  in  the  substance  of  the  gland,  and  are  said  to  terminate  in 
the  internal  jugular  vein.  The  nerves  are  exceedingly  minute;  they  are  derived 
from  the  pneumogastric  and  sympathetic.  Branches  from  the  descendens  hypo- 
glossi  and  phrenic  reach  the  investing  capsule,  but  do  not  penetrate  into  the  sub- 
stance of  the  gland. 


THE  URINARY  ORGANS. 


THE    KIDNEYS. 

Kidneys,  two  in  number,  are  situated  in  the  back  part  of  the  abdomen,  and 
_L  are  for  the  purpose  of  separating  from  the  blood  certain  materials  which, 
when  dissolved  in  a  quantity  of  water,  also  separated  from  the  blood  by  the  kid- 
constitute  the  urine. 

They  are  placed  in  the  loins,  one  on  each  side  of  the  vertebral  column,  behind 
the  peritoneum,  and  surrounded  by  a  mass  of  fat  and  loose  areolar  tissue.  Their 
upper  extremity  is  on  a  level  with  the  upper  border  of  the  twelfth  dorsal  vertebra, 
their  lower  extremity  on  a  level  with  the  third  lumbar.  The  right  kidney  is 
usually  on  a  slightly  lower  level  than  the  left,  probably  on  account  of  the  vicinity 
of  the  liver. 

The  kidneys  rest  on  the  lower  part  of  the  Diaphragm  and  the  fascia  covering 
the  Quadratus  lumborum  and  the  Psoas  magnus  muscles.  The  right  is  covered  in 
front  by  right  lobe  of  liver,  peritoneum  intervening,  the  descending  portion  of  the 
duodenum,  and  the  beginning  of  the  transverse  colon;  the  left  has  in  front  the  fun- 
dus  of  the  stomach,  the  tail  of  the  pancreas,  and  the  descending  colon  (upper  part). 

Each  kidney  is  about  four  inches  in  length,  two  to  two  and  a  half  in  breadth, 
and  rather  more  than  one  inch  in  thickness.  The  left  is  somewhat  longer,  though 
narrower,  than  the  right.  The  weight  of  the  kidney  in  the  adult  male  varies  from 
4J  ounces  to  6  ounces,  in  the  adult  female  from  4  ounces  to  5J  ounces.  The  com- 
bined weight  of  the  two  kidneys  in  proportion  to  the  body  is  about  1  in  240. 

The  kidney  has  a  characteristic  form.  It  is  flattened  and  presents  at  one  part 
of  its  circumference  a  hollow.  It  is  larger  at  its  upper  than  at  its  lower  extremity. 
It  has  two  surfaces,  two  borders,  and  an  upper  and  lower  extremity. 

Its  ant'  rior  surt\n-e  is  convex,  looks  forward  and  outward,  and  is  covered  by 
peritoneum.  The  upper  part  of  this  surface  on  the  right  side  is  in  contact  with  the 
under  surface  of  the  right  lobe  of  the  liver,  on  which  it  produces  a  slight  concave 
impression,  the  «'//?/>/v.yxA>  renalis  ;  below  this  the  descending  portion  of  the  duode- 
num and  the  hepatic  flexure  of  the  colon  are  connected  to  this  surface,  the  former 
by  areolar  tissue  and  the  latter  by  its  mesocolon.  On  the  left  side  the  upper  part 
of  the  anterior  surface  of  the  kidney  (covered  by  peritoneum  of  lesser  sac)  is  in 
contact  with  the  under  surface  of  the  stomach,  and  below  this  with  the  left  extrem- 
ity of  the  pancreas,  whilst  the  lower  part  has  anteriorly  the  splenic  flexure  of  the 
colon,  and  internally  the  last  portion  of  the  duodenum. 

The  posterior  surface  is  flatter  than  the  anterior,  and  is  imbedded  in  areolar 
tissue,  which  separates  it  from  the  Diaphragm  and  from  the  anterior  lamella  of  the 
lumbar  fascia  covering  the  Quadratus  lumborum  and  Psoas  magnus  muscle.  It  is 
also  in  relation  with  the  last  dorsal,  ilio-inguinal.  and  ilio-hypogastric  nerves. 

The  external  border  is  convex,  and  is  directed  outward  and  backward.  On  the 
left  side  it  is  in  contact,  at  its  upper  half  or  more,  with  the  spleen,  and  below  with 
the  descending  colon.  On  the  right  side,  upper  two-thirds,  liver ;  below,  ascending 
colon. 

The  internal  border  is  concave,  and  is  directed  forward  and  a  little  downward. 
It  presents  a  deep  longitudinal  fissure  bounded  by  prominent  anterior  and  poste- 
rior lip.  This  fissure  is  the  hilum,  and  allows  of  the  passage  of  the  vessels,  nerves, 
and  ureter. 

The  superior  extremity,  directed  slightly  inward  as  well  as  upward,  is  thick 

1127 


1128 


THE    URINARY   ORGANS. 


and  rounded,  and  is  surmounted  by  the  suprarenal  capsule,  which  covers  also  a 
small  portion  of  the  anterior  surface. 

The  inferior  extremity,  directed  a  little  outward  as  well  as  downward,  is 
smaller  and  thinner  than  the  superior.  It  extends  to  within  two  inches  of  the 
crest  of  the  ilium. 

At  the  hilum  of  the  kidney  the  relative  position  of  the  main  structures  passing 
into  and  out  of  the  kidney  is  as  follows  :  the  vein  is  in  front,  the  artery  in  the 
middle,  and  the  duct  or  ureter  behind  and  toward  the  lower  part.  By  a  knowledge 
of  these  relations  the  student  may  distinguish  between  the  right  and  left  kidney. 
The  kidney  is  to  be  laid  on  the  table  before  the  student  on  its  posterior  surface, 
with  its  lower  extremity  toward  the  observer — that  is  to  say,  with  the  ureter 
behind  and  below  the  other  vessels ;  the  hilum  will  then  be  directed  to  the  side  to 
which  the  kidney  belongs. 

General  Structure  of  the  Kidney. — The  kidney  is  surrounded  by  a  distinct 
investment  of  fibrous  tissue  which  forms  a  firm,  smooth  covering  to  the  organ.  It 
closely  invests  it,  but  can  be  easily  stripped  off,  in  doing  which,  however, 
numerous  fine  processes  of  connective  tissue  and  small  blood-vessels  are  torn 
through.  Beneath  this  coat  a  thin  wide-meshed  network  of  unstriped  muscular 
fibre  forms  an  incomplete  covering  to  the  organ.  When  the  fibrous  coat  is  stripped 
off,  the  surface  of  the  kidney  is  found  to  be  smooth  and  even  and  of  a  deep-red  color. 
In  infants  fissures  extending  for  some  depth  may  be  seen  on  the  surface  of  the 
organ,  a  remnant  of  the  lobular  construction  of  the  gland.  The  kidney  is  dense 

in  texture,  but  is  easily  lacerable  by  mechanical 
force.  In  order  to  obtain  a  knowledge  of  the 
structure  of  the  gland,  a  vertical  section  must 
be  made  from  its  convex  to  its  concave  border, 
and  the  loose  tissue  and  fat  removed  from  around 
the  vessels  and  the  excretory  duct  (Fig.  716). 
It  will  be  then  seen  that  the  kidney  consists  of 
a  central  cavity  surrounded  at  all  parts  but  one 
by  the  proper  kidney-substance.  This  central 
cavity  is  called  the  sinus,  and  is  lined  by  a  pro- 
longation of  the  fibrous  coat  of  the  kidney, 
which  enters  through  a  longitudinal  fissure,  the 
hilum  (before  mentioned),  which  is  situated  at 
that  part  of  the  cavity  which  is  not  surrounded 
by  kidney-structure.  Through  this  fissure  the 
blood-vessels  of  the  kidney  and  its  excretory 
duct  pass,  and  therefore  these  structures,  upon 
entering  the  kidney,  are  contained  within  the 
sinus.  The  excretory  duct,  or  ureter,  after 
entering,  dilates  into  a  wide,  funnel-shaped  sac 
named  the  pelvis.  This  divides  into  two  or  three 
tubular  divisions,  which  subdivide  into  several 
short,  truncated  branches  named  calices  or  in- 
fundibula,  all  of  which  are  contained  in  the 
central  cavity  of  the  kidney.  The  blood-vessels 
of  the  kidney,  after  passing  through  the  hilum, 
are  contained  in  the  sinus  or  central  cavity,  lying  between  its  lining  membrane 
and  the  excretory  apparatus,  before  entering  the  kidney-substance. 

This  central  cavity,  as  before  mentioned,  is  surrounded  on  all  sides  except  at 
the  hilum  by  the  substance  of  the  kidney,  which  is  at  once  seen  to  consist  of  two 
parts — viz.  of  an  external  granular  investing  part,  which  is  called  the  cortical 
portion  ;  and  of  an  internal  part,  the  medullary  portion,  made  up  of  a  number  of 
dark-colored  pyramidal  masses,  with  their  bases  resting  on  the  cortical  part  and 
their  apices  converging  toward  the  centre,  where  they  form  prominent  papillae 
which  project  into  the  interior  of  the  calices. 


FIG.  716.— Vertical  section  of  kidney. 


THE   KIDNEYS. 


1129 


The  cortical  substance  is  of  a  bright  reddish-brown  color,  soft,  granular,  and 
easily  lacerable.  It  is  found  everywhere  immediately  beneath  the  capsule,  and  is 
seen  to  extend  in  an  arched  form  over  the  base  of  each  medullary  pyramid.  The 
part  separating  the  sides  of  any  two  pyramids  through  which  the  arteries  and 
nerves  enter,  and  the  veins  and  lymphatics  emerge,  from  the  kidney,  is  called  a 
cortical  column  or  column  of  Bertin  (A,  A',  Fig.  716) ;  whilst  that  portion  which 
stretches  from  one  cortical  column  to  the  next,  and  intervenes  between  the  base  of 
the  pyramid  and  the  capsule  (marked  by  the  dotted  line  from  A  to  A'  in  Fig.  716), 
is  called  a  cortical  arch,  the  depth  of  which  varies  from  a  third  to  half  an  inch. 

The  medullary  substance,  as  before  stated,  is  seen  to  consist  of  pale  red- 
colored,  striated,  conical  masses,  the  pyramids  of  Malpighi,  the  number  of  which, 
varying  from  eight  to  eighteen,  correspond  to  the  number  of  lobes  of  which  the 
organ  in  the  foetal  state  is  composed.  The  base  of  each  pyramid  is  surrounded 
by  a  cortical  arch,  and  directed  toward  the  circumference  of  the  kidney ;  the  sides 
are  contiguous  with  the  cortical  columns ;  whilst  the  apex,  known  as  the  papilla 
or  ma/iuinUa  of  the  kidney,  projects  into  one  of  the 
calices  of  the  ureter,  one  calyx  receiving  two  or  three 
papillae. 

These  two  parts,  cortical  and  medullary,  so  dissimilar 
in  appearance,  are  very  similar  in  structure,  being 
made  up  of  urinary  tubes  and  blood-vessels  united  and 
bound  together  by  a  connecting  matrix  or  stroma. 

Minute  Anatomy. — The  tubuli  uriniferi,  of  which 
the  kidney  is  for  the  most  part  made  up,  commence  in 
the  cortical  portion  of  the  kidney,  and,  after  pursuing 
a  very  circuitous  course  through  the  cortical  and  med- 
ullary parts  of  the  kidney,  finally  terminate  at  the 
anices  of  the  Malpighian  pyramids  by  open  mouths 
(Fig.  717),  so  that  the  fluid  which  they  contain  is 
emptied  into  the  dilated  extremity  of  the  ureter  con- 
tained in  the  sinus  of  the  kidney.  If  the  surface  of 
one  of  the  papillae  is  examined  with  a  lens,  it  will  be 
seen  to  be  studded  over  with  a  number  of  small  depres- 
sions from  sixteen  to  twenty  in  number,  and  in  a  fresh 
kidney,  upon  pressure  being  made,  fluid  will  be  seen  to 
exude  from  these  depressions.  They  are  the  orifices  of 
the  tubuli  uriniferi.  which  terminate  in  this  situation. 
They  commence  in  the  cortical  portion  of  the  kidney 
as  the  Malpighian  bodies,  which  are  small  rounded 
masses,  varying  in  size,  but  of  an  average  of  about 
y|-ij  of  an  inch  in  diameter.  They  are  of  a  deep-red 
color,  and  are  found  only  in  the  cortical  portion  of  the 
kidney.  Each  of  these  little  bodies  is  composed  of  two 
parts — a  central  glomerulus  of  vessels,  called  a  Mal- 
pighian  tuft,  and  a  membranous  envelope,  the  Mal- 
[>i</]ii<in  capsule,  or  capsule  of  Bowman,  which  latter  is 
a  small  pouch-like  commencement  of  a  uriniferous  tubule. 

The  Malpighian  tuft,  or  vascular  glomerulus,  is  a  network  of  convoluted 
capillary  blood-vessels  held  together  by  scanty  connective  tissue  and  grouped  into 
from  two  to  five  lobules.  This  capillary  network  is  derived  from  a  small  arterial 
twig,  the  afferent  vessel,  which  pierces  the  wall  of  the  capsule,  generally  at  a  point 
opposite  that  at  which  the  latter  is  connected  with  the  tube  ;  and  the  resulting 
vein,  the  efferent  vessel,  emerges  from  the  capsule  at  the  same  point.  The  afferent 
vessel  is  usually  the  larger  of  the  two  (Fig.  718).  The  Malpighian  or  Bowman  s 
capsule,  which  surrounds  the  glomerulus,  is  formed  of  a  hyaline  membrane  sup- 
ported by  a  small  amount  of  connective  tissue  which  is  continuous  with  the  con- 
nective tissue  of  the  tube.  It  is  lined  on  its  inner  surface  by  a  layer  of  squa- 


FIG.  717.— A,  A.  Malpighian 
bodies.  B,B.  Margin  of  medullary 
structure,  c,  c,  c.  Loops  of  Henle. 
D,  D,  D.  Straight  tubes  cut  off.  E. 
Commencing  straight  tubes.  F. 
Termination  of  straight  tube. 


1130 


THE    URINARY   ORGANS. 


mous  epithelial  cells  which  are  reflected  from  the  lining  membrane  on  to  the 
glomerulus  at  the  point  of  entrance  or  exit  of  the  afferent  and  efferent  vessels. 
The  whole  surface  of  the  glomerulus  is  covered  with  a  continuous  layer  of  the 
same  cells  on  a  delicate  supporting  membrane,  which  with  the  cells  dips  in  between 
the  lobules  of  the  glomerulus,  closely  surrounding  them  (Fig.  719).  Thus,  between 
the  glomerulus  and  the  capsule  a  space  is  left,  forming  a  cavity  lined  by  a  con- 


FIG.  718.— Minute  structure  of  kidney. 


1  IG.  719.— Malpighian  body. 


tinuous  layer  of  cells,  which  varies  in  size  according  to  the  state  of  secretion  and 
the  amount  of  fluid  present  in  it.     The  cells  are  squamous  or  flattened. 

The  tubuli  uriniferi,  commencing  in  the  Malpighian  bodies,  in  their  course 
present  many  changes  in  shape  and  direction,  and  are  contained  partly  in  the 
medullary  and  partly  in  the  cortical  portions  of  the  organ.  At  their  junction  with 
the  Malpighian  capsule  they  present  a  somewhat  constricted  portion  which  is 
termed  the  neck.  Beyond  this  the  tube  becomes  convoluted,  and  pursues  a  con- 
siderable course  in  the  cortical  structure,  constituting  the  proximal  convoluted 
tube.  After  a  time  the  convolutions  disappear,  and  the  tube  approaches  the 
medullary  portion  of  the  kidney  in  a  more  or  less  spiral  manner.  This  section  of 
the  tube  has  been  called  the  spiral  tube  of  Schaclioiva.  Throughout  this  portion 
of  their  course  the  tubuli  uriniferi  have  been  contained  entirely  in  the  cortical 
structure,  and  have  presented  a  pretty  uniform  calibre.  They  now  enter  the 
medullary  portion,  and  suddenly  become  much  smaller,  quite  straight  in  direction, 
and  dip  down  for  a  variable  depth  into  the  pyramids,  constituting  the  descending 
limb  of  Henle's  loop.  Bending  on  themselves,  they  form  a  kind  of  loop,  the  loop 
of  ffenle,  and,  reascending,  become  suddenly  enlarged  and  again  spiral  in 
direction,  forming  the  ascending  limb  of  Henle's  loop,  and  re-enter  the  cortical 
structure.  This  portion  of  the  tube  does  not  present  a  uniform  calibre,  but 
becomes  narrower  as  it  ascends  and  irregular  in  outline.  As  a  narrow  tube  it  now 
is  found  in  the  cortex  along  the  medullary  ray  and  ascends  for  a  short  distance, 
when  it  again  becomes  dilated,  irregular,  and  angular,  and  leaves  the  medullary 
ray  to  enter  the  labyrinth  of  the  cortex.  This  section  is  termed  the  irregular 
tubule, ;  it  terminates  in  a  convoluted  tube  which  exactly  resembles  the  proximal 
convoluted  tubule,  and  is  called  the  distal  convoluted  tubule.  This  again  terminates 
in  a  narrow  curved  or  junctional  tube,  which  enters  the  straight  or  collecting  tube. 

Each  straight,  otherwise  called  a  collecting  or  receiving,  tube  commences  by  a 
small  orifice  on  the  summit  of  one  of  the  papillae,  thus  opening  and  discharging 
its  contents  into  the  interior  of  one  of  the  calices.  Traced  into  the  substance  of 
the  pyramid,  these  tubes  are  found  to  run  from  apex  to  base,  dividing  dichotomously 
in  their  course  and  slightly  diverging  from  each  other.  Thus  dividing  and  sub- 
dividing, they  reach  the  base  of  the  pyramid,  and  enter  the  cortical  structure 
greatly  increased  in  number.  Upon  entering  the  cortical  portion  they  continue  a 
straight  course  for  a  variable  distance,  and  are  arranged  in  groups  called  medullary 
rays,  several  of  these  groups  corresponding  to  a  single  pyramid.  The  tubes  in  the 


THE   KIDNEYS. 


1131 


centre  of  the  group  are  the  longest,  and  reach  almost  to  the  surface  of  the  kidney, 
while  the  external  ones  are  shorter,  and  advance  only  a  short  distance  into  the 


....  ,       Curved 
Dutal     collecting 
cmivo- 

luted 
tubule. 
I 


Descending  limb  \ 
of  Henle' sloop,  j 


FIG.  720.— Uriniferons  tube.    For  the  sake  of  clearness  the  epithelial  cells  have  been  represented  more 
highly  magnified  than  the  tubes  in  which  they  are  contained, 

cortex.  In  consequence  of  this  arrangement  the  cortical  portion  presents  a  number 
of  conical  masses,  the  apices  of  which  reach  the  periphery  of  the  organ,  and  the 
bases  are  applied  to  the  medullary  portion.  These  are  termed  the  pyramids  of 
F-rrein.  As  they  run  through  the  cortical  portion  the  straight  tubes  receive  on 
either  side  the  curved  extremity  of  the  convoluted  tubes,  which,  as  stated  above, 
commence  at  the  Malpighian  bodies.  The  portions  of  the  cortex  between  the 
medullary  rays  are  known  as  the  labyrinth  of  the  cortex. 

It  will  be  seen  from  the  above  description  that  there  is  a  continuous  series 
of  tubes  from  their  commencement  in  the  Malpighian  bodies  to  their  termina- 
tion at  the  orifices  on  the  apices  of  the  pyramids  of  Malpighi,  and  that  the 
urine,  the  secretion  of  which  commences  in  the  capsule,  finds  its  way  through 
these  tubes  into  the  calices  of  the  kidney,  and  so  into  the  ureter.  To  recapitulate : 
the  tube  first  presents  a  constricted  portion,  (1)  the  neck.  2.  It  forms  a  wide 
convoluted  tube,  the  proximal  convoluted  tube.  3.  It  becomes  spiral,  the  spiral 
tubule  "f  Sekaehowa.  4.  It  enters  the  medullary  structure  as  a  narrow,  straight 
tube,  the  descending  limb  of  Henle  s  loop.  5.  Forming  a  loop  and  becoming 
dilated,  it  ascends  somewhat  spirally,  and.  gradually  diminishing  in  calibre, 
again  enters  the  cortical  structure,  the  ascending  limb  of  Henle' s  loop.  6.  It  now 
becomes  irregular  and  angular  in  outline,  the  irregular  tubule.  7.  It  then  becomes 
convoluted,  the  distal  convoluted  tubule.  8.  Diminishing  in  size,  it  forms  a  curve, 
the  curved  tubule.  9.  Finally,  it  joins  a  straight  tube,  the  straight  collecting  tube,, 
which  is  continued  downward  through  the  medullary  substance  to  open  at  the  apex 
of  a  pyramid. 

The  Tubuli  Uriniferi:  their  Structure. — The  tubuli  uriniferi  consist  of  base- 


1132 


THE    URINARY   ORGANS. 


ment  membrane  lined  with  epithelium.  The  epithelium  varies  considerably  in 
different  sections  of  the  uriniferous  tubes.  In  the  neck  the  epithelium  is  con- 
tinuous with  that  lining  the  Malpighian  capsule,  and,  like  it,  consists  of  flattened 
cells  with  an  oval  nucleus  (Fig.  720  A).  The  cells  are,  however,  very  indistinct  and 
difficult  to  trace,  and  the  tube  has  here  the  appearance  of  a  simple  basement 
membrane  unlined  by  epithelium.  In  the  proximal  convoluted  tubule  and  the 
spiral  tubule  of  Schachowa  the  epithelium  is  polyhedral  in  shape,  the  sides  of  the 
cells  not  being  straight,  but  fitting  into  each  other,  and  in  some  animals  so  fused 


FIG.  721.1— Longitudinal  section  of  Henle's 
descending  limb.  a.  Membrana  propria.  6. 
Epithelium. 


FIG.  722. — Longitudinal  section  of  straight 
tube.  a.  Cylindrical  or  cubical  epithelium. 
b.  Membrana  propria. 


together  that  it  is  impossible  to  make  out  the  lines  of  junction.  In  the  human 
kidney  the  cells  often  present  an  angular  projection  of  the  surface  next  the  base- 
ment membrane.  These  cells  are  made  up  of  more  or  less  rod-like  fibres,  which 
rest  by  one  extremity  on  the  basement  membrane,  whilst  the  other  projects  toward 
the  lumen  of  the  tube.  This  gives  to  the  cells  the  appearance  of  distinct  striation 
(Heidenhain)  (Fig.  720  B).  In  the  descending  limb  of  Henle's  loop  the  epithelium 
resembles  that  found  in  the  Malpighian  capsule  and  the  commencement  of  the  tube, 
consisting  of  flat  transparent  epithelial  plates  with  an  oval  nucleus  (Figs.  720  A, 
721).  In  the  ascending  limb,  on  the  other  hand,  the  cells  partake  more  of  the 
character  of  those  described  as  existing  in  the  proximal  convoluted  tubule,  being 
polyhedral  in  shape  and  presenting  the  same  appearance  of  striation.  The 
nucleus,  however,  is  not  situated  in  the  centre  of  the  cell,  but  near  the  lumen 
(Fig.  720  c).  After  the  ascending  limb  of  Henle's  loop  becomes  narrower  upon 
entering  the  cortical  structure,  the  striation  appears  to  be  confined  to  the  outer 
part  of  the  cell :  at  all  events,  it  is  much  more  distinct  in  this  situation,  the 
nucleus,  which  appears  flattened  and  angular,  being  still  situated  near  the  lumen 
(Fig.  720  D).  In  the  irregular  tubule  the  cells  undergo  a  still  farther  change, 
becoming  very  angular,  and  presenting  thick  bright  rods  or  markings,  which 
render  the  striation  much  more  distinct  than  in  any  other  section  of  the  urinary 
tubules  (Fig.  720  H).  In  the  distal  convoluted  tubule  the  epithelial  cells  are  long 
in  shape,  are  highly  refractive,  and  their  nuclei  are  comparatively  large.  In  other 
respects  they  resemble  those  in  the  proximal  convoluted  tubule  (Fig.  720  B).  In 
the  curved  tubule,  just  before  its  entrance  into  the  straight  collecting  tube,  the 
epithelium  varies  greatly  as  regards  the  shape  of  the  cells,  some  being  angular 
with  short  processes,  others  spindle-shaped,  others  polyhedral  (Fig.  720  E). 

In  the  straight  tubes  the  epithelium  is  more  or  less  columnar  ;  in  its  papillary 
portion  the  cells  are  distinctly  columnar  and  transparent  (Figs.  722,  723),  but  as 
the  tube  approaches  the  cortex   the  cells  are  less  uniform  in  shape  ;  some  are 
polyhedral,  and  others  angular  with  short  processes  (Fig.  720  F  and  G). 
1  From  the  Handbook  for  the  Physiological  Laboratory. 


THE   KIDNEYS. 


1133 


The  Renal  Blood-vessels. — The  kidney  is   plentifully  supplied  with  blood  by 
the  renal  arterv.  a  large  offset  of  the  abdominal  aorta.     Previously  to  entering 


\ 


FIG.  723.— Tran  -  n  of  pyramidal  substance  of  kidney  of  pig,  the  blood-vessels  of  which  are  injected, 

a.  Large  collecting  tube  cut  across,  lined  with  cylindrical  epithelium,  b.  Branch  of  collecting  tube  cut  across, 
lined  with  epithelium  with  shorter  cylinders,  c  and  d.  Henle's  loops  cut  across,  e.  Blood-vessels  cut  across. 
D.  Connective-tissue  ground-substance. 

the  kidney,  each  arterv  divides  into  four  or  five  branches,  which  are  distributed 
to  its  substance.  At  the  hilum  these  branches  lie  between  the  renal  vein  and 
ureter,  the  vein  being  usually  in  front,  the  ureter  behind.  Each  vessel  gives 
off  some  small  branches  to  the  suprarenal  capsules,  the  ureter,  and  the  sur- 


Fio.  724.-Diagrammatical  sketch  of  kidney. 


FIG.  725.— A  portion  of  Fig.  593  enlarged.    (The 
references  are  the  same.) 


A,  o.  Proper  renal  artery  and  vein,  the  former  giving  off  the  renal  afferents,  the  latter  receiving  the  renal 
efferents.  B,  b.  Interlobular  arterv  and  vein,  the  latter  commencing  from  the  stellate  veins,  and  receiving 
branches  from  the  plexus  around  the  tubuli  contorti.the  former  giving  off  renal  afferents.  c.  Straight  tube,  sur- 
rounded by  tubuli  contorti,  with  which  it  communicates,  as  more  fully  shown  in  Fig.  586.  D.  Margin  of  medul- 
lary substance.  E.  E.  E.  Receiving  tubes  cut  off.  F,/.  Arteriolae  et  venae  rectse,  the  latter  arising  from  (G)  the 
plexus  at  the  medullary  apex. 

rounding  cellular  tissue  and  muscles.  Frequently  there  is  a  second  renal  artery, 
which  is  given  off  from  the  abdominal  aorta  at  a  lower  level,  and  supplies  the 
lower  portion  of  the  kidney.  It  is  termed  the  inferior  renal  artery.  The 
branches  of  the  renal  artery  whilst  in  the  sinus  give  off  a  few  twigs  for  the 
nutrition  of  the  surrounding  tissues,  and  terminate  in  the  arterice  proprice  renales, 
which  enter  the  kidney  proper  in  the  columns  of  Bertin.  Two  of  these  pass 
to  each  pyramid  of  Malpighi  and  run  along  its  sides  for  its  entire  length, 


1134 


THE    URINARY   ORGANS. 


giving  off  as  they  advance  the  afferent  vessels  of  the  Malpighian  bodies  in 
the  columns.  Having  arrived  at  the  bases  of  the  pyramids,  they  make  a  bend 
in  their  course,  so  as  to  lie  between  the  bases  of  the  pyramids  and  the  cortical 
arches,  where  they  break  up  into  two  distinct  sets  of  branches  devoted  to  the 
supply  of  the  remaining  portions  of  the  kidney. 

The  first  set,  the  interlobular  arteries  (Figs.  724,  725  B),  are  given  off  at  right 

angles  from  the  side  of  the  arterige  propriae  re- 
nales  looking  toward  the  cortical  substance,  and, 
passing  directly  outward  between  the  pyramids 
of  Ferrein,  they  reach  the  capsule,  where  they 
terminate  in  the  capillary  network  of  this  part. 
In  their  outward  course  they  give  off  lateral 
branches ;  these  are  the  afferent  vessels  for  the 
Malpighian  bodies  (see  page  1130),  and,  having 
pierced  the  capsule,  end  in  the  Malpighian  tufts. 
From  each  tuft  the  corresponding  renal  efferent 
arises,  and,  having  made  its  egress  from  the 
capsule  near  to  the  point  where  the  afferent  ves- 
sel entered,  anastomoses  with  other  efferents 
from  other  tufts,  and  contributes  to  form  a 
dense  venous  plexus  around  the  adjacent  urin- 
ary tubes  (Fig.  726). 

The  second  set  of  branches  from  the  arterige 
propiae  renales  are  for  the  supply  of  the  medul- 
lary pyramids,  which  they  enter  at  their  bases ; 
and,  passing  straight  through  their  substance 
to  their  apices,  terminate  in  the  venous  plex- 
They  are  called  the  arteriolce  rectce  (Figs.  724, 


FIG.  726.— Diagrammatic  representation 
of  the  blood-vessels  in  the  substance  of  the 
cortex  of  the  kidney,  m.  Region  of  the 
medullary  ray.  b.  Region  of  the  tortuous 
portion  of  the  tubules,  ai.  Arteria  inter- 
lobularis. vi.  Vena  interlobularis.  va.  Vas 
afferens.  gl.  Glomerulus.  ve.  Vas  efferens. 
vz.  Venous  twig  of  the  interlobularis.  (From 
Ludwig,  in  Strieker's  Handbook.) 


uses  found  in  that  situation. 
725  F). 

The  Renal  Veins  arise  from  three  sources — the  veins  beneath  the  capsule,  the 
plexuses  around  the  tubuli  contorti  in  the  cortical  arches,  and  the  plexuses  situated 
at  the  apices  of  the  pyramids  of  Malpighi.  The  veins  beneath  the  capsule  are 
stellate  in  arrangement,  and  are  derived  from  the  capillary  network  of  the  capsule, 
into  which  the  terminal  branches  of  the  interlobular  arteries  break  up.  These 
join  to  form  the  vence  interlobular 'es,  which  pass  inward  between  the  pyramids  of 
Ferrein,  receive  branches  from  the  plexuses  around  the  tubuli  contorti,  and, 
having  arrived  at  the  bases  of  the  Malpighian  pyramids,  join  with  the  venae  rectge, 
next  to  be  described  (Figs.  724,  725  ft). 

The  Vence  Rectce  are  branches  from  the  plexuses  at  the  apices  of  the  medullary 
pyramids,  formed  by  the  terminations  of  the  arteriolae  rectae.  They  pass  outward 
in  a  straight  course  between  the  tubes  of  the  medullary  structure,  and  joining,  as 
above  stated,  the  venae  interlobulares,  form  the  proper  renal  veins  (Figs.  724, 725/). 

These  vessels,  Vence  Proprice  Renales,  accompany  the  arteries  of  the  same  name, 
running  along  the  entire  length  of  the  sides  of  the  pyramids  ;  and,  having  received 
in  their  course  the  efferent  vessels  from  the  Malpighian  bodies  in  the  cortical 
structure  adjacent,  quit  the  kidney  substance  to  enter  the  sinus.  In  this  cavity 
they  inosculate  with  the  corresponding  veins  from  the  other  pyramids  to  form  the 
renal  vein,  which  emerges  from  the  kidney  at  the  hilum  and  opens  into  the  inferior 
vena  cava,  the  left  being  longer  than  the  right,  from  having  to  cross  in  front  of 
the  abdominal  aorta. 

Nerves  of  the  Kidney. — The  nerves  of  the  kidney,  although  small,  are  about 
fifteen  in  number.  They  have  small  ganglia  developed  upon  them,  and  are  derived 
from  the  renal  plexus,  which  is  formed  by  branches  from  the  solar  plexus,  the 
lower  and  outer  part  of  the  semilunar  ganglion  and  aortic  plexus,  and  from  the 
lesser  and  smallest  splanchnic  nerves.  They  communicate  with  the  spermatic 
plexus,  a  circumstance  which  may  explain  the  occurrence  of  pain  in  the  testicle  in 
affections  of  the  kidney.  So  far  as  they  have  been  traced,  they  seem  to  accompany 


THE  KIDNEYS.  1135 

the  renal  artery  and  its  branches,  but  their  exact  mode  of  termination  is  not 
known. 

The  lymphatics  consist  of  a  superficial  and  deep  set  which  terminate  in  the 
lumbar  glands. 

Connective  Tissue,  or  Intertubular  Stroma. — Although  the  tubules  and  vessels 
are  closely  packed,  a  certain  small  amount  of  connective  tissue,  continuous  with 
the  capsule,  binds  them  firmly  together.  This  tissue  was  first  described  by  Goodsir, 
and  subsequently  by  Bowman.  Ludwig  and  Zawarykin  have  observed  distinct 
fibres  passing  around  the  Malpighian  bodies,  and  Henle  has  seen  them  between 
the  straight  tubes  composing  the  medullary  structure. 

Surface  Form. — The  kidneys,  being  situated  at  the  back  part  of  the  abdominal  cavity  and 
deeply  placed,  cannot  be  felt  unless  enlarged  or  misplaced.  They  are  situated  on  the  confines 
of  the  epigastric  and  umbilical  regions  internally,  with  the  hypochondriac  and  lumbar  regions 
externally.  The  left  is  somewhat  higher  than  the  right.  According  to  Morris,  the  position  of 
the  kidney  may  be  thus  defined:  Anteriorly:  "1.  A  horizontal  line  through  the  umbilicus  is 
below  the  lower  edge  of  each  kidney.  2.  A  vertical  line  carried  upward  to  the  costal  arch  from 
the  middle  of  Poupart's  ligament  has  one-third  of  the  kidney  to  its  outer  side  and  two-thirds  to 
its  inner  side — i.  e.  between  this  line  and  the  median  line  of  the  body."  In  adopting  these  lines 
it  must  be  borne  in  mind  that  the  axes  of  the  kidneys  are  not  vertical,  but  oblique,  and  if  con- 
tinued upward  would  meet  about  the  ninth  dorsal  vertebra.  Posteriorly  :  The  upper  end  of  the 
left  kidney  would  be  defined  by  a  line  drawn  horizontally  outward  from  the  spinous  process  of  the 
eleventh  dorsal  vertebra,  and  its  lower  end  by  a  point  two  inches  above  the  iliac  crest.  The  right 
kidney  would  be  half  to  three-quarters  of  an  inch  lower.  Morris  lays  down  the  following  rules 
for  indicating  the  position  of  the  kidney  on  the  posterior  surface  of  the  body  :  "1.  A  line  par- 
allel with,  and  one  inch  from,  the  spine,  between  the  lower  edge  of  the  tip  of  the  spinous  pro- 
it'  the  eleventh  dorsal  vertebra  and  the  lower  edge  of  the  spinous  process  of  the  third 
lumbar  vertebra.  '2.  A  line  from  the  top  of  this  first  line  outward  at  right  angles  to  it  for 
2f  inches.  3.  A  line  from  the  lower  end  of  the  first  transversely  outward  for  2f  inches.  4.  A 
line  parallel  to  the  first  and  connecting  the  outer  extremities  of  the  second  and  third  lines  just 
described. 

The  hilum  of  the  kidney  lies  about  two  inches  from  the  middle  line  of  the  back,  at  the  level 
of  the  spinous  process  of  the  first  lumbar  vertebra. 

Surgical  Anatomy. — The  kidney  is  imbedded  in  a  large  quantity  of  loose  fatty  tissue,  and 
is  but  slightly  covered  by  peritoneum  ;  hence  rupture  of  this  organ  is  not  nearly  so  serious  an 
accident  as  rupture  of  the  liver  or  spleen,  since  the  extravasation  of  blood  and  urine  which 
follows  is  outside  the  peritoneal  cavity.  Occasionally  the  kidney  may  be  bruised  by  blows  in  the 
loin  or  by  being  compressed  between  the  lower  ribs  and  the  ilium  when  the  body  is  violently  bent 
forward.  This  is  followed  by  a  little  transient  haematuria.  which,  however,  speedily  passes  off. 
Occasionally,  when  rupture  involves  the  pelvis  of  the  kidney  or  the  commencement  of  the  ureter, 
this  duct  may  become  blocked,  and  hydronephrosis  follow. 

The  loose  cellular  tissue  around  the  kidney  may  be  the  seat  of  suppuration,  constituting 
parinephritie  <il>*c?ss.  This  may  be  due  to  injury,  to  disease  of  the  kidney  itself,  or  to  extension 
of  inflammation  from  neighboring  parts.  It  may  burst  into  the  pleura,  constituting  empyema ; 
into  the  colon  or  bladder ;  or  may  point  externally  in  the  groin  or  loin.  Tumors  of  the  kidney, 
of  which,  perhaps,  sarcoma  in  children  is  the  most  common,  maybe  recognized  by  their  position 
and  fixity  ;  by  the  resonant  colon  lying  in  front  of  it ;  by  their  not  moving  with  respiration ;  and 
by  their  rounded  outline,  not  presenting  a  notched  anterior  margin  like  the  spleen,  with  which 
they  are  most  likely  to  be  confounded.  The  examination  of  the  kidney  should  be  bimanual ; 
that  is  to  say.  one  hand  should  be  placed  in  the  flank  and  firm  pressure  made  forward,  while  the 
other  hand  is  buried  in  the  abdominal  wall  just  external  to  the  semilunar  line.  Manipulation  of 
the  kidney  frequently  produces  a  peculiar  sickening  sensation,  with  sometimes  faintness. 

The  kidney  is  mainly  held  in  position  by  the  mass  of  fatty  matter  in  which  it  is  imbedded 
and  over  which  the  peritoneum  is  stretched.  If  this  fatty  matter  is  loose  or  lax  or  is  absorbed, 
the  kidney  may  become  movable  and  may  give  rise  to  great  pain.  This  condition  occurs,  there- 
fore, in  badly-nourished  people  or  in  those  who  have  become  emaciated  from  any  cause,  and  is 
more  common  in  women  than  in  men.  It  must  not  be  confounded  with  the  floating  kidney :  this 
is  a  congenital  condition  due  to  the  development  of  a  meso-nephron,  which  permits  the  organ  to 
move  more  or  less  freely.  The  two  conditions  cannot,  however,  be  distinguished  until  the 
abdomen  is  opened  or  the  kidney  explored  from  the  loin. 

The  kidney  has,  of  late  years,  been  frequently  the  seat  of  surgical  interference.  It  may  be 
exposed  for  exploration  or  the  evacuation  of  pus  (nephrotomy) ;  it  may  be  incised  for  the 
removal  of  stone  (nephro-lithotomy) ;  it  may  be  sutured  when  movable  or  floating  (nephrorraphy) ; 
or  it  may  be  removed  (nephrectomy). 

The  kidney  may  be  exposed  either  by  a  lumbar  or  abdominal  incision.  The  lumbar  opera- 
tion is  the  one  which  is  generally  adopted,  unless  in  cases  of  very  large  tumors  or  of  wandering 
kidneys  with  a  loose  meso-nephron,  on  account  of  the  advantages  which  it  possesses  of  not 
opening  the  peritoneum  and  of  affording  admirable  drainage.  It  may  be  performed  either  by 
an  oblique,  a  vertical,  or  a  transverse  incision.  Perhaps  the  preferable,  as  affording  the  best 


1136  THE    URINARY   ORGANS. 

means  for  exploring  the  whole  surface  of  the  kidney,  is  an  incision  from  the  tip  of  the  last  rib 
backward  to  the  edge  of  the  Erector  spinae.  This  incision  must  not  be  quite  parallel  to  the  rib, 
but  its  posterior  end  must  be  at  least  three-quarters  of  an  inch  below  it,  lest  the  pleura  be 
wounded.  This  cut  is  quite  sufficient  for  an  exploration  of  the  organ.  Should  it  require  removal, 
a  vertical  incision  can  be  made  downward  to  the  crest  of  the  ilium,  along  the  outer  border  of  the 
Quadratus  lumborum.  The  structures  divided  are  the  skin,  the  superficial  fascia  with  the 
cutaneous  nerves,  the  deep  fascia,  the  posterior  border  of  the  External  oblique  muscle  of  the 
abdomen,  and  the  outer  border  of  the  Latissimus  dorsi ;  the  Internal  oblique  and  the  posterior 
aponeurosis  of  the  Transversalis  muscle  ;  the  outer  border  of  the  Quadratus  lumborum,  and  the 
deep  layer  of  the  transversalis  aponeurosis,  and  the  transversalis  fascia.  The  fatty  tissue 
around  the  kidney  is  now  exposed  to  view,  and  must  be  separated  by  the  fingers  or  a  director  in 
order  to  reach  the  kidney. 

The  abdominal  operation  is  best  performed  by  an  incision  in  the  linea  semilunaris  on  the 
side  of  the  kidney  to  be  removed,  as  recommended  by  Langenbuch.  The  incision  is  made  of 
varying  length  according  to  the  size  of  the  kidney ;  its  mid-point  should  be  on  a  level  with  the 
umbilicus.  The  abdominal  cavity  is  opened.  The  intestines  are  then  held  aside  and  the  outer 
layer  of  the  meso-colon  opened,  so  that  the  fingers  can  be  introduced  behind  the  peritoneum  and 
the  renal  vessels  sought  for.  These  are  then  to  be  ligatured ;  if  tied  separately,  care  must  be 
taken  to  ligature  the  artery  first.  The  kidney  must  now  be  enucleated,  and  the  vessels  and 
ureter  divided,  and  the  latter  tied  or,  if  thought  necessary,  stitched  to  the  edge  of  the  wound. 

THE  URETERS. 

The  Ureters  are  the  two  tubes  which  conduct  the  urine  from  the  kidneys  into 
the  bladder.  They  commence  within  the  sinus  of  the  kidney  by  a  number  of 
short  truncated  branches,  the  calices  or  infundibula,  which  unite  either  directly 
or  indirectly  to  form  a  dilated  pouch,  the  pelvis,  from  which  the  ureter,  after 
passing  through  the  hilum  of  the  kidney,  descends  to  the  bladder.  The  calices  are 
cup-like  tubes  encircling  the  apices  of  the  Malpighian  pyramids ;  but  inasmuch  as 
one  calyx  may  include  two  or  even  more  papillae,  their  number  is  generally  less 
than  the  pyramids  themselves,  the  former  being  from  seven  to  thirteen,  whilst  the 
latter  vary  from  eight  to  eighteen.  These  calices  converge  into  two  or  three 
tubular  divisions  which  by  their  junction  form  the  pelvis  or  dilated  portion  of  the 
ureter.  The  portion  last  mentioned,  where  the  pelvis  merges  into  the  ureter 
proper,  is  found  opposite  the  spinous  process  of  the  first  lumbar  vertebra,  in  which 
situation  it  is  accessible  behind  the  peritoneum. 

The  ureter  proper  is  a  cylindrical  membranous  tube,  about  sixteen  inches  in 
length  and  of  the  diameter  of  a  goosequill,  extending  from  the  pelvis  of  the 
kidney  to  the  bladder.  Its  course  is  obliquely  downward  and  inward  through 
the  lumbar  region  into  the  cavity  of  the  pelvis,  where  it  passes  downward, 
forward,  and  inward  across  that  cavity  to  the  base  of  the  bladder,  into  which  it 
then  opens  by  a  constricted  orifice,  after  having  passed  obliquely  for  nearly  an  inch 
between  its  muscular  and  mucous  coats. 

Relations. — In  its  course  it  rests  upon  the  Psoas  muscle,  being  covered  by 
the  peritoneum,  and  crossed  obliquely,  from  within  outward,  by  the  spermatic 
vessels ;  the  right  ureter  lying  close  to  the  outer  side  of  the  inferior  vena  cava. 
Opposite  the  first  piece  of  the  sacrum  it  crosses  either  the  common  or  external 
iliac  artery,  lying  behind  the  ileum  on  the  right  side  and  the  sigmoid  flexure 
of  the  colon  on  the  left.  In  the  pelvis  it  enters  the  posterior  false  ligament  of  the 
bladder  below  the  obliterated  hypogastric  artery,  the  vas  deferens  in  the  male 
passing  between  it  and  the  bladder.  In  the  female  the  ureter  passes  along  the 
side  of  the  cervix  of  the  uterus  and  upper  part  of  the  vagina.  At  the  level  of  the 
external  os  it  is  three-fifths  of  an  inch  external  to  the  cervix,  and  is  crossed  by 
the  uterine  artery,  a  venous  plexus  intervening  (Holl).  At  the  base  of  the  bladder 
it  is  situated  about  two  inches  from  its  fellow,  lying,  in  the  male,  about  an  inch  and 
a  half  behind  the  prostate. 

Structure. — The  ureter  has  three  coats — a  fibrous,  muscular,  and  mucous. 

The  fibrous  coat  is  the  same  throughout  the  entire  length  of  the  duct,  being 
continuous  at  one  end  with  the  capsule  of  the  kidney  at  the  floor  of  the  sinus, 
whilst  at  the  other  it  is  lost  in  the  fibrous  structure  of  the  bladder. 

In  the  pelvis  of  the  kidney  the  muscular  coat  consists  of  two  layers,  longitudinal 
and  circular :  the  longitudinal  fibres  become  lost  upon  the  sides  of  the  papillre  at 


THE   SUPRARENAL    c.\  /'>7  'LES.  1137 

the  extremities  of  the  calices ;  the  circular  fibres  may  be  traced  surrounding  the 
medullary  structure  in  the  same  situation.  In  the  ureter  proper  the  muscular 
fibres  are  very  distinct,  and  are  arranged  in  three  layers — an  external  longitudinal, 
a  middle  circular,  and  an  internal  layer,  less  distinct  than  the  other  two,  but 
having  a  general  longitudinal  direction.  According  to  Kolliker.  this  internal  layer 
is  <>nly  found  in  the  neighborhood  of  the  bladder. 

The  mucous  coat  is  smooth,  and  presents  a  few  longitudinal  folds  which 
become  effaced  by  distension.  It  is  continuous  with  the  mucous  membrane  of  the 
bladder  below,  whilst  it  is  prolonged  over  the  papillae  of  the  kidney  above.  Its 
epithelium  is  of  a  peculiar  character,  and  resembles  that  found  in  the  bladder.  It 
is  known  by  the  name  of  "  transitional  "  epithelium.  It  consists  of  several  layers 
of  cells,  of  which  the  innermost — that  is  to  say,  the  cells  in  contact  with  the 
U1-ine — are  quadrilateral  in  shape,  with  a  concave  margin  on  their  outer  surface, 
into  which  fits  the  rounded  end  of  the  cells  of  the  second  layer.  These,  the  inter- 
mediate cells,  more  or  less  resemble  columnar  epithelium,  and  are  pear-shaped, 
with  a  rounded  internal  extremity  which  fits  into  the  concavity  of  the  cells  of  the 
first  layer,  and  a  narrow  external  extremity  which  is  wedged  in  between  the  cells 
of  the  third  layer.  The  external  or  third  layer  consists  of  conical  or  oval  cells 
varying  in  number  in  different  parts,  and  presenting  processes  which  extend  down 
into  the  basement  membrane. 

The  arteries  supplying  the  ureter  are  branches  from  the  renal,  spermatic, 
internal  iliac,  and  inferior  vesical. 

The  nerves  are  derived  from  the  inferior  mesenteric,  spermatic,  and  pelvic 
plexr 

THE  SUPRARENAL  CAPSULES. 

The  Suprarenal  Capsules  are  classified,  together  with  the  spleen,  thymus,  and 
thyroid,  under  the  head  of  "ductless  glands,"  as  they  have  no  excretory  duct. 
They  are  two  small  flattened  glandular  bodies,  of  a  yellowish  color,  situated  at  the 
back  part  of  the  abdomen,  behind  the  peritoneum  and  immediately  above  and  a 
little  in  front  of  the  upper  part  of  each  kidney  ;  hence  their  name.  The  right  one 
is  somewhat  triangular  in  shape,  bearing  a  resemblance  to  a  cocked  hat ;  the  left  is 
more  semilunar.  and  usually  larger  and  higher  than  the  right.  They  vary  in  size  in 
different  individuals,  being  sometimes  so  small  as  to  be  scarcely  detected ;  their 
usual  size  is  from  an  inch  and  a  quarter  to  nearly  two  inches  in  length,  rather  less 
in  width,  and  from  two  to  three  lines  in  thickness.  Their  average  weight  is  about 
a  drachm  each. 

Relations. — The  relations  of  the  suprarenal  capsules  differ  on  the  two  sides  of 
the  body.  The  ru/ht  suprarenal  presents  on  its  anterior  surface  two  areas:  along 
its  upper  and  inner  borders  a  depressed  area,  which  is  in  contact  in  front  with  the 
under  surface  of  the  right  lobe  of  the  liver,  and  along  its  inner  border  with  the 
inferior  vena  cava  (Rolleston).  and  behind  rests  on  the  crus  of  the  Diaphragm  ; 
over  the  remainder  of  the  anterior  surface  is  an  elevated  area,  which  is  covered  in 
front  by  peritoneum  passing  from  the  upper  part  of  the  kidney  to  the  under  sur- 
face of  the  liver,  and  behind  rests  on  the  upper  and  inner  part  of  the  kidney. 
The  left  suprarenal  is  in  contact  by  its  anterior  surface,  superiorly,  with  the 
spleen :  below  and  internal  to  this  it  is  in  contact  with  the  peritoneum  forming 
the  lesser  sac.  which  separates  it  from  the  cardiac  extremity  of  the  stomach;  and 
at  its  lower  part  it  is  covered  by  the  pancreas  and  splenic  artery,  and  is  therefore 
nit  in  contact  with  the  peritoneum.  By  its  posterior  surface,  at  its  outer  and 
back  part,  it  rests  upon  the  kidney,  whilst  below  and  internally  it  is  in  contact 
with  the  left  crus  of  the  Diaphragm. 

Structure. — The  surface  of  the  suprarenal  gland  is  surrounded  by  areolar  tissue 
containing  much  fat,  and  closely  invested  by  a  thin  fibrous  coat,  which  is  difficult 
to  remove  on  account  of  the  numerous  fibrous  processes  and  vessels  which  enter  the 
organ  through  the  furrows  on  its  anterior  surface  and  base. 

Small  accessory  suprarenals   are  often  to  be    found  in   the  connective    tissue 


1138 


THE    URINARY   ORGANS. 


around  the  suprarenals.     The  smaller  of  these,  on  section,  show  a  uniform  surface, 
but  in  some  of  the  larger  a  distinct  medulla  can  be  made  out. 

On  making  a  perpendicular  section,  the  gland  is  seen  to  consist  of  two 
substances  — external  or  cortical  and  internal  or  medullary.  The  former, 
which  constitutes  the  chief  part  of  the  organ,  is 
of  a  deep-yellow  color.  The  medullary  sub- 
stance is  soft,  pulpy,  and  of  a  dark-brown  or 
black  color,  whence  the  name  atrabiliary  cap- 
sides  formerly  given  to  these  organs.  In  the 
centre  is  often  seen  a  space,  not  natural,  but 
formed  by  the  breaking  down  after  death  of  the 
medullarv  substance. 


Capsule. 

Zona 
glomerulosa. 


Zona  retieularit. 


Medulla. 


ipillary. 


FIG.  727.— Vertical   section  of  the    suprarenal 
capsule.    From  Elberth,  in  Strieker's  Manual. 

The  cortical  portion  consists  chiefly  of  narrow  columnar  masses  placed  perpen- 
dicularly to  the  surface.  This  arrangement  is  due  to  the  disposition  of  the  cap- 
sule, which  sends  into  the  interior  of  the  gland  processes  passing  in  vertically  and 
communicating  with  each  other  by  transverse  bands  so  as  to  form  spaces  which 
open  into  each  other.  These  spaces  are  of  slight  depth  near  the  surface  of  the 
organ,  so  that  ,there  the  section  somewhat  resembles  a  net ;  this  is  termed  the 
zona  glomerulosa  ;  but  they  become  much  deeper  or  longer  farther  in,  so  as  to 
resemble  pipes  or  tubes  placed  endwise,  the  zona  fasciculate.  Still  deeper  down. 
near  the  medullary  part,  the  spaces  become  again  of  small  extent;  this  is  named 
the  zona  reticularis.  These  processes  or  trabeculse,  derived  from  the  capsule  and 
forming  the  framework  of  the  spaces,  are  composed  of  fibrous  connective  tissue 
with  longitudinal  bundles  of  unstriped  muscular  fibres.  Within  the  interior  of 
the  spaces  are  contained  groups  of  polyhedral  cells,  which  are  finely  granular  m 
appearance,  and  contain  a  spherical  nucleus,  and  not  unfrequently  fat-molecules. 
These  groups  of  cells  do  not  entirely  fill  the  spaces  in  which  they  are  contained, 


THE   BLADDER.  1139 

but  between  them  and  the  trabeculae  of  the  framework  is  a  channel  which 
is  believed  to  be  a  lymph-path  or  sinus,  and  which  communicates  with  certain 
passages  between  the  cells  composing  the  group.  The  lymph-path  is  supposed 
to  Mpen  into  a  plexus  of  efferent  lymphatic  vessels  which  are  contained  in  the 
capsule. 

In  the  medullary  portion  the  fibrous  stroma  seems  to  be  collected  together 
into  a  much  closer  arrangement,  and  forms  bundles  of  connective  tissue  which  are 
looselv  applied  to  the  large  plexus  of  veins  of  which  this  part  of  the  organ  mainly 
consists.  In  the  interstices  lie  a  number  of  cells  compared  by  Frey  to  those  of 
columnar  epithelium.  They  are  coarsely  granular,  do  not  contain  any  fat- 
niolecules.  and  some  of  them  are  branched.  Luschka  has  affirmed  that  these 
branches  are  connected  with  the  nerve-fibres  of  a  very  intricate  plexus  which  is 
found  in  the  medulla  :  this  statement  has  not  been  verified  by  other  observers, 
for  the  tissue  of  the  medullary  substance  is  less  easy  to  make  out  than  that  of  the 
cortical,  owing  to  its  rapid  decomposition. 

The  numerous  arteries  which  enter  the  suprarenal  bodies  from  the  sources 
mentioned  below  penetrate  the  cortical  part  of  the  gland,  where  they  break  up 
into  capillaries  in  the  fibrous  septa,  and  these  converge  to  the  very  numerous  veins 
of  the  medullary  portion,  which  are  collected  together  into  the  suprarenal  vein, 
which  usually  emerges  as  a  single  vessel  from  the  centre  of  the  gland. 

The  art' /•/•  -x  supplying  the  suprarenal  capsules  are  numerous  and  of  large 
size :  they  are  derived  from  the  aorta,  the  phrenic,  and  the  renal :  they  sub- 
divide into  numerous  minute  branches  previous  to  entering  the  substance  of  the 
gland. 

The  suprarenal  i-ffn  returns  the  blood  from  the  medullary  venous  plexus,  and 
receives  several  branches  from  the  cortical  substance :  it  opens  on  the  right  side 
into  the  inferior  vena  cava,  on  the  left  side  into  the  renal  vein. 

The  lymphatics  terminate  in  the  lumbar  glands. 

The  nerves  are  exceedingly  numerous  :  they  are  found  chiefly,  if  not  entirely, 
in  the  medulla,  and  are  derived  from  the  solar  and  renal  plexuses,  and,  according 
to  Bergmann,  from  the  phrenic  and  pneumogastric  nerves.  They  have  numerous 
small  ganglia  developed  upon  them,  from  which  circumstance  the  organ  has  been 
conjectured  to  have  some  function  in  connection  with  the  sympathetic  nervous 
system. 

THE  CAVITY  OF  THE  PELVIS. 

The  cavity  of  the  pelvis  is  that  part  of  the  general  abdominal  cavity  which  is 
below  the  level  of  the  linea  ilio-pectinea  and  the  promontory  of  the  sacrum. 

Boundaries. — It  is  bounded  behind  by  the  sacrum,  the  coccyx,  the  Pyriformis 
muscle,  and  the  great  sacro-sciatic  ligaments  :  in  front  and  at  the  sides  by  theossa 
pubis  and  ischia,  covered  by  the  Obturator  muscles  ;  above,  it  communicates  with 
the  cavity  of  the  abdomen ;  and  below,  the  outlet  is  closed  by  the  triangular 
ligament,  the  Levatores  ani  and  Coccygei  muscles,  and  the  visceral  layer  of  the 
pelvic  fascia,  which  is  reflected  from  the  wall  of  the  pelvis  on  to  the  viscera. 

Contents. — The  viscera  contained  in  this  cavity  are — the  urinary  bladder,  the 
rectum,  and  some  of  the  generative  organs  peculiar  to  each  sex.  and  some  convo- 
lutions of  the  small  intestines  :  they  are  partially  covered  by  the  peritoneum, 
and  supplied  with  blood-vessels,  lymphatics,  and  nerves. 

THE  BLADDER. 

The  bladder  is  the  reservoir  for  the  urine.  It  is  a  musculo-membranous  sac 
situated  in  the  pelvis,  behind  the  pubes.  and  in  front  of  the  rectum  in  the  male, 
the  cervix  uteri  and  upper  part  of  the  vagina  intervening  in  the  female.  The 
shape,  position,  and  relations  of  the  bladder  are  greatly  influenced  by  age.  sex, 
and  the  degree  of  distention  of  the  organ.  During  infancy  it  is  conical  in  shape,  and 
projects  above  the  upper  border  of  the  os  pubis  into  the  hypogastric  region.  In  the 
adult,  when  quite  empty  and  contracted,  it.  together  with  the  urethra,  in  a  median 


THE    URINARY    ORGANS. 


vertical  section,  is  Y-shaped,  the  urethra  forming  the  stem  of  the  Y.  It  is  placed 
deeply  in  the  pelvis,  flattened  from  before  backward,  the  anterior  limb  of  the  Y 
reaching  as  high  as  the  upper  border  of  the  symphysis  pubis.  When  slightly  dis- 
tended it  has  a  rounded  form,  and  is  still  contained  within  the  pelvic  cavity  ;  and 
when  fully  distended  it  is  ovoid  in  shape,  and  rises  into  the  abdominal  cavity.  When 
greatly  distended  it  may  reach  nearly  as  high  as  the  umbilicus.  It  is  larger  in  its 
vertical  diameter  than  from  side  to  side,  and  its  long  axis  is  directed  from  above 
obliquely  downward  and  backward,  in  a  line  directed  from  some  point  between  the 
os  pubis  and  umbilicus  (according  to  its  distention)  to  the  end  of  the  coccyx.  The 
bladder,  when  distended,  is  slightly  curved  forward  toward  the  anterior  wall  of 
the  abdomen,  so  as  to  be  more  convex  behind  than  in  front.  In  the  female 
it  is  larger  in  the  transverse  than  in  the  vertical  diameter,  and  its  capacity  is 


Preface. 

FIG.  73£. — Vertical  section  of  bladder,  penis,  and  urethra. 

said  to  be  greater  than  in  the  male.1  When  moderately  distended  it  contains 
about  a  pint. 

The  bladder  has  a  summit  and  five  surfaces,  superior  or  abdominal,  postero- 
inferior  .or  base,  antero-inferior  or  pubic,  and  two  lateral  or  sides. 

The  summit  or  apex  of  the  bladder  looks  forward  and  upward  ;  it  is  connected 
to  the  abdominal  wall  by  a  fibro-muscular  cord,  the  urachus,  which  is  the  obliterated 
remains  of  a  tubular  canal  which,  in  the  embryo,  prolongs  the  cavity  of  the  bladder 
into  the  allantois.  It  passes  upward  from  the  apex  of  the  bladder  between  the 
transversalis  fascia  and  peritoneum  to  the  umbilicus,  becoming  thinner  as  it  ascends. 
On  each  side  of  it  is  placed  a  fibrous  cord,  the  obliterated  portion  of  the  hypogastric 
artery,  which,  passing  upward  from  the  side  of  the  bladder,  approaches  the  urachus 
above  its  summit.  In  the  infant,  at  birth,  the  urachus  is  sometimes  found  por- 
1  According  to  Henle,  the  bladder  is  considerably  smaller  in  the  female  than  in  the  male. 


THE   BLADDER. 


1141 


vious.  so  that  the  urine  escapes  at  the  umbilicus,  and  calculi  have  been  found  in 
its  canal. 

The  SHp'-rinr  or  abdominal  surface  is  free,  and  extends  antero-posteriorly  from 
the  summit  to  the  base :  laterally,  it  reaches  to  the  sides  of  the  bladder  from  which 
it  is  approximately  marked  off  by  the  obliterated  hypogastric  arteries.  This  sur- 
face is  entirely  covered  by  peritoneum,  and  is  in  relation  with  the  uterus,  in  the 
female,  the  sigmoid  flexure,  in  the  male,  and  in  either  sex  with  some  loops  of  the 
small  intestine.  Posteriorly  on  each  side,  beneath  the  peritoneum,  is,  in  the  male, 
a  part  of  the  vas  deferens. 

The  antero-infcrior  or  pubic  surface  is  not  covered  in  front  by  peritoneum, 
but  is  in  relation  with  the  triangular  ligament,  the  posterior  surface  of  the  sym- 
pliysis  pubis.  the  anterior  parts  of  Levator  ani  and  Internal  obturator  muscles, 


Vermiform  appendix 


External  Him- 
artery. 


Anterior  crural 


External  oblique 
muscle. 


V 

Profunda  vessels. 


FIG.  731.— Frontal  section  of  the  lower  part  of  the  abdomen.    Viewed  from  the  front.    (Braune.) 

and.    when    distended,    with    the   abdominal    parietes,   recto-vesical    fascia   being 
interposed. 

The  side  of  the  bladder  is  crossed  obliquely  from  below,  upward  and  forward, 
by  the  obliterated  hypogastric  artery  :  above  and  behind  this  cord  the  side  of  the 
bladder  is  covered  by  peritoneum,  but  below  and  in  front  of  it  the  serous  covering 
is  wanting,  and  it  is  connected  to  the  recto-vesical  fascia.  The  vas  deferens  passes, 
in  an  arched  direction,  from  before  backward,  along  the  posterior  portion  (sub- 
peritoneal)  of  the  side  of  the  bladder,  toward  its  base,  crossing  the  obliterated 
hypogastric  artery,  and  passing  along  the  inner  side  of  the  ureter.  The  space 
occupied  by  recto-vesical  fascia,  which  lies  between  the  pubic  surface  and  those 
portions  of  the  sides  of  the  bladder  which  are  uncovered  by  peritoneum  on  the  one 
hand,  and  their  antero-inferior  relations  on  the  other,  is  knoVn  as  the  Cavum  Retzii 
or  space  of  Retzius. 


1142 


THE    URINARY   ORGANS. 


The  base  (fundus)  of  the  bladder  is  directed  downward  and  backward.  It 
varies  in  extent  according  to  the  state  of  distention  of  the  organ,  being  very  broad 
when  full,  but  much  narrower  when  empty.  In  the  male  it  rests  upon  the  second 
portion  of  the  rectum,  from  which  it  is  separated  by  a  reflection  of  the  recto-vesical 
fascia.  It  is  covered  superiorly,  for  a  slight  extent,  by  the  peritoneum,  which  is 
reflected  from  it  upon  the  rectum,  forming  the  recto-vesical  fold.  The  portion  of 
the  bladder  in  relation  with  the  rectum  corresponds  to  a  triangular  space  bounded 
in  front  by  the  prostate  gland,  and  on  each  side  by  the  vesicula  seminalis  and  vas 
deferens.  In  the  female  the  base  of  the  bladder  lies  in  contact  with  the  cervix 


pocularis 


FIG.  732.— Antero-posterior  median  section  of  lower  part  of  bladder,  prostate  gland,  and  prostatic  urethra. 
(Henle.) 


uteri  and  upper  part  of  the  anterior  wall  of  the  vagina.  Above  this  connection  is 
the  peritoneal  utero-vesical  pouch. 

The  so-called  neck  of  the  bladder  is  the  point  of  commencement  of  the  urethra. 
The  portion  of  the  bladder  immediately  surrounding  it  is  in  relation  with  the 
prostate  gland. 

Ligaments. — The  bladder  is  retained  in  its  place  by  ligaments  which  are  divided 
into  true  and  false.  The  true  ligaments  are  five  in  number :  two  anterior,  two 
lateral,  and  the  urachus.  The  false  ligaments,  also  five  in  number,  are  formed  by 
folds  of  the  peritoneum. 

The  anterior  ligaments  (pubo-prostati<i)  extend  from  the  back  of  the  os  pubis, 
one  on  each  side  of  the  symphysis,  to  the  pubic  surface  of  the  bladder,  over  the 
upper  surface  of  the  prostate  gland.  These  ligaments  are  formed  by  the  recto- 
vesical  fascia,  and  contain  muscular  fibres  prolonged  from  the  bladder. 


THE  BLADDER.  1143 

The  lateral  tii/ament*.  also  formed  by  the  recto-vesical  fascia,  are  broader  and 
thinner  than  the  preceding.  They  are  attached  to  the  lateral  parts  of  the  prostate 
and  to  the  -ides  of  the  bladder  and  the  pelvic  wall.  The  posterior  prolongation  of 
this  ligament  is  known  as  the  ligament  of  the  rectum. 

The  ui-achu*  is  the  fibro-muscular  cord  already  mentioned,  extending  between 
the  summit  of  the  bladder  and  the  umbilicus.  It  is  broad  below,  and  becomes 
narrower  as  it  ascends. 

The  fah>-  ligament*  of  the  bladder  are — two  posterior,  two  lateral,  and  one 
superior. 

The  t>i'o  posterior  pass  forward,  in  the  male,  from  the  sides  of  the  rectum ;  in 
the  female,  from  the  sides  of  the  uterus  to  the  posterior  and  lateral  aspect  of  the 
bladder :  they  form  the  lateral  boundaries  of  the  recto-vesical  cul-de-sac  of  the 
peritoneum,  and  contain  the  obliterated  hypogastric  arteries  and  the  ureters, 
together  with  vessels  and  nerves. 

The  two  lateral  ligaments  are  reflections  of  the  peritoneum  from  the  iliac  fossae 
to  the  sides  of  the  bladder,  along  the  line  of  the  obliterated  hypogastric  arteries. 

The  superior  ligament  is  the  prominent  fold  of  the  peritoneum  extending  from 
the  summit  of  the  bladder  to  the  umbilicus.  It  covers  the  urachus  and  the  oblit- 
erated hypogastric  arteries. 

Structure. — The  bladder  is  composed  of  four  coats — serous,  muscular,  sub- 
mucous,  and  mucous. 

The  xermix  --"at  is  derived  from  the  peritoneum.  It  invests  the  entire  superior 
surface,  the  upper  part  of  the  base,  and  each  side,  above  and  behind  the  '*  hypo- 
gastric  cord."  and  is  reflected  on  to  the  abdominal  and  pelvic  walls. 

The  muscular  coat  consists  of  three  layers  of  unstriped  muscular  fibre :  an 
external  layer,  composed  of  fibres  having  for  the  most  part  a  longitudinal  arrange- 
ment :  a  middle  layer,  in  which  the  fibres  are  arranged,  more  or  less,  in  a  circular 
manner:  and  an  internal  layer,  in  which  the  fibres  have  a  general  longitudinal 
arrangement. 

The  fibre*  of  the  external  longitudinal  layer  arise  from  the  posterior  surface  of 
the  body  of  the  os  pubis  in  both  sexes  (musculi  pubo-vesicalis).  and  in  the  male  from 
the  adjacent  part  of  the  prostate  gland  and  its  capsule.  They  pass,  in  a  more  or 
less  longitudinal  manner,  up  the  anterior  surface  of  the  bladder,  over  its  apex, 
and  then  descend  along  its  posterior  surface  to  its  base,  where  they  become 
attached  to  the  prostate  in  the  male  and  to  the  front  of  the  vagina  in  the  female. 
At  the  sides  of  the  bladder  the  fibres  are  arranged  obliquely  and  intersect  one 
another.  This  layer  has  been  named  the  detrusor  urince  muscle. 

The  middle  circular  layers  are  very  thinly  and  irregularly  scattered  on  the  body 
of  the  organ,  and,  though  to  some  extent  placed  transversely  to  the  long  axis  of  the 
bladder,  are  f»r  the  most  part  arranged  obliquely.  Toward  the  lower  part  of  the 
bladder,  round  the  cervix  and  commencement  of  the  urethra,  they  are  disposed  in 
a  thick  circular  layer,  forming  the  sphincter  vesica>.  which  is  continuous  with  the 
muscular  fibres  of  the  prostate  gland. 

The  internal  longitudinal  layer  is  thin,  and  its  fasciculi  have  a  reticular 
arrangement,  but  with  a  tendency  to  assume  for  the  most  part  a  longitudinal 
direction. 

Two  bands  of  oblique  fibres,  originating  behind  the  orifices  of  the  ureters, 
pa<-  between  these  orifices  and  also  converge  to  the  back  part  of  the  prostate  gland, 
and  are  inserted,  by  means  of  a  fibrous  process,  into  the  middle  lobe  of  that  organ. 
They  are  the  //;//.^-/V.<  of  the  ureters,  described  by  Sir  C.  Bell,  who  supposed  that 
during  the  contraction  of  the  bladder  they  served  to  retain  the  oblique  direction  of 
the  ureters,  and  so  prevent  the  reflux  of  the  urine  into  them. 

The  sitbmueotu  coat  consists  of  a  layer  of  areolar  tissue  connecting  together  the 
muscular  and  mucous  coats,  and  intimately  united  to  the  latter. 

The  mucous  coat  is  thin,  smooth,  and  of  a  pale  rose  color.  It  is  continuous 
through  the  ureters  with  the  lining  membrane  of  the  uriniferous  tubes,  and  below 
with  that  of  the  urethra.  It  is  connected  loosely  to  the  muscular  coat  by  a  layei 


1144  THE    URINARY    ORGANS. 

of  areolar  tissue,  excepting  at  the  trigone,  where  its  adhesion  is  more  close.  It  is 
provided  with  mucous  follicles,  more  numerous  than  elsewhere  near  the  neck  of  the 
organ,  but  which  are  not  regarded  as  definite  glands.  The  epithelium  covering 
it  is  of  the  transitional  stratified  variety,  consisting  of  a  superficial  layer  of  poly- 
hedral, flattened  cells,  each  with  one,  two,  or  three  nuclei ;  beneath  these  a 
stratum  of  large  club-shaped  cells,  with  the  narrow  extremity  directed  downward 


FIG.  733.— Superficial  layer  of  the  epithelium  ol  FIG.  734.— Deep  layers  of  epithelium  of  bladder 

the  bladder.     Composed  of  polyhedral  cells  of  vari-  showing  large  club-shaped  cells  above,  and  smaller, 

ous  sizes,  each  with  one,  two,  or   three   nuclei.  more  spindle-shaped    cells  below,  each  with  an 

(Klein  and  Noble  Smith.)  oval  nucleus.    (Klein  and  Noble  Smith.) 

and  wedged  in  between  smaller  spindle-shaped  cells,  containing  an  oval  nucleus 
(Figs.  733,  734). 

Objects  Seen  on  the  Inner  Surface. — Upon  the  inner  surface  of  the  bladder  are 
seen  the  orifices  of  the  ureters,  the  trigone,  and  the  orifice  of  the  urethra. 

The  Orifices  of  the  Ureters. — These  are  situated  at  each  end  of  the  base  of  the 
trigone,  being  distant  from  each  other  by  less  than  two  inches ;  they  are  about  an 
inch  and  a  half  from  the  base  of  the  prostate  and  the  commencement  of  the  urethra. 

The  trigonum  vesicce  (Lieutaud),  or  trigone  vesicate,  is  a  triangular  smooth  sur- 
face, with  the  apex  directed  forward,  situated  in  the  base  of  the  bladder  immedi- 
ately behind  the  urethral  orifice.  It  is  paler  in  color  than  the  rest  of  the  mucous 
membrane,  and  never  presents  any  rugae,  even  in  the  collapsed  condition  of  the 
organ,  owing  to  its  intimate  adhesion  to  the  subjacent  tissue.  It  is  bounded  at 
each  posterior  angle  by  the  orifice  of  the  ureter.  Its  antero-inferior  angle  is  occu- 
pied by  the  orifice  of  the  urethra.  Between  the  orifices  of  the  ureters  is  seen  an 
arched  fold  (plica  ureterica)  of  mucous  membrane  caused  by  the  projection  of 
muscular  fibres  which  have  a  similar  direction  (see  preceding  page).  Projecting 
from  the  lower  and  anterior  part  and  reaching  to  the  orifice  of  the  urethra  is  a 
slight  elevation  of  mucous  membrane  called  the  uvula  vesicce.  It  is  formed  by  a 
thickening  of  the  submucous  tissue.  In  the  female,  the  uvula  vesicae  and  trigonum 
are  small  and  ill-defined. 

The  arteries  supplying  the  bladder  are  the  superior,  middle,  and  inferior  vesi- 
cal  in  the  male,  with  additional  branches  from  the  uterine  and  vaginal  in  the 
female.  They  are  all  derived  from  the  anterior  trunk  of  the  internal  iliac. 
The  obturator  and  sciatic  arteries  also  supply  small  visceral  branches  to  the 
bladder. 

The  veins  form  a  complicated  plexus  round  the  neck,  sides,  and  base  of  the 
bladder,  and  terminate  in  the  internal  iliac  vein. 

The  lymphatics  accompany  the  blood-vessels,  passing  through  the  glands  sur- 
rounding them. 

The  nerves  are  derived  from  the  pelvic  plexus  of  the  sympathetic  and  from 
the  third  and  the  fourth  sacral  nerves ;  the  former  supplying  the  upper  part  of 
the  organ,  the  latter  its  base  and  neck.  According  to  F.  Darwin,  the  sympa- 
thetic fibres  have  ganglia  connected  with  them,  which  send  branches  to  the  ves- 
sels and  muscular  coat. 

Surface  Form. — The  surface  form  of  the  bladder  varies  with  its  degree  of  distension  and 
under  other  circumstances.  In  the  young  child  it  is  represented  by  a  conical  figure,  the  apex 


THE   BLADDER. 


1145 


Cowpefs  Gtand.< 


Orifices  of  ducts 
of  Cowper's  Glands 


of  which,  even  when  the  viscus  is  empty,  is  situated  in  the  hypogastrie  region,  about  an  inch 
above  the  level  of  the  symphysis  pubis.  In  the  adult,  when  the  bladder  is  empty,  its  apex  does 
not  reach  above  the  level  of  the  upper  border  of  the 
symphysis  pubis,  and  the  whole  organ  is  situated  in 
the  pelvis ;  the  neck,  in  the  mule,  corresponding  to  a 
line  drawn  horizontally  backward  through  the  s5Tmphysis 
a  little  below  its  middle.  As  the  bladder  becomes  dis- 
tended it  gradually  rises  out  of  the  pelvis  into  the 
abdomen,  ^ind  forms  a  swelling  in  the  hypogastric 
region  which  is  perceptible  to  the  hand  as  well  as  to 
percussion.  In  extreme  distension  it  reaches  into  the 
umbilical  region.  Under  these  circumstances  it  is 
closely  applied  to  the  abdominal  wall,  without  the 
intervention  of  peritoneum.  so  that  it  can  be  tapped  by 
an  opening  in  the  middle  line  just  above  the  pubes 
without  any  fear  of  wounding  the  serous  membrane. 
When  the  rectum  is  distended  the  prostatic  portion  of 
the  urethra  is  elongated  and  the  bladder  lifted  out  of 
the  pelvis  and  the  peritoneum  pushed  upward.  Ad- 
vantage is  taken  of  this  in  performing  the  operation  of 
suprapubic  cystotomy.  The  rectum  is  distended  by  an 
india-rubber  hair,  which  is  introduced  into  this  cavity 
empty,  and  then  filled  with  ten  or  twelve  ounces  of 
water.  If  now  the  bladder  is  injected  with  about  half 
a  pint  of  some  antiseptic  fluid,  it  will  appear  above  the 
pubes.  plainly  perceptible  to  the  sight  and  touch.  The 
peritoneum  will  be  pushed  out  of  the  way.  and  an  in- 
cision three  inches  long  may  be  made  in  the  linea  alba 
from  the  symphysis  pubis  upward  without  any  great 
risk  of  wounding  the  peritoneum. 

\Vhen  distended  the  bladder  can  be  felt  in  the 
male,  from  the  rectum,  behind  the  prostate,  and  fluc- 
tuation can  be  perceived  by  a  bimanual  examination, 
one  finger  being  introduced  into  the  rectum  and  the 
distended  bladder  tapped  on  the  front  of  the  abdomen 
with  the  finger  of  the  other  hand.  This  portion  of  the 
bladder — that  is.  the  portion  felt  in  the  rectum  by  the 
finger — is  also  uncovered  by  peritoneum,  and  the  blad- 
der may  here  be  punctured  from  the  rectum,  in  the 
middle  line,  without  risk  of  wounding  the  serous  mem- 
brane. 

Surgical  Anatomy. — A  defect  of  development  in 
which  the  bladder  is  implicated  is  known  under  the 
name  of  extroversion  of  the  bladder.  In  this  condition 
the  lower  part  of  the  abdominal  wall  and  the  anterior 
wall  of  the  bladder  are  wanting,  so  that  the  posterior 
surface  of  the  bladder  presents  on  the  abdominal  sur- 
face, and  is  pushed  forward  by  the  pressure  of  the  vis- 
cera within  the  abdomen,  forming  a  red  vascular  tumor 
on  which  the  openings  of  the  ureters  are  visible.  The 
penis,  except  the  glans,  is  rudimentary  and  is  cleft  on  its  dorsal  surface,  exposing  the  floor  of 
the  urethra — a  condition  known  as  qpixpadiax.  The  pelvic  bones  are  also  arrested  in  develop- 
ment (see  page  283). 

The  bladder  may  be  ruptured  by  violence  applied  to  the  abdominal  wall,  when  the  viscus 
is  distended  without  any  injury  to  the  bony  pelvis,  or  it  may  be  torn  in  cases  of  fracture  of  the 
pelvis.  The  rupture  may  be  either  intraperitoneal  or  extraperitoneal — that  is,  may  implicate  the 
superior  surface  of  the  bladder  in  the  former  case,  or  one  of  the  other  surfaces  in  the  latter. 
Rupture  of  the  anterior  surface  alone  is.  however,  very  rare.  Until  recently  intraperitoneal 
rupture  was  uniformly  fatal,  but  now  abdominal  section  and  suturing  the  rent  with  Lembert's 
suture  is  resorted  to.  with  a  very  considerable  amount  of  success.  The  sutures  are  inserted  only 
throusrh  the  peritoneal  and  muscular  coats  in  such  a  way  as  to  bring  the  serous  surfaces  at  the 
inaririns  of  the  wound  into  apposition,  and  orte  is  inserted  just  beyond  the  end  of  the  wound. 
The  bladder  should  be  tested  as  to  whether  it  is  water-tight  before  closing  the  external  wound. 

The  muscular  coat  of  the  bladder  undergoes  hypertrophy  in  cases  in  which  there  is  any 
obstruction  to  the  flow  of  urine.  Under  these  circumstances  the  bundles  of  which  the  muscular 
coat  consists  become  much  increased  in  size.  and.  interlacing  in  all  directions,  give  rise  to  what 
is  known  as  the  fasciculated  bladder.  Between  these  bundles  of  muscular  fibres  the  mucous  mem- 
brane may  bukre  out.  forming  sacculi.  constituting  the  sacculated  bladder,  and  in  these  little 
pouches  phosphatic  secretions  may  collect,  forming  encysted  calculi.  The  mucous  membrane  is 
very  loose  and  lax.  except  over  the  trigone.  to  allow  of  the  distension  of  the  viscus. 

Various  forms  of  tumor  have  been  found  springing  from  the  wall  of  the  bladder.     The 


Meatut. 

FIG.  735.— The  bladder  and  urethra  laid 
open.    Seen  from  above. 


1146  THE    URINARY   ORGANS. 

innocent  tumors  are  the  papilloma  and  the  mucous  polypus,  arising  from  the  mucous  membrane  ; 
the  fibrous,  from  the  submucous  tissue  ;  and  the  myoma,  originating  in  the  muscular  tissue : 
and,  very  rarely,  dermoid  tumors,  the  exact  origin  of  which  it  is  difficult  to  explain.  Of  the 
malignant  tumors,  epithelioma  is  the  most  common,  but  sarcomata  are  occasionally  found  in  the 
bladder  of  children. 

Puncture  of  the  bladder  may  be  performed  either  above  the  pubes  or  through  the  .rectum, 
in  both  cases  without  wounding  the  peritoneum.  The  former  plan  is  generally  to  be  preferred, 
since  in  puncture  by  the  rectum  a  permanent  fistula  may  be  left  from  abscess  forming  between 
the  rectum  and  the  bladder ;  or  pelvic  cellulitis  may  be  set  up ;  moreover,  it  is  exceedingly 
inconvenient  to  keep  a  cannula  in  the  rectum.  In  some  cases  in  performing  this  operation  the 
recto-vesical  pouch  of  peritoneum  has  been  wounded,  inducing  fatal  peritonitis.  The  operation, 
therefore,  has  been  almost  completely  abandoned. 

THE  MALE  URETHRA. 

The  urethra  in  the  male  extends  from  the  neck  of  the  bladder  to  the  meat  us 
urinarius.  It  presents  a  double  curve  in  the  flaccid  state  of  the  penis,  but  in  the 
erect  state  it  forms  only  a  single  curve,  the  concavity  of  Avhich  is  directed  upward 
(Fig.  599).  Its  length  varies  from  eight  to  nine  inches,  and  it  is  divided  into 
three  portions,  the  prostatic,  membranous,  and  spongy,  the  structure  and  relations 
of  which  are  essentially  different.  Except  during  the  passage  of  the  urine  or 
semen  the  urethra  is  a  mere  transverse  cleft  or  slit,  Avith  its  upper  and  under 
surfaces  in  contact.  At  the  orifice  of  the  urethra  at  the  end  of  the  penis  the  slit 
is  vertical,  and  in  the  prostatic  portion  somewhat  arched. 

The  Prostatic  Portion  is  the  widest  and  most  dilatable  part  of  the  canal.  It 
passes  through  the  prostate  gland,  from  its  base  to  its  apex,  lying  nearer  its  upper 
than  its  lower  surface.  It  is  about  an  inch  and  a  quarter  in  length  ;  the  form  of 
the  canal  is  spindle-shaped,  being  wider  in  the  middle  than  at  either  extremity,  and 
narrowest  in  front,  where  it  joins  the  membranous  portion.  A  transverse  section  of 
the  canal  as  it  lies  in  the  prostate  is  horseshoe  in  shape,  the  convexity  being 
directed  upward  (Fig.  736)  or  rather  forward,  since  its  direction  is  nearly  vertical. 

Upon  the  floor  of  the  canal  is  a  narrow  longitudinal  ridge,  the  verumont<nnun, 
or  colliculm  seminalis,  or  caput  gallinaginis,  formed  by  an  elevation  of  the  mucous 
membrane  and  its  subjacent  tissue.  It  is  eight  or  nine  lines  in  length  and  a  line 
and  a  half  in  height,  and  contains,  according  to  Kobelt,  muscular  and  erectile  tis- 
sues. When  distended  it  may  serve  to  prevent  the  passage  of  the  semen  backward 
into  the  bladder.  On  each  side  of  the  verumontanum  is  a  slightly  depressed  fossa, 
the  prostatic  sinus,  the  floor  of  which  is  perforated  by  numerous  apertures,  the 
orifices  of  the  prostatic  ducts,  the  ducts  of  the  middle  lobe  opening  behind  the 
verumontanum.  At  the  fore  part  of  the  verumontanum,  in  the  middle  line,  is  a 
depression,  the  sinus  pocularis  (vesicula  prostatica},  and  upon  or  within  its  margins 
are  the  slit-like  openings  of  the  ejaculatory  ducts.  The  sinus  pocularis  forms  a 
cul-de-sac  about  a  quarter  of  an  inch  in  length,  which  runs  upward  and  backward 
in  the  substance  of  the  prostate  beneath  the  middle  lobe ;  its  prominent  upper  wall 
partly  forms  the  verumontanum.  Its  walls  are  composed  of  fibrous  tissue,  muscu- 
lar fibres,  and  mucous  membrane,  and  numerous  small  glands  open  on  its  inner 
surface.  It  has  been  called  by  Weber,  who  discovered  it,  the  uterus  masculinus, 
from  its  being  developed  from  the  united  ends  of  the  rudimentary  Miillerian  ducts, 
and  therefore  homologous  with  the  uterus  in  the  female. 

The  Membranous  portion  of  the  urethra  extends  between  the  apex  of  the 
prostate  and  the  bulb  of  the  corpus  spongiosum.  It  is  the  narrowest  part  of  the 
canal  (excepting  the  orifice),  and  measures  three-quarters  of  an  inch  along  its 
anterior  and  half  an  inch  along  its  posterior  surface,  in  consequence  of  the  bulb 
projecting  backward  beneath  it.  Its  anterior  concave  surface  is  placed  about  an 
inch  beneath  the  pubic  arch,  from  which  it  is  separated  by  the  dorsal  vessels  and 
nerves  of  the  penis  and  some  muscular  fibres.  Its  posterior  convex  surface  is 
separated  from  the  rectum  by  a  triangular  space,  which  is  part  of  the  perinamm. 
The  membranous  portion  of  the  urethra  perforates  both  the  anterior  and  posterior 
layers  of  the  deep  perineal  fascia,  and  receives  an  investment  from  them.  As  it 
pierces  the  posterior  layer,  the  fibres  around  the  opening  are  prolonged  backward 


THE   MALE    URETHRA.  1147 

over  the  posterior  part  of  the  membranous  portion  of  the  urethra,  and  as  it  pierces 
the  anterior  layer,  a  similar  prolongation  takes  place  in  the  opposite  direction, 
investing  the  anterior  part  of  the  membranous  portion.  It  is  also  surrounded  by 
the  Compressor  urethrse  muscle. 

The  Spongy  portion  is  the  longest  part,  and  is  contained  in  the  corpus  spongi- 
osum.  It  is  about  six  inches  in  length,  and  extends  from  the  termination  of  the 
membranous  portion  of  the  meatus  urinarius.  Its  direction  at  first  is  downward  and 
forward  then  upward  for  a  short  distance  and  then  downward  again.  It  is  narrow 
and  of  uniform  size  in  the  body  of  the  penis,  measuring  about  a  quarter  of  an  inch 
in  diameter,  being  dilated  behind,  within  the  bulb,  and  again  anteriorly  within  the 
glans  penis,  where  it  forms  the  fossa  navicularis. 

The  Bulbous  portion  is  a  name  given,  in  some  descriptions  of  the  urethra,  to 
the  posterior  part  of  the  spongy  portion  contained  within  the  bulb. 

The  meatus  urinarius  is  the  most  contracted  part  of  the  urethra ;  it  is  a  vertical 
slit,  about  three  lines  in  length,  bounded  on  each  side  by  two  small  labia. 

The  inner  surface  of  the  lining  membrane  of  the  urethra,  especially  on  the  floor 
of  the  spongy  portion,  presents  the  orifices  of  numerous  mucous  glands  and  follicles 
situated  in  the  submucous  tissue,  and  named  the  glands  of  Littre.  They  vary  in 
size,  and  their  orifices  are  directed  forward,  so  that  they  may  easily  intercept  the 
point  of  a  catheter  in  its  passage  along  the  canal.  One  of  these  lacunae,  larger  than 
the  rest,  is  situated  in  the  upper  surface  of  the  fossa  navicularis,  about  an  inch  and 
a  half  from  the  orifice ;  it  is  called  the  lacuna  magna.  Into  the  bulbous  portion 
are  found  opening  the  ducts  of  Cowper'a  glands. 

Structure. — The  urethra  is  composed  of  a  continuous  mucous  membrane, 
supported  by  a  submucous  tissue  which  connects  it  with  the  various  structures 
through  which  it  passes. 

The  niuci'iu*  coat  forms  part  of  the  genitourinary  mucous  membrane.  It  is 
continuous  with  the  mucous  membrane  of  the  bladder,  ureters,  and  kidneys; 
externally  with  the  integument  covering  the  glans  penis  ;  and  is  prolonged  into 
the  ducts  of  the  glands  which  open  into  the  urethra — viz.  Cowper's  glands  and  the 
prostate  gland — and  into  the  vasa  deferentia  and  vesiculae  seminales  through  the 
ejaculatory  ducts.  In  the  spongy  and  membranous  portions  the  mucous  membrane 
is  arranged  in  longitudinal  folds  Avhen  the  organ  is  contracted.  Small  papillae 
are  found  upon  it  near  the  orifice,  and  its  epithelial  lining  is  of  the  columnar  and 
stratified  variety,  excepting  near  the  meatus,  where  it  is  squamous. 

The  submucous  tissue  consists  of  a  vascular  erectile  layer,  outside  which  is  a 
layer  of  unstriped  muscular  fibres,  arranged  in  a  circular  direction,  which  sepa- 
rates the  mucous  membrane  and  submucous  tissue  from  the  tissue  of  the  corpus 
spongiosum. 

Surgical  Anatomy. — The  urethra  maybe  ruptured  by  the  patient  falling  astride  of  any 
hard  substance  and  striking  his  perinaeum,  so  that  the  urethra  is  crushed  against  the  pubic  arch. 
Bleeding  will  at  once  take  place  from  the  urethra,  and  this,  together  with  the  bruising  in  the 
perinaeum  and  the  history  of  the  accident,  will  at  once  point  to  the  nature  of  the  injury. 

The  surgical  anatomy  of  the  urethra  is  of  considerable  importance  in  connection  with  the 
passage  of  instruments  into  the  bladder.  Otis  was  the  first  to  point  out  that  the  urethra  is 
capable  of  great  dilat ability,  so  that,  excepting  through  the  external  meatus,  an  instrument  cor- 
responding to  1 8  English  gauge  (29  French)  can  usually  be  passed  without  damage.  The  orifice 
of  the  urethra  is  not  so  dilatable,  and  therefore  frequently  requires  slitting.  A  recognition  of 
this  dilatability  caused  Bigelow  to  very  considerably  modify  the  operation  of  lithotrity  and  intro- 
duce that  of  litholapaxy.  In  passing  catheters,  especially  fine  ones,  the  point  of  the  instrument 
should  be  kept  as  far  as  possible  along  the  upper  wall  of  the  canal,  as  the  point  is  otherwise  very 
liable  to  enter  one  of  the  lacunae.  Stricture  of  the  urethra  is  a  disease  of  very  common  occur- 
rence, and  is  generally  situated  in  the  spongy  portion  of  the  urethra,  most  commonly  in  the 
bulbous  portion,  just  in  front  of  the  membranous  urethra,  but  in  a  very  considerable  number  of 
cases  in  the  penile  or  ante-scrotal  part  of  the  canal. 


MALE    GENERATIVE    ORGANS. 


THE  PROSTATE  GLAND. 

THE  Prostate  Gland  (xpotffryfju,  to  stand  before)  is  a  firm,  muscular,  glandular 
body,  which  is  placed  immediately  in  front  of  the  neck  of  the  bladder  and 
around  the  commencement  of  the  urethra.     It  is  placed  in  the  pelvic  cavity,  behind 
and  below  the  symphysis  pubis,  posterior  to  the  deep  perineal  fascia,  and  rests  upon 


/ 


--*>  A 


s*"?2r»  o    * 

FIG.  736. — Transverse  section  of  normal  prostate  through  the  middle  of  the  verumontanum.  from  a  subject 
aged  nineteen  years.  (Taylor.)  n.  Longitudinal  sections  of  ducts  leading  from  the  lobules  of  the  prostatic 
glands:  b,  verumontanum ;  c,  sinus  pocularis:  d,  urethra;  e,  ejaculatory  ducts :/,  arteries,  veins,  and  venous 
sinuses  in  capsule  of  prostate  :  t),  nerve  trunks  in  capsule  ;  h,  point  of  origin  of  fibro-muscular  bands  encircling 
urethra;  i,  zone  of  striated  voluntary  muscle  on  superior  surface.  (Drawii  from  Krdinger  projection  apparatus.) 

the  rectum,  through  which  it  may  be  distinctly  felt,  especially  when  enlarged. 
In  shape  and  size  it  is  said  to  resemble  a  chestnut. 

Its  base  is  directed  upward  and  backward  and  rests  against  the  neck  of  the 
bladder. 

Its  apex  is  directed  downward  and  forward  to  the  deep  perineal  fascia,  which  it 
touches. 

Its  posterior  surface  is  smooth  and  flat,  marked  by  a  slight  longitudinal  furrow, 
and  rests  on  the  rectum,  to  which  it  is  connected  by  dense  areolar  tissue. 

Its  anterior  surface  is  convex,  and  is  placed  about  three-quarters  of  an  inch 
behind  the  lower  part  of  the  pubic  symphysis. 

It  measures  about  an  inch  and  a  half  in  its  transverse  diameter  at  the  base,  an 
inch  in  its  antero-posterior  diameter,  and  three-quarters  of  an  inch  in  depth.  Its 
weight  is  about  five  drachms.  It  is  held  in  its  position  by  the  anterior  ligaments 
of  the  bladder  (pubo-prostatic] ;  by  the  posterior  layer  of  the  deep  perineal  fascia, 
which  invests  the  commencement  of  the  membranous  portion  of  the  urethra  and 

1148 


THE  PROSTATE   GLAND.  1149 

prostate  gland  :  and  by  the  anterior  portion  of  the  Levator  ani  muscle  (levator 
prostatce),  which  passes  down  on  each  side  from  the  symphysis  pubis  and  anterior 
ligament  of  the  bladder  to  the  sides  of  the  prostate. 

The  prostate  consists  of  two  lateral  lobes  and  a  middle  lobe. 

The  two  lateral  lobes  are  of  equal  size,  separated  by  a  deep  notch  behind,  and 
by  a  slight  furrow  upon  the  anterior  and  posterior  surfaces  of  the  gland,  which 
indicates  the  bilobed  condition  of  the  organ  in  some  animals. 

The  third,  or  middle  lobe,  is  a  small  transverse  band,  occasionally  a  rounded  or 
triangular  prominence,  placed  between  the  two  lateral  lobes  at  the  posterior  part 
of  the  organ.  It  lies  immediately  beneath  the  neck  of  the  bladder,  behind  the 
commencement  of  the  urethra,  and  above  and  between  the  ejaculatory  ducts.  Its 
existence  is  not  constant,  but  it  is  occasionally  found  at  an  early  period  of  life,  as 
well  as  in  adults  and  in  old  age. 

The  prostate  gland  is  perforated  by  the  urethra  and  the  ejaculatory  ducts. 
The  urethra  usually  lies  about  one-third  nearer  its  posterior  than  its  anterior  sur- 
face ;  occasionally,  the  prostate  surrounds  only  the  lower  three-fourths  of  the  tube, 
and  more  rarely  the  urethra  runs  through  the  lower  instead  of  the  upper  part  of 
the  gland.  The  ejaculatory  ducts  pass  forward  obliquely  between  the  middle  and 
each  lateral  lobe  of  the  prostate  and  open  into  the  prostatic  portion  of  the  urethra. 

Structure. — The  prostate  is  enclosed  in  a  thin  but  firm  fibrous  capsule,  distinct 
from  that  derived  from  the  posterior  layer  of  the  deep  perineal  fascia,  and  separated 
from  it  by  a  plexus  of  veins.  Its  substance  is  of  a  pale  reddish-gray  color,  of 
great  density  and  not  easily  torn.  It  consists  of  glandular  substance  and  muscular 
tissue. 

The  muscular  tissue,  according  to  Kolliker,  constitutes  the  proper  stroma  of  the 
prostate,  the  connective  tissue  being  very  scanty,  and  simply  forming  thin  trabeculae 
between  the  muscular  fibres,  in  which  the  vessels  and  nerves  of  the  gland  ramify. 
The  muscular  tissue  is  arranged  as  follows  :  Immediately  beneath  the  fibrous  capsule 
is  a  dense  layer,  which  forms  an  investing  sheath  for  the  gland :  secondly,  around 
the  urethra  as  it  lies  in  the  prostate,  is  another  dense  layer  of  circular  fibres, 
continuous  behind  with  the  internal  layer  of  the  muscular  coat  of  the  bladder, 
and  in  front  blending  with  the  fibres  surrounding  the  membranous  portion  of  the 
urethra.  Between  these  two  layers  strong  bands  of  muscular  tissue,  which 
decussate  freely,  form  meshes  in  which  the  glandular  structure  of  the  organ  is 
imbedded.  In  that  part  of  the  gland  which  is  situated  above  the  urethra  the 
muscular  tissue  is  especially  dense,  and  there  is  here  little  or  no  gland  tissue; 
while  in  that  part  which  is  below  the  urethra  the  muscular  tissue  presents  a  wide- 
meshed  structure,  which  is  densest  at  the  upper  part  of  the  gland — that  is.  near 
the  bladder — becoming  looser  and  more  sponge-like  toward  the  apex  of  the 
organ. 

The  glandular  substance  is  composed  of  numerous  follicular  pouches,  opening 
into  elongated  canals,  which  join  to  form  from  twelve  to  twenty  small  excretory 
ducts.  The  follicles  are  connected  together  by  areolar  tissue,  supported  by 
prolongations  from  the  fibrous  capsule  and  muscular  stroma.  and  enclosed  in  a 
delicate  capillary  plexus.  The  epithelium  lining  of  both  the  canals  and  the 
terminal  vesicles  is  of  the  columnar  variety.  The  prostatic  ducts  open  into  the 
floor  of  the  prostatic  portion  of  the  urethra. 

Vessels  and  Nerves. — The  arteries  supplying  the  prostate  are  derived  from  the 
internal  pudic,  vesical,  and  haemorrhoidal.  Its  veins  form  a  plexus  around  the  sides 
and  base  of  the  gland ;  they  receive  in  front  the  dorsal  vein  of  the  penis,  and 
terminate  in  the  internal  iliac  vein.  The  nerves  are  derived  from  the  pelvic 
plexus. 

Surgical  Anatomy. — The  relation  of  the  prostate  to  the  rectum  should  be  noted :  by  means 
of  the  finger  introduced  into  the  gut  the  surgeon  detects  enlargement  or  other  disease  of  this 
organ ;  he  can  feel  the  apex  of  the  gland,  which  is  the  guide  to  Cock's  operation  for  stricture  ; 
he  is  enabled  also  by  the  same  means  to  direct  the  point  of  a  catheter  when  its  introduction  is 
attended  with  difficulty  either  from  injury  or  disease  of  the  membranous  or  prostatic  portions  of 


1150  MALE    GENERATIVE    ORGANS. 

the  urethra.  When  the  finger  is  introduced  into  the  bowel  the  surgeon  may,  in  some  cases, 
especially  in  boys,  learn  the  position,  as  well  as  the  size  and  weight,  of  a  calculus  in  the  bladder ; 
and  in  the  operation  for  its  removal,  if,  as  is  not  un frequently  the  case,  it  should  be  lodged  behind 
an  enlarged  prostate,  it  may  be  displaced  from  its  position  by  pressing  upward  the  base  of  the 
bladder  from  the  rectum.  The  prostate  gland  is  occasionally  the  seat  of  suppuration,  either  due  to 
injury,  gonorrhoea,  or  tuberculous  disease.  The  gland,  being  enveloped  in  a  dense  unyielding 
capsule,  determines  the  course  of  the  abscess,  and  also  explains  the  great  pain  which  is  present 
in  the  acute  form  of  the  disease.  The  abscess  most  frequently  bursts  into  the  urethra,  tlu> 
direction  in  which  there  is  least  resistance,  but  may  occasionally  burst  into  the  rectum ,  or  more 
rarely  in  the  perinaeum.  In  adyanced  life  the  prostate  becomes  considerably  enlarged,  and  pro- 
jects into  the  bladder  so  as  to  impede  the  passage  of  the  urine.  According  to  Dr.  Messer's 
researches,  conducted  at  Greenwich  Hospital,  it  would  seem  that  such  obstruction  exists  in  20 
per  cent,  of  all  men  over  sixty  years  of  age.  In  some  cases  the  enlargement  affects  principally 
the  lateral  lobes,  which  may  undergo  considerable  enlargement  without  causing  much  incon- 
venience. In  other  cases  it  would  seem  that  the  middle  lobe  enlarges  most,  and  even  a  small 
enlargement  of  this  lobe  may  act  injuriously,  by  forming  a  sort  of  valve  over  the  urethral  orifice, 
preventing  the  passage  of  the  urine,  and  blocking  more  completely  the  orifice  the  more  the 
patient  strains.  In  consequence  of  the  enlargement  of  the  prostate  a  pouch  is  formed  at  the 
base  of  the  bladder  behind  the  projection,  in  which  water  collects  and  cannot  be  entirely  expelled. 
It  becomes  decomposed  and  ammoniacal,  and  leads  to  cystitis.  For  this  condition  "  prostatec- 
tomy "  is  sometimes  done.  The  bladder  is  opened  by  an  incision  above  the  symphysis  pubis,  the 
mucous  membrane  incised,  and  the  enlarged  and  projecting  middle  lobe  enucleated. 

COWPER'S  GLANDS. 

Cowper's  Glands  are  two  small  rounded  and  somewhat  tabulated  bodies  of 
a  yellow  color,  about  the  size  of  peas,  placed  behind  the  fore  part  of  the  mem- 
branous portion  of  the  urethra,  between  the  two  layers  of  the  deep  perineal  fascia. 
They  lie  close  above  the  bulb,  and  are  enclosed  by  the  transverse  fibres  of  the 
Compressor  urethras  muscle.  Their  existence  is  said  to  be  constant :  they  gradually 
diminish  in  size  as  age  advances. 

Structure. — Each  gland  consists  of  several  lobules  held  together  by  a  fibrous 
investment.  Each  lobule  consists  of  a  number  of  acini  lined  by  columnar 
epithelial  cells,  opening  into  one  duct,  which,  joining  with  the  ducts  of  other 
lobules  outside  the  gland,  form  a  single  excretory  duct.  The  excretory  duct  of 
each  gland,  nearly  an  inch  in  length,  passes  obliquely  forward  beneath  the 
mucous  membrane,  and  opens  by  a  minute  orifice  on  the  floor  of  the  bulbous 
portion  of  the  urethra.  Their  existence  is  said  to  be  constant ;  they  gradually 
diminish  in  size  as  age  advances. 

THE  PENIS. 

The  Penis  is  the  organ  of  copulation.  It  consists  of  a  root,  body,  and  extremity, 
or  glans  penis. 

The  root  is  firmly  connected  to  the  rami  of  the  os  pubis  and  ischium  by  two 
strong  tapering,  fibrous  processes,  the  crura,  and  to  the  front  of  the  symphysis 
pubis  by  the  suspensory  ligament,  a  strong  band  of  fibrous  tissue  which  passes 
downward  from  the  front  of  the  symphysis  pubis  to  the  upper  surface  of  the  root 
of  the  penis,  where  it  blends  with  the  fascial  sheath  of  the  organ. 

The  extremity  or  glans  penis,  presents  the  form  of  an  obtuse  cone,  flattened 
from  above  downward.  At  its  summit  is  a  vertical  fissure,  the  orifice  of  the 
urethra  (meatus  urinarius).  The  base  of  the  glans  forms  a  rounded  projecting 
border,  the  corona  glandis,  and  behind  the  corona  is  a  deep  constriction,  the 
cervix.  Upon  both  of  these  parts  numerous  small  sebaceous  glands  are  found, 
the  glandulce  Tysonii  odoriferce.  They  secrete  a  sebaceous  matter  of  very  peculiar 
odor,  which  probably  contains  caseine  and  becomes  easily  decomposed. 

The  body  of  the  penis  is  the  part  between  the  root  and  extremity.  In  the 
flaccid  condition  of  the  organ  it  is  cylindrical,  but  when  erect  has  a  triangular 
prismatic  form  with  rounded  angles,  the  broadest  side  being  turned  upward,  and 
called  the  dorsum.  The  body  is  covered  by  integument,  and  contains  in  its  interior 
a  large  portion  of  the  urethra.  The  integument  covering  the  penis  is  remarkable 
for  its  thinness,  its  dark  color,  its  looseness  of  connection  with  the  deeper  parts 
of  the  organ,  and  its  containing  no  adipose  tissue.  At  the  root  of  the  penis  the 


THE   PKXIS.  1151 

integument  is  continuous  with  that  upon  the  pubes  and  scrotum,  and  at  the 
neck  of  the  glans  it  leaves  the  surface  and  becomes  folded  upon  itself  to  form  the 
prepuce. 

The  internal  layer  of  the  prepuce  is  attached  behind  to  the  cervix,  and 
approaches  in  character  to  a  mucous  membrane;  from  the  cervix  it  is  reflected 
over  the  glans  penis,  and  at  the  meatus  urinarius  is  continuous  with  the  mucous 
lining  of  the  urethra. 

The  mucous  membrane  covering  the  glans  penis  contains  no  sebaceous  glands. 
but  projecting  from  its  free  surface  are  a  number  of  small,  highly  sensitive  papillae. 
Ar  the  back  part  of  the  meatus  urinarius  a  fold  of  mucous  membrane  passes  back- 
Avard  to  the  bottom  of  a  depressed  raphe,  where  it  is  continuous  with  the  prepuce ; 
this  fold  is  termed  the  free nu»i  pwputli. 

Structure  of  the  Penis. — The  penis  is  composed  of  a  mass  of  erectile  tissue 
enclosed  in  three  cylindrical  fibrous  compartments.  Of  these,  two,  the  corpora 
,  are  placed  side  by  side  along  the  upper  part  of  the  organ ;  the  third,  or 
jinmun*  encloses  the  urethra  and  is  placed  below. 

The  Corpora  Cavernosa  form  the  chief  part  of  the  body  of  the  penis.  They 
consist  of  tAvo  fibrous  cylindrical  tubes,  placed  side  by  side,  and  intimately 
connected  along  the  median  line  for  their  anterior  three-fourths,  whilst  at  their 
back  part  they  separate  from  each  other  to  form  the  crura,  which  are  two  strong 
tapering  fibrous  processes  firmly  connected  to  the  rami  of  the  os  pubis  and 
ischium.  Each  cms  commences  by  a  blunt -pointed  process  in  front  of  the 
tuberosity  of  the  ischium,  and  before  its  junction  Avith  its  felloAv  to  form  the 
bodv  of  the  penis  it  presents  a  slight  enlargement,  named  by  Kobelt  the  bulb 
<>f  tin  ••ni-fixx  cio'i't'itoxion.  Just  beyond  this  point  they  become  constricted, 
and  retain  an  equal  diameter  to  their  anterior  extremity,  Avhere  they  form  a 
single  rounded  end  which  is  received  into  a  fossa  in  the  base  of  the  glans  penis. 
A  median  groove  on  the  upper  surface  lodges  the  dorsal  vein  of  the  penis,  and  the 
groove  on  the  under  surface  receives  the  corpus  spongiosum.  The  root  of  the 
penis  is  connected  to  the  symphysis  pubis  by  the  suspensory  ligament. 

Structure. — The  corpora  cavernosa  are  surrounded  by  a  strong  fibrous  em-elope, 
consisting  of  two -sets  of  fibres — the  one,  longitudinal  in  direction,  being  common 
to  the  tAvo  corpora  cavernosa,  and  investing  them  in  a  common  covering ;  the 
other,  internal,  being  circular  in  direction,  and  being  proper  to  each  corpus 
cavernosum.  The  internal  circular  fibres  by  their  junction  at  one  part  form  an 
incomplete  partition  or  septum  between  the  tAvo  bodies. 

The  septum  between  the  tAvo  corpora  cavernosa  forms  an  imperfect  partition ; 
it  is  thick  and  complete  behind,  but  in  front  it  is  incomplete,  and  consists  of  a 
number  of  vertical  bands,  Avhich  are  arranged  like  the  teeth  of  a  comb,  whence  the 
name  which  it  has  received,  septum  pectiniforme.  These  bands  extend  betAveen 
the  dorsal  and  the  urethral  surface  of  the  corpora  cavernosa.  This  fibrous  invest- 
ment is  extremely  dense,  of  considerable  thickness,  and  consists  of  bundles  of 
shining  white  fibres,  with  an  admixture  of  Avell-deA'eloped  elastic  fibres,  so  that  it 
is  possessed  of  great  elasticity. 

From  the  internal  surface  of  the  fibrous  envelope,  as  Avell  as  from  the  sides  of 
the  septum,  are  given  off  a  number  of  bands  or  cords  Avhich  cross  the  interior  of 
the  corpora  cavernosa  in  all  directions,  subdividing  them  into  a  number  of 
separate  compartments,  and  giving  the  entire  structure  a  spongy  appearance. 
These  bands  and  cords  are  called  trabeeulce,  and  consist  of  Avhite  fibrous  tissue, 
elastic  fibres,  and  plain  muscular  fibres.  In  them  are  contained  numerous 
arteries  and  nerves. 

The  component  fibres  of  which  the  trabeculae  are  composed  are  larger  and 
stronger  round  the  circumference  than  at  the  centre  of  the  corpora  cavernosa; 
they  are  also  thicker  behind  than  in  front.  The  interspaces,  on  the  contrary,  are 
larger  at  the  centre  than  at  the  circumference,  their  long  diameter  being  directed 
transversely  :  they  are  largest  anteriorly.  They  are  occupied  by  venous  blood, 
and  are  lined  bv  a  laver  of  flattened  cells  similar  to  the  endothelial  lining  of  veins. 


1152 


MALE    GENERATIVE    ORGANS. 


The  whole  of  the  structure  of  the  corpora  cavernosa  contained  within  the 
fibrous  sheath  consists,  therefore,  of  a  sponge-like  tissue  of  areolar  spaces  freely 
communicating  with  each  other  and  filled  with  venous  blood.  The  spaces  may 
therefore  be  regarded  as  large  cavernous  veins. 

The  arteries  bringing  the  blood  to  these  spaces  are  the  arteries  of  the  corpora 
cavernosa  and  branches  from  the  dorsal  artery  of  the  penis,  which  perforate  the 
fibrous  capsule,  along  the  upper  surface,  especially  near  the  fore  part  of  the 
organ. 

These  arteries  on  entering  the  cavernous  structure  divide  into  branches  which 
are  supported  and  enclosed  by  the  trabeculee.  Some  of  these  terminate  in  a 
capillary  network,  the  branches  of  which  open  directly  into  the  cavernous  spaces ; 
others  assume  a  tendril-like  appearance,  and  form  convoluted  and  somewhat 
dilated  vessels,  which  were  named  by  Miiller  helicine  arteries.  They  project 
into  the  spaces,  and  from  them  are  given  off  small  capillary  branches  to  supply 
the  trabecular  structure.  They  are  bound  down  in  the  spaces  by  fine  fibrous 
processes,  and  are  more  abundant  in  the  back  part  of  the  corpora  cavernosa 
(Fig.  737). 

The  blood  from  the  cavernous  spaces  is  returned  by  a  series  of  vessels,  some 
of  which  emerge  in  considerable  numbers  from  the  base  of  the  glans  penis  and 


Frc.  737.— From  the  peripheral  portion  of  the  corpus 


(Copied  from  Langer.)    1".  a.  "Capillary  network, 
with  the  cavernous  spaces. 


corpus  cavernosum  penis  under  a  low  magnifying  power. 
.  Cavernous  spaces.    2.  Connection  of  the  arterial  twigs  (a) 


converge  on  the  dorsum  of  the  organ  to  form  the  dorsal  vein ;  others  pass  out  on 
the  upper  surface  of  the  corpora  cavernosa  and  join  the  dorsal  vein;  some  emerge 
from  the  under  surface  of  the  corpora  cavernosa,  and,  receiving  branches  from  the 
corpus  spongiosum,  wind  round  the  sides  of  the  penis  to  terminate  in  the  dorsal 
vein;  but  the  greater  number  pass  out  at  the  root  of  the  penis  and  join  the 
prostatic  plexus. 

The  Corpus  Spongiosum  encloses  the  urethra,  and  is  situated  in  the  groove  on 
the  under  surface  of  the  corpora  cavernosa.  It  commences  posteriorly  in  front  of 
the  deep  perineal  fascia,  between  the  divei'ging  crura  of  the  corpora  cavernosa. 
where  it  forms  a  rounded  enlargement,  the  bulb,  and  terminates  anteriorly  in 
another  expansion,  the  glans  penis,  which  overlaps  the  anterior  rounded  extremity 
of  the  corpora  cavernosa.  The  central  portion,  or  body  of  the  corpus  spongiosum, 
is  cylindrical,  and  tapers  slightly  from  behind  forward. 

The  bulb  varies  in  size  in  different  subjects  ;  it  receives  a  fibrous  investment 
from  the  anterior  layer  of  the  deep  perineal  fascia,  and  is  surrounded  by  the 
Accelerator  urinse  muscle.  The  urethra  enters  the  bulb  nearer  its  upper  than  its 
lower  surface,  being  surrounded  by  a  layer  of  erectile  tissue,  a  thin  prolongation 
of  which  is  continued  backward  round  the  membranous  and  prostatic  portions  of 
the  canal  to  the  neck  of  the  bladder,  lying  between  the  two  layers  of  muscular 
tissue.  The  portion  of  the  bulb  below  the  urethra  presents  a  partial  division  into 
two  lobes,  being  marked  externally  by  a  linear  raphe,  whilst  internally  there 
projects  inward,  for  a  short  distance,  a  thin  fibrous  septum,  more  distinct  in 
early  life. 


THE    TESTES.  1153 

Structure. — The  corpus  spongiosum  consists  of  a  strong  fibrous  envelope, 
enclosing  a  trabecular  structure,  which  contains  in  its  meshes  erectile  tissue.  The 
fibrous  envelope  is  thinner,  whiter  in  color,  and  more  elastic  than  that  of  the 
corpora  cavernosa.  The  trabectilse  are  delicate,  uniform  in  size,  and  the  meshes 
between  them  small,  their  long  diameter,  for  the  most  part,  corresponding  with 
that  of  the  penis.  The  external  envelope  or  outer  coat  of  the  corpus  spongiosum 
is  formed  partly  of  unstriped  muscular  fibre,  and  a  layer  of  the  same  tissue  imme- 
diately surrounds  the  canal  of  the  urethi'a. 

The  lymphatics  of  the  penis  consist  of  a  superficial  and  deep  set ;  the  former 
are  derived  from  a  dense  network  on  the  skin  of  the  glans  and  prepuce  and  from 
the  mucous  membrane  of  the  urethra,  and  terminate  in  the  superficial  inguinal 
glands ;  the  latter  emerge  from  the  corpora  cavernosa  and  corpus  spongiosum,  and, 
passing  beneath  the  pubic  arch,  join  the  deep  lymphatics  of  the  pelvis. 

The  nerd1*  are  derived  from  the  internal  pudic  nerve  and  the  pelvic  plexus.  On 
the  glans  and  bulb  some  filaments  of  the  cutaneous  nerves  have  Pacinian  bodies 
connected  with  them,  and,  according  to  Krause,  many  of  them  terminate  in  a 
peculiar  form  of  end-bulb. 

Surgical  Anatomy. — The  penis  occasionally  requires  removal  for  malignant  disease. 
Usually,  removal  of  the  ante-scrotal  portion  is  all  that  is  necessary,  but  sometimes  it  is  requisite 
to  remove  the  whole  or<ran  from  its  attachment  to  the  rarni  of  the  os  pubis  and  ischium.  The 
former  operation  is  performed  either  by  cutting  off  the  whole  of  the  anterior  part  of  the  penis 
with  one  sweep  of  the  knife,  or,  what  is  better,  cutting  through  the  corpora  cavernosa  from  the 
dorsum,  and  then  separating  the  corpus  spongiosum  from  them,  dividing  it  at  a  level  nearer  the 
glans  penis.  The  mucous  membrane  of  the  urethra  is  then  slit  up,  and  the  edges  of  the  flap 
attached  to  the  external  skin,  in  order  to  prevent  contraction  of  the  orifice,  which  would  other- 
wise take  place.  The  vessels  which  require  ligature  are  the  two  dorsal  arteries  of  the  penis,  the 
arteries  of  the  corpora  cavernosa,  and  the  artery  of  the  septum.  When  the  entire  organ  requires 
removal  the  patient  is  placed  in  the  lithotomy  position,  and  an  incision  is  made  round  the  root 
of  the  penis,  and  carried  down  the  median  line  of  the  scrotum  as  far  as  the  perinaeum.  The 
two  halves  of  the  scrotum  are  then  separated  from  each  other,  and,  a  catheter  having  been  intro- 
duced into  the  bladder  as  a  guide,  the  membranous  portion  of  the  urethra  is  separated  from  the 
corpus  spongiosum  and  divided,  the  catheter  having  been  withdrawn,  just  behind  the  bulb.  The 
su<i ien;< »ry  ligament  is  now  severed,  and  the  crura  separated  from  the  bone  with  a  periosteum 
scraper,  and  the  whole  penis  removed.  The  membranous  portion  of  the  urethra,  which  has  not 
been  removed,  is  nmv  to  be  attached  to  the  skin  at  the  posterior  extremity  of  the  incision  in 
the  periiuvum.  The  remainder  of  the  wound  is  to  be  brought  together,  free  drainage  being 
provided  for. 

THE  TESTES  AND  THEIR  COVERINGS  (Fig.  738). 

The  Testes  are  two  glandular  organs,  which  secrete  the  semen ;  they  are  sit- 
uated in  the  scrotum,  being  suspended  by  the  spermatic  cords.  At  an  early 
period  of  foetal  life  the  testes  are  contained  in  the  abdominal  cavity,  behind  the 
peritoneum.  Before  birth  they  descend  to  the  inguinal  canal,  along  which  they 
]>as>  with  the  spermatic  cord,  and,  emerging  at  the  external  abdominal  ring,  they 
descend  into  the  scrotum,  becoming  invested  in  their  course  by  numerous  coverings 
derived  from  the  serous,  muscular,  and  fibrous  layers  of  the  abdominal  parietes, 
as  well  as  by  the  scrotum.  The  coverings  of  the  testes  are — the 

Skin     \  ( 

TA  >  ocrotum. 

Dartos  J 

Intel-columnar,  or  External  spermatic  fascia. 

Cremasteric  fascia. 

Infundibuliform,  or  Fascia  propria  (Internal  spermatic  fascia). 

Tunica  vaginalis. 

The  Scrotum  is  a  cutaneous  pouch  which  contains  the  testes  and  part  of  the 
spermatic  cords.  It  is  divided  superficially  into  two  lateral  halves  by  a  median  line, 
or  raphe,  which  is  continued  forward  to  the  under  surface  of  the  penis  and  backward 
along  the  middle  line  of  the  perinaeum  to  the  anus.  Of  these  two  lateral  portions,  the 
left  is  longer  than  the  right,  and  corresponds  with  the  greater  length  of  the  spermatic 
cord  on  the  left  side.  Its  external  aspect  varies  under  different  circumstances : 
73 


1154 


MALE    GENERATIVE    ORGANS. 


thus,  under  the  influence  of  warmth  and  in  old  and  debilitated  persons  it  becomes 
elongated  and  flaccid,  but  under  the  influence  of  cold  and  in  the  young  and 
robust  it  is  short,  corrugated,  and  closely  applied  to  the  testes. 

The  scrotum  consists  of  two  layers,  the  integument  and  the  dartos. 

The  integument  is  very  thin,  of  a  brownish  color,  and  generally  thrown  into 
folds  or  rugae.  It  is  provided  with  sebaceous  follicles,  the  secretion  of  which  has 
a  peculiar  odor,  and  is  beset  with  thinly-scattered,  crisp  hairs,  the  roots  of  which 
are  seen  through  the  skin. 

The  dartos  is  a  thin  layer  of  loose  reddish  tissue,  endowed  with  contractility : 
it  forms  the  proper  tunic  of  the  scrotum,  is  continuous,  around  the  base  of  the 
scrotum,  with  the  two  layers  of  the  superficial  fascia  of  the  groin  and  perinaeum, 

Skin. 

Dartos. 

External  spermatic  fascia. 

Cremasteric  fascia.-- 

Infundibuliform  fascia 

Parietal  tunica  vaginalis 

Visceral  tunica  vaginalis 

Tunica  albuginea. ... 
A  lobule  of  the  testicle..^ 

A  septum. .. 

Mediastinum. 

Digital  fossa 

Spermatic  vein.^ 
Epididymis... 

Vas  deferens 

Artery  to  vas.  — • 

Spermatic  artery _ 

Internal  muscular — 
tunic  of  Kolliker. 

FIG.  738.— Transverse  section  through  the  left  side  of  the  scrotum  and  the  left  testicle.    The  sac  of  the 
tunica  vaginalis  represented  in  a  distended  condition.    (Delepine.) 

and  sends  inward  a  distinct  septum,  septum  scroti,  which  divides  it  into  two 
cavities  for  the  two  testes,  the  septum  extending  between  the  raphe  and  the  under 
surface  of  the  penis  as  far  as  its  root. 

The  dartos  is  closely  united  to  the  skin  externally,  but  connected  with  the 
subjacent  parts  by  delicate  areolar  tissue,  upon  which  it  glides  with  the  greatest 
facility.  The  dartos  is  very  vascular,  and  consists  of  a  loose  areolar  tissue  con- 
taining unstriped  muscular  fibre,  but  no  fat.  Its  contractility  is  slow,  and  excited 
by  cold  and  mechanical  stimuli,  but  not  by  electricity. 

The  intercolumnar  fascia  is  a  thin  membrane  derived  from  the  margin  of  the 
pillars  of  the  external  abdominal  ring,  during  the  descent  of  the  testes  in  the 
foetus,  which  is  prolonged  downward  around  the  surface  of  the  cord  and  testis.  It 
is  separated  from  the  dartos  by  loose  areolar  tissue,  which  allows  of  considerable 
movement  of  the  latter  upon  it,  but  is  intimately  connected  with  the  succeeding 
layers. 

The  cremasteric  fascia  consists  of  scattered  bundles  of  muscular  fibres 
(Cremaster  muscle)  connected  together  into  a  continuous  covering  by  intermediate 
areolar  tissue.  The  muscular  fibres  are  continuous  with  the  lower  border  of  the 
Internal  oblique  muscle  of  the  abdomen. 

The  fascia  propria  is  a  thin  membranous  layer  which  loosely  invests  the 
surface  of  the  cord.  It  is  a  continuation  downward  of  the  infundibuliform  process 
of  the  fascia  transversalis  and  the  subperitoneal  areolar  tissue,  and  is  acquired 
during  the  descent  of  the  testis  in  the  foetus. 


THE    TESTES.  1155 

The  tunica  vaginalis  is  described  with  the  proper  covering  of  the  testis. 

Vessels  and  Nerves. — The  arteries  supplying  the  coverings  of  the  testis  are  : 
the  superficial  and  deep  external  pudic,  from  the  femoral ;  the  superficial  perineal 
branch  of  the  internal  pudic  ;  and  the  cremasteric  branch  from  the  epigastric.  The 
veins  follow  the  course  of  the  corresponding  arteries.  The  lymphatic*  terminate 
in  the  inguinal  glands.  The  nerves  are  :  the  ilio-inguinal  branch  of  the  lumbar 
plexus,  the  two  superficial  perineal  branches  of  the  internal  pudic  nerve,  the  inferior 
pudendal  branch  of  the  small  sciatic  nerve,  and  the  genital  branch  of  the  genito- 
crural  nerve. 

The  Spermatic  Cord  extends  from  the  internal  abdominal  ring,  where  the 
structures  of  which  it  is  composed  converge,  to  the  back  part  of  the  testicle.  In 
the  abdominal  wall  the  cord  passes  obliquely  along  the  inguinal  canal,  resting  on 
Poupart's  ligament.  It  lies  at  first  between  the  Internal  oblique  and  the  fascia 
transversal  is  :  but  nearer  the  pubes  it  has  the  aponeurosis  of  the  External  oblique 
in  front  of  it  and  the  conjoined  tendon  behind  it.  It  then  escapes  at  the  external 
ring,  and  descends  nearly  vertically  into  the  scrotum.  The  left  cord  is  rather 
longer  than  the  right,  consequently  the  left  testis  hangs  somewhat  lower  than  its 
fellow. 

Structure  of  the  Spermatic  Cord. — The  spermatic  cord  is  composed  of  arteries, 
veins,  lymphatics,  nerves,  the  excretory  duct  of  the  testicle,  and  a  thin  fibrous 
cord,  the  remains  of  the  peritoneal  pouch,  caused  by  the  descent  of  the  testicle. 
These  structures  are  connected  together  by  areolar  tissue,  and  invested  by  the  fas- 
ciae brought  down  by  the  testicle  in  its  descent. 

The  arteries  of  the  cord  are  :  the  spermatic,  from  the  aorta  ;  the  artery  of  the 
vas  tk't'erens.  from  the  superior  vesical ;  the  cremasteric,  from  the  deep  epigastric. 

The  spermatic  artery,  a  branch  of  the  abdominal  aorta,  escapes  from  the 
abdomen  at  the  internal  or  deep  abdominal  ring,  and  accompanies  the  other  con- 
stituents of  the  spermatic  cord  along  the  inguinal  canal  and  through  the  external 
abdominal  ring  into  the  scrotum.  It  then  descends  to  the  testicle,  and,  becoming 
tortuous,  divides  into  several  branches,  two  or  three  of  which  accompany  the 
vas  deferens  and  supply  the  epididyinis,  anastomosing  with  the  artery  of  the  vas 
deferens  ;  others  pierce  the  back  of  the  tunica  albuginea  and  supply  the  substance 
of  the  testis. 

The  cremasteric  art, -ry  is  a  branch  of  the  deep  epigastric  artery.  It  accom- 
panies the  spermatic  cord  and  supplies  the  Cremaster  muscle  and  other  coverings 
of  the  cord,  anastomosing  \vith  the  spermatic  artery, 

The  artery  of  the  vas  deferens,  a  branch  of  the  superior  vesical,  is  a  long  slender 
vessel  which  accompanies  the  vas  deferens,  ramifying  upon  the  coats  of  that  duct, 
and  anastomosing  with  the  spermatic  artery  near  the  testis. 

The  spermatic  veins  emeYge  from  the  back  of  the  testis  and  receive  tributaries 
from  the  epididymis ;  they  unite  and  form  a  convoluted  plexus  (plexus  pampini- 
f nr  ID  !.-<},  which  forms  the  chief  mass  of  the  cord  :  the  vessels  composing  this  plexus 
are  very  numerous,  and  ascend  along  the  cord  in  front  of  the  vas  deferens ;  below 
the  external  or  superficial  abdominal  ring  thev  unite  to  form  three  or  four  veins, 
which  pass  along  the  spermatic  canal,  and,  entering  the  abdomen  through  the 
internal  or  deep  abdominal  ring,  coalesce  to  form  two  veins.  These  again  unite  to 
form  a  single  vein,  which  opens  on  the  right  side  into  the  inferior  vena  cava  at  an 
acute  angle,  and  on  the  left  side  into  the  renal  vein  at  a  right  angle. 

The  lymphatic  vessels  terminate  in  the  lumbar  glands. 

The  nerves  are  the  spermatic  plexus  from  the  sympathetic,  joined  by  filaments 
from  the  pelvic  plexus  which  accompany  the  artery  of  the  vas  deferens. 

Surgical  Anatomy. — The  scrotum  forms  an  admirable  covering  for  the  protection  of  the 
testicle.  This  body,  lying  suspended  and  loose  in  the  cavity  of  the  scrotum  and  surrounded  by 
a  serous  membrane,  is  capable  of  great  mobility,  and  can  therefore  easily  slip  about  within  the 
scrotum,  and  thus  avoid  injuries  from  blows  or  squeezes.  The  skin  of  the  scrotum  is  very 
elastic  and  capable  of  great  distension,  and  on  account  of  the  looseness  and  amount  of  subcu- 
taneous tissue  the  scrotum  becomes  greatly  enlarged  in  cases  of  oedema,  to  which  this  part  is 
especially  liable  on  account  of  its  dependent  position.  The  scrotum  is  frequently  the  seat  of 


1156  MALE    GENERATIVE    ORGANS. 

epithelioma ;  this  is  no  doubt  due  to  the  rugae  on  its  surface,  which  favor  the  lodgment  of  dirt, 
and  this,  causing  irritation,  is  the  exciting  cause  of  the  disease,  which  is  especially  common  in 
chimney-sweeps  from  the  lodgment  of  soot.  The  scrotum  is  also  the  part  most  frequently 
affected  by  elephantiasis. 

On  account  of  the  looseness  of  the  subcutaneous  tissue  considerable  extravasations  of  blood 
may  take  place  from  very  slight  injuries.  It  is  therefore  generally  recommended  never  to  apply 
leeches  to  the  scrotum,  since  they  may  lead  to  considerable  ecchymosis,  but  rather  to  puncture 
one  or  more  of  the  superficial  veins  of  the  scrotum  in  cases  where  local  bloodletting  from  this 
part  is  judged  to  be  desirable.  The  muscular  fibre  in  the  dartos  causes  contraction  and  consider- 
able diminution  in  the  size  of  a  wound  of  the  scrotum,  as  after  the  operation  of  castration,  and 
is  of  assistance  in  keeping  the  edges  together  and  covering  the  exposed  parts. 

THE  TESTES. 

The  Testes  are  suspended  in  the  scrotum  by  the  spermatic  cords.  As  the  left 
spermatic  cord  is  rather  longer  than  the  right  one,  the  left  testicle  hangs  somewhat 
lower  than  its  fellow.  Each  gland  is  of  an  oval  form,  compressed  laterally,  and 
having  an  oblique  position  in  the  scrotum,  the  upper  extremity  being  directed 
forward  and  a  little  outward,  the  lower,  backward  and  a  little  inward ;  the  anterior 
convex  border  looks  forward,  outward,  and  downward  ;  the  posterior  or  straight 
border,  to  which  the  cord  is  attached,  inward,  backward,  and  upward. 

The  anterior  border  and  lateral  surfaces,  as  well  as  both  extremities  of  the 
organ,  are  convex,  free,  smooth,  and  invested  by  the  tunica  vaginalis.  The 
posterior  border,  to  which  the  cord  is  attached,  receives  only  a  partial  invest- 
ment from  that  membrane.  Lying  along  this  posterior  border  is  a  long,  narrow, 
flattened  body,  named  from  its  relation  to  the  testis,  the  epididymis  (&'ou//oc, 
testis).  It  consists  of  a  central  portion,  or  body  ;  an  upper  enlarged  extremity,  the 
globus  major,  or  head ;  and  a  lower  pointed  extremity,  the  tail,  or  globus  minor. 
The  globus  major  is  intimately  connected  with  the  upper  end  of  the  testicle  by 
means  of  its  efferent  ducts,  and  the  globus  minor  is  connected  with  its  lower  end 
by  cellular  tissue  and  a  reflection  of  the  tunica  vaginalis.  The  outer  surface  and 
upper  and  lower  ends  of  the  epididymis  are  free  and  covered  by  serous  membrane  ; 
the  body  is  also  completely  invested  by  it,  excepting  along  its  posterior  border. 
The  epididymis  is  connected  to  the  back  of  the  testis  by  a  fold  of  the  serous  mem- 
brane. Attached  to  the  upper  end  of  the  testis  or  to  the  epididymis  are  one  or 
more  small  pedunculated  bodies.  One  of  them  is  pretty  constantly  found  between 
the  globus  major  of  the  epididymis  and  the  testicle,  and  is  believed  to  be  the 
remains  of  the  upper  extremity  of  the  Miillerian  duct  (page  136).  It  is  termed 
the  hydatid  of  Morgagni.  When  the  testicle  is  removed  from  the  body,  the 
position  of  the  vas  deferens,  on  the  posterior  surface  of  the  testicle  and  inner  side 
of  the  epididymis,  marks  the  side  to  which  the  gland  has  belonged. 

Size  and  Weight. — The  average  dimensions  of  this  gland  are  from  one  and  a 
half  to  two  inches  in  length,  one  inch  in  breadth,  and  an  inch  and  a  quarter  in  the 
antero-posterior  diameter,  and  the  weight  varies  from  six  to  eight  drachms,  the 
left  testicle  being  a  little  the  larger. 

The  testis  is  invested  by  three  tunics — the  tunica  vaginalis,  tunica  albuginea, 
and  tunica  vasculosa. 

The  Tunica  Vaginalis  is  the  serous  covering  of  the  testis.  It  is  a  pouch  of 
serous  membrane,  derived  from  the  peritoneum  during  the  descent  of  the  testis  in 
the  foetus  from  the  abdomen  into  the  scrotum.  After  its  descent  that  portion  of 
the  pouch  which  extends  from  the  internal  ring  to  near  the  upper  part  of  the  gland 
becomes  obliterated,  the  lower  portion  remaining  as  a  shut  sac,  which  invests 
the  outer  surface  of  the  testis,  and  is  reflected  on  to  the  internal  surface  of  the 
scrotum ;  hence  it  may  be  described  as  consisting  of  -a  visceral  and  parietal 
portion. 

The  visceral  portion  (tunica  vaginalis  proprid)  covers  the  outer  surface  of  the 
testis,  as  well  as  the  epididymis,  connecting  the  latter  to  the  testis  by  means  of  a 
distinct  fold  forming  a  depression,  the  digital  fossa.  From  the  posterior  border  of 
the  gland  it  is  reflected  on  to  the  internal  surface  of  the  scrotum. 


THE    TESTES. 


1157 


Spermatic  cord. 


Artery  of 
cord. 


Tunica  raginalis, 
parietal  layer. 


The  parietal  portion  of  the  serous  membrane  (tunica  vaginalis  refiexa)  is  far 
more  extensive  than  the  visceral  portion,  extending  upward  for  some  distance  in 
front  and  on  the  inner  side  of  the  cord,  and  reaching  below  the  testis.  The  inner 
surface  of  the  tunica  vaginalis  is  free,  smooth,  and  covered  by  a  layer  of  endothelial 
cells.  The  interval  between  the  visceral  and  parietal  layers  of  this  membrane 
constitutes  the  cavity  of  the  tunica  vaginalis. 

The  obliterated  portion  of  the  pouch  may  generally  be  seen  as  a  fibro-cellular 
thread  lying  in  the  loose  areolar  tissue  around  the  spermatic  cord;  sometimes  this 
may  be  traced  as  a  distinct  band  from  the  upper  end  of  the  inguinal  canal,  where 
ir  is  connected  with  the  peritoneum,  down  to  the  tunica  vaginalis;  sometimes  it 
gradual]  v  becomes  lost  on  the  spermatic  cord. 
Occasionally  no  trace  of  it  can  be  detected.  In 
some  cases  it  happens  that  the  pouch  of  peri- 
toneum does  not  become  obliterated,  but  the  sac 
of  the  peritoneum  communicates  with  the  tunica 
vaginalis.  This  may  give  rise  to  one  of  the 
varieties  of  oblique  inguinal  hernia  (page  1191). 
Or  in  other  cases  the  pouch  may  contract,  but 
not  become  entirely  obliterated ;  it  then  forms 
a  minute  canal  leading  from  the  peritoneum  to 
the  tunica  vaginalis,1 

The  Tunica  Albuginea  is  the  fibrous  cover- 
ing of  the  testis.  It  is  a  dense  fibrous  mem- 
brane, of  a  bluish-white  color,  composed  of 
bundles  of  white  fibrous  tissue,  which  interlace 
in  every  direction.  Its  outer  surface  is  covered 
by  the  tunica  vaginalis,  except  along  its  poste- 
rior border,  at  the  points  of  attachment  of  the 
epididymis  :  hence  the  tunica  albuginea  may 
be  considered  as  a  fibro-serous  membrane, 
like  the  pericardium.  This  membrane  sur- 
rounds the  glandular  structure  of  the  testicle, 
and  at  its  posterior  border  is  reflected  into  the  interior  of  the  gland,  forming  an 
incomplete  vertical  septum,  called  the  mediastinum  testis  (corpus  Hiyhmorianuni). 

The  mediastinum  testis  extends  from,  the  upper,  nearly  to  the  lower,  border  of 
the  gland,  and  is  wider  above  than  below.  From  the  front  and  sides  of  this  septum 
numerous  slender  fibrous  cords  and  imperfect  septa  (trabeculae)  are  given  off,  which 
radiate  toward  the  surface  of  the  organ,  and  are  attached  to  the  inner  surface  of 
the  tunica  albuginea.  They  therefore  divide  the  interior  of  the  organ  into  a 
number  of  incomplete  spaces,  which  are  somewhat  cone-shaped,  being  broad  at 
their  bases  at  the  surface  of  the  gland,  and  becoming  narrower  as  they  converge  to 
the  mediastinum.  The  mediastinum  supports  the  vessels  and  ducts  of  the  testis 
in  their  passage  to  and  from  the  substance  of  the  gland. 

The  Tunica  Vasculosa  ( pi  a  mnffr  testis)  is  the  vascular  layer  of  the  testis, 
consisting  of  a  plexus  of  blood-vessels  held  together  by  a  delicate  areolar  tissue. 
It  covers  the  inner  surface  of  the  tunica  albuginea  and  the  different  septa  in  the 
interior  of  the  gland,  and  therefore  forms  an  internal  investment  to  all  the  spaces 
of  which  the  gland  is  composed. 

Structure. — The  glandular  structure  of  the  testis  consists  of  numerous  lobules 
(lobnl!  tt'*tfx).  Their  number,  in  a  single  testis,  is  estimated  by  Berres  at  250,  and 
by  Krause  at  400.  They  differ  in  size  according  to  their  position,  those  in  the 
middle  of  the  gland  being  larger  and  longer.  The  lobules  are  conical  in  shape, 
the  base  being  directed  toward  the  circumference  of  the  organ,  the  apex  toward  the 

1  It  is  recorded  that  in  the  post-mortem  examination  of  Sir  Astley  Cooper  this  minute  canal 
was  found  on  botli  sides  of  the  body.  Sir  Astley  Cooper  states  that  when  a  student  he  suffered  from 
inguinal  hernia ;  probably  this  was  of  the  congenital  variety,  and  the  canal  found  after  death  was  the 
remains  of  the  one  down  which  the  hernia  travelled  (Lancet,  vol.  ii.,  1824,  p.  116). 


FIG.  739.— The  testis  in  fitu,  the  tunica 
vaginalis  having  been  laid  open. 


1158  MALE    GENERATIVE    ORGANS. 

mediastinum.  Each  lobule  is  contained  in  one  of  the  intervals  between  the  fibrous 
cords  and  vascular  processes  which  extend  between  the  mediastinum  testis  and 
the  tunica  albuginea,  and  consists  of  from  one  to  three  or  more  minute  convoluted 
tubes,  the  tubuli  seminiferi.  The  tubes  may  be  separately  unravelled  by  careful 
dissection  under  water,  and  may  be  seen  to  commence  either  by  free  cgecal  ends  or 
by  anastomotic  loops.  The  total  number  of  tubes  is  considered  by  Munro  to  be 
about  300,  and  the  length  of  each  about  sixteen  feet ;  by  Lauth  their  number  is 
estimated  at  840,  and  their  average  length  two  feet  and  a  quarter.  The  diameter 
varies  from  2-^-  to  yi^-  of  an  inch.  The  tubuli  are  pale  in  color  in  early  life,  but 
in  old  age  they  acquire  a  deep  yellow  tinge  from  containing  much  fatty  matter. 
They  consist  of  a  membrana  propria,  inside  which  are  several  layers  of  epithelial  cells, 
the  seminal  cells.  The  membrana  propria  is  a  hyaline  structure,  consisting  of  several 
membranous  layers,  containing  oval  flattened  nuclei  at  regular  intervals,  super- 
imposed on  one  another.  The  seminal  cells  or  lining  epithelium  differ  in  different 
tubules.  In  some  tubes  they  may  be  seen  to  consist  of  an  outer  layer,  next  the 
membrana  propria,  and  two  or  more  layers  of  inner  cells.  The  former  cells  are 
more  or  less  polyhedral  in  shape,  uniform  in  size,  and  contain  an  oval  or  spherical 
nucleus  ;  the  latter  cells,  those  comprising  the  inner  layers,  are  spherical  and  more 
loosely  connected  together.  The  nucleus  of  most  or  all  of  them  is  in  the  process 
of  indirect  division  (karyokinesis,  page  40),  and  in  consequence  of  this  numerous 
small  spherical  daughter-cells  are  to  be  seen,  lying  nearest  to  the  lumen  and  closely 
connected  together.  These  small  daughter-cells  are  named  spermatoblasts,  and  by 
-a  series  of  changes  become  converted  into  spermatozoa.  In  other  tubes  the  gradual 
transition  of  the  spermatoblasts  into  spermatozoa  may  be  traced.  In  some  tubes 
or  parts  of  tubes  the  daughter-cells  may  be  seen  to  have  assumed  a  pear  shape, 
with  the  pointed  end,  in  which  the  nucleus  is  to  be  found,  directed  toward  the 
inner  seminal  cells,  while  the  broad  part  is  directed  into  the  lumen  of  the  tube. 
In  other  parts  of  a  tube  the  broad  end  may  be  seen  to  have  become  elongated  into 
a  rod-shaped  body,  which  constitutes  the  middle  piece  of  the  spermatozoon,  Avhile 
the  nucleus  forms  the  head.  Again,  in  other  parts  of  the  tubes  these  young 
spermatozoa  may  be  seen  collected  together  into  fan-shaped  groups,  and  from  their 
distal -end — that  is  to  say,  the  end  projecting  into  the  lumen  of  the  tube — a  thin 
long  filament,  called  the  tail,  is  growing  out.  In  the  young  subject  the  seminal 
cells  present  somewhat  the  appearance  of  an  epithelial  lining,  and  do  not  almost 
fill  the  tube,  as  in  the  adult  testis.  % 

The  tubules  are  enclosed  in  a  delicate  plexus  of  capillary  vessels,  and  are  held 
together  by  anintertubular  connective  tissue,  which  presents  large  interstitial  spaces 
lined  by  endothelium,  which  are  believed  to  be  the  rootlets  of  lymphatic  vessels 
of  the  testis. 

In  the  apices  of  the  lobules  the  tubuli  become  less  convoluted,  assume  a  nearly 
straight  course,  and  unite  together  to  form  from  twenty  to  thirty  larger  ducts,  of 
about  -^  of  an  inch  in  diameter,  and  these,  from  their  straight  course,  are  called 
vasa  recta  or  tubuli  recti. 

The  vasa  recta  enter  the  fibrous  tissue  of  the  mediastinum,  and  pass  upward 
and  backward,  forming,  in  their  ascent,  a  close  network  of  anastomosing  tubes, 
which  are  merely  channels  in  the  fibrous  stroma,  having  no  proper  walls  ;  this 
constitutes  the  rete  testis.  At  the  upper  end  of  the  mediastinum  the  vessels  of 
the  rete  testis  terminate  in  from  twelve  to  fifteen  or  twenty  ducts,  the  vasa 
efferentia  :  they  perforate  the  tunica  albuginea,  and  carry  the  seminal  fluid  from 
the  testis  to  the  epididymis.  Their  course  is  at  first  straight ;  they  then  become 
enlarged  and  exceedingly  convoluted,  and  form  a  series  of  conical  masses,  the  coni 
vasculosi,  which,  together,  constitute  the  globus  major  of  the  epididymis.  Each 
cone  consists  of  a  single  convoluted  duct  from  six  to  eight  inches  in  length,  the 
diameter  of  which  gradually  decreases  from  the  testis  to  the  epididymis.  Oppo- 
site the  bases  of  the  cones  the  efferent  vessels  open  at  narrow  intervals  into  a 
single  duct,  which  constitutes,  by  its  complex  convolutions,  the  body  and  globus 
minor  of  the  epididymis.  When  the  convolutions  of  this  tube  are  unravelled  it 


THE    TESTES. 


1159 


Tunica  Yaginalis. 


Tunica  Albuginea. 


Its  Septa 


FIG.  7-10. — Vertical  section  of  the  testi- 
cle, to  show  the  arrangement  of  the  ducts. 


measures  upward  of  twenty  feet  in  length,  and  increases  in  breadth  and  thick- 
ness as  it  approaches  the  vas  deferens.  The  convolutions  are  held  together  by  fine 
areolar  tissue  and  by  bands  of  fibrous  tissue. 

The  vasa  recta  are  of  smaller  diameter  than 
the  seminal  tubes,  and  have  very  thin  parietes. 
They,  as  well  as  the  channels  of  the  rete  testis, 
are  lined  bv  a  single  layer  of  flattened  epithe- 
lium. The  vasa  efterentia  and  the  tube  of  the 
epididymis  have  walls  of  considerable  thickness, 
on  account  of  the  presence  in  them  of  muscular 
tissue,  which  is  principally  arranged  in  a  circular 
manner.  These  tubes  are  lined  by  columnar 
ciliated  epithelium. 

The  Vas  Deferens,  the  excretory  duct  of  the 
testis.  is  the  continuation  of  the  epididymis. 
Commencing  at  the  lower  part  of  the  globus 
minor,  it  ascends  along  the  posterior  border  of 
the  testis  and  inner  side  of  the  epididymis,  and 
along  the  back  part  of  the  spermatic  cord, 
through  the  spermatic  canal  to  the  internal  or 
deep  abdominal  ring.  From  the  ring  it  curves 
round  the  outer  side  of  the  epigastric  artery, 

-<-s  the  external  iliac  vessels,  and  descends 
into  the  pelvis  at  the  side  of  the  bladder ;  it 
arches  backward  and  downward  to  its  base, 
crossing  over  the  obliterated  hypogastric  artery 
and  to  the  inner  side  of  the  ureter.  At  the  base 

of  the  bladder  it  lies  between  that  viscus  and  the  rectum,  running  along  the  inner 
border  of  the  vesicula  serninalis.  In  this  situation  it  becomes  enlarged  and 
sacculated,  forming  the  ampulla,  and  then,  becoming  narrowed  at  the  base  of  the 
prostate,  unites  with  the  duct  of  the  vesicula  seininalis  to  form  the  ejaculatory 
duct.  The  vas  deferens  presents  a  hard  and  cord-like  sensation  to  the  fingers ;  it 
is  about  two  feet  in  length,  of  cylindrical  form,  and  about  a  line  and  a  quarter  in 
diameter.  Its  Avails  are  dense,  measuring  one-third  of  a  line,  and  its  canal  is 
extremely  small,  measuring  about  half  a  line. 

Structure. — The  vas  deferens  consists  of  three  coats  :  1.  An  external  or  cellular 
coat.  2.  A  muscular  coat,  which  in  the  greater  part  of  the  tube  consists  of  two 
layers  of  tmstriped  muscular  fibre  :  an  outer,  longitudinal  in  direction,  and  an 
inner,  circular  ;  but  in  addition  to  these,  at  the  commencement  of  the  vas  deferens, 
there  is  a  third  layer,  consisting  of  longitudinal  fibres,  placed  internal  to  the  circular 
stratum,  between  it  and  the  mucous  membrane.  B.  An  internal  or  mucous  coat, 
which  is  pale,  and  arranged  in  longitudinal  folds ;  its  epithelial  covering  is  of  the 
columnar  variety. 

A  long  narrow  tube,  the  vas  abcrrans  of  Haller,  is  occasionally  found  connected 
with  the  lower  part  of  the  canal  of  the  epididymis  or  with  the  commencement  of 
the  vas  deferens.  It  extends  up  into  the  cord  for  about  two  or  three  inches,  where 
it  terminates  by  a  blind  extremity,  which  is  occasionally  bifurcated.  Its  length 
varies  from  an  inch  and  a  half  to  fourteen  inches,  and  sometimes  it  becomes  dilated 
toward  its  extremity ;  more  commonly  it  retains  the  same  diameter  throughout. 
Its  structure  is  similar  to  that  of  the  vas  deferens.  Occasionally  it  is  found  uncon- 
nected with  the  epididymis.  (For  organ  of  Giraldes  or  paradidymis  see  page  136). 

Surgical  Anatomy. — The  testicle  frequently  requires  removal  for  malignant  disease ;  in 
tuberculous  disease,  to  prevent  systemic  infection:  in  cystic  disease;  in  cases  of  large  hernia 
testis,  and  in  some  instances  of  incompletely  descended  or  misplaced  testicle,  and  for  prostatie 
hypertrophy.  The  operation  is  a  comparatively  simple  one.  An  incision  is  made  from  the 
external  ring  to  the  bottom  of  the  scrotum  into  the  tunica  vaginalis.  The  coverings  are  shelled 
off  the  organ,  and  the  mesorchimn.  stretrhinir  between  the  back  of  the  testicle  and  the  scrotum, 
divided.  The  cord  is  then  isolated,  and  an  aneurism  needle,  armed  with  a  double  ligature, 


1160 


MALE    GENERATIVE    ORGANS. 


passed  under  it,  as  high  as  is  thought  necessary,  and  the  cord  tied  in  two  places,  and  divided 
between  the  ligatures.  Sometimes,  in  cases  of  malignant  disease,  it  is  desirable  to  open  the 
inguinal  canal  and  tie  the  cord  as  near  the  internal  abdominal  ring  as  possible. 

VESICUKE    SEMINA1ES. 

The  Seminal  Vesicles  are  two  lobulated  membranous  pouches  placed  between  the 
base  of  the  bladder  and  the  rectum,  serving  as  reservoirs  for  the  semen,  and  secreting 
a  fluid  to  be  added  to  the  secretion  of  the  testicles.  Each  sac  is  somewhat  pyramidal 


Right  Ejaculatory 
duct. 


FIG.  741. — Base  of  the  bladder,  with  the  vasa  deferentia  and  vesiculee  seminales. 

in  form,  the  broad  end  being  directed  backward  and  the  narrow  end  forward  toward 
the  prostate.  They  measure  about  two  and  a  half  inches  in  length,  about  five  lines 
in  breadth,  and  two  or  three  lines  in  thickness.  They  vary,  however,  in  size, 
not  only  in  different  individuals,  but  also  in  the  same  individual  on  the  two  sides. 
Their  upper  surface  is  in  contact  with  the  base  of  the  bladder,  extending  from  near 
the  termination  of  the  ureters  to  the  base  of  the  prostate  gland.  Their  under  surface 
rests  upon  the  rectum,  from  which  they  are  separated  by  the  recto-vesical  fascia. 
Their  posterior  extremities  diverge  from  each  other.  Their  anterior  extremities  are 
pointed,  and  converge  toward  the  base  of  the  prostate  gland,  where  each  joins  with 
the  corresponding  vas  deferens  to  form  the  ejaculatory  duct.  Along  the  inner 
margin  of  each  vesicula  runs  the  enlarged  and  convoluted  vas  deferens.  The  inner 
border  of  the  vesiculae  and  the  corresponding  vas  deferens  form  the  lateral 
boundaries  of  a  triangular  space,  limited  behind  by  the  recto-vesical  peritoneal 
fold ;  the  portion  of  the  bladder  included  in  this  space  rests  on  the  rectum,  its 
antero-inferior  portion  corresponding  with  the  trigonum  vesicse  in  its  interior. 

Each  vesicula  consists  of  a  single  tube,  coiled  upon  itself  and  giving  off  several 
irregular  caecal  diverticula,  the  separate  coils,  as  well  as  the  diverticula,  being 
connected  together  by  fibrous  tissue.  When  uncoiled  this  tube  is  about  the 
diameter  of  a  quill,  and  varies  in  length  from  four  to  six  inches ;  it  terminates 
posteriorly  in  a  cul-de-sac  ;  its  anterior  extremity  becomes  constricted  into  a  nar- 
row straight  duct,  which  joins  on  its  inner  side  with  the  corresponding  vas  deferens, 
and  forms  the  ejaculatory  duct. 

The  ejaculatory  ducts,  two  in  number,  one  on  each  side,  are  formed  by  the 
junction  of  the  ducts  of  the  vesiculae  seminales  with  the  vasa  deferentia.  Each 
duct  is  about  three-quarters  of  an  inch  in  length  ;  it  commences  at  the  base  of  the 
prostate,  and  runs  forward  and  downward  between  the  middle  and  lateral  lobes,  and 
along  the  side  of  the  sinus  pocularis,  to  terminate  by  a  separate  slit-like  orifice  close 


DESCENT   OF    THE    TESTES.  1161 

to  or  just  within  the  margins  of  the  sinus  (verumontanum).  The  ducts  diminish  in 
size  and  converge  toward  their  termination. 

Structure. — The  vesiculae  seminales  are  composed  of  three  coats :  an  external 
or  libra-cellular;  a  middle  or  muscular  coat,  which  is  thinner  than  in  the  vas 
deferens :  the  muscular  fibres  are  arranged  in  three  layers,  consisting  of  an  inner 
and  outer  longitudinal  stratum  and  an  intermediate  layer  of  circular  fibres ;  and 
an  inter  tu'd  or  mucous  coat,  which  is  pale,  of  a  whitish-brown  color,  and  presents 
a  delicate  reticular  structure,  like  that  seen  in  the  gall-bladder,  but  the  meshes  are 
finer.  The  epithelium  is  columnar. 

The  coats  of  the  ejaculatory  ducts  are  extremely  thin.  They  are:  an  outer 
fibrous  layer,  which  is  almost  entirely  lost  after  their  entrance  into  the  prostate; 
a  J'ii/er  »f  muscular  fibres,  consisting  of  an  outer  thin  circular  and  an  inner 
longitudinal  layer;  and  the  mucous  membrane,  forming  the  only  constituents  of 
the  tubes. 

Vessels  and  Nerves. — The  arteries  supplying  the  vesiculse  seminales  are  derived 
from  the  middle  and  inferior  vesical  and  middle  hsemorrhoidal.  The  veins  and 
lymphatics  accompany  the  arteries.  The  nerves  are  derived  from  the  pelvic 
j  ilex  us. 

Surgical  Anatomy. — The  vesiculae  seminales  are  often  the  seat  of  an  extension  of  the 
<lisoa>f  in  ru-es  of  tuberculous  disease  of  the  testicle,  and  should  always  be  examined  from  the 
rectum  before  coming  to  a  decision  with  regard  to  castration  in  this  affection. 

Descent  of  the  Testes. 

The  testes  at  an  early  period  of  foetal  life  are  placed  at  the  back  part  of  the 
abdominal  cavity,  behind  the  peritoneum,  in  front  and  a  little  below  the  kidneys. 
The  anterior  surface  and  sides  are  invested  by  peritoneum.  At  about  the  third 
month  of  infra-uterine  life  a  peculiar  structure,  the  gubernaculum  testis,  makes  its 
appearance.  This  structure  is  at  first  a  slender  band  which  extends  from  the 
situation  of  the  internal  ring  to  the  epididymis  and  body  of  the  testicle,  and  is 
then  continued  upward  in  front  of  the  kidney  toward  the  Diaphragm.  As 
development  advances  the  peritoneum  covering  the  testicle  encloses  it  and  forms 
a  mesentery,  the  mesorchium,  which  also  encloses  the  gubernaculum  and  forms  two 
folds — one  above  the  testicle,  and  the  other  below  it.  The  one  above  the  testicle  is 
the  plica  vascularis,  and  contains  ultimately  the  spermatic  vessels;  the  one  below, 
the  plica  yubernatrix.  contains  the  lower  part  of  the  gubernaculum,  which  has  now 
grown  into  a  thick  cord  ;  it  terminates  below  at  the  internal  ring  in  a  tube  of  peri- 
toneum, the  processus  vaginalis,  which  now  lies  in  the  inguinal  canal.  The  lower 
part  of  the  gubernaculum  by  the  fifth  month  has  become  a  thick  cord,  whilst  the 
upper  part  has  disappeared.  The  lower  part  can  now  be  seen  to  consist  of  a  central 
core  of  unstriped  muscle-fibre,  and  outside  this  of  a  firm  layer  of  striped  elements, 
connected,  behind  the  peritoneum,  with  the  abdominal  wall.  Later  on,  about 
the  sixth  month,  the  lower  end  of  the  gub  ernaculum  can  be  traced  into  the  inguinal 
canal,  extending  to  the  pubes,  and,  at  a  later  period,  to  the  bottom  of  the  scro- 
tum. The  fold  of  peritoneum  constituting  the  processus  raginalis  projects  itself 
downward  into  the  inguinal  canal,  forming  a  gradually  elongating  depression  or 
cul-de-sac,  which  eventually  reaches  the  bottom  of  the  scrotum.  This  cul-de- 
sac  is  now  invaginated  by  the  testicle,  as  the  body  of  the  foetus  grows,  for  the 
gubernaculum  does  not  grow  commensurately  with  the  growth  of  other  parts,  and 
therefore  the  testicle,  being  attached  by  the  gubernaculum  to  the  bottom  of  the 
scrotum,  is  prevented  from  rising  as  the  body  grows,  and  is  drawn  first  into  the 
inguinal  canal,  and  eventually  into  the  scrotum.  By  the  eighth  month  the 
testicle  has  reached  the  scrotum,  preceded  by  the  lengthened  pouch  of  peritoneum, 
the  processus  vaginalis,  which  communicates  by  its  upper  extremity  with  the  per- 
itoneal cavity.  Just  before  birth  the  upper  part  of  the  pouch  usually  becomes 
closed,  and  this  obliteration  extends  gradually  downward  to  within  a  short  dis- 
tance of  the  testis.  The  process  of  peritoneum  surrounding  the  testis,  which  is 


1162  MALE    GENERATIVE    ORGANS. 

now   entirely  cut   off  from  the  general  peritoneal  cavity,  constitutes  the  tunica 
vaginalis.1 

In  the  female,  a  small  cord,  corresponding  to  the  gubernaculum  in  the 
male,  descends  to  the  inguinal  region,  and  ultimately  forms  the  round  ligament 
of  the  uterus.  A  pouch  of  peritoneum  accompanies  it  along  the  inguinal  canal, 
analogous  to  the  processus  vaginalis  in  the  male :  it  is  called  the  canal  of  Nuck. 

Surgical  Anatomy. — Abnormalities  in  the  formation  and  in  the  descent  of  the  testicle  may 
occur.  The  testicle  may  fail  to  be  developed,  or  the  testicle  may  be  fully  developed  and  tbe  vas 
deferens  may  be  undeveloped  in  whole  or  part ;  or,  again,  both  testicle  and  vas  deferens  may  be 
fully  developed,  but  the  duct  may  not  become  connected  to  the  gland.  The  testicle  may  fail  in  its 
descent  (cryptorchismus),  or  it  may  descend  into  some  abnormal  position.  Thus  it  may  be  retained 
in  the  position  where  it  was  primarily  developed,  below  the  kidney  ;  or  it  may  descend  to  the 
internal  abdominal  ring,  but  fail  to  pass  through  this  opening  ;  it  may  be  retained  in  the  inguinal 
canal,  which  is  perhaps  the  most  common  position ;  or  it  may  pass  through  the  external 
abdominal  ring  and  remain  just  outside  it,  failing  to  pass  to  the  bottom  of  the  scrotum.  On  the 
other  hand,  it  may  get  into  some  abnormal  position :  it  may  pass  the  scrotum  and  reach  the 
perinseum,  or  it  may  fail  to  enter  the  inguinal  canal,  and  may  find  its  way  through  the  femoral 
ring  into  the  crural  canal,  and  present  itself  on  the  thigh  at  the  saphenous  opening.  There  is 
still  a  third  class  of  cases  of  abnormality  of  the  testicle,  where  the  organ  has  descended  in  due 
course  into  the  scrotum,  but  is  malplaced.  The  most  common  form  of  this  is  where  the  testicle 
is  inverted ;  that  is  to  say,  the  organ  is  rotated,  so  that  the  epididymis  is  connected  to  the  front 
of  the  scrotum,  and  the  body,  surrounded  by  the  tunica  vaginalis,  is  directed  backward.  In 
these  cases  the  vas  deferens  is  to  be  felt  in  the  front  of  the  cord.  The  condition  is  of  importance 
in  connection  with  hydrocele  and  haematocele,  and  the  position  of  the  testicle  should  always  be 
carefully  ascertained  before  performing  any  operation  for  these  affections.  Again,  more  rarely, 
the  testicle  may  be  reversed.  This  is  a  condition  in  which  the  top  of  the  testicle,  indicated  by 
the  globus  major  of  the  epididymis,  is  at  the  bottom  of  the  scrotum,  and  the  vas  deferens  comes 
off  from  the  summit  of  the  organ. 

1  The  obliteration  of  the  process  of  peritoneum  which  accompanies  the  cord,  and  is  hence  called 
the  funicular  process,  is  often  incomplete.  See  section  on  Inguinal  Hernia. 


THE  FEMALE  GENERATIVE  ORGANS. 


EXTERNAL  ORGANS. 


THE  External  Organs  of  Generation  in  the  Female  are :  the  mons  Veneris,  the 
labia  inajora  and  minora,  the  clitoris,  the  meatus  urinarius,  and  the  orifice  of 


FIG.  742.— The  vulva.    External  female  organs  of  generation. 

the  vagina.  The  term  "  vulva  "or  ;'  pudendum,"  as  generally  applied,  includes 
all  these  parts. 

The  Mons  Veneris  is  the  rounded  eminence  in  front  of  the  pubic  symphysis, 
formed  by  a  collection  of  fatty  tissue  beneath  the  integument.  It  surmounts  the 
vulva,  and  becomes  covered  with  hair  at  the  time  of  puberty.  ' 

The  Labia  Majora  are  two  prominent  longitudinal  cutaneous  folds  extending 
downward  from  the  mons  Veneris  to  the  anterior  boundary  of  the  perinaeum,  and 

1163 


1164 


FEMALE    GENERATIVE    ORGANS. 


enclosing  the  common  urine-sexual  opening.  Each  labium  is  formed  of  two  folds 
of  integument :  covered  with  hair  externally ;  internally,  smooth  and  pinkish. 
The  inner  fold  is  continuous  with  the  genito-urinary  mucous  tract.  Between  the 
two  folds  is  a  quantity  of  areolar  tissue,  fat,  and  a  tissue  resembling  the  dartos  of 
the  scrotum,  besides  vessels,  nerves,  and  glands.  The  labia  are  thicker  in  front, 
where  they  form  by  their  meeting  the  anterior  commissure.  Posteriorly  they  are 
not  really  joined,  but  appear  to  become  lost  in  the  neighboring  integument, 
terminating  close  to,  and  nearly  parallel  with,  each  other.  Together  with  the 
connecting  skin  between  them,  they  form  the  posterior  commissure  or  posterior 
boundary  of  the  vulval  orifice.  The  interval  between  the  posterior  commissure  and 


x:S         Urethra.  \          3      - 


Dee 


\ransv.  pennsei.  Unstriped  muscular  •••-':-..'•& 

J»«- 


^•Vagina. 


FIG.  743.— Vertical  median  section  of  the  temaie  pelvis. 

the  anus,  about  an  inch  to  an  inch  and  a  quarter  in  length,  constitutes  the  peri- 
naeum  or  base  of  the'perineal  body.  The  fourchette  is  the  anterior  edge  of  the 
latter,  and  between  it  and  the  hymen  is  a  depression,  the  fossa  navicularis.  The 
labia  correspond  to  the  scrotum  in  the  male. 

The  Labia  Minora,  or  Nymphae,  are  two  small  cutaneous  folds,  situated  within 
the  labia  majora,  and  extending  from  the  clitoris  obliquely  downward,  outward, 
and  backward  for  about  an  inch  and  a  half  on  each  side  of  the  orifice  of  the 
vagina,  between  which  and  the  labia  majora  they  are  lost.  Anteriorly,  the  two 
labia  minora  meet  and  form  ihefrcenum  of  the  clitoris.  The  prepuce  of  the  clitoris, 
passing  backward  on  each  side,  is  inserted,  as  it  were,  into  each  labium  minus. 
The  nymphae  are  really  modified  skin.  Their  nternal  surfaces  have  numerous 
sebaceous  follicles. 

The  Clitoris  is  an  erectile  structure  analogous  to  the  corpora  cavernosa  of  the 
penis.  It  is  situated  beneath  the  anterior  commissure,  partially  hidden  between  the 
anterior  extremities  of  the  labia  minora.  It  is  connected  to  the  rami  of  the  os  pubis 


EXTEKXA L    OR GA  N& 


1165 


and  iscbium  on  each  side  by  a  crus  ;  the  body  is  short  and  concealed  beneath  the 
labia ;  the  free  extremity,  or  glans  clitoridis,  is  a  small  rounded  tubercle,  consisting 
of  spongy  erectile  tissue,  and  highly  sensitive.  It  is  provided,  like  the  penis,  with 
a  suspensory  ligament,  and  with  two  small  muscles,  the  Erectores  clitoridis,  which 
are  inserted  into  the  crura  of  the  clitoris.  The  clitoris  consists  of  two  corpora 
cavernosa,  composed  of  erectile  tissue  enclosed  in  a  dense  layer  of  fibrous 
membrane,  united  together  along  their  inner  surfaces  by  an  incomplete  fibrous 
pectiniform  septum. 

Between  the  clitoris  and  the  entrance  of  the  vagina  is  a  triangular  smooth 
surface,  bounded  on  each  side  by  the  nymphse ;  this  is  the  vestibule. 

The  orifice  of  the  urethra  (meatus  urinarius)  is  situated  at  the  back  part  of  the 
vestibule,  about  an  inch  below  the  clitoris  and  near  the  margin  of  the  vagina, 
surrounded  by  a  prominent  elevation  of  the  mucous  membrane.  Below  the  meatus 
urinarius  is  the  orifice  of  the  vagina,  more  or  less  closed  in  the  virgin  by  a  mem- 
branous fold,  the  hymen. 


Ovary 


Douglas' 
pouch. 


Vaginal 

orifice  of 
uterus 


Round 
ligament 
of  uterus 

Transverse 
vesical 
fold 


FIG.  744.— Longitudinal  section  through  the  pelvis  of  a  young  woman.    (Bardeleben.) 

The  Hymen  is  a  membranous  fold  which  closes  to  a  greater  or  less  extent  the 
opening  of  the  vagina.  It  varies  much  in  shape.  Its  commonest  form  is  that  of 
a  ring,  generally  broadest  posteriorly  :  sometimes  it  is  represented  by  a  semilunar 
fold,  with  its  concave  margin  turned  toward  the  pubes.  A  complete  septum 
stretched  across  the  lower  part  of  the  vaginal  orifice  is  called  "  imperforate  hymen." 
Occasional! v  it  is  cribriform,  or  its  free  margin  forms  a  membranous  fringe,  or  it 
may  be  entirely  absent.  It  may  persist  after  copulation,  so  that  it  cannot  be 
considered  us  a  test  of  virginity.  After  parturition  the  small  rounded  elevations 
known  as  the  <-<irun<:ulce  myrtiformes  are  found  as  the  i-emains  of  the  hymen. 

Glands  of  Bartholin. — On  each  side  of  the  commencement  of  the  vagina,  and 


1166 


FEMALE   GENERATIVE   ORGANS. 


behind  the  hymen,  is  a  round  or  oblong  body,  of  a  reddish-yellow  color,  and  of  the 
size  of  a  horse-bean,  analogous  to  Cowper's  gland  in  the  male.  It  is  called  the 
gland  of  Bartliolin.  Each  gland  opens  by  means  of  a  long  single  duct  on  each 
side  external  to  the  hymen. 


Suspensorij  ligament 
of  clitoris 


Glans  clitoris 


Ischio- 
cavernous 
muscle 


Bulbo- 
cavernous 
muscle 


Deep  perineal 
muscle,  with 
its  under 
layer  of  fascia 


External 
obturator 
muscle 


Sacro- 
sciatic 
ligament 


External  sphincter 

ani  muscle 
Os  coccyx 

FIG.  745.— The  female  perinseum  after  removal  of  the  skin  and  superficial  fascia.    (Bardeleben.) 

Bulbi  Vestibuli. — Extending  from  the  clitoris,  along  either  side  of  the  vestibule, 
and  lying  a  little  behind  the  nymphse,  are  two  large  oblong  masses,  about  an  inch 
in  length,  consisting  of  a  plexus  of  veins  enclosed  in  a  thin  layer  of  fibrous 
membrane.  These  bodies  are  narrow  in  front,  rounded  below,  and  are  connected 
with  the  crura  of  the  clitoris  and  rami  of  the  pubes  :  they  are  termed  by  Kobelt  the 
bulbi  vestibuli,  and  he  considers  them  analogous  to  the  bulb  of  the  corpus 
spongiosum  in  the  male.  Immediately  in  front  of  these  bodies  is  a  smaller  venous 
plexus,  continuous  with  the  bulbi  vestibuli  behind  and  the  glans  clitoridis  in  front : 
it  is  called  by  Kobelt  the  pars  intermedia,  and  is  considered  by  him  as  analogous 
to  that  part  of  the  body  of  the  corpus  spongiosum  which  immediately  succeeds 
the  bulb. 

RELATIONS  OF  THE  BLADDER. 

The  Bladder  is  situated  at  the  anterior  part  of  the  pelvis.  It  is  in  relation,  in 
front,  with  the  symphysis  pubis  ;  behind,  with  the  utero-vesical  pouch  of  peritoneum, 
which  separates  it  from  the  body  of  the  uterus ;  its  base  lies  in  contact  with  the 
connective  tissue  in  front  of  the  cervix  and  upper  part  of  the  vagina.  Laterally, 
is  the  recto-vesical  fascia.  The  bladder  is  said  by  some  anatomists  to  be  larger  in 


IXTERXAL    (XRGJ-V.S.  1167 


the  female  than  in  the  male.  At  any  rate,  it  does  not  rise  above  the  symphysis 
pubis  till  more  distended  than  in  the  male,  but  this  is  perhaps  owing  to  the  more 
capacious  pelvis  rather  than  to  its  being  of  actually  larger  size. 

THE  URETHRA. 

The  Urethra  is  a  narrow  membranous  canal,  about  an  inch  and  a  half  in 
length,  extending  from  the  neck  of  the  bladder  to  the  meatus  urinarius.  It  is 
placed  beneath  the  symphysis  pubis.  imbedded  in  the  anterior  wall  of  the  vagina  ; 
and  its  direction  is  obliquely  downward  and  forward,  its  course  being  slightly- 
curved.  the  concavity  directed  forward  and  upward.  Its  diameter  when  undilated 
is  about  a  quarter  of  an  inch.  The  urethra  perforates  the  triangular  ligament 
precisely  as  in  the  male. 

Structure.  —  The  urethra  consists  of  three  coats  :  muscular,  erectile,  and  mucous. 

The  mmeul'ir  •••".it  is  continuous  with  that  of  the  bladder  ;  it  extends  the  -whole 
length  of  the  tube,  and  consists  of  a  circular  stratum  of  muscular  fibres.  In 
addition  to  this,  between  the  two  layers  of  the  triangular  ligament,  the  female 
urethra  is  surrounded  by  the  Compressor  urethra,  as  in  the  male. 

A  tltin  layer  of  spongy  erectile  f  /**>/,  •.  containing  a  plexus  of  large  veins  inter- 
mixed with  bundles  of  unstriped  muscular  fibre,  lies  immediately  beneath  the 
mucous  coat. 

The  mucous  coat  is  pale,  continuous  externally  with  that  of  the  vulva,  and 
internallv  with  that  of  the  bladder  near  which  it  contains  many  tubular  mucous 
glands.  It  is  thrown  into  longitudinal  folds,  one  of  which  placed  along  the  floor 
of  the  canal,  resembles  the  verumontanum  in  the  male  urethra.  It  is  lined  by 
laminated  epithelium,  which  becomes  transitional  near  the  bladder.  Its  external 
orifice  is  surrounded  bv  a  few  mucous  follicles. 

tt 

The  urethra,  from  not  being  surrounded  by  dense  resisting  structures,  as  in  the  male,  admits 
of  considerable  dilatation,  which  enables  the  surgeon  to  remove  with  considerable  facility  calculi 
or  other  foreign  bodies  from  the  cavity  of  the  bladder. 

THE  RECTUM. 

The  Rectum  is  more  capacious  and  less  curved  in  the  female  than  in  the 
male. 

The  first  portion  extends  from  the  left  sacro-iliac  articulation  to  the  middle 
of  the  sacrum.  Its  connections  are  similar  to  those  in  the  male. 

The  second  portion  extends  to  the  tip  of  the  coccyx.  It  is  covered  in  front  by 
the  peritoneum  for  a  short  distance,  at  its  upper  part  :  it  is  in  relation  with  the 
posterior  wall  of  the  vagina. 

The  third  portion  curves  backward  from  the  vagina  to  the  anus,  leaving 
a  space  which  corresponds  on  the  surface  of  the  body  to  the  perinseum.  Its 
extremity  is  surrounded  by  the  Sphincter  muscles,  and  its  sides  are  supported  by 
the  Leva  tores  ani. 

INTERNAL  ORGANS. 

The  Internal  Organs  of  Generation  are  —  the  vagina,  the  uterus  and  its  append- 
ages. the  Fallopian  tubes,  the  ovaries  and  their  ligaments,  and  the  round  ligaments. 

The  Vagina  extends  from  the  vulva  to  the  uterus.  It  is  situated  in  the  cavity 
of  the  pelvis,  behind  the  bladder  and  in  front  of  the  rectum.  Its  direction  is 
curved  upward  and  backward,  at  first  in  the  line  of  the  outlet,  and  afterward  in 
that  of  the  axis  of  the  cavity  of  the  pelvis.  Its  walls  are  ordinarily  in  contact. 
and  its  usual  shape  on  transverse  section  is  that  of  an  H,  the  transverse  limb 
being  slightly  curved  forward  or  backward,  whilst  the  lateral  limbs  are  somewhat 
convex  toward  the  median  line.  Its  length  is  about  two  and  a  half  inches  along 
its  anterior  wall,  and  three  and  a  half  inches  along  its  posterior  wall.  It  is  con- 
stricted at  its  commencement,  and  becomes  dilated  medially,  and  narrowed  near  its 
uterine  extremity  :  it  surrounds  the  vaginal  portion  of  the  cervix  uteri,  a  short 


1168  FEMALE    GENERATIVE    ORGANS. 

distance  from  the  os,  its  attachment  extending  higher  up  on  the  posterior  than  on 
the  anterior  wall  of  the  uterus. 

Relations. — Its  anterior  surface  is  in  relation  with  the  base  of  the  bladder  and 
with  the  urethra.  Its  posterior  surface  is  connected  for  the  lower  three-fourths  of 
its  extent  to  the  anterior  wall  of  the  rectum,  the  upper  fourth  being  separated  from 
that  tube  by  the  recto-vaginal  fold  of  peritoneum,  which  forms  a  cul-de-sac  between 
the  vagina  and  rectum.  Its  sides  give  attachment  superiorly  to  the  broad  ligaments, 
and  inferiorly  to  the  Levatores  ani  muscles  and  recto-vesical  fascia. 

Structure. — The  vagina  consists  of  an  internal  mucous  lining,  of  a  muscular 
coat,  and  between  the  two  of  a  layer  of  erectile  tissue. 

The  mucous  membrane  is  continuous  above  with  that  lining  the  uterus.  Its 
inner  surface  presents,  along  the  anterior  arid  posterior  walls,  a  longitudinal  ridge 
or  raphe,  called  the  columns  of  the  vagina,  and  numerous  transverse  ridges  or 
rugae,  extending  outward  from  the  raphe  on  either  side.  These  rugae  are  divided 
by  furrows  of  variable  depth,  giving  to  the  mucous  membrane  the  appearance  of 
being  studded  over  with  conical  projections.  There  are  also  microscopic  papillae  ; 
the  projections  are  most  numerous  near  the  orifice  of  the  vagina,  especially  in 
females  before  parturition.  The  epithelium  covering  the  mucous  membrane  is  of 
the  squamous  variety.  The  submucous  tissue  is  very  loose  and  contains  numerous 
large  veins,  which  by  their  anastomoses  form  a  plexus,  together  with  smooth  muscular 
fibres  derived  from  the  muscular  coat ;  it  is  regarded  by  Gussenbauer  as  an  erectile 
tissue.  It  contains  a  number  of  mucous  crypts,  but  no  true  glands. 

The  muscular  coat  consists  of  two  layers :  an  external  longitudinal,  which  is 
far  the  stronger,  and  an  internal  circular  layer.  The  longitudinal  fibres  are 
continuous  with  the  superficial  muscular  fibres  of  the  uterus.  The  strongest 
fasciculi  are  those  attached  to  the  recto-vesical  fascia  on  each  side.  The  two  layers 
are  not  distinctly  separable  from  each  other,  but  are  connected  by  oblique  decus- 
sating fasciculi  which  pass  from  the  one  layer  to  the  other.  In  addition  to  this 
the  vagina  at  its  lower  end  is  surrounded  by  a  band  of  striped  muscular  fibres,  the 
sphincter  vagina?  (see  page  464). 

External  to  the  muscular  coat  is  a  layer  of  connective  tissue  containing  a 
large  plexus  of  blood-vessels. 

The  erectile  tissue  consists  of  a  layer  of  loose  connective  tissue  situated  between 
the  mucous  membrane  and  the  muscular  coat;  imbedded  in  it  is  a  plexus  of  large 
veins,  and  numerous  bundles  of  unstriped  muscular  fibres  derived  from  the  circular 
muscular  layer.  The  arrangement  of  the  veins  is  similar  to  that  found  in  other 
erectile  tissues. 

THE  UTEEUS. 

The  Uterus  is  the  organ  of  gestation,  receiving  the  fecundated  ovum  in  its  cavity, 
retaining  and  supporting  it  during  the  development  of  the  foetus,  and  becoming 
the  principal  agent  in  its  expulsion  at  the  time  of  parturition. 

In  the  virgin  state  it  is  pear-shaped,  flattened  from  before  backward,  and 
situated  in  the  cavity  of  the  pelvis  between  the  bladder  and  the  rectum ;  it  is 
retained  in  its  position  by  the  round  and  broad  ligaments  on  each  side,  and  projects 
into  the  upper  end  of  the  vagina  below.  Its  upper  end,  or  base,  is  directed 
upward  and  forward ;  its  lower  end,  or  apex,  downward  and  backward,  in  the 
line  of  the  axis  of  the  inlet  of  the  pelvis.  It  therefore  forms  an  angle  with  the 
vagina,  since  the  direction  of  the  vagina  corresponds  to  the  axis  of  the  cavity  and 
outlet  of  the  pelvis.  The  uterus  measures  about  three  inches  in  length,  two  in 
breadth  at  its  upper  part,  and  nearly  an  inch  in  thickness,  and  it  weighs  from  an 
ounce  to  an  ounce  and  a  half. 

It  consists  of  two  parts  :  (1)  the  body,  with  its  upper  broad  extremity,  the 
fundus  ;  and  (2)  the  cervix,  or  neck,  which  is  partly  above  the  vagina  and  partly 
in  the  vagina.  The  fundus  is  placed  on  a  line  below  the  level  of  the  brim  of  the 
pelvis,  being  directed  forward  behind  the  upper  portion  of  the  anterior  pelvie 
wall. 


THE    UTERUS. 


1169 


The  division  between  the  body  and  cervix  is  indicated  externally  by  a  slight 
constriction,  and  by  the  reflection  of  the  peritoneum  from  the  anterior  surface  of 
the  uterus  on  to  the  bladder,  and  internally  by  a  narrowing  of  the  canal,  called 
the  internal  os. 

The  body  gradually  narrows  from  the  fundus  to  the  neck.  Its  anterior  surface 
is  flattened,  compared  to  the  posterior,  covered  by  peritoneum  throughout,  and 


Rectum 


Ova 


Suspensory 
ligament 
of  ovary 

Broad 
ligament 
of  uterus 


FIG.  746.— Female  pelvic  organs  fa  situ  (seen  from  above).    (Bardeleben.) 

separated  from  the  bladder  by  the  utero-vesical  pouch.  Its  posterior  surface  is 
convex  transversely,  covered  by  peritoneum  throughout,  and  separated  from  the 
rectum  by  some  convolutions  of  the  intestine.  Its  lateral  margins  are  concave,  and 
give  attachment  to  the  Fallopian  tube  above,  the  round  ligament  below  and  in  front 
of  this,  and  the  ligament  of  the  ovary  behind  both  of  these  structures. 

The  cervix  is  the  lower  constricted  segment  of  the  uterus ;  around  its  circum- 
ference is  attached  the  upper  end  of  the  vagina,  which  extends  upward  a  greater 
distance  behind  than  in  front. 

The  supravaginal  portion  is  not  covered  by  peritoneum  in  front ;  a  pad  of 
cellular  tissue  is  interposed  between  it  and  the  bladder.  Behind,  the  peritoneum  is 
extended  over  its  upper  part.  The  vaginal  portion  is  the  rounded  lower  end  pro- 
jecting into  the  vagina.  On  its  surface  is  a  small  aperture,  the  os  uteri,  generally 
circular  in  shape,  but  sometimes  oval  or  almost  linear.  The  margin  of  the  opening 
is,  in  the  absence  of  past  parturition  or  disease,  quite  smooth. 

Ligaments. — The  ligaments  of  the  uterus  are  eight  in  number :  one  anterior ; 
one  posterior ;  two  lateral  or  broad  ;  two  sacro-uterine, — all  these  being  formed  of 
peritoneum — and,  lastly,  two  round  ligaments. 

The  anterior  ligament  (vesico-uterine)  is  reflected  on  to  the  bladder  from  the 
front  of  the  uterus,  at  the  junction  of  the  supravaginal  cervix  and  body. 

The  posterior  ligament  (recto-uterine)  passes  from  the  posterior  wall  of  the 
uterus  over  the  upper  fourth  of  the  vagina,  and  thence  on  to  the  rectum  and  sacrum. 
It  thus  forms  a  pouch  called  Douglas's  pouch  (Fig.  747),  the  boundaries  of  which  are, 
in  front,  the  posterior  Avail  of  the  uterus,  the  supravaginal  cervix,  and  the  upper 

74 


1170 


FEMALE    GENERATIVE    ORGANS. 


fourth  of  the  vagina ;  behind,  the  rectum  and  sacrum ;  above,  the  small  intestine  ; 
and,  laterally,  the  sacro-uterine  ligaments  investing  recto-vesical  fascia. 

The  two  lateral  or  broad  ligaments  pass  from  the  sides  of  the  uterus  to  the 
lateral  walls  of  the  pelvis,  forming  a  septum  across  the  pelvis,  which  divides  that 
cavity  into  two  portions.  In  the  anterior  part  are  contained  the  bladder, 


Round 
ligament. 


Douglas'  pmich. 
FIG.  747.— Douglas's  pouch.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons.) 

urethra,  and  vagina ;  in  the  posterior  part,  the  rectum.  Between  the  two  layers 
of  each  broad  ligament  are  contained — (1)  the  Fallopian  tubes  superiorly ;  (2)  the 
round  ligament ;  (3)  the  ovary  and  its  ligament ;  (4)  the  parovarium,  or  organ 
of  Rosenmuller ;  (5)  connective  tissue ;  and  (6)  unstriped  muscular  fibre. 
Between  the  fimbriated  extremity  of  the  tube  and  the  lower  attachment  of 
the  broad  ligament  is  a  concave  rounded  margin  called  the  infundibulo-pelvic  liga- 
ment (Fig.  752).  The  upper  border  is  often  known  as  the  mesosalpinx. 

The  sacro-uterine  ligaments  pass  from  the  second  and  third  bones  of  the  sacrum, 
downward  and  forward,  to  be  attached  one  on  each  side  of  the  uterus  at  the  junc- 
tion of  the  supravaginal  cervix  and  the  body,  this  point  corresponding  internally 
to  the  position  of  the  os  internum.  (For  the  round  ligaments,  see  page  1177.) 

The  cavity  of  the  uterus  is  small  in  comparison  with  the  size  of  the  organ  ; 
that  portion  of  the  cavity  which  corresponds  to  the  body  is  triangular,  flattened 
from  before  backward,  so  that  its  walls  are  closely  approximated,  and  having  its 
base  directed  upward  toward  the  fundus.  At  each  superior  angle  is  a  funnel- 
shaped  cavity,  which  constitutes  the  remains  of  the  division  of  the  body  of  the 
uterus  into  two  cornua,  and  at  the  bottom  of  each  cavity  is  the  minute  orifice  of 
the  Fallopian  tube.  At  the  inferior  angle  of  the  uterine  cavity  is  a  small  con- 
stricted opening,  the  internal  orifice  (ostium  internum),  which  leads  into  the 
cavity  of  the  cervix. 


THE    UTERUS. 


1171 


The  cavity  of  the  cervix  is  somewhat  fusiform,  flattened  from  before  backward, 
broader  at  the  middle  than  at  either  extremity,  and  communicates  below  with  the 


FIG.  748.-- Side  view  of  the  female  pelvic  organs.    (From  a  preparation  in  the  Museum  of  the  Royal  College 
of  Surgeons.) 

vagina.  The  wall  of  the  canal  presents,  anteriorly  and  posteriorly,  a  longitudinal 
column,  from  which  proceed  a  number  of  small  oblique  columns,  giving  the  appear- 
ance of  branches  from  the  stem  of  a  tree ;  and  hence  the  name  arbor  vitce  uterina 


uttri  Peritoneal 

covering 


Cervix 


Vaginal  portion 
of  uterus 


Os  uteri 


FIG.  749.— Anterior  section  through  the  virgin  FIG.  750.— Opening  in  the  wall  of  the  cervical  canal 

uterus.     (Bardeleben.)  in  a  human  uterus,  showing  the  plicae  palmatae.    (Bar- 

deleben.l 


(plicae  palmatfe)  applied  to  it.     These  folds  usually  become  very  indistinct  after  the 
first  labor  (Fig.  750). 

Structure. — The  uterus  is  composed  of  three  coats — an  external  serous  coat,  a 
middle  or  muscular,  and  an  internal  mucous  coat. 


1172  FEMALE    GENERATIVE    ORGANS. 

The  serous  coat  is  derived  from  the  peritoneum ;  it  invests  the  fundus  and  the 
whole  of  the  posterior  surface  of  the  body  of  the  uterus,  but  only  the  upper 
three-fourths  of  its  anterior  surface.  In  the  lo\ver  fourth  of  the  posterior  sur- 
face the  peritoneum,  though  covering  the  uterus,  is  not  closely  connected  with 
it,  being  separated  from  it  by  a  layer  of  loose  cellular  tissue  and  some  large 
veins. 

The  muscular  coat  forms  the  chief  bulk  of  the  substance  of  the  uterus.  In 
the  uniinpregnated  state  it  is  dense,  firm,  of  a  grayish  color,  and  cuts  almost  like 
cartilage.  It  is  thick  opposite  the  middle  of  the  body  and  fundus,  and  thin  at 
the  orifices  of  the  Fallopian  tubes.  It  consists  of  bundles  of  unstriped  muscular 
fibres,  disposed  in  layers,  intermixed  with  areolar  tissue,  blood-vessels,  lymphatic 
vessels,  and  nerves.  In  the  impregnated  state  the  muscular  tissue  becomes  more 
prominently  developed,  and  is  disposed  in  three  layers — external,  middle,  and 
internal. 

The  external  layer  is  placed  beneath  the  peritoneum,  disposed  as  a  thin  plane 
on  the  anterior  and  posterior  surfaces.  It  consists  of  fibres  which  pass  trans- 
versely across  the  fundus,  and,  converging  at  each  superior  angle  of  the  uterus, 
are  continued  on  the  Fallopian  tube,  the  round  ligament,  the  ligament  of  the 
ovary :  some  passing  at  each  side  into  the  broad  ligament,  and  others  running 
backward  from  the  cervix  into  the  sacro-uterine  ligaments. 

The  middle  layer  of  fibres,  which  is  thickest,  presents  no  regularity  in  its 
arrangement,  being  disposed  longitudinally,  obliquely,  and  transversely.  It  con- 
tains most  blood-vessels. 

The  internal  or  deep  layer  is  the  greatly  hypertrophied  muscularis  inucosce  of 
the  mucous  membrane.  It  consists  of  circular  fibres  arranged  in  the  form  of  two 
hollow  cones.  :he  apices  of  which  surround  the  orifices  of  the  Fallopian  tubes, 
their  bases  intermingling  with  one  another  on  the  middle  of  the  body  of  the  uterus. 
At  the  internal  os  these  circular  fibres  form  a  distinct  sphincter. 

The  mucous  membrane  is  smooth,  and  closely  adherent  to  the  subjacent  tissue. 
It  is  continuous,  through  the  fimbrinated  extremity  of  the  Fallopian  tubes,  with 
the  peritoneum,  and  through  the  os  uteri  with  the  lining  of  the  vagina. 

In  the  body  of  the  uterus  it  is  smooth,  soft,  of  a  pale  red  color  lined  by  colum- 
nar ciliated  epithelium,  and  presents,  when  viewed  with  a  lens,  the  orifices  of 
numerous  tubular  follicles  arranged  perpendicularly  to  the  surface.  It  is  unpro- 
vided with  any  submucosa,  but  is  intimately  connected  Avith  the  innermost  layer 
of  the  muscular  coat,  which  is  regarded  as  the  muscularis  mucosae.  In  structure 
its  corium  differs  from  ordinary  mucous  membrane,  consisting  of  an  embryonic 
nucleated  and  highly  cellular  form  of  connective  tissue  in  which  run  numerous 
large  lymphatics.  In  it  are  the  tube-like  uterine  glands,  which  are  of  small  size 
in  the  unimpregnated  uterus,  but  shortly  after  impregnation  become  enlarged, 
elongated,  presenting  a  contorted  or  waved  appearance  toward  their  closed  extrem- 
ities, which  reaches  into  the  muscularis,  and  may  be  single  or  bifid.  They  consist 
of  a  delicate  membrane,  lined  by  an  epithelium,  which  becomes  ciliated  toward  the 
orifices.  In  the  impregnated  uterus  the  epithelium  loses  its  ciliated  character,  is 
thicker  and  tougher,  and  is  provided  with  a  submucous  layer  of  areolar  tissue. 

In  the  cervix  the  mucous  membrane  is  sharply  differentiated  from  that  of  the 
uterine  cavity.  It  is  thrown  into  numerous  transverse  folds,  which  are  arranged 
along  an  anterior  and  posterior  longitudinal  raphe,  presenting  an  appearance  which 
has  received  the  name  of  arbor  vitce.  In  the  upper  two-thirds  of  the  canal  the 
mucous  membrane  is  provided  with  numerous  deep  glandular  follicles,  Avhich  secrete 
a  clear  viscid  alkaline  mucus ;  and  in  addition,  extending  through  the  whole  length 
of  the  canal,  are  a  variable  number  of  little  cysts,  presumably  follicles,  which  have 
become  occluded  and  distended  with  retained  secretion.  They  are  called  the  ovula 
Nabothi.  The  mucous  membrane  covering  the  lower  half  of  the  cervical  canal 
presents  numerous  papillae.  The  epithelium  of  the  upper  two-thirds  is  columnar 
and  ciliated,  but  below  this  it  loses  its  cilia,  and  gradually  changes  to  squamous 
epithelium  close  to  the  external  os. 


THE    UTEItls. 


1173 


Vessels  and  Nerves. — The  arteries  of  tin-  n.t>  /•"•«  are  the  uterine,  from  the  internal 
iliac,  and  the  ovarian,  from  the  aorta.  They  are  remarkable  for  their  tortuous 
course  in  the  substance  of  the  organ  and  for  their  frequent  anastomoses.  The 
termination  of  the  ovarian  artery  meets  the  termination  of  the  uterine  artery,  and 
forms  an  auastomotic  trunk  from  which  branches  are  given  off  to  supply  the 
uterus,  their  disposition  being,  as  shown  by  John  Williams,  circular.  The  veins 
are  of  large  size,  and  correspond  with  the  arteries.  In  the  impregnated  uterus 
these  vessels  are  termed  the  uterine  sinuses,  consisting  of  the  lining  membrane  of 
the  veins  adhering  to  the  walls  of  the  canal  channelled  through  the  substance  of 
the  uterus.  They  terminate  in  the  uterine  plexuses.  The  lymphatics  of  the  body 
terminate  in  the  lumbar  glands,  those  of  the  cervix  in  the  pelvic  glands.  The 


Internal  iliac 
artery. 


FIG.  751.— The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind.     (After  HyrtL) 

nerres  are  derived  from  the  inferior  hypogastric  and  ovarian  plexuses,  and  from 
the  third  and  fourth  sacral  nerves. 

The  form.  size,  and  situation  of  the  uterus  van*  at  different  periods  of  life  and  under  dif- 
ferent circumstancfs. 

///  the  ffftiis  the  uterus  is  contained  in  the  abdominal  cavity,  projecting  beyond  the  brim  of 
the  pelvis.  The  cervix  is  considerably  larger  than  the  body. 

At  p»f»:rty  the  uterus  is  pyriform  in  shape,  and  weighs  from  eight  to  ten  drachms.  It  has 
descended  into  the  pelvis,  the  fundus  being  just  below  the  level  of  the  brim  of  this  cavity.  The 
arbor  vita?  is  distinct,  and  extends  to  the  upper  part  of  the  cavity  of  the  organ. 

During  m?i<xti-n<it!on  the  organ  is  enlarged,  and  more  vascular,  its  surfaces  rounder :  the 
termini  is  rounded,  its  labia  swollen,  and  the  lining  membrane  of  the  body  thickened, 
.•-otter  and  of  a  darker  color.  According  to  J.  Williams,  at  each  recurrence  of  menstruation  a 
molecular  disintegration  of  the  mucous  membrane  takes  place,  which  leads  to  its  complete 
removal,  only  the  bases  of  the  glands  imbedded  in  the  muscle  being  left.  At  the  cessation 
of  menstruation  by  a  proliferation  of  the  remaining  structures  a  fresh  mucous  membrane  is 
formed 

During  pregnancy  the  uterus  becomes  enormously  enlarged,  and  in  the  ninth  month  reaches 
the  epigastric  region.  The  increase  in  size  is  partly  due  to  growth  of  pre-existing  muscle  and 
partly  to  development  of  new  fibres. 

^  Aft.fr  j»:irtur>'tion  the  uterus  nearly  regains  its  usual  size,  weiebine  about  an  ounce  and  a 
half:  but  its  cavity  is  larger  than  in  the  vinrin  state,  the  external  orifice  is  more  marked,  its 
ed<.:es  present  a  fissured  surface,  its  vessels  are  tortuous,  and  its  muscular  layers  are  more 
defined. 


1174 


FEMALE    GENERATIVE    ORGANS. 


In  old  age  the  uterus  becomes  atrophied,  and  paler  and  denser  in  texture  ;  a  more  distinct 
constriction  separates  the  body  and  cervix.  The  ostiuni  internum  and.  occasionally,  the  vaginal 
orifice  often  become  obliterated;  and  its  labia  almost  entirely  disappear. 

APPENDAGES  OF  THE  UTERUS. 

The  appendages  of  the  uterus  are  the  Fallopian  tubes,  the  ovaries  and  their 
ligaments,  and  the  round  ligaments.  They  are  placed  in  the  following  order :  in 
front  is  the  round  ligament ;  the  Fallopian  tube  occupies  the  upper  margin  of  the 
broad  ligament ;  the  ovary  and  its  ligament  are  behind  and  below  both. 

THE  FALLOPIAN  TUBES. 

The  Fallopian  Tubes,  or  Oviducts,  convey  the  ova  from  the  ovaries  to  the  cavity 
of  the  uterus.  They  are  two  in  number,  one  on  each  side,  situated  in  the  upper 
margin  of  the  broad  ligament,  extending  from  each  superior  angle  of  the  uterus  to 
the  sides  of  the  pelvis.  Each  tube  is  about  four  inches  in  length  ;  and  is  described 
as  consisting  of  three  portions  :  (1)  the  isthmus,  or  inner  constricted  half;  (2)  the 
ampulla,  or  outer  dilated  portion,  which  curves  over  the  ovary ;  and  (3)  the 


I'll- run. 


Fimbria 

ovaricn. 

FIG.  752.— Uterine  appendages,  seen  from  behind.    (Henle.) 

infundibulum  with  its  ostium  abdominale,  surrounded  by  fimbrise,  one  of  which  is 
attached  to  the  ovary,  the  fimbria  ovarica.  The  general  direction  of  the  Fallopian 
tube  is  outward  and  upward,  backward  and  downward.  The  uterine  opening  is 
minute,  and  will  only  admit  a  fine  bristle ;  the  abdominal  opening  is  comparatively 
much  larger.  In  connection  with  the  fimbriae  of  the  Fallopian  tube  or  with  the  broad 
ligament  close  to  them  there  is  frequently  one  or  more  small  vesicles  floating  on 
a  long  stalk  of  peritoneum.  These  are  termed  the  hydatids  of  Morgagni,  and  arc 
probably  of  peritoneal  origin. 

Structure. — The  Fallopian  tube  consists  of  three  coats — serous,  muscular,  and 
mucous. 

The  external  or  serous  coat  is  peritoneal. 

The  middle  or  muscular  coat  consists  of  an  external  longitudinal  and  an  internal 
circular  layer  of  muscular  fibres  continuous  with  those  of  the  uterus. 

The  internal  or  mucous  coat  is  continuous  with  the  mucous  lining  of  the  uterus 
and,  at  the  free  extremity  of  the  tube,  with  the  peritoneum.  It  is  thrown  into 
longitudinal  folds,  which  in  the  outer,  larger  part  of  the  tube,  or  ampulla,  are  much 
more  extensive  than  in  the  narrow  canal  of  the  isthmus.  The  lining  epithelium 
is  columnar  ciliated.  This  form  of  epithelium  is  also  found  on  the  inner  surface 
of  the  fimbriae,  while  on  the  outer  or  serous  surfaces  of  these  processes  the 
epithelium  gradually  merges  into  the  endotheliurn  of  the  peritoneum. 


THE    OVARIES. 


1175 


THE  OVARIES. 

The  Ovaries  (tettes  muliebres,  Galen)  are  analogous  to  the  testes  in  the  male. 
They  are  oval-shaped,  flattened  bodies  of  an  elongated  form,  situated  one  on  each 
side  of  the  uterus,  connected  to  the  posterior  layer  of  the  broad  ligament  behind 
and  below  the  Fallopian  tubes.  Each  ovary  is  connected  by  its  anterior  straight 
margin  to  the  broad  ligaments :  by  its  lower  extremity  to  the  uterus  by  a  proper 
ligament,  the  ligament  of  the  ovary  ;  and  by  its  upper  end  to  the  fimbriated  extremity 
of  the  Fallopian  tube  by  the  ovarian  fimbria ;  its  mesial  and  lateral  surfaces  and 
posterior  convex  border  are  free.  The  ovaries  are  of  a  grayish-pink  color,  and  pre- 
sent either  a  smooth  or  puckered,  uneven  surface.  They  are  each  about  an  inch 
and  a  half  in  length,  three-quarters  of  an  inch  in  width,  and  about  a  third  of  an 
inch  thick,  and  weight  from  one  to  two  drachms. 

The  exact  position  of  the  ovary  has  been  the  subject  of  considerable  difference 
of  opinion,  and  writers  differ  much  as  to  what  is  to  be  regarded  as  the  normal  posi- 
tion. The  fact  appears  to  be  that  it  is  differently  placed  in  different  individuals. 
Hasse  has  described  it  as  being  situated  with  its  long  axis  transverse,  or  almost 
transverse,  to  the  pelvic  cavity.  Schultze,  on  the  other  hand,  believes  that  its 


Fimbriated  extremity   Fallopian  tube. 
oj  tube. 


Artery. 
I  "an. 


Anterior  wall  of  vagina. 


FIG.  753.— The  uterus  and  its  appendages.  Posterior  view.  The  parts  have  been  somewhat  displaced  from 
their  proper  position  in  the  preparation  of  the  specimen;  thus  the  right  ovary  has  been  raised  above  the 
Fallopian  tube,  and  the  fimbriated  extremities  of  the  tubes  have  been  turned  upward  and  outward.  (From  a 
preparation  in  the  Royal  College  of  Surgeons.) 

long  axis  is  antero-posterior.  Kolliker  asserts  that  the  truth  lies  between  these 
two  views,  and  that  the  ovary  is  placed  obliquely  in  the  pelvis,  its  long  axis  lying 
parallel  to  the  external  iliac  vessels,  with  its  surface  directed  inward  and  outward,  and 
its  convex  free  border  upward.  His  has  made  some  important  observations  on  this 
subject,  and  his  views  are  largely  accepted.  He  teaches  that  the  uterus  rarely  lies 
symmetrically  in  the  middle  of  the  pelvic  cavity,  but  is  generally  inclined  to  one 
or  other  side,  most  frequently  to  the  left,  in  the  proportion  of  three  to  two.  The 
position  of  the  two  ovaries  varies  according  to  the  inclination  of  the  uterus.  "\Vhen 
the  uterus  is  inclined  to  the  left,  the  ovary  of  this  side  lies  with  its  long  axis 
vertical  and  with  one  side  closely  applied  to  the  outer  wall  of  the  pelvis,  while  the 
ovary  of  the  opposite  side,  being  dragged  upon  by  the  inclination  of  the  uterus, 
lies  obliquely,  its  outer  extremity  being  retained  in  close  apposition  to  the  side  of 
the  pelvis  by  the  infundibulo-pelvic  ligament  (page  1170).  When,  on  the  other 
hand,  the  uterus  is  inclined  to  the  right,  the  position  of  the  two  ovaries  is  exactly 
reversed,  the  right  being  vertical  and  the  left  oblique.  In  whichever  position  the 
ovary  is  placed,  the  Fallopian  tube  forms  a  loop  around  it.  the  uterine  half 
ascending  obliquely  over  it.  and  the  outer  half,  including  the  dilated  extremity, 
descending  and  bulging  freely  behind  it.  From  this  extremity  the  firnbrise  pass 
upward  on  to  the  ovary  and  closely  embrace  it. 

Structure. — The  ovarv  consists  of  a  number  of  Graafian  vesicles  imbedded  in 


1176 


FEMALE    GENERATIVE    ORGANS. 


the  meshes  of  a  stroma  or  framework,  and  invested  by  a  serous  covering  derived 
from  the  peritoneum. 

Serous  Covering. — Though  the  investing  membrane  of  the  ovary  is  derived 
from  the  peritoneum,  it  differs  essentially  from  that  structure,  inasmuch  as  its 
epithelium  consists  of  a  single  layer  of  columnar  cells,  instead  of  the  flattened 
endothelial  cells  of  other  parts  of  the  membrane ;  this  has  been  termed  the  ger- 
minal epithelium  of  Waldeyer,  and  gives  to  the  surface  of  the  ovary  a  dull  gray 
aspect  instead  of  the  shining  smoothness  of  serous  membranes  generally. 

Stroma. — The  stroma  is  a  peculiar  soft  tissue,  abundantly  supplied  with  blood- 
vessels, consisting  for  the  most  part  of  spindle-shaped  cells,  with  a  small  amount 
of  ordinary  connective  tissue.  These  cells  have  been  regarded  by  some  anatomists 
as  unstriped  muscle-cells,  which,  indeed,  they  most  resemble  (His) ;  by  others  as 
connective-tissue  cells  (Waldeyer,  Henle,  and  Kolliker).  On  the  surface  of  the 
organ  this  tissue  is  much  condensed,  and  forms  a  layer  composed  of  short  connec- 
tive-tissue fibres,  with  fusiform  cells  between  them.  This  was  formerly  regarded 
as  a  distinct  fibrous  covering,  and  was  termed  the  tunica  albuginea,  but  is  nothing 
more  than  a  condensed  layer  of  the  stroma  of  the  ovary. 

Graafian  Follicles. — Upon  making  a  section  of  an  ovary  numerous  round  trans- 
parent vesicles  of  various  sizes  are  to  be  seen  ;  they  are  the  Grraafian  vesicles  or  fol- 
licles, the  ovisacs  containing  the  ova.  Immediately  beneath  the  superficial  covering 
is  a  layer  of  stroma,  in  which  are  a  large  number  of  minute  vesicles  of  uniform  size, 
about  Tft-fr  of  an  inch  in  diameter.  These  are  the  Graafian  vesicles  in  their  earliest 
condition,  and  the  layer  where  they  are  found  has  been  termed  the  cortical  layer. 
They  are  especially  numerous  in  the  ovary  of  the  young  child.  After  puberty 

and  during  the  whole  of  the  child- 
bearing  period  large  and  mature, 
or  almost  mature,  Graafian  vesi- 
cles are  also  found  in  the  cortical 
layer  in  small  numbers,  and  also 
"corpora  lutea,"  the  remains  of 
vesicles  which  have  burst  and  are 

Granular  zone. 


Peritoneum. 


FIG.  754.— Section  of  the  ovary.  (After  Schron.)  1. 
Outer  covering.  1'.  Attached  border.  2.  Central  stroma. 
3.  Peripheral  stroma.  4.  Blood-vessels.  5.  Graafian  fol- 
licles in  their  earliest  stage.  6,  7,  8.  More  advanced  folli- 
cles. 9.  An  almost  mature  follicle.  9'.  Follicle  from 
which  the  ovum  has  escaped.  10.  Corpus  luteum. 


Coats  of  the 
Stroma  of  the  ovary         \  Graafian  vesicle, 
witkbloodrvessels.    Membrana 
granulosa. 

FIG.  755.— Section  of  the  Graafian  ves- 
icle.   (After  Von  Baer.) 


undergoing  atrophy  and  absorption.  Beneath  this  superficial  stratum  other  large 
and  more  mature  Graafian  vesicles  are  found  imbedded  in  the  ovarian  stroma. 
These  increase  in  size  as  they  recede  from  the  surface  toward  a  highly  vascular 
stroma  in  the  centre  of  the  organ,  termed  the  medullary  substance  (zona  vasculosa, 
Waldeyer).  This  stroma  forms  the  tissue  of  the  hilum  by  which  the  ovary  is 
attached,  and  through  which  the  blood-vessels  enter;  it  does  not  contain  any 
Graafian  vesicles. 

The  larger  Graafian  follicles  consist  of  an  external  fibro- vascular  coat  connected 
with  the  surrounding  stroma  of  the  ovary  by  a  network  of  blood-vessels ;  and  an 
internal  coat,  named  ovicapsule,  which  is  lined  by  a  layer  of  nucleated  cells,  called 
the  membrana  granulosa.  The  fluid  contained  in  the  interior  of  the  vesicles  is 
transparent  and  albuminous,  and  in  it  is  suspended  the  ovum.  In  that  part  of 
the  mature  Graafian  vesicle  which  is  nearest  the  surface  of  the  ovary  the  cells  of 
the  membrana  granulosa  are  collected  into  a  mass  which  projects  into  the  cavity 


THE    OVARIES.  1177 

of  the  vesicle.  This  is  termed  the  discus  proligerus,  and  in  this  the  ovum  is 
imbedded.1 

The  ova  are  formed  from  the  germ-epithelium  on  the  surface  of  the  ovary :  the 
cells  become  enlarged  and  involuted,  forming  little  depressions  on  the  surface  of 
the  ovary  As  they  sink  deeper  into  the  tissue  they  become  enclosed  by  the  out- 
growth of  processes  from  the  stroma  of  the  ovary,  and,  becoming  surrounded,  their 
connection  with  the  surface  is  cut  off.  and  the  germ-epithelium  forming  the 
involution  is  contained  in  a  cavity,  the  future  Graafian  follicle.  The  germ-cell  or 
cells  now  form  the  ovum  ;  the  cell-wall  forms  the  vitelline  membrane  ;  the  nucleus, 
the  germinal  area  or  vesicle :  and  a  nucleolus,  which  soon  appears,  the  germinal 
spot.  A  clear  homogeneous  protoplasm  is  formed  within  the  cell,  constituting  the 
yelk,  and  thus  the  primordial  ovum  is  developed.  According  to  Dr.  Foullis,  the 
cells  of  the  membrana  granulosa  are  formed  out  of  the  nuclei  of  the  fibro-cellular 
stroma  of  the  ovary.2 

The  development  and  maturation  of  the  Graafian  vesicles  and  ova  continue 
uninterruptedly  from  puberty  to  the  end  of  the  fruitful  period  of  woman's  life, 
while  their  formation  commences  before  birth.  Before  puberty  the  ovaries  are 
small,  the  Graafian  vessels  contained  in  them  are  disposed  in  a  comparatively 
thick  layer  in  the  cortical  substance  ;  here  they  present  the  appearance  of  a  large 
number  of  minute  closed  vesicles,  constituting  the  early  condition  of  the  Graafian 
vesicle ;  many,  however,  never  attain  full  development,  but  shrink  and  disappear, 
their  ova  being  incapable  of  impregnation.  At  puberty  the  ovaries  enlarge,  are 
more  vascular,  the  Graafian  vesicles  are  developed  in  greater  abundance,  and  their 
ova  are  capable  of  fecundation. 

Discharge  of  the  Ovum. — The  Graafian  vesicles,  after  gradually  approaching 
the  surface  of  the  ovary,  burst :  the  ovum  and  fluid  contents  are  liberated,  and 
escape  on  the  exterior  of  the  ovary,  passing  thence  into  the  Fallopian  tube.3 

In  the  foetus  the  ovaries  are  situated,  like  the  testes.  in  the  lumbar  region,  near 
the  kidneys.  They  may  be  distinguished  from  those  bodies  at  an  early  period  by 
their  elongated  and  flattened  form,  and  by  their  position,  which  is  at  first  oblique 
and  then  nearly  transverse.  They  gradually  descend  into  the  pelvis. 

Lying  above  the  ovary  in  the  broad  ligament  between  it  and  the  Fallopian  tube 
is  the  organ  of  Eosenmiiller.  called  also  the  parovarium.  This  is  the  remnant  of  a 
foetal  structure,  described  at  page  137.  In  the  adult  it  consists  of  a  few  closed  con- 
voluted tubes  lined  with  epithelium,  which  converge  toward  the  ovary,  but  which 
are  connected  at  their  opposite  extremities  with  a  longitudinal  tube,  the  duct  of 
Gartner  (epoophoron],  which  ends  in  a  bulbous  or  hydated  swelling.  The  paro- 
varium is  connected  at  its  uterine  extremity  with  the  remains  of  the  Wolffian  duct. 

The  paroophoron  corresponds  to  the  paradidymis  of  the  male,  and  is  found, 
when  present,  near  the  uterus. 

The  Ligament  of  the  Ovary  is  a  rounded  cord  which  extends  from  each  superior 
angle  of  the  uterus  to  the  lower  extremity  of  the  ovary  ;  it  consists  of  fibrous  tissue 
and  a  few  muscular  fibres  derived  from  the  uterus. 

The  Round  Ligaments  are  two  rounded  cords,  between  four  and  five  inches  in 
length,  situated  between  the  layers  of  the  broad  ligament  in  front  of  and  below  the 
Fallopian  tube.  Commencing  on  each  side  at  the  superior  angle  of  the  uterus,  this 
ligament  passes  forward,  upward,  and  outward  through  the  internal  abdominal 
ring,  along  the  inguinal  canal,  to  the  labia  majora,  in  which  it  becomes  lost.  The 
round  ligament  consists  principally  of  muscular  tissue  prolonged  from  the  uterus : 
also  of  some  fibrous  and  areolar  tissue,  besides  blood-vessels  and  nerves,  enclosed 
in  a  duplicature  of  peritoneum,  which  in  the  foetus  is  prolonged  in  the  form  of  a 
tubular  process  for  a  short  distance  into  the  inguinal  canal.  This  process  is  called 
the  canal  nf  Xuck.  It  is  generally  obliterated  in  the  adult,  but  sometimes  remains 

1  For  a  description  of  the  ovum,  see  page  100. 

2  P'-oceedina?  of  the  Royal  Society  of  Edinburgh,  April,  1875. 

3  This  is  effected  either  by  application  of  the  tube  to  the  ovary,  or  by  a  curling  upward  of  the 
fimbriated  extremity,  so  that  the  ovum  is  caught  as  it  falls. 


1178 


FEMALE    GENERATIVE    ORGANS. 


pervious  even  in  advanced  life.     It  is   analogous   to  the  peritoneal  pouch  which 
accompanies  the  descent  of  the  testis. 

Vessels  and  Nerves. — The  arteries  of  the  ovaries  and  Fallopian  tubes  are  the 
ovarian  from  the  aorta.  They  enter  the  attached  border,  or  hilum,  of  the  ovary. 
The  veins  follow  the  course  of  the  arteries  ;  they  form  a  plexus  near  the  ovary,  the 
pampiniform  plexus.  The  nerves  are  derived  from  the  inferior  hypogastric  or 
pelvic  plexus,  and  from  the  ovarian  plexus,  the  Fallopian  tube  receiving  a  branch 
from  one  of  the  uterine  nerves. 

THE    MAMMARY    GLANDS. 

The  mammae,  or  breasts,  are  accessory  glands  of  the  generative  system,  which 
secrete  the  milk.  They  exist  in  the  male  as  well  as  in  the  female,  but  in  the 
former  only  in  the  rudimentary  state,  unless  their  growth  is  excited  by  peculiar 
circumstances.  In  the  female  they  are  two  large  hemispherical  eminences  situated 


Fat. 
Lobule  unravelled. 


•*  Lactiferous  duct. 

K 
X 

Ampulla. 

** 

•*> 
Loculi  in  connective  tissue. 

FIG.  756.— Dissection  of  the  lower  half  of  the  female  breast  during  the  period  of  lactation.     (From  Luschka.) 


Lobule' 


toward  the  lateral  aspect  of  the  pectoral  region,  corresponding  to  the  intervals 
between  the  third  and  sixth  or  seventh  ribs,  and  extending  from  the  side  of  the 
sternum  to  the  axilla.  Their  weight  and  dimensions  differ  at  different  periods 
of  life  and  in  different  individuals.  Before  puberty  they  are  of  small  size,  but 
enlarge  as  the  generative  organs  become  more  completely  developed.  They 
increase  during  pregnancy,  and  especially  after  delivery,  and  become  atrophied  in 
old  age.  The  left  mamma  is  generally  a  little  larger  than  the  right.  Their  base 
is  nearly  circular,  flattened  or  slightly  concave,  and  has  its  long  diameter  directed 
upward  and  outward  toward  the  axilla ;  they  are  separated  from  the  Pectoral  and 
Serratus  magnus  muscles  by  a  layer  of  fascia.  The  outer  surface  of  the  mamma 
is  convex,  and  presents,  just  below  the  centre,  a  small  conical  prominence,  the  nipple 
(mammilla).  The  surface  of  the  nipple  is  dark-colored  and  surrounded  by  an 
areola  having  a  colored  tint.  In  the  virgin  the  areola  is  of  a  delicate  rosy  hue ; 
about  the  second  month  after  impregnation  it  enlarges  and  acquires  a  darker  tinge, 
which  increases  as  pregnancy  advances,  becoming  in  some  cases  of  a  dark-brown 
or  even  black  color.  This  color  diminishes  as  soon  as  lactation  is  over,  but  is 
never  entirely  lost  throughout  life.  These  changes  in  the  color  of  the  areola  are 
of  importance  in  forming  a  conclusion  in  a  case  of  suspected  first  pregnancy. 


THE   MAJ^^fARY   GLANDS.  1179 

The  nipple  is  a  cylindrical  or  conical  eminence  capable  of  undergoing  a  sort  of 
erection  from  mechanical  excitement,  a  change  mainly  due  to  the  contraction  of  its 
muscular  fibres.  It  is  of  a  pink  or  brownish  hue,  its  surface  wrinkled  and  provided 
with  papillae,  and  it  is  perforated  at  the  tip  by  numerous  orifices,  the  apertures  of 
the  lactiferous  ducts.  Near  the  base  of  the  nipple  and  upon  the  surface  of  the 
areoli  are  numerous  sebaceous  glands,  which  become  much  enlarged  during  lacta- 
tion, and  present  the  appearance  of  small  tubercles  beneath  the  skin.  These 
glands  secrete  a  peculiar  fatty  substance,  which  serves  as  a  protection  to  the  integu- 
ment of  the  nipple  during  the  act  of  sucking.  The  nipple  consists  of  numerous 
vessels,  intermixed  with  plain  muscular  fibres,  which  are  principally  arranged  in  a 
circular  manner  around  the  base,  some  few  fibres  radiating  from  base  to  apex. 

Structure. — The  mamma  consists  of  gland-tissue  ;  of  fibrous  tissue,  connecting  its 
lobes ;  and  of  fatty  tissue  in  the  intervals  between  the  lobes.  The  gland-tissue, 
when  freed  from  fibrous  tissue  and  fat,  is  of  a  pale  reddish  color,  firm  in  texture, 
circular  in  form,  flattened  from  before  backward,  thicker  in  the  centre  than  at  the 
circumference,  and  presenting  several  inequalities  on  its  surface,  especially  in  front. 
It  consists  of  numerous  lobes,  and  these  are  composed  of  lobules  connected  together 
by  areolar  tissue,  blood-vessels,  and  ducts.  The  smallest  lobules  consist  of  a  cluster 
of  rounded  alveoli,  which  open  into  the  smallest  branches  of  the  lactiferous  ducts  ; 
these  ducts,  uniting,  form  larger  ducts,  which  terminate  in  a  single  canal,  correspond- 
ing with  one  of  the  chief  subdivisions  of  the  gland.  The  number  of  excretory  ducts 
varies  from  fifteen  to  twenty  :  they  are  termed  the  tnbitU  lactiferi,  or  galactophori. 
They  converge  toward  the  areola.  beneath  which  they  form  dilatations,  OTampuUw. 
which  serve  as  reservoirs  for  the  milk,  and  at  the  base  of  the  nipple  become 
contracted  and  pursue  a  straight  course  to  its  summit,  perforating  it  by  separate 
orifices  considerably  narrower  than  the  ducts  themselves.  The  ducts  are  composed 
of  areolar  tissue,  with  longitudinal  and  transverse  elastic  fibres  and  longitudinal 
muscular  fibres  :  their  mucous  lining  is  continuous,  at  the  point  of  the  nipple,  with 
the  integument.  The  epithelium  of  the  mammary  gland  differs  according  to  the 
state  of  activity  of  the  organ.  In  the  gland  of  a  woman  who  is  not  pregnant  or 
suckling  the  alveoli  are  very  small  and  solid,  being  filled  with  a  mass  of  granular 
polyhedral  cells.  During  pregnancy  the  alveoli  enlarge  and  the  cells  undergo 
rapid  multiplication.  At  the  commencement  of  lactation  the  cells  in  the  centre 
of  the  alveolus  undergo  fatty  degeneration,  and  are  eliminated  in  the  first  milk 
tost  rum-corpuscles.  The  peripheral  cells  of  the  alveolus  remain,  and  form 
a  single  layer  of  granular,  short  columnar  cells,  with  a  spherical  nucleus,  lining 
the  limiting  membrana  propria.  These  cells  during  the  state  of  activity  of  the  gland 
are  capable  of  forming,  in  their  interior,  oil-globules,  which  are  then  ejected  into 
the  lumen  of  the  alveolus  and  constitute  the  milk-globules. 

The  librou*  f/W»-  invests  the  entire  surface  of  the  breast,  and  sends  down 
septa  between  its  lobes,  connecting  them  together. 

The  faff  >/  tissue  surrounds  the  surface  of  the  gland  and  occupies  the  interval 
between  its  lobes.  It  usually  exists  in  considerable  abundance,  and  determines 
the  form  and  size  of  the  gland.  There  is  no  fat  immediately  beneath  the  areola 
and  nipple.  (The  colostrom-corpuscles  may  be  emigrated  white  corpuscles.) 

Vessels  and  Nerves, — The  arteries  supplying  the  mamma?  are  derived  from  the 
thoracic  branches  of  the  axillary,  the  intercostals.  and  internal  mammary.  The 

%  describe  an  anastomotic  circle  round  the  base  of  the  nipple,  called  by  Haller 
the  cimiliix  i-cnosus.  From  this  large  branches  transmit  the  blood  to  the 
circumference  of  the  gland  and  end  in  the  axillary  and  internal  mammary  veins. 
The  lymphatics,  for  the  most  part,  run  along  the  lower  border  of  the  Pectoralis 
major  to  the  axillary  glands  ;  some  few.  from  the  inner  side  of  the  breast,  perforate 
the  intercostal  spaces  and  empty  themselves  into  the  anterior  mediastinal  glands. 
The  nerves  are  derived  from  the  anterior  and  lateral  cutaneous  nerves  of  the  thorax. 


THE  SURGICAL  ANATOMY  OF  HERNIA. 


Dissection  (Fig.  757). — For  dissection  of  the  parts  concerned  in  inguinal  hernia  a  male 
subject,  free  from  fat,  should  always  be  selected.  The  body  should  be  placed  in  the  supine  posi- 
tion, the  abdomen  and  pelvis  raised  by  means  of  blocks  placed  beneath  them,  and  the  lower 
extremities  rotated  outward,  so  as  to  make  the  parts  as  tense  as  possible.  If  the  abdominal  walls 
are  flaccid,  the  cavity  of  the  abdomen  should  be  inflated  by  an  aperture  through  the  umbilicus. 
An  incision  should  be  made  along  the  middle  line  from  the  umbilicus  to  the  symphysis  pubis, 
and  continued  along  the  front  of  the  scrotum,  and  a  second  incision  from  the  anterior  superior 
spine  of  the  ilium  to  just  below  the  umbilicus.  These  incisions  should  divide  the  integument, 
and  the  triangular-shaped  flap  included  between  them  should  be  reflected  downward  and  outward, 
when  the  superficial  fascia  will  be  exposed. 

The  Superficial  Fascia  of  the  Abdomen. — This,  over  the  greater  part  of  the 
abdominal  wall,  consists  of  a  single  layer  of  fascia,  which  contains  a  variable 
amount  of  fat ;  but  as  it  approaches  the  groin  it  is  easily  divisible  into  two  layers, 
between  which  are  found  the  superficial  vessels  and  nerves  and  the  superficial 
inguinal  lymphatic  glands. 

The  superficial  layer  is  thick,  areolar  in  texture,  containing  adipose  tissue  in 
its  meshes,  the  quantity  of  which  varies  in  different  subjects.  Below,  it  passes 
over  Poupart's  ligament,  and  is  continuous  with  the  outer  layer  of  the  superficial 
fascia  of  the  thigh.  In  the  male  this  fascia  is  continued  over  the  penis  and  over 
the  outer  surface  of  the  cord  to  the  scrotum,  where  it  helps  to  form  the  dartos 
As  it  passes  to  the  penis  and  over  the  cord  to  the  scrotum  it  changes  its  character, 
becoming  thin,  destitute  of  adipose  tissue,  and  of  a  pale  reddish  color  ;  and  in  the 
scrotum  it  acquires  some  involuntary  muscular  fibres.  From  the  scrotum  it  may 
be  traced  backward,  to  be  continuous  with  the  superficial  fascia  of  the  perinseum. 
In  the  female  this  fascia  is  continued  into  the  labia  majora. 

The  hypogastric  branch  of  the  ilio-hypogastric  nerve  perforates  the  aponeurosis 
of  the  External  oblique  muscle  about  an  inch  above  and  a  little  to  the  outer  side  of 
the  external  abdominal  ring,  and  is  distributed  to  the  integument  of  the  hypogastric 
region. 

The  ilio-inguinal  nerve  escapes  at  the  external  abdominal  ring,  and  is  distributed 
to  the  integument  of  the  upper  and  inner  part  of  the  thigh,  to  the  scrotum  in  the 
male  and  to  the  labium  in  the  female. 

The  superficial  epigastric  artery  arises  from  the  femoral  about  half  an  inch 
below  Poupart's  ligament,  and,  passing  through  the  saphenous  opening  in  the  fascia 
lata,  ascends  on  to  the  abdomen,  in  the  superficial  fascia  covering  the  External 
oblique  muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches  to  the 
superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and  the  integument, 
anastomosing  with  branches  of  the  deep  epigastric  and  internal  mammary  arteries. 

The  superficial  circumflex  iliac  artery,  the  smallest  of  the  cutaneous  branches, 
arises  close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel 
with  Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches 
which  supply  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and 
the  integument,  anastomosing  with  the  deep  circumflex  iliac  and  with  the  gluteal 
and  external  circumflex  arteries. 

The  superficial  external  pudic  (superior)  artery  arises  from  the  inner  side  of 
the  femoral  artery  close  to  the  preceding  vessels,  and,  after  passing  through  the 
saphenous  opening,  courses  inward  across  the  spermatic  cord,  to  be  distributed  to 
the  integument  on  the  lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male, 
and  the  labium  in  the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The.  Superficial  Veins. — The  veins  accompanying  these  superficial  vessels  are 

1180 


THE  SUPERFICIAL    FASCIA. 


1181 


usually  much  larger  than  the  arteries;  they  terminate  in  the  internal  saphenous 


vein. 


The  superficial  inguinal  lymphatic  glands  are  placed  immediately  beneath  the 
integument,  are  of  large  size,  and  vary  from  eight  to  ten  in  number.  They  are 
divisible  into  two  groups :  an  upper,  disposed  irregularly  along  Poupart's  liga- 
ment, which  receive  the  lymphatic  vessels  from  the  integument  of  the  scrotum, 
penis,  pariotes  of  the  abdomen,  perineal  and  gluteal  regions,  and  the  mucous 
membrane  of  the  urethra ;  and  an  inferior  group,  which  surround  the  saphenous 
opening  in  the  fascia  lata,  a  few  being  sometimes  continued  along  the  saphenous 


External  abdominal 
ring. 


FIG.  757. — Inguinal  hernia.    Superficial  dissection. 

vein  to  a  variable  extent.  This  latter  group  receive  the  superficial  lymphatic 
vessels  from  the  lower  extremity. 

The  deep  layer  of  the  superficial  fascia  (fascia  of  Scarpa]  is  thinner  and  more 
membranous  in  character  than  the  superficial  layer.  In  the  middle  line  it  is 
intimately  adherent  to  the  linea  alba ;  above,  it  is  continuous  with  the  superficial 
fascia  over  the  rest  of  the  trunk  ;  below,  it  is  connected  with  the  fascia  lata 
(thigh)  a  little  below  Poupart's  ligament ;  below  and  internally,  in  the  male,  it  is 
continued  over  the  penis  and  over  the  outer  surface  of  the  cord  to  the  scrotum, 
where  it  helps  to  form  the  dartos.  From  the  scrotum  it  may  be  traced  backward 
to  be  continuous  with  the  deep  layer  of  the  superficial  fascia  of  the  perineum. 
In  the  female  it  is  continuous  with  the  labia  majora. 

The  scrotum  is  a  cutaneous  pouch  which  contains  the  testes  and  part  of  the 
spermatic  cords,  and  into  which  an  inguinal  hernia  frequently  descends  (see 
page  1153). 

The  Aponeurosis  of  the  External  Oblique  Muscle. — This  is  a  thin  but  strong 


1182  THE   SURGICAL    ANATOMY   OF  HERNIA. 

membranous  aponeurosis.  the  fibres  of  which  are  directed  obliquely  downward 
and  inward.  That  portion  of  the  aponeurosis  which  extends  between  the  anterior 
superior  spine  of  the  ilium  and  the  spine  of  the  os  pubis  is  a  broad  band,  folded 
inward  and  continuous  below  with  the  fascia  lata;  it  is  called  Poupart's  ligament. 
The  portion  which  is  reflected  from  Poupart's  ligament  at  the  spine  of  the  os  pubis, 
along  the  pectineal  line,  is  called  Gimbernafs  ligament.  From  the  point  of  attach- 
ment of  the  latter  to  the  pectineal  line  a  few  fibres  pass  upward  and  inward, 
behind  the  inner  pillar  of  the  ring,  to  the  linea  alba.  They  diverge  as  they  ascend, 
and  form  a  thin,  triangular,  fibrous  band,  which  is  called  the  triangular  ligament 
of  the  abdomen.  In  the  aponeurosis  of  the  External  oblique,  immediately  above  the 
crest  of  the  os  pubis,  is  a  triangular  opening,  the  external  or  superficial  abdominal 
ring,  formed  by  the  separation  of  the  fibres  of  the  aponeurosis  in  this  situation. 

The  External  or  Superficial  Abdominal  Ring. — Just  above  and  to  the  outer  side 
of  the  crest  of  the  os  pubis  an  interval  is  seen  in  the  aponeurosis  of  the  External 
oblique,  called  the  external  abdominal  ring.  This  aperture  is  oblique  in  direction, 
somewhat  triangular  in  form,  and  corresponds  with  the  course  of  the  fibres  of  the 
aponeurosis.  It  usually  measures  from  base  to  apex  about  an  inch,  and  trans- 
versely about  half  an  inch.  It  is  bounded  below  by  the  crest  of  the  os  pubis ; 
above,  by  a  series  of  curved  fibres,  the  inter  columnar,  which  pass  across  the  upper 
angle  of  the  ring,  so  as  to  increase  its  strength ;  and  on  either  side,  by  the  mar- 
gins of  the  opening  in  the  aponeurosis,  which  are  called  the  columns  or  pillars  of 
the  ring. 

The  external  pillar,  Avhich  at  the  same  time  is  inferior  from  the  obliquity  of 
its  direction,  is  the  stronger ;  it  is  formed  by  that  portion  of  Poupart-'s  ligament 
which  is  inserted  into  the  spine  of  the  os  pubis;  it  is  curved,  so  as  to  form  a  kind 
of  groove,  upon  which  the  spermatic  cord  rests. 

The  internal  or  superior  pillar  is  a  broad,  thin,  flat  band,  which  is  attached 
to  the  front  of  the  body  of  the  os  pubis,  interlacing  with  its  fellow  of  the  oppo- 
site side  in  front  of  the  symphysis  pubis,  that  of  the  right  side  being  superficial. 

The  external  abdominal  ring  gives  passage  to  the  spermatic  cord  in  the  male 
and  round  ligament  in  the  female  ;  it  is  much  larger  in  men  than  in  women,  on 
account  of  the  large  size  of  the  spermatic  cord,  and  hence  the  great  frequency 
of  inguinal  hernia  in  men. 

The  inter  columnar  fibres  are  a  series  of  curved  tendinous  fibres  which  arch 
across  the  lower  part  of  the  aponeui'osis  of  the  External  oblique.  They  have 
received  their  name  from  stretching  across  between  the  two  pillars  of  the  external 
ring;  they  increase  the  strength  of  the  lower  part  of  the  aponeurosis  and  prevent 
the  divergence  of  the  pillars  from  one  another.  They  are  thickest  below,  where 
they  are  connected  to  the  outer  third  of  Poupart's  ligament,  and  are  inserted  into 
the  linea  alba,  describing  a  curve,  with  the  convexity  downward.  They  are  much 
thicker  and  stronger  at  the  outer  angle  of  the  external  ring  than  internally,  and 
are  more  strongly  developed  in  the  male  than  in  the  female.  These  intercolumnar 
fibres,  as  they  pass  across  the  external  abdominal  ring,  are  themselves  connected 
together  by  delicate  fibrous  tissue,  thus  forming  a  fascia  which,  as  it  is  attached 
to  the  pillars  of  the  ring,  covers  it  in,  and  is  called  the  intercolumnar  fascia.  This 
intercolumnar  fascia  is  continued  downward  as  a  tubular  prolongation  around  the 
outer  surface  of  the  cord  and  testis,  and  encloses  them  in  a  distinct  sheath ;  hence 
it  is  also  called  the  external  spermatic  fascia.  The  sac  of  an  inguinal  hernia  in 
passing  through  the  external  abdominal  ring  receives  an  investment  from  the 
intercolumnar  fascia. 

If  the  finger  is  introduced  a  short  distance  into  the  external  ring,  and  then,  if 
the  limb  is  extended  and  rotated  outward,  the  aponeurosis  of  the  External  oblique, 
together  with  the  iliac  portion  of  the  fascia  lata,  will  be  felt  to  become  tense  and 
the  external  ring  much  contracted  ;  if  the  limb  is,  on  the  contrary,  flexed  upon  the 
pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax,  and  the  external  ring 
sufficiently  enlarged  to  admit  the  finger  with  comparative  ease  ;  hence  the  patient 
should  always  be  put  in  the  latter  position  when  the  taxis  is  applied  for  the  reduc- 


GIMBERXA T\S   LIGAMENT. 


1183 


tion  of  an  inguinal  hernia,  in  order  that  the  abdominal  walls  may  be  relaxed  as 
much  as  possible. 

The  aponeurosis  of  the  External  oblique  should  be  removed  by  dividing  it  across  in  the  same 
direction  as  the  external  incisions,  and  reflecting  it  downward  and  outward :  great  care  is  requisite 
in  separating  it  from  the  aponeurosis  of  the  muscle  beneath.  The  lower  part  of  the  Internal 
oblique  an  I  the  Cremaster  are  then  exposed,  together  with  the  inguinal  canal,  which  contains 
the  spermatic  cord  i  Vis.  75>).  The  mode  of  insertion  of  Poupart's  and  Gimbernat's  ligaments 
into  the  us  pubis  should  also  be  examined. 

Poupart's  ligament,  or  the  crural  arch,  is  the  lower  border  of  the  aponeurosis 
of  the  External  oblique  muscle,  which  extends  from  the  anterior  superior  spine  of 
the  ilium  to  the  spine  of  the  os  pubis.  From  this  latter  point  it  is  reflected 
outward  to  be  attached  to  the  pectineal  line  for  about  half  an  inch,  forming 


FIG.  TON— Inguinal  hernia,  showing  the  Internal  oblique,  Cremaster,  and  spermatic  canal 

Gimbernat's  ligament.  Its  general  direction  is  curved  downward  toward  the 
thigh,  where  it  is  continuous  with  the  fascia  lata.  Its  outer  half  is  rounded  and 
oblique  in  direction :  its  inner  half  gradually  widens  at  its  attachment  to  the  os 
pubis,  is  more  horizontal  in  direction,  and  lies  beneath  the  spermatic  cord. 

Gimbernat's  ligament  (Fig.  765)  is  that  portion  of  the  External  oblique  muscle 
which  is  reflected  downward  and  outward  from  the  spine  of  the  os  pubis  to  be 
inserted  into  the  pectineal  line.  It  is  about  half  an  inch  in  length,  larger  in  the 
male  than  in  the  female,  almost  horizontal  in  direction  in  the  erect  posture,  and 
of  a  triangular  form,  with  the  base  directed  outward.  Its  base  or  outer  margin  is 
concave,  thin,  and  sharp,  and  lies  in  contact  with  the  crural  sheath,  forming  the 
inner  boundary  of  the  crural  ring  (see  Fig.  766).  Its  apex  corresponds  to  the 
spine  of  the  os  pubis.  Its  posterior  margin  is  attached  to  the  pectineal  line,  and 
is  continuous  with  the  pubic  portion  of  the  fascia  lata.  Its  anterior  margin  is 
continuous  with  Poupart's  ligament. 

The  triangular  ligament  of  the  abdomen  is  a  band  of  tendinous  fibres,  of  a 
triangular  shape,  which  is  attached  by  its  apex  to  the  pectineal  line,  where  it  is 


]184  THE   SURGICAL    ANATOMY   OF  HERNIA. 

continuous  with  Gimbernat's  ligament.  It  passes  inward  beneath  the  spermatic 
cord,  and  expands  into  a  somewhat  fan-shaped  fascia,  lying  behind  the  inner  pillar 
of  the  external  abdominal  ring  and  in  front  of  the  conjoined  tendon,  and  interlaces 
with  the  ligament  of  the  other  side  at  the  linea  alba. 

The  Internal  oblique  muscle  has  been  previously  described  (page  451).  The 
part  which  is  now  exposed  is  partly  muscular  and  partly  tendinous  in  structure. 
Those  fibres  Avhich  arise  from  Poupart's  ligament,  few  in  number  and  paler  in 
color  than  the  rest,  arch  downward  and  inward  across  the  spermatic  cord,  and, 
becoming  tendinous,  are  inserted,  conjointly  with  those  of  the  Transversalis,  into  the 
crest  of  the  os  pubis  and  pectineal  line,  forming  what  is  known  as  the  conjoined 
tendon  of  the  Internal  oblique  and  Transversalis.  This  tendon  is  inserted  imme- 
diately behind  the  external  abdominal  ring,  serving  to  protect  what  would  other- 
wise be  a  weak  point  in  the  abdominal  wall.  Sometimes  this  tendon  is  insufficient 
to  resist  the  pressure  from  within,  and  is  carried  forward  in  front  of  the  protrusion 
through  the  external  ring,  forming  one  of  the  coverings  of  direct  inguinal  hernia, 
or  the  hernia  forces  its  way  through  the  fibres  of  the  conjoined  tendon. 

The  Cremaster  is  a  thin  muscular  layer  composed  of  a  number  of  fasciculi 
which  arise  from  the  middle  of  Poupart's  ligament  at  the  inner  side  of  the  Internal 
oblique,  being  connected  Avith  that  muscle  and  also  occasionally  with  the 
Transversalis.  It  passes  along  the  outer  side  of  the  spermatic  cord,  descends  with 
it  through  the  external  ring  upon  the  front  and  sides  of  the  cord,  and  forms  a 
series  of  loops  which  differ  in  thickness  and  length  in  different  subjects.  Those 
at  the  upper  part  of  the  cord  are  exceedingly  short,  but  they  become  in  succession 
longer  and  longer,  the  longest  reaching  down  as  low  as  the  testicle,  where  a  few 
are  inserted  into  the  tunica  vaginalis.  These  loops  are  united  together  by  areolar 
tissue,  and  form  a  thin  covering  over  the  cord  and  testis,  the  fascia  cremasterica. 
The  fibres  ascend  along  the  inner  side  of  the  cord,  and  are  inserted  by  a  small 
pointed  tendon  into  the  crest  of  the  os  pubis  and  front  of  the  sheath  of  the  Rectus 
muscle. 

It  will  be  observed  that  the  origin  and  insertion  of  the  Cremaster  is  precisely 
similar  to  that  of  the  lower  fibres  of  the  Internal  oblique.  This  fact  affords  an  easy 
explanation  of  the  manner  in  which  the  testicle  and  cord  are  invested  by  this  muscle. 
At  an  early  period  of  foetal  life  the  testis  is  placed  at  the  lower  and  back  part  of  the 
abdominal  cavity,  but  during  its  descent  toward  the  scrotum,  which  takes  place 
before  birth,  it  passes  beneath  the  arched  border  of  the  Internal  oblique.  In  its 
passage  beneath  this  muscle  some  fibres  are  derived  from  its  lower  part  which 
accompany  the  testicle  and  cord  into  the  scrotum. 

It  occasionally  happens  that  the  loops  of  the  Cremaster  surround  the  cord,  some 
lying  behind  as  well  as  in  front.  It  is  probable  that  under  these  circumstances 
the  testis  in  its  descent  passes  through,  instead  of  beneath,  the  fibres  of  the  Internal 
oblique. 

In  the  descent  of  an  oblique  inguinal  hernia,  which  takes  the  same  course  as 
the  spermatic  cord,  the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle 
becomes  largely  developed  in  cases  of  hydrocele  and  large  old  scrotal  hernias.  No 
such  muscle  exists  in  the  female,  except  a  few  fibres  on  the  surface  of  the  round 
ligament,  but  an  analogous  structure  is  developed  in  those  cases  where  an  oblique 
inguinal  hernia  descends  beneath  the  margin  of  the  Internal  oblique.. 

The  Internal  oblique  should  be  detached  from  Poupart's  ligament,  separated  from  the 
Transversalis  to  the  same  extent  as  in  the  previous  incisions,  and  reflected  inward  on  to  the 
sheath  of  the  Rectus  (Fig.  759).  The  circumflex  iliac  vessels,  which  lie  between  these  t\vo 
muscles,  form  a  valuable  guide  to  their  separation. 

The  Transversalis  muscle  has  been  previously  described  (page  453).  The  part 
which  is  now  exposed  is  partly  muscular  and  partly  tendinous  in  structure  ;  this 
portion  arises  from  the  outer  third  of  Poupart's  ligament,  its  fibres  curve  down- 
ward and  inward,  and  are  inserted,  together  with  those  of  the  Internal  oblique, 
into  the  lower  part  of  the  linea  alba,  into  the  crest  of  the  os  pubis  and  pectineal 
line,  forming  what  is  known  as  the  conjoined  tendon  of  the  Internal  oblique  and 


THE  FASCIA     TRANS VER8ALI8. 


1185 


Trausversalis.     Between  the  lower  border  of  this  muscle  and  Poupart's  ligament 
a  space  is  left  in  which  is  seen  the  fascia  transversalis. 

The  inguinal  or  spermatic  canal  contains  the  spermatic  cord  in  the  male  and 
the  round  ligament  in  the  female.  It  is  an  oblique  canal,  about  an  inch  and  a  half 
in  length,  directed  downward  and  inward  and  placed  parallel  with,  and  a  little 
above,  Poupart's  ligament.  It  commences  above  at  the  internal  abdominal  ring, 
which  is  the  point  where  the  cord  enters  the  spermatic  canal,  and  terminates 
below  at  the  external  ring.  It  is  bounded,  in  front,  by  the  integument  and 
superficial  fascia,  by  the  aponeurosis  of  the  External  oblique  throughout  its  whole 
length,  and  by  the  Internal  oblique  for  its  outer  third ;  behind,  by  the  triangular 
ligament,  the  conjoined  tendon  of  the  Internal  oblique  and  Transversalis,  trans- 
versalis fascia,  and  the  subperitoneal  fat  and  peritoneum  ;  above,  by  the  arched 
fibres  of  the  Internal  oblique  and  Transversalis  ;  below,  by  the  union  of  the  fascia 
transversalis  with  Poupart's  ligament.  That  form  of  protrusion  in  which  the 


Internal  . 
abdominal  ring. 


Epigastric  artery. 


FIG.  759.— Inguinal  hernia  showing   the  Transversalis  muscle,  the   transversalis  fascia,  and  the  internal 
abdominal  ring. 

intestine  follows  the  course  of  the  spermatic  cord  along  the  spermatic  canal  is 
called  oblique  inguinal  hernia. 

The  fascia  transversalis  is  a  thin  aponeurotic  membrane  which  lies  between 
the  inner  surface  of  the  Transversalis  muscle  and  the  peritoneum.  It  forms  part 
of  the  general  layer  of  fascia  which  lines  the  interior  of  the  abdominal  and  pelvic 
cavities,  and  is  directly  continuous  with  the  iliac  and  pelvic  fasciae. 

In  the  inguinal  region  the  transversalis  fascia  is  thick  and  dense  in  structure, 
and  joined  by  fibres  from  the  aponeurosis  of  the  Transversalis  muscle;  but  it 
becomes  thin  and  cellular  as  it  ascends  to  the  Diaphragm.  Below,  it  has  the 
following  attachments  :  external  to  the  femoral  vessels  it  is  connected  to  the 
posterior  margin  of  Poupart's  ligament,  and  is  there  continuous  with  the  iliac 
fascia.  Internal  to  the  vessels  it  is  thin,  and  attached  to  the  os  pubis  and  pectineal 
line  behind  the  conjoined  tendon,  with  which  it  is  united;  and,  corresponding  to 
the  points  where  the  femoral  vessels  pass  into  the  thigh,  this  fascia  descends  in 
front  of  them,  forming  the  anterior  wall  «.f  the  crural  sheath.  The  spermatic  cord 

75 


1186  THE  SURGICAL    ANATOMY   OF  HERNIA. 

in  the  male  and  the  round  ligament  in  the  female  pass  through  this  fascia ;  the 
point  where  they  pass  through  is  called  the  internal  or  deep  abdominal  ring.  This 
opening  is  not  visible  externally,  owing  to  a  prolongation  of  the  transversalis  fascia 
on  these  structures,  forming  the  infundibuliform  process. 

The  internal  or  deep  abdominal  ring  is  situated  in  the  transversalis  fascia, 
midway  between  the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis, 
and  about  half  an  inch  above  Poupart's  ligament.  It  is  of  an  oval  form,  the 
extremities  of  the  oval  directed  upward  and  downward ;  it  varies  in  size  in  dif- 
ferent subjects,  and  is  much  larger  in  the  male  than  in  the  female.  It  is  bounded 
above  and  externally  by  the  arched  fibres  of  the  Transversalis  muscle,  below  and 
internally  by  the  deep  epigastric  vessels.  It  transmits  the  spermatic  cord  in  the 
male  and  the  round  ligament  in  the  female.  From  its  circumference  a  thin, 
funnel-shaped  membrane,  the  infundibuliform  fascia,  is  continued  round  the  cord 
and  testis,  enclosing  them  in  a  distinct  pouch.  When  the  sac  of  an  oblique 
inguinal  hernia  passes  through  the  internal  or  deep  abdominal  ring,  the  infundi- 
buliform process  of  the  transversalis  fascia  forms  one  of  its  coverings. 

The  Subperitoneal  Areolar  Tissue. — Between  the  fascia  transversalis  and  the 
peritoneum  is  a  quantity  of  loose  areolar  tissue.  In  some  subjects  it  is  of  con- 
siderable thickness  and  loaded  with  adipose  tissue.  Opposite  the  internal  ring  it 
is  continued  round  the  surface  of  the  cord,  forming  a  loose  sheath  for  it. 

The  deep  epigastric  artery  arises  from  the  external  iliac  artery  a  few  lines  above 
Poupart's  ligament.  It  at  first  descends  to  reach  this  ligament,  and  then  ascends 
obliquely  along  the  inner  margin  of  the  internal  or  deep  abdominal  ring,  lying 
between  the  transversalis  fascia  and  the  peritoneum,  and  passing  upward  pierces 
the  transversalis  fascia  and  enters  the  sheath  of  the  Rectus  muscle  just  below  the 
semilunar  fold  of  Douglas.  Consequently  the  deep  epigastric  artery  bears  a  very 
important  relation  to  the  internal  abdominal  ring  as  it  passes  obliquely  upward 
and  inward  from  its  origin  from  the  external  iliac.  In  this  part  of  its  course  it 
lies  along  the  lower  and  inner  margin  of  the  internal  ring  and  beneath  the 
commencement  of  the  spermatic  cord.  As  it  winds  round  the  internal  abdominal 
ring  it  is  crossed  by  the  vas  deferens  in  the  male  and  by  the  round  ligament  in  the 
female. 

The  peritoneum,  corresponding  to  the  inner  surface  of  the  internal  ring,  presents 
a  well-marked  depression,  the  depth  of  which  varies  in  diiferent  subjects.  A  thin 
fibrous  band  is  continued  from  it  along  the  front  of  the  cord  for  a  variable  distance, 
and  becomes  ultimately  lost.  This  is  the  remains  of  the  pouch  of  peritoneum 
which,  in  the  foetus,  accompanies  the  cord  and  testis  into  the  scrotum,  the 
obliteration  of  which  commences  soon  after  birth.  In  some  cases  the  fibrous  band 
can  only  be  traced  a  short  distance,  but  occasionally  it  may  be  followed,  as  a  fine 
cord,  as  far  as  the  upper  end  of  the  tunica  vaginalis.  Sometimes  the  tube  of 
peritoneum  is  only  closed  at  intervals  and  presents  a  sacculated  appearance,  or  a 
single  pouch  may  extend  along  the  whole  length  of  the  cord,  which  may  be  closed 
above,  or  the  pouch  may  be  directly  continuous  with  the  peritoneum  by  an 
opening  at  its  upper  part. 

In  the  female  (in  the  foetus)  the  peritoneum  is  also  prolonged  in  the  form  of  a 
tubular  process  for  a  short  distance  into  the  inguinal  canal.  This  process  is  called 
the  canal  of  Nuck.  It  is  generally  obliterated  in  the  adult,  but  sometimes  it  remains 
pervious  even  in  advanced  life.  It  is  analogous  to  the  peritoneal  pouch  which 
accompanies  the  descent  of  the  testis. 

INGUINAL    HERNIA. 

Inguinal  hernia  is  that  form  of  protrusion  which  makes  its  way  through  the 
abdomen  in  the  inguinal  region. 

There  are  two  principal  varieties  of  inguinal  hernia — external  or  oblique,  and 
internal  or  direct. 

External  or  oblique  inguinal  hernia,  the  more  frequent  of  the  two,  takes  the 


OBLIQUE   INGUINAL    HERNIA. 


1187 


same  course  as  the  spermatic  cord.     It  is  called  external  from  the  neck  of  the  sac 
being  on  the  outer  or  iliac  side  of  the  deep  epigastric  artery. 

Internal  or  direct  inguinal  hernia  does  not  follow  the  same  course  as  the  cord, 
but  protrudes  through  the  abdominal  wall  on  the  inner  or  pubic  side  of  the  deep 
epigastric  artery. 

Oblique  Inguinal  Hernia. 

In  oblique  inguinal  hernia  the  intestine  escapes  from  the  abdominal  cavity  at 
the  internal  ring,  pushing  before  it  a  pouch  of  peritoneum,  which  forms  the  hernial 


\Femoral  artery. 
Femoral  vein. 


FIG.  760.— Oblique  inguinal  hernia,  showing  its  various  coverings, 
the  Royal  College  of  Surgeons.) 


(From  a  preparation  in  the  Museum  of 


sac  (Fig.  761,  A).  As  it  enters  the  inguinal  canal  it  receives  an  investment  from 
the  subserous  areolar  tissue,  and  is  enclosed  in  the  infundibuliform  process  of  the 
transversalis  fascia.  In  passing  along  the  inguinal  canal  it  displaces  upward  the 
arched  fibres  of  the  Transversalis  and  Internal  oblique  muscles,  and  is  surrounded 
by  the  fibres  of  the  Cremaster.  It  then  passes  along  the  front  of  the  cord,  and 
escapes  from  the  inguinal  canal  at  the  external  ring,  receiving  an  investment  from 
the  intercolumnar  fascia.  Lastly,  it  descends  into  the  scrotum,  receiving  coverings 
from  the  superficial  fascia  and  the  integument. 

The  coverings  of  this  form  of  hernia,  after  it  has  passed  through  the  external 
ring,  are,  from  without  inward,  the  integument,  superficial  fascia,  intercolumnar 
fascia,  Cremaster  muscle,  infundibuliform  fascia,  subserous  areolar  tissue,  and 
peritoneum. 

This   form  of  hernia  lies  in  front  of  the  vessels  of  the  spermatic  cord  and 


1188 


THE   SURGICAL    ANATOMY    OF   HERNIA. 


seldom  extends  below  the  testis,  on  account  of  the  intimate  adhesion  of  the  cover- 
ings of  the  cord  to  the  tunica  vaginalis. 


Sac  of  hernia. 


Tunica      J> 
Is.-' 
A.  Common  scrotal  hernia. 


Tunica 
• — vaginalis. 


B.  Congenital  hernia. 


Sacof__ 
hernia. 


— ~Sac  of  hernia. 


Tunica  vaginalis.-i- 


-j — .Sac  of  hernia. 


E.  Hernia  into  the  funicular  process. 
FIG.  761. — Varieties  of  oblique  inguinal  hernia. 


The  seat  of  stricture  in  oblique  inguinal  hernia  is  either  at  the  external  ring , 
m  the  inguinal  canal,  caused  by  the  fibres  of  the  Internal  oblique  or  Trans- 


DIRECT  IXGUHTAL   HERXIA.  1189 

versalis ;  or  at  the  internal  ring,  most  frequently  in  the  latter  situation.  If  it  is 
situated  at  the  external  ring,  the  division  of  a  few  fibres  at  one  point  of  its 
circumference  is  all  that  is  necessary  for  the  replacement  of  the  hernia.  If 
in  the  inguinal  canal  or  at  the  internal  ring,  it  may  be  necessary  to  divide  the 
aponeuro.sis  of  the  External  oblique  so  as  to  lay  open  the  inguinal  canal.  In 
dividing  the  stricture  the  direction  of  the  incision  should  be  upward. 

When  the  intestine  passes  along  the  spermatic  canal  and  escapes  from  the 
external  ring  into  the  scrotum,  it  is  called  complete  oblique  inyuinal  or  scrotal 
hernia.  If  the  intestine  does  not  escape  from  the  external  ring,  but  is  retained 
in  the  inguinal  canal,  it  is  called  incomplete  inyuinal  hernia,  or  bubonocele.  In 
each  of  these  cases  the  coverings  which  invest  it  will  depend  upon  the  extent  to 
which  it  descends  in  the  inguinal  canal. 

There  are  some  other  varieties  of  oblique  inguinal  hernia  depending  upon  con- 
genital defects  in  the  process  us  vaginalis.  The  testicle  in  its  descent  from  the 
abdomen  into  the  scrotum  is  accompanied  by  a  pouch  of  peritoneum,  which  about 
the  period  of  birth  becomes  shut  off  from  the  general  peritoneal  cavity  by  a  closure 
of  that  portion  of  the  pouch  which  extends  from  the  internal  abdominal  ring  to 
near  the  upper  part  of  the  testicle,  the  lower  portion  of  the  pouch  remaining  per- 
sistent as  the  tunica  vaginalis.  It  would  appear  that  this  closure  commences  at 
two  points — viz.  at  the  internal  abdominal  ring  and  at  the  top  of  the  epididymis — 
and  gradually  extends  until,  in  the  normal  condition,  the  whole  of  the  inter- 
vening portion  is  converted  into  a  fibrous  cord.  From  failure  in  the  completion 
of  this  process  variations  in  the  relation  of  the  hernial  protrusion  to  the 
testicle  and  tunica  vaginalis  are  produced,  which  constitute  distinct  varieties 
of  inguinal  hernia,  and  which  have  received  separate  names  and  are  of  surgical 
importance.  These  are  congenital,  infantile,  encysted,  and  hernia  of  the  funicu- 
lar proce— 

Congenital  Hernia  (Fig.  761,  B). — Where  the  pouch  of  peritoneum  which 
accompanies  the  cord  and  testis  in  its  descent  remains  patent  throughout  and  is 
unclosed  at  any  point,  the  cavity  of  the  tunica  vaginalis  communicates  directly 
with  the  peritoneum.  The  intestine  descends  along  this  pouch  into  the  cavity  of 
the  tunica  vaginalis.  which  constitutes  the  sac  of  the  hernia,  and  the  gut  lies  in 
contact  with  the  testicle. 

Infantile  and  Encysted  Hernia. — Where  the  pouch  of  peritoneum  is  occluded 
at  the  internal  ring  only,  and  remains  patent  throughout  the  rest  of  its  extent, 
two  varieties  of  oblique  inguinal  hernia  may  be  produced,  which  have  received 
the  names  of  infantile  and  encysted  hernia.  In  the  infantile  form  (Fig.  761,  c) 
the  bowel,  pressing  upon  the  septum  and  the  peritoneum  in  its  immediate 
neighborhood,  causes  it  to  yield  and  form  a  sac.  which  descends  behind  the 
tunica  vaginalis.  so  that  in  front  of  the  bowel  there  are  three  layers  of  per- 
itoneum, the  two  layers  of  the  tunica  vaginalis  and  its  own  sac.  In  the  encysted 
form  (Fig.  761,  D)  pressure  in  the  same  position — namely,  at  the  occluded  spot  in 
the  pouch — causes  the  septum  to  yield  and  form  a  sac  which  projects  into  and  not 
behind  the  tunica  vaginalis.  as  in  the  infantile  form,  and  thus  it  constitutes  a  sac 
within  a  sac.  so  that  in  front  of  the  bowel  there  are  two  layers  of  peritoneum — one 
layer  of  the  tunica  vaginalis  and  its  own  sac. 

Hernia  into  the  Funicular  Process  (Fig.  761,  E). — Where  the  pouch  of  perito- 
neum is  occluded  at  the  lower  point  only — that  is.  just  above  the  testicle — the 
intestine  descends  into  the  pouch  of  peritoneum  as  far  as  the  testicle,  but  is  pre- 
vented from  entering  the  sac  of  the  tunica  vaginalis  by  the  septum  which  has 
formed  between  it  and  the  pouch,  so  that  it  resembles  the  congenital  form  in  all 
respects,  except  that,  instead  of  enveloping  the  testicle,  that  body  can  be  felt 
below  the  rupture. 

Direct  Inguinal  Hernia. 

In  direct  inguinal  hernia  the  protrusion  makes  its  way  through  some  part  of 
the  abdominal  wall  internal  to  the  epigastric  artery. 


1190          *T        THE  SURGICAL    ANATOMY   OF  HERNIA. 


At  the  lower  part  of  the  abdominal  Avail  is  a  triangular  space  (Ifesselbaeh's 
triangle],  bounded  externally  by  the  deep  epigastric  artery  covered  by  peritoneum 
(plica  epigastriea),  internally  by  the  margin  of  the  Rectus  muscle,  below  by  Pou- 
part's  ligament.  The  conjoined  tendon  is  stretched  across  the  inner  two-thirds  of 
this  space,  the  remaining  portion  of  the  space  having  only  the  subperitoneal  areo- 
lar  tissue  and  the  transversalis  fascia  between  the  peritoneum  and  the  aponeurosis 
of  the  External  oblique  muscle.  — 

In  some  cases  the  hernial  protrusion  escapes  from  the  abdomen  on  the  outer 
side  of  the  conjoined  tendon,  pushing  before  it  the  peritoneum,  the  subserous 
areolar  tissue,  and  the  transversalis  fascia.  It  then  enters  the  inguinal  canal, 
passing  along  nearly  its  whole  length,  and  finally  emerges  from  the  external  ring, 
receiving  an  investment  from  the  intercolumnar  fascia.  The  coverings  of  this 
form  of  hernia  are  precisely  similar  to  those  investing  the  oblique  form,  with  the 
insignificant  difference  that  the  infundibuliform  fascia  is  replaced  by  a  portion 
derived  from  the  general  layer  of  the  fascia  transversalis. 

In  other  cases — and  this  is  the  more  frequent  variety — the  hernia  is  either  forced 
through  the  fibres  of  the  conjoined  tendon  or  the  tendon  is  gradually  distended  in 
front  of  it  so  as  to  form  a  complete  investment  for  it.  The  intestine  then  enters 
the  lower  end  of  the  inguinal  canal,  escapes  at  the  external  ring  lying  on  the 
inner  side  of  the  cord,  and  receives  additional  coverings  from  the  superficial  fascia 
and  the  integument.  This  form  of  hernia  has  the  same  coverings  as  the  oblique 
variety,  excepting  that  the  conjoined  tendon  is  substituted  for  the  Cremaster,  and 
the  infundibuliform  fascia  is  replaced  by  a  portion  derived  from  the  general  layer 
of  the  fascia  transversalis. N 

The  difference  between  the  position  of  the  neck  of  the  sac  in  these  two  forms 
of  direct  inguinal  hernia  has  been  referred,  Avith  some  probability,  to  a  difference 
in  the  relative  positions  of  the  obliterated  hypogastric  artery  and  the  deep 
epigastric  artery.  When  the  course  of  the  obliterated  hypogastric  artery  cor- 
responds pretty  nearly  Avith  that  of  the  deep  epigastric — which  is  regarded  as  the 
normal  arrangement — the  projection  of  these  arteries  toAvard  the  cavity  of  the 
abdomen  produces  two  fossae  in  the  peritoneum.  The  bottom  of  the  external  fossa 
of  the  peritoneum  corresponds  to  the  position  of  the  internal  abdominal  ring,  and 
a  hernia  which  distends  and  pushes  out  the  peritoneum  lining  this  fossa  is  an 
oblique  hernia.  When,  on  the  other  hand,  the  obliterated  hypogastric  artery  lies 
considerably  to  the  inner  side  of  the  deep  epigastric  artery,  corresponding  to  the 
outer  margin  of  the  conjoined  tendon,  the  projection  of  the  peritoneum  over  it 
(plica  hypogastricd)  divides  the  triangle  of  Hesselbach  into  tAA'o  parts,  so  that 
three  depressions  will  be  seen  on  the  inner  surface  of  the  lower  part  of  the  abdom- 
inal wall — viz.  an  external  one,  on  the  outer  side  of  the  deep  epigastric  artery  ;  a 
middle  one,  between  the  deep  epigastric  and  the  obliterated  hypogastric  arteries; 
and  an  internal  one,  on  the  inner  side  of  the  obliterated  hypogastric  artery.  In 
such  a  case  a  hernia  may  distend  and  push  out  the  peritoneum  forming  the  bottom 
of  the  external  fossa,  it  is  an  oblique  or  external  inguinal  hernia.  These  fossae 
are  the  inguinal  fossce. , 

When  the  hernia  distends  and  pushes  out  the  peritoneum  forming  the  bottom 
of  either  the  middle  or  the  internal  fossa,  it  is  a  direct  or  internal  hernia. 

The  anatomical  difference  betAveen  these  two  forms  of  direct  or  internal 
inguinal  hernia  is  that,  when  the  hernia  protrudes  through  the  middle  fossa — that 
is,  the  fossa  between  the  deep  epigastric  and  the  obliterated  hypogastric  arteries — 
it  will  enter  the  upper  part  of  the  inguinal  canal ;  consequently  its  coverings  wUl  be 
the  same  as  those  of  an  oblique  hernia,  with  the  insignificant  difference  that  the 
infundibuliform  fascia  is  replaced  by  a  portion  derived  from  the  general  layer  of 
the  fascia  transversalis,  whereas  Avhen  the  hernia  protrudes  through  the  internal 
fossa  it  is  either  forced  through  the  fibres  of  the  conjoined  tendon  or  the  tendon  is 
gradually  distended  in  front  of  it  so  as  to  form  a  complete  investment  for  it.  The 
intestine  then  enters  the  lower  part  of  the  inguinal  canal,  and  escapes  from  the 
external  abdominal  ring  lying  on  the  inner  side  of  the  cord. 


FEMORAL    HERNIA.  1191 

This  form  of  hernia  has  the  same  coverings  as  the  oblique  variety,  excepting 
that  the  conjoined  tendon  is  substituted  for  the  Cremaster,  and  the  infundibuli- 
form  fascia  is  replaced  by  a  portion  derived  from  the  general  layer  of  the  fascia 
transversalis. 

The  scat  of  stricture  in  both  varieties  of  direct  hernia  is  most  frequently  at  the 
neck  of  the  sac  or  at  the  external  ring.  In  that  form  of  hernia  which  perforates 
the  conjoined  tendon  it  not  unfrequently  occurs  at  the  edges  of  the  fissure  through 
which  the  gut  passes.  In  dividing  the  stricture  the  incision  should  in  all  cases  bo 
directed  upward.1 

If  the  hernial  protrusion  passes  into  the  inguinal  canal,  but  does  not  escape 
from  the  external  abdominal  ring,  it  forms  what  is  called  incomplete  direct  hernia. 
This  form  of  hernia  is  usually  of  small  size,  and  in  corpulent  persons  very  difficult 
of  detection. 

Direct  inguinal  hernia  is  of  much  less  frequent  occurrence  than  the  oblique, 
their  comparative  frequency  being,  according  to  Cloquet,  as  one  to  five.  It  occurs 
far  more  frequently  in  men  than  in  women,  on  account  of  the  larger  size  of  the 
external  ring  in  the  former  sex.  It  differs  from  the  oblique  in  its  smaller  size  and 
globular  form,  dependent  most  probably  on  the  resistance  offered  to  its  progress  by 
the  transversalis  fascia  and  conjoined  tendon.  It  differs  also  in  its  position,  being 
placed  over  the  os  pubis  and  not  in  the  course  of  the  inguinal  canal.  The  deep 
epigastric  artery  runs  on  the  outer  or  iliac  side  of  the  neck  of  the  sac,  and  the 
spermatic  cord  along  its  external  and  posterior  side,  not  directly  behind  it,  as  in 
oblique  inguinal  hernia. 

FEMORAL   HERNIA. 

The  dissection  of  the  parts  comprised  in  the  anatomy  of  femoral  hernia  should  be  per- 
formed, if  possible,  upon  a  female  subject  free  from  fat.  The  subject  should  lie  upon  its  back  : 
a  block  is  first  placed  under  the  pelvis,  the  thigh  everted,  and  the  knee  slightly  bent  and 
retained  in  this  position.  An  incision  should  then  be  made  from  the  anterior  superior  spinous 
process  of  the  ilium  along  Poupart's  ligament  to  the  symphysis  pubis ;  a  second  incision  should 
be  carried  transversely  across  the  thigh  about  six  inches  beneath  the  preceding ;  and  these  are 
to  be  connected  together  by  a  vertical  one  carried  along  the  inner  side  of  the  thigh.  These 
several  incisions  should  divide  merely  the  integument ;  this  is  to  be  reflected  outward,  when  the 
superficial  fascia  will  be  exposed. 

The  superficial  fascia  forms  a  continuous  layer  over  the  whole  of  the  thigh, 
consisting  of  areolar  tissue,  containing  in  its  meshes  much  fat,  and  capable  of 
being  separated  into  two  or  more  layers,  between  which  are  found  the  superficial 
vessels  and  nerves.  It  varies  in  thickness  in  different  parts  of  the  limb.  In  the 
groin  it  is  thick,  and  the  two  layers  are  separated  from  one  another  by  the  super- 
ficial inguinal  lymphatic  glands,  the  internal  saphenous  vein,  and  several  smaller 
vessels.  One  of  these  layers,  the  superficial,  is  continuous  with  the  superficial 
fascia  of  the  abdomen. 

The  superficial  layer  should  be  detached  by  dividing  it  across  in  the  same  direction  as  the 
external  incisions :  its  removal  will  be  facilitated  by  commencing  at  the  lower  and  inner  angle  of 
the  space,  detaching  it  at  first  from  the  front  of  the  internal  saphenous  vein,  and  dissecting  it 
off  from  the  anterior  surface  of  that  vessel  and  its  tributaries ;  it  should  then  be  reflected  out- 
ward in  the  same  manner  as  the  integument.  The  cutaneous  vessels  and  nerves  and  superficial 
inguinal  glands  are  then  exposed,  lying  upon  the  deep  layer  of  the  superficial  fascia.  These  are 
the  internal  saphenous  vein  and  the  superficial  epigastric,  superficial  circumflex  iliac,  and  super- 
ficial external  pudic  vessels,  as  well  as  numerous  lymphatics,  ascending  with  the  saphenous  vein 
to  the  inguinal  glands. 

The  internal  or  long  saphenous  vein  ascends  along  the  inner  side  of  the  thigh, 
and.  passing  through  the  saphenous  opening  in  the  fascia  lata,  terminates  in  the 
femoral  vein  about  an  inch  and  a  half  below  Poupart's  ligament.  This  vein 

1  In  all  cases  of  inguinal  hernia,  whether  oblique  or  direct,  it  is  proper  to  divide  the  stricture 
directly  upward  :  the  reason  of  this  is  obvious,  for  by  cutting  in  this  direction  the  incision  is  made 
parallel  to  the  deep  epigastric  artery — either  external  to  it  in  the  oblique  variety,  or  internal  to  it  in 
the  direct  form  of  hernia — and  thus  all  chance  of  wounding  the  vessel  is  avoided.  If  the  incision 
was  made  outward,  the  artery  might  be  divided  if  the  hernia  was  direct ;  and  if  made  inward,  it  would 
stand  an  equal  chance  of  injury  if  the  case  was  one  of  oblique  inguinal  hernia. 


1192 


THE   SURGICAL    ANATOMY   OF  HERNIA. 


receives  at  the  saphenous  opening  the  superficial  epigastric,  the  superficial 
circumflex  iliac,  and  the  superficial  external  pudic  veins. 

The  superficial  external  pudic  artery  (superior)  arises  from  the  inner  side  of 
the  femoral  artery,  and,  after  passing  through  the  saphenous  opening,  courses 
inward  across  the  spermatic  cord,  to  be  distributed  to  the  integument  on  the 
lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male  and  the  labium  in 
the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The  superficial  epigastric  artery  arises  from  the  femoral  about  half  an  inch 
below  Poupart's  ligament,  and,  passing  through  the  saphenous  opening  in  the 
fascia  lata,  ascends  on  to  the  abdomen,  in  the  superficial  fascia  covering  the 


FIG.  762.— Femoral  hernia.    Superficial  dissection. 

External  oblique  muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches 
to  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and  the  integu- 
ment, anastomosing  with  branches  of  the  deep  epigastric  and  internal  mammary 
arteries. 

The  superficial  circumflex  iliac  artery,  the  smallest  of  the  cutaneous  branches, 
arises  close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel 
with  Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches 
which  supply  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and 
the  integument  of  the  groin,  anastomosing  Avith  the  deep  circumflex  iliac,  and  with 
the  gluteal  and  external  circumflex  arteries. 

The  Superficial  Veins. — The  veins  accompanying  these  superficial  arteries  are 
usually  much  larger  than  the  arteries  :  they  terminate  in  the  internal  or  long 
saphenous  vein  at  the  saphenous  opening. 


FEMORAL    HERNIA.  1193 

The  sup> rri'-t't!  inguinal  lymphatic  glands,  placed  immediately  beneath  the 
integument,  are  of  large  size  and  vary  from  eight  to  ten  in  number.  They  are 
divisible  into  two  groups  :  an  upper,  disposed  irregularly  along  Poupart's  ligament, 
which  receive  the  lymphatic  vessels  from  the  integument  of  the  scrotum,  penis, 
parietes  of  the  abdomen,  perineal  and  gluteal  regions,  and  the  mucous  membrane 
of  the  urethra  ;  and  an  inferior  group,  which  surround  the  saphenous  opening  in 
the  fascia  lata.  a  few  being  sometimes  continued  along  the  saphenous  vein  to  a 
variable  extent.  This  latter  group  receive  the  superficial  lymphatic  vessels  from 
the  lower  extremity. 

The  ilio-inguinal  nerve  arises  from  the  first  lumbar  nerve.  It  escapes  at  the 
external  abdominal  ring,  and  is  distributed  to  the  integument  of  the  upper  and 
inner  part  of  the  thigh — to  the  scrotum  in  the  male  and  to  the  labium  in  the 
female.  The  size  of  this  nerve  is  in  inverse  proportion  to  that  of  the  ilio-hypo- 
gastric. Occasionally  it  is  very  small,  and  ends  by  joining  the  ilio-hypogastric : 
in  such  cases  a  branch  of  the  ilio-hypogastric  takes  the  place  of  the  ilio-inguinal, 
or  the  latter  nerve  may  be  altogether  absent.  The  crural  branch  of  the  genito- 
crural  nerve  passes  along  the  inner  margin  of  the  Psoas  muscle,  beneath  Poupart's 
ligament,  into  the  thigh,  entering  the  sheath  of  the  femoral  vessels,  and  lying 
superficial  and  a  little  external  to  the  femoral  artery.  It  pierces  the  anterior  layer 
of  the  sheath  of  the  vessels,  and,  becoming  superficial  by  passing  through  the  fascia 
lata.  it  supplies  the  skin  of  the  anterior  aspect  of  the  thigh  as  far  as  midway 
between  the  pelvis  and  knee.  On  the  front  of  the  thigh  it  communicates  with 
the  outer  branch  of  the  middle  cutaneous  nerve,  derived  from  the  anterior  crural. 

The  deep  layer  of  the  superficial  fascia  is  a  very  thin  fibrous  layer,  best  marked 
on  the  inner  side  of  the  long  saphenous  vein  and  below  Poupart's  ligament.  It  is 
placed  beneath  the  subcutaneous  vessels  and  nerves,  and  upon  the  surface  of  the 
fascia  lata.  to  which  it  is  intimately  adherent  at  the  lower  margin  of  Poupart's 
iigament.  It  covers  the  saphenous  opening  in  the  fascia  lata,  is  closely  united  to 
its  circumference,  and  is  connected  to  the  sheath  of  the  femoral  vessels  corre- 
sponding to  its  under  surface.  The  portion  of  fascia  covering  this  aperture  is 
perforated  by  the  internal  saphenous  vein  and  by  numerous  blood-  and  lymphatic 
vessels :  hence  it  has  been  termed  the  cribriform  fascia,  the  openings  for  these 
vessels  having  been  likened  to  the  holes  in  a  sieve.  The  cribriform  fascia  adheres 
closely  both  to  the  superficial  fascia  and  to  the  fascia  lata.  so  that  it  is  described 
by  some  anatomists  as  a  part  of  the  fascia  lata.  but  it  is  usually  considered  (as  in  this 
work)  as  belonging  to  the  superficial  fascia.  It  is  not  till  the  cribriform  fascia  has 
been  cleared  away  that  the  saphenous  opening  is  seen,  so  that  this  opening  does 
not  in  ordinary  oases  exist  naturally,  but  is  the  result  of  dissection.  A  femoral 
hernia  in  passing  through  the  saphenous  opening  receives  the  cribriform  fascia  as 
one  of  its  coverings. 

The  deep  layer  of  superficial  fascia,  together  with  the  cribriform  fascia,  having 
been  removed,  the  fascia  lata  is  exposed. 

The  Fascia  Lata  has  been  already  described  with  the  muscles  of  the  front  of 
the  thigh  (page  506).  At  the  upper  and  inner  part  of  the  thigh,  a  little  below 
Poupart's  ligament,  a  large  oval-shaped  aperture  is  observed  after  the  superficial 
fascia  has  been  cleared  away  :  it  transmits  the  internal  saphenous  vein  and  other 
smaller  vessels,  and  is  called  the  saphenous  opening.  In  order  the  more  correctly 
to  consider  the  mode  of  formation  of  this  aperture,  the  fascia  lata  in  this  part  of  the 
thigh  is  described  as  consisting  of  two  portions,  an  iliac  portion  and  a  pubic  portion. 

The  iliac  portion  is  all  that  part  of  the  fascia  lata  on  the  outer  side  of  the 
saphenous  opening.  It  is  attached  externally  to  the  crest  of  the  ilium  and  its 
anterior  superior  spine  ;  to  the  whole  length  of  Poupart's  ligament  as  far  internally 
as  the  spine  of  the  os  pubis ;  and  to  the  pectineal  line  in  conjunction  with  Gimbernat's 
ligament.  From  the  spine  of  the  os  pubis  it  is  reflected  downward  and  outward, 
forming  an  arched  margin,  the  outer  boundary  or  falciform  process  or  superior 
cornu  of  the  saphenous  opening.  This  margin  overlies  and  is  adherent  to  the 
anterior  layer  of  the  sheath  of  the  femoral  vessels;  to  its  edge  is  attached  the 


1194 


THE   SURGICAL    ANATOMY   OF  HERNIA. 


cribriform  fascia,  and  below  it  is  continuous  with  the  pubic  portion  of  the  fascia 
lata. 

The  pubic  portion  of  the  fascia  lata  is  situated  at  the  inner  side  of  the  saphenous 
opening  :  at  the  lower  margin  of  this  aperture  it  is  continuous  with  the  iliac 
portion  :  traced  upward,  it  covers  the  surface  of  the  Pectineus,  Adductor  longus, 
and  Gracilis  muscles ;  and,  passing  behind  the  sheath  of  the  femoral  vessels,  to 
which  it  is  closely  united,  is  continuous  with  the  sheath  of  the  Psoas  and  Iliacus 
muscles,  and  is  attached  above  to  the  ilio-pectineal  line,  where  it  becomes 
continuous  with  the  fascia  covering  the  Iliacus  muscle.  From  this  description  it 
may  be  observed  that  the  iliac  portion  of  the  fascia  lata  passes  in  front  of  the 
femoral  vessels  and  the  pubic  portion  behind  them,  so  that  an  apparent  aperture 


FIG.  763.— Femoral  hernia,  showing  fascia  lata  and  saphenous  opening. 


consequently  exists  between  the  two,  through  which  the  internal  saphenous  joins 
the  femoral  vein. 

The  Saphenous  Opening  is  an  oval-shaped  aperture  measuring  about  an  inch 
and  a  half  in  length  and  half  an  inch  in  width.  It  is  situated  at  the  upper  and 
inner  part  of  the  front  of  the  thigh,  below  Poupart's  ligament,  and  is  directed 
obliquely  downward  and  outward. 

Its  outer  margin  is  of  a  semilunar  form,  thin,  strong,  sharply  defined,  and  lies 
on  a  plane  considerably  anterior  to  the  inner  margin.  If  this  edge  is  traced 
upward,  it  will  be  seen  to  form  a  curved  elongated  process,  the  falciform  process 
or  superior  cornu,  which  ascends  in  front  of  the  femoral  vessels,  and,  curving 
inward,  is  attached  to  Poupart's  ligament  and  to  the  spine  of  the  os  pubis  and 
pectineal  line,  where  it  is  continuous  with  the  pubic  portion.  If  traced  down- 
ward, it  is  found  continuous  with  another  curved  margin,  the  concavity  of  which 
is  directed  upward  and  inward :  this  is  the  inferior  cornu  of  the  saphenous 


FEMORAL    HERNIA. 


1195 


opening,  and  is  blended  with  the  pubic  portion  of  the  fascia  lata  covering  the 
Pectineus  muscle. 

The  inner  ln\rn<l<inj  "f  tlie  opening  is  on  a  plane  posterior  to  the  outer  margin 
and  behind  the  level  of  the  femoral  vessels  ;  it  is  much  less  prominent  and  defined 
than  the  outer,  from  being  stretched  over  the  subjacent  Pectineus  muscle.  It  is 
through  the  saphenous  opening  that  a  femoral  hernia  passes  after  descending  along 
the  crural  canal. 

If  the  finger  is  introduced  into  the  saphenous  opening  while  the  limb  is  moved 
in  different  directions,  the  aperture  will  be  found  to  be  greatly  constricted  on 
extending  the  limb  or  rotating  it  outward,  and  to  be  relaxed  on  flexing  the  limb 


FIG.  7&1.— Femoral  hernia.    Iliac  portion  of  fascia  lata  removed,  and  sheath  of  femoral. Vessels  and  femoral 
canal  exposed. 

and  inverting  it :  hence  the  necessity  for  placing  the  limb  in  the  latter  position  in 
employing  the  taxis  for  the  reduction  of  a  femoral  hernia. 

The  iliac  portion  of  the  fascia  lata.  but  not  its  falciform  process,  should  now  be  removed  by 
detaching  it  from  the  lower  margin  of  Poupart's  ligament,  carefully  dissecting  it  from  the  sub- 
jacent structures,  and  turning  it  inward,  when  the  sheath  of  the  femoral  vessels  is  exposed, 
descending  beneath  Poupart's  ligament  (Fig.  764). 

Poupart's  Ligament,  or  the  Crural  Arch,  is  the  lower  border  of  the  aponeurosis 
of  the  External  oblique  muscle,  which  extends  from  the  anterior  superior  spine  of 
the  ilium  to  the  spine  of  the  os  pubis.  From  this  latter  point  it  is  reflected  outward, 
to  be  attached  to  the  pectineal  line  for  about  half  an  inch,  forming  Gimbernat's 
ligament.  Its  general  direction  is  curved  downward  toward  the  thigh,  where  it 
is  continuous  with  the  fascia  lata.  Its  outer  half  is  rounded  and  oblique  in 
direction.  Its  inner  half  gradually  widens  at  its  attachment  to  the  os  pubis,  is 
more  horizontal  in  direction,  and  lies  beneath  the  spermatic  cord.  Nearly  the 


1196 


THE   SURGICAL    ANATOMY   OF  HERNIA. 


whole  of  the  space  included  between  the  crural  arch  and  innominate  bone  is  filled 
in  by  the  parts  which  descend  from  the  abdomen  into  the  thigh.  The  outer  half 
of  the  space  is  occupied  by  the  Iliacus  and  Psoas  muscles,  together  with  the 
external  cutaneous  and  anterior  crural  nerves.  The  pubic  half  of  the  space  is 
occupied  by  the  femoral  vessels  included  in  their  sheath,  a  small  oval-shaped 
interval  existing  between  the  femoral  vein  and  the  inner  wall  of  the  sheath, 
which  is  occupied  merely  by  a  little  loose  areolar  tissue,  a  few  lymphatic  vessels, 


Crural 

Poupart  s  ligament.      imnch     Anterior  crural, 
of  genito- 
cniral. 


External 
cutaneous  nerve. 


Iliac  portion  of 
fascia  lata. 


Femoral  vein. 
Femoral  ring. 


Gimbernat' s 
ligament. 


Femoral  artery. 
FIG.  765.— Structures  which  pass  beneath  the  crural  arch. 

and  occasionally  by  a  small  lymphatic  gland :  this  is  the  crural  ring,  through 
which  the  gut  descends  in  femoral  hernia. 

Gimbernat's  Ligament  (Fig.  766)  is  that  part  of  the  aponeurosis  of  the  External 
oblique  muscle  which  is  reflected  downward  and  outward  from  the  spine  of  the 
os  pubis,  to  be  inserted  into  the  pectineal  line.  It  is  about  half  an  inch  in  length, 
larger  in  the  male  than  in  the  female,  almost  horizontal  in  direction  in  the  erect 
posture,  and  of  a  triangular  form,  with  the  base  directed  outward.  Its  base.,  or 
outer  margin,  is  concave,  thin,  and  sharp,  and  lies  in  contact  with  the  crural  sheath. 
Its  apex  corresponds  to  the  spine  of  the  os  pubis.  Its  posterior  margin  is  attached 
to  the  pectineal  line,  and  is  continuous  with  the  pubic  portion  of  the  fascia  lata. 
Its  anterior  margin  is  continuous  with  Poupart's  ligament. 

Crural  Sheath. — The  femoral  or  crural  sheath  is  a  continuation  downward  of 
the  fasciae  that  line  the  abdomen,  the  transversalis  fascia  passing  down  in  front  of 
the  femoral  vessels,  and  the  iliac  fascia  descending  behind  them  ;  these  fasciae 
are  directly  continuous  on  the  iliac  side  of  the  femoral  artery,  but  a  small  space 
exists  between  the  femoral  vein  and  the  point  where  they  are  continuous  on  the 
pubic  side  of  that  vessel,  which  constitutes  the  femoral  or  crural  canal.  The 


FEMORAL    HERNIA. 


1197 


femoral  sheath  is  closely  adherent  to  the  contained  vessels  about  an  inch  below 
the  saphenous  opening,  being  blended  with  the  areolar  sheath  of  the  vessels, 
but  opposite  Poupart's  ligament  it  is  much  larger  than  is  required  to  contain  them  ; 
hence  the  funnel-shaped  form  which  it  presents.  The  outer  border  of  the  sheath 
is  perforated  by  the  genito-crural  nerve.  Its  inner  border  is  pierced  by  the  internal 
saphenous  vein  and  numerous  lymphatic  vessels.  In  front  it  is  covered  by  the 
iliac  portion  of  the  fascia  lata ;  and  behind  it  is  the  pubic  portion  of  the  same 
fascia. 

If  the  anterior  wall  of  the  sheath  is  removed,  the  femoral  artery  and  vein  are 
seen  lyin»  side  by  side,  a  thin  septum  separating  the  two  vessels,  while  another 
septum  may  be  seen  lying  just  internal  to  the  vein,  and  cutting  off  a  small  space 
between  the  vein  and  the  inner  wall  of  the  sheath.  The  septa  are  stretched  between 
the  anterior  and  posterior  walls  of  the  sheath,  so  that  each  vessel  is  enclosed  in 
a  separate  compartment.  The  interval  left  between  the  vein  and  the  inner 
wall  of  the  sheath  is  not  filled  up  by  any  structure,  excepting  a  little  loose 
areolar  tissue,  a  few  lymphatic  vessels,  and  occasionally  by  a  small  lymphatic 


FIG.  766.— Hernia.    The  relations  of  the  femoral  and  internal  abdominal  rings,  seen  from  within  the  abdo- 
men.   Right  side. 

gland :  this  is  the  femoral  or  crural  canal,  through  which  the  intestine  descends  in 
femoral  hernia. 

Deep  Crural  Arch. — Passing  across  the  front  of  the  crural  sheath  on  the 
abdominal  side  of  Poupart's  ligament,  and  closely  connected  with  it,  is  a  thickened 
band  of  fibres  called  the  deep  crural  arch.  It  is  apparently  a  thickening  of  the 
fascia  transversalis,  joining  externally  to  the  centre  of  Poupart's  ligament,  and 
arching  across  the  front  of  the  crural  sheath,  to  be  inserted  by  a  broad  attachment 
into  the  pectineal  line  behind  the  conjoined  tendon.  In  some  subjects  this 
structure  is  not  very  prominently  marked,  and  not  unfrequently  it  is  altogether 
wanting. 

The  crural  canal  is  the  narrow  interval  between  the  femoral  vein  and  the  inner 
wall  of  the  crural  sheath.  It  exists  as  a  distinct  canal  only  when  the  sheath  has 
been  separated  from  the  vein  by  dissection  or  by  the  pressure  of  a  hernia  or  tumor. 
Its  length  is  from  a  quarter  to  half  an  inch,  and  it  extends  from  Gimbernat's  liga- 
ment to  the  upper  part  of  the  saphenous  opening. 

Its  anterior  wall  is  very  narrow,  and  formed  by  a  continuation  downward  of 
the  fascia  transversalis,  under  Poupart's  ligament,  covered  by  the  falciform  pro- 
cess of  the  fascia  lata. 


1198  THE  SURGICAL    ANATOMY   OF  HERNIA. 

Its  posterior  wall  is  formed  by  a  continuation  downward  of  the  iliac  fascia 
covering  the  pubic  portion  of  the  fascia  lata. 

Its  outer  wall  is  formed  by  the  fibrous  septum  separating  it  from  the  inner 
side  of  the  femoral  vein. 

Its  inner  wall  is  formed  by  the  junction  of  the  processes  of  the  trans versalis 
and  iliac  fasciae,  which  form  the  inner  side  of  the  femoral  sheath,  and  lies  in 
contact  at  its  commencement  with  the  outer  edge  of  Gimbernat's  ligament. 

This  canal  has  two  orifices — an  upper  one,  the  femoral  or  crural  ring,  closed 
by  the  septum  crurale ;  and  a  lower  one,  the  saphenous  opening,  closed  by  the 
cribriform  fascia. 

The  femoral  or  crural  ring  (Fig.  766)  is  the  upper  opening  of  the  femoral  canal, 
and  leads  into  the  cavity  of  the  abdomen.  It  is  bounded  in  front  by  Poupart's 
ligament  and  the  deep  crural  arch  ;  behind,  by  the  os  pubis,  covered  by  the  Pectineus 
muscle  and  the  pubic  portion  of  the  fascia  lata ;  internally,  by  the  base  of 
Gimbernat's  ligament,  the  conjoined  tendon,  the  trans  versalis  fascia,  and  the 
deep  crural  arch ;  externally,  by  the  fibrous  septum  lying  on  the  inner  side  of  the 
femoral  vein.  The  femoral  ring  is  of  an  oval  form ;  its  long  diameter,  directed 
transversely,  measures  about  half  an  inch,  and  it  is  larger  in  the  female  than  in 
the  male,  which  is  one  of  the  reasons  of  the  greater  frequency  of  femoral  hernia 
in  the  former  sex. 

Position  of  Parts  around  the  Ring. — The  spermatic  cord  in  the  male  and  round 
ligament  in  the  female  lie  immediately  above  the  anterior  margin  of  the  femoral 
ring,  and  may  be  divided  in  an  operation  for  femoral  hernia  if  the  incision  for  the 
relief  of  the  stricture  is  not  of  limited  extent.  In  the  female  this  is  of  little 
importance,  but  in  the  male  the  spermatic  artery  and  vas  deferens  may  be 
divided. 

The  femoral  vein  lies  on  the  outer  side  of  the  ring. 

The  deep  epigastric  artery  in  its  passage  upward  and  inward  from  the  external 
iliac  artery  passes  across  the  upper  and  outer  angle  of  the  crural  ring,  and  is 
consequently  in  danger  of  being  wounded  if  the  stricture  is  divided  in  a  direction 
upward  and  outward. 

The  communicating  branch  between  the  deep  epigastric  and  obturator  lies  in 
front  of  the  ring. 

The  circumference  of  the  ring  is  thus  seen  to  be  bounded  by  vessels  in  every 
part,  excepting  internally  and  behind.  It  is  in  the  former  position  that  the 
stricture  is  divided  in  cases  of  strangulated  femoral  hernia. 

The  obturator  artery,  when  it  arises  by  a  common  trunk  with  the  deep  epigastric, 
which  occurs  once  in  every  three  subjects  and  a  half,  bears  a  very  important 
relation  to  the  crural  ring.  In  some  cases  it  descends  on  the  inner  side  of  the 
external  iliac  vein  to  the  obturator  foramen,  and  will  consequently  lie  on  the  outer 
side  of  the  crural  ring,  where  there  is  no  danger  of  its  being  wounded  in  the 
operation  for  dividing  the  'stricture  in  femoral  hernia  (see  Fig.  373,  page  623, 
fig.  A).  Occasionally,  however,  the  obturator  artery  curves  along  the  free  margin 
of  Gimbernat's  ligament  in  its  passage  to  the  obturator  foramen :  it  would  conse- 
quently skirt  along  the  greater  part  of  the  circumference  of  the  crural  ring,  and 
could  hardly  avoid  being  wounded  in  the  operation  (see  Fig.  373,  page  623,  fig.  B). 

Septum  Crurale. — The  femoral  ring  is  closed  by  a  layer  of  condensed  areolar 
tissue  called,  by  J.  Cloquet,  the  septum  crurale.  This  serves  as  a  barrier  to  the 
protrusion  of  a  hernia  through  this  part.  Its  upper  surface  is  slightly  concave 
(fovea  femoralis),  and  supports  a  small  lymphatic  gland  by  which  it  is  separated 
from  the  subserous  areolar  tissue  and  peritoneum.  Its  under  surface  is  turned 
toward  the  femoral  canal.  The  septum  crurale  is  perforated  by  numerous  aper- 
tures for  the  passage  of  lymphatic  vessels  connecting  the  deep  inguinal  lymphatic 
glands  with  those  surrounding  the  external  iliac  artery. 

The  size  of  the  femoral  canal,  the  degree  of  tension  of  its  orifices,  and  con- 
sequently the  degree  of  constriction  of  a  hernia,  vary  according  to  the  position 
of  the  limb.  If  the  leg  and  thigh  are  extended,  abducted,  or  everted,  the  femoral 


FEMOHAL    HERXIA.  1199 

canal  and  its  orifices  are  rendered  tense  from  the  traction  on  these  parts  by 
Poupart's  ligament  and  the  fascia  lata,  as  may  be  ascertained  by  passing  the  finger 
along  the  canal.  If,  on  the  contrary,  the  thigh  is  flexed  upon  the  pelvis,  and  at 
the  same  time  adducted  and  rotated  inward,  the  femoral  canal  and  its  orifices 
become  considerably  relaxed ;  for  this  reason  the  limb  should  always  be  placed  in 
the  latter  position  when  the  application  of  the  taxis  is  made  in  attempting  the 
reduction  of  a  femoral  hernia. 

The  sulperitoneal  areolar  tissue  is  continuous  with  the  subserous  areolar  tissue 
of  surrounding  parts.  It  is  usually  thickest  and  most  fibrous  where  the  iliac 
•Is  leave  the  abdominal  cavity.  It  covers  over  the  small  interval  (crural  ring) 
on  the  inner  side  of  the  femoral  vein.  In  some  subjects  it  contains  a  considerable 
amount  of  adipose  tissue.  In  such  cases,  where  it  is  protruded  forward  in  front 
of  the  sac  of  a  femoral  hernia,  it  may  be  mistaken  for  a  portion  of  omentum.  The 
peritoneum  lining  the  portion  of  the  abdominal  wall  between  Poupart's  ligament 
and  the  brim  of  the  pelvis  is  similar  to  that  lining  any  other  portion  of  the 
abdominal  wall,  being  very  thin.  It  has  here  no  natural  aperture  for  the  escape 
of  intestine. 

Descent  of  the  Hernia. — From  the  preceding  description  it  follows  that  the 
femoral  ring  must  be  a  weak  point  in  the  abdominal  wall :  hence  it  is  that  when 
violent  or  long-continued  pressure  is  made  upon  the  abdominal  viscera  a  portion 
of  intestine  may  be  forced  into  it,  constituting  a  femoral  hernia ;  and  the  changes 
in  the  tissues  of  the  abdomen  which  are  produced  by  pregnancy,  together  with  the 
larger  size  of  this  aperture  in  the  female,  serve  to  explain  the  frequency  of  this 
form  of  hernia  in  women. 

When  a  portion  of  the  intestine  is  forced  through  the  femoral  ring,  it  carries 
before  it  a  pouch  of  peritoneum,  which  forms  what  is  called  the  hernial  sac ;  it 
receives  an  investment  from  the  subserous  areolar  tissue  and  from  the  septum 
crurale.  and  descends  vertically  along  the  crural  canal  in  the  inner  compartment  of 
the  sheath  of  the  femoral  vessels  as  far  as  the  saphenous  opening ;  at  this  point  it 
changes  its  course,  being  prevented  from  extending  farther  down  the  sheath  on 
account  of  the  narrowing  of  the  sheath  and  its  close  contact  with  the  vessels,  and 
from  the  close  attachment  of  the  superficial  fascia  and  crural  sheath  to  the 
lower  part  of  the  circumference  of  the  saphenous  opening ;  the  tumor  is  conse- 
quently directed  forward,  pushing  before  it  the  cribriform  fascia,  and  then  curves 
upward  on  to  the  falciform  process  of  the  fascia  iata  and  lower  part  of  the  tendon 
of  the  External  oblique,  being  covered  by  the  superficial  fascia  and  integument. 
While  the  hernia  is  contained  in  the  femoral  canal  it  is  usually  of  small  size, 
owing  to  the  resisting  nature  of  the  surrounding  parts;  but  when  it  has  escaped 
from  the  saphenous  opening  into  the  loose  areolar  tissue  of  the  groin,  it  becomes 

-iderably  enlarged.  The  direction  taken  by  a  femoral  hernia  in  its  descent  is 
at  first  downward,  then  forward  and  upward  ;  this  should  be  borne  in  mind,  as 
in  the  application  of  the  taxis  for  the  reduction  of  a  femoral  hernia  pressure  should 
be  directed  in  the  reverse  order. 

Coverings  of  the  Hernia. — The  coverings  of  a  femoral  hernia,  from  within 
outward,  are — peritoneum,  subserous  areolar  tissue,  the  septum  crurale,  crural 
sheath,  cribriform  fascia,  superficial  fascia,  and  integument.1 

Varieties  of  Femoral  Hernia. — If  the  intestine  descends  along  the  femoral  canal 
only  as  far  as  the  saphenous  opening,  and  does  not  escape  from  this  aperture,  it  is 
called  in'-<>iii.i  rul  In nna.  The  small  size  of  the  protrusion  in  this  form 

of  hernia,  on  account  of  the  firm  and  resisting  nature  of  the  canal  in  which  it  is 
contained,  renders  it  an  exceedingly  dangerous  variety  of  the  disease,  from  the 

1  Sir  Astley  Cooper  has  described  an  investment  for  femoral  hernia,  under  the  name  of  "fascia 
propria,''  lying  immediately  external  to  the  peritoneal  sac,  but  frequently  separated  from  it  by  more 
or  less  adipose  tissue.  Surgically,  it  is  important  to  remember  the  existence  (at  any  rate,  the  occa- 
sional existence)  of  this  layer,  on  account  of  the  ease  with  which  an  inexperienced  operator  may  mis- 
take the  fascia  for  the  peritoneal  sac  and  the  contained  fat  for  omentum.  Anatomically,  this  fascia 
appears  identical  with  what  is  called  in  the  text  "  subserous  areolar  tissue,"  the  areolar  tissue  being 
thickened  and  caused  to  assume  a  membranous  appearance  by  the  pressure  of  the  hernia. 


1200  THE   SURGICAL    ANATOMY   OF  HERNIA. 

extreme  difficulty  of  detecting  the  existence  of  the  swelling,  especially  in  corpulent 
subjects.  The  coverings  of  an  incomplete  femoral  hernia  would  be,  from  without 
inward,  integument,  superficial  fascia,  falciform  process  of  fascia  lata,  crural 
sheath,  septum  crurale,  subserous  areolar  tissue,  and  peritoneum.  When,  however, 
the  hernial  tumor  protrudes  through  the  saphenous  opening  and  directs  itself 
forward  and  upward,  it  forms  a  complete  femoral  hernia.  Occasionally  the  hernial 
sac  descends  on  the  iliac  side  of  the  femoral  vessels  or  in  front  of  these  vessels,  or 
even  sometimes  behind  them. 

The  seat  of  stricture  of  a  femoral  hernia  varies  :  it  may  be  in  the  peritoneum 
at  the  neck  of  the  hernial  sac ;  in  the  greater  number  of  cases  it  would  appear  to 
be  at  the  point  of  junction  of  the  falciform  process  of  the  fascia  lata  with  the 
lunated  edge  of  Gimbernat's  ligament,  or  at  the  margin  of  the  saphenous  opening 
in  the  thigh.  The  stricture  should  in  every  case  be  divided  in  a  direction  upward 
and  inward,  and  the  extent  necessary  in  the  majority  of  cases  is  about  two  or 
three  lines.  By  these  means  all  vessels  or  other  structures  of  importance  in 
relation  with  the  neck  of  the  hernial  sac  will  be  avoided. 


SURGICAL  AXATOMY  OF  THE  ISCHIO-RECTAL 
REGIOX  AND  PERINEUM. 


Dissection.— The  student  should  select  a  well-developed  muscular  subject,  free  from  fat, 
and  the  dissection  should  be  commenced  early,  in  order  that  the  parts  may  be  examined  in  as 
recent  a  state  as  possible.  A  staff  having  been  introduced  into  the  bladder  and  the  subject 
placed  in  the  position  shown  in  Fit:.  767.  the  scrotum  should  be  raised  upward,  and  retained  in 
that  position,  and  the  rectum  moderately  distended  with  tow. 

The  space  which  is  now  to  be  examined  corresponds  to  the  inferior  aperture 
or  outlet  of  the  pelvis.  Its  deep  boundaries  are,  in  front,  the  pubic  arch 
and  subpubic  ligament :  behind,  the  tip  of  the  coccyx ;  and  on  each  side,  the 
rami  of  the  pubes  and  ischium,  the  tuberosities  of  the  ischium.  and  great  sacro- 
sriarie  ligaments.  The  space  included  by  these  boundaries  is  somewhat  lozenge- 
shaped,  and  is  limited  on  the  surface  of  the  body  by  the  scrotum  in  front,  by 
the  buttocks  behind,  and  on  each  side  by  the  inner  side  of  the  thighs.  A  line 
drawn  transversely  between  the  anterior  part  of  the  tuberosity  of  the  ischium  on 
each  side,  in  front  of  the  anus,  divides  this  space  into  two  portions.  The 
anterior  portion  contains  the  penis  and  urethra,  and  is  called  the  peri n<eum.  The 
posterior  portion  contains  the  termination  of  the  rectum,  and  is  called  the  ischio- 
'  i-'.'ji'-n. 

THE  ISCHIO-RECTAL  REGION. 

The  ischio-rectal  region  corresponds  to  the  portion  of  the  outlet  of  the 
pelvis  situated  immediately  behind  the  perinaeum :  it  contains  the  termination 
of  the  rectum  and  a  deep  fossa,  filled  with  fat,  on  each  side  of  the  intestine, 
between  it  and  the  tuberosity  of  the  ischium  :  this  is  called  the  ischio-rectal 
fossa. 

The  ischio-rectal  region  presents  in  the  middle  line  the  aperture  of  the  anus: 
around  this  orifice  the  integument  is  thrown  into  numerous  folds,  which  are 
obliterated  on  distension  of  the  intestine.  The  integument  is  of  a  dark  color, 
continuous  with  the  mucous  membrane  of  the  rectum,  and  provided  with  numerous 
follicles,  which  occasionally  inflame  and  suppurate,  and  may  be  mistaken  for 
fistula?.  The  veins  around  the  margin  of  the  anus  are  occasionally  much  dilated, 
forming  a  number  of  hard  pendent  masses,  of  a  dark  bluish  color,  covered  partly 
by  mucous  membrane  and  partly  by  the  integument.  These  tumors  constitute  the 
disease  called  external  piles. 

Dissection  Fig.  767). — Make  an  incision  through  the  integument,  along  the  median 
line,  from  ^the  base  of  the  scrotum  to  the  anterior  extremity  of  the  anus :  carry  it  round  the 
margins  of  this  aperture  to  its  posterior  extremity,  and  continue  it  backward  to  about  an  inch 
behind  the  tip  of  the  coccyx.  A  transverse  incision  should  now  be  carried  across  the  base  of 
the  scrotum,  joining  the  anterior  extremity  of  the  preceding ;  a  second,  carried  in  the  same 
direction,  should  be  made  in  front  of  the  anus ;  and  a  third  at  the  posterior  extremity  of  the 
first  incision.  These  incisions  should  be  sufficiently  extensive  to  enable  the  dissector  to  raise  the 
integument  from  the  inner  side  of  the  thighs.  The  flaps  of  skin  corresponding  to  the  ischio- 
rectal  region  should  now  be  removed.  In  dissecting  the  integument  from  this  region  great  care 
is  required,  otherwise  the  Corrugator  cutis  ani  and  External  sphincter  will  be  removed,  as  they 
are  intimately  adherent  to  the  skin. 

The  superficial  fascia  is  exposed  on  the  removal  of  the  skin :  it  is  very  thick, 
areolar  in  texture,  and  contains  much  fat  in  its  meshes.  In  it  are  found  ramifying 
two  or  three  cutaneous  branches  of  the  small  sciatic  nerve :  these  turn  round  the 
inferior  border  of  the  Gluteus  maximus  and  are  distributed  to  the  integument 
around  the  anus. 

76  1201 


1202  SURGICAL    ANATOMY   OF    THE   PERINEUM. 

In  this  region,  and  connected  with  the  lower  end  of  the  rectum,  are  four  muscles : 
the  Corrugator  cutis  ani ;  the  two  Sphincters,  External  and  Internal ;  and  the 
Levator  ani. 

These  muscles  have  been  already  described  (see  pages  458  and  459). 

The  ischio-rectal  fossa  is  situated  between  the  end  of  the  rectum  and  the 
tuberosity  of  the  ischium  on  each  side.  It  is  triangular  in  shape ;  its  base,  directed 
to  the  surface  of  the  body,  is  formed  by  the  integument  of  the  ischio-rectal  region  ; 
its  apex,  directed  upward,  corresponds  to  the  point  of  division  of  the  obturator 
fascia  and  the  thin  membrane  given  off  from  it,  which  covers  the  outer  sui-face  of 
the  Levator  ani  (ischio-rectal  or  anal  fascia).  Its  dimensions  are  about  an  inch 
in  breadth  at  the  base  and  about  two  inches  in  depth,  being  deeper  behind  than 
in  front.  It  is  bounded,  internally,  by  the  Sphincter  ani,  Levator  ani,  and  Coc- 
cygeus  muscles;  externally,  by  the  tuberosity  of  the  ischium  and  the  obturator 
fascia,  which  covers  the  inner  surface  of  the  Obturator  internus  muscle;  in  front, 
it  is  limited  by  the  line  of  junction  of  the  superficial  and  deep  perineal  fasciae; 
and  behind,  by  the  margin  of  the  Gluteus  maximus  and  the  great  sacro-sciatic  liga- 
ment. This  space  is  filled  with  a  large  mass  of  adipose  tissue,  which  explains  the 
frequency  with  which  abscesses  in  the  neighborhood  of  the  rectum  burrow  to  a 
considerable  depth. 

If  the  subject  has  been  injected,  on  placing  the  finger  on  the  outer  wall  of  this 
fossa  the  internal  pudic  artery,  with  its  accompanying  veins  and  nerve,  will  be 
felt  about  an  inch  and  a  half  above  the  margin  of  the  ischiatic  tuberosity,  but 
approaching  nearer  the  surface  as  they  pass  forward  along  the  inner  margin  of  the 
pubic  arch.  These  structures  are  enclosed  in  a  sheath  (canal  of  Alcock)  formed 
by  the  obturator  fascia,  the  pudic  nerve  lying  below  the  artery  (Fig.  374).  Cross- 
ing the  space  transversely,  about  its  centre  are  the  inferior  haemorrhoidal  vessels 
and  nerves,  branches  of  the  internal  pudic  ;  they  are  distributed  to  the  integu- 
ment of  the  anus  and  to  the  muscles  of  the  lower  end  of  the  rectum.  These 
vessels  are  occasionally  of  large  size,  and  may  give  rise  to  troublesome  haemorrhage 
when  divided  in  the  operation  of  lithotomy  or  of  fistula  in  ano.  At  the  back  part 
of  this  space  may  be  seen  a  branch  of  the  fourth  sacral  nerve,  and,  at  the  fore 
part  of  the  space  the  superficial  perineal  vessels  and  nerves  can  be  seen  for  a  short 
distance. 

THE  PERINEUM  IN  THE  MALE. 

The  perineal  space  is  of  a  triangular  form ;  its  deep  boundaries  are  limited, 
laterally,  by  the  rami  of  the  pubic  bones  and  ischia,  meeting  in  front  at  the 
pubic  arch;  behind,  by  an  imaginary  transverse  line  extending  between  the 
tuberosities  of  the  ischia.  The  lateral  boundaries  are,  in  the  adult,  from  three 
inches  to  three  inches  and  a  half  in  length,  and  the  base  from  two  to  three  inches 
and  a  half  in  breadth,  the  average  extent  of  the  space  being  two  inches  and  three- 
quarters. 

The  variations  in  the  diameter  of  this  space  are  of  extreme  interest  in  connection  with  the 
operation  of  lithotomy  and  the  extraction  of  a  stone  from  the  cavity  of  the  bladder.  In  those 
cases  where  the  tuberosities  of  the  ischia  are  near  together  it  would  be  necessary  to  make  the 
incisions  in  the  lateral  operation  of  lithotomy  less  oblique  than  if  the  tuberosities  were  widely 
separated,  and  the  perineal  space  consequently  wider.  The  peringeum  is  subdivided  by  the 
median  raphe  into  two  equal  parts.  Of  these,  the  left  is  the  one  in  which  the  operation  of 
lithotomy  is  performed. 

In  the  middle  line  the  perinaeum  is  convex,  and  corresponds  to  the  bulb  of  the 
urethra.  The  skin  covering  it  is  of  a  dark  color,  thin,  freely  movable  upon  the 
subjacent  parts,  and  covered  with  sharp  crisp  hairs,  which  should  be  removed 
before  the  dissection  of  the  part  is  commenced.  In  front  of  the  anus  a  prominent 
line  commences,  the  raphe,  continuous  in  front  with  the  raphe  of  the  scrotum. 

Upon  removing  the  skin  and  superficial  structures  from  this  region,  in  the 
manner  shown  in  Fig.  767,  a  plane  of  fascia  will  be  exposed,  covering  in  the 
triangular  space  and  stretching  across  from  one  ischio-pubic  ramus  to  the  other. 
This  is  the  deep  layer  of  the  superficial  fascia  or  fascia  of  Colles.  It  has  already 


THE  PERINEUM  ix  THE  MALE. 


1203 


been  described  (page  460).  It  is  a  layer  of  considerable  strength,  and  encloses  and 
covers  a  space  in  which  are  contained  muscles,  vessels,  and  nerves.  It  is  continuous 
in  front  with  the  dartos  of  the  scrotum ;  on  each  side  it  is  firmly  attached  to  the 
margin  of  the  ischio-pubic  ramus  and  to  the  tuberosity  of  the  ischium ;  and 
posteriorly  it  curves  down  behind  the  Trans  versus  perinaei  muscles  to  join  the 
lower  margin  of  the  deep  perineal  fascia. 

It  is  between  this  layer  of  fascia  and  the  next  layer,  the  superficial  layer  of  the  deep  perineal 
fascia,  that  extravasation  of  urine  most  frequently  takes  place  in  cases  of  rupture  of  the  urethra. 
The  superficial  layer  of  the  deep  perineal  fascia  (see  page  463)  is  also  attached  to  the  ischio^pubic 
rarni,  and  in  front  to  the  subpubic  ligament.  It  is  clear,  therefore,  that  when  extravasation  of 
fluid  takes  place  between  these  two  layers,  it  cannot  pass  backward,  because  the  two  layers  are 
continuous  with  each  other  around  the  Transversus  perinaei  muscles  ;  it  cannot  extend  laterally, 
on  account  of  the  connection  of  both  these  layers  to  the  rami  of  the  os  pubis  and  ischium ;  it 
cannot  find  its  way  into  the  pelvis,  because  the  opening  into  this  cavity  is  closed  by  the  deep 
perineal  fascia :  and  therefore,  so  long  as  these  two  layers  remain  intact,  the  only  direction  in 
which  the  fluid  can  make  its  way  is  forward  into  the  areolar  tissue  of  the  scrotum  and  penis, 
and  from  thence  on  to  the  anterior  wall  of  the  abdomen. 

When  the  deep  layer  of  the  superficial  fascia  is  removed,  a  space  is  exposed 
between  this  fascia  and  the  deep  perineal  fascia  in  which  are  contained  the  peri- 


FIG.  767. — Dissection  of  perinseum  and  ischio- rectal  region. 


neal  branches  of  the  internal  pudic  artery,  with  their  accompanying  veins;  the 
perineal  branches  of  the  internal  pudic  nerve;  some  of  the  muscles  connected 
with  the  penis  and  urethra ; — in  the  middle  line,  the  Accelerator  urinae  ;  on  each 
side,  the  Erector  penis ;  and  behind,  the  Transversus  perinaei ; — the  crura 
of  the  corpora  cavernosa ;  and  the  bulb  of  the  corpus  spongiosum.  Here  also  is 
seen  the  eentriil  f-///<7/,/«,/x  point  of  the  perinceum.  This  is  a  fibrous  point  in  the 
middle  line  of  the  perinaeum  between  the  urethra  and  the  rectum,  being  about  half 
an  inch  in  front  of  the  anus.  At  this  point  five  muscles  converge  and  are 
attached — viz.  the  External  sphincter  ani,  the  Acceleratores  urinae,  and  the  two 
Transversi  perinaei  muscles — so  that  by  the  contraction  of  these  muscles,  which 
extend  in  opposite  directions,  it  serves  as  a  fixed  point  of  support. 

The  Accelerator  urinae.  the  Erector  penis,  and  the  Transversus  perinaei  muscles 
have  been  already  described  (page  461).  They  form  a  triangular  space,  bounded 
internally  by  the  Accelerator  urinae.  externally  by  the  Erector  penis,  and  behind 
by  the  Transversus  perinaei.  The  floor  of  this  space  is  formed  by  the  triangular 
ligament  of  the  urethra  (deep  perineal  fascia),  and  running  from  behind  forward 
in  it  are  the  superficial  perineal  vessels  and  nerves,  and  the  transverse  perineal 
artery  coursing  along  the  posterior  boundary  of  the  space  on  the  Transversus 
perinaei  muscle.  The  two  terminal  branches  of  the  internal  pudic  artery  are 
not  to  be  seen  in  this  space,  as  they  as  well  as  the  dorsal  nerve  of  the  penis  are 
dorsal  to  the  superficial  layer  of  the  triangular  ligament :  the  dorsal  artery  of  the 
penis  ascending  between  the  two  layers  of  the  ligament ;  and  the  artery  to  the  cor- 
pus cavernosum  entering  the  crus  immediately  after  piercing  from  above  downward 


1204 


SURGICAL    ANATOMY   OF    THE  PERINEUM. 


the  lower  layer.  The  dorsal  nerve  of  the  penis  is  also  contained  within  the  two 
layers,  accompanying  the  dorsal  artery  along  the  ischio-pubic  ramus,  and  with  it 
piercing  the  anterior  layer  and  the  suspensory  ligament  to  be  distributed  to  the 
penis. 

The  Accelerator  urinae  and  Erector  penis  should  now  be  removed,  when  the  deep  perineal 
fascia  will  be  exposed,  stretching  across  the  front  part  of  the  outlet  of  the  pelvis.  The  urethra 
is  seen  perforating  its  centre  just  behind  the  bulb,  and  on  each  side  is  the  crus  penis,  connecting 
the  corpus  cavernosum  with  the  rami  of  the  ischium  and  os  pubis. 

The  deep  perineal  fascia  (triangular  ligament),  which  has  already  been  described 
(see  page  463),  consists  of  two  layers,  the  inferior  or  superficial  layer  of  which, 
sometimes  called  the  anterior  layer  of  the  triangular  ligament,  is  now  exposed.  It 
is  united  to  the  superior  or  deep  layer  behind,  but  is  separated  in  front  by  a  sub- 
fascial  space,  in  which  are  contained  certain  structures. 

The  superficial  layer  of  the  deep  perineal  fascia  consists  of  a  strong  fibrous 
membrane,  the  fibres  of  which  are  disposed  transversely,  which  stretches  across 


GREAT    SACRO- 
SCIATIC   LIGAMENT 


Superficial  perineal  artery. 
Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


FIG.  768.— The  superficial  muscles  and  vessels  of  the  perinseum. 

from  one  ischio-pubic  ramus  to  the  other  and  completely  fills  in  the  pubic  arch ; 
it  is  attached  in  front  to  the  subpubic  ligament,  except  just  in  the  centre,  where  a 
small  interspace  is  left  for  the  dorsal  vein  of  the  penis.  In  the  erect  position  of 
the  body  it  is  almost  horizontal.  It  is  perforated  by  the  urethra  in  the  middle 
line,  and  on  each  side  by  the  ducts  of  Cowper's  glands.  It  is  pierced  also  by  the 
dorsal  artery  of  the  penis  close  to  the  base  of  the  ligament ;  by  the  artery  to  the 
corpus  cavernosum  more  anteriorly  and  in  the  opposite  direction,  close  to  the  lateral 
margin  of  the  ligament ;  and  by  the  artery  to  the  bulb  also  from  above  downward 
in  front  of  the  opening  for  Cowper's  duct.  The  dorsal  nerve  of  the  penis  also 
passes  through  the  ligament  in  company  with  the  artery  of  the  same  name.  The 
crura  penis  are  exposed,  lying  superficial  to  this  ligament.  They  will  be  seen  to 
be  attached  by  blunt-pointed  processes  to  the  rami  of  the  os  pubis  and  ischium,  in 
front  of  the  tuberosities,  and  passing  forward  and  inward,  joining  to  form  the  body 
of  the  penis.  In  the  middle  line  is  the  bulb  and  corpus  spongiosum,  exposed  by 
the  removal  of  the  Accelerator  urinse  muscle. 


FASCIA. 


1205 


If  the  superficial  layer  of  the  deep  perineal  fascia  is  detached  on  either  side, 
the  deep  perineal  interspace  will  be  exposed  and  the  following  parts  will  be  seen 
between  it  and  the  deep  layer  of  the  fascia  :  the  subpubic  ligament  in  front,  close 
to  the  symphysis  pubis  ;  the  dorsal  vein  of  the  penis ;  the  membranous  portion  of 
the  urethra  and  the  Compressor  urethrae  muscle;  Cowper's  glands  and  their 
ducts  :  the  dorsal  artery  and  the  dorsal  nerve  of  the  penis  ;  the  artery  and  nerve  of 
the  bulb  and  a  plexus  of  veins. 

The  superior  or  deep  layer  of  the  deep  perineal  fascia  is  derived  from  the  obturator 
fascia  or  is  continuous  with  it  along  the  pubic  arch.  Behind,  it  joins  with  the 
superficial  layer  of  the  deep  perineal  fascia  and  is  continuous  with  the  anal  fascia. 
Above  it  is  the  recto-vesical  fascia,  separated  from  it  on  each  side  by  the  anterior 
fibres  of  the  Levator  ani.  but  in  the  median  line  these  two  layers  of  fascia  are 
continuous  and  form  a  median  septum,  in  consequence  of  the  recto-vesical  fascia 
dipping  down  to  join  the  deep  layer  of  the  deep  perineal  fascia.  Thus  on  each 


Anterior  layer  of 

deep  perineal  fascia  removed, 

showing 

^COMPRESSOR    URETHRA. 

'nternal  pudic  artery. 
Artery  of  the  bulb. 
Cowper's  gland. 


FIG.  769.— Deep  perineal  fascia.    On  the  left  side  the  anterior  layer  has  been  removed. 

side  of  the  middle  line,  beneath  this  fascia,  is  a  little  interspace  in  which  is 
contained  the  anterior  fibres  of  the  Levator  ani  (Levator  prostatse).  It  is  bounded, 
below,  by  the  deep  layer  of  the  deep  perineal  fascia ;  above,  by  the  recto-vesical 
fascia,  and  is  separated  internally  from  the  space  on  the  other  side  by  the  median 
septum.  The  deep  layer  of  the  deep  perineal  fascia  is  pierced  by  the  urethra,  and 
is  continued  backward  around  the  posterior  part  of  the  membranous  portion  of 
the  urethra  and  the  outer  surface  of  the  prostate  gland. 

The  Compressor  urethrae  has  already  been  described  (page  464).  In  addition  to 
this  muscle  and  immediately  beneath  it  cirriOar  muscular  fibres  surround  the  mem- 
branous portion  of  the  urethra  from  the  bulb  in  front  to  the  prostate  behind,  and  are 
continuous  with  the  muscular  fibres  of  the  bladder.  These  fibres  are  involuntary. 

Cowper's  glands  are  situated  immediately  below  the  membranous  portion  of 
the  urethra,  close  behind  the  bulb,  and  below  the  artery  of  the  bulb. 

The  dorsal  artery  and  dorsal  nerve  of  the  penis  are  placed  along  the  inner  mar- 
gin of  the  pubic  arch  (pages  623  and  861). 

The  artery  of  the  bulb  passes  transversely  inward,  from  the  internal  pudic 
along  the  base  of  the  triangular  ligament,  between  its  two  layers  of  fascia, 


1206 


SURGICAL    ANATOMY    OF    THE   PERINEUM. 


accompanied  by  a  branch  of  the  pudic  nerve  (page  861).  If  the  posterior  layer  of 
the  deep  perineal  fascia  is  removed  and  the  crus  penis  of  one  side  detached  from 
the  bone,  the  under  or  perineal  surface  of  the  Levator  ani  is  brought  fully  into 
view.  This  muscle,  with  the  triangular  ligament  in  front  and  the  Coccygeus  and 
Pyriformis  behind,  closes  the  outlet  of  the  pelvis. 

The  Levator  ani  and  Coccygeus  muscles  have  already  been  described  (page  459). 

Position  of  the  Viscera  at  the  Outlet  of  the  Pelvis. — Divide  the  central  tendinous  point 
of  the  perinseum,  separate  the  rectum  from  its  connections  by  dividing  the  fibres  of  the  Levator 
ani,  which  descend  upon  the  sides  of  the  prostate  gland,  and  draw  the  gut  backward  toward  the 
coccyx,  when  the  under  surface  of  the  prostate  gland,  the  neck  and  base  of  the  bladder,  the 
vesiculse  seminales,  and  the  vasa  deferentia  will  be  exposed. 

The  Prostate  Gland  is  a  pale,  firm,  glandular  body  which  is  placed  immediately 
in  front  of  the  neck  of  the  bladder  around  the  commencement  of  the  urethra.  It  is 


Artery  of  corpus  cavernosum 
Dorsal  artery  of  penis 


Artery  of  bulb. 
Internal  pudic  artery. 

Cowper's  gland. 


FIG.  770.— A  view  of  the  position  of  the  viscera  at  the  outlet  of  the  pelvis. 

placed  in  the  pelvic  cavity,  behind  and  below  the  symphysis  pubis,  posterior  to  the 
deep  perineal  fascia,  and  rests  upon  the  rectum,  through  which  it  may  be  distinctly 
felt,  especially  when  enlarged.  In  shape  and  size  it  resembles  a  chestnut.  Its 
base  is  directed  backward  toward  the  neck  of  the  bladder.  Its  apex  is  directed 
forward  to  the  deep  perineal  fascia,  which  it  touches. 

Its  posterior  surface  is  smooth,  marked  by  a  slight  longitudinal  furrow,  and  rests 
on  the  rectum,  to  which  it  is  connected  by  areolar  tissue.  Its  anterior  surface  is 
flattened,  marked  by  a  slight  longitudinal  furrow,  and  placed  about  three-quarters 
of  an  inch  below  the  pubic  symphysis.  It  measures  about  an  inch  and  a  half  in 
its  transverse  diameter  at  the  base,  an  inch  in  its  antero-posterior  diameter,  and 
three-quarters  of  an  inch  in  depth.  Hence  the  greatest  extent  of  incision  that  can 
be  made  in  it  without  dividing  its  substance  completely  across  is  obliquely  back- 
ward and  outward.  This  is  the  direction  in  which  the  incision  is  made  in  it  in 
the  lateral  operation  of  lithotomy. 

Behind  the  prostate  is  the  posterior  surface  of  the  neck  and  base  of  the  bladder, 
a  small  triangular  portion  of  the  bladder  being  seen,  bounded,  in  front,  by  the 
prostate  gland ;  behind,  by  the  recto-vesical  fold  of  the  peritoneum ;  on  each  side, 
by  the  vesicula  seminalis  and  the  vas  deferens.  It  is  separated  from  direct  contact 


THE   FEMALE   PERH\EU1L  1207 

with  the  rectum  by  the  recto-vesical  fascia.  The  relation  of  this  portion  of  the 
bladder  to  the  rectum  is  of  extreme  interest  to  the  surgeon.  In  cases  of  retention 
of  urine  this  portion  of  the  organ  is  found  projecting  into  the  rectum,  between 
three  and  four  inches  from  the  margin  of  the  anus,  and  may  be  easily  perforated 
without  injury  to  any  important  parts :  this  portion  of  the  bladder  is,  consequently. 
occasionally  selected  for  the  performance  of  the  operation  of  tapping  the  bladder. 

Surgical  Anatomy. — The  student  should  consider  the  position  of  the  various  parts  in 
reference  to  the  lateral  operation  of  lithotomy.  This  operation  is  performed  on  the  left  side  of 
the  perinaaum.  as  it  is  most  convenient  for  the  right  hand  of  the  operator.  A  staff  having  been 
introduced  into  the  bladder,  the  first  incision  is  commenced  midway  between  the  anus  and  the 
back  of  the  scrotum  ( i.  e.  in  an  ordinary  adult  perinaeum  about  an  inch  and  a  half  in  front  of 
the  anus  i  a  little  on  the  left  side  of  the  raphe,  and  carried  obliquely  backward  an3  outward  to 
midway  between  the  anus  and  tuberosity  of  the  ischium.  The  incision  divides  the  integument 
and  superficial  fascia,  the  inferior  haemorrhoidal  vessels  and  nerves,  and  the  superficial  and  trans- 
verse perineal  vessels.  If  the  forefinger  of  the  left  hand  is  thrust  upward  and  forward  into 
the  wound,  pressing  at  the  same  time  the  rectum  inward  and  backward,  the  staff  may  be  felt  in 
the  membranous  portion  of  the  urethra.  The  finger  is  fixed  upon  the  staff,  and  the  structures 
coverins  it  are  divided  with  the  point  of  the  knife,  which  must  be  directed  along  the  groove  toward 
the  bladder,  the  edge  of  the  knife  being  turned  outward  and  backward,  dividing  in  its  course 
the  membranous  portion  of  the  urethra  and  part  of  the  left  lobe  of  the  prostate  gland  to  the 
extent  of  about  an  inch.  The  knife  is  then  withdrawn,  and  the  forefinger  of  the  left  hand 
passed  along  the  staff  into  the  bladder.  The  position  of  the  stone  having  been  ascertained,  the 
staff  is  to  be  withdrawn,  and  the  forceps  is  introduced  over  the  finger  into  the  bladder.  If  the 
stone  is  very  large,  the  opposite  side  of  the  prostate  may  be  notched  before  the  forceps  is  intro- 
duced :  the  finger  is  now  withdrawn,  and  the  blades  of  the  forceps  opened  and  made  to  grasp 
the  stone,  which  must  be  extracted  by  slow  and  cautious  undulating  movements. 

Parts  Divided  in  the  Operation. — The  various  structures  divided  in  this  operation  are  as 
follows  :  the  integument,  superficial  fascia,  inferior  haemorrhoidal  vessels  and  nerves,  and  prob- 
ably the  superficial  perineal  vessels  and  nerves,  the  posterior  fibres  of  the  Accelerator  urina?,  the 
Transversus  perinaei  muscle  and  artery,  the  deep  perineal  fascia,  the  anterior  fibres  of  the  Levator 
ani.  part  of  the  Compressor  urethrae.  the  membranous  and  prostatic  portions  of  the  urethra,  and 
part  ut'  the  prostate  gland. 

Parts  to  be  Avoided  in  the  Operation. — In  making  the  necessary  incisions  in  the  peri- 
naeurn  for  the  extraction  of  a  calculus  the  following  parts  should  be  avoided :  The  primary  incis- 
ion should  not  be  made  too  near  the  middle  line,  lor  fear  of  wounding  the  bulb  of  the  corpus 
spon  giosum  or  the  rectum  :  nor  too  far  externally,  otherwise  the  pudic  artery  may  be  implicated 
as  it  ascends  along  the  inner  border  of  the  pubic  arch.  If  the  incisions  are  carried  too  far 
forward,  the  artery  of  the  bulb  may  be  divided ;  if  carried  too  far  backward,  the  entire  breadth 
of  the  prostate  and  neck  of  the  bladder  may  be  cut  through,  which  allows  the  urine  to  become 
infiltrated  behind  the  pelvic  fascia  into  the  loose  areolar  tissue  between  the  bladder  and  rectum, 
instead  of  escaping  externally  ;  diffuse  inflammation  is  consequently  set  up,  and  peritonitis,  from 
the  close  proximity  of  the  recto-vesical  peritoneal  fold,  is  the  result.  If.  on  the  contrary,  the 
prostate  is  divided  in  front  of  the  base  of  the  gland,  the  urine  makes  its  way  externally,  and 
there  is  less  danger  of  infiltration  taking  place. 

Durius  the  operation  it  is  of  great  importance  that  the  finger  should  be  passed  into  the 
bladder  before  the  staff  is  removed ;  if  this  is  neglected,  and  if  the  incision  made  in  the  prostate 
and  neck  of  the  bladder  is  too  small,  great  difficulty  may  be  experienced  in  introducing  the 
finger  afterward :  and  in  the  child,  where  the  connections  of  the  bladder  to  the  surrounding 
parts  are  very  loose,  the  force  made  in  the  attempt  is  sufficient  to  displace  the  bladder  upward 
into  the  abdomen,  out  of  the  reach  of  the  operator.  Such  a  proceeding  has  not  unfrequently 
occurred,  producing  the  most  embarrassing  results  and  total  failure  of  the  operation. 

It  is  necessary  to  bear  in  mind  that  the  arteries  in  the  perinaeum  occasionally  take  an  abnor- 
mal course.  Thus  the  artery  of  the  bulb,  when  it  arises,  as  sometimes  happens,  from  the  pudic 
opposite  the  tuber  iscbii.  is  liable  to  be  wounded  in  the  operation  for  lithotomy  in  its  passage 
forward  to  the  bulb.  The  accessory  pudic  may  be  divided  near  the  posterior  border  of  the  pros- 
tate trlan-J.  if  this  is  completely  cut  across;  and  the  prostatic  veins,  especially  in  people  advanced 
in  life,  are  of  large  size,  and  give  rise,  when  divided,  to  troublesome  haemorrhage. 

THE    FEMALE   PERINEUM. 

The  female  perinaeum  presents  certain  differences  from  that  of  the  male,  in 
consequence  of  the  whole  of  the  structures  which  constitute  it  being  perforated 
in  the  middle  .line  by  the  vulvo-vaginal  passage. 

The  superficial  fascia,  as  in  the  male,  consists  of  two  layers,  of  which  the 
superficial  one  is  continuous  with  the  superficial  fascia  over  the  rest  of  the  body, 
and  the  deep  layer,  corresponding  to  the  fascia  of  Colles  in  the  male,  is  like  it 
attached  to  the  ischio-pubic  ramus.  and  in  front  is  continued  forward  through 


1208 


SURGICAL    ANATOMY    OF    THE   PERINEUM. 


the  labia  majora  to  the  inguinal  region.  It  is  of  less  extent  than  the  male,  in 
consequence  of  being  perforated  by  the  aperture  of  the  vulva. 

On  removing  this  fascia  the  muscles  of  the  female  perinseum,  which  have 
already  been  described  (page  464),  are  exposed.  The  Sphincter  vaginae,  corre- 
sponding to  the  Accelerator  urinse  in  the  male,  consists  of  an  attenuated  plane  of 
fibres,  forming  an  orbicular  muscle  around  the  orifice  of  the  vagina,  instead  of 
being  united  in  a  median  raphe,  as  in  the  male.  The  Erector  clitoridis  is  propor- 
tionately reduced  in  size,  but  differs  in  no  other  respect,  and  the  Transversus 
perinaei  is  similar  to  the  muscle  of  the  same  name  in  the  male. 

The  deep  perineal  fascia  is  not  so  strongly  marked  as  in  the  male.  It 
transmits  the  urethra,  and  is  wide,  separated  in  the  median  line  by  the  aperture 
of  the  vagina. 

The  Compressor  Urethrse  (Transversus  perin cei  profundus)  is  the  analogue  of 
the  Compressor  urethrae  in  the  male.  It  arises  from  the  ischio-pubic  ramus,  and, 
passing  inward,  its  anterior  fibres  blend  with  the  muscle  of  the  opposite  side,  in 
front  of  the  urethra ;  its  middle  fibres,  the  most  numerous,  are  inserted  into  the 
side  of  the  vagina,  and  the  posterior  fibres  join  the  central  point  of  the  perinaeum. 

The  distribution  of  the  internal  pudic  artery  is  the  same  as  in  the  male  (see 
page  625),  and  the  pudic  nerve  has  also  a  similar  arrangement,  the  dorsal  nerve 
being,  however,  very  small  and  supplying  the  clitoris. 

The  corpus  spongiosum  is  divided  into  two  lateral  halves,  which  are  represented 
by  the  bulbi  vestibuli  and  paries  intermediates  (see  page  1165). 

The  perineal  body  fills  up  the  interval  between  the  lower  part  of  the  vagina 
and  the  rectum.  Its  base  is  covered  by  the  skin  lying  between  the  anus  and 


Femoral  vessels. 


Obturator  fascia. 


Internal  pudic  vessels 
and  nerve. 


Tuberosity  of 
ischium. 

FIG.  771.— A  transverse  section  of  the  pelvis,  showing  the  pelvic  fascia  from  behind. 

vagina  on  what  is  called  the  u  perinaeum."  Its  anterior  surface  lies  behind  the 
posterior  vaginal  wall,  and  its  posterior  surface  lies  in  front  of  the  anterior  rectal 
wall  and  the  anus.  It  measures  about  an  inch  and  a  quarter  from  before  backward, 
and  laterally  extends  from  one  tuberosity  of  the  ischium  to  the  other.  In  it  are 
attached  the  muscles  belonging  to  the  external  organs  of  generation.  Through  its 


PELVIC  FASCIA. 


1209 


centre  runs  the  transverse  perineal  septum,  which  is  of  great  strength  in  women, 
and  forms  on  either  side,  behind  the  posterior  commissure,  a  hard,  ill-defined  body, 
consisting  of  connective  tissue,  with  much  yellow  elastic  tissue  and  interlacing 
bundles  of  involuntary  muscular  fibres,  in  which  the  voluntary  muscles  of  the 
perinseum  are  inserted. 

PELVIC   FASCIA. 

The  Pelvic  fascia  (Fig.  772)  is  a  thin  membrane  which  lines  the  whole  of  the 
cavity  of  the  pelvis  and  is  continuous  with  the  transversalis  and  iliac  fasciae.  It  is 
attached  to  the  brim  of  the  pelvis,  for  a  short  distance,  at  the  side  of  the  cavity,  and 
to  the  inner  surface  of  the  bone  round  the  attachment  of  the  Obturator  internus. 
At  the  posterior  border  of  this  muscle  it  is  continued  backward  as  a  very  thin 
membrane  in  front  of  the  Pyriformis  muscle  and  sacral  nerves  to  the  front  of  the 
sacrum.  In  front  it  follows  the  attachment  of  the  Obturator  internus  to  the  bone, 
arches  beneath  the  obturator  vessels,  completing  the  orifice  of  the  obturator  canal, 
and  at  the  front  of  the  pelvis  is  attached  to  the  lower  part  of  the  symphysis  pubis. 
At  the  level  of  a  line  extending  from  the  lower  part  of  the  symphysis  pubis  to  the 


FIG.  772. — Side  view  of  the  pelvic  viscera  of  the  male  subject,  showing  the  pelvic  and  perineal  fasciae. 

spine  of  the  ischium  is  a  thickened  whitish  band  ;  this  marks  the  attachment  of 
the  Levator  ani  muscle  to  the  pelvic  fascia,  and  corresponds  to  its  point  of  division 
into  two  layers,  the  obturator  and  recto-vesical. 

The  obturator  fascia  descends  and  covers  the  Obturator  internus  muscle.  It 
is  a  direct  continuation  of  the  pelvic  fascia  below  the  white  line  above  mentioned, 
and  is  attached  to  the  pubic  arch  and  to  the  margin  of  the  great  sacro-sciatic  liga- 
ment. From  its  attachment  to  the  rami  of  the  os  pubis  and  ischium  a  process  is 
given  off  Avhich  is  continuous  with  a  similar  process  from  the  opposite  side,  so  as 
to  close  the  front  part  of  the  outlet  of  the  pelvis,  forming  the  superior  layer  of 
the  triangular  ligament.  This  fascia  forms  a  canal  for  the  pudic  vessels  and 
nerve  in  their  passage  forward  to  the  perineum,  and.  gives  off  a  thin  membrane 


1210  SURGICAL   ANATOMY   OF   THE  PERINEUM. 

which  covers  the  perineal  aspect  of  the  Levator  ani  muscle,  called  the  ischio-rectal 
(anal)  fascia. 

The  recto-vesical  fascia  (visceral  layer  of  the  pelvic  fascia)  descends  into  the 
pelvis  upon  the  upper  surface  of  the  Levator  ani  muscle,  and  invests  the  prostate, 
bladder,  and  rectum.  From  the  inner  surface  of  the  symphysis  pubis  a  short 
rounded  band  is  continued  to  the  anterior  surface  of  the  prostate  and  neck  of  the 
bladder,  forming  the  pubo-prostatic  or  anterior  true  ligaments  of  the  bladder.  At 
the  side  this  fascia  is  connected  to  the  side  of  the  prostate,  enclosing  this  gland 
and  the  vesico-prostatic  plexus  of  veins,  and  is  continued  upward  on  the  side  of 
the  bladder,  forming  the  lateral  true  ligaments  of  the  organ.  Another  prolonga- 
tion invests  the  vesiculae  seminales,  and  passes  across  between  the  bladder  and 
rectum,  being  continuous  with  the  same  fascia  of  the  opposite  side.  Another  thin 
prolongation  is  reflected  round  the  surface  of  the  lower  end  of  the  rectum.  The 
Levator  ani  muscle  arises  from  the  point  of  division  of  the  pelvic  fascia,  the  vis- 
ceral layer  of  the  fascia  descending  upon  and  being  intimately  adherent  to  the 
upper  surface  of  the  muscle,  while  the  under  surface  of  the  muscle  is  covered  by  a 
thin  layer  derived  from  the  obturator  fascia,  called  the  ischio-rectal  or  anal  fascia. 
In  the  female  the  vagina  perforates  the  recto-vesical  fascia,  and  receives  a  pro- 
longation from  it. 


INDEX. 


Abdomen,  955 

contents  of,  959,  999 
lymphatics  of,  689 
muscles  of,  447 
regions  of,  959 
Abdominal  aorta,  608 
branches  of,  609 
surface-marking  of,  609 
surgical  anatomy  of,  609 
cavity,  955,  959 
muscles,  447 
ring,  external,  449 

internal.  1186 
wall,  957.  959 

Abdomino-thoracic  arch,  237 
Abducent  nerve,  810 

surgical  anatomy  of,  811 
Abductor  hallucis  muscle,  530 
indicis  muscle,  496 
minimi  digiti  muscle,  foot,  531 

hand, 494 

Absorbent  glands,  679 
Absorbents,  679 
A.:cessorii  orbicularis  oris,  402 
Aecessorius  ad  ilio-costalem  mus- 
cle, 436 
Accessory    descending    palatine 

canals,  197 
obturator  nerve,  854 
portal  vein,  1 
processes,  152 
pudic  artery,  623 
spleen,  1073 
Aceu'bulum,  278 
Acrornial  end  of  clavicle,  frac- 
ture of,  500 
region,  muscles  of,  471 
thoracic  artery.  592 
Acromio-clavicular  joint,  342 
surface  form  of,  344 
surgical  anatomy  of,  344 
Acromion  process.  244 

fracture  of,  500 
Actions   of  muscles.     See   each 

group  of  muscles. 
Adamantoblasts,  940 
Adductor  brevis  muscle,  512 
longns  muscle,  512 
magnus  muscle,  513 
obliquus  hallucis,  533 

pollicis,  493 
transversus  hallticis,  533 

pollicis,  493 
tubercle,  287 

Adenoid  connective  tissue,  49 
Adipose  tissue,  49 
Adminiculum  lineae  alba?,  962 
Afferent  nerves.  75 

vessels  of  kidney,  1134 
After-brain,  707 


Agminated  glands,  1025 

Air-cells,  1119 

Ala  cinerea.  724 

Alse  of  cerebellum,  729,  730 

of  vomer,  201 
Alar  ligaments,  326 
of  knee,  372 

thoracic  artery,  592 
Alcock,  canal  of,  1202 
Alimentary  canal,  930 
development  of,  132 
subdivisions  of,  930 
Allantoic  vesicle,  113 
Allantois,  113,  1140 
Alveolar  artery,  562 

passage,  1119 

process,  193,  203 
Alveoli,  1119 

formation  of,  941 

of  lower  jaw,  203 

of  upper  jaw,  193 
A 1  veus,  763 
Amnion,  111 
Amniotic  cavity,  112 
Amphiarthrosis,  315 
Ampullae  of  rectum,  1039 

of  semicircular  canals,  922 

of  tubuli  lactiferi,  1179 
Amygdalae,  945 

of  cerebellum,  732 
Anal  canal,  1038,  1040 

fascia,  1210 

orifice,  1038 

Anastomosis  of  arteries,  539 
Anastomotica  magna  of  brachial, 

596 

of  femoral,  637 
Anatomical    neck   of   humerus, 

248 

fracture  of,  253 
Anconeus  muscle,  486 
Andersch,  ganglion  of,  816 
Aneurisms  of  abdominal  aorta, 
609 

of  arch  of  aorta.  544 

of  thoracic  aorta,  606 
Angle  of  floor  of  fourth  ventricle, 
723 

inferior  lateral,  of  sacrum,  157 

of  jaw,  206 

lateral.  738 

of  rib,  233 

sacro-vertebral,  155 
Angular  artery,  556 

process,  external,  171 
internal,  171 

vein,  651 
Ankle-joint,  377 

relations  of  tendons  and  ves- 
sels to,  379 

surface  form  of,  379 

surgical  anatomy  of.  379 


Annular  ligament  of  ankle,  ante- 
rior, 528 
external,  529 
internal,  528 
of  radius  and  ulna,  353 
of  stapes,  919 
of  wrist,  anterior,  489 

posterior,  490 
Annulus,  1101 
ovalis,  1089 
Ansa  lenticularis,  747 

peduncularis,  747 
Anterior      annular      ligament, 

ankle,  528 
wrist,  489 

chamber  of  eye,  903 
crural  nerve,  855 

surgical  anatomy  of,  866 
dental  canal,  190 
ethmoidal  cells,  186 
fontanelle,  188 
fossa  of  skull,  208 
and    internal   frontal    artery, 

572 

nasal  spine,  194 
palatine  canal,  194 

fossa,  194,  213 
perforated  space,  784 
region  of  skull,  217 
triangle  of  neck,  563 
Antero-lateral  ganglionic  artery, 

572 

Antero-median    ganglionic    ar- 
tery, 571 
Antihelix',  912 
fossa  of,  912 

Antitragicus  muscle,  914 
Antitragus,  912 
Antrum  duodeni,  1000 
of  Highmore,  190 
pyloricum,  1000 
Anus,  1201 

development  of,  134 
muscles  of,  458 
Aorta,  541 

abdominal,  608 
branches  of,  609 
development  of,  128 
surgical  anatomv  of  arch  at 

544 

arch  of,  543 
branches  of,  545 
peculiarities  of,  543 

branches  of.  545 
sinuses  of,  542 
surgical  anatomy  of,  544 
descending,  605 
thoracic,  605 
branches  of,  606 
sinuses  of,  542 
surgical  anatomy  of,  606 
transverse,  541.  543 
1211 


1212 


INDEX. 


Aortic   opening   of   diaphragm, 

446 

of  heart,  1092 
plexus,  878 

seuiilunar  valves,  1093 
sinuses,  1093 
vestibule,  1094 

Apertura  scalse  vestibuii   coch- 
leae, 922 

Aponeurosis,  389 
of  deltoid,  471 
of  external  oblique  in  inguinal 

region,  448 

of  occipito-frontalis,  393 
posterior,  of  transverse  muscle, 

453,  458 

of  soft  palate,  944 
suprahyoid,  413 
Apophysis,  144 

Apparatus  ligamentosus  coli,  326 
Appendages  of  eye,  907 

surgical  anatomy  of,  911 
of  skin,  89 
of  uterus,  1174 

Appendices  epiploicae,  1028, 1041 
Appendix  of  left  auricle,  1091 
of  right  auricle,  1088 
vermiformis,  1032 
Aqua  labyrinthi,  926 
Aquaeductus  cochleae,  178,  923 
Fallopii,  177,  919 
Sylvius,  707,  741,  744 
vestibuii,  177,  921 
Aqueous  humor,  903 
Arantii  corpora,  1091 
Arbor  uterina,  1171 

vitse,  734 

Arch  of  aorta,  543 
branches  of,  545 
peculiarities  of,  543 
surgical  anatomy  of,  544 
crural  or  femoral,  1195 
deep,  598 
of  os  pubis,  283 
plantar,  647 
supraorbital,  171 
of  a  vertebra,  144 
zygomatic,  216 
Arches,  aortic,  foetal,  129 
Archoplasm  apheres,  40 
Arciform  fibres,  deep,  719 

external  or  superficial,  710, 

712,  718 
internal,  719 
superficial  or  external,  710, 

712,  718 

Area  of  Broca,  783 
cribrosa,  media,  928 

superior,  928 
germination,  103 
Areas  of  Cohnheim,  66 

of  medulla,  712,  713.  714 
Areola  of  breast,  1178 
Areolae  of  bone,  primary,  60 

secondary,  61 
Areolar  tissue,  46 
Arm,  arteries  of,  576 
back  of,  muscles  of,  477 
bones  of,  248 
fascia  of,  475 
front  of,  muscles  of,  475 
lymphatic  glands  of,  681 
lymphatics  of,  684 
superficial  fascia  of,  471 
veins  of,  662 


Arnold's  ganglion,  807 
nerve,  821 

canal  for,  178 
Arrectores  pili,  94 
Arteria  centralis  retinae,  570 
Arterise  propriae  renales,  1133 

receptaculi,  568 
Arteries,  development  of,  128 
anastomoses  of,  539 
capillary,  82 
distribution  of,  539 
mode  of  division,  539 

of  origin  of  branches,  539 
nerves  of,  82 
sheath  of,  82 
structure  of,  80 
subdivision  of,  539 
systemic,  539 
vessels  of,  82 
Arteries  or  artery,  accessory  pu- 

dic,  623 

acromial,  thoracic,  592 
alar  thoracic,  592 
alveolar,  562 
anastomotica    magna  of   bra- 

chial,  597 
of  femoral,  637 
angular,  556 
anterior  cerebral,  570 
ciliary,  570 
communicating,  572 
inferior  cerebellar,  583 
intercostal,  586 
and  internal  frontal,  670 
spinal,  582 

antero-lateral  ganglionic,  572 
antero-median  ganglionic,  571 
aorta,  541 

abdominal,  608 
arch  of,  543 
ascending  part,  542 
descending  part,  605 
thoracic,  605 
articular,  knee,  639 
ascending  cervical,  584 

pharyngeal,  558 
auditory,  583,  927 
auricular  anterior,  559 

posterior,  557 
axillary,  589 

accessory     external     mam- 
mary, 592 
cutaneous,  593 
external  mammary,  592 

accessory,  592 
humeral  branch,  592 
azygos  of  knee,  641 
basilar,  583 
brachial,  593 
bronchial,  606,  1120 
buccal,  562 
of  bulb,  625 
calcanean,  external,  647 

internal,  647 

carotid,  common,  547 

external,  551 

internal,  565 

carpal,  radial,  599 

ulnar,  603 

of  cavernous  body,  625 
centralis  retinae,  570 
cerebellar,  583 
cerebral,  570,  572,  583 
ascending  cervical,  584 
princeps,  557 


Arteries  or  artery,  cerebral  pro- 

funda,  587 

superficial  cervical,  585 
choroid  anterior,  573 

posterior,  584 
ciliarv,  570 

circle"  of  Willis,  573,  584 
circumflex,  of  arm,  593 

of  iliac,  superficial,  635 

of  thigh,  636 
coccygeal,  626 
cochlear,  927 
coeliac  axis,  610 
colica  dextra,  614 

media,  614 

sinistra,  614 
comes  nervi  ischiadici,  626 

phrenici,  586 
common  carotid,  547 

iliac,  618 

communicating,  anterior  cere- 
bri,  572 

branch  of  ulnar,  604 

posterior  cerebri,  573 
coronary,  descending,  542,  543 

of  heart,  542 

infundibular,  542 

of  lip,  556 

marginal,  542 

transverse,  542,  543 
cremasteric,  629 
crico-thyroid,  552 
cystic,  611 
deep  branch  of  ulnar,  605 

cervical,  587 

temporal,  561 
dental  anterior,  562 

inferior,  561 

posterior,  562 
descending  aorta,  605 

palatine,  562 
digital  plantar,  648 

of  nlnar,  604 
dorsal,  of  penis,  624 

of  scapula,  592 
dorsalis  hallucis,  643,  644 

indicis,  600 

linguae,  553 

pedis,  643 

communicating,  643,  644 
first    dorsal    interosseous, 

643,  644 
plantar  digital,  643,  644 

pollicis,  600 
epigastric,  deep,  629 

superficial,  635 

superior,  587 
ethmoidal,  569 
external  carotid,  551 

iliac,  628 

plantar,  647 

anterior  perforating,  644, 

648 

facial,  554 
femoral.  630 

deep,  635 
frontal,  570 
gastric,  611,  612 
gastro-duodenalis,  611 
gastro-epiploica  dextra,  611 

sinistra,  612 
gluteal,  627 

inferior,  626 
helicine,  1152 
haemorrhoidal  inferior,  625 


IXDEX. 


1213 


Arteries  or  arterv.  hsemorrhoidal, 
middle.  622 

superior,  615 
hepatic,  611,  1057 
hyoid  branch  of  lingual,  553 

of  superior  thyroid, 
hyposastric.  in  foetus,  621, 1097 
ileo-colic,  614 
iliac,  common,  618 

external. 

internal,  620 
ilio-lumbar.  626 
inferior  cerebellar,  583 

dental,  561 

labial,  555 

laryngeal,  584 

mesenteric,  614 

profunda,  596 

pyloric,  611 

thyroid.  5^4 
infraorbital,  562 
innominate.  545 
intercostal,  606 

anterior. 

superior.  587 
internal  auditory,  927 

carotid.  565 

iliac,  620 

mammary,  586 

maxillary,  559 

plantar.  647 
interosseous,  of  foot,  644 

of  hand. 

ulnar.  602 
intestini  tennis,  614 
labial  inferior,  555 
lachrymal 
laryngeal  inferior,  584 

superior,  552 
lateral  sacral,  627 

spinal,  •" 

lateralis  nasi,  556 
lingual.  553 
long  ciliary,  570 

thoracic,  592 
lumbar,  617 
malleolar.  643 
mammary,  internal,  586 
rua<seteri 

maxillary,  internal,  559 
median,  of  forearm,  603 

of  spinal  cord,  583 
media<tinal,  586 

posterior,  606 
meningeal  anterior,  568 

middle,  560 

small,  561 

from  occipital . 
from  pharyngeal.  55  S 
from  vertebral,  581 
mesenteric  inferior,  614 

superior,  613 
metacarpal,  600 
metatarsal.  644 
middle  cerebral,  572 

sacral,  617 

musculo-phrenic,  586 
mylo-hyoid,  561 
nasal,  of  ophthalmic,  570 

of  septum,  556 
inferior,  556 
superior,  562 
nutrient,  of  fibula,  646 

humeru>. 

radius  and  ulnar,  602 


Arteries   or   artery,   radius   and 

tibia,  646 
obturator.  022 
occipital,  556 
cesophageal,  606 
ophthalmic,  568 
orbital,  562 
ovarian,  616 
palatine,  ascending,  555 

descending,  562 

palmar  arch,  deep,  604 
superficial.  6t>4 

of  pharyngeal. 
palmar  interossei,  601 
palpebral,  570 
pancreatic.  612 
pancreatico-duodenalis,  611 

inferior,  613 
perforating,  of  foot,  648 

of  hand,  601 

of  intercostal,  586 

of  thigh,  636 
pericardiac,  586,  606 
perineal,  superficial,  625 

transverse,  625 
peroneal,  646 

anterior,  646 

posterior,  646 
phrenic,  616 
plantar,  647 
popliteal,  638 
posterior  auricular,  557 

carpal,  inferior   perforating 
of  radial,  600 

cerebral,  583 

communicating,  573 

meningeal,   from   vertebral, 
5^2 

tibial,  644 
princeps  cervicis,  557 

pollicis,  600 

profunda  of  arm,  inferior,  596 
superior,  596 

cervicis,  587 

femoris,  635 
pterygoid,  562 
pterygo-palatine,  562 
pudic,  deep  external,  635 

superficial  external,  635 

internal,  623 
pulmonary,  540,  1119 
pyloric  inferior,  611 

of  hepatic,  611 
radial,  597 

posterior     carpal,     inferior 

perforating,  600 
radialis  indicis,  601 
ranine,  553 
recurrent  interosseous,  603 

radial,  599 

tibial,  642 
posterior,  642 

ulnar,  anterior,  602 

posterior,  602 
renal,  616 
sacral  lateral,  627 

middle,  617 

scapular,  posterior,  585 
sciatic,  626 
short  ciliary,  570 
sigmoid,  614 
spermatic,  616,  1155 
spheno-palatine,  562 
spinal,  anterior,  582 

lateral.  582 


Arteries  or   artery,  spinal,  me- 
dian, 583 

posterior,  582 
splenic,  611 
sterno-mastoid,  557 
stylo-mastoid,  557 
subclavian,  576 
sublingual,  553 
submaxillary,  555 
submental,  555 
subscapular,  592 
superficial  cervical,  585 

circumflex  iliac,  630 

palmar  arch,  604 

perineal,  625 
superficialis  volae.  599 
superior  cerebellar,  583 

epigastric,  587 

hsemorrhoidal,  615 

intercostal,  587 

laryngeal,  552 

mesenteric,  613 

profunda,  596 

thoracic,  592 

thyroid,  554 
supraorbital,  569 
suprarenal,  615 
suprascapular,  585 
sural,  639 
tarsal,  644 
temporal,  558 

anterior,  558 

deep,  561 

middle,  559 

posterior,  558 
thoracic,  acromial,  592 

alar,  592 

aorta,  605 

long,  592 

superior,  592 
thyroid  axis,  584 

inferior,  584 

superior,  552 
thyroidea  ima,  545 
tibial  anterior,  641 

posterior,  644 

recurrent,  642 
tonsillar,  555 
transverse  facial,  559 
transversalis  colli,  585 
tympanic,  from  internal  caro- 
tid, 568 

from  internal  maxillary,  500 
ulnar.  601 

recurrent  anterior,  602 

posterior,  602 

umbilical  in  fetus,  621,  1099 
uterine,  622 
vaginal,  622 
vasa  aberrantia  of  arm,  595 

brevia,  612 

intestini  tennis.  614 
vertebral,  581 
vesical  inferior,  622 

middle,  622 

superior,  622 
vestibular,  927 
Vidian,  562 
Arteriolse  rectse,  1134 
Arthrodia,  316 
Articular  arteries  (knee),  from 

popliteal,  641 
cartilage,  143 
end-bulbs,  76 
lamella  of  bone,  313 


1214 


INDEX. 


Articular  processes  of  vertebrae, 

146 
Articulations,     acromio-clavicu- 

lar,  342 
ankle,  377 
astragalo-calcanean,  381 

navicular,  382 
atlanto-axial,  323 
calcaneo-astragaloid,  381 

-cuboid,  381 

navicular,  382 
carpal,  357 

carpo-metacarpal,  359 
chondro-sternal,  334 
classification  of,  314 
coccygeal,  339 
costo-central,  330 

-transverse,  331 
of  cuboid  with  external  cunei- 
form, 384 
of  cuneiform  with  each  other, 

383 

different  kinds  of,  84 
elbow,  349 
femoro-tibial,  368 
in  general,  313 
hip,  362 
immovable,  314 
knee,  368 
metacarpal,  357 
metacarpo-phalangeal,  361 
metatarsal,  385 
metatarso-phalangeal,  386 
mixed,  315 
movable,  315 
movements  of,  316 
naviculo-cuboid,  383 

-cuneiform,  383 
occipito-atlantal,  325 

-axial,  326 
pelvis,  336 

with  spine,  336 
phalanges,  362 
pubic,  339 
radio-carpal,  356 

-ulnar,  inferior,  355 
middle,  354 
superior,  353 
sacro-coccygeal,  339 

-iliac,  337 

-sciatic,  337,  338 

-vertebral,  336 
scapulo-clavicular,  343 

-numeral,  345 
shoulder,  345 
stcrno-clavicular,  341 
of  sternum,  336 
tarsal,  380 

tarso-metatarsal,  384 
temporo-maxillary,  327 
tibio-fibular,  inferior,  376 

middle,  376 

superior,  376 
of  tympanic  bones,  918 
vertebral  column,  319 
wrist,  356 

Articular  nerve,  842 
Arytfeno-epiglottic  folds,  1104 
Arytseno-epiglottideus,    inferior, 

1107 

superior,  1107 
Arytenoid  cartilages,  1102 
glands,  1108 
muscle,  1106 
Arytenoideus  rectus,  1106 


Ascending  colon,  1035 
cutaneous  nerve,  862 
frontal  artery,  572 
oblique   muscle   of   abdomen, 

451 

palatine  artery,  556 
parietal  artery,  572 
pharyngeal  artery,  558 

surgical  anatomy  of,  558 
Astragalus,  303 

development  of,  308 
Atlanto-axial  articulation,  323 

-odontoid  joint,  323 
Atlas,  146 

development  of,  153 
Atrabiliary  capsules,  1137 
Atrium,  1088,  1091,  1119 

bursse  omentalis,  974,  994, 1012, 

1052 

Attic,  917 

Attollens  aurem  muscle,  394 
Attrahens  aurem  muscle,  393 
Auditory  artery,  927 
canal,  914 
meatus,  external,  177 

internal,  177 
nerve,  815 

surgical  anatomy  of,  816 
process,  177 
veins,  927 
vesicle,  124 
Auricle  of  ear,  912 
cartilage  of,  912 
ligaments  of,  913 
of  heart,  left,  1091 
appendix  of,  1091 
septum,  1092 
sinus  of,  1091 
right,  1088 

openings  in,  1088 
septum  of,  1089 
sinus  of,  1088 
valves  in,  1089 
Auricular  artery,  anterior,  559 

posterior,  557 
fissure,  179,  214 
lymphatic  glands,  681 
nerve  of  vagus,  821 

posterior  from  facial,  813 
surface  of  sacrum,  157 
veins,  anterior,  652 

posterior,  653 

Auricularis  anterior  muscle,  393 
magnus  nerve,  831 
posterior  muscle,  394 
superior  muscle,  394 . 
Auriculo-temporal  nerve,  806 
Auriculo-ventricular  groove  of 

heart,  1087 
opening,  left,  1092 

right,  1089 

Axes  of  the  pelvis,  282 
Axilla,  587 

dissection  of,  466 
surgical  anatomy  of,  589 
Axillary  artery,  589 
branches  of,  592 
lymphatic  glands,  684 
peculiarities  of,  590 
space,  587 

surface-marking  of,  591 
surgical  anatomy  of,  591 
vein,  664 

surgical  anatomy  of,  665 
Axis,  or  second  vertebra,  147 


Axis,  cerebro-spinal,  693 

cceliac,  610 

development  of,  154 

thyroid,  584 

Axis-cylinder  of  nerve-tubes,  71 
Azygos  artery,  articular,  641 

uvula?  muscle,  422 

veins,  667 

B. 

Bacillary  layer  of  retina,  901 
Back,  muscles  of,  fifth  layer,  437 
first  layer,  428 
fourth  layer,  434 
second  layer,  431 
third  layer,  432 
Ball-and-socket  joint.    SeeEnar- 

throdia. 
Bartholin,  duct  of,  948 

glands  of,  1165 
Basal  ridge,  933 
Base  of  brain,  784 
of  skull,  208 

external  surface,  211 
internal  surface,  208 
Basement  membranes,  49 
Basi-hyal  of  hyoid  bone,  227 
Basilar  artery,  583 
groove,  720,  721 
membrane  of  cochlea,  924 
process,  165 
suture,  207 
Basilic  vein,  663 
median,  663 

Basis  vertebrarum  venae,  668 
Bauhin,  valve  of,  1033 
Beaunis  et  Bouchard,  Table  of 
Development    of    Foetus 
from,  141 
Belly-stalk,  113 
Bend  of  elbow,  593 
Biceps  flexor  cruris,  518 

cubiti,  476 
Bicipital  fascia,  476 
groove,  248 
ridges,  248 
tuberosity,  259 
Bicuspid  te'eth.  933 
Biliary  ducts,  1062,  1063 
Biventer  cervicis  muscle,  437 
Bladder,  1139 
exstrophy  of,  959 
female,  1166 
ligaments  of,  1142 
surface  form  of,  1144 
surgical  anatomy  of,  1145 
trigone  of,  1144 
vessels  and  nerves  of,  1144 
Blastodermic  vesicle,  103 
Blood,   circulation  of,  in    adult, 

1087 

in  foetus,  1097 
gases  of,  37 

general  composition  of,  33 
Blood-cells,  127 
Blood-corpuscles,  34 
Blood-crystals,  37 
Blood-globules,  34 
Blood-plaques,  36 
Blood-vessels,  of  brain,  573 
Boehdalek,  cavity,  955 
ganglion  of,  802,  804 
on   musculus  triticeo - glossus, 
1107,  note. 


IXDEX. 


1215 


Body  of  lateral  ventricle,  757 

perineal,  1164 

of  a  tooth,  932 

of  a  vertebra,  145 
Bone,  animal  constituent  of,  58 

apophysis  of,  144 

articular  lamella  of,  313 

canaliculi  of,  56 

cancellous  tissue  of,  54 

cells,  58 

chemical  analysis  of,  58 

compact  tissue  of,  54 

development  of,  59 

diploe  of,  144 

earthy  constituent  of,  59 

eminences  and  depressions  of, 
144 

epiphysis  of,  144 

growth  of,  63 

Haversian  canals  of,  56 
systems  of,  56 

inorganic  constituent  of,  59 

lacunae  of,  58 

lamellae  of,  57 

lymphatics  of,  56 

marrow  of,  55 

medullary  canal  of,  54,  143 

membrane  of,  54 

microscopic  appearances.  55 

nerves  of,  55 

organic  constituent  of,  59 

ossific  centres,  number  of,  64 

ossification  of,  60 

periosteum  of,  54 

spongy  tissue  of,  143 

structure  of,  54 

vessels  of,  55 

Bones,  forms  of,  viz.  lone,  flat, 
short,  mixed,  irregular, 
143 

number  of,  in  the  body,  143 
Bones  or  bone,  astragalus,  303 

atlas.  146 

axis.  147 

calcaneum.  299 

carpal,  i 

clavicle.  238 

coccyx,  159 

craniaL  164 

cuboid,  303 

cuneiform,  of  carpus.  264 

of  tarsus,  305 

descriptive  anatomy  of,  143 
ear,  916 
ethmoid,  185 
facial,  188 
femur,  2-4 
fibula.  I'.-: 
frontal.  170 
hand,  262 
humerus,  248 
hyoid,  227 
iliun 

incus,  919 
inferior  maxillary,  201 

turbinated,  200" 
innominatt 
ischium,  272.  275 
lachrymal,  195 
lesser  lachrymal,  195 
lingual.  _ 
magnum,  266 
malar,  196 
malleus,  919 
maxillary,  inferior,  201 


Bones  or  bone,  maxillary,  supe-  '  Broad  ligament  of  liver,  1053 


rior,  189 
metacarpal,  267 
metatarsal,  306 
nasal.  189 
navicular,  304 
occipital,  164 
palate,  197 
parietal,  168 
patella,  291 
pelvic.  279 
phalanges  of  foot,  308 

of  hand,  270 
pisiform,  264 
pubic,  277 
radius,  259 
ribs,  232 
sacrum,  155 
scaphoid,  262 
scapula,  242 
semilunar,  266 
sesamoid,  312 
sphenoid,  180 
sphenoidal,  spongy,  184 
stapes,  919 
sternum,  228 
superior  maxillarv,  189 
tarsal,  299 
temporal,  173 
tibia,  293 
trapezium,  266 
trapezoid,  266 
triqnetral,  188 
turbinate,  inferior,  200 

middle,  186 

superior,  187 
tympanic,  179 
ulna,  254 
unciform,  267 
vertebra  prominens,  149 
vertebra?,  cervical,  145 

dorsal,  149 

lumbar.  151 
vomer.  201 
Wormian,  188 
Bowman,  glands  of.  889 

sarcous  elements  of,  66 
Bowman's  capsule,  1 1 29 
Brachial  artery,  593 

branches  of,  596 

peculiarities  of,  596 

surface  marking  of,  595 

surgical  anatomy  of,  595 
lymphatic  glands,  684 
plexus,  834 

surgical  anatomy  of,  844 
region,    anterior,  muscles    of, 
479,  481 

posterior,  muscles  of,  485 
veins,  664 
Brachialis  anticus  muscle,  477 


Brachio-cephalic    artery. 
Innominate. 

Brachiura,  anterior,  743 
posterior,  743 

Brain,  706 

development  of,  120 
general  anatomy  of,  93 
membranes  and  dissection,  702 
subdivision  into  parts,  706 

Branchial  clefts,  118 

Breasts.  1178 

Bregm; 

Brim  of  pelvis.  281 

Broad  ligament,  988 


of  uterus,  1169 
Broca,  area  of,  783 
Bronchi,  1110 

dorsal,  1110 

right  and  left,  1108,  1109 

septum  of,  1111 
in  lung,  1119 

subdivisions   of   according   to 
Aeby,  1119 

ventral,  IllO 
Bronchial  arteries,  606,  1120 

lymphatic  glands,  692 

septum,  1111 

tubes.     See  Bronchi. 

veins,  668,  1120 
Bronchiole,  1119 
Bronchus,  accessorv,  1110 

eparterial,  1108,*1109 

heart,  1110 

hyparterial,  1108,  1109 
Brunner's  glands,  1024 
Bubonocele,  1189 
Buccal  arteries,  562 

cavity,  930 

development  of,  133 

glands,  931 

lymphatic  glands,  681 

nerve  of  facial,  815 

of  inferior  maxillary,  806 
Buccinator  muscle,  402 
Bulb,  artery  of,  625 

of  corpus  cavernosum,  1151 
spongiosum,  1152 

olfactory,  782,  788 

posterior  cornu,  758 

spinal,  708 
Bulbi  vestibuli,  1166 
Bulbous  portion  of  the  urethra, 

1147 

Bundle  of  Yieq  d'Azyr,  748,  750 
Burdach's  column,  700 
Bursa  omentalis,  974,  981,  993 
Bursae  of  knee,  372 

mncosae,  314 

of  shoulder,  346 

synovia?.  314 
Bursal  synovial  membranes,  314 

c. 

Caeca,  types  of,  1031 

Caecum,  1030 

Calcanean  arteries,  external,  647 

internal,  647 
Calcaneo-astragaloid    ligaments, 

381 

Calcaneo-cuboid  ligaments,  381 
Calcaneo-navicular      ligaments, 

382 
Calcaneum,  299 


See    Calcaneus  scriptorius,  724 
Calcar  avis,  758 
femorale,  289 
Calices  of  kidney,  1128 
Camper's  ligament.     See  Trian- 
gular Ligament  of  Urethra, 
Canals  or  canal,  accessory  pala- 
tine, 197 
alimentary,  929 
anal,  1038,  1040 
anterior,  for  Arnold's  nerve, 

178 

dental,  191 
palatine,  194 


1216 


INDEX. 


Canals  or  canal,  auditory,  914 

carotid,  178 

for  chorda  tympani,  916 
of  cochlea,  923 

central,  of  modiolus,  923 

crural,  1197 

dental,  posterior,  190 

ethmoidal,  172 

Haversian,  of  bone,  56 

of  Huguier,  175 

incisive,  213 

inferior  dental,  203 

infraorbital,  191 

inguinal,  1185 

intestinal,  1008 

for     Jacobson's      (tympanic) 
nerve,  178 

lachrymal,  910 

of  modiolus,  923 

naso-palatine,  194 

of  Nuck,  1162,  1177 

of  Petit,  905 

palatine,  anterior,  194 
posterior,  191 

portal,  1057 

pterygo-palatine,  182 

sacral,  157 

of  Schlemm,  893 

semicircular,  922 

spermatic,  1185 

of  spinal  cord,  121 

spiral,  of  cochlea,  923 

of  Stilling,  903 

temporo-malar,  197 

for      tensor      tympani,     179, 
895 

vertebral,  162 

Vidian,  183 

of  Wirsung,  1070 
Canaliculi  of  bone,  58 
Canalis  centralis  modioli,  924 

spiralis  modioli,  924 
Cancellous  tissue  of  bone,  53 
Canine  eminence,  190 

fossa,  190 

teeth,  933 

Canthi  of  eyelids,  907 
Capillaries,  82 

structure  of,  83 
Capitellum  of  humerus,  251 
Capsular  ligament  of  hip,  362 
of  knee,  368 
of  shoulder,  346 
of  thumb,  359 
of  vertebrae,  321 

Capsule,  external,  of  brain,  759, 
760 

in  foetus,  124 

of  Glisson,  982,  992 

internal,  of  brain,  759,  760 

of  kidney,  1128 

of  lens,  904 

of  Tenon,  890 
Capsules,  suprarenal,  1137 
Caput  cornu  posterioris,  700 

gallinaginis,  1146 
Cardia,  999 
Cardiac  lymphatics,  692 

nerves,  871 

from  pneumogastric,  822 

plexus  of  nerves,  deep,  874 
superficial,  874 

veins,  677 

Cardinal  veins,  foetal,  131 
Carotid  artery,  common,  547 


Carotid  artery,  common,branches 
of  (occasional),  549 
peculiarities  of,  549 
surface-marking  of,  549 
surgical  anatomy  of,  549 
external,  551 
branches  of,  552 
surface-marking  of,  551 
surgical  anatomy  of,  551 
internal,  565 
branches  of,  568 
peculiarities  of,  567 
surgical  anatomy  of,  568 
tubercle,  146 
branch  of  Vidian,  804 
canal,  178 
ganglion,  869 
groove,  181 
plexus,  869 
triangle,  anterior,  563 
inferior,  563 
superior,  564 
Carpal  arteries,  from  radial,  599 

from  ulnar,  603 
•  ligaments,  357 
Carpo-metacarpal    articulations,  ' 

359 
Carpus,  262 

articulations  of,  357 
development  of,  271 
surface  form  of,  270 
surgical  anatomy  of,  271 
Cartilage,  articular,  52 
arytenoid,  1102 
of  auricle,  912 
of  bronchi,  1110 
cellular,  51 
costal,  52,  236 
cricoid,  1101 
cuneiform,  1102 
descriptive  anatomy  of,  51 
of  ear,  912,  914,  918 
ensiform,  228 
of  epiglottis.  1102 
fibro-,  52,  53 
hyaline,  51 

intercellular  substance  of,  51 
of  larynx,  1 100 
of  the  nose,  885 
of  the  pinna,  912 
reticular,  53 
of  Santorini,  1102 
semilunar,  of  knee,  370 
of  septum  of  nose,  885 
structure  of,  52 
tarsal,  908 
temporary,  54 
thyroid,  1200 
of  trachea,  1110 
white  fibro-,  52 
of  Wrisberg,  1202 
yellow  elastic,  53 
xiphoid,  228 
Cartilage-cells,  51 
Cartilage-lacunae,  51 
Cartilagines  minores,  886 
Cartilage  triticea,  1103 
Caruncula  lachrymalis,  909 
Carunculse  myrtiformes,  1165 
Cauda  equina,  693 
Caudate  lobe  of  liver,  1052 
Cava,  inferior,  673 

peculiarities  of,  674 
superior,  667 
Cavernous  body,  artery  of,  625 


Cavernous  groove,  181 

nerves  of  penis,  878 

plexus,  869 

sinus,  659 

nerves  in,  810 

surgical  anatomy  of,  659 
Cavity,  abdominal,  955,  959 

body,  955 

cotyloid,  278 

glenoid,  245 

pelvic,  955 

of  pelvis,  281 

pericardial,  955 

pericardio-thoracic,  955 

pleural,  955 

sigmoid,  256 
Cavum  Meckelii,  797 

Ketzii,  1141 
Cells,  38 

of  bone,  58 

definition  of,  38 

division  of,  direct,  41 
indirect,  39 

ethmoidal,  186 

fusiform,  787 

hepatic,  1060 

mastoid,  176 

mitral,  788 

polymorphous,  787 

prickle,  43 

pyramidal,  787 

reproduction  of,  40 

structure  of,  38 

wall,  41 

Cement  of  teeth,  941 
formation  of,  941 
Central  canal  of  cord,  698 

ganglionic  vessels  of  brain,  574 

lobule,  729 

Centres  of  ossification,  63 
Centrifugal  nerve-fibres,  75 
Centripetal  nerve-fibres,  75 
Centrosomes,  40 
Centrum  ovale  majus,  756 
minus,  755 

vertebra,  145 
Cephalic  vein,  63 
median,  663 

Cerato-hyal  of  hyoid  bone,  227 
Cerebellar  arteries,  anterior,  583 
inferior,  583 
superior,  583 

column,  700 

tract,  700 
direct,  710 

veins,  657 
Cerebellum,  725,  737 

gray  matter,  735-737 
cortical,  735-737 

peduncles,  inferior,  712 
middle,  720 
superior,  720 

weight  of,  725 

white  matter,  733-735 
Cerebral  arteries,  570 
anterior,  570 
middle,  572 
posterior,  583 

localization,  789-791 

lymphatics,  682 

topography,  789-791 

veins,  656 

vesicles,  706 
Cerebro-spinal  nxis,  693 

nerves,  69 


IXDEX. 


1217 


Cerebro-spinal  system,  69 
Cerebrum,  706 

gray  matter  of,  73 
Cervical  artery,  ascending,  584 

superficia 
fascia,  4<.>7 

ganglion,  inferior,  STu 
middle,  872 
superior,  869 
lymphatic  glands,  deep,  684 

superficial,  684 
nerves,  828 

anterior  divisions  of,  830 
posterior  divisions  of,  828 
plexus,  831 

deep  branches  of,  833 
Interior  branches  of,  823 
superficial  branches  of,  831 
veins,  deep,  655 
vertebrae.  145 

surgical  anatomy  of,  327 
Cervicalis  ascendens  muscle,  436 
Cervicis  princeps,  -557 

profunda 

Cervico-facial  nerve.  >1~> 
Cervix  cornu  posterioris.  701 

uteri,  1171 
Chalice  cells.  43 
Chambers  of  the  eye,  903 
Check  ligament.-. 
Cheek,  muscles  of,  401 
Cheeks,  structure  of,  931 
Chest,  muscles  of  front.  4I?>7 

of  side,  470 
surface  form  of,  236 
surgical  anatomy  of,  237 
Chiasma,  or  optic  commissure, 

793 

Chondro-glossus  muscle,  416 
Chondro-sternal  ligaments,  334 
Chondro-xiphoid  ligament,  334 
Chorda  dorsal  is.  107,  115,  96S 

tympani  nerve,  812,  921 
Chordse    tendineae,  of    left   ven- 
tricle, 1092 

of  right  ventricle,  1090 
vocales,  1 1  '.'5 
Willisii,  657 
Chorion.  112 
Choroid  arteries,  anterior,  573 

posterior,  ">S4 
coat  of  eve,  894 
plexus,  766.  769,  770 
of  fourth  ventricle.  740 
of  lateral  recess.  740 
of  ventricle,  749 
veins  of  brain,  656 
Choroidal  fissure.  123 
Chyle,  38 

Chyli  receptaculum,  680 
Cilia,  or  eyelashes,  907 
Ciliary  arteries,  570,  905 
ganglion,  799 
muscle.  898 
nerves,  long,  799 

short,  800 

processes  of  eye,  895 
Cinffiilura,  786,  933 
Circle  of  Willis,  584 
Circular  sinus,  660 
Circulation   of    blood   in   adult, 

1087 

in  foetus.  1097 
Circiimanal  glands,  1040 
Circumduction,  322 


Circumferential     fibro-cartilage, 

53 

Circumflex  artery  of  arm,  ante- 
rior, 593 
posterior,  593 
of  thigh,  external,  636 
internal,  636 

iliac  artery,  630 
superficial,  635 

nerve,  839 

surgical  anatomy  of,  844 

vein,  672 

superficial,  670 

Circumflexus  palati  muscle,  422 
Circumvallate  papillae  of  tongue, 

880 

Clava.  711.  714,  715 
Clavicle.  238 

development  of.  241 

fracture  of,  499 

peculiarities  in  sexes,  241 

surface  form  of.  241 

surgical  anatomy  of.  241 
Cleft  palate,  423 
Clinoid  processes,  anterior,  183 
middle,  180 
posterior,  181 
Clitoris,  1164 

fnenurn  of,  1164 

lymphatics  of,  689 

muscles  of.  465,  1165 

prepuce  of,  1165 
Clivus,  181.  730 
C«K.-cygeal  artery,  626 

gland,  617 

nerves,  858 

Coccygeus  muscle,  460 
Coccyx,  159 

development  of,  160 
Cochlea.  922 

aqueduct  of,  178 

arteries  of,  927 

central  axis  of,  923 

cupola  of,  923 

denticulate  lamina  of,  924 

infundibulum  of,  923 

lamina  spiralis  of.  923 

nerves  of,  928 

scala?  of,  924 

spiral  canal  of,  923 

veins  of.  928 
Cochlear  artery,  928 

nerve 

Cochleariform  process,  179,  916 
Coeliac  axis.  610 

plexus,  876 
Colic;t  dextra  artery,  614 

media,  614 

?inistra,  614 

Collateral    branches    of   nerve 
fibres,  70 

circulation.     See  Surgical  An- 
atomy of  each  A  rtery. 

ulnaa  nerve,  843 
Collaterals,  700,  787 
Collecting     tubes     of     kidney, 

1130 
Colliculus  nervi  optici,  898 

seminal  is,  1146 
Colon,  1035 

Colostrum  corpuscles,  1179 
Colotomy,  1046,  1047 
Coliiraella  cochleae,  923 
'•  Column  of  Burdach,  700 

cerebellar,  700 


Column,  Clarke's   vesicular,   of 

spinal  cord,  701 
ofGoll,  700 
mixed  lateral,  700 
of  Morgagni,  1042 
vesicular,  of   anterior   cornu, 

701 
Columnae  ani,  1042 

carneap  of  left  ventricle,  1093 
fomicis,  anterior  pillars,  761 

of  right  ventricle,  1090 
papillaries,  1090,  1093 
Columns  of  abdominal  ring,  1182 
of  spinal  cord,  697,  700 
antero-lateral,  697,  700 
postero-lateral,  697,  700 
postero-median,  697,  700 
of  vagina.  1168 
Conies  nervi  ischiadici  artery,  626 

phrenici  artery,  586 
Commissures  of  brain,  anterior, 

753,  762,  786 
middle  or  soft,  751 
posterior,  748 
of  Guddeu,  793 
optic,  752 

of  spinal  cord,  697,  698 
gray,  698 
white,  697 
Common  ligaments  of  vertebra?, 

319 

dental  germ,  938 
Communicans  hypoglossi  nerve, 

833 

peronei,  865 
Communicating  artery  of  brain, 

anterior,  572 
posterior,  573 
from  dorsalis  pedis,  643 

ulnar,  604 

Compact  tissue  of  hone,  54.  143 
Complexus  muscle,  437 
Compressor  narium  minor,  399 
nasi,  399 

sacculi  larvngis,  1107 
urethne,  464 

in  female,  1208 
Conarium,  748 

Conception,  where  effected,  100 
Concha,  912 

Condyles  of  bones.     See  Bones. 
Condyloid  articulations,  316 
process.  204 
veins,  posterior,  657 
Congenital   fissures  in   cranium, 

188 

hernia,  1189 
Conglobate  glands,  679 
Coni  vasculosi,  1042 
Conjoined  tendon  of  "internal  ob- 
lique   and    transversalis, 
451,  1184 
Conjunctiva,  908 
Connecting  fibro-cartilages.  53 
Connective  tissue,  45 
development  of,  48 
lymphatics  of,  48 
lympboid,  48 
mucoid,  48 
nerves  of,  48 
retiform,  48 
Conoid  ligament,  344 

tubercle,  239 

Constrictor  inferior  muscle,  419 
isthmi  faucium,  420 


1218 


INDEX. 


Constrictor  inedius  muscle,  420 
superior  muscle,  420 
urethrse,  464 

Contents  of  abdomen,  959,  999 
Contractile  fibre-cells,  68 
Conus  terminalis,  693 
Convolutions,  772,  773 
angular,  777 
annectant,  777,  779 
frontal,  775 
ascending,  775 
inferior,  775,  776 
superior,  775,  776 
hippocampal,  781 
infracalcarine,  780 
marginal,  780 
occipital,  777 
orbital,  775 
parietal,  776,  777 
ascending,  776,  777 
superior,  777 
supramarginal,  777 
temporal,  778,  779,  781 
Coraco-acromial  ligament,  344 
Coraco-brachialis  muscle,  476 

nerve,  837,  839 

Coraco-clavicular  ligament,  343 
Coraco-humeral  ligament,  346 
Coracoid  ligament,  345 
process,  245 

fracture  of,  500 
Cord,  spermatic,  1155 

umbilical,  115 
Cords,  vocal,  1103,  1105 
Cordiform  tendon  of  diaphragm, 

445 
Corium  of  skin,  89 

of  tongue,  880 
Cornea,  892 
Corneal  corpuscles,  893 

spaces,  893 
Cornu  Ammonis,  763 
formation  of,  788 
lateral  ventricles,  anterior,  758 
descending,  758 
middle,  758 
posterior,  758 
Cornua  of  the  coccyx,  159 
of  hyoid  bone,  227 
of  lateral  ventricles,  755 

radiata,  760 
of  the  sacrum,  156 
Corona  glandis,  1150 

radiata,  785 
Coronal  suture,  206 
Coronaria  ventricnli  artery,  611 
Coronary  arteries  of  lip,  556 
of  heart,  542 

peculiarities  of,  543 
ligament,  379,  981,  988 

of  liver,  1053 
ligaments  of  knee,  371 
plexus,  anterior,  875 

posterior,  874 
sinus,  677 

opening  of,  1088 
valve,  678,  1090 
Coronoid  depression,  251 
process  of  jaw,  204 

of  ulna,  254 
Corpora  albicantia,  750 
Arantii,  1091 
cavernosa  penis,  1151 

crnra  of,  1151 
geniculata,  743 


Corpora  geniculata,  external,  743, 

744,  746 

internal,  743,  744,  746 
mamillaria,  750 
quadrigemina,  743 
third  ventricle,  751 
veins  of,  657 

Corpus  callosum,  753,  772,  786 
fimbriatum,  763,  768 
genu  of,  756,  758 
peduncles  of,  757 
rostrum  of,  756 
splenium  of,  757 
cavernosum,  artery  of,  525 
dentatum  of  cerebellum,  737 
fimbriatum,  759 
Highmorianum,  1157 
spongiosum,  1152 
striatum,  759 
Corpuscles,  blood-,  34 
colored,  34 
development  of,  126 
of  Herbst,  77 

Malpighian,  of  kidney,  1129 
of  Purkinje,  736 
of  spleen,  1080 
tactile,  76 
of  Vater,  77,  note. 
white,  35 
Corrugator  cutis  ani,  458,  1040 

supercilii  muscle,  395 
Corset-liver,  1053 
Cortex  of  hemispheres,  786 
layers,  787 
white  centre,  787 
Corti,  membrane  of,  924 
organ  of,  925 
rods  of,  925 
Cortical  arches,  1129 
arteries  of  brain,  574 
columns,  1129 
substance  of  kidney,  1129 

of  suprarenal  capsules,  1138 
Costal  cartilages,  52,  236 
connection  with  ribs,  334 
process,  146 
vertebral  ligaments,  330 
Costo-chrondral  articulation,  335 
Costo-clavicular  ligament,  341 
Costo-colic  ligament,  1077 
Costo-coracoid  fascia,  468 

ligament,  468 
Costo-phrenic  sinus,  1114 
Costo-transverse       articulations, 

331 

Costo- vertebral  articulations,  330 
Cotunnius,  nerve  of,  805 
Cotyloid  cavity,  278 
ligament,  364 
notch,  278 

Coverings  of  direct  inguinal  her- 
nia, 1190 

of  femoral  hernia,  1199 
of  oblique,  1187 
of  testis,  1156 

Cowper's  glands,  1150,  1205 
Cranial  bones,  163 

articulations  of,  208 
fossa;,  208 
nerves,  792 

development  of,  117 
eighth,  815 
eleventh,  823 
fifth,  796 
first  pair,  792 


Cranial  nerves  :  fourth,  796 
ninth,  816 
second,  793 
seventh,  811 
sixth,  810 
tenth,  819 
third,  794 
twelfth,  823 
sutures,  205 
Cranium,  164 

congenital  fissures  in,  188 
development  of,  187 
lymphatics  of,  682 
Cremaster  muscle,  452 
formation  of,  1184 
Cremasteric  artery,  629 

fascia,  452 

Crescents  of  Gianuzzi,  948 
Crest,  frontal,  171 
of  ilium,  272 
lachrymal,  195 
nasal,  189 
occipital,  164 

internal,  166 
supra-mastoid,  174 
turbinated,  of  palate,  198 
of  pubes,  277 
of  the   superior  maxillary, 

192 

of  tibia,  293,  294 
Cribriform  fascia,  1193 
plate  of  ethmoid,  185 
Crico-arytenoid  ligament,  1104 
Crico-arytenoideus  lateral  is 

muscle,  1106 
Crico-thyro-arytenoid    ligament, 

1103 

Crico-thyroid  artery,  552 
ligament,  1104 
membrane,  1103 
muscle,  1105 

Crico-tracheal  ligament,  1104 
Cricoid  cartilage,  1101 
Crista  falciformis,  177,  928 
galli,  185,  208 
pubis,  277 
terminalis,  1089 
vestibuli,  921 

Crossed  pyramidal  tract,  710 
Crown  of  a  tooth,  933 
Crucial  anastomosis,  636 
ligaments  of  knee,  369 
Cruciform  ligament,  324 
Crura  of  corpora  cavernosa,  1151 
of  diaphragm,  445 
of   fornicis,    posterior  pillars, 

761 
Crural  arch,  450,  1195 

deep,  457,  1197 
canal,  1197 
nerve,  anterior,  855 

surgical  anatomy  of,  866 
ring,  1198 
sheath,  1196 
septum,  1198 
Crureus  muscle,  510 
Crus  cerebri,  740,  742 

penis,  1151 
Crusta,  741,  742,  785 

petrosa  of  teeth,  936 
Cryptorchismus,  1162 
Crypts    of     Lieberkiihn,     1024, 

1029 

Crystalline  lens,  904 
Crystals,  blood,  37 


IXDHX. 


1219 


Cuboid  bone,  303 

Cul-de-sac  of  Douglas,  981 

Culmen,  730 

Cuneiform  bone,  foot,  external, 

306 

internal.  305 
middle,  305 
hand,  264 
cartilages,  1102 
Cupola  of  cochlea,  923 
Curvatures  of  the  spine,  161 
Curves  of  rectum,  1039 
Cuspidate  teeth.  933 
Cutaneous  branches  of  accessory 

obturator. 

of  anterior  tibial  nerve,  865 
of  arm,  inusculo-cutaneous. 

839 

internal.  - 
lesser  internal.  V40 
of  buttock  and  thigh,  862 
of  cervical  plexus,  831 
of  circumflex,  839 
of  dorsal  nerve  of  penis,  861 
of  dorsal  nerves,  848 
of  external  popliteal,  865 
of  ilio-hypogastric.  Sol 
of  ilio-inguinal,  851 
of    inferior     luemorrhoidal 

ner\v 

of  inguinal  region,  1193 
of  intercostal  nerves,  848 
of  internal  popliteal,  863 
of  ischio-reetal  region,  1201 

from  obturator.  ^'A 
of  lesser  sciatic  nerve,  862 
of  lumbar  nerves.  849 
of  median.  >41 
of  musculo-spiral,  844 
of  patella,  856 
of  perineal  nerve,  861 
of  plantar  nerv. 
of  posterior  tibial,  863 
of  radial,  844 
of  sacral  nerve- 
of  thigh,  external,  852 
internal,  856 
middle,  856 
of  ulnar  nerve,  S42 
Cuticle  of  skin.  89 
Cutic'ula  dentis,  940 
Cutis  vera.  ','1 
Cnvier.  ducts  of.  131 
Cystic  arterv.  till 
"duct.  1064.  1065 
valve  of,  1065 
plexus  of  nerves,  877 
vein- 

D. 

Dartos.  1154 
Decidua.  114 

reflex  a,  114 

serotina,  114 

vera,  114 

Deciduous  teeth,  932 
Declive.  730 
Deciissation  of  fillet,  719 

of  optic  nerves,  794 

of  pyramids.  710 
Deep  crural  arch.  457,  1197 

palmar  arch.  598 

perineal  fascia,  463,  1204 
Deferent  artery,  622 


Deglutition,  actions  of,  423 
Deltoid  aponeurosis,  471 

muscle,  471 

tubercle,  239 

Demilunes  of  Heidenhain,  948 
Demours,  membrane  of,  892 
Dendrites,  70,  737,  787,  788 
Dental  artery,  anterior.  562 
inferior,  561 
posterior,  562 

canal,  anterior,  191 
inferior,  203 
posterior.  190 

furrow,  938 

germ,  common,  938 
special,  939 

groove,  938 

lamina,  938 

nerves,  anterior,  802 
inferior,  807 
middle,  802 
posterior,  802 

pulp,  935 

ridges,  938 

sacs,  940 

tubuli,  936 

vein,  inferior,  653 
Dentate  nucleus,  710,  717 
Denticulate   lamina   of  cochlea, 

924 
Dentinal  sac,  942 

sheath,  937 
Dentine,  935 

formation  of,  941 
Depressions      of       Pacchionian 

bodies,  169 
Depressor  alae  nasi,  399 

anguli  oris,  401 

epiglottidis,  1107 

labii  inferioris.  401 
Derma,  or  true  skin,  91 
Descemet,  membrane  of,  892 
Descendens,    hypoglossi    nerve, 

825 
Descending  aorta,  605 

colon,  1035 

oblique   muscle   of   abdomen, 

44< 

Descent  of  testicle,  1161 
Development  of  alimentary  canal 
and  its  appendages,  132 

arteries,  128 

atlas,  153 

axis,  154 

bone,  59 

carpus,  271 

clavicle,  241 

coccyx,  160 

cranium,  117,  187 

ear,  124 

ethmoid,  187 

eye,  122_ 

face,  117 

femur,  290 

fibula,  298 

foot,  308 

frontal  bone,  173 

genital  organs,  137 

hand 

heart,  120 

humertis.  252 

hyoid  bone,  227 

inferior  turbinated  bone,  200 

lachrymal  bone,  196 

lens,  122 


Development  of  lower  jaw,  204 

lumbar  vertebrae,  152 

malar  bone,  197 

mammae,  125 

metacarpus,  272 

metatarsus,  309 

muscles,  126 

nasal  bone,  189 

nervous  centres,  120 

nose,  125 

occipital  bone,  167 

os  innominatum,  278 

Organs,   Chronological   Table 
of,  141 

palate,  119 
bone,  199 

parietal  bone,  170 

patella.  292 

peritoneum,  967 

permanent  teeth,  942 

phalanges  of  foot,  309 
of  hand,  272 

radius.  260 

ribs,  235 

sacrum,  158 

scapula,  246 

seventh  cervical,  154 

skin,  125 

sphenoid,  184 

spine,  115 

sternum,  231 

superior  maxillary  bone,  194 

tarsus,  308 

temporal  bone,  179 

temporary  teeth,  938 

tibia,  296' 

ulna,  258 

veins,  130 

vertebrae,  152 

vomer,  201 

Wormian,  188 
Diameters  of  pelvis,  280 
Diaphragm,  444,  995 

development  of,  134 

lymphatics  of,  692 
Diaphysis,  64 
Diarthrosis,  315 
Digastric  fossa,  176 

muscle.  413 

nerve,  from  facial,  813 
Digestion,  organs  of,  930 
Digital  arteries  from  plantar,  647 
from  ulnar,  604 

fossa,  285,  1156 

nerves,  from  median.  *41 
from  radial,  844 
from  ulnar,  842 
Dilatator  naris.  anterior,  399 

posterior,  399 
Diploe,  144 

veins  of,  655 

Direct  inguinal  hernia,  1189 
course  of,  1190 
coverings  of,  1190 

pyramidal  tract,  710 
Discus  proligerus,  100,  1177 
Disks.  bloodT  36 

Dissection  of  abdominal  muscles, 
447 

arm.  475 

auricular  region,  393 

axilla,  466 

back,  428 

epicranial  region,  391 

eye,  894 


1220 


INDEX. 


Dissection  of  face,  394 
femoral  hernia,  1190 
foot,  528 
forearm,  478 
gluteal  region,  514 
hand, 489 

heart,  left  auricle,  1091 
left  ventricle,  1092 
right  auricle,  1088 
right  ventricle,  1089 
hernia,  femoral,  1191 

inguinal,  1180 
iliac  region,  503 
inferior  maxillary  region,  400 
infrahyoid  region,  411 
inguinal  hernia,  1180 
intermaxillary  region,  401 
ischio-rectal  region,  1201 
leg,  520 

lingual  region,  415 
neck,  406 
orbit,  396 

palatal  region,  421 
palm  of  hand,  490 
palpebral  region,  394 
pancreas,  1067 
pectoral  region,  466 
perineum,  1201 
pharynx,  419 
pterygoid  muscles,  404 
radial  region,  483 
scalp,  391 
sole  of  foot,  529 
spinal   cord   and    membranes, 

693 

suprahyoid  region,  413 
temporal  muscle,  403 
thigh,  back  of,  518 
front  of,  505 
inner  side  of,  511 
Diverticulum,  Vateri,  1070 
Division  of  cells,  39 
direct,  41 
indirect,  41 

Dorsal  artery  of  penis,  624 
nerve  of  penis,  861 
nerves,  845 

anterior  divisions  of,  846 
peculiar,  848 
posterior  divisions  of,  845 
roots  of,  845 
vein  of  penis,  673 
vertebrae,  149 

peculiar,  151 

Dorsales  pollicis  arteries,  600 
Dorsalis  chorda,  968 
hallucis  artery,  644 
indicis,  600 
lingua?,  553 
pedis,  643 

branches  of,  644 
peculiarities  of,  643 
surface  marking  of,  643 
surgical  anatomy  of,  643 
scapulae,  592 
Dorsi-lumbar  nerve,  849 
Dorsi-spinal  veins,  668 
Dorsum  of  scapula,  243 
ephippii  or  sellse,  181 
Douglas,  pouch  of,  981,  988 

semilunar  fold  of,  455 
Ducts  or  duct,  of  Bartholin,  948 
biliary,  1062,  1063 
common  bile-,  1064 
of  Cowper's  glands,  1147 


Ducts  or  duct  of  Cuvier,  131 

cystic,  1064,  1065 

ejaculatory,  1160 

galactophorous,  1179 

of  gall-bladder,  1865 

of  Gartner,  139 

hepatic,  1057,  1063 

of  kidney,  1134 

lactiferous,  1179 

lymphatics,  681 

nasal,  911 

of  pancreas,  1070 

parotid,  945 

Kivini,  948 

seminal,  1160 

Stenson's,  946 

thoracic,  680 

vitelline,  967,  970 

Wharton's,  947 
Ductless  glands : 
spleen,  1073 
suprarenal  capsule,  1137 
thyroid,  1122 
thymns,  1124 
Ductus  arteriosus,  540,  1097 

how    obliterated    in    foetus, 
1099 

choledochus,  1064 

endolymphaticus,  921,  926 

pancreaticus,  1070 
accessorius,  1070 

Kivini,  948 

Santorini,  1070 

venosus,  Arantii,  1050 

how  obliterated,  1099 
Duodenal  fossae,  994 

glands,  1024 

loop,  969 
Duodeno-jejunal  flexure,  1008 

fossa,  995 
Duodenum,  1008 

fixation  of,  1018 

relations  of,  1011,  1014 

types  of,  1009 
Dura  mater  of  cord,  693 
peculiarities  of,  693 

E. 

Ear,  912 

arteries  of,  915,  920,  927 

auditory  canal,  914 

cochlea,  922 

internal,  or  labyrinth,  921 

membranous  labyrinth,  926 

muscles  of  auricle,  913 
of  tympanum,  918 

ossicula  of,  918 

pinna,  or  auricle  of,  912 

semicircular  canals,  922 

surface  form  of,  915 

surgical  anatomy  of,  928 

tympanum,  916 

vestibule,  921 

Earthy  constituents  of  bone,  59 
Ectoderm,  104 
Efferent  nerves,  75 
Eighth  nerve,  815 

surgical  anatomy  of,  816 
Ejaculator  seminis  muscle,  461 
Ejaculatory  ducts,  1160 
Elastic  lamina  of  cornea,  893 
Elbow,  anastomoses  around,  597 

bend  of,  593 

joint,  349 


Elbow,  surface  form  of,  352 

surgical  anatomy  of,  352 

vessels  and  nerves  of.  351 
Eleidin,  90 
Eleventh  nerve,  823 

surgical  anatomy  of,  823 
Embryo,  first  rudiments  of,  107 
Eminence   of    aquseductus   Fal- 
lopii,  917 

canine,  190 

frontal,  171 

ilio-pectineal,  277 

nasal,  171 

parietal,  168 
Eminences   and   depressions  of 

bones,  144 
Erninentia  articularis,  174 

cinerea,  724 

collateralis,  759,  765 
Emissary  veins,  661 
Enamel  epithelium,  940 

germ,  939 

neck  of.  939 

organ,  939,  940 

pulp,  940 

of  teeth,  937 

formation  of,  940 
Enarthrosis,  317 
Encephalon,  706 

weight  of,  789 
End-bulbs  of  Krause,  76 
End-plates,  motorial,  of  Kiihne, 

78 

Endolymph,  927 
Endomysium,  65 
Endoneurism,  74 
Endothelium,  44 
Ensiform  appendix,  228 
Entoderm,  104 
Epencephalon,  706 
Ependyma,  755 
Epi  blast,  104 
Epidermis,  development  of,  125 

structure  of,  89 
Epididymis,  1159 

development  of,  1 25 
Epigastric  artery,  deep,  629 
peculiarities,  630 
relation     to     femoral    ring, 

1198 

with  internal  ring,  1186 
superficial,  635 
superior,  587 

plexus,  875 

region,  955 

vein,  672 

superficial,  670 
Epigastrium,  960 
Epiglottic  glands,  1108 
Epiglottis,  1102 

tubercle  or  cushion  of,  1102 
Epimysium,  65 
Epineurium,  74 
Epiphysial  cartilage,  64 
Epiphysis,  64,  144 

cerebri,  748 
Epithelial  floor  of  ventricle,  768 

sheath  of  Hertwig,  941 

wall  of  descending  cornu,  768 
Epithelium,  41 

ciliated,  43 

columnar,  43 

enamel,  940 
external,  940 
internal,  940 


IXDEX. 


1221 


Epithelium  pavement,  42 

spheroidal   or  glandular,   43. 

1'i'trious  Organs. 
stratified,  44 
Epoophoron,  1177 
Erectile  tissue  of  penis.  1151 

it-  -tructure.  11-51 
Erector  clitoridis,  465 
penis.  4'12 
spinpe,  434 

Eruption  of  the  teeth.  V42 
Erythroblasts,  ->3 
Ethnio-frontal  suture,  208 
Ethmo-spheooidal  suture,  208 
Ethmoid  bone.  lv"> 

articulations  of,  187 
cribriform  plate  of,  1  >•"> 
development  of,  187 
lateral  masses  of,  186 
os  planum  of,  186 
perpendicular  plate  of,  186 
unciform  process  of,  186 
Ethmoidal  artery,  569 
canal,  anterior,  172 

posterior,  172 
cell-. 

notch,  172,  186 
process  of  inferior  turbinated, 

200 

spine.  ISO 
Eustachian  tube,  179,  917 

surgical  anatomy  of,  952 
valver 1089 

in  fcetal  heart,  1096 
Excretory    apparatus    of    liver, 

1063 

Expiration,  muscles  of,  444 ' 
Exstrophy  of  bladder,  959 
Extensor  brevis  digitorum  mus- 
cle, 530 
carpi  radialis  brevior,  484 

longior,  4*4 
ulnaris,  486 
coccygis,  438 
communis   digitorum   (hand), 

485 

indicis.  4>^ 

longus  digitorum  (foot),  521 
minimi  digiti,  483 
ossis  metacarpi  pollicis,  486 
proprius  hallucis,  521 

pollicis,  488 
External   abdominal    ring,    4-">7. 

1182 

annular  ligament,  529 
and    inferior    frontal    artery, 

572 

inguinal  hernia,  1186 
orbital  foramina,  183 
pterygoid  plate,  183 
spermatic  fascia,  1182 
sphincter  ani,  458 
Extrinsic  muscles  of  tongue,  417 
Eye.  890 

appendages  of,  907 
aqueous  humors  of,  903 
chambers  of,  903 
ciliary  muscle,  898 
processes  of,  895 
choroid.  894 
conjunctiva,  908 
cornea,  892 
crystalline  lens,  904 
elastica  lamina  of  cornea,  893 
hyaloid  membrane,  903 


Eye,  humors  of,  903 

"iris,  896 

Jacob's  membrane,  901 

membrana  pnpillaris,  898 

pupil  of,  896 

retina,  898 

sclerotic,  891 

surgical  anatomy  of.  905 

tunics  of,  890 

uvea  of,  896 

vessels  of  globe  of,  905 

vitreous  humors  of,  903 
Eyeball,  muscles  of,  396 

nerves  of,  905 

vessels  of,  905 
Evebrows,  907 
Eyelashes,  907 
Eyelids,  907 

cartilages  or  plates  of,  908 

Meibomian  glands  of,  908 

muscles  of,  390 

tarsal  ligament  of,  908 
Eye-teeth,  932 

F. 

Face,  arteries  of,  554 
bones  of,  163,  188 

development  of,  117 
lymphatics  of,  682 
muscles  of,  390 
nerves  of,  811 
veins  of,  650 
Facial  artery,  554 

peculiarities  of,  556 
t       surgical  anatomy  of,  556 

transverse,  559 
bones,  188 
nerve.  811 

surgical  anatomy  of,  815 
vein,  652 

surgical  anatomy  of,  652 
Falciform  ligament  of  liver,  971, 

1053 

process  of  fascia  lata,  508 
Fallopian  tubes,  1174 
development  of,  138 
fimbriated  extremity  of,  1174 
lymphatics  of,  689 
nerves  of,  1178 
structure  of,  1174 
vessels  of,  1178 

False  ligaments  of  bladder,  1143 
pelvis,  280 
ribs,  232 

Fangs  of  teeth,  932 
Fascia,  anal,  1210 
dentata,  763,  765 
Fasciae  of  arm,  475 
cervical,  deep,  407 

superficial,  407 
of  Colles,  460 
costo-coracoid,  468 
of  cranial  region,  391 
cremasteric,  452 
cribriform,  1193 
deep,  390 
dorsal,  of  foot,  530 
fibro-areolar,  its  structure,  389 
general   description   of,  388 
iliac,  503 

infundibuliform,  1186 
intercolumnar,  452,  1182 
intercostal,  441 
intermuscular,  of  aria,  475 


Fascia?,   intermuscular,   of  foot, 

529 

ischio-rectal,  1210 
lata,  1193 

falciform  process  of,  1194 

iliac  portion,  508,  1193 

pubic  portion,  508,  1194 
of  leg,  521 

deep  transverse,  524 
lumborum,  433 
of  mamma,  465 
masseteric,  403 
of  neck,  406 
obturator,  1209 
palmar,  490 
parotid,  403,  408 
pelvic,  1209 
perineal,  deep,  1204 

superficial,  1204 
plantar,  529 

of  foot,  529 

of  forearm,  478 

of  hand.  490 
propria    of    femoral     hernia 

1191 

recto- vesical,  1210 
spermatic,  450,  1182 
superficial,  389 

of  inguinal  region,  1180 

of  ischio-rectal  region,  1201 

of  thigh,  506 
temporal,  403 

of  thigh,  deep,  506 
superficial,  506 

of  thorax,  441,  466 
visceral  layer  of  pelvic,  121 
Fasciculus,  700 

longitudinal,  inferior,  786 

superior,  786 
perpendicular,  786 
of  Turck,  700 
uncinate,  786 
Fasciola  cinerea,  765 
Fat,  50 
Fat-cells,  50 
Fauces,  isthmus  of,  944 
Fecundation  of  ovum,  107 
Female  organs  of  generation  : 
bulbi  vestibuli,  1166 
carunculse  myrtiformes.  1165 
clitoris,  1164" 
development  of,  138 
fossa  navicularis,  1164 
glands  of  Bartholin,  1165 
hymen,  1165 
labia  majora,  1163 

minora,  1164 
nympha?.  1164 
uterus,  1167 
vagina,  1166 
vestibule,  1165 
Femoral  artery,  630 

branches  of,  635 

common,  631 

deep,  635 

peculiarities  of,  633 

superficial,  632 

surface  marking  of,  633 

surgical  anatomy  of,  633 
or  crural  canal,  1198 

variation  in  size  of,  accord- 
ing to  position  of  limb, 
1198 

cutaneous  nerve,  862 
hernia,  complete,  1200 


1222 


INDEX. 


Femoral    hernia,    coverings    of, 

1199 

descent  of,  1199 
dissection  of,  1191 
incomplete,  1199 
seat  of  stricture,  1200 
surgical  anatomy  of,  1191 
position  of  surrounding  parts, 

1198 
region,   muscles    of,  anterior, 

505 

internal,  511 
posterior,  518 
ring,  1198 
sheath,  1196 
spur,  289 
vein,  672 

relation    of    femoral    ring, 

1198 
Femur,  284 

articulations  of,  290 
attachment  of  muscles  to,  290 
condyles  of,  288 
development  of,  290 
fracture  of,  above  condyles,  537 

below  trochanters,  537 
head  of,  284 
neck  of,  284 
structure  of,  288 
surface  form  of,  290 
surgical  anatomy  of,  290 
trochanters  of,  285 
Fenestra  ovalis,  916 
rotunda,  916,  923 
Fenestrated  membrane  of  Henle, 

81 

Ferrein,  pyramids  of,  1131 
Fibre-cells,  contractile,  68 
Fibres,  association,  785,  786 
of  cerebellum,  735 
collateral,  700,  787 
commissural,  785,  786 
of  Miiller,  901 
of  muscle,  67 
of  nerves,  69 
peduncular,  785 
projection,  785 
Fibrin,  33 

ferment,  33 
Fibrinogen,  33 
Fibro-cartilage,  52 
circumferential,  53 
connecting,  53 
interarticular,  53 
stratiform,  53 
yellow,  53 
Fibro-cartilages,  acromio-clavic- 

ular,  343 

intervertebral,  320 
of  knee,  371 
of  lower  jaw,  329 
pubic,  340 
radio-ulnar,  355 
sacro-coccygean,  339 
Fibro-serous  membranes,  96 
Fibrous  cartilage,  52 
connective  tissue,  45 
nervous  matter,  69 
rings  of  heart,  1 094 
tissue,  white,  45 

yellow,  45 
Fibula,  297 

articulations  of,  298 
attachment  of  muscles  to,  299 
development  of,  298 


Fibula,  fracture  of,  with  disloca-  i 

tion  of  the  tibia,  538 
surface  form  of,  299 
Fibular  region,  muscles  of,  527    i 
Fifth  nerve,  796 

surface  marking  of,  809 
surgical  anatomy  of,  809 
Filiform  papillae  of  tongue,  880 
Fillet,  718,  742,  743 
Filum  terminate  of  cord,  693,  695 
Fimbriae  of  Fallopian  tube,  1174 
First  nerve,  792 

surgical  anatomy  of,  793 
Fissura  prima,  783 
Fissure   or  Fissures,    auricular, 

179 

brain,  772 
calcarine,  779 
calloso-marginal,  778 
cerebellum,  727-733 

interlobular,  727,  728 
collateral,  765,  779 
congenital,  in  cranium,  188 
dentate,  779 
of  ductus  venosus,  1051 
frontal,  inferior,  791 

superior,  791 
Glaserian,  175,  916 
great    horizontal,    of  cerebel- 
lum, 727 
longitudinal,  of    cerebrum, 

772,  784 

hippocampal,  763,  779 
intraparietal,  791 
left  longitudinal,  1051 
of  liver,  1051 
longitudinal,  790 
parieto-occipital,  774,  779,  791 
post-limbic,  780 
precental,  778 
pterygo-maxillary,  216 
right  longitudinal,  1051 
of  Kolando,  774,  790 
sphenoidal,  182 
spheno-maxillary,  216 
spinal  cord,  696,  697 
antero-lateral,  697 

-median,  696 
lateral,  697 

posterior  intermediate,  697 
postero-lateral,  697 
-median,  696,  697 
of  Sylvius,  755,  774,  790 
transverse,  of  cerebrum,  770 

of  liver,  1051 
umbilical,  1051 
for  vena  cava,  1052 
vesical,  1052 

Fixation  of  duodenum,  1018 
of  liver,  1056 
of  small  intestine,  1020 
of  spleen,  1026 
of  stomach,  1003 
Flat  bones,  143 

Flexor  accessorius  muscle,  532 
brevis  digitorum,  530 
hallucis,  532 
minimi  digiti  (foot),  533 

(hand),  495 
pollicis,  492 
carpi  radial  is,  479 

ulnaris.  480 
digitorum  sublimis,  480 

profundus,  481 
longus  digitorum,  527 


Flexor  longus  hallucis,  525 
pollicis  (hand),  482. 

ossi  metacarpi  pollicis,  494 
Flexure,  duodeno-jejunal,  1008 

hepatic,  1035 

sigmoid.  1036,  1044 

splenic,  1036 
Floating  ribs,  232 
Flocculus,  732 
Flood's  ligament,  346 
Floor,    epithelial,    of  ventricle, 
768 

of  fourth   ventricle,  711,  720, 
723 

of  third  ventricle,  745,  750 
Fluids  of  the  body,  33 
Foetus,  circulation  in,  1097 

Eustachian  valve  in,  1096 

foramen  ovale  in,  128,  1096 

liver    of,    distribution   of    its 
vessels,  1097 

ovaries  in,  138 

vascular  system  in,  peculiari- 
ties, 1097 

Fold  of  Douglas,  455 
Folds,  aryteno-epiglottic,  1104 

genital,  140 

of  Houston,  1041 

interarytenoid,  1104 

recto-uterine.  1169 

recto-vesical,  1142 

vesico-uterine,  1169 
Folium  cacuminis,  730 
Follicle  of  hair,  93 
Follicles,  Graafian,  1176 

sebaceous,  94 
Fontana,  spaces  of,  893 
Fontanelles,  167,  188 
Foot,  arteries  of,  643 

bones  of,  299 

development  of,  308 

dorsum,  muscles  of,  530 

fascia  of,  530 

ligaments  of,  528,  529 

nerves  of,  863 

sole  of,  muscles  of,  529 
fascia  of,  529 

surface  form  of,  310 

surgical  anatomy  of,  311 

veins  of,  670 
Foramen  caecum,  709 

of  frontal  bone,  171,  208 
of  tongue,  880 

carotid,  178 

centrale  cochleae,  928 

condyloid,  165 

dental  inferior,  203 

ethmoidal,  209 

faciale,  928 

incisive,  213 

infraorbital,  190 

jugular,  211 

lacerum  anterius,  210 
posterius,  211 

magnum,  165 

of  Majendie,  740 

mastoid,  175 

medium,  211 

mental,  202 

of  Monro,  708,  751,  752,  761 

obturator,  278 

optic,  183,  210 

ovale  of  sphenoid,  182 

palatine,  anterior,  194,  211 
posterior,  198,  213 


INDEX. 


1223 


Foramen,  parietal,  169 
ptervgo-pal  aline,  182 
rotundum.  1>2.  2H» 

275,  337 

-,-arpa.  194,  21:-! 
of  Sommerring,  898 
spheno-palatine.  199,  221 
spinosum,  182,  -10 
of  Stenson,  194,  213 
sternal.  - 
•tylo-mastoid,  178 
supraorbital,  171 
thyroid.  2 
Veaalii,  182,  210 
of  >Vinslow,  975,  992 
Foramina  of  diaphragm,  446 
external  orbital,  182 
malar,  196 
olfactory,  185 
sacral,  156 
ThebeMi.  67*.  1088 
Forceps,  major.  757,  758 

minor,  757.  7  "  - 
Forearm,  arteries  of.  597 
bones  of,  254 
fascia  of.  47  x 
lymphatics  of,  684 
muscles  of.  47  > 
nerves  of,  838 
veins  of,  662 
Fore-brain,  706.  707 
Form  of  bones,  143 
Formatio  reticularis  of  medulla, 

713,  714,  715,  718 
of  pons,  721 
Fornix.  753.  76" 

anterior  pillar,  748,  750,  761 
conjunctive.  908 
acetabuli.  27  - 
of  antihelix,  912 
canine,  190 
condyloid.  165 
digastric,  176 
digital,  285,  1156 
duodeno-jejunal,  995 
glenoid.  174 

of  helix,  912 

ileo-csecal,  997 

ileo-colic,  997 

iliac.  274 

incisive,  190,  202 

infra-  and  supraspinous,  244 

inguinal,  964,  1190 

innominata,  912 

intersigmoid,  996 

ischio-rectal,  1201 

jugular,  179 

lachrymal,  172 

myrtiform,  190 

navicularis  of  urethra,  1146 
of  vulva,  1164 

occipital,  165 

olfactory,  of  fcetus.  125 

oval  is,  1089 

palatine,  anterior,  194 

perii-jeeai. 

phrenico-hepatic,  994 

pituitary,  180 

pterygoid,  of  sphenoid,  183 
of  lower  jaw,  204 

rhomboidalis,  723 

scaphoid,  183 

scaphoidea,  912 

sigmoidea,  176 

singulare,  928 


Fossa  of  skull,  anterior,  208 
middle,  21 U 

trior,  211 

spheno-maxillary,  216 
subcaecal,  997 
sublingual.  -"- 
submaxillary,  203 
subscapular,  243 
subsigmoid,  996 
temporal,  215 
of  Trietz,  995 
triangularis,  1102 
trochanteric,  285 
venae  cavae,  1052 
ve-icalis  1050,  1052 
zygomatic,  216 

duodenal,  994 
nasal,  219,  889 
retro- peritoneal,  994 
of  skull  208 
Fourchette,  1164 
Fourth  nerve,  796 

surgical  anatomy  of,  796 
ventricle,  708,  737-740 
Fovea,  boundaries  of,  738 
centralis  retinae,  898 
femoralis,  1198 
hemispherica,  921 
inferior,  724 
larynx,  1101 
roof  of,  738 
semi-elliptica,  921 
superior.  724 

Fracture  of  acromial  end  of  clav- 
icle, 500 

acromion  process,  500 
centre  of  clavicle,  499 
coracoid  process,  500 
coronoid  process  of  ulna,  501 
femur  above  condyles,  537 

below  trochanters,  537 
fibula,    with     dislocation     of 

tibia,  538 

humerus.  anatomical  neck,  500 
shaft  of,  500 

non-union  of,  253 
surgical  neck,  500 
neck  of  femur,  537 
olecranon  process,  501 
patella.  537 
PottV 
radius.  501 

lower  end  of,  502 
neck  of,  501 
shaft  of,  501 
and  ulna,  502 
Fnenula  cerebellum,  729 
Fnenulum  cerebellum,  734 
Fra-nurn  clitoridis,  1164 
labii   superioris  et   inferioris, 

931 

lingua?,  879 
pneputii,  1151 
Frontal  artery.  570 
bone.  170 

articulations  of,  173 
attachment   of   muscles    to, 

173 

development  of,  173 
structure  of.  173 
crest.  171 
eminence,  171 
nerve.  798 

process  of  malar,  196 
sinuses.  173 


Frontal  suture,  171,  173 

vein,  651 

Fronto-nasal  process,  119 
Fronto-sphenoidal    suture,    206, 

207 
Fundus  of  bladder,  1142 

of  uterus,  1168 
Fungiform   papilla?    of   tongue, 

880 

Funiculi  of  nerve,  73 
Funiculus    cuneatus,    710,    711, 
714 

gracilis,  710,  711,  714 

of  Rolando,  710,  711,  714 

solitarius,  718 

teres,  724 

Furrow,       auriculo-ventricular, 
1087 

dental,  938 

genital,  140 

interventricular,  1087 

labio-dental,  938 

posterior  intermediate,  697 

G. 

Galactophorous  ducts,  1179 
Galen,  veins  of,  657 
Gall-bladder,  1064 

development  of,  134 

ducts  of,  1065 

nerves  of,  1064 

relations  of,  1064 

structure  of,  1065 

surface  form  of,  1065 

vessels  of,  1064 

Ganglion    or    ganglia,    general 
anatomy  of,  79 

of  Andersen,  816 

Arnold's,  807 

of  Bpchdalek,  802,  804 

cardiac,  874 

carotid,  869 

cephalic,  799 

cervical  inferior,  892 
middle,  892 
superior,  869 

ciliary,  799 

on  circumflex  nerve,  839 

diaphragmatic,  875 

on  facial  nerve,  811 

of  fifth  nerve,  799 

Gasserian,  797 

of  glosso-pharyngeal,  816 

iinpar,  867,  874 

intercarotid,  872 

jugular,  816 

lateral  root  of  eighth  nerve, 
815 

lenticular,  799 

lingual,  872 

lumbar,  873 

Meckel's.  803 

mesenteric,  877 

ophthalmic,  799 

otic.  807 

petrous,  817 

pharyngeal,  871 

of  pneumogastric,  819 

of  portio  dura,  811 

on  posterior  interosseous nerve, 
844 

of  Ribes,  871 

of  root  of  vagus,  820 

sacral,  871 


INDEX. 


Ganglion  or  ganglia,  semilunar, 

of  abdomen,  875 
of  fifth  nerve,  797 
spheno-palatine,  803 
of  spinal  nerves,  827 
spirale,  928 
submaxillary,  808 
suprarenal,  875 
of  sympathetic  nerve,  867 
temporal,  872 
thoracic,  872 
thyroid,  872 
of  trunk  of  vagus,  820 
of  Wrisberg,  874 
Ganglionic  branch  of  nasal  nerve, 

799 

Gartner,  duct  of,  139 
Gases  of  the  blood,  37 
Gasserian  ganglion,  797 
Gastric    arteries   (vasa   brevia), 

612 

artery,  611 
follicles,  1006 
glands,  1006 
nerves  from  vagus,  822 
plexus,  877 
vein,  676 

Gastrocnemius  muscle,  522 
Gastro-colic  omentum,  991 
Gastro-duodenal  artery,  611 

plexus,  877 
Gastro-epiploic  plexus,  877 

veins,  676 
Gastro-epiploica    dextra  artery, 

611 

sinistra,  612 
G  astro-splenic    omentum,     971, 

991,  1076 
Gelatinous  connective  tissue,  48 

nerve-fibres,  72 
Gemellus  inferior  muscle,  517 

superior  muscle,  517 
Generative  organs,  development 
.    of,  137 
female,  1163 
male,  1148 
Genial  tubercles,  202 
Geniculate  bodies,  743 

ganglion,  811 

Genio-hyo-glossus  muscle,  415 
Genio-hyoid  muscle,  414 
Genital  cord,  136 
corpuscles,  76 
folds,  140 
furrow,  140 
tubercle.  140 
Genito-crural  nerve,  852 
Genu   of    the    corpus   callosum, 

756,  758 

of  the  internal  capsule,  760 
Gerlach's  nerve  network,  702 
Germ,  common  dental,  938 

special  dental,  939 
Germinal  area,  103 
disk,  103 
spot,  101 
vesicle,  101 

Giacemini,  band  of,  765 
Giant  cells,  55 
Gianuzzi,  crescents  of,  948 
Gimbernat's  ligament,  448,  1183 
Ginglymus,  316 
Giraldes,  organ  of,  139 
Girdle,  pelvic,  238 
shoulder,  238 


Glabella  of  frontal  bone,  171,  217 
Gladiolus,  229 

Gland  or   glands,   accessory,   of 
parotid,  947 

agminated,  1025 
arytenoid,  1108 
of  Bartiiolin,  1165 

Brunner's,  1024 

buccal,  931 

circumanal,  1040 

coccygeal,  617 

Cowper's,  1150,  1205 

development  of,  125 

ductless,  spleen,  1073 
suprarenal,  1137 
thymus,  1124 
thyroid,  1122 

duodenal,  1024 

epiglottic,  1108 

gastric,  1006 

of  Havers,  314 

labial,  931 

lachrymal,  909 

of  larynx,  1108 

of  Lieberkulm,  1024 

lingual,  882 

of  Littre,  1147 

of  Lusclika,  617 

lymphatic,  87 

mammary,  1178 

Meibomian,  908 

mucilaginous,  of  Havers,  314 

odoriferse,  1150 

o?sophageal,  953 

of  Pacchioni,  657 

palatal,  944 

parotid,  945 

peptic,  1006 

Peyer's,  1025 

pharyngeal,  951 

prostate,  1148 

pyloric,  1006 

salivary,  945 

sebaceous,  94 

secreting,  98 

solitary,  1025,  1029 

sublingual,  948 

submaxillary,  947 

sudoriferous,  95 

suprarenal,  1137 

thymus,  1124 

thyroid,  1122 

tracheal,  1111 

of  Tyson,  1150 

uterine,  1172 

of  vulva,  1166 
Glandulse  odoriferse,  1150 

Pacchioni,  657 
Glans  penis,  1150 

clitoridis,  1165 
Glaserian  fissure,  174,  916 
Glenoid  cavity,  245 

fossa,  174 

ligament  of  Cruveilhier,  361 
of  phalanges,  361 
of  shoulder,  346 
Gliding  movement,  318 
Glisson's  capsule,  982,  992 
Globules,  blood-,  34 

development  of,  127 
Globus  major  of  epididymus,!  158 

minor,  1158 

pallidus,  760 

Glosso-epiglottidean     ligaments, 
879, 


Glosso-pharyngeal  nerve,  816 
Glottis,  rima  of,  1104 
Gluteal  aponeurosis,  515 
artery,  627 

inferior,  626 
lines,  272,  273 
lymphatic  glands,  686 
nerve,  interior,  861 

superior,  861 
region,  lymphatics  of,  689 

muscles  of,  514 
ridge,  286 

Glutens  maximus  muscle,  514 
medius,  515 
minimus,  516 
Goblet  cells,  43 
Golgi,  organs  of,  78 
Goll's  column,  700 
Gomphosis,  315 
Graafian  follicles,  1176 

membrana  granulosa  of,  1176 
ovicapsule  of,  1 1 76 
structure  of,  1176 
Gracilis  muscle,  511 
Gray  nervous  matter,  69 

of  spinal  cord,  701 
Great  omentum,  971,  973,  975, 

991 
sciatic  nerve,  862 

surgical  anatomy  of,  866 
Greater  wings  of  sphenoid,  182 
Groove,  auriculo-ventricular, 

1087 

basilar,  720,  721 
bicipital,  248 
cavernous,  181 
dorso-lateral,  709,  717 
infraorbital,  191 
lachrymal,  192 
longitudinal,   floor   of    fourth 

ventricle,  723 
mylo-hyoid,  203 
nasal,  189 
occipital,  176 
optic,  180 

primitive  dental,  938 
subclavian,  234 
ventro-lateral,  709,  7  17 
Grooves  in  the  radius,  260 

interventricular,  1087 
Growth  of  bones.  63 
Gubernaculum  dentis,  942 

testis,  1161 

Gudden,  commissure  of,  793 
Gums,  932 
Gustatory  nerve,  807 
Gyrus  or  Gyri,  772,  773 
dentate,  782 
fornicatus,  779,  792 

fillet  of,  786 
operati,  778 
supracallosal,  782 
uncinate,  781 

H. 

Habenula,  749 
Haematoidin  crystals,  37 
Hsemin  crystals,  37 
Haemoglobin,  34 

crystals,  37 
Hsemorrhoidal   artery,   inferior, 

625 

middle,  622 
superior,  615 


1225 


Haeraorrhoidal    nerve,    inferior, 

plexus  of  nerves.  878 
veins,  interior,  672 
middle,  672 
superior.  672 
venous  nlexus.  674.  675 

surgical  anatomy  of,  672 
Hair-cells  of  internal  ear.  926 
Hair-follicles,  93 
Hairs, 

•-sheath  of.  93 
?h  in  of.  ','4 
structure  of,  93 
Hamstring      tendons,      surgical 

anatomy  of,  520 
Hamular    proofs   of    humerus, 

2"»0.  note. 

of  lachrymal,  195 
of  sphenoid,  183 
Hamulus,  924 
Hand,  arteries  of,  601 
bones  of.  2 '12 
fascia  of,  489 
ligaments  of,  356,  357 
muscles  of,  489 
nerves  of,  from  median,  839 
from  radial,  >44 
from  ulnar.  -41 
surface  form  of.  270.  497 
veins  of.  662 
Hard  palate.  944 
Hasner,  valve  of,  911 
Haustrum.  l"i'- 
Havers,  glands  of,  314 
Haversian  canals  of  bone,  56 
He:ul.  lymphatics  of,  681 
muscles  of,  390 
veins  of,  650 
Heart.  lu>6 

annular  fibres  of  auricles,  1094 

arteries  of,  545,  1095 

deep  fibres  of  auricles,  1094 

development  of,  126 

endocardium,  1094 

fibres  of  the  auricles,  1094 

of  the  ventricles.  1094 
fibrous  rings  of,  1094 
tVetal  relics  in,  1088 
infundibulum  of,  1089 
left  auricle,  1091 
ventricle,  1092 

looped  fibres  of  auricles,  1094 
lymphatics  of,  692.  1096 
muscular  fibres  of,  67 

structure  of,  1094 
nerves  of.  V_M.  -74.  1095 
position  of,  1086 
right  auricle,  1088 

ventricle,  1089 
septum  ventriculorum,  1089 
size  and  weight,  1087 
structure  of,  1094 
subdivision  into  cavities.  10S7 
superficial   fibres  of   auricles, 

1094 

surface-marking  of,  1096 
veins  of.  677 
vortex  of,  1095 

Heidenhain,  demilunes  of,  948 
Helicis  major  muscle,  914 

minor,  914 

Helicotrema  of  cochlea,  923 
Helix,  912 
fossa  of,  912 


Helix,  muscles  of,  913 

process  of,  913 
Hemisphere  vesicles.  707 
Hemispheres,    cerebellum,   725, 
727 

cerebrum,  752 

development. 

gray  matter,  786 
cortex,  786 

structure,  785-788 

surface  aspect,  771-785 

white  matter,  785,  786 
Henle,  looped  tubes  of,  1130 
Henle's  layer  of  hair-follicle,  94 
Hepatic  artery,  611,  1057 

cells,  1060  ' 

duct,  1057.  1063 

flexure,  1035 

plexus,  877 

veins,  675,  1057,  1061 
Hepatico-gastric  omentum,  979, 
991 

-renalis  recessus,  1012 
Hernia,  congenital,  1189 

direct  inguinal,  1189 
dissection  of,  1190 

encysted,  1189 

femoral,  coverings  of,  1199 
descent  of.  1199 

of  funicular  process,  1189 

infantile,  1189 

inguinal,  1180 
dissection  of,  1186 

oblique  inguinal,  1187 

scrotal,  1189 

Hesselbach's  triangle,  1190 
Hiatus  Fallopii,  177 
Highmore,  untrum  of,  192 
Hilton's  muscle,  1107 
Hilum  of  kidney,  1128 
Hind-brain.  70»f.  724 
Hinge-joint,  316 
Hip-joi'nt,  362 

muscles  of,  514 

in  relation  with,  365 

surface  form  of,  366 

surgical  anatomy  of,  366 
Hippocampus  major,  759,  763 

minor,  758 
Horizontal  plate  of  ethmoid,  185 

of  palate,  197 
Homer's  muscle,  395 
Houston's  folds  of  rectum,  1041 
Howship's  lacunae,  55 
Huguier,  canal  of,  175 
Humerus,  24^ 

anatomical  neck,  fracture   of, 
500 

articulations  of,  252 

attachment  of  muscles  to,  252 

development  of,  252 

head  of,  248 

neck  of,  24- 

nutrient  artery  of,  596 

shaft  of,  fracture  of,  500 

surgical  anatomy  of,  253 

tuberosities    of,    greater    and 

lesser.  248 

Humors  of  the  eye,  903 
Hunter's  canal.  630 
Huxley's  layer  of  hair-follicle,  94 
Hyaline  cartilage.  51 
Hyaloid  membrane  of  eye,  903 
Hydatid  of  Morgagni,  138 
Hymen,  1165 


Hyo-epiglottic  ligament.  1103 
Hyo-glossal  membrane,  882 
Hyo-glossus  muscle,  416 
Hyoid  arch  (foetal),  119 

artery  of  superior  thyroid,  552 
bone,  227 

attachment  of  muscles  to,  227 
cornua  of,  227 
development  of,  227 
branch  of  lingual  artery,  553 
region,  muscles  of,  infra-,  411 

supra-,  413 

Hypertrophy  of  prostate,  1159 
Hypoblast,  i04 
Hypochondriac  regions,  955 
Hypogastric    arteries   in    fcetus, 

620,  1097 

how  obliterated,  1099 
plexus,  877 
Hypogastrium.  961 
Hypoglossal  nerve,  823 

surgical  anatomy  of,  825 
Hypophysis  cerebri,  751 
of  pituitary  body,  121 

I. 

Ileo-csecal  fossa,  997 

valve,  1033 
Ileo-colic  artery,  614 
fossa,  997 
valve,  1033 
Ileum,  1020 

Iliac  arteries,  common,  618 
peculiarities  of,  618 
surface-marking  of,  619 
surgical  anatomy  of,  619 
external,  628 

surface-marking  of,  628 
surgical  anatomv  of,  628 
internal,  620 
at  birth,  621 
peculiarity  in  the  foetus, 

621 

surgical  anatomy  of,  621 
fascia,  503 
fossa,  274 

lymphatic  glands,  689 
portion  of  fascia  lata.  503 
region,  muscles  of,  503 
veins,  common,  673 

peculiarities  of,  673 
external,  672 
internal,  672 
Iliacus  muscle,  504 
llio-costalis  muscle,  434 
Ilio-femoral  ligament,  363 
Ilio-hypogastric  nerve,  851 
Ilio-inguinal  nerve,  851 
Ilio-lumbar  arterv,  626 
ligament,  336 
vein,  674 

Jlio-pectineal  eminence,  277 
Ilio-tibial  band,  507 
Ilium,  272 
crest  of,  275 
dorsum  of,  272 
spines  of,  272 
venter  of,  274 

Impres^io  colica.  1050,  1052 
duodenalis,  1050,  ]• 
gastrica,  1052 
pylorica,  1050 
renalis,  1050,  1052 
suprarenalis,  1050,  1052 


1226 


INDEX. 


Incisive  foramina,  213 
fossa,  191,  202 
pad,  944 

Incisor  teeth,  932 
Incisura,  1.100 
cerebellum,  726 
intertragica,  912 
cesophageal,  1052 
Santorini,  914 
umbilicalis,  1049,  1052 
vesicalis,  1049,  1052 
Incremental  lines  of  dentine,  937 
Incus,  919 

development  of,  125 
ligament  of,  919 

suspensory,  919 
Infantile  hernia,  1189 
Inferior  dental  artery,  561 

canal,  203 
maxillary  bone,  201 

changes  produced  by  age  in, 

204 

meatus  of  nose,  221 
occipital  fossa,  166 
peduncle  of  cerebellum,  702 
profunda  artery,  596 
turbinated  bones,  200 
articulations  of,  200 
development  of,  200 
ethmoidal  process  of,  200 
lachrymal  process  of,  200 
maxillary  process  of,  200 
vena  cava,  673 
Infracostal  muscles,  442 
Infraglenoid  tubercle,  245 
Inframaxillarv  nerves  from   fa- 
cial, 815 
Infraorbital  artery,  562 

branches  of  facial  nerve,  814 
canal,  191 
foramen,  190 
groove,  191 
plexus  of  nerves,  801 
Infraspinatus  muscle,  473 
Infraspinous  fascia,  473 

fossa,  244 

Infratrochlear  nerve,  799 
Infimdibula,  1119 
of  kidney,  1128 

Infundibuliform  fascia,  457, 1186 
Infundibulum  of  brain,  750 
of  cochlea,  923 
of  ethmoid,  187 
of  heart,  1089 

Ingrassias,  processes  of,  183 
Inguinal  canal,  1185 
fossa,  964,  1190 
glands,  deep,  686 

superficial,  686,  1181 
hernia,  1186 

dissection  of,  1180 
Inlet  of  pelvis,  281 
Innominate  artery,  545 
peculiarities  of,  546 
surgical  anatomy  of,  546 
bone,  272 

articulations  of,  278 
attachment  of    muscles    to, 

279 

development  of,  278 
veins,  665 

peculiarities  of,  665 
Inorganic   constituents  of  bone, 

59 
Inspiration,  muscles  of,  444 


Interarticular  fibro-cartilage,  53 
of  acromio-clavicular  joint, 

343 

of  jaw,  329 
of  knee,  370,  371 
of  radio-ulnar  joint,  355 
ligament  of  ribs,  334 
Interarytenoid  fold,  1104 
Inter-brain,  706,  745-752 
Intercarotid  ganglion,  872 
Intercellular  substance  of  carti- 
lage, 51 

Interchondral  ligaments,  334 
Interclavicular  ligaments,  341 
Intercolumnar  fascia,  450 

fibres,  450,  1182 
Intercondyloid  notch,  288 
Intercostal  arteries,  606 
anterior,  607 
superior,  587 
fasciae,  442 

lymphatic  glands,  691 
lymphatics,  692 
muscles,  442 
nerves,  846 
spaces,  228 
veins,  superior,  666 
Intercosto-humeral  nerves,  840, 

848 

Interglobular  spaces,  937 
Interlobular  arteries  of  kidney, 

1134 

biliary  plexus,  1061 
notch,  1049 
vein,  1057,  1061 
Intermaxillary  suture,  217 
Intermediate   disk   of  muscular 

fibre,  66 

Intermembranous  ossification,  63 
Internal  annular  ligament,  528 
capsule,  785 
carotid  artery,  565 
cutaneous  nerve,  840 
inguinal  hernia,  1187 
mammary  artery,  586 

vein,  666 

maxillary  artery,  559 
brandies  of,  560 
peculiarities  of,  559 
surgical  anatomy  of,  561 
occipital  crest,  166 
pterygoid  plate,  183 
sphincter,  1041 
Internasal  suture,  217 
Internodal  segment  of  nerves,  71 
Internodia  or  phalanges,  270 
Interossei     muscles,    dorsal,   of 

foot,  534 
of  hand,  496 
palmar,  496 
plantar,  534 
Interosseous  artery  of    foot,  644 

of  forearm,  601 
membrane  of  forearm,  354 

of  leg,  377 
nerve,  anterior,  841 

posterior,  844 
veins  of  forearm,  664 
Intersigmoid  fossa,  896 
Interspinales  muscles,  438 
Interspinous  ligaments,  322 
Intertransversales  muscles,  438 
Intertransverse  ligaments,  322 
Intertubular  stroma  of    kidney, 
1135 


Intervertebral  notches,  145 

substance,  320 
Intestinal  canal,  1008 
Intestine,  development  of,  133 

large,  coats  of,  1027 

lymphatics  of,  691 

small,  970, 1008 

surface  form  of,  1045 

surgical  anatomy  of,  1045 

torsion  of,  972 

Intracartilaginous  ossification,  60 
Intralobular  veins,  1057 
Intrinsic  muscle  of  tongue,  417 
Intumescentia  gangliformis,  811 
Investing  mass  of  Rathke,  118 
Involuntarv  muscle,  78 
Iris,  896 

Irregular  bones,  144 
Ischiatic  lymphatic  glands,  686 
Ischio-rectal  fascia,  1210 

fossa,  1202 

position  of  vessels  and  nerves 
in,  1202 

region,   surgical   anatomy   of, 

1201 
Ischium,  275 

body  of,  275 

ramus  of,  276 

spine  of,  276 

tuberosity  of,  276 
Island  of  Reil,  778 
Isthmus  cerebri,  740 

of  the  fauces,  944 

of  thyroid  gland,  1123 
Iter  a  tertio  ad   quartum   ven 
triculum,  744,  752 

chordse  anterius,  916 

posterius,  916 
Ivory  of  tooth,  935 

J. 

Jacob's  membrane,  901 
Jacobson's  cartilage,  888 
nerve,  818,  921 
canal  for,  178 
organ,  888 
Jaw,  lower,  201 

articulations  of,  204 
attachment   of    muscles   to, 

204 
changes  produced  in,  bv  age, 

204 

condyle  of,  204 
development  of,  204 
ligaments  of,  327,  328 
oblique  line  of.  202 
ptervgoid  fossa  of,  204 
rarai  of,  203 
sigmoid  notch  of,  204 
symphysis  of,  202 
upper.     See  Maxillary  Bone. 
Jejunum,  1020 
Joint.     See  Articulations. 
Jugular  foramen,  211 
fossa,  179 
ganglion,  816 
surface,  178 
vein,  anterior,  654 
external,  653 

surgical  anatomy  of,  653 
internal,  654 

sinus  or  gulf  of,  654 
surgical  anatomy  of,  655 
posterior,  external,  654 


IXDEX. 


1227 


K. 

Karyokinesis,  39 
Karyomitosis,  39 
Kidney.  11 27 

calices,  11 28 

cortical  substance  of,  1129 

development  of,  135 

hilum  of,  1128 

infundibula  of,  112> 

labyrinth  of  cortex  of,  1131 

lymphatics  of,  690,  1135 

Malpighian  bodies  of,  1129 

mammillae  of,  1129 

medullary  substance,  1129 

nerves  of,  1134 

papillae  of,  1129 

pel  vis  of,  112> 

pyramids  of  Ferrein,  1131 

renal  artery,  616,  1133 

sinus  of,  11 2S 

surface-marking  of,  1135 

surgical  anatomy  of,  1135 

tubuli  uriniferi,  1130 

veins  of,  675.  1134 

weight  and  dimensions,  1127 
Knee-joint. 

surface  form  of.  374 

surgical  anatomy  of.  374 
Krause's  membrane,  66 

end-bulbs  of,  76 

Kiihne's  views  on  the  termina- 
tions of  motor  nerves,  78 

L. 

Labia  cerebri,  756 

pudendi  majora,  1163 

minora,  1164 
Labial  artery,  556 

glands,  931 

veins,  inferior.  652 

superior,  652 
Labio-dental  furrow,  938 

strand,  938 
Labyrinth,  921 

arteries  of.  927 

cortex  of  kidney,  1131 

fibro-serous  membrane  of,  926 
Lachrymal  apparatus,  909 

artery.  568 

bone,  195 

articulations  of,  196 
attachment    of   muscles   to, 

196 
development  of,  196 

canals,  910 

caruncula,  909 

crest,  195 
.  172 

gland,  909 

groove,  192 

nerve,  798 

notch,  191 

papilla,  907,  910 

process  of  inferior  turbinated 
bone,  200 

puncta,  910 

sac,  910 

tubercle,  193 
Lacteals,  679 
Lactiferous  ducts,  1179 
Lacuna  magna,   1147 
Lacunse  of  bom 

Howship's,  55 
Lacus  lachrymalis,  909 


Lambda,  208 
Lambdoid  suture,  206 
Lamella  of  bone,  articular,  313 
horizontal,  of  ethmoid.  185 
perpendicular,  of  ethmoid,  186 
Lamellae  of  bone,  57 
Lamina,  1101 
cinerea,  751 
of  cornea,  elastic,  893 
cribrosa,  177,  928 
of  sclerotic,  893 
dental,  938 
fusca,  891 
medullary,  747 
posterior  perforated,  745.  750 
quadrigemina,  743 
spiralis  ossea  of  cochlea,  923 

membranacea,  £25,  note. 
suprachoroidea,  895 
terrninalis,  751 
of  the  vertebra?,  144 
vitrea,  895 

Laminae  dorsales,  107 
Lancisi,  nerves  of.  757 
Lanugo  (foetal  hairs  i,  125 
Large  intestine,  1027 
caecum,  1030 
colon,  1035 
ileo-caecal  valve,  1033 
muscular  coat,  1041 
rectum,  1038 
relations  of,  1036 
f    structure  of,  1028 

vessels  of,  1029 
Laryngeal  artery,  inferior,  5S4 

superior,  552 
nerve,  external,  821 
internal,  821 
recurrent,  821 
superior,  821 
surgical  anatomy  of,  822 
from  sympathetic,  871 
pouch,  1105 
veins,  666 

Laryngectomy,  1113 
Laryngo-tracheotomy,  1112 
Larvngotomy,  1112 
Larynx,  1100 

actions  of  muscles  of,  1107 
arteries  of,  1108 
cartilages  of,  1100 
cavity  of,  1104 
glands  of,  1108 
interior  of,  1103 
ligaments  of.  1102 
lymphatics  of,  1108 
mucous  membrane  of,  1107 
muscles  of.  1105 
nerves  of,  1108 
rima  glottidis.  1104 
superior  aperture  of,  1103 
surface  form  of,  1111 
surgical  anatomy  of,  1111 
veins  of,  1108 
ventricle  of,  1104 
Lateral  disk  of  muscular  fibre,  66 
horn  of  spinal  cord,  701 
ligaments  of  liver,  1053 
masses  of  ethmoid,  186 
recess,  734.  738,  739 
region  of  skull.  214 
sinus  of  brain.  658 
tract    of   medulla    oblongata, 

710 
ventricles,  755 


Lateralis  nasi  artery.  556 
Latissimus  dorsi  muscle,  430 
Left  lobe  of  liver,  1052 

longitudinal    fissure  of  liver. 

1051 

Leg,  arteries  of,  641 
bones  of,  291 
fascia  of,  520 

deep  transverse.  524 
ligaments  of,  362 
lymphatics  of,  686 
muscles  of,  520 
back  of,  522 
front  of,  521 
nerves  of,  859 
veins  of,  670 
Lemniscus,  718 
Lens,  904 
changes  produced  in.  by  age, 

904 

suspensory  ligament  of,  905 
Lenticular  ganglion,  799 
Lesser  lachrymal  bone,  195 
omentum/971,  991,  1053 
pancreas,  1070 
sac,  993 

sciatic  nerve,  862 
wings  of  sphenoid,  183 
Levator  anguli  oris,  400 

scapulae,  431 
ani,  459 

glandulae  thyroida?,  1123 
labii  inferioris,  400 
superior  alseque  nasi,  400 
superioris,  400 
menti,  400 
palati.  421 
palpebrae,  395 
Levatores  costarum.  442 
Lieberkiihn,  crvpts  of.  1024, 1029 

glands  of,  1024 
Lienculi,  1073 
Ligament,  structure  of.  313 
acromio-clavicular,      inferior, 

343 

superior,  343 
alar,  of  knee,  372 
of  ankle,  anterior,  377 

lateral,  378 
annular,  of  ankle,  377 
external.  378 
internal,  378 
of  radius.  353 
of  wrist,  anterior.  356 

posterior,  357 
anterior,  of  knee,  368 
arcuate,  444 
aryteno-epiglottic.  1102 
astragalo-navicular.  383 
atlamo-axial,  anterior,  323 

posterior,  323 
of  bladder,  false,  1143 

true,  1142 

broad,  of  liver.  988,  1053 
calcaneo-astragaloid.  external, 

381 

internal,  381 
interosseous,  381 
posterior,  381 

calcaneo-cuboid.  internal,  381 
long,  381 
short.  3-1 
superior.  381 

calcaneo-navicular,      inferior, 
382 


1228 


INDEX. 


Ligament,  calcaneo-navicular,  su- 
perior, 382 

capsular.  See  Individual  Joints. 
carpo-metacarpal,  dorsal,  357 

interosseous,  358 

palmar,  357 
of  carpus,  357 
central,  ot  spinal  cord,  695 
check,  326 
chondro-sternal,  anterior,   334 

posterior,  334 
common    vertebral,    anterior, 

319 

posterior,  319 
conoid,  344 
coraco-acromial,  344 
coraco-clavicular,  343 
coraco-humeral,  346 
coracoid,  345 
coronary,   of  liver.    979,    981, 

988,  1053 
costo-central,  330 

anterior,  330 
costo-colic,  1077 
costo-transven<e,  331 

posterior,  332 

superior,  331 
anterior,  331 
posterior,  331 

costo-vertebral,  or  stellate,  330 
cotyloid,  364 
crico-arytenoid,  1104 
crico-thyro-arytenoid,  1103 
crico-thyroid,  1104 
crico-tracheal,  1104 
crucial,  of  knee,  369 
cruciform,  324 
deltoid,  378 

dorsal.      See  Individual  Joints. 
of  elbow,  349 

anterior,  349 

external  lateral,  350 

internal  lateral,  350 

posterior,  350 

falciform,  of  liver,  971,  1053 
Flood's,  346 

Gimbernat's,  448,  1183,  1196 
glenoid,  346 

glosso-epiglottidean,  1102 
of  hip,  362 
hyo-epiglottic,  1103 
ilio-femoral,  363 
ilio-lumbar,  336 
of  incus,  919 
interarticular,  of  ribs,  331 
interclavicular,  341 
interchondral,  334 
interosseous.       See   Individual 

Joints. 

interspinous.  322 
intertransverse,  322 
interverteliral,  320 
of  jaw,  327 
kerato-cricoid,  1104 
of  knee,  368 
of  larynx,  1102 
lateral.     See  Individual  Joints. 
longitudinal,  of  liver,  1053 
long  plantar,  381 
lumbo-iliac,  336 
lumbo-sacral,  336 
of  Luschka,  1084 
of  malleus,  919 
metacarpal,  361 
metacarpo-phalangeal,  361 


Ligament,  metatarsal,  385 
metatarso-phalangeal,  386 
mucosuin,  of  knee,  368 
nucha?,  430 
oblique,  354 
obturator,  516 
occipito-atlantal,  anterior,  325 

lateral,  325 

posterior,  325 
occipito-axial,  326 
odontoid,  326 

lateral,  326 

middle,  326 
orbicular,  353 
of  ossicula,  919 
of  ovary,  1175 
palpebral  or  tarsal,  908 
of  patella,  368 
of  pelvis,  336 
of  the  phalanges,  (foot),  387 

(hand),  362 
phreno-colic,  1036 
of  the  pinna,  373 
plantar,  385 
posterior  of  knee,  or  posticum 

Winslowii,  368 
Poupart's,  448,  1183,  1195 
pterygo-maxillary,  402 
pubic,  anterior,  340 

posterior,  340 

superior,  340 
radio-carpal,  356 
radio-ulnar  joint,  inferior,  355 
middle,  354 
superior,  353 
recto-uterine,  1169 
of  rectum,  1143 
rhomboid,  341 
round,  of  hip,  363 

of  liver,  983,  1053 

of  radius  and  ulna,  354' 

of  uterus,  1177 
sacro-coccygeal,  anterior,  339 

interarticular,  339 

lateral,  339 

posterior,  339 
deep,  339 
superficial,  339 
sacro-iliac,  anterior,  337 

oblique,  337 

posterior,  337 
sacro-sciatic,  greater,  337 

lesser,  338 
sacro-uterine,  1169 
sacro-vertebral,  336 
of  scapula,  344 
Schlemm's,  346 
of    shoulder-joint,    gleno-hu- 

meral,  346 
inferior,  346 
middle,  346 
superior,  346 
stellate,  330 
sterno-clavicular,  anterior,  341 

posterior,  341 
sterno-pericardial,  1084 
of  sternum,  336 
stylo-maxill;iry,  328 
subpubic,  340 
supraspinous,  321 
suspensory,  of  incus,  919 

of  lens,  905 

of  liver,  1053,  1076 

of  malleus,  919 

of  mamma,  466 


Ligament,  suspensory,  of  spleen, 

1150 

sutural,  313 
tarsal,  of  eyelids,  908 
tarso-metatarsal,  3S4 
of  tarsus,  380 
of  thumb,  359 
thyro-arytenoid,  inferior,  1103 

superior,  1105 
thyro-epiglottic,  1103 
thyro-hyoid,  1103 
tibio-tarsal,  377 
transverse,  of  atlas,  323 

of  hip,  361 

of  knee,  371 

of  scapula,  345 
trapezoid,  344 
of  Treitz,  1018 
triangular,  of  liver,  1053 

of  urethra,  1024 
of  tympanic  bones,  919 
of  uterus,  1169 
of  vertebrae,  320 
vesico-uterine,  1169 
of  Winslow,  368 
of  wrist,  anterior,  356 

lateral  external,  356 
internal,  356 

posterior,  357 
of  Zinn,  397 
Ligamenta  alaria,  372 
subflava,  321 

suspensoria  of  mamma,  466 
Ligamentum     arcuatum     exter- 
num,  445 

internum,  444 
coli,  1028 
colico-lienale,  1077 
coronarium  hepatis,  988 
cystico-duodenale,   989,    1012, 

1054 

denticulatum,  695 
duodeno-mesocolicum,  1014 

-pancreaticum,  971 

-renale,  1012 
gastro-hepaticum,  1053 

-lienale,  1076 

-pancreaticum,  994 
hepato-colicum,  989,  1054 

-duodenale,    971,   982,   989, 
1000,  1054 

-ga  stricu  m,  989 

-gastro-duodenale,  971 

-renale,  989,  1012,  1054 

-umbilicalis,  1053 
latum  pulmonalis,  1114 
lieno-gastricum,  985,  988 

-pancreaticum,  986 

-renale,  985,  1077 
mesenterico-mesocolicum,  987 
mucosum,  371 
nucha?,  430 

pancreatico-lienale,  1077 
patellae,  368 
pectinatum  iridis,  896 
phrenico-colicum,  988,  1077 

-gastricum,  988 
phreno-lienale,  975,  988,  1076 
posticum  Winslowii,  368 
pyloricum,  1000,  1005 
suspensorium,  326 

duodeni,  1014 

hepatis,  971,  988 

lienis,  1076 
teres,  364 


I XI)  EX. 


1229 


Ligarnentuni  venosum.  1051 
Ligature  of  arteries.     See  each 

Artery. 

Limbs,  development  of.  125 
Limbus  laminae  spiralis,  924 

luteus,  898 
Linea  aspera.  --''* 
eminens,  1101 
gluteal,  inferior,  273 
middle.  273 
superior,  272 
ilio-pectinea,  274 
quadrati. 
splendens.  695 
supracomiylar,  2^7 
suprema,  165 
Linea?  semilunare>.  4-"itj 

transverse  of  abdomen,  456 
Lingual  artery.  553 

surgical  anatomy  of,  553 
bone,  2'J7 
ganglion,  872 
nerve,  807 
veins,  654 

Lingualis  muscle,  inferior,  418 
superior,  417 
traii!-ver>f.  41  > 
vertical,  418 
Lingula,  729 

of  sphenoid,  181 
Lips,  930 

arteries  of,  556 
Liquor  amnii.  112 
Cotunnii.  926 
-    ;rpa?,  927 
sanguinis,  36 
Lissauer,  tract  of,  700 
Lithotomy,  parts  avoided  in  op-  , 

eration,  1207 
concerned    in   operation  of, 

1207 

divided,  in  operation,  12"7 
Littre,  glands  of.  1147 
Liver,  971,  1047 
corset,  1053 
development  of,  134 
distribution  of  vessels   to,   in 

foetus,  1097 
ducts  of,  1064,  1065 
excretory  apparatus  of,  1063 
fissures  of.  1051 
fixation  of,  1056 
hepatic  artery,  611,  1058 
cells.  U>.-,s" 
duct,  1058 
veins,  675,  1057 
ligaments  of,  1053 
broad,  1053 
coronary,  1053 
falciform,  1853 
lateral,  1053 
longitudinal,  1053 
round,  1053 
suspensory.  1053,  1076 
triangular,  1053 
lobes  of,  1052 
caudate,  1052 
left,  Ino-J 
quadrate,  1052 
right,  105-J 
lobules  of,  1059 
lymphatics  of,  690,  1058 
nerves  of,  877,  1058 
peritoneal  relations  of,  1054 
portal  vein,  675 


Liver,  relations  of,  1055 

structure  of,  1059 

surface  form  of,  1065 

surfaces  of,  1049 

surgical  anatomy  of,  1066 

vessels  of,  1060  ' 
Lobe  or  lobes,  central,  729,  778 

caudate,  1052 

cuneate,  780 

frontal,  753,  775 

of  kidney,  1128 

limbic,  781 

of  liver,  1052 

of  lung, 1118 

occipital,  753,  777,  780 

olfactory,  782,  784 

orbital,  775 

paracentral,  780 

parietal,  753.  776 

of  prostate,  1149 

quadrate,  730,  780 
of  liver,  1052 
of  prostate,  730,  780 

Spigelian,  1050,  1050 

of  testis,  1158 

of  thymus,  1125 

of  thyroid.  1123 

temporal,  754,  777 

temporo-sphenoidnl,  777 
Lobular  bronchial  tube,  1119 
Lobule,  729 

anterior  crescentic,  730 
slender,  731 

biventral,  731 

digastric,  731 

of  the  ear,  912 

fusiform,  781 

inferior  semilunar,  730 

lingual,  781 

pneumogastric,  733 

posterior  crescentic,  730 
slender.  731 

postero-inferior,  730 
-superior.  7 '•'<<> 

quadrangular,  730 

superior  semilunar,  730 
Lobules  of  cerebellum.  728-733 
structure  of.  728 

of  kidney,  1128 

of  liver,  "1059 

of  lung,  1119 
Lobuli  testes,  1158 
Lobulus  centralis,  729 
Locus  cceruleus,  724 

niger,  substantia  nigra,  744 
Long  bones,  143 

saphenous  nerve,  856 
Longissimiis  dorsi  muscle,  436 
Longitudinal    fissure    of    liver, 
1051 

ligament  of  liver,  1053 

sinus  of  brain,  inferior,  658 

superior,  657 
Loop,  duodenal,  969 

omega,  1044 

umbilical,  969 

Looped  tubes  of  Henle,  1131 
Lower  extremity,  arteries  of,  630 
bones  of.  \ 
fascia  of,  502 
ligaments  of,  362 
lymphatics  of,  686 
muscles  of,  502 
nerves  of,  849 
surface  form  of,  535 


Lower      extremity,      veins     of, 

670 

Lower,  tubercle  of,  1088 
Lumbar  arteries,  617 
fuscia,  433 
ganglia.  873 
glands,  688 
nerves,  849 

anterior  divisions  of,  850 
posterior  divisions  of,  849 
roots  of,  849 

surgical  anatomy  of,  866 
plexus  of  nerves,  850 
vein,  ascending,  674 
veins,  674 
vertebrae,  151 

development  of,  152 
Lumbo-iliac  ligament,  336 
Lumbo-sacral  ligament,  336 

nerve,  850 
Lumbricales  muscles  (foot),  532 

(hand),  496 
Lungs,  1116 
air-cells  of,  1119 
bronchial  arteries,  1120 

veins,  1120 
capillaries  of,  1119 
development  of,  134 
in  foetus.  1097 
lobes  and  fissures  of,  1117 
lobules  of,  1119 
lymphatics  of,  692,  1120 
nerves  of,  1120 
pulmonary  artery.  1119 

veins,  1119 
root  of,  1118 
structure  of,  1118 
surface-marking,  1120 
weight,  color,  etc.,  1118 
Lunula?,  1091 
of  nails,  92 
Luschka's  gland.  617 

ligaments,  1084 
Lymph,  37 
path  or  sinus,  88 
-vessels  of  liver,  1058 

of  pancreas,  1072 
Lymphatic  or  lymphatics,  struc- 
ture of,  85 
bone,  56 
origin  of,  86 
plexus  of,  86 

subdivision  into  deep  and  su- 
perficial, 679 
terminations  of,  87 
valves  of,  86 

descriptive  anatomy: 
abdomen,  687 
arm,  684 
bladder,  689 
broad  ligaments,  689 
cardiac,  692 
cerebral,  682 
cervical,  superficial  and  deep, 

683 

chest,  692 
of  clitoris,  689 
of  cranium,  682 
diaphragm,  692 
duct,  right,  681 
face,  deep,  682 

superficial,  682 
Fallopian  tubes,  689 
glands,  structure  of,  87 
anterior  mediastinal,  691 


1230 


INDEX. 


Lymphatic   or    lymphatics,   de- 
scriptive anatomy  : 
glands,  auricular  posterior,  681 

axillary,  684 

brachial,  684 

bronchial,  692 

buccal,  681 

cervical,  deep,  683 
superficial,  683 

in  front  of  elbow,  684 

glu teal,  686 

of  head,  681 

iliac,  external,  687 
internal,  688 

inguinal,  deep,  686 
superficial,  686 

intercostal,  691 

internal  mammary,  691 

ischiatic,  686 

of  large  intestine,  691 

of  lower  extremity,  686 

lumbar,  688 

of  neck,  684 

occipital,  681 

parotid,  681 

of  pelvis,  687 

popliteal,  686 

radial,  684 

sacral,  688 

of  small  intestines,  691 

of  spleen,  690 

of  stomach,  690 

submaxillarv,  681 

of  thorax,  691 

tibial  anterior,  686 

of  upper  extremity,  684 

zygomatic,  681 
gluteal  region,  689 
head,  superficial,  681 
heart,  692 
intercostal,  691 
internal  mammary,  692 
intestines,  691 
kidneys,  690 
labia,*690 
lacteals,  691 
large  intestine,  691 
leg,  686 
liver,  690 

lower  extremity,  686 
lung,  692 

lymphatic  duct,  681 
meningeal,  682 
mouth,  682 
neck,  681 
nose,  682 
esophagus,  692 
ovaries,  690 
pancreas,  690 
pelvis,  689 
penis,  689 
perina?urn,  689 
pharynx,  683 
pia  mater,  682 
prostate,  689 
rectum,  689 
scrotum,  689 
small  intestine,  691 
spleen,  690 
stomach,  690 
testicle.  690 
thoracic  duct,  680 
thorax,  691 
thymic,  692 
thyroid,  692 


Lymphatic   or    lymphatics,   de- 
scriptive anatomy: 
upper  extremity,  685 
deep,  686 
superficial,  685 
uterus,  689 
vagina,  689 

Lymphoid  connective  tissue,  49 
of  tongue,  882 

M. 

Macula  cribrosa,  921 

lutea,  902 

Magnum  of  carpus,  266 
Majendie,  foramen  of,  694 
Malar  bone,  1 96 

articulations  of,  197 
attachment   of   muscles  to, 

197 

development  of,  197 
frontal  process  of,  196 
maxillary  process  of,  197 
orbital  process  of,  197 
zygomatic  process  of,  197 

canals,  196 

nerves,  from  fascial,  814 

process  of  superior  maxillary, 

192 

Male  urethra,  1146 
Malleolar  arteries,  external  and 

internal,  643 
Malleolus,  external,  297 

internal,  297 
Malleus,  918 

development  of,    125 

suspensory  ligament  of,  919 
Malpighi,  pyramids  of,  1129 
Malpighian    bodies   of    kidnev, 
1129 

capsules.  1129 

corpuscles  of  spleen,  1080 

tufts,  1129 
Mamma,  areola  of,  1178 

lobules  of,  1179 

nerves  of,  1179 

nipple  or  mammilla  of,  1179 

vessels  of,  1179 
Mammae,  development  of,  125 
Mammary  artery,  internal,  586 

glands,  1178 

lymphatic  glands,  681 

veins,  internal,  666 
Mammilla  of  breast,  1178 

of  kidney,  1129 
Mammillary  processes,  152 
Manubrium  of  malleus,  918 

of  sternum,  228 
Margo,  crenatus,  1074 

intermedius,  1074 

obtusus,  1074 
Marrow  of  bone,  55 
Marshall,  vestigial  fold  of,  666 
Masseter  muscle,  403 
Masseteric  arteries,  562 

nerve,  805 

veins,  652 
Mastoid  cells,  176 

foramen,  175 

portion  of  temporal  bone,  175 

process,  176 

vein,  653 

Masto-occipital  suture,  207 
Masto-parietal  suture,  207 
Matrix  of  nail,  92 


Maxillary  arch,  foetal,  119 
artery,  internal,  559 
bone,  inferior,  201 
superior,  189 

development  of,  194 
nerve,  inferior,  805 

superior,  801 
process  of  inferior  turbinated, 

200 

of  malar  bone,  197 
processes,  foetal,  119 
tuberosity,  190 
vein,  internal,  652 
Measurements  of  thorax,   1083, 

1099 
Meatus  auditorius  externus,  177 

interims,  177 
of  nose,  inferior,  221,  888 
middle,  221,  887 
superior,  221,  887 
urinarius,  female,  1165 

male,  1147 
Meatuses  of  the  nose,  221,  887, 

888 

Meckel's  cartilage,  119 
cavum,  797 
ganglion,  803    - 
Median  artery  of  forearm,  603 

of  spinal  cord,  583 
disk  of  Hensen,  67 
nerve,  840 

surgical  anatomv  of,  844 
vein,  663 

Mediastinal  arteries,  from  inter- 
nal mammary,  586 
posterior,  from  aorta,  606 
lymphatic  glands,  651 
Mediastinum,  anterior,  1116 
middle,  1116 
posterior,  1116 
superior,  1115 
testis,  1157 

Medio-tarsal  joint,  379 
Medulla,  closed  part  of,  713 
gray  matter  of,  713,  715 
oblongata,  706-719 
open  part,  715 
spinal  is,  695 
Medullary    canal    of  bone,    62, 

143 

formation  of,  63 
of  spine,  development  of.  120 
membrane  of  bone,  54 
plates,  107 

sheath  of  nerve-fibres,  71 
spaces  of  bone,  7 1 
of  kidney,  112S 
of  suprarenal  capsules,  1139 
velum,  inferior  of  cerebellum, 

733,  734,  738 
superior,  733,  734,  738 
Medullated  nerve-fibres,  71 
Medullo-spinal  veins,  668 
Meibomian  glands,  908 
Mi'inbrana  basilaris,  924 

fusca,  891 
flaccida,  918 
grannlosa,  of  Graafian  vesicle, 

1176 

limitans  of  retina,  899 
pupillaris,  898 
sacciformis,  360 
tectoria,  924 
tympani.  918 
secnndaria,  923 


IXDEX. 


1231 


Mt- uibrane  of  aqueous  chamber, 

- 

arachnoid,  spinal,  694 
choroid.  894 
of  Corti,  t'24 

•-ooracoid,  468 
crico-thyroid,  1103 
of  i  ^92 

fene?traU- 
hyaloid. 
Jacob's.  901 
limiting,  899 
pituitarv,  887 
pupillary,  898 

i~ner.  ','24  _ 
-    .neiderian.  -  - 
thyro-hyoid,  1103 
Membranes  of  spinal  cord,  693 
Membranous  labyrinth.  926 
portion  of  urethra,  114'i 
semicircular  canaU 
Meningeal  artery,  from  ascending 

pharyngea 
anterior,   from  internal   ca- 

rotii : 

middle,  from  internal  maxil- 
lary, 560 

from  occipital.  557 
posterior,  from  vertebral.  5'»2 
small,  from  internal  maxil- 
lary. 561 
lymphatics, 

Meninges.     See  Membranes. 
Mental  foramen.  202,  217 
pr 

spines.  '- 
tuberc1--.  2u2 

Mesencephalon,  121.  706,  740 
Mc-t-rneric  artery,  inferior,  614 

superior,  613 
glands.  Ota 
plexus  of  nerves,  inferi'  : 

superior.  ^~~ 
vein,  inferior.  675 
superior. 

iteriolum,  989 

Mesentery.  970,  976,  979,  989 
Mt-  blast,  104 
M-:-  'iila.rtic  somites.  107 

•Ion.  979 
transverse.  970 
:eriii.  104 
_  :-tric  zoiit-. 

:um,  970,  973 
\\.-~  inei.ihros.  135 
Mesorciiium,  137 
Mt-  irectum,  1"   - 
M..-'>salpinx.  1170 
-termini.  229 
riuii).  Io7 
Metacarpal  artery,  600 

articulations,  361 
Metacarpo-phalangeal     articula- 
tion^ 
Metacarpu- 

common  characters  ol    - 
.development  of.  272 
peculiar  bones  of,  268 
Metanephros.  135 
M-  'Msternum,  229 
Metatarsal  artery.  H44 
articulations,  385 
bone- 

Metatarso-phalangeal     articula- 
tions, 386 


Metatarsus,  306 

development  of,  308 

Metencephalon,  120,  706 

Mid-brain,  706,  740-745 

Middle     and     internal     frontal 

artery,  572 

clinoid  processes,  180 

ear,  or  tympanum,  916 

fossa  of  skull,  210 

meatus,  221,  887 
Mid-frontal  process,  fetal,  119 
Milk  teeth,  935 
Mitral  valve,  1093 
Mixed  bones.  144 
Modiolus  of  cochlea,  923 
Mohl,  glands  of,  907 
Molar  glands,  931 

teeth,  933 
Monro,  foramen  of,  708,  751, 752, 

761 

Monticulus,  730 
Morgagni,  column  of,  1042 

hydatid  of,  138 

sinus  of,  420.  1042 

valves  of,  1042 
Motor  nerves,  78 

oculi  nerve.  7 '.'4 

surgical  anatomy  of,  795 
Motorial  end-plates,  78 
Mouth,  930 

mucous  membrane  of,  931 

muscles  of,  400 

surface  form  of,  949 
Movement   admitted    in   joints, 

316 

Mucilaginous  glands.  314 
Mucoid  connective  tissue,  48 
Mucous  glands  of  tongue,  882 

membrane.  V7 
Miiller,  duct  of,  136 

fibres  of,  902 
Multicuspidati  teeth,  933 
Multifidus  spina?  muscle,  438 
Muscle,     general     anatomv     of, 
64 

of  animal  life,  64 

arrangement  of  fibres  of, 
65 

bipenniform.  388 

blood-vessels  of.  >'<~ 

chemical  composition  of,  68 

derivation  of  names,  388 

development  of,  126 

fasciculi  of,  65 

fibres  of,  65 

fibrils  of,  65 

form  of,  388 

involuntary,  78 

lymphatics  of,  68 

meaning  of  the  terms  "  origin  " 
and  "insertion,"  389 

mode  of  connection  of,  with 
bone,  cartilage,  skin,  etc., 
389 

nerves  of,  68,  78 

of  organic  life.  ~  - 

sarcous  elements  of,  66 

sheath  of,  65 

size  of.  888 

striped,  65 

structure  of.  65 

tendons  of,  389 

triangular,  388 

unstriped,  68 

voluntary.  04 


Muscles  or    muscle,  descriptive 

anatomy : 
of  abdomen,  447 
abductor  hallucis.  530 

indicis,  496 

minimi  digiti  (foot),  531 
(hand),  494 

pollicis  (hand  ,  492 
accelerator  urinae,  461 
accessorii  orbicularis  oris,  401 
accessorius  pedis,  532 

ad  ilio-costalem,  436 
adductor  brevis,  512 

longus,  512 

magnus,  513 

obliquas  hallucis,  533 
pollicis  (hand),  493 

transversus  hallucis,  533 

pollicis,  493 
anconeus,  486 
antitragicus,  914 
arvteno-epiglottideus,  inferior, 
1107 

superior,  1107 
arytenoideus,  1106 
attollens  aurem,  394 
attrahens  aurem.  393 
azygos  uvulae,  422 
biceps  (arm\  476 

(thigh),  518 
biventer  cervicis,  437 
brachialis  anticus,  477 
buccinator,  402 
bulbo-cavernosus,  461 
cervicalis  ascendens,  436 
chondro-glossus.  416 
ciliary,  of  eye,  898 
circumflexus  palati,  422 
coccygeus,  460 
complexus,  437 
compressor  narium  minor,  399 

nasi,  399 

sacculi  laryngis.  1107 

urethrae.  465 

in  female,  1208 
constrictor  isthmi  faucium,  416 

pharyngeus  inferior,  419 
medius,  420 
superior,  420 
coraco-brachialis,  476 
corrngator  of  cranial  region, 
391 

cutis  ani.  1040 

supercilii,  395 
cremaster.  452 

crico-arytenoideus       lateralis, 
1106 

posticus,  1105 
crico-thyroid.  1105 
crureus.  510 
cutis  ani.  45S 
deltoid,  471 
depressor  ala?  nasi.  399 

anguli  oris,  401 

labii  inferioris.  401 
diaphragm,  444 
digastric,  413 
dilatator  naris.  anterior,  399 

posterior,  399 
erector  clitoridis,  465 

penis,  4»'>2 

spina>.  4:>4 
of  external  ear,  394 

sphincter, 
extensor  brevis  digitorum.  530 


1232 


INDEX. 


Muscles  or    muscle,   descriptive 

anatomy : 

extensor  brevis  pollicis,  488 
carpi  longior,  484 
radialis  brevior,  484 
ulnaris,  486 
coccygis,  438 
digitorum  communis,  485 
indicis,  488 
longus  digitorum,  521 

pollicis,  488 
minimi  digiti,  485 
ossi  metacarpi  pollicis,  486 
primi     internodii     pollicis, 

488 

proprius  hallucis,  521 
of  face,  394 

femoral  region,  anterior,  505 
internal,  511 
posterior,  518 
fibula r  region,  527 
flexor  accessorius,  532 
brevis  digitorum,  530 
hallucis,  532 
minimi  digiti  (foot),  533 

(hand),  494 
pollicis  (hand),  492 
carpi  radialis,  479 

ulnaris,  480 

digitorum  sublimis,  480 
longus  digitorum,  525 
hallucis,  525 
pollicis  (hand),  482 
ossis  metacarpi  pollicis,  492 
profundus  digitorum,  481 
fusiform,  388 
gastrocnemius,  522 
gemellus  inferior,  517 

superior,  517 
genio-hyo-glossus,  415 
genio-hyoid,  414 
glutens  maximus,  514 
medius,  515 
minimus,  516 
gracilis,  511 
of  hand.  492 
of  head  and  face,  390 
helicis,  major,  914 

minor,  914 
Hilton's,  1107 
of  hip,  514 
Horner's  395 
hyo-glossus,  416 
iliac  region,  503 
iliacus,  504 
ilio-costalis,  434 
infracostal,  442 
infraspinatus,  473 
intercostal,  441 
internal  sphincter,  459,  1041 
interossei  of  foot,  534 

of  hand, 496 
interspinales,  438 
intertransversales,  438 
ischio-cavernous,  462 
labial,  400 
of  larynx,  1105 
latissimus  dorsi,  430 

of  leg,  520 

levator  anguli  oris,  400 
ani,  414 

glandulae  thyroidese,  1123 
labii  inferioris,  400 
inenti,  400 
superioris,  400 


Muscles   or   muscle,  descriptive 

anatomy  : 

levator  labia  superioris  alseque 
nasi,  399 

palati,  421 

palpebroe,  395 

prostate,  460 
levatores  costarum,  442 
lingualis,  415 
longissimus  dorsi,  436 
longus  colli,  425 
lumbricales  (foot),  532 

(hand),  496 
masseter,  403 
multifidus  spinse,  438 
musculus  accessorius   ad   ilio- 

costalem,  436 
mylo-hyoid,  414 
naso-labialis,  399 
of  neck,  406 
obliquus  abdominus  ex  tern  us, 

448 
intern  us,  451 

auris,  914 

capitis  inferior,  439 

superior,  439 
obturator,  externus,  518 

internus,  516 
occipito-frontalis,  391 
oculi,  inferior,  397 

superior,  397 
omo-hyoid,  412 
opponens  minimi  digiti,  495 

pollicis,  492 
orbicularis  oris,  401 

palpebrarum,  394 
palate,  421 
palato-glossus,  422 
pulato-pharyngeus,  422 
palmaris  brevis,  494 

longus,  480 
pectineus,  511 
pectoralis,  major,  467 

minor,  469 
penniform,  388 
of  perineum,  female,  464 

male,  458 
peroneus  brevis,  527 

longus,  527 

tertius,  522 
of  pharynx,  419 
plantaris,  524 
platysma  myoides,  407 
popiiteus,  524 
pronator  quadratus,  483 

radii  teres,  479 
psoas  magnus,  504 

parvus,  504 
pterygoid,  external,  404 

internal,  405 
pyramidalis  abdominis,  455 

'  nasi,  399 
pyriformis,  516 
quadratus  femoris,  517 

lumborum,  458 

menti,  401 
quadriceps     extensor    cruris, 

509 

quadrilateral,  388 
recto-coccygeus,  1041 
rectus  abdominis,  453 

capitis  anticis  major,  424 
minor,  424 

femoris,  509 
•  lateralis,  425 


Muscles   or   muscle,   descriptive 

anatomy  : 

rectus  oculi,  externus,  superior, 
inferior,  and  internus,  397 

posticus  major,  439 

minor,  439 
retrahens  aurern,  394 
rhomboidal,  388 
rhomboides  major,  431 

minor,  431 
risorius,  402 
rotatores  spins?,  438 
sacro-lurnbalis,  434 
salpingo-phiiryngeus,  423 
sartorius,  508 
scalenus  anticus.  425 

medius,  425 

posticus,  426 
scapulse,  431 
semimembranosus,  519 
semispinalis  colli,  437 

dorsi,  437 

semitendinosus,  519 
serratus  magnus,  470 

posticus,  inferior,  432 

superior,  432 
sole  of  foot,  529 
first  layer,  530 
fourth  layer,  534 
second  layer,  532 
third  layer,  532 
soleus,  523 
sphincter,  external,  458 

internal,  459 

tertius,  1042 

vagi  me,  464 
spinalis  colli,  436 

dorsi,  436 
splenius,  433 

capitis,  433 

colli,  433 
stapedius.  920 
sterno-cleido-mastoid,  409 
sterno-hyoid,  409 
sterno-thyroid,  409 
stylo-glossus,  416 
stylo-hyoid,  413 
stylo-pharyngeus,  420 
subanconeus,  478 
subclavius,  469 
subcrureus,  510 
subscapularis,  472 
supinator  brevis,  486 

longus,  483 
supraspinales,  438 
supraspinatus,  473 
temporal,  403 
tensor  palati,  422 

tarsi,  395 

tympani,  920 

vaginae  femoris,  508 
teres  major,  474 

minor,  474 

thyro-arytenoideus,  1106 
thyro-epiglottic,  1107 
thyro-hyoid,  411 
tibialis  anticus,  521 

posticus,  526 
of  tongue,  416 
trachelo-mastoid,  436 
tragicus,  914 
transversalis  abdominis,  453 

colli,  436 
transversus  auricula?,  914 

perinsei,  461 


IXDEX. 


1233 


Muscles  or  muscle,   descriptive 

anatomy : 
transversus    perinaei  (female), 

404 

profundus. 
trapezium.  4:> 
of  Treitz. 
triangular 

triangularis  sterni,  442 
triceps,  extensor  cruris,  509 

cubiti.  477 

femoralis,  510 

of  tympanum,  920 

of  ureters.  1146 

vastus  externus,  509 

internus  and  crurens,  510 
zygomatieus  major,  4"U 

minor,  400 

Muscles  of  inspiration  and  ex- 
piration, 444 
Muscular  coluui; 
fibres  of  bear- 
process,  1U>2 
Muscularis  mucosse,  97 

ili  i>apillares,  left  ventricle, 
1093 

right  ventricle,  1090 
pectinati  in  left  auricle,  1092 

in  right  auricle,  1089 
Musculo-cutaneous  nerve  of  arm, 

839 

from  peroneal,  864 
Musculo-spiral  groove,  250 

surgical  anatomy  <.[.  > -14 
nervr 

Musculo-phrenic  artery,  586 
Musculus     accessorius    ad    ilio- 

costalem,  436 
Myelo-plaques.  55 
Mylo-hyoid  artery,  561 
groove,  203 
muscle.  414 
nerve,  807 
ridgt 

Myocardium,  1094 
Myrtiform  fossa,  190 

X. 

Nails.  92 

Nares.  anterior.  222.  886 
:   ;    _ .  -.  886,  951 

sepiurij  of,  22U,  886 
Na*ai  angk 

artery,  of  internal  maxillarv. 

of  ophthalmic,  570 
of  septum,  556 

bone- 
articulations  of,  189 
development  of,  189 

cartilages.  -  3 

cre^: 

duct.  911 

eminence,  171 

fossa?,  219,  886 
arteries  of,  889 
mucous  membrane  of,  888 
nerves  of.  889 
surgical  anatomy  of,  889 
veins  of,  889 

groove,  189 

nerve,  798 

nerves  from  Meckel's  ganglion, 


Nasal  notch,  171 
process,  192 
spine.  171 

anterior,  194,  217 
-  posterior,  196 
venous  arch,  651 
Nasion,  217 

Nasmy  th's  membrane,  940 
Naso-maxillary  suture,  217 
Nas<>- palatine  nerve.  803 
Navicular  bone,  304 

articulations  of,  305 

attachment   of    muscles   to, 
30-5 

tuberositv  of,  304 
Neck,  glands'of,  683 
lymphatics  of,  681 
muscles  of,  406 
triangle  of,  anterior,  563 

posterior,  565 
veins  of,  653 
Nerve-cells,  70 
Nerve-epithelium  cells,  78 
Nerves,  structure  of,  73 
cerebro-spinal,  73 
en •loneiiriurn,  74 
epineurium.  74 
funiculi  of,  73 
origin  of.  7"> 
perineum,  74 
plexus  of,  75 
sheath  of.  74 
sympathetic,  75 
termination  of,  75 
vessels  of,  74 
Nerves    or     nerve,    descriptive 

anatomy : 
of  alxlucens,  810 
accessory  obturator,  854 
anterior  crural,  855 
articular.  V4'_' 
ascending  cutaneous,  862 
auditory,  ,S15 

roots  of  lateral,  815 

mesial,  815 
auricular,  posterior,  813 

of  vagus,  821 
auricularis  magnus.  831 
of  auriculo-temporal,  806 
of  brachial  plexus,  834 
buccal,  S0« 

of  facial.  <15 
cardiac,  S72 

inferior,  872 

middle,  872 

plexus,  deep.  8 
superficial.  >74 

of  pneumogastric,  819 

superior,  871 
cavernous,  of  penis,  878 
cervical,  anterior,  830 

posterior.  828 

superficial,  831 
cervico- facial,  815 
chorda  tympani,  812,  921 
ciliary,  long,  799 

short,  799 
circumflex,  839 
coccvgeal. 
cochlear. 
communicans  hypoglossi,  833 

peronei,  8H3 

coraco-brachialis,  837,  839 
of  Cotunnius,  805 
cranial,  792 


Nerves    or     nerve,    descriptive 

anatomy : 

crural  anterior,  855 
cutaneous.     See  that  heading. 
deep  palmar,  842 

temporal,  805 
dental  anterior,  802 

inferior,  807 

posterior,  802 
descendens  hypoglossi,  825 
digastric,  from  facial,  813 
digital,  865 

foot,  864 

hand.  841,  842 
dorsal  (hand),  845 

]>eculiar,  848 

of  penis,  861 

spinal,  846 
dorsi-lumbar,  848 
eighth  pair.  >l-r> 
eleventh  pair,  823 
of  eyeball.  793 
facial,  811 

femoral  cutaneous,  862 
fifth,  796 
fourth,  796 
frontal,  798 
ganglionic    branch    of   nasal, 

799 

gastric  branches  of  vagus,  877 
genito-crural,  852 
glosso-pharyngeal,  816 
gluteal.  inferior,  861 

superior,  861 
great  petrosal,  804 

splanchnic,  873 
gustatory,  807 
hsemorrhoidal,  inferior,  861 

of  heart.     See  Cardiac. 
hepatic,  877 
hypoglossal,  823 
ilio-hypogastric,  851 
ilio-ingiiinal,  851 
incisive,  807 
inferior  maxillary.  805 
inframaxillary,  of  facial,  815 
infraorbital,  of  facial,  815 
infratrochlear,  799 
intercostal,  848 
intercosto-humeral,  848 
interosseous,  anterior.  841 

posterior,  844 
ischiadic,  great,  862 

sinal 

Jacobson's,  818 
labial.  803 
of  labyrinth,  927 
lachrymal.  798 
large  cavernous,  878 
laryngeal,  external,  821 

internal,  821 

recurrent,  821 

superior,  821 
lesser  splanchnic,  873 
lingual  of  fifth,  807 

of  glosso-pharyngeal,  818 

of  liver,  1058" 
long  ciliary,  799 

saphenous,  856 

thoracic.  - 
lumbar,  849 
lum bo-sacral,  850 
malar  branch  of  orbital  nerve, 

801 
of  facial,  814 


1234 


INDEX. 


Nerves     or    nerve,    descriptive 

anatomy : 
masseteric,  805 
maxillary,  inferior,  805 

superior,  801 
median,  840 
mental,  807 
middle  cardiac,  872 
motor  of  the  eye,  common,  794 

external,  808 
miisculo-cutaneous,  of  arm,  839 

leg,  865 

musciilo-spiral,  842 
mylo-hyoid,  807 
nasal,  from  Meckel's  ganglion. 
803 

from  ophthalmic,  798 

from  Vidian,  803 
naso-palatine,  805 
ninth,  816 
obturator,  854 
occipital,  of  facial,  813 

great,  828 

small,  831 

of  third  cervical,  829 
O3sophageal,  822 
olfactory.  792 
ophthalmic,  797 
optic,  793 

orbital    nerves    in    cavernous 
sinus,  810 

in  orbit,  811 

their  relation,  810 

in  sphenoidal  fissure,  810 

of  superior  maxillary,  801 
palatine,  anterior  or  large,  804 

external,  804 

posterior  or  small,  804 
palmar,  cutaneous,  of  median, 

841 

ulnar,  842 
palpebral,  803 
of  pancreas,  1022 
par  vagum,  819 
pathetic,  796 
pectineus,  855 
perforans  Casserii,  839 
perforating  cutaneous,  861 
perineal,  861 

cutaneous,  862 

superficial,  861 
peroneal,  864 
petrosal,  deep  large,  804 
small,  816 

long,  816 

superficial,  external,  or  large, 

804 

small,  816 

pharyngeal,  of  external  laryn- 
geal,  821 

of  glosso-pharyngeal,  818 

of  Meckel's  ganglion,  805 

of  pneumogastric,  821 

of  sympathetic,  871 
phrenic,  833 
plantar,  cutaneous,  863 

external,  864 

internal,  863 
pneumogastric,  819 

lingual  branch,  821,  824 
popliteal,  external,  864 

internal,  863 
portia  dura,  811 

inter  duram  et  mollem,  811 

mollis,  811 


Nerves     or     nerve,    descriptive 

anatomy : 

posterior  auricular,  813 
pterygoid,  805 
pterygo-palatine,  805 
pudenda!,  inferior,  862 
pudic,  861 

pulmonary,  from  vagus,  822 
radial,  844 
of  rectum,  1042 
recurrent  laryngeal,  821 

to  tentorium,  796 
renal  splanchnic,  873 
respiratory,  external,  837 

internal",  833 
sacral,  857 

plexus,  859 

saphenous,   long   or    internal, 
856 

short  or  external,  863 
sartorius,  855 
sciatic,  great,  862 

of  second  cervical,  828 

small,  862 
short  ciliary,  799 
sixth,  810  " 
small  cavernous,  878 

occipital,  831 
spinal,  826 

accessory,  823 

recurrent  branch,  827 

roots  of,  826 
splanchnic,  great,  873 

small,  873 

smallest,  873 
of  stomach,  1007 
stylo-hyoid  of  facial,  813 
subclavian,  873 
subcostal,  848 
suboccipital,  828 

posterior  branch  of,  828 
snbscapular,  838 
superficialis  colli,  831 
superior  cardiac,  872 

maxillary,  801 
supra-acromial,  832 
supraclavicular,  832 
supramaxillary  of  facial,  815 
supra-orbital,  798 
suprascapular,  837 
suprasternal,  732 
supratrochlear,  798 
sympathetic,  867 
temporal,   of    auriculo-tempo- 
ral,  806 

deep,  805 

of  facial,  814 
temporo-facial,  813 
temporo-malar,  801 
tenth,  819 

third,  or  motor  oculi,  794 
thoracic  anterior,  838 

posterior,  837 
thyro-hyoid,  825 
tibial,  anterior,  865 

posterior,  863 
of  tongue,  883 
trifacial  or  trigeminus,  796 
twelfth,  823 
tympanic  of  facial,  812 

of  glosso-pharyngeal,  816 
ulnar,  841 

collateral,  843 
uterine,  878 
vaginal,  878 


Nerves     or     nerve,    descriptive 
anatomy : 

vagus,  819 

vestibular,  928 

Vidian,  804 

sphenoidal  filament,  804, 808 

of  Wrisberg,  840 
Nervi  cluninm,  inferiores,  862 
medii,  857 
superiores,  850 

-nervorum,  74 

tentorii,  797 

Nervous  fibrous  matter,  70 
ganglia,  79 

gelatinous  fibres,  72 

layer  of  retina,  899 

substance,   chemical    analvsis, 

72 

gray,  69 
white,  70 

sympathetic,  73 
composition  of,  73 

svstem,    general   anatomy   of, 
69 

white,  or  medullarv  substance, 

70 

Nervus  cardiacus  magnus,  872 
minor,  872 

petrosus  pro  fund  us,  804 

superficialis  cordis,  871 
Neumann,   dentinal    sheath   of, 

937 

Neuroblasts,  121 
Neurokeratin,  73 
Neurilemma,  71,  note. 
Neuroglia,  73 

of  cord,  698 
Neuron,  69 
Ninth  nerve.  816 
Nipple,  1179 
Nodes  of  Ranvier,  71 
Nodulus,  732 

Non-medullated  nerve-fibres,  72 
Nose,  885 

arteries  of,  886 

bones  of,  189 

cartilage  of  septum  of,  886 

cartilages  of,  885 

development  of,  125 

fossa;  of,  219,  886 

mucous  membrane  of,  886 

muscles  of,  398 

nerves  of,  886 

surgical  anatomy  of,  889 

veins  of,  886 
Notch,  anterior  cerebellar,  726 

cotyloid,  278 

ethmoidal,  173,  185 

great  scapular,  244 

intercondyloid,  288 

interlobular,  1049 

nasal,  171 

posterior  cerebellar,  726 

Rivini,  914 

sacro-sciatic,  greater,  276 
lesser,  276 

sigmoid,  204 

spheno-palatine,  199 

supra  orbital,  171 

suprascapular,  245 

thyroid,  1100 

umbilical,  1049,  1051 
Notochord,  107,  115 
Nuck,  canal  of,  1162,  1177 
Nuclei  of  medulla,  515 


1235 


Nuclei  of  optic  thalamus,   747, 
748 

pontis,  721 

StilliiiL'. 
Nucleus.  717 

amygdala?,  760 

of  auditory  nerve,  716, 
acci- 

dorsal.  xl-"' 
ventral. 

caudal  u>. 

of  :i  cell,  39 

cuneatus,  714 
access"  <ri  us.  714 

dentate,  of  medulla,  710,  717 

facial  nerve.  723 

fifth  nerve.  722 

fourth  nerve.  744 

glosso-pharyngeal  nerve,  716 

gracilis,  714 

hypoglossal  nerve,  716 

lenticularis,  759 

Luvs.  745 

olivary.  710,  743 

red.  743 

Rolando,  711 

sixth  nerve.  722 

spinal  accessory  nerve,  716 

superior  olivary.  722 

third  nerve,  744 

vagus  nerve.  716 
Nutrient  artery  of  bone,  55 
Nympha?,  1164 

lymphatics  of,  689 

O. 

Obelion,  208 

Obex,  740 

Oblique  inguinal  hernia.  1187 

coverings  of,  1187 
ligament.  354 
line  of  the  clavicle,  239 
of  lower  jaw.  .   I 
of  radius,  259 
ridge  of  ulna.  _ 
Obliquus  auris  muscle,  914 
externus  abdominis,  448 
inferior  capitis,  439 

ocuL 

internus  abdominis,  449 
superior  capitis.  439 

oculi.  3y7 
Obturator  artery. 

peculiarities  of,  623 
relation  of,  to  femoral  ring, 

1123 
externus  muscle,  518 

ia,  1209 
foramen.  23  - 
internus  muscle,  516 

|  .raent  or  membrane,  516 
nerve,  854 
accessory,  854 
surgical  anatomy  of,  866 
vein-. 

Occipital  artery,  556 
bone,  U'«4 

articulations  of.  168 
attachment  of  muscles  to,  1G8 
development  of,  lt>7 
crests,  164.  166 

protuberances,  164,  166 
fossae,  165 
lymphatic  glands,  681 


Occipital  lymphatic  groove,  176 

sinus,  659 

triangle,  565 

vein,  653 
Oecipito-atlantal       articulation, 

325 

Occipito-axial  articulation,  326 
Occipito-frontalis  muscle,  391 
Occiput,  arteries  of,  556 
Ocular  cleft,  123 

cup,  123 

vesicle,  primitive,  123 

secondary.  123 
Odontoblasts.  935 
Odontoclasts,  943 
Odontoid  ligaments,  326 

process  of  axis,  148 
CEsophageal  arteries.  606 

branches  of  vagus  nerve,  822 

glands,  953 

incisure,  1052 

opening  of  diaphragm,  446 

plexus.  K 
CEsophagus,  952 

lymphatics  of,  692 

nerves  of,  954 

structure  of,  953 

surgical  anatomy  of,  954 

vessels  of,  953 
Olecranon  process,  254 

fracture  of,  501 
Olfactory  bulb,  782,  788 

cells,  888 

foramina,  185 

fossae,  fretal.  125 

lobe 

lobule,  anterior,  782 
posterior,  784 

nerve,  792 

roots,  784 

sulcus,  7'.'2 

surgical  anatomy  of,  793 

tract,  782,  783 

Olivary  bodies  of  medulla  ob- 
longata,  710,  717 

nucleus.  710 

peduncle,  715 

process,  180 
Olive,  710 
Omega  loop,  1044 
Omental  plate,  975 
Omentula,  Iu2> 
Omentum  colicum,  988,  991 

gastro-colic,  991 

gastro-splenic,  971.  991.  1076 

great,  971,  973,  975,  991 

hepato-gastric,  971,  991 

lesser,  971,  991,  1053 
Omo-hyoid  muscle.  412 
Omphalo-mesenteric  arteries,  foe- 
tal. 127 

duct,  109 

veins.  127 

Opening  of  aorta  in  left  ventricle, 
1092 

aortic,  in  diaphragm,  446 

canal,  in  diaphragm.  44'j 

of  coronary  sinus.  1089 

of  inferior  cava,  1088 

left  auriculo-ventricular,  1092 

of  pulmonary  artery,  1090 
veins,  1091 

right      auriculo  -  ventricular, 
1092 

saphenous,  507,  1092 


Opening  of  superior  cava,  1090 
Operations : 

amputations  of  foot,  311 

of  penis,  1037 
arteries,  ligature  of,  abdominal 

aorta,  609 
axillary,  591 
brachial,  596 
carotid,  common,  550 
external,  551 
internal.  568 
femoral,  633 
iliac,  common,  619 
external,  628 
internal,  621 
innominate,  546 
lingual,  553 
popliteal,  638 
radial,  598 
subclavian,  579 
thyroid,  inferior,  585 
tibial,  anterior,  642 

posterior,  645 
ulnar,  602 
catheterism     of      Eustachian 

tube,  952 

cholecystotomy,  1066 
for  cleft  palate,  423 
colotomy,  1047 

division  of  nerves,  facial,  815 
infraorbital,  809 
lingual,  809 
sciatic,  great,  866 
spinal  accessory,  822 
supra-orbital,  809 
excision  of  ankle,  380 
elbow,  353 
hip,  367 
knee,  375 
of  shoulder,  349 
extirpation  of  spleen,  1082 

of  thyroid,  1124 
gastrostomy,  1008 
gastrotomy,  1007 
hamstring     tendons,    division 

of,  520 

laryngotomy,  1112 
lithotomy,  12<'7 
nephrotomy  and  nephrectomy, 

1135 

oesophagotomy,  954 
paracentesis    of   pericardium, 

1086 

prostatectomy,  1150 
puncture  of  the  bladder,  1145 
removal  of  the  bladder,  241 
lower  jaw,  226 
scapula,  247 
testis,  1159 
tongue.  418,  883 
upper  jaw,  226 
for  strabismus,  398 
topping  chest,  238 
for  torticollis,  411 
tracheotomy  1112 
venesection,  663 
Opercular,  778 
Ophthalmic  artery,  568 
ganglion.  799 
nerve,  797 
vein,  659 
Opponens  minimi  digiti  muscle, 

495 

pollicis  muscle,  492 
Optic  commissure,  752 


1236 


INDEX. 


Optic  foramen,  180,  210 

groove,  180,  210 

nerve,  793 

intercerebral  fibres  of,  793 
interretinal  fibres  of,  793 
surgical  anatomy  of,  794 

recess,  751 

thalamus,  746-748 

tract,  752 

vesicle,  752 
Ora  serrata,  898 
Oral  cavity,  930 

sinus,  119 
Orbicular  bone,  919 

ligament,  353 
Orbicularis  oris  muscle,  401 

palpebrarum,  394 
Orbit,  217 

arteries  of,  569 

muscles  of,  396 

relation  of  nerves  in,  811 
Orbital  artery,  562 

foramina,  183 

nerve,  801 

process  of  malar,  197 

of  palate,  199 

Organic  constituent  of  bone,  60 
Organs  of  Golgi,  78 
Orifice,  anal,  1038 
Os  calcis,  299 

development  of,  308 

hyoids,  227 

innominatum,  272 
development  of,  278 

magnum  of  carpus,  266 

orbiculare,  919 

planum,  186 

unguis,  195 

uteri,  1169 
Ossa  triquetra,  188 
Ossicula  auditus,  919 
ligaments  of,  919 
Ossification  of  bone,  60 

defects  in,  163 

intracartilaginous,  60 

intramembranous,  63 

period  of,  64 

of  spine,  progress  in,  154 

subperiosteal,  59 
Osteoblasts,  60 
Osteoclasts,  55 
Osteology,  143 

Ostinm  abdominale  of  Fallopian 
tube,  1174 

internum  or  nterinum,  1170 
Otic  ganglion,  807 
Otoliths,  927 
Outlet  of  pelvis,  281 
Ovarian  arteries,  616 

plexus  of  nerves,  876 

veins,  674 
Ovary,  1175 

development  of,  137 

Graafian  follicles  of,  1176 

ligament  of.  1177 

lymphatics  of,  690 

nerves  of,  1178 

ovicapsule  of,  1176 

shape,  position,    and    dimen- 
sions, 1175 

stroma  of,  1176 

tunica  albuginea  of,  1176 

vessels  of,  1 1 78 

Ovicapsule  of  Graafian  follicles, 
1176 


Oviducts,  1174 
Ovisacs  of  ovarv,  1176 
Ovula  of  Naboth,  1172 
Ovum,  100 

cleavage  of,  102 

discharge  of,  1177 

discus  proligerus  of,  100 

fecundation  of,  102 

germinal  spot  of,  101 
vesicle  of,  101 

vitelline  membrane  of.  100 

yolk  of,  101 

zona  pellucida  of,  100 
Oxyntie  cells  of  peptic  .glands, 
1007 

P. 

Pacchionian  depressions,  169 

glands,  657 

Pacinian  corpuscles,  77 
Pad,  incisive,  944 
Palatal  glands,  944 
Palate,  aponeurosis  of,  422 
arches  of,  944 
bone,  197 

articulations  of,  200 
attachment   of    muscles   to, 

200 

development  of,  199 
horizontal  plate  of,  197 
orbital  process  of,  11)9 
process   of   superior   maxil- 
lary, 193 

splienoidal  process  of,  199 
turbinated  crest  of,  1 98 
vertical  plate  of,  198 
development  of,  119 
hard,  944 
muscles  of,  421 
soft,  944 
Palatine  artery,  ascending,  555 

descending  or  posterior,  562 
canal,  accessory,  197 
anterior,  194 
posterior,  197 
fossa,  anterior,  194 
nerves,  804 
process  of  superior  maxillary, 

193 

Palato-glossus  muscle,  416,  422 
Palato-pharyngeus,  422 
Palmar  arch,  superficial,  604 
branches  of,  604 
surface-marking  of,  604 
cutaneous  nerve,  841,  842 
fascia,  490 

interossei  arteries,  601 
nerve,  deep,  of  ulnar,  842 
superficial,  of  ulnar,  842 
veins,  663 
I  almaris  brevis  muscle,  494 

longus  muscle,  480 
Palpebrse,  907 
Palpebral  arteries,  570 
cartilages  or  plates,  907 
fissures,  907 

surface  form  of,  911 
folds  of  conjunctiva,  908 
ligaments,  908 
muscles,  394 
veins,  inferior,  652 

superior,  652 

Pampiniform    plexus    of    veins, 
674,  1155,  1178 


Pancreas,  971,  1067 

development  of,  134 

lesser,  1070 

lymph-vessels  of,  1072 

lymphatics  of,  690 

relations  of,  1 07 1 

structure  of,  1072 

surface  form  of,  1073 

surfaces  of,  10(i9 

surgical  anatomy  of,  1073 

vessels  and  nerves  of,  1072 
Pancreatic  arteries,  612 

duct,  1070 

plexus  of  nerves,  877 

veins,  675 

Panereatica  magnu  artery,  612 
Pancreatico-duodenal  artery,  in- 
ferior, 613 
superior,  611 

plexus  of  nerves,  .^77 
Papilla  lachrymalis,  910 

spiralis,  925 

Yateri,  1070 
Papillae  conic*  vel  filiformes,  881 

fungiformes  (medi»),  880 

maxima;  (circumvallatio),  880 

of  skin,  91 

of  teeth,  939,  941 

of  tongue,  880 
Papillary  layer  of  skin,  91 
|  Par  vagum,  819 
Paraglobulin,  36 
Paramastoid  process,  165 
Parietal  bones,  HiN 

articulations  of,  170 
attachment  of  muscles  to,  170 
development  of,  170 

cells  of  peptic  glands,  1007 

eminence,  108 

foramen,  169 

veins,  131 

Parieto-sphenoid  artery,  573 
Paroophoron,  138,  1177 
Parotid  fascia,  403,  408 

gland,  945 

accessory  portion  of,  947 
duct  of,'94(i 
nerves  of,  947 
vessels  of,  947 

lymphatic  glands,  681 

veins,  652 

Parovarium,  138,  1177 
Pars  pylorica,  1000 
Patella,  291 

articulations  of,  292 

attachment  of  muscles  to,  292 

development  of,  292 

fracture  of,  537 

structure  of,  292 

surface  form  of,  292 

surgical  anatomy  of,  292 
Pecquet,  reservoir  of,  180 
Pectineus  muscle,  511 

nerve,  855 

Pectiniform,  septum,  11 51 
Pectoral  region,  dissection  of,  467 

ridge,  248 
Pectoralis  major,  467 

minor,  469 

Peculiar  dorsal  vertebrae,  151 
Pedicles  of  a  vertebra,  144 
Peduncles   of  cerebellum,    infe- 
rior, 734,  735,  738 
middle,  734,  735,  738 
superior,  734,  735,  738 


IXDKX. 


1237 


Peduncles,  inferior,   of  cerebel- 
lum, 712 

middle,  of  cerebellum,  720 

olivary,  715 

superior,  of  cerebellum. 
Pedunculi  cerebri,  742 
Pelvic  cavity.  955 

fascia.  1209 

parietal  or  obturator  layer, 
1209 

ral  layer,  1210 

gird! 

plexu-.  878 
Pelvis,  279 

arteries  of,  620 

articulations  of,  336 

axes  of.  i 

boundaries  of,  279 

brim  of.  i 

cavity  of.  2s  1 

diameters  of,  _ 

fal.-t 

inlet  of,  281 

of  kidney,  1 1 2S 

ligaments  of,  336 

lymphatics  of,  687 

male   and  female,   differences 
of.  2 

outlet  of.  2-1 

position  o- 

of  viscera  at  outlet  of,  1206 

surface  form  of,  283 

surgical  anatomy  of,  283 
Penis.  11 50 

arteries  of.  1152 

body  of.  1150 

corpora  cavernosa,  1151 

corpus  spongiosurn,  1152 

development  of.  140 

dorsal  artery  of,  624 
nerve  of,  861 
vein  of,  673 

lymphatics  of,  689,  1153 

muscles  of.  4' '.'2 

nerves  of,  1 1 53 

prepuce  of,  1151 

root  of.  1151 

structure  of,  1153 

surgical  anatomy  of,  1153 

suspensory  ligament,  1150 
Penniform  muscle,  388 
Peptic  glands,  1006 
Perforans  Casserii  nerve.  839 
Perforating  arteries  of  hand,  601 
from  mammary  artery,  586 
from  plantar,  )>47 
from  profunda,  636 

cutaneous  nerve,  861 
Perieeoal  fosse,  997 
Pericardiac  arteries,  586,  606 
Pericardia!  cavity 
Pericardio-thoracic  cavity. 
Pericardium,  diverticula  of,  1084 

fibrous  layer  of,  1084 

nerves  of. 

relations  of,  1083 

serous  layer  of,  1085 

structure"  of,  1084 

vestigial  fold  of,  1085 
Perichondrium,  51 
Perilyrnph,  926 
Perimysium.  »'>5 
Perineal  artery,  superficial,  625 
tran<vei>' 


Perineal  body,  1164 
fascia,  deep,  463,  1204 

superficial,  460 
nerve,  861 

cutaneous,  862 
superficial,  861 
Perineum,  1201 

abnormal  course  of  arteries  in, 

1208 

deep  boundaries  of,  1203 
development  of,  140 
in  the  female,  12*  )7 
lymphatics  of,  689 
in  the  male,  1202 
muscles  of,  458 
surgical  anatomy  of,  1201 
Perineurium,  74 
Periosteum,  54 
of  teeth,  932 
Peripheral  termination  of  nerves, 

76 
Peritoneal     relations    of    liver, 

1054 

spleen,  986,  1076 
sac,  986 

Peritoneum,  955,  962,  978 
development  of,  967 
parietal,  986 
visceral,  988 
Perivascular  lymph-sheaths,  87, 

657 

Permanent  cartilage,  51 
''teeth,  932 
Peroneal  artery,  646 
anterior,  646 
peculiarities  of,  646 
nerve,  864 
ridge,  301 
veins,  671 

Peroneus  brevis  muscl 
longus  muscle,  527 
tertius  muscle,  522 
Perpendicular  plate  of  ethmoid, 

186 

line  of  ulna,  258 
Pes  accessorius,  759,  765 
anserinus,  812 
hippocampi,  759 
Petit,  canal  of,  905 

triangle  of.  44!  • 
Petrosal  nerve,  deep  large,  from 

Vidian,  804 
small,  818 
long,  818 

small  superficial,  818 
superficial  large,  804 
sinus  inferior,  660 

superior,  660 

Petro-mastoid    portion    of   tem- 
poral bone,  179 
Perro-occipital  suture,  207 
Petro-sphenoidal  suture,  207 
Petrous  ganglion,  817 

portion  of  temporal  bone,  1 76 
Fever's  glands,  1025 
Phalanges,  han-i 

articulations  of.  270.  362 
development  of. 
foot,  308 

articulations  of,  308,  387 
development  of,  308 
Pharyngeal  aponeurosis,  951 
artery,  ascending,  558 
ganglion.  871 
glands,  951 


Pharvngeal  nerve,  from  external 
"  laryngeal,  821 
from  glosso-pharyngeal,  818 
from  Meckel'  s  ganglion,  805 
from  sympathetic,  .^71 
from  vagus,  821 
plexus  of  nerves,  821,  871 
spine,  165 
tonsil,  953 
vein,  654 
Pharynx,  951 

aponeurosis  of,  951 
arteries  of,  558 
development  of,  132 
mucous  membrane  of,  951 
muscles  of,  419 
surgical  anatomy  of,  952 
Phlebolitbs,  673 
Phrenic  arteries,  616 
nerve,  833 

plexus  of  nerves,  875 
veins,  675 

Phrenico-hepatic  fossa,  994 
Phreno-colic  ligament,  1036 
Pia  mater  of  cord,  705 
Pigment,  50 
of  iris,  897 
of  skin,  91 

Pigmentary  layer  of  retina,  901 
Pillars  of  diaphragm,  446 
of  external    abdominal    ring, 

449,  1182 
of  fauces,  944 
Pineal  gland,  748 
recess,  748 

arteries  of,  914 
Pinna  of  ear,  912 
cartilage  of,  912 
ligaments  of,  913 
muscles  of,  913 
nerves  of,  914 
structure  of,  912 
vessels  of,  914 
Pisiform  bone,  264 
Pituitary  body,  751 

development  of,  119 
fossa,  180 
membrane,  887 
Pivot-joint,  316 
Placenta,  115 
Placental  sinus,  115 

circulation,  129 
Plantar  artery,  external,  647 

internal,  647 
cutaneous  nerve,  863 
fascia,  529 
ligaments,  381 
nerve,  external,  864 

internal,  863 
veins,  external,  671 

internal,  671 
Plantaris  muscle,  524 
Plasma,  36 
Plates,  omental,  975 
tarsal,  908 
tympanic,  914 
Platysma  myoides,  407 
Pleura,  955,"  1113 
cavity  of,  955,  1113 
costaiis,  1113 
pulmonalis,  1113 
reflections  of,  traced,  1113 
surgical  anatomy  of.  1114 
vessels  and  nerves  of,  1114 
Pleural  cavity,  955 


1238 


INDEX. 


Plenral  sinuses,  1114 
Plexus  of  nerves,  75 

brachial,  834 

cardiac,  deep,  874 
superficial,  874 

carotid,  869 
external,  869 

cavernous,  869 

cervical,  831 
superficial,  831 

choroid,  766,  769,  770 

coeliac,  876 

coronary,  anterior,  875 
posterior,  874 

cystic,  877 

diaphragmatic,  875 

epigastric  or  solar,  875 

facial,  871 

gastric,  877 

gastro-duodenal,  877 

gastro-epiploic,  877 
left,  877 

great  cardiac,  874 

haemorrhoidal,  inferior,  978 
superior,  878 

hepatic,  877 

hypogastric,  877 
inferior,  878 

lumbar,  850 

mesenteric,  inferior,  877 
superior,  877 

cesophageal,  822 

ophthalmic,  869 

ovarian,  876 

pancreatic,  877 

pancreatico-duodenal,  877 

patellae,  856 

pharyngeal,  821,  871 

phrenic,  875 

prostatic,  878 

pulmonary,  anterior,  822 
posterior,  822 

pyloric,  877 

renal,  875 

sacral,  857 

sigmoid,  877 

solar,  875 

spermatic,  875 

splenic,  877 

superficial  cardiac,  874 

suprarenal,  875 

tonsillar,  818 

tympanic,  810 

uterine,  878 

vaginal,  878 

vertebral,  872 

vesical,  878 
Plexus  magnus  profundus,  874 

of  veins.     See  Veins. 
Plica  epigastrica,  964,  1190 

hypogastrica,  964,  1190 

prsepylorica,  1000 

recti,'  1041 

semilunaris,  909,  987 

transversalis,  1042 

urachi,  964 

ureterica,  1144 
Plicae  adiposse,  986 

palmatae,  1171 
Pneumogastric  nerve,  819 
Polar  globules  of  Robin,  101 
Pomum  Adami,  1100 
Pons,  gray  matter  of,  721 

hepatis,  1051,  1062 

nuclei  of,  721 


Pons,  raphe  of,  721 

Tarini,  750 

Varolii,  719,  724 
Ponticulus,  710 
Popliteal  artery,  637 
branches  of,  639 
peculiarities  of,  638 
surface-marking  of,  638 
surgical  anatomy  of,  638 
unusual  branches.  638 

lymphatic  glands,  686 

nerve,  external,  864 

surgical  anatomy  of,  866 
internal,  863 

space,  637 

surface  of  femur,  286 

vein,  671 

Popliteus  muscle,  524 
Pores  of  the  skin,  95 
Portal  canals,  1057 

vein,  674,  1057 
Portio  dura  of  seventh  nerve,  811 

inter  durem  et  mollem,  811 

mollis,  811 

Porus  opticus  of  sclerotic,  892 
Posterior.     See  under  each  sepa- 
rate head. 
Posterior  glenoid  process,  174 

and  interior  choroid  artery,  584 
frontal  artery,  572 

longitudinal  bundle,  718,  742 
Postero-lateral   ganglionic   arte- 
ries, 584 

median  ganglionic  arteries,  584 
Post-glenoid  process,  174 
Post-pa tellar  bursa,  510 
Pott's  fracture,  538 
Pouch  of  Douglas,  971,  988 

recto-uterine,  981 

recto- vaginal,  981 

recto- vesical,  981,  987 

vesico-uterine,  981,  988 
Pouches,  laryngeal,  1105 
Poupart's  ligament,  1183,  1195 
Precuneus,  780 
Prepatellar  bursa,  510 
Prepuce,  1151 

of  clitoris,  1164 
Presternal  notch,  229 
Presternum,  229 
Prevertebral  fascia,  409 
Prevesical  space  of  Retzius,  981 
Prickle  cells,  43 
Primary  areola?  of  bone,  60 
Primitive  aorta,  127 

fibrillse  of  Schultze,  71 

jugular  veins,  132 

otic  vesicle,  124 

sheath  of  nerve-fibre,  71 

trace,  104 
Princeps  cervicis  artery,  557 

pollicis  artery,  600 
Processes  or  process:   acromion, 
244 

alveolar,  193 

angular,  external,  171 
internal,  171 

auditory,  177 

ciliary,  895 

clinoid,  anterior,  183 
middle,  180 
posterior,  181 

cochleariform,  179,  917 

condyloid  of  lower  jaw,  204 

coracoid,  245 


Processes   or  process :   coronoid, 

of  lower  jaw,  204 
of  ulna,  254 
costal,  146 
ethmoidal    of    inferior    turbi- 

nated,  200 

frontal  of  malar,  196 
hamular  of  lachrymal,  195 

of  sphenoid,  183 
of  helix,  913 
of  Ingrassias,  183 
jugular,  166 
lachrymal,    of   inferior   turbi- 

nated  bone,  200 
malar,  192 
of  malar  bone,  196 
mammillary,  152 
mastoid,  176 
maxillary,  of    inferior    turbi- 

nated,  200 
mental,  202 
muscular,  1102 
nasal,  192 

odontoid  of  axis,  147 
olecranon,  254 
olivary,  180 
orbital,  of  malar,  196 

of  palate,  199 

palatine,    of   superior    maxil- 
lary, 193 
post-glenoid,  174 
pterygoid,  of  palate  bone,  198 

of  sphenoid,  183 
sphenoidal,  of  palate,  199 
spinous  of  ilium,  275 
of  sphenoid,  182 
of  tibia,  293 
styloid,  of  radius,  260 
of  temporal,  178 
of  ulna,  258 
unciform,  267 

of  ethmoid,  186 
vaginal,  of  sphenoid,  182 

of  temporal,  178 
vermiform,  of  cerebellum,  727 

inferior,  727 
vocal,  1102 
zygomatic,  197 

Processus  brevis  of  malleus,  919 
caudatus,  913 
cochleariformis,  179,  917 
gracilis  of  malleus,  919 
Profunda  cervicis  artery,  587 
femoris  artery,  635 
inferior  artery  of  arm,  o96 
superior  artery  of  arm,  596 
vein,  672 

Projection  fibres,  785,  786 
Promontory  of  sacrum,  155 

of  tympanum,  916 
Pronator  quadratus  muscle,  483 
radii  teres  muscle,  479 
ridge,  256 
Pronephros,  135 
Pronucleus,  female,  103 

male,  103 

Prosencephalon,  121,  706,  751 
Prostate,  hypertrophv  of,  1159 
gland,  1148 

levator  muscle  of,  460 
lobes  of,  1149 
lymphatics  of,  689 
surgical  anatomy  of,  1149 
vessels  and  nerves  of,  1149 
Prostatic  plexus  of  nerves.  878 


IXDEX. 


1239 


Prostatic  plexus  of  veins,  673 

portion  of  urethra,  1146 

sinus.  114»i 
Protoplasm,  39 

Protoplasmic   process  of  nerve- 
cells.  To 

Proto  vertebra?,  107 
Prot overt ebral  column,  116 

somites,  107 
Protuberance,  occipital,  external, 

164 

internal,  166 
Psbas  magnus  muscle,  504 

surgical  anatomy  of,  505 

parvus,  504 
Pterion  ossicle,  188 
Pterygoid  arteries,  562 

fossa  of  lower  jaw,  '204 
of  sphenoid,  163 

muscles.  4i.»4 

nerv. 

plexus  of  veins,  652 

process  of  palate  bone,  198 

processes  of  sphenoid.  1X3 

ridge.  1X2 
Pterygo-maxillary  fissure,  216 

ligament.  402 
Pterygo-palatine  artery,  562 

canal 

nerve,  805 
Pubes,  angle  of,  2TT 

crest  of.  H77 

OS. 

spine  of.  '27  T 
symphysis  of,  277,  339 
Pubic  arch. 

articulations  of,  339 
portion  of  fascia  lata,  508 
Pubo-prostatic  ligaments.  1142 
Pudendum,  1163" 
Pudic  artery,  accessory,  624 
deep  external.  635 
internal,  62o 
in  female,  625 
in  male,  624 
peculiarities  of,  624 
superficial  external,  635 
nerve,  861 
vein,  external,  670 

internal.  <>7'J 
Pulmonary  artery.  540,  1119 

opening  of,  in  right  ventri- 
cle, 1090 
capillaries,  1119 
sinuses.  Io91 
veins,  649,  650,  1119 

openings    of,    left    auricle, 

1091 

Pulp-cavity  of  tooth,  935 
enamel,  940 
formative,  941 
permanent,  941 
of  teeth,  development  of,  943 
Pulvinar,  746,  758 
Puncta  lachrymalia,  911 

vasculosa,  755 
Pupil  of  eye,  896 

membrane  of,  898 
Purkinje,  axis-cylinder  of,  71 
corpuscles  of,  7:!'i 
granular  layer  of,  936 
vesicle  of,  iOl 
Putamen,  760 
Pyloric  artery,  611 
glands,  1006 


Pyloric  plexus,  877 
Pylorus,  1000 
Pyramid,  716 

of  cerebellum,  731 
of  thyroid  gland,  1123 
of  tympanum,  916 
in  vestibule,  921 
Pyramidal  tract,  700 
crossed,  710 
direct,  710 
Pyramidalis  muscle,  455 

"iiasi,  399 
Pyramids  of  Ferrein,  1131 
"of  Malpighi,  1129 
of  medulla,  709 

decussation  of,  710 
of  the  spine,  161 
Pyriformis  muscle,  516 

Q- 

Quadrate  lobe  of  liver,  1052 
Quadratus  femoris  muscle,  517 
lumborum,  458 

fascia  covering,  458 
menti,  401 

Quadriceps  extensor  cruris  mus- 
cle, 509 

R. 

Racemose  glands,  99 
Recessus  peritonei,  994 
''•  Radial  artery,  597 
branches  of,  599 
peculiarities  of,  598 
surface-marking  of,  598 
surgical  anatomy  of,  598 
lymphatic  glands,  684 
nerve.  S44 
recurrent  artery,  599 
region,  muscles  of,  483 
vein,  663 

Radialis  indicis  artery,  601 
Radiations,  optic,  747 
Radicular  zone,  anterior,  700 
Radio-carpal  articulation.  356 
surface  form  of,  357 
surgical  anatomy  of,  357 
]  Radio-ulnar    articulations,    infe- 
rior. 

middle,  354 
superior.  353 
Radius.  259 

articulations  of,  261 
development  of,  260 
fracture  of,  501 
grooves  in  lower  end  of,  260 
muscles  attached  to,  261 
oblique  line  of,  259 
sigmoid  cavity  of,  260 
surface  form  of,  261 
surgical  anatomy  of,  261 
tuberosity  of,  2-'  P 
and  ulna,  fracture  of,  502 
Radix  mesenterii,  990 
Rami  of  the  lower  jaw,  203 
Ramus,  horizontal,  of  pubes,  277 
of  ischium,  276 

descending:.  277 
of  pubes,  277 
Ranine  artery.  553 

vein,  652,  654 
Ranvier,  nodes  of,  71 
Raphe  of  medulla,  712,  719 


Raphe  of  perineum,  1202 
of  pons,  721 
of  scrotum,  1153 
Receiving  tubes  of  kidney,  1130 
Receptaculi  arterise,  568 
Receptaculum  chyli,  680 
Recess,  epitympanic,  917 
lateral,  734,  738,739 
optic,  751 
Recessus  hepato-renalis,  1054 

labyrinthi,  124 
Recto-coccygeus  muscle,  1041 
Recto-uterine  ligament^  1169 

pouch,  981 

Recto-vaginal  pouch,  981 
Recto-vesical  fascia,  1210 
fold,  peritoneal,  1142 
pouch,  981,  987 
Rectum,  1038 
ampulla  of,  1039 
curves  of,  1039 
development  of,  133 
lymphatics  of,  689 
nerves  of,  1042 
relations  of,  1043 
structure  of,  1040 
surgical  anatomy  of,  1045 
valves  of,  1041 
vessels  of,  1042 
Rectus  abdominis,  453 
capitis  anticus  major,  424 

minor,  424 
lateralis,  425 
femoris  muscle,  509 

surgical  anatomy  of,  511 
oculi,  internus,  superior,  infe- 
rior, and  externus,  397 
posticus  major,  439 

minor,  439 
Recurrent    artery,    interosseous, 

603 

radial,  599 
tibial,  anterior,  642 

posterior,  642 
ulnar,  anterior,  602 

posterior,  602 
laryngeal  nerve,  821 
nerves  to  tentorium,  797 
Region,  abdominal,  959 

muscles  of,  447 
acromial,  muscles  of  471 
auricular,  393 
back,  muscles  of,  427 
brachial,  anterior,  479 
cervical  superficial,  muscles  of, 

407 

diaphragmatic,  444 
epicranial,  muscles  of,  391 
epigastric.  955 
femoral,  muscles  of,  anterior, 

505 

internal,  511 
posterior,  518 
fibular,  527 
foot,  dorsum  of,  530 

sole  of,  530 

gluteal,  muscles  of,  514 
of  hand,  muscles  of,  489 
humeral,  anterior,  475 

posterior,  477 
hypochondriac,  955 
iliac,  muscles  of,  503 
infrahyoid,  411 
inguinal,  1189 
intermaxillary,  muscles  of.  401 


1240 


INDEX. 


Region,  ischio-rectal,  1201 

laryngo-tracheal,  surgical  anat- 
omy of,  \\\'l 
lingual,  muscles  of,  415 
maxillary,  muscles  of,  inferior, 

400 

superior,  400 
nasal,  muscles  of,  398 
orbital,  muscles  of,  396 
palatal,  muscles  of,  421 
palmar,  469 
palpebral,  394 
perineum,  1201 
pharyngeal,  muscles  of,  419 
popliteal,  637 
ptervgo-maxillarv,  muscles  of, 

404 

radial,  muscles  of,  483 
radio-ulnar,  posterior,  muscles 

of,  485 
scapular,  muscles  of,  anterior, 

472 

posterior,  473 
Scarpa'  s  triangle,  630 
suprahyoid,  muscles  of,  413 
tern poro- maxillary,  muscles  of, 

403 

thoracic,  441 
anterior,  467 
lateral,  470 
tibio-fibular,  anterior,  521 

posterior,  522 
ulnar,  494 
vertebral,  muscles  of,  anterior, 

424 

lateral,  425 
Eeil,  island  of,  778 
Kelations   of   duodenum,    1011, 

1014 

of  gall-bladder,  1064 
of  large  intestine,  1036 
of  liver,  1055 
of  pancreas,  1071 
of  rectum,  1043 
of  spleen,  1076 
of  stomach,  1001 
of  vermiform  appendix,  1032 
Remak,  fibres  of,  72 
Renal  afferent  vessels,  1129,  1134 
artery,  616,  1133 
efferent  vessels,  1129,  1134 
plexus,  875 
veins,  675,  1134 
Respiration,  muscles  of,  444 

organs  of,  1 1 00 

Respiratory  nerves  of  Bell,  ex- 
ternal, 837 
internal,  833 

organs,  development  of,  134 
Rete  Malpighii,  90 
mucosum  of  skin,  90 
testis,  1158 

Reticular  cartilage,  53 
formation,  713,  714 
layer  of  skin,  91 
lamina  of  Kolliker,  926 
Retiform  body,    712,   717,   735, 

738 

connective  tissue,  48 
Retina,  898 

arteria  centralis  of,  570,  902 
fovea  centralis  of,  902 
limbus  luteus  of,  898 
membrana,  layers  of,  899,  900 
limitans  externa,  901 


Retina  membrana,   iimitans  in- 
terna,  S99 

structure  of,  899 
Retrahens  aurem  muscle,  394 
Retro-peritoneal  fossae,  994 
Retzius,  prevesical  space  of,  981 

space  of,  1141 
Rhomboid  impression,  240 

ligament,  341 
Rhomboidal  sinus,  1 20 
Rhomboideus  major,  431 

minor,  431 

Ribes,  ganglion  of,  867 
Ribs,  232 

angle  of,  233 

articulations  of,  330 

attachment  of  muscles  to,  235 

development  of,  117,  235 

false,  232 

floating,  232 

head  of,  233 

ligaments  of,  330,  331 

neck  of,  233 

peculiar,  234 

true,  232 

tuberosity  of,  233 
Ridge,  basal  of  teeth,  933 

internal  occipital,  !('(> 

mylo-hvoidean,  202 

pectoral,  2-48 

pterygoid,  182 

superciliary,  171 

supracondylar,  250 

temporal,  173,  174,  215 
Eight  lobe  of  liver,  1052 

longitudinal   fissure   of   liver, 

1051 

Eimaglottidis,  1104 
Kimfe  csecse,  1053 
Ring,  abdominal,  external,  449, 

1182 
internal,  1186 

femoral  or  crural,  1198 

fibrous,  of  heart,  1094 
Risorius  muscle,  402 
Rivini,  ducts  of,  948 

notch  of,  914,  918 
Robin,  polar  globules  of,  101 
Rods  of  Corti,  925 
Rolando,  funiculus  of,  710 

nucleus  of,  711 

tubercle  of,  711,  715 
Roof  of   fourth   ventricle,    738, 
739 

of  third  ventricle,  748-750 
Root,  ascending,  of  fifth  nerve, 
723 

of  auditory  nerve,  815 

descending,  of  fifth  nerve,  723 

of  lung,  1118 

of  olfactory  nerve,  784 

of  spinal  nerves,  826 

of  teeth,  934 

of  zygomatic  process,  174 
Rosenmiiller,  accessory  gland  of, 
910 

organ  of,  138,  1177 
Rostrum  of  sphenoid  bone,  182 
Rotation,  :',!> 

Rotatores  spinae  muscles,  4.'-i* 
Round  ligaments  of  uterus,  1177 
relations    of,    to    femoral 

rinu,  119S 
of  liver,  9X3,  1 053 
Rugae  of  vagina,  1168 


Rupture  of  urethra,  course  taken 
by  urine  in,  1203 


Sac,  lachrymal,  910 
Saccular  secretory  glands,  98 
Saccule  of  vestibule,  926 
Saccus  lienalis,  1077 
Sacra-media  artery,  617 
Sacral  arteries,  lateral,  627 
canal,  157 
cornua,  156 
foramina,  155 
ganglia,  874 
groove,  156 
lymphatic  glands,  688 
nerves,  851 

anterior  divisions  of,  858 
posterior  divisions  of,  857 
roots  of,  857 
plexus,  859 
vein,  lateral,  673 
middle,  673 
peculiarities  of,  673 
Sacro-coccygeal  ligaments,  339 
Sacro-iliac  articulation,  337 
iSacro-lumbalis  muscle,  434 
Sacro- sciatic    foramen,    greater, 

276,  337 
lesser,  276,  338 
ligaments,  337 
notch,  greater,  276 

lesser,  276 

Sacro-uterine  ligament,  1171 
i  Sacro-vertebral  angle,  155 

ligament,  337 
Sacrum,  155 
ala  of,  157 
articulations  of,  159 
attachment  of  muscles  to,  159 
development  of,  158 
peculiarities  of,  158 
structure  of,  158 
Sacs,  dental,  940 
Saddle-joint,  316 
Sagittal  suture,  206 
Salivary  glands,  945 
structure  of,  948 
Salpingo-pharyngeus,  423 
Salter,  incremental  lines  of,  937 
Santorini,  cartilages  of,  1102 
Saphena  veins,  surgical  anatomy 

of,  671 

Saphenous  nerve,  long  or  inter- 
nal, 856 
short,  862 
opening,  507,  1194 
vein,  external  or  short,  672 
internal  or  long,  670,  1190 
surgical  anatomy  of,  671 
Sarcolemma,  (>•"> 
Sarcoplasm,  66 
Sarcostyles,  66 

Sarcous  elements  of  muscle,  66 
Sartorius  muscle,  508 
Scala  media,  924 

tympani  of  cochlea,  923 
vestibuli  of  cochlea,  £23 
Scalae  of  cochlea,  924 
Scalenus  antieus,  425 
medius,  425 
post  ions,  426 

Scaphoid  bone  (foot),  304 
(hand),  262 


INDEX. 


1241 


Scaphoid  fossa  of  sphenoid.  183 
Scapula,  242 

articulations  of,  '1  (7 

attachment  of  muscles  to,  '247 

development  of,  246 

dorsum  of,  243 

glenoid  cavity  of,  245 

head  of,  469' 

ligaments  of,  344.  345 

muscles  of,  472,  473 

spine  of,  214 

surface  form  of,  247 

surgical  anatomy  of,  247 

venter  of,  242 
Scapular  artery,  posterior,  585 

region,    muscles   of,    anterior, 

472 
posterior,  473 

veins,  00' I 
Scarfskin,  89 

Scarpa,  foramina  of,  194,  213 
Scarpa's  triangle,  630 
Schachowa,  spiral  tubes  of,  1130 
Schindylesis,  315 
Schlemm,  canal  of,  893 

ligaments,  346 

Schneiderian  membrane,  887 
Schreger,  lines  of,  937 
Schnltze,  cells  of,  792 

primitive  fibrillae  of,  71 
Schwann,  white  substance  of,  71 
Sciatic  artery,  626 

nerve,  greater,  862 

surtrical  anatomy  of,  866 
lesser.  x''>2 

veins,  073 
Sclerotic,  891 
Scrobiculus  cordis,  237 
Scrotal  hernia,  1189 
Scrotum,  1153 

dartos  of,  1 154 

development  of,  140 

lymphatics  of,  689 

nerves  of,  1155 

septum  of,  1153 

surgical  anatomy  of,  1155 

vessels  of,  1155 
Sebaceous  glands,  94 
Second  nerve,  793 

surgical  anatomy  of,  794 
Secreting  glands,  '.is' 
Segmental  duct,  135 
>t-i;-Hientation  spherules,  103 
Sella  Turcica,  180 
Semicircular  canals,  922 
Semilunar  bone,  204 

cartilages  of  knee,  370 

fascia.  47 *i 

fold  of  Douglas,  455 

ganglion  of  abdomen,  872 
of  liTth  nerve,  797 

valves,  aortic.  li".i:; 

pulmonic,  109U 

Semimembranosns  muscle,  519 
Seminal  cells,  1158 

tubes,  llos 

vesicles,  1160 
Semispinalis  muscle,  437 
Semitendinosus  muscle,  519 
Senses,  organs  of  the,  879 
Septum,  cartilage  of,  886 

crnrale,  1198 

lucidum,  754,  762 

of  medulla,  712 

of  nose,  221 


Septum  pectiniforme,  1151 

of  pons,  721 

scroti,  1153 

subarachnoid,  694 

of  tongue,  882 

ventriculorum.  1089 
Septum  between  bronchi,  1109 
Serous  glands  of  tongue,  882 

membranes,  96 
Serratus  magnus,  470 

posticus,  inferior,  432 

superior,  432 
Serum,  33 

albumen,  36 

globulin,  36 
Sesamoid  bones.  312 

cartilages,  886 
Seventh  nerve,  814 

surgical  anatomy  of,  815 
Shaft   of  a   bone,   its  structure, 

143 
Sheath  of  arteries,  81 

epithelial,  of  Hertwig,  941 

of  femoral  or  crural,  1196 

of  muscles,  65 

of  nerves,  74 

of  rectus  muscle,  454 
Shin,  294 
Short  bones,  143 
Shoulder  girdle,  238 

joint,  345 

surface  form  of,  348 
surgical  anatomy  of,  348 

muscles  of,  467 

vessels  and  nerves  of,  347 
Sigmoid  artery,  614 

cavity,  greater  and  lesser,  of 
radius,  260 
ulna.  256 

flexure  of  colon,  1036 
of  rectum,  1044 

notch  of  lower  jaw,  204 
Sinus  circularis  iridis,  893 

coronarv,  great,  677 
left,  677 
right,  677 
small,  677 

costo-phrenic,  1114 

of  external  jugular  vein,  653 

of  internal  jugular  vein,  654 

of  kidney,  1128 

of  Morgagni,  420,  1042 

pocularis,  1146 

prostaticus,  137,  1146 

transverse  pericardia!,  1085 

vena?  portte,  1057 

venosus,  130 
Sinuses,  cavernous,  659 

circular,  660 

of  coronary  vein,  677,  1088 

cranial,  171,  650,  657 

ethmoidal,  185 

frontal.  171 

of  heart,  of  left  auricle,  1091 
of  right  auricle,  1088 

lateral,  658 

longitudinal  inferior,  658 
superior,  657 

maxillary,  192 

of  nose,  171 

occipital,  659 

petrosal.  inferior,  660 
superior.  660 

plural,  1114 

pulmonary,  1091 


Sinuses,  sphenoidal,  181 
straight,  658 
transverse,  661 
of  Valsalva,  542,  1093 
Sixth  nerve,  810 

surgical  anatomv  of,  811 
Skeleton,  143 

number  of  its  pieces,  143 
Skin,  appendages  of,  92 
arteries  of,  92 
corium  of,  91 
cuticle  of,  89 
derma,  or  true  skin,  91 
development  of,  125 
epidermis  of,  89 
furrows  of,  91 
hairs,  93 

muscular  fibres  of,  94 
nails,  92 
nerves  of,  92 
papillary  layer  of,  91 
rete  mucosum  of,  90 
sebaceous  glands  of,  94 
structure  of,  89 
sudoriferous  or  sweat-glands  of, 

95 

tactile  corpuscles  of,  76 
vessels  of,  92 
SkuU,  163,  208 

anterior  region,  217 

base  of,  external  surface,  208 

internal  surface,  208 
fossa  of,  anterior,  208 
middle,  210 
posterior,  211 
lateral  region  of,  214 
surface-marking  of,  222 
tables  of,  143 
vertex  of,  208 
vitreous  table  of,  144 
Small  intestine,  1008 
fixation  of,  1020 
structure  of,  1020 
valvuke  conniventes,  1021 
villi  of,  1022 
vessels  of,  1026 
Soft  palate,  944 

aponeurosis  of,  944 
arches  or  pillars  of,  944 
muscles  of,  422 
structure  of,  944 
Solar  plexus,  875 
Sole  of  foot,  muscles  of,  first  layer, 

530 

fourth  layer,  534 
second  layer,  532 
third  layer,  532 
Soleus  muscle,  523 
Solitary  glands,  1025,  1029 
!  Somatopleure,  108 
i  Sommerring,  yellow  spot  of,  898 
Space,  anterior  perforated,  784 
axillary,  587 
intercostal.  232 
interpeduncular,  784 
popliteal,  637 
posterior  perforated,  750 
of  Ketzius,  1141 
Spaces  of  Fontana,  893 
Spermatic  artery,  616,  1155 
canal,  1185 
cord,  1155 

arteries  of,  1155     • 
course  of,  1155 
lymphatics  of,  1155 


1242 


INDEX. 


Spermatic  cord,  nerves  of,  1155 
fascia,  external,  450,  1182 
plexus  of  nerves,  875 

of  veins,  674 

relation  to  femoral  ring,  1198 
of,  in  inguinal  canal,  1155, 

1185 
veins,  674,  1155 

surgical  anatomy  of,  674 
Sphenoid  bone,  180 

articulations  of,  185 
attachment    of    muscles   to, 

185 

body  of,  180 
development  of,  184 
greater  wings  of,  182 
lesser  wings  of,  183 
pterygoid  processes  of,  183 
rostrum  of,  182 
spinous  processes  of,  182 
vaginal  processes  of,  182 
Sphenoidal  fissure.  183 

nerves  in,  810 
process  of  palate,  199 
sinuses,  181 
spongy   or    turbinated    bones, 

184 
Spheno-maxillary  fissure,  216 

fossa,  216 

Spheno-palatine  artery,  562 
foramen,  199 
ganglion,  803 
nerves,  803 
notch,  199 

Spheno-parietal  suture,  207 
Sphincter    muscle    of    bladder, 

1143 

pyloricus,  1000 
of  rectum,  external,  458 

internal,  459 
tertius,  1042 
of  vagina,  464 
Spigelian  lobe,  1050,  1052 
Spina  bifida,  162 
Spinal  accessory  nerve,  823 

surgical  anatomy  of,  823 
arteries,  anterior,  582 
lateral,  582 
median,  582 
posterior,  582 
bulb,  708 
canal,  162 
cord,  695-702 
arachnoid  of,  694 
arrangement   of   gray    and 

white  matter  in,  699 
central  canal  of,  698 

ligament  of,  695 
columns  of,  697 
commissures  of,  697,  698 
development  of,  115 
dura  mater  of,  693 
fissures  of,  696,  697 
foetal,  peculiarity  of,  695 
gray  commissure  of,  697 
internal  structure  of,  697 
ligamentum  denticulatum  of, 

695 

membranes  of,  693 
minute  structure  of,  698 
neuroglia  of,  698 
pia  mater  of,  695 
sections  of,  696 
structure  of,  697 
white  commissure  of,  697 


Spinal   cord,    white    matter    of, 

699 

foramen,  145 
nerves,  826 

arrangement     into     groups, 

826 

development  of,  122 
distribution  of,  827 
divisions  of,  anterior,  827 

posterior,  827 
origin  of,  in  cord,  702 
of  roots,  anterior,  826 

posterior,  826 

points  of  emergence  of,  827 
veins,  668 

longitudinal,  anterior,  669 

posterior,  669 
Spinalis  colli  muscle,'  436 

dorsi  muscle,  436 
Spine,  144 

articulations  of,  319 
development  of,  115 
general  description  of,  160 
ossification  of,  154 
Spines  of  bones,  ethmoidal,  180 
of  ischium,  276 
mental,  202 
nasal,  171 
anterior,  194 
posterior,  197 
of  os  pubis,  277 
pharyngeal,  165 
of  scapula,  244 
tympanic,  914 

Spinous  process  of  ilium,  275 
of  sphenoid,  182 
of  tibia,  293 
of  vertebrae,  145 
Spiral  canal  of  cochlea,  923 
Splanchnic  nerve,  greater,  873 
lesser,  873 

smallest  or  renal,  873 
Splanchnopleure,  108 
Spleen,  971,  1073 
accessory,  1073 
fixation  of,  1076 
lymphatics  of,  690,  1077,  1081 
nerves  of,  1077 
peritoneal    relations    of,   986, 

1076 

pulp  of,  1078 
relations  of,  1076 
structure  of,  1077 
surface-marking  of,  1081 
surfaces  of,  1074 
surgical  anatomy  of,  1081 
vessels  of,  1077,  1079 
Splenic  arterv,  611 
flexure,  1036 
plexus,  877 
vein,  675 

Splenius  muscle,  433 
Spongioblasts,  121 
Spongy  portion  of  urethra,  1147 

tissue  of  bone,  143 
Squamo-parietal  suture,  207 
Squamo-sphenoidal  suture,  207 
Squamo-zygomatic     portion    of 

temporal  bone,  179 
Squamous  portion   of  temporal 

bone,  173 

Stapedius  muscle,  920 
Stapes,  919 

annular  ligament  of,  919 
development  of,  125 


Stellate  ligament,  330 

plexus  of  kidney,  1134 
Stenson,  foramina  of,  194,  213 
Stenson's  duct,  946 
Sternal  end  of  clavicle,  fracture 
of,  499 

foramen,  231 

furrow,  236 

ligaments,  336 
Sterno-clavicular       articulation. 

341 

surface  form  of,  342 
surgical  anatomy  of,  342 
Sterno-hyoid  muscle,  411 
Sterno-mastoid  muscle,  409 

artery,  557 

Sterno-pericardial  ligament,  1084 
•Sterno-thyroid  muscle,  411 
Sternum,  "228 

articulations  of,  232 

attachment  of  muscles  to,  232 

development  of,  117,  231 

ligaments  of,  336 

structure  of,  231 
Stilling,  canal  of,  903 
Stomach,  969,  999 

alteration  in  position  of,  1004 

development  of,  133 

fixation  of,  1003 

lymphatics  of,  690 

mucous  membrane  of,  1005 

peptic  glands  of,  1007 

position  of,  1004 

pvloric  end  of,  1006 
"glands  of,  1006 

pylorus,  1000 

relations  of,  1001 

structure  of,  1004 

submucous  coat  of,  1005 

surgical  anatomy  of,  1007 

torsion  of,  973 

vessels  and  nerves  of,  1007 
Stomodceum,  120 
Straight  sinus,  658 

tubes  of  kidney,  11 30 
Strand,  labio-dental,  938 
Stratiform  fibro-cartilage,  53 
Stratum  cinereum,  743 

corneum,  90 

dorsal  e,  745 

lucidum,  91 

opticum,  743 

zonale,  747 
Stria?  acusticse,  724 

laterales,  757 

longitudinales,  757 

of  muscle,  66 
Striped  muscle,  64 
Stroma  of  ovary,  1176 
Structure  of  gall-bladder,  1065 

of  large  intestine,  1028 

of  liver,  1059 

of  pancreas,  1072 

of  rectum,  1040 

of  a  villus,  1023 
Stylo-glossus  muscle,  416 
Stylo-hyoid  ligament,  414 

muscle,  413 

nerve  from  facial,  813 
Stylo-mastoid  artery,  557 

foramen,  178 

vein,  653 

Stylo-maxillary  ligament,  328 
Stylo-pharyngeus  muscle,  420 
Styloid  process  of  radius,  260 


IXDEX. 


1243 


Styloid  process  of  temporal  bone, 

178 

of  ulna,  258 

Subanconeus  muscle,  478 
Subarachnoid  of  cord,  694 
of  septum,  694 
tissue,  694 
Subcsecal  fossa,  997 
Subclavian  arteries,  576 
branches  of,  581 
first  part  of,  left,  577 

right,  577 

peculiarities  of,  579 
second  portion  of,  578 
surface  form  of,  579 
surgical  anatomy  of,  579 
third  portion  of,  578 
groove,  '234 
triangle.  565 
vein,  665 

Subclavius  muscle,  469 
Subcostal  angle,  228 
muscle,  442 
nerve,  848 

Subcrureus  muscle,  510 
Subdural  space,  694 
Sublingual  artery,  553 
fossa,  202 
gland,  948 

vessels  and  nerves  of,  948 
Sublobular  veins,  1057,  1061 
Submaxillarv  arterv,  555 
fossa,  203 " 
ganglion,  808 
gland.  947 
nerves  of,  947 
vessels  of,  947 
lymphatic  gland,  683 
triangle,  564 
vein,  652 

Submental  artery,  555 
Suboccipital  nerve,  826 

posterior  branch  of,  826 
triangle,  582 
Subpleural   mediastinal    plexus, 

586 

Subpubic  ligament,  340 
Subscapular  angle,  243 
arterv,  592 
fascia.  472 
fossa,  242 
nerves,  838 

Subscapularis  muscle,  472 
Subsigmoid  fossa,  996 
Substantia     cinerea     gelatinosa, 

701 

ferruginea.  724 
nigra,  741,  742.  744 
Subthalmic  region,  745 
Sudoriferous  glands,  95 
Sulci  of  brain,  772 
frontal,  775 
intrnparietal,  776 
occipital.  777 
parallel,  778 
post-central.  776 
precentral,  77"> 
of  ReiU/78 
temporal,  778 
Sulcus  basilaris,  721 
callosal,  780 
centralis  insulae,  778 
lateralis.  741,  742 
oculo-motorius.  741 
for  olfactory  tract.  775,  783 


Sulcus,  orbital,  775 
precentral,  791 
pyloricus,  1000 
spiralis.  924 
tympanicus,  914 
valleciiue,  726 
Supercilia,  907 
Superciliary  ridge,  171 
Superficial  cervical  artery,  585 
circumflex  iliac  artery,  635 
epigastric,  artery,  635 
external  pudic  artery,  635 
palmar  arch,  604 
perineal  artery,  625 
temporal  artery,  558 

surgical  anatomy  of,  559 
transverse  ligament  of  fingers, 

492 
Superficialis  colli  nerve,  831 

volae  artery,  599 
Superior  maxillary  bone,  189 
articulations  of,  195 
attachment  of  muscles  to, 

195 
changes  in,  produced  by 

age,  195 

development  of,  194 
nerve,  801 
meatus,  221 
mediastinum,  1115 
profunda  artery,  596 
thyroid  artery,  552 

surgical  anatomy  of,  552 
turbiuated  crest,  192 

of  palate,  198 
vena  cava,  667 
Supinator  brevis  muscle,  486 

longus  muscle,  483 
Supracondylar  line.  2*7 
Suprahyoid  aponeurosis,  413 
Suprarnastoid  crest,  1 74 
Supramaxillary  nerves  from  fa- 
cial, 815 

Supraorbital  arch,  171- 
artery,  569 
foramen,  171,  217 
nerve,  798 
notch, 171 

Suprarenal  arteries,  615 
capsules,  1137 
nerves  of,  1139 
vessels  of,  1139 
plexus,  875 
veins,  675 

Suprascapular  artery,  585 
nerve,  838 
notch, 245 

Supraspinales  muscles,  438 
SnpraspinaUis  muscle,  473 
Supraspinous  fascia,  473 
fossa,  2-14 
ligaments,  321 
Supratrochlear  foramen,  251 

nerve,  798 
Sural  arteries,  639 

veins,  672 

Surface  form  or  marking  of  ab- 
dominal aorta,  609 
of  acromio-clavicular  joint, 

344 

of  ankle-joint,  379 
of  anterior  tibial  artery.  642 
of  axillary  artery,  591 
of  back,  440 
of  bladder,  1144 


Surface   form    or     marking    of 

brachial  artery,  595 
of  branches  of  internal  iliac 

artery,  627 
of  carpus,  270 
of  clavicle,  241 
of  common   carotid   artery, 

549 

iliac  artery,  619 
of  cranium.  222 
of  dorsalis  pedis  arterv,  643 
of  elbow,  352 
of  external  auditory  meatus, 

915 

carotid  artery,  551 
iliac  artery,  619 
of  femoral  artery,  633 
of  femur,  290 
of  fibula,  299 

of  fifth  cranial  nerve,  809 
of  foot,  310 
of  head  and  face,  406 
of  heart.  1096 
of  hip-joint,  386 
of  humerus,  253 
of  hyoid  bone,  228 
of  intestines.  1045 
of  kidney,  1135 
of  knee-joint.  374 
of  knuckles,  362 
of  larynx,  1111 
of  liver,  1065 
of  lower  extremity,  535 
of  lungs,  1120 
of  mouth,  949 
of  muscles  of  abdomen,  457 
of  neck,  427 
of  palmar  arches,  604 
of  palpebral  fissure,  911 
of  pancreas.  1073 
of  patella,  292 
of  pelvis,  283 
of  plantar  arch,  648 
of  popliteal  artery,  638 
of    posterior    tibial    artery, 

645 

of  radial  artery,  598 
of  radio-ulnar  joint,  inferior, 
356 

superior,  353 
of  radius,  261 
of  scapula.  247 
of  shoulder-joint,  348 
of  skull,  222 
of  spleen,  1081 
of  spine,  1 62 

of  sterno-clavicular  joint,  342 
of  sterno-mastoid,  411 
of  stomach,  1007 
of  subclavian  artery,  579 
of  tarsus  and  foot,  310 
of  temporo-maxillarv  joint, 

330 

of  thorax,  236 
of  tibia,  296 
of  ulna,  259 
of  ulnar  artery,  802 
of  upper  extremity,  497 
of  vertebral  column,  162 
of  wrist  and  hand,  270 
of  wrist-joint,  357 
Surfaces  of  liver,  1049 
of  pancreas,  1069 
of  popliteal  of  femur,  286 
of  spleen,  1074 


1244 


INDEX. 


Surgical  anatomy  of  abdominal 

aorta,  609 

of  abducent  nerve,  811 
of  acromio-clavicular  joint, 

344 
of  adductor  longus  muscle, 

513 

of  ankle-joint,  379 
of  anterior  tibial  artery,  642  i 
of  arch  of  aorta,  544 
of  artery  of  the  bulb,  625 
of  ascending  pharyngeal  ar- 
tery, 558 

of  auditory  nerve,  816 
of  axilla,  589 
of  axillary  artery,  591 

glands,  684 

vein,  665 

of  azygos  veins,  668 
of  base  of  bladder,  1207 
of  bend  of  elbow,  593 
of  bones  of  face,  224 
of  brachial  artery,  595 

plexus,  844 
of  branches  of  internal  iliac, 

628 

of  cavernous  sinus,  659 
of  cervical  glands,  684 

vertebrae,  327 
of  clavicle,  241 
of  club-foot,  528 
of  common  carotid,  549 

iliac,  619 

of  deep  epigastric,  630 
of  deltoid  muscle,  472 
of  descending  aorta,  606 
of  dorsal  is  pedis  artery,  643 
of  elbow-joint,  352 
of  Eustachian  tube,  952 
of  extensor  muscles  of  thumb, 

489 

of  external   carotid  artery, 
551 

ear,  928 

iliac  artery,  619 
of  jugular  vein,  653 
of  eye,  905 
of  facial  artery,  556 

nerve,  815 

vein,  652 
of  femoral  artery,  653 

hernia,  1190 
of  femur,  290 
of  foot,  bones  of,  311 
of  forearm,  bones  of,  261 
of  gluteal  artery,  627 
of  hsemorrhoidal  veins,  672 
of  hamstrings,  520 
of  hand,  bones  of,  271 
of  hip-joint,  366 
of  humerus,  253 
of  hyoid  bone,  228 
of  hypoglossal  nerve,  825 
of  iliac  fascia,  505 
of  inferior  thyroid  artery, 
585 

vena  cava,  668 
of  inguinal  hernia,  1180 

glands,  686 

of  innominate  artery,  546 
of  intercostal  nerves,  848 
of  internal   carotid   artery, 
568 

iliac  artery,  621 

jugular  vein,  655 


Surgical    anatomy    of    internal 

mammary  artery,  687 
pudic  artery,  624 

of  intestines,  1045 

of  ischio- rectal  region,  1201 

of  joints  of  cervical  verte- 
bra, 327 

of  kidneys,  1135 

of  knee  joint,  374 

of  lachrymal  apparatus,  911 

of  laryngeal  nerves,  822 

of  laryngo-tracheal    region, 
1111 

of  larynx,  1111 

of  leg,  bones  of,  299 

of  lingual  artery,  553 

of  liver,  1066 

of  lumbar  plexus,  866 

of  lungs,  1122 

of  middle  meningeal  artery, 
561 

of  motor  oculi  nerve,  795 

of  muscles  of  eye,  398 
of  lower  extremity,  537 
of  soft  palate,  423 
of  upper  extremity,  499 

of  musculo-spiral  nerve,  844 

of  nasal  fossae,  889 

of  nose,  889 

of  o?sophagus,  954 

of  olfactory  nerve,  793 

of  optic  nerve,  794 

of  palmar  arch,  605 
fascia,  492 

of  pancreas,  1073 

of  patella,  292 

of  pelvis,  bones  of,  283 

of  penis,  1153 

of  perinaeum,  1201 

of  peroneal  or  external  pop- 
liteal nerve,  866 

of  pharynx,  952 

of  plantar  arch,  648 
ligaments,  382 

of  pleura,  1114 

of  popliteal  artery,  638 

of  posterior  tibial,  645 

of  pronator  radii  teres  mus- 
cle, 479 

of  prostate  gland,  1149 

of  psoas  magnus,  505 

of  radial  artery,  598 

of  radio-ulnar  joint,  354 

of  rectum,  1046 

of    rectus    femoris    muscle, 
511 

of  ribs,  237 

of  saphena  veins,  671 

of  scapula,  247 

of  Scarpa's  triangle,  630 

of  sciatic  artery,  628 
nerve  (great),  866 

of  scrotum,  1155 

of  serratus  magnus  muscle, 
471 

of  shoulder-joint,  348 

of  skull,  '2-24 

of  spermatic  veins,  674 

of   spinal    accessory  nerve, 
823 

of  spine,  162 

of  spleen,  1081 

of  sterno-clavicular  joint,  342 

of  sterno-miistoid  muscle,  411 

of  sternum,  237 


Surgical    anatomy    of    stomach 

1007 

of  subclavian  artery,  579 
of  superior   thyroid    arterv. 

552 

of  synovial  sheaths  of  ten- 
dons of  wrist,  490 
of  talipes,  528 
of  tarsal  joints,  382,  384 
of  temporal  artery,  559 
of  temporo-maxillary  joint, 

330 

of  testis,  1159 
of  thoracic  aorta,  606 
of  thorax,  237 
of  thyroid  gland.  1124 
of  tongue,  418,  883 
of  triangles  of  neck,  563 
of  triceps,  478 
of  tri facial  nerve,  809 
of  trochlear  nerve,  796 
of  ulnar  artery,  602 
of  upper  extremity,  499 
of  urethra,  1147 
of  vertebral  artery,  583 
of    vesico-prostatic    plexus, 

673 

of  vesicnlae  seminales,  1161 
of  wrist-joint,  357 
Suspensory    ligament    of    incus, 

920 

of  lens,  905 
of  liver,  1053,  1076 
of  malleus,  919 
of  penis,  1151 
Sustentaculum  lienis,  1036,  1077 

tali,  301 
Stitura.  315 

dentata,  315 

false,  715 

harmonia,  315 

limbosa,  315 

notha,  315 

serrata,  315 

squamosa,  315 

vera,  315 
Suture,  basilar,  207 

coronal,  206 

cranial,  206 

frontal,  206 

fronto-parietal,  206 

fronto-sphenoidal,  206,  207 

intermaxillary,  217 

internasal,  217 

interparietal,  206 

lambdoid,  206 

masto-occipital,  207 

masto-parietal,  207 

occi  pi  to- parietal,  206 

petro-occipital,  207 

petro-sphenoidal,  207 

sagittal,  206 

spheno-parietal.  207 

squamo-parietal,  207 

squamo-sphenoidal,  207 

temporal,  177 

transverse  facial,  207 
Sweat-glands,  95 
Sylvius,   aqueduct   of,  707,  741, 
744 

fissure  of,  755 

Sympathetic  nerve,  75,  867 
cervical  portion.  >i'»'.i 
cranial  portion,  869 
lumbar  portion.  873 


INDEX. 


1245 


Sympathetic  nerve,   pelvic  por- 
tion, 874 

thoracic  portion,  872 
plexuses,  874 
cardiac,  874 
epigastric,  875 
hvjiogastric,  877 
pelvic,  878 
solar.  875 

Symphysis,  315,  317 
of  jaw,  202 
pubis,  277,  339 
Synarthrosis,  314 
Synchondrosis,  315,  317 
Syndesmo-odontoid  joint,  323 
Syndosmosis.  315,  317 
Synostosis,  315 
Synovia,  314 

Synovial  membrane,  96,  313 
articular,  313 
bursal,  314 

vaginal,  314.     See  also  Indi- 
vidual Joints. 
System,  Haversian,  56 
Systemic  arteries,  539 
veins,  649 

T. 

Tables  of  the  skull,  143 
Tactile  corpuscles,  76 

of  Grandy,  77 
Taenia  coli,  1028 

hippocampi,  763 

semicircularis,  760,  768 

tectue,  757 
Tapeium,  757 

lucidum,  901 

nigrum,  901 
Tarsal  artery,  643 

bones.  299 

ligament  of  eyelid,  908 

ligaments,  380 

plates  of  eyelid,  908 
Tarso-metatarsal      articulations, 

384 
Tarsus,  299 

articulations  of,  380 

surface  form  of,  310 

surgical  anatomy  of,  311 

synovial  nu-mbranes  of,  381 

development  of,  308 
Taste- goblets,  881 
Teeth,  932 

bicuspid,  933 

bodv  of,  932 

canine.  933 

cement  of.  <i'!7 

cortical  substance  of,  938 

crown  of.  !».'!2 

crusta  petrosa.  of,  938 

cuspidate,  933 

deciduous,  932 

dental  uihiili  of,  936 

dentine  of,  935 

development  of,  938 

enamel  of,  938 

eruption  of,  944 

eye,  932 

false  molars,  933 

fang  of.  933 

general  characters  of,  932 

growth  of,  942 

incisors,  932 

intertubular  substance  of,  037 


Teeth,  ivory  of,  935 
milk.  932,  935 
molar,  933 
multicuspidate,  933 
permanent,  932 
pulp-cavity  of,  935 
root  of,  932 
structure  of,  935 
temporary,  932,  935 
true  or  large  molars,  933 
wisdom,  935 
Tegmen  tympani,  177 
Tegnientum,  741,  742,  785 
Tela  choroidea,  inferior,  738, 739 

superior,  750 
Temporal  artery,  558 
anterior,  558 
deep,  561 
middle,  559 
posterior,  558 
surgical  anatomy  of,  559 
bone,  173 

articulations  of,  180 
attachment  of  muscles  to,  180 
development  of,  179 
mastoid  portion,  175 
petrous  portion,  176 
squamous  portion,  173 
structure  of,  179 
fascia,  403 
fossa?,  215 
ganglion,  871 
muscle,  403 
nerves    of   auriculo-temporal, 

806 

deep,  806 
of  facial,  814 
ridge,  171,  173,  174,  215 
suture,  177 
veins.  652 
Temporary  cartilage,  51 

teeth,  932,  935 
Temporo-facial  nerve,  813 
Temporo-malar  nerve,  801 
Temporo-maxillary  articulation, 

32< 

surface  form  of,  330 
surgical  anatomy  of,  330 
vein,  653 
Tendo  Achillis,  523 

palpebrarum  or  oculi,  395 
Tendon,  central  or  cordiform,  of 

diaphragm,  445 
conjoined,  of  internal,  oblique 
and      transversalis,     452, 
1184 

structure  of,  389 
of  wrist,  relation  of,  490 
Tenon,  capsule  of,  890 
Tensor  palati  muscle,  422 
tarsi  muscle,  395 
tvmpani  muscle,  920 
'  canal  for,  179,  917 
vaginae  femoris  muscle,  508 
Tent,  734 
Tenth  nerve,  819 

surgical  anatomy  of,  822 
Teres  major  muscle,  474 
minor  muscle,  474 

1156 

coni  vasculosi  of,  1158 
coverings  of,  1153 
development  of,  137 
gubernaculum  test  is,  1161 
lobules  of,  1158 


Testes,  lymphatics  of,  689 
mode  of  descent,  1161 
rete  testis,  1158 
size  and  weight  of,  1156 
structure  of,  1157 
surgical  anatomy  of,  1159 
tubuli  seminiferi  of,  1158 
tunica  albuginea,  1157 
vaginalis,  1156 
vasculosa,  1157 
vas  aberrans  of,  1159 
vas  deferens  of,  1159 
vas  recta  of,  1 158 
vasa  efferentia  of,  1158 
Testes  muliebres,  1175 
Thalamencephalon,  121,  706,  745 
Thalamus  opticus,  746-748 
Thebesii  foramina,  678 
valve  of,  1088 
vense,  678 
Thigh,   deep  fascia,  fascia   lata, 

506 
muscles  of  back  of,  518 

of  front  of,  507 
superficial  fascia  of,  506,  1190 
Third  nerve,  794 

surgical  anatomy  of,  795 
ventricle  of  the  brain,  707,  745, 

748 
Thoracic  aorta,  605 

surgical  anatomy  of,  606 
artery,  acromial,  592 
alar,  592 
long,  592 
superior,  592 
duct,  680 

ganglia  of  sympathetic,  872 
nerves,  anterior,  838 

posterior,  or  long,  837 
region,  muscles  of  anterior,  467 

lateral.  470 
Thorax,  base 'of,  1083 
bones  of,  228 
boundaries  of,  1083 
cavity  of,  1083 
cutaneous  nerves  of,  anterior, 

848 

lateral,  848 
fasciae  of,  441 

general  description  of,  1083 
lymphatics  of,  691 
measurements  of,  1083,  1099 
muscles  of,  441 
parts   passing  through  upper 

opening  of,  1083 
surface  form  of,  236 
Thumb,    articulation     of,    with 

carpus,  359 
muscles  of,  492 
Thymus  gland,  1124 
lobes  of,  1125 
lymphatics  of,  1126 
Thyro-arytenoideus  muscle,  1106 
Thyro-epiglottic  ligament,  1102 
Thyro-epiglottideus  muscle,  1107 
Thyro-hyal  of  hyoid  bone,  -'27 
Thyro-hyoid  arch  (foetal),  1119 
ligaments,  1103 
membrane,  1103 
muscle,  41 1 
nerve,  825 

Thyroid  artery,  inferior,  584 
superior,  552 

surgical  anatomy  of,  552 
axis,  584 


1246 


INDEX. 


Thyroid  branches  of  sympathetic, 
872 

cartilage,  1100 

foramen,  278 

ganglion,  872 

gland,  1122 

isthmus  of,  1123 
lymphatics  of,  692 

notch,  1100 

veins,  inferior,  666 
middle,  655 
superior,  654 

Thyroidea  ima  artery,  545 
Tibia,  293 

articulations  of,  296 

attachment  of  muscles  to,  296 

crest  of,  293,  294 

development  of,  296 

fracture  of  shaft  of,  538 

nutrient  artery  of,  646 

spinous  process  of,  293 

surface  form  of,  296 

surgical  anatomy  of,  299 

tubercle  of,  293 

tuberosities  of,  293 
Tibial  artery,  anterior,  641 
branches  of,  642 
peculiarities  of,  642 
surface-marking  of,  642 
surgical  anatomy  of,  642 

lymphatic  glands,  686 

nerve,  anterior,  865 
posterior,  863 

recurrent  artery,  642 

veins,  anterior,  671 

posterior,  671 
Tibialis  anticus  muscle,  521 

posticus  muscle,  526 
Tibio-fibular  articulations,  376 

region,    anterior,    muscles    of, 

521 

posterior,  muscles  of,  522 
Tibio-tarsal  ligament,  377,  378 
Tongue,  879 

arteries  of,  882 

fibrous  septum  of,  882 

fraenum  of,  879 

mucous  glands  of,  882 
membrane  of,  879 

muscles  of,  416 

nerves  of,  883 

papilla-  of,  880 

serous  glands  of,  882 

surgical  anatomy  of,  883 
Tonsillar  artery,  5*55 

nerves,  818 
Tonsils,  945 

of  cerebellum,  732 

nerves  of,  945 

vessels  of,  945 

Torcular  Herophili,  166,  658 
Torsion  of  intestine,  972 

of  stomach,  972 
Trabeculse,  1090 

of  corpus  cavernosum,  1151 

of  foetal  skull,  118 

of  testis,  1157 
Trachea,  1108 

cartilages  of,  1110 

glands  of,  1111 

relations  of,  1108 

structure  of,  1110 

surface  form  of,  1111 

surgical  anatomy  of,  1111 

vessels  and  nerves  of,  1111 


Trachelo-mastoid  muscle,  436 
Tracheotomy,  1092 
Trachoma  glands,  909 
Tract,    antero-lateral    ascending 

cerebellar,  700,  710,  717 
descending   cerebellar,   700, 

710,  717 
direct  cerebellar,  700,  710 

sensory,  742 
lateral,  710 
of  Lissauer,  700 
olfactory,  782,  783 
optic,  752 

pyramidal,  710,  742 
crossed,  700 
direct,  700 

Tractus  intermedio-lateralis,  702 
opticus,  793 

spiralis  foramenulentus,  928 
Tragicus  muscle,  914 
Tragus,  912 
Transversalis  colli  artery,  585 

muscle,  436 
fascia,  1185 

muscle,  453 
humeri  artery,  585 
Transverse    arteries    of    basilar, 

583 

colon,  1035 

disks  of  muscular  fibre,  66 
facial  artery,  559 

vein,  652 
fissure  of  brain,  770 

of  liver,  1051 
joint  of  foot,  379 
ligament  of  atlas,  323 
of  hip,  364 
of  knee,  371 
of  scapula,  345 
of  shoulder,  346 
superficial,  of  fingers,  492 
tibio-fibular,  377 
pericardial  sinus,  1085 
process  of  a  vertebra,  1 45 
sinus,  661 
suture,  207 

Transversus  auriculae,  914 
perinsei,  461 

(in  female),  464 
Trapezium,  816 
bone,  266 
of  pons,  721 
Trapezius  muscle,  428 
Trapezoid  bone,  266 

ligament,  344 
Treitz,  fossa  of,  995 
ligament  of,  1018 
muscle  of,  1018 
Triangle  of  elbow,  593 
of  Hesselbach,  1190 
inferior  carotid,  563 
of  neck,  anterior.  563 

posterior,  565 
occipital,  565 
Scar  pa's,  630 
subclavian,  565 
submaxillary,  564 
suboccipital,  582 
superior  carotid,  564 
Triangular    interarticular   fibro- 

•cartilage,  355 
ligament    of    abdomen,    448, 

1183 

of  liver,  1053 
of  urethra,  463,  1204 


Triangularis  sterni  muscle,  442 
Triceps  extensor  cruris,  509 

cubiti,  477 

Tricuspid  valves,  1090 
Trifacial   or   trigeminus  nerves, 

796 

surface-marking  of,  809 
surgical  anatomy  of,  809 
Trigone  of  bladder,  1144 
Trigonum,  acustici,  724 

habenulte,  749 

hypoglossi,  724,  823 

olfactorium,  783,  784 

vagi,  724 

ventriculi,  758 
Trochanter,  greater,  285 

lesser,  286 

Trochanteric  fossa,  285 
Trochlea,397 

of  femur,  288 

of  burner  us,  251 
Trochlear  nerve,  796 

surgical  anatomv  of,  796 
Trochoides,  316 
True  ligaments  of  bladder,  1142 

pelvis,  280 

ribs,  232 
Trunk,  articulations  of,  319 

muscles  of,  427 
Tube,  Eustachian,  916 

Fallopian,  1174 
Tuber  annnlare,  720 

cinereum,  750 

omentale,  1049,  1069 

papillare,  1050 

valvula?,  730 

Tubercle,   carotid    or   Chassaig- 
nac's,  146 

of  the  clavicle,  239 

cuneate,  711,  715 

of  the  femur,  286 

genial,  202 

genital,  140 

of  hyoid  bone,  227 

lachrymal,  193 

of  Lower,  1088 

rnamillarv,  750 

mental,  202 

of  navicular,  304 

for  odontoid  ligaments,  165 

of  optic  thalamus,  746 

of  ribs,  233 

of  Kolando,  711,  715 

of  scaphoid  of  carpus,  262 

of  tibia,  293 

of  ulna,  254,  256 

of  zygoma,  174 
Tubercula  quadrigemina,  743 
Tuberciilum  caudatum,  1052 
Tuberosities  of  hnmerus,  greater 
and  lesser,  248 

of  tibia,  293 
Tuberosity,  cuboid,  304 

of  ischium,  276 

maxillary,  190 

of  palate  bone,  199 

of  radius,  259 

of  ribs,  233 
Tubes,  bronchial,  1108 

structure  of,  in  lung,  1119 
Tubular  secreting  glands,  98 

substance  of  kidney,  1129 
Tubuli,  dental,  936 

of  Ferrein,  1131 

lactiferi,  1179 


INDEX. 


1247 


Tubuli  recti,  1158 
seminiferi,  1158 
uriniferi,  1129 
Tuft,   vascular,    in    Malpighian 

bodies  of  kidney,  1129 
Tunica  adventitia,  81 
albuginea,  1157 

of  eye,  397 

intiina,  of  arteries,  80 
media,  81 
of  ovary,  1175 
Kuysfliiana,  895 
vaginalis,  1156 
oculi,  891 
propria,  1156 
reflexa,  1156 
vasculosa  test  is,  1158 
Turbinated  bone,  inferior,  200 
middle,  186 
superior,  187 
crest,  inferior,  192 

superior,  192 
Tutamina  oculi.  907 
Twelfth  nerve,  823 
Tympanic  artery,  from  internal 

carotid.  568 
maxillarv,  560 
nerve,  818,  920 
of  facial,  812 
plate,  175,  914 
ring,  914 
spines,  913 
Tympanum,  916 
arteries  of,  920 
cavity  of,  916 
membrane  of,  918 
mucous  membrane  of,  920 
muscles  of,  920 
nerves  of,  920 
ossicula  of,  918 
veins  of,  920 
Types  of  caeca,  1031 
of  duodenum,  1009 

U. 

Ulna.  254 

articulations  of,  258 
coronoid  process  of,  254 
development  of,  258 
fracture  of  coronoid  process  of, 

501 

muscles  attached  to,  258 
of  olecranon,  501 
process  of.  254 
of  shaft,  501 
sigmoid  cavities  of,  256 
styloid  process  of,  258 
surface  form  of,  259 
surgical  anatomy  of,  261 
tubercle  of.  254,  256 
Ulnar  arlery,  601 
branches  of,  602 
peculiarities  of,  601 
recurrent,  anterior,  602 

posterior,  602 
surface-marking  of,  602 
surgical  anatomy  of,  602 
collateral  nerve,  843 
nerve,  841 

surgical  anatomy  of,  844 
vein,  anterior,  663 

posterior,  663 

Umbilical  arteries  in  fetus,  130, 
1097 


Umbilical  arteries  in  foetus,  how 

obliterated,  1099 
cord,  115 

fissure  of  liver,  1051 
loop,  969 
notch,  1049,  1051 
vein,  130 
vesicle,  109 
Umbilicus.  109 
Unciform  bone,  267 

process  of  ethmoid,  186 
Uncus,  781 

Ungual  phalanges,  270 
Unstriped  muscle,  68 
Upper   extremities,   arteries  of, 

575 

bones  of,  238 
fascia  of,  465 
ligaments  of,  340 
lymphatics  of,  684 
muscles  of,  465 
nerves  of,  837 
surface  form  of,  497 
surgical  anatomy  of,  499 
veins  of,  662 
Urachus,  113,  963, 1143 
Ureters,  Jf36 
muscles  of,  1137 
nerves  of,  1137 
vessels  of,  1137 
Urethra,    bulbous     portion     of, 

1147 

caput  gallinaginis,  1146 
development  of,  140 
female,  1167 
male,  1146 

membranous  portion,  1146 
prostatic  portion,  1146 

sinus  of,  1146 
rupture  of,   course    taken   by 

urine,  1203 

sinus  pocularis  of,  1146 
spongy  portion  of,  1147 
structure  of,  1147 
surgical  anatomy  of,  1147 
verumontanum,  1146 
Urinary  organs,  1127 

development  of,  135 
Urogenital  sinus,  140 
Uterine  arteries,  622 
plexus,  878 

of  veins,  673 
Uterus,  1168 
after  parturition,  1173 
appendages  of,  1174 
arbor  vitse  of,  1172 
broad  ligaments  of,  1171 
cavity  of,  1172 
development  of,  137 
during  menstruation,  1173 

pregnancy,  1173 
in  foetus,  10~73 
fundus,  bodv,  and   cervix    of, 

1168 
ganglia  of,  878 

nerves  of,  878 
ligaments  of,  1169 
lymphatics  of,  689 
masculinus,  138,  1146 
nerves  of,  1173 
in  old  age.  1174 
at  puberty,  1173 
round  ligaments  of,  1177 
shape,    position,     dimensions, 
1168 


Uterus,  structure  of,  1 1 70 

vessels,  1173 
Utricle  of  vestibule,  926 
Uvea,  896 
Uvula  of  cerebellum,  732 

of  throat,  944 

vesicae,  1144 

V. 

Vagina,  1167 
columns  of,  1168 
lymphatics  of,  689 
orifice  of,  1163 
Vaginal  arteries,  622 
plexus  of  nerves,  878 

of  veins,  673 

process  of  temporal,  175,  178 
processes  of  sphenoid,  182 
synovial  membranes,  313 
Vagus,  ganglion  of  root  of,  819 
nerve,  819 

of  trunk  of,  819 
Vallecula,  726 

Sylvii,  774,  784 
Valsalva,  sinuses  of,  542,  1091, 

1094 

Valve,  coronary,  1088 
Eustachian,  1089 
of  Gerlach,  1033 
of  Hasner,  911 
ileo-ca?cal,  1033 
ileo-colic,  1033 
mitral,  1093 
of  Morgagni,  1042 
of  Thebesius.  1088 
tricuspid      flaps,     infundular, 

1090 

right,  1090 
septal,  1090 

of  Vieussens,  720,  733,  734 
Valves  of  lymphatics,  86 
pulmonic,  1089 
of  rectum,  1041 
in  right  auricle,  1088 
semilunar  aortic,  1093 
of  veins,  84 
Valvula  Bauhini,  1033 
Heisteri,  1064 
pylorica,  1000 
Valvulae  conniventes,  1021 
Vas  aberrans,  1159 
deferens,  1159 

structure  of,  1159 
Vasa  aberrantia,  1062 

from  brachial  artery,  595 
afferentia  of  lymphatic  glands, 

680 
brevia  arteries.  612 

veins,  675 
efferentia  of  testis,  1158 

of  lymphatic  glands,  680 
intestini  tenuis,  1158 
recta,  1158 
vasorum  of  arteries,  82 

of  veins,  85 
Vascular  system,  changes  in,  at 

birth,  1099 

general  anatomy  of,  80 
peculiarities   in   the   foetus. 

1097 

Vaso-motor  nerves,  74 
Vastus  externus  muscle,  509 
internus  and  crureus,  510 
Vater,  corpuscles  of,  77,  note. 


1248 


IXDEX. 


Vater,  diverticulum  of,  1070 

papilla  of,  1070 
Veins,  structure  of,  84 
anastomoses  of,  649 
of  bone,  56 
coats  of,  84 
development  of,  130 
muscular  tissue  of,  84 
plexuses  of,  649 
size,  form,  etc.,  649 
structure  of,  84 
valves  of,  84 
vessels  and  nerves  of,  85 
Veins  or  Vein,  descriptive  anat- 
omy of,  649 
accessory  portal.  1057 
of  ahe  nasi,  652 
angular,  651 
articular,  of  knee,  672 
auditory,  927 
auricular  anterior,  652 

posterior,  653 
axillary,  664 
azygos,  left  lower,  667 

left  upper,  667 

right,  667 
basilic,  664 
basi-vertebral.  669 
brachial,  664 

brachio-cephalic    or    innomi- 
nate, 665 
bronchial,  668 
buccal,  653 
cardiac,  677 

anterior,  677 

great,  677 

left,  677 

middle,  677 

posterior,  677 

right,  677 
cardinal,  131 
cava  inferior,  673 

superior,  667 
cephalic,  663 
cerebellar.  657 
cerebral,  657 
cervical,  ascending,  655 

deep,  655 

choroid  of  brain,  657 
circumflex,  iliac,  672 

superficial,  670 
condyloid  posterior,  655,  659 
of  corpora  cavernosa,  1152 
of  corpus  spongiosum,  673 

striatum,  657 

deep,  or  vense  comites,  649 
dental  inferior,  653 
digital,  of  hand,  663 
of  diploe,  655 
dorsal  of  penis,  673 
dorsi-spinal,  668 
emissary,  661 

surgical  anatomy  of,  662 
epigastric,  672 

superficial,  670 
of  eyeball,  905 
facial,  652 
femoral,  672 
first  intercostal,  655 
frontal,  651 
of  Galen,  657 
gastric.  676 
gluteal,  672 
hsemorrhoidal,  672 
of  head,  650 


Veins  or  vein,  hepatic,  675,  1057, 

1061 
iliac,  common,  673 

external,  672 

internal,  672 
ilio-lumbar,  674 
inferior  cava,  673 
innominate,  665 
intercostal,  first,  655 

superior,  666 
interlobular,  of  kidney,  1134 

of  liver,  1057 

interosseous,  of  forearm,  664 
iutralobular,  of  liver,  1057 
jugular,  anterior,  654 

external,  653 

internal,  654 

posterior,  654 
of  kidney,  1134 
labial,  inferior,  652 

superior,  652 
laryngeal,  666 
lateral  sacral,  673 
lingual,  654 
of  liver,  1057 
longitudinal  inferior,  658 
lumbar,  674 

ascending,  674 
mammary  internal,  666 
masseteric,  652 
mastoid,  653 
maxillary  internal,  652 
median  basilic,  663 

cephalic,  663 
medulli-spinal,  668 
meningeal,  653 
meningo-rachidian,  668 
mesenteric  inferior,  675 

superior,  675 
nasal,  650 
oblique,  677 
occipital,  653 
cesophageal,  667 
ophthalmic,  659 
ovarian,  674 
palmar,  deep,  664 
parotid,  652 
parumbilicalis,  958 
peroneal,  671 
pharyngeal,  t>54 
phrenic,  675 
plantar,  external,  671 

internal,  671 
popliteal,  671 
plexuses  of  ovarian,  1178 

pampiniform,     674,     1155, 
1178 

pharyngeal.  654 

pterygoid,  652 

spermatic,  674,  1155 

uterine,  673 

vaginal,  873 

vesico-prostatic,  655 
portal,  649,  677,  1057,  1060 
profunda  femoris,  672 
pterygoid  plexus,  652 
pubic,  external,  670 

internal,  672 
pulmonary,  650 
radial,  663 
ranine,  652,  654 
renal,  675,  1134 
sacral,  lateral,  673 

middle,  673 
Salvatella,  663 


Veins  or  vein,  saphenous,  exter- 
nal, or  short,  670 
internal,  or  long,  670,  1190 
sciatic,  672 
spermatic,  674 
spheno-palatine,  655 
spinal,  668 
splenic,  675 
stylo- mastoid,  653 
subclavian,  665 
sublobular,  1057,  1061 
submaxillary,  652 
submental,  654 
superficial,  649 
supraorbital,  651 
suprarenal,  675 
suprascapular,  654 
sural,  672 
systemic,  649 
temporal,  654 
middle,  652 

ternporo-maxillary,  653 
thoracico-epigasirica,  957 
thyroid  inferior,  666 
middle,  655 
superior,  654 
tibial  anterior,  671 

posterior,  671 
transverse  cervical,  654 

facial,  652 
ulnar  anterior.  663 
common,  663 
deep,  664 
posterior,  663 
umbilical,  1099 
vertebral,  655 

first  intercostal,  655 
Vidian,  654 
Velum   medullary,  inferior,  733, 

734,  738 

superior,  733,  734,  738 
pendulum  palaii,  944 
interposition,  749,  766,  769 
Vena  cava,  fissure  for,  1052 
inferior,  t>7o 
peculiarities  of,  674 
superior,  667 
Venae  comites,  649 

hepaticse  advehentes,  131 

revehentes,  131 

interlobulares  of  kidney,  1134 
rectse  of  kidney,  1134 
Thebesii,   or   minima?   cordis, 

678,  1088 
vorticosse,  895 
Venesection,  663 
Venter  of  ilium,  274 
Ventricle  of  brain,  fifth,  763 
fourth,  708,  737-740 

floor  of,  720,  723 
third,  707,  745,  74* 
of  corpus  callosnm,  756 
of  heart,  left,  1092 

right,  1089 
of  larynx,  1105 
lateral,  704,  755 
Vermicular  motion,  68 
Vermiform  appendix,  1032 

relations  of,  1033 
process  of  cerebellum,  inferior 

727 

superior,  727 
Vernix  caseosa,  125 
Vertebra  prominens,  149 
development  of,  152 


INDEX. 


1249 


Vertebrae,  144 
cervical.  145 
development  of,  152 
dorsal.  149 

general  characters,  144 
ligaments  of,  319 
lumbar,  151 
sacral,  155 
structure  of,  152 
Vertebral  aponeurosis,  433 
artery,  581 
column,  160 

articulation  of,  319 
unification  of,  152 
surface  form  of,  162 
ligaments,  319 
region,   muscles    of,   anterior 

424 

lateral.  42") 
vein,  6o"> 

Vertex  of  skull.  ~2(^ 
Vertical    plate   of   palate   bone, 

198 

Verumontanum,  1146 
Vesical  artery,  inferior,  622 
middle,  •)•_'•_' 
superior,  622 
plexus  of  nerves,  878 
Vesicle,  auditors-,  124 
cerebral,  119,"  706 
lissure,  1052 
germinal,  101 
hemisphere,  707 
ocular,  123 
optic,  752 
of  Purkinje,  101 
umbilical,  109 
Vesicles,  (iraafian,  1176 
Vesico-prostatic  plexus  of  veins. 

6<  3 
Vesico-uterine  ligaments.  1169 

pouch,  9S1 

Vesicula  prostatica,  1146 
Vesiculte  seminales.  1160 

surgical  anatomy  of,  1161 
vessels  and  nerves  of,  1161 
Vesicular    column    of    anterior 

cornu  of  spine,  702 
Vessels  of  large  intestine,  1029 
of  liver,  1060 
of  rectum,  1042 
of  small  intestine,  1026 
of  spleen,  1077,  1079 

79 


Vessels  of  stomach,  1007 
Vestibular  artery,  927 

nerve,  927 
Vestibule,  aortic,  1094 

of  ear,  921 

aqueduct  of,  177,  921 
Vestigial  fold  of  pericardium,  666 
Vibrissa?,  885 
Vidian  artery,  562 

canal,  184 

nerve,  804 

sphenoidal  filament,  804,  808 
Vieussens,    valve   of,    733,   734, 

796 
Villi,  1022 

structure  of,  1023 
Viscera,   pelvic   position    of,   at 

outlet  of  pelvis,  1206 
Visceral  clefts,  118 
Vitelline  circulation,  126 

duct,  967,  970 

membrane,  100 
Vitellus,  100 
Vitreous  humor  of  the  eye,  903 

table  of  the  skull,  144' 
Vocal    cords,   inferior   or    true, 

1103 
superior  or  faise,  1105 

process,  1102 
Voice,  organs  of,  1100 
Voluntary  muscles,  64 
Vomer,  201 

ate  of,  201 

articulations  of,  201 

development  of,  201 
Vortex  of  heart,  1095 
Vulva,  1163 

development  of,  140 


Wagner,  tactile  corpuscles  of,  76 
Wall,  abdominal,  957,  959 
Watney    on    the    structure    of 

thymiis.   1126 

Weight  of  organs.     See  Individ- 
ual Organs. 
Wharton's  duct,  947 
White  fibrous  tissue.  45 
nerve-matter,  69 
substance  of  cord,  699 

of  Schwann,  71 
Willis,  circle  of,  573,  584 


Winslow,  foramen  of,  975,  992 

ligament  of,  368 
Wirsung,  canal  of,  1070 
Wisdom  tooth,  935 
!  Wolffian  duct,  135 
Womb.     See  Uterus. 
WTorm  of  cerebellum,  725,  727 
Wormian  bones,  188 
Wrisberg,  cartilages  of,  1102 

ganglion  of,  874 

nerve  of,  840 
Wrist-joint,  356 

surface  form  of,  270,  357 

surgical  anatomy  of,  357 
Wry-neck,  411 

X. 

Xiphoid  appendix,  229 

Y. 

Y-ligament,  364 

Y-shaped  centre  of  acetabulum, 

278 
Yellow  cartilage,  53 

elastic  fibrous  tissue,  45 

spot  of  retina,  898 
Yolk,  101 

sac.  109.  967 

stalk,  967 

Z. 

Zinn,  ligament  of,  397 
Zona  arcuata,  925 

fasciculata,  1138 

glomerulosa,  1138 

incerta,  745 

mesogastric,  961 

pellucida,  101 

radiata,  101 

reticularis,    1138 

vasculosa,  1176 
Zygoma,  174 

roots  of,  174 

tubercle  of,  174 
Zygomatic  arch,  216 

fossa,  216 

lymphatic  glands,  681 

process  of  malar.  197 
Zygomaticus  major  muscle,  400 

minor,  400 
ft 


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A  Quarterly  Digest  of  Xew  Methods,  Discoveries  and  Improvements  in  the  Medical  and 
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ABBOTT  (A.  0.).  PRINCIPLES  OF  BACTERIOLOGY:  a  Practical  Manual  for 
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ALLEN  (HARRISON).  A  SYSTEM  OF  HUMAN  ANATOMY;  WITH  AN 
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A  TREATISE  ON  SURGERY  BY  AMERICAN  AUTHORS.  FOR  STUDENTS 
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AMERICAN  TEXT-BOOK  OF  ANATOMY.    See  Gerrish,  page  7. 

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ASHHURST  (JOHN,  JR.).  THE  PRINCIPLES  AND  PRACTICE  OF  SUR- 
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A  PRACTICE  OF  OBSTETRICS  BY  AMERICAN  AUTHORS.  See  Jewett, 
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ATTFIELD  (JOHN).  CHEMISTRY;  GENERAL,  MEDICAL  AND  PHAR- 
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BARNES  (ROBERT  AND  FANCOURT).  A  SYSTEM  OF  OBSTETRIC  MED- 
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BILLINGS  (JOHN  S.).  THE  NATIONAL  MEDICAL  DICTIONARY.  Includ- 
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BROCKWAY  (FRED.  J.).   A  POCKET  TEXT-BOOK  OF  ANATOMY.    12mo. 

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BRUCE    (J.   MITCHELL).     MATERIA    MEDIC  A    AND    THERAPEUTICS. 

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BRYANT  (THOMAS).  THE  PRACTICE  OF  SURGERY.  Fourth  American 
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BUMSTEAD  (F.  J.)  AND  TAYLOR  (R.  W.).  THE  PATHOLOGY  AND 
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page  15. 

BURCHARD  (HENRY  H.).  DENTAL  PATHOLOGY  AND  THERAPEUTICS, 
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BURNETT  (CHARLES  H.).  THE  EAR:  ITS  ANATOMY,  PHYSIOLOGY 
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Second  edition.  In  one  8vo.  volume  of  580  pages,  with  107  illustrations.  Cloth,  $4 ; 
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CARTER  (R.  BRUDENELL)  AND  FROST  (W.  ADAMS).  OPHTHALMIC 
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CASPARI  (CHARLES,  JR.).  A  TREATISE  ON  PHARMACY.  For  Students 
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Cloth,  $4.50. 

CHAPMAN  (HENRY  C.).    A  TREATISE  ON  HUMAN  PHYSIOLOGY.    New 

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CHARLES  (T.  CRANSTOUN).  THE  ELEMENTS  OF  PHYSIOLOGICAL 
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CHEYNE  (W.WATSON)  AND  BURGH ARD  (F.  P.).  SURGICAL  TREAT- 
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CHEMISTRY  AND  QUALITATIVE  INORGANIC  ANALYSIS.    From  the 

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COAKLEY  (CORNELIUS  G.).  THE  DIAGNOSIS  AND  TREATMENT  OF 
DISEASES  OF  THE  NOSE,  THROAT,  NASO-PHARYNX  AND  TRACHEA. 
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COATS  (JOSEPH).  A  TREATISE  ON  PATHOLOGY.  In  one  volume  of  829 
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COLEMAN  (ALFRED).  A  MANUAL  OF  DENTAL  SURGERY  AND  PATH- 
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COLLINS  (C.  P.).  A  POCKET  TEXT-BOOK  OF  MEDICAL  DIAGNOSIS. 
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COLLINS  (H.  D.)  AND  ROCKWELL  (W.  H.,  JR.).  A  POCKET  TEXT- 
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CONDIE  (D.  FRANCIS).  A  PRACTICAL  TREATISE  ON  THE  DISEASES 
OF  CHILDREN.  Sixth  edition.  8vo.  719  pages.  Cloth,  $5.25 ;  leather,  $6.25. 

CORNIL  (V.).  SYPHILIS:  ITS  MORBID  ANATOMY,  DIAGNOSIS  AND 
TREATMENT.  Translated,  with  Notes  and  Additions,  by  J.  HENRY  C.  SIMES,  M.D., 
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CROOK    JAMES  K.'i.    MINERAL  WATERS  OF  UNITED  STATES.     Octavo 

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CULBRETH  (DAVID  M.  R.  .     MATERIA  MEDICA  AND  PHARMACOLOGY 

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CTJSHNY  ARTHUR  R.I  A  TEXT-BOOK  OF  PHARMACOLOGY  AND 
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DALTON   (JOHN   C.  .    A  TREATISE  Oy  HUMAN  PHYSIOLOGY.    Seventh 

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DOCTRINES  OF  THE  CIRCULATION  OF  THE  BLOOD.  In  one  hand- 
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DAVENPORT  (F.  H.).  DISEASES  OF  WOMEN.  A  Manual  of  Gynecology. 
For  the  use  of  Students  and  General  Practitioners.  New  (3d)  edition.  In  one  hand- 
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DAVIS    F.  H.  .     LECTURES  ON  CLINICAL  MEDICINE.    Second  edition.     In 

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DAVIS  EDWARD  PA  A  TREATISE  ON  OBSTETRICS.  For  Students  and 
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DE  LA  BECHE'S  GEOLOGICAL  OBSERVER.  In  one  large  octavo  volume  of  700 
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DENNIS     FREDERIC    S.     AND    BILLINGS  (JOHN   S.).     A    SYSTEM  OF 

SURGERY.  In  Contributions  by  American  Authors.  In  four  very  handsome  octavo 
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DERCUM  FRANCIS  X.  ,  Editor.  A  TEXT-BOOK  ON  NERVOUS  DIS- 
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DE  SCHWEINITZ  GEORGE  E.).  THE  TOXIC  AMBLYOPIAS ;  THEIR 
CLASSIFICATION,  HISTORY,  SYMPTOMS,  PATHOLOGY  AND  TREAT- 
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DRAPER  JOHN  C.  .  MEDICAL  PHYSICS.  A  Text-book  for  Students  and  Prac- 
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DRUITT  i ROBERT  .     THE  PRINCIPLES  AND  PRACTICE  OF  MODERN 

SURGERY.  A  new  American,  from  the  twelfth  London  edition,  edited  by  STAJTLEY 
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DUANE  f  ALEXANDER  .  A  DICTIONARY  OF  MEDICINE  AND  THE 
ALLIED  SCIENCES.  Comprising  the  Pronunciation,  Derivation  and  Full  Explan- 
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Collateral  Descriptive  Matter.  Numerous  Tables,  etc.  New  (3d)  edition.  Square  octavo 
volume  of  652  pages  with  8  colored  plates.  Just  Ready.  Cloth,  $3.00,  net;  limp 
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DUDLEY  (B.C.).  A  TREATISE  ON  THE  PRINCIPLES  AND  PRACTICE 
OF  GYNECOLOGY.  For  Students  and  Practitioners.  New  (2d)  edition.  In  one 
very  handsome  octavo  volume  of  717  pages,  with  4o3  engravings,  of  which  47  are 
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DUNCAN  ( J.  MATTHEWSK  CLINICAL  LECTURES  ON  THE  DISEASES 
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taining a  full  Explanation  of  the  Various  Subjects  and  Terms  of  Anatomy,  Physiology, 
Medical  Chemistry,  Pharmacy,  Pharmacology,  Therapeutics,  Medicine,  Hygiene,  Dietetics. 
Pathology,  Surgery,  Ophthalmology,  Otology,  Laryngology,  Dermatology,  Gynecology, 
Obstetrics,  Pediatrics,  Medical  Jurisprudence,  Dentistry,  etc.,  etc.  By  ROBLEY  DUNGLI- 
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lege of  Philadelphia.  Edited  by  EICHARD  J.  DUNGLISON,  A.M.,  M.D.  Twenty-second 
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Accentuation  and  Derivation  of  the  Terms.  With  Appendix.  Imperial  octavo  of  about 
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DUNHAM  (EDWARD  K.).  MORBID  AND  NORMAL  HISTOLOGY.  Octavo, 
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MEDIC  A.  In  one  8vo.  volume  of  544  pages.  Cloth,  $3.50;  leather,  $4.50. 

EDIS  (ARTHUR  W.).  DISEASES  OF  WOMEN.  A  Manual  for  Students  and 
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Cloth,  $3 ;  leather,  $4. 

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ELLIS  (GEORGE  VINER).     DEMONSTRATIONS  IN  ANATOMY.     Being  a 

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English  edition.     Octavo,  716  pages,  with  249  engravings.     Cloth,  $4.25 ;  leather,  $5.25. 

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ERICHSEN  (JOHN  E.).     THE  SCIENCE  AND  ART  OF  SURGERY.    A  new 

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volumes  containing  2316  pages,  with  984  engravings.  Cloth,  $9 ;  leather,  $11. 

ESSIG  (CHARLES  J.).  PROSTHETIC  DENTISTRY.  See  American  Text-books 
of  Dentistry,  page  2. 

EVANS  (DAVID  J.).  A  POCKET  TEXT-BOOK  OF  OBSTETRICS.  12mo. 
of  about  300  pages,  amply  illustrated.  Shortly. 

FARQUHARSON  (ROBERT).  A  GUIDE  TO  THERAPEUTICS.  Fourth 
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12mo.  volume  of  581  pages.  Cloth,  $2.50. : 

FIELD  (GEORGE  P.).  A  MANUAL  OF  DISEASES  OF  THE  EAR.  Fourth 
edition.  Octavo,  391  pages,  with  73  engravings  and  21  colored  plates.  Cloth,  $3.75. 

FLINT  (AUSTIN).  A  TREATISE  ON  THE  PRINCIPLES  AND  PRACTICE 
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• A  MANUAL  OF  AUSCULTATION  AND  PERCUSSION;  of  the  Physi- 
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ume of  591  pages.  Cloth,  $4.50. 

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ON  PHTHISIS :  ITS  MORBID  ANA  TO  MY,  ETIOL  OGY,  ETC.    A  Series 


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FORMULARY,  THE  NATIONAL.  See  Stilie,  Maisch  &  Caspari's  National  Dispensa- 
tory, page  14. 

FORMULARY,  POCKET.    See  page  1. 

FOSTER  (MICHAEL).  A  TEXT-BOOK  OF  PHYSIOLOGY.  New  (6th)  and 
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pages,  with  257  illustrations.  Cloth,  $4.50 ;  leather,  $5.50. 

FOTHERGILL  (J.  MILNER).  THE  PRACTITIONERS  HAND-BOOK  OF 
TREATMENT.  Third  edition.  In  one  handsome  octavo  volume  of  664  pages. 
Cloth,  $3.75 ;  leather,  $4.75. 

FOWNES  (GEORGE).  A  MANUAL  OF  ELEMENTARY  CHEMISTRY  (IN- 
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handsome  octavo  volume  of  677  pages,  with  51  engravings  and  2  plates.  Cloth,  $3.75 ; 
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FULLER  (EUGENE).  DISORDERS  OF  THE  SEXUAL  ORGANS  IN  THE 
MALE.  In  one  very  handsome  octavo  volume  of  238  pages,  with  25  engravings  and 
8  full-page  plates.  Cloth,  $2. 

FULLER  (HENRY).  ON  DISEASES  OF  THE  L  UNGS  AND  AIR-PASSAGES. 
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edition.  In  one  8vo.  volume  of  475  pages.  Cloth,  $3.50. 

GALLAUDET  (BERN  B.).  A  POCKET  TEXT-BOOK  ON  SURGERY. 
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GANT  ( FREDERICK  JAMES ) .  THE  STUDENT'S  S UR GER  Y.  A  Multum  in 
Parvo.  In  one  square  octavo  volume  of  845  pages,  with  159  engravings.  Cloth,  $3.75. 

GERRISH  ( FREDERIC  H.).  A  TEXT-BOOK  OF  ANATOMY.  By  American 
Authors.  Edited  by  FREDERIC  H.  GERRISH,  M.  D.  In  one  imp.  octavo  volume  of  915 
pages,  with  950  illustrations  in  black  and  colors.  Cloth,  $6. 50 ;  flexible  water-proof, 
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TOL  OGY.  Octavo  of  314  pages,  with  60  illustrations,  mostly  photographic.  Cloth,  $2.75. 

GOULD  (A.  PEARCE).  SURGICAL  DIAGNOSIS.  In  one  12mo.  volume  of  589 
pages.  Cloth,  $2.  See  Students'  Series  of  Manuals,  page  14. 

GRAY  (HENRY).  ANATOMY,  DESCRIPTIVE  AND  SURGICAL.  New 
American  edition  thoroughly  revised.  In  one  imperial  octavo  volume  of  1239  pages, 
with  772  large  and  elaborate  engravings.  Price  with  illustrations  in  colors,  cloth,  $7 ; 
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GREEN  (T.  HENRY).  AN  INTRODUCTION  TO  PATHOLOGY  AND  MOR- 
BID ANATOMY.  New  (8th)  American  from  eighth  and  revised  English  edition. 
Oct.  595  pages,  with  215  engravings  and  a  colored  plate.  Cloth,  $2.50,  net. 

GREENE  (WILLIAM  H.).  A  MANUAL  OF  MEDICAL  CHEMISTRY.  For 
the  Use  of  Students.  Based  upon  BOWMAN'S  Medical  Chemistry.  In  one  12mo.  volume 
of  310  pages,  with  74  illustrations.  Cloth,  $1.75. 

GRINDON  (JOSEPH).     A   POCKET  TEXT-BOOK  OF  SKIN  DISEASES. 

12mo.  of  350  pages,  with  many  illustrations.     Shortly. 

GROSS  (SAMUEL  D.).  A  PRACTICAL  TREATISE  ON  THE  DISEASES, 
INJURIES  AND  MALFORMATIONS  OF  THE  URINARY  BLADDER, 
THE  PROSTATE  GLAND  AND  THE  URETHRA.  Third  edition,  revised  by 
SAMCEL  W.  GROSS,  M.D.  Octavo  of  574  pages,  with  170  illustrations.  Cloth,  $4.50. 

HABERSHON  (S.  0.).  ON  THE  DISEASES  OF  THE  ABDOMEN,  comprising 
those  of  the  Stomach,  (Esophagus,  Caecum,  Intestines  and  Peritoneum.  Second  Amer- 
ican from  the  third  English  edition.  In  one  octavo  volume  of  554  pages,  with  11  eftgrav- 
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HAMILTON  (ALLAN  McLANE ) .  NEE  VO  US  DISEASES,  THEIR  DESCRIP- 
TION AND  TREATMENT.  Second  and  revised  edition.  In  one  octavo  volume  of 
598  pages,  with  72  engravings.  Cloth,  $4. 

HARDAWAY  (W.  A.).  MANUAL  OF  SKIN  DISEASES.  New  (2d)  edition. 
In  one  12mo.  volume,  560  pages  with  40  illustrations  and  2  colored  platfs.  Cloth, 
$2.25,  net. 

HARE  (HOBART  AMORY).  A  TEXT-BOOK  OF  PRACTICAL  THERA- 
PEUTICS, with  Special  Reference  to  the  Application  of  Remedial  Measures  to  Disease 
and  their  Employment  upon  a  Rational  Basis.  With  articles  on  various  subjects  by  well- 
known  specialists.  New  (8th)  and  revised  edition.  .In  one  octavo  volume  of  796  pages, 
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with  205  engravings,  and  14  full-page  plates.     Cloth,  $5,  net. 

Editor.    A  SYSTEM  OF  PRACTICAL  THERAPEUTICS.     By  American 

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large  octavo  volumes  comprising  4600  pages,  with  476  engravings.    Vol.  IV.,  now  ready. 
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HARTSHORNE  (HENRY).  ESSENTIALS  OF  THE  PRINCIPLES  AND 
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A  CONSPECTUS  OF  THE  MEDICAL  SCIENCES.     Comprising  Manuals 


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trations. Cloth,  $4. 25 ;  leather,  $5. 

HAYDEN  (JAMES  R.).  A  MANUAL  OF  VENEREAL  DISEASES.  New  (2d) 
edition.  In  one  12mo.  volume  of  304  pages,  with  54  engravings.  Cloth,  $1.50,  net. 

HAYEM  (GEORGES)  AND  HARE  (H.  A.).  PHYSICAL  AND  NATURAL 
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pheric Pressure,  CILmates  and  Mineral  Waters.  Edited  by  Prof.  H.  A.  HARE,  M.D. 
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HERMAN  (G.  ERNEST).  FIRST  LINES  IN  MIDWIFERY.  12mo.,  198  pages' 
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HERMANN  ( L. ) .  EXPERIMENTAL  PHARMA  COL  OGY.  A  Handbook  of  the 
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HILL  ( BERKELEY ) .  S YPHILIS  AND  LOCAL  CONTA  GIO  US  DISORDERS, 
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HILLIER  (THOMAS).  A  HANDBOOK  OF  SKIN  DISEASES.  Second  edition. 
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HIRST  (BARTON  C.)  AND  PIERSOL  (GEORGE  A.).  HUMAN  MONSTROS- 
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HODGE  (HUGH  L.).  ON  DISEASES  PECULIAR  TO  WOMEN,  INCLUDING 
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8vo.  volume  of  519  pages,  with  illustrations.  Cloth,  $4.50. 

HOFFMANN  (FREDERICK)  AND  POWER  (FREDERICK  B.).  A  MANUAL 
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HOLMES  (TIMOTHY).  A  TREATISE  ON  SURGERY.  Its  Principles  and 
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edition,  revised  and  modified.  In  two  large  8vo.  volumes  of  1007  pages,  containing  320 
engravings.  Cloth,  $6. 

HUDSON  (A.).  LECTURES  ON  THE  STUDY  OF  FEVER.  In  one  octavo 
volume  of  308  pages.  Cloth,  $2.50. 

HUTCHISON  (ROBERT)   AND  RAINY  (HARRY).      CLINICAL  METHODS. 

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with  137  engravings  and  8  colored  plates,     Cloth,  $3.00. 

HYDE  (JAMES  NEVINS).  A  PRACTICAL  TREATISE  ON  DISEASES  OF 
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engravings  and  24  full-page  plates,  8  of  which  are  colored.  Just  Ready.  Cloth,  $4.50, 
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JACKSON  ( GEORGE  THOMAS ) .  THE  READ  Y-REFERENCE  HANDS  0  OK 
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JAMTESON  (W.  ALLAN).  DISEASES  OF  THE  SKIN.  Third  edition.  Octavo, 
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JEWETT  (CHARLES).  ESSENTIALS  OF  OBSTETRICS.  In  one  12mo.  volume 
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THE  PRACTICE  OF  OBSTETRICS.   By  American  Authors.    One  large  octavo 

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JONES  ( C .  HANDFIELD ) .  CLINICAL  OBSER  VA  TIONS  ON  FUNCTIONAL 
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pages.  Cloth,  $3.25. 

JULER  (HENRY).  A  HANDBOOK  OF  OPHTHALMIC  SCIENCE  AND 
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KIRK  (EDWARD  C.).  OPERATIVE  DENTISTRY.  See  American  Textbooks  of 
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12mo.  volume  of  612  pages,  with  264  illustrations.  Just  Ready.  Cloth,  $2,50.  net. 

KLEIN  (E.).     ELEMENTS  OF  HISTOLOGY.     New  (5th)  edition.     In  one  pocket- 
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LA  ROCHE  (R.).  YELLOW  FEVER.  In  two  8vo.  volumes  of  1468  pages. 
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LAURENCE  (J.  Z.)  AND  MOON  (ROBERT  0.).  A  HANDY-BOOK  OF 
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with  66  engravings.  Cloth,  $2.75. 

LEA  (HENRY  C.).  CHAPTERS  FROM  THE  RELIGIOUS  HISTORY  OF 
SPAIN;  CENSORSHIP  OF  THE  PRESS;  MYSTICS  AND  ILLUMINATI; 
THE  ENDEMONIADAS ;  EL  SANTO  NINO  DE  LA  GUARDIA;  BRI- 
ANDA  DE  BARDAXI.  In  one  12mo.  volume  of  522  pages.  Cloth,  $2.50. 


A  HISTORY  OF  AURICULAR  CONFESSION  AND  INDULGENCES 

IN  THE  LATIN  CHURCH.     In  three  octavo  volumes  of  about  500  pages  each. 
Per  volume,  cloth,  $3.     Complete  work  just  ready. 

—  FORMULARY   OF    THE   PAPAL    PENITENTIARY.     In    one  octavo 
volume  of  221  pages,  with  frontispiece.     Cloth,  $2.50. 


STUDIES  IN  CHURCH  HISTORY.  The  Eise  of  the  Temporal  Power- 
Benefit  of  Clergy — Excommunication.  New  edition.  In  one  handsome  12mo.  volume 
of  605  pages.  Cloth,  $2.50. 


SUPERSTITION  AND  FORCE;  ESSAYS  ON  THE  WAGER  OF  LAW, 

THE    WAGER    OF  BATTLE,   THE   ORDEAL  AND    TORTURE.     Fourth 
edition,  thoroughly  revised.     In  one  royal  12mo.  volume  of  629  pages.     Cloth,  $2.75. 

AN  HISTORICAL  SKETCH  OF  SACERDOTAL  CELIBACY  IN  THE 

CHRISTIAN  CHURCH.     Second  edition.     In  one  handsome  octavo  volume  of  685 
pages.     Cloth,  $4.50. 

LOOMIS  (ALFRED  L.)  AND  THOMPSON  (W.  OILMAN),  Editors.  A  SYS- 
TEM OF  PR  A  CTICAL  MEDICINE.  In  Contributions  by  Various  American  Authors. 
In  four  very  handsome  octavo  volumes  of  about  900  pages  each,  fully  illustrated  in  black 
and  colors.  Complete  work  now  ready.  Per  volume,  cloth,  $5 ;  leather,  $6 ;  half 
Morocco,  $7.  For  sale  by  subscription  only.  Full  prospectus  free  on  application  to  the 
Publishers. 

LUFF  (ARTHUR  P.).  MANUAL  OF  CHEMISTRY,  for  the  use  of  Students  of 
Medicine.  In  one  12mo.  volume  of  522  pages,  with  36  engravings.  Cloth,  $2.  See 
Students'  Series  of  Manuals,  page  14. 

LYMAN  (HENRY  M.).  THE  PRACTICE  OF  MEDICINE.  In  one  very  hand- 
some octavo  volume  of  925  pages  with  170  engravings.  Cloth,  $4.75;  leather,  $5.75. 

LYONS  (ROBERT  D.).  A  TREATISE  ON  FEVER.  In  one  octavo  volume  of  362 
pages.  Cloth,  $2.25. 

MACKENZIE  (JOHN  NOLAND).  THE  DISEASES  OF  THE  NOSE  AND 
THROAT.  Octavo,  of  about  600  pages,  richly  illustrated.  Preparing. 

MAISCH  (JOHN  M.).  A  MANUAL  OF  ORGANIC  MATERIA  MEDICA. 
New  (7th)  edition,  thoroughly  revised  by  H.  C.  C.  MAISCH,  Ph.G.,  Ph.D.  In  one  very 
handsome  12mo.  of  512  pages,  with  285  engravings.  Cloth,  $2.50,  net. 

MALSBARY  (GEO.  E.).  A  POCKET  TEXT-BOOK  OF  THEORY  AND 
PRACTICE  OF  MEDICINE.  12mo.  405  pages,  with  45  illustrations.  Just  Ready. 
Cloth,  $1.75,  net;  flexible  red  leather,  $2.25,  net. 

MANUALS.  See  Students'  Quiz  Series,  page  14,  Students'  Series  of  Manuals,  page  14,  and 
Series  of  Clinical  Manuals,  page  13. 

MARSH  (HOWARD).  DISEASES  OF  THE  JOINTS.  In  one  12mo.  volume  of 
468  pages,  with  64  engravings  and  a  colored  plate.  Cloth,  $2.  See  Series  of  Clinical 
Manuals,  page  13. 

Philadelphia,  706,  708  and  710  Sansom  St.— Hew  York,  111  Fifth  Avenue. 


LEA    BROTHERS    &     CO.' S    PUBLICATIONS.  11 

MARTIN  (EDWARD.)     SURGICAL  DIAGNOSIS.     One  12mo.   volume  of  400 

pages,  richly  illustrated.     Preparing. 

MARTIN  ( WALTON  >  AND  ROCKWELL  fW.  H.,  JR.).  A  POCKET  TEXT- 
BOOK OF  CHEMISTRY  AND  PHYSICS.  12mo.  366  pages,  with  137  illus- 
trations. Just  ready.  Cloth,  $1.50,  net;  flexible  red  leather,  $2.00,  net. 

MAY  (0.  H.).  MANUAL  OF  THE  DISEASES  OF  WOMEN.  For  the  use  of 
Students  and  Practitioners.  Second  edition,  revised  by  L.  S.  BAIT,  M.D.  In  one  12mo. 
volume  of  360  pages,  with  31  engravings.  Cloth,  $1.75. 

MEDICAL  NEWS  POCKET  FORMULARY.    See  page  1. 

MITCHELL  (JOHN  K.).  REMOTE  CONSEQUENCES  OF  INJURIES  OF 
NERVES  AND  THEIR  TREATMENT.  In  one  handsome  12mo.  volume  of  239 
pages,  with  12  illustrations.  Cloth  $1.75. 

MITCHELL  (S.  WEIR).  CLINICAL  LESSONS  ON  NERVOUS  DISEASES. 
In  one  very  handsome  12mo.  volume  of  299  pages,  with  17  engravings  and  2  colored  plates. 
Cloth,  §2.50. 

MORRIS  (MALCOLM).  DISEASES  OF  THE  SKIN.  New  (2d)  edition.  In  one 
12mo.  volume  of  601  pages,  with  10  chromo-lithographic  plates  and  26  engravings. 
Cloth,  $3.25,  net. 

MULLER  (J.).    PRINCIPLES  OF  PHYSICS  AND  METEOROLOGY.     In  one 

large  8vo.  volume  of  623  pages,  with  538  engravings.     Cloth,  $4. 50. 

MUSSER  (JOHN  H.).  A  PRACTICAL  TREATISE  ON  MEDICAL  DIAG- 
NOSIS, for  Students  and  Physicians.  New  (3d)  edition.  In  one  octavo  volume  of 
1082  pages,  with  253  engravings  and  48  full-page  colored  plates.  Just  Ready.  Cloth, 
$6.00,  net;  leather,  $7.00,  net. 

NATIONAL  DISPENSATORY.    See  StiMe,  Maisch  &  Caspari,  page  14. 
NATIONAL    FORMULARY.      See  National  Dispensatory,  page  14. 
NATIONAL  MEDICAL  DICTIONARY.    See  Billings,  page  3. 

NETTLESHIP  (E.).  DISEASES  OF  THE  EYE.  New  (6th)  American  from  sixth 
English  edition.  Thoroughly  revised.  In  one  12mo.  volume  of  562  pages,  with  192 
engravings,  5  colored  plates,  test-types,  formulae  and  color-blindness  test.  Just  Ready. 
Cloth,  $2.25.  net. 

NICHOLS  (JOHN  B.  t  AND  VALE  (F.  P.).  A  POCKET  TEXT-BOOK  OF 
HISTOLOGY  AND  PATHOLOGY.  12mo.  of  459  pages,  with  213  illustrations. 
Just  ready.  Cloth,  *1.75,  net;  flexible  red  leather,  $2.25,  net. 

NORRIS  (WM.  F.)  AND  OLIVER  (CHAS.  A.).  TEXT-BOOK  OF  OPHTHAL- 
MOLOGY. In  one  octavo  volume  of  641  pages,  with  357  engravings  and  5  colored 
plates.  Cloth,  $5 ;  leather,  $6. 

OWEN  (EDMUND).  SURGICAL  DISEASES  OF  CHILDREN.  In  one  12mo. 
volume  of  525  pages,  with  85  engravings  and  4  colored  plates.  Cloth,  $2.  See  Series  of 
Clinical  Manuals,  page  13. 

PARK  (WILLIAM  H.).    BACTERIOLOG  Y  IN  MEDICINE  AND  SURGER  Y. 

12mo.  688  pages,  with  87  engravings  in  black  and  colors  and  2  colored  plates.     Just 
Ready.     Cloth,  $3.00,  net. 

PARK  (ROSWELL),  Editor.  A  TREATISE  ON  SURGERY,  by  American  Authors. 
For  Students  and  Practitioners  of  Surgery  and  Medicine.  New  condensed  edition. 
In  one  large  octavo  volume  of  1261  pages,  with  625  engravings  and  38  plates.  Just 
Ready.  Cloth,  net,  $6.00;  leather,  net,  $7.00.  8&°This  work  is  published  also  in  a 
large  edition,  comprising  two  octavo  volumes.  Vol.  I.,  General  Surgery,  799  pages,  with 
356  engravings  and  21  full-page  plates  in  colors  and  monochrome.  Vol.  II.,  Special 
Surgery,  796  pages,  with  451  engravings  and  17  full-page  plates  in  colors  and  mono- 
chrome. Price  per  volume,  cloth,  $4.50;  leather,  $5.50,  net. 

PARVEN  (THEOPHILUS).  THE  SCIENCE  AND  ART  OF  OBSTETRICS. 
Third  edition.  In  one  handsome  octavo  volume  of  677  pages,  with  267  engravings  and 
2  colored  plates.  Cloth,  $4.25;  leather,  $5.25. 

Philadelphia,  706,  708  and  710  Sansom  St.— Mew  York,  111  Fifth  Avenue. 


12  LEA    BROTHERS    &     CO.'S    PUBLICATIONS. 

PEPPER'S  SYSTEM  OF  MEDICINE.    See  page  2. 

PEPPER  (A.  J.).  SURGICAL  PATHOLOGY.  In  one  12mo  volume  of  511  pages, 
with  81  engravings.  Cloth,  $2.  See  Students'  Series  of  Manuals,  page  14. 

PICK  (T.  PICKERING).  FRACTURES  AND  DISLOCATIONS.  In  one  12mo. 
volume  of  530  pages,  with  93  engravings.  Cloth,  $2.  See  Series  of  Clinical  Manuals,  p.  13. 

PLAYFAIR  (W.  8.).  A  TREATISE  ON  THE  SCIENCE  AND  PRACTICE 
OF  MIDWIFERY.  New  (7th)  American  from  the  Ninth  English  edition.  In  one 
octavo  volume  of  700  pages,  with  207  engravings  and  7  full  page  plates.  Cloth,  $3.75, 
net;  leather,  $4.75,  net. 

THE  SYSTEMATIC  TREATMENT  OF  NERVE  PROSTRATION  iND 

HYSTERIA.     In  one  12mo.  volume  of  97  pages.     Cloth,  $1. 

OLITZER  (ADAM).  A  TEXT-BOOK  OF  THE  DISEASES  6F  THE  EAR 
AND  ADJACENT  ORGANS.  Second  American  from  the  third  German  edition. 
In  one  octavo  volume  of  748  pages,  with  330  original  engravings. 

POCKET  FORMULARY.    See  page  1. 

POCKET  TEXT-BOOKS  Cover  the  entire  domain  of  medicine  in  sixteen  volumes  of 
350  to  450  pages  each,  written  by  teachers  in  leading  American  medical  colleges. 
Issued  under  the  editorial  supervision  of  BERN  B.  GALLATJDET,  M.D. ,  of  the  College  of 
Physicians  and  Surgeons,  New  York.  Thoroughly  modern  and  authoritative,  concise 
and  clear,  amply  illustrated  with  engravings  and  plates,  handsomely  printed  and 
bound.  The  series  is  constituted  as  follows  :  Anatomy  (preparing),  Physiology  (ready}, 
Chemistry  and  Physics  (ready},  Histology  and  Pathology  (ready),  Materia  Medica, 
Therapeutics,  Medical  Pharmacy,  Prescription  Writing  and  Medical  Latin  (ready}, 
Practice  (ready},  Diagnosis  (shortly},  Nervous  and  Mental  Diseases  (ready),  Surgery 
(preparing),  Genito-Urinary  and  Venereal  Diseases  (preparing),  Skin  Diseases 
(preparing),  Eye,  Ear,  Nose  and  Throat  (shortly),  Obstetrics  (shortly),  Gynecology 
(ready),  Diseases  of  Children  (ready),  Bacteriology  and  Hvgiene  (shortly).  For  further 
details  see  under  respective  authors  in  this  catalogue.  Special  circular  free  on  appli- 
cation. 

POTTS  (CHAS.  S.).  A  POCKET  TEXT-BOOK  OF  NERVOUS  AND 
MENTAL  DISEASES.  12mo.  of  455  pages,  with  88  illustrations.  Just  ready. 
Cloth,  $1.75,  net;  flexible  red  leather,  $2.25,  net. 

PROGRESSIVE  MEDICINE.    See  page  1. 

PURDY  (CHARLES  W.).  BRIGHT'S  DISEASE  AND  ALLIED  AFFEC- 
TIONS OF  THE  KIDNEY.  In  one  octavo  volume  of  288  pages,  with  18  engrav- 
ings. Cloth,  $2. 

PYE-SMITH  (PHILIP  H.).  DISEASES  OF  THE  SKIN.  In  one  12mo.  volume 
of  407  pages,  with  28  illustrations,  18  of  which  are  colored.  Cloth,  $2. 

QUIZ  SERIES.     See  Students'  Quiz  Series,  page  14. 

RALFE  (CHARLES  H.).  CLINICAL  CHEMISTRY.  In  one  12mo.  volume  of 
314  pages,  with  16  engravings.  Cloth,  $1.50.  See  Students'  Series  of  Manuals,  page  14. 

RAMSBOTHAM  (FRANCIS  H.).  THE  PRINCIPLES  AND  PRACTICE  OF 
OBSTETRIC  MEDICINE  AND  SURGERY.  Imperial  octavo,  of  640  pages, 
with  64  plates  and  numerous  engravings  in  the  text.  Leather,  $7. 

REMSEN  (IRA).  THE  PRINCIPLES  OF  THEORETICAL  CHEMISTRY. 
New  (5th)  edition,  thoroughly  revised.  In  one  12mo.  volume  of  326  pages.  Cloth,  $2. 

RICHARDSON  (BENJAMIN  WARD).    PREVENTIVE  MEDICINE.    In  one 

octavo  volume  of  729  pages.     Cloth,  $4 ;  leather,  $5. 

ROBERTS  (JOHN  B.).  THE  PRINCIPLES  AND  PRACTICE  OF  MODERN 
SURGERY.  New  (2d)  edition.  In  one  octavo  volume  of  838  pages,  with  474 
engravings  and  8  plates.  Just  Ready.  Cloth,  $4.25,  net;  leather,  $5.25,  net. 

-  THE  COMPEND  OF  ANATOMY.     For  use  in  the  Dissecting  Room  and  in 
preparing  for  Examinations.     In  one  16mo.  volume  of  196  pages.     Limp  cloth,  75  cents. 


Philadelphia,  706,  708  and  710  Sansom  St. — New  York,  111  Fifth  Avenue. 


LEA    BROTHERS    &     CO.'S    PUBLICATIONS. 


ROSS  JAMES).  A  HANDBOOK  OF  THE  DISEASES  OF  THE  NERVOUS 
SYSTEM.  In  one  handsome  octavo  volume  of  726  pages,  with  184  engravings.  Cloth, 
$450;  leather,  $5.50. 

SCHAFER  ( EDWARD  A. ).  THE  ESSENTIALS  OF  HISTOLOG T,  DESCRIP- 
TIVE AND  PRACTICAL.  For  the  use  of  Students.  New  (5th)  edition.  In  one 
handsome  octavo  volume  of  350  pages,  with  325  illustrations.  Cloth,  $3,  neL 

A    COURSE    OF  PRACTICAL    HISTOLOGY.     Second  edition.     In    one 


12mo.  volume  of  307  pages,  with  59  engravings.     Cloth,  $2.25. 

SCHLEIF  WM.  .  A  POCKET  TEXT-BOOK  OF  MATERIA  MEDIC  A, 
THERAPEUTICS,  PRESCRIPTION  WRITING.  MEDICAL  LATIN  AND 
MEDICAL  PHARMACY.  12mo.  352  pages.  Just  Ready.  Cloth,  $1.50,  net; 
flexible  red  leather,  $2.00,  net. 

SCHMITZ  AND  ZUMPT'S  CLASSICAL  SERIES. 

ADVANCED  LATIN  EXERCISES     Cloth,  60  cents;  half  bound,  70  cents. 
SCHMITZ' S  ELEMENTARY  LATIN  EXERCISES.     Cloth,  50  cents. 
SALL  UST.     Cloth,  60  cents ;  half  bound,  70  cents. 
NEPOS.     Cloth,  60  cents ;  half  bound,  70  cents. 
VIRGIL.     Cloth,  85  cents;  half  bound,  $1. 
CURTIUS.     Cloth,  80  cents;  half  bound.  90  cents. 

SCHOFIELD  (ALFRED  T.).  ELEMENTARY  PHYSIOLOGY  FOR  STU- 
DENTS. In  one  12mo.  volume  of  380  pages,  with  227  engravings  and  2  colored  plates. 
Cloth,  $2. 

SCHREIBER  JOSEPH).  A  MANUAL  OF  TREATMENT  BY  MASSAGE 
AND  METHODICAL  MUSCLE  EXERCISE.  Translated  by  WAI/TER  MEXDEL- 
SON,  M.D.,  of  New  York.  In  one  handsome  octavo  volume  of  274  pages,  with  117  fine 
engravings. 

SENN  (NICHOLAS).  SURGICAL  BACTERIOLOGY.  Second  edition.  In  one 
octavo  volume  of  268  pages,  with  13  plates,  10  of  which  are  colored,  and  9  engravings. 
Cloth,  $2. 

SERIES  OF  CLINICAL  MANUALS.  A  Series  of  Authoritative  Monographs  on 
Important  Clinical  Subjects,  in  12mo.  volumes  of  about  550  pages,  well  illustrated.  The 
following  volumes  are  now  ready :  YEO  on  Food  in  Health  and  Disease,  new  (2d) 
edition,  $2.50;  CARTER  and  FROST'S  Ophthalmic  Surgery,  $2.25;  MARSH  on  Diseases 
of  the  Joints,  $2 ;  OWEN  on  Surgical  Diseases  of  Children,  $2 ;  PICK  on  Fractures  and 
Dislocation 
For  separate  notices,  see  under  various  authors'  names. 

SERIES  OF  POCKET  TEXT-BOOKS.    See  page  12. 
SERIES  OF  STUDENTS'  MANUALS.    See  next  page. 

SIMON  iCHARLES  E.).  CLINICAL  DIAGNOSIS,  BY  MICROSCOPICAL 
AND  CHEMICAL  METHODS.  New  (3d)  and  revised  edition.  In  one  handsome 
octavo  volume  of  563  pages,  with  138  engravings  and  18  full-page  plates  in  colors. 
Just  Ready.  Cloth,  $3.50,  net. 

SIMON  (W.).  MANUAL  OF  CHEMISTRY.  A  Guide  to  Lectures  and  Laboratory 
Work  for  Beginners  in  Chemistry.  A  Text-book  specially  adapted  for  Students  of  Phar- 
macy and  Medicine.  New  (6th)  edition.  In  one  8vo.  volume  of  536  pages,  with  46 
engravings  and  8  plates  showing  colors  of  64  tests.  Cloth,  $3.00,  net. 

SLADE  (D.  D. ) .  DIPHTHERIA  ;  ITS  NATURE  AND  TREA TMENT.  Second 
edition.  In  one  royal  12mo.  volume,  158  pages.  Cloth,  $1.25. 

SMITH  (EDWARD).  CONSUMPTION;  ITS  EARLY  AND  REMEDIABLE 
STAGES.  In  one  8vo.  volume  of  253  pages.  Cloth,  $2.25. 

SMITH  (J.  LEWIS).  A  TREATISE  ON  THE  DISEASES  OF  INFANCY 
AND  CHILDHOOD.  Eighth  edition,  thoroughly  revised  and  rewritten  and  greatly 
enlarged.  In  one  large  8vo.  volume  of  983  pages,  with  273  illustrations  and  4  full- 
page  plates.  Cloth,  $4.50  ;  leather,  $5.50. 


Philadelphia.  706,  708  and  710  Sansom  St.— Mew  York,  111  Fifth  Avenue. 


14  LEA    BROTHERS    &     CO.'S    PUBLICATIONS. 

SMITH  (STEPHEN).  OPERATIVE  SURGERY.  Second  and  thoroughly  revised 
edition.  In  one  octavo  vol.  of  892  pages,  with  1005  engravings.  Cloth,  $4 ;  leather,  $5 

SOLLY  (S.  EDWIN).  A  HANDBOOK  OF  MEDICAL  CLIMATOLOGY. 
In  one  handsome  octavo  volume  of  462  pages,  with  engravings  and  11  full-page  plates, 
5  of  which  are  in  colors.  Cloth,  $4.00. 

STILLE  (ALFRED).  CHOLERA;  ITS  ORIGIN,  HISTORY,  CAUSATION, 
SYMPTOMS,  LESIONS,  PREVENTION  AND  TREATMENT.  In  one  12mo. 
volume  of  163  pages,  with  a  chart  showing  routes  of  previous  epidemics.  Cloth,  $1.25. 

THERAPEUTICS  AND  MATERIA  MEDIC  A.    Fourth  and  revised  edition. 


In  two  octavo  volumes,  containing  1936  pages.     Cloth,  $10 ;  leather,  $12. 

STILLE  (ALFRED),  MAISCH  (JOHN  M.)  AND  CASPARI  (CHAS.  JR.). 
THE  NATIONAL  DISPENSATORY:  Containing  the  Natural  History,  Chemistry, 
Pharmacy,  Actions  and  Uses  of  Medicines,  including  those  recognized  in  the  latest  Phar- 
macopoeias of  the  United  States,  Great  Britian  and  Germany,  with  numerous  references 
to  the  French  Codex.  Fifth  edition,  revised  and  enlarged  in  accordance  with  and  em- 
bracing the  new  U.  S.  Pharmacopoeia,  Seventh  Decennial  .Revision.  With  Supplement 
containing  the  new  edition  of  the  National  Formulary.  In  one  magnificent  imperial 
octavo  volume  of  2025  pages,  with  320  engravings  Cloth,  $7.25;  leather,  $8.  With 
ready  reference  Thumb-letter  Index.  Cloth,  $7.75 ;  leather,  $8.50. 

STIMSON  (LEWIS  A.).  A  MANUAL  OF  OPERATIVE  SURGERY.  New 
(4th)  edition.  In  one  royal  12mo.  volume  of  581  pages,  with  293  engravings.  Cloth,  $3.00, 
net.  Just  Ready. 

A  TREATISE  ON  FRACTURES  AND  DISLOCATIONS.  In  one  hand- 
some octavo  volume  of  831  pages,  with  326  engravings  and  20  full-page  plates.  Cloth, 
$5 ;  leather,  $6,  net. 

STUDENTS'  QUIZ  SERIES.  A  New  Series  of  Manuals  in  question  and  answer  for 
Students  and  Practitioners,  covering  the  essentials  of  medical  science.  Thirteen  volumes, 
pocket  size,  convenient,  authoritative,  well  illustrated,  handsomely  bound  in  limp  cloth, 
and  issued  at  a  low  price.  1.  Anatomy  (double  number) ;  2.  Physiology ;  3.  Chemistry 
and  Physics ;  4.  Histology,  Pathology  and  Bacteriology ;  5.  Materia  Medica  and  Thera- 
peutics ;  6.  Practice  of  Medicine ;  7.  Surgery  (double  number) ;  8.  Genito-Urinary  and 
Venereal  Diseases ;  9.  Diseases  of  the  Skin ;  10.  Diseases  of  the  Eye,  Ear,  Throat  and 
Nose ;  11.  Obstetrics ;  12.  Gynecology ;  13.  Diseases  of  Children.  Price,  $1  each,  except 
Nos.  1  and  7,  Anatomy  and  Surgery,  which  being  double  numbers  are  priced  at  $1.75  each. 
Full  specimen  circular  on  application  to  publishers. 

STUDENTS'  SERIES  OF  MANUALS.  A  Series  of  Fifteen  Manuals  by  Eminent 
Teachers  or  Examiners.  The  volumes  are  pocket-size  12mos.  of  from  300-540  pages,  pro- 
fusely illustrated,  and  bound  in  red  limp  cloth.  The  following  volumes  may  now  be 
announced:  HERMAN'S  First  Lines  in  Midwifery,  $1.25;  LUFF'S  Manual  of  Chemistry, 
$2;  BRUCE'S  Materia  Medica  and  Therapeutics  (sixth  edition),  $1.50,  net;  GOULD'S  Sur- 
gical Diagnosis,  $2;  KLEIN'S  Elements  of  Histology  (5th  edition),  $2.00,  net;  PEPPER'S 
Surgical  Pathology,  $2;  TREVES'  Surgical  Applied  Anatomy,  $2;  RALFE'S  Clinical 
Chemistry,  $1.50;  and  CLARKE  and  LOCKWOOD'S  Dissector's  Manual,  $1.50. 
For  separate  notices,  see  under  various  authors'  names. 

STURGES  (OCTAVIUS).  AN  INTRODUCTION  TO  THE  STUDY  OF  CLIN- 
ICAL MEDICINE.  In  one  12mo.  volume.  Cloth,  $1.25. 

BUTTON  (JOHN  BLAND).  SURGICAL  DISEASES  OF  THE  OVARIES 
AND  FALLOPIAN  TUBES.  Including  Abdominal  Pregnancy.  In  one  12mo.  vol- 
ume of  513  pages,  with  119  engravings  and  5  colored  plates.  Cloth,  $3. 

TAIT  (LAWSON  .  DISEASES  OF  WOMEN  AND  ABDOMINAL  SURGERY 
Vol.  I.  contains  554  pages,  62  engravings,  and  3  plates.  Cloth,  $3. 

TANNER  (THOMAS  HAWKES).  ON  THE  SIGNS  AND  DISEASES  OF 
PREGNANCY.  From  the  second  English  edition.  In  one  octavo  volume  of  490  pages, 
with  4  colored  plates  and  16  engravings.  Cloth,  $4.25. 


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TAYLOR  (ALFRED  S.).  MEDICAL  JURISPRUDENCE.  New  American 
from  the  twelfth  English  edition,  specially  revised  by  CLARK  BKLL,  ESQ.,  of  the  N.  Y. 
Bar.  In  one  octavo  volume  of  831  pages,  with  54  engravings  and  8  full-page  plates. 
Cloth,  $4.50;  leather,  $5.50. 

ON  POISONS    IN    RELATION    TO    MEDICINE    AND    MEDICAL 

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volume  of  788  pages,  with  104  illustrations.     Cloth,  $5.50;  leather,  $6.50. 

TAYLOR  (ROBERT  W.).  THE  PATHOLOGY  AND  TREATMENT  OF 
VENEREAL  DISEASES.  New  (2d)  edition.  In  one  very  handsome  octavo  volume 
of  about  800  pages,  with  about  230  engravings  and  many  colored  plates.  Shortly. 

A  PRACTICAL  TREATISE  ON  SEXUAL  DISORDERS  IN  THE  MALE 

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A    CLINICAL   ATLAS    OF    VENEREAL   AND    SKIN    DISEASES. 

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THOMAS    (T.   GAILLARD)    AND    MTJNDE  (PAUL     P.).  A    PRACTICAL 

TREATISE  ON  THE  DISEASES  OF  WOMEN.  Sixth  edition,  thoroughly 
revised  by  PATTL  F.  MnfDE,  M.  D.  In  one  handsome  octavo  volume  of  824  pages,  with 
347  engravings.  Cloth,  $5 ;  leather,  $6. 

THOMPSON  (W.  OILMAN).    A    TEXT-BOOK  OF  PRACTICAL  MEDICINE. 

For  Students  and  Practitioners.  In  one  handsome  octavo  volume  of  1012  pages,  with 
79  illustrations.  Just  Ready.  Cloth,  $5.00,  net;  leather,  $6.00,  net. 

THOMPSON  'SIR  HENRY).  CLINICAL  LECTURES  ON  DISEASES  OF 
THE  URINARY  ORGANS.  Second  and  revised  edition.  In  one  octavo  volume  of 
203  pages,  with  25  engravings.  Cloth,  $2.25. 

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THOMSON  JOHN  .  A  GUIDE  TO  THE  CLINICAL  EXAMINATION  AND 
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TODD  f ROBERT  BENTLEY).  CLINICAL  LECTURES  ON  CERTAIN 
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TREVES  FREDERICK).  OPERATIVE  SURGERY.  In  two  8vo.  volumes  con- 
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A  SYSTEM  OF  SURGERY.  In  Contributions  by  Twenty-five  English  Sur- 
geons. In  two  large  octavo  volumes,  containing  2298  pages,  with  950  engravings  and 
4  full-page  plates.  Per  volume,  cloth,  $8. 

-  SURGICAL  APPLIED   ANATOMY.     In  one  12mo.  volume  of  583  pages, 
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TUTTLE  GEO.  M.).  A  POCKET  TEXT-ROOK  OF  DISEASES  OF 
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VAUGHAN  (VICTOR  C.)  AND  NOVY  (FREDERICK  G.).  PTOMAINS, 
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Causation  of  Disease.  Third  edition.  In  one  12mo.  volume  of  603  pages. 

VISITING  LIST.  THE  MEDICAL  NEWS  VISITING  LIST  for  1900.  Four 
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WATSON  (THOMAS).  LECTURES  ON  THE  PRINCIPLES  AND  PRAC- 
TICE OF  PHYSIC.  A  new  American  from  the  fifth  and  enlarged  English  edition, 
with  additions  by  H.  HARTSHORNE,  M.D.  In  two  large  8vo.  volumes  of  1840  pages,  with 
190  engravings.  Cloth,  $9 ;  leather,  $11. 

WEST  (CHARLES).  LECTURES  ON  THE  DISEASES  PECULIAR  TO 
WOMEN.  Third  American  from  the  third  English  edition.  In  one  octavo  volume  of 
543  pages.  Cloth,  $3.75;  leather,  $4.75. 


ON  SOME  DISORDERS  OF  THE  NERVOUS  SYSTEM  IN  CHILD- 
HOOD. In  one  small  12mo.  volume  of  127  pages.  Cloth,  $1. 

WHARTON  (HENRY  R.).  MINOR  SURGERY  AND  BANDAGING.  New 
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are  photographic.  Just  Ready.  Cloth,  $3.00,  net. 

WHITLA  (WILLIAM).  DICTIONARY  OF  TREATMENT,  OR  THERA- 
PEUTIC INDEX.  Including  Medical  and  Surgical  Therapeutics.  In  one  square 
octavo  volume  of  917  pages.  Cloth,  $4. 

WILLIAMS  (DAWSON).  MEDICAL  DISEASES  OF  INFANCY  AND 
CHILDHOOD.  In  one  12mo.  volume  of  629  pages,  with  18  illustrations.  Cloth, 
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WILSON  (ERASMUS).  A  SYSTEM  OF  HUMAN  ANATOMY.  A  new  and 
revised  American  from  the  last  English  edition.  Illustrated  with  397  engravings.  In 
one  octavo  volume  of  616  pages.  Cloth,  $4 ;  leather,  $5. 

WINCKEL  ON  PATHOLOGY  AND  TREATMENT  OF  CHILDBED  In  one 
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WIPPERN  (A.  G.)  AND  BALLENGER  (W.  L.).  A  POCKET  TEXT-BOOK 
OF  DISEASES  OF  THE  EYE,  EAR,  NOSE  AND  THROAT.  12mo.  of 
about  400  pages  with  many  illustrations.  Shortly. 

WOHLER'S  OUTLINES  OF  ORGANIC  CHEMISTRY  Translated  from  the 
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YEAR-BOOK  OF  TREATMENT  FOR  1898.  A  Critical  Keview  for  Practitioners  of 
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YEO  (I.  BURNEY).  FOOD  IN  HEALTH  AND  DISEASE.  New  (2d)  edition. 
In  one  12mo.  volume  of  592  pages,  with  4  engravings.  Cloth,  $2.50.  See  Series  oj 
Clinical  Manuals,  page  13. 

YOUNG  (JAMES  K.).  ORTHOPEDIC  SURGERY.  In  one  8vo.  volume  of  475 
pages,  with  286  illustrations.  Cloth,  $4 ;  leather,  $5. 


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